Targeted deletion of Tgr5 in the intestine leads to less biliary damage in cholestasis

Introduction Tgr5 (Gpbar1) is a G protein coupled receptor responsive to bile acids (BA) which is expressed in cholangiocytes and the epithelium of the small intestine (1). We have previously demonstrated that mice with a targeted deletion of Tgr5 are more susceptible towards cholestatic liver injury (2,3). Aim of this study was to investigate the role of Tgr5 in the intestine during cholestasis, which was induced by a 1 % lithocholic acid (LCA) diet for 84h (3) using the Tgr5 Villin Cre knockout mouse model.

Methods 8-12 week old Tgr5 Villin Cre knockout (Tgr5^Vil-Cre-/-) and wildtype (Wt) mice were fed a 1 % LCA diet for 84h or standard chow diet. After 84h serum, as well as liver and intestinal tissue were collected. Serum markers of liver and biliary damage were determined using Spotchem-biochemical analyzer. Tgr5, Asbt, Fgf15, Col1a1, Col1a2 and α-SMA mRNA and protein expression was analyzed by real-time PCR and western blotting.

Results Both genotypes showed severe liver damage in response to LCA feeding, which was reflected by high serum levels of aspartate (AST) and alanine aminotransferase (ALT). However, Tgr5^Vil-Cre-/- were less susceptible towards LCA-induced biliary damage as demonstrated by a significantly lower increase of alkaline phosphatase (ALP) and bilirubin levels as well as by histopathology of extrahepatic bile ducts. Tgr5^Vil-Cre-/- mice had lower expression of fibrosis markers (Col1a1, Col1a2 and α-SMA) after 84h of BS-enriched diet. Tgr5 mRNA and protein expression were significantly suppressed in the small and large intestine, while Tgr5 mRNA and protein expression in the hepatobiliary system was not altered in comparison to Wt levels. In the ileum, a significant reduction of Asbt mRNA expression and higher Asbt protein levels were observed together with a significant increase of Fgf15 mRNA in Tgr5^Vil-Cre-/- mice.

Conclusion Deletion of TGR5 in the intestinal epithelium reduced LCA induced biliary damage. Mechanisms contributing are upregulation of Fgf15 and retained TGR5 expression in cholangiocytes.

• References

• 1 Keitel V, Cupisti K, Ullmer C, Knoefel WT, Kubitz R, Häussinger D. The membrane-bound bile acid receptor TGR5 is localized in the epithelium of human gallbladders. Hepatology 2009; 50: 861-70
• 2 Klindt C, Reich M, Hellwig B, Stindt J, Rahnenführer J, Hengstler JG. et al. The G Protein-Coupled Bile Acid Receptor TGR5 (Gpbar1) Modulates Endothelin-1 Signaling in Liver. Cells 2019; 8: 11
• 3 Deutschmann K, Reich M, Klindt C, Dröge C, Spomer L, Häussinger D. et al. Bile acid receptors in the biliary tree: TGR5 in physiology and disease. Biochim Biophys Acta Mol Basis Dis 2018; 1864: 1319-25.

Publication History

Article published online:
04 January 2021