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The inhibition of renal transport proteins organic cation transporter 2 (OCT2), multidrug and toxin extrusion proteins (MATE1, MATE2-K), and organic anion transporters (OAT1, OAT3) causes clinically relevant drug-drug interactions (DDI). Endogenous biomarkers could be used to improve risk prediction of such renal DDIs. While a number of biomarkers for renal DDIs have been described so far, multiple criteria for valid biomarkers have frequently not been investigated, for example, specificity, metabolism, or food effects. Therefore, there is a need for novel biomarkers of renal DDIs. Here, we investigated the global metabolomic effects following the administration of two classical inhibitors of renal transport proteins [cimetidine (OCT2/MATEs), probenecid (OATs)] in human plasma and urine of healthy volunteers. Additionally, we investigated metabolomic effects of two inhibitors of other transporters [verapamil (P-glycoprotein), rifampin (organic anion transporting polypeptides)] as controls. This analysis shows that both cimetidine and probenecid affect compounds involved in caffeine metabolism, carnitines, and sulfates. Hierarchical cluster analysis of the effects of all four inhibitors on endogenous compounds identified multiple promising new sensitive and specific biomarker candidates for OCT2/MATE- or OAT-mediated DDIs. For OCT2/MATEs, 5-amino valeric acid betaine (median log 2 -fold change of estimated renal elimination: -3.62) presented itself as a promising candidate. For OATs, estimated renal elimination of 7-methyluric acid and cinnamoylglycine (median log 2 -fold changes -3.10 and -1.92, respectively) was both sensitive and specific. This study provides comprehensive information on metabolomic effects of transport protein inhibition in humans and identifies putative new sensitive and specific biomarkers for renal transporter-mediated DDIs., (© 2024 The Author(s). Clinical Pharmacology & Therapeutics published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.)

The anticholinergic drug trospium is secreted into urine and, to a smaller extent, into bile. Chemically, it is an organic cation, and it is a substrate of the uptake transporters OCT1 and OCT2 as well as for the export proteins MATE1 and MATE2-K as determined in uptake studies using HEK293 cells. So far, neither MATE-mediated export nor the interplay of OCT-mediated uptake and MATE-mediated export have been investigated. Therefore, we used polarized monolayers of single- and double-transfected MDCKII cells (MDCK-OCT1, MDCK-OCT2, MDCK-MATE1, MDCK-OCT1-MATE1, and MDCK-OCT2-MATE1) and the respective control cells (MDCK-Co) for transcellular transport assays. We demonstrate that the transcellular, basal-to-apical transport of trospium is significantly higher in all cell lines compared to control cells over nearly the complete concentration range tested. The transcellular transport mediated by double-transfected MDCK-OCT1-MATE1 and MDCK-OCT2-MATE1 exceeded that in the single-transfected cells (MDCK-OCT1-MATE1 vs MDCK-OCT1: 2.2-fold; MDCK-OCT1-MATE1 vs MDCK-MATE1: 1.7-fold; MDCK-OCT2-MATE1 vs MDCK-OCT2: 6.1-fold; MDCK-OCT2-MATE1 vs MDCK-MATE1: 1.8-fold at a trospium concentration of 1.0 μM; p < 0.001 each). Thus, we show that MATE1 does not only mediate the uptake of trospium into HEK293 cells but also the efflux of trospium out of polarized MDCKII-cells. Furthermore, our results indicate that OCT1 or OCT2 as uptake transporters and MATE1 as an export protein contribute to the transcellular transport of trospium at concentrations normally reached during trospium therapy. These data suggest that both, OCT-mediated uptake as well as MATE1-mediated efflux may contribute to trospium renal and biliary elimination.

