β-sitosterol protects against ANIT-induced hepatotoxicity and cholestasis via FXR activation

Cholestasis, a condition marked by bile acid accumulation in the liver and body systems, leads to liver dysfunction and cirrhosis. Currently, ursodeoxycholic acid (UDCA) and obeticholic acid (OCA) are the only two FDA-approved drugs for Cholestasis. Thus, new therapeutic approaches need to be developed. In this study, we validated the liver-protective properties of β-sitosterol (SIT), a key bioactive element abundant in plants, against hepatic toxicity and cholestasis induced by alpha-naphthylisothiocyanate(ANIT), while elucidating its mechanisms of action both in vivo and in vitro. SIT's FXR activation was confirmed via molecular docking and dual-luciferase assays. In the mechanisms of SIT hepatoprotection, the expression levels of bile salt export pump (Bsep) and multidrug resistance protein2 (Mrp2) which are bile acid efflux transporter, and sulfate transferase 2a1 (Sult2a1) which is a bile acid metabolizing enzyme were all increased by SIT, whereas the expression of uptake transporter sodium taurocholate transporting polypeptide (Ntcp), bile acid synthesis enzyme cholesterol 7α-hydroxylase (Cyp7a1) and oxysterol 12α-hydroxylase (Cyp8b1) was decreased by SIT. In addition, SIT alleviated liver inflammation by suppressing inflammatory factor expression. However, FXR antagonist guggulsterone and FXR siRNA abolished SIT's improvements in liver histology, bile acid transporters, and enzymes. Conclusively, through activating FXR, SIT provides a protective effect against hepatotoxicity and cholestasis. SIT might serve as a new potential therapeutic strategy for the treatment of cholestatic liver diseases.