Note: This page contains sample records for the topic p-glycoprotein p-gp activity from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

P-glycoprotein (P-gp)-mediated efflux limits intestinal absorption of the Hsp90 inhibitor SNX-2112 in rats.  

PubMed

Abstract 1.?The promising anticancer agent SNX-2112 (a novel Hsp90 inhibitor) is poorly bioavailable after oral administration. Here, we aim to determine the role of P-glycoprotein (P-gp) in the intestinal absorption of SNX-2112. 2.?We found that SNX-2112 significantly stimulated P-gp ATPase activity in in vitro ATPase assay with a small EC50 (the half-maximal effective concentration) value of 0.32?µM. 3.?In the single-pass perfused rat intestine model, absorption of SNX-2112 was not favored in the small intestine with a [Formula: see text] (the wall permeability) value of 0.38-0.64. By contrast, the compound was well absorbed in the colon with a [Formula: see text] value of 1.19. The P-gp inhibitors cyclosporine and elacridar (i.e. GF120918A) markedly enhanced SNX-2112 absorption in all four intestinal segments (i.e. duodenum, jejunum, ileum and colon) and the fold change ranged from 3.1 to 14.1. Pharmacokinetic study revealed that cyclosporine increased the systemic exposure of SNX-2112 by a 2.5-fold after oral administration. 4.?This is the first report that P-gp-mediated efflux is a limiting factor for intestinal absorption of SNX-2112 in rats. PMID:24555822

Liu, Hongming; Sun, Hua; Wu, Zhufeng; Zhang, Xingwang; Wu, Baojian

2014-08-01

2

Risperidone and Paliperidone Inhibit P-Glycoprotein Activity In Vitro  

Microsoft Academic Search

Risperidone (RSP) and its major active metabolite, 9-hydroxy-risperidone (paliperidone, PALI), are substrates of the drug transporter P-glycoprotein (P-gp). The goal of this study was to examine the in vitro effects of RSP and PALI on P-gp-mediated transport. The intracellular accumulation of rhodamine123 (Rh123) and doxorubicin (DOX) were examined in LLC-PK1\\/MDR1 cells to evaluate P-gp inhibition by RSP and PALI. Both

Hao-Jie Zhu; Jun-Sheng Wang; John S Markowitz; Jennifer L Donovan; Bryan B Gibson; C Lindsay DeVane

2007-01-01

3

P-glycoprotein (P-gp) in the monogonont rotifer, Brachionus koreanus: molecular characterization and expression in response to pharmaceuticals.  

PubMed

P-glycoprotein is involved in the efflux of diverse chemicals, including hydrophobic compounds and pharmaceuticals as a first line of defense. Here, we firstly identified and characterized the P-gp (Bk-P-gp) gene in the rotifer, Brachionus koreanus. Bk-P-gp was highly conserved in genomic organization compared to the human P-gp gene. Messenger RNA expression of Bk-P-gp revealed that it would be regulated by temperature change via 14 heat shock response elements in its promoter region. Bk-P-gp showed a high similarity of motifs/domains compared to those of vertebrates in its amino acid sequences. To check whether Bk-P-gp would be inducible, we exposed B. koreanus to six pharmaceuticals including antibiotics for use in aquaculture and observed dose- and time-dependency on transcripts of Bk-P-gp for 24h over a wide range of concentration. Efflux assay and membrane topology supported its conserved function for transportation of a number of chemicals upon cellular damage. To reveal the effect of pharmaceuticals on the rotifer, we measured survival rate and population growth rate after exposure to six pharmaceuticals. In an acute toxicity test, both NOEC and LC?? values for all the pharmaceuticals were high for 24 h. ATP, CBZ, SMX, and TMP markedly inhibited the population growth of B. koreanus after exposure up to 100 mg/L for 10 days. In this paper, we demonstrated that various pharmaceuticals can retard growth rate with up-regulation of the P-gp gene as a cellular defense system. This finding provides a better understanding of molecular mechanisms involved in pharmaceutical-mediated cellular damage in B. koreanus. PMID:22446822

Rhee, Jae-Sung; Jeong, Chang-Bum; Kim, Bo-Mi; Lee, Jae-Seong

2012-06-15

4

Mucoadhesive properties and interaction with P-glycoprotein (P-gp) of thiolated-chitosans and -glycol chitosans and corresponding parent polymers: a comparative study.  

PubMed

The aim of the present work was to compare the mucoadhesive and efflux pump P-glycoprotein (P-gp) interacting properties of chitosan (CS)- and glycolchitosan (GCS)-based thiomers and corresponding unmodified parent polymers. For this purpose, the glycol chitosan-N-acetyl-cysteine (GCS-NAC) and glycol chitosan-glutathione (GCS-GSH) thiomers were prepared under simple and mild conditions. Their mucoadhesive characteristics were studied by turbidimetric and zeta potential measurements. The P-gp interacting properties were evaluated measuring the effects of thiolated- and unmodified-polymers on the bidirectional transport (BA/AB) of rhodamine-123 across Caco-2 cells as well as in the calcein-AM and ATPase activity assays. Although all the thiomers and unmodified polymers showed optimal-excellent mucoadhesive properties, the best mucoadhesive performances have been obtained by CS and CS-based thiomers. Moreover, it was found that the pretreatment of Caco-2 cell monolayer with GCS-NAC or GCS restores Rho-123 cell entrance by inhibiting P-gp activity. Hence, GCS-NAC and GCS may constitute new biomaterials useful for improving the bioavailability of P-gp substrates. PMID:24521085

Trapani, Adriana; Palazzo, Claudio; Contino, Marialessandra; Perrone, Maria Grazia; Cioffi, Nicola; Ditaranto, Nicoletta; Colabufo, Nicola Antonio; Conese, Massimo; Trapani, Giuseppe; Puglisi, Giovanni

2014-03-10

5

P-glycoprotein activity and biological response  

SciTech Connect

P-glycoprotein (P-gp) is a transmembrane drug efflux pump encoded by the MDR-1 gene in humans. Most likely P-gp protects organs against endogenous and exogenous toxins by extruding toxic compounds such as chemotherapeutics and other drugs. Many drugs are substrates for P-gp. Since P-gp is also expressed in the blood-brain barrier, P-gp substrates reach lower concentrations in the brain than in P-gp-negative tissues. Failure of response to chemotherapy of malignancies can be due to intrinsic or acquired drug resistance. Many tumors are multidrug resistant (MDR); resistant to several structurally unrelated chemotherapeutic agents. Several mechanisms are involved in MDR of which P-gp is studied most extensively. P-gp extrudes drugs out of tumor cells resulting in decreased intracellular drug concentrations, leading to the MDR phenotype. Furthermore, the MDR-1 gene exhibits several single nucleotide polymorphisms, some of which result in different transport capabilities. P-gp functionality and the effect of P-gp modulation on the pharmacokinetics of novel and established drugs can be studied in vivo by positron emission tomography (PET) using carbon-11 and fluorine-18-labeled P-gp substrates and modulators. PET may demonstrate the consequences of genetic differences on tissue pharmacokinetics. Inhibitors such as calcium-channel blockers (verapamil), cyclosporin A, ONT-093, and XR9576 can modulate the P-gp functionality. With PET the effect of P-gp modulation on the bioavailability of drugs can be investigated in humans in vivo. PET also allows the measurement of the efficacy of newly developed P-gp modulators.

Vaalburg, W. [Groningen University Hospital, PO Box 30.001, 9700 RB Groningen (Netherlands)]. E-mail: w.vaalburg@pet.umcg.nl; Hendrikse, N.H. [Groningen University Hospital, PO Box 30.001, 9700 RB Groningen (Netherlands); Elsinga, P.H. [Groningen University Hospital, PO Box 30.001, 9700 RB Groningen (Netherlands); Bart, J. [Groningen University Hospital, PO Box 30.001, 9700 RB Groningen (Netherlands); Waarde, A. van [Groningen University Hospital, PO Box 30.001, 9700 RB Groningen (Netherlands)

2005-09-01

6

Inhibitory effects of herbal constituents on P-glycoprotein in vitro and in vivo: herb-drug interactions mediated via P-gp.  

PubMed

Modulation of drug transporters via herbal medicines which have been widely used in combination with conventional prescription drugs may result in herb-drug interactions in clinical practice. The present study was designed to investigate the inhibitory effects of 50 major herbal constituents on P-glycoprotein (P-gp) in vitro and in vivo as well as related inhibitory mechanisms. Among these herbal medicines, four constituents, including emodin, 18?-glycyrrhetic acid (18?-GA), dehydroandrographolide (DAG), and 20(S)-ginsenoside F? [20(S)-GF?] exhibited significant inhibition (>50%) on P-gp in MDR1-MDCKII and Caco-2 cells. Emodin was the strongest inhibitor of P-gp (IC??=9.42 ?M), followed by 18?-GA (IC??=21.78 ?M), 20(S)-GF? (IC??=76.08 ?M) and DAG (IC??=77.80 ?M). P-gp ATPase activity, which was used to evaluate the affinity of substrates to P-gp, was stimulated by emodin and DAG with Km and Vmax values of 48.61, 29.09 ?M and 71.29, 38.45 nmol/min/mg protein, respectively. However, 18?-GA and 20(S)-GF? exhibited significant inhibition on both basal and verapamil-stimulated P-gp ATPase activities at high concentration. Molecular docking analysis (CDOCKER) further elucidated the mechanism for structure-inhibition relationships of herbal constituents with P-gp. When digoxin was co-administered to male SD rats with emodin or 18?-GA, the AUC(??t) and Cmax of digoxin were increased by approximately 51% and 58%, respectively. Furthermore, 18?-GA, DAG, 20(S)-GF? and Rh? at 10 ?M significantly inhibited CYP3A4/5 activity, while emodin activated the metabolism of midazolam in human liver microsomes. In conclusion, four herbal constituents demonstrated inhibition of P-gp to specific extents in vitro and in vivo. Taken together, our findings provided the basis for the reliable assessment of the potential risks of herb-drug interactions in humans. PMID:24380838

Li, Xue; Hu, Jinping; Wang, Baolian; Sheng, Li; Liu, Zhihao; Yang, Shuang; Li, Yan

2014-03-01

7

Acetaminophen inhibits intestinal p-glycoprotein transport activity.  

PubMed

Repeated acetaminophen (AP) administration modulates intestinal P-glycoprotein (P-gp) expression. Whether AP can modulate P-gp activity in a short-term fashion is unknown. We investigated the acute effect of AP on rat intestinal P-gp activity in vivo and in vitro. In everted intestinal sacs, AP inhibited serosal-mucosal transport of rhodamine 123 (R123), a prototypical P-gp substrate. R123 efflux plotted against R123 concentration adjusted well to a sigmoidal curve. Vmax decreased 50% in the presence of AP, with no modification in EC50, or slope, ruling out the possibility of inhibition to be competitive. Inhibition by AP was absent at 0°C, consistent with interference of the active transport of R123 by AP. Additionally, AP showed no effect on normal localization of P-gp at the apical membrane of the enterocyte and neither affected paracellular permeability. Consistent with absence of a competitive inhibition, two further strategies strongly suggested that AP is not a P-gp substrate. First, serosal-mucosal transport of AP was not affected by the classical P-gp inhibitors verapamil or Psc 833. Second, AP accumulation was not different between P-gp knock-down and wild-type HepG2 cells. In vivo intestinal absorption of digoxin, another substrate of P-gp, was assessed in the presence or absence of AP (100 ?M). Portal digoxin concentration was increased by 214%, in average, by AP, as compared with digoxin alone. In conclusion, AP inhibited P-gp activity, increasing intestinal absorption of digoxin, a prototypical substrate. These results suggest that therapeutic efficacy of P-gp substrates can be altered if coadministered with AP. PMID:23897240

Novak, Analia; Carpini, Griselda Delli; Ruiz, María Laura; Luquita, Marcelo G; Rubio, Modesto C; Mottino, Aldo D; Ghanem, Carolina I

2013-10-01

8

Cyclosporine A (CsA) affects the pharmacodynamics and pharmacokinetics of the atypical antipsychotic amisulpride probably via inhibition of P-glycoprotein (P-gp)  

Microsoft Academic Search

Summary.  The importance of P-glycoprotein (P-gp) in the pharmacokinetics of amisulpride and the effects of a P-gp inhibitor cyclosporine\\u000a A (CsA) was investigated both, in vitro and in vivo.\\u000a \\u000a In vitro and in vivo results indicated amisulpride as a substrate of P-gp. Amisulpride was not metabolized by rat liver microsomes. Open field\\u000a behavior showed time dependent abolishment in locomotion by amisulpride

U. Schmitt; A. Abou El-Ela; L. J. Guo; H. Glavinas; P. Krajcsi; J. M. Baron; C. Tillmann; C. Hiemke; P. Langguth; S. Härtter

2006-01-01

9

In vitro effects of Mangifera indica and polyphenols derived on ABCB1\\/P-glycoprotein activity  

Microsoft Academic Search

Many plant-derived compounds, including polyphenols, are able to affect the function of MDR-1\\/P-glycoprotein (P-gp ABCB1) multidrug transporter, leading to potential herb–drug interactions.This study evaluated the effects of mango (Mangifera indica L.) stem bark extract, MSBE, and related phenols on P-gp activity in both the HK-2 proximal tubule cell line, constitutively expressing P-gp, and in a Caco-2 cell sub-line selected by

Elisabetta Chieli; Nadia Romiti; Idania Rodeiro; Gabino Garrido

2009-01-01

10

Colchicine effect on P-glycoprotein expression and activity: In silico and in vitro studies.  

PubMed

Colchicine is a P-glycoprotein (P-gp) substrate that induces its expression, thus increasing the risk for unexpected pharmacokinetic interactions with this drug. Because increased P-gp expression does not always correlate with increased activity of this efflux pump, we evaluated the changes in both P-gp expression and activity induced by colchicine using an in vitro model. Caco-2 cells were incubated with 0.1-100?M colchicine up to 96h. Cytotoxicity was evaluated by the MTT and LDH leakage assays, P-gp expression and activity were evaluated by flow cytometry and P-gp ATPase activity was measured in MDR1-Sf9 membrane vesicles. Furthermore, colchicine fitting in P-gp induction and competitive inhibition pharmacophore hypothesis, and docking studies evaluating the interaction between colchicine and P-gp drug binding pocket were tested in silico. Significant cytotoxicity was noted after 48h. At 24h a significant increase in P-gp expression was observed, which was not accompanied by an increase in transport activity. Moreover, colchicine significantly increased P-gp ATPase activity, demonstrating to be actively transported by the pump. New pharmacophores were constructed to predict P-gp modulatory activity. Colchicine fitted both the P-gp induction and competitive inhibition models. In silico, colchicine was predicted to bind to the P-gp drug-binding pocket suggesting a competitive mechanism of transport. These results show that colchicine induced P-gp expression in Caco-2 cells but the activity of the protein remained unchanged, highlighting the need to simultaneously evaluate P-gp expression and activity. With the newly constructed pharmacophores, new drugs can be initially screened in silico to predict such potential pharmacokinetic interactions. PMID:24759273

Silva, Renata; Carmo, Helena; Vilas-Boas, Vânia; Barbosa, Daniel José; Palmeira, Andreia; Sousa, Emília; Carvalho, Félix; Bastos, Maria de Lourdes; Remião, Fernando

2014-07-25

11

Risperidone and paliperidone inhibit p-glycoprotein activity in vitro.  

PubMed

Risperidone (RSP) and its major active metabolite, 9-hydroxy-risperidone (paliperidone, PALI), are substrates of the drug transporter P-glycoprotein (P-gp). The goal of this study was to examine the in vitro effects of RSP and PALI on P-gp-mediated transport. The intracellular accumulation of rhodamine123 (Rh123) and doxorubicin (DOX) were examined in LLC-PK1/MDR1 cells to evaluate P-gp inhibition by RSP and PALI. Both compounds significantly increased the intracellular accumulation of Rh123 and DOX in a concentration-dependent manner. The IC(50) values of RSP for inhibiting P-gp-mediated transport of Rh123 and DOX were 63.26 and 15.78 microM, respectively, whereas the IC(50) values of PALI were >100 microM, indicating that PALI is a less potent P-gp inhibitor. Caco-2 and primary cultured rat brain microvessel endothelial cells (RBMECs) were utilized to investigate the possible influence of RSP on intestinal absorption and blood-brain barrier (BBB) transport of coadministered drugs that are P-gp substrates. RSP, 1-50 microM, significantly enhanced the intracellular accumulation of Rh123 in Caco-2 cells by inhibiting P-gp activity with an IC(50) value of 5.87 microM. Following exposure to 10 microM RSP, the apparent permeability coefficient of Rh123 across Caco-2 and RBMECs monolayers was increased to 2.02 and 2.63-fold in the apical to basolateral direction, but decreased to 0.37 and 0.21-fold in the basolateral to apical direction, respectively. These data suggest that RSP and PALI, to a lesser extent, have a potential to influence the pharmacokinetics and hence the pharmacodynamics of coadministered drugs via inhibition of P-gp-mediated transport. However, no human data exist that address this issue. In particular, RSP may interact with its own active metabolite PALI by promoting its brain concentration through inhibiting P-gp-mediated efflux of PALI across endothelial cells of the BBB. PMID:16936711

Zhu, Hao-Jie; Wang, Jun-Sheng; Markowitz, John S; Donovan, Jennifer L; Gibson, Bryan B; DeVane, C Lindsay

2007-04-01

12

Induction and activation of P-glycoprotein by dihydroxylated xanthones protect against the cytotoxicity of the P-glycoprotein substrate paraquat.  

PubMed

Xanthones are a family of compounds with several known biological activities and therapeutic potential for which information on their interaction with membrane transporters is lacking. Knowing that P-glycoprotein (P-gp) acts as a cellular defense mechanism by effluxing its toxic substrates, the aim of this study was to investigate the potential of five dihydroxylated xanthones as inducers of P-gp expression and/or activity and to evaluate whether they could protect Caco-2 cells against the cytotoxicity induced by the toxic P-gp substrate paraquat (PQ). After 24 h of incubation, all tested xanthones caused a significant increase in both P-gp expression and activity, as evaluated by flow cytometry using the UIC2 antibody and rhodamine 123, respectively. Additionally, after a short 45-min incubation, all the tested xanthones induced a rapid increase in P-gp activity, indicating direct pump activation without increased P-gp protein expression. The tested compounds also increased P-gp ATPase activity in MDR1-Sf9 membrane vesicles, demonstrating to be P-gp substrates. Moreover, when simultaneously incubated with PQ, all xanthones significantly reduced the cytotoxicity of the herbicide, and these protective effects were completely reversed upon incubation with a specific P-gp inhibitor. In silico studies evaluating the interactions between xanthones and P-gp in the presence of PQ suggested that a co-transport mechanism may be operating. A quantitative structure-activity relationship model was developed and validated, and the maximal partial charge for an oxygen atom was the descriptor predicted as being implicated in P-gp activation by the dihydroxylated xanthones. These results disclose new perspectives in preventing PQ- and other P-gp substrates-induced poisonings. PMID:24464498

Silva, Renata; Sousa, Emília; Carmo, Helena; Palmeira, Andreia; Barbosa, Daniel José; Gameiro, Mariline; Pinto, Madalena; Bastos, Maria de Lourdes; Remião, Fernando

2014-04-01

13

Structure-activity relationships and in silico models of P-glycoprotein (ABCB1) inhibitors.  

PubMed

1. The efflux pump p-glycoprotein (P-gp/ABCB1) has received enormous attention in drug (xenobiotic) disposition due to its role in modulation of the drug availability and in protection of sensitive organs. 2. P-gp mediated efflux is one of main mechanisms for multidrug resistance in cancer cells. A main approach to reverse the resistance and restore the drug efficacy is to use specific inhibitors of P-gp that suppress the efflux activity. 3. This review summarizes the binding capabilities of known chemical inhibitors based on the analyses of structure-activity relationships, and computational modeling of the inhibitors as well as the binding site of P-gp protein. 4. The molecular models will facilitate the design of lead inhibitors as drug candidates. Also, it helps scientists in early drug discovery phase to synthesize chemical series with better understanding of their P-gp binding liabilities. PMID:23617855

Liu, Hongming; Ma, Zhiguo; Wu, Baojian

2013-11-01

14

Grapefruit Juice Activates P-Glycoprotein-Mediated Drug Transport  

Microsoft Academic Search

Purpose. Grapefruit juice (GJ) is known to increase the oral bioavailability of many CYP3A-substrates by inhibiting intestinal phase-I metabolism. However, the magnitude of AUC increase is often insignificant and highly variable. Since we earlier suggested that CYP3A and P-glycoprotein (P-gp) form a concerted barrier to drug absorption, we investigated the role of P-gp in GJ-drug interactions.

Andrea Soldner; Uwe Christians; Miki Susanto; Vincent J. Wacher; Jeffrey A. Silverman; Leslie Z. Benet

1999-01-01

15

In vitro effects of Mangifera indica and polyphenols derived on ABCB1/P-glycoprotein activity.  

PubMed

Many plant-derived compounds, including polyphenols, are able to affect the function of MDR-1/P-glycoprotein (P-gp ABCB1) multidrug transporter, leading to potential herb-drug interactions. This study evaluated the effects of mango (Mangifera indica L.) stem bark extract, MSBE, and related phenols on P-gp activity in both the HK-2 proximal tubule cell line, constitutively expressing P-gp, and in a Caco-2 cell sub-line selected by resistance to vincristine (Caco-2/VCR) and overexpressing P-gp. The effects of MSBE, mangiferin, norathyriol, catechin, quercetin and gallic acid on P-gp activity were tested by the rhodamine-123 accumulation as well as by the Calcein-AM assays. Effects on esterase activity, which could influence the results of Calcein-AM test, were also assessed. All investigated compounds except for catechin and gallic acid inhibited P-gp activity in HK-2 cells, in the order of mangiferinactivity. Similar effects were obtained in resistant Caco-2/VCR cells, but were negligible in the wild-type ones, expressing low amounts of P-gp. Our results demonstrate, for the first time, that M. indica and polyphenols derived may affect the activity of the multidrug transporter P-gp ABCB1, suggesting the possibility of herb-drug interactions to be explored in depth. PMID:19632288

Chieli, Elisabetta; Romiti, Nadia; Rodeiro, Idania; Garrido, Gabino

2009-11-01

16

Opioids and Efflux Transporters. Part 2: P-Glycoprotein Substrate Activity of 3- and 6-Substituted Morphine Analogs  

PubMed Central

Continuing our studies investigating opioids with reduced P-glycoprotein (P-gp) substrate activity, a series of known 3- and 6-hydroxy, -methoxy, and -desoxymorphine analogs was synthesized and analyzed for P-gp substrate activity and opioid binding affinity. 6-Desoxymorphine (7) showed high affinity for opioid receptors and did not induce P-gp-mediated ATP hydrolysis. Additionally, 7 demonstrated morphine-like antinociceptive potency in mice, indicating this compound as an ideal lead to further evaluate the role of P-gp in opioid analgesic tolerance development.

Cunningham, Christopher W.; Mercer, Susan L.; Hassan, Hazem E.; Traynor, John R.; Eddington, Natalie D.; Coop, Andrew

2012-01-01

17

Inhibition of the multidrug resistance P-glycoprotein activity by green tea polyphenols.  

PubMed

Many beneficial proprieties have been associated with polyphenols from green tea, such as chemopreventive, anticarcinogenic, antiatherogenic and antioxidant actions. In this study, we investigated the effects of green tea polyphenols (GTPs) and their principal catechins on the function of P-glycoprotein (P-gp), which is involved in the multidrug resistance phenotype of cancer cells. GTPs (30 microg/ml) inhibit the photolabeling of P-gp by 75% and increase the accumulation of rhodamine-123 (R-123) 3-fold in the multidrug-resistant cell line CH(R)C5, indicating that GTPs interact with P-gp and inhibit its transport activity. Moreover, the modulation of P-gp transport by GTPs was a reversible process. Among the catechins present in GTPs, EGCG, ECG and CG are responsible for inhibiting P-gp. In addition, EGCG potentiates the cytotoxicity of vinblastine (VBL) in CH(R)C5 cells. The inhibitory effect of EGCG on P-gp was also observed in human Caco-2 cells, which form an intestinal epithelial-like monolayer. Our results indicate that, in addition to their anti-cancer properties, GTPs and more particularly EGCG inhibit the binding and efflux of drugs by P-gp. Thus, GTPs or EGCG might be potential agents for modulating the bioavailability of P-gp substrates at the intestine and the multidrug resistance phenotype associated with expression of this transporter in cancer cells. PMID:11853888

Jodoin, Julie; Demeule, Michel; Beliveau, Richard

2002-01-30

18

Co-administration strategy to enhance brain accumulation of vandetanib by modulating P-glycoprotein (P-gp/Abcb1) and breast cancer resistance protein (Bcrp1/Abcg2) mediated efflux with m-TOR inhibitors  

PubMed Central

The objectives of this study were (i) to characterize the interaction of vandetanib with P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp1) in vitro and in vivo (ii) to study the modulation of P-gp and BCRP mediated efflux of vandetanib with specific transport inhibitors and m-TOR inhibitors, everolimus and temsirolimus. Cellular accumulation and bi-directional transport studies in MDCKII cell monolayers were conducted to delineate the role of efflux transporters on disposition of vandetanib. Brain distribution studies were conducted in male FVB wild-type mice with vandetanib administered intravenously either alone or in the presence of specific inhibitors and m-TOR inhibitors. In vitro studies suggested that vandetanib is a high affinity substrate of Bcrp1 but is not transported by P-gp. Interestingly, in vivo brain distribution studies in FVB wild type mice indicated that vandetanib penetration into the brain is restricted by both Bcrp1 and P-gp mediated active efflux at the blood brain barrier (BBB). Co-administration of elacridar, a dual P-gp/BCRP inhibitor increased the brain to plasma concentration ratio of vandetanib upto 5 fold. Of the two m-TOR pathway inhibitors examined; everolimus showed potent effect on modulating vandetanib brain penetration whereas no significant affect on vandetanib brain uptake was observed following temsirolimus co-administration. This finding could be clinically relevant as everolimus can provide synergistic pharmacological effect in addition to primary role of vandetanib efflux modulation at BBB for the treatment of brain tumors.

Minocha, Mukul; Khurana, Varun; Qin, Bin; Pal, Dhananjay; Mitra, Ashim K

2012-01-01

19

Inhibition mechanism of P-glycoprotein mediated efflux by mPEG-PLA and influence of PLA chain length on P-glycoprotein inhibition activity.  

PubMed

The present study aimed to investigate the effect of monomethoxy poly(ethylene glycol)-block-poly(D,L-lactic acid) (mPEG-PLA) on the activity of P-glycoprotein (P-gp) in Caco-2 cells and further unravel the relationship between PLA chain length in mPEG-PLA and influence on P-gp efflux and the action mechanism. The transport results of rhodamine 123 (R123) across Caco-2 cell monolayers suggested that mPEG-PLA unimers were responsible for its P-gp inhibitory effect. Furthermore, transport studies of R123 revealed that the inhibitory potential of P-gp efflux by mPEG-PLA analogues was strongly correlated with their structural features and showed that the hydrophilic mPEG-PLA copolymers with an intermediate PLA chain length and 10.20 of hydrophilic-lipophilic balance were more effective at inhibiting P-gp efflux in Caco-2 cells. The fluorescence polarization measurement results ruled out the plasma membrane fluidization as a contributor for inhibition of P-gp by mPEG-PLA. Concurrently, mPEG-PLA inhibited neither basal P-gp ATPase (ATP is adenosine triphosphate) activity nor substrate stimulated P-gp ATPase activity, suggesting that mPEG-PLA seemed not to be a substrate of P-gp and a competitive inhibitor. No evident alteration in P-gp surface level was detected by flow cytometry upon exposure of the cells to mPEG-PLA. The depletion of intracellular ATP, which was likely to be a result of partial inhibition of cellular metabolism, was directly correlated with inhibitory potential for P-gp mediated efflux by mPEG-PLA analogues. Hence, intracellular ATP-depletion appeared to be possible explanation to the inhibition mechanism of P-gp by mPEG-PLA. Taken together, the establishment of a relationship between PLA chain length and impact on P-gp efflux activity and interpretation of action mechanism of mPEG-PLA on P-gp are of fundamental importance and will facilitate future development of mPEG-PLA in the drug delivery area. PMID:24256068

Li, Wenjing; Li, Xinru; Gao, Yajie; Zhou, Yanxia; Ma, Shujin; Zhao, Yong; Li, Jinwen; Liu, Yan; Wang, Xinglin; Yin, Dongdong

2014-01-01

20

Differential Modulation of P-Glycoprotein Expression and Activity by Non-Nucleoside HIV1 Reverse Transcriptase Inhibitors in Cell Culture  

Microsoft Academic Search

Purpose. This study investigated the effects of the non-nucleoside HIV-1 reverse transcriptase inhibitors (NNRTI) nevirapine (NVR), efavirenz (EFV), and delavirdine (DLV) on P-glycoprotein (P-gp) activity and expression to anticipate P-gp related drug-drug interactions associated with combination therapy.

Elke Störmer; Lisa L. von Moltke; Michael D. Perloff; David J. Greenblatt

2002-01-01

21

A Novel Non-Natural Nucleoside that Influences P-glycoprotein Activity and Mediates Drug Resistance  

PubMed Central

Multi drug resistance during cancer chemotherapy is commonly acquired by overexpression of the ATP binding cassette transporter, P-glycoprotein (P-gp). As such, inhibitors that target P-gp activity represent potential therapeutic agents against this form of drug resistance. This study evaluated the ability of various non-natural nucleosides that mimic the core structure of adenosine to modulate drug resistance by inhibiting the ATPase activity to P-gp. Of several analogs tested, only one novel non-natural nucleoside, 5-cyclohexyl-indolyl 2?-deoxyribose (5-CHInd), behaves as a P-gp inhibitor. Although 5-CHInd is an adenosine analog that should block the binding of ATP, the non-natural nucleoside surprisingly stimulates the ATPase activity of P-gp in vitro. However, 5-CHInd is not an exportable substrate for P-gp as it is not transported across an MDCK-MDR1 monolayer. In addition, 5-CHInd differentially modulates MDR by decreasing or increasing the cytotoxicity of several chemotherapeutic agents. Although 5-CHInd displays variable activity in modulating the efflux of various drugs, efflux by P-gp, there is a correlation between changes observed in the drug-stimulated ATPase catalytic efficiency induced by 5-CHInd with its effect on drug efflux. The paradoxical behavior of 5-CHInd is rationalized within the context of contemporary models of P-gp function. In addition, the data are used to develop a predictive in vitro model to rapidly identify define potential drug-drug interactions with P-gp.

Eng, Kevin T.; Berdis, Anthony J.

2011-01-01

22

Use of rhodamine 123 to examine the functional activity of P-glycoprotein in primary cultured brain microvessel endothelial cell monolayers  

Microsoft Academic Search

The fluorescent dye, rhodamine 123, was used to evaluate the functional activity of the P-glycoprotein (P-gp) efflux transport system in primary cultured bovine brain microvessel endothelial cell (BBMEC) monolayers. Rhodamine 123 accumulation was increased significantly in BBMEC monolayers treated with the P-gp modifying agent, cyclosporin A (CSA). Rhodamine 123 accumulation was also increased by other P-gp modifying agents. The rank

Michele Fontaine; William F. Elmquist; Donald W. Miller

1996-01-01

23

Three-dimensional quantitative structure-activity relationships of inhibitors of P-glycoprotein.  

PubMed

P-glycoprotein (P-gp) is an efflux transporter involved in limiting the oral bioavailability and tissue penetration of a variety of structurally divergent molecules. A better understanding of the structural requirements of modulators of P-gp function will aid in the design of therapeutic agents. Toward this goal, three-dimensional quantitative structure-activity relationship (3D-QSAR) models were generated using in vitro data associated with inhibition of P-gp function. Several approaches were undertaken with multiple iterations, yielding Catalyst 3D-QSAR models being able to qualitatively rank-order and predict IC(50) values for P-gp inhibitors excluded from the model in question. The success of these validations suggests that a P-gp pharmacophore for 27 inhibitors of digoxin transport in Caco-2 cells consisted of four hydrophobes and one hydrogen bond acceptor. A second pharmacophore generated with 21 inhibitors of vinblastine binding to plasma membrane vesicles derived from CEM/VLB(100) cells contained three ring aromatic features and one hydrophobic feature. A third pharmacophore generated with 17 inhibitors of vinblastine accumulation in P-gp expressing LLC-PK1 cells contained four hydrophobes and one hydrogen bond acceptor. A final pharmacophore was generated for inhibition of calcein accumulation in P-gp expressing LLC-PK1 cells and found to contain two hydrophobes, a ring aromatic feature, and a hydrogen bond donor. The similarity of features for the pharmacophores of P-gp inhibitors of digoxin transport and vinblastine binding suggest some commonality in their binding sites. Utilization of such models may prove to be of value for prediction of molecules that may modulate one or more P-gp binding sites. PMID:11961113

Ekins, Sean; Kim, Richard B; Leake, Brenda F; Dantzig, Anne H; Schuetz, Erin G; Lan, Lu-Bin; Yasuda, Kazuto; Shepard, Robert L; Winter, Mark A; Schuetz, John D; Wikel, James H; Wrighton, Steven A

2002-05-01

24

Structure-activity relationships for xenobiotic transport substrates and inhibitory ligands of P-glycoprotein.  

PubMed Central

The multixenobiotic resistance phenotype is characterized by the reduced accumulation of xenobiotics by cells or organisms due to increased efflux of the compounds by P-glycoprotein (P-gp) or related transporters. An extensive xenobiotic database, consisting primarily of pesticides, was utilized in this study to identify molecular characteristics that render a xenobiotic susceptible to transport by or inhibition of P-gp. Transport substrates were differentiated by several molecular size/shape parameters, lipophilicity, and hydrogen bonding potential. Electrostatic features differentiated inhibitory ligands from compounds not catagorized as transport substrates and that did no interact with P-gp. A two-tiered system was developed using the derived structure-activity relationships to identify P-gp transport substrates and inhibitory ligands. Prediction accuracy of the approach was 82%. We then validated the system using six additional pesticides of which tow were predicted to be P-gp inhibitors and four were predicted to be noninteractors, based upon the structure-activity analyses. Experimental determinations using cells transfected with the human MDR1 gene demonstrated that five of the six pesticides were properly catagorized by the structure-activity analyses (83% accuracy). Finally, structure-activity analyses revealed that among P-gp inhibitors, relative inhibitory potency can be predicted based upon the surface area or volume of the compound. These results demonstrate that P-gp transport substrates and inhibitory ligands can be distinguished using molecular characteristics. Molecular characteristics of transport substrates suggest that P-gp may function in the elimination of hydroxylated metabolites of xenobiotics. Images Figure 1. A Figure 1. B Figure 1. C Figure 1. D Figure 1. E Figure 1. F Figure 1. G Figure 1. H Figure 2. Figure 2. Figure 2. Figure 2. Figure 2. Figure 2. Figure 3. A Figure 3. B

Bain, L J; McLachlan, J B; LeBlanc, G A

1997-01-01

25

Changes in P-glycoprotein activity are mediated by the growth of a tumour cell line as multicellular spheroids  

PubMed Central

Background Expression of P-glycoprotein (P-gp), the multidrug resistance (MDR) 1 gene product, can lead to multidrug resistance in tumours. However, the physiological role of P-gp in tumours growing as multicellular spheroids is not well understood. Recent evidence suggests that P-gp activity may be modulated by cellular components such as membrane proteins, membrane-anchoring proteins or membrane-lipid composition. Since, multicellular spheroids studies have evidenced alterations in numerous cellular components, including those related to the plasma membrane function, result plausible that some of these changes might modulate P-gp function and be responsible for the acquisition of multicellular drug resistance. In the present study, we asked if a human lung cancer cell line (INER-51) grown as multicellular spheroids can modify the P-gp activity to decrease the levels of doxorubicin (DXR) retained and increase their drug resistance. Results Our results showed that INER-51 spheroids retain 3-folds lower doxorubicin than the same cells as monolayers however; differences in retention were not observed when the P-gp substrate Rho-123 was used. Interestingly, neither the use of the P-gp-modulating agent cyclosporin-A (Cs-A) nor a decrease in ATP-pools were able to increase DXR retention in the multicellular spheroids. Only the lack of P-gp expression throughout the pharmacological selection of a P-gp negative (P-gpneg) mutant clone (PSC-1) derived from INER-51 cells, allow increase of DXR retention in spheroids. Conclusion Thus, multicellular arrangement appears to alter the P-gp activity to maintain lower levels of DXR. However, the non expression of P-gp by cells forming multicellular spheroids has only a minor impact in the resistance to chemotherapeutic agents.

Valeria, Ponce de Leon; Raul, Barrera-Rodriguez

2005-01-01

26

From Taxuspine X to Structurally Simplified Taxanes with Remarkable P-Glycoprotein Inhibitory Activity  

PubMed Central

Three simplified “non-natural” natural taxanes, related to taxuspine X, were synthetized and assayed as P-glycoprotein (P-gp) inhibitors. One of them (6) proved to be a very efficient P-gp inhibitor with an IC50 = 7.2 × 10?6 M. In addition, to rationalize biological data, a pharmacophoric model was built through a ligand-based approach. This model represents the first example of a pharmacophore, which describes interactions of taxanes with P-gp.

2010-01-01

27

Contribution of radixin to P-glycoprotein expression and transport activity in mouse small intestine in vivo.  

PubMed

The ERM proteins, ezrin, radixin, and moesin, are membrane-cytoskeleton cross-linkers with multiple physiological functions. We previously showed that radixin is involved in posttranslational regulation of P-glycoprotein (P-gp) in human hepatoblastoma HepG2 cells. Here, we investigated the physiological role of radixin in regulating P-gp expression and activity in the small intestine by comparing wild-type- and radixin knockout (Rdx) mice. In intestinal tissue homogenates, P-gp protein levels increased markedly from the upper part to the lower part of the small intestine in both wild-type- and Rdx(-/-) mice. In the membrane fractions, a similar pattern was seen in wild-type mice. However, the membrane expression of P-gp protein remained at the same level from the upper to the lower part of the small intestine in Rdx(-/-) mice. When rhodamine123 (Rho123), a substrate of P-gp, was orally administered to Rdx(-/-) and wild-type mice, the absorption phase of Rho123 was greater in Rdx(-/-) than in wild-type mice, whereas the elimination phase in Rdx(-/-) mice was not different from that of wild-type mice. Our results indicate that radixin plays an important role in regulating P-gp localization and P-gp functional activity at the intestinal membrane. PMID:23754525

Yano, Kentaro; Tomono, Takumi; Sakai, Riyo; Kano, Takashi; Morimoto, Kaori; Kato, Yukio; Ogihara, Takuo

2013-08-01

28

Glutathione and thiolated chitosan inhibit multidrug resistance P-glycoprotein activity in excised small intestine.  

PubMed

The aim of the present study was to evaluate the influence of glutathione (GSH), the thiomer chitosan-4-thiobutylamidine (chitosan-TBA) and a combination of both compounds on P-glycoprotein (P-gp) activity. Permeation studies were performed with freshly excised guinea pig ileum mounted in Ussing chambers using the fluorescent dye rhodamine-123 (Rho-123) as P-gp substrate. Apparent permeability coefficients (Papp) as well as efflux ratios (secretory Papp/absorptive Papp) were calculated and compared with values gained from experiments with the well-established P-gp inhibitors terfenadine and verapamil. In the presence of terfenadine, verapamil as well as GSH, the absorptive transport of Rho-123 across intestinal tissue increased, while the secretory decreased with efflux ratios around 1.0. Chitosan-TBA and especially chitosan-TBA/GSH not only enhanced absorption of Rho-123, but also reduced the basolateral to apical secretion of Rho-123 resulting in efflux ratios of 1.1, 0.8 and 0.5. The study indicates that chitosan-TBA/GSH is a potentially valuable tool for inhibiting the ATPase activity of P-gp in the intestine. PMID:16377016

Werle, Martin; Hoffer, Martin

2006-03-10

29

Active brain targeting of a fluorescent P-gp substrate using polymeric magnetic nanocarrier system  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles (NP) were developed for the active brain targeting of water-soluble P-glycoprotein (P-gp) substrate rhodamine 123 (Rh123). The NP matrix of poly(lactide-co-glycolide) (PLGA) and methoxy poly(ethyleneglycol)-poly(lactic acid) (M-PEG-PLA) was prepared by single emulsion solvent evaporation of polymers with oleic acid-coated magnetic nanoparticles (OAMNP) and Rh123. All formulations were characterized in terms of morphology, particle size, magnetic content and Rh123 encapsulation efficiency. The maximum encapsulation efficiency of Rh123 was 45 ± 3% and of OAMNP was 42 ± 4%. The brain targeting and biodistribution study was performed on Sprague Dawley rats (3 groups, n = 6). Rh123 (0.4 mg kg-1) was administered in saline form, NP containing Rh123, and NP containing Rh123 in the presence of a magnetic field (0.8 T). The fluorimetric analysis of brain homogenates revealed a significant uptake (p < 0.05) of Rh123 in the magnetically targeted group relative to controls. These results were supported by fluorescence microscopy. This study reveals the ability of magnetically targeted nanoparticles to deliver substances to the brain, the permeation of which would otherwise be inhibited by the P-gp system.

Kirthivasan, B.; Singh, D.; Bommana, M. M.; Raut, S. L.; Squillante, E.; Sadoqi, M.

2012-06-01

30

Active brain targeting of a fluorescent P-gp substrate using polymeric magnetic nanocarrier system.  

PubMed

Magnetic nanoparticles (NP) were developed for the active brain targeting of water-soluble P-glycoprotein (P-gp) substrate rhodamine 123 (Rh123). The NP matrix of poly(lactide-co-glycolide) (PLGA) and methoxy poly(ethyleneglycol)-poly(lactic acid) (M-PEG-PLA) was prepared by single emulsion solvent evaporation of polymers with oleic acid-coated magnetic nanoparticles (OAMNP) and Rh123. All formulations were characterized in terms of morphology, particle size, magnetic content and Rh123 encapsulation efficiency. The maximum encapsulation efficiency of Rh123 was 45 ± 3% and of OAMNP was 42 ± 4%. The brain targeting and biodistribution study was performed on Sprague Dawley rats (3 groups, n = 6). Rh123 (0.4 mg kg(-1)) was administered in saline form, NP containing Rh123, and NP containing Rh123 in the presence of a magnetic field (0.8 T). The fluorimetric analysis of brain homogenates revealed a significant uptake (p < 0.05) of Rh123 in the magnetically targeted group relative to controls. These results were supported by fluorescence microscopy. This study reveals the ability of magnetically targeted nanoparticles to deliver substances to the brain, the permeation of which would otherwise be inhibited by the P-gp system. PMID:22652439

Kirthivasan, B; Singh, D; Bommana, M M; Raut, S L; Squillante, E; Sadoqi, M

2012-06-29

31

Liposomal sphingomyelin influences the cellular lipid profile of human lymphoblastic leukemia cells without effect on P-glycoprotein activity.  

PubMed

Sphingomyelin (SM)/cholesterol liposomes are currently investigated as drug carriers in cancer therapy. However, no data is available on the influence of SM itself on P-glycoprotein (P-gp) mediated multidrug resistance. P-gp is at least partly located in sphingolipid-enriched lipid raft domains of the plasma membrane, and its activity depends on the lipid profile of the membrane, which could be altered by therapeutical SM liposomes. Therefore, the aim of this study was to analyze the effect of liposomal SM on P-gp activity, P-gp distribution in microdomains, SM content of the membrane domains, and sensitivity of human lymphoblastic CEM cells toward cytotoxic drugs in vitro. Assays were conducted in CEM and multidrug resistant CEM/ADR5000 cells. SM-only liposomes were prepared by a newly developed ethanol injection protocol and thoroughly characterized. Inclusion of SM into the membrane was analyzed by fluorescence microscopy and flow cytometry. Influence of SM liposomes on P-gp activity was assessed by rhodamine efflux and calcein assay, and sensitivity toward cytotoxic drugs was analyzed by flow cytometric 7-AAD staining. Influence on P-gp distribution was analyzed by Western blot after density gradient centrifugation. SM 16:0, 18:0, and 24:1 were quantified by liquid chromatography coupled to tandem mass spectrometry. P-gp was mainly located in nonraft fractions, which did not change upon liposome treatment. Liposomes increased SM 16:0 and SM 24:1 content in nonraft domains, but not in raft domains of multidrug resistant cells. SM-only liposomes did not influence P-gp activity and chemosensitivity. In conclusion, SM-only liposomes in therapeutic amounts did not influence P-gp mediated multidrug resistance in CEM cells. PMID:23379426

Zembruski, Nadine C L; Nguyen, Chi D L; Theile, Dirk; Ali, Ramadan M M; Herzog, Melanie; Hofhaus, Götz; Heintz, Udo; Burhenne, Jürgen; Haefeli, Walter E; Weiss, Johanna

2013-03-01

32

P-Glycoprotein Expression and DNA Topoisomerase I and II Activity in Benign Tumors of the Ovary and in Malignant Tumors of the Ovary, before and after Platinum\\/Cyclophosphamide Chemotherapy1  

Microsoft Academic Search

P-glycoprotein (P-gp) expression and DNA topoisomerase (Topo) II are important variables in multidrug resistant tumor cell lines. The aim of this study was to evaluate P-gp expression and Topo I and II activity in benign and malignant epithelial ovarian tumors. P-gp expression was analyzed immunohistochemically in cryostat sections of fresh tumor specimens. In the same specimens Topo I and II

Steven de Jong; Henk Boonstra; Annette Gouw; Pax H. B. Willemse; Jan G. Zijlstra; Elisabeth G. E. de Vries

1991-01-01

33

Induction of Expression and Functional Activity of P-glycoprotein Efflux Transporter by Bioactive Plant Natural Products  

PubMed Central

The effect of bioactive plant natural products on the expression and functional activity of P-glycoprotein (P-gp) is poorly understood. Interactions of bioactive plant-based food and dietary supplements with P-gp can cause significant alteration of pharmacokinetic properties of P-gp substrate drugs when used in combination. This can augment toxicity and/or interfere with the drug’s therapeutic outcomes. This study investigated the effects of diverse commonly used plant natural products on the expression and activity of P-gp in human adenocarcinoma cells (LS-180). These natural products included the tobacco cembranoid (1S,2E,4R,6R,7E,11E)-2,7,11-cembratriene-4,6-diol (cembratriene), the palm oil-derived ?-tocotrienol, the extra-virgin olive oil-derived secoiridoid oleocanthal, and the triterpene acid asiatic acid derived from Melaleuca ericifolia and abundant in several other common plant dietary supplements. Treatment with 25 ?M of cembratriene, oleocanthal, ?-tocotrienol, or asiatic acid showed 2.3-3.0-fold increase in P-gp expression as demonstrated by Western blotting. These results were consistent with those obtained by quantitative analysis of fluorescent micrographs for P-gp. Accumulation studies demonstrated 31-38% decrease in rhodamine 123 intracellular levels when LS-180 cells were treated with the investigated compounds as a result of P-gp induction. Bioactive natural products can up-regulate the P-gp expression and functionality, which may induce herb/food-drug interactions when concomitantly used with P-gp substrate drugs.

Abuznait, Alaa H.; Qosa, Hisham; O'Connell, Nicholas D.; Akbarian-Tefaghi, Jessica; Sylvester, Paul W.; El Sayed, Khalid A.; Kaddoumi, Amal

2011-01-01

34

Induction of expression and functional activity of P-glycoprotein efflux transporter by bioactive plant natural products.  

PubMed

The effect of bioactive plant natural products on the expression and functional activity of P-glycoprotein (P-gp) is poorly understood. Interactions of bioactive plant-based food and dietary supplements with P-gp can cause significant alteration of pharmacokinetic properties of P-gp substrate drugs when used in combination. This can augment toxicity and/or interfere with the drug's therapeutic outcomes. This study investigated the effects of diverse commonly used plant natural products on the expression and activity of P-gp in human adenocarcinoma cells (LS-180). These natural products included the tobacco cembranoid (1S,2E,4R,6R,7E,11E)-2,7,11-cembratriene-4,6-diol (cembratriene), the palm oil-derived ?-tocotrienol, the extra-virgin olive oil-derived secoiridoid oleocanthal, and the triterpene acid asiatic acid derived from Melaleuca ericifolia and abundant in several other common plant dietary supplements. Treatment with 25?M of cembratriene, oleocanthal, ?-tocotrienol, or asiatic acid showed 2.3-3.0-fold increase in P-gp expression as demonstrated by Western blotting. These results were consistent with those obtained by quantitative analysis of fluorescent micrographs for P-gp. Accumulation studies demonstrated 31-38% decrease in rhodamine 123 intracellular levels when LS-180 cells were treated with the investigated compounds as a result of P-gp induction. Bioactive natural products can up-regulate the P-gp expression and functionality, which may induce herb/food-drug interactions when concomitantly used with P-gp substrate drugs. PMID:21851848

Abuznait, Alaa H; Qosa, Hisham; O'Connell, Nicholas D; Akbarian-Tefaghi, Jessica; Sylvester, Paul W; El Sayed, Khalid A; Kaddoumi, Amal

2011-11-01

35

Opioids and efflux transporters. Part 4: Influence of N-substitution on P-glycoprotein substrate activity of noroxymorphone analogues.  

PubMed

The efflux transporter protein P-glycoprotein (P-gp) is capable of affecting the central distribution of diverse neurotherapeutics, including opioid analgesics, through their active removal from the brain. P-gp located at the blood brain barrier has been implicated in the development of tolerance to opioids and demonstrated to be up-regulated in rats tolerant to morphine and oxycodone. We have previously examined the influence of hydrogen-bonding oxo-substitutents on the P-gp-mediated efflux of 4,5-epoxymorphinan analgesics, as well as that of N-substituted analogues of meperidine. Structure-activity relationships (SAR) governing N-substituent effects on opioid efficacy is well-established, however the influence of such structural modifications on P-gp-mediated efflux is unknown. Here, we present SAR describing P-gp recognition of a short series of N-modified 4,5-epoxymorphinans. Oxymorphone, naloxone, naltrexone, and nalmexone all failed to demonstrate P-gp substrate activity, indicating these opioid scaffolds contain structural features that preclude recognition by the transporter. These results are examined using mathematical molecular modeling and discussed in comparison to other opioid scaffolds bearing similar N-substituents. PMID:24915880

Metcalf, Matthew D; Rosicky, Andrew D; Hassan, Hazem E; Eddington, Natalie D; Coop, Andrew; Cunningham, Christopher W; Mercer, Susan L

2014-08-01

36

Inhibition of the multidrug resistance P-glycoprotein activity by green tea polyphenols  

Microsoft Academic Search

Many beneficial proprieties have been associated with polyphenols from green tea, such as chemopreventive, anticarcinogenic, antiatherogenic and antioxidant actions. In this study, we investigated the effects of green tea polyphenols (GTPs) and their principal catechins on the function of P-glycoprotein (P-gp), which is involved in the multidrug resistance phenotype of cancer cells. GTPs (30 ?g\\/ml) inhibit the photolabeling of P-gp

Julie Jodoin; Michel Demeule; Richard Béliveau

2002-01-01

37

Loxapine P-glycoprotein interactions in vitro.  

PubMed

The antipsychotic drugs risperidone, paliperidone, olanzapine, quetiapine, aripiprazole, clozapine, haloperidol, and chlorpromazine have been reported to have various degrees of interaction (substrate or inhibitor) with the multidrug resistance transporter, P-glycoprotein (P-gp). An interaction of the antipsychotic drug loxapine with P-gp was recently reported, but an IC50 value was not determined. Loxapine (as the succinate salt) was evaluated as a P-gp substrate, and inhibitor of P-gp mediated transport of digoxin in vitro in Caco-2 cells. Loxapine was not a substrate for P-gp but did exhibit weak-to-moderate inhibition (IC50 = 9.1 ?M). Since the typical steady state maximal plasma concentrations of loxapine in clinical use have been reported to be in the nanomolar range, pharmacokinetic interactions due to the inhibition of P-gp activity are not expected. PMID:22300294

Reed, Andrea; Huie, Keith; Perloff, Elke S; Cassella, James V; Takahashi, Lori H

2012-03-01

38

Active elimination of the marine biotoxin okadaic acid by P-glycoprotein through an in vitro gastrointestinal barrier.  

PubMed

The consumption of okadaic acid (OA) contaminated shellfish can induce acute toxic symptoms in humans such as diarrhea, nausea, vomiting and abdominal pain; carcinogenic and embryotoxic effects have also been described. Toxicokinetic studies with mice have shown that high cytotoxic doses of OA can pass the gastrointestinal barrier presumably by paracellular passage. However, in vitro studies using human intestinal Caco-2 cell monolayers to represent the intestinal barrier have shown that at low-dose exposure OA is transported against a concentration gradient suggesting an active efflux mechanism. Since P-glycoprotein (P-gp) transports a wide variety of substrates, we investigated its possible influence on the observed elimination of OA. We used two different cellular transwell models: (i) Caco-2 cell monolayer endogenously expressing human P-gp and simulating the intestinal barrier and (ii) MDCK-II cell monolayer stably over-expressing P-gp. Our study demonstrates clearly that OA at non-cytotoxic concentrations passes the monolayer barrier only to a low degree, and that it is actively eliminated by P-gp over the apical membrane. Therefore, our in vitro data indicate that humans appear to have efficient defense mechanisms to protect themselves against low-dose contaminated shellfish by exhibiting a low bioavailability as a result of active elimination of OA by P-gp. PMID:24374049

Ehlers, Anke; These, Anja; Hessel, Stefanie; Preiss-Weigert, Angelika; Lampen, Alfonso

2014-03-01

39

The Role of Turmerones on Curcumin Transportation and P-Glycoprotein Activities in Intestinal Caco-2 Cells  

PubMed Central

Abstract The rhizome of Curcuma longa (turmeric) is often used in Asia as a spice and as a medicine. Its most well-studied component, curcumin, has been shown to exhibit poor bioavailability in animal studies and clinical trials. We hypothesized that the presence of lipophilic components (e.g., turmerones) in turmeric extract would affect the absorption of curcumin. The effects of turmerones on curcumin transport were evaluated in human intestinal epithelial Caco-2 cells. The roles of turmerones on P-glycoprotein (P-gp) activities and mRNA expression were also evaluated. Results showed that in the presence of ?- and aromatic turmerones, the amount of curcumin transported into the Caco-2 cells in 2 hours was significantly increased. ?-Turmerone and verapamil (a P-gp inhibitor) significantly inhibited the efflux of rhodamine-123 and digoxin (i.e., inhibited the activity of P-gp). It is interesting that aromatic turmerone significantly increased the rhodamine-123 efflux and P-gp (MDR1 gene) mRNA expression levels. The effects of ?- and aromatic turmerones on curcumin transport as well as P-gp activities were shown here for the first time. The presence of turmerones did affect the absorption of curcumin in vitro. These findings suggest the potential use of turmeric extract (including curcumin and turmerones), rather than curcumin alone, for treating diseases.

Yue, Grace G.L.; Cheng, Sau-Wan; Yu, Hua; Xu, Zi-Sheng; Lee, Julia K.M.; Hon, Po-Ming; Lee, Mavis Y.H.; Kennelly, Edward J.; Deng, Gary; Yeung, Simon K.; Cassileth, Barrie R.; Fung, Kwok-Pui; Leung, Ping-Chung

2012-01-01

40

Impact of P-glycoprotein on clopidogrel absorption  

Microsoft Academic Search

Objective: The antiplatelet activity of clopidogrel is characterized by considerable interindividual differences. Variable intestinal absorption is suggested to contribute to the inconsistencies in response. We tested the hypothesis that the intestinal efflux transporter P-glycoprotein (P-gp) limits the oral bioavailability of clopidogrel and that variance in the MDR1 gene encoding P-gp predicts absorption variability.Methods and Results: P-gp–mediated transport of clopidogrel was

Dirk Taubert; Nicolas von Beckerath; Gundula Grimberg; Andreas Lazar; Norma Jung; Tobias Goeser; Adnan Kastrati; Albert Schömig; Edgar Schömig

2006-01-01

41

Application of three-dimensional quantitative structure-activity relationships of P-glycoprotein inhibitors and substrates.  

PubMed

Using in vitro data, we previously built Catalyst 3-dimensional quantitative structure activity relationship (3D-QSAR) models that qualitatively rank and predict IC(50) values for P-glycoprotein (P-gp) inhibitors. These models were derived and tested with data for inhibition of digoxin transport, calcein accumulation, vinblastine accumulation, and vinblastine binding. In the present study, 16 inhibitors of verapamil binding to P-gp were predicted using these models. These inhibition results were then used to generate a new pharmacophore that consisted of one hydrogen bond acceptor, one ring aromatic feature, and two hydrophobes. This model predicted the rank order of the four data sets described previously and correctly ranked the inhibitory potency of a further four verapamil metabolites identified in the literature. The degree of similarity in rank ordering prediction by these inhibitor pharmacophore models generated to date confirms a likely overlap in the sites to which the three P-gp substrates used in these studies (verapamil, vinblastine, and digoxin) bind. Alignment of the three substrate probes indicated that they are likely to bind the same or overlapping sites within P-gp. Important features on these substrates include multiple hydrophobic and hydrogen bond acceptor features, which are widely dispersed and in agreement among most of the five inhibitor pharmacophores we have described so far. These 3D-QSAR models will be useful for future prediction of likely substrates and inhibitors of P-gp. PMID:11961114

Ekins, Sean; Kim, Richard B; Leake, Brenda F; Dantzig, Anne H; Schuetz, Erin G; Lan, Lu-Bin; Yasuda, Kazuto; Shepard, Robert L; Winter, Mark A; Schuetz, John D; Wikel, James H; Wrighton, Steven A

2002-05-01

42

Impact of the basic amine on the biological activity and intracellular distribution of an aza-anthrapyrazole: BBR 3422 4 4 Abbreviations: MDR, multidrug resistance; NHS-ASA, N-hydroxysuccinimidyl-4-azidosalicylic acid; SRB, sulforhodomine B; and P-gp, P-glycoprotein  

Microsoft Academic Search

The anthrapyrazoles have entered clinical trials and show significant activity against breast cancer. However, these drugs are cardiotoxic and ineffective in multidrug-resistant (MDR) tumor cells. We have reported previously on the synthesis and antitumor characteristics of the 9-aza-anthrapyrazoles and their lack of cardiotoxicity; unfortunately, the leading candidates are cross-resistant in MDR-expressing cells. The results also indicated that the side arm

Kai-Ming Chou; A. Paul Krapcho; Miles P. Hacker

2001-01-01

43

Pharmacodynamic consequences of P-glycoprotein-dependent pharmacokinetics of risperidone and haloperidol in mice  

Microsoft Academic Search

Efflux transporters, like P-glycoprotein (P-gp), may limit the access of drugs to the brain via the blood–brain barrier. The antipsychotic drug risperidone and its active metabolite 9-hydroxyrisperidone (paliperidone) are substrates of P-gp. Motor behavior of P-gp deficient mice (mdr1a\\/1b (?\\/?, ?\\/?)) and wild type animals on a rotarod after acute doses of risperidone or haloperidol, a nonsubstrate of P-gp, were

Katrin M. Kirschbaum; Stefanie Henken; Christoph Hiemke; Ulrich Schmitt

2008-01-01

44

Inhibitory effect of a bitter melon extract on the P-glycoprotein activity in intestinal Caco-2 cells  

PubMed Central

Extracts of bitter melon, soybean, dokudami and welsh onion by 40% methanol increased the accumulation of rhodamine-123 by Caco-2 cells, suggesting that these extracts inhibited P-glycoprotein (P-gp). The extract of bitter melon was separated in a tC18 cartridge column and the eluate from 80% acetonitrile most markedly increased the [3H]-daunomycin accumulation by Caco-2 cells. The inhibitory compounds in the bitter melon fraction were isolated by HPLC with Pegasil C4 and Pegasil ODS columns. The HPLC fraction having the highest activity was analyzed by 1H-NMR and FAB-MS, and the active compound was identified as 1-monopalmitin. The inhibitory activities of 1-monopalmitin and its related compounds suggested that the inhibition of P-gp activity was not dependent on the degree of unsaturation of fatty acid in the monoglyceride, but on the chain length. It was also suggested that the monoglyceride structure played an important role in the inhibition of P-gp activity. Monoglycerides could therefore alter the pharmacokinetics of drugs by inhibiting the P-gp-mediated efflux.

Konishi, Tomoko; Satsu, Hideo; Hatsugai, Yasuo; Aizawa, Koichi; Inakuma, Takahiro; Nagata, Shinji; Sakuda, Sho-hei; Nagasawa, Hiromichi; Shimizu, Makoto

2004-01-01

45

Pregnancy Does Not Increase CYP3A or P-Glycoprotein Activity in the Non-Human Primate, Macaca nemestrina  

PubMed Central

Plasma concentrations of protease inhibitors are lower in pregnant women than in nonpregnant women or men. Using nelfinavir as a model protease inhibitor, we have shown that this phenomenon can be reproduced in a representative non-human primate model, Macaca nemestrina (J Pharmacol Exp Ther 329:1016–1022, 2009). Nelfinavir is cleared from the body predominantly by CYP3A metabolism and P-glycoprotein (P-gp) efflux. Therefore, using midazolam (MDZ) as a CYP3A probe and digoxin (DIG) as a P-gp probe, we determined the antepartum (73–118 days) and postpartum (61–130 days) in vivo intestinal and hepatic CYP3A or P-gp activity in the macaque. Although the systemic clearance of MDZ was significantly increased (?70%) during pregnancy after intra-arterial (IA) administration of the drug (15N-labeled MDZ; 40 ?g/kg), pregnancy did not affect the oral clearance of the drug administered simultaneously (1 mg/kg p.o.) with the IA dose. In vitro studies in hepatic and intestinal S-9 fractions indicated no effect of pregnancy on CYP3A activity or protein expression in the small intestine or liver. In contrast, neither the oral (100 ?g/kg) nor the IA (10 ?g/kg) clearance of DIG was significantly altered by pregnancy, indicating no effect of pregnancy on P-gp activity. Assuming that MDZ and DIG are selective substrates of the macaque CYP3A enzymes and P-gp, respectively, these results suggest that factors other than increased CYP3A or P-gp activity contribute to the increased clearance of protease inhibitors during M. nemestrina pregnancy.

Zhang, Huixia; Wu, Xiaohui; Naraharisetti, Suresh Babu; Chung, Francisco; Whittington, Dale; Mirfazaelian, Ahmad; Unadkat, Jashvant D.

2009-01-01

46

Enhancement effect of P-gp inhibitors on the intestinal absorption and antiproliferative activity of bestatin.  

PubMed

Bestatin is an immunomodulator with antitumor activity. This study was performed to investigate the effect of P-gp on the intestinal absorption and antiproliferative activity of bestatin. Our results showed that P-gp inhibitors significantly increased rat intestinal absorption of bestatin in vivo and in vitro. The net efflux ratio of bestatin was 2.2 across mock-/MDR1-MDCK cell monolayers and was decreased by P-gp inhibitors, indicating bestatin was a substrate of P-gp. Furthermore, the IC50 values of bestatin on U937 and K562 cells were decreased dramatically and the intracellular concentrations of bestatin were increased by incubation of cells with verapamil or Cyclosporin A. K562/ADR cells exhibited a higher IC50 value and a lower intracellular level of bestatin. The bestatin level in K562/ADR cells was partially restored by incubation with doxorubicin. However, P-gp and APN mRNA levels were not changed by bestatin. These results suggested that the intestinal absorption and accumulation in cancer cells for bestatin were limited by P-gp-mediated efflux. Additional attention should be paid to the alternative exposure of bestatin when bestatin was coadministered with drugs as P-gp substrates in clinic. PMID:23981338

Huo, Xiaokui; Liu, Qi; Wang, Changyuan; Meng, Qiang; Sun, Huijun; Peng, Jinyong; Ma, Xiaochi; Liu, Kexin

2013-11-20

47

Role of P-glycoprotein in the transport of tanshinone I, one active triterpenoid from Salvia miltiorrhiza.  

PubMed

The extracts from the root of Salvia miltiorrhiza are widely used in the treatment of angina and stroke. In this study, we have investigated the role of P-glycoprotein (P-gp) in the transport of tanshinone I (TSI), a major active constituent of S. miltiorrhiza. The TSI transport across Caco-2 monolayers was pH-, energy-, and temperature-dependent, but not sodium-dependent. TSI exhibited a polarized transport in Caco-2 monolayers which was attenuated by P-gp inhibitors. The permeability (P(app)) values of TSI in the basolateral to apical direction were significantly higher in MDCK-II cells over-expressing MDR1, as compared to the wild-type control cells. Furthermore, TSI significantly inhibited the transport of digoxin in Caco-2 cells with an IC(50) value of 0.53 +/- 0.09 microM. TSI also moderately stimulated P-gp ATPase activity with K(m) and V(max) values of 31.70 +/- 7.09 microM and 57.71 +/- 5.26 nmol/min/mg protein, respectively. Our findings indicate that TSI is a substrate and inhibitor of P-gp, which has important clinical and toxicological implications. PMID:19356097

Li, Xing-Xiao; Zhou, Zhi-Wei; Zhou, Shu-Feng

2008-08-01

48

Jatrophane diterpenoids from the latex of Euphorbia dendroides and their anti-P-glycoprotein activity in human multi-drug resistant cancer cell lines.  

