Serotonin is an endogenous regulator of intestinal CYP1A1 via AhR.

PubMed

Manzella, Christopher; Singhal, Megha; Alrefai, Waddah A; Saksena, Seema; Dudeja, Pradeep K; Gill, Ravinder K

2018-04-17

Aryl hydrocarbon receptor (AhR) is a nuclear receptor that controls xenobiotic detoxification via induction of cytochrome P450 1A1 (CYP1A1) and regulates immune responses in the intestine. Metabolites of L-tryptophan activate AhR, which confers protection against intestinal inflammation. We tested the hypothesis that serotonin (5-HT) is an endogenous activator of AhR in intestinal epithelial cells. Treatment of Caco-2 monolayers with 5-HT induced CYP1A1 mRNA in a time- and concentration-dependent manner and also stimulated CYP1A1 activity. CYP1A1 induction by 5-HT was dependent upon uptake via serotonin transporter (SERT). Antagonism of AhR and knockdown of AhR and its binding partner aryl hydrocarbon receptor nuclear translocator (ARNT) attenuated CYP1A1 induction by 5-HT. Activation of AhR was evident by its nuclear translocation after 5-HT treatment and by induction of an AhR-responsive luciferase reporter. In vivo studies showed a dramatic decrease in CYP1A1 expression and other AhR target genes in SERT KO ileal mucosa by microarray analysis. These results suggest that intracellular accumulation of 5-HT via SERT induces CYP1A1 expression via AhR in intestinal epithelial cells, and SERT deficiency in vivo impairs activation of AhR. Our studies provide a novel link between the serotonergic and AhR pathways which has implications in xenobiotic metabolism and intestinal inflammation.

Potential involvement of placental AhR in unexplained recurrent spontaneous abortion.

PubMed

Wu, Y; Chen, X; Chang, X; Huang, Y J; Bao, S; He, Q; Li, Y; Zheng, J; Duan, T; Wang, K

2016-01-01

Recurrent spontaneous abortion (RSA) is a common complication of pregnancy. Recent studies have demonstrated that the aryl hydrocarbon receptor (AhR) might play important roles in establishing and maintaining early pregnancy. In this study, we found that placental AhR protein levels were significantly lower and placental CYP1A1 mRNA levels were higher in unexplained RSA (URSA) patients than in control subjects. The results of immunohistochemical analyzes showed that placental AhR was expressed in syncytiotrophoblast cells and that the level of AhR was markedly lower in these cells in URSA subjects than in control subjects. β-Naphthoflavone (β-NF, an AhR ligand) at 5μM significantly inhibited proliferation and migration in HTR-8/SVneo cells and was associated with the activation of AhR. Moreover, overexpressing AhR in JAR cells significantly increased CYP1A1 mRNA levels and inhibited cell migration. These results indicate that AhR is highly activated in URSA placentas and that the activation of AhR in the placenta might impair trophoblast cell proliferation and migration, possibly leading to the occurrence of URSA. Copyright © 2015 Elsevier Inc. All rights reserved.

The regulation mechanisms of AhR by molecular chaperone complex.

PubMed

Kudo, Ikuru; Hosaka, Miki; Haga, Asami; Tsuji, Noriko; Nagata, Yuhtaroh; Okada, Hirotaka; Fukuda, Kana; Kakizaki, Yuka; Okamoto, Tomoya; Grave, Ewa; Itoh, Hideaki

2018-03-01

The AhR, so called the dioxin receptor, is a member of the nuclear receptor superfamily. The ligand-free AhR forms a cytosolic protein complex with the molecular chaperone HSP90, co-chaperone p23, and XAP2 in the cytoplasm. Following ligand binding like 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), the AhR translocates into the nucleus. Although it has been reported that HSP90 regulates the translocation of the AhR to the nucleus, the precise activation mechanisms of the AhR have not yet been fully understood. AhR consists of the N-terminal bHLH domain containing NLS and NES, the middle PAS domain and the C-terminal transactivation domain. The PAS domain is familiar as a ligand and HSP90 binding domain. In this study, we focused on the bHLH domain that was thought to be a HSP90 binding domain. We investigated the binding properties of bHLH to HSP90. We analyzed the direct interaction of bHLH with HSP90, p23 and XAP2 using purified proteins. We found that not only the PAS domain but also the bHLH domain bound to HSP90. The bHLH domain forms complex with HSP90, p23 and XAP2. We also determined the bHLH binding domain was HSP90 N-domain. The bHLH domain makes a complex with HSP90, p23 and XAP2 via the HSP90 N-domain. Although the NLS is closed in the absence of a ligand, the structure of AhR will be changed in the presence of a ligand, which leads to NLS open, result in the nuclear translocation of AhR.

Use of natural AhR ligands as potential therapeutic modalities against inflammatory disorders

PubMed Central

Busbee, Philip B; Rouse, Michael; Nagarkatti, Mitzi; Nagarkatti, Prakash S

2014-01-01

The aim of this review is to discuss research involving ligands for the aryl hydrocarbon receptor (AhR) and their role in immunomodulation. While activation of the AhR is well known for its ability to regulate the biochemical and toxic effects of environmental chemicals, more recently an exciting discovery has been made indicating that AhR ligation can also regulate T-cell differentiation, specifically through activation of Foxp3+ regulatory T cells (Tregs) and downregulation of the proinflammatory Th17 cells. Such findings have opened new avenues of research on the possibility of targeting the AhR to treat inflammatory and autoimmune diseases. Specifically, this review will discuss the current research involving natural and dietary AhR ligands. In addition, evidence indicating the potential use of these ligands in regulating inflammation in various diseases will be highlighted. The importance of the AhR in immunological processes can be illustrated by expression of this receptor on a majority of immune cell types. In addition, AhR signaling pathways have been reported to influence a number of genes responsible for mediating inflammation and other immune responses. As interest in the AhR and its ligands increases, it seems prudent to consolidate current research on the contributions of these ligands to immune regulation during the course of inflammatory diseases. PMID:23731446

Ablating the aryl hydrocarbon receptor (AhR) in CD11c+ cells perturbs intestinal epithelium development and intestinal immunity.

PubMed

Chng, Song Hui; Kundu, Parag; Dominguez-Brauer, Carmen; Teo, Wei Ling; Kawajiri, Kaname; Fujii-Kuriyama, Yoshiaki; Mak, Tak Wah; Pettersson, Sven

2016-04-12

Diet and microbiome derived indole derivatives are known to activate the ligand induced transcription factor, the Aryl hydrocarbon Receptor (AhR). While the current understanding of AhR biology has confirmed its role in mucosal lymphocytes, its function in intestinal antigen presenting cells (APCs) is poorly understood. Here, we report that Cre-mediated deletion of AhR in CD11c-expressing cells in C57/BL6 mice is associated with altered intestinal epithelial morphogenesis in vivo. Moreover, when co-cultured with AhR-deficient DCs ex vivo, intestinal organoids showed reduced SRY (sex determining region Y)-box 9 and increased Mucin 2 expression, which correlates with reduced Paneth cells and increased goblet cell differentiation, similar to the data obtained in vivo. Further, characterization of intestinal APC subsets, devoid of AhR, revealed an expression pattern associated with aberrant intrinsic Wnt pathway regulation. At a functional level, the loss of AhR in APCs resulted in a dysfunctional epithelial barrier, associated with a more aggressive chemically induced colitis compared to wild type animals. Our results are consistent with a model whereby the AhR signalling pathway may participate in the regulation of innate immunity through intestinal epithelium development and mucosal immunity.

AhR mediates an anti-inflammatory feedback mechanism in human Langerhans cells involving FcεRI and IDO.

PubMed

Koch, S; Stroisch, T J; Vorac, J; Herrmann, N; Leib, N; Schnautz, S; Kirins, H; Förster, I; Weighardt, H; Bieber, T

2017-11-01

Aryl hydrocarbon receptor (AhR), an important regulator of immune responses, is activated by UVB irradiation in the skin. Langerhans cells (LC) in the epidermis of patients with atopic dermatitis (AD) carry the high-affinity receptor for IgE, FcεRI, and are crucially involved in the pathogenesis of AD by inducing inflammatory responses and regulating tolerogenic processes. We investigated AhR and AhR repressor (AhRR) expression and functional consequences of AhR activation in human ex vivo skin cells and in in vitro-generated LC. Epidermal cells from healthy skin were analyzed for their expression of AhR and AhRR. LC generated from CD34 + hematopoietic stem cells (CD34LC) were treated with the UV photoproduct and AhR ligand 6-formylindolo[3,2-b]carbazole (FICZ). Cell surface receptors, transcription factors, and the tolerogenic tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) were analyzed using flow cytometry and quantitative PCR. Epidermal LC and CD34LC express AhR and AhRR. AhR was also found in keratinocytes, which lack AhRR. AhR activation of LC by FICZ caused downregulation of FcεRI in CD34LC without affecting their maturation. AhR-mediated regulation of FcεRI did not involve any known transcription factors related to this receptor. Furthermore, we could show upregulation of IDO mediated by AhR engagement. Our study shows that AhR activation by FICZ reduces FcεRI and upregulates IDO expression in LC. This AhR-mediated anti-inflammatory feedback mechanism may dampen the allergen-induced inflammation in AD. © 2017 EAACI and John Wiley and Sons A/S. Published by John Wiley and Sons Ltd.

The aryl hydrocarbon receptor repressor - More than a simple feedback inhibitor of AhR signaling: Clues for its role in inflammation and cancer.

PubMed

Vogel, Christoph F A; Haarmann-Stemmann, Thomas

2017-02-01

The aryl hydrocarbon receptor repressor (AhRR) was first described as a specific competitive repressor of aryl hydrocarbon receptor (AhR) activity based on its ability to dimerize with the AhR nuclear translocator (ARNT) and through direct competition of AhR/ARNT and AhRR/ARNT complexes for binding to dioxin-responsive elements (DREs). Like AhR, AhRR belongs to the basic Helix-Loop-Helix/Per-ARNT-Sim (bHLH/PAS) protein family but lacks functional ligand-binding and transactivation domains. Transient transfection experiments with ARNT and AhRR mutants examining the inhibitory mechanism of AhRR suggested a more complex mechanism than the simple mechanism of negative feedback through sequestration of ARNT to regulate AhR signaling. Recently, AhRR has been shown to act as a tumor suppressor gene in several types of cancer cells. Furthermore, epidemiological studies have found epigenetic changes and silencing of AhRR associated with exposure to cigarette smoke and cancer development. Additional studies from our laboratories have demonstrated that AhRR represses other signaling pathways including NF-κB and is capable of regulating inflammatory responses. A better understanding of the regulatory mechanisms of AhRR in AhR signaling and adverse outcome pathways leading to deregulated inflammatory responses contributing to tumor promotion and other adverse health effects is expected from future studies. This review article summarizes the characteristics of AhRR as an inhibitor of AhR activity and highlights more recent findings pointing out the role of AhRR in inflammation and tumorigenesis.

Pityriazepin and other potent AhR ligands isolated from Malassezia furfur yeast

PubMed Central

Mexia, Nikitia; Gaitanis, George; Velegraki, Aristea; Soshilov, Anatoly; Denison, Michael S.; Magiatis, Prokopios

2015-01-01

Malassezia furfur yeast strains isolated from diseased human skin preferentially biosynthesize indole alkaloids which can be detected in human skin and are highly potent activators of the aryl hydrocarbon receptor (AhR) and AhR-dependent gene expression. Chemical analysis of an EtOAc extract of a M. furfur strain obtained from diseased human skin and grown on L-tryptophan agar revealed several known AhR active tryptophan metabolites along with a previously unidentified compound, pityriazepin. While its structure resembled that of the known alkaloid pityriacitrin, the comprised pyridine ring had been transformed into an azepinone. The indoloazepinone scaffold of pityriazepin is extremely rare in nature and has only been reported once previously. Pityriazepin, like the other isolated compounds, was found to be a potent activator of the AhR-dependent reporter gene assays in recombinant cell lines derived from four different species, although significant species differences in relative potency was observed. The ability of pityriazepin to competitively bind to the AhR and directly stimulate AhR DNA binding classified it as a new naturally-occurring potent AhR agonist. Malassezia furfur produces an expanded collection of extremely potent naturally occurring AhR agonists, which produce their biological effects in a species-specific manner.1 PMID:25721496

Mixed-ligand copper(II) complexes activate aryl hydrocarbon receptor AhR and induce CYP1A genes expression in human hepatocytes and human cell lines.

PubMed

Kubešová, Kateřina; Dořičáková, Aneta; Trávníček, Zdeněk; Dvořák, Zdeněk

2016-07-25

The effects of four copper(II) mixed-ligand complexes [Cu(qui1)(L)]NO3·H2O (1-3) and [Cu(qui2)(phen)]NO3 (4), where qui1=2-phenyl-3-hydroxy-4(1H)-quinolinone, Hqui2=2-(4-amino-3,5-dichlorophenyl)-N-propyl-3-hydroxy-4(1H)-quinolinone-7-carboxamide, L=1,10-phenanthroline (phen) (1), 5-methyl-1,10-phenanthroline (mphen) (2), bathophenanthroline (bphen) (3), on transcriptional activities of steroid receptors, nuclear receptors and xenoreceptors have been studied. The complexes (1-4) did not influence basal or ligand-inducible activities of glucocorticoid receptor, androgen receptor, thyroid receptor, pregnane X receptor and vitamin D receptor, as revealed by gene reporter assays. The complexes 1 and 2 dose-dependently induced luciferase activity in stable gene reporter AZ-AhR cell line, and this induction was reverted by resveratrol, indicating involvement of aryl hydrocarbon receptor (AhR) in the process. The complexes 1, 2 and 3 induced CYP1A1 mRNA in LS180 cells and CYP1A1/CYP1A2 in human hepatocytes through AhR. Electrophoretic mobility shift assay EMSA showed that the complexes 1 and 2 transformed AhR in its DNA-binding form. Collectively, we demonstrate that the complexes 1 and 2 activate AhR and induce AhR-dependent genes in human hepatocytes and cancer cell lines. In conclusion, the data presented here might be of toxicological importance, regarding the multiple roles of AhR in human physiology and pathophysiology. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

The tertiary structures of porcine AhR and ARNT proteins and molecular interactions within the TCDD/AhR/ARNT complex.

PubMed

Orlowska, Karina; Molcan, Tomasz; Swigonska, Sylwia; Sadowska, Agnieszka; Jablonska, Monika; Nynca, Anna; Jastrzebski, Jan P; Ciereszko, Renata E

2016-06-01

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that can be activated by structurally diverse synthetic and natural chemicals, including toxic environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In the present study, homology models of the porcine AhR-ligand binding domain (LBD) and the porcine aryl hydrocarbon receptor nuclear translocator-ligand binding domain (ARNT-LBD) were created on the basis of structures of closely related respective proteins i.e., human Hif-2α and ARNT. Molecular docking of TCDD to the porcine AhR-LBD model revealed high binding affinity (-8.8kcal/mol) between TCDD and the receptor. Moreover, formation of the TCDD/AhR-LBD complex was confirmed experimentally with the use of electrophoretic mobility shift assay (EMSA). It was found that TCDD (10nM, 2h of incubation) not only bound to the AhR in the porcine granulosa cells but also activated the receptor. The current study provides a framework for examining the key events involved in the ligand-dependent activation of the AhR. Copyright © 2016 Elsevier Inc. All rights reserved.

The AhR agonist VAF347 augments retinoic acid-induced differentiation in leukemia cells

PubMed Central

Ibabao, Christopher N.; Bunaciu, Rodica P.; Schaefer, Deanna M.W.; Yen, Andrew

2015-01-01

In binary cell-fate decisions, driving one lineage and suppressing the other are conjoined. We have previously reported that aryl hydrocarbon receptor (AhR) promotes retinoic acid (RA)-induced granulocytic differentiation of lineage bipotent HL-60 myeloblastic leukemia cells. VAF347, an AhR agonist, impairs the development of CD14+CD11b+ monocytes from granulo-monocytic (GM) stage precursors. We thus hypothesized that VAF347 propels RA-induced granulocytic differentiation and impairs D3-induced monocytic differentiation of HL-60 cells. Our results show that VAF347 enhanced RA-induced cell cycle arrest, CD11b integrin expression and neutrophil respiratory burst. Granulocytic differentiation is known to be driven by MAPK signaling events regulated by Fgr and Lyn Src-family kinases, the CD38 cell membrane receptor, the Vav1 GEF, the c-Cbl adaptor, as well as AhR, all of which are embodied in a putative signalsome. We found that the VAF347 AhR ligand regulates the signalsome. VAF347 augments RA-induced expression of AhR, Lyn, Vav1, and c-Cbl as well as p47phox. Several interactions of partners in the signalsome appear to be enhanced: Fgr interaction with c-Cbl, CD38, and with pS259c-Raf and AhR interaction with c-Cbl and Lyn. Thus, we report that, while VAF347 impedes monocytic differentiation induced by 1,25-dihydroxyvitamin D3, VAF347 promotes RA-induced differentiation. This effect seems to involve but not to be limited to Lyn, Vav1, c-Cbl, AhR, and Fgr. PMID:25941627

The AhR agonist VAF347 augments retinoic acid-induced differentiation in leukemia cells.

PubMed

Ibabao, Christopher N; Bunaciu, Rodica P; Schaefer, Deanna M W; Yen, Andrew

2015-01-01

In binary cell-fate decisions, driving one lineage and suppressing the other are conjoined. We have previously reported that aryl hydrocarbon receptor (AhR) promotes retinoic acid (RA)-induced granulocytic differentiation of lineage bipotent HL-60 myeloblastic leukemia cells. VAF347, an AhR agonist, impairs the development of CD14(+)CD11b(+) monocytes from granulo-monocytic (GM) stage precursors. We thus hypothesized that VAF347 propels RA-induced granulocytic differentiation and impairs D3-induced monocytic differentiation of HL-60 cells. Our results show that VAF347 enhanced RA-induced cell cycle arrest, CD11b integrin expression and neutrophil respiratory burst. Granulocytic differentiation is known to be driven by MAPK signaling events regulated by Fgr and Lyn Src-family kinases, the CD38 cell membrane receptor, the Vav1 GEF, the c-Cbl adaptor, as well as AhR, all of which are embodied in a putative signalsome. We found that the VAF347 AhR ligand regulates the signalsome. VAF347 augments RA-induced expression of AhR, Lyn, Vav1, and c-Cbl as well as p47(phox). Several interactions of partners in the signalsome appear to be enhanced: Fgr interaction with c-Cbl, CD38, and with pS259c-Raf and AhR interaction with c-Cbl and Lyn. Thus, we report that, while VAF347 impedes monocytic differentiation induced by 1,25-dihydroxyvitamin D3, VAF347 promotes RA-induced differentiation. This effect seems to involve but not to be limited to Lyn, Vav1, c-Cbl, AhR, and Fgr.

AhR transcriptional activity in serum of Inuits across Greenlandic districts

PubMed Central

Long, Manhai; Deutch, Bente; Bonefeld-Jorgensen, Eva C

2007-01-01

Background Human exposure to lipophilic persistent organic pollutants (POPs) including polychlorinated dibenzo-p-dioxins/furans (PCDDs/PCDFs), polychlorinated biphenyls (PCBs) and organochlorine pesticide is ubiquitous. The individual is exposed to a complex mixture of POPs being life-long beginning during critical developmental windows. Exposure to POPs elicits a number of species- and tissue-specific toxic responses, many of which involve the aryl hydrocarbon receptor (AhR). The aim of this study was to compare the actual level of integrated AhR transcriptional activity in the lipophilic serum fraction containing the actual POP mixture among Inuits from different districts in Greenland, and to evaluate whether the AhR transactivity is correlated to the bio-accumulated POPs and/or lifestyle factors. Methods The study included 357 serum samples from the Greenlandic districts: Nuuk and Sisimiut (South West Coast), Qaanaaq (North Coast) and Tasiilaq (East Coast). The bio-accumulated serum POPs were extracted by ethanol: hexane and clean-up on Florisil columns. Effects of the serum extract on the AhR transactivity was determined using the Hepa 1.12cR mouse hepatoma cell line carrying an AhR-luciferase reporter gene, and the data was evaluated for possible association to the serum levels of 14 PCB congeners, 10 organochlorine pesticide residues and/or lifestyle factors. Results In total 85% of the Inuit samples elicited agonistic AhR transactivity in a district dependent pattern. The median level of the AhR-TCDD equivalent (AhR-TEQ) of the separate genders was similar in the different districts. For the combined data the order of the median AhR-TEQ was Tasiilaq > Nuuk ≥ Sisimiut > Qaanaaq possibly being related to the different composition of POPs. In overall, the AhR transactivity was inversely correlated to the levels of sum POPs, age and/or intake of marine food. Conclusion i) We observed that the proportion of dioxin like (DL) compounds in the POP mixture was the

AIP mutations impair AhR signaling in pituitary adenoma patients fibroblasts and in GH3 cells.

PubMed

Lecoq, Anne-Lise; Viengchareun, Say; Hage, Mirella; Bouligand, Jérôme; Young, Jacques; Boutron, Audrey; Zizzari, Philippe; Lombès, Marc; Chanson, Philippe; Kamenický, Peter

2016-05-01

Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene predispose humans to pituitary adenomas through unknown molecular mechanisms. The best-known interacting partner of AIP is the aryl hydrocarbon receptor (AhR), a transcription factor that mediates the effects of xenobiotics implicated in carcinogenesis. As 75% of AIP mutations disrupt the physical and/or functional interaction with AhR, we postulated that the tumorigenic potential of AIP mutations might result from altered AhR signaling. We evaluated the impact of AIP mutations on the AhR signaling pathway, first in fibroblasts from AIP-mutated patients with pituitary adenomas, by comparison with fibroblasts from healthy subjects, then in transfected pituitary GH3 cells. The AIP protein level in mutated fibroblasts was about half of that in cells from healthy subjects, but AhR expression was unaffected. Gene expression analyses showed significant modifications in the expression of the AhR target genes CYP1B1 and AHRR in AIP-mutated fibroblasts, both before and after stimulation with the endogenous AhR ligand kynurenine. Kynurenine increased Cyp1b1 expression to a greater extent in GH3 cells overexpressing wild type compared with cells expressing mutant AIP Knockdown of endogenous Aip in these cells attenuated Cyp1b1 induction by the AhR ligand. Both mutant AIP expression and knockdown of endogenous Aip affected the kynurenine-dependent GH secretion of GH3 cells. This study of human fibroblasts bearing endogenous heterozygous AIP mutations and transfected pituitary GH3 cells shows that AIP mutations affect the AIP protein level and alter AhR transcriptional activity in a gene- and tissue-dependent manner. © 2016 Society for Endocrinology.

Screening a mouse liver gene expression Compendium Identifies Effectors of the Aryl Hydrocarbon receptor (AhR)

EPA Science Inventory

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates the biological and toxic effects of 2,3, 7 ,8-tetrachlorodibenzo-p-dioxin {TCDD), dioxin-like compounds (DLC) as well as some drugs and endogenous tryptophan metabolites. Short-term act...

NcoA2-Dependent Inhibition of HIF-1α Activation Is Regulated via AhR.

PubMed

Tsai, Chi-Hao; Li, Ching-Hao; Liao, Po-Lin; Cheng, Yu-Wen; Lin, Cheng-Hui; Huang, Shih-Hsuan; Kang, Jaw-Jou

2015-12-01

High endogenous levels of aryl hydrocarbon receptor (AhR) contribute to hypoxia signaling pathway inhibition following exposure to the potent AhR ligand benzo[a]pyrene (B[a]P) and could alter cellular homeostasis and disease condition. Increasing evidence indicates that AhR might compete with AhR nuclear translocator (ARNT) for complex formation with hypoxia-inducible factor-1α (HIF-1α) for transactivation, which could alter several physiological variables. Nuclear receptor coactivator 2 (NcoA2) is a transcription coactivator that regulates transcription factor activation and inhibition of basic helix-loop-helix Per (Period)-ARNT-SIM (single-minded) (bHLH-PAS) family proteins, such as HIF-1α, ARNT, and AhR, through protein-protein interactions. In this study, we demonstrated that both hypoxia and hypoxia-mimic conditions decreased NcoA2 protein expression in HEK293T cells. Hypoxia response element (HRE) and xenobiotic-responsive element (XRE) transactivation also were downregulated with NcoA2 knockdown under hypoxic conditions. In addition, B[a]P significantly decreased NcoA2 protein expression be accompanied with AhR degradation. We next evaluated whether the absence of AhR could affect NcoA2 protein function under hypoxia-mimetic conditions. NcoA2 and HIF-1α nuclear localization decreased in both B[a]P-pretreated and AhR-knockdown HepG2 cells under hypoxia-mimic conditions. Interestingly, NcoA2 overexpression downregulated HRE transactivation by competing with HIF-1α and AhR to form protein complexes with ARNT. Both NcoA2 knockdown and overexpression inhibited endothelial cell tube formation in vitro. We also demonstrated using the in vivo plug assay that NcoA2-regulated vascularization decreased in mice. Taken together, these results revealed a biphasic role of NcoA2 between AhR and hypoxic conditions, thus providing a novel mechanism underlying the cross talk between AhR and hypoxia that affects disease development and progression. © The Author 2015

DDE and PCB 153 independently induce aryl hydrocarbon receptor (AhR) expression in peripheral blood mononuclear cells.

PubMed

Gaspar-Ramírez, Octavio; Pérez-Vázquez, Francisco J; Salgado-Bustamante, Mariana; González-Amaro, Roberto; Hernandez-Castro, Berenice; Pérez-Maldonado, Ivan N

2015-01-01

Recent studies have demonstrated that compounds inducing pro-inflammatory cytokines enhance AhR expression. The aim of this study was 2-fold: (1) to determine if two pro-inflammatory compounds, dichlorodiphenyldichloroethylene (DDE) and 2,2',4,4',5,5'-hexa-chlorobiphenyl (PCB 153), independently affect AhR gene expression in peripheral blood mononuclear cells (PBMC); and (2) if affected, to determine whether the mechanism involved was due to AhR activation or to a pro-inflammatory effect of the chemicals. PBMC isolated from healthy individuals were incubated in the presence of DDE (10 µg/ml) and PCB 153 (20 ng/ml) over time and AhR and CYP1A1 expression was assessed with a real-time PCR technique. The results indicated there was over-expression of the AhR mRNA in PBMC when the cells were treated with DDE and PCB 153. No changes in expression levels of CYP1A1 mRNA were found. Importantly, when the cells were exposed to DDE and PCB 153 in the presence of an antagonist of tumor necrosis factor (TNF)-α, the over-expression of AhR was abolished; as expected, the expression of CYP1A1 was unaffected. In conclusion, these studies demonstrated for the first time an increment of AhR expression "in vitro" in PBMC treated with two pro-inflammatory environmental pollutants, DDE and PCB153. Moreover, the over-expression of AhR was dependent of TNFα induced by DDE and PCB 153 and was independent of AhR activation.

Estrogenic and AhR activities in dissolved phase and suspended solids from wastewater treatment plants.

PubMed

Dagnino, Sonia; Gomez, Elena; Picot, Bernadette; Cavaillès, Vincent; Casellas, Claude; Balaguer, Patrick; Fenet, Hélène

2010-05-15

The distribution of estrogen receptor (ERalpha) and Aryl Hydrocarbon Receptor (AhR) activities between the dissolved phase and suspended solids were investigated during wastewater treatment. Three wastewater treatment plants with different treatment technologies (waste stabilization ponds (WSPs), trickling filters (TFs) and activated sludge supplemented with a biofilter system (ASB)) were sampled. Estrogenic and AhR activities were detected in both phases in influents and effluents. Estrogenic and AhR activities in wastewater influents ranged from 41.8 to 79 ng/L E(2) Eq. and from 37.9 to 115.5 ng/L TCDD Eq. in the dissolved phase and from 5.5 to 88.6 ng/g E(2) Eq. and from 15 to 700 ng/g TCDD Eq. in the suspended solids. For both activities, WSP showed greater or similar removal efficiency than ASB and both were much more efficient than TF which had the lowest removal efficiency. Moreover, our data indicate that the efficiency of removal of ER and AhR activities from the suspended solid phase was mainly due to removal of suspended solids. Indeed, ER and AhR activities were detected in the effluent suspended solid phase indicating that suspended solids, which are usually not considered in these types of studies, contribute to environmental contamination by endocrine disrupting compounds and should therefore be routinely assessed for a better estimation of the ER and AhR activities released in the environment. Copyright 2010 Elsevier B.V. All rights reserved.

ITE Suppresses Angiogenic Responses in Human Artery and Vein Endothelial Cells: Differential Roles of AhR.

PubMed

Li, Yan; Wang, Kai; Zou, Qing-Yun; Jiang, Yi-Zhou; Zhou, Chi; Zheng, Jing

2017-12-01

Aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor is involved in regulation of many essential biological processes including vascular development and angiogenesis. 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) is an AhR ligand, which regulates immune responses and cancer cell growth. However, the roles of the ITE/AhR pathway in mediating placental angiogenesis remains elusive. Here, we determined if ITE affected placental angiogenic responses via AhR in human umbilical vein (HUVECs) and artery endothelial (HUAECs) cells in vitro. We observed that ITE dose- and time-dependently inhibited proliferation and viability of HUAECs and HUVECs, whereas it inhibited migration of HUAECs, but not HUVECs. While AhR siRNA significantly suppressed AhR protein expression in HUVECs and HUAECs, it attenuated the ITE-inhibited angiogenic responses of HUAECs, but not HUVECs. Collectively, ITE suppressed angiogenic responses of HUAECs and HUVECs, dependent and independent of AhR, respectively. These data suggest that ITE may regulate placental angiogenesis. Copyright © 2017 Elsevier Inc. All rights reserved.

Essential oils of culinary herbs and spices display agonist and antagonist activities at human aryl hydrocarbon receptor AhR.

PubMed

Bartoňková, Iveta; Dvořák, Zdeněk

2018-01-01

Essential oils (EOs) of culinary herbs and spices are used to flavor, color and preserve foods and drinks. Dietary intake of EOs is significant, deserving an attention of toxicologists. We examined the effects of 31 EOs of culinary herbs and spices on the transcriptional activity of human aryl hydrocarbon receptor (AhR), which is a pivotal xenobiotic sensor, having also multiple roles in human physiology. Tested EOs were sorted out into AhR-inactive ones (14 EOs) and AhR-active ones, including full agonists (cumin, jasmine, vanilla, bay leaf), partial agonists (cloves, dill, thyme, nutmeg, oregano) and antagonists (tarragon, caraway, turmeric, lovage, fennel, spearmint, star anise, anise). Major constituents (>10%) of AhR-active EOs were studied in more detail. We identified AhR partial agonists (carvacrol, ligustilide, eugenol, eugenyl acetate, thymol, ar-turmerone) and antagonists (trans-anethole, butylidine phtalide, R/S-carvones, p-cymene), which account for AhR-mediated activities of EOs of fennel, anise, star anise, caraway, spearmint, tarragon, cloves, dill, turmeric, lovage, thyme and oregano. We also show that AhR-mediated effects of some individual constituents of EOs differ from those manifested in mixtures. In conclusion, EOs of culinary herbs and spices are agonists and antagonists of human AhR, implying a potential for food-drug interactions and interference with endocrine pathways. Copyright © 2017 Elsevier Ltd. All rights reserved.

Relationships between serum-induced AhR bioactivity or mitochondrial inhibition and circulating polychlorinated biphenyls (PCBs).

PubMed

Park, Wook Ha; Kang, Sora; Lee, Hong Kyu; Salihovic, Samira; Bavel, Bert van; Lind, P Monica; Pak, Youngmi Kim; Lind, Lars

2017-08-24

Metabolic syndrome and mitochondrial dysfunction have been linked to elevated serum levels of persistent organic pollutants (POPs). However, it is not clear which specific POPs contribute to aryl hydrocarbon receptor (AhR)-dependent bioactivity or inhibit mitochondrial function in human subjects. Here, we measured the cumulative bioactivity of AhR ligand mixture (AhR bioactivity) and the effects on mitochondrial function (ATP concentration) in recombinant Hepa1c1c7 cells incubated with raw serum samples obtained from 911 elderly subjects in the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) cohort. Plasma concentrations of 30 POPs and plastic chemicals have previously been determined in the same PIVUS subjects. Linear regression analysis demonstrated that total toxic equivalence (TEQ) values and polychlorinated biphenyls (PCBs) were significantly correlated with AhR bioactivity (positively) and ATP concentration (negatively). Serum AhR bioactivities were positively associated with some PCBs, regardless of their dioxin-like properties, but only dioxin-like PCBs stimulated AhR bioactivity. By contrast, PCBs mediated a reduction in ATP content independently of their dioxin-like properties. This study suggests that AhR bioactivity and ATP concentrations in serum-treated cells may be valuable surrogate biomarkers of POP exposure and could be useful for the estimation of the effects of POPs on human health.

Functional and phenotypic effects of AhR activation in inflammatory dendritic cells

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

Bankoti, Jaishree; Center for Environmental Health Sciences, University of Montana, Missoula, MT; Rase, Ben

2010-07-15

Aryl hydrocarbon receptor (AhR) activation by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces immune suppression. Dendritic cells (DCs) are key antigen presenting cells governing T cell activation and differentiation. However, the consequences of AhR activation in DCs are not fully defined. We hypothesized that AhR activation alters DC differentiation and generates dysfunctional DCs. To test this hypothesis, inflammatory bone marrow-derived DCs (BMDCs) from C57Bl/6 mice were generated in the presence of vehicle or TCDD. TCDD decreased CD11c expression but increased MHC class II, CD86 and CD25 expression on the BMDCs. The effects of TCDD were strictly AhR-dependent but not exclusively DRE-mediated. Similar effects weremore » observed with two natural AhR ligands, 6-formylindolo[3,2-b]carbazole (FICZ) and 2-(1H-Indol-3-ylcarbonyl)-4-thiazolecarboxylic acid (ITE). TCDD increased LPS- and CpG-induced IL-6 and TNF-{alpha} production by BMDCs but decreased their NO production. TCDD decreased CpG-induced IL-12p70 production by BMDCs but did not affect their secretion of IL-10. TCDD downregulated LPS- and CpG-induced NF-kB p65 levels and induced a trend towards upregulation of RelB levels in the BMDCs. AhR activation by TCDD modulated BMDC uptake of both soluble and particulate antigens. Induction of indoleamine-2,3-dioxygenase (IDO) and TGF-{beta}3 has been implicated in the generation of regulatory T cells following AhR activation. TCDD increased IDO1, IDO2 and TGF-{beta}3 mRNA levels in BMDCs as compared to vehicle. Despite the induction of regulatory mediators, TCDD-treated BMDCs failed to suppress antigen-specific T cell activation. Thus, AhR activation can directly alter the differentiation and innate functions of inflammatory DCs without affecting their ability to successfully interact with T cells.« less

Apoptotic cell-induced AhR activity is required for immunological tolerance and suppression of systemic lupus erythematosus in mice and humans.

PubMed

Shinde, Rahul; Hezaveh, Kebria; Halaby, Marie Jo; Kloetgen, Andreas; Chakravarthy, Ankur; da Silva Medina, Tiago; Deol, Reema; Manion, Kieran P; Baglaenko, Yuriy; Eldh, Maria; Lamorte, Sara; Wallace, Drew; Chodisetti, Sathi Babu; Ravishankar, Buvana; Liu, Haiyun; Chaudhary, Kapil; Munn, David H; Tsirigos, Aristotelis; Madaio, Michael; Gabrielsson, Susanne; Touma, Zahi; Wither, Joan; De Carvalho, Daniel D; McGaha, Tracy L

2018-06-01

The transcription factor AhR modulates immunity at multiple levels. Here we report that phagocytes exposed to apoptotic cells exhibited rapid activation of AhR, which drove production of the cytokine IL-10. Activation of AhR was dependent on interactions between apoptotic-cell DNA and the pattern-recognition receptor TLR9 that was required for the prevention of immune responses to DNA and histones in vivo. Moreover, disease progression in mouse systemic lupus erythematosus (SLE) correlated with strength of the AhR signal, and the disease course could be altered by modulation of AhR activity. Deletion of AhR in the myeloid lineage caused systemic autoimmunity in mice, and an enhanced AhR transcriptional signature correlated with disease in patients with SLE. Thus, AhR activity induced by apoptotic cell phagocytes maintains peripheral tolerance.

Excessive activation of AhR signaling disrupts neuronal migration in the hippocampal CA1 region in the developing mouse.

PubMed

Kimura, Eiki; Kubo, Ken-Ichiro; Endo, Toshihiro; Nakajima, Kazunori; Kakeyama, Masaki; Tohyama, Chiharu

2017-01-01

The aryl hydrocarbon receptor (AhR) avidly binds dioxin, a ubiquitous environmental contaminant. Disruption of downstream AhR signaling has been reported to alter neuronal development, and rodent offspring exposed to dioxin during gestation and lactation showed abnormalities in learning and memory, emotion, and social behavior. However, the mechanism behind the disrupted AhR signaling and developmental neurotoxicity induced by xenobiotic ligands remains elusive. Therefore, we studied how excessive AhR activation affects neuronal migration in the hippocampal CA1 region of the developing mouse brain. We transfected constitutively active (CA)-AhR, AhR, or control vector plasmids into neurons via in utero electroporation on gestational day 14 and analyzed neuronal positioning in the hippocampal CA1 region of offspring on postnatal day 14. CA-AhR transfection affected neuronal positioning, whereas no change was observed in AhR-transfected or control hippocampus. These results suggest that constitutively activated AhR signaling disrupts neuronal migration during hippocampal development. Further studies are needed to investigate whether such developmental disruption in the hippocampus leads to the abnormal cognition and behavior of rodent offspring upon maternal exposure to AhR xenobiotic ligands.

Phytomonitoring and phytoremediation of agrochemicals and related compounds based on recombinant cytochrome P450s and aryl hydrocarbon receptors (AhRs).

PubMed

Shimazu, Sayuri; Inui, Hideyuki; Ohkawa, Hideo

2011-04-13

Molecular mechanisms of metabolism and modes of actions of agrochemicals and related compounds are important for understanding selective toxicity, biodegradability, and monitoring of biological effects on nontarget organisms. It is well-known that in mammals, cytochrome P450 (P450 or CYP) monooxygenases metabolize lipophilic foreign compounds. These P450 species are inducible, and both CYP1A1 and CYP1A2 are induced by aryl hydrocarbon receptor (AhR) combined with a ligand. Gene engineering of P450 and NADPH cytochrome P450 oxidoreductase (P450 reductase) was established for bioconversion. Also, gene modification of AhRs was developed for recombinant AhR-mediated β-glucronidase (GUS) reporter assay of AhR ligands. Recombinant P450 genes were transformed into plants for phytoremediation, and recombinant AhR-mediated GUS reporter gene expression systems were each transformed into plants for phytomonitoring. Transgenic rice plants carrying CYP2B6 metabolized the herbicide metolachlor and remarkably reduced the residues in the plants and soils under paddy field conditions. Transgenic Arabidopsis plants carrying recombinant guinea pig (g) AhR-mediated GUS reporter genes detected PCB126 at the level of 10 ng/g soils in the presence of biosurfactants MEL-B. Both phytomonitoring and phytoremediation plants were each evaluated from the standpoint of practical uses.

T-cell expression of AhR inhibits the maintenance of pTreg cells in the gastrointestinal tract in acute GVHD.

PubMed

Dant, Trisha A; Lin, Kaifeng L; Bruce, Danny W; Montgomery, Stephanie A; Kolupaev, Oleg V; Bommiasamy, Hemamalini; Bixby, Lisa M; Woosley, John T; McKinnon, Karen P; Gonzalez, Frank J; Blazar, Bruce R; Vincent, Benjamin G; Coghill, James M; Serody, Jonathan S

2017-07-20

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that affects the function and development of immune cells. Here, we show that recipient mice receiving AhR -/- T cells have improved survival and decreased acute graft-versus-host disease (aGVHD) in 2 different murine allogeneic bone marrow transplant (BMT) models. We also show that CD4 + T cells lacking AhR demonstrate reduced accumulation in secondary lymphoid tissue because of low levels of proliferation 4 days after BMT. Additionally, we found a significant increase in the quantity of peripherally induced regulatory donor T (pT reg ) cells in the colon of recipients transplanted with AhR -/- T cells 14 days after transplant. Blockade of AhR using a clinically available AhR antagonist greatly enhanced the in vitro generation of inducible T reg (iT reg ) cells from naïve CD4 + human T cells. We have identified AhR as a novel target on donor T cells that is critical to the pathogenesis of aGVHD.

An endogenous aryl hydrocarbon receptor (AhR) ligand, ITE induces regulatory T cells (Tregs) and ameliorates experimental colitis.

PubMed

Abron, Jessicca D; Singh, Narendra P; Mishra, Manoj K; Price, Robert L; Nagarkatti, Mitzi; Nagarkatti, Prakash S; Singh, Udai P

2018-04-19

Inflammatory bowel disease (IBD) is a chronic intestinal inflammatory condition that affects millions of people with high morbidity and health-care cost. The precise etiology of IBD is unknown, but clear evidence suggests that intestinal inflammation is caused by an excessive immune response to mucosal antigens. Recent studies have shown that activation of the aryl hydrocarbon receptor (AhR) induces regulatory T cells (Tregs) and suppresses autoimmune diseases. In the current study, we investigated if nontoxic ligand of AhR, 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE), can attenuate dextran sodium sulphate (DSS)-induced colitis. Our studies demonstrated that in mice that received ITE treatment, in-vivo colitis pathogenesis, including a decrease in body weight, was significantly reversed along with the systemic and intestinal inflammatory cytokines. ITE increased the expression of Tregs in spleen, mesenteric lymph nodes (MLNs) and colon lamina propria lymphocytes (cLPL) of mice with colitis when compared to controls. This induction of Tregs was reversed by AhR antagonist treatment in-vitro. ITE treatment also increased dendritic cells (DCs; CD11c+) and decreased F4/80+ (macrophage) from the spleen, MLNs and cLPL in mice with colitis. ITE also reversed the systemic and intestinal frequency of CD4+T cells during colitis and suppressed inflammatory cytokines including IFN-γ, TNF-α, IL-17, IL-6 and IL-1 as well as induced IL-10 levels. These findings suggest that ITE attenuates colitis through induction of Tregs and reduction in inflammatory CD4+ T cells and cytokines. Thus, our work demonstrates that the nontoxic endogenous AhR ligand ITE, may serve as a therapeutic modality to treat IBD.

Tapinarof Is a Natural AhR Agonist that Resolves Skin Inflammation in Mice and Humans.

PubMed

Smith, Susan H; Jayawickreme, Channa; Rickard, David J; Nicodeme, Edwige; Bui, Thi; Simmons, Cathy; Coquery, Christine M; Neil, Jessica; Pryor, William M; Mayhew, David; Rajpal, Deepak K; Creech, Katrina; Furst, Sylvia; Lee, James; Wu, Dalei; Rastinejad, Fraydoon; Willson, Timothy M; Viviani, Fabrice; Morris, David C; Moore, John T; Cote-Sierra, Javier

2017-10-01

Tapinarof (GSK2894512) is a naturally derived topical treatment with demonstrated efficacy for patients with psoriasis and atopic dermatitis, although the biologic target and mechanism of action had been unknown. We demonstrate that the anti-inflammatory properties of tapinarof are mediated through activation of the aryl hydrocarbon receptor (AhR). We show that tapinarof binds and activates AhR in multiple cell types, including cells of the target tissue-human skin. In addition, tapinarof moderates proinflammatory cytokine expression in stimulated peripheral blood CD4+ T cells and ex vivo human skin, and impacts barrier gene expression in primary human keratinocytes; both of these processes are likely to be downstream of AhR activation based on current evidence. That the anti-inflammatory properties of tapinarof derive from AhR agonism is conclusively demonstrated using the mouse model of imiquimod-induced psoriasiform skin lesions. Topical treatment of AhR-sufficient mice with tapinarof leads to compound-driven reductions in erythema, epidermal thickening, and tissue cytokine levels. In contrast, tapinarof has no impact on imiquimod-induced skin inflammation in AhR-deficient mice. In summary, these studies identify tapinarof as an AhR agonist and confirm that its efficacy is dependent on AhR. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

The AhR is involved in the regulation of LoVo cell proliferation through cell cycle-associated proteins.

PubMed

Yin, Jiuheng; Sheng, Baifa; Han, Bin; Pu, Aimin; Yang, Kunqiu; Li, Ping; Wang, Qimeng; Xiao, Weidong; Yang, Hua

2016-05-01

Some ingredients in foods can activate the aryl hydrocarbon receptor (AhR) and arrest cell proliferation. In this study, we hypothesized that 6-formylindolo [3, 2-b] carbazole (FICZ) arrests the cell cycle in LoVo cells (a colon cancer line) through the AhR. The AhR agonist FICZ and the AhR antagonist CH223191 were used to treat LoVo cells. Real-time PCR and Western blot analyses were performed to detect the expression of the AhR, CYP1A1, CDK4, cyclinD1, cyclin E, CDK2, P27, and pRb. The distribution and activation of the AhR were detected with immunofluorescence. A 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and flow cytometric analysis were performed to measure cell viability, cell cycle stage, and apoptosis. Our results show that FICZ inhibited LoVo cell proliferation by inducing G1 cell cycle arrest but had no effect on epithelial apoptosis. Further analysis found that FICZ downregulated cyclinD1 and upregulated p27 expression to arrest Rb phosphorylation. The downregulation of cyclinD1 and upregulation of p27 were abolished by co-treatment with CH223191. We conclude that the AhR, when activated by FICZ (an endogenous AhR ligand), can arrest the cell cycle and block LoVo cell proliferation. © 2016 International Federation for Cell Biology.

Involvement of the cytokine-IDO1-AhR loop in zinc oxide nanoparticle-induced acute pulmonary inflammation.

PubMed

Ho, Chia-Chi; Lee, Hui-Ling; Chen, Chao-Yu; Luo, Yueh-Hsia; Tsai, Ming-Hsien; Tsai, Hui-Ti; Lin, Pinpin

2017-04-01

Zinc oxide nanoparticles (ZnONPs) are widely used in our daily life, such as in sunscreens and electronic nanodevices. However, pulmonary exposure to ZnONPs causes acute pulmonary inflammation, which is considered as an initial event for various respiratory diseases. Thus, elucidation of the underlying cellular mechanisms of ZnONPs can help us in predicting their potential effects in respiratory diseases. In this study, we observed that ZnONPs increased proinflammatory cytokines, accompanied with an increased expression of aryl hydrocarbon receptor (AhR) and its downstream target cytochrome P450 1A1 (CYP1A1) in macrophages in vitro and in mouse lung epithelia in vivo. Moreover, zinc nitrate, but not silica or titanium dioxide nanoparticles (NPs), had similar effects on macrophages, indicating that the zinc element or ion released from ZnONPs is likely responsible for the activation of the AhR pathway. Cotreatment with an AhR antagonist or AhR knockout reduced ZnONPs-induced cytokine secretion in macrophages or mice, respectively. Furthermore, kynurenine (KYN), an endogenous AhR agonist and a tryptophan metabolite catalyzed by indoleamine 2,3-dioxygenase (IDO), was increased in the serums of mice that aspirated ZnONPs. Consistently, ZnONPs increased IDO1 expression in lung cells in vitro and in vivo. Finally, AhR knockout reduced ZnONPs-induced pulmonary inflammation, cytokine secretion and KYN production in mice, suggesting that AhR activation is involved in ZnONPs-induced cytokine secretion and pulmonary inflammation. In summary, we demonstrated that the pulmonary exposure of ZnONPs stimulated the cytokine-IDO1-AhR loop in the lungs, which has been implied to play roles in immune dysfunctions.

AhR and Arnt differentially regulate NF-κB signaling and chemokine responses in human bronchial epithelial cells

PubMed Central

2014-01-01

Background The aryl hydrocarbon receptor (AhR) has gradually emerged as a regulator of inflammation in the lung and other tissues. AhR may interact with the p65-subunit of the nuclear factor (NF)-κB transcription factors, but reported outcomes of AhR/NF-κB-interactions are conflicting. Some studies suggest that AhR possess pro-inflammatory activities while others suggest that AhR may be anti-inflammatory. The present study explored the impact of AhR and its binding partner AhR nuclear translocator (Arnt) on p65-activation and two differentially regulated chemokines, CXCL8 (IL-8) and CCL5 (RANTES), in human bronchial epithelial cells (BEAS-2B). Results Cells were exposed to CXCL8- and CCL5-inducing chemicals, 1-nitropyrene (1-NP) and 1-aminopyrene (1-AP) respectively, or the synthetic double-stranded RNA analogue, polyinosinic-polycytidylic acid (Poly I:C) which induced both chemokines. Only CXCL8, and not CCL5, appeared to be p65-dependent. Yet, constitutively active unligated AhR suppressed both CXCL8 and CCL5, as shown by siRNA knock-down and the AhR antagonist α-naphthoflavone. Moreover, AhR suppressed activation of p65 by TNF-α and Poly I:C as assessed by luciferase-assay and p65-phosphorylation at serine 536, without affecting basal p65-activity. In contrast, Arnt suppressed only CXCL8, but did not prevent the p65-activation directly. However, Arnt suppressed expression of the NF-κB-subunit RelB which is under transcriptional regulation by p65. Furthermore, AhR-ligands alone at high concentrations induced a moderate CXCL8-response, without affecting CCL5, but suppressed both CXCL8 and CCL5-responses by Poly I:C. Conclusion AhR and Arnt may differentially and independently regulate chemokine-responses induced by both inhaled pollutants and pulmonary infections. Constitutively active, unligated AhR suppressed the activation of p65, while Arnt may possibly interfere with the action of activated p65. Moreover, ligand-activated AhR suppressed CXCL8 and CCL5

Newspapers and Newspaper Ink Contain Agonists for the Ah Receptor

PubMed Central

Bohonowych, Jessica E. S.; Zhao, Bin; Timme-Laragy, Alicia; Jung, Dawoon; Di Giulio, Richard T.; Denison, Michael S.

2010-01-01

Ligand-dependent activation of the aryl hydrocarbon receptor (AhR) pathway leads to a diverse array of biological and toxicological effects. The best-studied ligands for the AhR include polycyclic and halogenated aromatic hydrocarbons, the most potent of which is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, as new AhR ligands are identified and characterized, their structural and physiochemical diversity continues to expand. Our identification of AhR agonists in crude extracts from diverse materials raises questions as to the magnitude and extent of human exposure to AhR ligands through normal daily activities. We have found that solvent extracts of newspapers from countries around the world stimulate the AhR signaling pathway. AhR agonist activity was observed for dimethyl sulfoxide (DMSO), ethanol, and water extracts of printed newspaper, unprinted virgin paper, and black printing ink, where activation of luciferase reporter gene expression was transient, suggesting that the AhR active chemical(s) was metabolically labile. DMSO and ethanol extracts also stimulated AhR transformation and DNA binding, and also competed with [3H]TCDD for binding to the AhR. In addition, DMSO extracts of printed newspaper induced cytochrome P450 1A associated 7-ethoxyresorufin-O-deethylase activity in zebrafish embryos in vivo. Although the responsible bioactive chemical(s) remain to be identified, our results demonstrate that newspapers and printing ink contain relatively potent metabolically labile agonists of the AhR. Given the large amount of recycling and reprocessing of newspapers throughout the world, release of these easily extractable AhR agonists into the environment should be examined and their potential effects on aquatic organisms assessed. PMID:18203687

Hexachlorobenzene induces cell proliferation, and aryl hydrocarbon receptor expression (AhR) in rat liver preneoplastic foci, and in the human hepatoma cell line HepG2. AhR is a mediator of ERK1/2 signaling, and cell cycle regulation in HCB-treated HepG2 cells.

PubMed

de Tomaso Portaz, Ana Clara; Caimi, Giselle Romero; Sánchez, Marcela; Chiappini, Florencia; Randi, Andrea S; Kleiman de Pisarev, Diana L; Alvarez, Laura

2015-10-02

Hexachlorobenzene (HCB) is a widespread environmental pollutant, and a liver tumor promoter in rodents. Depending on the particular cell lines studied, exposure to these compounds may lead to cell proliferation, terminal differentiation, or apoptosis. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is involved in drug and xenobiotic metabolism. AhR can also modulate a variety of cellular and physiological processes that can affect cell proliferation and cell fate determination. The mechanisms by which AhR ligands, both exogenous and endogenous, affect these processes involve multiple interactions between AhR and other signaling pathways. In the present study, we examined the effect of HCB on cell proliferation and AhR expression, using an initiation-promotion hepatocarcinogenesis protocol in rat liver and in the human-derived hepatoma cell line, HepG2. Female Wistar rats were initiated with a single dose of 100 mg/kg of diethylnitrosamine (DEN) at the start of the experiment. Two weeks later, daily dosing of 100 mg/kg HCB was maintained for 10 weeks. Partial hepatectomy was performed 3 weeks after initiation. The number and area of glutathione S-transferase-P (GST-P)-positive foci, in the rat liver were used as biomarkers of liver precancerous lesions. Immunohistochemical staining showed an increase in proliferating cell nuclear antigen (PCNA)-positive cells, along with enhanced AhR protein expression in hepatocytes within GST-P-positive foci of (DEN HCB) group, when compared to DEN. In a similar manner, Western blot analysis demonstrated that HCB induced PCNA and AhR protein expression in HepG2 cells. Flow cytometry assay indicated that the cells were accumulated at S and G2/M phases of the cell cycle. HCB increased cyclin D1 protein levels and ERK1/2 phosphorylation in a dose-dependent manner. Treatment of cells with a selective MEK1 inhibitor, prevented HCB-stimulatory effect on PCNA and cyclinD1, indicating that these effects

Deciphering Dimerization Modes of PAS Domains: Computational and Experimental Analyses of the AhR:ARNT Complex Reveal New Insights Into the Mechanisms of AhR Transformation

PubMed Central

Corrada, Dario; Soshilov, Anatoly A.; Denison, Michael S.

2016-01-01

The Aryl hydrocarbon Receptor (AhR) is a transcription factor that mediates the biochemical response to xenobiotics and the toxic effects of a number of environmental contaminants, including dioxins. Recently, endogenous regulatory roles for the AhR in normal physiology and development have also been reported, thus extending the interest in understanding its molecular mechanisms of activation. Since dimerization with the AhR Nuclear Translocator (ARNT) protein, occurring through the Helix-Loop-Helix (HLH) and PER-ARNT-SIM (PAS) domains, is needed to convert the AhR into its transcriptionally active form, deciphering the AhR:ARNT dimerization mode would provide insights into the mechanisms of AhR transformation. Here we present homology models of the murine AhR:ARNT PAS domain dimer developed using recently available X-ray structures of other bHLH-PAS protein dimers. Due to the different reciprocal orientation and interaction surfaces in the different template dimers, two alternative models were developed for both the PAS-A and PAS-B dimers and they were characterized by combining a number of computational evaluations. Both well-established hot spot prediction methods and new approaches to analyze individual residue and residue-pairwise contributions to the MM-GBSA binding free energies were adopted to predict residues critical for dimer stabilization. On this basis, a mutagenesis strategy for both the murine AhR and ARNT proteins was designed and ligand-dependent DNA binding ability of the AhR:ARNT heterodimer mutants was evaluated. While functional analysis disfavored the HIF2α:ARNT heterodimer-based PAS-B model, most mutants derived from the CLOCK:BMAL1-based AhR:ARNT dimer models of both the PAS-A and the PAS-B dramatically decreased the levels of DNA binding, suggesting this latter model as the most suitable for describing AhR:ARNT dimerization. These novel results open new research directions focused at elucidating basic molecular mechanisms underlying the

Deciphering Dimerization Modes of PAS Domains: Computational and Experimental Analyses of the AhR:ARNT Complex Reveal New Insights Into the Mechanisms of AhR Transformation.

PubMed

Corrada, Dario; Soshilov, Anatoly A; Denison, Michael S; Bonati, Laura

2016-06-01

The Aryl hydrocarbon Receptor (AhR) is a transcription factor that mediates the biochemical response to xenobiotics and the toxic effects of a number of environmental contaminants, including dioxins. Recently, endogenous regulatory roles for the AhR in normal physiology and development have also been reported, thus extending the interest in understanding its molecular mechanisms of activation. Since dimerization with the AhR Nuclear Translocator (ARNT) protein, occurring through the Helix-Loop-Helix (HLH) and PER-ARNT-SIM (PAS) domains, is needed to convert the AhR into its transcriptionally active form, deciphering the AhR:ARNT dimerization mode would provide insights into the mechanisms of AhR transformation. Here we present homology models of the murine AhR:ARNT PAS domain dimer developed using recently available X-ray structures of other bHLH-PAS protein dimers. Due to the different reciprocal orientation and interaction surfaces in the different template dimers, two alternative models were developed for both the PAS-A and PAS-B dimers and they were characterized by combining a number of computational evaluations. Both well-established hot spot prediction methods and new approaches to analyze individual residue and residue-pairwise contributions to the MM-GBSA binding free energies were adopted to predict residues critical for dimer stabilization. On this basis, a mutagenesis strategy for both the murine AhR and ARNT proteins was designed and ligand-dependent DNA binding ability of the AhR:ARNT heterodimer mutants was evaluated. While functional analysis disfavored the HIF2α:ARNT heterodimer-based PAS-B model, most mutants derived from the CLOCK:BMAL1-based AhR:ARNT dimer models of both the PAS-A and the PAS-B dramatically decreased the levels of DNA binding, suggesting this latter model as the most suitable for describing AhR:ARNT dimerization. These novel results open new research directions focused at elucidating basic molecular mechanisms underlying the

AhR and SHP regulate phosphatidylcholine and S-adenosylmethionine levels in the one-carbon cycle.

PubMed

Kim, Young-Chae; Seok, Sunmi; Byun, Sangwon; Kong, Bo; Zhang, Yang; Guo, Grace; Xie, Wen; Ma, Jian; Kemper, Byron; Kemper, Jongsook Kim

2018-02-07

Phosphatidylcholines (PC) and S-adenosylmethionine (SAM) are critical determinants of hepatic lipid levels, but how their levels are regulated is unclear. Here, we show that Pemt and Gnmt, key one-carbon cycle genes regulating PC/SAM levels, are downregulated after feeding, leading to decreased PC and increased SAM levels, but these effects are blunted in small heterodimer partner (SHP)-null or FGF15-null mice. Further, aryl hydrocarbon receptor (AhR) is translocated into the nucleus by insulin/PKB signaling in the early fed state and induces Pemt and Gnmt expression. This induction is blocked by FGF15 signaling-activated SHP in the late fed state. Adenoviral-mediated expression of AhR in obese mice increases PC levels and exacerbates steatosis, effects that are blunted by SHP co-expression or Pemt downregulation. PEMT, AHR, and PC levels are elevated in simple steatosis patients, but PC levels are robustly reduced in steatohepatitis-fibrosis patients. This study identifies AhR and SHP as new physiological regulators of PC/SAM levels.

Immuno-detection of dioxins using a recombinant protein of aryl hydrocarbon receptor (AhR) fused with sfGFP.

PubMed

Faiad, Walaa; Hanano, Abdulsamie; Kabakibi, Mohamed Maher; Abbady, Abdul Qader

2016-06-21

Dioxins are one of the most toxic groups of persistent organic pollutants. Their bioaccumulation through the food chain constitutes a potential risk for human health. Upon cell entry, dioxins bind specifically and firmly to the aryl hydrocarbon receptor (AhR), leading to the stimulation of several enzymes responsible for its detoxification. Dioxin/AhR interaction could be exploited as an affordable alternative to a variety of analytical methods for detecting dioxin contamination in the environment. In this work, the ligand binding domain (LBD) of the AhR was cloned downstream a superfolder form of the green fluorescent protein (sfGFP), resulting in the construct pRSET-sfGFP-AhR. High level of expressed sfGFP-AhR fusion protein (50 kDa) was recovered from the inclusion bodies of E. coli by simple solubilization with the Arginine, and purified by affinity chromatography via its N-terminal 6 × His tag. Its purity was confirmed by SDS-PAGE analysis and immunoblotting with anti-His or anti-GFP antibodies. Indirect ELISA revealed the ability of the sfGFP-AhR, but not the sfGFP, to bind to the immobilized dioxin with the possibility to detect such interaction by both its 6 × His and GFP tags,Competitive ELISA showed that anti-dioxin antibody was more sensitive to low dioxin concentrations than sfGFP-AhR. Nevertheless,the detection range of sfGFP-AhR fusion was much wider and the detection limit was of about 10 ppt (parts per trillion) of free dioxin in the tested artificial samples. this highly expressed and functional sfGFP-AhR fusion protein provides a promising molecular tool for detecting and quantifying different congeners of dioxins.

Studies on the Role of The Ah Receptor (AhR) on the Etiology of Breast Cancer: A Novel Idea of Identifying this Receptor as a New Therapeutic Target

DTIC Science & Technology

2010-09-01

found that the most potent phytochemical suppressors of cell proliferation of P20E cells were curcumin (10 µM approximately 80 to 90% suppression...effectiveness of a number of phytochemicals from edible plants known to block AhR in attenuating the expression of high rates of cell proliferation...selected number of those phytochemicals , by xenografting those AhR overexpressing human breast cancer cells into athymic nude mice, and by treating

Polycyclic Aromatic Hydrocarbons (PAHs) Mediate Transcriptional Activation of the ATP Binding Cassette Transporter ABCB6 Gene via the Aryl Hydrocarbon Receptor (AhR)*

PubMed Central

Chavan, Hemantkumar; Krishnamurthy, Partha

2012-01-01

Liver is endowed with a mechanism to induce hepatic cytochromes P450 (CYP450s) in response to therapeutic drugs and environmental contaminants, leading to increased detoxification and elimination of the xenobiotics. Each CYP450 is composed of an apoprotein moiety and a heme prosthetic group, which is required for CYP450 activity. Thus, under conditions of CYP450 induction, there is a coordinate increase in heme biosynthesis to compensate for the increased expression of CYP450s. ABCB6, a mitochondrial ATP binding cassette transporter, which regulates coproporphyrinogen transport from the cytoplasm into the mitochondria to complete heme biosynthesis, represents a previously unrecognized rate-limiting step in heme biosynthesis. However, it is not known if exposure to drugs and environmental contaminants induces ABCB6 expression, to assure an adequate and apparently coordinated supply of heme for the generation of functional cytochrome holoprotein. In the present study, we demonstrate that polycyclic aromatic hydrocarbons (PAHs), the widely distributed environmental toxicants shown to induce porphyrin accumulation causing hepatic porphyria, up-regulate ABCB6 expression in both mice and humans. Using siRNA technology and Abcb6 knock-out mice, we demonstrate that PAH-mediated increase in hepatic porphyrins is compromised in the absence of ABCB6. Moreover, in vivo studies in aryl hydrocarbon receptor (AhR) knock-out mice demonstrate that PAH induction of ABCB6 is mediated by AhR. Promoter activation studies combined with electrophoretic mobility shift assay and chromatin immunoprecipitation assay demonstrate direct interactions between the AhR binding sites in the ABCB6 promoter and the AhR receptor, implicating drug activation mechanisms for ABCB6 similar to those found in inducible cytochrome P450s. These studies are the first to describe direct transcriptional activation of both mouse and human ABCB6 by xenobiotics. PMID:22761424

Novel cellular targets of AhR underlie alterations in neutrophilic inflammation and iNOS expression during influenza virus infection

PubMed Central

Head Wheeler, Jennifer L.; Martin, Kyle C.; Lawrence, B. Paige

2012-01-01

The underlying reasons for variable clinical outcomes from respiratory viral infections remain uncertain. Several studies suggest that environmental factors contribute to this variation, but limited knowledge of cellular and molecular targets of these agents hampers our ability to quantify or modify their contribution to disease and improve public health. The aryl hydrocarbon receptor (AhR) is an environment sensing transcription factor that binds many anthropogenic and natural chemicals. The immunomodulatory properties of AhR ligands are best characterized with extensive studies of changes in CD4+ T cell responses. Yet, AhR modulates other aspects of immune function. We previously showed that during influenza virus infection, AhR activation modulates neutrophil accumulation in the lung, and this contributes to increased mortality in mice. Enhanced levels of inducible nitric oxide synthase (iNOS) in infected lungs are observed during the same timeframe as AhR-mediated increased pulmonary neutrophilia. In this study, we evaluated whether these two consequences of AhR activation are causally linked. Reciprocal inhibition of AhR-mediated elevations in iNOS and pulmonary neutrophilia reveal that, although they are contemporaneous, they are not causally related. We show using Cre/loxP technology that elevated iNOS levels and neutrophil number in the infected lung result from separate, AhR-dependent signaling in endothelial and respiratory epithelial cells, respectively. Studies using mutant mice further reveal that AhR-mediated alterations in these innate responses to infection require a functional nuclear localization signal and DNA binding domain. Thus, gene targets of AhR in non-hematopoietic cells are important new considerations for understanding AhR-mediated changes in innate anti-viral immunity. PMID:23233726

Interaction of Diuron and Related Substituted Phenylureas with the Ah Receptor Pathway

PubMed Central

Zhao, Bin; Baston, David S.; Hammock, Bruce; Denison, Michael S.

2011-01-01

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates many of the biological and toxicological actions of structurally diverse chemicals, including the ubiquitous environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin. Here, we have examined the ability of diuron, a widely used herbicide, and several structurally related substituted phenylureas to bind to and activate/inhibit the AhR and AhR signal transduction. Diuron induced CYP1A1 mRNA levels in mouse hepatoma (Hepa1c1c7) cells and AhR-dependent luciferase reporter gene expression in stably transfected mouse, rat, guinea pig, and human cell lines. In addition, ligand binding and gel retardation analysis demonstrated the ability of diuron to competitively bind to and stimulate AhR transformation and DNA binding in vitro and in intact cells. Several structurally related substituted phenylureas competitively bound to the guinea pig hepatic cytosolic AhR, inhibited 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced AhR-dependent luciferase reporter gene expression in a species-specific manner and stimulated AhR transformation and DNA binding, consistent with their role as partial AhR agonists. These results demonstrate not only that diuron and related substituted phenylureas are AhR ligands but also that exposure to these chemicals could induce/inhibit AhR-dependent biological effects. PMID:16788953

Dibutyl Phthalate (DBP)-Induced Apoptosis and Neurotoxicity are Mediated via the Aryl Hydrocarbon Receptor (AhR) but not by Estrogen Receptor Alpha (ERα), Estrogen Receptor Beta (ERβ), or Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) in Mouse Cortical Neurons.

PubMed

Wójtowicz, Anna K; Szychowski, Konrad A; Wnuk, Agnieszka; Kajta, Małgorzata

2017-01-01

Dibutyl phthalate (di-n-butyl phthalate, DBP) is one of the most commonly used phthalate esters. DBP is widely used as a plasticizer in a variety of household industries and consumer products. Because phthalates are not chemically bound to products, they can easily leak out to enter the environment. DBP can pass through the placental and blood-brain barriers due to its chemical structure, but little is known about its mechanism of action in neuronal cells. This study demonstrated the toxic and apoptotic effects of DBP in mouse neocortical neurons in primary cultures. DBP stimulated caspase-3 and LDH activities as well as ROS formation in a concentration (10 nM-100 µM) and time-dependent (3-48 h) manner. DBP induced ROS formation at nanomolar concentrations, while it activated caspase-3 and LDH activities at micromolar concentrations. The biochemical effects of DBP were accompanied by decreased cell viability and induction of apoptotic bodies. Exposure to DBP reduced Erα and Pparγ mRNA expression levels, which were inversely correlated with protein expression of the receptors. Treatment with DBP enhanced Ahr mRNA expression, which was reflected by the increased AhR protein level observed at 3 h after exposure. ERα, ERβ, and PPARγ antagonists stimulated DBP-induced caspase-3 and LDH activities. AhR silencing demonstrated that DBP-induced apoptosis and neurotoxicity are mediated by AhR, which is consistent with the results from DBP-induced enhancement of AhR mRNA and protein expression. Our study showed that AhR is involved in DBP-induced apoptosis and neurotoxicity, while the ERs and PPARγ signaling pathways are impaired by the phthalate.

Novel roles for AhR and ARNT in the regulation of alcohol dehydrogenases in human hepatic cells.

PubMed

Attignon, Eléonore A; Leblanc, Alix F; Le-Grand, Béatrice; Duval, Caroline; Aggerbeck, Martine; Rouach, Hélène; Blanc, Etienne B

2017-01-01

The mechanisms by which pollutants participate in the development of diverse pathologies are not completely understood. The pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) activates the AhR (aryl hydrocarbon receptor) signaling pathway. We previously showed that TCDD (25 nM, 30 h) decreased the expression of several alcohol metabolism enzymes (cytochrome P450 2E1, alcohol dehydrogenases ADH1, 4 and 6) in differentiated human hepatic cells (HepaRG). Here, we show that, as rapidly as 8 h after treatment (25 nM TCDD) ADH expression decreased 40 % (p < 0.05). ADH1 and 4 protein levels decreased 40 and 27 %, respectively (p < 0.05), after 72 h (25 nM TCDD). The protein half-lives were not modified by TCDD which suggests transcriptional regulation of expression. The AhR antagonist CH-223191 or AhR siRNA reduced the inhibitory effect of 25 nM TCDD on ADH1A, 4 and 6 expression 50-100 % (p < 0.05). The genomic pathway (via the AhR/ARNT complex) and not the non-genomic pathway involving c-SRC mediated these effects. Other AhR ligands (3-methylcholanthrene and PCB 126) decreased ADH1B, 4 and 6 mRNAs by more than 78 and 55 %, respectively (p < 0.01). TCDD also regulated the expression of ADH4 in the HepG2 human hepatic cell line, in primary human hepatocytes and in C57BL/6J mouse liver. In conclusion, activation of the AhR/ARNT signaling pathway by AhR ligands represents a novel mechanism for regulating the expression of ADHs. These effects may be implicated in the toxicity of AhR ligands as well as in the alteration of ethanol or retinol metabolism and may be associated further with higher risk of liver diseases or/and alcohol abuse disorders.

4-Nitrophenol exposure alters the AhR signaling pathway and related gene expression in the rat liver.

PubMed

Li, Ruonan; Song, Meiyan; Li, Zhi; Li, Yansen; Watanabe, Gen; Nagaoka, Kentaro; Taya, Kazuyoshi; Li, Chunmei

2017-02-01

4-Nitrophenol (PNP) is well known as an environmental endocrine disruptor. The aim of this study was to clarify the mechanism of PNP-induced liver damage and determine the regulatory involvement of the aryl hydrocarbon receptor (AhR) signaling pathway and associated gene expression. Immature male Wistar-Imamichi rats (28 days old) were randomly divided into control and PNP groups, which consisted of 1- and 3-day exposure (1 DE and 3 DE, respectively) and 3-day exposure followed by 3-day recovery (3 DE + 3 DR), groups. Each group was administered the vehicle or PNP (200 mg kg -1 body weight). The body and liver weight were significantly decreased in the 3 DE group. The mRNA expression levels of estrogen receptor-α (ERα), glutathione S-transferase (GST) and AhR exhibited a significant increase in the 1 DE group whereas, in contrast, that of cytochrome P450 (CYP) 1A1 decreased significantly in the 3 DE +3 DR group. AhR and CYP1A1 proteins were detected in the cytoplasm of hepatocytes of the 1 DE and 3 DE +3 DR groups whereas the ERα protein was found in the hepatocyte nuclei of the 1 DE and 3 DE groups. The present study demonstrates that PNP activated the AhR signaling pathway and regulated related CYP1A1 and GST gene expression in the liver. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Integration of Genome-Wide Computation DRE Search, AhR ChIP-chip and Gene Expression Analyses of TCDD-Elicited Responses in the Mouse Liver

PubMed Central

2011-01-01

Background The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor (TF) that mediates responses to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Integration of TCDD-induced genome-wide AhR enrichment, differential gene expression and computational dioxin response element (DRE) analyses further elucidate the hepatic AhR regulatory network. Results Global ChIP-chip and gene expression analyses were performed on hepatic tissue from immature ovariectomized mice orally gavaged with 30 μg/kg TCDD. ChIP-chip analysis identified 14,446 and 974 AhR enriched regions (1% false discovery rate) at 2 and 24 hrs, respectively. Enrichment density was greatest in the proximal promoter, and more specifically, within ± 1.5 kb of a transcriptional start site (TSS). AhR enrichment also occurred distal to a TSS (e.g. intergenic DNA and 3' UTR), extending the potential gene expression regulatory roles of the AhR. Although TF binding site analyses identified over-represented DRE sequences within enriched regions, approximately 50% of all AhR enriched regions lacked a DRE core (5'-GCGTG-3'). Microarray analysis identified 1,896 number of TCDD-responsive genes (|fold change| ≥ 1.5, P1(t) > 0.999). Integrating this gene expression data with our ChIP-chip and DRE analyses only identified 625 differentially expressed genes that involved an AhR interaction at a DRE. Functional annotation analysis of differentially regulated genes associated with AhR enrichment identified overrepresented processes related to fatty acid and lipid metabolism and transport, and xenobiotic metabolism, which are consistent with TCDD-elicited steatosis in the mouse liver. Conclusions Details of the AhR regulatory network have been expanded to include AhR-DNA interactions within intragenic and intergenic genomic regions. Moreover, the AhR can interact with DNA independent of a DRE core suggesting there are alternative mechanisms of AhR-mediated gene regulation. PMID:21762485

Low levels of the AhR in chronic obstructive pulmonary disease (COPD)-derived lung cells increases COX-2 protein by altering mRNA stability

PubMed Central

Zago, Michela; Sheridan, Jared A.; Traboulsi, Hussein; Hecht, Emelia; Zhang, Yelu; Guerrina, Necola; Matthews, Jason; Nair, Parameswaran; Eidelman, David H.; Hamid, Qutayba

2017-01-01

Heightened inflammation, including expression of COX-2, is associated with chronic obstructive pulmonary disease (COPD) pathogenesis. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is reduced in COPD-derived lung fibroblasts. The AhR also suppresses COX-2 in response to cigarette smoke, the main risk factor for COPD, by destabilizing the Cox-2 transcript by mechanisms that may involve the regulation of microRNA (miRNA). Whether reduced AhR expression is responsible for heightened COX-2 in COPD is not known. Here, we investigated the expression of COX-2 as well as the expression of miR-146a, a miRNA known to regulate COX-2 levels, in primary lung fibroblasts derived from non-smokers (Normal) and smokers (At Risk) with and without COPD. To confirm the involvement of the AhR, AhR knock-down via siRNA in Normal lung fibroblasts and MLE-12 cells was employed as were A549-AhRko cells. Basal expression of COX-2 protein was higher in COPD lung fibroblasts compared to Normal or Smoker fibroblasts but there was no difference in Cox-2 mRNA. Knockdown of AhR in lung structural cells increased COX-2 protein by stabilizing the Cox-2 transcript. There was less induction of miR-146a in COPD-derived lung fibroblasts but this was not due to the AhR. Instead, we found that RelB, an NF-κB protein, was required for transcriptional induction of both Cox-2 and miR-146a. Therefore, we conclude that the AhR controls COX-2 protein via mRNA stability by a mechanism independent of miR-146a. Low levels of the AhR may therefore contribute to the heightened inflammation common in COPD patients. PMID:28749959

Low levels of the AhR in chronic obstructive pulmonary disease (COPD)-derived lung cells increases COX-2 protein by altering mRNA stability.

