GLI1-mediated regulation of side population is responsible for drug resistance in gastric cancer

PubMed Central

Yu, Beiqin; Gu, Dongsheng; Zhang, Xiaoli; Li, Jianfang; Liu, Bingya; Xie, Jingwu

2017-01-01

Gastric cancer is the third leading cause of cancer-related mortality worldwide. Chemotherapy is frequently used for gastric cancer treatment. Most patients with advanced gastric cancer eventually succumb to the disease despite some patients responded initially to chemotherapy. Thus, identifying molecular mechanisms responsible for cancer relapse following chemotherapy will help design new ways to treat gastric cancer. In this study, we revealed that the residual cancer cells following treatment with chemotherapeutic reagent cisplatin have elevated expression of hedgehog target genes GLI1, GLI2 and PTCH1, suggestive of hedgehog signaling activation. We showed that GLI1 knockdown sensitized gastric cancer cells to CDDP whereas ectopic GLI1 expression decreased the sensitivity. Further analyses indicate elevated GLI1 expression is associated with an increase in tumor sphere formation, side population and cell surface markers for putative cancer stem cells. We have evidence to support that GLI1 is critical for maintenance of putative cancer stem cells through direct regulation of ABCG2. In fact, GLI1 protein was shown to be associated with the promoter fragment of ABCG2 through a Gli-binding consensus site in gastric cancer cells. Disruption of ABCG2 function, through ectopic expression of an ABCG2 dominant negative construct or a specific ABCG2 inhibitor, increased drug sensitivity of cancer cells both in culture and in mice. The relevance of our studies to gastric cancer patient care is reflected by our discovery that high ABCG2 expression was associated with poor survival in the gastric cancer patients who underwent chemotherapy. Taken together, we have identified a molecular mechanism by which gastric cancer cells gain chemotherapy resistance. PMID:28404967

The multidrug transporter ABCG2 (BCRP) is inhibited by plant-derived cannabinoids

PubMed Central

Holland, M L; Lau, D T T; Allen, J D; Arnold, J C

2007-01-01

Background and purpose: Cannabinoids are used therapeutically for the palliation of the adverse side effects associated with cancer chemotherapy. However, cannabinoids also inhibit both the activity and expression of the multidrug transporter, P-glycoprotein in vitro. Here we address the interaction of cannabinol (CBN), cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC) with the related multidrug transporter, ABCG2. Experimental approach: Cannabinoid inhibition of Abcg2/ABCG2 was assessed using flow cytometric analysis of substrate accumulation and ATPase activity assays. The cytotoxicity and chemosensitization by cannabinoids was determined with cell viability assays. Expression of cannabinoid and vanilloid receptors was assessed using reverse transcriptase polymerase chain reaction, and cannabinoid modulation of ABCG2 expression was examined using immunoblotting. Key results: CBN, CBD and THC increased the intracellular accumulation of the Abcg2/ABCG2 substrate, mitoxantrone, in an over-expressing cell line. The THC metabolite, (−)-11-nor-9-carboxy-Δ9-THC was much less potent. The plant cannabinoids inhibited both basal and substrate stimulated ATPase activity of human ABCG2. Cannabinoid cytotoxicity occurred in the absence of known cannabinoid cell surface receptors, and only at concentrations higher than those required for Abcg2/ABCG2 inhibition. Sub-toxic concentrations of the cannabinoids resensitized the overexpressing cell line to the cytotoxic effect of Abcg2/ABCG2 substrates, mitoxantrone and topotecan. This occurred in the absence of any effect on ABCG2 expression. Conclusions and implications: Cannabinoids are novel Abcg2/ABCG2 inhibitors, reversing the Abcg2-mediated multidrug-resistant phenotype in vitro. This finding may have implications for the co-administration of cannabinoids with pharmaceuticals that are ABCG2 substrates. PMID:17906686

Regulators of floral fragrance production and their target genes in petunia are not exclusively active in the epidermal cells of petals

PubMed Central

Van Moerkercke, Alex; Galván-Ampudia, Carlos S.; Verdonk, Julian C.; Haring, Michel A.; Schuurink, Robert C.

2012-01-01

In which cells of the flower volatile biosynthesis takes place is unclear. In rose and snapdragon, some enzymes of the volatile phenylpropanoid/benzenoid pathway have been shown to be present in the epidermal cells of petals. It is therefore generally believed that the production of these compounds occurs in these cells. However, whether the entire pathway is active in these cells and whether it is exclusively active in these cells remains to be proven. Cell-specific transcription factors activating these genes will determine in which cells they are expressed. In petunia, the transcription factor EMISSION OF BENZENOIDS II (EOBII) activates the ODORANT1 (ODO1) promoter and the promoter of the biosynthetic gene isoeugenol synthase (IGS). The regulator ODO1 in turn activates the promoter of the shikimate gene 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Here the identification of a new target gene of ODO1, encoding an ABC transporter localized on the plasma membrane, PhABCG1, which is co-expressed with ODO1, is described. PhABCG1 expression is up-regulated in petals overexpressing ODO1 through activation of the PhABCG1 promoter. Interestingly, the ODO1, PhABCG1, and IGS promoters were active in petunia protoplasts originating from both epidermal and mesophyll cell layers of the petal, suggesting that the volatile phenylpropanoid/benzenoid pathway in petunia is active in these different cell types. Since volatile release occurs from epidermal cells, trafficking of (volatile) compounds between cell layers must be involved, but the exact function of PhABCG1 remains to be resolved. PMID:22345641

Assessment of ABCG2-mediated transport of pesticides across the rabbit placenta barrier using a novel MDCKII in vitro model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halwachs, Sandra

In humans, the ATP-binding cassette efflux transporter ABCG2 contributes to the fetoprotective barrier function of the placenta, potentially limiting the toxicity of transporter substrates to the fetus. During testing of chemicals including pesticides, developmental toxicity studies are performed in rabbit. Despite its toxicological relevance, ABCG2-mediated transport of pesticides in rabbit placenta has not been yet elucidated. We therefore generated polarized MDCK II cells expressing the ABCG2 transporter from rabbit placenta (rbABCG2) and evaluated interaction of the efflux transporter with selected insecticides, fungicides, and herbicides. The Hoechst H33342 accumulation assay indicated that 13 widely used pesticidal active substances including azoxystrobin, carbendazim,more » chlorpyrifos, chlormequat, diflufenican, dimethoate, dimethomorph, dithianon, ioxynil, methiocarb, propamocarb, rimsulfuron and toclofos-methyl may be rbABCG2 inhibitors and/or substrates. No such evidence was obtained for chlorpyrifos-methyl, epoxiconazole, glyphosate, imazalil and thiacloprid. Moreover, chlorpyrifos (CPF), dimethomorph, tolclofos-methyl and rimsulfuron showed concentration-dependent inhibition of H33342 excretion in rbABCG2-transduced MDCKII cells. To further evaluate the role of rbABCG2 in pesticide transport across the placenta barrier, we generated polarized MDCKII-rbABCG2 monolayers. Confocal microscopy confirmed correct localization of rbABCG2 protein in the apical plasma membrane. In transepithelial flux studies, we showed the time-dependent preferential basolateral to apical (B > A) directed transport of [{sup 14}C] CPF across polarized MDCKII-rbABCG2 monolayers which was significantly inhibited by the ABCG2 inhibitor fumitremorgin C (FTC). Using this novel in vitro cell culture model, we altogether showed functional secretory activity of the ABCG2 transporter from rabbit placenta and identified several pesticides like the insecticide CPF as potential rbABCG2 substrates. - Highlights: • Generation of MDCKII-rbABCG2 monolayers with epithelial barrier function • Detection of rbABCG2 in the apical plasma membrane of polarized MDCKII cells • Several pesticides interact with the ABCG2 transporter from rabbit placenta. • rbABCG2 mediates transport of the insecticide chlorpyrifos. • MDCKII-rbABCG2 cells are a suitable model to study transport in rabbit placenta.« less

Molecular genetic basis for fluoroquinolone-induced retinal degeneration in cats.

PubMed

Ramirez, Christina J; Minch, Jonathan D; Gay, John M; Lahmers, Sunshine M; Guerra, Dan J; Haldorson, Gary J; Schneider, Terri; Mealey, Katrina L

2011-02-01

Distribution of fluoroquinolones to the retina is normally restricted by ABCG2 at the blood-retinal barrier. As the cat develops a species-specific adverse reaction to photoreactive fluoroquinolones, our goal was to investigate ABCG2 as a candidate gene for fluoroquinolone-induced retinal degeneration and blindness in cats. Feline ABCG2 was sequenced and the consensus amino acid sequence was compared with that of 10 other mammalian species. Expression of ABCG2 in feline retina was assessed by immunoblot. cDNA constructs for feline and human ABCG2 were constructed in a pcDNA3 expression vector and expressed in HEK-293 cells, and ABCG2 expression was analyzed by western blot and immunofluorescence. Mitoxantrone and BODIPY-prazosin efflux measured by flow cytometry and a phototoxicity assay were used to assess feline and human ABCG2 function. Four feline-specific (compared with 10 other mammalian species) amino acid changes in conserved regions of ABCG2 were identified. Expression of ABCG2 on plasma membranes was confirmed in feline retina and in cells transfected with human and feline ABCG2, although some intracellular expression of feline ABCG2 was detected by immunofluorescence. Function of feline ABCG2, compared with human ABCG2, was found to be deficient as determined by flow cytometric measurement of mitoxantrone and BODIPY-prazosin efflux and enrofloxacin-induced phototoxicity assays. Feline-specific amino acid changes in ABCG2 cause a functional defect of the transport protein in cats. This functional defect may be owing, in part, to defective cellular localization of feline ABCG2. Regardless, dysfunction of ABCG2 at the blood-retinal barrier likely results in accumulation of photoreactive fluoroquinolones in feline retina. Exposure of the retina to light would then generate reactive oxygen species that would cause the characteristic retinal degeneration and blindness documented in some cats receiving high doses of some fluoroquinolones. Pharmacological inhibition of ABCG2 in other species might result in retinal damage if fluoroquinolones are concurrently administered.

Effect of apoA-I Mutations in the Capacity of Reconstituted HDL to Promote ABCG1-Mediated Cholesterol Efflux.

PubMed

Daniil, Georgios; Zannis, Vassilis I; Chroni, Angeliki

2013-01-01

ATP binding cassette transporter G1 (ABCG1) mediates the cholesterol transport from cells to high-density lipoprotein (HDL), but the role of apolipoprotein A-I (apoA-I), the main protein constituent of HDL, in this process is not clear. To address this, we measured cholesterol efflux from HEK293 cells or J774 mouse macrophages overexpressing ABCG1 using as acceptors reconstituted HDL (rHDL) containing wild-type or various mutant apoA-I forms. It was found that ABCG1-mediated cholesterol efflux was severely reduced (by 89%) when using rHDL containing the carboxyl-terminal deletion mutant apoA-I[Δ(185-243)]. ABCG1-mediated cholesterol efflux was not affected or moderately decreased by rHDL containing amino-terminal deletion mutants and several mid-region deletion or point apoA-I mutants, and was restored to 69-99% of control by double deletion mutants apoA-I[Δ(1-41)Δ(185-243)] and apoA-I[Δ(1-59)Δ(185-243)]. These findings suggest that the central helices alone of apoA-I associated to rHDL can promote ABCG1-mediated cholesterol efflux. Further analysis showed that rHDL containing the carboxyl-terminal deletion mutant apoA-I[Δ(185-243)] only slightly reduced (by 22%) the ABCG1-mediated efflux of 7-ketocholesterol, indicating that depending on the sterol type, structural changes in rHDL-associated apoA-I affect differently the ABCG1-mediated efflux of cholesterol and 7-ketocholesterol. Overall, our findings demonstrate that rHDL-associated apoA-I structural changes affect the capacity of rHDL to accept cellular cholesterol by an ABCG1-mediated process. The structure-function relationship seen here between rHDL-associated apoA-I mutants and ABCG1-mediated cholesterol efflux closely resembles that seen before in lipid-free apoA-I mutants and ABCA1-dependent cholesterol efflux, suggesting that both processes depend on the same structural determinants of apoA-I.

Global identification of genes regulated by estrogen signaling and demethylation in MCF-7 breast cancer cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putnik, Milica, E-mail: milica.putnik@ki.se; Zhao, Chunyan, E-mail: chunyan.zhao@ki.se; Gustafsson, Jan-Ake, E-mail: jan-ake.gustafsson@ki.se

Highlights: Black-Right-Pointing-Pointer Estrogen signaling and demethylation can both control gene expression in breast cancers. Black-Right-Pointing-Pointer Cross-talk between these mechanisms is investigated in human MCF-7 breast cancer cells. Black-Right-Pointing-Pointer 137 genes are influenced by both 17{beta}-estradiol and demethylating agent 5-aza-2 Prime -deoxycytidine. Black-Right-Pointing-Pointer A set of genes is identified as targets of both estrogen signaling and demethylation. Black-Right-Pointing-Pointer There is no direct molecular interplay of mediators of estrogen and epigenetic signaling. -- Abstract: Estrogen signaling and epigenetic modifications, in particular DNA methylation, are involved in regulation of gene expression in breast cancers. Here we investigated a potential regulatory cross-talk between thesemore » two pathways by identifying their common target genes and exploring underlying molecular mechanisms in human MCF-7 breast cancer cells. Gene expression profiling revealed that the expression of approximately 140 genes was influenced by both 17{beta}-estradiol (E2) and a demethylating agent 5-aza-2 Prime -deoxycytidine (DAC). Gene ontology (GO) analysis suggests that these genes are involved in intracellular signaling cascades, regulation of cell proliferation and apoptosis. Based on previously reported association with breast cancer, estrogen signaling and/or DNA methylation, CpG island prediction and GO analysis, we selected six genes (BTG3, FHL2, PMAIP1, BTG2, CDKN1A and TGFB2) for further analysis. Tamoxifen reverses the effect of E2 on the expression of all selected genes, suggesting that they are direct targets of estrogen receptor. Furthermore, DAC treatment reactivates the expression of all selected genes in a dose-dependent manner. Promoter CpG island methylation status analysis revealed that only the promoters of BTG3 and FHL2 genes are methylated, with DAC inducing demethylation, suggesting DNA methylation directs repression of these genes in MCF-7 cells. In a further analysis of the potential interplay between estrogen signaling and DNA methylation, E2 treatment showed no effect on the methylation status of these promoters. Additionally, we show that the ER{alpha} recruitment occurs at the FHL2 promoter in an E2- and DAC-independent fashion. In conclusion, we identified a set of genes regulated by both estrogen signaling and DNA methylation. However, our data does not support a direct molecular interplay of mediators of estrogen and epigenetic signaling at promoters of regulated genes.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palsamy, Periyasamy; Ayaki, Masahiko; Elanchezhian, Rajan

Highlights: Black-Right-Pointing-Pointer We found significant Keap1 promoter demethylation in diabetic cataractous lenses. Black-Right-Pointing-Pointer Demethylation of Keap1 gene upregulated the expression of Keap1 mRNA and protein. Black-Right-Pointing-Pointer Elevated levels of Keap1 are known to decrease the levels of Nrf2. Black-Right-Pointing-Pointer Thereby, the levels of antioxidant enzymes are suppressed by decreased Nrf2 level. -- Abstract: Age-related cataracts (ARCs) are the major cause of visual impairments worldwide, and diabetic adults tend to have an earlier onset of ARCs. Although age is the strongest risk factor for cataracts, little is known how age plays a role in the development of ARCs. It is knownmore » that oxidative stress in the lens increases with age and more so in the lenses of diabetics. One of the central adaptive responses against the oxidative stresses is the activation of the nuclear transcriptional factor, NF-E2-related factor 2 (Nrf2), which then activates more than 20 different antioxidative enzymes. Kelch-like ECH associated protein 1 (Keap1) targets and binds to Nrf2 for proteosomal degradation. We hypothesized that hyperglycemia will lead to a dysfunction of the Nrf2-dependent antioxidative protection in the lens of diabetics. We studied the methylation status of the CpG islands in 15 clear and 21 diabetic cataractous lenses. Our results showed significant levels of demethylated DNA in the Keap1 promoter in the cataractous lenses from diabetic patients. In contrast, highly methylated DNA was found in the clear lens and tumorized human lens epithelial cell (HLEC) lines (SRA01/04). HLECs treated with a demethylation agent, 5-aza-2 Prime deoxycytidine (5-Aza), had a 10-fold higher levels of Keap1 mRNA, 3-fold increased levels of Keap1 protein, produced higher levels of ROS, and increased cell death. Our results indicated that demethylation of the CpG islands in the Keap1 promoter will activate the expression of Keap1 protein, which then increases the targeting of Nrf2 for proteosomal degradation. Decreased Nrf2 activity represses the transcription of many antioxidant enzyme genes and alters the redox-balance towards lens oxidation. Thus, the failure of antioxidant protection due to demethylation of the CpG islands in the Keap1 promoter is linked to the diabetic cataracts and possibly ARCs.« less

Functional characterization of rainbow trout (Oncorhynchus mykiss) Abcg2a (Bcrp) transporter.

PubMed

Zaja, Roko; Popović, Marta; Lončar, Jovica; Smital, Tvrtko

2016-12-01

ABCG2 (BCRP - breast cancer resistance protein) belongs to the ATP-binding cassette (ABC) superfamily. It plays an important role in the disposition and elimination of xeno- and endobiotics and/or their metabolites in mammals. Likewise, the protective role of ABC transporters, including Abcg2, has been reported for aquatic organisms. In our previous study we have cloned the full gene sequence of rainbow trout (Oncorhynchus mykiss) Abcg2a and showed its high expression in liver and primary hepatocytes. Based on those insights, the main goal of this study was to perform a detailed functional characterization of trout Abcg2a using insect ovary cells (Spodoptera frugiperda, Sf9) as a heterologous expression system. Membrane vesicles preparations from Sf9 cells were used for the ATPase assay determinations and basic biochemical properties of fish Abcg2a versus human ABCG2 have been compared. A series of 39 physiologically and/or environmentally relevant substances was then tested on interaction with trout Abcg2a and human ABCG2. Correlation analysis reveals highly similar pattern of activation and inhibition. Significant activation of trout Abcg2a ATPase was observed for prazosin, doxorubicine, sildenafil, furosemid, propranolol, fenofibrate and pheophorbide. Pesticides showed either a weak activation (malathione) or strong (endosulfan) to weak (chlorpyrifos, fenoxycarb, DDE) inhibition of trout Abcg2a ATPase while the highest activation was obtained for benzo(a)pyrene, curcumine and testosterone. In conclusion, data from this study offer the first characterization of fish Abcg2a, reveal potent interactors among physiologically or environmentally relevant substances and point to similarities regarding strengths and interactor preferences between human ABCG2 and fish Abcg2a. Copyright © 2016 Elsevier Inc. All rights reserved.

In vitro and in vivo modulation of ABCG2 by functionalized aurones and structurally related analogs

PubMed Central

Sim, Hong-May; Wu, Chung-Pu; Ambudkar, Suresh V.; Go, Mei-Lin

2013-01-01

Over-expression of ABCG2 is linked to multidrug resistance in cancer chemotherapy. We have previously shown that functionalized aurones effectively reduced the efflux of pheophorbide A (an ABCG2 substrate) from ABCG2 over-expressing MDA-MB-231/R (“R”) cells. In the present report, we investigated the functional relevance of this observation and the mechanisms by which it occurs. Aurones and related analogs were investigated for re-sensitization of R cells to mitoxantrone (MX, a chemotherapeutic substrate of ABCG2) in cell-based assays, accumulation of intracellular MX by cell cytometry, interaction with ABCG2 by biochemical assays and in vivo efficacy in MX resistant nude mice xenografts. We found that methoxylated aurones interacted directly with ABCG2 to inhibit efflux activity, possibly by competing for occupancy of one of the substrate binding sites on ABCG2. The present evidence suggests that they are not transported by ABCG2 although they stimulate ABCG2-ATPase activity. Alteration of ABCG2 protein expression was also discounted. One member was found to re-sensitize R cells to MX in both in vitro and in vivo settings. Our study identified methoxylated aurones as promising compounds associated with low toxicities and potent modulatory effects on the ABCG2 efflux protein. Thus, they warrant further scrutiny as lead templates for development as reversal agents of multidrug resistance. PMID:21855533

Human in vitro induced T regulatory cells and memory T cells share common demethylation of specific FOXP3 promoter region.

PubMed

Bégin, Philippe; Schulze, Janika; Baron, Udo; Olek, Sven; Bauer, Rebecca N; Passerini, Laura; Baccheta, Rosa; Nadeau, Kari C

2015-01-01

The FOXP3 gene is the master regulator for T regulatory cells and is under tight DNA methylation control at the Treg specific demethylated region (TSDR) in its first intron. This said, methylation of its promoter region, the significance of which is unknown, has also been associated with various immune-related disease states such as asthma, food allergy, auto-immunity and cancer. Here, we used induced T regulatory cells (iTreg) as a target cell population to identify candidate hypomethylated CpG sites in the FOXP3 gene promoter to design a DNA methylation quantitative assay for this region. Three CpG sites at the promoter region showed clear demethylation pattern associated with high FOXP3 expression after activation in presence of TGFβ and were selected as primary targets to design methylation-dependent RT-PCR primers and probes. We then examined the methylation of this 'inducible-promoter-demethylated-region' (IPDR) in various FOXP3+ T cell subsets. Both naïve and memory thymic-derived Treg cells were found to be fully demethylated at both the IPDR and TSDR. Interestingly, in addition to iTregs, both CD25- and CD25(lo) conventional memory CD4+CD45RA- T cells displayed a high fraction of IPDR demethylated cells in absence of TSDR demethylation. This implies that the fraction of memory T cells should be taken in account when interpreting FOXP3 promoter methylation results from clinical studies. This approach, which is available for testing in clinical samples could have diagnostic and prognostic value in patients with immune or auto-inflammatory diseases.

The Full-Size ABCG Transporters Nb-ABCG1 and Nb-ABCG2 Function in Pre- and Postinvasion Defense against Phytophthora infestans in Nicotiana benthamiana

PubMed Central

Shibata, Yusuke; Ojika, Makoto; Sugiyama, Akifumi; Yazaki, Kazufumi; Jones, David A.; Kawakita, Kazuhito

2016-01-01

The sesquiterpenoid capsidiol is the major phytoalexin produced by Nicotiana and Capsicum species. Capsidiol is produced in plant tissues attacked by pathogens and plays a major role in postinvasion defense by inhibiting pathogen growth. Using virus-induced gene silencing-based screening, we identified two Nicotiana benthamiana (wild tobacco) genes encoding functionally redundant full-size ABCG (PDR-type) transporters, Nb-ABCG1/PDR1 and Nb-ABCG2/PDR2, which are essential for resistance to the potato late blight pathogen Phytophthora infestans. Silencing of Nb-ABCG1/2 compromised secretion of capsidiol, revealing Nb-ABCG1/2 as probable exporters of capsidiol. Accumulation of plasma membrane-localized Nb-ABCG1 and Nb-ABCG2 was observed at the site of pathogen penetration. Silencing of EAS (encoding 5-epi-aristolochene synthase), a gene for capsidiol biosynthesis, reduced resistance to P. infestans, but penetration by P. infestans was not affected. By contrast, Nb-ABCG1/2-silenced plants showed reduced penetration defense, indicating that Nb-ABCG1/2 are involved in preinvasion defense against P. infestans. Plastidic GGPPS1 (geranylgeranyl diphosphate synthase) was also found to be required for preinvasion defense, thereby suggesting that plastid-produced diterpene(s) are the antimicrobial compounds active in preinvasion defense. These findings suggest that N. benthamiana ABCG1/2 are involved in the export of both antimicrobial diterpene(s) for preinvasion defense and capsidiol for postinvasion defense against P. infestans. PMID:27102667

Icotinib antagonizes ABCG2-mediated multidrug resistance, but not the pemetrexed resistance mediated by thymidylate synthase and ABCG2

PubMed Central

Shukla, Suneet; Zhang, Yun-Kai; Wang, Yi-Jun; Kathawala, Rishil J.; Robey, Robert W.; Zhang, Li; Yang, Dong-Hua; Talele, Tanaji T.; Bates, Susan E.; Ambudkar, Suresh V.; Chen, Zhe-Sheng

2014-01-01

ABCG2 is a potential biomarker causing multidrug resistance (MDR) in Non-Small Cell Lung Cancer (NSCLC). We conducted this study to investigate whether Icotinib, a small-molecule inhibitor of EGFR tyrosine kinase, could interact with ABCG2 transporter in NSCLC. Our results showed that Icotinib reversed ABCG2-mediated MDR by antagonizing the drug efflux function of ABCG2. Icotinib stimulated the ATPase activity in a concentration-dependent manner and inhibited the photolabeling of ABCG2 with [125I]-Iodoarylazidoprazosin, demonstrating that it interacts at the drug-binding pocket. Homology modeling predicted the binding conformation of Icotinib at Asn629 centroid-based grid of ABCG2. However, Icotinib at reversal concentration did not affect the expression levels of AKT and ABCG2. Furthermore, a combination of Icotinib and topotecan exhibited significant synergistic anticancer activity against NCI-H460/MX20 tumor xenografts. However, the inhibition of transport activity of ABCG2 was insufficient to overcome pemetrexed resistance in NCI-H460/MX20 cells, which was due to the co-upregulated thymidylate synthase (TS) and ABCG2 expression. This is the first report to show that the up-regulation of TS in ABCG2-overexpressing cell line NCI-H460/MX20 may play a role of resistance to pemetrexate. Our findings suggested different possible strategies of overcoming the resistance of topotecan and pemetrexed in the NSCLC patients. PMID:24980828

Icotinib antagonizes ABCG2-mediated multidrug resistance, but not the pemetrexed resistance mediated by thymidylate synthase and ABCG2.

PubMed

Wang, De-Shen; Patel, Atish; Shukla, Suneet; Zhang, Yun-Kai; Wang, Yi-Jun; Kathawala, Rishil J; Robey, Robert W; Zhang, Li; Yang, Dong-Hua; Talele, Tanaji T; Bates, Susan E; Ambudkar, Suresh V; Xu, Rui-Hua; Chen, Zhe-Sheng

2014-06-30

ABCG2 is a potential biomarker causing multidrug resistance (MDR) in Non-Small Cell Lung Cancer (NSCLC). We conducted this study to investigate whether Icotinib, a small-molecule inhibitor of EGFR tyrosine kinase, could interact with ABCG2 transporter in NSCLC. Our results showed that Icotinib reversed ABCG2-mediated MDR by antagonizing the drug efflux function of ABCG2. Icotinib stimulated the ATPase activity in a concentration-dependent manner and inhibited the photolabeling of ABCG2 with [125I]-Iodoarylazidoprazosin, demonstrating that it interacts at the drug-binding pocket. Homology modeling predicted the binding conformation of Icotinib at Asn629 centroid-based grid of ABCG2. However, Icotinib at reversal concentration did not affect the expression levels of AKT and ABCG2. Furthermore, a combination of Icotinib and topotecan exhibited significant synergistic anticancer activity against NCI-H460/MX20 tumor xenografts. However, the inhibition of transport activity of ABCG2 was insufficient to overcome pemetrexed resistance in NCI-H460/MX20 cells, which was due to the co-upregulated thymidylate synthase (TS) and ABCG2 expression. This is the first report to show that the up-regulation of TS in ABCG2-overexpressing cell line NCI-H460/MX20 may play a role of resistance to pemetrexate. Our findings suggested different possible strategies of overcoming the resistance of topotecan and pemetrexed in the NSCLC patients.

Identification of Inhibitors of ABCG2 by a Bioluminescence Imaging-based High-throughput Assay

PubMed Central

Zhang, Yimao; Byun, Youngjoo; Ren, Yunzhao R.; Liu, Jun O.; Laterra, John; Pomper, Martin G.

2009-01-01

ABCG2 is a member of the ATP-binding cassette (ABC) family of transporters, the overexpression of which is associated with tumor resistance to a variety of chemotherapeutic agents. Accordingly, combining ABCG2 inhibitor(s) with chemotherapy has the potential to improve treatment outcome. To search for clinically useful ABCG2 inhibitors, a bioluminescence imaging (BLI)-based assay was developed to allow high-throughput compound screening. This assay exploits our finding that D-luciferin, the substrate of firefly luciferase (fLuc), is a specific substrate of ABCG2, and ABCG2 inhibitors block the export of D-luciferin and enhance bioluminescence signal by increasing intracellular D-luciferin concentrations. HEK293 cells, engineered to express ABCG2 and fLuc, were used to screen the Hopkins Drug Library that includes drugs approved by the US Food and Drug Administration (FDA) as well as drug candidates that have entered phase II clinical trials. Forty seven compounds demonstrated BLI enhancement, a measure of anti-ABCG2 activity, of five-fold or greater, the majority of which were not previously known as ABCG2 inhibitors. The assay was validated by its identification of known ABCG2 inhibitors and by confirming previously unknown ABCG2 inhibitors using established in vitro assays (e.g. mitoxantrone resensitization and BODIPY-prazosin assays). Glafenine, a potent new inhibitor, also inhibited ABCG2 activity in vivo. The BLI-based assay is an efficient method to identify new inhibitors of ABCG2. As they were derived from an FDA-approved compound library, many of the inhibitors uncovered in this study are ready for clinical testing. PMID:19567678

Induced DNA demethylation by targeting Ten-Eleven Translocation 2 to the human ICAM-1 promoter

PubMed Central

Chen, Hui; Kazemier, Hinke G; de Groote, Marloes L.; Ruiters, Marcel H. J.; Xu, Guo-Liang; Rots, Marianne G.

2014-01-01

Increasing evidence indicates that active DNA demethylation is involved in several processes in mammals, resulting in developmental stage-specificity and cell lineage-specificity. The recently discovered Ten-Eleven Translocation (TET) dioxygenases are accepted to be involved in DNA demethylation by initiating 5-mC oxidation. Aberrant DNA methylation profiles are associated with many diseases. For example in cancer, hypermethylation results in silencing of tumor suppressor genes. Such silenced genes can be re-expressed by epigenetic drugs, but this approach has genome-wide effects. In this study, fusions of designer DNA binding domains to TET dioxygenase family members (TET1, -2 or -3) were engineered to target epigenetically silenced genes (ICAM-1, EpCAM). The effects on targeted CpGs’ methylation and on expression levels of the target genes were assessed. The results indicated demethylation of targeted CpG sites in both promoters for targeted TET2 and to a lesser extent for TET1, but not for TET3. Interestingly, we observed re-activation of transcription of ICAM-1. Thus, our work suggests that we provided a mechanism to induce targeted DNA demethylation, which facilitates re-activation of expression of the target genes. Furthermore, this Epigenetic Editing approach is a powerful tool to investigate functions of epigenetic writers and erasers and to elucidate consequences of epigenetic marks. PMID:24194590

Ethanol-induced changes in Poly (ADP ribose) Polymerase and neuronal developmental gene expression

PubMed Central

Gavin, David P.; Kusumo, Handojo; Sharma, Rajiv P.; Guizzetti, Marina

2016-01-01

Prenatal alcohol exposure has profound effects on neuronal growth and development. Poly-ADP Ribose Polymerase (PARP) enzymes are perhaps unique in the field of epigenetics in that they directly participate in histone modifications, transcription factor modifications, DNA methylation/demethylation and are highly inducible by ethanol. It was our hypothesis that ethanol would induce PARP enzymatic activity leading to alterations in neurodevelopmental gene expression. Mouse E18 cortical neurons were treated with ethanol, PARP inhibitors, and nuclear hormone receptor transcription factor PPARγ agonists and antagonists. Subsequently, we measured PARP activity and changes in Bdnf, OKSM (Oct4, Klf4, Sox2, c-Myc), DNA methylating/demethylating factors, and Pparγ mRNA expression, promoter 5-methylcytosine (5MC) and 5-hydroxymethylcytosine (5HMC), and PPARγ promoter binding. We found that ethanol reduced Bdnf4, 9a, and Klf4 mRNA expression, and increased c-Myc expression. These changes were reversed with a PARP inhibitor. In agreement with its role in DNA demethylation PARP inhibition increased 5MC levels at the c-Myc promoter. In addition, we found that elevated PARP enzymatic activity reduced PPARγ promoter binding, and this corresponded to decreased Bdnf and Klf4 mRNA expression. Our results suggest that PARP participates in DNA demethylation and reduces PPARγ promoter binding. The current study underscores the importance of PARP in ethanol-induced changes to neurodevelopmental gene expression. PMID:27497606

Ethanol-induced changes in poly (ADP ribose) polymerase and neuronal developmental gene expression.

PubMed

Gavin, David P; Kusumo, Handojo; Sharma, Rajiv P; Guizzetti, Marina

2016-11-01

Prenatal alcohol exposure has profound effects on neuronal growth and development. Poly-ADP Ribose Polymerase (PARP) enzymes are perhaps unique in the field of epigenetics in that they directly participate in histone modifications, transcription factor modifications, DNA methylation/demethylation and are highly inducible by ethanol. It was our hypothesis that ethanol would induce PARP enzymatic activity leading to alterations in neurodevelopmental gene expression. Mouse E18 cortical neurons were treated with ethanol, PARP inhibitors, and nuclear hormone receptor transcription factor PPARγ agonists and antagonists. Subsequently, we measured PARP activity and changes in Bdnf, OKSM (Oct4, Klf4, Sox2, c-Myc), DNA methylating/demethylating factors, and Pparγ mRNA expression, promoter 5-methylcytosine (5MC) and 5-hydroxymethylcytosine (5HMC), and PPARγ promoter binding. We found that ethanol reduced Bdnf4, 9a, and Klf4 mRNA expression, and increased c-Myc expression. These changes were reversed with a PARP inhibitor. In agreement with its role in DNA demethylation PARP inhibition increased 5MC levels at the c-Myc promoter. In addition, we found that inhibition of PARP enzymatic activity increased PPARγ promoter binding, and this corresponded to increased Bdnf and Klf4 mRNA expression. Our results suggest that PARP participates in DNA demethylation and reduces PPARγ promoter binding. The current study underscores the importance of PARP in ethanol-induced changes to neurodevelopmental gene expression. Published by Elsevier Ltd.

Cichorium intybus L. promotes intestinal uric acid excretion by modulating ABCG2 in experimental hyperuricemia.

PubMed

Wang, Yu; Lin, Zhijian; Zhang, Bing; Nie, Anzheng; Bian, Meng

2017-01-01

Excessive production and/or reduced excretion of uric acid could lead to hyperuricemia, which could be a major cause of disability. Hyperuricemia has received increasing attention in the last few decades due to its global prevalence. Cichorium intybus L., commonly known as chicory, is a perennial herb of the asteraceae family. It was previously shown to exert potent hypouricemic effects linked with decreasing uric acid formation in the liver by down-regulating the activity of xanthine oxidase, and increasing uric acid excretion by up-regulating the renal OAT3 mRNA expression. The present study aimed to evaluate its extra-renal excretion and possible molecular mechanism underlying the transporter responsible for intestinal uric acid excretion in vivo. Chicory was administered intragastrically to hyperuricemic rats induced by drinking 10% fructose water. The uricosuric effect was evaluated by determining the serum uric acid level as well as the intestinal uric acid excretion by HPLC. The location and expression levels of ATP-binding cassette transporter, sub-family G, member 2 (ABCG2) in jejunum and ileum were analyzed. The administration of chicory decreased the serum uric acid level significantly and increased the intestinal uric acid excretion obviously in hyperuricemic rats induced by 10% fructose drinking. Staining showed that ABCG2 was expressed in the apical membrane of the epithelium and glands of the jejunum and ileum in rats. Further examination showed that chicory enhanced the mRNA and protein expressions of ABCG2 markedly in a dose-dependent manner in jejunum and ileum. These findings indicate that chicory increases uric acid excretion by intestines, which may be related to the stimulation of intestinal uric acid excretion via down-regulating the mRNA and protein expressions of ABCG2.

AST1306, a potent EGFR inhibitor, antagonizes ATP-binding cassette subfamily G member 2-mediated multidrug resistance.

PubMed

Zhang, Hui; Wang, Yi-Jun; Zhang, Yun-Kai; Wang, De-Shen; Kathawala, Rishil J; Patel, Atish; Talele, Tanaji T; Chen, Zhe-Sheng; Fu, Li-Wu

2014-08-01

AST1306, an inhibitor of EGFR and ErbB2, is currently in phase I of clinical trials. We evaluated the effect of AST306 on the reversal of multidrug resistance (MDR) induced by ATP-binding cassette (ABC) transporters. We found that AST1306 significantly sensitized the ABC subfamily G member 2 (ABCG2)-overexpressing cells to ABCG2 substrate chemotherapeutics. AST1306 significantly increased intracellular accumulation of [(3)H]-mitoxantrone in ABCG2-overexpressing cells by blocking ABCG2 efflux function. Moreover, AST1306 stimulated the ATPase activity of ABCG2. Homology modeling predicted the binding conformation of AST1306 to be within the transmembrane region of ABCG2. In conclusion, AST1306 could notably reverse ABCG2-mediated MDR. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Glutathione Transport Is a Unique Function of the ATP-binding Cassette Protein ABCG2*

PubMed Central

Brechbuhl, Heather M.; Gould, Neal; Kachadourian, Remy; Riekhof, Wayne R.; Voelker, Dennis R.; Day, Brian J.

2010-01-01

Glutathione (GSH) transport is vital for maintenance of intracellular and extracellular redox balance. Only a few human proteins have been identified as transporters of GSH, glutathione disulfide (GSSG) and/or GSH conjugates (GS-X). Human epithelial MDA1586, A549, H1975, H460, HN4, and H157 cell lines were exposed to 2′,5′-dihydroxychalcone, which induces a GSH efflux response. A real-time gene superarray for 84 proteins found in families that have a known role in GSH, GSSG, and/or GS-X transport was employed to help identify potential GSH transporters. ABCG2 was identified as the only gene in the array that closely corresponded with the magnitude of 2′,5′-dihydroxychalcone (2′,5′-DHC)-induced GSH efflux. The role of human ABCG2 as a novel GSH transporter was verified in a Saccharomyces cerevisiae galactose-inducible gene expression system. Yeast expressing human ABCG2 had 2.5-fold more extracellular GSH compared with those not expressing ABCG2. GSH efflux in ABCG2-expressing yeast was abolished by the ABCG2 substrate methotrexate (10 μm), indicating competitive inhibition. In contrast, 2′,5′-DHC treatment of ABCG2-expressing yeast increased extracellular GSH levels in a dose-dependent manner with a maximum 3.5-fold increase in GSH after 24 h. In addition, suppression of ABCG2 with short hairpin RNA or ABCG2 overexpression in human epithelial cells decreased or increased extracellular GSH levels, respectively. Our data indicate that ABCG2 is a novel GSH transporter. PMID:20332504

Glutathione transport is a unique function of the ATP-binding cassette protein ABCG2.

PubMed

Brechbuhl, Heather M; Gould, Neal; Kachadourian, Remy; Riekhof, Wayne R; Voelker, Dennis R; Day, Brian J

2010-05-28

Glutathione (GSH) transport is vital for maintenance of intracellular and extracellular redox balance. Only a few human proteins have been identified as transporters of GSH, glutathione disulfide (GSSG) and/or GSH conjugates (GS-X). Human epithelial MDA1586, A549, H1975, H460, HN4, and H157 cell lines were exposed to 2',5'-dihydroxychalcone, which induces a GSH efflux response. A real-time gene superarray for 84 proteins found in families that have a known role in GSH, GSSG, and/or GS-X transport was employed to help identify potential GSH transporters. ABCG2 was identified as the only gene in the array that closely corresponded with the magnitude of 2',5'-dihydroxychalcone (2',5'-DHC)-induced GSH efflux. The role of human ABCG2 as a novel GSH transporter was verified in a Saccharomyces cerevisiae galactose-inducible gene expression system. Yeast expressing human ABCG2 had 2.5-fold more extracellular GSH compared with those not expressing ABCG2. GSH efflux in ABCG2-expressing yeast was abolished by the ABCG2 substrate methotrexate (10 microM), indicating competitive inhibition. In contrast, 2',5'-DHC treatment of ABCG2-expressing yeast increased extracellular GSH levels in a dose-dependent manner with a maximum 3.5-fold increase in GSH after 24 h. In addition, suppression of ABCG2 with short hairpin RNA or ABCG2 overexpression in human epithelial cells decreased or increased extracellular GSH levels, respectively. Our data indicate that ABCG2 is a novel GSH transporter.

PPAR-gamma pathways attenuate pulmonary granuloma formation in a carbon nanotube induced murine model of sarcoidosis.

PubMed

McPeek, Matthew; Malur, Anagha; Tokarz, Debra A; Murray, Gina; Barna, Barbara P; Thomassen, Mary Jane

2018-06-15

Peroxisome proliferator activated receptor gamma (PPARγ), a ligand activated nuclear transcription factor, is constitutively expressed in alveolar macrophages of healthy individuals. PPARγ deficiencies have been noted in several lung diseases including the alveolar macrophages of pulmonary sarcoidosis patients. We have previously described a murine model of multiwall carbon nanotubes (MWCNT) induced pulmonary granulomatous inflammation which bears striking similarities to pulmonary sarcoidosis, including the deficiency of alveolar macrophage PPARγ. Further studies demonstrate alveolar macrophage PPARγ deficiency exacerbates MWCNT-induced pulmonary granulomas. Based on these observations we hypothesized that activation of PPARγ via administration of the PPARγ-specific ligand rosiglitazone would limit MWCNT-induced granuloma formation and promote PPARγ-dependent pathways. Results presented here show that rosiglitazone significantly limits the frequency and severity of MWCNT-induced pulmonary granulomas. Furthermore, rosiglitazone attenuates alveolar macrophage NF-κB activity and downregulates the expression of the pro-inflammatory mediators, CCL2 and osteopontin. PPARγ activation via rosiglitazone also prevents the MWCNT-induced deficiency of PPARγ-regulated ATP-binding cassette lipid transporter-G1 (ABCG1) expression. ABCG1 is crucial to pulmonary lipid homeostasis. ABCG1 deficiency results in lipid accumulation which promotes pro-inflammatory macrophage activation. Our results indicate that restoration of homeostatic ABCG1 levels by rosiglitazone correlates with both reduced pulmonary lipid accumulation, and decreased alveolar macrophage activation. These data confirm and further support our previous observations that PPARγ pathways are critical in regulating MWCNT-induced pulmonary granulomatous inflammation. Copyright © 2018 Elsevier Inc. All rights reserved.

Induction of anti-aging gene klotho with a small chemical compound that demethylates CpG islands

PubMed Central

Jung, Dongju; Xu, Yuechi; Sun, Zhongjie

2017-01-01

Klotho (KL) is described as an anti-aging gene because mutation of Kl gene leads to multiple pre-mature aging phenotypes and shortens lifespan in mice. Growing evidence suggests that an increase in KL expression may be beneficial for age-related diseases such as arteriosclerosis and diabetes. It remains largely unknown, however, how Kl expression could be induced. Here we discovered novel molecular mechanism for induction of Kl expression with a small molecule ‘Compound H’, N-(2-chlorophenyl)-1H-indole-3-caboxamide. Compound H was originally identified through a high-throughput screening of small molecules for identifying Kl inducers. However, how Compound H induces Kl expression has never been investigated. We found that Compound H increased Kl expression via demethylation in CpG islands of the Kl gene. The demethylation was accomplished by activating demethylases rather than inhibiting methylases. Due to demethylation, Compound H enhanced binding of transcription factors, Pax4 and Kid3, to the promoter of the Kl gene. Pax4 and Kid3 regulated Kl promoter activity positively and negatively, respectively. Thus, our results show that demethylation is an important molecular mechanism that mediates Compound H-induced Kl expression. Further investigation is warranted to determine whether Compound H demethylates the Kl gene in vivo and whether it can serve as a therapeutic agent for repressing or delaying the onset of age-related diseases. PMID:28657902

Substrate affinity of photosensitizers derived from chlorophyll-a: The ABCG2 transporter affects the phototoxic response of side population stem cell-like cancer cells to photodynamic therapy

PubMed Central

Morgan, Janet; Jackson, Jennifer D.; Zheng, Xiang; Pandey, Suresh K.; Pandey, Ravindra K.

2010-01-01

Photosensitizers (PS) synthesized with the aim of optimizing photodynamic therapy (PDT) of tumors do not always fulfill their potential when tested in vitro and in vivo in different tumor models. The ATP-dependent transporter ABCG2 a multi-drug resistant pump expressed at variable levels in cancerous cells, can bind and efflux a wide range of structurally different classes of compounds including several PS used pre-clinically and clinically such as porphyrins and chlorins. ABCG2 may lower intracellular levels of substrate PS below the threshold for cell death in tumors treated by PDT, leaving resistant cells to re-populate the tumor. To determine some of the structural factors that affect substrate affinity of PS for ABCG2, we used an ABCG2 expressing cell line (HEK 293 482R) and its non-expressing counterpart, and tyrosine kinase ABCG2 inhibitors in a simple flow cytometric assay to identify PS effluxed by the ABCG2 pump. We tested a series of conjugates of substrate PS with different groups attached at different positions on the tetrapyrrole macrocycle to examine whether a change in affinity for the pump occurred and whether such changes depended on the position or the structure/type of the attached group. PS without substitutions including pyropheophorbides and purpurinimides were generally substrates for ABCG2, but carbohydrate groups conjugated at positions 8, 12, 13 and 17 but not at position 3 abrogated ABCG2 affinity regardless of structure or linking moiety. At position 3, affinity was retained with the addition of iodobenzene, alkyl chains and monosaccharides, but not with disaccharides. This suggests that structural characteristics at position 3 may offer important contributions to requirements for binding to ABCG2. We examined several tumor cell lines for ABCG2 activity, and found that although some cell lines had negligible ABCG2 activity in bulk, they contained a small ABCG2-expressing side population (SP) thought to contain cells which are responsible for initiating tumor regrowth. We examined the relevance of the SP to PDT resistance with ABCG2 substrates in vitro and in vivo in the murine mammary tumor 4T1. We show for the first time in vivo that the substrate PS HPPH (2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a) but not the non-substrate PS HPPH-Gal (a galactose conjugate of HPPH) selectively preserved the SP which was primarily responsible for regrowth in vitro. The SP could be targeted by addition of imatinib mesylate, a tyrosine kinase inhibitor which inhibits the ATPase activity of ABCG2, and prevents efflux of substrates. A PDT resistant SP may be responsible for recurrences observed both pre-clinically and clinically. To prevent ABCG2 mediated resistance, choosing non-substrate PS or administering an ABCG2 inhibitor alongside a substrate PS might be advantageous when treating ABCG2 expressing tumors with PDT. PMID:20684544

Role of Abcg2 During Mouse Embroyonic Stem Cell Diffferentiation

EPA Science Inventory

Role of Abcg2 During Mouse Embryonic Stem Cell Differentiation. Abcg2 is a multidrug resistance ATP-binding cassette (ABC) transporter whose activity may be considered a hallmark of stem cell plasticity. The role of Abcg2 during early embryogenesis, however, is unclear. Studies...

Effects of the lipid environment, cholesterol and bile acids on the function of the purified and reconstituted human ABCG2 protein.

PubMed

Telbisz, Ágnes; Özvegy-Laczka, Csilla; Hegedűs, Tamás; Váradi, András; Sarkadi, Balázs

2013-03-01

The human ABCG2 multidrug transporter actively extrudes a wide range of hydrophobic drugs and xenobiotics recognized by the transporter in the membrane phase. In order to examine the molecular nature of the transporter and its effects on the lipid environment, we have established an efficient protocol for the purification and reconstitution of the functional protein. We found that the drug-stimulated ATPase and the transport activity of ABCG2 are fully preserved by applying excess lipids and mild detergents during solubilization, whereas a detergent-induced dissociation of the ABCG2 dimer causes an irreversible inactivation. By using the purified and reconstituted protein we demonstrate that cholesterol is an essential activator, whereas bile acids are important modulators of ABCG2 activity. Both wild-type ABCG2 and its R482G mutant variant require cholesterol for full activity, although they exhibit different cholesterol sensitivities. Bile acids strongly decrease the basal ABCG2-ATPase activity both in the wild-type ABCG2 and in the mutant variant. These data reinforce the results for the modulatory effects of cholesterol and bile acids of ABCG2 investigated in a complex cell membrane environment. Moreover, these experiments open the possibility to perform functional and structural studies with a purified, reconstituted and highly active ABCG2 multidrug transporter.

Repression of adenosine triphosphate-binding cassette transporter ABCG2 by estrogen increases intracellular glutathione in brain endothelial cells following ischemic reperfusion injury.

PubMed

Shin, Jin A; Jeong, Sae Im; Kim, Hye Won; Jang, Gyeonghui; Ryu, Dong-Ryeol; Ahn, Young-Ho; Choi, Ji Ha; Choi, Youn-Hee; Park, Eun-Mi

2018-06-01

The adenosine triphosphate-binding cassette efflux transporter ABCG2, which is located in the blood-brain barrier limits the entry of endogenous compounds and xenobiotics into the brain, and its expression and activity are regulated by estrogen. This study was aimed to define the role of ABCG2 in estrogen-mediated neuroprotection against ischemic injury. ABCG2 protein levels before and after ischemic stroke were increased in the brain of female mice by ovariectomy, which were reversed by estrogen replacement. In brain endothelial cell line bEnd.3, estrogen reduced the basal ABCG2 protein level and efflux activity and protected cells from ischemic injury without inducing ABCG2 expression. When bEnd.3 cells were transfected with ABCG2 small interfering RNA, ischemia-induced cell death was reduced, and the intracellular concentration of glutathione, an antioxidant that is transported by ABCG2, was increased. In addition, after ischemic stroke in ovariectomized mice, estrogen prevented the reduction of intracellular glutathione level in brain microvessels. These data suggested that the suppression of ABCG2 by estrogen is involved in neuroprotection against ischemic injury by increasing intracellular glutathione, and that the modulation of ABCG2 activity offers a therapeutic target for brain diseases in estrogen-deficient aged women. Copyright © 2018 Elsevier Inc. All rights reserved.

Interaction of mammary bovine ABCG2 with AFB1 and its metabolites and regulation by PCB 126 in a MDCKII in vitro model.

PubMed

Manzini, L; Halwachs, S; Girolami, F; Badino, P; Honscha, W; Nebbia, C

2017-12-01

The ATP-binding cassette efflux transporter ABCG2 plays a key role in the mammary excretion of drugs and toxins in humans and animals. Aflatoxins (AF) are worldwide contaminants of food and feed commodities, while PCB 126 is a dioxin-like PCB which may contaminate milk and dairy products. Both compounds are known human carcinogens. The interactions between AF and bovine ABCG2 (bABCG2) as well as the effects of PCB 126 on its efflux activity have been investigated by means of the Hoechst H33342 transport assay in MDCKII cells stably expressing mammary bABCG2. Both AFB1 and its main milk metabolite AFM1 showed interaction with bABCG2 even at concentrations approaching the legal limits in feed and food commodities. Moreover, PCB 126 significantly enhanced bABCG2 functional activity. Specific inhibitors of either AhR (CH233191) or ABCG2 (Ko143) were able to reverse the PCB 126-induced increase in bABCG2 transport activity, showing the specific upregulation of the efflux protein by the AhR pathway. The incubation of PCB 126-pretreated cells with AFM1 was able to substantially reverse such effect, with still unknown mechanism(s). Overall, results from this study point to AFB1 and AFM1 as likely bABCG2 substrates. The PCB 126-dependent increased activity of the transporter could enhance the ABCG2-mediated excretion into dairy milk of chemicals (i.e., drugs and toxins) potentially harmful to neonates and consumers. © 2017 John Wiley & Sons Ltd.

TSA-induced DNMT1 down-regulation represses hTERT expression via recruiting CTCF into demethylated core promoter region of hTERT in HCT116.

PubMed

Choi, Jee-Hye; Min, Na Young; Park, Jina; Kim, Jin Hong; Park, Soo Hyun; Ko, Young Jong; Kang, Yoonsung; Moon, Young Joon; Rhee, Sangmyung; Ham, Seung Wook; Park, Ae Ja; Lee, Kwang-Ho

2010-01-01

Trichostatin A (TSA), an inhibitor of histone deacetylase, is a well-known antitumor agent that effectively and selectively induces tumor growth arrest and apoptosis. Recently, it was reported that hTERT is one of the primary targets for TSA-induced apoptosis in cancer cells but the mechanism of which has not yet been elucidated. In the present study, to better understand the epigenetic regulation mechanism responsible for the repression of hTERT by TSA, we examined expression of hTERT in the HCT116 colon cancer cell line after treatment with TSA and performed site-specific CpG methylation analysis of the hTERT promoter. We found that TSA-induced the demethylation of site-specific CpGs on the promoter of hTERT, which was caused by down-regulation of DNA methyltransferase 1 (DNMT1). Among the demethylated region, the 31st-33rd CpGs contained a binding site for CTCF, an inhibitor of hTERT transcription. ChIP analysis revealed that TSA-induced demethylation of the 31st-33rd CpGs promoted CTCF binding on hTERT promoter, leading to repression of hTERT. Taken together, down-regulation of DNMT1 by TSA caused demethylation of a CTCF binding site on the hTERT promoter, the result of which was repression of hTERT via recruitment of CTCF to the promoter. Copyright 2009 Elsevier Inc. All rights reserved.

ABCG2-mediated suppression of chlorin e6 accumulation and photodynamic therapy efficiency in glioblastoma cell lines can be reversed by KO143.

PubMed

Abdel Gaber, Sara A; Müller, Patricia; Zimmermann, Wolfgang; Hüttenberger, Dirk; Wittig, Rainer; Abdel Kader, Mahmoud H; Stepp, Herbert

2018-01-01

Photodynamic therapy (PDT) of malignant brain tumors is a promising adjunct to standard treatment, especially if tumor stem cells thought to be responsible for tumor progression and therapy resistance were also susceptible to this kind of treatment. However, some photosensitizers have been reported to be substrates of ABCG2, one of the membrane transporters mediating resistance to chemotherapy. Here we investigate, whether inhibition of ABCG2 can restore sensitivity to photosensitizer chlorin e6-mediated PDT. Accumulation of chlorin e6 in wild type U87 and doxycycline-inducible U251 glioblastoma cells with or without induction of ABCG2 expression or ABCG2 inhibition by KO143 was analyzed using flow cytometry. In U251 cells, ABCG2 was inducible by doxycycline after stable transfection with a tet-on expression plasmid. Tumor sphere cultivation under low attachment conditions was used to enrich for cells with stem cell-like properties. PDT was done on monolayer cell cultures by irradiation with laser light at 665nm. Elevated levels of ABCG2 in U87 cells grown as tumor spheres or in U251 cells after ABCG2 induction led to a 6-fold lower accumulation of chlorin e6 and the light dose needed to reduce cell viability by 50% (LD50) was 2.5 to 4-fold higher. Both accumulation and PDT response can be restored by KO143, an efficient non-toxic inhibitor of ABCG2. Glioblastoma stem cells might escape phototoxic destruction by ABCG2-mediated reduction of photosensitizer accumulation. Inhibition of ABCG2 during photosensitizer accumulation and irradiation promises to restore full susceptibility of this crucial tumor cell population to photodynamic treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Breast cancer resistance protein (BCRP)-mediated glyburide transport: effect of the C421A/Q141K BCRP single-nucleotide polymorphism.

PubMed

Pollex, Erika K; Anger, Gregory; Hutson, Janine; Koren, Gideon; Piquette-Miller, Micheline

2010-05-01

The antidiabetic agent glyburide (glibenclamide) is frequently used for the treatment of type II diabetes and is increasingly being used for the treatment of gestational diabetes. Evidence suggests that breast cancer resistance protein/ATP-binding cassette, subfamily G, member 2 (ABCG2) expressed in the placenta protects the fetus against the accumulation of glyburide. A number of studies have investigated the significance of several single-nucleotide polymorphisms (SNPs) in the ABCG2 gene. Associations between the Q141K (C421A) SNP and ABCG2 protein expression, membrane surface translocation, efflux activity, or ATPase activity have been shown. Therefore, alterations in glyburide transport across the placenta, resulting in increased fetal glyburide exposure, may be seen in individuals carrying the C421A allele. The purpose of this study is to investigate whether the Q141K SNP causes alterations in ABCG2-mediated glyburide transport. Glyburide accumulation assays were carried out with stably transfected human embryonic kidney (HEK)-293 cells expressing wild-type ABCG2 (Arg482) and polymorphic ABCG2 (Q141K). Glyburide kinetic parameters were determined for comparison of wild-type and SNP ABCG2 activity by simultaneously fitting data for ABCG2-expressing cells (saturable transport) and empty vector-expressing cells (nonsaturable transport) by nonlinear regression analysis. The apparent K(t) and V(max) values for the transfected HEK-293 cells expressing the polymorphic variant (Q141K) of ABCG2 were significantly higher than those values determined for the wild-type ABCG2-expressing cells (p < 0.05). Our results indicate that the Q141K variant of ABCG2 may have the potential to alter the placental pharmacokinetics of glyburide used in pregnancy.

Regulatory link between DNA methylation and active demethylation in Arabidopsis

PubMed Central

Lei, Mingguang; Zhang, Huiming; Julian, Russell; Tang, Kai; Xie, Shaojun; Zhu, Jian-Kang

2015-01-01

De novo DNA methylation through the RNA-directed DNA methylation (RdDM) pathway and active DNA demethylation play important roles in controlling genome-wide DNA methylation patterns in plants. Little is known about how cells manage the balance between DNA methylation and active demethylation activities. Here, we report the identification of a unique RdDM target sequence, where DNA methylation is required for maintaining proper active DNA demethylation of the Arabidopsis genome. In a genetic screen for cellular antisilencing factors, we isolated several REPRESSOR OF SILENCING 1 (ros1) mutant alleles, as well as many RdDM mutants, which showed drastically reduced ROS1 gene expression and, consequently, transcriptional silencing of two reporter genes. A helitron transposon element (TE) in the ROS1 gene promoter negatively controls ROS1 expression, whereas DNA methylation of an RdDM target sequence between ROS1 5′ UTR and the promoter TE region antagonizes this helitron TE in regulating ROS1 expression. This RdDM target sequence is also targeted by ROS1, and defective DNA demethylation in loss-of-function ros1 mutant alleles causes DNA hypermethylation of this sequence and concomitantly causes increased ROS1 expression. Our results suggest that this sequence in the ROS1 promoter region serves as a DNA methylation monitoring sequence (MEMS) that senses DNA methylation and active DNA demethylation activities. Therefore, the ROS1 promoter functions like a thermostat (i.e., methylstat) to sense DNA methylation levels and regulates DNA methylation by controlling ROS1 expression. PMID:25733903

α7 nAChR mediated Fas demethylation contributes to prenatal nicotine exposure-induced programmed thymocyte apoptosis in mice.

PubMed

Liu, Han-Xiao; Liu, Sha; Qu, Wen; Yan, Hui-Yi; Wen, Xiao; Chen, Ting; Hou, Li-Fang; Ping, Jie

2017-11-07

This study aimed to investigate the effects of prenatal nicotine exposure (PNE) on thymocyte apoptosis and postnatal immune impairments in vivo and further explore the epigenetic mechanisms of the pro-apoptotic effect of nicotine in vitro . The results showed that PNE caused immune impairments in offspring on postnatal day 49, manifested as increased IL-4 production and an increased IgG1/IgG2a ratio in serum. Enhanced apoptosis of total and CD4+SP thymocytes was observed both in fetus and in offspring. Further, by exposing thymocytes to 0-100 μM of nicotine in vitro for 48 h, we found that nicotine increased α7 nicotinic acetylcholine receptor (nAChR) expression, activated the Fas apoptotic pathway, and promoted thymocyte apoptosis in concentration-dependent manners. In addition, nicotine could induce Tet methylcytosine dioxygenase (TET) 2 expression and Fas promoter demethylation, which can be abolished by TET2 siRNA transfection. Moreover, the α7 nAChR specific antagonist α-bungarotoxin can abrogate nicotine-induced TET2 increase, and the following Fas demethylation and Fas-mediated apoptosis. In conclusion, our findings showed, for the first time, that α7 nAChR activation could induce TET2-mediated Fas demethylation in thymocytes and results in the upregulation of Fas apoptotic pathway, which provide evidence for elucidating the PNE-induced programmed thymocyte apoptosis.

Methylation of an intragenic alternative promoter regulates transcription of GARP.

PubMed

Haupt, Sonja; Söntgerath, Viktoria Sophie Apollonia; Leipe, Jan; Schulze-Koops, Hendrik; Skapenko, Alla

2016-02-01

Alternative promoter usage has been proposed as a mechanism regulating transcriptional and translational diversity in highly elaborated systems like the immune system in humans. Here, we report that transcription of human glycoprotein A repetitions predominant (GARP) in regulatory CD4 T cells (Tregs) is tightly regulated by two alternative promoters. An intragenic promoter contains several CpGs and acts as a weak promoter that is demethylated and initiates transcription Treg-specifically. The strong up-stream promoter containing a CpG-island is, in contrast, fully demethylated throughout tissues. Transcriptional activity of the strong promoter was surprisingly down-regulated upon demethylation of the weak promoter. This demethylation-induced transcriptional attenuation regulated the magnitude of GARP expression and correlated with disease activity in rheumatoid arthritis. Treg-specific GARP transcription was initiated by synergistic interaction of forkhead box protein 3 (Foxp3) with nuclear factor of activated T cells (NFAT) and was underpinned by permissive chromatin remodeling caused by release of the H3K4 demethylase, PLU-1. Our findings describe a novel function of alternative promoters in regulating the extent of transcription. Moreover, since GARP functions as a transporter of transforming growth factor β (TGFβ), a cytokine with broad pleiotropic traits, GARP transcriptional attenuation by alternative promoters might provide a mechanism regulating peripheral TGFβ to avoid unwanted harmful effects. Copyright © 2015 Elsevier B.V. All rights reserved.

Control of DEMETER DNA demethylase gene transcription in male and female gamete companion cells in Arabidopsis thaliana.

PubMed

Park, Jin-Sup; Frost, Jennifer M; Park, Kyunghyuk; Ohr, Hyonhwa; Park, Guen Tae; Kim, Seohyun; Eom, Hyunjoo; Lee, Ilha; Brooks, Janie S; Fischer, Robert L; Choi, Yeonhee

2017-02-21

The DEMETER (DME) DNA glycosylase initiates active DNA demethylation via the base-excision repair pathway and is vital for reproduction in Arabidopsis thaliana DME-mediated DNA demethylation is preferentially targeted to small, AT-rich, and nucleosome-depleted euchromatic transposable elements, influencing expression of adjacent genes and leading to imprinting in the endosperm. In the female gametophyte, DME expression and subsequent genome-wide DNA demethylation are confined to the companion cell of the egg, the central cell. Here, we show that, in the male gametophyte, DME expression is limited to the companion cell of sperm, the vegetative cell, and to a narrow window of time: immediately after separation of the companion cell lineage from the germline. We define transcriptional regulatory elements of DME using reporter genes, showing that a small region, which surprisingly lies within the DME gene, controls its expression in male and female companion cells. DME expression from this minimal promoter is sufficient to rescue seed abortion and the aberrant DNA methylome associated with the null dme-2 mutation. Within this minimal promoter, we found short, conserved enhancer sequences necessary for the transcriptional activities of DME and combined predicted binding motifs with published transcription factor binding coordinates to produce a list of candidate upstream pathway members in the genetic circuitry controlling DNA demethylation in gamete companion cells. These data show how DNA demethylation is regulated to facilitate endosperm gene imprinting and potential transgenerational epigenetic regulation, without subjecting the germline to potentially deleterious transposable element demethylation.

Antibody validation and scoring guidelines for ABCG2 immunohistochemical staining in formalin-fixed paraffin-embedded colon cancer tissue

PubMed Central

Cederbye, Camilla Natasha; Palshof, Jesper Andreas; Hansen, Tine Plato; Duun-Henriksen, Anne Katrine; Linnemann, Dorte; Stenvang, Jan; Nielsen, Dorte Lisbet; Brünner, Nils; Viuff, Birgitte Martine

2016-01-01

Overexpression of the ATP-dependent drug efflux pump ABCG2 is a major molecular mechanism of multidrug resistance in cancer and might be a predictive biomarker for drug response. Contradictory results have been reported for immunohistochemical studies of ABCG2 protein expression in colorectal cancer (CRC), probably because of the use of different antibodies and scoring approaches. In this study, we systematically studied six commercially available anti-ABCG2 antibodies, using cell lines with up-regulation of ABCG2, and selected one antibody for validation in CRC tissue. Furthermore, we established scoring guidelines for ABCG2 expression based on the clinically used guidelines for HER2 immunohistochemistry assessment in gastric cancer. The guidelines provide a semi-quantitative measure of the basolateral membrane staining of ABCG2 and disregard the apical membrane staining and the cytoplasmic signal. Intra-tumor heterogeneity in ABCG2 immunoreactivity was observed; however, statistical analyses of tissue microarrays (TMAs) and the corresponding whole sections from primary tumors of 57 metastatic CRC patients revealed a strong positive correlation between maximum TMA scores and whole sections, especially when more than one core was used. In conclusion, here, we provide validated results to guide future studies on the associations between ABCG2 immunoreactivity in tumor cells and the benefits of chemotherapeutic treatment in patients with CRC. PMID:27257141

Suppression of ABCG2 mediated MDR in vitro and in vivo by a novel inhibitor of ABCG2 drug transport.

PubMed

Patel, Atish; Li, Tian-Wen; Anreddy, Nagaraju; Wang, De-Shen; Sodani, Kamlesh; Gadhia, Sanket; Kathawala, Rishil; Yang, Dong-Hua; Cheng, Changmei; Chen, Zhe-Sheng

2017-07-01

Cancer is a disease whose treatment is often limited due to the development of a phenomenon known as multidrug resistance (MDR). There is an immense demand for development of novel agents that can overcome the MDR in cancer. A group of transmembrane proteins called ATP-binding cassette transporters, present ubiquitously in the human body possesses a modular architecture, contributing immensely towards the development of MDR. An analysis of structural congeners among a group of compounds led to the discovery of CCTA-1523 that could selectively reverse ABCG2-mediated MDR in cancer cells in vitro and in vivo. CCTA-1523 (5μM) sensitized the ABCG2 overexpressing cancer cells and ABCG2 transfected cells to the substrate chemotherapeutic drugs. The reversal ability of CCTA-1523 was primarily due to the inhibition of the efflux function of ABCG2; also there was no change in the protein expression or the localization of the ABCG2 in the presence of CCTA-1523. The reversal effect of CCTA-1523 was reversible. Importantly, co-administration of CCTA-1523 restored the in vivo antitumor activity of doxorubicin in ABCG2 overexpressing tumor xenografts. Taken together, our findings indicate that CCTA-1523 is a potent, selective and reversible modulator of ABCG2 that may offer therapeutic promise for multidrug- resistant malignancies. Copyright © 2017 Elsevier Ltd. All rights reserved.

DNA methylation and soy phytoestrogens: quantitative study in DU-145 and PC-3 human prostate cancer cell lines.

PubMed

Adjakly, Mawussi; Bosviel, Rémy; Rabiau, Nadège; Boiteux, Jean-Paul; Bignon, Yves-Jean; Guy, Laurent; Bernard-Gallon, Dominique

2011-12-01

DNA hypermethylation is an epigenetic mechanism which induces silencing of tumor-suppressor genes in prostate cancer. Many studies have reported that specific components of food plants like soy phytoestrogens may have protective effects against prostate carcinogenesis or progression. Genistein and daidzein, the major phytoestrogens, have been reported to have the ability to reverse DNA hypermethylation in cancer cell lines. The aim of this study was to investigate the potential demethylating effects of these two soy compounds on BRCA1, GSTP1, EPHB2 and BRCA2 promoter genes. Prostate cell lines DU-145 and PC-3 were treated with genistein 40 µM, daidzein 110 µM, budesonide (methylating agent) 2 µM and 5-azacytidine (demethylating agent) 2 µM. In these two human prostate cancer cell lines we performed methylation quantification by using Methyl Profiler DNA methylation analysis. This technique is based on a methylation-specific digestion followed by quantitative PCR. We analyzed the corresponding protein expression by western blotting. Soy phytoestrogens induced a demethylation of all promoter regions studied except for BRCA2, which is not methylated in control cell lines. An increase in their protein expression was also demonstrated by western blot analysis and corroborated the potential demethylating effect of soy phytoestrogens. This study showed that the soy phytoestrogens, genistein and daidzein, induce a decrease of methylation of BRCA1, GSTP1 and EPHB2 promoters. Therefore, soy phytoestrogens may have a protective effect on prostate cancer. However, more studies are needed in order to understand the mechanism by which genistein and daidzein have an inhibiting action on DNA methylation.

The naphthoquinones, vitamin K3 and its structural analogue plumbagin, are substrates of the multidrug resistance linked ATP binding cassette drug transporter ABCG2.

PubMed

Shukla, Suneet; Wu, Chung-Pu; Nandigama, Krishnamachary; Ambudkar, Suresh V

2007-12-01

Vitamin K3 (menadione; 2-methyl-1,4-naphthoquinone) is a structural precursor of vitamins K1 and K2, which are essential for blood clotting. The naturally occurring structural analogue of this vitamin, plumbagin (5-hydroxy-menadione), is known to modulate cellular proliferation, apoptosis, carcinogenesis, and radioresistance. We here report that both vitamin K3 and plumbagin are substrates of the multidrug resistance-linked ATP binding cassette drug transporter, ABCG2. Vitamin K3 and plumbagin specifically inhibited the ABCG2-mediated efflux of mitoxantrone but did not have any effect on the ABCB1-mediated efflux of rhodamine 123. This inhibition of ABCG2 function was due to their interaction at the substrate-binding site(s). Vitamin K3 and plumbagin inhibited the binding of [(125)I]iodoarylazidoprazosin, a substrate of ABCG2, to this transporter in a concentration-dependent manner with IC(50) values of 7.3 and 22.6 micromol/L, respectively, but had no effect on the binding of the photoaffinity analogue to ABCB1. Both compounds stimulated ABCG2-mediated ATP hydrolysis and also inhibited the mitoxantrone-stimulated ATPase activity of the ABCG2 transporter, but did not have any significant effect on the ATPase activity of ABCB1. In a cytotoxicity assay, ABCG2-expressing HEK cells were 2.8- and 2.3-fold resistant to plumbagin and vitamin K3, respectively, compared with the control cells, suggesting that they are substrates of this transporter. Collectively, these data show for the first time that vitamin K3 is a substrate of the ABCG2 transporter. Thus, ABCG2 may have a role in the regulation of vitamin K3 levels in the body. In addition, vitamin K3 and its structural derivative, plumbagin, could potentially be used to modulate ABCG2 function.

Cloning and functional expression of novel cholesterol transporters ABCG1 and ABCG4 in gonadotropin-releasing hormone neurons of the tilapia.

PubMed

Phang, Y L; Soga, T; Kitahashi, T; Parhar, I S

2012-02-17

In addition to reproduction, gonadotropin-releasing hormone (GnRH) has been postulated to control cholesterol metabolism via cholesterol transport, which is carried out partly by the members of ATP-binding cassette (ABC) transporters G1 (ABCG1) and G4 (ABCG4). However, there is yet to be evidence demonstrating the relationship between these transporters with reference to GnRH neurons. In the present study, we cloned two ABCG1 messenger RNA (mRNA) variants and one ABCG4 mRNA and examined their expression in the brain including GnRH neurons (GnRH1, GnRH2, and GnRH3) in the cichlid tilapia (Oreochromis niloticus). Comparison of nucleotide sequences of the tilapia ABCG1 and ABCG4 with that of other fish species showed that both of these genes are evolutionarily conserved among fishes. ABCG1 and ABCG4 were shown to have high mRNA expressions in the CNS, pituitary, and gonads. In the brain, real-time polymerase chain reaction (PCR) showed that ABCG4 mRNA was higher than ABCG1a in all brain regions including the olfactory bulb (ABCG1=13.34, ABCG4=6796.35; P<0.001), dorsal telencephalon (ABCG1=8.64, ABCG4=10149.13; P=0.001), optic tectum (ABCG1=22.12, ABCG4=13931.04; P<0.01), cerebellum (ABCG1=8.68, ABCG4=12382.90; P<0.01), and preoptic area-midbrain-hypothalamus (ABCG1=21.36, ABCG4=13255.41; P=0.001). Similarly, although ABCG1 mRNA level is much higher in the pituitary compared with the brain, it was still significantly lower compared with ABCG4 (ABCG1=337.73, ABCG4=1157.87; P=0.01). The differential pattern of expression of ABCG1 and ABCG4 in the brain versus pituitary suggests that the two transporters are regulated by different mechanisms. Furthermore, ABCG1 and ABCG4 mRNA expressions were found in all three types of laser-captured GnRH neurons with highly similar percentage of expressions, suggesting that cholesterol efflux from GnRH neurons may require heterodimerization of both ABCG1 and ABCG4. Copyright © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.

Masitinib antagonizes ATP-binding cassette subfamily G member 2-mediated multidrug resistance

PubMed Central

KATHAWALA, RISHIL J.; CHEN, JUN-JIANG; ZHANG, YUN-KAI; WANG, YI-JUN; PATEL, ATISH; WANG, DE-SHEN; TALELE, TANAJI T.; ASHBY, CHARLES R.; CHEN, ZHE-SHENG

2014-01-01

In this in vitro study, we determined whether masitinib could reverse multidrug resistance (MDR) in cells overexpressing the ATP binding cassette subfamily G member 2 (ABCG2) transporter. Masitinib (1.25 and 2.5 μM) significantly decreases the resistance to mitoxantrone (MX), SN38 and doxorubicin in HEK293 and H460 cells overexpressing the ABCG2 transporter. In addition, masitinib (2.5 μM) significantly increased the intracellular accumulation of [3H]-MX, a substrate for ABCG2, by inhibiting the function of ABCG2 and significantly decreased the efflux of [3H]-MX. However, masitinib (2.5 μM) did not significantly alter the expression of the ABCG2 protein. In addition, a docking model suggested that masitinib binds within the transmembrane region of a homology-modeled human ABCG2 transporter. Overall, our in vitro findings suggest that masitinib reverses MDR to various anti-neoplastic drugs in HEK293 and H460 cells overexpressing ABCG2 by inhibiting their transport activity as opposed to altering their levels of expression. PMID:24626598

Vitamin C induces specific demethylation of H3K9me2 in mouse embryonic stem cells via Kdm3a/b.

PubMed

Ebata, Kevin T; Mesh, Kathryn; Liu, Shichong; Bilenky, Misha; Fekete, Alexander; Acker, Michael G; Hirst, Martin; Garcia, Benjamin A; Ramalho-Santos, Miguel

2017-01-01

Histone methylation patterns regulate gene expression and are highly dynamic during development. The erasure of histone methylation is carried out by histone demethylase enzymes. We had previously shown that vitamin C enhances the activity of Tet enzymes in embryonic stem (ES) cells, leading to DNA demethylation and activation of germline genes. We report here that vitamin C induces a remarkably specific demethylation of histone H3 lysine 9 dimethylation (H3K9me2) in naïve ES cells. Vitamin C treatment reduces global levels of H3K9me2, but not other histone methylation marks analyzed, as measured by western blot, immunofluorescence and mass spectrometry. Vitamin C leads to widespread loss of H3K9me2 at large chromosomal domains as well as gene promoters and repeat elements. Vitamin C-induced loss of H3K9me2 occurs rapidly within 24 h and is reversible. Importantly, we found that the histone demethylases Kdm3a and Kdm3b are required for vitamin C-induced demethylation of H3K9me2. Moreover, we show that vitamin C-induced Kdm3a/b-mediated H3K9me2 demethylation and Tet-mediated DNA demethylation are independent processes at specific loci. Lastly, we document Kdm3a/b are partially required for the upregulation of germline genes by vitamin C. These results reveal a specific role for vitamin C in histone demethylation in ES cells and document that DNA methylation and H3K9me2 cooperate to silence germline genes in pluripotent cells.

The Pim kinase inhibitor SGI-1776 decreases cell surface expression of P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) and drug transport by Pim-1-dependent and -independent mechanisms

PubMed Central

Natarajan, Karthika; Bhullar, Jasjeet; Shukla, Suneet; Burcu, Mehmet; Chen, Zhe-Sheng; Ambudkar, Suresh V.; Baer, Maria R.

2013-01-01

Overexpression of the ATP-binding cassette (ABC) drug efflux proteins P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) on malignant cells is associated with inferior chemotherapy outcomes. Both, ABCB1 and ABCG2, are substrates of the serine/threonine kinase Pim-1; Pim-1 knockdown decreases their cell surface expression, but SGI-1776, the first clinically tested Pim inhibitor, was shown to reverse drug resistance by directly inhibiting ABCB1-mediated transport. We sought to characterize Pim-1-dependent and -independent effects of SGI-1776 on drug resistance. SGI-1776 at the Pim-1-inhibitory and non-cytotoxic concentration of 1 μM decreased the IC50s of the ABCG2 and ABCB1 substrate drugs in cytotoxicity assays in resistant cells, with no effect on the IC50 of non-substrate drug, nor in parental cells. SGI-1776 also increased apoptosis of cells overexpressing ABCG2 or ABCB1 exposed to substrate chemotherapy drugs and decreased their colony formation in the presence of substrate, but not non-substrate, drugs, with no effect on parental cells. SGI-1776 decreased ABCB1 and ABCG2 surface expression on K562/ABCB1 and K562/ABCG2 cells, respectively, with Pim-1 overexpression, but not HL60/VCR and 8226/MR20 cells, with lower-level Pim-1 expression. Finally, SGI-1776 inhibited uptake of ABCG2 and ABCB1 substrates in a concentration-dependent manner irrespective of Pim-1 expression, inhibited ABCB1 and ABCG2 photoaffinity labeling with the transport substrate [125I]iodoarylazidoprazosin ([125I]IAAP) and stimulated ABCB1 and ABCG2 ATPase activity. Thus SGI-1776 decreases cell surface expression of ABCB1 and ABCG2 and inhibits drug transport by Pim-1-dependent and -independent mechanisms, respectively. Decrease in ABCB1 and ABCG2 cell surface expression mediated by Pim-1 inhibition represents a novel mechanism of chemosensitization. PMID:23261525

The Pim kinase inhibitor SGI-1776 decreases cell surface expression of P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) and drug transport by Pim-1-dependent and -independent mechanisms.

PubMed

Natarajan, Karthika; Bhullar, Jasjeet; Shukla, Suneet; Burcu, Mehmet; Chen, Zhe-Sheng; Ambudkar, Suresh V; Baer, Maria R

2013-02-15

Overexpression of the ATP-binding cassette (ABC) drug efflux proteins P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) on malignant cells is associated with inferior chemotherapy outcomes. Both, ABCB1 and ABCG2, are substrates of the serine/threonine kinase Pim-1; Pim-1 knockdown decreases their cell surface expression, but SGI-1776, the first clinically tested Pim inhibitor, was shown to reverse drug resistance by directly inhibiting ABCB1-mediated transport. We sought to characterize Pim-1-dependent and -independent effects of SGI-1776 on drug resistance. SGI-1776 at the Pim-1-inhibitory and non-cytotoxic concentration of 1 μM decreased the IC(50)s of the ABCG2 and ABCB1 substrate drugs in cytotoxicity assays in resistant cells, with no effect on the IC(50) of non-substrate drug, nor in parental cells. SGI-1776 also increased apoptosis of cells overexpressing ABCG2 or ABCB1 exposed to substrate chemotherapy drugs and decreased their colony formation in the presence of substrate, but not non-substrate, drugs, with no effect on parental cells. SGI-1776 decreased ABCB1 and ABCG2 surface expression on K562/ABCB1 and K562/ABCG2 cells, respectively, with Pim-1 overexpression, but not HL60/VCR and 8226/MR20 cells, with lower-level Pim-1 expression. Finally, SGI-1776 inhibited uptake of ABCG2 and ABCB1 substrates in a concentration-dependent manner irrespective of Pim-1 expression, inhibited ABCB1 and ABCG2 photoaffinity labeling with the transport substrate [(125)I]iodoarylazidoprazosin ([(125)I]IAAP) and stimulated ABCB1 and ABCG2 ATPase activity. Thus SGI-1776 decreases cell surface expression of ABCB1 and ABCG2 and inhibits drug transport by Pim-1-dependent and -independent mechanisms, respectively. Decrease in ABCB1 and ABCG2 cell surface expression mediated by Pim-1 inhibition represents a novel mechanism of chemosensitization. Copyright © 2012 Elsevier Inc. All rights reserved.

Influence of the ABCG2 gout risk 141 K allele on urate metabolism during a fructose challenge.

PubMed

Dalbeth, Nicola; House, Meaghan E; Gamble, Gregory D; Pool, Bregina; Horne, Anne; Purvis, Lauren; Stewart, Angela; Merriman, Marilyn; Cadzow, Murray; Phipps-Green, Amanda; Merriman, Tony R

2014-01-30

Both genetic variation in ATP-binding cassette sub-family G member 2 (ABCG2) and intake of fructose-containing beverages are major risk factors for hyperuricemia and gout. This study aimed to test the hypothesis that the ABCG2 gout risk allele 141 K promotes the hyperuricaemic response to fructose loading. Healthy volunteers (n = 74) provided serum and urine samples immediately before and 30, 60, 120 and 180 minutes after ingesting a 64 g fructose solution. Data were analyzed based on the presence or absence of the ABCG2 141 K gout risk allele. The 141 K risk allele was present in 23 participants (31%). Overall, serum urate (SU) concentrations during the fructose load were similar in those with and without the 141 K allele (PSNP = 0.15). However, the 141 K allele was associated with a smaller increase in SU following fructose intake (PSNP <0.0001). Those with the 141 K allele also had a smaller increase in serum glucose following the fructose load (PSNP = 0.002). Higher fractional excretion of uric acid (FEUA) at baseline and throughout the fructose load was observed in those with the 141 K risk allele (PSNP <0.0001). However, the change in FEUA in response to fructose was not different in those with and without the 141 K risk allele (PSNP = 0.39). The 141 K allele effects on serum urate and glucose were more pronounced in Polynesian participants and in those with a body mass index ≥25 kg/m². In contrast to the predicted responses for a hyperuricemia/gout risk allele, the 141 K allele is associated with smaller increases in SU and higher FEUA following a fructose load. The results suggest that ABCG2 interacts with extra-renal metabolic pathways in a complex manner to regulate SU and gout risk. The study was registered by the Australian Clinical Trials Registry (ACTRN12610001036000).

Control of DEMETER DNA demethylase gene transcription in male and female gamete companion cells in Arabidopsis thaliana

PubMed Central

Park, Jin-Sup; Frost, Jennifer M.; Park, Kyunghyuk; Ohr, Hyonhwa; Park, Guen Tae; Kim, Seohyun; Eom, Hyunjoo; Lee, Ilha; Brooks, Janie S.; Fischer, Robert L.; Choi, Yeonhee

2017-01-01

The DEMETER (DME) DNA glycosylase initiates active DNA demethylation via the base-excision repair pathway and is vital for reproduction in Arabidopsis thaliana. DME-mediated DNA demethylation is preferentially targeted to small, AT-rich, and nucleosome-depleted euchromatic transposable elements, influencing expression of adjacent genes and leading to imprinting in the endosperm. In the female gametophyte, DME expression and subsequent genome-wide DNA demethylation are confined to the companion cell of the egg, the central cell. Here, we show that, in the male gametophyte, DME expression is limited to the companion cell of sperm, the vegetative cell, and to a narrow window of time: immediately after separation of the companion cell lineage from the germline. We define transcriptional regulatory elements of DME using reporter genes, showing that a small region, which surprisingly lies within the DME gene, controls its expression in male and female companion cells. DME expression from this minimal promoter is sufficient to rescue seed abortion and the aberrant DNA methylome associated with the null dme-2 mutation. Within this minimal promoter, we found short, conserved enhancer sequences necessary for the transcriptional activities of DME and combined predicted binding motifs with published transcription factor binding coordinates to produce a list of candidate upstream pathway members in the genetic circuitry controlling DNA demethylation in gamete companion cells. These data show how DNA demethylation is regulated to facilitate endosperm gene imprinting and potential transgenerational epigenetic regulation, without subjecting the germline to potentially deleterious transposable element demethylation. PMID:28130550

Pathways by which reconstituted high-density lipoprotein mobilizes free cholesterol from whole body and from macrophages.

PubMed

Cuchel, Marina; Lund-Katz, Sissel; de la Llera-Moya, Margarita; Millar, John S; Chang, David; Fuki, Ilia; Rothblat, George H; Phillips, Michael C; Rader, Daniel J

2010-03-01

Reconstituted high-density lipoprotein (rHDL) is of interest as a potential novel therapy for atherosclerosis because of its ability to promote free cholesterol (FC) mobilization after intravenous administration. We performed studies to identify the underlying molecular mechanisms by which rHDL promote FC mobilization from whole body in vivo and macrophages in vitro. Wild-type (WT), SR-BI knockout (KO), ABCA1 KO, and ABCG1 KO mice received either rHDL or phosphate-buffered saline intravenously. Blood was drawn before and at several time points after injection for apolipoprotein A-I, phosphatidylcholine, and FC measurement. In WT mice, serum FC peaked at 20 minutes and rapidly returned toward baseline levels by 24 hours. Unexpectedly, ABCA1 KO and ABCG1 KO mice did not differ from WT mice regarding the kinetics of FC mobilization. In contrast, in SR-BI KO mice the increase in FC level at 20 minutes was only 10% of that in control mice (P<0.01). Bone marrow-derived macrophages from WT, SR-BI O, ABCA1 KO, and ABCG1 KO mice were incubated in vitro with rHDL and cholesterol efflux was determined. Efflux from SR-BI KO and ABCA1 KO macrophages was not different from WT macrophages. In contrast, efflux from ABCG1 KO macrophages was approximately 50% lower as compared with WT macrophages (P<0.001). The bulk mobilization of FC observed in circulation after rHDL administration is primarily mediated by SR-BI. However, cholesterol mobilization from macrophages to rHDL is primarily mediated by ABCG1.

The naphthoquinones, vitamin K3 and its structural analog plumbagin, are substrates of the multidrug resistance-linked ABC drug transporter ABCG2

PubMed Central

Shukla, Suneet; Wu, Chung-Pu; Nandigama, Krishnamachary; Ambudkar, Suresh V.

2008-01-01

Vitamin K3 (Menadione; 2-methyl-1,4-naphthoquinone) is a structural precursor of vitamins K1 and K2 which are essential for blood clotting. The naturally occurring structural analog of this vitamin, plumbagin (5-hydroxy-menadione), is known to modulate cellular proliferation, apoptosis, carcinogenesis, and radioresistance. We, here, report that both vitamin K3 and plumbagin are substrates of the multidrug resistance-linked ATP binding cassette (ABC) drug transporter, ABCG2. Vitamin K3 and plumbagin specifically inhibited the ABCG2-mediated efflux of mitoxantrone, but did not have any effect on the ABCB1-mediated efflux of rhodamine 123. This inhibition of ABCG2 function was due to their interaction at the substrate-binding site(s). They inhibited the binding of [125I]-Iodoarylazidoprazosin (IAAP), a substrate of ABCG2, to this transporter in a concentration-dependent manner with IC50 values of 7.3 and 22.6 μM, respectively, but had no effect on the binding of this photoaffinity analog to ABCB1. Both compounds stimulated ABCG2-mediated ATP hydrolysis and also inhibited the mitoxantrone-stimulated ATPase activity of this transporter, but did not have any significant effect on the ATPase activity of ABCB1. In a cytotoxicity assay, ABCG2-expressing HEK cells were 2.8- and 2.3-fold resistant to plumbagin and vitamin K3, respectively, compared to the control cells, suggesting that they are substrates of this transporter. Collectively, these data demonstrate for the first time that vitamin K3 is a substrate of the ABCG2 transporter. Thus, ABCG2 may have a role in the regulation of vitamin K3 levels in the body. In addition, vitamin K3 and its structural derivative, plumbagin, could potentially be used to modulate ABCG2 function. PMID:18065489

The xenoestrogens, bisphenol A and para-nonylphenol, decrease the expression of the ABCG2 transporter protein in human term placental explant cultures.

PubMed

Sieppi, E; Vähäkangas, K; Rautio, A; Ietta, F; Paulesu, L; Myllynen, P

2016-07-05

Many endogenous and xenobiotic compounds are substrates and regulators of human placental ABC transporters. ABCG2 is protecting fetus against foreign chemicals. Environmental xenoestrogens, like bisphenol A (BPA) and p-nonylphenol (p-NP), mimic natural estrogens and can affect hormonal systems. Effects of BPA, p-NP, DES (diethylstilbestrol) and estradiol (E2), on ABCG2 expression were studied using human first trimester and term placental explants. Role of estrogen receptors (ER) in the effects of chemicals was studied by ER antagonist. Term placenta expressed less ABCG2 protein. In term placentas BPA (p < 0.05), p-NP (p < 0.01) and E2 (p < 0.05) decreased the ABCG2 protein expression after 48 h exposure while after 24 h exposure, only E2 decreased the expression (p < 0.05). The chemicals did not affect ABCG2 in first trimester placentas. The ER antagonist affected differently the responses of chemicals. In conclusion, environmental xenoestrogens downregulate placental ABCG2 protein expression depending on gestational age. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Alectinib (CH5424802) antagonizes ABCB1- and ABCG2-mediated multidrug resistance in vitro, in vivo and ex vivo.

PubMed

Yang, Ke; Chen, Yifan; To, Kenneth Kin Wah; Wang, Fang; Li, Delan; Chen, Likun; Fu, Liwu

2017-03-17

Alectinib, an inhibitor of anaplastic lymphoma kinase (ALK), was approved by the Food and Drug Administration (FDA) for the treatment of patients with ALK-positive non-small cell lung cancer (NSCLC). Here we investigated the reversal effect of alectinib on multidrug resistance (MDR) induced by ATP-binding cassette (ABC) transporters, which is the primary cause of chemotherapy failure. We provide the first evidence that alectinib increases the sensitivity of ABCB1- and ABCG2-overexpressing cells to chemotherapeutic agents in vitro and in vivo. Mechanistically, alectinib increased the intracellular accumulation of ABCB1/ABCG2 substrates such as doxorubicin (DOX) and Rhodamine 123 (Rho 123) by inhibiting the efflux function of the transporters in ABCB1- or ABCG2-overexpressing cells but not in their parental sensitive cells. Furthermore, alectinib stimulated ATPase activity and competed with substrates of ABCB1 or ABCG2 and competed with [125I] iodoarylazidoprazosin (IAAP) photolabeling bound to ABCB1 or ABCG2 but neither altered the expression and localization of ABCB1 or ABCG2 nor the phosphorylation levels of AKT and ERK. Alectinib also enhanced the cytotoxicity of DOX and the intracellular accumulation of Rho 123 in ABCB1-overexpressing primary leukemia cells. These findings suggest that alectinib combined with traditional chemotherapy may be beneficial to patients with ABCB1- or ABCG2-mediated MDR.

Alectinib (CH5424802) antagonizes ABCB1- and ABCG2-mediated multidrug resistance in vitro, in vivo and ex vivo

PubMed Central

Yang, Ke; Chen, Yifan; To, Kenneth Kin Wah; Wang, Fang; Li, Delan; Chen, Likun; Fu, Liwu

2017-01-01

Alectinib, an inhibitor of anaplastic lymphoma kinase (ALK), was approved by the Food and Drug Administration (FDA) for the treatment of patients with ALK-positive non-small cell lung cancer (NSCLC). Here we investigated the reversal effect of alectinib on multidrug resistance (MDR) induced by ATP-binding cassette (ABC) transporters, which is the primary cause of chemotherapy failure. We provide the first evidence that alectinib increases the sensitivity of ABCB1- and ABCG2-overexpressing cells to chemotherapeutic agents in vitro and in vivo. Mechanistically, alectinib increased the intracellular accumulation of ABCB1/ABCG2 substrates such as doxorubicin (DOX) and Rhodamine 123 (Rho 123) by inhibiting the efflux function of the transporters in ABCB1- or ABCG2-overexpressing cells but not in their parental sensitive cells. Furthermore, alectinib stimulated ATPase activity and competed with substrates of ABCB1 or ABCG2 and competed with [125I] iodoarylazidoprazosin (IAAP) photolabeling bound to ABCB1 or ABCG2 but neither altered the expression and localization of ABCB1 or ABCG2 nor the phosphorylation levels of AKT and ERK. Alectinib also enhanced the cytotoxicity of DOX and the intracellular accumulation of Rho 123 in ABCB1-overexpressing primary leukemia cells. These findings suggest that alectinib combined with traditional chemotherapy may be beneficial to patients with ABCB1- or ABCG2-mediated MDR. PMID:28303028

The Role of Arabidopsis ABCG9 and ABCG31 ATP Binding Cassette Transporters in Pollen Fitness and the Deposition of Steryl Glycosides on the Pollen Coat[W

PubMed Central

Choi, Hyunju; Ohyama, Kiyoshi; Kim, Yu-Young; Jin, Jun-Young; Lee, Saet Buyl; Yamaoka, Yasuyo; Muranaka, Toshiya; Suh, Mi Chung; Fujioka, Shozo; Lee, Youngsook

2014-01-01

The pollen coat protects pollen grains from harmful environmental stresses such as drought and cold. Many compounds in the pollen coat are synthesized in the tapetum. However, the pathway by which they are transferred to the pollen surface remains obscure. We found that two Arabidopsis thaliana ATP binding cassette transporters, ABCG9 and ABCG31, were highly expressed in the tapetum and are involved in pollen coat deposition. Upon exposure to dry air, many abcg9 abcg31 pollen grains shriveled up and collapsed, and this phenotype was restored by complementation with ABCG9pro:GFP:ABCG9. GFP-tagged ABCG9 or ABCG31 localized to the plasma membrane. Electron microscopy revealed that the mutant pollen coat resembled the immature coat of the wild type, which contained many electron-lucent structures. Steryl glycosides were reduced to about half of wild-type levels in the abcg9 abcg31 pollen, but no differences in free sterols or steryl esters were observed. A mutant deficient in steryl glycoside biosynthesis, ugt80A2 ugt80B1, exhibited a similar phenotype. Together, these results indicate that steryl glycosides are critical for pollen fitness, by supporting pollen coat maturation, and that ABCG9 and ABCG31 contribute to the accumulation of this sterol on the surface of pollen. PMID:24474628

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xiaolin; Li, Qian; Pang, Liewen

Highlights: •Arctigenin enhanced cholesterol efflux in oxLDL-loaded THP-1 macrophages. •The expression of ABCA1, ABCG1 and apoE was upregulated in arctigenin-treated cells. •Arctigenin promoted the expression of PPAR-γ and LXR-α. •Inhibition of PPAR-γ or LXR-α reversed arctigenin-mediated biological effects. •Arctigenin promotes cholesterol efflux via activation of PPAR-γ/LXR-α/ABCA1 pathway. -- Abstract: Cholesterol efflux from macrophages is a critical mechanism to prevent the development of atherosclerosis. Here, we sought to investigate the effects of arctigenin, a bioactive component of Arctium lappa, on the cholesterol efflux in oxidized low-density lipoprotein (oxLDL)-loaded THP-1 macrophages. Our data showed that arctigenin significantly accelerated apolipoprotein A-I- and high-densitymore » lipoprotein-induced cholesterol efflux in both dose- and time-dependent manners. Moreover, arctigenin treatment enhanced the expression of ATP binding cassette transporter A1 (ABCA1), ABCG1, and apoE, all of which are key molecules in the initial step of cholesterol efflux, at both mRNA and protein levels. Arctigenin also caused a concentration-dependent elevation in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and liver X receptor-alpha (LXR-α). The arctigenin-mediated induction of ABCA1, ABCG1, and apoE was abolished by specific inhibition of PPAR-γ or LXR-α using small interfering RNA technology. Our results collectively indicate that arctigenin promotes cholesterol efflux in oxLDL-loaded THP-1 macrophages through upregulation of ABCA1, ABCG1 and apoE, which is dependent on the enhanced expression of PPAR-γ and LXR-α.« less

Synthetic Analogs of Curcumin Modulate the Function of Multidrug Resistance-Linked ATP-Binding Cassette Transporter ABCG2.

PubMed

Murakami, Megumi; Ohnuma, Shinobu; Fukuda, Michihiro; Chufan, Eduardo E; Kudoh, Katsuyoshi; Kanehara, Keigo; Sugisawa, Norihiko; Ishida, Masaharu; Naitoh, Takeshi; Shibata, Hiroyuki; Iwabuchi, Yoshiharu; Ambudkar, Suresh V; Unno, Michiaki

2017-11-01

Multidrug resistance (MDR) caused by the overexpression of ATP-binding cassette (ABC) transporters in cancer cells is a major obstacle in cancer chemotherapy. Previous studies have shown that curcumin, a natural product and a dietary constituent of turmeric, inhibits the function of MDR-related ABC transporters, including ABCB1, ABCC1, and especially ABCG2. However, the limited bioavailability of curcumin prevents its use for modulation of the function of these transporters in the clinical setting. In this study, we investigated the effects of 24 synthetic curcumin analogs with increased bioavailability on the transport function of ABCG2. The screening of the 24 synthetic analogs by means of flow cytometry revealed that four of the curcumin analogs (GO-Y030, GO-Y078, GO-Y168, and GO-Y172) significantly inhibited the efflux of the ABCG2 substrates, mitoxantrone and pheophorbide A, from ABCG2-overexpressing K562/breast cancer resistance protein (BCRP) cells. Biochemical analyses showed that GO-Y030, GO-Y078, and GO-Y172 stimulated the ATPase activity of ABCG2 at nanomolar concentrations and inhibited the photolabeling of ABCG2 with iodoarylazidoprazosin, suggesting that these analogs interact with the substrate-binding sites of ABCG2. In addition, when used in cytotoxicity assays, GO-Y030 and GO-Y078 were found to improve the sensitivity of the anticancer drug, SN-38, in K562/BCRP cells. Taken together, these results suggest that nontoxic synthetic curcumin analogs with increased bioavailability, especially GO-Y030 and GO-Y078, inhibit the function of ABCG2 by directly interacting at the substrate-binding site. These synthetic curcumin analogs could therefore be developed as potent modulators to overcome ABCG2-mediated MDR in cancer cells. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

An HDAC2-TET1 switch at distinct chromatin regions significantly promotes the maturation of pre-iPS to iPS cells

PubMed Central

Wei, Tingyi; Chen, Wen; Wang, Xiukun; Zhang, Man; Chen, Jiayu; Zhu, Songcheng; Chen, Long; Yang, Dandan; Wang, Guiying; Jia, Wenwen; Yu, Yangyang; Duan, Tao; Wu, Minjuan; Liu, Houqi; Gao, Shaorong; Kang, Jiuhong

2015-01-01

The maturation of induced pluripotent stem cells (iPS) is one of the limiting steps of somatic cell reprogramming, but the underlying mechanism is largely unknown. Here, we reported that knockdown of histone deacetylase 2 (HDAC2) specifically promoted the maturation of iPS cells. Further studies showed that HDAC2 knockdown significantly increased histone acetylation, facilitated TET1 binding and DNA demethylation at the promoters of iPS cell maturation-related genes during the transition of pre-iPS cells to a fully reprogrammed state. We also found that HDAC2 competed with TET1 in the binding of the RbAp46 protein at the promoters of maturation genes and knockdown of TET1 markedly prevented the activation of these genes. Collectively, our data not only demonstrated a novel intrinsic mechanism that the HDAC2-TET1 switch critically regulates iPS cell maturation, but also revealed an underlying mechanism of the interplay between histone acetylation and DNA demethylation in gene regulation. PMID:25934799

Eicosapentaenoic acid induces DNA demethylation in carcinoma cells through a TET1-dependent mechanism.

PubMed

Ceccarelli, Veronica; Valentini, Virginia; Ronchetti, Simona; Cannarile, Lorenza; Billi, Monia; Riccardi, Carlo; Ottini, Laura; Talesa, Vincenzo Nicola; Grignani, Francesco; Vecchini, Alba

2018-05-14

In cancer cells, global genomic hypomethylation is found together with localized hypermethylation of CpG islands within the promoters and regulatory regions of silenced tumor suppressor genes. Demethylating agents may reverse hypermethylation, thus promoting gene re-expression. Unfortunately, demethylating strategies are not efficient in solid tumor cells. DNA demethylation is mediated by ten-eleven translocation enzymes (TETs). They sequentially convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), which is associated with active transcription; 5-formylcytosine; and finally, 5-carboxylcytosine. Although α-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid, the major n-3 polyunsaturated fatty acids, have anti-cancer effects, their action, as DNA-demethylating agents, has never been investigated in solid tumor cells. Here, we report that EPA demethylates DNA in hepatocarcinoma cells. EPA rapidly increases 5hmC on DNA, inducing p21 Waf1/Cip1 gene expression, which slows cancer cell-cycle progression. We show that the underlying molecular mechanism involves TET1. EPA simultaneously binds peroxisome proliferator-activated receptor γ (PPARγ) and retinoid X receptor α (RXRα), thus promoting their heterodimer and inducing a PPARγ-TET1 interaction. They generate a TET1-PPARγ-RXRα protein complex, which binds to a hypermethylated CpG island on the p21 gene, where TET1 converts 5mC to 5hmC. In an apparent shuttling motion, PPARγ and RXRα leave the DNA, whereas TET1 associates stably. Overall, EPA directly regulates DNA methylation levels, permitting TET1 to exert its anti-tumoral function.-Ceccarelli, V., Valentini, V., Ronchetti, S., Cannarile, L., Billi, M., Riccardi, C., Ottini, L., Talesa, V. N., Grignani, F., Vecchini, A., Eicosapentaenoic acid induces DNA demethylation in carcinoma cells through a TET1-dependent mechanism.

ABCG2-overexpressing S1-M1-80 cell xenografts in nude mice keep original biochemistry and cell biological properties.

PubMed

Wang, Fang; Liang, Yong-Ju; Wu, Xing-Ping; Su, Xiao-Dong; Fu, Li-Wu

2012-03-01

S1-M1-80 cells, derived from human colon carcinoma S1 cells, are mitoxantrone-selected ABCG2-overexpressing cells and are widely used in in vitro studies of multidrug resistance(MDR). In this study, S1-M1-80 cell xenografts were established to investigate whether the MDR phenotype and cell biological properties were maintained in vivo. Our results showed that the proliferation, cell cycle, and ABCG2 expression level in S1-M1-80 cells were similar to those in cells isolated from S1-M1-80 cell xenografts (named xS1-M1-80 cells). Consistently, xS1-M1-80 cells exhibited high levels of resistance to ABCG2 substrates such as mitoxantrone and topotecan, but remained sensitive to the non-ABCG2 substrate cisplatin. Furthermore, the specific ABCG2 inhibitor Ko143 potently sensitized xS1-M1-80 cells to mitoxantrone and topotecan. These results suggest that S1-M1-80 cell xenografts in nude mice retain their original cytological characteristics at 9 weeks. Thus, this model could serve as a good system for further investigation of ABCG2-mediated MDR.

