title: Farnesoid X receptor agonists attenuate colonic epithelial secretory function and prevent experimental diarrhoea in vivo.
abstract: OBJECTIVE
  Bile acids are important regulators of intestinal physiology, and the nuclear bile acid receptor, farnesoid X receptor (FXR), is emerging as a promising therapeutic target for several intestinal disorders. Here, we investigated a role for FXR in regulating intestinal fluid and electrolyte transport and the potential for FXR agonists in treating diarrhoeal diseases.
  
  
  METHODS
  Electrogenic ion transport was measured as changes in short-circuit current across voltage-clamped T84 cell monolayers or mouse tissues in Ussing chambers. NHE3 activity was measured as BCECF fluorescence in Caco-2 cells. Protein expression was measured by immunoblotting and cell surface biotinylation. Antidiarrhoeal efficacy of GW4064 was assessed using two in vivo mouse models: the ovalbumin-induced diarrhoea model and cholera toxin (CTX)-induced intestinal fluid accumulation.
  
  
  RESULTS
  GW4064 (5 μmol/L; 24 h), a specific FXR agonist, induced nuclear translocation of the receptor in T84 cells and attenuated Cl(-) secretory responses to both Ca(2+) and cAMP-dependent agonists. GW4064 also prevented agonist-induced inhibition of NHE3 in Caco-2 cells. In mice, intraperitoneal administration of GW4064 (50 mg/mL) also inhibited Ca(2+) and cAMP-dependent secretory responses across ex vivo colonic tissues and prevented ovalbumin-induced diarrhoea and CTX-induced intestinal fluid accumulation in vivo. At the molecular level, FXR activation attenuated apical Cl(-) currents by inhibiting expression of cystic fibrosis transmembrane conductance regulator channels and inhibited basolateral Na(+)/K(+)-ATPase activity without altering expression of the protein.
  
  
  CONCLUSIONS
  These data reveal a novel antisecretory role for the FXR in colonic epithelial cells and suggest that FXR agonists have excellent potential for development as a new class of antidiarrheal drugs.
authors.affiliation: Department of Molecular Medicine, RCSI Education and Research Centre, Beaumont Hospital, , Dublin, Ireland.
authors.forename: Magdalena S
authors.initials: MS
authors.lastname: Mroz
authors.forename: Niamh
authors.initials: N
authors.lastname: Keating
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Ward
authors.forename: Rafiquel
authors.initials: R
authors.lastname: Sarker
authors.forename: Silvie
authors.initials: S
authors.lastname: Amu
authors.forename: Gabriella
authors.initials: G
authors.lastname: Aviello
authors.forename: Mark
authors.initials: M
authors.lastname: Donowitz
authors.forename: Padraic G
authors.initials: PG
authors.lastname: Fallon
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Keely
mesh_terms: D000818:Animals; D000930:Antidiarrheals / Q000494:pharmacology* / Q000627:therapeutic use; D015153:Blotting, Western; D018938:Caco-2 Cells; D002478:Cells, Cultured; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D003967:Diarrhea / Q000378:metabolism / Q000517:prevention & control*; D004568:Electrodiagnosis; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D007555:Isoxazoles / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D000099150:Receptor, Farnesoid X-Activated
chemical_list: D000930:Antidiarrheals; D007555:Isoxazoles; D018160:Receptors, Cytoplasmic and Nuclear; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D000099150:Receptor, Farnesoid X-Activated; C000613385:SLC9A3 protein, human; C000613386:Slc9a3 protein, mouse; C412815:GW 4064
keywords: Bile Acid; Cell Biology; Diarrhoea; Epithelial Transport; Intestinal Ion Transport