Farnesoid X receptor and nuclear factor erythroid 2-related factor 2 synergistically ameliorate cholestatic liver injury by coordinating bile acid metabolism and transport.

Cholestatic liver injury (CLI) is a clinical syndrome characterized by bile acid (BA) accumulation, yet the interplay between farnesoid X receptor (FXR) and nuclear factor erythroid 2-related factor 2 (NRF2) in this process remains poorly understood. In this study, we investigated whether and how FXR and NRF2 synergistically alleviate CLI through coordinated regulation of BA homeostasis. An alpha-naphthyl isothiocyanate (ANIT)-induced CLI rat model was used, and the FXR agonist obeticholic acid (OCA) and NRF2 agonist sulforaphane (SFN) were administered either alone or in combination. Hepatic injury was evaluated by serum biochemistry and histopathology. The expression levels of FXR, NRF2, and the key BA-related genes CYP7A1, UGT1A1, BSEP, and NTCP were measured. Parallel experiments were performed in BRL and L02 hepatocytes, and β-catenin was silenced both in vitro and in vivo to explore the underlying mechanism. Our research results indicate that, compared to monotherapy, the combination therapy of OCA and SFN yielded superior therapeutic effects, as evidenced by more significant reductions in serum-related biochemical indicators and more pronounced regulation of BA metabolism and transporter gene expression. Quantitatively, the combination therapy reduced serum ALT levels by approximately 67%, whereas OCA or SFN monotherapy only reduced them by about 43% and 30%, respectively. Similarly, the combination therapy decreased serum TBA levels by approximately 59%, whereas OCA or SFN monotherapy only reduced them by about 39% and 34%, respectively. Similar results were observed for other biochemical parameters, including AST, ALP, γ-GT, and TBIL. Mechanistically, the combination enhanced nuclear translocation of both FXR and NRF2, an effect mediated by the β-catenin/P300 axis via competitive protein binding. Notably, silencing β-catenin significantly attenuated these synergistic protective effects. In conclusion, FXR and NRF2 synergistically ameliorate cholestatic liver injury through β-catenin/P300-mediated crosstalk that coordinately regulates BA metabolism and transport, suggesting that dual activation of these pathways represents a promising therapeutic strategy for CLI.