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1

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

2

Vitamin E formulation affects digoxin absorption by inhibiting P-glycoprotein (P-GP) in humans  

Microsoft Academic Search

Water-soluble vitamin E(D-?-tocopheryl polyethylene glycol 1000 succinate (TPGS) may increase oral drug absorption. In vitro and animal data suggest that TPGS inhibits P-gp. It is unknown whether ?-tocopherol acetate(TA), the more common formulation of vitamin E, has similar drug interaction potential. This study aimed to determine whether TPGS and TA cause comparable P-gp inhibition in humans. Ten healthy subjects received

L. Chan; L. M. Humma; C. A. Schriever; L. A. Fahsingbauer; C. P. Dominguez; C. L. Baum

2004-01-01

3

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

4

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

Microsoft Academic Search

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

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

2012-01-01

5

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

PubMed

Abstract 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

2013-04-25

6

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

7

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

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. PMID:22633931

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

2012-05-23

8

Opioids and Efflux Transporters. 1. P-Glycoprotein Substrate Activity of N-Substituted Analogs of Meperidine.  

PubMed Central

P-Glycoprotein (P-gp) is an efflux transporter which is up-regulated at the blood brain barrier in both morphine and oxycodone tolerant rats. Numerous studies have shown that many clinically employed opioid analgesics are substrates for P-gp, suggesting that up-regulation of P-gp may contribute to the development of central tolerance to opioids. The studies herein focus on the development of SAR for P-gp substrate activity in the meperidine series of compounds, and show that a meperidine analog of greater potency, N-phenylbutyl-N-normeperidine, has low activity as a P-gp substrate and has the potential to be utilized as a tool to study the contribution of P-gp on the development of central tolerance to opioids.

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

2007-01-01

9

Effect of insecticides and inhibitors on P-glycoprotein ATPase (M-type) activity of resistant pest Helicoverpa armigera  

Microsoft Academic Search

P-glycoprotein (P-gp) was detected using C219 anti- bodies from the membrane preparation of the insecticide resistant pest, Helicoverpa armigera. This protein was partially purified and found to be a glycoprotein having ATPase activity. Its molecular mass as determined by SDS-PAGE was 150 kDa. Insecticides, viz. monocro- tophos, endosulfan, cypermethrin, fenvalerate and methyl parathion stimulated P-gp ATPase activity. Orthovana- date at

R. Srinivas; G. S. Shamsundar; S. K. Jayalakshmi; K. Sreeramulu

2005-01-01

10

P-glycoprotein inhibition increases the brain distribution and antidepressant-like activity of escitalopram in rodents.  

PubMed

Despite the clinical prevalence of the antidepressant escitalopram, over 30% of escitalopram-treated patients fail to respond to treatment. Recent gene association studies have highlighted a potential link between the drug efflux transporter P-glycoprotein (P-gp) and response to escitalopram. The present studies investigated pharmacokinetic and pharmacodynamic interactions between P-gp and escitalopram. In vitro bidirectional transport studies revealed that escitalopram is a transported substrate of human P-gp. Microdialysis-based pharmacokinetic studies demonstrated that administration of the P-gp inhibitor cyclosporin A resulted in increased brain levels of escitalopram without altering plasma escitalopram levels in the rat, thereby showing that P-gp restricts escitalopram transport across the blood-brain barrier (BBB) in vivo. The tail suspension test (TST) was carried out to elucidate the pharmacodynamic impact of P-gp inhibition on escitalopram effect in a mouse model of antidepressant activity. Pre-treatment with the P-gp inhibitor verapamil enhanced the response to escitalopram in the TST. Taken together, these data indicate that P-gp may restrict the BBB transport of escitalopram in humans, potentially resulting in subtherapeutic brain concentrations in certain patients. Moreover, by verifying that increasing escitalopram delivery to the brain by P-gp inhibition results in enhanced antidepressant-like activity, we suggest that adjunctive treatment with a P-gp inhibitor may represent a beneficial approach to augment escitalopram therapy in depression. PMID:23670590

O'Brien, Fionn E; O'Connor, Richard M; Clarke, Gerard; Dinan, Timothy G; Griffin, Brendan T; Cryan, John F

2013-05-14

11

Reversal of P-glycoprotein-mediated multidrug resistance in SGC7901\\/VCR cells by PPAR? activation by troglitazone  

Microsoft Academic Search

Summary  Over-expression of P-glycoprotein (P-gp), an ATP-dependent drug efflux pump, represents one of the major mechanisms that contribute\\u000a to multidrug resistance (MDR) in cancer cells. This study examined the effects of troglitazone, a ligand of peroxisome proliferator-activated\\u000a receptor gamma (PPAR?), on P-gp-mediated MDR in SGC7901\\/VCR cells (a vincristine-resistant human gastric cancer cell line).\\u000a The expression of P-gp was detected by RT-PCR

Qing Chen; Jie Zhou; Chunfang Jiang; Juan Chen

2010-01-01

12

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

13

Blonanserin, a novel atypical antipsychotic agent not actively transported as substrate by P-glycoprotein.  

PubMed

Although blonanserin, a novel atypical antipsychotic agent with dopamine D(2)/serotonin 5-HT(2A) antagonistic properties, displays good brain distribution, the mechanism of this distribution has not been clarified. P-glycoprotein [(P-gp) or multidrug resistance protein 1 (MDR1)] is an efflux transporter expressed in the brain and plays an important role in limiting drug entry into the central nervous system (CNS). In particular, P-gp can affect the pharmacokinetics and efficacy of antipsychotics, and exacerbate or soothe their adverse effects. In this study, we conducted in vitro and in vivo experiments to determine whether blonanserin is a P-gp substrate. Risperidone and its active metabolite 9-hydroxyrisperidone, both of which are P-gp substrates, were used as reference drugs. Affinity of blonanserin, risperidone, and 9-hydroxyrisperidone for P-gp was evaluated by in vitro transcellular transport across LLC-PK1, human MDR1 cDNA-transfected LLC-PK1 (LLC-MDR1), and mouse Mdr1a cDNA-transfected LLC-PK1 (LLC-Mdr1a). In addition, pharmacokinetic parameters in the brain and plasma (B/P ratio) of test compounds were measured in mdr1a/1b knockout (KO) and wild-type (WT) mice. The results of in vitro experiments revealed that P-gp does not actively transport blonanserin as a substrate in humans or mice. In addition, blonanserin displayed comparable B/P ratios in KO and WT mice, whereas B/P ratios of risperidone and 9-hydroxyrisperidone differed markedly in these animals. Our results indicate that blonanserin is not a P-gp substrate and therefore its brain distribution is unlikely to be affected by this transporter. PMID:22691713

Inoue, Tomoko; Osada, Kenichi; Tagawa, Masaaki; Ogawa, Yuriko; Haga, Toshiaki; Sogame, Yoshihisa; Hashizume, Takanori; Watanabe, Takashi; Taguchi, Atsushi; Katsumata, Takashi; Yabuki, Masashi; Yamaguchi, Noboru

2012-06-09

14

Relationship between structure and P-glycoprotein inhibitory activity of dimeric peptides related to the Dmt-Tic pharmacophore.  

PubMed

To develop novel inhibitors of P-glycoprotein (P-gp), dimeric peptides related to an opioid peptide containing the Dmt-Tic pharmacophore were synthesized and their P-gp inhibitory activities were analyzed. Of the 30 analogs synthesized, N(?),N(?)-[(CH(3))(2)Mle-Tic](2)Lys-NH(2) and its D-Lys analog were found to exhibit potent P-gp inhibitory activity, twice that of verapamil, in doxorubicin-resistant K562 cells. Structure-activity studies indicated that the correct hydrophobicity and spacer length between two aromatic rings are important structural elements in this series of analogs for inhibition of P-gp. PMID:22365753

Ambo, Akihiro; Ohkatsu, Hiromichi; Minamizawa, Motoko; Watanabe, Hideko; Sugawara, Shigeki; Nitta, Kazuo; Tsuda, Yuko; Okada, Yoshio; Sasaki, Yusuke

2012-02-04

15

Expression of P-glycoprotein in southeastern oysters, Crassostrea virginica  

Microsoft Academic Search

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,

C. J. Keppler; A. H. Ringwood

2001-01-01

16

TRAIL sensitize MDR cells to MDR-related drugs by down-regulation of P-glycoprotein through inhibition of DNA-PKcs\\/Akt\\/GSK-3? pathway and activation of caspases  

Microsoft Academic Search

BACKGROUND: The development of new modulator possessing high efficacy, low toxicity and high selectivity is a pivotal approach to overcome P-glycoprotein (P-gp) mediated multidrug resistance (MDR) in cancer treatment. In this study, we suggest a new molecular mechanism that TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) down-regulates P-glycoprotein (P-gp) through inhibition of DNA-PKcs\\/Akt\\/GSK-3? pathway and activation of caspases and thereby sensitize

Suk-Bin Seo; Jung-Gu Hur; Mi-Ju Kim; Jae-Won Lee; Hak-Bong Kim; Jae-Ho Bae; Dong-Wan Kim; Chi-Dug Kang; Sun-Hee Kim

2010-01-01

17

Structure-activity relationship of natural and synthetic coumarins inhibiting the multidrug transporter P-glycoprotein.  

PubMed

A set of 32 natural and synthetic coumarins were tested in order to evaluate their activity on human leukemic cells (K562/R7) overexpressing P-glycoprotein (P-gp). Their ability to reduce the P-gp-mediated drug efflux of daunorubicin out of cells was evaluated at 10 microM. Four natural compounds, previously isolated from Calophyllum dispar (Clusiaceae) and substituted by a common alpha-(hydroxyisopropyl)dihydrofuran moiety, exhibited a significant inhibitory effect on P-gp when compared to the positive control cyclosporin A. A 3D-quantitative structure-activity relationship (3D-QSAR) analysis of the coumarins was performed using the biological results obtained by comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) of P-gp. Results showed a favorable electrostatic and steric volume, like the alpha-(hydroxyisopropyl)dihydrofuran moiety, beside C(5)-C(6) or C(7)-C(8) positions. In addition, the analysis revealed an important hydrophobic, neutral charge group, like phenyl, in position C(4) on the coumarinic ring. PMID:16824763

Raad, Imad; Terreux, Raphael; Richomme, Pascal; Matera, Eva-Laure; Dumontet, Charles; Raynaud, Jean; Guilet, David

2006-07-07

18

First characterization of fish P-glycoprotein (abcb1) substrate specificity using determinations of its ATPase activity and calcein-AM assay with PLHC-1\\/dox cell line  

Microsoft Academic Search

P-glycoprotein (P-gp; abcb1) is one of the major ABC transport proteins that mediates multixenobiotic resistance (MXR) defense in fish. In order to offer a sound evaluation of its ecotoxicological relevance it is critical to characterize substrate specificity of fish P-gp. Measurement of the ATPase activity is a reliable approach often used to discern type of interaction of various drugs with

Roko Zaja; Jovica Lon?ar; Marta Popovic; Tvrtko Smital

2011-01-01

19

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

2011-08-10

20

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

21

Activation of ERM-family proteins via RhoA-ROCK signaling increases intestinal P-gp expression and leads to attenuation of oral morphine analgesia.  

PubMed

Previously, we reported that repeated oral treatment with etoposide (ETP) causes attenuation of oral morphine analgesia through upregulation of ileal P-glycoprotein (P-gp) mediated by Ras homolog gene family, member A (RhoA) activation. However, the detailed mechanism of the increase in ileal P-gp via RhoA activation remains unknown. Recently, it has been reported that ezrin-radixin-moesin (ERM) proteins, linking several plasma-membrane proteins to the actin cytoskeleton, are involved in the membrane localization and functional activity of P-gp. Moreover, the cross-linking activities of ERM are known to be regulated by RhoA and Rho-associated coiled-coil containing kinase (ROCK). Here, we examined the involvement of ERM in the changes in expression of P-gp via RhoA and ROCK in ileal membrane induced by ETP. Repeated oral treatment with ETP significantly increased the ileal membrane localization of ERM and phosphorylated ERM (p-ERM) in association with upregulation of P-gp and activation of RhoA and ROCK. Interestingly, coadministration of rosuvastatin (inhibitor of RhoA activation) and fasudil (ROCK inhibitor) prevented increments in the activation and phosphorylation of ERM, respectively. In conclusion, upregulation of ileal membrane localization of ERM and p-ERM via activation of RhoA/ROCK induced by ETP treatment may be involved in the regulation of ileal membrane localization of P-gp. PMID:23303573

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

2013-01-09

22

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

23

P-glycoprotein retains function when reconstituted into a sphingolipid- and cholesterol-rich environment  

Microsoft Academic Search

P-glycoprotein (P-gp) appears to be associated within specialized raftlike membrane microdomains. The activity of P-gp is sensitive to its lipid environment, and a functional association in raft microdomains will require that P-gp retains activity in the microenvironment. Purified ham- ster P-gp was reconstituted in liposomes comprising sphin- gomyelin and cholesterol, both highly enriched in mem- brane microdomains and known to

Szabolcs Modok; Catherine Heyward; Richard Callaghan

2004-01-01

24

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

PubMed

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 [(3)H]-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 (1)H-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. PMID:15351776

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

2004-09-06

25

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

2013-08-25

26

In vitro activity of uva-ursi against cytochrome P450 isoenzymes and P-glycoprotein.  

PubMed

Some natural health products (NHPs) affect drug metabolism enzymes and transport proteins, potentially affecting the safety and efficacy of the drug or other NHPs. This study was undertaken to characterize the effect of uva-ursi (Arctostaphylos uva-ursi) on cytochrome P450 isozyme (3A4, 3A5, 3A7, 2C19, and 19)-mediated metabolism and P-glycoprotein (P-gp) transport. Three bulk and 2 capsulated uva-ursi samples were obtained from commercial outlets. The capsules were batched, and herbal samples were ground to a common consistency. Aqueous and methanol extracts were freshly prepared. Cytochrome P450 isozyme-mediated metabolism was determined by using in vitro bioassays. P-gp transport function was determined by using a rhodamine 123 (Rh123) uptake test in human (THP-1) monocytes and human Caco-2 cells. All products were analyzed by HPLC for arbutin, gallic acid, myricitrin, and isoquercetin. A large variation was observed in the biomarkers found between the bulk and capsulated samples. Our data indicate that both the aqueous and methanol extracts of all 5 uva-ursi products showed high cytochrome P450 isozyme inhibition, with the exception of the methanol extracts against cytochromes P3A4 and P19, which had low to moderate activity. The aqueous extracts of uva-ursi showed an inhibitory effect on Rh123 efflux by P-gp at 1 h and an inductive effect at 18 h for both cell lines. Our results show that the uva-ursi herbal products tested here have pharmacological properties, including the potential capacity to affect drug safety and efficacy. Further studies are warranted against a wider range of cytochrome P450 isozymes and to determine whether these effects are clinically significant. PMID:18066112

Chauhan, B; Yu, C; Krantis, A; Scott, I; Arnason, J T; Marles, R J; Foster, B C

2007-11-01

27

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

2012-10-15

28

Modulation of the Cellular Accumulation and Intracellular Activity of Daptomycin towards Phagocytized Staphylococcus aureus by the P-Glycoprotein (MDR1) Efflux Transporter in Human THP1 Macrophages and Madin-Darby Canine Kidney Cells  

Microsoft Academic Search

P-glycoprotein (P-gp; MDR1), a major efflux transporter, recognizes various antibiotics and is present in macrophages. We have examined its effect on the modulation of the intracellular accumulation and activity of daptomycin towards phagocytized Staphylococcus aureus (ATCC 25923) in human THP-1 macrophages, in comparison with MDCK epithelial cells (wild type and MDCK-MDR1 overexpressing P-gp; the bulk of the protein was immunodetected

Sandrine Lemaire; Francoise Van Bambeke; Marie-Paule Mingeot-Leclercq; Paul M. Tulkens

2007-01-01

29

Effect of TSHAC on human cytochrome P450 activity, and transport mediated by P-glycoprotein.  

PubMed

TSAHC [4'-(p-toluenesulfonylamido)-4-hydroxychalcone] is a promising antitumorigenic chalcone compound, especially against TM4SF5 (four-transmembrane L6 family member 5)-mediated hepatocarcinoma. We evaluated the potential of TSAHC to inhibit the catalytic activities of nine cytochrome P450 isoforms and of P-glycoprotein (Pgp). The abilities of TSAHC to inhibit phenacetin Odeethylation (CYP1A2), coumarin 6-hydroxylation (CYP2A6), bupropion hydroxylation (CYP2B6), amodiaquine Ndeethylation (CYP2C8), diclofenac 4-hydroxylation (CYP2C9), omeprazole 5-hydroxylation (CYP2C19), dextromethorphan O-demethylation (CYP2D6), chlorzoxazone 6-hydroxylation (CYP2E1), and midazolam 1'-hydroxylation (CYP3A) were tested using human liver microsomes. The P-gp inhibitory effect of TSAHC was assessed by [3H]digoxin accumulation in the LLCPK1-MDR1 cell system. TSAHC strongly inhibited CYP2C8, CYP2C9, and CYP2C19 isoform activities with Ki values of 0.81, 0.076, and 3.45 microM, respectively. It also enhanced digoxin accumulation in a dose-dependent manner in the LLCPK1-MDR1 cells. These findings indicate that TSAHC has the potential to inhibit CYP2C isoforms and P-gp activities in vitro. TSAHC might be used as a nonspecific inhibitor of CYP2C isoforms based on its negligible inhibitory effect on other P450 isoforms such as CYP1A2, CYP2A6, CYP2B6, CYP2D6, CYP2E1, and CYP3A. PMID:23221528

Im, Yelim; Kim, Yang-Weon; Song, Im-Sook; Joo, Jeongmin; Shin, Jung-Hoon; Wu, Zhexue; Lee, Hye Suk; Park, Ki Hun; Liu, Kwang-Hyeon

2012-12-01

30

In Silico Quantitative StructureActivity Relationship Studies on P-gp Modulators of Tetrahydroisoquinoline-Ethyl-Phenylamine Series  

Microsoft Academic Search

BACKGROUND: Multidrug resistance (MDR) is a major obstacle in cancer chemotherapy. The drug efflux by a transport protein is the main reason for MDR. In humans, MDR mainly occurs when the ATP-binding cassette (ABC) family of proteins is overexpressed simultaneously. P-glycoprotein (P-gp) is most commonly associated with human MDR; it utilizes energy from adenosine triphosphate (ATP) to transport a number

Changdev G Gadhe; Thirumurthy Madhavan; Gugan Kothandan; Seung Joo Cho

2011-01-01

31

Concentration dependency of modulatory effect of amlodipine on P-glycoprotein efflux activity of doxorubicin--a comparison with tamoxifen.  

PubMed

Modulators of P-glycoprotein (P-gp) can enhance or limit the permeability of a number of therapeutic agents that are considered substrates of this efflux pump protein. The modulatory effect of amlodipine (4-dihydropyridine calcium antagonist) on P-gp efflux activity has not been fully elucidated. We have studied the concentration dependency of its modulatory effect and compared it qualitatively with tamoxifen (a non-esteroid anti-estrogen). The investigation was conducted on transmembrane efflux of doxorubicin at a fixed concentration of 5 microM across a Caco-2 monolayer in the presence of various concentrations of amlodipine or tamoxifen. The maximum flux of doxorubicin from basolateral to apical (ba) occurred at 4.5 microM amlodipine and at 0.02 microM tamoxifen. At higher concentrations, the apical to basolateral (ab) flux and the net flux of doxorubicin (ba - ab) declined steadily in a concentration-dependent manner. We analysed the observed net flux data by fitting different mathematical models to the data. A composite sigmoidal Emax/Imax (stimulatory/inhibitory) model was found to be the most appropriate to define the system. The observed and calculated parameters supported the modulatory role of both compounds and clearly indicated that the stimulation and inhibition of transmembrane efflux occurred simultaneously in the presence of amlodipine or tamoxifen. It was concluded that amlodipine, similar to tamoxifen, modulated the transporter-dependent transmembrane flux of the P-gp substrate in a concentration-dependent manner. PMID:15285842

Darvari, Ramin; Boroujerdi, Mehdi

2004-08-01

32

1-Cyclohexyl-4-(4-arylcyclohexyl)piperazines: Mixed ? and human ?(8)-?(7) sterol isomerase ligands with antiproliferative and P-glycoprotein inhibitory activity.  

PubMed

Many new chemotherapeutic agents are under preclinical investigation and, despite efforts to more selectively target cancer cells, limitations such as toxicity and inherent resistance are often encountered. Therefore, alternative strategies are needed to treat cancer and overcome such limitations. We describe novel cyclohexylpiperazine derivatives, designed as mixed affinity ligands for sigma (?) receptors and human ??-?? sterol isomerase (HSI) ligands, which also exhibit P-glycoprotein (P-gp) inhibitory activity, with the aim of exploiting the antiproliferative effects mediated by ? and HSI sites while overcoming P-gp-mediated resistance. All of the compounds displayed high affinities for ? receptors and HSI sites, P-gp inhibitory activity, and ?? receptor agonist antiproliferative activity. Antiproliferative activity was also tested in PC-3 cells to establish ?? and HSI contribution. Compound cis-11, which displayed the best antiproliferative and P-gp inhibitory activities, was co-administered with 0.1??M doxorubicin in MDCK-MDR1 cells. Compound cis-11 caused 70?% and 90?% cell death when co-administered at 30??M and 50??m, respectively. When administered alone, cis-11 resulted in 50?% cell death, demonstrating its single agent antitumor properties in a tumor cell line overexpressing P-gp. PMID:21069657

Abate, Carmen; Niso, Mauro; Contino, Marialessandra; Colabufo, Nicola Antonio; Ferorelli, Savina; Perrone, Roberto; Berardi, Francesco

2011-01-01

33

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

PubMed

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. PMID:19794400

Zhong, Yu; Hennig, Bernhard; Toborek, Michal

2009-09-30

34

Study of expression and functional activity of P-GP membrane glycoprotein in children with acute leukemia.  

PubMed

We studied expression and functional activity of tumor cell P-gp in children with various leukemia variants and analyzed its prognostic role in acute lymphoblastic leukemia. Functional activity of P-gp increased in acute myeloid leukemia, relapses of acute lymphoblastic leukemia (in comparison with primary disease), and in a group of patients in whom no remission was attained. The survival of patients with acute lymphoblastic leukemia was lower in cases with increased expression and function of P-gp. PMID:17364061

Shman, T V; Savitskii, V P; Potapnev, M P; Aleinikova, O V

2006-06-01

35

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

36

Prediction of Promiscuous P-Glycoprotein Inhibition Using a Novel Machine Learning Scheme  

Microsoft Academic Search

BackgroundP-glycoprotein (P-gp) is an ATP-dependent membrane transporter that plays a pivotal role in eliminating xenobiotics by active extrusion of xenobiotics from the cell. Multidrug resistance (MDR) is highly associated with the over-expression of P-gp by cells, resulting in increased efflux of chemotherapeutical agents and reduction of intracellular drug accumulation. It is of clinical importance to develop a P-gp inhibition predictive

Max K. Leong; Hong-Bin Chen; Yu-Hsuan Shih

2012-01-01

37

Prediction of P-Glycoprotein Substrates by a Support Vector Machine Approach  

Microsoft Academic Search

P-glycoproteins (P-gp) actively transport a wide variety of chemicals out of cells and function as drug efflux pumps that mediate multidrug resistance and limit the efficacy of many drugs. Methods for facilitating early elimination of potential P-gp substrates are useful for facilitating new drug discovery. A computational ensemble pharmacophore model has recently been used for the prediction of P-gp substrates

Ying Xue; Chun Wei Yap; Li Zhi Sun; Zhi Wei Cao; J. F. Wang; Yu Zong Chen

2004-01-01

38

Inhibition of P-glycoprotein activity by limonin and other secondary metabolites from Citrus species in human colon and leukaemia cell lines.  

PubMed

P-glycoprotein (P-gp), a membrane transporter encoded by the MDR1 gene in human cells, mediates drug efflux from cells and plays a major role in causing multidrug resistance; which is one of the most accepted mechanisms for failure of chemotherapy in cancer treatment. In this study, we investigated the effects of nine naturally occurring compounds isolated from Citrus jambhiri Lush and Citrus pyriformis Hassk (Rutaceae) for their potential to modulate the activity of P-gp in the multidrug-resistant human leukaemia cell line CEM/ADR5000. Limonin, deacetylnomilin, hesperidin, neohesperidin, stigmasterol and ss-sitosterol-O-glucoside inhibited the efflux of the P-gp substrate rhodamine 123 in a concentration-dependent manner. Some of these compounds were more active than verapamil, which was used as a positive control. Treatment of drug-resistant Caco-2 cells with the most active C. jambhiri and C. pyriformis compounds increased their sensitivity to doxorubicin and completely reversed doxorubicin resistance, which agrees with a decreased P-gp activity. Limonin was the most potent P-glycoprotein inhibitor - when it was applied at a non-toxic concentration of 20 microM, it significantly enhanced doxorubicin cytotoxicity 2.98-fold (P<0.001) and 2.2-fold (P<0.001) in Caco2 and CEM/ADR5000 cells, respectively. These isolated Citrus compounds could be considered as good candidates for the development of novel P-gp/MDR1 reversal agents which may enhance the accumulation and efficacy of chemotherapy agents. PMID:19782062

El-Readi, Mahmoud Zaki; Hamdan, Dalia; Farrag, Nawal; El-Shazly, Assem; Wink, Michael

2009-09-24

39

Anthelmintics Are Substrates and Activators of Nematode P Glycoprotein?  

PubMed Central

P glycoproteins (Pgp), members of the ABC transporter superfamily, play a major role in chemoresistance. In nematodes, Pgp are responsible for resistance to anthelmintics, suggesting that they are Pgp substrates, as they are in mammalian cells. However, their binding to nematode Pgp and the functional consequences of this interaction have not been investigated. Our study showed that levamisole and most of the macrocyclic lactones (MLs) are Pgp substrates in nematodes. Ivermectin, although a very good substrate in mammalian cells, is poorly transported. In contrast to their inhibitory effect on mammalian Pgp, these drugs had a stimulatory effect on the transport activity of the reference Pgp substrate rhodamine 123 (R123) in the nematode. This may be due to a specific sequence of nematode Pgp, which shares only 44% identity with mammalian Pgp. Other factors, such as the affinity of anthelmintics for Pgp and their concentration in the Pgp microenvironment, could also differ in nematodes, as suggested by the specific relationship observed between the octanol-water partition coefficient (log P) of MLs and R123 efflux. Nevertheless, some similarities were also observed in the functional activities of the mammalian and nematode Pgp. As in mammalian cells, substrates known to bind the H site (Hoechst 33342 and colchicine) activated the R site, resulting in an increased R123 efflux. Our findings thus show that ML anthelmintics, which inhibit Pgp-mediated efflux in mammals, activate transport activity in nematodes and suggest that several substituents in the ML structure are involved in modulating the stimulatory effect.

Kerboeuf, Dominique; Guegnard, Fabrice

2011-01-01

40

Functional role of P-glycoprotein in limiting intestinal absorption of drugs: contribution of passive permeability to P-glycoprotein mediated efflux transport.  

PubMed

The aim of the present study is to evaluate the quantitative contribution of passive permeability to P-glycoprotein-mediated (P-gp-mediated) efflux and the functional activity of P-gp in determining intestinal absorption of drugs, and demonstrate the relationship between efflux parameters and intestinal permeability. MDRI-MDCKII cell monolayer permeability, human intestinal absorption (HIA), and solubility data were systematically collected from the literature. Drugs were classified as a total of 63 P-gp substrates (P-gpS) and 73 nonsubstrates (NS) on the basis of efflux ratio or calcein AM inhibition and ATPase activity assays. Efflux parameters, efflux ratio (ER) and absorption quotient (AQ), were correlated to the monolayer permeability. MDRI-MDCKII cell monolayer permeability characteristics were found to be distinctly different between P-gpS and NS datasets. The ER for P-gpS was found to increase with absorptive permeability until 20 nm.s(-1), but reduced for P-gpS with high absorptive permeability. The AQ showed a linear inverse relationship with absorptive permeability. Overall, efflux parameters, ER and AQ, indicated that the transport of P-gpS with moderate passive permeability is highly attenuated by P-gp, while passive permeability overrules the P-gp-mediated efflux for high-permeability molecules. Most of the P-gpS were found towards the upper limits of molecular weight (>500) and calculated total polar surface area (>75 A(2)). This dataset indicated that unfavorable chemical features of P-gpS limit passive permeability and thus are more susceptible to P-gp-mediated efflux. In conclusion, passive permeability versus P-gp-mediated efflux determines intestinal permeability of P-gpS, where P-gp limits absorption of only moderately permeable compounds. Thus, integrating these factors with drug characteristics of the Biopharmaceutics Classification System (BCS) class better predicts the functional role of P-gp in limiting intestinal drug absorption. PMID:15804173

Varma, Manthena V S; Sateesh, Khandavilli; Panchagnula, Ramesh

41

Blood-brain barrier (BBB) pharmacoproteomics: reconstruction of in vivo brain distribution of 11 P-glycoprotein substrates based on the BBB transporter protein concentration, in vitro intrinsic transport activity, and unbound fraction in plasma and brain in mice.  

PubMed

The purpose of this study was to examine whether in vivo drug distribution to the brain can be reconstructed by integrating P-glycoprotein (P-gp)/mdr1a expression levels, P-gp in vitro activity, and drug unbound fractions in mouse plasma and brain. For 11 P-gp substrates, in vitro P-gp transport activities were determined by measuring transcellular transport across monolayers of mouse P-gp-transfected LLC-PK1 (L-mdr1a) and parental cells. P-gp expression amounts were determined by quantitative targeted absolute proteomics. Unbound drug fractions in plasma and brain were obtained from the literature and by measuring brain slice uptake, respectively. Brain-to-plasma concentration ratios (K(p brain)) and its ratios between wild-type and mdr1a/1b(-/-) mice (K(p brain) ratio) were obtained from the literature or determined by intravenous constant infusion. Unbound brain-to-plasma concentration ratios (K(p,uu,brain)) were estimated from K(p brain) and unbound fractions. Based on pharmacokinetic theory, K(p brain) ratios were reconstructed from in vitro P-gp transport activities and P-gp expression amounts in L-mdr1a cells and mouse brain capillaries. All reconstructed K(p brain) ratios were within a 1.6-fold range of observed values. K(p brain) then was reconstructed from the reconstructed K(p brain) ratios and unbound fractions. K(p,uu,brain) was reconstructed as the reciprocal of the reconstructed K(p brain) ratios. For quinidine, loperamide, risperidone, indinavir, dexamethasone, paclitaxel, verapamil, loratadine, and diazepam, the reconstructed K(p brain) and K(p,uu,brain) agreed with observed and estimated in vivo values within a 3-fold range, respectively. Thus, brain distributions of P-gp substrates can be reconstructed from P-gp expression levels, in vitro activity, and drug unbound fractions. PMID:21828264

Uchida, Yasuo; Ohtsuki, Sumio; Kamiie, Junichi; Terasaki, Tetsuya

2011-08-09

42

Effects of monoglycerides on P-glycoprotein: modulation of the activity and expression in Caco-2 cell monolayers.  

PubMed

The purpose of this study was to analyze the effects of two common monoglyceride components of lipid excipients, 1-monoolein and 1-monostearin, on the activity and expression of P-glycoprotein (P-gp) in Caco-2 cells. Non-cytotoxic concentrations of 1-monoolein and 1-monostearin were determined by assessing membrane permeability and mitochondrial activity in Caco-2 cells, a human colon adenocarcinoma cell line. Concentrations of 500 and 100 microM were used to evaluate P-gp activity through Rh123 accumulation and bifunctional transport studies. The P-gp protein expression levels were quantified through the use of immunoblots. The changes in cell membrane fluidity and nuclear membrane integrity upon the addition of monoglycerides were analyzed by fluorescence anisotropy using DPH and TMA-DPH as the fluorescent labels and by using increasing salt concentrations to release the nuclear contents, respectively. The absorptive flux (apical to basolateral) in the bifunctional transport studies was not found to be statistically significant for the non-cytotoxic concentrations of 1-monoolein and 1-monostearin. However, treatments of 500 and 100 microM of 1-monoolein or 1-monostearin displayed statistically lowered efflux (basolaterial to apical, P < 0.05) compared to the controls (7.9 +/- 0.8, 12.9 +/- 2.6 x 10 (6) cm/s for 1-monoolein or 11.1 +/- 2.0, 11.4 +/- 2.3 x 10 (6) cm/s for 1-monostearin, respectively, compared to the untreated control, 21.1 +/- 2.9 x 10 (6) cm/s, n = 5). Rh123 accumulation was also found to be enhanced upon 24 h incubation with both concentrations of the monoglycerides; however, only concentrations of 500 muM of the monoglycerides were shown to significantly reduce the P-gp protein expression. The results from this study suggest that these two monoglycerides, common components in various lipid excipients, are inhibitors of P-gp. PMID:18651749

Barta, Cheri A; Sachs-Barrable, Kristina; Feng, Florina; Wasan, Kishor M

2008-07-24

43

Compounds and methods to increase anti-P-glycoprotein activity of baicalein by alkylation on the A ring  

US Patent & Trademark Office Database

The present invention is directed to analogs of baicalein according to formula (I): where R.sup.5 is H, (C.sub.1-C.sub.12)alkyl, (C.sub.2-C.sub.13)acyl, or an optionally substituted phenyl or benzyl group, an acyl group, a C.sub.1-C.sub.20 alkyl or ether group, a phosphate, diphosphate, triphosphate or phosphodiester group; R.sup.6 and R.sup.7 are each independently H, (C.sub.1-C.sub.12)alkyl, (C.sub.2-C.sub.13)acyl, or an optionally substituted phenyl or benzyl or together form a --OCR.sup.1R.sup.2O-- group wherein each of R.sup.1 and R.sup.2 is independently H, a C.sub.1-C.sub.3 alkyl group or an optionally substituted phenyl or benzyl group; and R.sup.8 is H, OH, an O-acyl group, a C.sub.1,-C.sub.4 alkyl or alkoxy group, F, Cl, Br or I, or a pharmaceutically acceptable salt thereof, which exhibit anti-P-glycoprotein activity and methods of enhancing the bioavailability of active compounds, especially orally administered compounds, by inhibition of P-glycoprotein 170 (P-gp 170) and/or CYP450 enzyme, especially CYP450 3A4 enzyme. Pharmaceutical compositions based upon these novel derivatives according to the present invention are also described herein.

2011-01-25

44

Influence of Panax ginseng on Cytochrome P450 (CYP)3A and P-glycoprotein (Pgp) Activity in Healthy Subjects  

PubMed Central

A number of herbal preparations have been shown to interact with prescription medications secondary to modulation of cytochrome P450 (CYP) and/or P-glycoprotein (P-gp). The purpose of this study was to determine the influence of Panax ginseng on CYP3A and P-gp function using the probe substrates midazolam and fexofenadine, respectively. Twelve healthy subjects (8 males) completed this open label, single sequence pharmacokinetic study. Healthy volunteers received single oral doses of midazolam 8 mg and fexofenadine 120 mg, before and after 28 days of P. ginseng 500 mg twice daily. Midazolam and fexofenadine pharmacokinetic parameter values were calculated and compared pre-and post P. ginseng administration. Geometric mean ratios (post-ginseng/pre-ginseng) for midazolam area under the concentration vs. time curve from zero to infinity (AUC0-?), half life (T1/2), and maximum concentration (Cmax) were significantly reduced at 0.66 (0.55 – 0.78), 0.71 (0.53 – 0.90), and 0.74 (0.56 – 0.93), respectively. Conversely, fexofenadine pharmacokinetics were unaltered by P. ginseng administration. Based on these results, Panax ginseng appeared to induce CYP3A activity in the liver and possibly the gastrointestinal tract. Patients taking Panax ginseng in combination with CYP3A substrates with narrow therapeutic ranges should be monitored closely for adequate therapeutic response to the substrate medication.

Malati, Christine Y.; Robertson, Sarah M.; Hunt, Jennifer D.; Chairez, Cheryl; Alfaro, Raul M.; Kovacs, Joseph A.; Penzak, Scott R.

2012-01-01

45

The co-expression of p53 protein and P-glycoprotein is correlated to a poor prognosis in osteosarcoma  

Microsoft Academic Search

Multidrug resistance (MDR), mediated by P-glycoprotein (P-gp), is an in vitro phenomenon observed within tumour cells, suggesting cross-resistance to unrelated drugs, and expression of P-gp may therefore affect the prognosis and incidence of recurrence after treatment. The mutant p53 protein causes reduced tumour suppression. Co-expression of p53 and P-gp is related to short survival, increased tumour activity and drug resistance.

Y. B. Park; H. S. Kim; J. H. Oh; S. H. Lee

2001-01-01

46

The importance of P-glycoprotein multidrug transporter activity measurement in patients with Helicobacter pylori infection.  

PubMed

P-glycoprotein is important in local antibiotic resistance. Aim was to evaluate the role of P-glycoprotein in local antibiotic resistance in patients with antral gastritis during antibiotic therapy to Helicobacter pylori infection. In the group of 53 patients with pathohistologically verified gastritis and microbiologically confirmed H. pylori infection (no signs of antimicrobial resistance) we have determined P-glycoprotein activity in gastric mucosa biopsy specimens, and compared them with the P-glycoprotein activity in 12 control subjects with normal endoscopic findings. The H. pylori positive patients were treated according to Maastricht protocol with short-term 7-day therapy consisting of two antibiotics (amoxicillin and azithromycin/metronidazole and clarithromycin) and a proton pump inhibitor P-glycoprotein activity was determined in rhodamine dye efflux test and quantified by ratio of the mean fluorescence (RMF) in flow cytometry analysis. H. pylori was successfully eradicated in the first cycle in 20 patients, whereas therapy was continued in 33 patients. The mean pre-treatment RMF values were higher in patients with H. pylori infection then in control subjects (p < 0.0046). RMF was also higher in patients with multiple therapeutic failure than in those with successful H. pylori eradication (p < 0.0001). RMF increased significantly during the antibiotic therapy (p < 0.05). P-glycoprotein might be one of the causes of therapy failure in patients with H. pylori. Our study confirms the importance of quantitative evaluation of P-glycoprotein expression during antibiotic treatment response. PMID:20102060

Babi?, Zarko; Kucisec-Tepes, Nastja; Troskot, Rosana; Dorosuli?, Zdravko; Svoboda-Beusan, Ivna

2009-12-01

47

1?,25-Dihydroxyvitamin D3-liganded vitamin D receptor increases expression and transport activity of P-glycoprotein in isolated rat brain capillaries and human and rat brain microvessel endothelial cells.  

PubMed

Induction of the multidrug resistance protein 1 (MDR1)/P-glycoprotein (P-gp) by the vitamin D receptor (VDR) was investigated in isolated rat brain capillaries and rat (RBE4) and human (hCMEC/D3) brain microvessel endothelial cell lines. Incubation of isolated rat brain capillaries with 10 nM of the VDR ligand, 1?,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] for 4 h increased P-gp protein expression fourfold. Incubation with 1,25(OH)(2)D(3) for 4 or 24 h increased P-gp transport activity (specific luminal accumulation of NBD-CSA, the fluorescent P-gp substrate) by 25-30%. In RBE4 cells, Mdr1b mRNA was induced in a concentration-dependent manner by exposure to 1,25(OH)(2)D(3). Concomitantly, P-gp protein expression increased 2.5-fold and was accompanied by a 20-35% reduction in cellular accumulation of the P-gp substrates, rhodamine 6G (R6G), and HiLyte Fluor 488-labeled human amyloid beta 1-42 (hA?(42)). In hCMEC/D3 cells, a 3 day exposure to 100 nM 1,25(OH)(2)D(3) increased MDR1 mRNA expression (40%) and P-gp protein (threefold); cellular accumulation of R6G and hA?(42) was reduced by 30%. Thus, VDR activation up-regulates Mdr1/MDR1 and P-gp protein in isolated rat brain capillaries and rodent and human brain microvascular endothelia, implicating a role for VDR in increasing the brain clearance of P-gp substrates, including hA?(42), a plaque-forming precursor in Alzheimer's disease. PMID:23035695

Durk, Matthew R; Chan, Gary N Y; Campos, Christopher R; Peart, John C; Chow, Edwin C Y; Lee, Eason; Cannon, Ronald E; Bendayan, Reina; Miller, David S; Pang, K Sandy

2012-11-01

48

Regulation of P-glycoprotein 1 and 2 gene expression and protein activity in two MCF-7/Dox cell line subclones.  

PubMed Central

The MCF-7 doxorubicin-resistant cell line MCF-7/Dox has been used extensively for studies of the multidrug resistance phenomenon. Using fluorescence-activated cell sorting (FACS), these cells were separated into two populations on the basis of rhodamine 123 (R123) accumulation. We designated these as low P-glycoprotein (LP-gp) and high P-gp (HP-gp) cells on the basis of their P-gp content. Using the reverse transcriptase polymerase chain reaction technique controlled by homologous internal standards, we analysed levels of MDR1 and MDR2 mRNA in each cell type. LP-gp and HP-gp cells had MDR1 mRNA levels of 2.17 +/- 0.17 and 6.65 +/- 2.29 amol ng-1 total RNA respectively, compared with 0.00088 +/- 0.00005 amol ng-1 in wild-type MCF-7 cells (MCF-7/WT). MCF-7/WT cells additionally contained 0.023 +/- 0.016 amol ng-1 of MDR2 mRNA, which was unchanged in LP-gp cells, but lower than in HP-gp cells, which contained 0.42 +/- 0.08 amol ng-1. Both LP-gp and HP-gp cells contained increased copies of the MDR1 gene. However, the degree of gene amplification did not correlate with the changes in MDR1 mRNA levels, indicating further regulatory levels of gene expression. The level of P-gp detected by MRK 16 correlated with R123 accumulation. HP-gp cells expressed a 10-fold higher level of P-gp1 than LP-gp cells. However, there was only a 3-fold increase in MDR1 mRNA level in HP-gp cells compared with LP-gp cells. These data suggest that some regulation of P-gp1 expression also occurred at the post-translational level. Phosphorylation of P-gp by protein kinase C (PKC)-alpha is necessary for its activity. Our analysis of PKC-alpha, 0 and epsilon isozyme levels, and subcellular distribution, shows a co-regulation of expression with P-gp, suggesting a necessary role for PKC in P-gp regulation. Images Figure 6

Davies, R.; Budworth, J.; Riley, J.; Snowden, R.; Gescher, A.; Gant, T. W.

1996-01-01

49

Algal products as naturally occurring substrates for p-glycoprotein in Mytilus californianus  

Microsoft Academic Search

Mytilus californianus is a filter feeder that removes seaweed particulates, phytoplankton, and their byproducts from the water. The gills of this animal express high multixenobiotic resistance (MXR) and multixenobiotic transport activity that is related to the mammalian p-glycoprotein (p-gp). The high p-gp observed in mussel gills may provide the mussel protection from natural toxins in the diet. To test this

N. Eufemia; S. Clerte; S. Girshick; D. Epel

2002-01-01

50

Influence of the pro-inflammatory cytokines on P-glycoprotein expression and functionality  

Microsoft Academic Search

Purpose: P-glycoprotein (P-gp) is involved in the transport of many drugs at different barriers with consequence in terms of drug distribution and elimina- tion. The expression and activity of P-gp can be modu- lated by different factors and pathologies. The present article reviews the knowledge regarding the effect of pro-inflammatory cytokines (TNF?, IL-1?, IL-6, IL-2, IFN? ) on the expression

Christine Fernandez; Marion Buyse; Michèle German-Fattal; François Gimenez

51

Flow cytometric analysis of P-glycoprotein function using rhodamine 123  

Microsoft Academic Search

The MDR1 gene product, P-glycoprotein (P-gp), works as a transmembrane efflux pump for several cytotoxic products, representing a major cause for cancer treatment failure. Rhodamine 123 (Rh123), a low toxic fluorescent probe commonly used to assess mitochondrial bioenergetics in living cells, has also been used to measure the efflux activity of P-gp in both normal and malignant cells. Analysis of

J Pétriz; J García-López

1997-01-01

52

Rapid identification of P-glycoprotein substrates and inhibitors.  

PubMed

Identifying molecules that interact with P-glycoprotein (P-gp) is important for drug discovery but is also generally reliant on time-consuming in vitro and in vivo studies. As an alternative approach, the current study applied pharmacophore models and database screening to rapidly retrieve molecules that bind as substrates or inhibitors for P-gp from commercial databases and then confirmed their affinity as inhibitors in vitro. Seven molecules (acitretin, cholecalciferol, misoprostol, nafcillin, repaglinide, salmeterol, and telmisartan) with no published details for P-gp affinity, one positive control inhibitor (miconazole), and two negative control molecules (phenelzine and zonisamide) were selected for testing. The MDCK-MDR1 in vitro cell model was used to confirm their inhibitory effect on [3H]digoxin transport, and the ATPase assay was used as an additional in vitro tool to indicate P-gp activation. All seven test drugs were confirmed to have P-gp affinity. Additionally, our experimental results provided plausible explanations for the published pharmacokinetic profiles of the tested drugs and their classification according to the biopharmaceutics and drug disposition classification system. In this study, we showed the successful application of pharmacophore models to accurately predict P-gp binding, which holds promise to anticipate drug-drug interactions from screening drug databases and a priori prediction of novel P-gp inhibitors or substrates. PMID:16997908

Chang, Cheng; Bahadduri, Praveen M; Polli, James E; Swaan, Peter W; Ekins, Sean

2006-09-22

53

In Silico Quantitative Structure-Activity Relationship Studies on P-gp Modulators of Tetrahydroisoquinoline-Ethyl-Phenylamine Series  

PubMed Central

Background Multidrug resistance (MDR) is a major obstacle in cancer chemotherapy. The drug efflux by a transport protein is the main reason for MDR. In humans, MDR mainly occurs when the ATP-binding cassette (ABC) family of proteins is overexpressed simultaneously. P-glycoprotein (P-gp) is most commonly associated with human MDR; it utilizes energy from adenosine triphosphate (ATP) to transport a number of substrates out of cells against concentration gradients. By the active transport of substrates against concentration gradients, intracellular concentrations of substrates are decreased. This leads to the cause of failure in cancer chemotherapy. Results Herein, we report Topomer CoMFA (Comparative Molecular Field Analysis) and HQSAR (Hologram Quantitative Structure Activity Relationship) models for third generation MDR modulators. The Topomer CoMFA model showed good correlation between the actual and predicted values for training set molecules. The developed model showed cross validated correlation coefficient (q2) = 0.536 and non-cross validated correlation coefficient (r2) = 0.975 with eight components. The best HQSAR model (q2 = 0.777, r2 = 0.956) with 5-8 atom counts was used to predict the activity of test set compounds. Both models were validated using test set compounds, and gave a good predictive values of 0.604 and 0.730. Conclusions The contour map near R1 indicates that substitution of a bulkier and polar group to the ortho position of the benzene ring enhances the inhibitory effect. This explains why compounds with a nitro group have good inhibitory potency. Molecular fragment analyses shed light on some essential structural and topological features of third generation MDR modulators. Fragments analysis showed that the presence of tertiary nitrogen, a central phenyl ring and an aromatic dimethoxy group contributed to the inhibitory effect. Based on contour map information and fragment information, five new molecules with variable R1 substituents were designed. The activity of these designed molecules was predicted by the Topomer CoMFA and HQSAR models. The novel compounds showed higher potency than existing compounds.

2011-01-01

54

Susceptibility of juvenile and adult blood-brain barrier to endothelin-1: regulation of P-glycoprotein and breast cancer resistance protein expression and transport activity  

PubMed Central

Background P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) play a critical role in keeping neurotoxic substances from entering the brain. We and others have previously reported an impact of inflammation on the regulation of adult blood–brain barrier (BBB) efflux transporters. However, studies in children have not been done. From the pediatric clinical perspective, it is important to understand how the central nervous system (CNS) and BBB drug efflux transporters differ in childhood from those of adults under normal and inflammatory conditions. Therefore, we examined and compared the regulation of P-gp and BCRP expression and transport activity in young and adult BBB and investigated the molecular mechanisms underlying inflammatory responses. Methods Rats at postnatal day (P) P21 and P84, corresponding to the juvenile and adult stages of human brain maturation, respectively, were treated with endothelin-1 (ET-1) given by the intracerebroventricular (icv) route. Twenty-four hours later, we measured P-gp and BCRP protein expression in isolated brain capillary by immunoblotting as well as by transport activity in vivo by measuring the unbound drug partitioning coefficient of the brain (Kp,uu,brain) of known efflux transporter substrates administered intravenously. Glial activation was measured by immunohistochemistry. The release of cytokines/chemokines (interleukins-1?, 1-? (IL-1?), -6 (IL-6), -10 (IL-10), monocyte chemoattractant protein (MCP-1/CCL2), fractalkine and tissue inhibitor of metalloproteinases-1 (TIMP-1)) were simultaneously measured in brain and serum samples using the Agilent Technology cytokine microarray. Results We found that juvenile and adult BBBs exhibited similar P-gp and BCRP transport activities in the normal physiological conditions. However, long-term exposure of the juvenile brain to low-dose of ET-1 did not change BBB P-gp transport activity but tended to decrease BCRP transport activity in the juvenile brain, while a significant increase of the activity of both transporters was evidenced at the BBB in the adult brain. Moreover, juvenile and adult brain showed differences in their expression profiles of cytokines and chemokines mediated by ET-1. Conclusions BBB transporter activity during neuroinflammation differs between the juvenile and adult brains. These findings emphasize the importance of considering differential P-gp and BCRP transport regulation mechanisms between adult and juvenile BBB in the context of neuroinflammation.

2012-01-01

55

Failure of P-glycoprotein (MDR1) expressed in Xenopus oocytes to produce swelling-activated chloride channel activity.  

PubMed Central

1. P-glycoprotein, the protein product of the multidrug resistance (MDR1) gene, has ATP-dependent transporter activity. It has been suggested that P-glycoprotein may also function as a volume-regulated chloride channel or chloride channel regulator. To assess the chloride channel function of P-glycoprotein, we examined swelling-activated chloride conductances in Xenopus oocytes injected with human MDR1 cRNA. 2. Functional expression of P-glycoprotein in Xenopus oocytes was confirmed using Western blot analysis and by assessing transport of the P-glycoprotein substrate, calcein AM. 3. Endogenous, swelling-activated chloride conductances were virtually absent by the time P-glycoprotein expression was confirmed. Thus, this expression system afforded the advantage of assessing putative MDR1-associated chloride currents in the absence of background currents. 4. The currents activated by hypotonic shock (50%) in both MDR1-injected and control (water-injected) oocytes were not significantly different. The swelling response was due in part to the activation of a potassium-selective conductance which could be inhibited by barium. No chloride-selective currents were activated by hypotonic shock in the presence or absence of barium. Therefore, we conclude that P-glycoprotein expression does not produce a swelling-activated chloride conductance in the Xenopus oocyte expression system. Images Figure 1

Morin, X K; Bond, T D; Loo, T W; Clarke, D M; Bear, C E

1995-01-01

56

Factors affecting the expression and function of P-glycoprotein in rats: drug treatments and diseased states.  

PubMed

The expression and function of P-glycoprotein (P-gp), an ATP-dependent efflux pump, were examined in rats pretreated with dexamethasone (DEX), an inducer of P-gp, and in rats with glycerol-induced acute renal failure (ARF) and with CCl4-induced acute hepatic failure (AHF). DEX pretreatment increased the P-gp level and its functional activity in the intestine. In contrast, in ARF and AHF rats, the in vivo P-gp function was systemically suppressed, even though the level of P-gp remained unchanged or rather increased. In Caco-2 cells, the plasma collected from diseased rats exhibited a greater inhibitory effect on P-gp function than did plasma from control rats. A higher-plasma level of corticosterone, an endogenous P-gp substrate/inhibitor, was observed in the disease rats. These findings indicate that the actual in vivo function of P-gp cannot be predicted merely from the expression level of P-gp, and suggest that some endogenous P-gp-related compounds such as corticosterone participate in the regulation of in vivo P-gp function in diseased states. PMID:11878184

Murakami, T; Yumoto, R; Nagai, J; Takano, M

2002-02-01

57

Interaction of macrocyclic lactones with P-glycoprotein: structure-affinity relationship.  