PubMed

Zago, Michela; Sheridan, Jared A; Traboulsi, Hussein; Hecht, Emelia; Zhang, Yelu; Guerrina, Necola; Matthews, Jason; Nair, Parameswaran; Eidelman, David H; Hamid, Qutayba; Baglole, Carolyn J

2017-01-01

Heightened inflammation, including expression of COX-2, is associated with chronic obstructive pulmonary disease (COPD) pathogenesis. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is reduced in COPD-derived lung fibroblasts. The AhR also suppresses COX-2 in response to cigarette smoke, the main risk factor for COPD, by destabilizing the Cox-2 transcript by mechanisms that may involve the regulation of microRNA (miRNA). Whether reduced AhR expression is responsible for heightened COX-2 in COPD is not known. Here, we investigated the expression of COX-2 as well as the expression of miR-146a, a miRNA known to regulate COX-2 levels, in primary lung fibroblasts derived from non-smokers (Normal) and smokers (At Risk) with and without COPD. To confirm the involvement of the AhR, AhR knock-down via siRNA in Normal lung fibroblasts and MLE-12 cells was employed as were A549-AhRko cells. Basal expression of COX-2 protein was higher in COPD lung fibroblasts compared to Normal or Smoker fibroblasts but there was no difference in Cox-2 mRNA. Knockdown of AhR in lung structural cells increased COX-2 protein by stabilizing the Cox-2 transcript. There was less induction of miR-146a in COPD-derived lung fibroblasts but this was not due to the AhR. Instead, we found that RelB, an NF-κB protein, was required for transcriptional induction of both Cox-2 and miR-146a. Therefore, we conclude that the AhR controls COX-2 protein via mRNA stability by a mechanism independent of miR-146a. Low levels of the AhR may therefore contribute to the heightened inflammation common in COPD patients.

Adaptive changes in global gene expression profile of lung carcinoma A549 cells acutely exposed to distinct types of AhR ligands.

PubMed

Procházková, Jiřina; Strapáčová, Simona; Svržková, Lucie; Andrysík, Zdeněk; Hýžďalová, Martina; Hrubá, Eva; Pěnčíková, Kateřina; Líbalová, Helena; Topinka, Jan; Kléma, Jiří; Espinosa, Joaquín M; Vondráček, Jan; Machala, Miroslav

2018-08-01

Exposure to persistent ligands of aryl hydrocarbon receptor (AhR) has been found to cause lung cancer in experimental animals, and lung adenocarcinomas are often associated with enhanced AhR expression and aberrant AhR activation. In order to better understand the action of toxic AhR ligands in lung epithelial cells, we performed global gene expression profiling and analyze TCDD-induced changes in A549 transcriptome, both sensitive and non-sensitive to CH223191 co-treatment. Comparison of our data with results from previously reported microarray and ChIP-seq experiments enabled us to identify candidate genes, which expression status reflects exposure of lung cancer cells to TCDD, and to predict processes, pathways (e.g. ER stress, Wnt/β-cat, IFNɣ, EGFR/Erbb1), putative TFs (e.g. STAT, AP1, E2F1, TCF4), which may be implicated in adaptive response of lung cells to TCDD-induced AhR activation. Importantly, TCDD-like expression fingerprint of selected genes was observed also in A549 cells exposed acutely to both toxic (benzo[a]pyrene, benzo[k]fluoranthene) and endogenous AhR ligands (2-(1H-Indol-3-ylcarbonyl)-4-thiazolecarboxylic acid methyl ester and 6-formylindolo[3,2-b]carbazole). Overall, our results suggest novel cellular candidates, which could help to improve monitoring of AhR-dependent transcriptional activity during acute exposure of lung cells to distinct types of environmental pollutants. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of TBT and PAHs on CYP1A, AhR and Vitellogenin Gene Expression in the Japanese Eel, Anguilla japonica.

PubMed

Choi, Min Seop; Kwon, Se Ryun; Choi, Seong Hee; Kwon, Hyuk Chu

2012-12-01

Gene expressions of cytochrome P4501A (CYP1A), aryl hydrocarbon receptor (AhR) and vitellogenin (Vg) by endocrine disruptors, benzo[α]pyrene (B[a]P) and tributyltin (TBT) were examined in cultured eel hepatocytes which were isolated from eels treated previously with B[a]P (10 mg/kg) or estradiol-17β (20 mg/kg) in vivo, and the relationship between CYP1A, AhR and Vg genes were studied. When the cultured eel hepatocytes were treated with B[a]P (10(-6)-10(-5) M) the gene expressions of CYP1A and AhR were enhanced in a concentration-dependent manner. However, when treated with TBT (10(-9)-10(-5) M) the gene expressions of CYP1A and AhR were suppressed at high concentrations (10(-6)-10(-5) M), while having no effects at low concentrations (10(-9)-10(-7) M). Gene expression of Vg was also suppressed by TBT in a concentration-dependent manner in cultured eel hepatocytes which was previously treated in vivo with estradiol-17β.

Effect of TBT and PAHs on CYP1A, AhR and Vitellogenin Gene Expression in the Japanese Eel, Anguilla japonica

PubMed Central

Choi, Min Seop; Kwon, Se Ryun; Choi, Seong Hee; Kwon, Hyuk Chu

2012-01-01

Gene expressions of cytochrome P4501A (CYP1A), aryl hydrocarbon receptor (AhR) and vitellogenin (Vg) by endocrine disruptors, benzo[α]pyrene (B[a]P) and tributyltin (TBT) were examined in cultured eel hepatocytes which were isolated from eels treated previously with B[a]P (10 mg/kg) or estradiol-17β (20 mg/kg) in vivo, and the relationship between CYP1A, AhR and Vg genes were studied. When the cultured eel hepatocytes were treated with B[a]P (10-6-10-5 M) the gene expressions of CYP1A and AhR were enhanced in a concentration-dependent manner. However, when treated with TBT (10-9-10-5 M) the gene expressions of CYP1A and AhR were suppressed at high concentrations (10-6-10-5 M), while having no effects at low concentrations (10-9-10-7 M). Gene expression of Vg was also suppressed by TBT in a concentration-dependent manner in cultured eel hepatocytes which was previously treated in vivo with estradiol-17β. PMID:25949102

Effects of 4-nitrophenol on expression of the ER-α and AhR signaling pathway-associated genes in the small intestine of rats.

PubMed

Tang, Juan; Song, Meiyan; Watanabe, Gen; Nagaoka, Kentaro; Rui, Xiaoli; Li, ChunMei

2016-09-01

4-Nitrophenol (PNP) is a persistent organic pollutant that was proven to be an environmental endocrine disruptor. The aim of this study was to evaluate the role of the estrogen receptor-α (ER-α) and aryl hydrocarbon receptor (AhR) signaling pathway in regulating the damage response to PNP in the small intestine of rats. Wistar-Imamichi male rats (21 d) were randomly divided into two groups: the control group and PNP group. Each group had three processes that were gavaged with PNP or vehicle daily: single dose (1 d), repeated dose (3 consecutive days) (3 d), and repeated dose with recovery (3 consecutive days and 3 recovery days) (6 d). The weight of the body, the related viscera, and small intestine were examined. Histological parameters of the small intestine and the quantity of mucus proteins secreted by small goblet cells were determined using HE staining and PAS staining. The mRNA expression of AhR, ER-α, CYP1A1, and GST was measured by real-time qPCR. In addition, we also analyzed the AhR, ER-α, and CYP1A1 expression in the small intestine by immunohistochemical staining. The small intestines histologically changed in the PNP-treated rat and the expression of AhR, CYP1A1, and GST was increased. While ER-α was significantly decreased in the small intestine, simultaneously, when rats were exposed to a longer PNP treatment, the damages disappeared. Our results demonstrate that PNP has an effect on the expression of AhR signaling pathway genes, AhR, CYP1A1, and GST, and ER-α in the rat small intestine. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of artificial sweeteners on the AhR- and GR-dependent CYP1A1 expression in primary human hepatocytes and human cancer cells.

PubMed

Kamenickova, Alzbeta; Pecova, Michaela; Bachleda, Petr; Dvorak, Zdenek

2013-12-01

Food constituents may cause a phenomenon of food-drug interactions. In the current study, we examined the effects of artificial sweeteners (aspartame, acesulfame, cyclamate, saccharin) on the aryl hydrocarbon receptor (AhR) and glucocorticoid receptor (GR)-dependent expression of CYP1A1 in human hepatocytes, hepatic HepG2 and intestinal LS174T cancer cell lines. Sweeteners were tested in concentrations up to those occurring in non-alcoholic beverages. Basal and ligand-inducible AhR- and GR-dependent reporter gene activation in stably transfected HepG2 and HeLa cells, respectively, were not affected by either of the sweeteners tested after 24h of incubation. The expression of CYP1A1 mRNA and protein in primary cultures of human hepatocytes and in LS174T and HepG2 cells was not induced by any of the tested sweeteners. Overall, aspartame, acesulfame, saccharin and cyclamate had no effects on CYP1A1 expression and transcriptional activities of AhR and GR. These data imply the safety of artificial sweeteners in terms of interference with AhR, GR and CYP1A1. Copyright © 2013 Elsevier Ltd. All rights reserved.

Aryl hydrocarbon receptor (AhR)-dependent regulation of pulmonary miRNA by chronic cigarette smoke exposure.

PubMed

Rogers, Sarah; de Souza, Angela Rico; Zago, Michela; Iu, Matthew; Guerrina, Necola; Gomez, Alvin; Matthews, Jason; Baglole, Carolyn J

2017-01-12

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor historically known for its toxic responses to man-made pollutants such as dioxin. More recently, the AhR has emerged as a suppressor of inflammation, oxidative stress and apoptosis from cigarette smoke by mechanisms that may involve the regulation of microRNA. However, little is known about the AhR regulation of miRNA expression in the lung in response to inhaled toxicants. Therefore, we exposed Ahr -/- and Ahr +/- mice to cigarette smoke for 4 weeks and evaluated lung miRNA expression by PCR array. There was a dramatic regulation of lung miRNA by the AhR in the absence of exogenous ligand. In response to cigarette smoke, there were more up-regulated miRNA in Ahr -/- mice compared to Ahr +/- mice, including the cancer-associated miRNA miR-96. There was no significant change in the expression of the AhR regulated proteins HuR and cyclooxygenase-2 (COX-2). There were significant increases in the anti-oxidant gene sulfiredoxin 1 (Srxn1) and FOXO3a- predicted targets of miR-96. Collectively, these data support a prominent role for the AhR in regulating lung miRNA expression. Further studies to elucidate a role for these miRNA may further uncover novel biological function for the AhR in respiratory health and disease.

Dose- and time-dependent expression of aryl hydrocarbon receptor (AhR) and aryl hydrocarbon receptor nuclear translocator (ARNT) in PCB-, B[a]P-, and TBT-exposed intertidal copepod Tigriopus japonicus.

PubMed

Kim, Bo-Mi; Rhee, Jae-Sung; Hwang, Un-Ki; Seo, Jung Soo; Shin, Kyung-Hoon; Lee, Jae-Seong

2015-02-01

The aryl hydrocarbon receptor (AhR) and aryl hydrocarbon nuclear translocator (ARNT) genes from the copepod Tigriopus japonicus (Tj) were cloned to examine their potential functions in the invertebrate putative AhR-CYP signaling pathway. The amino acid sequences encoded by the Tj-AhR and Tj-ARNT genes showed high similarity to homologs of Daphnia and Drosophila, ranging from 68% and 70% similarity for the AhR genes to 56% for the ARNT genes. To determine whether Tj-AhR and Tj-ARNT are modulated by environmental pollutants, transcriptional expression of Tj-AhR and Tj-ARNT was analyzed in response to exposure to five concentrations of polychlorinated biphenyl (PCB 126) (control, 10, 50, 100, 500 μg L(-1)), benzo[a]pyrene (B[a]P) (control, 5, 10, 50, 100 μg L(-1)), and tributyltin (TBT) (control, 1, 5, 10, 20 μg L(-1)) 24h after exposure. A time-course experiment (0, 3, 6, 12, 24h) was performed to analyze mRNA expression patterns after exposure to PCB, B[a]P, and TBT. T. japonicus exhibited dose-dependent and time-dependent upregulation of Tj-AhR and Tj-ARNT in response to pollutant exposure, and the degree of expression was dependent on the pollutant, suggesting that pollutants such as PCB, B[a]P, and TBT modulate expression of Tj-AhR and Tj-ARNT genes in the putative AhR-CYP signaling pathway. Copyright © 2014 Elsevier Ltd. All rights reserved.

Combined chemical and toxicological long-term monitoring for AhR agonists with SPMD-based virtual organisms in drinking water Danjiangkou Reservoir, China.

PubMed

Wang, Jingxian; Song, Guoqiang; Li, Aimin; Henkelmann, Bernhard; Pfister, Gerd; Tong, Anthony Z; Schramm, Karl-Werner

2014-08-01

SPMD-based virtual organisms (VOs) were employed for time-integrating, long-term sampling combined biological and chemical analyses for exposure assessment of hydrophobic organic pollutants (HOPs) in a drinking water reservoir, China. The SPMDs were deployed at four and five sites in the Danjiangkou (DJK) reservoir over two periods of 26 and 31 d to sequester the hydrophobic contaminants in water. The chosen bioassay response for the extracts of the SPMDs, the induction of 7-ethoxyresorufin-o-deethylase (EROD) was assayed using a rat hepatoma cell line (H4IIE). The known aryl hydrocarbon receptor (AhR) agonists PAHs and PCBs were analyzed by HRGC/HRMS instrument. The cause-effect relationship between the observed AhR activities and chemical concentrations of detected AhR agonists was examined. The results show that the extracts from the SPMD samples could induce AhR activity significantly, whereas the chemically derived 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalent (TEQcal) was not correlated with the bioassay-derived TCDD equivalent (TEQbio). The known AhR agonists could only account for 2-10% of the observed AhR responses among which the contribution of PCBs could almost be neglected. Unidentified AhR-active compounds represented a greater proportion of the TCDD equivalent (TCDD-EQ) in SPMD samples from DJK. Based on the first assessment, the VO followed by the combination of chemical and biological analyses emerges as a resource efficient water monitoring device in ecotoxicological assessment for toxicologically relevant compounds which are readily available for uptake by resident aquatic biota in drinking water resources. Copyright © 2014 Elsevier Ltd. All rights reserved.

Is chronic AhR activation by rapidly metabolized ligands safe for the treatment of immune-mediated diseases?

PubMed

Ehrlich, Allison K; Kerkvliet, Nancy I

2017-02-01

There is a long standing perception that AhR ligands are automatically disqualified from pharmaceutical development due to their induction of Cyp1a1 as well as their potential for causing "dioxin-like" toxicities. However, recent discoveries of new AhR ligands with potential therapeutic applications have been reported, inviting reconsideration of this policy. One area of exploration is focused on the activation of AhR to promote the generation of regulatory T cells, which control the intensity and duration of immune responses. Rapidly metabolized AhR ligands (RMAhRLs), which do not bioaccumulate in the same manner as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) have been discovered that induce Tregs and display impressive therapeutic efficacy in a broad range of preclinical models of immune-mediated diseases. Given the promise of these RMAhRLs, is the bias against AhR activators still valid? Can RMAhRLs be given chronically to maintain therapeutic levels of AhR activation without producing the same toxicity profile as dioxin-like compounds? Based on our review of the data, there is little evidence to support the indiscriminate exclusion of AhR activators/Cyp1a1 inducers from early drug developmental pipelines. We also found no evidence that short-term treatment with RMAhRLs produce "dioxin-like toxicity" and, in fact, were well tolerated. However, safety testing of individual RMAhRLs under therapeutic conditions, as performed with all promising new drugs, will be needed to reveal whether or not chronic activation of AhR leads to unacceptable adverse outcomes.

Regulatory effects of dioxin-like and non-dioxin-like PCBs and other AhR ligands on the antioxidant enzymes paraoxonase 1/2/3.

PubMed

Shen, Hua; Robertson, Larry W; Ludewig, Gabriele

2016-02-01

Paraoxonase 1 (PON1), an antioxidant enzyme, is believed to play a critical role in many diseases, including cancer. PCBs are widespread environmental contaminants known to induce oxidative stress and cancer and to produce changes in gene expression of various pro-oxidant and antioxidant enzymes. Thus, it appeared of interest to explore whether PCBs may modulate the activity and/or gene expression of PON1 as well. In this study, we compared the effects of dioxin-like and non-dioxin-like PCBs and of various aryl hydrocarbon receptor (AhR) ligands on PON1 regulation and activity in male and female Sprague-Dawley rats. Our results demonstrate that (i) the non-dioxin-like PCB154, PCB155, and PCB184 significantly reduced liver and serum PON1 activities, but only in male rats; (ii) the non-dioxin-like PCB153, the most abundant PCB in many matrices, did not affect PON1 messenger RNA (mRNA) level in the liver but significantly decreased serum PON1 activity in male rats; (iii) PCB126, an AhR ligand and dioxin-like PCB, increased both PON1 activities and gene expression; and (iv) even though three tested AhR ligands induced CYP1A in several tissues to a similar extent, they displayed differential effects on the three PONs and AhR, i.e., PCB126 was an efficacious inducer of PON1, PON2, PON3, and AhR in the liver, while 3-methylcholantrene induced liver AhR and lung PON3, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent AhR agonist, increased only PON3 in the lung, at the doses and exposure times used in these studies. These results show that PCBs may have an effect on the antioxidant protection by paraoxonases in exposed populations and that regulation of gene expression through AhR is highly diverse.

Deficiency in Aryl Hydrocarbon Receptor (AHR) Expression throughout Aging Alters Gene Expression Profiles in Murine Long-Term Hematopoietic Stem Cells

PubMed Central

Bennett, John A.; Singh, Kameshwar P.; Unnisa, Zeenath; Welle, Stephen L.; Gasiewicz, Thomas A.

2015-01-01

Dysregulation of hematopoietic stem cell (HSC) signaling can contribute to the development of diseases of the blood system. Lack of aryl hydrocarbon receptor (AhR) has been associated with alterations in gene expression related to HSC function and the subsequent development of a myeloproliferative disorder in aging female mice. We sorted the most primitive population of HSCs with the highest stem cell potential (Long-term, or LT-HSCs) from 18-month-old AhR-null-allele (AhR-KO) and WT mice and analyzed gene expression using microarray to determine alterations in gene expression and cell signaling networks in HSCs that could potentially contribute to the aging phenotype of AhR-KO mice. Comparisons with previous array data from 8-week old mice indicated that aging alone is sufficient to alter gene expression. In addition, a significant number of gene expression differences were observed in aged LT-HSCs that are dependent on both aging and lack of AhR. Pathway analysis of these genes revealed networks related to hematopoietic stem cell activity or function. qPCR was used to confirm the differential expression of a subset of these genes, focusing on genes that may represent novel AhR targets due to the presence of a putative AhR binding site in their upstream regulatory region. We verified differential expression of PDGF-D, Smo, Wdfy1, Zbtb37 and Zfp382. Pathway analysis of this subset of genes revealed overlap between cellular functions of the novel AhR targets and AhR itself. Lentiviral-mediated knockdown of AhR in lineage-negative hematopoietic cells was sufficient to induce changes in all five of the candidate AhR targets identified. Taken together, these data suggest a role for AhR in HSC functional regulation, and identify novel HSC AhR target genes that may contribute to the phenotypes observed in AhR-KO mice. PMID:26208102

Aryl hydrocarbon receptor (AhR)-dependent regulation of pulmonary miRNA by chronic cigarette smoke exposure

PubMed Central

Rogers, Sarah; de Souza, Angela Rico; Zago, Michela; Iu, Matthew; Guerrina, Necola; Gomez, Alvin; Matthews, Jason; Baglole, Carolyn J.

2017-01-01

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor historically known for its toxic responses to man-made pollutants such as dioxin. More recently, the AhR has emerged as a suppressor of inflammation, oxidative stress and apoptosis from cigarette smoke by mechanisms that may involve the regulation of microRNA. However, little is known about the AhR regulation of miRNA expression in the lung in response to inhaled toxicants. Therefore, we exposed Ahr−/− and Ahr+/− mice to cigarette smoke for 4 weeks and evaluated lung miRNA expression by PCR array. There was a dramatic regulation of lung miRNA by the AhR in the absence of exogenous ligand. In response to cigarette smoke, there were more up-regulated miRNA in Ahr−/− mice compared to Ahr+/− mice, including the cancer-associated miRNA miR-96. There was no significant change in the expression of the AhR regulated proteins HuR and cyclooxygenase-2 (COX-2). There were significant increases in the anti-oxidant gene sulfiredoxin 1 (Srxn1) and FOXO3a- predicted targets of miR-96. Collectively, these data support a prominent role for the AhR in regulating lung miRNA expression. Further studies to elucidate a role for these miRNA may further uncover novel biological function for the AhR in respiratory health and disease. PMID:28079158

Molecular modeling of the AhR structure and interactions can shed light on ligand-dependent activation and transformation mechanisms.

PubMed

Bonati, Laura; Corrada, Dario; Tagliabue, Sara Giani; Motta, Stefano

2017-02-01

Molecular modeling has given important contributions to elucidation of the main stages in the AhR signal transduction pathway. Despite the lack of experimentally determined structures of the AhR functional domains, information derived from homologous systems has been exploited for modeling their structure and interactions. Homology models of the AhR PASB domain have provided information on the binding cavity and contributed to elucidate species-specific differences in ligand binding. Molecular Docking simulations of the ligand binding process have given insights into differences in binding of diverse agonists, antagonists, and selective AhR modulators, and their application to virtual screening of large databases of compounds have allowed identification of novel AhR ligands. Recently available structural information on protein-protein and protein-DNA complexes of other bHLH-PAS systems has opened the way for modeling the AhR:ARNT dimer structure and investigating the mechanisms of AhR transformation and DNA binding. Future research directions should include simulation of the protein dynamics to obtain a more reliable description of intermolecular interactions involved in signal transmission.

AhR modulates the IL-22-producing cell proliferation/recruitment in imiquimod-induced psoriasis mouse model.

PubMed

Cochez, Perrine M; Michiels, Camille; Hendrickx, Emilie; Van Belle, Astrid B; Lemaire, Muriel M; Dauguet, Nicolas; Warnier, Guy; de Heusch, Magali; Togbe, Dieudonnée; Ryffel, Bernhard; Coulie, Pierre G; Renauld, Jean-Christophe; Dumoutier, Laure

2016-06-01

IL-22 has a detrimental role in skin inflammatory processes, for example in psoriasis. As transcription factor, AhR controls the IL-22 production by several cell types (i.e. Th17 cells). Here, we analyzed the role of Ahr in IL-22 production by immune cells in the inflamed skin, using an imiquimod-induced psoriasis mouse model. Our results indicate that IL-22 is expressed in the ear of imiquimod-treated Ahr(-/-) mice but less than in wild-type mice. We then studied the role of AhR on three cell populations known to produce IL-22 in the skin: γδ T cells, Th17 cells, and ILC3, and a novel IL-22-producing cell type identified in this setting: CD4(-) CD8(-) TCRβ(+) T cells. We showed that AhR is required for IL-22 production by Th17, but not by the three other cell types, in the imiquimod-treated ears. Moreover, AhR has a role in the recruitment of γδ T cells, ILC3, and CD4(-) CD8(-) TCRβ(+) T cells into the inflamed skin or in their local proliferation. Taken together, AhR has a direct role in IL-22 production by Th17 cells in the mouse ear skin, but not by γδ T cells, CD4(-) CD8(-) TCRβ(+) T cells and ILCs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Baicalein induces G1 arrest in oral cancer cells by enhancing the degradation of cyclin D1 and activating AhR to decrease Rb phosphorylation

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

Cheng, Ya-Hsin, E-mail: yhcheng@mail.cmu.edu.tw; Li, Lih-Ann; Lin, Pinpin

Baicalein is a flavonoid, known to have anti-inflammatory and anti-cancer effects. As an aryl hydrocarbon receptor (AhR) ligand, baicalein at high concentrations blocks AhR-mediated dioxin toxicity. Because AhR had been reported to play a role in regulating the cell cycle, we suspected that the anti-cancer effect of baicalein is associated with AhR. This study investigated the molecular mechanism involved in the anti-cancer effect of baicalein in oral cancer cells HSC-3, including whether such effect would be AhR-mediated. Results revealed that baicalein inhibited cell proliferation and increased AhR activity in a dose-dependent manner. Cell cycle was arrested at the G1 phasemore » and the expression of CDK4, cyclin D1, and phosphorylated retinoblastoma (pRb) was decreased. When the AhR was suppressed by siRNA, the reduction of pRb was partially reversed, accompanied by a decrease of cell population at G1 phase and an increase at S phase, while the reduction of cyclin D1 and CDK4 did not change. This finding suggests that the baicalein activation of AhR is indeed associated with the reduction of pRb, but is independent of the reduction of cyclin D1 and CDK4. When cells were pre-treated with LiCl, the inhibitor of GSK-3β, the decrease of cyclin D1 was blocked and the reduction of pRb was recovered. The data indicates that in HSC-3 the reduction of pRb is both mediated by baicalein through activation of AhR and facilitation of cyclin D1 degradation, which causes cell cycle arrest at the G1 phase, and results in the inhibition of cell proliferation. -- Highlights: ► Baicalein causes the G1 phase arrest by decreasing Rb phosphorylation. ► Baicalein modulates AhR-mediated cell proliferation. ► Both AhR activation and cyclin D1 degradation results in hypophosphorylation of Rb. ► Baicalein facilitates cyclin D1 degradation by signalling the GSK-3β pathway.« less

The AhR and NF-κB/Rel Proteins Mediate the Inhibitory Effect of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin on the 3′ Immunoglobulin Heavy Chain Regulatory Region

PubMed Central

Salisbury, Richard L.; Sulentic, Courtney E. W.

2015-01-01

Transcriptional regulation of the murine immunoglobulin (Ig) heavy chain gene (Igh) involves several regulatory elements including the 3′Igh regulatory region (3′IghRR), which is composed of at least 4 enhancers (hs3A, hs1.2, hs3B, and hs4). The hs1.2 and hs4 enhancers exhibit the greatest transcriptional activity and contain binding sites for several transcription factors including nuclear factor kappaB/Rel (NF-κB/Rel) proteins and the aryl hydrocarbon receptor (AhR). Interestingly, the environmental immunosuppressant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which potently inhibits antibody secretion, also profoundly inhibits 3′IghRR and hs1.2 enhancer activation induced by the B-lymphocyte activator lipopolysaccharide (LPS), but enhances LPS-induced activation of the hs4 enhancer. Within the hs1.2 and hs4 enhancers, the AhR binding site is in close proximity or overlaps an NF-κB/Rel binding site suggesting a potential reciprocal modulation of the 3′IghRR by AhR and NF-κB/Rel. The objective of the current study was to evaluate the role of NF-κB/Rel and the AhR on the 3′IghRR and its enhancers using the AhR ligand TCDD, the AhR antagonist CH223191, and toll-like receptor agonists LPS, Resiquimod (R848), or cytosine-phosphate-guanine-oligodeoxynucleotides (CpG). Utilizing the CH12.LX B-lymphocyte cell line and variants expressing either a 3′IghRR-regulated transgene reporter or an inducible IκBα (inhibitor kappa B-alpha protein) superrepressor (IκBαAA), we demonstrate an AhR- and NF-κB/Rel-dependent modulation of 3′IghRR and hs4 activity. Additionally, in mouse splenocytes or CH12.LX cells, binding within the hs1.2 and hs4 enhancer of the AhR and the NF-κB/Rel proteins RelA and RelB was differentially altered by the cotreatment of LPS and TCDD. These results suggest that the AhR and NF-κB/Rel protein binding profile within the 3′IghRR mediates the inhibitory effects of TCDD on Ig expression and therefore antibody levels. PMID:26377645

TOXICITY OF AHR AGONISTS TO FISH EARLY LIFE STAGES

EPA Science Inventory

Fish early life stages are exceptionally sensitive to the lethal toxicity of chemicals that act as arylhydrocarbon receptor (AhR) agonists. Toxicity characterizations based on 2,3,7,8-tetrachlorodibenzo-p-dioxin, generally the most potent AhR agonist, support the toxicity equiva...

Tumor-Repopulating Cells Induce PD-1 Expression in CD8+ T Cells by Transferring Kynurenine and AhR Activation.

PubMed

Liu, Yuying; Liang, Xiaoyu; Dong, Wenqian; Fang, Yi; Lv, Jiadi; Zhang, Tianzhen; Fiskesund, Roland; Xie, Jing; Liu, Jinyan; Yin, Xiaonan; Jin, Xun; Chen, Degao; Tang, Ke; Ma, Jingwei; Zhang, Huafeng; Yu, Jing; Yan, Jun; Liang, Huaping; Mo, Siqi; Cheng, Feiran; Zhou, Yabo; Zhang, Haizeng; Wang, Jing; Li, Jingnan; Chen, Yang; Cui, Bing; Hu, Zhuo-Wei; Cao, Xuetao; Xiao-Feng Qin, F; Huang, Bo

2018-03-12

Despite the clinical successes fostered by immune checkpoint inhibitors, mechanisms underlying PD-1 upregulation in tumor-infiltrating T cells remain an enigma. Here, we show that tumor-repopulating cells (TRCs) drive PD-1 upregulation in CD8 + T cells through a transcellular kynurenine (Kyn)-aryl hydrocarbon receptor (AhR) pathway. Interferon-γ produced by CD8 + T cells stimulates release of high levels of Kyn produced by TRCs, which is transferred into adjacent CD8 + T cells via the transporters SLC7A8 and PAT4. Kyn induces and activates AhR and thereby upregulates PD-1 expression. This Kyn-AhR pathway is confirmed in both tumor-bearing mice and cancer patients and its blockade enhances antitumor adoptive T cell therapy efficacy. Thus, we uncovered a mechanism of PD-1 upregulation with potential tumor immunotherapeutic applications. Copyright © 2018 Elsevier Inc. All rights reserved.

SLC6A19 is a novel putative gene, induced by dioxins via AhR in human hepatoma HepG2 cells.

PubMed

Tian, Wenjing; Fu, Hualing; Xu, Tuan; Xu, Sherry Li; Guo, Zhiling; Tian, Jijing; Tao, Wuqun; Xie, Heidi Qunhui; Zhao, Bin

2018-06-01

The aryl hydrocarbon receptor (AhR) plays an important role in mediating dioxins toxicity. Currently, genes of P450 families are major research interests in studies on AhR-mediated gene alterations caused by dioxins. Genes related to other metabolic pathways or processes may be also responsive to dioxin exposures. Amino acid transporter B0AT1 (encoded by SLC6A19) plays a decisive role in neutral amino acid transport which is present in kidney, intestine and liver. However, effects of dioxins on its expression are still unknown. In the present study, we focused on the effects of dioxin and dioxin-like compounds on SLC6A19 expression in HepG2 cells. We identified SLC6A19 as a novel putative target gene of AhR activation in HepG2 cells. 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) increased the expression of SLC6A19 in time- and concentration-dependent manners. Using AhR antagonist CH223191 and/or siRNA assays, we demonstrated that certain AhR agonists upregulated SLC6A19 expression via AhR, including TCDD, 1,2,3,7,8-pentachlorodibenzo-p-dioxin (1,2,3,7,8-PeCDD), 2,3,4,7,8- pentachlorodibenzofuran (2,3,4,7,8-PeCDF) and PCB126. In addition, the expression of B0AT1 was also significantly induced by TCDD in HepG2 cells. Our study suggested that dioxins might affect the transcription and translation of SLC6A19 in HepG2 cells, which might be a novel putative gene to assess dioxins' toxicity in amino acid transport and metabolism in liver. Copyright © 2018 Elsevier Ltd. All rights reserved.

TCDD, FICZ, and Other High Affinity AhR Ligands Dose-Dependently Determine the Fate of CD4+ T Cell Differentiation.

PubMed

Ehrlich, Allison K; Pennington, Jamie M; Bisson, William H; Kolluri, Siva K; Kerkvliet, Nancy I

2018-02-01

FICZ and TCDD, two high-affinity AhR ligands, are reported to have opposite effects on T cell differentiation with TCDD inducing regulatory T cells and FICZ inducing Th17 cells. This dichotomy has been attributed to ligand-intrinsic differences in AhR activation, although differences in sensitivity to metabolism complicate the issue. TCDD is resistant to AhR-induced metabolism and produces sustained AhR activation following a single dose in the μg/kg range, whereas FICZ is rapidly metabolized and AhR activation is transient. Nonetheless, prior studies comparing FICZ with TCDD have generally used the same 10-50 μg/kg dose range, and thus the two ligands would not equivalently activate AhR. We hypothesized that high-affinity AhR ligands can promote CD4+ T cell differentiation into both Th17 cells and Tregs, with fate depending on the extent and duration of AhR activation. We compared the immunosuppressive effects of TCDD and FICZ, along with two other rapidly metabolized ligands (ITE and 11-Cl-BBQ) in an acute alloresponse mouse model. The dose and timing of administration of each ligand was optimized for TCDD-equivalent Cyp1a1 induction. When optimized, all of the ligands suppressed the alloresponse in conjunction with the induction of Foxp3- Tr1 cells on day 2 and the expansion of natural Foxp3+ Tregs on day 10. In contrast, a low dose of FICZ induced transient expression of Cyp1a1 and did not induce Tregs or suppress the alloresponse but enhanced IL-17 production. Interestingly, low doses of the other ligands, including TCDD, also increased IL-17 production on day 10. These findings support the conclusion that the dose and the duration of AhR activation by high-affinity AhR ligands are the primary factors driving the fate of T cell differentiation. © The Author 2017. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

A rapid and reagent-free bioassay for the detection of dioxin-like compounds and other aryl hydrocarbon receptor (AhR) agonists using autobioluminescent yeast.

PubMed

Xu, Tingting; Young, Anna; Marr, Enolia; Sayler, Gary; Ripp, Steven; Close, Dan

2018-02-01

An autonomously bioluminescent Saccharomyces cerevisiae BLYAhS bioreporter was developed in this study for the simple and rapid detection of dioxin-like compounds (DLCs) and aryl hydrocarbon receptor (AhR) agonists. This recombinant yeast reporter was based on a synthetic bacterial luciferase reporter gene cassette (lux) that can produce the luciferase as well as the enzymes capable of self-synthesizing the requisite substrates for bioluminescent production from endogenous cellular metabolites. As a result, bioluminescent signal production is generated continuously and autonomously without cell lysis or exogenous reagent addition. By linking the expression of the autobioluminescent lux reporter cassette to AhR activation via the use of a dioxin-responsive promoter, the S. cerevisiae BLYAhS bioreporter emitted a bioluminescent signal in response to DLC exposure in a dose-responsive manner. The model dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), could be detected within 4 h with a half maximal effective concentration (EC 50 ) of ~ 8.1 nM and a lower detection limit of 500 pM. The autobioluminescent response of BLYAhS to other AhR agonists, including 2,3,7,8-tetrachlorodibenzofuran (TCDF), polychlorinated bisphenyl congener 126 (PCB-126) and 169 (PCB-169), 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin (HxCDD), 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD), benzo[a]pyrene (BaP), and β-naphthoflavone (bNF), were also characterized in this study. The non-destructive and reagent-free nature of the BLYAhS reporter assay facilitated near-continuous, automated signal acquisition without additional hands-on effort and cost, providing a simple and cost-effective method for rapid DLC detection.

The Role of AhR in Autoimmune Regulation and Its Potential as a Therapeutic Target against CD4 T Cell Mediated Inflammatory Disorder

PubMed Central

Zhu, Conghui; Xie, Qunhui; Zhao, Bin

2014-01-01

AhR has recently emerged as a critical physiological regulator of immune responses affecting both innate and adaptive systems. Since the AhR signaling pathway represents an important link between environmental stimulators and immune-mediated inflammatory disorder, it has become the object of great interest among researchers recently. The current review discusses new insights into the mechanisms of action of a select group of inflammatory autoimmune diseases and the ligand-activated AhR signaling pathway. Representative ligands of AhR, both exogenous and endogenous, are also reviewed relative to their potential use as tools for understanding the role of AhR and as potential therapeutics for the treatment of various inflammatory autoimmune diseases, with a focus on CD4 helper T cells, which play important roles both in self-immune tolerance and in inflammatory autoimmune diseases. Evidence indicating the potential use of these ligands in regulating inflammation in various diseases is highlighted, and potential mechanisms of action causing immune system effects mediated by AhR signaling are also discussed. The current review will contribute to a better understanding of the role of AhR and its signaling pathway in CD4 helper T cell mediated inflammatory disorder. Considering the established importance of AhR in immune regulation and its potential as a therapeutic target, we also think that both further investigation into the molecular mechanisms of immune regulation that are mediated by the ligand-specific AhR signaling pathway, and integrated research and development of new therapeutic drug candidates targeting the AhR signaling pathway should be pursued urgently. PMID:24905409

INSIGHTS FROM AHR AND ARNT GENE KNOCKOUT STUDIES REGARDING RESPONSES TO TCDD AND REGULATION OF NORMAL EMBRYONIC DEVELOPMENT

EPA Science Inventory

The aryl hydrocarbon receptor (AhR) and the AhR nuclear translocator (ARNT) are members of the Per-ARNT-Sim (PAS) family of proteins. The AhR binds members of the chemical family that includes dioxins, furans and coplanar polychlorinated biphenyls (PCBs). A ligand-AhR-ARNT comp...

Identification of a Raloxifene Analog That Promotes AhR-Mediated Apoptosis in Cancer Cells.

PubMed

Jang, Hyo Sang; Pearce, Martin; O'Donnell, Edmond F; Nguyen, Bach Duc; Truong, Lisa; Mueller, Monica J; Bisson, William H; Kerkvliet, Nancy I; Tanguay, Robert L; Kolluri, Siva Kumar

2017-12-01

We previously reported that raloxifene, an estrogen receptor modulator, is also a ligand for the aryl hydrocarbon receptor (AhR). Raloxifene induces apoptosis in estrogen receptor-negative human cancer cells through the AhR. We performed structure-activity studies with seven raloxifene analogs to better understand the structural requirements of raloxifene for induction of AhR-mediated transcriptional activity and apoptosis. We identified Y134 as a raloxifene analog that activates AhR-mediated transcriptional activity and induces apoptosis in MDA-MB-231 human triple negative breast cancer cells. Suppression of AhR expression strongly reduced apoptosis induced by Y134, indicating the requirement of AhR for Y134-induced apoptosis. Y134 also induced apoptosis in hepatoma cells without having an effect on cell cycle regulation. Toxicity testing on zebrafish embryos revealed that Y134 has a significantly better safety profile than raloxifene. Our studies also identified an analog of raloxifene that acts as a partial antagonist of the AhR, and is capable of inhibiting AhR agonist-induced transcriptional activity. We conclude that Y134 is a promising raloxifene analog for further optimization as an anti-cancer agent targeting the AhR.

Protective effects of levamisole, acetylsalicylic acid, and α-tocopherol against dioxin toxicity measured as the expression of AhR and COX-2 in a chicken embryo model.

PubMed

Gostomska-Pampuch, Kinga; Ostrowska, Alicja; Kuropka, Piotr; Dobrzyński, Maciej; Ziółkowski, Piotr; Kowalczyk, Artur; Łukaszewicz, Ewa; Gamian, Andrzej; Całkosiński, Ireneusz

2017-04-01

Polychlorinated dibenzo-p-dioxins and dibenzofurans (dioxins) are classed as persistent organic pollutants and have adverse effects on multiple functions within the body. Dioxins are known carcinogens, immunotoxins, and teratogens. Dioxins are transformed in vivo, and interactions between the products and the aryl hydrocarbon receptor (AhR) lead to the formation of proinflammatory and toxic metabolites. The aim of this study was to determine whether α-tocopherol (vitamin E), acetylsalicylic acid (ASA), and levamisole can decrease the amount of damage caused by dioxins. Fertile Hubbard Flex commercial line chicken eggs were injected with solutions containing 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or containing TCDD and the test compounds. The chicken embryos and organs were analyzed after 7 and 13 days. The levels at which AhR and cyclooxygenase-2 (COX-2) proteins (which are induced during inflammation) were expressed were evaluated by performing immunohistochemical analyses on embryos treated with TCDD alone or with TCDD and the test compounds. TCDD caused developmental disorders and increased AhR and COX-2 expression in the chicken embryo tissues. Vitamin E, levamisole, ASA, and ASA plus vitamin E inhibited AhR and COX-2 expression in embryos after 7 days and decreased AhR and COX-2 expression in embryos after 13 days. ASA, levamisole, and ASA plus vitamin E weakened the immune response and prevented multiple organ changes. Vitamin E was not fully protective against developmental changes in the embryos.

Perturbation effect of reduced graphene oxide quantum dots (rGOQDs) on aryl hydrocarbon receptor (AhR) pathway in zebrafish.

PubMed

Zhang, Jing-Hui; Sun, Tai; Niu, Aping; Tang, Yu-Mei; Deng, Shun; Luo, Wei; Xu, Qun; Wei, Dapeng; Pei, De-Sheng

2017-07-01

Graphene quantum dots (GQDs) has been widely used in enormous fields, however, the inherent molecular mechanism of GQDs for potential risks in biological system is still elusive to date. In this study, the outstanding reduced graphene quantum dots (rGOQDs) with the QY as high as 24.62% were successfully synthesized by the improved Hummers method and DMF hydrothermal treatment approach. The rGOQDs were N-doped photoluminescent nanomaterials with functional groups on the surface. The fluorescent bio-imaging was performed by exposing zebrafish in different concentrations of the as-prepared rGOQDs, and the distribution of rGOQDs was successfully observed. Moreover, the developmental toxicity and genotoxicity were evaluated to further investigate the potential hazard of rGOQDs. The result indicated that rGOQDs were responsible for the dose-dependent abnormalities on the development of zebrafish. Since the real-time polymerase chain reaction (RT-PCR) results showed that the expression of cyp1a was the highest expression in the selected genes and significantly up-regulated 8.49 fold in zebrafish, the perturbation of rGOQDs on aryl hydrocarbon receptor (AhR) pathway was investigated by using the Tg(cyp1a:gfp) zebrafish for the first time. The results demonstrated that rGOQDs significantly increased the green fluorescent protein (GFP) expression promoted by cyp1a in a dose-dependent manner, which was also further confirmed by the western blotting. This study offered an opportunity to reveal the potential hazards of in vivo bio-probes, which provided a valuable reference for investigating the graphene-based materials on the disturbance of AhR pathway in biological organisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

TCDD and a putative endogenous AhR ligand, ITE, elicit the same immediate changes in gene expression in mouse lung fibroblasts.

PubMed

Henry, Ellen C; Welle, Stephen L; Gasiewicz, Thomas A

2010-03-01

The aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor, mediates toxicity of several classes of xenobiotics and also has important physiological roles in differentiation, reproduction, and immunity, although the endogenous ligand(s) mediating these functions is/are as yet unidentified. One candidate endogenous ligand, 2-(1'H-indolo-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE), is a potent AhR agonist in vitro, activates the murine AhR in vivo, but does not induce toxicity. We hypothesized that ITE and the toxic ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), may modify transcription of different sets of genes to account for their different toxicity. To test this hypothesis, primary mouse lung fibroblasts were exposed to 0.5muM ITE, 0.2nM TCDD, or vehicle for 4 h, and total gene expression was evaluated using microarrays. After this short-term and low-dose treatment, several hundred genes were changed significantly, and the response to ITE and TCDD was remarkably similar, both qualitatively and quantitatively. Induced gene sets included the expected battery of AhR-dependent xenobiotic-metabolizing enzymes, as well as several sets that reflect the inflammatory role of lung fibroblasts. Real time quantitative RT-qPCR assay of several selected genes confirmed these microarray data and further suggested that there may be kinetic differences in expression between ligands. These data suggest that ITE and TCDD elicit an analogous change in AhR conformation such that the initial transcription response is the same. Furthermore, if the difference in toxicity between TCDD and ITE is mediated by differences in gene expression, then it is likely that secondary changes enabled by the persistent TCDD, but not by the shorter lived ITE, are responsible.

TCDD and a Putative Endogenous AhR Ligand, ITE, Elicit the Same Immediate Changes in Gene Expression in Mouse Lung Fibroblasts

PubMed Central

Henry, Ellen C.; Welle, Stephen L.; Gasiewicz, Thomas A.

2010-01-01

The aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor, mediates toxicity of several classes of xenobiotics and also has important physiological roles in differentiation, reproduction, and immunity, although the endogenous ligand(s) mediating these functions is/are as yet unidentified. One candidate endogenous ligand, 2-(1′H-indolo-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE), is a potent AhR agonist in vitro, activates the murine AhR in vivo, but does not induce toxicity. We hypothesized that ITE and the toxic ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), may modify transcription of different sets of genes to account for their different toxicity. To test this hypothesis, primary mouse lung fibroblasts were exposed to 0.5μM ITE, 0.2nM TCDD, or vehicle for 4 h, and total gene expression was evaluated using microarrays. After this short-term and low-dose treatment, several hundred genes were changed significantly, and the response to ITE and TCDD was remarkably similar, both qualitatively and quantitatively. Induced gene sets included the expected battery of AhR-dependent xenobiotic-metabolizing enzymes, as well as several sets that reflect the inflammatory role of lung fibroblasts. Real time quantitative RT-qPCR assay of several selected genes confirmed these microarray data and further suggested that there may be kinetic differences in expression between ligands. These data suggest that ITE and TCDD elicit an analogous change in AhR conformation such that the initial transcription response is the same. Furthermore, if the difference in toxicity between TCDD and ITE is mediated by differences in gene expression, then it is likely that secondary changes enabled by the persistent TCDD, but not by the shorter lived ITE, are responsible. PMID:19933214

Crosstalk between AhR and wnt/β-catenin signal pathways in the cardiac developmental toxicity of PM2.5 in zebrafish embryos.

PubMed

Zhang, Hang; Yao, Yugang; Chen, Yang; Yue, Cong; Chen, Jiahong; Tong, Jian; Jiang, Yan; Chen, Tao

2016-04-29

Recent studies have shown an association between congenital heart defects and air fine particle matter (PM2.5), but the molecular mechanisms remain elusive. It is well known that a number of organic compounds in PM2.5 can act as AhR agonists, and activation of AhR can antagonize Wnt/β-catenin signaling. Therefore, we hypothesized that PM2.5 could activate AhR and then repress the expression of wnt/β-catenin targeted genes essential for cardiogenesis, resulting in heart defects. To test this hypothesis, we investigated the effects of extractable organic matter (EOM) from PM2.5 on AhR and Wnt/β-catenin signal pathways in zebrafish embryos. We confirmed that EOM could cause malformations in the heart and decreased heart rate in zebrafish embryos at 72hpf, and found that the EOM-induced heart defects were rescued in embryos co-exposed with EOM plus AhR antagonist CH223191 or β-catenin agonist CHIR99021. We further found that EOM had increased the expression levels of AhR targeted genes (Cyp1a1, Cyp1b1 and Ahrra) and reduced the mRNA levels of β-catenin targeted genes (axin2, nkx2.5 and sox9b). The mRNA expression level of Rspo2, a β-catenin upstream gene, was also decreased in embryos exposed to EOM. Supplementation with CH223191 or CHIR99021 attenuated most of the EOM-induced expression changes of genes involved in both AhR and wnt/β-catenin signal pathways. However, the mRNA expression level of AhR inhibitor Ahrrb, which did not change by EOM treatment alone, was increased in embryos co-exposed to EOM plus CH223191 or CHIR99021. We conclude that the activation of AhR by EOM from PM2.5 might repress wnt/β-catenin signaling, leading to heart defects in zebrafish embryos. Furthermore, our results indicate that the cardiac developmental toxicity of PM2.5 might be prevented by targeting AhR or wnt/β-catenin signaling. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Malassezia yeasts produce a collection of exceptionally potent activators of the Ah (dioxin) receptor detected in diseased human skin

PubMed Central

Magiatis, Prokopios; Pappas, Periklis; Gaitanis, George; Mexia, Nikitia; Melliou, Eleni; Galanou, Maria; Vlachos, Christophoros; Stathopoulou, Konstantina; Skaltsounis, Alexios Leandros; Marselos, Marios; Velegraki, Aristea; Denison, Michael S.; Bassukas, Ioannis D.

2013-01-01

Malassezia yeasts are commensal microorganisms which under insufficiently understood conditions can become pathogenic. We have previously shown that specific strains isolated from diseased human skin can preferentially produce agonists of the aryl hydrocarbon receptor (AhR), whose activation has been linked to certain skin diseases. Investigation of skin scale extracts from patients with Malassezia associated diseases demonstrated 10–1000 fold higher AhR activating capacity than control skin extracts. LC/MS/MS analysis of the patients’ extracts revealed the presence of indirubin, 6-formylindolo[3,2-b]carbazole (FICZ), indolo[3,2-b]carbazole (ICZ), malassezin, and pityriacitrin. The same compounds were also identified in 9/12 Malassezia species culture extracts tested, connecting their presence in skin scales with this yeast. Studying the activity of the Malassezia culture-extracts and pure metabolites in HaCaT cells by Reverse Transcriptase Real-Time PCR revealed significant alterations in mRNA levels of the endogenous AhR-responsive genes Cyp1A1, Cyp1B1 and AhRR. Indirubin and FICZ activated AhR in HaCaT and human HepG2 cells with significantly higher, yet transient, potency as compared to the prototypical AhR ligand, dioxin. In loco synthesis of these highly potent AhR inducers by Malassezia yeasts could have a significant impact on skin homeostatic mechanisms and disease development. PMID:23448877

AhR activation increases IL-2 production by alloreactive CD4+ T cells initiating the differentiation of mucosal-homing Tim3+ Lag3+ Tr1 cells.

PubMed

Ehrlich, Allison K; Pennington, Jamie M; Tilton, Susan; Wang, Xisheng; Marshall, Nikki B; Rohlman, Diana; Funatake, Castle; Punj, Sumit; O'Donnell, Edmond; Yu, Zhen; Kolluri, Siva K; Kerkvliet, Nancy I

2017-11-01

Activation of the aryl hydrocarbon receptor (AhR) by immunosuppressive ligands promotes the development of regulatory T (Treg) cells. Although AhR-induced Foxp3 + Treg cells have been well studied, much less is known about the development and fate of AhR-induced Type 1 Treg (AhR-Tr1) cells. In the current study, we identified the unique transcriptional and functional changes in murine CD4 + T cells that accompany the differentiation of AhR-Tr1 cells during the CD4 + T-cell-dependent phase of an allospecific cytotoxic T lymphocyte (allo-CTL) response. AhR activation increased the expression of genes involved in T-cell activation, immune regulation and chemotaxis, as well as a global downregulation of genes involved in cell cycling.  Increased IL-2 production was responsible for the early AhR-Tr1 activation phenotype previously characterized as CD25 + CTLA4 + GITR + on day 2. The AhR-Tr1 phenotype was further defined by the coexpression of the immunoregulatory receptors Lag3 and Tim3 and non-overlapping expression of CCR4 and CCR9. Consistent with the increased expression of CCR9, real-time imaging showed enhanced migration of AhR-Tr1 cells to the lamina propria of the small intestine and colon. The discovery of mucosal imprinting of AhR-Tr1 cells provides an additional mechanism by which therapeutic AhR ligands can control immunopathology. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The crystal structure of the AhRR-ARNT heterodimer reveals the structural basis of the repression of AhR-mediated transcription.

PubMed

Sakurai, Shunya; Shimizu, Toshiyuki; Ohto, Umeharu

2017-10-27

2,3,7,8-Tetrachlorodibenzo- p -dioxin and related compounds are extraordinarily potent environmental toxic pollutants. Most of the 2,3,7,8-tetrachlorodibenzo- p -dioxin toxicities are mediated by aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor belonging to the basic helix-loop-helix (bHLH) Per-ARNT-Sim (PAS) family. Upon ligand binding, AhR forms a heterodimer with AhR nuclear translocator (ARNT) and induces the expression of genes involved in various biological responses. One of the genes induced by AhR encodes AhR repressor (AhRR), which also forms a heterodimer with ARNT and represses the activation of AhR-dependent transcription. The control of AhR activation is critical for managing AhR-mediated diseases, but the mechanisms by which AhRR represses AhR activation remain poorly understood, because of the lack of structural information. Here, we determined the structure of the AhRR-ARNT heterodimer by X-ray crystallography, which revealed an asymmetric intertwined domain organization presenting structural features that are both conserved and distinct among bHLH-PAS family members. The structures of AhRR-ARNT and AhR-ARNT were similar in the bHLH-PAS-A region, whereas the PAS-B of ARNT in the AhRR-ARNT complex exhibited a different domain arrangement in this family reported so far. The structure clearly disclosed that AhRR competitively represses AhR binding to ARNT and target DNA and further suggested the existence of an AhRR-ARNT-specific repression mechanism. This study provides a structural basis for understanding the mechanism by which AhRR represses AhR-mediated gene transcription. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

The inhibition of lung cancer cell migration by AhR-regulated autophagy

PubMed Central

Tsai, Chi-Hao; Li, Ching-Hao; Cheng, Yu-Wen; Lee, Chen-Chen; Liao, Po-Lin; Lin, Cheng-Hui; Huang, Shih-Hsuan; Kang, Jaw-Jou

2017-01-01

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is highly expressed in multiple organs and tissues. Whereas AhR mediates the metabolism of xenobiotic and endogenous compounds, its novel function in cancer epithelial-mesenchymal transition (EMT) remains controversial. Autophagy also participates in tumour progression through its functions in cell homeostasis and facilitates adaptation to EMT progression. In the present study, we found that AhR-regulated autophagy positively modulates EMT in non-small cell lung cancer cells. The motility of A549, H1299, and CL1-5 cells were correlated with different AhR expression levels. Invasive potential and cell morphology also changed when AhR protein expression was altered. Moreover, AhR levels exerted a contrasting effect on autophagy potential. Autophagy was higher in CL1-5 and H1299 cells with lower AhR levels than in A549 cells. Both AhR overexpression and autophagy inhibition decreased CL1-5 metastasis in vivo. Furthermore, AhR promoted BNIP3 ubiquitination for proteasomal degradation. AhR silencing in A549 cells also reduced BNIP3 ubiquitination. Taken together, these results provide a novel insight into the cross-linking between AhR and autophagy, we addressed the mechanistic BNIP3 modulation by endogenous AhR, which affect cancer cell EMT progression. PMID:28195146

The inhibition of lung cancer cell migration by AhR-regulated autophagy.

PubMed

Tsai, Chi-Hao; Li, Ching-Hao; Cheng, Yu-Wen; Lee, Chen-Chen; Liao, Po-Lin; Lin, Cheng-Hui; Huang, Shih-Hsuan; Kang, Jaw-Jou

2017-02-14

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is highly expressed in multiple organs and tissues. Whereas AhR mediates the metabolism of xenobiotic and endogenous compounds, its novel function in cancer epithelial-mesenchymal transition (EMT) remains controversial. Autophagy also participates in tumour progression through its functions in cell homeostasis and facilitates adaptation to EMT progression. In the present study, we found that AhR-regulated autophagy positively modulates EMT in non-small cell lung cancer cells. The motility of A549, H1299, and CL1-5 cells were correlated with different AhR expression levels. Invasive potential and cell morphology also changed when AhR protein expression was altered. Moreover, AhR levels exerted a contrasting effect on autophagy potential. Autophagy was higher in CL1-5 and H1299 cells with lower AhR levels than in A549 cells. Both AhR overexpression and autophagy inhibition decreased CL1-5 metastasis in vivo. Furthermore, AhR promoted BNIP3 ubiquitination for proteasomal degradation. AhR silencing in A549 cells also reduced BNIP3 ubiquitination. Taken together, these results provide a novel insight into the cross-linking between AhR and autophagy, we addressed the mechanistic BNIP3 modulation by endogenous AhR, which affect cancer cell EMT progression.

TCDD promoted EMT of hFPECs via AhR, which involved the activation of EGFR/ERK signaling

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

Gao, Zhan; The Fifth Affiliated Hospital, Zhengzhou University, 450052; Bu, Yongjun

2016-05-01

One critical step of second palatal fusion is the newly formed medial epithelia seam (MES) disintegration, which involves apoptosis, epithelial to mesenchymal transition (EMT), and cell migration. Although the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) produces cleft palate at high rates, little is known about the effects of TCDD exposure on the fate of palatal epithelial cells. By using primary epithelial cells isolated from human fetal palatal shelves (hFPECs), we show that TCDD increased cell proliferation and EMT, as demonstrated by increased the epithelial markers (E-cadherin and cytokeratin14) and enhanced the mesenchymal markers (vimentin and fibronectin), but had no effect on cellmore » migration and apoptosis. TCDD exposure led to a dose-dependent increase in Slug protein expression. Coimmunoprecipitation revealed that TCDD promoted AhR to form a protein complex with Slug. ChIP assay confirmed that TCDD exposure recruited AhR to the xenobiotic responsive element of Slug promoter. Knockdown of AhR by siRNA remarkably weakened TCDD-induced binding of AhR to the XRE promoter of slug, thereby suppressed TCDD-induced vimentin. Further experiment showed that TCDD stimulated EGFR phosphorylation did not influence the TGFβ3/Smad signaling; whereas TCDD increased phosphorylation of ERK1/2 and p38 with no effect on activation of JNK. By using varieties of inhibitors, we confirmed that TCDD promoted proliferation and EMT of hFPECs via activation of EGFR/ERK pathway. These data make a novel contribution to the molecular mechanism of cleft palate by TCDD. - Highlights: • TCDD exposure promoted cell proliferation and EMT of hFPECs; • AhR signaling was activated and required for TCDD-induced EMT; • TCDD-mediated EMT of hFPECs involved the activation of EGFR/ERK signaling; • TCDD exposure had no effect on TGFβ3/Smad pathway.« less

Characterization of AhR agonists reveals antagonistic activity in European herring gull (Larus argentatus) eggs.

PubMed

Muusse, Martine; Christensen, Guttorm; Gomes, Tânia; Kočan, Anton; Langford, Katherine; Tollefsen, Knut Erik; Vaňková, Lenka; Thomas, Kevin V

2015-05-01

European herring gull (Larus argentatus) eggs from two Norwegian islands, Musvær in the south east and Reiaren in Northern Norway, were screened for dioxins, furans, and dioxin-like and selected non-dioxin-like polychlorinated biphenyls (PCBs), and subjected to non-target analysis to try to identify the aryl hydrocarbon receptor (AhR) agonists, responsible for elevated levels measured using the dioxin responsive chemically activated luciferase expression (DR-CALUX) assay. Eggs from Musvær contained chemically calculated toxic equivalent (WHO TEQ) levels of between 109 and 483 pg TEQ/g lw, and between 82 and 337 pg TEQ/g lw was determined in eggs from Reiaren. In particular PCB126 contributed highly to the total TEQ (69-82%). In 19 of the 23 samples the calculated WHO TEQ was higher than the TEQCALUX. Using CALUX specific relative effect potencies (REPs), the levels were lower at between 77 and 292 pg/g lw in eggs from Musvær and between 55 and 223 pg/g lw in eggs from Reiaren, which was higher than the TEQCALUX in 16 of the 23 samples. However, the means of the REP values and the TEQCALUX were not significantly different. This suggests the presence of compounds that can elicit antagonist effects, with a low binding affinity to the AhR. Non-target analysis identified the presence of hexachlorobenzene (HCB) (quantified at 9.6-185 pg/g lw) but neither this compound nor high concentrations of PCB126 and non-dioxin-like PCBs could explain the differences between the calculated TEQ or REP values and the TEQCALUX. Even though, for most AhR agonists, the sensitivity of herring gulls is not known, the reported levels can be considered to represent a risk for biological effects in the developing embryo, compared to LC50 values in chicken embryos. For human consumers of herring gull eggs, these eggs contain TEQ levels up to four times higher than the maximum tolerable weekly intake. Copyright © 2015 Elsevier B.V. All rights reserved.

Pregnane X receptor regulates the AhR/Cyp1A1 pathway and protects liver cells from benzo-[α]-pyrene-induced DNA damage.

PubMed

Cui, Hongmei; Gu, Xinsheng; Chen, Jingshu; Xie, Ying; Ke, Sui; Wu, Jing; Golovko, Andrei; Morpurgo, Benjamin; Yan, Chunhong; Phillips, Timothy D; Xie, Wen; Luo, Jianyuan; Zhou, Zhijun; Tian, Yanan

2017-06-05

Pregnane X receptor (PXR) plays an important role in protecting cells from mutagenic DNA damages induced by endogenous and exogenous toxicants. This protective function is often attributed to the PXR-regulated metabolic detoxification. Here we report a novel potential mechanism that PXR reduces benzo-[α]-pyrene(BaP)-induced DNA damage through inhibiting the transcriptional activity of aryl hydrocarbon receptor (AhR) which plays a pivotal role in the bioactivation of BaP. We have utilized three well-characterized cell lines, i.e. Hepa1c1c7, AhR +/+; Bpr lacks AhR obligatory partner ARNT; Tao, lacks AhR, to analyze pivotal role of AhR/ARNT complex in mediating the BaP-induced DNA damages using comet assay (single-cell gel electrophoresis). We found that PXR activation could significantly inhibit BaP-induced DNA damage in the HepG2 cells as well as mouse hepatocytes. Using PXR-null and wild type mouse hepatocytes we showed that PXR activation by pregnenolone 16α-carbonitrile (PCN) significantly inhibited BaP-induced DNA damage and this protective effect was abolished in PXR-null hepatocytes. Mechanistically, PXR activation inhibited expression of AhR-target genes for CYP1A1, CYP1B1 and CYP1A2 that are required for BaP biotransformation in cultured liver cells, or in the livers of C57BL/6J mice. Using an AhR-responsive reporter assay as well as chromatin immunoprecipitation assay we found that PXR activation transcriptionally represses AhR-regulated gene expression. Furthermore, we found that PXR directly bound AhR at its DNA-binding domain, and this association may play a role in preventing of the AhR from binding to its target genes as shown in the ChIP assay. Taken together, our study has revealed a novel mechanism by which PXR protects liver cells from BaP-induced DNA damage through inhibiting the BaP biotransformation. Copyright © 2017 Elsevier B.V. All rights reserved.

Ligand-dependent interactions of the Ah receptor with coactivators in a mammalian two-hybrid assay

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

Zhang Shu; Rowlands, Craig; Safe, Stephen

2008-03-01

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a high affinity ligand for the aryl hydrocarbon receptor (AhR). In this study, we investigated structure-dependent differences in activation of the AhR by a series of halogenated aromatic hydrocarbons. TCDD, 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and 3,3',4,4',5-pentachlorobiphenyl (PCB126) induced CYP1A1-dependent activities in HEK293 human embryonic kidney, Panc1 pancreatic cancer, and Hepa1c1c7 mouse hepatoma cell lines. There was a structure-dependent difference in the efficacy of TCDF and PCB126 in HEK293 and Panc1 cells since induced CYP1A1 mRNA levels were lower than observed for the other congeners. A mammalian two-hybrid assay in cells transfected with GAL4-coactivator and AhR-VP16more » chimeras was used to investigate structure-dependent interactions of these chimeras in Panc1, HEK293, and Hepa1c1c7 cells. The reporter construct pGAL4-luc contains five tandem GAL4 response elements linked to the luciferase gene and the GAL4-coactivator chimeras express several coactivators including steroid receptor coactivator 1 (SRC-1), SRC-2 and SRC-3, the mediator coactivator TRAP220, coactivator associated arginine methyl transferase 1 (CARM-1), and peroxisome proliferator-activated receptor {gamma} coactivator 1 (PGC-1). Results of the mammalian two-hybrid studies clearly demonstrate that activation of pGAL4-luc in cells transfected with VP-AhR and GAL4-coactivator chimeras is dependent on the structure of the HAH congener, cell context, and coactivator, suggesting that the prototypical HAH congeners used in this study exhibit selective AhR modulator activity.« less

Malassezia yeasts produce a collection of exceptionally potent activators of the Ah (dioxin) receptor detected in diseased human skin.

PubMed

Magiatis, Prokopios; Pappas, Periklis; Gaitanis, George; Mexia, Nikitia; Melliou, Eleni; Galanou, Maria; Vlachos, Christophoros; Stathopoulou, Konstantina; Skaltsounis, Alexios Leandros; Marselos, Marios; Velegraki, Aristea; Denison, Michael S; Bassukas, Ioannis D

2013-08-01

Malassezia yeasts are commensal microorganisms, which under insufficiently understood conditions can become pathogenic. We have previously shown that specific strains isolated from diseased human skin can preferentially produce agonists of the aryl hydrocarbon receptor (AhR), whose activation has been linked to certain skin diseases. Investigation of skin scale extracts from patients with Malassezia-associated diseases demonstrated 10- to 1,000-fold higher AhR-activating capacity than control skin extracts. Liquid chromatography-tandem mass spectrometry analysis of the patients' extracts revealed the presence of indirubin, 6-formylindolo[3,2-b]carbazole (FICZ), indolo[3,2-b]carbazole (ICZ), malassezin, and pityriacitrin. The same compounds were also identified in 9 out of 12 Malassezia species culture extracts tested, connecting their presence in skin scales with this yeast. Studying the activity of the Malassezia culture extracts and pure metabolites in HaCaT cells by reverse transcriptase real-time PCR revealed significant alterations in mRNA levels of the endogenous AhR-responsive genes Cyp1A1, Cyp1B1, and AhRR. Indirubin- and FICZ-activated AhR in HaCaT and human HepG2 cells with significantly higher, yet transient, potency as compared with the prototypical AhR ligand, dioxin. In loco synthesis of these highly potent AhR inducers by Malassezia yeasts could have a significant impact on skin homeostatic mechanisms and disease development.

Benzo[ghi]perylene activates the AHR pathway to exert biological effects on the NL-20 human bronchial cell line.

PubMed

Zaragoza-Ojeda, Montserrat; Eguía-Aguilar, Pilar; Perezpeña-Díazconti, Mario; Arenas-Huertero, Francisco

2016-08-10

Polycyclic aromatic hydrocarbons (PAH) are produced by incomplete combustion of organic material. In the Mexico City atmosphere, the most abundant PAH is benzo[ghi]perylene (BghiP), a gasoline combustion marker. At present, there are no reports of the effects of BghiP on human bronchial cells, so the aim of the study was to evaluate the effects in vitro of BghiP on the NL-20 cell line. Results showed that BghiP induced the formation of small vesicles throughout the cytoplasm, with absence of nuclear fragmentation. At 48h exposition, damage in cell membrane increased significantly at 1.24μg/mL of BghiP (p<0.05). Immunocytochemistry revealed that BghiP provokes nuclear translocation of AhR receptor, which indicates that this compound can induce transcription of genes via receptor binding (AhR pathway activation). BghiP induced a two-fold increase (p<0.05) in the expression of AhR and CYP4B1 (a lung-specific pathway effector). In the presence of the receptor antagonist CH-223191, the loss of viability, the nuclear translocation and the overexpression of genes decreased, though this did not prevent the formation of vesicles. BghiP induced oxidative stress and in presence of the receptor antagonist this increased significantly. In conclusion, BghiP can activate the overexpression of AhR and CYP4B1, and the effects are abated by the AhR receptor antagonist. This is the first report to prove that BghiP utilizes the AhR pathway to exert its toxic effects on the NL-20 human bronchial cell line . Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Role of Sequence Variations in AhR Gene Towards Modulating Smoking Induced Lung Cancer Susceptibility in North Indian Population: A Multiple Interaction Analysis.

PubMed

Budhwar, Sneha; Bahl, Charu; Sharma, Siddharth; Singh, Navneet; Behera, Digambar

2018-05-01

AhR, a ubiquitously expressed ligand-activated transcription factor, upon its encounter with the foreign ligands activates the transcriptional machinery of genes encoding for bio-transformation enzymes like CYP1A1 hence, mediating the metabolism of Poly aromatic hydrocarbons and nitrosamines which account for the maximally found carcinogen in cigarette smoke. Polymorphic variants of AhR play a significant role and are held responsible for disposing the individuals with greater chances of acquiring lung cancer. To study the role of AhR variants (rs2282885, rs10250822, rs7811989, rs2066853) in affect-ing lung cancer susceptibility. 297 cases and 320 controls have been genotyped using PCR-RFLP technique. In order to find out the association, unconditional logistic regression approach was used. To analyze high order in-teractions Multifactor Dimensionality Reduction and Classification and regression tree was used. Subjects carrying the variant genotype for AhR rs7811989 showed a two-fold risk (p=0.007) and a marginal risk was also seen in case of individuals carrying either single or double copy of suscep-tible allele for rs102550822 (p=0.02). Whereas the variant allele for rs2066853 showcased a strong pro-tective effect (p=0.003). SQCC individuals with mutant genotype of rs2066853 also exhibited a protec-tive effect towards lung cancer (OR=0.30, p=0.0013). The association of rs7811989 mutant genotype and rs10250822 mutant genotype was evident especially in smokers as compared to non-smokers. AhR rs2066853 showed a decreased risk in smokers with mutant genotype (p=0.002). MDR approach gave the best interaction model of AhR rs2066853 and smoking (CVC=10/10, prediction error=0.42). AhR polymorphic variations can significantly contribute towards lung cancer predisposi-tion.

A human intervention study with foods containing natural Ah-receptor agonists does not significantly show AhR-mediated effects as measured in blood cells and urine.

PubMed

de Waard, Pim W J; Peijnenburg, Ad A C M; Baykus, Hakan; Aarts, Jac M M J G; Hoogenboom, Ron L A P; van Schooten, Frederik J; de Kok, Theo M C M

2008-10-22

Binding and activation of the aryl hydrocarbon receptor (AhR) is thought to be an essential step in the toxicity of the environmental pollutants dioxins and dioxin-like PCBs. However, also a number of natural compounds, referred to as NAhRAs (natural Ah-receptor agonists), which are present in, for example, fruits and vegetables, can bind and activate this receptor. To study their potential effects in humans, we first investigated the effect of the prototypical AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on gene expression in ex vivo exposed freshly isolated human lymphocytes, and compared the resulting gene expression profile with those caused by the well-known NAhRA indolo[3,2-b]carbazole (ICZ), originating from cruciferous vegetables, and by a hexane extract of NAhRA-containing grapefruit juice (GJE). Only ICZ induced a gene expression profile similar to TCDD in the lymphocytes, and both significantly up-regulated CYP1B1 and TIPARP (TCDD-inducible poly (ADP-ribose) polymerase) mRNA. Next, we performed a human intervention study with NAhRA-containing cruciferous vegetables and grapefruit juice. The expression of the prototypical AhR-responsive genes CYP1A1, CYP1B1 and NQO1 in whole blood cells and in freshly isolated lymphocytes was not significantly affected. Also enzyme activities of CYP1A2, CYP2A6, N-acetyltransferase 2 (NAT2) and xanthine oxidase (XO), as judged by caffeine metabolites in urine, were unaffected, except for a small down-regulation of NAT2 activity by grapefruit juice. Examination of blood plasma with DR CALUX showed a 12% increased AhR agonist activity 3 and 24 h after consumption of cruciferous vegetables, but did not show a significant effect of grapefruit juice consumption. We conclude that intake of NAhRAs from food may result in minor AhR-related effects measurable in human blood and urine.

