Abstract
PURPOSE: The organic cation transporters (OCTs) and multidrug and toxin extrusions (MATEs), located in the basolateral and apical membrane of proximal tubular cells respectively, are crucial determinants of renal elimination and/or toxicity of cationic drugs such as cisplatin. The purpose of this study was to discover selective OCT inhibitors over MATEs, and explore their potential to protect against cisplatin-induced nephrotoxicity that is clinically common. METHODS: The inhibition by select compounds on the uptake of the probe substrate metformin was assessed in HEK293 cells overexpressing human OCT2, OCT1, MATE1, MATE2-K, and mouse Oct2, Oct1, and Mate1. Furthermore, the effects of carvedilol on organic cation transporter-mediated cellular and renal accumulation of metformin and cisplatin, and particularly the toxicity associated with cisplatin, were investigated in HEK293 cells and mice. RESULTS: Five selective OCT inhibitors were identified through the screening of forty-one drugs previously reported as the inhibitors of OCTs and/or MATEs. Among them, carvedilol showed the most selectivity on OCTs over MATEs (IC(50): 3.6 μM for human OCT2, 103 μM for human MATE1 and 202 μM for human MATE2-K) in the cellular assays in vitro, with the selectivity in mice as well. Moreover, carvedilol treatment could significantly decrease cisplatin accumulation and ameliorate its toxicity both in vitro in cells and in vivo in mouse kidney. CONCLUSIONS: Our data indicate that selective inhibition of OCTs by carvedilol may protect from cisplatin-induced nephrotoxicity by restraining the cellular entry of cisplatin via OCTs, while having no impact on its elimination through MATEs.