Nonalcoholic steatohepatitis (NASH), the progressive form of nonalcoholic fatty liver disease (NAFLD), is becoming a common chronic liver disease with the characteristics of steatosis, inflammation and fibrosis. Macrophage plays an important role in the development of NASH. In this study, Annexin A5 (Anx A5) is identified with the special effect on hepatic macrophage phenotype shift from M1 to M2. And it is further demonstrated that Anx A5 significantly switches metabolic reprogramming from glycolysis to oxidative phosphorylation in activated macrophages. Mechanistically, the main target of Anx A5 in energy metabolism is confirmed to be pyruvate kinase M2 (PKM2). And we following reveal that Anx A5 directly interacts with PKM2 at ASP101, LEU104 and ARG106, inhibits phosphorylation of Y105, and promotes PKM2 tetramer formation. In addition, based on the results of PKM2 inhibitor (compound 3k) and the phosphorylated mutation (PKM2 (Y105E)), it is proved that Anx A5 exhibits the function in macrophage polarization dependently on PKM2 activity. In vivo studies also show that Anx A5 improves steatosis, inflammation and fibrosis in NASH mice due to specially regulating hepatic macrophages via interaction with PKM2. Therefore, we have revealed a novel function of Anx A5 in hepatic macrophage polarization and HFD-induced NASH, providing important insights into the metabolic reprogramming, which is important for NASH therapy.

Excessive activation of hepatic stellate cells (HSCs) is a key step in liver fibrogenesis. Here we report that CUG-binding protein 1 (CUGBP1) expression is elevated in HSCs and positively correlates with liver fibrosis severity in human liver biopsies. Transforming growth factor-beta (TGF-β) selectively increases CUGBP1 expression in cultured HSCs in a p38 mitogen-activated protein kinase (MAPK)-dependent manner. Knockdown of CUGBP1 inhibits alpha smooth muscle actin (α-SMA) expression and promotes interferon gamma (IFN-γ) production in HSCs in vitro. We further show that CUGBP1 specifically binds to the 3′ untranslated region (UTR) of human IFN-γ mRNA and promotes its decay. In mice, knockdown of CUGBP1 alleviates, whereas its overexpression exacerbates, bile duct ligation (BDL)-induced hepatic fibrosis. Therefore, CUGBP1-mediated IFN-γ mRNA decay is a key event for profibrotic TGF-β-dependent activation of HSCs, and inhibiting CUGBP1 to promote IFN-γ signalling in activated HSCs could be a novel strategy to treat liver fibrosis.