Red Clover Aryl Hydrocarbon Receptor (AhR) and Estrogen Receptor (ER) Agonists Enhance Genotoxic Estrogen Metabolism

PubMed Central

2017-01-01

Many women consider botanical dietary supplements (BDSs) as safe alternatives to hormone therapy for menopausal symptoms. However, the effect of BDSs on breast cancer risk is largely unknown. In the estrogen chemical carcinogenesis pathway, P450 1B1 metabolizes estrogens to 4-hydroxylated catechols, which are oxidized to genotoxic quinones that initiate and promote breast cancer. In contrast, P450 1A1 catalyzed 2-hydroxylation represents a detoxification pathway. The current study evaluated the effects of red clover, a popular BDS used for women’s health, and its isoflavones, biochanin A (BA), formononetin (FN), genistein (GN), and daidzein (DZ), on estrogen metabolism. The methoxy estrogen metabolites (2-MeOE1, 4-MeOE1) were measured by LC-MS/MS, and CYP1A1 and CYP1B1 gene expression was analyzed by qPCR. Nonmalignant ER-negative breast epithelial cells (MCF-10A) and ER-positive breast cancer cells (MCF-7) were derived from normal breast epithelial tissue and ER+ breast cancer tissue. Red clover extract (RCE, 10 μg/mL) and isoflavones had no effect on estrogen metabolism in MCF-10A cells. However, in MCF-7 cells, RCE treatments downregulated CYP1A1 expression and enhanced genotoxic metabolism (4-MeOE1/CYP1B1 > 2-MeOE1/CYP1A1). Experiments with the isoflavones showed that the AhR agonists (BA, FN) preferentially induced CYP1B1 expression as well as 4-MeOE1. In contrast, the ER agonists (GN, DZ) downregulated CYP1A1 expression likely through an epigenetic mechanism. Finally, the ER antagonist ICI 182,780 potentiated isoflavone-induced XRE-luciferase reporter activity and reversed GN and DZ induced downregulation of CYP1A1 expression. Overall, these studies show that red clover and its isoflavones have differential effects on estrogen metabolism in “normal” vs breast cancer cells. In breast cancer cells, the AhR agonists stimulate genotoxic metabolism, and the ER agonists downregulate the detoxification pathway. These data may suggest that especially breast

Ultraviolet B inhibition of DNMT1 activity via AhR activation dependent SIRT1 suppression in CD4+ T cells from systemic lupus erythematosus patients.

PubMed

Wu, Zhouwei; Mei, Xingyu; Ying, Zuolin; Sun, Yue; Song, Jun; Shi, Weimin

2017-06-01

Previous studies have reported that ultraviolet B (UVB) inhibits DNA methyltransferase1 (DNMT1) activity in CD4+ T cells from systemic lupus erythematosus (SLE) patients. Silent mating type information regulation 2 homolog 1 (SIRT1) is a type of Class III histone deacetylases (HDACs), and has been reported to play roles in the pathogenesis of different autoimmune diseases and can modulate DNMT1 activity. Moreover, aryl hydrocarbon receptor (AhR) has been reported to link UVB with SLE. However, the exact mechanisms by which DNMT1 activity is inhibited by UVB in lupus CD4+ T cells remain largely unknown. To elucidate the exact mechanisms by which DNMT1 activity is inhibited by UVB in lupus CD4+ T cells. Twenty-two newly diagnosed active SLE patients and 30 healthy controls were enrolled in the study. CD4+ T cells were isolated, cultured and treated. DNMT1 activity assay, quantitative real-time PCR (qRT-PCR), Western blotting, RNA interference using small interfering RNA and Chromatin Immunoprecipitation (ChIP) assay were employed. DNMT1 activity was inhibited in si-SIRT1-transfected CD4+ T cells, and increased by the established SIRT1 activator, SRT1720. Moreover, the mRNA and protein expression of SIRT1 were suppressed by UVB exposure in lupus CD4+ T cells. UVB-inhibited DNMT1 activity was reversed by SRT1720 in si-control-transfected lupus CD4+ T cells, but not in si-SIRT1-transfected lupus CD4 + T cells. Furthermore, AhR activation by VAF347 reduced the mRNA and protein expression of SIRT1. ChIP using an antibody against AhR in normal CD4+ T cells revealed a 16-fold stronger signal at the site about 1.6kb upstream from the translation start site of the SIRT1 promoter. Finally, UVB could activate AhR and inhibit the mRNA and protein expression of SIRT1. AhR knockdown abrogated the inhibition of UVB-mediated SIRT1 mRNA and protein expression and DNMT1 activity in lupus CD4+ T cells. UVB suppressed SIRT1 expression via activating AhR, and subsequently inhibited DNMT1

Examination of Zolpidem effects on AhR- and PXR-dependent expression of drug-metabolizing cytochromes P450 in primary cultures of human hepatocytes.

PubMed

Bachleda, Petr; Vrzal, Radim; Pivnicka, Jakub; Cvek, Boris; Dvorak, Zdenek

2009-12-01

A hypnotic drug Zolpidem is used in clinical practice for more than 25 years. Surprisingly, the effects of Zolpidem on the expression of drug-metabolizing cytochromes P450 (CYPs) were not examined yet. Recently, the unexpected capacity of several "old drugs", such as valproic acid or azoles, to induce CYPs was reported. Therefore, we tested whether Zolpidem induces the expression of important CYPs in primary cultures of human hepatocytes. Cells were treated for 24h with Zolpidem in therapeutic (0.1mg/L) and toxic (1mg/L) concentrations. The levels of CYP1A1, CYP1A2, CY2C9 and CYP3A4 mRNAs were not altered by Zolpidem, whereas model inducers dioxin and rifampicin significantly induced CYP1A and CYP2/3 gene expression, respectively. Consistently, Zolpidem did not activate aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR), the key regulators of cytochromes P450s, as revealed by transient transfection gene reporter assays using HepG2 cells. We conclude Zolpidem be considered a safe drug with respect to the possible interactions through AhR- and PXR-dependent induction of drug-metabolizing CYPs.

Dihydromethysticin (DHM) Blocks Tobacco Carcinogen 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-Induced O6-Methylguanine in a Manner Independent of the Aryl Hydrocarbon Receptor (AhR) Pathway in C57BL/6 Female Mice.

PubMed

Narayanapillai, Sreekanth C; Lin, Shang-Hsuan; Leitzman, Pablo; Upadhyaya, Pramod; Baglole, Carolyn J; Xing, Chengguo

2016-11-21

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a key carcinogen responsible for tobacco smoke-induced lung carcinogenesis. Among the types of DNA damage caused by NNK and its metabolite, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), O 6 -methylguanine (O 6 -mG) is likely the most carcinogen in A/J mice. Results of our previous studies showed that levels of O 6 -mG and other types of NNAL-derived DNA damage were preferentially reduced in the lung of female A/J mice upon dietary treatment with dihydromethysticin (DHM), a promising lung cancer chemopreventive agent from kava. Such a differential blockage may be mediated via an increased level of NNAL glucuronidation, thereby leading to its detoxification. The potential of the aryl hydrocarbon receptor (AhR) as an upstream target of DHM mediating these events was evaluated herein using Ahr +/- and Ahr -/- C57BL/6 female mice because DHM was reported as an AhR agonist. DHM (0.05, 0.2, and 1.0 mg/g of diet) and dihydrokavain (DHK, an inactive analogue, 1.0 mg/g of diet) were given to mice for 7 days, followed by a single intraperitoneal dose of NNK at 100 mg/kg of body weight. The effects of DHM on the amount of O 6 -mG in the lung, on the urinary ratio of glucuronidated NNAL (NNAL-Gluc) and free NNAL, and on CYP1A1/2 activity in the liver microsomes were analyzed. As observed in A/J mice, DHM treatment significantly and dose-dependently reduced the level of O 6 -mG in the target lung tissue, but there were no significant differences in O 6 -mG reduction between mice from Ahr +/- and Ahr -/- backgrounds. Similarly, in both strains, DHM at 1 mg/g of diet significantly increased the urinary ratio of NNAL-Gluc to free NNAL and CYP1A1/2 enzymatic activity in liver with no changes detected at lower DHM dosages. Because none of these effects of DHM were dependent on Ahr status, AhR clearly is not the upstream target for DHM.

A constitutively active dioxin/aryl hydrocarbon receptor induces stomach tumors

NASA Astrophysics Data System (ADS)

Andersson, Patrik; McGuire, Jacqueline; Rubio, Carlos; Gradin, Katarina; Whitelaw, Murray L.; Pettersson, Sven; Hanberg, Annika; Poellinger, Lorenz

2002-07-01

The dioxin/aryl hydrocarbon receptor (AhR) functions as a ligand-activated transcription factor regulating transcription of a battery of genes encoding xenobiotic metabolizing enzymes. Known receptor ligands are environmental pollutants including polycyclic aromatic hydrocarbons and polychlorinated dioxins. Loss-of-function (gene-disruption) studies in mice have demonstrated that the AhR is involved in toxic effects of dioxins but have not yielded unequivocal results concerning the physiological function of the receptor. Gain-of-function studies therefore were performed to unravel the biological functions of the AhR. A constitutively active AhR expressed in transgenic mice reduced the life span of the mice and induced tumors in the glandular part of the stomach, demonstrating the oncogenic potential of the AhR and implicating the receptor in regulation of cell proliferation.

Plant polyphenols differentially modulate inflammatory responses of human keratinocytes by interfering with activation of transcription factors NF{kappa}B and AhR and EGFR-ERK pathway

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

Potapovich, Alla I.; Biology Department, Belarus State University, Skorina Prosp. 10, Minsk 220050; Lulli, Daniela

Molecular mechanisms underlying modulation of inflammatory responses in primary human keratinocytes by plant polyphenols (PPs), namely the glycosylated phenylpropanoid verbascoside, the stilbenoid resveratrol and its glycoside polydatin, and the flavonoid quercetin and its glycoside rutin were evaluated. As non-lethal stimuli, the prototypic ligand for epidermal growth factor receptor (EGFR) transforming growth factor alpha (TGFalpha), the combination of tumor necrosis factor (TNFalpha) and interferon (IFNgamma) (T/I), UVA + UVB irradiation, and bacterial lipopolysaccharide (LPS) were used. We demonstrated differential modulation of inflammatory responses in keratinocytes at signal transduction, gene transcription, and protein synthesis levels as a function of PP chemical structure,more » the pro-inflammatory trigger used, and PP interaction with intracellular detoxifying systems. The PPs remarkably inhibited constitutive, LPS- and T/I-induced but not TGFalpha-induced ERK phosphorylation. They also suppressed NFkappaB activation by LPS and T/I. Verbascoside and quercetin invariably impaired EGFR phosphorylation and UV-associated aryl hydrocarbon receptor (AhR)-mediated signaling, while rutin, polydatin and resveratrol did not affect EGFR phosphorylation and further activated AhR machinery in UV-exposed keratinocytes. In general, PPs down-regulated gene expression of pro-inflammatory cytokines/enzymes, except significant up-regulation of IL-8 observed under stimulation with TGFalpha. Both spontaneous and T/I-induced release of IL-8 and IP-10 was suppressed, although 50 {mu}M resveratrol and polydatin up-regulated IL-8. At this concentration, resveratrol activated both gene expression and de novo synthesis of IL-8 and AhR-mediated mechanisms were involved. We conclude that PPs differentially modulate the inflammatory response of human keratinocytes through distinct signal transduction pathways, including AhR and EGFR. - Graphical abstract: Display Omitted

AhR-deficiency as a cause of demyelinating disease and inflammation.

PubMed

Juricek, Ludmila; Carcaud, Julie; Pelhaitre, Alice; Riday, Thorfinn T; Chevallier, Aline; Lanzini, Justine; Auzeil, Nicolas; Laprévote, Olivier; Dumont, Florent; Jacques, Sebastien; Letourneur, Frank; Massaad, Charbel; Agulhon, Cendra; Barouki, Robert; Beraneck, Mathieu; Coumoul, Xavier

2017-08-29

The Aryl hydrocarbon Receptor(AhR) is among the most important receptors which bind pollutants; however it also regulates signaling pathways independently of such exposure. We previously demonstrated that AhR is expressed during development of the central nervous system(CNS) and that its deletion leads to the occurrence of a congenital nystagmus. Objectives of the present study are to decipher the origin of these deficits, and to identify the role of the AhR in the development of the CNS. We show that the AhR-knockout phenotype develops during early infancy together with deficits in visual-information-processing which are associated with an altered optic nerve myelin sheath, which exhibits modifications in its lipid composition and in the expression of myelin-associated-glycoprotein(MAG), a cell adhesion molecule involved in myelin-maintenance and glia-axon interaction. In addition, we show that the expression of pro-inflammatory cytokines is increased in the impaired optic nerve and confirm that inflammation is causally related with an AhR-dependent decreased expression of MAG. Overall, our findings demonstrate the role of the AhR as a physiological regulator of myelination and inflammatory processes in the developing CNS. It identifies a mechanism by which environmental pollutants might influence CNS myelination and suggest AhR as a relevant drug target for demyelinating diseases.

High AHR expression in breast tumors correlates with expression of genes from several signaling pathways namely inflammation and endogenous tryptophan metabolism

PubMed Central

Castagnet, Patrice; Chemlali, Walid; Lallemand, François; Meseure, Didier; Pocard, Marc; Bieche, Ivan; Perrot-Applanat, Martine

2018-01-01

Increasing epidemiological and animal experimental data provide substantial support for the role of aryl hydrocarbon receptor (AhR) in mammary tumorigenesis. The effects of AhR have been clearly demonstrated in rodent models of breast carcinogenesis and in several established human breast cancer cell lines following exposure to AhR ligands or AhR overexpression. However, relatively little is known about the role of AhR in human breast cancers. AhR has always been considered to be a regulator of toxic and carcinogenic responses to environmental contaminants such as TCDD (dioxin) and benzo[a]pyrene (BaP). The aim of this study was to identify the type of breast tumors (ERα-positive or ERα-negative) that express AHR and how AhR affects human tumorigenesis. The levels of AHR, AHR nuclear translocator (ARNT) and AHR repressor (AHRR) mRNA expression were analyzed in a cohort of 439 breast tumors, demonstrating a weak association between high AHR expression and age greater than fifty years and ERα-negative status, and HR-/ERBB2 breast cancer subtypes. AHRR mRNA expression was associated with metastasis-free survival, while AHR mRNA expression was not. Immunohistochemistry revealed the presence of AhR protein in both tumor cells (nucleus and/or cytoplasm) and the tumor microenvironment (including endothelial cells and lymphocytes). High AHR expression was correlated with high expression of several genes involved in signaling pathways related to inflammation (IL1B, IL6, TNF, IL8 and CXCR4), metabolism (IDO1 and TDO2 from the kynurenine pathway), invasion (MMP1, MMP2 and PLAU), and IGF signaling (IGF2R, IGF1R and TGFB1). Two well-known ligands for AHR (TCDD and BaP) induced mRNA expression of IL1B and IL6 in an ERα-negative breast tumor cell line. The breast cancer ER status likely influences AhR activity involved in these signaling pathways. The mechanisms involved in AhR activation and target gene expression in breast cancers are also discussed. PMID:29320557

High AHR expression in breast tumors correlates with expression of genes from several signaling pathways namely inflammation and endogenous tryptophan metabolism.

PubMed

Vacher, Sophie; Castagnet, Patrice; Chemlali, Walid; Lallemand, François; Meseure, Didier; Pocard, Marc; Bieche, Ivan; Perrot-Applanat, Martine

2018-01-01

Increasing epidemiological and animal experimental data provide substantial support for the role of aryl hydrocarbon receptor (AhR) in mammary tumorigenesis. The effects of AhR have been clearly demonstrated in rodent models of breast carcinogenesis and in several established human breast cancer cell lines following exposure to AhR ligands or AhR overexpression. However, relatively little is known about the role of AhR in human breast cancers. AhR has always been considered to be a regulator of toxic and carcinogenic responses to environmental contaminants such as TCDD (dioxin) and benzo[a]pyrene (BaP). The aim of this study was to identify the type of breast tumors (ERα-positive or ERα-negative) that express AHR and how AhR affects human tumorigenesis. The levels of AHR, AHR nuclear translocator (ARNT) and AHR repressor (AHRR) mRNA expression were analyzed in a cohort of 439 breast tumors, demonstrating a weak association between high AHR expression and age greater than fifty years and ERα-negative status, and HR-/ERBB2 breast cancer subtypes. AHRR mRNA expression was associated with metastasis-free survival, while AHR mRNA expression was not. Immunohistochemistry revealed the presence of AhR protein in both tumor cells (nucleus and/or cytoplasm) and the tumor microenvironment (including endothelial cells and lymphocytes). High AHR expression was correlated with high expression of several genes involved in signaling pathways related to inflammation (IL1B, IL6, TNF, IL8 and CXCR4), metabolism (IDO1 and TDO2 from the kynurenine pathway), invasion (MMP1, MMP2 and PLAU), and IGF signaling (IGF2R, IGF1R and TGFB1). Two well-known ligands for AHR (TCDD and BaP) induced mRNA expression of IL1B and IL6 in an ERα-negative breast tumor cell line. The breast cancer ER status likely influences AhR activity involved in these signaling pathways. The mechanisms involved in AhR activation and target gene expression in breast cancers are also discussed.

Dysregulation of Notch and ERα signaling in AhR−/− male mice

PubMed Central

Huang, Bo; Butler, Ryan; Miao, Yifei; Dai, Yubing; Wu, Wanfu; Su, Wen; Fujii-Kuriyama, Yoshiaki; Warner, Margaret; Gustafsson, Jan-Åke

2016-01-01

The aryl hydrocarbon receptor (AhR) is now recognized as an important physiological regulator in the immune and reproductive systems, and in the development of the liver and vascular system. AhR regulates cell cycle, cell proliferation, and differentiation through interacting with other signaling pathways, like estrogen receptor α (ERα), androgen receptor (AR), and Notch signaling. In the present study, we investigated Notch and estrogen signaling in AhR−/− mice. We found low fertility with degenerative changes in the testes, germ cell apoptosis, and a reduced number of early spermatids. There was no change in aromatase, AR, ERα, or ERβ expression in the testis and no detectable change in serum estrogen levels. However, expression of Notch receptors (Notch1 and Notch3) and their target Hairy and Enhancer of Split homolog 1 (HES1) was reduced. In addition, the testosterone level was slightly reduced in the serum. In the mammary fat pad, AhR appeared to regulate estrogen signaling because, in AhR−/− males, there was significant growth of the mammary ducts with high expression of ERα in the ductal epithelium. The enhanced mammary ductal growth appears to be related to overexpression of ERα accompanied by a high proliferation index, whereas the reduced fertility appears to be related defects in Notch signaling that leads to reduced expression of HES1 and, consequently, early maturation of spermatocytes and a depletion of primary spermatids. Previous reports have indicated that AhR pathway is associated with infertility in men. Our results provide a mechanistic explanation for this defect. PMID:27688768

Polychlorinated biphenyls (PCBs) contamination and aryl hydrocarbon receptor (AhR) agonist activity of Omega-3 polyunsaturated fatty acid supplements: implications for daily intake of dioxins and PCBs.

PubMed

Bourdon, J A; Bazinet, T M; Arnason, T T; Kimpe, L E; Blais, J M; White, P A

2010-11-01

Omega-3 polyunsaturated fatty acid (n-3 PUFA) rich oils derived primarily from fish are frequently consumed as supplements. Due to the tendency of persistent organic pollutants (POPs) to accumulate in exposed organisms, n-3 PUFA supplements can contain sufficient POPs to present a risk to consumers. Here we investigated PCB concentrations and aryl hydrocarbon receptor (AhR) agonist activity in 17 n-3 PUFA supplements available in Canada. PCBs ranged from <0.8 to 793 ng g(-1) oil, with salmon- and seal-derived products yielding the highest values. AhR agonist activity from a reporter gene assay ranged from 1.3 to 72.2 pg TEQ g(-1) oil, with salmon and tuna yielding the highest values. When consumed at the recommended doses and as a supplement to the average Canadian diet, seal-derived oil can contribute to exceedance of the tolerable daily intake of 20 ng PCBs kg-BW(-1)day(-1), and salmon-, tuna-, and sea herring-derived oils can contribute to exceedance of the tolerable daily intake limit of 2.3 pg TEQ kg-BW(-1)day(-1). The beneficial properties of fish and n-3 PUFA supplements, and the results of this study suggest that it is prudent to consume supplements derived from small, cold-water fatty fish. Further research will be necessary to draw firm conclusions. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

AhR ligands, malassezin, and indolo[3,2-b]carbazole are selectively produced by Malassezia furfur strains isolated from seborrheic dermatitis.

PubMed

Gaitanis, George; Magiatis, Prokopios; Stathopoulou, Konstantina; Bassukas, Ioannis D; Alexopoulos, Evangelos C; Velegraki, Aristea; Skaltsounis, Alexios-Leandros

2008-07-01

Malassezia yeasts are connected with seborrheic dermatitis (SD) whereas M. furfur pathogenicity is associated with the production of bioactive indoles. In this study, the production of indoles by M. furfur isolates from healthy and diseased skin was compared, the respective HPLC patterns were analyzed, and substances that are preferentially synthesized by strains isolated from SD lesions were isolated and characterized. Malassezin, pityriacitrin, indole-3-carbaldehyde, and indolo[3,2-b]carbazole (ICZ) were isolated by HPLC from extracts of M. furfur grown in L-tryptophan agar, and identified by nuclear magnetic resonance and mass spectroscopy. Of these, ICZ, a potent ligand of the aryl hydrocarbon receptor (AhR), is described for the first time to our knowledge as a M. furfur metabolite. HPLC-photodiode array detection analysis of strain extracts from 7 healthy subjects and 10 SD patients showed that M. furfur isolates from only SD patients consistently produce malassezin and ICZ. This discriminatory production of AhR agonists provides initial evidence for a previously unreported mechanism triggering development of SD and indicates that the variable pathogenicity patterns recorded for M. furfur-associated SD conditions may be attributed to selective production (P<0.001) of measurable bioactive indoles.

Norisoboldine, a natural AhR agonist, promotes Treg differentiation and attenuates colitis via targeting glycolysis and subsequent NAD+/SIRT1/SUV39H1/H3K9me3 signaling pathway.

PubMed

Lv, Qi; Wang, Kai; Qiao, Simiao; Yang, Ling; Xin, Yirong; Dai, Yue; Wei, Zhifeng

2018-02-15

Norisoboldine (NOR), a natural aryl hydrocarbon receptor (AhR) agonist, has been demonstrated to attenuate ulcerative colitis (UC) and induce the generation of Treg cells. Under UC condition, hypoxia widely exists in colonic mucosa, and secondary changes of microRNAs (miRs) expressions and glycolysis contribute to Treg differentiation. At present, we worked for exploring the deep mechanisms for NOR-promoted Treg differentiation in hypoxia and its subsequent anti-UC action from the angle of AhR/miR or AhR/glycolysis axis. Results showed that NOR promoted Treg differentiation in hypoxia and the effect was stronger relative to normoxia. It activated AhR in CD4 + T cells under hypoxic microenvironment; CH223191 (a specific AhR antagonist) and siAhR-3 abolished NOR-promoted Treg differentiation. Furthermore, the progress of glycolysis, levels of Glut1 and HK2, and expression of miR-31 rather than miR-219 and miR-490 in CD4 + T cells were downregulated by NOR treatment under hypoxic microenvironment. However, HK2 plasmid but not miR-31 mimic significantly interfered NOR-enhanced Treg polarization. In addition, NOR reduced NAD + and SIRT1 levels, facilitated the ubiquitin-proteasomal degradation of SUV39H1 protein, and inhibited the enrichment of H3K9me3 at -1, 201 to -1,500 region of Foxp3 promoter in CD4 + T cells under hypoxic microenvironment, which was weakened by HK2 plasmid, CH223191, and siAhR-3. Finally, the correlation between NOR-mediated activation of AhR, repression of glycolysis, regulation of NAD + /SIRT1/SUV39H1/H3K9me3 signals, induction of Treg cells, and remission of colitis was confirmed in mice with DSS-induced colitis by using CH223191 and HK2 plasmid. In conclusion, NOR promoted Treg differentiation and then alleviated the development of colitis by regulating AhR/glycolysis axis and subsequent NAD + /SIRT1/SUV39H1/H3K9me3 signaling pathway.

Assessment of energetic costs of AhR activation by β-naphthoflavone in rainbow trout (Oncorhynchus mykiss) hepatocytes using metabolic flux analysis

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

Nault, Rance, E-mail: naultran@msu.edu; Abdul-Fattah, Hiba; Mironov, Gleb G.

2013-08-15

Exposure to environmental contaminants such as activators of the aryl hydrocarbon receptor (AhR) leads to the induction of defense and detoxification mechanisms. While these mechanisms allow organisms to metabolize and excrete at least some of these environmental contaminants, it has been proposed that these mechanisms lead to significant energetic challenges. This study tests the hypothesis that activation of the AhR by the model agonist β-naphthoflavone (βNF) results in increased energetic costs in rainbow trout (Oncorhynchus mykiss) hepatocytes. To address this hypothesis, we employed traditional biochemical approaches to examine energy allocation and metabolism including the adenylate energy charge (AEC), protein synthesismore » rates, Na{sup +}/K{sup +}-ATPase activity, and enzyme activities. Moreover, we have used for the first time in a fish cell preparation, metabolic flux analysis (MFA) an in silico approach for the estimation of intracellular metabolic fluxes. Exposure of trout hepatocytes to 1 μM βNF for 48 h did not alter hepatocyte AEC, protein synthesis, or Na{sup +}/K{sup +}-ATPase activity but did lead to sparing of glycogen reserves and changes in activities of alanine aminotransferase and citrate synthase suggesting altered metabolism. Conversely, MFA did not identify altered metabolic fluxes, although we do show that the dynamic metabolism of isolated trout hepatocytes poses a significant challenge for this type of approach which should be considered in future studies. - Highlights: • Energetic costs of AhR activation by βNF was examined in rainbow trout hepatocytes. • Metabolic flux analysis was performed on a fish cell preparation for the first time. • Exposure to βNF led to sparing of glycogen reserves and altered enzyme activities. • Adenylate energy charge was maintained despite temporal changes in metabolism.« less

Induction of AhR-Mediated Gene Transcription by Coffee

PubMed Central

Ishikawa, Toshio; Takahashi, Satoshi; Morita, Koji; Okinaga, Hiroko; Teramoto, Tamio

2014-01-01

Background Aryl hydrocarbon receptor (AhR) is classically known to be activated by xenobiotics such as dioxins and polycyclic aromatic hydrocarbons (PAHs). Although it has been reported that PAHs are contained in roasted coffee beans, in general coffee beverages are not considered to be AhR activators. We tested whether exposure to coffee would activate AhR in cultured cells. Methods HepG2 cells stably expressing an AhR-responsive reporter gene were treated with coffee samples. Also, expression of CYP1A1, an endogenous AhR-responsive gene, was quantitated by RT-PCR and Western blotting in HepG2, Caco-2, and MCF-7 cells, after treatment with coffee. In order to obtain sensitive and reproducible results, all the experiments were performed with the cells placed in either phosphate-buffered saline (PBS) or pure serum, instead of routinely-used culture medium, whose intrinsic AhR-stimulating activity turned out to be so strong as to interfere with the analyses. Results All the coffee samples tested robustly stimulated AhR-mediated transcription in the reporter gene assays. Of note, to what extent coffee and other AhR agonists activated AhR was different, depending on whether the experiments were done in PBS or serum. CYP1A1 mRNA was induced by coffee, in HepG2, Caco-2, and MCF-7 cells placed in either PBS or serum. CYP1A1 protein expression, which was not detected in these cells incubated in PBS, was also increased by coffee in cells placed in serum. Conclusions By using culture medium-free experimental settings, we have shown that coffee is a strong AhR activator. Our observation may help elucidate as-yet-unrecognized effects of coffee on human health. PMID:25007155

Dioxin Receptor Expression Inhibits Basal and Transforming Growth Factor β-induced Epithelial-to-mesenchymal Transition*

PubMed Central

Rico-Leo, Eva M.; Alvarez-Barrientos, Alberto; Fernandez-Salguero, Pedro M.

2013-01-01

Recent studies have emphasized the role of the dioxin receptor (AhR) in maintaining cell morphology, adhesion, and migration. These novel AhR functions depend on the cell phenotype, and although AhR expression maintains mesenchymal fibroblasts migration, it inhibits keratinocytes motility. These observations prompted us to investigate whether AhR modulates the epithelial-to-mesenchymal transition (EMT). For this, we have used primary AhR+/+ and AhR−/− keratinocytes and NMuMG cells engineered to knock down AhR levels (sh-AhR) or to express a constitutively active receptor (CA-AhR). Both AhR−/− keratinocytes and sh-AhR NMuMG cells had increased migration, reduced levels of epithelial markers E-cadherin and β-catenin, and increased expression of mesenchymal markers Snail, Slug/Snai2, vimentin, fibronectin, and α-smooth muscle actin. Consistently, AhR+/+ and CA-AhR NMuMG cells had reduced migration and enhanced expression of epithelial markers. AhR activation by the agonist FICZ (6-formylindolo[3,2-b]carbazole) inhibited NMuMG migration, whereas the antagonist α-naphthoflavone induced migration as did AhR knockdown. Exogenous TGFβ exacerbated the promigratory mesenchymal phenotype in both AhR-expressing and AhR-depleted cells, although the effects on the latter were more pronounced. Rescuing AhR expression in sh-AhR cells reduced Snail and Slug/Snai2 levels and cell migration and restored E-cadherin levels. Interference of AhR in human HaCaT cells further supported its role in EMT. Interestingly, co-immunoprecipitation and immunofluorescence assays showed that AhR associates in common protein complexes with E-cadherin and β-catenin, suggesting the implication of AhR in cell-cell adhesion. Thus, basal or TGFβ-induced AhR down-modulation could be relevant in the acquisition of a motile EMT phenotype in both normal and transformed epithelial cells. PMID:23382382

Activation of aryl hydrocarbon receptor reduces carbendazim-induced cell death

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

Wei, Kuo-Liang

Carbendazim inhibits microtubule assembly, thus blocking mitosis and inhibiting cancer cell proliferation. Accordingly, carbendazim is being explored as an anticancer drug. Data show that carbendazim increased mRNA and protein expressions and promoter activity of CYP1A1. In addition, carbendazim activated transcriptional activity of the aryl hydrocarbon response element, and induced nuclear translocation of the aryl hydrocarbon receptor (AhR), a sign the AhR is activated. Carbendazim-induced CYP1A1 expression was blocked by AhR antagonists, and was abolished in AhR signal-deficient cells. Results demonstrated that carbendazim activated the AhR, thereby stimulating CYP1A1 expression. In order to understand whether AhR-induced metabolic enzymes turn carbendazim intomore » less-toxic metabolites, Hoechst 33342 staining to reveal carbendazim-induced nuclear changes and flow cytometry to reveal the subG{sub 0}/G{sub 1} population were applied to monitor carbendazim-induced cell apoptosis. Carbendazim induced less apoptosis in Hepa-1c1c7 cells than in AhR signal-deficient Hepa-1c1c7 mutant cells. Pretreatment with β-NF, an AhR agonist that highly induces CYP1A1 expression, decreased carbendazim-induced cell death. In addition, the lower the level of AhR was, the lower the vitality present in carbendazim-treated cells, including hepatoma cells and their derivatives with AhR RNA interference, also embryonic kidney cells, bladder carcinoma cells, and AhR signal-deficient Hepa-1c1c7 cells. In summary, carbendazim is an AhR agonist. The toxicity of carbendazim was lower in cells with the AhR signal. This report provides clues indicating that carbendazim is more potent at inducing cell death in tissues without than in those with the AhR signal, an important reference for applying carbendazim in cancer chemotherapy. - Highlights: • Carbendazim induced transcriptional activity of the aryl hydrocarbon response element. • Carbendazim induced nuclear translocation of the

Lipophilic components of diesel exhaust particles induce pro-inflammatory responses in human endothelial cells through AhR dependent pathway(s).

PubMed

Brinchmann, Bendik C; Skuland, Tonje; Rambøl, Mia H; Szoke, Krisztina; Brinchmann, Jan E; Gutleb, Arno C; Moschini, Elisa; Kubátová, Alena; Kukowski, Klara; Le Ferrec, Eric; Lagadic-Gossmann, Dominique; Schwarze, Per E; Låg, Marit; Refsnes, Magne; Øvrevik, Johan; Holme, Jørn A

2018-05-11

Exposure to traffic-derived particulate matter (PM), such as diesel exhaust particles (DEP), is a leading environmental cause of cardiovascular disease (CVD), and may contribute to endothelial dysfunction and development of atherosclerosis. It is still debated how DEP and other inhaled PM can contribute to CVD. However, organic chemicals (OC) adhered to the particle surface, are considered central to many of the biological effects. In the present study, we have explored the ability of OC from DEP to reach the endothelium and trigger pro-inflammatory reactions, a central step on the path to atherosclerosis. Exposure-relevant concentrations of DEP (0.12 μg/cm 2 ) applied on the epithelial side of an alveolar 3D tri-culture, rapidly induced pro-inflammatory and aryl hydrocarbon receptor (AhR)-regulated genes in the basolateral endothelial cells. These effects seem to be due to soluble lipophilic constituents rather than particle translocation. Extractable organic material of DEP (DEP-EOM) was next fractionated with increasing polarity, chemically characterized, and examined for direct effects on pro-inflammatory and AhR-regulated genes in human microvascular endothelial (HMEC-1) cells and primary human endothelial cells (PHEC) from four healthy donors. Exposure-relevant concentrations of lipophilic DEP-EOM (0.15 μg/cm 2 ) induced low to moderate increases in IL-1α, IL-1β, COX2 and MMP-1 gene expression, and the MMP-1 secretion was increased. By contrast, the more polar EOM had negligible effects, even at higher concentrations. Use of pharmacological inhibitors indicated that AhR and protease-activated receptor-2 (PAR-2) were central in regulation of EOM-induced gene expression. Some effects also seemed to be attributed to redox-responses, at least at the highest exposure concentrations tested. Although the most lipophilic EOM, that contained the majority of PAHs and aliphatics, had the clearest low-concentration effects, there was no straight-forward link

Increased arylhydrocarbon receptor expression offers a potential therapeutic target for pancreatic cancer.

PubMed

Koliopanos, Alexander; Kleeff, Jörg; Xiao, Yi; Safe, Stephen; Zimmermann, Arthur; Büchler, Markus W; Friess, Helmut

2002-09-05

The arylhydrocarbon receptor (AhR) was initially identified as a member of the adaptive metabolic and toxic response pathway to polycyclic aromatic hydrocarbons and to halogenated dibenzo-p-dioxins and dibenzofurans. In the present study, we sought to determine the functional significance of the AhR pathway in pancreatic carcinogenesis. AhR expression was analysed by Northern blotting. The exact site of AhR expression was analysed by in situ hybridization and immunohistochemistry. The effects of TCDD and four selective AhR agonists on pancreatic cancer cell lines were investigated by growth assays, apoptosis assays, and induction of the cyclin-dependent kinase inhibitor p21. There was strong AhR mRNA expression in 14 out of 15 pancreatic cancer samples, weak expression in chronic pancreatitis tissues, and faint expression in all normal pancreata. In pancreatic cancer tissues, AhR mRNA and protein expression were localized in the cytoplasm of pancreatic cancer cells. TCDD and the four AhR agonists inhibited pancreatic cancer cell growth in a dose-dependent manner, and decreased anchorage-independent cell growth. DAPI staining did not reveal nuclear fragmentation and CYP1A1 and was not induced by TCDD and AhR agonists. In contrast, TCDD and AhR agonists induced the expression of the cyclin-dependent kinase inhibitor p21. In conclusion, the relatively non-toxic AhR agonists caused growth inhibition in pancreatic cancer cells with high AhR expression levels via cell cycle arrest. In addition, almost all human pancreatic cancer tissues expressed this receptor at high levels, suggesting that these or related compounds may play a role in the therapy of pancreatic cancer in the future.

Genetic and epigenetic regulation of AHR gene expression in MCF-7 breast cancer cells: role of the proximal promoter GC-rich region

PubMed Central

Englert, Neal A.; Turesky, Robert J.; Han, Weiguo; Bessette, Erin E.; Spivack, Simon D.; Caggana, Michele; Spink, David C.; Spink, Barbara C.

2014-01-01

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, contributes to carcinogenesis through its role in the regulation of cytochrome P450 1 (CYP1)-catalyzed metabolism of carcinogens. Here, we investigated genetic and epigenetic mechanisms that affect AhR expression. Analyses of the human AHR proximal promoter in MCF-7 human breast cancer cells using luciferase assays and electrophoretic mobility shift assays revealed multiple specificity protein (Sp) 1 binding sequences that are transcriptional activators in vitro. The regulation of AhR expression was evaluated in long-term estrogen exposed (LTEE) MCF-7 cells, which showed increased AhR expression, enhanced CYP1 inducibility, and increased capacity to form DNA adducts when exposed to the dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. The increased AhR expression in LTEE cells was found not to result from increased mRNA stability, differential RNA processing, or decreased DNA methylation. Analysis of the AHR proximal promoter region using chromatin immunoprecipitation confirmed that enhanced expression of AhR in LTEE cells involves changes in histone modifications, notably decreased trimethylation of histone 3, lysine 27. Upon further examination of the GC-rich Sp1-binding region, we confirmed that it contains a polymorphic (GGGGC)n repeat. In a population of newborns from New York State, the allele frequency of (GGGGC)n was n = 4>5≫6, 2. Circular dichroism spectroscopy revealed the ability of sequences of this GC-rich region to form guanine-quadruplex structures in vitro. These studies revealed multiple levels at which AhR expression may be controlled, and offer additional insights into mechanisms regulating AhR expression that can ultimately impact carcinogenesis. PMID:22728919

Enhanced thyroid hormone breakdown in hepatocytes by mutual induction of the constitutive androstane receptor (CAR, NR1I3) and arylhydrocarbon receptor by benzo[a]pyrene and phenobarbital.

PubMed

Schraplau, Anne; Schewe, Bettina; Neuschäfer-Rube, Frank; Ringel, Sebastian; Neuber, Corinna; Kleuser, Burkhard; Püschel, Gerhard P

2015-02-03

Xenobiotics may interfere with the hypothalamic-pituitary-thyroid endocrine axis by inducing enzymes that inactivate thyroid hormones and thereby reduce the metabolic rate. This induction results from an activation of xeno-sensing nuclear receptors. The current study shows that benzo[a]pyrene, a frequent contaminant of processed food and activator of the arylhydrocarbon receptor (AhR) activated the promoter and induced the transcription of the nuclear receptor constitutive androstane receptor (CAR, NR1I3) in rat hepatocytes. Likewise, phenobarbital induced the AhR transcription. This mutual induction of the nuclear receptors enhanced the phenobarbital-dependent induction of the prototypic CAR target gene Cyp2b1 as well as the AhR-dependent induction of UDP-glucuronosyltransferases. In both cases, the induction by the combination of both xenobiotics was more than the sum of the induction by either substance alone. By inducing the AhR, phenobarbital enhanced the benzo[a]pyrene-dependent reduction of thyroid hormone half-life and the benzo[a]pyrene-dependent increase in the rate of thyroid hormone glucuronide formation in hepatocyte cultures. CAR ligands might thus augment the endocrine disrupting potential of AhR activators by an induction of the AhR. Copyright © 2014. Published by Elsevier Ireland Ltd.

Genetic dissection of endothelial transcriptional activity of zebrafish aryl hydrocarbon receptors (AHRs).

PubMed

Sugden, Wade W; Leonardo-Mendonça, Roberto C; Acuña-Castroviejo, Darío; Siekmann, Arndt F

2017-01-01

The aryl hydrocarbon receptor (AHR) is a basic helix-loop-helix transcription factor conserved across phyla from flies to humans. Activated by a number of endogenous ligands and environmental toxins, studies on AHR function and gene regulation have largely focused on a toxicological perspective relating to aromatic hydrocarbons generated by human activities and the often-deleterious effects of exposure on vertebrates mediated by AHR activation. A growing body of work has highlighted the importance of AHR in physiologic processes, including immune cell differentiation and vascular patterning. Here we dissect the contribution of the 3 zebrafish AHRs, ahr1a, ahr1b and ahr2, to endothelial cyp1a1/b1 gene regulation under physiologic conditions and upon exposure to the AHR ligand Beta-naphthoflavone. We show that in fish multiple AHRs are functional in the vasculature, with vessel-specific differences in the ability of ahr1b to compensate for the loss of ahr2 to maintain AHR signaling. We further provide evidence that AHR can regulate the expression of the chemokine receptor cxcr4a in endothelial cells, a regulatory mechanism that may provide insight into AHR function in the endothelium.

In Vitro Antitumor Effects of AHR Ligands Aminoflavone (AFP 464) and Benzothiazole (5F 203) in Human Renal Carcinoma Cells.

PubMed

Luzzani, Gabriela A; Callero, Mariana A; Kuruppu, Anchala I; Trapani, Valentina; Flumian, Carolina; Todaro, Laura; Bradshaw, Tracey D; Loaiza Perez, Andrea I

2017-12-01

We investigated activity and mechanism of action of two AhR ligand antitumor agents, AFP 464 and 5F 203 on human renal cancer cells, specifically examining their effects on cell cycle progression, apoptosis, and migration. TK-10, SN12C, Caki-1, and ACHN human renal cancer cell lines were treated with AFP 464 and 5F 203. We evaluated cytotoxicity by MTS assays, cell cycle arrest, and apoptosis by flow cytometry and corroborated a mechanism of action involving AhR signal transduction activation. Changes in migration properties by wound healing assays were investigated: 5F 203-sensitive cells show decreased migration after treatment, therefore, we measured c-Met phosphorylation by Western blot in these cells. A 5F 203 induced a decrease in cell viability which was more marked than AFP 464. This cytotoxicity was reduced after treatment with the AhR inhibitor α-NF for both compounds indicating AhR signaling activation plays a role in the mechanism of action. A 5F 203 is sequestered by TK-10 cells and induces CYP1A1 expression; 5F 203 potently inhibited migration of TK-10, Caki-1, and SN12C cells, and inhibited c-Met receptor phosphorylation in TK-10 cells. AhR ligand antitumor agents AFP 464 and 5F 203 represent potential new candidates for the treatment of renal cancer. A 5F 203 only inhibited migration of sensitive cells and c-Met receptor phosphorylation in TK-10 cells. c-Met receptor signal transduction is important in migration and metastasis. Therefore, we consider that 5F 203 offers potential for the treatment of metastatic renal carcinoma. J. Cell. Biochem. 118: 4526-4535, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Normal mast cell numbers in the tissues of AhR-deficient mice.

PubMed

Pilz, Caroline; Feyerabend, Thorsten; Sonner, Jana; Redaelli, Chiara; Peter, Katharina; Kunze, Anja; Haas, Katharina; Esser, Charlotte; Schäkel, Knut; Wick, Wolfgang; Rodewald, Hans-Reimer; Lanz, Tobias V; Platten, Michael

2016-01-01

The transcription factor aryl hydrocarbon receptor (AhR) acts as an immunomodulatory molecule in several immune cell lineages. Recently, it has been implicated in development and maintenance of immune cells in barrier tissues such as skin and mucosa. To investigate its role on mast cell development and maintenance in skin, peritoneal exudate cells (PECs) and lymph nodes, we studied in depth their phenotype in AhR-deficient mice. Our findings do not provide any evidence for a suspected role of the AhR in mast cell homeostasis. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Kynurenine promotes the goblet cell differentiation of HT-29 colon carcinoma cells by modulating Wnt, Notch and AhR signals.

PubMed

Park, Joo-Hung; Lee, Jeong-Min; Lee, Eun-Jin; Kim, Da-Jeong; Hwang, Won-Bhin

2018-04-01

Various amino acids regulate cell growth and differentiation. In the present study, we examined the ability of HT-29 cells to differentiate into goblet cells in RPMI and DMEM which are largely different in the amounts of numerous amino acids. Most of the HT-29 cells differentiated into goblet cells downregulating the stem cell marker Lgr5 when cultured in DMEM, but remained undifferentiated in RPMI. The goblet cell differentiation in DMEM was inhibited by 1-methyl-tryptophan (1-MT), an inhibitor of indoleamine 2,3 dioxygenase-1 which is the initial enzyme in tryptophan metabolism along the kynurenine (KN) pathway, whereas tryptophan and KN induced goblet cell differentiation in RPMI. The levels of Notch1 and its activation product Notch intracytoplasmic domain in HT-29 cells were lower in DMEM than those in RPMI and were increased by 1-MT in both media. HT-29 cells grown in both media expressed β-catenin at the same level on day 2 when goblet cell differentiation was not observed. β-catenin expression, which was increased by 1-MT in both media, was decreased by KN. DMEM reduced Hes1 expression while enhancing Hath1 expression. Finally, aryl hydrocarbon receptor (AhR) activation moderately induced goblet cell differentiation. Our results suggest that KN promotes goblet cell differentiation by regulating Wnt, Notch, and AhR signals and expression of Hes1 and Hath1.

Aryl hydrocarbon receptor and intestinal immunity.

PubMed

Lamas, Bruno; Natividad, Jane M; Sokol, Harry

2018-04-07

Aryl hydrocarbon receptor (AhR) is a member of the basic helix-loop-helix-(bHLH) superfamily of transcription factors, which are associated with cellular responses to environmental stimuli, such as xenobiotics and oxygen levels. Unlike other members of bHLH, AhR is the only bHLH transcription factor that is known to be ligand activated. Early AhR studies focused on understanding the role of AhR in mediating the toxicity and carcinogenesis properties of the prototypic ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In recent years, however, it has become apparent that, in addition to its toxicological involvement, AhR is highly receptive to a wide array of endogenous and exogenous ligands, and that its activation leads to a myriad of key host physiological functions. In this study, we review the current understanding of the functions of AhR in the mucosal immune system with a focus on its role in intestinal barrier function and intestinal immune cells, as well as in intestinal homeostasis.

A dioxin-like compound induces hyperplasia and branching morphogenesis in mouse mammary gland, through alterations in TGF-β1 and aryl hydrocarbon receptor signaling.

PubMed

Miret, Noelia; Rico-Leo, Eva; Pontillo, Carolina; Zotta, Elsa; Fernández-Salguero, Pedro; Randi, Andrea

2017-11-01

Hexachlorobenzene (HCB) is a widespread environmental pollutant and a dioxin-like compound that binds weakly to the aryl hydrocarbon receptor (AhR). Because AhR and transforming growth factor β1 (TGF-β1) converge to regulate common signaling pathways, alterations in this crosstalk might contribute to developing preneoplastic lesions. The aim of this study was to evaluate HCB action on TGF-β1 and AhR signaling in mouse mammary gland, through AhR+/+ and AhR-/- models. Results showed a differential effect in mouse mammary epithelial cells (NMuMG), depending on the dose: 0.05μM HCB induced cell migration and TGF-β1 signaling, whereas 5μM HCB reduced cell migration, promoted cell cycle arrest and stimulated the dioxin response element (DRE) -dependent pathway. HCB (5μM) enhanced α-smooth muscle actin expression and decreased TGF-β receptor II mRNA levels in immortalized mouse mammary fibroblasts AhR+/+, resembling the phenotype of transformed cells. Accordingly, their conditioned medium was able to enhance NMuMG cell migration. Assays in C57/Bl6 mice showed HCB (3mg/kg body weight) to enhance ductal hyperplasia, cell proliferation, estrogen receptor α nuclear localization, branch density, and the number of terminal end buds in mammary gland from AhR+/+ mice. Primary culture of mammary epithelial cells from AhR+/+ mice showed reduced AhR mRNA levels after HCB exposure (0.05 and 5μM). Interestingly, AhR-/- mice exhibited an increase in ductal hyperplasia and mammary growth in the absence of HCB treatment, thus revealing the importance of AhR in mammary development. Our findings show that environmental HCB concentrations modulate AhR and TGF-β1 signaling, which could contribute to altered mammary branching morphogenesis, likely leading to preneoplastic lesions and retaining terminal end buds. Copyright © 2017. Published by Elsevier Inc.

Activation of AhR-mediated toxicity pathway by emerging ...

EPA Pesticide Factsheets

Polychlorinated diphenyl sulfides (PCDPSs) are a group of environmental pollutants for which limited toxicological information is available. This study tested the hypothesis that PCDPSs could activate the mammalian aryl hydrocarbon receptor (AhR) mediated toxicity pathways. Eighteen PCDPSs were tested in the H4IIE-luc transactivation assay, with 13/18 causing concentration-dependent AhR activation. Potencies of several congeners were similar to those of mono-ortho substituted polychlorinated biphenyls. A RNA sequencing (RNA-seq)-based transcriptomic analysis was performed on H4IIE cells treated with two PCDPS congeners, 2,2',3,3',4,5,6-hepta-CDPS, and 2,4,4',5-tetra-CDPS. Results of RNA-seq revealed a remarkable modulation on a relatively short gene list by exposure to the tested concentrations of PCDPSs, among which, Cyp1 responded with the greatest fold up-regulation. Both the identities of the modulated transcripts and the associated pathways were consistent with targets and pathways known to be modulated by other types of AhR agonists and there was little evidence for significant off-target effects within the cellular context of the H4IIE bioassay. The results suggest AhR activation as a toxicologically relevant mode of action for PCDPSs suggests the utility of AhR-related toxicity pathways for predicting potential hazards associated with PCDPS exposure in mammals and potentially other vertebrates. Polychlorinated diphenyl sulfides (PCDPSs) are a group of en

Human and rodent aryl hydrocarbon receptor (AHR): from mediator of dioxin toxicity to physiologic AHR functions and therapeutic options.

PubMed

Bock, Karl Walter

2017-04-01

Metabolism of aryl hydrocarbons and toxicity of dioxins led to the discovery of the aryl hydrocarbon receptor (AHR). Tremendous advances have been made on multiplicity of AHR signaling and identification of endogenous ligands including the tryptophan metabolites FICZ and kynurenine. However, human AHR functions are still poorly understood due to marked species differences as well as cell-type- and cell context-dependent AHR functions. Observations in dioxin-poisoned individuals may provide hints to physiologic AHR functions in humans. Based on these observations three human AHR functions are discussed: (1) Chemical defence and homeostasis of endobiotics. The AHR variant Val381 in modern humans leads to reduced AHR affinity to aryl hydrocarbons in comparison with Neanderthals and primates expressing the Ala381 variant while affinity to indoles remains unimpaired. (2) Homeostasis of stem/progenitor cells. Dioxins dysregulate homeostasis in sebocyte stem cells. (3) Modulation of immunity. In addition to microbial defence, AHR may be involved in a 'disease tolerance defence pathway'. Further characterization of physiologic AHR functions may lead to therapeutic options.

Overexpression of aryl hydrocarbon receptor (AHR) signalling pathway in human meningioma.

PubMed

Talari, Noble Kumar; Panigrahi, Manas K; Madigubba, Sailaja; Phanithi, Prakash Babu

2018-04-01

Aryl hydrocarbon receptor (AHR) is a ligand activated transcription factor and involved in tumorigenesis of many cancers. However there are no reports on AHR in human meningioma. Therefore we examined the status of the AHR and its signalling molecules in human meningioma by using tumor biopsy samples and autopsy control meninges. We report the up regulation of AHR pathway genes like aryl hydrocarbon receptor nuclear translocator (ARNT), aldehyde dehydrogenase1family memberA3 (ALDH1A3), cytochrome P450, family1, subfamily A polypeptide1 (CYP1A1) and TCCD induced poly ADP ribose polymerase (TIPARP) gene expression in human meningioma. Further, AHR protein expression was found to be up regulated in all grades of human meningioma. We found that AHR localized in the nucleus for high grade anaplastic meningioma through immunohistochemical analysis. Since AHR signalling pathway was known to involve in inhibition of apoptosis in cancer cells, we evaluated the cyclophilin D levels which maintains mitochondrial permeability transition pore a critical event during apoptosis. We report that cyclophilin D levels were upregulated in all grades of human meningioma compared to control meninges. Finally we also evaluated c-Fos protein levels as its levels were regulated by AHR. Here we report that c-Fos protein levels were down regulated in all grades of human meningioma compared to control meninges. To sum-up we found that AHR signalling pathway components were upregulated, as the grade of the meningioma progresses from low to high grade, suggesting an important role of AHR signalling pathway in human meningioma.

Allergic responses and aryl hydrocarbon receptor novel pathway of mast cell activation.

PubMed

Sibilano, Riccardo; Pucillo, Carlo E; Gri, Giorgia

2015-01-01

The activation of the transcription factor aryl hydrocarbon receptor (AhR) is modulated by a wide variety of xenobiotics and ligands deriving from products of metabolism. The study of the contribution of AhR to allergic diseases has gained much interest in recent years. Here we discuss the role that environmental factors and metabolic products, particularly acting on AhR-expressing mast cells (MCs), could have in the development of local allergic/atopic response. Thus, this review will cover: a brief overview of the AhR mechanism of action in the immune system; a description of different AhR ligands and their effects to IgE-mediated MC activation in the allergic response, with particular attention to the role of IL-17; a discussion about the potential involvement of AhR in immune tolerance; and a conclusion on human diseases in which direct AhR activation of MC might have a major impact. Copyright © 2014 Elsevier Ltd. All rights reserved.

An introduction to the molecular basics of aryl hydrocarbon receptor biology.

PubMed

Abel, Josef; Haarmann-Stemmann, Thomas

2010-11-01

Depending on their chemical structure and properties, environmental chemicals and other xenobiotics that enter the cell can affect cellular function by either nonselective binding to cellular macromolecules or by interference with cellular receptors, which would initiate a more defined cell biological response. One of these intracellular chemosensor molecules is the aryl hydrocarbon receptor (AhR), a transcription factor of the bHLH/PAS family that is known to mediate the biochemical and toxic effects of dioxins, polyaromatic hydrocarbons and related compounds. Numerous investigations have revealed that the AhR is not only a master regulator of drug metabolism activated by anthropogenic chemicals, but is also triggered by natural and endogenous ligands and can influence cell biological endpoints such as growth and differentiation. Cutting-edge research has identified new intriguing functions of the AhR, such as during proteasomal degradation of steroid hormone receptors, the cellular UVB stress response and the differentiation of certain T-cell subsets. In this review we provide both a survey of the fundamental basics of AhR biology and an insight into new functional aspects of AhR signaling to further stimulate research on this intriguing transcription factor at the interface between toxicology, cell biology and immunology.

Tissue distribution of aryl hydrocarbon receptor in the intestine: Implication of putative roles in tumor suppression

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

Ikuta, Togo, E-mail: togo@cancer-c.pref.saitama.jp; Kurosumi, Masafumi, E-mail: mkurosumi@cancer-c.pref.saitama.jp; Yatsuoka, Toshimasa, E-mail: yatsuoka-gi@umin.ac.jp

Intestinal homeostasis is maintained by complex interactions between intestinal microorganisms and the gut immune system. Dysregulation of gut immunity may lead to inflammatory disorders and tumorigenesis. We previously have shown the tumor suppressive effects of aryl hydrocarbon receptor (AhR) in intestinal carcinogenesis. In the present study, we investigated AhR distribution in the mouse and human intestine by histochemical analysis. In the normal intestine, AhR was mainly localized in the stroma containing immune cells in the lamina propria and lymphoid follicles. On the other hand, in the tumor tissue from human colon cancer and that developed in Apc{sup Min/+}mice, AhR expressionmore » was elevated. AhR immunostaining was found in both stromal and tumor cells. Although AhR was localized in the cytoplasm of tumor cells in most cases, nuclear AhR was also observed in some. AhR knockdown using siRNA resulted in significant promotion of cell growth in colon cancer cell lines. Furthermore, AhR activation by AhR ligands supplemented in culture medium suppressed cell growth. Our study results suggest that tumor suppressive roles of AhR are estimated in two distinct ways: in normal tissue, AhR is associated with tumor prevention by regulating gut immunity, whereas in tumor cells, it is involved in growth suppression. - Highlights: • In the normal intestine, AhR was mainly localized in stroma containing immune cells. • In the tumor tissue, AhR expression was found in both stromal and tumor cells. • AhR knockdown promoted cell growth in colon cancer cell lines.« less

Suppression of aberrant choroidal neovascularization through activation of the aryl hydrocarbon receptor.

PubMed

Choudhary, Mayur; Safe, Stephen; Malek, Goldis

2018-05-01

The aryl hydrocarbon receptor (AhR) is a ligand activated transcription factor, initially discovered for its role in regulating xenobiotic metabolism. There is extensive evidence supporting a multi-faceted role for AhR, modulating physiological pathways important in cell health and disease. Recently we demonstrated that the AhR plays a role in the pathogenesis of age-related macular degeneration (AMD), the leading cause of vision loss in the elderly. We found that loss of AhR exacerbates choroidal neovascular (CNV) lesion formation in a murine model. Herein we tested the therapeutic impact of AhR activation on CNV lesion formation and factors associated with aberrant neovascularization. We screened a panel of synthetic drugs and endogenous AhR ligands, assessed their ability to activate AhR in choroidal endothelial cells, and inhibit angiogenesis in vitro. Drugs with an anti-angiogenic profile were then administered to a murine model of CNV. Two compounds, leflunomide and flutamide, significantly inhibited CNV formation concurrent with positive modifying effects on angiogenesis, inflammation, extracellular matrix remodeling, and fibrosis. These results validate the role of the AhR pathway in regulating CNV pathogenesis, identify mechanisms of AhR-based therapies in the eye, and argue in favor of developing AhR as a drug target for the treatment of neovascular AMD. Copyright © 2018 Elsevier B.V. All rights reserved.

The aryl hydrocarbon receptor (AHR) transcription factor regulates megakaryocytic polyploidization

PubMed Central

Lindsey, Stephan; T. Papoutsakis, Eleftherios

2012-01-01

Summary We propose that the aryl hydrocarbon receptor (AHR) is a novel transcriptional regulator of megakaryopoietic polyploidization. Functional evidence was obtained that AHR impacts in vivo megakaryocytic differentiation and maturation; compared to wild-type mice, AHR-null mice had lower platelet counts, fewer numbers of newly synthesized platelets, increased bleeding times and lower-ploidy megakaryocytes (Mks). AHR mRNA increased 3·6-fold during ex vivo megakaryocytic differentiation, but reduced or remained constant during parallel isogenic granulocytic or erythroid differentiation. We interrogated the role of AHR in megakaryopoiesis using a validated Mk model of megakaryopoiesis, the human megakaryoblastic leukaemia CHRF cell line. Upon CHRF Mk differentiation, AHR mRNA and protein levels increased, AHR protein shifted from the cytoplasm to the nucleus and AHR binding to its consensus DNA binding sequence increased. Protein and mRNA levels of the AHR transcriptional target HES1 also increased. Mk differentiation of CHRF cells where AHR or HES1 was knocked-down using RNAi resulted in lower ploidy distributions and cells that were incapable of reaching ploidy classes ≥16n. AHR knockdown also resulted in increased DNA synthesis of lower ploidy cells, without impacting apoptosis. Together, these data support a role for AHR in Mk polyploidization and in vivo platelet function, and warrant further detailed investigations. PMID:21226706

The aryl hydrocarbon receptor (AHR) transcription factor regulates megakaryocytic polyploidization.

PubMed

Lindsey, Stephan; Papoutsakis, Eleftherios T

2011-02-01

We propose that the aryl hydrocarbon receptor (AHR) is a novel transcriptional regulator of megakaryopoietic polyploidization. Functional evidence was obtained that AHR impacts in vivo megakaryocytic differentiation and maturation; compared to wild-type mice, AHR-null mice had lower platelet counts, fewer numbers of newly synthesized platelets, increased bleeding times and lower-ploidy megakaryocytes (Mks). AHR mRNA increased 3·6-fold during ex vivo megakaryocytic differentiation, but reduced or remained constant during parallel isogenic granulocytic or erythroid differentiation. We interrogated the role of AHR in megakaryopoiesis using a validated Mk model of megakaryopoiesis, the human megakaryoblastic leukaemia CHRF cell line. Upon CHRF Mk differentiation, AHR mRNA and protein levels increased, AHR protein shifted from the cytoplasm to the nucleus and AHR binding to its consensus DNA binding sequence increased. Protein and mRNA levels of the AHR transcriptional target HES1 also increased. Mk differentiation of CHRF cells where AHR or HES1 was knocked-down using RNAi resulted in lower ploidy distributions and cells that were incapable of reaching ploidy classes ≥16n. AHR knockdown also resulted in increased DNA synthesis of lower ploidy cells, without impacting apoptosis. Together, these data support a role for AHR in Mk polyploidization and in vivo platelet function, and warrant further detailed investigations. © 2011 Blackwell Publishing Ltd.

An endogenous aryl hydrocarbon receptor ligand inhibits proliferation and migration of human ovarian cancer cells

PubMed Central

Jiang, Yi-Zhou; Dai, Cai-Feng; Patankar, Manish S.; Song, Jia-Sheng; Zheng, Jing

2013-01-01

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor mediates many biological processes. Herein, we investigated if 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE, an endogenous AhR ligand) regulated proliferation and migration of human ovarian cancer cells via AhR. We found that AhR was widely present in many histotypes of ovarian cancer tissues. ITE suppressed OVCAR-3 cell proliferation and SKOV-3 cell migration in vitro, which were blocked by AhR knockdown. ITE also suppressed OVCAR-3 cell growth in mice. These data suggest that the ITE might potentially be used for therapeutic intervention for at least a subset of human ovarian cancer. PMID:23851185

Rats fed soy protein isolate (SPI) have impaired hepatic CYP1A1 induction by polycyclic aromatic hydrocarbons as a result of interference with aryl hydrocarbon receptor signaling

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

Singhal, Rohit; Badger, Thomas M.; Arkansas Children's Nutrition Center, Little Rock, AR 72202

2008-03-01

Consumption of soy diets has been found to reduce cancer incidence in animals and is associated with reduced cancer risk in humans. Previously, we have demonstrated that female Sprague-Dawley rats fed purified AIN-93G diets with soy protein isolate (SPI) as the sole protein source had reduced CYP1A1 induction and basal aryl hydrocarbon receptor (AhR) levels relative to those fed the same diet containing casein (CAS). In the present study, the molecular mechanisms underlying reduced AhR expression have been studied. The SPI-effect on AhR was not observed after feeding diets containing the purified soy isoflavones genistein or daidzein. Rat hepatoma FGC-4more » cells were treated with the serum obtained from rats fed CAS- or SPI-containing diets. Reduced AhR levels (P < 0.05) were observed after 24 h exposure to SPI-serum without any changes in the overall expression of chaperone proteins-HSP90 and XAP2. SPI-serum-stimulated AhR degradation was inhibited by treating the cells with the proteasome inhibitor, MG132, and was observed to be preceded by ubiquitination of the receptor. A reduced association of XAP2 with the immunoprecipitated AhR complex was observed. SPI-serum-mediated AhR degradation was preceded by nuclear translocation of the receptor. However, the translocated receptor was found to be unable to heterodimerize with ARNT or to bind to XRE elements on the CYP1A1 enhancer. These data suggest that feeding SPI-containing diets antagonizes AhR signaling by a novel mechanism which differs from those established for known AhR antagonists.« less

Aryl‐hydrocarbon receptor activity modulates prolactin expression in the pituitary

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

Moran, Tyler B.; Brannick, Katherine E.; Raetzman, Lori T., E-mail: raetzman@life.illinois.edu

2012-11-15

Pituitary tumors account for 15% of intracranial neoplasms, however the extent to which environmental toxicants contribute to the proliferation and hormone expression of pituitary cells is unknown. Aryl-hydrocarbon receptor (AhR) interacting protein (AIP) loss of function mutations cause somatotrope and lactotrope adenomas in humans. AIP sequesters AhR and inhibits its transcriptional function. Because of the link between AIP and pituitary tumors, we hypothesize that exposure to dioxins, potent exogenous ligands for AhR that are persistent in the environment, may predispose to pituitary dysfunction through activation of AhR. In the present study, we examined the effect of AhR activation on proliferationmore » and endogenous pituitary hormone expression in the GH3 rat somatolactotrope tumor cell line and the effect of loss of AhR action in knockout mice. GH3 cells respond to nM doses of the reversible AhR agonist β-naphthoflavone with a robust induction of Cyp1a1. Although mRNA levels of the anti-proliferative signaling cytokine TGFbeta1 are suppressed upon β-naphthoflavone treatment, we did not observe an alteration in cell proliferation. AhR activation with β-naphthoflavone suppresses Ahr expression and impairs expression of prolactin (PRL), but not growth hormone (GH) mRNA in GH3 cells. In mice, loss of Ahr similarly leads to a reduction in Prl mRNA at P3, while Gh is unaffected. Additionally, there is a significant reduction in pituitary hormones Lhb and Fshb in the absence of Ahr. Overall, these results demonstrate that AhR is important for pituitary hormone expression and suggest that environmental dioxins can exert endocrine disrupting effects at the pituitary. -- Highlights: ► AhR signaling suppresses Prl mRNA expression. ► AhR signaling does not influence pituitary proliferation in culture. ► AhR is necessary for Prl, Lhb and Fshb expression at postnatal day 3.« less

Aryl Hydrocarbon Receptor Protects Lungs from Cockroach Allergen-Induced Inflammation by Modulating Mesenchymal Stem Cells.

PubMed

Xu, Ting; Zhou, Yufeng; Qiu, Lipeng; Do, Danh C; Zhao, Yilin; Cui, Zhuang; Wang, Heng; Liu, Xiaopeng; Saradna, Arjun; Cao, Xu; Wan, Mei; Gao, Peisong

2015-12-15

Exposure to cockroach allergen leads to allergic sensitization and increased risk of developing asthma. Aryl hydrocarbon receptor (AhR), a receptor for many common environmental contaminants, can sense not only environmental pollutants but also microbial insults. Mesenchymal stem cells (MSCs) are multipotent progenitor cells with the capacity to modulate immune responses. In this study, we investigated whether AhR can sense cockroach allergens and modulate allergen-induced lung inflammation through MSCs. We found that cockroach allergen-treated AhR-deficient (AhR(-/-)) mice showed exacerbation of lung inflammation when compared with wild-type (WT) mice. In contrast, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an AhR agonist, significantly suppressed allergen-induced mouse lung inflammation. MSCs were significantly reduced in cockroach allergen-challenged AhR(-/-) mice as compared with WT mice, but increased in cockroach allergen-challenged WT mice when treated with TCDD. Moreover, MSCs express AhR, and AhR signaling can be activated by cockroach allergen with increased expression of its downstream genes cyp1a1 and cyp1b1. Furthermore, we tracked the migration of i.v.-injected GFP(+) MSCs and found that cockroach allergen-challenged AhR(-/-) mice displayed less migration of MSCs to the lungs compared with WT. The AhR-mediated MSC migration was further verified by an in vitro Transwell migration assay. Epithelial conditioned medium prepared from cockroach extract-challenged epithelial cells significantly induced MSC migration, which was further enhanced by TCDD. The administration of MSCs significantly attenuated cockroach allergen-induced inflammation, which was abolished by TGF-β1-neutralizing Ab. These results suggest that AhR plays an important role in protecting lungs from allergen-induced inflammation by modulating MSC recruitment and their immune-suppressive activity. Copyright © 2015 by The American Association of Immunologists, Inc.

Trace derivatives of kynurenine potently activate the aryl hydrocarbon receptor (AHR).

PubMed

Seok, Seung-Hyeon; Ma, Zhi-Xiong; Feltenberger, John B; Chen, Hongbo; Chen, Hui; Scarlett, Cameron; Lin, Ziqing; Satyshur, Kenneth A; Cortopassi, Marissa; Jefcoate, Colin R; Ge, Ying; Tang, Weiping; Bradfield, Christopher A; Xing, Yongna

2018-02-09

Cellular metabolites act as important signaling cues, but are subject to complex unknown chemistry. Kynurenine is a tryptophan metabolite that plays a crucial role in cancer and the immune system. Despite its atypical, non-ligand-like, highly polar structure, kynurenine activates the aryl hydrocarbon receptor (AHR), a PER, ARNT, SIM (PAS) family transcription factor that responds to diverse environmental and cellular ligands. The activity of kynurenine is increased 100-1000-fold by incubation or long-term storage and relies on the hydrophobic ligand-binding pocket of AHR, with identical structural signatures for AHR induction before and after activation. We purified trace-active derivatives of kynurenine and identified two novel, closely related condensation products, named trace-extended aromatic condensation products (TEACOPs), which are active at low picomolar levels. The synthesized compound for one of the predicted structures matched the purified compound in both chemical structure and AHR pharmacology. Our study provides evidence that kynurenine acts as an AHR pro-ligand, which requires novel chemical conversions to act as a receptor agonist. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Novel cell-based assay reveals associations of circulating serum AhR-ligands with metabolic syndrome and mitochondrial dysfunction.

PubMed

Park, Wook-Ha; Jun, Dae Won; Kim, Jin Taek; Jeong, Jae Hoon; Park, Hyokeun; Chang, Yoon-Seok; Park, Kyong Soo; Lee, Hong Kyu; Pak, Youngmi Kim

2013-01-01

Serum concentrations of environmental pollutants have been positively correlated with diabetes and metabolic syndrome in epidemiologic studies. In turn, abnormal mitochondrial function has been associated with the diseases. The relationships between these variables, however, have not been studied. We developed novel cell-based aryl hydrocarbon receptor (AhR) agonist bioassay system without solvent extraction process and analyzed whether low-dose circulating AhR ligands in human serum are associated with parameters of metabolic syndrome and mitochondrial function. Serum AhR ligand activities were measured as serum 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent (sTCDDeq) in pM using 10 μL human sera from 97 Korean participants (47 with glucose intolerance and 50 matched controls, average age of 46.6 ± 9.9 years, 53 male and 45 female). sTCDDeq were higher in participants with glucose intolerance than normal controls and were positively associated (P < 0.01) with obesity, blood pressure, serum triglyceride, and fasting glucose, but not with HDL-cholesterol. Body mass index was in a positive linear relationship with serum AhR ligands in healthy participants. When myoblast cells were incubated with human sera, ATP generating power of mitochondria became impaired in an AhR ligand concentration-dependent manner. Our results support that circulating AhR ligands may directly reduce mitochondrial function in tissues, leading to weight gain, glucose intolerance, and metabolic syndrome. Our rapid cell-based assay using minute volume of human serum may provide one of the best monitoring systems for circulating AhR ligands, good clinical biomarkers for the progress of disease and therapeutic efficacy. Copyright © 2013 International Union of Biochemistry and Molecular Biology, Inc.

Comparison of hepatic NRF2 and AHR binding in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) treated mice demonstrates NRF2-independent PKM2 induction.

PubMed

Nault, Rance; Doskey, Claire M; Fader, Kelly A; Rockwell, Cheryl E; Zacharewski, Timothy R

2018-05-11

2,3,7,8-Tetrachlorodibenzo- p -dioxin (TCDD) induces hepatic oxidative stress following activation of the aryl hydrocarbon receptor (AhR). Our recent studies showed TCDD induced pyruvate kinase muscle isoform 2 ( Pkm2 ) as a novel antioxidant response in normal differentiated hepatocytes. To investigate cooperative regulation between nuclear factor, erythroid derived 2, like 2 ( Nrf2 ) and the AhR in the induction of Pkm2 , hepatic ChIP-seq analyses were integrated with RNA-seq time course data from mice treated with TCDD for 2 - 168h. ChIP-seq analysis 2h after TCDD treatment identified genome-wide NRF2 enrichment. Approximately 842 NRF2 enriched regions were located in the regulatory region of differentially expressed genes (DEGs) while 579 DEGs showed both NRF2 and AhR enrichment. Sequence analysis of regions with overlapping NRF2 and AhR enrichment showed over-representation of either antioxidant or dioxin response elements (ARE and DRE, respectively), although 18 possessed both motifs. NRF2 exhibited negligible enrichment within a closed Pkm chromatin region while the AhR was enriched 29-fold. Furthermore, TCDD induced Pkm2 in primary hepatocytes from wild-type and Nrf2 null mice, indicating NRF2 is not required. Although NRF2 and AhR cooperate to regulate numerous antioxidant gene expression responses, the induction of Pkm2 by TCDD is independent of ROS-mediated NRF2 activation. The American Society for Pharmacology and Experimental Therapeutics.

Omeprazole Attenuates Hyperoxic Injury in H441 Cells via Aryl hydrocarbon Receptor

PubMed Central

Shivanna, Binoy; Chu, Chun; Welty, Stephen E.; Jiang, Weiwu; Wang, Lihua; Moorthy, Bhagavatula

2014-01-01

Hyperoxia contributes to the development of bronchopulmonary dysplasia in premature infants. Earlier we observed that aryl hydrocarbon receptor (AhR)-deficient mice are more susceptible to hyperoxic lung injury than AhR-sufficient mice, and this phenomenon was associated with a lack of expression of cytochrome P450 1A enzymes. Omeprazole, a proton pump inhibitor, used in humans with gastric acid related disorders, activates AhR in hepatocytes in vitro. However, the effects of omeprazole on AhR activation in the lungs and its impact on hyperoxia-induced ROS generation and inflammation are unknown. In this study, we tested the hypothesis that omeprazole attenuates hyperoxia-induced cytotoxicity, ROS generation, and expression of monocyte chemoattractant protein-1 (MCP-1) in the human lung derived H441 cells via AhR activation. Experimental groups included cells transfected with AhR small interfering RNA (siRNA). Hyperoxia resulted in significant increases in cytotoxicity, ROS generation, and MCP-1 production, which were significantly attenuated with the functional activation of AhR by omeprazole. The protective effects of omeprazole on cytotoxicity, ROS production, and MCP-1 production were lost in H441 cells whose AhR gene was silenced by AhR siRNA. These findings support the hypothesis that omeprazole protects against hyperoxic injury in vitro via AhR activation that is associated with decreased ROS generation and expression of MCP-1. PMID:21906671

Pure non-dioxin-like PCB congeners suppress induction of AhR-dependent endpoints in rat liver cells.