Efavirenz (EFV) is a non-nucleoside reverse transcriptase inhibitor used in first-line combination antiretroviral therapy (cART). It is usually administered with nucleoside reverse transcriptase inhibitors (NRTI), many of which are substrates of OCT uptake solute carriers (SLC22A) and MATE (SLC47A), P-gp (MDR1, ABCB1), BCRP (ABCG2), or MRP2 (ABCC2) efflux transporters. The aim of this study was to evaluate the inhibitory potential of efavirenz towards these transporters and investigate its effects on the pharmacokinetics and tissue distribution of a known Oct/Mate substrate, lamivudine, in rats. Accumulation and transport assays showed that efavirenz inhibits the uptake of metformin by OCT1-, OCT2- and MATE1-expressing MDCK cells and reduces transcellular transport of lamivudine across OCT1/OCT2- and MATE1-expressing MDCK monolayers. Only negligible inhibition of MATE2-K was observed in HEK-MATE2-K cells. Efavirenz also reduced the efflux of calcein from MDCK-MRP2 cells, but had a rather weak inhibitory effect on Hoechst 33342 accumulation in MDCK-MDR1 and MDCK-BCRP cells. An in vivo pharmacokinetic interaction study in male Wistar rats revealed that intravenous injection of efavirenz or the control Oct/Mate inhibitor cimetidine significantly reduced the recovery of lamivudine in urine and greatly increased lamivudine retention in the renal tissue. Co-administration with efavirenz or cimetidine also increased the AUC0-∞ value and reduced total body clearance of lamivudine. These data suggest that efavirenz is a potent inhibitor of OCT/Oct and MATE/Mate transporters. Consequently, it can engage in drug-drug interactions that reduce renal excretion of co-administered substrates and enhance their retention in the kidneys, potentially compromising therapeutic safety., Competing Interests: The authors have declared that no competing interests exist.

Cimetidine decreases the renal clearance of metformin by inhibition of renal tubular cation transport, and the underlying molecular mechanisms are still not fully understood. We investigated polarized metformin transport without and with the addition of cimetidine as well as polarized cimetidine transport in double-transfected MDCK-OCT2-MATE1 cells that mimic organic cation transport processes in proximal renal tubule cells and in MDCK vector control and single-transfected MDCK-OCT2 and MDCK-MATE1 cells. At all tested concentrations (1, 10, 100 μM), the intracellular accumulation of cimetidine after administration to the basal compartment was considerably higher in MDCK-OCT2 cells compared to that in all other cells ( p < 0.001). Whereas cimetidine transcellular, basal-to-apical transport was only slightly higher in MDCK-OCT2 cells, the presence of MATE1 in the apical membrane caused a pronounced translocation of cimetidine in both single- and double-transfected cells ( p < 0.001). Transcellular, basal-to-apical metformin net transport was reduced by 89.1, 74.5, and 91.0% in MDCK-OCT2-MATE1 cells after the addition of cimetidine (100 μM) to the basal, the apical, or both compartments ( p < 0.001). In MDCK-MATE1 and MDCK-OCT2-MATE1 cells, transcellular net transport of metformin was inhibited by cimetidine with IC 50 values of 8.0 and 6.6 μM, respectively. Our data confirm the relevance of MATE1 and suggest the relevance of OCT2 for the cimetidine-metformin interaction, primarily because OCT2 mediates uptake of the perpetrator cimetidine into renal proximal tubular cells and thereby to the site of the metformin exporter MATE1. This work supports the notion that a thorough understanding of transporter-mediated drug-drug interactions may require investigations on the impact of transporters on cellular uptake and transcellular transport of victim as well as perpetrator drugs.

Trimethylamine-N-oxide (TMAO) gained considerable attention because of its role as a cardiovascular risk biomarker. Organic cation transporter 2 (OCT2) mediates TMAO uptake into renal proximal tubular cells. Here we investigated the potential role of multidrug and toxin extrusion protein 1 (MATE1) for translocation of TMAO across the luminal membrane of proximal tubular cells. HEK293 cells stably expressing OCT2 (HEK-OCT2) or MATE1 (HEK-MATE1) were used for uptake studies. Transcellular transport of TMAO was investigated using monolayers of MDCK control cells (MDCK-Co) as well as single- (MDCK-OCT2, MDCK-MATE1) and double-transfected cells (MDCK-OCT2-MATE1). In line with previous studies, HEK-OCT2 cells revealed a 2.4-fold uptake of TMAO compared to control cells (p < 0.001), whereas no significant uptake was observed in HEK-MATE1. In monolayers of MDCK cells, polarised TMAO transcellular transport was not significantly different between MDCK-Co and MDCK-OCT2 cells, but significantly increased in MDCK-MATE1 (p < 0.05) and MDCK-OCT2-MATE1 cells (p < 0.001). The OCT/MATE inhibitor trimethoprim abolished TMAO translocation in MDCK-OCT2-MATE1 cells (p < 0.05). The present data suggest that MATE1 contributes to renal elimination of TMAO. For selected MATE substrates, such as TMAO, uptake studies using non-polarised MATE-expressing cells can reveal false negative results compared to studies using polarised monolayers.