PubMed

P-glycoprotein (P-gp) is involved in the ATP-dependant cellular efflux of a large number of drugs including ivermectin, a macrocyclic lactone (ML) endectocide, widely used in livestock and human antiparasitic therapy. The interactions of P-gp with ivermectin and other MLs were studied. In a first approach, the ability of ivermectin (IVM), eprinomectin (EPR), abamectin (ABA), doramectin (DOR), selamectin (SEL), or moxidectin (MOX) to inhibit the rhodamine123 efflux was measured in recombinant cells overexpressing P-gp. Then, the influence of these compounds on the P-gp ATPase activity was tested on membrane vesicles prepared from fibroblasts overexpressing P-gp. All the MLs tested increased the intracellular rhodamine123. However, the potency of MOX to inhibit P-gp function was 10 times lower than the other MLs. They all inhibited the basal and decreased the verapamil-stimulated P-gp ATPase activity. But SEL and MOX were less potent than the other MLs when competing with verapamil. According to the structural specificity of SEL and MOX, we conclude that the integrity of the sugar moiety is determinant to achieve the optimal interaction of macrocyclic lactones with P-gp. The structure-affinity relationship for interaction with P-gp is important information for improving ML bioavailability and reversal of multidrug resistance (MDR). PMID:17134887

Lespine, Anne; Martin, Solenne; Dupuy, Jacques; Roulet, Alain; Pineau, Thierry; Orlowski, Stéphane; Alvinerie, Michel

2006-10-26

58

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

2012-03-27

59

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

Microsoft Academic Search

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

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

60

Elevation of P-glycoprotein function by a catechin in green tea.  

PubMed

The ABC transporter P-glycoprotein (P-gp) exerts a critical role in the systemic disposition of and exposure to lipophilic and amphipathic drugs, carcinogens, toxins, and other xenobiotics. The ability of P-gp to transfer a wide variety of structurally unrelated compounds from the cell interior across the membrane bilayer remains intriguing. Since dietary chemicals in green tea (and several other foods) appear to exert anticarcinogenic effects by an unknown mechanism, the constituents are frequently studied for interactions with various biomacromolecules as well as cytotoxins or isolated cells. We characterized several green tea catechins for their interaction with P-gp and their specific effects on P-gp export activity of several marker substrates. Some of these compounds inhibit the active efflux of the fluorescent markers LDS-751 (LDS) and rhodamine 123 (Rho) with low potency. Remarkably, others of these catechins facilitate the P-gp-mediated transport of LDS without affecting daunorubicin (DNR) transport or Rho. Moreover, (-)epicatechin, though an inhibitor of Rho transport, can significantly enhance the active net transport of another P-gp marker substrate, LDS. This result indicates that (-)epicatechin may bind to and activate an allosteric site that enhances P-gp overall function or efficiency. Such a mechanism of heterotropic allosteric enhancement of P-gp could serve as chemoprotective to many cells and contribute to the purported anticarcinogenic effect of green tea consumption. PMID:12237135

Wang, Er-jia; Barecki-Roach, Mary; Johnson, William W

2002-09-20

61

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

62

Modulation and absorption of xenobiotics: the synergistic role of CYP450 and P-gp activities in cancer and neurodegenerative disorders.  

PubMed

P-glycoprotein (P-gp) is involved in MDR and in neurodegenerative disorders such as Parkinson disease (PD), Alzheimer disease (AD) and epilepsy. Cytochrome P450 enzymes (CYP450s) catalyze the metabolism of a wide variety of endogenous and exogenous compounds including xenobiotics, drugs, environmental toxins, steroids, and fatty acids. P-gp substrates, inhibitors and inducers should be designed and developed studying interacting mechanism with both P-gp an CYP450 enzymes before they could be employed in MDR and/or in neurodegenerative disorders. Here, the ex vivo rat everted gut sac assay has been proposed as an immediate approach to simultaneously study metabolism and transport of drugs. Elacridar, verapamil and cyclosporine A (CsA), P-gp inhibitor, substrate and modulator respectively, have been tested to validate this ex vivo approach. The new model have been used yet to develop our ligands MC18, MC266 and MC80, both as potential drugs for MDR and radiotracers for diagnosis of neurodegenerative disorders. Herein, a comparative evaluation of transport and metabolic results, by using in vitro, ex vivo and in vivo assays, is reported. PMID:21434860

Inglese, Carmela; Perrone, Maria Grazia; Berardi, Francesco; Perrone, Roberto; Colabufo, Nicola Antonio

2011-10-01

63

Influence of lipid lowering fibrates on P-glycoprotein activity in vitro  

Microsoft Academic Search

Statin\\/fibrate combinations are frequently used to treat mixed dyslipidemia. However, these combinations may cause life-threatening drug interactions (e.g. rhabdomyolysis) possibly induced by modifications of cytochrome P450 isozyme activities. Some statins are also transported by P-glycoprotein (Pgp) and may act as inhibitors of this drug efflux pump. So far, nothing is known about possible Pgp modulating effects of fibrates. We tested

Manuela Ehrhardt; Heike Lindenmaier; Juergen Burhenne; Walter Emil Haefeli; Johanna Weiss

2004-01-01

64

Aripiprazole brain concentration is altered in P-glycoprotein deficient mice.  

PubMed

P-glycoprotein (P-gp) is a transporter that mediates the tissue disposition of numerous drugs. To evaluate the role of P-glycoprotein (P-gp) in aripiprazole tissue distribution and penetration across the blood-brain barrier, mice deficient in the P-gp gene (Abcb1a/b-/-) were dosed intraperitoneally with 2 microg/g mouse of the antipsychotic drug aripiprazole. Wildtype FVB mice were administered the same dose as transgenic animals. At one, two, and three hours after dosing, blood and tissue samples were collected and assayed for aripiprazole concentration by HPLC. Deficiency of P-gp did not result in significantly altered plasma drug concentrations but had dramatic effects on drug concentrations in brain tissue. At 1, 2, and 3 h after dosing, aripiprazole brain concentrations in the Abcb1a/b-/- mice were 4.6-, 4.1- and 3.0-fold higher, respectively (P<0.01), compared with the wildtype mice. Increases in drug concentration were also observed in testes and muscle in Abcb1a/b -/- mice. All other tissues including gut, lung, heart, kidney, liver, and spleen did not show significant differences between the two groups. These data provide evidence that aripiprazole is a transportable substrate of P-gp. Thus, factors influencing P-gp activity within the blood brain barrier in humans may have implications for the therapeutic effects and tolerability of aripiprazole. PMID:19239981

Wang, Jun-Sheng; Zhu, Hao-Jie; Donovan, Jennifer L; Yuan, Hong-Jie; Markowitz, John S; Geesey, Mark E; Devane, C Lindsay

2009-02-23

65

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

66

Lobeline, a piperidine alkaloid from Lobelia can reverse P-gp dependent multidrug resistance in tumor cells.  

PubMed

Multidrug resistance (MDR) can limit efficacy of chemotherapy. The best studied mechanism involves P-gp (P-glycoprotein) mediated drug efflux. This study focuses on MDR reversal agents from medicinal plants, which can interfere with P-gp. Rhodamine 123 accumulation assay and flow cytometry analysis were employed to screen for P-gp dependant efflux inhibitors. Lobeline, a piperidine alkaloid from Lobelia inflata and several other Lobelia species, inhibited P-gp activity. MDR reversal potential of lobeline could be demonstrated in cells treated with doxorubicin in that lobeline can sensitize resistant tumor cells at non-toxic concentrations. However, lobeline cannot block BCRP (Breast Cancer Resistance Protein) dependent mitoxantrone efflux. Lobeline could be a good candidate for the development of new MDR reversal agents. PMID:18222670

Ma, Yonggang; Wink, Michael

2008-01-28

67

A Unique Interaction between Polyamine and Multidrug Resistance (P-glycoprotein) Transporters in Cultured Chinese Hamster Ovary Cells Transfected with Mouse mdr-1 Gene  

Microsoft Academic Search

We have shown that a functional link exists between the polyamine transporter and the multi-drug resistance (MDR) efflux transporter (P-glycoprotein, P-gp) in MDR-positive cancer cells. To further explore the nature of this interaction, we have examined the effect of reduced polyamine transport activity on cellular expression and activity of P-gp acquired by either selection or transfection. Chinese hamster ovary (CHO)

Shewan M. Aziz; David R. Worthen; Mustafa Yatin; Kenneth B. Ain; Peter A. Crooks

1998-01-01

68

Assessing p-Glycoprotein (Pgp) Activity In Vivo Utilizing 68 Ga–Schiff Base Complexes  

Microsoft Academic Search

Purpose  The p-glycoprotein (Pgp) is the most prominent member of active drug transporters leading to a multidrug-resistant phenotype.\\u000a For identification of tumors functionally overexpressing Pgp in vivo, non-invasive imaging techniques are needed.\\u000a \\u000a \\u000a \\u000a \\u000a Procedures  Six Schiff base compounds were synthesized and labeled with 68Ge\\/68Ga generator-derived 68Ga. The compounds were studied in vitro in Pgp-positive tumor cells. The property of being a Pgp substrate

Marco Fellner; Wolfgang Dillenburg; Hans-Georg Buchholz; Nicole Bausbacher; Mathias Schreckenberger; Franz Renz; Frank Rösch; Oliver Thews

69

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

PubMed

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(-6) cm/s) compared to the inhaled corticosteroids (>5×10(-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. PMID:22464980

Crowe, Andrew; Tan, Ai May

2012-03-23

70

Influence of time to achieve substrate distribution equilibrium between brain tissue and blood on quantitation of the blood–brain barrier P-glycoprotein effect  

Microsoft Academic Search

Active efflux transport processes at the blood–brain barrier (BBB), such as P-glycoprotein (P-gp)-mediated efflux, can limit brain uptake of therapeutics. Accurate determination of the consequent impact on brain uptake is assumed to require sampling post-attainment of brain-to-blood distribution equilibrium. Because this approach is not always feasible, understanding the relationship between apparent degree of efflux (e.g., calculated BBB P-gp effect) and

Jeannie M. Padowski; Gary M. Pollack

2011-01-01

71

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

72

Structureactivity relationships of P-glycoprotein interacting drugs: kinetic characterization of their effects on ATPase activity  

Microsoft Academic Search

We have determined the kinetic parameters for stimulation and inhibition by 34 drugs of the P-glycoprotein ATPase in membranes derived from CR1R12 Chinese hamster ovary cells. The drugs chosen were sets of calmodulin antagonists, steroids, hydrophobic cations, hydrophobic peptides, chemotherapeutic substrates of P-glycoprotein, and some other drugs with lower affinity for P-glycoprotein. We studied how these kinetic parameters correlated with

Thomas Litman; Thomas Zeuthen; Torben Skovsgaard; Wilfred D. Stein

1997-01-01

73

HIV-1 integrase inhibitors are substrates for the multidrug transporter MDR1-P-glycoprotein  

PubMed Central

Background The discovery of diketoacid-containing derivatives as inhibitors of HIV-1 Integrase (IN) (IN inhibitors, IINs) has played a major role in validating this enzyme as an important target for antiretroviral therapy. Since the in vivo efficacy depends on access of these drugs to intracellular sites where HIV-1 replicates, we determined whether the IINs are recognized by the multidrug transporter MDR1-P-glycoprotein (P-gp) thereby reducing their intracellular accumulation. To address the effect of IINs on drug transport, nine quinolonyl diketo acid (DKA) derivatives active on the HIV-1 IN strand transfer (ST) step and with EC50 ranging from 1.83 to >50 ?m in cell-based assays were tested for their in vitro interaction with P-gp in the CEM-MDR cell system. IINs were investigated for the inhibition and induction of the P-gp function and expression as well as for multidrug resistance (MDR) reversing ability. Results The HIV-1 IINs act as genuine P-gp substrates by inhibiting doxorubicin efflux and inducing P-gp functional conformation changes as evaluated by the modulation of UIC2 mAb epitope. Further, IINs chemosensitize MDR cells to vinblastine and induce P-gp expression in drug sensitive revertants of CEM-MDR cells. Conclusion To our knowledge, this is the first demonstration that HIV-1 IINs are P-gp substrates. This biological property may influence the absorption, distribution and elimination of these novels anti HIV-1 compounds.

Cianfriglia, Maurizio; Dupuis, Maria Luisa; Molinari, Agnese; Verdoliva, Antonio; Costi, Roberta; Galluzzo, Clementina Maria; Andreotti, Mauro; Cara, Andrea; Di Santo, Roberto; Palmisano, Lucia

2007-01-01

74

Quantitative evaluation of the impact of active efflux by p-glycoprotein and breast cancer resistance protein at the blood-brain barrier on the predictability of the unbound concentrations of drugs in the brain using cerebrospinal fluid concentration as a surrogate.  

PubMed

This study investigated the impact of the active efflux mediated by P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) at the blood-brain barrier (BBB) on the predictability of the unbound brain concentration (C(u,brain)) by the concentration in the cerebrospinal fluid (CSF) (C(u,CSF)) in rats. C(u,brain) is obtained as the product of the total brain concentration and unbound fraction in the brain (f(u,brain)) determined in vitro in brain slices. Twenty-five compounds, including P-gp and/or Bcrp substrates, were given a constant intravenous infusion, and their plasma, brain, and CSF concentrations were determined. P-gp and/or Bcrp substrates, such as verapamil, loperamide, flavopiridol, genistein, quinidine, dantrolene, daidzein, cimetidine, and pefloxacin, showed a higher CSF-to-brain unbound concentration ratio (K(p,uu,CSF/brain)) compared with non-P-gp and non-Bcrp substrates. K(p,uu,CSF/brain) values of P-gp-specific (quinidine and verapamil) and Bcrp-specific (daidzein and genistein) substrates were significantly decreased in Mdr1a/1b(-/-) and Bcrp(-/-) mice, respectively. Furthermore, consistent with the contribution of P-gp and Bcrp to the net efflux at the BBB, K(p,uu,CSF/brain) values of the common substrates (flavopiridol and erlotinib) were markedly decreased in Mdr1a/1b(-/-)/Bcrp(-/-) mice, but only moderately or weakly in Mdr1a/1b(-/-) mice and negligibly in Bcrp(-/-) mice. In conclusion, predictability of C(u,brain) by C(u,CSF) decreases along with the net transport activities by P-gp and Bcrp at the BBB. C(u,CSF) of non-P-gp and non-Bcrp substrates can be a reliable surrogate of C(u,brain) for lipophilic compounds. PMID:21934030

Kodaira, Hiroshi; Kusuhara, Hiroyuki; Fujita, Takuya; Ushiki, Junko; Fuse, Eiichi; Sugiyama, Yuichi

2011-09-20

75

Role of P-glycoprotein in transplacental transfer of methadone?  

PubMed Central

Methadone is the therapeutic agent of choice for treatment of the pregnant opiate addict. However, little is known on the factors affecting its concentration in the fetal circulation during pregnancy and how it might relate to neonatal outcome. Therefore, a better understanding of the function of placental metabolic enzymes and transporters should add to the knowledge of the role of the tissue in the disposition of methadone and its relation to neonatal outcome. We hypothesized that the expression and activity of the placental efflux transporter P-glycoprotein (P-gp) would affect the transfer of methadone to the fetal circulation. Data obtained utilizing dual perfusion of placental lobule and monolayers of Be–Wo cell line indicated that methadone is extruded by P-gp. Transfer of methadone to the fetal circuit was increased by 30% in the presence of the P-gp inhibitor GF120918 while the transfer of paclitaxel, a typical substrate of the glycoprotein, was increased by 50%. In the Be–Wo cell line, methadone and paclitaxel uptake was also increased in the presence of the P-gp inhibitor cyclosporin A. Moreover, the expression of P-gp in placental brush–border membranes varied between term placentas. Taken together, these data strongly suggest that the concentration of methadone in the fetal circulation is affected by the expression and activity of P-gp. It is reasonable to speculate that placental disposition of methadone affects its concentration in the fetal circulation. If true, this may also be directly related to the incidence and intensity of neonatal abstinence syndrome (NAS).

Nanovskaya, Tatiana; Nekhayeva, Ilona; Karunaratne, Nedra; Audus, Kenneth; Hankins, Gary D.V.; Ahmed, Mahmoud S.

2008-01-01

76

Recognition of Sulfonylurea Receptor (ABCC8/9) Ligands by the Multidrug Resistance Transporter P-glycoprotein (ABCB1)  

PubMed Central

ATP-sensitive K+ (KATP) channels are the target of a number of pharmacological agents, blockers like hypoglycemic sulfonylureas and openers like the hypotensive cromakalim and diazoxide. These agents act on the channel regulatory subunit, the sulfonylurea receptor (SUR), which is an ABC protein with homologies to P-glycoprotein (P-gp). P-gp is a multidrug transporter expressed in tumor cells and in some healthy tissues. Because these two ABC proteins both exhibit multispecific recognition properties, we have tested whether SUR ligands could be substrates of P-gp. Interaction with P-gp was assayed by monitoring ATPase activity of P-gp-enriched vesicles. The blockers glibenclamide, tolbutamide, and meglitinide increased ATPase activity, with a rank order of potencies that correlated with their capacity to block KATP channels. P-gp ATPase activity was also increased by the openers SR47063 (a cromakalim analog), P1075 (a pinacidil analog), and diazoxide. Thus, these molecules bind to P-gp (although with lower affinities than for SUR) and are possibly transported by P-gp. Competition experiments among these molecules as well as with typical P-gp substrates revealed a structural similarity between drug binding domains in the two proteins. To rationalize the observed data, we addressed the molecular features of these proteins and compared structural models, computerized by homology from the recently solved structures of murine P-gp and bacterial ABC transporters MsbA and Sav1866. Considering the various residues experimentally assigned to be involved in drug binding, we uncovered several hot spots, which organized spatially in two main binding domains, selective for SR47063 and for glibenclamide, in matching regions of both P-gp and SUR.

Bessadok, Anis; Garcia, Elisabeth; Jacquet, Helene; Martin, Solenne; Garrigues, Alexia; Loiseau, Nicolas; Andre, Francois; Orlowski, Stephane; Vivaudou, Michel

2011-01-01

77

Targeting blood-brain barrier sphingolipid signaling reduces basal P-glycoprotein activity and improves drug delivery to the brain.  

PubMed

P-glycoprotein, an ATP-driven drug efflux pump, is a major obstacle to the delivery of small-molecule drugs across the blood-brain barrier and into the CNS. Here we test a unique signaling-based strategy to overcome this obstacle. We used a confocal microscopy-based assay with isolated rat brain capillaries to map a signaling pathway that within minutes abolishes P-glycoprotein transport activity without altering transporter protein expression or tight junction permeability. This pathway encompasses elements of proinflammatory- (TNF-?) and sphingolipid-based signaling. Critical to this pathway was signaling through sphingosine-1-phosphate receptor 1 (S1PR1). In brain capillaries, S1P acted through S1PR1 to rapidly and reversibly reduce P-glycoprotein transport activity. Sphingosine reduced transport by a sphingosine kinase-dependent mechanism. Importantly, fingolimod (FTY720), a S1P analog recently approved for treatment of multiple sclerosis, also rapidly reduced P-glycoprotein activity; similar effects were found with the active, phosphorylated metabolite (FTY720P). We validated these findings in vivo using in situ brain perfusion in rats. Administration of S1P, FTY720, or FTY729P increased brain uptake of three radiolabeled P-glycoprotein substrates, (3)H-verapamil (threefold increase), (3)H-loperamide (fivefold increase), and (3)H-paclitaxel (fivefold increase); blocking S1PR1 abolished this effect. Tight junctional permeability, measured as brain (14)C-sucrose accumulation, was not altered. Therefore, targeting signaling through S1PR1 at the blood-brain barrier with the sphingolipid-based drugs, FTY720 or FTY720P, can rapidly and reversibly reduce basal P-glycoprotein activity and thus improve delivery of small-molecule therapeutics to the brain. PMID:22949658

Cannon, Ronald E; Peart, John C; Hawkins, Brian T; Campos, Christopher R; Miller, David S

2012-09-04

78

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

79

Abamectin resistance in Drosophila is related to increased expression of P-glycoprotein via the dEGFR and dAkt pathways.  

PubMed

Many insects have evolved resistance to abamectin but the mechanisms involved in this resistance have not been well characterized. P-glycoprotein (P-gp), an ATP-dependent drug-efflux pump transmembrane protein, may be involved in abamectin resistance. We investigated the role of P-gp in abamectin (ABM) resistance in Drosophila using an ABM-resistant strain developed in the laboratory. A toxicity assay, Western blotting analysis and a vanadate-sensitive ATPase activity assay all demonstrated the existence of a direct relationship between P-gp expression and ABM resistance in these flies. Our observations indicate that P-gp levels in flies' heads were higher than in their thorax and abdomen, and that both P-gp levels and LC(50) values were higher in resistant than in susceptible and P-gp-deficient strains. In addition, P-gp levels in the blood-brain barrier (BBB) of resistant flies were higher than in susceptible and P-gp-deficient flies, which is further evidence that a high level of P-gp in the BBB is related to ABM resistance. Furthermore, we found greater expression of Drosophila EGFR (dEGFR) in the resistant strain than in the susceptible strain, and that the level of Drosophila Akt (dAkt) was much higher in resistant than in susceptible flies, whereas that in P-gp-deficient flies was very low. Compared to susceptible flies, P-gp levels in the resistant strain were markedly suppressed by the dEGFR and dAkt inhibitors lapatinib and wortmannin. These results suggest that the increased P-gp in resistant flies was regulated by the dEGFR and dAkt pathways and that increased expression of P-gp is an important component of ABM resistance in insects. PMID:23648830

Luo, Liang; Sun, Ying-Jian; Wu, Yi-Jun

2013-05-03

80

P-glycoprotein--implications of metabolism of neoplastic cells and cancer therapy.  

PubMed

Multidrug resistance (MDR) of neoplastic tissues is a major obstacle in cancer chemotherapy. The predominant cause of MDR is the overexpression and drug transport activity of P-glycoprotein (P-gp, a product of the MDR gene). P-gp is a member of the ATP binding cassette (ABC) transporters family, with broad substrate specificity for several substances including anticancer drugs, linear and cyclic peptides, inhibitors of HIV protease, and several other substances. The development of P-gp-mediated MDR is often associated with several changes in cell structure and metabolism of resistant cells. In the present review are discussed the relations between glucosylceramide synthase activity, Pregnane X receptor and development of P-gp mediated MDR phenotype. Attention is also focused on the changes in protein kinase systems (mitogen-activated protein kinases, protein kinase C, Akt kinase) that are associated with the development of MDR phenotype and to the possible role of these kinase cascades in modulation of P-gp expression and function. The overexpression of P-gp may be associated with changes in metabolism of sugars as well as energy production. Structural and ultrastructural characteristics of multidrug resistant cells expressing P-gp are typical for cells engaged in a metabolically demanding process of protein synthesis and transport. P-gp mediated MDR phenotype is often also associated with alterations in cytoskeletal elements, microtubule and mitochondria distribution, Golgi apparatus, chromatin texture, vacuoles and caveolae formation. The current review also aims at bringing some state-of-the-art information on interactions of P-glycoprotein with various substances. To capture and transport the numerous unrelated substances, P-gp should contain site(s) able to bind compounds with a molecular weight of several hundreds and comprising hydrophobic and/or base regions that are protonated under physiological conditions. Drug binding sites that are able to recognize substances with different chemical structures may have a complex architecture in which different parts are responsible for binding of different drugs. For P-gp substrates and inhibitors, a pharmacophore-based model has been described. The pharmacophores have to contain parts with hydrophobic and aromatic characteristics and functional groups that can act as hydrogen-bond donors and/or acceptors. Several drugs are known to be P-glycoprotein antagonizing agents. They represent a large group of structurally unrelated substances that can act via direct interaction with P-gp and inhibition of its transport activity, or via possible modulation of processes (such as phosphorylation) regulating P-gp transport activity. Effects of MDR reversal agents on the P-gp expression have also been reported. Function and expression of P-gp can be affected indirectly as well, e.g. through cyclooxygenase-2 or carbonic anhydrase-IX expression and effects. PMID:16178819

Breier, Albert; Barancík, Miroslav; Sulová, Zdenka; Uhrík, Branislav

2005-09-01

81

Induction of p-glycoprotein by antiretroviral drugs in human brain microvessel endothelial cells.  

PubMed

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. PMID:23836171

Chan, Gary N Y; Patel, Rucha; Cummins, Carolyn L; Bendayan, Reina

2013-07-08

82

Effect of efavirenz on intestinal p-glycoprotein and hepatic p450 function in rats  

Microsoft Academic Search

Purpose: P-glycoprotein (P-gp) and cytochrome P450 (P450) affect drug disposition. Efavirenz (EFV) is an anti-HIV drug used in combination. Since most anti-HIV medications are substrate and modulators of P-gp and\\/or P450, we investigated the effects of EFV on intestinal P-gp and hepatic P450 function to predict drug interactions. Methods: (i) The effect of EFV on rat intestinal P-gp function was

Nathalie Berruet; Stephanie Sentenac; Daniel Auchere; François Gimenez; Robert Farinotti; Christine Fernandez

83

Determination of P-glycoprotein surface expression and functional ability after in vitro treatment with darunavir or raltegravir in lymphocytes of healthy donors.  

PubMed

It has been shown that P-glycoprotein (P-gp) can greatly affect the cell uptake of antiretroviral drugs, thus hampering their access to HIV-1 replication sites. Lymphocytes are important sites of replication of HIV and target of other drugs, modification on these cells of P-gp could have an effect on pharmacokinetic of antiretrovirals and drug substrates. Blood samples from 16 healthy volunteers were used to determine the expression of P-gp on total, T and T helper lymphocytes after exposure to darunavir, a second generation protease inhibitor, and raltegravir, the first approved integrase inhibitor. Moreover, the effect of the drugs on P-gp functional activity was also studied by the rhodamine-123 efflux test. Darunavir, but not raltegravir, exposure caused a moderate, dose-dependent increment in P-gp expression in total, T and T helper lymphocytes, as demonstrated by the relative frequency of P-gp+ cells and by the amount of P-gp molecules present on cell surface. Functionally, incubation with darunavir led to a marked inhibition of P-gp activity measured by the efflux of rhodamine-123 similar to that observed by verapamil, a specific P-gp inhibitor. Raltegravir was not able to modify the efflux of rhodamine-123 level. Data show that darunavir, unlike raltegravir, may modify the expression and functionality of P-gp on human lymphocytes, thus leading to potential changes in intracellular concentrations of darunavir in patients treated with other drugs substrate of P-gp and vice versa. Our study highlights the need for studies on drug interactions via the P-gp modulation mechanism, especially with the current multi-drug regimens. PMID:23707228

Tempestilli, Massimo; Gentilotti, Elisa; Tommasi, Chiara; Nicastri, Emanuele; Martini, Federico; De Nardo, Pasquale; Narciso, Pasquale; Pucillo, Leopoldo P

2013-05-23

84

Molecular dissection of dual pseudosymmetric solute translocation pathways in human P-glycoprotein.  

PubMed

The human multispecific drug efflux transporter P-glycoprotein (P-gp) causes drug resistance and modulates the pharmacological profile of systemically administered medicines. It has arisen from a homodimeric ancestor by gene duplication. Crystal structures of mouse MDR1A indicate that P-gp shares the overall architecture with two homodimeric bacterial exporters, Sav1866 and MsbA, which have complete rotational symmetry. For ATP-binding cassette transporters, nucleotide binding occurs in two symmetric positions in the motor domains. Based on the homology with entirely symmetric half-transporters, the present study addressed the key question: can biochemical evidence for the existence of dual drug translocation pathways in the transmembrane domains of P-gp be found? P-gp was photolabeled with propafenone analogs, purified, and digested proteolytically, and peptide fragments were identified by high-resolution mass spectrometry. Labeling was assigned to two regions in the protein by projecting data into homology models. Subsequently, symmetric residue pairs in the putative translocation pathways were identified and replaced by site-directed mutagenesis. Transport assays corroborated the existence of two pseudosymmetric translocation pathways. Although rhodamine123 has a preference to take one path, verapamil, propafenones, and vinblastine preferentially use the other. Two major findings ensued from this study: the existence of two solute translocation pathways in P-gp as a reflection of evolutionary origin from a homodimeric ancestor and selective but not exclusive use of one of these pathways by different P-gp solutes. The pseudosymmetric behavior reconciles earlier kinetic and thermodynamic data, suggesting an alternative concept of drug transport by P-gp that will aid in understanding the off-target quantitative structure activity relationships of P-gp interacting drugs. PMID:21177413

Parveen, Zahida; Stockner, Thomas; Bentele, Caterina; Pferschy, Sandra; Kraupp, Martin; Freissmuth, Michael; Ecker, Gerhard F; Chiba, Peter

2010-12-21

85

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.  

PubMed

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. Plasma and urine concentrations were determined by liquid chromatography-mass spectrometry and analyzed by noncompartmental methods. Midazolam CL/F(unbound) (593 +/- 237 l/min vs. 345 +/- 103 l/min; P = 0.007), digoxin CL(Renal, unbound) (272 +/- 45 ml/min vs. 183 +/- 37 ml/min; P < 0.002) and digoxin CL(secretion,) (unbound) (109 +/- 34 ml/min vs. 58 +/- 22 ml/min; P < 0.002) were higher during pregnancy than postpartum. These data are consistent with increased hepatic and/or intestinal CYP3A and renal P-gp activities during pregnancy. PMID:18288078

Hebert, M F; Easterling, T R; Kirby, B; Carr, D B; Buchanan, M L; Rutherford, T; Thummel, K E; Fishbein, D P; Unadkat, J D

2008-02-20

86

p53 and P-glycoprotein are often co-expressed and are associated with poor prognosis in breast cancer.  

PubMed Central

Expression of both P-glycoprotein (P-gp) and mutant p53 have recently been reported to be associated with poor prognosis of breast cancer. The expression of P-gp is associated in vitro and in vivo with cross-resistance to several anti-cancer drugs. p53 plays a regulatory role in apoptosis, and mutant p53 has been suggested to be involved in drug resistance. Interestingly, in vitro experiments have shown that mutant p53 can activate the promoter of the MDR1 gene, which encodes P-gp. We investigated whether p53 and P-gp are simultaneously expressed in primary breast cancer cells and analysed the impact of the co-expression on patients prognosis. Immunohistochemistry was used to investigate P-gp expression (JSB-1, C219) and nuclear p53 accumulation (DO-7) in 20 operable chemotherapy untreated and 30 locally advanced breast cancers undergoing neoadjuvant chemotherapy with doxorubicin and cyclophosphamide. Double immunostaining showed that P-gp expression and nuclear p53 accumulation often occur concomitantly in the same tumour cells. A correlation between p53 and P-gp expression was found in all 50 breast cancers (P = 0.003; Fisher's exact test). P-gp expression, nuclear p53 accumulation, and co-expression of p53 and P-gp were more frequently observed in locally advanced breast cancers than in operable breast cancers (P = 0.0004, P = 0.048; P = 0.002 respectively. Fisher's exact test). Co-expression of p53 and P-gp was the strongest prognostic factor for shorter survival by multivariate analysis (P = 0.004) in the group of locally advanced breast cancers (univariate analysis: P = 0.0007). Only 3 out of 13 samples sequentially taken before and after chemotherapy displayed a change in P-gp or p53 staining. In conclusion, nuclear p53 accumulation is often associated with P-gp expression in primary breast cancer, and simultaneous expression of p53 and P-gp is associated with shorter survival in locally advanced breast cancer patients. Co-expression of P-gp and mutant p53 belong to a series of molecular events resulting in a more aggressive phenotype, drug resistance and poor prognosis. Images Figure 1

Linn, S. C.; Honkoop, A. H.; Hoekman, K.; van der Valk, P.; Pinedo, H. M.; Giaccone, G.

1996-01-01

87

The drug efflux protein, P-glycoprotein, additionally protects drug-resistant tumor cells from multiple forms of caspase-dependent apoptosis  

PubMed Central

Multidrug resistance mediated by the drug efflux protein, P-glycoprotein (P-gp), is one mechanism that tumor cells use to escape death induced by chemotherapeutic agents. However, the mechanism by which P-gp confers resistance to a large variety of structurally diverse molecules has remained elusive. In this study, classical multidrug resistant human CEM and K562 tumor cell lines expressing high levels of P-gp were less sensitive to multiple forms of caspase-dependent cell death, including that mediated by cytotoxic drugs and ligation of Fas. The DNA fragmentation and membrane damage inflicted by these stimuli were defined as caspase dependent by various soluble peptide fluoromethylketone caspase inhibitors. Inhibition of P-gp function by the anti-P-gp mAb MRK-16 or verapamil could reverse resistance to these forms of cell death. Inhibition of P-gp function also enhanced drug or Fas-mediated activation of caspase-3 in drug-resistant CEM cells. By contrast, caspase-independent cell death events in the same cells, including those mediated by pore-forming proteins or intact NK cells, were not affected by P-gp expression. These observations suggest that, in addition to effluxing drugs, P-gp may play a specific role in regulating some caspase-dependent apoptotic pathways.

Smyth, Mark J.; Krasovskis, Erika; Sutton, Vivien R.; Johnstone, Ricky W.

1998-01-01

88

Functional impairment of P-glycoprotein by sodium nitroprusside pretreatment in mouse brain capillary endothelial cells.  

PubMed

We examined whether pretreatment of mouse brain blood vessel endothelial cell clone 4 (MBEC4) cells with sodium nitroprusside (SNP), a NO(x) donor, as an in vitro model of the bloodbrain barrier could affect P-glycoprotein (P-gp) functional activity. Uptake into the cells and MBEC4 plasma membrane vesicles (MPMVs) in the presence or absence of SNP pretreatment was used to investigate functional changes. Increased accumulation of [(3)H]vincristine, a widely used substrate for P-gp, into MBEC4 was observed upon SNP pretreatment, likely due to impaired P-gp function. To better understand the mechanism of the impairment, MPMVs were prepared and characterized in terms of purity and Na(+)-dependent glucose uptake. [(3)H]daunomycin uptake into MPMVs was diminished after SNP pretreatment in the presence of an ATP-regenerating system, indicating that the functional activity of P-gp was impaired after exposure to SNP. Under conditions of excess ATP, daunomycin uptake into the vesicles was still decreased after SNP pretreatment, indicating that SNP interacted directly with the transport system, but not with the ATP-regenerating system. Together, these results suggest that NO or NO(x) functionally impairs P-gp in the in vitro blood-brain barrier model with SNP pretreatment. PMID:22864744

Maeng, Han-Joo; Bang, Yu-Jin; Chung, Suk-Jae

2012-08-03

89

Inhibition of the ATPase activity of P-glycoprotein by porphyrin photosensitization of multidrug-resistant cells in vitro.  

PubMed

The effectiveness of photodynamic therapy against P-glycoprotein ATPase activity in multidrug-resistant cells was studied. Chinese hamster ovary AUXB1 (drug-sensitive) and CR1R12 (multidrug-resistant) cell lines were compared with respect to uptake of 14C-polyhematoporphyrin and porphyrin photosensitization. Phototoxicity of Photofrin was similar in both cell lines, and no major differences in uptake or efflux of 14C-polyhematoporphyrin were observed. Porphyrin photosensitization in vitro of CR1R12 cells or isolated plasma membranes from these cells caused inhibition of P-glycoprotein ATPase activity. Application of porphyrin photosensitization at a sublethal level to CR1R12 cells resulted in a small but significant increase in adriamycin-induced cytotoxicity. The hydrophobic "picket-fence" porphyrin, meso-tetrakis-(o-propionamidophenyl)porphyrin, alpha,alpha,alpha,beta-isomer, was more inhibitory toward P-glycoprotein ATPase activity than the two less hydrophobic porphyrins tetraphenylporphine tetrasulfonate and Photofrin. PMID:7740083

Gibson, S L; al-Shawi, M K; Senior, A E; Hile, R

1995-04-01

90

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

91

Activation of PKC isoform ?I at the blood–brain barrier rapidly decreases P-glycoprotein activity and enhances drug delivery to the brain  

Microsoft Academic Search

P-glycoprotein is an ATP (adenosine triphosphate)-driven drug efflux transporter that is highly expressed at the blood–brain barrier (BBB) and is a major obstacle to the pharmacotherapy of central nervous system diseases, including brain tumors, neuro-AIDS, and epilepsy. Previous studies have shown that P-glycoprotein transport activity in rat brain capillaries is rapidly reduced by the proinflammatory cytokine, tumor necrosis factor-? (TNF-?)

Robert R Rigor; Brian T Hawkins; David S Miller

2010-01-01

92

Effects of Sertraline and Fluoxetine on P-Glycoprotein at Barrier Sites: In Vivo and In Vitro Approaches  

PubMed Central

Background and Purpose Retention of substances from systemic circulation in the brain and testes are limited due to high levels of P-glycoprotein (P-gp) in the luminal membranes of brain and testes capillary endothelial cells. From a clinical perspective, P-gp rapidly extrudes lipophilic therapeutic agents, which then fail to reach efficacious levels. Recent studies have demonstrated that acute administration of selective serotonin reuptake inhibitors (SSRI) can affect P-gp function, in vitro and in vivo. However, little is known concerning the time-course of these effects or the effects of different SSRI in vivo. Experimental Approach The P-gp substrate, tritiated digoxin ([3H] digoxin), was co-administered with fluoxetine or sertraline to determine if either compound increased drug accumulation within the brains and testes of mice due to inhibition of P-gp activity. We undertook parallel studies in endothelial cells derived from brain microvessels to determine the dose-response and time-course of effects. Key Results In vitro, sertraline resulted in rapid and potent inhibition of P-gp function in brain endothelial cells, as determined by cellular calcein accumulation. In vivo, a biphasic effect was demonstrated. Brain accumulation of [3H] digoxin was increased 5 minutes after treatment with sertraline, but by 60 minutes after sertraline treatment, brain accumulation of digoxin was reduced compared to control. By 240 minutes after sertraline treatment brain digoxin accumulation was elevated compared to control. A similar pattern of results was obtained in the testes. There was no significant effect of fluoxetine on P-gp function, in vitro or in vivo. Conclusions and Implications Acute sertraline administration can modulate P-gp activity in the blood-brain barrier and blood-testes barrier. This clearly has implications for the ability of therapeutic agents that are P-gp substrates, to enter the brain when co-administered with SSRI.

Kapoor, Amita; Iqbal, Majid; Petropoulos, Sophie; Ho, Hay Lam; Gibb, William; Matthews, Stephen G.

2013-01-01

93

Interaction of Verapamil with Lipid Membranes and P-Glycoprotein: Connecting Thermodynamics and Membrane Structure with Functional Activity  

PubMed Central

Verapamil and amlodipine are calcium ion influx inhibitors of wide clinical use. They are partially charged at neutral pH and exhibit amphiphilic properties. The noncharged species can easily cross the lipid membrane. We have measured with solid-state NMR the structural changes induced by verapamil upon incorporation into phospholipid bilayers and have compared them with earlier data on amlodipine and nimodipine. Verapamil and amlodipine produce a rotation of the phosphocholine headgroup away from the membrane surface and a disordering of the fatty acid chains. We have determined the thermodynamics of verapamil partitioning into neutral and negatively charged membranes with isothermal titration calorimetry. Verapamil undergoes a pK-shift of ?pKa = 1.2 units in neutral lipid membranes and the percentage of the noncharged species increases from 5% to 45%. Verapamil partitioning is increased for negatively charged membranes and the binding isotherms are strongly affected by the salt concentration. The electrostatic screening can be explained with the Gouy-Chapman theory. Using a functional phosphate assay we have measured the affinity of verapamil, amlodipine, and nimodipine for P-glycoprotein, and have calculated the free energy of drug binding from the aqueous phase to the active center of P-glycoprotein in the lipid phase. By combining the latter results with the lipid partitioning data it was possible, for the first time, to determine the true affinity of the three drugs for the P-glycoprotein active center if the reaction takes place exclusively in the lipid matrix.

Meier, M.; Blatter, X. Li; Seelig, A.; Seelig, J.

2006-01-01

94

Structure of P-Glycoprotein Reveals a Molecular Basis for Poly-Specific Drug Binding  

SciTech Connect

P-glycoprotein (P-gp) detoxifies cells by exporting hundreds of chemically unrelated toxins but has been implicated in multidrug resistance (MDR) in the treatment of cancers. Substrate promiscuity is a hallmark of P-gp activity, thus a structural description of poly-specific drug-binding is important for the rational design of anticancer drugs and MDR inhibitors. The x-ray structure of apo P-gp at 3.8 angstroms reveals an internal cavity of -6000 angstroms cubed with a 30 angstrom separation of the two nucleotide-binding domains. Two additional P-gp structures with cyclic peptide inhibitors demonstrate distinct drug-binding sites in the internal cavity capable of stereoselectivity that is based on hydrophobic and aromatic interactions. Apo and drug-bound P-gp structures have portals open to the cytoplasm and the inner leaflet of the lipid bilayer for drug entry. The inward-facing conformation represents an initial stage of the transport cycle that is competent for drug binding.

Aller, Stephen G.; Yu, Jodie; Ward, Andrew; Weng, Yue; Chittaboina, Srinivas; Zhuo, Rupeng; Harrell, Patina M.; Trinh, Yenphuong T.; Zhang, Qinghai; Urbatsch, Ina L.; Chang, Geoffrey; (Scripps); (TTU)

2009-04-22

95

Marine sponge-derived sipholane triterpenoids reverse P-glycoprotein (ABCB1)-mediated multidrug resistance in cancer cells  

PubMed Central

Previously, we reported sipholenol A, a sipholane triterpenoid from the Red Sea sponge Callyspongia siphonella, as a potent reversal of multidrug resistance (MDR) in cancer cells that overexpressed P-glycoprotein (P-gp). Through extensive screening of several related sipholane triterpenoids that have been isolated from the same sponge, we identified sipholenone E, sipholenol L and siphonellinol D as potent reversals of MDR in cancer cells. These compounds enhanced the cytotoxicity of several P-gp substrate anticancer drugs, including colchicine, vinblastine and paclitaxel, and significantly reversed the MDR-phenotype in P-gp-overexpressing MDR cancer cells KB-C2 in a dose-dependent manner. Moreover, these three sipholanes had no effect on the response to cytotoxic agents in cells lacking P-gp expression or expressing MRP1 (ABCC1) or MRP7 (ABCC7) or breast cancer resistance protein (BCRP/ABCG2). All three sipholanes (IC50 >50 ?M) were not toxic to all the cell lines that were used. [3H]-Paclitaxel accumulation and efflux studies demonstrated that all three triterpenoids time-dependently increased the intracellular accumulation of [3H]-paclitaxel by directly inhibiting P-gp-mediated drug efflux. Sipholanes also inhibited calcein-AM transport from P-gp-overexpressing cells. The Western blot analysis revealed that these three triterpenoids did not alter the expression of P-gp. However, they stimulated P-gp ATPase activity in a concentration-dependent manner and inhibited the photolabeling of this transporter with its transport substrate [125I]-iodoarylazidoprazosin. In silico molecular docking aided the virtual identification of ligand binding sites of these compounds. In conclusion, sipholane triterpenoids efficiently inhibit the function of P-gp through direct interactions and may represent potential reversal agents for the treatment of MDR.

Abraham, Ioana; Jain, Sandeep; Wu, Chung-Pu; Khanfar, Mohammad A.; Kuang, Yehong; Dai, Chun-Ling; Shi, Zhi; Chen, Xiang; Fu, Liwu; Ambudkar, Suresh V.; Sayed, Khalid El; Chen, Zhe-Sheng

2010-01-01

96

Characterization of P-glycoprotein Expression as a Multixenobiotic Resistance Mechanism in Fish.  

National Technical Information Service (NTIS)

P-glycoproteins, responsible for multidrug resistance, function as energy dependent efflux flippases that prevent the cellular accumulation of moderately hydrophobic chemicals. We characterized P-gp expression in populations of several fish species expose...

S. M. Bard

2001-01-01

97

Expression of multidrug resistance P-glycoprotein in kidney allografts from cyclosporine A-treated patients  

Microsoft Academic Search

Expression of multidrug resistance P-glycoprotein in kidney allografts from cyclosporine A-treated patients.BackgroundThe multidrug resistance (MDR) gene product P-glycoprotein (P-gp) is a transmembrane efflux pump for hydrophobic, potentially toxic compounds, including the immunosuppressant cyclosporine A (CsA). We have previously shown that CsA increases P-gp expression in proximal tubule and endothelial cells in vitro. The aim of the present study was to

Michael J Koziolek; Regine Riess; Helmut Geiger; Frank Thévenod; Ingeborg A Hauser

2001-01-01

98

P glycoprotein: a new mechanism to control drug-induced nephrotoxicity.  

PubMed

The role of P glycoprotein (P-gp) in kidney is now being explored, and under physiological conditions, this protein is thought to be an excretory pump of cationic xenobiotics and metabolites. Functionally, two different types of P-gp have been described, but only the class I has been related to drug transport, and its overexpression confers the multidrug resistance phenotype in tumoral cells. It has been proposed that P-gp is involved in the energy-dependent transport of substrates through the cell membrane (toxic metabolites, toxins, nutrients, ions, peptides, etc.)--like a 'hydrophobic molecule vacuum cleaner'. Several physiological functions have been attributed to P-gp: defense against xenobiotic aggression and transmembrane transport of prenylcysteine methyl esters, removing these cytotoxic metabolites from cells. A variety of substrates ranging from chemotherapeutics to steroid hormones, antibiotics, and calcium channel blockers can be transported by P-gp, suggesting the possible involvement of this protein in other unknown functions. Results from our group and others have suggested that overexpression of P-gp in renal tubular and mesangial cells prevents pharmacological nephrotoxicity by cyclosporin A (CsA). On the other hand CsA, a substrate of the pump, could act as a blocker in tubular cells by competitive inhibition. One relevant aspect in kidney is the possible relationship between P-gp and protein kinase C. Several reports suggest that protein kinase C may play a role in inducing the P-gp overexpression in cells under xenobiotic pressure, through activation of the ras oncoprotein family. This could be mediated directly by angiotensin II as a ras activator. This way, the detoxicant function of P-gp against products of the ras catabolism could mediate their accumulation when the 'vacuum cleaner' function is blocked by CsA or tacrolimus, contributing to the initial development of fibroblastic activation that leads to interstitial fibrosis associated with nephrotoxicity by these immunosuppressor drugs. In conclusion, P-gp expression could be an important component of a complex detoxifying system in kidney against xenobiotics or regulating the traffic of endogenous metabolites responsible for the susceptibility of subjects to the development of nephrotoxicity against different drugs. PMID:9567214

del Moral, R G; Olmo, A; Aguilar, M; O'Valle, F

99

A Salt Bridge in Intracellular Loop 2 is Essential for Folding of Human P-glycoprotein"  

PubMed

There is no high-resolution structure of the human P-glycoprotein (P-gp; ABCB1) drug pump. Homology models based on the crystal structures of mouse and C. elegans P-gps show extensive contacts between ICL2 (in the first transmembrane domain) and the second nucleotide-binding domain. Human P-gp modeled on these P-gp structures yield different ICL2 structures. Only the model based on the C. elegans P-gp structure predicts the presence of a salt bridge. We show that the Glu256-Arg276 salt bridge was critical for P-gp folding. PMID:23634976

Loo, Tip W; Clarke, David M

2013-05-01

100

Activation of PKC isoform ?I at the blood-brain barrier rapidly decreases P-glycoprotein activity and enhances drug delivery to the brain  

PubMed Central

P-glycoprotein is an ATP (adenosine triphosphate)-driven drug efflux transporter that is highly expressed at the blood–brain barrier (BBB) and is a major obstacle to the pharmacotherapy of central nervous system diseases, including brain tumors, neuro-AIDS, and epilepsy. Previous studies have shown that P-glycoprotein transport activity in rat brain capillaries is rapidly reduced by the proinflammatory cytokine, tumor necrosis factor-? (TNF-?) acting through protein kinase C (PKC)-dependent signaling. In this study, we used isolated rat brain capillaries to show that the TNF-?-induced reduction of P-glycoprotein activity was prevented by a PKC?I/II inhibitor, LY333531, and mimicked by a PKC?I/II activator, 12-deoxyphorbol-13-phenylacetate-20-acetate (dPPA). Western blotting of brain capillary extracts with phospho-specific antibodies showed that dPPA activated PKC?I, but not PKC?II. Moreover, in intact rats, intracarotid infusion of dPPA potently increased brain accumulation of the P-glycoprotein substrate, [3H]-verapamil without compromising tight junction integrity. Thus, PKC?I activation selectively reduced P-glycoprotein activity both in vitro and in vivo. Targeting PKC?I at the BBB may prove to be an effective strategy for enhancing the delivery of small molecule therapeutics to the brain.

Rigor, Robert R; Hawkins, Brian T; Miller, David S

2010-01-01

101

Acetaminophen modulates p-glycoprotein functional expression at the blood-brain barrier by a constitutive androstane receptor-dependent mechanism.  

PubMed

Effective pharmacologic treatment of pain with opioids requires that these drugs attain efficacious concentrations in the central nervous system (CNS). A primary determinant of CNS drug permeation is P-glycoprotein (P-gp), an endogenous blood-brain barrier (BBB) efflux transporter that is involved in brain-to-blood transport of opioid analgesics (i.e., morphine). Recently, the nuclear receptor constitutive androstane receptor (CAR) has been identified as a regulator of P-gp functional expression at the BBB. This is critical to pharmacotherapy of pain/inflammation, as patients are often administered acetaminophen (APAP), a CAR-activating ligand, in conjunction with an opioid. Our objective was to investigate, in vivo, the role of CAR in regulation of P-gp at the BBB. Following APAP treatment, P-gp protein expression was increased up to 1.4-1.6-fold in a concentration-dependent manner. Additionally, APAP increased P-gp transport of BODIPY-verapamil in freshly isolated rat brain capillaries. This APAP-induced increase in P-gp expression and activity was attenuated in the presence of CAR pathway inhibitor okadaic acid or transcriptional inhibitor actinomycin D, suggesting P-gp regulation is CAR-dependent. Furthermore, morphine brain accumulation was enhanced by P-gp inhibitors in APAP-treated animals, suggesting P-gp-mediated transport. A warm-water (50°C) tail-flick assay revealed a significant decrease in morphine analgesia in animals treated with morphine 3 or 6 hours after APAP treatment, as compared with animals treated concurrently. Taken together, our data imply that inclusion of APAP in a pain treatment regimen activates CAR at the BBB and increases P-gp functional expression, a clinically significant drug-drug interaction that modulates opioid analgesic efficacy. PMID:24019224

Slosky, Lauren M; Thompson, Brandon J; Sanchez-Covarrubias, Lucy; Zhang, Yifeng; Laracuente, Mei-Li; Vanderah, Todd W; Ronaldson, Patrick T; Davis, Thomas P

2013-09-09

102

A common P-glycoprotein polymorphism is associated with nortriptyline-induced postural hypotension in patients treated for major depression  

Microsoft Academic Search

The multi-drug resistance gene ABCB1 (or MDR1) encodes a P-glycoprotein (P-gp) that regulates passage of many substances across the blood–brain barrier. The antidepressant amitriptyline and its metabolites (including nortriptyline) are substrates for P-gp, and in mice lacking P-gp, penetration of amitriptyline, but not fluoxetine, into the brain is enhanced. We reasoned that polymorphic variation of P-gp may contribute to differing

R L Roberts; P R Joyce; R T Mulder; E J Begg; M A Kennedy

2002-01-01

103

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

104

Reversion of P-Glycoprotein-Mediated Multidrug Resistance in Human Leukemic Cell Line by Carnosic Acid  

Microsoft Academic Search

One of the common hindrances to successful chemotherapy is the development of multidrug resistance (MDR) by tumor cells to multiple chemotherapeutic agents. In this regard, P-glycoprotein (P- gp) acts as an energized drug pump that reduces the intracellular concentration of drugs, even of structurally unrelated ones. The modulators of P-gp function can restore the sensitivity of MDR cells to anticancer

Xiao-Ning Yu; Xue-Liang Chen; Hao Li; Xiang-Xin Li; Hui-Qing Li; Wen-Rui Jin

2008-01-01

105

Interaction of verapamil with lipid membranes and P-glycoprotein: connecting thermodynamics and membrane structure with functional activity.  