PubMed

Brenerová, Petra; Hamers, Timo; Kamstra, Jorke H; Vondráček, Jan; Strapáčová, Simona; Andersson, Patrik L; Machala, Miroslav

2016-02-01

The relative potencies of non-ortho-substituted coplanar polychlorinated biphenyl (PCB) congeners to activate the aryl hydrocarbon receptor (AhR) and to cause the AhR-dependent toxic events are essential for their risk assessment. Since some studies suggested that abundant non-dioxin-like PCB congeners (NDL-PCBs) may alter the AhR activation by PCB mixtures and possibly cause non-additive effects, we evaluated potential suppressive effects of NDL-PCBs on AhR activation, using a series of 24 highly purified NDL-PCBs. We investigated their impact on the model AhR agonist-induced luciferase reporter gene expression in rat hepatoma cells and on induction of CYP1A1/1B1 mRNAs and deregulation of AhR-dependent cell proliferation in rat liver epithelial cells. PCBs 128, 138, and 170 significantly suppressed AhR activation (with IC50 values from 1.4 to 5.6 μM), followed by PCBs 28, 47, 52, and 180; additionally, PCBs 122, 153, and 168 showed low but still significant potency to reduce luciferase activity. Detection of CYP1A1 mRNA levels in liver epithelial cells largely confirmed these results for the most abundant NDL-PCBs, whereas the other AhR-dependent events (CYP1B1 mRNA expression, induction of cell proliferation in confluent cells) were less sensitive to NDL-PCBs, thus indicating a more complex regulation of these endpoints. The present data suggest that some NDL-PCBs could modulate overall dioxin-like effects in complex mixtures.

Identification of benzothiazole derivatives and polycyclic aromatic hydrocarbons as aryl hydrocarbon receptor agonists present in tire extracts.

PubMed

He, Guochun; Zhao, Bin; Denison, Michael S

2011-08-01

Leachate from rubber tire material contains a complex mixture of chemicals previously shown to produce toxic and biological effects in aquatic organisms. The ability of these leachates to induce Ah receptor (AhR)-dependent cytochrome P4501A1 expression in fish indicated the presence of AhR active chemicals, but the responsible chemicals and their direct interaction with the AhR signaling pathway were not examined. Using a combination of AhR-based bioassays, we have demonstrated the ability of tire extract to stimulate both AhR DNA binding and AhR-dependent gene expression and confirmed that the responsible chemicals were metabolically labile. The application of CALUX (chemical-activated luciferase gene expression) cell bioassay-driven toxicant identification evaluation not only revealed that tire extract contained a variety of known AhR-active polycyclic aromatic hydrocarbons but also identified 2-methylthiobenzothiazole and 2-mercaptobenzothiazole as AhR agonists. Analysis of a structurally diverse series of benzothiazoles identified many that could directly stimulate AhR DNA binding and transiently activate the AhR signaling pathway and identified benzothiazoles as a new class of AhR agonists. In addition to these compounds, the relatively high AhR agonist activity of a large number of fractions strongly suggests that tire extract contains a large number of physiochemically diverse AhR agonists whose identities and toxicological/biological significances are unknown. Copyright © 2011 SETAC.

An endogenous aryl hydrocarbon receptor ligand inhibits proliferation and migration of human ovarian cancer cells.

PubMed

Wang, Kai; Li, Yan; Jiang, Yi-Zhou; Dai, Cai-Feng; Patankar, Manish S; Song, Jia-Sheng; Zheng, Jing

2013-10-28

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor mediates many biological processes. Herein, we investigated if 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE, an endogenous AhR ligand) regulated proliferation and migration of human ovarian cancer cells via AhR. We found that AhR was widely present in many histotypes of ovarian cancer tissues. ITE suppressed OVCAR-3 cell proliferation and SKOV-3 cell migration in vitro, which were blocked by AhR knockdown. ITE also suppressed OVCAR-3 cell growth in mice. These data suggest that the ITE might potentially be used for therapeutic intervention for at least a subset of human ovarian cancer. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

AhR-mediated gene expression in the developing mouse telencephalon.

PubMed

Gohlke, Julia M; Stockton, Pat S; Sieber, Stella; Foley, Julie; Portier, Christopher J

2009-11-01

We hypothesize that TCDD-induced developmental neurotoxicity is modulated through an AhR-dependent interaction with key regulatory neuronal differentiation pathways during telencephalon development. To test this hypothesis we examined global gene expression in both dorsal and ventral telencephalon tissues in E13.5 AhR-/- and wildtype mice exposed to TCDD or vehicle. Consistent with previous biochemical, pathological and behavioral studies, our results suggest TCDD initiated changes in gene expression in the developing telencephalon are primarily AhR-dependent, as no statistically significant gene expression changes are evident after TCDD exposure in AhR-/- mice. Based on a gene regulatory network for neuronal specification in the developing telencephalon, the present analysis suggests differentiation of GABAergic neurons in the ventral telencephalon is compromised in TCDD exposed and AhR-/- mice. In addition, our analysis suggests Sox11 may be directly regulated by AhR based on gene expression and comparative genomics analyses. In conclusion, this analysis supports the hypothesis that AhR has a specific role in the normal development of the telencephalon and provides a mechanistic framework for neurodevelopmental toxicity of chemicals that perturb AhR signaling.

Ligand independent aryl hydrocarbon receptor inhibits lung cancer cell invasion by degradation of Smad4.

PubMed

Lee, Chen-Chen; Yang, Wen-Hao; Li, Ching-Hao; Cheng, Yu-Wen; Tsai, Chi-Hao; Kang, Jaw-Jou

2016-07-01

The aryl hydrocarbon receptor (AhR) is a ligand-dependent-activated transcriptional factor that regulates the metabolism of xenobiotic and endogenous compounds. Although AhR plays a crucial role in air toxicant-induced carcinogenesis, AhR expression was shown to negatively regulate tumorigenesis. Therefore, in the present study, we investigated the effect of AhR without ligand treatment on cancer invasion in lung cancer cell lines. Lung cancer cells expressing lower levels of AhR showed higher invasion ability (H1299 cells) compared with cells expressing higher levels of AhR (A549 cells). Overexpression of AhR in H1299 cells inhibited the invasion ability. We found that vimentin expression was inhibited in AhR-overexpressing H1299 cells. Additionally, the expression of EMT-related transcriptional factors Snail and ID-1 decreased. Interestingly, we found that Smad4 degradation was induced in AhR-overexpressing H1299 cells. Our data showed that AhR could interact with Jun-activation domain binding protein (Jab1) and Smad4, which may cause degradation of Smad4 by the proteasome. Our data suggest that AhR affects the transforming growth factor-β signaling pathway by inducing Smad4 degradation by the proteasome and suppressing tumor metastasis via epithelial to mesenchymal transition reduction in lung cancer cells. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Lupinalbin A as the most potent estrogen receptor α- and aryl hydrocarbon receptor agonist in Eriosema laurentii de Wild. (Leguminosae).

PubMed

Ateba, Sylvin Benjamin; Njamen, Dieudonné; Medjakovic, Svjetlana; Zehl, Martin; Kaehlig, Hanspeter; Jungbauer, Alois; Krenn, Liselotte

2014-08-09

Eriosema laurentii De Wild. (Leguminosae) is a plant used in Cameroon against infertility and gynecological or menopausal complaints. In our previous report, a methanol extract of its aerial parts was shown to exhibit estrogenic and aryl hydrocarbon receptor agonistic activities in vitro and to prevent menopausal symptoms in ovariectomized Wistar rats. In order to determine the major estrogen receptor α (ERα) agonists in the extract, an activity-guided fractionation was performed using the ERα yeast screen. To check whether the ERα active fractions/compounds also accounted for the aryl hydrocarbon receptor (AhR) agonistic activity of the crude methanol extract, they were further tested on the AhR yeast screen. This study led to the identification of 2'-hydroxygenistein, lupinalbin A and genistein as major estrogenic principles of the extract. 2'-hydroxygenistein and lupinalbin A were, for the first time, also shown to possess an AhR agonistic activity, whereas genistein was not active in this assay. In addition, it was possible to deduce structure-activity relationships. These results suggest that the identified compounds are the major active principles responsible for the estrogenic and AhR agonistic activities of the crude methanol extract of the aerial parts of Eriosema laurentii.

Hypoxia perturbs aryl hydrocarbon receptor signaling and CYP1A1 expression induced by PCB 126 in human skin and liver-derived cell lines

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

Vorrink, Sabine U.; Department of Radiation Oncology, The University of Iowa, Iowa City, IA; Severson, Paul L.

2014-02-01

The aryl hydrocarbon receptor (AhR) is an important mediator of toxic responses after exposure to xenobiotics including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and dioxin-like polychlorinated biphenyls (PCBs). Activation of AhR responsive genes requires AhR dimerization with the aryl hydrocarbon receptor nuclear translocator (ARNT), a heterodimeric partner also shared by the hypoxia-inducible factor-1α (HIF-1α) protein. TCDD-stimulated AhR transcriptional activity can be influenced by hypoxia; however, it less well known whether hypoxia interferes with AhR transcriptional transactivation in the context of PCB-mediated AhR activation in human cells. Elucidation of this interaction is important in liver hepatocytes which extensively metabolize ingested PCBs and experience varying degreesmore » of oxygen tension during normal physiologic function. This study was designed to assess the effect of hypoxia on AhR transcriptional responses after exposure to 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126). Exposure to 1% O{sub 2} prior to PCB 126 treatment significantly inhibited CYP1A1 mRNA and protein expression in human HepG2 and HaCaT cells. CYP1A1 transcriptional activation was significantly decreased upon PCB 126 stimulation under conditions of hypoxia. Additionally, hypoxia pre-treatment reduced PCB 126 induced AhR binding to CYP1 target gene promoters. Importantly, ARNT overexpression rescued cells from the inhibitory effect of hypoxia on XRE-luciferase reporter activity. Therefore, the mechanism of interference of the signaling crosstalk between the AhR and hypoxia pathways appears to be at least in part dependent on ARNT availability. Our results show that AhR activation and CYP1A1 expression induced by PCB 126 were significantly inhibited by hypoxia and hypoxia might therefore play an important role in PCB metabolism and toxicity. - Highlights: • Significant crosstalk exists between AhR and HIF-1α signaling. • Hypoxia perturbs PCB 126 induced AhR

Activation of the aryl hydrocarbon receptor sensitises human keratinocytes for CD95L- and TRAIL-induced apoptosis

PubMed Central

Stolpmann, K; Brinkmann, J; Salzmann, S; Genkinger, D; Fritsche, E; Hutzler, C; Wajant, H; Luch, A; Henkler, F

2012-01-01

In this study, we have analysed the apoptotic effects of the ubiquitous environmental toxin benzo[a]pyrene (BP) in HaCaT cells and human keratinocytes. Although prolonged exposure to BP was not cytotoxic on its own, a strong enhancement of CD95 (Fas)-mediated apoptosis was observed with BP at concentrations activating the aryl hydrocarbon receptor (AhR). Importantly, the ultimately mutagenic BP-metabolite, that is, (+)-anti-BP-7,8-diol-9,10-epoxide (BPDE), failed to enhance CD95-mediated cell death, suggesting that the observed pro-apoptotic effect of BP is neither associated with DNA adducts nor DNA-damage related signalling. CD95-induced apoptosis was also enhanced by β-naphtoflavone, a well-known agonist of the AhR that does not induce DNA damage, thus suggesting a crucial role for AhR activation. Consistently, BP failed to sensitise for CD95L-induced apoptosis in AhR knockdown HaCaT cells. Furthermore, inhibition of CYP1A1 and/or 1B1 expression did not affect the pro-apoptotic crosstalk. Exposure to BP did not increase expression of CD95, but led to augmented activation of caspase-8. Enhancement of apoptosis was also observed with the TRAIL death receptors that activate caspase-8 and apoptosis by similar mechanisms as CD95. Together, these observations indicate an interference of AhR signalling with the activity of receptor-associated signalling intermediates that are shared by CD95 and TRAIL receptors. Our data thus suggest that AhR agonists can enhance cytokine-mediated adversity upon dermal exposure. PMID:22951985

New Trends in Aryl Hydrocarbon Receptor Biology.

PubMed

Mulero-Navarro, Sonia; Fernandez-Salguero, Pedro M

2016-01-01

Traditionally considered as a critical intermediate in the toxic and carcinogenic response to dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD), the Aryl hydrocarbon/Dioxin receptor (AhR) has proven to be also an important regulator of cell physiology and organ homeostasis. AhR has become an interesting and actual area of research mainly boosted by a significant number of recent studies analyzing its contribution to the proper functioning of the immune, hepatic, cardiovascular, vascular and reproductive systems. At the cellular level, AhR establishes functional interactions with signaling pathways governing cell proliferation and cell cycle, cell morphology, cell adhesion and cell migration. Two exciting new aspects in AhR biology deal with its implication in the control of cell differentiation and its more than likely involvement in cell pluripotency and stemness. In fact, it is possible that AhR could help modulate the balance between differentiation and pluripotency in normal and transformed tumor cells. At the molecular level, AhR regulates an increasingly large array of physiologically relevant genes either by traditional transcription-dependent mechanisms or by unforeseen processes involving genomic insulators, chromatin dynamics and the transcription of mobile genetic elements. AhR is also closely related to epigenetics, not only from the point of view of target gene expression but also with respect to its own regulation by promoter methylation. It is reasonable to consider that deregulation of these many functions could have a causative role, or at least contribute to, human disease. Consequently, several laboratories have proposed that AhR could be a valuable tool as diagnostic marker and/or therapeutic target in human pathologies. An additional point of interest is the possibility of regulating AhR activity by endogenous non-toxic low weight molecules agonist or antagonist molecules that could be present or included in the diet. In this review, we will

Aryl Hydrocarbon Receptor Plays Protective Roles against High Fat Diet (HFD)-induced Hepatic Steatosis and the Subsequent Lipotoxicity via Direct Transcriptional Regulation of Socs3 Gene Expression*

PubMed Central

Wada, Taira; Sunaga, Hiroshi; Miyata, Kazuki; Shirasaki, Haruno; Uchiyama, Yuki; Shimba, Shigeki

2016-01-01

Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor regulating the expression of genes involved in xenobiotic response. Recent studies have suggested that AhR plays essential roles not only in xenobiotic detoxification but also energy metabolism. Thus, in this study, we studied the roles of AhR in lipid metabolism. Under high fat diet (HFD) challenge, liver-specific AhR knock-out (AhR LKO) mice exhibited severe steatosis, inflammation, and injury in the liver. Gene expression analysis and biochemical study revealed that de novo lipogenesis activity was significantly increased in AhR LKO mice. In contrast, induction of suppressor of cytokine signal 3 (Socs3) expression by HFD was attenuated in the livers of AhR LKO mice. Rescue of the Socs3 gene in the liver of AhR LKO mice cancelled the HFD-induced hepatic lipotoxicities. Promoter analysis established Socs3 as novel transcriptional target of AhR. These results indicated that AhR plays a protective role against HFD-induced hepatic steatosis and the subsequent lipotoxicity effects, such as inflammation, and that the mechanism of protection involves the direct transcriptional regulation of Socs3 expression by AhR. PMID:26865635

Identification of Benzothiazole Derivatives and Polycyclic Aromatic Hydrocarbons as Aryl Hydrocarbon Receptor Agonists Present in Tire Extracts

PubMed Central

He, Guochun; Zhao, Bin; Denison, Michael S.

2012-01-01

Leachate from rubber tire material contains a complex mixture of chemicals previously shown to produce toxic and biological effects in aquatic organisms. While the ability of these leachates to induce Ah receptor (AhR)-dependent cytochrome P4501A1 expression in fish indicated the presence of AhR active chemicals, the responsible chemical(s) and their direct interaction with the AhR signaling pathway were not examined. Using a combination of AhR-based bioassays, we have demonstrated the ability of tire extract to stimulate both AhR DNA binding and AhR-dependent gene expression and confirmed that the responsible chemical(s) was metabolically labile. The application of CALUX (Chemical-Activated LUciferase gene eXpression) cell bioassay-driven toxicant identification evaluation not only revealed that tire extract contained a variety of known AhR-active polycyclic aromatic hydrocarbons, but also identified 2-methylthiobenzothiazole and 2-mercaptobenzothiazole as AhR agonists. Analysis of a structurally diverse series of benzothiazoles identified many that could directly stimulate AhR DNA binding and transiently activate the AhR signaling pathway and identified benzothiazoles as a new class of AhR agonists. In addition to these compounds, the relatively high AhR agonist activity of a large number of fractions strongly suggests that tire extract contains a large number of physiochemically diverse AhR agonists whose identities and toxicological/biological significances are unknown. PMID:21590714

Dioxin Sensitivity-Related Two Critical Amino Acids of Arylhydrocarbon Receptor May Not Correlate with the Taxonomy or Phylogeny in Avian Species

PubMed Central

FUJISAWA, Nozomi; KAWAI, Yusuke K.; NAKAYAMA, Shouta M. M.; IKENAKA, Yoshinori; YAMAMOTO, Hideaki; ISHIZUKA, Mayumi

2013-01-01

ABSTRACT There are two arylhydrocarbon receptor (AhR) isoforms in birds, AhR1 and AhR2. The varying sensitivity of AhR is reported to be related to two critical amino acids at positions 325 and 381 in the AhR1 ligand-binding domain. In this study, seven avian species whose in vivo dioxin sensitivity was known, and 13 species with no data regarding their in vivo dioxin sensitivity were examined. The two critical amino acids in the ligand-binding domain were investigated in avian species, and the results were compared with the taxonomy or phylogenetic trees for the bird AhR proteins. We found that the two critical amino acids did not correlate with the taxonomy or phylogeny of these proteins, suggesting that dioxin sensitivity was independent of taxonomy. PMID:23912877

Molokhia (Corchorus olitorius L.) extract suppresses transformation of the aryl hydrocarbon receptor induced by dioxins.

PubMed

Nishiumi, Shin; Yabushita, Yoshiyuki; Fukuda, Itsuko; Mukai, Rie; Yoshida, Ken-Ichi; Ashida, Hitoshi

2006-02-01

Dioxins enter the body mainly through diet and cause the various toxicological effects by binding to the cytosolic aryl hydrocarbon receptor (AhR) followed by its transformation. In recent reports, it has been shown that certain natural compounds suppress AhR transformation in vitro. In this study, we demonstrated that ethanolic extract from molokhia, known as Egyptian spinach, showed the strongest suppressive effect on AhR transformation induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in cell-free system using rat hepatic cytosol among 41 kinds of extracts from vegetables and fruits. The molokhia extract also suppressed TCDD-induced AhR transformation in mouse hepatoma Hepa-1c1c7 cells and in intestinal permeability system constructed with human colon adenocarcinoma Caco-2 cells and human hepatoma HepG2 cells. Moreover, oral administration of the molokhia extract (100mg/kg body weight) decreased 3-methylcholanthrene-induced AhR transformation to the control level by inhibiting translocation of the AhR from cytosol into the nucleus in the liver of rats. The molokhia extract-administered rat liver showed a tolerance to TCDD-induced AhR transformation by ex vivo experiment. These results indicate that molokhia is an attractive food for isolation and identification of a natural antagonist for the AhR.

Activation of estrogen receptor signaling by the dioxin-like aryl hydrocarbon receptor agonist, 3,3',4,4',5-Pentachlorobiphenyl (PCB126) in salmon in vitro system

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

Mortensen, Anne Skjetne; Arukwe, Augustine

2008-03-01

Available toxicological evidence indicates that environmental contaminants with strong affinity to the aryl hydrocarbon receptor (AhR) have anti-estrogenic properties in both mammalian and non-mammalian in vivo and in vitro studies. The primary objective of the present study was to investigate the interactions between the AhR and estrogen receptor (ER) in salmon in vitro system. Two separate experiments were performed and gene expression patterns were analyzed using real-time PCR, while protein analysis was done by immunoblotting. Firstly, salmon primary hepatocytes were exposed to the dioxin-like PCB126 at 1, 10 and 50 pM and ER agonist nonylphenol (NP) at 5 and 10more » {mu}M, singly or in combination. Our data showed increased levels of ER-mediated gene expression (vitellogenin: Vtg, zona radiata protein: Zr-protein, ER{alpha}, ER{beta} and vigilin) as well as increased cellular ER{alpha} protein levels after treatment with NP and PCB126, singly or in combination. PCB126 treatment alone produced, as expected, increased transcription of AhR nuclear translocator (Arnt), CYP1A1 and AhR repressor (AhRR) mRNA, and these responses were reduced in the presence of NP concentrations. PCB126 exposure alone did not produce significant effect on AhR2{alpha} mRNA but increased (at 1 and 50 pM) and decreased (at 10 pM) AhR2{beta} mRNA below control level. For AhR2{delta} and AhR2{gamma} isotypes, PCB126 (at 1 pM) produced significant decreases (total inhibition for AhR2{gamma}) of mRNA levels but was indifferent at 10 and 50 pM, compared to control. NP exposure alone produced concentration-dependent significant decrease of AhR2{beta} mRNA. In contrast, while 5 {mu}M NP produced an indifferent effect on AhR2{delta} and AhR2{gamma}, 10 {mu}M NP produced significant decrease (total inhibition for AhR2{gamma}) and the presence of NP produced apparent PCB126 concentration-specific modulation of all AhR isotypes. A second experiment was performed to evaluate the involvement of ER

Growth suppression of Leydig TM3 cells mediated by aryl hydrocarbon receptor

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

Iseki, Minoru; Department of Regulation Biology, Faculty of Science, Saitama University, Saitama; Ikuta, Togo

2005-06-17

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin induces developmental toxicity in reproductive organs. To elucidate the function of AhR, we generated stable transformants of TM3 cells overexpressing wild-type aryl hydrocarbon receptor (AhR) or its mutants which carried mutations in nuclear localization signal or nuclear export signal. In the presence of 3-methylcholanthrene (MC), proliferation of the cells transfected with wild-type AhR was completely suppressed, whereas cells expressing AhR mutants proliferated in a manner equivalent to control TM3 cells, suggesting AhR-dependent growth inhibition. The suppression was associated with up-regulation of cyclin-dependent kinase inhibitor p21{sup Cip1}, which was abolished by pretreatment with actinomycin D. A p38 MAPKmore » specific inhibitor, SB203580, blocked the increase of p21{sup Cip1} mRNA in response to MC. Treatment with indigo, another AhR ligand, failed to increase of p21{sup Cip1} mRNA, although up-regulation of mRNA for CYP1A1 was observed. These data suggest AhR in Leydig cells mediates growth inhibition by inducing p21{sup Cip1}.« less

Increased aryl hydrocarbon receptor expression in patients with allergic rhinitis.

PubMed

Wei, P; Hu, G-H; Kang, H-Y; Yao, H-B; Kou, W; Liu, H; Hong, S-L

2014-02-01

A predominant Th17 population is a marker of allergic rhinitis (AR). As a ligand-activated transcription factor, the aryl hydrocarbon receptor (AhR) plays a vital role in promoting or inhibiting the development of specific Th cells. However, its role in AR remains undefined. To analyze the potential role of AhR in the pathogenesis of AR. In total, 30 AR patients and 13 healthy controls were recruited for this study and AR patients had clinical features, as demonstrated by rhinoconjunctivitis quality of life questionnaires, total symptom scores and visual analog scale scores. The expression of AhR, IL-17 and IL-22 and the presence of Th17 cells in peripheral blood mononuclear cells were measured before and after treatment with the nontoxic AhR ligand 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). Pretreatment ITE studies revealed that all AR patients had a significant increase in AhR expression compared with controls and AhR expression positively correlated with clinical parameters. After ITE intervention, a severe reduction in the differentiation of Th17 cells and the production of IL-17 and IL-22 was noted in both AR patients and normal subjects. Simultaneously, a dramatic enhancement of AhR expression was also observed in all healthy controls, but not in AR patients. The results suggested that the AhR may be one of the mechanisms underlying the Th17 response during the pathogenesis of AR and AhR levels were closely related to clinical severity in all AR patients. Additionally, ITE may represent a new drug candidate in the treatment of AR.

Activation of AhR-mediated toxicity pathway by emerging pollutants polychlorinated diphenyl sulfides

EPA Science Inventory

Polychlorinated diphenyl sulfides (PCDPSs) are a group of environmental pollutants for which limited toxicological information is available. This study tested the hypothesis that PCDPSs could activate the mammalian aryl hydrocarbon receptor (AhR) mediated toxicity pathways. Eight...

Cynaropicrin attenuates UVB-induced oxidative stress via the AhR-Nrf2-Nqo1 pathway.

PubMed

Takei, Kenjiro; Hashimoto-Hachiya, Akiko; Takahara, Masakazu; Tsuji, Gaku; Nakahara, Takeshi; Furue, Masutaka

2015-04-16

Due to its antioxidant and anti-inflammatory activities, artichoke (Cynara scolymus) has been used as folk medicine to treat various diseases. Cynaropicrin (Cyn), a sesquiterpene lactone, is the major bioactive phytochemical in the artichoke; however, its pharmacological mechanism remains unknown. Because some phytochemicals exert their antioxidant activity by activating aryl hydrocarbon receptor (AhR), leading to subsequent induction of the antioxidant pathway including nuclear factor E2-related factor 2 (Nrf2) and quinone oxidoreductase 1 (Nqo1), we investigated whether Cyn also activates the AhR-Nrf2-Nqo1 pathway. Cyn indeed induced the activation (nuclear translocation) of AhR, leading to nuclear translocation of Nrf2 and dose-dependent upregulation of Nrf2 and Nqo1 mRNAs in human keratinocytes. The Cyn-induced AhR-Nrf2-Nqo1 activation was AhR- and Nrf2-dependent, as demonstrated by the observation that it was absent in keratinocytes transfected by siRNA against either AhR or Nrf2. In accordance with these findings, Cyn actively inhibited generation of reactive oxygen species from keratinocytes irradiated with ultraviolet B (UVB) in a Nrf2-dependent manner. Cyn also inhibited the production of proinflammatory cytokines such as interleukin 6 and tumor necrosis factor-α from UVB-treated keratinocytes. Our findings demonstrate that Cyn is a potent activator of the AhR-Nrf2-Nqo1 pathway, and could therefore be applied to prevention of UVB-induced photo aging. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Common Commercial and Consumer Products Contain Activators of the Aryl Hydrocarbon (Dioxin) Receptor

PubMed Central

Zhao, Bin; Bohonowych, Jessica E. S.; Timme-Laragy, Alicia; Jung, Dawoon; Affatato, Alessandra A.; Rice, Robert H.; Di Giulio, Richard T.; Denison, Michael S.

2013-01-01

Activation of the Ah receptor (AhR) by halogenated aromatic hydrocarbons (HAHs), such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin), can produce a wide variety of toxic and biological effects. While recent studies have shown that the AhR can bind and be activated by structurally diverse chemicals, how widespread of these AhR agonists are in environmental, biological and synthetic materials remains to be determined. Using AhR-based assays, we demonstrate the presence of potent AhR agonists in a variety of common commercial and consumer items. Solvent extracts of paper, rubber and plastic products contain chemicals that can bind to and stimulate AhR DNA binding and/or AhR-dependent gene expression in hepatic cytosol, cultured cell lines, human epidermis and zebrafish embryos. In contrast to TCDD and other persistent dioxin-like HAHs, activation of AhR-dependent gene expression by these extracts was transient, suggesting that the agonists are metabolically labile. Solvent extracts of rubber products produce AhR-dependent developmental toxicity in zebrafish in vivo, and inhibition of expression of the metabolic enzyme CYP1A, significantly increased their toxic potency. Although the identity of the responsible AhR-active chemicals and their toxicological impact remain to be determined, our data demonstrate that AhR active chemicals are widely distributed in everyday products. PMID:23441220

Oculomotor Deficits in Aryl Hydrocarbon Receptor Null Mouse

PubMed Central

Chevallier, Aline; Mialot, Antoine; Petit, Jean-Maurice; Fernandez-Salguero, Pedro; Barouki, Robert

2013-01-01

The Aryl hydrocarbon Receptor or AhR, a ligand-activated transcription factor, is known to mediate the toxic and carcinogenic effects of various environmental pollutants such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD). Recent studies in Caenorhabditis elegans and Drosophila melanogaster show that the orthologs of the AhR are expressed exclusively in certain types of neurons and are implicated in the development and the homeostasis of the central nervous system. While physiological roles of the AhR were demonstrated in the mammalian heart, liver and gametogenesis, its ontogenic expression and putative neural functions remain elusive. Here, we report that the constitutive absence of the AhR in adult mice (AhR−/−) leads to abnormal eye movements in the form of a spontaneous pendular horizontal nystagmus. To determine if the nystagmus is of vestibular, visual, or cerebellar origin, gaze stabilizing reflexes, namely vestibulo-ocular and optokinetic reflexes (VOR and OKR), were investigated. The OKR is less effective in the AhR−/− mice suggesting a deficit in the visuo-motor circuitry, while the VOR is mildly affected. Furthermore, the AhR is expressedin the retinal ganglion cells during the development, however electroretinograms revealed no impairment of retinal cell function. The structure of the cerebellum of the AhR−/− mice is normal which is compatible with the preserved VOR adaptation, a plastic process dependent on cerebellar integrity. Finally, intoxication with TCDD of control adults did not lead to any abnormality of the oculomotor control. These results demonstrate that the absence of the AhR leads to acquired central nervous system deficits in the adults. Given the many common features between both AhR mouse and human infantile nystagmus syndromes, the AhR−/− mice might give insights into the developmental mechanisms which lead to congenital eye disorders. PMID:23301081

The aryl hydrocarbon receptor is required for normal gonadotropin responsiveness in the mouse ovary.

PubMed

Barnett, Kimberly R; Tomic, Dragana; Gupta, Rupesh K; Babus, Janice K; Roby, Katherine F; Terranova, Paul F; Flaws, Jodi A

2007-08-15

The aryl hydrocarbon receptor (AHR) mediates the toxicity of a variety of environmental chemicals. Although little is known about the physiological role of the AHR, studies suggest that it plays an important role in regulating ovulation because Ahr deficient (AhRKO) mice have a reduced number of ovulations compared to wild-type (WT) mice. The reasons for the reduced ability of AhRKO mice to ovulate are unknown. Normal ovulation, however, requires estrous cyclicity, appropriate luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, and LH and FSH responsiveness. Thus, the purpose of this study was to test the hypothesis that Ahr deletion regulates ovulation by altering cyclicity, FSH and LH levels, follicle-stimulating hormone receptor (Fshr) and luteinizing hormone receptor (Lhcgr) levels and/or gonadotropin responsiveness. The data indicate that AhRKO and WT mice have similar levels of FSH and LH, but AhRKO mice have reduced Fshr and Lhcgr mRNA levels compared to WT mice. Furthermore, AhRKO ovaries contain fewer corpora lutea compared to WT ovaries after 5 IU equine chorionic gonadotropin (eCG) treatment. Lastly, both AhRKO and WT mice ovulate a similar number of eggs in response to 5 IU human chorionic gonadotropin (hCG), but AhRKO mice ovulate fewer eggs than WT mice in response to 2.5 IU and 1.25 IU hCG. Collectively, these data indicate that AhRKO follicles have a reduced capacity to ovulate compared to WT follicles and that this is due to reduced responsiveness to gonadotropins. Thus, in addition to mediating toxicity of environmental chemicals, the Ahr is required for normal ovulation.

The aryl hydrocarbon receptor is required for normal gonadotropin responsiveness in the mouse ovary

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

Barnett, Kimberly R.; Tomic, Dragana; Gupta, Rupesh K.

2007-08-15

The aryl hydrocarbon receptor (AHR) mediates the toxicity of a variety of environmental chemicals. Although little is known about the physiological role of the AHR, studies suggest that it plays an important role in regulating ovulation because Ahr deficient (AhRKO) mice have a reduced number of ovulations compared to wild-type (WT) mice. The reasons for the reduced ability of AhRKO mice to ovulate are unknown. Normal ovulation, however, requires estrous cyclicity, appropriate luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, and LH and FSH responsiveness. Thus, the purpose of this study was to test the hypothesis that Ahr deletion regulatesmore » ovulation by altering cyclicity, FSH and LH levels, follicle-stimulating hormone receptor (Fshr) and luteinizing hormone receptor (Lhcgr) levels and/or gonadotropin responsiveness. The data indicate that AhRKO and WT mice have similar levels of FSH and LH, but AhRKO mice have reduced Fshr and Lhcgr mRNA levels compared to WT mice. Furthermore, AhRKO ovaries contain fewer corpora lutea compared to WT ovaries after 5 IU equine chorionic gonadotropin (eCG) treatment. Lastly, both AhRKO and WT mice ovulate a similar number of eggs in response to 5 IU human chorionic gonadotropin (hCG), but AhRKO mice ovulate fewer eggs than WT mice in response to 2.5 IU and 1.25 IU hCG. Collectively, these data indicate that AhRKO follicles have a reduced capacity to ovulate compared to WT follicles and that this is due to reduced responsiveness to gonadotropins. Thus, in addition to mediating toxicity of environmental chemicals, the Ahr is required for normal ovulation.« less

Hypoxia perturbs aryl hydrocarbon receptor signaling and CYP1A1 expression induced by PCB 126 in human skin and liver-derived cell lines.

PubMed

Vorrink, Sabine U; Severson, Paul L; Kulak, Mikhail V; Futscher, Bernard W; Domann, Frederick E

2014-02-01

The aryl hydrocarbon receptor (AhR) is an important mediator of toxic responses after exposure to xenobiotics including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and dioxin-like polychlorinated biphenyls (PCBs). Activation of AhR responsive genes requires AhR dimerization with the aryl hydrocarbon receptor nuclear translocator (ARNT), a heterodimeric partner also shared by the hypoxia-inducible factor-1α (HIF-1α) protein. TCDD-stimulated AhR transcriptional activity can be influenced by hypoxia; however, it less well known whether hypoxia interferes with AhR transcriptional transactivation in the context of PCB-mediated AhR activation in human cells. Elucidation of this interaction is important in liver hepatocytes which extensively metabolize ingested PCBs and experience varying degrees of oxygen tension during normal physiologic function. This study was designed to assess the effect of hypoxia on AhR transcriptional responses after exposure to 3,3',4,4',5-pentachlorobiphenyl (PCB 126). Exposure to 1% O2 prior to PCB 126 treatment significantly inhibited CYP1A1 mRNA and protein expression in human HepG2 and HaCaT cells. CYP1A1 transcriptional activation was significantly decreased upon PCB 126 stimulation under conditions of hypoxia. Additionally, hypoxia pre-treatment reduced PCB 126 induced AhR binding to CYP1 target gene promoters. Importantly, ARNT overexpression rescued cells from the inhibitory effect of hypoxia on XRE-luciferase reporter activity. Therefore, the mechanism of interference of the signaling crosstalk between the AhR and hypoxia pathways appears to be at least in part dependent on ARNT availability. Our results show that AhR activation and CYP1A1 expression induced by PCB 126 were significantly inhibited by hypoxia and hypoxia might therefore play an important role in PCB metabolism and toxicity. Copyright © 2013 Elsevier Inc. All rights reserved.

RNA Editing Modulates Human Hepatic Aryl Hydrocarbon Receptor Expression by Creating MicroRNA Recognition Sequence.

PubMed

Nakano, Masataka; Fukami, Tatsuki; Gotoh, Saki; Takamiya, Masataka; Aoki, Yasuhiro; Nakajima, Miki

2016-01-08

Adenosine to inosine (A-to-I) RNA editing is the most frequent type of post-transcriptional nucleotide conversion in humans, and it is catalyzed by adenosine deaminase acting on RNA (ADAR) enzymes. In this study we investigated the effect of RNA editing on human aryl hydrocarbon receptor (AhR) expression because the AhR transcript potentially forms double-stranded structures, which are targets of ADAR enzymes. In human hepatocellular carcinoma-derived Huh-7 cells, the ADAR1 knockdown reduced the RNA editing levels in the 3'-untranslated region (3'-UTR) of the AhR transcript and increased the AhR protein levels. The ADAR1 knockdown enhanced the ligand-mediated induction of CYP1A1, a gene downstream of AhR. We investigated the possibility that A-to-I RNA editing creates miRNA targeting sites in the AhR mRNA and found that the miR-378-dependent down-regulation of AhR was abolished by ADAR1 knockdown. These results indicated that the ADAR1-mediated down-regulation of AhR could be attributed to the creation of a miR-378 recognition site in the AhR 3'-UTR. The interindividual differences in the RNA editing levels within the AhR 3'-UTR in a panel of 32 human liver samples were relatively small, whereas the differences in ADAR1 expression were large (220-fold). In the human liver samples a significant inverse association was observed between the miR-378 and AhR protein levels, suggesting that the RNA-editing-dependent down-regulation of AhR by miR-378 contributes to the variability in the constitutive hepatic expression of AhR. In conclusion, this study uncovered for the first time that A-to-I RNA editing modulates the potency of xenobiotic metabolism in the human liver. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Decreased expression of the aryl hydrocarbon receptor in ocular Behcet's disease.

PubMed

Wang, Chaokui; Ye, Zi; Kijlstra, Aize; Zhou, Yan; Yang, Peizeng

2014-01-01

Recent studies show that the aryl hydrocarbon receptor (AhR) is involved in immune responses. AhR is activated following interaction with its ligands, such as 6-formylindolo[3,2-b]carbazole (FICZ) and 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). In this study, we investigated the role of AhR activation by its endogenous ligands in the pathogenesis of ocular Behcet's disease (BD). The expression of AhR was significantly decreased in active BD patients as compared to inactive BD patients and normal controls. Both FICZ and ITE inhibited Th1 and Th17 polarization and induced the expression of IL-22 by PBMCs and by CD4(+)T cells in active BD patients and normal controls. Stimulation of purified CD4(+)T cells with FICZ or ITE caused a decreased expression of RORC, IL-17, IL-23R, and CCR6 and an increased phosphorylation of STAT3 and STAT5. The present study suggests that a decreased AhR expression is associated with disease activity in BD patients. The activation of AhR by either FICZ or ITE was able to inhibit Th1 and Th17 cell polarization. Further studies are needed to investigate whether modulation of AhR might be used in the treatment of BD.

Decreased Expression of the Aryl Hydrocarbon Receptor in Ocular Behcet's Disease

PubMed Central

Wang, Chaokui; Ye, Zi; Kijlstra, Aize; Zhou, Yan; Yang, Peizeng

2014-01-01

Recent studies show that the aryl hydrocarbon receptor (AhR) is involved in immune responses. AhR is activated following interaction with its ligands, such as 6-formylindolo[3,2-b]carbazole (FICZ) and 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). In this study, we investigated the role of AhR activation by its endogenous ligands in the pathogenesis of ocular Behcet's disease (BD). The expression of AhR was significantly decreased in active BD patients as compared to inactive BD patients and normal controls. Both FICZ and ITE inhibited Th1 and Th17 polarization and induced the expression of IL-22 by PBMCs and by CD4+T cells in active BD patients and normal controls. Stimulation of purified CD4+T cells with FICZ or ITE caused a decreased expression of RORC, IL-17, IL-23R, and CCR6 and an increased phosphorylation of STAT3 and STAT5. The present study suggests that a decreased AhR expression is associated with disease activity in BD patients. The activation of AhR by either FICZ or ITE was able to inhibit Th1 and Th17 cell polarization. Further studies are needed to investigate whether modulation of AhR might be used in the treatment of BD. PMID:25045206

The Aryl Hydrocarbon Receptor Mediates Leflunomide-Induced Growth Inhibition of Melanoma Cells

PubMed Central

O’Donnell, Edmond F.; Kopparapu, Prasad Rao; Koch, Daniel C.; Jang, Hyo Sang; Phillips, Jessica Lynne; Tanguay, Robert L.; Kerkvliet, Nancy I.; Kolluri, Siva Kumar

2012-01-01

A novel role of the dihydroorotatedehydrogenase (DHODH) inhibitor leflunomide as a potential anti-melanoma therapy was recently reported (Nature 471∶518-22, 2011). We previously reported that leflunomide strongly activates the transcriptional activity of the Aryl Hydrocarbon Receptor (AhR). We therefore tested whether the AhR regulates the anti-proliferative effects of leflunomide in melanoma. We first evaluated the expression of AhR in melanoma cells and found that AhR is highly expressed in A375 melanoma as well as in several other cancer cell types. To evaluate whether AhR plays a role in regulating the growth inhibitory effects of leflunomide in A375 cells, we generated a stable cell line from parental A375 cells expressing a doxycycline (DOX) inducible AhR shRNA. Using these cells in the absence or presence of DOX (normal AhR levels or AhR-knockdown, respectively) we found that the anti-proliferative effects of leflunomide, but not its metabolite A771726, were strongly dependent upon AhR expression. It has been well established that supplementation of cells with exogenous uridine completely rescues the anti-proliferative effects due to DHODH inhibition. Thus, we performed uridine rescue experiments in A375 cells to determine whether the anti-proliferative effects of leflunomide are solely due to DHODH inhibition as previously reported. Interestingly, saturating levels of uridine only modestly rescued A375 cells from the anti-proliferative effects of both leflunomide and A771726, indicating additional mechanism(s), apart from DHODH inhibition are responsible for the anti-proliferative effects of leflunomide in melanoma cells. Uridine also did not rescue MDA-MB-435S melanoma cell proliferation after leflunomide treatment. Our results reveal that the AhR is a molecular target of leflunomide and support the feasibility of the clinical application of leflunomide for treating melanoma. Furthermore, analysis of expression data from 967 cancer cell lines revealed

Ambient particulate matter activates the aryl hydrocarbon receptor in dendritic cells and enhances Th17 polarization.

PubMed

Castañeda, Alejandro R; Pinkerton, Kent E; Bein, Keith J; Magaña-Méndez, Alfonso; Yang, Houa T; Ashwood, Paul; Vogel, Christoph F A

2018-08-01

The objective of this study was to explore the role of the aryl hydrocarbon receptor (AhR) in ambient particulate matter (PM)-mediated activation of dendritic cells (DCs) and Th17-immune responses in vitro. To assess the potential role of the AhR in PM-mediated activation of DCs, co-stimulation, and cytokine expression, bone marrow (BM)-derived macrophages and DCs from C57BL/6 wildtype or AhR knockout (AhR -/- ) mice were treated with PM. Th17 differentiation was assessed via co-cultures of wildtype or AhR -/- BMDCs with autologous naive T cells. PM 2.5 significantly induced AhR DNA binding activity to dioxin responsive elements (DRE) and expression of the AhR repressor (AhRR), cytochrome P450 (CYP) 1A1, and CYP1B1, indicating activation of the AhR. In activated (OVA sensitized) BMDCs, PM 2.5 induced interleukin (IL)-1β, CD80, CD86, and MHC class II, suggesting enhanced DC activation, co-stimulation, and antigen presentation; responses that were abolished in AhR deficient DCs. DC-T cell co-cultures treated with PM and lipopolysaccharide (LPS) led to elevated IL-17A and IL-22 expression at the mRNA level, which is mediated by the AhR. PM-treated DCs were essential in endowing T cells with a Th17-phenotype, which was associated with enhanced expression of MHC class II and cyclooxygenase (COX)-2. In conclusion, PM enhances DC activation that primes naive T cell differentiation towards a Th17-like phenotype in an AhR-dependent manner. Copyright © 2018 Elsevier B.V. All rights reserved.

Aryl hydrocarbon receptor-dependent retention of nuclear HuR suppresses cigarette smoke-induced cyclooxygenase-2 expression independent of DNA-binding.

PubMed

Zago, Michela; Sheridan, Jared A; Nair, Parameswaran; Rico de Souza, Angela; Gallouzi, Imed-Eddine; Rousseau, Simon; Di Marco, Sergio; Hamid, Qutayba; Eidelman, David H; Baglole, Carolyn J

2013-01-01

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that responds to man-made environmental toxicants, has emerged as an endogenous regulator of cyclooxygenase-2 (Cox-2) by a mechanism that is poorly understood. In this study, we first used AhR-deficient (AhR(-/-) ) primary pulmonary cells, together with pharmacological tools to inhibit new RNA synthesis, to show that the AhR is a prominent factor in the destabilization of Cox-2 mRNA. The destabilization of Cox-2 mRNA and subsequent suppression of cigarette smoke-induced COX-2 protein expression by the AhR was independent of its ability to bind the dioxin response element (DRE), thereby differentiating the DRE-driven toxicological AhR pathway from its anti-inflammatory abilities. We further describe that the AhR destabilizes Cox-2 mRNA by sequestering HuR within the nucleus. The role of HuR in AhR stabilization of Cox-2 mRNA was confirmed by knockdown of HuR, which resulted in rapid Cox-2 mRNA degradation. Finally, in the lungs of AhR(-/-) mice exposed to cigarette smoke, there was little Cox-2 mRNA despite robust COX-2 protein expression, a finding that correlates with almost exclusive cytoplasmic HuR within the lungs of AhR(-/-) mice. Therefore, we propose that the AhR plays an important role in suppressing the expression of inflammatory proteins, a function that extends beyond the ability of the AhR to respond to man-made toxicants. These findings open the possibility that a DRE-independent AhR pathway may be exploited therapeutically as an anti-inflammatory target.

Molecular identification and partial sequence analysis of an aryl hydrocarbon receptor from beluga (Delphinapterus leucas)

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

Jensen, B.A.; Hahn, M.E.

1995-12-31

The aryl hydrocarbon receptor (AhR) mediates the effects of many common and potentially toxic organic hydrocarbons, including some polychlorinated biphenyls and dioxins. Since small cetaceans often inhabit industrially polluted coastal waters, comparison of the molecular structure and function of this protein in cetaeans with other marine and mammalian species is important for evaluating the sensitivity of cetaceans to these pollutants. An AhR protein has been identified in beluga liver by photoaffinity labeling. In the present study, the authors sought to clone and sequence an AhR cDNA from beluga as a prelude to studying its structure and function, using reverse-transcription polymerasemore » chain reaction (RT-PCR) and degenerate primers, a 515 base pair fragment was amplified, cloned and sequenced, revealing homology to the PAS domain (ligand binding and dimerization region) of AhRs from terrestrial mammals. This portion of the putative beluga AhR has 82% amino acid and 81% nucleotide sequence identity to the mouse AhR, and 63% amino acid and 64% nucleotide sequence identity to an AhR from the marine fish Fundulus heteroclitus. A beluga cDNA library was synthesized and is currently being screened with the PCR-generated fragment to obtain the complete coding sequence. This is the first molecular evidence of AhR presence in cetaceans.« less

piRNA-associated proteins and retrotransposons are differentially expressed in murine testis and ovary of aryl hydrocarbon receptor deficient mice

PubMed Central

Rico-Leo, Eva M.; Moreno-Marín, Nuria; González-Rico, Francisco J.; Barrasa, Eva; Ortega-Ferrusola, Cristina; Martín-Muñoz, Patricia; Sánchez-Guardado, Luis O.; Llano, Elena; Alvarez-Barrientos, Alberto; Infante-Campos, Ascensión; Catalina-Fernández, Inmaculada; Hidalgo-Sánchez, Matías; de Rooij, Dirk G.; Pendás, Alberto M.; Peña, Fernando J.; Merino, Jaime M.

2016-01-01

Previous studies suggested that the aryl hydrocarbon receptor (AhR) contributes to mice reproduction and fertility. However, the mechanisms involved remain mostly unknown. Retrotransposon silencing by Piwi-interacting RNAs (piRNAs) is essential for germ cell maturation and, remarkably, AhR has been identified as a regulator of murine B1-SINE retrotransposons. Here, using littermate AhR+/+ and AhR−/− mice, we report that AhR regulates the general course of spermatogenesis and oogenesis by a mechanism likely to be associated with piRNA-associated proteins, piRNAs and retrotransposons. piRNA-associated proteins MVH and Miwi are upregulated in leptotene to pachytene spermatocytes with a more precocious timing in AhR−/− than in AhR+/+ testes. piRNAs and transcripts from B1-SINE, LINE-1 and IAP retrotransposons increased at these meiotic stages in AhR-null testes. Moreover, B1-SINE transcripts colocalize with MVH and Miwi in leptonema and pachynema spermatocytes. Unexpectedly, AhR−/− males have increased sperm counts, higher sperm functionality and enhanced fertility than AhR+/+ mice. In contrast, piRNA-associated proteins and B1-SINE and IAP-derived transcripts are reduced in adult AhR−/− ovaries. Accordingly, AhR-null female mice have lower numbers of follicles when compared with AhR+/+ mice. Thus, AhR deficiency differentially affects testis and ovary development possibly by a process involving piRNA-associated proteins, piRNAs and transposable elements. PMID:28003471

Structural modeling of the AhR:ARNT complex in the bHLH-PASA-PASB region elucidates the key determinants of dimerization.

PubMed

Corrada, Dario; Denison, Michael S; Bonati, Laura

2017-05-02

Elucidation of the dimerization process of the aryl hydrocarbon receptor (AhR) with the AhR nuclear translocator (ARNT) is crucial for understanding the mechanisms underlying the functional activity of AhR, including mediation of the toxicity of environmental contaminants. In this work, for the first time a structural model of the AhR:ARNT dimer encompassing the entire bHLH-PASA-PASB domain region is proposed. It is developed by using a template-based modeling approach, relying on the recently available crystallographic structures of two dimers of homologous systems in the bHLH-PAS family of proteins: the CLOCK:BMAL1 and the HIF2α:ARNT heterodimers. The structural and energetic characteristics of the modeled AhR:ARNT protein-protein interface are determined by evaluating the variations in solvent accessible surface area, the total binding free energy and the per-residue free energy contributions obtained by the MM-GBSA method and the Energy Decomposition Analysis. The analyses of the intricate network of inter-domain interactions at the dimerization interfaces provide insights into the key determinants of dimerization. These are confirmed by comparison of the computational findings with the available experimental mutagenesis and functional analysis data. The results presented here on the AhR:ARNT dimer structure and interactions provide a framework to start analyzing the mechanism of AhR transformation into its functional DNA binding form.

Genetic Ablation of the Aryl Hydrocarbon Receptor Causes Cigarette Smoke-induced Mitochondrial Dysfunction and Apoptosis*

PubMed Central

Rico de Souza, Angela; Zago, Michela; Pollock, Stephen J.; Sime, Patricia J.; Phipps, Richard P.; Baglole, Carolyn J.

2011-01-01

Cigarette smoke is the primary risk factor for chronic obstructive pulmonary disease (COPD). Alterations in the balance between apoptosis and proliferation are involved in the etiology of COPD. Fibroblasts and epithelial cells are sensitive to the oxidative properties of cigarette smoke, and whose loss may precipitate the development of COPD. Fibroblasts express the aryl hydrocarbon receptor (AhR), a transcription factor that attenuates pulmonary inflammation and may also regulate apoptosis. We hypothesized the AhR would prevent apoptosis caused by cigarette smoke. Using genetically deleted in vitro AhR expression models and an established method of cigarette smoke exposure, we report that AhR expression regulates fibroblasts proliferation and prevents morphological features of apoptosis, including membrane blebbing and chromatin condensation caused by cigarette smoke extract (CSE). Absence of AhR expression results in cleavage of PARP, lamin, and caspase-3. Mitochondrial dysfunction, including cytochrome c release, was associated with loss of AhR expression, indicating activation of the intrinsic apoptotic cascade. Heightened sensitivity of AhR-deficient fibroblasts was not the result of alterations in GSH, Nrf2, or HO-1 expression. Instead, AhR−/− cells had significantly less MnSOD and CuZn-SOD expression, enzymes that protects against oxidative stress. The ability of the AhR to suppress apoptosis was not restricted to fibroblasts, as siRNA-mediated knockdown of the AhR in lung epithelial cells also increased sensitivity to smoke-induced apoptosis. Collectively, these results suggest that cigarette smoke induced loss of lung structural support (i.e. fibroblasts, epithelial cells) caused by aberrations in AhR expression may explain why some smokers develop lung diseases such as COPD. PMID:21984831

Aryl hydrocarbon receptor-dependent regulation of miR-196a expression controls lung fibroblast apoptosis but not proliferation

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

Hecht, Emelia; Zago, Michela; Sarill, Miles

2014-11-01

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor implicated in the regulation of apoptosis and proliferation. Although activation of the AhR by xenobiotics such as dioxin inhibits the cell cycle and control apoptosis, paradoxically, AhR expression also promotes cell proliferation and survival independent of exogenous ligands. The microRNA (miRNA) miR-196a has also emerged as a regulator of proliferation and apoptosis but a relationship between the AhR and miR-196a is not known. Therefore, we hypothesized that AhR-dependent regulation of endogenous miR-196a expression would promote cell survival and proliferation. Utilizing lung fibroblasts from AhR deficient (AhR{sup −/−}) and wild-type (AhR{supmore » +/+}) mice, we show that there is ligand-independent regulation of miRNA, including low miR-196a in AhR{sup −/−} cells. Validation by qRT-PCR revealed a significant decrease in basal expression of miR-196a in AhR{sup −/−} compared to AhR{sup +/+} cells. Exposure to AhR agonists benzo[a]pyrene (B[a]P) and FICZ as well as AhR antagonist CH-223191 decreased miR-196a expression in AhR{sup +/+} fibroblasts concomitant with decreased AhR protein levels. There was increased proliferation only in AhR{sup +/+} lung fibroblasts in response to serum, corresponding to a decrease in p27{sup KIP1} protein, a cyclin-dependent kinase inhibitor. Increasing the cellular levels of miR-196a had no effect on proliferation or expression of p27{sup KIP1} in AhR{sup −/−} fibroblasts but attenuated cigarette smoke-induced apoptosis. This study provides the first evidence that AhR expression is essential for the physiological regulation of cellular miRNA levels- including miR-196a. Future experiments designed to elucidate the functional relationship between the AhR and miR-196a may delineate additional novel ligand-independent roles for the AhR. - Highlights: • The AhR controls proliferation and apoptosis in lung cells. • The AhR regulates

Identification of a probiotic bacteria-derived activator of the aryl hydrocarbon receptor that inhibits colitis.

PubMed

Fukumoto, Suguru; Toshimitsu, Takayuki; Matsuoka, Shuji; Maruyama, Atsushi; Oh-Oka, Kyoko; Takamura, Takeyuki; Nakamura, Yuki; Ishimaru, Kayoko; Fujii-Kuriyama, Yoshiaki; Ikegami, Shuji; Itou, Hiroyuki; Nakao, Atsuhito

2014-01-01

The aryl hydrocarbon receptor (AhR) recognizes environmental xenobiotics and is originally thought to be involved in the metabolism (detoxification) of the substances. Recently, AhR is highlighted as an important regulator of inflammation. Notably, accumulating evidence suggests that activation of the AhR suppresses inflammatory bowel diseases (IBDs). Therefore, non-toxic AhR activators become attractive drug candidates for IBD. This study identified 1,4-dihydroxy-2-naphthoic acid (DHNA), a precursor of menaquinone (vitamin K2) abundantly produced by Propionibacterium freudenreichii ET-3 isolated from Swiss-type cheese, as an AhR activator. DHNA activated the AhR pathway in human intestinal epithelial cell line Caco2 cells and in the mouse intestine. Oral treatment of mice with DHNA induced anti-microbial proteins RegIIIβ and γ in the intestine, altered intestinal microbial flora and inhibited dextran sodium sulfate (DSS)-induced colitis, which recapitulated the phenotypes of AhR activation in the gut. As DHNA is commercially available in Japan as a prebiotic supplement without severe adverse effects, DHNA or its derivatives might become a promising drug candidate for IBD via AhR activation. The results also implicate that intestinal AhR might act not only as a sensor for xenobiotics in diet and water but also for commensal bacterial activity because DHNA is a precursor of vitamin K2 produced by vitamin K2-synthesizing commensal bacteria as well as propionic bacteria. Hence, DHNA might be a key bacterial metabolite in the host-microbe interaction to maintain intestinal microbial ecosystem.

Different regulation of aryl hydrocarbon receptor-regulated genes in response to dioxin in undifferentiated and neuronally differentiated human neuroblastoma SH-SY5Y cells.

PubMed

Imran, Saima; Ferretti, Patrizia; Vrzal, Radim

2015-01-01

Some environmental pollutants derived from industrial processes have been suggested to be responsible for neurological impairment in children, especially in heavily polluted areas. Since these compounds are usually activators of aryl hydrocarbon receptor (AhR), it would be important to better understand the molecular pathways downstream of AhR leading to neural deficits. To this purpose, appropriate in vitro human neural model is much needed. Here we have investigated whether undifferentiated and neuronally differentiated human neuroblastoma cells, SH-SY5Y cells, can provide a suitable model for monitoring AhR activity induced by environmental pollutants, focusing on 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD), a known activator of AhR. Further characterization of differentiated SH-SY5Y showed an increase in AhRR (aryl hydrocarbon receptor repressor), no change in ARNT1 (AhR nuclear translocator 1), and a decrease in ARNT2 expression with differentiation; in contrast, AhR was undetectable in both undifferentiated and differentiated cells. Nonetheless, treatment of parental as well as differentiated SH-SY5Y cells with TCDD resulted in the induction of AhR-regulated genes, CYP1A1 and CYP1B1; AhRR expression was also affected, but to a much smaller extent. These results indicate that undifferentiated SH-SY5Y are less sensitive to TCDD than neuronally differentiated ones, suggesting a higher resistance of the undifferentiated tumor cells to toxic insults. They also suggest that TCDD in these cells may not act via direct activation of AhR that is undetectable in SH-SY5Y as well as in differentiated neurons. Hence, these cells do not provide an appropriate model for studying ligand-mediated activation of AhR.

Induction of a chloracne phenotype in an epidermal equivalent model by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is dependent on aryl hydrocarbon receptor activation and is not reproduced by aryl hydrocarbon receptor knock down.

PubMed

Forrester, Alison R; Elias, Martina S; Woodward, Emma L; Graham, Mark; Williams, Faith M; Reynolds, Nick J

2014-01-01

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent activator of the aryl hydrocarbon receptor (AhR) and causes chloracne in humans. The pathogenesis and role of AhR in chloracne remains incompletely understood. To elucidate the mechanisms contributing to the development of the chloracne-like phenotype in a human epidermal equivalent model and identify potential biomarkers. Using primary normal human epidermal keratinocytes (NHEK), we studied AhR activation by XRE-luciferase, AhR degradation and CYP1A1 induction. We treated epidermal equivalents with high affinity TCDD or two non-chloracnegens: β-naphthoflavone (β-NF) and 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). Using Western blotting and immunochemistry for filaggrin (FLG), involucrin (INV) and transglutaminase-1 (TGM-1), we compared the effects of the ligands on keratinocyte differentiation and development of the chloracne-like phenotype by H&E. In NHEKs, activation of an XRE-luciferase and CYP1A1 protein induction correlated with ligand binding affinity: TCDD>β-NF>ITE. AhR degradation was induced by all ligands. In epidermal equivalents, TCDD induced a chloracne-like phenotype, whereas β-NF or ITE did not. All three ligands induced involucrin and TGM-1 protein expression in epidermal equivalents whereas FLG protein expression decreased following treatment with TCDD and β-NF. Inhibition of AhR by α-NF blocked TCDD-induced AhR activation in NHEKs and blocked phenotypic changes in epidermal equivalents; however, AhR knock down did not reproduce the phenotype. Ligand-induced CYP1A1 and AhR degradation did not correlate with their chloracnegenic potential, indicating that neither CYP1A1 nor AhR are suitable biomarkers. Mechanistic studies showed that the TCDD-induced chloracne-like phenotype depends on AhR activation whereas AhR knock down did not appear sufficient to induce the phenotype. Copyright © 2013 Japanese Society for Investigative Dermatology. Published by Elsevier

Induction of a chloracne phenotype in an epidermal equivalent model by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is dependent on aryl hydrocarbon receptor activation and is not reproduced by aryl hydrocarbon receptor knock down

PubMed Central

Forrester, Alison R.; Elias, Martina S.; Woodward, Emma L.; Graham, Mark; Williams, Faith M.; Reynolds, Nick J.

2014-01-01

Background 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent activator of the aryl hydrocarbon receptor (AhR) and causes chloracne in humans. The pathogenesis and role of AhR in chloracne remains incompletely understood. Objective To elucidate the mechanisms contributing to the development of the chloracne-like phenotype in a human epidermal equivalent model and identify potential biomarkers. Methods Using primary normal human epidermal keratinocytes (NHEK), we studied AhR activation by XRE-luciferase, AhR degradation and CYP1A1 induction. We treated epidermal equivalents with high affinity TCDD or two non-chloracnegens: β-naphthoflavone (β-NF) and 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). Using Western blotting and immunochemistry for filaggrin (FLG), involucrin (INV) and transglutaminase-1 (TGM-1), we compared the effects of the ligands on keratinocyte differentiation and development of the chloracne-like phenotype by H&E. Results In NHEKs, activation of an XRE-luciferase and CYP1A1 protein induction correlated with ligand binding affinity: TCDD > β-NF > ITE. AhR degradation was induced by all ligands. In epidermal equivalents, TCDD induced a chloracne-like phenotype, whereas β-NF or ITE did not. All three ligands induced involucrin and TGM-1 protein expression in epidermal equivalents whereas FLG protein expression decreased following treatment with TCDD and β-NF. Inhibition of AhR by α-NF blocked TCDD-induced AhR activation in NHEKs and blocked phenotypic changes in epidermal equivalents; however, AhR knock down did not reproduce the phenotype. Conclusion Ligand-induced CYP1A1 and AhR degradation did not correlate with their chloracnegenic potential, indicating that neither CYP1A1 nor AhR are suitable biomarkers. Mechanistic studies showed that the TCDD-induced chloracne-like phenotype depends on AhR activation whereas AhR knock down did not appear sufficient to induce the phenotype. PMID:24161567

Functional Expression of Aryl Hydrocarbon Receptor on Mast Cells Populating Human Endometriotic Tissues

PubMed Central

Orsaria, Maria; Marzinotto, Stefania; Londero, Ambrogio P; Bulfoni, Michela; Candotti, Veronica; Zanello, Andrea; Ballico, Maurizio; Mimmi, Maria C; Calcagno, Angelo; Marchesoni, Diego; Di Loreto, Carla; Beltrami, Antonio P; Cesselli, Daniela; Gri, Giorgia

2016-01-01

Endometriosis is an inflammatory disease characterized by the presence of ectopic endometrial tissue outside the uterus. A diffuse infiltration of mast cells (MCs) is observed throughout endometriotic lesions, but little is known about how these cells contribute to the network of molecules that modulate the growth of ectopic endometrial implants and promote endometriosis-associated inflammation. The Aryl Hydrocarbon Receptor (AhR), a transcription factor known to respond to environmental toxins and endogenous compounds, is present in MCs. In response to AhR activation, MCs produce IL-17 and reactive oxygen species, highlighting the potential impact of AhR ligands on inflammation via MCs. Here, we investigated the possibility that endometrial MCs promote an inflammatory microenvironment by sensing AhR ligands, thus sustaining endometriosis development. Using human endometriotic tissue (ET) samples, we performed the following experiments: i) examined the cytokine expression profile; ii) counted AhR-expressing MCs; iii) verified the phenotype of AhR-expressing MCs to establish whether MCs have a tolerogenic (IL-10-positive) or inflammatory (IL-17-positive) phenotype; iv) measured the presence of AhR ligands (tryptophan-derived kynurenine) and tryptophan-metabolizing enzymes (indoleamine 2,3-dioxygenase 1 (IDO1)); v) treated ET organ cultures with an AhR antagonist in vitro to measure changes in the cytokine milieu; and vi) measured the growth of endometrial stromal cells cultured with AhR-activated MC-conditioned medium. We found that ET tissue was conducive to cytokine production, orchestrating chronic inflammation and a population of AhR-expressing MCs that are both IL-17 and IL-10-positive. ET was rich in IDO1 and the AhR-ligand kynurenine compared with control tissue, possibly promoting MC activation through AhR. ET was susceptible to treatment with an AhR antagonist, and endometrial stromal cell growth was improved in the presence of soluble factors released by

Functional expression of aryl hydrocarbon receptor on mast cells populating human endometriotic tissues.

PubMed

Mariuzzi, Laura; Domenis, Rossana; Orsaria, Maria; Marzinotto, Stefania; Londero, Ambrogio P; Bulfoni, Michela; Candotti, Veronica; Zanello, Andrea; Ballico, Maurizio; Mimmi, Maria C; Calcagno, Angelo; Marchesoni, Diego; Di Loreto, Carla; Beltrami, Antonio P; Cesselli, Daniela; Gri, Giorgia

2016-09-01

Endometriosis is an inflammatory disease characterized by the presence of ectopic endometrial tissue outside the uterus. A diffuse infiltration of mast cells (MCs) is observed throughout endometriotic lesions, but little is known about how these cells contribute to the network of molecules that modulate the growth of ectopic endometrial implants and promote endometriosis-associated inflammation. The aryl hydrocarbon receptor (AhR), a transcription factor known to respond to environmental toxins and endogenous compounds, is present in MCs. In response to AhR activation, MCs produce IL-17 and reactive oxygen species, highlighting the potential impact of AhR ligands on inflammation via MCs. Here, we investigated the possibility that endometrial MCs promote an inflammatory microenvironment by sensing AhR ligands, thus sustaining endometriosis development. Using human endometriotic tissue (ET) samples, we performed the following experiments: (i) examined the cytokine expression profile; (ii) counted AhR-expressing MCs; (iii) verified the phenotype of AhR-expressing MCs to establish whether MCs have a tolerogenic (IL-10-positive) or inflammatory (IL-17-positive) phenotype; (iv) measured the presence of AhR ligands (tryptophan-derived kynurenine) and tryptophan-metabolizing enzymes (indoleamine 2,3-dioxygenase 1 (IDO1)); (v) treated ET organ cultures with an AhR antagonist in vitro to measure changes in the cytokine milieu; and (vi) measured the growth of endometrial stromal cells cultured with AhR-activated MC-conditioned medium. We found that ET tissue was conducive to cytokine production, orchestrating chronic inflammation and a population of AhR-expressing MCs that are both IL-17 and IL-10-positive. ET was rich in IDO1 and the AhR-ligand kynurenine compared with control tissue, possibly promoting MC activation through AhR. ET was susceptible to treatment with an AhR antagonist, and endometrial stromal cell growth was improved in the presence of soluble factors

Induction of Colonic Regulatory T Cells by Mesalamine by Activating the Aryl Hydrocarbon Receptor.

PubMed

Oh-Oka, Kyoko; Kojima, Yuko; Uchida, Koichiro; Yoda, Kimiko; Ishimaru, Kayoko; Nakajima, Shotaro; Hemmi, Jun; Kano, Hiroshi; Fujii-Kuriyama, Yoshiaki; Katoh, Ryohei; Ito, Hiroyuki; Nakao, Atsuhito

2017-07-01

Mesalamine is a first-line drug for treatment of inflammatory bowel diseases (IBD). However, its mechanisms are not fully understood. CD4 + Foxp3 + regulatory T cells (Tregs) play a potential role in suppressing IBD. This study determined whether the anti-inflammatory activity of mesalamine is related to Treg induction in the colon. We examined the frequencies of Tregs in the colons of wild-type mice, mice deficient for aryl hydrocarbon receptor ( AhR -/- mice), and bone marrow-chimeric mice lacking AhR in hematopoietic cells (BM- AhR -/- mice), following oral treatment with mesalamine. We also examined the effects of mesalamine on transforming growth factor (TGF)-β expression in the colon. Treatment of wild-type mice with mesalamine increased the accumulation of Tregs in the colon and up-regulated the AhR target gene Cyp1A1 , but this effect was not observed in AhR -/- or BM- AhR -/- mice. In addition, mesalamine promoted in vitro differentiation of naive T cells to Tregs, concomitant with AhR activation. Mice treated with mesalamine exhibited increased levels of the active form of TGF-β in the colon in an AhR-dependent manner and blockade of TGF-β signaling suppressed induction of Tregs by mesalamine in the colon. Furthermore, mice pretreated with mesalamine acquired resistance to dextran sodium sulfate-induced colitis. We propose a novel anti-inflammatory mechanism of mesalamine for colitis: induction of Tregs in the colon via the AhR pathway, followed by TGF-β activation.

The Aryl Hydrocarbon Receptor: Differential Contribution to T Helper 17 and T Cytotoxic 17 Cell Development

PubMed Central

Hayes, Mark D.; Ovcinnikovs, Vitalijs; Smith, Andrew G.; Kimber, Ian; Dearman, Rebecca J.

2014-01-01

The aryl hydrocarbon receptor (AhR) has been shown to be required for optimal Thelper (Th) 17 cell activation. Th17 cells provide immunity against extracellular pathogens and are implicated in autoimmune diseases. Herein, the role of the AhR in cytokine production by Th17, and by the analogous population of T cytotoxic (Tc)17 cells, has been examined. Lymph node Tc (CD8+) and Th (CD4+) cells were isolated by negative selection from naive AhR+/− and AhR−/− mice and polarised to Tc1/Th1 or Tc17/Th17 phenotypes with appropriate cytokines. Cell differentiation was assessed as a function of mRNA and protein (ELISA and flow cytometry) expression for interferon (IFN)-γ and for key Th17 cytokines. In AhR+/− mice, Th17 cells displayed an exclusive IL-17 profile, which was markedly inhibited by a selective AhR antagonist to levels observed in AhR knockout mice. Addition of the natural AhR agonist 6-formylindolo[3,2-b]carbazole (FICZ) markedly enhanced Th17 cell activity in the heterozygotes. In contrast, Tc17 cells polarised into 3 distinct subsets: producing either IL-17 or IFN-γ alone, or both cytokines. Blocking AhR was also detrimental to Tc17 development, with reduced responses recorded in AhR−/− mice and antagonist-mediated reduction of IL-17 expression in the heterozygotes. However, Tc17 cells were largely refractory to exogenous FICZ, presumably because Tc17 cells express baseline AhR mRNA, but unlike Th17 cells, there is no marked up-regulation during polarisation. Thus, Th17 cell development is more dependent upon AhR activation than is Tc17 cell development, suggesting that endogenous AhR ligands play a much greater role in driving Th17 cell responses. PMID:25203682

Detection of Aryl Hydrocarbon Receptor Activation by Some Chemicals in Food Using a Reporter Gene Assay

PubMed Central

Amakura, Yoshiaki; Tsutsumi, Tomoaki; Yoshimura, Morio; Nakamura, Masafumi; Handa, Hiroshi; Matsuda, Rieko; Teshima, Reiko; Watanabe, Takahiro

2016-01-01

The purpose of this study was to examine whether a simple bioassay used for the detection of dioxins (DXNs) could be applied to detect trace amounts of harmful DXN-like substances in food products. To identify substances with possible DXN-like activity, we assessed the ability of various compounds in the environment to bind the aryl hydrocarbon receptor (AhR) that binds specifically to DXNs. The compounds tested included 19 polycyclic aromatic hydrocarbons (PAHs), 20 PAH derivatives (nitrated, halogenated, and aminated derivatives), 23 pesticides, six amino acids, and eight amino acid metabolites. The AhR binding activities (AhR activity) of these compounds were measured using the chemical activated luciferase gene expression (CALUX) reporter gene assay system. The majority of the PAHs exhibited marked AhR activity that increased in a concentration-dependent manner. Furthermore, there was a positive link between AhR activity and the number of aromatic rings in the PAH derivatives. Conversely, there appeared to be a negative correlation between AhR activity and the number of chlorine residues present on halogenated PAH derivatives. However, there was no correlation between AhR activity and the number and position of substituents among nitrated and aminated derivatives. Among the pesticides tested, the indole-type compounds carbendazim and thiabendazole showed high levels of activity. Similarly, the indole compound tryptamine was the only amino acid metabolite to induce AhR activity. The results are useful in understanding the identification and characterization of AhR ligands in the CALUX assay. PMID:28231110

Role of aryl hydrocarbon receptor in mesenchymal stromal cell activation: A minireview.

PubMed

de Almeida, Danilo Candido; Evangelista, Laura Sibele Martins; Câmara, Niels Olsen Saraiva

2017-09-26

Mesenchymal stromal cells (MSCs) possess great therapeutic advantages due to their ability to produce a diverse array of trophic/growth factors related to cytoprotection and immunoregulation. MSC activation via specific receptors is a crucial event for these cells to exert their immunosuppressive response. The aryl-hydrocarbon receptor (AhR) is a sensitive molecule for external signals and it is expressed in MSCs and, upon positive activation, may potentially regulate the MSC-associated immunomodulatory function. Consequently, signalling pathways linked to AhR activation can elucidate some of the molecular cascades involved in MSC-mediated immunosuppression. In this minireview, we have noted some important findings concerning MSC regulation via AhR, highlighting that its activation is associated with improvement in migration and immunoregulation, as well as an increase in pro-regenerative potential. Thus, AhR-mediated MSC activation can contribute to new perspectives on MSC-based therapies, particularly those directed at immune-associated disorders.

Xenobiotics and loss of cell adhesion drive distinct transcriptional outcomes by aryl hydrocarbon receptor signaling.

PubMed

Hao, Nan; Lee, Kian Leong; Furness, Sebastian G B; Bosdotter, Cecilia; Poellinger, Lorenz; Whitelaw, Murray L

2012-12-01

The aryl hydrocarbon receptor (AhR) is a signal-regulated transcription factor, which is canonically activated by the direct binding of xenobiotics. In addition, switching cells from adherent to suspension culture also activates the AhR, representing a nonxenobiotic, physiological activation of AhR signaling. Here, we show that the AhR is recruited to target gene enhancers in both ligand [isopropyl-2-(1,3-dithietane-2-ylidene)-2-[N-(4-methylthiazol-2-yl)carbamoyl]acetate (YH439)]-treated and suspension cells, suggesting a common mechanism of target gene induction between these two routes of AhR activation. However, gene expression profiles critically differ between xenobiotic- and suspension-activated AhR signaling. Por and Cldnd1 were regulated predominantly by ligand treatments, whereas, in contrast, ApoER2 and Ganc were regulated predominantly by the suspension condition. Classic xenobiotic-metabolizing AhR targets such as Cyp1a1, Cyp1b1, and Nqo1 were regulated by both ligand and suspension conditions. Temporal expression patterns of AhR target genes were also found to vary, with examples of transient activation, transient repression, or sustained alterations in expression. Furthermore, sequence analysis coupled with chromatin immunoprecipitation assays and reporter gene analysis identified a functional xenobiotic response element (XRE) in the intron 1 of the mouse Tiparp gene, which was also bound by hypoxia-inducible factor-1α during hypoxia and features a concatemer of four XRE cores (GCGTG). Our data suggest that this XRE concatemer site concurrently regulates the expression of both the Tiparp gene and its cis antisense noncoding RNA after ligand- or suspension-induced AhR activation. This work provides novel insights into how AhR signaling drives different transcriptional programs via the ligand versus suspension modes of activation.