Plasma membrane dynamics and tetrameric organisation of ABCG2 transporters in mammalian cells revealed by single particle imaging techniques.

PubMed

Wong, Kelvin; Briddon, Stephen J; Holliday, Nicholas D; Kerr, Ian D

2016-01-01

ABCG2 is one of three human ATP binding cassette (ABC) transporters involved in the export from cells of a chemically and structurally diverse range of compounds. This multidrug efflux capability, together with a broad tissue distribution in the body, means that ABCG2 exerts a range of effects on normal physiology such as kidney urate transport, as well as contributing towards the pharmacokinetic profiles of many exogenous drugs. The primary sequence of ABCG2 contains only half the number of domains required for a functioning ABC transporter and so it must oligomerise in order to function, yet its oligomeric state in intact cell membranes remains uncharacterized. We have analysed ABCG2 in living cell membranes using a combination of fluorescence correlation spectroscopy, photon counting histogram analysis, and stepwise photobleaching to demonstrate a predominantly tetrameric structure for ABCG2 in the presence or absence of transport substrates. These results provide the essential basis for exploring pharmacological manipulation of oligomeric state as a strategy to modulate ABCG2 activity in future selective therapeutics. Copyright © 2015 Elsevier B.V. All rights reserved.

Arsenic induces functional re-expression of estrogen receptor α by demethylation of DNA in estrogen receptor-negative human breast cancer.

PubMed

Du, Juan; Zhou, Nannan; Liu, Hongxia; Jiang, Fei; Wang, Yubang; Hu, Chunyan; Qi, Hong; Zhong, Caiyun; Wang, Xinru; Li, Zhong

2012-01-01

Estrogen receptor α (ERα) is a marker predictive for response of breast cancers to endocrine therapy. About 30% of breast cancers, however, are hormone- independent because of lack of ERα expression. New strategies are needed for re-expression of ERα and sensitization of ER-negative breast cancer cells to selective ER modulators. The present report shows that arsenic trioxide induces reactivated ERα, providing a target for therapy with ER antagonists. Exposure of ER-negative breast cancer cells to arsenic trioxide leads to re-expression of ERα mRNA and functional ERα protein in in vitro and in vivo. Luciferase reporter gene assays and 3-(4,5-dimethylthiazol-2-yl)- 5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays show that, upon exposure to arsenic trioxide, formerly unresponsive, ER-negative MDA-MB-231 breast cancer cells become responsive to ER antagonists, 4-hydroxytamoxifen and ICI 182,780. Furthermore, methylation- specific PCR and bisulfite-sequencing PCR assays show that arsenic trioxide induces partial demethylation of the ERα promoter. A methyl donor, S-adenosylmethionine (SAM), reduces the degree of arsenic trioxide-induced re-expression of ERα and demethylation. Moreover, Western blot and ChIP assays show that arsenic trioxide represses expression of DNMT1 and DNMT3a along with partial dissociation of DNMT1 from the ERα promoter. Thus, arsenic trioxide exhibits a previously undefined function which induces re-expression ERα in ER-negative breast cancer cells through demethylation of the ERα promoter. These findings could provide important information regarding the application of therapeutic agents targeting epigenetic changes in breast cancers and potential implication of arsenic trioxide as a new drug for the treatment of ER-negative human breast cancer.

Abcg2 expression marks tissue-specific stem cells in multiple organs in a mouse progeny tracking model.

PubMed

Fatima, Soghra; Zhou, Sheng; Sorrentino, Brian P

2012-02-01

The side population phenotype is associated with the Hoechst dye efflux activity of the Abcg2 transporter and identifies hematopoietic stem cells (HSCs) in the bone marrow. This association suggests the direct use of Abcg2 expression to identify adult stem cells in various other organs. We have generated a lineage tracing mouse model based on an allele that coexpresses both Abcg2 and a CreERT2 expression cassette. By crossing these mice with lox-STOP-lox reporter lines (LacZ or YFP), cells that express Abcg2 and their progeny were identified following treatment with tamoxifen (Tam). In the liver and kidney, in which mature cells express Abcg2, reporter gene expression verified the expected physiologic expression pattern of the recombinant allele. Long-term marking of HSCs was seen in multiple peripheral blood lineages from adult mice, demonstrating that Abcg2(+) bone marrow HSCs contribute to steady-state hematopoiesis. Stem cell tracing patterns were seen in the small intestine and in seminiferous tubules in the testis 20 months after Tam treatment, proving that stem cells from these organs express Abcg2. Interstitial cells from skeletal and cardiac muscle were labeled, and some cells were costained with endothelial markers, raising the possibility that these cells may function in the repair response to muscle injury. Altogether, these studies prove that Abcg2 is a stem cell marker for blood, small intestine, testicular germ cells, and possibly for injured skeletal and/or cardiac muscle and provide a new model for studying stem cell activity that does not require transplant-based assays. Copyright © 2011 AlphaMed Press.

Osimertinib (AZD9291) Enhanced the Efficacy of Chemotherapeutic Agents in ABCB1- and ABCG2-Overexpressing Cells In Vitro, In Vivo, and Ex Vivo.

PubMed

Chen, Zhen; Chen, Yifan; Xu, Meng; Chen, Likun; Zhang, Xu; To, Kenneth Kin Wah; Zhao, Hongyun; Wang, Fang; Xia, Zhongjun; Chen, Xiaoqin; Fu, Liwu

2016-08-01

The overexpression of ATP-binding cassette (ABC) transporters has been proved to be a major trigger for multidrug resistance (MDR) in certain types of cancer. In our study, we investigated whether osimertinib (AZD9291), a third-generation irreversible tyrosine kinase inhibitor of both activating EGFR mutations and resistance-associated T790M point mutation, could reverse MDR induced by ABCB1 and ABCG2 in vitro, in vivo, and ex vivo Our results showed that osimertinib significantly increased the sensitivity of ABCB1- and ABCG2-overexpressing cells to their substrate chemotherapeutic agents in vitro and in the model of ABCB1-overexpressing KBv200 cell xenograft in nude mice. Mechanistically, osimertinib increased the intracellular accumulations of doxorubicin (DOX) and Rhodamine 123 (Rho 123) by inhibiting the efflux function of the transporters in ABCB1- or ABCG2-overexpressing cells but not in their parental sensitive cells. Furthermore, osimertinib stimulated the ATPase activity of both ABCB1 and ABCG2 and competed with the [(125)I] iodoarylazidoprazosin photolabeling bound to ABCB1 or ABCG2, but did not alter the localization and expression of ABCB1 or ABCG2 in mRNA and protein levels nor the phosphorylations of EGFR, AKT, and ERK. Importantly, osimertinib also enhanced the cytotoxicity of DOX and intracellular accumulation of Rho 123 in ABCB1-overexpressing primary leukemia cells. Overall, these findings suggest osimertinib reverses ABCB1- and ABCG2-mediated MDR via inhibiting ABCB1 and ABCG2 from pumping out chemotherapeutic agents and provide possibility for cancer combinational therapy with osimertinib in the clinic. Mol Cancer Ther; 15(8); 1845-58. ©2016 AACR. ©2016 American Association for Cancer Research.

The structure of the human ABC transporter ABCG2 reveals a novel mechanism for drug extrusion.

PubMed

Khunweeraphong, Narakorn; Stockner, Thomas; Kuchler, Karl

2017-10-23

The human ABC transporter ABCG2 (Breast Cancer Resistance Protein, BCRP) is implicated in anticancer resistance, in detoxification across barriers and linked to gout. Here, we generate a novel atomic model of ABCG2 using the crystal structure of ABCG5/G8. Extensive mutagenesis verifies the structure, disclosing hitherto unrecognized essential residues and domains in the homodimeric ABCG2 transporter. The elbow helix, the first intracellular loop (ICL1) and the nucleotide-binding domain (NBD) constitute pivotal elements of the architecture building the transmission interface that borders a central cavity which acts as a drug trap. The transmission interface is stabilized by salt-bridge interactions between the elbow helix and ICL1, as well as within ICL1, which is essential to control the conformational switch of ABCG2 to the outward-open drug-releasing conformation. Importantly, we propose that ICL1 operates like a molecular spring that holds the NBD dimer close to the membrane, thereby enabling efficient coupling of ATP hydrolysis during the catalytic cycle. These novel mechanistic data open new opportunities to therapeutically target ABCG2 in the context of related diseases.

Cholesterol efflux in megakaryocyte progenitors suppresses platelet production and thrombocytosis

PubMed Central

Murphy, Andrew J.; Bijl, Nora; Yvan-Charvet, Laurent; Welch, Carrie B.; Bhagwat, Neha; Reheman, Adili; Wang, Yiming; Shaw, James A.; Levine, Ross L.; Ni, Heyu; Tall, Alan R.; Wang, Nan

2013-01-01

Platelets play a key role in atherogenesis and its complications. Both hypercholesterolemia and increased platelet production promote athero-thrombosis; however, a potential link between altered cholesterol homeostasis and platelet production has not been explored. Transplantation of bone marrow (BM) deficient in ABCG4, a transporter of unknown function, into Ldlr−/− mice resulted in thrombocytosis, accelerated thrombosis and atherosclerosis. While not detected in lesions, Abcg4 was highly expressed in BM megakaryocyte progenitors (MkP). Abcg4−/− MkPs displayed defective cholesterol efflux to HDL, increased cell surface levels of thrombopoietin (TPO) receptor (c-MPL) and enhanced proliferation. This appeared to reflect disruption of the negative feedback regulation of c-MPL levels and signaling by E3 ligase c-CBL and cholesterol-sensing LYN kinase. HDL infusions reduced platelet counts in Ldlr−/− mice and in a mouse model of myeloproliferative neoplasm, in a completely ABCG4-dependent fashion. HDL infusions may offer a novel approach to reducing athero-thrombotic events associated with increased platelet production. PMID:23584088

ABCG2/BCRP interaction with the sea grass Thalassia testudinum.

PubMed

Miguel, Verónica; Otero, Jon A; Barrera, Borja; Rodeiro, Idania; Prieto, Julio G; Merino, Gracia; Álvarez, Ana I

2015-12-01

The aqueous ethanolic extract from leaves of the marine plant Thalassia testudinum has shown antioxidant, cytoprotective, and neuroprotective properties. The chemical composition of this extract, rich in polyphenols, could interfere with active transport of drugs out of the cell and circumvent the phenomenon of multidrug resistance (MDR). The extract can act as an MDR modulator through its interaction with efflux transporters. The ABCG2/BCRP has been shown to confer MDR acting in tumor cells. To evaluate the interaction of ABCG2/BCRP with the extract, studies in cells overexpressing human BCRP transporter and its murine ortholog Bcrp1 were performed. T. testudinum extract could be included as MDR modulator, as interaction with ABCG2/BCRP has been shown through flow cytometry and MTT assays. The cells overexpressing ABCG2/BCRP in the presence of the extract (25-150 μg/mL) decreased the survival rates of the anti-tumoral mitoxantrone. Our results support its inclusion as a possible MDR modulator against tumor cells that overexpress ABCG2/BCRP.

Low-dose hydralazine prevents fibrosis in a murine model of acute kidney injury-to-chronic kidney disease progression.

PubMed

Tampe, Björn; Steinle, Ulrike; Tampe, Désirée; Carstens, Julienne L; Korsten, Peter; Zeisberg, Elisabeth M; Müller, Gerhard A; Kalluri, Raghu; Zeisberg, Michael

2017-01-01

Acute kidney injury (AKI) and progressive chronic kidney disease (CKD) are intrinsically tied syndromes. In this regard, the acutely injured kidney often does not achieve its full regenerative capacity and AKI directly transitions into progressive CKD associated with tubulointerstitial fibrosis. Underlying mechanisms of such AKI-to-CKD progression are still incompletely understood and specific therapeutic interventions are still elusive. Because epigenetic modifications play a role in maintaining tissue fibrosis, we used a murine model of ischemia-reperfusion injury to determine whether aberrant promoter methylation of RASAL1 contributes causally to the switch between physiological regeneration and tubulointerstitial fibrogenesis, a hallmark of AKI-to-CKD progression. It is known that the antihypertensive drug hydralazine has demethylating activity, and that its optimum demethylating activity occurs at concentrations below blood pressure-lowering doses. Administration of low-dose hydralazine effectively induced expression of hydroxylase TET3, which catalyzed RASAL1 hydroxymethylation and subsequent RASAL1 promoter demethylation. Hydralazine-induced CpG promoter demethylation subsequently attenuated renal fibrosis and preserved excretory renal function independent of its blood pressure-lowering effects. In comparison, RASAL1 demethylation and inhibition of tubulointerstitial fibrosis was not detected upon administration of the angiotensin-converting enzyme inhibitor Ramipril in this model. Thus, RASAL1 promoter methylation and subsequent transcriptional RASAL1 suppression plays a causal role in AKI-to-CKD progression. Copyright © 2016 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Localization of ABCG5 and ABCG8 proteins in human liver, gall bladder and intestine

PubMed Central

Klett, Eric L; Lee, Mi-Hye; Adams, David B; Chavin, Kenneth D; Patel, Shailendra B

2004-01-01

Background The molecular mechanisms that regulate the entry of dietary sterols into the body and their removal via hepatobiliary secretion are now beginning to be defined. These processes are specifically disrupted in the rare autosomal recessive disease, Sitosterolemia (MIM 210250). Mutations in either, but not both, of two genes ABCG5 or ABCG8, comprising the STSL locus, are now known to cause this disease and their protein products are proposed to function as heterodimers. Under normal circumstances cholesterol, but not non-cholesterol sterols, is preferentially absorbed from the diet. Additionally, any small amounts of non-cholesterol sterols that are absorbed are rapidly taken up by the liver and preferentially excreted into bile. Based upon the defects in sitosterolemia, ABCG5 and ABCG8 serve specifically to exclude non-cholesterol sterol entry at the intestinal level and are involved in sterol excretion at the hepatobiliary level. Methods Here we report the biochemical and immuno-localization of ABCG5 and ABCG8 in human liver, gallbladder and intestine using cell fractionation and immunohistochemical analyses. Results We raised peptide antibodies against ABCG5 and ABCG8 proteins. Using human liver samples, cell fractionation studies showed both proteins are found in membrane fractions, but they did not co-localize with caveolin-rafts, ER, Golgi or mitochondrial markers. Although their distribution in the sub-fractions was similar, they were not completely contiguous. Immunohistochemical analyses showed that while both proteins were readily detectable in the liver, ABCG5 was found predominately lining canalicular membranes, whereas ABCG8 was found in association with bile duct epithelia. At the cellular level, ABCG5 appeared to be apically expressed, whereas ABCG8 had a more diffuse expression pattern. Both ABCG5 and ABCG8 appeared to localize apically as shown by co-localization with MRP2. The distribution patterns of ABCG5 and ABCG8 in the gallbladder were very similar to each other. In the small intestine both ABCG5 and ABCG8 appear to line the brush border. However, at the level of the enterocyte, the cellular distribution patterns of ABCG5 and ABCG8 differed, such that ABCG5 was more diffuse, but ABCG8 was principally apical. Using standard deglycosylation methods, ABCG5 and ABCG8 do not appear to be glycosylated, suggesting a difference between human and mouse proteins. Conclusion We report the distribution patterns of ABCG5 and ABCG8 in human tissues. Cell fractionation studies showed that both proteins co-fractionated in general, but could also be found independent of each other. As predicted, they are expressed apically in both intestine and liver, although their intracellular expression patterns are not completely congruent. These studies support the concept of heterodimerization of ABCG5 and ABCG8, but also support the notion that these proteins may have an independent function. PMID:15383151

Correlation between clinical response to sorafenib in hepatocellular carcinoma treatment and polymorphisms of P-glycoprotein (ABCB1) and of breast cancer resistance protein (ABCG2): monocentric study.

PubMed

Tandia, Mahamadou; Mhiri, Asma; Paule, Bernard; Saffroy, Raphaël; Cailliez, Valérie; Noé, Gaëlle; Farinotti, Robert; Bonhomme-Faivre, Laurence

2017-04-01

We studied the relation between the polymorphism of P-glycoprotein (P-gp) and of breast cancer resistance protein (BCRP), encoded by ABCB1 and ABCG2 genes, respectively, and the pharmacokinetic variability and clinical response during the treatment with sorafenib of hepatocellular carcinoma. At the Paul Brousse Hospital in Villejuif, France, 47 consecutive patients with advanced HCC treated with a single agent sorafenib, were enrolled. Sorafenib exposure was measured by its plasma concentration 3 h after oral administration of 400 mg (bid) by liquid chromatography. All enrolled patients were genotyped for ABCB1 (rs2032582; rs1045642) and ABCG2 (rs2231137; rs2231142; rs2622604) by blood genomic DNA extraction and Mass ARRAY genotyping. The clinical response was evaluated after 3months of treatment according to the RECIST criteria. Significant associations between sorafenib exposure and the studied polymorphisms were observed for ABCB1 3435C>T, ABCG2 34G>A, ABCG2 1143C>T and ABCG2 421C>A, but not for ABCB1 2677G>TA SNP. In heterozygous patients for ABCB1 3435 C>T, ABCG2 34 G>A and ABCG2 1143 C>T polymorphisms were significantly associated with the lowest sorafenib plasma levels. Those patients presented a tendency to have the best clinical evolution. Heterozygous forms of the studied polymorphisms could be associated with a better therapeutic response.

Genome-Wide Identification and Expression Profiling of ATP-Binding Cassette (ABC) Transporter Gene Family in Pineapple (Ananas comosus (L.) Merr.) Reveal the Role of AcABCG38 in Pollen Development

PubMed Central

Chen, Piaojuan; Li, Yi; Zhao, Lihua; Hou, Zhimin; Yan, Maokai; Hu, Bingyan; Liu, Yanhui; Azam, Syed Muhammad; Zhang, Ziyan; Rahman, Zia ur; Liu, Liping; Qin, Yuan

2017-01-01

Pineapple (Ananas comosus L.) cultivation commonly relies on asexual reproduction which is easily impeded by many factors in agriculture production. Sexual reproduction might be a novel approach to improve the pineapple planting. However, genes controlling pineapple sexual reproduction are still remain elusive. In different organisms a conserved superfamily proteins known as ATP binding cassette (ABC) participate in various biological processes. Whereas, till today the ABC gene family has not been identified in pineapple. Here 100 ABC genes were identified in the pineapple genome and grouped into eight subfamilies (5 ABCAs, 20 ABCBs, 16 ABCCs, 2 ABCDs, one ABCEs, 5 ABCFs, 42 ABCGs and 9 ABCIs). Gene expression profiling revealed the dynamic expression pattern of ABC gene family in various tissues and different developmental stages. AcABCA5, AcABCB6, AcABCC4, AcABCC7, AcABCC9, AcABCG26, AcABCG38 and AcABCG42 exhibited preferential expression in ovule and stamen. Over-expression of AcABCG38 in the Arabidopsis double mutant abcg1-2abcg16-2 partially restored its pollen abortion defects, indicating that AcABCG38 plays important roles in pollen development. Our study on ABC gene family in pineapple provides useful information for developing sexual pineapple plantation which could be utilized to improve pineapple agricultural production. PMID:29312399

Genome-Wide Identification and Expression Profiling of ATP-Binding Cassette (ABC) Transporter Gene Family in Pineapple (Ananas comosus (L.) Merr.) Reveal the Role of AcABCG38 in Pollen Development.

PubMed

Chen, Piaojuan; Li, Yi; Zhao, Lihua; Hou, Zhimin; Yan, Maokai; Hu, Bingyan; Liu, Yanhui; Azam, Syed Muhammad; Zhang, Ziyan; Rahman, Zia Ur; Liu, Liping; Qin, Yuan

2017-01-01

Pineapple ( Ananas comosus L .) cultivation commonly relies on asexual reproduction which is easily impeded by many factors in agriculture production. Sexual reproduction might be a novel approach to improve the pineapple planting. However, genes controlling pineapple sexual reproduction are still remain elusive. In different organisms a conserved superfamily proteins known as ATP binding cassette (ABC) participate in various biological processes. Whereas, till today the ABC gene family has not been identified in pineapple. Here 100 ABC genes were identified in the pineapple genome and grouped into eight subfamilies (5 ABCAs , 20 ABCB s, 16 ABCCs , 2 ABCDs , one ABCEs , 5 ABCFs , 42 ABCGs and 9 ABCIs ). Gene expression profiling revealed the dynamic expression pattern of ABC gene family in various tissues and different developmental stages. AcABCA5, AcABCB6, AcABCC4 , AcABCC7 , AcABCC9 , AcABCG26 , AcABCG38 and AcABCG42 exhibited preferential expression in ovule and stamen. Over-expression of AcABCG38 in the Arabidopsis double mutant abcg1-2abcg16-2 partially restored its pollen abortion defects, indicating that AcABCG38 plays important roles in pollen development. Our study on ABC gene family in pineapple provides useful information for developing sexual pineapple plantation which could be utilized to improve pineapple agricultural production.

Black Raspberry-Derived Anthocyanins Demethylate Tumor Suppressor Genes Through the Inhibition of DNMT1 and DNMT3B in Colon Cancer Cells

PubMed Central

Wang, Li-Shu; Kuo, Chieh-Ti; Cho, Seung-Ju; Seguin, Claire; Siddiqui, Jibran; Stoner, Kristen; Weng, Yu-I; Huang, Tim H.-M.; Tichelaar, Jay; Yearsley, Martha; Stoner, Gary D.; Huang, Yi-Wen

2013-01-01

We previously reported that oral administration of black raspberry powder decreased promoter methylation of tumor suppressor genes in tumors from patients with colorectal cancer. The anthocyanins (ACs) in black raspberries are responsible, at least in part, for their cancer-inhibitory effects. In the present study, we asked if ACs are responsible for the demethylation effects observed in colorectal cancers. Three days of treatment of ACs at 0.5, 5, and 25 μg/ml suppressed activity and protein expression of DNMT1 and DNMT3B in HCT116, Caco2 and SW480 cells. Promoters of CDKN2A, and SFRP2, SFRP5, and WIF1, upstream of Wnt pathway, were demethylated by ACs. mRNA expression of some of these genes was increased. mRNA expression of β-catenin and c-Myc, downstream of Wnt pathway, and cell proliferation were decreased; apoptosis was increased. ACs were taken up into HCT116 cells and were differentially localized with DNMT1 and DNMT3B in the same cells visualized using confocal laser scanning microscopy. Although it was reported that DNMT3B is regulated by c-Myc in mouse lymphoma, DNMT3B did not bind with c-Myc in HCT116 cells. In conclusion, our results suggest that ACs are responsible, at least in part, for the demethylation effects of whole black raspberries in colorectal cancers. PMID:23368921

Jump into a New Fold—A Homology Based Model for the ABCG2/BCRP Multidrug Transporter

PubMed Central

László, Laura; Sarkadi, Balázs

2016-01-01

ABCG2/BCRP is a membrane protein, involved in xenobiotic and endobiotic transport in key pharmacological barriers and drug metabolizing organs, in the protection of stem cells, and in multidrug resistance of cancer. Pharmacogenetic studies implicated the role of ABCG2 in response to widely used medicines and anticancer agents, as well as in gout. Its Q141K variant exhibits decreased functional expression thus increased drug accumulation and decreased urate secretion. Still, there has been no reliable molecular model available for this protein, as the published structures of other ABC transporters could not be properly fitted to the ABCG2 topology and experimental data. The recently published high resolution structure of a close homologue, the ABCG5-ABCG8 heterodimer, revealed a new ABC transporter fold, unique for ABCG proteins. Here we present a structural model of the ABCG2 homodimer based on this fold and detail the experimental results supporting this model. In order to describe the effect of mutations on structure and dynamics, and characterize substrate recognition and cholesterol regulation we performed molecular dynamics simulations using full length ABCG2 protein embedded in a membrane bilayer and in silico docking simulations. Our results show that in the Q141K variant the introduced positive charge diminishes the interaction between the nucleotide binding and transmembrane domains and the R482G variation alters the orientation of transmembrane helices. Moreover, the R482 position, which plays a role the substrate specificity of the transporter, is located in one of the substrate binding pockets identified by the in silico docking calculations. In summary, the ABCG2 model and in silico simulations presented here may have significant impact on understanding drug distribution and toxicity, as well as drug development against cancer chemotherapy resistance or gout. PMID:27741279

TET1 promotes cisplatin-resistance via demethylating the vimentin promoter in ovarian cancer.

PubMed

Han, Xi; Zhou, Yuanyuan; You, Yuanyi; Lu, Jiaojiao; Wang, Lijie; Hou, Huilian; Li, Jing; Chen, Wei; Zhao, Le; Li, Xu

2017-04-01

The development of chemo-resistance impairs the outcome of the first line platinum-based chemotherapies for ovarian cancer. Deregulation of DNA methylation/demethylation provides a critical mechanism for the occurrence of chemo-resistance. The ten-eleven translocation (TET) family of dioxygenases including TET1/2/3 plays an important part in DNA demethylation, but their roles in cisplatin resistance have not been elucidated. Using cisplatin-sensitive and cisplatin-resistant ovarian cancer cell models, we found that TET1 was significantly upregulated in cisplatin-resistant CP70 cells compared with that in cisplatin-sensitive A2780 cells. Ectopic expression of TET1 in A2780 cells promoted cisplatin resistance and decreased cytotoxicity induced by cisplatin, while inhibition of TET1 by siRNA transfection in CP70 cells attenuated cisplatin resistance and enhanced cytotoxicity of cisplatin. Increased TET1 induced re-expression of vimentin through active DNA demethylation, and cause partial epithelial-to-mesenchymal (EMT) in A2780 cells. Contrarily, knocking down of TET1 in CP70 cells reduced vimentin expression and reversed EMT process. Immunohistochemical analysis of TET1 in human ovarian cancer tissues revealed that TET1 existed in nucleus and cytoplasm in ovarian cancer tissues. And the expression of nuclear TET1 was positively correlated with residual tumor and chemotherapeutic response. Thus, TET1 expression causes resistance to cisplatin and one of the targets of TET1 action is vimentin in ovarian cancer. © 2017 International Federation for Cell Biology.

ROLE OF ATP BINDING CASSETTE SUB-FAMILY MEMBER 2 (ABCG2) IN MOUSE EMBRYONIC STEM CELL DEVELOPMENT.

EPA Science Inventory

ATP binding cassette sub-family member 2 (ABCG2), is a member of the ABC transporter superfamily and a principal xenobiotic transporter. ABCG2 is also highly expressed in certain stem cell populations where it is thought to be related to stem cell plasticity, although the role o...

Apatinib (YN968D1) reverses multidrug resistance by inhibiting the efflux function of multiple ATP-binding cassette transporters

PubMed Central

Mi, Yan-jun; Liang, Yong-ju; Huang, Hong-bing; Zhao, Hong-yun; Wu, Chung-Pu; Wang, Fang; Tao, Li-yang; Zhang, Chuan-zhao; Dai, Chun-Ling; Tiwari, Amit K.; Ma, Xiao-xu; Wah To, Kenneth Kin; Ambudkar, Suresh V.; Chen, Zhe-Sheng; Fu, Li-wu

2010-01-01

Apatinib, a small-molecule multi-targeted tyrosine kinase inhibitor, is in phase III clinical trial for treatment of patients with non-small cell lung cancer and gastric cancer in China. In this study, we determined the effect of apatinib on the interaction of specific antineoplastic compounds with P-glycoprotein (P-gp, ABCB1), multidrug resistance protein 1 (MRP1, ABCC1) and breast cancer resistance protein (BCRP, ABCG2). Our results showed that apatinib significantly enhanced the cytotoxicity of ABCB1 or ABCG2 substrate drugs in KBv200, MCF-7/adr and HEK293/ABCB1 cells overexpressing ABCB1 and S1-M1-80, MCF-7/FLV1000 and HEK293/ABCG2-R2 cells overexpressing ABCG2 (wild-type). In contrast, apatinib did not alter the cytotoxicity of specific substrates in the parental cells and cells overexpressing ABCC1. Apatinib significantly increased the intracellular accumulation of rhodamine 123 and doxorubicin in the multidrug resistance (MDR) cells. Furthermore, apatinib significantly inhibited the photolabeling of both ABCB1 and ABCG2 with [125I]-iodoarylazidoprazosin in a concentration-dependent fashion. The ATPase activity of both ABCB1 and ABCG2 was significantly increased by apatinib. However, apatinib, at a concentration the produced a reversal of MDRl, did not significantly alter the expression of the ABCB1 or ABCG2 protein or mRNA levels or the phosphorylation of AKT and ERK1/2. Importantly, apatinib significantly enhanced the effect of paclitaxel against the ABCB1 resistant KBv200 cancer cell xenografts in nude mice. In conclusion, apatinib reverses ABCB1- and ABCG2-mediated MDR by inhibiting their transport function, but not by blocking AKT or ERK1/2 pathway or downregulating ABCB1 or ABCG2 expression. Apatinib may be useful in circumventing MDR to other conventional antineoplastic drugs. PMID:20876799

LXR-dependent regulation of macrophage-specific reverse cholesterol transport is impaired in a model of genetic diabesity.

PubMed

Errico, Teresa L; Méndez-Lara, Karen Alejandra; Santos, David; Cabrerizo, Núria; Baila-Rueda, Lucía; Metso, Jari; Cenarro, Ana; Pardina, Eva; Lecube, Albert; Jauhiainen, Matti; Peinado-Onsurbe, Julia; Escolà-Gil, Joan Carles; Blanco-Vaca, Francisco; Julve, Josep

2017-08-01

Diabesity and fatty liver have been associated with low levels of high-density lipoprotein cholesterol, and thus could impair macrophage-specific reverse cholesterol transport (m-RCT). Liver X receptor (LXR) plays a critical role in m-RCT. Abcg5/g8 sterol transporters, which are involved in cholesterol trafficking into bile, as well as other LXR targets, could be compromised in the livers of obese individuals. We aimed to determine m-RCT dynamics in a mouse model of diabesity, the db/db mice. These obese mice displayed a significant retention of macrophage-derived cholesterol in the liver and reduced fecal cholesterol elimination compared with nonobese mice. This was associated with a significant downregulation of the hepatic LXR targets, including Abcg5/g8. Pharmacologic induction of LXR promoted the delivery of total tracer output into feces in db/db mice, partly due to increased liver and small intestine Abcg5/Abcg8 gene expression. Notably, a favorable upregulation of the hepatic levels of ABCG5/G8 and NR1H3 was also observed postoperatively in morbidly obese patients, suggesting a similar LXR impairment in these patients. In conclusion, our data show that downregulation of the LXR axis impairs cholesterol transfer from macrophages to feces in db/db mice, whereas the induction of the LXR axis partly restores impaired m-RCT by elevating the liver and small intestine expressions of Abcg5/g8. Copyright © 2017 Elsevier Inc. All rights reserved.

Evaluation of ABCG2 and p63 expression in canine cornea and cultivated corneal epithelial cells.

PubMed

Morita, Maresuke; Fujita, Naoki; Takahashi, Ayaka; Nam, Eun Ryel; Yui, Sho; Chung, Cheng Shu; Kawahara, Naoya; Lin, Hsing Yi; Tsuzuki, Keiko; Nakagawa, Takayuki; Nishimura, Ryohei

2015-01-01

To examine the expressions of ABCG2 and p63 in canine corneal epithelia and to evaluate their significance in corneal regeneration. Canine corneal and limbal epithelial cells were obtained from five healthy beagle dogs. We analyzed the morphological properties of cultivated limbal and corneal epithelial cells. We compared the expressions of ABCG2 and p63 in the limbus and central cornea by immunohistochemistry and real-time quantitative PCR. We analyzed the expression of these markers in cultivated cells by immunocytochemistry and real-time quantitative PCR. The limbal epithelial cells were smaller and proliferated more rapidly than the corneal epithelial cells in primary cultures. The corneal cells failed to be subcultured, whereas the limbal cells could be subcultured with increasing cell size. ABCG2 was localized in the basal layer of the limbal epithelium, and p63 was widely detected in the entire corneal epithelia. ABCG2 expression was significantly higher, and p63 was slightly higher in the limbus compared with the central cornea. ABCG2 was detected only in limbal cells in primary culture, not in corneal cells or passaged limbal cells. p63 was detected in both limbal and corneal cells and decreased gradually in the limbal cells with the cell passages. ABCG2 was localized in canine limbal epithelial cells, and p63 was widely expressed in canine corneal epithelia. ABCG2 and p63 could prove to be useful markers in dogs for putative corneal epithelial stem cells and for corneal epithelial cell proliferation, respectively. © 2014 American College of Veterinary Ophthalmologists.

Association of ABCB1 and ABCG2 single nucleotide polymorphisms with clinical findings and response to chemotherapy treatments in Kurdish patients with breast cancer.

PubMed

Ghafouri, Houshiyar; Ghaderi, Bayazid; Amini, Sabrieh; Nikkhoo, Bahram; Abdi, Mohammad; Hoseini, Abdolhakim

2016-06-01

The possible interaction between gene polymorphisms and risk of cancer progression is very interesting. Polymorphisms in multi-drug resistance genes have an important role in response to anti-cancer drugs. The present study was aimed to evaluate the possible effects of ABCB1 C3435T and ABCG2 C421A single nucleotide polymorphisms on clinical and pathological outcomes of Kurdish patients with breast cancer. One hundred breast cancer patients and 200 healthy controls were enrolled in this case-control study. Clinical and pathological findings of all individuals were reported, and immunohistochemistry staining was used to assess the tissue expression of specific breast cancer proteins. The ABCB1 C3435T and ABCG2 C421 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP). The distribution of different genotypes between patient and control groups was only significant for ABCG2 C421A. A allele of ABCG2 C421A polymorphisms were significantly higher in patients than in controls. Patients with AA genotype of ABCG2 C421A were at higher risk of progressing breast cancer. Patients with A allele of ABCG2 had complete response to chemotherapeutic agents. There was no statistically significant association between ABCB1 C3435T and ABCG2 C421A polymorphisms and tissue expression of ER, PR, Her2/neu, and Ki67. The ABCB1 C3435T has no correlation with clinical findings and treatment with chemotherapy drugs. The A allele of ABCG2 C421A may be a risk factor for progression of breast cancer in Kurdish patients. In addition, breast cancer patients with C allele of this polymorphism have weaker response to treatments with anthracyclines and Paclitaxol.

Tet1 and Tet2 maintain mesenchymal stem cell homeostasis via demethylation of the P2rX7 promoter.

PubMed

Yang, Ruili; Yu, Tingting; Kou, Xiaoxing; Gao, Xiang; Chen, Chider; Liu, Dawei; Zhou, Yanheng; Shi, Songtao

2018-06-01

Ten-eleven translocation (Tet) family-mediated DNA oxidation represents an epigenetic modification capable of converting 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC), which regulates various biological processes. However, it is unknown whether Tet family affects mesenchymal stem cells (MSCs) or the skeletal system. Here we show that depletion of Tet1 and Tet2 results in impaired self-renewal and differentiation of bone marrow MSCs (BMMSCs) and a significant osteopenia phenotype. Tet1 and Tet2 deficiency reduces demethylation of the P2rX7 promoter and downregulates exosome release, leading to intracellular accumulation of miR-297a-5p, miR-297b-5p, and miR-297c-5p. These miRNAs inhibit Runx2 signaling to impair BMMSC function. We show that overexpression of P2rX7 rescues the impaired BMMSCs and osteoporotic phenotype in Tet1 and Tet2 double knockout mice. These results indicate that Tet1 and Tet2 play a critical role in maintaining BMMSC and bone homeostasis through demethylation of P2rX7 to control exosome and miRNA release. This Tet/P2rX7/Runx2 cascade may serve as a target for the development of novel therapies for osteopenia disorders.

Emodin As an Effective Agent in Targeting Cancer Stem-Like Side Population Cells of Gallbladder Carcinoma

PubMed Central

Li, Xin-xing; Dong, Ying; Wang, Wei; Wang, Hao-lu; Chen, Yu-ying; Shi, Gui-ying; Yi, Jing

2013-01-01

Side population (SP) cells are previously identified from bone marrow based on their capacity to efflux of the fluorescent dye Hoechst 33342. Recent studies demonstrate that SP cells isolated from various cancer cell lines and primary tumors possess stem-cell-like properties. Thus, targeting tumor SP cells may provide new strategies for treatment in clinic. We previously showed that 1,3,8-trihydroxy-6-methylanthraquinone (emodin), a reactive oxygen species (ROS) generator, enhanced sensitivity of gallbladder cancer SGC-996 cells to cisplatin (CDDP) via generation of ROS and downregulation of multidrug-resistance-associated protein 1 (MRP1). To determine whether emodin also acts effectively on cancer stem cells of gallbladder carcinoma, we use SP cells as a model of cancer stem-cell-like cells. Here, we found that emodin, via ROS-related mechanism and suppressing the function of ATP-binding cassette super-family G member (ABCG2), which is known to be associated with Hoechst dye efflux activity of SP cells, not only reduced the ratio, inhibited clone formation, and eliminated sphere formation of SP cells effectively, but also promoted obviously the intracellular accumulation of doxorubicin, the main substrate of the efflux pump ABCG2. In addition, emodin could sensitize CDDP, via inhibition of expression of ABCG2, to overcome chemoresistance of SP cells. Importantly, similar to the experiment in vitro, emodin/CDDP co-treatment in vivo suppressed the tumor growth derived from SP cells through downregulating ABCG2 expression. Our results suggest that emodin is an effective agent targeting cancer stem-like SP cells of gallbladder carcinoma, either alone or acts as a chemotherapy enhancer. PMID:22974371

DNA-Demethylase Regulated Genes Show Methylation-Independent Spatiotemporal Expression Patterns

PubMed Central

Schumann, Ulrike; Lee, Joanne; Kazan, Kemal; Ayliffe, Michael; Wang, Ming-Bo

2017-01-01

Recent research has indicated that a subset of defense-related genes is downregulated in the Arabidopsis DNA demethylase triple mutant rdd (ros1 dml2 dml3) resulting in increased susceptibility to the fungal pathogen Fusarium oxysporum. In rdd plants these downregulated genes contain hypermethylated transposable element sequences (TE) in their promoters, suggesting that this methylation represses gene expression in the mutant and that these sequences are actively demethylated in wild-type plants to maintain gene expression. In this study, the tissue-specific and pathogen-inducible expression patterns of rdd-downregulated genes were investigated and the individual role of ROS1, DML2, and DML3 demethylases in these spatiotemporal regulation patterns was determined. Large differences in defense gene expression were observed between pathogen-infected and uninfected tissues and between root and shoot tissues in both WT and rdd plants, however, only subtle changes in promoter TE methylation patterns occurred. Therefore, while TE hypermethylation caused decreased gene expression in rdd plants it did not dramatically effect spatiotemporal gene regulation, suggesting that this latter regulation is largely methylation independent. Analysis of ros1-3, dml2-1, and dml3-1 single gene mutant lines showed that promoter TE hypermethylation and defense-related gene repression was predominantly, but not exclusively, due to loss of ROS1 activity. These data demonstrate that DNA demethylation of TE sequences, largely by ROS1, promotes defense-related gene expression but does not control spatiotemporal expression in Arabidopsis. Summary: Ros1-mediated DNA demethylation of promoter transposable elements is essential for activation of defense-related gene expression in response to fungal infection in Arabidopsis thaliana. PMID:28894455

Arid5b facilitates chondrogenesis by recruiting the histone demethylase Phf2 to Sox9-regulated genes

NASA Astrophysics Data System (ADS)

Hata, Kenji; Takashima, Rikako; Amano, Katsuhiko; Ono, Koichiro; Nakanishi, Masako; Yoshida, Michiko; Wakabayashi, Makoto; Matsuda, Akio; Maeda, Yoshinobu; Suzuki, Yutaka; Sugano, Sumio; Whitson, Robert H.; Nishimura, Riko; Yoneda, Toshiyuki

2013-11-01

Histone modification, a critical step for epigenetic regulation, is an important modulator of biological events. Sox9 is a transcription factor critical for endochondral ossification; however, proof of its epigenetic regulation remains elusive. Here we identify AT-rich interactive domain 5b (Arid5b) as a transcriptional co-regulator of Sox9. Arid5b physically associates with Sox9 and synergistically induces chondrogenesis. Growth of Arid5b-/- mice is retarded with delayed endochondral ossification. Sox9-dependent chondrogenesis is attenuated in Arid5b-deficient cells. Arid5b recruits Phf2, a histone lysine demethylase, to the promoter region of Sox9 target genes and stimulates H3K9me2 demethylation of these genes. In the promoters of chondrogenic marker genes, H3K9me2 levels are increased in Arid5b-/- chondrocytes. Finally, we show that Phf2 knockdown inhibits Sox9-induced chondrocyte differentiation. Our findings establish an epigenomic mechanism of skeletal development, whereby Arid5b promotes chondrogenesis by facilitating Phf2-mediated histone demethylation of Sox9-regulated chondrogenic gene promoters.

Dioxin induces Ahr-dependent robust DNA demethylation of the Cyp1a1 promoter via Tdg in the mouse liver.

PubMed

Amenya, Hesbon Z; Tohyama, Chiharu; Ohsako, Seiichiroh

2016-10-07

The aryl hydrocarbon receptor (Ahr) is a highly conserved nuclear receptor that plays an important role in the manifestation of toxicity induced by polycyclic aromatic hydrocarbons. As a xenobiotic sensor, Ahr is involved in chemical biotransformation through activation of drug metabolizing enzymes. The activated Ahr cooperates with coactivator complexes to induce epigenetic modifications at target genes. Thus, it is conceivable that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent Ahr ligand, may elicit robust epigenetic changes in vivo at the Ahr target gene cytochrome P450 1a1 (Cyp1a1). A single dose of TCDD administered to adult mice induced Ahr-dependent CpG hypomethylation, changes in histone modifications, and thymine DNA glycosylase (Tdg) recruitment at the Cyp1a1 promoter in the liver within 24 hrs. These epigenetic changes persisted until 40 days post-TCDD treatment and there was Cyp1a1 mRNA hyperinduction upon repeat administration of TCDD at this time-point. Our demethylation assay using siRNA knockdown and an in vitro methylated plasmid showed that Ahr, Tdg, and the ten-eleven translocation methyldioxygenases Tet2 and Tet3 are required for the TCDD-induced DNA demethylation. These results provide novel evidence of Ahr-driven active DNA demethylation and epigenetic memory. The epigenetic alterations influence response to subsequent chemical exposure and imply an adaptive mechanism to xenobiotic stress.

Dioxin induces Ahr-dependent robust DNA demethylation of the Cyp1a1 promoter via Tdg in the mouse liver

NASA Astrophysics Data System (ADS)

Amenya, Hesbon Z.; Tohyama, Chiharu; Ohsako, Seiichiroh

2016-10-01

The aryl hydrocarbon receptor (Ahr) is a highly conserved nuclear receptor that plays an important role in the manifestation of toxicity induced by polycyclic aromatic hydrocarbons. As a xenobiotic sensor, Ahr is involved in chemical biotransformation through activation of drug metabolizing enzymes. The activated Ahr cooperates with coactivator complexes to induce epigenetic modifications at target genes. Thus, it is conceivable that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent Ahr ligand, may elicit robust epigenetic changes in vivo at the Ahr target gene cytochrome P450 1a1 (Cyp1a1). A single dose of TCDD administered to adult mice induced Ahr-dependent CpG hypomethylation, changes in histone modifications, and thymine DNA glycosylase (Tdg) recruitment at the Cyp1a1 promoter in the liver within 24 hrs. These epigenetic changes persisted until 40 days post-TCDD treatment and there was Cyp1a1 mRNA hyperinduction upon repeat administration of TCDD at this time-point. Our demethylation assay using siRNA knockdown and an in vitro methylated plasmid showed that Ahr, Tdg, and the ten-eleven translocation methyldioxygenases Tet2 and Tet3 are required for the TCDD-induced DNA demethylation. These results provide novel evidence of Ahr-driven active DNA demethylation and epigenetic memory. The epigenetic alterations influence response to subsequent chemical exposure and imply an adaptive mechanism to xenobiotic stress.

PI3K/AKT/mTOR Signaling Mediates Valproic Acid-Induced Neuronal Differentiation of Neural Stem Cells through Epigenetic Modifications.

PubMed

Zhang, Xi; He, Xiaosong; Li, Qingqing; Kong, Xuejian; Ou, Zhenri; Zhang, Le; Gong, Zhuo; Long, Dahong; Li, Jianhua; Zhang, Meng; Ji, Weidong; Zhang, Wenjuan; Xu, Liping; Xuan, Aiguo

2017-05-09

Although valproic acid (VPA), has been shown to induce neuronal differentiation of neural stem cells (NSCs), the underlying mechanisms remain poorly understood. Here we investigated if and how mammalian target of rapamycin (mTOR) signaling is involved in the neuronal differentiation of VPA-induced NSCs. Our data demonstrated that mTOR activation not only promoted but also was necessary for the neuronal differentiation of NSCs induced by VPA. We further found that inhibition of mTOR signaling blocked demethylation of neuron-specific gene neurogenin 1 (Ngn1) regulatory element in induced cells. These are correlated with the significant alterations of passive DNA demethylation and the active DNA demethylation pathway in the Ngn1 promoter, but not the suppression of lysine-specific histone methylation and acetylation in the promoter region of Ngn1. These findings highlight a potentially important role for mTOR signaling, by working together with DNA demethylation, to influence the fate of NSCs via regulating the expression of Ngn1 in VPA-induced neuronal differentiation of NSCs. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

ABCG2 in peptic ulcer: gene expression and mutation analysis.

PubMed

Salagacka-Kubiak, Aleksandra; Żebrowska, Marta; Wosiak, Agnieszka; Balcerczak, Mariusz; Mirowski, Marek; Balcerczak, Ewa

2016-08-01

The aim of this study was to evaluate the participation of polymorphism at position C421A and mRNA expression of the ABCG2 gene in the development of peptic ulcers, which is a very common and severe disease. ABCG2, encoded by the ABCG2 gene, has been found inter alia in the gastrointestinal tract, where it plays a protective role eliminating xenobiotics from cells into the extracellular environment. The materials for the study were biopsies of gastric mucosa taken during a routine endoscopy. For genotyping by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) at position C421A, DNA was isolated from 201 samples, while for the mRNA expression level by real-time PCR, RNA was isolated from 60 patients. The control group of healthy individuals consisted of 97 blood donors. The dominant genotype in the group of peptic ulcer patients and healthy individuals was homozygous CC. No statistically significant differences between healthy individuals and the whole group of peptic ulcer patients and, likewise, between the subgroups of peptic ulcer patients (infected and uninfected with Helicobacter pylori) were found. ABCG2 expression relative to GAPDH expression was found in 38 of the 60 gastric mucosa samples. The expression level of the gene varies greatly among cases. The statistically significant differences between the intensity (p = 0.0375) of H. pylori infection and ABCG2 gene expression have been shown. It was observed that the more intense the infection, the higher the level of ABCG2 expression.

Identification of residues in ABCG2 affecting protein trafficking and drug transport, using co-evolutionary analysis of ABCG sequences.

PubMed

Haider, Ameena J; Cox, Megan H; Jones, Natalie; Goode, Alice J; Bridge, Katherine S; Wong, Kelvin; Briggs, Deborah; Kerr, Ian D

2015-07-17

ABCG2 is an ABC (ATP-binding cassette) transporter with a physiological role in urate transport in the kidney and is also implicated in multi-drug efflux from a number of organs in the body. The trafficking of the protein and the mechanism by which it recognizes and transports diverse drugs are important areas of research. In the current study, we have made a series of single amino acid mutations in ABCG2 on the basis of sequence analysis. Mutant isoforms were characterized for cell surface expression and function. One mutant (I573A) showed disrupted glycosylation and reduced trafficking kinetics. In contrast with many ABC transporter folding mutations which appear to be 'rescued' by chemical chaperones or low temperature incubation, the I573A mutation was not enriched at the cell surface by either treatment, with the majority of the protein being retained in the endoplasmic reticulum (ER). Two other mutations (P485A and M549A) showed distinct effects on transport of ABCG2 substrates reinforcing the role of TM helix 3 in drug recognition and transport and indicating the presence of intracellular coupling regions in ABCG2. © 2015 Authors.

Genistein promotes DNA demethylation of the steroidogenic factor 1 (SF-1) promoter in endometrial stromal cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsukura, Hiroshi, E-mail: hmatsukura.epi@mri.tmd.ac.jp; Aisaki, Ken-ichi; Igarashi, Katsuhide

2011-08-26

Highlights: {yields} Genistein (GEN) is a phytoestrogen found in soy products. {yields} GEN demethylated/unsilenced the steroidogenic factor 1 gene in endometrial tissue. {yields} GEN thus altered mRNA expression in uteri of ovariectomized (OVX) mice. {yields} A high-resolution melting assay was used to screen for epigenetic change. {yields} We isolated an endometrial cell clone that was epigenetically modulated by GEN. -- Abstract: It has recently been demonstrated that genistein (GEN), a phytoestrogen in soy products, is an epigenetic modulator in various types of cells; but its effect on endometrium has not yet been determined. We investigated the effects of GEN onmore » mouse uterine cells, in vivo and in vitro. Oral administration of GEN for 1 week induced mild proliferation of the endometrium in ovariectomized (OVX) mice, which was accompanied by the induction of steroidogenic factor 1 (SF-1) gene expression. GEN administration induced demethylation of multiple CpG sites in the SF-1 promoter; these sites are extensively methylated and thus silenced in normal endometrium. The GEN-mediated promoter demethylation occurred predominantly on the luminal side, as opposed to myometrium side, indicating that the epigenetic change was mainly shown in regenerated cells. Primary cultures of endometrial stromal cell colonies were screened for GEN-mediated alterations of DNA methylation by a high-resolution melting (HRM) method. One out of 20 colony-forming cell clones showed GEN-induced demethylation of SF-1. This clone exhibited a high proliferation capacity with continuous colony formation activity through multiple serial clonings. We propose that only a portion of endometrial cells are capable of receiving epigenetic modulation by GEN.« less

[The Role of 5-Aza-CdR on Methylation of Promoter in RASSF1A Gene in Endometrial Carcinoma].

PubMed

Huang, Li-ping; Chen, Chen; Wang, Xue-ping; Liu, Hui

2015-05-01

To explore the effect of demethylating drug 5-Aza-2'-deoxycytidine (5-Aza-CdR) on methtylation status of the Ras-association domain familylA gene (RASSF1A) in human endometrial carcinoma. Randomly'assign the human endometrial carcinoma cell line HEC-1-B into groups and use demethylating drug 5-Aza-CdR of different concentration to treat them. Then Methylation-specific polymerase chain reaction (MSP), real-time PCR, Western blot, TUNEL technology were used to analyze methylation status of RASSF1A promoter CpG islands, RASSF1A mRNA expression, RASSF1A protein expression and apoptosis of HEC-1-B cell. High DNA methylation in RASSF1A gene promoter region, low RASSF1A mRNA level and protein expression and out of control of human endometrial carcinoma cell HEC-1-B apoptosis were observed. 5-Aza-CdR of different concentration could reverse RASSF1A gene's methylation status, recover the expression of mRNA and protein, and control the growth of HEC-1-B by inducing apoptosis. Aberrant methylation of RASSF1A in endometrial cancer as a therapeutic target, demethylating agent 5-Aza-CdR could be an effective way of gene therapy.

Sodium-dependent Vitamin C transporter 2 deficiency impairs myelination and remyelination after injury: Roles of collagen and demethylation.

PubMed

Röhr, Dominik; Halfter, Hartmut; Schulz, Jörg B; Young, Peter; Gess, Burkhard

2017-07-01

Peripheral nerve myelination involves rapid production of tightly bound lipid layers requiring cholesterol biosynthesis and myelin protein expression, but also a collagen-containing extracellular matrix providing mechanical stability. In previous studies, we showed a function of ascorbic acid in peripheral nerve myelination and extracellular matrix formation in adult mice. Here, we sought the mechanism of action of ascorbic acid in peripheral nerve myelination using different paradigms of myelination in vivo and in vitro. We found impaired myelination and reduced collagen expression in Sodium-dependent Vitamin C Transporter 2 heterozygous mice (SVCT2 +/- ) during peripheral nerve development and after peripheral nerve injury. In dorsal root ganglion (DRG) explant cultures, hypo-myelination could be rescued by precoating with different collagen types. The activity of the ascorbic acid-dependent demethylating Ten-eleven-translocation (Tet) enzymes was reduced in ascorbic acid deprived and SVCT2 +/- DRG cultures. Further, in ascorbic acid-deprived DRG cultures, methylation of a CpG island in the collagen alpha1 (IV) and alpha2 (IV) bidirectional promoter region was increased compared to wild-type and ascorbic acid treated controls. Taken together, these results provide further evidence for the function of ascorbic acid in myelination and extracellular matrix formation in peripheral nerves and suggest a putative molecular mechanism of ascorbic acid function in Tet-dependent demethylation of collagen promoters. © 2017 Wiley Periodicals, Inc.

The sensitivity of glioma cells to pyropheophorbide-αmethyl ester-mediated photodynamic therapy is enhanced by inhibiting ABCG2.

PubMed

Pan, Li; Lin, Haidan; Tian, Si; Bai, Dingqun; Kong, Yuhan; Yu, Lehua

2017-09-01

To study the mechanisms of human glioblastoma cell resistance to methyl ester pyropheophorbide-a-mediated photodynamic therapy (MPPa-PDT) and the relationship between the cells and adenosine triphosphate-binding cassette superfamily G member 2 (ABCG2). The sensitivity of four human glioma cell lines (U87, A172, SHG-44, and U251) to MPPa-PDT was detected with a CCK-8 assay. Cell apoptosis, intracellular MPPa, and singlet oxygen were tested with flow cytometry. The mRNA and protein expression of ATP-binding cassette transporters (ABCG2, MRP1, and MDR1) were detected by PCR and Western blot, respectively. Both the sensitivity to MPPa-PDT and intracellular MPPa in A172 were the lowest among the four cell lines, while expression of ABCG2 mRNA and protein in A172 were the highest. The intracellular MPPa and ROS in A172 receiving MPPa-PDT significantly increased after using the ABCG2 inhibitor fumitremorgin C (FTC). Both cell viability and apoptosis in A172 cells undergoing MPPa-PDT were significantly improved with FTC. ABCG2 plays a significant role in the resistance of A172 to MPPa-PDT. Lasers Surg. Med. 49:719-726, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Short communication: The gain-of-function Y581S polymorphism of the ABCG2 transporter increases secretion into milk of danofloxacin at the therapeutic dose for mastitis treatment.

PubMed

Otero, J A; Barrera, B; de la Fuente, A; Prieto, J G; Marqués, M; Álvarez, A I; Merino, G

2015-01-01

The ATP-binding cassette transporter ABCG2 restricts the exposure of certain drugs and natural compounds in different tissues and organs. Its expression in the mammary gland is induced during lactation and is responsible for the active secretion of many compounds into milk, including antimicrobial agents. This particular function of ABCG2 may affect drug efficacy against mastitis and the potential presence of drug residues in the milk. Previous in vitro and in vivo studies showed increased transport of several compounds, including fluoroquinolones, by the bovine ABCG2 Y581S polymorphism. Our main purpose was to study the potential effect of this bovine ABCG2 polymorphism on the secretion into milk of the antimicrobial danofloxacin administered at the therapeutic dose of 6mg/kg used for mastitis treatment. In addition, the effect of this polymorphism on the relative mRNA and protein levels of ABCG2 by quantitative real-time PCR and Western blot were studied. Danofloxacin 18% (6mg/kg) was administered to 6 Y/Y homozygous and 5 Y/S heterozygous cows. Danofloxacin levels in milk and milk-to-plasma concentration ratios were almost 1.5- and 2-fold higher, respectively, in Y/S cows compared with the Y/Y cows, showing a higher capacity of this variant to transport danofloxacin into milk. Furthermore, the higher activity of this polymorphism is not linked to higher ABCG2 mRNA or protein levels. These results demonstrate the relevant effect of the Y581S polymorphism of the bovine ABCG2 transporter in the secretion into milk of danofloxacin after administration of 6mg/kg, with potentially important consequences for mastitis treatment and for milk residue handling. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Karanjin interferes with ABCB1, ABCC1, and ABCG2.

PubMed

Michaelis, Martin; Rothweiler, Florian; Nerreter, Thomas; Sharifi, Mohsen; Ghafourian, Taravat; Cinatl, Jindrich

2014-01-01

The prominent ATP-binding cassette (ABC) transporters ABCB1, ABCC1, and ABCG2 are involved in substance transport across physiological barriers and therefore in drug absorption, distribution, and elimination. They also mediate multi-drug resistance in cancer cells. Different flavonoids are known to interfere with different ABC transporters. Here, the effect of the furanoflavonol karanjin, a potential drug with antiglycaemic, gastroprotective, antifungal, and antibacterial effects, was investigated on ABCB1, ABCC1, and ABCG2-mediated drug transport in comparison to the flavonoids apigenin, genistein, and naringenin. Cells expressing the relevant transporters (ABCB1: UKF-NB-3(ABCB1), UKF-NB-3(r)VCR¹⁰; ABCC1: G62, PC-3(r)VCR²⁰; ABCG2: UKF-NB-3(ABCG2)) were used in combination with specific fluorescent and cytotoxic ABC transporter substrates and ABC transporter inhibitors to study ABC transporter function. Moreover, the effects of the investigated flavonoids were determined on the ABC transporter ATPase activities. Karanjin interfered with drug efflux mediated by ABCB1, ABCC1, and ABCG2 and enhanced the ATPase activity of all three transporters. Moreover, karanjin exerted more pronounced effects than the control flavonoids apigenin, genistein, and naringenin on all three transporters. Most notably, karanjin interfered with ABCB1 at low concentrations being about 1 µM. Taken together, these findings should be taken into account during further consideration of karanjin as a potential drug for different therapeutic indications. The effects on ABCB1, ABCC1, and ABCG2 may affect the pharmacokinetics of co-administered drugs.

Activation of Liver X Receptor Decreases Atherosclerosis in Ldlr−/− mice in the Absence of ABCA1 and ABCG1 in Myeloid Cells

PubMed Central

Kappus, Mojdeh S.; Murphy, Andrew J.; Abramowicz, Sandra; Ntonga, Vusisizwe; Welch, Carrie L.; Tall, Alan R.; Westerterp, Marit

2014-01-01

Objective Liver X Receptor (LXR) activators decrease atherosclerosis in mice. LXR activators (1) directly up-regulate genes involved in reverse cholesterol transport (RCT) and (2) exert anti-inflammatory effects mediated by transrepression of NFκB target genes. We investigated whether myeloid cell deficiency of ATP-binding cassette transporters A1 and G1 (ABCA1/G1), principal targets of LXR that promote macrophage cholesterol efflux and initiate RCT, would abolish the beneficial effects of LXR activation on atherosclerosis. Approach and Results LXR activator T0901317 (T0) substantially reduced inflammatory gene expression in macrophages lacking ABCA1/G1. Ldlr−/− mice were transplanted with Abca1−/−Abcg1−/− or wild-type bone marrow (BM) and fed a Western-type diet (WTD) for 6 weeks with or without T0 supplementation. Abca1/g1 BM deficiency increased atherosclerotic lesion complexity and inflammatory cell infiltration into the adventitia and myocardium. T0 markedly decreased lesion area, complexity and inflammatory cell infiltration in the Abca1−/−Abcg1−/− BM transplanted mice. To investigate whether this was due to macrophage Abca1/g1 deficiency, Ldlr−/− mice were transplanted with LysmCreAbca1fl/flAbcg1fl/fl or Abca1fl/flAbcg1fl/fl BM and fed WTD with or without the more specific LXR agonist GW3965 for 12 weeks. GW3965 decreased lesion size in both groups and the decrease was more prominent in the LysmCreAbca1fl/flAbcg1fl/fl group. Conclusions The results suggest that anti-inflammatory effects of LXR activators are of key importance to their anti-atherosclerotic effects in vivo independent of cholesterol efflux pathways mediated by macrophage ABCA1/G1. This has implications for the development of LXR activators that lack adverse effects on lipogenic genes while maintaining the ability to trans-repress inflammatory genes. PMID:24311381

CpG methylation at the USF binding site mediates cell-specific transcription of human ascorbate transporter SVCT2 exon 1a

PubMed Central

Qiao, Huan; May, James M.

2013-01-01

SVCT2 is the major transporter mediating vitamin C uptake in most organs. Its expression is driven by two promoters (CpG-poor exon 1a promoter and CpG-rich exon 1b promoter). In this work we mapped discrete elements within the proximal CpG-poor promoter responsible for the exon 1a transcription. We identified two E boxes for USF binding and one Y box for NF-Y binding. We further show that the formation of an NFY/USF complex on the exon 1a promoter amplifies each other's ability to bind to the promoter in a cooperativity-dependent manner and is absolutely required for the full activity of the exon 1a promoter. The analysis of the CpG site located at the upstream USF binding site in the promoter showed a strong correlation between expression and demethylation. It was also shown that the exon 1a transcription was induced in cell culture treated with demethylating agent decitabine. The specific methylation of this CpG site impaired both the binding of USF and the formation of the functional NF-Y/USF complex as well as promoter activity, suggesting its importance for the cell-specific transcription. Thus CpG methylation at the upstream USF binding site functions in establishing and maintaining cell-specific transcription from the CpG-poor SVCT2 exon 1a promoter. PMID:21770893

Lentivirus-ABCG1 instillation reduces lipid accumulation and improves lung compliance in GM-CSF knock-out mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malur, Anagha; Huizar, Isham; Wells, Greg

2011-11-18

Highlights: Black-Right-Pointing-Pointer Lentivirus-ABCG1 reduces lipid accumulation in lungs of GM-CSF knock-out mice. Black-Right-Pointing-Pointer Up-regulation of ABCG1 improves lung function. Black-Right-Pointing-Pointer Upregulation of ABCG1 improves surfactant metabolism. -- Abstract: We have shown decreased expression of the nuclear transcription factor, peroxisome proliferator-activated receptor-gamma (PPAR{gamma}) and the PPAR{gamma}-regulated ATP-binding cassette transporter G1 (ABCG1) in alveolar macrophages from patients with pulmonary alveolar proteinosis (PAP). PAP patients also exhibit neutralizing antibodies to granulocyte-macrophage colony stimulating factor (GM-CSF), an upregulator of PPAR{gamma}. In association with functional GM-CSF deficiency, PAP lung is characterized by surfactant-filled alveolar spaces and lipid-filled alveolar macrophages. Similar pathology characterizes GM-CSF knock-out (KO)more » mice. We reported previously that intratracheal instillation of a lentivirus (lenti)-PPAR{gamma} plasmid into GM-CSF KO animals elevated ABCG1 and reduced alveolar macrophage lipid accumulation. Here, we hypothesized that instillation of lenti-ABCG1 might be sufficient to decrease lipid accumulation and improve pulmonary function in GM-CSF KO mice. Animals received intratracheal instillation of lenti-ABCG1 or control lenti-enhanced Green Fluorescent Protein (eGFP) plasmids and alveolar macrophages were harvested 10 days later. Alveolar macrophage transduction efficiency was 79% as shown by lenti-eGFP fluorescence. Quantitative PCR analyses indicated a threefold (p = 0.0005) increase in ABCG1 expression with no change of PPAR{gamma} or ABCA1 in alveolar macrophages of lenti-ABCG1 treated mice. ABCG1 was unchanged in control lenti-eGFP and PBS-instilled groups. Oil Red O staining detected reduced intracellular neutral lipid in alveolar macrophages from lenti-ABCG1 treated mice. Extracellular cholesterol and phospholipids were also decreased as shown by analysis of bronchoalveolar lavage fluid. Lung compliance was diminished in untreated GMCSF KO mice but improved significantly after lenti-ABCG1 treatment. Data demonstrate that in vivo instillation of lenti-ABCG1 in GM-CSF KO mice is sufficient to restore pulmonary homeostasis by: (1) upregulating ABCG1; (2) reducing intra and extracellular lipids; and (3) improving lung function. Results suggest that the ABCG1 lipid transporter is the key downstream target of GM-CSF-induced PPAR{gamma} necessary for surfactant catabolism.« less

Hepatic Oval Cells Have the Side Population Phenotype Defined by Expression of ATP-Binding Cassette Transporter ABCG2/BCRP1

PubMed Central

Shimano, Koichi; Satake, Makoto; Okaya, Atsuhito; Kitanaka, Junichi; Kitanaka, Nobue; Takemura, Motohiko; Sakagami, Masafumi; Terada, Nobuyuki; Tsujimura, Tohru

2003-01-01

Organ-specific stem cells can be identified by the side population (SP) phenotype, which is defined by the property to effectively exclude the Hoechst 33342 dye. The ATP-binding cassette transporter ABCG2/BCRP1 mediates the SP phenotype. Because hepatic oval cells possess several characteristics of stem cells, we examined whether they have the SP phenotype using the 2-acetylaminofluorene/partial hepatectomy (PH) model. Fluorescence-activated cell sorting analysis showed that a population of non-parenchymal cells containing oval cells, prepared on day 7 after PH, carried a significant number of SP cells, whereas that of non-parenchymal cells without oval cells, prepared on day 0 after PH, did not. Northern blot analysis using total liver RNA obtained on various days after PH showed that the expression of ABCG2/BCRP1 mRNA increased after PH, reaching the highest level on day 7, and then gradually decreased. This pattern of changes in the ABCG2/BCRP1 mRNA level was well correlated to that in the number of oval cells. Furthermore, in situ hybridization revealed that oval cells were the sites of expression of ABCG2/BCRP1 mRNA. These results indicate that oval cells have the SP phenotype defined by expression of ABCG2/BCRP1, suggesting that oval cells may represent stem cells in the liver. PMID:12819005

The cytosolic Fe-S cluster assembly component MET18 is required for the full enzymatic activity of ROS1 in active DNA demethylation.

PubMed

Wang, Xiaokang; Li, Qi; Yuan, Wei; Cao, Zhendong; Qi, Bei; Kumar, Suresh; Li, Yan; Qian, Weiqiang

2016-05-19

DNA methylation patterns in plants are dynamically regulated by DNA methylation and active DNA demethylation in response to both environmental changes and development of plant. Beginning with the removal of methylated cytosine by ROS1/DME family of 5-methylcytosine DNA glycosylases, active DNA demethylation in plants occurs through base excision repair. So far, many components involved in active DNA demethylation remain undiscovered. Through a forward genetic screening of Arabidopsis mutants showing DNA hypermethylation at the EPF2 promoter region, we identified the conserved iron-sulfur cluster assembly protein MET18. MET18 dysfunction caused DNA hypermethylation at more than 1000 loci as well as the silencing of reporter genes and some endogenous genes. MET18 can directly interact with ROS1 in vitro and in vivo. ROS1 activity was reduced in the met18 mutant plants and point mutation in the conserved Fe-S cluster binding motif of ROS1 disrupted its biological function. Interestingly, a large number of DNA hypomethylated loci, especially in the CHH context, were identified from the met18 mutants and most of the hypo-DMRs were from TE regions. Our results suggest that MET18 can regulate both active DNA demethylation and DNA methylation pathways in Arabidopsis.

The cytosolic Fe-S cluster assembly component MET18 is required for the full enzymatic activity of ROS1 in active DNA demethylation

PubMed Central

Wang, Xiaokang; Li, Qi; Yuan, Wei; Cao, Zhendong; Qi, Bei; Kumar, Suresh; Li, Yan; Qian, Weiqiang

2016-01-01

DNA methylation patterns in plants are dynamically regulated by DNA methylation and active DNA demethylation in response to both environmental changes and development of plant. Beginning with the removal of methylated cytosine by ROS1/DME family of 5-methylcytosine DNA glycosylases, active DNA demethylation in plants occurs through base excision repair. So far, many components involved in active DNA demethylation remain undiscovered. Through a forward genetic screening of Arabidopsis mutants showing DNA hypermethylation at the EPF2 promoter region, we identified the conserved iron-sulfur cluster assembly protein MET18. MET18 dysfunction caused DNA hypermethylation at more than 1000 loci as well as the silencing of reporter genes and some endogenous genes. MET18 can directly interact with ROS1 in vitro and in vivo. ROS1 activity was reduced in the met18 mutant plants and point mutation in the conserved Fe-S cluster binding motif of ROS1 disrupted its biological function. Interestingly, a large number of DNA hypomethylated loci, especially in the CHH context, were identified from the met18 mutants and most of the hypo-DMRs were from TE regions. Our results suggest that MET18 can regulate both active DNA demethylation and DNA methylation pathways in Arabidopsis. PMID:27193999

Dynamics and biological relevance of DNA demethylation in Arabidopsis antibacterial defense.

PubMed

Yu, Agnès; Lepère, Gersende; Jay, Florence; Wang, Jingyu; Bapaume, Laure; Wang, Yu; Abraham, Anne-Laure; Penterman, Jon; Fischer, Robert L; Voinnet, Olivier; Navarro, Lionel

2013-02-05

DNA methylation is an epigenetic mark that silences transposable elements (TEs) and repeats. Whereas the establishment and maintenance of DNA methylation are relatively well understood, little is known about their dynamics and biological relevance in plant and animal innate immunity. Here, we show that some TEs are demethylated and transcriptionally reactivated during antibacterial defense in Arabidopsis. This effect is correlated with the down-regulation of key transcriptional gene silencing factors and is partly dependent on an active demethylation process. DNA demethylation restricts multiplication and vascular propagation of the bacterial pathogen Pseudomonas syringae in leaves and, accordingly, some immune-response genes, containing repeats in their promoter regions, are negatively regulated by DNA methylation. This study provides evidence that DNA demethylation is part of a plant-induced immune response, potentially acting to prime transcriptional activation of some defense genes linked to TEs/repeats.

Population-specific association between ABCG2 variants and tophaceous disease in people with gout.

PubMed

He, Wendy; Phipps-Green, Amanda; Stamp, Lisa K; Merriman, Tony R; Dalbeth, Nicola

2017-03-07

Tophi contribute to musculoskeletal disability, joint damage and poor health-related quality of life in people with gout. The aim of this study was to examine the role of SLC2A9 and ABCG2 variants in tophaceous disease in people with gout. Participants (n = 1778) with gout fulfilling the 1977 American Rheumatism Association (ARA) classification criteria, who were recruited from primary and secondary care, attended a detailed study visit. The presence of palpable tophi was recorded. SLC2A9 rs11942223, ABCG2 rs2231142 and ABCG2 rs10011796 were genotyped. Data were analysed according to tophus status. Compared to participants without tophi, those with tophi were older, had longer disease duration and higher serum creatinine, and were more likely to be of Māori or Pacific (Polynesian) ancestry. SLC2A9 rs11942223 was not associated with tophi. However, the risk alleles for both ABCG2 single nucleotide polymorphisms (SNPs) were present more frequently in those with tophi (OR (95% CI) 1.24 (1.02-1.51) for rs2231142 and 1.33 (1.01-1.74) for rs10011796, p < 0.05 for both). The effect of rs2231142 was limited to participants of Māori or Pacific ancestry (OR 1.50 (1.14-1.99), p = 0.004), with a significant effect observed in those of Western Polynesian ancestry only (OR 1.71 (1.07-2.72), p = 0.017). The rs10011796 risk allele was strongly associated with tophi in the Western Polynesian group (OR 3.76 (1.61-8.77), p = 0.002), but not in the Eastern Polynesian group (OR 0.87 (0.52-1.46), p = 0.60) nor in the non-Polynesian group (OR 1.16 (0.81-1.66), p = 0.32). The ABCG2 associations persisted in the Western Polynesian group after adjusting for serum urate, creatinine, and disease duration, and when including both ABCG2 variants in the regression models. Variation in ABCG2 function may play a role in the development of tophaceous disease in some populations with high prevalence of severe gout.

Abcb1a but not Abcg2 played a predominant role in limiting the brain distribution of Huperzine A in mice.

PubMed

Li, Jiajun; Yue, Mei; Zhou, Dandan; Wang, Meiyu; Zhang, Hongjian

2017-09-01

Huperzine A has been used for improving symptoms of Alzheimer's disease. Its cholinergic side effect is thought to be an exaggerated pharmacological outcome linked to its high brain or CNS concentrations. Although Huperzine A is brain penetrable, its interaction with efflux transporters (ABCB1 and ABCG2) has not been fully investigated. The aim of the present study was to characterize roles of ABCB1 and ABCG2 in the transmembrane transport of Huperzine A and identify a rate limiting step in its brain distribution. Data obtained from stably transfected MDCK II cells showed that Huperzine A is a substrate of ABCB1 but not ABCG2. ABCB1 inhibitors significantly inhibited ABCB1 mediated efflux of Huperzine A. In Abcb1a -/- mice, the brain to plasma concentration ratio of Huperzine A was significantly increased as compared to the wild type mice, while there were no obvious differences between the wild type and Abcg2 -/- mice. Taken together, the present study demonstrated that ABCB1 but not ABCG2 played a predominant role in the efflux of Huperzine A across BBB. The current finding is clinically relevant as changes in ABCB1 activity in the presence of ABCB1 inhibitors or genetic polymorphism may affect efficacy and safety of Huperzine A. Copyright © 2017 Elsevier Ltd. All rights reserved.

Activation of liver X receptor decreases atherosclerosis in Ldlr⁻/⁻ mice in the absence of ATP-binding cassette transporters A1 and G1 in myeloid cells.

PubMed

Kappus, Mojdeh S; Murphy, Andrew J; Abramowicz, Sandra; Ntonga, Vusisizwe; Welch, Carrie L; Tall, Alan R; Westerterp, Marit

2014-02-01

Liver X receptor (LXR) activators decrease atherosclerosis in mice. LXR activators (1) directly upregulate genes involved in reverse cholesterol transport and (2) exert anti-inflammatory effects mediated by transrepression of nuclear factor-κB target genes. We investigated whether myeloid cell deficiency of ATP-binding cassette transporters A1 and G1 (ABCA1/G1), principal targets of LXR that promote macrophage cholesterol efflux and initiate reverse cholesterol transport, would abolish the beneficial effects of LXR activation on atherosclerosis. LXR activator T0901317 substantially reduced inflammatory gene expression in macrophages lacking ABCA1/G1. Ldlr(-/-) mice were transplanted with Abca1(-/-)Abcg1(-/-) or wild-type bone marrow (BM) and fed a Western-type diet for 6 weeks with or without T0901317 supplementation. Abca1/g1 BM deficiency increased atherosclerotic lesion complexity and inflammatory cell infiltration into the adventitia and myocardium. T0901317 markedly decreased lesion area, complexity, and inflammatory cell infiltration in the Abca1(-/-)Abcg1(-/-) BM-transplanted mice. To investigate whether this was because of macrophage Abca1/g1 deficiency, Ldlr(-/-) mice were transplanted with LysmCreAbca1(fl/fl)Abcg1(fl/fl) or Abca1(fl/fl)Abcg1(fl/fl) BM and fed Western-type diet with or without the more specific LXR agonist GW3965 for 12 weeks. GW3965 decreased lesion size in both groups, and the decrease was more prominent in the LysmCreAbca1(fl/fl)Abcg1(fl/fl) group. The results suggest that anti-inflammatory effects of LXR activators are of key importance to their antiatherosclerotic effects in vivo independent of cholesterol efflux pathways mediated by macrophage ABCA1/G1. This has implications for the development of LXR activators that lack adverse effects on lipogenic genes while maintaining the ability to transrepress inflammatory genes.

Evidence of progenitor cells in the adult human cochlea: sphere formation and identification of ABCG2.

PubMed

Massucci-Bissoli, Milene; Lezirovitz, Karina; Oiticica, Jeanne; Bento, Ricardo Ferreira

2017-11-01

The aim of this study was to search for evidence of stem or progenitor cells in the adult human cochlea by testing for sphere formation capacity and the presence of the stem cell marker ABCG2. Cochleas removed from patients undergoing vestibular schwannoma resection (n=2) and from brain-dead organ donors (n=4) were dissociated for either flow cytometry analysis for the stem cell marker ABCG2 or a sphere formation assay that is widely used to test the sphere-forming capacity of cells from mouse inner ear tissue. Spheres were identified after 2-5 days in vitro, and the stem cell marker ABCG2 was detected using flow cytometric analysis after cochlear dissociation. Evidence suggests that there may be progenitor cells in the adult human cochlea, although further studies are required.

The Inhibitor Ko143 Is Not Specific for ABCG2.

PubMed

Weidner, Lora D; Zoghbi, Sami S; Lu, Shuiyu; Shukla, Suneet; Ambudkar, Suresh V; Pike, Victor W; Mulder, Jan; Gottesman, Michael M; Innis, Robert B; Hall, Matthew D

2015-09-01

Imaging ATP-binding cassette (ABC) transporter activity in vivo with positron emission tomography requires both a substrate and a transporter inhibitor. However, for ABCG2, there is no inhibitor proven to be specific to that transporter alone at the blood-brain barrier. Ko143 [[(3S,6S,12aS)-1,2,3,4,6,7,12,12a-octahydro-9-methoxy-6-(2-methylpropyl)-1,4-dioxopyrazino[1',2':1,6]pyrido[3,4- b]indole-3-propanoic acid 1,1-dimethylethyl ester], a nontoxic analog of fungal toxin fumitremorgin C, is a potent inhibitor of ABCG2, although its specificity in mouse and human systems is unclear. This study examined the selectivity of Ko143 using human embryonic kidney cell lines transfected with ABCG2, ABCB1, or ABCC1 in several in vitro assays. The stability of Ko143 in rat plasma was measured using high performance liquid chromatography. Our results show that, in addition to being a potent inhibitor of ABCG2, at higher concentrations (≥1 μM) Ko143 also has an effect on the transport activity of both ABCB1 and ABCC1. Furthermore, Ko143 was found to be unstable in rat plasma. These findings indicate that Ko143 lacks specificity for ABCG2 and this should be taken into consideration when using Ko143 for both in vitro and in vivo experiments. U.S. Government work not protected by U.S. copyright.

Arctigenin promotes cholesterol efflux from THP-1 macrophages through PPAR-γ/LXR-α signaling pathway.

PubMed

Xu, Xiaolin; Li, Qian; Pang, Liewen; Huang, Guoqian; Huang, Jiechun; Shi, Meng; Sun, Xiaotian; Wang, Yiqing

2013-11-15

Cholesterol efflux from macrophages is a critical mechanism to prevent the development of atherosclerosis. Here, we sought to investigate the effects of arctigenin, a bioactive component of Arctium lappa, on the cholesterol efflux in oxidized low-density lipoprotein (oxLDL)-loaded THP-1 macrophages. Our data showed that arctigenin significantly accelerated apolipoprotein A-I- and high-density lipoprotein-induced cholesterol efflux in both dose- and time-dependent manners. Moreover, arctigenin treatment enhanced the expression of ATP binding cassette transporter A1 (ABCA1), ABCG1, and apoE, all of which are key molecules in the initial step of cholesterol efflux, at both mRNA and protein levels. Arctigenin also caused a concentration-dependent elevation in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and liver X receptor-alpha (LXR-α). The arctigenin-mediated induction of ABCA1, ABCG1, and apoE was abolished by specific inhibition of PPAR-γ or LXR-α using small interfering RNA technology. Our results collectively indicate that arctigenin promotes cholesterol efflux in oxLDL-loaded THP-1 macrophages through upregulation of ABCA1, ABCG1 and apoE, which is dependent on the enhanced expression of PPAR-γ and LXR-α. Copyright © 2013 Elsevier Inc. All rights reserved.

Estrogen Enhances the Expression of the Multidrug Transporter Gene ABCG2-Increasing Drug Resistance of Breast Cancer Cells through Estrogen Receptors.

PubMed

Chang, Fung-Wei; Fan, Hueng-Chuen; Liu, Jui-Ming; Fan, Tai-Ping; Jing, Jin; Yang, Chia-Ling; Hsu, Ren-Jun

2017-01-14

Multidrug resistance is a major obstacle in the successful therapy of breast cancer. Studies have proved that this kind of drug resistance happens in both human cancers and cultured cancer cell lines. Understanding the molecular mechanisms of drug resistance is important for the reasonable design and use of new treatment strategies to effectively confront cancers. In our study, ATP-binding cassette sub-family G member 2 (ABCG2), adenosine triphosphate (ATP) synthase and cytochrome c oxidase subunit VIc (COX6C) were over-expressed more in the MCF-7/MX cell line than in the normal MCF7 cell line. Therefore, we believe that these three genes increase the tolerance of MCF7 to mitoxantrone (MX). The data showed that the high expression of COX6C made MCF-7/MX have more stable on mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) expression than normal MCF7 cells under hypoxic conditions. The accumulation of MX was greater in the ATP-depleted treatment MCF7/MX cells than in normal MCF7/MX cells. Furthermore, E2 increased the tolerance of MCF7 cells to MX through inducing the expression of ABCG2. However, E2 could not increase the expression of ABCG2 after the inhibition of estrogen receptor α (ERα) in MCF7 cells. According to the above data, under the E2 treatment, MDA-MB231, which lacks ER, had a higher sensitivity to MX than MCF7 cells. E2 induced the expression of ABCG2 through ERα and the over-expressed ABCG2 made MCF7 more tolerant to MX. Moreover, the over-expressed ATP synthase and COX6c affected mitochondrial genes and function causing the over-expressed ABCG2 cells pumped out MX in a concentration gradient from the cell matrix. Finally lead to chemoresistance.

Estrogen Enhances the Expression of the Multidrug Transporter Gene ABCG2—Increasing Drug Resistance of Breast Cancer Cells through Estrogen Receptors

PubMed Central

Chang, Fung-Wei; Fan, Hueng-Chuen; Liu, Jui-Ming; Fan, Tai-Ping; Jing, Jin; Yang, Chia-Ling; Hsu, Ren-Jun

2017-01-01

Background: Multidrug resistance is a major obstacle in the successful therapy of breast cancer. Studies have proved that this kind of drug resistance happens in both human cancers and cultured cancer cell lines. Understanding the molecular mechanisms of drug resistance is important for the reasonable design and use of new treatment strategies to effectively confront cancers. Results: In our study, ATP-binding cassette sub-family G member 2 (ABCG2), adenosine triphosphate (ATP) synthase and cytochrome c oxidase subunit VIc (COX6C) were over-expressed more in the MCF-7/MX cell line than in the normal MCF7 cell line. Therefore, we believe that these three genes increase the tolerance of MCF7 to mitoxantrone (MX). The data showed that the high expression of COX6C made MCF-7/MX have more stable on mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) expression than normal MCF7 cells under hypoxic conditions. The accumulation of MX was greater in the ATP-depleted treatment MCF7/MX cells than in normal MCF7/MX cells. Furthermore, E2 increased the tolerance of MCF7 cells to MX through inducing the expression of ABCG2. However, E2 could not increase the expression of ABCG2 after the inhibition of estrogen receptor α (ERα) in MCF7 cells. According to the above data, under the E2 treatment, MDA-MB231, which lacks ER, had a higher sensitivity to MX than MCF7 cells. Conclusions: E2 induced the expression of ABCG2 through ERα and the over-expressed ABCG2 made MCF7 more tolerant to MX. Moreover, the over-expressed ATP synthase and COX6c affected mitochondrial genes and function causing the over-expressed ABCG2 cells pumped out MX in a concentration gradient from the cell matrix. Finally lead to chemoresistance. PMID:28098816

ABCA1, ABCG1, and ABCG4 are distributed to distinct membrane meso-domains and disturb detergent-resistant domains on the plasma membrane.

PubMed

Sano, Osamu; Ito, Shiho; Kato, Reiko; Shimizu, Yuji; Kobayashi, Aya; Kimura, Yasuhisa; Kioka, Noriyuki; Hanada, Kentaro; Ueda, Kazumitsu; Matsuo, Michinori

2014-01-01

ATP-binding cassette A1 (ABCA1), ABCG1, and ABCG4 are lipid transporters that mediate the efflux of cholesterol from cells. To analyze the characteristics of these lipid transporters, we examined and compared their distributions and lipid efflux activity on the plasma membrane. The efflux of cholesterol mediated by ABCA1 and ABCG1, but not ABCG4, was affected by a reduction of cellular sphingomyelin levels. Detergent solubility and gradient density ultracentrifugation assays indicated that ABCA1, ABCG1, and ABCG4 were distributed to domains that were solubilized by Triton X-100 and Brij 96, resistant to Triton X-100 and Brij 96, and solubilized by Triton X-100 but resistant to Brij 96, respectively. Furthermore, ABCG1, but not ABCG4, was colocalized with flotillin-1 on the plasma membrane. The amounts of cholesterol extracted by methyl-β-cyclodextrin were increased by ABCA1, ABCG1, or ABCG4, suggesting that cholesterol in non-raft domains was increased. Furthermore, ABCG1 and ABCG4 disturbed the localization of caveolin-1 to the detergent-resistant domains and the binding of cholera toxin subunit B to the plasma membrane. These results suggest that ABCA1, ABCG1, and ABCG4 are localized to distinct membrane meso-domains and disturb the meso-domain structures by reorganizing lipids on the plasma membrane; collectively, these observations may explain the different substrate profiles and lipid efflux roles of these transporters.

Cellular Localization and Trafficking of the Human ABCG1 Transporter

PubMed Central

Neufeld, Edward B.; O’Brien, Katherine; Walts, Avram D.; Stonik, John A.; Demosky, Steven J.; Malide, Daniela; Combs, Christian A.; Remaley, Alan T.

2014-01-01

We have developed a suitable heterologous cell expression system to study the localization, trafficking, and site(s) of function of the human ABCG1 transporter. Increased plasma membrane (PM) and late endosomal (LE) cholesterol generated by ABCG1 was removed by lipoproteins and liposomes, but not apoA-I. Delivery of ABCG1 to the PM and LE was required for ABCG1-mediated cellular cholesterol efflux. ABCG1 LEs frequently contacted the PM, providing a collisional mechanism for transfer of ABCG1-mobilized cholesterol, similar to ABCG1-mediated PM cholesterol efflux to lipoproteins. ABCG1-mobilized LE cholesterol also trafficked to the PM by a non-vesicular pathway. Transfer of ABCG1-mobilized cholesterol from the cytoplasmic face of LEs to the PM and concomitant removal of cholesterol from the outer leaflet of the PM bilayer by extracellular acceptors suggests that ABCG1 mobilizes cholesterol on both sides of the lipid bilayer for removal by acceptors. ABCG1 increased uptake of HDL into LEs, consistent with a potential ABCG1-mediated cholesterol efflux pathway involving HDL resecretion. Thus, ABCG1 at the PM mobilizes PM cholesterol and ABCG1 in LE/LYS generates mobile pools of cholesterol that can traffic by both vesicular and non-vesicular pathways to the PM where it can also be transferred to extracellular acceptors with a lipid surface. PMID:25405320

REPRESSOR OF SILENCING5 Encodes a Member of the Small Heat Shock Protein Family and Is Required for DNA Demethylation in Arabidopsis[C][W

PubMed Central

Zhao, Yusheng; Xie, Shaojun; Li, Xiaojie; Wang, Chunlei; Chen, Zhongzhou; Lai, Jinsheng; Gong, Zhizhong

2014-01-01

In Arabidopsis thaliana, active DNA demethylation is initiated by the DNA glycosylase REPRESSOR OF SILENCING1 (ROS1) and its paralogs DEMETER, DEMETER-LIKE2 (DML2), and DML3. How these demethylation enzymes are regulated, however, is poorly understood. Here, using a transgenic Arabidopsis line harboring the stress-inducible RESPONSIVE TO DEHYDRATION29A (RD29A) promoter–LUCIFERASE (LUC) reporter gene and the cauliflower mosaic virus 35S promoter (35S)–NEOMYCIN PHOSPHOTRANSFERASE II (NPTII) antibiotic resistance marker gene, we characterize a ROS locus, ROS5, that encodes a protein in the small heat shock protein family. ROS5 mutations lead to the silencing of the 35S-NPTII transgene due to DNA hypermethylation but do not affect the expression of the RD29A-LUC transgene. ROS5 physically interacts with the histone acetyltransferase ROS4/INCREASED DNA METHYLATION1 (IDM1) and is required to prevent the DNA hypermethylation of some genes that are also regulated by ROS1 and IDM1. We propose that ROS5 regulates DNA demethylation by interacting with IDM1, thereby creating a chromatin environment that facilitates the binding of ROS1 to erase DNA methylation. PMID:24920332

PDK2 and ABCG2 genes polymorphisms are correlated with blood glucose levels and uric acid in Tibetan gout patients.

PubMed

Ren, Y C; Jin, T B; Sun, X D; Geng, T T; Zhang, M X; Wang, L; Feng, T; Kang, L L; Chen, C

2016-02-11

Previous studies have shown that the PDK2 and ABCG2 genes play important roles in many aspects of gout development in European populations. However, a detailed genotype-phenotype analysis was not performed. The aim of the present study was to investigate the potential association between variants in these two genes and metabolism-related quantitative phenotypes relevant to gout in a Chinese Tibetan population. In total, 316 Chinese Tibetan gout patients were recruited from rheumatology outpatient clinics and 6 single nucleotide polymorphisms in PDK2 and ABCG2 were genotyped, which were possible etiologic variants as identified in the HapMap Chinese Han Beijing population. A significant difference in blood glucose levels was detected between different genotypes of rs2728109 (P = 0.005) in the PDK2 gene. We also detected a significant difference in the mean serum uric levels between different genotypes of rs3114018 (P = 0.004) in the ABCG2 gene. All P values remained significant after Bonferroni's correction for multiple testing. Our data demonstrate potential roles for PDK2 and ABCG2 polymorphisms in the metabolic phenotypes of Tibetan gout patients, which may provide new insights into the etiology of gout. Further studies are required to confirm these findings.

Promoter hypermethylation and downregulation of the FAS gene may be involved in colorectal carcinogenesis

PubMed Central

MANOOCHEHRI, MEHDI; BORHANI, NASIM; KARBASI, ASHRAF; KOOCHAKI, AMENEH; KAZEMI, BAHRAM

2016-01-01

Aberrant DNA methylation has been investigated in carcinogenesis and as biomarker for the early detection of colorectal cancer (CRC). The present study aimed to define the methylation status in the regulatory elements of two proapoptotic genes, Fas cell surface death receptor (FAS) and BCL2-associated X protein (BAX). DNA methylation analysis was performed in tumor and adjacent normal tissue using HpaII/MspI restriction digestion and methylation-specific polymerase chain reaction (PCR). The results observed downregulation of the FAS and BAX genes in the CRC tissues compared with the adjacent normal samples. Furthermore, demethylation using 5-aza-2′-deoxycytidine treatment followed by reverse-transcription quantitative PCR were performed on the HT-29 cell line to measure BAX and FAS mRNA expression following demethylation. The 5-aza-2′-deoxycytidine treatment resulted in significant FAS gene upregulation in the HT-29 cell line, but no significant difference in BAX expression. Furthermore, analysis of CpG islands in the FAS gene promoter revealed that the FAS promoter was significantly hypermethylated in 53.3% of tumor tissues compared with adjacent normal samples. Taken together, the results indicate that decreased expression of the FAS gene due to hypermethylation of its promoter may lead to apoptotic resistance, and acts as an important step during colorectal carcinogenesis. PMID:27347139

Promoter hypermethylation and downregulation of the FAS gene may be involved in colorectal carcinogenesis.

PubMed

Manoochehri, Mehdi; Borhani, Nasim; Karbasi, Ashraf; Koochaki, Ameneh; Kazemi, Bahram

2016-07-01

Aberrant DNA methylation has been investigated in carcinogenesis and as biomarker for the early detection of colorectal cancer (CRC). The present study aimed to define the methylation status in the regulatory elements of two proapoptotic genes, Fas cell surface death receptor (FAS) and BCL2-associated X protein (BAX). DNA methylation analysis was performed in tumor and adjacent normal tissue using Hpa II/ Msp I restriction digestion and methylation-specific polymerase chain reaction (PCR). The results observed downregulation of the FAS and BAX genes in the CRC tissues compared with the adjacent normal samples. Furthermore, demethylation using 5-aza-2'-deoxycytidine treatment followed by reverse-transcription quantitative PCR were performed on the HT-29 cell line to measure BAX and FAS mRNA expression following demethylation. The 5-aza-2'-deoxycytidine treatment resulted in significant FAS gene upregulation in the HT-29 cell line, but no significant difference in BAX expression. Furthermore, analysis of CpG islands in the FAS gene promoter revealed that the FAS promoter was significantly hypermethylated in 53.3% of tumor tissues compared with adjacent normal samples. Taken together, the results indicate that decreased expression of the FAS gene due to hypermethylation of its promoter may lead to apoptotic resistance, and acts as an important step during colorectal carcinogenesis.

ABCA1, ABCG1, and ABCG4 Are Distributed to Distinct Membrane Meso-Domains and Disturb Detergent-Resistant Domains on the Plasma Membrane

PubMed Central

Sano, Osamu; Ito, Shiho; Kato, Reiko; Shimizu, Yuji; Kobayashi, Aya; Kimura, Yasuhisa; Kioka, Noriyuki; Hanada, Kentaro; Ueda, Kazumitsu; Matsuo, Michinori

2014-01-01

ATP-binding cassette A1 (ABCA1), ABCG1, and ABCG4 are lipid transporters that mediate the efflux of cholesterol from cells. To analyze the characteristics of these lipid transporters, we examined and compared their distributions and lipid efflux activity on the plasma membrane. The efflux of cholesterol mediated by ABCA1 and ABCG1, but not ABCG4, was affected by a reduction of cellular sphingomyelin levels. Detergent solubility and gradient density ultracentrifugation assays indicated that ABCA1, ABCG1, and ABCG4 were distributed to domains that were solubilized by Triton X-100 and Brij 96, resistant to Triton X-100 and Brij 96, and solubilized by Triton X-100 but resistant to Brij 96, respectively. Furthermore, ABCG1, but not ABCG4, was colocalized with flotillin-1 on the plasma membrane. The amounts of cholesterol extracted by methyl-β-cyclodextrin were increased by ABCA1, ABCG1, or ABCG4, suggesting that cholesterol in non-raft domains was increased. Furthermore, ABCG1 and ABCG4 disturbed the localization of caveolin-1 to the detergent-resistant domains and the binding of cholera toxin subunit B to the plasma membrane. These results suggest that ABCA1, ABCG1, and ABCG4 are localized to distinct membrane meso-domains and disturb the meso-domain structures by reorganizing lipids on the plasma membrane; collectively, these observations may explain the different substrate profiles and lipid efflux roles of these transporters. PMID:25302608

Imatinib-mediated inactivation of Akt regulates ABCG2 function in head and neck squamous cell carcinoma.

PubMed

Chu, Theresa S; Chen, Jocelyn S; Lopez, Jay Patrick; Pardo, Francisco S; Aguilera, Joseph; Ongkeko, Weg M

2008-09-01

To investigate whether the mechanism for the reversal of ABCG2 (also known as ABCP, MXR, and BCRP)-mediated drug resistance by imatinib mesylate (Gleevec, STI571; Novartis Pharmaceuticals Corp, East Hanover, New Jersey) is caused by the downregulation of Akt kinase. The adenosine triphosphatase-binding cassette protein ABCG2 has been suggested to be involved in the resistance against various anticancer drugs. Recent studies show that imatinib reverses ABCG2-mediated drug resistance to topotecan hydrochloride and SN-38. In addition, we have previously reported that imatinib downregulates Akt kinase activity, which is elevated in head and neck squamous cell carcinoma. Flow cytometric analysis was used to determine the levels of drug or dye extrusion from the cells. We used Akt kinase inhibitors, transfection with short interfering RNA (siRNA) Akt, and the tyrosine kinase inhibitor imatinib to show that these treatments decreased the side population by 50% to 70% in Hoechst 33342 extrusion studies. Doxorubicin hydrochloride extrusion experiments also demonstrated 20% to 26% decrease in doxorubicin efflux on cells treated with imatinib, 1L6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate, and transfection with siRNA Akt. With Western blot and immunofluorescence experiments, our data suggest that ABCG2 translocation is the mechanism by which imatinib and Akt regulate drug resistance. Clonogenic survival assays performed with imatinib-treated cells resulted in a dose-dependent decrease in cell survival compared with the control population. Our findings demonstrate that imatinib confers greater doxorubicin retention, presumably via inhibition of Akt, which regulates ABCG2 function.

Overexpression of Tet3 in donor cells enhances goat somatic cell nuclear transfer efficiency.

PubMed

Han, Chengquan; Deng, Ruizhi; Mao, Tingchao; Luo, Yan; Wei, Biao; Meng, Peng; Zhao, Lu; Zhang, Qing; Quan, Fusheng; Liu, Jun; Zhang, Yong

2018-05-23

Ten-eleven translocation 3 (TET3) mediates active DNA demethylation of paternal genomes during mouse embryonic development. However, the mechanism of DNA demethylation in goat embryos remains unknown. In addition, aberrant DNA methylation reprogramming prevalently occurs in embryos cloned by somatic cell nuclear transfer (SCNT). In this study, we reported that TET3 is a key factor in DNA demethylation in goat pre-implantation embryos. Knockdown of Tet3 hindered DNA demethylation at the two- to four-cell stage in goat embryos and decreased Nanog expression in blastocysts. Overexpression of Tet3 in somatic cells can initiate DNA demethylation, reduce 5-methylcytosine level, increase 5-hydroxymethylcytosine level and promote the expression of key pluripotency genes. After SCNT, overexpression of Tet3 in donor cells corrected abnormal DNA hypermethylation of cloned embryos and significantly enhanced in vitro and in vivo developmental rate (P < 0.05). We conclude that overexpression of Tet3 in donor cells significantly improves goat SCNT efficiency. © 2018 Federation of European Biochemical Societies.

Functional non-synonymous variants of ABCG2 and gout risk.

PubMed

Stiburkova, Blanka; Pavelcova, Katerina; Zavada, Jakub; Petru, Lenka; Simek, Pavel; Cepek, Pavel; Pavlikova, Marketa; Matsuo, Hirotaka; Merriman, Tony R; Pavelka, Karel

2017-11-01

Common dysfunctional variants of ATP binding cassette subfamily G member 2 (Junior blood group) (ABCG2), a high-capacity urate transporter gene, that result in decreased urate excretion are major causes of hyperuricemia and gout. In the present study, our objective was to determine the frequency and effect on gout of common and rare non-synonymous and other functional allelic variants in the ABCG2 gene. The main cohort recruited from the Czech Republic consisted of 145 gout patients; 115 normouricaemic controls were used for comparison. We amplified, directly sequenced and analysed 15 ABCG2 exons. The associations between genetic variants and clinical phenotype were analysed using the t-test, Fisher's exact test and a logistic and linear regression approach. Data from a New Zealand Polynesian sample set and the UK Biobank were included for the p.V12M analysis. In the ABCG2 gene, 18 intronic (one dysfunctional splicing) and 11 exonic variants were detected: 9 were non-synonymous (2 common, 7 rare including 1 novel), namely p.V12M, p.Q141K, p.R147W, p.T153M, p.F373C, p.T434M, p.S476P, p.D620N and p.K360del. The p.Q141K (rs2231142) variant had a significantly higher minor allele frequency (0.23) in the gout patients compared with the European-origin population (0.09) and was significantly more common among gout patients than among normouricaemic controls (odds ratio = 3.26, P < 0.0001). Patients with non-synonymous allelic variants had an earlier onset of gout (42 vs 48 years, P = 0.0143) and a greater likelihood of a familial history of gout (41% vs 27%, odds ratio = 1.96, P = 0.053). In a meta-analysis p.V12M exerted a protective effect from gout (P < 0.0001). Genetic variants of ABCG2, common and rare, increased the risk of gout. Non-synonymous allelic variants of ABCG2 had a significant effect on earlier onset of gout and the presence of a familial gout history. ABCG2 should thus be considered a common and significant risk factor for gout. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Impact of ABCB1, ABCG2, and CYP3A5 polymorphisms on plasma trough concentrations of apixaban in Japanese patients with atrial fibrillation.

PubMed

Ueshima, Satoshi; Hira, Daiki; Fujii, Ryo; Kimura, Yuuma; Tomitsuka, Chiho; Yamane, Takuya; Tabuchi, Yohei; Ozawa, Tomoya; Itoh, Hideki; Horie, Minoru; Terada, Tomohiro; Katsura, Toshiya

2017-09-01

During anticoagulant therapy, major bleeding is one of the most severe adverse effects. This study aimed to evaluate the relationships between ABCB1, ABCG2, and CYP3A5 polymorphisms and plasma trough concentrations of apixaban, a direct inhibitor of coagulation factor X. A total of 70 plasma concentrations of apixaban from 44 Japanese patients with atrial fibrillation were analyzed. In these analyses, the plasma trough concentration/dose (C/D) ratio of apixaban was used as a pharmacokinetic index and all data were stratified according to the presence of ABCB1 (ABCB1 1236C>T, 2677G>T/A, and 3435C>T), ABCG2 (ABCG2 421C>A), and CYP3A5 (CYP3A5*3) polymorphisms. Influences of various clinical laboratory parameters (age, serum creatinine, estimated glomerular filtration rate, aspartate amino transferase, and alanine amino transferase) on the plasma trough C/D ratio of apixaban were included in analyses. Although no ABCB1 polymorphisms affected the plasma trough C/D ratio of apixaban, the plasma trough C/D ratio of apixaban was significantly higher in patients with the ABCG2 421A/A genotype than in patients with the ABCG2 421C/C genotype (P<0.01). The plasma trough C/D ratio of apixaban in patients with CYP3A5*1/*3 or *3/*3 genotypes was also significantly higher than that in patients with the CYP3A5*1/*1 genotype (P<0.05). Furthermore, the plasma trough C/D ratio of apixaban decreased with increased estimated glomerular filtration rate. These results indicate that ABCG2 421A/A and CYP3A5*3 genotypes and renal function are considered potential factors affecting trough concentrations of apixaban.

Association between ABCG1 polymorphism rs1893590 and high-density lipoprotein (HDL) in an asymptomatic Brazilian population.