PubMed

Verapamil and amlodipine are calcium ion influx inhibitors of wide clinical use. They are partially charged at neutral pH and exhibit amphiphilic properties. The noncharged species can easily cross the lipid membrane. We have measured with solid-state NMR the structural changes induced by verapamil upon incorporation into phospholipid bilayers and have compared them with earlier data on amlodipine and nimodipine. Verapamil and amlodipine produce a rotation of the phosphocholine headgroup away from the membrane surface and a disordering of the fatty acid chains. We have determined the thermodynamics of verapamil partitioning into neutral and negatively charged membranes with isothermal titration calorimetry. Verapamil undergoes a pK-shift of DeltapK(a) = 1.2 units in neutral lipid membranes and the percentage of the noncharged species increases from 5% to 45%. Verapamil partitioning is increased for negatively charged membranes and the binding isotherms are strongly affected by the salt concentration. The electrostatic screening can be explained with the Gouy-Chapman theory. Using a functional phosphate assay we have measured the affinity of verapamil, amlodipine, and nimodipine for P-glycoprotein, and have calculated the free energy of drug binding from the aqueous phase to the active center of P-glycoprotein in the lipid phase. By combining the latter results with the lipid partitioning data it was possible, for the first time, to determine the true affinity of the three drugs for the P-glycoprotein active center if the reaction takes place exclusively in the lipid matrix. PMID:16877510

Meier, M; Blatter, X Li; Seelig, A; Seelig, J

2006-07-28

106

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

107

Quercetin as a potential modulator of P-glycoprotein expression and function in cells of human pancreatic carcinoma line resistant to daunorubicin.  

PubMed

P-glycoprotein (P-gp) is one of the ABC transporters responsible for the resistance of several tumours to successful chemotherapy. Numerous agents are capable of interfering with the P-gp-mediated export of drugs but unfortunately most of them produce serious side effects. Some plant polyphenols, including the flavonol quercetin (Q), manifest anti-neoplastic activity mainly due to their influence on cell cycle control and apoptosis. Reports are also available which show that Q may intensify action of cytostatic drugs and suppress the multidrug resistance (MDR) phenomenon. The study aimed at determination if Q sensitizes cells resistant to daunorubicin (DB) through its effect on P-gp expression and action. The experiments were conducted on two cell lines of human pancreatic carcinoma, resistant to DB EPP85-181RDB and sensitive EPP85-181P as a comparison. Cells of both lines were exposed to selected concentrations of Q and DB, and then membranous expression of P-gp and its transport function were examined. The influence on expression of gene for P-gp (ABCB1) was also investigated. Results of the studies confirmed that Q affects expression and function of P-gp in a concentration-dependent manner. Moreover it decreased expression of ABCB1. Thus, Q may be considered as a potential modulator of P-gp. PMID:20335952

Borska, Sylwia; Sopel, Miroslaw; Chmielewska, Magdalena; Zabel, Maciej; Dziegiel, Piotr

2010-02-09

108

Protein kinase C-mediated down-regulation of MDR3 mRNA expression in Chang liver cells 1 1 Abbreviations: MDR, multidrug resistance; P-gp, P-glycoprotein; PCR, polymerase chain reaction; PMA, phorbol 12-myristate 13-acetate; 4?-PDD, 4?-phorbol 12,13-didecanoate; and PKC, protein kinase C  

Microsoft Academic Search

MDR3 is a phospholipid translocator homologous to MDR1 P-glycoprotein. MDR3 localizes to the canalicular membrane and contributes to the secretion of bile. To elucidate the role of protein kinase C in the regulation of MDR3 gene expression, we investigated the effect of phorbol 12-myristate 13-acetate (PMA) on the level of MDR3 mRNA in human Chang liver cells by a reverse

Ritsuko Ikeda; Yuhta Shiono; Hisao Hayashi

2001-01-01

109

Sertraline and its metabolite desmethylsertraline, but not bupropion or its three major metabolites, have high affinity for P-glycoprotein.  

PubMed

The ATP-binding cassette (ABC) transporter protein subfamily B1 line (ABCB1) transporter P-glycoprotein (P-gp) plays an important role in the blood-brain barrier limiting a broad spectrum of substrates from entering the central nervous system. In the present study, the transport activity of P-gp for sertraline, desmethylsertraline, bupropion, and the major metabolites of bupropion, threo-amino alcohol (TB), erythro-amino alcohol (EB), and hydroxy metabolite (HB) was studied using an ATPase assay in expressed human P-gp membranes by measuring concentrations of inorganic P(i) in expressed human P-gp membranes. Verapamil was included as a positive control. The Michaelis-Menten equation was used for characterizing the kinetic data. Sertraline and desmethylsertraline showed high affinity for P-gp. The V(max)/K(m) values of sertraline (1.6 min(-1) x 10(-3)) and desmethylsertraline (1.4 min(-1) x 10(-3)) were comparable with that of verapamil (1.7 min(-1) x 10(-3)). Bupropion and its three metabolites showed very weak affinity for P-gp, with V(max)/K(m) values lower than 0.01 min(-1) x 10(-3). The results of the present study indicate that sertraline and desmethylsertraline have high affinity for P-gp, whereas bupropion and its three major metabolites TB, EB, and HB have very weak affinity for P-gp. These findings may help to explain observed drug-drug interactions among antidepressants. PMID:18239278

Wang, Jun-Sheng; Zhu, Hao-Jie; Gibson, Bryan Bradford; Markowitz, John Seth; Donovan, Jennifer Lyn; DeVane, Carl Lindsay

2008-02-01

110

Interaction of CJY, an Isoflavone, with ATPase of P-glycoprotein in Doxorubicin-resistant Human Myelogenous Leukemia (K562/DOX) Cells.  

PubMed

The previous study reported CJY, an isoflavone, can reverse P-glycoprotein (P-gp)-mediated multidrug-resistance (MDR) in doxorubicin-resistant human myelogenous leukemia (K562/DOX) cells. This study will investigate the exact mechanism of CJY on P-gp.By assessment of ATPase activity, we gained further insight into the nature of the CJY interactions with P-gp. Kinetic studies on ATPase activity were applied to show the effects of Verapamil (Ver) on CJY-stimulated, CJX1 on Ver-stimulated, and CJX1 on CJY-stimulated P-gp ATPase activity. Furthermore, the combined effects of CJY with Ver, and CJY with CJX1 were also evaluated isobolographically in numerous fixed-ratio combinations of 1:1, 1:2, 1:4, 1:8, and 1:10.The results showed that basal P-gp ATPase activity was increased by CJY with half-maximal activity concentration (Km) of 2.9±0.3 ?M and the maximal ATPase activity velocity (Vmax) of 265±21 nM · min-1 · mg-1. Kinetic studies on ATPase activity showed the effects of Verapamil (Ver) on CJY-stimulated, CJX1 on Ver-stimulated, and CJX1 on CJY-stimulated P-gp ATPase activity were all non-competitive inhibition, indicating that these substrates can simultaneously but independently bind to diverse sites on P-gp. The combined effects of CJY with Ver, and CJY with CJX1 show that mixtures of both drugs at these fixed-ratios displayed synergistic interactions.CJY, CJX1 and Ver bind P-gp on different sites. CJY could be applied combining with other P-gp inhibitors to get better reversal of multidrug resistance than it used alone. PMID:23720244

Cen, J; Liu, L; He, L; Ji, B-S

2013-05-29

111

Relationship between P-glycoprotein and second-generation antipsychotics.  

PubMed

The membrane transport protein P-glycoprotein (P-gp) is an interesting candidate for individual differences in response to antipsychotics. To present an overview of the current knowledge of P-gp and its interaction with second-generation antipsychotics (SGAs), an internet search for all relevant English original research articles concerning P-gp and SGAs was conducted. Several SGAs are substrates for P-gp in therapeutic concentrations. These include amisulpride, aripiprazole, olanzapine, perospirone, risperidone and paliperidone. Clozapine and quetiapine are not likely to be substrates of P-gp. However, most antipsychotics act as inhibitors of P-gp, and can therefore influence plasma and brain concentrations of other substrates. No information was available for sertindole, ziprasidone or zotepine. Research in animal models demonstrated significant differences in antipsychotic brain concentration and behavior owing to both P-gp knockout and inhibition. Results in patients are less clear, as several external factors have to be accounted for. Patients with polymorphisms which decrease P-gp functionality tend to perform better in clinical settings. There is some variability in the findings concerning adverse effects, and no definitive conclusions can be drawn at this point. PMID:21843066

Moons, Tim; de Roo, Mariska; Claes, Stephan; Dom, Geert

2011-08-01

112

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

2006-01-26

113

Limited Oral Bioavailability and Active Epithelial Excretion of Paclitaxel (Taxol) Caused by P-glycoprotein in the Intestine  

Microsoft Academic Search

In mice, the mdr1a and mdr1b genes encode drug-transporting proteins that can cause multidrug resistance in tumor cells by lowering intracellular drug levels. These P-glycoproteins are also found in various normal tissues such as the intestine. Because mdr1b P-glycoprotein is not detectable in the intestine, mice with a homozygously disrupted mdr1a gene [mdr1a(-\\/-) mice] do not contain functional P-glycoprotein in

Alex Sparreboom; Judith van Asperen; Ulrich Mayer; Alfred H. Schinkel; Johan W. Smit; Dirk K. F. Meijer; Piet Borst; Willem J. Nooijen; Jos H. Beijnen; Olaf van Tellingen

1997-01-01

114

Prediction of Promiscuous P-Glycoprotein Inhibition Using a Novel Machine Learning Scheme  

PubMed Central

Background P-glycoprotein (P-gp) is an ATP-dependent membrane transporter that plays a pivotal role in eliminating xenobiotics by active extrusion of xenobiotics from the cell. Multidrug resistance (MDR) is highly associated with the over-expression of P-gp by cells, resulting in increased efflux of chemotherapeutical agents and reduction of intracellular drug accumulation. It is of clinical importance to develop a P-gp inhibition predictive model in the process of drug discovery and development. Methodology/Principal Findings An in silico model was derived to predict the inhibition of P-gp using the newly invented pharmacophore ensemble/support vector machine (PhE/SVM) scheme based on the data compiled from the literature. The predictions by the PhE/SVM model were found to be in good agreement with the observed values for those structurally diverse molecules in the training set (n?=?31, r2?=?0.89, q2?=?0.86, RMSE?=?0.40, s?=?0.28), the test set (n?=?88, r2?=?0.87, RMSE?=?0.39, s?=?0.25) and the outlier set (n?=?11, r2?=?0.96, RMSE?=?0.10, s?=?0.05). The generated PhE/SVM model also showed high accuracy when subjected to those validation criteria generally adopted to gauge the predictivity of a theoretical model. Conclusions/Significance This accurate, fast and robust PhE/SVM model that can take into account the promiscuous nature of P-gp can be applied to predict the P-gp inhibition of structurally diverse compounds that otherwise cannot be done by any other methods in a high-throughput fashion to facilitate drug discovery and development by designing drug candidates with better metabolism profile.

Leong, Max K.; Chen, Hong-Bin; Shih, Yu-Hsuan

2012-01-01

115

A role for P-glycoprotein in environmental toxicology.  

PubMed

P-Glycoprotein (P-gp) is a transmembrane protein, playing significant roles in the process of drug discovery and development and in pest resistance to pesticides. P-gp affects absorption, disposition, and elimination of different compounds and is mainly expressed in intestines, liver, kidneys, heart, colon, and placenta. The expression of P-gp in the blood-brain barrier (BBB) has been associated with the restricted access of many compounds to the central nervous system. Generated knockout mice by disruption of mdr 1a gene, encoding for P-gp, showed that this protein was expressed in the BBB. The absence or the low levels of P-gp elevated drug concentrations in tissues and decreased drug elimination. P-gp is responsible for resistance of cells to agents, particularly the anticancer drugs, by removing these drugs from cells. Increased expression of P-gp is implicated in decreased HIV drug availability at certain intracellular sites. The role of P-gp in affecting efficacy and toxicity of environmental toxicants such as pesticides and heavy metals has not been adequately investigated. Studies showed that P-gp contributes to resistance to pesticides in certain pest species, and to decrease toxicity by removing compounds from cells in mammals. Placental drug-transporting P-gp plays a significant role in limiting the transport of toxicants such as potential teratogens to the fetus. Several in vitro or in vivo assays, including using P-gp knockout or naturally deficient mice, were described for testing P-gp modulators. The role of P-gp following concurrent exposure to more multiple compounds needs further research. P-gp modulators should be carefully used, since some modulators that reverse P-gp efflux action in vitro may lead to alterations of tissue function and increase toxicity of xenobiotics in normal tissues. Recent reports from the pharmaceutical studies on the significance of P-gp as transporters in altering the efficacy and toxicity clearly highlight the need for further research in interaction with environmental toxicants. PMID:12746142

Abu-Qare, Aqel W; Elmasry, Eman; Abou-Donia, Mohamed B

116

[11C]sorafenib: radiosynthesis and preliminary PET study of brain uptake in P-gp/Bcrp knockout mice.  

PubMed

Sorafenib (Nexavar, BAY43-9006, 1) is a second-generation, orally active multikinase inhibitor that is approved for the treatment of some cancers in patients. In this Letter, we developed [(11)C]1 as a novel positron emission tomography (PET) probe, and evaluated the influence of ABC transporters-mediated efflux on brain uptake using PET with [(11)C]1 in P-glycoprotein (P-gp)/breast cancer resistance protein (Bcrp) knockout mice versus wild-type mice. [(11)C]1 was synthesized by the reaction of hydrochloride of aniline 2 with [(11)C]phosgene ([(11)C]COCl(2)) to give isocyanate [(11)C]6, followed by reaction with another aniline 3. Small-animal PET study with [(11)C]1 indicated that the radioactivity level (AUC(0-60 min), SUV×min) in the brains of P-gp/Bcrp knockout mice was about three times higher than in wild-type mice. PMID:21419625

Asakawa, Chiharu; Ogawa, Masanao; Kumata, Katsushi; Fujinaga, Masayuki; Kato, Koichi; Yamasaki, Tomoteru; Yui, Joji; Kawamura, Kazunori; Hatori, Akiko; Fukumura, Toshimitsu; Zhang, Ming-Rong

2011-03-06

117

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

PubMed

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. PMID:24058883

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

2013-09-12

118

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

119

Inhibition of P-glycoprotein enhances transport of imipramine across the blood-brain barrier: microdialysis studies in conscious freely moving rats  

PubMed Central

BACKGROUND AND PURPOSE Recent studies indicate that efflux of antidepressants by the multidrug resistance transporter P-glycoprotein (P-gp) at the blood–brain barrier (BBB) may contribute to treatment-resistant depression (TRD) by limiting intracerebral antidepressant concentrations. In addition, clinical experience shows that adjunctive treatment with the P-gp inhibitor verapamil may improve the clinical outcome in TRD. Therefore, the present study aimed to investigate the effect of P-gp inhibition on the transport of the tricyclic antidepressant imipramine and its active metabolite desipramine across the BBB. EXPERIMENTAL APPROACH Intracerebral microdialysis in rats was used to monitor brain levels of imipramine and desipramine following i.v. imipramine administration, with or without pretreatment with one of the P-gp inhibitors verapamil or cyclosporin A (CsA). Plasma drug levels were also determined at regular intervals. KEY RESULTS Pretreatment with either verapamil or CsA resulted in significant increases in imipramine concentrations in the microdialysis samples, without altering imipramine plasma pharmacokinetics. Furthermore, pretreatment with verapamil, but not CsA, led to a significant elevation in plasma and brain levels of desipramine. CONCLUSIONS AND IMPLICATIONS The present study demonstrated that P-gp inhibition enhanced the intracerebral concentration of imipramine, thus supporting the hypothesis that P-gp activity restricts brain levels of certain antidepressants, including imipramine. These findings may help to explain reports of a beneficial response to adjunctive therapy with verapamil in TRD.

O'Brien, FE; Clarke, G; Fitzgerald, P; Dinan, TG; Griffin, BT; Cryan, JF

2012-01-01

120

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

121

Michaelis-Menten kinetic analysis of drugs of abuse to estimate their affinity to human P-glycoprotein.  

PubMed

The pharmacokinetics of various important drugs are known to be significantly influenced by the human ABC transporter P-glycoprotein (P-gp), which may lead to clinically relevant drug-drug interactions. In contrast to therapeutic drugs, emerging drugs of abuse (DOA) are sold and consumed without any safety pharmacology testing. Only some studies on their metabolism were published, but none about their affinity to the transporter systems. Therefore, 47 DOAs from various classes were tested for their P-gp affinity using human P-gp (hP-gp) to predict possible drug-drug interactions. DOAs were initially screened for general hP-gp affinity and further characterized by modeling classic Michaelis-Menten kinetics and assessing their K(m) and V(max) values. Among the tested drugs, 12 showed a stimulation of ATPase activity. The most intensive stimulating DOAs were further investigated and compared with the known P-gp model substrates sertraline and verapamil. ATPase stimulation kinetics could be modeled for the entactogen 3,4-methylenedioxy-?-ethylphenethylamine (3,4-BDB), the hallucinogen 2,5-dimethoxy-4-iodoamphetamine (DOI), the abused alkaloid glaucine, the opioid-like drugs N-iso-propyl-1,2-diphenylethylamine (NPDPA), and N-(1-phenylcyclohexyl)-3-ethoxypropanamine (PCEPA), with K(m) and V(max) values within the same range as for verapamil or sertraline. As a consequence interactions with other drugs being P-gp substrates might be considered to be very likely and further studies should be encouraged. PMID:23273999

Meyer, Markus R; Orschiedt, Tina; Maurer, Hans H

2012-12-27

122

Inhibition of P-glycoprotein functionality by vandetanib may reverse cancer cell resistance to doxorubicin.  

PubMed

P-glycoprotein belongs to the ATP binding cassette transporters, responsible for the multidrug resistance of cancer cells. These transporters efflux hydrophobic drugs outside cells and decrease their therapeutic efficacy. The aim of this study was to investigate the effect of vandetanib, an oral tyrosine kinase inhibitor of EGFR, VEGFR 2 and RET kinases, on the functionality of P-gp after a 24h-treatment at therapeutic concentration (2?M), and its ability to increase the cytotoxicity of chemotherapeutic agents in multidrug resistance cancer cells. In this study we found that IGROV1-DXR and IGROV1-CDDP cells were resistant to doxorubicin and cisplatin respectively, compare to parental cell line IGROV1. The parental sensitive and the two resistant cell lines similarly expressed MRP1 and did not express BCRP. Moreover, in contrast to the IGROV1 and IGROV1-CDDP cells, IGROV1-DXR cell line overexpressed P-gp. Functional activity studies demonstrated that MRP1 was not functional and the MDR phenotype in IGROV1-DXR cells was linked to P-gp functionality. Results also showed that vandetanib reversed resistance to doxorubicin in IGROV1-DXR cells, but not to cisplatin in IGROV1-CDDP cells. After 24h of treatment, vandetanib increased the accumulation of rhodamine 123 and calcein AM, demonstrating a functional inhibition of the transporter. In IGROV1-DXR cell line, vandetanib reverse resistance to doxorubicin by inhibiting the functionality of P-gp. In conclusion, vandetanib should be an option for drug combination in patients already developing a P-gp mediated multidrug resistance. PMID:22484209

Jovelet, C; Bénard, J; Forestier, F; Farinotti, R; Bidart, J M; Gil, S

2012-03-30

123

Toward Eradicating HIV Reservoirs in the Brain: Inhibiting P-glycoprotein at the Blood-Brain Barrier with Prodrug Abacavir Dimers  

PubMed Central

Eradication of HIV reservoirs in the brain necessitates penetration of antiviral agents across the blood-brain barrier (BBB), a process limited by drug efflux proteins such as P-glycoprotein (P-gp) at the membrane of brain capillary endothelial cells. We present an innovative chemical strategy toward the goal of therapeutic brain penetration of the P-gp substrate and anti-viral agent abacavir, in conjunction with a traceless tether. Dimeric prodrugs of abacavir were designed to have two functions: inhibit P-gp efflux at the BBB and revert to monomeric therapeutic within cellular reducing environments. The prodrug dimers are potent P-gp inhibitors in cell culture and in a brain capillary model of the BBB. Significantly, these agents demonstrate anti-HIV activity in two T-cell-based HIV assays, a result that is linked to cellular reversion of the prodrug to abacavir. This strategy represents a platform technology that may be applied to other therapies with limited brain penetration due to P-glycoprotein.

Namanja, Hilda A.; Emmert, Dana; Davis, David A.; Campos, Christopher; Miller, David S.; Hrycyna, Christine A.; Chmielewski, Jean

2011-01-01

124

Advances in PET imaging of P-glycoprotein function at the blood-brain barrier.  

PubMed

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. PMID:23421673

Syvänen, Stina; Eriksson, Jonas

2012-12-04

125

N-desmethyl-Loperamide Is Selective for P-Glycoprotein among Three ATP-Binding Cassette Transporters at the Blood-Brain Barrier  

PubMed Central

[11C]N-desmethyl-Loperamide ([11C]dLop) is used in positron emission tomography (PET) to measure the in vivo activity of efflux transporters that block the passage of drugs across the blood-brain barrier. The three most prevalent ATP-binding cassette efflux transporters at the blood-brain barrier are P-glycoprotein (P-gp), multidrug resistance protein 1 (Mrp1), and breast cancer resistance protein (BCRP). We sought to measure the selectivity of dLop among these three transporters. The selectivity of dLop at low concentrations (?1 nM) was measured both as the accumulation of [3H]dLop in human cells that overexpress each transporter and as the uptake of [11C]dLop in brains of mice that lack genes encoding P-gp, Mrp1, or BCRP. The selectivity of dLop at high concentrations (?20 ?M) was measured as the inhibition of uptake of a fluorescent substrate and the change in cytotoxicity of drugs effluxed at each transporter. Accumulation of [3H]dLop was lowest in cells overexpressing P-gp, and the uptake of [11C]dLop was highest in brains of mice lacking P-gp. At high concentrations, dLop selectively inhibited P-gp function and also decreased the resistance of only the P-gp-expressing cells to cytotoxic agents. dLop is selective for P-gp among these three transporters, but its activity is dependent on concentration. At low concentrations (?1 nM), dLop acts only as a substrate; at high concentrations (?20 ?M), it acts as both a substrate and an inhibitor (i.e., a competitive substrate). Because low concentrations of radiotracer are used for PET imaging, [11C]dLop acts selectively and only as a substrate for P-gp.

Kannan, Pavitra; Brimacombe, Kyle R.; Zoghbi, Sami S.; Liow, Jeih-San; Morse, Cheryl; Taku, Andrew K.; Pike, Victor W.; Halldin, Christer; Gottesman, Michael M.; Hall, Matthew D.

2010-01-01

126

In vitro study of P-glycoprotein induction as an antidotal pathway to prevent cytotoxicity in Caco-2 cells  

Microsoft Academic Search

The Caco-2 cell line is a reliable in vitro model for predicting drug intestinal absorption and P-glycoprotein (P-gp)-mediated\\u000a excretion in humans. Recent in vivo studies suggested the induction of P-gp as a cellular protection tool against paraquat\\u000a poisoning, through the increase in its pulmonary and intestinal excretion. Thus, the aim of the present work was to evaluate\\u000a P-gp expression and

Renata Silva; Helena Carmo; Ricardo Dinis-Oliveira; Anabela Cordeiro-da-Silva; Sofia Costa Lima; Félix Carvalho; Maria de Lourdes Bastos; Fernando Remião

2011-01-01

127

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

128

Zosuquidar, a novel modulator of P-glycoprotein, does not improve the outcome of older patients with newly diagnosed acute myeloid leukemia: a randomized, placebo-controlled trial of the Eastern Cooperative Oncology Group 3999  

PubMed Central

Zosuquidar, which modulates P-glycoprotein (P-gp) with minimal delay of anthracycline clearance, may reverse P-gp–mediated resistance in acute myeloid leukemia without increased toxicity. A total of 449 adults older than 60 years with acute myeloid leukemia or high-risk myelodysplastic syndrome enrolled in a randomized placebo-controlled double-blind trial (Eastern Cooperative Oncology Group 3999). Overall survival was compared between patients receiving conventional-dose cytarabine and daunorubicin and either zosuquidar (550 mg; 212 patients) or placebo (221 patients). Median and 2-year overall survival values were 7.2 months and 20% on zosuquidar and 9.4 months and 23% on placebo, respectively (P = .281). Remission rate was 51.9% on zosuquidar and 48.9% on placebo. All cause mortality to day 42 was not different (zosuquidar 22.2% vs placebo 16.3%; P = .158). In vitro modulation of P-gp activity by zosuquidar and expression of P-gp, multidrug resistance-related protein 1, lung resistance protein, and breast cancer resistance protein, were comparable in the 2 arms. Poor-risk cytogenetics were more common in P-gp+ patients. P-gp expression and cytogenetics were correlated, though independent prognostic factors. We conclude that zosuquidar did not improve outcome in older acute myeloid leukemia, in part, because of the presence P-gp independent mechanisms of resistance. This trial is registered at www.clinicaltrials.gov as #NCT00046930.

Uno, Hajime; Paietta, Elisabeth M.; Litzow, Mark R.; Ketterling, Rhett P.; Bennett, John M.; Rowe, Jacob M.; Lazarus, Hillard M.; Luger, Selina; Tallman, Martin S.

2010-01-01

129

Evaluation of the Near Infrared Compound Indocyanine Green as a Probe Substrate of P-Glycoprotein.  

PubMed

The efflux transporter P-glycoprotein (P-gp) affects the pharmacokinetics of many drugs. Currently used methods for characterization of P-gp's functional activity in vivo involve the use of radiolabeled substrates, are costly, and are technically demanding. Our objective was to evaluate whether the FDA-approved near-infrared compound indocyanine green (ICG) can be used as a probe substrate of P-gp. We also characterized the interaction of ICG with another efflux transporter, the breast cancer resistance protein (BCRP). We evaluated ICG accumulation and transport in MDCK cells overexpressing P-gp or BCRP (MDCK-MDR1 and MDCK-BCRP, respectively) compared to control MDCK cells, in the presence or the absence of transporter inhibitors. In vivo imaging of ICG biodistribution in mice was conducted over 3.5 h using valspodar as the P-gp inhibitor. The EC(50) values for ICG accumulation in control MDCK and MDCK-MDR1 cells were 9.0 × 10(-6) ± 5.7 × 10(-7) M and 1.5 × 10(-5) ± 1.1 × 10(-6) M, respectively. The efflux ratio for ICG in MDCK-MDR1 cells was 6.8-fold greater than in control cells. P-gp inhibition attenuated ICG efflux from MDR1-MDCK cells, and their effects in those cells were greater than in control MDCK cells. In contrast, BCRP level of expression or pharmacological inhibition did not significantly affect ICG cellular accumulation. In vivo imaging indicated enhanced cerebral ICG distribution with valspodar (brain - foot area under the concentration-time curves of 3.0 × 10(10), 5.6 × 10(10) and 3.7 × 10(10) h·[p/s/sr]/?W in valspodar-treated mice vs 9.0 × 10(9) and 5.3 × 10(9) h·[p/s/sr]/?W in controls). The findings from this pilot study suggest that near-infrared imaging using ICG as the probe substrate should be further characterized as a methodology for in vivo evaluation of P-gp activity. PMID:23098218

Portnoy, Emma; Gurina, Marina; Magdassi, Shlomo; Eyal, Sara

2012-11-12

130

Enhanced daunomycin accumulation in human intestinal Caco-2 cells from non-ionic food emulsifiers unrelated to the p-glycoprotein inhibitory mechanism.  

PubMed

Some of the non-ionic surfactants used in pharmaceutical formulations inhibit P-glycoprotein (P-gp), the multi-drug transporter. The effect of such food emulsifiers as polyglycerol esters (PGE) and sugar esters (SE) of fatty acids on the P-gp activity was studied by using human intestinal Caco-2 cells. The cellular accumulation of [(3)H]-daunomycin, a P-gp substrate, was markedly enhanced by PGE and SE. This accumulation-enhancing activity varied among the emulsifiers, but was correlated with their surface activity. The uptake of soluble nutrients such as amino acids was only slightly reduced by PGE and SE. These results suggest that these emulsifiers specifically inhibited P-gp. When the basal-to-apical transport of daunomycin across the Caco-2 monolayers was measured, however, the emulsifiers did not decrease the efflux of daunomycin to the apical chamber. The enhanced accumulation of daunomycin would therefore not have been due to P-gp inhibition, but instead to the increased daunomycin permeability of cell membranes caused by the emulsifiers. PMID:17090932

Takaishi, Naoki; Satsu, Hideo; Shimizu, Makoto

2006-11-07

131

Polycationic nanodrug covered with hyaluronic acid for treatment of P-glycoprotein overexpressing cancer cells.  

PubMed

To treat cancer cells overexpressing P-glycoprotein (P-gp), we propose a new concept using a nanodrug. The nanodrug was prepared from polyethyleneimine (PEI)/all-trans retinoic acid (ATRA) conjugates (PRA) and covered with hyaluronic acid (HA) to control the cytotoxicity of PRA (yielding PRA-H). The size distribution of PRA-H was narrow, with an average particle size of approximately 143 nm. Its superior stability in phosphate-buffered saline (PBS) was verified by monitoring changes in particle size and zeta potential for 24 h, which were negligible. In contrast, PEI-H (not conjugated with ATRA) exhibited a significant change in particle size and zeta potential. Although PRA was highly cytotoxic against HCT-8 and SNU-484 cancer cells, both of which overexpress P-gp, the cytotoxicity was significantly reduced by shielding with HA. The cytotoxicity of PRA-H was recovered by treatment with hyaluronidase (HAase), which degrades HA and is present in tumors at high concentrations. These results were confirmed by optical microscopy, fluorescence-activated cell sorting (FACs) analysis, and confocal microscopy. The cytotoxic mechanism of PRA was revealed as a type of necrotic lysis by FACs analysis with propidium iodide (PI) staining. Furthermore, PRA increased HCT-8 cell (colon cancer) permeability to doxorubicin (DOX). Therefore, we concluded that PRA-H is a promising new candidate for the treatment of cells with multidrug resistance (MDR) induced by overexpression of P-gp and cancer stem cells. PMID:20687538

Yim, Hyeona; Na, Kun

2010-09-13

132

Modulation of P-glycoprotein function by amlodipine derivatives in brain microvessel endothelial cells of rats  

Microsoft Academic Search

Aim:To investigate whether the amlodipine derivatives, CJX1 and CJX2, have a modulative effect on P-glycoprotein (P-gp) function in rat brain microvessel endothelial cells (RBMEC).Methods:Isolated RBMEC were cultured in DMEM\\/F12 (1:1) medium. The amount of intracellular rhodamine (Rh123) was determined, using a fluorescence spectrophotometer, to evaluate the function of P-gp.Results:The accumulation of Rh123 in RBMEC was potentiated in a concentration dependent

Bian-sheng Ji; Ling He; Guo-qing Liu

2005-01-01

133

Altered intestinal P-glycoprotein expression levels in a monosodium glutamate-induced obese mouse model  

Microsoft Academic Search

AimsP-glycoprotein (P-gp) is an important drug efflux transporter located in many tissues such as the blood–brain barrier, intestines, liver and kidneys. We have previously reported that ileal P-gp expression levels decrease via a nitric oxide synthase (NOS)-mediated pathway in a streptozotocin (STZ)-induced type 1 diabetic mouse model. Herein, our objective was to assess whether there are differences in the expression

Ayaka Nawa; Wakako Fujita-Hamabe; Shogo Tokuyama

134

Modulation of vinca-alkaloid induced P-glycoprotein expression by indole-3-carbinol  

Microsoft Academic Search

The over-expression of mdr-1 gene transcript P-glycoprotein (P-gp), responsible for multiple drug resistance, is one of the major obstacles in cancer chemotherapy. In the present study, indole-3-carbinol (I3C), a well-known chemopreventive agent present in cruciferous vegetables, has been evaluated for its potential to modulate the over-expression of P-gp induced by vinblastine or vincristine, which are known inducers of mdr-1 gene.

Annu Arora; Yogeshwer Shukla

2003-01-01

135

Altered brain concentrations of citalopram and escitalopram in P-glycoprotein deficient mice after acute and chronic treatment.  

PubMed

According to both in vitro and in vivo data P-glycoprotein (P-gp) may restrict the uptake of several antidepressants into the brain, thus contributing to the poor success rate of current antidepressant therapies. The therapeutic activity of citalopram resides in the S-enantiomer, whereas the R-enantiomer is practically devoid of serotonin reuptake potency. To date, no in vivo data are available that address whether the enantiomers of citalopram and its metabolites are substrates of P-gp. P-gp knockout (abcb1ab (-/-)) and wild-type (abcb1ab (+/+)) mice underwent acute (single-dose) and chronic (two daily doses for 10 days) treatment with citalopram (10mg/kg) or escitalopram (5mg/kg) Serum and brain samples were collected 1-6h after the first or last i.p. injection for subsequent drug analysis by an enantioselective HPLC method. In brain, 3-fold higher concentrations of S- and R-citalopram, and its metabolites, were found in abcb1ab (-/-) mice than in abcb1ab (+/+) mice after both acute and chronic citalopram treatments. After escitalopram treatment, the S-citalopram brain concentration was 3-5 times higher in the knockout mice than in controls. The results provide novel evidence that the enantiomers of citalopram are substrates of P-gp. Possible clinical and toxicological implications of this finding need to be further elucidated. PMID:23428338

Karlsson, Louise; Carlsson, Björn; Hiemke, Christoph; Ahlner, Johan; Bengtsson, Finn; Schmitt, Ulrich; Kugelberg, Fredrik C

2013-02-18

136

Can P-glycoprotein mediate resistance to nilotinib in human leukaemia cells?  

PubMed

The effect of P-glycoprotein (P-gp, ABCB1, MDR1) expression on cell resistance to nilotinib was studied in human leukaemia cells. We used K562/Dox cells overexpressing P-gp and their variants (subclones) with a gradually decreased P-gp expression. These subclones were established by stable transfection of K562/Dox cells with a plasmid vector expressing shRNA targeting the ABCB1 gene. Functional analysis of P-gp using a specific fluorescent probe indicated gradually decreased dye efflux which was proportional to the P-gp expression. We observed that K562/Dox cells overexpressing P-gp contained a significantly reduced intracellular level of nilotinib when compared to their counter partner K562 cells, which do not express P-gp. This effect was accompanied by a decreased sensitivity of the K562/Dox cells to nilotinib. Importantly, cells with downregulated expression of P-gp gradually lost their ability to decrease the intracellular level of nilotinib although they still significantly decreased the intracellular level of daunorubicin (DNR). Accordingly, cells with the reduced expression of P-gp concomitantly failed to provide resistance to nilotinib, however, they exhibited a significant resistance to DNR. Taken together, we demonstrated that the conclusion as to whether P-gp is involved in nilotinib resistance or not strongly depends on its expression at protein level. PMID:23103446

Kosztyu, Petr; Dolezel, Petr; Mlejnek, Petr

2012-10-26

137

In vivo evaluation of an oral delivery system for P-gp substrates based on thiolated chitosan  

Microsoft Academic Search

Recently, thiolated polymers, so called thiomers, have been reported to modulate drug absorption by inhibition of intestinal P-glycoprotein (P-gp). The aim of the present study was to provide a proof-of-principle for a delivery system based on thiolated chitosan in vivo in rats, using rhodamine-123 (Rho-123) as representative P-gp substrate. In vitro, the permeation enhancing effect of unmodified chitosan, chitosan-4 thiobutylamidine

Florian Föger; Thierry Schmitz; Andreas Bernkop-Schnürch

2006-01-01

138

Is Ciprofloxacin a Substrate of P-glycoprotein?  

PubMed Central

Introduction Studies using MDCKII and LLC-PK1 cells transfected with MDR1 cDNA indicate that ciprofloxacin is not a substrate of P-glycoprotein. However, our data has shown that transport studies done using different P-gp overexpressing cell lines (MDCKI-MDR1, MDCKII-MDR1 and L-MDR1), could lead to contradictory conclusion on whether a compound is a substrate of P-gp. The aim of our study was to determine if ciprofloxacin is indeed not a P-glycoprotein substrate using MDCKI cells transfected with human MDR1 cDNA. Methods Semi-quantitative RT-PCR was used to determine the mRNA level of MDR1 while Western blot was performed to determine the protein expression level of P-gp, MRP1 and MRP2 in various cells. Ciprofloxacin bidirectional transport studies were performed in MDCKI, MDCKI-MDR1, MDCKII, MDCKII-MDR1, MDCKII-MRP2, LLC-PK1, L-MRP1 and L-MDR1 cells. Results Ciprofloxacin showed net secretion in MDCKI-MDR1 but net absorption in MDCKI cells. Various P-gp inhibitors decreased the B to A and increased the A to B transport of ciprofloxacin in MDCKI-MDR1 cells while having no effect in MDCKI cells. The B to A transport of ciprofloxacin in MDCKI-MDR1 cells was not affected by non-P-gp inhibitors. In the presence of indomethacin, ciprofloxacin showed net secretion instead of net absorption in MDCKI cells while in the presence of probenecid and sulfinpyrazone, there was no net secretion and absorption. There was no difference in ciprofloxacin transport between MDCKII and MDCKII-MDR1, LLC-PK1 and L-MDR1, LLC-PK1 and L-MRP1 and MDCKII and MDCKII-MRP2. Conclusions Transport data in MDCKI and MDCKI-MDR1 cells indicate that ciprofloxacin is a substrate of P-gp but data from MDCKII, MDCKII-MDR1, LLC-PK1 and L-MDR1 cells indicate that ciprofloxacin is not a substrate of P-gp. Vinblastine, a well-known P-gp substrate, also did not show differences between LLC-PK1 and L-MDR1 cells. Further studies need to be performed to characterize these P-gp overexpressing cell lines and the transport of ciprofloxacin.

Park, Miki Susanto; Okochi, Hideaki; Benet, Leslie Z

2011-01-01

139

Limited oral bioavailability and active epithelial excretion of paclitaxel (Taxol) caused by P-glycoprotein in the intestine  

PubMed Central

In mice, the mdr1a and mdr1b genes encode drug-transporting proteins that can cause multidrug resistance in tumor cells by lowering intracellular drug levels. These P-glycoproteins are also found in various normal tissues such as the intestine. Because mdr1b P-glycoprotein is not detectable in the intestine, mice with a homozygously disrupted mdr1a gene [mdr1a(?/?) mice] do not contain functional P-glycoprotein in this organ. We have used these mdr1a(?/?) mice to study the effect of gut P-glycoprotein on the pharmacokinetics of paclitaxel. The area under the plasma concentration-time curves was 2- and 6-fold higher in mdr1a(?/?) mice than in wild-type (wt) mice after i.v. and oral drug administration, respectively. Consequently, the oral bioavailability in mice receiving 10 mg paclitaxel per kg body weight increased from only 11% in wt mice to 35% in mdr1a(?/?) mice. The cumulative fecal excretion (0–96 hr) was markedly reduced from 40% (after i.v. administration) and 87% (after oral administration) of the administered dose in wt mice to below 3% in mdr1a(?/?) mice. Biliary excretion was not significantly different in wt and mdr1a(?/?) mice. Interestingly, after i.v. drug administration of paclitaxel (10 mg/kg) to mice with a cannulated gall bladder, 11% of the dose was recovered within 90 min in the intestinal contents of wt mice vs. <3% in mdr1a(?/?) mice. We conclude that P-glycoprotein limits the oral uptake of paclitaxel and mediates direct excretion of the drug from the systemic circulation into the intestinal lumen.

Sparreboom, Alex; van Asperen, Judith; Mayer, Ulrich; Schinkel, Alfred H.; Smit, Johan W.; Meijer, Dirk K. F.; Borst, Piet; Nooijen, Willem J.; Beijnen, Jos H.; van Tellingen, Olaf

1997-01-01

140

Characterization of Cyclosporin A Transport in Cultured Rabbit Corneal Epithelial Cells: P-Glycoprotein Transport Activity and Binding to Cyclophilin  

Microsoft Academic Search

PURPOSE. The purpose of this study was to characterize cyclosporin A (CsA) uptake and transport in cultured rabbit corneal epithelial cells (RCECs) . METHODS. CsA uptake was evaluated by measuring time-dependent 3H-CsA accumulation in con- fluent RCECs. Bidirectional 3H-CsA fluxes were measured across the RCEC layers grown on Transwell-COL culture plate inserts. The anti-P-gp monoclonal antibody C219 was used in

Kouichi Kawazu; Kazuhito Yamada; Masatsugu Nakamura; Atsutoshi Ota

141

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

142

Inducibility of the P-glycoprotein transport activity in the marine mussel Mytilus galloprovincialis and the freshwater mussel Dreissena polymorpha.  

PubMed

Previous investigations directed to the determination of the P-glycoprotein (Pgp) expression in aquatic organisms have indicated the possibility of the multixenobiotic resistance mechanism (MXR) induction as a response to organic pollution. However, in numerous cases no significant and/or no clear relationship between Pgp contents and pollution level was detected. Concerning these discrepancies the results of an extensive, 3-year study of the Pgp mediated MXR induction in the selected freshwater (Dreissena polymorpha) and marine (Mytilus galloprovincialis) bivalves are presented here. The main goals of the study were to ascertain the rate-dynamic, level, as well as the possible usability of MXR in environmental biomonitoring. Since the primary result of MXR induction should be the decreased intracellular accumulation of xenobiotics, the determination of MXR induction was performed using the measurement of Pgp transport activity. We measured the accumulation or the efflux rate of the model Pgp substrate rhodamine B (RB) in gills of the mussels previously exposed to pollution. The study was performed in several steps: from the exposure experiments in laboratory, using model inducers rhodamine 123 (R123) and water extract of Diesel-2 oil (D2), to the final in situ testing in real environmental conditions. Our results confirmed that Pgp activity is induced/induces according to the level of pollution, and that 4-days period was already long enough for the significant induction and deinduction of MXR activity. However, the inducibility of Pgp transport activity was significantly limited--the maximal level of induction obtained in this study resulted in 50-60% lower RB accumulation in the gills of induced specimens (laboratory or in situ exposed to pollution), when compared to control, non-induced animals. The obtained level of Pgp related MXR induction, resulting in halfway lesser accumulation of a model pollutant (RB), extrapolated to the similar scenario with toxic xenobiotics may have significant environmental relevance. However, our results also suggest that for the use of the MXR as a relevant biomarker the Pgp transport activity should be measured along with the determination of DNA, mRNA or/and protein expression. Based on the data from this study several factors that may have had critical influence on the effectiveness and the level of MXR induction are additionally discussed. PMID:14568358

Smital, Tvrtko; Sauerborn, Roberta; Hackenberger, Branimir K

2003-12-10

143

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

144

High-Speed Screening and StructureActivity Relationship Analysis for the Substrate Specificity of P-Glycoprotein (ABCB1)  

Microsoft Academic Search

Human ABCB1 (P-glycoprotein or MDR1) mediates the elimination of a variety of drugs from cells and thereby plays a critical role in determining the pharmacokinetic profiles of drugs in our body. In the present study, we have developed a high-speed screening system to investigate the substrate specificity of ABCB1 towards a variety of drugs and compounds. The plasma membrane fraction

Yuko Onishi; Hiroyuki Hirano; Kunio Nakata; Keisuke Oosumi; Makoto Nagakura; Shigeki Tarui; Toshihisa Ishikawa

2003-01-01

145

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

146

P-Glycoprotein Acts as an Immunomodulator during Neuroinflammation  

PubMed Central

Background Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system in which autoreactive myelin-specific T cells cause extensive tissue damage, resulting in neurological deficits. In the disease process, T cells are primed in the periphery by antigen presenting dendritic cells (DCs). DCs are considered to be crucial regulators of specific immune responses and molecules or proteins that regulate DC function are therefore under extensive investigation. We here investigated the potential immunomodulatory capacity of the ATP binding cassette transporter P-glycoprotein (P-gp). P-gp generally drives cellular efflux of a variety of compounds and is thought to be involved in excretion of inflammatory agents from immune cells, like DCs. So far, the immunomodulatory role of these ABC transporters is unknown. Methods and Findings Here we demonstrate that P-gp acts as a key modulator of adaptive immunity during an in vivo model for neuroinflammation. The function of the DC is severely impaired in P-gp knockout mice (Mdr1a/1b?/?), since both DC maturation and T cell stimulatory capacity is significantly decreased. Consequently, Mdr1a/1b ?/? mice develop decreased clinical signs of experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. Reduced clinical signs coincided with impaired T cell responses and T cell-specific brain inflammation. We here describe the underlying molecular mechanism and demonstrate that P-gp is crucial for the secretion of pro-inflammatory cytokines such as TNF-? and IFN-?. Importantly, the defect in DC function can be restored by exogenous addition of these cytokines. Conclusions Our data demonstrate that P-gp downmodulates DC function through the regulation of pro-inflammatory cytokine secretion, resulting in an impaired immune response. Taken together, our work highlights a new physiological role for P-gp as an immunomodulatory molecule and reveals a possible new target for immunotherapy.

Kooij, Gijs; Reijerkerk, Arie; van Horssen, Jack; van der Pol, Susanne M. A.; Drexhage, Joost; Schinkel, Alfred; Dijkstra, Christine D.; den Haan, Joke M. M.; Geijtenbeek, Teunis B. H.; de Vries, Helga E.

2009-01-01

147

Exhaustive sampling of docking poses reveals binding hypotheses for propafenone type inhibitors of P-glycoprotein.  

PubMed

Overexpression of the xenotoxin transporter P-glycoprotein (P-gp) represents one major reason for the development of multidrug resistance (MDR), leading to the failure of antibiotic and cancer therapies. Inhibitors of P-gp have thus been advocated as promising candidates for overcoming the problem of MDR. However, due to lack of a high-resolution structure the concrete mode of interaction of both substrates and inhibitors is still not known. Therefore, structure-based design studies have to rely on protein homology models. In order to identify binding hypotheses for propafenone-type P-gp inhibitors, five different propafenone derivatives with known structure-activity relationship (SAR) pattern were docked into homology models of the apo and the nucleotide-bound conformation of the transporter. To circumvent the uncertainty of scoring functions, we exhaustively sampled the pose space and analyzed the poses by combining information retrieved from SAR studies with common scaffold clustering. The results suggest propafenone binding at the transmembrane helices 5, 6, 7 and 8 in both models, with the amino acid residue Y307 playing a crucial role. The identified binding site in the non-energized state is overlapping with, but not identical to, known binding areas of cyclic P-gp inhibitors and verapamil. These findings support the idea of several small binding sites forming one large binding cavity. Furthermore, the binding hypotheses for both catalytic states were analyzed and showed only small differences in their protein-ligand interaction fingerprints, which indicates only small movements of the ligand during the catalytic cycle. PMID:21589945

Klepsch, Freya; Chiba, Peter; Ecker, Gerhard F

2011-05-12

148

[11C]Flumazenil brain uptake is influenced by the blood-brain barrier efflux transporter P-glycoprotein  

PubMed Central

Background [11C]Flumazenil and positron emission tomography (PET) are used clinically to assess gamma-aminobutyric acid (GABA)-ergic function and to localize epileptic foci prior to resective surgery. Enhanced P-glycoprotein (P-gp) activity has been reported in epilepsy and this may confound interpretation of clinical scans if [11C]flumazenil is a P-gp substrate. The purpose of this study was to investigate whether [11C]flumazenil is a P-gp substrate. Methods [11C]Flumazenil PET scans were performed in wild type (WT) (n = 9) and Mdr1a/1b, (the genes that encode for P-gp) double knockout (dKO) (n = 10) mice, and in naive rats (n = 10). In parallel to PET scanning, [11C]flumazenil plasma concentrations were measured in rats. For 6 of the WT and 6 of the dKO mice a second, [11C]flumazenil scan was acquired after administration of the P-gp inhibitor tariquidar. Cerebral [11C]flumazenil concentrations in WT and Mdr1a/1b dKO mice were compared (genetic disruption model). Furthermore, pre and post P-gp-blocking cerebral [11C]flumazenil concentrations were compared in all animals (pharmacological inhibition model). Results Mdr1a/1b dKO mice had approximately 70% higher [11C]flumazenil uptake in the brain than WT mice. After administration of tariquidar, cerebral [11C]flumazenil uptake in WT mice increased by about 80% in WT mice, while it remained the same in Mdr1a/1b dKO mice. In rats, cerebral [11C]flumazenil uptake increased by about 60% after tariquidar administration. Tariquidar had only a small effect on plasma clearance of flumazenil. Conclusions The present study showed that [11C]flumazenil is a P-gp substrate in rodents. Consequently, altered cerebral [11C]flumazenil uptake, as observed in epilepsy, may not reflect solely GABAA receptor density changes but also changes in P-gp activity.

2012-01-01

149

P-glycoprotein expression as a predictor of response to neoadjuvant chemotherapy in breast cancer.  

PubMed

Background: Chemoresistance is an important factor determining the response of tumor to neoadjuvant chemotherapy (NACT). P-glycoprotein (P-gp) expression-mediated drug efflux is one of the mechanisms responsible for multi-drug resistance. Our study was aimed to determine the role of P-gp expression as a predictor of response to NACT in locally advanced breast cancer (LABC) patients. Materials and Methods: P-gp expression was performed by real-time quantitative polymerase chain reaction [qRT-PCR] in 76 patients with LABC. Response to adriamycin-based regimen was assessed both clinically and with contrast enhanced computed tomography (CECT) scan before and after NACT. The significance of correlation between tumor and P-gp levels was determined with Chi-square test. Results: Twenty-one had high and 55 had low P-gp expression. On analyzing P-gp expression with response by World Health Organization (WHO) criteria, statistical significance was obtained (P = 0.038). Similarly, assessment of P-gp expression with response by Response Evaluation in Solid Tumors (RECIST) criteria in 48 patients showed statistical significance (P = 0.0005). Conclusion: This study proves that P-gp expression is a determinant factor in predicting response to NACT. Finally, detection of P-gp expression status before initiation of chemotherapy can be used as a predictive marker for NACT response and will also aid in avoiding the toxic side effects of NACT in non-responders. PMID:24061458

Vishnukumar, S; Umamaheswaran, G; Anichavezhi, D; Indumathy, S; Adithan, C; Srinivasan, K; Kadambari, D

150

Changes in the localization of ileal P-glycoprotein induced by intestinal ischemia/reperfusion.  

PubMed

P-glycoprotein is one of the most important transporters in the ATP binding cassette transporter. Moreover, it is well known that the efficacy of immunosuppressants, which are used after organ transplantation, is controlled by P-glycoprotein (P-gp). We investigated how ischemia/reperfusion (I/R), which occurs after transplantation, influences the expression level and function of P-gp. To clarify the influence of intestinal I/R on the localization of P-gp, an intestinal ischemia model was produced using a spring scale and surgical sutures for 1 h, followed by reperfusion for 24 h. The expression levels of mRNA and protein of P-gp were examined. The protein expression levels of P-gp in ileal homogenate and the brush border membrane (BBM) were significantly decreased until 3 h after reperfusion. While the protein expression level of P-gp in homogenate showed a tendency to increase, that in the BBM continued to significantly decrease until 24 h after reperfusion. In contrast, the protein expression level of P-gp in the basolateral membrane (BLM) increased significantly until 24 h after reperfusion. While no significant change in multidrug resistance (mdr)-1a mRNA was found, the levels of mdr-1b and mdr-2 significantly increased during intestinal I/R. In addition, the levels of inflammatory cytokines mRNA and nitric oxide (NO) also significantly increased. It was shown that mdr-1b and mdr-2 mRNA strongly participate in the recovery of P-gp protein level after intestinal I/R. We detected the abnormal localization of P-gp in the ileal membrane during intestinal I/R, suggesting NO and/or inflammatory cytokines participate in the abnormal localization of P-gp. PMID:21372393

Takizawa, Yusuke; Kishimoto, Hisanao; Kitazato, Takuya; Tomita, Mikio; Hayashi, Masahiro

2011-01-01

151

FBXO15 regulates P-glycoprotein/ABCB1 expression through the ubiquitin--proteasome pathway in cancer cells.  

