title: Epithelium-dependent modulation of responsiveness of airways from caveolin-1 knockout mice is mediated through cyclooxygenase-2 and 5-lipoxygenase.
abstract: OBJECTIVE
  Acute silencing of caveolin-1 (Cav-1) modulates receptor-mediated contraction of airway smooth muscle. Moreover, COX-2- and 5-lipoxygenase (5-LO)-derived prostaglandin and leukotriene biosynthesis can influence smooth muscle reactivity. COX-2 half-life can be prolonged through association with Cav-1. We suggested that lack of Cav-1 modulated levels of COX-2 which in turn modulated tracheal contraction, when arachidonic acid signalling was disturbed by inhibition of COX-2.
  
  
  METHODS
  Using tracheal rings from Cav-1 knockout (KO) and wild-type mice (B6129SF2/J), we measured isometric contractions to methacholine and used PCR, immunoblotting and immunohistology to monitor expression of relevant proteins.
  
  
  RESULTS
  Tracheal rings from Cav-1 KO and wild-type mice exhibited similar responses, but the COX-2 inhibitor, indomethacin, increased responses of tracheal rings from Cav-1 KO mice to methacholine. The phospholipase A₂ inhibitor, eicosatetraynoic acid, which inhibits formation of both COX-2 and 5-LO metabolites, had no effect on wild-type or Cav-1 KO tissues. Indomethacin-mediated hyperreactivity was ablated by the LTD₄ receptor antagonist (montelukast) and 5-LO inhibitor (zileuton). The potentiating effect of indomethacin on Cav-1 KO responses to methacholine was blocked by epithelial denudation. Immunoprecipitation showed that COX-2 binds Cav-1 in wild-type lungs. Immunoblotting and qPCR revealed elevated levels of COX-2 and 5-LO protein, but not COX-1, in Cav-1 KO tracheas, a feature that was prevented by removal of the epithelium.
  
  
  CONCLUSIONS
  The indomethacin-induced hypercontractility observed in Cav-1 KO tracheas was linked to increased expression of COX-2 and 5-LO, which probably enhanced arachidonic acid shunting and generation of pro-contractile leukotrienes when COX-2 was inhibited.
authors.affiliation: Department of Physiology, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Pawan
authors.initials: P
authors.lastname: Sharma
authors.forename: Min H
authors.initials: MH
authors.lastname: Ryu
authors.forename: Sujata
authors.initials: S
authors.lastname: Basu
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Maltby
authors.forename: Behzad
authors.initials: B
authors.lastname: Yeganeh
authors.forename: Mark M
authors.initials: MM
authors.lastname: Mutawe
authors.forename: Richard W
authors.initials: RW
authors.lastname: Mitchell
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Halayko
mesh_terms: D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D016718:Arachidonic Acid / Q000378:metabolism; D016535:Bronchial Hyperreactivity / Q000473:pathology; D016084:Bronchoconstriction / Q000187:drug effects; D051242:Caveolin 1 / Q000235:genetics*; D051546:Cyclooxygenase 2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D047468:Immunoprecipitation; D007213:Indomethacin / Q000494:pharmacology*; D016210:Methacholine Chloride / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D014132:Trachea / Q000187:drug effects / Q000378:metabolism
chemical_list: D051242:Caveolin 1; D016861:Cyclooxygenase Inhibitors; D016210:Methacholine Chloride; D016718:Arachidonic Acid; D001094:Arachidonate 5-Lipoxygenase; D051546:Cyclooxygenase 2; D007213:Indomethacin