The weak base memantine is actively secreted into urine, however the underlying mechanisms are insufficiently understood. Potential candidates involved in memantine renal secretion are organic cation transporter 2 (OCT2) and multidrug and toxin extrusion proteins (MATE1, MATE2-K). The aim of this in vitro study was the examination of the interaction of memantine with OCT2 and MATEs. Memantine transporter inhibition and transport were examined in HEK cells expressing human OCT2, MATE1, or MATE2-K. Monolayers of single- (MDCK-OCT2, MDCK-MATE1) and double-transfected MDCK cells (MDCK-OCT2-MATE1) were used for studies on vectorial, basal to apical memantine transport. Memantine inhibited OCT2-, MATE1-, and MATE2-K-mediated metformin transport with IC 50 values of 3.2, 40.9, and 315.3 μM, respectively. In HEK cells, no relevant memantine uptake by OCT2, MATE1, or MATE2-K was detected. Vectorial transport experiments, however, indicated a role of MATE1 for memantine export: After memantine administration to the basal side of the monolayers, memantine cellular accumulation was considerably lower (MDCK-MATE1 vs MDCK control cells, P < 0.01) and memantine transcellular, basal to apical transport was higher in MATE1 expressing cells (MDCK-MATE1 vs MDCK control cells, P < 0.001 at 60 and 180 min). Both effects were abolished upon addition of the MATE inhibitor cimetidine. These experiments suggest a relevant role of MATE1 for renal secretion of memantine. In the clinical setting, renal elimination of memantine could be impaired by coadministration of MATE inhibitors.

Nadolol is a nonmetabolized β-adrenoceptor antagonist and is a substrate of OATP1A2, but not of OATP2B1. However, other drug transporters involved in translocation of nadolol have not been characterized in detail. We therefore investigated nadolol as a potential substrate of the hepatic uptake transporters OATP1B1, OATP1B3, and OCT1 and of the renal transporters OCT2, MATE1, and MATE2-K expressed in HEK cells. Moreover, the importance of P-glycoprotein (P-gp) for nadolol transport was studied using double transfected MDCK-OCT1-P-gp cells. Nadolol was not transported by OATP1B1 and OATP1B3. In contrast, a significantly higher nadolol accumulation (at 1 and 10 μM) was found in OCT1, OCT2, MATE1, and MATE2-K cells compared to control cells (P < 0.01). Km values for OCT2-, MATE1-, and MATE2-K-mediated nadolol uptake were 122, 531, and 372 μM, respectively. Cimetidine (100 μM, P < 0.01) and trimethoprim (100 μM, P < 0.001) significantly inhibited OCT1-, OCT2-, MATE1-, and MATE2-K-mediated nadolol transport. The P-gp inhibitor zosuquidar significantly reduced basal to apical nadolol transport in monolayers of MDCK-OCT1-P-gp cells. In summary, nadolol is a substrate of the cation transporters OCT1, OCT2, MATE1, MATE2-K, and of P-gp. These data will aid future in vivo studies on potential transporter-mediated drug-drug or drug-food interactions with involvement of nadolol.

