title: Activation of intestinal Cl- secretion by lubiprostone requires the cystic fibrosis transmembrane conductance regulator.
abstract: OBJECTIVE
  Lubiprostone alleviates constipation by stimulating intestinal fluid secretion, purportedly through activation of ClC-2-type Cl(-) channels. Intestinal obstruction is also a recurrent cause of distress in cystic fibrosis (CF) patients, caused by loss of CF transmembrane conductance regulator (CFTR) Cl(-) channel activity. Because ClC-2 recruitment might be beneficial to CF patients, we investigated lubiprostone's mode of action.
  
  
  METHODS
  Cl(-) transport was measured in an Ussing chamber, in 3 model systems: (1) T84 colonocytes, (2) intestinal epithelium of wild-type and CF mice, and (3) intestinal epithelium of CF patients and controls.
  
  
  RESULTS
  In T84 monolayers, lubiprostone induced a robust secretory response. Selective permeabilization of the basolateral plasma membrane revealed that lubiprostone activated an apical Cl(-) conductance. The lubiprostone response was attenuated by H89, an inhibitor of the cAMP-dependent protein kinase, and lubiprostone precluded responsiveness to the cAMP agonist forskolin. CFTR blockage by CFTRinh172, but not ClC-2 blockage by CdCl(2), inhibited the lubiprostone response. Lubiprostone induced a CdCl(2)-insensitive secretory response in mouse intestine, but failed to induce intestinal Cl(-) secretion in Cftr-null mice. Correspondingly, lubiprostone induced a secretory response in human intestinal epithelium, but not in tissue of CF patients. The EP(4)-type prostanoid receptor antagonist L-161,982 blocked the lubiprostone response in all 3 models studied. In T84 cells, lubiprostone induced a rise in cAMP levels that was sensitive to EP(4)-receptor blockage.
  
  
  CONCLUSIONS
  Lubiprostone enhances intestinal Cl(-) and fluid secretion via prostanoid receptor signaling, triggering activation of CFTR. Therefore, it is of limited use for treatment of CF-related intestinal disease.
authors.affiliation: Department of Biochemistry, Sophia Children's Hospital, Erasmus MC, Rotterdam, The Netherlands. m.bijvelds@erasmusmc.nl
authors.forename: Marcel J C
authors.initials: MJ
authors.lastname: Bijvelds
authors.forename: Alice G M
authors.initials: AG
authors.lastname: Bot
authors.forename: Johanna C
authors.initials: JC
authors.lastname: Escher
authors.forename: Hugo R
authors.initials: HR
authors.lastname: De Jonge
mesh_terms: D000328:Adult; D000527:Alprostadil / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D045744:Cell Line, Tumor; D002648:Child; D018118:Chloride Channels / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D003106:Colon / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007082:Ileum / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D017136:Ion Transport; D000068238:Lubiprostone; D008564:Membrane Potentials; D051379:Mice; D018345:Mice, Knockout; D018078:Receptors, Prostaglandin E / Q000037:antagonists & inhibitors / Q000378:metabolism; D058307:Receptors, Prostaglandin E, EP2 Subtype; D014407:Tumor Cells, Cultured
chemical_list: D018118:Chloride Channels; D002712:Chlorides; C545644:PTGER2 protein, human; C545645:Ptger2 protein, mouse; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D000068238:Lubiprostone; D002217:Carbachol; D000242:Cyclic AMP; D000527:Alprostadil