PubMed

Expression of P-glycoprotein (P-gp)/ABCB1 on cancer cell surfaces is a critical determinant of anticancer drug resistance. Regulators of P-gp expression and function are key molecules controlling drug resistance. Here we report the mechanism underlying the ubiquitin-proteasome pathway-mediated degradation of P-gp. The proteasome inhibitor MG132 increased the P-gp level, enhanced its ubiquitination, and delayed the disappearance of the ubiquitinated P-gp. To search for regulators of P-gp ubiquitination, MALDI-time of flight mass spectrometry analyses were carried out, and 22 candidates were identified as P-gp binding partners. Among them, FBXO15/Fbx15 is known as an F-box protein in the ubiquitin E3 ligase complex, Skp1-Cullin1-FBXO15 (SCF(Fbx15) ); therefore, we further studied the involvement of FBXO15 on P-gp degradation. Coprecipitation assays revealed that FBXO15 bound to P-gp. We screened ubiquitin-conjugating enzyme E2s that bind to FBXO15 and P-gp; Ube2r1/Cdc34/Ubc3 was found to be a binding partner. Exogenous FBXO15 expression enhanced P-gp ubiquitination, but FBXO15 knockdown suppressed it. FBXO15 knockdown increased P-gp expression without affecting its mRNA level. Ube2r1 knockdown decreased P-gp ubiquitination, and simultaneous knockdown of Ube2r1 with FBXO15 further suppressed the ubiquitination. Ube2r1 knockdown increased P-gp expression, suggesting that Ube2r1 is a partner of FBXO15 in P-gp ubiquitination. FBXO15 knockdown enhanced vincristine resistance and lowered intracellular levels of rhodamine 123. These data suggest that FBXO15 and Ube2r1 regulate P-gp expression through the ubiquitin-proteasome pathway. PMID:23465077

Katayama, Kazuhiro; Noguchi, Kohji; Sugimoto, Yoshikazu

2013-04-15

152

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

153

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

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. PMID:23397054

Sane, Ramola; Agarwal, Sagar; Mittapalli, Rajendar K; Elmquist, William F

2013-02-08

154

Histone deacetylase inhibitor induction of P-glycoprotein transcription requires both histone deacetylase 1 dissociation and recruitment of CAAT/enhancer binding protein beta and pCAF to the promoter region.  

PubMed

Although histone deacetylase (HDAC) inhibitors are appreciated as a promising class of anticancer drugs, recent reports show that P-glycoprotein (P-gp) is induced by HDAC inhibitor treatment in cancer cells, resulting in multidrug resistance of cancer cells to other chemotherapeutic agents. In this study, we investigated the molecular mechanism of HDAC inhibitor induction of P-gp expression. HDAC inhibitor treatment causes cell type-specific induction of P-gp expression without changes in the CpG methylation status of the promoter region. In addition, our data show that HDAC inhibitor does not alter the DNA binding activity of Sp1 but facilitates both the recruitment of a coactivator complex that includes CAAT/enhancer binding protein beta and pCAF and the dissociation of the repressive complex, HDAC1, to the Sp1 binding region. Subsequently, the hyperacetylated histone H3 becomes enriched in the promoter region, leading to RNA polymerase II recruitment to activate P-gp gene transcription. Furthermore, specific down-regulation of HDAC1, but not HDAC2, by RNA silencing was enough to induce P-gp expression in HeLa cells, strongly supporting the essential role of HDAC1 in HDAC inhibitor induction of P-gp. Concomitantly, cell type-specific induction of P-gp expression seems to be dependent on phosphatidylinositol 3-kinase activity. Taken together, our findings show that HDAC inhibitor treatment leads to an increase in P-gp expression through dynamic changes in chromatin structure and transcription factor association within the promoter region. PMID:19435809

Kim, Su-Nam; Kim, Nam Hyun; Lee, Woojung; Seo, Dong-Wan; Kim, Yong Kee

2009-05-12

155

Influence of the multidrug transporter P-glycoprotein on the intracellular pharmacokinetics of vandetanib.  

PubMed

Efflux transporters play an important role in the resistance of tumor cells against anticancer agents. Interaction between these transporters, including P-glycoprotein (P-gp), and drugs might influence their pharmacological properties and toxicities. The aim of this study was to investigate whether vandetanib (Caprelsa(®)), a small tyrosine kinase inhibitor, could interact with the multidrug transporter P-gp. Interaction of vandetanib with the P-gp was investigated using the parental cell line (IGROV1) and the P-gp doxorubicin-resistant (IGROV1-DXR) cell line, derived from the parental drug-sensitive IGROV1 cells. Cytotoxicity tests were assessed in both cell lines to examine the impact of P-gp on the cell survival after a vandetanib treatment. The effects of P-gp on vandetanib intracellular pharmacokinetics were investigated. To this aim, we developed a quantitative liquid chromatography tandem mass spectrometry to quantify vandetanib in cell medium. Results showed that overexpression of P-gp confers resistance to vandetanib in the IGROV1-DXR cell line. Using a LC-MS/MS assay validated in cell medium, cellular pharmacokinetic studies revealed that in cells overexpressing the P-gp intracellular concentrations of vandetanib were decreased compared to parental cell line. For the first time, vandetanib is described as a substrate of P-gp. In tumor cells, P-gp could be responsible for cellular resistance to vandetanib. It may be relevant to the clinical efficacy of vandetanib. Moreover, interaction of vandetanib with P-gp could modify the pharmacodynamics of other conventional chemotherapeutics, substrates of P-gp. It could impact on the overall response to anticancer therapy. PMID:23446814

Jovelet, C; Deroussent, A; Broutin, S; Paci, A; Farinotti, R; Bidart, J M; Gil, S

2013-02-28

156

Specific detection of multidrug resistance proteins MRP1, MRP2, MRP3, MRP5, and MDR3 P-glycoprotein with a panel of monoclonal antibodies  

Microsoft Academic Search

Tumor cells may display a multidrug resistance phenotype by overex- pression of ATP binding cassette transporter genes such as multidrug resistance (MDR) 1 P-glycoprotein (P-gp) or the multidrug resistance pro- tein 1 (MRP1). MDR3 P-gp is a close homologue of MDR1 P-gp, but its role in MDR is probably minor and remains to be established. The MRP1 protein belongs to

George L. Scheffer; Marcel Kool; Marc Heijn; Haas de M; A. C. L. M. Pijnenborg; J. Wijnholds; Helvoort van A; M. C. Jong; J. H. Hooijberg; C. A. A. M. Mol; Linden van der M; Vree de J. M. L; Valk van der P; R. P. J. Oude Elferink; P. Borst; R. J. Scheper

2000-01-01

157

CJX1, an amlodipine derivative, interacts with ATPase of human P-glycoprotein  

Microsoft Academic Search

Our aim has been to elucidate the possible mechanism of CJX1, an amlodipine derivative, in the modulation of P-gp function by determining its effect on P-gp ATPase activity. Basal P-gp ATPase activity was increased by CJX1 with half-maximal activity concentration (Km) of 8.6±1.4?M. Kinetic analysis indicated a non-competitive inhibition of Verapamil (Ver)-stimulated P-gp ATPase activity by CJX1 and competitive inhibition

Bian-Sheng Ji; Ling He

2009-01-01

158

Regulation of BCRP (ABCG2) and P-glycoprotein (ABCB1) by cytokines in a model of the human blood-brain barrier.  

PubMed

Brain capillary endothelial cells form the blood-brain barrier (BBB), a highly selective permeability membrane between the blood and the brain. Besides tight junctions that prevent small hydrophilic compounds from passive diffusion into the brain tissue, the endothelial cells express different families of drug efflux transport proteins that limit the amount of substances penetrating the brain. Two prominent efflux transporters are the breast cancer resistance protein and P-glycoprotein (P-gp). During inflammatory reactions, which can be associated with an altered BBB, pro-inflammatory cytokines are present in the systemic circulation. We, therefore, investigated the effect of the pro-inflammatory cytokines interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) on the expression and activity of BCRP and P-gp in the human hCMEC/D3 cell line. BCRP mRNA levels were significantly reduced by IL-1beta, IL-6 and TNF-alpha. The strongest BCRP suppression at the protein level was observed after IL-1beta treatment. IL-1beta, IL-6 and TNF-alpha also significantly reduced the BCRP activity as assessed by mitoxantrone uptake experiments. P-gp mRNA levels were slightly reduced by IL-6, but significantly increased after TNF-alpha treatment. TNF-alpha also increased protein expression of P-gp but the uptake of the P-gp substrate rhodamine 123 was not affected by any of the cytokines. This in vitro study indicates that expression levels and activity of BCRP, and P-gp at the BBB may be altered by acute inflammation, possibly affecting the penetration of their substrates into the brain. PMID:19629677

Poller, Birk; Drewe, Jürgen; Krähenbühl, Stephan; Huwyler, Jörg; Gutmann, Heike

2009-07-23

159

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

160

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

2010-02-10

161

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

PubMed Central

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–? 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.

Dumond, JB; Vourvahis, M; Rezk, NL; Patterson, KB; Tien, H-C; White, N; Jennings, SH; Choi, SO; Li, J; Wagner, MJ; La-Beck, NM; Drulak, M; Sabo, JP; Castles, MA; MacGregor, TR; Kashuba, ADM

2010-01-01

162

Overcoming of P-glycoprotein-mediated multidrug resistance in K562/A02 cells using riccardin F and pakyonol, bisbibenzyl derivatives from liverworts.  

PubMed

Riccardin F and pakyonol, macrocyclic bisbibenzyls from Plagiochasm intermedium, have been confirmed to possess antifungic activities against Candida albicans. Herein, we evaluated their anti-tumor activity in vitro by employing K562 and K562/A02 cells, the well-known adriamycin (ADR)-induced multidrug resistance (MDR) tumor cell lines over-expressing P-glycoprotein (P-gp). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assays showed that riccardin F and pakyonol ranging from 0 to 6 ?g/mL exhibited no inhibitory effects on the growth of the two cell lines. However, in the presence of 3 ?g/mL riccardin F or pakyonol (non-cytotoxic concentration), the IC50 of ADR against K562/A02 cells decreased by 2.51- and 4.78-fold, respectively. Flow cytometry showed that riccardin F and pakyonol significantly enhanced the accumulation of ADR in K562/A02 cells. Furthermore, fluorescence intensity detection revealed that the two natural products remarkably increased the retention of rhodamine-123 in K562/A02 cells rather than in K562 cells, indicating that the major cause for riccardin F and pakyonol to reverse P-gp-mediated MDR in K562/A02 cells is probably due to the constrained transport activity of P-gp. This study explores the potential application of bisbibenzyl type compounds as modulators of P-gp-mediated MDR in tumor cells. PMID:22101374

Ji, Mei; Shi, Yanquiu; Lou, Hongxiang

2011-01-01

163

Disposition of Delta tetrahydrocannabinol in CF1 mice deficient in mdr1a P-glycoprotein.  

PubMed

P-glycoprotein (P-gp) plays a major role in drug efflux. All the transported substrates are more or less hydrophobic and amphiphatic in nature. Being lipophilic, Delta(9) tetrahydrocannabinol (THC), the main cannabis component, could be a potential P-gp substrate. The aim of this project was to determine the contribution of the mdr1a gene product to THC disposition. Therefore, oral THC and digoxin (substrate test for P-gp) pharmacokinetics have been investigated in the intestinal epithelium and in the brain capillary endothelium of CF1 mdr1a-/- mice (mice naturally deficient in P-gp). These pharmacokinetics were compared to THC and digoxin oral pharmacokinetics in wild type mice mdr1a+/+ (not P-gp deficient). The application of Bailer's method showed that THC total exposure measured by the area under the plasma concentration time curve was 2.17-fold higher in CF1 mice naturally deficient in P-gp than in wild type mice after oral administration of 25 mg/kg of THC, and 2.4-fold higher after oral administration of 33 microg/kg of digoxin. As a consequence, the oral bioavailability of THC and digoxin was higher in naturally P-gp-deficient mice. We concluded that P-gp limits THC oral uptake and mediates direct drug excretion from the systemic circulation into the intestinal lumen. PMID:18331373

Bonhomme-Faivre, Laurence; Benyamina, Amine; Reynaud, Michel; Farinotti, Robert; Abbara, Chadi

2008-03-07

164

Substrate versus inhibitor dynamics of P-glycoprotein.  

PubMed

By far the most studied multidrug resistance protein is P-glycoprotein. Despite recent structural data, key questions about its function remain. P-glycoprotein (P-gp) is flexible and undergoes large conformational changes as part of its function and in this respect, details not only of the export cycle, but also the recognition stage are currently lacking. Given the flexibility, molecular dynamics (MD) simulations provide an ideal tool to examine this aspect in detail. We have performed MD simulations to examine the behaviour of P-gp. In agreement with previous reports, we found that P-gp undergoes large conformational changes which tended to result in the nucleotide-binding domains coming closer together. In all simulations, the approach of the NBDs was asymmetrical in agreement with previous observations for other ABC transporter proteins. To validate the simulations, we make extensive comparison to previous cross-linking data. Our results show very good agreement with the available data. We then went on to compare the influence of inhibitor compounds bound with simulations of a substrate (daunorubicin) bound. Our results suggest that inhibitors may work by keeping the NBDs apart, thus preventing ATP-hydrolysis. On the other hand, repeat simulations of daunorubicin (substrate) in one particular binding pose suggest that the approach of the NBDs is not impaired and that the structure would be still be competent to perform ATP hydrolysis, thus providing a model for inhibition or substrate transport. Finally we compare the latter to earlier QSAR data to provide a model for the first part of substrate transport within P-gp. Proteins 2013. © 2013 Wiley Periodicals, Inc. PMID:23670856

Ma, Jerome; Biggin, Philip C

2013-06-17

165

Reversal of P-glycoprotein-mediated multidrug resistance in human sarcoma MES-SA/Dx-5 cells by nonsteroidal anti-inflammatory drugs.  

PubMed

Multidrug resistance (MDR) mediated by P-glycoprotein (P-gp) is one of the major reasons for the failure of cancer therapy. Several chemosensitizers are able to reverse in vitro MDR by inhibiting P-gp, although high toxicity limits their clinical application. In this study, we aimed to investigate the in vitro effectiveness of four common non-steroidal anti-inflammatory drugs (NSAIDs) such as Curcumin (Cur), Sulindac (Sul), Ibuprofen (Ibu) and NS-398 (NS) to inhibit P-gp activity at clinically achievable doses and to evaluate their potential use as sensitizers in anti-cancer chemotherapy. The human doxorubicin (doxo) resistant uterine sarcoma cells (MES-SA/Dx-5) expressing high levels of P-gp, were treated with different doxo concentrations in the presence or absence of NSAIDs. Cellular accumulation of doxo, cytotoxicity and apoptosis induction were measured in comparison with Verapamil, a specific P-gp inhibitor, used as a reference molecule. We found that Ibu, Cur and NS-398 enhanced significantly doxo retention, cytotoxicity and apoptosis on resistant MES-SA/Doxo-5 cells when compared with doxo alone. In contrast, no significant changes were found in resistant cells treated with Sul-doxo combinations. Our results demonstrate that Ibu, Cur and NS-398 below their therapeutic plasma concentrations were able to overcome P-gp-mediated MDR in MES-SA/Dx-5 cells. These findings provide the rationale for clinical studies of NSAIDs and/or derivatives as a new potential generation of chemosensitizers to improve effectiveness of the anti-cancer drugs in the treatment of human cancer. PMID:18813811

Angelini, Antonio; Iezzi, Manuela; Di Febbo, Concetta; Di Ilio, Carmine; Cuccurullo, Franco; Porreca, Ettore

2008-10-01

166

Modulation of P-glycoprotein-mediated multidrug resistance in K562 leukemic cells by indole-3-carbinol  

Microsoft Academic Search

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

Annu Arora; Kavita Seth; Neetu Kalra; Yogeshwer. Shukla

2005-01-01

167

P-glycoprotein expression does not change the apoptotic pathway induced by curcumin in HL60 cells  

Microsoft Academic Search

Purpose One of the mechanisms responsible for the multidrug resistance (MDR) phenotype of cancer cells is overexpression of so-called ATP-dependent drug efflux proteins: the 170-kDa P-glycoprotein (P-gp) encoded by the MDR1 gene and the 190-kDa multidrug resistance-associated protein 1 encoded by the MRP1 gene. The purpose of the present study was to verify the hypothesis postulating that P-gp expression, apart

Anna Bielak-?mijewska; Katarzyna Piwocka; Adriana Magalska; Ewa Sikora

2004-01-01

168

Drug Rescue Distinguishes between Different Structural Models of Human P-Glycoprotein.  

PubMed

There is no high-resolution crystal structure of the human P-glycoprotein (P-gp) drug pump. Homology models of human P-gp based on the crystal structures of mouse or Caenorhabditis elegans P-gps show large differences in the orientation of transmembrane segment 5 (TM5). TM5 is one of the most important transmembrane segments involved in drug-substrate interactions. Drug rescue of P-gp processing mutants containing an arginine at each position in TM5 was used to identify positions facing the lipid or internal aqueous chamber. Only the model based on the C. elegans P-gp structure was compatible with the drug rescue results. PMID:24083983

Loo, Tip W; Clarke, David M

2013-10-02

169

Drug Rescue Distinguishes between Different Structural Models of Human P-Glycoprotein  

PubMed Central

There is no high-resolution crystal structure of the human P-glycoprotein (P-gp) drug pump. Homology models of human P-gp based on the crystal structures of mouse or Caenorhabditis elegans P-gps show large differences in the orientation of transmembrane segment 5 (TM5). TM5 is one of the most important transmembrane segments involved in drug–substrate interactions. Drug rescue of P-gp processing mutants containing an arginine at each position in TM5 was used to identify positions facing the lipid or internal aqueous chamber. Only the model based on the C. elegans P-gp structure was compatible with the drug rescue results.

2013-01-01

170

Small P-gp modulating molecules: SAR studies on tetrahydroisoquinoline derivatives  

Microsoft Academic Search

The development of small molecules as P-gp modulating agents and SAR studies on these ligands represented the aim of the present work. A series of 6,7-dimethoxytetrahydroisoquinoline derivatives was prepared and their ability to inhibit P-gp activity has been evaluated. The basic nucleus of these compounds, common to the best P-gp inhibitors such as Tariquidar and Elacridar, has been functionalized with

Nicola Antonio Colabufo; Francesco Berardi; Mariangela Cantore; Maria Grazia Perrone; Marialessandra Contino; Carmela Inglese; Mauro Niso; Roberto Perrone; Amalia Azzariti; Grazia Maria Simone; Letizia Porcelli; Angelo Paradiso

2008-01-01

171

The distribution of drug-efflux pumps, P-gp, BCRP, MRP1 and MRP2, in the normal blood–testis barrier and in primary testicular tumours  

Microsoft Academic Search

The drug-efflux pumps P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP1) are present in the blood–testis barrier (BTB) and may hamper the delivery of cytotoxic drugs to the testis. The precise localisation of P-gp and MRP1 in testicular tissue and the presence of the efflux pumps MRP2 and breast cancer resistance protein (BCRP) in the BTB are unknown. We therefore

J. Bart; H. Hollema; H. J. M. Groen; E. G. E. de Vries; N. H. Hendrikse; D. T. Sleijfer; T. D. Wegman; W. Vaalburg

2004-01-01

172

Enhanced sensitivity of P-glycoprotein-positive multidrug resistant tumor cells to complement-mediated lysis.  

PubMed

The interaction of KB-V1, a multidrug resistant (MDR) variant of the KB-3-1 human oral carcinoma, with human complement was investigated. KB-V1 cells were found to be more sensitive than KB-3-1 cells to complement-mediated lysis. Detailed analysis of the capacity of KB cells to activate human complement demonstrated that both C3b deposition and formation of the membrane attack complex (MAC) are higher on KB-V1 than on KB-3-1 cells. Furthermore, the MAC formed on KB-V1 cells, but not on KB-3-1 cells, was found to be resistant to trypsin treatment, i.e. more stably inserted into the plasma membrane. Immunofluorescence analysis by flow cytometry showed that KB-V1 cells express less decay-accelerating factor (DAF, CD55) than KB-3-1 cells. Two other complement regulatory proteins, membrane cofactor protein (MCP, CD46) and CD59 are expressed to a similar extent on both KB-V1 and KB-3-1 cells. Treatment of KB-V1 cells with neutralizing anti-P-glycoprotein (P-gp) monoclonal antibodies reduced their sensitivity to complement. In addition, KB-V1 revertants which cease to express P-gp become more resistant to complement. These results indicate that multiple factors, such as reduced expression of DAF, enhanced deposition of C3b and increased binding and stability of the MAC may contribute to the increased complement sensitivity of KB-V1 cells. It is suggested that P-gp is responsible for the complement-sensitive phenotype of KB-V1 cells. PMID:9341760

Bomstein, Y; Fishelson, Z

1997-09-01

173

Expression of P-glycoprotein in killifish (Fundulus heteroclitus) exposed to environmental xenobiotics.  

PubMed

P-glycoproteins (P-gp) are transmembrane efflux flippases that prevent the cellular accumulation of moderately hydrophobic compounds and are responsible for certain multidrug resistance phenotypes in tumor cell lines and human patients. We investigated whether P-gps could be involved in a contaminant resistant phenotype observed in a population of fish exposed over generations to high levels of planar halogenated aromatic hydrocarbons (PHAHs). Hepatic and intestinal epithelial P-gp expression was examined by immunoblot and immunohistochemistry in killifish (Fundulus heteroclitus) from New Bedford Harbor, MA (NBH), a Superfund site highly contaminated with PHAHs, and from Scorton Creek on Cape Cod, MA (SC), a relatively unpolluted site. The NBH population has developed resistance to the toxicity of PHAHs. Hepatic P-gp levels were more than 40% greater in fish freshly collected from SC than in fish freshly collected from NBH. When killifish from either site were maintained in clean water for up to 78 days to permit depuration of bioaccumulated contaminants, hepatic P-gp levels decreased approximately 50% by day 8. P-glycoprotein expression was detected in the intestinal epithelium in 55% of freshly collected NBH fish. However, depurated NBH fish and freshly caught and depurated SC fish rarely expressed P-gp in the intestine. In an effort to determine whether environmental chemicals at the two sites might contribute to altered P-gp expression, depurated fish were exposed either to sediment collected from SC or 2,3,7,8-tetrachlorodibenzofuran, a contaminant found at the NBH site and a model aryl hydrocarbon receptor agonist. Neither exposure affected hepatic P-gp levels in killifish. Elevated intestinal P-gp in NBH fish might counter the absorption of P-gp substrates/inducers and thus limit the amount of these compounds reaching the liver, which might account for the lower hepatic P-gp levels in NBH fish compared to SC fish. The differences in hepatic P-gp levels (SC>NBH) and intestinal P-gp (NBH>SC) in freshly collected fish also might reflect environmental exposure to different anthropogenic contaminants or microbial, algal, plant or other natural products via the water column, sediment, or diet at each site. PMID:12127740

Bard, Shannon Mala; Bello, Susan M; Hahn, Mark E; Stegeman, John J

2002-09-24

174

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

PubMed

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 the study the drug was withdrawn and, after 22 days, added back to the culture medium. Cells were harvested at various time points and xenografted in nude mice. P-gp content in cells was measured by self-competitive binding assay and in tumors, by quantitative autoradiography (QAR). Both assays were carried out using 125I-labeled monoclonal antibody MRK16, reactive with P-gp. Concentration of P-gp in cells varied from a maximum of 1,361 pmol/g in the presence of colchicine to a minimum of 374 pmol/g in the absence of colchicine in the culture medium. P-gp concentration in the tumors ranged from 929 to 188 pmol/g, which correlated with P-gp content in the cells at the time of their injection in the mice. QAR is an accurate and reliable method to quantify P-gp expression in tumors. Changes in colchicine concentration in the ambient medium of BE(2)-C/CHCb(0.2) cells growing in vitro resulted in a change in phenotype of P-gp expression, which was stable under conditions of in vivo growth over approximately 9 cell divisions in nude mice xenografts. Therefore, P-gp content in xenografts depends only on the level of resistance of the cells at the time of their injection in the mice. PMID:10096499

Fonti, R; Levchenko, A; Mehta, B M; Zhang, J; Tsuruo, T; Larson, S M

1999-01-01

175

Inhibition of P-glycoprotein-mediated efflux of digoxin and its metabolites by macrolide antibiotics.  

PubMed

This study was conducted to determine the rate of P-glycoprotein (P-gp)-mediated efflux of digoxin analogues and metabolites and to assess the effects of macrolide antibiotics on this efflux. Bidirectional transport studies were conducted using our Caco-2 sub clone with high P-gp expression (CLEFF9). HPLC methods were employed to measure drug transport. All digoxin metabolites were P-gp substrates, although digoxin had the greatest efflux ratio. Erythromycin had no effect on the transport of digoxin, maintaining a basolateral to apical efflux ratio of 14.8, although it did reduce the efflux ratio of dihydrodigoxin and digoxigenin by 34% and 43%, respectively. Azithromycin also had little effect on the transport of digoxin or any of its metabolites. In contrast, clarithromycin and roxithromycin almost eliminated basolateral targeted efflux. Using paclitaxel as a known P-gp substrate, erythromycin demonstrated only partial P-gp inhibitory capacity, maintaining an efflux ratio over 100. In contrast, clarithromycin and roxithromycin were 10-fold greater P-gp inhibitors. Clarithromycin and roxithromycin are likely to exhibit drug interactions with digoxin via inhibition of efflux mechanisms. Azithromycin appears to have little influence on P-gp-mediated digoxin absorption or excretion and would be the safest macrolide to use concurrently with oral digoxin. PMID:20724802

Hughes, Jeff; Crowe, Andrew

2010-01-01

176

Selamectin is a potent substrate and inhibitor of human and canine P-glycoprotein.  

PubMed

The transport of the antiparasitic agents, ivermectin, selamectin and moxidectin was studied in human intestinal epithelial cell monolayers (Caco-2) and canine peripheral blood lymphocytes (PBL). Both models expressed the mdr1-coded 170 kDa ATP-binding cassette (ABC) transporter P-glycoprotein (P-gp). Fluxes of the P-gp substrate rhodamine-123 (Rh-123) across Caco-2 monolayers showed that ivermectin and selamectin acted as potent P-gp inhibitors with IC50 values of 0.1 microm. In contrast, moxidectin was a weaker P-gp inhibitor with an IC50 of 10 microm. The transport of radiolabelled ivermectin, selamectin and moxidectin through Caco-2 monolayers showed that ivermectin, selamectin and moxidectin were P-gp substrates with secretory/absorptive ratios of 7.5, 4.7 and 2.6 respectively. Secretory transport of [3H]-ivermectin and [3H]-selamectin was blocked by the P-gp inhibitor, verapamil. Ivermectin and selamectin inhibited the efflux of Rh-123 from PBL and the concentration of inhibition was similar to that of verapamil. In contrast, moxidectin did not have a significant effect on Rh-123 efflux from PBL. The data suggest that ivermectin and selamectin are potent P-gp substrates, while moxidectin is a weak one. PMID:15953199

Griffin, J; Fletcher, N; Clemence, R; Blanchflower, S; Brayden, D J

2005-06-01

177

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

178

The two enantiomers of tetrahydropalmatine are inhibitors of P-gp, but not inhibitors of MRP1 or BCRP.  

PubMed

Tetrahydropalmatine (THP), with one chiral centre, is one of the major constituents of Rhizoma corydalis. THP is considered to possess analgesic, sedative, hypnotic actions and cardiac protection. The aim of this study was to elucidate the stereoselective interaction between THP and ABC transporters. The present study investigated three most important ABC transporters, including P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1) and breast cancer resistance protein (BCRP). The intracellular accumulation and bidirectional transport suggested THP enantiomers were inhibitors of P-gp, but not of MRP1 or BCRP. The IC(50) values of (-)-THP and (+)-THP on rhodamine 123 (P-gp substrate) efflux were 48.6 and 20.0 µM, respectively, which showed obvious stereoselective difference. In the bidirectional transport, THP enantiomers showed high passive permeability and the contribution of P-gp could not be testified. The western blot and real-time RT-PCR assays showed that THP enantiomers reduced the protein expression of P-gp, but did not affect its mRNA expression. In in vitro cytotoxicity test, THP enantiomers showed the potential of increasing the cytotoxicity of doxorubicin in P-gp-mediated multidrug resistant tumour cells. The present study showed the stereoselective interaction between THP enantiomers and P-gp, which should be considered in clinical practice. PMID:22900779

Sun, Siyuan; Chen, Zhongjian; Li, Liping; Sun, Dongli; Tian, Ye; Pan, Hao; Bi, Huichang; Huang, Min; Zeng, Su; Jiang, Huidi

2012-08-19

179

In vivo efficacy of XR9051, a potent modulator of P-glycoprotein mediated multidrug resistance  

Microsoft Academic Search

Overexpression of P-glycoprotein (P-gp) is a potential cause of multidrug resistance (MDR) in tumours. We have previously reported that XR9051 (N-(4-(2-(6,7-dimethoxy-1,2,3,4-tetrahydro-2-isoquinolyl)ethyl)phenyl)-3-((3Z,6Z)-6-benzylidene-1-methyl-2,5-dioxo-3-piperazinylidene)-methylbenzamide) is a potent and specific inhibitor of P-gp, which reverses drug resistance in several murine and human MDR cell lines. In this study we have evaluated the in vivo efficacy of this novel modulator in a panel of murine

P Mistry; J Plumb; S Eccles; S Watson; I Dale; H Ryder; G Box; P Charlton; D Templeton; P B Bevan

1999-01-01

180

Low bioavailability of cyclosporine microemulsion and tacrolimus in a small bowel transplant recipient: possible relationship to intestinal P-glycoprotein activity.  

PubMed

With intestine transplants the allograft is dependent on itself for maintenance of adequate immunosuppression. We evaluated an intestinal transplant recipient who required very large doses of either tacrolimus or cyclosporine emulsion to achieve acceptable blood concentrations. Pharmacokinetic studies revealed bioavailabilities of 2% and 6% respectively, while D-xylose and B12 absorption were found to be within normal limits and fecal fat was only slightly increased, suggesting that there was a selective absorptive defect for these drugs. Biopsies of the allograft ileum revealed a high P-glycoprotein activity compared to the jejunum or to intestinal biopsies from other normal subjects. This may be a contributing factor to poor immunosuppressive drug absorption in this patient and others. PMID:10075604

Kaplan, B; Lown, K; Craig, R; Abecassis, M; Kaufman, D; Leventhal, J; Stuart, F; Meier-Kriesche, H U; Fryer, J

1999-01-27

181

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

182

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

183

P-Glycoprotein Limits Oral Availability, Brain Penetration, and Toxicity of an Anionic Drug, the Antibiotic Salinomycin  

Microsoft Academic Search

Salinomycin is a polyether organic anion that is extensively used as a coccidiostatic antibiotic in poultry and commonly fed to ruminant animals to improve feed efficiency. However, salinomycin also causes severe toxicity when accidentally fed to animals in high doses. In addition, humans are highly sensitive to salinomycin and severe toxicity has been reported. Multidrug efflux transporters like P-glycoprotein (P-gp),

Jurjen S. Lagas; Rolf W. Sparidans; Robert A. B. van Waterschoot; Els Wagenaar; Jos H. Beijnen; Alfred H. Schinkel

2008-01-01

184

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

185

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

Microsoft Academic Search

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

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

2012-01-01

186

Lymphokine-activated killer cell susceptibility and adhesion molecule expression of multidrug resistant breast carcinoma  

Microsoft Academic Search

Reports showing susceptibility of multidrug resistant (MDR) cancer cells to immune effectors, together with P-glycoprotein (P-gp) expression in immune effector subsets, including immature natural killer (NK) cells, and some activated T cells, suggest P-gp or some changes associated with it, have implications in immune-mediated mechanisms. A series of experiments were done to determine the nature of alterations associated with susceptibility

Burhan Savas; Pauline E Kerr; Hugh F Pross

2006-01-01

187

Effects of borneol on the intestinal transport and absorption of two P-glycoprotein substrates in rats.  

PubMed

As the most prevalent route of delivery, oral administration has the challenge of potentially low bioavailability in part because P-glycoprotein (P-gp) in the intestinal tract affects absorption. Therefore, absorption enhancers or P-gp inhibitors are strategies to solve this problem. The aim of the present study was to investigate the effects of borneol on transportation of colchicine and rhodamine123, two P-gp substrates, in rats. In vitro transportation was assessed with a diffusion chamber system with isolated rat intestines. Different concentrations of borneol (10, 40 and 80 ?g/mL) were prepared in solutions with two P-gp substrates compared with blank solutions. The in vivo effects on colchicine were assessed by a pharmacokinetic study. Borneol enhanced the absorptive transport of two P-gp substrates, which was relevant to the concentration. A pharmacokinetic study showed that in the presence of borneol, a significant increase in C(max) and AUC(0?8) of colchicine occurred when compared to colchicine alone. The study showed that borneol affected two P-gp substrates in the intestine, possibly by inhibiting the effects of P-gp and enhancing intestinal absorption of drugs. Therefore, borneol could be developed as a P-gp inhibitor and absorptive enhancer. PMID:21811923

He, Huijuan; Shen, Qi; Li, Jian

2011-08-03

188

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

PubMed Central

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.

Quesada, A. R.; Garcia Gravalos, M. D.; Fernandez Puentes, J. L.

1996-01-01

189

Influence of P-glycoprotein on embryotoxicity of the antifouling biocides to sea urchin (Strongylocentrotus intermedius).  

PubMed

P-glycoprotein (P-gp), as an ATP-binding cassette transporter, transports a wide variety of substrates varying from small molecules like steroids to large polypeptides across the cell membrane in human and animals, even in aquatic animals. Although P-gp protein has attracted much attention of research, its effect on the toxicity of environmental toxicants such as antifouling biocides is still poorly understood. The goal of this study is to evaluate whether copper pyrithione (CuPT), Sea-Nine 211, dichlofluanid and tolylfluanid, four widely used antifouling agents, can be transported by P-gp in embryos of sea urchin Strongylocentrotus intermedius in the presence and absence of the P-gp inhibitor verapamil. Cytotoxcicities of Sea-Nine 211 (EC50 = 99 nM, at 4-arm pluteus) and dichlofluanid (EC50 = 144 nM, at multi-cell) are enhanced by the addition of the P-gp inhibitor, indicating that the two biocides are potential P-gp substrates. Tolylfluanid and CuPT are not transported by P-gp out of the cell, since no obvious changes in the cytotoxicities of the two biocides are observed no matter whether verapamil is added or not. In addition, to understand the mechanisms of ligand binding and its interaction with P-gp, a three-dimensional model of the sea urchin P-gp is generated based on the mouse crystal structure by using homology modeling approach. With this model, a flexible docking is performed and the results indicate that Sea-Nine 211 and dichlofluanid share the same binding site with verapamil, composed of key residues Lys677, Lys753, Thr756, Ala780, Met1033 and Phe1037, whereas tolylfluanid and CuPT display totally different binding modes to P-gp. This further demonstrates that Sea-Nine 211 and dichlofluanid are P-gp substrates, which provides us with new insights into the interactions of P-gp with the antifouling contaminants in aquatic invertebrate embryos. PMID:21229388

Xu, Xue; Fu, Jingxuan; Wang, Heng; Zhang, Baidong; Wang, Xia; Wang, Yonghua

2011-01-13

190

The effects of cannabinoids on P-glycoprotein transport and expression in multidrug resistant cells.  

PubMed

Cannabis is the most widely used illicit drug in the world. Cannabinoids are used therapeutically by some patients as they have analgesic, anti-emetic and appetite stimulant properties which palliate adverse symptoms. Use of these agents in an oncology setting raises the question of whether they act to modulate the effectiveness of concurrently administered anti-cancer drugs. The transporter, P-glycoprotein (P-gp) confers multiple drug resistance (MDR) by effluxing a diverse array of anti-cancer agents. This study was undertaken to examine the effect of cannabinoids on P-gp. Unlike the known P-gp inhibitor, PSC833, short 1h exposure to three plant-derived cannabinoids, cannabinol (CBN), cannabidiol (CBD) and Delta(9)-tetrahydrocannabinol (THC) and the synthetic cannabinoid receptor agonist, WIN55, 212-2 (WIN) did not inhibit the efflux of the P-gp substrate Rhodamine 123 (Rh123) in either a drug-selected human T lymphoblastoid leukaemia cell line (CEM/VLB(100)) or in a mouse fibroblast MDR1 transfected cell line (77.1). However, in CEM/VLB(100) cells, prolonged 72 h exposure to the cannabinoids, THC and CBD, decreased P-gp expression to a similar extent as the flavonoid, curcumin (turmeric). This correlated with an increase in intracellular accumulation of Rh123 and enhanced sensitivity of the cells to the cytotoxic actions of the P-gp substrate, vinblastine. Taken together, these results provide preliminary evidence that cannabinoids do not exacerbate P-gp mediated MDR. Further, plant-derived cannabinoids are moderately effective in reversing MDR in CEM/VLB(100) cells by decreasing P-gp expression. PMID:16458258

Holland, M L; Panetta, J A; Hoskins, J M; Bebawy, M; Roufogalis, B D; Allen, J D; Arnold, J C

2006-02-02

191

Down-regulation of c-fos by shRNA sensitizes adriamycin-resistant MCF-7/ADR cells to chemotherapeutic agents via P-glycoprotein inhibition and apoptosis augmentation.  

PubMed

Multidrug resistance (MDR) is a major hurdle in the treatment of cancer. Research indicated that the main mechanisms of most cancers included so-called "pump" (P-glycoprotein, P-gp) and "non-pump" (apoptosis) resistance. Identification of novel signaling molecules associated with both P-gp and apoptosis will facilitate the development of more effective strategies to overcome MDR in tumor cells. Since the proto-oncogene c-fos has been implicated in cell adaptation to environmental changes, we analyzed its role in mediating "pump" and "non-pump" resistance in MCF-7/ADR, an adriamycin (ADR)-selected human breast cancer cell line with the MDR phenotype. Elevated expression of c-fos in MCF-7/ADR cells and induction of c-fos by ADR in the parental drug-sensitive MCF-7 cells suggested a link between c-fos and MDR phenotype. Down-regulation of c-fos expression via shRNA resulted in sensitization of MCF-7/ADR cells to chemotherapeutic agents, including both P-gp and non-P-gp substrates. Further results proved that c-fos down-regulation in MCF-7/ADR cells resulted in decreased P-gp expression and activity, enhanced apoptosis, and altered expression of apoptosis-associated proteins (i.e., Bax, Bcl-2, p53, and PUMA). All above facts indicate that c-fos is involved in both P-gp- and anti-apoptosis-mediated MDR of MCF-7/ADR cells. Based on these results, we propose that c-fos may represent a potential molecular target for resistant cancer therapy, and suppressing c-fos gene expression may therefore be an effective means to temper breast cancer cell's MDR to cytotoxic chemotherapy. PMID:23494858

Shi, Ruizan; Peng, Hongwei; Yuan, Xiangfei; Zhang, Xiuli; Zhang, Yanjun; Fan, Dongmei; Liu, Xuyi; Xiong, Dongsheng

2013-08-01

192

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

193

Overexpression of P-glycoprotein, STAT3, phospho-STAT3 and KIT in spontaneous canine cutaneous mast cell tumours before and after prednisolone treatment.  

PubMed

Prednisolone is a glucocorticoid (GC) commonly used in the treatment of canine mast cell tumours (MCTs); however, resistance to GCs develops in many MCTs following repeated treatment. P-glycoprotein (P-gp), signal transducer and activator of transcription 3 (STAT3) and KIT (CD117) are involved in GC resistance. The aim of this study was to evaluate the response to prednisolone treatment in canine cutaneous MCTs and to investigate the levels of P-gp, STAT3, phospho-STAT3 (pSTAT3) and KIT proteins in MCTs with or without prednisolone treatment. Immunohistochemistry was performed on tumour samples from 41 dogs with cutaneous MCTs. The overall objective response rate (including complete and partial responses) was 51.8% for dogs treated with prednisolone; poorly differentiated or higher stage MCTs had a lower response rate. The median time-span of tumours to reach maximal tumour regression was 14 d (range 3-77 d); 22 (81.5%) reached maximal regression at 21 d. The majority of MCTs overexpressed both P-gp and STAT3 before and after prednisolone treatment. Reduced expression of pSTAT3 and alterations in the KIT expression pattern were observed in MCTs post-treatment. Prednisolone treatment that caused a marked reduction in tumour volume was correlated with reduced pSTAT3 expression. A cytoplasmic KIT staining pattern was correlated with a lower tumour response rate to prednisolone treatment. PMID:22398132

Teng, Shr-Ping; Hsu, Wei-Li; Chiu, Cheng-Yang; Wong, Min-Liang; Chang, Shih-Chieh

2012-03-06

194

Electrochemical immunoassay of membrane P-glycoprotein by immobilization of cells on gold nanoparticles modified on a methoxysilyl-terminated butyrylchitosan matrix.  

PubMed

A strategy to detect P-glycoprotein (P-gp) on cell membrane and quantify the cell number using electrochemical immunoassay was developed by effective surface immunoreactions and immobilization of cells on a highly hydrophilic interface, which was constructed by adsorption of colloidal gold nanoparticles on a methoxysilyl-terminated (Mos) butyrylchitosan modified glassy carbon electrode (Au-CS/GCE). Atomic force microscopy studies proved that the nanoparticles adsorbed on Mos-butyrylchitosan were efficient in preventing the cell leakage and retaining the activity of immobilized living K562/ADM leukemic cells. The incubation with P-gp monoclonal antibody and then the secondary alkaline phosphatase (AP) conjugated antibody introduced AP onto the K562/ADM cell immobilized on Au-CS/GCE. The bound AP led to an amperometric response of 1-naphthyl phosphate. Under optimal conditions the response was proportional to the logarithm of cell concentration in the range from 5.0 x 10(4) to 1.0 x 10(7) cells mL(-)(1) with a detection limit of 1.0 x 10(4) cells mL(-)(1). The results were comparable to flow cytometric analysis of P-gp expression. This proposed method was practical, convenient, and significant in the clinic and cytobiology. PMID:16114890

Du, Dan; Ju, Huangxian; Zhang, Xueji; Chen, Jing; Cai, Jie; Chen, Hongyuan

2005-08-30

195

In silico modeling for the nonlinear absorption kinetics of UK-343,664: a P-gp and CYP3A4 substrate.  

PubMed

The aim of this work was to extrapolate in vitro and preclinical animal data to simulate the pharmacokinetic parameters of UK-343,664, a P-glycoprotein (P-gp) and CYP3A4 substrate, in human. In addition, we aimed to develop a simulation model to demonstrate the involvement and the controversial complex interaction of intestinal P-gp and CYP3A4 in its nonlinear absorption, first-pass extraction, and pharmacokinetics using the advanced compartmental absorption and transit (ACAT) model. Finally, we aimed to compare the results predicted from the model to the reported findings in human clinical studies. In situ perfusion, allometric scaling, PBPK Rodger mechanistic approach, in vitro metabolism, and fitting to in vivo data were used to mechanistically explain the absorption, distribution and metabolism, respectively. GastroPlus was used to build the integrated simulation model in human for UK-343,664 to mechanistically explain the observed clinical data at 30, 100, 200, 400, and 800 mg oral doses. The measured in vitro value for CYP3A4 K(m) (465 ?M) in rCYPs was converted to units of ?g/mL, corrected for assumed microsomal binding (17.8%) and applied to all metabolic processes. The measured in vitro values of V(max) for CYP3A4 (38.9 pmol/min/pmol), 2C8, 2C9, 2C19, and 2D6 were used along with the in vitro CYP3A4 K(m) to simulate liver first pass extraction and systemic clearance. The measured in vitro values of V(max) for CYP3A4 and 2D6 were used along with the in vitro CYP3A4 K(m) to simulate gut first pass extraction. V(max) and K(m) values for P-gp were obtained by fitting to in vivo data and used to simulate gut efflux transport activity. Investigation of the interaction mechanism of P-gp and CYP3A4 in the intestine was achieved by comparing the influence of a virtual knockout of P-gp or gut metabolism on the fraction absorbed, fraction reaching the portal vein, and fraction metabolized in the gut. Comparison between simulation and in vivo results showed that the in silico simulation provided a mechanistic explanation of the observed nonlinear absorption kinetics of UK-343,664 in human following its administration in the range of 30-800 mg as oral solutions. The simulation results of the pharmacokinetic parameters, AUC and C(max), by GastroPlus were comparable with those observed in vivo. This simulation model is one possible mechanistic explanation of the observed in vivo data and suggests that the nonlinear dose dependence could be attributed to saturation of both the efflux transport by P-gp and the intestinal metabolism. However, the concentration ranges for either protein saturation did not overlap and resulted in much greater than dose proportional increases in AUC. At low doses, producing intraenterocyte concentrations below the fitted value of K(m) for P-gp, the influence of P-gp appears to be protective and results in a lower fraction of gut 3A4 metabolism. At higher doses, as P-gp becomes saturated the fraction of gut 3A4 extraction increases, and eventually at the highest doses, where 3A4 becomes saturated, the fraction of gut 3A4 extraction again decreases. Such a complex interpretation of this in vitro-in vivo extrapolation (IVIVE) is another example of the value and insight obtained by physiologically based absorption simulation. PMID:22264132

Abuasal, Bilal S; Bolger, Michael B; Walker, Don K; Kaddoumi, Amal

2012-02-02

196

Induction of autoantibodies to murine P-glycoprotein: Consequences on drug sensitivity in MDR cancer cells and on the expression of mdr genes in organs  

Microsoft Academic Search

Overexpression of the 170kDa plasma membrane P-glycoprotein (P-gp) represents the most common MDR mechanism in chemotherapy. In this work, specific autoantibodies to fragments from extracellular loops 1, 2, and 4 of the murine MDR1 P-gp were elicited in mice using synthetic palmitoylated peptides reconstituted in liposomes and alum. The highest IgG level was observed after the third immunization and the

Laura Perrin; Grégory Gatouillat; Emilie Balasse; Johann Odot; Claude Nicolau; Pierre-François Tosi; Claudie Madoulet

2007-01-01

197

Reversal of p-glycoprotein-mediated multidrug resistance by CJX1, an amlodipine derivative, in doxorubicin-resistant human myelogenous leukemia (K562\\/DOX) cells  

Microsoft Academic Search

P-glycoprotein-mediated drug efflux can yield a multidrug resistance (MDR) phenotype that is associated with a poor response to cancer chemotherapy. Development of safe and effective MDR reversing agents is an important approach in the clinic. The aim of this study was to observe the effects of CJX1, an amlodipine derivative, on the inhibition of P-gp function and P-gp-mediated MDR in

Bian-Sheng Ji; Ling He; Guo-Qing Liu

2005-01-01

198

Quantitative assessment of P-glycoprotein function in the rat blood–brain barrier by distribution volume of [ 11C]verapamil measured with PET  

Microsoft Academic Search

The blood–brain barrier (BBB) is a functional barrier that hampers the delivery of various drugs to the brain by its physicoanatomical properties and by the presence of ATP-driven drug efflux pumps, such as P-glycoprotein (P-gp). The aims of this study were (1) to study whether the distribution volume (DV) is useful for quantification of (labeled) P-gp substrate kinetics over the

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

2003-01-01

199

Induction of multidrug resistance in MOLT4 cells by anticancer agents is closely related to increased expression of functional P-glycoprotein and MDR1 mRNA  

Microsoft Academic Search

Purpose: The aim of this study was to investigate the multidrug resistance (MDR) pattern, MDR gene and P-glycoprotein (P-gp) expression, and P-gp function in drug-induced human T-lymphoblastoid leukemia MOLT-4 sublines. Methods: The MDR sublines were developed by exposing the parental MOLT-4 cells to stepwise increasing concentrations of anticancer drugs daunorubicin (DNR), vinblastine (VBL) and doxorubicin (DOX). Degrees of resistance were

Zhen-Li Liu; Kenji Onda; Sachiko Tanaka; Tsugutoshi Toma; Toshihiko Hirano; Kitaro Oka

2002-01-01

200

Small P-gp modulating molecules: SAR studies on tetrahydroisoquinoline derivatives.  

PubMed

The development of small molecules as P-gp modulating agents and SAR studies on these ligands represented the aim of the present work. A series of 6,7-dimethoxytetrahydroisoquinoline derivatives was prepared and their ability to inhibit P-gp activity has been evaluated. The basic nucleus of these compounds, common to the best P-gp inhibitors such as Tariquidar and Elacridar, has been functionalized with no-basic moiety from our studied sigma receptor ligands displaying potent P-gp inhibition. The best results were obtained for compounds 3c and 3a (EC(50)=1.64 and 4.86 microM, respectively) and these results were remarkable because Elacridar showed in the same biological evaluation similar inhibitory activity (EC(50)=2 microM). SAR studies displayed that the removal of double bond on the spacer or its shifting into tetraline ring decreased the P-gp inhibiting activity. Moreover, the P-gp inhibition mechanism of tested compounds was investigated by three selected biological experiments. The results displayed that only compound 3c was P-gp inhibitor as Elacridar, while compound 3a and reference compounds Cyclosporin A and Verapamil modulated P-gp activity saturating the efflux pump as substrates. Flow cytometry studies carried out in Doxorubicin resistant breast cancer cell line (MCF7/Adr) confirmed that compound 3c increased Doxorubicin cell accumulation 5.7-fold. In addition, in MCF7/Adr, antiproliferative effect of 5 microM Doxorubicin shifted from 5% to 95% when co-administered with compound 3c (20 microM). The present study suggested a new class of small molecules displaying P-gp inhibitor activity differing from reference compounds Elacridar and Tariquidar for a simplified, and in the meantime, efficacious no-basic moiety. PMID:17936633

Colabufo, Nicola Antonio; Berardi, Francesco; Cantore, Mariangela; Perrone, Maria Grazia; Contino, Marialessandra; Inglese, Carmela; Niso, Mauro; Perrone, Roberto; Azzariti, Amalia; Simone, Grazia Maria; Porcelli, Letizia; Paradiso, Angelo

2007-09-25

201

Functional Fluo-3\\/AM Assay on P-Glycoprotein Transport Activity in L1210\\/VCR Cells by Confocal Microscopy  

Microsoft Academic Search

Multidrug resistance (MDR) phenotype of L1210\\/VCR cell line, ac- quired by selection for vincristine (VCR), is predominantly mediated by P-glyco- protein(Pgp). Calcein\\/AM(Cal)was recently describedas afluorescentsubstrate for Pgp and may be used for measuring of transport activity of Pgp. Expression of Pgp in the cells prevents them to be loaded with the fluorescent marker. To detectthe activityofPgp,verapamil(Ver)orcyclosporineA(CsA)hastobe used as Pgpinhibitors. Multidrug

J. Orlick; Z. SulovÆ; I. DovinovÆ; R. Fiala; A. ZahradnÌkovÆ Jr; A. Breier

2004-01-01

202

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

2012-03-30

203

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

204

Enhanced complement resistance in drug-selected P-glycoprotein expressing multi-drug-resistant ovarian carcinoma cells  

PubMed Central

Multi-drug resistance (MDR) is a major obstacle in cancer chemotherapy. There are contrasting data on a possible correlation between the level of expression of the drug transporter P-glycoprotein (P-gp) and susceptibility to complement-dependent cytotoxicity (CDC). We therefore investigated the sensitivity of human ovarian carcinoma cells and their P-gp expressing MDR variants to complement. Chemoselected P-gp expressing MDR cells showed increased resistance to CDC associated with overexpression of membrane-bound complement regulatory proteins (mCRP) and increased release of the soluble inhibitors C1 inhibitor and factor I. MDR1 gene transfection alone did not alter the susceptibility of P-gp expressing A2780-MDR and SKOV3-MDR cells to CDC. However, subsequent vincristine treatment conferred an even higher resistance to complement to these cells, again associated with increased expression of mCRP. Blocking the function of P-gp with verapamil, cyclosporine A or the anti-P-gp-antibody MRK16 had no impact on their complement resistance, whereas blocking of mCRP enhanced their susceptibility to complement. These results suggest that enhanced resistance of chemoselected MDR ovarian carcinoma cells to CDC is not conferred by P-gp, but is due at least partly to overexpression of mCRP, probably induced by treatment with the chemotherapeutic agents.