The importance of the organic cation transporter OCT2 in the renal excretion of cationic drugs raises the possibility of drug-drug interactions (DDIs) in which an inhibitor (perpetrator) drug decreases OCT2-dependent renal clearance of a victim (substrate) drug. In fact, there are clinically significant interactions for drugs that are known substrates of OCT2 such as metformin. To identify drugs as inhibitors for OCT2, individual drugs or entire drug libraries have been investigated in vitro by using experimental probe substrates such as 1-methyl-4-phenylpyridinium (MPP+) or 4-4-dimethylaminostyryl-N-methylpyridinium (ASP+). It has been questioned whether the inhibition data obtained with an experimental probe substrate such as MPP+ or ASP+ might be used to predict the inhibition against other, clinical relevant substrates such as metformin. Here we compared the OCT2 inhibition profile data for the substrates metformin, MPP+ and ASP+. We used human embryonic kidney (HEK 293) cells stably overexpressing human OCT2 as the test system to screen 125 frequently prescribed drugs as inhibitors of OCT2-mediated metformin and MPP+ uptake. Data on inhibition of OCT2-mediated ASP+ uptake were obtained from previous literature. A moderate correlation between the inhibition of OCT2-mediated MPP+, ASP+, and metformin uptake was observed (pairwise rs between 0.27 and 0.48, all P < 0.05). Of note, the correlation in the inhibition profile between structurally similar substrates such as MPP+ and ASP+ (Tanimoto similarity T = 0.28) was even lower (rs = 0.27) than the correlation between structurally distinct substrates, such as ASP+ and metformin (T = 0.01; rs = 0.48) or MPP+ and metformin (T = 0.01; rs = 0.40). We identified selective as well as universal OCT2 inhibitors, which inhibited transport by more than 50% of one substrate only or of all substrates, respectively. Our data suggest that the predictive value for drug-drug interactions using experimental substrates rather than the specific victim drug is limited.

Purpose: N(1)-methylnicotinamide (NMN) was proposed as an in vivo probe for drug interactions involving renal cation transporters, which, for example, transport the oral antidiabetic drug metformin, based on a study with the inhibitor pyrimethamine. The role of NMN for predicting other interactions with involvement of renal cation transporters (organic cation transporter 2, OCT2; multidrug and toxin extrusion proteins 1 and 2-K, MATE1 and MATE2-K) is unclear., Methods: We determined inhibition of metformin or NMN transport by trimethoprim using cell lines expressing OCT2, MATE1, or MATE2-K. Moreover, a randomized, open-label, two-phase crossover study was performed in 12 healthy volunteers. In each phase, 850 mg metformin hydrochloride was administered p.o. in the evening of day 4 and in the morning of day 5. In phase B, 200 mg trimethoprim was administered additionally p.o. twice daily for 5 days. Metformin pharmacokinetics and effects (measured by OGTT) and NMN pharmacokinetics were determined., Results: Trimethoprim inhibited metformin transport with K i values of 27.2, 6.3, and 28.9 μM and NMN transport with IC50 values of 133.9, 29.1, and 0.61 μM for OCT2, MATE1, and MATE2-K, respectively. In the clinical study, trimethoprim increased metformin area under the plasma concentration-time curve (AUC) by 29.5 % and decreased metformin and NMN renal clearances by 26.4 and 19.9 %, respectively (p ≤ 0.01). Moreover, decreases of NMN and metformin renal clearances due to trimethoprim correlated significantly (r S=0.727, p=0.010)., Conclusions: These data on the metformin-trimethoprim interaction support the potential utility of N(1)-methylnicotinamide as an endogenous probe for renal drug-drug interactions with involvement of renal cation transporters.