PubMed

Thirteen jatrophane diterpenoids (1-10, 13-15), three previously isolated (11, 12, 16) and a known tigliane (17) were isolated from the latex of Euphorbia dendroides. The structures and relative configurations of compounds were elucidated by spectroscopic techniques. The P-glycoprotein (P-gp) inhibiting activities of the representative set of jatrophanes (1-6 and 11-16) have been assessed. Jatrophanes 2 and 5 demonstrated the most powerful inhibition of P-gp, higher than R(+)-verapamil and tariquidar in colorectal multi-drug resistant (MDR) cells (DLD1-TxR). PMID:23079764

Jadranin, Milka; Peši?, Milica; Aljan?i?, Ivana S; Milosavljevi?, Slobodan M; Todorovi?, Nina M; Podolski-Reni?, Ana; Bankovi?, Jasna; Tani?, Nikola; Markovi?, Ivanka; Vajs, Vlatka E; Teševi?, Vele V

2013-02-01

49

The role of inter-segmental differences in P-glycoprotein expression and activity along the rat small intestine in causing the double-peak phenomenon of substrate plasma concentration.  

PubMed

  Conflicting results have been reported on segmental differences in expression of P-glycoprotein (P-gp) along the small intestine of animals and humans. In this study, we investigated P-gp mRNA and protein levels within each of nine segments of rat small intestine. In addition, P-gp activity in each segment was evaluated in terms of permeability of rhodamine123 (Rho123), a typical P-gp substrate, using the serial intestinal non-everted sac method. The P-gp mRNA levels tended to increase from the duodenum to the ileum, with peaks in the upper and lower ileum, while P-gp protein level reached its maximum in the middle ileum. The activity of P-gp was also the highest in the middle ileum, and was highly correlated with P-gp protein level. The double-peaked plasma concentration profile that was observed following oral administration of Rho123 to rats could be well reproduced by an intestinal compartmental kinetic model incorporating inter-segmental differences of absorption and excretion rate constants. Our results suggest that the heterogeneous distribution of P-gp along the small intestine plays a key role in causing the double-peak of plasma concentration of P-gp substrates following oral administration to rats. PMID:22850759

Wada, Sho; Kano, Takashi; Mita, Suzune; Idota, Yoko; Morimoto, Kaori; Yamashita, Fumiyoshi; Ogihara, Takuo

2013-01-01

50

Expression of P-glycoprotein in southeastern oysters, Crassostrea virginica.  

PubMed

These studies provide important fundamental information regarding the expression of P-glycoprotein (p-gp) in southeastern oysters (Crassostrea virginica). Using rhodamine transport studies, p-gp activity was detected in newly fertilized embryos. A monoclonal antibody (C219) was used to evaluate p-gp expression in oyster tissues. On the basis of laboratory studies, p-gp expression tended to be higher in gill tissues than mantle tissues, and was generally not related to salinity differences. Seasonal studies were conducted with oysters collected monthly for 1 year from Lighthouse Creek, an unpolluted site. There was a general pattern of higher p-gp expression in the warmer months and lower expression in the colder months. In contrast, total gill protein concentrations decreased during the warmer months and increased during the colder months. These studies indicate that there are seasonal patterns in p-gp expression which may represent an adaptive response to natural stressors associated with summer conditions. PMID:11488357

Keppler, C J; Ringwood, A H

2001-07-01

51

Sinapine as an active compound for inhibiting the proliferation of Caco-2 cells via downregulation of P-glycoprotein.  

PubMed

Sinapine, an alkaloid from seeds of the cruciferous species, shows favorable biological activities such as antioxidant and radio-protective activities. However, the inhibitory effect of sinapine on tumors, and the molecular mechanisms have not been completely understood thus far. In this study, we determined anti-proliferative effects of sinapine. We examined the anti-tumor effects of the combination of sinapine and doxorubicin. The results of the MTT assay and apoptosis showed that sinapine increased the sensitivity of Caco-2 cells to doxorubicin in a dose-dependent manner, whereas no or less effect was observed in the cells treated with doxorubicin alone. The combination of sinapine and doxorubicin had a synergistic effect and increased the cytotoxicity of doxorubicin against Caco-2 cells. Doxorubicin accumulation assay showed that sinapine increased the intracellular accumulation of doxorubicin in dose-dependent manner. Immunoblotting and QT-PCR analysis showed that sinapine suppressed P-glycoprotein (P-gp) expression via ubiquitination. A significant correlation was observed between the expression of p-ERK1/2 and P-gp. These results indicated that sinapine played an important role in the down-regulation of P-gp expression through suppression of FGFR4-FRS2?-ERK1/2 signaling pathway. To our knowledge, this is the first study to show that sinapine can be used as an effective natural compound for chemo-resistance. PMID:24607798

Guo, Ying; An, Hongli; Feng, Liuxin; Liu, Qi; Wang, Sicen; Zhang, Tao

2014-05-01

52

Influence of combinations of digitonin with selected phenolics, terpenoids, and alkaloids on the expression and activity of P-glycoprotein in leukaemia and colon cancer cells.  

PubMed

P-glycoprotein (P-gp or MDR1) is an ATP-binding cassette (ABC) transporter. It is involved in the efflux of several anticancer drugs, which leads to chemotherapy failure and multidrug resistance (MDR) in cancer cells. Representative secondary metabolites (SM) including phenolics (EGCG and thymol), terpenoids (menthol, aromadendrene, ?-sitosterol-O-glucoside, and ?-carotene), and alkaloids (glaucine, harmine, and sanguinarine) were evaluated as potential P-gp inhibitors (transporter activity and expression level) in P-gp expressing Caco-2 and CEM/ADR5000 cancer cell lines. Selected SM increased the accumulation of the rhodamine 123 (Rho123) and calcein-AM (CAM) in a dose dependent manner in Caco-2 cells, indicating that they act as competitive inhibitors of P-gp. Non-toxic concentrations of ?-carotene (40?M) and sanguinarine (1?M) significantly inhibited Rho123 and CAM efflux in CEM/ADR5000 cells by 222.42% and 259.25% and by 244.02% and 290.16%, respectively relative to verapamil (100%). Combination of the saponin digitonin (5?M), which also inhibits P-gp, with SM significantly enhanced the inhibition of P-gp activity. The results were correlated with the data obtained from a quantitative analysis of MDR1 expression. Both compounds significantly decreased mRNA levels of the MDR1 gene to 48% (p<0.01) and 46% (p<0.01) in Caco-2, and to 61% (p<0.05) and 1% (p<0.001) in CEM/ADR5000 cells, respectively as compared to the untreated control (100%). Combinations of digitonin with SM resulted in a significant down-regulation of MDR1. Our findings provide evidence that the selected SM interfere directly and/or indirectly with P-gp function. Combinations of different P-gp substrates, such as digitonin alone and together with the set of SM, can mediate MDR reversal in cancer cells. PMID:23999162

Eid, Safaa Yehia; El-Readi, Mahmoud Zaki; Eldin, Essam Eldin Mohamed Nour; Fatani, Sameer Hassan; Wink, Michael

2013-12-15

53

Intact lipid rafts regulate HIV-1 Tat protein-induced activation of the Rho signaling and upregulation of P-glycoprotein in brain endothelial cells  

PubMed Central

The Rho signaling has an essential function in human immunodeficiency virus (HIV)-1-mediated disruption of the integrity of the blood–brain barrier (BBB). However, it is unknown how membrane domains, such as lipid rafts, can influence HIV-1-mediated activation of the Rho pathway and how these processes can affect the expression of the efflux transporters at the BBB level. This study is focused on the function of HIV-1 protein Tat in activation of the Rho signaling and upregulation of P-glycoprotein (P-gp) in human brain endothelial cells. Treatment with Tat markedly elevated GTP-RhoA levels and the potential downstream effectors, such as myosin phosphatase target subunit 1 and myosin light chain. In addition, Tat upregulated expression and promoter activity of P-gp as well as its efflux function. Inhibition of the Rho signaling cascade effectively blocked P-gp overexpression at the level of promoter activity. Disruption of lipid rafts by depletion of membrane cholesterol by methyl-beta-cyclodextrin, but not caveolin-1 silencing, also abolished Tat-mediated RhoA activation and P-gp upregulation. The present data indicate the critical function of intact lipid rafts and the Rho signaling in HIV-1-mediated upregulation of P-gp and potential development of drug resistance in brain endothelial cells.

Zhong, Yu; Hennig, Bernhard; Toborek, Michal

2010-01-01

54

Interaction of Common Azole Antifungals with P Glycoprotein  

Microsoft Academic Search

Both eucaryotic and procaryotic cells are resistant to a large number of antibiotics because of the activities of export transporters. The most studied transporter in the mammalian ATP-binding cassette transporter superfamily, P glycoprotein (P-gp), ejects many structurally unrelated amphiphilic and lipophilic xenobiotics. Observed clinical interactions and some in vitro studies suggest that azole antifungals may interact with P-gp. Such an

Er-jia Wang; Karen Lew; Christopher N. Casciano; Robert P. Clement; William W. Johnson

2002-01-01

55

Identification of P-glycoprotein inhibitors in contaminated freshwater sediments.  

PubMed

P-glycoprotein (P-gp, ABCB1) is an important part of the multixenobiotic resistance (MXR) defense system in aquatic organisms. The main goal of this study was identification of P-gp inhibitors in contaminated sediments using the effect-directed analysis (EDA) approach. The samples were collected from the Gorjak creek (Zagreb, Croatia), a recipient of wastewater effluents from the pharmaceutical industry. Sediment samples were extracted and fractionated using a two-tiered approach. Resulting nonpolar, medium polar, and polar fractions were tested on the inhibition of P-gp activity using P-gp overexpressing PLHC-1/dox cells and calcein-AM as model substrate. The obtained EC50 values (up to 757 ?g/g, expressed in toxicity equivalents of model P-gp inhibitor cyclosporine A) revealed high inhibitory potential of polar fractions of investigated sediments and clearly reflected the impact of pharmaceutical wastewater. P-gp specific ATPase assay and the cytotoxicity modulation experiments with colchicine indicated that most of the observed P-gp inhibition was due to the presence of noncompetitive inhibitors. A detailed chemical analysis by ultrahigh-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UPLC-QTOFMS) revealed nonionic surfactants, including alcohol polyethoxylates (LAEOs) and polypropylene glycols (PPGs), as the major components of the most active subfractions. Testing of several LAEO and PPG commercial mixtures confirmed their potential to inhibit the fish P-glycoprotein and modulate toxicity of other xenobiotics present in complex environmental samples. PMID:23570494

Zaja, Roko; Terzi?, Senka; Senta, Ivan; Lon?ar, Jovica; Popovi?, Marta; Ahel, Marijan; Smital, Tvrtko

2013-05-01

56

Antisense to MDR1 mRNA reduces P-glycoprotein expression, swelling-activated C1- current and volume regulation in bovine ciliary epithelial cells.  

PubMed

Native ciliary epithelial cells from the ciliary epithelium of the eye exhibit anti-P-glycoprotein (P-gp) immunofluorescence. We have used an antisense 'knock-down' approach to investigate the relationship between P-gp and the volume-activated chloride current (IC1,swell) and its role in volume regulation. An antisense oligonucleotide to the human multidrug resistance (MDR1) gene, taken up by the cells in a dose-dependent manner, reduced P-gp immunofluorescence, inhibited IC1,swell and significantly increased the latency of activation of IC1,swell. Increasing the hypotonic stress did not result in an increased activation of ICl,swell. MDR1 antisense 'knock-down' also reduced the ability of the cells to volume regulate following a hypotonic challenge. These cells are known to express at least two volume-activated chloride channels, and the data suggest that P-gp is involved in the activation pathway of a subset of channels that contribute to whole-cell IC1,swell and participate in volume regulation. PMID:9679161

Wang, L; Chen, L; Walker, V; Jacob, T J

1998-08-15

57

MDR1 (ABCB1) gene polymorphism C3435T is associated with P-glycoprotein activity in B-cell chronic lymphocytic leukemia  

Microsoft Academic Search

Functional single nucleotide polymorphism (SNP) C3435T in exon 26 of the MDR1 (ABCB1) gene encoding the xenobiotic transporter P-glycoprotein (P-gp, MDR1, ABCB1) may influence susceptibility to several diseases as well as clinical outcome of treatment with P-gp substrates. Exposure to environmental chemicals is thought to be involved in the pathogenesis of B-cell chronic lymphocytic leukemia (B-CLL) and P-gp-transported drugs are

Krzysztof Jamroziak; Ewa Balcerczak; Piotr Smolewski; Robert W. Robey; Barbara Cebula; Mariusz Panczyk; Monika Kowalczyk; Anna Szmigielska; Marek Mirowski; Susan E. Bates; Tadeusz Robak

58

P-glycoprotein is fully active after multiple tryptophan substitutions  

PubMed Central

P-glycoprotein (Pgp) is an important contributor to multidrug resistance of cancer. Pgp contains eleven native tryptophans (Trps) that are highly conserved among orthologs. We replaced each Trp by a conservative substitution to determine which Trps are important for function. Individual Trp mutants W44R, W208Y, W132Y, W704Y and W851Y, situated at the membrane surface, revealed significantly reduced Pgp induced drug resistance against one or more fungicides and/or reduced mating efficiencies in Saccharomyces cerevisiae. W158F and W799F, located in the intracellular coupling helices, abolished mating but retained resistance against most drugs. In contrast, W228F and W311Y, located within the membrane, W694L, at the cytoplasmic membrane interface, and W1104Y in NBD2 retained high levels of drug resistance and mating efficiencies similar to wild-type Pgp. Those were combined into pair (W228F/W311Y and W694L/W1104Y) and quadruple (W228F/W311Y/W694L/W1104Y) mutants that were fully active in yeast, and could be purified to homogeneity. Purified pair and quad mutants exhibited drug-stimulated ATPase activity with binding affinities very similar to wild-type Pgp. The combined mutations reduced Trp fluorescence by 35%, but drug induced fluorescence quenching was unchanged from wild-type Pgp suggesting that several membrane-bound Trps are sensitive to drug binding. Overall, we conclude that Trps at the membrane surface are critical for maintaining the integrity of the drug binding sites, while Trps in the coupling helices are important for proper interdomain communication. We also demonstrate that functional single Trp mutants can be combined to form a fully active Pgp that maintains drug polyspecificity, while significantly reducing intrinsic fluorescence.

Swartz, Douglas J.; Weber, Joachim; Urbatsch, Ina L.

2013-01-01

59

Telaprevir is a substrate and moderate inhibitor of P-glycoprotein, a strong inductor of ABCG2, but not an activator of PXR in vitro.  

PubMed

Triple therapy combining the protease inhibitor telaprevir with interferon-? and ribavirin is a promising new option for long-term treatment of hepatitis C. The interaction potential of telaprevir has not yet been fully elucidated. The in vitro potency of telaprevir to inhibit P-glycoprotein (P-gp, ABCB1) and breast cancer resistance protein (BCRP, ABCG2) was assessed and its substrate characteristics for P-gp, BCRP and the multidrug resistance-associated proteins (MRPs, ABCCs) 1-3 were evaluated. The inducing properties of telaprevir on important drug-metabolising enzymes and transporters were also assessed and its ability to activate the pregnane X receptor (PXR) was investigated. Using growth inhibition assays, it was confirmed that telaprevir is a substrate of P-gp and it was demonstrated for the first time that it is not transported by BCRP and MRPs. Telaprevir only moderately inhibited P-gp in the calcein assay and did not inhibit BCRP in the pheophorbide A assay. In LS180 cells, telaprevir strongly induced mRNA expression of ABCG2 (4.3-fold at 30 ?mol/L) and weakly induced ABCB11, CYP2C19 and UGT1A3. In contrast, telaprevir had no significant influence on mRNA expression of CYP3A4, UGT1A9, ABCB1, ABCC2 and SLCO1B1. In a reporter gene assay, telaprevir did not activate PXR. Thus, it appears unlikely that telaprevir induces CYP3A4 and P-gp in vivo in such a way as to provoke clinically relevant drug interactions. From the numerous perpetrator characteristics, telaprevir's inhibitor properties, especially of CYP3A4 and P-gp, appear to be the most relevant mechanism for drug interactions. The clinical relevance of the strong inducing effects on ABCG2 requires proper assessment. PMID:24332840

Weiss, Johanna; Becker, Jonas Philipp; Haefeli, Walter Emil

2014-02-01

60

Deactivation of Signal Transducer and Activator of Transcription 3 Reverses Chemotherapeutics Resistance of Leukemia Cells via Down-Regulating P-gp  

PubMed Central

Multidrug resistance (MDR) caused by overexpression of p-glycoprotein is a major obstacle in chemotherapy of malignant cancer, which usually is characterized by constitutive activation of signal transducer and activator of transcription 3 (STAT3), but their relation between MDR and STAT3 remains unclear. Here, we showed that STAT3 was overexpressed and highly activated in adriamycin-resistant K562/A02 cells compared with its parental K562 cells. Blockade of activation of STAT3 by STAT3 decoy oligodeoxynucleotide (ODN) promoted the accumulation and increased their sensitivity to adriamycin by down-regulating transcription of mdr1 and expression of P-gp, which were further confirmed by using STAT3-specific inhibitor JSI-124. Inhibition of STAT3 could also decrease mdr1 promoter mediated luciferase expression by using mdr1 promoter luciferase reporter construct. Otherwise, activation of STAT3 by STAT3C improved mdr1 transcription and P-gp expression. The ChIP results demonstrated that STAT3 could bind to the potential promoter region of mdr1, and STAT3 decoy depressed the binding. Further mutation assay show +64?+72 region could be the STAT3 binding site. Our data demonstrate a role of STAT3 in regulation of mdr1 gene expression in myeloid leukemia and suggest that STAT3 may be a promising therapeutic target for overcoming MDR resistance in myeloid leukemia.

Zhang, Xulong; Xiao, Weihua; Wang, Lihua; Tian, Zhigang; Zhang, Jian

2011-01-01

61

ABCB1 haplotypes are associated with P-gp activity and affect a major molecular response in chronic myeloid leukemia patients treated with a standard dose of imatinib  

PubMed Central

Despite the high efficacy of imatinib mesylate (IM) treatment for chronic myeloid leukemia (CML) patients, some individuals develop resistance due to impaired bioavailability. It has been previously demonstrated that the haplotypes for ATP-binding cassette subfamily B member 1 (ABCB1)with c.1236C>T, c.3435C>T and c.2677G>T/A polymorphisms markedly affect the secondary structure of ABCB1 mRNA and its activity. These modifications may affect efflux transporter activity and response to treatment with IM. The aim of the present study was to investigate the influence of ABCB1 haplotypes on P-glycoprotein (P-gp) activity, IM plasma levels and IM response. In total, 28 chronic-phase CML patients treated with a standard dose of IM (400 mg/day) were studied. The patients were selected according to the haplotypes of ABCB1, with c.1236C>T, c.3435C>T and c.2677G>T polymorphisms, and were classified into two groups based on the presence of the mutated allele in each genotype for the three ABCB1 polymorphisms. In addition, expression of P-gp and breakpoint cluster region-abelson 1 (BCR-ABL1), ABCB1 and solute carrier family 22 member 1 (SLC22A1) mRNA were evaluated. The P-gp activity in the wild-type group was found to be higher than that in the mutated group (59.1 vs. 38.3%; P=0.001). Furthermore, the patients who did not achieve major molecular response (MMR) showed a higher rate of efflux mediated by P-gp when compared with individuals who achieved MMR (64.7 vs. 45.7%; P=0.001). All patients without MMR demonstrated effluxes of >60%. In addition, patients without MMR exhibited lower plasma concentrations of IM compared with those with MMR (0.51 vs. 1.42 ?g/ml; P=0.001). Higher levels of SLC22A1 mRNA were observed in patients who achieved MMR and complete molecular response (P<0.05). In conclusion, the ABCB1 1236CT/3435CT/2677GT and 1236TT/3435TT/2677TT haplotypes are associated with reduced P-gp activity and MMR in chronic-phase CML patients treated with a standard dose of IM.

VIVONA, DOUGLAS; LIMA, LUCIENE TEREZINA; RODRIGUES, ALICE CRISTINA; BUENO, CAROLINA TOSIN; ALCANTARA, GREYCE KELLY STEINHORST; BARROS, LUIZA SALDANHA RIBEIRO; DE MORAES HUNGRIA, VANIA TIESTSCHE; CHIATTONE, CARLOS SERGIO; DE LOURDES LOPES FERRARI CHAUFFAILLE, MARIA; GUERRA-SHINOHARA, ELVIRA MARIA

2014-01-01

62

Effects of Pregnancy on CYP3A and P-glycoprotein Activities as Measured by Disposition of Midazolam and Digoxin: A University of Washington Specialized Center of Research Study  

Microsoft Academic Search

The objectives of the study were to evaluate the effects of pregnancy on CYP3A and P-glycoprotein (P-gp) activities, as measured by disposition of midazolam and digoxin, respectively. Thirteen women received digoxin (0.25 mg p.o.) and midazolam (2 mg p.o.) in random order, separated by 1–2 weeks at 28–32 weeks gestation, and the same order was repeated at 6–10 weeks postpartum.

MF Hebert; TR Easterling; B Kirby; DB Carr; ML Buchanan; T Rutherford; KE Thummel; DP Fishbein; JD Unadkat

2008-01-01

63

Psychotropic drug-drug interactions involving P-glycoprotein.  

PubMed

Multidrug resistance P-glycoprotein (P-gp; also known as MDR1 and ABCB1) is expressed in the luminal membrane of the small intestine and blood-brain barrier, and the apical membranes of excretory cells such as hepatocytes and kidney proximal tubule epithelia. P-gp regulates the absorption and elimination of a wide range of compounds, such as digoxin, paclitaxel, HIV protease inhibitors and psychotropic drugs. Its substrate specificity is as broad as that of cytochrome P450 (CYP) 3A4, which encompasses up to 50 % of the currently marketed drugs. There has been considerable interest in variations in the ABCB1 gene as predictors of the pharmacokinetics and/or treatment outcomes of several drug classes, including antidepressants and antipsychotics. Moreover, P-gp-mediated transport activity is saturable, and is subject to modulation by inhibition and induction, which can affect the pharmacokinetics, efficacy or safety of P-gp substrates. In addition, many of the P-gp substrates overlap with CYP3A4 substrates, and several psychotropic drugs that are P-gp substrates are also CYP3A4 substrates. Therefore, psychotropic drugs that are P-gp substrates may cause a drug interaction when P-gp inhibitors and inducers are coadministered, or when psychotropic drugs or other medicines that are P-gp substrates are added to a prescription. Hence, it is clinically important to accumulate data about drug interactions through studies on P-gp, in addition to CYP3A4, to assist in the selection of appropriate psychotropic medications and in avoiding inappropriate combinations of therapeutic agents. There is currently insufficient information available on the psychotropic drug interactions related to P-gp, and therefore we summarize the recent clinical data in this review. PMID:23023659

Akamine, Yumiko; Yasui-Furukori, Norio; Ieiri, Ichiro; Uno, Tsukasa

2012-11-01

64

Oral and inhaled corticosteroids: Differences in P-glycoprotein (ABCB1) mediated efflux  

SciTech Connect

There is concern that P-glycoprotein mediated efflux contributes to steroid resistance. Therefore, this study examined bidirectional corticosteroid transport and induction capabilities for P-glycoprotein (P-gp) to understand which of the systemic and inhaled corticosteroids interacted with P-gp to the greatest extent. Hydrocortisone, prednisolone, prednisone, methylprednisolone, and dexamethasone represented systemically active drugs, while fluticasone propionate, beclomethasone dipropionate, ciclesonide and budesonide represented inhaled corticosteroids. Aldosterone and fludrocortisone represented mineralocorticoids. All drugs were detected using individually optimised HPLC protocols. Transport studies were conducted through Caco-2 monolayers. Hydrocortisone and aldosterone had efflux ratios below 1.5, while prednisone showed a P-gp mediated efflux ratio of only 1.8 compared to its active drug, prednisolone, with an efflux ratio of 4.5. Dexamethasone and beclomethasone had efflux ratios of 2.1 and 3.3 respectively, while this increased to 5.1 for methylprednisolone. Fluticasone showed an efflux ratio of 2.3. Protein expression studies suggested that all of the inhaled corticosteroids were able to induce P-gp expression, from 1.6 to 2 times control levels. Most of the systemic corticosteroids had higher passive permeability (> 20 × 10{sup ?6} cm/s) compared to the inhaled corticosteroids (> 5 × 10{sup ?6} cm/s), except for budesonide, with permeability similar to the systemic corticosteroids. Inhaled corticosteroids are not transported by P-gp to the same extent as systemic corticosteroids. However, they are able to induce P-gp production. Thus, inhaled corticosteroids may have greater interactions with other P-gp substrates, but P-gp itself is less likely to influence resistance to the drugs. -- Highlights: ? Inhaled corticosteroids are only weak substrates for P-gp, including budesonide. ? Inhaled corticosteroid potent P-gp inducers especially fluticasone and beclomethasone. ? Systemic corticosteroids are weak P-gp inducers. ? Mineralocorticoids not affected by P-gp mediated efflux.

Crowe, Andrew, E-mail: a.p.crowe@curtin.edu.au; Tan, Ai May

2012-05-01

65

In vitro modulation of ABCB1\\/P-glycoprotein expression by polyphenols from Mangifera indica  

Microsoft Academic Search

Many plant compounds are able to modulate the activity and\\/or the expression of the major multidrug transporter ABCB1\\/P-glycoprotein (P-gp). In this study, mango (Mangifera indica L.) stem bark extract (MSBE), its main polyphenol mangiferin and the mangiferin aglycone derivative norathyriol, as well as catechin, gallic acid and quercetin, were investigated for their potential ability to influence ABCB1 gene and P-gp

Elisabetta Chieli; Nadia Romiti; Idania Rodeiro; Gabino Garrido

2010-01-01

66

Modification of the P-Glycoprotein Dependent Pharmacokinetics of Digoxin in Rats by Human Recombinant Interferon-?  

Microsoft Academic Search

Purpose. This study was conducted to investigate in vivo the impact of interferon-alpha (IFN)-a on P-glycoprotein (P-gp) activity in rats by studying how its administration modifies the bioavailability of digoxin, a fairly pure P-gp substrate. Methods. Human recombinant IFN-a was given to rats (n =5 Y7 per group) daily for 8 days at different doses (IntronA \\\\ 10 6 ,

Makrem Ben Reguiga; Laurence Bonhomme-Faivre; Simone Orbach-Arbouys; Robert Farinotti

2005-01-01

67

Predicting P-Glycoprotein-Mediated Drug Transport Based On Support Vector Machine and Three-Dimensional Crystal Structure of P-glycoprotein  

PubMed Central

Human P-glycoprotein (P-gp) is an ATP-binding cassette multidrug transporter that confers resistance to a wide range of chemotherapeutic agents in cancer cells by active efflux of the drugs from cells. P-gp also plays a key role in limiting oral absorption and brain penetration and in facilitating biliary and renal elimination of structurally diverse drugs. Thus, identification of drugs or new molecular entities to be P-gp substrates is of vital importance for predicting the pharmacokinetics, efficacy, safety, or tissue levels of drugs or drug candidates. At present, publicly available, reliable in silico models predicting P-gp substrates are scarce. In this study, a support vector machine (SVM) method was developed to predict P-gp substrates and P-gp-substrate interactions, based on a training data set of 197 known P-gp substrates and non-substrates collected from the literature. We showed that the SVM method had a prediction accuracy of approximately 80% on an independent external validation data set of 32 compounds. A homology model of human P-gp based on the X-ray structure of mouse P-gp as a template has been constructed. We showed that molecular docking to the P-gp structures successfully predicted the geometry of P-gp-ligand complexes. Our SVM prediction and the molecular docking methods have been integrated into a free web server (http://pgp.althotas.com), which allows the users to predict whether a given compound is a P-gp substrate and how it binds to and interacts with P-gp. Utilization of such a web server may prove valuable for both rational drug design and screening.

Bikadi, Zsolt; Hazai, Istvan; Malik, David; Jemnitz, Katalin; Veres, Zsuzsa; Hari, Peter; Ni, Zhanglin; Loo, Tip W.; Clarke, David M.; Hazai, Eszter; Mao, Qingcheng

2011-01-01

68

Predicting P-glycoprotein-mediated drug transport based on support vector machine and three-dimensional crystal structure of P-glycoprotein.  

PubMed

Human P-glycoprotein (P-gp) is an ATP-binding cassette multidrug transporter that confers resistance to a wide range of chemotherapeutic agents in cancer cells by active efflux of the drugs from cells. P-gp also plays a key role in limiting oral absorption and brain penetration and in facilitating biliary and renal elimination of structurally diverse drugs. Thus, identification of drugs or new molecular entities to be P-gp substrates is of vital importance for predicting the pharmacokinetics, efficacy, safety, or tissue levels of drugs or drug candidates. At present, publicly available, reliable in silico models predicting P-gp substrates are scarce. In this study, a support vector machine (SVM) method was developed to predict P-gp substrates and P-gp-substrate interactions, based on a training data set of 197 known P-gp substrates and non-substrates collected from the literature. We showed that the SVM method had a prediction accuracy of approximately 80% on an independent external validation data set of 32 compounds. A homology model of human P-gp based on the X-ray structure of mouse P-gp as a template has been constructed. We showed that molecular docking to the P-gp structures successfully predicted the geometry of P-gp-ligand complexes. Our SVM prediction and the molecular docking methods have been integrated into a free web server (http://pgp.althotas.com), which allows the users to predict whether a given compound is a P-gp substrate and how it binds to and interacts with P-gp. Utilization of such a web server may prove valuable for both rational drug design and screening. PMID:21991360

Bikadi, Zsolt; Hazai, Istvan; Malik, David; Jemnitz, Katalin; Veres, Zsuzsa; Hari, Peter; Ni, Zhanglin; Loo, Tip W; Clarke, David M; Hazai, Eszter; Mao, Qingcheng

2011-01-01

69

Multidrug-resistant cells overexpressing P-glycoprotein are susceptible to DNA crosslinking agents due to attenuated Src/nuclear EGFR cascade-activated DNA repair activity.  

PubMed

We synthesized several novel bifunctional alkylating derivatives of 3a-aza-cyclopenta[a]indene (BO-1012, BO-1005, BO-1099 and BO-1101) that are potent DNA interstrand crosslinking agents. In in vitro cytotoxicity assay, these compounds were more cytotoxic to multidrug-resistant (MDR) cells, such as KBvin10, KBtax50 and CEM/VBL, than their parental cells. Using a xenograft model, BO-1012, at a dose of 5?mg/kg, partially suppressed the growth of parental KB cells but completely suppressed the growth of KBvin10 cells in nude mice. In exploring the possible mechanism, we found that DNA double-strand break (DSB) repair activity in MDR cells, KBvin10 and CEM/VBL, was significantly reduced compared with their parental cells, KB and CEM. Reduced DSB repair activity in KBvin10 cells was likely due to a defect in nuclear translocation of DNA-dependent protein kinase (DNA-PK), a component of the non-homologous end-joining repair machinery. Furthermore, BO-1012-induced DNA-PK translocation from the cytosol into the nucleus in KB cells is associated with the activation of the Src/nuclear epidermal growth factor receptor (EGFR) cascade, which is defective in MDR cells. As knockdown of P-glycoprotein (P-gp) by siRNA reactivated the Src/nuclear EGFR cascade, DNA-PK translocation and DNA repair activity in MDR cells, overexpression of P-gp attenuates the activity of DNA DSB repair through suppression of Src/nuclear EGFR cascade. Therefore, DNA interstrand crosslinking agents may have potential therapeutic use against P-gp-overexpressing MDR cells. PMID:22525278

Lee, P-C; Lee, H-J; Kakadiya, R; Sanjiv, K; Su, T-L; Lee, T-C

2013-02-28

70

Rhodamine Inhibitors of P-glycoprotein: An Amide/Thioamide "Switch" for ATPase Activity  

PubMed Central

We have examined 46 tetramethylrosamine/rhodamine derivatives with structural diversity in the heteroatom of the xanthylium core, the amino substituents of the 3- and 6-positions, and the alkyl, aryl, or heteroaryl group at the 9-substituent. These compounds were examined for affinity and ATPase stimulation in isolated MDR3 CL P-gp and human P-gp-His10, for their ability to promote uptake of calcein AM and vinblastine in multidrug-resistant MDCKII-MDR1 cells, and for transport in monolayers of MDCKII-MDR1 cells. Thioamide 31-S gave KM of 0.087 ?M in human P-gp. Small changes in structure among this set of compounds affected affinity as well as transport rate (or flux) even though all derivatives examined were substrates for P-gp. With isolated protein, tertiary amide groups dictate high affinity and high stimulation while tertiary thioamide groups give high affinity and inhibition of ATPase activity. In MDCKII-MDR1 cells, the tertiary thioamide-containing derivatives promote uptake of calcein AM and have very slow passive, absorptive, and secretory rates of transport relative to transport rates for tertiary amide-containing derivatives. Thioamide 31-S promoted uptake of calcein AM and inhibited efflux of vinblastine with IC50’s of ~2 ?M in MDCKII-MDR1 cells.

Gannon, Michael K.; Holt, Jason J.; Bennett, Stephanie M.; Wetzel, Bryan R.; Loo, Tip W.; Bartlett, M. Claire; Clarke, David M.; Sawada, Geri A.; Higgins, J. William; Tombline, Gregory; Raub, Thomas J.; Detty, Michael R.

2012-01-01

71

Impact of endogenous esterase activity on in vitro p-glycoprotein profiling of dabigatran etexilate in Caco-2 monolayers.  

PubMed

Dabigatran etexilate, a double prodrug of dabigatran, is a reversible, competitive, direct thrombin inhibitor that has been approved for use in many countries. A recent guideline from the European Medicines Agency on drug-drug interactions proposed dabigatran etexilate as a sensitive in vivo and in vitro probe substrate for intestinal P-glycoprotein (P-gp) inhibition. We therefore performed a series of in vitro studies to determine the best experimental conditions for evaluation of P-gp involvement on the transport process of dabigatran etexilate across colorectal adenocarcinoma Caco-2 cell monolayers. Experiments using expressed carboxylesterase 1 (CES1) and CES2 bactosomes revealed that dabigatran etexilate was hydrolyzed into BIBR 1087 by CES1 expressed in our Caco-2 cells. The impact of CES1-mediated BIBR 1087 formation during transcellular transport experiments was assessed by comparing several combinations of three experimental approaches: radioactivity detection using [(14)C]dabigatran etexilate as substrate, liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantification of dabigatran etexilate, and in the presence and absence of a CES inhibitor bis(p-nitrophenyl) phosphate (BNPP). The experimental approach that was based on the use of nonlabeled dabigatran etexilate together with LC-MS/MS quantification and the addition of BNPP was selected as the most favorable condition in which to correctly evaluate the permeability coefficient (Papp) of dabigatran etexilate and its transcellular transport by P-gp. The in vitro Caco-2 study at the selected condition revealed that dabigatran etexilate is a P-gp substrate with an efflux ratio of 13.8 and an intrinsic Papp, which is the Papp under the condition of complete blockage of P-gp by P-gp inhibitor, of 29 × 10(-6) cm/s. PMID:24212377

Ishiguro, Naoki; Kishimoto, Wataru; Volz, Astrid; Ludwig-Schwellinger, Eva; Ebner, Thomas; Schaefer, Olaf

2014-02-01

72

The chemosensitizing activity of inhibitors of glucosylceramide synthase is mediated primarily through modulation of P-gp function.  

PubMed

Glucosylceramide synthase (GCS) is a key enzyme engaged in the biosynthesis of glycosphingolipids and in regulating ceramide metabolism. Studies exploring alterations in GCS activity suggest that the glycolase may have a role in chemosensitizing tumor cells to various cancer drugs. The chemosensitizing effect of inhibitors of GCS (e.g. PDMP and selected analogues) has been observed with a variety of tumor cells leading to the proposal that the sensitizing activity of GCS inhibitors is primarily through increases in intracellular ceramide leading to induction of apoptosis. The current study examined the chemosensitizing activity of the novel GCS inhibitor, Genz-123346 in cell culture. Exposure of cells to Genz-123346 and to other GCS inhibitors at non-toxic concentrations can enhance the killing of tumor cells by cytotoxic anti-cancer agents. This activity was unrelated to lowering intracellular glycosphingolipid levels. Genz-123346 and a few other GCS inhibitors are substrates for multi-drug resistance efflux pumps such as P-gp (ABCB1, gP-170). In cell lines selected to over-express P-gp or which endogenously express P-gp, chemosensitization by Genz-123346 was primarily due to the effects on P-gp function. RNA interference studies using siRNA or shRNA confirmed that lowering GCS expression in tumor cells did not affect their responsiveness to commonly used cytotoxic drugs. PMID:21186402

Chai, Lilly; McLaren, Rajashree P; Byrne, Ann; Chuang, Wei-Lien; Huang, Yinyin; Dufault, Michael R; Pacheco, Joshua; Madhiwalla, Shruti; Zhang, Xiaokui; Zhang, Mindy; Teicher, Beverly A; Carter, Kara; Cheng, Seng H; Leonard, John P; Xiang, Yibin; Vasconcelles, Michael; Goldberg, Mark A; Copeland, Diane P; Klinger, Katherine W; Lillie, James; Madden, Stephen L; Jiang, Yide A

2011-03-01

73

Structure-activity relationships, ligand efficiency, and lipophilic efficiency profiles of benzophenone-type inhibitors of the multidrug transporter P-glycoprotein.  

PubMed

The drug efflux pump P-glycoprotein (P-gp) has been shown to promote multidrug resistance (MDR) in tumors as well as to influence ADME properties of drug candidates. Here we synthesized and tested a series of benzophenone derivatives structurally analogous to propafenone-type inhibitors of P-gp. Some of the compounds showed ligand efficiency and lipophilic efficiency (LipE) values in the range of compounds which entered clinical trials as MDR modulators. Interestingly, although lipophilicity plays a dominant role for P-gp inhibitors, all compounds investigated showed LipE values below the threshold for promising drug candidates. Docking studies of selected analogues into a homology model of P-glycoprotein suggest that benzophenones show an interaction pattern similar to that previously identified for propafenone-type inhibitors. PMID:22452412

Jabeen, Ishrat; Pleban, Karin; Rinner, Uwe; Chiba, Peter; Ecker, Gerhard F

2012-04-12

74

Regulation of brain endothelial cells migration and angiogenesis by P-glycoprotein/caveolin-1 interaction.  

PubMed

We have investigated the involvement of P-glycoprotein (P-gp)/caveolin-1 interaction in the regulation of brain endothelial cells (EC) migration and tubulogenesis. P-gp overexpression in MDCK-MDR cells was correlated with enhanced cell migration whereas treatment with P-gp inhibitors CsA or PSC833 reduced it. Transfection of RBE4 rat brain endothelial cells with mutated versions of MDR1, in the caveolin-1 interaction motif, decreased the interaction between P-gp and caveolin-1, enhanced P-gp transport activity and cell migration. Moreover, down-regulation of caveolin-1 in RBE4 cells by siRNA against caveolin-1 stimulated cell migration. Interestingly, the inhibition of P-gp/caveolin-1 interaction increased also EC tubulogenesis. Furthermore, decrease of P-gp expression by siRNA inhibited EC tubulogenesis. These data indicate that the level of P-gp/caveolin-1 interaction can modulate brain endothelial angiogenesis and P-gp dependent cell migration. PMID:18485890

Barakat, Stéphane; Turcotte, Sandra; Demeule, Michel; Lachambre, Marie-Paule; Régina, Anthony; Baggetto, Loris G; Béliveau, Richard

2008-08-01

75

Investigation of the Functional Role of P-Glycoprotein in Limiting the Oral Bioavailability of Lumefantrine  

PubMed Central

In the quest to explore the reason for the low and variable bioavailability of lumefantrine, we investigated the possible role of P-glycoprotein (P-gp) in lumefantrine intestinal absorption. An in situ single-pass intestinal perfusion study in rats with the P-gp inhibitor verapamil or quinidine and an ATPase assay with human P-gp membranes indicated that lumefantrine is a substrate of P-gp which limits its intestinal absorption. To confirm these findings, an in vivo pharmacokinetic study was performed in rats. The oral administration of verapamil (10 mg/kg of body weight) along with lumefantrine caused a significant increase in its bioavailability with a concomitant decrease in clearance. The increase in bioavailability of lumefantrine could be due to inhibition of P-gp and/or cytochrome P450 3A in the intestine/liver by verapamil. However, in a rat intestinal microsomal stability study, lumefantrine was found to be resistant to oxidative metabolism. Further, an in situ permeation study clearly showed a significant role of P-gp in limiting the oral absorption of lumefantrine. Thus, the increase in lumefantrine bioavailability with verapamil is attributed in part to the P-gp-inhibitory ability of verapamil. In conclusion, lumefantrine is a substrate of P-gp, and active efflux by P-gp across the intestine partly contributed to the low/variable bioavailability of lumefantrine.

Raju, Kanumuri S. R.; Singh, Sheelendra P.; Taneja, Isha

2014-01-01

76

Functional Impact of ABCB1 Variants on Interactions between P-Glycoprotein and Methadone  

PubMed Central

Methadone is a widely used substitution therapy for opioid addiction. Large inter-individual variability has been observed in methadone maintenance dosages and P-glycoprotein (P-gp) was considered to be one of the major contributors. To investigate the mechanism of P-gp’s interaction with methadone, as well as the effect of genetic variants on the interaction, Flp-In™-293 cells stably transfected with various genotypes of human P-gp were established in the present study. The RNA and protein expression levels of human P-gp were confirmed by real-time quantitative RT-PCR and western blot, respectively. Utilizing rhodamine 123 efflux assay and calcein-AM uptake study, methadone was demonstrated to be an inhibitor of wild-type human P-gp via non-competitive kinetic (IC50?=?2.17±0.10 µM), while the variant-type human P-gp, P-gp with 1236T-2677T-3435T genotype and P-gp with 1236T-2677A-3435T genotype, showed less inhibition potency (IC50?=?2.97±0.09 µM and 4.43±1.10 µM, respectively) via uncompetitive kinetics. Methadone also stimulated P-gp ATPase and inhibited verapamil-stimulated P-gp ATPase activity under therapeutic concentrations. These results may provide a possible explanation for higher methadone dosage requirements in patients carrying variant-type of P-gp and revealed the possible drug-drug interactions in patients who receive concomitant drugs which are also P-gp substrates.

Hung, Chin-Chuan; Chiou, Mu-Han; Teng, Yu-Ning; Hsieh, Yow-Wen; Huang, Chieh-Liang; Lane, Hsien-Yuan

2013-01-01

77

P-glycoprotein: from genomics to mechanism  

Microsoft Academic Search

Resistance to chemically different natural product anti-cancer drugs (multidrug resistance, or MDR) results from decreased drug accumulation, resulting from expression of one or more ATP-dependent efflux pumps. The first of these to be identified was P-glycoprotein (P-gp), the product of the human MDR1 gene, localized to chromosome 7q21. P-gp is a member of the large ATP-binding cassette (ABC) family of

Suresh V Ambudkar; Chava Kimchi-Sarfaty; Zuben E Sauna; Michael M Gottesman

2003-01-01

78

Pharmacodynamic consequences of P-glycoprotein-dependent pharmacokinetics of risperidone and haloperidol in mice.  

PubMed

Efflux transporters, like P-glycoprotein (P-gp), may limit the access of drugs to the brain via the blood-brain barrier. The antipsychotic drug risperidone and its active metabolite 9-hydroxyrisperidone (paliperidone) are substrates of P-gp. Motor behavior of P-gp deficient mice (mdr1a/1b (-/-, -/-)) and wild type animals on a rotarod after acute doses of risperidone or haloperidol, a nonsubstrate of P-gp, were analysed aiming to show that P-gp substrate properties of an antipsychotic drug have functional consequences. Behavioral tests revealed dose-dependent effects of 0.3-3 mg/kg risperidone in wild type animals 0.5-12 h after i.p. injection of the drug. In knockout mice the 0.3 mg/kg dose of risperidone was as effective as the 3 mg/kg dose in wild type mice. A dose of 0.3 mg/kg haloperidol, however, exhibited similar pharmacodynamic effects in both genotypes. Brain concentrations of risperidone plus 9-hydroxyrisperidone were 10-fold higher in knockout than in wild type animals whereas brain concentrations of haloperidol did not differ between the two genotypes. P-gp-dependent brain distribution kinetics and behavioral effects of risperidone give evidence that the expression of P-gp has an impact on psychotropic drug actions when treating patients with drugs that are substrates of P-gp. PMID:18164477

Kirschbaum, Katrin M; Henken, Stefanie; Hiemke, Christoph; Schmitt, Ulrich

2008-04-01

79

Small molecules that dramatically alter multidrug resistance phenotype by modulating the substrate specificity of P-glycoprotein  

PubMed Central

By screening a chemical library for the compounds protecting cells from adriamycin (Adr), a series of small molecules was isolated that interfered with the accumulation of Adr in mouse fibroblasts by enhancing efflux of the drug. Isolated compounds also stimulated efflux of Rhodamine 123 (Rho-123), another substrate of multidrug transporters. Stimulation of drug efflux was detectable in the cells expressing P-glycoprotein (P-gp), but not in their P-gp-negative variants, and was completely reversible by the P-gp inhibitors. A dramatic stimulation of P-gp activity against Adr and Rho-123 by the identified compounds was accompanied by suppression of P-gp-mediated efflux of other substrates, such as Taxol (paclitaxel) or Hoechst 33342, indicating that they act as modulators of substrate specificity of P-gp. Consistently, P-gp modulators dramatically altered the pattern of cross-resistance of P-gp-expressing cells to different P-gp substrates: an increase in resistance to Adr, daunorubicin, and etoposide was accompanied by cell sensitization to Vinca alkaloids, gramicidin D, and Taxol with no effect on cell sensitivity to colchicine, actinomycin D, puromycin, and colcemid, as well as to several non-P-gp substrates. The relative effect of P-gp modulators against different substrates varied among the isolated compounds that can be used as fine tools for analyzing mechanisms of drug selectivity of P-gp. These results raise the possibility of a rational control over cell sensitivity to drugs and toxins through modulation of P-gp activity by small molecules.

Kondratov, Roman V.; Komarov, Pavel G.; Becker, Yigal; Ewenson, Ariel; Gudkov, Andrei V.

2001-01-01

80

Cytocompatibility and P-glycoprotein inhibition of block copolymers: structure-activity relationship.  

PubMed

Amphiphilic polymeric micelles greatly improve the solubilization and sustained release of hydrophobic drugs and provide a protective environment for the cargo molecules in aqueous media, which favors lower drug administration doses, reduces adverse side effects, and increases blood circulation times and passive targeting to specific cells. These capabilities depend, among other variables, on the structure and composition of the polymer chains. Composition and, in particular, block length have been shown to play an important role in the modification of cellular responses such as drug internalization processes or transduction pathways when polymeric unimer/micelles are in close contact with cells. Here we present a detailed study about the role copolymer structure and composition play on cell viability and cellular response of several cell lines. To do that, more than 30 structurally related copolymers with diblock and triblock architectures containing different hydrophobic blocks and poly(ethylene oxide) as the common hydrophilic unit have been analyzed regarding cytocompatibility and potential as "active" cell response modifiers by testing their influence on the P-gp pump efflux mechanism responsible of multidrug resistance in cancerous cells. An empirical threshold for cell viability could be established at a copolymer EO/POeffective value above ca. 1.5 for copolymers with triblock structure, whereas no empirical rule could be observed for diblocks. Moreover, some of the tested copolymers (e.g., BO12EO227BO12 and EO57PO46EO57 that notably increased and C16EO455C16 that decreased the P-gp ATPase activity) were observed to act as efficient inhibitors of the P-gp efflux pump promoting an enhanced doxorubicin (DOXO) accumulation inside multidrug resistant (MDR) NCI-ADR-RES cells. PMID:23763603

Cambón, A; Brea, J; Loza, M I; Alvarez-Lorenzo, C; Concheiro, A; Barbosa, S; Taboada, P; Mosquera, V

2013-08-01

81

Role of P-glycoprotein in the intestinal absorption of tanshinone IIA, a major active ingredient in the root of Salvia miltiorrhiza Bunge.  

PubMed

The extracts from the roots of Salvia miltiorrhiza Bunge (Danshen) are widely and traditionally used in the treatment of angina pectoris, acute myocardial infarct, hyperlipidemia and stroke in China and other Asian countries. In this study, we have investigated the role of P-glycoprotein (P-gp) in the intestinal absorption of tanshinone IIA (TSA), a major active constituent of Danshen, using several in vitro and in vivo models. The oral bioavailability of TSA was about 2.9-3.4% in rats, with non-linear pharmacokinetics when its dosage increased. In a single pass rat intestinal perfusion model, the permeability coefficients (P(app)) based on TSA disappearance from the luminal perfusates (P(lumen)) were 6.2- to 7.2-fold higher (P < 0.01) than those based on drug appearance in mesenteric venous blood (P(blood)). The P(blood), but not P(lumen), was significantly increased when co-perfused with verapamil, or quinidine (both P-gp inhibitors). The uptake and efflux of TSA in confluent Caco-2 cells were significantly altered in the presence of verapamil, quinidine, MK-571, or probenecid. The transport of TSA across Caco-2 monolayers was pH-, temperature- and ATP-dependent. Furthermore, the transport from the apical (AP) to basolateral (BL) side of the Caco-2 monolayers was 3.3- to 8.5-fold lower than that from the BL to AP side, but such a polarized transport was attenuated by co-incubated verapamil or quinidine. A polarized transport was also observed in the control MDCKII cells and more apparent in MDR1-MDCKII monolayers, with the P(app) values of TSA in the BL-AP direction being 7- to 9-fold higher in MDR1-MDCKII monolayers than those in the control MDCKII cells. Moreover, TSA significantly inhibited P-gp-mediated transport of digoxin in P-gp-overexpressing membrane vesicles with an IC(50) of 2.6 microM, but stimulated vanadate-sensitive P-gp ATPase activity with estimated K(m) and V(max) values of 10.70 +/- 0.69 microM and 67.65 +/- 1.31 nmol/min/mg protein, respectively. TSA was extensively metabolized to tanshinone IIB (TSB), and two other oxidative metabolites in rat liver microsomes, but the formation rate of TSB in rat intestinal microsomes was only about 1/10 of that in liver microsomes. These findings indicate that TSA is a substrate and reversing agent for P-gp; and P-gp-mediated efflux of TSA into the gut lumen and the first-pass metabolism contribute to the low oral bioavailability. Further studies are needed to explore the role of other drug transporters and first-pass metabolism in the low bioavailability of TSA. PMID:17504222

Yu, Xi-Yong; Lin, Shu-Guang; Zhou, Zhi-Wei; Chen, Xiao; Liang, Jun; Liu, Pei-Qing; Duan, Wei; Chowbay, Balram; Wen, Jing-Yuan; Li, Chun-Guang; Zhou, Shu-Feng

2007-05-01

82

Reciprocal competition between lipid nanocapsules and P-gp for paclitaxel transport across Caco-2 cells.  

PubMed

Lipid nanocapsules (LNCs) have been shown to improve paclitaxel (Ptx) bioavailability and transport across an intestinal barrier model. In the present study, the interaction between P-glycoprotein (P-gp) and LNC transport across Caco-2 cells are investigated. Transport experiments have been performed on Caco-2 cells displaying different P-gp activities (early and later cell passages). The permeability of Ptx encapsulated in LNCs has been studied in the presence of P-gp inhibitors (verapamil and vinblastin) or unloaded LNCs. The uptake of dye-labelled LNCs was also observed in the presence of the same inhibitors. It was found that the permeability of Ptx varied depending on the passages with later ones showing higher absolute values (5.74+/-1.21 cms(-1) vs 133.41+/-5.74 cms(-1)). P-gp inhibition obtained with verapamil or vinblastin improved Ptx transport up to 98%. LNCs have also demonstrated their capacity to increase their own transport. Experiments performed with dye-labelled LNCs demonstrated an enhancement of the uptake of dye (Nile red), only in the presence of verapamil. These results demonstrated an effect of P-gp on the transport of Ptx when loaded in LNCs and support a direct effect of P-gp on their endocytosis in Caco-2 cells. These finding may assist in the development of new nanomedicine for oral administration. PMID:20438839

Roger, E; Lagarce, F; Garcion, E; Benoit, J-P

2010-08-11

83

Differential Involvement of P-Glycoprotein (ABCB1) in Permeability, Tissue Distribution, and Antinociceptive Activity of Methadone, Buprenorphine, and Diprenorphine: In Vitro and In Vivo Evaluation  

PubMed Central

Conclusions based on either in vitro or in vivo approach to evaluate the P-gp affinity status of opioids may be misleading. For example, in vitro studies indicated that fentanyl is a P-gp inhibitor while in vivo studies indicated that it is a P-gp substrate. Quite the opposite was evident for meperidine. The objective of this study was to evaluate the P-gp affinity status of methadone, buprenorphine and diprenorphine to predict P-gp-mediated drug-drug interactions and to determine a better candidate for management of opioid dependence. Two in vitro (P-gp ATPase and monolayer efflux) assays and two in vivo (tissue distribution and antinociceptive evaluation in mdr1a/b (?/?) mice) assays were used. Methadone stimulated the P-gp ATPase activity only at higher concentrations, while verapamil and GF120918 inhibited its efflux (p <0.05). The brain distribution and antinociceptive activity of methadone were enhanced (p <0.05) in P-gp knockout mice. Conversely, buprenorphine and diprenorphine were negative in all assays. P-gp can affect the PK/PD of methadone, but not buprenorphine or diprenorphine. Our report is in favor of buprenorphine over methadone for management of opioid dependence. Buprenorphine most likely is not a P-gp substrate and concerns regarding P-gp-mediated drug-drug interaction are not expected.

HASSAN, HAZEM E.; MYERS, ALAN L.; COOP, ANDREW; EDDINGTON, NATALIE D.

2012-01-01

84

Identification of the distance between the homologous halves of P-glycoprotein that triggers the high/low ATPase activity switch.  

PubMed

P-glycoprotein (P-gp, ABCB1) is an ATP-binding cassette drug pump that protects us from toxic compounds and confers multidrug resistance. Each homologous half contains a transmembrane domain with six transmembrane segments followed by a nucleotide-binding domain (NBD). The drug- and ATP-binding sites reside at the interface between the transmembrane domain and NBDs, respectively. Drug binding activates ATPase activity by an unknown mechanism. There is no high resolution structure of human P-gp, but homology models based on the crystal structures of bacterial, mouse, and Caenorhabditis elegans ATP-binding cassette drug pumps yield both open (NBDs apart) and closed (NBDs together) conformations. Molecular dynamics simulations predict that the NBDs can be separated over a range of distances (over 20 ?). To determine the distance that show high or low ATPase activity, we cross-linked reporter cysteines L175C (N-half) and N820C (C-half) with cross-linkers of various lengths that separated the halves between 6 and 30 ? (?-carbons). We observed that ATPase activity increased over 10-fold when the cysteines were cross-linked at distances between 6 and 19 ?, although cross-linking at distances greater than 20 ? yielded basal levels of activity. The results suggest that the ATPase activation switch appears to be turned on or off when L175C/N820 are clamped at distances less than or greater than 20 ?, respectively. We predict that the high/low ATPase activity switch may occur at a distance where the NBDs are predicted in molecular dynamic simulations to undergo pronounced twisting as they approach each other (Wise, J. G. (2012) Biochemistry 51, 5125-5141). PMID:24523403

Loo, Tip W; Clarke, David M

2014-03-21

85

Tetrandrine and fangchinoline, bisbenzylisoquinoline alkaloids from Stephania tetrandra can reverse multidrug resistance by inhibiting P-glycoprotein activity in multidrug resistant human cancer cells.  

PubMed

The overexpression of ABC transporters is a common reason for multidrug resistance (MDR) in cancer cells. In this study, we found that the isoquinoline alkaloids tetrandrine and fangchinoline from Stephania tetrandra showed a significant synergistic cytotoxic effect in MDR Caco-2 and CEM/ADR5000 cancer cells in combination with doxorubicin, a common cancer chemotherapeutic agent. Furthermore, tetrandrine and fangchinoline increased the intracellular accumulation of the fluorescent P-glycoprotein (P-gp) substrate rhodamine 123 (Rho123) and inhibited its efflux in Caco-2 and CEM/ADR5000 cells. In addition, tetrandrine and fangchinoline significantly reduced P-gp expression in a concentration-dependent manner. These results suggest that tetrandrine and fangchinoline can reverse MDR by increasing the intracellular concentration of anticancer drugs, and thus they could serve as a lead for developing new drugs to overcome P-gp mediated drug resistance in clinic cancer therapy. PMID:24856768

Sun, Yan Fang; Wink, Michael

2014-01-01

86

Expression of P-glycoprotein in adult T-cell leukemia cells  

Microsoft Academic Search

We have examined the expression of P-glycoprotein (P-gp) in adult T-cell leukemia (ATL) samples from 25 patients. Based on immunoblotting with a monoclonal antibody against P-gp, C219, 8 of 20 ATL patients were P-gp positive at the initial presentation. All 6 patients at the relapsed stage were P-gp positive, and refractory to chemotherapy. The expression of MDR1 mRNA in P-gp-positive

Yasuo Kuwazuru; Shuichi Hanada; Tatsuhiko Furukawa; Akihiko Yoshimura; Tomoyuki Sumizawa; Atae Utsunomiya; Kazuaki Ishibashi; Takeshi Saito; Kimiharu Uozumi; Masao Maruyama

1990-01-01

87

P-glycoprotein associates with Anxa2 and promotes invasion in multidrug resistant breast cancer cells.  

PubMed

Several recent studies have suggested that the acquisition of the multidrug resistance (MDR) phenotype is associated with elevated invasion and metastasis of tumor cells. P-glycoprotein (P-gp), the major determinant in the generation of the MDR phenotype, was reported to be correlated with a more aggressive phenotype and poor prognosis in many forms of malignancies. However, a clear understanding of the association is still lacking. We previously showed that Anxa2, a calcium-dependent phospholipid-binding protein, interacts with P-gp and contributes to the invasiveness of MDR breast cancer cells. In the present study, a strong positive correlation between MDR1 and Anxa2 mRNA expression in invasive breast cancer tissues during cancer progression was observed. In addition, exposure to adriamycin significantly enhanced motility in breast cancer cells and increased levels of P-gp and Anxa2. Moreover, inhibition of P-gp activity, using selective P-gp modulators, was found to significantly inhibit the invasive capacity of MCF-7/ADR cells without affecting the interaction and co-localization between P-gp and Anxa2. However, suppression of P-gp pump activity and knockdown of MDR1 expression both disrupted adriamycin-induced Anxa2 phosphorylation. Interestingly, P-gp was further demonstrated to interact with Src, a tyrosine kinase upstream of Anxa2. Taken together, our results indicate that P-gp may promote the invasion of MDR breast cancer cells by modulating the tyrosine phosphorylation of Anxa2. The interaction between Anxa2 and P-gp is possibly, at least in part, responsible for the association between MDR and invasive potential in breast cancer cells. PMID:24239898

Zhang, Fei; Zhang, Haichang; Wang, Zhiyong; Yu, Man; Tian, Ran; Ji, Wei; Yang, Yi; Niu, Ruifang

2014-01-15

88

Biochemical Mechanism of Modulation of Human P-glycoprotein by Stemofoline  

PubMed Central

The resistance to chemotherapeutic drugs by cancer cells is considered to be one of the major obstacles for success in the treatment of cancer. A major mechanism underlying this multidrug resistance is the overexpression of P-glycoprotein (P-gp), resulting in an insufficient drug delivery to the tumor sites. A previous study has shown that stemofoline, an alkaloid isolated from Stemona burkillii could enhance the sensitivity of chemotherapeutics in a synergistic fashion. In the present study, we have focused on the effect of stemofoline on the modulation of P-gp function in a multidrug resistant human cervical carcinoma cell line (KB-V1). The effects of stemofoline on a radiolabeled drug, [3H]-vinblastine, and fluorescent P-gp substrates, rhodamine123, and, calcein-AM accumulation or retention were investigated to confirm this finding. Stemofoline could increase the accumulation or retention of radiolabeled drugs or fluorescent P-gp substrates in a dose-dependent manner. For additional studies on drug-P-gp binding, P-gp ATPase activity was stimulated by stemofoline in a concentration-dependent manner. More evidence was offered that stemofoline inhibits the effect on photoaffinity labeling of P-gp with the [125I]-iodoarylazidoprazosin in a concentration-dependent manner. These data indicate that stemofoline may interact directly with P-gp and inhibit P-gp activity, whereas stemofoline has no effect on P-gp expression. Taken together, the results exhibit that stemofoline possesses an effective MDR modulator, and may be used in combination with conventional chemotherapeutic drugs to reverse MDR in cancer cells.

Chanmahasathien, Wisinee; Ohnuma, Shinobu; Ambudkar, Suresh V.; Limtrakul, Pornngarm

2013-01-01

89

Upregulation of P-glycoprotein activity in porcine oocytes and granulosa cells during in vitro maturation.  

PubMed

Multidrug resistance P-glycoprotein (Pgp), coded by the multidrug resistance type I (MDR1/ABCB1) gene, is an energy-dependent efflux pump and functions in systemic detoxification processes. In the present study, the expression and development of Pgp were evaluated in the porcine oocyte during in vitro maturation to compare with the expression of Pgp in cultured granulosa cells. As revealed by Western blotting using anti-human Pgp antibody, a single band of Pgp with an apparent molecular size of 170 kDa was detected in the germinal vesicle stage oocytes. The surface of GV oocyte was positively labeled by immunostaining. In the second metaphase oocyte after culture in the maturation medium containing porcine follicular fluid and human chorionic gonadotropin, the level of Pgp was increased. The elevation of the oocyte Pgp level was associated with increased activity of rhodamine 6G efflux from the oocyte, and its efflux was suppressed by verapamil, an inhibitor of Pgp. Removal of porcine follicular fluid from the maturation medium resulted in little alteration of the oocyte Pgp level. Expression of Pgp was also elevated in cultured porcine granulosa cells during cell maturation when stimulated with follicle-stimulating hormone or luteinizing hormone for 24-48 h. Collectively, the present results indicate that the transporting activity of P-glycoprotein upregulates in porcine oocytes and granulosa cells during exposure to gonadotropins or prior to ovulation. PMID:21289467

Yokota, Kazuko; Hirano, Takuro; Urata, Narumi; Yamauchi, Nobuhiko; Hattori, Masa-aki

2011-06-01

90

Reversal of P-glycoprotein-associated multidrug resistance by ivermectin  

Microsoft Academic Search

P-Glycoprotein (P-gp) causes a multidrug resistance (MDR) phenotype in tumour cells. In some cancers, the expression of P-gp has been correlated with low clinical response to chemotherapy and survival of patients. Previous studies have shown that certain lipophilic drugs bind to P-gp and reverse the MDR phenotype of tumour cells. In this study, we extend that list of compounds and

Jean-François Pouliot; Françoise L'Heureux; Zhi Liu; Roger K. Prichard; Elias Georges

1997-01-01

91

Regulation of volume-activated chloride channels by P-glycoprotein: phosphorylation has the final say!  

PubMed Central

P-glycoprotein (Pgp) is a transmembrane transporter causing efflux of a number of chemically unrelated drugs and is responsible for resistance to a variety of anticancer drugs during chemotherapy.Pgp overexpression in cells is also associated with volume-activated chloride channel activity; Pgp is thought to regulate such activity.Reversible phosphorylation is a possible mechanism for regulating the transport and chloride channel regulation functions of Pgp. Protein kinase C (PKC) is a good candidate for inducing such phosphorylation.Hierarchical multiple phosphorylation (e.g. of different serines and with different PKC isoforms) may shuttle the protein between its different states of activity (transport or channel regulation). Cell volume changes may trigger phosphorylation of Pgp at sites causing inhibition of transport.The possible regulation of chloride channels by Pgp and the potential involvement of reversible phosphorylation in such regulation is reviewed.

Idriss, Haitham T; Hannun, Yusuf A; Boulpaep, Emile; Basavappa, Srisaila

2000-01-01

92

The elimination of P-glycoprotein over-expressing cancer cells by antimicrobial cationic peptide NK-2: the unique way of multi-drug resistance modulation.  

PubMed

Most chemotherapeutics harm normal cells causing severe side effects and induce the development of resistance in cancer cells. Antimicrobial peptides (AMPs), recognized as anti-cancer agents, may overcome these limitations. The most studied mechanism underlying multi-drug resistance (MDR) is the over-expression of cell membrane transporter P-glycoprotein (P-gp), which extrudes a variety of hydrophobic drugs. Additionally, P-gp contributes to cell membrane composition and increases the net negative charge on cell surface. We postulated that NK-lysin derived cationic peptide NK-2 might discriminate and preferentially eliminate P-gp over-expressing cancer cells. To test this hypothesis, we employed MDR non-small cell lung carcinoma (NCI-H460/R) and colorectal carcinoma (DLD1-TxR) cell lines with high P-gp expression. MDR cancer cells that survived NK-2 treatment had decreased P-gp expression and were more susceptible to doxorubicin. We found that NK-2 more readily eliminated P-gp high-expressing cells. Acting in 'carpet-like' manner NK-2 co-localized with P-gp on the MDR cancer cell membrane. The inhibition of P-gp reduced the NK-2 effect in MDR cancer cells and, vice versa, NK-2 decreased P-gp transport activity. In conclusion, NK-2 could modulate MDR in unique way, eliminating the P-gp high-expressing cells from heterogeneous cancers and making them more vulnerable to classical drug treatment. PMID:23298945

Bankovi?, Jasna; Andrä, Jörg; Todorovi?, Nataša; Podolski-Reni?, Ana; Miloševi?, Zorica; Miljkovi?, Dor?e; Krause, Jannike; Ruždiji?, Sabera; Tani?, Nikola; Peši?, Milica

2013-04-15

93

Effect of knockdown of ezrin, radixin, and moesin on P-glycoprotein function in HepG2 cells.  

