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The cytotoxicity of platinum(II) complexes coordinated to a chiral diamine, 1S,2S-diaminocyclohexane or 1R,2R-diaminocyclohexane and 1,10-phenanthroline or 3,4,7,8-tetramethyl-1,10-phenanthroline has been investigated in the renal proximal tubule HK-2 cell line. All platinum(II) complexes exhibited lower cytotoxicity in HK-2 cells (IC 50 1.7-25μM) than in A2780 ovarian cancer cells or cisplatin-resistant A2780cisR cells (IC 50 0.2-2.1μM) (at 48h). PHENSS ([Pt(1,10-phenanthroline)(1S,2S-dach)] 2+ ) induced apoptosis and necrosis in ovarian cancer cells at concentrations that are relatively cytostatic to renal cells. Cisplatin was similarly or more cytotoxic to renal cells than ovarian cancer cells. Similar trends were reflected with shorter term exposure (1.5h). PHENSS demonstrated a comparatively cytostatic mode of action in renal cell cultures than cisplatin, as demonstrated by lower toxicity at higher concentrations (90μM). PHENSS induced an elongated renal cell morphology, cytoskeletal stress fibre thickening, and increased β-galactosidase activity, but no detectable change in reactive oxygen species generation or cell cycle distribution. In contrast, cisplatin treatment was associated with increased oxidative stress, cellular enlargement, G2/M arrest and apoptosis. The cytotoxicity of all platinum(II) complexes in both renal and ovarian cell lines were reduced in the presence of organic cation transporter (OCT) inhibitors cimetidine, disopyramide and amantadine. PHENSS and analogues demonstrated low level genotoxicity in an in vitro micronuclei assay compared to cisplatin or etoposide. These findings highlight PHENSS and other phen-based unconventional platinum(II) complexes as promising anticancer agents with alternative modes of action that induce lower kidney cell toxicity and genotoxicity, while demonstrating greater cisplatin-resistant ovarian cancer cell toxicity., (Copyright © 2017. Published by Elsevier Inc.)

Clopidogrel (CP) is metabolized by CYPs to the active metabolite, or hydrolyzed by esterase to clopidogrel carboxylate (CPC) in liver, and CPC is partly excreted from urine. Therefore, the objective of the present study was to evaluate the interactions of CP and CPC with organic cation transporter 1 (OCT1) (in liver), and CPC with organic cation transporter 2 (OCT2) and organic anion transporter 1 (OAT1) (in kidney). Both CP and CPC inhibited the uptake of 1-methyl-4-phenylpyridinium (MPP(+)) and metformin, typical substrates of OCT1, in MDCK-hOCT1 cells with low IC₅₀ (0.307-14.0 μM). CPC (100 μM) reduced the uptake of MPP(+) and metformin mediated by OCT2 in MDCK-hOCT2 cells to 60.8% and 33.6% of the control, CPC (500 μM) decreased the uptake of 6-carboxyfluorescein (6-CFL) and para-aminohippuric acid (PAH), substrates of OAT1, in MDCK-hOAT1 cells to 64.6% and 79.4% of the control. CP and CPC were also found to inhibit other drugs of OCT1 substrates, such as lamivudine and amantadine, in MDCK-hOCT1 cells with the IC₅₀ of 1.97-4.15μM, except CPC on amantadine (IC₅₀>100 μM). The inhibition of CP and CPC on lamivudine uptake in primary rat hepatocytes was also confirmed with the IC₅₀ of 2.91 and 1.25μM, respectively. Additionally, CP and CPC were not substrates of OCT1 and OCT2, whereas CPC was a substrate of OAT1 with the Km of 5.61 μM. In conclusion, CP and CPC are strong inhibitors of OCT1, but weak inhibitors of OCT2 and OAT1, and CPC is a high affinity substrate of OAT1., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Human organic cation transporters (hOCTs; SLC22) are expressed in many organs, including intestine, liver, kidney, heart and brain, where they contribute to the absorption, distribution, and elimination of endogenous and exogenous substances. The alkaloids matrine and oxymatrine are widely used in herbal medicine for the treatment of cancer, as well as viral, and cardiac diseases. Their physicochemical properties indicated that they are potential inhibitors for hOCTs, leading to drug-drug interactions in vivo. Therefore, we assessed the inhibitory effects of matrine and oxymatrine on the function of hOCT1 (SLC22A1), hOCT2 (SLC22A2) and hOCT3 (SLC22A3) using stably transfected transporter-expressing cells. At 100-fold excess, oxymatrine exhibited marked inhibition of hOCT1-mediated substrate uptake (p<0.05), while matrine failed to produce significant