Odening, K E; Li, W; Rutz, R; Laufs, S; Fruehauf, S; Fishelson, Z; Kirschfink, M

2009-01-01

205

Flavonoids inhibit breast cancer resistance protein-mediated drug resistance: transporter specificity and structure–activity relationship  

Microsoft Academic Search

Purpose  ATP-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug\\u000a resistance-related protein 1 (MRP1), confer resistance to various anticancer agents. We previously reported that some flavonoids\\u000a have BCRP-inhibitory activity. Here we show the reversal effects of an extensive panel of flavonoids upon BCRP-, P-gp-, and\\u000a MRP1-mediated drug resistance.\\u000a \\u000a \\u000a \\u000a Methods  Reversal effects of flavonoids upon BCRP-, P-gp-,

Kazuhiro Katayama; Kazuto Masuyama; Sho Yoshioka; Hitomi Hasegawa; Junko Mitsuhashi; Yoshikazu Sugimoto

2007-01-01

206

In vivo induction of P-glycoprotein expression at the mouse blood-brain barrier: an intracerebral microdialysis study.  

PubMed

Intracerebral microdialysis was utilized to investigate the effect of P-glycoprotein (a drug efflux transporter) induction at the mouse blood-brain barrier (BBB) on brain extracellular fluid concentrations of quinidine, an established substrate of P-glycoprotein. Induction was achieved by treating male CD-1 mice for 3 days with 5 mg/kg/day dexamethasone (DEX), a ligand of the nuclear receptor, pregnane X receptor, and a P-glycoprotein inducer. Tandem liquid chromatography mass spectrometric method was used to quantify analytes in dialysate, blood and plasma. P-glycoprotein, pregnane X receptor and Cyp3a11 (metabolizing enzyme for quinidine) protein expression in capillaries and brain homogenates was measured by immunoblot analysis. Following quinidine i.v. administration, the average ratio of unbound quinidine concentrations in brain extracellular fluid (determined from dialysate samples) to plasma at steady state (375-495 min) or Kp, uu, ECF /Plasma in the DEX-treated animals was 2.5-fold lower compared with vehicle-treated animals. In DEX-treated animals, P-glycoprotein expression in brain capillaries was 1.5-fold higher compared with vehicle-treated animals while Cyp3a11 expression in brain capillaries was not significantly different between the two groups. These data demonstrate that P-gp induction mediated by DEX at the BBB can significantly reduce quinidine brain extracellular fluid concentrations by decreasing its brain permeability and further suggest that drug-drug interactions as a result of P-gp induction at the BBB are possible. Applying microdialysis, distribution of quinidine, a P-gp substrate, in mouse brain extracellular fluid (ECF) was investigated following ligand-mediated P-glycoprotein (P-gp) induction at the blood-brain barrier (BBB). We demonstrated that a PXR agonist (dexamethasone) significantly up-regulated P-gp in brain capillaries and reduced quinidine brain ECF concentrations. Our data suggest that drug-drug interactions as a result of P-gp induction at the BBB are possible. PMID:23777437

Chan, Gary N Y; Saldivia, Victor; Yang, Yingbo; Pang, Henrianna; de Lannoy, Inés; Bendayan, Reina

2013-07-15

207

Nanoparticle Mediated P-Glycoprotein Silencing for Improved Drug Delivery across the Blood-Brain Barrier: A siRNA-Chitosan Approach  

PubMed Central

The blood-brain barrier (BBB), composed of tightly organized endothelial cells, limits the availability of drugs to therapeutic targets in the central nervous system. The barrier is maintained by membrane bound efflux pumps efficiently transporting specific xenobiotics back into the blood. The efflux pump P-glycoprotein (P-gp), expressed at high levels in brain endothelial cells, has several drug substrates. Consequently, siRNA mediated silencing of the P-gp gene is one possible strategy how to improve the delivery of drugs to the brain. Herein, we investigated the potential of siRNA-chitosan nanoparticles in silencing P-gp in a BBB model. We show that the transfection of rat brain endothelial cells mediated effective knockdown of P-gp with subsequent decrease in P-gp substrate efflux. This resulted in increased cellular delivery and efficacy of the model drug doxorubicin.

Malmo, Jostein; Sandvig, Axel; Varum, Kjell M.; Strand, Sabina P.

2013-01-01

208

The "Specific" P-Glycoprotein Inhibitor Tariquidar Is Also a Substrate and an Inhibitor for Breast Cancer Resistance Protein (BCRP/ABCG2)  

PubMed Central

Tariquidar was developed as a specific inhibitor of the efflux transporter ABCB1. Recent positron emission tomographic brain imaging studies using [11C]tariquidar to measure ABCB1 (P-gp, P-glycoprotein) density in mice indicate that the inhibitor may not be as specific as previously thought. We examined its selectivity as an inhibitor and a substrate for the human transporters P-gp, breast cancer resistance protein (BCRP, ABCG2), and multidrug resistance protein 1 (MRP1, ABCC1). Our results show that at low concentrations, tariquidar acts selectively as an inhibitor of P-gp and also as a substrate of BCRP. At much higher concentrations (?100 nM), tariquidar acts as an inhibitor of both P-gp and BCRP. Thus, the in vivo specificity of tariquidar depends on concentration and the relative density and capacity of P-gp vs BCRP.

2010-01-01

209

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; Baggetto, Loris; Jardillier, Jean-Claude; Alix, Alain J.; Nabiev, Igor R.

1999-04-01

210

Desipramine treatment has minimal effects on the brain accumulation of glucocorticoids in P-gp-deficient and wild-type mice  

PubMed Central

Summary Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis in patients with depression can be reduced by antidepressants, which are thought to improve endogenous glucocorticoid-mediated negative feedback. A proportion of peripherally released glucocorticoids need to enter brain tissue, protected by the blood–brain barrier (BBB), in order to achieve this negative feedback effect at the level of the central nervous systems (CNS). The multidrug resistance transporter P-glycoprotein (P-gp) has been shown to actively transport glucocorticoid hormones and has been implicated in the regulation of glucocorticoid access to the CNS. Using an in situ brain/choroid plexus perfusion method, we tested the hypothesis that the antidepressant desipramine increases glucocorticoid accumulation in the mouse brain by inhibiting P-gp, following either chronic treatment (8 days, 20 mg/kg/day, IP) or acute administration (20 min brain perfusion in the presence of either 0.9 ?M or 10 ?M desipramine). Contrary to our hypothesis, chronic treatment with desipramine did not affect the accumulation of [3H]dexamethasone in any sample compared to saline-treated mice. Acute desipramine had limited and variable effects on glucocorticoid accumulation in the CNS, with accumulation of [3H]dexamethasone increased in the cerebellum, accumulation of [3H]cortisol reduced in the frontal cortex, hypothalamus, and cerebellum, and accumulation of [3H]corticosterone (the endogenous glucocorticoid in rodents) not affected. Overall, under the conditions tested, these results do not support the hypothesis that treatment with desipramine can inhibit P-gp at the BBB and subsequently increase the accumulation of glucocorticoids in the brain.

Mason, Brittany L.; Thomas, Sarah A.; Lightman, Stafford L.; Pariante, Carmine M.

2011-01-01

211

Docking and 3D-QSAR (quantitative structure activity relationship) studies of flavones, the potent inhibitors of p-glycoprotein targeting the nucleotide binding domain  

Microsoft Academic Search

In order to explore the interactions between flavones and P-gp, in silico methodologies such as docking and 3D-QSAR were performed. CoMFA and CoMSIA analyses were done using ligand based and receptor guided alignment schemes. Validation statistics include leave-one-out cross-validated R2 (q2), internal prediction parameter by progressive scrambling (Q?2), external prediction with test set. They show that models derived from this

Gugan Kothandan; Changdev G. Gadhe; Thirumurthy Madhavan; Cheol Hee Choi; Seung Joo Cho

2011-01-01

212

Short-term effect of quercetin on the pharmacokinetics of fexofenadine, a substrate of P-glycoprotein, in healthy volunteers  

Microsoft Academic Search

Objective  The aim of the present study was to assess whether quercetin exhibited any inhibitory effect on P-glycoprotein (P-gp)-mediated\\u000a drug disposition in humans using fexofenadine as a P-gp substrate.\\u000a \\u000a \\u000a \\u000a Methods  Twelve healthy subjects were enrolled in the study and treated daily for 7 days with 500 mg quercetin or placebo 3 times a\\u000a day. On day 7, a single dose of 60 mg fexofenadine was

Kyoung-Ah Kim; Pil-Whan Park; Ji-Young Park

2009-01-01

213

MDR1-P-glycoprotein behaves as an oncofetal protein that promotes cell survival in gastric cancer cells.  

PubMed

P-glycoprotein (P-gp), traditionally linked to cancer poor prognosis and multidrug resistance, is undetectable in normal gastric mucosa and overexpressed in gastric cancer (GC). We propose that P-gp may be involved in Helicobacter pylori (Hp)-related gastric carcinogenesis by inhibiting apoptosis. Aim of the study was to evaluate the expression of P-gp in fetal stomach and in Hp-related gastric carcinogenesis, the epigenetic control of the multi-drug resistance-1 (MDR1) gene, the localization and interaction between P-gp and Bcl-x(L) and the effect of the selective silencing of P-gp on cell survival. P-gp and Bcl-xl expression was evaluated by immunohistochemistry on 28 spontaneously abortive human fetuses, 66 Hp-negative subjects, 138 Hp-positive chronic gastritis (CG) of whom 28 with intestinal metaplasia (IM) and 45 intestinal type GCs. P-gp/Bcl-x(L) colocalization was investigated by confocal immunofluorescence microscopy and protein-protein interaction by co-immunoprecipitation, in basal conditions and after stress-induced apoptosis, in GC cell lines AGS and MKN-28 and hepatocellular carcinoma cell line Hep-G2. The role of P-gp in controlling apoptosis was evaluated by knocking down its expression with a specific small interfering RNAs in stressed AGS and MKN-28 cell lines. P-gp is expressed in the gastric mucosa of all human fetuses while, it is undetectable in adult normal mucosa and re-expressed in 30/110 Hp-positive non-IM-CG, 28/28 IM-CG and 40/45 GCs. P-gp expression directly correlates with that of Bcl-x(L) and with the promoter hypomethylation of the MDR1 gene. In GC cell lines, P-gp is localized on the plasma membrane and mitochondria where it colocalizes with Bcl-x(L). Co-immunoprecipitation confirms the physical interaction between P-gp and Bcl-x(L) in AGS, MKN-28 and Hep-G2, at both basal level and after stress-induced apoptosis. The selective silencing of P-gp sensitizes GC cells to stress-induced apoptosis. P-gp behaves as an oncofetal protein that, by cross-talking with Bcl-x(L), acts as an anti-apoptotic agent in Hp-related gastric carcinogenesis. PMID:22751348

Rocco, Alba; Compare, Debora; Liguori, Eleonora; Cianflone, Alessandra; Pirozzi, Giuseppe; Tirino, Virginia; Bertoni, Alessandra; Santoriello, Margherita; Garbi, Corrado; D'Armiento, Maria; Staibano, Stefania; Nardone, Gerardo

2012-07-02

214

Involvement of P-gp in the process of apoptosis in peripheral blood mononuclear cells  

Microsoft Academic Search

Multidrug resistance mediated by the drug-efflux protein P (P-gp) is one of mechanisms that cells use to escape death induced by drugs and other agents. The aim of the study was to evaluate the effect of P-gp inhibition on apoptosis of PHA-activated peripheral blood mononuclear cells (MNC) as well as apoptosis induced by methotrexate (MTX), dexamethasone (DEX), methylprednisolone (MP) and

A. Pawlik; M. Baskiewicz-Masiuk; B. Machalinski; B. Gawronska-Szklarz

2005-01-01

215

Effects of Astragalus polysaccharides on P-glycoprotein efflux pump function and protein expression in H22 hepatoma cells in vitro  

PubMed Central

Background Astragalus polysaccharides (APS) are active constituents of Astragalus membranaceus. They have been widely studied, especially with respect to their immunopotentiating properties, their ability to counteract the side effects of chemotherapeutic drugs, and their anticancer properties. However, the mechanism by which APS inhibit cancer and the issue of whether that mechanism involves the reversal of multidrug resistance (MDR) is not completely clear. The present paper describes an investigation of the effects of APS on P-glycoprotein function and expression in H22 hepatoma cell lines resistant to Adriamycin (H22/ADM). Methods H22/ADM cell lines were treated with different concentrations of APS and/or the most common chemotherapy drugs, such as Cyclophosphamid, Adriamycin, 5-Fluorouracil, Cisplatin, Etoposide, and Vincristine. Chemotherapeutic drug sensitivity, P-glycoprotein function and expression, and MDR1 mRNA expression were detected using MTT assay, flow cytometry, Western blotting, and quantitative RT-PCR. Results When used alone, APS had no anti-tumor activity in H22/ADM cells in vitro. However, it can increase the cytotoxicity of certain chemotherapy drugs, such as Cyclophosphamid, Adriamycin, 5-Fluorouracil, Cisplatin, Etoposide, and Vincristine, in H22/ADM cells. It acts in a dose-dependent manner. Compared to a blank control group, APS increased intracellular Rhodamine-123 retention and decreased P-glycoprotein efflux function in a dose-dependent manner. These factors were assessed 24?h, 48?h, and 72?h after administration. APS down regulated P-glycoprotein and MDR1 mRNA expression in a concentration-dependent manner within a final range of 0.8–500?mg/L and in a time-dependent manner from 24–72?h. Conclusion APS can enhance the chemosensitivity of H22/ADM cells. This may involve the downregulation of MDR1 mRNA expression, inhibition of P-GP efflux pump function, or both, which would decrease the expression of the MDR1 protein.

2012-01-01

216

Mechanism of ritonavir changes in methadone pharmacokinetics and pharmacodynamics. II. Ritonavir effects on CYP3A and P-glycoprotein activities  

PubMed Central

Ritonavir diminishes methadone plasma concentrations, attributed to CYP3A, but mechanisms are unknown. We determined short-term (2 day) and steady-state (2 week) ritonavir effects on intestinal/hepatic CYP3A (probed with IV and oral alfentanil, and miosis), P-glycoprotein (fexofenadine) and methadone pharmacokinetics and pharmacodynamics in healthy volunteers. Acute ritonavir increased the AUC0-?/dose ratio (ritonavir/control) for oral alfentanil 25-fold. Steady-state ritonavir increased the AUC0-?/dose ratio for intravenous and oral alfentanil 4- and 10-fold, respectively, reduced hepatic extraction (0.26 to 0.07), intestinal extraction (0.51 to zero), and increased bioavailability (37 to 95%). Acute ritonavir inhibits first-pass CYP3A >96%. Chronic ritonavir inhibits hepatic (>70%) and first-pass (>90%) CYP3A. Acute and steady-state ritonavir increased fexofenadine AUC0-? 2.8- and 1.4-fold, suggesting P-glycoprotein inhibition. Steady-state ritonavir caused mild apparent induction of P-glycoprotein and hepatic CYP3A, but net inhibition still predominated. Ritonavir inhibits both intestinal and hepatic CYP3A and drug transport. Alfentanil miosis noninvasively determined CYP3A inhibition by ritonavir.

Kharasch, Evan D.; Bedynek, Pamela Sheffels; Walker, Alysa; Whittington, Dale; Hoffer, Christine; Park, Sang

2013-01-01

217

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

218

Lysosomal trapping of a radiolabeled substrate of P-glycoprotein as a mechanism for signal amplification in PET  

PubMed Central

The radiotracer [11C]N-desmethyl-loperamide (dLop) images the in vivo function of P-glycoprotein (P-gp), a transporter that blocks the entry of drugs that are substrates into brain. When P-gp is inhibited, [11C]dLop, a potent opiate agonist, enters and becomes trapped in the brain. This trapping is beneficial from an imaging perspective, because it amplifies the PET signal, essentially by accumulating radioactivity over time. As we previously demonstrated that this trapping was not caused by binding to opiate receptors, we examined whether [11C]dLop, a weak base, is ionically trapped in acidic lysosomes. To test this hypothesis, we measured [3H]dLop accumulation in human cells by using lysosomotropics. Because the in vivo trapping of dLop was seen after P-gp inhibition, we also measured [3H]dLop uptake in P-gp–expressing cells treated with the P-gp inhibitor tariquidar. All lysosomotropics decreased [3H]dLop accumulation by at least 50%. In P-gp–expressing cells, tariquidar (and another P-gp inhibitor) surprisingly decreased [3H]dLop uptake. Consequently, we measured [11C]dLop uptake before and after tariquidar preadministration in lysosome-rich organs of P-gp KO mice and humans. After tariquidar pretreatment in both species, radioactivity uptake in these organs decreased by 35% to 40%. Our results indicate that dLop is trapped in lysosomes and that tariquidar competes with dLop for lysosomal accumulation in vitro and in vivo. Although tariquidar and dLop compete for lysosomal trapping in the periphery, such competition does not occur in brain because tariquidar has negligible entry into brain. In summary, tariquidar and [11C]dLop can be used in combination to selectively measure the function of P-gp at the blood–brain barrier.

Kannan, Pavitra; Brimacombe, Kyle R.; Kreisl, William C.; Liow, Jeih-San; Zoghbi, Sami S.; Telu, Sanjay; Zhang, Yi; Pike, Victor W.; Halldin, Christer; Gottesman, Michael M.; Innis, Robert B.; Hall, Matthew D.

2011-01-01

219

Factors that limit positron emission tomography imaging of p-glycoprotein density at the blood-brain barrier.  

PubMed

Efflux transporters located at the blood-brain barrier, such as P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), regulate the passage of many drugs in and out of the brain. Changes in the function and density of these proteins, in particular P-gp, may play a role in several neurological disorders. Several radioligands have been developed for measuring P-gp function at the blood-brain barrier of human subjects with positron emission tomography (PET). However, attempts to measure P-gp density with radiolabeled inhibitors that bind to these proteins in vivo have not thus far provided useful, quantifiable PET signals. Herein, we argue that not only the low density of transporters in the brain as a whole but also their very high density in brain capillaries act to lower the concentration of ligand in the plasma and thereby contribute to absent or low signals in PET studies of P-gp density. Our calculations, based on published data and theoretical approximations, estimate that whole brain densities of many efflux transporters at the blood-brain barrier range from 0.04 to 5.19 nM. We conclude that the moderate affinities (>5 nM) of currently labeled inhibitors may not allow measurement of efflux transporter density at the blood-brain barrier, and inhibitors with substantially higher affinity will be needed for density imaging of P-gp and other blood-brain barrier transporters. PMID:23597242

Kannan, Pavitra; Pike, Victor W; Halldin, Christer; Langer, Oliver; Gottesman, Michael M; Innis, Robert B; Hall, Matthew D

2013-05-02

220

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

221

CJX1, an amlodipine derivative, interacts with ATPase of human P-glycoprotein.  

PubMed

Our aim has been to elucidate the possible mechanism of CJX1, an amlodipine derivative, in the modulation of P-gp function by determining its effect on P-gp ATPase activity. Basal P-gp ATPase activity was increased by CJX1 with half-maximal activity concentration (Km) of 8.6+/-1.4 microM. Kinetic analysis indicated a non-competitive inhibition of Verapamil (Ver)-stimulated P-gp ATPase activity by CJX1 and competitive inhibition of CJX1-stimulated P-gp ATPase activity by tetrandrine (Tet). The effect of CsA on CJX1-stimulated and Ver-stimulated P-gp ATPase activity was non-competitive and competitive inhibition, respectively. These findings implying that CJX1 and Tet can bind P-gp either on overlapping sites or distinct but interacting sites, while CJX1 and Ver as well as CsA can bind P-gp on separated sites in K562/DOX cells. Furthermore, the combined effect of CJX1 and Ver has been evaluated isobolographically in numerous fixed-ratio combinations of 1:1, 1:2, 1:4, 1:8, 1:10 in K562/DOX cells. The results show that mixtures of both drugs at these fixed-ratios exerted synergistic interactions, indicating that when the two reverses that bind P-gp on separated sites are combined, each can contribute to the overall interaction with P-gp, leading to the greater effect than that by either agent alone. PMID:19589390

Ji, Bian-Sheng; He, Ling

2009-07-07

222

Murine P-glycoprotein Deficiency Alters Intestinal Injury Repair and Blunts Lipopolysaccharide-Induced Radioprotection  

PubMed Central

P-glycoprotein (P-gp) has been reported to increase stem cell proliferation and regulate apoptosis. Absence of P-gp results in decreased repair of intestinal epithelial cells after chemical injury. To further explore the mechanisms involved in the effects of P-gp on intestinal injury and repair, we used the well-characterized radiation injury model. In this model, injury repair is mediated by production of prostaglandins (PGE2) and lipopolysaccharide (LPS) has been shown to confer radioprotection. B6.mdr1a?/? mice and wild-type controls were subjected to 12 Gy total body X-ray irradiation and surviving crypts in the proximal jejunum and distal colon were evaluated 3.5 days after irradiation. B6.mdr1a?/?mice exhibited normal baseline stem cell proliferation and COX dependent crypt regeneration after irradiation. However, radiation induced apoptosis was increased and LPS-induced radioprotection was blunted in the C57BL6.mdr1a?/?distal colon, compared to B6 wild-type controls. The LPS treatment induced gene expression of the radioprotective cytokine IL-1?, in B6 wild-type controls but not in B6.mdr1a?/? animals. Lipopolysaccharid-induced radioprotection was absent in IL-1R1?/? animals, indicating a role for IL-1? in radioprotection, and demonstrating that P-gp deficiency interferes with IL-1? gene expression in response to systemic exposure to LPS.

Staley, Elizabeth M.; Yarbrough, Vanisha R.; Schoeb, Trenton R.; Daft, Joseph G.; Tanner, Scott M.; Steverson, Dennis; Lorenz, Robin G.

2012-01-01

223

Potent galloyl-based selective modulators targeting multidrug resistance associated protein 1 and P-glycoprotein.  

PubMed

The multifactorial nature of chemotherapy failure in controlling cancer is often associated with the occurrence of multidrug resistance (MDR), a phenomenon likely related to the increased expression of members of the ATP binding cassette (ABC) transporter superfamily. In this respect, the most extensively characterized MDR transporters include ABCB1 (also known as MDR1 or P-glycoprotein) and ABCC1 (also known as MRP1) whose inhibition remains a priority to circumvent drug resistance. Herein, we report how the simple galloyl benzamide scaffold can be easily and properly decorated for the preparation of either MRP1 or P-gp highly selective inhibitors. In particular, some gallamides and pyrogallol-1-monomethyl ethers showed remarkable affinity and selectivity toward MRP1. On the other hand, trimethyl ether galloyl anilides, with few exceptions, exhibited moderate to very high and selective P-gp inhibition. PMID:22112208

Pellicani, Raffaella Zoe; Stefanachi, Angela; Niso, Mauro; Carotti, Angelo; Leonetti, Francesco; Nicolotti, Orazio; Perrone, Roberto; Berardi, Francesco; Cellamare, Saverio; Colabufo, Nicola Antonio

2011-12-23

224

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

225

The use of microdialysis techniques in mice to study P-gp function at the blood-brain barrier.  

PubMed

An integrated assay system involving dual/triple-probe microdialysis techniques in rats was developed earlier for testing interactions with P-glycoprotein (P-gp) at the blood-brain barrier using quinidine/PSC-833 as a P-gp substrate/inhibitor combination. The aim of the present study was to expand our assay system to mice using microdialysis with simultaneous sampling of blood and brain and to compare the result with a primary mouse brain endothelial cell monolayer (pMBMEC) assay. Brain penetration of quinidine was dose dependent in both anesthetized and awake mice after intraperitoneal drug administration. PSC-833 pretreatment caused a 2.5- to 3.4-fold increase in quinidine levels of brain dialysate samples in anesthetized or awake animals, after single or repeated administration of PSC-833. In pMBMEC, a 2.0- to 2.5-fold efflux ratio was observed in the transcellular transport of quinidine. The P-gp-mediated vectorial transport of quinidine was eliminated by PSC-833. These results indicate that quinidine with PSC-833 is a good probe substrate-reference inhibitor combination for testing drug-drug interactions with P-gp in the in vivo and in vitro mouse systems. With increasing number of humanized transgenic mice, a test system with mouse microdialysis experimentation becomes more important to predict drug-drug interactions in humans. PMID:23204072

Sziráki, István; Erd?, Franciska; Trampus, Péter; Sike, Mirabella; Molnár, Petra Magdolna; Rajnai, Zsuzsanna; Molnár, Judit; Wilhelm, Imola; Fazakas, Csilla; Kis, Emese; Krizbai, István; Krajcsi, Péter

2012-11-29

226

Synthesis and uptake of fluorescence-labeled Combi-molecules by P-glycoprotein-proficient and -deficient uterine sarcoma cells MES-SA and MES-SA/DX5.  

PubMed

Here, we report on the first synthesis of fluorescent-labeled epidermal growth factor receptor-DNA targeting combi-molecules, and we studied the influence of P-glycoprotein status of human sarcoma MES-SA cells on their growth inhibitory effect and cellular uptake. The results showed that 6, bearing a longer spacer between the quinazoline ring and the dansyl group, was more stable and more cytotoxic than 4. In contrast to the latter, it induced significant levels of DNA damage in human tumor cells. Moreover, in contrast to doxorubicin, a drug known to be actively effluxed by P-gp, the more stable combi-molecule 6 induced almost identical levels of drug uptake and DNA damage in P-gp-proficient and -deficient cells. Likewise, in contrast to doxorubicin, 4 and 6 exerted equal levels of antiproliferative activity against the two cell types. The results in toto suggest that despite their size, the antiproliferative effects of 4 and 6 were independent of P-gp status of the cells. PMID:20151639

Larroque-Lombard, Anne-Laure; Todorova, Margarita; Golabi, Nahid; Williams, Christopher; Jean-Claude, Bertrand J

2010-03-11

227

Transport characteristics of peptides and peptidomimetics: II. Hydroxyethylamine bioisostere-containing peptidomimetics as substrates for the oligopeptide transporter and P-glycoprotein in the intestinal mucosa.  

PubMed

Peptide bond bioisosteres, such as hydroxyethylamine (Hea), have frequently been used to stabilize metabolically labile peptide bonds in peptidomimetic drug design in an effort to increase the oral bioavailability of drug candidates. However, the impact of the peptide bond bioisosteres on the cell permeation characteristics of peptidomimetics is not well understood, particularly with respect to the effects on the substrate activity for proteins that can restrict (e.g. P-glycoprotein, P-gp) or facilitate (e.g. the oligopeptide transporter, OPT) intestinal mucosal permeation of peptidomimetics. In this study, terminally free and terminally modified (N-acetylated and C-amidated) peptidomimetics of H-Ala-Phe-OH and H-Ala-Phe-Ala-OH with the Ala-Phe peptide bonds replaced by Hea bioisosteres were synthesized. Transport characteristics of these peptidomimetics were investigated using Caco-2 cell monolayers as an in vitro model of the intestinal mucosa. The study showed that the Hea bioisostere stabilized the peptidomimetics to protease metabolism in Caco-2 cells. All terminally free peptidomimetics showed significant affinity and substrate activity for OPT. The affinity and substrate activity for OPT were stereoselective for peptidomimetics containing an S,S-configuration for the two adjacent chiral centers related to the Hea bioisostere. Three of the four terminally modified peptidomimetics showed significant substrate activity for P-gp and, interestingly, the substrate activity for P-gp was also stereoselective; however, it was in favor of an R,R-configuration for the two adjacent chiral centers related to the Hea bioisostere. PMID:11350596

Gao, J; Winslow, S L; Vander Velde, D; Aubé, J; Borchardt, R T

2001-05-01

228

Restricted brain penetration of the tyrosine kinase inhibitor erlotinib due to the drug transporters P-gp and BCRP  

Microsoft Academic Search

Summary  \\u000a Purpose Erlotinib (Tarceva®, OSI-774) is a small molecule inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase.\\u000a As high-grade gliomas frequently show amplification, overexpression and\\/or mutation of EGFR, this drug has been tested in\\u000a several clinical trials with glioblastoma patients, but unfortunately, with little success. As erlotinib is a known substrate\\u000a of P-glycoprotein (P-gp) and Breast Cancer Resistance

Nienke A. de Vries; Tessa Buckle; Jin Zhao; Jos H. Beijnen; Jan H. M. Schellens; Olaf van Tellingen

229

Stereoselective Regulations of P-Glycoprotein by Ginsenoside Rh2 Epimers and the Potential Mechanisms From the View of Pharmacokinetics  

PubMed Central

Chirality is an interesting topic and it is meaningful to explore the interactions between chiral small molecules and stereoselective biomacromolecules, with pre-clinical and clinical significances. We have previously demonstrated that 20(S)-ginsenoside Rh2 is an effective P-glycoprotein (P-gp) inhibitor in vitro and in vivo. Considering the stereochemistry of ginsenoside Rh2, in our present study, the regulatory effects of 20(R)-Rh2 on P-gp were assayed in vivo, and the differential regulations of P-gp by ginsenoside Rh2 epimers in vivo were compared and studied. Results showed that 20(S)-Rh2 enhanced the oral absorption of digoxin in rats in a dose-dependent manner; 20(R)-Rh2 at low dosage increased the oral absorption of digoxin, but this effect diminished with elevated dosage of 20(R)-Rh2. Further studies indicated stereoselective pharmacokinetic profiles and intestinal biotransformations of Rh2 epimers. In vitro studies showed that Rh2 epimers and their corresponding deglycosylation metabolites protopanaxadiol (Ppd) epimers all exhibited stereoselective regulations of P-gp. In conclusion, in view of the in vitro and in vivo dispositions of Rh2 and the regulations of P-gp by Rh2 and Ppd, it is suggested that the P-gp regulatory effect of Rh2 in vivo actually is a double actions of both Rh2 and Ppd, and the net effect is determined by the relative balance between Rh2 and Ppd with the same configuration. Our study provides new evidence of the chiral characteristics of P-gp, and is helpful to elucidate the stereoselective P-gp regulation mechanisms of ginsenoside Rh2 epimers in vivo from a pharmacokinetic view.

Niu, Fang; Lu, Meng; Wu, Xiaolan; Sun, Jianguo; Wang, Guangji

2012-01-01

230

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

231

Curcuma drugs and curcumin regulate the expression and function of P-gp in Caco-2 cells in completely opposite ways.  

PubMed

Curcumin is a phenolic compound isolated from rhizomes of C. longa, C. aromatica and other Curcumas except C. zedoaria. Recently, both curcumin and Curcumas have become prevalent as supplement. P-gp has been reported as an important determinant for drug absorption in small intestine. In this study, Caco-2 cell monolayers were treated with methanol extracts of Curcumas (0.1 mg/ml) or curcumin (30 microM) for 72h to investigate the relationship between the potential affects of Curcumas and curcumin on P-gp. [(3)H]-digoxin and rhodamine 123 were used to evaluate P-gp activity. All Curcumas significantly increased the activity of P-gp by up-regulating the expressions of P-gp protein and MDR1 mRNA levels. Interestingly, contrary to Curcumas, curcumin treatment inhibited the activity of P-gp with a decrease in P-gp protein and MDR1 mRNA expression levels. Curcumas might alter the pharmacokinetics of co-administrated drugs by up-regulating the function and expression levels of intestinal P-gp. However, curcumin has no relationship with the inductive effect of Curcumas since curcumin showed an opposite effects. Caution should be exercised when Curcumas or curcumin are to be consumed with drugs that are P-gp substrates because Curcumas and curcumin might regulate the function of P-gp in completely opposite ways. PMID:18439772

Hou, Xiao-Long; Takahashi, Kyoko; Tanaka, Ken; Tougou, Katsuhiko; Qiu, Feng; Komatsu, Katsuko; Takahashi, Koichi; Azuma, Junichi

2008-03-18

232

P-Glycoprotein-ATPase Modulation: The Molecular Mechanisms  

PubMed Central

P-glycoprotein-ATPase is an efflux transporter of broad specificity that counteracts passive allocrit influx. Understanding the rate of allocrit transport therefore matters. Generally, the rates of allocrit transport and ATP hydrolysis decrease exponentially with increasing allocrit affinity to the transporter. Here we report unexpectedly strong down-modulation of the P-glycoprotein-ATPase by certain detergents. To elucidate the underlying mechanism, we chose 34 electrically neutral and cationic detergents with different hydrophobic and hydrophilic characteristics. Measurement of the P-glycoprotein-ATPase activity as a function of concentration showed that seven detergents activated the ATPase as expected, whereas 27 closely related detergents reduced it significantly. Assessment of the free energy of detergent partitioning into the lipid membrane and the free energy of detergent binding from the membrane to the transporter revealed that the ratio, q, of the two free energies of binding determined the rate of ATP hydrolysis. Neutral (cationic) detergents with a ratio of q = 2.7 ± 0.2 (q > 3) followed the aforementioned exponential dependence. Small deviations from the optimal ratio strongly reduced the rates of ATP hydrolysis and flopping, respectively, whereas larger deviations led to an absence of interaction with the transporter. P-glycoprotein-ATPase inhibition due to membrane disordering by detergents could be fully excluded using 2H-NMR-spectroscopy. Similar principles apply to modulating drugs.

Li-Blatter, Xiaochun; Beck, Andreas; Seelig, Anna

2012-01-01

233

Interaction of forskolin with the P-glycoprotein multidrug transporter  

SciTech Connect

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 1,9-dideoxyforskolin both increased the cytotoxic effects of adriamycin in SKVLB cells, yet had no effect on SKOV3 cells. Two photoactive derivatives of forskolin have been synthesized, 7-O-((2-(3-(4-azido-3-({sup 125}I)iodophenyl)propionamido)ethyl)carbamyl)forskolin, {sup 125}I-6-AIPP-Fsk, and 6-O-((2-(3-(4-azido-3-({sup 125}I)iodophenyl)propionamido)ethyl)carbamyl)forskolin, {sup 125}I-6-AIPP-Fsk, which exhibit specificity for labeling the glucose transporter and aing lyl cyclase, respectively. Both photolabels identified a 140-kDa protein in membranes from SKVLB cells whose labeling was inhibited by forskolin and 1,9-dideoxyforskolin. The data are consistent with forskolin binding to the P-glycoprotein analogous to that of other chemosensitizing drugs that have been shown to partially reverse MDR. The ability of forskolin photolabels to specifically label the transporter, the adenylyl cyclase, and the P-glycoprotein suggests that these proteins may share a common biing g domain for forskolin analogues.

Ming s, D.I.; Seamon, K.B. (Food and Drug Administration, Bethesda, MD (United States)); Speicher, L.A.; Tew, K.D. (Fox Chase Cancer Research Center, Philadelphia, PA (United States)); Ruoho, A.E. (Univ. of Wisconsin, Madison (United States))

1991-08-27

234

Immunohistochemical detection of DNA topoisomerase IIalpha, P-glycoprotein and multidrug resistance protein (MRP) in small-cell and non-small-cell lung cancer.  

PubMed Central

Non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC) differ significantly in their clinical response to topoisomerase IIalpha (topo-IIalpha)-directed drugs, such as etoposide and teniposide, as NSCLC is virtually insensitive to single-agent therapy, while SCLC responds in two-thirds of cases. Preclinical studies have indicated that resistance to topo-IIalpha drugs depends on topo-IIalpha content and/or activity, the altered-topo-II multidrug resistance phenotype (at-MDR) and/or one of two different drug efflux pumps, P-glycoprotein (P-gp) and the multidrug resistance protein (MRP). Immunohistochemical analysis on paraffin-embedded tissue from 27 cases of untreated NSCLC and 29 cases of untreated SCLC (of which additional tumour biopsies after treatment with topo-IIalpha-directed drugs were available in ten cases) yielded the following results: NSCLC had significantly less topo-IIalpha than SCLC (P < 0.0001), as only 5 out of 27 NSCLC cases had > 5% positive cells compared with 28 out of 29 SCLC, and 0 out of 27 NSCLC had > 25% positive cells compared with 26 out of 29 SCLC. P-gp was detected in > 5% of cells in only 3 out of 27 NSCLC and in 6 out of 29 SCLC, and MRP in 5 out of 27 of NSCLC and 9 out of 29 SCLC. After treatment of patients with SCLC with either etoposide or teniposide, which are topo-IIalpha-directed drugs, there was an increase in MRP (P < 0.1) and P-gp (P < 0.05) positivity, while topo-IIalpha decreased (P < 0.05). In conclusion, the major difference between untreated NSCLC and SCLC was in topo-IIalpha content. In the small series of ten patients treated for SCLC, all three MDR phenotypes appeared to increase. Images Figure 1 Figure 2 Figure 3 Figure 4

Kreisholt, J.; Sorensen, M.; Jensen, P. B.; Nielsen, B. S.; Andersen, C. B.; Sehested, M.

1998-01-01

235

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

2012-06-09

236

mdm2 gene mediates the expression of mdr1 gene and P-glycoprotein in a human glioblastoma cell line.  

PubMed Central

The overexpression of the multidrug resistance (mdr1) gene and its product, P-glycoprotein (P-gp), is thought to limit the successful chemotherapy of human tumours. The mechanism by which mdr1 gene and P-gp are overexpressed in human tumours, however, is not yet clear. In this report, we show that the mdm2 (murine double minute 2) gene induced the expression of the mdr1 gene and P-gp in human glioblastoma U87-MG cells, which did not express the MDM2 protein or P-gp. The mdm2 gene, in addition, conferred the resistance of U87-MG cells to the apoptotic cell death induced by etoposide (VP-16) or doxorubicin. Furthermore, treatment with mdm2 antisense oligonucleotides inhibited the expression of P-gp in MDM2-expressing U87-MG cells. These findings suggest that the mdm2 gene may play an important role in the development of MDR phenotype in human tumours. Images Figure 1 Figure 3 Figure 5

Kondo, S.; Kondo, Y.; Hara, H.; Kaakaji, R.; Peterson, J. W.; Morimura, T.; Takeuchi, J.; Barnett, G. H.

1996-01-01

237

Beta-Amyloid Downregulates MDR1-P-Glycoprotein (Abcb1) Expression at the Blood-Brain Barrier in Mice  

PubMed Central

Neurovascular dysfunction is an important component of Alzheimer's disease, leading to reduced clearance across the blood-brain barrier and accumulation of neurotoxic ?-amyloid (A?) peptides in the brain. It has been shown that the ABC transport protein P-glycoprotein (P-gp, ABCB1) is involved in the export of A? from the brain into the blood. To determine whether A? influences the expression of key A? transporters, we studied the effects of 1-day subcutaneous A?1-40 and A?1-42 administration via Alzet mini-osmotic pumps on P-gp, BCRP, LRP1, and RAGE expression in the brain of 90-day-old male FVB mice. Our results demonstrate significantly reduced P-gp, LRP1, and RAGE mRNA expression in mice treated with A?1-42 compared to controls, while BCRP expression was not affected. The expression of the four proteins was unchanged in mice treated with A?1-40 or reverse-sequence peptides. These findings indicate that, in addition to the age-related decrease of P-gp expression, A?1-42 itself downregulates the expression of P-gp and other A?-transporters, which could exacerbate the intracerebral accumulation of A? and thereby accelerate neurodegeneration in Alzheimer's disease and cerebral ?-amyloid angiopathy.

Brenn, Anja; Grube, Markus; Peters, Michele; Fischer, Andrea; Jedlitschky, Gabriele; Kroemer, Heyo K.; Warzok, Rolf W.; Vogelgesang, Silke

2011-01-01

238

Polarized P-glycoprotein expression by the immortalised human brain endothelial cell line, hCMEC/D3, restricts apical-to-basolateral permeability to rhodamine 123.  

PubMed

P-glycoprotein (P-gp) expression at the blood-brain barrier prevents unwanted blood-borne toxins and signalling molecules from entering the brain. Primary and immortalised human brain endothelial cells (BECs) represent two suitable options for studying P-gp function in vitro. The limited supply of primary human BECs and their instability over passage number make this choice unattractive for medium/high throughput studies. The aim of this study was to further characterise the expression of P-gp by an immortalised human BEC line, hCMEC/D3, in order to evaluate their use as an in vitro human blood-brain barrier model. P-gp expression was stable over a high passage number (up to passage 38) and was polarised on the apical plasma membrane, consistent with human BECs in vivo. In addition, hCMEC/D3 cell P-gp expression was comparable, albeit slightly lower to that observed in primary isolated human BECs although P-gp function was similar in both cell lines. The P-gp inhibitors tariquidar and vinblastine prevented the efflux of rhodamine 123 (rh123) from hCMEC/D3 cells, indicative of functional P-gp expression. hCMEC/D3 cells also displayed polarised P-gp transport, since both tariquidar and vinblasine selectively increased the apical-to-basolateral permeability of hCMEC/D3 cells to rh123. The results presented here demonstrate that hCMEC/D3 cells are a suitable model to investigate substrate specificity of P-gp in BECs of human origin. PMID:19631619

Tai, Leon M; Reddy, P Sreekanth; Lopez-Ramirez, M Alejandro; Davies, Heather A; Male, David K; Male, A David K; Loughlin, A Jane; Romero, Ignacio A

2009-07-23

239

Parguerenes: Marine red alga bromoditerpenes as inhibitors of P-glycoprotein (ABCB1) in multidrug resistant human cancer cells.  

PubMed

High intrinsic or acquired expression of membrane spanning, adenosine triphosphate binding cassette (ABC) transporter proteins, such as P-glycoprotein (P-gp), in cancers represents a major impediment to chemotherapy, with accelerated drug efflux leading to multi-drug resistance (MDR). Although ABC transporter inhibitors offer the prospect of reversing the MDR phenotype, no inhibitors have advanced to the clinic. We employed a range of intracellular fluorescence and radio-ligand accumulation and efflux assays, together with cytotoxicity and MDR reversal assays, as well as flow cytometry, fluorescence microscopy and radioimmunoprecipitation, to discover and evaluate new P-gp inhibitors from a unique library of southern Australian and Antarctic marine natural products. This study successfully characterized two rare bromoditerpenes, parguerenes I and II, sourced from a southern Australian collection of the red alga Laurencia filiformis, as P-gp inhibitors. We determined that the parguerenes were non-cytotoxic, dose-dependent inhibitors of P-gp mediated drug efflux, that modify the extracellular antibody binding epitope of P-gp in a manner that differs markedly from that of the known inhibitors verapamil and cyclosporine A. We confirmed that parguerenes were capable of reversing P-gp mediated vinblastine, doxorubicin and paclitaxel MDR, that inhibitory properties span both P-gp and multidrug resistant protein 1 (MRP1), but do not extend to breast cancer resistance protein (BCRP), and that parguerene II is superior (more potent) to verapamil. Our investigations validate the proposition that marine natural products can deliver new ABC transporter inhibitor scaffolds, with structure characteristics fundamentally different from existing inhibitor classes. PMID:23415901

Huang, Xiao-Cong; Sun, Yue-Li; Salim, Angela A; Chen, Zhe-Sheng; Capon, Robert J

2013-02-13

240

Dynamics and structural changes induced by ATP and/or substrate binding in the inward-facing conformation state of P-glycoprotein  

NASA Astrophysics Data System (ADS)

P-glycoprotein (P-gp) is a multidrug transporter that catalyzes the transport of a substrate. To elucidate the underlying mechanism of this type of substrate transport, we performed molecular dynamics (MD) simulations using the X-ray crystal structure of P-gp, which has an inward-facing conformation. Our simulations indicated that the dimerization of the nucleotide binding domains (NBDs) is driven by the binding of ATP to the NBDs and/or the binding of the substrate to a cavity in the transmembrane domains (TMDs). Based on these results, we discuss a role of ATP in the allosteric communication that occurs between the NBDs and the TMDs.

Watanabe, Yurika; Hsu, Wei-Lin; Chiba, Shuntaro; Hayashi, Tomohiko; Furuta, Tadaomi; Sakurai, Minoru

2013-02-01

241

SDZ 280-125: a cyclopeptolide endowed with an in vitro cyclosporin A-like profile of activity for the reversion of the P-glycoprotein-mediated multidrug resistance of tumor cells.  

PubMed

Tumor cells whose multidrug resistance is caused by the P-glycoprotein (Pgp) mediated anti-cancer drug (ACD) efflux can be chemosensitized by cyclosporins, whose derivatives were found to display a whole range of resistance-modulating activities. Similarly, derivatives of the non-immunosuppressive natural fungus cyclic peptolide SDZ 90-215 were recently shown to display a broad range of chemosensitizing activities. With highly resistant cells expressing high levels of Pgp, one such compound (SDZ 280-125) was shown here to restore both a normal sensitivity to the growth-inhibitory effects of ACD and a normal retention of an anthracycline antibiotic. With both read-outs, SDZ 280-125 activity was about 3-fold that of cyclosporin A (CsA). SDZ 280-125 also displayed the same profile of chemosensitization as CsA for different ACD classes. PMID:7919456

Jachez, B; Boesch, D; Emmer, G; Loor, F

1994-06-01

242

Effect of some P-glycoprotein modulators on Rhodamine-123 absorption in guinea-pig ileum.  

PubMed

Several reference compounds such as Cyclosporin A, Tamoxifen, Verapamil, and our compound 1, known as P-gp modulators, have been tested for their P-gp modulating activity in isolated organ bath. Compound 1 showed the best result in organ bath experiment (EC(50)=14.7 microM), Cyclosporin A and Tamoxifen displayed EC(50)=25.2 and 39.4 microM, respectively. PMID:18524592

Colabufo, Nicola Antonio; Berardi, Francesco; Contino, Marialessandra; Inglese, Carmela; Niso, Mauro; Perrone, Roberto

2008-05-20

243

Contribution of Cholesterol and Phospholipids to Inhibitory Effect of Dimethyl-?-Cyclodextrin on Efflux Function of P-Glycoprotein and Multidrug Resistance-Associated Protein 2 in Vinblastine-Resistant Caco-2 Cell Monolayers  

Microsoft Academic Search

Purpose. The purpose of this study is to reveal the contribution of membrane components to the inhibitory effect of 2,6-di-O-methyl-ß-cyclodextrin (DM-ß-CyD) on P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 (MRP2) function in vinblastine-resistant Caco-2 (Caco-2R) cell monolayers.

Hidetoshi Arima; Kiyokazu Yunomae; Tadatoshi Morikawa; Fumitoshi Hirayama; Kaneto Uekama

2004-01-01

244

Enantioselective disposition of fexofenadine with the P-glycoprotein inhibitor verapamil  

PubMed Central

AIMS The aim was to compare possible effects of verapamil, as a P-glycoprotein (P-gp) inhibitor, on the pharmacokinetics of each fexofenadine enantiomer, as a P-gp substrate. METHODS Thirteen healthy Japanese volunteers (10 male and three female) were enrolled. In a randomized, two-phase, crossover design, verapamil was dosed 80 mg three times daily (with total daily doses of 240 mg) for 6 days, and on day 6, a single 120-mg dose of fexofenadine was administered along with an 80-mg dose of verapamil. Subsequently, fexofenadine was administered alone after a 2-week wash-out period. The plasma concentrations of fexofenadine enantiomers were measured up to 24 h after dosing. RESULTS During the control phase, the mean AUC0–? of S(?)- and R(+)-fexofenadine was 700 ng h–1 ml–1[95% confidence interval (CI) 577, 823] and 1202 ng h–1 ml–1 (95% CI 1007, 1396), respectively, with a significant difference (P < 0.001). Verapamil had a greater effect on the pharmacokinetic parameters of S(?)-fexofenadine compared with those of the R(+)-enantiomer, and increased AUC0–? of S(?)-fexofenadine and R(+)-fexofenadine by 3.5-fold (95% CI of differences 1.9, 5.1; P < 0.001) and by 2.2-fold (95% CI of differences 1.7, 3.0; P < 0.001), respectively. The R/S ratio for the AUC0–? was reduced from 1.76 to 1.32 (P < 0.001) by verapamil treatments. CONCLUSION This study indicates that P-gp plays a key role in the stereoselectivity of fexofenadine pharmacokinetics, since the pharmacokinetics of fexofenadine enantiomers were altered by the P-gp inhibitor verapamil, and this effect was greater for S-fexofenadine compared with R-fexofenadine.

Sakugawa, Takashi; Miura, Masatomo; Hokama, Nobuo; Suzuki, Toshio; Tateishi, Tomonori; Uno, Tsukasa

2009-01-01

245

Interaction between Topically and Systemically Coadministered P-Glycoprotein Substrates/Inhibitors: Effect on Vitreal Kinetics  

PubMed Central

The objective of the present study was to investigate the effect of topically coadministered P-glycoprotein (P-gp) substrates/inhibitors on the vitreal kinetics of a systemically administered P-gp substrate. Anesthetized male rabbits were used in these studies. The concentration-time profile of quinidine in the vitreous humor, after intravenous administration, was determined alone and in the presence of topically coadministered verapamil, prednisolone sodium phosphate (PP), and erythromycin. The vitreal pharmacokinetic parameters of quinidine in the presence of verapamil [apparent elimination rate constant (?z), 0.0027 ± 0.0002 min?1; clearance (CL_F), 131 ± 21 ml/min; area under the curve (AUC0–?), 39 ± 7.0 ?g · min/ml; and mean residence time, 435 ± 20 min] were significantly different from those of the control (0.0058 ± 0.0006 min?1, 296 ± 46 ml/min, 17 ± 3 ?g · min/ml, and 232 ± 20 min, respectively). A 1.7-fold decrease in the vitreal ?z and a 1.5-fold increase in the vitreal AUC of quinidine were observed in the presence of topical PP. Statistically significant differences between the vitreal profiles of the control and erythromycin-treated group were also observed. Plasma concentration-time profiles of quinidine, alone or in the presence of the topically instilled compounds, remained unchanged, indicating uniform systemic quinidine exposure across groups. This study demonstrates an interaction between topically and systemically coadministered P-gp substrates, probably through the modulation of P-gp on the basolateral membrane of the retinal pigmented epithelium, leading to changes in the vitreal kinetics of the systemically administered agent.

Hippalgaonkar, Ketan; Srirangam, Ramesh; Avula, Bharathi; Khan, Ikhlas A.

2010-01-01

246

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

247

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

248

FG020326 sensitized multidrug resistant cancer cells to docetaxel-mediated apoptosis via enhancement of caspases activation.  

PubMed

Apoptotic resistance is the main obstacle for treating cancer patients with chemotherapeutic drugs. Multidrug resistance (MDR) is often characterized by the expression of P-glycoprotein (P-gp), a 170-KD ATP-dependent drug efflux protein. Functional P-gp can confer resistance to activate caspase-8 and -3 dependent apoptosis induced by a range of different stimuli, including tumor necrosis and chemotherapeutic drugs such as docetaxel and vincristine. We demonstrated here that comparison of sensitive KB cells, P-gp positive (P-gp(+ve)) KBv200 cells were extremely resistant to apoptosis induced by docetaxel. FG020326, a pharmacological inhibitor of P-gp function, could enhance concentration-dependently the effect of docetaxel on cell apoptosis and sensitize caspase-8, -9 and -3 activation in P-gp overexpressing KBv200 cells, but not in KB cells. Therefore, the enhancement of caspase-8, -9 and -3 activation induced by docetaxel may be one of the key mechanisms of the reversal of P-gp mediated docetaxel resistance by FG020326. PMID:22572929

Wang, Xiu-Wen; Wang, Xiao-Kun; Zhang, Xu; Liang, Yong-Ju; Shi, Zhi; Chen, Li-Ming; Fu, Li-Wu

2012-05-09

249

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

250

Thyroxine (T 4) transfer from CSF to choroid plexus and ventricular brain regions in rabbit: Contributory role of P-glycoprotein and organic anion transporting polypeptides  

Microsoft Academic Search

This study investigated the transfer of T4 from cerebrospinal fluid (CSF) into the choroid plexuses (CP) and ventricular brain regions, and the role of P-glycoprotein (P-gp), multidrug resistance protein 1 (mrp1) and organic anion transporting polypeptides (oatps). During in vivo ventriculo-cisternal (V-C) perfusion in the anesthetized rabbit (meditomidine hydrochloride 0.5 mg kg?1, pentobarbitone 10 mg kg?1 i.v.), 125I-T4 was perfused continuously into

Nouhad A. Kassem; Rashid Deane; Malcolm B. Segal; RuoLi Chen; Jane E. Preston

2007-01-01

251

The coordinated role of CYP450 enzymes and P-gp in determining cancer resistance to chemotherapy.  

