title: Ursodeoxycholic acid stimulates cholangiocyte fluid secretion in mice via CFTR-dependent ATP secretion.
abstract: OBJECTIVE
  Cholangiopathies are characterized by impaired cholangiocyte secretion. Ursodeoxycholic acid (UDCA) is widely used for cholangiopathy treatment, but its effects on cholangiocyte secretory functions remain unclear and are the subject of this study.
  
  
  METHODS
  Polarized mouse cholangiocytes in tubular (isolated bile-duct units [IBDU]) or monolayer configuration were obtained from wild-type (WT) and B6-129-Cftr(tm1Kth) and Cftr(tm1Unc) mice that are defective in CFTR, an adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated Cl(-) channel expressed in cholangiocytes. Fluid secretion was assessed by video-optical planimetry, Cl(-) and Ca(2+) efflux by microfluorimetry (6-methoxy-N-ethylquinolinium chloride, fura-2, and fluo-4), adenosine triphosphate (ATP) secretion by luciferin-luciferase assay, and protein kinase C (PKC) by Western blot.
  
  
  RESULTS
  UDCA stimulated fluid secretion and Cl(-) efflux in WT-IBDU but not in CFTR-KO-IBDU or in WT-IBDU exposed to CFTR inhibitors. UDCA did not affect intracellular cAMP levels but increased [Ca(2+)]i in WT and not in CFTR-KO cholangiocytes. UDCA stimulated apical ATP secretion in WT but not in CFTR-KO cholangiocytes. UDCA-stimulated [Ca(2+)]i increase was inhibited by suramin, a purinergic 2Y-receptor inhibitor. UDCA stimulated the translocation of PKC-alpha and PKC-epsilon to the plasma membrane. UDCA-stimulated secretion was inhibited by 2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid and by phospholipase C and PKC inhibitors. UDCA increased ATP output in isolated perfused livers from WT but not from CFTR-KO mice.
  
  
  CONCLUSIONS
  Our data indicate that UDCA stimulates a CFTR-dependent apical ATP release in cholangiocytes. Secreted ATP activates purinergic 2Y receptors, and, through [Ca(2+)]i increase and PKC activation stimulates Cl(-) efflux and fluid secretion. These data support the concept that CFTR plays a role in modulating purinergic signaling in secretory epithelia and suggest a novel mechanism explaining the choleretic effect of UDCA.
authors.affiliation: Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine and Liver Center, New Haven, Connecticut, USA.
authors.forename: Romina
authors.initials: R
authors.lastname: Fiorotto
authors.forename: Carlo
authors.initials: C
authors.lastname: Spirlì
authors.forename: Luca
authors.initials: L
authors.lastname: Fabris
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Cadamuro
authors.forename: Lajos
authors.initials: L
authors.lastname: Okolicsanyi
authors.forename: Mario
authors.initials: M
authors.lastname: Strazzabosco
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001653:Bile Ducts, Intrahepatic / Q000378:metabolism* / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002756:Cholagogues and Choleretics / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D011493:Protein Kinase C / Q000378:metabolism; D014580:Ursodeoxycholic Acid / Q000494:pharmacology*; D051153:Wnt Proteins / Q000378:metabolism
chemical_list: D002756:Cholagogues and Choleretics; D051153:Wnt Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D014580:Ursodeoxycholic Acid; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011493:Protein Kinase C; D002118:Calcium