Prohibitin protects proximal tubule epithelial cells against oxidative injury through mitochondrial pathways

Oxidative stress mediated by reactive oxygen species (ROS) contributes to renal tubular atrophy and fibrosis following renal transplantation. Studies have shown that mitochondrial chaperone prohibitin (PHB) has antioxidant effects. Here we used the human renal proximal tubule epithelial cell line, HK-2 cells as an in vitro model to assess the role of PHB in hydrogen peroxide (H2O2)-induced renal tubular oxidative injury. Our results showed that H2O2 treatment inhibited PHB expression in a time-dependent manner in HK-2 cells. PHB overexpression could protect cell from oxidative stress-induced injury by inhibiting H2O2-induced cell apoptosis and intracellular ROS generation and promoting endogenous antioxidant defense components including glutathione peroxidase, catalase, superoxide dismutase, and glutathione. Furthermore, oxidative stress-induced cell injury was suppressed in PHB-overexpressed tubule epithelial cells through mitochondria-mediated pathway, including inhibition of mitochondrial uncoupling protein 2 or UCP2 and Bax expression, mitochondrial ROS production, promotion of ATP production and Bcl-2 expression, inhibition of mitochondrial membrane potential loss and release of cytochrome c from mitochondria to cytoplasm, and followed by caspase-3 activation. Meanwhile, inhibition of PHB expression by small interference RNA resulted in less resistance of HK-2 cells to H2O2 toxicity as shown in decreased cell viability, increased apoptosis, ROS production, and mitochondrial dysfunction. These data indicated that PHB protected the tubule epithelial cells from oxidative stress-induced damage through the inhibition of oxidative damage, mitochondria dysfunction, and ultimately inhibition of cell apoptosis, and that increasing PHB content in mitochondria constituted a new therapeutic target for transient ischemic injury and chronic allograft nephropathy or CAN following renal transplantation.