Triclosan activates aryl hydrocarbon receptor (AhR)-dependent apoptosis and affects Cyp1a1 and Cyp1b1 expression in mouse neocortical neurons.

PubMed

Szychowski, Konrad A; Wnuk, Agnieszka; Kajta, Małgorzata; Wójtowicz, Anna K

2016-11-01

Triclosan (TCS) is an antimicrobial agent that is used extensively in personal care and in sanitizing products, such as soaps, toothpastes, and hair products. A number of studies have revealed the presence of TCS in human tissues, such as fat, liver and brain, in addition to blood and breast milk. The aim of the present study was to investigate the impact of TCS on AhR and Cyp1a1/Cyp1b1 signaling in mouse neocortical neurons in primary cultures. In addition to the use of selective ligands and siRNAs, expression levels of mRNA and proteins as well as caspase-3 activity, reactive oxygen species (ROS) formation, and lactate dehydrogenase (LDH) release have been measured. We also studied the involvement of the AhR in TCS-induced LDH release and caspase-3 activation as well as the effect of TCS on ROS generation. Cultures of neocortical neurons were prepared from Swiss mouse embryos on day 15/16 of gestation. The cells were cultured in phenol red-free Neurobasal medium with B27 and glutamine, and the neurons were exposed to 1 and 10µM TCS. Our experiments showed that the expression of AhR and Cyp1a1 mRNA decreased in cells exposed to 10µM TCS for 3 or 6h. In the case of Cyp1b1, mRNA expression remained unchanged compared with the control group following 3h of exposure to TCS, but after 6h, the mRNA expression of Cyp1b1 was decreased. Our results confirmed that the AhR is involved in the TCS mechanism of action, and our data demonstrated that after the cells were transfected with AhR siRNA, the cytotoxic and pro-apoptotic properties of TCS were decreased. The decrease in Cyp1a1 mRNA and protein expression levels accompanied by a decrease in its activity. The stimulation of Cyp1a1 activity produced by the application of an AhR agonist (βNF) was attenuated by TCS, whereas the addition of AhR antagonist (αNF) reversed the inhibitory effects of TCS. In our experiments, TCS diminished Cyp1b1 mRNA and enhanced its protein expression. In case of Cyp1a1 we observed

Towards Targeting the Aryl Hydrocarbon Receptor in Cystic Fibrosis

PubMed Central

Paolicelli, Giuseppe; De Luca, Antonella; Renga, Giorgia; Borghi, Monica; Pariano, Marilena; Stincardini, Claudia; Scaringi, Lucia; Ricci, Maurizio; Romani, Luigina

2018-01-01

Tryptophan (trp) metabolism is an important regulatory component of gut mucosal homeostasis and the microbiome. Metabolic pathways targeting the trp can lead to a myriad of metabolites, of both host and microbial origins, some of which act as endogenous low-affinity ligands for the aryl hydrocarbon receptor (AhR), a cytosolic, ligand-operated transcription factor that is involved in many biological processes, including development, cellular differentiation and proliferation, xenobiotic metabolism, and the immune response. Low-level activation of AhR by endogenous ligands is beneficial in the maintenance of immune health and intestinal homeostasis. We have defined a functional node whereby certain bacteria species contribute to host/microbial symbiosis and mucosal homeostasis. A microbial trp metabolic pathway leading to the production of indole-3-aldehyde (3-IAld) by lactobacilli provided epithelial protection while inducing antifungal resistance via the AhR/IL-22 axis. In this review, we highlight the role of AhR in inflammatory lung diseases and discuss the possible therapeutic use of AhR ligands in cystic fibrosis. PMID:29670460

Divergent Ah Receptor Ligand Selectivity during Hominin Evolution

PubMed Central

Hubbard, Troy D.; Murray, Iain A.; Bisson, William H.; Sullivan, Alexis P.; Sebastian, Aswathy; Perry, George H.; Jablonski, Nina G.; Perdew, Gary H.

2016-01-01

We have identified a fixed nonsynonymous sequence difference between humans (Val381; derived variant) and Neandertals (Ala381; ancestral variant) in the ligand-binding domain of the aryl hydrocarbon receptor (AHR) gene. In an exome sequence analysis of four Neandertal and Denisovan individuals compared with nine modern humans, there are only 90 total nucleotide sites genome-wide for which archaic hominins are fixed for the ancestral nonsynonymous variant and the modern humans are fixed for the derived variant. Of those sites, only 27, including Val381 in the AHR, also have no reported variability in the human dbSNP database, further suggesting that this highly conserved functional variant is a rare event. Functional analysis of the amino acid variant Ala381 within the AHR carried by Neandertals and nonhuman primates indicate enhanced polycyclic aromatic hydrocarbon (PAH) binding, DNA binding capacity, and AHR mediated transcriptional activity compared with the human AHR. Also relative to human AHR, the Neandertal AHR exhibited 150–1000 times greater sensitivity to induction of Cyp1a1 and Cyp1b1 expression by PAHs (e.g., benzo(a)pyrene). The resulting CYP1A1/CYP1B1 enzymes are responsible for PAH first pass metabolism, which can result in the generation of toxic intermediates and perhaps AHR-associated toxicities. In contrast, the human AHR retains the ancestral sensitivity observed in primates to nontoxic endogenous AHR ligands (e.g., indole, indoxyl sulfate). Our findings reveal that a functionally significant change in the AHR occurred uniquely in humans, relative to other primates, that would attenuate the response to many environmental pollutants, including chemicals present in smoke from fire use during cooking. PMID:27486223

Aryl Hydrocarbon Receptor-Dependent Retention of Nuclear HuR Suppresses Cigarette Smoke-Induced Cyclooxygenase-2 Expression Independent of DNA-Binding

PubMed Central

Zago, Michela; Sheridan, Jared A.; Nair, Parameswaran; Rico de Souza, Angela; Gallouzi, Imed-Eddine; Rousseau, Simon; Di Marco, Sergio; Hamid, Qutayba; Eidelman, David H.; Baglole, Carolyn J.

2013-01-01

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that responds to man-made environmental toxicants, has emerged as an endogenous regulator of cyclooxygenase-2 (Cox-2) by a mechanism that is poorly understood. In this study, we first used AhR-deficient (AhR−/−) primary pulmonary cells, together with pharmacological tools to inhibit new RNA synthesis, to show that the AhR is a prominent factor in the destabilization of Cox-2 mRNA. The destabilization of Cox-2 mRNA and subsequent suppression of cigarette smoke-induced COX-2 protein expression by the AhR was independent of its ability to bind the dioxin response element (DRE), thereby differentiating the DRE-driven toxicological AhR pathway from its anti-inflammatory abilities. We further describe that the AhR destabilizes Cox-2 mRNA by sequestering HuR within the nucleus. The role of HuR in AhR stabilization of Cox-2 mRNA was confirmed by knockdown of HuR, which resulted in rapid Cox-2 mRNA degradation. Finally, in the lungs of AhR−/− mice exposed to cigarette smoke, there was little Cox-2 mRNA despite robust COX-2 protein expression, a finding that correlates with almost exclusive cytoplasmic HuR within the lungs of AhR−/− mice. Therefore, we propose that the AhR plays an important role in suppressing the expression of inflammatory proteins, a function that extends beyond the ability of the AhR to respond to man-made toxicants. These findings open the possibility that a DRE-independent AhR pathway may be exploited therapeutically as an anti-inflammatory target. PMID:24086407

Bioactive terpenoids and flavonoids from ginkgo biloba extract induce the expression of hepatic drug-metabolizing enzymes through Pregnane X receptor, Constitutive androstane receptor, and Aryl hydrocarbon receptor-mediated pathways

PubMed Central

Li, Linhao; Stanton, Joseph D; Tolson, Antonia H; Luo, Yuan; Wang, Hongbing

2008-01-01

Purpose The objective of the current study is to investigate the hypothesis that bioactive terpenoids and flavonoids of Ginkgo biloba extract (GBE) induce human hepatic drug metabolizing enzymes (DMEs) and transporters through the selective activation of pregnane X receptor (PXR), constitutive androstane receptor (CAR), and aryl hydrocarbon receptor (AhR). Methods Human primary hepatocyte (HPH), and HepG2 cells are used as in vitro models for enzyme induction and nuclear receptor activation studies. A combination of real-time RT-PCR, transient transfection, and cell-based reporter assays were employed. Results In human primary hepatocytes, real-time PCR analysis showed induction of CYP2B6, CYP3A4, UGT1A1, MDR1, and MRP2 by EGb 761, ginkgolide A (GA) and ginkgolide B (GB), but not by bilobalide (BB) or the flavonoids (quercetin, kaempferol and tamarixetin) of GBE. Cell-based reporter assays in HepG2 revealed that GA and GB are potent activators of PXR; quercetin and kaempferol activate PXR, CAR, and AhR, whereas BB exerts no effects on these xenobiotic receptors. Notably, the flavonoids induced the expression of UGT1A1 and CYP1A2 in HepG2 cells but not in HPH. Conclusion Our results indicate that terpenoids and flavonoids of GBE exhibit differential induction of DMEs through the selective activation of PXR, CAR, and AhR. PMID:19034627

Omeprazole Attenuates Pulmonary Aryl Hydrocarbon Receptor Activation and Potentiates Hyperoxia-Induced Developmental Lung Injury in Newborn Mice.

PubMed

Shivanna, Binoy; Zhang, Shaojie; Patel, Ananddeep; Jiang, Weiwu; Wang, Lihua; Welty, Stephen E; Moorthy, Bhagavatula

2015-11-01

Hyperoxia contributes to the development of bronchopulmonary dysplasia (BPD) in human preterm infants and a similar lung phenotype characterized by alveolar simplification in newborn mice. Omeprazole (OM) is a proton pump inhibitor that is used to treat humans with gastric acid related disorders. OM-mediated aryl hydrocarbon receptor (AhR) activation attenuates acute hyperoxic lung injury (HLI) in adult mice. Whether OM activates pulmonary AhR and protects C57BL/6J newborn mice against hyperoxia-induced developmental lung (alveolar and pulmonary vascular simplification, inflammation, and oxidative stress) injury (HDLI) is unknown. Therefore, we tested the hypothesis that OM will activate pulmonary AhR and mitigate HDLI in newborn mice. Newborn mice were treated daily with i.p. injections of OM at doses of 10 (OM10) or 25 (OM25) mg/kg while being exposed to air or hyperoxia (FiO2 of 85%) for 14 days, following which their lungs were harvested to determine alveolarization, pulmonary vascularization, inflammation, oxidative stress, vascular injury, and AhR activation. To our surprise, hyperoxia-induced alveolar and pulmonary vascular simplification, inflammation, oxidative stress, and vascular injury were augmented in OM25-treated animals. These findings were associated with attenuated pulmonary vascular endothelial growth factor receptor 2 expression and decreased pulmonary AhR activation in the OM25 group. We conclude that contrary to our hypothesis, OM decreases functional activation of pulmonary AhR and potentiates HDLI in newborn mice. These observations are consistent with our previous findings, which suggest that AhR activation plays a protective role in HDLI in newborn mice. © The Author 2015. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Introducing the "TCDD-inducible AhR-Nrf2 gene battery".

PubMed

Yeager, Ronnie L; Reisman, Scott A; Aleksunes, Lauren M; Klaassen, Curtis D

2009-10-01

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces genes via the transcription factor aryl hydrocarbon receptor (AhR), including Cyp1a1, NAD(P)H:quinone oxidoreductase 1 (Nqo1), UDP-glucuronosyltransferase 1a6 (Ugt1a6), and glutathione S-transferase a1 (Gsta1). These genes are referred to as the "AhR gene battery." However, Nqo1 is also considered a prototypical target gene of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2). In mice, TCDD induction of Nrf2 and Nrf2 target, Nqo1, is dependent on AhR, and thus TCDD induction of drug-processing genes may be routed through an AhR-Nrf2 sequence. There has been speculation that Nrf2 may be involved in the TCDD induction of drug-processing genes; however, the data are not definitive. Therefore, to address whether TCDD induction of Nqo1, Ugts, and Gsts is dependent on Nrf2, we conducted the definitive experiment by administering TCDD (50 mug/kg, ip) to Nrf2-null and wild-type (WT) mice and collecting livers 24 h later to quantify the mRNA of drug-processing genes. TCDD induction of Cyp1a1 and Ugt1a1 was similar in WT and Nrf2-null mice, whereas TCDD induction of Ugt1a5 and 1a9 was blunted in Nrf2-null mice. TCDD induced Nqo1, Ugt1a6, 2b34, 2b35, 2b36, UDP-glucuronic acid-synthesizing gene UDP-glucose dehydrogenase, and Gsta1, m1, m2, m3, m6, p2, t2, and microsomal Gst1 in WT mice but not in Nrf2-null mice. Therefore, the present study demonstrates the novel finding that Nrf2 is required for TCDD induction of classical AhR battery genes Nqo1, Ugt1a6, and Gsta1, as well as most Ugt and Gst isoforms in livers of mice.

Integrated in silico and in vivo approaches to investigate effects of BDE-99 mediated by the nuclear receptors on developing zebrafish.

PubMed

Zhang, Li; Jin, Yaru; Han, Zhihua; Liu, Hongling; Shi, Laihao; Hua, Xiaoxue; Doering, Jon A; Tang, Song; Giesy, John P; Yu, Hongxia

2018-03-01

One of the most abundant polybrominated diphenyl ethers (PBDEs) is 2,2',4,4',5-pentabromodiphenyl ether (BDE-99), which persists and potentially bioaccumulates in aquatic wildlife. Previous studies in mammals have shown that BDE-99 affects development and disrupts certain endocrine functions through signaling pathways mediated by nuclear receptors. However, fewer studies have investigated the potential of BDE-99 to interact with nuclear receptors in aquatic vertebrates such as fish. In the present study, interactions between BDE-99 and nuclear receptors were investigated by in silico and in vivo approaches. This PBDE was able to dock into the ligand-binding domain of zebrafish aryl hydrocarbon receptor 2 (AhR2) and pregnane X receptor (PXR). It had a significant effect on the transcriptional profiles of genes associated with AhR or PXR. Based on the developed cytoscape of all zebrafish genes, it was also inferred that AhR and PXR could interact via cross-talk. In addition, both the in silico and in vivo approaches found that BDE-99 affected peroxisome proliferator-activated receptor alpha (PPARα), glucocorticoid receptor, and thyroid receptor. Collectively, our results demonstrate for the first time detailed in silico evidence that BDE-99 can bind to and interact with zebrafish AhR and PXR. These findings can be used to elaborate the molecular mechanism of BDE-99 and guide more objective environmental risk assessments. Environ Toxicol Chem 2018;37:780-787. © 2017 SETAC. © 2017 SETAC.

The nuclear aryl hydocarbon receptor is involved in regulation of DNA repair and cell survival following treatment with ionizing radiation.

PubMed

Dittmann, K H; Rothmund, M C; Paasch, A; Mayer, C; Fehrenbacher, B; Schaller, M; Frauenstein, K; Fritsche, E; Haarmann-Stemmann, T; Braeuning, A; Rodemann, H P

2016-01-05

In the present study, we explored the role of the aryl hydrocarbon receptor (AhR) for γ-H2AX associated DNA repair in response to treatment with ionizing radiation. Ionizing radiation was able to stabilize AhR protein and to induce a nuclear translocation in a similar way as described for exposure to aromatic hydrocarbons. A comparable AhR protein stabilization was obtained by treatment with hydroxyl-nonenal-generated by radiation-induced lipid peroxidation. AhR knockdown resulted in significant radio-sensitization of both A549- and HaCaT cells. Under these conditions an increased amount of residual γ-H2AX foci and a delayed decline of γ-H2AX foci was observed. Knockdown of the co-activator ARNT, which is essential for transcriptional activation of AhR target genes, reduced AhR-dependent CYP1A expression in response to irradiation, but was without effect on the amount of residual γ-H2AX foci. Nuclear AhR was found in complex with γ-H2AX, DNA-PK, ATM and Lamin A. AhR and γ-H2AX form together nuclear foci, which disappear during DNA repair. Presence of nuclear AhR protein is associated with ATM activation and chromatin relaxation indicated by acetylation of histone H3. Taken together, we could show, that beyond the function as a transcription factor the nuclear AhR is involved in the regulation of DNA repair. Reduction of nuclear AhR inhibits DNA-double stand repair and radiosensitizes cells. First hints for its molecular mechanism suggest a role during ATM activation and chromatin relaxation, both essential for DNA repair. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Effects of currently used pesticides and their mixtures on the function of thyroid hormone and aryl hydrocarbon receptor in cell culture

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

Ghisari, Mandana; Long, Manhai; Tabbo, Agnese

Evidence suggest that exposure to pesticides can interfere with the endocrine system by multiple mechanisms. The endocrine disrupting potential of currently used pesticides in Denmark was analyzed as single compounds and in an equimolar mixture of 5 selected pesticides. The pesticides were previously analyzed for effects on the function of estrogen and androgen receptors, the aromatase enzyme and steroidogenesis in vitro. In this study, the effect on thyroid hormone (TH) function and aryl hydrocarbon receptor (AhR) transactivity was assessed using GH3 cell proliferation assay (T-screen) and AhR responsive luciferase reporter gene bioassay, respectively. Thirteen pesticides were analyzed as follows: 2-methyl-4-chlorophenoxyaceticmore » acid, terbuthylazine, iodosulfuron-methyl-sodium, mesosulfuron-methyl, metsulfuron-methyl, chlormequat chloride, bitertanol, propiconazole, prothioconazole, mancozeb and its metabolite ethylene thiourea, cypermethrin, tau-fluvalinate, and malathion (currently banned in DK). In the T-screen, prothioconazole, malathion, tau-fluvalinate, cypermethrin, terbuthylazine and mancozeb significantly stimulated and bitertanol and propiconazole slightly reduced the GH3 cell proliferation. In the presence of triiodothyronine (T3), prothioconazole, tau-fluvalinate, propiconazole, cypermethrin and bitertanol significantly antagonized the T3-induced GH3 cell proliferation. Eleven of the tested pesticides agonized the AhR function, and bitertanol and prothioconazole inhibited the basal AhR activity. Bitertanol, propiconazole, prothioconazole and cypermethrin antagonized the TCDD-induced AhR transactivation at the highest tested concentration. The 5-component mixture had inducing effect but the combined effect could not be predicted due to the presence of bitertanol eliciting inhibitory effect. Upon removal of bitertanol from the mixture, the remaining four pesticides acted additively. In conclusion, our data suggest that pesticides currently used in

The aryl hydrocarbon receptor modulates acute and late mast cell responses.

PubMed

Sibilano, Riccardo; Frossi, Barbara; Calvaruso, Marco; Danelli, Luca; Betto, Elena; Dall'Agnese, Alessandra; Tripodo, Claudio; Colombo, Mario P; Pucillo, Carlo E; Gri, Giorgia

2012-07-01

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor whose activity is modulated by xenobiotics as well as physiological ligands. These compounds may modulate inflammatory responses and contribute to the rising prevalence of allergic diseases observed in industrialized countries. Mast cells (MCs), located within tissues at the boundary of the external environment, represent a potential target of AhR ligands. In this study, we report that murine and human MCs constitutively express AhR, and its activation by the high-affinity ligand 6-formylindolo[3,2-b]carbazole (FICZ) determines a boost in degranulation. On the contrary, repeated exposure to FICZ inhibits MC degranulation. Accordingly, histamine release, in an in vivo passive systemic anaphylactic model, is exacerbated by a single dose and is attenuated by repetitive stimulation of AhR. FICZ-exposed MCs produce reactive oxygen species and IL-6 in response to cAMP-dependent signals. Moreover, AhR-activated MCs produce IL-17, a critical player in chronic inflammation and autoimmunity, suggesting a novel pathway for MC activation in the pathogenesis of these diseases. Indeed, histological analysis of patients with chronic obstructive pulmonary disease revealed an enrichment in AhR/IL-6 and AhR/IL-17 double-positive MCs within bronchial lamina propria. Thus, tissue-resident MCs could translate external chemical challenges through AhR by modulating allergic responses and contributing to the generation of inflammation-related diseases.

Aryl hydrocarbon receptor (AHR): "pioneer member" of the basic-helix/loop/helix per-Arnt-sim (bHLH/PAS) family of "sensors" of foreign and endogenous signals.

PubMed

Nebert, Daniel W

2017-07-01

The basic-helix/loop/helix per-Arnt-sim (bHLH/PAS) family comprises many transcription factors, found throughout all three kingdoms of life; bHLH/PAS members "sense" innumerable intracellular and extracellular "signals" - including endogenous compounds, foreign chemicals, gas molecules, redox potential, photons (light), gravity, heat, and osmotic pressure. These signals then initiate downstream signaling pathways involved in responding to that signal. The term "PAS", abbreviation for "per-Arnt-sim" was first coined in 1991. Although the mouse Arnt gene was not identified until 1991, evidence of its co-transcriptional binding partner, aryl hydrocarbon receptor (AHR), was first reported in 1974 as a "sensor" of foreign chemicals, up-regulating cytochrome P450 family 1 (CYP1) and other enzyme activities that usually metabolize the signaling chemical. Within a few years, AHR was proposed also to participate in inflammation. The mouse [Ah] locus was shown (1973-1989) to be relevant to chemical carcinogenesis, mutagenesis, toxicity and teratogenesis, the mouse Ahr gene was cloned in 1992, and the first Ahr(-/-) knockout mouse line was reported in 1995. After thousands of studies from the early 1970s to present day, we now realize that AHR participates in dozens of signaling pathways involved in critical-life processes, affecting virtually every organ and cell-type in the animal, including many invertebrates. Copyright © 2017 Elsevier Ltd. All rights reserved.

Maternal smoking during pregnancy and genetic polymorphisms in the Ah receptor, CYP1A1 and GSTM1 affect infant birth size in Japanese subjects.

PubMed

Sasaki, S; Kondo, T; Sata, F; Saijo, Y; Katoh, S; Nakajima, S; Ishizuka, M; Fujita, S; Kishi, R

2006-02-01

Genetic susceptibility to tobacco smoke might have relation to adverse pregnancy outcomes. To estimate the effects of maternal smoking and genetic polymorphisms on infant birth weight and length, we conducted a prospective cohort study of 293 women who delivered singleton live births in Sapporo, Japan. Birth weight and length were significantly lower among infants born to continuously smoking women having the aryl hydrocarbon receptor (AhR) wild type genotype (Arg/Arg; 211 g +/- 76 g; 1.2 cm +/- 0.4 cm, p < 0.01 and p < 0.01, respectively), the CYP1A1 variant genotype (m1/m2 + m2/m2; 170 g +/- 64 g, 0.8 cm +/- 0.3 cm, p < 0.01 and p < 0.05, respectively), or the GSTM1 null genotype (171 g +/- 58 g, 0.6 cm +/- 0.3 cm, p < 0.01 and p < 0.05, respectively). When combinations of these genotypes were considered, birth weight and length were significantly lower for infants of continuously smoking women in the AhR wild type + CYP1A1 variant group (315 g +/- 116 g; 1.7 cm +/- 0.6 cm, p < 0.01 and p < 0.01, respectively) and in the CYP1A1 variant + GSTM1 null group (237 g +/- 92 g; 1.3 cm +/- 0.5 cm, p < 0.05 and p < 0.01, respectively). These genotypes did not confer adverse effects among women who had never smoked; therefore, maternal smoking in combination with maternal AhR, CYP1A1 and GSTM1 genetic polymorphisms may adversely affect infant birth size.

Aryl hydrocarbon receptor (AHR) is a potential tumour suppressor in pituitary adenomas.

PubMed

Formosa, R; Borg, J; Vassallo, J

2017-08-01

Pituitary adenomas (PA) represent the largest group of intracranial neoplasms and yet the molecular mechanisms driving this disease remain largely unknown. The aim of this study was to use a high-throughput screening method to identify molecular pathways that may be playing a significant and consistent role in PA. RNA profiling using microarrays on eight local PAs identified the aryl hydrocarbon receptor (AHR) signalling pathway as a key canonical pathway downregulated in all PA types. This was confirmed by real-time PCR in 31 tumours. The AHR has been shown to regulate cell cycle progression in various cell types; however, its role in pituitary tissue has never been investigated. In order to validate the role of AHR in PA behaviour, further functional studies were undertaken. Over-expression of AHR in GH3 cells revealed a tumour suppressor potential independent of exogenous ligand activation by benzo α-pyrene (BαP). Cell cycle analysis and quantitative PCR of cell cycle regulator genes revealed that both unstimulated and BαP-stimulated AHR reduced E2F-driven transcription and altered expression of cell cycle regulator genes, thus increasing the percentage of cells in G 0 /G 1 phase and slowing the proliferation rate of GH3 cells. Co-immunoprecipitation confirmed the interaction between AHR and retinoblastoma (Rb1) protein supporting this as a functional mechanism for the observed reduction. Endogenous Ahr reduction using silencing RNA confirmed the tumour suppressive function of the Ahr. These data support a mechanistic pathway for the putative tumour suppressive role of AHR specifically in PA, possibly through its role as a cell cycle co-regulator, even in the absence of exogenous ligands. © 2017 The authors.

Aryl hydrocarbon receptor (AHR) is a potential tumour suppressor in pituitary adenomas

PubMed Central

Formosa, R; Borg, J

2017-01-01

Pituitary adenomas (PA) represent the largest group of intracranial neoplasms and yet the molecular mechanisms driving this disease remain largely unknown. The aim of this study was to use a high-throughput screening method to identify molecular pathways that may be playing a significant and consistent role in PA. RNA profiling using microarrays on eight local PAs identified the aryl hydrocarbon receptor (AHR) signalling pathway as a key canonical pathway downregulated in all PA types. This was confirmed by real-time PCR in 31 tumours. The AHR has been shown to regulate cell cycle progression in various cell types; however, its role in pituitary tissue has never been investigated. In order to validate the role of AHR in PA behaviour, further functional studies were undertaken. Over-expression of AHR in GH3 cells revealed a tumour suppressor potential independent of exogenous ligand activation by benzo α-pyrene (BαP). Cell cycle analysis and quantitative PCR of cell cycle regulator genes revealed that both unstimulated and BαP-stimulated AHR reduced E2F-driven transcription and altered expression of cell cycle regulator genes, thus increasing the percentage of cells in G0/G1 phase and slowing the proliferation rate of GH3 cells. Co-immunoprecipitation confirmed the interaction between AHR and retinoblastoma (Rb1) protein supporting this as a functional mechanism for the observed reduction. Endogenous Ahr reduction using silencing RNA confirmed the tumour suppressive function of the Ahr. These data support a mechanistic pathway for the putative tumour suppressive role of AHR specifically in PA, possibly through its role as a cell cycle co-regulator, even in the absence of exogenous ligands. PMID:28649092

Microbiome-Derived Tryptophan Metabolites and Their Aryl Hydrocarbon Receptor-Dependent Agonist and Antagonist Activities

PubMed Central

Jin, Un-Ho; Lee, Syng-Ook; Sridharan, Gautham; Lee, Kyongbum; Davidson, Laurie A.; Jayaraman, Arul; Chapkin, Robert S.; Alaniz, Robert

2014-01-01

The tryptophan metabolites indole, indole-3-acetate, and tryptamine were identified in mouse cecal extracts and fecal pellets by mass spectrometry. The aryl hydrocarbon receptor (AHR) agonist and antagonist activities of these microbiota-derived compounds were investigated in CaCo-2 intestinal cells as a model for understanding their interactions with colonic tissue, which is highly aryl hydrocarbon (Ah)–responsive. Activation of Ah-responsive genes demonstrated that tryptamine and indole 3-acetate were AHR agonists, whereas indole was an AHR antagonist that inhibited TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin)–induced CYP1A1 expression. In contrast, the tryptophan metabolites exhibited minimal anti-inflammatory activities, whereas TCDD decreased phorbol ester-induced CXCR4 [chemokine (C-X-C motif) receptor 4] gene expression, and this response was AHR dependent. These results demonstrate that the tryptophan metabolites indole, tryptamine, and indole-3-acetate modulate AHR-mediated responses in CaCo-2 cells, and concentrations of indole that exhibit AHR antagonist activity (100–250 μM) are detected in the intestinal microbiome. PMID:24563545

Activation of aryl hydrocarbon receptor regulates the LPS/IFNγ-induced inflammatory response by inducing ubiquitin-proteosomal and lysosomal degradation of RelA/p65.

PubMed

Domínguez-Acosta, O; Vega, L; Estrada-Muñiz, E; Rodríguez, M S; Gonzalez, F J; Elizondo, G

2018-06-21

Several studies have identified the aryl hydrocarbon receptor (AhR) as a negative regulator of the innate and adaptive immune responses. However, the molecular mechanisms by which this transcription factor exerts such modulatory effects are not well understood. Interaction between AhR and RelA/p65 has previously been reported. RelA/p65 is the major NFκB subunit that plays a critical role in immune responses to infection. The aim of the present study was to determine whether the activation of AhR disrupted RelA/p65 signaling in mouse peritoneal macrophages by decreasing its half-life. The data demonstrate that the activation of AhR by TCDD and β-naphthoflavone (β-NF) decreased protein levels of the pro-inflammatory cytokines TFN-α, IL-6 and IL-12 after macrophage activation with LPS/IFNγ. In an AhR-dependent manner, TCDD treatment induces RelA/p65 ubiquitination and proteosomal degradation, an effect dependent on AhR transcriptional activity. Activation of AhR also induced lysosome-like membrane structure formation in mouse peritoneal macrophages and RelA/p65 lysosome-dependent degradation. In conclusion, these results demonstrate that AhR activation promotes RelA/p65 protein degradation through the ubiquitin proteasome system, as well as through the lysosomes, resulting in decreased pro-inflammatory cytokine levels in mouse peritoneal macrophages. Copyright © 2018. Published by Elsevier Inc.

In vitro re-expression of the aryl hydrocarbon receptor (Ahr) in cultured Ahr-deficient mouse antral follicles partially restores the phenotype to that of cultured wild-type mouse follicles.

PubMed

Ziv-Gal, A; Gao, L; Karman, B N; Flaws, J A

2015-03-01

The aryl hydrocarbon receptor (AHR) mediates the toxic effects of various endocrine disrupting chemicals. In female mice, global deletion of the Ahr (AhrKO) results in slow growth of ovarian antral follicles. No studies, however, have examined whether injection of the Ahr restores the phenotypes of cultured AhrKO ovarian antral follicles to wild-type levels. We developed a system to construct a recombinant adenovirus containing the Ahr to re-express the Ahr in AhrKO granulosa cells and whole antral follicles. We then compared follicle growth and levels of factors in the AHR signaling pathway (Ahr, Ahrr, Cyp1a1, and Cyp1b1) in wild-type, AhrKO, and Ahr re-expressed follicles. Further, we compared the response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in wild-type, AhrKO, and Ahr re-expressed follicles. Ahr injection into AhrKO follicles partially restored their growth pattern to wild-type levels. Further, Ahr re-expressed follicles had significantly higher levels of Ahr, Ahrr, Cyp1a1, and Cyp1b1 compared to wild-type follicles. Upon TCDD treatment, only Cyp1a1 levels were significantly higher in Ahr re-expressed follicles compared to the levels in wild-type follicles. Our system of re-expression of the Ahr partially restores follicle growth and transcript levels of factors in the AHR signaling pathway to wild-type levels. Copyright © 2014 Elsevier Ltd. All rights reserved.

Aryl hydrocarbon receptor

PubMed Central

Kiss, Elina A.; Vonarbourg, Cedric

2012-01-01

Intestinal homeostasis results from a complex mutualism between gut microbiota and host cells. Defining the molecular network regulating such mutualism is currently of increasing interest, as its deregulation is reported to lead to increased susceptibility to infections, chronic inflammatory bowel diseases and cancer. Until now, the focus has been on the mechanism, by which the composition of indigenous microbiota shapes the immune system. In a recent study, we have shown that dietary compounds have also the ability to affect innate immune system. This regulation involves aryl hydrocarbon receptor (AhR), a sensor of plant-derived phytochemicals, which mediates the maintenance of Retinoic acid related orphan receptor γ t-expressing innate lymphoid cells (RORγt+ ILC) in the gut and consequently formation of postnatal lymphoid follicles. Thus, AhR represents the first evidence of a molecular link between diet and immunity at intestinal mucosal surfaces. PMID:22909905

Buprenorphine, Norbuprenorphine, R-Methadone, and S-Methadone Upregulate BCRP/ABCG2 Expression by Activating Aryl Hydrocarbon Receptor in Human Placental Trophoblasts

PubMed Central

Neradugomma, Naveen K.; Liao, Michael Z.

2017-01-01

Opioid dependence during pregnancy is a rising concern. Maintaining addicted pregnant women on long-acting opioid receptor agonist is the most common strategy to manage drug abuse in pregnant women. Methadone (MET) and buprenorphine (BUP) are widely prescribed for opiate maintenance therapy. Norbuprenorphine (NBUP) is the primary active metabolite of BUP. These medications can cross the placenta to the fetus, leading to postpartum neonatal abstinence syndrome. Despite their use during pregnancy, little is known about the cellular changes in the placenta brought about by these drugs. In this study, we showed that BUP, NBUP, and MET at clinically relevant plasma concentrations significantly induced BCRP mRNA up to 10-fold in human model placental JEG3 and BeWo cells and in primary human villous trophoblasts, and this induction was abrogated by CH223191, an aryl hydrocarbon receptor (AhR)-specific antagonist. These drugs increased AhR recruitment onto the AhR-response elements and significantly induced breast cancer resistance protein (BCRP) gene transcription. AhR overexpression further increased BCRP mRNA and protein expression. Knockdown of AhR by shRNA decreased BCRP expression, and this decrease was reversed by rescuing AhR expression. Finally, induction of BCRP expression in JEG3 and BeWo cells was accompanied by an increase in its efflux activity. Collectively, we have demonstrated, for the first time, that BUP, NBUP, and MET are potent AhR agonists and can induce BCRP in human placental trophoblasts by activating AhR. Given the critical role of BCRP in limiting fetal exposure to drugs and xenobiotics, long-term use of these medications may affect fetal drug exposure by altering BCRP expression in human placenta. PMID:27974484

The aryl hydrocarbon receptor: multitasking in the immune system.

PubMed

Stockinger, Brigitta; Di Meglio, Paola; Gialitakis, Manolis; Duarte, João H

2014-01-01

The aryl hydrocarbon receptor (AhR), for many years almost exclusively studied by the pharmacology/toxicology field for its role in mediating the toxicity of xenobiotics such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), has more recently attracted the attention of immunologists. The evolutionary conservation of this transcription factor and its widespread expression in the immune system point to important physiological functions that are slowly being unraveled. In particular, the emphasis is now shifting from the role of AhR in the xenobiotic pathway toward its mode of action in response to physiological ligands. In this article, we review the current understanding of the molecular interactions and functions of AhR in the immune system in steady state and in the presence of infection and inflammation, with a focus on barrier organs such as the skin, the gut, and the lung.

γ-Tocotrienol upregulates aryl hydrocarbon receptor expression and enhances the anticancer effect of baicalein

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

Yamashita, Shuya; Baba, Kiwako; Makio, Akiko

2016-05-13

Previous studies have identified biomolecules that mediate the physiological actions of food factors, such as amino acids, vitamins, fatty acids, minerals, plant polyphenols, and lactobacilli, suggesting that our bodies are equipped with an innate system that senses which food factors are required to maintain our health. However, the effects of environmental factors on food factor sensing (FFS) remains largely unknown. Tocotorienols (T3s), which belongs to the vitamin E family, possess several physiological functions, including cholesterol lowering and neuroprotective effects. Here, we investigated the effects of naturally abundant γ-T3 on FFS-related gene expressions in melanoma using a DNA chip. Our resultsmore » showed that γ-T3 increased the expression level of aryl hydrocarbon receptor (AhR), a sensing molecule to plant polyphenol baicalein. The co-treatment with γ-T3 and baicalein enhanced the anti-proliferative activity of baicalein, accompanied by the downstream events of AhR-activation induced by baicalein. These data suggest that γ-T3 upregulates AhR expression and enhances its sensitivity to baicalein. - Highlights: • γ-T3 upregulated the expression of AhR in mouse melanoma. • Promotion of the binding activity of Sp1 is associated with the increasing effect of γ-T3 on AhR expression. • γ-T3 enhanced the anti-proliferative activity of baicalein that has an AhR ligand activity. • γ-T3 enhanced the inducing activity of baicalein on the expression of AhR target genes.« less

Water exposure assessment of aryl hydrocarbon receptor agonists in Three Gorges Reservoir, China using SPMD-based virtual organisms.

PubMed

Wang, Jingxian; Bernhöft, Silke; Pfister, Gerd; Schramm, Karl-Werner

2014-10-15

SPMD-based virtual organisms (VOs) were deployed at five to eight sites in the Three Gorges Reservoir (TGR), China for five periods in 2008, 2009 and 2011. The water exposure of aryl hydrocarbon receptor (AhR) agonists was assessed by the VOs. The chosen bioassay response for the extracts of the VOs, the induction of 7-ethoxyresorufin-O-deethylase (EROD) was assayed using a rat hepatoma cell line (H4IIE). The results show that the extracts from the VOs could induce AhR activity significantly, whereas the chemically derived 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalent (TEQcal) accounted for <11% of the observed AhR responses (TEQbio). Unidentified AhR-active compounds represented a greater proportion of the TCDD equivalent in VOs from TGR. High TEQbio value in diluted extract and low TEQbio in concentrated extract of the same sample was observed suggesting potential non-additive effects in the mixture. The levels of AhR agonists in VOs from upstream TGR were in general higher than those from downstream reservoir, indicating urbanization effect on AhR agonist pollution. The temporal variation showed that levels of AhR agonists in 2009 and 2011 were higher than those in 2008, and the potential non-additive effects in the area close to the dam were also obviously higher in 2009 and 2011 than in 2008, indicating big changes in the composition of pollutants in the area after water level reached a maximum of 175 m. Although the aqueous concentration of AhR agonists of 0.8-4.8 pg TCDDL(-1) in TGR was not alarming, the tendency of accumulating high concentration of AhR agonists in VO lipid and existence of possible synergism or antagonism in the water may exhibit a potential hazard to local biota being exposed to AhR agonists. Copyright © 2014 Elsevier B.V. All rights reserved.

Identification of the Ah-Receptor Structural Determinants for Ligand Preferences

PubMed Central

Xing, Yongna

2012-01-01

The aryl hydrocarbon receptor (AHR) is a transcription factor that responds to diverse ligands and plays a critical role in toxicology, immune function, and cardiovascular physiology. The structural basis of the AHR for ligand promiscuity and preferences is critical for understanding AHR function. Based on the structure of a closely related protein HIF2α, we modeled the AHR ligand binding domain (LBD) bound to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and benzo(a)pyrene (BaP) and identified residues that control ligand preferences by shape and H-bond potential. Mutations to these residues, particularly Q377 and G298, resulted in robust and opposite changes in the potency of TCDD and BaP and up to a 20-fold change in the ratio of TCDD/BaP efficacy. The model also revealed a flexible “belt” structure; molecular dynamic (MD) simulation suggested that the “belt” and several other structural elements in the AHR-LBD are more flexible than HIF2α and likely contribute to ligand promiscuity. Molecular docking of TCDD congeners to a model of human AHR-LBD ranks their binding affinity similar to experimental ranking of their toxicity. Our study reveals key structural basis for prediction of toxicity and understanding the AHR signaling through diverse ligands. PMID:22659362

Persistent aryl hydrocarbon receptor inducers increase with altitude, and estrogen-like disrupters are low in soils of the Alps.

PubMed

Levy, Walkiria; Henkelmann, Bernhard; Bernhöft, Silke; Bovee, Toine; Buegger, Franz; Jakobi, Gert; Kirchner, Manfred; Bassan, Rodolfo; Kräuchi, Norbert; Moche, Wolfgang; Offenthaler, Ivo; Simončič, Primoz; Weiss, Peter; Schramm, Karl-Werner

2011-01-01

Soil samples from remote Alpine areas were analyzed for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans and polychlorinated biphenyls by high-resolution gas chromatography/high-resolution gas spectrometry. Additionally, the EROD micro-assay and a genetically modified yeast estrogen bioassay were carried out to determine persistent aryl hydrocarbon receptors (AhR) and estrogen receptors (ER) agonists, respectively. Regarding the AhR agonists, the toxicity equivalents of analytical and EROD determined values were compared, targeting both altitude of samples and their soil organic content. The ratio between bioassay derived equivalents and analytical determinations suggested no significant contribution of unknown AhR inducers in these sampling sites and some antagonism in soils with relatively high PCB loading. More CYP1A1 expression was induced at the highest sites or about 1400-1500 m a.s.l. along the altitude profiles. Surprisingly, no clear tendencies with the soil organic content were found for dioxin-like compounds. Mean values obtained in the present study were for ER agonists, 2: 0.37±0.12ng 17ß-estradiol EQ g-1 dry soil [corrected] and 6.1 ± 4.2 pg TCDD-EQ g⁻¹ dry soil for AhR agonists. Low bioassay responses with a higher relative amount of ER disrupters than AhR inducers were detected,indicating the higher abundance of estrogen-like than persistent dioxin-like compounds in these forested areas [corrected].

Aryl Hydrocarbon Receptor activation by diesel exhaust particles mediates epithelium-derived cytokines expression in severe allergic asthma.

PubMed

Weng, Chih-Ming; Wang, Chun-Hua; Lee, Meng-Jung; He, Jung-Re; Huang, Hsin-Yu; Chao, Ming-Wei; Chung, Kian Fan; Kuo, Han-Pin

2018-04-19

Exposure to environmental pollutants promotes Th2 cell responses. Aryl hydrocarbon receptor (AhR) activation aggravates allergic responses. Epithelium-derived thymic stromal lymphopoietin (TSLP), interleukin (IL)-25 and IL-33 are implicated in the dysregulation of Th2 immune responses in severe allergic asthma. Bronchial biopsies of 28 allergic severe asthma and 6 mild asthma subjects from highly polluted areas were analyzed for AhR nuclear translocation (NT), cytokine expression and gene activation. Cultured primary epithelial cells were stimulated with diesel exhausted particles (DEP) to determine AhR-mediated IL-33, Il-25 and TSLP synthesis and release. Primary bronchial epithelial cells exposed to DEP showed up-regulation of IL-33, IL-25 and TSLP. These effects were abolished by knock-down of AhR by siRNA. Increased AhR/ARNT binding to promoters of IL-33, IL-25, and TSLP was found using chromatin immunoprecipitation (ChIP) assay. Allergic severe asthma with high AhR NT had higher bronchial gene and protein expression of IL-33, IL-25 and TSLP. These patients derived clinical benefit from anti-IgE treatment. AhR activation by DEP mediates up-regulation of IL-33, IL-25 and TSLP with Th2 activation, potentially linking environmental pollution and allergic severe asthma. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Recruitment of CREB1 and Histone Deacetylase 2 (HDAC2) to the Mouse Ltbp-1 Promoter Regulates its Constitutive Expression in a Dioxin Receptor-dependent Manner

PubMed Central

Gomez-Duran, Aurea; Ballestar, Esteban; Carvajal-Gonzalez, Jose M.; Marlowe, Jennifer L.; Puga, Alvaro; Esteller, Manel; Fernandez-Salguero, Pedro M.

2010-01-01

Latent TGFβ-binding protein 1 (LTBP-1) is a key regulator of TGFβ targeting and activation in the extracellular matrix. LTBP-1 is recognized as a major docking molecule to localize, and possibly to activate, TGFβ in the extracellular matrix. Despite this relevant function, the molecular mechanisms regulating Ltbp-1 transcription remain largely unknown. Previous results from our laboratory revealed that mouse embryonic fibroblasts (MEF) lacking dioxin receptor (AhR) had increased Ltbp-1 mRNA expression and elevated TGFβ activity, suggesting that AhR repressed Ltbp-1 transcription. Here, we have cloned the mouse Ltbp-1 gene promoter and analysed its mechanism of transcriptional repression by AhR. Reporter gene assays, AhR over-expression and site-directed mutagenesis showed that basal Ltbp-1 transcription is AhR-dependent. Chromatin immunoprecipitation (ChIP) and RNA interference (RNAi) revealed that AhR regulates Ltbp-1 transcription by a mechanism involving recruitment of co-activators such as CREB1 and co-repressors such as HDAC2 to the Ltbp-1 promoter. In AhR-expressing (AhR+/+) MEF cells, the recruitment of HDAC1, 2 and 4 correlated with decreased K8H4 acetylation and impaired binding of pCREBSer133 to the Ltbp-1 promoter, likely maintaining a constitutive repressed state. AhR−/− MEF cells had the opposite pattern of HDACs and pCREB1Ser133 binding to Ltbp-1 promoter, and therefore, over-expressed Ltbp-1 mRNA. In agreement, siRNA for HDAC2 increased Ltbp-1 expression and K8H4 acetylation in AhR+/+ but not in AhR−/− MEF cells. We suggest that HDAC2 binding keeps Ltbp-1 promoter repressed in AhR+/+ MEF cells, whereas in AhR-null MEF cells the absence of HDAC2 and the binding of pCREBSer133 allow Ltbp-1 transcription. Thus, epigenetics can contribute to constitutive Ltbp-1 repression by a mechanism requiring AhR activity. PMID:18508077

A potential endogenous ligand for the aryl hydrocarbon receptor has potent agonist activity in vitro and in vivo.

PubMed

Henry, E C; Bemis, J C; Henry, O; Kende, A S; Gasiewicz, T A

2006-06-01

The aryl hydrocarbon receptor (AhR) is best known as a mediator of toxicity of a diverse family of xenobiotic chemicals such as dioxins and PCBs. However, many naturally occurring compounds also activate AhR. One such compound, 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE), was isolated from tissue and found to be potent in preliminary tests [J. Song, M. Clagett-Dame, R.E. Peterson, M.E. Hahn, W.M. Westler, R.R. Sicinski, H.F. DeLuca, Proc. Natl. Acad. Sci. USA 99 (2002) 14694-14699]. We have synthesized ITE and [(3)H]ITE and further evaluated its AhR activity in several in vitro and in vivo assays in comparison with the toxic ligand, TCDD. AhR in Hepa1c1c7 cell cytosol bound [(3)H]ITE with high affinity and the AhR.ITE complex formed in vitro bound dioxin response element (DRE) oligonucleotide as potently as TCDD.AhR. In cells treated with ITE, nuclear translocation of AhR, and induction of CYP1A1 protein and of a DRE-dependent luciferase reporter gene were observed. ITE administered to pregnant DRE-LacZ transgenic mice activated fetal AhR, observed as X-gal staining in the same sites as in TCDD-treated mice. However, unlike TCDD, ITE did not induce cleft palate or hydronephrosis. TCDD but not ITE induced thymic atrophy in young adult mice, but both ITE and TCDD caused similar loss of cells and alterations of cell profiles in cultured fetal thymi. These data demonstrate that ITE is a potent AhR agonist in cell extracts, cultured cells, and intact animals, but does not cause the toxicity associated with the more stable xenobiotic ligand, TCDD.

Indole-3-Carbinol Promotes Goblet-Cell Differentiation Regulating Wnt and Notch Signaling Pathways AhR-Dependently.

PubMed

Park, Joo-Hung; Lee, Jeong-Min; Lee, Eun-Jin; Hwang, Won-Bhin; Kim, Da-Jeong

2018-04-30

Using an in vitro model of intestinal organoids derived from intestinal crypts, we examined effects of indole-3-carbinol (I3C), a phytochemical that has anticancer and aryl hydrocarbon receptor (AhR)-activating abilities and thus is sold as a dietary supplement, on the development of intestinal organoids and investigated the underlying mechanisms. I3C inhibited the in vitro development of mouse intestinal organoids. Addition of α-naphthoflavone, an AhR antagonist or AhR siRNA transfection, suppressed I3C function, suggesting that I3C-mediated interference with organoid development is AhR-dependent. I3C increased the expression of Muc2 and lysozyme, lineage-specific genes for goblet cells and Paneth cells, respectively, but inhibits the expression of IAP, a marker gene for enterocytes. In the intestines of mice treated with I3C, the number of goblet cells was reduced, but the number of Paneth cells and the depth and length of crypts and villi were not changed. I3C increased the level of active nonphosphorylated β-catenin, but suppressed the Notch signal. As a result, expression of Hes1, a Notch target gene and a transcriptional repressor that plays a key role in enterocyte differentiation, was reduced, whereas expression of Math1, involved in the differentiation of secretory lineages, was increased. These results provide direct evidence for the role of AhR in the regulation of the development of intestinal stem cells and indicate that such regulation is likely mediated by regulation of Wnt and Notch signals.

AHR-16303B, a novel antagonist of 5-HT2 receptors and voltage-sensitive calcium channels

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

Barrett, R.J.; Appell, K.C.; Kilpatrick, B.F.

1991-01-01

In vivo and in vitro methods were used to characterize AHR-16303B, a novel compound with antagonistic action at 5-HT2 receptors and voltage-sensitive calcium channels. The 5-HT2 receptor-antagonistic properties of AHR-16303B were demonstrated by inhibition of (a) (3H)ketanserin binding to rat cerebral cortical membranes (IC50 = 165 nM); (b) 5-hydroxytryptamine (5-HT)-induced foot edema in rats (minimum effective dose, (MED) = 0.32 mg/kg orally, p.o.); (c) 5-HT-induced vasopressor responses in spontaneously hypertensive rats (SHR) (ID50 = 0.18 mg/kg intravenously (i.v.), 1.8 mg/kg p.o.), (d) 5-HT-induced antidiuresis in rats (MED = 1 mg/kg p.o.), and (e) platelet aggregation induced by 5-HT + ADPmore » (IC50 = 1.5 mM). The calcium antagonist properties of AHR-16303B were demonstrated by inhibition of (a) (3H)nimodipine binding to voltage-sensitive calcium channels on rabbit skeletal muscle membranes (IC50 = 15 nM), (b) KCl-stimulated calcium flux into cultured PC12 cells (IC50 = 81 nM), and (c) CaCl2-induced contractions of rabbit thoracic aortic strips (pA2 = 8.84). AHR-16303B had little or no effect on binding of radioligands to dopamine2 (DA2) alpha 1, alpha 2, H1, 5-HT1 alpha, beta 2, muscarinic M1, or sigma opioid receptors; had no effect on 5-HT3 receptor-mediated vagal bradycardia; and had only minor negative inotropic, chronotropic, and dromotropic effects on isolated guinea pig atria. In conscious SHR, 30 mg/kg p.o. AHR-16303B completely prevented the vasopressor responses to i.v. 5-HT, and decreased blood pressure (BP) by 24% 3 h after dosing.« less

The aryl hydrocarbon receptor and food allergy.

PubMed

Schulz, V J; Smit, J J; Pieters, R H H

2013-06-01

The immune system is important for protection against pathogens and malignant cells. However, malfunction of the immune system can also result in detrimental auto-immune diseases, inflammatory diseases, cancers and allergies. The aryl hydrocarbon receptor (AhR), present in numerous tissues and cell subsets, including cells of the immune system, plays an important role in the functioning of the immune system. Activation of the AhR is for example associated with various effects on dendritic cells (DCs), regulatory T cells and the Th1/Th2 cell balance. These cells play a major role in the development of food allergy. Food allergy is an increasing health problem in both humans and animals. Despite the knowledge in risk factors and cellular mechanisms for food allergy, no approved treatments are available yet. Recently, it has been shown that activation of the AhR by dioxin-like compounds suppresses allergic sensitization by suppressing the absolute number of precursor and effector T cells, by preserving CD4(+)CD25(+)Foxp3(+) Treg cells and by affecting DCs and their interaction with effector T cells. Future research should elucidate whether and how AhR activation can be used to interfere in food allergic responses in humans and in animals. This may lead to new prevention strategies and therapeutic possibilities for food allergy.

Ahr function in lymphocytes: emerging concepts

PubMed Central

Zhou, Liang

2015-01-01

The aryl hydrocarbon receptor (Ahr) is an important regulator of the development and function of both innate and adaptive immune cells through roles associated with Ahr's ability to respond to cellular and dietary ligands. Recent findings have revealed tissue and context-specific functions for Ahr in both homeostasis and in during an immune response. I review these findings here, and integrate them into the current understanding of the mechanisms that regulate Ahr transcription and function. I propose a conceptual framework in which Ahr function is determined by three factors: the amount of Ahr in any given cell, the abundance and potency of Ahr ligands within certain tissues, and the tissue microenvironment wherein Ahr+ cells reside. This complexity emphasizes the necessity cell-type specific genetic approaches towards the study of Ahr function. PMID:26700314

Differential Effects of Omeprazole and Lansoprazole Enantiomers on Aryl Hydrocarbon Receptor in Human Hepatocytes and Cell Lines

PubMed Central

Novotna, Aneta; Srovnalova, Alzbeta; Svecarova, Michaela; Korhonova, Martina; Bartonkova, Iveta; Dvorak, Zdenek

2014-01-01

Proton pump inhibitors omeprazole and lansoprazole contain chiral sulfur atom and they are administered as a racemate, i.e. equimolar mixture of S- and R-enantiomers. The enantiopure drugs esomeprazole and dexlansoprazole have been developed and introduced to clinical practice due to their improved clinical and therapeutic properties. Since omeprazole and lansoprazole are activators of aryl hydrocarbon receptor (AhR) and inducers of CYP1A genes, we examined their enantiospecific effects on AhR-CYP1A pathway in human cancer cells and primary human hepatocytes. We performed gene reporter assays for transcriptional activity of AhR, RT-PCR analyses for CYP1A1/2 mRNAs, western blots for CYP1A1/2 proteins and EROD assay for CYP1A1/2 catalytic activity. Lansoprazole and omeprazole enantiomers displayed differential effects on AhR-CYP1A1/2 pathway. In general, S-enantiomers were stronger activators of AhR and inducers of CYP1A genes as compared to R-enantiomers in lower concentrations, i.e. 1–10 µM for lansoprazole and 10–100 µM for omeprazole. In contrast, R-enantiomers were stronger AhR activators and CYP1A inducers than S-enantiomers in higher concentrations, i.e. 100 µM for lansoprazole and 250 µM for omeprazole. In conclusion, we provide the first evidence of enantiospecific effects of omeprazole and lansoprazole on AhR signaling pathway. PMID:24887303

Macrophages from Behcet's Disease Patients Express Decreased Level of Aryl Hydrocarbon Receptor (AHR) mRNA.

PubMed

Palizgir, Mohammad Taghi; Akhtari, Maryam; Mahmoudi, Mahdi; Mostafaei, Shayan; Rezaeimanesh, Alireza; Akhlaghi, Massoomeh; Shahram, Farhad

2017-10-01

Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor, connecting environmental stimulators with the immune system. M1 macrophages are a part of immune system that contribute to the inflammatory events in the pathogenesis of Behcet's disease (BD). The effect of AHR on the macrophages in BD patients is still unclear. In this study, we investigated the mRNA expression of AHR in the monocyte-derived and M1 macrophages in active BD patients in comparison to healthy controls. Isolated monocytes from 10 healthy controls and 10 active BD patients were differentiated to macrophages by macrophage-colony stimulating factor (M-CSF) for 7 days. Cells were then polarized to M1 macrophages by lipopolysaccharide (LPS) and interferon-γ (IFNγ) for 24h. Monocyte purity and macrophage markers expression were analyzed by flow cytometry. Analysis of AHR mRNA expression was performed by SYBR Green real-time PCR. Our results showed that AHR expression is significantly down-regulated in M1 macrophages compare to monocyte-derived macrophages. It was shown that both monocyte-derived macrophages and M1 macrophages from BD patients significantly express lower level of AHR mRNA compared to healthy individuals. Our results demonstrate an anti-inflammatory role for AHR in macrophages, which suggest that decreased AHR expression is associated with pro-inflammatory M1 macrophage and BD susceptibility.

Genome-wide mapping and analysis of aryl hydrocarbon receptor (AHR)- and aryl hydrocarbon receptor repressor (AHRR)-binding sites in human breast cancer cells.

PubMed

Yang, Sunny Y; Ahmed, Shaimaa; Satheesh, Somisetty V; Matthews, Jason

2018-01-01

The aryl hydrocarbon receptor (AHR) mediates the toxic actions of environmental contaminants, such as 2,3,7,8-tetrachlorodibenzo-ρ-dioxin (TCDD), and also plays roles in vascular development, the immune response, and cell cycle regulation. The AHR repressor (AHRR) is an AHR-regulated gene and a negative regulator of AHR; however, the mechanisms of AHRR-dependent repression of AHR are unclear. In this study, we compared the genome-wide binding profiles of AHR and AHRR in MCF-7 human breast cancer cells treated for 24 h with TCDD using chromatin immunoprecipitation followed by next-generation sequencing (ChIP-Seq). We identified 3915 AHR- and 2811 AHRR-bound regions, of which 974 (35%) were common to both datasets. When these 24-h datasets were also compared with AHR-bound regions identified after 45 min of TCDD treatment, 67% (1884) of AHRR-bound regions overlapped with those of AHR. This analysis identified 994 unique AHRR-bound regions. AHRR-bound regions mapped closer to promoter regions when compared with AHR-bound regions. The AHRE was identified and overrepresented in AHR:AHRR-co-bound regions, AHR-only regions, and AHRR-only regions. Candidate unique AHR- and AHRR-bound regions were validated by ChIP-qPCR and their ability to regulate gene expression was confirmed by luciferase reporter gene assays. Overall, this study reveals that AHR and AHRR exhibit similar but also distinct genome-wide binding profiles, supporting the notion that AHRR is a context- and gene-specific repressor of AHR activity.

Benzo[a]pyrene activates an AhR/Src/ERK axis that contributes to CYP1A1 induction and stable DNA adducts formation in lung cells.

PubMed

Vázquez-Gómez, G; Rocha-Zavaleta, L; Rodríguez-Sosa, M; Petrosyan, P; Rubio-Lightbourn, J

2018-06-01

Benzo[a]pyrene (B[a]P), the most extensively studied carcinogen in cigarette smoke, has been regarded as a critical mediator of lung cancer. It is known that B[a]P-mediated Aryl hydrocarbon Receptor (AhR) activation stimulates the mitogen activated protein kinases (MAPK) signaling cascade in different cell models. MAPK pathway disturbances drive alterations in cellular processes, such as differentiation, proliferation, and apoptosis, and the disturbances may also modify the AhR pathway itself. However, MAPK involvement in B[a]P metabolic activation and toxicity in lung tissues is not well understood. Here, we used a non-transformed human bronchial epithelial lung cell line, BEAS-2B, to study the participation of ERK 1/2 kinases in the metabolic activation of B[a]P and in its related genotoxic effects. Our results indicate that B[a]P is not cytotoxic to BEAS-2B cells at relatively low concentrations, but it enhances CYP1A1 gene transcription and protein induction. Additionally, B[a]P promotes Src and ERK 1/2 phosphorylation. Accordingly, inhibition of both Src and ERK 1/2 phosphorylation decreases CYP1A1 protein induction, AhR nuclear translocation and production of B[a]P adducts. Together, these data suggest a crosstalk between AhR and the members of the MAPK pathway, ERK 1/2 mediated by Src kinase. This interaction is important for the adequate AhR pathway signaling that in turn induces transcription and protein induction of CYP1A1 and B[a]P-induced DNA damage in BEAS-2B cells. Copyright © 2018 Elsevier B.V. All rights reserved.

Inhibitory Ah Receptor-Androgen Receptor Crosstalk in Prostate Cancer

DTIC Science & Technology

2005-02-01

Balk,S.P. Selection for androgen receptor mutations in prostate cancers treated with androgen antagonist. Cancer Res. 59:2511-2515, 1999. 5. Ris...expression, 24-hydroxylase activity, and inhibition of growth hydrocarbon receptor modulators ( SARMs ) for treatment of breast by lca,25-dihydroxyvitamin D3...Safe, A. McDougal, M.S. Gupta, K. Ramamoorthy, Selective Ah [20] D.M. Peehl, R.J. Skowronski, G.K. Leung, S.T. Wong, T.A. Stamey, receptor modulators

Technical aspects of gel-based proteomics designed for elucidating an aryl hydrocarbon receptor complex.

PubMed

Wada, Yoshinao; Nakano, Norihiko

2004-01-01

The identification of proteins by mass spectrometry has revolutionalized the basic method of identifying proteins constituting an intracellular unit or network for certain biological functions. The gel-based strategy following immunoprecipitation was applied to elucidating proteins associated with the aryl hydrocarbon receptor (AhR). Two hundred femtomoles of AhR was recovered from approximately 2 x 10(7) HepG2 cells by immunoprecipitation and was sufficient for identification by peptide mass fingerprinting. Possible candidates for the AhR-associated proteins were also identified. Improvements of the current strategy to increase the overall sensitivity tenfold are required to clarify the AhR complex in full detail. For example, a combination of trypsin and Achromobacter protease I for in-gel digestion allows the number of missed cleavage sites to be set at zero for database searching, thereby reducing random matches and facilitating identification. There is also room for improvement in each step of sample preparation prior to mass spectrometry.

Potencies of red seabream AHR1- and AHR2-mediated transactivation by dioxins: implication of both AHRs in dioxin toxicity.

PubMed

Bak, Su-Min; Iida, Midori; Hirano, Masashi; Iwata, Hisato; Kim, Eun-Young

2013-03-19

To evaluate species- and isoform-specific responses to dioxins and related compounds (DRCs) via aryl hydrocarbon receptor (AHR) in the red seabream ( Pagrus major ), we constructed a reporter gene assay system. Each expression plasmid of red seabream AHR1 (rsAHR1) and AHR2 (rsAHR2) together with a reporter plasmid containing red seabream CYP1A 5'-flanking region were transfected into COS-7 cells. The cells were treated with graded concentrations of seven DRC congeners including 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 1,2,3,4,7,8-HxCDD, 2,3,7,8-TCDF, 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, and PCB126. Both rsAHR1 and rsAHR2 exhibited dose-dependent responses for all the tested congeners. The rsAHR isoform-specific TCDD induction equivalency factors (rsAHR1- and rsAHR2-IEFs) were calculated on the basis of 2,3,7,8-TCDD relative potency derived from the dose-response of each congener. The rsAHR1-IEFs of PeCDD, HxCDD, TCDF, PeCDF, and HxCDF were estimated as 0.17, 0.29, 2.5, 1.5, and 0.27, respectively. For PCB126, no rsAHR1-IEF was given because of less than 10% 2,3,7,8-TCDD maximum response. The rsAHR2-IEFs of PeCDD, HxCDD, TCDF, PeCDF, HxCDF, and PCB126 were estimated as 0.38, 0.13, 1.5, 0.93, 0.20, and 0.0085, respectively. The rsAHR1/2-IEF profiles were different from WHO toxic equivalency factors for fish. In silico docking simulations supported that both rsAHRs have potentials to bind to these congeners. These results suggest that dioxin toxicities may be mediated by both rsAHRs in red seabreams.

The aryl hydrocarbon receptor ligand ITE inhibits TGFβ1-induced human myofibroblast differentiation.

PubMed

Lehmann, Geniece M; Xi, Xia; Kulkarni, Ajit A; Olsen, Keith C; Pollock, Stephen J; Baglole, Carolyn J; Gupta, Shikha; Casey, Ann E; Huxlin, Krystel R; Sime, Patricia J; Feldon, Steven E; Phipps, Richard P

2011-04-01

Fibrosis can occur in any human tissue when the normal wound healing response is amplified. Such amplification results in fibroblast proliferation, myofibroblast differentiation, and excessive extracellular matrix deposition. Occurrence of these sequelae in organs such as the eye or lung can result in severe consequences to health. Unfortunately, medical treatment of fibrosis is limited by a lack of safe and effective therapies. These therapies may be developed by identifying agents that inhibit critical steps in fibrotic progression; one such step is myofibroblast differentiation triggered by transforming growth factor-β1 (TGFβ1). In this study, we demonstrate that TGFβ1-induced myofibroblast differentiation is blocked in human fibroblasts by a candidate endogenous aryl hydrocarbon receptor (AhR) ligand 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). Our data show that ITE disrupts TGFβ1 signaling by inhibiting the nuclear translocation of Smad2/3/4. Although ITE functions as an AhR agonist, and biologically persistent AhR agonists, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin, cause severe toxic effects, ITE exhibits no toxicity. Interestingly, ITE effectively inhibits TGFβ1-driven myofibroblast differentiation in AhR(-/-) fibroblasts: Its ability to inhibit TGFβ1 signaling is AhR independent. As supported by the results of this study, the small molecule ITE inhibits myofibroblast differentiation and may be useful clinically as an antiscarring agent. Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

Considerations for potency equivalent calculations in the Ah receptor-based CALUX bioassay: normalization of superinduction results for improved sample potency estimation.

PubMed

Baston, David S; Denison, Michael S

2011-02-15

The chemically activated luciferase expression (CALUX) system is a mechanistically based recombinant luciferase reporter gene cell bioassay used in combination with chemical extraction and clean-up methods for the detection and relative quantitation of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related dioxin-like halogenated aromatic hydrocarbons in a wide variety of sample matrices. While sample extracts containing complex mixtures of chemicals can produce a variety of distinct concentration-dependent luciferase induction responses in CALUX cells, these effects are produced through a common mechanism of action (i.e. the Ah receptor (AhR)) allowing normalization of results and sample potency determination. Here we describe the diversity in CALUX response to PCDD/Fs from sediment and soil extracts and not only report the occurrence of superinduction of the CALUX bioassay, but we describe a mechanistically based approach for normalization of superinduction data that results in a more accurate estimation of the relative potency of such sample extracts. Copyright © 2010 Elsevier B.V. All rights reserved.

Considerations for potency equivalent calculations in the Ah receptor-based CALUX bioassay: Normalization of superinduction results for improved sample potency estimation

PubMed Central

Baston, David S.; Denison, Michael S.

2011-01-01

The chemically activated luciferase expression (CALUX) system is a mechanistically based recombinant luciferase reporter gene cell bioassay used in combination with chemical extraction and clean-up methods for the detection and relative quantitation of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related dioxin-like halogenated aromatic hydrocarbons in a wide variety of sample matrices. While sample extracts containing complex mixtures of chemicals can produce a variety of distinct concentration-dependent luciferase induction responses in CALUX cells, these effects are produced through a common mechanism of action (i.e. the Ah receptor (AhR)) allowing normalization of results and sample potency determination. Here we describe the diversity in CALUX response to PCDD/Fs from sediment and soil extracts and not only report the occurrence of superinduction of the CALUX bioassay, but we describe a mechanistically based approach for normalization of superinduction data that results in a more accurate estimation of the relative potency of such sample extracts. PMID:21238730

Aryl hydrocarbon receptor (AHR) in the cnidarian Nematostella vectensis: comparative expression, protein interactions, and ligand binding.

PubMed

Reitzel, Adam M; Passamaneck, Yale J; Karchner, Sibel I; Franks, Diana G; Martindale, Mark Q; Tarrant, Ann M; Hahn, Mark E

2014-02-01

The aryl hydrocarbon receptor (AHR) is a member of the basic helix-loop-helix/Per-ARNT-Sim (bHLH-PAS) family of transcription factors and has diverse roles in development, physiology, and environmental sensing in bilaterian animals. Studying the expression of conserved genes and function of proteins in outgroups to protostomes and deuterostomes assists in understanding the antiquity of gene function and deciphering lineage-specific differences in these bilaterian clades. We describe the developmental expression of AHR from the sea anemone Nematostella vectensis and compare its expression with three other members of the bHLH-PAS family (AHR nuclear translocator (ARNT), Cycle, and a proto-Single-Minded/Trachealess). NvAHR expression was highest early in the larval stage with spatial expression in the basal portion of the ectoderm that became increasingly restricted to the oral pole with concentrated expression in tentacles of the juvenile polyp. The other bHLH-PAS genes showed a divergent expression pattern in later larval stages and polyps, in which gene expression was concentrated in the aboral end, with broader expression in the endoderm later in development. In co-immunoprecipitation assays, we found no evidence for heterodimerization of AHR with ARNT, contrary to the conservation of this specific interaction in all bilaterians studied to date. Similar to results with other invertebrate AHRs but in contrast to vertebrate AHRs, NvAHR failed to bind two prototypical xenobiotic AHR ligands (2,3,7,8-tetrachlorodibenzo-p-dioxin, β-naphthoflavone). Together, our data suggest that AHR's original function in Eumetazoa likely involved developmental patterning, potentially of neural tissue. The role of heterodimerization in the function of AHR may have arisen after the cnidarian-bilaterian ancestor. The absence of xenobiotic binding to NvAHR further supports a hypothesis for a derived role of this protein in chemical sensing within the chordates.

Aryl hydrocarbon receptor (AHR) in the cnidarian Nematostella vectensis: comparative expression, protein interactions, and ligand binding

PubMed Central

Reitzel, Adam M.; Passamaneck, Yale J.; Karchner, Sibel I.; Franks, Diana G.; Martindale, Mark Q.; Tarrant, Ann M.; Hahn, Mark E.

2014-01-01

The aryl hydrocarbon receptor (AHR) is a member of the basic-helix-loop-helix/Per-ARNT-Sim (bHLH-PAS) family of transcription factors and has diverse roles in development, physiology, and environmental sensing in bilaterian animals. Studying the expression of conserved genes and function of proteins in outgroups to protostomes and deuterostomes assists in understanding the antiquity of gene function and deciphering lineage-specific differences in these bilaterian clades. We describe the developmental expression of AHR from the sea anemone Nematostella vectensis and compare its expression with three other members of the bHLH-PAS family (AHR nuclear translocator (ARNT), Cycle, and a proto-Single-Minded/Trachaeless). NvAHR expression was highest early in the larval stage with spatial expression in the basal portion of the ectoderm that became increasingly restricted to the oral pole with concentrated expression in tentacles of the juvenile polyp. The other bHLH-PAS genes showed a divergent expression pattern in later larval stages and polyps, in which gene expression was concentrated in the aboral end, with broader expression in the endoderm later in development. In co-immunoprecipitation assays, we found no evidence for heterodimerization of AHR with ARNT, contrary to the conservation of this specific interaction in all bilaterians studied to date. Similar to results with other invertebrate AHRs but in contrast to vertebrate AHRs, NvAHR failed to bind two prototypical xenobiotic AHR ligands (TCDD, BNF). Together, our data suggest that AHR's original function in Eumetazoa likely involved developmental patterning, potentially of neural tissue. The role of heterodimerization in the function of AHR may have arisen after the cnidarian-bilaterian ancestor. The absence of xenobiotic binding to NvAHR further supports a hypothesis for a derived role of this protein in chemical sensing within the chordates. PMID:24292160

Coal dust alters β-naphthoflavone-induced aryl hydrocarbon receptor nuclear translocation in alveolar type II cells

PubMed Central

Ghanem, Mohamed M; Battelli, Lori A; Law, Brandon F; Castranova, Vincent; Kashon, Michael L; Nath, Joginder; Hubbs, Ann F

2009-01-01

Background Many polycyclic aromatic hydrocarbons (PAHs) can cause DNA adducts and initiate carcinogenesis. Mixed exposures to coal dust (CD) and PAHs are common in occupational settings. In the CD and PAH-exposed lung, CD increases apoptosis and causes alveolar type II (AT-II) cell hyperplasia but reduces CYP1A1 induction. Inflammation, but not apoptosis, appears etiologically associated with reduced CYP1A1 induction in this mixed exposure model. Many AT-II cells in the CD-exposed lungs have no detectable CYP1A1 induction after PAH exposure. Although AT-II cells are a small subfraction of lung cells, they are believed to be a potential progenitor cell for some lung cancers. Because CYP1A1 is induced via ligand-mediated nuclear translocation of the aryl hydrocarbon receptor (AhR), we investigated the effect of CD on PAH-induced nuclear translocation of AhR in AT-II cells isolated from in vivo-exposed rats. Rats received CD or vehicle (saline) by intratracheal (IT) instillation. Three days before sacrifice, half of the rats in each group started daily intraperitoneal injections of the PAH, β-naphthoflavone (BNF). Results Fourteen days after IT CD exposure and 1 day after the last intraperitoneal BNF injection, AhR immunofluorescence indicated that proportional AhR nuclear expression and the percentage of cells with nuclear AhR were significantly increased in rats receiving IT saline and BNF injections compared to vehicle controls. However, in CD-exposed rats, BNF did not significantly alter the nuclear localization or cytosolic expression of AhR compared to rats receiving CD and oil. Conclusion Our findings suggest that during particle and PAH mixed exposures, CD alters the BNF-induced nuclear translocation of AhR in AT-II cells. This provides an explanation for the modification of CYP1A1 induction in these cells. Thus, this study suggests that mechanisms for reduced PAH-induced CYP1A1 activity in the CD exposed lung include not only the effects of inflammation on

Indole-3-carbinol induces G1 cell cycle arrest and apoptosis through aryl hydrocarbon receptor in THP-1 monocytic cell line.