PubMed

Zago, V H S; Scherrer, D Z; Parra, E S; Panzoldo, N B; Alexandre, F; Nakandakare, E R; Quintão, E C R; de Faria, E C

2015-03-01

ATP binding cassette transporter G1 (ABCG1) promotes lipidation of nascent high-density lipoprotein (HDL) particles, acting as an intracellular transporter. SNP rs1893590 (c.-204A > C) of ABCG1 gene has been previously studied and reported as functional over plasma HDL-C and lipoprotein lipase activity. This study aimed to investigate the relationships of SNP rs1893590 with plasma lipids and lipoproteins in a large Brazilian population. Were selected 654 asymptomatic and normolipidemic volunteers from both genders. Clinical and anthropometrical data were taken and blood samples were drawn after 12 h fasting. Plasma lipids and lipoproteins, as well as HDL particle size and volume were determined. Genomic DNA was isolated for SNP rs1893590 detection by TaqMan(®) OpenArray(®) Real-Time PCR Plataform (Applied Biosystems). Mann-Whitney U, Chi square and two-way ANOVA were the used statistical tests. No significant differences were found in the comparison analyses between the allele groups for all studied parameters. Conversely, significant interactions were observed between SNP and age over plasma HDL-C, were volunteers under 60 years with AA genotype had increased HDL-C (p = 0.048). Similar results were observed in the group with body mass index (BMI) < 25 kg/m(2), where volunteers with AA genotype had higher HDL-C levels (p = 0.0034), plus an increased HDL particle size (p = 0.01). These findings indicate that SNP rs1893590 of ABCG1 has a significant impact over HDL-C under asymptomatic clinical conditions in an age and BMI dependent way.

Abscisic Acid Transport and Homeostasis in the Context of Stomatal Regulation.

PubMed

Merilo, Ebe; Jalakas, Pirko; Laanemets, Kristiina; Mohammadi, Omid; Hõrak, Hanna; Kollist, Hannes; Brosché, Mikael

2015-09-01

The discovery of cytosolic ABA receptors is an important breakthrough in stomatal research; signaling via these receptors is involved in determining the basal stomatal conductance and stomatal responsiveness. However, the source of ABA in guard cells is still not fully understood. The level of ABA increases in guard cells by de novo synthesis, recycling from inactive conjugates via β-glucosidases BG1 and BG2 and by import, whereas it decreases by hydroxylation, conjugation, and export. ABA importers include the NRT1/PTR family protein AIT1, ATP-binding cassette protein ABCG40, and possibly ABCG22, whereas the DTX family member DTX50 and ABCG25 function as ABA exporters. Here, we review the proteins involved in ABA transport and homeostasis and their physiological role in stomatal regulation. Recent experiments suggest that functional redundancy probably exists among ABA transporters between vasculature and guard cells and ABA recycling proteins, as stomatal functioning remained intact in abcg22, abcg25, abcg40, ait1, and bg1bg2 mutants. Only the initial response to reduced air humidity was significantly delayed in abcg22. Considering the reports showing autonomous ABA synthesis in guard cells, we discuss that rapid stomatal responses to atmospheric factors might depend primarily on guard cell-synthesized ABA, whereas in the case of long-term soil water deficit, ABA synthesized in the vasculature might have a significant role. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

Functional Polymorphisms of the ABCG2 Gene Are Associated with Gout Disease in the Chinese Han Male Population

PubMed Central

Zhou, Danqiu; Liu, Yunqing; Zhang, Xinju; Gu, Xiaoye; Wang, Hua; Luo, Xinhua; Zhang, Jin; Zou, Hejian; Guan, Ming

2014-01-01

Background Gout is a common type of arthritis that is characterized by hyperuricemia, tophi and joint inflammation. Genetic variations in the ABCG2 gene have been reported to influence serum uric acid levels and to participate in the pathogenesis of gout, but no further data have been reported in the Han Chinese population. Methods Peripheral blood DNA was isolated from 352 male patients with gout and 350 gout-free normal male controls. High-resolution melting analysis and Sanger sequencing were performed to identify the genetic polymorphisms V12M, Q141K and Q126X in the ABCG2 gene. Genotype and haplotype analyses were utilized to determine the disease odds ratios (ORs). A prediction model for gout risk using ABCG2 protein function was established based on the genotype combination of Q126X and Q141K. Results For Q141K, the A allele frequency was 49.6% in the gout patients and 30.9% in the controls (OR 2.20, 95% confidence interval (CI): 1.77–2.74, p = 8.99 × 10−13). Regarding Q126X, the T allele frequency was 4.7% in the gout patients and 1.7% in the controls (OR 2.91, 95% CI: 1.49–5.68, p = 1.57 × 10−3). The A allele frequency for V12M was lower (18.3%) in the gout patients than in the controls (29%) (OR 0.55, 95% CI 0.43–0.71, p = 2.55 × 10−6). In the order of V12M, Q126X and Q141K, the GCA and GTC haplotypes indicated increased disease risk (OR = 2.30 and 2.71, respectively). Patients with mild to severe ABCG2 dysfunction accounted for 78.4% of gout cases. Conclusion The ABCG2 126X and 141K alleles are associated with an increased risk of gout, whereas 12M has a protective effect on gout susceptibility in the Han Chinese population. ABCG2 dysfunction can be used to evaluate gout risk. PMID:24857923

Functional polymorphisms of the ABCG2 gene are associated with gout disease in the Chinese Han male population.

PubMed

Zhou, Danqiu; Liu, Yunqing; Zhang, Xinju; Gu, Xiaoye; Wang, Hua; Luo, Xinhua; Zhang, Jin; Zou, Hejian; Guan, Ming

2014-05-22

Gout is a common type of arthritis that is characterized by hyperuricemia, tophi and joint inflammation. Genetic variations in the ABCG2 gene have been reported to influence serum uric acid levels and to participate in the pathogenesis of gout, but no further data have been reported in the Han Chinese population. Peripheral blood DNA was isolated from 352 male patients with gout and 350 gout-free normal male controls. High-resolution melting analysis and Sanger sequencing were performed to identify the genetic polymorphisms V12M, Q141K and Q126X in the ABCG2 gene. Genotype and haplotype analyses were utilized to determine the disease odds ratios (ORs). A prediction model for gout risk using ABCG2 protein function was established based on the genotype combination of Q126X and Q141K. For Q141K, the A allele frequency was 49.6% in the gout patients and 30.9% in the controls (OR 2.20, 95% confidence interval (CI): 1.77-2.74, p=8.99×10⁻¹³). Regarding Q126X, the T allele frequency was 4.7% in the gout patients and 1.7% in the controls (OR 2.91, 95% CI: 1.49-5.68, p=1.57×10⁻³). The A allele frequency for V12M was lower (18.3%) in the gout patients than in the controls (29%) (OR 0.55, 95% CI 0.43-0.71, p=2.55×10⁻⁶). In the order of V12M, Q126X and Q141K, the GCA and GTC haplotypes indicated increased disease risk (OR=2.30 and 2.71, respectively). Patients with mild to severe ABCG2 dysfunction accounted for 78.4% of gout cases. The ABCG2 126X and 141K alleles are associated with an increased risk of gout, whereas 12M has a protective effect on gout susceptibility in the Han Chinese population. ABCG2 dysfunction can be used to evaluate gout risk.

Clinically used selective estrogen receptor modulators affect different steps of macrophage-specific reverse cholesterol transport

PubMed Central

Fernández-Suárez, María E.; Escolà-Gil, Joan C.; Pastor, Oscar; Dávalos, Alberto; Blanco-Vaca, Francisco; Lasunción, Miguel A.; Martínez-Botas, Javier; Gómez-Coronado, Diego

2016-01-01

Selective estrogen receptor modulators (SERMs) are widely prescribed drugs that alter cellular and whole-body cholesterol homeostasis. Here we evaluate the effect of SERMs on the macrophage-specific reverse cholesterol transport (M-RCT) pathway, which is mediated by HDL. Treatment of human and mouse macrophages with tamoxifen, raloxifene or toremifene induced the accumulation of cytoplasmic vesicles of acetyl-LDL-derived free cholesterol. The SERMs impaired cholesterol efflux to apolipoprotein A-I and HDL, and lowered ABCA1 and ABCG1 expression. These effects were not altered by the antiestrogen ICI 182,780 nor were they reproduced by 17β-estradiol. The treatment of mice with tamoxifen or raloxifene accelerated HDL-cholesteryl ester catabolism, thereby reducing HDL-cholesterol concentrations in serum. When [3H]cholesterol-loaded macrophages were injected into mice intraperitoneally, tamoxifen, but not raloxifene, decreased the [3H]cholesterol levels in serum, liver and feces. Both SERMs downregulated liver ABCG5 and ABCG8 protein expression, but tamoxifen reduced the capacity of HDL and plasma to promote macrophage cholesterol efflux to a greater extent than raloxifene. We conclude that SERMs interfere with intracellular cholesterol trafficking and efflux from macrophages. Tamoxifen, but not raloxifene, impair M-RCT in vivo. This effect is primarily attributable to the tamoxifen-mediated reduction of the capacity of HDL to promote cholesterol mobilization from macrophages. PMID:27601313

Growth-inducing effects of argon plasma on soybean sprouts via the regulation of demethylation levels of energy metabolism-related genes.

PubMed

Zhang, Jiao Jiao; Jo, Jin Oh; Huynh, Do Luong; Mongre, Raj Kumar; Ghosh, Mrinmoy; Singh, Amit Kumar; Lee, Sang Baek; Mok, Young Sun; Hyuk, Park; Jeong, Dong Kee

2017-02-07

This study was conducted to determine the effects of argon plasma on the growth of soybean [Glycine max (L.) Merr.] sprouts and investigate the regulation mechanism of energy metabolism. The germination and growth characteristics were modified by argon plasma at different potentials and exposure durations. Upon investigation, plasma treatment at 22.1 kV for 12 s maximized the germination and seedling growth of soybean, increasing the concentrations of soluble protein, antioxidant enzymes, and adenosine triphosphate (ATP) as well as up-regulating ATP a1, ATP a2, ATP b1, ATP b2, ATP b3, target of rapamycin (TOR), growth-regulating factor (GRF) 1-6, down-regulating ATP MI25 mRNA expression, and increasing the demethylation levels of the sequenced region of ATP a1, ATP b1, TOR, GRF 5, and GRF 6 of 6-day-old soybean sprouts. These observations indicate that argon plasma promotes soybean seed germination and sprout growth by regulating the demethylation levels of ATP, TOR, and GRF.

Zscan4 Inhibits Maintenance DNA Methylation to Facilitate Telomere Elongation in Mouse Embryonic Stem Cells.

PubMed

Dan, Jiameng; Rousseau, Philippe; Hardikar, Swanand; Veland, Nicolas; Wong, Jiemin; Autexier, Chantal; Chen, Taiping

2017-08-22

Proper telomere length is essential for embryonic stem cell (ESC) self-renewal and pluripotency. Mouse ESCs (mESCs) sporadically convert to a transient totipotent state similar to that of two-cell (2C) embryos to recover shortened telomeres. Zscan4, which exhibits a burst of expression in 2C-like mESCs, is required for telomere extension in these cells. However, the mechanism by which Zscan4 extends telomeres remains elusive. Here, we show that Zscan4 facilitates telomere elongation by inducing global DNA demethylation through downregulation of Uhrf1 and Dnmt1, major components of the maintenance DNA methylation machinery. Mechanistically, Zscan4 recruits Uhrf1 and Dnmt1 and promotes their degradation, which depends on the E3 ubiquitin ligase activity of Uhrf1. Blocking DNA demethylation prevents telomere elongation associated with Zscan4 expression, suggesting that DNA demethylation mediates the effect of Zscan4. Our results define a molecular pathway that contributes to the maintenance of telomere length homeostasis in mESCs. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Growth-inducing effects of argon plasma on soybean sprouts via the regulation of demethylation levels of energy metabolism-related genes

NASA Astrophysics Data System (ADS)

Zhang, Jiao Jiao; Jo, Jin Oh; Huynh, Do Luong; Mongre, Raj Kumar; Ghosh, Mrinmoy; Singh, Amit Kumar; Lee, Sang Baek; Mok, Young Sun; Hyuk, Park; Jeong, Dong Kee

2017-02-01

This study was conducted to determine the effects of argon plasma on the growth of soybean [Glycine max (L.) Merr.] sprouts and investigate the regulation mechanism of energy metabolism. The germination and growth characteristics were modified by argon plasma at different potentials and exposure durations. Upon investigation, plasma treatment at 22.1 kV for 12 s maximized the germination and seedling growth of soybean, increasing the concentrations of soluble protein, antioxidant enzymes, and adenosine triphosphate (ATP) as well as up-regulating ATP a1, ATP a2, ATP b1, ATP b2, ATP b3, target of rapamycin (TOR), growth-regulating factor (GRF) 1-6, down-regulating ATP MI25 mRNA expression, and increasing the demethylation levels of the sequenced region of ATP a1, ATP b1, TOR, GRF 5, and GRF 6 of 6-day-old soybean sprouts. These observations indicate that argon plasma promotes soybean seed germination and sprout growth by regulating the demethylation levels of ATP, TOR, and GRF.

Endothelial ATP-binding cassette G1 in mouse endothelium protects against hemodynamic-induced atherosclerosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, Shanshan; Department of Pediatrics, Baodi District People’s Hospital of Tianjin City, Tianjin, 301800; Wang, Jiaxing

Activated vascular endothelium inflammation under persistent hyperlipidemia is the initial step of atherogenesis. ATP-binding cassette G1 (ABCG1) is a crucial factor maintaining sterol and lipid homeostasis by transporting cholesterol efflux to high-density lipoprotein. In this study, we investigated the protective effects of ABCG1 in endothelial inflammation activation during early-stage atherogenesis in mice and the underlying mechanisms. Endothelial cell (EC)-specific ABCG1 transgenic (EC-ABCG1-Tg) mice were generated and cross-bred with low-density lipoprotein receptor–deficient (Ldlr{sup −/−}) mice. After a 4-week Western-type diet, the mice were sacrificed for assessing atherosclerosis. Human umbilical vein ECs were treated with different flows, and ABCG1 was adenovirally overexpressedmore » to investigate the mechanism in vitro. Compared with Ldlr{sup −/−} mouse aortas, EC-ABCG1-Tg/Ldlr{sup −/−} aortas showed decreased early-stage lesions. Furthermore, the lesion area in the EC-ABCG1-Tg/Ldlr{sup −/−} mouse aortic arch but not thoracic aorta was significantly reduced, which suggests a protective role of ABCG1 under atheroprone flow. In vitro, overexpression of ABCG1 attenuated EC activation caused by oscillatory shear stress. Overexpression of ABCG1 blunted cholesterol-activated ECs in vitro. In exploring the mechanisms of ABCG1 attenuating endothelial inflammation, we found that ABCG1 inhibited oscillatory flow-activated nuclear factor kappa B and NLRP3 inflammasome in ECs. ABCG1 may play a protective role in early-stage atherosclerosis by reducing endothelial activation induced by oscillatory shear stress via suppressing the inflammatory response. - Highlights: • EC-ABCG1-Tg mice in a Ldlr{sup −/−} background showed decreased atherosclerosis. • Overexpression of ABCG1 in ECs decreased OSS-induced EC activation. • NLRP3 and NF-κB might be an underlying mechanism of ABCG1 protective role.« less

ABCG2 Is a Selectable Marker for Enhanced Multilineage Differentiation Potential in Periodontal Ligament Stem Cells

PubMed Central

Szepesi, Áron; Matula, Zsolt; Szigeti, Anna; Várady, György; Szabó, Gyula; Uher, Ferenc; Sarkadi, Balázs

2015-01-01

Periodontal ligament stem cells (PDLSCs) provide an important source for tissue regeneration and may become especially useful in the formation of osteogenic seeds. PDLSCs can be cultured, expanded, and differentiated in vitro; thus, they may be applied in the long-term treatment of the defects in the dental regions. Here we studied numerous potential markers allowing the selection of human PDLSCs with a maximum differentiation potential. We followed the expression of the ATP-binding cassette subfamily G member 2 (ABCG2) membrane transporter protein and isolated ABCG2-expressing cells by using a monoclonal antibody, recognizing the transporter at the cell surface in intact cells. The expression of the ABCG2 protein, corresponding to the so-called side-population phenotype in various tissue-derived stem cells, was found to be a useful marker for the selection of PDLSCs with enhanced osteogenic, chondrogenic, and adipogenic differentiation. These findings may have important applications in achieving efficient dental tissue regeneration by using stem cells from extracted teeth. PMID:25101689

Tissue expression pattern of ABCG transporter indicates functional roles in reproduction of Toxocara canis.

PubMed

Luo, Yong-Li; Ma, Guang-Xu; Luo, Yong-Fang; Kuang, Ce-Yan; Jiang, Ai-Yun; Li, Guo-Qing; Zhou, Rong-Qiong

2018-03-01

Toxocara canis is a zoonotic parasite with worldwide distribution. ATP-binding cassette (ABC) transporters are integral membrane proteins which involve in a range of biological processes in various organisms. In present study, the full-length coding sequence of abcg-5 gene of T. canis (Tc-abcg-5) was cloned and characterized. A 633 aa polypeptide containing two conserved Walker A and Walker B motifs was predicted from a continuous 1902 nt open reading frame. Quantitative real-time PCR was employed to determine the transcriptional levels of Tc-abcg-5 gene in adult male and female worms, which indicated high mRNA level of Tc-abcg-5 in the reproductive tract of adult female T. canis. Tc-abcg-5 was expressed to produce rabbit polyclonal antiserum against recombinant TcABCG5. Indirect-fluorescence immunohistochemical assays were carried out to detect the tissue distribution of TcABCG5, which showed predominant distribution of TcABCG5 in the uterus (especially in the germ cells) of adult female T. canis. Tissue transcription and expression pattern of Tc-abcg-5 indicated that Tc-abcg-5 might play essential roles in the reproduction of this parasitic nematode.

Molecular Imaging of ABCB1 and ABCG2 Inhibition at the Human Blood-Brain Barrier Using Elacridar and 11C-Erlotinib PET.

PubMed

Verheijen, Remy B; Yaqub, Maqsood; Sawicki, Emilia; van Tellingen, Olaf; Lammertsma, Adriaan A; Nuijen, Bastiaan; Schellens, Jan H M; Beijnen, Jos H; Huitema, Alwin D R; Hendrikse, N Harry; Steeghs, Neeltje

2018-06-01

Transporters such as ABCB1 and ABCG2 limit the exposure of several anticancer drugs to the brain, leading to suboptimal treatment in the central nervous system. The purpose of this study was to investigate the effects of the ABCB1 and ABCG2 inhibitor elacridar on brain uptake using 11 C-erlotinib PET. Methods: Elacridar and cold erlotinib were administered orally to wild-type (WT) and Abcb1a/b;Abcg2 knockout mice. In addition, brain uptake was measured using 11 C-erlotinib imaging and ex vivo scintillation counting in knockout and WT mice. Six patients with advanced solid tumors underwent 11 C-erlotinib PET scans before and after a 1,000-mg dose of elacridar. 11 C-erlotinib brain uptake was quantified by pharmacokinetic modeling using volume of distribution (V T ) as the outcome parameter. In addition, 15 O-H 2 O scans to measure cerebral blood flow were acquired before each 11 C-erlotinib scan. Results: Brain uptake of 11 C-erlotinib was 2.6-fold higher in Abcb1a/b;Abcg2 knockout mice than in WT mice, measured as percentage injected dose per gram of tissue ( P = 0.01). In WT mice, the addition of elacridar (at systemic plasma concentrations of ≥200 ng/mL) resulted in an increased brain concentration of erlotinib, without affecting erlotinib plasma concentration. In patients, the V T of 11 C-erlotinib did not increase after intake of elacridar (0.213 ± 0.12 vs. 0.205 ± 0.07, P = 0.91). 15 O-H 2 O PET showed no significant changes in cerebral blood flow. Elacridar exposure in patients was 401 ± 154 ng/mL. No increase in V T with increased elacridar plasma exposure was found over the 271-619 ng/mL range. Conclusion: When Abcb1 and Abcg2 were disrupted in mice, brain uptake of 11 C-erlotinib increased both at a tracer dose and at a pharmacologic dose. In patients, brain uptake of 11 C-erlotinib was not higher after administration of elacridar. The more pronounced role that ABCG2 appears to play at the human blood-brain barrier and the lower potency of elacridar to inhibit ABCG2 may be an explanation of these interspecies differences. © 2018 by the Society of Nuclear Medicine and Molecular Imaging.

Mercury exposure induces cytoskeleton disruption and loss of renal function through epigenetic modulation of MMP9 expression.

PubMed

Khan, Hafizurrahman; Singh, Radha Dutt; Tiwari, Ratnakar; Gangopadhyay, Siddhartha; Roy, Somendu Kumar; Singh, Dhirendra; Srivastava, Vikas

2017-07-01

Mercury is one of the major heavy metal pollutants occurring in elemental, inorganic and organic forms. Due to ban on most inorganic mercury containing products, human exposure to mercury generally occurs as methylmercury (MeHg) by consumption of contaminated fish and other sea food. Animal and epidemiological studies indicate that MeHg affects neural and renal function. Our study is focused on nephrotoxic potential of MeHg. In this study, we have shown for the first time how MeHg could epigenetically modulate matrix metalloproteinase 9(MMP9) to promote nephrotoxicity using an animal model of sub chronic MeHg exposure. MeHg caused renal toxicity as was seen by increased levels of serum creatinine and expression of early nephrotoxicity markers (KIM-1, Clusterin, IP-10, and TIMP). MeHg exposure also correlated strongly with induction of MMP9 mRNA and protein in a dose dependent manner. Further, while induction of MMP9 promoted cytoskeleton disruption and loss of cell-cell adhesion (loss of F-actin, Vimentin and Fibronectin), inhibition of MMP9 was found to reduce these disruptions. Mechanistic studies by ChIP analysis showed that MeHg modulated MMP9 by promoting demethylation of its regulatory region to increase its expression. Bisulfite sequencing identified critical CpGs in the first exon of MMP9 which were demethylated following MeHg exposure. ChIP studies also showed loss of methyl binding protein, MeCP2 and transcription factor PEA3 at the demethylated site confirming decreased CpG methylation. Our studies thus show how MeHg could epigenetically modulate MMP9 to promote cytoskeleton disruption leading to loss of renal function. Copyright © 2017 Elsevier B.V. All rights reserved.

Total bile acids in the maternal and fetal compartment in relation to placental ABCG2 expression in preeclamptic pregnancies complicated by HELLP syndrome.

PubMed

Jebbink, Jiska; Veenboer, Geertruda; Boussata, Souad; Keijser, Remco; Kremer, Andreas E; Elferink, Ronald Oude; van der Post, Joris; Afink, Gijs; Ris-Stalpers, Carrie

2015-01-01

To investigate total bile acid (TBA) levels in maternal (MB) and umbilical cord blood (UCB) in normotensive, preeclamptic (PE), and PE pregnancies complicated by hemolysis elevated liver enzymes and low platelets (HELLP) syndrome in the context of ABCG2 placental gene expression levels, a recently reported placental bile acid transporter. TBA levels were determined in 83 paired MB and UCB samples of normotensive, PE and PE/HELLP pregnancies and in 22 paired arterial and venous UCB samples from uncomplicated term pregnancies. ABCG2 gene expression was measured in 104 human placentas by reverse transcriptase quantitative polymerase chain reaction. Overall, TBA levels in MB are higher compared to levels in UCB (p<0.0001), but this comparison looses statistical significance for the 11 PE/HELLP cases. TBA levels in maternal blood are increased in PE/HELLP compared to PE pregnancies (p=0.016). TBA levels in arterial and venous UCB from 22 normotensive pregnancies are not statistically different. ABCG2 expression is reduced in pregnancies where preeclampsia is further complicated by HELLP syndrome. ABCG2 expression in human placenta is not correlated with TBA levels in either the maternal or fetal compartment. Increased maternal TBA levels in PE/HELLP pregnancies indicate a relation between bile acids in the maternal circulation and HELLP syndrome. As overall TBA levels in maternal blood are increased compared to UCB, we conclude that the placenta partly protects the fetus from increased maternal TBA levels. This consistent difference in TBA levels between the maternal and fetal compartment is unrelated to the placental expression of ABCG2. Copyright © 2014 Elsevier B.V. All rights reserved.

Overexpression of ATP-Binding Cassette Transporter ABCG2 as a Potential Mechanism of Acquired Resistance to Vemurafenib in BRAF(V600E) Mutant Cancer Cells

PubMed Central

Wu, Chung-Pu; Sim, Hong-May; Huang, Yang-Hui; Liu, Yen-Chen; Hsiao, Sung-Han; Cheng, Hsing-Wen; Li, Yan-Qing; Ambudkar, Suresh V.; Hsu, Sheng-Chieh

2012-01-01

Melanoma is the most serious type of skin cancer with a high potential for metastasis and very low survival rates. The discovery of constitutive activation of the BRAF kinase caused by activating BRAF(V600E) kinase mutation in most melanoma patients led to the discovery of the first potent BRAF(V600E) signaling inhibitor, vemurafenib. Vemurafenib was effective in treating advanced melanoma patients and was proposed for the treatment of other BRAF(V600E) mutant cancers as well. Unfortunately, the success of vemurafenib was hampered by the rapid development of acquired resistance in different types of BRAF(V600E) mutant cancer cells. It becomes important to identify and evaluate all of the potential mechanisms of cellular resistance to vemurafenib. In this study, we characterized the interactions of vemurafenib with three major ATP-binding cassette (ABC) transporters, ABCB1, ABCC1 and ABCG2. We found that vemurafenib stimulated the ATPase activity and potently inhibited drug efflux mediated by ABCB1 and ABCG2. Vemurafenib also restored drug sensitivity in ABCG2-overexpressing cells. Moreover, we revealed that in the presence of functional ABCG2, BRAF kinase inhibition by vemurafenib is reduced in BRAF(V600E) mutant A375 cells. Taken together, our findings indicate that ABCG2 confers resistance to vemurafenib in A375 cells, suggesting involvement of this transporter in acquired resistance to vemurafenib. Thus, combination chemotherapy targeting multiple pathways could be an effective therapeutic strategy to overcome acquired resistance to vemurafenib for cancers harboring the BRAF(V600E) mutation. PMID:23153455

Monkey liver cytochrome P450 2C9 is involved in caffeine 7-N-demethylation to form theophylline.

PubMed

Utoh, Masahiro; Murayama, Norie; Uno, Yasuhiro; Onose, Yui; Hosaka, Shinya; Fujino, Hideki; Shimizu, Makiko; Iwasaki, Kazuhide; Yamazaki, Hiroshi

2013-12-01

Caffeine (1,3,7-trimethylxanthine) is a phenotyping substrate for human cytochrome P450 1A2. 3-N-Demethylation of caffeine is the main human metabolic pathway, whereas monkeys extensively mediate the 7-N-demethylation of caffeine to form pharmacological active theophylline. Roles of monkey P450 enzymes in theophylline formation from caffeine were investigated using individual monkey liver microsomes and 14 recombinantly expressed monkey P450 enzymes, and the results were compared with those for human P450 enzymes. Caffeine 7-N-demethylation activity in microsomes from 20 monkey livers was not strongly inhibited by α-naphthoflavone, quinidine or ketoconazole, and was roughly correlated with diclofenac 4'-hydroxylation activities. Monkey P450 2C9 had the highest activity for caffeine 7-N-demethylation. Kinetic analysis revealed that monkey P450 2C9 had a high Vmax/Km value for caffeine 7-N-demethylation, comparable to low Km value for monkey liver microsomes. Caffeine could dock favorably with monkey P450 2C9 modeled for 7-N-demethylation and with human P450 1A2 for 3-N-demethylation. The primary metabolite theophylline was oxidized to 8-hydroxytheophylline in similar ways by liver microsomes and by recombinant P450s in both humans and monkeys. These results collectively suggest a high activity for monkey liver P450 2C9 toward caffeine 7-N-demethylation, whereas, in humans, P450 1A2-mediated caffeine 3-N-demethylation is dominant.

Dexamethasone reduces side population fraction through downregulation of ABCG2 transporter in MCF-7 breast cancer cells.

PubMed

Kim, Jong Bin; Hwang, Sung Eun; Yoon, Sang-Pil

2017-07-01

Side population (SP) cells represent a rare population among breast cancer cells. SP cells have been reported to act as cancer stem‑like cells, and to participate in the development of multidrug resistance via modulating the expression of ATP-binding cassette subfamily G member 2 (ABCG2). Dexamethasone is a corticosteroid drug that has been used as an adjuvant treatment to enhance the efficacy of chemotherapeutic agents; however, its effects in breast cancer have yet to be thoroughly investigated. In the present study, the effects of dexamethasone were investigated using the human MCF‑7 breast cancer cell line, and SPs were examined in detail. Cellular proliferation, SP fractions and ABCG2 expression were examined following treatment of MCF‑7 cells with dexamethasone. Dexamethasone was revealed to cause a dose‑ and time‑dependent decrease in cancer cell proliferation, and it also decreased the size of the SP fraction of MCF‑7 cells and the expression of the ABCG2 transporter. The effects of dexamethasone on cellular proliferation, SP fraction and ABCG2 expression were abolished following the administration of the glucocorticoid antagonist RU486. These results suggested that dexamethasone may target breast cancer cell SPs and thus increase the sensitivity of tumor cells to chemotherapy. Therefore, it may be hypothesized that dexamethasone can be used as a chemosensitizer in the adjuvant treatment of patients with breast cancer.

Hydrogen Peroxide-Induced Secreted Frizzled-Related Protein 1 Gene Demethylation Contributes to Hydrogen Peroxide-Induced Apoptosis in Human U251 Glioma Cells.

PubMed

Xing, Zhiguo; Ni, Yaping; Zhao, Junjie; Ma, Xudong

2017-05-01

Glioblastoma multiforme is a type of central nervous system tumor with extremely poor prognosis. Previously, hydrogen peroxide (H 2 O 2 ), which promotes the oxidative stress response, has been reported to induce the apoptosis of glioma cells. Recently, secreted frizzled-related protein 1 (SFRP1) has been shown to be associated with various types of malignant tumors and with H 2 O 2 -induced oxidative stress in cardiomyocytes by negatively regulating the Wnt signaling pathway. This study aimed to explore SFRP1 expression and its roles in H 2 O 2 -induced apoptosis in human glioma cells. We found that the SFRP1 level was decreased in several human glioma cell lines, including U87, U251, and SW1783 cells. In U251 cells, SFRP1 could function as a cancer suppressor gene, and the growth of U251 cells could be inhibited not only by H 2 O 2 but also by the overexpression of SFRP1. Furthermore, we demonstrated that H 2 O 2 -induced SFRP1 gene demethylation partially contributed to H 2 O 2 -induced U251 cell apoptosis, which was verified by studies using an SFRP inhibitor (WAY-316606). Our research identified that H 2 O 2 -induced SFRP1 gene demethylation contributes to H 2 O 2 -induced apoptosis in human U251 glioma cells.

Impact of a high-cholesterol diet on expression levels of Niemann-Pick C1-like 1 and intestinal transporters in rats and mice.

PubMed

Kawase, Atsushi; Araki, Yasuha; Ueda, Yukiko; Nakazaki, Sayaka; Iwaki, Masahiro

2016-08-01

Niemann-Pick C1-like 1 (NPC1L1), ATP-binding cassette (ABC)G5, and ABCG8 are all involved in intestinal cholesterol absorption. It is unclear whether a high-cholesterol (HC) diet affects the expression of these transporters in rats and mice as well as humans. We examined the effects of an HC diet on their expression in small intestine and the differences between rats and mice in the responsive of this expression to an HC diet. In addition to these transporters, alterations in six representative drug and nutrient transporters (multidrug resistance-associated protein, breast cancer resistance protein, peptide transporter, sodium-glucose linked transporter, glucose transporter, and L-type amino acid transporter) and transcriptional factors such as hepatocyte nuclear factor (HNF)4α, sterol regulatory element-binding protein (SREBP)2, and liver X receptor (LXR)α were determined. In rats and mice fed an HC diet for 7 days, the mRNA and protein levels of NPC1L1 in the small intestine were determined by real-time reverse transcription polymerase chain reaction and western blotting, respectively. The mRNA levels of ABCG5 and ABCG8, six representative transporters, and transcriptional factors such as HNF4α, SREBP2, and LXR were examined. Significant decreases in the expression levels of NPC1L1 were observed in mice, but not rats, fed the HC diet. The mRNA levels of ABCG5 and ABCG8 were significantly increased in HC rats but not in mice. Only minor changes in the mRNA levels of the other transporters were seen in HC rats and mice. Decreased mRNA levels of HNF4α and SREBP2 in mice could be involved in the reduction in NPC1L1 expression observed upon the introduction of an HC diet. These results indicate that the effects of an HC diet on the expression levels of NPC1L1, ABCG5, and ABCG8 differ between mice and rats.

Melanocortin 1 Receptor Signaling Regulates Cholesterol Transport in Macrophages.

PubMed

Rinne, Petteri; Rami, Martina; Nuutinen, Salla; Santovito, Donato; van der Vorst, Emiel P C; Guillamat-Prats, Raquel; Lyytikäinen, Leo-Pekka; Raitoharju, Emma; Oksala, Niku; Ring, Larisa; Cai, Minying; Hruby, Victor J; Lehtimäki, Terho; Weber, Christian; Steffens, Sabine

2017-07-04

The melanocortin 1 receptor (MC1-R) is expressed by monocytes and macrophages, where it exerts anti-inflammatory actions on stimulation with its natural ligand α-melanocyte-stimulating hormone. The present study was designed to investigate the specific role of MC1-R in the context of atherosclerosis and possible regulatory pathways of MC1-R beyond anti-inflammation. Human and mouse atherosclerotic samples and primary mouse macrophages were used to study the regulatory functions of MC1-R. The impact of pharmacological MC1-R activation on atherosclerosis was assessed in apolipoprotein E-deficient mice. Characterization of human and mouse atherosclerotic plaques revealed that MC1-R expression localizes in lesional macrophages and is significantly associated with the ATP-binding cassette transporters ABCA1 and ABCG1, which are responsible for initiating reverse cholesterol transport. Using bone marrow-derived macrophages, we observed that α-melanocyte-stimulating hormone and selective MC1-R agonists similarly promoted cholesterol efflux, which is a counterregulatory mechanism against foam cell formation. Mechanistically, MC1-R activation upregulated the levels of ABCA1 and ABCG1. These effects were accompanied by a reduction in cell surface CD36 expression and in cholesterol uptake, further protecting macrophages from excessive lipid accumulation. Conversely, macrophages deficient in functional MC1-R displayed a phenotype with impaired efflux and enhanced uptake of cholesterol. Pharmacological targeting of MC1-R in atherosclerotic apolipoprotein E-deficient mice reduced plasma cholesterol levels and aortic CD36 expression and increased plaque ABCG1 expression and signs of plaque stability. Our findings identify a novel role for MC1-R in macrophage cholesterol transport. Activation of MC1-R confers protection against macrophage foam cell formation through a dual mechanism: It prevents cholesterol uptake while concomitantly promoting ABCA1- and ABCG1-mediated reverse cholesterol transport. © 2017 American Heart Association, Inc.

Characterization and expression of the ABC family (G group) in 'Dangshansuli' pear (Pyrus bretschneideri Rehd.) and its russet mutant.

PubMed

Hou, Zhaoqi; Jia, Bing; Li, Fei; Liu, Pu; Liu, Li; Ye, Zhenfeng; Zhu, Liwu; Wang, Qi; Heng, Wei

2018-01-01

The plant genes encoding ABCGs that have been identified to date play a role in suberin formation in response to abiotic and biotic stress. In the present study, 80 ABCG genes were identified in 'Dangshansuli' Chinese white pear and designated as PbABCGs. Based on the structural characteristics and phylogenetic analysis, the PbABCG family genes could be classified into seven main groups: classes A-G. Segmental and dispersed duplications were the primary forces underlying the PbABCG gene family expansion in 'Dangshansuli' pear. Most of the PbABCG duplicated gene pairs date to the recent whole-genome duplication that occurred 30~45 million years ago. Purifying selection has also played a critical role in the evolution of the ABCG genes. Ten PbABCG genes screened in the transcriptome of 'Dangshansuli' pear and its russet mutant 'Xiusu' were validated, and the expression levels of the PbABCG genes exhibited significant differences at different stages. The results presented here will undoubtedly be useful for better understanding of the complexity of the PbABCG gene family and will facilitate the functional characterization of suberin formation in the russet mutant.

The hypocholesterolemic activity of açaí (Euterpe oleracea Mart.) is mediated by the enhanced expression of the ATP-binding cassette, subfamily G transporters 5 and 8 and low-density lipoprotein receptor genes in the rat.

PubMed

de Souza, Melina Oliveira; Souza E Silva, Lorena; de Brito Magalhães, Cíntia Lopes; de Figueiredo, Bianca Barros; Costa, Daniela Caldeira; Silva, Marcelo Eustáquio; Pedrosa, Maria Lúcia

2012-12-01

Previous studies have demonstrated that the ingestion of açaí pulp can improve serum lipid profile in various animal models; therefore, we hypothesized that açaí pulp (Euterpe oleracea Mart.) may modulate the expression of the genes involved in cholesterol homeostasis in the liver and increase fecal excretion, thus reducing serum cholesterol. To test this hypothesis, we analyzed the expression of 7α-hydroxylase and ATP-binding cassette, subfamily G transporters (ABCG5 and ABCG8), which are genes involved with the secretion of cholesterol in the rat. We also evaluated the expression of sterol regulatory element-binding protein 2, 3-hydroxy-3-methylglutaryl CoA reductase, low-density lipoprotein receptor (LDL-R), and apolipoprotein B100, which are involved in cholesterol biosynthesis. Female Fischer rats were divided into 4 groups: the C group, which was fed a standard AIN-93 M diet; the CA group, which was fed a standard diet supplemented with 2% açaí pulp; the H group, which was fed a hypercholesterolemic diet (25% soy oil and 1% cholesterol); and the HA group, which was fed a hypercholesterolemic diet supplemented with 2% açaí pulp. At the end of the experimental period, the rats were euthanized, and their blood and livers were collected. The HA group exhibited a significant decrease in serum total cholesterol, low-density lipoprotein cholesterol, and atherogenic index and also had increased high-density lipoprotein cholesterol and cholesterol excretion in feces compared with the H group. In addition, the expression of the LDL-R, ABCG5, and ABCG8 genes was significantly increased by the presence of açaí pulp. These results suggest that açaí pulp promotes a hypocholesterolemic effect in a rat model of dietary-induced hypercholesterolemia through an increase in the expression of ATP-binding cassette, subfamily G transporters, and LDL-R genes. Copyright © 2012 Elsevier Inc. All rights reserved.

Characterization of the Role of a Highly Conserved Sequence in ATP Binding Cassette Transporter G (ABCG) Family in ABCG1 Stability, Oligomerization, and Trafficking

PubMed Central

2013-01-01

ATP-binding cassette transporter G1 (ABCG1) mediates cholesterol and oxysterol efflux onto lipidated lipoproteins and plays an important role in macrophage reverse cholesterol transport. Here, we identified a highly conserved sequence present in the five ABCG transporter family members. The conserved sequence is located between the nucleotide binding domain and the transmembrane domain and contains five amino acid residues from Asn at position 316 to Phe at position 320 in ABCG1 (NPADF). We found that cells expressing mutant ABCG1, in which Asn316, Pro317, Asp319, and Phe320 in the conserved sequence were replaced with Ala simultaneously, showed impaired cholesterol efflux activity compared with wild type ABCG1-expressing cells. A more detailed mutagenesis study revealed that mutation of Asn316 or Phe 320 to Ala significantly reduced cellular cholesterol and 7-ketocholesterol efflux conferred by ABCG1, whereas replacement of Pro317 or Asp319 with Ala had no detectable effect. To confirm the important role of Asn316 and Phe320, we mutated Asn316 to Asp (N316D) and Gln (N316Q), and Phe320 to Ile (F320I) and Tyr (F320Y). The mutant F320Y showed the same phenotype as wild type ABCG1. However, the efflux of cholesterol and 7-ketocholesterol was reduced in cells expressing ABCG1 mutant N316D, N316Q, or F320I compared with wild type ABCG1. Further, mutations N316Q and F320I impaired ABCG1 trafficking while having no marked effect on the stability and oligomerization of ABCG1. The mutant N316Q and F320I could not be transported to the cell surface efficiently. Instead, the mutant proteins were mainly localized intracellularly. Thus, these findings indicate that the two highly conserved amino acid residues, Asn and Phe, play an important role in ABCG1-dependent export of cellular cholesterol, mainly through the regulation of ABCG1 trafficking. PMID:24320932

N-demethylation of N-methyl-4-aminoantipyrine, the main metabolite of metamizole.

PubMed

Bachmann, Fabio; Duthaler, Urs; Rudin, Deborah; Krähenbühl, Stephan; Haschke, Manuel

2018-05-08

Metamizole is an old analgesic used frequently in some countries. Active metabolites of metamizole are the non-enzymatically generated N-methyl-4-aminoantipyrine (4-MAA) and its demethylation product 4-aminoantipyrine (4-AA). Previous studies suggested that 4-MAA demethylation can be performed by hepatic cytochrome P450 (CYP) 3A4, but the possible contribution of other CYPs remains unclear. Using human liver microsomes (HLM), liver homogenate and HepaRG cells, we could confirm 4-MAA demethylation by CYPs. Based on CYP induction (HepaRG cells) and CYP inhibition (HLM) we could identify CYP2B6, 2C8, 2C9 and 3A4 as major contributors to 4-MAA demethylation. The 4-MAA demethylation rate by HLM was 280 pmol/mg protein/h, too low to account for in vivo 4-MAA demethylation in humans. Since peroxidases can perform N-demethylation, we investigated horseradish peroxidase and human myeloperoxidase (MPO). Horse radish peroxidase efficiently demethylated 4-MAA, depending on the hydrogen peroxide concentration. This was also true for MPO; this reaction was saturable with a K m of 22.5 μM and a maximal velocity of 14 nmol/min/mg protein. Calculation of the entire body MPO capacity revealed that the demethylation capacity by granulocyte/granulocyte precursors was approximately 600 times higher than the liver capacity and could account for 4-MAA demethylation in humans. 4-MAA demethylation could also be demonstrated in MPO-expressing granulocyte precursor cells (HL-60). In conclusion, 4-MAA can be demethylated in the liver by several CYPs, but hepatic metabolism cannot fully explain 4-MAA demethylation in humans. The current study suggests that the major part of 4-MAA is demethylated by circulating granulocytes and granulocyte precursors in bone marrow. Copyright © 2018 Elsevier B.V. All rights reserved.

ABCG5 gene responses to treadmill running with or without administration of Pistachio atlantica in female rats

PubMed Central

Ghanbari-Niaki, Abbass; Zare-Kookandeh, Navabeh; Zare-Kookandeh, Asghar

2014-01-01

Objective(s): ABC transporters comprise a large family of transmembrane proteins that use the energy provided by ATP hydrolysis to translocate a variety of substrates across biological membranes. All members of the human ABCG subfamily, except for ABCG2, are cholesterol-transporter. The aim of this study was to determine the liver, the small intestine and kidney ABCG5 relative gene expression in response to treadmill-running training in female rats. Materials and Methods: Twenty Wistar rats (6-8 weeks old and 125-135 g weight) were used. Animals were randomly assigned to saline-control (SC), saline-training (ST), and Baneh-control (BC), and Baneh-training (BT) groups. Training groups did the exercise on a motor-driven treadmill at 25 m/min (0% grade) for 60 min/day for eight weeks (5 days/week). Rats were fed orally, with Baneh extraction and saline for six weeks. The two-way ANOVA was employed for statistical analysis. ABCG5 relative gene expression was detected by Real-time PCR method. Results: The current findings indicate that the Baneh-treated tissues had significantly lower levels of ABCG5 gene expression in the liver, small intestine, and kidneys (P< 0.001, P< 0.003, P< 0.001, respectively), when compared with saline-treated tissues. However, a higher level of gene expression was observed in exercise groups. A lower level of HDL-c but not triglyceride (TG) and total cholesterol (TC) levels were found in Baneh-treated animals at rest. Conclusion: Exercise training increases ABCG5 relative gene expression in the liver, small intestine and kidney tissues; therefore exercise training may adjust the reduction of ABCG5 relative gene expression in Baneh-training group. PMID:24847418

P-glycoprotein (MDR1/ABCB1) restricts brain accumulation and Cytochrome P450-3A (CYP3A) limits oral availability of the novel ALK/ROS1 inhibitor lorlatinib.

PubMed

Li, Wenlong; Sparidans, Rolf W; Wang, Yaogeng; Lebre, Maria C; Wagenaar, Els; Beijnen, Jos H; Schinkel, Alfred H

2018-05-09

Lorlatinib (PF-06463922) is a promising oral anaplastic lymphoma kinase (ALK) and ROS1 inhibitor currently in Phase III clinical trials for treatment of non-small cell lung cancer (NSCLC) containing an ALK rearrangement. With therapy-resistant brain metastases a major concern in NSCLC, lorlatinib was designed to have high membrane and blood-brain barrier permeability. We investigated the roles of the multidrug efflux transporters ABCB1 and ABCG2, and the multispecific drug-metabolizing enzyme CYP3A in plasma pharmacokinetics and tissue distribution of lorlatinib using genetically modified mouse strains. In vitro, human ABCB1 and mouse Abcg2 modestly transported lorlatinib. Following oral lorlatinib administration (at 10 mg/kg), brain accumulation of lorlatinib, while relatively high in wild-type mice, was still 4-fold increased in Abcb1a/1b -/- and Abcb1a/1b;Abcg2 -/- mice, but not in single Abcg2 -/- mice. Lorlatinib plasma levels were not altered. Oral coadministration of the ABCB1/ABCG2 inhibitor elacridar increased the brain accumulation of lorlatinib in wild-type mice 4-fold, i.e. to the same level as in Abcb1a/1b;Abcg2 -/- mice, without altering plasma exposure. Similar results were obtained for lorlatinib testis accumulation. In Cyp3a -/- mice, the plasma exposure of lorlatinib was increased 1.3-fold, but was then 2-fold reduced upon transgenic over-expression of human CYP3A4 in liver and intestine, whereas relative tissue distribution of lorlatinib remained unaltered. Our data indicate that lorlatinib brain accumulation is substantially limited by P-glycoprotein in the blood-brain barrier, but this can be effectively reversed by elacridar coadministration. Moreover, oral availability of lorlatinib is markedly restricted by CYP3A4 activity. These insights may be used in optimizing the therapeutic application of lorlatinib. This article is protected by copyright. All rights reserved. © 2018 UICC.

Potential pharmacokinetic effect of rifampicin on enrofloxacin in broilers: Roles of P-glycoprotein and BCRP induction by rifampicin.

PubMed

Guo, Mengjie; Dai, Xiaohua; Hu, Dongmin; Zhang, Yu; Sun, Yong; Ren, Weilong; Wang, Liping

2016-09-01

P-glycoprotein ( P-GP: , encoding gene Abcb1) and Breast Cancer Resistance Protein ( BCRP: , encoding gene Abcg2) are transport proteins that play a major role in modulating the bioavailability of oral drugs in humans and rodents. It has been shown that rifampicin is the typical inducer of P-gp in rodents by activating the nuclear receptor. However, its effect on Abcb1, Abcg2, CYP3A, and chicken xenobiotic-sensing orphan nuclear receptor ( CXR: ) mRNA expression in broilers is poorly understood. This study explored the effect of rifampicin on mRNA expression of Abcb1, Abcg2, CYP3A37, CXR as well as its effect on the pharmacokinetics of enrofloxacin in broilers. The mRNA levels of Abcb1, Abcg2, CYP3A37, and CXR were significantly increased in the liver (except Abcg2), kidney, jejunum, and ileum (P < 0.05) but not significantly changed in the duodenum (P > 0.05) after treated with rifampicin. Further analysis revealed that the variation tendencies of Abcb1, Abcg2, and CYP3A37 expression levels were significantly correlated with CXR mRNA expression levels in liver, kidney, jejunum, and ileum. Coadministration of rifampicin significantly changed the pharmacokinetic behavior of enrofloxacin orally administered by showing clearly lower AUC0-∞, AUC0-t, and Cmax as well as longer Tmax. The bioavailability of orally administered enrofloxacin was decreased from 72.5% to 24.8% by rifampicin. However, rifampicin did not significantly change the pharmacokinetics of enrofloxacin following intravenous administration. Our study shows that rifampicin up-regulated the small intestinal level of P-gp and BCRP and suggests that P-gp and BCRP are key factors that affected pharmacokinetic behavior of orally administered enrofloxacin by limiting its absorption from the intestine in broilers. © 2016 Poultry Science Association Inc.

The Silencing of RECK Gene is Associated with Promoter Hypermethylation and Poor Survival in Hepatocellular Carcinoma

PubMed Central

Zhang, Changsong; Ling, Yang; Zhang, Chenghui; Xu, Yun; Gao, Lu; Li, Rong; Zhu, Jing; Fan, Lieying; Wei, Lixin

2012-01-01

Background: To evaluate the promoter methylation status of RECK gene and mRNA expression in patients with hepatocellular carcinoma (HCC). Methods: We analyzed RECK methylation by MSP, and RECK mRNA by real-time PCR in 74 HCC. The liver cell lines (7721, Chang and Hep-G2) were treated with 5-Aza-CdR and TSA. Results: RECK mRNA were lower in HCC tissues (Mean -∆Ct = -3.29) than that in Non-Hcc tissues (Mean -∆Ct = -2.42). Expression of RECK was elevated in only 24 (32.43%) of the 74 HCC patients but decreased (-∆∆Ct<0) in 50 (67.57%) of the patients. RECK promoter was hypermethylated in 55.4% (41/74) of HCCs, and in only 17.6% (13/74) of Non-Hcc samples. RECK mRNA were lower in HCC patients with hypermethylation (∆MI>=0.5) (Mean -∆∆Ct = -1.75) than those with demethylation (∆MI<0.5) (Mean -∆∆Ct = 0.05), and there is a decreased tendency for RECK mRNA in HCC patients with promoter hypermethylation (p = 0.002). There was a significantly correlation found between RECK mRNA and poor survival after surgery. After treated by 5-Aza-CdR and TSA, we found that RECK mRNA induced different changes in 7721, Chang and Hep-G2 cells. And RECK demethylation also induced by epigenetic inhibitors. Conclusion: The results suggested that the hypermethylation may lead to promoter silencing of RECK mRNA and associated with poor survival in HCC. PMID:22419890

The role of CYP2D6 in primary and secondary oxidative metabolism of dextromethorphan: in vitro studies using human liver microsomes.

PubMed Central

Kerry, N L; Somogyi, A A; Bochner, F; Mikus, G

1994-01-01

1. The enzyme kinetics of dextromethorphan O-demethylation in liver microsomes from three extensive metabolisers (EM) with respect to CYP2D6 indicated high (Km1 2.2-9.4 microM) and low (Km2 55.5-307.3 microM) affinity sites whereas microsomes from two poor metabolisers (PM) indicated a single site (Km 560 and 157 microM). Similar differences were shown for 3-methoxymorphinan O-demethylation to 3-hydroxymorphinan (Km 6.9-9.6 microM in EM subjects; Km 307 and 213 microM in PM subjects). 2. Dextromethorphan O-demethylation was inhibited competitively by quinidine (Ki 0.1 microM), rac-perhexiline (Ki 0.4 microM), dextropropoxyphene (Ki 6 microM), rac-methadone (Ki 8 microM), and 3-methoxymorphinan (Ki 15 microM). These compounds were also potent inhibitors of 3-methoxymorphinan O-demethylation with IC50 values ranging from 0.02-12 microM. Anti-LKM1 serum inhibited both dextromethorphan and 3-methoxymorphinan O-demethylations in a titre-dependent manner. 3. The Michaelis-Menten constant for dextromethorphan N-demethylation to 3-methoxymorphinan (Km 632-977 microM) and dextrorphan N-demethylation to 3-hydroxymorphinan (Km 1571-4286 microM) did not differ between EM and PM microsomes. These N-demethylation reactions were not inhibited by quinidine and rac-methadone or LKM1 antibodies. 4. Dextromethorphan and 3-methoxymorphinan are metabolised by the same P450 isoform, CYP2D6, whereas the N-demethylation reactions are not carried out by CYP2D6. PMID:7826826

Stimulation of ribosomal RNA gene promoter by transcription factor Sp1 involves active DNA demethylation by Gadd45-NER pathway.

PubMed

Rajput, Pallavi; Pandey, Vijaya; Kumar, Vijay

2016-08-01

The well-studied Pol II transcription factor Sp1 has not been investigated for its regulatory role in rDNA transcription. Here, we show that Sp1 bound to specific sites on rDNA and localized into the nucleoli during the G1 phase of cell cycle to activate rDNA transcription. It facilitated the recruitment of Pol I pre-initiation complex and impeded the binding of nucleolar remodeling complex (NoRC) to rDNA resulting in the formation of euchromatin active state. More importantly, Sp1 also orchestrated the site-specific binding of Gadd45a-nucleotide excision repair (NER) complex resulting in active demethylation and transcriptional activation of rDNA. Interestingly, knockdown of Sp1 impaired rDNA transcription due to reduced engagement of the Gadd45a-NER complex and hypermethylation of rDNA. Thus, the present study unveils a novel role of Sp1 in rDNA transcription involving promoter demethylation. Copyright © 2016 Elsevier B.V. All rights reserved.

Integrated genomic analysis of colorectal cancer progression reveals activation of EGFR through demethylation of the EREG promoter

PubMed Central

Qu, X; Sandmann, T; Frierson, H; Fu, L; Fuentes, E; Walter, K; Okrah, K; Rumpel, C; Moskaluk, C; Lu, S; Wang, Y; Bourgon, R; Penuel, E; Pirzkall, A; Amler, L; Lackner, M R; Tabernero, J; Hampton, G M; Kabbarah, O

2016-01-01

Key molecular drivers that underlie transformation of colonic epithelium into colorectal adenocarcinoma (CRC) are well described. However, the mechanisms through which clinically targeted pathways are activated during CRC progression have yet to be elucidated. Here, we used an integrative genomics approach to examine CRC progression. We used laser capture microdissection to isolate colonic crypt cells, differentiated surface epithelium, adenomas, carcinomas and metastases, and used gene expression profiling to identify pathways that were differentially expressed between the different cell types. We identified a number of potentially important transcriptional changes in developmental and oncogenic pathways, and noted a marked upregulation of EREG in primary and metastatic cancer cells. We confirmed this pattern of gene expression by in situ hybridization and observed staining consistent with autocrine expression in the tumor cells. Upregulation of EREG during the adenoma–carcinoma transition was associated with demethylation of two key sites within its promoter, and this was accompanied by an increase in the levels of epidermal growth factor receptor (EGFR) phosphorylation, as assessed by reverse-phase protein analysis. In CRC cell lines, we demonstrated that EREG demethylation led to its transcriptional upregulation, higher levels of EGFR phosphorylation, and sensitization to EGFR inhibitors. Low levels of EREG methylation in patients who received cetuximab as part of a phase II study were associated with high expression of the ligand and a favorable response to therapy. Conversely, high levels of promoter methylation and low levels of EREG expression were observed in tumors that progressed after treatment. We also noted an inverse correlation between EREG methylation and expression levels in several other cancers, including those of the head and neck, lung and bladder. Therefore, we propose that upregulation of EREG expression through promoter demethylation might be an important means of activating the EGFR pathway during the genesis of CRC and potentially other cancers. PMID:27270421

LAL (Lysosomal Acid Lipase) Promotes Reverse Cholesterol Transport In Vitro and In Vivo.

PubMed

Bowden, Kristin L; Dubland, Joshua A; Chan, Teddy; Xu, You-Hai; Grabowski, Gregory A; Du, Hong; Francis, Gordon A

2018-05-01

To explore the role of LAL (lysosomal acid lipase) in macrophage cholesterol efflux and whole-body reverse cholesterol transport. Immortalized peritoneal macrophages from lal -/- mice showed reduced expression of ABCA1 (ATP-binding cassette transporter A1) and ABCG1 (ATP-binding cassette transporter G1), reduced production of the regulatory oxysterol 27-hydroxycholesterol, and impaired suppression of cholesterol synthesis on exposure to acetylated low-density lipoprotein when compared with lal +/+ macrophages. LAL-deficient mice also showed reduced hepatic ABCG5 (ATP-binding cassette transporter G5) and ABCG8 (ATP-binding cassette transporter G8) expression compared with lal +/+ mice. LAL-deficient macrophages loaded with [ 3 H]-cholesteryl oleate-labeled acetylated low-density lipoprotein showed impaired efflux of released [ 3 H]-cholesterol to apoA-I (apolipoprotein A-I), with normalization of [ 3 H]-cholesteryl ester levels and partial correction of ABCA1 expression and cholesterol efflux to apoA-I when treated with exogenous rhLAL (recombinant human LAL protein). LAL-deficient mice injected intraperitoneally with lal -/- macrophages cholesterol loaded and labeled in the same way exhibited only 1.55±0.35% total injected [ 3 H]-cholesterol counts appearing in the feces for 48 h (n=30), compared with 5.38±0.92% in lal +/+ mice injected with labeled lal +/+ macrophages (n=27), P <0.001. To mimic the therapeutic condition of delivery of supplemental LAL in vivo, injection of labeled lal -/- macrophages into lal +/+ mice resulted in a significant increase in reverse cholesterol transport (2.60±0.46% of 3 H-cholesterol counts in feces at 48 hours [n=19]; P <0.001 when compared with injection into lal -/- mice). These results indicate a critical role for LAL in promoting both macrophage and whole-body reverse cholesterol transport and the ability of supplemental LAL to be taken up and correct reverse cholesterol transport in vivo. © 2018 American Heart Association, Inc.

Co-administration of rivaroxaban with drugs that share its elimination pathways: pharmacokinetic effects in healthy subjects

PubMed Central

Mueck, Wolfgang; Kubitza, Dagmar; Becka, Michael

2013-01-01

Aims The anticoagulant rivaroxaban is an oral, direct Factor Xa inhibitor for the management of thromboembolic disorders. Metabolism and excretion involve cytochrome P450 3A4 (CYP3A4) and 2J2 (CYP2J2), CYP-independent mechanisms, and P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) (ABCG2). Methods The pharmacokinetic effects of substrates or inhibitors of CYP3A4, P-gp and Bcrp (ABCG2) on rivaroxaban were studied in healthy volunteers. Results Rivaroxaban did not interact with midazolam (CYP3A4 probe substrate). Exposure to rivaroxaban when co-administered with midazolam was slightly decreased by 11% (95% confidence interval [CI] −28%, 7%) compared with rivaroxaban alone. The following drugs moderately affected rivaroxaban exposure, but not to a clinically relevant extent: erythromycin (moderate CYP3A4/P-gp inhibitor; 34% increase [95% CI 23%, 46%]), clarithromycin (strong CYP3A4/moderate P-gp inhibitor; 54% increase [95% CI 44%, 64%]) and fluconazole (moderate CYP3A4, possible Bcrp [ABCG2] inhibitor; 42% increase [95% CI 29%, 56%]). A significant increase in rivaroxaban exposure was demonstrated with the strong CYP3A4, P-gp/Bcrp (ABCG2) inhibitors (and potential CYP2J2 inhibitors) ketoconazole (158% increase [95% CI 136%, 182%] for a 400 mg once daily dose) and ritonavir (153% increase [95% CI 134%, 174%]). Conclusions Results suggest that rivaroxaban may be co-administered with CYP3A4 and/or P-gp substrates/moderate inhibitors, but not with strong combined CYP3A4, P-gp and Bcrp (ABCG2) inhibitors (mainly comprising azole-antimycotics, apart from fluconazole, and HIV protease inhibitors), which are multi-pathway inhibitors of rivaroxaban clearance and elimination. PMID:23305158

ABCG2 variant has opposing effects on onset ages of Parkinson's disease and gout

PubMed Central

Matsuo, Hirotaka; Tomiyama, Hiroyuki; Satake, Wataru; Chiba, Toshinori; Onoue, Hiroyuki; Kawamura, Yusuke; Nakayama, Akiyoshi; Shimizu, Seiko; Sakiyama, Masayuki; Funayama, Manabu; Nishioka, Kenya; Shimizu, Toru; Kaida, Kenichi; Kamakura, Keiko; Toda, Tatsushi; Hattori, Nobutaka; Shinomiya, Nariyoshi

2015-01-01

Uric acid (urate) has been suggested to play a protective role in Parkinson's disease onset through its antioxidant activity. Dysfunction of ABCG2, a high-capacity urate exporter, is a major cause for early-onset gout based on hyperuricemia. In this study, the effects of a dysfunctional ABCG2 variant (Q141K, rs2231142) were analyzed on the ages at onset of gout patients (N = 507) and Parkinson's disease patients (N = 1015). The Q141K variant hastened the gout onset (P = 0.0027), but significantly associated with later Parkinson's disease onset (P = 0.025). Our findings will be helpful for development of more effective prevention of Parkinson's disease. PMID:25815357

ABCG2 variant has opposing effects on onset ages of Parkinson's disease and gout.

PubMed

Matsuo, Hirotaka; Tomiyama, Hiroyuki; Satake, Wataru; Chiba, Toshinori; Onoue, Hiroyuki; Kawamura, Yusuke; Nakayama, Akiyoshi; Shimizu, Seiko; Sakiyama, Masayuki; Funayama, Manabu; Nishioka, Kenya; Shimizu, Toru; Kaida, Kenichi; Kamakura, Keiko; Toda, Tatsushi; Hattori, Nobutaka; Shinomiya, Nariyoshi

2015-03-01

Uric acid (urate) has been suggested to play a protective role in Parkinson's disease onset through its antioxidant activity. Dysfunction of ABCG2, a high-capacity urate exporter, is a major cause for early-onset gout based on hyperuricemia. In this study, the effects of a dysfunctional ABCG2 variant (Q141K, rs2231142) were analyzed on the ages at onset of gout patients (N = 507) and Parkinson's disease patients (N = 1015). The Q141K variant hastened the gout onset (P = 0.0027), but significantly associated with later Parkinson's disease onset (P = 0.025). Our findings will be helpful for development of more effective prevention of Parkinson's disease.

Demethylation regulation of BDNF gene expression in dorsal root ganglion neurons is implicated in opioid-induced pain hypersensitivity in rats.

PubMed

Chao, Yu-Chieh; Xie, Fang; Li, Xueyang; Guo, Ruijuan; Yang, Ning; Zhang, Chen; Shi, Rong; Guan, Yun; Yue, Yun; Wang, Yun

2016-07-01

Repeated administration of morphine may result in opioid-induced hypersensitivity (OIH), which involves altered expression of numerous genes, including brain-derived neurotrophic factor (BDNF) in dorsal root ganglion (DRG) neurons. Yet, it remains unclear how BDNF expression is increased in DRG neurons after repeated morphine treatment. DNA methylation is an important mechanism of epigenetic control of gene expression. In the current study, we hypothesized that the demethylation regulation of certain BDNF gene promoters in DRG neurons may contribute to the development of OIH. Real-time RT-PCR was used to assess changes in the mRNA transcription levels of major BDNF exons including exon I, II, IV, VI, as well as total BDNF mRNA in DRGs from rats after repeated morphine administration. The levels of exon IV and total BDNF mRNA were significantly upregulated by repeated morphine administration, as compared to that in saline control group. Further, ELISA array and immunocytochemistry study revealed a robust upregulation of BDNF protein expression in DRG neurons after repeated morphine exposure. Correspondingly, the methylation levels of BDNF exon IV promoter showed a significant downregulation by morphine treatment. Importantly, intrathecal administration of a BDNF antibody, but not control IgG, significantly inhibited mechanical hypersensitivity that developed in rats after repeated morphine treatment. Conversely, intrathecal administration of an inhibitor of DNA methylation, 5-aza-2'-deoxycytidine (5-aza-dC) markedly upregulated the BDNF protein expression in DRG neurons and enhanced the mechanical allodynia after repeated morphine exposure. Together, our findings suggest that demethylation regulation of BDNF gene promoter may be implicated in the development of OIH through epigenetic control of BDNF expression in DRG neurons. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Hypocholesterolemic Effects of Eryngium carlinae F. Delaroche Are Mediated by the Involvement of the Intestinal Transporters ABCG5 and ABCG8

PubMed Central

De la O-Arciniega, Minarda; Naranjo-Rodríguez, Elia Brosla; Castro-Torres, Víctor Alberto; Domínguez-Ortíz, Miguel Ángel

2017-01-01

Hypercholesterolemia is a metabolic disorder characterized by a high concentration of cholesterol in the blood. Eryngium carlinae is a medicinal plant used to treat lipid diseases. The goal of this work was to evaluate, in a model of hypercholesterolemia in mice, the hypocholesterolemic effect of a hydroalcoholic extract of E. carlinae and its main metabolite, D-mannitol. Biochemical analyses of serum lipids and hepatic enzymes were performed by photocolorimetry. We performed histopathological studies of the liver and the expression of the intestinal cholesterol transporters Abcg5 and Abcg8 was determined by standard western blot method. Our results showed that hydroalcoholic extract at doses of 100 mg/kg and D-mannitol at doses of 10 mg/kg reduced the concentration of both total cholesterol and non-HDL cholesterol, without altering the concentration of HDL cholesterol and without damage to hepatocytes. Treatment with the extract increased Abcg8 intestinal transporter expression, while D-mannitol decreased the expression of the two Abcg5/Abcg8 transporters, compared with the hypercholesterolemic group. Considering that Abcg5/Abcg8 transporters perform cholesterol efflux, our results demonstrate that the lipid-lowering effect of the hydroalcoholic extract may be associated with the increase of Abcg8 expression, but the hypocholesterolemic effect of D-mannitol is independent of overexpression of these intestinal transporters and probably they have another mechanism of action. PMID:29387127

ATP-binding cassette (ABC) transporters in caprine preantral follicles: gene and protein expression.

PubMed

Guerreiro, Denise Damasceno; de Lima, Laritza Ferreira; Mbemya, Gildas Tetaping; Maside, Carolina Mielgo; Miranda, André Marrocos; Tavares, Kaio César Simiano; Alves, Benner Geraldo; Faustino, Luciana Rocha; Smitz, Johan; de Figueiredo, José Ricardo; Rodrigues, Ana Paula Ribeiro

2018-06-01

The multidrug resistance proteins ABCB1, ABCC2 and ABCG2 are an energy-dependent efflux pump that functions in systemic detoxification processes. Physiologically expressed in a variety of tissues, most abundantly in the liver and intestinal epithelia, placenta, blood-brain barrier and various stem cells, until now, these pumps were not identified in goat ovarian tissue. Therefore, the aim of this study is to analyze ABCB1, ABCC2, and ABCG2 mRNA and protein expression in goat preantral follicles. Fragments (3 × 3 × 1 mm) from five pairs of ovary (n = 10) obtained from five goat were collected and immediately submitted to qPCR, Western blot, and immunofluorescence assay for mRNA detection and identification and localization of the ABC transporters, respectively. mRNA for ABCB1, ABCC2, and ABCG2 and the presence of their proteins were observed on ovarian tissue samples. Positive marks were observed for the three transport proteins in all follicular categories studied. However, the marks were primarily localized in the oocyte of primordial, transition and primary follicle categories. In conclusion, goat ovarian tissue expresses mRNA for the ABCB1, ABCC2 and ABCG2 transporters and the expression of these proteins in the preantral follicles is a follicle-dependent stage.

ABCG8 polymorphisms and renal disease in type 2 diabetic patients.

PubMed

Nicolas, Anthony; Fatima, Sehrish; Lamri, Amel; Bellili-Muñoz, Naima; Halimi, Jean-Michel; Saulnier, Pierre-Jean; Hadjadj, Samy; Velho, Gilberto; Marre, Michel; Roussel, Ronan; Fumeron, Frédéric

2015-06-01

Sterols, bile acids and their receptors have been involved in diabetic nephropathy. The ATP-binding cassette transporters G5 and G8 (ABCG5 and ABCG8) play an important role in intestinal sterol absorption and bile acid secretion. The aim of our study was to assess the associations between two ABCG8 coding polymorphisms, T400K and D19H, and the incidence of renal events in type 2 diabetic subjects. Participants were the 3137 French type 2 diabetic subjects with micro- or macro-albuminuria from the genetic substudy of the DIABHYCAR trial. The mean duration of follow-up was 4years. Renal events were defined as a doubling of serum creatinine concentration or end-stage renal disease at follow-up. We then used a second population (DIAB2NEPHROGENE) of 2140 type 2 diabetic patients for the purpose of validation. In DIABHYCAR, the 400K allele was significantly associated with a higher risk of incident renal events in a multiple adjusted model (HR: 1.75 [95% CI 1.20-2.56], P=0.003). This association was still significant after further adjustments for baseline values of estimated glomerular filtration rate and urinary albumin excretion. In the validation population, the 400K allele was associated with the prevalence of end-stage renal disease (OR=2.01 [95% CI 1.15-3.54], P=0.015). No significant association was found between the D19H polymorphism and the risk of diabetic nephropathy. A polymorphism of the sterol transporter ABCG8 has been associated with the prevalence of end-stage renal disease and with the incidence of new renal events in type 2 diabetic patients. Copyright © 2015. Published by Elsevier Inc.

Activation-induced cytidine deaminase (AID) is necessary for the epithelial–mesenchymal transition in mammary epithelial cells

PubMed Central

Muñoz, Denise P.; Lee, Elbert L.; Takayama, Sachiko; Coppé, Jean-Philippe; Heo, Seok-Jin; Boffelli, Dario; Di Noia, Javier M.; Martin, David I. K.

2013-01-01

Activation-induced cytidine deaminase (AID), which functions in antibody diversification, is also expressed in a variety of germ and somatic cells. Evidence that AID promotes DNA demethylation in epigenetic reprogramming phenomena, and that it is induced by inflammatory signals, led us to investigate its role in the epithelial–mesenchymal transition (EMT), a critical process in normal morphogenesis and tumor metastasis. We find that expression of AID is induced by inflammatory signals that induce the EMT in nontransformed mammary epithelial cells and in ZR75.1 breast cancer cells. shRNA–mediated knockdown of AID blocks induction of the EMT and prevents cells from acquiring invasive properties. Knockdown of AID suppresses expression of several key EMT transcriptional regulators and is associated with increased methylation of CpG islands proximal to the promoters of these genes; furthermore, the DNA demethylating agent 5 aza-2'deoxycytidine (5-Aza-dC) antagonizes the effects of AID knockdown on the expression of EMT factors. We conclude that AID is necessary for the EMT in this breast cancer cell model and in nontransformed mammary epithelial cells. Our results suggest that AID may act near the apex of a hierarchy of regulatory steps that drive the EMT, and are consistent with this effect being mediated by cytosine demethylation. This evidence links our findings to other reports of a role for AID in epigenetic reprogramming and control of gene expression. PMID:23882083

Mutations of the central tyrosines of putative cholesterol recognition amino acid consensus (CRAC) sequences modify folding, activity, and sterol-sensing of the human ABCG2 multidrug transporter.

PubMed

Gál, Zita; Hegedüs, Csilla; Szakács, Gergely; Váradi, András; Sarkadi, Balázs; Özvegy-Laczka, Csilla

2015-02-01

Human ABCG2 is a plasma membrane glycoprotein causing multidrug resistance in cancer. Membrane cholesterol and bile acids are efficient regulators of ABCG2 function, while the molecular nature of the sterol-sensing sites has not been elucidated. The cholesterol recognition amino acid consensus (CRAC, L/V-(X)(1-5)-Y-(X)(1-5)-R/K) sequence is one of the conserved motifs involved in cholesterol binding in several proteins. We have identified five potential CRAC motifs in the transmembrane domain of the human ABCG2 protein. In order to define their roles in sterol-sensing, the central tyrosines of these CRACs (Y413, 459, 469, 570 and 645) were mutated to S or F and the mutants were expressed both in insect and mammalian cells. We found that mutation in Y459 prevented protein expression; the Y469S and Y645S mutants lost their activity; while the Y570S, Y469F, and Y645F mutants retained function as well as cholesterol and bile acid sensitivity. We found that in the case of the Y413S mutant, drug transport was efficient, while modulation of the ATPase activity by cholesterol and bile acids was significantly altered. We suggest that the Y413 residue within a putative CRAC motif has a role in sterol-sensing and the ATPase/drug transport coupling in the ABCG2 multidrug transporter. Copyright © 2014. Published by Elsevier B.V.

Organochloride pesticides induced hepatic ABCG5/G8 expression and lipogenesis in Chinese patients with gallstone disease

PubMed Central

Ji, Guixiang; Xu, Cheng; Sun, Haidong; Liu, Qian; Hu, Hai; Gu, Aihua; Jiang, Zhao-Yan

2016-01-01

Background Organochlorine pesticides (OCPs) are one kind of persistent organic pollutants. Although they are reported to be associated with metabolic disorders, the underlying mechanism is unclear. We explored the association of OCPs with gallstone disease and its influence on hepatic lipid metabolism. Materials and Methods OCPs levels in omentum adipose tissues from patients with and without gallstone disease between 2008 and 2011 were measured by GC-MS. Differences of gene expression involved in hepatic lipid metabolism and hepatic lipids content were compared in liver biopsies between groups with high and low level of OCPs. Using HepG2 cell lines, the influence on hepatic lipid metabolism by individual OCP was evaluated in vitro. Results In all patients who were from non-occupational population, there were high levels of β-hexachlorocyclohexane (β-HCH) and p',p'-dichloroethylene (p',p'-DDE) accumulated in adipose tissues. Both β-HCH and p', p'-DDE levels were significantly higher in adipose tissues from patients with gallstone disease (294.3± 313.5 and 2222± 2279 ng/g of lipid) than gallstone-free controls (282.7± 449.0 and 2025±2664 ng/g of lipid, P< 0.01) and they were strongly related with gallstone disease (P for trend = 0.0004 and 0.0138). Furthermore, higher OCPs in adipose tissue led to increase in the expression of hepatic cholesterol transporters ABCG5 and G8 (+34% and +27%, P< 0.01) and higher cholesterol saturation index in gallbladder bile, and induced hepatic fatty acids synthesis, which was further confirmed in HepG2 cells. Conclusion OCPs might enhance hepatic secretion of cholesterol into bile via ABCG5/G8 which promoting gallstone disease as well as lipogenesis. PMID:27203212

NF-κB mediates Gadd45β expression and DNA demethylation in the hippocampus during fear memory formation.

PubMed

Jarome, Timothy J; Butler, Anderson A; Nichols, Jessica N; Pacheco, Natasha L; Lubin, Farah D

2015-01-01

Gadd45-mediated DNA demethylation mechanisms have been implicated in the process of memory formation. However, the transcriptional mechanisms involved in the regulation of Gadd45 gene expression during memory formation remain unexplored. NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) controls transcription of genes in neurons and is a critical regulator of synaptic plasticity and memory formation. In silico analysis revealed several NF-κB (p65/RelA and cRel) consensus sequences within the Gadd45β gene promoter. Whether NF-κB activity regulates Gadd45 expression and associated DNA demethylation in neurons during memory formation is unknown. Here, we found that learning in a fear conditioning paradigm increased Gadd45β gene expression and brain-derivedneurotrophic factor (BDNF) DNA demethylation in area CA1 of the hippocampus, both of which were prevented with pharmacological inhibition of NF-κB activity. Further experiments found that conditional mutations in p65/RelA impaired fear memory formation but did not alter changes in Gadd45β expression. The learning-induced increases in Gadd45β mRNA levels, Gadd45β binding at the BDNF gene and BDNF DNA demethylation were blocked in area CA1 of the c-rel knockout mice. Additionally, local siRNA-mediated knockdown of c-rel in area CA1 prevented fear conditioning-induced increases in Gadd45β expression and BDNF DNA demethylation, suggesting that c-Rel containing NF-κB transcription factor complex is responsible for Gadd45β regulation during memory formation. Together, these results support a novel transcriptional role for NF-κB in regulation of Gadd45β expression and DNA demethylation in hippocampal neurons during fear memory.

Islet cells share promoter hypomethylation independently of expression, but exhibit cell-type-specific methylation in enhancers.

PubMed

Neiman, Daniel; Moss, Joshua; Hecht, Merav; Magenheim, Judith; Piyanzin, Sheina; Shapiro, A M James; de Koning, Eelco J P; Razin, Aharon; Cedar, Howard; Shemer, Ruth; Dor, Yuval

2017-12-19

DNA methylation at promoters is an important determinant of gene expression. Earlier studies suggested that the insulin gene promoter is uniquely unmethylated in insulin-expressing pancreatic β-cells, providing a classic example of this paradigm. Here we show that islet cells expressing insulin, glucagon, or somatostatin share a lack of methylation at the promoters of the insulin and glucagon genes. This is achieved by rapid demethylation of the insulin and glucagon gene promoters during differentiation of Neurogenin3 + embryonic endocrine progenitors, regardless of the specific endocrine cell-type chosen. Similar methylation dynamics were observed in transgenic mice containing a human insulin promoter fragment, pointing to the responsible cis element. Whole-methylome comparison of human α- and β-cells revealed generality of the findings: genes active in one cell type and silent in the other tend to share demethylated promoters, while methylation differences between α- and β-cells are concentrated in enhancers. These findings suggest an epigenetic basis for the observed plastic identity of islet cell types, and have implications for β-cell reprogramming in diabetes and diagnosis of β-cell death using methylation patterns of circulating DNA. Copyright © 2017 the Author(s). Published by PNAS.

Methylation-Sensitive Expression of a DNA Demethylase Gene Serves As an Epigenetic Rheostat

PubMed Central

Williams, Ben P.; Pignatta, Daniela; Henikoff, Steven; Gehring, Mary

2015-01-01

Genomes must balance active suppression of transposable elements (TEs) with the need to maintain gene expression. In Arabidopsis, euchromatic TEs are targeted by RNA-directed DNA methylation (RdDM). Conversely, active DNA demethylation prevents accumulation of methylation at genes proximal to these TEs. It is unknown how a cellular balance between methylation and demethylation activities is achieved. Here we show that both RdDM and DNA demethylation are highly active at a TE proximal to the major DNA demethylase gene ROS1. Unexpectedly, and in contrast to most other genomic targets, expression of ROS1 is promoted by DNA methylation and antagonized by DNA demethylation. We demonstrate that inducing methylation in the ROS1 proximal region is sufficient to restore ROS1 expression in an RdDM mutant. Additionally, methylation-sensitive expression of ROS1 is conserved in other species, suggesting it is adaptive. We propose that the ROS1 locus functions as an epigenetic rheostat, tuning the level of demethylase activity in response to methylation alterations, thus ensuring epigenomic stability. PMID:25826366

Overcoming Multidrug Resistance via Photodestruction of ABCG2-Rich Extracellular Vesicles Sequestering Photosensitive Chemotherapeutics

PubMed Central

Goler-Baron, Vicky; Assaraf, Yehuda G.

2012-01-01

Multidrug resistance (MDR) remains a dominant impediment to curative cancer chemotherapy. Efflux transporters of the ATP-binding cassette (ABC) superfamily including ABCG2, ABCB1 and ABCC1 mediate MDR to multiple structurally and functionally distinct antitumor agents. Recently we identified a novel mechanism of MDR in which ABCG2-rich extracellular vesicles (EVs) form in between attached neighbor breast cancer cells and highly concentrate various chemotherapeutics in an ABCG2-dependent manner, thereby sequestering them away from their intracellular targets. Hence, development of novel strategies to overcome MDR modalities is a major goal of cancer research. Towards this end, we here developed a novel approach to selectively target and kill MDR cancer cells. We show that illumination of EVs that accumulated photosensitive cytotoxic drugs including imidazoacridinones (IAs) and topotecan resulted in intravesicular formation of reactive oxygen species (ROS) and severe damage to the EVs membrane that is shared by EVs-forming cells, thereby leading to tumor cell lysis and the overcoming of MDR. Furthermore, consistent with the weak base nature of IAs, MDR cells that are devoid of EVs but contained an increased number of lysosomes, highly accumulated IAs in lysosomes and upon photosensitization were efficiently killed via ROS-dependent lysosomal rupture. Combining targeted lysis of IAs-loaded EVs and lysosomes elicited a synergistic cytotoxic effect resulting in MDR reversal. In contrast, topotecan, a bona fide transport substrate of ABCG2, accumulated exclusively in EVs of MDR cells but was neither detected in lysosomes of normal breast epithelial cells nor in non-MDR breast cancer cells. This exclusive accumulation in EVs enhanced the selectivity of the cytotoxic effect exerted by photodynamic therapy to MDR cells without harming normal cells. Moreover, lysosomal alkalinization with bafilomycin A1 abrogated lysosomal accumulation of IAs, consequently preventing lysosomal photodestruction of normal breast epithelial cells. Thus, MDR modalities including ABCG2-dependent drug sequestration within EVs can be rationally converted to a pharmacologically lethal Trojan horse to selectively eradicate MDR cancer cells. PMID:22530032

Taraxasterol suppresses the growth of human liver cancer by upregulating Hint1 expression.

PubMed

Bao, Tianhao; Ke, Yang; Wang, Yifan; Wang, Weiwei; Li, Yuehua; Wang, Yan; Kui, Xiang; Zhou, Qixin; Zhou, Han; Zhang, Cheng; Zhou, Dongming; Wang, Lin; Xiao, Chunjie

2018-07-01

Taraxasterol has potent anti-inflammatory and anti-tumor activity. However, the effect and potential mechanisms of Taraxasterol on the growth of human liver cancer have not been clarified. Histidine triad nucleotide-binding protein 1 (Hint1) is a tumor suppressor and its downregulated expression is associated with the development of cancer. Here, we report that Taraxasterol treatment significantly suppressed cell proliferation and induced cell cycle arrest at G0/G1 phase and apoptosis in liver cancer cells, but not in non-tumor hepatocytes. Furthermore, Taraxasterol upregulated Hint1 and Bax, but downregulated Bcl2 and cyclin D1 expression, accompanied by promoting the demethylation in the Hint1 promoter region in liver cancer cells. The effects of Taraxasterol were abrogated by Hint1 silencing and partially mitigated by Bax silencing, Bcl2 or cyclin D1 over-expression in HepG2 cells. Moreover, oral administration with Taraxasterol did not affect body weight, urinary protein levels, and the heart, liver, and kidney morphology in BALB/c mice but effectively inhibited the growth of implanted SK-Hep1 tumor in vivo. Collectively, we demonstrate that Taraxasterol inhibits the growth of liver cancer at least partially by enhancing Hint1 expression to regulate Bax, Bcl2, and cyclin D1 expression. Taraxasterol may be a drug candidate for the treatment of human liver cancer. Taraxasterol inhibits growth and induces apoptosis in human liver cancer cells. Taraxasterol enhances Hint1 expression by promoting demethylation in Hint1 promoter. Taraxasterol increases Hint1 levels to regulate Bax, Bcl2, and cyclinD1 expression. The effects of Taraxasterol are abrogated by Hint1 silencing in liver cancer cells. Taraxasterol inhibits the growth of subcutaneously implanted liver cancers in mice.

ABCG2 contributes to the development of gout and hyperuricemia in a genome-wide association study.

PubMed

Chen, Chung-Jen; Tseng, Chia-Chun; Yen, Jeng-Hsien; Chang, Jan-Gowth; Chou, Wen-Cheng; Chu, Hou-Wei; Chang, Shun-Jen; Liao, Wei-Ting

2018-02-16

Although many genome-wide association studies (GWASs) of hyperuricemia or gout have been reported, the related genetic factors and the mechanisms from hyperuricemia to gouty attack remain unclear. This study aimed to identify genetic factors and pathogenesis of gout from hyperuricemia by genome-wide association study (GWAS). 747 gout patients, 747 hyperuricemia and 2071 age-matched controls were recruited and analyzed with Affymetrix 650 K chip to find the related genetic variants. The functions of the related genes were investigated in an endothelial cell (EC) with urate crystal stimulation. The GWAS results showed 36 SNPs to be strongly associated with gout compared to controls (all p-values < 10 -7 ). Whereas the rs2231142 in ABCG2 gene had significant associations between gout and controls, between gout and hyperuricemia, and between hyperuricemia and controls (all p-values < 10 -7 ), and the ORs were 4.34, 3.37 and 2.15 (all p-values < 0.001) after adjustment of potential confounders, respectively. The cell model showed significantly higher IL-8 release from EC combined with ABCG2 knockdown. We concluded that ABCG2 gene contributed to hyperuricemia but also gout, and that it was involved in the inflammation dysregulation via augmented IL-8 release in EC.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Anna D.; Malur, Anagha; Barna, Barbara P.

Peroxisome proliferator-activated receptor-gamma (PPAR{gamma}) is a nuclear transcription factor involved in lipid metabolism that is constitutively expressed in the alveolar macrophages of healthy individuals. PPAR{gamma} has recently been implicated in the catabolism of surfactant by alveolar macrophages, specifically the cholesterol component of surfactant while the mechanism remains unclear. Studies from other tissue macrophages have shown that PPAR{gamma} regulates cholesterol influx, efflux, and metabolism. PPAR{gamma} promotes cholesterol efflux through the liver X receptor-alpha (LXR{alpha}) and ATP-binding cassette G1 (ABCG1). We have recently shown that macrophage-specific PPAR{gamma} knockout (PPAR{gamma} KO) mice accumulate cholesterol-laden alveolar macrophages that exhibit decreased expression of LXR{alpha} andmore » ABCG1 and reduced cholesterol efflux. We hypothesized that in addition to the dysregulation of these cholesterol efflux genes, the expression of genes involved in cholesterol synthesis and influx was also dysregulated and that replacement of PPAR{gamma} would restore regulation of these genes. To investigate this hypothesis, we have utilized a Lentivirus expression system (Lenti-PPAR{gamma}) to restore PPAR{gamma} expression in the alveolar macrophages of PPAR{gamma} KO mice. Our results show that the alveolar macrophages of PPAR{gamma} KO mice have decreased expression of key cholesterol synthesis genes and increased expression of cholesterol receptors CD36 and scavenger receptor A-I (SRA-I). The replacement of PPAR{gamma} (1) induced transcription of LXR{alpha} and ABCG1; (2) corrected suppressed expression of cholesterol synthesis genes; and (3) enhanced the expression of scavenger receptors CD36. These results suggest that PPAR{gamma} regulates cholesterol metabolism in alveolar macrophages.« less

Icariin may benefit the mesenchymal stem cells of patients with steroid-associated osteonecrosis by ABCB1-promoter demethylation: a preliminary study.

PubMed

Sun, Z-B; Wang, J-W; Xiao, H; Zhang, Q-S; Kan, W-S; Mo, F-B; Hu, S; Ye, S-N

2015-01-01

In this study, we found out a previously undefined function of icariin which restored the dynamic balance between osteogenic and adipogenic differentiation of mesenchymal stem cells (MSCs) in patients with osteonecrosis of femoral head (ONFH) via ABCB1-promoter demethylation. These findings provided important information regarding potential implication of icariin targeting epigenetic changes for the treatment of steroid -associated ONFH. Here, we investigated whether icariin can also exert a beneficial role in the reactivation of MSCs in the patients with steroid-associated ONFH via ABCB1-promoter demethylation. Bone marrow was collected from the proximal femur in patients with steroid-associated ONFH (n = 20) and patients with new femoral neck fractures (n = 22), and then MSCs were isolated. We investigated cell viability, intracellular reactive oxygen species (ROS) level, mitochondrial membrane potential (MMP), P-glycoprotein (P-gp) activity, the transcript levels of ABCB1 and oxidative stress-related genes, methylation extent at CpG islands of ABCB1 promoter, and osteogenic and adipogenic differentiation ability of MSCs from the femoral neck fractures group and from the steroid-associated ONFH group treated with or without icariin. We observed that MSCs from the steroid-associated ONFH group showed reduced proliferation ability, elevated ROS level, depressed MMP, weakened osteogenesis, and enhanced adipogenesis while low P-gp activity, transcription level of ABCB1, and oxidative stress-related genes as well as aberrant CpG islands hypermethylation of ABCB1 were also noted in steroid-associated ONFH group. Treatment with icariin obviously induced de novo P-gp expression, decreased oxidative stress, and promoted osteogenesis. Icariin may be a potential drug targeting epigenetic changes for the treatment of steroid-associated ONFH.

Two ATP Binding Cassette G Transporters, Rice ATP Binding Cassette G26 and ATP Binding Cassette G15, Collaboratively Regulate Rice Male Reproduction1[OPEN

PubMed Central

Zhao, Guochao; Shi, Jianxin; Liang, Wanqi; Xue, Feiyang; Luo, Qian; Zhu, Lu; Qu, Guorun; Chen, Mingjiao; Schreiber, Lukas; Zhang, Dabing

2015-01-01

Male reproduction in higher plants requires the support of various metabolites, including lipid molecules produced in the innermost anther wall layer (the tapetum), but how the molecules are allocated among different anther tissues remains largely unknown. Previously, rice (Oryza sativa) ATP binding cassette G15 (ABCG15) and its Arabidopsis (Arabidopsis thaliana) ortholog were shown to be required for pollen exine formation. Here, we report the significant role of OsABCG26 in regulating the development of anther cuticle and pollen exine together with OsABCG15 in rice. Cytological and chemical analyses indicate that osabcg26 shows reduced transport of lipidic molecules from tapetal cells for anther cuticle development. Supportively, the localization of OsABCG26 is on the plasma membrane of the anther wall layers. By contrast, OsABCG15 is polarly localized in tapetal plasma membrane facing anther locules. osabcg26 osabcg15 double mutant displays an almost complete absence of anther cuticle and pollen exine, similar to that of osabcg15 single mutant. Taken together, we propose that OsABCG26 and OsABCG15 collaboratively regulate rice male reproduction: OsABCG26 is mainly responsible for the transport of lipidic molecules from tapetal cells to anther wall layers, whereas OsABCG15 mainly is responsible for the export of lipidic molecules from the tapetal cells to anther locules for pollen exine development. PMID:26392263

Simulated vibrational spectra of aflatoxins and their demethylated products and the estimation of the energies of the demethylation reactions.

PubMed

Billes, Ferenc; Móricz, Agnes M; Tyihák, Erno; Mikosch, Hans

2006-06-01

The structure of four natural mycotoxins, the aflatoxin B1, B2, G1 and G2 and their demethylated products were optimized with quantum chemical method. The energies and the thermodynamic functions of the molecules were calculated and applied to calculation of the reaction energies of the demethylations. Further results of the calculations are the vibrational force constants, the infrared spectra of the molecules and the assignments of the spectral bands.

Purification and biochemical characterization of NpABCG5/NpPDR5, a plant pleiotropic drug resistance transporter expressed in Nicotiana tabacum BY-2 suspension cells.

PubMed

Toussaint, Frédéric; Pierman, Baptiste; Bertin, Aurélie; Lévy, Daniel; Boutry, Marc

2017-05-04

Pleiotropic drug resistance (PDR) transporters belong to the ABCG subfamily of ATP-binding cassette (ABC) transporters and are involved in the transport of various molecules across plasma membranes. During evolution, PDR genes appeared independently in fungi and in plants from a duplication of a half-size ABC gene. The enzymatic properties of purified PDR transporters from yeast have been characterized. This is not the case for any plant PDR transporter, or, incidentally, for any purified plant ABC transporter. Yet, plant PDR transporters play important roles in plant physiology such as hormone signaling or resistance to pathogens or herbivores. Here, we describe the expression, purification, enzymatic characterization and 2D analysis by electron microscopy of NpABCG5/NpPDR5 from Nicotiana plumbaginifolia , which has been shown to be involved in the plant defense against herbivores. We constitutively expressed NpABCG5/NpPDR5, provided with a His-tag in a homologous system: suspension cells from Nicotiana tabacum (Bright Yellow 2 line). NpABCG5/NpPDR5 was targeted to the plasma membrane and was solubilized by dodecyl maltoside and purified by Ni-affinity chromatography. The ATP-hydrolyzing specific activity (27 nmol min -1  mg -1 ) was stimulated seven-fold in the presence of 0.1% asolectin. Electron microscopy analysis indicated that NpABCG5/NpPDR5 is monomeric and with dimensions shorter than those of known ABC transporters. Enzymatic data (optimal pH and sensitivity to inhibitors) confirmed that plant and fungal PDR transporters have different properties. These data also show that N. tabacum suspension cells are a convenient host for the purification and biochemical characterization of ABC transporters. © 2017 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society.

Multixenobiotic resistance in Mytilus edulis: Molecular and functional characterization of an ABCG2- type transporter in hemocytes and gills.

PubMed

Ben Cheikh, Yosra; Xuereb, Benoit; Boulangé-Lecomte, Céline; Le Foll, Frank

2018-02-01

Among the cellular protection arsenal, ABC transporters play an important role in xenobiotic efflux in marine organisms. Two pumps belonging to B and C subfamily has been identified in Mytilus edulis. In this study, we investigated the presence of the third major subtype ABCG2/BCRP protein in mussel tissues. Transcript was expressed in hemocytes and with higher level in gills. Molecular characterization revealed that mussel ABCG2 transporter shares the sequence and organizational structure with mammalian and molluscan orthologs. Overall identity of the predicted amino acid sequence with corresponding homologs from other organisms was between 49% and 98%. Moreover, protein efflux activity was demonstrated using a combination of fluorescent allocrites and specific inhibitors. The accumulation of bodipy prazosin and pheophorbide A was heterogeneous in gills and hemocytes. Most of the used blockers enhanced probe accumulation at different levels, most significantly for bodipy prazosin. Moreover, Mrp classical blocker MK571 showed a polyspecificity. In conclusion, our data demonstrate that several ABC transporters contribute to MXR phenotype in the blue mussel including ABCG2 that forms an active pump in hemocytes and gills. Efforts are needed to distinguish between the different members and to explore their single function and specificity towards allocrites and chemosensitizers. Copyright © 2017 Elsevier B.V. All rights reserved.

Metabolic Interactions of Purine Derivatives with Human ABC Transporter ABCG2: Genetic Testing to Assess Gout Risk.

PubMed

Ishikawa, Toshihisa; Aw, Wanping; Kaneko, Kiyoko

2013-11-04

In mammals, excess purine nucleosides are removed from the body by breakdown in the liver and excretion from the kidneys. Uric acid is the end product of purine metabolism in humans. Two-thirds of uric acid in the human body is normally excreted through the kidney, whereas one-third undergoes uricolysis (decomposition of uric acid) in the gut. Elevated serum uric acid levels result in gout and could be a risk factor for cardiovascular disease and diabetes. Recent studies have shown that human ATP-binding cassette transporter ABCG2 plays a role of renal excretion of uric acid. Two non-synonymous single nucleotide polymorphisms (SNPs), i.e., 421C>A (major) and 376C>T (minor), in the ABCG2 gene result in impaired transport activity, owing to ubiquitination-mediated proteosomal degradation and truncation of ABCG2, respectively. These genetic polymorphisms are associated with hyperuricemia and gout. Allele frequencies of those SNPs are significantly higher in Asian populations than they are in African and Caucasian populations. A rapid and isothermal genotyping method has been developed to detect the SNP 421C>A, where one drop of peripheral blood is sufficient for the detection. Development of simple genotyping methods would serve to improve prevention and early therapeutic intervention for high-risk individuals in personalized healthcare.

Endocytosis of ABCG2 drug transporter caused by binding of 5D3 antibody: trafficking mechanisms and intracellular fate.

PubMed

Studzian, Maciej; Bartosz, Grzegorz; Pulaski, Lukasz

2015-08-01

ABCG2, a metabolite and xenobiotic transporter located at the plasma membrane (predominantly in barrier tissues and progenitor cells), undergoes a direct progressive endocytosis process from plasma membrane to intracellular compartments upon binding of 5D3 monoclonal antibody. This antibody is specific to an external epitope on the protein molecule and locks it in a discrete conformation within its activity cycle, presumably providing a structural trigger for the observed internalization phenomenon. Using routine and novel assays, we show that ABCG2 is endocytosed by a mixed mechanism: partially via a rapid, clathrin-dependent pathway and partially in a cholesterol-dependent, caveolin-independent manner. While the internalization process is entirely dynamin-dependent and converges initially at the early endosome, subsequent intracellular fate of ABCG2 is again twofold: endocytosis leads to only partial lysosomal degradation, while a significant fraction of the protein is retained in a post-endosomal compartment with the possibility of at least partial recycling back to the cell surface. This externally triggered, conformation-related trafficking pathway may serve as a general regulatory paradigm for membrane transporters, and its discovery was made possible thanks to consistent application of quantitative methods. Copyright © 2015 Elsevier B.V. All rights reserved.

Methylmercury oxidative degradation potentials in contaminated and pristine sediments of the Carson River, Nevada

USGS Publications Warehouse

Oremland, R.S.; Miller, L.G.; Dowdle, P.; Connell, T.; Barkay, T.

1995-01-01

Sediments from mercury-contaminated and uncontaminated reaches of the Carson River, Nevada, were assayed for sulfate reduction, methanogenesis, denitrification, and monomethylmercury (MeHg) degradation. Demethylation of [14C]MeHg was detected at all sites as indicated by the formation of 14CO2 and 14CH4. Oxidative demethylation was indicated by the formation of 14CO2 and was present at significant levels in all samples. Oxidized/reduced demethylation product ratios (i.e., 14CO2/14CH4 ratios) generally ranged from 4.0 in surface layers to as low as 0.5 at depth. Production of 14CO2 was most pronounced at sediment surfaces which were zones of active denitrification and sulfate reduction but was also significant within zones of methanogenesis. In a core taken from an uncontaminated site having a high proportion of oxidized, coarse-grain sediments, sulfate reduction and methanogenic activity levels were very low and 14CO2 accounted for 98% of the product formed from [14C]MeHg. There was no apparent relationship between the degree of mercury contamination of the sediments and the occurrence of oxidative demethylation. However, sediments from Fort Churchill, the most contaminated site, were most active in terms of demethylation potentials. Inhibition of sulfate reduction with molybdate resulted in significantly depressed oxidized/reduced demethylation product ratios, but overall demethylation rates of inhibited and uninhibited samples were comparable. Addition of sulfate to sediment slurries stimulated production of 14CO2 from [14C]MeHg, while 2-bromoethanesulfonic acid blocked production of 14CH4. These results reveal the importance of sulfate-reducing and methanogenic bacteria in oxidative demethylation of MeHg in anoxic environments.

Effect of sulfonylurea agents on reverse cholesterol transport in vitro and vivo.

PubMed

Terao, Yoshio; Ayaori, Makoto; Ogura, Masatsune; Yakushiji, Emi; Uto-Kondo, Harumi; Hisada, Tetsuya; Ozasa, Hideki; Takiguchi, Shunichi; Nakaya, Kazuhiro; Sasaki, Makoto; Komatsu, Tomohiro; Iizuka, Maki; Horii, Shunpei; Mochizuki, Seibu; Yoshimura, Michihiro; Ikewaki, Katsunori

2011-01-01

Reverse cholesterol transport (RCT) is a critical mechanism for the anti-atherogenic property of HDL. The inhibitory effect of the sulfonylurea agent (SUA) glibenclamide on ATP binding-cassette transporter (ABC) A1 may decrease HDL function but it remains unclear whether it attenuates RCT in vivo. We therefore investigated how the SUAs glibenclamide and glimepiride affected the functionality of ABCA1/ABCG1 and scavenger receptor class B type I (SR-BI) expression in macrophages in vitro and overall RCT in vivo. RAW264.7, HEK293 and BHK-21 cells were used for in vitro studies. To investigate RCT in vivo, 3H-cholesterol-labeled and acetyl LDL-loaded RAW264.7 cells were injected into mice. High dose (500µM) of glibenclamide inhibited ABCA1 function and apolipoprotein A-I (apoA-I)-mediated cholesterol efflux, and attenuated ABCA1 expression. Although glimepiride maintained apoA-I-mediated cholesterol efflux from RAW264.7 cells, like glibenclamide, it inhibited ABCA1-mediated cholesterol efflux from transfected HEK293 cells. Similarly, the SUAs inhibited SR-BI-mediated cholesterol efflux from transfected BHK-21 cells. High doses of SUAs increased ABCG1 expression in RAW264.7 cells, promoting HDL-mediated cholesterol efflux in an ABCG1-independent manner. Low doses (0.1-100 µM) of SUAs did not affect cholesterol efflux from macrophages despite dose-dependent increases in ABCA1/G1 expression. Furthermore, they did not change RCT or plasma lipid levels in mice. High doses of SUAs inhibited the functionality of ABCA1/SR-BI, but not ABCG1. At lower doses, they had no unfavorable effects on cholesterol efflux or overall RCT in vivo. These results indicate that SUAs do not have adverse effects on atherosclerosis contrary to previous findings for glibenclamide.

Resveratrol modulates ATPase activity of liposome-reconstituted ABCG1.

PubMed

de Athayde Moncorvo Collado, Alejandro; Corbalán, Natalia; Homolya, László; Morero, Roberto; Minahk, Carlos

2013-08-02

ABCG1 is a half-sized transporter with an unquestionable importance in cholesterol homeostasis. So far, its expression and thus its activity was suggested to be regulated at transcriptional level by LXR and PPAR agonists including polyphenols. However, it is unknown whether there are other mechanisms of up-regulation of ABCG1 activity. In the present work resveratrol was shown to induce a nearly twofold increase in ATPase activity of reconstituted ABCG1. Evidence is presented for the first time suggesting that resveratrol is able to activate ABCG1 activity by an alternative mechanism that involves an indirect interaction. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

The ABC transporter ABCG29 is involved in H2O2 tolerance and biocontrol traits in the fungus Clonostachys rosea.

PubMed

Dubey, Mukesh; Jensen, Dan Funck; Karlsson, Magnus

2016-04-01

For successful biocontrol interactions, biological control organisms must tolerate toxic metabolites produced by themselves or plant pathogens during mycoparasitic/antagonistic interactions, by host plant during colonization of the plant, and xenobiotics present in the environment. ATP-binding cassette (ABC) transporters can play a significant role in tolerance of toxic compounds by mediating active transport across the cellular membrane. This paper reports on functional characterization of an ABC transporter ABCG29 in the biocontrol fungus Clonostachys rosea strain IK726. Gene expression analysis showed induced expression of abcG29 during exposure to the Fusarium spp. mycotoxin zearalenone (ZEA) and the fungicides Cantus, Chipco Green and Apron. Expression of abcG29 in C. rosea was significantly higher during C. rosea-C. rosea (Cr-Cr) interaction or in exposure to C. rosea culture filtrate for 2 h, compared to interaction with Fusarium graminearum or 2 h exposure to F. graminearum culture filtrate. In contrast with gene expression data, ΔabcG29 strains did not display reduced tolerance towards ZEA, fungicides or chemical agents known for inducing oxidative, cell wall or osmotic stress, compared to C. rosea WT. The exception was a significant reduction in tolerance to H2O2 (10 mM) in ΔabcG29 strains when conidia were used as an inoculum. The antagonistic ability of ΔabcG29 strains towards F. graminearum, Fusarium oxysporum or Botrytis cinerea in dual plate assays were not different compared with WT. However, in biocontrol assays ΔabcG29 strains displayed reduced ability to protect Arabidopsis thaliana leaves from B. cinerea, and barley seedling from F. graminearum as measured by an A. thaliana detached leaf assay and a barley foot rot disease assay, respectively. These data show that the ABCG29 is dispensable for ZEA and fungicides tolerance, and antagonism but not H2O2 tolerance and biocontrol effects in C. rosea.

