Role of Rho-kinase in maintaining airway smooth muscle contractile phenotype.
This study aims to investigate the role of Rho-kinase in phenotype switching and proliferation of bovine tracheal smooth muscle. To induce different phenotypic states, bovine tracheal smooth muscle strips were cultured (8 days) in 10% foetal bovine serum (foetal bovine serum, less contractile phenotype) or insulin (1 microM, hypercontractile phenotype) and compared to strips cultured in serum-free medium. In contraction experiments, the Rho-kinase inhibitor (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexane carboxamide (Y-27632, 1 microM) decreased sensitivity to methacholine and KCl and lowered maximal responsiveness to KCl in all strips irrespective of the phenotype present. To investigate the effects of Rho-kinase bovine tracheal smooth muscle phenotypic regulation, strips were pretreated with Y-27632 (1 microM) for 8 days. This resulted in a decreased maximal contractility to both methacholine and KCl, quantitatively comparable to the decrease in contractility induced by platelet-derived growth factor (PDGF, 10 ng/ml). The combination of Y-27632 and PDGF responded additively. Y-27632 did not affect basal or PDGF-induced bovine tracheal smooth muscle cell proliferation, determined both as increases in [3H]thymidine incorporation and cell number. Inhibitors of the p42/p44 mitogen-activated protein kinase (MAPK) pathway, the p38 MAPK pathway and the phosphatidyl inositol (PI) 3-kinase pathway all inhibited PDGF-induced proliferation and phenotype changes. These results show that the functional contribution of Rho-kinase to bovine tracheal smooth muscle contraction is not dependent on phenotypic state. In addition, Rho-kinase is not involved in phenotypic modulation or proliferation induced by PDGF, whereas p42/p44 MAPK, p38 MAPK and PI 3-kinase are. Rho-kinase is, however, a major regulator involved in the basal maintenance of contractility in bovine tracheal smooth muscle.
Gosens
Reinoud
R
Department of Molecular Pharmacology, University Centre for Pharmacy, A. Deusinglaan 1, 9713 AV, Groningen, The Netherlands. R.Gosens@farm.rug.nl
Schaafsma
Dedmer
D
Meurs
Herman
H
Zaagsma
Johan
J
Nelemans
S Adriaan
SA
D000818:Animals; D001993:Bronchodilator Agents / Q000494:pharmacology; D002417:Cattle; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D007537:Isometric Contraction; D016210:Methacholine Chloride / Q000494:pharmacology; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D010641:Phenotype; D011189:Potassium Chloride / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D013778:Tetrazolium Salts; D013844:Thiazoles; D013936:Thymidine / Q000378:metabolism; D014132:Trachea / Q000187:drug effects / Q000502:physiology*; D054460:rho-Associated Kinases
D001993:Bronchodilator Agents; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D013778:Tetrazolium Salts; D013844:Thiazoles; D016210:Methacholine Chloride; D011189:Potassium Chloride; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; C022616:thiazolyl blue; D013936:Thymidine