title: Relaxation of contracted rabbit tracheal and human bronchial smooth muscle by Y-27632 through inhibition of Ca2+ sensitization.
abstract: The mechanism of Ca2+ sensitization of contraction has not been elucidated in airway smooth muscle (SM). To determine the role of a small G protein, rhoA p21, and its target protein, rho-associated coiled coil-forming protein kinase (ROCK), in receptor-coupled Ca2+ sensitization of airway SM, we studied the effect of (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexane carboxamide dihydrochloride, monohydrate (Y-27632), a ROCK inhibitor, on isometric contractions in rabbit tracheal and human bronchial SM. Y-27632 completely reversed 1 microM carbachol (CCh)-induced contraction of intact trachea with a concentration producing half-maximum inhibition of effect (IC50) of 1.29 +/- 0.2 microM (n = 5). Although 4beta-phorbol 12,13-dibutyrate (1 microM)-induced Ca2+ sensitization was relatively resistant to Y-27632 in alpha-toxin-permeabilized trachea, CCh (100 microM) plus guanosine triphosphate (GTP) (3 microM)- and guanosine 5'-O-(3'-thiotriphosphate) (10 microM)-induced contractions were relaxed completely by Y-27632 with IC50 of 1.44 +/- 0.3 (n = 6) and 1.15 +/- 0.3 microM (n = 6). Endothelin-1 (1 microM) plus GTP (3 microM)- developed force was also reversed by Y-27632 with IC50 of 4. 10 +/- 1.1 microM (n = 6) in the alpha-toxin-permeabilized bronchus. Both the rabbit and human SM expressed rhoA p21, ROCK I, and its isoform ROCK II. Collectively, rho/ROCK-mediated Ca2+ sensitization plays a central role in the sustained phase of airway SM contraction, and selective inhibition of this pathway may become a new strategy to resolve airflow limitation in asthma.
authors.affiliation: First Department of Internal Medicine, Faculty of Medicine, School of Medicine, Gunma University, Maebashi, Gunma, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Yoshii
authors.forename: K
authors.initials: K
authors.lastname: Iizuka
authors.forename: K
authors.initials: K
authors.lastname: Dobashi
authors.forename: T
authors.initials: T
authors.lastname: Horie
authors.forename: T
authors.initials: T
authors.lastname: Harada
authors.forename: T
authors.initials: T
authors.lastname: Nakazawa
authors.forename: M
authors.initials: M
authors.lastname: Mori
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology*; D000818:Animals; D001980:Bronchi / Q000378:metabolism*; D002118:Calcium / Q000037:antagonists & inhibitors*; D002217:Carbachol / Q000494:pharmacology; D018678:Cholinergic Agents / Q000494:pharmacology; D003902:Detergents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008387:Marine Toxins; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D017830:Octoxynol / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D011817:Rabbits; D015398:Signal Transduction; D014132:Trachea / Q000378:metabolism*; D010738:Type C Phospholipases / Q000494:pharmacology; D054460:rho-Associated Kinases
chemical_list: D000577:Amides; D018678:Cholinergic Agents; D003902:Detergents; D019332:Endothelin-1; D047908:Intracellular Signaling Peptides and Proteins; D008387:Marine Toxins; D010080:Oxazoles; D010726:Phosphodiesterase Inhibitors; D011725:Pyridines; C108830:Y 27632; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C059041:calyculin A; D002217:Carbachol; D017830:Octoxynol; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D009219:Myosin-Light-Chain Kinase; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine