Schisandrin B Targets PXR to Enhance Bile Acid Metabolism and Alleviate ANIT-Induced Cholestatic Liver Injury via Dual Pathways

Cholestatic liver injury (CLI) is a rapid progressive liver disorder characterized by the accumulation of bile acids (BA). Although pregnane X receptor (PXR) is a critical regulator of BA metabolism, the synergistic mechanisms of natural compounds targeting these pathways remain unclear. In this study, we demonstrated a positive correlation between BA accumulation and disease severity in clinical samples. Further, we identified Schisandrin B (Sin B), a lignan from Schisandra chinensis, as a potent hepatoprotective agent in α-naphthyl isothiocyanate (ANIT)- induced CLI. We demonstrated that Sin B treatment reduced BA levels and inflammation in ANIT-induced WRL68 cells, liver lobule chips, and mice. Notably, Sin B activated PXR, increased the levels of UDP-glucuronosyltransferase 1A1 (UGT1A1), CYP3A4 (in humans) / CYP3A11 (in mice) and MRPs, and enhanced TFEB transcriptional activity and autophagic flux in vivo and in vitro. Knockout of hepatic Pxr or Tfeb blocked these effects of Sin B. Mechanistic investigation revealed that Sin B is directly binds to PXR at residues S106, G144, and W299, inducing conformational changes in the ligand-binding domain (LBD) was verified through target fishing, molecular dynamics (MD) simulations, drug affinity responsive target stability assay, isothermal titration calorimetry and surface plasmon resonance. Our findings provide structural and functional insights into the dual-pathway mechanism of Sin B and support its therapeutic potential for CLI.