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Ieiri I, Takane H, Otsubo K. The MDR1 (ABCB1) gene polymorphism and its clinical implications. Clin Pharmacokinet 2004; 43:553-76. [PMID: 15217301 DOI: 10.2165/00003088-200443090-00001] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
There has been an increasing appreciation of the role of drug transporters in the pharmacokinetic and pharmacodynamic profiles of certain drugs. Among various drug transporters, P-glycoprotein, the MDR1 gene product, is one of the best studied and characterised. P-glycoprotein is expressed in normal human tissues such as liver, kidney, intestine and the endothelial cells of the blood-brain barrier. Apical (or luminal) expression of P-glycoprotein in these tissues results in reduced drug absorption from the gastrointestinal tract, enhanced drug elimination into bile and urine, and impeded entry of certain drugs into the central nervous system. The clinical relevance of P-glycoprotein depends on the localisation in human tissues (i.e. vectorial or directional movement), the therapeutic index of the substrate drug and the inherent inter- and intra-individual variability. With regard to the variability, polymorphisms of the MDR1 gene have recently been reported to be associated with alterations in disposition kinetics and interaction profiles of clinically useful drugs, including digoxin, fexofenadine, ciclosporin and talinolol. In addition, polymorphism may play a role in patients who do not respond to drug treatment. Moreover, P-glycoprotein is an important prognostic factor in malignant diseases, such as tumours of the gastrointestinal tract.A growing number of preclinical and clinical studies have demonstrated that polymorphism of the MDR1 gene may be a factor in the overall outcome of pharmacotherapy for numerous diseases. We believe that further understanding the physiology and biochemistry of P-glycoprotein with respect to its genetic variations will be important to establish individualised pharmacotherapy with various clinically used drugs.
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Affiliation(s)
- Ichiro Ieiri
- Department of Hospital Pharmacy, Faculty of Medicine, Tottori University, Yonago, Japan.
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52
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Wright SH, Dantzler WH. Molecular and cellular physiology of renal organic cation and anion transport. Physiol Rev 2004; 84:987-1049. [PMID: 15269342 DOI: 10.1152/physrev.00040.2003] [Citation(s) in RCA: 342] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Organic cations and anions (OCs and OAs, respectively) constitute an extraordinarily diverse array of compounds of physiological, pharmacological, and toxicological importance. Renal secretion of these compounds, which occurs principally along the proximal portion of the nephron, plays a critical role in regulating their plasma concentrations and in clearing the body of potentially toxic xenobiotics agents. The transepithelial transport involves separate entry and exit steps at the basolateral and luminal aspects of renal tubular cells. It is increasingly apparent that basolateral and luminal OC and OA transport reflects the concerted activity of a suite of separate transport processes arranged in parallel in each pole of proximal tubule cells. The cloning of multiple members of several distinct transport families, the subsequent characterization of their activity, and their subcellular localization within distinct regions of the kidney now allows the development of models describing the molecular basis of the renal secretion of OCs and OAs. This review examines recent work on this issue, with particular emphasis on attempts to integrate information concerning the activity of cloned transporters in heterologous expression systems to that observed in studies of physiologically intact renal systems.
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Affiliation(s)
- Stephen H Wright
- Dept. of Physiology, College of Medicine, Univ. of Arizona, Tucson, AZ 85724, USA.
