Serpina3c deficiency induced necroptosis promotes non-alcoholic fatty liver disease through β-catenin/Foxo1/TLR4 signaling

Abstract

Non-alcoholic fatty liver disease (NAFLD) is a public health challenge and an increasing cause of chronic liver disease worldwide. However, the underlying molecular mechanism remains unclear. The aim of this study was to determine the precise role of serpina3c in the process of NAFLD. Male Apoe^-/- /serpina3c^-/- double knockout (DKO) and Apoe^-/- mice were fed a high-fat diet (HFD) for 12 weeks. Several markers of steatosis and inflammation were evaluated. In vitro cell models induced by palmitic acid (PA) treatment were used to evaluate the beneficial effect of serpina3c on necroptosis and the underlying molecular mechanism. Compared with Apoe^-/- mice, DKO mice exhibited a significantly exacerbated hepatic steatosis, increased hepatic triglyceride content and expression of genes involved in lipid metabolism (SREBP1c and SCD1), promoted hepatic inflammation and fibrosis, promoted necroptosis by increasing expression of receptor-interacting protein 3 (RIP3), phosphorylated mixed lineage kinase domain-like (MLKL) and high mobility group box 1 (HMGB1). Notably, serpina3c deficiency increased β-catenin, Foxo1, and Toll-like receptor 4 (TLR4) protein expression. In vitro , serpina3c knockdown promoted necroptosis and lipid droplet formation under condition of lipotoxicity. However, these phenomena were reversed by the overexpression of serpina3c. Mechanistically, downregulation of serpina3c expression promoted Foxo1 and β-catenin colocalized in the nucleus under condition of lipotoxicity, consequently upregulating the expression of TLR4. Conversely, disruption of Foxo1-β/catenin by Foxo1 and β-catenin inhibitors decreased TLR4 expression and ameliorated hepatic necroptosis in vitro. This study highlights a novel mechanism that serpina3c modulates NAFLD development by inhibiting necroptosis via β-catenin/Foxo1/TLR4.

Keywords: NAFLD; necroptosis; serpina3c; β-catenin/Foxo1/TLR4.