PubMed

Ezrin, radixin, and moesin (ERM) proteins regulate functional expression of certain transporters, but little is known about their effect on P-glycoprotein (P-gp). Here, we investigated the influence of ERM proteins on the expression and activity of P-gp at the transcriptional, translational, and posttranslational levels, using HepG2 as a model cell line. Knockdown of ezrin with RNA interference decreased the level of P-gp messenger RNA. On the contrary, knockdown of radixin caused a decrease of the P-gp gene product at the cell surface, but not in whole cell lysate. Furthermore, a significant increase in accumulation of rhodamine123, a typical P-gp substrate, was observed in radixin knockdown cells, compared with control cells. Knockdown of moesin did not influence the expression or function of P-gp. These results indicate that ezrin influences the expression of P-gp at the translational level, whereas radixin is involved in membrane localization of P-gp in HepG2 cells. PMID:21837648

Kano, Takashi; Wada, Sho; Morimoto, Kaori; Kato, Yukio; Ogihara, Takuo

2011-12-01

94

Inhibition of P-Glycoprotein by HIV Protease Inhibitors Increases Intracellular Accumulation of Berberine in Murine and Human Macrophages  

PubMed Central

Background HIV protease inhibitor (PI)-induced inflammatory response in macrophages is a major risk factor for cardiovascular diseases. We have previously reported that berberine (BBR), a traditional herbal medicine, prevents HIV PI-induced inflammatory response through inhibiting endoplasmic reticulum (ER) stress in macrophages. We also found that HIV PIs significantly increased the intracellular concentrations of BBR in macrophages. However, the underlying mechanisms of HIV PI-induced BBR accumulation are unknown. This study examined the role of P-glycoprotein (P-gp) in HIV PI-mediated accumulation of BBR in macrophages. Methodology and Principal Findings Cultured mouse RAW264.7 macrophages, human THP-1-derived macrophages, Wild type MDCK (MDCK/WT) and human P-gp transfected (MDCK/P-gp) cells were used in this study. The intracellular concentration of BBR was determined by HPLC. The activity of P-gp was assessed by measuring digoxin and rhodamine 123 (Rh123) efflux. The interaction between P-gp and BBR or HIV PIs was predicated by Glide docking using Schrodinger program. The results indicate that P-gp contributed to the efflux of BBR in macrophages. HIV PIs significantly increased BBR concentrations in macrophages; however, BBR did not alter cellular HIV PI concentrations. Although HIV PIs did not affect P-gp expression, P-gp transport activities were significantly inhibited in HIV PI-treated macrophages. Furthermore, the molecular docking study suggests that both HIV PIs and BBR fit the binding pocket of P-gp, and HIV PIs may compete with BBR to bind P-gp. Conclusion and Significance HIV PIs increase the concentration of BBR by modulating the transport activity of P-gp in macrophages. Understanding the cellular mechanisms of potential drug-drug interactions is critical prior to applying successful combinational therapy in the clinic.

Zha, Weibin; Wang, Guangji; Xu, Weiren; Liu, Xuyuan; Wang, Yun; Zha, Beth S.; Shi, Jian; Zhao, Qijin; Gerk, Phillip M.; Studer, Elaine; Hylemon, Phillip B.; Pandak, William M.; Zhou, Huiping

2013-01-01

95

Grape Seed Procyanidin Reversal of P-glycoprotein Associated Multi-Drug Resistance via Down-regulation of NF-?B and MAPK/ERK Mediated YB-1 Activity in A2780/T Cells  

PubMed Central

The expression and function of P-glycoprotein (P-gp) is associated with the phenotype of multi-drug resistance (MDR), leading chemotherapy failure of patients suffered with cancer. Grape seed procyanidin(GSP) is a natural polyphenol supplement with anti-inflammatory effect. Present study assessed a new use of GSP on the MDR reversal activity and its possible molecular mechanisms in MDR1-overpressing paclitaxel resistant ovarian cancer cells. Our results showed GSP significantly enhanced the cytotoxicity of paclitaxel and adriamycin in paclitaxel resistant A2780/T cells but its parental A2780 cells. Furthermore, GSP strongly inhibited P-gp expression by blocking MDR1 gene transcription, as well as, increased the intracellular accumulation of the P-gp substrate rhodamine-123 in A2780/T cells. Nuclear factor-?B(NF-?B) activity, I?B degradation level and NF-?B/p65 nuclear translocation induced by lipopolysaccharide (LPS) and receptor activator for nuclear factor-?B ligand (RANKL) were markedly inhibited by pre-treatment with GSP. Meanwhile, GSP inhibited MAPK/ERK pathway by decreasing the phosphorylation of ERK1/2, resulting in reduced the Y-box binding protein 1 (YB-1) activation with blocking its nuclear translocation. Moreover, the up-regulation of P-gp expression, the activation of AKT/NF-?B and MAPK/ERK pathway induced by LPS was attenuated by GSP administration. Compared with PDTC and U1026, inhibitor of NF-?B and MAPK/ERK respectively, GSP showed the same tendency of down-regulating NF-?B and MAPK/ERK mediated YB-1 activities. Thus, GSP reverses P-gp associated MDR by inhibiting the function and expression of P-gp through down-regulation of NF-?B activity and MAPK/ERK pathway mediated YB-1 nuclear translocation, offering insight into the mechanism of reversing MDR by natural polyphenol supplement compounds. GSP could be a new potential MDR reversal agent used for combination therapy with chemotherapeutics in clinic.

Wang, Sheng-qi; Duan, Lian; Huo, Qi-lu; Ren, Fei; Li, Guo-feng

2013-01-01

96

P-gp efflux pump inhibition potential of common environmental contaminants determined in vitro.  

PubMed

Across different species, cellular efflux pumps such as P-glycoprotein (P-gp; also termed multidrug resistance protein 1 [MDR1]) serve as a first line of defense by transporting toxic xenobiotics out of the cell. This mechanism is also active in aquatic organisms such as mussels, fish, and their larvae. Modulation of this resistance mechanism by chemical agents occurring in the environment could result in either higher or lower internal concentrations of toxic or endogenous compounds in cells. The aim of the present study was to explore and quantify the inhibition of the P-gp efflux pumps by several ubiquitous aquatic contaminants. The calcein-acetoxymethyl ester (calcein-AM) assay commonly used in pharmacological research was established with P-gp-overexpressing Madin-Darby canine kidney cells (MDCKII-MDR1) in a 96-well plate, avoiding extra washing, centrifugation, and lysis steps. This calcein-AM-based P-gp cellular efflux pump inhibition assay (CEPIA) was used to study the inhibition by commonly occurring environmental contaminants. Among others, the compounds pentachlorophenol, perfluorooctane sulfonate, and perfluorooctanoate strongly inhibited the P-gp-mediated efflux of calcein-AM while the chloninated alkanes did not seem to interact with the transporter. The fact that common pollutants can be potent modulators of the efflux transporters is a motive to further study whether this increases the toxicity of other contaminants present in the same matrices. PMID:24375866

Georgantzopoulou, Anastasia; Skoczy?ska, Ewa; Van den Berg, Johannes H J; Brand, Walter; Legay, Sylvain; Klein, Sebastian G; Rietjens, Ivonne M C M; Murk, Albertinka J

2014-04-01

97

P-glycoprotein activity in the blood-brain barrier is affected by virus-induced neuroinflammation and antipsychotic treatment.  

PubMed

A large percentage of schizophrenic patients respond poorly to antipsychotic treatment. This could be explained by inefficient drug transport across the blood-brain barrier due to P-glycoprotein mediated efflux. P-glycoprotein activity and expression in the blood-brain barrier can be affected by inflammation and pharmacotherapy. We therefore investigated the effect of herpes simplex virus type-1 (HSV-1) induced neuroinflammation and antipsychotic treatment on P-glycoprotein activity. Rats were inoculated with HSV-1 or PBS (control) on day 0 and treated with saline, clozapine or risperidone from day 0 up until day 4 post-inoculation. Positron emission tomography with the P-glycoprotein substrate [(11)C]verapamil was used to assess P-glycoprotein activity at day 6 post-inoculation. Disease symptoms in HSV-1 inoculated rats increased over time and were not significantly affected by treatment. The volume of distribution (VT) of [(11)C]verapamil was significantly lower (10-22%) in HSV-1 inoculated rats than in control rats. In addition, antipsychotic treatment significantly affected the VT of [(11)C]verapamil in all brain regions, although this effect was drug dependent. In fact, VT of [(11)C]verapamil was significantly increased (22-39%) in risperidone treated rats in most brain regions when compared to clozapine treated rats and in midbrain when compared to saline treated rats. No interaction between HSV-1 inoculation and antipsychotic treatment on VT of [(11)C]verapamil was found. In this study we demonstrated that HSV-1 induced neuroinflammation increased and risperidone treatment decreased P-glycoprotein activity. This finding is of importance for the understanding of treatment resistance in schizophrenia, and warrants further investigation of the underlying mechanism and the importance in clinical practice. PMID:24973705

Doorduin, Janine; de Vries, Erik F J; Dierckx, Rudi A; Klein, Hans C

2014-10-01

98

Effect of P-glycoprotein on intestinal absorption and brain penetration of antiallergic agent bepotastine besilate.  

PubMed

The antiallergic agent bepotastine besilate is a nonsedating, second-generation H1-antagonist with high oral absorption and negligible distribution into brain. To clarify the role of P-glycoprotein (P-gp) in the pharmacokinetics of bepotastine, intestinal absorption and brain penetration studies were performed. [(14)C]Bepotastine transport in P-gp-overexpressed LLC-PK1 cells indicated that bepotastine was a substrate of P-gp. The affinity of bepotastine to P-gp estimated by ATPase activity assay was low, with a K(m) value of 1.25 mM. After i.v. administration, the brain/plasma free concentration ratio in mdr1-knockout mice was 3 times higher than that in wild-type mice. The in situ intestinal absorption studies of [(14)C]bepotastine in rats showed a clear regional difference, showing highest permeability at the upper part of small intestine with a decreasing permeability in the descending part of small intestine. The apparent absorption rate constant (ka) of [(14)C]bepotastine in the small intestine was greatly increased by cyclosporin A and verapamil, especially in the distal portion, and the site-specific absorption of [(14)C]bepotastine disappeared. The concentration dependence of ka of [(14)C]bepotastine was observed with a higher ka at higher concentration (20 mM) compared with that at lower concentration (1 microM). In conclusion, bepotastine is a substrate for P-gp, and P-gp clearly limited the brain distribution of bepotastine, whereas the effect of P-gp on intestinal absorption of bepotastine was minimal, presumably because of high membrane permeability at the upper region of small intestine where P-gp is less expressed. Such intestinal absorption property of bepotastine is distinctly different from the low membrane-permeable P-gp substrate fexofenadine. PMID:16455807

Ohashi, Rikiya; Kamikozawa, Yukari; Sugiura, Mika; Fukuda, Hajime; Yabuuchi, Hikaru; Tamai, Ikumi

2006-05-01

99

Modulation of P-glycoprotein-Mediated Anticancer Drug Accumulation, Cytotoxicity, and ATPase Activity by Flavonoid Interactions  

Microsoft Academic Search

Flavonoids are components of plant foods and of many herbal medicines taken in combination with anticancer drugs. We have examined the potential of flavonoids to affect the accumulation and cytotoxicity of 3 cytotoxic drugs [vinblastine (VLB), daunorubicin (DNR), and colchicine (COL)] that are substrates for the ABC transporter, P-glycoprotein in a vinblastine-resistant T-cell leukemia, CEM\\/VBL100, that overexpresses P-glycoprotein. The effects

Van H. Tran; Denese Marks; Rujee K. Duke; Mary Bebawy; Colin C. Duke; Basil D. Roufogalis

2011-01-01

100

P-glycoprotein expression in Perna viridis after exposure to Prorocentrum lima, a dinoflagellate producing DSP toxins.  

PubMed

Bivalves naturally exposed to toxic algae have mechanisms to prevent from harmful effects of diarrhetic shellfish poisoning (DSP) toxins. However, quite few studies have examined the mechanisms associated, and the information currently available is still insufficient. Multixenobiotic resistance (MXR) is ubiquitous in aquatic invertebrates and plays an important role in defense against xenobiotics. Here, to explore the roles of P-glycoprotein (P-gp) in the DSP toxins resistance in shellfish, complete cDNA of P-gp gene in the mussel Perna viridis was cloned and analyzed. The accumulation of okadaic acid (OA), a main component of DSP toxins, MXR activity and expression of P-gp in gills of P. viridis were detected after exposure to Prorocentrum lima, a dinoflagellate producing DSP toxins in the presence or absence of P-gp inhibitors PGP-4008, verapamil (VER) and cyclosporin A (CsA). The mussel P. viridis P-gp closely matches MDR/P-gp/ABCB protein from various organisms, having a typical sequence organization as full transporters from the ABCB family. After exposure to P. lima, OA accumulation, MXR activity and P-gp expression significantly increased in gills of P. viridis. The addition of P-gp-specific inhibitors PGP-4008 and VER decreased MXR activity induced by P. lima, but had no effect on the OA accumulation in gills of P. viridis. However, CsA, a broad-spectrum inhibitor of ABC transporter not only decreased MXR activity, but also increased OA accumulation in gills of P. viridis. Together with the ubiquitous presence of other ABC transporters such as MRP/ABCC in bivalves and potential compensatory mechanism in P-gp and MRP-mediated resistance, we speculated that besides P-gp, other ABC transporters, especially MRP might be involved in the resistance mechanisms to DSP toxins. PMID:24811006

Huang, Lu; Wang, Jie; Chen, Wen-Chang; Li, Hong-Ye; Liu, Jie-Sheng; Tao Jiang; Yang, Wei-Dong

2014-08-01

101

Induction of P-Glycoprotein by Antiretroviral Drugs in Human Brain Microvessel Endothelial Cells  

PubMed Central

The membrane-associated drug transporter P-glycoprotein (P-gp) plays an essential role in drug efflux from the brain. Induction of this protein at the blood-brain barrier (BBB) could further affect the ability of a drug to enter the brain. At present, P-gp induction mediated by antiretroviral drugs at the BBB has not been fully investigated. Since P-gp expression is regulated by ligand-activated nuclear receptors, i.e., human pregnane X receptor (hPXR) and human constitutive androstane receptor (hCAR), these receptors could represent potential pathways involved in P-gp induction by antiretroviral drugs. The aims of this study were (i) to determine whether antiretroviral drugs currently used in HIV pharmacotherapy are ligands for hPXR or hCAR and (ii) to examine P-gp function and expression in human brain microvessel endothelial cells treated with antiretroviral drugs identified as ligands of hPXR and/or hCAR. Luciferase reporter gene assays were performed to examine the activation of hPXR and hCAR by antiretroviral drugs. The hCMEC/D3 cell line, which is known to display several morphological and biochemical properties of the BBB in humans, was used to examine P-gp induction following 72 h of exposure to these agents. Amprenavir, atazanavir, darunavir, efavirenz, ritonavir, and lopinavir were found to activate hPXR, whereas abacavir, efavirenz, and nevirapine were found to activate hCAR. P-gp expression and function were significantly induced in hCMEC/D3 cells treated with these drugs at clinical concentrations in plasma. Together, our data suggest that P-gp induction could occur at the BBB during chronic treatment with antiretroviral drugs identified as ligands of hPXR and/or hCAR.

Chan, Gary N. Y.; Patel, Rucha; Cummins, Carolyn L.

2013-01-01

102

Synthesis, and the antioxidant, neuroprotective and P-glycoprotein induction activity of 4-arylquinoline-2-carboxylates.  

PubMed

An efficient formic acid catalyzed one-pot synthesis of 4-arylquinoline 2-carboxylates in water via three-component coupling of arylamines, glyoxylates and phenylacetylenes has been described. 4-Arylquinoline 2-carboxylates 1o and 1q displayed significant antioxidant activity as indicated by their Fe-reducing power in the ferric reducing ability of plasma (FRAP) assay. The compounds were found to react directly with hydrogen peroxide, which might be one of the mechanisms of their antioxidant effect. Compounds 1o and 1q effectively quenched H2O2 and amyloid-?-generated reactive oxygen species (ROS) and also displayed significant protection against H2O2-induced neurotoxicity in human neuroblastoma SH-SY5Y cells. Additionally, all compounds exhibited promising P-glycoprotein induction activity in human adenocarcinoma LS-180 cells, indicating their potential to enhance amyloid-? clearance from Alzheimer's brains. Furthermore, all compounds were relatively non-toxic to SH-SY5Y and LS-180 cells (IC50 > 50 ?M). The promising antioxidant, ROS quenching, neuroprotective and Pgp-induction activity of these compounds strongly indicate their potential as anti-Alzheimer's agents. PMID:25007760

Bharate, Jaideep B; Wani, Abubakar; Sharma, Sadhana; Reja, Shahi Imam; Kumar, Manoj; Vishwakarma, Ram A; Kumar, Ajay; Bharate, Sandip B

2014-08-28

103

P-glycoprotein is localized in caveolae in resistant cells and in brain capillaries  

Microsoft Academic Search

A significant proportion of P-glycoprotein (P-gp) and caveolin was co-localized in caveolae isolated from resistant (CHRC5) cells overexpressing P-gp and from drug-sensitive Chinese hamster ovary cells (AuxB1). The proportion of P-gp and caveolin associated with caveolar microdomains was higher in CHRC5 cells grown in the presence of P-gp substrates (cyclosporin A or colchicine) than in untreated CHRC5 cells. Co-immunoprecipitation of

Michel Demeule; Julie Jodoin; Denis Gingras; Richard Béliveau

2000-01-01

104

7-Ketocholesterol induces P-glycoprotein through PI3K/mTOR signaling in hepatoma cells.  

PubMed

7-Ketocholesterol (7-KC) is found at an elevated level in patients with cancer and chronic liver disease. The up-regulation of an efflux pump, P-glycoprotein (P-gp) leads to drug resistance. To elucidate the effect of 7-KC on P-gp, P-gp function and expression were investigated in hepatoma cell lines Huh-7 and HepG2 and in primary hepatocyte-derived HuS-E/2 cells. At a subtoxic concentration, 48-h exposure to 7-KC reduced the intracellular accumulation and cytotoxicity of P-gp substrate doxorubicin in hepatoma cells, but not in HuS-E/2 cells. In Huh-7 cells, 7-KC elevated efflux function through the activation of phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway. 7-KC activated the downstream protein synthesis initiation factor 4E-BP1 and induced P-gp expression post-transcriptionally. The stimulation of efflux was reversible and could not be prevented by N-acetyl cysteine. Total cellular ATP content remained the same, whereas the lactate production was increased and fluorescence lifetime of protein-bound NADH was shortened. These changes suggested a metabolic shift to glycolysis, but glycolytic inhibitors did not eliminate 7-KC-mediated P-gp induction. These results demonstrate that 7-KC induces P-gp through PI3K/mTOR signaling and decreased the cell-killing efficacy of doxorubicin in hepatoma cells. PMID:23792120

Wang, Sheng-Fan; Chou, Yueh-Ching; Mazumder, Nirmal; Kao, Fu-Jen; Nagy, Leslie D; Guengerich, F Peter; Huang, Cheng; Lee, Hsin-Chen; Lai, Ping-Shan; Ueng, Yune-Fang

2013-08-15

105

Different Modalities of Intercellular Membrane Exchanges Mediate Cell-to-cell P-glycoprotein Transfers in MCF-7 Breast Cancer Cells*  

PubMed Central

Multi-drug resistance (MDR) is a phenomenon by which tumor cells exhibit resistance to a variety of chemically unrelated chemotherapeutic drugs. The classical form of multidrug resistance is connected to overexpression of membrane P-glycoprotein (P-gp), which acts as an energy dependent drug efflux pump. P-glycoprotein expression is known to be controlled by genetic and epigenetic mechanisms. Until now processes of P-gp gene up-regulation and resistant cell selection were considered sufficient to explain the emergence of MDR phenotype within a cell population. Recently, however, “non-genetic” acquisitions of MDR by cell-to-cell P-gp transfers have been pointed out. In the present study we show that intercellular transfers of functional P-gp occur by two different but complementary modalities through donor-recipient cells interactions in the absence of drug selection pressure. P-glycoprotein and drug efflux activity transfers were followed over 7 days by confocal microscopy and flow cytometry in drug-sensitive parental MCF-7 breast cancer cells co-cultured with P-gp overexpressing resistant variants. An early process of remote transfer was established based on the release and binding of P-gp-containing microparticles. Microparticle-mediated transfers were detected after only 4 h of incubation. We also identify an alternative mode of transfer by contact, consisting of cell-to-cell P-gp trafficking by tunneling nanotubes bridging neighboring cells. Our findings supply new mechanistic evidences for the extragenetic emergence of MDR in cancer cells and indicate that new treatment strategies designed to overcome MDR may include inhibition of both microparticles and Tunneling nanotube-mediated intercellular P-gp transfers.

Pasquier, Jennifer; Galas, Ludovic; Boulange-Lecomte, Celine; Rioult, Damien; Bultelle, Florence; Magal, Pierre; Webb, Glenn; Le Foll, Frank

2012-01-01

106

P-glycoprotein restricts access of cortisol and dexamethasone to the glucocorticoid receptor in placental BeWo cells.  

PubMed

Exposure of the fetus and placenta to maternal glucocorticoids is normally limited by the placental glucocorticoid barrier, which consists primarily of placental 11beta-hydroxy-steroid dehydrogenase type 2-mediated conversion of cortisol to the biologically inactive cortisone. Studies in the rodent brain show that P-glycoprotein (P-gp) is also an important physiological regulator of glucocorticoid access to the glucocorticoid receptor (GR) in target cells because it exports cortisol back into peripheral circulation against a concentration gradient. Whether P-gp of placental origin also has this capacity is unknown. Therefore, we used the human placental choriocarcinoma cell line BeWo and its daughter cell line, BeWoMDR, virally transduced with P-gp, to assess whether placental P-gp regulates access of glucocorticoids to the GR. Quantitative PCR showed that BeWoMDR cells express approximately 10-fold higher levels of P-gp mRNA than BeWo cells, and syncytialization increased P-gp mRNA by approximately 7-fold. Elevated P-gp expression in BeWoMDR cells reduced activation of the GR by dexamethasone and cortisol (10(-9) to 10(-6) M) to around 40% of that in BeWo cells. Inhibition of P-gp-mediated glucocorticoid efflux by cyclosporin A in BeWoMDR cells returned GR activation to levels similar to those in BeWo cells. Diffusion of dexamethasone across BeWoMDR monolayers occurred at a slower rate than that across BeWo monolayers, but this difference was eliminated by cyclosporin A. These data support the hypothesis that P-gp contributes to the placental glucocorticoid barrier. Thus, 11beta-hydroxysteroid dehydrogenase type 2 and P-gp may act in unison to reduce fetal and placental exposure to maternal glucocorticoids and thereby minimize their growth inhibitory actions. PMID:16873536

Mark, Peter J; Waddell, Brendan J

2006-11-01

107

Emerging significance of flavonoids as P-glycoprotein inhibitors in cancer chemotherapy.  

PubMed

Chemotherapy forms the mainstay of cancer treatment particularly for patients who do not respond to local excision or radiation treatment. However, cancer treatment by drugs is seriously limited by P-glycoprotein (P-gp) associated multi-drug resistance (MDR) in various tumor cells. On the other hand, it is now widely recognized that P-gp also influences drug transport across various biological membranes. P-gp transporter is widely present in the luminal surface of enterocytes, biliary canalicular surface of hepatocytes, apical surface of proximal tubular cells of kidney, endothelial cells of blood brain barrier, etc. thus affecting absorption, distribution, metabolism and excretion of xenobiotics. Clinical significance of above mentioned carrier is appreciated from the fact that more than fifty percent of existing anti-cancer drugs undergo inhibitable and saturable P-gp mediated efflux. Consequently, there is an increasing trend to optimize pharmacokinetics, enhance antitumour activity and reduce systemic toxicity of existing anti-cancer drugs by inhibiting P-gp mediated transport. Although a wide variety of P-gp inhibitors have been discovered, research efforts are underway to identify the most appropriate one. Flavonoids (polyphenolic herbal constituents) form the third generation, non-pharmaceutical category of P-gp inhibitors. The effects produced by some of these components are found to be comparable to those of well-known P-gp inhibitors verapamil and cyclosporine. Identification of effective P-gp modulator among herbal compounds have an added advantage of being safe, thereby making them ideal candidates for bioavailability enhancement, tissue-penetration (e.g. blood brain barrier (BBB)), decreasing biliary excretion and multi-drug resistance modulating agents. The dual effects, i.e. P-gp modulation and antitumor activity, of these herbal derivatives may synergistically act in cancer chemotherapy. This paper presents an overview of the investigations on the feasibility and application of flavonoids as P-gp modulators for improved efficacy of anti-cancer drugs like taxanes, anthracyclines, epipodophyllotoxins, camptothecins and vinca alkaloids. The review also focuses on flavonoid-drug interactions as well as the reversal activity of flavonoids useful against MDR. In addition, the experimental models which could be used for investigation on P-gp mediated efflux are also discussed. PMID:19470292

Bansal, Tripta; Jaggi, Manu; Khar, Roop K; Talegaonkar, Sushama

2009-01-01

108

Overexpression of P-glycoprotein but not its mRNA in multidrug resistant cells selected with hydroxyrubicin.  

PubMed

Previous studies have revealed that cultured cells treated with lipophilic natural products containing aromatic rings and basic amino group usually yielded multidrug resistant (MDR) variants. These MDR cells overexpress P-glycoprotein (P-gp), most often due to gene amplification or transcriptional activation of mdr/P-gp genes. Doxorubicin (Dox) is an anthracycline that belongs to this group of compounds. To explore the possible resistance mechanism(s) to anthracyclines that do not involve P-gp, we use a Dox analog, hydroxyrubicin (HyR) or WP159, which contains a C3' hydroxy group in replacement of the amino group in the sugar moiety of Dox thereby reducing basicity and eliminating positive charge in the parental compound to establish HyR-resistant cell lines. These resistant cells displayed the MDR phenotype and overexpressed P-gp as analyzed by Western blot analyses and immunohistochemical staining using two different anti-P-gp antibodies. Strikingly, the levels of P-gp mRNA in the majority of these MDR cells remained comparable to those in the drug-sensitive counterparts by slot blot hybridization. These results implicate that the basic center of the selecting agent is a critical determinant for generating diverse MDR variants, and that HyR may have a posttranscriptional effect on P-gp biosynthesis. This is the first report suggesting that cultured cells exposed to a particular selecting agent may give rise to particular subtype of MDR variants. PMID:7531410

Zhao, J Y; Savaraj, N; Song, R; Priebe, W; Kuo, M T

1994-01-01

109

Inhibition of P-glycoprotein-mediated paclitaxel resistance by reversibly linked quinine homodimers.  

PubMed

P-glycoprotein (P-gp), an ATP-dependent drug efflux pump, has been implicated in multidrug resistance of several cancers as a result of its overexpression. In this work, rationally designed second-generation P-gp inhibitors are disclosed, based on dimerized versions of the substrates quinine and quinidine. These dimeric agents include reversible tethers with a built-in clearance mechanism. The designed agents were potent inhibitors of rhodamine 123 efflux in cultured cancer cell lines that display high levels of P-gp expression at the cell surface and in transfected cells expressing P-gp. The quinine homodimer Q2, which was tethered by reversible ester bonds, was particularly potent (IC(50) approximately 1.7 microM). Further studies revealed that Q2 inhibited the efflux of a range of fluorescent substrates (rhodamine 123, doxorubicin, mitoxantrone, and BODIPY-FL-prazosin) from MCF-7/DX1 cells. The reversibility of the tether was confirmed in experiments showing that Q2 was readily hydrolyzed by esterases in vitro (t(1/2) approximately 20 h) while demonstrating high resistance to nonenzymatic hydrolysis in cell culture media (t(1/2) approximately 21 days). Specific inhibition of [(125)I]iodoarylazidoprazosin binding to P-gp by Q2 verified that the bivalent agent interacted specifically with the drug binding site(s) of P-gp. Q2 was also an inhibitor of verapamil-stimulated ATPase activity. In addition, low concentrations of Q2 stimulated basal P-gp ATPase levels. Finally, Q2 was shown to inhibit the transport of radiolabeled paclitaxel (Taxol) in MCF-7/DX1 cells, and it completely reversed the P-gp-mediated paclitaxel resistance phenotype. PMID:18945821

Pires, Marcos M; Emmert, Dana; Hrycyna, Christine A; Chmielewski, Jean

2009-01-01

110

Species differences of inhibitory effects on P-glycoprotein-mediated drug transport.  

PubMed

Previously, we clarified the species differences in P-glycoprotein (P-gp)-mediated drug transport activity using human MDR1, monkey MDR1, canine MDR1, rat MDR1a, rat MDR1b, mouse mdr1a, and mouse mdr1b transfected LLC-PK(1) cell lines. However, the species differences in the inhibitory effects on P-gp-mediated drug transport have not been clarified yet. The purpose of the present study was to evaluate the species differences in the inhibitory effects of typical P-gp inhibitors, quinidine and verapamil, on P-gp-mediated drug transport using MDR1 transfected cell lines. The transcellular transport of [(3)H]daunorubicin, [(3)H]digoxin, and [mebmt-beta-(3)H]cyclosporin A across monolayers of the MDR1 transfected cells were measured in the presence or absence of P-gp inhibitors. On daunorubicin transport, the relative IC(50) value (quinidine IC(50)/verapamil IC(50)) of human P-gp was 5.25 and those from other species ranged from 0.89 to 10.70. The transport of digoxin and cyclosporin A also showed different relative IC(50) values among human, monkey, canine, rat, and mouse P-gps. The present study revealed that species differences in the inhibitory effects on P-gp-mediated drug transport should not be disregarded among human, monkey, canine, rat, and mouse. This study will provide useful information for predicting drug interactions mediated by P-gp. PMID:17094122

Suzuyama, Naoto; Katoh, Miki; Takeuchi, Toshiyuki; Yoshitomi, Sumie; Higuchi, Tomoaki; Asashi, Satoru; Yokoi, Tsuyoshi

2007-06-01

111

Ligand and Structure-Based Classification Models for Prediction of P-Glycoprotein Inhibitors  

PubMed Central

The ABC transporter P-glycoprotein (P-gp) actively transports a wide range of drugs and toxins out of cells, and is therefore related to multidrug resistance and the ADME profile of therapeutics. Thus, development of predictive in silico models for the identification of P-gp inhibitors is of great interest in the field of drug discovery and development. So far in silico P-gp inhibitor prediction was dominated by ligand-based approaches because of the lack of high-quality structural information about P-gp. The present study aims at comparing the P-gp inhibitor/noninhibitor classification performance obtained by docking into a homology model of P-gp, to supervised machine learning methods, such as Kappa nearest neighbor, support vector machine (SVM), random fores,t and binary QSAR, by using a large, structurally diverse data set. In addition, the applicability domain of the models was assessed using an algorithm based on Euclidean distance. Results show that random forest and SVM performed best for classification of P-gp inhibitors and noninhibitors, correctly predicting 73/75% of the external test set compounds. Classification based on the docking experiments using the scoring function ChemScore resulted in the correct prediction of 61% of the external test set. This demonstrates that ligand-based models currently remain the methods of choice for accurately predicting P-gp inhibitors. However, structure-based classification offers information about possible drug/protein interactions, which helps in understanding the molecular basis of ligand-transporter interaction and could therefore also support lead optimization.

2013-01-01

112

Modulation of drug-stimulated ATPase activity of human MDR1/P-glycoprotein by cholesterol  

PubMed Central

MDR1 (multidrug resistance 1)/P-glycoprotein is an ATP-driven transporter which excretes a wide variety of structurally unrelated hydrophobic compounds from cells. It is suggested that drugs bind to MDR1 directly from the lipid bilayer and that cholesterol in the bilayer also interacts with MDR1. However, the effects of cholesterol on drug–MDR1 interactions are still unclear. To examine these effects, human MDR1 was expressed in insect cells and purified. The purified MDR1 protein was reconstituted in proteoliposomes containing various concentrations of cholesterol and enzymatic parameters of drug-stimulated ATPase were compared. Cholesterol directly binds to purified MDR1 in a detergent soluble form and the effects of cholesterol on drug-stimulated ATPase activity differ from one drug to another. The effects of cholesterol on Km values of drug-stimulated ATPase activity were strongly correlated with the molecular mass of that drug. Cholesterol increases the binding affinity of small drugs (molecular mass <500 Da), but does not affect that of drugs with a molecular mass of between 800 and 900 Da, and suppresses that of valinomycin (molecular mass >1000 Da). Vmax values for rhodamine B and paclitaxel are also increased by cholesterol, suggesting that cholesterol affects turnover as well as drug binding. Paclitaxel-stimulated ATPase activity of MDR1 is enhanced in the presence of stigmasterol, sitosterol and campesterol, as well as cholesterol, but not ergosterol. These results suggest that the drug-binding site of MDR1 may best fit drugs with a molecular mass of between 800 and 900 Da, and that cholesterol may support the recognition of smaller drugs by adjusting the drug-binding site and play an important role in the function of MDR1.

Kimura, Yasuhisa; Kioka, Noriyuki; Kato, Hiroaki; Matsuo, Michinori; Ueda, Kazumitsu

2006-01-01

113

P-Glycoprotein-Mediated Resistance to Hsp90Directed Therapy Is Eclipsed by the Heat Shock Response  

Microsoft Academic Search

Despite studies that show the antitumor activity of Hsp90 inhibitors, such as geldanamycin (GA) and its derivative 17-allylamino-demethoxygeldanamycin (17-AAG), recent reports indicate that these inhibitors lack significant single- agent clinical activity. Resistance to Hsp90 inhibitors has been previously linked to expression of P-glycoprotein (P-gp) and the multidrug resistant (MDR) phenotype. However, the stress response induced by GA treatment can also

Andrea K. McCollum; Cynthia J. TenEyck; Bridget Stensgard; Bruce W. Morlan; Karla V. Ballman; Robert B. Jenkins; David O. Toft; Charles Erlichman

2008-01-01

114

Interaction of drugs with P-glycoprotein in brain capillaries  

Microsoft Academic Search

P-glycoprotein (P-gp) is expressed at high levels in a variety of non-cancerous tissues such as the endothelial cells of the blood-brain barrier (BBB) capillaries. These thin capillaries tightly regulate the movement of substrates from the circulating blood into the brain. P-gp may be involved in the exclusion of various drugs from the capillary endothelial cells, blocking their entry into the

Lucie Jetté; Gérard F. Murphy; Jean-Marie Leclerc; Richard Béliveau

1995-01-01

115

Blood-brain barrier pharmacoproteomics-based reconstruction of the in vivo brain distribution of p-glycoprotein substrates in cynomolgus monkeys.  

PubMed

The aim of this study was to investigate whether in vivo drug distribution in brain in monkeys can be reconstructed by integrating four factors: protein expression levels of P-glycoprotein (P-gp)/multidrug resistance protein 1 at the blood-brain barrier (BBB), in vitro transport activity per P-gp molecule, and unbound drug fractions in plasma and brain. For five P-gp substrates (indinavir, quinidine, loperamide, paclitaxel, and verapamil) and one nonsubstrate (diazepam), in vitro P-gp transport activities were determined by measuring transcellular transport across monolayers of cynomolgus monkey P-gp-transfected LLC-PK1 and parental cells. In vivo P-gp functions at the BBB were reconstructed from in vitro P-gp transport activities and P-gp expression levels in transfected cells and cynomolgus brain microvessels. Brain-to-plasma concentration ratios (Kp,brain) were reconstructed by integrating the reconstructed in vivo P-gp functions with drug unbound fractions in plasma and brain. For all compounds, the reconstructed Kp,brain values were within a 3-fold range of observed values, as determined by constant intravenous infusion in adult cynomolgus monkeys. Among four factors, plasma unbound fraction was the most sensitive factor to species differences in Kp,brain between monkeys and mice. Unbound brain-to-plasma concentration ratios (Kp,uu,brain) were reconstructed as the reciprocal of the reconstructed in vivo P-gp functions, and the reconstructed Kp,uu,brain values were within a 3-fold range of in vivo values, which were estimated from observed Kp,brain and unbound fractions. This study experimentally demonstrates that brain distributions of P-gp substrates and nonsubstrate can be reconstructed on the basis of pharmacoproteomic concept in monkeys, which serve as a robust model of drug distribution in human brain. PMID:24947467

Uchida, Yasuo; Wakayama, Kentaro; Ohtsuki, Sumio; Chiba, Masato; Ohe, Tomoyuki; Ishii, Yasuyuki; Terasaki, Tetsuya

2014-09-01

116

The brain entry of risperidone and 9-hydroxyrisperidone is greatly limited by P-glycoprotein.  

PubMed

P-glycoprotein (P-gp) in the brain capillary endothelial cell limits the entry of many drugs into the brain. Our previous in-vitro study using ATPase as a marker of P-gp activity suggested that risperidone might be effectively transported by P-gp. In the present study, we compared the concentrations of risperidone and its major pharmacologically active metabolite 9-hydroxyrisperidone (9-OH-risperidone), in plasma, brain and various other tissues between abcb1ab-/- knockout mice which are functionally devoid of P-gp in their blood-brain barrier vs. FVB wild-type mice. One hour after intraperitoneal injection of 4 microg/g risperidone, the brain concentrations and ratios of brain:plasma concentrations of risperidone (13.1-fold and 12-fold respectively, p<0.05) and 9-OH-risperidone (29.4-fold and 29-fold respectively, p<0.01) were significantly higher in the abcb1ab-/- mice than those in the FVB mice. These results indicate that P-gp in the blood-brain barrier significantly influences the brain concentrations of risperidone and 9-OH-risperidone by limiting their CNS access. PMID:15683552

Wang, Jun-Sheng; Ruan, Ying; Taylor, Robin M; Donovan, Jennifer L; Markowitz, John S; DeVane, C Lindsay

2004-12-01

117

Uncoupled Active Transport Mechanisms Accounting for Low Selectivity in Multidrug Carriers: P-Glycoprotein and SMR Antiporters  

Microsoft Academic Search

.   The extraordinarily low substrate specificity of P-glycoprotein conflicts with the notion that specific substrate interactions\\u000a are required in the control of the reaction path in an active transport system. The difficulty is shown to be overcome by\\u000a a half-coupled mechanism in which the ATP reaction is linked to carrier transformations, as in a fully coupled system, but\\u000a in which

R. M. Krupka

1999-01-01

118

Kuguacin J isolated from Momordica charantia leaves inhibits P-glycoprotein (ABCB1)-mediated multidrug resistance  

PubMed Central

Multidrug-resistance (MDR), a phenomenon in which cancer cells exhibit simultaneous resistance to chemically unrelated drugs, is a major factor in the failure of chemotherapy in cancer patients. Resistance to chemotherapy has been correlated to the overexpression of ABC drug transporters including P-glycoprotein (P-gp) that actively efflux chemotherapeutic drugs from cancer cells. Our previous study showed that bitter melon (Momordica charantia) leaf extract (BMLE) was able to reverse the MDR phenotype by increasing the intracellular accumulation of chemotherapeutic drugs. In the present study, bioguided fractionation was used to identify the active component(s) of BMLE, which is able to modulate the function of P-gp and the MDR phenotype in a human cervical carcinoma cell line (KB-V1). We found that kuguacin J, one of the active components in BMLE, increased sensitivity to vinblastine and paclitaxel in KB-V1 cells. A flow cytometry assay indicated that kuguacin J inhibits the transport function of P-gp and thereby significantly increase the accumulation of rhodamine123 and calcein AM in the cells. These results were confirmed by [3H]-vinblastine transport assay. Kuguacin J significantly increases intracellular [3H]-vinblastine accumulation and decreased the [3H]-vinblastine efflux in the cells. Kuguacin J also inhibited the incorporation of [125I]-iodoarylazidoprazosin into P-gp in a concentration-dependent manner, indicating that kuguacin J directly interacts with the drug-substrate-binding site on P-gp. These results indicate that kuguacin J modulates the function of P-gp by directly interacting at the drug-substrate-binding site and it appears to be an effective inhibitor of P-gp activity in vitro, and thus could be developed as an effective chemosensitizer to treat multidrug-resistant cancers.

Pitchakarn, Pornsiri; Ohnuma, Shinobu; Pintha, Komsak; Pompimon, Wilart; Ambudkar, Suresh V.; Limtrakul, Pornngarm

2012-01-01

119

Kuguacin J isolated from Momordica charantia leaves inhibits P-glycoprotein (ABCB1)-mediated multidrug resistance.  

PubMed

Multidrug resistance (MDR) is a major factor in the failure of chemotherapy in cancer patients. Resistance to chemotherapy has been correlated to the overexpression of ABC drug transporters including P-glycoprotein (P-gp) that actively efflux chemotherapeutic drugs from cancer cells. Our previous study showed that bitter melon (Momordica charantia) leaf extract (BMLE) was able to reverse the MDR phenotype by increasing the intracellular accumulation of chemotherapeutic drugs. In the present study, bioguided fractionation was used to identify the active component(s) of BMLE that is able to modulate the function of P-gp and the MDR phenotype in a human cervical carcinoma cell line (KB-V1). We found that kuguacin J, one of the active components in BMLE, increased sensitivity to vinblastine and paclitaxel in KB-V1 cells. A flow cytometry assay indicated that kuguacin J inhibits the transport function of P-gp and thereby significantly increases the accumulation of rhodamine 123 and calcein AM in the cells. These results were confirmed by [³H]-vinblastine transport assay. Kuguacin J significantly increases intracellular [³H]-vinblastine accumulation and decreased the [³H]-vinblastine efflux in the cells. Kuguacin J also inhibited the incorporation of [¹²?I]-iodoarylazidoprazosin into P-gp in a concentration-dependent manner, indicating that kuguacin J directly interacts with the drug-substrate-binding site on P-gp. These results indicate that kuguacin J modulates the function of P-gp by directly interacting at the drug-substrate-binding site, and it appears to be an effective inhibitor of P-gp activity in vitro and thus could be developed as an effective chemosensitizer to treat multidrug-resistant cancers. PMID:21414769

Pitchakarn, Pornsiri; Ohnuma, Shinobu; Pintha, Komsak; Pompimon, Wilart; Ambudkar, Suresh V; Limtrakul, Pornngarm

2012-01-01

120

The impact of advancing age on P-glycoprotein expression and activity: current knowledge and future directions.  

PubMed

With the progressive ageing of the population, an increasing number of elderly patients are being exposed to multiple drugs because of co-existing morbidity states requiring pharmacological management. However, the knowledge of the effects of ageing on the pharmacokinetics and pharmacodynamics of individual drugs is far from being optimal as very few elderly subjects are studied in Phase I and II premarketing trials. The efflux transporter P-glycoprotein has recently emerged as a major determinant of drug disposition in humans. This review discusses the current knowledge about the effects of advancing age on P-glycoprotein expression and activity. A critical appraisal of the published literature and an overview on future research directions are also provided. PMID:17539740

Mangoni, Arduino A

2007-06-01

121

Inhibition of P-glycoprotein activity and reversal of cancer multidrug resistance by Momordica charantia extract  

Microsoft Academic Search

Purpose Multidrug resistance (MDR) is known as a problem limiting the success of therapy in patients treated long term with chemotherapeutic drugs. The drug resistance is mainly due to the overexpression of the 170 kDa P-glycoprotein (Pgp), which causes a reduction in drug accumulation in the cancer cells. In this study, novel chemical modulator(s) from bitter melon ( Momordica charantia L.)

Pornngarm Limtrakul; Orawan Khantamat; Komsak Pintha

2004-01-01

122

Intestinal transporters: enhanced absorption through P-glycoprotein-related drug interactions.  

PubMed

Introduction: There are many factors that can affect the absorption process of orally administered drugs. Intestinal transporters play an important role in drug absorption. These transporters are divided into two major classes: the solute carriers and the ATP-binding cassette (ABC) transporters. P-glycoprotein (P-gp), belonging to the ABC transporter superfamily, flushes out the substrate drugs from a cell, thus regulating the intestinal absorption of drugs. Areas covered: This review gives a brief overview of uptake and efflux transporters localized in the intestine. However, because P-gp has been identified as an important underlying mechanism of drug interactions in humans, the review is strongly focused on summarizing the currently available data on the impact of P-gp for absorption of drugs. Expert opinion: The concomitant use of P-gp substrates and inhibitors (preferably in a single nanocarrier formulation) could be an effective and safe way to improve the bioavailability of drugs. It seems the study of P-gp and modulating its activity may be an interesting therapeutic goal to be considered in future research. PMID:24708201

Zakeri-Milani, Parvin; Valizadeh, Hadi

2014-06-01

123

Down-regulation of P-gp expression and function after Mulberroside A treatment: Potential role of protein kinase C and NF-kappa B.  

PubMed

P-Glycoprotein (P-gp) plays a major role in drug-drug and herb-drug interactions. Mulberroside A (Mul A) is one of the main bioactive constituents of Sangbaipi, the dried root-bark of Morus alba L. (white mulberry), which is officially listed in the Chinese Pharmacopoeia. In the present study, we investigated the effect of Mul A treatment on mRNA expression and protein expression of P-gp in the Caco-2 cells by real-time qPCR and Western blot analysis. The effect of Mul A treatment on the function of P-gp in vitro and in vivo was assessed by Rho123 transport assay and a pharmacokinetic study. The potential roles of protein kinase C (PKC) and nuclear factor kappa B (NF-?B) in the expression regulation of P-gp after Mul A treatment were also investigated. The results revealed that Mul A treatment significantly decreased the mRNA and protein expression of P-gp in Caco-2 cells after treatment with Mul A (5-20?M). Furthermore, Mul A treatment displayed apparently inhibitory effect on the function of P-gp both in vitro and in vivo. In addition, activation of PKC activity and NF-?B nuclear translocation were observed in the presence of Mul A, which suggested that PKC and NF-?B might play crucial roles in Mul A-induced suppression of P-gp. Our study demonstrated that Mul A treatment could down-regulate P-gp expression and function accompanied by the activation of PKC and NF-?B, and this should be taken into consideration in potential herb-drug interactions when Mul A or M. alba are co-administered with other drugs transported by P-gp. PMID:24530447

Li, Yuhua; Huang, Ling; Zeng, Xuezhen; Zhong, Guoping; Ying, Mengjia; Huang, Min; Bi, Huichang

2014-04-25

124

The antiepileptic and anticancer agent, valproic acid, induces P-glycoprotein in human tumour cell lines and in rat liver  

PubMed Central

Background and purpose: The antiepileptic drug valproic acid, a histone deacetylase (HDAC) inhibitor, is currently being tested as an anticancer agent. However, HDAC inhibitors may interact with anticancer drugs through induction of P-glycoprotein (P-gp, MDR1) expression. In this study we assessed whether valproic acid induces P-gp function in tumour cells. We also investigated effects of valproic acid on the mRNA for P-gp and the cytochrome P450, CYP3A, in rat livers. >Experimental approach: Effects of valproic acid on P-gp were assessed in three tumour cell lines, SW620, KG1a and H4IIE. Accumulation of acetylated histone H3 in rats' livers treated for two or seven days with valproic acid was evaluated using a specific antibody. Hepatic expression of the P-gp genes, mdr1a, mdr1b and mdr2, was determined by real-time polymerase chain reaction. The effects of valproic acid on CYP3A were assessed by Northern blot analysis and CYP3A activity assays. Key results: Valproic acid (0.5–2.0?mM) induced P-gp expression and function up to 4-fold in vitro. The effect of a series of valproic acid derivatives on P-gp expression in SW620 and KG1a cells correlated with their HDAC inhibition potencies. Treatment of rats with 1?mmol kg?1 valproic acid for two and seven days increased hepatic histone acetylation (1.3- and 3.5-fold, respectively) and the expression of mdr1a and mdr2 (2.2–4.1-fold). Valpromide (0.5–2.0?mM) did not increase histone acetylation or P-gp expression in rat livers, but induced CYP3A expression. Conclusions: Valproic acid increased P-gp expression and function in human tumour cell lines and in rat liver. The clinical significance of this increase merits further investigation.

Eyal, S; Lamb, J G; Smith-Yockman, M; Yagen, B; Fibach, E; Altschuler, Y; White, H S; Bialer, M

2006-01-01

125

P-glycoprotein-dependent trafficking of nanoparticle-drug conjugates.  

PubMed

P-glycoprotein (P-gp) is considered to be the most prevalent and single most important cause of multidrug-resistance (MDR) in humans. Although the protein is well known to modulate the cellular trafficking of small molecule fluorophores, antimicrobials, and up to 50% of all cytotoxic chemotherapeutics, little is known about its interactions with nanoscale drug conjugates. Here, we use P-gp substrate-conjugated gold nanorods as model drug carriers to investigate P-gp-dependent cellular trafficking of nanoparticles. PMID:24616407

Dreaden, Erik C; Raji, Idris O; Austin, Lauren A; Fathi, Shaghayegh; Mwakwari, Sandra C; Humphries, William H; Kang, Bin; Oyelere, Adegboyega K; El-Sayed, Mostafa A

2014-05-01

126

Thiorhodamines Containing Amide and Thioamide Functionality as Inhibitors of the ATP-Binding Cassette Drug Transporter P-glycoprotein (ABCB1)  

PubMed Central

Twelve thiorhodamine derivatives have been examined for their ability to stimulate the ATPase activity of purified human P-glycoprotein (P-gp)-His10, to promote uptake of calcein AM and vinblastine into multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells, and for their rates of transport in monolayers of multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells. The thiorhodamine derivatives have structural diversity from amide and thioamide functionality (N,N-diethyl and N-piperidyl) at the 5-position of a 2-thienyl substituent on the thiorhodamine core and from diversity at the 3-amino substituent with N,N-dimethylamino, fused azadecalin (julolidyl), and fused N-methylcyclohexylamine (half-julolidyl) substituents. The julolidyl and half-julolidyl derivatives were more effective inhibitors of P-gp than the dimethylamino analogues. Amide-containing derivatives were transported much more rapidly than thioamide-containing derivatives.

Orchard, Alexandra; Schamerhorn, Gregory A.; Calitree, Brandon D.; Sawada, Geri A.; Loo, Tip W.; Bartlett, M. Claire; Clarke, David M.; Dettya, Michael R.

2012-01-01

127

Spinosad is a potent inhibitor of canine P-glycoprotein.  

PubMed

Inhibition of the drug transporter P-glycoprotein (P-gp) by the oral flea preventative spinosad has been suggested as the underlying cause of the drug-drug interaction with ivermectin. In this study, an in vitro model consisting of canine cells was validated to describe the inhibitory effect of drugs on canine P-gp. In this model, ivermectin, cyclosporin, verapamil, loperamide and ketoconazole inhibited P-gp function with IC50 values ranging from 0.1 to 3.7 ?mol/L. Spinosad was a potent inhibitor of canine P-gp with an IC50 value of 0.27 ?mol/L or 0.2 ?g/mL. The risk of spinosad causing P-gp related drug-drug interactions in the dog could be predicted by the IC50 value, the oral dosage and plasma concentrations. PMID:24582422

Schrickx, Johannes A

2014-04-01

128

Effects of curcumin on the pharmacokinetics of tamoxifen and its active metabolite, 4-hydroxytamoxifen, in rats: possible role of CYP3A4 and P-glycoprotein inhibition by curcumin.  

PubMed

The effects of curcumin, a natural anti-cancer compound, on the bioavailability and pharmacokinetics of tamoxifen and its metabolite, 4-hydroxytamoxifen, were investigated in rats. Tamoxifen and curcumin interact with cytochrom P450 (CYP) enzymes and P-glycoprotein, and the increase in the use of health supplements may result in curcumin being taken concomitantly with tamoxifen as a combination therapy to treat or prevent cancer. A single dose of tamoxifen was administered orally (9 mg x kg(-1)) with or without curcumin (0.5, 2.5 and 10 mg x kg(-1)) and intravenously (2mg x kg(-1)) with or without curcumin (2.5 and 10 mg x kg(-1)) to rats. The effects of curcumin on P-glycoprotein (P-gp) and CYP3A4 activity were also evaluated. Curcumin inhibited CYP3A4 activity with 50% inhibition concentration (IC50) values of 2.7 microM. In addition, curcumin significantly (P < 0.01 at 10 microM) enhanced the cellular accumulation of rhodamine-123 in MCF-7/ADR cells overexpressing P-gp in a concentration-dependent manner. This result suggested that curcumin significantly inhibited P-gp activity. Compared to the oral control group (given tamoxifen alone), the area under the plasma concentration-time curve (AUC(0-infinity)) and the peak plasma concentration (C(max)) of tamoxifen were significantly (P < 0.05 for 2.5 mg x kg(-1); P < 0.01 for 10 mg x kg(-1)) increased by 33.1-64.0% and 38.9-70.6%, respectively, by curcumin. Consequently, the absolute bioavailability of tamoxifen in the presence of curcumin (2.5 and 10 mg x kg(-1)) was 27.2-33.5%, which was significantly enhanced (P < 0.05 for 2.5 mg x kg(-1); P < 0.01 for 10 mg x kg(-1)) compared to that in the oral control group (20.4%). Moreover, the relative bioavailability of tamoxifen was 1.12- to 1.64-fold greater than that in the control group. Furthermore, concurrent use of curcumin significantly decreased (P < 0.05 for 10 mg x kg(-1)) the metabolite-parent AUC ratio (MR), implying that curcumin may inhibit the CYP-mediated metabolism of tamoxifen to its active metabolite, 4-hydroxytamoxifen. The enhanced bioavailability of tamoxifen by curcumin may be mainly due to inhibition of the CYP3A4-mediated metabolism of tamoxifen in the small intestine and/or in the liver and to inhibition of the P-gp efflux transporter in the small intestine rather than to reduction of renal elimination of tamoxifen, suggesting that curcumin may reduce the first-pass metabolism of tamoxifen in the small intestine and/or in the liver by inhibition of P-gp or CYP3A4 subfamily. PMID:22512082

Cho, Y A; Lee, W; Choi, J S

2012-02-01

129

Astragaloside ? reduces the expression level of P?glycoprotein in multidrug?resistant human hepatic cancer cell lines.  

PubMed

Astragaloside is a saponin widely used in traditional Chinese medicine and has been reported to be a potent multidrug resistance (MDR) reversal agent. The present study investigated the role of astragaloside ? (ASIV) in the regulation of P?glycoprotein (P?gp, encoded by the mdr1 gene) and its effect on the reversal of MDR. The activity of ASIV was evaluated using human hepatic cancer cells Bel?7402 and the corresponding 5?fluorouracil (5?FU) resistant cells Bel?7402/FU. ASIV (0.08 mg/ml) potentiated the cytotoxicity of 5?FU which was demonstrated using the MTT assay on Bel?7402/FU cells. ASIV reduced the expression of P?gp as was revealed by immunocytochemistry. Accumulation and efflux studies with the P?gp substrate, rhodamine 123 (Rh123), demonstrated that ASIV inhibited P?gp?mediated drug efflux. Furthermore, it was demonstrated that AS? enhanced the drug accumulation of 5?FU using a high performance liquid chromatography (HPLC) assay for drug resistant cells. Furthermore, ASIV may downregulate the expression of P?gp, which was examined using western blot analysis and polymerase chain reaction. In conclusion, the results of the present study indicated that ASIV reverses the drug resistance of Bel?7402/FU cells by downregulating the expression of mdr1. ASIV may represent a potent modulator of P?gp?mediated MDR in hepatic cancer therapy. PMID:24676670

Wang, Pei-Pei; Xu, Du-Juan; Huang, Can; Wang, Wei-Ping; Xu, Wen-Ke

2014-06-01

130

In silico structure-based screening of versatile P-glycoprotein inhibitors using polynomial empirical scoring functions  

PubMed Central

P-glycoprotein (P-gp) is an ATP (adenosine triphosphate)-binding cassette transporter that causes multidrug resistance of various chemotherapeutic substances by active efflux from mammalian cells. P-gp plays a pivotal role in limiting drug absorption and distribution in different organs, including the intestines and brain. Thus, the prediction of P-gp–drug interactions is of vital importance in assessing drug pharmacokinetic and pharmacodynamic properties. To find the strongest P-gp blockers, we performed an in silico structure-based screening of P-gp inhibitor library (1,300 molecules) by the gradient optimization method, using polynomial empirical scoring (POLSCORE) functions. We report a strong correlation (r2=0.80, F=16.27, n=6, P<0.0157) of inhibition constants (Kiexp or pKiexp; experimental Ki or negative decimal logarithm of Kiexp) converted from experimental IC50 (half maximal inhibitory concentration) values with POLSCORE-predicted constants (KiPOLSCORE or pKiPOLSCORE), using a linear regression fitting technique. The hydrophobic interactions between P-gp and selected drug substances were detected as the main forces responsible for the inhibition effect. The results showed that this scoring technique might be useful in the virtual screening and filtering of databases of drug-like compounds at the early stage of drug development processes.

Shityakov, Sergey; Forster, Carola

2014-01-01

131

Astragaloside IV reduces the expression level of P-glycoprotein in multidrug-resistant human hepatic cancer cell lines  

PubMed Central

Astragaloside is a saponin widely used in traditional Chinese medicine and has been reported to be a potent multidrug resistance (MDR) reversal agent. The present study investigated the role of astragaloside IV (ASIV) in the regulation of P-glycoprotein (P-gp, encoded by the mdr1 gene) and its effect on the reversal of MDR. The activity of ASIV was evaluated using human hepatic cancer cells Bel-7402 and the corresponding 5-fluorouracil (5-FU) resistant cells Bel-7402/FU. ASIV (0.08 mg/ml) potentiated the cytotoxicity of 5-FU which was demonstrated using the MTT assay on Bel-7402/FU cells. ASIV reduced the expression of P-gp as was revealed by immunocytochemistry. Accumulation and efflux studies with the P-gp substrate, rhodamine 123 (Rh123), demonstrated that ASIV inhibited P-gp-mediated drug efflux. Furthermore, it was demonstrated that ASIV enhanced the drug accumulation of 5-FU using a high performance liquid chromatography (HPLC) assay for drug resistant cells. Furthermore, ASIV may downregulate the expression of P-gp, which was examined using western blot analysis and polymerase chain reaction. In conclusion, the results of the present study indicated that ASIV reverses the drug resistance of Bel-7402/FU cells by downregulating the expression of mdr1. ASIV may represent a potent modulator of P-gp-mediated MDR in hepatic cancer therapy.

WANG, PEI-PEI; XU, DU-JUAN; HUANG, CAN; WANG, WEI-PING; XU, WEN-KE

2014-01-01

132

ADME evaluation in drug discovery. 10. Predictions of P-glycoprotein inhibitors using recursive partitioning and naive Bayesian classification techniques.  

PubMed

P-Glycoprotein (P-gp), an efflux transporter, plays a crucial role in drug pharmacokinetic properties (ADME), and is critical for multidrug resistance (MDR) by mediating the active transport of anticancer drugs from the intracellular to the extracellular compartment. Here we reported an original database of 1273 molecules that are categorized into P-gp inhibitors and noninhibitors. The impact of various physicochemical properties on P-gp inhibition was examined. We then built the decision trees from a training set of 973 compounds using the recursive partitioning (RP) technique and validated by an external test set of 300 compounds. The best decision tree correctly predicted 83.5% of the inhibitors and 67.0% of the noninhibitors in the test set. Finally, we applied naive Bayesian categorization modeling to establish classifiers for P-gp inhibitors. The Bayesian classifier gave average correct prediction for 81.7% of 973 compounds in the training set with leave-one-out cross-validation procedure and 81.2% of 300 compounds in the test set. By establishing multiple decision trees and Bayesian classifiers, we evaluated the impact of molecular fingerprints on classification by the prediction accuracy for the test set, and we found that the inclusion of molecular fingerprints improves the prediction obviously. As an unsupervised learner without tuning parameters, the Bayesian classifier employing fingerprints highlights the important structural fragments favorable or unfavorable for P-gp transport, which provides critical information for designing new efficient P-gp inhibitors. PMID:21413792

Chen, Lei; Li, Youyong; Zhao, Qing; Peng, Hui; Hou, Tingjun

2011-06-01

133

Predicting Binding to P-Glycoprotein by Flexible Receptor Docking  

PubMed Central

P-glycoprotein (P-gp) is an ATP-dependent transport protein that is selectively expressed at entry points of xenobiotics where, acting as an efflux pump, it prevents their entering sensitive organs. The protein also plays a key role in the absorption and blood-brain barrier penetration of many drugs, while its overexpression in cancer cells has been linked to multidrug resistance in tumors. The recent publication of the mouse P-gp crystal structure revealed a large and hydrophobic binding cavity with no clearly defined sub-sites that supports an “induced-fit” ligand binding model. We employed flexible receptor docking to develop a new prediction algorithm for P-gp binding specificity. We tested the ability of this method to differentiate between binders and nonbinders of P-gp using consistently measured experimental data from P-gp efflux and calcein-inhibition assays. We also subjected the model to a blind test on a series of peptidic cysteine protease inhibitors, confirming the ability to predict compounds more likely to be P-gp substrates. Finally, we used the method to predict cellular metabolites that may be P-gp substrates. Overall, our results suggest that many P-gp substrates bind deeper in the cavity than the cyclic peptide in the crystal structure and that specificity in P-gp is better understood in terms of physicochemical properties of the ligands (and the binding site), rather than being defined by specific sub-sites.

Dolghih, Elena; Bryant, Clifford; Renslo, Adam R.; Jacobson, Matthew P.

2011-01-01

134

In vitro modulation of ABCB1/P-glycoprotein expression by polyphenols from Mangifera indica.  

PubMed

Many plant compounds are able to modulate the activity and/or the expression of the major multidrug transporter ABCB1/P-glycoprotein (P-gp). In this study, mango (Mangifera indica L.) stem bark extract (MSBE), its main polyphenol mangiferin and the mangiferin aglycone derivative norathyriol, as well as catechin, gallic acid and quercetin, were investigated for their potential ability to influence ABCB1 gene and P-gp expression in HK-2 cells, a proximal tubule line constitutively expressing this transporter. Western blot analysis demonstrated a concentration-dependent decrease in P-gp in cells cultured in the presence of MSBE for 72 h. Gallic acid and quercetin also decreased the levels of P-gp at all studied concentrations, whereas catechin was almost ineffective. However, in cells exposed to mangiferin (10-200 microM), the P-gp amount showed a concentration- and time-dependent increase, being 2-fold higher than the controls after 72 h. Norathyriol (5 microM) induced P-gp, but the effect decreased at higher concentrations. The changes in the P-gp protein amount were correlated with relative changes in the ABCB1 mRNA content and with the efflux activity of the transporter. The transcriptional inhibitor 1-d-ribofuranosylbenzimidazole (DRB) contrasted the increased expression of ABCB1 by mangiferin, suggesting that the increase could be due to transcriptional up-regulation of ABCB1 mRNA. Mangiferin-treated cells overexpressing the transporter were protected against the cytotoxicity of the known P-gp substrate cyclosporine A. However, the opposite effect was not observed in cells pretreated with MSBE. These results demonstrate that MSBE and mango polyphenols, already shown in our previous studies to influence P-gp activity, may also interact with ABCB1/P-gp at the expression level. In particular, we show for the first time that the main mango polyphenol mangiferin up-regulates this multidrug transporter. The molecular mechanisms and the consequences of these effects, including the possibility of interactions with conventional drugs or other herbal constituents, remain to be elucidated. PMID:20513373

Chieli, Elisabetta; Romiti, Nadia; Rodeiro, Idania; Garrido, Gabino

2010-08-01

135

Involvement of AP-1 and NF-?B in the up-regulation of P-gp in vinblastine resistant Caco-2 cells.  

