title: Direct effects of hydrogen peroxide on airway smooth muscle tone: roles of Ca2+ influx and Rho-kinase.
abstract: Reactive oxidant species are implicated in the chronic airway inflammation related to asthma and chronic obstructive pulmonary disease. This study was designed to determine mechanisms underlying contraction induced by hydrogen peroxide (H(2)O(2)), a clinical marker of oxidative stress, in airway smooth muscle. Isometric tension and fluorescent intensities of fura-2, an index of intracellular Ca(2+) concentrations ([Ca(2+)](i)), were measured in epithelium-denuded tracheal smooth muscle tissues isolated from guinea pigs. H(2)O(2) (0.01-1 mM) caused contraction with an augmentation of [Ca(2+)](i) in a concentration-dependent manner in the normal physiological solution containing 2.4 mM of extracellular Ca(2+) concentrations. The contractile force and [Ca(2+)](i) by H(2)O(2) (1 mM) were approximately half of those in response to 1 microM methacholine. However, contraction by H(2)O(2) was not generated under the condition that extracellular Ca(2+) concentrations were less than 0.15 mM. Verapamil (10 microM), an inhibitor of voltage-operated Ca(2+) channels, partially but significantly inhibited the H(2)O(2)-induced contraction. In contrast, SKF-96365 (1-{beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl}-1H-imidazole hydrochloride) (100 microM), a non-selective inhibitor of Ca(2+) channels, completely abolished both the contraction and the increase in [Ca(2+)](i) elicited by H(2)O(2). Moreover, Y-27632 ((R)-(+)-trans-N-(4-Pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide) (0.03-10 microM), an inhibitor of Rho-kinase, caused a concentration-dependent inhibition of the H(2)O(2)-induced contraction. In conclusion, both the Ca(2+) influx from the extracellular side and the Ca(2+) sensitization by Rho-kinase are involved in the regulation of airway smooth muscle tone induced by H(2)O(2). An inhibition of the Rho/Rho-kinase pathway may be beneficial for the treatment of airflow limitation mediated by oxidative stress.
authors.affiliation: Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kojima
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kume
authors.forename: Satoru
authors.initials: S
authors.lastname: Ito
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Oguma
authors.forename: Akira
authors.initials: A
authors.lastname: Shiraki
authors.forename: Masashi
authors.initials: M
authors.lastname: Kondo
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ito
authors.forename: Kaoru
authors.initials: K
authors.lastname: Shimokata
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004848:Epithelium / Q000502:physiology; D006168:Guinea Pigs; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D009129:Muscle Tonus / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D018384:Oxidative Stress; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D014132:Trachea / Q000187:drug effects / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology; D054460:rho-Associated Kinases
chemical_list: D000577:Amides; D016085:Bronchoconstrictor Agents; D002121:Calcium Channel Blockers; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; D016210:Methacholine Chloride; C108830:Y 27632; D006861:Hydrogen Peroxide; D014700:Verapamil; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium