title: Roles of stretch-activated cation channel and Rho-kinase in the spontaneous contraction of airway smooth muscle.
abstract: In guinea pigs, it is well-known that mechanical stretch of airway smooth muscle exhibits spontaneous tone which is mediated by cyclooxygenase (COX) activation. We tested the hypothesis that this spontaneous contraction of airway smooth muscle is mediated by stretch-activated non-selective cation channels and the Rho/Rho-kinase pathway, as well as COX-2 using a pharmacological approach. Isometric force and intracellular Ca(2+) concentrations ([Ca(2+)](i)) were assessed in isolated guinea pig tracheal smooth muscle tissues. The samples were stretched to a given level and the muscle behavior was monitored under isometric conditions. We observed an increase in [Ca(2+)](i) and subsequent force generation over a 15-min period. The augmented [Ca(2+)](i) and spontaneous contraction due to the stretch were markedly attenuated by application of Gd(3+), an inhibitor of stretch-activated channels, and removal of extracellular Ca(2+). In contrast, nifedipine only had a mild inhibitory effect on the contraction. (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexane-carboxamide (Y-27632; a Rho-kinase inhibitor) abolished the spontaneous contraction with no changes in [Ca(2+)](i). Simvastatin, which down-regulates Rho activity, also significantly inhibited the contraction. Moreover, indomethacin, an inhibitor of COX-1 and -2, and N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide (NS-398; a COX-2 inhibitor) abolished the stretch-induced contraction without affecting [Ca(2+)](i), whereas the inhibitory effect of 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole (SC560; a COX-1 inhibitor) on the contraction was much less. These findings demonstrated that Ca(2+) entry via stretch-activated channels, the Rho/Rho-kinase pathway, and COX-2 are involved in the mechanotransduction in guinea pig tracheal smooth muscle. Additionally, while the Rho/Rho-kinase pathway and COX-2 regulate the spontaneous contraction independently of [Ca(2+)](i), COX-1 is not involved in the stretch-induced force generation.
authors.affiliation: Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Ito
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kume
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Oguma
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ito
authors.forename: Masashi
authors.initials: M
authors.lastname: Kondo
authors.forename: Kaoru
authors.initials: K
authors.lastname: Shimokata
authors.forename: Béla
authors.initials: B
authors.lastname: Suki
authors.forename: Keiji
authors.initials: K
authors.lastname: Naruse
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000502:physiology; D002412:Cations / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005682:Gadolinium / Q000494:pharmacology; D006168:Guinea Pigs; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000502:physiology*; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D009578:Nitrobenzenes / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D019821:Simvastatin / Q000494:pharmacology; D013314:Stress, Mechanical; D013449:Sulfonamides / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D054460:rho-Associated Kinases
chemical_list: D000577:Amides; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002412:Cations; D016861:Cyclooxygenase Inhibitors; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D007473:Ion Channels; D009578:Nitrobenzenes; D011720:Pyrazoles; D011725:Pyridines; C115461:SC 560; D013449:Sulfonamides; D016210:Methacholine Chloride; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; C108830:Y 27632; D019821:Simvastatin; D005682:Gadolinium; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D009543:Nifedipine; D002118:Calcium; D007213:Indomethacin