PubMed

The relationship between CYP450 and P-gp occurs at different levels. It is known that certain substrates of P-gp undergo metabolic transformations by various CYP450 isoforms; in addition some of them demonstrated to be activators of both P-gp and CYP450. The majority of such compounds are well-known chemotherapeutics, therefore the purpose of this review is to clarify whether there is a relationship between the simultaneous modulation of CYP450 and P-gp and the onset of drug resistance in tumors treatment. Here, we discuss the biological aspects of the topic in relation to the various tissues distribution of CYP450 and P-gp, the recent findings regarding the ability of some chemotherapeutics in modulating both P-gp and CYP450, whether this modulation is ultimately responsible for the onset of drug resistance in cancer treatment and the promising role of gene polymorphisms in determining the interindividual variability in drug responses in clinical practice. PMID:21434858

Azzariti, Amalia; Porcelli, Letizia; Quatrale, Anna Elisa; Silvestris, Nicola; Paradiso, Angelo

2011-10-01

252

Oxymatrine inhibits development of morphine-induced tolerance associated with decreased expression of P-glycoprotein in rats.  

PubMed

The effect of oxymatrine on the development of tolerance to the antinociceptive effects of morphine was investigated in rats. The degree of tolerance was assessed using the tail-flick test before and after 6 days of twice daily administration of oxymatrine premorphine (10/20/30 mg/kg). High doses of oxymatrine inhibited the development of morphine tolerance (resembling the effect of 7.5 mg/kg of the NMDA receptor antagonist memantine) while also increasing the antinociceptive effects. A high dose of oxymatrine (30 mg/kg) also significantly inhibited the dramatic increase in expression of morphine-induced P-glycoprotein (P-gp), an ATP-dependent efflux pump acting at the blood-brain barrier, by Western blot analysis. Furthermore, these studies suggest that P-gp modulates the development of morphine tolerance while not affecting the magnitude of the analgesic effect of morphine. These results imply that oxymatrine prevention of the development of tolerance of morphine may be related to a considerable inhibition of P-gp expression. In contrast, the authors' data suggest that the mechanism of oxymatrine enhancement of morphine's analgesic effects is not associated with increase in the level of expression of P-gp. However, they believe that their findings can be used by researchers to develop therapies that will allow patients to take morphine without becoming tolerant of its benefits. PMID:20587445

Li, Yanwei; Yue, Hui; Xing, Yanmin; Sun, Haiyan; Pan, Zhanyu; Xie, Guangru

2010-06-01

253

Herbal modulation of P-glycoprotein.  

PubMed

P-glycoprotein (Pgp) is a 170 kDa phosphorylated glycoprotein encoded by human MDR1 gene. It is responsible for the systemic disposition of numerous structurally and pharmacologically unrelated lipophilic and amphipathic drugs, carcinogens, toxins, and other xenobiotics in many organs, such as the intestine, liver, kidney, and brain. Like cytochrome P450s (CYP3A4), Pgp is vulnerable to inhibition, activation, or induction by herbal constituents. This was demonstrated by using an ATPase assay, purified Pgp protein or intact Pgp-expressing cells, and proper probe substrates and inhibitors. Curcumin, ginsenosides, piperine, some catechins from green tea, and silymarin from milk thistle were found to be inhibitors of Pgp, while some catechins from green tea increased Pgp-mediated drug transport by heterotropic allosteric mechanism, and St. John's wort induced the intestinal expression of Pgp in vitro and in vivo. Some components (e.g., bergamottin and quercetin) from grapefruit juice were reported to modulate Pgp activity. Many of these herbal constituents, in particular flavonoids, were reported to modulate Pgp by directly interacting with the vicinal ATP-binding site, the steroid-binding site, or the substrate-binding site. Some herbal constituents (e.g., hyperforin and kava) were shown to activate pregnane X receptor, an orphan nuclear receptor acting as a key regulator of MDR1 and many other genes. The inhibition of Pgp by herbal constituents may provide a novel approach for reversing multidrug resistance in tumor cells, whereas the stimulation of Pgp expression or activity has implication for chemoprotective enhancement by herbal medicines. Certain natural flavonols (e.g., kaempferol, quercetin, and galangin) are potent stimulators of the Pgp-mediated efflux of 7,12-dimethylbenz(a)-anthracene (a carcinogen). The modulation of Pgp activity and expression by these herb constituents may result in altered absorption and bioavailability of drugs that are Pgp substrates. This is exemplified by increased oral bioavailability of phenytoin and rifampin by piperine and decreased bioavailability of indinavir, tacrolimus, cyclosporine, digoxin, and fexofenadine by coadministered St. John's wort. However, many of these drugs are also substrates of CYP3A4. Thus, the modulation of intestinal Pgp and CYP3A4 represents an important mechanism for many clinically important herb-drug interactions. Further studies are needed to explore the relative role of Pgp and CYP3A4 modulation by herbs and the mechanism for the interplay of these two important proteins in herb-drug interactions. PMID:15072439

Zhou, Shufeng; Lim, Lee Yong; Chowbay, Balram

2004-02-01

254

The catalytic cycle of P-glycoprotein  

Microsoft Academic Search

P-glycoprotein is a plasma-membrane glycoprotein which confers multidrug-resistance on cells and displays ATP-driven drug-pumping in vitro. It contains two nucleotide-binding domains, and its structure places it in the ‘ABC transporter’ family. We review recent evidence that both nucleotide-sites bind and hydrolyse Mg-ATP. The two catalytic sites interact strongly. A minimal scheme for the MgATP hydrolysis reaction is presented. An alternating

Alan E. Senior; Marwan K. Al-Shawi; Ina L. Urbatsch

1995-01-01

255

P-glycoprotein and breast cancer resistance protein restrict apical-to-basolateral permeability of human brain endothelium to amyloid-beta.  

PubMed

The clearance of amyloid beta (Abeta) from the brain represents a novel therapeutic target for Alzheimer's disease. Conflicting data exist regarding the contribution of adenosine triphosphate-binding cassette transporters to the clearance of Abeta through the blood-brain barrier. Therefore, we investigated whether Abeta could be a substrate for P-glycoprotein (P-gp) and/or for breast cancer resistance protein (BCRP) using a human brain endothelial cell line, hCMEC/D3. Inhibition of P-gp and BCRP increased apical-to-basolateral, but not basolateral-to-apical, permeability of hCMEC/D3 cells to (125)I Abeta 1-40. Our in vitro data suggest that P-gp and BCRP might act to prevent the blood-borne Abeta 1-40 from entering the brain. PMID:19367293

Tai, Leon M; Loughlin, A Jane; Male, David K; Romero, Ignacio A

2009-04-15

256

Evaluation of Limiting Brain Penetration Related to P-glycoprotein and Breast Cancer Resistance Protein Using [ 11 C]GF120918 by PET in Mice  

Microsoft Academic Search

Purpose  GF120918 has a high inhibitory effect on P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP). We developed [11C]GF120918 as a positron emission tomography (PET) probe to assess if dual modulation of P-gp and BCRP is useful to evaluate\\u000a brain penetration.\\u000a \\u000a \\u000a \\u000a \\u000a Procedures  PET studies using [11C]GF120918 were conducted on P-gp and\\/or Bcrp knockout mice as well as wild-type mice.\\u000a \\u000a \\u000a \\u000a \\u000a Results  In PET studies,

Kazunori Kawamura; Tomoteru Yamasaki; Fujiko Konno; Joji Yui; Akiko Hatori; Kazuhiko Yanamoto; Hidekatsu Wakizaka; Makoto Takei; Yuichi Kimura; Toshimitsu Fukumura; Ming-Rong Zhang

2011-01-01

257

Function of P-Glycoprotein Expressed in Placenta and Mole  

Microsoft Academic Search

We examined the expression of P-glycoprotein in human placentas and hydatidiform moles. Trophoblasts in all the examined placentas and moles expressed P-glycoprotein, and the size of the P-glycoprotein was smaller than that in multidrug-resistant human epidermoid carcinoma KB cells. The P-glycoprotein in the placenta and mole was photolabeled with [3H]azidopine, and [3H]vincristine was transported in an ATP-dependent manner into membrane

Yukihiko Nakamura; Shun-ichi Ikeda; Tatsuhiko Furukawa; Tomoyuki Sumizawa; Ayako Tani; Shin-ichi Akiyama; Yukihiro Nagata

1997-01-01

258

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

259

Inhibition of P-Glycoprotein Leads to Improved Oral Bioavailability of Compound K, an Anticancer Metabolite of Red Ginseng Extract Produced by Gut Microflora  

PubMed Central

Ginsenosides are hydrolyzed extensively by gut microflora after oral administration, and their metabolites are pharmacologically active against lung cancer cells. In this study, we measured the metabolism of various ginsenosides by gut microflora and determined the mechanisms responsible for the observed pharmacokinetic behaviors of its active metabolite, Compound K (C-K). The results showed that biotransformation into C-K is the major metabolic pathway of ginsenosides after the oral administration of the red ginseng extract containing both protopanaxadiol and protopanaxatriol ginsenosides. Pharmacokinetic studies in normal mice showed that C-K exhibited low oral bioavailability. To define the mechanisms responsible for this low bioavailability, two P-glycoprotein (P-gp) inhibitors, verapamil and cyclosporine A, were used, and their presence substantially decreased C-K's efflux ratio in Caco-2 cells (from 26.6 to <3) and significantly increased intracellular concentrations (by as much as 40-fold). Similar results were obtained when transcellular transport of C-K was determined using multidrug resistance 1 (MDR1)-overexpressing Madin-Darby canine kidney II cells. In MDR1a/b(?/?) FVB mice, its plasma Cmax and AUC0–24h were increased substantially by 4.0- and 11.7-fold, respectively. These increases appear to be due to slower elimination and faster absorption of C-K in MDR1a/b(?/?) mice. In conclusion, C-K is the major active metabolite of ginsenosides after microflora hydrolysis of primary ginsenosides in the red ginseng extract, and inhibition/deficiency of P-gp can lead to large enhancement of its absorption and bioavailability.

Yang, Zhen; Wang, Jing-Rong; Niu, Tao; Gao, Song; Yin, Taijun; You, Ming; Jiang, Zhi-Hong

2012-01-01

260

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

2013-03-29

261

Effects of capsaicin on P-gp function and expression in Caco-2 cells  

Microsoft Academic Search

Capsaicin is the pungent component of hot chilli, a popular spice in many populations. The aim of the present study was to evaluate the chronicity and reversibility of the modulating effect of capsaicin on both the P-gp expression and activity in the Caco-2 cell monolayers. Capsaicin at concentrations ranging from 10 to 100?M, which were found to be non-cytotoxic towards

Yi Han; Theresa May Chin Tan; Lee-Yong Lim

2006-01-01

262

Effects of Schisandra lignans on P-glycoprotein-mediated drug efflux in human intestinal Caco-2.  

PubMed

Schisandra fruits (Schisandraceae) are often used in traditional medicine and can be taken concomitantly with conventional medicine. In this study, the effects of dibenzocyclooctadiene lignans from Schizandra chinensis on P-gp-mediated efflux were examined to investigate a possible interaction with P-gp substrates. The cellular accumulation of rhodamine-123 in Caco-2 cells was measured with 12 Schisandra lignans. Most compounds resulted in slight or moderate increases of rhodamin-123 cellular uptake, indicating their P-gp inhibitory activity. Among them, deoxyschizandrin exhibited the most potent effect on the accumulation of rhodamine-123. Subsequently, bidirectional transports of digoxin and rhodamine-123 in Caco-2 cells were determined with deoxyschizandrin, the most active compound for the rhodamine-123 assay. In the bidirectional transport study, apical-to-basal (A-to-B) transports of digoxin and rhodamine-123 were increased, whereas basal-to-apical (B-to-A) transports were decreased by deoxyschizandrin in concentration- and time-dependent manners. At 50 microM of deoxyschizandrin, the transport ratios (B-A/A-B) for digoxin and rhodamine-123 were 2.2 and 2.1 compared with the control ratios of 15.2 and 12.2, respectively. These results demonstrated that deoxyschizandrin effectively inhibited the P-gp-mediated efflux in Caco-2 cells, suggesting they could potentially increase the absorption of drugs that can act as a P-gp substrate. PMID:17566147

Yoo, Hye Hyun; Lee, Mijin; Lee, Min Woo; Lim, Sun Young; Shin, Jongheon; Kim, Dong-Hyun

2007-05-01

263

Selective cyclooxygenase inhibitors increase paclitaxel sensitivity in taxane-resistant ovarian cancer by suppressing P-glycoprotein expression  

PubMed Central

Objective The purpose of this study was to investigate whether selective cyclooxygenase (COX) inhibitors promote paclitaxel-induced apoptosis in taxane-resistant ovarian cancer cells by suppressing MDR1/P-glycoprotein (P-gp) expression. Methods Taxane-resistant ovarian cancer cells were cultured with paclitaxel alone or combined with a selective COX inhibitors. The expression patterns of MDR1/P-gp and the ability of COX inhibitors to inhibit growth of taxane-resistant ovarian cancer cells were measured. The efficacy of prostaglandin E2 (PGE2) supplementation was measured to evaluate the mechanisms involved in suppressing MDR1 gene expression. Results P-gp was upregulated in taxane-resistant ovarian cancer cells compared to paired paclitaxel-sensitive ovarian cancer cells. An 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that selective COX inhibitors significantly enhanced the cytotoxic effects of paclitaxel in taxane-resistant ovarian cancer cells via a prostaglandin-independent mechanism. These increased apoptotic effects were further verified by measuring an increased percentage of cells in sub-G1 stage using flow cytometry. Selective COX inhibitors suppressed MDR1 and P-gp expression. Moreover, combined treatment with paclitaxel and selective COX inhibitors increased poly (ADP-ribose) polymerase (PARP) cleavage in taxane-resistant ovarian cancer cells. Conclusion Selective COX inhibitors significantly promote paclitaxel-induced cell death in taxane-resistant ovarian cancer cells in a prostaglandin-independent manner. COX inhibitors could be potent therapeutic tools to promote paclitaxel sensitization of taxane-resistant ovarian cancers by suppressing MDR1/P-gp, which is responsible for the efflux of chemotherapeutic agents.

Lee, Jung-Pil; Hahn, Ho-Suap; Hwang, Soo-Jin; Choi, Ji-Young; Lee, In-Ho

2013-01-01

264

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

265

Annotating Human P-Glycoprotein Bioassay Data.  

PubMed

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. PMID:23293680

Zdrazil, Barbara; Pinto, Marta; Vasanthanathan, Poongavanam; Williams, Antony J; Balderud, Linda Zander; Engkvist, Ola; Chichester, Christine; Hersey, Anne; Overington, John P; Ecker, Gerhard F

2012-08-07

266

Localization of P-gp (Abcb1) and Mrp2 (Abcc2) in Freshly Isolated Rat Hepatocytes  

PubMed Central

Freshly isolated hepatocytes are widely accepted as the “gold standard” for providing reliable data on drug uptake across the sinusoidal (basolateral) membrane. However, the suitability of freshly isolated hepatocytes in suspension to assess efflux by canalicular (apical) proteins or predict biliary excretion in the intact organ is unclear. After collagenase digestion, hepatocytes rapidly lose polarity, but localization of canalicular transport proteins in the first few hours after isolation has not been well characterized. In this study, immunostaining and confocal microscopy have provided, for the first time, a detailed examination of canalicular transport protein localization in freshly isolated rat hepatocytes fixed within 1 h of isolation and in cells cultured for 1 h. Organic anion transporting polypeptide 1a1 (Oatp1a1) was expressed in all hepatocytes and distributed evenly across the basolateral membrane; there was no evidence for colocalization of Oatp1a1 with P-glycoprotein (P-gp) or multidrug resistance-associated protein 2 (Mrp2). In contrast, P-gp and Mrp2 expression was lower than Oatp1a1 and confined to junctions between adjacent cells, intracellular compartments, and “legacy” network structures at or near the cell surface. P-gp and Mrp2 staining was more predominant in regions adjacent to former canalicular spaces, identified by zonula occludens-1 staining. Functional analysis of rat hepatocytes cultured for 1 h demonstrated that the fluorescent anion and Mrp2 substrate, 5-(and-6)-carboxy-2?,7?-dichlorofluorescein (CDF), accumulated in cellular compartments; compartmental accumulation of CDF was sensitive to (E)-3-[[[3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-[[3-dimethylamino)-3-oxopropyl]thio]methyl]thio]-propanoic acid (MK571, Mrp inhibitor) and was not observed in hepatocytes isolated from Mrp2-deficient rats. Drug efflux from freshly isolated hepatocytes as an estimate of apical efflux/biliary excretion would give an inaccurate assessment of true apical elimination and, as such, should not be used to make in vivo extrapolations.

Bow, Daniel A. J.; Perry, Jennifer L.; Miller, David S.; Pritchard, John B.; Brouwer, Kim L. R.

2009-01-01

267

Phenylsulfonylfuroxans as modulators of multidrug-resistance-associated protein-1 and P-glycoprotein.  

PubMed

A series of furoxan derivatives were studied for their ability to interact with P-gp and MRP1 transporters in MDCK cells overexpressing these proteins. 3-Phenylsulfonyl substituted furoxans emerged as the most interesting compounds. All of them were capable of inhibiting P-gp, and a few also were capable of inhibiting MRP1. Substituents at the 4-position of 3-phenylsulfonylfuroxan scaffold were able to modulate the selectivity and the intensity of inhibition. In some cases, they reverted MRP1 inhibitor activity, namely, they were capable of potentiating MRP1 dependent efflux. When compounds 16 and 17 were coadministered with doxorubicin, they restored a high degree of the activity of the antibiotic. Preliminary immunoblotting studies carried out on these two compounds indicate that they are capable of nitrating P-gp, which in this form is likely unable to efflux the antibiotic. PMID:20684594

Fruttero, Roberta; Crosetti, Marco; Chegaev, Konstantin; Guglielmo, Stefano; Gasco, Alberto; Berardi, Francesco; Niso, Mauro; Perrone, Roberto; Panaro, Maria Antonietta; Colabufo, Nicola Antonio

2010-08-12

268

Altered drug disposition of the platelet activating factor antagonist apafant in mdr1a knockout mice  

Microsoft Academic Search

The aim of the present study was to determine a potential impact of P-glycoprotein (P-gp) on the tissue distribution and disposition of apafant (WEB 2086, CAS 105219-56-5), a selective platelet-activating factor antagonist, and on digoxin in mdr1a(?\\/?) and wildtype mice. Transport experiments in Caco-2 monolayers at low concentrations (<10 ?M) showed that the secretory flux of [14C]apafant and [3H]digoxin exceeded

Andreas Leusch; Astrid Volz; Gabriele Müller; Andrea Wagner; Achim Sauer; Andreas Greischel; Willy Roth

2002-01-01

269

Rifampicin enhances anti-cancer drug accumulation and activity in multidrug-resistant cells  

Microsoft Academic Search

Rifampicin, a semi-synthetic antibiotic used in the treatment of tuberculosis and belonging to the chemical class of rifamycins, was examined for its effect on anti-cancer drug accumulation and activity in multidrug resistant cells overexpressing P-glycoprotein (P-gp). Rifampicin was shown to strongly enhance vinblastine accumulation in both rat hepatoma RHC1 and human leukemia K562 R7 multidrug resistant cells, but had no

Olivier Fardel; Valérie Lecureur; Pascal Loyer; André Guillouzo

1995-01-01

270

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

271

Age-related p-glycoprotein expression in the intestine and affecting the pharmacokinetics of orally administered enrofloxacin in broilers.  

PubMed

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. PMID:24066110

Guo, Mengjie; Bughio, Shamsuddin; Sun, Yong; Zhang, Yu; Dong, Lingling; Dai, Xiaohua; Wang, Liping

2013-09-16

272

Enhanced Brain Disposition and Effects of ?9-Tetrahydrocannabinol in P-Glycoprotein and Breast Cancer Resistance Protein Knockout Mice  

PubMed Central

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.

Spiro, Adena S.; Wong, Alexander; Boucher, Aurelie A.; Arnold, Jonathon C.

2012-01-01

273

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

2012-04-20

274

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

2013-06-07

275

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

276

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

277

[Modulation on the P-glycoprotein in the jejunum by combined use of Glycyrrhiza inflata and Kansui].  

PubMed

To investigate the modulation on the P-glycoprotein in the jejunum by combined use of Glycyrrhiza inflata and Kansui with ussing chamber and rt-pcr, Rhodamine 123 (R123), a P-gp substrate and fluorescein sodium (CF), a model drug of non-P-gp substrate transported by a passive diffusion were taken as investigational drugs. Because these two drugs can be easily assayed and widely used in various research fields. The permeability of R123 or CF via Wistar rat jejunum membranes was evaluated by in vitro ussing chamber after oral administration of four different decoctions of Glycyrrhiza inflata and Kansui for 1 week. And the concentration of R123 or CF was determined by the fluorospectrophotometry in the receiving solution. Meanwhile the expression of mdr1a in P-glycoprotein was detected by real-time fluorescent quantitative PCR. After oral administration of combined decoction of the single drug, the absorptive directed permeability of R123 increased significantly (P < 0.01). On the other hand, Kansui and combine decoction of the two drugs also decrease the permeability of secretory directed transport (P < 0.05). No action of Glycyrrhiza inflata was found on the secretory transport of R123 [Papp = (2.56 +/- 0.38) x 10(-5), cm x s(-1)] across the jejunum tissues, while Papp of control group was found [Papp = (2.35 +/- 0.27) x 10(-5), cm x s(-1)]. After oral administration of Kansui decoction for 1 week and 2 weeks, the levels of mdr1a expression in Wistar rats were lower than that of the control group, but there were no significant difference in the results. Meanwhile, Glycyrrhiza inflata had no effect on transport of CF across the jejunum tissues, though the other three groups could decrease the permeability of CF, as compared with control group. Kansui may slightly inhibit P-glycoprotein function in the intestinal membrane. For another, some compositions in Kansui inhibit P-glycoprotein function, and some others strengthen the tight junction between cells in the intestinal membrane to decrease permeability of CF. As the inhibitory action to P-glycoprotein was enhanced by combination of Glycyrrhiza inflata and Kansui, based on the results, it may be one of the mechanisms of creating toxicity once co-administration of Glycyrrhiza inflata and Kansui. PMID:21355220

Sun, Ya-Bin; Li, Guo-Feng; Tang, Zhong-Kun; Wu, Bing-Yi

2010-04-01

278

4-Biphenyl and 2-naphthyl substituted 6,7-dimethoxytetrahydroisoquinoline derivatives as potent P-gp modulators.  

PubMed

Starting from lead compound 1 (EC(50)=1.64 microM), its non-basic nucleus has been conformationally restricted by 4-biphenyl and 2-naphthyl moieties. In each series we investigated if the presence of H-bond donor or acceptor substituents, the basicity and the lipophilicity (clogP) were correlated with the P-gp inhibiting activity of tested compounds. In the biphenyl series, derivative 4d displayed the best results (EC(50)=0.05 microM). The corresponding amide 3d was found less active (EC(50)=3.5 microM) ascertaining the importance of basicity in this series whilst the presence of hydroxy or methoxy substituents seems to be negligible. In the naphthyl series, both the basicity and the presence of H-bond donor or acceptor groups seem to be negligible. Moreover, the lipophilicity did not influence the P-gp inhibition activity of each series. Specific biological assays have been carried out to establish the P-gp interacting mechanism of tested compounds discriminating between substrates and inhibitors. Moreover, compound 4d displayed a potent P-gp inhibition activity with good selectivity towards BCRP pump. PMID:18276145

Colabufo, Nicola Antonio; Berardi, Francesco; Cantore, Mariangela; Perrone, Maria Grazia; Contino, Marialessandra; Inglese, Carmela; Niso, Mauro; Perrone, Roberto; Azzariti, Amalia; Simone, Grazia Maria; Paradiso, Angelo

2008-02-02

279

Vitreal Kinetics of Quinidine in Rabbits in the Presence of Topically Coadministered P-Glycoprotein Substrates/Modulators  

PubMed Central

The purpose of this study was to investigate whether topically administered P-glycoprotein (P-gp) substrates/modulators can alter vitreal kinetics of intravitreally administered quinidine. Male New Zealand rabbits were used under anesthesia. Vitreal kinetics of intravitreally administered quinidine (0.75-?g dose) was determined alone and in the presence of verapamil (coadministered topically/intravitreally) or prednisolone hemisuccinate sodium (PHS) (coadministered topically). In the presence of topically instilled verapamil (1% w/v), elimination half-life (t1/2) (176 ± 7 min), apparent elimination rate constant (?z) (0.0039 ± 0.0001 min–1), and mean retention time (MRT) (143 ± 30 min) of intravitreally administered quinidine were significantly different from those of the control (105 ± 11 min, 0.0066 ± 0.0007 min–1, and 83 ± 13 min, respectively). A 2-fold increase in the t1/2 with a corresponding decrease in ?z and a 1.5-fold increase in the MRT of quinidine were observed in the presence of topically coadministered 2% w/v PHS. Intravitreal coadministration of quinidine and verapamil resulted in a significant increase in t1/2 (159 ± 9 min) and a decrease in ?z (0.0043 ± 0.0002 min–1) of quinidine. The vitreal pharmacokinetic parameters of sodium fluorescein, alone or in the presence of topically instilled verapamil, did not show any statistically significant difference, indicating that ocular barrier integrity was not affected by topical verapamil administration. Results from this study suggest that topically applied P-gp substrates/modulators can alter vitreal pharmacokinetics of intravitreally administered P-gp substrates, possibly through the inhibition of P-gp expressed on the basolateral membrane of the retinal pigmented epithelium.

Majumdar, Soumyajit; Hippalgaonkar, Ketan; Srirangam, Ramesh

2009-01-01

280

Enhanced intestinal absorption of etoposide by self-microemulsifying drug delivery systems: Roles of P-glycoprotein and cytochrome P450 3A inhibition.  

PubMed

Etoposide is recognized as a dual P-glycoprotein (P-gp) and cytochrome P450 3A (CYP3A) substrate drug with poor water-solubility. To improve its solubility and bioavailability, three novel self-microemulsifying drug delivery systems (SMEDDS) contained the known P-gp and CYP3A inhibitory surfactants, Cremophor RH40, Cremophor EL, or Polysorbate 80, were prepared. This work aims to evaluate the enhanced intestinal absorption of etoposide SMEDDS as well as to explore the roles of P-gp and CYP3A inhibition in the absorption process. Etoposide SMEDDS were orally administered to rats for in vivo bioavailability investigation. In situ single-pass intestinal perfusion with mesenteric vein cannulation was employed to study the drug permeability and intestinal metabolism. In vitro Caco-2 cell models were applied to study the effects of P-gp and CYP3A inhibition by SMEDDS on the cellular accumulation of etoposide. It was found that the bioavailability and in situ intestinal absorption were significantly enhanced by SMEDDS with the order of Polysorbate 80-based SMEDDS>Cremophor EL-based SMEDDS>Cremophor RH40-based SMEDDS. In addition, there was a dramatically high linear correlation between the AUC0-t values and the apparent permeability coefficient values based on the appearance of the drug in mesenteric vein blood. Cellular uptake studies demonstrated that P-gp inhibition by SMEDDS played an important role in etoposide uptake. Moreover, etoposide metabolism was demonstrated to be dramatically inhibited by the three kinds of SMEDDS. These finding may assist in the improvement of the intestinal absorption of P-gp and/or CYP3A substrate drugs. PMID:23981337

Zhao, Gang; Huang, Jiangeng; Xue, Kewen; Si, Luqin; Li, Gao

2013-08-25

281

Cytogenetic and molecular characterization of random chromosomal rearrangements activating the drug resistance gene, MDR1/P-glycoprotein, in drug-selected cell lines and patients with drug refractory ALL.  

PubMed

Drug resistance, both primary and acquired, is a major obstacle to advances in cancer chemotherapy. In vitro, multidrug resistance can be mediated by P-glycoprotein (PGY1), a cell surface phosphoglycoprotein that acts to efflux natural products from cells. PGY1 is encoded by the MDR1 gene located at 7q21.1. Overexpression of MDR1 has been demonstrated in many cancers, both in patient tumors and in cell lines selected with a variety of chemotherapeutic agents. Recent studies in drug-selected cell lines and patients samples have identified hybrid mRNAs comprised of an active, but apparently random, gene fused 5' to MDR1. This observation indicates that random chromosomal rearrangements, such as translocations and inversions, leading to "capture" of MDR1 by constitutively expressed genes may be a mechanism for activation of this gene following drug exposure. In this study, fluorescence in situ hybridization (FISH) using whole chromosome paints (WCP) and bacterial artificial chromosome (BAC)-derived probes showed structural rearrangements involving 7q in metaphase and interphase cells, and comparative genomic hybridization (CGH) revealed high levels of amplification at chromosomal breakpoints. In an adriamycin-selected resistant colon cancer line (S48-3s/Adr), WCP4/WCP7 revealed t(4;7)(q31;q21) and BAC-derived probes demonstrated that the breakpoint lay between MDR1 and sequences 500-1000 KB telomeric to it. Similarly, in a subline isolated following exposure to actinomycin D (S48-3s/ActD), a hybrid MDR1 gene composed of heme oxygenase-2 sequences (at 16p13) fused to MDR1 was identified and a rearrangement confirmed with WCP7 and a subtelomeric 16p probe. Likewise, in a paclitaxel-selected MCF-7 subline where CASP sequences (at 7q22) were shown to be fused to MDR1, WCP7 showed an elongated chromosome 7 with a homogeneously staining regions (hsr); BAC-derived probes demonstrated that the hsr was composed of highly amplified MDR1 and CASP sequences. In all three selected cell lines, CGH demonstrated amplification at breakpoints involving MDR1 (at 7q21) and genes fused to MDR1 at 4q31, 7q22, and 16p13.3. Finally, in samples obtained from two patients with drug refractory ALL, BAC-derived probes applied to archived marrow cells demonstrated that a breakpoint occurred between MDR1 and sequences 500-1000 KB telomeric to MDR1, consistent with a random chromosomal rearrangement. These results support the proposal that random chromosomal rearrangement leading to capture and activation of MDR1 is a mechanism of acquired drug resistance. PMID:9713996

Knutsen, T; Mickley, L A; Ried, T; Green, E D; du Manoir, S; Schröck, E; Macville, M; Ning, Y; Robey, R; Polymeropoulos, M; Torres, R; Fojo, T

1998-09-01

282

Interactions between verapamil and digoxin in Langendorff-perfused rat hearts: the role of inhibition of P-glycoprotein in the heart.  

PubMed

P-glycoprotein (P-gp) is expressed in tumour cells as well as normal tissues including heart. Modulation of P-gp transport in vivo may lead to increased drug penetrance to tissues with resulting increases in toxicity. We aimed to investigate the effects of P-gp on the isolated heart by digoxin infusion in the absence and presence of verapamil. The study was performed in Langendorff isolated perfused rat hearts. After a 20 min. stabilisation period with Tyrode Buffer, digoxin (125 ?g/5 mL) was infused for 10 min. in the control group (n = 7). The same dose of digoxin was infused during perfusion with verapamil (1 nm) containing Tyrode Buffer (n = 8) in the study group. Outflow concentration and cardiac parameters of digoxin were measured at frequent intervals for 40 min. AUEC((0-40 min)) for left ventricular developed pressure was significantly increased in the presence of verapamil (4260 ± 39.37 mmHg min versus 4607 ± 98.09 mmHg min; 95% CI -587.7 to -105.8; p = 0.0083). The significant increases in left ventricular developed pressure were at 20, 25, 30, 35 and 40 min. AUC((0-40 min)) value for outflow digoxin concentration-time curve was significantly lower in the presence of verapamil. Verapamil increased the positive inotropic effect of digoxin, probably through the inhibition of P-gp, which effluxes digoxin out of cardiac cells. PMID:22545967

Aylin Arici, Mualla; Kilinc, Emrah; Demir, Omer; Ates, Mehmet; Yesilyurt, Alaattin; Gelal, Ayse

2010-11-01

283

Effect of methotrexate treatment on expression levels of organic anion transporter polypeptide 2, P-glycoprotein and bile salt export pump in rats.  

PubMed

High-dose methotrexate (HDMTX) chemotherapy with leucovorin (LV) rescue has been used as a therapeutic strategy in oncology since the 1970s. Adverse reactions following extension of methotrexate (MTX) elimination are a crucial problem in HDMTX chemotherapy. MTX is a substrate for drug transporters, which are multidrug resistance protein 2 (Mrp2), organic anion transporter polypeptide 2 (Oatp2) and other transporters. We previously reported that MTX treatment downregulated the expression level of Mrp2 in rats. Here we examined the effect of MTX treatment on the expression of Oatp2, P-glycoprotein (P-gp) and bile salt export pump (Bsep) in rats. MTX was single-injected intraperitoneally at a dose of 150 mg/kg, and Western blot analysis was performed. The levels of Oatp2, P-gp and Bsep in the liver on day 4 after treatment were downregulated to 36.3 +/- 6.9%, 51.5 +/- 5.2% and 61.8 +/- 5.5% (mean +/- S.E.M.) of controls, respectively. Expression levels of P-gp in the kidney and ileum were also downregulated to 38.5 +/- 1.6% and 16.2 +/- 1.6% of controls, respectively. These effects of MTX were partially recovered by LV, which rescues normal cells from MTX toxicity. In conclusion, the result indicates that MTX treatment downregulates expression levels of Oatp2, P-gp and Bsep. PMID:19252302

Shibayama, Yoshihiko; Takeda, Yasuo; Yamada, Katsushi

2009-03-01

284

Gauging the clinical significance of P-glycoprotein-mediated herb-drug interactions: Comparative effects of St. John's wort, echinacea, clarithromycin, and rifampin on digoxin pharmacokinetics  

PubMed Central

Concomitant administration of botanical supplements with drugs that are P-glycoprotein (P-gp) substrates may produce clinically significant herb-drug interactions. This study evaluated the effects of St. John's wort and Echinacea on the pharmacokinetics of digoxin, a recognized P-gp substrate. Eighteen healthy volunteers were randomly assigned to receive a standardized St. John's wort (300 mg three times daily) or Echinacea (267 mg three times daily) supplement for 14 days, followed by a 30-day washout period. Subjects were also randomized to receive rifampin (300 mg twice daily, 7 days) and clarithromycin (500 mg twice daily, 7 days) as positive controls for P-gp induction and inhibition, respectively. Digoxin (Lanoxin® 0.25 mg) was administered orally before and after each supplementation and control period. Serial digoxin plasma concentrations were obtained over 24 hours and analyzed by chemiluminescent immunoassay. Comparisons of AUC(0-3), AUC(0-24), T1/2, and Cmax, were used to assess the effects of St. John's wort, Echinacea, rifampin, and clarithromycin on digoxin disposition. St. John's wort and rifampin both produced significant reductions (p<0.05) in AUC(0-3), AUC(0-24), and Cmax, while clarithromycin increased these parameters significantly (p<0.05). Echinacea supplementation did not affect digoxin pharmacokinetics. Clinically significant P-gp-mediated herb-drug interactions are more likely to occur with St. John's wort than with Echinacea.

Gurley, Bill J.; Swain, Ashley; Williams, D. Keith; Barone, Gary; Battu, Sunil Kumar

2007-01-01

285

Modulation of P-glycoprotein at the Blood-Brain Barrier: Opportunities to Improve CNS Pharmacotherapy  

PubMed Central

Pharmacotherapy of CNS disorders, e.g., neurodegenerative diseases, epilepsy, brain cancer, and neuro-AIDS, is limited by the blood-brain barrier. P-glycoprotein, an ATP-driven, drug efflux transporter, is a critical element of that barrier. High level of expression, luminal membrane location, specificity and high transport potency make P-glycoprotein a selective gate-keeper of the blood-brain barrier and thus a primary obstacle to drug delivery into the brain. As such, P-glycoprotein limits entry into the CNS for a large number of prescribed drugs, contributes to the poor success rate of CNS drug candidates and likely contributes to patient-to-patient variability in response to CNS pharmacotherapy. Modulating P-glycoprotein could therefore improve drug delivery into the brain. Here we review the current understanding of signaling mechanisms responsible for the modulation of P-glycoprotein activity/expression at the blood-brain barrier with an emphasis on recent studies from our laboratories. Using intact brain capillaries from rats and mice, we have identified multiple extracellular and intracellular signals that regulate this transporter; several signaling pathways have been mapped. Three pathways are triggered by elements of the brain's innate immune response, one by glutamate, one by xenobiotic-nuclear receptor (PXR) interactions and one by elevated ?-amyloid levels. Signaling is complex, with several pathways sharing common signaling elements (TNF-R1, ETB receptor, PKC, NOS), suggesting a regulatory network. Several pathways utilize autocrine/paracrine elements, involving release of the proinflammatory cytokine, TNF-?, and the polypeptide hormone, ET-1. Finally, several steps in signaling are potential therapeutic targets that could be used to modulate P-glycoprotein activity in the clinic.

Miller, David S.; Bauer, Bjorn; Hartz, Anika M.S.

2009-01-01

286

The P-glycoprotein multidrug transporter.  

PubMed

Pgp (P-glycoprotein) (ABCB1) is an ATP-powered efflux pump which can transport hundreds of structurally unrelated hydrophobic amphipathic compounds, including therapeutic drugs, peptides and lipid-like compounds. This 170 kDa polypeptide plays a crucial physiological role in protecting tissues from toxic xenobiotics and endogenous metabolites, and also affects the uptake and distribution of many clinically important drugs. It forms a major component of the blood-brain barrier and restricts the uptake of drugs from the intestine. The protein is also expressed in many human cancers, where it probably contributes to resistance to chemotherapy treatment. Many chemical modulators have been identified that block the action of Pgp, and may have clinical applications in improving drug delivery and treating cancer. Pgp substrates are generally lipid-soluble, and partition into the membrane before the transporter expels them into the aqueous phase, much like a 'hydrophobic vacuum cleaner'. The transporter may also act as a 'flippase', moving its substrates from the inner to the outer membrane leaflet. An X-ray crystal structure shows that drugs interact with Pgp within the transmembrane regions by fitting into a large flexible binding pocket, which can accommodate several substrate molecules simultaneously. The nucleotide-binding domains of Pgp appear to hydrolyse ATP in an alternating manner; however, it is still not clear whether transport is driven by ATP hydrolysis or ATP binding. Details of the steps involved in the drug-transport process, and how it is coupled to ATP hydrolysis, remain the object of intensive study. PMID:21967057

Sharom, Frances J

2011-09-01

287

Modulation of multidrug resistance p-glycoprotein activity by flavonoids and honokiol in human doxorubicin- resistant sarcoma cells (MES-SA/DX-5): implications for natural sedatives as chemosensitizing agents in 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. Sedatives are often used to control anxiety and depression in cancer patients. In this in vitro study we investigated the effects of three plant derived sedatives such as apigenin (Api), fisetin (Fis), flavonoids and honokiol (Hnk) on Pgp activity and cellular GSH content in order to evaluate their potential use as chemosensitizing agents in anticancer chemotherapy. Human doxorubicin (doxo) resistant uterine sarcoma cells (MES-SA/Dx5) that overexpress Pgp, were treated with each sedative alone (10 microM) or in combination with different doxo concentrations (2-8 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 and 8 microM doxo concentrations in the presence of Api, Fis and Hnk enhanced significantly doxo accumulation by 29+/-3.3, 20+/-4.8, 24+/-6.6 percent and 14+/-1.7, 8.3+/-4.2, 10.7+/-3.1 percent, respectively, when compared with doxo alone. These results were consistent with the increase of sensitivity towards doxo in MES-SA/Dx5, resulting in 1.7, 1.2, 1.4-fold and 1.2, 1.0 and 1.1-fold increases, respectively. Moreover, treatment with Api decreased markedly cellular GSH content (18 percent) and increased ROS production (greater than 20 percent) on MES-SA/Dx5 cells, while a significant reduction in ROS levels was observed in Hnk and Fis treated cells, when compared to untreated control. Our in vitro findings provide a rationale for innovative clinical trials to assess the use of natural sedatives or their derivatives as potential adjuvants to anticancer treatment for overcoming multidrug resistance Pgp-mediated in cancer patients. PMID:20487633

Angelini, Aantonio; Di Ilio, C; Castellani, M L; Conti, P; Cuccurullo, F

288

Importance of P-glycoprotein for Drug–Drug Interactions  

Microsoft Academic Search

\\u000a P-glycoprotein (ABCB1) is one of the most extensively studied transporters regarding drug resistance and drug–drug interactions.\\u000a P-glycoprotein is expressed in multiple key organs in drug disposition such as small intestine, blood–brain barrier, kidney,\\u000a and liver. Therefore, P-glycoprotein mediated drug–drug interactions can occur at various organs and tissues. This chapter\\u000a will mainly focus on drug–drug interactions that are mediated by the

Hartmut Glaeser

289

Molecular models of human P-glycoprotein in two different catalytic states  

Microsoft Academic Search

BACKGROUND: P-glycoprotein belongs to the family of ATP-binding cassette proteins which hydrolyze ATP to catalyse the translocation of their substrates through membranes. This protein extrudes a large range of components out of cells, especially therapeutic agents causing a phenomenon known as multidrug resistance. Because of its clinical interest, its activity and transport function have been largely characterized by various biochemical

Jean-Paul Becker; Grégoire Depret; Françoise Van Bambeke; Paul M Tulkens; Martine Prévost

2009-01-01

290

Effects of dietary chemopreventive phytochemicals on P-glycoprotein function  

Microsoft Academic Search

The effects of dietary phytochemicals on P-glycoprotein function were investigated using human multidrug-resistant carcinoma KB-C2 cells and the fluorescent P-glycoprotein substrates daunorubicin and rhodamine 123. The effects of natural chemopreventive compounds, capsaicin found in chilli peppers, curcumin in turmeric, [6]-gingerol in ginger, resveratrol in grapes, sulforaphane in broccoli, 6-methylsulfinyl hexyl isothiocyanate (6-HITC) in Japanese horseradish wasabi, indole-3-carbinol (I3C) in cabbage,

Tomohiro Nabekura; Shizu Kamiyama; Shuji Kitagawa

2005-01-01

291

Detection of human P-glycoprotein-like molecule in azole-resistant Candida albicans from HIV+ patients.  

PubMed

Azole resistance in Candida albicans may be due to several mechanisms. It has been demonstrated that C. albicans possesses sequences with a high degree of homology with the human MDR-1 gene coding for P-glycoprotein (P-gp), belonging to the ATP-binding cassette transporter (ABC) superfamily and responsible for the multidrug resistance (MDR) in tumor cells. On this basis, the expression and intracellular localization of human P-gp-like molecule in C. albicans strains showing different sensitivity to fluconazole were investigated by flow cytometry and immunoelectron microscopy. Post-embedding immunolabeling revealed that monoclonal antibody (mAb) MM4.17, which recognizes an external epitope of human P-gp, reacted with both fluconazole-sensitive (3153 and CO 23-1) and fluconazole-resistant (AIDS 68 and CO 23-2, isolated from AIDS patient and in vitro drug-selected, respectively) strains of C. albicans. However, the resistant strains displayed a number of MM4.17-reactive epitopes much higher than the drug-sensitive ones. The C. krusei ATCC 6458 strain, whose resistance is not mediated by the presence of ABC transporters, was not reactive at all with mAb MM4.17. The specificity of the immunolabeling was confirmed by a competitive inhibition assay performed by using phage clone particles capable of mimicking the MM4.17-reactive epitope. The flow cytometric analysis confirmed a higher level of intracytoplasmic P-gp expression in azole-resistant strains of C. albicans. Both cyclosporin A and verapamil, which are well-known MDR inhibitors, strongly reduced the MICs for fluconazole and itraconazole of the tested azole-resistant AIDS 68 strain, while they did not influence the MICs of either the sensitive 3153 strain of C. albicans or the ATCC 6458 strain of C. krusei. Overall, our data suggest the existence of a P-gp-like drug efflux pump in C. albicans that may participate in the mechanisms of azole-resistance of this fungus. PMID:12363014

Stringaro, Annarita; Molinari, Agnese; Calcabrini, Annarica; Arancia, Giuseppe; Ceddia, Pier Giuseppe; Cianfriglia, Maurizio; Poloni, Francesca; Mondello, Francesca; Angiolella, Letizia; De Bernardis, Flavia; Cassone, Antonio

2002-01-01

292

The acridonecarboxamide GF120918 potently reverses P-glycoprotein-mediated resistance in human sarcoma MES-Dx5 cells  

PubMed Central

The doxorubicin-selected, P-glycoprotein (P-gp)-expressing human sarcoma cell line MES-Dx5 showed the following levels of resistance relative to the non-P-gp-expressing parental MES-SA cells in a 72 h exposure to cytotoxic drugs: etoposide twofold, doxorubicin ninefold, vinblastine tenfold, taxotere 19-fold and taxol 94-fold. GF120918 potently reversed resistance completely for all drugs. The EC50s of GF120918 to reverse resistance of MES-Dx5 cells were: etoposide 7 ± 2 nM, vinblastine 19 ± 3 nM, doxorubicin 21 ± 6 nM, taxotere 57 ± 14 nM and taxol 91 ± 23 nM. MES-Dx5 cells exhibited an accumulation deficit relative to the parental MES-SA cells of 35% for [3H]-vinblastine, 20% for [3H]-taxol and [14C]-doxorubicin. The EC50 of GF120918, to reverse the accumulation deficit in MES-Dx5 cells, ranged from 37 to 64 nM for all three radiolabelled cytotoxics. [3H]-vinblastine bound saturably to membranes from MES-Dx5 cells with a KD of 7.8 ± 1.4 nM and a Bmax of 5.2 ± 1.6 pmol mg–1 protein. Binding of [3H]-vinblastine to P-gp in MES-Dx5 membranes was inhibited by GF120918 (Ki = 5 ± 1 nM), verapamil (Ki = 660 ± 350 nM) and doxorubicin (Ki = 6940 ± 2100 nM). Taxol, an allosteric inhibitor of [3H]-vinblastine binding to P-gp, could only displace 40% of [3H]-vinblastine (Ki = 400 ± 140 nM). The novel acridonecarboxamide derivative GF120918 potently overcomes P-gp-mediated multidrug resistance in the human sarcoma cell line MES-Dx5. Detailed analysis revealed that five times higher GF120918 concentrations were needed to reverse drug resistance to taxol in the cytotoxicity assay compared to doxorubicin, vinblastine and etoposide. An explanation for this phenomenon had not been found. © 1999 Cancer Research Campaign

Traunecker, H C L; Stevens, M C G; Kerr, D J; Ferry, D R

1999-01-01

293

Nonlinear accumulation in the brain of the new taxoid TXD258 following saturation of P-glycoprotein at the blood-brain barrier in mice and rats  

PubMed Central

TXD258, a new taxoid antitumor agent, is a poor substrate for the P-glycoprotein (P-gp) in Caco-2 cells. In this study, we investigated the amount of drug accumulating in the brains of rats and mice under a variety of conditions (dose and infusion time, species and plasma concentration) using conventional in vivo pharmacokinetic techniques and in situ brain perfusion. Mice were infused with radiolabeled TXD258 at 15, 30, 45 and 90 mg m?2 for 45 s or 1 h and rats were infused with 15 and 60 mg m?2 over 2.3 min. The radioactivity in the plasma and brains was measured. The brain concentrations of TXD258 in mice and rats were maximal from 2 min to 1 h postinfusion and radioactivity was still detectable at 168 h. While the plasma concentration of TXD258 increased linearly in mice with the infused dose, the brain content increased more than proportionally with the dose between 15 and 90 mg m?2. This nonlinear uptake of TXD258 also occurred in the plasma and brain of the rat. These findings suggest that the protein-mediated efflux across the blood–brain barrier (BBB) becomes saturated. In situ brain perfusion studies confirmed that TXD258 is a P-gp substrate at the BBB of mice and rats. The P-gp of both species was saturated at the half-inhibitory concentration (?13 ?M) produced by i.v. infusion. Thus, the observed nonlinear accumulation of TXD258 in the brain seems to occur by saturation of the P-gp at the rodent BBB. This saturation could have several advantages, such as overcoming a P-gp-mediated efflux, but the nonlinear pharmacokinetics could increase the risk of toxicity.

Cisternino, Salvatore; Bourasset, Fanchon; Archimbaud, Yves; Semiond, Dorothee; Sanderink, Gerard; Scherrmann, Jean-Michel

2003-01-01

294

A Multi-System Approach Assessing the Interaction of Anticonvulsants with P-gp  

PubMed Central

30% of epilepsy patients receiving antiepileptic drugs (AEDs) are not fully controlled by therapy. The drug transporter hypothesis for refractory epilepsy proposes that P-gp is over expressed at the epileptic focus with a role of P-gp in extruding AEDs from the brain. However, there is controversy regarding whether all AEDs are substrates for this transporter. Our aim was to investigate transport of phenytoin, lamotrigine and carbamazepine by using seven in-vitro transport models. Uptake assays in CEM/VBL cell lines, oocytes expressing human P-gp and an immortalised human brain endothelial cell line (hCMEC/D3) were carried out. Concentration equilibrium transport assays were performed in Caco-2, MDCKII ±P-gp and LLC-PK1±P-gp in the absence or presence of tariquidar, an inhibitor of P-gp. Finally, primary porcine brain endothelial cells were used to determine the apparent permeability (Papp) of the three AEDs in the absence or presence of P-gp inhibitors. We detected weak transport of phenytoin in two of the transport systems (MDCK and LLC-PK1 cells transfected with human P-gp) but not in the remaining five. No P-gp interaction was observed for lamotrigine or carbamazepine in any of the seven validated in-vitro transport models. Neither lamotrigine nor carbamazepine was a substrate for P-gp in any of the model systems tested. Our data suggest that P-gp is unlikely to contribute to the pathogenesis of refractory epilepsy through transport of carbamazepine or lamotrigine.

Dickens, David; Yusof, Siti R.; Abbott, N. Joan; Weksler, Babette; Romero, Ignacio A.; Couraud, Pierre-Olivier; Alfirevic, Ana; Pirmohamed, Munir; Owen, Andrew

2013-01-01

295

Heterogeneity in the rat brain vasculature revealed by quantitative confocal analysis of endothelial barrier antigen and P-glycoprotein expression  

PubMed Central

While phenotypic endothelial heterogeneity is well documented in peripheral organs, it is only now being explored in the brain. We used confocal imaging of thick sections of rat brain to qualitatively and quantitatively examine the expression of two key markers of the blood–brain barrier (BBB) in the rat, P-glycoprotein (P-gp), and endothelial barrier antigen (EBA). We found that these markers were not uniformly distributed throughout the whole vasculature of the cortex and hippocampus. P-glycoprotein displayed a gradient of expression from an almost undetectable level in large penetrating arterioles to a high and uniform level in capillaries and venules. While EBA was lacking in all cerebral arterioles, regardless of their size, its expression varied greatly among endothelial cells in capillaries and venules, yielding a striking mosaic pattern. A detailed quantitative analysis of the distribution of these markers at the single cell level in capillaries is provided. These results challenge the view of a uniform BBB and suggest that regulatory mechanisms might differentially modulate BBB features not only among arterioles/capillaries/venules but also at the single cell level within the capillaries. Hypotheses are made regarding the underlying mechanisms and physiopathological consequences of this heterogeneity.

Saubamea, Bruno; Cochois-Guegan, Veronique; Cisternino, Salvatore; Scherrmann, Jean-Michel

2012-01-01

296

4Biphenyl and 2-naphthyl substituted 6,7-dimethoxytetrahydroisoquinoline derivatives as potent P-gp modulators  

Microsoft Academic Search

Starting from lead compound 1 (EC50=1.64?M), its non-basic nucleus has been conformationally restricted by 4-biphenyl and 2-naphthyl moieties. In each series we investigated if the presence of H-bond donor or acceptor substituents, the basicity and the lipophilicity (clogP) were correlated with the P-gp inhibiting activity of tested compounds. In the biphenyl series, derivative 4d displayed the best results (EC50=0.05?M). The

Nicola Antonio Colabufo; Francesco Berardi; Mariangela Cantore; Maria Grazia Perrone; Marialessandra Contino; Carmela Inglese; Mauro Niso; Roberto Perrone; Amalia Azzariti; Grazia Maria Simone; Angelo Paradiso

2008-01-01

297

The combined use of paclitaxel-loaded nanoparticles with a low-molecular-weight copolymer inhibitor of P-glycoprotein to overcome drug resistance.  