PubMed

Caco-2 is a widely used cell model in drug absorption and P-glycoprotein (P-gp, MDR1) substrate identification. Long-term vinblastine treatment of Caco-2 cells could increase the expression of P-gp; thus, the vinblastine resistant Caco-2 (Caco-2 vbl) cells can be used as a rapid and sensitive alternative model in identifying P-gp substrates. The mechanism of P-gp induction in this model is not clear; this study was therefore intended to clarify the possible factors involved in P-gp up-regulation in Caco-2 vbl cells. Since vinblastine is the inducer of both activator protein-1 (AP-1) and nuclear factor kappa B (NF-?B), we investigated the role of AP-1 and NF-?B in the regulation of MDR1 gene expression. Our results indicated that the AP-1 and NF-?B luciferase activity was higher in Caco-2 vbl cells than that in Caco-2 cells according to reporter gene assay. The mRNA expression of AP-1 subunit c-Jun and NF-?B was increased in Caco-2 vbl cells. The c-Jun inhibitor SP600125 and NF-?B inhibitor pyrrolidine dithiocarbamate (PDTC) suppressed the expression of MDR1 mRNA in Caco-2 vbl cells. In conclusion, this study provides the evidence that AP-1 and NF-?B are involved in the P-gp induction in Caco-2 vbl cells. PMID:24088727

Chen, Qiuxia; Bian, Yicong; Zeng, Su

2014-01-01

136

Inhibition of the multidrug transporter P-glycoprotein improves seizure control in phenytoin-treated chronic epileptic rats  

Microsoft Academic Search

Purpose: Overexpression of multidrug transporters such as P-glycoprotein (P-gp) may play a significant role in pharmacoresistance, by preventing antiepileptic drugs (AEDs) from reaching their targets in the brain. Until now, many studies have described increased P-gp expression in epileptic tissue or have shown that several AEDs act as substrates for P-gp. However, definitive proof showing the functional involvement of P-gp

Vliet van E. A; Rosalinde van Schaik; Peter M. Edelbroek; A. M. J. Redeker; Eleonora Aronica; Wytse J. Wadman; Nicola Marchi; Annamaria Vezzani; Jan A. Gorter

2006-01-01

137

Anti-AIDS agents 89. Identification of DCX derivatives as anti-HIV and chemosensitizing dual function agents to overcome P-gp-mediated drug resistance for AIDS therapy  

PubMed Central

In this study, 19 dicamphanoyl-dihydropyranochromone (DCP) and dicamphanoyl-dihydropyranoxanthone (DCX) derivatives, previously discovered as novel anti-HIV agents, were evaluated for their potential to reverse multi-drug resistance (MDR) in a cancer cell line over-expressing P-glycoprotein (P-gp). Seven compounds fully reversed resistance to vincristine (VCR) at 4 ?M, a 20-fold enhancement compared to the first generation chemosensitizer, verapamil (4 ?M). The mechanism of action of DCPs and DCXs was also resolved, since the most active compounds (3, 4, and 7) significantly increased intracellular drug accumulation due, in part, to inhibiting the P-gp mediated drug efflux from cells. We conclude that DCPs (3 and 4) and DCXs (7, 11, and 17) can exhibit polypharmacologic behavior by acting as dual inhibitors of HIV replication and chemoresistance mediated by P-gp. As such, they may be useful in combination therapy to overcome P-gp-associated drug resistance for AIDS treatment.

Zhou, Ting; Ohkoshi, Emika; Shi, Qian; Bastow, Kenneth F.; Lee, Kuo-Hsiung

2012-01-01

138

Activating PKC-?1 at the blood-brain barrier reverses induction of P-glycoprotein activity by dioxin and restores drug delivery to the CNS  

PubMed Central

Upregulation of blood–brain barrier (BBB) P-glycoprotein expression causes central nervous system (CNS) pharmacoresistance. However, activation of BBB protein kinase C-?1 (PKC-?1) rapidly reduces basal P-glycoprotein transport activity. We tested whether PKC-?1 activation would reverse CNS drug resistance caused by dioxin acting through aryl hydrocarbon receptor. A selective PKC-?1 agonist abolished the increase in P-glycoprotein activity induced by dioxin in isolated rat brain capillaries and reversed the effect of dioxin on brain uptake of verapamil in dioxin-dosed rats. Thus, targeting BBB PKC-?1 may be an effective strategy to improve drug delivery to the brain, even in drug-resistant individuals.

Wang, Xueqian; Hawkins, Brian T; Miller, David S

2011-01-01

139

Inhibition of P-glycoprotein-mediated transport by extracts of and monoterpenoids contained in Zanthoxyli Fructus  

Microsoft Academic Search

Citrus (rutaceous) herbs are often used in traditional medicine and Japanese cuisine and can be taken concomitantly with conventional medicine. In this study, the effect of various citrus-herb extracts on P-glycoprotein (P-gp)-mediated transport was examined in vitro to investigate a possible interaction with P-gp substrates. Component monoterpenoids of the essential oil in Zanthoxyli Fructus was screened to find novel P-gp

Naoko Yoshida; Akiyoshi Takagi; Hidenori Kitazawa; Junichi. Kawakami; Isao Adachi

2005-01-01

140

Nanoparticles attenuate P-glycoprotein\\/MDR1 function in A549 human alveolar epithelial cells  

Microsoft Academic Search

P-glycoprotein\\/MDR1 (P-gp) is a well-characterised membrane transporter relevant in drug disposition and multi-drug resistance. In this study, we aimed to investigate how far nanoparticulates impair the function of the P-gp transport system and which particle properties govern these interactions.Expression and function of P-gp was confirmed in A549 cell monolayers. Rhodamine 123 (Rh123) release studies were carried out in the presence

Johanna J. Salomon; Carsten Ehrhardt

2011-01-01

141

In vitro P-glycoprotein affinity for atypical and conventional antipsychotics  

Microsoft Academic Search

The transmembrane transporter P-glycoprotein (P-gp) is an ATP-dependent efflux pump for a wide range of drugs. P-gp potentially limits access to brain tissue of psychoactive substrates, but little is known about its specificity for antipsychotics. The objective of this study was to assess the affinity of some atypical antipsychotic drugs in vitro for P-gp as indicative of their potential as

David W. Boulton; C. Lindsay DeVane; Heidi L. Liston; John S. Markowitz

2002-01-01

142

Limited interaction between tacrolimus and P-glycoprotein in the rat small intestine  

Microsoft Academic Search

The significance of intestinal P-glycoprotein (P-gp) in determining the oral bioavailability of tacrolimus has been still controversial. In this study, we reevaluated the interaction of tacrolimus with P-gp in the rat small intestine, by evaluating its absorption from the rat small intestine and its modulating effect on the absorption of known P-gp substrates (digoxin, methylprednisolone, and vinblastine). Intestinal absorption of

Hiroshi Saitoh; Yuko Saikachi; Mikako Kobayashi; Michiko Yamaguchi; Masako Oda; Yoshimitsu Yuhki; Kazuhito Achiwa; Koji Tadano; Yasushi Takahashi; Bruce J. Aungst

2006-01-01

143

Marine natural products with P-glycoprotein inhibitor properties.  

PubMed

P-glycoprotein (P-gp) is a protein belonging to the ATP-binding cassette (ABC) transporters superfamily that has clinical relevance due to its role in drug metabolism and multi-drug resistance (MDR) in several human pathogens and diseases. P-gp is a major cause of drug resistance in cancer, parasitic diseases, epilepsy and other disorders. This review article aims to summarize the research findings on the marine natural products with P-glycoprotein inhibitor properties. Natural compounds that modulate P-gp offer great possibilities for semi-synthetic modification to create new drugs and are valuable research tools to understand the function of complex ABC transporters. PMID:24451193

Lopez, Dioxelis; Martinez-Luis, Sergio

2014-01-01

144

Binding of modulators to mouse and human multidrug resistance P-glycoprotein. A computational study.  

PubMed

The human multidrug resistance (MDR) P-glycoprotein (P-gp) mediates the extrusion of chemotherapeutic drugs from cancer cells. Modulators are relevant pharmaceutical targets since they are intended to control or to inhibit its pumping activity. In the present work, a common binding site for Rhodamine 123 and modulators with different modulation activity was found by molecular docking over the crystal structure of the mouse P-gp. The modulators involved a family of compounds, including derivatives of propafenone (3-phenylpropiophenone nucleus) and XR9576 (tariquidar). Our results showed that the relative binding energies estimated by molecular docking were in good correlation with the experimental activities. Preliminary classical molecular dynamics results on selected P-gp/modulator complexes were also performed in order to understand the nature of the prevalent molecular interactions and the possible main molecular features that characterize a modulator. Besides, the results obtained with a human P-gp homology model from the mouse structure are also presented and analyzed. Our observations suggest that the hydrophobicity and molecular flexibility are the main features related to the inhibitory activity. The latter factor would increase the modulator ability to fit the aromatic rings inside the transmembrane domain. PMID:24095875

Jara, Gabriel E; Vera, D Mariano A; Pierini, Adriana B

2013-11-01

145

Aspirin decreases systemic exposure to clopidogrel through modulation of P-glycoprotein but does not alter its antithrombotic activity.  

PubMed

Decreased oral clopidogrel absorption caused by induction of intestinal permeability glycoprotein (P-gp) expression after aspirin administration was observed in rats. This study evaluated the effect of aspirin coadministration on the pharmacokinetics/pharmacodynamics of clopidogrel in humans. A single 75-mg dose of clopidogrel was orally administered before and after 2 and 4 weeks of once-daily 100-mg aspirin administration in 18 healthy volunteers who were recruited based on CYP2C19 and PON1 genotypes. Plasma concentrations of clopidogrel and its active metabolite, H4, and relative platelet inhibition (RPI) were determined. The P-gp microRNA miR-27a increased by up to 7.67-fold (P = 0.004) and the clopidogrel area under the concentration-time curve (AUC) decreased by 14% (P > 0.05), but the AUC of H4 remained unchanged and RPI increased by up to 15% (P = 0.002) after aspirin administration. These findings indicate low-dose aspirin coadministration may decrease clopidogrel bioavailability but does not decrease its efficacy. PMID:24566733

Oh, J; Shin, D; Lim, K S; Lee, S; Jung, K-H; Chu, K; Hong, K S; Shin, K-H; Cho, J-Y; Yoon, S H; Ji, S C; Yu, K-S; Lee, H; Jang, I-J

2014-06-01

146

P-glycoprotein expression induced by glucose depletion enhanced the chemosensitivity in human hepatocellular carcinoma cell-lines.  

PubMed

Chemoresistance in cancer cells is frequently associated with an over-expression of the P-glycoprotein (P-gp). The expression of P-gp can be regulated as the cells encounter a number of chemical, physical or environmental stimuli. In this study, P-gp was found gradually expressed in a human hepatocellular carcinoma (HCC) QGY-7703 cells after 48 h of culturing in glucose-free medium. This phenomenon disappeared after the removal of glucose deprivation culture conditions. Mdr1-cDNA isolated from the cell line cultured in glucose-free conditions (namely QGY-7703G), was transiently transformed into the parent QGY-7703 cells, and multi-drug resistance was eventually induced. Results from XTT cytotoxicity assays indicated that the mdr1 gene was functional and the P-gp could restore the QGY-7703 cell's ability to withstand high concentrations of a number of chemotherapeutic agents. A P-gp inhibitor, verapamil, could completely reverse the cellular drug resistance when applied to the QGY-7703G cells. Our results indicated that an alteration of a specific state in cells caused by an external stimulus in vitro may lead to an expression of stress proteins (e.g. P-gp), which may enhance the cells' survival in adverse conditions. The expressed P-gp induced by glucose deprivation has a functional role in affecting the chemosensitivity in HCC QGY-7703G cells. Inhibition of P-gp activity may enhance the effect of the cancer cells towards cancer chemotherapy. PMID:15914037

Cheng, Samuel Chak-Sum; Zhou, Jing; Xie, Yong

2005-04-01

147

Farnesiferol A from Ferula persica and galbanic acid from Ferula szowitsiana inhibit P-glycoprotein-mediated rhodamine efflux in breast cancer cell lines.  

PubMed

In multidrug resistance (MDR), cancer cells exposed to anticancer agents develop resistance to a wide variety of chemicals and chemotherapeutic agents. Sesquiterpene coumarins are reported to inhibit P-glycoprotein and/or increase cytotoxicity of anticancer drugs in P-gp-overexpressing cell lines. In the current study, we investigated the effects of galbanic acid (from the roots of Ferula szowitsiana) and farnesiferol A (from the roots of Ferula persica) on functionality of the drug transporter P-glycoprotein (P-gp) using a rhodamine 123 efflux assay in a doxorubicin resistant breast cancer cell line (MCF7/Adr). Compared to verapamil, the well-known inhibitor of P-gp, galbanic acid (5, 10, and 25 µg/mL), significantly inhibited the P-gp activity. In inhibition of the P-gp transporter, farnesiferol A (0.5?µg/mL) was more potent than verapamil at 15 min exposure. Our results indicate that the plant derived sesquiterpene coumarins, farnesiferol A and galbanic acid, may be promising candidates to be considered for further studies on the reversal of multidrug resistance phenotype in chemotherapy of cancer patients. PMID:21484672

Hanafi-Bojd, Mohammad Yahya; Iranshahi, Mehrdad; Mosaffa, Fatemeh; Tehrani, Shahireh Omidvar; Kalalinia, Fatemeh; Behravan, Javad

2011-09-01

148

Edoxaban transport via P-glycoprotein is a key factor for the drug's disposition.  

PubMed

Edoxaban (the free base of DU-176b), an oral direct factor Xa inhibitor, is mainly excreted unchanged into urine and feces. Because active membrane transport processes such as active renal secretion, biliary excretion, and/or intestinal secretion, and the incomplete absorption of edoxaban after oral administration have been observed, the involvement of drug transporters in the disposition of edoxaban was investigated. Using a bidirectional transport assay in human colon adenocarcinoma Caco-2 cell monolayers, we observed the vectorial transport of [(14)C]edoxaban, which was completely inhibited by verapamil, a strong P-glycoprotein (P-gp) inhibitor. In an in vivo study, an increased distribution of edoxaban to the brain was observed in Mdr1a/1b knockout mice when compared with wild-type mice, indicating that edoxaban is a substrate for P-gp. However, there have been no observations of significant transport of edoxaban by renal or hepatic uptake transporters, organic anion transporter (OAT)1, OAT3, organic cation transporter (OCT)2, or organic anion transporting polypeptide (OATP)1B1. Edoxaban exhibited no remarkable inhibition of OAT1, OAT3, OCT1, OCT2, OATP1B1, OATP1B3, or P-gp up to 30 ?M; therefore, the risk of clinical drug-drug interactions due to any edoxaban-related transporter inhibition seems to be negligible. Our results demonstrate that edoxaban is a substrate of P-gp but not of other major uptake transporters tested. Because metabolism is a minor contributor to the total clearance of edoxaban and strong P-gp inhibitors clearly impact edoxaban transport, the P-gp transport system is a key factor for edoxaban's disposition. PMID:24459178

Mikkaichi, Tsuyoshi; Yoshigae, Yasushi; Masumoto, Hiroshi; Imaoka, Tomoki; Rozehnal, Veronika; Fischer, Thomas; Okudaira, Noriko; Izumi, Takashi

2014-04-01

149

Characterization of P-glycoprotein inhibition by major cannabinoids from marijuana.  

PubMed

The ATP-dependent drug efflux transporter P-glycoprotein (P-gp) plays a significant role in the absorption and disposition of many compounds. The purpose of this study was to investigate the possible interaction of P-gp with each of four major marijuana constituents: Delta(9)-tetrahydrocannabinol (THC), 11-nor-Delta(9)-tetrahydrocannabinol-carboxylic acid (THC-COOH), cannabinol (CBN), and cannabidiol (CBD). The results of a P-gp ATPase activity screen showed that THC-COOH, CBN, THC, and CBD all stimulated P-gp ATPase activity with a Michaelis-Menten parameter (V(max)/K(m)) value of 1.3, 0.7, 0.1, and 0.05, respectively. Furthermore, CBD showed a concentration-dependent inhibitory effect on verapamil-stimulated ATPase activity with an IC(50) value of 39.6 microM, whereas all other tested cannabinoids did not display appreciable inhibitory effects. Thus, the inhibitory effects of CBD on P-gp transport were further studied. At concentrations ranging from 5 to 100 microM, CBD robustly enhanced the intracellular accumulation of known P-gp substrates rhodamine 123 and doxorubicin in a concentration-dependent manner in Caco-2 and LLC-PK1/MDR1 cells. An IC(50) value of 8.44 microM was obtained for inhibition of P-gp function in LLC-PK1/MDR1 cells as determined by flow cytometry using rhodamine 123 as a fluorescence probe. Following exposure to 30 microM CBD, the apparent permeability coefficient of rhodamine 123 across Caco-2 and rat brain microvessel endothelial cell monolayers was increased to 2.2- and 2.6-fold in the apical-to-basolateral direction but decreased to 0.69- and 0.47-fold in the basolateral-to-apical direction, respectively. These findings indicate that CBD significantly inhibits P-gp-mediated drug transport, suggesting CBD could potentially influence the absorption and disposition of other coadministered compounds that are P-gp substrates. PMID:16439618

Zhu, Hao-Jie; Wang, Jun-Sheng; Markowitz, John S; Donovan, Jennifer L; Gibson, Bryan B; Gefroh, Holly A; Devane, C Lindsay

2006-05-01

150

In vivo activation of human pregnane X receptor tightens the blood-brain barrier to methadone through P-glycoprotein up-regulation.  

PubMed

The ATP-driven drug export pump, P-glycoprotein, is a primary gatekeeper of the blood-brain barrier and a major impediment to central nervous system (CNS) pharmacotherapy. Reducing P-glycoprotein activity dramatically increases penetration of many therapeutic drugs into the CNS. Previous studies in rat showed that brain capillary P-glycoprotein was transcriptionally up-regulated by the pregnane X receptor (PXR), a xenobiotic-activated nuclear receptor. Here we used a transgenic mouse expressing human PXR (hPXR) to determine the consequences of increased blood-brain barrier P-glycoprotein activity. P-glycoprotein expression and transport activity in brain capillaries from transgenic mice was significantly increased when capillaries were exposed to the hPXR ligands, rifampin and hyperforin, in vitro and when the mice were dosed with rifampin in vivo. Plasma rifampin levels in induced mice were comparable with literature values for patients. We also administered methadone, a CNS-acting, P-glycoprotein substrate, to control and rifampin-induced transgenic mice and measured the drug's antinociceptive effect. In rifampin-induced mice, the methadone effect was reduced by approximately 70%, even though plasma methadone levels were similar to those found in transgenic controls not exposed to rifampin. Thus, hPXR activation in vivo increased P-glycoprotein activity and tightened the blood-brain barrier to methadone, reducing the drug's CNS efficacy. This is the first demonstration of the ability of blood-brain barrier PXR to alter the efficacy of a CNS-acting drug. PMID:16837625

Bauer, Björn; Yang, Xiaodong; Hartz, Anika M S; Olson, Emily R; Zhao, Rong; Kalvass, J Cory; Pollack, Gary M; Miller, David S

2006-10-01

151

Tetrandrine potentiates the hypoglycemic efficacy of berberine by inhibiting P-glycoprotein function.  

PubMed

This study was designed to improve the absorption and hypoglycemic efficacy of berberine (BBR), which is a substrate of P-glycoprotein (P-gp), by combination with a P-gp inhibitor tetrandrine (Tet). Flow cytometry and LC-MS/MS were used to determine the cellular efflux or retention of chemicals. Pharmacokinetic study was performed in ICR mice following oral administration of the study compounds. The hypoglycemic efficacies of the compounds were evaluated in diabetic KK-Ay mice. In the in vitro experiments, Tet significantly inhibited the efflux and increased the uptake of P-gp substrates rhodamine-123 as well as BBR in MCF7/DOX cells and Caco-2 intestinal cells. Meanwhile, Tet greatly reduced the expression of P-gp in Caco-2 cells. The inhibition of BBR efflux by Tet was translated into improved pharmacokinetics in vivo. When co-administered, Tet dose-dependently increased the average maximum concentration (C(max)) and area under concentration-time curve (AUC????) of BBR in mice. Tet itself had no impact on glucose metabolism. However, it greatly potentiated the hypoglycemic efficacy of BBR in diabetic KK-Ay mice. In addition, we found that Tet had moderate inhibitory effect on the catalytic activity of CYP3A4, which played a role in the bio-transformation of BBR, and this may also take part in the improvement of the pharmacokinetics of BBR. In summary, combination with P-gp inhibitors such as Tet can improve the pharmacokinetics and hypoglycemic efficacy of BBR greatly; this implicates a feasible strategy for exploring the therapeutic effects of BBR and other pharmaceuticals which are substrates of P-gp. PMID:23924821

Shan, Yong-Qiang; Zhu, Yan-Ping; Pang, Jing; Wang, Yan-Xiang; Song, Dan-Qing; Kong, Wei-Jia; Jiang, Jian-Dong

2013-01-01

152

Effect of Repeated Oral Treatment with Etoposide on the Expression of Intestinal P-glycoprotein and Oral Morphine Analgesia.  

PubMed

  Currently, the World Health Organization recommends oral administration of opioid analgesics for patients with cancer to treat cancer-related pain from the initial stage of treatment. Furthermore, many anticancer drugs have been newly-developed and approved as oral form. Because of this trend, the chances of drug-drug interactions between anticancer drugs and opioid analgesics during absorption process from the intestine are likely to increase. To investigate these possible drug-drug interactions, we have focused on intestinal P-glycoprotein (P-gp) which regulates the absorption of various substrate drugs administered orally. Previously, we have found that repeated oral treatment with etoposide (ETP), an anticancer drug, attenuates analgesia of oral morphine, a substrate drug for P-gp, by increasing the expression and activity of intestinal P-gp. However, the mechanism by which ETP treatment increases the intestinal P-gp expression and decreases oral morphine analgesia remains unclear. RhoA, a small G-protein, and ROCK, an effector of RhoA, pathway has been attracted attention with regard to their involvement in the regulatory mechanism of the expression and activity of P-gp. Interestingly, this pathway is activated in response to various signaling induced by some anticancer drugs. Furthermore, it has been reported that ezrin/radixin/moesin (ERM) play a key role in the plasma membrane localization of P-gp, and that RhoA/ROCK pathway regulates the activation process of ERM. This review article introduces the result of our previous research as well as recent findings on the involvement of ERM via activation of RhoA/ROCK in the increased expression of intestinal P-gp and decreased oral morphine analgesia induced by repeated oral treatment with ETP. PMID:24882643

Kobori, Takuro; Harada, Shinichi; Nakamoto, Kazuo; Tokuyama, Shogo

2014-01-01

153

Anti-inflammatory properties of anthraquinones and their relationship with the regulation of P-glycoprotein function and expression.  

PubMed

There is a growing interest in natural products that potentially have anti-inflammatory properties and inhibit P-glycoprotein (P-gp) function. In this report, we assessed the effects of anthraquinone derivatives from rhubarb on LPS-induced RAW 264.7 macrophages to determine their anti-inflammatory potential. The derivatives were also tested in Caco-2 cell lines to evaluate the inhibition of the drug efflux function of P-gp. The transport abilities were examined and the cellular accumulation of rhodamine-123 (R-123) was also measured. Electorphoretic mobility shift assay (EMSA) was performed to check the activator protein-1 (AP-1) DNA binding affinity. Five anthraquinones were tested to determine their inhibitory activities on NO production and the protein and mRNA expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, the level of prostaglandin E(2) (PGE(2)) was determined in LPS-induced RAW264.7 macrophages. Emodin was found to be the most potent inhibitor, and it also reduced paw swelling in the mouse model of carrageenan-induced paw edema. In Caco-2 cells, emodin elevated the accumulation of R-123 and decreased the efflux ratio of R-123, which indicates the inhibition of P-gp function. The inhibition of COX-2 protein by emodin paralleled the decrease in P-gp expression. In addition, mitogen-activated protein kinase (MAPK) expression was decreased through the prevention of AP-1 DNA binding, which leads to downregulation in the expression of P-gp. Our data indicate that the decrease of P-gp expression is caused by the decreased expression of COX-2 through the MAPK/AP-1 pathway. Based on our results, we suggest that anti-inflammatory drugs with COX-2 inhibitory activity might be used to modulate P-gp function and expression. PMID:23174748

Choi, Ran Joo; Ngoc, Tran Minh; Bae, Kihwan; Cho, Hyun-Jong; Kim, Dae-Duk; Chun, Jaemoo; Khan, Salman; Kim, Yeong Shik

2013-01-23

154

Expression of P-glycoprotein in adult T-cell leukemia cells  

SciTech Connect

We have examined the expression of P-glycoprotein (P-gp) in adult T-cell leukemia (ATL) samples from 25 patients. Based on immunoblotting with a monoclonal antibody against P-gp, C219, 8 of 20 ATL patients were P-gp positive at the initial presentation. All 6 patients at the relapsed stage were P-gp positive, and refractory to chemotherapy. The expression of MDR1 mRNA in P-gp-positive ATL cells was increased at the relapsed stage of one patient. P-gp of this patient was photolabeled with (3H)azidopine and the labeling was inhibited with nimodipine, vinblastine and progesterone. These results suggest that P-gp expressed in ATL cells from patients at relapsed stage has the same binding site(s) for the drugs as that in multidrug resistant cells, and is correlated with the refractory nature of the cells to chemotherapy.

Kuwazuru, Y.; Hanada, S.; Furukawa, T.; Yoshimura, A.; Sumizawa, T.; Utsunomiya, A.; Ishibashi, K.; Saito, T.; Uozumi, K.; Maruyama, M. (Kagoshima Univ. (Japan))

1990-11-15

155

Discovery and characterization of OC144-093, a novel inhibitor of P-glycoprotein-mediated multidrug resistance.  

PubMed

OC144-093 is a novel substituted diarylimidazole (Mr 495) generated using the OntoBLOCK system, a solid-phase combinatorial chemistry technology, in combination with high-throughput cell-based screening. OC144-093 reversed multidrug resistance (MDR) to doxorubicin, paclitaxel, and vinblastine in human lymphoma, breast, ovarian, uterine, and colorectal carcinoma cell lines expressing P-glycoprotein (P-gp) with an average EC50 of 0.032 microM. Inhibition of MDR by OC144-093 was reversible, but the effect persisted for at least 12 h after removal of compound from the culture medium. OC144-093 had no effect on the response to cytotoxic agents by cells in vitro lacking P-gp expression or expressing a multidrug resistance-associated protein (MRP-1). OC144-093 was not cytotoxic by itself against 15 normal, nontransformed, or tumor cell lines, regardless of P-gp status, with an average cytostatic IC50 of >60 microM. OC144-093 blocked the binding of [3H]azidopine to P-gp and inhibited P-gp ATPase activity. The compound was >50% p.o. bioavailable in rodents and dogs and did not alter the plasma pharmacokinetics of i.v.-administered paclitaxel. OC144-093 increased the life span of doxorubicin-treated mice engrafted with MDR P388 leukemia cells by >100% and significantly enhanced the in vivo antitumor activity of paclitaxel in MDR human breast and colon carcinoma xenograft models, without a significant increase in doxorubicin or paclitaxel toxicity. The results demonstrate that OC144-093 is an orally active, potent, and nontoxic inhibitor of P-gp-mediated multidrug resistance that exhibits all of the desired properties for treatment of P-gp-mediated MDR, as well as for prevention of MDR prior to selection and/or induction of refractory disease. PMID:10850444

Newman, M J; Rodarte, J C; Benbatoul, K D; Romano, S J; Zhang, C; Krane, S; Moran, E J; Uyeda, R T; Dixon, R; Guns, E S; Mayer, L D

2000-06-01

156

Overcoming multidrug-resistance in vitro and in vivo using the novel P-glycoprotein inhibitor 1416  

PubMed Central

MDR (multidrug-resistance) represents a major obstacle to successful cancer chemotherapy and is usually accomplished by overexpression of P-gp (P-glycoprotein). Much effort has been devoted to developing P-gp inhibitors to modulate MDR. However, none of the inhibitors on the market have been successful. 1416 [1-(2,6-dimethylphenoxy)-2-(3,4-dimethoxyphenylethylamino)propane hydrochloride (phenoprolamine hydrochloride)] is a new VER (verapamil) analogue with a higher IC50 for blocking calcium channel currents than VER. In the present paper, we examined the inhibition effect of 1416 on P-gp both in vitro and in vivo. 1416 significantly enhanced cytotoxicity of VBL (vinblastine) in P-gp-overexpressed human multidrug-resistant K562/ADM (adriamycin) and KBV cells, but had no such effect on the parent K562 and KB cells. The MDR-modulating function of 1416 was further confirmed by increasing intracellular Rh123 (rhodanmine123) content in MDR cells. Human K562/ADM xenograft-nude mice model verified that 1416 potentiates the antitumour activity of VBL in vivo. RT-PCR (reverse transcriptase-PCR) and FACS analysis demonstrated that the expression of MDR1/P-gp was not affected by 1416 treatment. All these observations suggest that 1416 could be a promising agent for overcoming MDR in cancer chemotherapy.

Xu, Yan; Zhi, Feng; Xu, Guangming; Tang, Xiaolei; Lu, Sheng; Wu, Jinhui; Hu, Yiqiao

2012-01-01

157

An in silico approach for screening flavonoids as P-glycoprotein inhibitors based on a Bayesian-regularized neural network.  

PubMed

P-glycoprotein (P-gp), an ATP-binding cassette (ABC) transporter, functions as a biological barrier by extruding cytotoxic agents out of cells, resulting in an obstacle in chemotherapeutic treatment of cancer. In order to aid in the development of potential P-gp inhibitors, we constructed a quantitative structure-activity relationship (QSAR) model of flavonoids as P-gp inhibitors based on Bayesian-regularized neural network (BRNN). A dataset of 57 flavonoids collected from a literature binding to the C-terminal nucleotide-binding domain of mouse P-gp was compiled. The predictive ability of the model was assessed using a test set that was independent of the training set, which showed a standard error of prediction of 0.146+/-0.006 (data scaled from 0 to 1). Meanwhile, two other mathematical tools, back-propagation neural network (BPNN) and partial least squares (PLS) were also attempted to build QSAR models. The BRNN provided slightly better results for the test set compared to BPNN, but the difference was not significant according to F-statistic at p=0.05. The PLS failed to build a reliable model in the present study. Our study indicates that the BRNN-based in silico model has good potential in facilitating the prediction of P-gp flavonoid inhibitors and might be applied in further drug design. PMID:16059668

Wang, Yong-Hua; Li, Yan; Yang, Sheng-Li; Yang, Ling

2005-03-01

158

A Phenotype–Genotype Approach to Predicting CYP450 and P-Glycoprotein Drug Interactions With the Mixed Inhibitor\\/Inducer Tipranavir\\/Ritonavir  

Microsoft Academic Search

The effects of tipranavir\\/ritonavir (TPV\\/r) on hepatic and intestinal P-glycoprotein (P-gp) and cytochrome P450 (CYP) enzyme activity were evaluated in 23 volunteers. The subjects received oral (p.o.) caffeine, warfarin + vitamin K, omeprazole, dextromethorphan, and midazolam and digoxin (p.o. and intravenous (i.v.)) at baseline, during the first three doses of TPV\\/r (500 mg\\/200 mg b.i.d.), and at steady state. Plasma

J B Dumond; M Vourvahis; N L Rezk; K B Patterson; H-C Tien; N White; S H Jennings; S O Choi; J Li; M J Wagner; N M La-Beck; M Drulak; J P Sabo; M A Castles; T R MacGregor; A D M Kashuba; ADM Kashuba

2010-01-01

159

P-glycoprotein of blood brain barrier: cross-reactivity of MAb C219 with a 190 kDa protein in bovine and rat isolated brain capillaries  

Microsoft Academic Search

P-glycoprotein (P-gp), an active efflux pump of antitumor drugs, is strongly expressed in endothelial cells of the blood brain barrier (BBB). Two proteins (155 and 190 kDa) were detected by Western blot analysis of beef and rat capillaries with the monoclonal antibody (MAb) C219. In order to characterize the nature of these proteins, their profile of solubilization by different detergents

Edith Beaulieu; Michel Demeule; Jean-François Pouliot; Diana A. Averill-Bates; Gérard F. Murphy; Richard Béliveau

1995-01-01

160

Quantitative investigation of the impact of P-glycoprotein inhibition on drug transport across blood-brain barrier in rats.  

PubMed

The magnitude of P-glycoprotein [(P-gp)/multidrug resistance protein 1 (MDR1)]-mediated drug-drug interaction (DDI) at the blood-brain barrier (BBB) in rats was estimated by in vitro-in vivo correlation (IVIVC). In in vitro studies, rat Mdr1a-expressing LLC-PK1 cells were examined for the evaluation of P-gp inhibitory activity using digoxin as a P-gp probe substrate. The in vitro K(i) value was calculated using a modified corrected flux ratio that reflects the P-gp function. In in vivo studies, digoxin with or without P-gp inhibitors was administered to rats by constant intravenous infusion to evaluate the effect of P-gp inhibition on digoxin transport to the brain under steady-state conditions. In the presence of elacridar, the brain-to-plasma concentration ratio (K(p,brain)) of digoxin was approximately 14 times the control value. However, no significant change in the K(p,brain) was observed in the presence of clinically used P-gp inhibitors, with the exception of cyclosporine A. A positive correlation was found between the in vivo K(p,brain) of digoxin and [I(,unbound)/K(i)] (where I(,unbound) is the unbound plasma concentration of P-gp inhibitors). Compounds with [I(,unbound)/K(i)] values of >1 increased K(p,brain) of digoxin in rats. In summary, we used a quantitative approach to evaluate the impact of P-gp-mediated DDI at the rat BBB. We successfully established the IVIVC, which indicated the potential DDI in the presence of potent P-gp inhibitors. On the basis of the IVIVC in rats and K(i) values in human MDR1, we speculated that clinically used P-gp inhibitors do not cause DDI at the human BBB, because none of the compounds studied showed [I(,unbound)/K(i)] values of >1 at therapeutic doses. PMID:20962062

Sugimoto, Hiroshi; Hirabayashi, Hideki; Kimura, Yoshiaki; Furuta, Atsutoshi; Amano, Nobuyuki; Moriwaki, Toshiya

2011-01-01

161

In vitro experimental system for evaluating inhibitory effect of investigational drugs on P-glycoprotein-mediated transcellular transport of tacrolimus (FK506).  

PubMed

In this study, an in vitro experimental system for evaluating the inhibitory effect of investigational drugs on the P-glycoprotein (P-gp, MDR1)-mediated transport of tacrolimus (FK506) was developed using LLC-PK1-MDR1 and LLC-PK1 wild-type (control) cells. The amount of tacrolimus (concentrations: 1 and 5 ?m) transported into P-gp-expressing and control cells increased with time in both the apical-to-basal and basal-to-apical directions at incubation times ranging from 40 min to 2 h. The corrected apparent permeability (Papp) ratio, obtained by dividing the Papp ratio in P-gp-expressing cells by that in the control cells, ranged from 2.6 to 5.3, showing significant differences in the transport of tacrolimus between the P-gp-expressing cells and the control cells. This system was then subsequently used to examine the P-gp transport of tacrolimus in the presence of verapamil (30 ?m), a model inhibitor for P-gp-mediated transport activity. The corrected Papp ratios in the absence and presence of verapamil were 6.9 and 0.8, respectively. Data derived in the present study suggest that our developed system has the ability to detect a sufficient difference in the P-gp transport of tacrolimus between P-gp-expressing and control cells, and we therefore believe our system to be suitable for use in evaluating the inhibitory effects of investigational drugs on the P-gp-mediated transport of tacrolimus. PMID:24822242

Oda, Kazuo; Nemoto, Hiroyuki; Nagasaka, Yasuhisa; Kawamura, Akio; Usui, Takashi

2014-04-01

162

Mitochondrial localization of P-glycoprotein and peptide transporters in corneal epithelial cells--novel strategies for intracellular drug targeting.  

PubMed

This study was designed to investigate functional localization of both efflux (P-glycoprotein, P-gp) and influx (peptide) transporters in the mitochondrial membrane of cultured rabbit primary corneal epithelial cells (rPCECs). Isolation and purification of mitochondria was performed by optimized cell fractionation method. Mitochondrial integrity was measured by JC-1 uptake experiment. The efflux activity of P-gp was assessed by performing in vitro uptake studies on isolated mitochondria with Rhodamine 123 (Rho-123) alone and in the presence of P-gp inhibitors (quinidine and cyclosporine A) using fluorimetry and flow cytometry analysis. Functional activity of peptide transporter was assessed by performing in vitro uptake studies of [3H] Gly-sar on isolated mitochondria in the presence or absence of peptide transporter substrate (Val-Val). Molecular characterization of P-gp and peptide transporter was assessed by western blot and confocal analysis. Enhanced JC-1 accumulation in the isolated fraction confirmed mitochondrial membrane integrity. Significantly higher uptake of Rho-123 on isolated mitochondria was observed in the presence of quinidine (75 and 100 ?M) and cyclosporine A (10 ?M). Significantly lower uptake of [3H] Gly-sar was observed in the presence of val-val due to competitive inhibition of peptide transporter on isolated mitochondria. Western blot and confocal analysis further confirmed the presence of P-gp and peptide transporter on the mitochondrial membrane of rPCECs. The present study demonstrates the functional and molecular characterization of P-gp and peptide transporters in the mitochondrial membranes of rPCECs. This knowledge of mitochondrial existence of P-gp and peptide transporter will aid in the development of subcellular ocular drug delivery strategies. PMID:23116562

Barot, Megha; Gokulgandhi, Mitan R; Pal, Dhananjay; Mitra, Ashim K

2013-01-01

163

Corrector-mediated rescue of misprocessed CFTR mutants can be reduced by the P-glycoprotein drug pump.  

PubMed

The most common cause of cystic fibrosis is deletion of Phe508 in the first nucleotide-binding domain (NBD) of the CFTR chloride channel, which inhibits protein folding. ?F508 CFTR can be rescued by indirect approaches such as low temperature but the protein is unstable. Here, we tested our predictions that (1) other CFTR mutants such V232D and H1085R were more stable at the cell surface than ?F508 CFTR after low temperature rescue and (2) the advantages of rescue with specific correctors (pharmacological chaperones) are that they may stabilize ?F508 CFTR and increase the effectiveness of the correctors by bypassing drug pumps such as P-glycoprotein (P-gp) (increased bioavailability). It was found that the stability of mutants V232D and H1085R after low-temperature (30°C) rescue was about 10-fold higher than ?F508 CFTR. We show that the corrector, 4,5,7-trimethyl-N-phenylquinolin-2-amine (5a), could stabilize ?F508 CFTR at the cell surface. Unlike most correctors, corrector 5a showed specificity for CFTR as it did not rescue the G268V P-gp processing mutant nor stimulate the ATPase activity of wild-type P-gp. By contrast, corrector KM11060 was a P-gp substrate as it stimulated P-gp ATPase activity and rescued the G268V mutant. Expression of wild-type P-gp reduced the effectiveness of CFTR rescue by corrector KM11060 by about 5-fold. The results underlie the importance of selecting correctors that are specific for CFTR because their efficiency can be reduced by drug pumps such as P-gp. PMID:22138447

Loo, Tip W; Bartlett, M Claire; Shi, Li; Clarke, David M

2012-02-01

164

P-glycoprotein antagonists confer synergistic sensitivity to short-chain ceramide in human multidrug-resistant cancer cells.  

PubMed

P-glycoprotein (P-gp) antagonists inhibit ceramide metabolism at the juncture of glycosylation. The purpose of this study was to test whether targeting P-gp would be a viable alternative to targeting glucosylceramide synthase (GCS) for enhancing ceramide cytotoxicity. A2780 wild-type, and multidrug-resistant 2780AD and NCI/ADR-RES human ovarian cancer cell lines and the cell-permeable ceramide analog, C6-ceramide (C6-cer), were employed. Compared to P-gp-poor A2780 cells, P-gp-rich 2780AD cells converted 3.7-fold more C6-cer to nontoxic C6-glucosylceramide (C6-GC), whereas cell-free GCS activities were equal. 2780AD cells displayed resistance to C6-cer (10 ?M) that was reversed by inclusion of the P-gp antagonist tamoxifen (5 ?M) but not by inclusion of a GCS inhibitor. Co-administration of C6-cer and P-gp antagonists was also effective in NCI/ADR-RES cells. For example, C6-cer, VX-710 (Biricodar), and cyclosporin A (cyc A) exposure resulted in viabilities of ~90% of control; however, C6-cer/VX-710 and C6-cer/cyc A additions were synergistic and resulted in viabilities of 22% and 17%, respectively. Further, whereas C6-ceramide and cyc A imparted 1.5- and 0-fold increases in caspase 3/7 activity, the combination produced a 3.5-fold increase. Although the upstream elements of cell death have not been elucidated, the novel C6-ceramide/P-gp antagonist combination merits further study and assessment of clinical translational potential. PMID:21396934

Chapman, Jacqueline V; Gouazé-Andersson, Valérie; Karimi, Ramin; Messner, Maria C; Cabot, Myles C

2011-07-15

165

Cannabidiol changes P-gp and BCRP expression in trophoblast cell lines  

PubMed Central

Objectives. Marijuana is the most commonly used illicit drug during pregnancy. Due to high lipophilicity, cannabinoids can easily penetrate physiological barriers like the human placenta and jeopardize the developing fetus. We evaluated the impact of cannabidiol (CBD), a major non-psychoactive cannabinoid, on P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) expression, and P-gp function in a placental model, BeWo and Jar choriocarcinoma cell lines (using P-gp induced MCF7 cells (MCF7/P-gp) for comparison). Study design. Following the establishment of the basal expression of these transporters in the membrane fraction of all three cell lines, P-gp and BCRP protein and mRNA levels were determined following chronic (24–72 h) exposure to CBD, by Western Blot and qPCR. CBD impact on P-gp efflux function was examined by uptake of specific P-gp fluorescent substrates (calcein-AM, DiOC2(3) and rhodamine123(rh123)). Cyclosporine A (CsA) served as a positive control. Results. Chronic exposure to CBD resulted in significant changes in the protein and mRNA levels of both transporters. While P-gp was down-regulated, BCRP levels were up-regulated in the choriocarcinoma cell lines. CBD had a remarkably different influence on P-gp and BCRP expression in MCF7/P-gp cells, demonstrating that these are cell type specific effects. P-gp dependent efflux (of calcein, DiOC2(3) and rh123) was inhibited upon short-term exposure to CBD. Conclusions. Our study shows that CBD might alter P-gp and BCRP expression in the human placenta, and inhibit P-gp efflux function. We conclude that marijuana use during pregnancy may reduce placental protective functions and change its morphological and physiological characteristics.

Erez, Offer; Ben-Zvi, Zvi; Erez, Noam; Eshkoli, Tamar; Sheizaf, Boaz; Sheiner, Eyal; Huleihel, Mahmud; Holcberg, Gershon

2013-01-01

166

Raltegravir does not revert efflux activity of MDR1-P-glycoprotein in human MDR cells  

PubMed Central

Background Raltegravir (Isentress®)(RALT) has demonstrated excellent efficacy in both treatment-experienced and naïve patients with HIV-1 infection, and is the first strand transfer integrase inhibitor to be approved for use in HIV infected adults worldwide. Since the in vivo efficacy of this class of antiviral drugs depends on their access to intracellular sites where HIV-1 replicates, we analyzed the biological effects induced by RALT on human MDR cell systems expressing multidrug transporter MDR1-P-glycoprotein (MDR1-Pgp). Methods Our study about RALT was performed by using a set of consolidated methodologies suitable for evaluating the MDR1-Pgp substrate nature of chemical and biological agents, namely: i) assay of drug efflux function; ii) analysis of MDR reversing capability by using cell proliferation assays; iii) monoclonal antibody UIC2 (mAb) shift test, as a sensitive assay to analyze conformational transition associated with MDR1-Pgp function; and iv) induction of MDR1-Pgp expression in MDR cell variant subjected to RALT exposure. Results Functional assays demonstrated that the presence of RALT does not remarkably interfere with the efflux mechanism of CEM-VBL100 and HL60 MDR cells. Accordingly, cell proliferation assays clearly indicated that RALT does not revert MDR phenotype in human MDR1-Pgp expressing cells. Furthermore, exposure of CEM-VBL10 cells to RALT does not induce MDR1-Pgp functional conformation intercepted by monoclonal antibody (mAb) UIC2 binding; nor does exposure to RALT increase the expression of this drug transporter in MDR1-Pgp expressing cells. Conclusions No evidence of RALT interaction with human MDR1-Pgp was observed in the in vitro MDR cell systems used in the present investigation, this incorporating all sets of studies recommended by the FDA guidelines. Taken in aggregate, these data suggest that RALT may express its curative potential in all sites were HIV-1 penetrates, including the MDR1-Pgp protected blood/tissue barrier. Moreover RALT, evading MDR1-Pgp drug efflux function, would not interfere with pharmacokinetic profiles of co-administered MDR1-Pgp substrate antiretroviral drugs.

2013-01-01

167

Differential sensitivities of the human ATP-binding cassette transporters ABCG2 and P-glycoprotein to cyclosporin A.  

PubMed

Several ATP-binding cassette (ABC) transporters can confer multidrug resistance to cancer cells by functioning as energy-dependent efflux pumps. The half-transporter ABCG2 and the widely studied P-glycoprotein (P-gp) are two ABC transporters that, when overexpressed, are capable of extruding a variety of structurally unrelated chemotherapy agents from cells. In this study, we demonstrate that human ABCG2 and P-glycoprotein, despite overlapping substrate specificities, differ in sensitivity to the immunomodulator cyclosporin A. In this study, we used human ABCG2 and human P-gp, each expressed separately in drug-selected MCF-7 sublines and transiently transfected HeLa cells. By flow cytometric analysis using the fluorescent substrates rhodamine 123 and mitoxantrone, we showed that cyclosporin A inhibits P-gp function at low micromolar concentrations, whereas ABCG2 function was unaffected. Furthermore, P-gp, but not ABCG2, was able to transport [3H]cyclosporin A directly in intact cells. We also demonstrated, for the first time, that [125I]iodoarylazidoprazosin, a photoaffinity analog of the substrate prazosin, labels multiple variants of ABCG2 specifically and that this labeling, although competed by some ABCG2 substrates, is unaffected by cyclosporin A. These labeling data also suggest the presence of multiple drug binding sites in ABCG2. In addition, cyclosporin A had no effect on the basal or prazosin-stimulated ATPase activity of ABCG2, whereas both the basal and verapamil-stimulated ATPase activities of P-gp were inhibited markedly. Together, our results suggest that cyclosporin A is neither a substrate nor an inhibitor of the human ABCG2 transporter, under the conditions and concentrations examined. PMID:15598974

Ejendal, Karin F K; Hrycyna, Christine A

2005-03-01

168

Imaging the Function of P-Glycoprotein With Radiotracers: Pharmacokinetics and In Vivo Applications  

PubMed Central

P-glycoprotein (P-gp), an efflux transporter, controls the pharmacokinetics of various compounds under physiological conditions. P-gp-mediated drug efflux has been suggested as playing a role in various disorders, including multidrug-resistant cancer and medication-refractory epilepsy. However, P-gp inhibition has had, to date, little or no clinically significant effect in multidrug-resistant cancer. To enhance our understanding of its in vivo function under pathophysiological conditions, substrates of P-gp have been radiolabeled and imaged using single-photon emission computed tomography (SPECT) and positron emission tomography (PET). To accurately quantify P-gp function, a radiolabeled P-gp substrate should be selective for P-gp, produce a large signal after P-gp blockade, and generate few radiometabolites that enter the target tissue. Furthermore, quantification of P-gp function via imaging requires pharmacological inhibition of P-gp, which requires knowledge of P-gp density at the target site. By meeting these criteria, imaging can elucidate the function of P-gp in various disorders and improve the efficacy of treatments.

Kannan, P; John, C; Zoghbi, SS; Halldin, C; Gottesman, MM; Innis, RB; Hall, MD

2009-01-01

169

Tumor necrosis factor alpha and endothelin-1 increase P-glycoprotein expression and transport activity at the blood-brain barrier.  

PubMed

The ATP-driven drug efflux pump, P-glycoprotein, is a critical and selective element of the blood-brain barrier and a primary impediment to pharmacotherapy of central nervous system (CNS) disorders. Thus, an understanding of how P-glycoprotein function is regulated has the potential to improve CNS therapy. We recently demonstrated rapid (minutes) and reversible inactivation of P-glycoprotein in rat brain capillaries signaled through tumor necrosis factor-alpha (TNF-alpha) and endothelin-1 (ET-1), components of the brain's innate immune response. In this study, we examined the longer-term consequences of continuous exposure of rat brain capillaries to low levels of TNF-alpha and ET-1. Exposing brain capillaries to TNF-alpha or ET-1 caused a rapid decrease in P-glycoprotein transport activity with no change in transporter protein expression. This was followed by a 2- to 3-h plateau at the low activity level and then by a sharp increase in both transport activity and protein expression. After 6 h, transport activity and transporter protein expression was double that of control samples. TNF-alpha signaled through TNF-R1, which in turn caused ET release and action through ETA and ETB receptors, nitric-oxide synthase, protein kinase C and nuclear factor-kappaB (NF-kappaB) and finally increased P-glycoprotein expression and transport activity. Assuming similar effects occur in vivo, the present results imply a tightening of the selective blood-brain barrier with chronic inflammation and thus reduced efficacy of CNS-acting drugs that are P-glycoprotein substrates. Moreover, involvement of NF-kappaB raises the possibility that other effectors acting through this transcription factor may have similar effects on this key blood-brain barrier transporter. PMID:17132686

Bauer, Björn; Hartz, Anika M S; Miller, David S

2007-03-01

170

Dietary regulation of P-gp function and expression.  

PubMed

Food-drug interactions have been associated with clinically important pharmacokinetic and pharmacodynamic changes of a drug. The aim of this paper is to review the regulation of P-glycoprotein (P-gp) by dietary components and to correlate the changes in cellular P-gp function and expression with drug bioavailability. In summary, the published literature has provided extensive data supporting the modulation of drug bioavailability through P-gp regulation by components in food groups such as fruit juices, spices, herbs, cruciferous vegetables and green tea. Most of these data were, however, derived from in vitro cell models and, except for the St John's wort, the clinical significance of most reported interactions remains to be clarified. Studies on piperine and capsaicin have underscored an often poor correlation between in vivo and in vitro data, whereas experiments involving curcumin highlighted differences between acute and chronic consumption of a dietary component on P-gp function and expression in vivo. A better understanding of the pharmacokinetic and pharmacodynamic profiles of the dietary components will aid in addressing these knowledge gaps. PMID:19545213

Zhang, Wenxia; Han, Yi; Lim, Siok Lam; Lim, Lee Yong

2009-07-01

171

Role of intestinal P-glycoprotein in the plasma and fecal disposition of docetaxel in humans.  

PubMed

Multidrug resistance (MDR)-1-P-glycoprotein (P-gp) is a drug-transporting protein that is abundantly present in biliary ductal cells and epithelial cells lining the gastrointestinal tract. Here, we have determined the role of P-gp in the metabolic disposition of the antineoplastic agent docetaxel (Taxotere) in humans. Pharmacokinetic profiles were evaluated in five cancer patients receiving treatment cycles with docetaxel alone (100 mg/m2 i.v. over a 1-h period) and in combination with a new potent inhibitor of P-gp activity, R101933 (200-300 mg b.i.d.). The terminal disposition half-life and total plasma clearance of docetaxel were not altered by treatment with oral R101933 (P > or = 0.27). The cumulative fecal excretion of docetaxel, however, was markedly reduced from 8.47 +/- 2.14% (mean +/- SD) of the dose with the single agent to less than 0.5% in the presence of R101933 (P = 0.0016). Levels of the major cytochrome P450 3A4-mediated metabolites of docetaxel in feces were significantly increased after combination treatment with R101933 (P = 0.010), indicating very prominent and efficient detoxification of reabsorbed docetaxel into hydroxylated compounds before reaching the systemic circulation. It is concluded that intestinal P-gp plays a principal role in the fecal elimination of docetaxel by modulating reabsorption of the drug after hepatobiliary secretion. In addition, the results indicate that inhibition of P-gp activity in normal tissues by effective modulators, and the physiological and pharmacological consequences of this treatment, cannot be predicted based on plasma drug monitoring alone. PMID:10914699

van Zuylen, L; Verweij, J; Nooter, K; Brouwer, E; Stoter, G; Sparreboom, A

2000-07-01

172

The human multidrug resistance P-glycoprotein is inactive when its maturation is inhibited: potential for a role in cancer chemotherapy  

Microsoft Academic Search

The human multidrug resistance P- glycoprotein (P-gp) contributes to the phenomenon of multidrug resistance during cancer and AIDS chemotherapy. A potential novel strategy to circum- vent the effects of P-gp during chemotherapy is to prevent maturation of P-gp during biosynthesis so that the transporter does not reach the cell surface. Here we report that immature, core-glycosylated P-gp that is prevented

TIP W. LOO; DAVID M. CLARKE

173

Cross-resistance to antifolates in multidrug resistant cell lines with P-glycoprotein or multidrug resistance protein expression  

Microsoft Academic Search

Resistance to some (lipophilic) antifolates has been associated with P-glycoprotein (P-gp)mediated multidrug resistance (MDR). A possible relationship with non-P-gp MDR has not been established. We studied resistance to antifolates in SW-1573 human lung carcinoma cells, a P-gp overexpressing variant SW-1573\\/2R160 and a multidrug resistance protein (MRP) overexpressing variant SW-1573\\/2R120. In this study, thymidylate synthase (TS) inhibitors with different properties concerning

Baukelien van Triest; Herbert M. Pinedo; Frank Telleman; Clasina L. van der Wilt; Gerrit Jansen; Godefridus J. Peters

1997-01-01

174

Advances in PET Imaging of P-Glycoprotein Function at the Blood-Brain Barrier  

PubMed Central

Efflux transporter P-glycoprotein (P-gp) at the blood-brain barrier (BBB) restricts substrate compounds from entering the brain and may thus contribute to pharmacoresistance observed in patient groups with refractory epilepsy and HIV. Altered P-gp function has also been implicated in neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. Positron emission tomography (PET), a molecular imaging modality, has become a promising method to study the role of P-gp at the BBB. The first PET study of P-gp function was conducted in 1998, and during the past 15 years two main categories of P-gp PET tracers have been investigated: tracers that are substrates of P-gp efflux and tracers that are inhibitors of P-gp function. PET, as a noninvasive imaging technique, allows translational research. Examples of this are preclinical investigations of P-gp function before and after administering P-gp modulating drugs, investigations in various animal and disease models, and clinical investigations regarding disease and aging. The objective of the present review is to give an overview of available PET radiotracers for studies of P-gp and to discuss how such studies can be designed. Further, the review summarizes results from PET studies of P-gp function in different central nervous system disorders.

2012-01-01

175

Assessing drug distribution in tissues expressing P-glycoprotein through physiologically based pharmacokinetic modeling: model structure and parameters determination  

PubMed Central

Background The expression and activity of P-glycoproteins due to genetic or environmental factors may have a significant impact on drug disposition, drug effectiveness or drug toxicity. Hence, characterization of drug disposition over a wide range of conditions of these membrane transporters activities is required to better characterize drug pharmacokinetics and pharmacodynamics. This work aims to improve our understanding of the impact of P-gp activity modulation on tissue distribution of P-gp substrate. Methods A PBPK model was developed in order to examine activity and expression of P-gp transporters in mouse brain and heart. Drug distribution in these tissues was first represented by a well-stirred (WS) model and then refined by a mechanistic transport-based (MTB) model that includes P-gp mediated transport of the drug. To estimate transport-related parameters, we developed an original three-step procedure that allowed extrapolation of in vitro measurements of drug permeability to the in vivo situation. The model simulations were compared to a limited set of data in order to assess the model ability to reproduce the important information of drug distributions in the considered tissues. Results This PBPK model brings insights into the mechanism of drug distribution in non eliminating tissues expressing P-gp. The MTB model accounts for the main transport mechanisms involved in drug distribution in heart and brain. It points out to the protective role of P-gp at the blood-brain barrier and represents thus a noticeable improvement over the WS model. Conclusion Being built prior to in vivo data, this approach brings an interesting alternative to fitting procedures, and could be adapted to different drugs and transporters. The physiological based model is novel and unique and brought effective information on drug transporters.

Fenneteau, Frederique; Turgeon, Jacques; Couture, Lucie; Michaud, Veronique; Li, Jun; Nekka, Fahima

2009-01-01

176

Absence of P-glycoprotein transport in the pharmacokinetics and toxicity of the herbicide paraquat.  

PubMed

Genetic variation in the multidrug resistance gene ABCB1, which encodes the efflux transporter P-glycoprotein (P-gp), has been associated with Parkinson disease. Our goal was to investigate P-gp transport of paraquat, a Parkinson-associated neurotoxicant. We used in vitro transport models of ATPase activity, xenobiotic-induced cytotoxicity, transepithelial permeability, and rhodamine-123 inhibition. We also measured paraquat pharmacokinetics and brain distribution in Friend leukemia virus B-type (FVB) wild-type and P-gp-deficient (mdr1a(-/-)/mdr1b(-/-)) mice following 10, 25, 50, and 100 mg/kg oral doses. In vitro data showed that: 1) paraquat failed to stimulate ATPase activity; 2) resistance to paraquat-induced cytotoxicity was unchanged in P-gp-expressing cells in the absence or presence of P-gp inhibitors GF120918 [N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide] and verapamil-37.0 [95% confidence interval (CI): 33.2-41.4], 46.2 (42.5-50.2), and 34.1 µM (31.2-37.2)-respectively; 3) transepithelial permeability ratios of paraquat were the same in P-gp-expressing and nonexpressing cells (1.55 ± 0.39 and 1.39 ± 0.43, respectively); and 4) paraquat did not inhibit rhodamine-123 transport. Population pharmacokinetic modeling revealed minor differences between FVB wild-type and mdr1a(-/-)/mdr1b(-/-) mice: clearances of 0.47 [95% confidence interval (CI): 0.42-0.52] and 0.78 l/h (0.58-0.98), respectively, and volume of distributions of 1.77 (95% CI: 1.50-2.04) and 3.36 liters (2.39-4.33), respectively; however, the change in clearance was in the opposite direction of what would be expected. It is noteworthy that paraquat brain-to-plasma partitioning ratios and total brain accumulation were the same across doses between FVB wild-type and mdr1a(-/-)/mdr1b(-/-) mice. These studies indicate that paraquat is not a P-gp substrate. Therefore, the association between ABCB1 pharmacogenomics and Parkinson disease is not attributed to alterations in paraquat transport. PMID:24297779

Lacher, Sarah E; Gremaud, Julia N; Skagen, Kasse; Steed, Emily; Dalton, Rachel; Sugden, Kent D; Cardozo-Pelaez, Fernando; Sherwin, Catherine M T; Woodahl, Erica L

2014-02-01

177

A new method to measure intestinal activity of P-glycoprotein in avian and mammalian species  

Microsoft Academic Search

Permeability-glycoprotein (Pgp) actively exports numerous potentially toxic compounds once they diffuse into the cell membrane of intestinal epithelial cells. We adapted the everted sleeve technique to make the first measures of intestinal Pgp function in an avian species (chicken) and in wild mammalian species, and compared them to laboratory rats. Tissues maintained both structural and functional integrity, and our method

Adam K. Green; David M. Barnes; William H. Karasov

2005-01-01

178

High Glucose Decreases Expression and Activity of p-glycoprotein in Cultured Human Retinal Pigment Epithelium Possibly through iNOS Induction  

PubMed Central

Inhibition of p-glycoprotein under hyperglycemic conditions has been reported in various barrier tissues including blood-brain barrier, intestine, and kidney, and has been linked to significant clinical complications. However, whether this is also true for the outer blood-retinal barrier constituted by retinal pigment epithelium, or has a role in pathogenesis of diabetic retinopathy is not yet clear. In this study, using cultured human retinal pigment epithelium cell line D407, we found that high glucose exposure induced a significant decrease in p-glycoprotein expression both at mRNA and at protein levels, accompanied by an attenuated p-glycoprotein activity determined by intracellular rhodamine 123 retention. In marked contrast, the expressions of both mRNA and protein levels of inducible nitrate oxide synthase (iNOS) increased, and were accompanied by increased extracellular nitrate/nitrite production by Griess reaction. In addition, mRNA levels of nuclear receptors revealed a decreased expression of pregnane X receptor after the exposure of high glucose. However, the subsequent alterations in production of nitrate/nitrite, functional expression of p-glycoprotein, and mRNA levels of pregnane X receptor were partially blocked when pretreated with S,S?-1,3-phenylene-bis(1,2-ethanediyl)-bis-isothiourea•2HBr (PBITU), a selective iNOS inhibitor. Moreover, the effects of PBITU were antagonized with the addition of L-arginine, a substrate for NO synthesis. Our in vitro results suggest for the first time that iNOS induction plays a novel role in decreased p-glycoprotein expression and transport function at the human outer blood-retinal barrier under hyperglycemic conditions and further support the concept of inhibiting iNOS pathway as a therapeutic strategy for diabetic retinopathy.

Zhang, Yuehong; Li, Chunmei; Sun, Xuerong; Kuang, Xielan; Ruan, Xiangcai

2012-01-01

179

Measurement of P-Glycoprotein expression in human neuroblastoma xenografts using in vitro quantitative autoradiography  

Microsoft Academic Search

P-glycoprotein (P-gp) has a role in multidrug resistance (MDR) encountered in human cancers. In this study, we used the colchicine-resistant cell line BE(2)-C\\/CHCb(0.2), a strain of neuroblastoma cell line BE(2)-C, as a model to measure variations of P-gp expression in cells grown in vitro and in vivo. Cells were cultured in the medium supplemented with colchicine. At the beginning of

Rosa Fonti; Andrey Levchenko; Bipin M Mehta; Jiaju Zhang; Takashi Tsuruo; Steven M Larson

1999-01-01

180

Immunocytochemical detection of P-glycoprotein in the management of malignant effusions  

Microsoft Academic Search

P-glycoprotein (P-gp), a cell membrane protein, has been found in multidrug-resistant cancer cells. A total of 104 smears from patients with breast-cancer-associated pleural effusions and ovarian-cancer-related peritoneal effusions were studied for P-gp with the antibody C-219 and the avidin-biotin-immunoperoxidase method. Samples were taken before and 3 and 7 days after intracavitary bleomycin therapy and reaccumulation of effusion was assessed at

Peter Athanassiades; Efthallia Petrakakou; Cherry Zerva; Myron Mavrikakis

1997-01-01

181

Modeling the Kinetics of Digoxin Absorption: Enhancement by P-Glycoprotein Inhibition  

Microsoft Academic Search

An increase in the area under the curve (AUC) after oral digoxin due to coadministration of drugs known as P-glycoprotein (P-gp) inhibitors has been reported in several studies, but there is very little information on the rate of absorption after P-gp inhibition. Based on an inverse Gaussian density absorption model and using a population approach, the authors reanalyzed data showing

Michael Weiss; Pakawadee Sermsappasuk; Werner Siegmund

2012-01-01

182

P-Glycoprotein and Cytochrome P-450 3A Inhibition: Dissociation of Inhibitory Potencies1  

Microsoft Academic Search

Many P-glycoprotein (P-gp) inhibitors studied in vitro and in vivo are also known or suspected to be substrates and\\/or inhibitors of cytochrome P-450 3A (CYP3A). Such overlap raises the question of whether CYP3A inhibition is an intrinsic characteristic of P-gp inhibitors, a matter of concern in the development and rational use of such agents. Thus, the purpose of the present

Christoph Wandel; Richard B. Kim; Shama Kajiji; F. Peter Guengerich; Grant R. Wilkinson; Alastair J. J. Wood

183

Dynamic and intracellular trafficking of P-glycoprotein-EGFP fusion protein: Implications in multidrug resistance in cancer.  

PubMed

In our present study, a P-glycoprotein-EGFP (P-gp-EGFP) fusion plasmid was constructed and functionally expressed in HeLa cells to investigate the intracellular localization and trafficking of P-glycoprotein (P-gp). Using immunocytochemistry and fluorescent confocal microscopy techniques, colocalization studies showed that after transfection, P-gp-EGFP was progressively transported from the endoplasmic reticulum (ER) to the Golgi and finally to the plasma membrane within 12-48 hr. The degree of intracellular accumulation of daunorubicin was related to the particular localization of P-gp-EGFP. Significant daunorubicin accumulation occurred in transfected cells when P-gp-EGFP was localized predominantly within the ER, and accumulation remained high when P-gp-EGFP was mainly localized in the Golgi. However, there was little or no intracellular accumulation of daunorubicin when P-gp-EGFP was localized predominantly on the plasma membrane. Blocking the intracellular trafficking of P-gp-EGFP with brefeldin A (BFA) and monensin resulted in inhibition of traffic of P-gp-EGFP and retention of P-gp-EGFP intracellularly. Intracellular accumulation of daunorubicin also increased in the presence of BFA or monensin. Our study shows that P-gp-EGFP can be used to define the dynamics of P-gp traffic in a transient expression system, and demonstrates that localization of P-gp on the plasma membrane is associated with the highest level of resistance to daunorubicin accumulation in cells. Modulation of intracellular localization of P-gp with agents designed to selectively modify its traffic may provide a new strategy for overcoming multidrug resistance in cancer cells. PMID:14750166

Fu, Dong; Bebawy, Mary; Kable, Eleanor P W; Roufogalis, Basil D

2004-03-20

184

Enhanced Oral Absorption of Paclitaxel in a Novel Self-Microemulsifying Drug Delivery System with or Without Concomitant Use of P-Glycoprotein Inhibitors  

Microsoft Academic Search

Purpose. The objective of this study was to evaluate the pharmacokinetics of paclitaxel in a novel self-microemulsifying drug delivery system (SMEDDS) for improved oral administration with or without P-glycoprotein (P-gp) inhibitors.

Shicheng Yang; R. Neslihan Gursoy; Gregory Lambert; Simon Benita

2004-01-01

185

P-Glycoprotein and Drug Resistance in Systemic Autoimmune Diseases  

PubMed Central

Autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and psoriatic arthritis (PsA) are chronic inflammatory disorders of unknown etiology characterized by a wide range of abnormalities of the immune system that may compromise the function of several organs, such as kidney, heart, joints, brain and skin. Corticosteroids (CCS), synthetic and biologic immunosuppressive agents have demonstrated the capacity to improve the course of autoimmune diseases. However, a significant number of patients do not respond or develop resistance to these therapies over time. P-glycoprotein (P-gp) is a transmembrane protein that pumps several drugs out of the cell, including CCS and immunosuppressants; thus, its over-expression or hyper-function has been proposed as a possible mechanism of drug resistance in patients with autoimmune disorders. Recently, different authors have demonstrated that P-gp inhibitors, such as cyclosporine A (CsA) and its analogue Tacrolimus, are able to reduce P-gp expression and or function in SLE, RA and PsA patients. These observations suggest that P-gp antagonists could be adopted to revert drug resistance and improve disease outcome. The complex inter-relationship among drug resistance, P-gp expression and autoimmunity still remains elusive.