PubMed

Mohammadi, Saeed; Seyedhosseini, Fakhri Sadat; Behnampour, Nasser; Yazdani, Yaghoub

2017-10-01

The role of aryl hydrocarbon receptor (AhR) in carcinogenesis has been studied recently. Indole-3-carbinol (I3C) is an AhR agonist and a potential anticancer agent. Here, we investigated the effects of I3C on cell cycle progression and apoptosis through activation of AhR on THP-1 acute myeloid leukemia (AML) cell line. MTT viability assay was used to measure the cytotoxic effects of I3C on THP-1 cells. Apoptosis and cell cycle assays were investigated using flow cytometry. Real time RT-PCR was conducted to measure the alterations in the expression of AhR gene, key genes associated with AhR activation (IL1β and CYP1A1) and major genes involved in cell cycle regulation and apoptosis including P27, P21, CDK2, P53, BCL2 and FasR. Our findings revealed that I3C inhibits the proliferation of THP-1 cells in a dose- and time-dependent manner with minimal toxicity over normal monocytes. The AhR target genes (CYP1A1, IL1β) were overexpressed upon I3C treatment (p < .05 to p < .001). The antiproliferative effects of I3C were in association with programed cell death. I3C downregulated BCL2 and upregulated FasR in THP-1 cells (p < .05 to p < .001). G1 cell cycle arrest was also observed using flow cytometry. G1-acting cell cycle genes (P21, P27 and P53) were overexpressed (p < .05 to p < .001), while CDK2 was downregulated upon I3C treatment (p < .01 to p < .001). I3C could exert its antileukemic effects through AhR activation which is associated with programed cell death and G1 cell cycle arrest in a dose- and time-dependent manner. Therefore, AhR could be targeted as a novel treatment possibility in AML.

Association of aryl hydrocarbon receptor gene polymorphism with the neurobehavioral function and autonomic nervous system function changes induced by benzo[a]pyrene exposure in coke oven workers.

PubMed

Zhang, Hongmei; Nie, Jisheng; Li, Xin; Niu, Qiao

2013-03-01

To analyze the association of aryl hydrocarbon receptor (AhR) gene polymorphism and the neurotoxicity induced by benzo[a]pyrene (B[a]P) in coke oven workers. Subjects, 214 coke oven workers and 81 controls, were detected for neurobehavioral function and autonomic nervous system (ANS) function. Airborne B[a]P concentration, urinary 1-hydroxypyrene level, and AhR gene polymorphisms were determined and analyzed for their association with B[a]P neurotoxicity. Neurobehavioral function and ANS function were significantly decreased and dependent on B[a]P dose. The AhR GG, GA, and AA genotypes in G1661A fitted the Hardy-Weinberg equation, whereas C1549T and G1708A gene mutants were not detected. Indices indicating neurotoxicity showed no significant difference among individuals with AA, GG, or GA genotype except for the confusion-bewilderment (P > 0.05). The AhR gene polymorphism is not thought to correlate with B[a]P neurotoxicity among coke oven workers.

Metformin suppresses CYP1A1 and CYP1B1 expression in breast cancer cells by down-regulating aryl hydrocarbon receptor expression

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

Do, Minh Truong; Kim, Hyung Gyun; Tran, Thi Thu Phuong

2014-10-01

Induction of cytochrome P450 (CYP) 1A1 and CYP1B1 by environmental xenobiotic chemicals or endogenous ligands through the activation of the aryl hydrocarbon receptor (AhR) has been implicated in a variety of cellular processes related to cancer, such as transformation and tumorigenesis. Here, we investigated the effects of the anti-diabetes drug metformin on expression of CYP1A1 and CYP1B1 in breast cancer cells under constitutive and inducible conditions. Our results indicated that metformin down-regulated the expression of CYP1A1 and CYP1B1 in breast cancer cells under constitutive and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced conditions. Down-regulation of AhR expression was required for metformin-mediated decreases in CYP1A1 andmore » CYP1B1 expression, and the metformin-mediated CYP1A1 and CYP1B1 reduction is irrelevant to estrogen receptor α (ERα) signaling. Furthermore, we found that metformin markedly down-regulated Sp1 protein levels in breast cancer cells. The use of genetic and pharmacological tools revealed that metformin-mediated down-regulation of AhR expression was mediated through the reduction of Sp1 protein. Metformin inhibited endogenous AhR ligand-induced CYP1A1 and CYP1B1 expression by suppressing tryptophan-2,3-dioxygenase (TDO) expression in MCF-7 cells. Finally, metformin inhibits TDO expression through a down-regulation of Sp1 and glucocorticoid receptor (GR) protein levels. Our findings demonstrate that metformin reduces CYP1A1 and CYP1B1 expression in breast cancer cells by down-regulating AhR signaling. Metformin would be able to act as a potential chemopreventive agent against CYP1A1 and CYP1B1-mediated carcinogenesis and development of cancer. - Graphical abstract: Schematic of the CYP1A1 and CYP1B1 gene regulation by metformin. - Highlights: • Metformin inhibits CYP1A1 and CYP1B1 expression. • Metformin down-regulates the AhR signaling. • Metformin reduces Sp1 protein expression. • Metformin suppresses TDO

Omeprazole induces NAD(P)H quinone oxidoreductase 1 via aryl hydrocarbon receptor-independent mechanisms: Role of the transcription factor nuclear factor erythroid 2–related factor 2

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

Zhang, Shaojie; Patel, Ananddeep; Moorthy, Bhagavatula

2015-11-13

Activation of the aryl hydrocarbon receptor (AhR) transcriptionally induces phase I (cytochrome P450 (CYP) 1A1) and phase II (NAD(P)H quinone oxidoreductase 1 (NQO1) detoxifying enzymes. The effects of the classical and nonclassical AhR ligands on phase I and II enzymes are well studied in human hepatocytes. Additionally, we observed that the proton pump inhibitor, omeprazole (OM), transcriptionally induces CYP1A1 in the human adenocarcinoma cell line, H441 cells via AhR. Whether OM activates AhR and induces the phase II enzyme, NAD(P)H quinone oxidoreductase 1 (NQO1), in fetal primary human pulmonary microvascular endothelial cells (HPMEC) is unknown. Therefore, we tested the hypothesis thatmore » OM will induce NQO1 in HPMEC via the AhR. The concentrations of OM used in our experiments did not result in cytotoxicity. OM activated AhR as evident by increased CYP1A1 mRNA expression. However, contrary to our hypothesis, OM increased NQO1 mRNA and protein via an AhR-independent mechanism as AhR knockdown failed to abrogate OM-mediated increase in NQO1 expression. Interestingly, OM activated Nrf2 as evident by increased phosphoNrf2 (S40) expression in OM-treated compared to vehicle-treated cells. Furthermore, Nrf2 knockdown abrogated OM-mediated increase in NQO1 expression. In conclusion, we provide evidence that OM induces NQO1 via AhR-independent, but Nrf2-dependent mechanisms. - Highlights: • We investigated whether omeprazole induces NQO1 in human fetal lung cells. • Omeprazole induces the phase II enzyme, NQO1, in human fetal lung cells. • AhR deficiency fails to abrogate omeprazole-mediated induction of NQO1. • Omeprazole increases phosphoNrf2 (S40) protein expression in human fetal lung cells. • Nrf2 knockdown abrogates the induction of NQO1 by omeprazole in human lung cells.« less

Levels of serum aryl hydrocarbon receptor were negatively associated with β-cell function in patients with no history of diabetes undergoing coronary angiography.

PubMed

Wang, Jun-Sing; Lee, Wen-Jane; Lee, I-Te; Lin, Shih-Yi; Lee, Wen-Lieng; Liang, Kae-Woei; Lin, Shing-Jong; Sheu, Wayne Huey-Herng

2018-05-26

We aimed to investigate the association of serum aryl hydrocarbon receptor (AhR) levels with insulin resistance and β-cell function in patients undergoing coronary angiography with no history of diabetes. Patients with no history of diabetes who had been admitted for coronary angiography were enrolled. An oral glucose tolerance test (OGTT) was conducted two to four weeks after the patients were discharged from the hospital, and a blood sample was collected for measurements of glucose, insulin, and AhR. Patients' glucose regulation status was determined using the results of OGTT. Insulin resistance was assessed using the homeostasis model assessment method (HOMA-IR). β-cell function was assessed using the insulinogenic index (IGI). A total of 473 patients were included in the analysis (mean age 61 ± 12 years, male 81.8%, mean body mass index 26.1 ± 3.6 kg/m 2 ). Overall, mean serum AhR level was 25.1 ± 12.2 pg/ml. Patients with normal glucose tolerance had a lower serum AhR level (23.4 ± 10.8 pg/ml) than those who had prediabetes (26.2 ± 13.2 pg/ml) or newly diagnosed diabetes (26.9 ± 12.3 pg/ml, p=0.029). Using linear regression analysis, serum AhR levels were not associated with HOMA-IR. In contrast, serum AhR levels were negatively associated with IGI after adjustment for several confounders including HOMA-IR (β coefficient -0.162, 95% CI -0.302 to -0.022, p=0.023). In patients with no history of diabetes, levels of serum AhR were negatively associated with β-cell function, independent of several confounders including insulin resistance. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

An in silico approach to investigate the source of the controversial interpretations about the phenotypic results of the human AhR-gene G1661A polymorphism.

PubMed

Aftabi, Younes; Colagar, Abasalt Hosseinzadeh; Mehrnejad, Faramarz

2016-03-21

Aryl hydrocarbon receptor (AhR) acts as an enhancer binding ligand-activated intracellular receptor. Chromatin remodeling components and general transcription factors such as TATA-binding protein (TBP) are evoked on AhR-target genes by interaction with its flexible transactivation domain (TAD). AhR-G1661A single nucleotide polymorphism (SNP: rs2066853) causes an arginine to lysine substitution in the acidic sub-domain of TAD at position 554 (R554K). Although, numerous studies associate the SNP with some abnormalities such as cancer, other reliable investigations refuse the associations. Consequently, the interpretation of the phenotypic results of G1661A-transition has been controversial. In this study, an in silico analysis were performed to investigate the possible effects of the transition on AhR-mRNA, protein structure, interaction properties and modifications. The analysis revealed that the R554K substitution affects secondary structure and solvent accessibility of adjacent residues. Also, it causes to decreasing of the AhR stability; altering the hydropathy features of the local sequence and changing the pattern of the residues at the binding site of the TAD-acidic sub-domain. Generating of new sites for ubiquitination and acetylation for AhR-K554 variant respectively at positions 544 and 560 was predicted. Our findings intensify the idea that the AhR-G1661A transition may affects AhR-TAD interactions, especially with the TBP, which influence AhR-target genes expression. However, the previously reported flexibility of the modular TAD could act as an intervening factor, moderate the SNP effects and causes distinct outcomes in different individuals and tissues. Copyright © 2016 Elsevier Ltd. All rights reserved.

The aryl hydrocarbon receptor is required for the maintenance of liver-resident natural killer cells

PubMed Central

2016-01-01

A tissue-resident population of natural killer cells (NK cells) in the liver has recently been described to have the unique capacity to confer immunological memory in the form of hapten-specific contact hypersensitivity independent of T and B cells. Factors regulating the development and maintenance of these liver-resident NK cells are poorly understood. The aryl hydrocarbon receptor (AhR) is a transcription factor modulated by exogenous and endogenous ligands that is important in the homeostasis of immune cells at barrier sites, such as the skin and gut. In this study, we show that liver-resident NK (NK1.1+CD3−) cells, defined as CD49a+TRAIL+CXCR6+DX5− cells in the mouse liver, constitutively express AhR. In AhR−/− mice, there is a significant reduction in the proportion and absolute number of these cells, which results from a cell-intrinsic dependence on AhR. This deficiency in liver-resident NK cells appears to be the result of higher turnover and increased susceptibility to cytokine-induced cell death. Finally, we show that this deficiency has functional implications in vivo. Upon hapten exposure, AhR−/− mice are not able to mount an NK cell memory response to hapten rechallenge. Together, these data demonstrate the requirement of AhR for the maintenance of CD49a+TRAIL+CXCR6+DX5− liver-resident NK cells and their hapten memory function. PMID:27670593

Deletion of Aryl Hydrocarbon Receptor AHR in Mice Leads to Subretinal Accumulation of Microglia and RPE Atrophy

PubMed Central

Kim, Soo-Young; Yang, Hyun-Jin; Chang, Yi-Sheng; Kim, Jung-Woong; Brooks, Matthew; Chew, Emily Y.; Wong, Wai T.; Fariss, Robert N.; Rachel, Rivka A.; Cogliati, Tiziana; Qian, Haohua; Swaroop, Anand

2014-01-01

Purpose. The aryl hydrocarbon receptor (AHR) is a ligand-activated nuclear receptor that regulates cellular response to environmental signals, including UV and blue wavelength light. This study was undertaken to elucidate AHR function in retinal homeostasis. Methods. RNA-seq data sets were examined for Ahr expression in the mouse retina and rod photoreceptors. The Ahr−/− mice were evaluated by fundus imaging, optical coherence tomography, histology, immunohistochemistry, and ERG. For light damage experiments, adult mice were exposed to 14,000 to 15,000 lux of diffuse white light for 2 hours. Results. In mouse retina, Ahr transcripts were upregulated during development, with continued increase in aging rod photoreceptors. Fundus examination of 3-month-old Ahr−/− mice revealed subretinal autofluorescent spots, which increased in number with age and following acute light exposure. Ahr−/− retina also showed subretinal microglia accumulation that correlated with autofluorescence changes, RPE abnormalities, and reactivity against immunoglobulin, complement factor H, and glial fibrillary acidic protein. Functionally, Ahr−/− mice displayed reduced ERG c-wave amplitudes. Conclusions. The Ahr−/− mice exhibited subretinal accumulation of microglia and focal RPE atrophy, phenotypes observed in AMD. Together with a recently published report on another Ahr−/− mouse model, our study suggests that AHR has a protective role in the retina as an environmental stress sensor. As such, its altered function may contribute to human AMD progression and provide a target for pharmacological intervention. PMID:25159211

ITE and TCDD differentially regulate the vascular remodeling of rat placenta via the activation of AhR.

PubMed

Wu, Yanming; Chen, Xiao; Zhou, Qian; He, Qizhi; Kang, Jiuhong; Zheng, Jing; Wang, Kai; Duan, Tao

2014-01-01

Vascular remodeling in the placenta is essential for normal fetal development. The previous studies have demonstrated that in utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, an environmental toxicant) induces the intrauterine fetal death in many species via the activation of aryl hydrocarbon receptor (AhR). In the current study, we compared the effects of 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) and TCDD on the vascular remodeling of rat placentas. Pregnant rats on gestational day (GD) 15 were randomly assigned into 5 groups, and were exposed to a single dose of 1.6 and 8.0 mg/kg body weight (bw) ITE, 1.6 and 8.0 µg/kg bw TCDD, or an equivalent volume of the vehicle, respectively. The dams were sacrificed on GD20 and the placental tissues were gathered. The intrauterine fetal death was observed only in 8.0 µg/kg bw TCDD-exposed group and no significant difference was seen in either the placental weight or the fetal weight among all these groups. The immunohistochemical and histological analyses revealed that as compared with the vehicle-control, TCDD, but not ITE, suppressed the placental vascular remodeling, including reduced the ratio of the placental labyrinth zone to the basal zone thickness (at least 0.71 fold of control), inhibited the maternal sinusoids dilation and thickened the trophoblastic septa. However, no marked difference was observed in the density of fetal capillaries in the labyrinth zone among these groups, although significant differences were detected in the expression of angiogenic growth factors between ITE and TCDD-exposed groups, especially Angiopoietin-2 (Ang-2), Endoglin, Interferon-γ (IFN-γ) and placenta growth factor (PIGF). These results suggest ITE and TCDD differentially regulate the vascular remodeling of rat placentas, as well as the expression of angiogenic factors and their receptors, which in turn may alter the blood flow in the late gestation and partially resulted in

ITE and TCDD Differentially Regulate the Vascular Remodeling of Rat Placenta via the Activation of AhR

PubMed Central

Zhou, Qian; He, Qizhi; Kang, Jiuhong; Zheng, Jing; Wang, Kai; Duan, Tao

2014-01-01

Vascular remodeling in the placenta is essential for normal fetal development. The previous studies have demonstrated that in utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, an environmental toxicant) induces the intrauterine fetal death in many species via the activation of aryl hydrocarbon receptor (AhR). In the current study, we compared the effects of 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) and TCDD on the vascular remodeling of rat placentas. Pregnant rats on gestational day (GD) 15 were randomly assigned into 5 groups, and were exposed to a single dose of 1.6 and 8.0 mg/kg body weight (bw) ITE, 1.6 and 8.0 µg/kg bw TCDD, or an equivalent volume of the vehicle, respectively. The dams were sacrificed on GD20 and the placental tissues were gathered. The intrauterine fetal death was observed only in 8.0 µg/kg bw TCDD-exposed group and no significant difference was seen in either the placental weight or the fetal weight among all these groups. The immunohistochemical and histological analyses revealed that as compared with the vehicle-control, TCDD, but not ITE, suppressed the placental vascular remodeling, including reduced the ratio of the placental labyrinth zone to the basal zone thickness (at least 0.71 fold of control), inhibited the maternal sinusoids dilation and thickened the trophoblastic septa. However, no marked difference was observed in the density of fetal capillaries in the labyrinth zone among these groups, although significant differences were detected in the expression of angiogenic growth factors between ITE and TCDD-exposed groups, especially Angiopoietin-2 (Ang-2), Endoglin, Interferon-γ (IFN-γ) and placenta growth factor (PIGF). These results suggest ITE and TCDD differentially regulate the vascular remodeling of rat placentas, as well as the expression of angiogenic factors and their receptors, which in turn may alter the blood flow in the late gestation and partially resulted in

Vehicular exhaust particles promote allergic airway inflammation through an aryl hydrocarbon receptor-notch signaling cascade.

PubMed

Xia, Mingcan; Viera-Hutchins, Loida; Garcia-Lloret, Maria; Noval Rivas, Magali; Wise, Petra; McGhee, Sean A; Chatila, Zena K; Daher, Nancy; Sioutas, Constantinos; Chatila, Talal A

2015-08-01

Traffic-related particulate matter (PM) has been linked to a heightened incidence of asthma and allergic diseases. However, the molecular mechanisms by which PM exposure promotes allergic diseases remain elusive. We sought to determine the expression, function, and regulation of pathways involved in promotion of allergic airway inflammation by PM. We used gene expression transcriptional profiling, in vitro culture assays, and in vivo murine models of allergic airway inflammation. We identified components of the Notch pathway, most notably Jagged 1 (Jag1), as targets of PM induction in human monocytes and murine dendritic cells. PM, especially ultrafine particles, upregulated TH cytokine levels, IgE production, and allergic airway inflammation in mice in a Jag1- and Notch-dependent manner, especially in the context of the proasthmatic IL-4 receptor allele Il4raR576. PM-induced Jag1 expression was mediated by the aryl hydrocarbon receptor (AhR), which bound to and activated AhR response elements in the Jag1 promoter. Pharmacologic antagonism of AhR or its lineage-specific deletion in CD11c(+) cells abrogated the augmentation of airway inflammation by PM. PM activates an AhR-Jag1-Notch cascade to promote allergic airway inflammation in concert with proasthmatic alleles. Copyright © 2015 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Third-generation Ah receptor-responsive luciferase reporter plasmids: amplification of dioxin-responsive elements dramatically increases CALUX bioassay sensitivity and responsiveness.

PubMed

He, Guochun; Tsutsumi, Tomoaki; Zhao, Bin; Baston, David S; Zhao, Jing; Heath-Pagliuso, Sharon; Denison, Michael S

2011-10-01

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, dioxin) and related dioxin-like chemicals are widespread and persistent environmental contaminants that produce diverse toxic and biological effects through their ability to bind to and activate the Ah receptor (AhR) and AhR-dependent gene expression. The chemically activated luciferase expression (CALUX) system is an AhR-responsive recombinant luciferase reporter gene-based cell bioassay that has been used in combination with chemical extraction and cleanup methods for the relatively rapid and inexpensive detection and relative quantitation of dioxin and dioxin-like chemicals in a wide variety of sample matrices. Although the CALUX bioassay has been validated and used extensively for screening purposes, it has some limitations when screening samples with very low levels of dioxin-like chemicals or when there is only a small amount of sample matrix for analysis. Here, we describe the development of third-generation (G3) CALUX plasmids with increased numbers of dioxin-responsive elements, and stable transfection of these new plasmids into mouse hepatoma (Hepa1c1c7) cells has produced novel amplified G3 CALUX cell bioassays that respond to TCDD with a dramatically increased magnitude of luciferase induction and significantly lower minimal detection limit than existing CALUX-type cell lines. The new G3 CALUX cell lines provide a highly responsive and sensitive bioassay system for the detection and relative quantitation of very low levels of dioxin-like chemicals in sample extracts.

The Aryl Hydrocarbon Receptor Ligand ITE Inhibits TGFβ1-Induced Human Myofibroblast Differentiation

PubMed Central

Lehmann, Geniece M.; Xi, Xia; Kulkarni, Ajit A.; Olsen, Keith C.; Pollock, Stephen J.; Baglole, Carolyn J.; Gupta, Shikha; Casey, Ann E.; Huxlin, Krystel R.; Sime, Patricia J.; Feldon, Steven E.; Phipps, Richard P.

2011-01-01

Fibrosis can occur in any human tissue when the normal wound healing response is amplified. Such amplification results in fibroblast proliferation, myofibroblast differentiation, and excessive extracellular matrix deposition. Occurrence of these sequelae in organs such as the eye or lung can result in severe consequences to health. Unfortunately, medical treatment of fibrosis is limited by a lack of safe and effective therapies. These therapies may be developed by identifying agents that inhibit critical steps in fibrotic progression; one such step is myofibroblast differentiation triggered by transforming growth factor-β1 (TGFβ1). In this study, we demonstrate that TGFβ1-induced myofibroblast differentiation is blocked in human fibroblasts by a candidate endogenous aryl hydrocarbon receptor (AhR) ligand 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). Our data show that ITE disrupts TGFβ1 signaling by inhibiting the nuclear translocation of Smad2/3/4. Although ITE functions as an AhR agonist, and biologically persistent AhR agonists, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin, cause severe toxic effects, ITE exhibits no toxicity. Interestingly, ITE effectively inhibits TGFβ1-driven myofibroblast differentiation in AhR−/− fibroblasts: Its ability to inhibit TGFβ1 signaling is AhR independent. As supported by the results of this study, the small molecule ITE inhibits myofibroblast differentiation and may be useful clinically as an antiscarring agent. PMID:21406171

Cross-regulatory circuit between AHR and microbiota.

PubMed

Ji, Jian; Qu, Hao

2018-01-29

The gut microbes have a close symbiotic relationship with their host. Interactions between host and the microbiota affect the nutritional, immunological, and physiological status of the host. The aryl hydrocarbon receptor (AHR) is a ligand activated transcription factor that mediates the toxicity of xenobiotics. Recently, the relationship between the gut microbiota and AHR has attracted the attention of many researchers. The AHR influences the intestinal microbiota population and mediates host-microbe homeostasis. Interestingly, the gut microbiota also produces ligands of AHR from bacterial metabolism and thereby activates the AHR signaling pathway. This review presents current knowledge of the cross-regulatory circuit between the AHR and intestinal microbiota. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

2,3,7,8-tetrachlorodibenzo-p-dioxin decrease expression of aryl hydrocarbon receptor in peripheral lymphocyte of β-thalassemia major patients.

PubMed

Ghatrehsamani, Mahdi; Soleimani, Masoud; Esfahani, Behjat Al-Sadat Moayedi; Hakemi, Mazdak Ganjalikhani; Shirzad, Hedayatollah; Eskandari, Nahid; Adib, Minoo

2015-01-01

β-thalassemia major is a hereditary disease with inefficient erythropoiesis. Level of inflammatory cytokine is elevated in these patients. In this study, we investigate the effect of aryl hydrocarbon receptor (AhR) ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), on the expression of inflammatory mediators in β-thalassemia major patient's lymphocytes. Peripheral blood mononuclear cells of patients and healthy participants was isolated and cultured in favor of lymphocytes increment. Based on the treatment, we divided the cell into four groups. The orders of group's treatments were no treatment, tumor necrosis factor-α (TNF-α) treatment, TNF-α and TCDD treatment, TCDD treatment in Group 1-4, respectively. After cell culture, we extracted the cells RNA and converted them to cDNA. Real-time polymerase chain reaction was performed to assessment relative expression of caspase-1, NLRP3, and AhR. We compared all patient groups with equal healthy (control) groups. Results showed that expression of caspase-1 in patients (Groups 1 and 2) was significantly lower than healthy individuals (P < 0.05). Although, no significant difference was found (Groups 1, 2, and control) in AhR gene expression (P > 0.05). Expression of AhR in other groups of patients (3 and 4) was significantly lower than control groups (P < 0.05). Expression of caspase-1 in Group 4 was significantly larger than the control group (P < 0.001). We show here that chronic inflammation decrease caspase-1 expression and exposure of human lymphocytes to TCDD promote caspase-1 expression. Furthermore, activation of AhR with TCDD decreases AhR expression in lymphocytes of β-thalassemia major disease.

AhR-dependent secretion of PDGF-BB by human classically activated macrophages exposed to DEP extracts stimulates lung fibroblast proliferation

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

Jaguin, Marie; Fardel, Olivier; Pôle Biologie, Centre Hospitalier Universitaire

2015-06-15

Lung diseases are aggravated by exposure to diesel exhaust particles (DEPs) found in air pollution. Macrophages are thought to play a crucial role in lung immune response to these pollutants, even if the mechanisms involved remain incompletely characterized. In the present study, we demonstrated that classically and alternative human macrophages (MΦ) exhibited increased secretion of PDGF-B in response to DEP extract (DEPe). This occurred via aryl hydrocarbon receptor (AhR)-activation because DEPe-induced PDGF-B overexpression was abrogated after AhR expression knock-down by RNA interference, in both M1 and M2 polarizing MΦ. In addition, TCDD and benzo(a)pyrene, two potent AhR ligands, also significantlymore » increased mRNA expression of PDGF-B in M1 MΦ, whereas some weak ligands of AhR did not. We next evaluated the impact of conditioned media (CM) from MΦ culture exposed to DEPe or of recombinant PDGF-B onto lung fibroblast proliferation. The tyrosine kinase inhibitor, AG-1295, prevents phosphorylations of PDGF-Rβ, AKT and ERK1/2 and the proliferation of MRC-5 fibroblasts induced by recombinant PDGF-B and by CM from M1 polarizing MΦ, strongly suggesting that the PDGF-BB secreted by DEPe-exposed MΦ is sufficient to activate the PDGF-Rβ pathway of human lung fibroblasts. In conclusion, we demonstrated that human MΦ, whatever their polarization status, secrete PDGF-B in response to DEPe and that PDGF-B is a target gene of AhR. Therefore, induction of PDGF-B by DEP may participate in the deleterious effects towards human health triggered by such environmental urban contaminants. - Highlights: • PDGF-B expression and secretion are increased by DEPe exposure in human M1 and M2 MΦ. • DEPe-induced PDGF-B expression is aryl-hydrocarbon-dependent. • DEPe-exposed M1 MΦ secrete sufficient PDGF-B to increase lung fibroblast proliferation.« less

Kynurenine 3-monooxygenase mediates inhibition of Th17 differentiation via catabolism of endogenous aryl hydrocarbon receptor ligands.

PubMed

Stephens, Geoffrey L; Wang, Qun; Swerdlow, Bonnie; Bhat, Geetha; Kolbeck, Roland; Fung, Michael

2013-07-01

The aryl hydrocarbon receptor (AhR) is a key transcriptional regulator of Th17-cell differentiation. Although endogenous ligands have yet to be identified, evidence suggests that tryptophan metabolites can act as agonists for the AhR. Tryptophan metabolites are abundant in circulation, so we hypothesized that cell intrinsic factors might exist to regulate the exposure of Th17 cells to AhR-dependent activities. Here, we find that Th17 cells preferentially express kynurenine 3-monooxygenase (KMO), which is an enzyme involved in catabolism of the tryptophan metabolite kynurenine. KMO inhibition, either with a specific inhibitor or via siRNA-mediated silencing, markedly increased IL-17 production in vitro, whereas IFN-γ production by Th1 cells was unaffected. Inhibition of KMO significantly exacerbated disease in a Th17-driven model of autoimmune gastritis, suggesting that expression of KMO by Th17 cells serves to limit their continuous exposure to physiological levels of endogenous AhR ligands in vivo. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aryl Hydrocarbon Receptor Ligands in Cigarette Smoke Induce Production of Interleukin-22 to Promote Pancreatic Fibrosis in Models of Chronic Pancreatitis.

PubMed

Xue, Jing; Zhao, Qinglan; Sharma, Vishal; Nguyen, Linh P; Lee, Yvonne N; Pham, Kim L; Edderkaoui, Mouad; Pandol, Stephen J; Park, Walter; Habtezion, Aida

2016-12-01

Cigarette smoke has been identified as an independent risk factor for chronic pancreatitis (CP). Little is known about the mechanisms by which smoking promotes development of CP. We assessed the effects of aryl hydrocarbon receptor (AhR) ligands found in cigarette smoke on immune cell activation in humans and pancreatic fibrosis in animal models of CP. We obtained serum samples from patients with CP treated at Stanford University hospital and healthy individuals (controls) and isolated CD4 + T cells. Levels of interleukin-22 (IL22) were measured by enzyme-linked immunosorbent assay and smoking histories were collected. T cells from healthy nonsmokers and smokers were stimulated and incubated with AhR agonists (2,3,7,8-tetrachlorodibenzo-p-dioxin or benzo[a]pyrene) or antagonists and analyzed by flow cytometry. Mice were given intraperitoneal injections of caerulein or saline, with or without lipopolysaccharide, to induce CP. Some mice were given intraperitoneal injections of AhR agonists at the start of caerulein injection, with or without an antibody against IL22 (anti-IL22) starting 2 weeks after the first caerulein injection, or recombinant mouse IL22 or vehicle (control) intraperitoneally 4 weeks after the first caerulein injection. Mice were exposed to normal air or cigarette smoke for 6 h/d for 7 weeks and expression of AhR gene targets was measured. Pancreata were collected from all mice and analyzed by histology and quantitative reverse transcription polymerase chain reaction. Pancreatic stellate cells and T cells were isolated and studied using immunoblot, immunofluorescence, flow cytometry, and enzyme-linked immunosorbent analyses. Mice given AhR agonists developed more severe pancreatic fibrosis (based on decreased pancreas size, histology, and increased expression of fibrosis-associated genes) than mice not given agonists after caerulein injection. In mice given saline instead of caerulein, AhR ligands did not induce fibrosis. Pancreatic T cells

Effects of anthocyanins on the AhR-CYP1A1 signaling pathway in human hepatocytes and human cancer cell lines

PubMed Central

Kamenickova, Alzbeta; Anzenbacherova, Eva; Pavek, Petr; Soshilov, Anatoly A.; Denison, Michael S.; Zapletalova, Michaela; Anzenbacher, Pavel; Dvorak, Zdenek

2013-01-01

Anthocyanins are plant pigments occurring in flowers and berry fruits. Since a phenomenon of food-drug interactions is increasingly emerging, we examined the effects of 21 major anthocyanins and the extracts from 3 food supplements containing anthocyanins on the aryl hydrocarbon receptor (AhR) – cytochrome P450 CYP1A1 signaling pathway in human hepatocytes and human hepatic HepG2 and intestinal LS174T cancer cells. Pelargonidin-3-O-rutinoside (PEL-2) and cyanidin-3,5-O-diglucoside (CYA-3) dose-dependently activated AhR, as revealed by gene reporter assay. PEL-2 and CYA-3 induced CYP1A1 mRNA but not protein in HepG2 and LS174T cells. Neither compound induced CYP1A1 mRNA and protein in four different primary human hepatocytes cultures. The effects of PEL-2 and CYA-3 on AhR occurred by ligand-dependent and ligand-independent mechanisms, respectively, as demonstrated by ligand binding assay. In a direct enzyme inhibition assay, none of the antocyanins tested inhibited the CYP1A1 marker activity to less than 50% even at 100 µM concentration. PEL-2 and CYA-3 at 100 µM inhibited CYP1A1 to 79% and 65%, respectively. In conclusion, with exception of PEL-2 and CYA-3, there were no effects of 19 major anthocyanins and 3 food supplements containing anthocyanins on AhR-CYP1A1 signaling, implying zero potential of these compounds for food-drug interactions with respect to AhR-CYP1A1 pathway. PMID:23735880

Indigo Naturalis ameliorates murine dextran sodium sulfate-induced colitis via aryl hydrocarbon receptor activation.

PubMed

Kawai, Shoichiro; Iijima, Hideki; Shinzaki, Shinichiro; Hiyama, Satoshi; Yamaguchi, Toshio; Araki, Manabu; Iwatani, Shuko; Shiraishi, Eri; Mukai, Akira; Inoue, Takahiro; Hayashi, Yoshito; Tsujii, Masahiko; Motooka, Daisuke; Nakamura, Shota; Iida, Tetsuya; Takehara, Tetsuo

2017-08-01

Indigo Naturalis (IN) is used as a traditional herbal medicine for ulcerative colitis (UC). However, the mechanisms of action of IN have not been clarified. We aimed to evaluate the efficacy of IN for ameliorating colonic inflammation. We further investigated the mechanisms of action of IN. Colitis severity was assessed in dextran sodium sulfate-induced colitis and trinitrobenzene sulfonic acid-induced colitis models with or without the oral administration of IN or indigo, which is a known major component of IN. Colonic lamina propria (LP) mononuclear cells isolated from IN-treated mice were analyzed with quantitative reverse transcription polymerase chain reaction (qRT-PCR) and flow cytometry. LP and splenic mononuclear cells cultured in vitro with IN or indigo were also analyzed. The role of the candidate receptor for indigo, the aryl hydrocarbon receptor (AhR), was analyzed using Ahr-deficient mice. Colitis severity was significantly ameliorated in the IN and indigo treatment groups compared with the control group. The mRNA expression levels of interleukin (Il)-10 and Il-22 in the LP lymphocytes were increased by IN treatment. The treatment of splenocytes with IN or indigo increased the expression of anti-inflammatory cytokines and resulted in the expansion of IL-10-producing CD4 + T cells and IL-22-producing CD3 - RORγt + cells, but not CD4 + Foxp3 + regulatory T cells. The amelioration of colitis by IN or indigo was abrogated in Ahr-deficient mice, in association with diminished regulatory cytokine production. IN and indigo ameliorated murine colitis through AhR signaling activation, suggesting that AhR could be a promising therapeutic target for UC.

Aryl hydrocarbon receptor activation impairs the priming but not the recall of influenza virus-specific CD8+ T cells in the lung.

PubMed

Lawrence, B Paige; Roberts, Alan D; Neumiller, Joshua J; Cundiff, Jennifer A; Woodland, David L

2006-11-01

The response of CD8+ T cells to influenza virus is very sensitive to modulation by aryl hydrocarbon receptor (AhR) agonists; however, the mechanism underlying AhR-mediated alterations in CD8+ T cell function remains unclear. Moreover, very little is known regarding how AhR activation affects anamnestic CD8+ T cell responses. In this study, we analyzed how AhR activation by the pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters the in vivo distribution and frequency of CD8+ T cells specific for three different influenza A virus epitopes during and after the resolution of a primary infection. We then determined the effects of TCDD on the expansion of virus-specific memory CD8+ T cells during recall challenge. Adoptive transfer of AhR-null CD8+ T cells into congenic AhR(+/+) recipients, and the generation of CD45.2AhR(-/-)-->CD45.1AhR(+/+) chimeric mice demonstrate that AhR-regulated events within hemopoietic cells, but not directly within CD8+ T cells, underlie suppressed expansion of virus-specific CD8+ T cells during primary infection. Using a dual-adoptive transfer approach, we directly compared the responsiveness of virus-specific memory CD8+ T cells created in the presence or absence of TCDD, which revealed that despite profound suppression of the primary response to influenza virus, the recall response of virus-specific CD8+ T cells that form in the presence of TCDD is only mildly impaired. Thus, the delayed kinetics of the recall response in TCDD-treated mice reflects the fact that there are fewer memory cells at the time of reinfection rather than an inherent defect in the responsive capacity of virus-specific memory CD8+ cells.

Endocrine-Disrupting Potential of Bisphenol A, Bisphenol A Dimethacrylate, 4-n-Nonylphenol, and 4-n-Octylphenol in Vitro: New Data and a Brief Review

PubMed Central

Bonefeld-Jørgensen, Eva C.; Long, Manhai; Hofmeister, Marlene V.; Vinggaard, Anne Marie

2007-01-01

Background An array of environmental compounds is known to possess endocrine disruption (ED) potentials. Bisphenol A (BPA) and bisphenol A dimethacrylate (BPA-DM) are monomers used to a high extent in the plastic industry and as dental sealants. Alkylphenols such as 4-n-nonylphenol (nNP) and 4-n-octylphenol (nOP) are widely used as surfactants. Objectives We investigated the effect in vitro of these four compounds on four key cell mechanisms including transactivation of a) the human estrogen receptor (ER), b) the human androgen receptor (AR), c) the aryl hydrocarbon receptor (AhR), and d) aromatase activity. Results All four compounds inhibited aromatase activity and were agonists and antagonists of ER and AR, respectively. nNP increased AhR activity concentration-dependently and further increased the 2,3,7,8-tetrachlorodibenzo-p-dioxin AhR action. nOP caused dual responses with a weak increased and a decreased AhR activity at lower (10−8 M) and higher concentrations (10−5–10−4 M), respectively. AhR activity was inhibited with BPA (10−5–10−4 M) and weakly increased with BPA-DM (10−5 M), respectively. nNP showed the highest relative potency (REP) compared with the respective controls in the ER, AhR, and aromatase assays, whereas similar REP was observed for the four chemicals in the AR assay. Conclusion Our in vitro data clearly indicate that the four industrial compounds have ED potentials and that the effects can be mediated via several cellular pathways, including the two sex steroid hormone receptors (ER and AR), aromatase activity converting testosterone to estrogen, and AhR; AhR is involved in syntheses of steroids and metabolism of steroids and xenobiotic compounds. PMID:18174953

Harman induces CYP1A1 enzyme through an aryl hydrocarbon receptor mechanism

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

El Gendy, Mohamed A.M.; El-Kadi, Ayman O.S., E-mail: aelkadi@pharmacy.ualberta.c

Harman is a common compound in several foods, plants and beverages. Numerous studies have demonstrated its mutagenic, co-mutagenic and carcinogenic effects; however, the exact mechanism has not been fully identified. Aryl hydrocarbon receptor (AhR) is a transcription factor regulating the expression of the carcinogen-activating enzyme; cytochrome P450 1A1 (CYP1A1). In the present study, we examined the ability of harman to induce AhR-mediated signal transduction in human and rat hepatoma cells; HepG2 and H4IIE cells. Our results showed that harman significantly induced CYP1A1 mRNA in a time- and concentration-dependent manner. Similarly, harman significantly induced CYP1A1 at protein and activity levels inmore » a concentration-dependent manner. Moreover, the AhR antagonist, resveratrol, inhibited the increase in CYP1A1 activity by harman. The RNA polymerase inhibitor, actinomycin D, completely abolished the CYP1A1 mRNA induction by harman, indicating a transcriptional activation. The role of AhR in CYP1A1 induction by harman was confirmed by using siRNA specific for human AhR. The ability of harman to induce CYP1A1 was strongly correlated with its ability to stimulate AhR-dependent luciferase activity and electrophoretic mobility shift assay. At post-transcriptional and post-translational levels, harman did not affect the stability of CYP1A1 at the mRNA and the protein levels, excluding other mechanisms participating in the obtained effects. We concluded that harman can directly induce CYP1A1 gene expression in an AhR-dependent manner and may represent a novel mechanism by which harman promotes mutagenicity, co-mutagenicity and carcinogenicity.« less

Activation of the aryl hydrocarbon receptor affects activation and function of human monocyte-derived dendritic cells.

PubMed

Wang, C; Ye, Z; Kijlstra, A; Zhou, Y; Yang, P

2014-08-01

Aryl hydrocarbon receptor (AhR) is well known for mediating the toxic effects of dioxin-containing pollutants, but has also been shown to be involved in the natural regulation of the immune response. In this study, we investigated the effect of AhR activation by its endogenous ligands 6-formylindolo[3,2-b]carbazole (FICZ) and 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) on the differentiation, maturation and function of monocyte-derived DCs in Behçet's disease (BD) patients. In this study, we showed that AhR activation by FICZ and ITE down-regulated the expression of co-stimulatory molecules including human leucocyte antigen D-related (HLA-DR), CD80 and CD86, while it had no effect on the expression of CD83 and CD40 on DCs derived from BD patients and normal controls. Lipopolysaccharide (LPS)-treated dendritic cells (DCs) from active BD patients showed a higher level of interleukin (IL)-1β, IL-6, IL-23 and tumour necrosis factor (TNF)-α production. FICZ or ITE significantly inhibited the production of IL-1β, IL-6, IL-23 and TNF-α, but induced IL-10 production by DCs derived from active BD patients and normal controls. FICZ or ITE-treated DCs significantly inhibited the T helper type 17 (Th17) and Th1 cell response. Activation of AhR either by FICZ or ITE inhibits DC differentiation, maturation and function. Further studies are needed to investigate whether manipulation of the AhR pathway may be used to treat BD or other autoimmune diseases. © 2014 British Society for Immunology.

Activation of the aryl hydrocarbon receptor affects activation and function of human monocyte-derived dendritic cells

PubMed Central

Wang, C; Ye, Z; Kijlstra, A; Zhou, Y; Yang, P

2014-01-01

Aryl hydrocarbon receptor (AhR) is well known for mediating the toxic effects of dioxin-containing pollutants, but has also been shown to be involved in the natural regulation of the immune response. In this study, we investigated the effect of AhR activation by its endogenous ligands 6-formylindolo[3,2-b]carbazole (FICZ) and 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) on the differentiation, maturation and function of monocyte-derived DCs in Behçet's disease (BD) patients. In this study, we showed that AhR activation by FICZ and ITE down-regulated the expression of co-stimulatory molecules including human leucocyte antigen D-related (HLA-DR), CD80 and CD86, while it had no effect on the expression of CD83 and CD40 on DCs derived from BD patients and normal controls. Lipopolysaccharide (LPS)-treated dendritic cells (DCs) from active BD patients showed a higher level of interleukin (IL)-1β, IL-6, IL-23 and tumour necrosis factor (TNF)-α production. FICZ or ITE significantly inhibited the production of IL-1β, IL-6, IL-23 and TNF-α, but induced IL-10 production by DCs derived from active BD patients and normal controls. FICZ or ITE-treated DCs significantly inhibited the T helper type 17 (Th17) and Th1 cell response. Activation of AhR either by FICZ or ITE inhibits DC differentiation, maturation and function. Further studies are needed to investigate whether manipulation of the AhR pathway may be used to treat BD or other autoimmune diseases. PMID:24749687

Epigenetic Programming of Breast Cancer and Nutrition Prevention

DTIC Science & Technology

2011-05-01

is to test the role of xenobiotics and food compounds that bind the aromatic hydrocarbon receptor (AhR). AhR-ligands include the dioxin -like and...tumor promoter 2,3,7,8 tetrachlorobenzo-p- dioxin (TCDD). The activated AhR regulates transcription through binding to xenobiotic response elements (XRE...phytoalexin resveratrol, selected as a prototype dietary AhR antagonist, antagonizes at physiologically relevant doses (1  mol /L) the TCDD-induced

Dioxin mediates downregulation of the reduced folate carrier transport activity via the arylhydrocarbon receptor signalling pathway

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

Halwachs, Sandra, E-mail: halwachs@vetmed.uni-leipzig.d; Lakoma, Cathleen; Gebhardt, Rolf

2010-07-15

Dioxins such as 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) are common environmental contaminants known to regulate several genes via activation of the transcription factor aryl hydrocarbon receptor (AhR) associated with the development of numerous adverse biological effects. However, comparatively little is known about the molecular mechanisms by which dioxins display their toxic effects in vertebrates. The 5' untranslated region of the hepatocellular Reduced folate carrier (Rfc1; Slc19a1) exhibits AhR binding sites termed dioxin responsive elements (DRE) that have as yet only been found in the promoter region of prototypical TCDD target genes. Rfc1 mediated transport of reduced folates and antifolate drugs such as methotrexatemore » (MTX) plays an essential role in physiological folate homeostasis and MTX cancer chemotherapy. In order to determine whether this carrier represents a target gene of dioxins we have investigated the influence of TCDD on functional Rfc1 activity in rat liver. Pre-treatment of rats with TCDD significantly diminished hepatocellular Rfc1 uptake activity in a time- and dose-dependent manner. In further mechanistic studies we demonstrated that this reduction was due to TCDD-dependent activation of the AhR signalling pathway. We additionally showed that binding of the activated receptor to DRE motifs in the Rfc1 promoter resulted in downregulation of Rfc1 gene expression and reduced carrier protein levels. As downregulation of pivotal Rfc1 activity results in functional folate deficiency associated with an elevated risk of cardiovascular diseases or carcinogenesis, our results indicate that deregulation of this essential transport pathway represents a novel regulatory mechanism how dioxins display their toxic effects through the Ah receptor.« less

The Aryl Hydrocarbon Receptor Binds to E2F1 and Inhibits E2F1-induced Apoptosis

PubMed Central

Marlowe, Jennifer L.; Fan, Yunxia; Chang, Xiaoqing; Peng, Li; Knudsen, Erik S.; Xia, Ying

2008-01-01

Cellular stress by DNA damage induces checkpoint kinase-2 (CHK2)-mediated phosphorylation and stabilization of the E2F1 transcription factor, leading to induction of apoptosis by activation of a subset of proapoptotic E2F1 target genes, including Apaf1 and p73. This report characterizes an interaction between the aryl hydrocarbon (Ah) receptor (AHR), a ligand-activated transcription factor, and E2F1 that results in the attenuation of E2F1-mediated apoptosis. In Ahr−/− fibroblasts stably transfected with a doxycycline-regulated AHR expression vector, inhibition of AHR expression causes a significant elevation of oxidative stress, γH2A.X histone phosphorylation, and E2F1-dependent apoptosis, which can be blocked by small interfering RNA-mediated knockdown of E2F1 expression. In contrast, ligand-dependent AHR activation protects these cells from etoposide-induced cell death. In cells expressing both proteins, AHR and E2F1 interact independently of the retinoblastoma protein (RB), because AHR and E2F1 coimmunoprecipitate from extracts of RB-negative cells. Additionally, chromatin immunoprecipitation assays indicate that AHR and E2F1 bind to the Apaf1 promoter at a region containing a consensus E2F1 binding site but no AHR binding sites. AHR activation represses Apaf1 and TAp73 mRNA induction by a constitutively active CHK2 expression vector. Furthermore, AHR overexpression blocks the transcriptional induction of Apaf1 and p73 and the accumulation of sub-G0/G1 cells resulting from ectopic overexpression of E2F1. These results point to a proproliferative, antiapoptotic function of the Ah receptor that likely plays a role in tumor progression. PMID:18524851

Feedback control of AHR signalling regulates intestinal immunity.

PubMed

Schiering, Chris; Wincent, Emma; Metidji, Amina; Iseppon, Andrea; Li, Ying; Potocnik, Alexandre J; Omenetti, Sara; Henderson, Colin J; Wolf, C Roland; Nebert, Daniel W; Stockinger, Brigitta

2017-02-09

The aryl hydrocarbon receptor (AHR) recognizes xenobiotics as well as natural compounds such as tryptophan metabolites, dietary components and microbiota-derived factors, and it is important for maintenance of homeostasis at mucosal surfaces. AHR activation induces cytochrome P4501 (CYP1) enzymes, which oxygenate AHR ligands, leading to their metabolic clearance and detoxification. Thus, CYP1 enzymes have an important feedback role that curtails the duration of AHR signalling, but it remains unclear whether they also regulate AHR ligand availability in vivo. Here we show that dysregulated expression of Cyp1a1 in mice depletes the reservoir of natural AHR ligands, generating a quasi AHR-deficient state. Constitutive expression of Cyp1a1 throughout the body or restricted specifically to intestinal epithelial cells resulted in loss of AHR-dependent type 3 innate lymphoid cells and T helper 17 cells and increased susceptibility to enteric infection. The deleterious effects of excessive AHR ligand degradation on intestinal immune functions could be counter-balanced by increasing the intake of AHR ligands in the diet. Thus, our data indicate that intestinal epithelial cells serve as gatekeepers for the supply of AHR ligands to the host and emphasize the importance of feedback control in modulating AHR pathway activation.

Aryl Hydrocarbon Receptor Antagonists Promote the Expansion of Human Hematopoietic Stem Cells

PubMed Central

Boitano, Anthony E.; Wang, Jian; Romeo, Russell; Bouchez, Laure C.; Parker, Albert E.; Sutton, Sue E.; Walker, John R.; Flaveny, Colin A.; Perdew, Gary H.; Denison, Michael S.; Schultz, Peter G.; Cooke, Michael P.

2011-01-01

Although practiced clinically for over 40 years, the use of hematopoietic stem cell (HSC) transplants remains limited by the ability to expand these cells ex vivo. An unbiased screen with primary human HSC identified a purine derivative, StemRegenin 1 (SR1), that promotes the ex vivo expansion of CD34+ cells. Culture of HSC with SR1 led to a fifty-fold increase in cells expressing CD34, and a 17-fold increase in cells that retain the ability to engraft immunodeficient mice. Mechanistic studies show that SR1 acts by antagonizing the aryl hydrocarbon receptor (AhR). The identification of SR1 and AhR modulation as a means to induce ex vivo HSC expansion should facilitate the clinical use of HSC therapy. PMID:20688981

Diphenylarsinic acid, a chemical warfare-related neurotoxicant, promotes liver carcinogenesis via activation of aryl hydrocarbon receptor signaling and consequent induction of oxidative DAN damage in rats

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

Wei, Min; Yamada, Takanori; Yamano, Shotaro

2013-11-15

Diphenylarsinic acid (DPAA), a chemical warfare-related neurotoxic organic arsenical, is present in the groundwater and soil in some regions of Japan due to illegal dumping after World War II. Inorganic arsenic is carcinogenic in humans and its organic arsenic metabolites are carcinogenic in animal studies, raising serious concerns about the carcinogenicity of DPAA. However, the carcinogenic potential of DPAA has not yet been evaluated. In the present study we found that DPAA significantly enhanced the development of diethylnitrosamine-induced preneoplastic lesions in the liver in a medium-term rat liver carcinogenesis assay. Evaluation of the expression of cytochrome P450 (CYP) enzymes inmore » the liver revealed that DPAA induced the expression of CYP1B1, but not any other CYP1, CYP2, or CYP3 enzymes, suggesting that CYP1B1 might be the enzyme responsible for the metabolic activation of DPAA. We also found increased oxidative DNA damage, possibly due to elevated CYP1B1 expression. Induction of CYP1B1 has generally been linked with the activation of AhR, and we found that DPAA activates the aryl hydrocarbon receptor (AhR). Importantly, the promotion effect of DPAA was observed only at a dose that activated the AhR, suggesting that activation of AhR and consequent induction of AhR target genes and oxidative DNA damage plays a vital role in the promotion effects of DPAA. The present study provides, for the first time, evidence regarding the carcinogenicity of DPAA and indicates the necessity of comprehensive evaluation of its carcinogenic potential using long-term carcinogenicity studies. - Highlights: • DPAA, an environmental neurotoxicant, promotes liver carcinogenesis in rats. • DPAA is an activator of AhR signaling pathway. • DPAA promoted oxidative DNA damage in rat livers. • AhR target gene CYP 1B1 might be involved in the metabolism of DPAA.« less

EGCG protects endothelial cells against PCB 126-induced inflammation through inhibition of AhR and induction of Nrf2-regulated genes

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

Han, Sung Gu; Department of Animal and Food Sciences, College of Agriculture, University of Kentucky, Lexington, KY 40536; Han, Seong-Su

Tea flavonoids such as epigallocatechin gallate (EGCG) protect against vascular diseases such as atherosclerosis via their antioxidant and anti-inflammatory functions. Persistent and widespread environmental pollutants, including polychlorinated biphenyls (PCB), can induce oxidative stress and inflammation in vascular endothelial cells. Even though PCBs are no longer produced, they are still detected in human blood and tissues and thus considered a risk for vascular dysfunction. We hypothesized that EGCG can protect endothelial cells against PCB-induced cell damage via its antioxidant and anti-inflammatory properties. To test this hypothesis, primary vascular endothelial cells were pretreated with EGCG, followed by exposure to the coplanar PCBmore » 126. Exposure to PCB 126 significantly increased cytochrome P450 1A1 (Cyp1A1) mRNA and protein expression and superoxide production, events which were significantly attenuated following pretreatment with EGCG. Similarly, EGCG also reduced DNA binding of NF-κB and downstream expression of inflammatory markers such as monocyte chemotactic protein-1 (MCP-1) and vascular cell adhesion protein-1 (VCAM-1) after PCB exposure. Furthermore, EGCG decreased endogenous or base-line levels of Cyp1A1, MCP-1 and VCAM-1 in endothelial cells. Most of all, treatment of EGCG upregulated expression of NF-E2-related factor 2 (Nrf2)-controlled antioxidant genes, including glutathione S transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1), in a dose-dependent manner. In contrast, silencing of Nrf2 increased Cyp1A1, MCP-1 and VCAM-1 and decreased GST and NQO1 expression, respectively. These data suggest that EGCG can inhibit AhR regulated genes and induce Nrf2-regulated antioxidant enzymes, thus providing protection against PCB-induced inflammatory responses in endothelial cells. -- Highlights: ► PCBs cause endothelial inflammation and subsequent atherosclerosis. ► Nutrition can modulate toxicity by environmental pollutants. �

Comparative liver accumulation of dioxin-like compounds in sheep and cattle: Possible role of AhR-mediated xenobiotic metabolizing enzymes.

PubMed

Girolami, F; Spalenza, V; Benedetto, A; Manzini, L; Badino, P; Abete, M C; Nebbia, C

2016-11-15

PCDDs, PCDFs, and PCBs are persistent organic pollutants (POPs) that accumulate in animal products and may pose serious health problems. Those able to bind the aryl hydrocarbon receptor (AhR), eliciting a plethora of toxic responses, are defined dioxin-like (DL) compounds, while the remainders are called non-DL (NDL). An EFSA opinion has highlighted the tendency of ovine liver to specifically accumulate DL-compounds to a greater extent than any other farmed ruminant species. To examine the possible role in such an accumulation of xenobiotic metabolizing enzymes (XME) involved in DL-compound biotransformation, liver samples were collected from ewes and cows reared in an area known for low dioxin contamination. A related paper reported that sheep livers had about 5-fold higher DL-compound concentrations than cattle livers, while the content of the six marker NDL-PCBs did not differ between species. Specimens from the same animals were subjected to gene expression analysis for AhR, AhR nuclear translocator (ARNT) and AhR-dependent oxidative and conjugative pathways; XME protein expression and activities were also investigated. Both AhR and ARNT mRNA levels were about 2-fold lower in ovine samples and the same occurred for CYP1A1 and CYP1A2, being approximately 3- and 9-fold less expressed in sheep compared to cattle, while CYP1B1 could be detectable in cattle only. The results of the immunoblotting and catalytic activity (most notably EROD) measurements of the CYP1A family enzymes were in line with the gene expression data. By contrast, phase II enzyme expression and activities in sheep were higher (UGT1A) or similar (GSTA1, NQO1) to those recorded in cattle. The overall low expression of CYP1 family enzymes in the sheep is in line with the observed liver accumulation of DL-compounds and is expected to affect the kinetics and the dynamics of other POPs such as many polycyclic aromatic hydrocarbons, as well as of toxins (e.g. aflatoxins) or drugs (e.g. benzimidazole

Dietary and Microbial Oxazoles Induce Intestinal Inflammation by Modulating Aryl Hydrocarbon Receptor Responses.

PubMed

Iyer, Shankar S; Gensollen, Thomas; Gandhi, Amit; Oh, Sungwhan F; Neves, Joana F; Collin, Frederic; Lavin, Richard; Serra, Carme; Glickman, Jonathan; de Silva, Punyanganie S A; Sartor, R Balfour; Besra, Gurdyal; Hauser, Russell; Maxwell, Anthony; Llebaria, Amadeu; Blumberg, Richard S

2018-05-17

Genome-wide association studies have identified risk loci associated with the development of inflammatory bowel disease, while epidemiological studies have emphasized that pathogenesis likely involves host interactions with environmental elements whose source and structure need to be defined. Here, we identify a class of compounds derived from dietary, microbial, and industrial sources that are characterized by the presence of a five-membered oxazole ring and induce CD1d-dependent intestinal inflammation. We observe that minimal oxazole structures modulate natural killer T cell-dependent inflammation by regulating lipid antigen presentation by CD1d on intestinal epithelial cells (IECs). CD1d-restricted production of interleukin 10 by IECs is limited through activity of the aryl hydrocarbon receptor (AhR) pathway in response to oxazole induction of tryptophan metabolites. As such, the depletion of the AhR in the intestinal epithelium abrogates oxazole-induced inflammation. In summary, we identify environmentally derived oxazoles as triggers of CD1d-dependent intestinal inflammatory responses that occur via activation of the AhR in the intestinal epithelium. Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.

Gene expression and inducibility of the aryl hydrocarbon receptor-dependent pathway in cultured bovine blood lymphocytes.

PubMed

Girolami, Flavia; Spalenza, Veronica; Carletti, Monica; Perona, Giovanni; Sacchi, Paola; Rasero, Roberto; Nebbia, Carlo

2011-10-10

The exposure to dioxin-like (DL) compounds, an important class of persistent environmental pollutants, results in the altered expression of target genes. This occurs through the binding to the aryl hydrocarbon receptor (AhR), the subsequent dimerization with the AhR nuclear translocator (ARNT), and the binding of the complex to DNA responsive elements. A number of genes are up-regulated, including, among others, the AhR repressor (AHRR) and several biotransformation enzymes, such as the members of CYP1 family and NAD(P)H-quinone oxidoreductase (NOQ1). The expression and the inducibility of the above genes were investigated in mitogen-stimulated cultured blood lymphocytes from cattle, which represent a notable source of DL-compound human exposure through dairy products and meat. As assessed by real-time PCR, all the examined genes except CYP1A2 and NQO1 were detected under basal conditions. Cell exposure to the DL-compounds PCB126 or PCB77 in the 10(-6)-10(-9)M concentration range resulted in a 2-4-fold induction of CYPIA1 and CYP1B1, which was antagonized by α-naphthoflavone or PCB153. This study demonstrates for the first time the presence and inducibility of the AhR pathway in easily accessible cells like bovine peripheral lymphocytes and prompts further investigations to verify whether similar changes could occur under in vivo conditions. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Quantitative High-Throughput Screening and Confirmation Studies for Identification of Compounds that Activate the Aryl Hydrocarbon Receptor Pathway (SETAC)

EPA Science Inventory

The aryl hydrocarbon receptor (AhR) is a transcription factor that mediates adaptive responses to known environmental pollutants, such as aromatic hydrocarbons, through regulation of Phase I and II xenobiotic metabolizing enzymes as well as important growth and differentiation pa...

Dietary Polyphenols Increase Paraoxonase 1 Gene Expression by an Aryl Hydrocarbon Receptor-Dependent Mechanism

PubMed Central

Gouédard, Cédric; Barouki, Robert; Morel, Yannick

2004-01-01

Human paraoxonase 1 (PON-1) is a serum high-density lipoprotein-associated enzyme mainly secreted by the liver. It has endogenous and exogenous substrates and displays protective properties with respect to cardiovascular disease and organophosphate intoxication. In the HuH7 human hepatoma cell line, PON-1 activity and mRNA levels were increased by dietary polyphenolic compounds such as quercetin but also by toxic ligands of the aryl hydrocarbon receptor (AhR) such as 3-methylcholanthrene (3-MC). However, the 2,3,7,8-tetrachlorobenzo(p)dioxin (TCDD) was a poor inducer. Transient and stable transfection assays indicated that these compounds increased the PON-1 gene promoter activity in an AhR-dependent manner, since their effect was inhibited by 7-keto-cholesterol and AhR-directed short interfering RNA. Deletions and mutations studies showed that a xenobiotic responsive element (XRE)-like sequence within the PON-1 promoter mediated the effect of 3-MC and quercetin. In contrast with consensus XREs from the cytochrome P450 1A1 gene, the PON-1 XRE-like element mediated preferentially the effect of quercetin compared to the results seen with TCDD. Furthermore, AhR binding to this element was preferentially activated by quercetin. These observations provide a molecular mechanism for the regulation of the cardioprotective enzyme PON-1 by polyphenols. They suggest also that AhR ligands may differentially regulate gene expression depending on the DNA target sequence. PMID:15169886

Are styrene oligomers in coastal sediments of an industrial area aryl hydrocarbon-receptor agonists?

PubMed

Hong, Seongjin; Lee, Junghyun; Lee, Changkeun; Yoon, Seo Joon; Jeon, Seungyeon; Kwon, Bong-Oh; Lee, Jong-Hyeon; Giesy, John P; Khim, Jong Seong

2016-06-01

Effect-directed analysis (EDA) was performed to identify the major aryl hydrocarbon receptor (AhR) agonists in sediments collected from a highly industrialized area (Lake Shihwa, Korea). Great AhR-mediated potencies were found in fractions containing aromatic compounds with log Kow values of 5-8, and relatively great concentrations of styrene oligomers (SOs) and polycyclic aromatic hydrocarbons (PAHs) were detected in those fractions. Until now, there was little information on occurrences and toxic relative potencies (RePs) of SOs in coastal environments. In the present study; i) distributions and compositions, ii) AhR binding affinities, and iii) contributions of SOs to total AhR-mediated potencies were determined in coastal sediments. Elevated concentrations of 10 SOs were detected in sediments of inland creeks ranging from 61 to 740 ng g(-1) dry mass (dm), while lesser concentrations were found in inner (mean = 33 ng g(-1) dm) and outer regions (mean = 25 ng g(-1) dm) of the lake. Concentrations of PAHs in sediments were comparable to those of SOs. 2,4-diphenyl-1-butene (SD3) was the predominant SO analogue in sediments. SOs and PAHs were accumulated in sediments near sources, and could not be transported to remote regions due to their hydrophobicity. RePs of 3 SOs could be derived, which were 1000- to 10,000-fold less than that of one representative potent AhR active PAH, benzo[a]pyrene. Although concentrations of SOs in sediments were comparable to those of PAHs, the collective contribution of SOs to total AhR-mediated potencies were rather small (<1%), primarily due to their smaller RePs. Overall, the present study provides information on distributions and AhR binding affinities for SOs as baseline data for degradation products of polystyrene plastic in the coastal environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Combining NMR spectral and structural data to form models of polychlorinated dibenzodioxins, dibenzofurans, and biphenyls binding to the AhR

NASA Astrophysics Data System (ADS)

Beger, Richard D.; Buzatu, Dan A.; Wilkes, Jon G.

2002-10-01

A three-dimensional quantitative spectrometric data-activity relationship (3D-QSDAR) modeling technique which uses NMR spectral and structural information that is combined in a 3D-connectivity matrix has been developed. A 3D-connectivity matrix was built by displaying all possible assigned carbon NMR chemical shifts, carbon-to-carbon connections, and distances between the carbons. Two-dimensional 13C-13C COSY and 2D slices from the distance dimension of the 3D-connectivity matrix were used to produce a relationship among the 2D spectral patterns for polychlorinated dibenzofurans, dibenzodioxins, and biphenyls (PCDFs, PCDDs, and PCBs respectively) binding to the aryl hydrocarbon receptor (AhR). We refer to this technique as comparative structural connectivity spectral analysis (CoSCoSA) modeling. All CoSCoSA models were developed using forward multiple linear regression analysis of the predicted 13C NMR structure-connectivity spectral bins. A CoSCoSA model for 26 PCDFs had an explained variance (r2) of 0.93 and an average leave-four-out cross-validated variance (q4 2) of 0.89. A CoSCoSA model for 14 PCDDs produced an r2 of 0.90 and an average leave-two-out cross-validated variance (q2 2) of 0.79. One CoSCoSA model for 12 PCBs gave an r2 of 0.91 and an average q2 2 of 0.80. Another CoSCoSA model for all 52 compounds had an r2 of 0.85 and an average q4 2 of 0.52. Major benefits of CoSCoSA modeling include ease of development since the technique does not use molecular docking routines.

Metformin inhibits 7,12-dimethylbenz[a]anthracene-induced breast carcinogenesis and adduct formation in human breast cells by inhibiting the cytochrome P4501A1/aryl hydrocarbon receptor signaling pathway

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

Maayah, Zaid H.; Ghebeh, Hazem; Alhaider, Abdulqader A.

2015-04-15

Recent studies have established that metformin (MET), an oral anti-diabetic drug, possesses antioxidant activity and is effective against different types of cancer in several carcinogen-induced animal models and cell lines. However, whether MET can protect against breast cancer has not been reported before. Therefore, the overall objectives of the present study are to elucidate the potential chemopreventive effect of MET in non-cancerous human breast MCF10A cells and explore the underlying mechanism involved, specifically the role of cytochrome P4501A1 (CYP1A1)/aryl hydrocarbon receptor (AhR) pathway. Transformation of the MCF10A cells into initiated breast cancer cells with DNA adduct formation was conducted usingmore » 7,12-dimethylbenz[a]anthracene (DMBA), an AhR ligand. The chemopreventive effect of MET against DMBA-induced breast carcinogenesis was evidenced by the capability of MET to restore the induction of the mRNA levels of basic excision repair genes, 8-oxoguanine DNA glycosylase (OGG1) and apurinic/apyrimidinic endonuclease1 (APE1), and the level of 8-hydroxy-2-deoxyguanosine (8-OHdG). Interestingly, the inhibition of DMBA-induced DNA adduct formation was associated with proportional decrease in CYP1A1 and in NAD(P)H:quinone oxidoreductase 1 (NQO1) gene expression. Mechanistically, the involvements of AhR and nuclear factor erythroid 2-related factor-2 (Nrf2) in the MET-mediated inhibition of DMBA-induced CYP1A1 and NQO1 gene expression were evidenced by the ability of MET to inhibit DMBA-induced xenobiotic responsive element and antioxidant responsive element luciferase reporter gene expression which suggests an AhR- and Nrf2-dependent transcriptional control. However, the inability of MET to bind to AhR suggests that MET is not an AhR ligand. In conclusion, the present work shows a strong evidence that MET inhibits the DMBA-mediated carcinogenicity and adduct formation by inhibiting the expression of CYP1A1 through an AhR ligand

Inhibition of the aryl hydrocarbon receptor prevents Western diet-induced obesity. Model for AHR activation by kynurenine via oxidized-LDL, TLR2/4, TGFβ, and IDO1

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

Moyer, Benjamin J.

Obesity is an increasingly urgent global problem, yet, little is known about its causes and less is known how obesity can be effectively treated. We showed previously that the aryl hydrocarbon receptor (AHR) plays a role in the regulation of body mass in mice fed Western diet. The AHR is a ligand-activated nuclear receptor that regulates genes involved in a number of biological pathways, including xenobiotic metabolism and T cell polarization. This study was an investigation into whether inhibition of the AHR prevents Western diet-based obesity. Male C57Bl/6J mice were fed control and Western diets with and without the AHRmore » antagonist α-naphthoflavone or CH-223191, and a mouse hepatocyte cell line was used to delineate relevant cellular pathways. Studies are presented showing that the AHR antagonists α-naphthoflavone and CH-223191 significantly reduce obesity and adiposity and ameliorates liver steatosis in male C57Bl/6J mice fed a Western diet. Mice deficient in the tryptophan metabolizing enzyme indoleamine 2,3-dioxygenase 1 (IDO1) were also resistant to obesity. Using an AHR-directed, luciferase-expressing mouse hepatocyte cell line, we show that the transforming growth factor β1 (TGFβ1) signaling pathway via PI3K and NF-κB and the toll-like receptor 2/4 (TLR2/4) signaling pathway stimulated by oxidized low-density lipoproteins via NF-κB, each induce luciferase expression; however, TLR2/4 signaling was significantly reduced by inhibition of IDO1. At physiological levels, kynurenine but not kynurenic acid (both tryptophan metabolites and known AHR agonists) activated AHR-directed luciferase expression. We propose a hepatocyte-based model, in which kynurenine production is increased by enhanced IDO1 activity stimulated by TGFβ1 and TLR2/4 signaling, via PI3K and NF-κB, to perpetuate a cycle of AHR activation to cause obesity; and inhibition of the AHR, in turn, blocks the cycle's output to prevent obesity. The AHR with its broad ligand binding

Aryl hydrocarbon receptor expression is associated with a family history of upper gastrointestinal tract cancer in a high-risk population exposed to aromatic hydrocarbons

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

Roth, M.J.; Wei, W.Q.; Baer, J.

2009-09-15

Polycyclic aromatic hydrocarbon (PAH) exposure is a risk factor for esophageal squamous cell carcinoma, and PAHs are ligands of the aryl hydrocarbon receptor (AhR). This study measured the expression of AhR and related genes in frozen esophageal cell samples from patients exposed to different levels of indoor air pollution, who did or did not have high-grade squamous dysplasia and who did or did not have a family history of upper gastrointestinal tract (UGI) cancer. 147 samples were evaluated, including 23 (16%) from patients with high-grade dysplasia and 48 (33%) from patients without dysplasia who heated their homes with coal, withoutmore » a chimney (a 'high' indoor air pollution group), and 27 (18%) from patients with high-grade dysplasia and 49 (33%) from patients without dysplasia who did not heat their homes at all (a 'low' indoor air pollution group). Sixty-four (44%) had a family history of UGI cancer. RNA was extracted and quantitative PCR analysis was done. AhR gene expression was detectable in 85 (58%) of the samples and was >9-fold higher in those with a family history of UGI cancer (median expression (interquartile range), -1,964 (-18,000, -610) versus -18,000 (-18,000, -1036); P = 0.02, Wilcoxon rank-sum test). Heating status, dysplasia category, age, gender, and smoking were not associated with AhR expression (linear regression; all P values {ge} 0.1). AhR expression was higher in patients with a family history of UGI cancer. Such individuals may be more susceptible to the deleterious effects of PAH exposure, including PAH-induced cancer.« less

Inhibition of the aryl hydrocarbon receptor prevents Western diet-induced obesity. Model for AHR activation by kynurenine via oxidized-LDL, TLR2/4, TGFβ, and IDO1.

PubMed

Moyer, Benjamin J; Rojas, Itzel Y; Kerley-Hamilton, Joanna S; Hazlett, Haley F; Nemani, Krishnamurthy V; Trask, Heidi W; West, Rachel J; Lupien, Leslie E; Collins, Alan J; Ringelberg, Carol S; Gimi, Barjor; Kinlaw, William B; Tomlinson, Craig R

2016-06-01

Obesity is an increasingly urgent global problem, yet, little is known about its causes and less is known how obesity can be effectively treated. We showed previously that the aryl hydrocarbon receptor (AHR) plays a role in the regulation of body mass in mice fed Western diet. The AHR is a ligand-activated nuclear receptor that regulates genes involved in a number of biological pathways, including xenobiotic metabolism and T cell polarization. This study was an investigation into whether inhibition of the AHR prevents Western diet-based obesity. Male C57Bl/6J mice were fed control and Western diets with and without the AHR antagonist α-naphthoflavone or CH-223191, and a mouse hepatocyte cell line was used to delineate relevant cellular pathways. Studies are presented showing that the AHR antagonists α-naphthoflavone and CH-223191 significantly reduce obesity and adiposity and ameliorates liver steatosis in male C57Bl/6J mice fed a Western diet. Mice deficient in the tryptophan metabolizing enzyme indoleamine 2,3-dioxygenase 1 (IDO1) were also resistant to obesity. Using an AHR-directed, luciferase-expressing mouse hepatocyte cell line, we show that the transforming growth factor β1 (TGFβ1) signaling pathway via PI3K and NF-κB and the toll-like receptor 2/4 (TLR2/4) signaling pathway stimulated by oxidized low-density lipoproteins via NF-κB, each induce luciferase expression; however, TLR2/4 signaling was significantly reduced by inhibition of IDO1. At physiological levels, kynurenine but not kynurenic acid (both tryptophan metabolites and known AHR agonists) activated AHR-directed luciferase expression. We propose a hepatocyte-based model, in which kynurenine production is increased by enhanced IDO1 activity stimulated by TGFβ1 and TLR2/4 signaling, via PI3K and NF-κB, to perpetuate a cycle of AHR activation to cause obesity; and inhibition of the AHR, in turn, blocks the cycle's output to prevent obesity. The AHR with its broad ligand binding specificity

α-Naphthoflavone Increases Lipid Accumulation in Mature Adipocytes and Enhances Adipocyte-Stimulated Endothelial Tube Formation.

PubMed

Wang, Mei-Lin; Lin, Shyh-Hsiang; Hou, Yuan-Yu; Chen, Yue-Hwa

2015-04-30

The aryl hydrocarbon receptor (AhR) is a ligand-activated factor that regulates biological effects associated with obesity. The AhR agonists, such as environmental contaminants 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and β-naphthoflavone (BNF), inhibit preadipocyte differentiation and interfere with the functions of adipose tissue, whereas the antagonist may have opposite or protective effects in obesity. This study investigated the effects of α-naphthoflavone (α-NF), an AhR antagonist, on adipogenesis- and angiogenesis-associated factors in mature adipocytes and on cross-talk of mature adipocytes with endothelial cells (ECs). Besides, the roles of the AhR on lipid accumulation and on secretion of vascular endothelial growth factor were also determined by introducing siRNA of AhR. Differentiated 3T3-L1 cells were treated with α-naphthoflavone (α-NF) (1-5 μM) for 16 h. Lipid accumulation and the expressions of AhR-associated factors in the cells were determined. The interaction between adipocytes and ECs was investigated by cultivating ECs with conditioned medium (CM) from α-NF-treated mature adipocytes, followed by the determination of endothelial tube formation. The results showed that α-NF significantly increased triglyceride (TG) accumulation in mature adipocytes, which was associated with increased expression of hormone-sensitive lipase (HSL), estrogen receptor (ER), as well as decreased expression of AhR, AhR nuclear translocator (ARNT), cytochrome P4501B1 (CYP1B1), and nuclear factor erythroid-2-related factor (NRF-2) proteins. In addition, CM stimulated formation of tube-like structures in ECs, and α-NF further enhanced such stimulation in association with modulated the secretions of various angiogenic mediators by mature adipocytes. Similarly, increased TG accumulation and vascular endothelial growth factor (VEGF) secretion were observed in AhR-knockout cells. In conclusion, α-NF increased TG accumulation in mature adipocytes and enhanced

Gene expression profiling of the Notch-AhR-IL22 axis at homeostasis and in response to tissue injury.