PubMed

Two types of nanoparticles were prepared using the diblock copolymer methoxy poly(ethylene glycol)-block-poly(caprolactone) (MePEG-b-PCL), with either a short PCL block length, which forms micelles, or with a longer PCL block length, which forms kinetically "frozen core" structures termed nanospheres. Paclitaxel (PTX)-loaded micelles and nanospheres were evaluated for their cytotoxicity, cellular polymer uptake, and drug accumulation in drug-sensitive (Madin-Darby Canine Kidney [MDCK]II) and multidrug-resistant (MDR) P-glycoprotein (P-gp)-overexpressing (MDCKII-MDR1) cell lines. Both types of PTX-loaded nanoparticles were equally effective at inhibiting proliferation of MDCKII cells, but PTX-loaded micelles were more cytotoxic than nanospheres in MDCKII-MDR1 cells. The intracellular accumulation of both PTX and the diblock copolymers were similar for both nanoparticles, suggesting that the difference in cytotoxicity might be due to the different drug-release profiles. Furthermore, the cytotoxicity of these PTX-loaded nanoparticles was enhanced when these systems were subsequently or concurrently combined with a low-molecular-weight MePEG-b-PCL diblock copolymer, which we have previously demonstrated to be an effective P-gp inhibitor. These results suggest that the dual functionality of MePEG-b-PCL might be useful in delivering drug intracellularly and in modulating P-gp in order to optimize the cytotoxicity of PTX in multidrug-resistant cells. PMID:23378760

Wan, Chung Ping Leon; Letchford, Kevin; Jackson, John K; Burt, Helen M

2013-01-22

298

Modulation of P-glycoprotein expression by triptolide in adriamycin-resistant K562/A02 cells  

PubMed Central

Multidrug resistance is a serious obstacle encountered in leukemia treatment. Previous studies have found drug resistance in human leukemia is mainly associated with overexpression of the multidrug resistance gene 1 (MDR1). The aim of the present study was to investigate the modulation of P-glycoprotein expression by triptolide in adriamycin-resistant K562/A02 cells. The reverse effects of triptolide on drug resistance in K562/A02 cells were assessed by 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyl-tetrazolium bromide (MTT) assay. The percentage of apoptotic cells was obtained from annexin V/fluorescein isothiocyanate (FITC) and propridium iodide (PI) double-staining. The effects of triptolide on P-glycoprotein activity were evaluated by measuring intracellular adriamycin accumulation. The expression of P-glycoprotein was determined by flow cytometry. A luciferase reporter gene assay was used to detect the transcriptional activity of the MDR1 promoter. Results revealed that triptolide decreased the degree of resistance of K562/A02 cells, and significantly inhibited P-glycoprotein expression and drug-transport function, and increased the accumulation of adriamycin in K562/A02 cells as measured by flow cytometry. A luciferase reporter gene assay demonstrated that triptolide was capable of inhibiting the transcriptional activity of the MDR1 promoter. Triptolide may effectively reverse the adriamycin resistance in K562/A02 cells via modulation of the P-glycoprotein expression and by increasing intracellular adriamycin accumulation.

LI, HAO; HUI, LULU; XU, WENLIN; SHEN, HUILING; CHEN, QIAOYUN; LONG, LULU; ZHU, XIAOLAN

2012-01-01

299

P-glycoprotein: clinical significance and methods of analysis.  

PubMed

Multidrug resistance (MDR) is responsible for a decrease in sensitivity of tumor cells tumor cells to unrelated, naturally occurring anticancer drugs. This resistance is correlated with expression and activity of a membrane protein, P-gp 170, functioning as a drug-extruding pump. It has been well described in in vitro situations; however, the clinical detection and implications are not yet clear. Multiple detection assays have been developed based on the discovery of the MDR gene family and the corresponding protein. Southern, Northern, or Western blot analysis, S1 nuclease protection or PCR-based assays, immunohistochemical detection or functionality tests by flow cytometry have been used extensively. However, by use of these techniques on clinical material, both normal and malignant, contradictory results have emerged. The sensitivity and specificity of a certain technique are always limited by unavoidable parameters, for example, skill of the technician. Moreover, the complexity of the development of resistance against anticancer agents (external determinants), such as the diversity of tumor tissues, the simultaneous presence of other resistance mechanisms, and the low expression level, make MDR detection equivocal and can lead to contradictory results. Previous treatment influencing the MDR profile and inappropriate timing of the test make a possible correlation between MDR expression and chemotherapeutic resistance difficult to establish and can lead to discordant results. In this review, the need for proper criteria is stressed. No single detection technique provides the ideal test to detect MDR. Tandem testing could give more certainty, although small sample size limit this application. Formulation of a standard assay with better definition of a positivity is essential before clinical trials are started. PMID:7495497

van der Heyden, S; Gheuens, E; DeBruijn, E; Van Oosterom, A; Maes, R

1995-01-01

300

In vitro activity of novel dual action MDR anthranilamide modulators with inhibitory activity on CYP450 (Part 2)  

Microsoft Academic Search

Synthesis and in vitro cytotoxicity assays of new anthranilamide MDR modulators have been performed to assess their inhibition potency on the P-glycoprotein (P-gp) transporter. Previous studies showed that the replacement of the aromatic spacer group between nitrogen atoms (N1 and N2) in the P-gp inhibitor XR9576 with ethyl or propyl chain is optimal for P-gp inhibition potency. To confirm that

Philippe Labrie; Shawn P. Maddaford; Jacques Lacroix; Concettina Catalano; David K. H. Lee; Suman Rakhit; René C. Gaudreault

2007-01-01

301

Reversal of p-glycoprotein-mediated multidrug resistance by CJX1, an amlodipine derivative, in doxorubicin-resistant human myelogenous leukemia (K562/DOX) cells.  

PubMed

P-glycoprotein-mediated drug efflux can yield a multidrug resistance (MDR) phenotype that is associated with a poor response to cancer chemotherapy. Development of safe and effective MDR reversing agents is an important approach in the clinic. The aim of this study was to observe the effects of CJX1, an amlodipine derivative, on the inhibition of P-gp function and P-gp-mediated MDR in K562/DOX cells and parental K562 cells. Based on the flow cytometric technology, the uptake, accumulation and efflux of rhodamine123 (Rh123) were detected in these cells by measuring Rh123-associated mean fluorescence intensity (MFI). The effects of CJX1 on the doxorubicin cytotoxicity were evaluated by assaying for MTT (3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide) reduction and the reversal fold (RF) values. The DNA content, percentage of apoptosis and cell cycle analysis were monitored with flow cytometry. Intracellular accumulation of doxorubicin was also assessed by the determination of doxorubicin-associated MFI. Verapamil was employed as a comparative agent. Incubation of K562/DOX cells with CJX1 caused a marked increase in uptake and a notable decrease in efflux of Rh123, No such results were found in parental K562 cells. The inhibitory effect of the agent of P-gp function was reversible, but it persisted at least for 90 min after removal of 2.5 microM CJX1 from incubation medium. The doxorubicin-induced cytotoxicity, apoptosis and cell cycle perturbations were significantly potentiated by CJX1. The intracellular accumulation of doxorubicin was enhanced in the presence of various concentrations of CJX1. The CJX1 exhibited potent effects in vitro in the reversal of P-gp-mediated MDR, suggesting that the compound may become a candidate of effective MDR reversing agent in cancer chemotherapy. PMID:15967469

Ji, Bian-Sheng; He, Ling; Liu, Guo-Qing

2005-09-16

302

Conserved Walker A Cysteines 431 and 1074 in Human P-Glycoprotein Are Accessible to Thiol-Specific Agents in the Apo and ADP-Vanadate Trapped Conformations.  

PubMed

P-Glycoprotein (P-gp) is an ATP-binding cassette efflux transporter involved in the development of multidrug resistance in cancer cells. Although the mechanism of P-gp efflux has been extensively studied, aspects of its catalytic and transport cycle are still unclear. In this study, we used conserved C431 and C1074 in the Walker A motif of nucleotide-binding domains (NBDs) as reporter sites to interrogate the interaction between the two NBDs during the catalytic cycle. Disulfide cross-linking of the C431 and C1074 residues in a Cys-less background can be observed in the presence of M14M and M17M cross-linkers, which have spacer arm lengths of 20 and 25 Å, respectively. However, cross-linking with both cross-linkers was prevented in the ADP-vanadate trapped (closed) conformation. Both C431 and C1074 alone or together (double mutant) in the apo and closed conformations were found to be accessible to fluorescein 5-maleimide (FM) and methanethiosulfonate derivatives of rhodamine and verapamil. In addition, C1074 showed 1.4- and 2-fold higher degrees of FM labeling than C431 in the apo and closed conformations, respectively, demonstrating that C1074 is more accessible than C431 in both conformations. In the presence of P-gp substrates, cross-linking with M17M is still observed, suggesting that binding of substrate in the transmembrane domains does not change the accessibility of the cysteines in the NBDs. In summary, the cysteines in the Walker A motifs of NBDs of human P-gp are differentially accessible to thiol-specific agents in the apo and closed conformations. PMID:24053441

Sim, Hong-May; Bhatnagar, Jaya; Chufan, Eduardo E; Kapoor, Khyati; Ambudkar, Suresh V

2013-10-04

303

Reversal of P-glycoprotein-mediated multidrug resistance by XR9051, a novel diketopiperazine derivative.  

PubMed Central

XR9051 (N-(4-(2-(6,7-Dimethoxy-1,2,3,4-tetrahydro-2-isoquinolyl)ethyl)phe nyl)-3-((3Z,6Z)-6-benzylidene-1-methyl-2,5-dioxo-3-pipera zinylidene) methylbenzamide) was identified as a potent modulator of P-glycoprotein-mediated multidrug resistance (MDR) following a synthetic chemistry programme based on a natural product lead compound. The activity of XR9051 was determined using a panel of human and murine drug-resistant cell lines (H69/LX4, 2780AD, EMT6/AR 1.0, MC26 and P388/DX Johnson). XR9051 was able to reverse resistance to a variety of cytotoxic drugs, including doxorubicin, etoposide and vincristine, which are associated with classical MDR. At a concentration of 0.3-0.5 microM, XR9051 was able to fully sensitize resistant cells to cytotoxics, whereas little or no effect was observed on the corresponding parental cell lines. No effect of XR9051 was observed on the response of cells to non-MDR cytotoxics such as methotrexate and 5-fluorouracil. XR9051 was consistently more potent than cyclosporin A (CsA) and verapamil (Vpm) in all assays used. XR9051 inhibited the efflux of [3H]daunorubicin from preloaded cells and, unlike CsA and Vpm, remained active for several hours after removal of resistance-modifying agent. In photoaffinity labelling experiments employing [3H]azidopine, XR9051 was able to displace binding to P-glycoprotein. In binding studies using [3H]vinblastine, XR9051 was shown to be a potent inhibitor of the binding of the cytotoxic to P-glycoprotein (EC50 = 1.4 +/- 0.5 nM). Taken together, the results indicate that XR9051 reverses the MDR phenotype through direct interaction with P-glycoprotein. Images Figure 5

Dale, I. L.; Tuffley, W.; Callaghan, R.; Holmes, J. A.; Martin, K.; Luscombe, M.; Mistry, P.; Ryder, H.; Stewart, A. J.; Charlton, P.; Twentyman, P. R.; Bevan, P.

1998-01-01

304

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

PubMed Central

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 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 drug pharmacokinetics. We have identified a novel MDR1GT1292-3TG (Cys431Leu) genetic variation through systematic profiling of subjects with leukemia. The cellular and transport function of this variation was investigated with recombinant human embryonic kidney cells expressing MDR1. Compared with the wild type, MDR1GT1292-3TG recombinant cells exhibited a lower drug resistance phenotype for a panel of chemotherapeutic agents. When compared with wild type, MDR1GT1292-3TG recombinant cells exposed exhibited a 75% decrease in IC50 for doxorubicin (162.6?±?17.4 to 37.9?±?2.6 nM) and a 50% decrease in IC50 for paclitaxel (155.7?±?27.5 to 87.7?±?9.2 nM), vinblastine (128.0?±?15.9 to 65.9?±?5.1 nM), and vincristine (593.7?±?61.8 to 307.3?±?17.0 nM). The effects of the Cys431Leu variation, due to MDR1GT1292-3TG nucleotide transition, on P-gp-dependent intracellular substrate accumulation appeared to be substrate dependent where doxorubicin, vinblastine, and paclitaxel exhibit an increased accumulation (p?P-gp may reduce drug resistance and that subjects with this genotype undergoing chemotherapy with drugs that are transported by P-gp could potentially be more responsive to therapy than those with MDR1 wild-type genotype.

Crouthamel, Matthew H.; Wu, Daniel; Yang, Ziping

2010-01-01

305

Synthesis and structure-activity evaluation of isatin-?-thiosemicarbazones with improved selective activity towards multidrug-resistant cells expressing P-glycoproteina  

PubMed Central

Cancer multidrug resistance (MDR) mediated by ATP-binding cassette (ABC) transporters presents a significant unresolved clinical challenge. One strategy to resolve MDR is to develop compounds that selectively kill cells over-expressing the efflux transporter P-glycoprotein (MDR1, P-gp, ABCB1). We have previously reported structure-activity studies based around the lead compound NSC73306 (1, 1-isatin-4-(4?-methoxyphenyl)-3-thiosemicarbazone, 4.3-fold selective). Here we sought to extend this work on MDR1-selective analogs by establishing whether 1 showed ‘robust’ activity against a range of cell lines expressing P-gp. We further aimed to synthesize and test analogs with varied substitution at the N4-position, and substitution around the N4-phenyl ring of isatin-?-thiosemicarbazones (IBTs), to identify compounds with increased MDR1-selectivity. Compound 1 demonstrated MDR1-selectivity against all P-gp-expressing cell lines examined. This selectivity was reversed by inhibitors of P-gp ATPase activity. Structural variation at the 4?-phenyl position of 1 yielded compounds of greater MDR1-selectivity. Two of these analogs, 1-isatin-4-(4?-nitrophenyl)-3-thiosemicarbazone (22, 8.3-fold selective) and 1-isatin-4-(4?-tert-butyl phenyl)-3-thiosemicarbazone (32, 14.8-fold selective), were selected for further testing, and were found to retain the activity profile of 1. These compounds are the most active IBTs identified to date.

Hall, Matthew D.; Brimacombe, Kyle R.; Varonka, Matthew S.; Pluchino, Kristen M.; Monda, Julie K.; Li, Jiayang; Walsh, Martin J.; Boxer, Matthew B.; Warren, Timothy H.; Fales, Henry M.; Gottesman, Michael M.

2011-01-01

306

Molecular models of human P-glycoprotein in two different catalytic states  

PubMed Central

Background P-glycoprotein belongs to the family of ATP-binding cassette proteins which hydrolyze ATP to catalyse the translocation of their substrates through membranes. This protein extrudes a large range of components out of cells, especially therapeutic agents causing a phenomenon known as multidrug resistance. Because of its clinical interest, its activity and transport function have been largely characterized by various biochemical studies. In the absence of a high-resolution structure of P-glycoprotein, homology modeling is a useful tool to help interpretation of experimental data and potentially guide experimental studies. Results We present here three-dimensional models of two different catalytic states of P-glycoprotein that were developed based on the crystal structures of two bacterial multidrug transporters. Our models are supported by a large body of biochemical data. Measured inter-residue distances correlate well with distances derived from cross-linking data. The nucleotide-free model features a large cavity detected in the protein core into which ligands of different size were successfully docked. The locations of docked ligands compare favorably with those suggested by drug binding site mutants. Conclusion Our models can interpret the effects of several mutants in the nucleotide-binding domains (NBDs), within the transmembrane domains (TMDs) or at the NBD:TMD interface. The docking results suggest that the protein has multiple binding sites in agreement with experimental evidence. The nucleotide-bound models are exploited to propose different pathways of signal transmission upon ATP binding/hydrolysis which could lead to the elaboration of conformational changes needed for substrate translocation. We identified a cluster of aromatic residues located at the interface between the NBD and the TMD in opposite halves of the molecule which may contribute to this signal transmission. Our models may characterize different steps in the catalytic cycle and may be important tools to understand the structure-function relationship of P-glycoprotein.

Becker, Jean-Paul; Depret, Gregoire; Van Bambeke, Francoise; Tulkens, Paul M; Prevost, Martine

2009-01-01

307

Transport Inhibition of Digoxin Using Several Common P-gp Expressing Cell Lines Is Not Necessarily Reporting Only on Inhibitor Binding to P-gp.  

PubMed

We have reported that the P-gp substrate digoxin required basolateral and apical uptake transport in excess of that allowed by digoxin passive permeability (as measured in the presence of GF120918) to achieve the observed efflux kinetics across MDCK-MDR1-NKI (The Netherlands Cancer Institute) confluent cell monolayers. That is, GF120918 inhibitable uptake transport was kinetically required. Therefore, IC50 measurements using digoxin as a probe substrate in this cell line could be due to inhibition of P-gp, of digoxin uptake transport, or both. This kinetic analysis is now extended to include three additional cell lines: MDCK-MDR1-NIH (National Institute of Health), Caco-2 and CPT-B2 (Caco-2 cells with BCRP knockdown). These cells similarly exhibit GF120918 inhibitable uptake transport of digoxin. We demonstrate that inhibition of digoxin transport across these cell lines by GF120918, cyclosporine, ketoconazole and verapamil is greater than can be explained by inhibition of P-gp alone. We examined three hypotheses for this non-P-gp inhibition. The inhibitors can: (1) bind to a basolateral digoxin uptake transporter, thereby inhibiting digoxin's cellular uptake; (2) partition into the basolateral membrane and directly reduce membrane permeability; (3) aggregate with digoxin in the donor chamber, thereby reducing the free concentration of digoxin, with concomitant reduction in digoxin uptake. Data and simulations show that hypothesis 1 was found to be uniformly acceptable. Hypothesis 2 was found to be uniformly unlikely. Hypothesis 3 was unlikely for GF120918 and cyclosporine, but further studies are needed to completely adjudicate whether hetero-dimerization contributes to the non-P-gp inhibition for ketoconazole and verapamil. We also find that P-gp substrates with relatively low passive permeability such as digoxin, loperamide and vinblastine kinetically require basolateral uptake transport over that allowed by +GF120918 passive permeability, while highly permeable P-gp substrates such as amprenavir, quinidine, ketoconazole and verapamil do not, regardless of whether they actually use the basolateral transporter. PMID:23976943

Lumen, Annie Albin; Li, Libin; Li, Jiben; Ahmed, Zeba; Meng, Zhou; Owen, Albert; Ellens, Harma; Hidalgo, Ismael J; Bentz, Joe

2013-08-16

308

Evidence for P-glycoprotein-modulated penetration of morphine-6-glucuronide into brain capillary endothelium.  

PubMed Central

1. Morphine-6-glucuronide is one of the major metabolites of morphine. The potent analgesic action of this compound together with its potential lower apparent toxicity in man, when compared with morphine, indicated its clinical importance. 2. Primary cultures of porcine brain capillary endothelial cells were used to study brain penetration of morphine-6-glucuronide. Biochemical characterization of the cell cultures revealed a marked enrichment in enzymatic activity of alkaline phosphatase (56 fold) and angiotensin converting enzyme (230 fold) as compared to whole brain tissue. By immunostaining the presence of vimentin, factor VIII, the tight junction associated protein ZO-1, and P-glycoprotein was shown. Functional characterization revealed that the carrier system responsible for transport of neutral amino acids was intact. 3. Uptake and transport of morphine-6-glucuronide was marginal and in the range of the extracellular marker sucrose. However, uptake of morphine-6-glucuronide was enhanced significantly (P < 0.0001) in presence of the inhibitors of P-glycoprotein, verapamil or vincristine. The finding that morphine-6-glucuronide may serve as a substrate for P-glycoprotein was confirmed in multidrug-resistant P388 tumour cells. 4. We conclude that penetration of the blood-brain barrier by morphine-6-glucuronide may depend on the expression of the product of the multidrug-resistance (MDR) gene in brain capillary endothelial cells. Images Figure 1 Figure 2 Figure 4 Figure 5

Huwyler, J.; Drewe, J.; Klusemann, C.; Fricker, G.

1996-01-01

309

"INVESTIGATION OF THE MICELLAR EFFECT OF PLURONIC P85 ON P-GLYCOPROTEIN INHIBITION: CELL ACCUMULATION AND EQUILIBRIUM DIALYSIS STUDIES"  

PubMed Central

The objective of this study was: (1) to characterize the P-gp inhibitory effect of different concentrations of Pluronic P85 on anti-HIV-1drug cellular accumulation, and (2) to investigate the relationship between cellular accumulation and free fraction of drug. Cellular accumulation studies in MDCKII-WT and MDCKII-MDR1 cell monolayers showed a biphasic dose response characterized by decline in accumulation at Pluronic concentrations greater than the CMC. This phenomenon was independent of the inhibition of P-gp efflux by Pluronic. Cell-free equilibrium dialysis was used to determine the effect of Pluronic P85 on drug free fraction and the affinity of Pluronic micelles for drug was modeled. Nelfinavir and saquinavir associated extensively with micelles and equilibrium free fractions were low at P85 concentrations above the CMC, with association constants being in the order nelfinavir > saquinavir >>> abacavir. Abacavir, a P-gp substrate, showed no association with micelles yet showed a biphasic response in cellular accumulation. These data suggest that, above the CMC, inhibition of P-gp is not affected but rather factors such as micellar trapping could contribute to decreased accumulation. Therefore, the in vitro evaluation of the effect of Pluronic formulations on active transport should take into account both the physicochemical properties of drug and the composition of Pluronic.

SHAIK, NAVEED; GIRI, NAGDEEP; ELMQUIST, WILLIAM F.

2009-01-01

310

Effect of levothyroxine administration on intestinal P-glycoprotein expression: Consequences for drug disposition  

Microsoft Academic Search

Objective: Thyroid function alters the pharmacokinetics of many drugs; one example is the cardiac glycoside digoxin. Because digoxin disposition is affected by intestinal expression of P-glycoprotein, we hypothesized that thyroid hormones may regulate P-glycoprotein and influence disposition of P-glycoprotein substrates.Methods: Duodenal expression of P-glycoprotein measured by reverse transcriptase-polymerase chain reaction of MDR1 messenger ribonucleic acid (mRNA) and by immunohistochemical examination

Werner Siegmund; Stephan Altmannsberger; Andrea Paneitz; Ute Hecker; Michael Zschiesche; Gerd Franke; Wieland Meng; Rolf Warzok; Eike Schroeder; Bernhard Sperker; Bernd Terhaag; Ingolf Cascorbi; Heyo K. Kroemer

2002-01-01

311

Expression and function of P-glycoprotein in rats with glycerol-induced acute renal failure  

Microsoft Academic Search

The effect of glycerol-induced acute renal failure on P-glycoprotein expression and function was evaluated in rats. The in vivo function of P-glycoprotein was evaluated by measuring renal secretory and biliary clearance and brain distribution of rhodamine 123 (Rho-123), a P-glycoprotein substrate, under a steady-state plasma concentration. In acute renal failure rats, the P-glycoprotein level increased 2.5-fold in the kidney, but

Zhao-Hui Huang; Teruo Murakami; Atsuko Okochi; Ryoko Yumoto; Junya Nagai; Mikihisa Takano

2000-01-01

312

The effect of quinidine, used as a probe for the involvement of P-glycoprotein, on the intestinal absorption and pharmacodynamics of methadone  

PubMed Central

Aims There is considerable unexplained interindividual variability in the methadone dose-effect relationship. The efflux pump P-glycoprotein (P-gp) regulates brain access and intestinal absorption of many drugs. Evidence suggests that methadone is a P-gp substrate in vitro, and P-gp affects methadone analgesia in animals. However the role of P-gp in human methadone disposition and pharmacodynamics is unknown. This investigation tested the hypothesis that the intestinal absorption and pharmacodynamics of oral and intravenous methadone are greater after inhibition of intestinal and brain P-gp, using the P-gp inhibitor quinidine as an in vivo probe. Methods Two randomized, double-blind, placebo-controlled, balanced crossover studies were conducted in healthy subjects. Pupil diameters and/or plasma concentrations of methadone and the primary metabolite EDDP were measured after 10 mg intravenous or oral methadone HCl, dosed 1 h after oral quinidine (600 mg) or placebo. Results Quinidine did not alter the effects of intravenous methadone. Miosis tmax (0.3 ± 0.3 vs 0.3 ± 0.2 h (?0.17, 0.22)), peak (5.3 ± 0.8 vs 5.1 ± 1.0 mm (0.39, 0.84)) and AUC vs time (25.0 ± 5.7 vs 26.8 ± 7.1 mm h (?6.1, 2.5)) were unchanged (placebo vs quinidine (95% confidence interval on the difference)). Quinidine increased (P < 0.05) plasma methadone concentrations during the absorptive phase, decreased tmax (2.4 ± 0.7 vs 1.6 ± 0.9 h (0.33, 1.2)), and increased peak miosis (3.2 ± 1.5 vs 4.3 ± 1.6 mm (?1.96, ?0.19)) after oral methadone. The Cmax (55.6 ± 10.3 vs 59.4 ± 14.1 ng ml?1 (?8.5, 0.65)) and AUC of methadone (298 ± 46 vs 316 ± 74 ng ml?1 h (?54, 18)) were unchanged, as were the EDDP : methadone AUC ratios. Quinidine had no effect on the rate constant for transfer of methadone between plasma and effect compartment (ke0) (2.6 ± 2.6 vs 2.5 ± 1.4 h?1 (?3.5, 4.2)). Conclusions Quinidine increased the plasma concentrations of oral methadone in the absorptive phase and the miosis caused by methadone, suggesting that intestinal P-gp affects oral methadone absorption and hence its clinical effects. Quinidine had no effect on methadone pharmacodynamics after intravenous administration, suggesting that if quinidine is an effective inhibitor of brain P-gp, then P-gp does not appear to be a determinant of the access of methadone to the brain.

Kharasch, Evan D; Hoffer, Christine; Whittington, Dale

2004-01-01

313

An atomic detail model for the human ATP binding cassette transporter P-glycoprotein derived from disulphide cross-linking and homology modeling  

Microsoft Academic Search

The multidrug resistance P-glycoprotein mediates the extrusion of chemotherapeutic drugs from cancer cells. Characterization of the drug binding and ATPase activities of the protein have made it the paradigm ATP binding cassette (ABC) transporter. P-glycoprotein has been imaged at low resolution by electron cryo-microscopy and extensively analyzed by disulphide cross-linking, but a high resolution structure solved ab initio remains elusive.

Daniella R. Stenham; Jeff D. Campbell; Mark S. P. Sansom; Christopher F. Higgins; Ian D. Kerr; Kenneth J. Linton

2003-01-01

314

C-di-GMP Hydrolysis by Pseudomonas aeruginosa HD-GYP Phosphodiesterases: Analysis of the Reaction Mechanism and Novel Roles for pGpG.  

PubMed

In biofilms, the bacterial community optimizes the strategies to sense the environment and to communicate from cell to cell. A key player in the development of a bacterial biofilm is the second messenger c-di-GMP, whose intracellular levels are modulated by the opposite activity of diguanylate cyclases and phosphodiesterases. Given the huge impact of bacterial biofilms on human health, understanding the molecular details of c-di-GMP metabolism represents a critical step in the development of novel therapeutic approaches against biofilms. In this study, we present a detailed biochemical characterization of two c-di-GMP phosphodiesterases of the HD-GYP subtype from the human pathogen Pseudomonas aeruginosa, namely PA4781 and PA4108. Upstream of the catalytic HD-GYP domain, PA4781 contains a REC domain typical of two-component systems, while PA4108 contains an uncharacterized domain of unknown function. Our findings shed light on the activity and catalytic mechanism of these phosphodiesterases. We show that both enzymes hydrolyse c-di-GMP in a two-step reaction via the linear intermediate pGpG and that they produce GMP in vitro at a surprisingly low rate. In addition, our data indicate that the non-phosphorylated REC domain of PA4781 prevents accessibility of c-di-GMP to the active site. Both PA4108 and phosphorylated PA4781 are also capable to use pGpG as an alternative substrate and to hydrolyse it into GMP; the affinity of PA4781 for pGpG is one order of magnitude higher than that for c-di-GMP. These results suggest that these enzymes may not work (primarily) as genuine phosphodiesterases. Moreover, the unexpected affinity of PA4781 for pGpG may indicate that pGpG could also act as a signal molecule in its own right, thus further widening the c-di-GMP-related signalling scenario. PMID:24066157

Stelitano, Valentina; Giardina, Giorgio; Paiardini, Alessandro; Castiglione, Nicoletta; Cutruzzolà, Francesca; Rinaldo, Serena

2013-09-16

315

C-di-GMP Hydrolysis by Pseudomonas aeruginosa HD-GYP Phosphodiesterases: Analysis of the Reaction Mechanism and Novel Roles for pGpG  

PubMed Central

In biofilms, the bacterial community optimizes the strategies to sense the environment and to communicate from cell to cell. A key player in the development of a bacterial biofilm is the second messenger c-di-GMP, whose intracellular levels are modulated by the opposite activity of diguanylate cyclases and phosphodiesterases. Given the huge impact of bacterial biofilms on human health, understanding the molecular details of c-di-GMP metabolism represents a critical step in the development of novel therapeutic approaches against biofilms. In this study, we present a detailed biochemical characterization of two c-di-GMP phosphodiesterases of the HD-GYP subtype from the human pathogen Pseudomonas aeruginosa, namely PA4781 and PA4108. Upstream of the catalytic HD-GYP domain, PA4781 contains a REC domain typical of two-component systems, while PA4108 contains an uncharacterized domain of unknown function. Our findings shed light on the activity and catalytic mechanism of these phosphodiesterases. We show that both enzymes hydrolyse c-di-GMP in a two-step reaction via the linear intermediate pGpG and that they produce GMP in vitro at a surprisingly low rate. In addition, our data indicate that the non-phosphorylated REC domain of PA4781 prevents accessibility of c-di-GMP to the active site. Both PA4108 and phosphorylated PA4781 are also capable to use pGpG as an alternative substrate and to hydrolyse it into GMP; the affinity of PA4781 for pGpG is one order of magnitude higher than that for c-di-GMP. These results suggest that these enzymes may not work (primarily) as genuine phosphodiesterases. Moreover, the unexpected affinity of PA4781 for pGpG may indicate that pGpG could also act as a signal molecule in its own right, thus further widening the c-di-GMP-related signalling scenario.

Stelitano, Valentina; Giardina, Giorgio; Paiardini, Alessandro; Castiglione, Nicoletta; Cutruzzola, Francesca; Rinaldo, Serena

2013-01-01

316

Restoring Blood-Brain Barrier P-Glycoprotein Reduces Brain Amyloid-? in a Mouse Model of Alzheimer's DiseaseS?  

PubMed Central

Reduced clearance of amyloid-? (A?) from brain partly underlies increased A? brain accumulation in Alzheimer's disease (AD). The mechanistic basis for this pathology is unknown, but recent evidence suggests a neurovascular component in AD etiology. We show here that the ATP-driven pump, P-glycoprotein, specifically mediates efflux transport of A? from mouse brain capillaries into the vascular space, thus identifying a critical component of the A? brain efflux mechanism. We demonstrate in a transgenic mouse model of AD [human amyloid precursor protein (hAPP)-overexpressing mice; Tg2576 strain] that brain capillary P-glycoprotein expression and transport activity are substantially reduced compared with wild-type control mice, suggesting a mechanism by which A? accumulates in the brain in AD. It is noteworthy that dosing 12-week-old, asymptomatic hAPP mice over 7 days with pregnenolone-16?-carbonitrile to activate the nuclear receptor pregnane X receptor restores P-glycoprotein expression and transport activity in brain capillaries and significantly reduces brain A? levels compared with untreated control mice. Thus, targeting intracellular signals that up-regulate blood-brain barrier P-glycoprotein in the early stages of AD has the potential to increase A? clearance from the brain and reduce A? brain accumulation. This mechanism suggests a new therapeutic strategy in AD.

Hartz, Anika M. S.; Miller, David S.

2010-01-01

317

The terminal phosphate in d(pGpG) reduces self-association.  

PubMed

An investigation of the self-association behavior of 2'-deoxy[5'-phosphate-guanylyl-(3'-5')-guanosine] (d(pGpG)) in the presence of Na+ and K+ ions has been carried out by 1H and 31P NMR and FTIR spectroscopy. A comparison has been made of the self- association behavior of d(pGpG) with that of the related dinucleotide d(GpG), which has been shown to form extended structures based on stacked G-tetrads. Chemically, d(pGpG) monomer differs from d(GpG) only by the addition of a phosphate at the 5'-OH of the sugar residue. It was found that the addition of the second phosphate interferes with self-association. A suitable counterion is all that is required by d(GpG) to induce the formation of large super structures, but for d(pGpG) a large excess of salt is needed to produce the same effect. However, once self-association occurs, d(pGpG) forms similar structures to d(GpG) and has nearly the same properties. For both compounds, the K+ ion induces a more stable structure than the Na+ ion. The 31P NMR chemical shift ranges of d(pGpG) were consistent with the reported data for a phosphodiester and terminal phosphate. The small change in the chemical shift of the terminal phosphate with increasing temperature suggests that no major change in the terminal phosphate conformation occurred upon self-association. It was concluded that the terminal phosphate did not result in steric hindrance to self-association, but that interference to self-association was due to electrostatic repulsion effects. PMID:10636090

Kawasaki, M M; Walmsley, J A

1999-12-01

318

No effect of CYP450 and P-glycoprotein on hydroxyurea in vitro metabolism.  

PubMed

Our objectives were (1) to study the HU metabolism via human cytochromes and (2) to test if HU is a substrate of P-gp. HU metabolism was investigated by determining the appearance of urea and HU decreasing upon incubation with human liver microsomes. Quantification was determined using HPLC coupled with UV-detection at 449 nm. Our method was linear between 5 and 1000 microm, precise (coefficients of variation ranging from 1.7 to 9.9%), accurate (97.7-103.9%). The limit of quantification was 7 microm. The ATPase activity of human P-gp membranes was determined by measuring inorganic phosphate liberation. HU and urea measurements in microsomes were not different between 0 and 60 min whatever HU concentration used from 30 to 300 microm. The presence of NADPH in the medium has no effect on HU and urea measurements. In the absence of verapamil, the ATPase activity was unaffected by HU at concentrations of 10, 30, 100 and 300 microm. HU is unlikely to cause clinically relevant drug interactions with the substrates of these enzymes/transporters. However, it will be necessary to validate these in vitro data in patients with sickle cell anemia to evaluate the impact of genetic polymorphisms of these enzymes in a black population. PMID:19817872

Sassi, Hind; Bachir, Dora; Habibi, Anoosha; Astier, Alain; Galactéros, Frédéric; Hulin, Anne

2009-10-09

319

Increased frequency of P-glycoprotein gene amplification in colchicine-resistant Rat-1 clones transformed by v-src.  

PubMed

A rat fibroblast cell line (Rat-1) carrying a temperature-sensitive mutation of v-src was used to determine whether inducible cellular transformation altered the ability of cells to amplify the p-glycoprotein gene in response to colchicine selection. Transformed and nontransformed Rat-1 fibroblasts selected under 4 times the LD50 generated the same number of colchicine-resistant colonies. We next examined colchicine-resistant colonies derived from transformed cells and compared them to colchicine-resistant colonies derived from nontransformed cells. When Rat-1 cells were selected at 35 degrees C (transforming temperature), 7 out of 7 clones exhibited a 3- to 5-fold p-glycoprotein gene amplification. These results contrasted to those found at the nontransforming temperature (40 degrees C); none of the 8 colchicine-resistant clones examined had amplified the p-glycoprotein gene. Thus in Rat-1 cells carrying a temperature-sensitive v-src gene, p-glycoprotein gene amplification was observed at a high frequency only in transformed clones selected at the temperature permissive for v-src activity. PMID:9216724

Lin, T; Trent, J M; Milliken, D; Shimm, D S; Donaldson, R; Hill, A B

1997-07-15

320

Insight into the Cooperation of P-glycoprotein (ABCB1) and Breast Cancer Resistance Protein (ABCG2) at the Blood-Brain Barrier: A Case Study Examining Sorafenib Efflux Clearance  

PubMed Central

The ATP-binding cassette transporters p-glycoprotein and breast cancer resistance protein have been shown to be critical determinants limiting drug transport across the BBB into the brain. Several therapeutic agents have been shown to be substrates for these two transporters, and as a result they have limited distribution to the brain. Recently, it has been shown that these two drug transporters cooperate at the BBB and brain penetration of dual substrates increase significantly only when both are absent, e.g., in the Mdr1a/1b-/-Bcrp1-/- mice. The present study uses the brain penetration of sorafenib to investigate these findings and attempts to explain the mechanistic basis of this cooperation with a simple theory based on affinity and capacity dependent carrier-mediated transport. The brain efflux index method, combined with the organotypic brain slices, were used to determine the net contribution of P-gp and BCRP to the total clearance of sorafenib out of the brain and show that its efflux at the BBB is mediated primarily by BCRP. Sorafenib clearance out of the brain decreased 2-fold in the Bcrp1-/- mice and 2.5-fold in the Mdr1a/1b-/-Bcrp1-/- mice. Clearance out of brain when P-gp was absent did not change significantly compared to wild-type. We also investigated the expression of P-gp and BCRP in the genetic knockout animals and saw no differences in either P-gp or BCRP in the transporter deficient mice compared to the wild-type mice. In conclusion, this study explains the cooperation of P-gp and BCRP by analysis of the efflux clearance of sorafenib and correlating it to the ‘mechanisms’ that determine the clearance, i.e., affinity and capacity.

Agarwal, Sagar; Elmquist, William F.

2012-01-01

321

Reversal of P-glycoprotein-mediated multidrug resistance by XR9051, a novel diketopiperazine derivative  

Microsoft Academic Search

XR9051 (N-(4-(2-(6,7-Dimethoxy-1,2,3,4-tetrahydro-2-isoquinolyl)ethyl)phe nyl)-3-((3Z,6Z)-6-benzylidene-1-methyl-2,5-dioxo-3-pipera zinylidene) methylbenzamide) was identified as a potent modulator of P-glycoprotein-mediated multidrug resistance (MDR) following a synthetic chemistry programme based on a natural product lead compound. The activity of XR9051 was determined using a panel of human and murine drug-resistant cell lines (H69\\/LX4, 2780AD, EMT6\\/AR 1.0, MC26 and P388\\/DX Johnson). XR9051 was able to reverse resistance to a

IL Dale; W Tuffley; R Callaghan; JA Holmes; K Martin; M Luscombe; P Mistry; H Ryder; AJ Stewart; P Charlton; PR Twentyman; P Bevan

1998-01-01

322

Randomized use of cyclosporin A (CsA) to modulate P-glycoprotein in children with AML in remission: Pediatric Oncology Group Study 9421  

PubMed Central

Relapse is a major obstacle in the cure of acute myeloid leukemia (AML). The Pediatric Oncology Group AML Study 9421 tested 2 different strategies to improve event-free survival (EFS) and overall survival (OS). Patients were randomized to receive standard-dose DAT (daunorubicin, cytarabine, and thioguanine) or high-dose DAT during induction. To interfere with P-glycoprotein (P-gp)-dependent drug efflux, the second randomization tested the benefit of cyclosporine (CsA) added to consolidation chemotherapy. Of the 282 children randomly assigned to receive standard DAT induction, 248 (87.9%) achieved remission compared to 253 (91%) of the 278 receiving high-dose DAT (P = ns). Children with HLA-identical sibling donors who achieved a complete remission received an allogeneic bone marrow transplant as consolidation. For the 83 patients receiving a matched related donor bone marrow transplantation (BMT), the 3-year disease-free survival (DFS) is 67%. Of the 418 children who achieved remission and went on to consolidation with and without CsA, the DFS was 40.6% and 33.9%, respectively (P = .24). Overexpression of P-gp was infrequent (14%) in this pediatric population. In this study, intensifying induction with high-dose DAT and the addition of CsA to consolidation chemotherapy did not prolong the durations of remission or improve overall survival for children with AML.

Becton, David; Dahl, Gary V.; Ravindranath, Yaddanapudi; Chang, Myron N.; Behm, Fred G.; Raimondi, Susana C.; Head, David R.; Stine, Kimo C.; Lacayo, Norman J.; Sikic, Branimir Ivan; Arceci, Robert J.; Weinstein, Howard

2006-01-01

323

Phase I Trial of Lenalidomide and CCI-779 in Patients With Relapsed Multiple Myeloma: Evidence for Lenalidomide-CCI-779 Interaction via P-Glycoprotein  

PubMed Central

Purpose Multiple myeloma (MM) is an incurable plasma-cell neoplasm for which most treatments involve a therapeutic agent combined with dexamethasone. The preclinical combination of lenalidomide with the mTOR inhibitor CCI-779 has displayed synergy in vitro and represents a novel combination in MM. Patients and Methods A phase I clinical trial was initiated for patients with relapsed myeloma with administration of oral lenalidomide on days 1 to 21 and CCI-779 intravenously once per week during a 28-day cycle. Pharmacokinetic data for both agents were obtained, and in vitro transport and uptake studies were conducted to evaluate potential drug-drug interactions. Results Twenty-one patients were treated with 15 to 25 mg lenalidomide and 15 to 20 mg CCI-779. The maximum-tolerated dose (MTD) was determined to be 25 mg lenalidomide with 15 mg CCI-779. Pharmacokinetic analysis indicated increased doses of CCI-779 resulted in statistically significant changes in clearance, maximum concentrations, and areas under the concentration-time curves, with constant doses of lenalidomide. Similar and significant changes for CCI-779 pharmacokinetics were also observed with increased lenalidomide doses. Detailed mechanistic interrogation of this pharmacokinetic interaction demonstrated that lenalidomide was an ABCB1 (P-glycoprotein [P-gp]) substrate. Conclusion The MTD of this combination regimen was 25 mg lenalidomide with 15 mg CCI-779, with toxicities of fatigue, neutropenia, and electrolyte wasting. Pharmacokinetic and clinical interactions between lenalidomide and CCI-779 seemed to occur, with in vitro data indicating lenalidomide was an ABCB1 (P-gp) substrate. To our knowledge, this is the first report of a clinically significant P-gp–based drug-drug interaction with lenalidomide.

Hofmeister, Craig C.; Yang, Xiaoxia; Pichiorri, Flavia; Chen, Ping; Rozewski, Darlene M.; Johnson, Amy J.; Lee, Seungsoo; Liu, Zhongfa; Garr, Celia L.; Hade, Erinn M.; Ji, Jia; Schaaf, Larry J.; Benson, Don M.; Kraut, Eric H.; Hicks, William J.; Chan, Kenneth K.; Chen, Ching-Shih; Farag, Sherif S.; Grever, Michael R.; Byrd, John C.; Phelps, Mitch A.

2011-01-01

324

In vitro evaluation of human cytochrome P450 and P-glycoprotein-mediated metabolism of some phytochemicals in extracts and formulations of African potato.  

PubMed

African potato (Hypoxis hemerocallidea, AP) is a traditional herbal medicine widely used as an immune booster and also for the treatment of various ailments such as urinary diseases, prostrate hypertrophy and cancer. Amongst the chemical components contained in AP, the norlignan glycoside, hypoxoside (HYP) is purported to be the most important phytochemical in terms of AP's medicinal value. Additional constituents in AP include the sterols, beta-sitosterol (BSS), stigmasterol (STG), and the stanol, stigmastanol (STN). The potential of extracts of AP, AP formulations as well as HYP, its aglycone rooperol (ROP) and the sterols to inhibit in vitro metabolism of drug marker substrates by human cytochrome P450 (CYP) enzymes such as CYP3A4, 3A5 and CYP19 were investigated. Samples were also assessed for their effect on drug transport proteins such as P-glycoprotein (P-gp). The effects on CYP-mediated metabolism were studied by fluorometric microtitre plate assay. The potential interaction with P-gp was investigated by measuring the efflux of the fluorescent dye rhodamine 123 (Rh 123) in the CaCo-2 (colon carcinoma) cell line. Various extracts of AP, AP formulations, only STG and the norlignans, in particular the aglycone ROP, exhibited inhibitory effects on CYP3A4-, 3A5- and 19-mediated metabolism. The extracts and the formulations that contained a significant amount of HYP showed high induction of P-gp compared to the positive control, ritonavir. Whilst extrapolation of the current in vitro findings to clinical effects may well be considered speculative, these in vitro data should be heeded as a signal of possible in vivo interactions. Appropriate measures are therefore necessary to explore the possibility of such in vitro-in vivo correlations. PMID:17336049

Nair, Vipin D P; Foster, Brian C; Thor Arnason, J; Mills, Edward J; Kanfer, Isadore

2007-03-01

325

Effects of dietary flavonoids on the transport of cimetidine via P-glycoprotein and cationic transporters in Caco-2 and LLC-PK1 cell models.  

PubMed

1. The hypotheses tested were to study cimetidine as a substrate of P-glycoprotein (P-gp) and organic cation transport systems and the modulatory effects of eight flavonoid aglycones and glycosides on these transport systems using Caco-2 and LLC-PK1 cells. 2. Transport and uptake experiments of (20 microM) (3)H-cimetidine were performed with and without co-exposure to quercetin, quercetrin, rutin, naringenin, naringin, genistein, genistin, and xanthohumol. Co-treatment decreased basolateral to apical (B to A) permeability (P(app)) of cimetidine from 2.02 to 1.24 (quercetin), 1.06 (naringenin), 1.24 (genistein), and 0.96 (xanthohumol) x 10(-6) cm s(-1) in Caco-2 cells and from 10.76 to 1.65 (quercetin), 2.05 (naringenin), 2.88 (genistein), and 1.95 (xanthohumol) x 10(-6) cm s(-1) in LLC-PK1 cells. Genistin significantly reduced B to A P(app) of cimetidine to 1.24 x 10(-6) cm s(-1) in Caco-2 cells. Basolateral intracellular uptake rate of cimetidine was enhanced 145-295% when co-treated with flavonoids. Co-treatment with P-glycoprotein and organic cation transporter inhibitors, verapamil and phenoxybenzamine, resulted in reduced B to A permeability and slower basolateral intracellular uptake rate of cimetidine. Intracellular uptake rate of (14)C-tetraethylammonium (TEA) was reduced in the presence of quercetin, naringenin and genistein in LLC-PK1 cells. 3. In conclusion, quercetin, naringenin, genistein, and xanthohumol reduced P-gp-mediated transport and increased the basolateral uptake rate of cimetidine. Quercetin, naringenin, genistein, but not xanthohumol, reduced intracellular uptake rate of TEA in LLC-PK1 cells. These results suggest that flavonoids may have potential to alter the disposition profile of cimetidine and possibly other therapeutics that are mediated by P-gp and/or cation transport systems. PMID:18951251

Taur, J-S; Rodriguez-Proteau, R

2008-12-01

326

Tanshinone IIA potentiates the efficacy of 5-FU in Colo205 colon cancer cells in vivo through downregulation of P-gp and LC3-II  

PubMed Central

Traditional Chinese herbal medicines are widely accepted as an option for the treatment of colorectal cancers. Danshen (Salviae miltiorrhizae Radix) is widely prescribed in traditional Chinese medicine for cardiovascular diseases. Tanshinone IIA (Tan-IIA) is extracted from Danshen. Our previous studies have shown that Tan-IIA induces apoptosis in Colo205 human colon cancer cells in vitro and in vivo. In the present study, we investigated the efficacy of Tan-IIA and 5-fluorouracil (5-FU) in a Colo205 cell xenograft model. For in vivo studies, SCID mice were engrafted with Colo205 cells and from day 10 onwards were randomly divided into 3 groups and treated with 5-FU plus Tan-IIA, 5-FU plus corn oil, and the vehicle alone. At the end of a 4-week dosing schedule, the SCID mice were sacrificed and xenograft tumors were dissected for protein western blot analysis. Our results showed that the Colo205 xenograft model co-treated with Tan-IIA plus 5-FU caused a reduction in the xenograft tumor volumes and decreased P-glycoprotein (P-gp) and microtubule-associated protein light chain 3 (LC3)-II expression compared to 5-FU alone. Based on these observations, it may be possible to develop Tan-IIA plus 5-FU as therapeutic agents for human colon cancer.

SU, CHIN-CHENG

2012-01-01

327

[P-glycoprotein and human immunodeficiency virus infection].  

PubMed

P-glycoprotein (PGP) is a membrane protein and product of the MDR-1 gene, which acts as an efflux pump for several drugs, such as protease inhibitors (PI) used in HIV. Numerous studies in vitro, in experimental animals, and in patients have analyzed the relationships between PGP and the pharmacokinetic and pharmacodynamic properties of antiretroviral agents, with differing conclusions. In addition, studies focusing on the impact of single nucleotide polymorphisms in the MDR-1 gene, mainly C3435T in exon 26 and G2677A/G2677T in exon 21, on antiretroviral plasma concentrations, efficacy and adverse effects, have reported varying results, which have been attributed to the influence of other polymorphisms, such as cytochrome P450. PMID:18358214

Peralta, Galo; Sánchez, María Blanca; Echevarría, Santiago; Valdizán, Elsa María; Armijo, Juan Antonio

2008-03-01

328

Drosophila melanogaster p-glycoprotein: a membrane detoxification system toward polycyclic aromatic hydrocarbon pollutants.  

PubMed

Polycyclic aromatic hydrocarbons (PAHs) are well-known ubiquitous environmental contaminants. Permeability glycoprotein (P-gp) is a transmembrane detoxification efflux pump transporting various lipophilic xenobiotics, such as PAHs, out of the cells. The existence of a P-gp detoxification system inducible by PAHs was investigated in Drosophila melanogaster. Western blot experiments showed that D. melanogaster expressed a 140-kDa P-gp in S12 cells, embryos, and adult flies. Permeability glycoprotein was expressed in adult flies in the head, abdomen, and thorax and sublocalized in the sexual and olfactory organs. Flow cytometry experiments using Drosophila S12 cells in the presence of PAHs and target P-gp drug compounds revealed that Drosophila P-gp acted as an efflux detoxification pump. In Drosophila exposed to benzo[a]pyrene or to ambient air polluted by higher or lower PAH concentrations, P-gp expression was clearly showed a dose-dependent increase response. The P-gp induction was detected both in adult flies and in different fly parts, such as the head, thorax, and antennae. Drosophila P-gp acts as a membrane barrier against PAH pollutants. PMID:16519321

Vaché, Christel; Camares, Olivier; De Graeve, Fabienne; Dastugue, Bernard; Meiniel, Annie; Vaury, Chantal; Pellier, Serge; Leoz-Garziandia, Eva; Bamdad, Mahchid

2006-02-01

329

Interaction with P-glycoprotein and transport of erythromycin, midazolam and ketoconazole in Caco-2 cells  

Microsoft Academic Search

The effect of cytochrome P-450 3A (CYP3A) substrates (erythromycin, midazolam) and an inhibitor (ketoconazole) on P-glycoprotein-mediated transport was studied in Caco-2, the human colon adenocarcinoma cell line expressing various functions of differentiated intestinal epithelial cells. The involvement of P-glycoprotein in the transport of these drugs was also examined. The basal-to-apical transport of rhodamine 123, a P-glycoprotein substrate, was inhibited by

Mikihisa Takano; Risa Hasegawa; Takeshi Fukuda; Ryoko Yumoto; Junya Nagai; Teruo Murakami

1998-01-01

330

Class III P-glycoproteins mediate the formation of lipoprotein X in the mouse.  