Picchianti-Diamanti, Andrea; Rosado, Maria Manuela; Scarsella, Marco; Lagana, Bruno; D'Amelio, Raffaele

2014-01-01

186

Role of P-glycoprotein in Limiting the Brain Penetration of Glabridin, An Active Isoflavan from the Root of Glycyrrhiza glabra  

Microsoft Academic Search

Purpose  Glabridin is a major active constituent of Glycyrrhiza glabra which is commonly used in the treatment of cardiovascular and central nervous system (CNS) diseases. Recently, we have found\\u000a that glabridin is a substrate of P-glycoprotein (PgP\\/MDR1). This study aimed to investigate the role of PgP in glabridin penetration\\u000a across the blood–brain barrier (BBB) using several in vitro and in vivo

Xi-Yong Yu; Shu-Guang Lin; Zhi-Wei Zhou; Xiao Chen; Jun Liang; Xue-Qing Yu; Balram Chowbay; Jing-Yuan Wen; Wei Duan; Eli Chan; Xiao-Tian Li; Jie Cao; Chun-Guang Li; Charlie Changli Xue; Shu-Feng Zhou

2007-01-01

187

Adaptive response to increased bile acids: induction of MDR1 gene expression and P -glycoprotein activity in renal epithelial cells  

Microsoft Academic Search

Cholestatic liver disease and increased serum bile acid concentrations are known to trigger various adaptive responses including\\u000a the induction of hepatic, intestinal and renal bile acid transport proteins, but renal P-glycoprotein (Pgp, multidrug resistance protein 1, MDR1) remained uninvestigated in this context. We show that treatment\\u000a of Madin Darby canine kidney (MDCK) cells with pathophysiologically relevant concentrations of chenodeoxycholic acid

Carsten Kneuer; Walther Honscha; Gotthold Gäbel; Kerstin U. Honscha

2007-01-01

188

Multiple Transport-Active Binding Sites Are Available for a Single Substrate on Human P-Glycoprotein (ABCB1)  

PubMed Central

P-glycoprotein (Pgp, ABCB1) is an ATP-Binding Cassette (ABC) transporter that is associated with the development of multidrug resistance in cancer cells. Pgp transports a variety of chemically dissimilar amphipathic compounds using the energy from ATP hydrolysis. In the present study, to elucidate the binding sites on Pgp for substrates and modulators, we employed site-directed mutagenesis, cell- and membrane-based assays, molecular modeling and docking. We generated single, double and triple mutants with substitutions of the Y307, F343, Q725, F728, F978 and V982 residues at the proposed drug-binding site with cys in a cysless Pgp, and expressed them in insect and mammalian cells using a baculovirus expression system. All the mutant proteins were expressed at the cell surface to the same extent as the cysless wild-type Pgp. With substitution of three residues of the pocket (Y307, Q725 and V982) with cysteine in a cysless Pgp, QZ59S-SSS, cyclosporine A, tariquidar, valinomycin and FSBA lose the ability to inhibit the labeling of Pgp with a transport substrate, [125I]-Iodoarylazidoprazosin, indicating these drugs cannot bind at their primary binding sites. However, the drugs can modulate the ATP hydrolysis of the mutant Pgps, demonstrating that they bind at secondary sites. In addition, the transport of six fluorescent substrates in HeLa cells expressing triple mutant (Y307C/Q725C/V982C) Pgp is also not significantly altered, showing that substrates bound at secondary sites are still transported. The homology modeling of human Pgp and substrate and modulator docking studies support the biochemical and transport data. In aggregate, our results demonstrate that a large flexible pocket in the Pgp transmembrane domains is able to bind chemically diverse compounds. When residues of the primary drug-binding site are mutated, substrates and modulators bind to secondary sites on the transporter and more than one transport-active binding site is available for each substrate.

Chufan, Eduardo E.; Kapoor, Khyati; Sim, Hong-May; Singh, Satyakam; Talele, Tanaji T.; Durell, Stewart R.; Ambudkar, Suresh V.

2013-01-01

189

Expression of P-glycoprotein in HeLa cells confers resistance to ceramide cytotoxicity.  

PubMed

The role of glucosylceramide synthase (GCS) in regulating ceramide-induced apoptosis has been widely studied. The purpose of this investigation was to evaluate the role of P-glycoprotein (P-gp) in regulating ceramide cytotoxicity by using C6-ceramide. To accomplish this, we employed HeLa cells with conditional expression of the multidrug resistance gene 1/P-gp. HeLa cells expressing P-gp (P-gp/on cells) challenged with [14C]C6-ceramide (6 µM), synthesized 4.5-fold the amount of C6-glucosylceramide (GC) compared to HeLa cells with suppressed expression of P-gp (P-gp/off cells), whereas the generated levels of C6-sphingomyelin were almost equal (33 and 29% of intracellular 14C, respectively). Tamoxifen, a P-gp antagonist, decreased the C6-GC levels from 3.5-1.0% in the P-gp/off and from 17-2.8% of the total lipid 14C levels in the P-gp/on cells. Tamoxifen did not inhibit cell-free C6-GC synthesis in the P-gp/off or P-gp/on homogenates. However, a specific GCS inhibitor, ethylenedioxy-1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol (ethylenedioxy-P4), blocked synthesis by 90%. In the cytotoxicity assays, the P-gp/off cells were sensitive to C6-ceramide and the P-gp/on cells were resistant. Resistance to C6-ceramide in the P-gp/on cells was reversed by tamoxifen but not by ethylenedioxy-P4. Experiments in another cervical cancer model showed that multidrug-resistant P-gp-rich KB-V1 cells synthesized 3-fold more C6-GC from C6-ceramide than the parental, P-gp-poor KB-3-1 cells, and whereas tamoxifen had no effect on the C6-GC synthesis in the KB-3-1 cells, it inhibited synthesis by 70% in the KB-V1 cells. This study demonstrates that P-gp potentiates C6-ceramide glycosylation and if antagonized augments C6-ceramide sensitivity, both features previously ascribed to GCS. We propose that P-gp can be an effective target for enhancing short-chain ceramide cytotoxicity in the treatment of drug-resistant cancer. PMID:21042729

Chapman, Jacqueline V; Gouazé-Andersson, Valérie; Cabot, Myles C

2010-12-01

190

Saturable Active Efflux by P-Glycoprotein and Breast Cancer Resistance Protein at the Blood-Brain Barrier Leads to Nonlinear Distribution of Elacridar to the Central Nervous System  

PubMed Central

The study objective was to investigate factors that affect the central nervous system (CNS) distribution of elacridar. Elacridar inhibits transport mediated by P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) and has been used to study the influence of transporters on brain distribution of chemotherapeutics. Adequate distribution of elacridar across the blood-brain barrier (BBB) and into the brain parenchyma is necessary to target tumor cells in the brain that overexpress transporters and reside behind an intact BBB. We examined the role of P-gp and Bcrp on brain penetration of elacridar using Friend leukemia virus strain B wild-type, Mdr1a/b(?/?), Bcrp1(?/?), and Mdr1a/b(?/?)Bcrp1(?/?) mice. Initially, the mice were administered 2.5 mg/kg of elacridar intravenously, and the plasma and brain concentrations were determined. The brain-to-plasma partition coefficient of elacridar in the wild-type mice was 0.82, as compared with 3.5 in Mdr1a/b(?/?) mice, 6.6 in Bcrp1(?/?) mice, and 15 in Mdr1a/b(?/?)Bcrp1(?/?) mice, indicating that both P-gp and Bcrp limit the brain distribution of elacridar. The four genotypes were then administered increasing doses of elacridar, and the CNS distribution of elacridar was determined. The observed and model predicted maximum brain-to-plasma ratios (Emax) at the highest dose were not significantly different in all genotypes. However, the ED50 was lower for Mdr1a/b(?/?) mice compared with Bcrp1(?/?) mice. These findings correlate with the relative expression of P-gp and Bcrp at the BBB in these mice and demonstrate the quantitative enhancement in elacridar CNS distribution as a function of its dose. Overall, this study provides useful concepts for future applications of elacridar as an adjuvant therapy to improve targeting of chemotherapeutic agents to tumor cells in the brain parenchyma.

Sane, Ramola; Agarwal, Sagar; Mittapalli, Rajendar K.

2013-01-01

191

Functional expression of P-glycoprotein in Saccharomyces cerevisiae confers cellular resistance to the immunosuppressive and antifungal agent FK520.  

PubMed Central

We have recently reported that expression in yeast cells of P-glycoprotein (P-gp) encoded by the mouse multidrug resistance mdr3 gene (Mdr3) can complement a null ste6 mutation (M. Raymond, P. Gros, M. Whiteway, and D. Y. Thomas, Science 256:232-234, 1992). Here we show that Mdr3 behaves as a fully functional drug transporter in this heterologous expression system. Photolabelling experiments indicate that Mdr3 synthesized in yeast cells binds the drug analog [125I]iodoaryl azidoprazosin, this binding being competed for by vinblastine and tetraphenylphosphonium bromide, two known multidrug resistance drugs. Spheroplasts expressing wild-type Mdr3 (Ser-939) exhibit an ATP-dependent and verapamil-sensitive decreased accumulation of [3H]vinblastine as compared with spheroplasts expressing a mutant form of Mdr3 with impaired transport activity (Phe-939). Expression of Mdr3 in yeast cells can confer resistance to growth inhibition by the antifungal and immunosuppressive agent FK520, suggesting that this compound is a substrate for P-gp in yeast cells. Replacement of Ser-939 in Mdr3 by a series of amino acid substitutions is shown to modulate both the level of cellular resistance to FK520 and the mating efficiency of yeast mdr3 transformants. The effects of these mutations on the function of Mdr3 in yeast cells are similar to those observed in mammalian cells with respect to drug resistance and transport, indicating that transport of a-factor and FK520 in yeast cells is mechanistically similar to drug transport in mammalian cells. The ability of P-gp to confer cellular resistance to FK520 in yeast cells establishes a dominant phenotype that can be assayed for the positive selection of intragenic revertants of P-gp inactive mutants, an important tool for the structure-function analysis of mammalian P-gp in yeast cells. Images

Raymond, M; Ruetz, S; Thomas, D Y; Gros, P

1994-01-01

192

Dose-response assessment of tariquidar and elacridar and regional quantification of P-glycoprotein inhibition at the rat blood-brain barrier using (R)-[11C]verapamil PET  

PubMed Central

Purpose Overactivity of the multidrug efflux transporter P-glycoprotein (P-gp) at the blood-brain barrier (BBB) is believed to play an important role in resistance to central nervous system drug treatment. (R)-[11C]verapamil (VPM) PET can be used to measure the function of P-gp at the BBB, but low brain uptake of VPM hampers the mapping of regional differences in cerebral P-gp function and expression. The aim of this study was to evaluate the dose-response relationship of two potent P-gp inhibitors and to investigate if increased brain uptake of VPM mediated by P-gp inhibition can be used to assess regional differences in P-gp activity. Methods Two groups of Sprague-Dawley rats (n=12) underwent single VPM PET scans at 120 min after administration of different doses of the P-gp inhibitors tariquidar and elacridar. In an additional 6 rats, paired VPM PET scans were performed before and after administration of 3 mg/kg tariquidar. Results Inhibitor administration resulted in an up to 11-fold increase in VPM brain distribution volumes (DV) with ED50 values of 3.0±0.2 and 1.2±0.1 mg/kg for tariquidar and elacridar, respectively. In paired PET scans, 3 mg/kg tariquidar resulted in regionally different enhancement of brain activity distribution, with lowest DV in cerebellum and highest DV in thalamus. Conclusion Our data show that tariquidar and elacridar are able to increase VPM brain distribution in rat brain up to 11-fold over baseline at maximum effective doses, with elacridar being about 3 times more potent than tariquidar. Regional differences in tariquidar-induced modulation of VPM brain uptake point to regional differences in cerebral P-gp function and expression in rat brain.

Kuntner, Claudia; Bankstahl, Jens P.; Bankstahl, Marion; Stanek, Johann; Wanek, Thomas; Stundner, Gloria; Karch, Rudolf; Brauner, Rebecca; Meier, Martin; Ding, Xiaoqi; Muller, Markus; Loscher, Wolfgang; Langer, Oliver

2013-01-01

193

A Novel MDR1 GT1292-3TG (Cys431Leu) Genetic Variation and Its Effect on P-glycoprotein Biologic Functions  

Microsoft Academic Search

P-glycoprotein (P-gp) is a membrane-bound transporter protein that is encoded by the human multidrug resistance gene MDR1 (ABCB1). P-gp recognizes a wide range of xenobiotics, is pivotal in mediating cancer drug resistance, and plays an important role\\u000a in limiting drug penetration across the blood–brain barrier. MDR1 genetic variation can lead to changes in P-gp function and may have implications on

Matthew H. Crouthamel; Daniel Wu; Ziping Yang; Rodney J. Y. Ho

2010-01-01

194

Use of Chemical Chaperones in the Yeast Saccharomyces cerevisiae to Enhance Heterologous Membrane Protein Expression: High-Yield Expression and Purification of Human P-Glycoprotein  

Microsoft Academic Search

Utilizing human P-glycoprotein (P-gp), we investigated methods to enhance the heterologous expression of ATP-binding cassette transporters in Saccharomyces cerevisiae. Human multidrug resistance gene MDR1 cDNA was placed in a high-copy 2? yeast expression plasmid under the control of the inducible GAL1 promoter or the strong constitutive PMA1 promoter from which P-gp was expressed in functional form. Yeast cells expressing P-gp

Robert A. Figler; Hiroshi Omote; Robert K. Nakamoto; Marwan K. Al-Shawi

2000-01-01

195

Evaluation of In Vivo P-Glycoprotein Function at the Blood-Brain Barrier Among MDR1 Gene Polymorphisms by Using 11C-Verapamil  

Microsoft Academic Search

P-glycoprotein (P-gp) is a membrane protein that functions as an adenosine triphosphate-dependent efflux pump for xenobiotics at the blood-brain barrier (BBB). Polymorphisms of MDR1 gene have been reported to be associated with the expression level of P-gp. 11C-Verapamil is considered to be one of the suitable radio- ligands for evaluating P-gp functions. However, the metabolites of verapamil might complicate the

Akihiro Takano; Hiroyuki Kusuhara; Tetsuya Suhara; Ichiro Ieiri; Takuya Morimoto; Young-Joo Lee; Jun Maeda; Yoko Ikoma; Hiroshi Ito; Kazutoshi Suzuki; Yuichi Sugiyama

2006-01-01

196

P-glycoprotein in adriamycin-resistant cells functions as an efflux pump for benzopyrene, a chemical carcinogen  

SciTech Connect

The physiological function of multidrug resistant gene (MDR 1) coded P-glycoprotein 170 (P-gp) in normal tissues remains unknown. The authors propose that P-gp functions as an efflux pump in normal tissues for benzopyrene and other xenobiotic substances. To examine their hypothesis the authors used a series of MDR human breast cancer MCF-7 cells with increasing degrees of drug resistance, expression of MDR and levels of P-gp. First, they found the IC{sub 50} for benzopyrene is linearly correlated with the levels of P-gp at different stages of adriamycin resistant MCF-7 cells. Using P-gp ({sup 3}H)azidopine labeling as a measurement of P-gp they found benzopyrene competes for labeling of P-gp. Finally, they directly measured cellular efflux of benzopyrene with adherent cell laser cytometry and found that resistant cells expressing high levels of P-gp showed rapid efflux of benzopyrene. By contrast, drug sensitive wild type cells with undetectable P-gp showed negligible efflux. They conclude that P-gp can function as an efflux pump for benzopyrene and suggest that P-gp may be a cellular mechanism for resistance to carcinogens.

Chao Yeh, G.; Poore, C.M.; Lopaczynska, J.; Phang, J.M. (NCI-FCRDC, Frederick, MD (United States))

1991-03-15

197

Involvement of PtdIns(4,5)P2 in the regulatory mechanism of small intestinal P-glycoprotein expression.  

PubMed

Previously, we reported that repeated oral administration of etoposide (ETP) activates the ezrin/radixin/moesin (ERM) scaffold proteins for P-glycoprotein (P-gp) via Ras homolog gene family member A (RhoA)/Rho-associated coiled-coil containing protein kinase (ROCK) signaling, leading to increased ileal P-gp expression. Recent studies indicate that phosphatidyl inositol 4,5-bisphosphate [PtdIns(4,5)P2] regulates the plasma-membrane localization of certain proteins, and its synthase, the type I phosphatidyl inositol 4-phosphate 5-kinase (PI4P5K), is largely controlled by RhoA/ROCK. Here, we examined whether PtdIns(4,5)P2 and PI4P5K are involved in the increased expression of ileal P-gp following the ERM activation by ETP treatment. Male ddY mice (4-week-old) were treated with ETP (10 mg/kg/day, per os, p.o.) for 5 days. Protein-expression levels were measured by either western blot or dot blot analysis and molecular interactions were assessed using immunoprecipitation assays. ETP treatment significantly increased PI4P5K, ERM, and P-gp expression in the ileal membrane. This effect was suppressed following the coadministration of ETP with rosuvastatin (a RhoA inhibitor) or fasudil (a ROCK inhibitor). Notably, the PtdIns(4,5)P2 expression in the ileal membrane, as well as both P-gp and ERM levels coimmunoprecipitated with anti-PtdIns(4,5)P2 antibody, were increased by ETP treatment. PtdIns(4,5)P2 and PI4P5K may contribute to the increase in ileal P-gp expression observed following the ETP treatment, possibly through ERM activation via the RhoA/ROCK pathway. PMID:24311454

Kobori, Takuro; Harada, Shinichi; Nakamoto, Kazuo; Tokuyama, Shogo

2014-02-01

198

A phenotype-genotype approach to predicting CYP450 and P-glycoprotein drug interactions with the mixed inhibitor/inducer tipranavir/ritonavir.  

PubMed

The effects of tipranavir/ritonavir (TPV/r) on hepatic and intestinal P-glycoprotein (P-gp) and cytochrome P450 (CYP) enzyme activity were evaluated in 23 volunteers. The subjects received oral (p.o.) caffeine, warfarin + vitamin K, omeprazole, dextromethorphan, and midazolam and digoxin (p.o. and intravenous (i.v.)) at baseline, during the first three doses of TPV/r (500 mg/200 mg b.i.d.), and at steady state. Plasma area under the curve (AUC)(0-infinity) and urinary metabolite ratios were used for quantification of protein activities. A single dose of TPV/r had no effect on the activity of CYP1A2 and CYP2C9; it weakly inhibited CYP2C19 and P-gp; and it potently inhibited CYP2D6 and CYP3A. Multiple dosing produced weak induction of CYP1A2, moderate induction of CYP2C19, potent induction of intestinal P-gp, and potent inhibition of CYP2D6 and CYP3A, with no significant effects on CYP2C9 and hepatic P-gp. Several P450/transporter single-nucleotide polymorphisms correlated with the baseline phenotype but not with the extent of inhibition or induction. Although mixed induction and inhibition are present, this approach offers an understanding of drug interaction mechanisms and ultimately assists in optimizing the clinical use of TPV/r. PMID:20147896

Dumond, J B; Vourvahis, M; Rezk, N L; Patterson, K B; Tien, H-C; White, N; Jennings, S H; Choi, S O; Li, J; Wagner, M J; La-Beck, N M; Drulak, M; Sabo, J P; Castles, M A; Macgregor, T R; Kashuba, A D M

2010-06-01

199

Photodynamic therapy inhibits p-glycoprotein mediated multidrug resistance via JNK activation in human hepatocellular carcinoma using the photosensitizer pheophorbide a  

PubMed Central

Background Multidrug resistance (MDR) is frequently observed after prolonged treatment in human hepatoma with conventional anti-tumor drugs, and photodynamic therapy (PDT) is a recently suggested alternative to overcome MDR. The therapeutic potential of PDT was evaluated in a multidrug resistance (MDR) human hepatoma cell line R-HepG2 with photosensitizer pheophorbide a (Pa). Results Our results demonstrated that intracellular accumulation of Pa was not reduced by the overexpression of P-glycoprotein. Pa-based PDT (Pa-PDT) significantly inhibited the growth of R-HepG2 cells with an IC50 value of 0.6 ?M. Mechanistic study demonstrated that genomic DNA fragmentation and phosphatidylserine externalization occurred where increase of intracellular singlet oxygen level triggers the phosphorylation of c-Jun N-terminal Kinase (JNK) and leads to activation of intrinsic apoptotic caspases cascade during the Pa-PDT treatment. The cytotoxicity of Pa-PDT, accumulation of sub-G1 population, and depolarization of mitochondrial membrane could be inhibited by JNK inhibitor in the Pa-PDT treated cells. Interestingly, the Pa-PDT induced JNK activation showed inhibitory effect on MDR by the down-regulation of P-glycoprotein in R-HepG2 cells in a dose-dependent manner. In addition, significant reduction of tumor size was obtained in Pa-PDT treated R-HepG2-bearing nude mice with no significant damages in liver and heart. Conclusion In summary, our findings provided the first evidence that PDT could inhibit the MDR activity by down-regulating the expression of P-glycoprotein via JNK activation using pheophorbide a as the photosensitizer, and our work proved that Pa-PDT inhibited the growth of MDR hepatoma cells by mitochondrial-mediated apoptosis induction.

Tang, Patrick Ming-Kuen; Zhang, Dong-Mei; Xuan, Ngoc-Ha Bui; Tsui, Stephen Kwok-Wing; Waye, Mary Miu-Yee; Kong, Siu-Kai; Fong, Wing-Ping; Fung, Kwok-Pui

2009-01-01

200

Fingerprint-based in silico models for the prediction of P-glycoprotein substrates and inhibitors  

PubMed Central

P-Glycoprotein (P-gp, ABCB1) plays a significant role in determining the ADMET properties of drugs and drug candidates. Substrates of P-gp are not only subject to multidrug resistance (MDR) in tumor therapy, they are also associated with poor pharmacokinetic profiles. In contrast, inhibitors of P-gp have been advocated as modulators of MDR. However, due to the polyspecificity of P-gp, knowledge on the molecular basis of ligand–transporter interaction is still poor, which renders the prediction of whether a compound is a P-gp substrate/non-substrate or an inhibitor/non-inhibitor quite challenging. In the present investigation, we used a set of fingerprints representing the presence/absence of various functional groups for machine learning based classification of a set of 484 substrates/non-substrates and a set of 1935 inhibitors/non-inhibitors. Best models were obtained using a combination of a wrapper subset evaluator (WSE) with random forest (RF), kappa nearest neighbor (kNN) and support vector machine (SVM), showing accuracies >70%. Best P-gp substrate models were further validated with three sets of external P-gp substrate sources, which include Drug Bank (n = 134), TP Search (n = 90) and a set compiled from literature (n = 76). Association rule analysis explores the various structural feature requirements for P-gp substrates and inhibitors.

Poongavanam, Vasanthanathan; Haider, Norbert; Ecker, Gerhard F.

2012-01-01

201

P-glycoprotein mediates the collateral sensitivity of multidrug resistant cells to steroid hormones.  

PubMed

The overexpression of P-glycoprotein (P-gp, ABCB1) in cancer cells often leads to multidrug resistance (MDR) through reduced drug accumulation. However, certain P-gp-positive cells display hypersensitivity, or collateral sensitivity, to certain compounds that are believed to induce Pgp-dependent oxidative stress. We have previously reported that MDR P-gp-positive CHO cells are collaterally sensitive to verapamil (VRP; Laberge et al. (2009) [1]). In this report we extend our previous findings and show that drug resistant CHO cells are also collaterally sensitive to physiologic levels of progesterone (PRO) and deoxycorticosterone (DOC). Both PRO and DOC collateral sensitivities in CH(R)C5 cells are dependent on P-gp-expression and ATPase, as knockdown of P-gp expression with siRNA or inhibition of P-gp-ATPase with PSC833 reverses PRO- and DOC-induced collateral sensitivity. Moreover, the mitochondrial complexes I and III inhibitors (antimycin-A and rotenone, respectively) synergize with PRO and DOC-induced collateral sensitivity. We also show that VRP inhibits PRO and DOC collateral sensitivity, consistent with earlier findings relating to the VRP's modulation of PRO and DOC-stimulation of P-gp ATPase. The findings of this study demonstrate a P-gp-dependent collateral sensitivity of MDR cells in the presence of physiologically achievable concentrations of progesterone and deoxycorticosterone. PMID:24747077

Laberge, Rémi-Martin; Ambadipudi, Raghuram; Georges, Elias

2014-05-16

202

Prognostic significance of the expressions of metallothionein, glutathione-S-transferase-pi, and P-glycoprotein in curatively resected gastric cancer.  

PubMed

Although experimental studies indicate that overexpression of metallothionein (MT), glutathione-S-transferase-pi (GST-pi), or P-glycoprotein (P-GP) is related to the drug resistance of cancer cells, the clinical significance of the overexpression remains to be elucidated. The expressions of MT, GST-pi, and P-GP wre evaluated immunohistochemically in 74 specimens of gastric adenocarcinoma in T1-3N1-2 stages which were resected with curative intent. Fluorinated pyrimidines, mitomycin C, and Adriamycin were prescribed in 73, 54, and 2 patients, respectively. The staining characteristics were investigated in relation to the clinical results. The cell-proliferative activity was studied with anti-proliferating cell nuclear antigen antibody. Expressions of GST-pi and P-GP correlated with the staining intensity of normal mucosa. Five-year disease-free survival rates (DFSRs) of GST-pi-negative and GST-pi-positive groups were 75.0 and 49.0%. The 5-year DFSRs of P-GP-negative and P-GP-positive groups were 68.2 and 38.6%. Concurrent expression among the three proteins was associated with the survival: 5-year DFSR of no- or one-protein-positive group was 75.0%, while those of 2- and 3-protein-positive groups were 56.0 and 38.9%, respectively. Tumors concurrently expressing 2 or 3 proteins have a high proliferative activity. Expressions of MT, GST-pi, and P-GP by the tumor are associated with a poorer prognosis of the patients. PMID:9260601

Monden, N; Abe, S; Sutoh, I; Hishikawa, Y; Kinugasa, S; Nagasue, N

1997-01-01

203

Irradiation of rat brain reduces P-glycoprotein expression and function  

PubMed Central

The blood–brain barrier (BBB) hampers delivery of several drugs including chemotherapeutics to the brain. The drug efflux pump P-glycoprotein (P-gp), expressed on brain capillary endothelial cells, is part of the BBB. P-gp expression on capillary endothelium decreases 5 days after brain irradiation, which may reduce P-gp function and increase brain levels of P-gp substrates. To elucidate whether radiation therapy reduces P-gp expression and function in the brain, right hemispheres of rats were irradiated with single doses of 2–25?Gy followed by 10?mg?kg?1 of the P-gp substrate cyclosporine A (CsA) intravenously (i.v.), with once 15?Gy followed by CsA (10, 15 or 20?mg?kg?1), or with fractionated irradiation (4 × 5?Gy) followed by CsA (10?mg?kg?1) 5 days later. Additionally, four groups of three rats received 25?Gy once and were killed 10, 15, 20 or 25 days later. The brains were removed and P-gp detected immunohistochemically. P-gp function was assessed by [11C]carvedilol uptake using quantitative autoradiography. Irradiation increased [11C]carvedilol uptake dose-dependently, to a maximum of 20% above non irradiated hemisphere. CsA increased [11C]carvedilol uptake dose-dependently in both hemispheres, but more (P<0.001) in the irradiated hemisphere. Fractionated irradiation resulted in a lost P-gp expression 10 days after start irradiation, which coincided with increased [11C]carvedilol uptake. P-gp expression decreased between day 15 and 20 after single dose irradiation, and increased again thereafter. Rat brain irradiation results in a temporary decreased P-gp function.

Bart, J; Nagengast, W B; Coppes, R P; Wegman, T D; van der Graaf, W T A; Groen, H J M; Vaalburg, W; de Vries, E G E; Hendrikse, N H

2007-01-01

204

Evaluation of P-glycoprotein (abcb1a/b) modulation of [(18)F]fallypride in MicroPET imaging studies.  

PubMed

[(18)F]Fallypride ([(18)F]FP) is an important and routinely used D2/D3 antagonist for quantitative imaging of dopaminergic neurotransmission in vivo. Recently it was shown that the brain uptake of the structurally related [(11)C]raclopride is modulated by P-glycoprotein (P-gp), an important efflux transporter at the blood-brain barrier. The purpose of this study was to determine whether the brain uptake of [(18)F]FP is influenced by P-gp. For examination of this possible modulation microPET studies were performed in a rat and a mouse model. Hence, [(18)F]FP was applied to Sprague Dawley rats, half of them being treated with the P-gp inhibitor cyclosporine A (CsA). In a second experimental series the tracer was applied to three different groups of FVB/N mice: wild type, P-gp double knockout (abcb1a/1b (-/-)) and CsA-treated mice. In CsA-treated Sprague Dawley rats [(18)F]FP showed an elevated standard uptake value in the striatum compared to the control animals. In FVB/N mice a similar effect was observed, showing an increasing uptake from wild type to CsA-treated and double knockout mice. Since genetically or pharmacologically induced reduction of P-gp activity increased the uptake of [(18)F]FP markedly, we conclude that [(18)F]FP is indeed a substrate of P-gp and that the efflux pump modulates its brain uptake. This effect - if true for humans - may have particular impact on clinical studies using [(18)F]FP for assessment of D2/3 receptor occupancy by antipsychotic drugs. This article is part of the Special Issue Section entitled 'Neuroimaging in Neuropharmacology'. PMID:23994301

Piel, Markus; Schmitt, Ulrich; Bausbacher, Nicole; Buchholz, Hans-Georg; Gründer, Gerhard; Hiemke, Christoph; Rösch, Frank

2014-09-01

205

Compounds from Chinese herbal medicines as reversal agents for P-glycoprotein-mediated multidrug resistance in tumours.  

PubMed

Multidrug resistance (MDR) is a major obstacle to successful cancer chemotherapy. One of the main underlying mechanisms of this resistance is the over-expression of P-glycoprotein (P-gp), an ATP-dependent transmembrane transporter protein encoded by the MDR1 gene. P-gp might transport anti-cancer drugs out of cancer cells and decrease effective intracellular drug concentrations. An effective approach to overcome MDR is to inhibit the function of P-gp or its expression on the surface of cancer cells. Thus, application of MDR reversal agents can be seen as a potentially important means by which to overcome the clinical drug resistance of tumour cells and improve the efficacy of chemotherapy. Recently, research efforts worldwide have focused on reversal mechanisms for MDR and on the identification of reversal agents. Chinese scholars have performed a great deal of exploratory work by screening for efficacy and low toxicity in drug resistance reversal compounds. These compounds may provide more lead compounds with greater activity, leading to the development of more effective therapies for MDR cancer cells. In this review, the function and efficiency of novel compounds derived from traditional Chinese medicines are described. PMID:24643703

Li, C; Sun, B-Q; Gai, X-D

2014-07-01

206

A genetic algorithm- back propagation artificial neural network model to quantify the affinity of flavonoids toward P-glycoprotein.  

PubMed

Flavonoids, the most diverse class of plant secondary metabolites, exhibit high affinity toward the purified cytosolic NBD2(C-terminal nucleotide-binding domain) of P-glycoprotein (P-gp). To explore the affinity of flavonoids for P-gp, quantitative structure-activity relationships (QSARs) models were developed using back-propagation artificial neural networks (BPANN) and multiple linear regression (MLR). Molecular descriptors were calculated using PaDELDescriptor, and the number of descriptors was then reduced using a genetic algorithm (GA) and stepwise regression. The MLR (R(2)=0.855, q(2)=0.8138, Rext(2)=0.6916), 14-3-1 BPANN (R(2)=0.8514, q(2)=0.7695, Rext (2)=0.8142), 14-4-1 BPANN(R(2)=0.9199, q(2)=0.7733, Rext(2) =0.8731), and 14-5-1 BPANN (R(2)=0.8660, q(2)=0.7432, Rext(2)=0.8292) models all showed good robustness. While BPANN models exceeded significantly MLR in predictable performance for their flexible characters, could be used to predict the affinity of flavonoids for P-gp and applied in further drug screening. PMID:24206113

Shen, Jibin; Cui, Ying; Gu, Jun; Li, Yaxiao; Li, Lingzhi

2014-02-01

207

P-glycoprotein: The intermediate end point of drug response to induction chemotherapy in locally advanced breast cancer  

Microsoft Academic Search

Expression and clinical relevance of p-glycoprotein (p-gp) were evaluated in 31 cases of locally advanced breast cancer and 9 cases involving inflammatory breast cancer after induction chemotherapy. The de novo p-gp expression rate was 26% and increased up to 58% (p = 0.03) with the FAC (5-fluorouracil, adriamycin, cyclophosphamide) regimen. Although more clinically complete responders were found in the secondary

Hyun Cheol Chung; Sun Young Rha; Joo Hang Kim; Jae Kyung Roh; Jin Sik Min; Kyung Sik Lee; Byung Soo Kim; Kyi Beom Lee

1997-01-01

208

Modulation of steady-state kinetics of digoxin by haplotypes of the P-glycoprotein MDR1 gene  

Microsoft Academic Search

Objective: We investigated the effect of polymorphisms in the P-glycoprotein (P-gp) MDR1 gene on steady-state pharmacokinetics of digoxin in Caucasians. According to earlier data, homozygous TT of the exon 26 complementary deoxyribonucleic acid (cDNA) 3435C>T polymorphism was associated with low P-gp expression in the human intestine.Methods: Eight healthy male homozygous carriers of the wild-type exon-26 3435C>T (CC), 8 heterozygous subjects

Andreas Johne; Karla Köpke; Thomas Gerloff; Ingrid Mai; Stephan Rietbrock; Christian Meisel; Sven Hoffmeyer; Reinhold Kerb; Martin F. Fromm; Ulrich Brinkmann; Michel Eichelbaum; Jürgen Brockmöller; Ingolf Cascorbi; Ivar Roots

2002-01-01

209

Drug transport to the brain: key roles for the efflux pump P-glycoprotein in the blood–brain barrier  

Microsoft Academic Search

1. The blood–brain barrier (BBB) contributes to brain homeostastis and fulfills a protective function by controlling the access of solutes and toxic substances to the central nervous system (CNS). The efflux transporter P-glycoprotein (P-gp) is a key element of the molecular machinery that confers special permeability properties to the BBB. 2. P-gp, which was initially recognized for its ability to

Michel Demeule; Anthony Régina; Julie Jodoin; Alain Laplante; Claude Dagenais; France Berthelet; Albert Moghrabi; Richard Béliveau

2002-01-01

210

Inhibitory effects of CYP3A4 substrates and their metabolites on P-glycoprotein-mediated transport  

Microsoft Academic Search

It is generally known that the substrates and\\/or inhibitors of cytochrome P450 (CYP) 3A4 and P-glycoprotein (P-gp) overlap with each other. In intestinal epithelial cells, it is surmised that the metabolites coexist with their parent drug. However, most studies on P-gp did not take the effects of those metabolites into consideration. Therefore, in the present study, we investigated the inhibitory

Miki Katoh; Miki Nakajima; Hiroshi Yamazaki; Tsuyoshi Yokoi

2001-01-01

211

Where is it and How Does it Get There - Intracellular Localization and Traffic of P-glycoprotein  

PubMed Central

P-glycoprotein (P-gp), an ATP-binding cassette, is able to transport structurally and chemically unrelated substrates. Over-expression of P-gp in cancer cells significantly decreases the intercellular amount of anticancer drugs, and results in multidrug resistance in cancer cells, a major obstacle in cancer chemotherapy. P-gp is mainly localized on the plasma membrane and functions as a drug efflux pump; however, P-gp is also localized in many intracellular compartments, such as endoplasmic reticulum, Golgi, endosomes, and lysosomes. P-gp moves between the intracellular compartments and the plasma membrane in a microtubule-actin dependent manner. This review highlights our current understanding of (1) the intracellular localization of P-gp; (2) the traffic and cycling pathways among the cellular compartments as well as between these compartments and the plasma membrane; and (3) the cellular factors regulating P-gp traffic and cycling. This review also presents a potential implication in overcoming P-gp-mediated multidrug resistance by targeting P-gp traffic and cycling pathways and impairing P-gp localization on the plasma membrane.

Fu, Dong

2013-01-01

212

P-glycoprotein increases portal bioavailability of loperamide in mouse by reducing first-pass intestinal metabolism.  

PubMed

P-glycoprotein (P-gp) and CYP3A (cytochrome P450 3A, generally; Cyp3a, rodent enzyme) in the intestine can attenuate absorption of orally administered drugs. While some suggest that P-gp enhances intestinal metabolism by CYP3A/Cyp3a during absorption of a dual substrate, others suggest that P-gp reduces the metabolism in the intestine when substrates are at subsaturating concentrations. Hence, to elucidate the cellular mechanisms that can address these divergent reports, we studied intestinal absorption of the dual substrate loperamide in portal vein-cannulated P-gp-competent and P-gp-deficient mice. These studies showed that at low doses of loperamide, which produced intestinal concentrations near the apparent K(m) for oxidative metabolism, the bioavailability across the intestine (F(G)) was 6-fold greater in the P-gp-competent mice than in P-gp-deficient mice. The higher F(G) of loperamide in the presence of P-gp was attributed to lower loperamide intestinal metabolism. However, at high doses of loperamide, the sparing of first-pass metabolism by P-gp was balanced against the attenuation of absorption by apical efflux, resulting in no net effect on F(G). In vitro studies with intestinal tissue from P-gp-competent and -deficient mice confirmed that P-gp reduced the metabolic rate of loperamide during absorptive flux at concentrations near K(m) but had little effect on metabolism at higher (saturating) concentrations. Further, studies in which Cyp3a was chemically inactivated by aminobenzotriazole in P-gp-competent and -deficient mice, showed that P-gp and Cyp3a individually attenuated F(G) by 8-fold and 70-fold, respectively. These results confirmed that P-gp effectively protects loperamide at low doses from intestinal first-pass metabolism during intestinal absorption. PMID:23288866

Dufek, Matthew B; Knight, Beverly M; Bridges, Arlene S; Thakker, Dhiren R

2013-03-01

213

Variability in P-Glycoprotein Inhibitory Potency (IC50) Using Various in Vitro Experimental Systems: Implications for Universal Digoxin Drug-Drug Interaction Risk Assessment Decision Criteria  

PubMed Central

A P-glycoprotein (P-gp) IC50 working group was established with 23 participating pharmaceutical and contract research laboratories and one academic institution to assess interlaboratory variability in P-gp IC50 determinations. Each laboratory followed its in-house protocol to determine in vitro IC50 values for 16 inhibitors using four different test systems: human colon adenocarcinoma cells (Caco-2; eleven laboratories), Madin-Darby canine kidney cells transfected with MDR1 cDNA (MDCKII-MDR1; six laboratories), and Lilly Laboratories Cells—Porcine Kidney Nr. 1 cells transfected with MDR1 cDNA (LLC-PK1-MDR1; four laboratories), and membrane vesicles containing human P-glycoprotein (P-gp; five laboratories). For cell models, various equations to calculate remaining transport activity (e.g., efflux ratio, unidirectional flux, net-secretory-flux) were also evaluated. The difference in IC50 values for each of the inhibitors across all test systems and equations ranged from a minimum of 20- and 24-fold between lowest and highest IC50 values for sertraline and isradipine, to a maximum of 407- and 796-fold for telmisartan and verapamil, respectively. For telmisartan and verapamil, variability was greatly influenced by data from one laboratory in each case. Excluding these two data sets brings the range in IC50 values for telmisartan and verapamil down to 69- and 159-fold. The efflux ratio-based equation generally resulted in severalfold lower IC50 values compared with unidirectional or net-secretory-flux equations. Statistical analysis indicated that variability in IC50 values was mainly due to interlaboratory variability, rather than an implicit systematic difference between test systems. Potential reasons for variability are discussed and the simplest, most robust experimental design for P-gp IC50 determination proposed. The impact of these findings on drug-drug interaction risk assessment is discussed in the companion article (Ellens et al., 2013) and recommendations are provided.

Bentz, Joe; O'Connor, Michael P.; Bednarczyk, Dallas; Coleman, JoAnn; Lee, Caroline; Palm, Johan; Pak, Y. Anne; Perloff, Elke S.; Reyner, Eric; Balimane, Praveen; Brannstrom, Marie; Chu, Xiaoyan; Funk, Christoph; Guo, Ailan; Hanna, Imad; Heredi-Szabo, Krisztina; Hillgren, Kate; Li, Libin; Hollnack-Pusch, Evelyn; Jamei, Masoud; Lin, Xuena; Mason, Andrew K.; Neuhoff, Sibylle; Patel, Aarti; Podila, Lalitha; Plise, Emile; Rajaraman, Ganesh; Salphati, Laurent; Sands, Eric; Taub, Mitchell E.; Taur, Jan-Shiang; Weitz, Dietmar; Wortelboer, Heleen M.; Xia, Cindy Q.; Xiao, Guangqing; Yabut, Jocelyn; Yamagata, Tetsuo; Zhang, Lei

2013-01-01

214

Effect of pregnancy on cytochrome P450 3a and P-glycoprotein expression and activity in the mouse: mechanisms, tissue specificity, and time course  

PubMed Central

The plasma concentrations of orally administered anti-HIV protease inhibitors are significantly reduced during human and mouse pregnancy. We have shown that in the mouse, at gestational day 19, this reduction is due to increased hepatic cytochrome P450 3a (Cyp3a) protein expression and activity. In the current study, we investigated the mechanisms by which Cyp3a activity is increased by pregnancy and the time course of change in expression of Cyp3a and P-gp in various tissues. We found hepatic transcripts of Cyp3a16, Cyp3a41 and Cyp3a44 were significantly increased during pregnancy, while those of Cyp3a11 and Cyp3a25 were significantly decreased. This resulted in a net increase in Cyp3a protein expression and activity in the liver during pregnancy. The increase in Cyp3a41 and Cyp3a44 transcripts was positively correlated (p<0.05) with HNF6 and ER? transcripts. The pregnancy-related factors that transcriptionally activated mouse Cyp3a isoforms also activated the human CYP3A4 promoter in pregnant CYP3A4-promoter-luciferase transgenic (CYP3A4-tg) mice. In contrast, intestinal Cyp3a protein expressions were not significantly affected by pregnancy. No change in P-gp protein expression was observed in the liver or kidney during pregnancy, though a significant decrease was observed in the placenta. Since hepatic CYP3A activity also appears to be induced during human pregnancy, the mouse (including CYP3A4-tg mouse) appears to be an excellent animal model to determine the molecular mechanisms for such induction.

Zhang, Huixia; Wu, Xiaohui; Wang, Honggang; Mikheev, Andrei M.; Mao, Qingcheng; Unadkat, Jashvant D.

2008-01-01

215

Predicting Efflux Ratios and Blood-Brain Barrier Penetration from Chemical Structure: Combining Passive Permeability with Active Efflux by P-Glycoprotein  

PubMed Central

In order to reach their pharmacologic targets, successful central nervous system (CNS) drug candidates have to cross a complex protective barrier separating brain from the blood. Being able to predict a priori which molecules can successfully penetrate this barrier could be of significant value in CNS drug discovery. Herein we report a new computational approach that combines two mechanism-based models, for passive permeation and for active efflux by P-glycoprotein, to provide insight into the multiparameter optimization problem of designing small molecules able to access the CNS. Our results indicate that this approach is capable of distinguishing compounds with high/low efflux ratios as well as CNS+/CNS– compounds and provides advantage over estimating P-glycoprotein efflux or passive permeability alone when trying to predict these emergent properties. We also demonstrate that this method could be useful for rank-ordering chemically similar compounds and that it can provide detailed mechanistic insight into the relationship between chemical structure and efflux ratios and/or CNS penetration, offering guidance as to how compounds could be modified to improve their access into the brain.

2012-01-01

216

In vitro inhibitory effects of scutellarin on six human/rat cytochrome P450 enzymes and P-glycoprotein.  

PubMed

Inhibition of cytochrome P450 (CYP) and P-glycoprotein (P-gp) are regarded as the most frequent and clinically important pharmacokinetic causes among the various possible factors for drug-drug interactions. Scutellarin is a flavonoid which is widely used for the treatment of cardiovascular diseases. In this study, the in vitro inhibitory effects of scutellarin on six major human CYPs (CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) and six rat CYPs (CYP1A2, CYP2C7, CYP2C11, CYP2C79, CYP2D4, and CYP3A2) activities were examined by using liquid chromatography-tandem mass spectrometry. Meanwhile, the inhibitory effects of scutellarin on P-gp activity were examined on a human metastatic malignant melanoma cell line WM-266-4 by calcein-AM fluorometry screening assay. Results demonstrated that scutellarin showed negligible inhibitory effects on the six major CYP isoenzymes in human/rat liver microsomes with almost all of the IC50 values exceeding 100 ?M, whereas it showed values of 63.8 ?M for CYP2C19 in human liver microsomes, and 63.1 and 85.6 ?M for CYP2C7 and CYP2C79 in rat liver microsomes, respectively. Scutellarin also showed weak inhibitory effect on P-gp. In conclusion, this study demonstrates that scutellarin is unlikely to cause any clinically significant herb-drug interactions in humans when co-administered with substrates of the six CYPs (CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) and P-gp. PMID:24802986

Han, Yong-Long; Li, Dan; Yang, Quan-Jun; Zhou, Zhi-Yong; Liu, Li-Ya; Li, Bin; Lu, Jin; Guo, Cheng

2014-01-01

217

Role of p-glycoprotein in regulating cilnidipine distribution to intact and ischemic brain.  

PubMed

Cilnidipine is reported to show antihypertensive and neuroprotective actions in a rat brain ischemia model, but is barely distributed to normal brain, suggesting that its uptake into normal brain is inhibited by efflux transporter(s), such as P-glycoprotein (P-gp). Here, we investigated whether P-gp regulates the brain distribution of cilnidipine. Intracellular accumulation of cilnidipine was decreased in P-gp-overexpressing porcine kidney epithelial cells (LLC-GA5-COL150 cells) compared with control LLC-PK1 cells and the decrease was markedly inhibited by verapamil, a P-gp inhibitor. Further, cilnidipine concentration in the brain of P-gp knockout mice was significantly increased after cilnidipine administration, compared with that in wild-type mice. Moreover, when cilnidipine was administered to male spontaneously hypertensive rats (SHR) with tandem occlusion of the distal middle cerebral and ipsilateral common carotid artery, its concentration in the ischemic hemisphere was 1.6-fold higher than that in the contralateral hemisphere. This result was supported by visualization of cilnidipine distribution using matrix-assisted laser desorption/ionization-time of flight/mass spectrometry (MALDI-TOF/MS) imaging. Our results indicated that cilnidipine is normally excluded from the brain by P-gp-mediated efflux transport, but P-gp function is impaired in ischemic brain and consequently cilnidipine is distributed to the ischemic region. PMID:24366438

Yano, Kentaro; Takimoto, Shinobu; Motegi, Toshimitsu; Tomono, Takumi; Hagiwara, Mihoko; Idota, Yoko; Morimoto, Kaori; Takahara, Akira; Ogihara, Takuo

2014-06-25

218

Murine P-glycoprotein on stromal vessels mediates multidrug resistance in intracerebral human glioma xenografts.  

PubMed Central

Human glioma usually shows intrinsic multidrug resistance because of the blood-brain barrier (BBB), in which membrane-associated P-glycoprotein (P-gp), encoded by the human multidrug resistance gene MDR1, plays a role. We studied drug sensitivity to vincristine (VCR), doxorubicin (DOX) and nimustine (ACNU) in both intracerebrally and subcutaneously xenotransplanted human glioma. We examined the levels of MDR1 and murine mdr3 gene expression in the xenografts by reverse transcriptase polymerase chain reaction and the localization of P-gp by immunohistochemistry. Six of seven subcutaneously transplanted xenografts (scX) were sensitive to the above three drugs. In contrast, all three intracerebrally transplanted human glioma xenografts (icX) were resistant to P-gp-mediated drugs VCR and DOX, but were sensitive to the non-P-gp-mediated drug ACNU. Neither icX nor scX showed any MDR1 expression. Intracerebrally transplanted human glioma xenografts showed an increased level of murine mdr3 gene expression, whereas scX showed only faint expression. The localization of P-gp was limited to the stromal vessels in icX by immunohistochemistry, whereas scX expressed no P-gp. Our findings suggest that the P-gp expressed on the stromal vessels in icX is a major contributing factor to multidrug resistance in human glioma in vivo. Images Figure 1 Figure 3 Figure 2

Takamiya, Y.; Abe, Y.; Tanaka, Y.; Tsugu, A.; Kazuno, M.; Oshika, Y.; Maruo, K.; Ohnishi, Y.; Sato, O.; Yamazaki, H.; Kijima, H.; Ueyama, Y.; Tamaoki, N.; Nakamura, M.

1997-01-01

219

Limited interaction between tacrolimus and P-glycoprotein in the rat small intestine.  

PubMed

The significance of intestinal P-glycoprotein (P-gp) in determining the oral bioavailability of tacrolimus has been still controversial. In this study, we reevaluated the interaction of tacrolimus with P-gp in the rat small intestine, by evaluating its absorption from the rat small intestine and its modulating effect on the absorption of known P-gp substrates (digoxin, methylprednisolone, and vinblastine). Intestinal absorption of tacrolimus itself was as extensive as other P-gp modulators such as cyclosporine and verapamil. While cyclosporine and verapamil significantly increased the absorption of methylprednisolone and vinblastine through potent inhibition of intestinal P-gp, tacrolimus failed to achieve this. When cyclosporine and tacrolimus were intravenously administered to rats, digoxin absorption was significantly increased by cyclosporine but not by tacrolimus. When tacrolimus was coadministered with clotrimazole, a specific CYP3A inhibitor, into the rat small intestine, the area under the curve of tacrolimus blood concentrations increased more than seven-fold compared with that of tacrolimus alone. Our present results strongly suggest that the interaction between tacrolimus and P-gp is limited in the rat small intestine and that extensive metabolism by CYP3A enzymes is more responsible for the low oral bioavailability of tacrolimus. It was considered that the extensive absorption of cyclosporine and verapamil was closely associated with their potent ability to inhibit intestinal P-gp. PMID:16457995

Saitoh, Hiroshi; Saikachi, Yuko; Kobayashi, Mikako; Yamaguchi, Michiko; Oda, Masako; Yuhki, Yoshimitsu; Achiwa, Kazuhito; Tadano, Koji; Takahashi, Yasushi; Aungst, Bruce J

2006-05-01

220

Anti-AIDS agents 89. Identification of DCX derivatives as anti-HIV and chemosensitizing dual function agents to overcome P-gp-mediated drug resistance for AIDS therapy.  

PubMed

In this study, 19 dicamphanoyl-dihydropyranochromone (DCP) and dicamphanoyl-dihydropyranoxanthone (DCX) derivatives, previously discovered as novel anti-HIV agents, were evaluated for their potential to reverse multi-drug resistance (MDR) in a cancer cell line over-expressing P-glycoprotein (P-gp). Seven compounds fully reversed resistance to vincristine (VCR) at 4 ?M, a 20-fold enhancement compared to the first generation chemosensitizer, verapamil (4 ?M). The mechanism of action of DCPs and DCXs was also resolved, since the most active compounds (3, 4, and 7) significantly increased intracellular drug accumulation due, in part, to inhibiting the P-gp mediated drug efflux from cells. We conclude that DCPs (3 and 4) and DCXs (7, 11, and 17) can exhibit polypharmacologic behavior by acting as dual inhibitors of HIV replication and chemoresistance mediated by P-gp. As such, they may be useful in combination therapy to overcome P-gp-associated drug resistance for AIDS treatment. PMID:22465634

Zhou, Ting; Ohkoshi, Emika; Shi, Qian; Bastow, Kenneth F; Lee, Kuo-Hsiung

2012-05-01

221

Regulation of P-Glycoprotein by Human Immunodeficiency Virus-1 in Primary Cultures of Human Fetal Astrocytes  

PubMed Central

P-glycoprotein (P-gp), a drug efflux pump, is known to alter the bioavailability of antiretroviral drugs at several sites, including the brain. We have previously shown that human immunodeficiency virus-1 (HIV-1) glycoprotein 120 (gp120) induces proinflammatory cytokine secretion and decreases P-gp functional expression in rat astrocytes, a cellular reservoir of HIV-1. However, whether P-gp is regulated in a similar way in human astrocytes is unknown. This study investigates the regulation of P-gp in an in vitro model of gp120-triggered human fetal astrocytes (HFAs). In this system, elevated levels of interleukin-6 (IL-6), IL-1?, and tumor necrosis factor-? were detected in culture supernatants. Pretreatment with CCR5 neutralizing antibody attenuated cytokine secretion, suggesting that gp120-CCR5 interaction mediated cytokine production. Treatment with gp120 (R5-tropic) resulted in reduced P-gp expression (64%) and function as determined by increased (1.6-fold) cellular accumulation of [3H]digoxin, a P-gp substrate. Exposure to R5 or R5/X4-tropic viral isolates led to a down-regulation in P-gp expression (75% or 90%, respectively), and treatment with IL-6 also showed lower P-gp expression (50%). Moreover, IL-6 neutralizing antibody blocked gp120-mediated P-gp downregulation, suggesting that IL-6 is a key modulator of P-gp. Gp120- or IL-6-mediated downregulation of P-gp was attenuated by SN50 (a nuclear factor-?B [NF-?B] inhibitor), suggesting involvement of NF-?B signaling in P-gp regulation. Our results suggest that, similarly to the case with rodent astrocytes, pathophysiological stressors associated with brain HIV-1 infection have a downregulatory effect on P-gp functional expression in human astrocytes, which may ultimately result in altered antiretroviral drug accumulation within brain parenchyma.

Ashraf, Tamima; Ronaldson, Patrick T.; Persidsky, Yuri; Bendayan, Reina

2014-01-01

222

Regulation of P-glycoprotein by human immunodeficiency virus-1 in primary cultures of human fetal astrocytes.  

PubMed

P-glycoprotein (P-gp), a drug efflux pump, is known to alter the bioavailability of antiretroviral drugs at several sites, including the brain. We have previously shown that human immunodeficiency virus-1 (HIV-1) glycoprotein 120 (gp120) induces proinflammatory cytokine secretion and decreases P-gp functional expression in rat astrocytes, a cellular reservoir of HIV-1. However, whether P-gp is regulated in a similar way in human astrocytes is unknown. This study investigates the regulation of P-gp in an in vitro model of gp120-triggered human fetal astrocytes (HFAs). In this system, elevated levels of interleukin-6 (IL-6), IL-1?, and tumor necrosis factor-? were detected in culture supernatants. Pretreatment with CCR5 neutralizing antibody attenuated cytokine secretion, suggesting that gp120-CCR5 interaction mediated cytokine production. Treatment with gp120 (R5-tropic) resulted in reduced P-gp expression (64%) and function as determined by increased (1.6-fold) cellular accumulation of [(3) H]digoxin, a P-gp substrate. Exposure to R5 or R5/X4-tropic viral isolates led to a downregulation in P-gp expression (75% or 90%, respectively), and treatment with IL-6 also showed lower P-gp expression (50%). Moreover, IL-6 neutralizing antibody blocked gp120-mediated P-gp downregulation, suggesting that IL-6 is a key modulator of P-gp. Gp120- or IL-6-mediated downregulation of P-gp was attenuated by SN50 (a nuclear factor-?B [NF-?B] inhibitor), suggesting involvement of NF-?B signaling in P-gp regulation. Our results suggest that, similarly to the case with rodent astrocytes, pathophysiological stressors associated with brain HIV-1 infection have a downregulatory effect on P-gp functional expression in human astrocytes, which may ultimately result in altered antiretroviral drug accumulation within brain parenchyma. PMID:21826700

Ashraf, Tamima; Ronaldson, Patrick T; Persidsky, Yuri; Bendayan, Reina

2011-11-01

223

Nilotinib Counteracts P-Glycoprotein-Mediated Multidrug Resistance and Synergizes the Antitumoral Effect of Doxorubicin in Soft Tissue Sarcomas  

PubMed Central

The therapeutic effect of doxorubicin (DXR) in the treatment of soft tissue sarcomas (STS) is limited by its toxicity and the development of multidrug resistance (MDR), the latter mainly induced by high expression of efflux pumps (e.g., P-glycoprotein [P-gp]). Therefore, the search for alternative therapies, which sensitize these tumors to chemotherapy while maintaining a low toxicity profile, is a rational approach. We assessed efficacy and molecular mechanisms involved in the antiproliferative effects of the tyrosine kinase inhibitors, nilotinib and imatinib, as single agents or in combination with DXR, in human synovial sarcoma SW982 and leiomyosarcoma SK-UT-1 cells. As single compound nilotinib (1–10 µM) was more potent than imatinib inhibiting the growth of SK-UT-1 and SW982 cells by 33.5–59.6%, respectively. Importantly, only nilotinib synergized the antitumoral effect of DXR (0.05–0.5 µM) by at least 2-fold, which clearly surpassed the mere sum of effects according to isobolographic analysis. Moreover, nilotinib in combination with DXR had a sustained effect on cell number (?70.3±5.8%) even 12 days after withdrawal of drugs compared to DXR alone. On the molecular level, only nilotinib fully blocked FBS-induced ERK1 and p38 MAPK activation, hence, reducing basal and DXR-induced up-regulation of P-gp levels. Moreover, efflux activity of the MDR-related proteins P-gp and MRP-1 was inhibited, altogether resulting in intracellular DXR retention. In high-risk STS tumors 53.8% and 15.4% were positive for P-gp and MRP-1 expression, respectively, with high incidence of P-gp in synovial sarcoma (72.7%). In summary, nilotinib exhibits antiproliferative effects on cellular models of STS and sensitizes them to DXR by reverting DXR-induced P-gp-mediated MDR and inhibiting MRP-1 activity, leading to a synergistic effect with potential for clinical treatment.

Villar, Victor Hugo; Vogler, Oliver; Martinez-Serra, Jordi; Ramos, Rafael; Calabuig-Farinas, Silvia; Gutierrez, Antonio; Barcelo, Francisca

2012-01-01

224

Nilotinib counteracts P-glycoprotein-mediated multidrug resistance and synergizes the antitumoral effect of doxorubicin in soft tissue sarcomas.  

PubMed

The therapeutic effect of doxorubicin (DXR) in the treatment of soft tissue sarcomas (STS) is limited by its toxicity and the development of multidrug resistance (MDR), the latter mainly induced by high expression of efflux pumps (e.g., P-glycoprotein [P-gp]). Therefore, the search for alternative therapies, which sensitize these tumors to chemotherapy while maintaining a low toxicity profile, is a rational approach. We assessed efficacy and molecular mechanisms involved in the antiproliferative effects of the tyrosine kinase inhibitors, nilotinib and imatinib, as single agents or in combination with DXR, in human synovial sarcoma SW982 and leiomyosarcoma SK-UT-1 cells. As single compound nilotinib (1-10 µM) was more potent than imatinib inhibiting the growth of SK-UT-1 and SW982 cells by 33.5-59.6%, respectively. Importantly, only nilotinib synergized the antitumoral effect of DXR (0.05-0.5 µM) by at least 2-fold, which clearly surpassed the mere sum of effects according to isobolographic analysis. Moreover, nilotinib in combination with DXR had a sustained effect on cell number (-70.3±5.8%) even 12 days after withdrawal of drugs compared to DXR alone. On the molecular level, only nilotinib fully blocked FBS-induced ERK1 and p38 MAPK activation, hence, reducing basal and DXR-induced up-regulation of P-gp levels. Moreover, efflux activity of the MDR-related proteins P-gp and MRP-1 was inhibited, altogether resulting in intracellular DXR retention. In high-risk STS tumors 53.8% and 15.4% were positive for P-gp and MRP-1 expression, respectively, with high incidence of P-gp in synovial sarcoma (72.7%). In summary, nilotinib exhibits antiproliferative effects on cellular models of STS and sensitizes them to DXR by reverting DXR-induced P-gp-mediated MDR and inhibiting MRP-1 activity, leading to a synergistic effect with potential for clinical treatment. PMID:22662203

Villar, Victor Hugo; Vögler, Oliver; Martínez-Serra, Jordi; Ramos, Rafael; Calabuig-Fariñas, Silvia; Gutiérrez, Antonio; Barceló, Francisca; Martín-Broto, Javier; Alemany, Regina

2012-01-01

225

Inhibition of P-glycoprotein-mediated transport by extracts of and monoterpenoids contained in Zanthoxyli fructus.  

PubMed

Citrus (rutaceous) herbs are often used in traditional medicine and Japanese cuisine and can be taken concomitantly with conventional medicine. In this study, the effect of various citrus-herb extracts on P-glycoprotein (P-gp)-mediated transport was examined in vitro to investigate a possible interaction with P-gp substrates. Component monoterpenoids of the essential oil in Zanthoxyli fructus was screened to find novel P-gp inhibitors. LLC-GA5-COL150 cells transfected with human MDR1 cDNA encoding P-gp were used. Cellular accumulation of [3H]digoxin was measured in the presence or absence of P-gp inhibitors or test samples. Aurantii fructus, Evodiae fructus, Aurantii fructus immaturus, Aurantii nobilis pericarpium, Phellodendri cortex, and Zanthoxyli fructus were extracted with hot water (decocted) and then fractionated with ethyl acetate. The cell to medium ratio of [3H]digoxin accumulation increased significantly in the presence of the decoction of Evodiae fructus, Aurantii nobilis pericarpium, and Zanthoxyli fructus, and the ethyl acetate fraction of all citrus herbs used. The ethyl acetate fraction of Zanthoxyli fructus exhibited the strongest inhibition of P-gp among tested samples with an IC50 value of 166 microg/mL. Then its component monoterpenoids, geraniol, geranyl acetate, (R)-(+)-limonene, (R)-(+)-linalool, citronellal, (R)-(+)-citronellal, DL-citronellol, (S)-(-)-beta-citronellol, and cineole, were screened. (R)-(+)-citronellal and (S)-(-)-beta-citronellol inhibited P-gp with IC50 values of 167 microM and 504 microM, respectively. These findings suggest that Zanthoxyli fructus may interact with P-gp substrates and that some monoterpenoids with the relatively lower molecular weight of about 150 such as (R)-(+)-citronellal can be potent inhibitors of P-gp. PMID:15890377

Yoshida, Naoko; Takagi, Akiyoshi; Kitazawa, Hidenori; Kawakami, Junichi; Adachi, Isao

2005-12-01

226

Inhibition of P-glycoprotein-mediated transport by extracts of and monoterpenoids contained in Zanthoxyli Fructus  

SciTech Connect

Citrus (rutaceous) herbs are often used in traditional medicine and Japanese cuisine and can be taken concomitantly with conventional medicine. In this study, the effect of various citrus-herb extracts on P-glycoprotein (P-gp)-mediated transport was examined in vitro to investigate a possible interaction with P-gp substrates. Component monoterpenoids of the essential oil in Zanthoxyli Fructus was screened to find novel P-gp inhibitors. LLC-GA5-COL150 cells transfected with human MDR1 cDNA encoding P-gp were used. Cellular accumulation of [{sup 3}H]digoxin was measured in the presence or absence of P-gp inhibitors or test samples. Aurantii Fructus, Evodiae Fructus, Aurantii Fructus Immaturus, Aurantii Nobilis Pericarpium, Phellodendri Cortex, and Zanthoxyli Fructus were extracted with hot water (decocted) and then fractionated with ethyl acetate. The cell to medium ratio of [{sup 3}H]digoxin accumulation increased significantly in the presence of the decoction of Evodiae Fructus, Aurantii Nobilis Pericarpium, and Zanthoxyli Fructus, and the ethyl acetate fraction of all citrus herbs used. The ethyl acetate fraction of Zanthoxyli Fructus exhibited the strongest inhibition of P-gp among tested samples with an IC{sub 5} value of 166 {mu}g/mL. Then its component monoterpenoids, geraniol, geranyl acetate (R)-(+)-limonene, (R)-(+)-linalool, citronellal (R)-(+)-citronellal, DL-citronellol (S)-(-)-{beta}-citronellol, and cineole, were screened. (R)-(+)-citronellal and (S)-(-)-{beta}-citronellol inhibited P-gp with IC{sub 5} values of 167 {mu}M and 504 {mu}M, respectively. These findings suggest that Zanthoxyli Fructus may interact with P-gp substrates and that some monoterpenoids with the relatively lower molecular weight of about 150 such as (R)-(+)-citronellal can be potent inhibitors of P-gp.

