RIPC Protects Against Renal Ischaemia-Reperfusion Injury by Activating SIRT3/Parkin-Mediated Mitophagy.

Remote ischaemic preconditioning (RIPC) protects against renal ischaemia-reperfusion injury (IRI), yet its precise mechanism remains incompletely understood, particularly regarding the role of mitochondrial quality control. This study investigated whether SIRT3-dependent mitophagy mediates the protective effects of RIPC against acute kidney injury (AKI) induced by IRI and further examined the integrity of mitophagic flux and involvement of the classic Parkin-mediated mitophagic pathway. We used a murine bilateral renal ischaemia-reperfusion injury (IRI) model, including RIPC pretreatment, 3-methyladenine (3-MA) intervention and SIRT3 knockout intervention, and a HK-2 cell hypoxia/reoxygenation (H/R) model, including SIRT3 siRNA knockdown, SIRT3 overexpression and chloroquine (CQ) intervention. Renal function, histopathological changes, apoptosis, mitochondrial membrane potential and mitophagy were assessed using biochemical analysis, histological and TUNEL staining, JC-1 staining, transmission electron microscopy, mitochondrial protein analysis and immunofluorescence colocalization of Parkin and LC3B. RIPC improved renal function, alleviated tubular injury and apoptosis, and enhanced mitophagy in mice, which was attenuated by SIRT3 knockout or 3-MA. In HK-2 cells, RIPC plasma protected against H/R injury and activated mitophagic flux, as verified by CQ treatment, while SIRT3 knockdown abolished these effects and SIRT3 overexpression maintained protective mitophagy levels. RIPC pretreatment restored the IRI-induced reduction in Parkin and LC3B colocalization in renal tubular epithelial mitochondria, and this effect was attenuated by 3-MA. RIPC alone had no detectable cytotoxicity or effect on basal mitophagy. In conclusion, RIPC mitigates renal IRI by activating SIRT3-dependent mitophagy, with involvement of the Parkin-mediated mitophagic pathway. Our in vivo and in vitro data support the central role of SIRT3 in RIPC-induced renoprotection and provide evidence for an intact mitophagic flux mechanism.