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Takane H, Kobayashi D, Hirota T, Kigawa J, Terakawa N, Otsubo K, Ieiri I. Haplotype-Oriented Genetic Analysis and Functional Assessment of Promoter Variants in theMDR1(ABCB1) Gene. J Pharmacol Exp Ther 2004; 311:1179-87. [PMID: 15280437 DOI: 10.1124/jpet.104.069724] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Recently, a number of nucleotide variants have been described in the multidrug resistance 1 (MDR1/ABCB1) gene; however, most studies have focused on the coding region. In the present study, we identified promoter variants of the MDR1 gene and evaluated their phenotypic consequences using a reporter gene assay and the real-time polymerase chain reaction method. Ten allelic variants were detected in the promoter region (approximately 2 kilobases), seven of which were newly identified. Certain mutations occurred simultaneously, and a total of 10 haplotypes were observed. These promoter polymorphisms were found more frequently in Japanese than Caucasians. Some haplotypes were associated with changes in luciferase activity and placental and hepatic mRNA levels. We also determined DNA methylation status in the proximal promoter region of the MDR1 gene. The promoter region around potential binding sites for transcription factors was found to be hypomethylated and thus likely to be independent of the gene expression. Nucleotide and/or haplotype variants not only in the coding region but also in the promoter region of the MDR1 gene may be important for interindividual differences of P-glycoprotein expression.
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Affiliation(s)
- Hiroshi Takane
- Department of Hospital Pharmacy, Faculty of Medicine, Tottori University, 36-1, Nishi-machi, Yonago, 683-8504, Japan.
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Uno T, Yasui-Furukori N, Takahata T, Sugawara K, Tateishi T. Liquid chromatographic determination of fexofenadine in human plasma with fluorescence detection. J Pharm Biomed Anal 2004; 35:937-42. [PMID: 15193739 DOI: 10.1016/j.jpba.2004.02.036] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2004] [Revised: 02/14/2004] [Accepted: 02/20/2004] [Indexed: 10/26/2022]
Abstract
A simple and sensitive method was developed for determination of fexofenadine by liquid chromatography with fluorescence detection. Fexofenadine in human plasma was extracted on a C18 bonded-phase extraction cartridge. The mobile phases were: (A) 0.05 M KH2PO4 buffer/acetonitrile/methanol (60:35:10, v/v/v) and (B) 0.05 M KH2PO4 buffer/acetonitrile (40:60, v/v). Chromatographic separation was achieved on an ODS-80A column (150 mm x 4.6 mm i.d., particle size 5 microm) using a linear gradient from A to B in 10 min. The peak was detected using a fluorescence detector set at Ex 220 nm and Em 290 nm, and the total time for a chromatographic separation was approximately 17 min. The validated quantitation ranges of this method were 1.0-500 ng/ml with coefficients of variation of 0.6-9.1%. Mean recoveries were 72.8-76.7% with coefficients of variation of 2.7-5.8%. This method is successfully applicable for therapeutic drug monitoring in patients treated with clinical doses of fexofenadine and for analyses within pharmacokinetic studies.
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Affiliation(s)
- Tsukasa Uno
- Department of Pharmacy, Hirosaki University Hospital, Hirosaki, Japan
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Kyrklund C, Backman JT, Neuvonen M, Neuvonen PJ. Effect of rifampicin on pravastatin pharmacokinetics in healthy subjects. Br J Clin Pharmacol 2004; 57:181-7. [PMID: 14748817 PMCID: PMC1884432 DOI: 10.1046/j.1365-2125.2003.01972.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS Previous work has shown that rifampicin, a potent inducer of several cytochrome P450 (CYP) enzymes and transporters, decreased the plasma concentrations of simvastatin acid by more than 90%. This study was conducted to investigate the effect of rifampicin on the pharmacokinetics of pravastatin. METHODS In a randomised, cross-over two-phase study with a washout of 4 weeks, 10 healthy volunteers received a 5-day pretreatment with rifampicin (600 mg daily) or placebo. On day 6, a single 40 mg dose of pravastatin was administered orally. Plasma concentrations of pravastatin were measured up to 12 h by a sensitive LC-MS-MS method. RESULTS During the rifampicin phase, the mean total area under the plasma concentration-time curve of pravastatin [AUC(0-infinity )] was 69% (range 24-220%) of the corresponding value during the placebo phase (P < 0.05, 95% confidence interval for the difference -51.9 - -0.4 ng ml-1.h). In five of the 10 subjects the AUC(0-infinity ) of pravastatin during the rifampicin phase was 50% or less of that during the placebo phase. Rifampicin had no significant effect on the peak concentration, elimination half-life or renal clearance of pravastatin. CONCLUSIONS Rifampicin caused a statistically significant decrease in the plasma concentration of pravastatin given as a single oral dose to healthy subjects. However, the effect of rifampicin varied greatly between subjects. The mean rifampicin-induced decrease in pravastatin concentration was considerably smaller than that observed previously for simvastatin.
