Deficiency of TGR5 Exacerbates Immune-Mediated Cholestatic Hepatic Injury by Stabilizing the β-Catenin Destruction Complex

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. In the study, we investigated the mechanism of TGR5 using wild-type (TGR5FL/FL) and TGR5 knockout (TGR5-/-) mice with CHI induced by bile duct ligation (BDL) in vivo, and bone marrow-derived macrophages (BMDMs) in vitro. TGR5 deficiency significantly exacerbated BDL-induced liver injury, and hepatic fibrosis compared with TGR5FL/FL mice. TGR5-/- macrophages were more susceptible to lipopolysaccharide (LPS) stimulation than TGR5FL/FL macrophages. TGR5 activation suppressed LPS-induced pro-inflammatory responses in TGR5FL/FL but not TGR5-/- BMDMs. Notably, expression of β-catenin was effectively inhibited by TGR5 deficiency. Furthermore, TGR5 directly interacted with Gsk3β to repress the interaction between Gsk3β and β-catenin, thus disrupting the β-catenin destruction complex. The pro-inflammatory nature of TGR5-knockout was almost abolished by lentivirus-mediated β-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. Our findings reveal that TGR5 plays a crucial role as a novel regulator of immune-mediated CHI by destabilizing the β-catenin destruction complex, with therapeutic implications for the human CHI. Funding: This study was supported by the Foundation of Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, the Priority Academic Program Development of Jiangsu Higher Education Institutions, the National Natural Science Foundation of China (81400650, 814700901, 81273261, and 81270583). Declaration of Interest: All authors declare no conflict of interests. Ethical Approval: Informed consent was obtained from all participants, and the study was approved by the local ethics committee of Nanjing Medical University.