PubMed

Weidenbusch, Marc; Rodler, Severin; Song, Shangqing; Romoli, Simone; Marschner, Julian A; Kraft, Franziska; Holderied, Alexander; Kumar, Santosh; Mulay, Shrikant R; Honarpisheh, Mohsen; Kumar Devarapu, Satish; Lech, Maciej; Anders, Hans-Joachim

2017-12-22

Notch and interleukin-22 (IL-22) signaling are known to regulate tissue homeostasis and respond to injury in humans and mice, and the induction of endogenous aryl hydrocarbon receptor (Ahr) ligands through Notch links the two pathways in a hierarchical fashion. However in adults, the species-, organ- and injury-specific gene expression of the Notch-AhR-IL22 axis components is unknown. We therefore performed gene expression profiling of DLL1, DLL3, DLL4, DLK1, DLK2, JAG1, JAG2, Notch1, Notch2, Notch3, Notch4, ADAM17/TNF-α ADAM metalloprotease converting enzyme (TACE), PSEN1, basigin (BSG)/CD147, RBP-J, HES1, HES5, HEY1, HEYL, AHR, ARNT, ARNT2, CYP1A1, CYP24A1, IL-22, IL22RA1, IL22RA2, IL10RB, and STAT3 under homeostatic conditions in ten mature murine and human organs. Additionally, the expression of these genes was assessed in murine models of acute sterile inflammation and progressive fibrosis. We show that there are organ-specific gene expression profiles of the Notch-AhR-IL22 axis in humans and mice. Although there is an overall interspecies congruency, specific differences between human and murine expression signatures do exist. In murine tissues with AHR/ARNT expression CYP1A1 and IL-22 were correlated with HES5 and HEYL expression, while in human tissues no such correlation was found. Notch and AhR signaling are involved in renal inflammation and fibrosis with specific gene expression changes in each model. Despite the presence of all Notch pathway molecules in the kidney and a model-specific induction of Notch ligands, IL-22 was only up-regulated in acute inflammation, but rapidly down-regulated during regeneration. This implies that for targeting injury responses, e.g. via IL-22, species-specific differences, injury type and time points have to be considered. © 2017 The Author(s).

Diphenylarsinic acid, a chemical warfare-related neurotoxicant, promotes liver carcinogenesis via activation of aryl hydrocarbon receptor signaling and consequent induction of oxidative DNA damage in rats.

PubMed

Wei, Min; Yamada, Takanori; Yamano, Shotaro; Kato, Minoru; Kakehashi, Anna; Fujioka, Masaki; Tago, Yoshiyuki; Kitano, Mistuaki; Wanibuchi, Hideki

2013-11-15

Diphenylarsinic acid (DPAA), a chemical warfare-related neurotoxic organic arsenical, is present in the groundwater and soil in some regions of Japan due to illegal dumping after World War II. Inorganic arsenic is carcinogenic in humans and its organic arsenic metabolites are carcinogenic in animal studies, raising serious concerns about the carcinogenicity of DPAA. However, the carcinogenic potential of DPAA has not yet been evaluated. In the present study we found that DPAA significantly enhanced the development of diethylnitrosamine-induced preneoplastic lesions in the liver in a medium-term rat liver carcinogenesis assay. Evaluation of the expression of cytochrome P450 (CYP) enzymes in the liver revealed that DPAA induced the expression of CYP1B1, but not any other CYP1, CYP2, or CYP3 enzymes, suggesting that CYP1B1 might be the enzyme responsible for the metabolic activation of DPAA. We also found increased oxidative DNA damage, possibly due to elevated CYP1B1 expression. Induction of CYP1B1 has generally been linked with the activation of AhR, and we found that DPAA activates the aryl hydrocarbon receptor (AhR). Importantly, the promotion effect of DPAA was observed only at a dose that activated the AhR, suggesting that activation of AhR and consequent induction of AhR target genes and oxidative DNA damage plays a vital role in the promotion effects of DPAA. The present study provides, for the first time, evidence regarding the carcinogenicity of DPAA and indicates the necessity of comprehensive evaluation of its carcinogenic potential using long-term carcinogenicity studies. © 2013.

An Estuarine Fish Bioassay for Sensitive Biomonitoring of Oil-related Contamination

EPA Science Inventory

An embryonic and larval bioassay using the estuarine fish, Fundulus heteroclitus, was modified for the rapid detection of bioavailable compounds that act through the aryl hydrocarbon receptor (AhR). The early development of fishes is particularly sensitive to AhR agonists, such ...

Tumor necrosis factor-α inhibits effects of aryl hydrocarbon receptor ligands on cell death in human lymphocytes.

PubMed

Ghatrehsamani, Mahdi; Soleimani, Masoud; Esfahani, Behjat A Moayedi; Shirzad, Hedayatollah; Hakemi, Mazdak G; Mossahebimohammadi, Majid; Eskandari, Nahid; Adib, Minoo

2015-01-01

Activation of aryl hydrocarbon receptor (AhR) leads to diverse outcome in various kinds of cells. AhR activation may induce apoptosis or prevent of apoptosis and cell death. Recent studies suggest that apoptosis effects of AhR can be modulated by inflammatory cytokine like tumor necrosis factor alpha (TNF-α). In this study, we try to investigate the possible interaction of TNF-α with the 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), a ligand of AhR, on peripheral lymphocytes. Human peripheral blood mononuclear cells (PBMCs) were isolated from peripheral blood by discontinuous density gradient centrifugation on ficoll. Isolated PBMCs were divided into four groups: Control group, TNF-α administered group, TCDD administered group, co-administered group with TCDD and TNF-α. Cells were maintained for a week in lymphocyte culture condition. Then, TNF-α was added to group 2 and 4. Finally, apoptosis and necrosis were analyzed in all samples using flowcytometry. In group 4, the mean percent of necrosis and apoptosis in TCDD treatment groups was significantly larger than other groups; (P < 0.05). Furthermore, there was no significant difference between the mean percent of cell death in TNF-α administered group and TCDD administered group (P > 0.05). However, the mean percent of cell death in co-administered group with TCDD and TNF-α was significantly lower than other groups; (P < 0.05). TNF-α could significantly inhibit effects of TCDD on lymphocytes apoptosis. Combination effects of TNF-α and TCDD on lymphocyte increase cell survival.

RELATIONSHIPS BETWEEN RESIDUES OF AHR AGONISTS IN FISH AND CONCENTRATIONS IN WATER AND SEDIMENTS

EPA Science Inventory

Relationships between Residues of AhR Agonists in Fish and Concentrations in Water and Sediment. Cook, PM*, Burkhard, LP, Mount, DR, US-EPA, NHEERL, MED, Duluth, MN. The bioaccumulation visualization approach of Burkhard et al. (2002) can be effectively used to describe the bioa...

Long interspersed element-1 is differentially regulated by food-borne carcinogens via the aryl hydrocarbon receptor

PubMed Central

Okudaira, N; Okamura, T; Tamura, M; Iijma, K; Goto, M; Matsunaga, A; Ochiai, M; Nakagama, H; Kano, S; Fujii-Kuriyama, Y; Ishizaka, Y

2013-01-01

A single human cell contains more than 5.0 × 105 copies of long interspersed element-1 (L1), 80–100 of which are competent for retrotransposition (L1-RTP). Recent observations have revealed the presence of de novo L1 insertions in various tumors, but little is known about its mechanism. Here, we found that 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx), food-borne carcinogens that are present in broiled meats, induced L1-RTP. This induction was dependent on a cellular cascade comprising the aryl hydrocarbon receptor (AhR), a mitogen-activated protein kinase, and CCAAT/enhancer-binding protein β. Notably, these compounds exhibited differential induction of L1-RTP. MeIQx-induced L1-RTP was dependent on AhR nuclear translocator 1 (ARNT1), a counterpart of AhR required for gene expression in response to environmental pollutants. By contrast, PhIP-induced L1-RTP did not require ARNT1 but was dependent on estrogen receptor α (ERα) and AhR repressor. In vivo studies using transgenic mice harboring the human L1 gene indicated that PhIP-induced L1-RTP was reproducibly detected in the mammary gland, which is a target organ of PhIP-induced carcinoma. Moreover, picomolar levels of each compound induced L1-RTP, which is comparable to the PhIP concentration detected in human breast milk. Data suggest that somatic cells possess machineries that induce L1-RTP in response to the carcinogenic compounds. Together with data showing that micromolar levels of heterocyclic amines (HCAs) were non-genotoxic, our observations indicate that L1-RTP by environmental compounds is a novel type of genomic instability, further suggesting that analysis of L1-RTP by HCAs is a novel approach to clarification of modes of carcinogenesis. PMID:23208499

Long interspersed element-1 is differentially regulated by food-borne carcinogens via the aryl hydrocarbon receptor.

PubMed

Okudaira, N; Okamura, T; Tamura, M; Iijma, K; Goto, M; Matsunaga, A; Ochiai, M; Nakagama, H; Kano, S; Fujii-Kuriyama, Y; Ishizaka, Y

2013-10-10

A single human cell contains more than 5.0 × 10(5) copies of long interspersed element-1 (L1), 80-100 of which are competent for retrotransposition (L1-RTP). Recent observations have revealed the presence of de novo L1 insertions in various tumors, but little is known about its mechanism. Here, we found that 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx), food-borne carcinogens that are present in broiled meats, induced L1-RTP. This induction was dependent on a cellular cascade comprising the aryl hydrocarbon receptor (AhR), a mitogen-activated protein kinase, and CCAAT/enhancer-binding protein β. Notably, these compounds exhibited differential induction of L1-RTP. MeIQx-induced L1-RTP was dependent on AhR nuclear translocator 1 (ARNT1), a counterpart of AhR required for gene expression in response to environmental pollutants. By contrast, PhIP-induced L1-RTP did not require ARNT1 but was dependent on estrogen receptor α (ERα) and AhR repressor. In vivo studies using transgenic mice harboring the human L1 gene indicated that PhIP-induced L1-RTP was reproducibly detected in the mammary gland, which is a target organ of PhIP-induced carcinoma. Moreover, picomolar levels of each compound induced L1-RTP, which is comparable to the PhIP concentration detected in human breast milk. Data suggest that somatic cells possess machineries that induce L1-RTP in response to the carcinogenic compounds. Together with data showing that micromolar levels of heterocyclic amines (HCAs) were non-genotoxic, our observations indicate that L1-RTP by environmental compounds is a novel type of genomic instability, further suggesting that analysis of L1-RTP by HCAs is a novel approach to clarification of modes of carcinogenesis.

Airborne polycyclic aromatic hydrocarbons trigger human skin cells aging through aryl hydrocarbon receptor.

PubMed

Qiao, Yuan; Li, Qiang; Du, Hong-Yang; Wang, Qiao-Wei; Huang, Ye; Liu, Wei

2017-07-01

Accumulating evidence suggests that polycyclic aromatic hydrocarbons (PAH) which adsorbed on the surface of ambient air particulate matters (PM), are the major toxic compound to cause cardiovascular and respiratory diseases, even cancer. However, its detrimental effects on human skin cell remain unclear. Here, we demonstrated that SRM1649b, a reference urban dust material of PAH, triggers human skin cells aging through cell cycle arrest, cell growth inhibition and apoptosis. Principally, SRM1649b facilitated Aryl hydrocarbon receptor (AhR) translocated into nucleus, subsequently activated ERK/MAPK signaling pathway, and upregulated aging-related genes expression. Most important, we found that AhR antagonist efficiently revert the aging of skin cells. Thus our novel findings firstly revealed the mechanism of skin aging under PAH contamination and provided potential strategy for clinical application. Copyright © 2017. Published by Elsevier Inc.

The citrus flavonone hesperetin attenuates the nuclear translocation of aryl hydrocarbon receptor.

PubMed

Tan, Yan Qin; Chiu-Leung, Leo Clement; Lin, Shu-Mei; Leung, Lai K

2018-08-01

The environmental polycyclic aromatic hydrocarbons (PAH) and dioxins are carcinogens and their adverse effects have been largely attributed to the activation of AhR. Hesperetin is a flavonone found abundantly in citrus fruits and has been shown to be a biologically active agent. In the present study, the effect of hesperetin on the nuclear translocation of AhR and the downstream gene expression was investigated in MCF-7 cells. Confocal microscopy indicated that 7, 12-dimethylbenz[α]anthracene (DMBA) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) -induced nuclear translocation of AhR was deterred by hesperetin treatment. The reduced nuclear translocation could also be observed in Western analysis. Reporter-gene assay further illustrated that the induced XRE transactivation was weakened by the treatment of hesperetin. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay demonstrated that the gene expressions of CYP1A1, 1A2, and 1B1 followed the same pattern of AhR translocation. These results suggested that hesperetin counteracted AhR transactivation and suppressed the downstream gene expression. Copyright © 2018 Elsevier Inc. All rights reserved.

The aryl hydrocarbon receptor-mediated disruption of vitellogenin synthesis in the fish liver: Cross-talk between AHR- and ERα-signalling pathways

PubMed Central

Bemanian, Vahid; Male, Rune; Goksøyr, Anders

2004-01-01

Background In the fish liver, the synthesis of egg yolk protein precursor vitellogenin (VTG) is under control of the estrogen receptor alpha (ERα). Environmental contaminants such as 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) are suspected to have antiestrogenic effects. The aryl hydrocarbon receptor (AHR) is the initial cellular target for TCDD and related compounds. The AHR is a ligand-activated transcription factor that stimulates the expression of the genes encoding xenobiotic metabolizing enzymes, such as cytochrome P450 1A (CYP1A). In this study, the effects of activation of AHR on the hepatic expression of VTG and ERα genes, in primary cultured salmon hepatocytes, have been investigated. Results The expression of the genes encoding VTG and ERα were strongly induced by 17β-estradiol (E2). However, the expression of VTG was disrupted by exposure of the cells to TCDD while CYP1A expression was enhanced. The effect of TCDD on VTG and CYP1A expression was annulled by the AHR-inhibitor α-naphthoflavone. Furthermore, exposure of the cells to TCDD abolished E2-induced accumulation of ERα mRNA. The AHR-mediated inhibitory effects on the expression of the VTG and ERα genes may occur at transcriptional and/or post-transcriptional levels. Nuclear run-off experiments revealed that simultaneous exposure of the cells to E2 and TCDD strongly inhibited the initiation of transcription of the VTG and ERα genes. In addition, inhibition of RNA synthesis by actinomycin D treatment showed that post-transcriptional levels of VTG and ERα mRNAs were not significantly altered upon treatment of the cells with TCDD. These results suggested that activation of AHR may inhibit the transactivation capacity of the ERα. Further, electrophoretic mobility shift assays using nuclear extracts prepared from cells treated for one or two hours with E2, alone or in mixture with TCDD, showed a strong reduction in the DNA binding activities upon TCDD treatment. These results also suggested

Immunological characterization of the aryl hydrocarbon receptor (AHR) knockout rat in the presence and absence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

PubMed

Phadnis-Moghe, Ashwini S; Chen, Weimin; Li, Jinpeng; Crawford, Robert B; Bach, Anthony; D'Ingillo, Shawna; Kovalova, Natalia; Suarez-Martinez, Jose E; Kaplan, Barbara L F; Harrill, Joshua A; Budinsky, Robert; Rowlands, J Craig; Thomas, Russell S; Kaminski, Norbert E

2016-08-10

The aryl hydrocarbon receptor (AHR) has been extensively characterized for the essential role it plays in mediating the toxic responses elicited by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Despite similarities across animal species, species-specific differences exist in the profile of toxicity and sensitivity to TCDD owing, in part, to differences in the AHR. Newer reports have implicated the importance of AHR in the development and regulation of the immune system. Our present studies seek to further explore the essential role of AHR in lymphoid tissue composition, B cell function and the immunological responses after TCDD administration using the recently established AHR KO rats. Comprehensive immune cell phenotyping showed a decrease in the CD8 + T cell, CD11c + populations and an increase in NKT cells in 3-week-old AHR KO rats compared to the WT controls. The lipopolysaccharide-induced IgM response and proliferation was markedly suppressed in the WT but not in the AHR KO B cells in the presence of TCDD. However, the percentage of LPS-activated IgM + B cells was significantly higher in the AHR KO B cells as compared to that of WT suggesting the role of AHR in regulating the IgM response. The use of an AHR antagonist further alluded to the endogenous role of AHR in regulating B cell responses in the rat. Overall, the studies report for the first time, comprehensive immune cell phenotyping of the AHR KO rat and the endogenous role of AHR in the regulation of B cell function in the rat. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Analysis of the AHR gene proximal promoter GGGGC-repeat polymorphism in lung, breast, and colon cancer

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

Spink, Barbara C.; Bloom, Michael S.; Wu, Susan

The aryl hydrocarbon receptor (AhR) regulates expression of numerous genes, including those of the CYP1 gene family. With the goal of determining factors that control AHR gene expression, our studies are focused on the role of the short tandem repeat polymorphism, (GGGGC){sub n}, located in the proximal promoter of the human AHR gene. When luciferase constructs containing varying GGGGC repeats were transfected into cancer cell lines derived from the lung, colon, and breast, the number of GGGGC repeats affected AHR promoter activity. The number of GGGGC repeats was determined in DNA from 327 humans and from 38 samples representing 5more » species of non-human primates. In chimpanzees and 3 species of macaques, only (GGGGC){sub 2} alleles were observed; however, in western gorilla, (GGGGC){sub n} alleles with n = 2, 4, 5, 6, 7, and 8 were identified. In all human populations examined, the frequency of (GGGGC){sub n} was n = 4 > 5 ≫ 2, 6. When frequencies of the (GGGGC){sub n} alleles in DNA from patients with lung, colon, or breast cancer were evaluated, the occurrence of (GGGGC){sub 2} was found to be 8-fold more frequent among lung cancer patients in comparison with its incidence in the general population, as represented by New York State neonates. Analysis of matched tumor and non-tumor DNA samples from the same individuals provided no evidence of microsatellite instability. These studies indicate that the (GGGGC){sub n} short tandem repeats are inherited, and that the (GGGGC){sub 2} allele in the AHR proximal promoter region should be further investigated with regard to its potential association with lung cancer susceptibility. - Highlights: • The AHR proximal promoter contains a polymorphism, (GGGGC){sub n}, where n = 4 > 5 ≫ 2, 6 • Matched tumor and non-tumor DNA did not show (GGGGC){sub n} microsatellite instability • AHR promoter activity of a construct with (GGGGC){sub 2} was lower than that of (GGGGC){sub 4} • The frequency of (GGGGC){sub 2

Lymphocyte-specific protein tyrosine kinase (LCK) is involved in the aryl hydrocarbon receptor (AHR)-mediated impairment of immunoglobulin secretion in human primary B cells.

PubMed

Zhou, Jiajun; Zhang, Qiang; Henriquez, Joseph E; Crawford, Robert B; Kaminski, Norbert E

2018-05-31

The aryl hydrocarbon receptor (AHR) is a cytosolic ligand-activated transcription factor involved in xenobiotic sensing, cell cycle regulation and cell development. In humans, the activation of AHR by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a high affinity AHR-ligand, impairs the secretion of immunoglobulin M (IgM) to suppress humoral immunity. However, the mechanisms bridging the activation of AHR and the impairment of IgM secretion by human primary B cells remain poorly understood. Recent transcriptomic analysis revealed upregulation of lymphocyte-specific protein tyrosine kinase (LCK) in AHR activated human primary B cells. LCK is a well-characterized tyrosine kinase that phosphorylates critical signaling proteins involved in activation and cytokine production in T cells. Conversely, the role of LCK in human primary B cells is not well understood. In the current studies, we have verified the transcriptomic finding by detecting AHR-mediated upregulation of LCK protein in human primary B cells. We also confirmed the role of AHR in the upregulation of LCK by using a specific AHR antagonist, which abolished the AHR-mediated increase of LCK. Furthermore, we have confirmed the role of LCK in the AHR-mediated suppression of IgM by using LCK specific inhibitors, which restored IgM secretion by human B cells in the presence of TCDD. Collectively, the current studies demonstrate a novel role of LCK in IgM secretion and provide new insights into the mechanism for AHR-mediated impairment of immunoglobulin secretion by human primary B cells.

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

Luo, Yueh-Hsia; Kuo, Yu-Chun; Tsai, Ming-Hsien

Exposure to environmental aryl hydrocarbon receptor (AhR) agonists, such as halogenated aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), has great impacts on the development of various lung diseases. As emerging molecular targets for AhR agonists, cytokines may contribute to the inflammatory or immunotoxic effects of environmental AhR agonists. However, general cytokine expression may not specifically indicate environmental AhR agonist exposure. By comparing cytokine and chemokine expression profiles in human lung adenocarcinoma cell line CL5 treated with AhR agonists and the non-AhR agonist polychlorinated biphenyl (PCB) 39, we identified a target cytokine of environmental AhR agonist exposure of in the lungs.more » Thirteen cytokine and chemokine genes were altered in the AhR agonists-treated cells, but none were altered in the PCB39-treated cells. Interleukin (IL)-24 was the most highly induced gene among AhR-modulated cytokines. Cotreatment with AhR antagonist completely prevented IL-24 induction by AhR agonists in the CL5 cells. Knockdown AhR expression with short-hairpin RNA (shRNA) significantly reduced benzo[a]pyrene (BaP)-induced IL-24 mRNA levels. We further confirmed that gene transcription, but not mRNA stability, was involved in IL-24 upregulation by BaP. Particulate matter (PM) in the ambient air contains some PAHs and is reported to activate AhR. Oropharyngeal aspiration of PM significantly increased IL-24 levels in lung epithelia and in bronchoalveolar lavage fluid of mice 4 weeks after treatment. Thus, our data suggests that IL-24 is a pulmonary exposure target cytokine of environmental AhR agonists. - Graphical abstract: (A) Cytokine and chemokine gene expressions were examined in CL5 cells treated with AhR and non-AhR agonists. Thirteen cytokines and chemokines genes were altered in the AhR agonist-treated cells, but not in the non-AhR agonist-treated cells. IL-24 was the most highly induced gene among the Ah

Shared epitope-aryl hydrocarbon receptor crosstalk underlies the mechanism of gene-environment interaction in autoimmune arthritis.

PubMed

Fu, Jiaqi; Nogueira, Sarah V; Drongelen, Vincent van; Coit, Patrick; Ling, Song; Rosloniec, Edward F; Sawalha, Amr H; Holoshitz, Joseph

2018-05-01

The susceptibility to autoimmune diseases is affected by genetic and environmental factors. In rheumatoid arthritis (RA), the shared epitope (SE), a five-amino acid sequence motif encoded by RA-associated HLA-DRB1 alleles, is the single most significant genetic risk factor. The risk conferred by the SE is increased in a multiplicative way by exposure to various environmental pollutants, such as cigarette smoke. The mechanism of this synergistic interaction is unknown. It is worth noting that the SE has recently been found to act as a signal transduction ligand that facilitates differentiation of Th17 cells and osteoclasts in vitro and in vivo. Intriguingly, the aryl hydrocarbon receptor (AhR), a transcription factor that mediates the xenobiotic effects of many pollutants, including tobacco combustion products, has been found to activate similar biologic effects. Prompted by these similarities, we sought to determine whether the SE and AhR signaling pathways interact in autoimmune arthritis. Here we uncovered a nuclear factor kappa B-mediated synergistic interaction between the SE and AhR pathways that leads to markedly enhanced osteoclast differentiation and Th17 polarization in vitro. Administration of AhR pathway agonists to transgenic mice carrying human SE-coding alleles resulted in a robust increase in arthritis severity, bone destruction, overabundance of osteoclasts, and IL17-expressing cells in the inflamed joints and draining lymph nodes of arthritic mice. Thus, this study identifies a previously unrecognized mechanism of gene-environment interaction that could provide insights into the well-described but poorly understood amplification of the genetic risk for RA upon exposure to environmental pollutants. Copyright © 2018 the Author(s). Published by PNAS.

PCB 126 and Other Dioxin-Like PCBs Specifically Suppress Hepatic PEPCK Expression via the Aryl Hydrocarbon Receptor

PubMed Central

Zhang, Wenshuo; Sargis, Robert M.; Volden, Paul A.; Carmean, Christopher M.; Sun, Xiao J.; Brady, Matthew J.

2012-01-01

Dioxins and dioxin-like compounds encompass a group of structurally related heterocyclic compounds that bind to and activate the aryl hydrocarbon receptor (AhR). The prototypical dioxin is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a highly toxic industrial byproduct that incites numerous adverse physiological effects. Global commercial production of the structurally similar polychlorinated biphenyls (PCBs), however, commenced early in the 20th century and continued for decades; dioxin-like PCBs therefore contribute significantly to total dioxin-associated toxicity. In this study, PCB 126, the most potent dioxin-like PCB, was evaluated with respect to its direct effects on hepatic glucose metabolism using primary mouse hepatocytes. Overnight treatment with PCB 126 reduced hepatic glycogen stores in a dose-dependent manner. Additionally, PCB 126 suppressed forskolin-stimulated gluconeogenesis from lactate. These effects were independent of acute toxicity, as PCB 126 did not increase lactate dehydrogenase release nor affect lipid metabolism or total intracellular ATP. Interestingly, provision of cells with glycerol instead of lactate as the carbon source completely restored hepatic glucose production, indicating specific impairment in the distal arm of gluconeogenesis. In concordance with this finding, PCB 126 blunted the forskolin-stimulated increase in phosphoenolpyruvate carboxykinase (PEPCK) mRNA levels without affecting glucose-6-phosphatase expression. Myricetin, a putative competitive AhR antagonist, reversed the suppression of PEPCK induction by PCB 126. Furthermore, other dioxin-like PCBs demonstrated similar effects on PEPCK expression in parallel with their ability to activate AhR. It therefore appears that AhR activation mediates the suppression of PEPCK expression by dioxin-like PCBs, suggesting a role for these pollutants as disruptors of energy metabolism. PMID:22615911

EXPRESSION OF AHR AND ARNT MRNA IN CULTURED HUMAN ENDOMETRIAL EXPLANTS EXPOSED TO TCDD

EPA Science Inventory

Expression of AhR and ARNT mRNA in cultured human endometrial explants exposed to TCDD.

Pitt JA, Feng L, Abbott BD, Schmid J, Batt RE, Costich TG, Koury ST, Bofinger DP.

Curriculum in Toxicology, University of North Carolina, Chapel Hill, NC 27599, USA.

Endom...

Combination effects of AHR agonists and Wnt/β-catenin modulators in zebrafish embryos: Implications for physiological and toxicological AHR functions

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

Wincent, Emma; Institute of Environmental Medicine, Karolinska Institutet, 17177 Stockholm; Stegeman, John J.

2015-04-15

Wnt/β-catenin signaling regulates essential biological functions and acts in developmental toxicity of some chemicals. The aryl hydrocarbon receptor (AHR) is well-known to mediate developmental toxicity of persistent dioxin-like compounds (DLCs). Recent studies indicate a crosstalk between β-catenin and the AHR in some tissues. However the nature of this crosstalk in embryos is poorly known. We observed that zebrafish embryos exposed to the β-catenin inhibitor XAV939 display effects phenocopying those of the dioxin-like 3,3′,4,4′,5-pentachlorobiphenyl (PCB126). This led us to investigate the AHR interaction with β-catenin during development and ask whether developmental toxicity of DLCs involves antagonism of β-catenin signaling. We examinedmore » phenotypes and transcriptional responses in zebrafish embryos exposed to XAV939 or to a β-catenin activator, 1-azakenpaullone, alone or with AHR agonists, either PCB126 or 6-formylindolo[3,2-b]carbazole (FICZ). Alone 1-azakenpaullone and XAV939 both were embryo-toxic, and we found that in the presence of FICZ, the toxicity of 1-azakenpaullone decreased while the toxicity of XAV939 increased. This rescue of 1-azakenpaullone effects occurred in the time window of Ahr2-mediated toxicity and was reversed by morpholino-oligonucleotide knockdown of Ahr2. Regarding PCB126, addition of either 1-azakenpaullone or XAV939 led to lower mortality than with PCB126 alone but surviving embryos showed severe edemas. 1-Azakenpaullone induced transcription of β-catenin-associated genes, while PCB126 and FICZ blocked this induction. The data indicate a stage-dependent antagonism of β-catenin by Ahr2 in zebrafish embryos. We propose that the AHR has a physiological role in regulating β-catenin during development, and that this is one point of intersection linking toxicological and physiological AHR-governed processes.« less

Diversity as Opportunity: Insights from 600 Million Years of AHR Evolution.

PubMed

Hahn, Mark E; Karchner, Sibel I; Merson, Rebeka R

2017-02-01

The aryl hydrocarbon receptor (AHR) was for many years of interest only to pharmacologists and toxicologists. However, this protein has fundamental roles in biology that are being revealed through studies in diverse animal species. The AHR is an ancient protein. AHR homologs exist in most major groups of modern bilaterian animals, including deuterostomes (chordates, hemichordates, echinoderms) and the two major clades of protostome invertebrates [ecdysozoans (e.g. arthropods and nematodes) and lophotrochozoans (e.g. molluscs and annelids)]. AHR homologs also have been identified in cnidarians such as the sea anemone Nematostella and in the genome of Trichoplax , a placozoan. Bilaterians, cnidarians, and placozoans form the clade Eumetazoa , whose last common ancestor lived approximately 600 million years ago (MYA). The presence of AHR homologs in modern representatives of all these groups indicates that the original eumetazoan animal possessed an AHR homolog. Studies in invertebrates and vertebrates reveal parallel functions of AHR in the development and function of sensory neural systems, suggesting that these may be ancestral roles. Vertebrate animals are characterized by the expansion and diversification of AHRs, via gene and genome duplications, from the ancestral protoAHR into at least five classes of AHR-like proteins: AHR, AHR1, AHR2, AHR3, and AHRR. The evolution of multiple AHRs in vertebrates coincided with the acquisition of high-affinity binding of halogenated and polynuclear aromatic hydrocarbons and the emergence of adaptive functions involving regulation of xenobiotic-metabolizing enzymes and roles in adaptive immunity. The existence of multiple AHRs may have facilitated subfunction partitioning and specialization of specific AHR types in some taxa. Additional research in diverse model and non-model species will continue to enrich our understanding of AHR and its pleiotropic roles in biology and toxicology.

Diversity as Opportunity: Insights from 600 Million Years of AHR Evolution

PubMed Central

Hahn, Mark E.; Karchner, Sibel I.; Merson, Rebeka R.

2017-01-01

The aryl hydrocarbon receptor (AHR) was for many years of interest only to pharmacologists and toxicologists. However, this protein has fundamental roles in biology that are being revealed through studies in diverse animal species. The AHR is an ancient protein. AHR homologs exist in most major groups of modern bilaterian animals, including deuterostomes (chordates, hemichordates, echinoderms) and the two major clades of protostome invertebrates [ecdysozoans (e.g. arthropods and nematodes) and lophotrochozoans (e.g. molluscs and annelids)]. AHR homologs also have been identified in cnidarians such as the sea anemone Nematostella and in the genome of Trichoplax, a placozoan. Bilaterians, cnidarians, and placozoans form the clade Eumetazoa, whose last common ancestor lived approximately 600 million years ago (MYA). The presence of AHR homologs in modern representatives of all these groups indicates that the original eumetazoan animal possessed an AHR homolog. Studies in invertebrates and vertebrates reveal parallel functions of AHR in the development and function of sensory neural systems, suggesting that these may be ancestral roles. Vertebrate animals are characterized by the expansion and diversification of AHRs, via gene and genome duplications, from the ancestral protoAHR into at least five classes of AHR-like proteins: AHR, AHR1, AHR2, AHR3, and AHRR. The evolution of multiple AHRs in vertebrates coincided with the acquisition of high-affinity binding of halogenated and polynuclear aromatic hydrocarbons and the emergence of adaptive functions involving regulation of xenobiotic-metabolizing enzymes and roles in adaptive immunity. The existence of multiple AHRs may have facilitated subfunction partitioning and specialization of specific AHR types in some taxa. Additional research in diverse model and non-model species will continue to enrich our understanding of AHR and its pleiotropic roles in biology and toxicology. PMID:28286876

Regulation of pregnane-X-receptor, CYP3A and P-glycoprotein genes in the PCB-resistant killifish (Fundulus heteroclitus) population from New Bedford Harbor.

PubMed

Gräns, Johanna; Wassmur, Britt; Fernández-Santoscoy, María; Zanette, Juliano; Woodin, Bruce R; Karchner, Sibel I; Nacci, Diane E; Champlin, Denise; Jayaraman, Saro; Hahn, Mark E; Stegeman, John J; Celander, Malin C

2015-02-01

Killifish survive and reproduce in the New Bedford Harbor (NBH) in Massachusetts (MA), USA, a site severely contaminated with polychlorinated biphenyls (PCBs) for decades. Levels of 22 different PCB congeners were analyzed in liver from killifish collected in 2008. Concentrations of dioxin-like PCBs in liver of NBH killifish were ∼400 times higher, and the levels of non-dioxin-like PCBs ∼3000 times higher than in killifish from a reference site, Scorton Creek (SC), MA. The NBH killifish are known to be resistant to the toxicity of dioxin-like compounds and to have a reduced aryl hydrocarbon receptor (AhR) signaling response. Little is known about the responses of these fish to non-dioxin-like PCBs, which are at extraordinarily high levels in NBH fish. In mammals, some non-dioxin-like PCB congeners act through nuclear receptor 1I2, the pregnane-X-receptor (PXR). To explore this pathway in killifish, a PXR cDNA was sequenced and its molecular phylogenetic relationship to other vertebrate PXRs was determined. Killifish were also collected in 2009 from NBH and SC, and after four months in the laboratory they were injected with a single dose of either the dioxin-like PCB 126 (an AhR agonist) or the non-dioxin-like PCB 153 (a mammalian PXR agonist). Gills and liver were sampled three days after injection and transcript levels of genes encoding PXR, cytochrome P450 3A (CYP3A), P-glycoprotein (Pgp), AhR2 and cytochrome P450 1A (CYP1A) were measured by quantitative PCR. As expected, there was little effect of PCB exposure on mRNA expression of AhR2 or CYP1A in liver and gills of NBH fish. In NBH fish, but not in SC fish, there was increased mRNA expression of hepatic PXR, CYP3A and Pgp upon exposure to either of the two PCB congeners. However, basal PXR and Pgp mRNA levels in liver of NBH fish were significantly lower than in SC fish. A different pattern was seen in gills, where there were no differences in basal mRNA expression of these genes between the two

Aryl hydrocarbon receptor (AHR) regulation of L-Type Amino Acid Transporter 1 (LAT-1) expression in MCF-7 and MDA-MB-231 breast cancer cells.

PubMed

Tomblin, Justin K; Arthur, Subha; Primerano, Donald A; Chaudhry, Ateeq R; Fan, Jun; Denvir, James; Salisbury, Travis B

2016-04-15

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that is regulated by environmental toxicants that function as AHR agonists such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). L-Type Amino Acid Transporter 1 (LAT1) is a leucine transporter that is overexpressed in cancer. The regulation of LAT1 by AHR in MCF-7 and MDA-MB-231 breast cancer cells (BCCs) was investigated in this report. Ingenuity pathway analysis (IPA) revealed a significant association between TCDD-regulated genes (TRGs) and molecular transport. Overlapping the TCDD-RNA-Seq dataset obtained in this study with a published TCDD-ChIP-seq dataset identified LAT1 as a primary target of AHR-dependent TCDD induction. Short interfering RNA (siRNA)-directed knockdown of AHR confirmed that TCDD-stimulated increases in LAT1 mRNA and protein required AHR expression. TCDD-stimulated increases in LAT1 mRNA were also inhibited by the AHR antagonist CH-223191. Upregulation of LAT1 by TCDD coincided with increases in leucine uptake by MCF-7 cells in response to TCDD. Chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) assays revealed increases in AHR, AHR nuclear translocator (ARNT) and p300 binding and histone H3 acetylation at an AHR binding site in the LAT1 gene in response to TCDD. In MCF-7 and MDA-MB-231 cells, endogenous levels of LAT1 mRNA and protein were reduced in response to knockdown of AHR expression. Knockdown experiments demonstrated that proliferation of MCF-7 and MDA-MB-231 cells is dependent on both LAT1 and AHR. Collectively, these findings confirm the dependence of cancer cells on leucine uptake and establish a mechanism for extrinsic and intrinsic regulation of LAT1 by AHR. Copyright © 2016 Elsevier Inc. All rights reserved.

DNA Methylation of the Aryl Hydrocarbon Receptor Repressor Associations with Cigarette Smoking and Subclinical Atherosclerosis

PubMed Central

Reynolds, Lindsay M.; Wan, Ma; Ding, Jingzhong; Taylor, Jackson R.; Mstat, Kurt Lohman; Su, Dan; Bennett, Brian D.; Porter, Devin K.; Gimple, Ryan; Pittman, Gary S.; Wang, Xuting; Howard, Timothy D.; Siscovick, David; Psaty, Bruce M.; Shea, Steven; Burke, Gregory L.; Jacobs, David R.; Rich, Stephen S.; Hixson, James E.; Stein, James H.; Stunnenberg, Hendrik; Barr, R. Graham; Kaufman, Joel D.; Post, Wendy S.; Hoeschele, Ina; Herrington, David M.; Bell, Douglas A.; Liu, Yongmei

2015-01-01

Background Tobacco smoke contains numerous agonists of the aryl-hydrocarbon receptor (AhR) pathway, and activation of the AhR pathway was shown to promote atherosclerosis in mice. Intriguingly, cigarette smoking is most strongly and robustly associated with DNA modifications to an AhR pathway gene, the aryl-hydrocarbon receptor repressor (AHRR). We hypothesized that altered AHRR methylation in monocytes, a cell type sensitive to cigarette smoking and involved in atherogenesis, may be a part of the biological link between cigarette smoking and atherosclerosis. Methods and Results DNA methylation profiles of AHRR in monocytes (542 CpG sites ± 150kb of AHRR, using Illumina 450K array) were integrated with smoking habits and ultrasound-measured carotid plaque scores from 1,256 participants of the Multi-Ethnic Study of Atherosclerosis (MESA). Methylation of cg05575921 significantly associated (p = 6.1×10−134) with smoking status (current vs. never). Novel associations between cg05575921 methylation and carotid plaque scores (p = 3.1×10−10) were identified, which remained significant in current and former smokers even after adjusting for self-reported smoking habits, urinary cotinine, and well-known CVD risk factors. This association replicated in an independent cohort using hepatic DNA (n = 141). Functionally, cg05575921 was located in a predicted gene expression regulatory element (enhancer), and had methylation correlated with AHRR mRNA profiles (p = 1.4×10−17) obtained from RNA sequencing conducted on a subset (n = 373) of the samples. Conclusions These findings suggest AHRR methylation may be functionally related to AHRR expression in monocytes, and represents a potential biomarker of subclinical atherosclerosis in smokers. PMID:26307030

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

Cheng, Ya-Hsin; Huang, Su-Chin; Lin, Chun-Ju

Environmental cigarette smoke has been suggested to promote lung adenocarcinoma progression through aryl hydrocarbon receptor (AhR)-signaled metabolism. However, whether AhR facilitates metabolic activation or detoxification in exposed adenocarcinoma cells remains ambiguous. To address this question, we have modified the expression level of AhR in two human lung adenocarcinoma cell lines and examined their response to an extract of cigarette sidestream smoke particulates (CSSP). We found that overexpression of AhR in the CL1-5 cell line reduced CSSP-induced ROS production and oxidative DNA damage, whereas knockdown of AhR expression increased ROS level in CSSP-exposed H1355 cells. Oxidative stress sensor Nrf2 and itsmore » target gene NQO1 were insensitive to AhR expression level and CSSP treatment in human lung adenocarcinoma cells. In contrast, induction of AhR expression concurrently increased mRNA expression of xenobiotic-metabolizing genes CYP1B1, UGT1A8, and UGT1A10 in a ligand-independent manner. It appeared that AhR accelerated xenobiotic clearing and diminished associated oxidative stress by coordinate regulation of a set of phase I and II metabolizing genes. However, the AhR-signaled protection could not shield cells from constant oxidative stress. Prolonged exposure to high concentrations of CSSP induced G0/G1 cell cycle arrest via the p53–p21–Rb1 signaling pathway. Despite no effect on DNA repair rate, AhR facilitated the recovery of cells from growth arrest when CSSP exposure ended. AhR-overexpressing lung adenocarcinoma cells exhibited an increased anchorage-dependent and independent proliferation when recovery from exposure. In summary, our data demonstrated that AhR protected lung adenocarcinoma cells against CSSP-induced oxidative stress and promoted post-exposure clonogenicity. -- Highlights: ► AhR expression level influences cigarette sidestream smoke-induced ROS production. ► AhR reduces oxidative stress by coordinate regulation of

Comparative Toxicogenomic Responses to the Flame Retardant mITP in Developing Zebrafish.

PubMed

Haggard, Derik E; Das, Siba R; Tanguay, Robert L

2017-02-20

Monosubstituted isopropylated triaryl phosphate (mITP) is a major component of Firemaster 550, an additive flame retardant mixture commonly used in polyurethane foams. Developmental toxicity studies in zebrafish established mITP as the most toxic component of FM 550, which causes pericardial edema and heart looping failure. Mechanistic studies showed that mITP is an aryl hydrocarbon receptor (AhR) ligand; however, the cardiotoxic effects of mITP were independent of the AhR. We performed comparative whole genome transcriptomics in wild-type and ahr2 hu3335 zebrafish, which lack functional ahr2, to identify transcriptional signatures causally involved in the mechanism of mITP-induced cardiotoxicity. Regardless of ahr2 status, mITP exposure resulted in decreased expression of transcripts related to the synthesis of all-trans-retinoic acid and a host of Hox genes. Clustered gene ontology enrichment analysis showed unique enrichment in biological processes related to xenobiotic metabolism and response to external stimuli in wild-type samples. Transcript enrichments overlapping both genotypes involved the retinoid metabolic process and sensory/visual perception biological processes. Examination of the gene-gene interaction network of the differentially expressed transcripts in both genetic backgrounds demonstrated a strong AhR interaction network specific to wild-type samples, with overlapping genes regulated by retinoic acid receptors (RARs). A transcriptome analysis of control ahr2-null zebrafish identified potential cross-talk among AhR, Nrf2, and Hif1α. Collectively, we confirmed that mITP is an AhR ligand and present evidence in support of our hypothesis that mITP's developmental cardiotoxic effects are mediated by inhibition at the RAR level.

Severe Liver Cirrhosis Markedly Reduces AhR-Mediated Induction of Cytochrome P450 in Rats by Decreasing the Transcription of Target Genes

PubMed Central

Floreani, Maura; De Martin, Sara; Gabbia, Daniela; Barbierato, Massimo; Nassi, Alberto; Mescoli, Claudia; Orlando, Rocco; Bova, Sergio; Angeli, Paolo; Gola, Elisabetta; Sticca, Antonietta; Palatini, Pietro

2013-01-01

Although the induction of cytochrome P450 (CYP) has long been investigated in patients with cirrhosis, the question whether liver dysfunction impairs the response to CYP inducers still remains unresolved. Moreover, the mechanism underlying the possible effect of cirrhosis on induction has not been investigated. Since ethical constraints do not permit methodologically rigorous studies in humans, this question was addressed by investigating the effect of the prototypical inducer benzo[a]pyrene (BP) on CYP1A1 and CYP1A2 in cirrhotic rats stratified according to the severity of liver dysfunction. We simultaneously assessed mRNA level, protein expression and enzymatic activity of the CYP1A enzymes, as well as mRNA and protein expressions of the aryl hydrocarbon receptor (AhR), which mediates the BP effect. Basal mRNA and protein expressions of CYP1A1 were virtually absent in both healthy and cirrhotic rats. On the contrary, CYP1A2 mRNA, protein and enzyme activity were constitutively present in healthy rats and decreased significantly as liver function worsened. BP treatment markedly increased the concentrations of mRNA and immunodetectable protein, and the enzymatic activities of both CYP1A enzymes to similar levels in healthy and non-ascitic cirrhotic rats. Induced mRNA levels, protein expressions and enzymatic activities of both CYPs were much lower in ascitic rats and were proportionally reduced. Both constitutive and induced protein expressions of AhR were significantly lower in ascitic than in healthy rats. These results indicate that the inducibility of CYP1A enzymes is well preserved in compensated cirrhosis, whereas it is markedly reduced when liver dysfunction becomes severe. Induction appears to be impaired at the transcriptional level, due to the reduced expression of AhR, which controls the transcription of CYP1A genes. PMID:23626760

Regulation of pregnane-X-receptor, CYP3A and P-glycoprotein genes in the PCB-resistant killifish (Fundulus heteroclitus) population from New Bedford Harbor1

PubMed Central

Gräns, Johanna; Wassmur, Britt; Fernández-Santoscoy, María; Zanette, Juliano; Woodin, Bruce R.; Karchner, Sibel I.; Nacci, Diane E.; Champlin, Denise; Jayaraman, Saro; Hahn, Mark E.; Stegeman, John J.; Celander, Malin C.

2015-01-01

Killifish survive and reproduce in the New Bedford Harbor (NBH) in Massachusetts (MA), USA, a site severely contaminated with polychlorinated biphenyls (PCBs) for decades. Levels of 22 different PCB congeners were analyzed in liver from killifish collected in 2008. Concentrations of dioxin-like PCBs in liver of NBH killifish were ~400 times higher, and the levels of non-dioxin-like PCBs ~3000 times higher than in killifish from a reference site, Scorton Creek (SC), MA. The NBH killifish are known to be resistant to the toxicity of dioxin-like compounds and to have a reduced aryl hydrocarbon receptor (AhR) signaling response. Little is known about the responses of these fish to non-dioxin-like PCBs, which are at extraordinarily high levels in NBH fish. In mammals, some non-dioxin-like PCB congeners act through nuclear receptor 1I2, the pregnane-X-receptor (PXR). To explore this pathway in killifish, a PXR cDNA was sequenced and its molecular phylogenetic relationship to other vertebrate PXRs was determined. Killifish were also collected in 2009 from NBH and SC, and after four months in the laboratory they were injected with a single dose of either the dioxin-like PCB 126 (an AhR agonist) or the non-dioxin-like PCB 153 (a mammalian PXR agonist). Gills and liver were sampled three days after injection and transcript levels of genes encoding PXR, cytochrome P450 3A (CYP3A), P-glycoprotein (Pgp), AhR2 and cytochrome P450 1A (CYP1A) were measured by quantitative PCR. As expected, there was little effect of PCB exposure on mRNA expression of AhR2 or CYP1A in liver and gills of NBH fish. In NBH fish, but not in SC fish, there was increased mRNA expression of hepatic PXR, CYP3A and Pgp upon exposure to either of the two PCB congeners. However, basal PXR and Pgp mRNA levels in liver of NBH fish were significantly lower than in SC fish. A different pattern was seen in gills, where there were no differences in basal mRNA expression of these genes between the two populations

Xenoestrogenic and dioxin-like activity in blood of East Greenland polar bears (Ursus maritimus).

PubMed

Erdmann, Simon E; Dietz, Rune; Sonne, Christian; Bechshøft, Thea Ø; Vorkamp, Katrin; Letcher, Robert J; Long, Manhai; Bonefeld-Jørgensen, Eva C

2013-07-01

The aims of the project were to (i) extract the lipophilic persistent organic pollutants (POPs) from the blood of 99 East Greenland polar bears and assess the combined mixture effect on the estrogen receptor (ER) and the aryl hydrocarbon receptor (AhR) mediated transactivity; (ii) To evaluate whether the receptor transactivities were associated with selected POP markers, and (iii) compare the receptor transactivities in polar bears with earlier studies on Greenlandic Inuit. Lipophilic POPs were extracted using a combination of solid-phase extraction (SPE) and high performance liquid chromatography (HPLC). ER mediated transactivity was determined using the ER luciferase reporter MVLN cell assay. The extracts were tested alone (XER) and together with 17β-estradiol (E2) as a physiological mimic (XERcomp). Dioxins and dioxin-like (DL) compounds were extracted by a combination of SPE and the Supelco Dioxin Prep System®. AhR mediated dioxin-like transactivity was determined using the AhR luciferase reporter Hepa 1.12cR cell assay. Agonistic ER transactivity was elicited by 19% of the samples, and a further increased E2 induced ER response was found for 52%, whereas 17% antagonized the E2 induced ER response. Positive correlations were found in subadult bears between XER and several POP biomarkers. XER and XERcomp correlated positively to each other. A total of 91% of the polar bear blood extracts elicited agonistic AhR transactivity. The AhR-TCDD equivalent (AhR-TEQ) median levels were higher among adult bears compared to subadult bears, but not significantly. Copyright © 2013 Elsevier Ltd. All rights reserved.

Disruption of Ah Receptor Signaling during Mouse Development Leads to Abnormal Cardiac Structure and Function in the Adult

PubMed Central

Carreira, Vinicius S.; Fan, Yunxia; Kurita, Hisaka; Wang, Qin; Ko, Chia-I; Naticchioni, Mindi; Jiang, Min; Koch, Sheryl; Zhang, Xiang; Biesiada, Jacek; Medvedovic, Mario; Xia, Ying; Rubinstein, Jack; Puga, Alvaro

2015-01-01

The Developmental Origins of Health and Disease (DOHaD) Theory proposes that the environment encountered during fetal life and infancy permanently shapes tissue physiology and homeostasis such that damage resulting from maternal stress, poor nutrition or exposure to environmental agents may be at the heart of adult onset disease. Interference with endogenous developmental functions of the aryl hydrocarbon receptor (AHR), either by gene ablation or by exposure in utero to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent AHR ligand, causes structural, molecular and functional cardiac abnormalities and altered heart physiology in mouse embryos. To test if embryonic effects progress into an adult phenotype, we investigated whether Ahr ablation or TCDD exposure in utero resulted in cardiac abnormalities in adult mice long after removal of the agent. Ten-months old adult Ahr -/- and in utero TCDD-exposed Ahr +/+ mice showed sexually dimorphic abnormal cardiovascular phenotypes characterized by echocardiographic findings of hypertrophy, ventricular dilation and increased heart weight, resting heart rate and systolic and mean blood pressure, and decreased exercise tolerance. Underlying these effects, genes in signaling networks related to cardiac hypertrophy and mitochondrial function were differentially expressed. Cardiac dysfunction in mouse embryos resulting from AHR signaling disruption seems to progress into abnormal cardiac structure and function that predispose adults to cardiac disease, but while embryonic dysfunction is equally robust in males and females, the adult abnormalities are more prevalent in females, with the highest severity in Ahr -/- females. The findings reported here underscore the conclusion that AHR signaling in the developing heart is one potential target of environmental factors associated with cardiovascular disease. PMID:26555816

Suppression of CYP1 members of the AHR response by pathogen-associated molecular patterns.

PubMed

Peres, Adam G; Zamboni, Robert; King, Irah L; Madrenas, Joaquín

2017-12-01

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that triggers a broad response, which includes the regulation of proinflammatory cytokine production by monocytes and macrophages. AHR is negatively regulated by a set of genes that it transcriptionally activates, including the AHR repressor ( Ahrr ) and the cytochrome P450 1 ( Cyp1 ) family, which are critical for preventing exacerbated AHR activity. An imbalance in these regulatory mechanisms has been shown to cause severe defects in lymphoid cells. Therefore, we wanted to assess how AHR activation is regulated in monocytes and macrophages in the context of innate immune responses induced by pathogen-associated molecular patterns (PAMPs). We found that concomitant stimulation of primary human monocytes with PAMPs and the AHR agonist 6-formylindolo(3,2-b)carbazole (FICZ) led to a selective dose-dependent inhibition of Cyp1 family members induction. Two other AHR-dependent genes [ Ahrr and NADPH quinone dehydrogenase 1 ( Nqo1 )] were not affected under these conditions, suggesting a split in the AHR regulation by PAMPs. This down-regulation of Cyp1 family members did not require de novo protein production nor signaling through p38, ERK, or PI3K-Akt-mammalian target of rapamycin (mTOR) pathways. Furthermore, such a split regulation of the AHR response was more apparent in GM-CSF-derived macrophages, a finding corroborated at the functional level by decreased CYP1 activity and decreased proinflammatory cytokine production in response to FICZ and LPS. Collectively, our findings identify a role for pattern recognition receptor (PRR) signaling in regulating the AHR response through selective down-regulation of Cyp1 expression in human monocytes and macrophages. © Society for Leukocyte Biology.

ITE inhibits growth of human pulmonary artery endothelial cells.

PubMed

Pang, Ling-Pin; Li, Yan; Zou, Qing-Yun; Zhou, Chi; Lei, Wei; Zheng, Jing; Huang, Shi-An

2017-10-01

Pulmonary arterial hypertension (PAH), a deadly disorder is associated with excessive growth of human pulmonary artery endothelial (HPAECs) and smooth muscle (HPASMCs) cells. Current therapies primarily aim at promoting vasodilation, which only ameliorates clinical symptoms without a cure. 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) is an endogenous aryl hydrocarbon receptor (AhR) ligand, and mediates many cellular function including cell growth. However, the roles of ITE in human lung endothelial cells remain elusive. Herein, we tested a hypothesis that ITE inhibits growth of human pulmonary artery endothelial cells via AhR. Immunohistochemistry was performed to localize AhR expression in human lung tissues. The crystal violet method and MTT assay were used to determine ITE's effects on growth of HPAECs. The AhR activation in HPAECs was confirmed using Western blotting and RT-qPCR. The role of AhR in ITE-affected proliferation of HPAECs was assessed using siRNA knockdown method followed by the crystal violet method. Immunohistochemistry revealed that AhR was present in human lung tissues, primarily in endothelial and smooth muscle cells of pulmonary veins and arteries, as well as in bronchial and alveolar sac epithelia. We also found that ITE dose- and time-dependently inhibited proliferation of HPAECs with a maximum inhibition of 83% at 20 µM after 6 days of treatment. ITE rapidly decreased AhR protein levels, while it increased mRNA levels of cytochrome P450 (CYP), family 1, member A1 (CYP1A1) and B1 (CYP1B1), indicating activation of the AhR/CYP1A1 and AhR/CYP1B1 pathways in HPAECs. The AhR siRNA significantly suppressed AhR protein expression, whereas it did not significantly alter ITE-inhibited growth of HPAECs. ITE suppresses growth of HPAECs independent of AhR, suggesting that ITE may play an important role in preventing excessive growth of lung endothelial cells.

Genetic and pharmacological analysis identifies a physiological role for the AHR in epidermal differentiation

PubMed Central

van den Bogaard, Ellen; Podolsky, Michael; Smits, Jos; Cui, Xiao; John, Christian; Gowda, Krishne; Desai, Dhimant; Amin, Shantu; Schalkwijk, Joost; Perdew, Gary H.

2015-01-01

Stimulation of the aryl hydrocarbon receptor (AHR) by xenobiotics is known to affect epidermal differentiation and skin barrier formation. The physiological role of endogenous AHR signaling in keratinocyte differentiation is not known. We used murine and human skin models to address the hypothesis that AHR activation is required for normal keratinocyte differentiation. Using transcriptome analysis of Ahr-/- and Ahr+/+ murine keratinocytes, we found significant enrichment of differentially expressed genes linked to epidermal differentiation. Primary Ahr-/- keratinocytes showed a significant reduction in terminal differentiation gene and protein expression, similar to Ahr+/+ keratinocytes treated with AHR antagonists GNF351 and CH223191, or the selective AHR modulator (SAhRM), SGA360. In vitro keratinocyte differentiation led to increased AHR levels and subsequent nuclear translocation, followed by induced CYP1A1 gene expression. Monolayer cultured primary human keratinocytes treated with AHR antagonists also showed an impaired terminal differentiation program. Inactivation of AHR activity during human skin equivalent development severely impaired epidermal stratification, terminal differentiation protein expression and stratum corneum formation. As disturbed epidermal differentiation is a main feature of many skin diseases, pharmacological agents targeting AHR signaling or future identification of endogenous keratinocyte-derived AHR ligands should be considered as potential new drugs in dermatology. PMID:25602157

DEVELOPMENTAL EXPRESSION OF TWO MEMBERS OF A NEW CLASS OF TRANSCRIPTION FACTORS: II. EXPRESSION OF ARYL HYDROCARBON RECEPTOR NUCLEAR TRANSLOCATOR IN THE C57BL/6N MOUSE EMBRYO

EPA Science Inventory

The Aryl hydrocarbon receptor (AhR) is a ligand-activated, transcription factor with a basic region/helix (bHLH) motif. hR has been sequenced and the functional domains defined and there is information on the formation of complexes with other peptides and interactions with DNA, a...

Caspase recruitment domain 9, microbiota, and tryptophan metabolism: dangerous liaisons in inflammatory bowel diseases.

PubMed

Lamas, Bruno; Richard, Mathias L; Sokol, Harry

2017-07-01

Inflammatory bowel diseases (IBDs) develop as a result of a combination of genetic predisposition, dysbiosis of the gut microbiota, and environmental influences. Here, we describe an example of how caspase recruitment domain 9 (CARD9), one of the numerous IBD susceptibility genes, participate to colitis susceptibility by shaping gut microbiota to produce tryptophan metabolites. Recent study showed that CARD9 mice are more susceptible to colitis as a result of impaired interleukin 22 signaling pathway. Furthermore, aryl hydrocarbon receptor (AhR) ligands from tryptophan metabolism by the gut microbiota participate to intestinal homeostasis by inducing production of interleukin 22 by intestinal immune cells. These data suggest an interaction between CARD9 and the ability of gut microbiota to produce AhR ligands. The microbiota from CARD9 mice fails to metabolize tryptophan leading to defective AhR activation which contributes to the susceptibility of mice to colitis by decreased interleukin 22 production. These effects were abrogated in the presence of AhR agonist. Reduced production of AhR ligands is also observed in the microbiota from individuals with IBD, particularly in those with CARD9 risk alleles associated with IBD. Correcting impaired microbiota functions, such as ability to produce AhR ligands, is an attractive strategy in IBD.

Effect of PCB 126 on aryl hydrocarbon receptor 1 (AHR1) and AHR1 nuclear translocator 1 (ARNT1) mRNA expression and CYP1 monooxygenase activity in chicken (Gallus domesticus) ovarian follicles.

PubMed

Wójcik, Dagmara; Antos, Piotr A; Katarzyńska, Dorota; Hrabia, Anna; Sechman, Andrzej

2015-12-03

The aim of the experiment was to study the in vitro effect of 3,3',4,4',5-pentachlorobiphenyl (PCB 126; a coplanar PCB congener) on aryl hydrocarbon receptor (AHR1) and AHR1 nuclear translocator (ARNT1) mRNA expression and the activity of CYP1 family monooxygenases in chicken ovarian follicles. White (1-4 mm) and yellowish (4-8 mm) prehierarchical follicles as well as fragments of the theca and granulosa layers of the 3 largest preovulatory follicles (F3-F1) were incubated in a medium supplemented with 0 (control group), 1, 10 or 100 nM PCB 126. The incubation was carried out for 6 h or 24 h for determination of mRNA expression of AHR1 and ARNT1 genes (real-time qPCR) and CYP1 monooxygenase activity (EROD and MROD fluorometric assays), respectively. It was found that chicken ovarian follicles express mRNA of AHR1 and ARNT1 genes. A modulatory effect of PCB 126 on AHR1 and ARNT1 expression depended not only on the biphenyl concentration but also on the follicular layer and the maturational state of the follicle. EROD and MROD activities appeared predominantly in the granulosa layer of the yellow preovulatory follicles. PCB 126 induced these activities in a dose-dependent manner in all ovarian follicles. The obtained results suggest that ovarian follicles, especially the granulosa layer, are involved in the detoxification process of PCBs in the laying hen. Taking this finding into consideration it can be suggested that the granulosa layer of the yellow hierarchical follicles plays a key role in the protective mechanism which reduces the amount of transferred dioxin-like compounds into the yolk of the oocyte. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Loss of aryl hydrocarbon receptor promotes gene changes associated with premature hematopoietic stem cell exhaustion and development of a myeloproliferative disorder in aging mice.

PubMed

Singh, Kameshwar P; Bennett, John A; Casado, Fanny L; Walrath, Jason L; Welle, Stephen L; Gasiewicz, Thomas A

2014-01-15

Loss of immune function and increased hematopoietic disease are among the most clinically significant consequences of aging. Hematopoietic stem cells (HSCs) from mice lacking aryl hydrocarbon receptor (AhR) have high rates of cell division. Studies were designed to test the hypothesis that aging AhR-null allele (AhR-KO) mice develop premature HSC exhaustion, and changes leading to hematological disease. Compared to wild-type, aging AhR-KO mice showed a decreased survival rate, splenomegaly, increased circulating white blood cells, hematopoietic cell accumulation in tissues, and anemia. Analysis of bone marrow indicated increased numbers of stem/progenitor and lineage-committed cells, but decreased erythroid progenitors. There was also decreased self-renewal capacity of HSCs determined by competitive repopulation and serial transplantation. HSCs also showed increased levels of reactive oxygen species (ROS), Ki-67, and γ-H2A.X, but decreased p16(Ink4a). Splenic cells from aging KO mice had abnormal expression of genes, including Gata-1, Sh2d3c, Gfi-1, p21, and c-myc, involved in trafficking and associated with leukemia. HSCs from AhR-KO mice had gene changes related to HSC maintenance and consistent with phenotype observed. The most prominent gene changes (overexpression of Srpk2, Creb1, Hes1, mtor, pdp1) have been associated with HSC hyperproliferation, leukemia, and accelerated aging. Pathway analyses also indicated an enrichment of genes associated with oxidative stress, acute myelogenous leukemia, aging, and heat shock response, and the β-catenin/Wnt pathways. These data indicate that loss of AhR and associated changes in multiple signaling pathways promote premature HSC exhaustion and development of a myeloproliferative disorder. They also implicate a critical role of the AhR in the regulation of HSCs.

Constitutive expression of the AHR signaling pathway in a bovine mammary epithelial cell line and modulation by dioxin-like PCB and other AHR ligands.

PubMed

Girolami, Flavia; Spalenza, Veronica; Manzini, Livio; Carletti, Monica; Nebbia, Carlo

2015-01-05

Environmental pollutants, such as dioxin-like (DL) PCBs, benzo(a) pyrene (B[a]P), and flavonoids are aryl hydrocarbon receptor (AHR) ligands and may be excreted in dairy milk. The expression of AHR-target genes, particularly those involved in xenobiotic biotransformation, and their modulation by two DL-PCBs, B[a]P, and β-naphthoflavone was investigated in a bovine mammary epithelial cell line (BME-UV). As assessed by quantitative PCR, BME-UV cells expressed a functional AHR signaling pathway. All the AHR ligands induced a concentration-related increase in the transcription of cytochrome P450 1A1 and 1B1, known to be implicated in the bioactivation of several xenobiotics. Conversely, genes encoding for antioxidant and detoxifying enzymes, like quinone oxidoreductase or glutathione S-transferase A2, were not affected or even depressed. This study demonstrates the occurrence and the modulation by different AHR-ligands of genes involved in xenobiotic metabolism in BME-UV cells, with the potential generation of (re) active metabolites that may damage mammary tissue and/or affect animal or human health via the contaminated milk. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Dioxin exerts anti-estrogenic actions in a novel dioxin-responsive telomerase-immortalized epithelial cell line of the porcine oviduct (TERT-OPEC).

PubMed

Hombach-Klonisch, Sabine; Pocar, Paola; Kauffold, Johannes; Klonisch, Thomas

2006-04-01

Oviduct epithelial cells are important for the nourishment and survival of ovulated oocytes and early embryos, and they respond to the steroid hormones estrogen and progesterone. Endocrine-disrupting polyhalogenated aromatic hydrocarbons (PHAH) are environmental toxins that act in part through the ligand-activated transcription factor arylhydrocarbon receptor (AhR; dioxin receptor), and exposure to PHAH has been shown to decrease fertility. To investigate effects of PHAHs on the oviduct epithelium as a potential target tissue of dioxin-type endocrine disruptors, we have established a novel telomerase-immortalized oviduct porcine epithelial cell line (TERT-OPEC). TERT-OPEC exhibited active telomerase and the immunoreactive epithelial marker cytokeratin but lacked the stromal marker vimentin. TERT-OPEC contained functional estrogen receptor (ER)-alpha and AhR, as determined by the detection of ER-alpha- and AhR-specific target molecules. Treatment of TERT-OPEC with the AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) resulted in a significant increase in the production of the cytochrome P-450 microsomal enzyme CYP1A1. Activated AhR caused a downregulation of ER nuclear protein fraction and significantly decreased ER-signaling in TERT-OPEC as determined by ERE-luciferase transient transfection assays. In summary, the TCDD-induced and AhR-mediated anti-estrogenic responses by TERT-OPEC suggest that PHAH affect the predominantly estrogen-dependent differentiation of the oviduct epithelium within the fallopian tube. This action then alters the local endocrine milieu, potentially resulting in a largely unexplored cause of impaired embryonic development and female infertility.

A novel prostate cancer therapeutic strategy using icaritin-activated arylhydrocarbon-receptor to co-target androgen receptor and its splice variants

PubMed Central

Sun, Feng; Indran, Inthrani R.; Zhang, Zhi Wei; Tan, M.H.Eileen; Li, Yu; Lim, Z.L.Ryan; Hua, Rui; Yang, Chong; Soon, Fen-Fen; Li, Jun; Xu, H.Eric; Cheung, Edwin; Yong, Eu-Leong

2015-01-01

Persistent androgen receptor (AR) signaling is the key driving force behind progression and development of castration-resistant prostate cancer (CRPC). In many patients, AR COOH-terminal truncated splice variants (ARvs) play a critical role in contributing to the resistance against androgen depletion therapy. Unfortunately, clinically used antiandrogens like bicalutamide (BIC) and enzalutamide (MDV), which target the ligand binding domain, have failed to suppress these AR variants. Here, we report for the first time that a natural prenylflavonoid, icaritin (ICT), can co-target both persistent AR and ARvs. ICT was found to inhibit transcription of key AR-regulated genes, such as KLK3 [prostate-specific antigen (PSA)] and ARvs-regulated genes, such as UBE2C and induce apoptosis in AR-positive prostate cancer (PC) cells. Mechanistically, ICT promoted the degradation of both AR and ARvs by binding to arylhydrocarbon-receptor (AhR) to mediate ubiquitin-proteasomal degradation. Therefore, ICT impaired AR transactivation in PC cells. Knockdown of AhR gene restored AR stability and partially prevented ICT-induced growth suppression. In clinically relevant murine models orthotopically implanted with androgen-sensitive and CRPC cells, ICT was able to target AR and ARvs, to inhibit AR signaling and tumor growth with no apparent toxicity. Our results provide a mechanistic framework for the development of ICT, as a novel lead compound for AR-positive PC therapeutics, especially for those bearing AR splice variants. PMID:25908644

Polymorphisms in aryl hydrocarbon receptor gene are associated with idiopathic male factor infertility.

PubMed

Safarinejad, Mohammad Reza; Shafiei, Nayyer; Safarinejad, Saba

2013-12-01

We wanted to determine whether genetic polymorphisms of aryl hydrocarbon receptor (AhR) gene are associated with susceptibility to male infertility. This study comprised 176 men with idiopathic infertility and 352 healthy fertile men who served as controls. Seven single-nucleotide polymorphisms (SNPs) of the AhR gene (rs2066853, rs1476080, rs10250822, rs10247158, rs2282885, rs6960165, and rs7811989) were selected and genotyped by the polymerase chain reaction-restriction fragment length polymorphism analysis. The serum levels of reproductive and thyroid hormones and inhibin B were also measured. After multiple regression analysis, 2 of the 7 studied SNPs were significantly associated with the occurrence of male infertility. Men with rs2066853 AA genotype had 33% decreased risk of being infertile (odds ratio [OR] = 0.67, 95% confidence interval [CI]: 0.46-0.87; P = .003). The C allele of rs2282885 was significantly associated with infertility risk, with an OR of 2.14 (95% CI: 1.64-3.72) for heterozygotes and 3.54 (95% CI: 2.25-5.84) for homozygotes. When haplotypes were composed of 7 AhR SNP sites, patients with AACACAG haplotype harbored more than 75% decreased risk of being infertile (OR = 0.21, 95% CI: 0.11-0.32; P = .001). Conversely, carriers of the AACACGA haplotype had more than 12-fold increased risk of being infertile (OR = 12.62, 95% CI: 2.77-52.74; P = .00001). Homozygosity for the rs2066853 A allele and rs2282885 C allele decreases and increases the risk of developing male infertility, respectively.

Structural hierarchy controlling dimerization and target DNA recognition in the AHR transcriptional complex.

PubMed

Seok, Seung-Hyeon; Lee, Woojong; Jiang, Li; Molugu, Kaivalya; Zheng, Aiping; Li, Yitong; Park, Sanghyun; Bradfield, Christopher A; Xing, Yongna

2017-05-23

The aryl hydrocarbon receptor (AHR) belongs to the PAS (PER-ARNT-SIM) family transcription factors and mediates broad responses to numerous environmental pollutants and cellular metabolites, modulating diverse biological processes from adaptive metabolism, acute toxicity, to normal physiology of vascular and immune systems. The AHR forms a transcriptionally active heterodimer with ARNT (AHR nuclear translocator), which recognizes the dioxin response element (DRE) in the promoter of downstream genes. We determined the crystal structure of the mammalian AHR-ARNT heterodimer in complex with the DRE, in which ARNT curls around AHR into a highly intertwined asymmetric architecture, with extensive heterodimerization interfaces and AHR interdomain interactions. Specific recognition of the DRE is determined locally by the DNA-binding residues, which discriminates it from the closely related hypoxia response element (HRE), and is globally affected by the dimerization interfaces and interdomain interactions. Changes at the interdomain interactions caused either AHR constitutive nuclear localization or failure to translocate to nucleus, underlying an allosteric structural pathway for mediating ligand-induced exposure of nuclear localization signal. These observations, together with the global higher flexibility of the AHR PAS-A and its loosely packed structural elements, suggest a dynamic structural hierarchy for complex scenarios of AHR activation induced by its diverse ligands.

Dioxin-like activities in serum across European and Inuit populations

PubMed Central

Long, Manhai; Andersen, Birgitte S; Lindh, Christian H; Hagmar, Lars; Giwercman, Aleksander; Manicardi, Gian-Carlo; Bizzaro, Davide; Spanò, Marcello; Toft, Gunnar; Pedersen, Henning S; Zvyezday, Valentyna; Bonde, Jens Peter; Bonefeld-Jorgensen, Eva C

2006-01-01

Background Persistent organic pollutants (POPs) such as polychlorinated dibenzo-p-dioxins/furans, polychlorinated biphenyls (PCBs) and organochlorine pesticides can cause a series of adverse effects on e.g. reproduction in animals and humans, many of which involve the aryl hydrocarbon receptor (AhR). The aim of the present study was to compare the integrated serum level of AhR mediated activity among European and Inuit populations, and evaluate whether the activity was associated to the selected POP markers, 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p'-DDE). Methods The study included 338 males from Greenland (Inuit's), Sweden, Warsaw (Poland) and Kharkiv (Ukraine). The AhR transactivity of serum extracts alone (AhRag) and competitive AhR activity (AhRcomp) upon co-exposure with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were determined in the lipophilic serum fraction containing the POPs using the AhR mediated luciferase reporter Hepa1.12cR cell assay. Results The European groups showed higher median level of AhR-TEQ (TCDD toxic equivalents) compared to the Inuit's, whereas higher incidence of Inuits sample further induced AhRcomp activity. Neither AhRag nor AhR-TEQ were correlated to CB-153 or p,p'-DDE for any of the study groups. Multiple regressions showed a significant heterogeneity of association between the CB-153 and the AhRcomp across the study groups, and accordingly a negative association between AhRcomp and CB-153 was found for the Kharkiv group. Conclusion No consistent correlation between AhR activities and two POP markers was found. Although the difference of AhRag between European and Inuit men could not be explained by CB-153 or p,p'-DDE levels alone, we believe that the variation of AhR serum activity reflects different pattern of POP exposure, genetics and/or life style factors. PMID:16725033

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

Zhang, Shaojie; Patel, Ananddeep; Chu, Chun

Hyperoxia contributes to the development of bronchopulmonary dysplasia (BPD) in premature infants. Activation of the aryl hydrocarbon receptor (AhR) protects adult and newborn mice against hyperoxic lung injury by mediating increases in the expression of phase I (cytochrome P450 (CYP) 1A) and phase II (NADP(H) quinone oxidoreductase (NQO1)) antioxidant enzymes (AOE). AhR positively regulates the expression of RelB, a component of the nuclear factor-kappaB (NF-κB) protein that contributes to anti-inflammatory processes in adult animals. Whether AhR regulates the expression of AOE and RelB, and protects fetal primary human lung cells against hyperoxic injury is unknown. Therefore, we tested the hypothesismore » that AhR-deficient fetal human pulmonary microvascular endothelial cells (HPMEC) will have decreased RelB activation and AOE, which will in turn predispose them to increased oxidative stress, inflammation, and cell death compared to AhR-sufficient HPMEC upon exposure to hyperoxia. AhR-deficient HPMEC showed increased hyperoxia-induced reactive oxygen species (ROS) generation, cleavage of poly(ADP-ribose) polymerase (PARP), and cell death compared to AhR-sufficient HPMEC. Additionally, AhR-deficient cell culture supernatants displayed increased macrophage inflammatory protein 1α and 1β, indicating a heightened inflammatory state. Interestingly, loss of AhR was associated with a significantly attenuated CYP1A1, NQO1, superoxide dismutase 1(SOD1), and nuclear RelB protein expression. These findings support the hypothesis that decreased RelB activation and AOE in AhR-deficient cells is associated with increased hyperoxic injury compared to AhR-sufficient cells. - Highlights: • AhR deficiency potentiates oxygen toxicity in human fetal lung cells. • Deficient AhR signaling increases hyperoxia-induced cell death. • AhR deficiency increases hyperoxia-induced ROS generation and inflammation. • Anti-oxidant enzyme levels are attenuated in AhR-deficient lung

The tryptophan-derived endogenous arylhydrocarbon receptor ligand 6-formylindolo[3,2-b]carbazole (FICZ) is a nanomolar UVA-photosensitizer in epidermal keratinocytes

PubMed Central

Williams, Joshua D.; Cabello, Christopher M.; Qiao, Shuxi; Wondrak, Georg T.

