NADPH oxidase-mediated upregulation of connexin43 contributes to podocyte injury

The gap junction protein connexin43 (Cx43) was markedly increased in podocytes in a rat model of nephrosis induced by puromycin. However, the mechanisms and roles of the altered Cx43 in podocytes are still unclear. Given that oxidative stress mediates podocyte injury under a variety of pathological situations, we examined the possible involvement of an oxidative stress-related mechanism in the regulation of Cx43. Incubation of podocytes with puromycin led to a time- and concentration-dependent loss of cell viability, which was preceded by an elevation in Cx43 levels. Concomitantly, puromycin also induced NOX4 expression and promoted superoxide (O2−) generation. Inhibition of NADPH oxidase with apocynin and diphenyleneiodonium chloride or addition of the superoxide dismutase mimetic tempol completely abrogated, whereas the O2− donors menadione and 2,3-dimethoxy-1,4-naphthoquinone reproduced, the effects of puromycin on Cx43 expression and cell injury. Further analysis demonstrated that treatment of podocytes with several structurally different gap-junction inhibitors significantly attenuated the cytotoxicity of puromycin. Our results thus indicate that NADPH oxidase-mediated upregulation of Cx43 contributes to podocyte injury.

► The mechanisms and roles of altered connexin43 (Cx43) in injured podocytes are unclear. ► Puromycin-triggered podocyte injury was preceded by increased expression of NOX4 and Cx43. ► Inhibition of NADPH oxidase abrogated the elevation in Cx43. ► Suppression of Cx43 attenuated the cytotoxic effect of puromycin.