Effect of drug efflux transporters on placental transport of antiretroviral agent abacavir.

PubMed

Neumanova, Zuzana; Cerveny, Lukas; Greenwood, Susan L; Ceckova, Martina; Staud, Frantisek

2015-11-01

Abacavir is as a frequent part of combination antiretroviral therapy used in pregnant women. The aim of this study was to investigate, using in vitro, in situ and ex vivo experimental approaches, whether the transplacental pharmacokinetics of abacavir is affected by ATP-binding cassette (ABC) efflux transporters functionally expressed in the placenta: P-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2), multidrug resistance-associated protein 2 (ABCC2) and multidrug resistance-associated protein 5 (ABCC5). In vitro transport assays revealed that abacavir is a substrate of human ABCB1 and ABCG2 transporters but not of ABCC2 or ABCC5. In addition, in situ experiments using dually perfused rat term placenta confirmed interactions of abacavir with placental Abcb1/Abcg2. In contrast, uptake studies in human placental villous fragments did not reveal any interaction of abacavir with efflux transporters suggesting a large contribution of passive diffusion and/or influx mechanisms to net transplacental abacavir transfer. Copyright © 2015 Elsevier Inc. All rights reserved.

Evaluation of a functional epigenetic approach to identify promoter region methylation in phaeochromocytoma and neuroblastoma

PubMed Central

Margetts, Caroline D E; Morris, Mark; Astuti, Dewi; Gentle, Dean C; Cascon, Alberto; McRonald, Fiona E; Catchpoole, Daniel; Robledo, Mercedes; Neumann, Hartmut P H; Latif, Farida; Maher, Eamonn R

2008-01-01

The molecular genetics of inherited phaeochromocytoma have received considerable attention, but the somatic genetic and epigenetic events that characterise tumourigenesis in sporadic phaeochromocytomas are less well defined. Previously, we found considerable overlap between patterns of promoter region tumour suppressor gene (TSG) hypermethylation in two neural crest tumours, neuroblastoma and phaeochromocytoma. In order to identify candidate biomarkers and epigenetically inactivated TSGs in phaeochromocytoma and neuroblastoma, we characterised changes in gene expression in three neuroblastoma cell lines after treatment with the demethylating agent 5-azacytidine. Promoter region methylation status was then determined for 28 genes that demonstrated increased expression after demethylation. Three genes HSP47, homeobox A9 (HOXA9) and opioid binding protein (OPCML) were methylated in >10% of phaeochromocytomas (52, 17 and 12% respectively). Two of the genes, epithelial membrane protein 3 (EMP3) and HSP47, demonstrated significantly more frequent methylation in neuroblastoma than phaeochromocytoma. These findings extend epigenotype of phaeochromocytoma and identify candidate genes implicated in sporadic phaeochromocytoma tumourigenesis. PMID:18499731

Role of ATP-binding cassette and solute carrier transporters in erlotinib CNS penetration and intracellular accumulation.

PubMed

Elmeliegy, Mohamed A; Carcaboso, Angel M; Tagen, Michael; Bai, Feng; Stewart, Clinton F

2011-01-01

To study the role of drug transporters in central nervous system (CNS) penetration and cellular accumulation of erlotinib and its metabolite, OSI-420. After oral erlotinib administration to wild-type and ATP-binding cassette (ABC) transporter-knockout mice (Mdr1a/b(-/-), Abcg2(-/-), Mdr1a/b(-/-)Abcg2(-/-), and Abcc4(-/-)), plasma was collected and brain extracellular fluid (ECF) was sampled using intracerebral microdialysis. A pharmacokinetic model was fit to erlotinib and OSI-420 concentration-time data, and brain penetration (P(Brain)) was estimated by the ratio of ECF-to-unbound plasma area under concentration-time curves. Intracellular accumulation of erlotinib was assessed in cells overexpressing human ABC transporters or SLC22A solute carriers. P(Brain) in wild-type mice was 0.27 ± 0.11 and 0.07 ± 0.02 (mean ± SD) for erlotinib and OSI-420, respectively. Erlotinib and OSI-420 P(Brain) in Abcg2(-/-) and Mdr1a/b(-/-)Abcg2(-/-) mice were significantly higher than in wild-type mice. Mdr1a/b(-/-) mice showed similar brain ECF penetration as wild-type mice (0.49 ± 0.37 and 0.04 ± 0.02 for erlotinib and OSI-420, respectively). In vitro, erlotinib and OSI-420 accumulation was significantly lower in cells overexpressing breast cancer resistance protein (BCRP) than in control cells. Only OSI-420, not erlotinib, showed lower accumulation in cells overexpressing P-glycoprotein (P-gp) than in control cells. The P-gp/BCRP inhibitor elacridar increased erlotinib and OSI-420 accumulation in BCRP-overexpressing cells. Erlotinib uptake was higher in OAT3- and OCT2-transfected cells than in empty vector control cells. Abcg2 is the main efflux transporter preventing erlotinib and OSI-420 penetration in mouse brain. Erlotinib and OSI-420 are substrates for SLC22A family members OAT3 and OCT2. Our findings provide a mechanistic basis for erlotinib CNS penetration, cellular uptake, and efflux mechanisms. ©2010 AACR.

Epigenetic modification of the PD-1 (Pdcd1) promoter in effector CD4+ T cells tolerized by peptide immunotherapy

PubMed Central

McPherson, Rhoanne C; Konkel, Joanne E; Prendergast, Catriona T; Thomson, John P; Ottaviano, Raffaele; Leech, Melanie D; Kay, Oliver; Zandee, Stephanie E J; Sweenie, Claire H; Wraith, David C; Meehan, Richard R; Drake, Amanda J; Anderton, Stephen M

2014-01-01

Clinically effective antigen-based immunotherapy must silence antigen-experienced effector T cells (Teff) driving ongoing immune pathology. Using CD4+ autoimmune Teff cells, we demonstrate that peptide immunotherapy (PIT) is strictly dependent upon sustained T cell expression of the co-inhibitory molecule PD-1. We found high levels of 5-hydroxymethylcytosine (5hmC) at the PD-1 (Pdcd1) promoter of non-tolerant T cells. 5hmC was lost in response to PIT, with DNA hypomethylation of the promoter. We identified dynamic changes in expression of the genes encoding the Ten-Eleven-Translocation (TET) proteins that are associated with the oxidative conversion 5-methylcytosine and 5hmC, during cytosine demethylation. We describe a model whereby promoter demethylation requires the co-incident expression of permissive histone modifications at the Pdcd1 promoter together with TET availability. This combination was only seen in tolerant Teff cells following PIT, but not in Teff that transiently express PD-1. Epigenetic changes at the Pdcd1 locus therefore determine the tolerizing potential of TCR-ligation. DOI: http://dx.doi.org/10.7554/eLife.03416.001 PMID:25546306

ABCG2 transporter inhibitor restores the sensitivity of triple negative breast cancer cells to aminolevulinic acid-mediated photodynamic therapy.

PubMed

Palasuberniam, Pratheeba; Yang, Xue; Kraus, Daniel; Jones, Patrick; Myers, Kenneth A; Chen, Bin

2015-08-18

Photosensitizer protoporphyrin IX (PpIX) fluorescence, intracellular localization and cell response to photodynamic therapy (PDT) were analyzed in MCF10A normal breast epithelial cells and a panel of human breast cancer cells including estrogen receptor (ER) positive, human epidermal growth factor receptor 2 (HER2) positive and triple negative breast cancer (TNBC) cells after treatment with PpIX precursor aminolevulinic acid (ALA). Although PpIX fluorescence was heterogeneous in different cells, TNBC cells showed significantly lower PpIX level than MCF10A and ER- or HER2-positive cells. PpIX fluorescence in TNBC cells also had much less mitochondrial localization than other cells. There was an inverse correlation between PpIX fluorescence and cell viability after PDT. Breast cancer cells with the highest PpIX fluorescence were the most sensitive to ALA-PDT and TNBC cells with the lowest PpIX level were resistant to PDT. Treatment of TNBC cells with ABCG2 transporter inhibitor Ko143 significantly increased ALA-PpIX fluorescence, enhanced PpIX mitochondrial accumulation and sensitized cancer cells to ALA-PDT. Ko143 treatment had little effect on PpIX production and ALA-PDT in normal and ER- or HER2-positive cells. These results demonstrate that enhanced ABCG2 activity renders TNBC cell resistance to ALA-PDT and inhibiting ABCG2 transporter is a promising approach for targeting TNBC with ALA-based modality.

ERRα induces H3K9 demethylation by LSD1 to promote cell invasion

PubMed Central

Carnesecchi, Julie; Forcet, Christelle; Zhang, Ling; Tribollet, Violaine; Barenton, Bruno; Boudra, Rafik; Cerutti, Catherine; Billas, Isabelle M. L.; Sérandour, Aurélien A.; Carroll, Jason S.; Beaudoin, Claude; Vanacker, Jean-Marc

2017-01-01

Lysine Specific Demethylase 1 (LSD1) removes mono- and dimethyl groups from lysine 4 of histone H3 (H3K4) or H3K9, resulting in repressive or activating (respectively) transcriptional histone marks. The mechanisms that control the balance between these two antagonist activities are not understood. We here show that LSD1 and the orphan nuclear receptor estrogen-related receptor α (ERRα) display commonly activated genes. Transcriptional activation by LSD1 and ERRα involves H3K9 demethylation at the transcriptional start site (TSS). Strikingly, ERRα is sufficient to induce LSD1 to demethylate H3K9 in vitro. The relevance of this mechanism is highlighted by functional data. LSD1 and ERRα coregulate several target genes involved in cell migration, including the MMP1 matrix metallo-protease, also activated through H3K9 demethylation at the TSS. Depletion of LSD1 or ERRα reduces the cellular capacity to invade the extracellular matrix, a phenomenon that is rescued by MMP1 reexpression. Altogether our results identify a regulatory network involving a direct switch in the biochemical activities of a histone demethylase, leading to increased cell invasion. PMID:28348226

ERRα induces H3K9 demethylation by LSD1 to promote cell invasion.

PubMed

Carnesecchi, Julie; Forcet, Christelle; Zhang, Ling; Tribollet, Violaine; Barenton, Bruno; Boudra, Rafik; Cerutti, Catherine; Billas, Isabelle M L; Sérandour, Aurélien A; Carroll, Jason S; Beaudoin, Claude; Vanacker, Jean-Marc

2017-04-11

Lysine Specific Demethylase 1 (LSD1) removes mono- and dimethyl groups from lysine 4 of histone H3 (H3K4) or H3K9, resulting in repressive or activating (respectively) transcriptional histone marks. The mechanisms that control the balance between these two antagonist activities are not understood. We here show that LSD1 and the orphan nuclear receptor estrogen-related receptor α (ERRα) display commonly activated genes. Transcriptional activation by LSD1 and ERRα involves H3K9 demethylation at the transcriptional start site (TSS). Strikingly, ERRα is sufficient to induce LSD1 to demethylate H3K9 in vitro. The relevance of this mechanism is highlighted by functional data. LSD1 and ERRα coregulate several target genes involved in cell migration, including the MMP1 matrix metallo-protease, also activated through H3K9 demethylation at the TSS. Depletion of LSD1 or ERRα reduces the cellular capacity to invade the extracellular matrix, a phenomenon that is rescued by MMP1 reexpression. Altogether our results identify a regulatory network involving a direct switch in the biochemical activities of a histone demethylase, leading to increased cell invasion.

Relative contribution of rat cytochrome P450 isoforms to the metabolism of caffeine: the pathway and concentration dependence.

PubMed

Kot, Marta; Daniel, Władysława A

2008-04-01

The aim of the present study was to estimate the relative contribution of rat P450 isoforms to the metabolism of caffeine and to assess the usefulness of caffeine as a marker substance for estimating the activity of P450 in rat liver and its potential for pharmacokinetic interactions in pharmacological experiments. The results obtained using rat cDNA-expressed P450s indicated that 8-hydroxylation was the main oxidation pathway of caffeine (70%) in the rat. CYP1A2 was found to be a key enzyme catalyzing 8-hydroxylation (72%) and substantially contributing to 3-N-demethylation (47%) and 1-N-demethylation (37.5%) at a caffeine concentration of 0.1mM (relevant to "the maximum therapeutic concentration in humans"). Furthermore, CYP2C11 considerably contributed to 3-N-demethylation (31%). The CYP2C subfamily (66%) - mainly CYP2C6 (27%) and CYP2C11 (29%) - played a major role in catalyzing 7-N-demethylation. At higher substrate concentrations, the contribution of CYP1A2 to the metabolism of caffeine decreased in favor of CYP2C11 (N-demethylations) and CYP3A2 (mainly 8-hydroxylation). The obtained results were confirmed with liver microsomes (inhibition and correlation studies). Therefore, caffeine may be used as a marker substance for assessing the activity of CYP1A2 in rats, using 8-hydroxylation (but not 3-N-demethylation-like in humans); moreover, caffeine may also be used to simultaneously, preliminarily estimate the activity of CYP2C using 7-N-demethylation as a marker reaction. Hence caffeine pharmacokinetics in rats may be changed by drugs affecting the activity of CYP1A2 and/or CYP2C, e.g. by some antidepressants.

Arabidopsis ABCG14 protein controls the acropetal translocation of root-synthesized cytokinins

NASA Astrophysics Data System (ADS)

Zhang, Kewei; Novak, Ondrej; Wei, Zhaoyang; Gou, Mingyue; Zhang, Xuebin; Yu, Yong; Yang, Huijun; Cai, Yuanheng; Strnad, Miroslav; Liu, Chang-Jun

2014-02-01

Cytokinins are a major group of phytohormones regulating plant growth, development and stress responses. However, in contrast to the well-defined polar transport of auxins, the molecular basis of cytokinin transport is poorly understood. Here we show that an ATP-binding cassette transporter in Arabidopsis, AtABCG14, is essential for the acropetal (root to shoot) translocation of the root-synthesized cytokinins. AtABCG14 is expressed primarily in the pericycle and stelar cells of roots. Knocking out AtABCG14 strongly impairs the translocation of trans-zeatin (tZ)-type cytokinins from roots to shoots, thereby affecting the plant’s growth and development. AtABCG14 localizes to the plasma membrane of transformed cells. In planta feeding of C14 or C13-labelled tZ suggests that it acts as an efflux pump and its presence in the cells directly correlates with the transport of the fed cytokinin. Therefore, AtABCG14 is a transporter likely involved in the long-distance translocation of cytokinins in planta.

Redistribution of cell cycle by arsenic trioxide is associated with demethylation and expression changes of cell cycle related genes in acute promyelocytic leukemia cell line (NB4).

PubMed

Hassani, Saeed; Khaleghian, Ali; Ahmadian, Shahin; Alizadeh, Shaban; Alimoghaddam, Kamran; Ghavamzadeh, Ardeshir; Ghaffari, Seyed H

2018-01-01

PML-RARα perturbs the normal epigenetic setting, which is essential to oncogenic transformation in acute promyelocytic leukemia (APL). Transcription induction and recruitment of DNA methyltransferases (DNMTs) by PML-RARα and subsequent hypermethylation are components of this perturbation. Arsenic trioxide (ATO), an important drug in APL therapy, concurrent with degradation of PML-RARα induces cell cycle change and apoptosis. How ATO causes cell cycle alteration has remained largely unexplained. Here, we investigated DNA methylation patterns of cell cycle regulatory genes promoters, the effects of ATO on the methylated genes and cell cycle distribution in an APL cell line, NB4. Analysis of promoter methylation status of 22 cell cycle related genes in NB4 revealed that CCND1, CCNE1, CCNF, CDKN1A, GADD45α, and RBL1 genes were methylated 60.7, 84.6, 58.6, 8.7, 33.4, and 73.7%, respectively, that after treatment with 2 μM ATO for 48 h, turn into 0.6, 13.8, 0.1, 6.6, 10.7, and 54.5% methylated. ATO significantly reduced the expression of DNMT1, 3A, and 3B. ATO induced the expression of CCND1, CCNE1, and GADD45α genes, suppressed the expression of CCNF and CDKN1A genes, which were consistent with decreased number of cells in G1 and S phases and increased number of cells in G2/M phase. In conclusion, demethylation and alteration in the expression level of the cell cycle related genes may be possible mechanisms in ATO-induced cell cycle arrest in APL cells. It may suggest that ATO by demethylation of CCND1 and CCNE1 and their transcriptional activation accelerates G1 and S transition into the G2/M cell cycle arrest.

Dietary compound isoliquiritigenin prevents mammary carcinogenesis by inhibiting breast cancer stem cells through WIF1 demethylation.

PubMed

Wang, Neng; Wang, Zhiyu; Wang, Yu; Xie, Xiaoming; Shen, Jiangang; Peng, Cheng; You, Jieshu; Peng, Fu; Tang, Hailin; Guan, Xinyuan; Chen, Jianping

2015-01-01

Breast cancer stem cells (CSCs) are considered as the root of mammary tumorigenesis. Previous studies have demonstrated that ISL efficiently limited the activities of breast CSCs. However, the cancer prevention activities of ISL and its precise molecular mechanisms remain largely unknown. Here, we report a novel function of ISL as a natural demethylation agent targeting WIF1 to prevent breast cancer. ISL administration suppressed in vivo breast cancer initiation and progression, accompanied by reduced CSC-like populations. A global gene expression profile assay further identified WIF1 as the main response gene of ISL treatment, accompanied by the simultaneous downregulation of β-catenin signaling and G0/G1 phase arrest in breast CSCs. In addition, WIF1 inhibition significantly relieved the CSC-limiting effects of ISL and methylation analysis further revealed that ISL enhanced WIF1 gene expression via promoting the demethylation of its promoter, which was closely correlated with the inhibition of DNMT1 methyltransferase. Molecular docking analysis finally revealed that ISL could stably dock into the catalytic domain of DNMT1. Taken together, our findings not only provide preclinical evidence to demonstrate the use of ISL as a dietary supplement to inhibit mammary carcinogenesis but also shed novel light on WIF1 as an epigenetic target for breast cancer prevention.

The Histone Demethylase Jhdm1a Regulates Hepatic Gluconeogenesis

PubMed Central

Zou, Tie; Yao, Annie Y.; Cooper, Marcus P.; Boyartchuk, Victor; Wang, Yong-Xu

2012-01-01

Hepatic gluconeogenesis is required for maintaining blood glucose homeostasis; yet, in diabetes mellitus, this process is unrestrained and is a major contributor to fasting hyperglycemia. To date, the impacts of chromatin modifying enzymes and chromatin landscape on gluconeogenesis are poorly understood. Through catalyzing the removal of methyl groups from specific lysine residues in the histone tail, histone demethylases modulate chromatin structure and, hence, gene expression. Here we perform an RNA interference screen against the known histone demethylases and identify a histone H3 lysine 36 (H3K36) demethylase, Jhdm1a, as a key negative regulator of gluconeogenic gene expression. In vivo, silencing of Jhdm1a promotes liver glucose synthesis, while its exogenous expression reduces blood glucose level. Importantly, the regulation of gluconeogenesis by Jhdm1a requires its demethylation activity. Mechanistically, we find that Jhdm1a regulates the expression of a major gluconeogenic regulator, C/EBPα. This is achieved, at least in part, by its USF1-dependent association with the C/EBPα promoter and its subsequent demethylation of dimethylated H3K36 on the C/EBPα locus. Our work provides compelling evidence that links histone demethylation to transcriptional regulation of gluconeogenesis and has important implications for the treatment of diabetes. PMID:22719268

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halvorsen, Bente, E-mail: Bente.Halvorsen@rr-research.no; Institute of Clinical Medicine, University of Oslo, Oslo; K.G. Jebsen Inflammation Research Center, University of Oslo, Oslo

Highlights: • IL-10 promotes reverse cholesterol efflux from lipid loaded macrophages. • IL-10 increases the expression of ABCA-1 and ABCG-1. • IL-10 exhibits cross-talk with the nuclear receptor LXRα. - Abstract: Interleukin (IL)-10 is a prototypical anti-inflammatory cytokine that has been shown to attenuate atherosclerosis development. In addition to its anti-inflammatory properties, the anti-atherogenic effect of IL-10 has recently also been suggested to reflect a complex effect of IL-10 on lipid metabolism in macrophages. In the present study we examined the effects of IL-10 on cholesterol efflux mechanism in lipid-loaded THP-1 macrophages. Our main findings were: (i) IL-10 significantly enhancedmore » cholesterol efflux induced by fetal-calf serum, high-density lipoprotein (HDL){sub 2} and apolipoprotein A-1. (ii) The IL-10-mediated effects on cholesterol efflux were accompanied by an increased IL-10-mediated expression of the ATP-binding cassette transporters ABCA1 and ABCG1, that was further enhanced when the cells were co-activated with the liver X receptor (LXR)α agonist (22R)-hydroxycholesterol. (iii) The effect of LXRα activation on the IL-10-mediated effects on the ATP-binding cassette transporters seems to include enhancing effects on the IL-10 receptor 1 (IL10R1) expression and interaction with STAT-3 signaling. (iv) These enhancing effects on ABCA1 and ABCG1 was not seen when the cells were stimulated with the IL-10 family members IL-22 and IL-24. This study suggests that the anti-atherogenic properties of IL-10 may include enhancing effects on cholesterol efflux mechanism that involves cross-talk with LXRα activation.« less

The ABCG2 gene Q141K polymorphism contributes to an increased risk of gout: a meta-analysis of 2185 cases.

PubMed

Qiu, Ya; Liu, Hua; Qing, Yufeng; Yang, Min; Tan, Xiaoyao; Zhao, Mingcai; Lin, Monica; Zhou, Jingguo

2014-09-01

Individual genetic association studies examining the relationship between the ABCG2 gene polymorphisms and gout have yielded inconsistent results. This study aims to evaluate the association between the ABCG2 gene variants and gout using meta-analysis. Relevant studies were identified by searching databases extensively. The odds ratio (OR) was calculated using a random-effect or fixed-effect model. A Q statistic was used to evaluate homogeneity, and Egger's test and funnel plot were used to assess publication bias. Subgroup analyses on ethnicities and sex were also performed. A total of 7 studies, including 2185 gout patients and 8028 controls from 5 countries or regions, were included and identified for the current meta-analysis. It was found that the A allele or AA genotype of the ABCG2 Q141K polymorphism (rs2231142) had an increased risk of gout in the general population (A allele, p < 0.00001 and AA genotype, p < 0.00001, respectively). On the contrary, CC homozygote played a protective role against the risk of gout (p < 0.00001). Similar results were found in subgroup analyses. However, there was a significant heterogeneity among studies. Existing evidence indicates that the Q141K polymorphism (rs2231142, the A allele and AA genotype) is associated with an increased risk of gout.

The phytoestrogen genistein enhances multidrug resistance in breast cancer cell lines by translational regulation of ABC transporters.

PubMed

Rigalli, Juan Pablo; Tocchetti, Guillermo Nicolás; Arana, Maite Rocío; Villanueva, Silvina Stella Maris; Catania, Viviana Alicia; Theile, Dirk; Ruiz, María Laura; Weiss, Johanna

2016-06-28

Breast cancer is the most frequent malignancy in women. Multidrug resistance due to overexpression of ABC drug transporters is a common cause of chemotherapy failure and disease recurrence. Genistein (GNT) is a phytoestrogen present in soybeans and hormone supplements. We investigated the effect of GNT on the expression and function of ABC transporters in MCF-7 and MDA-MB-231 breast cancer cell lines. Results demonstrated an induction at the protein level of ABCC1 and ABCG2 and of ABCC1 in MCF-7 and MDA-MB-231, respectively. MCF-7 cells showed a concomitant increase in doxorubicin and mitoxantrone efflux and resistance, dependent on ABCG2 activity. ABCC1 induction by GNT in MDA-MB-231 cells modified neither drug efflux nor chemoresistance due to simultaneous acute inhibition of the transporter activity by GNT. All inductions took place at the translational level, as no increment in mRNA was observed and protein increase was prevented by cycloheximide. miR-181a, already demonstrated to inhibit ABCG2 translation, was down-regulated by GNT, explaining translational induction. Effects were independent of classical estrogen receptors. Results suggest potential nutrient-drug interactions that could threaten chemotherapy efficacy, especially in ABCG2-expressing tumors treated with substrates of this transporter. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

An automated method measures variability in P-glycoprotein and ABCG2 densities across brain regions and brain matter.

PubMed

Kannan, Pavitra; Schain, Martin; Kretzschmar, Warren W; Weidner, Lora; Mitsios, Nicholas; Gulyás, Balázs; Blom, Hans; Gottesman, Michael M; Innis, Robert B; Hall, Matthew D; Mulder, Jan

2017-06-01

Changes in P-glycoprotein and ABCG2 densities may play a role in amyloid-beta accumulation in Alzheimer's disease. However, previous studies report conflicting results from different brain regions, without correcting for changes in vessel density. We developed an automated method to measure transporter density exclusively within the vascular space, thereby correcting for vessel density. We then examined variability in transporter density across brain regions, matter, and disease using two cohorts of post-mortem brains from Alzheimer's disease patients and age-matched controls. Changes in transporter density were also investigated in capillaries near plaques and on the mRNA level. P-glycoprotein density varied with brain region and matter, whereas ABCG2 density varied with brain matter. In temporal cortex, P-glycoprotein density was 53% lower in Alzheimer's disease samples than in controls, and was reduced by 35% in capillaries near plaque deposits within Alzheimer's disease samples. ABCG2 density was unaffected in Alzheimer's disease. No differences were detected at the transcript level. Our study indicates that region-specific changes in transporter densities can occur globally and locally near amyloid-beta deposits in Alzheimer's disease, providing an explanation for conflicting results in the literature. When differences in region and matter are accounted for, changes in density can be reproducibly measured using our automated method.

The combination of ezetimibe and ursodiol promotes fecal sterol excretion and reveals a G5G8-independent pathway for cholesterol elimination[S

PubMed Central

Wang, Yuhuan; Liu, Xiaoxi; Pijut, Sonja S.; Li, Jianing; Horn, Jamie; Bradford, Emily M.; Leggas, Markos; Barrett, Terrence A.; Graf, Gregory A.

2015-01-01

Previous studies suggest an interdependent relationship between liver and intestine for cholesterol elimination from the body. We hypothesized that a combination of ursodiol (Urso) and ezetimibe (EZ) could increase biliary secretion and reduce cholesterol reabsorption, respectively, to promote cholesterol excretion. Treatment with Urso increased hepatic ABCG5 ABCG8 (G5G8) protein and both biliary and fecal sterols in a dose-dependent manner. To determine whether the drug combination (Urso-EZ) further increased cholesterol excretion, mice were treated with Urso alone or in combination with two doses of EZ. EZ produced an additive and dose-dependent increase in fecal neutral sterol (FNS) elimination in the presence of Urso. Finally, we sequentially treated wide-type and G5G8-deficient mice with Urso and Urso-EZ to determine the extent to which these effects were G5G8 dependent. Although biliary and FNS were invariably lower in G5G8 KO mice, the relative increase in FNS following treatment with Urso alone or the Urso-EZ combination was not affected by genotype. In conclusion, Urso increases G5G8, biliary cholesterol secretion, and FNS and acts additively with EZ to promote fecal sterol excretion. However, the stimulatory effect of these agents was not G5G8 dependent. PMID:25635125

β3-Adrenoceptor activation upregulates apolipoprotein A-I expression in HepG2 cells, which might further promote cholesterol efflux from macrophage foam cells.

PubMed

Gao, Xia-Qing; Li, Yan-Fang; Jiang, Zhi-Li

2017-01-01

The aim of this study was to explore the effects of β 3 -adrenoceptor (β 3 -AR) activation on HepG2 cells and its influence on cholesterol efflux from macrophage foam cells. HepG2 cells were cultured and treated with the β 3 -AR agonist, BRL37344, and antagonist, SR52390A, and the expression of apolipoprotein (Apo) A-I, ApoA-II, ApoB, and β 3 -AR in the supernatants and cells was determined. The expression of peroxisome proliferator-activated receptor (PPAR) γ and PPARα in the HepG2 cells was also assessed. Next, using the RAW264.7 macrophage foam cell model, we also assessed the influence of the HepG2 cell supernatants on lipid efflux. The cholesterol content of the foam cells was also measured, and the cholesterol efflux from the macrophages was examined by determining 3 H-labeled cholesterol levels. Expression of ATP-binding cassette transporter (ABC) A1 and ABCG1 of the macrophage foam cells was also assessed. β 3 -AR activation increased ApoA-I expression in both the HepG2 cells and the supernatants; PPARγ expression was upregulated, but PPARα expression was not. Treatment with GW9662 abolished the increased expression of ApoA-I induced by the β 3 -AR agonist. The HepG2 cell supernatants decreased the lipid accumulation and increased the cholesterol efflux from the macrophage foam cells. ABCA1 expression, but not ABCG1 expression, increased in the macrophage foam cells treated with BRL37344-treated HepG2 cell supernatants. Activation of β 3 -AR in HepG2 cells upregulates ApoA-I expression, which might further promote cholesterol efflux from macrophage foam cells. PPARγ might be required for the induction of ApoA-I expression.

Cold acclimation alters DNA methylation patterns and confers tolerance to heat and increases growth rate in Brassica rapa

PubMed Central

Liu, Tongkun; Li, Ying; Duan, Weike; Huang, Feiyi

2017-01-01

Abstract Epigenetic modifications are implicated in plant adaptations to abiotic stresses. Exposure of plants to one stress can induce resistance to other stresses, a process termed cross-adaptation, which is not well understood. In this study, we aimed to unravel the epigenetic basis of elevated heat-tolerance in cold-acclimated Brassica rapa by conducting a genome-wide DNA methylation analysis of leaves from control (CK) and cold-acclimated (CA) plants. We found that both methylation and demethylation occurred during cold acclimation. Two significantly altered pathways, malate dehydrogenase activity and carbon fixation, and 1562 differentially methylated genes, including BramMDH1, BraKAT2, BraSHM4, and Bra4CL2, were identified in CA plants. Genetic validation and treatment of B. rapa with 5-aza-2-deoxycytidine (Aza) suggested that promoter demethylation of four candidate genes increased their transcriptional activities. Physiological analysis suggested that elevated heat-tolerance and high growth rate were closely related to increases in organic acids and photosynthesis, respectively. Functional analyses demonstrated that the candidate gene BramMDH1 (mMDH: mitochondrial malate dehydrogenase) directly enhances organic acids and photosynthesis to increase heat-tolerance and growth rate in Arabidopsis. However, Aza-treated B. rapa, which also has elevated BramMDH1 levels, did not exhibit enhanced heat-tolerance. We therefore suggest that DNA demethylation alone is not sufficient to increase heat-tolerance. This study demonstrates that altered DNA methylation contributes to cross-adaptation. PMID:28158841

Cellular cholesterol regulates ubiquitination and degradation of the cholesterol export proteins ABCA1 and ABCG1.

PubMed

Hsieh, Victar; Kim, Mi-Jurng; Gelissen, Ingrid C; Brown, Andrew J; Sandoval, Cecilia; Hallab, Jeannette C; Kockx, Maaike; Traini, Mathew; Jessup, Wendy; Kritharides, Leonard

2014-03-14

The objective of this study was to examine the influence of cholesterol in post-translational control of ABCA1 and ABCG1 protein expression. Using CHO cell lines stably expressing human ABCA1 or ABCG1, we observed that the abundance of these proteins is increased by cell cholesterol loading. The response to increased cholesterol is rapid, is independent of transcription, and appears to be specific for these membrane proteins. The effect is mediated through cholesterol-dependent inhibition of transporter protein degradation. Cell cholesterol loading similarly regulates degradation of endogenously expressed ABCA1 and ABCG1 in human THP-1 macrophages. Turnover of ABCA1 and ABCG1 is strongly inhibited by proteasomal inhibitors and is unresponsive to inhibitors of lysosomal proteolysis. Furthermore, cell cholesterol loading inhibits ubiquitination of ABCA1 and ABCG1. Our findings provide evidence for a rapid, cholesterol-dependent, post-translational control of ABCA1 and ABCG1 protein levels, mediated through a specific and sterol-sensitive mechanism for suppression of transporter protein ubiquitination, which in turn decreases proteasomal degradation. This provides a mechanism for acute fine-tuning of cholesterol transporter activity in response to fluctuations in cell cholesterol levels, in addition to the longer term cholesterol-dependent transcriptional regulation of these genes.

Cellular Cholesterol Regulates Ubiquitination and Degradation of the Cholesterol Export Proteins ABCA1 and ABCG1*

PubMed Central

Hsieh, Victar; Kim, Mi-Jurng; Gelissen, Ingrid C.; Brown, Andrew J.; Sandoval, Cecilia; Hallab, Jeannette C.; Kockx, Maaike; Traini, Mathew; Jessup, Wendy; Kritharides, Leonard

2014-01-01

The objective of this study was to examine the influence of cholesterol in post-translational control of ABCA1 and ABCG1 protein expression. Using CHO cell lines stably expressing human ABCA1 or ABCG1, we observed that the abundance of these proteins is increased by cell cholesterol loading. The response to increased cholesterol is rapid, is independent of transcription, and appears to be specific for these membrane proteins. The effect is mediated through cholesterol-dependent inhibition of transporter protein degradation. Cell cholesterol loading similarly regulates degradation of endogenously expressed ABCA1 and ABCG1 in human THP-1 macrophages. Turnover of ABCA1 and ABCG1 is strongly inhibited by proteasomal inhibitors and is unresponsive to inhibitors of lysosomal proteolysis. Furthermore, cell cholesterol loading inhibits ubiquitination of ABCA1 and ABCG1. Our findings provide evidence for a rapid, cholesterol-dependent, post-translational control of ABCA1 and ABCG1 protein levels, mediated through a specific and sterol-sensitive mechanism for suppression of transporter protein ubiquitination, which in turn decreases proteasomal degradation. This provides a mechanism for acute fine-tuning of cholesterol transporter activity in response to fluctuations in cell cholesterol levels, in addition to the longer term cholesterol-dependent transcriptional regulation of these genes. PMID:24500716

Overexpression of AtABCG25 enhances the abscisic acid signal in guard cells and improves plant water use efficiency.

PubMed

Kuromori, Takashi; Fujita, Miki; Urano, Kaoru; Tanabata, Takanari; Sugimoto, Eriko; Shinozaki, Kazuo

2016-10-01

In addition to improving drought tolerance, improvement of water use efficiency is a major challenge in plant physiology. Due to their trade-off relationships, it is generally considered that achieving stress tolerance is incompatible with maintaining stable growth. Abscisic acid (ABA) is a key phytohormone that regulates the balance between intrinsic growth and environmental responses. Previously, we identified AtABCG25 as a cell-membrane ABA transporter that export ABA from the inside to the outside of cells. AtABCG25-overexpressing plants showed a lower transpiration phenotype without any growth retardation. Here, we dissected this useful trait using precise phenotyping approaches. AtABCG25 overexpression stimulated a local ABA response in guard cells. Furthermore, AtABCG25 overexpression enhanced drought tolerance, probably resulting from maintenance of water contents over the common threshold for survival after drought stress treatment. Finally, we observed enhanced water use efficiency by overexpression of AtABCG25, in addition to drought tolerance. These results were consistent with the function of AtABCG25 as an ABA efflux transporter. This unique trait may be generally useful for improving the water use efficiency and drought tolerance of plants. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

p300 expression repression by hypermethylation associated with tumour invasion and metastasis in oesophageal squamous cell carcinoma

PubMed Central

Zhang, Changsong; Li, Ke; Wei, Lixin; Li, Zhengyou; Yu, Ping; Teng, Lijuan; Wu, Kusheng; Zhu, Jin

2007-01-01

Background Aberrant promoter methylation is an important mechanism for gene silencing. Aims To evaluate the promoter methylation status of p300 gene in patients with oesophageal squamous cell carcinoma (OSCC). Methods The methylation status of p300 promoter was analysed by methylation‐specific PCR (MSP) in 50 OSCC tissues and the matching non‐cancerous tissues. Oesophageal cancer cell lines (ECa‐109 and TE‐10) were treated with the demethylation agent 5‐aza‐2′‐deoxycytidine (5‐Aza‐CdR), and p300 mRNA expression was detected by RT‐PCR. Results p300 methylation was found in 42% (21/50) of the OSCC tissues, but in only 20% (10/50) of the corresponding non‐cancerous tissues (p = 0.017). In OSCC samples, 65% of those with deep tumour invasion (adventitia) and 63% samples with metastasis revealed p300 promoter methylation (p<0.05). p300 mRNA expression was observed in 19.0% (4/21) of methylated tumours and 58.6% (17/29) of unmethylated tumours (p = 0.005). In addition, p300 mRNA expression was observed in 40% (4/10) of methylated non‐neoplastic tissues and 87.5% (35/40) of unmethylated non‐tumours (p = 0.001). The demethylation caused by 5‐Aza‐CdR increased the p300 mRNA expression levels in oesophageal cancer cell lines. Conclusions p300 transcription silenced by promoter hypermethylation could play a role in the pathogenesis of oesophageal squamous cell carcinoma. PMID:17965222

The Metastatic Potential and Chemoresistance of Human Pancreatic Cancer Stem Cells

PubMed Central

Bhagwandin, Vikash J.; Bishop, J. Michael; Wright, Woodring E.; Shay, Jerry W.

2016-01-01

Cancer stem cells (CSCs) typically have the capacity to evade chemotherapy and may be the principal source of metastases. CSCs for human pancreatic ductal carcinoma (PDAC) have been identified, but neither the metastatic potential nor the chemoresistance of these cells has been adequately evaluated. We have addressed these issues by examining side-population (SP) cells isolated from the Panc-1 and BxPC3 lines of human PDAC cells, the oncogenotypes of which differ. SP cells could be isolated from monolayers of Panc-1, but only from spheroids of BxPC3. Using orthotopic xenografts into the severely immunocompromised NSG mouse, we found that SP cells isolated from both cell lines produced tumors that were highly metastatic, in contrast to previous experience with PDAC cell lines. SP cells derived from both cell lines expressed the ABCG2 transporter, which was demonstrably responsible for the SP phenotype. SP cells gave rise to non-SP (NSP) cells in vitro and in vivo, a transition that was apparently due to posttranslational inhibition of the ABCG2 transporter. Twenty-two other lines of PDAC cells also expressed ABCG2. The sensitivity of PDAC SP cells to the vinca alkaloid vincristine could be greatly increased by verapamil, a general inhibitor of transporters. In contrast, verapamil had no effect on the killing of PDAC cells by gemcitabine, the current first-line therapeutic for PDAC. We conclude that the isolation of SP cells can be a convenient and effective tool for the study of PDAC CSCs; that CSCs may be the principal progenitors of metastasis by human PDAC; that the ABCG2 transporter is responsible for the SP phenotype in human PDAC cells, and may be a ubiquitous source of drug-resistance in PDAC, but does not confer resistance to gemcitabine; and that inhibition of ABCG2 might offer a useful adjunct in a therapeutic attack on the CSCs of PDAC. PMID:26859746

MET18 Connects the Cytosolic Iron-Sulfur Cluster Assembly Pathway to Active DNA Demethylation in Arabidopsis

PubMed Central

Tang, Kai; Zhang, Huiming; Mangrauthia, Satendra K.; Lei, Mingguang; Hsu, Chuan-Chih; Hou, Yueh-Ju; Wang, Chunguo; Li, Yan; Tao, W. Andy; Zhu, Jian-Kang

2015-01-01

DNA demethylation mediated by the DNA glycosylase ROS1 helps determine genomic DNA methylation patterns and protects active genes from being silenced. However, little is known about the mechanism of regulation of ROS1 enzymatic activity. Using a forward genetic screen, we identified an anti-silencing (ASI) factor, ASI3, the dysfunction of which causes transgene promoter hyper-methylation and silencing. Map-based cloning identified ASI3 as MET18, a component of the cytosolic iron-sulfur cluster assembly (CIA) pathway. Mutation in MET18 leads to hyper-methylation at thousands of genomic loci, the majority of which overlap with hypermethylated loci identified in ros1 and ros1dml2dml3 mutants. Affinity purification followed by mass spectrometry indicated that ROS1 physically associates with MET18 and other CIA components. Yeast two-hybrid and split luciferase assays showed that ROS1 can directly interact with MET18 and another CIA component, AE7. Site-directed mutagenesis of ROS1 indicated that the conserved iron-sulfur motif is indispensable for ROS1 enzymatic activity. Our results suggest that ROS1-mediated active DNA demethylation requires MET18-dependent transfer of the iron-sulfur cluster, highlighting an important role of the CIA pathway in epigenetic regulation. PMID:26492035

CES2, ABCG2, TS and Topo-I primary and synchronous metastasis expression and clinical outcome in metastatic colorectal cancer patients treated with first-line FOLFIRI regimen.

PubMed

Silvestris, Nicola; Simone, Giovanni; Partipilo, Giulia; Scarpi, Emanuela; Lorusso, Vito; Brunetti, Anna Elisabetta; Maiello, Evaristo; Paradiso, Angelo; Mangia, Anita

2014-09-05

Enzymatic activation of irinotecan (CPT-11) is due to carboxylesterase (CES), and its pharmacological behavior is influenced by drug resistance-related proteins. We previously reported that the clinical response and prognosis of metastatic colorectal cancer (mCRC) patients did not differ in tumors with different thymidylate synthase (TS) or topoisomerase-I (Topo-I) expression. Using immunohistochemistry (IHC), we evaluated the biological role of CES2 and the expression of breast cancer resistance protein (BCRP/ABCG2) in 58 consecutive mCRC patients, who had undergone a first-line CPT-11/5-FU/leucovirin (FOLFIRI) regimen. The expression of these proteins was also examined in a group of synchronous lymph nodes and liver metastases. Furthermore, all samples were revaluated for TS and Topo-I expression. High expression of CES2, ABCG2, TS and Topo-I was observed in 55%, 56%, 38% and 49% of patients, respectively. There was a significant association between high TS and high ABCG2 expression (p = 0.049). Univariate analysis showed that only TS expression significantly impacted on time to progression (p = 0.005). Moreover, Cox' multivariate analysis revealed that TS expression was significantly associated with overall survival (p = 0.01). No significant correlation was found between investigated markers expression and clinical response. Topo-I expression resulted in being significantly higher in liver metastases with respect to the corresponding primary tumors (p < 0.0001), emphasizing the role of Topo-I expression in metastatic cancer biology. In primary tumor tissues, CES2 expression tended to be higher than that observed in liver metastasis tissues (p = 0.05). These preliminary data may suggest CES2 over-expression as a potential marker of malignant phenotype. In light of these findings, we suggest that Topo-I expression together with TS expression could be associated with metastatic progression of CRC. Further studies are warranted with the aim of evaluating the potential predictive and prognostic role of CES2 and ABCG2 in larger series of patients.

Characterization of the human cytochrome P450 enzymes involved in the metabolism of dihydrocodeine

PubMed Central

Kirkwood, L. C.; Nation, R. L.; Somogyi, A. A.

1997-01-01

Aims Using human liver microsomes from donors of the CYP2D6 poor and extensive metabolizer genotypes, the role of individual cytochromes P-450 in the oxidative metabolism of dihydrocodeine was investigated. Methods The kinetics of formation of N- and O-demethylated metabolites, nordihydrocodeine and dihydromorphine, were determined using microsomes from six extensive and one poor metabolizer and the effects of chemical inhibitors selective for individual P-450 enzymes of the 1A, 2A, 2C, 2D, 2E and 3A families and of LKM1 (anti-CYP2D6) antibodies were studied. Results Nordihydrocodeine was the major metabolite in both poor and extensive metabolizers. Kinetic constants for N-demethylation derived from the single enzyme Michaelis-Menten model did not differ between the two groups. Troleandomycin and erythromycin selectively inhibited N-demethylation in both extensive and poor metabolizers. The CYP3A inducer, α-naphthoflavone, increased N-demethylation rates. The kinetics of formation of dihydromorphine in both groups were best described by a single enzyme Michaelis-Menten model although inhibition studies in extensive metabolizers suggested involvement of two enzymes with similar Km values. The kinetic constants for O-demethylation were significantly different in extensive and poor metabolizers. The extensive metabolizers had a mean intrinsic clearance to dihydromorphine more than ten times greater than the poor metabolizer. The CYP2D6 chemical inhibitors, quinidine and quinine, and LKM1 antibodies inhibited O-demethylation in extensive metabolizers; no effect was observed in microsomes from a poor metabolizer. Conclusions CYP2D6 is the major enzyme mediating O-demethylation of dihydrocodeine to dihydromorphine. In contrast, nordihydrocodeine formation is predominantly catalysed by CYP3A. PMID:9431830

ABCG2/BCRP decreases the transfer of a food-born chemical carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in perfused term human placenta.

PubMed

Myllynen, Päivi; Kummu, Maria; Kangas, Tiina; Ilves, Mika; Immonen, Elina; Rysä, Jaana; Pirilä, Rauna; Lastumäki, Anni; Vähäkangas, Kirsi H

2008-10-15

We have studied the role of ATP binding cassette (ABC) transporters in fetal exposure to carcinogens using 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) a known substrate for ABC transporters as a model compound. In perfusion of human term placenta, transfer of (14)C-PhIP (2 microM) through the placenta resulted in fetal-to-maternal concentration ratio (FM ratio) of 0.72+/-0.09 at 6 h. The specific ABCG2 inhibitor KO143 increased the transfer of (14)C-PhIP from maternal to fetal circulation (FM ratio 0.90+/-0.08 at 6 h, p<0.05) while the ABCC1/ABCC2 inhibitor probenecid had no effect (FM ratio at 6 h 0.75+/-0.10, p=0.84). There was a negative correlation between the expression of ABCG2 protein in perfused tissue and the FM ratio of (14)C-PhIP (R=-0.81, p<0.01) at the end of the perfusion. The expression of ABCC2 protein did not correlate with FM ratio of PhIP (R: -0.11, p=0.76). In addition, PhIP induced the expression of ABC transporters in BeWo cells at mRNA level. In conclusion, our data indicates that ABCG2 decreases placental transfer of (14)C-PhIP in perfused human placenta. Also, PhIP may modify ABC transporter expression in choriocarcinoma cells.

ABCG2/BCRP decreases the transfer of a food-born chemical carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in perfused term human placenta

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myllynen, Paeivi; Kummu, Maria; Kangas, Tiina

2008-10-15

We have studied the role of ATP binding cassette (ABC) transporters in fetal exposure to carcinogens using 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) a known substrate for ABC transporters as a model compound. In perfusion of human term placenta, transfer of {sup 14}C-PhIP (2 {mu}M) through the placenta resulted in fetal-to-maternal concentration ratio (FM ratio) of 0.72 {+-} 0.09 at 6 h. The specific ABCG2 inhibitor KO143 increased the transfer of {sup 14}C-PhIP from maternal to fetal circulation (FM ratio 0.90 {+-} 0.08 at 6 h, p < 0.05) while the ABCC1/ABCC2 inhibitor probenecid had no effect (FM ratio at 6 h 0.75 {+-}more » 0.10, p = 0.84). There was a negative correlation between the expression of ABCG2 protein in perfused tissue and the FM ratio of {sup 14}C-PhIP (R = - 0.81, p < 0.01) at the end of the perfusion. The expression of ABCC2 protein did not correlate with FM ratio of PhIP (R: - 0.11, p = 0.76). In addition, PhIP induced the expression of ABC transporters in BeWo cells at mRNA level. In conclusion, our data indicates that ABCG2 decreases placental transfer of {sup 14}C-PhIP in perfused human placenta. Also, PhIP may modify ABC transporter expression in choriocarinoma cells.« less

[Effect of ferulic acid on cholesterol efflux in macrophage foam cell formation and potential mechanism].

PubMed

Chen, Fu-xin; Wang, Lian-kai

2015-02-01

The formation of macrophage-derived foam cells is a typical feature of atherosclerosis (AS). Reverse cholesterol efflux (RCT) is one of important factors for the formation of macrophage foam cells. In this study, macrophage form cells were induced by oxidized low density lipoprotein (ox-LDL) and then treated with different concentrations of ferulic acid, so as to observe the effect of ferulic acid on the intracellular lipid metabolism in the ox-LDL-induced macrophage foam cell formation, the cholesterol efflux and the mRNA expression and protein levels of ATP binding cassette transporter A1 (ABCA1) and ATP binding cassette transporter G1 (ABCG1) that mediate cholesterol efflux, and discuss the potential mechanism of ferulic acid in resisting AS. According to the findings, compared with the control group, the ox-LDL-treated group showed significant increase in intracellular lipid content, especially for the cholesterol content; whereas the intracellular lipid accumulation markedly decreased, after the treatment with ferulic acid. The data also demonstrated that the mRNA and protein expressions of ABCA1 and ABCG1 significantly increased after macrophage foam cells were treated with different concentrations of ferulic acid. In summary, ferulic acid may show the anti-atherosclerosis effect by increasing the surface ABCA1 and ABCG1 expressions of macrophage form cells and promoting cholesterol efflux.

The epigenetic effect of glucosamine and a nuclear factor-kappa B (NF-kB) inhibitor on primary human chondrocytes - Implications for osteoarthritis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imagawa, Kei, E-mail: k.Imagawa@soton.ac.uk; Tohoku University School of Medicine, Sendai; Andres, MC de

Research highlights: {yields} Glucosamine and a NF-kB inhibitor reduce inflammation in OA. {yields} Cytokine induced demethylation of CpG site in IL1{beta} promoter prevented by glucosamine. {yields} Glucosamine and NF-kB inhibitor have epigenetic effects on human chondrocytes. -- Abstract: Objective: Idiopathic osteoarthritis is the most common form of osteoarthritis (OA) world-wide and remains the leading cause of disability and the associated socio-economic burden in an increasing aging population. Traditionally, OA has been viewed as a degenerative joint disease characterized by progressive destruction of the articular cartilage and changes in the subchondral bone culminating in joint failure. However, the etiology of OAmore » is multifactorial involving genetic, mechanical and environmental factors. Treatment modalities include analgesia, joint injection with steroids or hyaluronic acid, oral supplements including glucosamine and chondroitin sulfate, as well as physiotherapy. Thus, there is significant interest in the discovery of disease modifying agents. One such agent, glucosamine (GlcN) is commonly prescribed even though the therapeutic efficacy and mechanism of action remain controversial. Inflammatory cytokines, including IL-1{beta}, and proteinases such as MMP-13 have been implicated in the pathogenesis and progression of OA together with an associated CpG demethylation in their promoters. We have investigated the potential of GlcN to modulate NF-kB activity and cytokine-induced abnormal gene expression in articular chondrocytes and, critically, whether this is associated with an epigenetic process. Method: Human chondrocytes were isolated from the articular cartilage of femoral heads, obtained with ethical permission, following fractured neck of femur surgery. Chondrocytes were cultured for 5 weeks in six separate groups; (i) control culture, (ii) cultured with a mixture of 2.5 ng/ml IL-1{beta} and 2.5 ng/ml oncostatin M (OSM), (iii) cultured with 2 mM N-acetyl GlcN (Sigma-Aldrich), (iv) cultured with a mixture of 2.5 ng/ml IL-1{beta}, 2.5 ng/ml OSM and 2 mM GlcN, (v) cultured with 1.0 {mu}M BAY 11-7082 (BAY; NF-kB inhibitor: Calbiochem, Darmstadt, Germany) and, (vi) cultured with a mixture of 2.5 ng/ml IL-1{beta}, 2.5 ng/ml OSM and 1.0 {mu}M BAY. The levels of IL1B and MMP13 mRNA were examined using qRT-PCR. The percentage DNA methylation in the CpG sites of the IL1{beta} and MMP13 proximal promoter were quantified by pyrosequencing. Result:IL1{beta} expression was enhanced over 580-fold in articular chondrocytes treated with IL-1{beta} and OSM. GlcN dramatically ameliorated the cytokine-induced expression by 4-fold. BAY alone increased IL1{beta} expression by 3-fold. In the presence of BAY, IL-1{beta} induced IL1B mRNA levels were decreased by 6-fold. The observed average percentage methylation of the -256 CpG site in the IL1{beta} promoter was 65% in control cultures and decreased to 36% in the presence of IL-1{beta}/OSM. GlcN and BAY alone had a negligible effect on the methylation status of the IL1B promoter. The cytokine-induced loss of methylation status in the IL1B promoter was ameliorated by both GlcN and BAY to 44% and 53%, respectively. IL-1{beta}/OSM treatment increased MMP13 mRNA levels independently of either GlcN or BAY and no change in the methylation status of the MMP13 promoter was observed. Conclusion: We demonstrate for the first time that GlcN and BAY can prevent cytokine-induced demethylation of a specific CpG site in the IL1{beta} promoter and this was associated with decreased expression of IL1{beta}. These studies provide a potential mechanism of action for OA disease modifying agents via NF-kB and, critically, demonstrate the need for further studies to elucidate the role that NF-kB may play in DNA demethylation in human chondrocytes.« less

Severe tremor after cotrimoxazole-induced elevation of venlafaxine serum concentrations in a patient with major depressive disorder.

PubMed

Geber, Christian; Ostad Haji, Elnaz; Schlicht, Konrad; Hiemke, Christoph; Tadić, André

2013-06-01

: We describe a female patient who was an extensive metabolizer of cytochrome P450 isoenzyme (CYP) 2D6 and an intermediate metabolizer of CYP2C19 (genotype: CYP2C19 *1/*2). She exhibited high serum concentrations of venlafaxine and O-desmethylvenlafaxine and developed severe tremor after comedication with cotrimoxazole (sulfamethazole/trimethoprim). Venlafaxine is mainly metabolized by O- and N-demethylation. O-demethylation is catalyzed by the highly polymorphic CYP2D6 and N-demethylation by several enzymes, CYP2C19, CYP2C9, and CYP3A4. The observed overall pharmacokinetic effect was most probably the result of decreased N-demethylation of venlafaxine by (1) reduced expression of CYP2C19 due to a genetic deficit and (2) inhibition of CYP2C9 by cotrimoxazole.

Genetic Variations at ABCG5/G8 Genes Modulate Plasma Lipids Concentrations in Patients with Familial Hypercholesterolemia

PubMed Central

Garcia-Rios, A; Perez-Martinez, P; Fuentes, F; Mata, P; Lopez-Miranda, J; Alonso, R; Rodriguez, F; Garcia-Olid, A; Ruano, J; Ordovas, JM; Perez-Jimenez, F

2010-01-01

Objective To investigate the association of four common single nucleotide polymorphisms (SNPs) at ABCG5 (i7892A>G, i18429C>T, Gln604GluC>G, i11836G>A) and five at ABCG8 (5U145T>G, Tyr54CysA>G, Asp19HisG>C, i14222T>C, and Thr400LysG>T) with plasma lipids concentrations and to explore the interaction between those SNPs and smoking in patients with FH. Methods and Results ABCG5/G8 SNPs were genotyped in 500 subjects with genetic diagnosis of FH. Carriers of the minor A allele at the ABCG5_i11836G>A SNP displayed significantly higher HDL-C concentrations (P=0.023) than G/G subjects. In addition, carriers of the minor G allele at the ABCG5_Gln604GluC>G SNP had significantly lower VLDL-C (P=0.011) and lower TG (P=0.017) concentrations than homozygous C/C. Interestingly, a significant gene-smoking interaction was found, in which carriers of the minor alleles at ABCG5 (i7892A>G, i18429C>T, i11836G>A) SNPs displayed significantly lower HDL-C, higher TC and higher TG respectively, only in smokers. On the other hand, non-smokers carriers of the minor alleles at ABCG5 (i18429C>T and Gln604GluC>G) SNPs had significantly lower TG concentrations (P=0.012 and P=0.035) compared with homozygous for the major allele. Conclusions Our data support the notion that ABCG5/G8 genetic variants modulate plasma lipids concentrations in patients with FH and confirm that this effect could be influenced by smoking. Therefore, these results suggest that gene-environmental interactions can affect the clinical phenotype of FH. PMID:20172523

Effect of levofloxacin, pazufloxacin, enrofloxacin, and meloxicam on the immunolocalization of ABCG-2 transporter protein in rabbit retina.

PubMed

Khan, Adil Mehraj; Rampal, Satyavan; Sood, Naresh Kumar

2018-03-01

Adenosine triphosphate-binding cassette (ABC) sub-family G member-2 (ABCG-2) is a transporter protein, implicated for multi-drug efflux from tissues. This study evaluated the effect of fluoroquinolones; levofloxacin, pazufloxacin and enrofloxacin, and non-steroidal anti-inflammatory drug, meloxicam; on the immunolocalization of ABCG-2 transporter protein of rabbit retinas. Thirty-two male rabbits were randomly divided in to eight groups. Control group was gavaged, 2% benzyl alcohol in 5% dextrose since these chemicals are excipients of the drug preparations used in the treatment groups of this study. Four groups were exclusively gavaged, levofloxacin hemihydrate (10 mg/kg body weight b.i.d 12 h), pazufloxacin mesylate (10 mg/kg body weight b.i.d 12 h), enrofloxacin (20 mg/kg body weight o.d.), and meloxicam (0.2 mg/kg body weight o.d.), respectively. Three other groups were co-gavaged meloxicam with above fluoroquinolones, respectively. These drugs were administered for 21 days. ABCG-2 immunolocalization was mild in the retinas of control and levofloxacin-alone-treated groups. The immunolocalization intensity was significantly higher in meloxicam-alone-treated group when compared to control and levofloxacin-alone-treated groups. Immunolocalization of this transporter increased in the levofloxacin-meloxicam co-treated group when compared to the levofloxacin-alone-treated group. Highest immunolocalization was observed in the enrofloxacin-meloxicam co-treated group although the immunolocalization of all treatment groups, except the levofloxacin-alone-treated group, was significantly higher than the control and levofloxacin-alone-treated groups.

Molecular cloning and expression profile of an ATP-binding cassette (ABC) transporter gene from the hemipteran insect Nilaparvata lugens.

PubMed

Zha, W J; Li, S H; Zhou, L; Chen, Z J; Liu, K; Yang, G C; Hu, G; He, G C; You, A Q

2015-03-30

The ATP-binding cassette (ABC) transporters belong to a large superfamily of proteins that have important physiological functions in all living organisms. In insects, ABC transporters have important functions in the transport of molecules, and are also involved in insecticide resistance, metabolism, and development. In this study, the Nilaparvata lugens Stal (Hemiptera: Delphacidae) ABCG (NlABCG) gene was identified and characterized. The complete mRNA sequence of NlABCG was 2608-bp long, with an open reading frame of 2064 bp encoding a protein comprised of 687 amino acids. The conserved regions include three N-glycosylation and 34 phosphorylation sites, as well as seven transmembrane domains. The amino acid identity with the closely related species Acyrthosiphon pisum was 42.8%. Developmental expression analysis using quantitative real-time reverse transcriptase PCR suggested that the NlABCG transcript was expressed at all developmental stages of N. lugens. The lowest expression of NlABCG was in the 1st instar, and levels increased with larval growth. The transcript profiles of NlABCG were analyzed in various tissues from a 5th instar nymph, and the highest expression was observed in the midgut. These results suggest that the sequence, characteristics, and expression of NlABCG are highly conserved, and basic information is provided for its functional analysis.

Pancreatic stellate cells enhance stem cell-like phenotypes in pancreatic cancer cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamada, Shin; Masamune, Atsushi, E-mail: amasamune@med.tohoku.ac.jp; Takikawa, Tetsuya

2012-05-04

Highlights: Black-Right-Pointing-Pointer Pancreatic stellate cells (PSCs) promote the progression of pancreatic cancer. Black-Right-Pointing-Pointer Pancreatic cancer cells co-cultured with PSCs showed enhanced spheroid formation. Black-Right-Pointing-Pointer Expression of stem cell-related genes ABCG2, Nestin and LIN28 was increased. Black-Right-Pointing-Pointer Co-injection of PSCs enhanced tumorigenicity of pancreatic cancer cells in vivo. Black-Right-Pointing-Pointer This study suggested a novel role of PSCs as a part of the cancer stem cell niche. -- Abstract: The interaction between pancreatic cancer cells and pancreatic stellate cells (PSCs), a major profibrogenic cell type in the pancreas, is receiving increasing attention. There is accumulating evidence that PSCs promote the progression ofmore » pancreatic cancer by increasing cancer cell proliferation and invasion as well as by protecting them from radiation- and gemcitabine-induced apoptosis. Recent studies have identified that a portion of cancer cells, called 'cancer stem cells', within the entire cancer tissue harbor highly tumorigenic and chemo-resistant phenotypes, which lead to the recurrence after surgery or re-growth of the tumor. The mechanisms that maintain the 'stemness' of these cells remain largely unknown. We hypothesized that PSCs might enhance the cancer stem cell-like phenotypes in pancreatic cancer cells. Indirect co-culture of pancreatic cancer cells with PSCs enhanced the spheroid-forming ability of cancer cells and induced the expression of cancer stem cell-related genes ABCG2, Nestin and LIN28. In addition, co-injection of PSCs enhanced tumorigenicity of pancreatic cancer cells in vivo. These results suggested a novel role of PSCs as a part of the cancer stem cell niche.« less

One for all: A standardized protocol for ex vivo culture of limbal, conjunctival and oral mucosal epithelial cells into corneal lineage.

PubMed

Dhamodaran, Kamesh; Subramani, Murali; Matalia, Himanshu; Jayadev, Chaitra; Shetty, Rohit; Das, Debashish

2016-04-01

Autologous transplantation of ex vivo cultured cells the treatment of choice for patients with limbal stem cell deficiency. The most commonly used cell sources for transplantation limbal, conjunctival or oral mucosal tissue. Protocols vary for culturing each tissue type, and there are no comparative studies on transplantation outcomes using these different culture techniques. To overcome this limitation, we devised a simple protocol that can uniformly promote growth and differentiation of cells from a limbal, conjunctival or oral mucosal biopsy into the corneal lineage. Biopsies were cultured as explants on de-epithelialized human amniotic membrane in the presence of recombinant epidermal growth factor and insulin. Cultured cells were characterized using immunohistochemistry and quantitative reverse transcriptase polymerase chain reaction for stem/progenitor markers (ABCG2 and P63α) and differentiation markers (CK3, CK12, CK4, CK13, CK15 and CONNEXIN 43). Fluorescence-activated cell sorter analysis was performed for ABCG2. The results revealed that cells of all three biopsies differentiated into the corneal lineage. Positivity of CK3/12, CK4, CK12 and CONNEXIN 43 immunostaining and the relative mRNA expression of CK3, CK4, CK12, CK13, CK15 and CONNEXIN 43 could be detected in the cultured biopsies. Unlike tissue-specific protocols, our protocol can unequivocally promote differentiation of cells from a limbal, conjunctival or oral mucosal biopsy into the corneal lineage. This simple standardized protocol can be adapted for ocular surface reconstruction using stem cell transplantation. Copyright © 2016 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.

Novel Epigenetic Controlling of Hypoxia Pathway Related to Overexpression and Promoter Hypomethylation of TET1 and TET2 in RPE Cells.

PubMed

Alivand, Mohammad Reza; Soheili, Zahra-Soheila; Pornour, Majid; Solali, Saeed; Sabouni, Farzaneh

2017-10-01

CpG methylation of DNA takes part in a specific epigenetic memory that plays crucial roles in the differentiation and abnormality of the cells. The methylation pattern aberration of genomes is affected in three ways, namely DNA methyltransferase (DNMT), ten-eleven translocation (TET), and methyl-binding domain (MBD) proteins. Of these, TET enzymes have recently been demonstrated to be master modifier enzymes in the DNA methylation process. Additionally, recent studies emphasize that not only epigenetic phenomena play a role in controlling hypoxia pathway, but the hypoxia condition also triggers hypomethylation of genomes that may help with the expression of hypoxia pathway genes. In this study, we suggested that TET1 and TET2 could play a role in the demethylation of genomes under chemical hypoxia conditions. Herein, the evaluating methylation status and mRNA expression of mentioned genes were utilized through real-time PCR and methylation-specific PCR (MSP), respectively. Our results showed that TET1 and TET2 genes were overexpressed (P < 0.05) under chemical hypoxia conditions in Retinal Pigment Epithelial (RPE) cells, whereas the promoter methylation status of them were hypomethylated in the same condition. Therefore, chemical hypoxia not only causes overexpression of TET1 and TET2 but also could gradually do promoter demethylation of same genes. This is the first study to show the relationship between epigenetics and the expression of mentioned genes related to hypoxia pathways. Furthermore, it seems that these associations in RPE cells are subjected to chemical hypoxia as a mechanism that could play a crucial role in methylation pattern changes of hypoxia-related diseases such as cancer and ischemia. J. Cell. Biochem. 118: 3193-3204, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Enzastaurin inhibits ABCB1-mediated drug efflux independently of effects on protein kinase C signalling and the cellular p53 status.

PubMed

Michaelis, Martin; Rothweiler, Florian; Löschmann, Nadine; Sharifi, Mohsen; Ghafourian, Taravat; Cinatl, Jindrich

2015-07-10

The PKCβ inhibitor enzastaurin was tested in parental neuroblastoma and rhabdomyosarcoma cell lines, their vincristine-resistant sub-lines, primary neuroblastoma cells, ABCB1-transduced, ABCG2-transduced, and p53-depleted cells. Enzastaurin IC50s ranged from 3.3 to 9.5 μM in cell lines and primary cells independently of the ABCB1, ABCG2, or p53 status. Enzastaurin 0.3125 μM interfered with ABCB1-mediated drug transport. PKCα and PKCβ may phosphorylate and activate ABCB1 under the control of p53. However, enzastaurin exerted similar effects on ABCB1 in the presence or absence of functional p53. Also, enzastaurin inhibited PKC signalling only in concentrations ≥ 1.25 μM. The investigated cell lines did not express PKCβ. PKCα depletion reduced PKC signalling but did not affect ABCB1 activity. Intracellular levels of the fluorescent ABCB1 substrate rhodamine 123 rapidly decreased after wash-out of extracellular enzastaurin, and enzastaurin induced ABCB1 ATPase activity resembling the ABCB1 substrate verapamil. Computational docking experiments detected a direct interaction of enzastaurin and ABCB1. These data suggest that enzastaurin directly interferes with ABCB1 function. Enzastaurin further inhibited ABCG2-mediated drug transport but by a different mechanism since it reduced ABCG2 ATPase activity. These findings are important for the further development of therapies combining enzastaurin with ABC transporter substrates.

RNA-dependent chromatin localization of KDM4D lysine demethylase promotes H3K9me3 demethylation

PubMed Central

Zoabi, Muhammad; Nadar-Ponniah, Prathamesh T.; Khoury-Haddad, Hanan; Usaj, Marko; Budowski-Tal, Inbal; Haran, Tali; Henn, Arnon; Mandel-Gutfreund, Yael; Ayoub, Nabieh

2014-01-01

The JmjC-containing lysine demethylase, KDM4D, demethylates di-and tri-methylation of histone H3 on lysine 9 (H3K9me3). How KDM4D is recruited to chromatin and recognizes its histone substrates remains unknown. Here, we show that KDM4D binds RNA independently of its demethylase activity. We mapped two non-canonical RNA binding domains: the first is within the N-terminal spanning amino acids 115 to 236, and the second is within the C-terminal spanning amino acids 348 to 523 of KDM4D. We also demonstrate that RNA interactions with KDM4D N-terminal region are critical for its association with chromatin and subsequently for demethylating H3K9me3 in cells. This study implicates, for the first time, RNA molecules in regulating the levels of H3K9 methylation by affecting KDM4D association with chromatin. PMID:25378304

Gadd45a Is an RNA Binding Protein and Is Localized in Nuclear Speckles

PubMed Central

Sytnikova, Yuliya A.; Kubarenko, Andriy V.; Schäfer, Andrea; Weber, Alexander N. R.; Niehrs, Christof

2011-01-01

Background The Gadd45 proteins play important roles in growth control, maintenance of genomic stability, DNA repair, and apoptosis. Recently, Gadd45 proteins have also been implicated in epigenetic gene regulation by promoting active DNA demethylation. Gadd45 proteins have sequence homology with the L7Ae/L30e/S12e RNA binding superfamily of ribosomal proteins, which raises the question if they may interact directly with nucleic acids. Principal Findings Here we show that Gadd45a binds RNA but not single- or double stranded DNA or methylated DNA in vitro. Sucrose density gradient centrifugation experiments demonstrate that Gadd45a is present in high molecular weight particles, which are RNase sensitive. Gadd45a displays RNase-sensitive colocalization in nuclear speckles with the RNA helicase p68 and the RNA binding protein SC35. A K45A point mutation defective in RNA binding was still active in DNA demethylation. This suggests that RNA binding is not absolutely essential for demethylation of an artificial substrate. A point mutation at G39 impared RNA binding, nuclear speckle localization and DNA demethylation, emphasizing its relevance for Gadd45a function. Significance The results implicate RNA in Gadd45a function and suggest that Gadd45a is associated with a ribonucleoprotein particle. PMID:21249130

The Arabidopsis DSO/ABCG11 transporter affects cutin metabolism in reproductive organs and suberin in roots.

PubMed

Panikashvili, David; Shi, Jian Xin; Bocobza, Samuel; Franke, Rochus Benni; Schreiber, Lukas; Aharoni, Asaph

2010-05-01

Apart from its significance in the protection against stress conditions, the cuticular cover is essential for proper development of the diverse surface structures formed on aerial plant organs. This layer mainly consists of a cutin matrix, embedded and overlaid with cuticular waxes. Following their biosynthesis in epidermal cells, cutin and waxes were suggested to be exported across the plasma membrane by ABCG-type transporters such as DSO/ABCG11 to the cell wall and further to extracellular matrix. Here, additional aspects of DSO/ABCG11 function were investigated, predominantly in reproductive organs, which were not revealed in the previous reports. This was facilitated by the generation of a transgenic DSO/ABCG11 silenced line (dso-4) that displayed relatively subtle morphological and chemical phenotypes. These included altered petal and silique morphology, fusion of seeds, and changes in levels of cutin monomers in flowers and siliques. The dso-4 phenotypes corresponded to the strong DSO/ABCG11 gene expression in the embryo epidermis as well as in the endosperm tissues of the developing seeds. Moreover, the DSO/ABCG11 protein displayed polar localization in the embryo protoderm. Transcriptome analysis of the dso-4 mutant leaves and stems showed that reduced DSO/ABCG11 activity suppressed the expression of a large number of cuticle-associated genes, implying that export of cuticular lipids from the plasma membrane is a rate-limiting step in cuticle metabolism. Surprisingly, root suberin composition of dso-4 was altered, as well as root expression of two suberin biosynthetic genes. Taken together, this study provides new insights into cutin and suberin metabolism and their role in reproductive organs and roots development.

Lidocaine and ropivacaine, but not bupivacaine, demethylate deoxyribonucleic acid in breast cancer cells in vitro.

PubMed

Lirk, P; Hollmann, M W; Fleischer, M; Weber, N C; Fiegl, H

2014-07-01

Lidocaine demethylates deoxyribonucleic acid (DNA) in breast cancer cells. This modification of epigenetic information may be of therapeutic relevance in the perioperative period, because a decrease in methylation can reactivate tumour suppressor genes and inhibit tumour growth. The objectives of this study were to determine the effect of two amide local anaesthetics, ropivacaine and bupivacaine, on methylation in two breast cancer cell lines and to detect whether the combination of lidocaine with the chemotherapy agent 5-aza-2'-deoxycytidine (DAC) would result in additive demethylating effects. Breast cancer cell lines BT-20 [oestrogen receptor (ER)-negative] and MCF-7 (ER-positive) were incubated with lidocaine, bupivacaine, and ropivacaine to assess demethylating properties. Then, we tested varying concentrations of lidocaine and DAC to assess whether their demethylating effects were additive. Cell numbers and global methylation status were analysed. Lidocaine decreased methylation in BT-20 and MCF-7 cells, ropivacaine decreased methylation in BT-20 cells, and bupivacaine had no demethylating effect. When combined, lidocaine and DAC had additive demethylating effects. At clinically relevant doses, lidocaine and ropivacaine exert demethylating effects on specific breast cancer cell lines, but bupivacaine does not. The demethylating effects of lidocaine and DAC are indeed additive. © The Author [2014]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Association of genotypes and haplotypes of multi-drug transporter genes ABCB1 and ABCG2 with clinical response to imatinib mesylate in chronic myeloid leukemia patients.

PubMed

Au, Anthony; Aziz Baba, Abdul; Goh, Ai Sim; Wahid Fadilah, S Abdul; Teh, Alan; Rosline, Hassan; Ankathil, Ravindran

2014-04-01

The introduction and success of imatinib mesylate (IM) has become a paradigm shift in chronic myeloid leukemia (CML) treatment. However, the high efficacy of IM has been hampered by the issue of clinical resistance that might due to pharmacogenetic variability. In the current study, the contribution of three common single nucleotide polymorphisms (SNPs) of ABCB1 (T1236C, G2677T/A and C3435T) and two SNPs of ABCG2 (G34A and C421A) genes in mediating resistance and/or good response among 215 CML patients on IM therapy were investigated. Among these patients, the frequency distribution of ABCG2 421 CC, CA and AA genotypes were significantly different between IM good response and resistant groups (P=0.01). Resistance was significantly associated with patients who had homozygous ABCB1 1236 CC genotype with OR 2.79 (95%CI: 1.217-6.374, P=0.01). For ABCB1 G2677T/A polymorphism, a better complete cytogenetic remission was observed for patients with variant TT/AT/AA genotype, compared to other genotype groups (OR=0.48, 95%CI: 0.239-0.957, P=0.03). Haplotype analysis revealed that ABCB1 haplotypes (C1236G2677C3435) was statistically linked to higher risk to IM resistance (25.8% vs. 17.4%, P=0.04), while ABCG2 diplotype A34A421 was significantly correlated with IM good response (9.1% vs. 3.9%, P=0.03). In addition, genotypic variant in ABCG2 421C>A was associated with a major molecular response (MMR) (OR=2.20, 95%CI: 1.273-3.811, P=0.004), whereas ABCB1 2677G>T/A variant was associated with a significantly lower molecular response (OR=0.49, 95%CI: 0.248-0.974, P=0.04). However, there was no significant correlation of these SNPs with IM intolerance and IM induced hepatotoxicity. Our results suggest the usefulness of genotyping of these single nucleotide polymorphisms in predicting IM response among CML patients. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Demethylation-mediated miR-129-5p up-regulation inhibits malignant phenotype of osteogenic osteosarcoma by targeting Homo sapiens valosin-containing protein (VCP).

PubMed

Long, Xin Hua; Zhou, Yun Fei; Peng, Ai Fen; Zhang, Zhi Hong; Chen, Xuan Yin; Chen, Wen Zhao; Liu, Jia Ming; Huang, Shan Hu; Liu, Zhi Li

2015-05-01

Previous studies demonstrated that increased Homo sapiens valosin-containing protein (VCP) may be involved in osteosarcoma (OS) metastasis. However, the underlying mechanism of VCP over-expression in OS remains unknown. In the present study, we found a significantly negative correlation between miR-129-5p and VCP protein expression in OS tissues with pulmonary metastasis (Spearman's rho, rs = -0.948). Bioinformatical prediction, Luciferase reporter assay, Western blot, and RT-PCR assays performed on OS cells indicated that VCP is a target of miR-129-5p. In addition, three CPG islands in the region of miR-129-5p promoter were detected by bioinformatical prediction, and significantly higher expression of miR-129-5p and lower methylation level of miR-129-2 gene in OS cells treated with 5-Aza-2'-deoxycytidine (a potent DNA demethylating agent) than in those untreated cells were observed. Furthermore, lower migratory and invasive ability was found in cells with elevated miR-129-5p than in those with decreased miR-129-5p. These findings indicated that increased miR-129-5p may be mediated by demethylation and inhibit OS cell migration and invasion by targeting VCP in OS, and targeting miR-129-5p/VCP signaling pathway may serve as a therapeutic strategy for OS management, although further studies will be necessary.

Population Pharmacokinetics of Oral Topotecan in Infants and Very Young Children with Brain Tumors Demonstrates a Role of ABCG2 rs4148157 on the Absorption Rate Constant

PubMed Central

Roberts, Jessica K.; Birg, Anna V.; Lin, Tong; Daryani, Vinay M.; Panetta, John C.; Broniscer, Alberto; Robinson, Giles W.; Gajjar, Amar J.

2016-01-01

For infants and very young children with brain tumors, chemotherapy after surgical resection is the main treatment due to neurologic and neuroendocrine adverse effects from whole brain irradiation. Topotecan, an anticancer drug with antitumor activity against pediatric brain tumors, can be given intravenous or orally. However, high interpatient variability in oral drug bioavailability is common in children less than 3 years old. Therefore, this study aimed to determine the population pharmacokinetics of oral topotecan in infants and very young children, specifically evaluating the effects of age and ABCG2 and ABCB1 on the absorption rate constant (Ka), as well as other covariate effects on all pharmacokinetic parameters. A nonlinear mixed effects model was implemented in Monolix 4.3.2 (Lixoft, Orsay, France). A one-compartment model with first-order input and first-order elimination was found to adequately characterize topotecan lactone concentrations with population estimates as [mean (S.E.)]; Ka = 0.61 (0.11) h−1, apparent volume of distribution (V/F) = 40.2 (7.0) l, and apparent clearance (CL/F) = 40.0 (2.9) l/h. After including the body surface area in the V/F and CL/F as a power model centered on the population median, the ABCG2 rs4148157 allele was found to play a significant role in the value of Ka. Patients homozygous or heterozygous for G>A demonstrated a Ka value 2-fold higher than their GG counterparts, complemented with a 2-fold higher maximal concentration as well. These results demonstrate a possible role for the ABCG2 rs4148157 allele in the pharmacokinetics of oral topotecan in infants and very young children, and warrants further investigation. PMID:27052877

Deficiency of ABCA1 and ABCG1 in Macrophages Increases Inflammation and Accelerates Atherosclerosis in Mice

PubMed Central

Westerterp, Marit; Murphy, Andrew J.; Wang, Mi; Pagler, Tamara A.; Vengrenyuk, Yuliya; Kappus, Mojdeh S.; Gorman, Darren J.; Nagareddy, Prabhakara R.; Zhu, Xuewei; Abramowicz, Sandra; Parks, John S.; Welch, Carrie; Fisher, Edward A.; Wang, Nan; Yvan-Charvet, Laurent; Tall, Alan R.

2013-01-01

Rationale Plasma HDL levels are inversely correlated with atherosclerosis. Although it is widely assumed that this is due to the ability of HDL to promote cholesterol efflux from macrophage foam cells, direct experimental support for this hypothesis is lacking. Objective To assess the role of macrophage cholesterol efflux pathways in atherogenesis. Methods and Results We developed MAC-ABCDKO mice with efficient deletion of the ATP Binding Cassette Transporters A1 and G1 (ABCA1 and ABCG1) in macrophages but not in hematopoietic stem or progenitor populations. MAC-ABCDKO bone marrow (BM) was transplanted into Ldlr-/- recipients. On the chow diet, these mice had similar plasma cholesterol and blood monocyte levels but increased atherosclerosis compared to controls. On the Western type diet (WTD), MAC-ABCDKO BM transplanted Ldlr-/- mice had disproportionate atherosclerosis, considering they also had lower VLDL/LDL cholesterol levels than controls. ABCA1/G1 deficient macrophages in lesions showed increased inflammatory gene expression. Unexpectedly, WTD-fed MAC-ABCDKO BM transplanted Ldlr-/- mice displayed monocytosis and neutrophilia in the absence of HSPC proliferation. Mechanistic studies revealed increased expression of M-CSF and G-CSF in splenic macrophage foam cells, driving BM monocyte and neutrophil production. Conclusion These studies 1) show that macrophage deficiency of ABCA1/G1 is pro-atherogenic likely by promoting plaque inflammation and 2) uncover a novel positive feedback loop in which cholesterol-laden splenic macrophages signal BM progenitors to produce monocytes, with suppression by macrophage cholesterol efflux pathways. PMID:23572498

Epigenetics Reactivation of Nrf2 in Prostate TRAMP C1 Cells by Curcumin Analogue FN1.

PubMed

Li, Wenji; Pung, Doug; Su, Zheng-Yuan; Guo, Yue; Zhang, Chengyue; Yang, Anne Yuqing; Zheng, Xi; Du, Zhi-Yun; Zhang, Kun; Kong, Ah-Ng

2016-04-18

It has previously been shown that curcumin can effectively inhibit prostate cancer proliferation and progression in TRAMP mice, potentially acting through the hypomethylation of the Nrf2 gene promoter and hence activation of the Nrf2 pathway to enhance cell antioxidative defense. FN1 is a synthetic curcumin analogue that shows stronger anticancer activity than curcumin in other reports. We aimed to explore the epigenetic modification of FN1 that restores Nrf2 expression in TRAMP-C1 cells. Stably transfected HepG2-C8 cells were used to investigate the effect of FN1 on the Nrf2- antioxidant response element (ARE) pathway. Real-time quantitative PCR and Western blotting were applied to study the influence of FN1 on endogenous Nrf2 and its downstream genes. Bisulfite genomic sequencing (BGS) and methylated DNA immunoprecipitation (MeDIP) were then performed to examine the methylation profile of the Nrf2 promoter. An anchorage-independent colony-formation analysis was conducted to examine the tumor inhibition activity of FN1. Epigenetic modification enzymes, including DNMTs and HDACs, were investigated by Western blotting. The luciferase reporter assay indicated that FN1 was more potent than curcumin in activating the Nrf2-ARE pathway. FN1 increased the expression of Nrf2 and its downstream detoxifying enzymes. FN1 significantly inhibited the colony formation of TRAMP-C1 cells. BGS and MeDIP assays revealed that FN1 treatment (250 nM for 3 days) reduced the percentage of CpG methylation of the Nrf2 promoter. FN1 also downregulated epigenetic modification enzymes. In conclusion, our results suggest that FN1 is a novel anticancer agent for prostate cancer. In the TRAMP-C1 cell line, FN1 can increase the level of Nrf2 and downstream genes via activating the Nrf2-ARE pathway and inhibit the colony formation potentially through the decreased expression of keap1 coupled with CpG demethylation of the Nrf2 promoter. This CpG demethylation effect may come from decreased epigenetic modification enzymes, such as DNMT1, DNMT3a, DNMT3b, and HDAC4.

Comparison of culture media for ex vivo cultivation of limbal epithelial progenitor cells

PubMed Central

Loureiro, Renata Ruoco; Cristovam, Priscila Cardoso; Martins, Caio Marques; Covre, Joyce Luciana; Sobrinho, Juliana Aparecida; Ricardo, José Reinaldo da Silva; Hazarbassanov, Rossen Myhailov; Höfling-Lima, Ana Luisa; Belfort, Rubens; Nishi, Mauro

2013-01-01

Purpose To compare the effectiveness of three culture media for growth, proliferation, differentiation, and viability of ex vivo cultured limbal epithelial progenitor cells. Methods Limbal epithelial progenitor cell cultures were established from ten human corneal rims and grew on plastic wells in three culture media: supplemental hormonal epithelial medium (SHEM), keratinocyte serum-free medium (KSFM), and Epilife. The performance of culturing limbal epithelial progenitor cells in each medium was evaluated according to the following parameters: growth area of epithelial migration; immunocytochemistry for adenosine 5′-triphosphate-binding cassette member 2 (ABCG2), p63, Ki67, cytokeratin 3 (CK3), and vimentin (VMT) and real-time reverse transcription polymerase chain reaction (RT–PCR) for CK3, ABCG2, and p63, and cell viability using Hoechst staining. Results Limbal epithelial progenitor cells cultivated in SHEM showed a tendency to faster migration, compared to KSFM and Epilife. Immunocytochemical analysis showed that proliferated cells in the SHEM had lower expression for markers related to progenitor epithelial cells (ABCG2) and putative progenitor cells (p63), and a higher percentage of positive cells for differentiated epithelium (CK3) when compared to KSFM and Epilife. In PCR analysis, ABCG2 expression was statistically higher for Epilife compared to SHEM. Expression of p63 was statistically higher for Epilife compared to SHEM and KSFM. However, CK3 expression was statistically lower for KSFM compared to SHEM. Conclusions Based on our findings, we concluded that cells cultured in KSFM and Epilife media presented a higher percentage of limbal epithelial progenitor cells, compared to SHEM. PMID:23378720

The systems biology of uric acid transporters: the role of remote sensing and signaling.

PubMed

Nigam, Sanjay K; Bhatnagar, Vibha

2018-07-01

Uric acid homeostasis in the body is mediated by a number of SLC and ABC transporters in the kidney and intestine, including several multispecific 'drug' transporters (e.g., OAT1, OAT3, and ABCG2). Optimization of uric acid levels can be viewed as a 'systems biology' problem. Here, we consider uric acid transporters from a systems physiology perspective using the framework of the 'Remote Sensing and Signaling Hypothesis.' This hypothesis explains how SLC and ABC 'drug' and other transporters mediate interorgan and interorganismal communication (e.g., gut microbiome and host) via small molecules (e.g., metabolites, antioxidants signaling molecules) through transporters expressed in tissues lining body fluid compartments (e.g., blood, urine, cerebrospinal fluid). The list of uric acid transporters includes: SLC2A9, ABCG2, URAT1 (SLC22A12), OAT1 (SLC22A6), OAT3 (SLC22A8), OAT4 (SLC22A11), OAT10 (SLC22A13), NPT1 (SLC17A1), NPT4 (SLC17A3), MRP2 (ABCC2), MRP4 (ABCC4). Normally, SLC2A9, - along with URAT1, OAT1 and OAT3, - appear to be the main transporters regulating renal urate handling, while ABCG2 appears to regulate intestinal transport. In chronic kidney disease (CKD), intestinal ABCG2 becomes much more important, suggesting remote organ communication between the injured kidney and the intestine. The remote sensing and signaling hypothesis provides a useful systems-level framework for understanding the complex interplay of uric acid transporters expressed in different tissues involved in optimizing uric acid levels under normal and diseased (e.g., CKD, gut microflora dysbiosis) conditions.

Demethylation and cleavage of dimethylsulfoniopropionate in marine intertidal sediments

USGS Publications Warehouse

Visscher, P.T.; Kiene, R.P.; Taylor, B.F.

1994-01-01

Demethylation and cleavage of dimethylsulfoniopropionate (DMSP) was measured in three different types of,intertidal marine sediments: a cyanobacterial mat, a diatom-covered tidal flat and a carbonate sediment. Consumption rates of added DMSP were highest in cyanobacterial mat slurries (59 ?? mol DMSP l-1 slurry h-1) and lower in slurries from a diatom mat and a carbonate tidal sediment (24 and 9 ??mol DMSP l-1 h-1, respectively). Dimethyl sulfide (DMS) and 3-mercaptopropionate (MPA) were produced simultaneously during DMSP consumption, indicating that cleavage and demethylation occurred at the same time. Viable counts of DMSP-utilizing bacteria revealed a population of 2 x 107 cells cm-3 sediment (90% of these cleaved DMSP to DMS, 10% demethylated DMSP to MPA) in the cyanobacterial mat, 7 x 105 cells cm-3 in the diatom mat (23% cleavers, 77% demethylators), and 9 x 104 cells cm-3 (20% cleavers and 80% demethylators) in the carbonate sediment. In slurries of the diatom mat, the rate of MPA production from added 3-methiolpropionate (MMPA) was 50% of the rate of MPA formation from DMSP. The presence of a large population of demethylating bacteria and the production of MPA from DMSP suggest that the demethylation pathway, in addition to cleavage, contributes significantly to DMSP consumption in coastal sediments.

Green synthesis of low-toxicity graphene-fulvic acid with an open band gap enhances demethylation of methylmercury.

PubMed

Hu, Xiangang; Mu, Li; Lu, Kaicheng; Kang, Jia; Zhou, Qixing

2014-06-25

The demethylation of methylmercury has received substantial attention. Here, a novel chemical method for the demethylation of methylmercury is proposed. The low-toxicity graphene-fulvic acid (FA, a ubiquitous material in the environment) was synthesized without the use of a chemical reagent. The hybridized graphene-FA presented an indirect open band gap of 2.25-2.87 eV as well as adequate aqueous dispersion. More importantly, the hybridized graphene-FA exhibited 6- and 10-fold higher photocatalytic efficiencies for the demethylation of methylmercury than FA and free FA with graphene, respectively. This result implies that immobilized, rather than free, FA accelerated the catalysis. Furthermore, inorganic mercuric ion, elemental mercury, and mercuric oxide were identified as the primary demethylation products. For free FA with graphene, graphene quenches the excited-state FA, inhibiting the demethylation by electron transfer. In contrast, the graphene of the self-assembled graphene-FA serves as an electron reservoir, causing electron-hole pair separation. Graphene-FA showed a negligible toxicity toward microalgae compared to graphene. The above results reveal that the green synthesis of graphene and organic molecules is a convenient strategy for obtaining effective cocatalysts.

Reduced Plasma HDL Cholesterol in Hyperthyroid Mice Coincides with Decreased Hepatic ABCA1 Expression

PubMed Central

TANCEVSKI, IVAN; WEHINGER, ANDREAS; DEMETZ, EGON; ELLER, PHILIPP; DUWENSEE, KRISTINA; HUBER, JULIA; HOCHEGGER, KATHRIN; SCHGOER, WILFRIED; FIEVET, CATHERINE; STELLAARD, FRANS; RUDLING, MATS; PATSCH, JOSEF R.; RITSCH, ANDREAS

2010-01-01

The aim of the study was to investigate the influence of severe hyperthyroidism on plasma high-density lipoprotein cholesterol (HDL-C). Recently, it was shown in mice that increasing doses of triiodothyronine (T3) upregulate hepatic expression of scavenger receptor-BI (SR-BI), resulting in increased clearance of plasma HDL-C. Here we show that severe hyperthyroidism in mice did not affect hepatic expression of SR-BI, but reduced hepatic expression of ATP-binding cassette transporter 1 (ABCA1), accompanied by a 40%-reduction of HDL-C. Sterol content of bile, liver and feces was markedly increased, accompanied by upregulation of hepatic CYP7A1, and ATP-binding cassette half-transporter ABCG5, which is known to promote biliary sterol secretion upon dimerization with ABCG8. Both control and hyperthyroid mice exerted identical plasma clearance of intravenously injected [3H] HDL-C, supporting the view that severe hyperthyroidism does not affect HDL-C clearance, but rather its formation via hepatic ABCA1. PMID:18388200

Gene variants associated with ischemic stroke: the cardiovascular health study.

PubMed

Luke, May M; O'Meara, Ellen S; Rowland, Charles M; Shiffman, Dov; Bare, Lance A; Arellano, Andre R; Longstreth, W T; Lumley, Thomas; Rice, Kenneth; Tracy, Russell P; Devlin, James J; Psaty, Bruce M

2009-02-01

The purpose of this study was to determine whether 74 single nucleotide polymorphisms (SNPs), which had been associated with coronary heart disease, are associated with incident ischemic stroke. Based on antecedent studies of coronary heart disease, we prespecified the risk allele for each of the 74 SNPs. We used Cox proportional hazards models that adjusted for traditional risk factors to estimate the associations of these SNPs with incident ischemic stroke during 14 years of follow-up in a population-based study of older adults: the Cardiovascular Health Study (CHS). In white CHS participants, the prespecified risk alleles of 7 of the 74 SNPs (in HPS1, ITGAE, ABCG2, MYH15, FSTL4, CALM1, and BAT2) were nominally associated with increased risk of stroke (one-sided P<0.05, false discovery rate=0.42). In black participants, the prespecified risk alleles of 5 SNPs (in KRT4, LY6G5B, EDG1, DMXL2, and ABCG2) were nominally associated with stroke (one-sided P<0.05, false discovery rate=0.55). The Val12Met SNP in ABCG2 was associated with stroke in both white (hazard ratio, 1.46; 90% CI, 1.05 to 2.03) and black (hazard ratio, 3.59; 90% CI, 1.11 to 11.6) participants of CHS. Kaplan-Meier estimates of the 10-year cumulative incidence of stroke were greater among Val allele homozygotes than among Met allele carriers in both white (10% versus 6%) and black (12% versus 3%) participants of CHS. The Val12Met SNP in ABCG2 (encoding a transporter of sterols and xenobiotics) was associated with incident ischemic stroke in white and black participants of CHS.

Organic anion transporter 4 (OAT 4) modifies placental transfer of perfluorinated alkyl acids PFOS and PFOA in human placental ex vivo perfusion system.

PubMed

Kummu, M; Sieppi, E; Koponen, J; Laatio, L; Vähäkangas, K; Kiviranta, H; Rautio, A; Myllynen, P

2015-10-01

Perfluorinated alkyl acids (PFAAs) are widely used in industry and consumer products. Pregnant women are exposed to PFAAs and their presence in umbilical cord blood represents fetal exposure. Interestingly, PFAAs are substrates for organic anion transporters (OAT) of which OAT4 is expressed in human placenta. To evaluate the contribution of OAT4 and ATP-binding cassette transporter G2 (ABCG2) proteins in the transplacental transfer of perfluoro octane sulfonate (PFOS) and perfluoro octanoate (PFOA) an ex vivo dual recirculating human placental perfusion was used. Altogether 8 placentas from healthy mothers with uncomplicated pregnancies were successfully perfused. Both PFOS and PFOA crossed the placenta as suggested by in vivo data in the literature. The expression of OAT4 and ABCG2 proteins were studied by immunoblotting and correlation with the transfer index %(TI %) of PFOS and PFOA at 120 and 240 min (n = 4) was studied. The expression of OAT4 was in negative correlation with TI % of PFOA (R(2) = 0.92, p = 0.043) and PFOS (R(2) = 0.99, p = 0.007) at 120 min while at 240 min the correlation was statistically significant only with PFOA. The expression of ABCG2 did not correlate with TI% of PFOS or PFOA. Data obtained in this study suggest the involvement of OAT4 in placental passage of PFAAs. Placental passage of PFOS and PFOA is modified by the transporter protein OAT4 but not by ABCG2. This is the first study indicating that OAT4 may decrease the fetal exposure to PFAAs and protect the fetus after maternal exposure to PFAAs but further studies are needed to confirm our findings. Copyright © 2015 Elsevier Ltd. All rights reserved.

Arsenic Demethylation by a C·As Lyase in Cyanobacterium Nostoc sp. PCC 7120.

PubMed

Yan, Yu; Ye, Jun; Xue, Xi-Mei; Zhu, Yong-Guan

2015-12-15

Arsenic, a ubiquitous toxic substance, exists mainly as inorganic forms in the environment. It is perceived that organoarsenicals can be demethylated and degraded into inorganic arsenic by microorganisms. Few studies have focused on the mechanism of arsenic demethylation in bacteria. Here, we investigated arsenic demethylation in a typical freshwater cyanobacterium Nostoc sp. PCC 7120. This bacterium was able to demethylate monomethylarsenite [MAs(III)] rapidly to arsenite [As(III)] and also had the ability to demethylate monomethylarsenate [MAs(V)] to As(III). The NsarsI encoding a C·As lyase responsible for MAs(III) demethylation was cloned from Nostoc sp. PCC 7120 and heterologously expressed in an As-hypersensitive strain Escherichia coli AW3110 (ΔarsRBC). Expression of NsarsI was shown to confer MAs(III) resistance through arsenic demethylation. The purified NsArsI was further identified and functionally characterized in vitro. NsArsI existed mainly as the trimeric state, and the kinetic data were well-fit to the Hill equation with K0.5 = 7.55 ± 0.33 μM for MAs(III), Vmax = 0.79 ± 0.02 μM min(-1), and h = 2.7. Both of the NsArsI truncated derivatives lacking the C-terminal 10 residues (ArsI10) or 23 residues (ArsI23) had a reduced ability of MAs(III) demethylation. These results provide new insights for understanding the important role of cyanobacteria in arsenic biogeochemical cycling in the environment.

Studies of metabolic pathways of trimebutine by simultaneous administration of trimebutine and its deuterium-labeled metabolite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miura, Y.; Chishima, S.; Takeyama, S.

1989-07-01

Trimebutine maleate (I), (+-)-2-dimethylamino-2-phenylbutyl 3,4,5-trimethoxybenzoate hydrogen maleate, and a deuterium-labeled sample of its hydrolyzed metabolite, 2-dimethylamino-2-phenylbutanol-d3 (II-d3), were simultaneously administered to experimental animals at an oral dose of 10 or 50 mumol/kg, and distribution ratios of the two alternative initial metabolic steps, i.e., ester hydrolysis and N-demethylation, were estimated by determining the composition of the urinary alcohol-moiety metabolites, II, and its mono- and di-demethylated metabolites, III and IV, by GC/MS. In dogs, the order of quantities of the metabolites from II-d3 was II much greater than III much greater than IV, showing predominance of conjugation over N-demethylation. However, this ordermore » was reversed when the amounts of the metabolites from I were compared, indicating that I was preferentially metabolized by N-demethylation followed by ester hydrolysis and conjugation in this order. In rats, a considerable proportion of I was presumed to be metabolized by ester hydrolysis before N-demethylation. In in vitro experiments employing the liver microsomes and homogenates of liver and small intestine from rats and dogs, it was found that both ester-hydrolizing and N-demethylating activities were higher in rats than in dogs, and the conjugating activity was higher in dogs than in rats. It was also found that I, having a high lipophilicity, was more susceptible to N-demethylation than less lipophilic II. These results from the in vitro experiments could account for the species differences in the distribution ratio of the metabolic pathways of I in vivo.« less

Impairment of DNA Methylation Maintenance Is the Main Cause of Global Demethylation in Naive Embryonic Stem Cells.

PubMed

von Meyenn, Ferdinand; Iurlaro, Mario; Habibi, Ehsan; Liu, Ning Qing; Salehzadeh-Yazdi, Ali; Santos, Fátima; Petrini, Edoardo; Milagre, Inês; Yu, Miao; Xie, Zhenqing; Kroeze, Leonie I; Nesterova, Tatyana B; Jansen, Joop H; Xie, Hehuang; He, Chuan; Reik, Wolf; Stunnenberg, Hendrik G

2016-06-16

Global demethylation is part of a conserved program of epigenetic reprogramming to naive pluripotency. The transition from primed hypermethylated embryonic stem cells (ESCs) to naive hypomethylated ones (serum-to-2i) is a valuable model system for epigenetic reprogramming. We present a mathematical model, which accurately predicts global DNA demethylation kinetics. Experimentally, we show that the main drivers of global demethylation are neither active mechanisms (Aicda, Tdg, and Tet1-3) nor the reduction of de novo methylation. UHRF1 protein, the essential targeting factor for DNMT1, is reduced upon transition to 2i, and so is recruitment of the maintenance methylation machinery to replication foci. Concurrently, there is global loss of H3K9me2, which is needed for chromatin binding of UHRF1. These mechanisms synergistically enforce global DNA hypomethylation in a replication-coupled fashion. Our observations establish the molecular mechanism for global demethylation in naive ESCs, which has key parallels with those operating in primordial germ cells and early embryos. Crown Copyright © 2016. Published by Elsevier Inc. All rights reserved.

DNA methylation and the potential role of demethylating agents in prevention of progressive chronic kidney disease.

PubMed

Larkin, Benjamin P; Glastras, Sarah J; Chen, Hui; Pollock, Carol A; Saad, Sonia

2018-04-24

Chronic kidney disease (CKD) is a global epidemic, and its major risk factors include obesity and type 2 diabetes. Obesity not only promotes metabolic dysregulation and the development of diabetic kidney disease but also may independently lead to CKD by a variety of mechanisms, including endocrine and metabolic dysfunction, inflammation, oxidative stress, altered renal hemodynamics, and lipotoxicity. Deleterious renal effects of obesity can also be transmitted from one generation to the next, and it is increasingly recognized that offspring of obese mothers are predisposed to CKD. Epigenetic modifications are changes that regulate gene expression without altering the DNA sequence. Of these, DNA methylation is the most studied. Epigenetic imprints, particularly DNA methylation, are laid down during critical periods of fetal development, and they may provide a mechanism by which maternal-fetal transmission of chronic disease occurs. Our current review explores the evidence for the role of DNA methylation in the development of CKD, diabetic kidney disease, diabetes, and obesity. DNA methylation has been implicated in renal fibrosis-the final pathophysiologic pathway in the development of end-stage kidney disease-which supports the notion that demethylating agents may play a potential therapeutic role in preventing development and progression of CKD.-Larkin, B. P., Glastras, S. J., Chen, H., Pollock, C. A., Saad, S. DNA methylation and the potential role of demethylating agents in prevention of progressive chronic kidney disease.

Study on the relationship between the methylation of the MMP-9 gene promoter region and diabetic nephropathy.

PubMed

Yang, Xiao-Hui; Feng, Shi-Ya; Yu, Yang; Liang, Zhou

2018-01-01

This study aims to explore the relationship between the methylation of matrix metalloproteinase (MMP)-9 gene promoter region and diabetic nephropathy (DN) through the detection of the methylation level of MMP-9 gene promoter region in the peripheral blood of patients with DN in different periods and serum MMP-9 concentration. The methylation level of the MMP-9 gene promoter region was detected by methylation-specific polymerase chain reaction (MSP), and the content of MMP-9 in serum was determined by enzyme-linked immunosorbent assay (ELISA). Results of the statistical analysis revealed that serum MMP-9 protein expression levels gradually increased in patients in the simple diabetic group, early diabetic nephropathy group and clinical diabetic nephropathy group, compared with the control group; and the difference was statistically significant (P < 0.05). Compared with the control group, the methylation levels of MMP-9 gene promoter regions gradually decreased in patients in the simple diabetic group, early diabetic nephropathy group, and clinical diabetic nephropathy group; and the difference was statistically significant (P < 0.05). Furthermore, correlation analysis results indicated that the demethylation levels of the MMP-9 gene promoter region was positively correlated with serum protein levels, urinary albumin to creatinine ratio (UACR), urea and creatinine; and was negatively correlated with GFR. The demethylation of the MMP-9 gene promoter region may be involved in the occurrence and development of diabetic nephropathy by regulating the expression of MMP-9 protein in serum.

[ROLE OF SLC2A9 AND ABCG2 GENE POLYMORPHISMS IN ORIGIN OF HYPERURICEMIA AND GOUT].

PubMed

Fadieieva, A; Prystupa, L; Pogorelova, O; Kirichenko, N; Dudchenko, I

2016-03-01

The polymorphisms V253I, Q126X, Q141K of SLC2A9 and ABCG2 genes were characterized. GCA и GTC haplotypes of Q126X and Q141K variants can be predictors of gout. The relationship of these polymorphisms with hyperuricaemia according to gender, metabolic syndrome components, with the response to allopurinol was analyzed. It has been established that Q141K polymorphism can directly modulate BCRP-mediated allopurinol and oxypurinol efflux, the K allele is associated with a lower reduction in serum uric acid in response to allopurinol treatment.

Human Platelet Lysate as a Replacement for Fetal Bovine Serum in Limbal Stem Cell Therapy.