inhibition on hOCT1. The IC50 value for oxymatrine on hOCT1 was estimated as 513±132 μM. While there was no significant inhibition of hOCT2 or hOCT3 at 100-fold excess, oxymatrine and matrine showed 42% and 88% inhibition of hOCT3-mediated substrate uptake at 3 and 6mM, respectively. Considering the potential intestinal lumen and reported plasma concentrations of matrine and oxymatrine, these data suggest that drug-drug interactions may occur during hOCT1-mediated hepatic and renal uptake and during hOCT3-mediated intestinal absorption., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Cimetidine, an H₂ receptor antagonist, has been used to investigate the tubular secretion of organic cations in human kidney. We report a systematic comprehensive analysis of the inhibition potency of cimetidine for the influx and efflux transporters of organic cations [human organic cation transporter 1 (hOCT1) and hOCT2 and human multidrug and toxin extrusion 1 (hMATE1) and hMATE2-K, respectively]. Inhibition constants (K(i)) of cimetidine were determined by using five substrates [tetraethylammonium (TEA), metformin, 1-methyl-4-phenylpyridinium, 4-(4-(dimethylamino)styryl)-N-methylpyridinium, and m-iodobenzylguanidine]. They were 95 to 146 μM for hOCT2, providing at most 10% inhibition based on its clinically reported plasma unbound concentrations (3.6-7.8 μM). In contrast, cimetidine is a potent inhibitor of MATE1 and MATE2-K with K(i) values (μM) of 1.1 to 3.8 and 2.1 to 6.9, respectively. The same tendency was observed for mouse Oct1 (mOct1), mOct2, and mouse Mate1. Cimetidine showed a negligible effect on the uptake of metformin by mouse kidney slices at 20 μM. Cimetidine was administered to mice by a constant infusion to achieve a plasma unbound concentration of 21.6 μM to examine its effect on the renal disposition of Mate1 probes (metformin, TEA, and cephalexin) in vivo. The kidney- and liver-to-plasma ratios of metformin both were increased 2.4-fold by cimetidine, whereas the renal clearance was not changed. Cimetidine also increased the kidney-to-plasma ratio of TEA and cephalexin 8.0- and 3.3-fold compared with a control and decreased the renal clearance from 49 to 23 and 11 to 6.6 ml/min/kg, respectively. These results suggest that the inhibition of MATEs, but not OCT2, is a likely mechanism underlying the drug-drug interactions with cimetidine in renal elimination.

(-)-N-{2-[(R)-3-(6,7-Dimethoxy-1,2,3,4-tetrahydroisoquinoline-2-carbonyl)piperidino]ethyl}-4-fluorobenzamide (YM758) is a novel inhibitor of the "funny" If current channel (If channel) that is expressed in the sinus node of heart and is being developed as a treatment for stable angina and atrial fibrillation. Its metabolites were identified in human urine, plasma, and feces by radio-high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry analyses after oral administration of [(14)C]YM758. 6,7-Dimethoxy-2-[(3R)-piperidin-3-ylcarbonyl]-1,2,3,4-tetrahydroisoquinoline (YM-252124), (5R)-5-[(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)carbonyl]piperidin-2-one (YM-385459), 2-{[(3R)-1-{2-[(4-fluorobenzoyl)amino]ethyl}piperidin-3-yl]carbonyl}-7-methoxy-1,2,3,4-tetrahydroisonolin-6-yl beta-D-glucopyranosiduronic acid (AS2036329), and the unchanged drug were detected as major constituents in both urine and plasma, whereas N-(4-fluorobenzoyl)glycine (YM-385461) was detected in plasma, but not in urine. The renal and hepatic uptake transporters for these metabolites were investigated by assessing their inhibitory effect on uptake activity in human (h) organic cation transporter (OCT) 1-3/rat (r) Oct1-3, human organic anion transporter (OAT) 1/rOat1, hOAT3/rOat3, and organic anion-transporting protein 1B1/1B3-expressing HEK293 cells. IC(50) values of YM-252124 for 1-methyl-4-phenylpyridinium uptake via hOCT2 and rOct2 were 93.9 and 1700 microM, respectively, suggesting that this metabolite is secreted into urine via hOCT2/rOct2 and that the large difference in the inhibitory potentials between hOCT2 and rOct2 explains the species difference in the urinary excretion ratio of the radioactivity. The renal secretion of YM-385461, one derivative of p-aminohippuric acid, via hOAT1/rOat1, and hepatic uptake of YM-252124 via hOCT1/rOct1 was also expected. This kind of study was useful in investigating the relationship between the urinary/hepatic elimination and the transport activity for metabolites.

