Open Access
Mechanisms of airway smooth muscle relaxation induced by beta2-adrenergic agonists
Philippe Delmotte1,Anna-Rebekka Ressmeyer1,Yan Bai1,Michael J Sanderson1
Department of Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
DOI: 10.2741/3644 Volume 15 Issue 2, pp.750-764
Published: 01 January 2010
(This article belongs to the Special Issue Beta2 agonists in airways disease: molecules to medicine)

Airway smooth muscle cell (ASMC) contraction is regulated by myosin phosphorylation to control actin-myosin cross-bridge activity. Myosin phosphorylation is determined by the antagonistic activity of myosin light chain (MLC) kinase (MLCK) and phosphatase (MLCP). MLCK activity is increased by increases in intracellular Ca2+ concentration ([Ca2+]i) associated with Ca2+ oscillations. MLCP activity is decreased by phosphorylation of MLCP or accessory proteins by kinases, including Rho-kinase or protein kinase C. During agonist-induced ASMC contraction, these 2 pathways are simultaneously activated. Because MLCP activity is often independent of [Ca2+]i, changes in MLCP activity can alter ASMC tone at a constant [Ca2+]i; a behavior termed Ca2+ sensitivity. In asthma, airway hyperresponsiveness (AHR) may result from an increase in the Ca2+-dependent contractile mechanisms and/or the Ca2+ sensitivity of ASMCs. Conversely, inhalation of beta2-adrenergic agonists induce airway relaxation by simultaneously slowing the Ca2+ oscillations and reducing the Ca2+ sensitivity of ASMCs. However, the action of beta2-adrenergic agonists varies with species. Consequently, the development of beta2-adrenergic agonists requires a characterization of their action in human airways.

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Philippe Delmotte, Anna-Rebekka Ressmeyer, Yan Bai, Michael J Sanderson. Mechanisms of airway smooth muscle relaxation induced by beta2-adrenergic agonists. Frontiers in Bioscience-Landmark. 2010. 15(2); 750-764.