MEOX1-mediated transcriptional regulation of circABHD3 exacerbates hepatic fibrosis through promoting m6A/YTHDF2-dependent YPEL3 mRNA decay to activate β-catenin signaling.

BACKGROUND: Hepatic fibrosis may progress to liver cirrhosis and eventually cause death. Epithelial-mesenchymal transition (EMT) of hepatocytes plays critical roles in hepatic fibrosis. Exploring the mechanisms underlying EMT is crucial for a better understanding of hepatic fibrosis pathogenesis.

METHODS: Hepatocyte EMT wad induced with TGF-β1 and evaluated by Western blotting and immunofluorescence staining. Methylated RNA immunoprecipitation (MeRIP) was applied to assess N6-methyladenosine (m6A) modification. RIP and RNA pull-down assays were performed to analyze the interaction between circABHD3, YTHDF2 and YPEL3 mRNA. MEOX1-mediated transcription of ABHD3 was examined by luciferase and chromatin immunoprecipitation (ChIP). Mice were intraperitoneally injected with CCl4 or treated with bile duct ligation (BDL) surgery for hepatic fibrosis induction. Liver injury and collagen deposition were examined with hematoxylin and eosin (HE), Masson, and Sirius Red staining. Alanine transaminase (ALT), aspartate transaminase (AST) and hydroxyproline (HYP) were examined using ELISA.

RESULTS: CircABHD3 was upregulated in in vitro and in vivo models of hepatic fibrosis and patients. Knockdown of circABHD3 inhibited TGF-β1-induced expression of fibrosis markers, EMT and mitochondrial impairment in hepatocytes. MEOX1 could directly bind to the promoter of ABHD3 to facilitate its transcription and subsequent circABHD3 generation. Knockdown of MEOX1 suppressed TGF-β1-induced EMT and mitochondrial impairment through suppression of circABHD3. CircABHD3 destabilized YPEL3 mRNA via promoting YTHDF2-dependent recognition of m6A-modified YPEL3 mRNA to trigger β-catenin signaling activation. Furthermore, circABHD3 silencing-mediated inhibition of EMT and mitochondrial impairment was counteracted by YPEL3 knockdown and activation of β-catenin signaling. Depletion of circABHD3 significantly reduced EMT, mitochondrial impairment and hepatic fibrosis via promoting YPEL3 expression and suppressing β-catenin signaling in vivo.

CONCLUSION: MEOX1-mediated generation of circABHD3 promotes EMT and mitochondrial impairment by enhancing YTHDF2-mediated degradation of YPEL3 mRNA and activating downstream β-catenin signaling, thus exacerbating hepatic fibrosis.