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Affiliation(s)
- Carl Kyrklund
- Department of Clinical Pharmacology, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland
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Vavricka SR, Jung D, Fried M, Grützner U, Meier PJ, Kullak-Ublick GA. The human organic anion transporting polypeptide 8 (SLCO1B3) gene is transcriptionally repressed by hepatocyte nuclear factor 3beta in hepatocellular carcinoma. J Hepatol 2004; 40:212-8. [PMID: 14739090 DOI: 10.1016/j.jhep.2003.10.008] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND/AIMS The organic anion transporting polypeptides (OATPs) mediate the uptake of numerous amphipathic compounds into hepatocytes. Our aim was to study the expression and regulation of OATP8 (OATP1B3, SLC21A8/SLCO1B3) and OATP-C (OATP1B1, SLC21A6/SLCO1B1) in hepatocellular carcinomas (HCC). METHODS RNA and protein levels in 13 paired HCC and adjacent non-tumor liver samples were quantified by real-time polymerase chain reaction or Western blot, respectively. The OATP8 and OATP-C gene promoters were characterized by luciferase reporter assays and electrophoretic mobility shift assays (EMSA). RESULTS The expression of OATP8 was decreased in 60% of HCC compared to surrounding non-tumor liver tissue, on both the mRNA and protein levels. Expression of the liver-enriched transcription factor hepatocyte nuclear factor 3beta (HNF3beta) was increased in 70% of HCC and correlated inversely with OATP8 mRNA (r=-0.75, P<0.05) and protein. In contrast to OATP8, expression of OATP-C was not significantly decreased in HCC. In transfected Huh7 cells, OATP8 promoter activity was inhibited by 70% when HNF3beta was cotransfected. An HNF3beta binding site was located at nt -39/-23 by EMSA. The OATP-C promoter was not inhibited by HNF3beta. CONCLUSIONS HNF3beta represses transcription of the OATP8 but not the OATP-C gene, providing a mechanism for reduced expression of OATP8 in HCC.
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Affiliation(s)
- Stephan R Vavricka
- Laboratory of Molecular Gastroenterology and Hepatology, Division of Gastroenterology and Hepatology, University Hospital, CH-8091 Zurich, Switzerland
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Kullak-Ublick GA, Stieger B, Meier PJ. Enterohepatic bile salt transporters in normal physiology and liver disease. Gastroenterology 2004; 126:322-42. [PMID: 14699511 DOI: 10.1053/j.gastro.2003.06.005] [Citation(s) in RCA: 464] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The vectorial transport of bile salts from blood into bile is essential for the generation of bile flow, solubilization of cholesterol in bile, and emulsification of lipids in the intestine. Major transport proteins involved in the enterohepatic circulation of bile salts include the hepatocellular bile salt export pump (BSEP, ABCB11), the apical sodium-dependent bile salt transporter (ASBT, SLC10A2) in cholangiocytes and enterocytes, the sodium-dependent hepatocyte bile salt uptake system NTCP (SLC10A1), the organic anion transporting polypeptides OATP-C (SLC21A6), OATP8 (SLC21A8) and OATP-A (SLC21A3), and the multidrug resistance protein MRP3 (ABCC3). Synthesis and transport of bile salts are intricately linked processes that undergo extensive feedback and feed-forward regulation by transcriptional and posttranscriptional mechanisms. A key regulator of hepatocellular bile salt homeostasis is the bile acid receptor/farnesoid X receptor FXR, which activates transcription of the BSEP and OATP8 genes and of the small heterodimer partner 1 (SHP). SHP is a transcriptional repressor that mediates bile acid-induced repression of the bile salt uptake systems rat Ntcp and human OATP-C. A nuclear receptor that activates rodent Oatp2 (Slc21a5) and human MRP2 (ABCC2) is the pregnane X receptor/steroid X receptor PXR/SXR. Intracellular trafficking and membrane insertion of bile salt transporters is regulated by lipid, protein, and extracellular signal-related kinases in response to physiologic stimuli such as cyclic adenosine monophosphate or taurocholate. Finally, dysfunction of individual bile salt transporters such as BSEP, on account of genetic mutations, steric inhibition, suppression of gene expression, or disturbed signaling, is an important cause of cholestatic liver disease.
