title: Chloride channel blockade relaxes airway smooth muscle and potentiates relaxation by β-agonists.
abstract: Severe bronchospasm refractory to β-agonists continues to cause significant morbidity and mortality in asthmatic patients. We questioned whether chloride channels/transporters are novel targets for the relaxation of airway smooth muscle (ASM). We have screened a library of compounds, derivatives of anthranilic and indanyloxyacetic acid, that were originally developed to antagonize chloride channels in the kidney. We hypothesized that members of this library would be novel calcium-activated chloride channel blockers for the airway. The initial screen of this compound library identified 4 of 20 compounds that relaxed a tetraethylammonium chloride-induced contraction in guinea pig tracheal rings. The two most effective compounds, compounds 1 and 13, were further studied for their potential to either prevent the initiation of or relax the maintenance phase of an acetylcholine (ACh)-induced contraction or to potentiate β-agonist-mediated relaxation. Both relaxed an established ACh-induced contraction in human and guinea pig ex vivo ASM. In contrast, the prevention of an ACh-induced contraction required copretreatment with the sodium-potassium-chloride cotransporter blocker bumetanide. The combination of compound 13 and bumetanide also potentiated relaxation by the β-agonist isoproterenol in guinea pig tracheal rings. Compounds 1 and 13 hyperpolarized the plasma cell membrane of human ASM cells and blocked spontaneous transient inward currents, a measure of chloride currents in these cells. These functional and electrophysiological data suggest that modulating ASM chloride flux is a novel therapeutic target in asthma and other bronchoconstrictive diseases.
authors.affiliation: Department of Anesthesiology, Columbia University, New York, New York; and jed9073@nyp.org.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Danielsson
authors.affiliation: Department of Anesthesiology, Columbia University, New York, New York; and.
authors.forename: Peter
authors.initials: P
authors.lastname: Yim
authors.affiliation: Department of Medicine, Columbia University, New York, New York.
authors.forename: Alison
authors.initials: A
authors.lastname: Rinderspacher
authors.affiliation: Department of Anesthesiology, Columbia University, New York, New York; and.
authors.forename: Xiao Wen
authors.initials: XW
authors.lastname: Fu
authors.affiliation: Department of Anesthesiology, Columbia University, New York, New York; and.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Medicine, Columbia University, New York, New York.
authors.forename: Donald W
authors.initials: DW
authors.lastname: Landry
authors.affiliation: Department of Anesthesiology, Columbia University, New York, New York; and.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Emala
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001249:Asthma / Q000188:drug therapy / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D019789:Tetraethylammonium / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects / Q000378:metabolism
chemical_list: D000318:Adrenergic beta-Agonists; D018118:Chloride Channels; D002712:Chlorides; D019789:Tetraethylammonium; D007545:Isoproterenol; D000109:Acetylcholine
keywords: NKCC; bumetanide; electrophysiology; niflumic acid; organ bath