Yoshida, Naoko [Department of Hospital Pharmacy, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194 (Japan); Takagi, Akiyoshi [Department of Hospital Pharmacy, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194 (Japan); Kitazawa, Hidenori [Department of Hospital Pharmacy, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194 (Japan); Kawakami, Junichi [Department of Hospital Pharmacy, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194 (Japan)]. E-mail: kawakami-tym@umin.ac.jp; Adachi, Isao [Department of Hospital Pharmacy, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194 (Japan)

2005-12-01

227

An in vitro evaluation of guanfacine as a substrate for P-glycoprotein  

PubMed Central

Background With a US Food and Drug Administration-labeled indication to treat attention-deficit/hyperactivity disorder (ADHD), the nonstimulant guanfacine has become the preferred ?2-agonist for ADHD treatment. However, significant interindividual variability has been observed in response to guanfacine. Consequently, hypotheses of a contributing interaction with the ubiquitously expressed drug transporter, P-glycoprotein (P-gp), have arisen. We performed an in vitro study to determine if guanfacine is indeed a substrate of P-gp. Methods Intracellular accumulation of guanfacine was compared between P-gp expressing LLC-PK1/MDR1 cells and P-gp-negative LLC-PK1 cells to evaluate the potential interaction between P-gp and guanfacine. Cellular retention of guanfacine was analyzed using a high-performance liquid chromatographic-ultraviolet method. Rhodamine6G, a known P-gp substrate, was included in the study as a positive control. Results At guanfacine concentrations of 50 ?M and 5 ?M, intracellular accumulation of guanfacine in LLC-PK1/MDR1 cells was, 35.9% ± 4.8% and 49.0% ± 28.3% respectively, of that in LLC-PK1 cells. In comparison, the concentration of rhodamine6G, the positive P-gp substrate, in LLC-PK1/MDR1 cells was only 5% of that in LLC-PK1 cells. Conclusion The results of the intracellular accumulation study suggest that guanfacine is, at best, a weak P-gp substrate. Therefore, it is unlikely that P-gp, or any genetic variants thereof, are a determining factor in the interindividual variability of response observed with guanfacine therapy.

Gillis, Nancy K; Zhu, Hao-Jie; Markowitz, John S

2011-01-01

228

Pre-clinical evidence for altered absorption and biliary excretion of irinotecan (CPT-11) in combination with quercetin: possible contribution of P-glycoprotein.  

PubMed

P-glycoprotein (P-gp) is found to play a very significant role in intestinal and biliary transport of irinotecan and its active metabolite, SN-38. This makes P-gp inhibition a logical strategy for improving irinotecan's oral efficacy and reducing its toxicity. The objective of the present study was to identify the most suitable P-gp inhibitor, amongst various commonly used herbal components via in vitro screening; followed by determination of in vivo effects in rats. Caco-2 cell monolayers were used to investigate the influence of various components (quercetin, hesperitin, piperine, curcumin and naringenin) on the transport of irinotecan. The secretory transport (basolateral-to-apical) was significantly decreased by all components (p<0.05) except piperine. In the apical-to-basolateral transport, quercetin showed the highest absorptive permeability enhancement and P-gp interaction potential making it an appropriate candidate for further in vivo studies in female Wistar rats. Quercetin pre-treatment resulted in increased irinotecan C(max) and area under curve (AUC) with a concomitant decrease in t(max), plasma clearance and volume of distribution (p<0.05). The absolute bioavailability (F) of irinotecan control was 33%, which was increased to 43% (1.3 fold) by quercetin administration. The amounts of irinotecan and SN-38 eliminated in bile in control rats, is reduced to almost half when treated with quercetin. Our studies not only propose a safe approach for bioavailability enhancement and reducing toxicity of irinotecan by P-gp inhibition but in another way also reiterate the significance of elucidating herb-drug interactions for future insights. PMID:18619980

Bansal, Tripta; Awasthi, Anshumali; Jaggi, Manu; Khar, Roop K; Talegaonkar, Sushama

2008-08-15

229

P-glycoprotein- and organic anion-transporting polypeptide-mediated transport of periplocin may lead to drug-herb/drug-drug interactions  

PubMed Central

Periplocin, an active and toxic component of the traditional Chinese herbal medicine Periploca sepium Bge, is a cardiac glycoside compound that has been implicated in various clinical accidents. This study investigated the role of transporters in the intestinal absorption and biliary excretion of periplocin, as well as the possible metabolic mechanism of periplocin in liver S9. In a bidirectional transport assay using Madin–Darby canine kidney (MDCK) and MDCK multidrug-resistance protein (MRP)-1 cell monolayers, both in situ intestinal and liver-perfusion models were used to evaluate the role of efflux and uptake transporters on the absorption and biliary excretion of periplocin. In addition, in vitro metabolism of periplocin was investigated by incubating with human/rat liver S9 homogenate fractions to evaluate its metabolic mechanisms in liver metabolic enzymes. The results showed that P-glycoprotein (P-gp) was involved in the intestinal absorption of periplocin, whereas MRP2 and breast cancer-resistance protein were not. The efflux function of P-gp may be partly responsible for the low permeability and bioavailability of periplocin. Moreover, both inhibitors of P-gp and organic anion-transporting polypeptides (OATPs) increased periplocin biliary excretion. No obvious indications of metabolism were observed in the in vitro incubation system, which suggests that periplocin did not interact with the hepatic drug metabolic enzymes. The results of this study showed that the efflux and uptake transporters P-gp and OATPs were involved in the absorption and biliary excretion of periplocin, which may partially account for its low permeability and bioavailability. As a toxic compound, potential drug–herb/herb–herb interactions based on OATPs and P-gp should be taken into account when using P. sepium Bge in the clinic.

Liang, Sheng; Deng, Fengchun; Xing, Haiyan; Wen, He; Shi, Xiaoyan; Martey, Orleans Nii; Koomson, Emmanuel; He, Xin

2014-01-01

230

P-glycoprotein- and organic anion-transporting polypeptide-mediated transport of periplocin may lead to drug-herb/drug-drug interactions.  

PubMed

Periplocin, an active and toxic component of the traditional Chinese herbal medicine Periploca sepium Bge, is a cardiac glycoside compound that has been implicated in various clinical accidents. This study investigated the role of transporters in the intestinal absorption and biliary excretion of periplocin, as well as the possible metabolic mechanism of periplocin in liver S9. In a bidirectional transport assay using Madin-Darby canine kidney (MDCK) and MDCK multidrug-resistance protein (MRP)-1 cell monolayers, both in situ intestinal and liver-perfusion models were used to evaluate the role of efflux and uptake transporters on the absorption and biliary excretion of periplocin. In addition, in vitro metabolism of periplocin was investigated by incubating with human/rat liver S9 homogenate fractions to evaluate its metabolic mechanisms in liver metabolic enzymes. The results showed that P-glycoprotein (P-gp) was involved in the intestinal absorption of periplocin, whereas MRP2 and breast cancer-resistance protein were not. The efflux function of P-gp may be partly responsible for the low permeability and bioavailability of periplocin. Moreover, both inhibitors of P-gp and organic anion-transporting polypeptides (OATPs) increased periplocin biliary excretion. No obvious indications of metabolism were observed in the in vitro incubation system, which suggests that periplocin did not interact with the hepatic drug metabolic enzymes. The results of this study showed that the efflux and uptake transporters P-gp and OATPs were involved in the absorption and biliary excretion of periplocin, which may partially account for its low permeability and bioavailability. As a toxic compound, potential drug-herb/herb-herb interactions based on OATPs and P-gp should be taken into account when using P. sepium Bge in the clinic. PMID:24872678

Liang, Sheng; Deng, Fengchun; Xing, Haiyan; Wen, He; Shi, Xiaoyan; Martey, Orleans Nii; Koomson, Emmanuel; He, Xin

2014-01-01

231

Prenylated xanthones as potential P-glycoprotein modulators  

Microsoft Academic Search

Dimethylallyl (DMA) derivatives of a naturally occurring xanthone (decussatin 1) were prepared. Their activity as potential P-glycoprotein inhibitors was monitored by affinity of direct binding and compared to that of corresponding DMA-flavones. Both classes of compounds exhibited the same structure–activity relationships. Decreasing polarity enhanced the binding affinity for the P-glycoprotein C-terminal cytosolic domain since DMA derivatives were more active, but

D. Noungoué Tchamo; M.-G Dijoux-Franca; A.-M Mariotte; E Tsamo; J. B Daskiewicz; C Bayet; D Barron; G Conseil; A Di Pietro

2000-01-01

232

Clinicopathological Parameters and Expression of P-Glycoprotein and MRP-1 in Retinoblastoma  

Microsoft Academic Search

Purpose: The immunohistochemical expressions of two multidrug resistance proteins, P-glycoprotein (P-gp) and multidrug resistance-related protein-1 (MRP-1), were studied in retinoblastoma and the correlations with the clinicopathological parameters were assessed. Method: Sixty-five enucleated eyes containing retinoblastoma were included in the study. Following hematoxylin-eosin staining, tumor differentiation, presence of choroidal invasion, optic nerve invasion, retinal invasion, necrosis and presence of calcification were

Hayyam Kiratli; Sevgül Bilgiç

2007-01-01

233

The role of P-glycoprotein ( MDR1 ) polymorphisms and mutations in colorectal cancer  

Microsoft Academic Search

To better understand physiological function of P-glycoprotein (P-gp), encoded by MDR1 gene, and its role in cancer, we analyzed tumor and corresponding normal tissue from 400 patients with previously non treated colorectal cancer for germline and somatic alterations in MDR1 gene and compared the results to histopathological data and microsatellite instability status of tumors. We have identified naturally occurring mutations

Uroš Poto?nik; Metka Ravnik Glava?; Rastko Golouh; Damjan Glava?

2001-01-01

234

Generation of multidrug resistant lymphoma cell lines stably expressing P-glycoprotein.  

PubMed

The objective of this study was to generate new P-glycoprotein (P-gp)-expressing multidrug resistant (MDR) cell lines by drug selection. Since our previous studies have been carried out with cells infected with a P-gp-containing vector, it was important to confirm our findings in cells generated by drug selection. In this report, we describe three B-lymphoma cell lines which became drug-resistant by stepwise exposure to vincristine (VCR): Raji cells resistant to 18 nM VCR (R18V), Namalwa cells resistant to 21 nM VCR (N21V) and DHL-4 cells resistant to 12 nM VCR (DHL-4/12V). Cells overexpressed P-gp and continued to express CD19, CD20 and CD22, all of which are targets for monoclonal antibody (MAb) therapy. The P-gp pump in these new cells was functional as determined by the efflux of Rhodamine 123 and DIOC2, and the three cell lines were resistant to several chemotherapeutic drugs. We further determined that their P-gp phenotype was stable in xenografted SCID mice and that the tumors were also resistant to chemotherapy. We will now use these new MDR cells to determine whether monoclonal antibodies against CD19 and -20 can reverse P-gp, as we previously demonstrated using Namalwa cells infected with a human mdr1 gene-containing retrovirus. PMID:18357372

Pop, Iliodora; Pop, Laurentiu; Vitetta, Ellen S; Ghetie, Maria-Ana

2008-04-01

235

The network of P-glycoprotein and microRNAs interactions.  

PubMed

Overexpression of P-glycoprotein (P-gp) contributes to the multidrug resistance (MDR) phenotype found in many cancer cells. P-gp has been identified as a promising molecular target, although attempts to find successful therapies to counteract its function as a drug efflux pump have largely failed to date. Apart from its role in drug efflux, P-gp may have other cellular functions such as being involved in apoptosis, and is found in various locations in the cell. Its expression is highly regulated, namely by microRNAs (miRNAs or miRs). In addition, P-gp may regulate the expression of miRs in the cell. Furthermore, both P-gp and miRs may be found in microvesicles or exosomes and may be transported to neighboring, drug-sensitive cells. Here, we review this current issue together with recent evidence of this network of interactions between P-gp and miRs. PMID:24122334

Lopes-Rodrigues, Vanessa; Seca, Hugo; Sousa, Diana; Sousa, Emília; Lima, Raquel T; Vasconcelos, M Helena

2014-07-15

236

Ontogeny of renal P-glycoprotein expression in mice: correlation with digoxin renal clearance.  

PubMed

Digoxin is eliminated mainly by the kidney through glomerular filtration and P-glycoprotein (P-gp) mediated tubular secretion. Toddlers and young children require higher doses of digoxin per kilogram of bodyweight than adults, although the reasons for this have not been elucidated. We hypothesized there is an age-dependant increase in P-gp expression in young children. The objectives of this study were to elucidate age-dependant expression of renal P-gp and its correlation with changes in the clearance rate of digoxin. FVB mice were killed at different ages to prepare total RNA for P-gp expression studies. Semi-quantitative RT-PCR was conducted to analyze mdr1a and mdr1b ontogeny in the kidney at: birth, 7, 14, 21, 28 and 45-d old adults. The pharmacokinetics of digoxin (7 microg/kg) was studied in mice of the same age groups. Newborn and Day 7 levels of both mdr1a and mdr1b were marginal. Day 21 mdr1b levels were significantly higher than both Day 14 and Day 28 levels. Digoxin clearance rates were the highest at Day 21, with significant correlation between P-gp expression and clearance values. Increases in digoxin clearance rates after weaning may be attributed, at least in part, to similar increases in P-gp expression. PMID:16306209

Pinto, Natasha; Halachmi, Naomi; Verjee, Zulfikarali; Woodland, Cindy; Klein, Julia; Koren, Gideon

2005-12-01

237

Intestinal first-pass metabolism by cytochrome p450 and not p-glycoprotein is the major barrier to amprenavir absorption.  

PubMed

Recent studies showed that P-glycoprotein (P-gp) increases the portal bioavailability (FG) of loperamide by sparing its intestinal first-pass metabolism. Loperamide is a drug whose oral absorption is strongly attenuated by intestinal P-gp-mediated efflux and first-pass metabolism by cytochrome P450 3A (CYP3A). Here the effect of the interplay of P-gp and Cyp3a in modulating intestinal first-pass metabolism and absorption was investigated for another Cyp3a/P-gp dual substrate amprenavir, which is less efficiently effluxed by P-gp than loperamide. After oral administration of amprenavir, the portal concentrations and FG of amprenavir were approximately equal in P-gp competent and P-gp deficient mice. Mechanistic studies on the effect of P-gp on Cyp3a-mediated metabolism of amprenavir using intestinal tissue from P-gp competent and P-gp deficient mice (Ussing-type diffusion chamber) revealed that P-gp-mediated efflux caused only a slight reduction of oxidative metabolism of amprenavir. Studies in which portal concentrations and FG were measured in P-gp competent and P-gp deficient mice whose cytochrome P450 (P450) enzymes were either intact or inactivated showed that intestinal first-pass metabolism attenuates the oral absorption of amprenavir by approximately 10-fold, whereas P-gp efflux has a relatively small effect (approximately 2-fold) in attenuating the intestinal absorption. Cumulatively, these studies demonstrate that P-gp has little influence on the intestinal first-pass metabolism and FG of amprenavir and that intestinal P450-mediated metabolism plays the dominant role in attenuating the oral absorption of this drug. PMID:23821186

Dufek, Matthew B; Bridges, Arlene S; Thakker, Dhiren R

2013-09-01

238

Polyaromatic alkaloids from marine invertebrates as cytotoxic compounds and inhibitors of multidrug resistance caused by P-glycoprotein.  

PubMed

The effects of several members of the family of lamellarins, polyaromatic alkaloids isolated from tunicates belonging to the genus Didemnum, on the growth of several tumour cell lines and on P-glycoprotein (P-gp)-mediated multidrug resistance (MDR), were investigated. Cytotoxicity experiments of lamellarins were performed on a panel of tumour cell lines, including two multidrug-resistant cell lines. Some lamellarins showed good anti-tumour activity, with similar levels of cytotoxicity against both the resistant and their corresponding parental cell lines. Two lamellarins displayed a high potency against lung carcinoma cells. Studies of the resistance modifier activity of the different lamellarins at non-toxic concentrations were also carried out in cells exhibiting MDR, and lamellarin I was selected for the highest chemosensitising activity. At non-toxic doses, verapamil and lamellarin I effectively increased the cytotoxicity of doxorubicin, vinblastine and daunorubicin in a concentration-dependent manner in multidrug-resistant cells, but the potency of lamellarin I as a MDR modulator was 9- to 16-fold higher than that of verapamil. In vitro measurements of rhodamine 123 accumulation in the multidrug-resistant Lo Vo/Dx cells suggest that lamellarin I reverses MDR by directly inhibiting the P-gp-mediated drug efflux. This work underscores the possibility of using these marine-derived compounds as a potential new source of anti-tumoral drugs active on resistant cells as well as of non-toxic modulators of the MDR phenotype. PMID:8795567

Quesada, A R; García Grávalos, M D; Fernández Puentes, J L

1996-09-01

239

In silico model for P-glycoprotein substrate prediction: insights from molecular dynamics and in vitro studies.  

PubMed

P-glycoprotein (P-gp) is a plasma membrane efflux transporter belonging to ATP-binding cassette superfamily, responsible for multidrug resistance in tumor cells. Over-expression of P-gp in cancer cells limits the efficacy of many anticancer drugs. A clear understanding of P-gp substrate binding will be advantageous in early drug discovery process. However, substrate poly-specificity of P-gp is a limiting factor in rational drug design. In this investigation, we report a dynamic trans-membrane model of P-gp that accurately identified the substrate binding residues of known anticancer agents. The study included homology modeling of human P-gp based on the crystal structure of C. elegans P-gp, molecular docking, molecular dynamics analyses and binding free energy calculations. The model was further utilized to speculate substrate propensity of in-house anticancer compounds. The model demonstrated promising results with one anticancer compound (NSC745689). As per our observations, the molecule could be a potential lead for anticancer agents devoid of P-gp mediated multiple drug resistance. The in silico results were further validated experimentally using Caco-2 cell lines studies, where NSC745689 exhibited poor permeability (P app 1.03 ± 0.16 × 10(-6) cm/s) and low efflux ratio of 0.26. PMID:23612916

Prajapati, Rameshwar; Singh, Udghosh; Patil, Abhijeet; Khomane, Kailas S; Bagul, Pravin; Bansal, Arvind K; Sangamwar, Abhay T

2013-04-01

240

Tumor endothelial expression of P-glycoprotein upon microvesicular transfer of TrpC5 derived from adriamycin-resistant breast cancer cells.  

PubMed

Treatment of carcinoma commonly fails due to chemoresistance. Studies have shown that endothelial cells acquire resistance via the tumor microenvironment. Microvesicle (MV) shedding from the cell membrane to the microenvironment plays an important role in communication between cells. The aim of the present study was to determine whether MCF-7 adriamycin-resistant cells (MCF-7/ADM) shed MVs that alter the characteristics of human microvessel endothelial cells (HMECs). MVs from tumor cells transferred a Ca(2+)-permeable channel TrpC5 to HMECs, inducing the expression of P-glycoprotein (P-gp) by activation of the transcription factor NFATc3 (nuclear factor of activated T cells isoform c3). Expression of the mdr1 gene was blocked by the TrpC5-blocking antibody T5E3, and the production of P-gp in HMECs was reduced by blockade of TrpC5. Thus, we postulate that endothelial cells acquire the resistant protein upon exposure to TrpC5-containg MVs in the microenvironment, and express P-gp in the TrpC5-NFATc3 signal pathway. PMID:24582564

Dong, YePing; Pan, QiongXi; Jiang, Li; Chen, Zhen; Zhang, FangFang; Liu, YanJun; Xing, Hui; Shi, Mei; Li, Jiao; Li, XiYuan; Zhu, YaoDan; Chen, Yun; Bruce, Iain C; Jin, Jian; Ma, Xin

2014-03-28

241

Novel formulation approaches for optimising delivery of anticancer drugs based on P-glycoprotein modulation.  

PubMed

Considerable research efforts have been directed towards understanding the enigma of P-glycoprotein (P-gp) in drug development and delivery. P-gp is a multi-specific drug efflux transporter that plays a significant role in governing the bioavailability of various anti-cancer drugs. Modulation of this efflux transporter by various traditional 'chemosensitisers' forms a distinctive approach in improving pharmacokinetics and conquering drug resistance. However, such inhibitors show limitations associated with their safety and unwanted pharmacokinetic drug interaction restraining their clinical applicability. To address these concerns, several research groups have used pharmaceutical excipients (functional excipients or additives) to inhibit P-gp and enhance drug permeability. This article focuses on such excipients, various co-development strategies for the formulation of cytotoxic drugs with this multi-drug resistance (MDR) reversing additives. PMID:19647803

Bansal, Tripta; Akhtar, Naseem; Jaggi, Manu; Khar, Roop K; Talegaonkar, Sushama

2009-11-01

242

Docking Applied to the Prediction of the Affinity of Compounds to P-Glycoprotein  

PubMed Central

P-glycoprotein (P-gp) is involved in the transport of xenobiotic compounds and responsible for the decrease of the drug accumulation in multi-drug-resistant cells. In this investigation we compare several docking algorithms in order to find the conditions that are able to discriminate between P-gp binders and nonbinders. We built a comprehensive dataset of binders and nonbinders based on a careful analysis of the experimental data available in the literature, trying to overcome the discrepancy noticeable in the experimental results. We found that Autodock Vina flexible docking is the best choice for the tested options. The results will be useful to filter virtual screening results in the rational design of new drugs that are not expected to be expelled by P-gp.

Palestro, Pablo H.; Gavernet, Luciana; Estiu, Guillermina L.; Bruno Blanch, Luis E.

2014-01-01

243

Interaction of forskolin with the P-glycoprotein multidrug transporter  

Microsoft Academic Search

Forskolin and 1,9-dideoxyforskolin, an analogue that does not activate adenylyl cyclase, were tested for their ability to enhance the cytotoxic effects of adriamycin in human ovarian carcinoma cells, SKOV3, which are sensitive to adriamycin and express low levels of P-glycoprotein, and a variant cell line, SKVLB, which overexpresses the P-glycoprotein and has the multidrug reing ance (MDR) phenotype. Forskolin and

D. I. Ming s; K. B. Seamon; L. A. Speicher; Kenneth D. Tew; A. E. Ruoho

1991-01-01

244

Estimation of the unbound brain concentration of P-glycoprotein substrates or nonsubstrates by a serial cerebrospinal fluid sampling technique in rats.  

PubMed

The unbound concentration in plasma drives the transport of the drug into the brain, and the unbound drug concentration in the central nervous system (CNS) drives the interaction with the target eliciting the pharmacological effect. Delivery of the drug to the CNS is a challenge because of the unique neurovascular unit, which restricts the passage of drugs into the brain. The efflux transporters [especially P-glycoprotein (P-gp)] present at the blood-brain barrier (BBB) act as one of the major detractors for keeping drugs outside the CNS. The cerebrospinal fluid (CSF) drug concentration has been used as a surrogate for unbound brain concentrations and has proven to be a good indicator to relate to CNS activity. Herein, we have established a serial CSF sampling technique in rats, which allowed CSF sampling from a single animal and reduced the number of animals required, as well as the interanimal variance associated with a composite/terminal study design. Concentrations in the CSF sampled from the cisterna magna serially from the same rat were compared with the concentrations obtained from discrete CSF sampling and with brain concentrations. The serial CSF sampling technique was also authenticated by ensuring no change in the barrier without any indication of damage caused by the repeated puncture of cisterna magna. This technique was corroborated using three passively permeable compounds (carbamazepine, theophylline, and propranolol), three P-gp substrates (quinidine, verapamil, and digoxin), and one l-amino acid uptake transporter substrate (gabapentin). The P-gp substrates were also used in separate studies with the P-gp inhibitor elacridar to assess the effect on CSF concentration versus brain concentration on P-gp inhibition. The CSF concentration and unbound brain concentration were comparable (within 3-fold) for all compounds, including P-gp substrates even in the presence of elacridar. Therefore, this technique can prove to be beneficial for predicting the unbound drug concentrations in the brain from the CSF concentrations and reduce the cost incurred in preclinical animal models. Chemical inhibition by elacridar and prediction of the brain unbound concentrations from the serial CSF sampling of P-gp substrates in the rat may be an attractive alternative to the use of genetically knocked out rodents. PMID:24380373

Mariappan, T Thanga; Kurawattimath, Vishwanath; Gautam, Shashyendra Singh; Kulkarni, Chetan P; Kallem, Rajareddy; Taskar, Kunal S; Marathe, Punit H; Mandlekar, Sandhya

2014-02-01

245

Functional Correlation of P-Glycoprotein Expression and Genotype with Expression of the Human Immunodeficiency Virus Type 1 Coreceptor CXCR4  

Microsoft Academic Search

The aim of this study was to investigate the relationship between lymphocyte P-glycoprotein (P-gp) expres- sion and genotype in vivo and the expression of lymphocyte receptors critical in the life cycle of human immunodeficiency virus type 1 (HIV-1), i.e., CD4, CCR5, and CXCR4. Using flow cytometry to quantify each membrane receptor\\/transporter, we demonstrate a highly significant correlation between P-gp protein

Andrew Owen; Becky Chandler; Patrick G. Bray; Stephen A. Ward; C. Anthony Hart; David J. Back; Saye H. Khoo

2004-01-01

246

Reversion of P-glycoprotein-mediated multidrug resistance by diallyl trisulfide in a human osteosarcoma cell line.  

PubMed

Diallyl trisulfide (DATS), the main sulfuric compound in garlic, has been shown to have antitumor effects. The present study aimed to ascertain whether DATS reverses the drug resistance of human osteosarcoma cells in vitro and to investigate its potential mechanisms. Human osteosarcoma U2-OS cells were treated with different concentrations of DATS. Cell proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, while P-glycoprotein (P-gp) expression and the proportion of apoptotic cells were measured by flow cyto-metry. Morphological changes were observed under an optical microscope. ?uclear factor-?B (NF-?B) and inhibitor of NF-?B (I?B) activities were measured by PCR and western blot analysis. Results showed that the proliferation of U2-OS cells treated with different concentrations of DATS was signi-ficantly decreased in a concentration- and time-dependent manner. DATS increased the toxic effect of adriamycin on U2-OS cells. Moreover, P-gp expression was decreased and the apoptosis rate was increased in a concentration-dependent manner following treatment of DATS. Additionally, NF-?B activity was inhibited by DATS while expression of I?B was increased. Our data clearly suggest that DATS has significant anticancer effects on human osteosarcoma cells. The potential mechanisms include reducing the multidrug resistance and inducing apoptosis. NF-?B suppression may be involved in DATS-induced inhibition of cell proliferation. PMID:24788927

Wang, Zhiyong; Xia, Qing; Cui, Jia; Diao, Yutao; Li, Jianmin

2014-06-01

247

Selective TRAIL-triggered apoptosis due to overexpression of TRAIL death receptor 5 (DR5) in P-glycoprotein-bearing multidrug resistant CEM/VBL1000 human leukemia cells  

PubMed Central

The death-inducing cytokine, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), holds enormous promise as a cancer therapeutic due to its highly selective apoptosis-inducing action on neoplastic versus normal cells. Our results revealed that TRAIL selectively triggered apoptosis in the P-glycoprotein (P-gp, ABCB1) and DR5 overexpressing CEM/VBL1000 multidrug resistant leukemia cell line, but not in the parental CEM cells. Moreover, TRAIL treatment reduced P-gp expression in these cells. Mechanistic analysis of TRAIL-induced apoptosis revealed that TRAIL hypersensitivity is due to robust upregulation of the TRAIL receptor DR5 at the protein and mRNA levels during development of MDR in the CEM/VBL1000 variant. DR5 upregulation was independent of the level of expression of endoplasmic reticulum stress regulator C/EBP homologous transcription factor (CH0P/GADD153). TRAIL-triggered apoptosis was associated with increased expression of FADD; activation of caspases-3, -8, -9, and -10; and cytochrome c release from mitochondria. Therefore, both the extrinsic and intrinsic apoptosis pathways are involved in this process. These findings for the first time reveal that TRAIL treatment selectively causes apoptosis in P-gp-overexpressing CEM/VBL1000 cells through strong upregulation of DR5. Moreover, this hypersensitivity to TRAIL and its effect on reducing P-gp expression in these cells hold significant clinical implications for using TRAIL to eradicate MDR malignant cells.

Park, Soo-Jung; Bijangi-Vishehsaraei, Khadijeh; Safa, Ahmad R.

2010-01-01

248

Pharmacokinetic Compatibility of Ginsenosides and Schisandra Lignans in Shengmai-san: From the Perspective of P-Glycoprotein  

PubMed Central

Background Phytochemical-mediated alterations in P-glycoprotein (P-gp) activity may result in herb-drug interactions by altering drug pharmacokinetics. Shengmai-san, a traditional Chinese herbal medicine composed by Panax Ginseng, Ophiopogon Japonicus, and Schisandra Chinensis, is routinely being used for treating various coronary heart diseases. In our previous studies, Schisandra Lignans Extract (SLE) was proved as a strong P-gp inhibitor, and herein, the compatibility of Shengmai-san was studied by investigating the influence of SLE on the pharmacokinetics of the ginsenosides from the perspective of P-gp. Methodology Pharmacokinetic experiments were firstly performed based on in vitro uptake, efflux and transport experiments in Caco-2, LLC-PK1 wild-type and MDR1-overexpressing L-MDR1 cells. During the whole experiment, digoxin, a classical P-gp substrate, was used as a positive control drug to verify the cells used are the valid models. Meanwhile, the effects of SLE on the pharmacokinetics of ginsenosides were further investigated in rats after single-dose and multi-dose of SLE. Results and Conclusions The efflux ratios of ginsenoside Rb2, Rc, Rg2, Rg3, Rd and Rb1 were found more than 3.5 in L-MDR1 cells and can be decreased significantly by verapamil (a classical P-gp inhibitor). Contrarily, the efflux ratios of other ginsenosides (Rh1, F1, Re, and Rg1) were lower than 2.0 and not affected by verapamil. Then, the effects of SLE on the uptake and transport of ginsenosides were investigated, and SLE was found can significantly enhance the uptake and inhibit the efflux ratio of ginsenoside Rb2, Rc, Rg2, Rg3, Rd and Rb1 in Caco-2 and L-MDR1 cells. Besides, In vivo experiments showed that single-dose and multi-dose of SLE at 500 mg/kg could increase the area under the plasma concentration time curve of Rb2, Rc and Rd significantly without affecting terminal elimination half-time. In conclusion, SLE could enhance the exposure of ginsenosides Rb2, Rc, Rg2, Rg3, Rd and Rb1 significantly.

Liang, Yan; Zhou, Yuanyuan; Zhang, Jingwei; Rao, Tai; Zhou, Lijun; Xing, Rong; Wang, Qian; Fu, Hanxu; Hao, Kun; Xie, Lin; Wang, Guangji

2014-01-01

249

Reversion of P-glycoprotein-mediated multidrug resistance by guggulsterone in multidrug-resistant human cancer cell lines.  

PubMed

Multidrug resistance (MDR) presents a serious problem in cancer chemotherapy. Our previous studies have shown that guggulsterone could reverse MDR through inhibiting the function and expression of P-glycoprotein (P-gp). The present study is to further investigate the reversal effects of guggulsterone on MDR in drug-resistant cancer cell lines. The effects of guggulsterone on MDR1mRNA gene expression, intracellular pH, P-gp ATPase activity and glucosylceramide synthase (GCS) expression were assessed by RT-PCR, Laser Scanning Confocal Microscope using the pH-sensitive fluorescent probe BCECF-AM, Pgp-Glo assay system, and flow cytometric technology, respectively. The results showed that guggulsterone ranging from 2.5 to 80 ?M significantly promoted the activity of P-gp ATPase in a dose-dependent manner. The intracellular pH of K562/DOX cells was found to be higher than K562 cells. After treatment with guggulsterone (1, 3, 10, 30, 100 ?M), intracellular pH of K562/DOX cells decreased in a dose- and time-dependent manner. However, the present study revealed that guggulsterone ranging from 3 to 100 ?M had little influence on MDR1 gene expression in K562/DOX cells. Further, the isogenic doxorubicin-resistant MCF-7/DOX cells exhibited a 4.9-fold increase in GCS level as compared with parental MCF-7 human breast cancer cells. After treatment with guggulsterone (0.1, 1, 10 ?M) for 48 h, MCF-7/DOX cells were found to have no change of GCS protein expression amount. Guggulsterone might be a potent MDR reversal agent, and its mechanism on MDR needs more research. PMID:22960326

Xu, Hong-Bin; Xu, Lu-Zhong; Li, Ling; Fu, Jun; Mao, Xia-Ping

2012-11-01

250

Lamellarins as inhibitors of P-glycoprotein-mediated multidrug resistance in a human colon cancer cell line.  

PubMed

Chemical analysis of a Didemnum sp. (CMB-01656) collected during scientific Scuba operations off Wasp Island, New South Wales, yielded five new lamellarins A1 (1), A2 (2), A3 (3), A4 (4) and A5 (5) and eight known lamellarins C (6), E (7), K (8), M (9), S (10), T (11), X (12) and ? (13). Analysis of a second Didemnum sp. (CMB-02127) collected during scientific trawling operations along the Northern Rottnest Shelf, Western Australia, yielded the new lamellarin A6 (14) and two known lamellarins G (15) and Z (16). Structures were assigned to 1-16 on the basis of detailed spectroscopic analysis with comparison to literature data and authentic samples. Access to this unique library of natural lamellarins (1-16) provided a rare opportunity for structure-activity relationship (SAR) investigations, probing interactions between lamellarins and the ABC transporter efflux pump P-glycoprotein (P-gp) with a view to reversing multidrug resistance in a human colon cancer cell line (SW620 Ad300). These SAR studies, which were expanded to include the permethylated lamellarin derivative (17) and a series of lamellarin-inspired synthetic coumarins (19-24) and isoquinolines (25-26), successfully revealed 17 as a promising new non-cytotoxic P-gp inhibitor pharmacophore. PMID:22473938

Plisson, Fabien; Huang, Xiao-Cong; Zhang, Hua; Khalil, Zeinab; Capon, Robert J

2012-06-01

251

Characterization of Human Colorectal Cancer MDR1/P-gp Fab Antibody  

PubMed Central

In this study, the peptide sized 21?kDa covering P-gp transmembrane region was first prepared for generating a novel mouse monoclonal antibody Fab fragment with biological activity against multiple drug resistance protein P-gp21 by phage display technology. Phage-displayed antibody library prepared from mice spleen tissues was selected against the recombinant protein P-gp21 with five rounds of panning. A number of clones expressing Fab bound to P-gp21, showing neutralized activity in vitro, were isolated and screened by enzyme-linked immunosorbent assay based on its recognition properties to P-gp21 and human colorectal cancer tissue homogenate, resulting in identification of an optimal recombinant Fab clone (Number 29). Further characterization by recloning number 29 into an expression vector showed significant induction of the Fab antibody in the clone number 29 by Isopropyl ?-D-1-thiogalactopyranoside (IPTG). After purified by HiTrap Protein L, the specificity of the Fab antibody to P-gp21 was also confirmed. Not only was the targeted region of this monoclonal Fab antibody identified as a 16-peptide epitope (ALKDKKELEGSGKIAT) comprising residues 883–898 within the transmembrane (TM) domain of human P-gp, but also the binding ability with it was verified. The clinical implication of our results for development of personalized therapy of colorectal cancer will be further studied.

Zhang, Xuemei; Xiao, Gary Guishan; Gao, Ying

2013-01-01

252

Population pharmacokinetic modelling of non-linear brain distribution of morphine: influence of active saturable influx and P-glycoprotein mediated efflux  

PubMed Central

Background and purpose: Biophase equilibration must be considered to gain insight into the mechanisms underlying the pharmacokinetic-pharmacodynamic (PK-PD) correlations of opioids. The objective was to characterise in a quantitative manner the non-linear distribution kinetics of morphine in brain. Experimental approach: Male rats received a 10-min infusion of 4 mg kg?1 of morphine, combined with a continuous infusion of the P-glycoprotein (Pgp) inhibitor GF120918 or vehicle, or 40 mg kg?1 morphine alone. Unbound extracellular fluid (ECF) concentrations obtained by intracerebral microdialysis and total blood concentrations were analysed using a population modelling approach. Key results: Blood pharmacokinetics of morphine was best described with a three-compartment model and was not influenced by GF120918. Non-linear distribution kinetics in brain ECF was observed with increasing dose. A one compartment distribution model was developed, with separate expressions for passive diffusion, active saturable influx and active efflux by Pgp. The passive diffusion rate constant was 0.0014 min?1. The active efflux rate constant decreased from 0.0195 min?1 to 0.0113 min?1 in the presence of GF120918. The active influx was insensitive to GF120918 and had a maximum transport (Nmax/Vecf) of 0.66 ng min?1 ml?1 and was saturated at low concentrations of morphine (C50=9.9 ng ml?1). Conclusions and implications: Brain distribution of morphine is determined by three factors: limited passive diffusion; active efflux, reduced by 42% by Pgp inhibition; low capacity active uptake. This implies blood concentration-dependency and sensitivity to drug-drug interactions. These factors should be taken into account in further investigations on PK-PD correlations of morphine.

Groenendaal, D; Freijer, J; de Mik, D; Bouw, M R; Danhof, M; de Lange, E C M

2007-01-01

253

First evidence of the P-glycoprotein gene expression and multixenobiotic resistance modulation in earthworm.  

PubMed

Multixenobiotic resistance (MXR) is an important mechanism of cellular efflux mediated by ATP binding cassette (ABC) transporters that bind and actively remove toxic substrates from the cell. This study was the first to identify ABC transporter P-glycoprotein (P-gp/ABCB1) as a representative of the MXR phenotype in earthworm (Eisenia fetida). The identified partial cDNA sequence of ABCB1 overlapped with ABCB1 homologues of other organisms from 58.5 % to 72.5 %. We also studied the effect of five modulators (verapamil, cyclosporine A, MK571, probenecid, and orthovanadate) on the earthworm's MXR activity by measuring the accumulation of model substrates rhodamine B and rhodamine 123 in whole body tissue of the adult earthworm. MK571, orthovanadate, and verapamil significantly inhibited MXR activity, and rhodamine 123 turned out to better reflect MXR activity in that species than rhodamine B. Our results show that E. fetida can serve well as a test organism for environmental pollutants that inhibit MXR activity. PMID:24622780

Bošnjak, Ivana; Bielen, Ana; Babi?, Sanja; Sver, Lidija; Popovi?, Natalija Topi?; Strunjak-Perovi?, Ivan?ica; Což-Rakovac, Rozelinda; Klobu?ar, Roberta Sauerborn

2014-03-01

254

The role of intestinal P-glycoprotein in the interaction of digoxin and rifampin  

PubMed Central

Recent data point to the contribution of P-glycoprotein (P-gp) to digoxin elimination. On the basis of clinical observations of patients in whom digoxin levels decreased considerably when treated with rifampin, we hypothesized that concomitant rifampin therapy may affect digoxin disposition in humans by induction of P-gp. We compared single-dose (1 mg oral and 1 mg intravenous) pharmacokinetics of digoxin before and after coadministration of rifampin (600 mg/d for 10 days) in 8 healthy volunteers. Duodenal biopsies were obtained from each volunteer before and after administration of rifampin. The area under the plasma concentration time curve (AUC) of oral digoxin was significantly lower during rifampin treatment; the effect was less pronounced after intravenous administration of digoxin. Renal clearance and half-life of digoxin were not altered by rifampin. Rifampin treatment increased intestinal P-gp content 3.5 ± 2.1–fold, which correlated with the AUC after oral digoxin but not after intravenous digoxin. P-gp is a determinant of the disposition of digoxin. Concomitant administration of rifampin reduced digoxin plasma concentrations substantially after oral administration but to a lesser extent after intravenous administration. The rifampin-digoxin interaction appears to occur largely at the level of the intestine. Therefore, induction of intestinal P-gp could explain this new type of drug-drug interaction.

Greiner, Bernd; Eichelbaum, Michel; Fritz, Peter; Kreichgauer, Hans-Peter; von Richter, Oliver; Zundler, Johannes; Kroemer, Heyo K.

1999-01-01

255

Role of P-glycoprotein in the disposition of macrocyclic lactones: A comparison between ivermectin, eprinomectin, and moxidectin in mice.  

PubMed

Macrocyclic lactones (MLs) are lipophilic anthelmintics and substrates for P-glycoprotein (P-gp), an ATP-binding cassette transporter involved in drug efflux out of both host and parasites. To evaluate the contribution of P-gp to the in vivo kinetic disposition of MLs, the plasma kinetics, brain concentration, and intestinal excretion of three structurally different MLs (ivermectin, eprinomectin, and moxidectin) were compared in wild-type and P-gp-deficient [mdr1ab(-/-)] mice. Each drug (0.2 mg/kg) was administered orally, intravenously, or subcutaneously to the mice. Plasma, brain, and intestinal tissue concentrations were measured by high-performance liquid chromatography. The intestinal excretion rate after intravenous administration was determined at different levels of the small intestine by using an in situ intestinal perfusion model. P-gp deficiency led to a significant increase in the area under the plasma concentration-time curve (AUC) of ivermectin (1.5-fold) and eprinomectin (3.3-fold), whereas the moxidectin AUC was unchanged. Ivermectin and to a greater extent eprinomectin were both excreted by the intestine via a P-gp-dependent pathway, whereas moxidectin excretion was weaker and mostly P-gp-independent. The three drugs accumulated in the brains of the mdr1ab(-/-) mice, but eprinomectin concentrations were significantly lower. We concluded that eprinomectin disposition in mice is controlled mainly by P-gp efflux, more so than that of ivermectin, whereas moxidectin disposition appears to be mostly P-gp-independent. Given that eprinomectin and ivermectin have higher affinity for P-gp than moxidectin, these findings demonstrated that the relative affinity of MLs for P-gp could be predictive of the in vivo kinetic behavior of these drugs. PMID:20089736

Kiki-Mvouaka, Solange; Ménez, Cécile; Borin, Christiane; Lyazrhi, Faouri; Foucaud-Vignault, Magali; Dupuy, Jacques; Collet, Xavier; Alvinerie, Michel; Lespine, Anne

2010-04-01

256

In vitro to in vivo evidence of the inhibitor characteristics of Schisandra lignans toward P-glycoprotein.  

PubMed

Concomitant administration of herbal medicines with drugs that are P-glycoprotein (P-gp) substrates may produce significant herb-drug interactions. The purpose of this study was to evaluate the effects of Schisandra lignans extract (SLE) on P-gp thoroughly in vitro and in vivo, and to investigate the possible P-gp-based herb-drug interactions. In the in vitro experiments, the effect of SLE on the uptake and transport for P-gp substrates in Caco-2, LLC-PK1 and L-MDR1 cells were carefully investigated. Verapamil, a known P-gp inhibitor, was used as a positive control drug. Results shown that, 10 ?M verapamil and SLE (0.5, 2.0, and 10.0 ?g/ml) were observed to significantly enhance the uptake and inhibit the efflux ratio of P-gp substrates in Caco-2 and L-MDR1 cells. In vivo experiments showed that single-dose SLE at 500 mg/kg could increase the area under the plasma concentration time curve of digoxin and vincrisine significantly without affecting terminal elimination half-time. Long-term treatment with SLE for continuous 10 days could also increase the absorption of P-gp substrates with greatly down regulation of P-gp expression in rat intestinal and brain tissues. In conclusion, SLE was a strong P-gp inhibitor, which indicated a potential herb-drug interaction when SLE was co-administered with P-gp substrate drugs. PMID:23731657

Liang, Yan; Zhou, Yuanyuan; Zhang, Jingwei; Liu, Yanna; Guan, Tianye; Wang, Yu; Xing, Lu; Rao, Tai; Zhou, Lijun; Hao, Kun; Xie, Lin; Wang, Guang-ji

2013-08-15

257

The Functional Influences of Common ABCB1 Genetic Variants on the Inhibition of P-glycoprotein by Antrodia cinnamomea Extracts  

PubMed Central

Antrodia cinnamomea is a traditional healthy food that has been demonstrated to possess anti-inflammatory, antioxidative, and anticacer effects. The purpose of this study was to evaluate whether the ethanolic extract of A. cinnamomea (EEAC) can affect the efflux function of P-glycoprotein (P-gp) and the effect of ABCB1 genetic variants on the interaction between EEAC and P-gp. To investigate the mechanism of this interaction, Flp-In™-293 cells stably transfected with various genotypes of human P-gp were established and the expression of P-gp was confirmed by Western blot. The results of the rhodamine 123 efflux assay demonstrated that EEAC efficiently inhibited wild-type P-gp function at an IC50 concentration of 1.51±0.08 µg/mL through non-competitive inhibition. The IC50 concentrations for variant-type 1236T-2677T-3435T P-gp and variant-type 1236T-2677A-3435T P-gp were 5.56±0.49 µg/mL and 3.33±0.67 µg/mL, respectively. In addition, the inhibition kinetics of EEAC also changed to uncompetitive inhibition in variant-type 1236T-2677A-3435T P-gp. The ATPase assay revealed that EEAC was an ATPase stimulator and was capable of reducing verapamil-induced ATPase levels. These results indicate that EEAC may be a potent P-gp inhibitor and higher dosages may be required in subjects carrying variant-types P-gp. Further studies are required to translate this basic knowledge into clinical applications.

Chen, Ying-Yi; Hung, Chin-Chuan

2014-01-01

258

The impact of P-glycoprotein on the disposition of drugs targeted for indications of the central nervous system: evaluation using the MDR1A/1B knockout mouse model.  

PubMed

Thirty-two structurally diverse drugs used for the treatment of various conditions of the central nervous system (CNS), along with two active metabolites, and eight non-CNS drugs were measured in brain, plasma, and cerebrospinal fluid in the P-glycoprotein (P-gp) knockout mouse model after subcutaneous administration, and the data were compared with corresponding data obtained in wild-type mice. Total brain-to-plasma (B/P) ratios for the CNS agents ranged from 0.060 to 24. Of the 34 CNS-active agents, only 7 demonstrated B/P area under the plasma concentration curve ratios between P-gp knockout and wild-type mice that did not differ significantly from unity. Most of the remaining drugs demonstrated 1.1- to 2.6-fold greater B/P ratios in P-gp knockout mice versus wild-type mice. Three, risperidone, its active metabolite 9-hydroxyrisperidone, and metoclopramide, showed marked differences in B/P ratios between knockout and wild-type mice (6.6- to 17-fold). Differences in B/P ratios and cerebrospinal fluid/plasma ratios between wild-type and knockout animals were correlated. Through the use of this model, it appears that most CNS-active agents demonstrate at least some P-gp-mediated transport that can affect brain concentrations. However, the impact for the majority of agents is probably minor. The example of risperidone illustrates that even good P-gp substrates can still be clinically useful CNS-active agents. However, for such agents, unbound plasma concentrations may need to be greater than values projected using receptor affinity data to achieve adequate receptor occupancy for effect. PMID:15502009

Doran, Angela; Obach, R Scott; Smith, Bill J; Hosea, Natilie A; Becker, Stacey; Callegari, Ernesto; Chen, Cuiping; Chen, Xi; Choo, Edna; Cianfrogna, Julie; Cox, Loretta M; Gibbs, John P; Gibbs, Megan A; Hatch, Heather; Hop, Cornelis E C A; Kasman, Ilana N; Laperle, Jennifer; Liu, Jianhua; Liu, Xingrong; Logman, Michael; Maclin, Debra; Nedza, Frank M; Nelson, Frederick; Olson, Emily; Rahematpura, Sandhya; Raunig, David; Rogers, Sabrinia; Schmidt, Kari; Spracklin, Douglas K; Szewc, Mark; Troutman, Matthew; Tseng, Elaine; Tu, Meihua; Van Deusen, Jeffrey W; Venkatakrishnan, Karthik; Walens, Gary; Wang, Ellen Q; Wong, Diane; Yasgar, Adam S; Zhang, Chenghong

2005-01-01

259

Modulation of multidrug resistance P-glycoprotein activity by antiemetic compounds in human doxorubicin-resistant sarcoma cells (MES-SA/Dx-5): implications on cancer therapy.  

PubMed

Multidrug resistance (MDR) in cancer cells is often caused by the high expression of the plasma membrane drug transporter P-glycoprotein (Pgp) associated with an elevated intracellular glutathione (GSH) content in various human tumors. Several chemosensitizers reverse MDR but have significant toxicities. Antiemetic medications are often used for controlling chemotherapy-induced nausea and vomiting in cancer patient. In this in vitro study we investigated if the effects of two common antiemetic drugs such as dimenhydrinate (dime) and ondansentron (onda) and a natural compound (6)-gingerol (ginger), the active principle of ginger root, interfere on Pgp activity and intracellular GSH content in order to evaluate their potential use as chemosensitizing agents in anticancer chemotherapy. The human doxorubicin (doxo) resistant uterine sarcoma cells (MES-SA/Dx5) that overexpress Pgp, were treated with each antiemetic alone (1, 10 and 20 microM) or in combination with different doxo concentrations (2, 4, and 8 microM). We measured the intracellular accumulation and cytotoxicity of doxo (MTT assay), the cellular GSH content (GSH assay) and ROS production (DFC-DA assay), in comparison with verapamil (Ver), a specific inhibitor for Pgp, used as reference molecule. We found that exposure at 2, 4 and 8 microM doxo concentrations in the presence of dime, onda and ginger enhanced significantly doxo accumulation and cytotoxicity on resistant MES-SA/Dx5 cells when compared with doxo alone. Moreover, treatment with ginger (20 microM) increased cellular GSH content (greater than 10 percent) in resistant cells, while ROS production remained below the control values for all antiemetic compounds at all concentrations. These findings provide the rationale for innovative clinical trials of antiemetics or their derivatives as a new potential generation of chemosensitizers to improve effectiveness of the anticancer drugs in MDR human tumours. PMID:24382184

Angelini, A; Conti, P; Ciofani, G; Cuccurullo, F; Di Ilio, C

2013-01-01

260

Characterization of the major metabolites of verapamil as substrates and inhibitors of P-glycoprotein.  

PubMed

Verapamil is subject to extensive oxidative metabolism mediated by cytochrome P450 enzymes with less than 5% of an oral dose being excreted unchanged in urine. Furthermore, verapamil is known to be a potent inhibitor of P-glycoprotein function. There is evidence from in vivo investigations that some verapamil metabolites might be actively transported. The aim of the present study was to investigate P-glycoprotein-mediated transport and inhibition properties of verapamil and its metabolites norverapamil, D-620, D-617, and D-703. Polarized transport of these compounds was assessed in P-glycoprotein-expressing Caco-2 and L-MDR1 cells (LLC-PK1 cells stably transfected with human MDR1-P-glycoprotein). Inhibition of P-glycoprotein-mediated transport by these compounds was determined using digoxin as P-glycoprotein substrate. At concentrations of 5 microM, significant differences between basal-to-apical and apical-to-basal apparent permeability coefficients were observed for D-617 and D-620 in all P-glycoprotein-expressing cell monolayers, indicating that both are P-glycoprotein substrates. In contrast, no P-glycoprotein-dependent transport was found for verapamil, norverapamil, and D-703 in Caco-2 cells and for D-703 in L-MDR1 cells. Moreover, verapamil, norverapamil, and D-703 inhibited P-glycoprotein-mediated digoxin transport with IC(50) values of 1.1, 0.3, and 1.6 microM, respectively, whereas D-617 and D-620 did not (at concentrations up to 100 microM). We conclude that verapamil phase I metabolites exhibit different P-glycoprotein substrate and inhibition characteristics, with the N-dealkylated metabolites D-617 and D-620 being P-glycoprotein substrates and norverapamil and D-703 being inhibitors of P-glycoprotein function, which may influence P-glycoprotein-dependent drug disposition and elimination. PMID:10773005

Pauli-Magnus, C; von Richter, O; Burk, O; Ziegler, A; Mettang, T; Eichelbaum, M; Fromm, M F

2000-05-01

261

Microvesicles mediate transfer of P-glycoprotein to paclitaxel-sensitive A2780 human ovarian cancer cells, conferring paclitaxel-resistance.  

PubMed

The overexpression of P-glycoprotein (P-gp) causes resistance to chemotherapy in human ovarian cancer. However, the underlying mechanism remains unclear. In the present study, we showed that, at membrane-bound protein level, P-gp was 'shared' between human ovarian cancer cells by the intercellular transfer of microvesicles (MVs). Paclitaxel-resistant human ovarian cancer cells (A2780/PTX) readily formed and released P-gp-containing MVs into the extracellular space compared with the wild-type parental line (A2780/WT). Shedding MVs bound to the chemosensitive A2780/WT cells in a time- and dose-dependent manner, transferring P-gp via the microenvironment. MV-mediated transfer of P-gp led to redistribution of the chemotherapeutic drug adriamycin in recipient cells (A2780/WT), which displayed 5- and 5-fold higher resistance to adriamycin and paclitaxel, respectively. Thus, these findings demonstrate a new mechanism of drug-resistance acquisition via MVs. PMID:24877693

Zhang, Fang-Fang; Zhu, Yi-Fei; Zhao, Qian-Nan; Yang, Dan-Tong; Dong, Ye-Ping; Jiang, Li; Xing, Wei-Xing; Li, Xi-Yuan; Xing, Hui; Shi, Mei; Chen, Yun; Bruce, Iain C; Jin, Jian; Ma, Xin

2014-09-01

262

Nuclear localization of P-glycoprotein is responsible for protection of the nucleus from doxorubicin in the resistant LoVo cell line.  

PubMed

The high expression of P-glycoprotein (P-gp) belongs to one of the most important factors causing multidrug-resistant (MDR) of cancer cells. P-gp is primarily associated with plasma membrane; however, small fraction of that protein is present in the nuclear envelope. Such phenomenon is observed in cancer cells and may result in the selection of MDR cells as the secondary tumor and/or resistant metastasis that significantly shorten patient survival rate. Here, we confirmed nuclear localization of P-gp in resistant LoVo cells and demonstrated its impact on doxorubicin efflux from the nucleus to cytoplasm. Furthermore, we showed that P-gp located at the nuclear envelope might have a different glycoside chain when compared to the form located in the cytoplasm. It suggests that the glycoside chain plays a role in the intracellular trafficking of P-gp and may decide about the destination place in the cell. PMID:23602050

Szaflarski, Witold; Sujka-Kordowska, Patrycja; Januchowski, Rados?aw; Wojtowicz, Karolina; Andrzejewska, Ma?gorzata; Nowicki, Micha?; Zabel, Maciej

2013-07-01

263

Raman, SERS, and induced circular dichroism techniques as a probe of pharmaceuticals in their interactions with the human serum albumin and p-glycoprotein  

NASA Astrophysics Data System (ADS)

Camptothecin (CPT) derivatives are the well known inhibitors of the human DNA topoisomerase (topo) I. Two of them, irinotecan and topotecan, are just in the clinics; 9-amino- CPT is on the stage II of clinical trials, and the active search for new derivatives is now in progress. Stability of the CPT derivatives on their way to the target and resistance of cancer cells to these drugs present the crucial problem of the chemotherapy. Human serum albumin (HSA) is the mediator of transport and metabolism of numerous pharmaceuticals in the blood and P-glycoprotein (P- gp) plays a crucial role of the mediator of the multidrug resistance (MDR) of the cancer cells. This paper present the result of analysis of molecular interactions of some drugs of CPT family with the HSA and P-gp. Induced circular dichroism (CD) and Raman techniques have been applied for monitoring molecular interaction of drugs with HSA as well as to identify the conformational transition of the protein induced by the drug binding. Drug molecular determinants responsible for interaction have been identified and their binding sites within the HSA have been localized. New cancer cells lines exhibiting an extremely high level of MDR resistance have been established and were shown to contain the P-gp overproduced in the quantities of 35 percent from the all membrane proteins. The membrane fractions of these cells with the controls presented by the membranes of the parental membrane proteins. The membrane fractions of these cells with the controls presented by the membranes of the parental sensitive cells may be used as a model system for spectroscopic analysis of the specific pharmaceuticals/P-gp interactions.

Fleury, Fabrice; Ianoul, Anatoli I.; Baggetto, Loris; Jardillier, Jean-Claude; Alix, Alain J.; Nabiev, Igor R.

1999-04-01

264

Unmasking the dynamic interplay between intestinal P-glycoprotein and CYP3A4.  

PubMed

Drug efflux by intestinal P-glycoprotein (P-gp) is known to decrease the oral bioavailability of many CYP3A4 substrates. We hypothesized that the interplay occurring between P-gp and CYP3A4 at the apical membrane would increase the opportunity for drug metabolism. To define the roles of P-glycoprotein (P-gp) and CYP3A4 in controlling the extent of intestinal absorption and metabolism, two substrates were tested. The transport, metabolism, and intracellular levels of N-methyl piperazine-Phe-homoPhe-vinylsulfone phenyl (K77, a cysteine protease inhibitor; P-gp and CYP3A4 substrate) and felodipine (CYP3A4 substrate only) were measured across CYP3A4-transfected Caco-2 cells in the presence of an inhibitor of CYP3A4 and P-gp, cyclosporine (CsA), or an inhibitor of P-gp and not CYP3A4, GG918 (N-[4-[2-(1,2,3,4-tetrahydro-6,7- dimethoxy-2-isoquinolinyl)-ethyl]-phenyl]-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamine). The extent of metabolism was measured by calculating the extraction ratio (ER) across the cells, while accounting for intracellular changes occurring with P-gp inhibition. The (A)pical to (B)asolateral and B-->A ERs for K77 were 0.33 and 0.06, respectively. These changed with GG918 to 0.14 and 0.12 and with CsA to 0.06 and 0.04. Felodipine ERs were similar in both directions, 0.26 and 0.24 (A-->B and B-->A), and were unchanged in the presence of GG918 but decreased with CsA (0.14 and 0.11). The K77 absorption rate was increased 5 and 4.2-fold in the presence of CsA and GG918, respectively, whereas no change was observed for felodipine absorption. The decreased A-->B ER and increased absorption of K77 with GG918 suggest that P-gp influences the extent of drug metabolism in the intestine via prolonging the access of drugs to CYP3A4 near the apical membrane and decreasing transport across the cells. PMID:11861813

Cummins, Carolyn L; Jacobsen, Wolfgang; Benet, Leslie Z

2002-03-01

265

[11C]phenytoin revisited: synthesis by [11C]CO carbonylation and first evaluation as a P-gp tracer in rats  

PubMed Central

Background At present, several positron emission tomography (PET) tracers are in use for imaging P-glycoprotein (P-gp) function in man. At baseline, substrate tracers such as R-[11C]verapamil display low brain concentrations with a distribution volume of around 1. [11C]phenytoin is supposed to be a weaker P-gp substrate, which may lead to higher brain concentrations at baseline. This could facilitate assessment of P-gp function when P-gp is upregulated. The purpose of this study was to synthesize [11C]phenytoin and to characterize its properties as a P-gp tracer. Methods [11C]CO was used to synthesize [11C]phenytoin by rhodium-mediated carbonylation. Metabolism and, using PET, brain pharmacokinetics of [11C]phenytoin were studied in rats. Effects of P-gp function on [11C]phenytoin uptake were assessed using predosing with tariquidar. Results [11C]phenytoin was synthesized via [11C]CO in an overall decay-corrected yield of 22?±?4%. At 45 min after administration, 19% and 83% of radioactivity represented intact [11C]phenytoin in the plasma and brain, respectively. Compared with baseline, tariquidar predosing resulted in a 45% increase in the cerebral distribution volume of [11C]phenytoin. Conclusions Using [11C]CO, the radiosynthesis of [11C]phenytoin could be improved. [11C]phenytoin appeared to be a rather weak P-gp substrate.

2012-01-01

266

New positron emission tomography tracer [11C]carvedilol reveals P-glycoprotein modulation kinetics  

PubMed Central

Imaging of P-glycoprotein (P-gp) function in the blood–brain barrier (BBB) may support development of strategies, which will improve drug delivery to the brain. [11C]verapamil has been developed as a positron emission tomography (PET) tracer, to image P-gp function in vivo. Ideally, for the purpose of brain imaging, tracers should have a log?P between 0.9 and 2.5. The ?-receptor antagonist carvedilol is a P-gp substrate with a log?P=2.0, and can be labeled with [11C]. The aim of this study was to determine whether the P-gp substrate [11C]carvedilol can be used as a PET tracer for visualisation and quantification of the P-gp function in the BBB. Cellular [11C]carvedilol accumulation in GLC4, GLC4/P-gp, and GLC4/Adr cells increased three-fold in the GLC4/P-gp cells after pretreatment with cyclosporin A (CsA) whereas no effect of MK571 could be determined in the GLC4/Adr cells. Ex vivo [11C]carvedilol biodistribution studies showed that [11C]carvedilol uptake in the brain was increased by CsA. [11C]carvedilol uptake in other organs was not affected by CsA. Autoradiography studies of rat brains showed that [11C]carvedilol was homogeneously distributed over the brain and that pretreatment with CsA increased [11C]carvedilol uptake. In vivo PET experiments were performed with and without P-gp modulation by CsA. P-gp mediated transport was quantified by Logan analysis of the PET data, calculating the distribution volume (DV) of [11C]carvedilol in the brain. Logan analysis resulted in excellent fits, revealing that [11C]carvedilol is not trapped in the brain. Brain DV of [11C]carvedilol showed a dose-dependent increase of maximal three-fold after CsA pretreatment. Above 15?mg?kg?1, no change in DV was found. Compared to [11C]verapamil less CsA was needed to reach maximal DV, suggesting that [11C]carvedilol kinetics is a more sensitive tool to in vivo measure P-gp function.

Bart, Joost; Dijkers, Eli C F; Wegman, Theodora D; de Vries, Elisabeth G E; van der Graaf, Winette T A; Groen, Harry J M; Vaalburg, Willem; Willemsen, Antoon T M; Hendrikse, N Harry

2005-01-01

267

Clitocine Reversal of P-Glycoprotein Associated Multi-Drug Resistance through Down-Regulation of Transcription Factor NF-?B in R-HepG2 Cell Line  

PubMed Central

Multidrug resistance(MDR)is one of the major reasons for failure in cancer chemotherapy and its suppression may increase the efficacy of therapy. The human multidrug resistance 1 (MDR1) gene encodes the plasma membrane P-glycoprotein (P-gp) that pumps various anti-cancer agents out of the cancer cell. R-HepG2 and MES-SA/Dx5 cells are doxorubicin induced P-gp over-expressed MDR sublines of human hepatocellular carcinoma HepG2 cells and human uterine carcinoma MES-SA cells respectively. Herein, we observed that clitocine, a natural compound extracted from Leucopaxillus giganteus, presented similar cytotoxicity in multidrug resistant cell lines compared with their parental cell lines and significantly suppressed the expression of P-gp in R-HepG2 and MES-SA/Dx5 cells. Further study showed that the clitocine increased the sensitivity and intracellular accumulation of doxorubicin in R-HepG2 cells accompanying down-regulated MDR1 mRNA level and promoter activity, indicating the reversal effect of MDR by clitocine. A 5?-serial truncation analysis of the MDR1 promoter defined a region from position ?450 to ?193 to be critical for clitocine suppression of MDR1. Mutation of a consensus NF-?B binding site in the defined region and overexpression of NF-?B p65 could offset the suppression effect of clitocine on MDR1 promoter. By immunohistochemistry, clitocine was confirmed to suppress the protein levels of both P-gp and NF-?B p65 in R-HepG2 cells and tumors. Clitocine also inhibited the expression of NF-?B p65 in MES-SA/Dx5. More importantly, clitocine could suppress the NF-?B activation even in presence of doxorubicin. Taken together; our results suggested that clitocine could reverse P-gp associated MDR via down-regulation of NF-?B.

Sun, Jianguo; Yeung, Chilam Au; Co, Ngai Na; Tsang, Tsun Yee; Yau, Esmond; Luo, Kewang; Wu, Ping; Wa, Judy Chan Yuet; Fung, Kwok-Pui; Kwok, Tim-Tak; Liu, Feiyan

2012-01-01

268

Prenylated xanthones as potential P-glycoprotein modulators.  

PubMed

Dimethylallyl (DMA) derivatives of a naturally occurring xanthone (decussatin 1) were prepared. Their activity as potential P-glycoprotein inhibitors was monitored by affinity of direct binding and compared to that of corresponding DMA-flavones. Both classes of compounds exhibited the same structure-activity relationships. Decreasing polarity enhanced the binding affinity for the P-glycoprotein C-terminal cytosolic domain since DMA derivatives were more active, but unsubstituted hydroxyl group close to the carbonyl was required for efficient activity. PMID:10890160

Tchamo, D N; Dijoux-Franca, M G; Mariotte, A M; Tsamo, E; Daskiewicz, J B; Bayet, C; Barron, D; Conseil, G; Di Pietro, A

2000-06-19

269

Functional polymorphisms of the human multidrug-resistance gene: Multiple sequence variations and correlation of one allele with P-glycoprotein expression and activity in vivo  

Microsoft Academic Search

To evaluate whether alterations in the multidrug-resistance (MDR)-1 gene correlate with intestinal MDR-1 expression and uptake of orally administered P-glycoprotein (PGP) substrates, we analyzed the MDR-1 sequence in 21 volunteers whose PGP expression and function in the duodenum had been determined by Western blots and quantitative immunohistology (n = 21) or by plasma concentrations after orally administered digoxin (n =

S. Hoffmeyer; O. Burk; O. von Richter; H. P. Arnold; J. Brockmöller; A. Johne; I. Cascorbi; T. Gerloff; I. Roots; M. Eichelbaum; U. Brinkmann

2000-01-01

270

Differential effects of the organochlorine pesticide DDT and its metabolite p,p'-DDE on p-glycoprotein activity and expression  

SciTech Connect

1,1-Bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) is an organochlorine pesticide. Its metabolite, 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethene (p,p'-DDE) is a persistent environmental contaminant and both compounds accumulate in animals. Because multidrug resistance transporters, such as p-glycoprotein, function as a defense against xenobiotic exposure, we analyzed the ability of DDT and p,p'-DDE to act as efflux modulators. Using a competitive intact cell assay based on the efflux of the fluorescent dye rhodamine 123, we found that DDT, but not p,p'-DDE, stimulated dye retention. Subsequent studies using verapamil as competitor suggested that DDT is a weak p-glycoprotein inhibitor. Further studies addressed the ability of DDT and p,p'-DDE to induce MDR1, the gene encoding p-glycoprotein. In HepG2 cells, we found that both compounds induced MDR1 by twofold to threefold. Similar results were observed in mouse liver after a single dose of p,p'-DDE, although some gender-specific induction differences were noted. By contrast, p,p'-DDE failed to induce MDR1 in HeLa cells, indicating some cell-specific effects for induction. Further expression studies demonstrated increased levels of the endoplasmic reticulum molecular chaperone, Bip, in response to DDT, but not p,p'-DDE. These results suggest that DDT, but not p,p'-DDE, induces an endoplasmic reticulum stress response.

