αKlotho modulates BNIP3-mediated mitophagy by regulating FoxO3 to decrease mitochondrial ROS and apoptosis in contrast-induced acute kidney injury

Contrast-induced acute kidney injury (CI-AKI) is one of the main causes of hospital-acquired renal failure, and still lacks of effective treatments. Previously, we demonstrated that alpha Klotho, which is an anti-aging protein that highly expresses in the kidney, has therapeutic activity in CI-AKI through promoting autophagy. However, the specific mechanism underlying alpha Klotho-mediated autophagy remains unclear. The RNA sequencing analysis of renal cortex revealed that the differentially expressed genes related to autophagy between alpha Klotho-treated CI-AKI mice and vehicle-treated CI-AKI mice were found to be associated with mitophagy and apoptosis. In the kidney of CI-AKI mice and HK-2 cells exposed to Iohexol, we revealed that alpha Klotho promoted mitophagy and decreased cell apoptosis. Mechanistically, alpha Klotho attenuated mitochondria damage, decreased mitochondrial ROS by upregulating BNIP3-mediated mitophagy. BNIP3 deletion abolished the beneficial effects of alpha Klotho both in vivo and in vitro. Moreover, we further demonstrated that alpha Klotho upregulated FoxO3 nuclear expression in Iohexol-treated HK-2 cells. Knockdown of FOXO3 gene inhibited alpha Klotho-promoted BNIP3-mediated mitophagy and subsequently increased the oxidative injury and cell apoptosis. Taken together, our results indicated a critical role of alpha Klotho in alleviating CI-AKI via mitophagy promotion involving the FoxO3-BNIP3 pathway.