Activation of WNT/Beta-Catenin Signaling and Regulation of the Farnesoid X Receptor/Beta-Catenin Complex After Murine Bile Duct Ligation

We have recently shown that loss of beta-catenin prevents the development of cholestatic liver injury and fibrosis after bile duct ligation (BDL) due to loss of the inhibitory farnesoid X receptor (FXR)/beta-catenin complex, which results in decreased hepatic bile acids (BAs) through activation of FXR. To further understand the role of Wnt/beta-catenin signaling in regulating BA metabolism and cholestasis, we performed BDL on mice in which hepatocyte Wnt signaling is deficient but beta-catenin is intact (low-density lipoprotein receptor-related protein [LRP]5/6 knockout [DKO]) as well as mice that have enhanced hepatocyte beta-catenin expression (serine 45 mutated to aspartic acid [S45D] transgenic [TG] mice). Despite decreased biliary injury after BDL, hepatic injury, fibrosis, and inflammation were comparable in DKO and wild-type (WT) mice. Notably, the FXR/beta-catenin complex was maintained in DKO livers after BDL, coincident with significantly elevated hepatic BA levels. Similarly, TG mice did not display accelerated injury or increased mortality despite overexpression of beta-catenin. There was no augmentation of FXR/beta-catenin association in TG livers; this resulted in equivalent hepatic BAs in WT and TG mice after BDL. Finally, we analyzed the effect of BDL on beta-catenin activity and identified an increase in periportal cytoplasmic stabilization and association with T-cell factor 4 that correlated with increased expression of distinct downstream target genes. Conclusion: Localization of beta-catenin and expression of Wnt-regulated genes were altered in liver after BDL; however, neither elimination of Wnt/beta-catenin signaling nor overexpression of beta-catenin in hepatocytes significantly impacted the phenotype or progression of BA-driven cholestatic injury.