ABSTRACT
Intrahepatic cholestasis induced by drug toxicity may cause cholestatic hepatic injury (CHI) leading to liver fibrosis and cirrhosis. The G protein-coupled bile acid receptor 1 (TGR5) is a membrane receptor with well-known roles in the regulation of glucose metabolism and energy homeostasis. However, the role and mechanism of TGR5 in the context of inflammation during CHI remains unclear. Wild-type (WT) and TGR5 knockout (TGR5-/-) mice with CHI induced by bile duct ligation (BDL) were involved in vivo, and WT and TGR5-/- bone marrow-derived macrophages (BMDMs) were used in vitro. TGR5 deficiency significantly exacerbated BDL-induced liver injury, inflammatory responses and hepatic fibrosis compared with WT mice in vivo. TGR5-/- macrophages were more susceptible to lipopolysaccharide (LPS) stimulation than WT macrophages. TGR5 activation by its ligand suppressed LPS-induced pro-inflammatory responses in WT but not TGR5-/- BMDMs. Notably, expression of ß-catenin was effectively inhibited by TGR5 deficiency. Furthermore, TGR5 directly interacted with Gsk3ß to repress the interaction between Gsk3ß and ß-catenin, thus disrupting the ß-catenin destruction complex. The pro-inflammatory nature of TGR5-knockout was almost abolished by lentivirus-mediated ß-catenin overexpression in BMDMs. BMDM migration in vitro was accelerated under TGR5-deficient conditions or supernatant from LPS-stimulated TGR5-/- BMDMs. From a therapeutic perspective, TGR5-/- BMDM administration aggravated BDL-induced CHI, which was effectively rescued by ß-catenin overexpression. Our findings reveal that TGR5 plays a crucial role as a novel regulator of immune-mediated CHI by destabilizing the ß-catenin destruction complex, with therapeutic implications for the management of human CHI.