Asymmetric dimethylarginine (ADMA), inhibiting the nitric oxide (NO) synthesis from L-arginine, is a known cardiovascular risk factor. Our aim was to investigate if ADMA and/or L-arginine are substrates of the human cationic amino acid transporters 2A (CAT2A, SLC7A2A) and 2B (CAT2B, SLC7A2B), the organic cation transporter 2 (OCT2, SLC22A2), and the multidrug and toxin extrusion protein 1 (MATE1, SLC47A1). We systematically investigated the kinetics of ADMA and L-arginine transport in human embryonic kidney (HEK293) cells stably overexpressing CAT2A, CAT2B, OCT2, or MATE1. Vector-only transfected HEK293 cells served as controls. Compared to vector control cells, uptake of ADMA and L-arginine was significantly higher (p < 0.05) in cells expressing CAT2B and OCT2 at almost all investigated concentrations, while cells expressing CAT2A only showed a significant uptake at concentrations above 300 μM. Uptake of MATE1 overexpressing cells was significantly (p < 0.05) higher at pH 7.8 and 8.2 than controls. Apparent V max values (nmol mg protein(-1) min(-1)) for cellular uptake of ADMA and L-arginine were ≈11.8 ± 1.2 and 19.5 ± 0.7 for CAT2A, ≈14.3 ± 1.0 and 15.3 ± 0.4 for CAT2B, and 6.3 ± 0.3 and >50 for OCT2, respectively. Apparent K m values (μmol/l) for cellular uptake of ADMA and L-arginine were ≈3,033 ± 675 and 3,510 ± 419 for CAT2A, ≈4,021 ± 532 and 952 ± 92 for CAT2B, and 967 ± 143 and >10,000 for OCT2, respectively. ADMA and L-arginine are substrates of human CAT2A, CAT2B, OCT2 and MATE1. Transport kinetics of CAT2A, CAT2B, and OCT2 indicate a low affinity, high capacity transport, which may be relevant for renal and hepatic elimination of ADMA or L-arginine.

The antiviral lamivudine is cleared predominantly by the kidney with a relevant contribution of renal tubular secretion. It is not clear which drug transporters mediate lamivudine renal secretion. Our aim was to investigate lamivudine as substrate of the renal drug transporters organic cation transporter 2 (OCT2) and multidrug and toxin extrusion proteins MATE1 and MATE2-K. Uptake experiments were performed in OCT2, MATE1, or MATE2-K single-transfected human embryonic kidney 293 (HEK) cells. Transcellular transport experiments were performed in OCT2 and/or MATE1 single- or double-transfected Madin-Darby canine kidney II (MDCK) cells grown on transwell filters. Lamivudine uptake was significantly increased in HEK-OCT2, HEK-MATE1, and HEK-MATE2-K cells compared to control cells. In transcellular experiments, OCT2 located in the basolateral membrane had no effect on transcellular lamivudine transport. MATE1 located in the apical membrane decreased intracellular concentrations and increased transcellular transport of lamivudine from the basal to the apical compartment. MATE1- or MATE2-K-mediated transport was increased by an oppositely directed pH gradient. Several simultaneously administered drugs inhibited OCT2- or MATE2-K-mediated lamivudine uptake. The strongest inhibitors were carvedilol for OCT2 and trimethoprim for MATE2-K (inhibition by 96.3 and 83.7% at 15 μM, respectively, p<0.001). Trimethoprim inhibited OCT2- and MATE2-K-mediated lamivudine uptake with IC₅₀ values of 13.2 and 0.66 μM, respectively. Transcellular lamivudine transport in OCT2-MATE1 double-transfected cells was inhibited by trimethoprim with an IC₅₀ value of 6.9 μM. Lamivudine is a substrate of renal drug transporters OCT2, MATE1, and MATE2-K. Concomitant administration of drugs that inhibit these transporters could decrease renal clearance of lamivudine., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Therapy with two or more drugs is more the rule than the exception, particularly in aging societies. Drug-drug interactions are frequently undesirable and may lead to increased toxicity and mortality. Inhibition of transporters is one major mechanism underlying drug-drug interactions. The myriad of potential drug combinations makes it very challenging to predict drug-drug interactions. This Commentary discusses potential advantages and limitations of endogenous compounds for predicting transporter-mediated drug-drug interactions.

The organic cation transporter 3 (OCT3, SLC22A3) contributes to the control of cardiac catecholamine concentrations and is important for the disposition and action of cationic drugs, such as metformin, in the myocardium. We sought to characterize the regulation of OCT3 in failing human hearts and to study commonly prescribed drugs for their potential to interact with OCT3-dependent uptake of metformin. SLC22A3 was expressed high in the human heart with strongest OCT3 immunoreactivity in vascular endothelial cells. SLC22A3/OCT3 expression was not changed in failing human left ventricular myocardium compared with nonfailing control tissues and thus is not involved in altered catecholamine homeostasis generally observed in failing hearts. Michaelis-Menten kinetics of OCT3-mediated uptake of prototypical OCT substrates 1-methyl-4-phenylpyridinium and metformin were studied in human embryonic kidney 293 cells stably overexpressing OCT3. The affinity of 1-methyl-4-phenylpyridinium for OCT3 was much higher (Km 157 ± 16 μM) than the affinity of metformin (Km 2.46 ± 0.36 mM; P < 0.01), whereas maximum transport rate of 1-methyl-4-phenylpyridinium was significantly lower than that of metformin. Verapamil, carvedilol, imipramine, and cimetidine were competitive inhibitors of OCT3-mediated metformin uptake (Ki 3.6-15.8 μM). Altogether, OCT3 might be important for the cardiac disposition of cationic drugs, and OCT3-dependent interaction with concomitantly administered compounds may limit their disposition and effect.