2014-01-01

Endogenous UVA-chromophores may act as sensitizers of oxidative stress underlying cutaneous photoaging and photocarcinogenesis, but the molecular identity of non-DNA key chromophores displaying UVA-driven photodyamic activity in human skin remains largely undefined. Here we report that 6-formylindolo[3,2-b]carbazole (FICZ), a tryptophan photoproduct and endogenous high affinity aryl hydrocarbon receptor (AhR) agonist, acts as a nanomolar photosensitizer potentiating UVA-induced oxidative stress irrespective of AhR ligand activity. In human HaCaT and primary epidermal keratinocytes, photodynamic induction of apoptosis was elicited by the combined action of solar simulated UVA and FICZ, whereas exposure to the isolated action of UVA or FICZ did not impair viability. In a human epidermal tissue reconstruct, FICZ/UVA-cotreatment caused pronounced phototoxicity inducing keratinocyte cell death, and FICZ photodynamic activity was also substantiated in a murine skin exposure model. Array analysis revealed pronounced potentiation of cellular heat shock, ER stress, and oxidative stress response gene expression observed only upon FICZ/UVA-cotreatment. FICZ photosensitization caused intracellular oxidative stress, and comet analysis revealed introduction of formamidopyrimidine-DNA glycosylase (FPG)-sensitive oxidative DNA lesions suppressible by antioxidant cotreatment. Taken together, our data demonstrate that the endogenous AhR ligand FICZ displays nanomolar photodynamic activity representing a molecular mechanism of UVA-induced photooxidative stress potentially operative in human skin. PMID:25431849

Linking Ah receptor mediated effects of sediments and impacts on fish to key pollutants in the Yangtze Three Gorges Reservoir, China - A comprehensive perspective.

PubMed

Floehr, Tilman; Scholz-Starke, Björn; Xiao, Hongxia; Hercht, Hendrik; Wu, Lingling; Hou, Junli; Schmidt-Posthaus, Heike; Segner, Helmut; Kammann, Ulrike; Yuan, Xingzhong; Roß-Nickoll, Martina; Schäffer, Andreas; Hollert, Henner

2015-12-15

The Three Gorges Reservoir (TGR), created in consequence of the Yangtze River's impoundment by the Three Gorges Dam, faces numerous anthropogenic impacts that challenge its unique ecosystem. Organic pollutants, particularly aryl hydrocarbon receptor (AhR) agonists, have been widely detected in the Yangtze River, but only little research was yet done on AhR-mediated activities. Hence, in order to assess effects of organic pollution, with particular focus on AhR-mediated activities, several sites in the TGR area were examined applying the "triad approach". It combines chemical analysis, in vitro, in vivo and in situ investigations to a holistic assessment. Sediments and the benthic fish species Pelteobagrus vachellii were sampled in 2011/2012, respectively, to identify relevant endpoints. Sediment was tested in vitro with the ethoxyresorufin-O-deethylase (EROD) induction assay, and in vivo with the Fish Embryo Toxicity Test and Sediment Contact Assay with Danio rerio. Activities of phase I (EROD) and phase II (glutathione-S-transferase) biotransformation enzymes, pollutant metabolites and histopathological alterations were studied in situ in P. vachellii. EROD induction was tested in vitro and in situ to evaluate possible relationships. Two sites, near Chongqing and Kaixian city, were identified as regional hot-spots and further investigated in 2013. The sediments induced in the in vitro/in vivo bioassays AhR-mediated activities and embryotoxic/teratogenic effects - particularly on the cardiovascular system. These endpoints could be significantly correlated to each other and respective chemical data. However, particle-bound pollutants showed only low bioavailability. The in situ investigations suggested a rather poor condition of P. vachellii, with histopathological alterations in liver and excretory kidney. Fish from Chongqing city exhibited significant hepatic EROD induction and obvious parasitic infestations. The polycyclic aromatic hydrocarbon (PAH) metabolite 1

Induction of c-Jun by air particulate matter (PM₁₀) of Mexico city: Participation of polycyclic aromatic hydrocarbons.

PubMed

Salcido-Neyoy, Martha Estela; Sánchez-Pérez, Yesennia; Osornio-Vargas, Alvaro Román; Gonsebatt, María Eugenia; Meléndez-Zajgla, Jorge; Morales-Bárcenas, Rocío; Petrosyan, Pavel; Molina-Servin, Edith Danny; Vega, Elizabeth; Manzano-León, Natalia; García-Cuellar, Claudia M

2015-08-01

The carcinogenic potential of urban particulate matter (PM) has been partly attributed to polycyclic aromatic hydrocarbons (PAHs) content, which activates the aryl hydrocarbon receptor (AhR). Here we report the effect of PM with an aerodynamic size of 10 μm (PM10) on the induction of AhR pathway in A549 cells, evaluating its downstream targets CYP1B1, IL-6, IL-8 and c-Jun. Significant increases in CYP1B1 protein and enzyme activity; IL-6 and IL-8 secretion and c-Jun protein were found in response to PM10. The formation of PAH-DNA adducts was also detected. The involvement of AhR pathway was confirmed with Resveratrol as AhR antagonist, which reversed CYP1B1 and c-Jun induction. Nevertheless, in IL-6 and IL-8 secretion, the Resveratrol was ineffective, suggesting an effect independent of this pathway. Considering the role of c-Jun in oncogenesis, its induction by PM may be contributing to its carcinogenic potential through induction of AhR pathway by PAHs present in PM10. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparative analysis of TCDD-induced AhR-mediated gene expression in human, mouse and rat primary B cells

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

Kovalova, Natalia, E-mail: kovalova@msu.edu

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental pollutant that activates the aryl hydrocarbon receptor (AhR) resulting in altered gene expression. In vivo, in vitro, and ex vivo studies have demonstrated that B cells are directly impaired by TCDD, and are a sensitive target as evidenced by suppression of antibody responses. The window of sensitivity to TCDD-induced suppression of IgM secretion among mouse, rat and human B cells is similar. Specifically, TCDD must be present within the initial 12 h post B cell stimulation, indicating that TCDD disrupts early signaling network(s) necessary for B lymphocyte activation and differentiation. Therefore, we hypothesized thatmore » TCDD treatment across three different species (mouse, rat and human) triggers a conserved, B cell-specific mechanism that is involved in TCDD-induced immunosuppression. RNA sequencing (RNA-Seq) was used to identify B cell-specific orthologous genes that are differentially expressed in response to TCDD in primary mouse, rat and human B cells. Time course studies identified TCDD-elicited differential expression of 515 human, 2371 mouse and 712 rat orthologous genes over the 24-h period. 28 orthologs were differentially expressed in response to TCDD in all three species. Overrepresented pathways enriched in all three species included cytokine-cytokine receptor interaction, ECM-receptor interaction, focal adhesion, regulation of actin cytoskeleton and pathways in cancer. Differentially expressed genes functionally associated with cell-cell signaling in humans, immune response in mice, and oxidation reduction in rats. Overall, these results suggest that despite the conservation of the AhR and its signaling mechanism, TCDD elicits species-specific gene expression changes. - Highlights: • Kovalova TAAP Highlights Nov. 2016 • RNA-Seq identified TCDD-induced gene expression in PWM-activated primary B cells. • TCDD elicited differential expression of 515 human, 2371 mouse

Structural hierarchy controlling dimerization and target DNA recognition in the AHR transcriptional complex

PubMed Central

Lee, Woojong; Jiang, Li; Molugu, Kaivalya; Zheng, Aiping; Li, Yitong; Park, Sanghyun; Bradfield, Christopher A.; Xing, Yongna

2017-01-01

The aryl hydrocarbon receptor (AHR) belongs to the PAS (PER-ARNT-SIM) family transcription factors and mediates broad responses to numerous environmental pollutants and cellular metabolites, modulating diverse biological processes from adaptive metabolism, acute toxicity, to normal physiology of vascular and immune systems. The AHR forms a transcriptionally active heterodimer with ARNT (AHR nuclear translocator), which recognizes the dioxin response element (DRE) in the promoter of downstream genes. We determined the crystal structure of the mammalian AHR–ARNT heterodimer in complex with the DRE, in which ARNT curls around AHR into a highly intertwined asymmetric architecture, with extensive heterodimerization interfaces and AHR interdomain interactions. Specific recognition of the DRE is determined locally by the DNA-binding residues, which discriminates it from the closely related hypoxia response element (HRE), and is globally affected by the dimerization interfaces and interdomain interactions. Changes at the interdomain interactions caused either AHR constitutive nuclear localization or failure to translocate to nucleus, underlying an allosteric structural pathway for mediating ligand-induced exposure of nuclear localization signal. These observations, together with the global higher flexibility of the AHR PAS-A and its loosely packed structural elements, suggest a dynamic structural hierarchy for complex scenarios of AHR activation induced by its diverse ligands. PMID:28396409

Structural hierarchy controlling dimerization and target DNA recognition in the AHR transcriptional complex

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

Seok, Seung-Hyeon; Lee, Woojong; Jiang, Li

he aryl hydrocarbon receptor (AHR) belongs to the PAS (PER-ARNT-SIM) family transcription factors and mediates broad responses to numerous environmental pollutants and cellular metabolites, modulating diverse biological processes from adaptive metabolism, acute toxicity, to normal physiology of vascular and immune systems. The AHR forms a transcriptionally active heterodimer with ARNT (AHR nuclear translocator), which recognizes the dioxin response element (DRE) in the promoter of downstream genes. We determined the crystal structure of the mammalian AHR–ARNT heterodimer in complex with the DRE, in which ARNT curls around AHR into a highly intertwined asymmetric architecture, with extensive heterodimerization interfaces and AHR interdomainmore » interactions. Specific recognition of the DRE is determined locally by the DNA-binding residues, which discriminates it from the closely related hypoxia response element (HRE), and is globally affected by the dimerization interfaces and interdomain interactions. Changes at the interdomain interactions caused either AHR constitutive nuclear localization or failure to translocate to nucleus, underlying an allosteric structural pathway for mediating ligand-induced exposure of nuclear localization signal. These observations, together with the global higher flexibility of the AHR PAS-A and its loosely packed structural elements, suggest a dynamic structural hierarchy for complex scenarios of AHR activation induced by its diverse ligands.« less

Tryptophan derivatives regulate the transcription of Oct4 in stem-like cancer cells.

PubMed

Cheng, Jie; Li, Wenxin; Kang, Bo; Zhou, Yanwen; Song, Jiasheng; Dan, Songsong; Yang, Ying; Zhang, Xiaoqian; Li, Jingchao; Yin, Shengyong; Cao, Hongcui; Yao, Hangping; Zhu, Chenggang; Yi, Wen; Zhao, Qingwei; Xu, Xiaowei; Zheng, Min; Zheng, Shusen; Li, Lanjuan; Shen, Binghui; Wang, Ying-Jie

2015-06-10

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that responds to environmental toxicants, is increasingly recognized as a key player in embryogenesis and tumorigenesis. Here we show that a variety of tryptophan derivatives that act as endogenous AhR ligands can affect the transcription level of the master pluripotency factor Oct4. Among them, ITE enhances the binding of the AhR to the promoter of Oct4 and suppresses its transcription. Reduction of endogenous ITE levels in cancer cells by tryptophan deprivation or hypoxia leads to Oct4 elevation, which can be reverted by administration with synthetic ITE. Consequently, synthetic ITE induces the differentiation of stem-like cancer cells and reduces their tumorigenic potential in both subcutaneous and orthotopic xenograft tumour models. Thus, our results reveal a role of tryptophan derivatives and the AhR signalling pathway in regulating cancer cell stemness and open a new therapeutic avenue to target stem-like cancer cells.

Tryptophan derivatives regulate the transcription of Oct4 in stem-like cancer cells

PubMed Central

Cheng, Jie; Li, Wenxin; Kang, Bo; Zhou, Yanwen; Song, Jiasheng; Dan, Songsong; Yang, Ying; Zhang, Xiaoqian; Li, Jingchao; Yin, Shengyong; Cao, Hongcui; Yao, Hangping; Zhu, Chenggang; Yi, Wen; Zhao, Qingwei; Xu, Xiaowei; Zheng, Min; Zheng, Shusen; Li, Lanjuan; Shen, Binghui; Wang, Ying-Jie

2015-01-01

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that responds to environmental toxicants, is increasingly recognized as a key player in embryogenesis and tumorigenesis. Here we show that a variety of tryptophan derivatives that act as endogenous AhR ligands can affect the transcription level of the master pluripotency factor Oct4. Among them, ITE enhances the binding of the AhR to the promoter of Oct4 and suppresses its transcription. Reduction of endogenous ITE levels in cancer cells by tryptophan deprivation or hypoxia leads to Oct4 elevation, which can be reverted by administration with synthetic ITE. Consequently, synthetic ITE induces the differentiation of stem-like cancer cells and reduces their tumorigenic potential in both subcutaneous and orthotopic xenograft tumour models. Thus, our results reveal a role of tryptophan derivatives and the AhR signalling pathway in regulating cancer cell stemness and open a new therapeutic avenue to target stem-like cancer cells. PMID:26059097

Intersection of AHR and Wnt Signaling in Development, Health, and Disease

PubMed Central

Schneider, Andrew J.; Branam, Amanda M.; Peterson, Richard E.

2014-01-01

The AHR (aryl hydrocarbon receptor) and Wnt (wingless-related MMTV integration site) signaling pathways have been conserved throughout evolution. Appropriately regulated signaling through each pathway is necessary for normal development and health, while dysregulation can lead to developmental defects and disease. Though both pathways have been vigorously studied, there is relatively little research exploring the possibility of crosstalk between these pathways. In this review, we provide a brief background on (1) the roles of both AHR and Wnt signaling in development and disease, and (2) the molecular mechanisms that characterize activation of each pathway. We also discuss the need for careful and complete experimental evaluation of each pathway and describe existing research that explores the intersection of AHR and Wnt signaling. Lastly, to illustrate in detail the intersection of AHR and Wnt signaling, we summarize our recent findings which show that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced disruption of Wnt signaling impairs fetal prostate development. PMID:25286307

The aryl hydrocarbon receptor and glucocorticoid receptor interact to activate human metallothionein 2A

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

Sato, Shoko, E-mail: satosho@rs.tus.ac.jp; Shirakawa, Hitoshi, E-mail: shirakah@m.tohoku.ac.jp; Tomita, Shuhei, E-mail: tomita@med.tottori-u.ac.jp

2013-11-15

Although the aryl hydrocarbon receptor (AHR) and glucocorticoid receptor (GR) play essential roles in mammalian development, stress responses, and other physiological events, crosstalk between these receptors has been the subject of much debate. Metallothioneins are classic glucocorticoid-inducible genes that were reported to increase upon treatment with AHR agonists in rodent tissues and cultured human cells. In this study, the mechanism of human metallothionein 2A (MT2A) gene transcription activation by AHR was investigated. Cotreatment with 3-methylcholanthrene and dexamethasone, agonists of AHR and GR respectively, synergistically increased MT2A mRNA levels in HepG2 cells. MT2A induction was suppressed by RNA interference against AHRmore » or GR. Coimmunoprecipitation experiments revealed a physical interaction between AHR and GR proteins. Moreover, chromatin immunoprecipitation assays indicated that AHR was recruited to the glucocorticoid response element in the MT2A promoter. Thus, we provide a novel mechanism whereby AHR modulates expression of human MT2A via the glucocorticoid response element and protein–protein interactions with GR. - Highlights: • Aryl hydrocarbon receptor forms a complex with glucocorticoid receptor in cells. • Human metallothionein gene is regulated by the AHR and GR interaction. • AHR–GR complex binds to glucocorticoid response element in metallothionein gene. • We demonstrated a novel transcriptional mechanism via AHR and GR interaction.« less

An aryl hydrocarbon receptor ligand acts on dendritic cells and T cells to suppress the Th17 response in allergic rhinitis patients.

PubMed

Wei, Ping; Hu, Guo-Hua; Kang, Hou-Yong; Yao, Hong-Bing; Kou, Wei; Liu, Hong; Zhang, Cheng; Hong, Su-Ling

2014-05-01

A predominant Th17 population is a marker of allergic rhinitis (AR). The aryl hydrocarbon receptor (AhR) exhibits strong immunomodulation potential via regulation of the differentiation of T lymphocytes and dendritic cells (DCs) after activation by its ligand, such as 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). The aim of this study was to analyze the effect of AhR on Th17 differentiation by investigating the action of ITE on DCs and CD4(+) T cells from patients with AR. In all, 26 AR patients and 12 healthy controls were included in this study. The expression of interleukin (IL)-1β, IL-6, IL-10, and IL-17 in the culture supernatant and the presence of Th17 cells in CD4(+) T cells and DC-CD4(+) T-cell co-culture system were measured before and after treatment with ITE. We show that ITE significantly induced cell secretion of IL-10 and inhibited IL-1β and IL-6 production in DCs, and promoted IL-10 production and suppressed IL-17 expression in CD4(+) T cells in vitro. It also suppressed the expansion of Th17 cells in vitro. Our work demonstrates that ITE acts on DCs and CD4(+) T cells to inhibit the Th17 response that suppresses AR; the AhR-DC-Th17 axis may be an important pathway in the treatment of AR. ITE, a nontoxic AhR ligand, attenuated the Th17 response; thus, it appears to be a promising therapeutic candidate for suppressing the inflammatory responses associated with AR.

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.

In vitro bioanalysis of drinking water from source to tap.

PubMed

Rosenmai, Anna Kjerstine; Lundqvist, Johan; le Godec, Théo; Ohlsson, Åsa; Tröger, Rikard; Hellman, Björn; Oskarsson, Agneta

2018-08-01

The presence of chemical pollutants in sources of drinking water is a key environmental problem threatening public health. Efficient removal of pollutants in drinking water treatment plants (DWTPs) is needed as well as methods for assessment of the total impact of all present chemicals on water quality. In the present study we have analyzed the bioactivity of water samples from source to tap, including effects of various water treatments in a DWTP, using a battery of cell-based bioassays, covering health-relevant endpoints. Reporter gene assays were used to analyze receptor activity of the aryl hydrocarbon receptor (AhR), estrogen receptor (ER), androgen receptor (AR), peroxisome proliferator-activated receptor alpha (PPARα) and induction of oxidative stress by the nuclear factor erythroid 2-related factor 2 (Nrf2). DNA damage was determined by Comet assay. Grab water samples were concentrated by HLB or ENV solid phase extraction and the water samples assayed at a relative enrichment factor of 50. The enrichment procedure did not induce any bioactivity. No bioactivity was detected in Milli-Q water or drinking water control samples. Induction of AhR, ER and Nrf2 activities was revealed in source to tap water samples. No cytotoxicity, PPARα or AR antagonist activity, or DNA damage were observed in any of the water samples. A low AR agonist activity was detected in a few samples of surface water, but not in the samples from the DWTP. The treatment steps at the DWTP, coagulation, granulated activated carbon filtration, UV disinfection and NH 2 Cl dosing had little or no effect on the AhR, Nrf2 and ER bioactivity. However, nanofiltration and passage through the distribution network drastically decreased AhR activity, while the effect on Nrf2 activity was more modest and no apparent effect was observed on ER activity. The present results suggest that bioassays are useful tools for evaluation of the efficiency of different treatment steps in DWTPs in reducing toxic

Assessment of potential biological activities and distributions of endocrine-disrupting chemicals in sediments of the west coast of South Korea.

PubMed

Jeon, Seungyeon; Hong, Seongjin; Kwon, Bong-Oh; Park, Jinsoon; Song, Sung Joon; Giesy, John P; Khim, Jong Seong

2017-02-01

The west coast of Korea has experienced environmental deterioration for more than half a century. In the present study, we specifically aimed to: i) evaluate potential toxicities of contaminants in sediments that cause effects mediated through the aryl hydrocarbon receptor (AhR) and estrogen receptor (ER); ii) determine spatio-temporal distributions of polycyclic aromatic hydrocarbons (PAHs) and alkylphenols (APs); and iii) identify causes of greater potencies of samples. From 2010 to 2014, sediments were collected from 12 major estuarine and coastal regions along the west coast of South Korea. In vitro cell bioassays were performed to determine AhR- and ER-mediated potencies using H4IIE-luc and MVLN cells, respectively. Fifteen PAHs and six APs in sediments were identified by GC/MSD. Results of bioassays generally showed a low-to-moderate degree of contamination, however, greater AhR- and ER-mediated potencies were measured at some locations. Concentrations of PAHs and APs varied among locations, which indicated that sources were independently affected by the surrounding environment (e.g., industrial complex and cities). Results of bioassays were generally well correlated with concentrations of putative causative chemicals. Benzo[k]fluoranthene, dibenz[a,h]anthracene, and benzo[b]fluoranthene were the major AhR agonists, explaining approximately 30% of the bioassay-derived benzo[a]pyrene equivalent concentration (BaP-EQ). Unknown AhR and ER agonists and potential mixture effects remain in question. Overall, the present study provides baseline information on chemical contaminations and potential toxicity of sediments in a fairly wide geographical region of the west coast of South Korea. Copyright © 2016 Elsevier Ltd. All rights reserved.

Hazard and risk assessment of chemical mixtures using the toxic equivalency factor approach.

PubMed

Safe, S H

1998-08-01

There is considerable public, regulatory, and scientific concern regarding human exposure to endocrine-disrupting chemicals, which include compounds that directly modulate steroid hormone receptor pathways (estrogens, antiestrogens, androgens, antiandrogens) and aryl hydrocarbon receptor (AhR) agonists, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. Based on quantitative structure-activity relationships for both AhR and estrogen receptor (ER) agonists, the relative potency (RP) of individual compounds relative to a standard (e.g. TCDD and 17-beta-estradiol) have been determined for several receptor-mediated responses. Therefore, the TCDD or estrogenic equivalent (TEQ or EQ, respectively) of a mixture is defined as TEQ = sigma[T(i)]xRP(i)or EQ=sigma[E(i)]xRP(i), where T(i) and E(i) are concentrations of individual AhR or ER agonists in any mixture. This approach for risk assessment of endocrine-disrupting mixtures assumes that for each endocrine response pathway, the effects of individual compounds are essentially additive. This paper will critically examine the utility of the TEQ/EQ approach for risk assessment, the validity of the assumptions used for this approach, and the problems associated with comparing low dose exposures to xeno and natural (dietary) endocrine disruptors.

Binding of Estrogenic Compounds to Recombinant Estrogen Receptor-α: Application to Environmental Analysis

PubMed Central

Pillon, Arnaud; Boussioux, Anne-Marie; Escande, Aurélie; Aït-Aïssa, Sélim; Gomez, Elena; Fenet, Hélène; Ruff, Marc; Moras, Dino; Vignon, Françoise; Duchesne, Marie-Josèphe; Casellas, Claude; Nicolas, Jean-Claude; Balaguer, Patrick

2005-01-01

Estrogenic activity in environmental samples could be mediated through a wide variety of compounds and by various mechanisms. High-affinity compounds for estrogen receptors (ERs), such as natural or synthetic estrogens, as well as low-affinity compounds such as alkylphenols, phthalates, and polychlorinated biphenyls are present in water and sediment samples. Furthermore, compounds such as polycyclic aromatic hydrocarbons, which do not bind ERs, modulate estrogen activity by means of the aryl hydrocarbon receptor (AhR). In order to characterize compounds that mediate estrogenic activity in river water and sediment samples, we developed a tool based on the ER-αligand-binding domain, which permitted us to estimate contaminating estrogenic compound affinities. We designed a simple transactivation assay in which compounds of high affinity were captured by limited amounts of recombinant ER-αand whose capture led to a selective inhibition of transactivation. This approach allowed us to bring to light that water samples contain estrogenic compounds that display a high affinity for ERs but are present at low concentrations. In sediment samples, on the contrary, we showed that estrogenic compounds possess a low affinity and are present at high concentration. Finally, we used immobilized recombinant ER-αto separate ligands for ER and AhR that are present in river sediments. Immobilized ER-α, which does not retain dioxin-like compounds, enabled us to isolate and concentrate ER ligands to facilitate their further analysis. PMID:15743715

Coal tar induces AHR-dependent skin barrier repair in atopic dermatitis

PubMed Central

van den Bogaard, Ellen H.; Bergboer, Judith G.M.; Vonk-Bergers, Mieke; van Vlijmen-Willems, Ivonne M.J.J.; Hato, Stanleyson V.; van der Valk, Pieter G.M.; Schröder, Jens Michael; Joosten, Irma; Zeeuwen, Patrick L.J.M.; Schalkwijk, Joost

2013-01-01

Topical application of coal tar is one of the oldest therapies for atopic dermatitis (AD), a T helper 2 (Th2) lymphocyte–mediated skin disease associated with loss-of-function mutations in the skin barrier gene, filaggrin (FLG). Despite its longstanding clinical use and efficacy, the molecular mechanism of coal tar therapy is unknown. Using organotypic skin models with primary keratinocytes from AD patients and controls, we found that coal tar activated the aryl hydrocarbon receptor (AHR), resulting in induction of epidermal differentiation. AHR knockdown by siRNA completely abrogated this effect. Coal tar restored filaggrin expression in FLG-haploinsufficient keratinocytes to wild-type levels, and counteracted Th2 cytokine–mediated downregulation of skin barrier proteins. In AD patients, coal tar completely restored expression of major skin barrier proteins, including filaggrin. Using organotypic skin models stimulated with Th2 cytokines IL-4 and IL-13, we found coal tar to diminish spongiosis, apoptosis, and CCL26 expression, all AD hallmarks. Coal tar interfered with Th2 cytokine signaling via dephosphorylation of STAT6, most likely due to AHR-regulated activation of the NRF2 antioxidative stress pathway. The therapeutic effect of AHR activation herein described opens a new avenue to reconsider AHR as a pharmacological target and could lead to the development of mechanism-based drugs for AD. PMID:23348739

Coal tar induces AHR-dependent skin barrier repair in atopic dermatitis.

PubMed

van den Bogaard, Ellen H; Bergboer, Judith G M; Vonk-Bergers, Mieke; van Vlijmen-Willems, Ivonne M J J; Hato, Stanleyson V; van der Valk, Pieter G M; Schröder, Jens Michael; Joosten, Irma; Zeeuwen, Patrick L J M; Schalkwijk, Joost

2013-02-01

Topical application of coal tar is one of the oldest therapies for atopic dermatitis (AD), a T helper 2 (Th2) lymphocyte-mediated skin disease associated with loss-of-function mutations in the skin barrier gene, filaggrin (FLG). Despite its longstanding clinical use and efficacy, the molecular mechanism of coal tar therapy is unknown. Using organotypic skin models with primary keratinocytes from AD patients and controls, we found that coal tar activated the aryl hydrocarbon receptor (AHR), resulting in induction of epidermal differentiation. AHR knockdown by siRNA completely abrogated this effect. Coal tar restored filaggrin expression in FLG-haploinsufficient keratinocytes to wild-type levels, and counteracted Th2 cytokine-mediated downregulation of skin barrier proteins. In AD patients, coal tar completely restored expression of major skin barrier proteins, including filaggrin. Using organotypic skin models stimulated with Th2 cytokines IL-4 and IL-13, we found coal tar to diminish spongiosis, apoptosis, and CCL26 expression, all AD hallmarks. Coal tar interfered with Th2 cytokine signaling via dephosphorylation of STAT6, most likely due to AHR-regulated activation of the NRF2 antioxidative stress pathway. The therapeutic effect of AHR activation herein described opens a new avenue to reconsider AHR as a pharmacological target and could lead to the development of mechanism-based drugs for AD.

Dietary Indoles Suppress Delayed-Type Hypersensitivity by Inducing a Switch from Pro-inflammatory Th17 cells to Anti-inflammatory Tregs through Regulation of microRNA

PubMed Central

Singh, Narendra P.; Singh, Udai P.; Rouse, Michael; Zhang, Jiajia; Chatterjee, Saurabh; Nagarkatti, Prakash S.; Nagarkatti, Mitzi

2015-01-01

Aryl hydrocarbon receptor (AhR) has been shown to have profound influence on T cell differentiation and use of distinct AhR ligands has shown that while some ligands induce Tregs, others induce Th17 cells. In the current study, we tested the ability of dietary AhR ligands (indole-3-carbinol; I3C and 3,3'-diindolylmethane; DIM), and an endogenous AhR ligand, 6-Formylindolo(3,2-b)carbazole (FICZ), on the differentiation and functions of Tregs and Th17 cells. Treatment of C57BL/6 mice with indoles (I3C or DIM), attenuated DTH response to mBSA and generation of Th17 cells while promoting Tregs. In contrast, FICZ exacerbated the DTH response and promoted Th17 cells. Indoles decreased the induction of IL-17 while promoted IL-10 and FoxP3 expression. Also, indoles caused reciprocal induction of Tregs and Th17 cells only in wild-type (AhR+/+) but not in AhR knockout (AhR−/−) mice. Upon analysis of microRNA (miR) profile in draining lymph nodes of mice with DTH, treatment with I3C and DIM decreased the expression of several miRs (miR-31, miR-219, and miR-490) that targeted FoxP3, while increasing the expression of miR-495 and miR-1192 that were specific to IL-17. Interestingly, treatment with FICZ had precisely the opposite effects on these miRs. Transfection studies using mature miR mimics of miR-490 and miR-1192 that target FoxP3 and IL-17 respectively or scrambled miR (mock) or inhibitors confirmed that these miRs specifically targeted FoxP3 and IL-17 genes. Our studies demonstrate for the first time that the ability of AhR ligands to regulate the differentiation of Tregs versus Th17 cells may depend on miR signature profile. PMID:26712945

From the Cover: Development and Application of a Dual Rat and Human AHR Activation Assay.

PubMed

Brown, Martin R; Garside, Helen; Thompson, Emma; Atwal, Saseela; Bean, Chloe; Goodall, Tony; Sullivan, Michael; Graham, Mark J

2017-12-01

Significant prolonged aryl hydrocarbon receptor (AHR) activation, classically exhibited following exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin, can cause a variety of undesirable toxicological effects. Novel pharmaceutical chemistries also have the potential to cause activation of AHR and consequent toxicities in pre-clinical species and man. Previous methods either employed relatively expensive and low-throughput primary hepatocyte dosing with PCR endpoint, or low resolution overexpressing reporter gene assays. We have developed, validated and applied an in vitro microtitre plate imaging-based medium throughput screening assay for the assessment of endogenous species-specific AHR activation potential via detection of induction of the surrogate transcriptional target Cytochrome P450 CYP1A1. Routine testing of pharmaceutical drug development candidate chemistries using this assay can influence the chemical design process and highlight AHR liabilities. This assay should be introduced such that human AHR activation liability is flagged early for confirmatory testing. © The Author 2017. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Daily treatment with {alpha}-naphthoflavone enhances follicular growth and ovulation rate in the rat

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

Barreiro, Karina A.; Di Yorio, Maria P.; Artillo-Guida, Romina D.

2011-04-01

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor and the first protein involved in a variety of physiological and toxicological processes, including those of xenobiotic metabolizing enzymes. AhR has been found in the ovary of many species and seems to mediate the ovarian toxicity of many environmental contaminants, which are AhR ligands. However, the role of AhR in the ovarian function is unknown. Therefore, the aim of this work was to study the action of {alpha}-naphthoflavone ({alpha}NF), known to be an AhR antagonist, on both follicular growth and ovulation. Immature Sprague-Dawley rats were daily injected intraperitoneally with {alpha}NFmore » (0.1-80 mg/kg) or vehicle for 12 days, and primed with gonadotrophins (eCG/hCG) to induce follicular growth and ovulation. Ovaries were obtained 20 h after hCG administration. By means of immunohistochemistry, we found that the numbers of primordial, primary and antral follicles were increased in rats treated with 80 mg/kg {alpha}NF and that there were no differences with other doses. Likewise, the ovarian weight and the ovulation rate, measured by both number of oocytes within oviducts and corpora lutea in ovarian sections, were increased when the rats received either 1 or 10 mg/kg daily. Although further studies are necessary to know the mechanism of action of {alpha}NF, it is possible that the different ovarian processes can be differentially responsive to the presence of different levels of {alpha}NF, and that the same or different endogenous AhR ligands can be involved in these ovarian processes in a cell type-dependent manner.« less

Third-Generation Ah Receptor–Responsive Luciferase Reporter Plasmids: Amplification of Dioxin-Responsive Elements Dramatically Increases CALUX Bioassay Sensitivity and Responsiveness

PubMed Central

He, Guochun; Tsutsumi, Tomoaki; Zhao, Bin; Baston, David S.; Zhao, Jing; Heath-Pagliuso, Sharon; Denison, Michael S.

2011-01-01

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, dioxin) and related dioxin-like chemicals are widespread and persistent environmental contaminants that produce diverse toxic and biological effects through their ability to bind to and activate the Ah receptor (AhR) and AhR-dependent gene expression. The chemically activated luciferase expression (CALUX) system is an AhR-responsive recombinant luciferase reporter gene–based cell bioassay that has been used in combination with chemical extraction and cleanup methods for the relatively rapid and inexpensive detection and relative quantitation of dioxin and dioxin-like chemicals in a wide variety of sample matrices. Although the CALUX bioassay has been validated and used extensively for screening purposes, it has some limitations when screening samples with very low levels of dioxin-like chemicals or when there is only a small amount of sample matrix for analysis. Here, we describe the development of third-generation (G3) CALUX plasmids with increased numbers of dioxin-responsive elements, and stable transfection of these new plasmids into mouse hepatoma (Hepa1c1c7) cells has produced novel amplified G3 CALUX cell bioassays that respond to TCDD with a dramatically increased magnitude of luciferase induction and significantly lower minimal detection limit than existing CALUX-type cell lines. The new G3 CALUX cell lines provide a highly responsive and sensitive bioassay system for the detection and relative quantitation of very low levels of dioxin-like chemicals in sample extracts. PMID:21775728

Hexachlorobenzene promotes angiogenesis in vivo, in a breast cancer model and neovasculogenesis in vitro, in the human microvascular endothelial cell line HMEC-1.

PubMed

Pontillo, Carolina; Español, Alejandro; Chiappini, Florencia; Miret, Noelia; Cocca, Claudia; Alvarez, Laura; Kleiman de Pisarev, Diana; Sales, María Elena; Randi, Andrea Silvana

2015-11-19

Exposure to environmental pollutants may alter proangiogenic ability and promotes tumor growth. Hexachlorobenzene (HCB) is an organochlorine pesticide found in maternal milk and in lipid foods, and a weak ligand of the aryl hydrocarbon receptor (AhR). HCB induces migration and invasion in human breast cancer cells, as well as tumor growth and metastasis in vivo. In this study, we examined HCB action on angiogenesis in mammary carcinogenesis. HCB stimulates angiogenesis and increases vascular endothelial growth factor (VEGF) expression in a xenograft model with the human breast cancer cell line MDA-MB-231. Human microvascular endothelial cells HMEC-1 exposed to HCB (0.005, 0.05, 0.5 and 5μM) showed an increase in cyclooxygenase-2 (COX-2) and VEGF protein expression involving AhR. In addition, we found that HCB enhances VEGF-Receptor 2 (VEGFR2) expression, and activates its downstream pathways p38 and ERK1/2. HCB induces cell migration and neovasculogenesis in a dose-dependent manner. Cells pretreatment with AhR, COX-2 and VEGFR2 selective inhibitors, suppressed these effects. In conclusion, our results show that HCB promotes angiogenesis in vivo and in vitro. HCB-induced cell migration and tubulogenesis are mediated by AhR, COX-2 and VEGFR2 in HMEC-1. These findings may help to understand the association among HCB exposure, angiogenesis and mammary carcinogenesis. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Quercetin-6-C-β-D-glucopyranoside, natural analog of quercetin exhibits anti-prostate cancer activity by inhibiting Akt-mTOR pathway via aryl hydrocarbon receptor.

PubMed

Hamidullah; Kumar, Rajeev; Saini, Karan Singh; Kumar, Amit; Kumar, Sudhir; Ramakrishna, E; Maurya, Rakesh; Konwar, Rituraj; Chattopadhyay, Naibedya

2015-12-01

Pre-clinical studies suggest mitigating effect of dietary flavonoid quercetin against cancer and other diseases. However, quercetin suffers from poor metabolic stability, which appears to offset its pharmacological efficacy. Recently, we isolated quercetin-6-C-β-D-glucopyranoside (QCG) from Ulmus wallichiana planchon that has greater stability profile over quercetin. In the present study, the cytotoxic and apoptotic effects of QCG on prostate cancer cells were assessed. QCG inhibited prostate cancer cell proliferation by arresting cells at G0/G1 phase of cell cycle and induces apoptosis as evident from cytochrome c release, cleavage of caspase 3 and poly (ADP-ribose) polymerase. Mechanistic studies revealed that QCG inhibited reactive oxygen species (ROS) generation and Akt/mTOR cell survival pathways. Aryl hydrocarbon receptor (AhR) was a critical mediator of QCG action as knockdown of AhR attenuated QCG-induced cell cycle arrest, apoptosis and inhibition of Akt/mTOR pathway in prostate cancer cells. Taken together, our results suggest that QCG exhibits anti-cancer activity against prostate cancer cells via AhR-mediated down regulation of Akt/mTOR pathway in PC-3 cells. Copyright © 2015 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

AHR prevents human IL-1R1hi ILC3 differentiation to natural killer cells

PubMed Central

Hughes, Tiffany; Briercheck, Edward L.; Freud, Aharon G.; Trotta, Rossana; McClory, Susan; Scoville, Steven D.; Keller, Karen; Deng, Youcai; Cole, Jordan; Harrison, Nicholas; Mao, Charlene; Zhang, Jianying; Benson, Don M.; Yu, Jianhua; Caligiuri, Michael A.

2014-01-01

SUMMARY Accumulating evidence indicates that human natural killer (NK) cells develop in secondary lymphoid tissue (SLT) through a so-called “stage 3” developmental intermediate minimally characterized by a CD34-CD117+CD94- immunophenotype that lacks mature NK cell function. This stage 3 population is heterogeneous, potentially composed of functionally distinct innate lymphoid cell (ILC) types that includes interleukin-1 receptor (IL-1R1) positive, IL-22-producing ILC3s. Whether human ILC3s are developmentally related to NK cells is a subject of ongoing investigation. Here we show that antagonism of the aryl hydrocarbon receptor (AHR) or silencing of AHR gene expression promotes differentiation of tonsillar IL-22-producing IL-1R1hi human ILC3s to CD56brightCD94+ IFN-gamma-producing cytolytic mature NK cells expressing eomesodermin (EOMES) and T-Box Protein 21 (TBX21 or TBET). Hence, AHR is a transcription factor that prevents human IL-1R1hi ILC3s from differentiating into NK cells. PMID:24953655

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

Kovalova, Natalia, E-mail: kovalova@msu.edu

Previous studies have demonstrated that most of the intraspecies variation in sensitivity to the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), including suppression of antibody responses, in murine models is due to single nucleotide polymorphisms (SNPs) within the aryl hydrocarbon receptor (AhR) gene. The underlying reason for variation in sensitivity to TCDD-induced suppression of IgM responses among humans is not well understood, but is thought, in part, to be a result of different polymorphic forms of the AhR expressed by different individuals. In this study, the functional properties of six (P517S, R554K, V570I, V570I + P517S, R554K + V570I and P517S +more » R554K + V570I) human AhR variants were examined in the human B cell line, SKW 6.4. TCDD-induced Cyp1B1 and Cyp1A2 mRNA expression levels and Cyp1B1-regulated reporter gene activity, used for comparative purposes, were markedly lower in SKW cells containing the R554K SNP than in SKW-AHR{sup +} (control AhR) cells. Furthermore, all AhR variants were able to mediate TCDD-induced suppression of the IgM response; however, a combined P517S + R554K + V570I variant partially reduced sensitivity to TCDD-mediated suppression of IgM secretion. Collectively, our findings show that the R554K human AhR SNP alone altered sensitivity of human B cells to TCDD-mediated induction of Cyp1B1 and Cyp1A2. By contrast, attenuation of TCDD-induced IgM suppression required a combination of all three SNPs P517S, R554K, and V570I. - Highlights: • Mouse, rat and SKW-AHR{sup +} B cells have a similar window of sensitivity to TCDD. • R554K AhR SNP alters B cell sensitivity to TCDD-mediated Cyp1B1 and Cyp1A2 induction. • Combination of P517S, R554K, and V570I SNPs attenuates TCDD-induced IgM suppression.« less

AHR2 morpholino knockdown reduces the toxicity of total particulate matter to zebrafish embryos

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

Massarsky, Andrey, E-mail: andrey.massarsky@duke.e

The zebrafish embryo has been proposed as a ‘bridge model’ to study the effects of cigarette smoke on early development. Previous studies showed that exposure to total particulate matter (TPM) led to adverse effects in developing zebrafish, and suggested that the antioxidant and aryl hydrocarbon receptor (AHR) pathways play important roles. This study investigated the roles of these two pathways in mediating TPM toxicity. The study consisted of four experiments. In experiment I, zebrafish embryos were exposed from 6 h post fertilization (hpf) until 96 hpf to TPM{sub 0.5} and TPM{sub 1.0} (corresponding to 0.5 and 1.0 μg/mL equi-nicotine units)more » in the presence or absence of an antioxidant (N-acetyl cysteine/NAC) or a pro-oxidant (buthionine sulfoximine/BSO). In experiment II, TPM exposures were performed in embryos that were microinjected with nuclear factor erythroid 2-related factor 2 (Nrf2), AHR2, cytochrome P450 1A (CYP1A), or CYP1B1 morpholinos, and deformities were assessed. In experiment III, embryos were exposed to TPM, and embryos/larvae were collected at 24, 48, 72, and 96 hpf to assess several genes associated with the antioxidant and AHR pathways. Lastly, experiment IV assessed the activity and protein levels of CYP1A and CYP1B1 after exposure to TPM. We demonstrate that the incidence of TPM-induced deformities was generally not affected by NAC/BSO treatments or Nrf2 knockdown. In contrast, AHR2 knockdown reduced, while CYP1A or CYP1B1 knockdowns elevated the incidence of some deformities. Moreover, as shown by gene expression the AHR pathway, but not the antioxidant pathway, was induced in response to TPM exposure, providing further evidence for its importance in mediating TPM toxicity. - Highlights: • Total particulate matter (TPM) is the particulate phase of cigarette smoke. • Zebrafish is proposed as a ‘bridge model’ to study the effects of TPM. • We investigate the roles of antioxidant and aryl hydrocarbon receptor (AHR

In situ microbiota distinguished primary anthropogenic stressor in freshwater sediments.

PubMed

Xie, Yuwei; Floehr, Tilman; Zhang, Xiaowei; Xiao, Hongxia; Yang, Jianghua; Xia, Pu; Burton, G Allen; Hollert, Henner

2018-08-01

Conventional assessment and evaluation of sediment quality are based on laboratory-based ecotoxicological and chemical measurements with lack of concern for ecological relevance. Microbiotas in sediment are responsive to pollutants and can be used as alternative ecological indicators of sediment pollutants; however, the linkage between the microbial ecology and ecotoxicological endpoints in response to sediment contamination has been poorly evaluated. Here, in situ microbiotas from the Three Gorges Reservoir (TGR) area of the Yangtze River were characterized by DNA metabarcoding approaches, and then, changes of in situ microbiotas were compared with the ecotoxicological endpoint, aryl hydrocarbon receptor (AhR) mediated activity, and level of polycyclic aromatic hydrocarbons (PAHs) in sediments. PAHs and organic pollutant mixtures mediating AhR activity had different effects on the structures of microbiotas. Specifically, Shannon indices of protistan communities were negatively correlated with the levels of AhR mediated activity and PAHs. The sediment AhR activity was positively correlated with the relative abundance of prokaryotic Acetobacteraceae, but had a negative correlation with protistan Oxytrichidae. Furthermore, a quantitative classification model was built to predict the level of AhR activity based on the relative abundances of Acetobacteraceae and Oxytrichidae. These results suggested that in situ Protista communities could provide a useful tool for monitoring and assessing ecological stressors. The observed responses of microbial community provided supplementary evidence to support that the AhR-active pollutants, such as PAHs, were the primary stressors of the aquatic community in TGR area. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of tributyltin (TBT) on in vitro hormonal and biotransformation responses in Atlantic salmon (Salmo salar).

PubMed

Mortensen, Anne S; Arukwe, Augustine

2009-01-01

The mechanisms by which the biocide tributyltin (TBT) and its metabolites affect the hormonal and xenobiotic biotransformation pathways in aquatic species are not well understood. In this study hepatocytes isolated from salmon were used to evaluate the mechanistical effects of TBT on fish hormonal and xenobiotic biotransformation pathways. Cells were exposed to 0.01, 0.1, 1, or 5 microM TBT and samples were collected at 0, 12, 24, or 48 h following exposure. Gene expression patterns were evaluated using quantitative polymerase chain reaction (PCR), and cytochrome P-450 (CYP)-mediated enzyme activities were evaluated by ethoxyresorufin, benzyloxyresorufin, and pentoxyresorufin O-deethylase (EROD, BROD, and PROD, respectively) activity assays. Generally, exposure of hepatocytes to 1 microM (at 48 h) and 5 microM TBT (at 12, 24, and 48 h) consistently produced reductions in all mRNA species investigated. TBT produced significant decreases of vitellogen (Vtg) expression at 48 h and modified the expression patterns of estrogen receptors (ERalpha and ERbeta) and androgen receptor-beta (ARbeta) that were dependent on time and TBT concentration. In the xenobiotic biotransformation pathway, TBT produced differential expression patterns that were dependent on exposure time and concentration for all salmonid AhR2 isoforms (AhR2alpha, AhR2beta, AhR2delta, and AhR2gamma). For CYP1A1, CYP3A, AhRR, and Arnt mRNA, TBT produced exposure- and time-specific modulations. Catalytic CYP activities showed that BROD activity increased in an apparent concentration-specific manner in cells exposed to TBT for 12 h. Interestingly, EROD activity showed a TBT concentration-dependent increase at 24 h and PROD at 12 and 48 h of exposure. In general our data show that TBT differentially modulated hormonal and biotransformation responses in the salmon in vitro system. The apparent and consistent decrease of the studied responses with time in 1 and 5 microM exposed hepatocytes suggest a possible

Induction of cytochrome P450 1A by cow milk-based formula: a comparative study between human milk and formula

PubMed Central

Xu, Haibo; Rajesan, Ratheishan; Harper, Patricia; Kim, Richard B; Lonnerdal, Bo; Yang, Mingdong; Uematsu, Satoko; Hutson, Janine; Watson-MacDonell, Jo; Ito, Shinya

2005-01-01

During the treatment of neonatal apnea, formula-fed infants, compared to breastfed infants, show nearly three-fold increase in clearance of caffeine, a substrate of cytochrome P450 1A (CYP1A) and in part CYP3A4. However, human milk is known to contain higher concentrations of environmental pollutants than infant formula, which are potent CYP1A inducers. To gain insight into the mechanism underlying this apparent contradiction, we characterized CYP1A and CYP3A4 induction by human milk and cow milk-based infant formula. The mRNA and protein expression of CYP1A1/1A2 were significantly induced by cow milk-based formula, but not by human milk, in HepG2 cells. Luciferase reporter assay demonstrated that cow milk-based formula but not human milk activated aryl hydrocarbon receptor (AhR) significantly. The cotreatment of 3,4-dimethoxyflavone, an AhR antagonist, abolished the formula-induced CYP1A expression. In addition, AhR activation by dibenzo[a,h]anthracene, a potent AhR agonist, was significantly suppressed by infant formula and even more by human milk. In contrast, CYP3A4 mRNA expression was only mildly induced by formula and human milk. Consistently, neither formula nor human milk substantially activated pregnane X receptor (PXR). Effects of whey and soy protein-based formulas on the AhR–CYP1A and the PXR–CYP3A4 pathways were similar to those of cow milk-based formula. In conclusion, infant formula, but not human milk, enhances in vitro CYP1A expression via an AhR-mediated pathway, providing a potential mechanistic basis for the increased caffeine elimination in formula-fed infants. PMID:15997229

Induction of cytochrome P450 1A by cow milk-based formula: a comparative study between human milk and formula.

PubMed

Xu, Haibo; Rajesan, Ratheishan; Harper, Patricia; Kim, Richard B; Lonnerdal, Bo; Yang, Mingdong; Uematsu, Satoko; Hutson, Janine; Watson-MacDonell, Jo; Ito, Shinya

2005-09-01

During the treatment of neonatal apnea, formula-fed infants, compared to breastfed infants, show nearly three-fold increase in clearance of caffeine, a substrate of cytochrome P450 1A (CYP1A) and in part CYP3A4. However, human milk is known to contain higher concentrations of environmental pollutants than infant formula, which are potent CYP1A inducers. To gain insight into the mechanism underlying this apparent contradiction, we characterized CYP1A and CYP3A4 induction by human milk and cow milk-based infant formula. The mRNA and protein expression of CYP1A1/1A2 were significantly induced by cow milk-based formula, but not by human milk, in HepG2 cells. Luciferase reporter assay demonstrated that cow milk-based formula but not human milk activated aryl hydrocarbon receptor (AhR) significantly. The cotreatment of 3,4-dimethoxyflavone, an AhR antagonist, abolished the formula-induced CYP1A expression. In addition, AhR activation by dibenzo[a,h]anthracene, a potent AhR agonist, was significantly suppressed by infant formula and even more by human milk. In contrast, CYP3A4 mRNA expression was only mildly induced by formula and human milk. Consistently, neither formula nor human milk substantially activated pregnane X receptor (PXR). Effects of whey and soy protein-based formulas on the AhR-CYP1A and the PXR-CYP3A4 pathways were similar to those of cow milk-based formula. In conclusion, infant formula, but not human milk, enhances in vitro CYP1A expression via an AhR-mediated pathway, providing a potential mechanistic basis for the increased caffeine elimination in formula-fed infants.

Micro124-mediated AHR expression regulates the inflammatory response of chronic rhinosinusitis (CRS) with nasal polyps.

PubMed

Liu, C C; Xia, M; Zhang, Y J; Jin, P; Zhao, L; Zhang, J; Li, T; Zhou, X M; Tu, Y Y; Kong, F; Sun, C; Shi, L; Zhao, M Q

2018-06-02

MicroRNAs represent a component of the innate immune responses that can restrain inflammatory signaling, miR124 is an important member of inflammation-associated miRNAs, and abnormal miR124 expression is observed in many inflammatory diseases and immune disorders. However, the role and signaling pathways of miR124 in chronic rhinosinusitis with nasal polyps (CRSwNPs) have not been studied in detail. The aryl hydrocarbon receptor (AHR) is a ligand-inducible transcription factor that is highly conserved in evolution and plays important roles in the inflammatory response process. In our study, we describe the role of miR124 in the inflammatory response of CRS with nasal polyps. We found that the expression of miR124 was decreased in nasal polyps, and negatively correlated with the expression of AHR. MiR124 can inhibit AHR expression by directly target 3' untranslated region (3'-UTR) of AHR. To further investigate the relationship between miR124, AHR and CRS inflammatory response, we transfect HNEpC cells with miR124 mimic, miR124 inhibitors or siRNA of AHR, then all the results showed that miR124 could regulates cellular inflammatory response through negatively regulating AHR expression. This study demonstrated that the regulation of AHR expression by miR124 is critical to the development of inflammatory response in CRSwNPs. Copyright © 2018. Published by Elsevier Inc.

Indoxyl Sulfate Promotes Macrophage IL-1β Production by Activating Aryl Hydrocarbon Receptor/NF-κ/MAPK Cascades, but the NLRP3 inflammasome Was Not Activated

PubMed Central

Wakamatsu, Takuya; Yamamoto, Suguru; Ito, Toru; Sato, Yoko; Matsuo, Koji; Takahashi, Yoshimitsu; Kaneko, Yoshikatsu; Goto, Shin; Kazama, Junichiro James; Gejyo, Fumitake; Narita, Ichiei

2018-01-01

In chronic kidney disease (CKD) patients, accumulation of uremic toxins is associated with cardiovascular risk and mortality. One of the hallmarks of kidney disease-related cardiovascular disease is intravascular macrophage inflammation, but the mechanism of the reaction with these toxins is not completely understood. Macrophages differentiated from THP-1 cells were exposed to indoxyl sulfate (IS), a representative uremic toxin, and changes in inflammatory cytokine production and intracellular signaling molecules including interleukin (IL)-1, aryl hydrocarbon receptor (AhR), nuclear factor (NF)-κ, and mitogen-activated protein kinase (MAPK) cascades as well as the NLRP3 inflammasome were quantified by real-time PCR, Western blot analysis, and enzyme-linked immunosorbent assay. IS induced macrophage pro-IL-1β mRNA expression, although mature IL-1 was only slightly increased. IS increased AhR and the AhR-related mRNA expression; this change was suppressed by administration of proteasome inhibitor. IS promoted phosphorylation of NF-κB p65 and MAPK enzymes; the reaction and IL-1 expression were inhibited by BAY11-7082, an inhibitor of NF-κB. In contrast, IS decreased NLRP3 and did not change ASC, pro-caspase 1, or caspase-1 activation. IS-inducing inflammation in macrophages results from accelerating AhR-NF-κB/MAPK cascades, but the NLRP3 inflammasome was not activated. These reactions may restrict mature IL-1β production, which may explain sustained chronic inflammation in CKD patients. PMID:29543732

Nrf2-Dependent Induction of NQO1 in Mouse Aortic Endothelial Cells Overexpressing Catalase

PubMed Central

Lin, Xinghua; Yang, Hong; Zhou, LiChun; Guo, ZhongMao

2011-01-01

Overexpression of catalase has been shown to accelerate benzo(a)pyrene (BaP) detoxification in mouse aortic endothelial cells (MAECs ). NAD(P)H:quinone oxidoreductase1 (NQO1) is an enzyme that catalyzes BaP-quinone detoxification. Aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor-2 (Nrf2) are transcription factors that control NQO1 expression. Here, we investigated the effect of catalase overexpression on NQO1, Nrf2 and AhR expressions. The levels of NQO1 mRNA and protein were comparable in MAECs isolated from wild-type and transgenic mice that overexpress human catalase (hCatTg). BaP treatment increased NQO1 mRNA and protein levels in both groups, with a significantly greater induction in hCatTg MAECs than in wild-type cells. BaP-induced NQO1 promoter activity was dramatically higher in hCatTg MAECs than in wild-type cells. Our data also showed that the basal level of AhR and the BaP-induced level of Nrf2 were significantly higher in hCatTg MAECs than in wild-type cells. Inhibition of specificity protein-1 (Sp1) binding to the AhR promoter region by mithramycin A reversed the enhanced effect of catalase overexpression on AhR expression. Knockdown of AhR by RNA interference diminished BaP-induced expression of Nrf2 and NQO1. Knockdown of Nrf2 significantly decreased NQO1 mRNA and protein levels in cells with or without BaP treatment. NQO1 promoter activity was abrogated by mutation of the Nrf2-binding site in this promoter. In contrast, mutation of the AhR-binding site in NQO1 promoter did not affect the promoter activity. These results suggest that catalase overexpression upregulates BaP-induced NQO1 expression via enhancing the Sp1-AhR-Nrf2 signaling cascade. PMID:21569840

Aryl hydrocarbon receptor-dependent up-regulation of the heterodimeric amino acid transporter LAT1 (SLC7A5)/CD98hc (SLC3A2) by diesel exhaust particle extract in human bronchial epithelial cells

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

Le Vee, Marc; Jouan, Elodie; Lecureur, Valérie

The heterodimeric L-type amino acid transporter (LAT) 1/CD98hc is overexpressed in lung cancers with a poor prognosis factor. Factors that contribute to LAT1/CD98hc overexpression in lung cells remain however to be determined, but the implication of atmospheric pollution can be suspected. The present study was therefore designed to analyze the effects of diesel exhaust particle (DEP) extract (DEPe) on LAT1/CD98hc expression in bronchial epithelial BEAS-2B cells. Exposure to DEPe up-regulated LAT1 and CD98hc mRNA levels in a concentration-dependent manner, with DEPe EC{sub 50} values (around 0.2 μg/mL) relevant to environmental situations. DEPe concomitantly induced LAT1/CD98hc protein expression and LAT1-mediated leucinemore » accumulation in BEAS-2B cells. Inhibition of the aryl hydrocarbon receptor (AhR) pathway through the use of a chemical AhR antagonist or the siRNA-mediated silencing of AhR expression was next found to prevent DEPe-mediated induction of LAT1/CD98hc, indicating that this regulation depends on AhR, known to be activated by major chemical DEP components like polycyclic aromatic hydrocarbons. DEPe exposure was finally shown to induce mRNA expression and activity of matrix metalloproteinase (MMP)-2 in BEAS-2B cells, in a CD98hc/focal adhesion kinase (FAK)/extracellular regulated kinase (ERK) manner, thus suggesting that DEPe-mediated induction of CD98hc triggers activation of the integrin/FAK/ERK signaling pathway known to be involved in MMP-2 regulation. Taken together, these data demonstrate that exposure to DEPe induces functional overexpression of the amino acid transporter LAT1/CD98hc in lung cells. Such a regulation may participate to pulmonary carcinogenic effects of DEPs, owing to the well-documented contribution of LAT1 and CD98hc to cancer development. - Highlights: • The amino acid transporter LAT1/CD98hc is up-regulated in DEPe-treated lung cells. • The aryl hydrocarbon receptor is involved in DEPe-triggered induction of LAT1/CD

The IDO-AhR Axis Controls Th17/Treg Immunity in a Pulmonary Model of Fungal Infection.

PubMed

de Araújo, Eliseu Frank; Feriotti, Claudia; Galdino, Nayane Alves de Lima; Preite, Nycolas Willian; Calich, Vera Lúcia Garcia; Loures, Flávio Vieira

2017-01-01

In infectious diseases, the enzyme indoleamine 2,3 dioxygenase-1 (IDO1) that catalyzes the tryptophan (Trp) degradation along the kynurenines (Kyn) pathway has two main functions, the control of pathogen growth by reducing available Trp and immune regulation mediated by the Kyn-mediated expansion of regulatory T (Treg) cells via aryl hydrocarbon receptor (AhR). In pulmonary paracoccidioidomycosis (PCM) caused by the dimorphic fungus Paracoccidioides brasiliensis , IDO1 was shown to control the disease severity of both resistant and susceptible mice to the infection; however, only in resistant mice, IDO1 is induced by TGF-β signaling that confers a stable tolerogenic phenotype to dendritic cells (DCs). In addition, in pulmonary PCM, the tolerogenic function of plasmacytoid dendritic cells was linked to the IDO1 activity. To further evaluate the function of IDO1 in pulmonary PCM, IDO1-deficient (IDO1 -/- ) C57BL/6 mice were intratracheally infected with P. brasiliensis yeasts and the infection analyzed at three postinfection periods regarding several parameters of disease severity and immune response. The fungal loads and tissue pathology of IDO1 -/- mice were higher than their wild-type controls resulting in increased mortality rates. The evaluation of innate lymphoid cells showed an upregulated differentiation of the innate lymphoid cell 3 phenotype accompanied by a decreased expansion of ILC1 and NK cells in the lungs of infected IDO1 -/- mice. DCs from these mice expressed elevated levels of costimulatory molecules and cytokine IL-6 associated with reduced production of IL-12, TNF-α, IL-1β, TGF-β, and IL-10. This response was concomitant with a marked reduction in AhR production. The absence of IDO1 expression caused an increased influx of activated Th17 cells to the lungs with a simultaneous reduction in Th1 and Treg cells. Accordingly, the suppressive cytokines IL-10, TGF-β, IL-27, and IL-35 appeared in reduced levels in the lungs of IDO1 -/- mice. In

In Vivo Characterization of an AHR-Dependent Long Noncoding RNA Required for Proper Sox9b Expression

PubMed Central

Garcia, Gloria R.; Goodale, Britton C.; Wiley, Michelle W.; La Du, Jane K.; Hendrix, David A.

2017-01-01

Xenobiotic activation of the aryl hydrocarbon receptor (AHR) by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) prevents the proper formation of craniofacial cartilage and the heart in developing zebrafish. Downstream molecular targets responsible for AHR-dependent adverse effects remain largely unknown; however, in zebrafish sox9b has been identified as one of the most-reduced transcripts in several target organs and is hypothesized to have a causal role in TCDD-induced toxicity. The reduction of sox9b expression in TCDD-exposed zebrafish embryos has been shown to contribute to heart and jaw malformation phenotypes. The mechanisms by which AHR2 (functional ortholog of mammalian AHR) activation leads to reduced sox9b expression levels and subsequent target organ toxicity are unknown. We have identified a novel long noncoding RNA (slincR) that is upregulated by strong AHR ligands and is located adjacent to the sox9b gene. We hypothesize that slincR is regulated by AHR2 and transcriptionally represses sox9b. The slincR transcript functions as an RNA macromolecule, and slincR expression is AHR2 dependent. Antisense knockdown of slincR results in an increase in sox9b expression during both normal development and AHR2 activation, which suggests relief in repression. During development, slincR was expressed in tissues with sox9 essential functions, including the jaw/snout region, otic vesicle, eye, and brain. Reducing the levels of slincR resulted in altered neurologic and/or locomotor behavioral responses. Our results place slincR as an intermediate between AHR2 activation and the reduction of sox9b mRNA in the AHR2 signaling pathway. PMID:28385905

Inhibition of aryl hydrocarbon receptor transactivation and DNA adduct formation by CYP1 isoform-selective metabolic deactivation of benzo[a]pyrene

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

Endo, Kaori; Uno, Shigeyuki; Seki, Taiichiro

Benzo[a]pyrene (BaP), a polyaromatic hydrocarbon produced by the combustion of cigarettes and coke ovens, is a known procarcinogen. BaP activates the aryl hydrocarbon receptor (AhR) and induces the expression of a battery of genes, including CYP1A1, which metabolize BaP to toxic compounds. The possible role of CYP1 enzymes in mediating BaP detoxification or metabolic activation remains to be elucidated. In this study, we assessed the effects of CYP1 enzymes (CYP1A1, CYP1A2 and CYP1B1) on BaP-induced AhR transactivation and DNA adduct formation in HEK293 cells and HepG2 cells. Transfection of CYP1A1 and CYP1B1, but not CYP1A2, suppressed BaP-induced activation of AhR.more » Expression of CYP1A1 and CYP1A2, but not CYP1B1, inhibited DNA adduct formation in BaP-treated HepG2 cells. These results indicate that CYP1A1 and CYP1B1 play a role in deactivation of BaP on AhR and that CYP1A1 and CYP1A2 are involved in BaP detoxification by suppressing DNA adduct formation. BaP treatment did not induce DNA adduct formation in HEK293 cells, even after transfection of CYP1 enzymes, suggesting that expression of CYP1 enzymes is not sufficient for DNA adduct formation. Lower expression of epoxide hydrolase and higher expression of glutathione S-transferase P1 (GSTP1) and GSTM1/M2 were observed in HEK293 cells compared with HepG2 cells. Dynamic expression of CYP1A1, CYP1A2 and CYP1B1 along with expression of other enzymes such as epoxide hydrolase and phase II enzymes may determine the detoxification or metabolic activation of BaP.« less

Antioxidant Artemisia princeps Extract Enhances the Expression of Filaggrin and Loricrin via the AHR/OVOL1 Pathway.

PubMed

Hirano, Akiko; Goto, Masashi; Mitsui, Tsukasa; Hashimoto-Hachiya, Akiko; Tsuji, Gaku; Furue, Masutaka

2017-09-11

The Japanese mugwort, Artemisia princeps ( yomogi in Japanese), has anti-inflammatory and antioxidant effects. Skin care products containing Artemisia princeps extract (APE) are known to improve dry skin symptoms in atopic dermatitis. Atopic dry skin is associated with a marked reduction of skin barrier proteins, such as filaggrin (FLG) and loricrin (LOR). Recently, aryl hydrocarbon receptor (AHR), and its downstream transcription factor OVO-like 1 (OVOL1), have been shown to regulate the gene expression of FLG and LOR. The focus of this paper is to evaluate the effects of APE on the AHR/OVOL1/FLG or LOR pathway since they have remained unknown to this point. We first demonstrated that non-cytotoxic concentrations of APE significantly upregulated antioxidant enzymes, NAD(P)H dehydrogenase quinone 1 and heme oxygenase 1, in human keratinocytes. Even at these low concentrations, APE induced nuclear translocation of AHR and significantly upregulated CYP1A1 (a specific target gene for AHR activation), FLG , and LOR expression. AHR knockdown downregulated OVOL1 expression. The APE-induced upregulation of FLG and LOR was canceled in keratinocytes with AHR or OVOL1 knockdown. In conclusion, antioxidant APE is a potent phytoextract that upregulates FLG and LOR expression in an AHR/OVOL1-dependent manner and this may underpin the barrier-repairing effects of APE in treating atopic dry skin.

Antioxidant Artemisia princeps Extract Enhances the Expression of Filaggrin and Loricrin via the AHR/OVOL1 Pathway

PubMed Central

Hirano, Akiko; Goto, Masashi; Mitsui, Tsukasa; Hashimoto-Hachiya, Akiko; Tsuji, Gaku; Furue, Masutaka

2017-01-01

The Japanese mugwort, Artemisia princeps (yomogi in Japanese), has anti-inflammatory and antioxidant effects. Skin care products containing Artemisia princeps extract (APE) are known to improve dry skin symptoms in atopic dermatitis. Atopic dry skin is associated with a marked reduction of skin barrier proteins, such as filaggrin (FLG) and loricrin (LOR). Recently, aryl hydrocarbon receptor (AHR), and its downstream transcription factor OVO-like 1 (OVOL1), have been shown to regulate the gene expression of FLG and LOR. The focus of this paper is to evaluate the effects of APE on the AHR/OVOL1/FLG or LOR pathway since they have remained unknown to this point. We first demonstrated that non-cytotoxic concentrations of APE significantly upregulated antioxidant enzymes, NAD(P)H dehydrogenase quinone 1 and heme oxygenase 1, in human keratinocytes. Even at these low concentrations, APE induced nuclear translocation of AHR and significantly upregulated CYP1A1 (a specific target gene for AHR activation), FLG, and LOR expression. AHR knockdown downregulated OVOL1 expression. The APE-induced upregulation of FLG and LOR was canceled in keratinocytes with AHR or OVOL1 knockdown. In conclusion, antioxidant APE is a potent phytoextract that upregulates FLG and LOR expression in an AHR/OVOL1-dependent manner and this may underpin the barrier-repairing effects of APE in treating atopic dry skin. PMID:28892018

Characterization and Potential Environmental Risks of Leachate from Shredded Rubber Mulches

PubMed Central

Kanematsu, Masakazu; Hayashi, Ai; Denison, Michael S.; Young, Thomas M.

2009-01-01

In order to determine whether shredded rubber mulches (RM) posed water quality risks when used in stormwater best management practices (BMPs) such as bioretention basins, batch leaching tests were conducted to identify and quantify constituents in leachates from RM such as metal ions, nutrients, total organic carbon (TOC), and aryl hydrocarbon receptor (AhR) activity (determined by the chemically activated luciferase gene expression (CALUX) bioassay) at varied temperature and initial pH values. The results indicate that aqueous extracts of RM contain high concentrations of zinc (Zn) compared with wood mulches (WM), and its concentration increased at lower pH and higher temperature. Although methanol extracts of RM displayed high AhR activity, none of the aqueous extracts of RM had significant activity. Hence, while unknown constituents that have significant AhR activity are present in RM, they appear to be not measurably extracted by water under environmental conditions relevant for stormwater (5 < pH < 9, 10 < T < 40°C). Our results suggests that organic constituents in water extracts of RM which have AhR activity may not be of significant concern while leaching of Zn from RM appears to be a potentially larger water quality issue for RM. PMID:19450864

Genome-wide transcriptional profiling of human glioblastoma cells in response to ITE treatment

PubMed Central

Kang, Bo; Zhou, Yanwen; Zheng, Min; Wang, Ying-Jie

2015-01-01

A ligand-activated transcription factor aryl hydrocarbon receptor (AhR) is recently revealed to play a key role in embryogenesis and tumorigenesis (Feng et al. [1], Safe et al. [2]) and 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) (Song et al. [3]) is an endogenous AhR ligand that possesses anti-tumor activity. In order to gain insights into how ITE acts via the AhR in embryogenesis and tumorigenesis, we analyzed the genome-wide transcriptional profiles of the following three groups of cells: the human glioblastoma U87 parental cells, U87 tumor sphere cells treated with vehicle (DMSO) and U87 tumor sphere cells treated with ITE. Here, we provide the details of the sample gathering strategy and show the quality controls and the analyses associated with our gene array data deposited into the Gene Expression Omnibus (GEO) under the accession code of GSE67986. PMID:26484269

Genome-wide transcriptional profiling of human glioblastoma cells in response to ITE treatment.

PubMed

Kang, Bo; Zhou, Yanwen; Zheng, Min; Wang, Ying-Jie

2015-09-01

A ligand-activated transcription factor aryl hydrocarbon receptor (AhR) is recently revealed to play a key role in embryogenesis and tumorigenesis (Feng et al. [1], Safe et al. [2]) and 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) (Song et al. [3]) is an endogenous AhR ligand that possesses anti-tumor activity. In order to gain insights into how ITE acts via the AhR in embryogenesis and tumorigenesis, we analyzed the genome-wide transcriptional profiles of the following three groups of cells: the human glioblastoma U87 parental cells, U87 tumor sphere cells treated with vehicle (DMSO) and U87 tumor sphere cells treated with ITE. Here, we provide the details of the sample gathering strategy and show the quality controls and the analyses associated with our gene array data deposited into the Gene Expression Omnibus (GEO) under the accession code of GSE67986.

In Vivo Characterization of an AHR-Dependent Long Noncoding RNA Required for Proper Sox9b Expression.

PubMed

Garcia, Gloria R; Goodale, Britton C; Wiley, Michelle W; La Du, Jane K; Hendrix, David A; Tanguay, Robert L

2017-06-01

Xenobiotic activation of the aryl hydrocarbon receptor (AHR) by 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) prevents the proper formation of craniofacial cartilage and the heart in developing zebrafish. Downstream molecular targets responsible for AHR-dependent adverse effects remain largely unknown; however, in zebrafish sox9b has been identified as one of the most-reduced transcripts in several target organs and is hypothesized to have a causal role in TCDD-induced toxicity. The reduction of sox9b expression in TCDD-exposed zebrafish embryos has been shown to contribute to heart and jaw malformation phenotypes. The mechanisms by which AHR2 (functional ortholog of mammalian AHR) activation leads to reduced sox9b expression levels and subsequent target organ toxicity are unknown. We have identified a novel long noncoding RNA ( slincR ) that is upregulated by strong AHR ligands and is located adjacent to the sox9b gene. We hypothesize that slincR is regulated by AHR2 and transcriptionally represses sox9b. The slincR transcript functions as an RNA macromolecule, and slincR expression is AHR2 dependent. Antisense knockdown of slincR results in an increase in sox9b expression during both normal development and AHR2 activation, which suggests relief in repression. During development, slincR was expressed in tissues with sox9 essential functions, including the jaw/snout region, otic vesicle, eye, and brain. Reducing the levels of slincR resulted in altered neurologic and/or locomotor behavioral responses. Our results place slincR as an intermediate between AHR2 activation and the reduction of sox9b mRNA in the AHR2 signaling pathway. Copyright © 2017 by The Author(s).

Loss of NR2E3 represses AHR by LSD1 reprogramming, is associated with poor prognosis in liver cancer.

PubMed

Khanal, Tilak; Choi, Kwangmin; Leung, Yuet-Kin; Wang, Jiang; Kim, Dasom; Janakiram, Vinothini; Cho, Sung-Gook; Puga, Alvaro; Ho, Shuk-Mei; Kim, Kyounghyun

2017-09-06

The aryl hydrocarbon receptor (AHR) plays crucial roles in inflammation, metabolic disorder, and cancer. However, the molecular mechanisms regulating AHR expression remain unknown. Here, we found that an orphan nuclear NR2E3 maintains AHR expression, and forms an active transcriptional complex with transcription factor Sp1 and coactivator GRIP1 in MCF-7 human breast and HepG2 liver cancer cell lines. NR2E3 loss promotes the recruitment of LSD1, a histone demethylase of histone 3 lysine 4 di-methylation (H3K4me2), to the AHR gene promoter region, resulting in repression of AHR expression. AHR expression and responsiveness along with H3K4me2 were significantly reduced in the livers of Nr2e3 rd7 (Rd7) mice that express low NR2E3 relative to the livers of wild-type mice. SP2509, an LSD1 inhibitor, fully restored AHR expression and H3K4me2 levels in Rd7 mice. Lastly, we demonstrated that both AHR and NR2E3 are significantly associated with good clinical outcomes in liver cancer. Together, our results reveal a novel link between NR2E3, AHR, and liver cancer via LSD1-mediated H3K4me2 histone modification in liver cancer development.

Baicalin Protects Mice from Aristolochic Acid I-Induced Kidney Injury by Induction of CYP1A through the Aromatic Hydrocarbon Receptor