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Background:Studies have reported mitophagy activation in renal tubular epithelial cells (RTECs) in acute kidney injury (AKI).Phosphatase and tensin homolog-induced putative kinase 1 (PINK1) and E3 ubiquitin-protein ligase Parkin are involved in mitophagy regulation;however,little is known about the role of PINK1-Parkin mitophagy in septic AKI.Here we investigated whether the PINK1-Parkin mitophagy pathway is involved in septic AKI and its effects on cell apoptosis in vitro and on renal functions in vivo.Methods:Mitophagy-related gene expression was determined using West blot assay in human RTEC cell line HK-2 stimulated with bacterial lipopolysaccharide (LPS) and in RTECs from septic AKI rats induced by cecal ligation and perforation (CLP).Autophagy-related ultrastructural features in rat RTECs were observed using electron microscopy.Gain-and loss-of-function approaches were performed to investigate the role of the PINK1-Parkin pathway in HK-2 cell mitophagy.Autophagy activators and inhibitors were used to assess the effects of mitophagy modulation on cell apoptosis in vitro and on renal functions in vivo.Results:LPS stimulation could significantly induce LC3-Ⅱ and BECN-1 protein expression (LC3-Ⅱ:1.72 ± 0.05 vs.1.00 ± 0.05,P＜0.05;BECN-1:5.33±0.57 vs.1.00±0.14,P＜ 0.05) at 4 h in vitro.Similarly,LC3-Ⅱ,and BECN-1 protein levels were significantly increased and peaked at 2 h after CLP (LC3-Ⅱ:3.33 ± 0.12 vs.1.03 ± 0.15,P ＜ 0.05;BECN-1:1.57± 0.26 vs.1.02 ± 0.11,P ＜ 0.05) in vivo compared with those after sham operation.Mitochondrial deformation and mitolysosome-mediated mitochondria clearance were observed in RTECs from septic rats.PINK1 knockdown significantly attenuated LC3-Ⅱ protein expression (1.35 ± 0.21 vs.2.38 ± 0.22,P ＜ 0.05),whereas PINK 1 overexpression markedly enhanced LC3-Ⅱ protein expression (2.07± 0.21 vs.1.29 ± 0.19,P ＜ 0.05) compared with LPS-stimulated HK-2 cells.LPS-induced proapoptotic protein expression remained unchanged in autophagy activator-treated HK-2 cells and was significantly attenuated in PINK1-overexpressing cells,but was remarkably upregulated in autophagy inhibitor-treated and in HNK1-depleted cells.Consistent results were observed in flow cytometric apoptosis assay and in renal function indicators in rats.Conclusion:PINK1-Parkin-mediated mitophagy might play a protective role in septic AKI,serving as a potential therapeutic target for septic AKI.