Role of contractile prostaglandins and Rho-kinase in growth factor-induced airway smooth muscle contraction.
BACKGROUND
In addition to their proliferative and differentiating effects, several growth factors are capable of inducing a sustained airway smooth muscle (ASM) contraction. These contractile effects were previously found to be dependent on Rho-kinase and have also been associated with the production of eicosanoids. However, the precise mechanisms underlying growth factor-induced contraction are still unknown. In this study we investigated the role of contractile prostaglandins and Rho-kinase in growth factor-induced ASM contraction.


METHODS
Growth factor-induced contractions of guinea pig open-ring tracheal preparations were studied by isometric tension measurements. The contribution of Rho-kinase, mitogen-activated protein kinase (MAPK) and cyclooxygenase (COX) to these reponses was established, using the inhibitors Y-27632 (1 microM), U-0126 (3 microM) and indomethacin (3 microM), respectively. The Rho-kinase dependency of contractions induced by exogenously applied prostaglandin F2alpha (PGF2alpha) and prostaglandin E2 (PGE2) was also studied. In addition, the effects of the selective FP-receptor antagonist AL-8810 (10 microM) and the selective EP1-antagonist AH-6809 (10 microM) on growth factor-induced contractions were investigated, both in intact and epithelium-denuded preparations. Growth factor-induced PGF2alpha-and PGE2-release in the absence and presence of Y-27632, U-0126 and indomethacin, was assessed by an ELISA-assay.


RESULTS
Epidermal growth factor (EGF)-and platelet-derived growth factor (PDGF)-induced contractions of guinea pig tracheal smooth muscle preparations were dependent on Rho-kinase, MAPK and COX. Interestingly, growth factor-induced PGF2alpha-and PGE2-release from tracheal rings was significantly reduced by U-0126 and indomethacin, but not by Y-27632. Also, PGF2alpha-and PGE2-induced ASM contractions were largely dependent on Rho-kinase, in contrast to other contractile agonists like histamine. The FP-receptor antagonist AL-8810 (10 microM) significantly reduced (approximately 50 %) and the EP1-antagonist AH-6809 (10 microM) abrogated growth factor-induced contractions, similarly in intact and epithelium-denuded preparations.


CONCLUSIONS
The results indicate that growth factors induce ASM contraction through contractile prostaglandins - not derived from the epithelium - which in turn rely on Rho-kinase for their contractile effects.
Schaafsma
Dedmer
D
Department of Molecular Pharmacology, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands. d.schaafsma@rug.nl
Gosens
Reinoud
R
Bos
I Sophie T
IS
Meurs
Herman
H
Zaagsma
Johan
J
Nelemans
S Adriaan
SA
D000818:Animals; D003285:Contractile Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000008:administration & dosage*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D010982:Platelet-Derived Growth Factor / Q000008:administration & dosage*; D011453:Prostaglandins / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013314:Stress, Mechanical; D014132:Trachea / Q000187:drug effects / Q000502:physiology*; D054460:rho-Associated Kinases
D003285:Contractile Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010982:Platelet-Derived Growth Factor; D011453:Prostaglandins; D004815:Epidermal Growth Factor; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases