title: Antagonists of the TMEM16A calcium-activated chloride channel modulate airway smooth muscle tone and intracellular calcium.
abstract: BACKGROUND
  Perioperative bronchospasm refractory to β agonists continues to challenge anesthesiologists and intensivists. The TMEM16A calcium-activated chloride channel modulates airway smooth muscle (ASM) contraction. The authors hypothesized that TMEM16A antagonists would relax ASM contraction by modulating membrane potential and calcium flux.
  
  
  METHODS
  Human ASM, guinea pig tracheal rings, or mouse peripheral airways were contracted with acetylcholine or leukotriene D4 and then treated with the TMEM16A antagonists: benzbromarone, T16Ainh-A01, N-((4-methoxy)-2-naphthyl)-5-nitroanthranilic acid, or B25. In separate studies, guinea pig tracheal rings were contracted with acetylcholine and then exposed to increasing concentrations of isoproterenol (0.01 nM to 10 μM) ± benzbromarone. Plasma membrane potential and intracellular calcium concentrations were measured in human ASM cells.
  
  
  RESULTS
  Benzbromarone was the most potent TMEM16A antagonist tested for relaxing an acetylcholine -induced contraction in guinea pig tracheal rings (n = 6). Further studies were carried out to investigate the clinical utility of benzbromarone. In human ASM, benzbromarone relaxed either an acetylcholine- or a leukotriene D4-induced contraction (n = 8). Benzbromarone was also effective in relaxing peripheral airways (n = 9) and potentiating relaxation by β agonists (n = 5 to 10). In cellular mechanistic studies, benzbromarone hyperpolarized human ASM cells (n = 9 to 12) and attenuated intracellular calcium flux from both the plasma membrane and the sarcoplasmic reticulum (n = 6 to 12).
  
  
  CONCLUSIONS
  TMEM16A antagonists work synergistically with β agonists and through a novel pathway of interrupting ion flux at both the plasma membrane and sarcoplasmic reticulum to acutely relax human ASM.
authors.affiliation: From the Department of Anesthesiology, Columbia University, New York, New York (J.D., K.B., M.B.B., Y.Z., G.G., C.W.E.); Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, Texas (J.P.-Z.); and Department of Chemistry, Kurukshetra University, Kurukshetra, Haryana, India (S.K., P.K.S.).
authors.forename: Jennifer
authors.initials: J
authors.lastname: Danielsson
authors.forename: Jose
authors.initials: J
authors.lastname: Perez-Zoghbi
authors.forename: Kyra
authors.initials: K
authors.lastname: Bernstein
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Barajas
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Satish
authors.initials: S
authors.lastname: Kumar
authors.forename: Pawan K
authors.initials: PK
authors.lastname: Sharma
authors.forename: George
authors.initials: G
authors.lastname: Gallos
authors.forename: Charles W
authors.initials: CW
authors.lastname: Emala
mesh_terms: D000818:Animals; D000075369:Anoctamin-1; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002461:Cell Line, Transformed; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000502:physiology*; D006168:Guinea Pigs; D006801:Humans; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D009924:Organ Culture Techniques; D014132:Trachea / Q000187:drug effects / Q000502:physiology*
chemical_list: C476213:ANO1 protein, human; D000075369:Anoctamin-1; D002121:Calcium Channel Blockers; D018118:Chloride Channels; D009363:Neoplasm Proteins; D002118:Calcium