Activation of TGR5 Promotes Hepatic Cystogenesis via cAMP

TATYANA V. MASYUK; ANATOLIY I. MASYUK; BRYNN N. HOWARD; MARIA LORENZO PISARELLO; BING Q. HUANG; ANTHONY PINKERTON; EDUARD SERGIENKO; THOMAS CHUNG; NICHOLAS F. LARUSSO

Congreso; Liver Meeting _ American Association for Study of Liver Disease; 2016

BACKGROUND: Hepatic cystogenesis in the Polycystic Liver Diseases (PLD), a group of genetic disorders, is associated with increased levels of cAMP in cholangiocytes lining liver cysts. TGR5, a G protein-coupled bile acid receptor, is linked to cAMP signaling and expressed in cholangiocytes. Therefore, our AIM here was to investigate the involvement of TGR5 in hepatic cystogenesis in PLD. METHODS: We examined TGR5 expression in cultured cholangiocytes and in livers of animal models of PLD (i.e., PCK rats and Pkhd1del2/del2 mice) and humans with PLD. In vitro, we assessed cholangiocyte prolifer- ation, intracellular cAMP levels, and cyst growth in 3-D cultures in response to TGR5 activation by taurolithocholic acid (TLCA) and oleanolic acid (OA). In vivo, we examined hepatic cystic and fibrotic areas in PCK rats in response TGR5 activation by OA and after genetic elimination of TGR5 by generating double mutant TGR5-/-;Pkhd1del2/del2 mice. Finally, we mea- sured proliferation of cultured cystic cholangiocytes treated with a novel small molecule TGR5 antagonist identified by high-throughput screening of a chemical library in CHO-K1 cells expressing TGR5. RESULTS: Compared to controls, TGR5 levels were increased ~3-fold in cystic cholangiocytes in vitro and in vivo. By confocal microscopy, TGR5 co-localized with Gas on the apical membrane of cystic cholangiocytes in PCK rats and this co-localization was increased ~2-fold (p