Airway smooth muscle contributes to both contractility and inflammation in the pathophysiology of asthma and COPD. Airway smooth muscle cells can change the degree of a variety of functions, including contraction, proliferation, migration, and the secretion of inflammatory mediators (phenotype plasticity). Airflow limitation, airway hyperresponsiveness, β2-adrenergic desensitization, and airway remodeling, which are fundamental characteristic features of these diseases, are caused by phenotype changes in airway smooth muscle cells. Alterations between contractile and hyper-contractile, synthetic/proliferative phenotypes result from Ca2+ dynamics and Ca2+ sensitization. Modulation of Ca2+ dynamics through the large-conductance Ca2+-activated K+ channel/L-type voltage-dependent Ca2+ channel linkage and of Ca2+ sensitization through the RhoA/Rho-kinase pathway contributes not only to alterations in the contractile phenotype involved in airflow limitation, airway hyperresponsiveness, and β2-adrenergic desensitization but also to alteration of the synthetic/proliferative phenotype involved in airway remodeling. These Ca2+ signal pathways are also associated with synergistic effects due to allosteric modulation between β2-adrenergic agonists and muscarinic antagonists. Therefore, airway smooth muscle may be a target tissue in the therapy for these diseases. Moreover, the phenotype changing in airway smooth muscle cells with focuses on Ca2+ signaling may provide novel strategies for research and development of effective remedies against both bronchoconstriction and inflammation.
Keywords: Allosteric effect; Ca2+signaling; Large-conductance Ca2+-activated K+ channels; Phenotype change; Rho-kinase; β2-adrenergic receptors.