NLRX1 and STING alleviate renal ischemia-reperfusion injury by regulating LC3 lipidation during mitophagy

Abstract

Mitophagy significantly influences renal ischemia/reperfusion (I/R) injury and recovery. NLRX1 is recognized for its regulatory role in governing mitochondrial damage, autophagy, and the expression of pro-inflammatory factors. Despite the acknowledged involvement of NLRX1 in these crucial cellular processes, its specific function in renal I/R injury remains unclear. We detected the expression of NLRX1, the cGAS-STING pathway, and autophagy-related proteins using Western Blot analysis. RT-qPCR was utilized to measure the expression of NLRX1 mRNA and cytokines, and changes in mitochondrial DNA (mtDNA) within the cytoplasm. Immunofluorescence was applied to observe alterations in DNA distribution within the cytoplasm. The EtBr drug, which depletes mtDNA, and the Mdivi-1 mitophagy inhibitor, were used to verify the promotion of mitophagy by NLRX1. The results demonstrated that NLRX1 was downregulated after hypoxic/reoxygenation (H/R) injury, and there was an increase in cytoplasmic DNA. NLRX1 overexpression not only reduced IL-1β and IL-6 levels, but also decreased mtDNA in the cytoplasm. Additionally, NLRX1 further increases mitochondrial LC3 lipidation after H/R injury, and this effect is inhibited by Mdivi-1 drugs. The activation of the cGAS-STING pathway after H/R injury is inhibited by EtBr drugs and NLRX1. Co-immunoprecipitation results showed that NLRX1 could bind to STING. Moreover, inhibiting STING reversed NLRX1-induced mitochondrial LC3 lipidation. Our study reveals that NLRX1 can bind to STING to promote mitophagy and inhibits inflammation caused by mtDNA/cGAS/STING signaling.

Keywords: Acute kidney injury; Mitophagy; NLRX1; STING.