Chronic Intermittent Hypoxia Aggravates the Pyroptosis of Renal Tubular Epithelial Cells Through Regulating Mitophagy‐Mediated NLRP3 Inflammasome Activation

Obstructive sleep apnea (OSA)-induced renal injury is triggered by chronic intermittent hypoxia (CIH). Our previous article has revealed that CIH triggers the pyroptosis of renal tubular epithelial cells through the activation of NLRP3 inflammasome, whereas the mechanism by which CIH activates NLRP3 inflammasome remains elusive. Rats and HK-2 cells were exposed to CIH to establish CIH models. Histopathological staining, blood urea nitrogen (BUN) and serum creatinine (Scr) levels were examined to assess renal injury. Western blot and immunofluorescence assay were used to assess proteins related to NLRP3 inflammasome, pyroptosis and mitophagy. Mitochondrial membrane potential and production of ROS and ATP were examined to evaluate mitochondrial function. CCK-8, LDH release and ELISA assays were performed to assess cell injury and inflammation. Mitochondrial division inhibitor 1 (Mdivi-1) was applied for a rescue assay. CIH induced renal injury and suppressed mitophagy in vivo, evidenced by worsening pathological features, elevated Scr and BUN levels, reduced colocalization of Tom20 with LC3B, and downregulated expression of LC3-II/I ratio, Atg5, PINK1 and Parkin. PINK1 overexpression restored mitophagy by enhancing colocalization of mitochondria with LC3B, upregulating LC3-II/I ratio and Atg5, and restored mitochondrial function of CIH-exposed HK-2 cells through enhancing mitochondrial membrane potential, reducing ROS production and increasing ATP content. PINK1 overexpression alleviated cell viability, inflammation and NLRP3 inflammasome-mediated pyroptosis in CIH-exposed HK-2 cells, which were partly abolished by Mdivi-1. PINK1 attenuated NLRP3 inflammasome-mediated pyroptosis in CIH-exposed HK-2 cells partially through restoring mitophagy and mitochondrial function, providing potential therapeutic strategies for OSA-related kidney diseases.