PubMed

Suri, Kunal; Gong, Hwee K; Yuan, Ching; Kaufman, Stephen C

2016-10-01

To evaluate the use of human platelet lysate (HPL) as an alternative supplement for limbal explant culture. Culture media were prepared using either 10% pooled HPL (PHPL), single donor HPL, or fetal bovine serum (FBS). Limbal tissues, obtained from the Minnesota Lions Eye Bank, were cultured in each medium on plastic plates or on denuded amniotic membrane (AM). Immunofluorescence staining was performed for ABCG2, tumor protein p63α, and cytokeratin 3 (K3). Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) was used to evaluate the expression of ABCG2 and p63. Limbal explants grown in each medium were labeled with bromodeoxyuridine (BrdU) to assess the proliferative capacity in each medium. Concentration of growth factors including epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), transforming growth factor-β (TGF-β), and platelet derived growth factor (PDGF) in HPL and PHPL was compared to that in human serum (HS). Immunofluorescence staining on AM showed prominent expression of ABCG2, p63α but sparse expression of K3 in HPL and PHPL supplemented medium. Real time-PCR showed 1.7 fold higher expression of ABCG2 in PHPL supplemented medium (p = 0.03), and similar expression of p63 in HPL and PHPL supplemented medium compared to FBS medium. The proliferation assay showed that LSCs retained their proliferative potential in HPL supplemented medium. Higher concentration of growth factors were found in HPL, compared to HS. Human platelet lysate has higher concentration of grown factors and is effective in maintaining growth and stem cell phenotype of corneal limbal explant cultures.

Enhancement of the Effect of Methyl Pyropheophorbide-a-Mediated Photodynamic Therapy was Achieved by Increasing ROS through Inhibition of Nrf2-HO-1 or Nrf2-ABCG2 Signaling.

PubMed

Tian, Si; Yong, Min; Zhu, Jiang; Zhang, Li; Pan, Li; Chen, Qing; Li, Kai-Ting; Kong, Yu-Han; Jiang, Yuan; Yu, Ting-He; Yu, Le-Hua; Bai, Ding-Qun

2017-01-01

Emerging evidence indicates that the transcription factor nuclear factor-E2-related factor 2 (Nrf2) plays an essential role in cellular defense against oxidative stress; its activation has been related to cytoprotection. Here, we investigated the role of Nrf2 in improving the efficacy of methyl pyropheophorbide-amediated photodynamic therapy (Mppa-PDT) via the downregulation of Nrf2. Human ovarian cancer A2780 cells and SKOV3 cells were treated with Mppa-PDT and siRNA transfection was performed to inhibit Nrf2. After treated with siRNA and Mppa-PDT, the cell viability was examined with CCK-8 assay; cell apoptosis was detected tested by flow cytometry with Annexin V-FITC/PI; the celluar reactive oxygen species (ROS) and mitochondrial membrane potential were measured with DCFHDA and JC-1 staining; expression of protein was assessed by western blot analysis. We found that Nrf2 translocated from the cytoplasm to the nucleus in vitro and in vivo, and the expression of Nrf2 and P-Nrf2 increased through a possible mechanism regulated by mitogen-activated protein kinase (MAPK) after Mppa-PDT treatment. Furthermore, cytotoxicity and apoptosis induced by Mppa-PDT increased after Nrf2down-regulation. Nrf2 down -regulation increased reactive oxygen species (ROS) levels by attenuating antioxidants or pumping Mppa out of cells,which resulted from the inhibition of Nrf2-HO-1 or Nrf2- ABCG2 signaling. In addition, SKOV3 cells exhibited increased resistance to Mppa-PDT, and the expression levels of P-Nrf2 and ABCG2 were higher in SKOV3 cells than in A2780 cells, suggesting that Nrf2-ABCG2 signaling might be involved in the intrinsic resistanceto Mppa-PDT. These results provided evidence that Nrf2 down-regulation can enhance the effect of Mppa-PDT. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Dietary xenosterols lead to infertility and loss of abdominal adipose tissue in sterolin-deficient mice[S

PubMed Central

Solca, Curzio; Tint, G. Stephen; Patel, Shailendra B.

2013-01-01

The investigation of the human disease sitosterolemia (MIM 210250) has shed light not only on the pathways by which dietary sterols may traffic but also on how the mammalian body rids itself of cholesterol and defends against xenosterols. Two genes, ABCG5 and ABCG8, located at the sitosterolemia locus, each encodes a membrane-bound ABC half-transporter and constitutes a functional unit whose activity has now been shown to account for biliary and intestinal sterol excretion. Knockout mice deficient in Abcg5 or Abcg8 recapitulate many of the phenotypic features of sitosterolemia. During the course of our studies to characterize these knockout mice, we noted that these mice, raised on normal rodent chow, exhibited infertility as well as loss of abdominal fat. We show that, although sitosterolemia does not lead to any structural defects or to any overt endocrine defects, fertility could be restored if xenosterols are specifically blocked from entry and that the loss of fat is also reversed by a variety of maneuvers that limit xenosterol accumulation. These studies show that xenosterols may have a significant biological impact on normal mammalian physiology and that the Abcg5 or Abcg8 knockout mouse model may prove useful in investigating the role of xenosterols on mammalian physiology. PMID:23180829

Identification of methylated genes in salivary gland adenoid cystic carcinoma xenografts using global demethylation and methylation microarray screening

PubMed Central

LING, SHIZHANG; RETTIG, ELENI M.; TAN, MARIETTA; CHANG, XIAOFEI; WANG, ZHIMING; BRAIT, MARIANA; BISHOP, JUSTIN A.; FERTIG, ELANA J.; CONSIDINE, MICHAEL; WICK, MICHAEL J.; HA, PATRICK K.

2016-01-01

Salivary gland adenoid cystic carcinoma (ACC) is a rare head and neck malignancy without molecular biomarkers that can be used to predict the chemotherapeutic response or prognosis of ACC. The regulation of gene expression of oncogenes and tumor suppressor genes (TSGs) through DNA promoter methylation may play a role in the carcinogenesis of ACC. To identify differentially methylated genes in ACC, a global demethylating agent, 5-aza-2′-deoxycytidine (5-AZA) was utilized to unmask putative TSG silencing in ACC xenograft models in mice. Fresh xenografts were passaged, implanted in triplicate in mice that were treated with 5-AZA daily for 28 days. These xenografts were then evaluated for genome-wide DNA methylation patterns using the Illumina Infinium HumanMethylation27 BeadChip array. Validation of the 32 candidate genes was performed by bisulfite sequencing (BS-seq) in a separate cohort of 6 ACC primary tumors and 6 normal control salivary gland tissues. Hypermethylation was identified in the HCN2 gene promoter in all 6 control tissues, but hypomethylation was found in all 6 ACC tumor tissues. Quantitative validation of HCN2 promoter methylation level in the region detected by BS-seq was performed in a larger cohort of primary tumors (n=32) confirming significant HCN2 hypomethylation in ACCs compared with normal samples (n=10; P=0.04). HCN2 immunohistochemical staining was performed on an ACC tissue microarray. HCN2 staining intensity and H-score, but not percentage of the positively stained cells, were significantly stronger in normal tissues than those of ACC tissues. With our novel screening and sequencing methods, we identified several gene candidates that were methylated. The most significant of these genes, HCN2, was actually hypomethylated in tumors. However, promoter methylation status does not appear to be a major determinant of HCN2 expression in normal and ACC tissues. HCN2 hypomethylation is a biomarker of ACC and may play an important role in the carcinogenesis of ACC. PMID:27212063

ABCG5/G8 gene is associated with hypercholesterolemias without mutation in candidate genes and noncholesterol sterols.

PubMed

Lamiquiz-Moneo, Itziar; Baila-Rueda, Lucía; Bea, Ana M; Mateo-Gallego, Rocío; Pérez-Calahorra, Sofía; Marco-Benedí, Victoria; Martín-Navarro, Antonio; Ros, Emilio; Cofán, Montserrat; Rodríguez-Rey, José Carlos; Pocovi, Miguel; Cenarro, Ana; Civeira, Fernando

Approximately 20% to 40% of clinically defined familial hypercholesterolemia (FH) cases do not show a causative mutation in candidate genes (mutation-negative FH), and some of them may have a polygenic origin. The aim of this work was to study the prevalence of ABCG5/G8 genetic variants in mutation-negative FH, as defects in these genes relate to intestinal hyperabsorption of cholesterol and thus ABCG5/G8 variants could explain in part the mechanism of hypercholesterolemia. We sequenced the ABCG5/G8 genes in 214 mutation-negative FH and 97 controls. Surrogate markers of cholesterol absorption (5α-cholestanol, β-sitosterol, campesterol, stigmasterol, and sitostanol) were quantified by high-performance liquid chromatography-tandem mass spectrometry in both studied groups. We found 8 mutation-negative FH patients (3.73%) with a pathogenic mutation in ABCG5/G8 genes. We observed significantly higher concentration of surrogate markers of cholesterol absorption in mutation-negative FH than in controls. In addition, we found significantly higher concentrations of cholesterol absorption markers in mutation-negative FH with ABCG5/G8 defects than in mutation-negative, ABCG5/G8-negative FH. A gene score reflecting the number of common single nucleotide variants associated with hypercholesterolemia was significantly higher in cases than in controls (P = .032). Subjects with a gene score above the mean had significantly higher 5α-cholestanol and stigmasterol than those with a lower gene score. Mutation-negative FH subjects accumulate an excess of rare and common gene variations in ABCG5/G8 genes. This variation is associated with increased intestinal absorption of cholesterol, as determined by surrogate makers, suggesting that these loci contribute to hypercholesterolemia by enhancing intestinal cholesterol absorption. Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.

Inhibition of DNA methylation and reactivation of silenced genes by zebularine.

PubMed

Cheng, Jonathan C; Matsen, Cindy B; Gonzales, Felicidad A; Ye, Wei; Greer, Sheldon; Marquez, Victor E; Jones, Peter A; Selker, Eric U

2003-03-05

Gene silencing by abnormal methylation of promoter regions of regulatory genes is commonly associated with cancer. Silenced tumor suppressor genes are obvious targets for reactivation by methylation inhibitors such as 5-azacytidine (5-Aza-CR) and 5-aza-2'-deoxycytidine (5-Aza-CdR). However, both compounds are chemically unstable and toxic and neither can be given orally. We characterized a new demethylating agent, zebularine [1-(beta-D-ribofuranosyl)-1,2-dihydropyrimidin-2-one], which is a chemically stable cytidine analog. We tested the ability of zebularine to reactivate a silenced Neurospora crassa gene using a hygromycin gene reactivation assay. We then analyzed the ability of zebularine to inhibit DNA methylation in C3H 10T1/2 Cl8 (10T1/2) mouse embryo cells as assayed by induction of a myogenic phenotype and in T24 human bladder carcinoma cells, using the methylation-sensitive single nucleotide primer extension (Ms-SNuPE) assay. We also evaluated the effects of zebularine (administered orally or intraperitoneally) on growth of EJ6 human bladder carcinoma cells grown in BALB/c nu/nu mice (five mice per group) and the in vivo reactivation of a methylated p16 gene in these cells. All statistical tests were two-sided. In N. crassa, zebularine inhibited DNA methylation and reactivated a gene previously silenced by methylation. Zebularine induced the myogenic phenotype in 10T1/2 cells, which is a phenomenon unique to DNA methylation inhibitors. Zebularine reactivated a silenced p16 gene and demethylated its promoter region in T24 bladder carcinoma cells in vitro and in tumors grown in mice. Zebularine was only slightly cytotoxic to T24 cells in vitro (1 mM zebularine for 48 hours decreased plating efficiency by 17% [95% confidence interval (CI) = 12.8% to 21.2%]) and to tumor-bearing mice (average maximal weight change in mice treated with 1000 mg/kg zebularine = 11% [95% CI = 4% to 19%]). Compared with those in control mice, tumor volumes were statistically significantly reduced in mice treated with high-dose zebularine administered by intraperitoneal injection (P<.001) or by oral gavage (P<.001). Zebularine is a stable DNA demethylating agent and the first drug in its class able to reactivate an epigenetically silenced gene by oral administration.

A DEMETER-like DNA demethylase governs tomato fruit ripening.

PubMed

Liu, Ruie; How-Kit, Alexandre; Stammitti, Linda; Teyssier, Emeline; Rolin, Dominique; Mortain-Bertrand, Anne; Halle, Stefanie; Liu, Mingchun; Kong, Junhua; Wu, Chaoqun; Degraeve-Guibault, Charlotte; Chapman, Natalie H; Maucourt, Mickael; Hodgman, T Charlie; Tost, Jörg; Bouzayen, Mondher; Hong, Yiguo; Seymour, Graham B; Giovannoni, James J; Gallusci, Philippe

2015-08-25

In plants, genomic DNA methylation which contributes to development and stress responses can be actively removed by DEMETER-like DNA demethylases (DMLs). Indeed, in Arabidopsis DMLs are important for maternal imprinting and endosperm demethylation, but only a few studies demonstrate the developmental roles of active DNA demethylation conclusively in this plant. Here, we show a direct cause and effect relationship between active DNA demethylation mainly mediated by the tomato DML, SlDML2, and fruit ripening- an important developmental process unique to plants. RNAi SlDML2 knockdown results in ripening inhibition via hypermethylation and repression of the expression of genes encoding ripening transcription factors and rate-limiting enzymes of key biochemical processes such as carotenoid synthesis. Our data demonstrate that active DNA demethylation is central to the control of ripening in tomato.

Aminolevulinic acid-mediated protoporphyrin IX and photodynamic therapy for breast cancers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Chen, Bin

2017-02-01

Photodynamic therapy (PDT) involves the combination of a photosensitizer and light of a specific wavelength. Upon light activation in the presence of oxygen, photosensitizer molecules generate reactive oxygen species that cause cytotoxicity by inducing oxidative stress. Aminolevulinic acid (ALA) is a pro-drug used for the diagnosis and PDT treatment of various solid tumors based on endogenous production of heme precursor protoporphyrin IX (PpIX). Although nearly all types of human cells express heme biosynthesis enzymes and produce PpIX, tumor cells are found to have more PpIX production and accumulation than normal cells, allowing for the detection and treatment of solid tumors. The objective of my research is to explore therapeutic approaches to enhance ALA-based tumor detection and therapy. We have found that high ABCG2 transporter activity in triple negative breast cancer cells (TNBC) contributed to reduced PpIX levels in cells, causing them to be more resistant towards ALA-PDT. The administration of an ABCG2 inhibitor, Ko143, was able to reverse cell resistance to ALA-PDT by enhancing PpIX mitochondrial accumulation and sensitizing cancer cells to ALA-PDT. Ko143 treatment had little effect on PpIX production and ALA-PDT in normal and ER- or HER2-positive cells. Furthermore, since some tyrosine kinase inhibitors (TKI) are known to block ABCG2 transporter activity, we screened a panel of tyrosine kinase inhibitors to examine its effect on enhancing PpIX fluorescence and ALA-PDT efficacy. Several TKIs including lapatinib and gefitinib showed effectiveness in increasing ALA-PpIX fluorescence in TNBC leading to increased cell death after PDT administration. These results indicate that inhibiting ABCG2 transporter using TKIs is a promising approach for targeting TNBC with ALA-based modality.

Induction of hepatic ABC transporter expression is part of the PPARalpha-mediated fasting response in the mouse.

PubMed

Kok, Tineke; Wolters, Henk; Bloks, Vincent W; Havinga, Rick; Jansen, Peter L M; Staels, Bart; Kuipers, Folkert

2003-01-01

Fatty acids are natural ligands of the peroxisome proliferator-activated receptor alpha (PPARalpha). Synthetic ligands of this nuclear receptor, i.e., fibrates, induce the hepatic expression of the multidrug resistance 2 gene (Mdr2), encoding the canalicular phospholipid translocator, and affect hepatobiliary lipid transport. We tested whether fasting-associated fatty acid release from adipose tissues alters hepatic transporter expression and bile formation in a PPARalpha-dependent manner. A 24-hour fasting/48-hour refeeding schedule was used in wild-type and Pparalpha((-/-)) mice. Expression of genes involved in the control of bile formation was determined and related to secretion rates of biliary components. Expression of Pparalpha, farnesoid X receptor, and liver X receptor alpha genes encoding nuclear receptors that control hepatic bile salt and sterol metabolism was induced on fasting in wild-type mice only. The expression of Mdr2 was 5-fold increased in fasted wild-type mice and increased only marginally in Pparalpha((-/-)) mice, and it normalized on refeeding. Mdr2 protein levels and maximal biliary phospholipid secretion rates were clearly increased in fasted wild-type mice. Hepatic expression of the liver X receptor target genes ATP binding cassette transporter a1 (Abca1), Abcg5, and Abcg8, implicated in hepatobiliary cholesterol transport, was induced in fasted wild-type mice only. However, the maximal biliary cholesterol secretion rate was reduced by approximately 50%. Induction of Mdr2 expression and function is part of the PPARalpha-mediated fasting response in mice. Fasting also induces expression of the putative hepatobiliary cholesterol transport genes Abca1, Abcg5, and Abcg8, but, nonetheless, maximal biliary cholesterol excretion is decreased after fasting.

The potential of clofarabine in MLL-rearranged infant acute lymphoblastic leukaemia.

PubMed

Stumpel, Dominique J P M; Schneider, Pauline; Pieters, Rob; Stam, Ronald W

2015-09-01

MLL-rearranged acute lymphoblastic leukaemia (ALL) in infants is the most difficult-to-treat type of childhood ALL, displaying a chemotherapy-resistant phenotype, and unique histone modifications, gene expression signatures and DNA methylation patterns. MLL-rearranged infant ALL responds remarkably well to nucleoside analogue drugs in vitro, such as cytarabine and cladribine, and to the demethylating agents decitabine and zebularine as measured by cytotoxicity assays. These observations led to the inclusion of cytarabine into the treatment regimens currently used for infants with ALL. However, survival chances for infants with MLL-rearranged ALL do still not exceed 30-40%. Here we explored the in vitro potential of the novel nucleoside analogue clofarabine for MLL-rearranged infant ALL. Therefore we used both cell line models as well as primary patient cells. Compared with other nucleoside analogues, clofarabine effectively targeted primary MLL-rearranged infant ALL cells at the lowest concentrations, with median LC50 values of ∼25 nM. Interestingly, clofarabine displayed synergistic cytotoxic effects in combination with cytarabine. Furthermore, at concentrations of 5-10nM clofarabine induced demethylation of the promoter region of the tumour suppressor gene FHIT (Fragile Histidine Triad), a gene typically hypermethylated in MLL-rearranged ALL. Demethylation of the FHIT promoter region was accompanied by subtle re-expression of this gene both at the mRNA and protein level. We conclude that clofarabine is an interesting candidate for further studies in MLL-rearranged ALL in infants. Copyright © 2015 Elsevier Ltd. All rights reserved.

Constitutive mRNA expression and protein activity levels of nine ABC efflux transporters in seven permanent cell lines derived from different tissues of rainbow trout (Oncorhynchus mykiss).

PubMed

Fischer, Stephan; Loncar, Jovica; Zaja, Roko; Schnell, Sabine; Schirmer, Kristin; Smital, Tvrtko; Luckenbach, Till

2011-01-25

Permanent fish cell lines have become common model systems for determining ecotoxicological effects of pollutants. For these cell lines little is known on the cellular active transport mechanisms that control the amount of a compound entering the cell, such as the MXR (multixenobiotic resistance) system mediated by ATP binding cassette (ABC) transport proteins. Therefore, for toxic evaluation of chemicals with those cells information on MXR is important. We here present data on constitutive mRNA expression and protein activity levels of a series of ABC efflux transporters in seven permanent cell lines derived from liver (RTL-W1; R1) and liver hepatoma (RTH-149), gill (RTgill-W1), gonad (RTG-2), gut (RTgutGC) and brain (RTbrain) of rainbow trout (Oncorhynchus mykiss). In addition to known transporters abcb1 (designated here abcb1a), abcb11, abcc1-3, abcc5 and abcg2, we quantified expression levels of a newly identified abcb1 isoform (abcb1b) and abcc4, previously unknown in trout. Quantitative real time PCR (qPCR) indicated that mRNA of the examined ABC transporters was constitutively expressed in all cell lines. Transporter mRNA expression patterns were similar in all cell lines, with expression levels of abcc transporters being 80 to over 1000 fold higher than for abcg2, abcb1a/b and abcb11 (abcc1-5>abcg2>abcb1a/b, 11). Transporter activity in the cell lines was determined by measuring uptake of transporter type specific fluorescent substrates in the presence of activity inhibitors. The combination of the ABCB1 and ABCC transporter substrate calcein-AM with inhibitors cyclosporine A, PSC833 and MK571 resulted in a concentration-dependent fluorescence increase of up to 3-fold, whereas reversin 205 caused a slight, but not concentration-dependent fluorescence increase. Accumulation of the dyes Hoechst 33342 and 2',7'-dichlorodihydrofluorescein diacetate was basically unchanged in the presence of Ko134 and taurocholate, respectively, indicating low Abcg2 and Abcb11 activities, in accordance with low abcg2 and abcb11 transcript levels. Our data indicate that transporter expression and activity patterns in the different trout cell lines are irrespective of the tissue of origin, but are determined by factors of cell cultivation. 2010 Elsevier B.V. All rights reserved.

Progression of Prostate Carcinogenesis and Dietary Methyl Donors: Temporal Dependence

PubMed Central

Shabbeer, Shabana; Williams, Simon A.; Simons, Brian W.; Herman, James G.; Carducci, Michael A.

2011-01-01

Insufficient dose of dietary methyl groups are associated with a host of conditions ranging from neural tube defects to cancer. On the other hand, it is not certain what effect excess dietary methyl groups could have on cancer. This is especially true for prostate cancer (PCa), a disease that is characterized by increasing DNA methylation changes with increasing grade of the cancer. In this three-part study in animals, we look at (i) the effect of excess methyl donors on the growth rate of PCa in vivo, (ii) the ability of 5-aza-2'-deoxycytidine, a demethylating agent, to demethylate in the presence of excess dietary methyl donors and (iii) the effect of in utero feeding of excess methyl donors to the later onset of PCa. The results show that when mice are fed a dietary excess of methyl donors, we do not see (i) an increase in the growth rate of DU-145 and PC-3 xenografts in vivo, or (ii) interference in the ability of 5-aza-2'-deoxycytidine to demethylate the promoters of Androgen Receptor or Reprimo of PCa xenografts but (iii) a protective effect on the development of higher grades of PCa in the “Hi-myc” mouse model of PCa which were fed the increased methyl donors in utero. We conclude that the impact of dietary methyl donors on PCa progression depends upon the timing of exposure to the dietary agents. When fed before the onset of cancer, i.e. in utero, excess methyl donors can have a protective effect on the progression of cancer. PMID:22139053

Effects of CO2 Lasers on Dental Pulp Biology in Rats.

PubMed

Ser-Od, Tungalag; Yasumoto, Masafumi; Al-Wahabi, Akram; Nakajima, Kei; Murakami, Satoshi; Matsuzaka, Kenichi; Inoue, Takashi

2016-04-01

The purpose of this study was to investigate the effects of CO2 lasers on the proliferation and differentiation of dental pulp cells, and their latent self-recovery in connection with their stemness using reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry. The first molars from male Sprague-Dawley rats, each weighing ∼150-200 g, were used for this study. The upper first molars were irradiated with a 10,600 nm wavelength CO2 laser under identical parameters (2 W CO2 laser, energy 4J, energy density 203.84 J/cm(2) for 8.8 sec) through the dentin of the occlusal surface. The molars were extracted immediately, or at 1, 3 or 5 days after the laser irradiation. RT-PCR analysis using primers specific for heat shock protein 70 (Hsp70), adenosine triphosphate (ATP)-binding cassette transporter G2 (ABCG2), dentin sialophosphoprotein (DSPP), and dentin matrix protein 1 (DMP1), and immunohistochemistry using antibodies specific for proliferating cell nuclear antigen (PCNA), ABCG2, CD34, and CD44 were performed. RT-PCR analysis revealed that Hsp70 mRNA expression in the immediate group and ABCG2 mRNA expression at day 1 were the highest. DSPP and DMP1 mRNA expression in the laser-irradiated groups increased gradually, reaching its peak on the 5th day of the experiment, although no significant difference found among groups with regard to DMP1 expression. Immunohistochemically, PCNA-positive cells were observed at all times after the laser irradiation; however, they were most evident on day 3. CD44-positive cells were observed strongly on day 1 and day 3, while ABCG2-positive cells were the most evident on day 3. These results demonstrate that CO2 laser irradiation induces degeneration in the pulp tissue, which is then repaired by newly formed odontoblast-like cells.

Curcumin-Mediated Reversal of p15 Gene Promoter Methylation: Implication in Anti-Neoplastic Action against Acute Lymphoid Leukaemia Cell Line.

PubMed

Sharma, V; Jha, A K; Kumar, A; Bhatnagar, A; Narayan, G; Kaur, J

2015-01-01

Curcumin has been documented to exert anticancer effects by interacting with altered proliferative and apoptotic pathways in cancer models. In this study, we evaluated the potential of curcumin to reverse promoter methylation of the p15 gene in Raji cells and its ability to induce apoptosis and genomic instability. Anti-neoplastic action of curcumin showed an augmentation in reactive oxygen species (ROS) and cell cycle arrest in G1 phase. Subsequently, curcumin- exposed Raji cells showed structural abnormalities in chromosomes. These observations suggest that curcumin also causes ROS-mediated apoptosis and genomic instability. The treatment of Raji cell line with 10 μM curcumin caused hypomethylation of the p15 promoter after six days. Hypomethylation of p15 was further found to be favoured by downregulation of DNA methyltransferase 1 after 10 μM curcumin treatment for six days. Methylation-specific PCR suggested demethylation of the p15 promoter. Demethylation was further validated by DNA sequencing. Reverse-transcription PCR demonstrated that treatment with curcumin (10 μM) for six days led to the up-regulation of p15 and down-regulation of DNA methyltransferase 1. Furthermore, curcumin- mediated reversal of p15 promoter methylation might be potentiated by down-regulation of DNA methyltransferase 1 expression, which was supported by cell cycle analysis. Furthermore, curcumin acts as a double-pronged agent, as it caused apoptosis and promoter hypomethylation in Raji cells.

Retinoic Acid Isomers Facilitate Apolipoprotein E Production and Lipidation in Astrocytes through the Retinoid X Receptor/Retinoic Acid Receptor Pathway*

PubMed Central

Zhao, Jing; Fu, Yuan; Liu, Chia-Chen; Shinohara, Mitsuru; Nielsen, Henrietta M.; Dong, Qiang; Kanekiyo, Takahisa; Bu, Guojun

2014-01-01

Apolipoprotein E (apoE) is the major cholesterol transport protein in the brain. Among the three human APOE alleles (APOE2, APOE3, and APOE4), APOE4 is the strongest genetic risk factor for late-onset Alzheimer disease (AD). The accumulation of amyloid-β (Aβ) is a central event in AD pathogenesis. Increasing evidence demonstrates that apoE isoforms differentially regulate AD-related pathways through both Aβ-dependent and -independent mechanisms; therefore, modulating apoE secretion, lipidation, and function might be an attractive approach for AD therapy. We performed a drug screen for compounds that modulate apoE production in immortalized astrocytes derived from apoE3-targeted replacement mice. Here, we report that retinoic acid (RA) isomers, including all-trans-RA, 9-cis-RA, and 13-cis-RA, significantly increase apoE secretion to ∼4-fold of control through retinoid X receptor (RXR) and RA receptor. These effects on modulating apoE are comparable with the effects recently reported for the RXR agonist bexarotene. Furthermore, all of these compounds increased the expression of the cholesterol transporter ABCA1 and ABCG1 levels and decreased cellular uptake of Aβ in an apoE-dependent manner. Both bexarotene and 9-cis-RA promote the lipidation status of apoE, in which 9-cis-RA promotes a stronger effect and exhibits less cytotoxicity compared with bexarotene. Importantly, we showed that oral administration of bexarotene and 9-cis-RA significantly increases apoE, ABCA1, and ABCG1 levels in mouse brains. Taken together, our results demonstrate that RXR/RA receptor agonists, including several RA isomers, are effective modulators of apoE secretion and lipidation and may be explored as potential drugs for AD therapy. PMID:24599963

DNA methylation of loci within ABCG1 and PHOSPHO1 in blood DNA is associated with future type 2 diabetes risk.

PubMed

Dayeh, Tasnim; Tuomi, Tiinamaija; Almgren, Peter; Perfilyev, Alexander; Jansson, Per-Anders; de Mello, Vanessa D; Pihlajamäki, Jussi; Vaag, Allan; Groop, Leif; Nilsson, Emma; Ling, Charlotte

2016-07-02

Identification of subjects with a high risk of developing type 2 diabetes (T2D) is fundamental for prevention of the disease. Consequently, it is essential to search for new biomarkers that can improve the prediction of T2D. The aim of this study was to examine whether 5 DNA methylation loci in blood DNA (ABCG1, PHOSPHO1, SOCS3, SREBF1, and TXNIP), recently reported to be associated with T2D, might predict future T2D in subjects from the Botnia prospective study. We also tested if these CpG sites exhibit altered DNA methylation in human pancreatic islets, liver, adipose tissue, and skeletal muscle from diabetic vs. non-diabetic subjects. DNA methylation at the ABCG1 locus cg06500161 in blood DNA was associated with an increased risk for future T2D (OR = 1.09, 95% CI = 1.02-1.16, P-value = 0.007, Q-value = 0.018), while DNA methylation at the PHOSPHO1 locus cg02650017 in blood DNA was associated with a decreased risk for future T2D (OR = 0.85, 95% CI = 0.75-0.95, P-value = 0.006, Q-value = 0.018) after adjustment for age, gender, fasting glucose, and family relation. Furthermore, the level of DNA methylation at the ABCG1 locus cg06500161 in blood DNA correlated positively with BMI, HbA1c, fasting insulin, and triglyceride levels, and was increased in adipose tissue and blood from the diabetic twin among monozygotic twin pairs discordant for T2D. DNA methylation at the PHOSPHO1 locus cg02650017 in blood correlated positively with HDL levels, and was decreased in skeletal muscle from diabetic vs. non-diabetic monozygotic twins. DNA methylation of cg18181703 (SOCS3), cg11024682 (SREBF1), and cg19693031 (TXNIP) was not associated with future T2D risk in subjects from the Botnia prospective study.

GLUT9 influences uric acid concentration in patients with Lesch-Nyhan disease.

PubMed

Torres, Rosa J; Puig, Juan G

2018-06-01

Patients with deficient hypoxanthine-guanine phosphoribosyltransferase (HPRT) activity present hyperuricemia and/or hyperuricosuria, with a variable degree of neurological manifestations. Hyperuricemia in HPRT deficiency is due to uric acid overproduction and is frequently treated with allopurinol. Renal uric acid excretion is sharply increased in these patients. In recent years, several renal tubular urate transporter single nucleotide polymorphisms (SNPs), including those of the GLUT9, ABCG2 and URAT1 genes, have been described that influence the renal handling of uric acid and modulate serum urate levels. In the present study, we analyzed whether GLUT9, ABCG2 and URAT1 gene SNPs are able to influence uric acid levels and allopurinol response in patients with HPRT deficiency. Three SNPs, URAT1 rs11231825, GLUT9 rs16890979 and ABCG2 rs2231142, previously associated in our population with hyperuricemia and gout, were analyzed in 27 patients with HPRT deficiency treated with allopurinol for at least 5 years. Patients with HPRT deficiency having allele A of rs16890979 in the GLUT9 gene present with a lower serum urate concentration at diagnosis, before allopurinol treatment is instituted, and need lower allopurinol doses to maintain serum urate levels between 268 and 446 μmol/L (4.5 and 7.5 mg/dL). No relationship between rs2231142 in the ABCG2 gene or rs11231825 in the URAT1 gene and serum urate levels or allopurinol response was found in our patients with HPRT deficiency. GLUT9 SNPs influence the renal handling of uric acid and modulate serum urate levels and the response to treatment in patients with uric acid overproduction due to HPRT deficiency. © 2018 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.

A DEMETER-like DNA demethylase governs tomato fruit ripening

PubMed Central

Liu, Ruie; How-Kit, Alexandre; Stammitti, Linda; Teyssier, Emeline; Rolin, Dominique; Mortain-Bertrand, Anne; Halle, Stefanie; Liu, Mingchun; Kong, Junhua; Wu, Chaoqun; Degraeve-Guibault, Charlotte; Chapman, Natalie H.; Maucourt, Mickael; Hodgman, T. Charlie; Tost, Jörg; Bouzayen, Mondher; Hong, Yiguo; Seymour, Graham B.; Giovannoni, James J.; Gallusci, Philippe

2015-01-01

In plants, genomic DNA methylation which contributes to development and stress responses can be actively removed by DEMETER-like DNA demethylases (DMLs). Indeed, in Arabidopsis DMLs are important for maternal imprinting and endosperm demethylation, but only a few studies demonstrate the developmental roles of active DNA demethylation conclusively in this plant. Here, we show a direct cause and effect relationship between active DNA demethylation mainly mediated by the tomato DML, SlDML2, and fruit ripening— an important developmental process unique to plants. RNAi SlDML2 knockdown results in ripening inhibition via hypermethylation and repression of the expression of genes encoding ripening transcription factors and rate-limiting enzymes of key biochemical processes such as carotenoid synthesis. Our data demonstrate that active DNA demethylation is central to the control of ripening in tomato. PMID:26261318

Alterations in microsomal electron transport, oxidative N-demethylation and azo-dye cleavage in carbon tetrachloride and dimethylnitrosamine-induced liver injury

PubMed Central

Smuckler, E. A.; Arrhenius, E.; Hultin, T.

1967-01-01

The effect of administration of carbon tetrachloride and dimethylnitrosamine in vivo on hepatic microsomal function related to drug metabolism was measured. It was found that the capacity of isolated microsomes to demethylate dimethylaniline was diminished during the first hour after carbon tetrachloride poisoning and during the second hour after dimethylnitrosamine poisoning. Thereafter the microsomes from carbon tetrachloride-poisoned livers showed a continuous decline in activity so that at 24hr. there was little residual capacity to undertake demethylation. Microsomes from dimethylnitrosamine-poisoned animals were not different from controls at 24hr. During the first 3hr. there was a transient rise in the accumulation of the N-oxide intermediate in carbon tetrachloride-poisoned livers, with a subsequent fall to below control values. In dimethylnitrosamine poisoning there was a parallel decrease in N-oxide accumulation with decreased demethylation. In the latter part of the first 24hr. the ratio of N-oxide accumulation to demethylation was increased in both instances. At 2hr. after poisoning with either compound there was no evidence of altered NADPH2-dependent neotetrazolium reduction or lipid peroxidation. NADPH2-dependent azo-dye cleavage was decreased. There was no difference in microsomal cytochrome b5 content, but there was a decrease in the amount of cytochrome P-450. This latter change was correlated with the decreased capacity for NADPH2-dependent oxidative demethylation. It is suggested that dimethylnitrosamine is associated with a defect in microsomal NADPH2-dependent electron transport at the level of cytochrome P-450. In addition to affecting cytochrome P-450, carbon tetrachloride is associated with a second severe block involving the release of formaldehyde from the N-oxide intermediate. PMID:6040018

Mindin deficiency in macrophages protects against foam cell formation and atherosclerosis by targeting LXR-β.

PubMed

Zhang, Cheng; Qin, Juan-Juan; Gong, Fu-Han; Tong, Jing-Jing; Cheng, Wen-Lin; Wang, Haiping; Zhang, Yan; Zhu, Xueyong; She, Zhi-Gang; Xia, Hao; Zhu, Li-Hua

2018-06-15

Mindin, which is a highly conserved extracellular matrix protein, has been documented to play pivotal roles in regulating angiogenesis, inflammatory processes, and immune responses. The aim of the present study was to assess whether mindin contributes to the development of atherosclerosis. A significant up-regulation of Mindin expression was observed in the serum, arteries and atheromatous plaques of ApoE -/- mice after high-fat diet treatment. Mindin -/- ApoE -/- mice and macrophage-specific mindin overexpression in ApoE -/- mice (Lyz2-mindin-TG) were generated to evaluate the effect of mindin on the development of atherosclerosis. The Mindin -/- ApoE -/- mice exhibited significantly ameliorated atherosclerotic burdens in the entire aorta and aortic root and increased atherosclerotic plaque stability. Moreover, bone marrow transplantation further demonstrated that mindin deficiency in macrophages was largely responsible for the alleviated atherogenesis. The Lyz2-mindin-TG mice exhibited the opposite phenotype. Mindin deficiency enhanced foam cell formation by increasing the expression of cholesterol effectors, including ABCA1 and ABCG1. The mechanistic study indicated that mindin ablation promoted LXR-β expression via a direct interaction. Importantly, LXR-β inhibition largely reversed the ameliorating effect of mindin deficiency on foam cell formation and ABCA1 and ABCG1 expression. The present study demonstrated that mindin deficiency serves as a novel mediator that protects against foam cell formation and atherosclerosis by directly interacting with LXR-β. © 2018 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

Epigenetic features of FoxP3 in children with cow's milk allergy.

PubMed

Paparo, Lorella; Nocerino, Rita; Cosenza, Linda; Aitoro, Rosita; D'Argenio, Valeria; Del Monaco, Valentina; Di Scala, Carmen; Amoroso, Antonio; Di Costanzo, Margherita; Salvatore, Francesco; Berni Canani, Roberto

2016-01-01

DNA methylation of the Th1 and Th2 cytokine genes is altered during cow's milk allergy (CMA). Forkhead box transcription factor 3 (FoxP3) is essential for the development and function of regulatory T cells (Tregs) and is involved in oral tolerance acquisition. We assessed whether tolerance acquisition in children with IgE-mediated CMA is associated with DNA demethylation of the Treg-specific demethylated region (TSDR) of FoxP3. Forty children (aged 3-18 months) were enrolled: 10 children with active IgE-mediated CMA (group 1), 10 children who outgrew CMA after dietary treatment with an extensively hydrolyzed casein formula containing the probiotic Lactobacillus rhamnosus GG (group 2), 10 children who outgrew CMA after treatment with other formulas (group 3), and 10 healthy controls (group 4). FoxP3 TSDR demethylation and expression were measured in mononuclear cells purified from peripheral blood of the four groups of children. FoxP3 TSDR demethylation was significantly lower in children with active IgE-mediated CMA than in either children who outgrew CMA or in healthy children. Formula selection influenced the FoxP3 TSDR demethylation profile. The FoxP3 TSDR demethylation rate and expression level were correlated. Tolerance acquisition in children with IgE-mediated CMA involves epigenetic regulation of the FoxP3 gene. This feature could be a new target for preventive and therapeutic strategies against CMA.

Genomic Influences on Hyperuricemia and Gout.

PubMed

Merriman, Tony

2017-08-01

Genome-wide association studies (GWAS) have identified nearly 30 loci associated with urate concentrations that also influence the subsequent risk of gout. The ABCG2 Q141 K variant is highly likely to be causal and results in internalization of ABCG2, which can be rescued by drugs. Three other GWAS loci contain uric acid transporter genes, which are also highly likely to be causal. However identification of causal genes at other urate loci is challenging. Finally, relatively little is known about the genetic control of progression from hyperuricemia to gout. Only 4 small GWAS have been published for gout. Copyright © 2017 Elsevier Inc. All rights reserved.

A new fluorescent dye accumulation assay for parallel measurements of the ABCG2, ABCB1 and ABCC1 multidrug transporter functions.

PubMed

Szabó, Edit; Türk, Dóra; Telbisz, Ágnes; Kucsma, Nóra; Horváth, Tamás; Szakács, Gergely; Homolya, László; Sarkadi, Balázs; Várady, György

2018-01-01

ABC multidrug transporters are key players in cancer multidrug resistance and in general xenobiotic elimination, thus their functional assays provide important tools for research and diagnostic applications. In this study we have examined the potential interactions of three key human ABC multidrug transporters with PhenGreen diacetate (PGD), a cell permeable fluorescent metal ion indicator. The non-fluorescent, hydrophobic PGD rapidly enters the cells and, after cleavage by cellular esterases, in the absence of quenching metal ions, PhenGreen (PG) becomes highly fluorescent. We found that in cells expressing functional ABCG2, ABCB1, or ABCC1 transporters, cellular PG fluorescence is strongly reduced. This fluorescence signal in the presence of specific transporter inhibitors is increased to the fluorescence levels in the control cells. Thus the PG accumulation assay is a new, unique tool for the parallel determination of the function of the ABCG2, ABCB1, and ABCC1 multidrug transporters. Since PG has very low cellular toxicity, the PG accumulation assay also allows the selection, separation and culturing of selected cell populations expressing either of these transporters.

Trough concentration and ABCG2 polymorphism are better to predict imatinib response in chronic myeloid leukemia: a meta-analysis.

PubMed

Jiang, Zhi-Ping; Zhao, Xie-Lan; Takahashi, Naoto; Angelini, Sabrina; Dubashi, Biswajit; Sun, Li; Xu, Ping

2017-01-01

The present study aimed to conduct a series of meta-analyses to investigate the influence of imatinib trough concentration (C 0 ), as well as ABCB1 and ABCG2 polymorphisms, on the clinical response in patients with chronic myeloid leukemia (CML). A literature search was conducted using the PubMed and Cochrane electronic databases to locate relevant papers from 2003 onward. Then, an initial meta-analysis of 14 studies involving 2184 patients was conducted to understand the effect of imatinib mesylate (IM) C 0 on clinical outcome in CML patients. Subsequently, a series of meta-analyses were performed, including up to 23 studies with 2577 patients, on the effect of genetic polymorphisms of ABCB1 and ABCG2 on the clinical response to IM. Meta-analysis revealed that patients who achieved a major molecular response (MMR) have a significantly higher IM C 0 than those who failed to achieve an MMR. We also found that the patients who achieved a complete cytogenic response (CCyR) have a significantly higher IM C 0 than those who did not achieve a CCyR. However, no significant difference in IM C 0 was found between the complete molecular response and non-complete molecular response groups. Additional analysis showed that ABCG2 421 variant A allele was significantly associated with a higher rate of MMR and overall response, especially in Asian patients. Meta-analysis did not reveal a correlation between ABCB1 C3435T and C1236T polymorphisms with any clinical response to IM. However, the G2677T/A polymorphism could play a role in IM response in the recessive model. This meta-analysis demonstrates that there was a significant correlation between the IM trough concentration and clinical responses, especially MMR and CCyR, in CML patients. Furthermore, we found that the probability of successful treatment was correlated with the ABCG2 C421A polymorphism, at least within the Asian population. We failed to determine an association between ABCB1 polymorphisms and IM response, although the G2677T/A polymorphism might be involved. However, further large-scale investigations using more sensitive genotyping methods would be required to confirm this.

SET oncoprotein accumulation regulates transcription through DNA demethylation and histone hypoacetylation.

PubMed

Almeida, Luciana O; Neto, Marinaldo P C; Sousa, Lucas O; Tannous, Maryna A; Curti, Carlos; Leopoldino, Andreia M

2017-04-18

Epigenetic modifications are essential in the control of normal cellular processes and cancer development. DNA methylation and histone acetylation are major epigenetic modifications involved in gene transcription and abnormal events driving the oncogenic process. SET protein accumulates in many cancer types, including head and neck squamous cell carcinoma (HNSCC); SET is a member of the INHAT complex that inhibits gene transcription associating with histones and preventing their acetylation. We explored how SET protein accumulation impacts on the regulation of gene expression, focusing on DNA methylation and histone acetylation. DNA methylation profile of 24 tumour suppressors evidenced that SET accumulation decreased DNA methylation in association with loss of 5-methylcytidine, formation of 5-hydroxymethylcytosine and increased TET1 levels, indicating an active DNA demethylation mechanism. However, the expression of some suppressor genes was lowered in cells with high SET levels, suggesting that loss of methylation is not the main mechanism modulating gene expression. SET accumulation also downregulated the expression of 32 genes of a panel of 84 transcription factors, and SET directly interacted with chromatin at the promoter of the downregulated genes, decreasing histone acetylation. Gene expression analysis after cell treatment with 5-aza-2'-deoxycytidine (5-AZA) and Trichostatin A (TSA) revealed that histone acetylation reversed transcription repression promoted by SET. These results suggest a new function for SET in the regulation of chromatin dynamics. In addition, TSA diminished both SET protein levels and SET capability to bind to gene promoter, suggesting that administration of epigenetic modifier agents could be efficient to reverse SET phenotype in cancer.

Influence of DNA-methylation on zinc homeostasis in myeloid cells: Regulation of zinc transporters and zinc binding proteins.

PubMed

Kessels, Jana Elena; Wessels, Inga; Haase, Hajo; Rink, Lothar; Uciechowski, Peter

2016-09-01

The distribution of intracellular zinc, predominantly regulated through zinc transporters and zinc binding proteins, is required to support an efficient immune response. Epigenetic mechanisms such as DNA methylation are involved in the expression of these genes. In demethylation experiments using 5-Aza-2'-deoxycytidine (AZA) increased intracellular (after 24 and 48h) and total cellular zinc levels (after 48h) were observed in the myeloid cell line HL-60. To uncover the mechanisms that cause the disturbed zinc homeostasis after DNA demethylation, the expression of human zinc transporters and zinc binding proteins were investigated. Real time PCR analyses of 14 ZIP (solute-linked carrier (SLC) SLC39A; Zrt/IRT-like protein), and 9 ZnT (SLC30A) zinc transporters revealed significantly enhanced mRNA expression of the zinc importer ZIP1 after AZA treatment. Because ZIP1 protein was also enhanced after AZA treatment, ZIP1 up-regulation might be the mediator of enhanced intracellular zinc levels. The mRNA expression of ZIP14 was decreased, whereas zinc exporter ZnT3 mRNA was also significantly increased; which might be a cellular reaction to compensate elevated zinc levels. An enhanced but not significant chromatin accessibility of ZIP1 promoter region I was detected by chromatin accessibility by real-time PCR (CHART) assays after demethylation. Additionally, DNA demethylation resulted in increased mRNA accumulation of zinc binding proteins metallothionein (MT) and S100A8/S100A9 after 48h. MT mRNA was significantly enhanced after 24h of AZA treatment also suggesting a reaction of the cell to restore zinc homeostasis. These data indicate that DNA methylation is an important epigenetic mechanism affecting zinc binding proteins and transporters, and, therefore, regulating zinc homeostasis in myeloid cells. Copyright © 2016 Elsevier GmbH. All rights reserved.

A plasmaless, photochemical etch process for porous organosilicate glass films

NASA Astrophysics Data System (ADS)

Ryan, E. Todd; Molis, Steven E.

2017-12-01

A plasmaless, photochemical etch process using ultraviolet (UV) light in the presence of NH3 or O2 etched porous organosilicate glass films, also called pSiCOH films, in a two-step process. First, a UV/NH3 or UV/O2 treatment removed carbon (mostly methyl groups bonded to silicon) from a pSiCOH film by demethylation to a depth determined by the treatment exposure time. Second, aqueous HF was used to selectively remove the demethylated layer of the pSiCOH film leaving the methylated layer below. UV in the presence of inert gas or H2 did not demethylate the pSiCOH film. The depth of UV/NH3 demethylation followed diffusion limited kinetics and possible mechanisms of demethylation are presented. Unlike reactive plasma processes, which contain ions that can damage surrounding structures during nanofabrication, the photochemical etch contains no damaging ions. Feasibility of the photochemical etching was shown by comparing it to a plasma-based process to remove the pSiCOH dielectric from between Cu interconnect lines, which is a critical step during air gap fabrication. The findings also expand our understanding of UV photon interactions in pSiCOH films that may contribute to plasma-induced damage to pSiCOH films.

Additive composite ABCG2, SLC2A9 and SLC22A12 scores of high-risk alleles with alcohol use modulate gout risk.

PubMed

Tu, Hung-Pin; Chung, Chia-Min; Min-Shan Ko, Albert; Lee, Su-Shin; Lai, Han-Ming; Lee, Chien-Hung; Huang, Chung-Ming; Liu, Chiu-Shong; Ko, Ying-Chin

2016-09-01

The aim of the present study was to evaluate the contribution of urate transporter genes and alcohol use to the risk of gout/tophi. Eight variants of ABCG2, SLC2A9, SLC22A12, SLC22A11 and SLC17A3 were genotyped in male individuals in a case-control study with 157 gout (33% tophi), 106 asymptomatic hyperuricaemia and 295 control subjects from Taiwan. The multilocus profiles of the genetic risk scores for urate gene variants were used to evaluate the risk of asymptomatic hyperuricaemia, gout and tophi. ABCG2 Q141K (T), SLC2A9 rs1014290 (A) and SLC22A12 rs475688 (C) under an additive model and alcohol use independently predicted the risk of gout (respective odds ratio for each factor=2.48, 2.03, 1.95 and 2.48). The additive composite Q141K, rs1014290 and rs475688 scores of high-risk alleles were associated with gout risk (P<0.0001). We observed the supramultiplicative interaction effect of genetic urate scores and alcohol use on gout and tophi risk (P for interaction=0.0452, 0.0033). The synergistic effect of genetic urate score 5-6 and alcohol use indicates that these combined factors correlate with gout and tophi occurrence.

Chemoprevention of colorectal cancer by black raspberry anthocyanins involved the modulation of gut microbiota and SFRP2 demethylation.

PubMed

Chen, Lili; Jiang, Bowen; Zhong, Chunge; Guo, Jun; Zhang, Lihao; Mu, Teng; Zhang, Qiuhua; Bi, Xiuli

2018-03-08

Freeze-dried black raspberry (BRB) powder is considered as a potential cancer chemopreventive agent. In this study, we fed azoxymethane (AOM)/dextran sodium sulfate (DSS)-treated C57BL/6J mice with a diet containing BRB anthocyanins for 12 weeks, and this led to a reduction in colon carcinogenesis. These animals had consistently lower tumor multiplicity compared with AOM/DSS-treated mice not receiving BRB anthocyanins. In AOM/DSS-treated mice, the number of pathogenic bacteria, including Desulfovibrio sp. and Enterococcus spp., was increased significantly, whereas probiotics such as Eubacterium rectale, Faecalibacterium prausnitzii and Lactobacillus were dramatically decreased, but BRB anthocyanins supplement could reverse this imbalance in gut microbiota. BRB anthocyanins also caused the demethylation of the SFRP2 gene promoter, resulting in increased expression of SFRP2, both at the mRNA and protein levels. Furthermore, the expression levels of DNMT31 and DNMT3B, as well as of p-STAT3 were downregulated by BRB anthocyanins in these animals. Taken together, these results suggested that BRB anthocyanins could modulate the composition of gut commensal microbiota, and changes in inflammation and the methylation status of the SFRP2 gene may play a central role in the chemoprevention of CRC.

An ATP-binding cassette subfamily G full transporter is essential for the retention of leaf water in both wild barley and rice.

PubMed

Chen, Guoxiong; Komatsuda, Takao; Ma, Jian Feng; Nawrath, Christiane; Pourkheirandish, Mohammad; Tagiri, Akemi; Hu, Yin-Gang; Sameri, Mohammad; Li, Xinrong; Zhao, Xin; Liu, Yubing; Li, Chao; Ma, Xiaoying; Wang, Aidong; Nair, Sudha; Wang, Ning; Miyao, Akio; Sakuma, Shun; Yamaji, Naoki; Zheng, Xiuting; Nevo, Eviatar

2011-07-26

Land plants have developed a cuticle preventing uncontrolled water loss. Here we report that an ATP-binding cassette (ABC) subfamily G (ABCG) full transporter is required for leaf water conservation in both wild barley and rice. A spontaneous mutation, eibi1.b, in wild barley has a low capacity to retain leaf water, a phenotype associated with reduced cutin deposition and a thin cuticle. Map-based cloning revealed that Eibi1 encodes an HvABCG31 full transporter. The gene was highly expressed in the elongation zone of a growing leaf (the site of cutin synthesis), and its gene product also was localized in developing, but not in mature tissue. A de novo wild barley mutant named "eibi1.c," along with two transposon insertion lines of rice mutated in the ortholog of HvABCG31 also were unable to restrict water loss from detached leaves. HvABCG31 is hypothesized to function as a transporter involved in cutin formation. Homologs of HvABCG31 were found in green algae, moss, and lycopods, indicating that this full transporter is highly conserved in the evolution of land plants.

An ATP-binding cassette subfamily G full transporter is essential for the retention of leaf water in both wild barley and rice

PubMed Central

Chen, Guoxiong; Komatsuda, Takao; Ma, Jian Feng; Nawrath, Christiane; Pourkheirandish, Mohammad; Tagiri, Akemi; Hu, Yin-Gang; Sameri, Mohammad; Li, Xinrong; Zhao, Xin; Liu, Yubing; Li, Chao; Ma, Xiaoying; Wang, Aidong; Nair, Sudha; Wang, Ning; Miyao, Akio; Sakuma, Shun; Yamaji, Naoki; Zheng, Xiuting; Nevo, Eviatar

2011-01-01

Land plants have developed a cuticle preventing uncontrolled water loss. Here we report that an ATP-binding cassette (ABC) subfamily G (ABCG) full transporter is required for leaf water conservation in both wild barley and rice. A spontaneous mutation, eibi1.b, in wild barley has a low capacity to retain leaf water, a phenotype associated with reduced cutin deposition and a thin cuticle. Map-based cloning revealed that Eibi1 encodes an HvABCG31 full transporter. The gene was highly expressed in the elongation zone of a growing leaf (the site of cutin synthesis), and its gene product also was localized in developing, but not in mature tissue. A de novo wild barley mutant named “eibi1.c,” along with two transposon insertion lines of rice mutated in the ortholog of HvABCG31 also were unable to restrict water loss from detached leaves. HvABCG31 is hypothesized to function as a transporter involved in cutin formation. Homologs of HvABCG31 were found in green algae, moss, and lycopods, indicating that this full transporter is highly conserved in the evolution of land plants. PMID:21737747

The rs2231142 variant of the ABCG2 gene is associated with uric acid levels and gout among Japanese people.

PubMed

Yamagishi, Kazumasa; Tanigawa, Takeshi; Kitamura, Akihiko; Köttgen, Anna; Folsom, Aaron R; Iso, Hiroyasu

2010-08-01

Recent genome-wide association and functional studies have shown that the ABCG2 gene encodes for a urate transporter, and a common causal ABCG2 variant, rs2231142, leads to elevated uric acid levels and prevalent gout among Whites and Blacks. We examined whether this finding is observed in a Japanese population, since Asians have a high reported prevalence of the T-risk allele. A total of 3923 Japanese people from the Circulatory Risk in Communities Study aged 40-90 years were genotyped for rs2231142. Associations of the rs2231142 variant with serum uric acid levels and prevalence of gout and hyperuricaemia were examined. The frequency of the T-risk allele was 31% in this Japanese sample. Multivariable adjusted mean uric acid levels were 7-9 micromol/l higher for TG and TT than GG carriers (P-additive = 0.0006). The multivariable-adjusted odds ratio (OR) of prevalent gout was 1.37 (95% CI 0.68, 2.76) for TG and 4.37 (95% CI 1.98, 9.62) for TT compared with the GG carriers (P-additive = 0.001). When evaluating the combined outcome of hyperuricaemia and gout, the respective ORs were 1.40 (95% CI 1.04, 1.87) for TG and 1.88 (95% CI 1.23, 2.89) for TT carriers. The population attributable risk was 29% for gout and 19% for gout and/or hyperuricaemia. The association of the causal ABCG2 rs2231142 variant with uric acid levels and gout was confirmed in a sample of Japanese ancestry. Our study emphasizes the importance of this common causal variant in a population with a high risk allele frequency, especially as more Japanese adopt a Western lifestyle with a concomitant increase in mean serum uric acid levels.

Factors affecting the persistence of drug-induced reprogramming of the cancer methylome

PubMed Central

Bell, Joshua S. K.; Kagey, Jacob D.; Barwick, Benjamin G.; Dwivedi, Bhakti; McCabe, Michael T.; Kowalski, Jeanne; Vertino, Paula M.

2016-01-01

ABSTRACT Aberrant DNA methylation is a critical feature of cancer. Epigenetic therapy seeks to reverse these changes to restore normal gene expression. DNA demethylating agents, including 5-aza-2′-deoxycytidine (DAC), are currently used to treat certain leukemias, and can sensitize solid tumors to chemotherapy and immunotherapy. However, it has been difficult to pin the clinical efficacy of these agents to specific demethylation events, and the factors that contribute to the durability of response remain largely unknown. Here we examined the genome-wide kinetics of DAC-induced DNA demethylation and subsequent remethylation after drug withdrawal in breast cancer cells. We find that CpGs differ in both their susceptibility to demethylation and propensity for remethylation after drug removal. DAC-induced demethylation was most apparent at CpGs with higher initial methylation levels and further from CpG islands. Once demethylated, such sites exhibited varied remethylation potentials. The most rapidly remethylating CpGs regained >75% of their starting methylation within a month of drug withdrawal. These sites had higher pretreatment methylation levels, were enriched in gene bodies, marked by H3K36me3, and tended to be methylated in normal breast cells. In contrast, a more resistant class of CpG sites failed to regain even 20% of their initial methylation after 3 months. These sites had lower pretreatment methylation levels, were within or near CpG islands, marked by H3K79me2 or H3K4me2/3, and were overrepresented in sites that become aberrantly hypermethylated in breast cancers. Thus, whereas DAC-induced demethylation affects both endogenous and aberrantly methylated sites, tumor-specific hypermethylation is more slowly regained, even as normal methylation promptly recovers. Taken together, these data suggest that the durability of DAC response is linked to its selective ability to stably reset at least a portion of the cancer methylome. PMID:27082926

The ABCG transporter PEC1/ABCG32 is required for the formation of the developing leaf cuticle in Arabidopsis.

PubMed

Fabre, Guillaume; Garroum, Imène; Mazurek, Sylwester; Daraspe, Jean; Mucciolo, Antonio; Sankar, Martial; Humbel, Bruno M; Nawrath, Christiane

2016-01-01

The cuticle is an essential diffusion barrier on aerial surfaces of land plants whose structural component is the polyester cutin. The PERMEABLE CUTICLE1/ABCG32 (PEC1) transporter is involved in plant cuticle formation in Arabidopsis. The gpat6 pec1 and gpat4 gapt8 pec1 double and triple mutants are characterized. Their PEC1-specific contributions to aliphatic cutin composition and cuticle formation during plant development are revealed by gas chromatography/mass spectrometry and Fourier-transform infrared spectroscopy. The composition of cutin changes during rosette leaf expansion in Arabidopsis. C16:0 monomers are in higher abundance in expanding than in fully expanded leaves. The atypical cutin monomer C18:2 dicarboxylic acid is more prominent in fully expanded leaves. Findings point to differences in the regulation of several pathways of cutin precursor synthesis. PEC1 plays an essential role during expansion of the rosette leaf cuticle. The reduction of C16 monomers in the pec1 mutant during leaf expansion is unlikely to cause permeability of the leaf cuticle because the gpat6 mutant with even fewer C16:0 monomers forms a functional rosette leaf cuticle at all stages of development. PEC1/ABCG32 transport activity affects cutin composition and cuticle structure in a specific and non-redundant fashion. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Hydration properties of natural and synthetic DNA sequences with methylated adenine or cytosine bases in the R.DpnI target and BDNF promoter studied by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Shanak, Siba; Helms, Volkhard

2014-12-01

Adenine and cytosine methylation are two important epigenetic modifications of DNA sequences at the levels of the genome and transcriptome. To characterize the differential roles of methylating adenine or cytosine with respect to their hydration properties, we performed conventional MD simulations and free energy perturbation calculations for two particular DNA sequences, namely the brain-derived neurotrophic factor (BDNF) promoter and the R.DpnI-bound DNA that are known to undergo methylation of C5-methyl cytosine and N6-methyl adenine, respectively. We found that a single methylated cytosine has a clearly favorable hydration free energy over cytosine since the attached methyl group has a slightly polar character. In contrast, capping the strongly polar N6 of adenine with a methyl group gives a slightly unfavorable contribution to its free energy of solvation. Performing the same demethylation in the context of a DNA double-strand gave quite similar results for the more solvent-accessible cytosine but much more unfavorable results for the rather buried adenine. Interestingly, the same demethylation reactions are far more unfavorable when performed in the context of the opposite (BDNF or R.DpnI target) sequence. This suggests a natural preference for methylation in a specific sequence context. In addition, free energy calculations for demethylating adenine or cytosine in the context of B-DNA vs. Z-DNA suggest that the conformational B-Z transition of DNA transition is rather a property of cytosine methylated sequences but is not preferable for the adenine-methylated sequences investigated here.

Hydration properties of natural and synthetic DNA sequences with methylated adenine or cytosine bases in the R.DpnI target and BDNF promoter studied by molecular dynamics simulations.

PubMed

Shanak, Siba; Helms, Volkhard

2014-12-14

Adenine and cytosine methylation are two important epigenetic modifications of DNA sequences at the levels of the genome and transcriptome. To characterize the differential roles of methylating adenine or cytosine with respect to their hydration properties, we performed conventional MD simulations and free energy perturbation calculations for two particular DNA sequences, namely the brain-derived neurotrophic factor (BDNF) promoter and the R.DpnI-bound DNA that are known to undergo methylation of C5-methyl cytosine and N6-methyl adenine, respectively. We found that a single methylated cytosine has a clearly favorable hydration free energy over cytosine since the attached methyl group has a slightly polar character. In contrast, capping the strongly polar N6 of adenine with a methyl group gives a slightly unfavorable contribution to its free energy of solvation. Performing the same demethylation in the context of a DNA double-strand gave quite similar results for the more solvent-accessible cytosine but much more unfavorable results for the rather buried adenine. Interestingly, the same demethylation reactions are far more unfavorable when performed in the context of the opposite (BDNF or R.DpnI target) sequence. This suggests a natural preference for methylation in a specific sequence context. In addition, free energy calculations for demethylating adenine or cytosine in the context of B-DNA vs. Z-DNA suggest that the conformational B-Z transition of DNA transition is rather a property of cytosine methylated sequences but is not preferable for the adenine-methylated sequences investigated here.

Methods for Measuring Specific Rates of Mercury Methylation and Degradation and Their Use in Determining Factors Controlling Net Rates of Mercury Methylation

PubMed Central

Ramlal, Patricia S.; Rudd, John W. M.; Hecky, Robert E.

1986-01-01

A method was developed to estimate specific rates of demethylation of methyl mercury in aquatic samples by measuring the volatile 14C end products of 14CH3HgI demethylation. This method was used in conjunction with a 203Hg2+ radiochemical method which determines specific rates of mercury methylation. Together, these methods enabled us to examine some factors controlling the net rate of mercury methylation. The methodologies were field tested, using lake sediment samples from a recently flooded reservoir in the Southern Indian Lake system which had developed a mercury contamination problem in fish. Ratios of the specific rates of methylation/demethylation were calculated. The highest ratios of methylation/demethylation were calculated. The highest ratios of methylation/demethylation occurred in the flooded shorelines of Southern Indian Lake. These results provide an explanation for the observed increases in the methyl mercury concentrations in fish after flooding. PMID:16346959

Dependence of microsomal methoxyflurane O-demethylation on cytochrome P-450 reductase and the stoichiometry of fluoride ion and formaldehyde release.

PubMed

Waskell, L; Gonzales, J

1982-07-01

In order to characterize further the in vitro liver microsomal O-demethylation and defluorination of the volatile anesthetic methoxyflurane, and obtain additional information regarding the participation of cytochrome P-450 in the oxidation, the stoichiometry of the reaction was determined and the effect of antibody to cytochrome P-450 reductase on this unique biotransformation was examined. Liver microsomes were isolated from rabbits and rats in which enzyme induction had previously been produced by phenobarbital. The O-demethylation of methoxyflurane by phenobarbital-induced microsomes results in the production of 1 mol of formaldehyde for every 2 mol of fluoride ion produced. Dichloroacetic acid is also a product of methoxyflurane O-demethylation. Antibody to cytochrome P-450 reductase inhibits by 85% the amount of fluoride ion produced by the microsomal metabolism of methoxyflurane. Thus critical indirect supportive data are contributed to the hypothesis that at least one, but perhaps more, cytochrome P-450 is indeed responsible for methoxyflurane O-demethylation and defluorination.

The Role of Epigenetic Regulation in Epstein-Barr Virus-Associated Gastric Cancer

PubMed Central

Nishikawa, Jun; Iizasa, Hisashi; Nakamura, Munetaka; Saito, Mari; Sasaki, Sho; Shimokuri, Kanami; Yanagihara, Masashi; Sakai, Kouhei; Suehiro, Yutaka; Yamasaki, Takahiro; Sakaida, Isao

2017-01-01

The Epstein–Barr virus (EBV) is detected in about 10% of gastric carcinoma cases throughout the world. In EBV-associated gastric carcinoma (EBVaGC), all tumor cells harbor the clonal EBV genome. The expression of latent EBV genes is strictly regulated through the methylation of EBV DNA. The methylation of viral DNA regulates the type of EBV latency, and methylation of the tumor suppressor genes is a key abnormality in EBVaGC. The methylation frequencies of several tumor suppressor genes and cell adhesion molecules are significantly higher in EBVaGC than in control cases. EBV-derived microRNAs repress translation from viral and host mRNAs. EBV regulates the expression of non-coding RNA in gastric carcinoma. With regard to the clinical application of demethylating agents against EBVaGC, we investigated the effects of decitabine against the EBVaGC cell lines. Decitabine inhibited the cell growth of EBVaGC cells. The promoter regions of p73 and Runt-related transcription factor 3(RUNX3) were demethylated, and their expression was upregulated by the treatment. We review the role of epigenetic regulation in the development and maintenance of EBVaGC and discuss the therapeutic application of DNA demethylating agents for EBVaGC. PMID:28757548

Human memory CD8 T cell effector potential is epigenetically preserved during in vivo homeostasis.

PubMed

Abdelsamed, Hossam A; Moustaki, Ardiana; Fan, Yiping; Dogra, Pranay; Ghoneim, Hazem E; Zebley, Caitlin C; Triplett, Brandon M; Sekaly, Rafick-Pierre; Youngblood, Ben

2017-06-05

Antigen-independent homeostasis of memory CD8 T cells is vital for sustaining long-lived T cell-mediated immunity. In this study, we report that maintenance of human memory CD8 T cell effector potential during in vitro and in vivo homeostatic proliferation is coupled to preservation of acquired DNA methylation programs. Whole-genome bisulfite sequencing of primary human naive, short-lived effector memory (T EM ), and longer-lived central memory (T CM ) and stem cell memory (T SCM ) CD8 T cells identified effector molecules with demethylated promoters and poised for expression. Effector-loci demethylation was heritably preserved during IL-7- and IL-15-mediated in vitro cell proliferation. Conversely, cytokine-driven proliferation of T CM and T SCM memory cells resulted in phenotypic conversion into T EM cells and was coupled to increased methylation of the CCR7 and Tcf7 loci. Furthermore, haploidentical donor memory CD8 T cells undergoing in vivo proliferation in lymphodepleted recipients also maintained their effector-associated demethylated status but acquired T EM -associated programs. These data demonstrate that effector-associated epigenetic programs are preserved during cytokine-driven subset interconversion of human memory CD8 T cells. © 2017 Abdelsamed et al.

The Role of Epigenetic Regulation in Epstein-Barr Virus-Associated Gastric Cancer.

PubMed

Nishikawa, Jun; Iizasa, Hisashi; Yoshiyama, Hironori; Nakamura, Munetaka; Saito, Mari; Sasaki, Sho; Shimokuri, Kanami; Yanagihara, Masashi; Sakai, Kouhei; Suehiro, Yutaka; Yamasaki, Takahiro; Sakaida, Isao

2017-07-25

The Epstein-Barr virus (EBV) is detected in about 10% of gastric carcinoma cases throughout the world. In EBV-associated gastric carcinoma (EBVaGC), all tumor cells harbor the clonal EBV genome. The expression of latent EBV genes is strictly regulated through the methylation of EBV DNA. The methylation of viral DNA regulates the type of EBV latency, and methylation of the tumor suppressor genes is a key abnormality in EBVaGC. The methylation frequencies of several tumor suppressor genes and cell adhesion molecules are significantly higher in EBVaGC than in control cases. EBV-derived microRNAs repress translation from viral and host mRNAs. EBV regulates the expression of non-coding RNA in gastric carcinoma. With regard to the clinical application of demethylating agents against EBVaGC, we investigated the effects of decitabine against the EBVaGC cell lines. Decitabine inhibited the cell growth of EBVaGC cells. The promoter regions of p73 and Runt-related transcription factor 3(RUNX3) were demethylated, and their expression was upregulated by the treatment. We review the role of epigenetic regulation in the development and maintenance of EBVaGC and discuss the therapeutic application of DNA demethylating agents for EBVaGC.

The metabolism of plant sterols is disturbed in postmenopausal women with coronary artery disease.

PubMed

Gylling, Helena; Hallikainen, Maarit; Rajaratnam, Radhakrishnan A; Simonen, Piia; Pihlajamäki, Jussi; Laakso, Markku; Miettinen, Tatu A

2009-03-01

In postmenopausal coronary artery disease (CAD) women, serum plant sterols are elevated. Thus, we investigated further whether serum plant sterols reflect absolute cholesterol metabolism in CAD as in other populations and whether the ABCG5 and ABCG8 genes, associated with plant sterol metabolism, were related to the risk of CAD. In free-living postmenopausal women with (n = 47) and without (n = 62) CAD, serum noncholesterol sterols including plant sterols were analyzed with gas-liquid chromatography, cholesterol absorption with peroral isotopes, absolute cholesterol synthesis with sterol balance technique, and bile acid synthesis with quantitating fecal bile acids. In CAD women, serum plant sterol ratios to cholesterol were 21% to 26% (P < .05) higher than in controls despite similar cholesterol absorption efficiency. Absolute cholesterol and bile acid synthesis were reduced. Only in controls were serum plant sterols related to cholesterol absorption (eg, sitosterol; in controls: r = 0.533, P < .001; in CAD: r = 0.296, P = not significant). However, even in CAD women, serum lathosterol (relative synthesis marker) and lathosterol-cholestanol (relative synthesis-absorption marker) were related to absolute synthesis and absorption percentage (P range from .05 to <.001) similarly to controls. Frequencies of the common polymorphisms of ABCG5 and ABCG8 genes did not differ between coronary and control women. In conclusion, plant sterol metabolism is disturbed in CAD women; so serum plant sterols only tended to reflect absolute cholesterol absorption. Other relative markers of cholesterol metabolism were related to the absolute ones in both groups. ABCG5 and ABCG8 genes were not associated with the risk of CAD.

The E3 ubiquitin ligase, HECTD1, is involved in ABCA1-mediated cholesterol export from macrophages.

PubMed

Aleidi, Shereen M; Yang, Alryel; Sharpe, Laura J; Rao, Geetha; Cochran, Blake J; Rye, Kerry-Anne; Kockx, Maaike; Brown, Andrew J; Gelissen, Ingrid C

2018-04-01

The ABC lipid transporters, ABCA1 and ABCG1, are essential for maintaining lipid homeostasis in cells such as macrophages by exporting excess cholesterol to extracellular acceptors. These transporters are highly regulated at the post-translational level, including protein ubiquitination. Our aim was to investigate the role of the E3 ubiquitin ligase HECTD1, recently identified as associated with ABCG1, on ABCG1 and ABCA1 protein levels and cholesterol export function. Here, we show that HECTD1 protein is widely expressed in a range of human and murine primary cells and cell lines, including macrophages, neuronal cells and insulin secreting β-cells. siRNA knockdown of HECTD1 unexpectedly decreased overexpressed ABCG1 protein levels and cell growth, but increased native ABCA1 protein in CHO-K1 cells. Knockdown of HECTD1 in unloaded THP-1 macrophages did not affect ABCG1 but significantly increased ABCA1 protein levels, in wild-type as well as THP-1 cells that do not express ABCG1. Cholesterol export from macrophages to apoA-I over time was increased after knockdown of HECTD1, however these effects were not sustained in cholesterol-loaded cells. In conclusion, we have identified a new candidate, the E3 ubiquitin ligase HECTD1, that may be involved in the regulation of ABCA1-mediated cholesterol export from unloaded macrophages to apoA-I. The exact mechanism by which this ligase affects this pathway remains to be elucidated. Copyright © 2018 Elsevier B.V. All rights reserved.

CXCR6, a newly defined biomarker of tissue-specific stem cell asymmetric self-renewal, identifies more aggressive human melanoma cancer stem cells.

PubMed

Taghizadeh, Rouzbeh; Noh, Minsoo; Huh, Yang Hoon; Ciusani, Emilio; Sigalotti, Luca; Maio, Michele; Arosio, Beatrice; Nicotra, Maria R; Natali, PierGiorgio; Sherley, James L; La Porta, Caterina A M

2010-12-22

A fundamental problem in cancer research is identifying the cell type that is capable of sustaining neoplastic growth and its origin from normal tissue cells. Recent investigations of a variety of tumor types have shown that phenotypically identifiable and isolable subfractions of cells possess the tumor-forming ability. In the present paper, using two lineage-related human melanoma cell lines, primary melanoma line IGR39 and its metastatic derivative line IGR37, two main observations are reported. The first one is the first phenotypic evidence to support the origin of melanoma cancer stem cells (CSCs) from mutated tissue-specific stem cells; and the second one is the identification of a more aggressive subpopulation of CSCs in melanoma that are CXCR6+. We defined CXCR6 as a new biomarker for tissue-specific stem cell asymmetric self-renewal. Thus, the relationship between melanoma formation and ABCG2 and CXCR6 expression was investigated. Consistent with their non-metastatic character, unsorted IGR39 cells formed significantly smaller tumors than unsorted IGR37 cells. In addition, ABCG2+ cells produced tumors that had a 2-fold greater mass than tumors produced by unsorted cells or ABCG2- cells. CXCR6+ cells produced more aggressive tumors. CXCR6 identifies a more discrete subpopulation of cultured human melanoma cells with a more aggressive MCSC phenotype than cells selected on the basis of the ABCG2+ phenotype alone. The association of a more aggressive tumor phenotype with asymmetric self-renewal phenotype reveals a previously unrecognized aspect of tumor cell physiology. Namely, the retention of some tissue-specific stem cell attributes, like the ability to asymmetrically self-renew, impacts the natural history of human tumor development. Knowledge of this new aspect of tumor development and progression may provide new targets for cancer prevention and treatment.

Mercury demethylation in waterbird livers: Dose-response thresholds and differences among species

USGS Publications Warehouse

Eagles-Smith, Collin A.; Ackerman, Joshua T.; Julie, Y.E.E.; Adelsbach, T.L.

2009-01-01

We assessed methylmercury (MeHg) demethylation in the livers of adults and chicks of four waterbird species that commonly breed in San Francisco Bay: American avocets, black-necked stilts, Caspian terns, and Forster's terns. In adults (all species combined), we found strong evidence for a threshold, model where MeHg demethylation occurred above a hepatic total mercury concentration threshold of 8.51 ?? 0.93 ??g/g dry weight, and there was a strong decline in %MeHg values as total mercury (THg) concentrations increased above 8.51 ??g/g dry weight. Conversely, there was no evidence for a demethylation threshold in chicks, and we found that %MeHg values declined linearly with increasing THg concentrations. For adults, we also found taxonomie differences in the demethylation responses, with avocets and stilts showing a higher demethylation rate than that of terns when concentrations exceeded the threshold, whereas terns had a lower demethylation threshold (7.48 ?? 1.48 ??g/g dry wt) than that of avocets and stilts (9.91 ?? 1.29 ??g/g dry wt). Finally, we assessed the role of selenium (Se) in the demethylation process. Selenium concentrations were positively correlated with inorganic Hg in livers of birds above the demethylation threshold but not below. This suggests that Se may act as a binding site for demethylated Hg and may reduce the potential for secondary toxicity. Our findings indicate that waterbirds demethylate mercury in their livers if exposure exceeds a threshold value and suggest that taxonomie differences in demethylation ability may be an important factor in evaluating species-specific risk to MeHg exposure. Further, we provide strong evidence for a threshold of approximately 8.5 ??g/g dry weight of THg in the liver where demethylation is initiated. ?? 2009 SETAC.

Early demethylation of non-CpG, CpC-rich, elements in the myogenin 5′-flanking region

PubMed Central

Fuso, Andrea; Ferraguti, Giampiero; Grandoni, Francesco; Ruggeri, Raffaella; Scarpa, Sigfrido; Strom, Roberto

2010-01-01

The dynamic changes and structural patterns of DNA methylation of genes without CpG islands are poorly characterized. The relevance of CpG to the non-CpG methylation equilibrium in transcriptional repression is unknown. In this work, we analyzed the DNA methylation pattern of the 5′-flanking of the myogenin gene, a positive regulator of muscle differentiation with no CpG island and low CpG density, in both C2C12 muscle satellite cells and embryonic muscle. Embryonic brain was studied as a non-expressing tissue. High levels of both CpG and non-CpG methylation were observed in non-expressing experimental conditions. Both CpG and non-CpG methylation rapidly dropped during muscle differentiation and myogenin transcriptional activation with active demethylation dynamics. Non-CpG demethylation occurred more rapidly than CpG demethylation. Demethylation spread from initially highly methylated short CpC-rich elements to a virtually unmethylated status. These short elements have a high CpC content and density, share some motifs and largely coincide with putative recognition sequences of some differentiation-related transcription factors. Our findings point to a dynamically controlled equilibrium between CpG and non-CpG active demethylation in the transcriptional control of tissue-specific genes. The short CpC-rich elements are new structural features of the methylation machinery, whose functions may include priming the complete demethylation of a transcriptionally crucial DNA region. PMID:20935518

Mitochondrial DNA copy number is regulated in a tissue specific manner by DNA methylation of the nuclear-encoded DNA polymerase gamma A

PubMed Central

Kelly, Richard D. W.; Mahmud, Arsalan; McKenzie, Matthew; Trounce, Ian A.; St John, Justin C.

2012-01-01

DNA methylation is an essential mechanism controlling gene expression during differentiation and development. We investigated the epigenetic regulation of the nuclear-encoded, mitochondrial DNA (mtDNA) polymerase γ catalytic subunit (PolgA) by examining the methylation status of a CpG island within exon 2 of PolgA. Bisulphite sequencing identified low methylation levels (<10%) within exon 2 of mouse oocytes, blastocysts and embryonic stem cells (ESCs), while somatic tissues contained significantly higher levels (>40%). In contrast, induced pluripotent stem (iPS) cells and somatic nuclear transfer ESCs were hypermethylated (>20%), indicating abnormal epigenetic reprogramming. Real time PCR analysis of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) immunoprecipitated DNA suggests active DNA methylation and demethylation within exon 2 of PolgA. Moreover, neural differentiation of ESCs promoted de novo methylation and demethylation at the exon 2 locus. Regression analysis demonstrates that cell-specific PolgA expression levels were negatively correlated with DNA methylation within exon 2 and mtDNA copy number. Finally, using chromatin immunoprecipitation (ChIP) against RNA polymerase II (RNApII) phosphorylated on serine 2, we show increased DNA methylation levels are associated with reduced RNApII transcriptional elongation. This is the first study linking nuclear DNA epigenetic regulation with mtDNA regulation during differentiation and cell specialization. PMID:22941637

Critical roles of DNA demethylation in the activation of ripening-induced genes and inhibition of ripening-repressed genes in tomato fruit

PubMed Central

Lang, Zhaobo; Wang, Yihai; Tang, Kai; Tang, Dengguo; Datsenka, Tatsiana; Cheng, Jingfei; Zhang, Yijing; Handa, Avtar K.

2017-01-01

DNA methylation is a conserved epigenetic mark important for genome integrity, development, and environmental responses in plants and mammals. Active DNA demethylation in plants is initiated by a family of 5-mC DNA glycosylases/lyases (i.e., DNA demethylases). Recent reports suggested a role of active DNA demethylation in fruit ripening in tomato. In this study, we generated loss-of-function mutant alleles of a tomato gene, SlDML2, which is a close homolog of the Arabidopsis DNA demethylase gene ROS1. In the fruits of the tomato mutants, increased DNA methylation was found in thousands of genes. These genes included not only hundreds of ripening-induced genes but also many ripening-repressed genes. Our results show that SlDML2 is critical for tomato fruit ripening and suggest that active DNA demethylation is required for both the activation of ripening-induced genes and the inhibition of ripening-repressed genes. PMID:28507144

Genetic polymorphisms of ATP-binding cassette (ABC) proteins, overall survival and drug toxicity in patients with Acute Myeloid Leukemia

PubMed Central

Hampras, Shalaka S; Sucheston, Lara; Weiss, Joli; Baer, Maria R; Zirpoli, Gary; Singh, Prashant K; Wetzler, Meir; Chennamaneni, Raj; Blanco, Javier G; Ford, LaurieAnn; Moysich, Kirsten B

2010-01-01

The overall survival of patients with acute myeloid leukemia (AML) remains poor due to both intrinsic and acquired chemotherapy resistance. Over expression of ATP binding cassette (ABC) proteins in AML cells has been suggested as a putative mechanism of drug resistance. Genetic variation among individuals affecting the expression or function of these proteins may contribute to inter-individual variation in treatment outcomes. DNA from pre-treatment bone marrow or blood samples from 261 patients age 20-85 years, who received cytarabine and anthracycline-based therapy at Roswell Park Cancer Institute between 1994 and 2006, was genotyped for eight non-synonymous single nucleotide polymorphisms in the ABCB1, ABCC1 and ABCG2 drug transporter genes. Heterozygous (AG) or homozygous (AA) variant genotypes for rs2231137 (G34A) in the ABCG2 (BRCP) gene, compared to the wild type (GG) genotype were associated with both significantly improved survival (HR=0.44, 95%CI=0.25-0.79), and increased odds for toxicity (OR=8.41, 95%CI= 1.10-64.28). Thus genetic polymorphisms in the ABCG2 (BRCP) gene may contribute to differential survival outcomes and toxicities in AML patients via a mechanism of decreased drug efflux in both, AML cells and normal progenitors. PMID:21311724

Regulation of ATP-binding Cassette Transporters and Cholesterol Efflux by Glucose in Primary Human Monocytes and Murine Bone Marrow-derived Macrophages

PubMed Central

Spartano, N. L.; Lamon-Fava, S.; Matthan, N. R.; Ronxhi, J.; Greenberg, A. S.; Obin, M. S.; Lichtenstein, A. H.

2014-01-01

Purpose Individuals with type 2 diabetes mellitus are at increased risk of developing atherosclerosis. This may be partially attributable to suppression of macrophage ATP-binding cassette (ABC) transporter mediated cholesterol efflux by sustained elevated blood glucose concentrations. 2 models were used to assess this potential relationship: human monocytes/leukocytes and murine bone marrow-derived macrophages (BMDM). Methods 10 subjects (4 F/6 M, 50–85 years, BMI 25–35 kg/m2) underwent an oral glucose challenge. Baseline and 1- and 2-h post-challenge ABC-transporter mRNA expression was determined in monocytes, leukocytes and peripheral blood mononuclear cells (PBMC). In a separate study, murine-BMDM were exposed to 5 mmol/L D-glucose (control) or additional 20 mmol/L D-or L-glucose and 25 ug/mL oxidized low density lipoprotein (oxLDL). High density lipoprotein (HDL)-mediated cholesterol efflux and ABC-transporter (ABCA1 and ABCG1) expression were determined. Results Baseline ABCA1and ABCG1 expression was lower (> 50 %) in human monocytes and PBMC than leukocytes (p < 0.05). 1 h post-challenge leukocyte ABCA1 and ABCG1 expression increased by 37 % and 30 %, respectively (p < 0.05), and began to return to baseline thereafter. There was no significant change in monocyte ABC-transporter expression. In murine BMDM, higher glucose concentrations suppressed HDL-mediated cholesterol efflux (10 %; p < 0.01) without significantly affecting ABCA1 and ABCG1 expression. Data demonstrate that leukocytes are not a reliable indicator of monocyte ABC-transporter expression. Conclusions Human monocyte ABC-transporter gene expression was unresponsive to a glucose challenge. Correspondingly, in BMDM, hyperglycemia attenuated macrophage cholesterol efflux in the absence of altered ABC-transporter expression, suggesting that hyperglycemia, per se, suppresses cholesterol transporter activity. This glucose-related impairment in cholesterol efflux may potentially contribute to diabetes-associated atherosclerosis. PMID:24838154

Hypoxia, Epithelial-Mesenchymal Transition, and TET-Mediated Epigenetic Changes

PubMed Central

Kao, Shih-Han; Wu, Kou-Juey; Lee, Wen-Hwa

2016-01-01

Tumor hypoxia is a pathophysiologic outcome of disrupted microcirculation with inadequate supply of oxygen, leading to enhanced proliferation, epithelial-mesenchymal transition (EMT), metastasis, and chemo-resistance. Epigenetic changes induced by hypoxia are well documented, and they lead to tumor progression. Recent advances show that DNA demethylation mediated by the Ten-eleven translocation (TET) proteins induces major epigenetic changes and controls key steps of cancer development. TET enzymes serve as 5mC (5-methylcytosine)-specific dioxygenases and cause DNA demethylation. Hypoxia activates the expression of TET1, which also serves as a co-activator of HIF-1α transcriptional regulation to modulate HIF-1α downstream target genes and promote epithelial-mesenchymal transition. As HIF is a negative prognostic factor for tumor progression, hypoxia-activated prodrugs (HAPs) may provide a favorable therapeutic approach to lessen hypoxia-induced malignancy. PMID:26861406

Future therapeutic targets for the treatment and prevention of cholesterol gallstones.

PubMed

Castro-Torres, Ibrahim Guillermo; de Jesús Cárdenas-Vázquez, René; Velázquez-González, Claudia; Ventura-Martínez, Rosa; De la O-Arciniega, Minarda; Naranjo-Rodríguez, Elia Brosla; Martínez-Vázquez, Mariano

2015-10-15

The formation of cholesterol gallstones involves very complex imbalances, such as alterations in the secretion of biliary lipids (which involves the ABCG5, ABCG8, ABCB4 and ABCB11 transporters), biochemical and immunological reactions in the gallbladder that produce biliary sludge (mucins), physicochemical changes in the structure of cholesterol (crystallization), alterations in gallbladder motility, changes in the intestinal absorption of cholesterol (ABCG5/8 transporters and Niemann-Pick C1L1 protein) and alterations in small intestine motility. Some of these proteins have been studied at the clinical and experimental levels, but more research is required. In this review, we discuss the results of studies on some molecules involved in the pathophysiology of gallstones that may be future therapeutic targets to prevent the development of this disease, and possible sites for treatment based mainly on the absorption of intestinal cholesterol (Niemann-Pick C1L1 and ABCG5/8 proteins). Copyright © 2015. Published by Elsevier B.V.

Phlpp1 facilitates post-traumatic osteoarthritis and is induced by inflammation and promoter demethylation in human osteoarthritis

PubMed Central

Bradley, Elizabeth W.; Carpio, Lomeli R.; McGee-Lawrence, Meghan E.; Becerra, Clara Castillejo; Amanatullah, Derek F.; Ta, Lauren E.; Otero, Miguel; Goldring, Mary B.; Kakar, Sanjeev; Westendorf, Jennifer J.

2016-01-01

OBJECTIVE Osteoarthritis (OA) is the most common form of arthritis and a leading cause of disability. OA is characterized by articular chondrocyte deterioration, subchondral bone changes and debilitating pain. One strategy to promote cartilage regeneration and repair is to accelerate proliferation and matrix production of articular chondrocytes. We previously reported that the protein phosphatase Phlpp1 controls chondrocyte differentiation by regulating the activities of anabolic kinases. Here we examined the role of Phlpp1 in osteoarthritis progression in a murine model. We also assessed PHLPP1 expression and promoter methylation. DESIGN Knee joints of WT and Phlpp1−/− mice were surgically destabilized by transection of the medial meniscal ligament (DMM). Mice were assessed for signs of OA progression via radiographic and histological analyses, and pain assessment for mechanical hypersensitivity using the von Frey assay. Methylation of the PHLPP1 promoter and PHLPP1 expression was evaluated in human articular cartilage and chondrocyte cell lines. RESULTS Following DMM surgeries, Phlpp1 deficient mice showed fewer signs of OA and cartilage degeneration. Mechanical allodynia associated with DMM surgeries was also attenuated in Phlpp1−/− mice. PHLPP1 was highly expressed in human articular cartilage from OA patients, but was undetectable in cartilage specimens from femoral neck fractures. Higher PHLPP1 levels correlated with less PHLPP1 promoter CpG methylation in cartilage from OA patients. Blocking cytosine methylation or treatment with inflammatory mediators enhanced PHLPP1 expression in human chondrocyte cell lines. CONCLUSION Phlpp1 deficiency protects against OA progression while CpG demethylation and inflammatory responses promote PHLPP1 expression. PMID:26746148

A class of tricyclic compounds blocking malaria parasite oocyst development and transmission.

PubMed

Eastman, Richard T; Pattaradilokrat, Sittiporn; Raj, Dipak K; Dixit, Saurabh; Deng, Bingbing; Miura, Kazutoyo; Yuan, Jing; Tanaka, Takeshi Q; Johnson, Ronald L; Jiang, Hongying; Huang, Ruili; Williamson, Kim C; Lambert, Lynn E; Long, Carole; Austin, Christopher P; Wu, Yimin; Su, Xin-Zhuan

2013-01-01

Malaria is a deadly infectious disease in many tropical and subtropical countries. Previous efforts to eradicate malaria have failed, largely due to the emergence of drug-resistant parasites, insecticide-resistant mosquitoes and, in particular, the lack of drugs or vaccines to block parasite transmission. ATP-binding cassette (ABC) transporters are known to play a role in drug transport, metabolism, and resistance in many organisms, including malaria parasites. To investigate whether a Plasmodium falciparum ABC transporter (Pf14_0244 or PfABCG2) modulates parasite susceptibility to chemical compounds or plays a role in drug resistance, we disrupted the gene encoding PfABCG2, screened the recombinant and the wild-type 3D7 parasites against a library containing 2,816 drugs approved for human or animal use, and identified an antihistamine (ketotifen) that became less active against the PfABCG2-disrupted parasite in culture. In addition to some activity against asexual stages and gametocytes, ketotifen was highly potent in blocking oocyst development of P. falciparum and the rodent parasite Plasmodium yoelii in mosquitoes. Tests of structurally related tricyclic compounds identified additional compounds with similar activities in inhibiting transmission. Additionally, ketotifen appeared to have some activity against relapse of Plasmodium cynomolgi infection in rhesus monkeys. Further clinical evaluation of ketotifen and related compounds, including synthetic new derivatives, in blocking malaria transmission may provide new weapons for the current effort of malaria eradication.

DNA demethylation of inflammasome-associated genes is enhanced in patients with cryopyrin-associated periodic syndromes.

PubMed

Vento-Tormo, Roser; Álvarez-Errico, Damiana; Garcia-Gomez, Antonio; Hernández-Rodríguez, José; Buján, Segundo; Basagaña, Maria; Méndez, Maria; Yagüe, Jordi; Juan, Manel; Aróstegui, Juan I; Ballestar, Esteban

2017-01-01

Inflammasomes are cytosolic multiprotein complexes in macrophages. They assemble after infection- or stress-associated stimuli, activating both caspase-1-mediated inflammatory cytokine secretion and pyroptosis. Increased inflammasome activity resulting from gene mutations is related to monogenic autoinflammatory syndromes. However, variable penetrance among patients with the same gene mutations suggests involvement of additional mechanisms associated with inflammasome gene regulation. We sought to investigate the role of DNA demethylation in activating inflammasome genes during macrophage differentiation and monocyte activation in healthy control subjects and patients with autoinflammatory syndrome. Inflammasome-related genes were tested for DNA methylation and mRNA levels by using bisulfite pyrosequencing and quantitative RT-PCR in monocytes in vitro differentiated to macrophages and exposed to inflammatory conditions. The contribution of Tet methylcytosine dioxygenase 2 (TET2) and nuclear factor κB to DNA demethylation was tested by using chromatin immunoprecipitation, small interfering RNA-mediated downregulation, and pharmacologic inhibition. We observed that inflammasome-related genes are rapidly demethylated in both monocyte-to-macrophage differentiation and on monocyte activation. Demethylation associates with increased gene expression, and both mechanisms are impaired when TET2 and nuclear factor κB are downregulated. We analyzed DNA methylation levels of inflammasome-related genes in patients with cryopyrin-associated periodic syndromes (CAPS) and familial Mediterranean fever, 2 archetypical monogenic autoinflammatory syndromes. Under the above conditions, monocytes from untreated patients with CAPS undergo more efficient DNA demethylation than those of healthy subjects. Interestingly, patients with CAPS treated with anti-IL-1 drugs display methylation levels similar to those of healthy control subjects. Our study is the first to demonstrate the involvement of DNA methylation-associated alterations in patients with monogenic autoinflammatory disease and opens up possibilities for novel clinical markers. Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Emodin enhances the demethylation by 5-Aza-CdR of pancreatic cancer cell tumor-suppressor genes P16, RASSF1A and ppENK.

PubMed

Pan, Feng-Ping; Zhou, Hong-Kun; Bu, He-Qi; Chen, Zi-Qiang; Zhang, Hao; Xu, Lu-Ping; Tang, Jian; Yu, Qing-Jiang; Chu, Yong-Quan; Pan, Jie; Fei, Yong; Lin, Sheng-Zhang; Liu, Dian-Lei; Chen, Liang

2016-04-01

5-Aza-2'-deoxycytidine (5-Aza-CdR) is currently acknowledged as a demethylation drug, and causes a certain degree of demethylation in a variety of cancer cells, including pancreatic cancer cells. Emodin, a traditional Chinese medicine (TCM), is an effective monomer extracted from rhubarb and has been reported to exhibit antitumor activity in different manners in pancreatic cancer. In the present study, we examined whether emodin caused demethylation and increased the demethylation of three tumor-suppressor genes P16, RASSF1A and ppENK with a high degree of methylation in pancreatic cancer when combined with 5-Aza-CdR. Our research showed that emodin inhibited the growth of pancreatic cancer Panc-1 cells in a dose- and time-dependent manner. Dot-blot results showed that emodin combined with 5-Aza-CdR significantly suppressed the expression of genome 5mC in PANC-1 cells. In order to verify the effect of methylation, methylation-specific PCR (MSP) and bisulfite genomic sequencing PCR (BSP) combined with TA were selected for the cloning and sequencing. Results of MSP and BSP confirmed that emodin caused faint demethylation, and 5-Aza-CdR had a certain degree of demethylation. When emodin was combined with 5-Aza-CdR, the demethylation was more significant. At the same time, fluorescent quantitative PCR and western blot analysis results confirmed that when emodin was combined with 5-Aza-CdR, the expression levels of P16, RASSF1A and ppENK were increased more significantly compared to either treatment alone. In contrast, the expression levels of DNA methyltransferase 1 (DNMT1) and DNMT3a were more significantly reduced with the combination treatment than the control or either agent alone, further proving that emodin in combination with 5-Aza-CdR enhanced the demethylation effect of 5-Aza-CdR by reducing the expression of methyltransferases. In conclusion, the present study confirmed that emodin in combination with 5-Aza-CdR enhanced the demethylation by 5-Aza-CdR of tumor-suppressor genes p16, RASSF1A and ppENK by reducing the expression of methyltransferases DNMT1 and DNMT3a.

Emodin enhances the demethylation by 5-Aza-CdR of pancreatic cancer cell tumor-suppressor genes P16, RASSF1A and ppENK

PubMed Central

PAN, FENG-PING; ZHOU, HONG-KUN; BU, HE-QI; CHEN, ZI-QIANG; ZHANG, HAO; XU, LU-PING; TANG, JIAN; YU, QING-JIANG; CHU, YONG-QUAN; PAN, JIE; FEI, YONG; LIN, SHENG-ZHANG; LIU, DIAN-LEI; CHEN, LIANG

2016-01-01

5-Aza-2′-deoxycytidine (5-Aza-CdR) is currently acknowledged as a demethylation drug, and causes a certain degree of demethylation in a variety of cancer cells, including pancreatic cancer cells. Emodin, a traditional Chinese medicine (TCM), is an effective monomer extracted from rhubarb and has been reported to exhibit antitumor activity in different manners in pancreatic cancer. In the present study, we examined whether emodin caused demethylation and increased the demethylation of three tumor-suppressor genes P16, RASSF1A and ppENK with a high degree of methylation in pancreatic cancer when combined with 5-Aza-CdR. Our research showed that emodin inhibited the growth of pancreatic cancer Panc-1 cells in a dose- and time-dependent manner. Dot-blot results showed that emodin combined with 5-Aza-CdR significantly suppressed the expression of genome 5mC in PANC-1 cells. In order to verify the effect of methylation, methylation-specific PCR (MSP) and bisulfite genomic sequencing PCR (BSP) combined with TA were selected for the cloning and sequencing. Results of MSP and BSP confirmed that emodin caused faint demethylation, and 5-Aza-CdR had a certain degree of demethylation. When emodin was combined with 5-Aza-CdR, the demethylation was more significant. At the same time, fluorescent quantitative PCR and western blot analysis results confirmed that when emodin was combined with 5-Aza-CdR, the expression levels of P16, RASSF1A and ppENK were increased more significantly compared to either treatment alone. In contrast, the expression levels of DNA methyltransferase 1 (DNMT1) and DNMT3a were more significantly reduced with the combination treatment than the control or either agent alone, further proving that emodin in combination with 5-Aza-CdR enhanced the demethylation effect of 5-Aza-CdR by reducing the expression of meth-yltransferases. In conclusion, the present study confirmed that emodin in combination with 5-Aza-CdR enhanced the demethylation by 5-Aza-CdR of tumor-suppressor genes p16, RASSF1A and ppENK by reducing the expression of methyltransferases DNMT1 and DNMT3a. PMID:26782786

DNA demethylation in the Arabidopsis genome

PubMed Central

Penterman, Jon; Zilberman, Daniel; Huh, Jin Hoe; Ballinger, Tracy; Henikoff, Steven; Fischer, Robert L.

2007-01-01

Cytosine DNA methylation is considered to be a stable epigenetic mark, but active demethylation has been observed in both plants and animals. In Arabidopsis thaliana, DNA glycosylases of the DEMETER (DME) family remove methylcytosines from DNA. Demethylation by DME is necessary for genomic imprinting, and demethylation by a related protein, REPRESSOR OF SILENCING1, prevents gene silencing in a transgenic background. However, the extent and function of demethylation by DEMETER-LIKE (DML) proteins in WT plants is not known. Using genome-tiling microarrays, we mapped DNA methylation in mutant and WT plants and identified 179 loci actively demethylated by DML enzymes. Mutations in DML genes lead to locus-specific DNA hypermethylation. Reintroducing WT DML genes restores most loci to the normal pattern of methylation, although at some loci, hypermethylated epialleles persist. Of loci demethylated by DML enzymes, >80% are near or overlap genes. Genic demethylation by DML enzymes primarily occurs at the 5′ and 3′ ends, a pattern opposite to the overall distribution of WT DNA methylation. Our results show that demethylation by DML DNA glycosylases edits the patterns of DNA methylation within the Arabidopsis genome to protect genes from potentially deleterious methylation. PMID:17409185

Epigenetic regulation of the transcription factor Foxa2 directs differential elafin expression in melanocytes and melanoma cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Kyung Sook; Jo, Ji Yoon; Kim, Su Jin

2011-04-29

Highlights: {yields} Elafin expression is epigenetically silenced in human melanoma cells. {yields} Foxa2 expression in melanoma cells is silenced by promoter hypermethylation. {yields} Foxa2 directs activation of the elafin promoter in vivo. {yields} Foxa2 expression induces apoptosis of melanoma cells via elafin re-expression. -- Abstract: Elafin, a serine protease inhibitor, induces the intrinsic apoptotic pathway in human melanoma cells, where its expression is transcriptionally silenced. However, it remains unknown how the elafin gene is repressed in melanoma cells. We here demonstrate that elafin expression is modulated via epigenetically regulated expression of the transcription factor Foxa2. Treatment of melanoma cells withmore » a DNA methyltransferase inhibitor induced elafin expression, which was specifically responsible for reduced proliferation and increased apoptosis. Suppression of Foxa2 transcription, mediated by DNA hypermethylation in its promoter region, was released in melanoma cells upon treatment with the demethylating agent. Luciferase reporter assays indicated that the Foxa2 binding site in the elafin promoter was critical for the activation of the promoter. Chromatin immunoprecipitation assays further showed that Foxa2 bound to the elafin promoter in vivo. Analyses of melanoma cells with varied levels of Foxa2 revealed a correlated expression between Foxa2 and elafin and the ability of Foxa2 to induce apoptosis. Our results collectively suggest that, in melanoma cells, Foxa2 expression is silenced and therefore elafin is maintained unexpressed to facilitate cell proliferation in the disease melanoma.« less

Evidence for tangeretin O-demethylation by rat and human liver microsomes.

PubMed

Canivenc-Lavier, M C; Brunold, C; Siess, M H; Suschetet, M

1993-03-01

1. Tangeretin, a polymethoxylated flavone, was studied as a substrate for cytochrome P450-catalysed demethylation reactions by rat and human liver microsomes. Evidence has been presented for the production of formaldehyde in the presence of tangeretin and NAD(P)H. Kinetic studies showed a Km value for tangeretin of about 18 microM in both species. 2. The reaction was inhibited by CO, piperonyl butoxide, 7,8-benzoflavone, propyl gallate, aminobenzothiazole and metyrapone. 3. Rats pretreated with classical cytochrome P450 inducers (Aroclor 1254, 3-methylcholanthrene, phenobarbital, dexamethasone and ciprofibrate) or with flavonoids (flavone, flavanone, quercetin and tangeretin) resulted in increased microsomal demethylation of tangeretin after 3-methylcholanthrene and flavone only. Tangeretin did not enhance its own metabolism. 4. Tangeretin interacted with the oxidized form of cytochrome P450 to produce a reverse type I spectrum. 5. Results indicate that tangeretin is metabolized in liver microsomes by an O-demethylation reaction involving cytochrome P450.

Epigenetic reprogramming - is deamination key to active DNA demethylation?

PubMed Central

Teperek-Tkacz, Marta; Pasque, Vincent; Gentsch, George; Ferguson-Smith, Anne C.

2013-01-01

DNA demethylation processes are important for reproduction being central in epigenetic reprogramming during embryonic and germ cell development. While the enzymes methylating DNA have been known for many years, identification of factors capable of mediating active DNA demethylation has been challenging. Recent findings suggest that cytidine deaminases may be key players in active DNA demethylation. One of the most investigated candidates is AID (activation-induced cytidine deaminase) best known for its role in generating secondary antibody diversity in B cells. We evaluate evidence for cytidine deaminases in DNA demethylation pathways in vertebrates and discuss possible models for their targeting and activity regulation. These findings are also considered alongside alternative demethylation pathways involving hydroxymethylation. PMID:21911441

The secreted protein ANGPTL2 promotes metastasis of osteosarcoma cells through integrin α5β1, p38 MAPK, and matrix metalloproteinases.

