title: The transmembrane protein 16A Ca(2+)-activated Cl- channel in airway smooth muscle contributes to airway hyperresponsiveness.
abstract: BACKGROUND
  Asthma is a chronic inflammatory disorder with a characteristic of airway hyperresponsiveness (AHR). Ca(2+)-activated Cl(-) [Cl((Ca))] channels are inferred to be involved in AHR, yet their molecular nature and the cell type they act within to mediate this response remain unknown.
  
  
  OBJECTIVE
  Transmembrane protein 16A (TMEM16A) and TMEM16B are Cl((Ca)) channels, and activation of Cl((Ca)) channels in airway smooth muscle (ASM) contributes to agonist-induced airway contraction. We hypothesized that Tmem16a and/or Tmem16b encode Cl((Ca)) channels in ASM and mediate AHR.
  
  
  METHODS
  We assessed the expression of the TMEM16 family, and the effects of niflumic acid and benzbromarone on AHR and airway contraction, in an ovalbumin-sensitized mouse model of chronic asthma. We also cloned TMEM16A from ASM and examined the Cl(-) currents it produced in HEK293 cells. We further studied the impacts of TMEM16A deletion on Ca(2+) agonist-induced cell shortening, and on Cl((Ca)) currents activated by Ca(2+) sparks (localized, short-lived Ca(2+) transients due to the opening of ryanodine receptors) in mouse ASM cells.
  
  
  RESULTS
  TMEM16A, but not TMEM16B, is expressed in ASM cells and its expression in these cells is up-regulated in ovalbumin-sensitized mice. Niflumic acid and benzbromarone prevent AHR and contraction evoked by methacholine in ovalbumin-sensitized mice. TMEM16A produces Cl((Ca)) currents with kinetics similar to native Cl((Ca)) currents. TMEM16A deletion renders Ca(2+) sparks unable to activate Cl((Ca)) currents, and weakens caffeine- and methacholine-induced cell shortening.
  
  
  CONCLUSIONS
  Tmem16a encodes Cl((Ca)) channels in ASM and contributes to Ca(2+) agonist-induced contraction. In addition, up-regulation of TMEM16A and its augmented activation contribute to AHR in an ovalbumin-sensitized mouse model of chronic asthma. TMEM16A may represent a potential therapeutic target for asthma.
authors.affiliation: Model Animal Research Center, Nanjing University, Nanjing, China.
authors.forename: Cheng-Hai
authors.initials: CH
authors.lastname: Zhang
authors.forename: Yinchuan
authors.initials: Y
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Lifshitz
authors.forename: Hequan
authors.initials: H
authors.lastname: Li
authors.forename: Brian D
authors.initials: BD
authors.lastname: Harfe
authors.forename: Min-Sheng
authors.initials: MS
authors.lastname: Zhu
authors.forename: Ronghua
authors.initials: R
authors.lastname: ZhuGe
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000075369:Anoctamin-1; D001249:Asthma / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D015153:Blotting, Western / Q000379:methods; D016535:Bronchial Hyperreactivity / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D018408:Patch-Clamp Techniques / Q000379:methods; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D015854:Up-Regulation / Q000235:genetics
chemical_list: C531181:ANO1 protein, mouse; D000075369:Anoctamin-1; D018118:Chloride Channels