The ileum-liver Farnesoid X Receptor signaling axis mediates the compensatory mechanism of 17α-ethynylestradiol-induced cholestasis via increasing hepatic biosynthesis of chenodeoxycholic acids in rats

Background and purpose: Estrogen-induced intrahepatic cholestasis is one of the most common pathogenic factors for liver diseases in clinic. It is, however, regrettable that effective medical therapies to ameliorate or reverse this cholestasis are limited. Fortunately, the novel insights now allow us to target crucial transporters, enzymes and their regulatory pathways therapeutically by restoring disrupted bile acids (BAs) transport and signaling thus ameliorating cholestasis. Additionally, it has been found that a compensatory effect could have been developed under the condition of estrogen-induced in cholestasis. Hence, exploring the molecular mechanism of the adaptive changes counteracting the cholestasis would be one of the approaches for development of new therapeutic targets. Methods: Parameters of BAs in different specimens, mRNA expressions of transporters, enzymes and farnesoid X receptor (Fxr) signaling pathways that relate to BAs homeostasis in liver and ileum were measured in rats with 7-day and 14-day 17 alpha-ethynylestradiol (EE)-induced cholestasis, and the molecular docking and HepaRG cells studies for verification were also evaluated. Key results: It has been found that the depression of "ileal Fxr-Fgf15 (fibroblast growth factor 15)-hepatic Cyp7a1 pathway" in coordinated with activation of "hepatic Fxr-Shp (small heterodimer partner)-Cyp8b1 pathway" as well as up-regulation of Cyp27a1 expression synergistically promoting the hepatic biosynthesis of chenodeoxycholic acids (CDCAs) that are the potent agonists of Fxr, contribute to the Bsep up-regulation mediated the bile flow restoration to alleviate the cholestasis. Conclusion: These findings suggest that the adaptive regulation of Fxr-mediated ileum-liver signaling axis on Cyp7a1/Cyp8b1 might be the potentially novel targets for amelioration or treatment of estrogen-induced cholestasis, and we expect that this study would be of great value to provide a cue for patients with estrogen-induced cholestasis.