The electrogenic cation transporters OCT1 and OCT2 in the basolateral membrane of renal proximal tubules mediate the first step during secretion of organic cations. Previously we demonstrated stimulation and change of selectivity for rat OCT1 (rOCT1) by protein kinase C. Here we investigated the effect of cGMP on cation transport by rOCT1 or human OCT2 (hOCT2) after expression in human embryonic kidney cells (HEK293) or oocytes of Xenopus laevis. In HEK293 cells, uptake was measured by microfluorimetry using the fluorescent cation 4-(4-(dimethyl-amino)styryl)-N-methylpyridinium iodide (ASP + ) as substrate, whereas uptake into Xenopus laevis oocytes was measured with radioactively labelled cations. In addition, ASP +-induced depolarizations of membrane voltages (Vm) were measured in HEK293 cells using the slow whole-cell patch-clamp method. Incubation of rOCT1-expressing HEK293 cells for 10 min with 100 mM 8-Br-cGMP reduced initial ASP + uptake by maximally 78% with an IC50 value of 24 +/- 16 mM. This effect was not abolished by the specific PKG inhibitor KT5823, indicating that a cGMP-dependent kinase is not involved. An inhibition of ASP + uptake by rOCT1 in HEK293 cells was also obtained when the cells were incubated for 10 min with 100 mM cGMP, whereas no effect was obtained when cGMP was given together with ASP +. ASP + (100 mM)-induced depolarizations of Vm were reduced in the presence of 8-Br-cGMP (100 mM) by 44 +/- 11% (n = 6). Since it could be demonstrated that [3H]cGMP is taken up by an endogeneous cyanine863-inhibitable transporter, the effect of cGMP is probably mediated from inside the cell. Uptake measurements with [14C]tetraethylammonium and [3H]2-methyl-4-phenylpyridinium in Xenopus laevis oocytes expressing rOCT1 performed in the absence and presence of 8-Br-cGMP showed that cGMP does not interact directly with the transporter. The data suggest that the inhibition mediated by cGMP observed in HEK293 cells occurs most likely via a mammalian cGMP-binding protein that interacts with OCT1-2 transporters.

Prostaglandin E(2) (PGE(2)) and prostaglandin F(2 alpha) (PGF(2 alpha)) have been used for the induction of labor and the termination of pregnancy. Renal excretion is shown to be an important pathway for the elimination of PGE(2) and PGF(2 alpha). The purpose of this study was to elucidate the molecular mechanism of renal PGE(2) and PGF(2 alpha) transport using cells stably expressing human organic anion transporter (hOAT) 1, hOAT2, hOAT3, and hOAT4, and human organic cation transporter (hOCT) 1 and hOCT2. A time- and dose-dependent increase in PGE(2) and PGF(2 alpha) uptake was observed in cells expressing hOAT1, hOAT2, hOAT3, hOAT4, hOCT1, and hOCT2. The K(m) values of PGE(2) uptake by hOAT1, hOAT2, hOAT3, hOAT4, hOCT1, and hOCT2 were 970, 713, 345, 154, 657, and 28.9 nM, respectively, whereas those of PGF(2 alpha) uptake by hOAT1, hOAT3, hOAT4, hOCT1, and hOCT2 were 575, 1092, 692, 477, and 334 nM, respectively. PGE(2) and PGF(2 alpha) significantly inhibited organic anion uptake by hOATs and organic cation uptake by hOCTs. In conclusion, considering the localization of these transporters, the results suggest that PGE(2) and PGF(2 alpha) transport in the basolateral membrane of the proximal tubule is mediated by multiple pathways including hOAT1, hOAT2, hOAT3, and hOCT2, whereas that in the apical side is mediated by hOAT4.