title: ATP release triggered by activation of the Ca2+-activated K+ channel in human airway Calu-3 cells.
abstract: Airway mucociliary clearance is subject to the autocrine/paracrine regulation of extracellular nucleotides released from the airway epithelial cells. The present study was performed in pursuit of effective modulators of ATP release under physiologic conditions in polarized human airway epithelial cells (Calu-3). Neither isoproterenol, forskolin, nor ionomycin augmented extracellular ATP release detected by luciferase assay. However, direct activation of the human intermediate conductance, Ca(2+)-activated K(+) channel (hIK-1) by 1-ethyl-2-benzimdazolinone (1-EBIO, 1 mM) and chlorzoxazone (CZ, 1 mM) increased ATP release predominantly in the apical compartment. Measurement of fluo-3 signals revealed that 1-EBIO- and CZ-stimulated cytosolic Ca(2+) mobilization was suppressed by the presence of MRS-2179, a specific P2Y(1) receptor antagonist. The hIK-1-mediated ATP release was inhibited by a hIK-1 blocker (charybdotoxin), and an Na(+)-K(+)-2Cl(-) cotransport blocker (bumetanide) without interruption by GdCl(3), an inhibitor of stretch-activated nonselective cation (SA) channels, or glybenclamide, a blocker of the cystic fibrosis transmembrane conductance regulator (CFTR). These results suggest that a cell volume decrease via the hIK-1-mediated KCl loss and the resultant induction of a regulatory volume increase via the Na(+)-K(+)-2Cl(-) transporter may trigger release of ATP, which causes P2Y(1)-mediated Ca(2+) mobilization, through mechanisms unrelated to the CFTR and SA channels.
authors.affiliation: Division of Respiratory Diseases, Department of Internal Medicine, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan. itoyasu@med.nagoya-u.ac.jp
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ito
authors.forename: Masami
authors.initials: M
authors.lastname: Son
authors.forename: Shinji
authors.initials: S
authors.lastname: Sato
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Masashi
authors.initials: M
authors.lastname: Kondo
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Nakayama
authors.forename: Kaoru
authors.initials: K
authors.lastname: Shimokata
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kume
mesh_terms: D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001562:Benzimidazoles / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D048429:Cell Size; D018999:Charybdotoxin / Q000494:pharmacology; D002753:Chlorzoxazone / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors; D003600:Cytosol / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D011189:Potassium Chloride / Q000378:metabolism; D058919:Purinergic P2 Receptor Antagonists; D058472:Receptors, Purinergic P2Y1
chemical_list: D001562:Benzimidazoles; C505032:CFTR protein, human; C111914:N(6)-methyl-2'-deoxyadenosine 3',5'-diphosphate; C546382:P2RY1 protein, human; D024681:Potassium Channels, Calcium-Activated; D058919:Purinergic P2 Receptor Antagonists; D058472:Receptors, Purinergic P2Y1; D002034:Bumetanide; D018999:Charybdotoxin; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D015759:Ionomycin; D000244:Adenosine Diphosphate; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D008156:Luciferases; D002753:Chlorzoxazone; D007545:Isoproterenol; C102635:1-ethyl-2-benzimidazolinone; D005905:Glyburide; D002118:Calcium