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Affiliation(s)
- Gerd A Kullak-Ublick
- Division of Clinical Pharmacology and Toxicology, Department of Internal Medicine, University Hospital, Zurich, Switzerland
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Nozawa T, Imai K, Nezu JI, Tsuji A, Tamai I. Functional Characterization of pH-Sensitive Organic Anion Transporting Polypeptide OATP-B in Human. J Pharmacol Exp Ther 2003; 308:438-45. [PMID: 14610227 DOI: 10.1124/jpet.103.060194] [Citation(s) in RCA: 283] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The pH-sensitive activity of human organic anion transporting polypeptide OATP-B, which is expressed at the apical membrane of human small intestinal epithelial cells, was functionally characterized. When initial uptake of estrone-3-sulfate, a typical substrate of OATP, was studied kinetically, we observed an increase in V(max) with decrease of pH from 7.4 to 5.0, whereas the change in K(m) was negligible. OATP-B-mediated uptake of estrone-3-sulfate was independent of sodium, chloride, bicarbonate, or glutathione, whereas the proton ionophore carbonylcyanide p-trifluoromethoxyphenylhydrazone exhibited a pH-dependent inhibitory effect, suggesting that a proton gradient is a driving force for OATP-B. When OATP-B was expressed in human embryonic kidney 293 cells, uptake activities for anionic compounds showed various kinds of pH sensitivity. Dehydroepiandrosterone-sulfate, estrone-3-sulfate, and fexofenadine were transported by OATP-B at both neutral and acidic pH, whereas estradiol-17beta-glucuronide, acetic acid, and lactic acid were not transported at all. Transport of taurocholic acid and pravastatin by OATP-B was observed only at acidic pH, demonstrating a pH-sensitive substrate specificity of OATP-B. Because the physiological pH close to the surface of intestinal epithelial cells is acidic, the roles of OATP-B in the small intestine might be different from those in other tissues, such as liver basolateral membrane. Although the driving force for OATP-B has not been fully established, the clarification of factors, such as pH, that affect the OATP-B-activity is essential for an understanding of the physiological and pharmacological relevance of the transporter in the small intestine.
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Affiliation(s)
- Takashi Nozawa
- Department of Molecular Biopharmaceutics, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Noda, Chiba, Japan
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Mizuno N, Niwa T, Yotsumoto Y, Sugiyama Y. Impact of drug transporter studies on drug discovery and development. Pharmacol Rev 2003; 55:425-61. [PMID: 12869659 DOI: 10.1124/pr.55.3.1] [Citation(s) in RCA: 344] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Drug transporters are expressed in many tissues such as the intestine, liver, kidney, and brain, and play key roles in drug absorption, distribution, and excretion. The information on the functional characteristics of drug transporters provides important information to allow improvements in drug delivery or drug design by targeting specific transporter proteins. In this article we summarize the significant role played by drug transporters in drug disposition, focusing particularly on their potential use during the drug discovery and development process. The use of transporter function offers the possibility of delivering a drug to the target organ, avoiding distribution to other organs (thereby reducing the chance of toxic side effects), controlling the elimination process, and/or improving oral bioavailability. It is useful to select a lead compound that may or may not interact with transporters, depending on whether such an interaction is desirable. The expression system of transporters is an efficient tool for screening the activity of individual transport processes. The changes in pharmacokinetics due to genetic polymorphisms and drug-drug interactions involving transporters can often have a direct and adverse effect on the therapeutic safety and efficacy of many important drugs. To obtain detailed information about these interindividual differences, the contribution made by transporters to drug absorption, distribution, and excretion needs to be taken into account throughout the drug discovery and development process.
