title: Lubiprostone activates non-CFTR-dependent respiratory epithelial chloride secretion in cystic fibrosis mice.
abstract: Periciliary fluid balance is maintained by the coordination of sodium and chloride channels in the apical membranes of the airways. In the absence of the cystic fibrosis transmembrane regulator (CFTR), chloride secretion is diminished and sodium reabsorption exaggerated. ClC-2, a pH- and voltage-dependent chloride channel, is present on the apical membranes of airway epithelial cells. We hypothesized that ClC-2 agonists would provide a parallel pathway for chloride secretion. Using nasal potential difference (NPD) measurements, we quantified lubiprostone-mediated Cl(-) transport in sedated cystic fibrosis null (gut-corrected), C57Bl/6, and A/J mice during nasal perfusion of lubiprostone (a putative ClC-2 agonist). Baseline, amiloride-inhibited, chloride-free gluconate-substituted Ringer with amiloride and low-chloride Ringer plus lubiprostone (at increasing concentrations of lubiprostone) were perfused, and the NPD was continuously recorded. A clear dose-response relationship was detected in all murine strains. The magnitude of the NPD response to 20 muM lubiprostone was -5.8 +/- 2.1 mV (CF, n = 12), -8.1 +/- 2.6 mV (C57Bl/6 wild-type, n = 12), and -5.3 +/- 1.2 mV (AJ wild-type, n = 8). A cohort of ClC-2 knockout mice did not respond to 20 muM lubiprostone (n = 6, P = 0.27). In C57Bl/6 mice, inhibition of CFTR with topical application of CFTR inhibitor-172 did not abolish the lubiprostone response, thus confirming the response seen is independent of CFTR regulation. RT-PCR confirmed expression of ClC-2 mRNA in murine lung homogenate. The direct application of lubiprostone in the CF murine nasal airway restores nearly normal levels of chloride secretion in nasal epithelia.
authors.affiliation: Eudowood Division of Pediatric Respiratory Sciences, Johns Hopkins Medical Institutions, 200 N. Wolfe Street, Baltimore, MD 21287, USA.
authors.forename: Kelvin D
authors.initials: KD
authors.lastname: MacDonald
authors.forename: Karen R
authors.initials: KR
authors.lastname: McKenzie
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Henderson
authors.forename: Charles E
authors.initials: CE
authors.lastname: Hawkins
authors.forename: Neeraj
authors.initials: N
authors.lastname: Vij
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Zeitlin
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000287:Administration, Topical; D000527:Alprostadil / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D004848:Epithelium / Q000187:drug effects* / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D000068238:Lubiprostone; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012137:Respiratory System / Q000378:metabolism*; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism
chemical_list: D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D002712:Chlorides; D012333:RNA, Messenger; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000068238:Lubiprostone; D000255:Adenosine Triphosphate; D000527:Alprostadil