PubMed

Odagiri, Haruki; Kadomatsu, Tsuyoshi; Endo, Motoyoshi; Masuda, Tetsuro; Morioka, Masaki Suimye; Fukuhara, Shigetomo; Miyamoto, Takeshi; Kobayashi, Eisuke; Miyata, Keishi; Aoi, Jun; Horiguchi, Haruki; Nishimura, Naotaka; Terada, Kazutoyo; Yakushiji, Toshitake; Manabe, Ichiro; Mochizuki, Naoki; Mizuta, Hiroshi; Oike, Yuichi

2014-01-21

The tumor microenvironment can enhance the invasive capacity of tumor cells. We showed that expression of angiopoietin-like protein 2 (ANGPTL2) in osteosarcoma (OS) cell lines increased and the methylation of its promoter decreased with time when grown as xenografts in mice compared with culture. Compared with cells grown in normal culture conditions, the expression of genes encoding DNA demethylation-related enzymes increased in tumor cells implanted into mice or grown in hypoxic, serum-starved culture conditions. ANGPTL2 expression in OS cell lines correlated with increased tumor metastasis and decreased animal survival by promoting tumor cell intravasation mediated by the integrin α5β1, p38 mitogen-activated protein kinase, and matrix metalloproteinases. The tolloid-like 1 (TLL1) protease cleaved ANGPTL2 into fragments in vitro that did not enhance tumor progression when overexpressed in xenografts. Expression of TLL1 was weak in OS patient tumors, suggesting that ANGPTL2 may not be efficiently cleaved upon secretion from OS cells. These findings demonstrate that preventing ANGPTL2 signaling stimulated by the tumor microenvironment could inhibit tumor cell migration and metastasis.

Association of Glioblastoma Multiforme Stem Cell Characteristics, Differentiation, and Microglia Marker Genes with Patient Survival

PubMed Central

Balz, Ellen; Herzog, Susann; Plantera, Laura; Vogelgesang, Silke; Seifert, Carolin; Bialke, Angela; Venugopal, Chitra; Singh, Sheila K.; Hoffmann, Wolfgang; Schroeder, Henry W. S.

2018-01-01

Patients with glioblastoma multiforme (GBM) are at high risk to develop a relapse despite multimodal therapy. Assumedly, glioma stem cells (GSCs) are responsible for treatment resistance of GBM. Identification of specific GSC markers may help to develop targeted therapies. Here, we performed expression analyses of stem cell (ABCG2, CD44, CD95, CD133, ELF4, Nanog, and Nestin) as well as differentiation and microglia markers (GFAP, Iba1, and Sparc) in GBM compared to nonmalignant brain. Furthermore, the role of these proteins for patient survival and their expression in LN18 stem-like neurospheres was analyzed. At mRNA level, ABCG2 and CD95 were reduced, GFAP was unchanged; all other investigated markers were increased in GBM. At protein level, CD44, ELF4, Nanog, Nestin, and Sparc were elevated in GBM, but only CD133 and Nestin were strongly associated with survival time. In addition, ABCG2 and GFAP expression was decreased in LN18 neurospheres whereas CD44, CD95, CD133, ELF4, Nanog, Nestin, and Sparc were upregulated. Altogether only CD133 and Nestin were associated with survival rates. This raises concerns regarding the suitability of the other target structures as prognostic markers, but makes both CD133 and Nestin candidates for GBM therapy. Nevertheless, a search for more specific marker proteins is urgently needed. PMID:29535786

Characterization of hair-follicle side population cells in mouse epidermis and skin tumors

PubMed Central

Kim, Sun Hye; Sistrunk, Christopher; Miliani de Marval, Paula L.; Rodriguez-Puebla, Marcelo L.

2017-01-01

A subset of cells, termed side-population (SP), which have the ability to efflux Hoeschst 33342, have previously been demonstrated to act as a potential method to isolate stem cells. Numerous stem/progenitor cells have been localized in different regions of the mouse hair follicle (HF). The present study identified a SP in the mouse HF expressing the ABCG2 transporter and MTS24 surface marker. These cells are restricted to the upper isthmus of the HF and have previously been described as progenitor cells. Consistent with their SP characteristic, they demonstrated elevated expression of ABCG2 transporter, which participates in the dye efflux. Analysis of tumor epidermal cell lines revealed a correlation between the number of SP keratinocytes and the grade of malignancy, suggesting that the SP may play a role in malignant progression. Consistent with this idea, the present study observed an increased number of cells expressing ABCG2 and MTS24 in chemically induced skin tumors and skin tumor cell lines. This SP does not express the CD34 surface marker detected in the multipotent stem cells of the bulge region of the HF, which have been defined as tumor initiation cells. The present study concluded that a SP with properties of progenitor cells is localized in the upper isthmus of the HF and is important in mouse skin tumor progression. PMID:29181098

γ-radiation induces cellular sensitivity and aberrant methylation in human tumor cell lines.

PubMed

Kumar, Ashok; Rai, Padmalatha S; Upadhya, Raghavendra; Vishwanatha; Prasada, K Shama; Rao, B S Satish; Satyamoorthy, Kapettu

2011-11-01

Ionizing radiation induces cellular damage through both direct and indirect mechanisms, which may include effects from epigenetic changes. The purpose of this study was to determine the effect of ionizing radiation on DNA methylation patterns that may be associated with altered gene expression. Sixteen human tumor cell lines originating from various cancers were initially tested for radiation sensitivity by irradiating them with γ-radiation in vitro and subsequently, radiation sensitive and resistant cell lines were treated with different doses of a demethylating agent, 5-Aza-2'-Deoxycytidine (5-aza-dC) and a chromatin modifier, Trichostatin-A (TSA). Survival of these cell lines was measured using 3-(4, 5-Dimethylthiazol- 2-yl)-2, 5-diphenyltetrazolium (MTT) and clonogenic assays. The effect of radiation on global DNA methylation was measured using reverse phase high performance liquid chromatography (RP-HPLC). The transcription response of methylated gene promoters, from cyclin-dependent kinase inhibitor 2A (p16(INK4a)) and ataxia telangiectasia mutated (ATM) genes, to radiation was measured using a luciferase reporter assay. γ-radiation resistant (SiHa and MDAMB453) and sensitive (SaOS2 and WM115) tumor cell lines were examined for the relationship between radiation sensitivity and DNA methylation. Treatment of cells with 5-aza-dC and TSA prior to irradiation enhanced DNA strand breaks, G2/M phase arrest, apoptosis and cell death. Exposure to γ-radiation led to global demethylation in a time-dependent manner in tumor cells in relation to resistance and sensitivity to radiation with concomitant activation of p16(INK4a) and ATM gene promoters. These results provide important information on alterations in DNA methylation as one of the determinants of radiation effects, which may be associated with altered gene expression. Our results may help in delineating the mechanisms of radiation resistance in tumor cells, which can influence diagnosis, prognosis and eventually therapy for human cancers.

The Mechanism of Autoinduction of Methadone N-demethylation in Human Hepatocytes

PubMed Central

Campbell, Scott D.; Crafford, Amanda; Williamson, Brian L.; Kharasch, Evan D.

2013-01-01

Background There is considerable inter-and intraindividual variability in methadone metabolism and clearance. Methadone dosing is particularly challenging during initiation of therapy, due to time-dependent increases in hepatic clearance (autoinduction). Although methadone N-demethylation is catalyzed in vitro by cytochrome P4502B6 (CYP2B6) and CYP3A4, and clearance in vivo depends on CYP2B6, mechanism(s) of autoinduction are incompletely understood. In this investigation we determined mechanism(s) of methadone autoinduction using human hepatocytes. Methods Fresh human hepatocytes were exposed to 0.1-10 μM methadone for 72 hr. Cells were washed and methadone N-demethylation assessed. CYP2B6, CYP3A4, and CYP3A5 mRNA, protein expression (by gel-free high performance liquid chromatography-mass spectrometry) and catalytic activity (bupropion hydroxylation and alfentanil dealkylation for CYP2B6 and CYP3A4/5, respectively) were measured. Mechanisms of CYP induction were characterized using pregnane X receptor and constitutive androstane receptor reporter gene assays. Results Methadone (10 μM) increased methadone N-demethylation 2-fold, CYP2B6 and CYP3A4 mRNA 3-fold, and protein expression 2-fold. CYP3A5 mRNA was unchanged. CYP2B6 and CYP3A4/5 activities increased 2-fold. Induction by methadone enantiomers (R- vs S-methadone) did not differ. Induction was relatively weak compared with maximum induction by phenobarbital and rifampin. Lower methadone concentrations had smaller effects. Methadone was an agonist for the pregnane X receptor but not the constitutive androstane receptor. Conclusions Methadone caused concentration-dependent autoinduction of methadone N-demethylation in human hepatocytes, related to induction of CYP2B6 and CYP3A4 mRNA expression, protein expression, and catalytic activity. Induction was related to pregnane X receptor but not constitutive androstane receptor activation. These in vitro findings provide mechanistic insights into clinical autoinduction of methadone metabolism and clearance. PMID:23733841

Novel understanding of ABC transporters ABCB1/MDR/P-glycoprotein, ABCC2/MRP2, and ABCG2/BCRP in colorectal pathophysiology

PubMed Central

Andersen, Vibeke; Svenningsen, Katrine; Knudsen, Lina Almind; Hansen, Axel Kornerup; Holmskov, Uffe; Stensballe, Allan; Vogel, Ulla

2015-01-01

AIM: To evaluate ATP-binding cassette (ABC) transporters in colonic pathophysiology as they had recently been related to colorectal cancer (CRC) development. METHODS: Literature search was conducted on PubMed using combinations of the following terms: ABC transporters, ATP binding cassette transporter proteins, inflammatory bowel disease, ulcerative, colitis, Crohns disease, colorectal cancer, colitis, intestinal inflammation, intestinal carcinogenesis, ABCB1/P-glycoprotein (P-gp/CD243/MDR1), ABCC2/multidrug resistance protein 2 (MRP2) and ABCG2/breast cancer resistance protein (BCRP), Abcb1/Mdr1a, abcc2/Mrp2, abcg2/Bcrp, knock-out mice, tight junction, membrane lipid function. RESULTS: Recently, human studies reported that changes in the levels of ABC transporters were early events in the adenoma-carcinoma sequence leading to CRC. A link between ABCB1, high fat diet and gut microbes in relation to colitis was suggested by the animal studies. The finding that colitis was preceded by altered gut bacterial composition suggests that deletion of Abcb1 leads to fundamental changes of host-microbiota interaction. Also, high fat diet increases the frequency and severity of colitis in specific pathogen-free Abcb1 KO mice. The Abcb1 KO mice might thus serve as a model in which diet/environmental factors and microbes may be controlled and investigated in relation to intestinal inflammation. Potential molecular mechanisms include defective transport of inflammatory mediators and/or phospholipid translocation from one side to the other of the cell membrane lipid bilayer by ABC transporters affecting inflammatory response and/or function of tight junctions, phagocytosis and vesicle trafficking. Also, diet and microbes give rise to molecules which are potential substrates for the ABC transporters and which may additionally affect ABC transporter function through nuclear receptors and transcriptional regulation. Another critical role of ABCB1 was suggested by the finding that ABCB1 expression identifies a subpopulation of pro-inflammatory Th17 cells which were resistant to treatment with glucocorticoids. The evidence for the involvement of ABCC2 and ABCG2 in colonic pathophysiology was weak. CONCLUSION: ABCB1, diet, and gut microbes mutually interact in colonic inflammation, a well-known risk factor for CRC. Further insight may be translated into preventive and treatment strategies. PMID:26557010

ERRα protein is stabilized by LSD1 in a demethylation-independent manner.

PubMed

Carnesecchi, Julie; Cerutti, Catherine; Vanacker, Jean-Marc; Forcet, Christelle

2017-01-01

The LSD1 histone demethylase is highly expressed in breast tumors where it constitutes a factor of poor prognosis and promotes traits of cancer aggressiveness such as cell invasiveness. Recent work has shown that the Estrogen-Related Receptor α (ERRα) induces LSD1 to demethylate the Lys 9 of histone H3. This results in the transcriptional activation of a number of common target genes, several of which being involved in cellular invasion. High expression of ERRα protein is also a factor of poor prognosis in breast tumors. Here we show that, independently of its demethylase activities, LSD1 protects ERRα from ubiquitination, resulting in overexpression of the latter protein. Our data also suggests that the elevation of LSD1 mRNA and protein in breast cancer (as compared to normal tissue) may be a key event to increase ERRα protein, independently of its corresponding mRNA.

ERRα protein is stabilized by LSD1 in a demethylation-independent manner

PubMed Central

Carnesecchi, Julie; Cerutti, Catherine; Vanacker, Jean-Marc

2017-01-01

The LSD1 histone demethylase is highly expressed in breast tumors where it constitutes a factor of poor prognosis and promotes traits of cancer aggressiveness such as cell invasiveness. Recent work has shown that the Estrogen-Related Receptor α (ERRα) induces LSD1 to demethylate the Lys 9 of histone H3. This results in the transcriptional activation of a number of common target genes, several of which being involved in cellular invasion. High expression of ERRα protein is also a factor of poor prognosis in breast tumors. Here we show that, independently of its demethylase activities, LSD1 protects ERRα from ubiquitination, resulting in overexpression of the latter protein. Our data also suggests that the elevation of LSD1 mRNA and protein in breast cancer (as compared to normal tissue) may be a key event to increase ERRα protein, independently of its corresponding mRNA. PMID:29190800

ABCA1, ABCG1 and SR-BI: hormonal regulation in primary rat hepatocytes and human cell lines

PubMed Central

Sporstøl, Marita; Mousavi, Seyed Ali; Eskild, Winnie; Roos, Norbert; Berg, Trond

2007-01-01

Background Scavenger receptor type B class I (SR-BI), ABC transporter A1 (ABCA1) -and G1 (ABCG1) all play important roles in the reverse cholesterol transport. Reverse cholesterol transport is a mechanism whereby the body can eliminate excess cholesterol. Here, the regulation of SR-BI, ABCA1, and ABCG1 by dexamethasone (a synthetic glucocorticoid) and insulin were studied in order to gain more insight into the role of these two hormones in the cholesterol metabolism. Results By use of real time RT-PCR and Western blotting we examined the expression of our target genes. The results show that SR-BI, ABCA1 and ABCG1 mRNA expression increased in response to dexamethasone while insulin treatment reduced the expression in primary rat hepatocytes. The stimulatory effect of dexamethasone was reduced by the addition of the anti-glucocorticoid mifepristone. In HepG2 cells and THP-1 macrophages, however, the effect of dexamethasone was absent or inhibitory with no significant change in the presence of mifepristone. The latter observation may be a result of the low protein expression of glucocorticoid receptor (GR) in these cell lines. Conclusion Our results illustrates that insulin and glucocorticoids, two hormones crucial in the carbohydrate metabolism, also play an important role in the regulation of genes central in reverse cholesterol transport. We found a marked difference in mRNA expression between the primary cells and the two established cell lines when studying the effect of dexamethasone which may result from the varying expression levels of GR. PMID:17241464

ABCA1, ABCG1 and SR-BI: hormonal regulation in primary rat hepatocytes and human cell lines.

PubMed

Sporstøl, Marita; Mousavi, Seyed Ali; Eskild, Winnie; Roos, Norbert; Berg, Trond

2007-01-22

Scavenger receptor type B class I (SR-BI), ABC transporter A1 (ABCA1) -and G1 (ABCG1) all play important roles in the reverse cholesterol transport. Reverse cholesterol transport is a mechanism whereby the body can eliminate excess cholesterol. Here, the regulation of SR-BI, ABCA1, and ABCG1 by dexamethasone (a synthetic glucocorticoid) and insulin were studied in order to gain more insight into the role of these two hormones in the cholesterol metabolism. By use of real time RT-PCR and Western blotting we examined the expression of our target genes. The results show that SR-BI, ABCA1 and ABCG1 mRNA expression increased in response to dexamethasone while insulin treatment reduced the expression in primary rat hepatocytes. The stimulatory effect of dexamethasone was reduced by the addition of the anti-glucocorticoid mifepristone. In HepG2 cells and THP-1 macrophages, however, the effect of dexamethasone was absent or inhibitory with no significant change in the presence of mifepristone. The latter observation may be a result of the low protein expression of glucocorticoid receptor (GR) in these cell lines. Our results illustrates that insulin and glucocorticoids, two hormones crucial in the carbohydrate metabolism, also play an important role in the regulation of genes central in reverse cholesterol transport. We found a marked difference in mRNA expression between the primary cells and the two established cell lines when studying the effect of dexamethasone which may result from the varying expression levels of GR.

Association between DNA Methylation in Whole Blood and Measures of Glucose Metabolism: KORA F4 Study

PubMed Central

Wahl, Simone; Kunze, Sonja; Molnos, Sophie; Volkova, Nadezda; Schramm, Katharina; Carstensen-Kirberg, Maren; Waldenberger, Melanie; Gieger, Christian; Peters, Annette; Illig, Thomas; Prokisch, Holger; Roden, Michael; Grallert, Harald

2016-01-01

Epigenetic regulation has been postulated to affect glucose metabolism, insulin sensitivity and the risk of type 2 diabetes. Therefore, we performed an epigenome-wide association study for measures of glucose metabolism in whole blood samples of the population-based Cooperative Health Research in the Region of Augsburg F4 study using the Illumina HumanMethylation 450 BeadChip. We identified a total of 31 CpG sites where methylation level was associated with measures of glucose metabolism after adjustment for age, sex, smoking, and estimated white blood cell proportions and correction for multiple testing using the Benjamini-Hochberg (B-H) method (four for fasting glucose, seven for fasting insulin, 25 for homeostasis model assessment-insulin resistance [HOMA-IR]; B-H-adjusted p-values between 9.2x10-5 and 0.047). In addition, DNA methylation at cg06500161 (annotated to ABCG1) was associated with all the aforementioned phenotypes and 2-hour glucose (B-H-adjusted p-values between 9.2x10-5 and 3.0x10-3). Methylation status of additional three CpG sites showed an association with fasting insulin only after additional adjustment for body mass index (BMI) (B-H-adjusted p-values = 0.047). Overall, effect strengths were reduced by around 30% after additional adjustment for BMI, suggesting that this variable has an influence on the investigated phenotypes. Furthermore, we found significant associations between methylation status of 21 of the aforementioned CpG sites and 2-hour insulin in a subset of samples with seven significant associations persisting after additional adjustment for BMI. In a subset of 533 participants, methylation of the CpG site cg06500161 (ABCG1) was inversely associated with ABCG1 gene expression (B-H-adjusted p-value = 1.5x10-9). Additionally, we observed an enrichment of the top 1,000 CpG sites for diabetes-related canonical pathways using Ingenuity Pathway Analysis. In conclusion, our study indicates that DNA methylation and diabetes-related traits are associated and that these associations are partially BMI-dependent. Furthermore, the interaction of ABCG1 with glucose metabolism is modulated by epigenetic processes. PMID:27019061

CTCF-KDM4A complex correlates with histone modifications that negatively regulate CHD5 gene expression in cancer cell lines

PubMed Central

Guerra-Calderas, Lissania; González-Barrios, Rodrigo; Patiño, Carlos César; Alcaraz, Nicolás; Salgado-Albarrán, Marisol; de León, David Cantú; Hernández, Clementina Castro; Sánchez-Pérez, Yesennia; Maldonado-Martínez, Héctor Aquiles; De la Rosa-Velazquez, Inti A.; Vargas-Romero, Fernanda; Herrera, Luis A.; García-Carrancá, Alejandro; Soto-Reyes, Ernesto

2018-01-01

Histone demethylase KDM4A is involved in H3K9me3 and H3K36me3 demethylation, which are epigenetic modifications associated with gene silencing and RNA Polymerase II elongation, respectively. KDM4A is abnormally expressed in cancer, affecting the expression of multiple targets, such as the CHD5 gene. This enzyme localizes at the first intron of CHD5, and the dissociation of KDM4A increases gene expression. In vitro assays showed that KDM4A-mediated demethylation is enhanced in the presence of CTCF, suggesting that CTCF could increase its enzymatic activity in vivo, however the specific mechanism by which CTCF and KDM4A might be involved in the CHD5 gene repression is poorly understood. Here, we show that CTCF and KDM4A form a protein complex, which is recruited into the first intron of CHD5. This is related to a decrease in H3K36me3/2 histone marks and is associated with its transcriptional downregulation. Depletion of CTCF or KDM4A by siRNA, triggered the reactivation of CHD5 expression, suggesting that both proteins are involved in the negative regulation of this gene. Furthermore, the knockout of KDM4A restored the CHD5 expression and H3K36me3 and H3K36me2 histone marks. Such mechanism acts independently of CHD5 promoter DNA methylation. Our findings support a novel mechanism of epigenetic repression at the gene body that does not involve promoter silencing. PMID:29682202

Redistribution of demethylated RNA helicase A during foot-and-mouth disease virus infection: Role of Jumonji C-domain containing protein 6 in RHA demethylation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawrence, Paul; Conderino, Joseph S.; Rieder, Elizabeth, E-mail: elizabeth.rieder@ars.usda.gov

Previously, RNA helicase A (RHA) re-localization from the nucleus to the cytoplasm in foot-and-mouth disease virus (FMDV) infected cells was shown to coincide with loss of RHA methylated arginine residues at its C-terminus. The potential interaction between RHA and Jumonji C-domain (JmjC) protein 6 (JMJD6) arginine demethylase in infected cells was investigated. Treatment with N-oxalylglycine (NOG) inhibitor of JmjC demethylases prevented FMDV-induced RHA demethylation and re-localization, and also decreased viral protein synthesis and virus titers. Physical interaction between JMJD6 and RHA was demonstrated via reciprocal co-immunoprecipitation, where RHA preferentially bound JMJD6 monomers. Nuclear efflux of demethylated RHA (DM-RHA) coincided withmore » nuclear influx of JMJD6, which was not observed using another picornavirus. A modified biochemical assay demonstrated JMJD6 induced dose-dependent demethylation of RHA and two RHA-derived isoforms, which could be inhibited by NOG. We propose a role for JMJD6 in RHA demethylation stimulated by FMDV, that appears to facilitate virus replication. - Highlights: • We examined the role of JMJD6 in FMDV-induced RHA demethylation process. • Using an arginine demethylation assay showed that JMJD6 is involved in RHA demethylation. • A demethylases inhibitor reduced cytoplasmic accumulation of RHA and FMDV titers.« less

Hydroxylation of the herbicide isoproturon by fungi isolated from agricultural soil.

PubMed

Rønhede, Stig; Jensen, Bo; Rosendahl, Søren; Kragelund, Birthe B; Juhler, René K; Aamand, Jens

2005-12-01

Several asco-, basidio-, and zygomycetes isolated from an agricultural field were shown to be able to hydroxylate the phenylurea herbicide isoproturon [N-(4-isopropylphenyl)-N',N'-dimethylurea] to N-(4-(2-hydroxy-1-methylethyl)phenyl)-N',N'-dimethylurea and N-(4-(1-hydroxy-1-methylethyl)phenyl)-N',N'-dimethylurea. Bacterial metabolism of isoproturon has previously been shown to proceed by an initial demethylation to N-(4-isopropylphenyl)-N'-methylurea. In soils, however, hydroxylated metabolites have also been detected. In this study we identified fungi as organisms that potentially play a major role in the formation of these hydroxylated metabolites in soils treated with isoproturon. Isolates of Mortierella sp. strain Gr4, Phoma cf. eupyrena Gr61, and Alternaria sp. strain Gr174 hydroxylated isoproturon at the first position of the isopropyl side chain, yielding N-(4-(2-hydroxy-1-methylethyl)phenyl)-N',N'-dimethylurea, while Mucor sp. strain Gr22 hydroxylated the molecule at the second position, yielding N-(4-(1-hydroxy-1-methylethyl)phenyl)-N',N'-dimethylurea. Hydroxylation was the dominant mode of isoproturon transformation in these fungi, although some cultures also produced traces of the N-demethylated metabolite N-(4-isopropylphenyl)-N'-methylurea. A basidiomycete isolate produced a mixture of the two hydroxylated and N-demethylated metabolites at low concentrations. Clonostachys sp. strain Gr141 and putative Tetracladium sp. strain Gr57 did not hydroxylate isoproturon but N demethylated the compound to a minor extent. Mortierella sp. strain Gr4 also produced N-(4-(2-hydroxy-1-methylethyl)phenyl)-N'-methylurea, which is the product resulting from combined N demethylation and hydroxylation.

Hydroxylation of the Herbicide Isoproturon by Fungi Isolated from Agricultural Soil

PubMed Central

Rønhede, Stig; Jensen, Bo; Rosendahl, Søren; Kragelund, Birthe B.; Juhler, René K.; Aamand, Jens

2005-01-01

Several asco-, basidio-, and zygomycetes isolated from an agricultural field were shown to be able to hydroxylate the phenylurea herbicide isoproturon [N-(4-isopropylphenyl)-N′,N′-dimethylurea] to N-(4-(2-hydroxy-1-methylethyl)phenyl)-N′,N′-dimethylurea and N-(4-(1-hydroxy-1-methylethyl)phenyl)-N′,N′-dimethylurea. Bacterial metabolism of isoproturon has previously been shown to proceed by an initial demethylation to N-(4-isopropylphenyl)-N′-methylurea. In soils, however, hydroxylated metabolites have also been detected. In this study we identified fungi as organisms that potentially play a major role in the formation of these hydroxylated metabolites in soils treated with isoproturon. Isolates of Mortierella sp. strain Gr4, Phoma cf. eupyrena Gr61, and Alternaria sp. strain Gr174 hydroxylated isoproturon at the first position of the isopropyl side chain, yielding N-(4-(2-hydroxy-1-methylethyl)phenyl)-N′,N′-dimethylurea, while Mucor sp. strain Gr22 hydroxylated the molecule at the second position, yielding N-(4-(1-hydroxy-1-methylethyl)phenyl)-N′,N′-dimethylurea. Hydroxylation was the dominant mode of isoproturon transformation in these fungi, although some cultures also produced traces of the N-demethylated metabolite N-(4-isopropylphenyl)-N′-methylurea. A basidiomycete isolate produced a mixture of the two hydroxylated and N-demethylated metabolites at low concentrations. Clonostachys sp. strain Gr141 and putative Tetracladium sp. strain Gr57 did not hydroxylate isoproturon but N demethylated the compound to a minor extent. Mortierella sp. strain Gr4 also produced N-(4-(2-hydroxy-1-methylethyl)phenyl)-N′-methylurea, which is the product resulting from combined N demethylation and hydroxylation. PMID:16332769

Rice Stomatal Closure Requires Guard Cell Plasma Membrane ATP-Binding Cassette Transporter RCN1/OsABCG5.

PubMed

Matsuda, Shuichi; Takano, Sho; Sato, Moeko; Furukawa, Kaoru; Nagasawa, Hidetaka; Yoshikawa, Shoko; Kasuga, Jun; Tokuji, Yoshihiko; Yazaki, Kazufumi; Nakazono, Mikio; Takamure, Itsuro; Kato, Kiyoaki

2016-03-07

Water stress is one of the major environmental stresses that affect agricultural production worldwide. Water loss from plants occurs primarily through stomatal pores. Here, we report that an Oryza sativa half-size ATP-binding cassette (ABC) subfamily G protein, RCN1/OsABCG5, is involved in stomatal closure mediated by phytohormone abscisic acid (ABA) accumulation in guard cells. We found that the GFP-RCN1/OsABCG5-fusion protein was localized at the plasma membrane in guard cells. The percentage of guard cell pairs containing both ABA and GFP-RCN1/OsABCG5 increased after exogenous ABA treatment, whereas they were co-localized in guard cell pairs regardless of whether exogenous ABA was applied. ABA application resulted in a smaller increase in the percentage of guard cell pairs containing ABA in rcn1 mutant (A684P) and RCN1-RNAi than in wild-type plants. Furthermore, polyethylene glycol (drought stress)-inducible ABA accumulation in guard cells did not occur in rcn1 mutants. Stomata closure mediated by exogenous ABA application was strongly reduced in rcn1 mutants. Finally, rcn1 mutant plants had more rapid water loss from detached leaves than the wild-type plants. These results indicate that in response to drought stress, RCN1/OsABCG5 is involved in accumulation of ABA in guard cells, which is indispensable for stomatal closure. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.

ABCG-like transporter of Trypanosoma cruzi involved in benznidazole resistance: gene polymorphisms disclose inter-strain intragenic recombination in hybrid isolates.

PubMed

Franco, Jaques; Ferreira, Renata C; Ienne, Susan; Zingales, Bianca

2015-04-01

Benznidazole (BZ) is one of the two drugs for Chagas disease treatment. In a previous study we showed that the Trypanosoma cruzi ABCG-like transporter gene, named TcABCG1, is over-expressed in parasite strains naturally resistant to BZ and that the gene of TcI BZ-resistant strains exhibited several single nucleotide polymorphisms (SNPs) as compared to the gene of CL Brener BZ-susceptible strain. Here we report the sequence of TcABCG1 gene of fourteen T. cruzi strains, with diverse degrees of BZ sensitivity and belonging to different discrete typing units (DTUs) and Tcbat group. Although DTU-specific SNPs and amino acid changes were identified, no direct correlation with BZ-resistance phenotype was found. Thus, it is plausible that the transporter abundance is a determinant factor for drug resistance, as pointed out above. Sequence data were used for Bayesian phylogenies and network genealogy analysis. The network showed a high degree of reticulation suggesting genetic exchange between the parasites. TcI and TcII clades were clearly separated. Tcbat sequences were close to TcI. A fourth clade clustered TcABCG1 haplotypes of TcV, TcVI and TcIII strains, with closer proximity to TcI. Analysis of the recombination patterns indicated that hybrid strains contain haplotypes that are mosaics most likely derived by intragenic recombination of parental sequences. The data confirm that TcII and TcIII as the parentals of TcV and TcVI DTUs. Since genetic fingerprint of TcI was found in TcIII, we sustain the previously proposed "Two Hybridization model" for the origin of hybrid strains. Among the twenty best BLASTP hits in databases, orthologues of TcABCG1 transporter were found in Leishmania spp. and African trypanosomes, though their function remains undescribed. Copyright © 2015 Elsevier B.V. All rights reserved.

Chiral analyses of dextromethorphan/levomethorphan and their metabolites in rat and human samples using LC-MS/MS.

PubMed

Kikura-Hanajiri, Ruri; Kawamura, Maiko; Miyajima, Atsuko; Sunouchi, Momoko; Goda, Yukihiro

2011-04-01

In order to develop an analytical method for the discrimination of dextromethorphan (an antitussive medicine) from its enantiomer, levomethorphan (a narcotic) in biological samples, chiral analyses of these drugs and their O-demethyl and/or N-demethyl metabolites in rat plasma, urine, and hair were carried out using LC-MS/MS. After the i.p. administration of dextromethorphan or levomethorphan to pigmented hairy male DA rats (5 mg/kg/day, 10 days), the parent compounds and their three metabolites in plasma, urine and hair were determined using LC-MS/MS. Complete chiral separation was achieved in 12 min on a Chiral CD-Ph column in 0.1% formic acid-acetonitrile by a linear gradient program. Most of the metabolites were detected as being the corresponding O-demethyl and N, O-didemethyl metabolites in the rat plasma and urine after the hydrolysis of O-glucuronides, although obvious differences in the amounts of these metabolites were found between the dextro and levo forms. No racemation was observed through O- and/or N-demethylation. In the rat hair samples collected 4 weeks after the first administration, those differences were more clearly detected and the concentrations of the parent compounds, their O-demethyl, N-demethyl, and N, O-didemethyl metabolites were 63.4, 2.7, 25.1, and 0.7 ng/mg for the dextro forms and 24.5, 24.6, 2.6, and 0.5 ng/mg for the levo forms, respectively. In order to fully investigate the differences of their metabolic properties between dextromethorphan and levomethorphan, DA rat and human liver microsomes were studied. The results suggested that there might be an enantioselective metabolism of levomethorphan, especially with regard to the O-demethylation, not only in DA rat but human liver microsomes as well. The proposed chiral analyses might be applied to human samples and could be useful for discriminating dextromethorphan use from levomethorphan use in the field of forensic toxicology, although further studies should be carried out using authentic human samples.

Impaired active DNA demethylation in zygotes generated by round spermatid injection.

PubMed

Kurotaki, Yoko Kakino; Hatanaka, Yuki; Kamimura, Satoshi; Oikawa, Mami; Inoue, Hiroki; Ogonuki, Narumi; Inoue, Kimiko; Ogura, Atsuo

2015-05-01

Is the poor development of embryos generated from round spermatid injection (ROSI) in humans and animals associated with abnormal active DNA demethylation? A significant proportion of ROSI-derived embryos failed to undergo active DNA demethylation. Active DNA demethylation is initiated by the conversion of 5-methylcytosine (5mC) to 5-hydroxycytosine (5hmC) by the Tet3 enzyme. Active demethylation proceeds in a more pronounced manner in the male pronucleus than in the female one. Mouse zygotes generated by ICSI or ROSI were analyzed for active DNA methylation by quantification of 5mC and 5hmC using specific antibodies. Some ROSI-derived embryos were subjected to time-lapse imaging for DNA methylation levels and were transferred into recipient pseudo-pregnant female mice. In ICSI-derived embryos, the male:female pronucleus (M/F) ratio of 5mC immunostaining intensity was decreased while that of 5hmC was increased. However, a significant proportion of ROSI-derived embryos showed unchanged M/F ratios for 5mC and 5hmC even at the late zygotic period, indicating that they failed to undergo asymmetric active DNA demethylation. Consistent with this, some ROSI-derived embryos did not show preferential localization of Tet3 to the male pronucleus. ROSI-derived embryos were classified into 'demethylated' or 'non-demethylated' groups by time-lapse imaging and transferred into recipient female mice separately. More normal-sized fetuses were retrieved from the 'demethylated' group than 'non-demethylated' group at Day 11.5 of pregnancy. A causal relationship between impaired active DNA demethylation and the poor developmental ability of ROSI-derived embryos remains to be determined. We identified two types of ROSI-derived embryos in terms of the degree of active DNA demethylation. Induction of normal DNA demethylation at the zygotic stage might help in the technical improvement of ROSI. The work was supported by Grants-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology of Japan and by the RIKEN Epigenetics Program. The authors have no competing interests to declare. © The Author 2015. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Elevation of β-galactoside α2,6-sialyltransferase 1 in a fructose-responsive manner promotes pancreatic cancer metastasis

PubMed Central

Hsieh, Chi-Che; Shyr, Yi-Ming; Liao, Wen-Ying; Chen, Tien-Hua; Wang, Shin-E; Lu, Peir-Chuen; Lin, Pei-Yu; Chen, Yan-Bo; Mao, Wan-Yu; Han, Hsin-Ying; Hsiao, Michael; Yang, Wen-Bin; Li, Wen-Shan; Sher, Yuh-Pyng; Shen, Chia-Ning

2017-01-01

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive type of pancreatic cancer with clinical characteristics of local invasion and early metastasis. Recent cohort studies indicate high fructose intake is associated with an increase in pancreatic cancer risk. However, the mechanisms by which fructose promotes pancreatic tumorigenesis remain unclear. Herein, Kras+/LSLG12D mice were crossed with Elas-CreER transgenic mice to determine whether fructose intake directly contributes to tumor formation. Orthotopic tumor-xenograft experiments were performed to determine whether fructose substitution enhances the metastatic potential of PDAC cells. The mechanisms underlying the effects of fructose were explored by RNAseq analysis in combination with high-performance anion exchange chromatography. Dietary fructose was initially found to promote the development of aggressive pancreatic cancer in mice conditionally expressing KrasG12D in the adult pancreas. We further revealed that fructose substitution enhanced the metastatic potential of human PDAC cell via selective outgrowth of aggressive ABCG2-positive subpopulations and elevating N-acetylmannosamine levels that upregulated β-galactoside α2,6-sialyltransferase 1 (ST6Gal1), thereby promoting distant metastasis. Finally, we observed that PDAC patients expressing higher levels of ST6Gal1 and GLUT5 presented poorer prognosis compared to other groups. In conclusion, our findings have elucidated a crucial role of ST6Gal1 in regulating the invasiveness of PDACs in a fructose-responsive manner. PMID:28032597

DNMT1 Maintains Progenitor Function in Self-Renewing Somatic Tissue

PubMed Central

Sen, George L.; Reuter, Jason A.; Webster, Daniel E.; Zhu, Lilly; Khavari, Paul A.

2010-01-01

Progenitor cells maintain self-renewing tissues throughout life by sustaining their capacity for proliferation while suppressing cell cycle exit and terminal differentiation1,2. DNA methylation3,4,5 provides a potential epigenetic mechanism for the cellular memory needed to preserve the somatic progenitor state through repeated cell divisions. DNA methyltransferase 1 (DNMT1)6,7 maintains DNA methylation patterns after cellular replication. Although dispensable for embryonic stem cell maintenance,8 a clear role for DNMT1 in maintaining the progenitor state in constantly replenished somatic tissues, such as mammalian epidermis, is unknown. Here we show that DNMT1 is essential for epidermal progenitor cell function. DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation. In tissue, DNMT1 depletion led to exit from the progenitor cell compartment, premature differentiation and eventual tissue loss. Genome-wide analysis revealed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation. Furthermore, we show that UHRF1,9,10 a component of the DNA methylation machinery that targets DNMT1 to hemi-methylated DNA, is also necessary to suppress premature differentiation and sustain proliferation. In contrast, Gadd45A11,12 and B13, which promote active DNA demethylation, are required for full epidermal differentiation gene induction. These data demonstrate that proteins involved in the dynamic regulation of DNA methylation patterns are required for progenitor maintenance and self-renewal in mammalian somatic tissue. PMID:20081831

Epigenetic hierarchy governing Nestin expression.

PubMed

Han, Dong Wook; Do, Jeong Tae; Araúzo-Bravo, Marcos J; Lee, Sung Ho; Meissner, Alexander; Lee, Hoon Taek; Jaenisch, Rudolf; Schöler, Hans R

2009-05-01

Nestin is an intermediate filament protein expressed specifically in neural stem cells and progenitor cells of the central nervous system. DNA demethylation and histone modifications are two types of epigenetic modifications working in a coordinate or synergistic manner to regulate the expression of various genes. This study investigated and elucidated the epigenetic regulation of Nestin gene expression during embryonic differentiation along the neural cell lineage. Nestin exhibits differential DNA methylation and histone acetylation patterns in Nestin-expressing and nonexpressing cells. In P19 embryonic carcinoma cells, activation of Nestin expression is mediated by both trichostatin A and 5-aza-2'-deoxycytidine treatment, concomitant with histone acetylation, but not with DNA demethylation. Nestin transcription is also mediated by treatment with retinoic acid, again in the absence of DNA demethylation. Thus, histone acetylation is sufficient to mediate the activation of Nestin transcription. This study proposed that the regulation of Nestin gene expression can be used as a model to study the epigenetic regulation of gene expression mediated by histone acetylation, but not by DNA demethylation.

Diurnal variability and biogeochemical reactivity of mercury species in an extreme high-altitude lake ecosystem of the Bolivian Altiplano.

PubMed

Alanoca, L; Amouroux, D; Monperrus, M; Tessier, E; Goni, M; Guyoneaud, R; Acha, D; Gassie, C; Audry, S; Garcia, M E; Quintanilla, J; Point, D

2016-04-01

Methylation and demethylation represent major transformation pathways regulating the net production of methylmercury (MMHg). Very few studies have documented Hg reactivity and transformation in extreme high-altitude lake ecosystems. Mercury (Hg) species concentrations (IHg, MMHg, Hg°, and DMHg) and in situ Hg methylation (M) and MMHg demethylation (D) potentials were determined in water, sediment, floating organic aggregates, and periphyton compartments of a shallow productive Lake of the Bolivian Altiplano (Uru Uru Lake, 3686 m). Samples were collected during late dry season (October 2010) and late wet season (May 2011) at a north (NS) and a south (SS) site of the lake, respectively. Mercury species concentrations exhibited significant diurnal variability as influenced by the strong diurnal biogeochemical gradients. Particularly high methylated mercury concentrations (0.2 to 4.5 ng L(-1) for MMHgT) were determined in the water column evidencing important Hg methylation in this ecosystem. Methylation and D potentials range were, respectively, <0.1-16.5 and <0.2-68.3 % day(-1) and were highly variable among compartments of the lake, but always higher during the dry season. Net Hg M indicates that the influence of urban and mining effluent (NS) promotes MMHg production in both water (up to 0.45 ng MMHg L(-1) day(-1)) and sediment compartments (2.0 to 19.7 ng MMHg g(-1) day(-1)). While the sediment compartment appears to represent a major source of MMHg in this shallow ecosystem, floating organic aggregates (dry season, SS) and Totora's periphyton (wet season, NS) were found to act as a significant source (5.8 ng MMHg g(-1) day(-1)) and a sink (-2.1 ng MMHg g(-1) day(-1)) of MMHg, respectively. This work demonstrates that high-altitude productive lake ecosystems can promote MMHg formation in various compartments supporting recent observations of high Hg contents in fish and water birds.

Enantiomeric metabolic interactions and stereoselective human methadone metabolism.

PubMed

Totah, Rheem A; Allen, Kyle E; Sheffels, Pamela; Whittington, Dale; Kharasch, Evan D

2007-04-01

Methadone is administered as a racemate, although opioid activity resides in the R-enantiomer. Methadone disposition is stereoselective, with considerable unexplained variability in clearance and plasma R/S ratios. N-Demethylation of methadone in vitro is predominantly mediated by cytochrome P450 CYP3A4 and CYP2B6 and somewhat by CYP2C19. This investigation evaluated stereoselectivity, models, and kinetic parameters for methadone N-demethylation by recombinant CYP2B6, CYP3A4, and CYP2C19, and the potential for interactions between enantiomers during racemate metabolism. CYP2B6 metabolism was stereoselective. CYP2C19 was less active, and stereoselectivity was opposite that for CYP2B6. CYP3A4 was not stereoselective. With all three isoforms, enantiomer N-dealkylation rates in the racemate were lower than those of (R)-(6-dimethyamino-4,4-diphenyl-heptan-3-one) hydrochloride (R-methadone) or (S)-(6-dimethyamino-4,4-diphenyl-heptan-3-one) hydrochloride (S-methadone) alone, suggesting an enantiomeric interaction and mutual metabolic inhibition. For CYP2B6, the interaction between enantiomers was stereoselective, with S-methadone as a more potent inhibitor of R-methadone N-demethylation than R-of S-methadone. In contrast, enantiomer interactions were not stereoselective with CYP2C19 or CYP3A4. For all three cytochromes P450, methadone N-demethylation was best described by two-site enzyme models with competitive inhibition. There were minor model differences between cytochromes P450 to account for stereoselectivity of metabolism and enantiomeric interactions. Changes in plasma R/S methadone ratios observed after rifampin or troleandomycin pretreatment in humans in vivo were successfully predicted by CYP2B6- but not CYP3A4-catalyzed methadone N-demethylation. CYP2B6 is a predominant catalyst of stereoselective methadone metabolism in vitro. In vivo, CYP2B6 may be a major determinant of methadone metabolism and disposition, and CYP2B6 activity and stereoselective metabolic interactions may confer variability in methadone disposition.

Targeted DNA demethylation in human cells by fusion of a plant 5-methylcytosine DNA glycosylase to a sequence-specific DNA binding domain

PubMed Central

Parrilla-Doblas, Jara Teresa; Ariza, Rafael R.; Roldán-Arjona, Teresa

2017-01-01

ABSTRACT DNA methylation is a crucial epigenetic mark associated to gene silencing, and its targeted removal is a major goal of epigenetic editing. In animal cells, DNA demethylation involves iterative 5mC oxidation by TET enzymes followed by replication-dependent dilution and/or replication-independent DNA repair of its oxidized derivatives. In contrast, plants use specific DNA glycosylases that directly excise 5mC and initiate its substitution for unmethylated C in a base excision repair process. In this work, we have fused the catalytic domain of Arabidopsis ROS1 5mC DNA glycosylase (ROS1_CD) to the DNA binding domain of yeast GAL4 (GBD). We show that the resultant GBD-ROS1_CD fusion protein binds specifically a GBD-targeted DNA sequence in vitro. We also found that transient in vivo expression of GBD-ROS1_CD in human cells specifically reactivates transcription of a methylation-silenced reporter gene, and that such reactivation requires both ROS1_CD catalytic activity and GBD binding capacity. Finally, we show that reactivation induced by GBD-ROS1_CD is accompanied by decreased methylation levels at several CpG sites of the targeted promoter. All together, these results show that plant 5mC DNA glycosylases can be used for targeted active DNA demethylation in human cells. PMID:28277978

Alteration of runt-related transcription factor 3 gene expression and biologic behavior of esophageal carcinoma TE-1 cells after 5-azacytidine intervention.

PubMed

Wang, Shuai; Liu, Hong; Akhtar, Javed; Chen, Hua-Xia; Wang, Zhou

2013-01-01

5-Azacytidine (5-azaC) was originally identified as an anticancer drug (NSC102876) which can cause hypomethylation of tumor suppressor genes. To assess its effects on runt-related transcription factor 3 (RUNX3), expression levels and the promoter methylation status of the RUNX3 gene were assessed. We also investigated alteration of biologic behavior of esophageal carcinoma TE-1 cells. MTT assays showed 5-azaC inhibited the proliferation of TE-1 cells in a time and dose-dependent way. Although other genes could be demethylated after 5-azaC intervention, we focused on RUNX3 gene in this study. The expression level of RUNX3 mRNA increased significantly in TE-1 cells after treatment with 5-azaC at hypotoxic levels. RT-PCR showed 5-azaC at 50 μM had the highest RUNX3-induction activity. Methylation-specific PCR indicated that 5-azaC induced RUNX3 expression through demethylation. Migration and invasion of TE-1 cells were inhibited by 5-azaC, along with growth of Eca109 xenografts in nude mice. In conclusion, we demonstrate that the RUNX3 gene can be reactivated by the demethylation reagent 5-azaC, which inhibits the proliferation, migration and invasion of esophageal carcinoma TE-1 cells.

ABCG1-mediated generation of extracellular cholesterol microdomains[S

PubMed Central

Freeman, Sebastian R.; Jin, Xueting; Anzinger, Joshua J.; Xu, Qing; Purushothaman, Sonya; Fessler, Michael B.; Addadi, Lia; Kruth, Howard S.

2014-01-01

Previous studies have demonstrated that the ATP-binding cassette transporters (ABC)A1 and ABCG1 function in many aspects of cholesterol efflux from macrophages. In this current study, we continued our investigation of extracellular cholesterol microdomains that form during enrichment of macrophages with cholesterol. Human monocyte-derived macrophages and mouse bone marrow-derived macrophages, differentiated with macrophage colony-stimulating factor (M-CSF) or granulocyte macrophage colony-stimulation factor (GM-CSF), were incubated with acetylated LDL (AcLDL) to allow for cholesterol enrichment and processing. We utilized an anti-cholesterol microdomain monoclonal antibody to reveal pools of unesterified cholesterol, which were found both in the extracellular matrix and associated with the cell surface, that we show function in reverse cholesterol transport. Coincubation of AcLDL with 50 μg/ml apoA-I eliminated all extracellular and cell surface-associated cholesterol microdomains, while coincubation with the same concentration of HDL only removed extracellular matrix-associated cholesterol microdomains. Only at an HDL concentration of 200 µg/ml did HDL eliminate the cholesterol microdomains that were cell-surface associated. The deposition of cholesterol microdomains was inhibited by probucol, but it was increased by the liver X receptor (LXR) agonist TO901317, which upregulates ABCA1 and ABCG1. Extracellular cholesterol microdomains did not develop when ABCG1-deficient mouse bone marrow-derived macrophages were enriched with cholesterol. Our findings show that generation of extracellular cholesterol microdomains is mediated by ABCG1 and that reverse cholesterol transport occurs not only at the cell surface but also within the extracellular space. PMID:24212237

Epigenetic Upregulation of HGF and c-Met Drives Metastasis in Hepatocellular Carcinoma

PubMed Central

Ogunwobi, Olorunseun O.; Puszyk, William; Dong, Hui-Jia; Liu, Chen

2013-01-01

Hepatocyte growth factor (HGF) and its receptor, c-Met, are important regulators of growth and differentiation of healthy hepatocytes. However, upregulation of HGF and c-Met have been associated with tumor progression and metastasis in hepatocellular carcinoma (HCC). Hematogenous dissemination is the most common route for cancer metastasis, but the role of HGF and c-Met in circulating tumor cells (CTCs) is unknown. We have isolated and established a circulating tumor cell line from the peripheral blood of a mouse HCC model. Our studies show that these CTCs have increased expression of HGF and c-Met in comparison to the primary tumor cells. The CTCs display phenotypic evidence of epithelial-mesenchymal transition (EMT) and the EMT appears to be inducible by HGF. Epigenetic analysis of the c-Met promoter identified significant loss of DNA methylation in CTCs which correlated with overexpression of c-Met and increased expression of HGF. Six specific CpG sites of c-Met promoter demethylation were identified. CTCs show significantly increased tumorigenicity and metastatic potential in a novel orthotopic syngeneic model of metastatic HCC. We conclude that during hematogenous dissemination in HCC, CTCs undergo EMT under the influence of increased HGF. This process also involves up regulation of c-Met via promoter demethylation at 6 CpG sites. Consequently, targeting HGF and c-Met expression by CTCs may be a novel non-invasive approach with potential clinical applications in HCC management. PMID:23723997

Epigenetic silencing of the NR4A3 tumor suppressor, by aberrant JAK/STAT signaling, predicts prognosis in gastric cancer

NASA Astrophysics Data System (ADS)

Yeh, Chung-Min; Chang, Liang-Yu; Lin, Shu-Hui; Chou, Jian-Liang; Hsieh, Hsiao-Yen; Zeng, Li-Han; Chuang, Sheng-Yu; Wang, Hsiao-Wen; Dittner, Claudia; Lin, Cheng-Yu; Lin, Jora M. J.; Huang, Yao-Ting; Ng, Enders K. W.; Cheng, Alfred S. L.; Wu, Shu-Fen; Lin, Jiayuh; Yeh, Kun-Tu; Chan, Michael W. Y.

2016-08-01

While aberrant JAK/STAT signaling is crucial to the development of gastric cancer (GC), its effects on epigenetic alterations of its transcriptional targets remains unclear. In this study, by expression microarrays coupled with bioinformatic analyses, we identified a putative STAT3 target gene, NR4A3 that was downregulated in MKN28 GC daughter cells overexpressing a constitutively activated STAT3 mutant (S16), as compared to an empty vector control (C9). Bisulphite pyrosequencing and demethylation treatment showed that NR4A3 was epigenetically silenced by promoter DNA methylation in S16 and other GC cell lines including AGS cells, showing constitutive activation of STAT3. Subsequent experiments revealed that NR4A3 promoter binding by STAT3 might repress its transcription. Long-term depletion of STAT3 derepressed NR4A3 expression, by promoter demethylation, in AGS GC cells. NR4A3 re-expression in GC cell lines sensitized the cells to cisplatin, and inhibited tumor growth in vitro and in vivo, in an animal model. Clinically, GC patients with high NR4A3 methylation, or lower NR4A3 protein expression, had significantly shorter overall survival. Intriguingly, STAT3 activation significantly associated only with NR4A3 methylation in low-stage patient samples. Taken together, aberrant JAK/STAT3 signaling epigenetically silences a potential tumor suppressor, NR4A3, in gastric cancer, plausibly representing a reliable biomarker for gastric cancer prognosis.

Regulation of Active DNA Demethylation by a Methyl-CpG-Binding Domain Protein in Arabidopsis thaliana

PubMed Central

Sun, Han; Zeng, Jun; Cao, Zhendong; Li, Yan; Qian, Weiqiang

2015-01-01

Active DNA demethylation plays crucial roles in the regulation of gene expression in both plants and animals. In Arabidopsis thaliana, active DNA demethylation is initiated by the ROS1 subfamily of 5-methylcytosine-specific DNA glycosylases via a base excision repair mechanism. Recently, IDM1 and IDM2 were shown to be required for the recruitment of ROS1 to some of its target loci. However, the mechanism(s) by which IDM1 is targeted to specific genomic loci remains to be determined. Affinity purification of IDM1- and IDM2- associating proteins demonstrated that IDM1 and IDM2 copurify together with two novel components, methyl-CpG-binding domain protein 7 (MBD7) and IDM2-like protein 1 (IDL1). IDL1 encodes an α-crystallin domain protein that shows high sequence similarity with IDM2. MBD7 interacts with IDM2 and IDL1 in vitro and in vivo and they form a protein complex associating with IDM1 in vivo. MBD7 directly binds to the target loci and is required for the H3K18 and H3K23 acetylation in planta. MBD7 dysfunction causes DNA hypermethylation and silencing of reporter genes and a subset of endogenous genes. Our results suggest that a histone acetyltransferase complex functions in active DNA demethylation and in suppression of gene silencing at some loci in Arabidopsis. PMID:25933434

The Influence of Hydroxylation on Maintaining CpG Methylation Patterns: A Hidden Markov Model Approach.

PubMed

Giehr, Pascal; Kyriakopoulos, Charalampos; Ficz, Gabriella; Wolf, Verena; Walter, Jörn

2016-05-01

DNA methylation and demethylation are opposing processes that when in balance create stable patterns of epigenetic memory. The control of DNA methylation pattern formation by replication dependent and independent demethylation processes has been suggested to be influenced by Tet mediated oxidation of 5mC. Several alternative mechanisms have been proposed suggesting that 5hmC influences either replication dependent maintenance of DNA methylation or replication independent processes of active demethylation. Using high resolution hairpin oxidative bisulfite sequencing data, we precisely determine the amount of 5mC and 5hmC and model the contribution of 5hmC to processes of demethylation in mouse ESCs. We develop an extended hidden Markov model capable of accurately describing the regional contribution of 5hmC to demethylation dynamics. Our analysis shows that 5hmC has a strong impact on replication dependent demethylation, mainly by impairing methylation maintenance.

Impact of CYP2C8*3 polymorphism on in vitro metabolism of imatinib to N-desmethyl imatinib.

PubMed

Khan, Muhammad Suleman; Barratt, Daniel T; Somogyi, Andrew A

2016-01-01

1. Imatinib is metabolized to N-desmethyl imatinib by CYPs 3A4 and 2C8. The effect of CYP2C8*3 genotype on N-desmethyl imatinib formation was unknown. 2. We examined imatinib N-demethylation in human liver microsomes (HLMs) genotyped for CYP2C8*3, in CYP2C8*3/*3 pooled HLMs and in recombinant CYP2C8 and CYP3A4 enzymes. Effects of CYP-selective inhibitors on N-demethylation were also determined. 3. A single-enzyme Michaelis-Menten model with autoinhibition best fitted CYP2C8*1/*1 HLM (n = 5) and recombinant CYP2C8 kinetic data (median ± SD Ki = 139 ± 61 µM and 149 µM, respectively). Recombinant CYP3A4 showed two-site enzyme kinetics with no autoinhibition. Three of four CYP2C8*1/*3 HLMs showed single-enzyme kinetics with no autoinhibition. Binding affinity was higher in CYP2C8*1/*3 than CYP2C8*1/*1 HLM (median ± SD Km = 6 ± 2 versus 11 ± 2 µM, P=0.04). CYP2C8*3/*3 (pooled HLM) also showed high binding affinity (Km = 4 µM) and single-enzyme weak autoinhibition (Ki = 449 µM) kinetics. CYP2C8 inhibitors reduced HLM N-demethylation by 47-75%, compared to 0-30% for CYP3A4 inhibitors. 4. In conclusion, CYP2C8*3 is a gain-of-function polymorphism for imatinib N-demethylation, which appears to be mainly mediated by CYP2C8 and not CYP3A4 in vitro in HLM.

Genetic effects of FASN, PPARGC1A, ABCG2 and IGF1 revealing the association with milk fatty acids in a Chinese Holstein cattle population based on a post genome-wide association study.

PubMed

Li, Cong; Sun, Dongxiao; Zhang, Shengli; Yang, Shaohua; Alim, M A; Zhang, Qin; Li, Yanhua; Liu, Lin

2016-07-28

A previous genome-wide association study deduced that one (ARS-BFGL-NGS-39328), two (Hapmap26001-BTC-038813 and Hapmap31284-BTC-039204), two (Hapmap26001-BTC-038813 and BTB-00246150), and one (Hapmap50366-BTA-46960) genome-wide significant single nucleotide polymorphisms (SNPs) associated with milk fatty acids were close to or within the fatty acid synthase (FASN), peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PPARGC1A), ATP-binding cassette, sub-family G, member 2 (ABCG2) and insulin-like growth factor 1 (IGF1) genes. To further confirm the linkage and reveal the genetic effects of these four candidate genes on milk fatty acid composition, genetic polymorphisms were identified and genotype-phenotype associations were performed in a Chinese Holstein cattle population. Nine SNPs were identified in FASN, among which SNP rs41919985 was predicted to result in an amino acid substitution from threonine (ACC) to alanine (GCC), five SNPs (rs136947640, rs134340637, rs41919992, rs41919984 and rs41919986) were synonymous mutations, and the remaining three (rs41919999, rs132865003 and rs133498277) were found in FASN introns. Only one SNP each was identified for PPARGC1A, ABCG2 and IGF1. Association studies revealed that FASN, PPARGC1A, ABCG2 and IGF1 were mainly associated with medium-chain saturated fatty acids and long-chain unsaturated fatty acids, especially FASN for C10:0, C12:0 and C14:0. Strong linkage disequilibrium was observed among ARS-BFGL-NGS-39328 and rs132865003 and rs134340637 in FASN (D´ > 0.9), and among Hapmap26001-BTC-038813 and Hapmap31284-BTC-039204 and rs109579682 in PPARGC1A (D´ > 0.9). Subsequently, haplotype-based analysis revealed significant associations of the haplotypes encompassing eight FASN SNPs (rs41919999, rs132865003, rs134340637, rs41919992, rs133498277, rs41919984, rs41919985 and rs41919986) with C10:0, C12:0, C14:0, C18:1n9c, saturated fatty acids (SFA) and unsaturated fatty acids (UFA) (P = 0.0204 to P < 0.0001). Our study confirmed the linkage between the significant SNPs in our previous genome-wide association study and variants in FASN and PPARGC1A. SNPs within FASN, PPARGC1A, ABCG2 and IGF1 showed significant genetic effects on milk fatty acid composition in dairy cattle, indicating their potential functions in milk fatty acids synthesis and metabolism. The findings presented here provide evidence for the selection of dairy cows with healthier milk fatty acid composition by marker-assisted breeding or genomic selection schemes, as well as furthering our understanding of technological processing aspects of cows' milk.

Loss of the retinoblastoma binding protein 2 (RBP2) histone demethylase suppresses tumorigenesis in mice lacking Rb1 or Men1

PubMed Central

Lin, Wenchu; Cao, Jian; Liu, Jiayun; Beshiri, Michael L.; Fujiwara, Yuko; Francis, Joshua; Cherniack, Andrew D.; Geisen, Christoph; Blair, Lauren P.; Zou, Mike R.; Shen, Xiaohua; Kawamori, Dan; Liu, Zongzhi; Grisanzio, Chiara; Watanabe, Hideo; Minamishima, Yoji Andrew; Zhang, Qing; Kulkarni, Rohit N.; Signoretti, Sabina; Rodig, Scott J.; Bronson, Roderick T.; Orkin, Stuart H.; Tuck, David P.; Benevolenskaya, Elizaveta V.; Meyerson, Matthew; Kaelin, William G.; Yan, Qin

2011-01-01

Aberrations in epigenetic processes, such as histone methylation, can cause cancer. Retinoblastoma binding protein 2 (RBP2; also called JARID1A or KDM5A) can demethylate tri- and dimethylated lysine 4 in histone H3, which are epigenetic marks for transcriptionally active chromatin, whereas the multiple endocrine neoplasia type 1 (MEN1) tumor suppressor promotes H3K4 methylation. Previous studies suggested that inhibition of RBP2 contributed to tumor suppression by the retinoblastoma protein (pRB). Here, we show that genetic ablation of Rbp2 decreases tumor formation and prolongs survival in Rb1+/− mice and Men1-defective mice. These studies link RBP2 histone demethylase activity to tumorigenesis and nominate RBP2 as a potential target for cancer therapy. PMID:21788502

Genetics of gout.

PubMed

Choi, Hyon K; Zhu, Yanyan; Mount, David B

2010-03-01

This review provides an update on recent findings with regards to the genetics of hyperuricemia and gout, including recent data from genome-wide association studies (GWAS). Five GWAS around the same time reported that genetic variants of SLC2A9/GLUT9 were associated with lower serum uric acid (SUA) levels and the effects were stronger among women (e.g. SUA level difference per copy of a minor allele, -0.46 mg/dl in women vs. -0.22 mg/dl in men). One study involving four cohorts and one meta-analysis of 14 genome-wide scans found that genetic variants of ABCG2 were associated with higher SUA concentrations and these effects were stronger among men (e.g. uric acid level difference per copy of the minor allele, 0.32 mg/dl in men vs. 0.18 mg/dl in women). Limited data indicate that these associations likely translate into those with the risk of gout. Functional determination that GLUT9 and ABCG2 can transport urate at the apical border of proximal tubules implicates them as substantial players in the renal excretion of urate. Furthermore, five novel genetic loci have been reported in the meta-analysis of 14 genome-wide scans. Combined with their activities as urate transporters and their strong associations with serum uric acid concentrations, GLUT9 and ABCG2 appeared to be important modulators of uric acid levels and likely of the risk of gout. Together with a growing list of environmental risk factors, these genetic data add considerably to our understanding of the pathogenesis of hyperuricemia and gout.

Identification of human cytochrome P450 2D6 as major enzyme involved in the O-demethylation of the designer drug p-methoxymethamphetamine.

PubMed

Staack, Roland F; Theobald, Denis S; Paul, Liane D; Springer, Dietmar; Kraemer, Thomas; Maurer, Hans H

2004-04-01

p-Methoxymethamphetamine (PMMA) is a new designer drug, listed in many countries as a controlled substance. Several fatalities have been attributed to the abuse of this designer drug. Previous in vivo studies using Wistar rats had shown that PMMA was metabolized mainly by O-demethylation. The aim of the study presented here was to identify the human hepatic cytochrome P450 (P450) enzymes involved in the biotransformation of PMMA to p-hydroxymethamphetamine. Baculovirus-infected insect cell microsomes, pooled human liver microsomes (pHLMs), and CYP2D6 poor-metabolizer genotype human liver microsomes (PM HLMs) were used for this purpose. Only CYP2D6 catalyzed O-demethylation. The apparent K(m) and V(max) values in baculovirus-infected insect cell microsomes were 4.6 +/- 1.0 microM and 92.0 +/- 3.7 pmol/min/pmol P450, respectively, and 42.0 +/- 4.0 microM and 412.5 +/- 10.8 pmol/min/mg protein in pHLMs. Inhibition studies with 1 microM quinidine showed significant inhibition of the metabolite formation (67.2 +/- 0.6%; p < 0.0001), and comparison of the metabolite formation between pHLMs and PM HLMs revealed significantly lower metabolite formation in the incubations with PM HLMs (87.3 +/- 1.1%; p < 0.0001). According to these studies, CYP2D6 is the major P450 involved in O-demethylation of PMMA.

EG-13GENOME-WIDE METHYLATION ANALYSIS IDENTIFIES GENOMIC DNA DEMETHYLATION DURING MALIGNANT PROGRESSION OF GLIOMAS

PubMed Central

Saito, Kuniaki; Mukasa, Akitake; Nagae, Genta; Aihara, Koki; Otani, Ryohei; Takayanagi, Shunsaku; Omata, Mayu; Tanaka, Shota; Shibahara, Junji; Takahashi, Miwako; Momose, Toshimitsu; Shimamura, Teppei; Miyano, Satoru; Narita, Yoshitaka; Ueki, Keisuke; Nishikawa, Ryo; Nagane, Motoo; Aburatani, Hiroyuki; Saito, Nobuhito

2014-01-01

Low-grade gliomas often undergo malignant progression, and these transformations are a leading cause of death in patients with low-grade gliomas. However, the molecular mechanisms underlying malignant tumor progression are still not well understood. Recent evidence indicates that epigenetic deregulation is an important cause of gliomagenesis; therefore, we examined the impact of epigenetic changes during malignant progression of low-grade gliomas. Specifically, we used the Illumina Infinium Human Methylation 450K BeadChip to perform genome-wide DNA methylation analysis of 120 gliomas and four normal brains. This study sample included 25 matched-pairs of initial low-grade gliomas and recurrent tumors (temporal heterogeneity) and 20 of the 25 recurring tumors recurred as malignant progressions, and one matched-pair of newly emerging malignant lesions and pre-existing lesions (spatial heterogeneity). Analyses of methylation profiles demonstrated that most low-grade gliomas in our sample (43/51; 84%) had a CpG island methylator phenotype (G-CIMP). Remarkably, approximately 50% of secondary glioblastomas that had progressed from low-grade tumors with the G-CIMP status exhibited a characteristic partial demethylation of genomic DNA during malignant progression, but other recurrent gliomas showed no apparent change in DNA methylation pattern. Interestingly, we found that most loci that were demethylated during malignant progression were located outside of CpG islands. The information of histone modifications patterns in normal human astrocytes and embryonal stem cells also showed that the ratio of active marks at the site corresponding to DNA demethylated loci in G-CIMP-demethylated tumors was significantly lower; this finding indicated that most demethylated loci in G-CIMP-demethylated tumors were likely transcriptionally inactive. A small number of the genes that were upregulated and had demethylated CpG islands were associated with cell cycle-related pathway. In summary, we demonstrated that characteristic DNA demethylation occurred during malignant progression of a subset of low-grade gliomas. The mechanisms underlying and consequences of such DNA demethylation should be studied further.

Association of Functional Polymorphism rs2231142 (Q141K) in the ABCG2 Gene With Serum Uric Acid and Gout in 4 US Populations

PubMed Central

Zhang, Lili; Spencer, Kylee L.; Voruganti, V. Saroja; Jorgensen, Neal W.; Fornage, Myriam; Best, Lyle G.; Brown-Gentry, Kristin D.; Cole, Shelley A.; Crawford, Dana C.; Deelman, Ewa; Franceschini, Nora; Gaffo, Angelo L.; Glenn, Kimberly R.; Heiss, Gerardo; Jenny, Nancy S.; Kottgen, Anna; Li, Qiong; Liu, Kiang; Matise, Tara C.; North, Kari E.; Umans, Jason G.; Kao, W. H. Linda

2013-01-01

A loss-of-function mutation (Q141K, rs2231142) in the ATP-binding cassette, subfamily G, member 2 gene (ABCG2) has been shown to be associated with serum uric acid levels and gout in Asians, Europeans, and European and African Americans; however, less is known about these associations in other populations. Rs2231142 was genotyped in 22,734 European Americans, 9,720 African Americans, 3,849 Mexican Americans, and 3,550 American Indians in the Population Architecture using Genomics and Epidemiology (PAGE) Study (2008–2012). Rs2231142 was significantly associated with serum uric acid levels (P = 2.37 × 10−67, P = 3.98 × 10−5, P = 6.97 × 10−9, and P = 5.33 × 10−4 in European Americans, African Americans, Mexican Americans, and American Indians, respectively) and gout (P = 2.83 × 10−10, P = 0.01, and P = 0.01 in European Americans, African Americans, and Mexican Americans, respectively). Overall, the T allele was associated with a 0.24-mg/dL increase in serum uric acid level (P = 1.37 × 10−80) and a 1.75-fold increase in the odds of gout (P = 1.09 × 10−12). The association between rs2231142 and serum uric acid was significantly stronger in men, postmenopausal women, and hormone therapy users compared with their counterparts. The association with gout was also significantly stronger in men than in women. These results highlight a possible role of sex hormones in the regulation of ABCG2 urate transporter and its potential implications for the prevention, diagnosis, and treatment of hyperuricemia and gout. PMID:23552988

Aberrant methylation of MUC1 and MUC4 promoters are potential prognostic biomarkers for pancreatic ductal adenocarcinomas.

PubMed

Yokoyama, Seiya; Higashi, Michiyo; Kitamoto, Sho; Oeldorf, Monika; Knippschild, Uwe; Kornmann, Marko; Maemura, Kosei; Kurahara, Hiroshi; Wiest, Edwin; Hamada, Tomofumi; Kitazono, Ikumi; Goto, Yuko; Tasaki, Takashi; Hiraki, Tsubasa; Hatanaka, Kazuhito; Mataki, Yuko; Taguchi, Hiroki; Hashimoto, Shinichi; Batra, Surinder K; Tanimoto, Akihide; Yonezawa, Suguru; Hollingsworth, Michael A

2016-07-05

Pancreatic cancer is still a disease of high mortality despite availability of diagnostic techniques. Mucins (MUC) play crucial roles in carcinogenesis and tumor invasion in pancreatic neoplasms. MUC1 and MUC4 are high molecular weight transmembrane mucins. These are overexpressed in many carcinomas, and high expression of these molecules is a risk factor associated with poor prognosis. We evaluated the methylation status of MUC1 and MUC4 promoter regions in pancreatic tissue samples from 169 patients with various pancreatic lesions by the methylation specific electrophoresis (MSE) method. These results were compared with expression of MUC1 and MUC4, several DNA methylation/demethylation factors (e.g. ten-eleven translocation or TET, and activation-induced cytidine deaminase or AID) and CAIX (carbonic anhydrase IX, as a hypoxia biomarker). These results were also analyzed with clinicopathological features including time of overall survival of PDAC patients. We show that the DNA methylation status of the promoters of MUC1 and MUC4 in pancreatic tissue correlates with the expression of MUC1 and MUC4 mRNA. In addition, the expression of several DNA methylation/demethylation factors show a significant correlation with MUC1 and MUC4 methylation status. Furthermore, CAIX expression significantly correlates with the expression of MUC1 and MUC4. Interestingly, our results indicate that low methylation of MUC1 and/or MUC4 promoters correlates with decreased overall survival. This is the first report to show a relationship between MUC1 and/or MUC4 methylation status and prognosis. Analysis of epigenetic changes in mucin genes may be of diagnostic utility and one of the prognostic predictors for patients with PDAC.

Aberrant methylation of MUC1 and MUC4 promoters are potential prognostic biomarkers for pancreatic ductal adenocarcinomas

PubMed Central

Yokoyama, Seiya; Higashi, Michiyo; Kitamoto, Sho; Oeldorf, Monika; Knippschild, Uwe; Kornmann, Marko; Maemura, Kosei; Kurahara, Hiroshi; Wiest, Edwin; Hamada, Tomofumi; Kitazono, Ikumi; Goto, Yuko; Tasaki, Takashi; Hiraki, Tsubasa; Hatanaka, Kazuhito; Mataki, Yuko; Taguchi, Hiroki; Hashimoto, Shinichi; Batra, Surinder K.; Tanimoto, Akihide; Yonezawa, Suguru; Hollingsworth, Michael A.

2016-01-01

Pancreatic cancer is still a disease of high mortality despite availability of diagnostic techniques. Mucins (MUC) play crucial roles in carcinogenesis and tumor invasion in pancreatic neoplasms. MUC1 and MUC4 are high molecular weight transmembrane mucins. These are overexpressed in many carcinomas, and high expression of these molecules is a risk factor associated with poor prognosis. We evaluated the methylation status of MUC1 and MUC4 promoter regions in pancreatic tissue samples from 169 patients with various pancreatic lesions by the methylation specific electrophoresis (MSE) method. These results were compared with expression of MUC1 and MUC4, several DNA methylation/demethylation factors (e.g. ten-eleven translocation or TET, and activation-induced cytidine deaminase or AID) and CAIX (carbonic anhydrase IX, as a hypoxia biomarker). These results were also analyzed with clinicopathological features including time of overall survival of PDAC patients. We show that the DNA methylation status of the promoters of MUC1 and MUC4 in pancreatic tissue correlates with the expression of MUC1 and MUC4 mRNA. In addition, the expression of several DNA methylation/demethylation factors show a significant correlation with MUC1 and MUC4 methylation status. Furthermore, CAIX expression significantly correlates with the expression of MUC1 and MUC4. Interestingly, our results indicate that low methylation of MUC1 and/or MUC4 promoters correlates with decreased overall survival. This is the first report to show a relationship between MUC1 and/or MUC4 methylation status and prognosis. Analysis of epigenetic changes in mucin genes may be of diagnostic utility and one of the prognostic predictors for patients with PDAC. PMID:27283771

Chemoresistance of CD133{sup +} colon cancer may be related with increased survivin expression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Mi-Ra; Ji, Sun-Young; Mia-Jan, Khalilullah

2015-07-31

CD133, putative cancer stem cell marker, deemed to aid chemoresistance. However, this claim has been challenged recently and we previously reported that patients with CD133{sup +} colon cancer have benefit from 5-fluorouracil (5-FU) chemotherapy incontrast to no benefit in patients with CD133{sup −} cancer. To elucidate the role of CD133 expression in chemoresistance, we silenced the CD133 expression in a colon cancer cell line and determined its effect on the biological characteristics downstream. We comparatively analyzed the sequential changes of MDR1, ABCG2, AKT1 and survivin expression and the result of proliferation assay (WST-1 assay) with 5-FU treatment in CD133{sup +}more » and siRNA-induced CD133{sup −} cells, derived from Caco-2 colon cancer cell line. 5-FU treatment induced significantly increase of the mRNA expression of MDR1, ABCG2 and AKT1genes, but not protein level. CD133 had little to no effect on the mRNA and protein expression of these genes. However, survivin expression at mRNA and protein level were significantly increased in CD133{sup +} cells compared with siRNA-induced CD133-cells and Mock (not sorted CD133{sup +} cells) at 96 h after siRNA transfection. The cytotoxicity assay demonstrated notable increase of chemoresistance to 5-FU treatment (10 μM) in CD133{sup +} cells at 96 h after siRNA transfection. From this study, we conclude that CD133{sup +} cells may have chemoresistance to 5-FU through the mechanism which is related with survivin expression, instead of MDR1, ABCG2 and AKT1 expression. Therefore a survivin inhibitor can be a new target for effective treatment of CD133{sup +} colon cancer. - Highlights: • We evaluate the role of CD133 in chemoresistance of colon cancer. • We compared the chemoresistance of CD133{sup +} cells and siRNA-induced CD133{sup −} cells. • CD133 had little to no effect on MDR1, ABCG2 and AKT1 expression. • Survivin expression and chemoresistance were increased in CD133{sup +} colon cancer cells.« less

[Analysis of expression of cancer stem cell-related markers in orbital adenoid cystic carcinoma].

PubMed

Lin, Ting-ting; Zhu, Li-min; He, Yan-jin; Zhang, Hong

2011-08-01

To observe the expression and distribution of CD44, CD133, and ABCG2 in orbital adenoid cystic carcinoma (ACC) and investigate their correlations with pathological type and prognosis. Two steps method of immunohistochemical staining was employed in 33 cases of paraffin embedded surgical specimens of human orbital ACC, 5 cases of recurrence samples, 3 cases of an excised lacrimal gland caused by neither inflammation nor tumor diseases, and 6 cases of xenograft tumors in nude mice. A retrospective analysis was performed on the clinical material of these patients, which were collected from Jan. 1991 to Mar. 2009. The positive rate of CD44 was 54.5% (18/33), with 76.9% (10/13) in solid type and 40.0% (8/20) in adeno-tubiform type. There was no statistically significant difference between them (P = 0.072). In solid type the positive expression cells were often located at the marginal part of the cancer nest. In the adeno-tubiform type, positive cells were often located at the outer layer of the tubiform structure (myoepithelial cells). CD44 was also expressed in normal tissues. The positive rate of CD133 was 57.6% (19/33), with 76.9% (10/13) in solid type and 45.0% (9/20) in adeno-tubiform type. There was no significant difference between them (P = 0.087). CD133 antigen was expressed in either the cytoplasm or nucleus, or expressed in both the cytoplasm and nucleus. The positive rate of ABCG2 was 21.2% (7/33), with 30.77% (4/13) in solid type and 15.0% (3/20) in adeno-tubiform type. There was no significant difference between them (P = 0.393). Many positive cells surrounded the vessels in tumor tissues. There were no significant differences between different prognosis groups of these surface phenotypes. The correlative analysis results of three surface phenotypes showed that CD44(+) cells have positive correlation with CD133(+) cells (Spearman, r(s) = 0.416, P = 0.016). In six transplanted tumors of nude mice, the number of positive cases for CD44(+), CD133(+) and ABCG2(+) was 1, 1 and 4 cases, respectively. The expression of CD44, CD133 and ABCG2 in ACC may influence the progress of ACC. However, they cannot be used as the markers for the evaluation of the prognosis of this tumor.

Methadone inhibits CYP2D6 and UGT2B7/2B4 in vivo: a study using codeine in methadone- and buprenorphine-maintained subjects

PubMed Central

Gelston, Eloise A; Coller, Janet K; Lopatko, Olga V; James, Heather M; Schmidt, Helmut; White, Jason M; Somogyi, Andrew A

2012-01-01

AIMS To compare the O-demethylation (CYP2D6-mediated), N-demethylation (CYP3A4-mediated) and 6-glucuronidation (UGT2B4/7-mediated) metabolism of codeine between methadone- and buprenorphine-maintained CYP2D6 extensive metabolizer subjects. METHODS Ten methadone- and eight buprenorphine-maintained subjects received a single 60 mg dose of codeine phosphate. Blood was collected at 3 h and urine over 6 h and assayed for codeine, norcodeine, morphine, morphine-3- and -6-glucuronides and codeine-6-glucuronide. RESULTS The urinary metabolic ratio for O-demethylation was significantly higher (P = 0.0044) in the subjects taking methadone (mean ± SD, 2.8 ± 3.1) compared with those taking buprenorphine (0.60 ± 0.43), likewise for 6-glucuronide formation (0.31 ± 0.24 vs. 0.053 ± 0.027; P < 0.0002), but there was no significant difference (P = 0.36) in N-demethylation. Similar changes in plasma metabolic ratios were also found. In plasma, compared with those maintained on buprenorphine, the methadone-maintained subjects had increased codeine and norcodeine concentrations (P < 0.004), similar morphine (P = 0.72) and lower morphine-3- and -6- and codeine-6-glucuronide concentrations (P < 0.008). CONCLUSION Methadone is associated with inhibition of CYP2D6 and UGTs 2B4 and 2B7 reactions in vivo, even though it is not a substrate for these enzymes. Plasma morphine was not altered, owing to the opposing effects of inhibition of both formation and elimination; however, morphine-6-glucuronide (analgesically active) concentrations were substantially reduced. Drug interactions with methadone are likely to include drugs metabolized by various UGTs and CYP2D6. PMID:22092298

Stereoselectivity of the demethylation of nicotine piperidine homologues by Nicotiana plumbaginifolia cell suspension cultures.

PubMed

Bartholomeusz, Trixie Ann; Molinié, Roland; Roscher, Albrecht; Felpin, François-Xavier; Gillet, Françoise; Lebreton, Jacques; Mesnard, François; Robins, Richard J

2005-08-01

The metabolism of (R,S)-N-methylanabasine and (R,S)-N-methylanatabine has been studied in a cell suspension culture of Nicotiana plumbaginifolia. Both substrates are effectively demethylated, anabasine or anatabine, respectively, accumulating in the medium. Similarly, there is strong stereoselectivity for the (R)-isomers of both substrates. The kinetics of metabolism of (R,S)-N-methylanabasine differ significantly from those of nicotine in that no further degradation of the initial demethylation product occurs. (R,S)-N-Methylanatabine, however, shows kinetics closer to those of nicotine, with loss of alkaloid from the system. Further more, (R,S)-N-methylanabasine does not diminish (S)-nicotine demethylation, indicating a lack of competition. However, the metabolism of (S)-nicotine is affected by the presence of (R,S)-N-methylanabasine. Hence, the demethylation of the piperidine homologues of nicotine is seen to be similar but not identical to that of the pyridine analogues. The implications of these different metabolic profiles in relation to the demethylation activity are discussed.

RCN1/OsABCG5, an ATP-binding cassette (ABC) transporter, is required for hypodermal suberization of roots in rice (Oryza sativa).

PubMed

Shiono, Katsuhiro; Ando, Miho; Nishiuchi, Shunsaku; Takahashi, Hirokazu; Watanabe, Kohtaro; Nakamura, Motoaki; Matsuo, Yuichi; Yasuno, Naoko; Yamanouchi, Utako; Fujimoto, Masaru; Takanashi, Hideki; Ranathunge, Kosala; Franke, Rochus B; Shitan, Nobukazu; Nishizawa, Naoko K; Takamure, Itsuro; Yano, Masahiro; Tsutsumi, Nobuhiro; Schreiber, Lukas; Yazaki, Kazufumi; Nakazono, Mikio; Kato, Kiyoaki

2014-10-01

Suberin is a complex polymer composed of aliphatic and phenolic compounds. It is a constituent of apoplastic plant interfaces. In many plant species, including rice (Oryza sativa), the hypodermis in the outer part of roots forms a suberized cell wall (the Casparian strip and/or suberin lamellae), which inhibits the flow of water and ions and protects against pathogens. To date, there is no genetic evidence that suberin forms an apoplastic transport barrier in the hypodermis. We discovered that a rice reduced culm number1 (rcn1) mutant could not develop roots longer than 100 mm in waterlogged soil. The mutated gene encoded an ATP-binding cassette (ABC) transporter named RCN1/OsABCG5. RCN1/OsABCG5 gene expression in the wild type was increased in most hypodermal and some endodermal roots cells under stagnant deoxygenated conditions. A GFP-RCN1/OsABCG5 fusion protein localized at the plasma membrane of the wild type. Under stagnant deoxygenated conditions, well suberized hypodermis developed in wild types but not in rcn1 mutants. Under stagnant deoxygenated conditions, apoplastic tracers (periodic acid and berberine) were blocked at the hypodermis in the wild type but not in rcn1, indicating that the apoplastic barrier in the mutant was impaired. The amount of the major aliphatic suberin monomers originating from C(28) and C(30) fatty acids or ω-OH fatty acids was much lower in rcn1 than in the wild type. These findings suggest that RCN1/OsABCG5 has a role in the suberization of the hypodermis of rice roots, which contributes to formation of the apoplastic barrier. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

De novo DNA methylation during monkey pre-implantation embryogenesis.

PubMed

Gao, Fei; Niu, Yuyu; Sun, Yi Eve; Lu, Hanlin; Chen, Yongchang; Li, Siguang; Kang, Yu; Luo, Yuping; Si, Chenyang; Yu, Juehua; Li, Chang; Sun, Nianqin; Si, Wei; Wang, Hong; Ji, Weizhi; Tan, Tao

2017-04-01

Critical epigenetic regulation of primate embryogenesis entails DNA methylome changes. Here we report genome-wide composition, patterning, and stage-specific dynamics of DNA methylation in pre-implantation rhesus monkey embryos as well as male and female gametes studied using an optimized tagmentation-based whole-genome bisulfite sequencing method. We show that upon fertilization, both paternal and maternal genomes undergo active DNA demethylation, and genome-wide de novo DNA methylation is also initiated in the same period. By the 8-cell stage, remethylation becomes more pronounced than demethylation, resulting in an increase in global DNA methylation. Promoters of genes associated with oxidative phosphorylation are preferentially remethylated at the 8-cell stage, suggesting that this mode of energy metabolism may not be favored. Unlike in rodents, X chromosome inactivation is not observed during monkey pre-implantation development. Our study provides the first comprehensive illustration of the 'wax and wane' phases of DNA methylation dynamics. Most importantly, our DNA methyltransferase loss-of-function analysis indicates that DNA methylation influences early monkey embryogenesis.

De novo DNA methylation during monkey pre-implantation embryogenesis

PubMed Central

Gao, Fei; Niu, Yuyu; Sun, Yi Eve; Lu, Hanlin; Chen, Yongchang; Li, Siguang; Kang, Yu; Luo, Yuping; Si, Chenyang; Yu, Juehua; Li, Chang; Sun, Nianqin; Si, Wei; Wang, Hong; Ji, Weizhi; Tan, Tao

2017-01-01

Critical epigenetic regulation of primate embryogenesis entails DNA methylome changes. Here we report genome-wide composition, patterning, and stage-specific dynamics of DNA methylation in pre-implantation rhesus monkey embryos as well as male and female gametes studied using an optimized tagmentation-based whole-genome bisulfite sequencing method. We show that upon fertilization, both paternal and maternal genomes undergo active DNA demethylation, and genome-wide de novo DNA methylation is also initiated in the same period. By the 8-cell stage, remethylation becomes more pronounced than demethylation, resulting in an increase in global DNA methylation. Promoters of genes associated with oxidative phosphorylation are preferentially remethylated at the 8-cell stage, suggesting that this mode of energy metabolism may not be favored. Unlike in rodents, X chromosome inactivation is not observed during monkey pre-implantation development. Our study provides the first comprehensive illustration of the 'wax and wane' phases of DNA methylation dynamics. Most importantly, our DNA methyltransferase loss-of-function analysis indicates that DNA methylation influences early monkey embryogenesis. PMID:28233770

The Arabidopsis acetylated histone-binding protein BRAT1 forms a complex with BRP1 and prevents transcriptional silencing

PubMed Central

Zhang, Cui-Jun; Hou, Xiao-Mei; Tan, Lian-Mei; Shao, Chang-Rong; Huang, Huan-Wei; Li, Yong-Qiang; Li, Lin; Cai, Tao; Chen, She; He, Xin-Jian

2016-01-01

Transposable elements and other repetitive DNA sequences are usually subject to DNA methylation and transcriptional silencing. However, anti-silencing mechanisms that promote transcription in these regions are not well understood. Here, we describe an anti-silencing factor, Bromodomain and ATPase domain-containing protein 1 (BRAT1), which we identified by a genetic screen in Arabidopsis thaliana. BRAT1 interacts with an ATPase domain-containing protein, BRP1 (BRAT1 Partner 1), and both prevent transcriptional silencing at methylated genomic regions. Although BRAT1 mediates DNA demethylation at a small set of loci targeted by the 5-methylcytosine DNA glycosylase ROS1, the involvement of BRAT1 in anti-silencing is largely independent of DNA demethylation. We also demonstrate that the bromodomain of BRAT1 binds to acetylated histone, which may facilitate the prevention of transcriptional silencing. Thus, BRAT1 represents a potential link between histone acetylation and transcriptional anti-silencing at methylated genomic regions, which may be conserved in eukaryotes. PMID:27273316

Interactive effects of polymethoxy flavones from Citrus on cell growth inhibition in human neuroblastoma SH-SY5Y cells.

PubMed

Akao, Yukihiro; Itoh, Tomohiro; Ohguchi, Kenji; Iinuma, Munekazu; Nozawa, Yoshinori

2008-03-15

Much evidence indicates that typical phytochemicals such as resveratrol, epigallocatechin gallate, and curcumin have a growth inhibitory effect against cancer cells when each is tested separately. However, when fruits and vegetables including a mixture of phytochemicals are consumed, it is unclear whether this anti-proliferative activity is elicited in the body. Initially, we found that nobiletin, a typical polymethoxy flavone from Citrus, had a preventive effect on H(2)O(2)-induced apoptosis at 20-30 microM in human neuroblastoma SH-SY5Y cells. Nobiletin acted as a signal modulator to attenuate the activation of the intrinsic pathway of the apoptosis induced by H(2)O(2) exposure. On the other hand, tangeretin and 5-demethyl nobiletin, which are also polymethoxy flavones from Citrus, were shown to have a growth inhibitory effect by us and others. These results led us to investigate the interactive effects of these polymethoxy flavones on cell growth. In the present study, we found that tangeretin, nobiletin, and 5-demethyl nobiletin exhibited a cancelling, synergistic, or additive effect when combinations of two of these three compounds were tested. As to the structure-activity relationship, the methyl group at C-5 in nobiletin was shown to contribute to the anti-proliferative effect. By the combined treatment with tangeretin and 5-demethyl nobiletin, the apoptotic cell population and the activity of caspase-3 were synergistically elevated. The finding that tangeretin and 5-demethyl nobiletin induced apoptosis by reducing the mitochondrial membrane potential suggested that an intrinsic pathway of apoptosis was synergistically activated by the combination treatment with tangeretin and 5-demethyl nobiletin. On the other hand, in the combined treatment including nobiletin, the growth inhibitory activity of tangeretin was reduced. These results indicate the relevance of the combination of phytochemicals for the enhancement of the anticancer effect.

Tubular urate transporter gene polymorphisms differentiate patients with gout who have normal and decreased urinary uric acid excretion.

PubMed

Torres, Rosa J; de Miguel, Eugenio; Bailén, Rebeca; Banegas, José R; Puig, Juan G

2014-09-01

Primary gout has been associated with single-nucleotide polymorphisms (SNP) in several tubular urate transporter genes. No study has assessed the association of reabsorption and secretion urate transporter gene SNP with gout in a single cohort of documented primary patients with gout carefully subclassified as normoexcretors or underexcretors. Three reabsorption SNP (SLC22A12/URAT1, SLC2A9/GLUT9, and SLC22A11/OAT4) and 2 secretion transporter SNP (SLC17A1/NPT1 and ABCG2/BRCP) were studied in 104 patients with primary gout and in 300 control subjects. The patients were subclassified into normoexcretors and underexcretors according to their serum and 24-h urinary uric acid levels under strict conditions of dietary control. Compared with control subjects, patients with gout showed different allele distributions of the 5 SNP analyzed. However, the diagnosis of underexcretor was only positively associated with the presence of the T allele of URAT1 rs11231825, the G allele of GLUT9 rs16890979, and the A allele of ABCG2 rs2231142. The association of the A allele of ABCG2 rs2231142 in normoexcretors was 10 times higher than in underexcretors. The C allele of NPT1 rs1165196 was only significantly associated with gout in patients with normal uric acid excretion. Gout with uric acid underexcretion is associated with transporter gene SNP related mainly to tubular reabsorption, whereas uric acid normoexcretion is associated only with tubular secretion SNP. This finding supports the concept of distinctive mechanisms to account for hyperuricemia in patients with gout with reduced or normal uric acid excretion.

Clinical and genetic features of diuretic-associated gout: a case-control study.

PubMed

Mitnala, Sirisha; Phipps-Green, Amanda; Franklin, Christopher; Horne, Anne; Stamp, Lisa K; Merriman, Tony R; Dalbeth, Nicola

2016-07-01

Hyperuricaemia and gout are well-recognized complications of diuretic use. The aim of this study was to examine the clinical and genetic features of diuretic-associated gout. Participants (n = 1365) fulfilling the 1977 ARA gout classification criteria, recruited from primary and secondary care, attended a study visit that included a detailed clinical assessment. Use of diuretic therapy was recorded during the study visit, and was confirmed by electronic dispensing data [n = 426 (31.2%) on diuretics]. Gout-associated single nucleotide polymorphisms were genotyped. Clinical and genetic features of diuretic-associated gout were analysed using a case-control study design (diuretics vs no diuretics). In the diuretic group there were more women, higher rates of comorbid conditions, higher BMI and lower estimated glomerular filtration rate compared with those not taking diuretics. Gout disease duration, frequency of gout flares and presence of tophi were similar in the two groups. Patients on diuretics had higher age of gout presentation and higher recorded serum urate. The ABCG2 rs2231142 risk allele was present less frequently in the diuretic group (36.1%) compared with those not on diuretics (47.6%, P = 1.2 × 10(-4)). The differences in ABCG2 were observed in both men and women with gout. Diuretic-associated gout represents a medically complex condition. Although age of gout onset is later and serum urate concentrations are higher in those on diuretics, other clinical features of gout are similar. The observed differences in the ABCG2 risk allele frequency suggest that some genetic factors play a less dominant role in diuretic-associated gout compared with primary gout. © The Author 2016. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Constitutive androstane receptor upregulates Abcb1 and Abcg2 at the blood-brain barrier after CITCO activation.

PubMed

Lemmen, Julia; Tozakidis, Iasson E P; Bele, Prachee; Galla, Hans-Joachim

2013-03-21

ATP-driven efflux transporters are considered to be the major hurdle in the treatment of central nervous system (CNS) diseases. Abcb1 (P-glycoprotein) and Abcg2 (breast cancer resistance protein/brain multidrug resistance protein) belong to the best known ABC-transporters. These ABC-transporters limit the permeability of the blood-brain barrier and protect the brain against toxic compounds in the blood but on the other hand they also reduce the efficacy of CNS pharmacotherapy. Even after 40 years of extensive research, the regulatory mechanisms of these efflux transporters are still not completely understood. To unravel the efflux transporter regulation, we analyzed the effect of the nuclear receptor CAR (constitutive androstane receptor) on the expression of Abcb1 and Abcg2 in primary cultures of porcine brain capillary endothelial cells (PBCEC). CAR is a xenobiotic-activated transcription factor, which is, like the other important nuclear receptor pregnane X receptor (PXR), highly expressed in barrier tissue and known to be a positive regulator of ABC-transporters. We demonstrate that activation of porcine CAR by the human CAR (hCAR) ligand CITCO (6-(4-chlorophenyl)-imidazo[2,1-b]thiazole-5-carbaldehyde) leads to an up-regulation of both transporters, whereas the mouse-specific CAR ligand TCPOBOP (1,4-bis-[2-(3,5-dichloropyridyloxy)]benzene) had no effect on transporter expression. The stimulation of PBCEC with CITCO caused a significant up-regulation of both efflux-transporters on RNA-level, protein level and transport level. Furthermore the additional application of a CAR inhibitor significantly decreased the transporter expression to control niveau. In conclusion our data prove CAR activation only by the human ligand CITCO leading to an increased ABC-transporter expression and transport activity. Copyright © 2013 Elsevier B.V. All rights reserved.

Persistence of RSV promotes proliferation and epithelial-mesenchymal transition of bronchial epithelial cells through Nodal signaling.

PubMed

Xiang, Zhao; Liang, Zhang; Yanfeng, Huang; Leitao, Kang

2017-10-01

Nodal may play an important role in the development of cancers. The present study was designed to determine the effects of Nodal induced by respiratory syncytial virus (RSV) infection on the occurrence and development of lung cancer and the underlying mechanisms. After verification of RSV infection by observation of cytopathic effect and indirect immunofluorescence, real-time PCR, Western blot and methylation assays were used to verify the influence of RSV on Nodal expression. Then, a Nodal overexpressed vector was constructed and the effects of Nodal on the proliferation and apoptosis of bronchial epithelial cells (BECs) and epithelial-mesenchymal transition (EMT) were assayed by flow cytometry and Western blot, respectively. Moreover, Lefty and pSmad2/3 were assayed by Western blot and Cyclin D1, CDK4, c-myc and Bcl-2 induced by Nodal overepression or RSV infection were also assayed by real-time PCR. The results showed that Nodal over expression and demethylation of the promoter were observed in BECs after RSV infection. Activation of Nodal promoted proliferation, colony formation and EMT and inhibited apoptosis of BECs. Nodal also promoted malignant change by promoting expression of cyclin D1 and related-dependent kinase and inhibiting apoptosis. Besides, RSV infection inhibited Lefty expression and promoted the activation of pSmad2/3. RSV also promoted Cyclin D1, CDK4, c-myc and Bcl-2 expression through the activation of pSmad2/3. Our data showed that persistence of RSV promoted the proliferation, epithelial-mesenchymal transition and expression of oncogenes through Nodal signaling, which may be associated with the occurrence and development of lung cancers.

IND2, a pyrimido[1”,2”:1,5]pyrazolo[3,4-b]quinoline derivative, circumvents multi-drug resistance and causes apoptosis in colon cancer cells

PubMed Central

Karthikeyan, Chandrabose; Lee, Crystal; Moore, Joshua; Mittal, Roopali; Suswam, Esther A.; Abbott, Kodye L; Pondugula, Satyanarayana R.; Manne, Upender; Narayanan, Narayanan K.; Trivedi, Piyush; Tiwari, Amit K.

2014-01-01

Naturally occurring condensed quinolines have anticancer properties. In efforts to find active analogues, we designed and synthesized eight polycyclic heterocycles with a pyrimido[1”,2”:1,5]pyrazolo[3,4-b]quinoline framework (IND series). The compounds were evaluated for activity against colon (HCT-116 and S1-MI-80), prostate (PC3 and DU-145), breast (MCF-7 and MDAMB-231), ovarian (ov2008 and A2780), and hepatocellular (HepG2) cancer cells and against non-cancerous Madin Darby canine kidney (MDCK), mouse embryonic fibroblast (NIH/3T3), and human embryonic kidney cells (HEK293). IND-2, a 4-chloro-2-methyl pyrimido[1”,2”:1,5]pyrazolo[3,4-b]quinoline, exhibited more than tenfold selectivity and potent cytotoxic activity against colon cancer cells relative to the other cancer and non-cancer cells. With five additional colon cancer cell lines (HT-29, HCT-15, LS-180, LS-174, and LoVo), IND-2 had similar cytotoxicity and selectivity, and submicromolar concentrations caused changes in the morphology of HCT-116 and HCT-15 cells. IND-2 did not activate the transactivating function of the pregnane X receptor (PXR), indicating that it does not induce PXR-regulated ABCB1 or ABCG2 transporters. Indeed, IND-2 was not a substrate of ABCB1 or ABCG2, and it induced cytotoxicity in HEK293 cells overexpressing ABCB1 or ABCG2 to the same extent as in normal HEK293 cells. IND-2 was cytotoxic to resistant colon carcinoma S1-MI-80 cells, approximately three- and fivefold more than SN-38 and topotecan, respectively. In HCT-116 colon cancer cells, IND-2 produced concentration-dependent changes in mitochondrial membrane potential, leading to apoptosis, and sub-micromolar concentrations caused chromosomal DNA fragmentation. These findings suggest that, by increasing apoptosis, IND-2 has potential therapeutic efficacy for colorectal cancer. PMID:25537531

Aberrant methylation of GCNT2 is tightly related to lymph node metastasis of primary CRC.

PubMed

Nakamura, Kazunori; Yamashita, Keishi; Sawaki, Hiromichi; Waraya, Mina; Katoh, Hiroshi; Nakayama, Nobukazu; Kawamata, Hiroshi; Nishimiya, Hiroshi; Ema, Akira; Narimatsu, Hisashi; Watanabe, Masahiko

2015-03-01

Glycoprotein expression profile is dramatically altered in human cancers; however, specific glycogenes have not been fully identified. A comprehensive real-time polymerase chain reaction (PCR) system for glycogenes (CRPS-G) identified several outstanding glycogenes. GCNT2 was of particular interest after GCNT2 expression and epigenetics were rigorously investigated in primary colorectal cancer (CRC). The highlights of this work can be summarized as follows: (i) Expression of GCNT2 was remarkably suppressed. (ii) Silenced expression of GCNT2 was reactivated by combined demethylating agents. (iii) Promoter DNA methylation of GCNT2 was silenced in CRC cell lines and tissues. Hypomethylation of GCNT2 variant 2 is tightly associated with lymph node metastasis in primary CRC. (iv) GCNT2 methylation level in the normal tissues also showed a close association with that in the tumor tissues and reflected lymph node metastasis. We identified aberrant expression of GCNT2, which can be explained by promoter DNA hypermethylation. Hypomethylation of the GCNT2 variant 2 reflected lymph node metastasis of CRC in the tumor and normal tissues. Copyright© 2015 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

Two-step iron(0)-mediated N-demethylation of N-methyl alkaloids.

PubMed

Kok, Gaik B; Pye, Cory C; Singer, Robert D; Scammells, Peter J

2010-07-16

A mild and simple two-step Fe(0)-mediated N-demethylation of a number of tertiary N-methyl alkaloids is described. The tertiary N-methylamine is first oxidized to the corresponding N-oxide, which is isolated as the hydrochloride salt. Subsequent treatment of the N-oxide hydrochloride with iron powder readily provides the N-demethylated amine. Representative substrates include a number of opiate and tropane alkaloids. Key intermediates in the synthesis of semisynthetic 14-hydroxy pharmaceutical opiates such as oxycodone and oxymorphone are also readily N-demethylated using this method.

The 14-3-3σ gene promoter is methylated in both human melanocytes and melanoma

PubMed Central

2009-01-01

Background Recent evidence demonstrates that 14-3-3σ acts as a tumor suppressor gene inactivated by methylation of its 5' CpG islands in epithelial tumor cells, while remaining un-methylated in normal human epithelia. The methylation analysis of 14-3-3σ has been largely overlooked in melanoma. Methods The methylation status of 14-3-3σ CpG island in melanocytes and melanoma cells was analyzed by methylation-specific sequencing (MSS) and quantitative methylation-specific PCR (Q-MSP). 14-3-3σ mRNA and protein expression in cell lines was detected by real-time RT-PCR and western blot. Melanoma cells were also treated by 5-aza-2'-deoxycytidine (DAC), a demethylating agent, and/or histone deacetylase inhibitor, Trichostatin A (TSA), to evaluate their effects on 14-3-3σ gene expression. Results 14-3-3σ is hypermethylated in both human melanocytes and most melanoma cells in a lineage-specific manner, resulting in the silencing of 14-3-3σ gene expression and the active induction of 14-3-3σ mRNA and protein expression following treatment with DAC. We also observed a synergistic effect upon gene expression when DAC was combined with TSA. The promoter methylation status of 14-3-3σ was analyzed utilizing Q-MSP in 20 melanoma tissue samples and 10 cell lines derived from these samples, showing that the majority of melanoma samples maintain their hypermethylation status of the 14-3-3σ gene. Conclusion 14-3-3σ is hypermethylated in human melanoma in a cell-linage specific manner. Spontaneous demethylation and re-expression of 14-3-3σ is a rare event in melanoma, indicating 14-3-3σ might have a tentative role in the pathogenesis of melanoma. PMID:19473536

5-azacytidine promotes microspore embryogenesis initiation by decreasing global DNA methylation, but prevents subsequent embryo development in rapeseed and barley

PubMed Central

Solís, María-Teresa; El-Tantawy, Ahmed-Abdalla; Cano, Vanesa; Risueño, María C.; Testillano, Pilar S.

