Human OAT1, OAT3, OAT4 and OATP1A2 Facilitate the Renal Accumulation of Ochratoxin A

Background/Objectives: Ochratoxin A (OTA) is a widespread foodborne mycotoxin linked to chronic kidney disease of unknown etiology. Despite evidence from animal models showing OTA accumulation in the kidney, the molecular mechanisms underlying its renal disposition in humans remain only partially understood. Here. we identify human renal transporters responsible for OTA kidney accumulation, elimination, and establish Michaelis-Menten kinetics under matched conditions to directly compare transport mechanisms. We also aim to identify inhibition potential of these transport mechanisms with common dietary polyphenols. Methods: Mammalian cells and membrane vesicles overexpressing human renal transporters were used to screen and profile the uptake and efflux of OTA. Miquelianin, (-)-Epicatechin-3-O-gallate, myricetin, luteolin, and caffeic acid were tested as potential concentration-dependent transporter inhibitors. Results: We demonstrate that OTA is a substrate for human organic anion transporter (hOAT) 1 (Km: 2.10 ± 0.50 μM, Vmax: 396.9 ± 27.0 pmol/mg/min), hOAT3 (Km: 2.58 ± 0.83 μM, Vmax: 141.4 ± 30.3 pmol/mg/min), hOAT4 (Km: 6.38 ± 1.45 μM, Vmax: 96.9 ± 18.8 pmol/mg/min), and human organic anion transporting polypeptide (hOATP) 1A2 (Km: 37.3 ± 6.2 μM, Vmax: 801.0 ± 133.9 pmol/mg/min). Among efflux transporters, OTA was transported only by human breast cancer resistance protein (hBCRP), which has minimal renal expression. While none of the uptake transporters were potently inhibited (>90%) by polyphenols at 10 μM, luteolin inhibited hBCRP-mediated transport of OTA with an IC50 of 22 μM and caffeic acid stimulated hBCRP-mediated efflux with an EC50 of 713.8 μM, both of which are physiologically relevant intestinal lumen concentrations. Conclusions: Our results confirm that exposures to OTA will lead to renal accumulation and increased health risks in affected populations, necessitating increased scrutiny of our food sources.