PubMed

Cholestasis is associated with hypercholesterolemia and appearance of the abnormal lipoprotein X (LpX) in plasma. Using mice with a disrupted Mdr2 gene, we tested the hypothesis that LpX originates as a biliary lipid vesicle. Mdr2-deficient mice lack Mdr2 P-glycoprotein, the canalicular translocator for phosphatidylcholine, and secrete virtually no phospholipid and cholesterol in bile. Bile duct ligation of Mdr2(+)/+ mice induced a dramatic increase in the plasma cholesterol and phospholipid concentration. Agarose electrophoresis, density gradient ultracentrifugation, gel permeation, and electron microscopy revealed that the majority of phospholipid and cholesterol was present as LpX, a 40-100 nm vesicle with an aqueous lumen. In contrast, the plasma cholesterol and phospholipid concentration in Mdr2(-)/- mice decreased upon bile duct ligation, and plasma fractionation revealed a complete absence of LpX. In mice with various expression levels of Mdr2 or MDR3, the human homolog of Mdr2, we observed that the plasma level of cholesterol and phospholipid during cholestasis correlated very closely with the expression level of these canalicular P-glycoproteins. These data demonstrate that during cholestasis there is a quantitative shift of lipid secretion from bile to the plasma compartment in the form of LpX. The concentration of this lipoprotein is determined by the activity of the canalicular phospholipid translocator. PMID:9802889

Elferink, R P; Ottenhoff, R; van Marle, J; Frijters, C M; Smith, A J; Groen, A K

1998-11-01

331

Behavioral Effects and Central Nervous System Levels of the Broadly Available ?-Agonist Hallucinogen Salvinorin A Are Affected by P-Glycoprotein Modulation In Vivo  

PubMed Central

Active blood-brain barrier mechanisms, such as the major efflux transporter P-glycoprotein (mdr1), modulate the in vivo/central nervous system (CNS) effects of many pharmacological agents, whether they are used for nonmedical reasons or in pharmacotherapy. The powerful, widely available hallucinogen salvinorin A (from the plant Salvia divinorum) is a high-efficacy, selective ?-opioid agonist and displays fast-onset behavioral effects (e.g., within 1 min of administration) and relatively short duration of action. In vitro studies suggest that salvinorin A may be a P-glycoprotein substrate; thus, the functional status of P-glycoprotein may influence the behavioral effects of salvinorin A or its residence in CNS after parenteral administration. We therefore studied whether a competing P-glycoprotein substrate (the clinically available agent loperamide; 0.032–0.32 mg/kg) or a selective P-glycoprotein blocker, tariquidar (0.32–3.2 mg/kg) could enhance unconditioned behavioral effects (ptosis and facial relaxation, known to be caused by ?-agonists in nonhuman primates) of salvinorin A, as well as its entry and residence in the CNS, as measured by cerebrospinal fluid sampling. Pretreatment with either loperamide or tariquidar dose-dependently enhanced salvinorin A-induced ptosis, but not facial relaxation. In a control study, loperamide and tariquidar were inactive when given as a pretreatment to ((+)-(5?,7?,8?)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4.5]dec-8-yl]-benzeneacetamide (U69,593), a ?-agonist known to be a very poor P-glycoprotein substrate. Furthermore, pretreatment with tariquidar (3.2 mg/kg) also enhanced peak levels of salvinorin A in cerebrospinal fluid after intravenous administration. These are the first studies in vivo showing the sensitivity of salvinorin A effects to modulation by the P-glycoprotein transporter, a major functional component of the blood-brain barrier.

Caspers, Michael; Lovell, Kimberly M.; Kreek, Mary Jeanne; Prisinzano, Thomas E.

2012-01-01

332

Behavioral effects and central nervous system levels of the broadly available ?-agonist hallucinogen salvinorin A are affected by P-glycoprotein modulation in vivo.  

PubMed

Active blood-brain barrier mechanisms, such as the major efflux transporter P-glycoprotein (mdr1), modulate the in vivo/central nervous system (CNS) effects of many pharmacological agents, whether they are used for nonmedical reasons or in pharmacotherapy. The powerful, widely available hallucinogen salvinorin A (from the plant Salvia divinorum) is a high-efficacy, selective ?-opioid agonist and displays fast-onset behavioral effects (e.g., within 1 min of administration) and relatively short duration of action. In vitro studies suggest that salvinorin A may be a P-glycoprotein substrate; thus, the functional status of P-glycoprotein may influence the behavioral effects of salvinorin A or its residence in CNS after parenteral administration. We therefore studied whether a competing P-glycoprotein substrate (the clinically available agent loperamide; 0.032-0.32 mg/kg) or a selective P-glycoprotein blocker, tariquidar (0.32-3.2 mg/kg) could enhance unconditioned behavioral effects (ptosis and facial relaxation, known to be caused by ?-agonists in nonhuman primates) of salvinorin A, as well as its entry and residence in the CNS, as measured by cerebrospinal fluid sampling. Pretreatment with either loperamide or tariquidar dose-dependently enhanced salvinorin A-induced ptosis, but not facial relaxation. In a control study, loperamide and tariquidar were inactive when given as a pretreatment to ((+)-(5?,7?,8?)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4.5]dec-8-yl]-benzeneacetamide (U69,593), a ?-agonist known to be a very poor P-glycoprotein substrate. Furthermore, pretreatment with tariquidar (3.2 mg/kg) also enhanced peak levels of salvinorin A in cerebrospinal fluid after intravenous administration. These are the first studies in vivo showing the sensitivity of salvinorin A effects to modulation by the P-glycoprotein transporter, a major functional component of the blood-brain barrier. PMID:22434677

Butelman, Eduardo R; Caspers, Michael; Lovell, Kimberly M; Kreek, Mary Jeanne; Prisinzano, Thomas E

2012-03-20

333

AZT and emodin exhibit synergistic growth-inhibitory effects on K562/ADM cells by inducing S phase cell cycle arrest and suppressing MDR1 mRNA/p-gp protein expression.  

PubMed

Abstract Context: Previous studies have demonstrated that both 3'-azido-3'-deoxythymidine (AZT) and emodin, a traditional chemotherapy agent, can inhibit the growth of many types of cancer cells. Objective: This study aimed to evaluate the effect of AZT and emodin on adriamycin-resistant human chronic myelogenous leukemia (K562/ADM) cells, determine the expression of multidrug resistance 1 (MDR1) mRNA/p-glycoprotein (p-gp) protein, a protein known to induce resistance to anticancer agents, and to elucidate the underlying molecular mechanisms. Materials and methods: K562/ADM cells were treated with AZT (10-160??M) or emodin (5-80??M) for 24,?48 and 72?h and cell viability was measured using the MTT assay. The effect of AZT (16.5, 33 and 66??M) and emodin (6.1,?17.6 and 33.2??M) on K562/ADM cell cycle distribution was determined by flow cytometry, and MDR1 mRNA/p-gp protein expression was determined by real time RT-PCR and western blotting. Results: The growth suppression of emodin was dramatically enhanced by AZT in K562/ADM cells. The IC50 of AZT and emodin was lower than that of emodin alone. All examined combinations of AZT and emodin yielded a synergetic effect (CI?p-gp protein was markedly decreased. Discussion and conclusion: These results show a synergistic growth-inhibitory effect of AZT and emodin in K562/ADM cells, which is achieved through S phase arrest. MDR1 might ultimately be responsible for these phenomena. PMID:24004004

Chen, Peng; Liu, Yingxia; Sun, Yanqing; Chen, Che; Qi, Yongmei; Zhang, Yingmei

2013-09-05

334

Role of intestinal P-glycoprotein (mdr1) in interpatient variation in the oral bioavailability of cyclosporine  

Microsoft Academic Search

Interpatient differences in the oral clearance of cyclosporine (INN, ciclosporin) have been partially attributed to variation in the activity of a single liver enzyme termed CYP3A4. Recently it has been shown that small bowel also contains CYP3A4, as well as P-glycoprotein, a protein able to transport cyclosporine. To assess the importance of these intestinal proteins, the oral pharmacokinetics of cyclosporine

Kenneth S. Lown; Robert R. Mayo; Alan B. Leichtman; Hsiu-ling Hsiao; D. Kim Turgeon; Phyllissa Schmiedlin-Ren; Morton B. Brown; Wensheng Guo; Stephen J. Rossi; Leslie Z. Benet; Paul B. Watkins

1997-01-01

335

P-glycoprotein-mediated drug efflux is a resistance mechanism of chronic myelogenous leukemia cells to treatment with imatinib mesylate  

Microsoft Academic Search

Imatinib (Glivec®, STI571) is an intracellular acting drug that demonstrates high activity against BCR-ABL-positive chronic myelogenous leukemia (CML) or acute lymphoblastic leukemia (ALL). However, many patients, especially with advanced disease, develop drug resistance. Here, we show by a novel high-performance liquid chromatography-based method that intracellular levels of imatinib decrease in P-glycoprotein (Pgp)-positive leukemic cells. In a model of K562 cells

T Illmer; M Schaich; U Platzbecker; J Freiberg-Richter; U Oelschlägel; M von Bonin; S Pursche; T Bergemann; G Ehninger; E Schleyer

2004-01-01

336

Increased sensitivity to gemcitabine of P-glycoprotein and multidrug resistance-associated protein-overexpressing human cancer cell lines  

Microsoft Academic Search

Gemcitabine (2?,2?-difluorodeoxycytidine) is a deoxycytidine analogue that is activated by deoxycytidine kinase (dCK) to its monophosphate and subsequently to its triphosphate dFdCTP, which is incorporated into both RNA and DNA, leading to DNA damage. Multidrug resistance (MDR) is characterised by an overexpression of the membrane efflux pumps P-glycoprotein (P-gP) or multidrug resistance-associated protein (MRP). Gemcitabine was tested against human melanoma,

A. M. Bergman; H. M. Pinedo; I Talianidis; G. Veerman; W J P Loves; C L van der Wilt; G. J. Peters

2003-01-01

337

Brain Distribution of Cediranib Is Limited by Active Efflux at the Blood-Brain Barrier  

PubMed Central

Cediranib is an orally active tyrosine kinase inhibitor that targets the vascular endothelial growth factor receptor family. Because of its potent antiangiogenic and antitumor activities, cediranib has been evaluated for therapy in glioma, a primary brain tumor. This study investigated the influence of two important efflux transporters at the blood-brain barrier, P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), on the delivery of cediranib to the central nervous system. In vitro studies indicated that cediranib is a dual substrate for both P-gp and Bcrp. It is noteworthy that in spite of the in vitro data the in vivo mouse disposition studies conclusively showed that P-gp was the dominant transporter restricting the brain distribution of cediranib. The brain-to-plasma partitioning (AUCbrain/AUCplasma, where AUC is area under the curve) and the steady-state brain-to-plasma concentration ratio of cediranib were approximately 20-fold higher in Mdr1a/b(?/?) and Mdr1a/b(?/?)Bcrp1(?/?) mice compared with wild-type and Bcrp1(?/?) mice. Moreover, there was no significant difference in brain distribution of cediranib between wild-type and Bcrp1(?/?) mice and between Mdr1a/b(?/?) and Mdr1a/b(?/?)Bcrp1(?/?) mice. These results show that, unlike other tyrosine kinase inhibitors that are dual substrates for P-gp and Bcrp, Bcrp does not restrict the distribution of cediranib across the blood-brain barrier. We also show that inhibition of P-gp using specific or nonspecific inhibitors resulted in significantly enhanced delivery of cediranib to the brain. Concurrent administration of cediranib with chemical modulators of efflux transporters can be used as a strategy to enhance delivery and thus efficacy of cediranib in the brain. These findings are clinically relevant to the efficacy of cediranib chemotherapy in glioma.

Wang, Tianli; Agarwal, Sagar

2012-01-01

338

Refining the in vitro and in vivo critical parameters for P-glycoprotein, [I]/IC50 and [I2]/IC50, that allow for the exclusion of drug candidates from clinical digoxin interaction studies.  

PubMed

The objective of this work was to further investigate the reasons for disconcordant clinical digoxin drug interactions (DDIs) particularly for false negative where in vitro data suggests no P-glycoprotein (P-gp) related DDI but a clinically relevant DDI is evident. Applying statistical analyses of binary classification and receiver operating characteristic (ROC), revised cutoff values for ratio of [I]/IC(50) < 0.1 and [I(2)]/IC(50) < 5 were identified to minimize the error rate, a reduction of false negative rate to 9% from 36% (based on individual ratios). The steady state total C(max) at highest dose of the inhibitor is defined as [I] and the ratio of the nominal maximal gastrointestinal concentration determined for highest dose per 250 mL volume defined [I(2)](.) We also investigated the reliability of the clinical data to see if recommendations can be made on values that would allow predictions of 25% change in digoxin exposure. The literature derived clinical digoxin interaction studies were statistically powered to detect relevant changes in exposure associated with digitalis toxicities. Our analysis identified that many co-meds administered with digoxin are cardiovascular (CV) agents. Moreover, our investigations also suggest that the presence of CV agents may alter cardiac output and/or kidney function that may act alone or are additional components to enhance digoxin exposure along with P-gp interaction. While we recommend digoxin as the probe substrate to define P-gp inhibitory potency for clinical assessment, we observed high concordance in P-gp inhibitory potency for calcein AM as a probe substrate. PMID:20025245

Cook, Jack A; Feng, Bo; Fenner, Katherine S; Kempshall, Sarah; Liu, Ray; Rotter, Charles; Smith, Dennis A; Troutman, Matthew D; Ullah, Mohammed; Lee, Caroline A

2010-04-01

339

Resistance to Paclitaxel in a Cisplatin-Resistant Ovarian Cancer Cell Line Is Mediated by P-Glycoprotein  

PubMed Central

The IGROVCDDP cisplatin-resistant ovarian cancer cell line is also resistant to paclitaxel and models the resistance phenotype of relapsed ovarian cancer patients after first-line platinum/taxane chemotherapy. A TaqMan low-density array (TLDA) was used to characterise the expression of 380 genes associated with chemotherapy resistance in IGROVCDDP cells. Paclitaxel resistance in IGROVCDDP is mediated by gene and protein overexpression of P-glycoprotein and the protein is functionally active. Cisplatin resistance was not reversed by elacridar, confirming that cisplatin is not a P-glycoprotein substrate. Cisplatin resistance in IGROVCDDP is multifactorial and is mediated in part by the glutathione pathway and decreased accumulation of drug. Total cellular glutathione was not increased. However, the enzyme activity of GSR and GGT1 were up-regulated. The cellular localisation of copper transporter CTR1 changed from membrane associated in IGROV-1 to cytoplasmic in IGROVCDDP. This may mediate the previously reported accumulation defect. There was decreased expression of the sodium potassium pump (ATP1A), MRP1 and FBP which all have been previously associated with platinum accumulation defects in platinum-resistant cell lines. Cellular localisation of MRP1 was also altered in IGROVCDDP shifting basolaterally, compared to IGROV-1. BRCA1 was also up-regulated at the gene and protein level. The overexpression of P-glycoprotein in a resistant model developed with cisplatin is unusual. This demonstrates that P-glycoprotein can be up-regulated as a generalised stress response rather than as a specific response to a substrate. Mechanisms characterised in IGROVCDDP cells may be applicable to relapsed ovarian cancer patients treated with frontline platinum/taxane chemotherapy.

Stordal, Britta; Hamon, Marion; McEneaney, Victoria; Roche, Sandra; Gillet, Jean-Pierre; O'Leary, John J.; Gottesman, Michael; Clynes, Martin

2012-01-01

340

Resistance to paclitaxel in a cisplatin-resistant ovarian cancer cell line is mediated by P-glycoprotein.  

PubMed

The IGROVCDDP cisplatin-resistant ovarian cancer cell line is also resistant to paclitaxel and models the resistance phenotype of relapsed ovarian cancer patients after first-line platinum/taxane chemotherapy. A TaqMan low-density array (TLDA) was used to characterise the expression of 380 genes associated with chemotherapy resistance in IGROVCDDP cells. Paclitaxel resistance in IGROVCDDP is mediated by gene and protein overexpression of P-glycoprotein and the protein is functionally active. Cisplatin resistance was not reversed by elacridar, confirming that cisplatin is not a P-glycoprotein substrate. Cisplatin resistance in IGROVCDDP is multifactorial and is mediated in part by the glutathione pathway and decreased accumulation of drug. Total cellular glutathione was not increased. However, the enzyme activity of GSR and GGT1 were up-regulated. The cellular localisation of copper transporter CTR1 changed from membrane associated in IGROV-1 to cytoplasmic in IGROVCDDP. This may mediate the previously reported accumulation defect. There was decreased expression of the sodium potassium pump (ATP1A), MRP1 and FBP which all have been previously associated with platinum accumulation defects in platinum-resistant cell lines. Cellular localisation of MRP1 was also altered in IGROVCDDP shifting basolaterally, compared to IGROV-1. BRCA1 was also up-regulated at the gene and protein level. The overexpression of P-glycoprotein in a resistant model developed with cisplatin is unusual. This demonstrates that P-glycoprotein can be up-regulated as a generalised stress response rather than as a specific response to a substrate. Mechanisms characterised in IGROVCDDP cells may be applicable to relapsed ovarian cancer patients treated with frontline platinum/taxane chemotherapy. PMID:22792399

Stordal, Britta; Hamon, Marion; McEneaney, Victoria; Roche, Sandra; Gillet, Jean-Pierre; O'Leary, John J; Gottesman, Michael; Clynes, Martin

2012-07-11

341

Effects of ?-cyclodextrin on the intestinal absorption of berberine hydrochloride, a P-glycoprotein substrate.  

PubMed

The major objective of this work is to investigate the enhancing effect of ?-cyclodextrin on the intestinal absorption of berberine hydrochloride, a P-glycoprotein (Pgp) substrate. The inclusion complexation behavior of BBH with ?-CD was investigated by phase-solubility diagram, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray powder diffractometry, NMR spectroscopy, and molecular modeling studies. Results indicated that the 1,3-benzodioxole of BBH was included into the cavity of ?-CD to form an inclusion complex which exhibited higher dissolution rate than BBH in vitro. The intestinal absorption of the inclusion complex in rats was significantly higher than the free drug due to its solubilizing effect and Pgp modulatory activity. The mechanisms of ?-CD on Pgp modulation were demonstrated by modifying the Pgp ATPase activity, the Pgp mRNA level and the Pgp expression. PMID:23664937

Zhang, Ye; Cui, Yuan-Lu; Gao, Li-Na; Jiang, Heng-Li

2013-05-07

342

Ex vivo and in vivo investigations of the effects of extracts of Vernonia amygdalina, Carica papaya and Tapinanthus sessilifolius on digoxin transport and pharmacokinetics: assessing the significance on rat intestinal P-glycoprotein efflux.  

PubMed

Vernonia amygdalina (VA), Carica papaya (CP), and Tapinanthus sessilifolius (ML) are widely used in some countries as medicinal herbs to treat ailments including malaria, cancer, and diabetes. We previously reported the inhibitory effects of these herbs on permeability glycoprotein (P-gp) in Caco-2 cell monolayers. This study used ex vivo and in vivo models to investigate the likelihood of P-gp-mediated herb-drug interactions occurring. The study utilized excised rat intestinal tissues mounted in Ussing chambers to predict changes in drug absorption and an in vivo study in rats using digoxin as the P-gp substrate. Apparent permeability values and pharmacokinetic parameters of digoxin were compared to determine if co-administration of digoxin with ML, CP, or VA modulated the activity of P-gp. When VA was co-administered, the total area under the plasma concentration-time curve was significantly higher (2.1-fold) than when digoxin was administered alone. Co-administration of ML, VA, and CP significantly increased the mean digoxin apparent permeability in the mucosal-to-serosal direction by 7.8, 43.3, and 54.5%, respectively, in comparison to when digoxin was administered alone. These findings suggest that VA increases intestinal absorption of digoxin in vivo by inhibiting P-gp and may also modulate the pharmacokinetic disposition of other p-gp substrate drugs. PMID:23291634

Oga, Enoche Florence; Sekine, Shuichi; Horie, Toshiharu

2013-01-01

343

Expression and induction of p-glycoprotein-1 on cultured human brain endothelium.  

PubMed

The ABC-transporter, p-glycoprotein-1 (pgp-1), is expressed on brain endothelium and is reported to be induced by several cytotoxic drugs, which are themselves substrates of pgp-1. Pgp-1 was increased on a human brain endothelial cell line (hCMEC/D3) after treatment with puromycin or verapamil. However, flow cytometry showed that the apparent upregulation caused by puromycin was not because of a global increase in expression levels, but selective cell death of a subpopulation of endothelium expressing the lowest levels of pgp-1. If a cytotoxic substrate of pgp-1 increases pgp-1 expression in vitro, it can easily be misinterpreted as a transcriptional activator of pgp-1. PMID:19638996

Male, David K

2009-07-29

344

Effect of an Antiretroviral Regimen Containing Ritonavir Boosted Lopinavir on Intestinal and Hepatic CYP3A, CYP2D6 and P-glycoprotein in HIV-infected Patients  

Microsoft Academic Search

This study aimed to quantify the inhibition of cytochrome P450 (CYP3A), CYP2D6, and P-glycoprotein in human immunodeficiency virus (HIV)-infected patients receiving an antiretroviral therapy (ART) containing ritonavir boosted lopinavir, and to identify factors influencing ritonavir and lopinavir pharmacokinetics. We measured activities of CYP3A, CYP2D6, and P-glycoprotein in 28 patients before and during ART using a cocktail phenotyping approach. Activities, demographics,

C. Wyen; U. Fuhr; D. Frank; R. E. Aarnoutse; T. Klaassen; A. Lazar; A. Seeringer; O. Doroshyenko; J. C. Kirchheiner; F. Abdulrazik; N. Schmeisser; C. Lehmann; W. Hein; E. Schomig; D. M. Burger; G. Fatkenheuer; A. Jetter

2008-01-01

345

P-glycoprotein inhibition potentiates the behavioural and neurochemical actions of risperidone in rats.  

PubMed

Antipsychotic drugs are the mainstay pharmacotherapy for schizophrenia and related psychiatric disorders. While the metabolic pathways of antipsychotic drugs have been well defined, the role of drug transporters in the disposition and effects of antipsychotic drugs has not been systematically explored. P-glycoprotein has ubiquitous expression in brain endothelial cells and plays a protective role by effluxing substrates for elimination and by limiting their accumulation in the central nervous system. Risperidone and several other antipsychotic drugs are substrates of P-glycoprotein. Increased antipsychotic drug entry into the brain via blockade of the P-glycoprotein transporter may facilitate the amount of available drug to its targets, particularly dopamine receptors. By increasing available antipsychotic drug concentrations, P-glycoprotein inhibition offers a novel means of enhanced drug delivery. This study evaluated whether selective P-glycoprotein transporter inhibition would increase the effects of risperidone on relevant indices of behaviour (catalepsy and locomotion) and neurochemistry (dopamine release and metabolism as measured by in-vivo microdialysis). We administered the P-glycoprotein inhibitor, PSC 833 (100 mg/kg p.o.), to rats prior to administration of risperidone at varying doses (0.01-4.0 mg/kg s.c.). P-glycoprotein inhibition significantly increased risperidone-induced cataleptic effects, blockade of amphetamine-induced locomotion, and effects on dopamine turnover as seen by increased striatal dopamine metabolite levels. These results provide functional evidence concordant with prior data for increased brain levels of risperidone following PSC 833 treatment. PMID:19835667

Pacchioni, Alejandra M; Gabriele, Amanda; Donovan, Jennifer L; DeVane, C Lindsay; See, Ronald E

2009-10-19

346

Diesel exhaust particles induce oxidative stress, proinflammatory signaling, and P-glycoprotein up-regulation at the blood-brain barrier  

PubMed Central

Here, we report that diesel exhaust particles (DEPs), a major constituent of urban air pollution, affect blood-brain barrier function at the tissue, cellular, and molecular levels. Isolated rat brain capillaries exposed to DEPs showed increased expression and transport activity of the key drug efflux transporter, P-glycoprotein (6 h EC50 was ?5 ?g/ml). Up-regulation of P-glycoprotein was abolished by blocking transcription or protein synthesis. Inhibition of NADPH oxidase or pretreatment of capillaries with radical scavengers ameliorated DEP-induced P-glycoprotein up-regulation, indicating a role for reactive oxygen species in signaling. DEP exposure also increased brain capillary tumor necrosis factor-? (TNF-?) levels. DEP-induced P-glycoprotein up-regulation was abolished when TNF-receptor 1 (TNF-R1) was blocked and was not evident in experiments with capillaries from TNF-R1 knockout mice. Inhibition of JNK, but not NF-?B, blocked DEP-induced P-glycoprotein up-regulation, indicating a role for AP-1 in the signaling pathway. Consistent with this, DEPs increased phosphorylation of c-jun. Together, our results show for the first time that a component of air pollution, DEPs, alters blood-brain barrier function through oxidative stress and proinflammatory cytokine production. These experiments disclose a novel blood-brain barrier signaling pathway, with clear implications for environmental toxicology, CNS pathology, and the pharmacotherapy of CNS disorders.—Hartz, A. M. S., Bauer, B., Block, M. L., Hong, J.-S., Miller, D.-S. Diesel exhaust particles induce oxidative stress, proinflammatory signaling, and P-glycoprotein up-regulation at the blood-brain barrier.

Hartz, Anika M. S.; Bauer, Bjorn; Block, Michelle L.; Hong, Jau-Shyong; Miller, David S.

2008-01-01

347

Effect of P-glycoprotein modulators on the pharmacokinetics of camptothecin using microdialysis  

PubMed Central

By performing microdialysis, this study investigated the pharmacokinetics of unbound camptothecin in rat blood, brain and bile in the presence of P-glycoprotein mediated transport modulators (cyclosporin A, berberine, quercetin, naringin and naringenin). Pharmacokinetic parameters of camptothecin were assessed using a non-compartmental model. Camptothecin rapidly crosses the blood-brain barrier (BBB) within 20?min after camptothecin administration. The disposition of camptothecin in rat bile appeared to have a slow elimination phase and a peak concentration after 20?min of camptothecin administration. The area under the concentration versus time curve (AUC) for camptothecin in bile significantly surpassed that in blood, suggesting active transport of hepatobiliary excretion. In the presence of cyclosporin A camptothecin AUC, in the brain, was significantly elevated but no significant change in the presence of berberine, quercetin, naringin and naringenin. With treatment by smaller doses of quercetin (0.1?mg?kg?1), naringin (10?mg?kg?1) and naringenin (10?mg?kg?1), they significantly diminished the camptothecin AUC in bile, but was not altered by the treatment of berberine (20?mg?kg?1), a higher dose of quercetin (10?mg?kg?1), and cyclosporin A treated (20?mg?kg?1) and pretreated groups. The distribution ratio (AUCbile/AUCblood) of camptothecin in bile was decreased in the cyclosporin A, quercetin, naringin and naringenin treated groups. However, the distribution ratio in the brain was increased in the cyclosporin A groups, but was decreased in the groups treated with quercetin, naringin and naringenin. These results revealed that P-glycoprotein might modulate hepatobiliary excretion and BBB penetration of camptothecin.

Tsai, T H; Lee, C H; Yeh, P H

2001-01-01

348

[Effect of cholesterol on the functional activity of proteins responsible for the resistance of human lymphocytes to xenobiotics].  

PubMed

The influence of agents modifying cholesterol in plasma membranes on the functional activity of transporter proteins (P-glycoprotein (P-gp) and the multidrug resistance protein 1 (MRP1)) in human lymphocytes has been studied. It was shown that changes in lateral distribution of cholesterol using the polyene antibiotic filipin, which disturb the structure and function of glycolipid microdomains in plasma membranes of lymphocytes lead to a decrease in the transport activity of both P-gp and MRP1. It was found that the treatment of human lymphocytes with the cyclic oligosaccharide methyl-beta-cyclodextrine, which leads to cholesterol depletion and reduction of lipid bilayer microviscosity in membranes of these cells, also decreases the functional activity of these proteins. It was concluded that the transport activity of P-gp and MRP1 depends on the modification of cholesterol in the membranes of human lymphocytes, i.e., is closely associated with the level of cholesterol and its lateral distribution. PMID:21786699

Tamashevski?, A V; Kozlova, N M; Goncharova, N V; Zubritskaia, G P; Slobozhanina, E I

349

Determining P-glycoprotein-drug interactions: evaluation of reconstituted P-glycoprotein in a liposomal system and LLC-MDR1 polarized cell monolayers  

PubMed Central

Introduction P-Glycoprotein (ABCB1, MDR1) is a multidrug efflux pump that is a member of the ATP-binding cassette (ABC) superfamily. Many drugs in common clinical use are either substrates or inhibitors of this transporter. Quantitative details of P-glycoprotein inhibition by pharmaceutical agents are essential for assessment of their pharmacokinetic behavior and prevention of negative patient reactions. Cell-based systems have been widely used for determination of drug interactions with P-glycoprotein, but they suffer from several disadvantages, and results are often widely variable between laboratories. We aimed to demonstrate that a novel liposomal system employing contemporary biochemical methodologies could measure the ability of clinically used drugs to inhibit the P-glycoprotein pump. To accomplish this we compared results with those of cell-based approaches. Methods Purified transport-competent hamster Abcb1a P-glycoprotein was reconstituted into a unilamellar liposomal system, Fluorosome-trans-pgp, whose aqueous interior contains fluorescent drug sensors. This provides a well-defined system for measuring P-glycoprotein transport inhibition by test drugs in real time using rapid fluorescence-based technology. Results Inhibition of ATP-driven transport by Fluorosome-trans-pgp employed a panel of 46 representative drugs. Resulting IC50 values correlated well (r2 = 0.80) with Kd values for drug binding to purified P-glycoprotein. They also showed a similar trend to transport inhibition data obtained using LLC-MDR1 cell monolayers. Fluorosome-trans-pgp IC50 values were in agreement with published results of digoxin drug-drug interaction studies in humans. Discussion This novel approach using a liposomal system and fluorescence-based technology is shown to be suitable to study whether marketed drugs and drug candidates are P-glycoprotein inhibitors. The assay is rapid, allowing a 7-point IC50 determination in <6 minutes, and requires minimal quantities of test drug. The method is amenable to robotics and offers a cost advantage relative to conventional cell-based assays. The well-defined nature of this assay also obviates many of the inherent complications and ambiguities of cell-based systems.

Melchior, Donald L.; Sharom, Frances J.; Evers, Raymond; Wright, George E.; Chu, Joseph W.K.; Wright, Stephen E.; Chu, Xiaoyan; Yabut, Jocelyn

2012-01-01

350

Enhanced Drug-Induced Apoptosis Associated with P-Glycoprotein Overexpression Is Specific to Antimicrotubule Agents  

Microsoft Academic Search

Purpose. We have reported that overexpression of mdr1 P-glycoprotein (Pgp) is associated with a higher sensitivity to paclitaxel-induced apoptosis (1,2). The present study examined the substrate specificity of this phenomenon.

Dong Li; Seong H. Jang; Jonghan Kim; M. Guillaume Wientjes; Jessie L.-S. Au

2003-01-01

351

P-Glycoprotein Is a Major Determinant of Norbuprenorphine Brain Exposure and Antinociception  

PubMed Central

Norbuprenorphine is a major metabolite of buprenorphine and potent agonist of ?, ?, and ? opioid receptors. Compared with buprenorphine, norbuprenorphine causes minimal antinociception but greater respiratory depression. It is unknown whether the limited antinociception is caused by low efficacy or limited brain exposure. Norbuprenorphine is an in vitro substrate of the efflux transporter P-glycoprotein (Mdr1), but the role of P-glycoprotein in norbuprenorphine transport in vivo is unknown. This investigation tested the hypothesis that limited norbuprenorphine antinociception results from P-glycoprotein-mediated efflux and limited brain access. Human P-glycoprotein-mediated transport in vitro of buprenorphine, norbuprenorphine, and their respective glucuronide conjugates was assessed by using transfected cells. P-glycoprotein-mediated norbuprenorphine transport and consequences in vivo were assessed by using mdr1a(+/+) and mdr1a(?/?) mice. Antinociception was determined by hot-water tail-flick assay, and respiratory effects were determined by unrestrained whole-body plethysmography. Brain and plasma norbuprenorphine and norbuprenorphine-3-glucuronide were quantified by mass spectrometry. In vitro, the net P-glycoprotein-mediated efflux ratio for norbuprenorphine was nine, indicating significant efflux. In contrast, the efflux ratio for buprenorphine and the two glucuronide conjugates was unity, indicating absent transport. The norbuprenorphine brain/plasma concentration ratio was significantly greater in mdr1a(?/?) than mdr1a(+/+) mice. The magnitude and duration of norbuprenorphine antinociception were significantly increased in mdr1a(?/?) compared with mdr1a(+/+) mice, whereas the reduction in respiratory rate was similar. Results show that norbuprenorphine is an in vitro and in vivo substrate of P-glycoprotein. P-glycoprotein-mediated efflux influences brain access and antinociceptive, but not the respiratory, effects of norbuprenorphine.

Brown, Sarah M.; Campbell, Scott D.; Crafford, Amanda; Regina, Karen J.; Holtzman, Michael J.

2012-01-01

352

3,3?,4,4?,5-Pentachlorobiphenyl Inhibits Drug Efflux Through P-Glycoprotein in KB-3 Cells Expressing Mutant Human P-Glycoprotein  

PubMed Central

The effects on the drug efflux of 3,3?,4,4?,5-pentachlorobiphenyl (PCB-126), the most toxic of all coplanar polychlorinated biphenyls (Co-PCBs), were examined in KB-3 cells expressing human wild-type and mutant P-glycoprotein in which the 61st amino acid was substituted for serine or phenylalanine (KB3-Phe61). In the cells expressing P-glycoproteins, accumulations of vinblastine and colchicine decreased form 85% to 92% and from 62% to 91%, respectively, and the drug tolerances for these chemicals were increased. In KB3-Phe61, the decreases in drug accumulation were inhibited by adding PCB-126 in a way similar to that with cyclosporine A: by adding 1??M PCB-126, the accumulations of vinblastine and colchicine increased up to 3.3- and 2.3-fold, respectively. It is suggested that PCB-126 decreased the drug efflux by inhibiting the P-glycoprotein in KB3-Phe61. Since there were various P-glycoproteins and many congeners of Co-PCBs, this inhibition has to be considered a new cause of the toxic effects of Co-PCBs.

Fujise, Hiroshi

2004-01-01

353

Mrp1 is essential for sphingolipid signaling to p-glycoprotein in mouse blood-brain and blood-spinal cord barriers.  

PubMed

At the blood-brain and blood-spinal cord barriers, P-glycoprotein, an ATP-driven drug efflux pump, is a major obstacle to central nervous system (CNS) pharmacotherapy. Recently, we showed that signaling through tumor necrosis factor-? (TNF-?), sphingolipids, and sphingosine-1-phosphate receptor 1 (S1PR1) rapidly and reversibly reduced basal P-glycoprotein transport activity in the rat blood-brain barrier. The present study extends those findings to the mouse blood-brain and blood-spinal cord barriers and, importantly, identifies multidrug resistance-associated protein 1 (Mrp1, Abcc1) as the transporter that mediates S1P efflux from brain and spinal cord endothelial cells. In brain and spinal cord capillaries isolated from wild-type mice, TNF-?, sphingosine, S1P, the S1PR agonist fingolimod (FTY720), and its active, phosphorylated metabolite, FTY720P, reduced P-glycoprotein transport activity; these effects were abolished by a specific S1PR1 antagonist. In brain and spinal cord capillaries isolated from Mrp1-null mice, neither TNF-? nor sphingosine nor FTY720 reduced P-glycoprotein transport activity. However, S1P and FTY720P had the same S1PR1-dependent effects on transport activity as in capillaries from wild-type mice. Thus, deletion of Mrp1 alone terminated endogenous signaling to S1PR1. These results identify Mrp1 as the transporter essential for S1P efflux from the endothelial cells and thus for inside-out S1P signaling to P-glycoprotein at the blood-brain and blood-spinal cord barriers. PMID:23168528

Cartwright, Tara A; Campos, Christopher R; Cannon, Ronald E; Miller, David S

2012-11-21

354

Interactions of attention-deficit/hyperactivity disorder therapeutic agents with the efflux transporter P-glycoprotein  

PubMed Central

The objective of this study was to assess the potential interactions of the drug transporter P-glycoprotein with attention-deficit/hyperactivity disorder (ADHD) therapeutic agents atomoxetine — and the individual isomers of methylphenidate, amphetamine, and modafinil utilizing established in vitro assay. An initial ATPase assay indicated that both d- and l-methylphenidate have weak affinity for P-glycoprotein. The intracellular accumulation of P-glycoprotein substrates doxorubicin and rhodamine123 in the P-glycoprotein overexpressing cell line LLC-PK1/MDR1 was determined to evaluate potential inhibitory effects on P-glycoprotein. The results demonstrated that all compounds, except both modafinil isomers, significantly increased doxorubicin and rhodamine123 accumulation in LLC-PK1/MDR1 cells at higher concentrations. To investigate the P-glycoprotein substrate properties, the intracellular concentrations of the tested compounds in LLC-PK1/MDR1 and P-glycoprotein negative LLC-PK1 cells were measured in the presence and absence of the P-glycoprotein inhibitor PSC833. The results indicate that the accumulation of d-methylphenidate in LLC-PK1 cells was 32.0% higher than in LLC-PK1/MDR1 cells. Additionally, coadministration of PSC833 leads to 52.9% and 45.6% increases in d-modafinil and l-modafinil accumulation, respectively, in LLC-PK1/MDR1 cells. Further studies demonstrated that l-modafinil transport across LLC-PK1/MDR1 cell monolayers in the basolateral-to-apical (B–A) direction was significantly higher than in the apical-to-basolateral (A–B) direction. PSC833 treatment significantly decreased the transport of l-modafinil in B–A direction. In conclusion, our results suggest that all tested agents with the exception of modafinil isomers are relatively weak P-glycoprotein inhibitors. Furthermore, P-glycoprotein may play a minor role in the transport of d-methylphenidate, d-modafinil, and l-modafinil.

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

2009-01-01

355

Tomato lectin labels the 180 kD glycoform of P-glycoprotein in rat brain capillary endothelia and mdr tumor cells.  

PubMed

Two main isoforms of P-glycoproteins can be distinguished according to their solubility in ionic and non-ionic detergents. Studies on mdr cell lines and brain capillary vessels support the evidence that tomato lectin reveals high affinity binding to the oligosaccharide chains of the SDS soluble isoform of P-glycoprotein, but not to the non-ionic detergent soluble isoform. Thus the SDS-soluble isoform represents a glycoform having polylactosamines in its oligosaccharide chains. The function of these oligosaccharides is still unknown, although the carbohydrate chains of P-glycoprotein were believed to take part in correct protein folding only. We also demonstrated that lectin binding to the extracellular lactosamine sequences of drug efflux pump does not change its efficiency on mdr cell lines, but interferes with the inhibitory action of some drugs, such as verapamil and promethazine. In accordance with earlier findings we assume that carbohydrate chains might be involved in stabilization of the active conformation of efflux pump. The possible role of lectin treatment in maintaining P-glycoprotein mediated blood-brain barrier functions has to be proved in further investigations. PMID:9713518

Fakla, I; Hever, A; Molnár, J; Fischer, J

356

Resolution of P-glycoprotein and non-P-glycoprotein effects on drug permeability using intestinal tissues from mdr1a (-/-) mice  

PubMed Central

Intestinal xenobiotic transporters are a significant barrier to the absorption of many orally administered drugs. P-glycoprotein (PGP) is the best known, but several others, including members of the multidrug resistance-associated protein (MRP) family, are also expressed. Definitive information on their precise effect on intestinal drug permeability is scarce due to a lack of specific inhibitors and the difficulty of studying non-PGP activity in the presence of high PGP expression.We have investigated the in vitro use of intestinal tissues from PGP knockout (mdr1a (?/?)) mice as a tool for dissecting the mechanisms of intestinal drug efflux. The permeability characteristics of digoxin (DIG), paclitaxel (TAX) and etoposide (ETOP) were measured in ileum from mdr1a (?/?) and wild-type (FVB) mice mounted in Ussing chambers.DIG and TAX exhibited marked efflux across FVB tissues (B-A?:?A-B apparent permeability (Papp) ratio 10 and 17 respectively) which was absent in mdr1a (?/?) tissues, confirming that PGP is the sole route of intestinal efflux for these compounds. The A-B Papp of both compounds was 3?–?5 fold higher in mdr1a (?/?) than in FVB.Polarized transport of ETOP in FVB tissues was reduced but not abolished in mdr1a (?/?) tissues. Residual ETOP efflux in mdr1a (?/?) tissues was abolished by the MRP inhibitor MK571, indicating involvement of both PGP and MRP.MK571 abolished calcein efflux in mdr1a (?/?) tissues, while quinidine had no parallel effect in FVB tissues, suggesting involvement of MRP but not PGP.Tissues from mdr1a (?/?) mice provide a novel approach for investigating the influence of PGP ablation on intestinal permeability and for resolving PGP and non-PGP mechanisms that modulate drug permeability.

Stephens, R H; O'Neill, C A; Bennett, J; Humphrey, M; Henry, B; Rowland, M; Warhurst, G

2002-01-01

357

Regulation of mdr2 P-glycoprotein expression by bile salts.  

PubMed

The phosphatidyl translocating activity of the mdr2 P-glycoprotein (Pgp) in the canalicular membrane of the mouse hepatocyte is a rate-controlling step in the biliary secretion of phospholipid. Since bile salts also regulate the secretion of biliary lipids, we investigated the influence of the type of bile salt in the circulation on mdr2 Pgp expression and activity. Male mice were led a purified diet to which either 0.1% (w/w) cholate or 0.5% (w/w) ursodeoxycholate was added. This led to a near-complete replacement of the endogenous bile salt pool (mainly tauromuricholate) by taurocholate or tauroursodeoxycholate respectively. The phospholipid secretion capacity was then determined by infusion of increasing amounts of tauroursodeoxycholate. Cholate feeding resulted in a 55% increase in maximal phospholipid secretion compared with that in mice on the control diet. Northern blotting revealed that cholate feeding increased mdr2 Pgp mRNA levels by 42%. Feeding with ursodeoxycholate did not influence the maximum rate of phospholipid output or the mdr2 mRNA content. Female mice had a higher basal mdr2 Pgp mRNA level than male mice, and this was also correlated with a higher phospholipid secretion capacity. This could be explained by the 4-fold higher basal cholate content in the bile of female compared with male mice. Our results suggest that the type of bile salts in the circulation influences the expression of the mdr2 gene. PMID:9020871

Frijters, C M; Ottenhoff, R; van Wijland, M J; van Nieuwkerk, C M; Groen, A K; Oude Elferink, R P

1997-01-15

358

Regulation of mdr2 P-glycoprotein expression by bile salts.  

PubMed Central

The phosphatidyl translocating activity of the mdr2 P-glycoprotein (Pgp) in the canalicular membrane of the mouse hepatocyte is a rate-controlling step in the biliary secretion of phospholipid. Since bile salts also regulate the secretion of biliary lipids, we investigated the influence of the type of bile salt in the circulation on mdr2 Pgp expression and activity. Male mice were led a purified diet to which either 0.1% (w/w) cholate or 0.5% (w/w) ursodeoxycholate was added. This led to a near-complete replacement of the endogenous bile salt pool (mainly tauromuricholate) by taurocholate or tauroursodeoxycholate respectively. The phospholipid secretion capacity was then determined by infusion of increasing amounts of tauroursodeoxycholate. Cholate feeding resulted in a 55% increase in maximal phospholipid secretion compared with that in mice on the control diet. Northern blotting revealed that cholate feeding increased mdr2 Pgp mRNA levels by 42%. Feeding with ursodeoxycholate did not influence the maximum rate of phospholipid output or the mdr2 mRNA content. Female mice had a higher basal mdr2 Pgp mRNA level than male mice, and this was also correlated with a higher phospholipid secretion capacity. This could be explained by the 4-fold higher basal cholate content in the bile of female compared with male mice. Our results suggest that the type of bile salts in the circulation influences the expression of the mdr2 gene.

Frijters, C M; Ottenhoff, R; van Wijland, M J; van Nieuwkerk, C M; Groen, A K; Oude Elferink, R P

1997-01-01

359

Characterization of multidrug resistance P-glycoprotein transport function with an organotechnetium cation  

SciTech Connect

Multidrug resistance (MDR) in mammalian cells and tumors is associated with overexpression of an {approximately}170 integral membrane efflux transporter, the MDR1 P-glycoprotein. Hexakis(2-methoxyisobutyl isonitrile) technetium(I) (Tc-SESTAMIBI), a {gamma}-emitting lipophilic cationic metallopharmaceutical, has recently been shown to be a P-glycoprotein transport substrate. Exploiting the negligible lipid membrane adsorption properties of this organometallic substrate, we studied the transport kinetics, pharmacology, drug binding, and modulation of P-glycoprotein in cell preparations derived from a variety of species and selection strategies, including SW-1573, V79, Alex, and CHO drug-sensitive cells and in 77A, LZ-8, and Alex/A.5 MDR cells. Rapid cell accumulation (T{sub 1/2} {approx} 6 min) of the agent to a steady state was observed which was inversely proportional to immunodetectable levels of P-glycoprotein. Many MDR cytotoxic agents inhibited P-glycoprotein-mediated Tc-SESTAMIBI efflux, thereby enhancing organometallic cation accumulation. 70 refs., 7 figs., 2 tabs.

Piwnica-Worms, D.; Vallabhaneni, V.R. [Washington Univ. Medical School, St. Louis, MO (United States); Kronauge, J.F. [Harvard Medical School, Boston, MA (United States)] [and others

1995-09-26

360

MDR1 P-Glycoprotein Is a Lipid Translocase of Broad Specificity, While MDR3 P-Glycoprotein Specifically Translocates Phosphatidylcholine  

Microsoft Academic Search

The human MDR1 P-glycoprotein (Pgp) extrudes a variety of drugs across the plasma membrane. The homologous MDR3 Pgp is required for phosphatidylcholine secretion into bile. After stable transfection of epithelial LLC-PK1 cells, MDR1 and MDR3 Pgp were localized in the apical membrane. At 15°C, newly synthesized short-chain analogs of various membrane lipids were recovered in the apical albumin-containing medium of

Ardy van Helvoort; Alexander J Smith; Hein Sprong; Ingo Fritzsche; Alfred H Schinkel; Piet Borst; Gerrit van Meer

1996-01-01

361

Arsenic trioxide induces apoptosis equally in T lymphoblastoid leukemia MOLT4 cells and P-gp-expressing daunorubicin-resistant MOLT4 cells  

Microsoft Academic Search

Purpose. To investigate the effects of arsenic trioxide (As2O3) on human T-lymphoblastoid leukemia MOLT-4 cells and P-gp-expressing daunorubicin-resistant MOLT-4 (MOLT-4\\/DNR) cells. Methods. Cell growth was measured by an MTT assay. Cell viability was determined by a dye exclusion test. The level of P-gp expression was estimated using phycoerythrin-conjugated anti-P-gp monoclonal antibody 17F9. The function of P-gp was evaluated in terms

Xiao-Mei Hu; Toshihiko Hirano; Kitaro Oka

2003-01-01

362

Exploring the P-Glycoprotein Binding Cavity with Polyoxyethylene Alkyl Ethers  

PubMed Central

P-glycoprotein (ABCB1) moves allocrits from the cytosolic to the extracellular membrane leaflet, preventing their intrusion into the cytosol. It is generally accepted that allocrit binding from water to the cavity lined by the transmembrane domains occurs in two steps, a lipid-water partitioning step, and a cavity-binding step in the lipid membrane, whereby hydrogen-bond (i.e., weak electrostatic) interactions play a crucial role. The remaining key question was whether hydrophobic interactions also play a role for allocrit binding to the cavity. To answer this question, we chose polyoxyethylene alkyl ethers, CmEOn, varying in the number of methylene and ethoxyl residues as model allocrits. Using isothermal titration calorimetry, we showed that the lipid-water partitioning step was purely hydrophobic, increasing linearly with the number of methylene, and decreasing with the number of ethoxyl residues, respectively. Using, in addition, ATPase activity measurements, we demonstrated that allocrit binding to the cavity required minimally two ethoxyl residues and increased linearly with the number of ethoxyl residues. The analysis provides the first direct evidence, to our knowledge, that allocrit binding to the cavity is purely electrostatic, apparently without any hydrophobic contribution. While the polar part of allocrits forms weak electrostatic interactions with the cavity, the hydrophobic part seems to remain associated with the lipid membrane. The interplay between the two types of interactions is most likely essential for allocrit flipping.

Li-Blatter, Xiaochun; Seelig, Anna

2010-01-01

363

BMS181321 accumulation in rodent and human cells: the role of P-glycoprotein.  

PubMed Central

A 2-nitroimidazole with a side chain that contains technetium-99m as a chelate, BMS181321, is undergoing evaluation as an imaging agent for myocardial and cerebral ischaemia, as well as a diagnostic probe for hypoxic cells in solid tumours. Its accumulation in hypoxic and aerobic populations of three lines of Chinese hamster ovary cells of differing P-glycoprotein status, as well as one rat and two human cell lines has been determined. There was selective accumulation of BMS181321 in hypoxic vs aerobic cells. P-glycoprotein level was not a factor in this accumulation and hypoxic human cells accumulated BMS181321 more rapidly than the rodent cells. These results indicate P-glycoprotein levels in tumour cells will not confound the use of BMS181321 as a hypoxic cell marker.

Cowan, D. S.; Melo, T.; Park, L.; Ballinger, J. R.; Rauth, A. M.

1996-01-01

364

Interaction of anthelmintic drugs with P-glycoprotein in recombinant LLC-PK1-mdr1a cells.  

PubMed

Given the widespread use of formulations combining anthelmintics which are possible P-glycoprotein interfering agents, the understanding of drug interactions with efflux ABC transporters is of concern for improving anthelmintic control. We determined the ability of 14 anthelmintics from different classes to interact with abcb1a (mdr1a, P-glycoprotein, Pgp) by following the intracellular accumulation of rhodamine 123 (Rho 123), a fluorescent Pgp substrate, in LLC-PK1 cells overexpressing Pgp. The cytotoxicity of the compounds that are able to interfere with Pgp activity was evaluated in cells overexpressing Pgp and compared with parental cells using the MTS viability assay. Among all the anthelmintics used, ivermectin (IVM), triclabendazole (TCZ), triclabendazole sulfoxide (TCZ-SO), closantel (CLOS) and rafoxanide (RAF) increased the intracellular Rho 123 in Pgp overexpressing cells, while triclabendazole sulfone, albendazole, mebendazole, oxfendazole, thiabendazole, nitroxynil, levamisole, praziquantel and clorsulon failed to have any effect. The concentration needed to reach the maximal Rho 123 accumulation (E(max)) was obtained with 10 microM for IVM, 80 microM for CLOS, 40 microM for TCZ and TCZ-SO, and 80 microM for RAF. We showed that for these five drugs parental cell line was more sensitive to drug toxicity compared with Pgp recombinant cell line. Such in vitro approach constitutes a powerful tool to predict Pgp-drug interactions when formulations combining several anthelmintics are administered and may contribute to the required optimization of efficacy of anthelmintics. PMID:20513441

Dupuy, Jacques; Alvinerie, Michel; Ménez, Cecile; Lespine, Anne

2010-06-01

365

[Pharmaceutical evaluation of hydroxycamptothecin nanosuspensions with the action of inhibiting P-gp].  

PubMed

Oral hydroxycamptothecin nanosuspension (HCPT-Nano) with high supersaturated dissolution level, high permeation and well physical stability, was manufactured by microprecipitation-high press homogenization method. Its pharmaceutical properties were investigated, such as size and distribution, zeta potential, particle shape, physical existence condition, supersaturated dissolution level and so on. Particle size was measured by laser diffraction, and the mean diameters before and after lyophilization were 138 +/- 11.72 nm and 175 +/- 12.74 nm, respectively, for HCPT-Nano. Zeta potentials of HCPT-Nano was over -20 mV. The nanoparticles, being observed by transmission electron microscopy (TEM), were claviform or column in shape. DSC and X-ray diffraction revealed that HCPT existed in the form of crystal for HCPT-Nano. And HCPT-Nano could maintain higher supersaturated dissolution level for long time. So it supplied the possibility of improving oral bioavailability of HCPT when combining together admoveatur of P-gp inhibitor, CsA. PMID:22010354

Pu, Xiao-Hui; Sun, Jin; Qin, Yi-Meng; Zhang, Xiao; Zhang, Peng; He, Zhong-Gui

2011-07-01

366

Nocardioazines: a novel bridged diketopiperazine scaffold from a marine-derived bacterium inhibits P-glycoprotein.  

PubMed

An Australian marine sediment-derived isolate, Nocardiopsis sp. (CMB-M0232), yielded a new class of prenylated diketopiperazine, indicative of the action of a uniquely regioselective diketopiperazine indole prenyltransferase. The bridged scaffold of nocardioazine A proved to be a noncytotoxic inhibitor of the membrane protein efflux pump P-glycoprotein, reversing doxorubicin resistance in a multidrug resistant colon cancer cell. PMID:21513295

Raju, Ritesh; Piggott, Andrew M; Huang, Xiao-Cong; Capon, Robert J

2011-04-22

367