Drug-drug interactions are a serious clinical issue. An important mechanism underlying drug-drug interactions is induction or inhibition of drug transporters that mediate the cellular uptake and efflux of xenobiotics. Especially drug transporters of the small intestine, liver and kidney are major determinants of the pharmacokinetic profile of drugs. Transporter-mediated drug-drug interactions in these three organs can considerably influence the pharmacokinetics and clinical effects of drugs. In this article, we focus on probe drugs lacking significant metabolism to highlight mechanisms of interactions of selected intestinal, hepatic and renal drug transporters (e.g., organic anion transporting polypeptide [OATP] 1A2, OATP2B1, OATP1B1, OATP1B3, P-gp, organic anion transporter [OAT] 1, OAT3, breast cancer resistance protein [BCRP], organic cation transporter [OCT] 2 and multidrug and toxin extrusion protein [MATE] 1). Genotype-dependent drug-drug interactions are also discussed.

Background and Purpose: The organic cation transporters 1 (OCT1) and 2 (OCT2) mediate drug uptake into hepatocytes and renal proximal tubular cells, respectively. Multidrug and toxin extrusion protein 1 (MATE1) is a major component of subsequent export into bile and urine. However, the functional interaction of OCTs and MATE1 for uptake and transcellular transport of the oral antidiabetic drug metformin or of the cation 1-methyl-4-phenylpyridinium (MPP(+)) has not fully been characterized., Experimental Approach: Single-transfected Madin-Darby canine kidney (MDCK) cells as well as double-transfected MDCK-OCT1-MATE1 and -OCT2-MATE1 cells were used to study metformin and MPP(+) uptake into and transcellular transport across cell monolayers, along with their concentration and pH dependence., Key Results: Cellular accumulation of MPP(+) and metformin was significantly reduced by 31% and 46% in MDCK-MATE1 single-transfected cells compared with MDCK control cells (10 µM; P < 0.01). Over a wide concentration range (10-2500 µM) metformin transcellular transport from the basal into the apical compartment was significantly higher in the double-transfected cells compared with the MDCK control and MDCK-MATE1 monolayers. This process was not saturated up to metformin concentrations of 2500 µM. In MDCK-OCT2-MATE1 cells basal to apical MPP(+) and metformin transcellular translocation decreased with increasing pH from 6.0 to 7.5., Conclusions and Implications: Our data demonstrate functional interplay between OCT1/OCT2-mediated uptake and efflux by MATE1. Moreover, MATE1 function in human kidney might be modified by changes in luminal pH values., (© 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological Society.)

Aim: The uptake of drugs from the blood into the renal tubular cells is a key determinant for renal secretion and may influence their systemic plasma concentrations and extrarenal effects. Metformin, used for treatment of type 2 diabetes, is taken up into renal tubular cells by the organic cation transporter 2 (OCT2). Because many patients with type 2 diabetes receiving metformin are concomitantly treated with beta-blockers, we tested whether beta-blockers can inhibit OCT2-mediated drug transport., Method: Using Madin-Darby canine kidney II cells stably expressing the uptake transporter OCT2, we analysed whether the beta-blockers bisoprolol, carvedilol, metoprolol and propranolol inhibit the transport of OCT2 substrates 1-methyl-4-phenylpyridinium (MPP(+)) and metformin., Results: Neither bisoprolol nor metoprolol significantly inhibited the uptake of MPP(+), whereas a significant inhibition was observed for carvedilol und propranolol (half maximal inhibitory concentration IC(50): 26.3 and 67.5 microM) respectively. Moreover, all beta-blockers significantly inhibited OCT2-mediated metformin uptake (IC(50) for bisoprolol: 2.4 microM, IC(50) for carvedilol: 2.3 microM, IC(50) for metoprolol: 50.2 microM and IC(50) for propranolol: 8.3 microM)., Conclusion: These in vitro results demonstrate that alterations of uptake transporter function by beta-blockers have to be considered as potential mechanisms underlying drug-drug interactions in the kidney.