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Affiliation(s)
- Naomi Mizuno
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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Eraly SA, Blantz RC, Bhatnagar V, Nigam SK. Novel aspects of renal organic anion transporters. Curr Opin Nephrol Hypertens 2003; 12:551-8. [PMID: 12920404 DOI: 10.1097/00041552-200309000-00011] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Organic anion transporters, transmembrane proteins present in the renal proximal tubule, are a critical component of the human drug excretion machinery. Recent advances have clarified the function of these transporters, with broad clinical implications for pharmacogenetics, drug interactions and adverse reactions. Here, we discuss these issues in the context of the basic biology of the transporters. RECENT FINDINGS Understanding of organic anion transporter function has proceeded on several fronts. The continued cataloging of organic anion transporter substrates has revealed that the transporters' activity likely underlies many common drug interactions and nephrotoxic adverse reactions. Meanwhile, immunohistochemical and physiological studies suggest their potential involvement in the apical as well as basolateral steps of renal organic anion secretion. In addition, studies of the genomic organization of these transporters reveal that they are found in pairs of similar and similarly expressed genes, suggesting that pair members are coordinately regulated. Finally, we hypothesize here that organic anion transporters might impact renal susceptibility to ischemia and toxic injury, because their uptake of substrates can result in the efflux of Krebs cycle intermediates, an important nutrient source for the proximal tubule. SUMMARY The study of these transporters will likely have a significant impact on renal pharmacology and pharmacogenetics. In this regard, the generation of organic anion transporter gene knockout mice could provide invaluable models for defects in renal drug-handling. Ultimately, detailed knowledge of organic anion transporter function will assist in the choice of optimum pharmacological therapies.
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Affiliation(s)
- Satish A Eraly
- Department of Medicine1, University of California, San Diego, 9500 Gilman Drive, La Jolla, Californian 92093-0693, USA.
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Matsunaga NK, Isawa M, Kizu J, Miyazaki N, Takanaka A, Nakashima E. Application of the PKCYP Test to Predict Caffeine Clearance Mediated by CYP1A2 in a Rat Acute Liver Injury Model. Drug Metab Pharmacokinet 2003; 18:296-302. [PMID: 15619608 DOI: 10.2133/dmpk.18.296] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We previously established a method for assessing in vivo drug-metabolizing capacity by pharmacokinetic estimation of the quantity of cytochrome P450 (CYP) in vivo (PKCYP test), in which an apparent liver-to-blood free concentration gradient in vivo (qg) is introduced (Matsunaga et al., Jpn. J. Hosp. Pharm., 26: 492-504 (2000)). This method was applied to estimate the amount of CYP2C11 in rats treated with carbon tetrachloride (CCl(4)-treated rats). In this study, we estimated the amount of CYP1A2 in CCl(4)-treated rats by using acetanilide and caffeine as a probe and a model drug, respectively. In CCl(4)-treated rats, the total body clearance (CL(tot)) of acetanilide and caffeine was about one-fifth and one-eighth of that in control rats, respectively. In CCl(4)-treated rats, the amount of CYP1A2 was predicted as 0.60+/-0.06 nmol/kg from the clearance of acetanilide mediated by CYP1A2. Moreover, the clearance of caffeine mediated by CYP1A2 in CCl(4)-treated rats was estimated as 0.47+/-0.05 mL/min/kg by using the predicted amount of CYP1A2. The observed value was 0.44+/-0.03 mL/min/kg, and the predicted value was within the 95% confidence interval of the observed value. In conclusion, we have demonstrated that the PKCYP test can also be applied for estimating the amount of CYP1A2 in CCl(4)-treated rats.
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