Effects of Astragaloside II on Activation of the PINK1/Parkin Pathway: Inhibition of Autophagy and Improvement of Mitochondrial Function in Podocytes

Abstract

Background: Type 2 diabetes may cause chronic kidney disease and damage podocytes, but Astragaloside II (AS II) may protect the function of podocytes. This study aims to verify whether AS II can exert protective effects on podocytes and explore the underlying mechanism. Method: MPC5 cells were treated with high glucose and AS II or transfected with siParkin. The cell counting kit-8 was used to detect the viability of MPC5 cells. Western blot was used to detect the expressions of Beclin1, microtubule associated protein 1 light chain 3 alpha (LC3)I, LC3II, wilms tumor type 1 (WT1), podocalyxin, mitochondrial fission 1 (Fis1), mitofusin-2 (Mfn2), PTEN induced kinase 1 (PINK1) and parkin RBR E3 ubiquitin protein ligase (Parkin). The MPC5 cells were infected with green fluorescent protein-red fluorescent protein-LC3 (GFP-RFP-LC3) adenovirus to evaluate the effect of AS II and silencing Parkin on autophagy. Mitophagy was detected by the co-localization of mitochondria with autophagosome via immunofluorescent staining. Result: High glucose damaged MPC5 cells and inhibited the expression of PINK1 and Parkin. AS II (0.33, 1, 3 μM) could improve cell viability, upregulate the expression of WT1 and podocalyxin, and reduce autophagy and cell damage. Among these treatments, 1 μM AS II had the best effect (p < 0.05). In addition, AS II could protect the mitochondrial dynamics and promote the co-localization of Parkin and mitochondria. However, silencing Parkin reversed the effects of AS II (p < 0.05). Conclusion: AS II promotes the viability, functions, mitophagy and mitochondrial dynamics but inhibits the autophagy of podocytes by activating the PINK1/Parkin signaling pathway.