2015-01-01

Microspores are reprogrammed by stress in vitro toward embryogenesis. This process is an important tool in breeding to obtain double-haploid plants. DNA methylation is a major epigenetic modification that changes in differentiation and proliferation. We have shown changes in global DNA methylation during microspore reprogramming. 5-Azacytidine (AzaC) cannot be methylated and leads to DNA hypomethylation. AzaC is a useful demethylating agent to study DNA dynamics, with a potential application in microspore embryogenesis. This work analyzes the effects of short and long AzaC treatments on microspore embryogenesis initiation and progression in two species, the dicot Brassica napus and the monocot Hordeum vulgare. This involved the quantitative analyses of proembryo and embryo production, the quantification of DNA methylation, 5-methyl-deoxy-cytidine (5mdC) immunofluorescence and confocal microscopy, and the analysis of chromatin organization (condensation/decondensation) by light and electron microscopy. Four days of AzaC treatments (2.5 μM) increased embryo induction, response associated with a decrease of DNA methylation, modified 5mdC, and heterochromatin patterns compared to untreated embryos. By contrast, longer AzaC treatments diminished embryo production. Similar effects were found in both species, indicating that DNA demethylation promotes microspore reprogramming, totipotency acquisition, and embryogenesis initiation, while embryo differentiation requires de novo DNA methylation and is prevented by AzaC. This suggests a role for DNA methylation in the repression of microspore reprogramming and possibly totipotency acquisition. Results provide new insights into the role of epigenetic modifications in microspore embryogenesis and suggest a potential benefit of inhibitors, such as AzaC, to improve the process efficiency in biotechnology and breeding programs. PMID:26161085

Nc886 is epigenetically repressed in prostate cancer and acts as a tumor suppressor through the inhibition of cell growth.

PubMed

Fort, Rafael Sebastián; Mathó, Cecilia; Geraldo, Murilo Vieira; Ottati, María Carolina; Yamashita, Alex Shimura; Saito, Kelly Cristina; Leite, Katia Ramos Moreira; Méndez, Manuel; Maedo, Noemí; Méndez, Laura; Garat, Beatriz; Kimura, Edna Teruko; Sotelo-Silveira, José Roberto; Duhagon, María Ana

2018-02-02

Nc886 is a 102 bp non-coding RNA transcript initially classified as a microRNA precursor (Pre-miR-886), later as a divergent homologue of the vault RNAs (vtRNA 2-1) and more recently as a novel type of RNA (nc886). Although nc886/vtRNA2-1/Pre-miR-886 identity is still controversial, it was shown to be epigenetically controlled, presenting both tumor suppressor and oncogenic function in different cancers. Here, we study for the first time the role of nc886 in prostate cancer. Nc886 promoter methylation status and its correlation with patient clinical parameters or DNMTs levels were evaluated in TCGA and specific GEO prostate tissue datasets. Nc886 level was measured by RT-qPCR to compare normal/neoplastic prostate cells from radical prostatectomies and cell lines, and to assess nc886 response to demethylating agents. The effect of nc886 recovery in cell proliferation (in vitro and in vivo) and invasion (in vitro) was evaluated using lentiviral transduced DU145 and LNCaP cell lines. The association between the expression of nc886 and selected genes was analyzed in the TCGA-PRAD cohort. Nc886 promoter methylation increases in tumor vs. normal prostate tissue, as well as in metastatic vs. normal prostate tissue. Additionally, nc886 promoter methylation correlates with prostate cancer clinical staging, including biochemical recurrence, Clinical T-value and Gleason score. Nc886 transcript is downregulated in tumor vs. normal tissue -in agreement with its promoter methylation status- and increases upon demethylating treatment. In functional studies, the overexpression of nc886 in the LNCaP and DU145 cell line leads to a decreased in vitro cell proliferation and invasion, as well as a reduced in vivo cell growth in NUDE-mice tumor xenografts. Finally, nc886 expression associates with the prostate cancer cell cycle progression gene signature in TCGA-PRAD. Our data suggest a tumor suppressor role for nc886 in the prostate, whose expression is epigenetically silenced in cancer leading to an increase in cell proliferation and invasion. Nc886 might hold clinical value in prostate cancer due to its association with clinical parameters and with a clinically validated gene signature.

Genetic polymorphisms of enzyme proteins and transporters related to methotrexate response and pharmacokinetics in a Japanese population.

PubMed

Hashiguchi, Masayuki; Shimizu, Mikiko; Hakamata, Jun; Tsuru, Tomomi; Tanaka, Takanori; Suzaki, Midori; Miyawaki, Kumika; Chiyoda, Takeshi; Takeuchi, Osamu; Hiratsuka, Jiro; Irie, Shin; Maruyama, Junya; Mochizuki, Mayumi

2016-01-01

Methotrexate (MTX) is currently the anchor drug widely used worldwide in the treatment of rheumatoid arthritis (RA). However, the therapeutic response to MTX has been shown to vary widely among individuals, genders and ethnic groups. The reason for this has been not clarified but it is considered to be partially due to several mechanisms in the cellular pathway of MTX including single-nucleotide polymorphisms (SNPs). The purpose of this study was to investigate the allelic frequencies in different ethnic and/or population groups in the 10 polymorphisms of enzyme proteins and transporters related to the MTX response and pharmacokinetics including MTHFR, TYMS, RFC1, FPGS, GGH, ABCB1, ABCC2 and ABCG2 in unrelated healthy Japanese adults and patients with RA. Ten polymorphisms, methylenetetrahydrofolate reductase (MTHFR) 1298, thymidylate synthase (TYMS) 3'-UTR, reduced folate carrier 1 (RFC1) 80 and-43, folypolyglutamyl synthase (FPGS) 1994, γ-glutamyl hydrolase (GGH) 452 and-401, the ABC transporters (ABCB1 3435, ABCC2 IVS23 + 56, ABCG2 914) of enzyme proteins and transporters related to MTX response and pharmacokinetics in 299 unrelated healthy Japanese adults and 159 Japanese patients with RA were investigated to clarify their contributions to individual variations in response and safety to MTX and establish personalized MTX therapy. SNPs were evaluated using real-time polymerase chain reaction (PCR). Comparison of allelic frequencies in our study with other ethnic/population groups of healthy adults and RA patients showed significant differences in 10 polymorphisms among healthy adults and 7 among RA patients. Allelic frequencies of MTHFR 1298 C, FPGS 1994A and ABCB1 3435 T were lower in Japanese than in Caucasian populations and those of ABCC2 IVS23 + 56 C and ABCG2 914A were higher in Japanese than in Caucasian/European populations in both healthy adults and RA patients. Allelic frequencies of MTHFR 1298 C, GGH-401 T, ABCB1 3435 T, and ABCG2 914A were higher in healthy Japanese adults than in an African population, and those of RFC1 80A, RFC1-43C and ABCC2 IVS23 + 56 C in healthy Japanese adults were lower than in Africans. However, no significant differences were seen in the distribution of allelic frequencies between healthy Japanese adults and RA patients. The variations in allelic frequencies in different ethnic and/or population groups in healthy adults and RA patients may contribute to individual variations in MTX response and toxicity.

Diverse Targets of β-Catenin during the Epithelial-Mesenchymal Transition Define Cancer Stem Cells and Predict Disease Relapse.

PubMed

Chang, Yi-Wen; Su, Ying-Jhen; Hsiao, Michael; Wei, Kuo-Chen; Lin, Wei-Hsin; Liang, Chi-Lung; Chen, Shin-Cheh; Lee, Jia-Lin

2015-08-15

Wnt signaling contributes to the reprogramming and maintenance of cancer stem cell (CSC) states that are activated by epithelial-mesenchymal transition (EMT). However, the mechanistic relationship between EMT and the Wnt pathway in CSC is not entirely clear. Chromatin immunoprecipitation with high-throughput sequencing (ChIP-seq) indicated that EMT induces a switch from the β-catenin/E-cadherin/Sox15 complex to the β-catenin/Twist1/TCF4 complex, the latter of which then binds to CSC-related gene promoters. Tandem coimmunoprecipitation and re-ChIP experiments with epithelial-type cells further revealed that Sox15 associates with the β-catenin/E-cadherin complex, which then binds to the proximal promoter region of CASP3. Through this mechanism, Twist1 cleavage is triggered to regulate a β-catenin-elicited promotion of the CSC phenotype. During EMT, we documented that Twist1 binding to β-catenin enhanced the transcriptional activity of the β-catenin/TCF4 complex, including by binding to the proximal promoter region of ABCG2, a CSC marker. In terms of clinical application, our definition of a five-gene CSC signature (nuclear β-catenin(High)/nuclear Twist1(High)/E-cadherin(Low)/Sox15(Low)/CD133(High)) may provide a useful prognostic marker for human lung cancer. ©2015 American Association for Cancer Research.

Kinetics of lipogenic genes expression in milk purified mammary epithelial cells (MEC) across lactation and their correlation with milk and fat yield in buffalo.

PubMed

Yadav, Poonam; Kumar, Parveen; Mukesh, Manishi; Kataria, R S; Yadav, Anita; Mohanty, A K; Mishra, B P

2015-04-01

Expression patterns of lipogenic genes (LPL, ABCG2, ACSS2, ACACA, SCD, BDH, LIPIN1, SREBF1, PPARα and PPARγ) were studied in milk purified MEC across different stages of lactation (15, 30, 45, 60, 90, 120 and 240 days relative to parturition) in buffalo. PPARα was the most abundant gene while ABCG2 and ACSS2 had moderate level of expression; whereas expression of SREBF and PPARγ was very low. The expression patterns of some genes (BDH1, ACSS2, and LIPIN1) across lactation were positively correlated with milk yield while negatively correlated with fat yield. SCD also showed weak correlation with milk yield (p, 0.53) and fat yield (p, -0.47). On the other hand, expression pattern of ACACA was negatively correlated with milk yield (p, -0.88) and positively correlated with fat yield (p, 0.62). Strong correlation was observed between genes involved in de novo milk fat synthesis (BDH1, ACSS2, LIPIN2 and SCD) and milk yield. Copyright © 2015 Elsevier Ltd. All rights reserved.

microRNA-150 inhibits the formation of macrophage foam cells through targeting adiponectin receptor 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jing; Zhang, Suhua, E-mail: drsuhuangzhang@qq.com

Transformation of macrophages into foam cells plays a critical role in the pathogenesis of atherosclerosis. The aim of this study was to determine the expression and biological roles of microRNA (miR)-150 in the formation of macrophage foam cells and to identify its functional target(s). Exposure to 50 μg/ml oxidized low-density lipoprotein (oxLDL) led to a significant upregulation of miR-150 in THP-1 macrophages. Overexpression of miR-150 inhibited oxLDL-induced lipid accumulation in THP-1 macrophages, while knockdown of miR-150 enhanced lipid accumulation. apoA-I- and HDL-mediated cholesterol efflux was increased by 66% and 43%, respectively, in miR-150-overexpressing macrophages relative to control cells. In contrast, downregulationmore » of miR-150 significantly reduced cholesterol efflux from oxLDL-laden macrophages. Bioinformatic analysis and luciferase reporter assay revealed adiponectin receptor 2 (AdipoR2) as a direct target of miR-150. Small interfering RNA-mediated downregulation of AdipoR2 phenocopied the effects of miR-150 overexpression, reducing lipid accumulation and facilitating cholesterol efflux in oxLDL-treated THP-1 macrophages. Knockdown of AdipoR2 induced the expression of proliferator-activated receptor gamma (PPARγ), liver X receptor alpha (LXRα), ABCA1, and ABCG1. Moreover, pharmacological inhibition of PPARγ or LXRα impaired AdipoR2 silencing-induced upregulation of ABCA1 and ABCG1. Taken together, our results indicate that miR-150 can attenuate oxLDL-induced lipid accumulation in macrophages via promotion of cholesterol efflux. The suppressive effects of miR-150 on macrophage foam cell formation are mediated through targeting of AdipoR2. Delivery of miR-150 may represent a potential approach to prevent macrophage foam cell formation in atherosclerosis. -- Highlights: •miR-150 inhibits macrophage foam cell formation. •miR-150 accelerates cholesterol efflux from oxLDL-laden macrophages. •miR-150 suppresses macrophage foam cell formation by targeting AdipoR2.« less

Chemical groups and structural characterization of lignin via thiol-mediated demethylation

Treesearch

Lihong Hu; Hui Pan; Yonghong Zhou; Chung-Yun Hse; Chengguo Liu; Baofang Zhang; Bin Xu

2014-01-01

A new approach to increase the reactivity of lignin by thiol-mediated demethylation was investigated in this study. Demethylated lignin was characterized by the changes in its hydroxyl and methoxyl groups, molecular weight, and other properties using titration and spectroscopy methods including FT-IR, 1H NMR, UV,and GPC. The total...

Retinoic Acid Isomers Up-Regulate ATP Binding Cassette A1 and G1 and Cholesterol Efflux in Rat Astrocytes: Implications for Their Therapeutic and Teratogenic Effects

PubMed Central

Chen, Jing; Costa, Lucio G.

2011-01-01

Recent studies suggest that retinoids may be effective in the treatment of Alzheimer's disease, although exposure to an excess of retinoids during gestation causes teratogenesis. Cholesterol is essential for brain development, but high levels of cholesterol have been associated with Alzheimer's disease. We hypothesized that retinoic acid may affect cholesterol homeostasis in rat astrocytes, which regulate cholesterol distribution in the brain, through the up-regulation of cholesterol transporters ATP binding cassette (Abc)a1 and Abcg1. Tretinoin, 13-cis retinoic acid (13-cis-RA), 9-cis-RA, and the selective retinoid X receptor (RXR) agonist methoprene significantly increased cholesterol efflux induced by cholesterol acceptors and protein levels of Abca1 by 2.3- (±0.25), 3.6- (±0.42), 4.1- (±0.5), and 1.75- (±0.43) fold, respectively, and Abcg1 by 2.1- (±0.26), 2.2- (±0.33), 2.5- (±0.23), and 2.2- (±0.21) fold, respectively. 13-cis-RA and 9-cis-RA also significantly increased mRNA levels of Abca1 (maximal induction 7.3 ± 0.42 and 2.7 ± 0.17, respectively) and Abcg1 (maximal induction 2.0 ± 0.18 and 1.8 ± 0.09, respectively), and the levels of membrane-bound Abca1 (2.5 ± 0.3 and 2.5 ± 0.40-fold increase, respectively), whereas they significantly decreased intracellular cholesterol content without affecting cholesterol synthesis. The effect of 9-cis-RA on cholesterol homeostasis in astrocytes can be ascribed to the activation of RXR, whereas the effects of 13-cis-RA and tretinoin were independent of either RXRs or retinoic acid receptors. These findings suggest that retinoids affect cholesterol homeostasis in astrocytes and that this effect may be involved in both their therapeutic and teratogenic actions. PMID:21628419

Characterization of cancer stem-like cells derived from a side population of a human gallbladder carcinoma cell line, SGC-996

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xin-xing; Wang, Jian, E-mail: dr_wangjian@yahoo.com.cn; Wang, Hao-lu

2012-03-23

Highlights: Black-Right-Pointing-Pointer We sorted SP cells from a human gallbladder carcinoma cell lines, SGC-996. Black-Right-Pointing-Pointer SP cells displayed higher proliferation and stronger clonal-generating capability. Black-Right-Pointing-Pointer SP cells showed more migratory and invasive abilities. Black-Right-Pointing-Pointer SP cells were more resistant and tumorigenic than non-SP counterparts. Black-Right-Pointing-Pointer ABCG2 might be a candidate as a marker for SP cells. -- Abstract: The cancer stem cell (CSC) hypothesis proposes that CSCs, which can renew themselves proliferate infinitely, and escape chemotherapy, become the root of recurrence and metastasis. Previous studies have verified that side population (SP) cells, characterized by their ability to efflux lipophilic substratemore » Hoechst 33342, to share many characteristics of CSCs in multiplying solid tumors. The purpose of this study was to sort SP cells from a human gallbladder carcinoma cell line, SGC-996 and to preliminarily identify the biological characteristics of SP cells from the cell line. Using flow cytometry we effectively sorted SP cells from the cell line SGC-996. SP cells not only displayed higher proliferative, stronger clonal-generating, more migratory and more invasive capacities, but showed stronger resistance. Furthermore, our experiments demonstrated that SP cells were more tumorigenic than non-SP counterparts in vivo. Real-time PCR analysis and immunocytochemistry showed that the expression of ATP-binding cassette subfamily G member 2 (ABCG2) was significantly higher in SP cells. Hence, these results collectively suggest that SP cells are progenitor/stem-like cells and ABCG2 might be a candidate marker for SP cells in human gallbladder cancer.« less

Dependence of corneal stem/progenitor cells on ocular surface innervation.

PubMed

Ueno, Hiroki; Ferrari, Giulio; Hattori, Takaaki; Saban, Daniel R; Katikireddy, Kishore R; Chauhan, Sunil K; Dana, Reza

2012-02-21

Neurotrophic keratopathy (NK) is a corneal degeneration associated with corneal nerve dysfunction. It can cause corneal epithelial defects, stromal thinning, and perforation. However, it is not clear if and to which extent epithelial stem cells are affected in NK. The purpose of this study was to identify the relationship between corneolimbal epithelial progenitor/stem cells and sensory nerves using a denervated mouse model of NK. NK was induced in mice by electrocoagulation of the ophthalmic branch of the trigeminal nerve. The absence of corneal nerves was confirmed with β-III tubulin immunostaining and blink reflex test after 7 days. ATP-binding cassette subfamily G member 2 (ABCG2), p63, and hairy enhancer of split 1 (Hes1) were chosen as corneolimbal stem/progenitor cell markers and assessed in denervated mice versus controls by immunofluorescent microscopy and real-time PCR. In addition, corneolimbal stem/progenitor cells were detected as side population cells using flow cytometry, and colony-forming efficiency assay was performed to assess their function. ABCG2, p63, and Hes1 immunostaining were significantly decreased in denervated eyes after 7 days. Similarly, the expression levels of ABCG2, p63, K15, Hes1, and N-cadherin transcripts were also significantly decreased in denervated eyes. Stem/progenitor cells measured as side population from NK mice were decreased by approximately 75% compared with normals. In addition, the authors found a significant (P = 0.038) reduction in colony-forming efficiency of stem/progenitor cells harvested from denervated eyes. Corneolimbal stem/progenitor cells are significantly reduced after depletion of sensory nerves. The data suggest a critical role of innervation in maintaining stem cells and/or the stem cell niche.

Dependence of Corneal Stem/Progenitor Cells on Ocular Surface Innervation

PubMed Central

Ueno, Hiroki; Ferrari, Giulio; Hattori, Takaaki; Saban, Daniel R.; Katikireddy, Kishore R.; Chauhan, Sunil K.

2012-01-01

Purpose. Neurotrophic keratopathy (NK) is a corneal degeneration associated with corneal nerve dysfunction. It can cause corneal epithelial defects, stromal thinning, and perforation. However, it is not clear if and to which extent epithelial stem cells are affected in NK. The purpose of this study was to identify the relationship between corneolimbal epithelial progenitor/stem cells and sensory nerves using a denervated mouse model of NK. Methods. NK was induced in mice by electrocoagulation of the ophthalmic branch of the trigeminal nerve. The absence of corneal nerves was confirmed with β-III tubulin immunostaining and blink reflex test after 7 days. ATP-binding cassette subfamily G member 2 (ABCG2), p63, and hairy enhancer of split 1 (Hes1) were chosen as corneolimbal stem/progenitor cell markers and assessed in denervated mice versus controls by immunofluorescent microscopy and real-time PCR. In addition, corneolimbal stem/progenitor cells were detected as side population cells using flow cytometry, and colony-forming efficiency assay was performed to assess their function. Results. ABCG2, p63, and Hes1 immunostaining were significantly decreased in denervated eyes after 7 days. Similarly, the expression levels of ABCG2, p63, K15, Hes1, and N-cadherin transcripts were also significantly decreased in denervated eyes. Stem/progenitor cells measured as side population from NK mice were decreased by approximately 75% compared with normals. In addition, the authors found a significant (P = 0.038) reduction in colony-forming efficiency of stem/progenitor cells harvested from denervated eyes. Conclusions. Corneolimbal stem/progenitor cells are significantly reduced after depletion of sensory nerves. The data suggest a critical role of innervation in maintaining stem cells and/or the stem cell niche. PMID:22232434

Inhibition of CYP2D6-mediated tramadol O-demethylation in methadone but not buprenorphine maintenance patients

PubMed Central

Coller, Janet K; Michalakas, Jennifer R; James, Heather M; Farquharson, Aaron L; Colvill, Joel; White, Jason M; Somogyi, Andrew A

2012-01-01

AIMS To compare the O- (CYP2D6 mediated) and N- (CYP3A4 mediated) demethylation metabolism of tramadol between methadone and buprenorphine maintained CYP2D6 extensive metabolizer subjects. METHODS Nine methadone and seven buprenorphine maintained subjects received a single 100 mg dose of tramadol hydrochloride. Blood was collected at 4 h and assayed for tramadol, methadone, buprenorphine and norbuprenorphine (where appropriate) and all urine over 4 h was assayed for tramadol and its M1 and M2 metabolites. RESULTS The urinary metabolic ratio [median (range)] for O-demethylation (M1) was significantly lower (P= 0.0002, probability score 1.0) in the subjects taking methadone [0.071 (0.012–0.103)] compared with those taking buprenorphine [0.192 (0.108–0.392)], but there was no significant difference (P= 0.21, probability score 0.69) in N-demethylation (M2). The percentage of dose [median (range)] recovered as M1 was significantly lower in subjects taking methadone compared with buprenorphine (0.069 (0.044–0.093) and 0.126 (0.069–0.187), respectively, P= 0.04, probability score 0.19), M2 was significantly higher in subjects taking methadone compared with buprenorphine (0.048 (0.033–0.085) and 0.033 (0.014–0.049), respectively, P= 0.04, probability score 0.81). Tramadol was similar (0.901 (0.635–1.30) and 0.685 (0.347–1.04), respectively, P= 0.35, probability score 0.65). CONCLUSIONS Methadone inhibited the CYP2D6-mediated metabolism of tramadol to M1. Hence, as the degree of opioid analgesia is largely dependent on M1 formation, methadone maintenance patients may not receive adequate analgesia from oral tramadol. PMID:22369095

Epigenetics and Breast Cancers

PubMed Central

Vo, An T.; Millis, Richard M.

2012-01-01

Several of the active compounds in foods, poisons, drugs, and industrial chemicals may, by epigenetic mechanisms, increase or decrease the risk of breast cancers. Enzymes that are involved in DNA methylation and histone modifications have been shown to be altered in several types of breast and other cancers resulting in abnormal patterns of methylation and/or acetylation. Hypermethylation at the CpG islands found in estrogen response element (ERE) promoters occurs in conjunction with ligand-bonded alpha subunit estrogen receptor (Erα) dimers wherein the ligand ERα dimer complex acts as a transcription factor and binds to the ERE promoter. Ligands could be 17-β-estradiol (E2), phytoestrogens, heterocyclic amines, and many other identified food additives and heavy metals. The dimer recruits DNA methyltransferases which catalyze the transfer of methyl groups from S-adenosyl-L-methionine (SAM) to 5′-cytosine on CpG islands. Other enzymes are recruited to the region by ligand-ERα dimers which activate DNA demethylases to act simultaneously to increase gene expression of protooncogenes and growth-promoting genes. Ligand-ERα dimers also recruit histone acetyltransferase to the ERE promoter region. Histone demethylases such as JMJD2B and histone methyltransferases are enzymes which demethylate lysine residues on histones H3 and/or H4. This makes the chromatin accessible for transcription factors and enzymes. PMID:22567014

Evaluation of mercury methylation and methylmercury demethylation rates in vegetated and non-vegetated saltmarsh sediments from two Portuguese estuaries.

PubMed

Cesário, Rute; Hintelmann, Holger; Mendes, Ricardo; Eckey, Kevin; Dimock, Brian; Araújo, Beatriz; Mota, Ana Maria; Canário, João

2017-07-01

Neurotoxic methylmercury (MMHg) is formed from inorganic divalent mercury (Hg 2+ ). However, it is poorly understood to what extent different mercury (Hg) pools contribute to existent MMHg levels. In this study, ambient concentrations of total Hg (THg) and MMHg as well as rates of methylation and demethylation were measured simultaneously in sediments with and without salt-marsh plant vegetation, which were collected in Guadiana and Tagus estuaries, Portugal. Concurrent processes of Hg methylation and MMHg demethylation were directly monitored and compared by spiking sediments cores with stable isotope tracers of 199 Hg 2+ and CH 3 201 Hg + followed by gas chromatographic separation and isotope-specific detection using inductively coupled plasma mass spectrometry. Compared to the Guadiana estuary, where concentrations were comparatively low, THg and MMHg levels varied between vegetated and non-vegetated sediments collected at the Rosário site (ROS) of the Tagus estuary. Methylation (K M ) and demethylation rates (K D ) were also different between estuaries being dependent on the presence of vegetation. In addition, the type of macrophyte species influenced K M and K D values. In fact, the highest K M value was found in Sarcocornia fruticosa vegetated sediments at the Castro Marim site in Guadiana (CM, 0.160 day -1 ) and the lowest K M was observed in non-vegetated sediments at the Alcochete site in Tagus (ALC, 0.009 day -1 ). K D varied by a factor of three among sites with highest rates of demethylation observed in non-vegetated sediments in Guadiana (12 ± 1.3 day -1 , corresponding to a half-life of 1.4 ± 0.2 h). This study clearly shows that the presence of vegetation in sediments favors the formation of MMHg. Moreover, this effect might be site specific and further studies are needed to confirm the findings reported here. Copyright © 2017 Elsevier Ltd. All rights reserved.

Large-scale gene-centric analysis identifies novel variants for coronary artery disease.

PubMed

2011-09-01

Coronary artery disease (CAD) has a significant genetic contribution that is incompletely characterized. To complement genome-wide association (GWA) studies, we conducted a large and systematic candidate gene study of CAD susceptibility, including analysis of many uncommon and functional variants. We examined 49,094 genetic variants in ∼2,100 genes of cardiovascular relevance, using a customised gene array in 15,596 CAD cases and 34,992 controls (11,202 cases and 30,733 controls of European descent; 4,394 cases and 4,259 controls of South Asian origin). We attempted to replicate putative novel associations in an additional 17,121 CAD cases and 40,473 controls. Potential mechanisms through which the novel variants could affect CAD risk were explored through association tests with vascular risk factors and gene expression. We confirmed associations of several previously known CAD susceptibility loci (eg, 9p21.3:p<10(-33); LPA:p<10(-19); 1p13.3:p<10(-17)) as well as three recently discovered loci (COL4A1/COL4A2, ZC3HC1, CYP17A1:p<5×10(-7)). However, we found essentially null results for most previously suggested CAD candidate genes. In our replication study of 24 promising common variants, we identified novel associations of variants in or near LIPA, IL5, TRIB1, and ABCG5/ABCG8, with per-allele odds ratios for CAD risk with each of the novel variants ranging from 1.06-1.09. Associations with variants at LIPA, TRIB1, and ABCG5/ABCG8 were supported by gene expression data or effects on lipid levels. Apart from the previously reported variants in LPA, none of the other ∼4,500 low frequency and functional variants showed a strong effect. Associations in South Asians did not differ appreciably from those in Europeans, except for 9p21.3 (per-allele odds ratio: 1.14 versus 1.27 respectively; P for heterogeneity = 0.003). This large-scale gene-centric analysis has identified several novel genes for CAD that relate to diverse biochemical and cellular functions and clarified the literature with regard to many previously suggested genes.

An Inhibitor of Mutant IDH1 Delays Growth and Promotes Differentiation of Glioma Cells

PubMed Central

Rohle, Dan; Popovici-Muller, Janeta; Palaskas, Nicolaos; Turcan, Sevin; Grommes, Christian; Campos, Carl; Tsoi, Jennifer; Clark, Owen; Oldrini, Barbara; Komisopoulou, Evangelia; Kunii, Kaiko; Pedraza, Alicia; Schalm, Stefanie; Silverman, Lee; Miller, Alexandra; Wang, Fang; Yang, Hua; Chen, Yue; Kernytsky, Andrew; Rosenblum, Marc K.; Liu, Wei; Biller, Scott A.; Su, Shinsan M.; Brennan, Cameron W.; Chan, Timothy A.; Graeber, Thomas G.; Yen, Katharine E.; Mellinghoff, Ingo K.

2013-01-01

The recent discovery of mutations in metabolic enzymes has rekindled interest in harnessing the altered metabolism of cancer cells for cancer therapy. One potential drug target is isocitrate dehydrogenase 1 (IDH1), which is mutated in multiple human cancers. Here, we examine the role of mutant IDH1 in fully transformed cells with endogenous IDH1 mutations. A selective R132H-IDH1 inhibitor (AGI-5198) identified through a high-throughput screen blocked, in a dose-dependent manner, the ability of the mutant enzyme (mIDH1) to produce R-2-hydroxyglutarate (R-2HG). Under conditions of near-complete R-2HG inhibition, the mIDH1 inhibitor induced demethylation of histone H3K9me3 and expression of genes associated with gliogenic differentiation. Blockade of mIDH1 impaired the growth of IDH1-mutant—but not IDH1–wild-type—glioma cells without appreciable changes in genome-wide DNA methylation. These data suggest that mIDH1 may promote glioma growth through mechanisms beyond its well-characterized epigenetic effects. PMID:23558169

Inhibition of CYP2D6-mediated tramadol O-demethylation in methadone but not buprenorphine maintenance patients.

PubMed

Coller, Janet K; Michalakas, Jennifer R; James, Heather M; Farquharson, Aaron L; Colvill, Joel; White, Jason M; Somogyi, Andrew A

2012-11-01

Management of pain in opioid dependent individuals is problematic due to numerous issues including cross-tolerance to opioids. Hence there is a need to find alternative analgesics to classical opioids and tramadol is potentially one such alternative. Methadone inhibits CYP2D6 in vivo and in vitro. We aimed to investigate the effect of methadone on the pathways of tramadol metabolism: O-demethylation (CYP2D6) to the opioid-active metabolite M1 and N-demethylation (CYP3A4) to M2 in subjects maintained on methadone or buprenorphine as a control. Compared with subjects on buprenorphine, methadone reduced the clearance of tramadol to active O-desmethyl-tramadol (M1) but had no effect on N-desmethyltramadol (M2) formation. Similar to other analgesics whose active metabolites are formed by CYP2D6 such as codeine, reduced formation of O-desmethyltramadol (M1) is likely to result in reduced analgesia for subjects maintained on methadone. Hence alternative analgesics whose metabolism is independent of CYP2D6 should be utilized in this patient population. To compare the O- (CYP2D6 mediated) and N- (CYP3A4 mediated) demethylation metabolism of tramadol between methadone and buprenorphine maintained CYP2D6 extensive metabolizer subjects. METHODS Nine methadone and seven buprenorphine maintained subjects received a single 100 mg dose of tramadol hydrochloride. Blood was collected at 4 h and assayed for tramadol, methadone, buprenorphine and norbuprenorphine (where appropriate) and all urine over 4 h was assayed for tramadol and its M1 and M2 metabolites. The urinary metabolic ratio [median (range)] for O-demethylation (M1) was significantly lower (P= 0.0002, probability score 1.0) in the subjects taking methadone [0.071 (0.012-0.103)] compared with those taking buprenorphine [0.192 (0.108-0.392)], but there was no significant difference (P= 0.21, probability score 0.69) in N-demethylation (M2). The percentage of dose [median (range)] recovered as M1 was significantly lower in subjects taking methadone compared with buprenorphine (0.069 (0.044-0.093) and 0.126 (0.069-0.187), respectively, P= 0.04, probability score 0.19), M2 was significantly higher in subjects taking methadone compared with buprenorphine (0.048 (0.033-0.085) and 0.033 (0.014-0.049), respectively, P= 0.04, probability score 0.81). Tramadol was similar (0.901 (0.635-1.30) and 0.685 (0.347-1.04), respectively, P= 0.35, probability score 0.65). Methadone inhibited the CYP2D6-mediated metabolism of tramadol to M1. Hence, as the degree of opioid analgesia is largely dependent on M1 formation, methadone maintenance patients may not receive adequate analgesia from oral tramadol. © 2012 The Authors. British Journal of Clinical Pharmacology © 2012 The British Pharmacological Society.

Prostacyclin synthase expression and epigenetic regulation in nonsmall cell lung cancer.

PubMed

Cathcart, Mary-Clare; Gray, Steven G; Baird, Anne-Marie; Boyle, Elaine; Gately, Kathy; Kay, Elaine; Cummins, Robert; Pidgeon, Graham P; O'Byrne, Kenneth J

2011-11-15

Prostacyclin synthase (PGIS) metabolizes prostaglandin H(2), into prostacyclin. This study aimed to determine the expression profile of PGIS in nonsmall cell lung cancer (NSCLC) and examine potential mechanisms involved in PGIS regulation. PGIS expression was examined in human NSCLC and matched controls by reverse transcriptase polymerase chain reaction (RT-PCR), Western analysis, and immunohistochemistry. A 204-patient NSCLC tissue microarray was stained for PGIS and cyclooxygenase 2 (COX2) expression. Staining intensity was correlated with clinical parameters. Epigenetic mechanisms underpinning PGIS promoter expression were examined using RT-PCR, methylation-specific PCR, and chromatin immunoprecipitation analysis. PGIS expression was reduced/absent in human NSCLC protein samples (P < .0001), but not mRNA relative to matched controls. PGIS tissue expression was higher in squamous cell carcinoma (P = .004) and in male patients (P < .05). No significant correlation of PGIS or COX2 expression with overall patient survival was observed, although COX2 was prognostic for short-term (2-year) survival (P < .001). PGIS mRNA expression was regulated by DNA CpG methylation and histone acetylation in NSCLC cell lines, with chromatin remodeling taking place directly at the PGIS gene. PGIS mRNA expression was increased by both demethylation agents and histone deacetylase inhibitors. Protein levels were unaffected by demethylation agents, whereas PGIS protein stability was negatively affected by histone deacetylase inhibitors. PGIS protein expression is reduced in NSCLC, and does not correlate with overall patient survival. PGIS expression is regulated through epigenetic mechanisms. Differences in expression patterns between mRNA and protein levels suggest that PGIS expression and protein stability are regulated post-translationally. PGIS protein stability may have an important therapeutic role in NSCLC. Copyright © 2011 American Cancer Society.

Design, synthesis, and biological activity of second-generation synthetic oleanane triterpenoids.

PubMed

Fu, Liangfeng; Lin, Qi-Xian; Onyango, Evans O; Liby, Karen T; Sporn, Michael B; Gribble, Gordon W

2017-07-19

We report the synthesis and biological activity of C-24 demethyl CDDO-Me 2 and the C-28 amide derivatives 3 and 4, which are analogues of the anti-inflammatory synthetic triterpenoid bardoxolone methyl (CDDO-Me) 1. Demethylation of the C-24 methyl group was accomplished via "abnormal Beckmann" rearrangement and subsequent ring A reformation. Amides 3 and 4 were found to be potent inhibitors of the production of the inflammatory mediator NO in vitro.

CMTM5 exhibits tumor suppressor activity through promoter methylation in oral squamous cell carcinoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Heyu; Nan, Xu; Li, Xuefen

Highlights: • Down-regulation of CMTM5 expression in OSCC tissues was found. • The promoter methylation status of CMTM5 was measured. • CMTM5-v1 inhibited cell proliferation and migration and induced apoptosis. • CMTM5 might act as a putative tumor suppressor gene in OSCC. - Abstract: Oral squamous cell carcinoma (OSCC) is one of the most common types of malignancies in the head and neck region. CKLF-like MARVEL transmembrane domain-containing member 5 (CMTM5) has been recently implicated as a tumor suppressor gene in several cancer types. Herein, we examined the expression and function of CMTM5 in oral squamous cell carcinoma. CMTM5 wasmore » down-regulated in oral squamous cell lines and tumor samples from patients with promoter methylation. Treatment with the demethylating agent 5-aza-2′-deoxycytidine restored CMTM5 expression. In the OSCC cell lines CAL27 and GNM, the ectopic expression of CMTM5-v1 strongly inhibited cell proliferation and migration and induced apoptosis. In addition, CMTM5-v1 inhibited tumor formation in vivo. Therefore, CMTM5 might act as a putative tumor suppressor gene through promoter methylation in oral squamous cell carcinoma.« less

Method for recovering and using lignin in adhesive resins by extracting demethylated lignin

DOEpatents

Schroeder, Herbert A.

1991-01-01

Lignin, or a lignin derived material, which has been significantly demethylated (e.g., the demethylated lignin found in the raffinate produced as a by-product of dimethyl sulfide production which can be carried out using the spent liquor from wood pulping operations) can be isolated by a process wherein an organic solvent is added to a lignin-containing aqueous solution. The organic solvent is typically a polar, and at least a partially water-immiscible substance such as, for example, ethyl acetate. The resulting lignin-containing aqueous solution/organic solvent mixture is acidified to produce a water layer which is discarded and an organic solvent layer which contains the demethylated lignin. Upon its recovery, the demethylated lignin is preferably dried and stored until it is used (along with an alkali, an aldehyde and an adhesive filler) in compounding an adhesive of the type generally used in the manufacture of plywood.

Method for recovering and using lignin in adhesive resins by extracting demethylated lignin

DOEpatents

Schroeder, Herbert A.

1991-01-01

Lignin, or a lignin derived material, which has been significantly demethylated (e.g., the demethylated lignin found in the raffinate produced as a by-product of dimethyl sulfide production which can be carried out using the spent liquor from wood pulping operations) can be isolated by a process wherein an organic solvent is added to a lignin-containing aqueous solution. The organic solvent is typically a polar, and at least a partially water-immiscible substance such as, for example, ethyl acetate. The resulting lignin-containing aqueous solution/organic solvent mixture is acidified to produce a water layer which is discarded and an organic solvent layer which contains the demethylated lignin. Upon its recovery, the demethylated lignin is dissolved in an alkaline solution to which an aldehyde source is added to produce a resol-type resin. The aldehyde source may be formaldehyde in solution, paraformaldehyde, hexamethylenetetramine, or other aldehydes including acetaldehyde, furfural, and their derivatives.

Automated extraction of lysergic acid diethylamide (LSD) and N-demethyl-LSD from blood, serum, plasma, and urine samples using the Zymark RapidTrace with LC/MS/MS confirmation.

PubMed

de Kanel, J; Vickery, W E; Waldner, B; Monahan, R M; Diamond, F X

1998-05-01

A forensic procedure for the quantitative confirmation of lysergic acid diethylamide (LSD) and the qualitative confirmation of its metabolite, N-demethyl-LSD, in blood, serum, plasma, and urine samples is presented. The Zymark RapidTrace was used to perform fully automated solid-phase extractions of all specimen types. After extract evaporation, confirmations were performed using liquid chromatography (LC) followed by positive electrospray ionization (ESI+) mass spectrometry/mass spectrometry (MS/MS) without derivatization. Quantitation of LSD was accomplished using LSD-d3 as an internal standard. The limit of quantitation (LOQ) for LSD was 0.05 ng/mL. The limit of detection (LOD) for both LSD and N-demethyl-LSD was 0.025 ng/mL. The recovery of LSD was greater than 95% at levels of 0.1 ng/mL and 2.0 ng/mL. For LSD at 1.0 ng/mL, the within-run and between-run (different day) relative standard deviation (RSD) was 2.2% and 4.4%, respectively.

Sitosterol prevents obesity-related chronic inflammation.

PubMed

Kurano, Makoto; Hasegawa, Koji; Kunimi, Motoei; Hara, Masumi; Yatomi, Yutaka; Teramoto, Tamio; Tsukamoto, Kazuhisa

2018-02-01

The physiological roles of phytosterols in chronic inflammation, which are believed to be involved in the underlying mechanisms for metabolic diseases, have yet to be elucidated. Therefore, in the present study, we aimed to elucidate the physiological roles of phytosterols in both clinical studies and animal experiments. We observed the existence of rather specific negative correlations between the serum sitosterol level and the serum IL-6 and the TNF-α levels in both diabetic subjects (n=46) and non-diabetic subjects (n=178). Multiple regression analyses also revealed that the serum IL-6 and TNF-α levels exhibited strong negative correlations with the serum sitosterol levels. When ABCG5/8 KO mice with markedly elevated plasma sitosterol levels and ABCG5/8 hetero mice were fed a high-fat diet, we observed that the increase in body weight, the fatty liver changes, and the expansion of perigonadal adipose tissues were suppressed in ABCG5/8 KO mice without any modulation of food intake. We also observed that the plasma IL-6 and TNF-α levels, the expressions of TNF-α and PAI-1 in the liver and the expressions of the IL-6, TNF-α, and MCP-1 levels in the adipose tissue were lower in ABCG5/8 KO mice. These results suggest that sitosterol might suppress obesity-related chronic inflammation and might be applicable to the treatment of metabolic diseases. Copyright © 2017 Elsevier B.V. All rights reserved.

ABCG2 Polymorphism rs2231142 and hypothyroidism in metastatic renal cell carcinoma patients treated with sunitinib.

PubMed

Werbrouck, Emilie; Bastin, Julie; Lambrechts, Diether; Verbiest, Annelies; Van Brussel, Thomas; Lerut, Evelyne; Machiels, Jean-Pascal; Verschaeve, Vincent; Richard, Vincent; Debruyne, Philip R; Decallonne, Brigitte; Schöffski, Patrick; Bechter, Oliver; Wolter, Pascal; Beuselinck, Benoit

2018-05-23

Background and aim Vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR-TKIs) cause significant adverse events including thyroid dysfunction, mainly hypothyroidism, in a considerable proportion of patients. In a series of metastatic renal cell carcinoma (mRCC) patients treated with sunitinib, we aimed to study the correlation between hypothyroidism and single nucleotide polymorphisms (SNPs) in genes involved in sunitinib pharmacokinetics and pharmacodynamics. Patients and methods We included 79 mRCC patients who started sunitinib between November 2005 and March 2016. Serum thyroid function markers were collected at start and during sunitinib therapy. Germ-line DNA genotyping for 16 SNPs in 8 candidate genes was performed. Endpoints were time to increase in thyroid stimulating hormone (TSH) and time to decrease in T4 or free T4 (FT4) on day 1 and day 28 of each sunitinib cycle. Results Patients with the ABCG2 rs2231142 CC-genotype had a significantly longer time-to-TSH-increase on day 1 (11 vs. 5 cycles; p = 0.0011), and time-to-T4/FT4-decrease on day 1 (not reached vs. 10 cycles; p = 0.013) and day 28 (28 vs. 7 cycles; p = 0.03) compared to CA-carriers. Patients with the CYP3A5 rs776746 GG-genotype had a significantly longer time-to-TSH-increase at day 1 compared to GA-patients: 11 vs. 5 cycles (p = 0.0071). Significant associations were also found between PDGFRA rs35597368 and rs1800812 and time-to-TSH-increase at day 28. Conclusion Polymorphism rs2231142 in the efflux pump ABCG2 is associated with hypothyroidism in mRCC patients treated with sunitinib.

Rosuvastatin pharmacokinetics and pharmacogenetics in Caucasian and Asian subjects residing in the United States.

PubMed

Birmingham, Bruce K; Bujac, Sarah R; Elsby, Robert; Azumaya, Connie T; Zalikowski, Julie; Chen, Yusong; Kim, Kenneth; Ambrose, Helen J

2015-03-01

Systemic exposure to rosuvastatin in Asian subjects living in Japan or Singapore is approximately twice that observed in Caucasian subjects in Western countries or in Singapore. This study was conducted to determine whether pharmacokinetic differences exist among the most populous Asian subgroups and Caucasian subjects in the USA. Rosuvastatin pharmacokinetics was studied in Chinese, Filipino, Asian-Indian, Korean, Vietnamese, Japanese and Caucasian subjects residing in California. Plasma concentrations of rosuvastatin and metabolites after a single 20-mg dose were determined by mass spectrometric detection. The influence of polymorphisms in SLCO1B1 (T521>C [Val174Ala] and A388>G [Asn130Asp]) and in ABCG2 (C421>A [Gln141Lys]) on exposure to rosuvastatin was also assessed. The average rosuvastatin area under the curve from time zero to time of last quantifiable concentration was between 64 and 84 % higher, and maximum drug concentration was between 70 and 98 % higher in East Asian subgroups compared with Caucasians. Data for Asian-Indians was intermediate to these two ethnic groups at 26 and 29 %, respectively. Similar increases in exposure to N-desmethyl rosuvastatin and rosuvastatin lactone were observed. Rosuvastatin exposure was higher in subjects carrying the SLCO1B1 521C allele compared with that in non-carriers of this allele. Similarly, exposure was higher in subjects carrying the ABCG2 421A allele compared with that in non-carriers. Plasma exposure to rosuvastatin and its metabolites was significantly higher in Asian populations residing in the USA compared with Caucasian subjects living in the same environment. This study suggests that polymorphisms in the SLCO1B1 and ABCG2 genes contribute to the variability in rosuvastatin exposure.

Dietary fish oil regulates gene expression of cholesterol and bile acid transporters in mice.

PubMed

Kamisako, Toshinori; Tanaka, Yuji; Ikeda, Takanori; Yamamoto, Kazuo; Ogawa, Hiroshi

2012-03-01

  Fish oil rich in n-3 polyunsaturated fatty acids is known to affect hepatic lipid metabolism. Several studies have demonstrated that fish oil may affect the bile acid metabolism as well as lipid metabolism, whereas only scarce data are available. The aim of this study was to investigate the effect of fish oil on the gene expression of the transporters and enzymes related to bile acid as well as lipid metabolism in the liver and small intestine.   Seven-week old male C57BL/6 mice were fed diets enriched in 10% soybean oil or 10% fish oil for 4 weeks. After 4 weeks, blood, liver and small intestine were obtained.   Hepatic mRNA expression of lipids (Abcg5/8, multidrug resistance gene product 2) and bile acids transporters (bile salt export pump, multidrug resistance associated protein 2 and 3, organic solute transporter α) was induced in fish oil-fed mice. Hepatic Cyp8b1, Cyp27a1 and bile acid CoA : amino acid N-acyltransferase were increased in fish oil-fed mice compared with soybean-oil fed mice. Besides, intestinal cholesterol (Abcg5/8) and bile acid transporters (multidrug resistance associated protein 2 and organic solute transporter α) were induced in fish oil-fed mice.   Fish oil induced the expression of cholesterol and bile acid transporters not only in liver but in intestine. The upregulation of Abcg5/g8 by fish oil is caused by an increase in cellular 27-HOC through Cyp27a1 induction. The hepatic induction of bile acid synthesis through Cyp27a1 may upregulate expression of bile acid transporters in both organs. © 2012 The Japan Society of Hepatology.

Genetic and Dietary Regulation of Glyburide Efflux by the Human Placental Breast Cancer Resistance Protein Transporter

PubMed Central

Bircsak, Kristin M.; Gupta, Vivek; Yuen, Poi Yu Sofia; Gorczyca, Ludwik; Weinberger, Barry I.; Vetrano, Anna M.

2016-01-01

Glyburide is frequently used to treat gestational diabetes owing to its low fetal accumulation resulting from placental efflux by the breast cancer resistance protein (BCRP)/ABCG2 transporter. Here we sought to determine how exposure to the dietary phytoestrogen genistein and expression of a loss-of-function polymorphism in the ABCG2 gene (C421A) impacted the transport of glyburide by BCRP using stably transfected human embryonic kidney 293 (HEK) cells, human placental choriocarcinoma BeWo cells, and human placental explants. Genistein competitively inhibited the BCRP-mediated transport of 3H-glyburide in both wild-type (WT) and C421A-BCRP HEK-expressing cells, with greater accumulation of 3H-glyburide in cells expressing the C421A variant. In BeWo cells, exposure to genistein for 60 minutes increased the accumulation of 3H-glyburide 30%–70% at concentrations relevant to dietary exposure (IC50 ∼180 nM). Continuous exposure of BeWo cells to genistein for 48 hours reduced the expression of BCRP mRNA and protein by up to 40%, which impaired BCRP transport activity. Pharmacologic antagonism of the estrogen receptor attenuated the genistein-mediated downregulation of BCRP expression, suggesting that phytoestrogens may reduce BCRP levels through this hormone receptor pathway in BeWo cells. Interestingly, genistein treatment for 48 hours did not alter BCRP protein expression in explants dissected from healthy term placentas. These data suggest that whereas genistein can act as a competitive inhibitor of BCRP-mediated transport, its ability to downregulate placental BCRP expression may only occur in choriocarcinoma cells. Overall, this research provides important mechanistic data regarding how the environment (dietary genistein) and a frequent genetic variant (ABCG2, C421A) may alter the maternal-fetal disposition of glyburide. PMID:26850786

Effect of ursodeoxycholic acid treatment on the altered progesterone and bile acid homeostasis in the mother-placenta-foetus trio during cholestasis of pregnancy

PubMed Central

Estiú, Maria C; Monte, Maria J; Rivas, Laura; Moirón, Maria; Gomez-Rodriguez, Laura; Rodriguez-Bravo, Tomas; Marin, Jose JG; Macias, Rocio IR

2015-01-01

Aim Intrahepatic cholestasis of pregnancy (ICP) is characterized by pruritus and elevated bile acid concentrations in maternal serum. This is accompanied by an enhanced risk of intra-uterine and perinatal complications. High concentrations of sulphated progesterone metabolites (PMS) have been suggested to be involved in the multifactorial aetiopathogenesis of ICP. The aim of this study was to investigate further the mechanism accounting for the beneficial effect of oral administration of ursodeoxycholic acid (UDCA), which is the standard treatment, regarding bile acid and PMS homeostasis in the mother-placenta-foetus trio. Method Using HPLC-MS/MS bile acids and PMS were determined in maternal and foetal serum and placenta. The expression of ABC proteins in placenta was determined by real time quantitative PCR (RT-QPCR) and immunofluorescence. Results In ICP, markedly increased concentrations of bile acids (tauroconjugates > glycoconjugates >> unconjugated), progesterone and PMS in placenta and maternal serum were accompanied by enhanced concentrations in foetal serum of bile acids, but not of PMS. UDCA treatment reduced bile acid accumulation in the mother-placenta-foetus trio, but had no significant effect on progesterone and PMS concentrations. ABCG2 mRNA abundance was increased in placentas from ICP patients vs. controls and remained stable following UDCA treatment, despite an apparent further increase in ABCG2. Conclusion UDCA administration partially reduces ICP-induced bile acid accumulation in mothers and foetuses despite the lack of effect on concentrations of progesterone and PMS in maternal serum. Up-regulation of placental ABCG2 may play an important role in protecting the foetus from high concentrations of bile acids and PMS during ICP. PMID:25099365

Effect of ursodeoxycholic acid treatment on the altered progesterone and bile acid homeostasis in the mother-placenta-foetus trio during cholestasis of pregnancy.

PubMed

Estiú, Maria C; Monte, Maria J; Rivas, Laura; Moirón, Maria; Gomez-Rodriguez, Laura; Rodriguez-Bravo, Tomas; Marin, Jose J G; Macias, Rocio I R

2015-02-01

Intrahepatic cholestasis of pregnancy (ICP) is characterized by pruritus and elevated bile acid concentrations in maternal serum. This is accompanied by an enhanced risk of intra-uterine and perinatal complications. High concentrations of sulphated progesterone metabolites (PMS) have been suggested to be involved in the multifactorial aetiopathogenesis of ICP. The aim of this study was to investigate further the mechanism accounting for the beneficial effect of oral administration of ursodeoxycholic acid (UDCA), which is the standard treatment, regarding bile acid and PMS homeostasis in the mother-placenta-foetus trio. Using HPLC-MS/MS bile acids and PMS were determined in maternal and foetal serum and placenta. The expression of ABC proteins in placenta was determined by real time quantitative PCR (RT-QPCR) and immunofluorescence. In ICP, markedly increased concentrations of bile acids (tauroconjugates > glycoconjugates > unconjugated), progesterone and PMS in placenta and maternal serum were accompanied by enhanced concentrations in foetal serum of bile acids, but not of PMS. UDCA treatment reduced bile acid accumulation in the mother-placenta-foetus trio, but had no significant effect on progesterone and PMS concentrations. ABCG2 mRNA abundance was increased in placentas from ICP patients vs. controls and remained stable following UDCA treatment, despite an apparent further increase in ABCG2. UDCA administration partially reduces ICP-induced bile acid accumulation in mothers and foetuses despite the lack of effect on concentrations of progesterone and PMS in maternal serum. Up-regulation of placental ABCG2 may play an important role in protecting the foetus from high concentrations of bile acids and PMS during ICP. © 2014 The British Pharmacological Society.

Andrographolide Inhibits Oxidized LDL-Induced Cholesterol Accumulation and Foam Cell Formation in Macrophages.

PubMed

Lin, Hung-Chih; Lii, Chong-Kuei; Chen, Hui-Chun; Lin, Ai-Hsuan; Yang, Ya-Chen; Chen, Haw-Wen

2018-01-01

oxLDL is involved in the pathogenesis of atherosclerotic lesions through cholesterol accumulation in macrophage foam cells. Andrographolide, the bioactive component of Andrographis paniculata, possesses several biological activities such as anti-inflammatory, anti-oxidant, and anticancer functions. Scavenger receptors (SRs), including class A SR (SR-A) and CD36, are responsible for the internalization of oxLDL. In contrast, receptors for reverse cholesterol transport, including ABCA1 and ABCG1, mediate the efflux of cholesterol from macrophage foam cells. Transcription factor liver X receptor [Formula: see text] (LXR[Formula: see text] plays a key role in lipid metabolism and inflammation as well as in the regulation of ABCA1 and ABCG1 expression. Because of the contribution of inflammation to macrophage foam cell formation and the potent anti-inflammatory activity of andrographolide, we hypothesized that andrographolide might inhibit oxLDL-induced macrophage foam cell formation. The results showed that andrographolide reduced oxLDL-induced lipid accumulation in macrophage foam cells. Andrographolide decreased the mRNA and protein expression of CD36 by inducing the degradation of CD36 mRNA; however, andrographolide had no effect on SR-A expression. In contrast, andrographolide increased the mRNA and protein expression of ABCA1 and ABCG1, which were dependent on LXR[Formula: see text]. Andrographolide enhanced LXR[Formula: see text] nuclear translocation and DNA binding activity. Treatment with the LXR[Formula: see text] antagonist GGPP and transfection with LXR[Formula: see text] siRNA reversed the ability of andrographolide to stimulate ABCA1 and ABCG1 protein expression. In conclusion, inhibition of CD36-mediated oxLDL uptake and induction of ABCA1- and ABCG1-dependent cholesterol efflux are two working mechanisms by which andrographolide inhibits macrophage foam cell formation, which suggests that andrographolide could be a potential candidate to prevent atherosclerosis.

Gene Expression in Single Cells Isolated from the CWR-R1 Prostate Cancer Cell Line and Human Prostate Tissue Based on the Side Population Phenotype.

PubMed

Gangavarapu, Kalyan J; Miller, Austin; Huss, Wendy J

2016-09-01

Defining biological signals at the single cell level can identify cancer initiating driver mutations. Techniques to isolate single cells such as microfluidics sorting and magnetic capturing systems have limitations such as: high cost, labor intense, and the requirement of a large number of cells. Therefore, the goal of our current study is to identify a cost and labor effective, reliable, and reproducible technique that allows single cell isolation for analysis to promote regular laboratory use, including standard reverse transcription PCR (RT-PCR). In the current study, we utilized single prostate cells isolated from the CWR-R1 prostate cancer cell line and human prostate clinical specimens, based on the ATP binding cassette (ABC) transporter efflux of dye cycle violet (DCV), side population assay. Expression of four genes: ABCG2; Aldehyde dehydrogenase1A1 (ALDH1A1); androgen receptor (AR); and embryonic stem cell marker, Oct-4, were determined. Results from the current study in the CWR-R1 cell line showed ABCG2 and ALDH1A1 gene expression in 67% of single side population cells and in 17% or 100% of non-side population cells respectively. Studies using single cells isolated from clinical specimens showed that the Oct-4 gene is detected in only 22% of single side population cells and in 78% of single non-side population cells. Whereas, AR gene expression is in 100% single side population and non-side population cells isolated from the same human prostate clinical specimen. These studies show that performing RT-PCR on single cells isolated by FACS can be successfully conducted to determine gene expression in single cells from cell lines and enzymatically digested tissue. While these studies provide a simple yes/no expression readout, the more sensitive quantitative RT-PCR would be able to provide even more information if necessary.

Gene Expression in Single Cells Isolated from the CWR-R1 Prostate Cancer Cell Line and Human Prostate Tissue Based on the Side Population Phenotype

PubMed Central

Gangavarapu, Kalyan J; Miller, Austin; Huss, Wendy J

2016-01-01

Defining biological signals at the single cell level can identify cancer initiating driver mutations. Techniques to isolate single cells such as microfluidics sorting and magnetic capturing systems have limitations such as: high cost, labor intense, and the requirement of a large number of cells. Therefore, the goal of our current study is to identify a cost and labor effective, reliable, and reproducible technique that allows single cell isolation for analysis to promote regular laboratory use, including standard reverse transcription PCR (RT-PCR). In the current study, we utilized single prostate cells isolated from the CWR-R1 prostate cancer cell line and human prostate clinical specimens, based on the ATP binding cassette (ABC) transporter efflux of dye cycle violet (DCV), side population assay. Expression of four genes: ABCG2; Aldehyde dehydrogenase1A1 (ALDH1A1); androgen receptor (AR); and embryonic stem cell marker, Oct-4, were determined. Results from the current study in the CWR-R1 cell line showed ABCG2 and ALDH1A1 gene expression in 67% of single side population cells and in 17% or 100% of non-side population cells respectively. Studies using single cells isolated from clinical specimens showed that the Oct-4 gene is detected in only 22% of single side population cells and in 78% of single non-side population cells. Whereas, AR gene expression is in 100% single side population and non-side population cells isolated from the same human prostate clinical specimen. These studies show that performing RT-PCR on single cells isolated by FACS can be successfully conducted to determine gene expression in single cells from cell lines and enzymatically digested tissue. While these studies provide a simple yes/no expression readout, the more sensitive quantitative RT-PCR would be able to provide even more information if necessary. PMID:27785389

Stable knockdown of PASG enhances DNA demethylation but does not accelerate cellular senescence in TIG-7 human fibroblasts

PubMed Central

Suzuki, Toshikazu; Farrar, Jason E.; Yegnasubramanian, Srinivasan; Zahed, Muhammed; Suzuki, Nobuo; Arceci, Robert J.

2009-01-01

Demethylation of 5-methylcytosine in genomic DNA is believed to be one of the mechanisms underlying replicative life-span of mammalian cells. Both proliferation associated SNF2-like gene (PASG, also termed Lsh) and DNA methyltransferase 3B (Dnmt3b) knockout mice result in embryonic genomic hypomethylation and a replicative senescent phenotype. However, it is unclear whether gradual demethylation of DNA during somatic cell division is directly involved in senescence. In this study, we retrovirally transduced TIG-7 human fibroblasts with a shRNA against PASG and compared the rate of change in DNA methylation as well as the replicative life-span to control cells under low (3%) and ambient (20%) oxygen. Expression of PASG protein was decreased by approximately 80% compared to control cells following transduction of PASG shRNA gene. The rate of cell growth was the same in both control and PASG-suppressed cells. The rate of demethylation of DNA was significantly increased in PASG-suppressed cells as compared control cells. However, decreased PASG expression did not shorten the replicative life-span of TIG-7 cells. Culture under low oxygen extended the life-span of TIG-7 cells but did not alter the rate of DNA demethylation. While knockout of PASG during development results in genomic hypomethylation and premature senescence, our results show that while downregulation of PASG expression in a somatic cell also leads to DNA hypomethylation, there is no associated senescent phenotype. These results suggest differences in cellular consequences of hypomethylation mediated by PASG during development compared to that in somatic cells. PMID:18948754

Stable knockdown of PASG enhances DNA demethylation but does not accelerate cellular senescence in TIG-7 human fibroblasts.

PubMed

Suzuki, Toshikazu; Farrar, Jason E; Yegnasubramanian, Srinivasan; Zahed, Muhammed; Suzuki, Nobuo; Arceci, Robert J

2008-09-01

Demethylation of 5-methylcytosine in genomic DNA is believed to be one of the mechanisms underlying replicative life-span of mammalian cells. Both proliferation associated SNF2-like gene (PASG, also termed Lsh) and DNA methyltransferase 3B (Dnmt3b) knockout mice result in embryonic genomic hypomethylation and a replicative senescent phenotype. However, it is unclear whether gradual demethylation of DNA during somatic cell division is directly involved in senescence. In this study, we retrovirally transduced TIG-7 human fibroblasts with a shRNA against PASG and compared the rate of change in DNA methylation as well as the replicative life-span to control cells under low (3%) and ambient (20%) oxygen. Expression of PASG protein was decreased by approximately 80% compared to control cells following transduction of PASG shRNA gene. The rate of cell growth was the same in both control and PASG-suppressed cells. The rate of demethylation of DNA was significantly increased in PASG-suppressed cells as compared control cells. However, decreased PASG expression did not shorten the replicative life-span of TIG-7 cells. Culture under low oxygen extended the life-span of TIG-7 cells but did not alter the rate of DNA demethylation. While knockout of PASG during development results in genomic hypomethylation and premature senescence, our results show that while downregulation of PASG expression in a somatic cell also leads to DNA hypomethylation, there is no associated senescent phenotype. These results suggest differences in cellular consequences of hypomethylation mediated by PASG during development compared to that in somatic cells.

The genetics of gout: towards personalised medicine?

PubMed

Dalbeth, Nicola; Stamp, Lisa K; Merriman, Tony R

2017-05-31

Over the last decade, there have been major advances in the understanding of the genetic basis of hyperuricaemia and gout as well as of the pharmacogenetics of urate-lowering therapy. Key findings include the reporting of 28 urate-associated loci, the discovery that ABCG2 plays a central role on extra-renal uric acid excretion, the identification of genes associated with development of gout in the context of hyperuricaemia, recognition that ABCG2 variants influence allopurinol response, and the impact of HLA-B*5801 testing in reducing the prevalence of allopurinol hypersensitivity in high-risk populations. These advances, together with the reducing cost of whole genome sequencing, mean that integrated personalised medicine approaches may soon be possible in clinical practice. Genetic data may inform assessment of disease prognosis in individuals with hyperuricaemia or established gout, personalised lifestyle advice, selection and dosing of urate-lowering therapy, and prevention of serious medication adverse effects. In this article, we summarise the discoveries from genome-wide association studies and discuss the potential for translation of these findings into clinical practice.

Human adipose tissue-derived mesenchymal stem cells differentiate into insulin, somatostatin, and glucagon expressing cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Timper, Katharina; Seboek, Dalma; Eberhardt, Michael

2006-03-24

Mesenchymal stem cells (MSC) from mouse bone marrow were shown to adopt a pancreatic endocrine phenotype in vitro and to reverse diabetes in an animal model. MSC from human bone marrow and adipose tissue represent very similar cell populations with comparable phenotypes. Adipose tissue is abundant and easily accessible and could thus also harbor cells with the potential to differentiate in insulin producing cells. We isolated human adipose tissue-derived MSC from four healthy donors. During the proliferation period, the cells expressed the stem cell markers nestin, ABCG2, SCF, Thy-1 as well as the pancreatic endocrine transcription factor Isl-1. The cellsmore » were induced to differentiate into a pancreatic endocrine phenotype by defined culture conditions within 3 days. Using quantitative PCR a down-regulation of ABCG2 and up-regulation of pancreatic developmental transcription factors Isl-1, Ipf-1, and Ngn3 were observed together with induction of the islet hormones insulin, glucagon, and somatostatin.« less

Redistribution of demethylated RNA helicase A during foot-and-mouth disease virus infection: role of jumonji C-domain containing protein 6 in RHA demethylation

USDA-ARS?s Scientific Manuscript database

We previously reported that RNA Helicase A (RHA) re-localized from the nucleus to the cytoplasm in foot-and-mouth disease virus (FMDV) infected cells, coincident with a reduction in methylation of arginine residues in the RHA C-terminus. To further define the mechanism of RHA demethylation in FMDV-...

Mercury methylation and demethylation in Hg-contaminated lagoon sediments (Marano and Grado Lagoon, Italy)

NASA Astrophysics Data System (ADS)

Hines, Mark E.; Poitras, Erin N.; Covelli, Stefano; Faganeli, Jadran; Emili, Andrea; Žižek, Suzana; Horvat, Milena

2012-11-01

Mercury (Hg) transformation activities and sulfate (SO42-) reduction were studied in sediments of the Marano and Grado Lagoons in the Northern Adriatic Sea region as part of the "MIRACLE" project. The lagoons, which are sites of clam (Tapes philippinarum) farming, have been receiving excess Hg from the Isonzo River for centuries. Marano Lagoon is also contaminated from a chlor-alkali plant. Radiotracer methods were used to measure mercury methylation (230Hg, 197Hg), methylmercury (MeHg) demethylation (14C-MeHg) and SO42- reduction (35S) in sediment cores collected in autumn, winter and summer. Mercury methylation rate constants ranged from near zero to 0.054 day-1, generally decreased with depth, and were highest in summer. Demethylation rate constants were much higher than methylation reaching values of ˜0.6 day-1 in summer. Demethylation occurred via the oxidative pathway, except in winter when the reductive pathway increased in importance in surficial sediments. Sulfate reduction was also most active in summer (up to 1600 nmol mL-1 day-1) and depth profiles reflected seasonally changing redox conditions near the surface. Methylation and demethylation rate constants correlated positively with SO42- reduction and pore-water Hg concentrations, and inversely with Hg sediment-water partition coefficients indicating the importance of SO42- reduction and Hg dissolution on Hg cycling. Hg transformation rates were calculated using rate constants and concentrations of Hg species. In laboratory experiments, methylation was inhibited by amendments of the SO42--reduction inhibitor molybdate and by nitrate. Lagoon sediments displayed a dynamic seasonal cycle in which Hg dissolution in spring/summer stimulated Hg methylation, which was followed by a net loss of MeHg in autumn from demethylation. Sulfate-reducing bacteria (SRB) tended to be responsible for methylation of Hg and the oxidative demethylation of MeHg. However, during winter in surficial sediments, iron-reducing bacteria seemed to contribute to methylation and Hg-resistant bacteria increased in importance in the reductive demethylation of MeHg. The high rates of MeHg demethylation in lagoon sediments may diminish the accumulation of MeHg.

The left end of rat L1 (L1Rn, long interspersed repeated) DNA which is a CpG island can function as a promoter.

PubMed Central

Nur, I; Pascale, E; Furano, A V

1988-01-01

Here we report that the 600 bp promoter-like region at the left end of a newly isolated and characterized rat L1 DNA element can activate the prokaryotic chloramphenicol acyltransferase gene in a rat cell line. Activation only occurs when the promoter region is oriented to the transferase gene as it is to the L1 protein encoding sequences and is 75% inhibited by methylation of just 5 of the 22 CpGs present in the promoter. The G + C rich promoter contains enough CpGs to qualify it as a CpG island, but in contrast to other CpG islands, genomic L1 promoters are fully methylated in both somatic cell and sperm DNA as judged by restriction enzyme analysis. Partial demethylation of the genomic promoters by treatment with 5-azacytidine failed to produce discrete L1 transcripts. The relationship of methylation to the evolutionary history and fate of the rat L1 promoter is discussed. Images PMID:2459662

Developmental modulation of DNA methylation in the fungus Phycomyces blakesleeanus.

PubMed Central

Antequera, F; Tamame, M; Vilanueva, J R; Santos, T

1985-01-01

DNA methylation is a rather sparse event among fungi. Phycomyces blakesleeanus seems to be one of the few exceptions in this context. 5-Methylcytosine represents 2.9% of the total cytosine in spore DNA and is located in approximately the same amount at any of the four CA, CT, CC or CG dinucleotides. A progressive and gradual drop in total 5-methylcytosine parallels the development of the fungus. This demethylation is non random but sequence specific and is not accounted for equally by the four different methylated dinucleotides, CG being much less affected (20% demethylated) than CA, CT and CC (more than 90% demethylated at the same time). "De novo" methylation to restore the initial pattern probably takes place during spore maturation. By using specific hybridization probes we have been able to show that the rRNA genes are not significantly methylated at any stage of development, regardless of their transcription status. Images PMID:2997714

Zebrafish AID is capable of deaminating methylated deoxycytidines

PubMed Central

Abdouni, Hala; King, Justin J.; Suliman, Mussa; Quinlan, Matthew; Fifield, Heather; Larijani, Mani

2013-01-01

Activation-induced cytidine deaminase (AID) deaminates deoxycytidine (dC) to deoxyuracil (dU) at immunoglobulin loci in B lymphocytes to mediate secondary antibody diversification. Recently, AID has been proposed to also mediate epigenetic reprogramming by demethylating methylated cytidines (mC) possibly through deamination. AID overexpression in zebrafish embryos was shown to promote genome demethylation through G:T lesions, implicating a deamination-dependent mechanism. We and others have previously shown that mC is a poor substrate for human AID. Here, we examined the ability of bony fish AID to deaminate mC. We report that zebrafish AID was unique among all orthologs in that it efficiently deaminates mC. Analysis of domain-swapped and mutant AID revealed that mC specificity is independent of the overall high-catalytic efficiency of zebrafish AID. Structural modeling with or without bound DNA suggests that efficient deamination of mC by zebrafish AID is likely not due to a larger catalytic pocket allowing for better fit of mC, but rather because of subtle differences in the flexibility of its structure. PMID:23585279

Identification of estrogen-responsive genes using a genome-wide analysis of promoter elements for transcription factor binding sites.

PubMed

Kamalakaran, Sitharthan; Radhakrishnan, Senthil K; Beck, William T

2005-06-03

We developed a pipeline to identify novel genes regulated by the steroid hormone-dependent transcription factor, estrogen receptor, through a systematic analysis of upstream regions of all human and mouse genes. We built a data base of putative promoter regions for 23,077 human and 19,984 mouse transcripts from National Center for Biotechnology Information annotation and 8793 human and 6785 mouse promoters from the Data Base of Transcriptional Start Sites. We used this data base of putative promoters to identify potential targets of estrogen receptor by identifying estrogen response elements (EREs) in their promoters. Our program correctly identified EREs in genes known to be regulated by estrogen in addition to several new genes whose putative promoters contained EREs. We validated six genes (KIAA1243, NRIP1, MADH9, NME3, TPD52L, and ABCG2) to be estrogen-responsive in MCF7 cells using reverse transcription PCR. To allow for extensibility of our program in identifying targets of other transcription factors, we have built a Web interface to access our data base and programs. Our Web-based program for Promoter Analysis of Genome, PAGen@UIC, allows a user to identify putative target genes for vertebrate transcription factors through the analysis of their upstream sequences. The interface allows the user to search the human and mouse promoter data bases for potential target genes containing one or more listed transcription factor binding sites (TFBSs) in their upstream elements, using either regular expression-based consensus or position weight matrices. The data base can also be searched for promoters harboring user-defined TFBSs given as a consensus or a position weight matrix. Furthermore, the user can retrieve putative promoter sequences for any given gene together with identified TFBSs located on its promoter. Orthologous promoters are also analyzed to determine conserved elements.

Inhibitors of histone demethylation and histone deacetylation cooperate in regulating gene expression and inhibiting growth in human breast cancer cells

PubMed Central

Vasilatos, Shauna N.; Boric, Lamia; Shaw, Patrick G.; Davidson, Nancy E.

2013-01-01

Abnormal activities of histone lysine demethylases (KDMs) and lysine deacetylases (HDACs) are associated with aberrant gene expression in breast cancer development. However, the precise molecular mechanisms underlying the crosstalk between KDMs and HDACs in chromatin remodeling and regulation of gene transcription are still elusive. In this study, we showed that treatment of human breast cancer cells with inhibitors targeting the zinc cofactor dependent class I/II HDAC, but not NAD+ dependent class III HDAC, led to significant increase of H3K4me2 which is a specific substrate of histone lysine-specific demethylase 1 (LSD1) and a key chromatin mark promoting transcriptional activation. We also demonstrated that inhibition of LSD1 activity by a pharmacological inhibitor, pargyline, or siRNA resulted in increased acetylation of H3K9 (AcH3K9). However, siRNA knockdown of LSD2, a homolog of LSD1, failed to alter the level of AcH3K9, suggesting that LSD2 activity may not be functionally connected with HDAC activity. Combined treatment with LSD1 and HDAC inhibitors resulted in enhanced levels of H3K4me2 and AcH3K9, and exhibited synergistic growth inhibition of breast cancer cells. Finally, microarray screening identified a unique subset of genes whose expression was significantly changed by combination treatment with inhibitors of LSD1 and HDAC. Our study suggests that LSD1 intimately interacts with histone deacetylases in human breast cancer cells. Inhibition of histone demethylation and deacetylation exhibits cooperation and synergy in regulating gene expression and growth inhibition, and may represent a promising and novel approach for epigenetic therapy of breast cancer. PMID:21452019

A DNA 3′-phosphatase functions in active DNA demethylation in Arabidopsis

PubMed Central

Martínez-Macías, María Isabel; Qian, Weiqiang; Miki, Daisuke; Pontes, Olga; Liu, Yunhua; Tang, Kai; Liu, Renyi; Morales-Ruiz, Teresa; Ariza, Rafael R.; Roldán-Arjona, Teresa; Zhu, Jian-Kang

2012-01-01

SUMMARY DNA methylation is an important epigenetic mark established by the combined actions of methylation and demethylation reactions. Plants use a base excision repair pathway for active DNA demethylation. After 5-methylcytosine removal, the Arabidopsis DNA glycosylase/lyase ROS1 incises the DNA backbone and part of the product has a single-nucleotide gap flanked by 3′- and 5′-phosphate termini. Here we show that the DNA phosphatase ZDP removes the blocking 3′-phosphate, allowing subsequent DNA polymerization and ligation steps needed to complete the repair reactions. ZDP and ROS1 interact in vitro and co-localize in vivo in nucleoplasmic foci. Extracts from zdp mutant plants are unable to complete DNA demethylation in vitro, and the mutations cause DNA hypermethylation and transcriptional silencing of a reporter gene. Genome-wide methylation analysis in zdp mutant plants identified hundreds of hypermethylated endogenous loci. Our results show that ZDP functions downstream of ROS1 in one branch of the active DNA demethylation pathway. PMID:22325353

PCFT/SLC46A1 promoter methylation and restoration of gene expression in human leukemia cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonen, Nitzan; Bram, Eran E.; Assaraf, Yehuda G.

2008-11-28

The proton-coupled folate transporter (PCFT/SLC46A1) displays optimal and prominent folate and antifolate transport activity at acidic pH in human carcinoma cells but poor activity in leukemia cells. Consistently herein, human leukemia cell lines expressed poor PCFT transcript levels, whereas various carcinoma cell lines showed substantial PCFT gene expression. We identified a CpG island with high density at nucleotides -200 through +100 and explored its role in PCFT promoter silencing. Leukemia cells with barely detectable PCFT transcripts consistently harbored 85-100% methylation of this CpG island, whereas no methylation was found in carcinoma cells. Treatment with 5-Aza-2'-deoxycytidine which induced demethylation but notmore » with the histone deacetylase inhibitor trichostatin A, restored 50-fold PCFT expression only in leukemia cells. These findings constitute the first demonstration of the dominant epigenetic silencing of the PCFT gene in leukemia cells. The potential translational implications of the restoration of PCFT expression in chemotherapy of leukemia are discussed.« less

Enzyme induction in neonates after fetal exposure to antiepileptic drugs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rating, D.; Jaeger-Roman, E.; Nau, H.

1983-01-01

The /sup 13/C-AP breath test is shown to be a convenient, noninvasive method to monitor velocity and capacity of P450-dependent AP N-demethylation in infancy and childhood. According to /sup 13/C-AP breath tests, neonates have a very low capacity to eliminate /sup 13/CO/sub 2/, which is only 15 to 21% of the activity in adults. During the first year of life AP N-demethylation increases to reach its maximum at about 2 years; afterwards a slight decrease occurs. In 25 neonates exposed prenatally to different antiepileptic drugs /sup 13/C-AP breath test was efficiently used to prove that cytochrome AP N-demethylation was considerablymore » stimulated. After primidone/phenobarbitone, especially in combination with phenytoin, /sup 13/C elimination reaches and even surpasses the range for older children. Valproate exposure during fetal life is not consistently followed by a significant increase in AP N-demethylation. The enzyme induction demonstrated by /sup 13/C-AP breath test was often accompanied by accelerated metabolic clearance and shortened half-life times of transplacentally acquired antiepileptic drugs. There was good agreement between /sup 13/C-AP breath tests and pharmacokinetic data for primidone/phenobarbitone but not for phenytoin. In contrast, in the case of phenytoin exposure during pregnancy the pharmacokinetic parameters and the /sup 13/C breath test data will transport very different informations about enzyme induction in these neonates.« less

Anaerobic Mercury Methylation and Demethylation by Geobacter bemidjiensis Bem

DOE PAGES

Lu, Xia; Liu, Yurong; Johs, Alexander; ...

2016-03-28

Two competing processes controlling the net production and bioaccumulation of neurotoxic methylmercury (MeHg) in natural ecosystems are microbial methylation and demethylation. Though mercury (Hg) methylation by anaerobic microorganisms and demethylation by aerobic Hg-resistant bacteria have both been extensively studied, little attention has been given to MeHg degradation by anaerobic bacteria, particularly the iron-reducing bacterium Geobacter bemidjensis Bem. Here we report, for the first time, that the strain G. bemidjensis Bem can methylate inorganic Hg and degrade MeHg concurrently under anoxic conditions. Our results suggest that G. bemidjensis cells utilize a reductive demethylation pathway to degrade MeHg, with elemental Hg(0) asmore » the major reaction product, possibly due to the presence of homologs encoding both organo-mercurial lyase (MerB) and mercuric reductase (MerA) in this organism. In addition, the cells can mediate multiple reactions including Hg/MeHg sorption, Hg reduction and oxidation, resulting in both time and concentration dependent Hg species transformations. Moderate concentrations (10 500 M) of Hg-binding ligands such as cysteine enhance Hg(II) methylation but inhibit MeHg degradation. These findings indicate a cycle of methylation and demethylation among anaerobic bacteria and suggest that mer-mediated demethylation may play a role in the net balance of MeHg production in anoxic water and sediments.« less

DS-8201a, a new HER2-targeting antibody-drug conjugate incorporating a novel DNA topoisomerase I inhibitor, overcomes HER2-positive gastric cancer T-DM1 resistance.

PubMed

Takegawa, Naoki; Nonagase, Yoshikane; Yonesaka, Kimio; Sakai, Kazuko; Maenishi, Osamu; Ogitani, Yusuke; Tamura, Takao; Nishio, Kazuto; Nakagawa, Kazuhiko; Tsurutani, Junji

2017-10-15

Anti-HER2 therapies are beneficial for patients with HER2-positive breast or gastric cancer. T-DM1 is a HER2-targeting antibody-drug conjugate (ADC) comprising the antibody trastuzumab, a linker, and the tubulin inhibitor DM1. Although effective in treating advanced breast cancer, all patients eventually develop T-DM1 resistance. DS-8201a is a new ADC incorporating an anti-HER2 antibody, a newly developed, enzymatically cleavable peptide linker, and a novel, potent, exatecan-derivative topoisomerase I inhibitor (DXd). DS-8201a has a drug-to-antibody-ratio (DAR) of 8, which is higher than that of T-DM1 (3.5). Owing to these unique characteristics and unlike T-DM1, DS-8201a is effective against cancers with low-HER2 expression. In the present work, T-DM1-resistant cells (N87-TDMR), established using the HER2-positive gastric cancer line NCI-N87 and continuous T-DM1 exposure, were shown to be susceptible to DS-8201a. The ATP-binding cassette (ABC) transporters ABCC2 and ABCG2 were upregulated in N87-TDMR cells, but HER2 overexpression was retained. Furthermore, inhibition of ABCC2 and ABCG2 by MK571 restored T-DM1 sensitivity. Therefore, resistance to T-DM1 is caused by efflux of its payload DM1, due to aberrant expression of ABC transporters. In contrast to DM1, DXd payload of DS-8201a inhibited the growth of N87-TDMR cells in vitro. This suggests that either DXd may be a poor substrate of ABCC2 and ABCG2 in comparison to DM1, or the high DAR of DS-8201a relative to T-DM1 compensates for increased efflux. Notably, N87-TDMR xenograft tumor growth was prevented by DS-8201a. In conclusion, the efficacy of DS-8201a as a treatment for patients with T-DM1-resistant breast or gastric cancer merits investigation. © 2017 UICC.

Clinical and biological effects of demethylating agents on solid tumours - A systematic review.

PubMed

Linnekamp, J F; Butter, R; Spijker, R; Medema, J P; van Laarhoven, H W M

2017-03-01

It is assumed that DNA methylation plays a key role in both tumour development and therapy resistance. Demethylating agents have been shown to be effective in the treatment of haematological malignancies. Based on encouraging preclinical results, demethylating agents may also be effective in solid tumours. This systematic review summarizes the evidence of the effect of demethylating agents on clinical response, methylation and the immune system in solid tumours. We conducted a systematic literature search from 1949 to December 2016, according to the PRISMA guidelines. Studies which evaluated treatment with azacitidine, decitabine, guadecitabine, hydralazine, procaine, MG98 and/or zebularine in patients with solid tumours were included. Data on clinical response, effects on methylation and immune response were extracted. Fifty-eight studies were included: in 13 studies complete responses (CR) were observed, 35 studies showed partial responses (PR), 47 studies stable disease (SD) and all studies except two showed progressive disease (PD). Effects on global methylation were observed in 11/15 studies and demethylation/re-expression of tumour specific genes was seen in 15/17 studies. No clear correlation between (de)methylation and clinical response was observed. In 14 studies immune-related responses were reported, such as re-expression of cancer-testis antigens and upregulation of interferon genes. Demethylating agents are able to improve clinical outcome and alter methylation status in patients with solid tumours. Although beneficial effect has been shown in individual patients, overall response is limited. Further research on biomarker predicting therapy efficacy is indicated, particularly in earlier stage and highly methylated tumours. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Hypocholesterolemic Properties and Prebiotic Effects of Mexican Ganoderma lucidum in C57BL/6 Mice.

PubMed

Meneses, María E; Martínez-Carrera, Daniel; Torres, Nimbe; Sánchez-Tapia, Mónica; Aguilar-López, Miriam; Morales, Porfirio; Sobal, Mercedes; Bernabé, Teodoro; Escudero, Helios; Granados-Portillo, Omar; Tovar, Armando R

2016-01-01

Edible and medicinal mushrooms contain bioactive compounds with promising effects on several cardiovascular risk biomarkers. However, strains of Ganoderma lucidum of Mexican origin have not yet been studied. Standardized extracts of G. lucidum (Gl) were given to C57BL/6 mice fed a high-cholesterol diet compared with the drug simvastatin. The effects of the extracts on serum biochemical parameters, liver lipid content, cholesterol metabolism, and the composition of gut microbiota were assessed. Acetylsalicylic acid (10 mM) added to the cultivation substrate modulated properties of Gl extracts obtained from mature basidiomata. Compared to the high-cholesterol diet group, the consumption of Gl extracts significantly reduced total serum cholesterol (by 19.2% to 27.1%), LDL-C (by 4.5% to 35.1%), triglyceride concentration (by 16.3% to 46.6%), hepatic cholesterol (by 28.7% to 52%) and hepatic triglycerides (by 43.8% to 56.6%). These effects were associated with a significant reduction in the expression of lipogenic genes (Hmgcr, Srebp1c, Fasn, and Acaca) and genes involved in reverse cholesterol transport (Abcg5 and Abcg8), as well as an increase in Ldlr gene expression in the liver. No significant changes were observed in the gene expression of Srebp2, Abca1 or Cyp7a1. In several cases, Gl-1 or Gl-2 extracts showed better effects on lipid metabolism than the drug simvastatin. A proposed mechanism of action for the reduction in cholesterol levels is mediated by α-glucans and β-glucans from Gl, which promoted decreased absorption of cholesterol in the gut, as well as greater excretion of fecal bile acids and cholesterol. The prebiotic effects of Gl-1 and Gl-2 extracts modulated the composition of gut microbiota and produced an increase in the Lactobacillaceae family and Lactobacillus genus level compared to the control group, high-cholesterol diet group and group supplemented with simvastatin. Mexican genetic resources of Gl represent a new source of bioactive compounds showing hypocholesterolemic properties and prebiotic effects.

Hypocholesterolemic Properties and Prebiotic Effects of Mexican Ganoderma lucidum in C57BL/6 Mice

PubMed Central

Meneses, María E.; Martínez-Carrera, Daniel; Torres, Nimbe; Sánchez-Tapia, Mónica; Aguilar-López, Miriam; Morales, Porfirio; Sobal, Mercedes; Bernabé, Teodoro; Escudero, Helios; Granados-Portillo, Omar; Tovar, Armando R.

2016-01-01

Edible and medicinal mushrooms contain bioactive compounds with promising effects on several cardiovascular risk biomarkers. However, strains of Ganoderma lucidum of Mexican origin have not yet been studied. Standardized extracts of G. lucidum (Gl) were given to C57BL/6 mice fed a high-cholesterol diet compared with the drug simvastatin. The effects of the extracts on serum biochemical parameters, liver lipid content, cholesterol metabolism, and the composition of gut microbiota were assessed. Acetylsalicylic acid (10 mM) added to the cultivation substrate modulated properties of Gl extracts obtained from mature basidiomata. Compared to the high-cholesterol diet group, the consumption of Gl extracts significantly reduced total serum cholesterol (by 19.2% to 27.1%), LDL-C (by 4.5% to 35.1%), triglyceride concentration (by 16.3% to 46.6%), hepatic cholesterol (by 28.7% to 52%) and hepatic triglycerides (by 43.8% to 56.6%). These effects were associated with a significant reduction in the expression of lipogenic genes (Hmgcr, Srebp1c, Fasn, and Acaca) and genes involved in reverse cholesterol transport (Abcg5 and Abcg8), as well as an increase in Ldlr gene expression in the liver. No significant changes were observed in the gene expression of Srebp2, Abca1 or Cyp7a1. In several cases, Gl-1 or Gl-2 extracts showed better effects on lipid metabolism than the drug simvastatin. A proposed mechanism of action for the reduction in cholesterol levels is mediated by α-glucans and β-glucans from Gl, which promoted decreased absorption of cholesterol in the gut, as well as greater excretion of fecal bile acids and cholesterol. The prebiotic effects of Gl-1 and Gl-2 extracts modulated the composition of gut microbiota and produced an increase in the Lactobacillaceae family and Lactobacillus genus level compared to the control group, high-cholesterol diet group and group supplemented with simvastatin. Mexican genetic resources of Gl represent a new source of bioactive compounds showing hypocholesterolemic properties and prebiotic effects. PMID:27438015

Structure of the cobalamin-binding protein of a putative O-demethylase from Desulfitobacterium hafniense DCB-2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sjuts, Hanno; Dunstan, Mark S.; Fisher, Karl

2013-08-01

The first crystal structure of the vitamin B12-binding protein from a three-component O-demethylase enzyme system is reported. During O-demethylation methyl groups are transferred from phenyl methyl ethers to tetrahydrofolate via methyl-B12 intermediates. This study describes the identification and the structural and spectroscopic analysis of a cobalamin-binding protein (termed CobDH) implicated in O-demethylation by the organohalide-respiring bacterium Desulfitobacterium hafniense DCB-2. The 1.5 Å resolution crystal structure of CobDH is presented in the cobalamin-bound state and reveals that the protein is composed of an N-terminal helix-bundle domain and a C-terminal Rossmann-fold domain, with the cobalamin coordinated in the base-off/His-on conformation similar tomore » other cobalamin-binding domains that catalyse methyl-transfer reactions. EPR spectroscopy of CobDH confirms cobalamin binding and reveals the presence of a cob(III)alamin superoxide, indicating binding of oxygen to the fully oxidized cofactor. These data provide the first structural insights into the methyltransferase reactions that occur during O-demethylation by D. hafniense.« less

Topographical cues of direct metal laser sintering titanium surfaces facilitate osteogenic differentiation of bone marrow mesenchymal stem cells through epigenetic regulation.

PubMed

Zheng, Guoying; Guan, Binbin; Hu, Penghui; Qi, Xingying; Wang, Pingting; Kong, Yu; Liu, Zihao; Gao, Ping; Li, Rui; Zhang, Xu; Wu, Xudong; Sui, Lei

2018-04-27

To investigate the role of hierarchical micro/nanoscale topography of direct metal laser sintering (DMLS) titanium surfaces in osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), as well as the possible underlying epigenetic mechanism. Three groups of titanium specimens were prepared, including DMLS group, sandblasted, large-grit, acid-etched (SLA) group and smooth titanium (Ti) group. BMSCs were cultured on discs followed by surface characterization. Cell adhesion and proliferation were examined by SEM and CCK-8 assay, while osteogenic-related gene expression was detected by real-time RT-PCR. Immunofluorescence, western blotting and in vivo study were also performed to evaluate the potential for osteogenic induction of materials. In addition, to investigate the underlying epigenetic mechanisms, immunofluorescence and western blotting were performed to evaluate the global level of H3K4me3 during osteogenesis. The H3K4me3 and H3K27me3 levels at the promoter area of the osteogenic gene Runx2 were detected by ChIP assay. The DMLS surface exhibits greater protein adsorption ability and shows better cell adhesion performance than SLA and Ti surfaces. Moreover, both in vitro and in vivo studies demonstrated that the DMLS surface is more favourable for the osteogenic differentiation of BMSCs than SLA and Ti surfaces. Accordingly, osteogenesis-associated gene expression in BMSCs is efficiently induced by a rapid H3K27 demethylation and increase in H3K4me3 levels at gene promoters upon osteogenic differentiation on DMLS titanium surface. Topographical cues of DMLS surfaces have greater potential for the induction of osteogenic differentiation of BMSCs than SLA and Ti surfaces both in vitro and in vivo. A potential epigenetic mechanism is that the appropriate topography allows rapid H3K27 demethylation and an increased H3K4me3 level at the promoter region of osteogenesis-associated genes during the osteogenic differentiation of BMSCs. © 2018 John Wiley & Sons Ltd.

Genomic sequencing and in vivo footprinting of an expression-specific DNase I-hypersensitive site of avian vitellogenin II promoter reveal a demethylation of a mCpG and a change in specific interactions of proteins with DNA.

PubMed Central

Saluz, H P; Feavers, I M; Jiricny, J; Jost, J P

1988-01-01

Genomic sequencing was used to study the in vivo methylation pattern of two CpG sites in the promoter region of the avian vitellogenin gene. The CpG at position +10 was fully methylated in DNA isolated from tissues that do not express the gene but was unmethylated in the liver of mature hens and estradiol-treated roosters. In the latter tissue, this site became demethylated and DNase I hypersensitive after estradiol treatment. A second CpG (position -52) was unmethylated in all tissues examined. In vivo genomic footprinting with dimethyl sulfate revealed different patterns of DNA protection in silent and expressed genes. In rooster liver cells, at least 10 base pairs of DNA, including the methylated CpG, were protected by protein(s). Gel-shift assays indicated that a protein factor, present in rooster liver nuclear extract, bound at this site only when it was methylated. In hen liver cells, the same unmethylated CpG lies within a protected region of approximately equal to 20 base pairs. In vitro DNase I protection and gel-shift assays indicate that this sequence is bound by a protein, which binds both double- and single-stranded DNA. For the latter substrate, this factor was shown to bind solely the noncoding (i.e., mRNA-like) strand. Images PMID:3413118

DNMT1 maintains progenitor function in self-renewing somatic tissue.

PubMed

Sen, George L; Reuter, Jason A; Webster, Daniel E; Zhu, Lilly; Khavari, Paul A

2010-01-28

Progenitor cells maintain self-renewing tissues throughout life by sustaining their capacity for proliferation while suppressing cell cycle exit and terminal differentiation. DNA methylation provides a potential epigenetic mechanism for the cellular memory needed to preserve the somatic progenitor state through repeated cell divisions. DNA methyltransferase 1 (DNMT1) maintains DNA methylation patterns after cellular replication. Although dispensable for embryonic stem cell maintenance, the role for DNMT1 in maintaining the progenitor state in constantly replenished somatic tissues, such as mammalian epidermis, is unclear. Here we show that DNMT1 is essential for epidermal progenitor cell function. DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation. In tissue, DNMT1 depletion led to exit from the progenitor cell compartment, premature differentiation and eventual tissue loss. Genome-wide analysis showed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation. Furthermore, UHRF1 (refs 9, 10), a component of the DNA methylation machinery that targets DNMT1 to hemi-methylated DNA, is also necessary to suppress premature differentiation and sustain proliferation. In contrast, Gadd45A and B, which promote active DNA demethylation, are required for full epidermal differentiation gene induction. These data demonstrate that proteins involved in the dynamic regulation of DNA methylation patterns are required for progenitor maintenance and self-renewal in mammalian somatic tissue.

Xenobiotic Metabolizing Enzyme and Transporter Gene Expression in Primary Cultures of Human Hepatocytes Modulated by ToxCast Chemicals

EPA Science Inventory

ToxCast chemicals were assessed for induction or suppression of xenobiotic metabolizing enzyme and transporter gene expression using primary human hepatocytes. The mRNA levels of 14 target and 2 control genes were measured: ABCB1, ABCB11, ABCG2, SLCO1B1, CYP1A1, CYP1A2, CYP2B6, C...

DNA methylcytosine dioxygenase ten-eleven translocation 2 enhances lipopolysaccharide-induced cytokine expression in human dental pulp cells by regulating MyD88 hydroxymethylation.

PubMed

Wang, Xinxuan; Feng, Zhihui; Li, Qimeng; Yi, Baicheng; Xu, Qiong

2018-04-13

Dental pulp inflammation is a bacterially driven inflammation process characterized by the local accumulation of cytokines/chemokines that participate in destructive processes in the pulp. Multiple mechanisms are involved in dental pulp inflammation, including epigenetic events, such as DNA methylation/demethylation. Ten-eleven translocation 2 (TET2) is a recently discovered DNA methylcytosine dioxygenase that plays important roles in inflammatory disease. However, its role in the inflammatory response of dental pulp is unknown. We observed elevated mRNA and protein levels of TET2 after lipopolysaccharide (LPS) stimulation in human dental pulp cells (hDPCs). To identify the effects of TET2 on cytokine expression, TET2 was knocked down and cytokines were detected using a cytokine antibody array after LPS stimulation. The protein expression of GM-CSF, IL-6, IL-8 and RANTES decreased in the LPS-induced hDPCs following TET2 knockdown. The downregulated expression levels of IL-6 and IL-8 were further confirmed by real-time quantitative polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA). Additionally, the phosphorylation levels of IKK-α/β, p65 and IκBα of the NF-κB signaling pathway were decreased in the TET2-silenced group. Furthermore, the global 5-hydroxymethylcytosine (5hmC) level was significantly decreased and the genomic 5-methylcytosine (5mC) level was increased in the TET2-deficient hDPCs; TET2 depletion resulted in a decrease in the 5hmC level of the MyD88 promoter following LPS stimulation. These findings indicate that TET2 knockdown inhibits LPS-induced inflammatory response in hDPCs by downregulating MyD88 hydroxymethylation. Thus, TET2-dependent DNA demethylation might play an important role in dental pulp inflammation as an epigenetic regulator.

Expression and purification of pheophorbidase, an enzyme catalyzing the formation of pyropheophorbide during chlorophyll degradation: comparison with the native enzyme.

PubMed

Suzuki, Yasuyo; Soga, Keiko; Yoshimatsu, Katsuhiko; Shioi, Yuzo

2008-10-01

Formation of pyropheophorbide (PyroPheid) during chlorophyll metabolism in some higher plants has been shown to involve the enzyme pheophorbidase (PPD). This enzyme catalyzes the conversion of pheophorbide (Pheid) a to a precursor of PyroPheid, C-13(2)-carboxylPyroPheid a, by demethylation, and then the precursor is decarboxylated non-enzymatically to yield PyroPheid a. In this study, expression, purification, and biochemical characterization of recombinant PPD from radish (Raphanus sativus L.) were performed, and its properties were compared with those of highly purified native PPD. Recombinant PPD was produced using a glutathione S-transferase (GST) fusion system. The PPD and GST genes were fused to a pGEX-2T vector and expressed in Escherichia coli under the control of a T7 promoter as a fusion protein. The recombinant PPD-GST was expressed as a 55 kDa protein as measured by SDS-PAGE and purified by single-step affinity chromatography through a GSTrap FF column. PPD-GST was purified to homogeneity with a yield of 0.42 mg L(-1) of culture. The protein purified by this method was confirmed to be PPD by measuring its activity. The purified PPD-GST fusion protein revealed potent catalytic activity for demethylation of the methoxycarbonyl group of Pheid a and showed a pH optimum, substrate specificity, and thermal stability quite similar to the native enzyme purified from radish, except for the Km values toward Pheid a: 95.5 microM for PPD-GST and about 15 microM for native PPDs.

Melanocortin 1 Receptor Deficiency Promotes Atherosclerosis in Apolipoprotein E-/- Mice.

PubMed

Rinne, Petteri; Kadiri, James J; Velasco-Delgado, Mauricio; Nuutinen, Salla; Viitala, Miro; Hollmén, Maija; Rami, Martina; Savontaus, Eriika; Steffens, Sabine

2018-02-01

The MC1-R (melanocortin 1 receptor) is expressed by monocytes and macrophages where it mediates anti-inflammatory actions. MC1-R also protects against macrophage foam cell formation primarily by promoting cholesterol efflux through the ABCA1 (ATP-binding cassette transporter subfamily A member 1) and ABCG1 (ATP-binding cassette transporter subfamily G member 1). In this study, we aimed to investigate whether global deficiency in MC1-R signaling affects the development of atherosclerosis. Apoe -/- (apolipoprotein E deficient) mice were crossed with recessive yellow (Mc1r e/e ) mice carrying dysfunctional MC1-R and fed a high-fat diet to induce atherosclerosis. Apoe -/- Mc1r e/e mice developed significantly larger atherosclerotic lesions in the aortic sinus and in the whole aorta compared with Apoe -/- controls. In terms of plaque composition, MC1-R deficiency was associated with less collagen and smooth muscle cells and increased necrotic core, indicative of more vulnerable lesions. These changes were accompanied by reduced Abca1 and Abcg1 expression in the aorta. Furthermore, Apoe -/- Mc1r e/e mice showed a defect in bile acid metabolism that aggravated high-fat diet-induced hypercholesterolemia and hepatic lipid accumulation. Flow cytometric analysis of leukocyte profile revealed that dysfunctional MC1-R enhanced arterial accumulation of classical Ly6C high monocytes and macrophages, effects that were evident in mice fed a normal chow diet but not under high-fat diet conditions. In support of enhanced arterial recruitment of Ly6C high monocytes, these cells had increased expression of L-selectin and P-selectin glycoprotein ligand 1. The present study highlights the importance of MC1-R in the development of atherosclerosis. Deficiency in MC1-R signaling exacerbates atherosclerosis by disturbing cholesterol handling and by increasing arterial monocyte accumulation. © 2017 The Authors.

Large-Scale Gene-Centric Analysis Identifies Novel Variants for Coronary Artery Disease

PubMed Central

2011-01-01

Coronary artery disease (CAD) has a significant genetic contribution that is incompletely characterized. To complement genome-wide association (GWA) studies, we conducted a large and systematic candidate gene study of CAD susceptibility, including analysis of many uncommon and functional variants. We examined 49,094 genetic variants in ∼2,100 genes of cardiovascular relevance, using a customised gene array in 15,596 CAD cases and 34,992 controls (11,202 cases and 30,733 controls of European descent; 4,394 cases and 4,259 controls of South Asian origin). We attempted to replicate putative novel associations in an additional 17,121 CAD cases and 40,473 controls. Potential mechanisms through which the novel variants could affect CAD risk were explored through association tests with vascular risk factors and gene expression. We confirmed associations of several previously known CAD susceptibility loci (eg, 9p21.3:p<10−33; LPA:p<10−19; 1p13.3:p<10−17) as well as three recently discovered loci (COL4A1/COL4A2, ZC3HC1, CYP17A1:p<5×10−7). However, we found essentially null results for most previously suggested CAD candidate genes. In our replication study of 24 promising common variants, we identified novel associations of variants in or near LIPA, IL5, TRIB1, and ABCG5/ABCG8, with per-allele odds ratios for CAD risk with each of the novel variants ranging from 1.06–1.09. Associations with variants at LIPA, TRIB1, and ABCG5/ABCG8 were supported by gene expression data or effects on lipid levels. Apart from the previously reported variants in LPA, none of the other ∼4,500 low frequency and functional variants showed a strong effect. Associations in South Asians did not differ appreciably from those in Europeans, except for 9p21.3 (per-allele odds ratio: 1.14 versus 1.27 respectively; P for heterogeneity = 0.003). This large-scale gene-centric analysis has identified several novel genes for CAD that relate to diverse biochemical and cellular functions and clarified the literature with regard to many previously suggested genes. PMID:21966275

Epigenome-wide association study of metabolic syndrome in African-American adults.

PubMed

Akinyemiju, Tomi; Do, Anh N; Patki, Amit; Aslibekyan, Stella; Zhi, Degui; Hidalgo, Bertha; Tiwari, Hemant K; Absher, Devin; Geng, Xin; Arnett, Donna K; Irvin, Marguerite R

2018-01-01

The high prevalence of obesity among US adults has resulted in significant increases in associated metabolic disorders such as diabetes, dyslipidemia, and high blood pressure. Together, these disorders constitute metabolic syndrome, a clinically defined condition highly prevalent among African-Americans. Identifying epigenetic alterations associated with metabolic syndrome may provide additional information regarding etiology beyond current evidence from genome-wide association studies. Data on metabolic syndrome and DNA methylation was assessed on 614 African-Americans from the Hypertension Genetic Epidemiology Network (HyperGEN) study. Metabolic syndrome was defined using the joint harmonized criteria, and DNA methylation was assessed using the Illumina HumanMethylation450K Bead Chip assay on DNA extracted from buffy coat. Linear mixed effects regression models were used to examine the association between CpG methylation at > 450,000 CpG sites and metabolic syndrome adjusted for study covariates. Replication using DNA from a separate sample of 69 African-Americans, as well as meta-analysis combining both cohorts, was conducted. Two differentially methylated CpG sites in the IGF2BP1 gene on chromosome 17 (cg06638433; p value = 3.10 × 10 - 7 ) and the ABCG1 gene on chromosome 21 (cg06500161; p value = 2.60 × 10 - 8 ) were identified. Results for the ABCG1 gene remained statistically significant in the replication dataset and meta-analysis. Metabolic syndrome was consistently associated with increased methylation in the ABCG1 gene in the discovery and replication datasets, a gene that encodes a protein in the ATP-binding cassette transporter family and is involved in intra- and extra-cellular signaling and lipid transport.

Regio- and Stereo-Selective Oxidation of a Cardiovascular Drug, Metoprolol, Mediated by Cytochrome P450 2D and 3A Enzymes in Marmoset Livers.

