title: Mechanisms of airway smooth muscle relaxation induced by beta2-adrenergic agonists.
abstract: 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.
authors.affiliation: Department of Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
authors.forename: Philippe
authors.initials: P
authors.lastname: Delmotte
authors.forename: Anna-Rebekka
authors.initials: AR
authors.lastname: Ressmeyer
authors.forename: Yan
authors.initials: Y
authors.lastname: Bai
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sanderson
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D008168:Lung / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D043263:Myosin-Light-Chain Phosphatase / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D000318:Adrenergic beta-Agonists; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019837:Ryanodine Receptor Calcium Release Channel; D009569:Nitric Oxide; D054460:rho-Associated Kinases; D009219:Myosin-Light-Chain Kinase; D043263:Myosin-Light-Chain Phosphatase; D009218:Myosins; D002118:Calcium