Shabbir, Arsalan [Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, NY 10029 (United States); DiStasio, Susan [Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, NY 10029 (United States); Zhao, Jingbo [Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029 (United States); VA Medical Center, Bronx, NY 10468 (United States); Cardozo, Christopher P. [Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029 (United States); VA Medical Center, Bronx, NY 10468 (United States); Wolff, Mary S. [Department of Community and Preventative Medicine, Mount Sinai School of Medicine, New York, NY 10029 (United States); Caplan, Avrom J. [Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, NY 10029 (United States)]. E-mail: avrom.caplan@mssm.edu

2005-03-01

271

Critical role for P-glycoprotein expression in hematopoietic cells in the FVB.mdr1a?/? model of colitis  

PubMed Central

Objective P-glycoprotein (P-gp), the functional product of the multi-drug resistance gene (mdr), is a transmembrane protein that extrudes substrates from the intracellular environment. P-gp is expressed on the apical surface of epithelial cells and on cells from the hematopoietic lineage. Human MDR polymorphisms have been associated with increased risk inflammatory bowel disease, and FVB/N animals deficient in mdr1a expression develop spontaneous colitis. Previous studies utilizing adult bone marrow chimeras indicated colitis development in this animal model was contingent on P-gp deficiency in radiation resistant epithelial cells. However, the use of adult animals may mask the role of hematopoietic immune cells in colitis initiation, due to pre-existing epithelial abnormalities. Methods To assess the importance of P-gp expression in intestinal epithelial and hematopoietic derived cells on colitis induction in FVB.mdr1a?/?animal we developed a neonatal model of bone marrow reconstitution. FVB/N and FVB.mdr1a?/?adult and neonatal animals were lethally irradiated and reconstituted with bone marrow from FVB/N or FVB.mdr1a?/?donors. Animals were observed for 20 weeks. Results Adult FVB/N animals deficient in P-gp expression in hematopoietically derived immune cells developed colitis similar to adult animals deficient in P-gp expression in radiation resistant epithelial/stromal cells. However, neonatal animals deficient in P-gp expression in hematopoietically derived immune cells developed a more histologically significant colitis than those deficient in P-gp expression in epithelial tissue. Conclusions The use of a neonatal model of bone marrow reconstitution has revealed a critical role for P-gp expression in hematopoietically derived immune cells in colitis development in the FVB.mdr1a?/? model.

Staley, Elizabeth M.; Dimmitt, Reed A.; Schoeb, Trenton R.; Tanner, Scott M.; Lorenz, Robin G.

2013-01-01

272

Role of P-glycoprotein in the uptake/efflux transport of oral vitamin K antagonists and rivaroxaban through the Caco-2 cell model.  

PubMed

Vitamin K antagonists (VKAs) are prescribed worldwide and remain the oral anticoagulant of choice. These drugs are characterized by a narrow therapeutic index and a large inter- and intra-individual variability. P-glycoprotein could contribute to this variability. The aim of this study was to investigate the involvement of P-gp in the transport of acenocoumarol, phenprocoumon and warfarin using an in vitro Caco-2 cell monolayer model. These results were compared with those obtained with rivaroxaban, a new oral anticoagulant known to be a P-gp substrate. The transport of these four drugs was assessed at pH conditions 6.8/7.4 in the presence or absence of the P-gp inhibitor cyclosporine A (10 ?M) and the more potent and specific P-gp inhibitor valspodar (5 ?M). Analytical quantification was performed by LC/MS. With an efflux ratio of 1.7 and a significant decrease in the efflux (Papp B-A), in the presence of P-gp inhibitors at a concentration of 50 ?M, acenocoumarol can be considered as a weak P-gp substrate. Concerning phenprocoumon, the results suggest that this molecule is a poor P-gp substrate. The P-gp inhibitors did not affect significantly the transport of warfarin. The efflux of rivaroxaban was strongly inhibited by the two P-gp inhibitors. In conclusion, none of the three VKAs tested are strong P-gp substrates. However, acenocoumarol can be considered as a weak P-gp substrate and phenprocoumon as a poor P-gp substrate. PMID:23663291

Gschwind, Liliane; Rollason, Victoria; Daali, Youssef; Bonnabry, Pascal; Dayer, Pierre; Desmeules, Jules Alexandre

2013-10-01

273

4,5-Di-substituted benzyl-imidazol-2-substituted amines as the structure template for the design and synthesis of reversal agents against P-gp-mediated multidrug resistance breast cancer cells.  

PubMed

Over-expression of P-glycoprotein (P-gp), a primary multidrug transporter which is located in plasma membranes, plays a major role in the multidrug resistance (MDR) of cytotoxic chemotherapy. Naamidines are a class of marine imidazole alkaloids isolated from Leucetta and Clathrina sponges, possessing a Y-shaped scaffold. Based on the results previously obtained from the third-generation MDR modulator ONT-093 and other modulators developed in our group, we designed and synthesized a series of novel 4,5-di-substituted benzyl-1-methyl-1H-imidazol-2-substituted amines using the Naamidine scaffold as the structure template. Subsequently, their reversing activity for Taxol resistance has been evaluated in P-gp-mediated multidrug resistance breast cancer cell line MDA435/LCC6MDR. Compounds 12c with a Y-shaped scaffold, and compound 17c which is 'X-shaped' scaffold and possesses a 4-diethylamino group at aryl ring B, turned out to be the most potent P-gp modulators. It appears that compounds 12c and 17c at 1 ?M concentration can sensitize LCC6MDR cells toward Taxol by 26.4 and 24.5 folds, with an EC50 212.5 and 210.5 nM, respectively. These two compounds are about 5-6 folds more potent than verapamil (RF = 4.5). Moreover, compounds 12c and 17c did not exhibit obvious cytotoxicity in either cancer cell lines or normal mouse fibroblast cell lines. This study has demonstrated that the synthetic Naamidine analogues can be potentially employed as effective, safe modulators for the P-gp-mediated drug resistance cancer cells. PMID:24952376

Zhang, Nan; Zhang, Zhaohui; Wong, Iris L K; Wan, Shengbiao; Chow, Larry M C; Jiang, Tao

2014-08-18

274

Reversal of P-glycoprotein mediated vincristine resistance of L1210\\/VCR cells by analogues of pentoxifylline  

Microsoft Academic Search

In our previous papers we described the ability of methylxanthine pentoxifylline (PTX) to depress the P-glycoprotein (P-gp) mediated multidrug resistance (MDR) of the mouse leukemic cell line L1210\\/VCR. Other methylxanthines like caffeine and theophylline were found to be ineffective in this respect. In the present paper we have analysed the capability of 25 methylxanthines to depress MDR of L1210\\/VCR cells.

Ivana Kupsáková; Alfons Rybár; Peter Do?olomanský; Zuzana Drobná; Ulrike Stein; Wolfgang Walther; Miroslav Baran???k; Albert Breier

2004-01-01

275

Treatment strategy based on targeting P-glycoprotein on peripheral lymphocytes in patients with systemic autoimmune disease  

Microsoft Academic Search

Although corticosteroids, immunosuppressants and disease-modifying antirheumatic drugs (DMARDs) are widely used in the treatment\\u000a of various systemic autoimmune diseases such as systemic lupus erythematosus (SLE), we often experience patients with systemic\\u000a autoimmune diseases who are resistant to these treatments. P-glycoprotein (P-gp) of membrane transporters, a product of the\\u000a multiple drug resistance (MDR)-1 gene, is known to play a pivotal role

Shizuyo TsujimuraYoshiya Tanaka; Yoshiya Tanaka

276

Interaction between CD147 and P-Glycoprotein and Their Regulation by Ubiquitination in Breast Cancer Cells  

Microsoft Academic Search

Background: Multidrug-resistant cancer cells overexpressing P-glycoprotein (P-gp) display variations in invasive and metastatic ability through the upregulation of the extracellular matrix metalloproteinase (MMP) inducer (CD147). However, the direct linkage between these two proteins is still unclear. Methods: We used immunoprecipitation, immunofluorescence analysis, migration and invasion assays, drug sensitivity assay and Western blot to measure the physical and functional interaction between

Wen-Juan Wang; Qing-Quan Li; Jing-Da Xu; Xi-Xi Cao; Hai-Xia Li; Feng Tang; Qi Chen; Jin-Ming Yang; Zu-De Xu; Xiu-Ping Liu

2008-01-01

277

Isolation of Endothelial Cells from Brain, Lung, and Kidney: Expression of the Multidrug Resistance P-Glycoprotein Isoforms  

Microsoft Academic Search

Endothelial cells (EC) were isolated from brain, lung, and renal cortex using magnetic microbeads cross-linked to an antibody directed against the platelet-endothelial cell adhesion molecule-1 (PECAM-1). Levels of endothelial nitric oxide synthase (eNOS) and PECAM-1 were measured by Western blots and both were enriched in the positively selected EC fractions. The multidrug resistance P-glycoprotein (P-gp) was strongly enriched (59-fold) in

Michel Demeule; Myriam Labelle; Anthony Régina; France Berthelet; Richard Béliveau

2001-01-01

278

Positron Emission Tomography Studies on Binding of Central Nervous System Drugs and P-Glycoprotein Function in the Rodent Brain  

Microsoft Academic Search

The permeability of the blood–brain barrier (BBB) is one of the factors determining the bioavailability of drugs in the brain. The BBB only allows passage of lipophilic drugs by passive diffusion. However, some lipophilic drugs hardly enter the brain. The transmembrane protein P-glycoprotein (P-gp) is one of the carrier systems that is responsible for transportation of drugs out of the

Philip H. Elsinga; N. Harry Hendrikse; Joost Bart; Aren van Waarde; Willem Vaalburg

2005-01-01

279

Functional expression of P-glycoprotein in primary cultures of human cytotrophoblasts and BeWo cells.  

PubMed

The objective of this study was to investigate the functional expression of the efflux transporter, P-glycoprotein (P-gp), in primary cultures of human cytotrophoblasts and BeWo cell monolayers. Uptake studies with primary cultures of human cytotrophoblasts or BeWo cells were conducted with calcein-AM and vinblastine (P-gp markers) or fluorescein (MRP marker) in the presence of specific P-gp or MRP inhibitors. Results showed that the accumulation of P-gp substrates calcein-AM and vinblastine by BeWo cells or primary cultures of human cytotrophoblasts was significantly enhanced in the presence of a typical P-gp inhibitor, cyclosporin-A, or other inhibitors such as quinidine, verapamil, and dipyridamole. MRP inhibitors had no effect on the accumulation of calcein or fluorescein by BeWo cells. Western blots confirmed the presence of multidrug resistant gene product 1 (MDR1) in both primary cultures of human cytotrophoblasts and BeWo cells. This study demonstrates functional P-gp in term human trophoblasts and further supports the use of primary cultures of human cytotrophoblasts and BeWo cells as in vitro models of the trophoblast to investigate mechanisms regulating drug distribution across the placenta. PMID:10838122

Utoguchi, N; Chandorkar, G A; Avery, M; Audus, K L

2000-01-01

280

P-glycoprotein: a focus on characterizing variability in cardiovascular pharmacotherapeutics.  

PubMed

According to the report of Agency for Healthcare Research and Quality in 2008, drug-related adverse outcomes exceed 2.7 million events per year. Therefore, it is requisite to understand the etiologies of those unpleasant outcomes. Polypharmacy especially in the elderly is considered one of the major sources of drug-related side effects. The drug-related membrane transporters play an indispensable role in the pharmacokinetics, safety, and efficacy of the drugs. P-glycoprotein, also known as P-gp, is considered one of the core drug transporters in vivo. Since its discovery in 1976, P-gp gained a tremendous attention of researchers and clinicians. The core objective of this review is to highlight the clinical correlation between the P-gp and a number of cardiovascular drugs and to address the drug-drug interaction in case of using those cardiovascular drugs with P-gp-related drugs whether substrates, inhibitors, or inducers. Bearing in mind that P-gp is found in liver and intestine, as well as cytochrome P450, a strong association between the 2 systems is expected. Yet, plenty of the drugs that can behave as substrates to P-gp can act as substrates to CYP450 too. Consequently, probable drug-drug interaction can occur between drugs that work on both systems. In other words, whenever these classes of medications prescribed together cautious monitoring of drug's level and eventually dose adjustment might be necessary to avoid drug-drug interactions, failure of therapy, or drug toxicity; especially with the use of drugs that possess narrow therapeutic index like digoxin. PMID:24401702

Al-Khazaali, Ali; Arora, Rohit

2014-01-01

281

Highly sensitive and specific detection of P-glycoprotein function for haematological and solid tumour cells using a novel nucleic acid stain.  

PubMed Central

Progress in our understanding of the contribution of P-glycoprotein (P-gp)-mediated resistance to chemotherapy failure in haematological as well as solid tumours has been hampered by the lack of highly sensitive, reliable methods for the detection of P-gp function in fresh human tumour cells. The present study identifies the novel nucleic acid stain SYTO16 as a highly sensitive and specific dye to assess P-gp function. The effect of P-gp is expressed here as the ratio of dye fluorescence (RF) from cells incubated with dye with or without 2 microM of the P-gp inhibitor PSC 833. Using flow cytometric analysis, an RF of 0.9 was found for SYTO16 in the KB3-1 (P-gp-) and 1.6 in KB8 (P-gp+) cells. Three types of patients' cells were studied: (1) in haematopoietic CD34+ cells, which are known to express P-gp, the RF was 6.0 for SYTO16 compared with 2.5 for rhodamine 123 and 1.3 for daunorubicin (mean of five individuals); (2) in acute myeloid leukaemia cells, the RF for SYTO16 was 1.0 in P-gp- and 4.5 in P-gp+ samples; (3) for the first time, we have quantitated P-gp function in fresh human solid tumour (sarcoma) cells. We found, in a P-gp+ leiomyosarcoma, an RF of 16 for SYTO16 and 2.7 for daunorubicin. This means that complete inhibition of P-gp function in these sarcoma cells would lead to an increase of daunorubicin accumulation with 170% compared with 30% in the CD34+ cells. Next, we showed that SYTO16 could be fixed in nuclei by 3.6% formaldehyde treatment, allowing quantification of the nuclear fluorescence on cytospins by laser scanning microscopy. In conclusion, SYTO16 proved to have a combination of favourable properties: it can be excited at 488 nm and has large fluorescence enhancement upon binding to nucleic acids, allowing the use of low, nontoxic (< 10 nM) concentrations. Because the RF for SYTO16 is much higher than for daunorubicin, it can be applied for the determination of P-gp function in relatively small numbers of low-P-gp-expressing tumour cells by laser scanning microscopy. Individual sarcomas were found to have high P-gp function compared with CD34+ cells. This assay may be used to select patients for P-gp modulation protocols. Images Figure 2 Figure 4

Broxterman, H. J.; Schuurhuis, G. J.; Lankelma, J.; Oberink, J. W.; Eekman, C. A.; Claessen, A. M.; Hoekman, K.; Poot, M.; Pinedo, H. M.

1997-01-01

282

Expression of P-glycoprotein and metallothionein in gastrointestinal stromal tumor and leiomyosarcomas. Clinical implications.  

PubMed

We investigated the expression of P-glycoprotein (P-GP) and metallothionein (MT) in a series of 92 GIST and 14 gastrointestinal leiomyosarcomas (GILMS) with the purpose to expand our knowledge on the biological bases of GIST chemo-resistance and to ascertain their significance in patients' prognosis. P-GP expression was more frequent in GIST than in GI-LMS (83.7% vs. 21.4%, p<0.001), with no difference between low- and high-risk GIST (p=1.000) or low- and high-grade GI-LMS (p=0.538). P-GP expression was unrelated to anatomic location (gastric vs. intestinal) in GIST (39/45 vs. 35/43, p=0.770) and in GI-LMS (0/2 vs. 2/6, p=1.000). MT expression was non-significantly higher in GI-LMS than in GIST (35.7% vs. 14.1%, p=0.060), with no difference between low- and high-risk GIST (p=1.000) or low- and high-grade GI-LMS (p=1.000). MT expression was unrelated to the anatomic location (gastric vs. intestinal) in GIST (7/45 vs. 6/43) and GI-LMS (0/2 vs. 1/6) (p=1.000 and p=0.1000, respectively). Overall tumor-specific survival (p< 0.001) and disease-free survival (p<0.001) were different in GIST as compared with GI-LMS, and the number of events was higher in GI-LMS. When the survival analysis took into consideration P-GP or MT expression, the overall survival in GIST was influenced by the expression of MT (p=0.021) but not by that of P-GP (p=0.638). However, in GI-LMS, P-GP expression influenced disease-free survival (p=0.050); in addition, it is important to recognize the limited value of these results because of the low number of cases involved in the study. Differential expression of P-GP and MT might explain the known variability in response to systemic chemotherapy in these tumors. Detection of P-GP and MT seems to add certain prognostic value in GIST (MT) or GI-LMS (P-GP). PMID:17922049

Pérez-Gutiérrez, Sofia; González-Cámpora, Ricardo; Amérigo-Navarro, Joaquín; Beato-Moreno, Antonio; Sánchez-León, María; Pareja Megía, Jesús María; Virizuela-Echaburu, Juan Antonio; López-Beltrán, Antonio

2007-01-01

283

Pro-Inflammatory Cytokine Regulation of P-glycoprotein in the Developing Blood-Brain Barrier  

PubMed Central

Placental P-glycoprotein (P-gp) acts to protect the developing fetus from exogenous compounds. This protection declines with advancing gestation leaving the fetus and fetal brain vulnerable to these compounds and potential teratogens in maternal circulation. This vulnerability may be more pronounced in pregnancies complicated by infection, which is common during pregnancy. Pro-inflammatory cytokines (released during infection) have been shown to be potent inhibitors of P-gp, but nothing is known regarding their effects at the developing blood-brain barrier (BBB). We hypothesized that P-gp function and expression in endothelial cells of the developing BBB will be inhibited by pro-inflammatory cytokines. We have derived brain endothelial cell (BEC) cultures from various stages of development of the guinea pig: gestational day (GD) 50, 65 (term ?68 days) and postnatal day (PND) 14. Once these cultures reached confluence, BECs were treated with various doses (100–104 pg/mL) of pro-inflammatory cytokines: interleukin-1? (IL-1?), interleukin-6 (IL-6) or tumor necrosis factor- ? (TNF-?). P-gp function or abcb1 mRNA (encodes P-gp) expression was assessed following treatment. Incubation of GD50 BECs with IL-1?, IL-6 or TNF-? resulted in no change in P-gp function. GD65 BECs displayed a dose-dependent decrease in function with all cytokines tested; maximal effects at 42%, 65% and 34% with IL-1?, IL-6 and TNF-? treatment, respectively (P<0.01). Inhibition of P-gp function by IL-1?, IL-6 and TNF-? was even greater in PND14 BECs; maximal effects at 36% (P<0.01), 84% (P<0.05) and 55% (P<0.01), respectively. Cytokine-induced reductions in P-gp function were associated with decreased abcb1 mRNA expression. These data suggest that BBB P-gp function is increasingly responsive to the inhibitory effects of pro-inflammatory cytokines, with increasing developmental age. Thus, women who experience infection and take prescription medication during pregnancy may expose the developing fetal brain to greater amounts of exogenous compounds – many of which are considered potentially teratogenic.

Iqbal, Majid; Ho, Hay Lam; Petropoulos, Sophie; Moisiadis, Vasilis G.; Gibb, William; Matthews, Stephen G.

2012-01-01

284

Modeling of P-glycoprotein-involved epithelial drug transport in MDCK cells.  

PubMed

P-glycoprotein (P-gp) on the apical membranes of epithelial cells is known as a drug efflux pump. However, unclear is its integral quantitative role in the overall epithelial drug transfer, which also involves distinct diffusion processes in parallel and sequence. We used a simple three-compartment model to obtain kinetic parameters of each drug transfer mechanism, which can quantitatively describe the transport time courses of P-gp substrates, digoxin and vinblastine, across P-gp-expressing MDCK cell monolayers grown on permeable filters. Our results show that the model, which assumes a functionally single drug efflux pump in the apical membrane with diffusion across two membranes and intercellular junctions, is the least complex model with which to quantitatively reproduce the characteristics of the data. Interestingly, the model predicts that the MDCK apical membranes are less diffusion permeable than the basolateral membrane for both drugs and that the distribution volume of vinblastine is 10-fold higher than that of digoxin. Additional experiments verified these model predictions. The modeling approach is feasible to quantitatively describe overall kinetic picture of epithelial drug transport. Further model refinement is necessary to incorporate other modes of drug transport such as transcytosis. Also, whether P-gp solely accounts for the pump function in this model awaits more studies. PMID:10409301

Ito, S; Woodland, C; Sarkadi, B; Hockmann, G; Walker, S E; Koren, G

1999-07-01

285

Interactions between antidepressants and P-glycoprotein at the blood-brain barrier: clinical significance of in vitro and in vivo findings  

PubMed Central

The drug efflux pump P-glycoprotein (P-gp) plays an important role in the function of the blood–brain barrier by selectively extruding certain endogenous and exogenous molecules, thus limiting the ability of its substrates to reach the brain. Emerging evidence suggests that P-gp may restrict the uptake of several antidepressants into the brain, thus contributing to the poor success rate of current antidepressant therapies. Despite some inconsistency in the literature, clinical investigations of potential associations between functional single nucleotide polymorphisms in ABCB1, the gene which encodes P-gp, and antidepressant response have highlighted a potential link between P-gp function and treatment-resistant depression (TRD). Therefore, co-administration of P-gp inhibitors with antidepressants to patients who are refractory to antidepressant therapy may represent a novel therapeutic approach in the management of TRD. Furthermore, certain antidepressants inhibit P-gp in vitro, and it has been hypothesized that inhibition of P-gp by such antidepressant drugs may play a role in their therapeutic action. The present review summarizes the available in vitro, in vivo and clinical data pertaining to interactions between antidepressant drugs and P-gp, and discusses the potential relevance of these interactions in the treatment of depression.

O'Brien, Fionn E; Dinan, Timothy G; Griffin, Brendan T; Cryan, John F

2012-01-01

286

The process behind the expression of mdr-1/P-gp and mrp/MRP in human leukemia/lymphoma.  

PubMed

There is a controversy over the link between phenotypes of multidrug resistance (MDR) and clinical outcome in leukemia/lymphoma patients. This may be because the process behind the induction and loss of expression of genotypes and phenotypes by which MDR develops and the role of MDR in fresh cells of human leukemia/lymphoma are not clearly defined. P-glycoprotein (P-gp) increased and decreased along with mdr-1 expression in three cell lines out of five vincristine (VCR)-resistant cell lines. MRP appeared with increased mrp expression in the other two cell lines. After the drug was removed from the culture system, mdr-1/P-gp changed in parallel with the level of VCR resistance, although mrp and MRP did not. It was concluded that P-gp is directly derived from mdr-1 and that mdr-1/P-gp supports the VCR-resistance but mrp/MRP is not directly linked to the VCR-resistance. These results should contribute to a better understanding of MDR phenomenon in cancer. PMID:19414348

Hirose, Masao

2009-04-01

287

A structural model for the mass action kinetic analysis of P-gp mediated transport through confluent cell monolayers.  

PubMed

The structural model for P-gp mediated transport across confluent cell monolayers uses the generally accepted mass action reactions for P-gp binding and efflux, together with the known structural parameters for P-gp (large substrate binding site accessible from the membrane) and the apical plasma membrane in which it resides (lipid bilayer partition coefficient of substrate and volume of apical plasma membrane allow estimation of substrate concentration at binding site). The model considers binding of substrate to P-gp from within the inner leaflet of the apical membrane, with an on rate constant, k 1 (M(-1)s(-1)), and off rate constant k r (s(-1)), as well as an efflux rate constant from P-gp into the apical chamber, k 2 (s(-1)). The model also explicitly estimates the active P-gp protein level, known as P-gp efflux active surface density T(0). For each new drug, fitting these parameters requires use of multiple initial drug concentrations and multiple time points at each concentration, until steady state is reached between P-gp-mediated efflux into the apical chamber and passive permeability from apical chamber back into the cytosol. Although this model optimally requires a larger than usual dataset for analysis, it does provide important mechanistic information through estimates of these on, off and efflux rate constants, as well as efflux active P-gp surface density. This more detailed description of efflux from polarized confluent cell monolayers has (1) provided insight into the unexpected relationship between P-gp IC50 and K i in this system, (2) highlighted the kinetic need for GF120918 inhibitable apical and basolateral uptake transporters for digoxin, and (3) provided possible explanations for the extreme lab-to-lab variability in P-gp IC50 values observed for inhibition of digoxin transport. This model can also be used to distinguish between efflux active P-gp and total apical plasma membrane P-gp, which may be important when P-gp is expressed in a microvillous membrane. PMID:24523118

Bentz, Joe; Ellens, Harma

2014-01-01

288

In vitro-to-in vivo prediction of P-glycoprotein-based drug interactions at the human and rodent blood-brain barrier.  

PubMed

In vitro inhibition of P-glycoprotein (P-gp) expressed in cells is routinely used to predict the potential of in vivo P-gp drug interactions at the human blood-brain barrier (BBB). The accuracy of such predictions has not been confirmed because methods to quantify in vivo P-gp drug interactions at the human BBB have not been available. With the development of a noninvasive positron emission topography (PET) imaging method by our laboratory to determine P-gp-based drug interactions at the human BBB, an in vitro-in vivo comparison is now possible. Therefore, we developed a high throughput cell-based assay to determine the potential of putative P-gp inhibitors [including cyclosporine A (CsA)] to inhibit (EC(50)) the efflux of verapamil-bodipy, a model P-gp substrate. LLCPK1-MDR1 cells, expressing recombinant human P-gp, or control cells lacking P-gp (LLCPK1) were used in our assay. Using this assay, quinine, quinidine, CsA, and amprenavir were predicted to be the most potent P-gp inhibitors in vivo at their respective therapeutic maximal unbound plasma concentrations. The in vitro EC(50) of CsA (0.6 microM) for P-gp inhibition was virtually the same as our previously determined in vivo unbound EC(50) at the rat BBB (0.5 microM). Moreover, at 2.8 microM CsA (total blood concentration), our in vitro data predicted an increase of 129% in [(11)C]verapamil distribution into the human brain, a value similar to that observed by us (79%) using PET. These data suggest that our high throughput cell assay has the potential to accurately predict P-gp drug interactions at the human BBB. PMID:18057117

Hsiao, Peng; Bui, Tot; Ho, Rodney J Y; Unadkat, Jashvant D

2008-03-01

289

The Connection between the Toxicity of Anthracyclines and Their Ability to Modulate the P-Glycoprotein-Mediated Transport in A549, HepG2, and MCF-7 Cells  

PubMed Central

Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of solid tumors. We compared the resistance of the most popular solid tumors, breast adenocarcinoma (MCF-7 cell line) and nonsmall cell lung (A549 cell line) hepatocellular liver carcinoma (HepG2 cells), to aclarubicin (ACL) and doxorubicin (DOX). This research aimed at determining the relation between the toxicity of ACL and DOX, their cell accumulation, and then effect on P-glycoprotein functionality. ACL is more cytotoxic for tumor cells compared to DOX. The intracellular concentration of drugs in cancer cells was dependent on the dose of the drugs and the time of incubation. The P-gp inhibitor Verapamil (V) increased DOX accumulation in all tested cell lines. By contrast, the intracellular level of ACL was not affected by this modifying agent. The assessment of the uptake of 5,5?,6,6?-tetrachloro-1,1?,3,3?-tetraethylbenzimidazolocarbocyanine iodide (JC-1) or Rhodamine 123 (R123) allows the evaluation of the different influence of drugs on P-gp activity which is in agreement with the estimation of expression measured by MDR-1 shift assay. These data suggest that ACL is less P-gp dependent than DOX and consequently may be used in a clinical setting to increase treatment efficacy in resistant human tumors.

Szwed, Marzena; Rychlik, Blazej

2014-01-01

290

Brain penetration of methadone (R)- and (S)-enantiomers is greatly increased by P-glycoprotein deficiency in the blood–brain barrier of Abcb1a gene knockout mice  

Microsoft Academic Search

Rationale Methadone maintenance treatment is complicated by the wide variability of efficacy among patients. The large interindividual variability of the plasma concentrations of methadone was previously thought to be responsible for the variable therapeutic efficacy. However, recent studies suggested that methadone may be a substrate of P-glycoprotein (P-gp). Therefore, the function of P-gp in blood–brain barrier (BBB) may affect the

Jun-Sheng Wang; Ying Ruan; Robin M. Taylor; Jennifer L. Donovan; John S. Markowitz; C. Lindsay DeVane

2004-01-01

291

P-glycoprotein trafficking at the blood-brain barrier altered by peripheral inflammatory hyperalgesia  

PubMed Central

P-glycoprotein (ABCB1/MDR1, EC 3.6.3.44), the major efflux transporter at the blood–brain barrier (BBB), is a formidable obstacle to CNS pharmacotherapy. Understanding the mechanism(s) for increased P-glycoprotein activity at the BBB during peripheral inflammatory pain is critical in the development of novel strategies to overcome the significant decreases in CNS analgesic drug delivery. In this study, we employed the ?-carrageenan pain model (using female Sprague–Dawley rats), combined with confocal microscopy and subcellular fractionation of cerebral microvessels, to determine if increased P-glycoprotein function, following the onset of peripheral inflammatory pain, is associated with a change in P-glycoprotein trafficking which leads to pain-induced effects on analgesic drug delivery. Injection of ?-carrageenan into the rat hind paw induced a localized, inflammatory pain (hyperalgesia) and simultaneously, at the BBB, a rapid change in colocalization of P-glycoprotein with caveolin-1, a key scaffolding/trafficking protein. Subcellular fractionation of isolated cerebral microvessels revealed that the bulk of P-glycoprotein constitutively traffics to membrane domains containing high molecular weight, disulfide-bonded P-glycoprotein-containing structures that cofractionate with membrane domains enriched with monomeric and high molecular weight, disulfide-bonded, caveolin-1-containing structures. Peripheral inflammatory pain promoted a dynamic redistribution between membrane domains of P-glycoprotein and caveolin-1. Disassembly of high molecular weight P-glycoprotein-containing structures within microvascular endothelial luminal membrane domains was accompanied by an increase in ATPase activity, suggesting a potential for functionally active P-glycoprotein. These results are the first observation that peripheral inflammatory pain leads to specific structural changes in P-glycoprotein responsible for controlling analgesic drug delivery to the CNS.

McCaffrey, Gwen; Staatz, William D.; Sanchez-Covarrubias, Lucy; Finch, Jessica D.; DeMarco, Kristen; Laracuente, Mei-Li; Ronaldson, Patrick T.; Davis, Thomas P.

2013-01-01

292

P-glycoprotein trafficking at the blood-brain barrier altered by peripheral inflammatory hyperalgesia.  

PubMed

P-glycoprotein (ABCB1/MDR1, EC 3.6.3.44), the major efflux transporter at the blood-brain barrier (BBB), is a formidable obstacle to CNS pharmacotherapy. Understanding the mechanism(s) for increased P-glycoprotein activity at the BBB during peripheral inflammatory pain is critical in the development of novel strategies to overcome the significant decreases in CNS analgesic drug delivery. In this study, we employed the ?-carrageenan pain model (using female Sprague-Dawley rats), combined with confocal microscopy and subcellular fractionation of cerebral microvessels, to determine if increased P-glycoprotein function, following the onset of peripheral inflammatory pain, is associated with a change in P-glycoprotein trafficking which leads to pain-induced effects on analgesic drug delivery. Injection of ?-carrageenan into the rat hind paw induced a localized, inflammatory pain (hyperalgesia) and simultaneously, at the BBB, a rapid change in colocalization of P-glycoprotein with caveolin-1, a key scaffolding/trafficking protein. Subcellular fractionation of isolated cerebral microvessels revealed that the bulk of P-glycoprotein constitutively traffics to membrane domains containing high molecular weight, disulfide-bonded P-glycoprotein-containing structures that cofractionate with membrane domains enriched with monomeric and high molecular weight, disulfide-bonded, caveolin-1-containing structures. Peripheral inflammatory pain promoted a dynamic redistribution between membrane domains of P-glycoprotein and caveolin-1. Disassembly of high molecular weight P-glycoprotein-containing structures within microvascular endothelial luminal membrane domains was accompanied by an increase in ATPase activity, suggesting a potential for functionally active P-glycoprotein. These results are the first observation that peripheral inflammatory pain leads to specific structural changes in P-glycoprotein responsible for controlling analgesic drug delivery to the CNS. PMID:22716933

McCaffrey, Gwen; Staatz, William D; Sanchez-Covarrubias, Lucy; Finch, Jessica D; Demarco, Kristen; Laracuente, Mei-Li; Ronaldson, Patrick T; Davis, Thomas P

2012-09-01

293

Discovery of the Inhibitory Effect of a Phosphatidylinositol Derivative on P-Glycoprotein by Virtual Screening Followed by In Vitro Cellular Studies  

PubMed Central

P-glycoprotein is capable of effluxing a broad range of cytosolic and membrane penetrating xenobiotic substrates, thus leading to multi-drug resistance and posing a threat for the therapeutic treatment of several diseases, including cancer and central nervous disorders. Herein, a virtual screening campaign followed by experimental validation in Caco-2, MDKCII, and MDKCII mdr1 transfected cell lines has been conducted for the identification of novel phospholipids with P-gp transportation inhibitory activity. Phosphatidylinositol-(1,2-dioctanoyl)-sodium salt (8?0 PI) was found to significantly inhibit transmembrane P-gp transportation in vitro in a reproducible-, cell line-, and substrate-independent manner. Further tests are needed to determine whether this and other phosphatidylinositols could be co-administered with oral drugs to successfully increase their bioavailability. Moreover, as phosphatidylinositols and phosphoinositides are present in the human diet and are known to play an important role in signal transduction and cell motility, our finding could be of substantial interest for nutrition science as well.

Lucas, Xavier; Simon, Silke; Schubert, Rolf; Gunther, Stefan

2013-01-01

294

The minimum functional unit of human P-glycoprotein appears to be a monomer.  

PubMed

Several studies have demonstrated the presence of oligomers of P-glycoprotein in multidrug-resistant cells. The minimum functional unit of P-glycoprotein, however, is not known. In order to determine whether the functional unit is an oligomer, we tested for associations between P-glycoproteins containing either a histidine tag or the epitope tag for monoclonal antibody A52 at the COOH-terminal end of the molecule. Both tagged molecules were active and had indistinguishable drug resistance profiles. The tagged P-glycoproteins were expressed contemporaneously in HEK 293 cells, purified by nickel-chelate chromatography followed by immunoblot analysis. We found that P-glycoprotein-A52 did not copurify with functionally active P-glycoprotein-(His)10, even when the former was overexpressed relative to the histidine-tagged protein. Similar results were obtained with phosphorylation-deficient mutants of P-glycoprotein. By contrast, we could purify and reconstitute drug-stimulated ATPase activity when the half-molecules NH2-terminal half-(His)10/COOH-terminal half-A52 or NH2-terminal half-A52/COOH-terminal half-(His)10 were coexpressed in HEK 293 cells. These results suggest that nickel-chelate chromatography may be a suitable method for studying protein-protein interactions in membrane proteins and that the minimal functional unit of P-glycoprotein is likely to be a monomer. PMID:8910332

Loo, T W; Clarke, D M

1996-11-01

295

Macelignan: a new modulator of P-glycoprotein in multidrug-resistant cancer cells.  

PubMed

The effect of macelignan, a phytoestrogen, on P-gp function was investigated using multidrug resistant cancer cells overexpressing P-gp (NCI/ADR-RES) and the fluorescent P-gp substrates, daunorubicin and rhodamine 123. Macelignan (40 microM) increased the cellular accumulation of daunorubicin by approximately threefold in NCI/ADR-RES cells, whereas it did not alter the cellular accumulation of daunorubicin in MCF-7/sensitive cells. Similarly, the presence of macelignan also enhanced significantly (P < 0.05) the cellular accumulation of rhodamine 123 in a concentration-dependent manner in NCI/ADR-RES cells. Furthermore, cancer cells were more susceptible to the cytotoxicity of vinblastine, a P-gp substrate, in the presence of macelignan. Those results suggest that macelignan has inhibitory effects on P-gp mediated cellular efflux. However, P-gp activity did not affect the cellular accumulation of macelignan itself. Taken all together, macelignan was identified as a novel inhibitor of P-gp activity and may be a promising lead compound for the rational design of more efficacious drugs to reverse multidrug resistance in cancer. PMID:19838926

Im, Young Bin; Ha, Ilho; Kang, Keon Wook; Lee, Moo-Yeol; Han, Hyo-Kyung

2009-01-01

296

Restoration of chemosensitivity by multifunctional micelles mediated by P-gp siRNA to reverse MDR.  

PubMed

One of the main obstacles in tumor therapy is multiple drug resistance (MDR) and an underlying mechanism of MDR is up-regulation of the transmembrane ATP-binding cassette (ABC) transporter proteins, especially P-glycoprotein (P-gp). In the synergistic treatment of siRNA and anti-cancer drug doxorubicin, it is crucial that both the siRNA and doxorubicin are simultaneously delivered to the tumor cells and the siRNA can fleetly down-regulate P-g before doxorubicin inactivates the P-gp and is pumped out. Herein, a type of micelles comprising a polycationic PEI-CyD shell to condense the siRNA and hydrophobic core to package doxorubicin is reported. The structure of the polymer is determined by (1)H NMR, FT-IR, DSC, and XRD and the micelles are characterized by DLS, 2D-NOESY NMR, and TEM to study the self-assembly of the micelles with siRNA and drugs. In vitro studies demonstrate controlled release and temporal enhancement of the therapeutic efficacy of P-gp siRNA and doxorubicin. Release of siRNA down-regulates the mRNA and protein levels of P-gp in the MCF-7/ADR cell lines effectively and the accumulated doxorubicin facilitates apoptosis of the cells to reverse MDR. Moreover, in vivo research reveals that the siRNA and doxorubicin loaded micelles induce tumor cell apoptosis and inhibit the growth of MDR tumor. The western blotting and RT-PCR results illustrate that the synergistic treatment of siRNA and doxorubicin leads to efficient reduction of the P-gp expression as well as cell apoptotic induction in MDR tumors at a small dosage of 0.5 mg/kg. The micelles have large clinical potential in drug/RNAi synergistic treatment via restoration of the chemosensitivity in MDR cancer therapy. PMID:25002258

Shen, Jie; Wang, Qiwen; Hu, Qida; Li, Yongbing; Tang, Guping; Chu, Paul K

2014-10-01

297

Enhanced brain accumulation of pazopanib by modulating P-gp and Bcrp1 mediated efflux with canertinib or erlotinib.  

PubMed

Primary objective of this investigation was to delineate the differential impact of efflux transporters P-glycoprotein (P-gp/Abcb1) and breast cancer resistance protein (Bcrp1/Abcg2) on brain disposition and plasma pharmacokinetics of pazopanib. In addition, this research investigated whether inhibition of these efflux transporters with clinically relevant efflux modulators canertinib or erlotinib could be a viable strategy for improving pazopanib brain delivery. In vitro assays with MDCKII cell monolayers suggested that pazopanib is a high affinity substrate for Bcrp1 and a moderate substrate for P-gp. Co-incubation with specific transport inhibitors restored cell accumulation and completely abolished the directionality of pazopanib flux. Brain and plasma pharmacokinetic studies were conducted in FVB wild type mice in the absence and presence of specific transport inhibitors. Drug levels in plasma and brain were determined using a validated high performance liquid chromatography method using vandetanib as an internal standard. In vivo studies indicated that specific inhibition of either P-gp (by zosuquidar or LY335979) or Bcrp1 (by Ko143) alone did not significantly alter pazopanib brain accumulation. However, dual P-gp/Bcrp1 inhibition by elacridar (GF120918), significantly enhanced pazopanib brain penetration by ~5-fold without altering its plasma concentrations. Thus, even though Bcrp1 showed higher affinity towards pazopanib in vitro, in vivo at the mouse BBB both P-gp and Bcrp1 act in concert to limit brain accumulation of pazopanib. Furthermore, erlotinib and canertinib as clinically relevant efflux modulators efficiently abrogated directionality in pazopanib efflux in vitro and their co-administration resulted in 2-2.5-fold increase in pazopanib brain accumulation in vivo. Further pre-clinical and clinical investigations are warranted as erlotinib or canertinib may have a synergistic pharmacological effect in addition to their primary role of pazopanib efflux modulation as a combination regimen for the treatment of recurrent brain tumors. PMID:22688250

Minocha, Mukul; Khurana, Varun; Qin, Bin; Pal, Dhananjay; Mitra, Ashim K

2012-10-15

298

Reversal effect of ST6GAL 1 on multidrug resistance in human leukemia by regulating the PI3K/Akt pathway and the expression of P-gp and MRP1.  

PubMed

?-Galactoside ?2, 6-sialyltransferse gene (ST6GAL) family has two members, which encode corresponding enzymes ST6Gal I and ST6Gal II. The present atudy was to investigate whether and how ST6GAL family involved in multidrug resistance (MDR) in human leukemia cell lines and bone marrow mononuclear cells (BMMC) of leukemia patients. Real-time PCR showed a high expression level of ST6GAL1 gene in both MDR cells and BMMCs (*P<0.05). Alternation of ST6GAL1 levels had a significant impact on drug-resistant phenotype changing of K562 and K562/ADR cells both in vitro and in vivo. However, no significant changes were observed of ST6GAL2 gene. Further data revealed that manipulation of ST6GAL1 modulated the activity of phosphoinositide 3 kinase (PI3K)/Akt signaling and consequently regulated the expression of P-glycoprotein (P-gp, *P<0.05) and multidrug resistance related protein 1 (MRP1, *P<0.05), which are both known to be associated with MDR. Therefore we postulate that ST6GAL1 is responsible for the development of MDR in human leukemia cells probably through medicating the activity of PI3K/Akt signaling and the expression of P-gp and MRP1. PMID:24454800

Ma, Hongye; Cheng, Lei; Hao, Keji; Li, Yanping; Song, Xiaobo; Zhou, Huimin; Jia, Li

2014-01-01

299

Inhibitory effects of CYP3A4 substrates and their metabolites on P-glycoprotein-mediated transport.  

PubMed

It is generally known that the substrates and/or inhibitors of cytochrome P450 (CYP) 3A4 and P-glycoprotein (P-gp) overlap with each other. In intestinal epithelial cells, it is surmised that the metabolites coexist with their parent drug. However, most studies on P-gp did not take the effects of those metabolites into consideration. Therefore, in the present study, we investigated the inhibitory effects of five substrates of CYP3A4 (nifedipine, testosterone, midazolam, amiodarone, and azelastine) and their metabolites on the P-gp-mediated transcellular transport. The transcellular transports of [(3)H]daunorubicin or [(3)H]digoxin by monolayers of LLC-GA5-COL150 cells in which P-gp was overexpressed were measured in the presence or absence of the CYP3A4 substrates and their metabolites. Nifedipine, testosterone, midazolam, and their metabolites exhibited no effects on the P-gp-mediated transport of [(3)H]daunorubicin and [(3)H]digoxin. On the other hand, the transport of [(3)H]daunorubicin was strongly inhibited by amiodarone, desethylamiodarone, azelastine, and desmethylazelastine, with IC(50) values of 22.5, 15.4, 16.0 and 11.8 microM, respectively. The transport of [(3)H]digoxin was also strongly inhibited by these compounds, with IC(50) values of 45.6, 25.2, 30.0 and 41.8 microM, respectively. Another metabolite of azelastine, 6-hydroxyazelastine, exhibited no effects on these transports. It was suggested that the CYP3A4 metabolites of which their parent drug exhibited inhibition on the P-gp-mediated transport are possibly also inhibitors. It would be possible more complicated drug-drug interactions would be caused by the metabolites as well as their parent drugs in the liver and the intestine via the inhibition of CYP3A4 and P-gp. PMID:11231118

Katoh, M; Nakajima, M; Yamazaki, H; Yokoi, T

2001-02-01

300

Influence of P-glycoprotein inhibition on the distribution of the tricyclic antidepressant nortriptyline over the blood-brain barrier.  

PubMed

The distribution of the antidepressant drug nortriptyline (NT) and its main metabolite E-10-hydroxy-nortriptyline (E-10-OH-NT) across the blood-brain barrier was considered in relation to inhibition of the multidrug transporter P-glycoprotein (P-gp). Rats received NT in doses of 25 mg/kg orally, 10 mg/kg i.p. or 25 mg/kg i.p. Half the rats were treated with the P-glycoprotein inhibitor cyclosporine A (CsA) (200 mg/kg) 2 h prior to NT administration, and the other half served as a control group. NT and the metabolite were extracted from brain and serum by liquid-liquid extraction and analysed by HPLC with UV-detection. The brain to serum ratio of NT was increased in the CsA treated groups (22.3-26.8) compared with the control groups (16.5-22.7), the difference being statistically significant in two of the three experiments (p<0.05). Increased brain-serum ratios were also found for E-10-OH-NT, but the differences were not statistically significant. These results suggest that inhibition of P-gp by CsA increases the accumulation of NT in the brain. Administration of the antipsychotic drug risperidone (0.5 mg/kg s.c.), which is a P-gp substrate, instead of CsA did not exert any measurable influence on the blood-brain ratio of NT concentrations. In conclusion, the results show that drug-drug interaction at P-gp may influence the intracerebral NT concentration, but apparently, a major inhibition of P-gp is necessary to attain a measurable effect. PMID:15624117

Ejsing, Thomas B; Linnet, Kristian

2005-03-01

301

Expression and significance of hypoxia-inducible factor-1 alpha and MDR1\\/P-glycoprotein in human colon carcinoma tissue and cells  

Microsoft Academic Search

Purpose  Hypoxia in tumors is generally associated with chemoresistance and radioresistance. However, the correlation between the heterodimeric\\u000a hypoxia-inducible factor-1 (HIF-1) and the multidrug resistance (MDR1) gene\\/transporter P-glycoprotein (P-gp) has not been\\u000a clearly investigated. This study aims at examining the expression levels of HIF-1? and MDR1\\/P-gp in human colon carcinoma\\u000a tissues and cell lines (HCT-116, HT-29, LoVo, and SW480) and ascertaining whether

Zhenyu Ding; Li Yang; Xiaodong Xie; Fangwei Xie; Feng Pan; Jianjun Li; Jianming He; Houjie Liang

2010-01-01

302

Characterization of multidrug resistance 1a/P-glycoprotein knockout rats generated by zinc finger nucleases.  

PubMed

The development of zinc finger nuclease (ZFN) technology has enabled the genetic engineering of the rat genome. The ability to manipulate the rat genome has great promise to augment the utility of rats for biological and pharmacological studies. A Wistar Hannover rat model lacking the multidrug resistance protein Mdr1a P-glycoprotein (P-gp) was generated using a rat Mdr1a-specific ZFN. Mdr1a was completely absent in tissues, including brain and small intestine, of the knockout rat. Pharmacokinetic studies with the Mdr1a P-gp substrates loperamide, indinavir, and talinolol indicated that Mdr1a was functionally inactive in the blood-brain barrier and intestine in Mdr1a(-/-) rats. To identify possible compensatory mechanisms in Mdr1a(-/-) rats, the expression levels of drug-metabolizing enzyme and transporter-related genes were compared in brain, liver, kidney, and intestine of male and female Mdr1a(-/-) and control rats. In general, alterations in gene expression of these genes in Mdr1a(-/-) rats seemed to be modest, with more changes in female than in male rats. Taken together, our studies demonstrate that the ZFN-generated Mdr1a(-/-) rat will be a valuable tool for central nervous system drug target validation and determining the role of P-gp in drug absorption and disposition. PMID:22049154

Chu, Xiaoyan; Zhang, Zuo; Yabut, Jocelyn; Horwitz, Sarah; Levorse, John; Li, Xiang-qing; Zhu, Lei; Lederman, Harmony; Ortiga, Rachel; Strauss, John; Li, Xiaofang; Owens, Karen A; Dragovic, Jasminka; Vogt, Thomas; Evers, Raymond; Shin, Myung K

2012-02-01

303

Specificity and sensitivity of immunocytochemistry for detecting P-glycoprotein in haematological malignancies.  

PubMed Central

AIMS--To determine the optimal working conditions of the alkaline phosphatase-antialkaline phosphatase (APAAP) method to establish a specific and sensitive assay for the detection of low numbers of MDR positive cells in patients with hematological malignancies. METHODS--Three monoclonal antibodies (C-219, JSB-1, MRK-16) were used for the detection of P-glycoprotein (P-gp) in cell lines and in samples from 43 patients with haematological malignancies. The results of the APAAP method were compared with western blotting for specificity and sensitivity. RESULTS--Excellent correlation was obtained between optimised APAAP and western blotting, except in the case of multiple myeloma. JSB-1 seemed to be the more useful monoclonal antibody for the APAAP which was more sensitive than western blotting in its ability to detect single P-gp positive cells. CONCLUSIONS--Methods for P-gp detection, as defined by multidrug resistant (MDR) cell lines, are not necessarily optimal and specific for clinical samples and may lead to higher false positive and negative results, according to the conditions and the monoclonal antibodies used. Images

Gala, J L; McLachlan, J M; Bell, D R; Michaux, J L; Ma, D D

1994-01-01

304

Evodiamine Synergizes with Doxorubicin in the Treatment of Chemoresistant Human Breast Cancer without Inhibiting P-Glycoprotein  

PubMed Central

Drug resistance is one of the main hurdles for the successful treatment of breast cancer. The synchronous targeting of apoptosis resistance and survival signal transduction pathways may be a promising approach to overcome drug resistance. In this study, we determined that evodiamine (EVO), a major constituent of the Chinese herbal medicine Evodiae Fructus, could induce apoptosis of doxorubicin (DOX)-sensitive MCF-7 and DOX-resistant MCF-7/ADR cells in a caspase-dependent manner, as confirmed by significant increases of cleaved poly(ADP-ribose) polymerase (PARP), caspase-7/9, and caspase activities. Notably, the reversed phenomenon of apoptosis resistance by EVO might be attributed to its ability to inhibit the Ras/MEK/ERK pathway and the expression of inhibitors of apoptosis (IAPs). Furthermore, our results indicated that EVO enhanced the apoptotic action of DOX by inhibiting the Ras/MEK/ERK cascade and the expression of IAPs without inhibiting the expression and activity of P-glycoprotein (P-gp). Taken together, our data indicate that EVO, a natural product, may be useful applied alone or in combination with DOX for the treatment of resistant breast cancer.

Shi, Zhi; Zhong, Zhangfeng; Chen, Meiwan; Wang, Yitao

2014-01-01

305

Changes in PtdIns(4,5)P2 Induced by Etoposide Treatment Modulates Small Intestinal P-Glycoprotein via Radixin.  

PubMed

Previously, we reported that repeated oral administration of etoposide (ETP) increases P-glycoprotein (P-gp) expression in association with activation of ezrin/radixin/moesin (ERM) via Ras homolog gene family member A (RhoA)/Rho-associated coiled-coil containing protein kinase (ROCK) signaling in the small intestine. However, the detailed mechanisms of this pathway have yet to be fully elucidated. Recently, phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], one of the most abundant phosphoinositides in the plasma membrane, has attracted attention regarding its involvement in the plasma membrane localization of various membrane proteins. PtdIns(4,5)P2 is an essential factor in the dissociation and subsequent membrane translocation (activation) of ERM, and its synthetic pathway is known to be highly regulated by RhoA/ROCK signaling. Here, we examined the involvement of PtdIns(4,5)P2 in the mechanism by which ETP treatment increases small intestinal P-gp levels, and we determined which protein within ERM contributes to this phenomenon. Repeated oral treatment with ETP (10?mg/kg/d) over 5?d significantly increased PtdIns(4,5)P2 expression in the ileal membrane as measured by dot blot. Furthermore, this increase was suppressed by co-administration of a RhoA inhibitor, rosuvastatin (5?mg/kg/d, per os (p.o.)), or a ROCK inhibitor, fasudil (5?mg/kg/d, p.o.). In immunoprecipitation assays, radixin (but not ezrin or moesin) binding to PtdIns(4,5)P2 was observed to increase in association with the up-regulation of P-gp in the same fraction, and immunofluorescence studies indicated that radixin co-localized with PtdIns(4,5)P2 in the ileal tissue. In conclusion, ETP treatment appears to up-regulate PtdIns(4,5)P2 expression via RhoA/ROCK signaling, leading to the activation of ERM, presumably through the physical interaction of radixin with PtdIns(4,5)P2. This in turn increases the expression of ileal P-gp. PMID:24989004

Kobori, Takuro; Harada, Shinichi; Nakamoto, Kazuo; Tokuyama, Shogo

2014-01-01

306

In vitro predictability of drug-drug interaction likelihood of P-glycoprotein-mediated efflux of dabigatran etexilate based on [I]2/IC50 threshold.  

PubMed

Dabigatran etexilate, an oral, reversible, competitive, and direct thrombin inhibitor, is an in vitro and in vivo substrate of P-glycoprotein (P-gp). Dabigatran etexilate was proposed as an in vivo probe substrate for intestinal P-gp inhibition in a recent guidance on drug-drug interactions (DDI) from the European Medicines Agency (EMA) and the Food and Drug Administration (FDA). We conducted transcellular transport studies across Caco-2 cell monolayers with dabigatran etexilate in the presence of various P-gp inhibitors to examine how well in vitro IC50 data, in combination with mathematical equations provided by regulatory guidances, predict DDI likelihood. From a set of potential P-gp inhibitors, clarithromycin, cyclosporin A, itraconazole, ketoconazole, quinidine, and ritonavir inhibited P-gp-mediated transport of dabigatran etexilate over a concentration range that may hypothetically occur in the intestine. IC50 values of P-gp inhibitors for dabigatran etexilate transport were comparable to those of digoxin, a well established in vitro and in vivo P-gp substrate. However, IC50 values varied depending whether they were calculated from efflux ratios or permeability coefficients. Prediction of DDI likelihood of P-gp inhibitors using IC50 values, the hypothetical concentration of P-gp inhibitors, and the cut-off value recommended by both the FDA and EMA were in line with the DDI occurrence in clinical studies with dabigatran etexilate. However, it has to be kept in mind that validity of the cut-off criteria proposed by the FDA and EMA depends on in vitro experimental systems and the IC50-calculation methods that are employed, as IC50 values are substantially influenced by these factors. PMID:24212378

Kishimoto, Wataru; Ishiguro, Naoki; Ludwig-Schwellinger, Eva; Ebner, Thomas; Schaefer, Olaf

2014-02-01

307

P-glycoprotein and multidrug resistance  

Microsoft Academic Search

Although the phenomenon of simultaneous resistance to multiple cytotoxic drugs (multidrug resistance) in cancer cells has been discussed for more than two decades, and the human and mouse genes encoding an energy-dependent transporter (the multidrug transporter or P-glycoprotein) responsible for multidrug resistance were cloned 10 years ago, there is still considerable controversy about the mechanism of action of this efflux

Michael M Gottesman; Ira Pastan; Suresh V Ambudkar

1996-01-01

308

Substrate-dependent bidirectional modulation of P-glycoprotein-mediated drug resistance by erlotinib.  

PubMed

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) inhibit the function of certain adenosine triphosphate (ATP)-binding cassette transporters, including P-glycoprotein/ABCB1 and breast cancer resistance protein (BCRP)/ABCG2. We previously reported an antagonistic activity of gefitinib towards BCRP. We have now analyzed the effects of erlotinib, another EGFR-TKI, on P-glycoprotein and BCRP. As with gefitinib, erlotinib effectively reversed BCRP-mediated resistance to SN-38 (7-ethyl-10-hydroxycamptothecin) and mitoxantrone. In contrast, we found that erlotinib effectively suppressed P-glycoprotein-mediated resistance to vincristine and paclitaxel, but did not suppress resistance to mitoxantrone and doxorubicin. Conversely, erlotinib appeared to enhance P-glycoprotein-mediated resistance to mitoxantrone in K562/MDR cells. This bidirectional activity of erlotinib was not observed with verapamil, a typical P-glycoprotein inhibitor. Flow cytometric analysis showed that erlotinib co-treatment restored intracellular accumulation of mitoxantrone in K562 cells expressing BCRP, but not in cells expressing P-glycoprotein. Consistently, erlotinib did not inhibit mitoxantrone efflux in K562/MDR cells although it did vincristine efflux in K562/MDR cells and mitoxantrone efflux in K562/BCRP cells. Intravesicular transport assay showed that erlotinib inhibited both P-glycoprotein-mediated vincristine transport and BCRP-mediated estrone 3-sulfate transport. Intriguingly, Lineweaver-Burk plot suggested that the inhibitory mode of erlotinib was a mixed type for P-glycoprotein-mediated vincristine transport whereas it was a competitive type for BCRP-mediated estrone 3-sulfate transport. Collectively, these observations indicate that the pharmacological activity of erlotinib on P-glycoprotein-mediated drug resistance is dependent upon the transporter substrate. These findings will be useful in understanding the pharmacological interactions of erlotinib used in combinational chemotherapy. PMID:19493273

Noguchi, Kohji; Kawahara, Haruka; Kaji, Airi; Katayama, Kazuhiro; Mitsuhashi, Junko; Sugimoto, Yoshikazu

2009-09-01

309

P-glycoprotein and breast cancer resistance protein affect disposition of tandutinib, a tyrosine kinase inhibitor.  

PubMed

Tandutinib is a tyrosine kinase inhibitor under investigation for the treatment of solid and hematological tumors. We evaluated efflux transporter substrate specificity of tandutinib in Caco-2 cells, and the role of efflux transporters in the disposition of tandutinib in rats and efflux transporter knock-out mice. These studies demonstrated that tandutinib is a substrate of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) in Caco-2 cells. In rats, administration of GF120918, before treatment with tandutinib orally resulted in approximately a seven-fold increase in the mean plasma area under the concentration-versus-time curve (AUC) compared to the vehicle control group. In mice, after intravenous administration of tandutinib, the mean plasma AUC values in the Bcrp1(-/-) mice and Mdr1a/b(-/-) mice was 1.53- and 1.20-fold greater than that of the wild type (WT) mice, respectively. After oral administration, the drug exposure in Mdr1a/b(-/-), Bcrp1(-/-), and Mdr1a/b(-/-)/Bcrp1(-/-) mice was higher than in the WT mice. The brain to plasma exposure ratio (B/P) of tandutinib in Mdr1a/b(-/-) mice increased by 2- to 3-fold over that in the WT mice. There was a 13-fold increase in B/P in Mdr1a/b(-/-)/Bcrp1(-/-) mice. This finding illustrates that P-gp and Bcrp play a role in oral absorption, systemic clearance, and brain penetration of tandutinib in the rodents. P-gp affected oral absorption and brain penetration of tandutinib to a greater extent than Bcrp, but Bcrp contribution to systemic clearance of tandutinib was greater than P-gp. Thus, co-administration of efflux pump inhibitors may be a useful strategy to enhance tandutinib absorption and brain penetration clinically. PMID:20670210

Yang, Johnny J; Milton, Mark N; Yu, Shaoxia; Liao, Mingxiang; Liu, Ning; Wu, Jing-Tao; Gan, Liangshang; Balani, Suresh K; Lee, Frank W; Prakash, Shimoga; Xia, Cindy Q

2010-12-01

310

Detection of P-glycoprotein in the Golgi apparatus of drug-untreated human melanoma cells.  

PubMed

The intracellular location of the MDR1 gene product, known as P-glycoprotein (P-gp), has been detected by flow cytometry in 3 stabilized human melanoma cell lines which had never undergone cytotoxic drug treatment and did not express P-gp on the plasma membrane. In addition, MDR1 mRNA expression was revealed by RT-PCR in the same cell lines. Immunofluorescence microscopy, performed by using the same 2 monoclonal antibodies (MM4.17 and MRK-16) as employed in the flow-cytometric analysis, revealed the presence of P-gp intracytoplasmically, in a well-defined perinuclear region. Double immunofluorescence labelling and immunoelectron microscopy strongly suggested the location of the transporter molecule in the Golgi apparatus. The same observations have been obtained on a primary culture from a metastasis of human melanoma. Analysis of the expression of another membrane transport protein, the multidrug-resistance-related protein (MRP1), showed that it was present in the cytoplasm of all the melanoma cell lines examined. MRP1 also showed Golgi-like localization. The study by laser scanning confocal microscopy on the intracellular localization of the anti-tumoral agent doxorubicin (DOX) during the drug-uptake and -efflux phases, indicated the Golgi apparatus as a preferential accumulation site for the anthracyclinic antibiotic. P-gp function modulators (verapamil and cyclosporin A) were able to modify DOX intracytoplasmic distribution and to increase drug intracellular concentration and cytotoxic effect in melanoma cells. On the contrary, MRP1 modulators (probenecid and genistein) did not significantly influence either DOX efflux and distribution or the sensitivity of melanoma cells to the cytotoxic drug. PMID:9506534

Molinari, A; Calcabrini, A; Meschini, S; Stringaro, A; Del Bufalo, D; Cianfriglia, M; Arancia, G

1998-03-16

311

In vitro and in vivo evaluation of the effects of piperine on P-gp function and expression  

SciTech Connect

Piperine, a major component of black pepper, is used as spice and nutrient enhancer. The purpose of the present study was to evaluate the effects of acute and prolonged piperine exposure on cellular P-gp expression and function in vitro and in vivo. Piperine at concentrations ranging from 10 to 100 {mu}M, determined by MTT assay to be non-cytotoxic, was observed to inhibit P-gp mediated efflux transport of [{sup 3}H]-digoxin across L-MDR1 and Caco-2 cell monolayers. The acute inhibitory effect was dependent on piperine concentration, with abolishment of [{sup 3}H]-digoxin polarized transport attained at 50 {mu}M of piperine. In contrast, prolonged (48 and 72 h) co-incubation of Caco-2 cell monolayers with piperine (50 and 100 {mu}M) increased P-gp activity through an up-regulation of cellular P-gp protein and MDR1 mRNA levels. The up-regulated protein was functionally active, as demonstrated by a higher degree of [{sup 3}H]-digoxin efflux across the cell monolayers, but the induction was readily reversed by the removal of the spice from the culture medium. Peroral administration of piperine at the dose of 112 {mu}g/kg body weight/day to male Wistar rats for 14 consecutive days also led to increased intestinal P-gp levels. However, there was a concomitant reduction in the rodent liver P-gp although the kidney P-gp level was unaffected. Our data suggest that caution should be exercised when piperine is to be co-administered with drugs that are P-gp substrates, particularly for patients whose diet relies heavily on pepper.

Han Yi [Department of Pharmacy, National University of Singapore, 18 Science Drive 4, 117543 (Singapore); Chin Tan, Theresa May [Department of Biochemistry, National University of Singapore, 18 Science Drive 4, 117543 (Singapore); Lim, Lee-Yong [Pharmacy, School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, WA 6009 (Australia)], E-mail: limly@cyllene.uwa.edu.au

2008-08-01

312

Enhanced cellular accumulation of a P-glycoprotein substrate, rhodamine-123, by caco-2 cells using low molecular weight methoxypolyethylene glycol- block-polycaprolactone diblock copolymers  

Microsoft Academic Search

A series of diblock copolymers based on methoxypolyethylene glycol-block-poly(caprolactone) (MePEG-b-PCL) was synthesized and evaluated for enhancing the cellular accumulation of a P-glycoprotein (P-gp) substrate, rhodamine-123 (R-123), into caco-2 cells. Altering MePEG:caprolactone feed weight ratio allowed diblocks with varying PCL lengths to be synthesized onto MePEG of molecular weight 750 or 2000. The critical micelle concentration (CMC) and the hydrophilic-lipophilic balance

Jason Zastre; John Jackson; Mandeep Bajwa; Richard Liggins; Famida Iqbal; Helen Burt

2002-01-01

313

Effects of Silibinin, Inhibitor of CYP3A4 and P-Glycoprotein in vitro, on the Pharmacokinetics of Paclitaxel after Oral and Intravenous Administration in Rats  

Microsoft Academic Search

Silibinin, a flavonoid, is an inhibitor of P-glycoprotein (P-gp)-mediated efflux transporters, and its oxidative metabolism is catalyzed by CYP3A4. The purpose of this study was to investigate the effect of oral silibinin on the bioavailability and pharmacokinetics of orally and intravenously administered paclitaxel in rats. The pharmacokinetic parameters of paclitaxel were determined in rats after oral (40 mg\\/kg) or intravenous

Chong-Ki Lee; Jun-Shik Choi

2010-01-01

314

Multidrug resistance markers P-glycoprotein, multidrug resistance protein 1, and lung resistance protein in non-small cell lung cancer: prognostic implications  

Microsoft Academic Search

Purpose: The aim of this retrospective study was to comparatively investigate the expression of the three drug-resistance genes P-glycoprotein (P-gp), mul- tidrug-resistance protein 1 (MRP1), and lung resistance protein (LRP), in non-small cell lung cancer (NSCLC) tissues, and to assess possible associations with clinico- pathologic features. Methods: Tumor specimens from 126 patients were analyzed by immunohistochemistry and, in selected cases,

Walter Berger; Ulrike Setinek; Peter Hollaus; Thomas Zidek; Elisabeth Steiner; L. Elbling; H. Cantonati; Johannes Attems; Andrea Gsur; Michael Micksche

2005-01-01

315

Absence of both cytochrome P450 3A and P-glycoprotein dramatically increases docetaxel oral bioavailability and risk of intestinal toxicity  

Microsoft Academic Search

Docetaxel is one of the most widely used anticancer drugs. A major problem with docetaxel treatment, however, is the considerable interpatient variability in docetaxel exposure. Another disadvantage of the drug is that it has a very low oral bioavailability and can therefore only be administered i.v. The drug-metabolizing enzyme cytochrome P450 3A (CYP3A) and the drug transporter P-glycoprotein (P-gp; MDR1)

R. A. B. van Waterschoot; J. S. Lagas; E. Wagenaar; C. M. M. van der Kruijssen; A. E. van Herwaarden; J.-Y. Song; R. W. Rooswinkel; O. van Tellingen; H. Rosing; J. H. Beijnen; A. H. Schinkel

2009-01-01

316

Establishment of in vitro P-glycoprotein inhibition assay and its exclusion criteria to assess the risk of drug-drug interaction at the drug discovery stage.  

