Geniposidic acid alleviates estrogen-induced cholestasis via farnesoid X receptor to restore bile acid and inflammatory homeostasis.

BACKGROUND

Estrogen-induced intrahepatic cholestasis (EIC) is characterized by toxic bile acid accumulation and hepatic inflammation. Farnesoid X receptor (FXR), a key nuclear receptor governing bile acid homeostasis, plays a pivotal role in cholestasis progression. Geniposidic acid (GPA), a natural iridoid glucoside, exerts hepatoprotective effects against various liver injuries, but its therapeutic potential in EIC remains obscure.

PURPOSE: To investigate the importance of FXR signaling in EIC progression and clarify the therapeutic efficacy and mechanism of GPA against EIC.

METHODS

Synthetic estrogen 17α-ethinylestradiol (EE) was used to establish EIC models both in vivo and in vitro. The protective effect of GPA on EE-treated mouse primary hepatocytes (MPHs), HepG2 and wild-type and FXR⁻/⁻ mice was evaluated by liver injury indicators and H&E staing. SPR, LanthaScreen TR-FRET, and hFXR transactivation assays were employed to characterize GPA as an FXR agonist. Co-administration with metformin, an AMP-activated protein kinase (AMPK) activator, was performed to confirm AMPK-FXR crosstalk in the protective mechanism of GPA.

RESULTS

GPA directly bound FXR ligand-binding domain via Tyr361 and His447 residues, activating FXR signaling to restore bile acid homeostasis and attenuate oxidative stress and inflammation in an FXR-dependent manner. FXR deficiency abolished GPA's hepatoprotection in vitro and in vivo. Mechanistically, EE-induced AMPK hyperactivation suppressed FXR, whereas GPA-activated FXR counter-regulated AMPK phosphorylation via negative feedback. This protection was partially diminished by co-administrated with the AMPK activator Metformin.

CONCLUSIONS

GPA acts as a natural FXR agonist, and targeting AMPK-FXR crosstalk represents a promising therapeutic strategy for EIC.