Hydrogen peroxide downregulates human organic anion transporters in the basolateral membrane of the proximal tubule.

Hydrogen peroxide (H2O2) is known to be involved in drug-induced and ischemic proximal tubular damage. The purpose of this study was to elucidate the effects of hydrogen peroxide on organic anion transport mediated by human organic anion transporters 1 and 3 (hOAT1 and hOAT3), which are localized at the basolateral side of the proximal tubule. For this purpose, we established and utilized the second segment of the proximal tubule cells from mice stably expressing hOAT1 or hOAT3 (S2 hOAT1 or S2hOAT3, respectively). H2O2 induced a dose- and a time-dependent decrease in organic anion transport mediated by hOAT1 and hOAT3. Kinetic analysis revealed that H2O2 decreased the Vmax, but not Km of organic anion transport both in S2hOAT1 and S2hOAT3. The effects of gentamicin, known to induce proximal tubular damage via the production of H2O2, on the organic anion transporters were also examined. Gentamicin induced a significant decrease in organic anion transport in S2hOAT1 but not S2hOAT3. H2O2-induced decrease in organic anion transport was significantly inhibited by pretreatment with pyruvate as well as catalase, whereas the gentamicin-induced decrease was significantly inhibited by pretreatment with pyruvate but not with catalase. In conclusion, these results suggest that H2O2, which is produced during tubular injuries, downregulates organic anion transport mediated by both hOAT1 and hOAT3, leading to further modulation of pathophysiology.