PINK1/Parkin mediated mitophagy ameliorates palmitic acid-induced apoptosis through reducing mitochondrial ROS production in podocytes.

Diabetic nephropathy (DN), the primary cause of end-stage renal disease (ESRD), is often accompanied by dyslipidemia, which is closely related to the occurrence and development of DN and even the progression to ESRD. Mitophagy, the selective degradation of damaged and dysfunctional mitochondria by autophagy, is a crucial mitochondrial quality control mechanism, and largely regulated by PINK1 (PTEN-induced putative kinase 1)/Parkin signaling pathway. In the present study, we demonstrated that PA induced mitochondrial damage and excessive mitoROS generation in podocytes. We also found PA treatment resulted in the activation of mitophagy by increasing co-localization of GFP-LC3 with mitochondria and enhancing the formation of mitophagosome, stabilization of PINK1 and mitochondrial translocation of Parkin, which indicated that PINK1/Parkin pathway was involved in PA-induced mitophagy in podocytes. Furthermore, inhibition of mitophagy by silencing Parkin dramatically aggravated PA-induced mitochondrial dysfunction, mitoROS production, and further enhanced PA-induced apoptosis of podocytes. Finally, we showed that PINK1/Parkin pathway were up-regulated in kidney of high fat diet (HFD)-induced obese rats. Taken together, our results suggest that PINK1/Parkin mediated mitophagy plays a protective role in PA-induced podocytes apoptosis through reducing mitochondrial ROS production and that enhancing mitophagy provides a potential therapeutic strategy for kidney diseases with hyperlipidemia, such as DN.

Activation of the Nrf2/ARE signaling pathway protects against palmitic acid-induced renal tubular epithelial cell injury by ameliorating mitochondrial reactive oxygen species-mediated mitochondrial dysfunction.

Chronic kidney disease (CKD) is often accompanied by dyslipidemia, and abnormal lipid metabolism in proximal tubule cells is considered closely related to the dysfunction of proximal tubule cells and eventually leads to accelerated kidney damage. Nuclear factor E2-related factor 2 (Nrf2), known as a redox-sensitive transcription factor, is responsible for regulating cellular redox homeostasis. However, the exact role of Nrf2 in dyslipidemia-induced dysfunction of proximal tubule cells is still not fully elucidated. In the present study, we showed that palmitic acid (PA) induced mitochondrial damage, excessive mitochondrial reactive oxygen species (ROS) (mtROS) generation, and cell injury in HK-2 cells. We further found that mtROS generation was involved in PA-induced mitochondrial dysfunction, cytoskeletal damage, and cell apoptosis in HK-2 cells. In addition, we demonstrated that the Nrf2/ARE signaling pathway was activated in PA-induced HK-2 cells and that silencing Nrf2 dramatically aggravated PA-induced mtROS production, mitochondrial damage, cytoskeletal damage and cell apoptosis in HK-2 cells. However, the mitochondrial antioxidant MitoTEMPOL effectively eliminated these negative effects of Nrf2 silencing in HK-2 cells under PA stimulation. Moreover, activation of the Nrf2/ARE signaling pathway with tBHQ attenuated renal injury, significantly reduced mtROS generation, and improved mitochondrial function in rats with HFD-induced obesity. Taken together, these results suggest that the Nrf2/ARE-mediated antioxidant response plays a protective role in hyperlipidemia-induced renal injury by ameliorating mtROS-mediated mitochondrial dysfunction and that enhancing Nrf2 antioxidant signaling provides a potential therapeutic strategy for kidney injury in CKD with hyperlipidemia.