IRGM/Irgm1 Increases Autophagy to Inhibit Activation of NLRP3 Inflammasome in Inflammatory Injury Induced Acute Liver Failure

Abstract

Abstract Immune-related GTPase M (IRGM) induces autophagy and suppresses inflammation, but its putative role and signaling mechanism remain undefined in the pathogenesis of liver failure. This study aimed to address how IRGM attenuates inflammatory injury by regulating autophagy in liver failure. In this study, a total of 10 patients with hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF) and 10 healthy controls were prospectively enrolled. Intrahepatic expression of IRGM/Irgm1, NLRP3 inflammasome (NLRP3, ASC, and caspase-1), autophagy-related proteins (LC3II, P62), and inflammatory cytokines (IL-1β, TNF-α) were measured. Autophagy was activated by rapamycin (4 mg/kg) in an acute liver failure (ALF) mouse model, which was used to further study the expression of Irgm1, NLRP3 inflammasome, autophagy-related proteins, and inflammatory cytokines using both qRT-PCR and Western blot analyses. Irgm1 expression was knocked down using Irgm1 short hairpin RNA (shRNA) in lipopolysaccharide (LPS)-induced AML12 cells to investigate the effects of Irgm1 deletion on autophagy and inflammation. We found that expression of IRGM and autophagy-related proteins was significantly downregulated while the NLRP3 inflammasome was significantly upregulated in the livers of HBV-ACLF patients and the ALF mouse model (all P<0.05). Rapamycin-induced autophagy ameliorated intrahepatic NLRP3 inflammasome activation and decreased inflammation and necrosis in the ALF mice. Irgm1 knockdown decreased autophagy and significantly upregulated NLRP3 inflammasome activation in AML12 cells (all P<0.05). Rapamycin-induced autophagy also protected against hepatocyte injury following LPS stimulation in vitro by inhibiting NLRP3 inflammasome activation. Thus, IRGM/Irgm1 alleviates inflammation-mediated hepatocyte injury by regulating autophagy. This study provides new insight into potential molecular targets to treat liver failure.