PubMed

The decision tree to determine whether the P-glycoprotein (P-gp)/multidrug resistance protein 1 (MDR1)-mediated drug-drug interaction (DDI) study is recommended has been proposed by the International Transporter Consortium. We, therefore, designed an in vitro P-gp inhibition assay and determined the appropriate risk criteria for P-gp-mediated DDI at the drug discovery stage. Effects of P-gp inhibitors on digoxin transport across a monolayer of MDR1-expressing cells were examined. The IC(50) (half-maximal inhibitory concentration) values generated from the efflux ratio (ER) were smaller than those generated from basolateral-to-apical directional apparent permeability. The difference in IC(50) values was kinetically described in a compartment model analysis. This analysis indicated that ER is a highly sensitive parameter that can be used for the degree of P-gp inhibition. Considering IC(50) values and the increase in digoxin exposure in clinical DDI studies, the risk criteria of [I(2)]/IC(50) = 30 ([I(2)], theoretically maximal gastrointestinal concentration) was the optimal cutoff value to predict a clinically relevant DDI. We also investigated whether the IC(50) value itself is applicable to assess the DDI risk. In conclusion, compounds with IC(50) values less than 2 ?M exhibit high risk for P-gp-mediated DDIs. However, compounds with IC(50) values greater than or equal to 2 ?M are inconclusive because clinical doses should be considered for the precise DDI risk assessment. PMID:21678427

Sugimoto, Hiroshi; Matsumoto, Shin-ichi; Tachibana, Miho; Niwa, Shin-ichi; Hirabayashi, Hideki; Amano, Nobuyuki; Moriwaki, Toshiya

2011-09-01

317

Drug transporter, P-glycoprotein (MDR1), is an integrated component of the mammalian blood-testis barrier.  

PubMed

Throughout spermatogenesis, leptotene spermatocytes traverse the blood-testis barrier (BTB) to enter the adluminal compartment of the seminiferous epithelium for continued development. At the same time, the integrity of the BTB, which is constituted by co-existing tight junctions (TJ), basal ectoplasmic specializations (basal ES) and desmosome-like junctions, must be maintained since a breach in barrier function can result in spermatogenic arrest and even infertility. There is evidence to suggest that drug transporters may function at the BTB, but little is known about how they contribute to spermatogenesis. In this study, we investigate the role of P-glycoprotein (P-gp), a drug efflux pump, in BTB dynamics. A survey by RT-PCR revealed several transporter genes to be expressed by the testis, including Mdr1 (gene symbol for P-gp), Mrp1, Abcc5 and Slc15a1. It was also demonstrated that P-gp localizes to the BTB in all stages of the seminiferous epithelial cycle in the adult rat testis, as well as to the Sertoli cell-elongated spermatid interface in stages VII and VIII. We continued our study by examining the levels of several transporters in the testis following oral administration of Adjudin, a compound known to affect Sertoli-germ cell adhesion. In this experiment, the steady-state levels of P-gp, MRP1, ABCG1 and SLC15A1 were all found to increase by several-fold within hours of Adjudin treatment during junction restructuring. More importantly, an increase in P-gp association with TJ proteins (e.g., occludin, claudin-11 and JAM-A) was noted when testis lysates from Adjudin-treated rats were used for co-immunoprecipitation experiments, suggesting that P-gp may enhance BTB function during Sertoli-germ cell junction restructuring. PMID:19720156

Su, Linlin; Cheng, C Yan; Mruk, Dolores D

2009-12-01

318

Modulation of P-glycoprotein-mediated multidrug resistance in K562 leukemic cells by indole-3-carbinol  

SciTech Connect

Resistance to chemotherapeutic drugs is one of the major problems in the treatment of cancer. P-glycoprotein (P-gp) encoded by the mdr gene is a highly conserved protein, acts as a multidrug transporter, and has a major role in multiple drug resistance (MDR). Targeting of P-gp by naturally occurring compounds is an effective strategy to overcome MDR. Indole-3-carbinol (I3C), a glucosinolates present in cruciferous vegetables, is a promising chemopreventive agent as it is reported to possess antimutagenic, antitumorigenic, and antiestrogenic properties in experimental studies. In the present investigation, the potential of I3C to modulate P-gp expression was evaluated in vinblastine (VBL)-resistant K562 human leukemic cells. The resistant K562 cells (K562/R10) were found to be cross-resistant to vincristine (VCR), doxorubicin (DXR), and other antineoplastic agents. I3C at a nontoxic dose (10 x 10{sup -3} M) enhanced the cytotoxic effects of VBL time dependently in VBL-resistant human leukemia (K562/R10) cells but had no effect on parent-sensitive cells (K562/S). The Western blot analysis of K 562/R 10 cells showed that I3C downregulates the induced levels of P-gp in resistant cells near to normal levels. The quantitation of immunocytochemically stained K562/R10 cells showed 24%, 48%, and 80% decrease in the levels of P-gp by I3C for 24, 48, and 72 h of incubation. The above features thus indicate that I3C could be used as a novel modulator of P-gp-mediated multidrug resistance in vitro and may be effective as a dietary adjuvant in the treatment of MDR cancers.

Arora, Annu [Environmental Carcinogenesis Division, Industrial Toxicology Research Centre, M.G. Marg, Lucknow-226001 (India); Seth, Kavita [Environmental Carcinogenesis Division, Industrial Toxicology Research Centre, M.G. Marg, Lucknow-226001 (India); Kalra, Neetu [Environmental Carcinogenesis Division, Industrial Toxicology Research Centre, M.G. Marg, Lucknow-226001 (India); Shukla, Yogeshwer [Environmental Carcinogenesis Division, Industrial Toxicology Research Centre, M.G. Marg, Lucknow-226001 (India)]. E-mail: yogeshwer_shukla@hotmail.com

2005-02-01

319

Topology and Function of Human p-Glycoprotein in Multidrug Resistant Breast Cancer Cells.  

National Technical Information Service (NTIS)

Overexpression of P-glycoprotein (Pgp) in breast and other cancers is thought to be largely responsible for the development of multidrug resistance to chemotherapy. Pgp actively extrudes various chemotherapeutic drugs out of cells and may also regulate Cl...

E. S. Han L. Reuss

1997-01-01

320

Evaluation of the P-glycoprotein (Abcb1) affinity status of a series of morphine analogs: Comparative study with meperidine analogs to identify opioids with minimal P-glycoprotein interactions  

PubMed Central

One of the major shortcomings of many commonly used opioids is the fact that they are P-gp substrates, which represents a major obstacle towards effective pain management. P-gp can affect opioids’ oral absorption, CNS accumulation, systemic clearance, antinociceptive activity, and tolerance development to their analgesic effects. Moreover, P-gp can be the locus of drug–drug interactions between opioids and other concomitantly administered drugs that are P-gp substrates/inhibitors. The objective of this study was to identify opioids that are non-P-gp substrates to overcome some of the mentioned shortcomings. We evaluated the P-gp affinity status (substrate, non-substrate, or inhibitor) of a series of morphine analogs (10 opioid agonist and 2 opioid antagonists) and compared them to previously reported meperidine analogs. The fold stimulation of the morphine analogs ranged from 1.01 to 1.54 while for the meperidine analogs the fold stimulation ranged from 1.10 to 3.66. From each series (morphine and meperidine analogs) we selected potential candidate opioids that are non-P-gp substrates and conducted in vivo assessments of their antinociceptive effects using P-gp knockout and P-gp competent mice. 6-Desoxymorphine, meperidine and N-phenylbutyl normeperidine did not significantly (p > 0.05) stimulate the basal P-gp ATPase activity, where, the fold stimulations of the basal P-gp ATPase activity were 1.01 ± 0.11, 1.51 ± 0.29 and 1.10 ± 0.23, respectively. Evaluation of the influence of P-gp ablation on their antinociceptive effects indicated that P-gp did not significantly (p > 0.05) affect their antinociceptive effects. Among the evaluated opioids in vivo, 6-desoxymorphine showed high potency and induced no apparent toxicity upon low- and high-dose administration. 6-Desoxymorphine is therefore an ideal lead compound to create a library of opioids that have negligible P-gp affinity for better management of pain.

Hassan, Hazem E.; Mercer, Susan L.; Cunningham, Christopher W.; Coop, Andrew; Eddington, Natalie D.

2012-01-01

321

In vitro modulation of P-glycoprotein, MRP-1 and BCRP expression by mangiferin in doxorubicin-treated MCF-7 cells.  

PubMed

The multidrug resistance phenotype is one of the major problems in development of cancer cell resistance to chemotherapy. Some natural compounds from medicinal plants have demonstrated promising capacity in enhancing anticancer effects in drug resistant cancer cells. We aimed to investigate whether mangiferin might have an ability to re-sensitize MCF-7 breast cancer cells previously treated with short-term doxorubicin in vitro, through the modulation of efflux transporters, P-glycoprotein (P-gp), MRP1 and BCRP. We exposed MCF-7 breast cancer cells pretreated with doxorubicin for 10 days to mangiferin (10, 25 or 50 ?M) for 96 hours. Afterwards, we evaluated influence on cell viability and level of mRNA expression of P-gp, MRP1 and BCRP. Doxorubicin given in combination with mangiferin at low concentrations (10 and 25 ?M) failed to give significant reduction in cell viability, while at the highest concentrations, the combination significantly reduced cell viability. The mRNA expression analysis of P-gp, MRP1 and BCRP showed that mangiferin had inhibitory effects on P-gp but no effects on MRP1 and BCRP. In conclusion, we suggest that mangiferin at high concentrations can be used as chemosensitizer for doxorubicin therapy. This effect might be attributed by inhibitory effects of mangiferin on P-glycoprotein expression. PMID:24641381

Louisa, Melva; Soediro, Tjahjani Mirawati; Suyatna, Frans Dhyanagiri

2014-01-01

322

Reversal of P-glycoprotein mediated multidrug resistance by a newly synthesized 1,4-benzothiazipine derivative, JTV-519  

Microsoft Academic Search

A newly synthesized 1,4-benzothiazipine derivate, 4-[3-(4-benzylpiperidin-1-yl) propionyl]-7-methoxy-2,3,4,5-tetrahydro-1, 4-benzothiazepine monohydrochloride (JTV-519) was examined for its ability to reverse P-glycoprotein (P-gp) and multidrug resistance protein 1 (MRP1) mediated multidrug resistance (MDR) in K562\\/MDR and KB\\/MRP cells, respectively. JTV-519 at 3?M reversed the resistance of K562\\/MDR cells to vincristine (VCR), taxol, etoposide (VP16), adriamycin (ADM) and actinomycin D and at 0.5 or 1?M

Xiao-Fang Che; Yuichi Nakajima; Tomoyuki Sumizawa; Ryuji Ikeda; Xiao-Qin Ren; Chun-Lei Zheng; Motoi Mukai; Tatsuhiko Furukawa; Misako Haraguchi; Hui Gao; Yoshikazu Sugimoto; Shin-ichi Akiyama

2002-01-01

323

ABC Transporter (P-gp/ABCB1, MRP1/ABCC1, BCRP/ABCG2) Expression in the Developing Human CNS  

PubMed Central

P-glycoprotein (P-gp/ABCB1), multidrug resistance protein 1 (MRP1/ABCC1), and breast cancer resistance protein (BCRP/ABCG2) are plasma membrane efflux pumps that limit the intracellular uptake and retention of numerous lipophilic, amphipathic xeno- and endobiotics. Little is known about the neonatal and developmental expression of P-gp/ABCB1, MRP1/ABCC1, and BCRP/ABCG2 in the human central nervous system (CNS), therefore postmortem CNS tissue from infants born 220/7- 420/7 week gestation and adults was immunostained to determine their ontogeny and cellular localization. P-gp/ABCB1 imunostaining was observed in microvessel endothelial cells as early as 220/7 weeks, increasing in prevalence and intensity with maturation, and later in gestation in large pyramidal neurons. MRP1/ABCC1 immunostaining was prominent early in the choroid plexus and ventricular ependyma, and noted later in large pyramidal neurons. BCRP/ABCG2 expression was limited to microvessel endothelial cells. P-gp/ABCB1, MRP1/ABCC1 and BCRP/ABCG2 in adult brain matched term newborn CNS but with more intense immunostaining. We conclude that P-gp/ABCB1, MRP1/ABCC1, and BCRP/ABCG2 are expressed in a developmental, cell specific, fashion in the human CNS. The complementary pattern of P-gp/ABCB1 and BCRP/ABCG2 at the blood-brain with MRP1/ABCC1 at the blood-CSF barriers may limit CNS uptake and retention of drugs and toxins in neonates.

Daood, Monica J.; Tsai, Cathy; Ahdab-Barmada, Mamdouha; Watchko, Jon F.

2010-01-01

324

Development of a quantitative LC-MS/MS analytical method coupled with turbulent flow chromatography for digoxin for the in vitro P-gp inhibition assay.  

PubMed

Caco-2 cells, the human colon carcinoma cells, are typically used for screening compounds for their permeability characteristics and P-glycoprotein (P-gp) interaction potential during discovery and development. The P-gp inhibition of test compounds is assessed by performing bi-directional permeability studies with digoxin, a well established P-gp substrate probe. Studies performed with digoxin alone as well as digoxin in presence of test compounds as putative inhibitors constitute the P-gp inhibition assay used to assess the potential liability of discovery compounds. Radiolabeled (3)H-digoxin is commonly used in such studies followed by liquid scintillation counting. This manuscript describes the development of a sensitive, accurate, and reproducible LC-MS/MS method for analysis of digoxin and its internal standard digitoxin using an on-line extraction turbulent flow chromatography coupled to tandem mass spectrometric detection that is amendable to high throughput with use of 96-well plates. The standard curve for digoxin was linear between 10 nM and 5000 nM with regression coefficient (R(2)) of 0.99. The applicability and reliability of the analysis method was evaluated by successful demonstration of efflux ratio (permeability B to A over permeability A to B) greater than 10 for digoxin in Caco-2 cells. Additional evaluations were performed on 13 marketed compounds by conducting inhibition studies in Caco-2 cells using classical P-gp inhibitors (ketoconazole, cyclosporin, verapamil, quinidine, saquinavir etc.) and comparing the results to historical data with (3)H-digoxin studies. Similarly, P-gp inhibition studies with LC-MS/MS analytical method for digoxin were also performed for 21 additional test compounds classified as negative, moderate, and potent P-gp inhibitors spanning multiple chemo types and results compared with the historical P-gp inhibition data from the (3)H-digoxin studies. A very good correlation coefficient (R(2)) of 0.89 between the results from the two analytical methods affords an attractive LC-MS/MS analytical option for labs that need to conduct the P-gp inhibition assay without using radiolabeled compounds. PMID:17524973

Smalley, James; Marino, Anthony M; Xin, Baomin; Olah, Timothy; Balimane, Praveen V

2007-07-01

325

B4GALT family mediates the multidrug resistance of human leukemia cells by regulating the hedgehog pathway and the expression of p-glycoprotein and multidrug resistance-associated protein 1  

PubMed Central

?-1, 4-Galactosyltransferase gene (B4GALT) family consists of seven members, which encode corresponding enzymes known as type II membrane-bound glycoproteins. These enzymes catalyze the biosynthesis of different glycoconjugates and saccharide structures, and have been recognized to be involved in various diseases. In this study, we sought to determine the expressional profiles of B4GALT family in four pairs of parental and chemoresistant human leukemia cell lines and in bone marrow mononuclear cells (BMMC) of leukemia patients with multidrug resistance (MDR). The results revealed that B4GALT1 and B4GALT5 were highly expressed in four MDR cells and patients, altered levels of B4GALT1 and B4GALT5 were responsible for changed drug-resistant phenotype of HL60 and HL60/adriamycin-resistant cells. Further data showed that manipulation of these two gene expression led to increased or decreased activity of hedgehog (Hh) signaling and proportionally mutative expression of p-glycoprotein (P-gp) and MDR-associated protein 1 (MRP1) that are both known to be related to MDR. Thus, we propose that B4GALT1 and B4GALT5, two members of B4GALT gene family, are involved in the development of MDR of human leukemia cells, probably by regulating the activity of Hh signaling and the expression of P-gp and MRP1.

Zhou, H; Ma, H; Wei, W; Ji, D; Song, X; Sun, J; Zhang, J; Jia, L

2013-01-01

326

Multidrug resistance protein P-gp interaction with nanoparticles (fullerenes and carbon nanotube) to assess their drug delivery potential: a theoretical molecular docking study.  

PubMed

P-glycoprotein (P-gp)-mediated efflux system plays an important role to maintain chemical balance in mammalian cells for endogenous and exogenous chemical compounds. However, despite the extensive characterisation of P-gp potential interaction with drug-like molecules, the interaction of carbon nanoparticles with this type of protein molecule is poorly understood. Thus, carbon nanoparticles were analysed, such as buckminsterfullerenes (C20, C60, C70), capped armchair single-walled carbon nanotube (SWCNT or C168), and P-gp interactions using different molecular docking techniques, such as gradient optimisation algorithm (ADVina), Lamarckian genetic algorithm (FastDock), and shape-based approach (PatchDock) to estimate the binding affinities between these structures. The theoretical results represented in this work show that fullerenes might be P-gp binders because of low levels of Gibbs free energy of binding (?G) and potential of mean force (PMF) values. Furthermore, the SWCNT binding is energetically unfavourable, leading to a total decrease in binding affinity by elevation of the residual area (Ares), which also affects the ?-? stacking mechanisms. Further, the obtained data could potentially call experimental studies using carbon nanostructures, such as SWCNT for development of drug delivery vehicles, to administer and assess drug-like chemical compounds to the target cells since organisms probably did not develop molecular sensing elements to detect these types of carbon molecules. PMID:24088267

Shityakov, Sergey; Förster, Carola

2013-01-01

327

Effects of Fluvastatin on the Pharmacokinetics of Repaglinide: Possible Role of CYP3A4 and P-glycoprotein Inhibition by Fluvastatin  

PubMed Central

The purpose of this study was to investigate the effects of fluvastatin on the pharmacokinetics of repaglinide in rats. The effect of fluvastatin on P-glycoprotein and CYP3A4 activity was evaluated. The pharmacokinetic parameters and blood glucose concentrations were also determined after oral and intravenous administration of repaglinide to rats in the presence and absence of fluvastatin. Fluvastatin inhibited CYP3A4 activity in a concentration-dependent manner with a 50% inhibition concentration(IC50) of 4.1 µM and P-gp activity. Compared to the oral control group, fluvastatin significantly increased the AUC and the peak plasma level of repaglinide by 45.9% and 22.7%, respectively. Fluvastatin significantly decreased the total body clearance (TBC) of repaglinide compared to the control. Fluvastatin also significantly increased the absolute bioavailability (BA) of repaglinide by 46.1% compared to the control group. Moreover, the relative BA of repaglinide was 1.14- to 1.46-fold greater than that of the control. Compared to the i.v. control, fluvastatin significantly increased the AUC0-? of i.v. administered repaglinide. The blood glucose concentrations showed significant differences compared to the oral controls. Fluvastatin enhanced the oral BA of repaglinide, which may be mainly attributable to the inhibition of the CYP3A4-mediated metabolism of repaglinide in the small intestine and/or liver, to the inhibition of the P-gp efflux transporter in the small intestine and/or to the reduction of TBC of repaglinide by fluvastatin. The study has raised the awareness of potential interactions during concomitant use of repaglinide with fluvastatin. Therefore, the concurrent use of repaglinide and fluvastatin may require close monitoring for potential drug interactions.

Lee, Chong-Ki; Choi, Jun-Shik

2013-01-01

328

Effect of P-glycoprotein inhibitor, verapamil, on oral bioavailability and pharmacokinetics of irinotecan in rats.  

PubMed

The objective of present investigation was to study the effect of verapamil on the pharmacokinetics of irinotecan in order to evaluate the role of P-glycoprotein (P-gp) in irinotecan disposition. An in vitro study using Caco-2 intestinal cell monolayer was first carried out to determine the effect of verapamil on the function of intestinal P-gp. Verapamil (25mg/kg) was administered orally 2h before irinotecan oral (80 mg/kg) or intravenous (20mg/kg) dosing in female Wistar rats. Plasma and biliary samples were collected at specified time points from control and treated animals to determine irinotecan and its metabolite, SN-38 concentrations. Bi-directional transport and inhibition studies in Caco-2 cells indicated irinotecan to be a P-gp substrate and the function of intestinal P-gp was significantly inhibited in presence of verapamil. After oral irinotecan dosing, the mean area under the plasma concentration-time curve (AUC) was found to be 14.03+/-2.18 microgh/ml which was increased significantly, i.e. 61.71+/-15.0 microgh/ml when verapamil was co-administered (P<0.05). Similarly, the mean maximum plasma concentration of irinotecan increased from 2.93+/-0.37 microg/ml (without verapamil) to 10.75+/-1.0 microg/ml (with verapamil) (P<0.05). There was approximately 4-5-folds increase in apparent bioavailability. On the other hand, the intravenous irinotecan administration with verapamil resulted in small but statistically significant effect on AUC (10.76+/-2.0 to 23.3+/-3.8 microgh/ml; P<0.05) and systemic clearance (1206.4+/-159.7 to 713.5+/-78.2 ml/(hkg)). In addition, SN-38 showed significant change in oral pharmacokinetic parameters and minor changes in intravenous pharmacokinetic profile. Biliary excretion curves of both irinotecan and SN-38 were lowered by verapamil. The mean percent of irinotecan excreted into bile over 5h following intravenous and oral administration was found to be 8% and 1%, respectively, which was further reduced to half when treated with verapamil. These results are quite stimulating for further development of a clinically useful oral formulation of irinotecan based on P-gp inhibition. PMID:19135530

Bansal, Tripta; Mishra, Gautam; Jaggi, Manu; Khar, Roop K; Talegaonkar, Sushama

2009-03-01

329

P-glycoprotein ABCB1: a major player in drug handling by mammals.  

PubMed

Mammalian P-glycoproteins are active drug efflux transporters located in the plasma membrane. In the early nineties, we generated knockouts of the three P-glycoprotein genes of mice, the Mdr1a, Mdr1b, and Mdr2 P-glycoproteins, now known as Abcb1a, Abcb1b, and Abcb4, respectively. In the JCI papers that are the subject of this Hindsight, we showed that loss of Mdr1a (Abcb1a) had a profound effect on the tissue distribution and especially the brain accumulation of a range of drugs frequently used in humans, including dexamethasone, digoxin, cyclosporin A, ondansetron, domperidone, and loperamide. All drugs were shown to be excellent substrates of the murine ABCB1A P-glycoprotein and its human counterpart, the MDR1 P-glycoprotein, ABCB1. We found that the ability of ABCB1 to prevent accumulation of some drugs in the brain is a prerequisite for their clinical use, as absence of the transporter led to severe toxicity or undesired CNS pharmacodynamic effects. Subsequent work has fully confirmed the profound effect of the drug-transporting ABCB1 P-glycoprotein on the pharmacokinetics of drugs in humans. In fact, every new drug is now screened for transport by ABCB1, as this limits oral availability and penetration into sanctuaries protected by ABCB1, such as the brain. PMID:24084745

Borst, Piet; Schinkel, Alfred H

2013-10-01

330

The impact of P-gp functionality on non-steady state relationships between CSF and brain extracellular fluid.  

PubMed

In the development of central nervous system (CNS)-targeted drugs, the prediction of human CNS target exposure is a big challenge. Cerebrospinal fluid (CSF) concentrations have often been suggested as a 'good enough' surrogate for brain extracellular fluid (brainECF, brain target site) concentrations in humans. However, brain anatomy and physiology indicates prudence. We have applied a multiple microdialysis probe approach in rats, for continuous measurement and direct comparison of quinidine kinetics in brainECF, CSF, and plasma. The data obtained indicated important differences between brainECF and CSF kinetics, with brainECF kinetics being most sensitive to P-gp inhibition. To describe the data we developed a systems-based pharmacokinetic model. Our findings indicated that: (1) brainECF- and CSF-to-unbound plasma AUC0-360 ratios were all over 100 %; (2) P-gp also restricts brain intracellular exposure; (3) a direct transport route of quinidine from plasma to brain cells exists; (4) P-gp-mediated efflux of quinidine at the blood-brain barrier seems to result of combined efflux enhancement and influx hindrance; (5) P-gp at the blood-CSF barrier either functions as an efflux transporter or is not functioning at all. It is concluded that in parallel obtained data on unbound brainECF, CSF and plasma concentrations, under dynamic conditions, is a complex but most valid approach to reveal the mechanisms underlying the relationship between brainECF and CSF concentrations. This relationship is significantly influenced by activity of P-gp. Therefore, information on functionality of P-gp is required for the prediction of human brain target site concentrations of P-gp substrates on the basis of human CSF concentrations. PMID:23539188

Westerhout, Joost; Smeets, Jean; Danhof, Meindert; de Lange, Elizabeth C M

2013-06-01

331

In vivo to in vitro effects of six bioactive lignans of Wuzhi tablet (Schisandra sphenanthera extract) on the CYP3A/P-glycoprotein-mediated absorption and metabolism of tacrolimus.  

PubMed

We recently reported that Wuzhi tablet (WZ; Schisandra sphenanthera extract) can inhibit P-glycoprotein (P-gp)-mediated efflux and CYP3A-mediated metabolism of tacrolimus (FK506) and thus increase the blood concentrations of FK506. Major active lignans of WZ include schisandrin A, schisandrin B, schisandrin C, schisandrol A, schisandrol B, and schisantherin A. Whether and how these six lignans affect the pharmacokinetics of FK506 remains unclear. Therefore, this study aimed to investigate the effects of these lignans on the first-pass absorption and metabolism of FK506 and the involved mechanisms in vitro and in vivo. The results showed that whole-blood concentrations of FK506 were increased to different degrees following coadministration of the six lignans, respectively. Schisandrol B showed the strongest effect on the increase of the area under the concentration-time curve, the oral bioavailability, the gut processes affecting availability, and the hepatic availability of FK506. The reduction of intestinal first-pass effect contributed most to the increase in oral bioavailability of FK506 when coadministered with schisandrol B. In vitro transport experiment showed that schisandrin A, schisandrin B, and schisandrol B inhibited P-gp-mediated efflux of FK506. In vitro metabolism study showed that the inhibitory effect of these six lignans on FK506 metabolism was dose-dependent. In conclusion, the exposure of FK506 in rats was increased when coadministered with these lignans, and schisandrol B showed the strongest effect. Lignans of WZ inhibited P-gp-mediated efflux and CYP3A-mediated metabolism of FK506, and the reduction of intestinal first-pass affected by the lignans was the major cause of the increased FK506 oral bioavailability. PMID:24195812

Qin, Xiao Ling; Chen, Xiao; Wang, Ying; Xue, Xin Ping; Wang, Ying; Li, Jia Li; Wang, Xue Ding; Zhong, Guo Ping; Wang, Chang Xi; Yang, Hui; Huang, Min; Bi, Hui Chang

2014-01-01

332

Ursodeoxycholic acid inhibits overexpression of P-glycoprotein induced by doxorubicin in HepG2 cells.  

PubMed

The hepatoprotective action of ursodeoxycholic acid (UDCA) was previously suggested to be partially dependent on its antioxidative effect. Doxorubicin (DOX) and reactive oxygen species have also been implicated in the overexpression of P-glycoprotein (P-gp), which is encoded by the MDR1 gene and causes antitumor multidrug resistance. In the present study, we assessed the effects of UDCA on the expression of MDR1 mRNA, P-gp, and intracellular reactive oxygen species levels in DOX-treated HepG2 cells and compared them to those of other bile acids. DOX-induced increases in reactive oxygen species levels and the expression of MDR1 mRNA were inhibited by N-acetylcysteine, an antioxidant, and the DOX-induced increase in reactive oxygen species levels and DOX-induced overexpression of MDR1 mRNA and P-gp were inhibited by UDCA. Cells treated with UDCA showed improved rhodamine 123 uptake, which was decreased in cells treated with DOX alone. Moreover, cells exposed to DOX for 24h combined with UDCA accumulated more DOX than that of cells treated with DOX alone. Thus, UDCA may have inhibited the overexpression of P-gp by suppressing DOX-induced reactive oxygen species production. Chenodeoxycholic acid (CDCA) also exhibited these effects, whereas deoxycholic acid and litocholic acid were ineffective. In conclusion, UDCA and CDCA had an inhibitory effect on the induction of P-gp expression and reactive oxygen species by DOX in HepG2 cells. The administration of UDCA may be beneficial due to its ability to prevent the overexpression of reactive oxygen species and acquisition of multidrug resistance in hepatocellular carcinoma cells. PMID:24370495

Komori, Yuki; Arisawa, Sakiko; Takai, Miho; Yokoyama, Kunihiro; Honda, Minako; Hayashi, Kazuhiko; Ishigami, Masatoshi; Katano, Yoshiaki; Goto, Hidemi; Ueyama, Jun; Ishikawa, Tetsuya; Wakusawa, Shinya

2014-02-01

333

Increased Expression of P-Glycoprotein and Doxorubicin Chemoresistance of Metastatic Breast Cancer Is Regulated by miR-298  

PubMed Central

MicroRNAs (miRNAs) are short, noncoding RNA molecules that regulate the expression of a number of genes involved in cancer; therefore, they offer great diagnostic and therapeutic targets. We have developed doxorubicin-resistant and -sensitive metastatic human breast cancer cell lines (MDA-MB-231) to study the chemoresistant mechanisms regulated by miRNAs. We found that doxorubicin localized exclusively to the cytoplasm and was unable to reach the nuclei of resistant tumor cells because of the increased nuclear expression of MDR1/P-glycoprotein (P-gp). An miRNA array between doxorubicin-sensitive and -resistant breast cancer cells showed that reduced expression of miR-298 in doxorubicin-resistant human breast cancer cells was associated with increased expression of P-gp. In a transient transfection experiment, miR-298 directly bound to the MDR1 3? untranslated region and regulated the expression of firefly luciferase reporter in a dose-dependent manner. Overexpression of miR-298 down-regulated P-gp expression, increasing nuclear accumulation of doxorubicin and cytotoxicity in doxorubicin-resistant breast cancer cells. Furthermore, down-regulation of miR-298 increased P-gp expression and induced doxorubicin resistance in sensitive breast cancer cells. In summary, these results suggest that miR-298 directly modulates P-gp expression and is associated with the chemoresistant mechanisms of metastatic human breast cancer. Therefore, miR-298 has diagnostic and therapeutic potential for predicting doxorubicin chemoresistance in human breast cancer.

Bao, Lili; Hazari, Sidhartha; Mehra, Smriti; Kaushal, Deepak; Moroz, Krzysztof; Dash, Srikanta

2012-01-01

334

TRANSFECTED MDCK CELL LINE WITH ENHANCED EXPRESSION OF CYP3A4 AND P-GLYCOPROTEIN AS A MODEL TO STUDY THEIR ROLE IN DRUG TRANSPORT AND METABOLISM  

PubMed Central

The aim of this study was to characterize and utilize MDCK cell line expressing CYP3A4 and P-glycoprotein as an in vitro model for evaluating drug-herb and drug-drugs of abuse interactions. MDCK cell line simultaneously expressing P-gp and CYP3A4 (MMC) was developed and characterized by using expression and activity studies. Cellular transport study of 200 ?M cortisol was performed to determine their combined activity. The study was carried across MDCK-WT, MDCK-MDR1 and MMC cell lines. Similar studies were also carried out in the presence of 50 ?M naringin and 3 ?M morphine. Samples were analyzed by HPLC for drug and its CYP3A4 metabolite. PCR, qPCR and western blot studies confirmed the enhanced expression of the proteins in the transfected cells. The vivid CYP3A4 assay and ketoconazole inhibition studies further confirmed the presence of active protein. Apical to basal transport of cortisol was found to be ten and three fold lower in MMC as compared to WT and MDCKMDR1 respectively. Higher amount of metabolite was formed in MMC than in MDCK-WT indicating enhanced expression of CYP3A4. Highest cortisol metabolite formation was observed in MMC cell line due to the combined metabolic activities of CYP3A4 and P-gp. Transport of cortisol increased fivefold in presence of naringin in MMC and doubled in MDCKMDR1. Cortisol transport in MMC was significantly lower than that in WT in presence of naringin. The permeability increased three fold in presence of morphine which is a weaker inhibitor of CYP3A4. Formation of 6?-hydroxy cortisol was found to decrease in presence of morphine and naringin. This new model cell line with its enhanced CYP3A4 and P-gp levels in addition to short culture time can serve as an invaluable model to study drug-drug interactions. This cell line can also be used to study the combined contribution of efflux transporter and metabolizing enzymes towards drug-drug interactions.

Kwatra, Deep; Budda, Balasubramanyam; Vadlapudi, Aswani Dutt; Vadlapatla, Ramya Krishna; Pal, Dhananjay; Mitra, Ashim K.

2012-01-01

335

Dual-functionalized PAMAM dendrimers with improved P-glycoprotein inhibition and tight junction modulating effect.  

PubMed

This study aims to surface modify poly(amido amine) or PAMAM dendrimers by sequentially grafting poly(ethylene glycol) or PEG and 4-thiobutylamidine (TBA) so as to reduce PAMAM cytotoxicity while improving the ability of PAMAM to modulate P-glycoprotein (P-gp) efflux and tight junction integrity. Conjugation of functional groups was determined by NMR spectroscopy, FT-IR, thiol group quantification and molecular weight estimation. The yield of the dual-functionalized dendrimers was >80%. The dual-functionalized dendrimer could significantly reduce PAMAM cytotoxicity to <15% as reflected by LDH release in Caco-2 and MDCK/MDR1 cells after 72 h of exposure. Thiolated dendrimers could increase cellular accumulation and permeation of the P-gp substrate R-123, and such effect could be affected by the extent of PEGylation of the dendrimer. Surface-modified PAMAM dendrimers, either by single or dual functionalization, could better modulate tight junction integrity in comparison with unmodified PAMAM, as demonstrated through immunostaining of the tight junction marker ZO-1, permeation of the model compound Lucifer Yellow (LY) and transepithelial electrical resistance (TEER). Of importance, reversible tight junction modulating effect was only observed in the dual-functionalized dendrimers. Collectively, dual functionalization with PEG and TBA represented a promising approach in altering PAMAM dendrimer surface for potential application in oral drug delivery. PMID:24219381

Liu, Yuanjie; Chiu, Gigi N C

2013-12-01

336

Protective mechanisms of coenzyme-Q10 may involve up-regulation of testicular P-glycoprotein in doxorubicin-induced toxicity.  

PubMed

The anticancer drug; doxorubicin (DOX), causes testicular toxicity as an adverse effect. P-glycoprotein (P-gp) is a multidrug resistance efflux transporter expressed in blood-testis barrier, which extrudes DOX from the testis. We investigated whether DOX-induced gonadal injury could be prevented by the use of antioxidant; coenzyme-Q10 (CoQ10). The involvement of P-gp expression, as a possible protective mechanism, was also investigated. CoQ10 was administered orally for 8 days, and DOX toxicity was induced via a single i.p. dose of 15 mg/kg at day 4. Concomitant administration of CoQ10 with DOX significantly restored testicular oxidative stress parameters and the distorted histopathological picture, reduced the up-regulation of caspase 3 caused by DOX, and increased P-gp expression. We show for the first time that CoQ10 up-regulates P-gp as a novel mechanism for gonadal protection. In conclusion, CoQ10 protects against DOX-induced testicular toxicity in rats via ameliorating oxidative stress, reducing apoptosis and up-regulating testicular P-gp. PMID:24632013

El-Sheikh, Azza A K; Morsy, Mohamed A; Mahmoud, Marwa M; Rifaai, Rehab A

2014-03-01

337

P-glycoprotein silencing with siRNA delivered by DOPE-modified PEI overcomes doxorubicin resistance in breast cancer cells  

PubMed Central

Aims Multidrug resistance (MDR) mediated by overexpression of drug efflux transporters such as P-glycoprotein (P-gp), is a major problem, limiting successful chemotherapy of breast cancer. The use of siRNA to inhibit P-gp expression in MDR tumors is an attractive strategy to improve the effectiveness of anticancer drugs. Method We have synthesized a novel conjugate between a phospholipid (dioleoylphosphatidylethanolamine) and polyethylenimine (PEI) for siRNA delivery, for the purpose of silencing P-gp to overcome doxorubicin resistance in MCF-7 human breast cancer cells. Results The dioleoylphosphatidylethanolamine-PEI conjugate enhanced the transfection efficacy of low-molecular-weight PEI, which was otherwise totally ineffective. In addition, the polyethylene glycol/lipid coating of the new complexes gave rise to small micelle-like nanoparticles with improved biocompatibility properties. Both coated and noncoated formulations delivered P-gp-specific siRNA to MDR cells. Discussion The combination of doxorubicin and P-gp silencing formulations led to a twofold increase of doxorubicin uptake and a significant improvement of the therapeutic effect of doxorubicin in resistant cells.

Navarro, Gemma; Sawant, Rupa R; Biswas, Swati; Essex, Sean; Tros de Ilarduya, Conchita; Torchilin, Vladimir P

2012-01-01

338

Annotating Human P-Glycoprotein Bioassay Data  

PubMed Central

Abstract Huge amounts of small compound bioactivity data have been entering the public domain as a consequence of open innovation initiatives. It is now the time to carefully analyse existing bioassay data and give it a systematic structure. Our study aims to annotate prominent in vitro assays used for the determination of bioactivities of human P-glycoprotein inhibitors and substrates as they are represented in the ChEMBL and TP-search open source databases. Furthermore, the ability of data, determined in different assays, to be combined with each other is explored. As a result of this study, it is suggested that for inhibitors of human P-glycoprotein it is possible to combine data coming from the same assay type, if the cell lines used are also identical and the fluorescent or radiolabeled substrate have overlapping binding sites. In addition, it demonstrates that there is a need for larger chemical diverse datasets that have been measured in a panel of different assays. This would certainly alleviate the search for other inter-correlations between bioactivity data yielded by different assay setups.

Zdrazil, Barbara; Pinto, Marta; Vasanthanathan, Poongavanam; Williams, Antony J; Balderud, Linda Zander; Engkvist, Ola; Chichester, Christine; Hersey, Anne; Overington, John P; Ecker, Gerhard F

2012-01-01

339

Effect of Pregnancy on Cytochrome P450 3a and P-Glycoprotein Expression and Activity in the Mouse: Mechanisms, Tissue Specificity, and Time Course  

Microsoft Academic Search

The plasma concentrations of orally administered anti-human immunodeficiency virus protease inhibitors are significantly re- duced during human and mouse pregnancy. We have shown that in the mouse, at gestational day 19, this reduction is due to increased hepatic cytochrome P450 3a (Cyp3a) protein expres- sion and activity. In the current study, we investigated the mechanisms by which Cyp3a activity is

Huixia Zhang; Xiaohui Wu; Honggang Wang; Andrei M. Mikheev; Qingcheng Mao; Jashvant D. Unadkat

2008-01-01

340

Breast Cancer Resistance Protein and P-glycoprotein in Brain Cancer: Two Gatekeepers Team Up  

PubMed Central

Brain cancer is a devastating disease. Despite extensive research, treatment of brain tumors has been largely ineffective and the diagnosis of brain cancer remains uniformly fatal. Failure of brain cancer treatment may be in part due to limitations in drug delivery, influenced by the ABC drug efflux transporters P-gp and BCRP at the blood-brain and blood-tumor barriers, in brain tumor cells, as well as in brain tumor stem-like cells. P-gp and BCRP limit various anti-cancer drugs from entering the brain and tumor tissues, thus rendering chemotherapy ineffective. To overcome this obstacle, two strategies – targeting transporter regulation and direct transporter inhibition – have been proposed. In this review, we focus on these strategies. We first introduce the latest findings on signaling pathways that could potentially be targeted to down-regulate P-gp and BCRP expression and/or transport activity. We then highlight in detail the new paradigm of P-gp and BCRP working as a “cooperative team of gatekeepers” at the blood-brain barrier, discuss its ramifications for brain cancer therapy, and summarize the latest findings on dual P-gp/BCRP inhibitors. Finally, we provide a brief summary with conclusions and outline the perspectives for future research endeavors in this field.

Agarwal, Sagar; Hartz, Anika M.S.; Elmquist, William F.; Bauer, Bjorn

2012-01-01

341

Detection of glycomic alterations induced by overexpression of p-glycoprotein on the surfaces of L1210 cells using sialic acid binding lectins.  

PubMed

P-glycoprotein (P-gp) overexpression is the most frequently observed cause of multidrug resistance in neoplastic cells. In our experiments, P-gp was expressed in L1210 mice leukemia cells (S cells) by selection with vincristine (R cells) or transfection with the gene encoding human P-gp (T cells). Remodeling of cell surface sugars is associated with P-gp expression in L1210 cells as a secondary cellular response. In this study, we monitored the alteration of cell surface saccharides by Sambucus nigra agglutinin (SNA), wheat germ agglutinin (WGA) and Maackia amurensis agglutinin (MAA). Sialic acid is predominantly linked to the surface of S, R and T cells via ?-2,6 branched sugars that tightly bind SNA. The presence of sialic acid linked to the cell surface via ?-2,3 branched sugars was negligible, and the binding of MAA (recognizing this branch) was much less pronounced than SNA. WGA induced greater cell death than SNA, which was bound to the cell surface and agglutinated all three L1210 cell-variants more effectively than WGA. Thus, the ability of lectins to induce cell death did not correlate with their binding efficiency and agglutination potency. Compared to S cells, P-gp positive R and T cells contain a higher amount of N-acetyl-glucosamine on their cell surface, which is associated with improved WGA binding. Both P-gp positive variants of L1210 cells are strongly resistant to vincristine as P-gp prototypical drug. This resistance could not be altered by liberalization of terminal sialyl residues from the cell surface by sialidase. PMID:23203118

Bubencíkova, Tatiana; Cholujová, Dana; Messingerová, Lucia; Mislovicova, Danica; Seres, Mario; Breier, Albert; Sulova, Zdena

2012-01-01

342

A novel approach to overcome multidrug resistance: Utilization of P-gp mediated efflux of paclitaxel to attack neighboring vascular endothelial cells in tumors.  

PubMed

We tried to overcome the paclitaxel (PTX) resistance of cancer cells due to P-glycoprotein (P-gp) overexpression in the in vivo anti-tumor chemotherapy by utilizing polyethylene glycol-modified liposomal paclitaxel (PL-PTX). First of all, established were PTX-resistant Colon-26 cancer cells (C26/PTX) overexpressing P-gp, which provided IC50 value of PTX solution about 30 times larger than that obtained for control C26 (C26/control) in the in vitro MTT assay. Western blot analysis confirmed P-gp expression in C26/PTX 10 times higher than that in C26/control, indicating that the resistance acquisition of C26/PTX to PTX would be ascribed to the enhanced efflux of PTX by P-gp overexpressed in C26/PTX. However, the in vivo anti-tumor effect of PL-PTX in C26/PTX-bearing mice was similar to that in C26/control-bearing mice. Double immunohistochemical staining of vascular endothelial cells and apoptotic cells within tumor tissues demonstrated that the apoptotic cell death was preferentially observed in vascular endothelial cells in C26/PTX tumors after intravenous administration of PL-PTX, while that was in tumor cells in C26/control tumors. These results suggest that the in vivo anti-tumor effect of PL-PTX in C26/PTX-bearing mice would be ascribed to the cytotoxic action of PTX pumped out of tumor cells by overexpressed P-gp to vascular endothelial cells in tumor tissues. PMID:24956463

Yoshizawa, Yuta; Ogawara, Ken-Ichi; Kimura, Toshikiro; Higaki, Kazutaka

2014-10-01

343

Characterization of SAGE Mdr1a (P-gp), Bcrp, and Mrp2 knockout rats using loperamide, paclitaxel, sulfasalazine, and carboxydichlorofluorescein pharmacokinetics.  

PubMed

Transporter gene knockout rats are practically advantageous over murine models for pharmacokinetic and excretion studies, but their phenotypic characterization is lacking. At present, relevant aspects of pharmacokinetics, metabolism, distribution, and excretion of transporter probes [P-glycoprotein (P-gp): loperamide and paclitaxel; breast cancer resistance protein (Bcrp): sulfasalazine; and multidrug resistance-associated protein 2 (Mrp2): carboxydichlorofluorescein] were studied systematically across SAGE P-gp, Bcrp, and Mrp2 knockout rats. In Mdr1a knockout rats, loperamide and paclitaxel oral bioavailability was 2- and 4-fold increased, respectively, whereas clearance was significantly reduced (40-42%), consistent with the expected 10- to 20-fold reduction in paclitaxel excretion. N-Desmethyl-loperamide pharmacokinetics were not altered in any of the three knockouts after oral loperamide. In rats lacking P-gp, paclitaxel brain partitioning was significantly increased (4-fold). This finding is consistent with observations of loperamide central nervous system opioid pharmacology in Mdr1a knockout rats. Sulfasalazine oral bioavailability was markedly increased 21-fold in Bcrp knockouts and, as expected, was also 2- to 3-fold higher in P-gp and Mrp2 knockout rats. The sulfapyridine metabolite/parent ratio was decreased 10-fold in rats lacking Bcrp after oral, but not intravenous, sulfasalazine administration. Carboxydichlorofluorescein biliary excretion was obliterated in Mrp2 knockout rats, resulting in 25% decreased systemic clearance and 35% increased half-life. In contrast, carboxydichlorofluorescein renal clearance was not impaired in the absence of Mrp2, Bcrp, or P-gp. In conclusion, SAGE Mdr1a, Bcrp, and Mrp2 knockout rats generally demonstrated the expected phenotypes with respect to alterations in pharmacokinetics of relevant probe substrates; therefore, these knockout rats can be used as an alternative to murine models whenever a larger species is practically advantageous or more relevant to the drug discovery/development program. PMID:22711747

Zamek-Gliszczynski, Maciej J; Bedwell, David W; Bao, Jing Q; Higgins, J William

2012-09-01

344

Interaction between Red Yeast Rice and CYP450 Enzymes/P-Glycoprotein and Its Implication for the Clinical Pharmacokinetics of Lovastatin.  

PubMed

Red yeast rice (RYR) can reduce cholesterol through its active component, lovastatin. This study was to investigate the pharmacokinetic properties of lovastatin in RYR products and potential RYR-drug interactions. Extracts of three registered RYR products (LipoCol Forte, Cholestin, and Xuezhikang) were more effective than pure lovastatin in inhibiting the activities of cytochrome P450 enzymes and P-glycoprotein. Among CYP450 enzymes, RYR showed the highest inhibition on CYP1A2 and CYP2C19, with comparable inhibitory potencies to the corresponding typical inhibitors. In healthy volunteers taking the RYR product LipoCol Forte, the pharmacokinetic properties of lovastatin and lovastatin acid were linear in the dose range of 1 to 4 capsules taken as a single dose and no significant accumulation was observed after multiple dosing. Concomitant use of one LipoCol Forte capsule with nifedipine did not change the pharmacokinetics of nifedipine. Yet, concomitant use of gemfibrozil with LipoCol Forte resulted in a significant increase in the plasma concentration of lovastatin acid. These findings suggest that the use of RYR products may not have effects on the pharmacokinetics of concomitant comedications despite their effects to inhibit the activities of CYP450 enzymes and P-gp, whereas gemfibrozil affects the pharmacokinetics of lovastatin acid when used concomitantly with RYR products. PMID:23227093

Chen, Chia-Hao; Uang, Yow-Shieng; Wang, Shang-Ta; Yang, Jyh-Chin; Lin, Chun-Jung

2012-01-01

345

Interaction between Red Yeast Rice and CYP450 Enzymes/P-Glycoprotein and Its Implication for the Clinical Pharmacokinetics of Lovastatin  

PubMed Central

Red yeast rice (RYR) can reduce cholesterol through its active component, lovastatin. This study was to investigate the pharmacokinetic properties of lovastatin in RYR products and potential RYR-drug interactions. Extracts of three registered RYR products (LipoCol Forte, Cholestin, and Xuezhikang) were more effective than pure lovastatin in inhibiting the activities of cytochrome P450 enzymes and P-glycoprotein. Among CYP450 enzymes, RYR showed the highest inhibition on CYP1A2 and CYP2C19, with comparable inhibitory potencies to the corresponding typical inhibitors. In healthy volunteers taking the RYR product LipoCol Forte, the pharmacokinetic properties of lovastatin and lovastatin acid were linear in the dose range of 1 to 4 capsules taken as a single dose and no significant accumulation was observed after multiple dosing. Concomitant use of one LipoCol Forte capsule with nifedipine did not change the pharmacokinetics of nifedipine. Yet, concomitant use of gemfibrozil with LipoCol Forte resulted in a significant increase in the plasma concentration of lovastatin acid. These findings suggest that the use of RYR products may not have effects on the pharmacokinetics of concomitant comedications despite their effects to inhibit the activities of CYP450 enzymes and P-gp, whereas gemfibrozil affects the pharmacokinetics of lovastatin acid when used concomitantly with RYR products.

Chen, Chia-Hao; Uang, Yow-Shieng; Wang, Shang-Ta; Yang, Jyh-Chin; Lin, Chun-Jung

2012-01-01

346

HIF-1? Inhibition Reverses Multidrug Resistance in Colon Cancer Cells via Downregulation of MDR1/P-Glycoprotein  

PubMed Central

Background Multidrug resistance (MDR) is one of the major reasons chemotherapy-based treatments fail. Hypoxia is generally associated with tumor chemoresistance. However, the correlation between the heterodimeric hypoxia-inducible factor-1 (HIF-1) and the multidrug resistance (MDR1) gene/transporter P-glycoprotein (P-gp) remains unclear. This study aims to explore the molecular mechanisms of reversing colon cancer MDR by focusing on the target gene HIF-1?. Methods A chemotherapeutic sensitivity assay was used to observe the efficiency of MDR reversal in LoVo multicellular spheroids (MCS). The apoptotic level induced by different drugs was examined by flow cytometry (FCM). Binding of HIF-1? to the MDR1 gene promoter was evaluated by Chromatin immunoprecipitation (ChIP). The relationship between HIF-1?/P-gp expression and sensitivity to chemotherapy was analyzed. Results The sensitivity of LoVo MCS to all four chemotherapy drugs was decreased to varying degrees under hypoxic conditions. After silencing the HIF-1? gene, the sensitivities of LoVo MCS to all four chemotherapy drugs were restored. The apoptotic levels that all the drugs induced were all decreased to various extents in the hypoxic group. After silencing HIF-1?, the apoptosis level induced by all four chemotherapy drugs increased. The expression of HIF-1? and P-gp was significantly enhanced in LoVo MCS after treatment with hypoxia. Inhibiting HIF-1? significantly decreased the expression of MDR1/P-gp mRNA or protein in both the LoVo monolayers and LoVo MCS. The ChIP assay showed that HIF-1? was bound to the MDR1 gene promoter. Advanced colon carcinoma patients with expression of both HIF-1? and P-gp were more resistant to chemotherapy than that with non expression. Conclusions HIF-1? inhibition reverses multidrug resistance in colon cancer cells via downregulation of MDR1/P-gp. The expression of HIF-1? and MDR1/P-gp can be used as a predictive marker for chemotherapy resistance in colon cancer.

Peng, Yonghai; Pan, Feng; Li, Jianjun; Zou, Lan; Zhang, Yanling; Liang, Houjie

2014-01-01

347

Age-Related P-Glycoprotein Expression in the Intestine and Affecting the Pharmacokinetics of Orally Administered Enrofloxacin in Broilers  

PubMed Central

Bioavailability is the most important factor for the efficacy of any drug and it is determined by P- glycoprotein (P-gp) expression. Confirmation of P-gp expression during ontogeny is needed for understanding the differences in therapeutic efficacy of any drug in juvenile and adult animals. In this study, Abcb1 mRNA levels in the liver and intestine of broilers during ontogeny were analysed by RT qPCR. Cellular distribution of P-gp was detected by immunohistochemstry. Age-related differences of enrofloxacin pharmacokinetics were also studied. It was found that broilers aged 4 week-old expressed significantly (P<0.01) higher levels of P-gp mRNA in the liver, jejunum and ileum, than at other ages. However, there was no significant (P>0.05) age-related difference in the duodenum. Furthermore, the highest and lowest levels of Abcb1 mRNA expression were observed in the jejunum, and duodenum, respectively. P-gp immunoreactivity was detected on the apical surface of the enterocytes and in the bile canalicular membranes of the hepatocytes. Pharmacokinetic analysis revealed that the 8 week-old broilers, when orally administrated enrofloxacin, exhibited significantly higher Cmax (1.97 vs. 0.98 ?g•ml-1, P=0.009), AUC(14.54 vs. 9.35 ?g•ml-1•h, P=0.005) and Ka (1.38 vs. 0.43 h-1, P=0.032), as well as lower Tpeak (1.78 vs. 3.28 h, P=0.048) and T1/2ka (0.6 vs. 1.64 h, P=0.012) than the 4 week-old broilers. The bioavailability of enrofloxacin in 8 week-old broilers was increased by 15.9%, compared with that in 4 week-old birds. Interestingly, combining verapamil, a P-gp modulator, significantly improved pharmacokinetic behaviour of enrofloxacin in all birds. The results indicate juvenile broilers had a higher expression of P-gp in the intestine, affecting the pharmacokinetics and reducing the bioavailability of oral enrofloxacin in broilers. On the basis of our results, it is recommended that alternative dose regimes are necessary for different ages of broilers for effective therapy.

Sun, Yong; Zhang, Yu; Dong, Lingling; Dai, Xiaohua; Wang, Liping

2013-01-01

348

Enhanced brain disposition and effects of ?9-tetrahydrocannabinol in P-glycoprotein and breast cancer resistance protein knockout mice.  

PubMed

The ABC transporters P-glycoprotein (P-gp, Abcb1) and breast cancer resistance protein (Bcrp, Abcg2) regulate the CNS disposition of many drugs. The main psychoactive constituent of cannabis ?(9)-tetrahydrocannabinol (THC) has affinity for P-gp and Bcrp, however it is unknown whether these transporters modulate the brain accumulation of THC and its functional effects on the CNS. Here we aim to show that mice devoid of Abcb1 and Abcg2 retain higher brain THC levels and are more sensitive to cannabinoid-induced hypothermia than wild-type (WT) mice. Abcb1a/b (-/-), Abcg2 (-/-) and wild-type (WT) mice were injected with THC before brain and blood were collected and THC concentrations determined. Another cohort of mice was examined for THC-induced hypothermia by measuring rectal body temperature. Brain THC concentrations were higher in both Abcb1a/b (-/-) and Abcg2 (-/-) mice than WT mice. ABC transporter knockout mice exhibited delayed elimination of THC from the brain with the effect being more prominent in Abcg2 (-/-) mice. ABC transporter knockout mice were more sensitive to THC-induced hypothermia compared to WT mice. These results show P-gp and Bcrp prolong the brain disposition and hypothermic effects of THC and offer a novel mechanism for both genetic vulnerability to the psychoactive effects of cannabis and drug interactions between CNS therapies and cannabis. PMID:22536451

Spiro, Adena S; Wong, Alexander; Boucher, Aurélie A; Arnold, Jonathon C

2012-01-01

349

Effect of P-glycoprotein and breast cancer resistance protein inhibition on the pharmacokinetics of sunitinib in rats.  

PubMed

The aim of this study was to elucidate the roles of P-glycoprotein (P-gp/ABCB1) and breast cancer resistance protein (BCRP/ABCG2) in the plasma concentration, biliary excretion, and distribution to the liver, kidney, and brain of sunitinib. The pharmacokinetics of sunitinib was examined in rats treated with PSC833 (valspodar) and pantoprazole, potent inhibitors of P-gp and BCRP, respectively. The sunitinib concentrations in plasma, bile, liver, kidney, and brain were determined by liquid chromatography-tandem mass spectrometry. It was found that the area under the concentration-time curve for 4 hours (AUC0-4) and maximum concentration (Cmax) of sunitinib administered intraintestinally were significantly increased by pretreatment with PSC833 or pantoprazole. Each inhibitor markedly reduced the biliary excretion of sunitinib for 60 minutes after an intravenous administration and significantly increased the distribution of sunitinib to the liver as well as kidney. In addition, the brain distribution of sunitinib was significantly increased by PSC833 but not pantoprazole, and coadministration of both inhibitors further enhanced the accumulation of sunitinib in the brain. These results demonstrate that plasma concentrations of sunitinib and the biliary excretion and distribution to the kidney, liver, and brain of sunitinib are influenced by pharmacologic inhibition of P-gp and/or BCRP. PMID:23749551

Kunimatsu, Sachiko; Mizuno, Tomoyuki; Fukudo, Masahide; Katsura, Toshiya

2013-08-01

350

Validation and application of Caco-2 assays for the in vitro evaluation of development candidate drugs as substrates or inhibitors of P-glycoprotein to support regulatory submissions.  

PubMed

1. An understanding of the role that transporters, in particular P-glycoprotein (P-gp), can play in the absorption, distribution, metabolism and excretion (ADME) of candidate drugs, and an assessment of how these processes might impact on toxicity and the potential for drug-drug interactions in the clinic, is required to support drug development and registration. It is therefore necessary to validate preclinical assays for the in vitro evaluation of candidate drugs as substrates or inhibitors of human P-gp. 2. The present study has characterized a Caco-2 cell monolayer model by determining the bi-directional apparent permeabilities and efflux ratios of the known P-gp substrates ([(3)H]-digoxin, [(3)H]-ketoconazole, [(3)H]-verapamil, [(3)H]-quinidine, dipyridamole and loratidine; 1-100 microM) a non-substrate ([(3)H]-propranolol; 10 microM), or by determining the inhibitory potencies (IC(50)) of inhibitors (verapamil, ketoconazole, quinidine, dipyridamole and probenecid; 0.1-100 microM) on the basolateral-to-apical transport of [(3)H]-digoxin (5 microM), in order to validate methodologies for the identification of substrates or inhibitors of P-gp, respectively. 3. The reproducibility of the [(3)H]-digoxin or verapamil data determined from replicate monolayers across different cell passages indicates that the functional expression of P-gp is consistent across the range of passages (25-40) utilized for transport experiments and that the determination of bi-directional apparent permeability, or IC(50) for inhibition of P-gp, respectively, need only be performed on one occasion for a test compound. [(3)H]-digoxin and [(3)H]-propranolol or verapamil and probenecid were considered to be appropriate positive and negative controls of P-gp-mediated transport, or inhibition of P-gp, respectively, to ensure performance of the assays when assessing candidate drugs. Additionally, the low IC(50) values determined for ketoconazole and quinidine indicated that these inhibitors were suitable to use to confirm the role of P-gp in the efflux of a test compound. 4. These validated Caco-2 assays are robust, reproducible and suitable for routine in vitro evaluation of candidate drugs. They have been successfully applied to development projects resulting in the identification of two candidate drugs as substrates and inhibitors of P-gp, whereas a third was neither a substrate nor an inhibitor of this transporter. PMID:18668443

Elsby, R; Surry, D D; Smith, V N; Gray, A J

2008-07-01

351

Expression and significance of hypoxia-inducible factor-1 alpha and MDR1/P-glycoprotein in human colon carcinoma tissue and cells  

PubMed Central

Purpose Hypoxia in tumors is generally associated with chemoresistance and radioresistance. However, the correlation between the heterodimeric hypoxia-inducible factor-1 (HIF-1) and the multidrug resistance (MDR1) gene/transporter P-glycoprotein (P-gp) has not been clearly investigated. This study aims at examining the expression levels of HIF-1? and MDR1/P-gp in human colon carcinoma tissues and cell lines (HCT-116, HT-29, LoVo, and SW480) and ascertaining whether HIF-1? plays an important role in tumor multidrug resistance with MDR1/P-gp. Methods The expression and distribution of HIF-1? and P-gp proteins were detected in human colon carcinoma tissues and cell lines by immunohistochemistry and immunocytochemistry using streptavidin/peroxidase (SP) and double-label immunofluorescence methods. HIF-1? and MDR1 mRNA expression levels in cell lines were analyzed using RT-PCR under normoxic and hypoxic conditions, respectively. Results The immunohistochemical method shows that HIF-1? and P-gp expression were not correlated with gender, age, location, and differentiation degree (P > 0.05). However, the expression of HIF-1? and P-gp at different Dukes’ stages and whether involved in lymphatic invasion shows a significant difference (P < 0.05). Correlation analysis displays that HIF-1? protein expression was correlated significantly with P-gp expression (P < 0.01). Double-label immunofluorescence demonstrates that coexpression of HIF-1? and P-gp does exist in human colon carcinoma tissues. The mRNA expression of HIF-1? and MDR1 was detected in the four human colon carcinoma cell lines under both normoxia and hypoxia. Optical density values representing mRNA expression levels of HIF-1? and MDR1 were found to be significantly higher in the same type cells under hypoxic conditions than that under normoxic conditions, respectively (P < 0.01). However, no significant differences of HIF-1? or MDR1 mRNA expression were found among these cell lines, which exposed under the same PaO2 cultural conditions (P > 0.05). And the immunocytochemistry results were corresponding with the analysis of mRNA expression. Conclusions These results suggest that hypoxia induce the expression of HIF-1? and MDR1/P-gp in colon carcinoma and HIF-1? expression may be associated with the gene MDR1 (P-gp) and interactively involved in the occurrence of tumor multidrug resistance.

Ding, Zhenyu; Yang, Li; Xie, Xiaodong; Xie, Fangwei; Pan, Feng; Li, Jianjun; He, Jianming

2010-01-01

352

Pro-inflammatory human Th17 cells selectively express P-glycoprotein and are refractory to glucocorticoids  

PubMed Central

IL-17A–expressing CD4+ T cells (Th17 cells) are generally regarded as key effectors of autoimmune inflammation. However, not all Th17 cells are pro-inflammatory. Pathogenic Th17 cells that induce autoimmunity in mice are distinguished from nonpathogenic Th17 cells by a unique transcriptional signature, including high Il23r expression, and these cells require Il23r for their inflammatory function. In contrast, defining features of human pro-inflammatory Th17 cells are unknown. We show that pro-inflammatory human Th17 cells are restricted to a subset of CCR6+CXCR3hiCCR4loCCR10?CD161+ cells that transiently express c-Kit and stably express P-glycoprotein (P-gp)/multi-drug resistance type 1 (MDR1). In contrast to MDR1? Th1 or Th17 cells, MDR1+ Th17 cells produce both Th17 (IL-17A, IL-17F, and IL-22) and Th1 (IFN-?) cytokines upon TCR stimulation and do not express IL-10 or other anti-inflammatory molecules. These cells also display a transcriptional signature akin to pathogenic mouse Th17 cells and show heightened functional responses to IL-23 stimulation. In vivo, MDR1+ Th17 cells are enriched and activated in the gut of Crohn’s disease patients. Furthermore, MDR1+ Th17 cells are refractory to several glucocorticoids used to treat clinical autoimmune disease. Thus, MDR1+ Th17 cells may be important mediators of chronic inflammation, particularly in clinical settings of steroid resistant inflammatory disease.

Ramesh, Radha; Kozhaya, Lina; McKevitt, Kelly; Djuretic, Ivana M.; Carlson, Thaddeus J.; Quintero, Maria A.; McCauley, Jacob L.; Abreu, Maria T.; Unutmaz, Derya

2014-01-01

353

Pro-inflammatory human Th17 cells selectively express P-glycoprotein and are refractory to glucocorticoids.  

PubMed

IL-17A-expressing CD4(+) T cells (Th17 cells) are generally regarded as key effectors of autoimmune inflammation. However, not all Th17 cells are pro-inflammatory. Pathogenic Th17 cells that induce autoimmunity in mice are distinguished from nonpathogenic Th17 cells by a unique transcriptional signature, including high Il23r expression, and these cells require Il23r for their inflammatory function. In contrast, defining features of human pro-inflammatory Th17 cells are unknown. We show that pro-inflammatory human Th17 cells are restricted to a subset of CCR6(+)CXCR3(hi)CCR4(lo)CCR10(-)CD161(+) cells that transiently express c-Kit and stably express P-glycoprotein (P-gp)/multi-drug resistance type 1 (MDR1). In contrast to MDR1(-) Th1 or Th17 cells, MDR1(+) Th17 cells produce both Th17 (IL-17A, IL-17F, and IL-22) and Th1 (IFN-?) cytokines upon TCR stimulation and do not express IL-10 or other anti-inflammatory molecules. These cells also display a transcriptional signature akin to pathogenic mouse Th17 cells and show heightened functional responses to IL-23 stimulation. In vivo, MDR1(+) Th17 cells are enriched and activated in the gut of Crohn's disease patients. Furthermore, MDR1(+) Th17 cells are refractory to several glucocorticoids used to trea