title: TGR5 is essential for bile acid-dependent cholangiocyte proliferation in vivo and in vitro.
abstract: OBJECTIVE
  Cholestatic liver diseases in humans as well as bile acid (BA)-feeding and common bile duct ligation (CBDL) in rodents trigger hyperplasia of cholangiocytes within the portal fields. Furthermore, elevation of BA levels enhances proliferation and invasiveness of cholangiocarcinoma (CCA) cells in animal models, thus promoting tumour progression. TGR5 is a G-protein coupled BA receptor, which is highly expressed in cholangiocytes and postulated to mediate the proliferative effects of BA.
  
  
  METHODS
  BA-dependent cholangiocyte proliferation was examined in TGR5-knockout and wild type mice following cholic acid (CA)-feeding and CBDL. TGR5-dependent proliferation and protection from apoptosis was studied in isolated cholangiocytes and CCA cell lines following stimulation with TGR5 ligands and kinase inhibitors. TGR5 expression was analysed in human CCA tissue.
  
  
  RESULTS
  Cholangiocyte proliferation was significantly reduced in TGR5-knockout mice in response to CA-feeding and CBDL. Taurolithocholic acid and TGR5-selective agonists induced cholangiocyte proliferation through elevation of reactive oxygen species and cSrc mediated epidermal growth factor receptor transactivation and subsequent Erk1/2 phosphorylation only in wild type but not in TGR5-knockout-derived cells. In human CCA tissue TGR5 was overexpressed and the pathway of TGR5-dependent proliferation via epidermal growth factor receptor and extracellular signal-regulated kinase (ERK)1/2 activation also translated to CCA cell lines. Furthermore, apoptosis was inhibited by TGR5-dependent CD95 receptor serine phosphorylation.
  
  
  CONCLUSIONS
  TGR5 is an important mediator of BA-induced cholangiocyte proliferation in vivo and in vitro. Furthermore, TGR5 protects cholangiocytes from death receptor-mediated apoptosis. These mechanisms may protect cholangiocytes from BA toxicity under cholestatic conditions, however, they may trigger proliferation and apoptosis resistance in malignantly transformed cholangiocytes, thus promoting CCA progression.
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Reich
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Deutschmann
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Annika
authors.initials: A
authors.lastname: Sommerfeld
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Caroline
authors.initials: C
authors.lastname: Klindt
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Kluge
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Kubitz
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Ullmer
authors.affiliation: Department of General, Visceral, and Pediatric Surgery, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Wolfram T
authors.initials: WT
authors.lastname: Knoefel
authors.affiliation: Department of General Pediatrics, Neonatalogy and Pediatric Cardiology, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Diran
authors.initials: D
authors.lastname: Herebian
authors.affiliation: Department of General Pediatrics, Neonatalogy and Pediatric Cardiology, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Ertan
authors.initials: E
authors.lastname: Mayatepek
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Häussinger
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Düsseldorf, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Keitel
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001647:Bile Acids and Salts / Q000502:physiology*; D001650:Bile Duct Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000502:physiology*; D018281:Cholangiocarcinoma / Q000378:metabolism*; D003135:Common Bile Duct / Q000378:metabolism / Q000502:physiology* / Q000601:surgery; D006801:Humans; D008026:Ligation; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D043562:Receptors, G-Protein-Coupled / Q000172:deficiency / Q000378:metabolism*
chemical_list: D001647:Bile Acids and Salts; C473772:GPBAR1 protein, human; C513561:Gpbar1 protein, mouse; D043562:Receptors, G-Protein-Coupled
keywords: APOPTOSIS; BILE ACID; CELL PROLIFERATION; CHOLANGIOCARCINOMA