title: Store-operated calcium entry is required for sustained contraction and Ca2+oscillations of airway smooth muscle.
abstract: Airway hyper-responsiveness in asthma is driven by excessive contraction of airway smooth muscle cells (ASMCs). Agonist-induced Ca2+oscillations underlie this contraction of ASMCs and the magnitude of this contraction is proportional to the Ca2+oscillation frequency. Sustained contraction and Ca2+oscillations require an influx of extracellular Ca2+, although the mechanisms and pathways mediating this Ca2+influx during agonist-induced ASMC contraction are not well defined. By inhibiting store-operated calcium entry (SOCE) or voltage-gated Ca2+channels (VGCCs), we show that SOCE, rather than Ca2+influx via VGCCs, provides the major Ca2+entry pathway into ASMCs to sustain ASMCs contraction and Ca2+oscillations. SOCE may therefore serve as a potential target for new bronchodilators to reduce airway hyper-responsiveness in asthma.
  
  
  
  Asthma is characterized by airway hyper-responsiveness: the excessive contraction of airway smooth muscle. The extent of this airway contraction is proportional to the frequency of Ca2+oscillations within airway smooth muscle cells (ASMCs). Sustained Ca2+oscillations require a Ca2+influx to replenish Ca2+losses across the plasma membrane. Our previous studies implied store-operated calcium entry (SOCE) as the major pathway for this Ca2+influx. In the present study, we explore this hypothesis, by examining the effects of SOCE inhibitors (GSK7975A and GSK5498A) as well as L-type voltage-gated Ca2+channel inhibitors (nifedipine and nimodipine) on airway contraction and Ca2+oscillations and SOCE-mediated Ca2+influx in ASMCs within mouse precision-cut lung slices. We found that both GSK7975A and GSK5498A were able to fully relax methacholine-induced airway contraction by abolishing the Ca2+oscillations, in a manner similar to that observed in zero extracellular Ca2+([Ca2+]e). In addition, GSK7975A and GSK5498A inhibited increases in intracellular Ca2+([Ca2+]i) in ASMCs with depleted Ca2+-stores in response to increased [Ca2+]e, demonstrating a response consistent with the inhibition of SOCE. However, GSK7975A and GSK5498A did not reduce Ca2+release via IP3receptors stimulated with IP3released from caged-IP3. By contrast, nifedipine and nimodipine only partially reduced airway contraction, Ca2+oscillation frequency and SOCE-mediated Ca2+influx. These data suggest that SOCE is the major Ca2+influx pathway for ASMCs with respect to sustaining agonist-induced airway contraction and the underlying Ca2+oscillations. The mechanisms of SOCE may therefore form novel targets for new bronchodilators.
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sanderson
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D005260:Female; D008168:Lung / Q000502:physiology*; D016210:Methacholine Chloride / Q000494:pharmacology; D008807:Mice, Inbred BALB C; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D009553:Nimodipine / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology
chemical_list: C583715:2,6-difluoro-N-(1-(2-fluoro-6-(trifluoromethyl)benzyl)-1H-pyrazol-3-yl)benzamide; C583716:2,6-difluoro-N-(1-(4-hydroxy-2-(trifluoromethyl)benzyl)-1H-pyrazol-3-yl)benzamide; D001549:Benzamides; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D011720:Pyrazoles; D016210:Methacholine Chloride; D009553:Nimodipine; D009543:Nifedipine; D002118:Calcium
keywords: Inositol trisphosphate receptor; airway smooth muscle cells; asthma; calcium oscillations; mouse precision cut lung slices (PCLS); store-operated calcium entry (SOCE); voltage-gated calcium channels (VGCCs)