PubMed

Uehara, Shotaro; Ishii, Sakura; Uno, Yasuhiro; Inoue, Takashi; Sasaki, Erika; Yamazaki, Hiroshi

2017-08-01

A β -blocker, metoprolol, is one of the in vivo probes for human cytochrome P450 (P450) 2D6. Investigation of nonhuman primate P450 enzymes helps to improve the accuracy of the extrapolation of pharmacokinetic data from animals into humans. Common marmosets ( Callithrix jacchus ) are a potential primate model for preclinical research, but the detailed roles of marmoset P450 enzymes in metoprolol oxidation remain unknown. In this study, regio- and stereo-selectivity of metoprolol oxidations by a variety of P450 enzymes in marmoset and human livers were investigated in vitro. Although liver microsomes from cynomolgus monkeys and rats preferentially mediated S -metoprolol O -demethylation and R -metoprolol α -hydroxylation, respectively, those from humans, marmosets, minipigs, and dogs preferentially mediated R -metoprolol O -demethylation, in contrast to the slow rates of R - and S -metoprolol oxidation in mouse liver microsomes. R - and S -metoprolol O -demethylation activities in marmoset livers were strongly inhibited by quinidine and ketoconazole, and were significantly correlated with bufuralol 1'-hydroxylation and midazolam 1'-hydroxylation activities and also with P450 2D and 3A4 contents, which is different from the case in human livers that did not have any correlations with P450 3A-mediated midazolam 1'-hydroxylation. Recombinant human P450 2D6 enzyme and marmoset P450 2D6/3A4 enzymes effectively catalyzed R -metoprolol O -demethylation, comparable to the activities of human and marmoset liver microsomes, respectively. These results indicated that the major roles of P450 2D enzymes for the regio- and stereo-selectivity of metoprolol oxidation were similar between human and marmoset livers, but the minor roles of P450 3A enzymes were unique to marmosets. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

New Psychoactive Substances 3-Methoxyphencyclidine (3-MeO-PCP) and 3-Methoxyrolicyclidine (3-MeO-PCPy): Metabolic Fate Elucidated with Rat Urine and Human Liver Preparations and their Detectability in Urine by GC-MS, “LC-(High Resolution)-MSn” and “LC-(High Resolution)-MS/MS”

PubMed Central

Michely, Julian A.; Manier, Sascha K.; Caspar, Achim T.; Brandt, Simon D.; Wallach, Jason; Maurer, Hans. H.

2017-01-01

Background: 3-Methoxyphencyclidine (3-MeO-PCP) and 3-methoxyrolicyclidine (3-MeO-PCPy) are two new psychoactive substances (NPS). The aims of the present study were the elucidation of their metabolic fate in rat and pooled human liver microsomes (pHLM) the identification of the cytochrome P450 (CYP) isoenzymes involved and the detectability using standard urine screening approaches (SUSA) after intake of common users’ doses using gas chromatography-mass spectrometry (GC-MS) liquid chromatography-multi-stage mass spectrometry (LC-MSn) and liquid chromatography-high-resolution tandem mass spectrometry (LC-HR-MS/MS) Methods: For metabolism studies rat urine samples were treated by solid phase extraction or simple precipitation with or without previous enzymatic conjugate cleavage. After analyses via LC-HR-MSn the phase I and II metabolites were identified Results: Both drugs showed multiple aliphatic hydroxylations at the cyclohexyl ring and the heterocyclic ring single aromatic hydroxylation carboxylation after ring opening O-demethylation and glucuronidation. The transferability from rat to human was investigated by pHLM incubations where O-demethylation and hydroxylation were observed. The involvement of the individual CYP enzymes in the initial metabolic steps was investigated after single CYP incubations. For 3-MeO-PCP CYP 2B6 was responsible for aliphatic hydroxylations and CYP 2C19 and CYP 2D6 for O-demethylation. For 3-MeO-PCPy aliphatic hydroxylation was again catalyzed by CYP 2B6 and O-demethylation by CYP 2C9 and CYP 2D6 Conclusions: As only polymorphically expressed enzymes were involved pharmacogenomic variations might occur but clinical data are needed to confirm the relevance. The detectability studies showed that the authors’ SUSAs were suitable for monitoring the intake of both drugs using the identified metabolites PMID:27758707

Probable Chemical Hypoxia Effects on Progress of CNV Through Induction of Promoter CpG Demethylation and Overexpression of IL17RC in Human RPE Cells.

PubMed

Alivand, Mohammad Reza; Sabouni, Farzaneh; Soheili, Zahra-Soheila

2016-09-01

To survey the changes of promoter CpG methylation status and mRNA expression of IL17RC (interleukin 17 receptor C) gene in retinal pigment epithelium (RPE) cells under chemical hypoxia condition for choroidal neovascularization (CNV) modeling in vitro. RPE cells were cultured in both untreated as a control group and treated by cobalt chloride media as a hypoxia group for various concentrations (100-150μM) and times (24-36 hrs.) To confirm chemical hypoxia condition, mRNA expression of HIF (Hypoxia Inducible Factor) -1α, -2α, and Vascular Endothelial Growth Factor (VEGF) was compared between two groups by Real-time PCR. Also, in normoxia and hypoxia conditions, IL17RC expression changes and promoter CpG methylation status were evaluated by Real-time PCR and methylation-specific PCR (MSP) techniques, respectively. Overexpression of HIF-1α, HIF-2α, and VEGF was significant in hypoxia versus normoxia conditions. Our data showed overexpression of IL17RC (2.1- to 6.3-fold) and decreasing of its promoter methylation in comparison with hypoxia and normoxia conditions. It was found that there are significant association between promoter methylation status and expression of IL17RC in chemical hypoxia condition. Therefore, methylation of IL17RC could play as a marker in CNV and degeneration of RPE cells in vitro. Additionally, HIF-α and methylation phenomena may be considered as critical targets for blocking in angiogenesis of age-related degeneration in future studies.

Early de novo DNA methylation and prolonged demethylation in the muscle lineage.

PubMed

Tsumagari, Koji; Baribault, Carl; Terragni, Jolyon; Varley, Katherine E; Gertz, Jason; Pradhan, Sirharsa; Badoo, Melody; Crain, Charlene M; Song, Lingyun; Crawford, Gregory E; Myers, Richard M; Lacey, Michelle; Ehrlich, Melanie

2013-03-01

Myogenic cell cultures derived from muscle biopsies are excellent models for human cell differentiation. We report the first comprehensive analysis of myogenesis-specific DNA hyper- and hypo-methylation throughout the genome for human muscle progenitor cells (both myoblasts and myotubes) and skeletal muscle tissue vs. 30 non-muscle samples using reduced representation bisulfite sequencing. We also focused on four genes with extensive hyper- or hypo-methylation in the muscle lineage (PAX3, TBX1, MYH7B/MIR499 and OBSCN) to compare DNA methylation, DNaseI hypersensitivity, histone modification, and CTCF binding profiles. We found that myogenic hypermethylation was strongly associated with homeobox or T-box genes and muscle hypomethylation with contractile fiber genes. Nonetheless, there was no simple relationship between differential gene expression and myogenic differential methylation, rather only for subsets of these genes, such as contractile fiber genes. Skeletal muscle retained ~30% of the hypomethylated sites but only ~3% of hypermethylated sites seen in myogenic progenitor cells. By enzymatic assays, skeletal muscle was 2-fold enriched globally in genomic 5-hydroxymethylcytosine (5-hmC) vs. myoblasts or myotubes and was the only sample type enriched in 5-hmC at tested myogenic hypermethylated sites in PAX3/CCDC140 andTBX1. TET1 and TET2 RNAs, which are involved in generation of 5-hmC and DNA demethylation, were strongly upregulated in myoblasts and myotubes. Our findings implicate de novo methylation predominantly before the myoblast stage and demethylation before and after the myotube stage in control of transcription and co-transcriptional RNA processing. They also suggest that, in muscle, TET1 or TET2 are involved in active demethylation and in formation of stable 5-hmC residues.

Early de novo DNA methylation and prolonged demethylation in the muscle lineage

PubMed Central

Tsumagari, Koji; Baribault, Carl; Terragni, Jolyon; Varley, Katherine E.; Gertz, Jason; Pradhan, Sirharsa; Badoo, Melody; Crain, Charlene M.; Song, Lingyun; Crawford, Gregory E.; Myers, Richard M.; Lacey, Michelle; Ehrlich, Melanie

2013-01-01

Myogenic cell cultures derived from muscle biopsies are excellent models for human cell differentiation. We report the first comprehensive analysis of myogenesis-specific DNA hyper- and hypo-methylation throughout the genome for human muscle progenitor cells (both myoblasts and myotubes) and skeletal muscle tissue vs. 30 non-muscle samples using reduced representation bisulfite sequencing. We also focused on four genes with extensive hyper- or hypo-methylation in the muscle lineage (PAX3, TBX1, MYH7B/MIR499 and OBSCN) to compare DNA methylation, DNaseI hypersensitivity, histone modification, and CTCF binding profiles. We found that myogenic hypermethylation was strongly associated with homeobox or T-box genes and muscle hypomethylation with contractile fiber genes. Nonetheless, there was no simple relationship between differential gene expression and myogenic differential methylation, rather only for subsets of these genes, such as contractile fiber genes. Skeletal muscle retained ~30% of the hypomethylated sites but only ~3% of hypermethylated sites seen in myogenic progenitor cells. By enzymatic assays, skeletal muscle was 2-fold enriched globally in genomic 5-hydroxymethylcytosine (5-hmC) vs. myoblasts or myotubes and was the only sample type enriched in 5-hmC at tested myogenic hypermethylated sites in PAX3/CCDC140 andTBX1. TET1 and TET2 RNAs, which are involved in generation of 5-hmC and DNA demethylation, were strongly upregulated in myoblasts and myotubes. Our findings implicate de novo methylation predominantly before the myoblast stage and demethylation before and after the myotube stage in control of transcription and co-transcriptional RNA processing. They also suggest that, in muscle, TET1 or TET2 are involved in active demethylation and in formation of stable 5-hmC residues. PMID:23417056

DNA methylation dynamics in mouse preimplantation embryos revealed by mass spectrometry.

PubMed

Okamoto, Yoshinori; Yoshida, Naoko; Suzuki, Toru; Shimozawa, Nobuhiro; Asami, Maki; Matsuda, Tomonari; Kojima, Nakao; Perry, Anthony C F; Takada, Tatsuyuki

2016-01-11

Following fertilization in mammals, paternal genomic 5-methyl-2'-deoxycytidine (5 mC) content is thought to decrease via oxidation to 5-hydroxymethyl-2'-deoxycytidine (5 hmC). This reciprocal model of demethylation and hydroxymethylation is inferred from indirect, non-quantitative methods. We here report direct quantification of genomic 5 mC and 5 hmC in mouse embryos by small scale liquid chromatographic tandem mass spectrometry (SMM). Profiles of absolute 5 mC levels in embryos produced by in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) were almost identical. By 10 h after fertilization, 5 mC levels had declined by ~40%, consistent with active genomic DNA demethylation. Levels of 5 mC in androgenotes (containing only a paternal genome) and parthenogenotes (containing only a maternal genome) underwent active 5 mC loss in the first 6 h, showing that both parental genomes can undergo demethylation independently. We found no evidence for net loss of 5 mC 10-48 h after fertilization, implying that any passive 'demethylation' following DNA replication was balanced by active 5 mC maintenance methylation. However, levels of 5 mC declined during development after 48 h, to 1% (measured as a fraction of G-residues) in blastocysts (~96 h). 5 hmC levels were consistently low (<0.2% of G-residues) throughout development in normal diploid embryos. This work directly quantifies the dynamics of global genomic DNA modification in mouse preimplantation embryos, suggesting that SMM will be applicable to other biomedical situations with limiting sample sizes.

Molecular Level Understanding of the Factors Affecting the Stability of Dimethoxy Benzene Catholyte Candidates from First-Principles Investigations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Assary, Rajeev S.; Zhang, Lu; Huang, Jinhua

First-principles simulations are performed to gain molecular level insights into the factors affecting the stability of seven 1,4-dimethoxybenzene (DMB) derivatives. These molecules are potential catholyte candidates for nonaqueous redox flow battery systems. Computations are performed to predict oxidation potentials in various dielectric mediums, intrinsic-reorganization energies, and structural changes of these representative catholyte molecules during the redox process. In order to understand the stability of the DMB-based radical cations, the thermodynamic feasibility of the following reactions is computed using density functional theory: (a) deprotonation, (b) dimerization, (c) hydrolysis, and (d) demethylation. The computations indicate that radical cations of the 2,3-dimethyl andmore » 2,5-dimethyl derivatives are the most stable among the DMB derivatives considered in this study. In the presence of solvents with high-proton solvating ability (water, DMSO, acetonitrile), degradation of cation radical occurring via deprotonation is the most likely mechanism. In the presence of solvents such as propylene carbonate (PC), demethylation was found to be the most likely reaction that causes degradation of radical cations. From the computed enthalpy of activation (Delta H-double dagger) for a demethylation reaction in PC, the 2,5-dimethyl DMB cation radical would exhibit better kinetic stability in comparison to the other candidates. Finally, this investigation suggests that computational studies of structural properties such as redox potentials, reorganization energies, and the computed reaction energetics (deprotonation and demethylation) of charged species can be used to predict the relative stability of a large set of molecules required for the discovery of novel redox active materials for flow battery applications« less

Molecular Level Understanding of the Factors Affecting the Stability of Dimethoxy Benzene Catholyte Candidates from First-Principles Investigations

DOE PAGES

Assary, Rajeev S.; Zhang, Lu; Huang, Jinhua; ...

2016-06-14

First-principles simulations are performed to gain molecular level insights into the factors affecting the stability of seven 1,4-dimethoxybenzene (DMB) derivatives. These molecules are potential catholyte candidates for nonaqueous redox flow battery systems. Computations are performed to predict oxidation potentials in various dielectric mediums, intrinsic-reorganization energies, and structural changes of these representative catholyte molecules during the redox process. In order to understand the stability of the DMB-based radical cations, the thermodynamic feasibility of the following reactions is computed using density functional theory: (a) deprotonation, (b) dimerization, (c) hydrolysis, and (d) demethylation. The computations indicate that radical cations of the 2,3-dimethyl andmore » 2,5-dimethyl derivatives are the most stable among the DMB derivatives considered in this study. In the presence of solvents with high-proton solvating ability (water, DMSO, acetonitrile), degradation of cation radical occurring via deprotonation is the most likely mechanism. In the presence of solvents such as propylene carbonate (PC), demethylation was found to be the most likely reaction that causes degradation of radical cations. From the computed enthalpy of activation (Delta H-double dagger) for a demethylation reaction in PC, the 2,5-dimethyl DMB cation radical would exhibit better kinetic stability in comparison to the other candidates. Finally, this investigation suggests that computational studies of structural properties such as redox potentials, reorganization energies, and the computed reaction energetics (deprotonation and demethylation) of charged species can be used to predict the relative stability of a large set of molecules required for the discovery of novel redox active materials for flow battery applications« less

Inactivation of parkin by promoter methylation correlated with lymph node metastasis and genomic instability in nasopharyngeal carcinoma.

PubMed

Ni, Haifeng; Zhou, Zhen; Jiang, Bo; Yuan, Xiaoyang; Cao, Xiaolin; Huang, Guangwu; Li, Yong

2017-03-01

This study aimed to investigate the inactivation of the parkin gene by promoter methylation and its relationship with genome instability in nasopharyngeal carcinoma. Parkin was considered as a tumor suppressor gene in various types of cancers. However, its role in nasopharyngeal carcinoma is unexplored. Genomic instabilities were detected in nasopharyngeal carcinoma tissues by the random amplified polymorphic DNA. The methylation-specific polymerase chain reaction, semi-quantitative reverse transcription polymerase chain reaction, and immunohistochemical analysis were used to detect methylation and mRNA and protein expression of parkin in 54 cases of nasopharyngeal carcinoma tissues and 16 cases of normal nasopharyngeal epithelia tissues, and in 5 nasopharyngeal carcinoma cell lines (CNE1, CNE2, TWO3, C666, and HONE1) and 1 normal nasopharyngeal epithelia cell line (NP69). mRNA expression of parkin in CNE1 and CNE2 was analyzed before and after methyltransferase inhibitor 5-aza-2-deoxycytidine treatment. The relationship between promoter methylation and mRNA expression, demethylation and mRNA expression, and mRNA and protein expression of the gene and clinical factors and genomic instabilities were analyzed. The mRNA and protein expression levels were significantly reduced in 54 cases of human nasopharyngeal carcinoma compared with 16 cases of normal nasopharyngeal epithelia. Parkin-methylated cases showed significantly lower mRNA and protein expression levels compared with unmethylated cases. After 5-aza-2-deoxycytidine treatment, parkin mRNA expression was restored in CNE1 and CNE2; 92.59% (50/54) of nasopharyngeal carcinoma demonstrated genomic instability. Parkin is frequently inactivated by promoter methylation, and its mRNA and protein expression correlate with lymph node metastasis and genomic instability. Parkin deficiency probably promotes tumorigenesis in nasopharyngeal carcinoma.

Identification of the First Marine-Derived Opioid Receptor "Balanced" Agonist with a Signaling Profile That Resembles the Endorphins.

PubMed

Johnson, Tyler A; Milan-Lobo, Laura; Che, Tao; Ferwerda, Madeline; Lambu, Eptisam; McIntosh, Nicole L; Li, Fei; He, Li; Lorig-Roach, Nicholas; Crews, Phillip; Whistler, Jennifer L

2017-03-15

Opioid therapeutics are excellent analgesics, whose utility is compromised by dependence. Morphine (1) and its clinically relevant derivatives such as OxyContin (2), Vicodin (3), and Dilaudid (4) are "biased" agonists at the μ opioid receptor (OR), wherein they engage G protein signaling but poorly engage β-arrestin and the endocytic machinery. In contrast, endorphins, the endogenous peptide agonists for ORs, are potent analgesics, show reduced liability for tolerance and dependence, and engage both G protein and β-arrestin pathways as "balanced" agonists. We set out to determine if marine-derived alkaloids could serve as novel OR agonist chemotypes with a signaling profile distinct from morphine and more similar to the endorphins. Screening of 96 sponge-derived extracts followed by LC-MS-based purification to pinpoint the active compounds and subsequent evaluation of a mini library of related alkaloids identified two structural classes that modulate the ORs. These included the following: aaptamine (10), 9-demethyl aaptamine (11), demethyl (oxy)-aaptamine (12) with activity at the δ-OR (EC 50 : 5.1, 4.1, 2.3 μM, respectively) and fascaplysin (17), and 10-bromo fascaplysin (18) with activity at the μ-OR (EC 50 : 6.3, 4.2 μM respectively). An in vivo evaluation of 10 using δ-KO mice indicated its previously reported antidepressant-like effects are dependent on the δ-OR. Importantly, 17 functioned as a balanced agonist promoting both G protein signaling and β-arrestin recruitment along with receptor endocytosis similar to the endorphins. Collectively these results demonstrate the burgeoning potential for marine natural products to serve as novel lead compounds for therapeutic targets in neuroscience research.

Effect of Storage Temperature on the Phenotype of Cultured Epidermal Cells Stored in Xenobiotic-Free Medium.

PubMed

Jackson, Catherine; Eidet, Jon R; Reppe, Sjur; Aass, Hans Christian D; Tønseth, Kim A; Roald, Borghild; Lyberg, Torstein; Utheim, Tor P

2016-06-01

Cultured epidermal cell sheets (CECS) are used in the treatment of large area burns to the body and have potential to treat limbal stem cell deficiency (LSCD) as shown in animal studies. Despite widespread use, storage options for CECS are limited. Short-term storage allows flexibility in scheduling surgery, quality control and improved transportation to clinics worldwide. Recent evidence points to the phenotype of cultured epithelial cells as a critical predictor of post-operative success following transplantation of CECS in burns and in transplantation of cultured epithelial cells in patients with LSCD. This study, therefore assessed the effect of a range of temperatures, spanning 4-37 °C, on the phenotype of CECS stored over a 2-week period in a xenobiotic-free system. Progenitor cell (p63, ΔNp63α and ABCG2) and differentiation (C/EBPδ and CK10) associated marker expression was assessed using immunocytochemistry. Immunohistochemistry staining of normal skin for the markers p63, ABCG2 and C/EBPδ was also carried out. Assessment of progenitor cell side population (SP) was performed using JC1 dye by flow cytometry. P63 expression remained relatively constant throughout the temperature range but was significantly lower compared to control between 20 and 28 °C (p < 0.05). High C/EBPδ together with low p63 suggested more differentiation beginning at 20 °C and above. Lower CK10 and C/EBPδ expression most similar to control was seen at 12 °C. The percentage of ABCG2 positive cells was most similar to control between 8 and 24 °C. Between 4 and 24 °C, the SP fluctuated, but was not significantly different compared to control. Results were supported by staining patterns indicating differentiation status associated with markers in normal skin sections. Lower storage temperatures, and in particular 12 °C, merit further investigation as optimal storage temperature for maintenance of undifferentiated phenotype in CECS.

Breast cancer resistance protein (ABCG2) and drug disposition: intestinal expression, polymorphisms and sulfasalazine as an in vivo probe

PubMed Central

Urquhart, Bradley L.; Ware, Joseph A.; Tirona, Rommel G.; Ho, Richard H.; Leake, Brenda F.; Schwarz, Ute I.; Zaher, Hani; Palandra, Joe; Gregor, Jamie C.; Dresser, George K.; Kim, Richard B.

2014-01-01

Breast cancer resistance protein (BCRP) is an efflux transporter expressed in tissues that act as barriers to drug entry. Given that single nucleotide polymorphisms (SNPs) in the ABCG2 gene encoding BCRP are common, the possibility exists that these genetic variants may be a determinant of interindividual variability in drug response. The objective of this study is to confirm the human BCRP-mediated transport of sulfasalazine in vitro, evaluate interindividual variation in BCRP expression in human intestine and to determine the role of ABCG2 SNPs to drug disposition in healthy patients using sulfasalazine as a novel in vivo probe. To evaluate these objectives, pinch biopsies were obtained from 18 patients undergoing esophagogastro–duodenoscopy or colonoscopy for determination of BCRP expression in relation to genotype. Wild-type and variant BCRP were expressed in a heterologous expression system to evaluate the effect of SNPs on cell-surface trafficking. A total of 17 healthy individuals participated in a clinical investigation to determine the effect of BCRP SNPs on sulfasalazine pharmacokinetics. In vitro, the cell surface protein expression of the common BCRP 421 C>A variant was reduced in comparison with the wild-type control. Intestinal biopsy samples revealed that BCRP protein and mRNA expression did not significantly differ between patients with 34GG/421CC versus patients with 34GG/421CA genotypes. Remarkably, in subjects with 34GG/421CA genotype, sulfasalazine area under the concentration-time curve was 2.4-fold greater compared with 34GG/421CC subjects (P<0.05). This study links commonly occurring SNPs in BCRP with significantly increased oral sulfasalazine plasma exposure in humans. Accordingly, sulfasalazine may prove to have utility as in vivo probe for assessing the clinical impact of BCRP for the disposition and efficacy of drugs. PMID:18408567

Role of UGT1A1*6, UGT1A1*28 and ABCG2 c.421C>A polymorphisms in irinotecan-induced neutropenia in Asian cancer patients.

PubMed

Jada, Srinivasa Rao; Lim, Robert; Wong, Chiung Ing; Shu, Xiaochen; Lee, Soo Chin; Zhou, Qingyu; Goh, Boon Cher; Chowbay, Balram

2007-09-01

The objectives of the present study were (i) to study the pharmacogenetics of UGT1A1*6, UGT1A1*28 and ABCG2 c.421C>A in three distinct healthy Asian populations (Chinese, Malays and Indians), and (ii) to investigate the polygenic influence of these polymorphic variants in irinotecan-induced neutropenia in Asian cancer patients. Pharmacokinetic and pharmacogenetic analyses were done after administration of irinotecan as a 90-min intravenous infusion of 375 mg/m(2) once every 3 weeks (n = 45). Genotypic-phenotypic correlates showed a non-significant influence of UGT1A1*28 and ABCG2 c.421C>A polymorphisms on the pharmacokinetics of SN-38 (P > 0.05), as well as severity of neutropenia (P > 0.05). Significantly higher exposure levels to SN-38 (P = 0.018), lower relative extent of glucuronidation (REG; P = 0.006) and higher biliary index (BI; P = 0.003) were found in cancer patients homozygous for the UGT1A1*6 allele compared with patients harboring the reference genotype. The mean absolute neutrophil count (ANC) was 85% lower and the prevalence of grade 4 neutropenia (ANC < or = 500/microL) was 27% in patients homozygous for UGT1A1*6 compared with the reference group. Furthermore, the presence of the UGT1A1*6 allele was associated with an approximately 3-fold increased risk of developing severe grade 4 neutropenia compared with patients harboring the reference genotype. These exploratory findings suggest that homozygosity for UGT1A1*6 allele may be associated with altered SN-38 disposition and may increase the risk of severe neutropenia in Asian cancer patients, particularly in the Chinese cancer patients who comprised 80% (n = 36) of the patient population in the present study.

Methylation of Wnt7a Is Modulated by DNMT1 and Cigarette Smoke Condensate in Non-Small Cell Lung Cancer

PubMed Central

Tennis, Meredith A.; VanScoyk, Michelle M.; Wilson, Lora A.; Kelley, Nicole; Winn, Robert A.

2012-01-01

Wnt7a is known to be a tumor suppressor that is lost in NSCLC, but no mechanism of loss has been established. Methylation of promoter regions has been established as a common mechanism of loss of tumor suppressor expression in NSCLC. We previously demonstrated that loss of Wnt7a in non-transformed lung epithelial cell lines led to increased cell growth, altered 3-D culture growth, and increased migration. The Wnt7a promoter has a higher percentage of methylation in NSCLC tumor tissue compared to matched normal lung tissue and methylation of the promoter region leads to decreased activity. We treated H157 and H1299 NSCLC cell lines with 5-Aza-2′-deoxycytidine and detected loss of Wnt7a promoter methylation, increased Wnt7a expression, and increased activity of the Wnt7a lung signaling pathway. When DNMT1 expression was knocked down by shRNA, expression of Wnt7a increased and methylation decreased. Together these data suggest that in NSCLC, Wnt7a is lost by methylation in a subset of tumors and that this methylation is maintained by DNMT1. Restoration of Wnt7a expression through demethylation could be an important therapeutic approach in the treatment of NSCLC. PMID:22403725

Effect and mechanism of dioscin from Dioscorea spongiosa on uric acid excretion in animal model of hyperuricemia.

PubMed

Zhang, Yi; Jin, Lijun; Liu, Jinchang; Wang, Wei; Yu, Haiyang; Li, Jian; Chen, Qian; Wang, Tao

2018-03-25

Dioscin, a spirostane glycoside, the rhizoma of Dioscorea septemloba (Diocoreacea) is used for diuresis, rheumatism, and joints pain. Given the poor solubility and stability of Dioscin, we proposed a hypothesis that Dioscin's metabolite(s) are the active substance(s) in vivo to contribute to the reducing effects on serum uric acid levels. The aim of this study is to identify the active metabolite(s) of Dioscin in vivo and to explore the mechanism of its antihyperuricemic activity. After oral administration of Dioscin in potassium oxonate (PO) induced hyperuricemia rats and adenine-PO induced hyperuricemia mice models, serum uric acid and creatinine levels, clearance of uric acid and creatinine, fractional excretion of uric acid, and renal pathological lesions were determined were used to evaluate the antihyperuricemic effects. Renal glucose transporter-9 (GLUT-9) and organic anion transporter-1 (OAT-1) expressions were analyzed by western blotting method. Renal uric acid excretion was evaluated using stably urate transporter-1 (URAT-1) transfected human epithelial kidney cell line. Intestinal uric acid excretion was evaluated by measuring the transcellular transport of uric acid in HCT116 cells. In hyperuricemia rats, both 25 and 50mg/kg of oral Dioscin decreased serum uric acid levels over 4h. In the hyperuricemia mice, two weeks treatment of Dioscin significantly decreased serum uric acid and creatinine levels, increased clearance of uric acid and creatinine, increased fractional excretion of uric acid, and reduced renal pathological lesions caused by hyperuricemia. In addition, renal GLUT -9 was significantly down-regulated and OAT-1 was up-regulated in Dioscin treated hyperuricemia mice. Dioscin's metabolite Tigogenin significantly inhibited uric acid re-absorption via URAT1 from 10 to 100μM. Diosgenin and Tigogenin increased uric acid excretion via ATP binding cassette subfamily G member 2 (ABCG2). Decreasing effect of Dioscin on serum uric acid level and enhancing effect on urate excretion were confirmed in hyperuricemia animal models. Tigogenin, a metabolite of Dioscin, was identified as an active substance with antihyperuricemic activity in vivo, through inhibition of URAT1 and promotion of ABCG2. Copyright © 2017 Elsevier B.V. All rights reserved.

Epigenetic regulation of the circadian clock: role of 5-aza-2′-deoxycytidine

PubMed Central

Tomita, Tatsunosuke; Kurita, Ryoji

2017-01-01

We have been investigating transcriptional regulation of the BMAL1 gene, a critical component of the mammalian clock system including DNA methylation. Here, a more detailed analysis of the regulation of DNA methylation of BMAL1 proceeded in RPMI8402 lymphoma cells. We found that CpG islands in the BMAL1 and the PER2 promoters were hyper- and hypomethylated, respectively and that 5-aza-2′-deoxycytidine (aza-dC) not only enhanced PER2 gene expression but also PER2 oscillation within 24 h in RPMI8402 cells. That is, such hypermethylation of CpG islands in the BMAL1 promoter restricted PER2 expression which was recovered by aza-dC within 1 day in these cells. These results suggest that the circadian clock system can be recovered through BMAL1 expression induced by aza-dC within a day. The RPIB9 promoter of RPMI8402 cells, which is a methylation hotspot in lymphoblastic leukemia, was also hypermethylated and aza-dC gradually recovered RPIB9 expression in 3 days. In addition, methylation-specific PCR revealed a different degree of aza-dC-induced methylation release between BMAL1 and RPIB9. These results suggest that the aza-dC-induced recovery of gene expression from DNA methylation is dependent on a gene, for example the rapid response to demethylation by the circadian system, and thus, is of importance to clinical strategies for treating cancer. PMID:28487473

Modulation of Xenobiotic Metabolizing Enzyme and Transporter Gene Expression in Primary Cultures of Human Hepatocytes by ToxCast Chemicals

EPA Science Inventory

ToxCast chemicals were assessed for induction or suppression of xenobiotic metabolizing enzyme and transporter gene expression using primary human hepatocytes. The mRNA levels of 14 target and 2 control genes were measured: ABCB1, ABCB11, ABCG2, SLCO1B1, CYP1A1, CYP1A2, CYP2B6, C...

Structure Elucidation and in Vitro Toxicity of New Azaspiracids Isolated from the Marine Dinoflagellate Azadinium poporum

PubMed Central

Krock, Bernd; Tillmann, Urban; Potvin, Éric; Jeong, Hae Jin; Drebing, Wolfgang; Kilcoyne, Jane; Al-Jorani, Ahmed; Twiner, Michael J.; Göthel, Qun; Köck, Matthias

2015-01-01

Two strains of Azadinium poporum, one from the Korean West coast and the other from the North Sea, were mass cultured for isolation of new azaspiracids. Approximately 0.9 mg of pure AZA-36 (1) and 1.3 mg of pure AZA-37 (2) were isolated from the Korean (870 L) and North Sea (120 L) strains, respectively. The structures were determined to be 3-hydroxy-8-methyl-39-demethyl-azaspiracid-1 (1) and 3-hydroxy-7,8-dihydro-39-demethyl-azaspiracid-1 (2) by 1H- and 13C-NMR. Using the Jurkat T lymphocyte cell toxicity assay, (1) and (2) were found to be 6- and 3-fold less toxic than AZA-1, respectively. PMID:26528990

Salvianolic acid B reverses multidrug resistance in nude mice bearing human colon cancer stem cells.

PubMed

Guo, Piaoting; Wang, Jianchao; Gao, Wencang; Liu, Xia; Wu, Shaofei; Wan, Boshun; Xu, Lei; Li, Yanhua

2018-05-29

Salvianolic acid B (SalB) is a water‑soluble phenolic compound, extractable from Salvia miltiorrhiza, and has previously been demonstrated to reverse tumor multidrug resistance (MDR) in colon cancer cells. Cancer stem cells (CSCs) are closely associated with drug resistance. Therefore, establishing a nude mouse model bearing human colon CSCs is important for the study of the mechanisms underlying colon cancer drug resistance as well as the reversal of drug resistance. The present study aimed to establish a nude mouse model bearing human colon CSCs and to investigate the effects of SalB on the drug resistance exhibited by the nude mouse model as well as determine its underlying mechanism. Cells from two colon cancer cell lines (LoVo and HCT‑116) were cultured in serum‑free medium to obtain CSCs‑enriched spheroid cells. Following this, nude mice were transplanted with LoVo and HCT‑116 colon CSCs to establish the CSC nude mouse model, which was subsequently demonstrated to exhibit MDR. The results of the present study revealed that following treatment with SalB, the chemotherapeutic drug resistance of xenografts was reversed to a certain extent. Western blot analysis was performed to investigate the expression levels of cluster of differentiation (CD)44, CD133, transcription factor sox‑2 (SOX2) and ATP‑binding cassette sub‑family G member 2 (ABCG2) proteins, and the results demonstrated that treatment with SalB downregulated the expression of CD44, SOX2 and ABCG2 proteins in both LoVo and HCT‑116 colon CSCs xenografts. In conclusion, the results of the present study revealed that a serum‑free suspension method can be performed to successfully isolate colon CSCs. In addition, a nude mice bearing colon CSCs animal model was successfully established, and associated tumors were confirmed to exhibit MDR. Furthermore, SalB was demonstrated to successfully reverse MDR in nude mice bearing LoVo and HCT‑116 colon CSCs, as well as suppress the expression of CD44, SOX2 and ABCG2 proteins.

Impaired dacarbazine activation and 7-ethoxyresorufin deethylation in vitro by polymorphic variants of CYP1A1 and CYP1A2: implications for cancer therapy.

PubMed

Lewis, Benjamin C; Korprasertthaworn, Porntipa; Miners, John O

2016-10-01

To extend our understanding of how interindividual variability mediates the efficacy of cancer treatment. The kinetics of dacarbazine (DTIC) N-demethylation by the most frequent polymorphic variants of CYP1A1 (T461N, I462V) and CYP1A2 (F186L, D348N, I386F, R431W, R456H) were characterized, along with kinetic parameters for the O-deethylation of the prototypic CYP1A substrate 7-ethoxyresorufin, using recombinant protein expression and high-performance liquid chromatographic techniques. A reduction of ∼30% in the catalytic efficiencies (measured as in-vitro intrinsic clearance, CLint) was observed for DTIC N-demethylation by the two CYP1A1 variants relative to wild type. Although a modest increase in the CLint value for DTIC N-demethylation was observed for the CYP1A2 D348N variant relative to the wild type, the CLint for the F186L variant was reduced and the I386F, R431W, and R456H variants all showed loss of catalytic function. Comparison of the kinetic data for DTIC N-demethylation and 7-ethoxyresorufin O-deethylation indicated that alterations in the kinetic parameters (Km, Vmax, CLint) observed with each of the CYP1A1 and CYP1A2 polymorphic variants were substrate dependent. These data indicate that cancer patients treated with DTIC who possess any of the CYP1A1-T461N and I462V variants or the CYP1A2-F186L, D348N, I386F, R431W, and R456H variants are likely to have decreased prodrug activation, and hence may respond less favorably to DTIC treatment compared with individuals with wild-type CYP1A alleles.

Novel, Highly Specific N-Demethylases Enable Bacteria To Live on Caffeine and Related Purine Alkaloids

PubMed Central

Summers, Ryan M.; Louie, Tai Man; Yu, Chi-Li; Gakhar, Lokesh; Louie, Kailin C.

2012-01-01

The molecular basis for the ability of bacteria to live on caffeine as a sole carbon and nitrogen source is unknown. Pseudomonas putida CBB5, which grows on several purine alkaloids, metabolizes caffeine and related methylxanthines via sequential N-demethylation to xanthine. Metabolism of caffeine by CBB5 was previously attributed to one broad-specificity methylxanthine N-demethylase composed of two subunits, NdmA and NdmB. Here, we report that NdmA and NdmB are actually two independent Rieske nonheme iron monooxygenases with N1- and N3-specific N-demethylation activity, respectively. Activity for both enzymes is dependent on electron transfer from NADH via a redox-center-dense Rieske reductase, NdmD. NdmD itself is a novel protein with one Rieske [2Fe-2S] cluster, one plant-type [2Fe-2S] cluster, and one flavin mononucleotide (FMN) per enzyme. All ndm genes are located in a 13.2-kb genomic DNA fragment which also contained a formaldehyde dehydrogenase. ndmA, ndmB, and ndmD were cloned as His6 fusion genes, expressed in Escherichia coli, and purified using a Ni-NTA column. NdmA-His6 plus His6-NdmD catalyzed N1-demethylation of caffeine, theophylline, paraxanthine, and 1-methylxanthine to theobromine, 3-methylxanthine, 7-methylxanthine, and xanthine, respectively. NdmB-His6 plus His6-NdmD catalyzed N3-demethylation of theobromine, 3-methylxanthine, caffeine, and theophylline to 7-methylxanthine, xanthine, paraxanthine, and 1-methylxanthine, respectively. One formaldehyde was produced from each methyl group removed. Activity of an N7-specific N-demethylase, NdmC, has been confirmed biochemically. This is the first report of bacterial N-demethylase genes that enable bacteria to live on caffeine. These genes represent a new class of Rieske oxygenases and have the potential to produce biofuels, animal feed, and pharmaceuticals from coffee and tea waste. PMID:22328667

Dynamic changes in DNA demethylation in the tree shrew (Tupaia belangeri chinensis) brain during postnatal development and aging.

PubMed

Wei, Shu; Hua, Hai-Rong; Chen, Qian-Quan; Zhang, Ying; Chen, Fei; Li, Shu-Qing; Li, Fan; Li, Jia-Li

2017-03-18

Brain development and aging are associated with alterations in multiple epigenetic systems, including DNA methylation and demethylation patterns. Here, we observed that the levels of the 5-hydroxymethylcytosine (5hmC) ten-eleven translocation (TET) enzyme-mediated active DNA demethylation products were dynamically changed and involved in postnatal brain development and aging in tree shrews ( Tupaia belangeri chinensis ). The levels of 5hmC in multiple anatomic structures showed a gradual increase throughout postnatal development, whereas a significant decrease in 5hmC was found in several brain regions in aged tree shrews, including in the prefrontal cortex and hippocampus, but not the cerebellum. Active changes in Tet mRNA levels indicated that TET2 and TET3 predominantly contributed to the changes in 5hmC levels. Our findings provide new insight into the dynamic changes in 5hmC levels in tree shrew brains during postnatal development and aging processes.

A functional cutin matrix is required for plant protection against water loss

PubMed Central

Ma, Jian Feng; Li, Chao; Yamaji, Naoki; Nevo, Eviatar

2011-01-01

The plant cuticle, a cutin matrix embedded with and covered by wax, seals the aerial organ's surface to protect the plant against uncontrolled water loss. The cutin matrix is essential for the cuticle to function as a barrier to water loss. Recently, we identified from wild barley a drought supersensitive mutant, eibi1, which is caused by a defective cutin matrix as the result of the loss of function of HvABCG31, an ABCG full transporter. Here, we report that eibi1 epidermal cells contain lipid-like droplets, which are supposed to consist of cutin monomers that have not been transported out of the cells. The eibi1 cuticle is fragile due to a defective cutin matrix. The rice ortholog of the EIBI1 gene has a similar pattern of expression, young shoot but not flag leaf blade, as the barley gene. The model of the function of Eibi1 is discussed. The HvABCG31 full transporter functions in the export of cutin components and contributed to land plant colonization, hence also to terrestrial life evolution. PMID:22019635

A functional cutin matrix is required for plant protection against water loss.

PubMed

Chen, Guoxiong; Komatsuda, Takao; Ma, Jian Feng; Li, Chao; Yamaji, Naoki; Nevo, Eviatar

2011-09-01

The plant cuticle, a cutin matrix embedded with and covered by wax, seals the aerial organ's surface to protect the plant against uncontrolled water loss. The cutin matrix is essential for the cuticle to function as a barrier to water loss. Recently, we identified from wild barley a drought supersensitive mutant, eibi1, which is caused by a defective cutin matrix as the result of the loss of function of HvABCG31, an ABCG full transporter. Here, we report that eibi1 epidermal cells contain lipid-like droplets, which are supposed to consist of cutin monomers that have not been transported out of the cells. The eibi1 cuticle is fragile due to a defective cutin matrix. The rice ortholog of the EIBI1 gene has a similar pattern of expression, young shoot but not flag leaf blade, as the barley gene. The model of the function of Eibi1 is discussed. The HvABCG31 full transporter functions in the export of cutin components and contributed to land plant colonization, hence also to terrestrial life evolution.

Comparative genomic analysis of isoproturon-mineralizing sphingomonads reveals the isoproturon catabolic mechanism.

PubMed

Yan, Xin; Gu, Tao; Yi, Zhongquan; Huang, Junwei; Liu, Xiaowei; Zhang, Ji; Xu, Xihui; Xin, Zhihong; Hong, Qing; He, Jian; Spain, Jim C; Li, Shunpeng; Jiang, Jiandong

2016-12-01

The worldwide use of the phenylurea herbicide, isoproturon (IPU), has resulted in considerable concern about its environmental fate. Although many microbial metabolites of IPU are known and IPU-mineralizing bacteria have been isolated, the molecular mechanism of IPU catabolism has not been elucidated yet. In this study, complete genes that encode the conserved IPU catabolic pathway were revealed, based on comparative analysis of the genomes of three IPU-mineralizing sphingomonads and subsequent experimental validation. The complete genes included a novel hydrolase gene ddhA, which is responsible for the cleavage of the urea side chain of the IPU demethylated products; a distinct aniline dioxygenase gene cluster adoQTA1A2BR, which has a broad substrate range; and an inducible catechol meta-cleavage pathway gene cluster adoXEGKLIJC. Furthermore, the initial mono-N-demethylation genes pdmAB were further confirmed to be involved in the successive N-demethylation of the IPU mono-N-demethylated product. These IPU-catabolic genes were organized into four transcription units and distributed on three plasmids. They were flanked by multiple mobile genetic elements and highly conserved among IPU-mineralizing sphingomonads. The elucidation of the molecular mechanism of IPU catabolism will enhance our understanding of the microbial mineralization of IPU and provide insights into the evolutionary scenario of the conserved IPU-catabolic pathway. © 2016 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Generation and Characterization of Induced Pluripotent Stem Cells from Aid-Deficient Mice

PubMed Central

Shimamoto, Ren; Amano, Naoki; Ichisaka, Tomoko; Watanabe, Akira; Yamanaka, Shinya; Okita, Keisuke

2014-01-01

It has been shown that DNA demethylation plays a pivotal role in the generation of induced pluripotent stem (iPS) cells. However, the underlying mechanism of this action is still unclear. Previous reports indicated that activation-induced cytidine deaminase (Aid, also known as Aicda) is involved in DNA demethylation in several developmental processes, as well as cell fusion-mediated reprogramming. Based on these reports, we hypothesized that Aid may be involved in the DNA demethylation that occurs during the generation of iPS cells. In this study, we examined the function of Aid in iPS cell generation using Aid knockout (Aid −/−) mice expressing a GFP reporter under the control of a pluripotent stem cell marker, Nanog. By introducing Oct3/4, Sox2, Klf4 and c-Myc, Nanog-GFP-positive iPS cells could be generated from the fibroblasts and primary B cells of Aid −/− mice. Their induction efficiency was similar to that of wild-type (Aid +/+) iPS cells. The Aid −/− iPS cells showed normal proliferation and gave rise to chimeras, indicating their capacity for self-renewal and pluripotency. A comprehensive DNA methylation analysis showed only a few differences between Aid +/+ and Aid −/− iPS cells. These data suggest that Aid does not have crucial functions in DNA demethylation during iPS cell generation. PMID:24718089

GPER signalling in both cancer-associated fibroblasts and breast cancer cells mediates a feedforward IL1β/IL1R1 response

PubMed Central

De Marco, Paola; Lappano, Rosamaria; Francesco, Ernestina Marianna De; Cirillo, Francesca; Pupo, Marco; Avino, Silvia; Vivacqua, Adele; Abonante, Sergio; Picard, Didier; Maggiolini, Marcello

2016-01-01

Cancer-associated fibroblasts (CAFs) contribute to the malignant aggressiveness through secreted factors like IL1β, which may drive pro-tumorigenic inflammatory phenotypes mainly acting via the cognate receptor named IL1R1. Here, we demonstrate that signalling mediated by the G protein estrogen receptor (GPER) triggers IL1β and IL1R1 expression in CAFs and breast cancer cells, respectively. Thereby, ligand-activation of GPER generates a feedforward loop coupling IL1β induction by CAFs to IL1R1 expression by cancer cells, promoting the up-regulation of IL1β/IL1R1 target genes such as PTGES, COX2, RAGE and ABCG2. This regulatory interaction between the two cell types induces migration and invasive features in breast cancer cells including fibroblastoid cytoarchitecture and F-actin reorganization. A better understanding of the mechanisms involved in the regulation of pro-inflammatory cytokines by GPER-integrated estrogen signals may be useful to target these stroma-cancer interactions. PMID:27072893

Xenobiotic interaction with and alteration of channel catfish estrogen receptor.

PubMed

Nimrod, A C; Benson, W H

1997-12-01

In teleostean in vivo studies, the vitellogenin response to environmental estrogens is not completely predicted by mammalian literature. One possible explanation for differences is heterogeneity of the estrogen receptor (ER) structure between species. Therefore, ER from channel catfish (Ictalurus punctatus) hepatic tissue was characterized by binding affinity for several compounds. Affinity was indirectly measured as potency of the chemical for inhibiting binding of radiolabeled estradiol (E2) to specific binding sites. The order of potency among therapeutic chemicals was ethinylestradiol > unlabeled E2 = diethylstilbestrol > mestranol > tamoxifen > testosterone. Unlabeled E2 had an IC50 of 2.2 nM. Several environmentally relevant chemicals were evaluated in a similar manner and the order of potency established was the o-demethylated metabolite of methoxychlor (MXC) > nonylphenol (NP) > chlordecone > MXC > o,p'-DDT > o,p'-DDE > beta-hexachlorocyclohexane. Demethylated MXC had an IC50 1000-fold greater than that of E2. Of the most potent inhibitors, NP appeared to be a competitive inhibitor for the same binding site as E2, while o-demethylated MXC had a more complex interaction with the receptor protein. ER from nonvitellogenic females was determined to have a Kd value of 1.0 to 1.3 nM. Because E2 has been reported to up-regulate teleostean ER, the hepatic ER population following in vivo xenobiotic exposure was assessed. NP significantly increased ER per milligram hepatic protein almost to the same extent as E2, but did not increase Kd to the same extent as E2.

ATP-binding cassette (ABC) proteins in aquatic invertebrates: Evolutionary significance and application in marine ecotoxicology.

PubMed

Jeong, Chang-Bum; Kim, Hui-Su; Kang, Hye-Min; Lee, Jae-Seong

2017-04-01

The ATP-binding cassette (ABC) protein superfamily is known to play a fundamental role in biological processes and is highly conserved across animal taxa. The ABC proteins function as active transporters for multiple substrates across the cellular membrane by ATP hydrolysis. As this superfamily is derived from a common ancestor, ABC genes have evolved via lineage-specific duplications through the process of adaptation. In this review, we summarized information about the ABC gene families in aquatic invertebrates, considering their evolution and putative functions in defense mechanisms. Phylogenetic analysis was conducted to examine the evolutionary significance of ABC gene families in aquatic invertebrates. Particularly, a massive expansion of multixenobiotic resistance (MXR)-mediated efflux transporters was identified in the absence of the ABCG2 (BCRP) gene in Ecdysozoa and Platyzoa, suggesting that a loss of Abcg2 gene occurred sporadically in these species during divergence of Protostome to Lophotrochozoa. Furthermore, in aquatic invertebrates, the ecotoxicological significance of MXR is discussed while considering the role of MXR-mediated efflux transporters in response to various environmental pollutants. Copyright © 2017 Elsevier B.V. All rights reserved.

DNA Methylation and Demethylation in Plant Immunity.

PubMed

Deleris, A; Halter, T; Navarro, L

2016-08-04

Detection of plant and animal pathogens triggers a massive transcriptional reprogramming, which is directed by chromatin-based processes, and ultimately results in antimicrobial immunity. Although the implication of histone modifications in orchestrating biotic stress-induced transcriptional reprogramming has been well characterized, very little was known, until recently, about the role of DNA methylation and demethylation in this process. In this review, we summarize recent findings on the dynamics and biological relevance of DNA methylation and demethylation in plant immunity against nonviral pathogens. In particular, we report the implications of these epigenetic regulatory processes in the transcriptional and co-transcriptional control of immune-responsive genes and discuss their relevance in fine-tuning antimicrobial immune responses. Finally, we discuss the possible yet elusive role of DNA methylation and demethylation in systemic immune responses, transgenerational immune priming, and de novo epiallelism, which could be adaptive.

Ligand-activated PPARα-dependent DNA demethylation regulates the fatty acid β-oxidation genes in the postnatal liver.

PubMed

Ehara, Tatsuya; Kamei, Yasutomi; Yuan, Xunmei; Takahashi, Mayumi; Kanai, Sayaka; Tamura, Erina; Tsujimoto, Kazutaka; Tamiya, Takashi; Nakagawa, Yoshimi; Shimano, Hitoshi; Takai-Igarashi, Takako; Hatada, Izuho; Suganami, Takayoshi; Hashimoto, Koshi; Ogawa, Yoshihiro

2015-03-01

The metabolic function of the liver changes sequentially during early life in mammals to adapt to the marked changes in nutritional environment. Accordingly, hepatic fatty acid β-oxidation is activated after birth to produce energy from breast milk lipids. However, how it is induced during the neonatal period is poorly understood. Here we show DNA demethylation and increased mRNA expression of the fatty acid β-oxidation genes in the postnatal mouse liver. The DNA demethylation does not occur in the fetal mouse liver under the physiologic condition, suggesting that it is specific to the neonatal period. Analysis of mice deficient in the nuclear receptor peroxisome proliferator-activated receptor α (PPARα) and maternal administration of a PPARα ligand during the gestation and lactation periods reveal that the DNA demethylation is PPARα dependent. We also find that DNA methylation of the fatty acid β-oxidation genes are reduced in the adult human liver relative to the fetal liver. This study represents the first demonstration that the ligand-activated PPARα-dependent DNA demethylation regulates the hepatic fatty acid β-oxidation genes during the neonatal period, thereby highlighting the role of a lipid-sensing nuclear receptor in the gene- and life-stage-specific DNA demethylation of a particular metabolic pathway. © 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

Quaternary ammonium oxidative demethylation: X-ray crystallographic, resonance Raman, and UV-visible spectroscopic analysis of a Rieske-type demethylase.

PubMed

Daughtry, Kelly D; Xiao, Youli; Stoner-Ma, Deborah; Cho, Eunsun; Orville, Allen M; Liu, Pinghua; Allen, Karen N

2012-02-08

Herein, the structure resulting from in situ turnover in a chemically challenging quaternary ammonium oxidative demethylation reaction was captured via crystallographic analysis and analyzed via single-crystal spectroscopy. Crystal structures were determined for the Rieske-type monooxygenase, stachydrine demethylase, in the unliganded state (at 1.6 Å resolution) and in the product complex (at 2.2 Å resolution). The ligand complex was obtained from enzyme aerobically cocrystallized with the substrate stachydrine (N,N-dimethylproline). The ligand electron density in the complex was interpreted as proline, generated within the active site at 100 K by the absorption of X-ray photon energy and two consecutive demethylation cycles. The oxidation state of the Rieske iron-sulfur cluster was characterized by UV-visible spectroscopy throughout X-ray data collection in conjunction with resonance Raman spectra collected before and after diffraction data. Shifts in the absorption band wavelength and intensity as a function of absorbed X-ray dose demonstrated that the Rieske center was reduced by solvated electrons generated by X-ray photons; the kinetics of the reduction process differed dramatically for the liganded complex compared to unliganded demethylase, which may correspond to the observed turnover in the crystal.

New structure–activity relationships of chalcone inhibitors of breast cancer resistance protein: polyspecificity toward inhibition and critical substitutions against cytotoxicity

PubMed Central

Rangel, Luciana Pereira; Winter, Evelyn; Gauthier, Charlotte; Terreux, Raphaël; Chiaradia-Delatorre, Louise D; Mascarello, Alessandra; Nunes, Ricardo J; Yunes, Rosendo A; Creczynski-Pasa, Tania B; Macalou, Sira; Lorendeau, Doriane; Baubichon-Cortay, Hélène; Ferreira-Pereira, Antonio; Di Pietro, Attilio

2013-01-01

Adenosine triphosphate-binding cassette subfamily G member 2 (ABCG2) plays a major role in cancer cell multidrug resistance, which contributes to low eifficacy of chemotherapy. Chalcones were recently found to be potent and specific inhibitors, but unfortunately display a significant cytotoxicity. A cellular screening against ABCG2-mediated mitoxantrone efflux was performed here by flow cytometry on 54 chalcone derivatives from three different series with a wide panel of substituents. The identified leads, with submicromolar IC50 (half maximal inhibitory concentration) values, showed that the previously identified 2′-OH-4′,6′-dimethoxyphenyl, as A-ring, could be efficiently replaced by a 2′-naphthyl group, or a 3′,4′-methylenedioxyphenyl with lower affinity. Such a structural variability indicates 3polyspecificity of the multidrug transporter for inhibitors. At least two methoxyl groups were necessary on B-ring for optimal inhibition, but substitution at positions 3, 4, and 5 induced cytotoxicity. The presence of a large O-benzyl substituent at position 4 and a 2′-naphthyl as A-ring markedly decreased the cytotoxicity, giving a high therapeutic ratio, which constitutes a critical requirement for future in-vivo assays in animal models. PMID:24109177

Genetic association analysis of ATP binding cassette protein family reveals a novel association of ABCB1 genetic variants with epilepsy risk, but not with drug-resistance.

PubMed

Balan, Shabeesh; Bharathan, Sumitha Prameela; Vellichiramal, Neetha Nanoth; Sathyan, Sanish; Joseph, Vijai; Radhakrishnan, Kurupath; Banerjee, Moinak

2014-01-01

Epilepsy constitutes a heterogeneous group of disorders that is characterized by recurrent unprovoked seizures due to widely different etiologies. Multidrug resistance remains a major issue in clinical epileptology, where one third of patients with epilepsy continue to have seizures. Role of efflux transporters in multidrug resistant epilepsy has been attributed to drug-resistant epilepsy although, with discrepant observation in genetic studies. These discrepancies could be attributed to variety of factors such as variable definition of the anti-epileptic drug (AED)-resistance, variable epilepsy phenotypes and ethnicities among the studies. In the present study we inquired the role of multidrug transporters ABCB1 and ABCG2 variants in determining AED-resistance and susceptibility to epilepsy in three well-characterized cohorts comprising of mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) (prototype for AED-resistant epilepsy); juvenile myoclonic epilepsy (JME) (prototype for AED-responsive epilepsy); and healthy non-epileptic controls, in 738 subjects of Malayalam speaking south Indian ancestry. ABCB1 and ABCG2 variants were not found to be associated with drug resistance when AED-resistant and AED-responsive cohorts were compared. However, a significant association was observed between ABCB1 (C3435T) rs1045642 and risk of having epilepsy (MTLE-HS and JME pooled cohort; genotypic p-value = 0.0002; allelic p-value = 0.004). This association was seen persistent with MTLE-HS (genotypic p-value = 0.0008; allelic p-value = 0.004) and also with JME (genotypic p-value = 0.01; allelic p-value = 0.05) cohort individually. In-silico functional prediction indicated that ABCB1 rs1045642 has a deleterious impact on protein coding function and in splicing regulation. We conclude that the ABCB1 and ABCG2 variants do not confer to AED-resistance in the study population. However, ABCB1 rs1045642 increases vulnerability to epilepsy with greater tendency for MTLE-HS in south Indian ancestry from Kerala.

Isolation and clonal characterization of hematopoietic and liver stem cells.

PubMed

Nakauchi, Hiromitsu

2004-11-01

Prospective isolation of stem cells is essential to understanding the mechanisms that control their proliferation and differentiation. Using 9 monoclonal antibodies and fluorescence-activated cell sorting (FACS), we have succeeded in prospectively identifying hematopoietic stem cells (HSCs) in adult mouse bone marrow. Mouse HSCs were exclusively enriched in CD34 negative, c-Kit Sca-1 Lineage Marker (CD34 KSL) cells representing 0.004% of bone marrow (BM) mononuclear cells. When single CD34-KSL cells were transplanted individually into a lethally irradiated mouse, 25% of the recipient mice survived and showed long-term reconstitution of the BM, providing evidence for multipotency and a self-renewal capacity of HSCs. Using a similar approach, we also prospectively identified hepatic stem cells with multilineage differentiation potential and self-renewal capability in the c-Met CD49f c-Kit CD45 Ter119 fraction of cells isolated from day 13.5 fetal mouse liver. On cell transplantation, these cells differentiated into hepatocytes and cholangiocytes. As an alternative to the antibody based stem cell isolation, Hoechst33342 staining is useful. To understand the mechanism responsible for SP phenotype, we performed an expression cloning and identified bcrp-1/ABCG2 gene, a member of ATP binding-cassette (ABC) transporter family. Bcrp-1 is almost exclusively expressed in CD34 KSL cells among blood cells; however their expression in other tissue specific stem cells remains to be studied. With the use of FACS and monoclonal antibodies, hematopoietic and liver stem cells were prospectively isolated and characterized. HSCs could also be purified by Hoechst 33342 staining. By expression cloning, we identify bcrp-1/ABCG2 transporter as a molecule responsible for SP phenotype. Elucidation of the physiological role of bcrp-1/ABCG2 in HSCs may provide us with clues to understand the molecular mechanisms of stem cell self-renewal and differentiation.

Genetic and Dietary Regulation of Glyburide Efflux by the Human Placental Breast Cancer Resistance Protein Transporter.

PubMed

Bircsak, Kristin M; Gupta, Vivek; Yuen, Poi Yu Sofia; Gorczyca, Ludwik; Weinberger, Barry I; Vetrano, Anna M; Aleksunes, Lauren M

2016-04-01

Glyburide is frequently used to treat gestational diabetes owing to its low fetal accumulation resulting from placental efflux by the breast cancer resistance protein (BCRP)/ABCG2 transporter. Here we sought to determine how exposure to the dietary phytoestrogen genistein and expression of a loss-of-function polymorphism in the ABCG2 gene (C421A) impacted the transport of glyburide by BCRP using stably transfected human embryonic kidney 293 (HEK) cells, human placental choriocarcinoma BeWo cells, and human placental explants. Genistein competitively inhibited the BCRP-mediated transport of (3)H-glyburide in both wild-type (WT) and C421A-BCRP HEK-expressing cells, with greater accumulation of (3)H-glyburide in cells expressing the C421A variant. In BeWo cells, exposure to genistein for 60 minutes increased the accumulation of (3)H-glyburide 30%-70% at concentrations relevant to dietary exposure (IC50 ∼180 nM). Continuous exposure of BeWo cells to genistein for 48 hours reduced the expression of BCRP mRNA and protein by up to 40%, which impaired BCRP transport activity. Pharmacologic antagonism of the estrogen receptor attenuated the genistein-mediated downregulation of BCRP expression, suggesting that phytoestrogens may reduce BCRP levels through this hormone receptor pathway in BeWo cells. Interestingly, genistein treatment for 48 hours did not alter BCRP protein expression in explants dissected from healthy term placentas. These data suggest that whereas genistein can act as a competitive inhibitor of BCRP-mediated transport, its ability to downregulate placental BCRP expression may only occur in choriocarcinoma cells. Overall, this research provides important mechanistic data regarding how the environment (dietary genistein) and a frequent genetic variant (ABCG2, C421A) may alter the maternal-fetal disposition of glyburide. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olsen, Todd Andrew; Brandt, Craig C.; Brooks, Scott C.

Mercury (Hg) methylation and methylmercury (MMHg) demethylation activity of periphyton biofilms from East Fork Poplar Creek, Tennessee, USA (EFPC) were measured during 2014-2015 using stable Hg isotopic rate assays. 201Hg II and MM 202Hg were added to intact periphyton samples and the formation of MM 201Hg and loss of MM 202Hg were monitored over time and used to calculate first-order rate constants for methylation and demethylation, respectively. The influence of location, temperature/season, light exposure and biofilm structure on methylation and demethylation were examined. Between-site differences in net methylation for samples collected from an upstream versus downstream location were driven bymore » differences in the demethylation rate constant (k d). In contrast, the within-site seasonal difference in net methylation was driven by changes in the methylation rate constant (k m). Samples incubated in the dark had lower net methylation due to km values that were 60% less than those incubated in the light. Disrupting the biofilm structure decreased km by 50% and resulted in net demethylating conditions. Overall, the measured rates resulted in a net excess of MMHg generated which could account for 27-85% of the MMHg flux in EFPC and suggests intact, actively photosynthesizing periphyton biofilms harbor zones of MMHg production.« less

An AP Endonuclease Functions in Active DNA Demethylation and Gene Imprinting in Arabidopsis

PubMed Central

Li, Yan; Córdoba-Cañero, Dolores; Qian, Weiqiang; Zhu, Xiaohong; Tang, Kai; Zhang, Huiming; Ariza, Rafael R.; Roldán-Arjona, Teresa; Zhu, Jian-Kang

2015-01-01

Active DNA demethylation in plants occurs through base excision repair, beginning with removal of methylated cytosine by the ROS1/DME subfamily of 5-methylcytosine DNA glycosylases. Active DNA demethylation in animals requires the DNA glycosylase TDG or MBD4, which functions after oxidation or deamination of 5-methylcytosine, respectively. However, little is known about the steps following DNA glycosylase action in the active DNA demethylation pathways in plants and animals. We show here that the Arabidopsis APE1L protein has apurinic/apyrimidinic endonuclease activities and functions downstream of ROS1 and DME. APE1L and ROS1 interact in vitro and co-localize in vivo. Whole genome bisulfite sequencing of ape1l mutant plants revealed widespread alterations in DNA methylation. We show that the ape1l/zdp double mutant displays embryonic lethality. Notably, the ape1l+/−zdp−/− mutant shows a maternal-effect lethality phenotype. APE1L and the DNA phosphatase ZDP are required for FWA and MEA gene imprinting in the endosperm and are important for seed development. Thus, APE1L is a new component of the active DNA demethylation pathway and, together with ZDP, regulates gene imprinting in Arabidopsis. PMID:25569774

Modifying effects of 5-azacytidine on metal-containing proteins profile in Guerin carcinoma with different sensitivity to cytostatics.

PubMed

Chekhun, V F; Lozovska, Y V; Naleskina, L A; Borikun, T V; Burlaka, A P; Todor, I N; Demash, D V; Yalovenko, T M; Zadvornyi, T V; Pavlova, A O; Storchay, D M; Lukianova, N Yu

2016-12-01

To assess the influence of the treatment with 5-azacytidine (5-aza) on the profile of metal-containing proteins and factors of their regulation in Guerin carcinoma cells in vivo. The study was conducted on Wistar rats transplanted with wild-type Guerin carcinoma (Guerin/WT) and its strains resistant to cisplatin (Guerin/CP) or doxorubicin (Guerin/Dox). Animals were distributed in 6 groups treated with 5-aza and control animals without treatment. 5-Aza was injected by i.v. route (1 injection in 4 days at a dose of 2 mg/kg starting from the 4 th day after tumor transplantation, 4 injections in total). Ferritin levels in blood serum and tumor tissue were measured by ELISA, transferrin and free iron complexes - by low-temperature EPR, miRNA-200b, -133a and -320a levels and promoter methylation - by real-time quantitative reverse transcription polymerase chain reaction. The study has shown that 5-aza treatment caused demethylation of promoter regions of fth1 and tfr1 genes in all studied Guerin carcinoma strains. 5-Aza treatment resulted in a significant decrease of ferritin levels in tumor tissue (by 32.1% in Guerin/WT strain, by 29.8% in Guerin/Dox and by 69.1% in Guerin/CP). These events were accompanied by 3.5-fold and 2-fold increase of free iron complexes levels in tumor tissue of doxorubicin and cisplatin resistant strains, respectively. Also, 5-aza treatment resulted in significantly elevated levels of miR-200b, -133a, 320a expression in tumor tissue. After 5-aza treatment, ferritin levels in blood serum of animals with Guerin/Dox were increased by 23.9%, while in Guerin/Wt and Guerin/CP they were decreased by 17 and 16%, respectively. Alterations of epigenetic regulation upon in vivo treatment with 5-aza change the levels of metal-containing proteins due to DNA demethylation and altered miRNA expression profiles in Guerin carcinoma cells.

Effects of Methylation Status of CpG Sites within the HPV16 Long Control Region on HPV16-Positive Head and Neck Cancer Cells.

PubMed

Zhang, Chunlin; Deng, Zeyi; Pan, Xiaoli; Uehara, Takayuki; Suzuki, Mikio; Xie, Minqiang

2015-01-01

To map comprehensively the methylation status of the CpG sites within the HPV16 long control region (LCR) in HPV-positive cancer cells, and to explore further the effects of methylation status of HPV16 LCR on cell bioactivity and E6 and E7 expression. In addition, to analyze the methylation status of the LCR in HPV-positive oropharyngeal squamous cell carcinoma (OPSCC) patients. Methylation patterns of HPV16 LCR in UM-SCC47, CaSki, and SiHa cells and HPV16-positiive OPSCC specimens were detected by bisulfite-sequencing PCR and TA cloning. For cells treated with 5-aza-2'-deoxycytidine and E6 and E7 knockdown, MTS and trypan blue staining, annexin-V and 7-AAD staining, and prodidium iodide were used to evaluate cell growth and cell proliferation, cell apoptosis, and cell cycle arrest, respectively. E6 and E7 mRNA and protein expression were analyzed by quantitative real-time PCR and immunocytochemistry, respectively. Hypermethylation status of the LCR in UM-SCC47 (79.8%) and CaSki cells (90.0%) and unmethylation status of the LCR in SiHa cells (0%) were observed. Upon demethylation, the cells with different methylation levels responded differently during growth, apoptosis, and cell cycle arrest, as well as in terms of their E6 and E7 expression. In HPV16-positive OPSCC patients, the methylation rates were 9.5% in the entire LCR region, 13.9% in the 5'-LCR, 6.0% in the E6 enhancer, and 9.5% in the p97 promoter, and hypermethylation of p97 promoter was found in a subset of cases (20.0%, 2/10). Our study revealed two different methylation levels of the LCR in HPV16-positive cancer cells and OPSCC patients, which may represent different carcinogenesis mechanisms of HPV-positive cancers cells. Demethylating the meCpGs in HPV16 LCR might be a potential target for a subgroup of HPV16-positive patients with head and neck squamous cell carcinoma.

Omega 3 Fatty Acids Promote Macrophage Reverse Cholesterol Transport in Hamster Fed High Fat Diet

PubMed Central

Kasbi Chadli, Fatima; Nazih, Hassane; Krempf, Michel; Nguyen, Patrick; Ouguerram, Khadija

2013-01-01

The aim of this study was to investigate macrophage reverse cholesterol transport (RCT) in hamster, a CETP-expressing species, fed omega 3 fatty acids (ω3PUFA) supplemented high fat diet (HFD). Three groups of hamsters (n = 6/group) were studied for 20 weeks: 1) control diet: Control, 2) HFD group: HF and 3) HFD group supplemented with ω3PUFA (EPA and DHA): HFω3. In vivo macrophage-to-feces RCT was assessed after an intraperitoneal injection of 3H-cholesterol-labelled hamster primary macrophages. Compared to Control, HF presented significant (p<0.05) increase in body weight, plasma TG (p<0.01) and cholesterol (p<0.001) with an increase in VLDL TG and in VLDL and LDL cholesterol (p<0.001). Compared to HF, HFω3 presented significant decrease in body weight. HFω3 showed less plasma TG (p<0.001) and cholesterol (p<0.001) related to a decrease in VLDL TG and HDL cholesterol respectively and higher LCAT activity (p<0.05) compared to HF. HFω3 showed a higher fecal bile acid excretion (p<0.05) compared to Control and HF groups and higher fecal cholesterol excretion (p<0.05) compared to HF. This increase was related to higher gene expression of ABCG5, ABCA1 and SR-B1 in HFω3 compared to Control and HF groups (<0.05) and in ABCG1 and CYP7A1 compared to HF group (p<0.05). A higher plasma efflux capacity was also measured in HFω3 using 3H- cholesterol labeled Fu5AH cells. In conclusion, EPA and DHA supplementation improved macrophage to feces reverse cholesterol transport in hamster fed HFD. This change was related to the higher cholesterol and fecal bile acids excretion and to the activation of major genes involved in RCT. PMID:23613796

Side population cells in the human vocal fold.

PubMed

Yamashita, Masaru; Hirano, Shigeru; Kanemaru, Shin-ichi; Tsuji, Shunichiro; Suehiro, Atsushi; Ito, Juichi

2007-11-01

The regenerative processes of the vocal fold, or the existence of stem cells in the folds, are unknown. Side population (SP) cells are defined as cells that have the ability to exclude the DNA binding dye, Hoechst 33342. They are regarded as a cell population enriched with stem cells and can be isolated from non-SP cells by a fluorescence-activated cell sorter. This study was designed to determine whether SP cells exist in the human vocal fold, as a first step in elucidating the regenerative mechanisms of the vocal fold. Seven human excised larynges were used in this study. Two were used for fluorescence-activated cell sorter analysis, and 5 were subjected to immunohistochemical analysis with antibodies against an adenosine triphosphate binding cassette transporter family member, ABCG2, which is expressed in SP cells. The number of SP cells in the human vocal fold was about 0.2% of the total number of cells. ABCG2-positive cells were identified in both the epithelium and subepithelial tissue throughout the entire vocal fold. This preliminary study demonstrated the existence of SP cells in the human vocal fold. Further studies are warranted to clarify how these cells work in the vocal fold, particularly in the regenerative process.

Stress enhances the gene expression and enzyme activity of phenylalanine ammonia-lyase and the endogenous content of salicylic acid to induce flowering in pharbitis.

PubMed

Wada, Kaede C; Mizuuchi, Kaori; Koshio, Aya; Kaneko, Kentaro; Mitsui, Toshiaki; Takeno, Kiyotoshi

2014-07-01

The involvement of salicylic acid (SA) in the regulation of stress-induced flowering in the short-day plant pharbitis (also called Japanese morning glory) Ipomoea nil (formerly Pharbitis nil) was studied. Pharbitis cv. Violet was induced to flower when grown in 1/100-strength mineral nutrient solution under non-inductive long-day conditions. All fully expanded true leaves were removed from seedlings, leaving only the cotyledons, and flowering was induced under poor-nutrition stress conditions. This indicates that cotyledons can play a role in the regulation of poor-nutrition stress-induced flowering. The expression of the pharbitis homolog of PHENYLALANINE AMMONIA-LYASE, the enzyme activity of phenylalanine ammonia-lyase (PAL; E.C. 4.3.1.5) and the content of SA in the cotyledons were all up-regulated by the stress treatment. The Violet was also induced to flower by low-temperature stress, DNA demethylation and short-day treatment. Low-temperature stress enhanced PAL activity, whereas non-stress factors such as DNA demethylation and short-day treatment decreased the activity. The PAL enzyme activity was also examined in another cultivar, Tendan, obtaining similar results to Violet. The exogenously applied SA did not induce flowering under non-stress conditions but did promote flowering under weak stress conditions in both cultivars. These results suggest that stress-induced flowering in pharbitis is induced, at least partly, by SA, and the synthesis of SA is promoted by PAL. Copyright © 2014 Elsevier GmbH. All rights reserved.

ERG induces epigenetic activation of Tudor domain-containing protein 1 (TDRD1) in ERG rearrangement-positive prostate cancer.

PubMed

Kacprzyk, Lukasz A; Laible, Mark; Andrasiuk, Tatjana; Brase, Jan C; Börno, Stefan T; Fälth, Maria; Kuner, Ruprecht; Lehrach, Hans; Schweiger, Michal R; Sültmann, Holger

2013-01-01

Overexpression of ERG transcription factor due to genomic ERG-rearrangements defines a separate molecular subtype of prostate tumors. One of the consequences of ERG accumulation is modulation of the cell's gene expression profile. Tudor domain-containing protein 1 gene (TDRD1) was reported to be differentially expressed between TMPRSS2:ERG-negative and TMPRSS2:ERG-positive prostate cancer. The aim of our study was to provide a mechanistic explanation for the transcriptional activation of TDRD1 in ERG rearrangement-positive prostate tumors. Gene expression measurements by real-time quantitative PCR revealed a remarkable co-expression of TDRD1 and ERG (r(2) = 0.77) but not ETV1 (r(2)<0.01) in human prostate cancer in vivo. DNA methylation analysis by MeDIP-Seq and bisulfite sequencing showed that TDRD1 expression is inversely correlated with DNA methylation at the TDRD1 promoter in vitro and in vivo (ρ = -0.57). Accordingly, demethylation of the TDRD1 promoter in TMPRSS2:ERG-negative prostate cancer cells by DNA methyltransferase inhibitors resulted in TDRD1 induction. By manipulation of ERG dosage through gene silencing and forced expression we show that ERG governs loss of DNA methylation at the TDRD1 promoter-associated CpG island, leading to TDRD1 overexpression. We demonstrate that ERG is capable of disrupting a tissue-specific DNA methylation pattern at the TDRD1 promoter. As a result, TDRD1 becomes transcriptionally activated in TMPRSS2:ERG-positive prostate cancer. Given the prevalence of ERG fusions, TDRD1 overexpression is a common alteration in human prostate cancer which may be exploited for diagnostic or therapeutic procedures.

Epigenetic alteration at the DLK1-GTL2 imprinted domain in human neoplasia: analysis of neuroblastoma, phaeochromocytoma and Wilms' tumour

PubMed Central

Astuti, D; Latif, F; Wagner, K; Gentle, D; Cooper, W N; Catchpoole, D; Grundy, R; Ferguson-Smith, A C; Maher, E R

2005-01-01

Epigenetic alterations in the 11p15.5 imprinted gene cluster are frequent in human cancers and are associated with disordered imprinting of insulin-like growth factor (IGF)2 and H19. Recently, an imprinted gene cluster at 14q32 has been defined and includes two closely linked but reciprocally imprinted genes, DLK1 and GTL2, that have similarities to IGF2 and H19, respectively. Both GTL2 and H19 are maternally expressed RNAs with no protein product and display paternal allele promoter region methylation, and DLK1 and IGF2 are both paternally expressed. To determine whether methylation alterations within the 14q32 imprinted domain occur in human tumorigenesis, we investigated the status of the GTL2 promoter differentially methylated region (DMR) in 20 neuroblastoma tumours, 20 phaeochromocytomas and, 40 Wilms' tumours. Hypermethylation of the GTL2 promoter DMR was detected in 25% of neuroblastomas, 10% of phaeochromocytoma and 2.5% of Wilms' tumours. Tumours with GTL2 promoter DMR hypermethylation also demonstrated hypermethylation at an upstream intergenic DMR thought to represent a germline imprinting control element. Analysis of neuroblastoma cell lines revealed that GTL2 DMR hypermethylation was associated with transcriptional repression of GTL2. These epigenetic findings are similar to those reported in Wilms' tumours in which H19 repression and DMR hypermethylation is associated with loss of imprinting (LOI, biallelic expression) of IGF2. However, a neuroblastoma cell line with hypermethylation of the GTL2 promoter and intergenic DMR did not show LOI of DLK1 and although treatment with a demethylating agent restored GTL2 expression and reduced DLK1 expression. As described for IGF2/H19, epigenetic changes at DLK1/GTL2 occur in human cancers. However, these changes are not associated with DLK1 LOI highlighting differences in the imprinting control mechanisms operating in the IGF2-H19 and DLK1-GTL2 domains. GTL2 promoter and intergenic DMR hypermethylation is associated with the loss of GTL2 expression and this may contribute to tumorigenesis in a subset of human cancers. PMID:15798773

Method for recovering and using lignin in adhesive resins

DOEpatents

Schroeder, Herbert A.

1993-01-01

Lignin, or a lignin derived material, which has been significantly demethylated (e.g., the demethylated lignin found in the raffinate produced as a by-product of dimethyl sulfide production which can be carried out using the spent liquor from wood pulping operations) can be isolated by a process wherein an organic solvent is added to a lignin-containing aqueous solution. The organic solvent is typically a polar, and at least a partially water-immiscible substance such as, for example, ethyl acetate. The resulting lignin-containing aqueous solution/organic solvent mixture is acidified to produce a water layer which is discarded and an organic solvent layer which contains the demethylated lignin. Upon its recovery, the demethylated lignin is dissolved in an alkaline solution to which an aldehyde source is added to produce a resol-type resin. The aldehyde source may be formaldehyde in solution, paraformaldehyde, hexamethylenetetramine, or other aldehydes including acetaldehyde, furfural, and their derivatives.

Effects of miR-33a-5P on ABCA1/G1-Mediated Cholesterol Efflux under Inflammatory Stress in THP-1 Macrophages

PubMed Central

Mao, Min; Lei, Han; Liu, Qing; Chen, Yaxi; Zhao, Lei; Li, Qing; Luo, Suxin; Zuo, Zhong; He, Quan; Huang, Wei; Zhang, Nan; Zhou, Chao; Ruan, Xiong Z.

2014-01-01

The present study is to investigate whether inflammatory cytokines inhibit ABCA1/ABCG1-mediated cholesterol efflux by regulating miR-33a-5P in THP-1 macrophages. We used interleukin-6 and tumor necrosis factor-alpha in the presence or absence of native low density lipoprotein (LDL) to stimulate THP-1 macrophages. THP-1 macrophages were infected by either control lentivirus vectors or lentivirus encoding miR-33a-5P or antisense miR-33a-5P. The effects of inflammatory cytokines, miR-33a-5P and antisense miR-33a-5P on intracellular lipids accumulation and intracellular cholesterol contents were assessed by oil red O staining and quantitative intracellular cholesterol assay. ApoA-I-mediated cholesterol efflux was examined using the fluorescent sterol (BODIPY-cholesterol). The gene and protein expressions of the molecules involved in cholesterol trafficking were examined using quantitative real-time polymerase chain reaction and Western blotting. Inflammatory cytokines or miR-33a-5P increased intracellular lipid accumulation and decreased apoA-I-mediated cholesterol efflux via decreasing the expression of ABCA1 and ABCG1 in the absence or presence of LDL in THP-1 macrophages. However, antisense miR-33a-5P reversed the effects of inflammatory cytokines on intracellular lipid accumulation, cholesterol efflux, and the expression of miR-33a-5P, ABCA1 and ABCG1 in the absence or presence of LDL in THP-1 macrophages. This study indicated that inflammatory cytokines inhibited ABCA1/ABCG1-mediated cholesterol efflux by up-regulating miR-33a-5P in THP-1 macrophages. PMID:25329888

Effect of vildagliptin and pravastatin combination on cholesterol efflux in adipocytes.

PubMed

Mostafa, Ahmed M; Hamdy, Nadia M; Abdel-Rahman, Sherif Z; El-Mesallamy, Hala O

2016-07-01

Many reports suggested that some statins are almost ineffective in reducing triglycerides or enhancing HDL-C plasma levels, although statin treatment was still efficacious in reducing LDL-C. In diabetic dyslipidemic patients, it may therefore be necessary to use a combination therapy with other drugs to achieve either LDL-C- and triglyceride-lowering or HDL-C-enhancing goals. Such ineffectiveness of statins can be attributed to their effect on the liver X receptor (LXR) which regulates the expression of the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. A decrease in the expression of these transporters eventually leads to decreased cholesterol efflux from peripheral tissues leading to low levels of HDL-C. Although manipulating the LXR pathway may complement the effects of statins, LXR synthetic ligands as T091317 have shown significant hypertriglyceridemic action which limits their use. We recently found that the antidiabetic drug vildagliptin stimulates LXR expression leading to increased ABCB1/ABCG1 expression which improves cholesterol efflux from adipocytes. Therefore, a combination of vildagliptin and statin may provide a solution without the hypertriglyceridemic action observed with LXR agonist. We hypothesize that a combination of vildagliptin and pravastatin will improve cholesterol efflux in adipocytes. Statin-treated 3T3-L1 adipocytes were treated with vildagliptin, and the expression of LXR-ABCA1/ABCG1 cascade and the cholesterol efflux were then determined. Our data indicate that a combination of vildagliptin and pravastatin significantly induces the expression of LXR-ABCA1/ABCG1 cascade and improves cholesterol efflux (P > 0.05) in adipocytes. Our data may explain, at least in part, the improvement in HDL-C levels observed in patients receiving both medications. © 2016 IUBMB Life, 68(7):535-543, 2016. © 2016 International Union of Biochemistry and Molecular Biology.

Euterpe oleracea Mart.-Derived Polyphenols Protect Mice from Diet-Induced Obesity and Fatty Liver by Regulating Hepatic Lipogenesis and Cholesterol Excretion.

PubMed

de Oliveira, Paola Raquel B; da Costa, Cristiane A; de Bem, Graziele F; Cordeiro, Viviane S C; Santos, Izabelle B; de Carvalho, Lenize C R M; da Conceição, Ellen Paula S; Lisboa, Patrícia Cristina; Ognibene, Dayane T; Sousa, Pergentino José C; Martins, Gabriel R; da Silva, Antônio Jorge R; de Moura, Roberto S; Resende, Angela C

2015-01-01

The aim of this study was to investigate the effect of a polyphenol-rich Açaí seed extract (ASE, 300 mg/kg-1d-1) on adiposity and hepatic steatosis in mice that were fed a high-fat (HF) diet and its underlying mechanisms based on hepatic lipid metabolism and oxidative stress. Four groups were studied: C57BL/6 mice that were fed with standard diet (10% fat, Control), 10% fat + ASE (ASE), 60% fat (HF), and 60% fat + ASE (HF + ASE) for 12 weeks. We evaluated the food intake, body weight gain, serum glucose and lipid profile, hepatic cholesterol and triacyglycerol (TG), hepatic expression of pAMPK, lipogenic proteins (SREBP-1c, pACC, ACC, HMG-CoA reductase) and cholesterol excretion transporters, ABCG5 and ABCG8. We also evaluated the steatosis in liver sections and oxidative stress. ASE reduced body weight gain, food intake, glucose levels, accumulation of cholesterol and TG in the liver, which was associated with a reduction of hepatic steatosis. The increased expressions of SREBP-1c and HMG-CoA reductase and reduced expressions of pAMPK and pACC/ACC in HF group were antagonized by ASE. The ABCG5 and ABCG8 transporters expressions were increased by the extract. The antioxidant effect of ASE was demonstrated in liver of HF mice by restoration of SOD, CAT and GPx activities and reduction of the increased levels of malondialdehyde and protein carbonylation. In conclusion, ASE substantially reduced the obesity and hepatic steatosis induced by HF diet by reducing lipogenesis, increasing cholesterol excretion and improving oxidative stress in the liver, providing a nutritional resource for prevention of obesity-related adiposity and hepatic steatosis.

Euterpe oleracea Mart.-Derived Polyphenols Protect Mice from Diet-Induced Obesity and Fatty Liver by Regulating Hepatic Lipogenesis and Cholesterol Excretion

PubMed Central

de Bem, Graziele F.; Cordeiro, Viviane S. C.; Santos, Izabelle B.; de Carvalho, Lenize C. R. M.; da Conceição, Ellen Paula S.; Lisboa, Patrícia Cristina; Ognibene, Dayane T.; Sousa, Pergentino José C.; Martins, Gabriel R.; da Silva, Antônio Jorge R.; de Moura, Roberto S.; Resende, Angela C.

2015-01-01

The aim of this study was to investigate the effect of a polyphenol-rich Açaí seed extract (ASE, 300 mg/kg-1d-1) on adiposity and hepatic steatosis in mice that were fed a high-fat (HF) diet and its underlying mechanisms based on hepatic lipid metabolism and oxidative stress. Four groups were studied: C57BL/6 mice that were fed with standard diet (10% fat, Control), 10% fat + ASE (ASE), 60% fat (HF), and 60% fat + ASE (HF + ASE) for 12 weeks. We evaluated the food intake, body weight gain, serum glucose and lipid profile, hepatic cholesterol and triacyglycerol (TG), hepatic expression of pAMPK, lipogenic proteins (SREBP-1c, pACC, ACC, HMG-CoA reductase) and cholesterol excretion transporters, ABCG5 and ABCG8. We also evaluated the steatosis in liver sections and oxidative stress. ASE reduced body weight gain, food intake, glucose levels, accumulation of cholesterol and TG in the liver, which was associated with a reduction of hepatic steatosis. The increased expressions of SREBP-1c and HMG-CoA reductase and reduced expressions of pAMPK and pACC/ACC in HF group were antagonized by ASE. The ABCG5 and ABCG8 transporters expressions were increased by the extract. The antioxidant effect of ASE was demonstrated in liver of HF mice by restoration of SOD, CAT and GPx activities and reduction of the increased levels of malondialdehyde and protein carbonylation. In conclusion, ASE substantially reduced the obesity and hepatic steatosis induced by HF diet by reducing lipogenesis, increasing cholesterol excretion and improving oxidative stress in the liver, providing a nutritional resource for prevention of obesity-related adiposity and hepatic steatosis. PMID:26630290

Effects of miR-33a-5P on ABCA1/G1-mediated cholesterol efflux under inflammatory stress in THP-1 macrophages.

PubMed

Mao, Min; Lei, Han; Liu, Qing; Chen, Yaxi; Zhao, Lei; Li, Qing; Luo, Suxin; Zuo, Zhong; He, Quan; Huang, Wei; Zhang, Nan; Zhou, Chao; Ruan, Xiong Z

2014-01-01

The present study is to investigate whether inflammatory cytokines inhibit ABCA1/ABCG1-mediated cholesterol efflux by regulating miR-33a-5P in THP-1 macrophages. We used interleukin-6 and tumor necrosis factor-alpha in the presence or absence of native low density lipoprotein (LDL) to stimulate THP-1 macrophages. THP-1 macrophages were infected by either control lentivirus vectors or lentivirus encoding miR-33a-5P or antisense miR-33a-5P. The effects of inflammatory cytokines, miR-33a-5P and antisense miR-33a-5P on intracellular lipids accumulation and intracellular cholesterol contents were assessed by oil red O staining and quantitative intracellular cholesterol assay. ApoA-I-mediated cholesterol efflux was examined using the fluorescent sterol (BODIPY-cholesterol). The gene and protein expressions of the molecules involved in cholesterol trafficking were examined using quantitative real-time polymerase chain reaction and Western blotting. Inflammatory cytokines or miR-33a-5P increased intracellular lipid accumulation and decreased apoA-I-mediated cholesterol efflux via decreasing the expression of ABCA1 and ABCG1 in the absence or presence of LDL in THP-1 macrophages. However, antisense miR-33a-5P reversed the effects of inflammatory cytokines on intracellular lipid accumulation, cholesterol efflux, and the expression of miR-33a-5P, ABCA1 and ABCG1 in the absence or presence of LDL in THP-1 macrophages. This study indicated that inflammatory cytokines inhibited ABCA1/ABCG1-mediated cholesterol efflux by up-regulating miR-33a-5P in THP-1 macrophages.

Epigenetic Heterogeneity of B-Cell Lymphoma: Chromatin Modifiers

PubMed Central

Hopp, Lydia; Nersisyan, Lilit; Löffler-Wirth, Henry; Arakelyan, Arsen; Binder, Hans

2015-01-01

We systematically studied the expression of more than fifty histone and DNA (de)methylating enzymes in lymphoma and healthy controls. As a main result, we found that the expression levels of nearly all enzymes become markedly disturbed in lymphoma, suggesting deregulation of large parts of the epigenetic machinery. We discuss the effect of DNA promoter methylation and of transcriptional activity in the context of mutated epigenetic modifiers such as EZH2 and MLL2. As another mechanism, we studied the coupling between the energy metabolism and epigenetics via metabolites that act as cofactors of JmjC-type demethylases. Our study results suggest that Burkitt’s lymphoma and diffuse large B-cell Lymphoma differ by an imbalance of repressive and poised promoters, which is governed predominantly by the activity of methyltransferases and the underrepresentation of demethylases in this regulation. The data further suggest that coupling of epigenetics with the energy metabolism can also be an important factor in lymphomagenesis in the absence of direct mutations of genes in metabolic pathways. Understanding of epigenetic deregulation in lymphoma and possibly in cancers in general must go beyond simple schemes using only a few modes of regulation. PMID:26506391

Investigating Methylmercury Exposure in North Atlantic Cetaceans Using Multiple Isotope Tracers

NASA Astrophysics Data System (ADS)

Li, M.; Mikkelsen, B.; Yin, R.; Krabbenhoft, D. P.; Sunderland, E. M.

2016-12-01

Anthropogenic emissions have substantially perturbed the global biogeochemical cycle of mercury (Hg) and high latitude ecosystems are particularly vulnerable to Hg pollution and climate change. We investigated temporal changes in methylmercury (MeHg) exposures of long-finned pilot whales (Globicephala melas, n=59) between 1985-2015 using multiple isotopes (δ202Hg, Δ199Hg, Δ200Hg, Δ201Hg, δ13C, δ15N) as tracers of the physical environment and foraging ecology. Mass-independent fraction (MIF) of Hg (Δ199Hg, Δ201Hg) is mainly driven by photochemical demethylation in seawater. Enriched δ202Hg has been shown to result from demethylation. The ranges in Δ199Hg and Δ201Hg values in whales are similar across time periods with the exception of a few years following the 2010 volcanic eruption in Iceland that may have affected light penetration in surface waters. The mean δ202Hg values of whale muscle samples are consistently 1.5 ‰ across the study period, which is 1 ‰ higher than their prey (squid, blue whiting, and greater argentine). This fractionation is consistent with in vivo demethylation as a detoxification mechanism in the whales. Individuals with the highest MeHg concentrations have the lowest δ202Hg values and we infer this may result from more limited MeHg demethylation. We find a linear relationship between Δ200Hg anomalies (-0.1 to 0.2‰) and Δ199Hg (R2=0.76) that has not previously been reported. Variability in Δ200Hg is thought to be driven by photochemical reactions in the tropopause and may provide an effective tracer for atmospheric Hg inputs to the ocean that are methylated and accumulated in aquatic biota.

Dioxygen Binding in the Active Site of Histone Demethylase JMJD2A and the Role of the Protein Environment.

PubMed

Cortopassi, Wilian A; Simion, Robert; Honsby, Charles E; França, Tanos C C; Paton, Robert S

2015-12-21

JMJD2A catalyses the demethylation of di- and trimethylated lysine residues in histone tails and is a target for the development of new anticancer medicines. Mechanistic details of demethylation are yet to be elucidated and are important for the understanding of epigenetic processes. We have evaluated the initial step of histone demethylation by JMJD2A and demonstrate the dramatic effect of the protein environment upon oxygen binding using quantum mechanics/molecular mechanics (QM/MM) calculations. The changes in electronic structure have been studied for possible spin states and different conformations of O2 , using a combination of quantum and classical simulations. O2 binding to this histone demethylase is computed to occur preferentially as an end-on superoxo radical bound to a high-spin ferric centre, yielding an overall quintet ground state. The favourability of binding is strongly influenced by the surrounding protein: we have quantified this effect using an energy decomposition scheme into electrostatic and dispersion contributions. His182 and the methylated lysine assist while Glu184 and the oxoglutarate cofactor are deleterious for O2 binding. Charge separation in the superoxo-intermediate benefits from the electrostatic stabilization provided by the surrounding residues, stabilizing the binding process significantly. This work demonstrates the importance of the extended protein environment in oxygen binding, and the role of energy decomposition in understanding the physical origin of binding/recognition. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biogeochemical factors influencing net mercury methylation in contaminated freshwater sediments from the St. Lawrence River in Cornwall, Ontario, Canada.

PubMed

Avramescu, Mary-Luyza; Yumvihoze, Emmanuel; Hintelmann, Holger; Ridal, Jeff; Fortin, Danielle; Lean, David R S

2011-02-01

The activity of various anaerobic microbes, including sulfate reducers (SRB), iron reducers (FeRP) and methanogens (MPA) has been linked to mercury methylation in aquatic systems, although the relative importance of each microbial group in the overall process is poorly understood in natural sediments. The present study focused on the biogeochemical factors (i.e. the relative importance of various groups of anaerobic microbes (FeRP, SRB, and MPA) that affect net monomethylmercury (MMHg) formation in contaminated sediments of the St. Lawrence River (SRL) near Cornwall (Zone 1), Ontario, Canada. Methylation and demethylation potentials were measured separately by using isotope-enriched mercury species ((200)Hg(2+) and MM(199)Hg(+)) in sediment microcosms treated with specific microbial inhibitors. Sediments were sampled and incubated in the dark at room temperature in an anaerobic chamber for 96h. The potential methylation rate constants (K(m)) and demethylation rates (K(d)) were found to differ significantly between microcosms. The MPA-inhibited microcosm had the highest potential methylation rate constant (0.016d(-1)), whereas the two SRB-inhibited microcosms had comparable potential methylation rate constants (0.003d(-1) and 0.002d(-1), respectively). The inhibition of methanogens stimulated net methylation by inhibiting demethylationand by stimulating methylation along with SRB activity. The inhibition of both methanogens and SRB was found to enhance the iron reduction rates but did not completely stop MMHg production. The strong positive correlation between K(m) and Sulfate Reduction Rates (SRR) and between K(d) and Methane Production Rates (MPR) supports the involvement of SRB in Hg methylation and MPA in MMHg demethylation in the sediments. In contrast, the strong negative correlation between K(d) and Iron Reduction Rates (FeRR) shows that the increase in FeRR corresponds to a decrease in demethylation, indicating that iron reduction may influence net methylation in the SLR sediments by decreasing demethylation rather than favouring methylation. Copyright © 2010 Elsevier B.V. All rights reserved.

FACT complex is required for DNA demethylation at heterochromatin during reproduction in Arabidopsis.

PubMed

Frost, Jennifer M; Kim, M Yvonne; Park, Guen Tae; Hsieh, Ping-Hung; Nakamura, Miyuki; Lin, Samuel J H; Yoo, Hyunjin; Choi, Jaemyung; Ikeda, Yoko; Kinoshita, Tetsu; Choi, Yeonhee; Zilberman, Daniel; Fischer, Robert L

2018-05-15

The DEMETER (DME) DNA glycosylase catalyzes genome-wide DNA demethylation and is required for endosperm genomic imprinting and embryo viability. Targets of DME-mediated DNA demethylation reside in small, euchromatic, AT-rich transposons and at the boundaries of large transposons, but how DME interacts with these diverse chromatin states is unknown. The STRUCTURE SPECIFIC RECOGNITION PROTEIN 1 (SSRP1) subunit of the chromatin remodeler FACT (facilitates chromatin transactions), was previously shown to be involved in the DME-dependent regulation of genomic imprinting in Arabidopsis endosperm. Therefore, to investigate the interaction between DME and chromatin, we focused on the activity of the two FACT subunits, SSRP1 and SUPPRESSOR of TY16 (SPT16), during reproduction in Arabidopsis We found that FACT colocalizes with nuclear DME in vivo, and that DME has two classes of target sites, the first being euchromatic and accessible to DME, but the second, representing over half of DME targets, requiring the action of FACT for DME-mediated DNA demethylation genome-wide. Our results show that the FACT-dependent DME targets are GC-rich heterochromatin domains with high nucleosome occupancy enriched with H3K9me2 and H3K27me1. Further, we demonstrate that heterochromatin-associated linker histone H1 specifically mediates the requirement for FACT at a subset of DME-target loci. Overall, our results demonstrate that FACT is required for DME targeting by facilitating its access to heterochromatin. Copyright © 2018 the Author(s). Published by PNAS.

Research on DNA methylation of human osteosarcoma cell MGMT and its relationship with cell resistance to alkylating agents.

PubMed

Guo, Jun; Cui, Qiu; Jiang, WeiHao; Liu, Cheng; Li, DingFeng; Zeng, Yanjun

2013-08-01

The objective of this study was to explore the O(6)-methylguanine-DNA methyltransferase (MGMT) gene methylation status and its protein expression, as well as the effects of demethylating agent 5-Aza-2'-deoxycytidine (5-Aza-CdR) on MGMT gene expression and its resistance to alkylating agents, and to elucidate MGMT expression mechanism and significance in osteosarcoma. The human osteosarcoma cell lines Saos-2 and MG-63 were collected and treated with 5-Aza-CdR for 6 days. The cells not treated with 5-Aza-CdR were set as a negative control. The genomic DNA was extracted from the Saos-2 and MG-63 cells using methylation-specific PCR to detect the promoter CpG island methylation status of the MGMT gene. Cell sensitivity to alkylating agents before and after drug administration was detected by the MTT method. The variation in MGMT gene mRNA and protein was detected by reverse transcription PCR (RT-PCR) and Western blotting. The MGMT promoter gene of normal Saos-2 cells was methylated, with reduced MGMT mRNA and protein expression; the MGMT mRNA and protein expression of Saos-2 cells treated with 5-Aza-CdR was obviously enhanced, and its sensitivity to alkylating agents was reversed. Meanwhile, with promoter CpG island unmethylation of the MGMT gene, MGMT protein was expressed in the normal MG-63 cells and the MG-63 cells treated with 5-Aza-CdR, and both showed resistance to alkylating agents. The methylation status of the MGMT gene promoter in human osteosarcoma cells reflected the cells' ability to induce MGMT protein expression and can be used as a molecular marker to project the sensitivity of cancer tissues to alkylating agent drugs.

Macrophage deficiency of miR-21 promotes apoptosis, plaque necrosis, and vascular inflammation during atherogenesis.

PubMed

Canfrán-Duque, Alberto; Rotllan, Noemi; Zhang, Xinbo; Fernández-Fuertes, Marta; Ramírez-Hidalgo, Cristina; Araldi, Elisa; Daimiel, Lidia; Busto, Rebeca; Fernández-Hernando, Carlos; Suárez, Yajaira

2017-09-01

Atherosclerosis, the major cause of cardiovascular disease, is a chronic inflammatory disease characterized by the accumulation of lipids and inflammatory cells in the artery wall. Aberrant expression of microRNAs has been implicated in the pathophysiological processes underlying the progression of atherosclerosis. Here, we define the contribution of miR-21 in hematopoietic cells during atherogenesis. Interestingly, we found that miR-21 is the most abundant miRNA in macrophages and its absence results in accelerated atherosclerosis, plaque necrosis, and vascular inflammation. miR-21 expression influences foam cell formation, sensitivity to ER-stress-induced apoptosis, and phagocytic clearance capacity. Mechanistically, we discovered that the absence of miR-21 in macrophages increases the expression of the miR-21 target gene, MKK3, promoting the induction of p38-CHOP and JNK signaling. Both pathways enhance macrophage apoptosis and promote the post-translational degradation of ABCG1, a transporter that regulates cholesterol efflux in macrophages. Altogether, these findings reveal a major role for hematopoietic miR-21 in atherogenesis. © 2017 The Authors. Published under the terms of the CC BY 4.0 license.

Aberrant Epigenetic Alterations of Glutathione-S-Transferase P1 in Age-Related Nuclear Cataract.

PubMed

Chen, Jia; Zhou, Jing; Wu, Jian; Zhang, Guowei; Kang, Lihua; Ben, Jindong; Wang, Yong; Qin, Bai; Guan, Huaijin

2017-03-01

Oxidative damage of lens tissue contributes to the formation of age-related cataract. Pi-class glutathione-S-transferase (GSTP1) plays a role in the removal of oxidative adducts by transferring them to glutathione. To assess epigenetic regulation of GSTP1 and its potential role in age-related nuclear cataract (ARNC) pathogenesis, we evaluated GSTP1 mRNA expression, methylation, and chromatin modifications in lenses from ARNC patients. The mRNA and protein of lens GSTP1 were assayed by relative quantitative real-time polymerase chain reaction (qRT-PCR) and Western blots. Methylation of the GSTP1 promoter was determined by bisulfite genomic sequencing. Chromatin modification was detected by chromatin immunoprecipitation. DNA methyltransferase (DNMT) and histone deacetylase (HDAC) activities were also assayed by enzyme-linked immunosorbent assay (ELISA)-like reaction. To assess the effect of DNA methylation on the mRNA expression of GSTP1, human lens epithelium HLE-B3 cells were treated with the demethylation compound 5-aza-dC, followed by qRT-PCR assay. GSTP1 mRNA and protein levels were significantly reduced in lens epithelium and cortex of ARNC cases versus age-matched controls. The changes corresponded to hypermethylation of the GSTP1 promoter CpG islands. The loss of GSTP1 mRNA and protein and the increased DNA promoter methylation might be correlated with the severity of the ARNC. ARNC lenses also had lower acetylation of histone proteins H3, H4, and lower methylation of H3K4, and higher methylation of H3K9. Histone modifications were not correlated with the severity of the ARNCs. DNMT and HDAC were elevated in lenses from ARNCs compared with controls. Demethylation treatment of HLE-B3 cells with 5-aza-dC enhanced the expression of GSTP1. Epigenetic alteration of GSTP1 regulates its expression in lens epithelial and cortical tissues. These changes likely contribute to the pathogenesis of ARNC.

Periphyton biofilms influence net methylmercury production in an industrially contaminated system

DOE PAGES

Olsen, Todd Andrew; Brandt, Craig C.; Brooks, Scott C.

2016-09-12

Mercury (Hg) methylation and methylmercury (MMHg) demethylation activity of periphyton biofilms from East Fork Poplar Creek, Tennessee, USA (EFPC) were measured during 2014-2015 using stable Hg isotopic rate assays. 201Hg II and MM 202Hg were added to intact periphyton samples and the formation of MM 201Hg and loss of MM 202Hg were monitored over time and used to calculate first-order rate constants for methylation and demethylation, respectively. The influence of location, temperature/season, light exposure and biofilm structure on methylation and demethylation were examined. Between-site differences in net methylation for samples collected from an upstream versus downstream location were driven bymore » differences in the demethylation rate constant (k d). In contrast, the within-site seasonal difference in net methylation was driven by changes in the methylation rate constant (k m). Samples incubated in the dark had lower net methylation due to km values that were 60% less than those incubated in the light. Disrupting the biofilm structure decreased km by 50% and resulted in net demethylating conditions. Overall, the measured rates resulted in a net excess of MMHg generated which could account for 27-85% of the MMHg flux in EFPC and suggests intact, actively photosynthesizing periphyton biofilms harbor zones of MMHg production.« less