The organic cation transporter 2 (OCT2, SLC22A2) plays an important role for renal drug elimination. Recent clinical studies indicate an impact of the frequent nonsynonymous c.808G>T (p.270Ala>Ser) polymorphism on renal clearance of metformin and the extent of the metformin-cimetidine interaction. The role of this polymorphism for renal disposition of endogenous compounds and drugs other than metformin has not been investigated. In addition, it is unclear whether the observed genotype dependence of an OCT2-mediated drug-drug interaction might occur also with other OCT inhibitors. To address these issues, we generated human embryonic kidney cells stably expressing wild-type OCT2 or the p.270Ala>Ser variant. No differences in protein expression levels and membrane incorporation pattern were observed between the two cell lines. The p.270Ala>Ser variant significantly impaired uptake kinetics of 1-methyl-4-phenylpyridinium, dopamine, norepinephrine, and propranolol. V(max) values were significantly reduced for uptake of all four compounds mediated by the p.270Ala>Ser variant compared with wild-type OCT2. In addition, a significant difference in the affinity to wild-type and mutant OCT2 was observed for dopamine (K(m) dopamine: 932 +/- 77 versus 1285 +/- 132 microM). Moreover, out of a set of 27 compounds p.270Ala>Ser OCT2 was significantly less sensitive to inhibition by cimetidine, flurazepam, metformin, mexiletine, propranolol, and verapamil than wild-type OCT2 (e.g., for propranolol: IC(50) wild type versus p.270Ala>Ser 189 versus 895 microM, P < 0.001). Our results indicate that the common OCT2 c.808G>T single nucleotide polymorphism significantly alters uptake of endogenous compounds and drugs. Moreover, for selected compounds the extent of OCT2-mediated drug interactions could depend on OCT2 c.808G>T genotype.

Background: Transport proteins, for example the drug export pump P-glycoprotein, are important for the absorption, distribution and excretion of drugs. Inhibition and induction of P-glycoprotein efflux function is a well-established mechanism of drug-drug interactions. Alteration of transporter-mediated drug uptake by concomitantly administered drugs may also result in a change in drug pharmacokinetics. These uptake transporter-mediated drug-drug interactions are the focus of this review., Objective: To examine the current in vitro evidence on interactions mediated by OATPs (organic anion transporting polypeptides) and OCTs (organic cation transporters)., Methods: Comparing data of in vivo observed drug-drug interactions with in vitro analysed alterations in drug transport mediated by the hepatic expressed uptake transporters OATP1B1, OATP1B3 and OCT1 and by the renal expressed OCT2 protein., Results/conclusions: Some of the previously in vivo described drug-drug interactions could be explained by alteration in uptake transporter function demonstrating that inhibition or induction of uptake transporters is a newly recognised mechanism of potential drug-drug interactions.

The organic cation transporter 2 (OCT2) provides an important pathway for the uptake of cationic compounds in the kidney, which is the essential step in their elimination from the organism. Although many drugs have been identified which interact with human OCT2, structural elements required for an interaction with OCT2 are not well defined. To address this issue, HEK293 cells stably expressing human OCT2 were generated. IC(50) values of commonly used drugs for inhibition of [(3)H]MPP(+) uptake were determined and correlated with physicochemical descriptors. We found only a significant correlation between the topological polar surface area (TPSA) and IC(50) values (r = 0.71, p < 0.0001). Structural alignment of most potent inhibitor drugs of OCT2-mediated MPP(+) uptake was used to construct a two-point pharmacophore consisting of an ion-pair interaction site and a hydrophobic aromatic site separated by 5.0 A. Taken together, our data identify structural determinants for inhibitor interactions with OCT2.