Hyodeoxycholic acid ameliorates cholestatic liver fibrosis by facilitating m6A-regulated expression of a novel anti-fibrotic target ETV4

Background & Aims

Cholestatic liver fibrosis is a common pathological feature of various biliary tract diseases. The underlying pathological mechanisms are not fully understood, posing significant obstacles to the discovery of new drug targets. The aims of the current study were to evaluate protective effects of hyodeoxycholic acid (HDCA) against cholestatic liver fibrosis and to ascertain whether ETV4 is a novel anti-fibrotic target involved in the therapeutic effects of HDCA.

Methods

The therapeutic effect of HDCA was verified using bile duct ligation and Abcb4^-/- mouse models. Etv4^-/- mice were subjected to bile duct ligation to investigate the role of ETV4 in liver fibrogenesis and the therapeutic effects of HDCA. The N⁶-methyladenosine (m⁶A) modification was investigated using methylated m⁶A RNA immunoprecipitation-qPCR and immunofluorescence/fluorescence in situ hybridization techniques.

Results

HDCA levels were decreased in both cholestatic patients and mice, while HDCA supplementation significantly ameliorated cholestatic liver fibrosis. By inducing ETV4 expression in cholangiocytes, HDCA induced MMP9 secretion, facilitating extracellular matrix degradation. Findings in patients with cholestatic fibrosis and Etv4^-/- mice further revealed a promising role of ETV4 in improving liver fibrosis and in mediating the therapeutic effects of HDCA. Mechanistically, HDCA promoted m⁶A modification of ETV4 mRNA, which thereby promotes IGF2BP1 recognition and PABPC1 recruitment to inhibit ETV4 mRNA deadenylation, leading to increased mRNA stability, storage in P-bodies, and prolonged translation. Mutation of the m⁶A site on ETV4 mRNA or knockdown of critical genes involved in m⁶A modification significantly abolished the therapeutic effects of HDCA.

Conclusions

The present study underscores ETV4 as a novel anti-fibrotic target and demonstrates that HDCA remodels extracellular matrix by facilitating m⁶A-regulated ETV4 expression, offering potential therapeutic approaches for cholestatic liver fibrosis.

Impact and implications

This study delves into the underlying mechanisms of cholestatic liver fibrosis and reveals potential therapeutic targets. The research highlights ETV4 as a novel anti-fibrotic target that is essential for the therapeutic effects of hyodeoxycholic acid against cholestatic liver fibrosis. These findings are important for both the scientific community and patients with cholestatic liver diseases, offering valuable insights for future therapeutic strategies that focus on regulating m⁶A-dependent epigenetic modifications of anti-fibrotic targets like ETV4 and developing new interventions utilizing hyodeoxycholic acid.