title: Platelet-activating factor induces ovine fetal pulmonary venous smooth muscle cell proliferation: role of epidermal growth factor receptor transactivation.
abstract: We have previously reported that platelet-activating factor (PAF) is present in very high levels in the ovine fetal lung and circulation and that PAF serves as an important physiological vasoconstrictor of the pulmonary circulation in utero. However, it is not known whether PAF stimulates pulmonary vascular smooth muscle cell (SMC) proliferation. In this study, we used ovine fetal pulmonary venous SMCs as our model system to study the effects and mechanisms of action of PAF on SMC proliferation. We found that PAF induced SMC proliferation in a dose-dependent manner. PAF also stimulated activation of both ERK and p38 but not c-Jun NH(2) terminal kinase (JNK) mitogen-activated protein (MAP) kinase pathways. PAF (10 nM) induced phosphorylation of epidermal growth factor receptor (EGFR). Specific inhibition of EGFR by AG-1478 and by the expression of a dominant-negative EGFR mutant in SMCs attenuated PAF-stimulated cell proliferation. Inhibition of heparin-binding EGF-like growth factor (HB-EGF) release by CRM-197 and inhibition of matrix metalloproteinases (MMP) by GM-6001 abolished PAF-induced MAP kinase activation and cell proliferation. Increased alkaline phosphatase (AP) activity after PAF treatment in AP-HB-EGF fusion construct-transfected SMCs indicated that PAF induced the release of HB-EGF within 1 min. Gelatin zymography data showed that PAF stimulated MMP-2 activity and MMP-9 activity within 1 min. These results suggest that PAF promotes pulmonary vascular SMC proliferation via transactivation of EGFR through MMP activation and HB-EGF, resulting in p38 and ERK activation and that EGFR transactivation is essential for the mitogenic effect of PAF in pulmonary venous SMC.
authors.affiliation: Division of Neonatology, Harbor-University of California, Los Angeles (UCLA) Medical Center, Los Angeles Biomedical Institute, 1124 West Carson St., Torrance, CA 90502, USA. wzhou@labiomed.org
authors.forename: Weilin
authors.initials: W
authors.lastname: Zhou
authors.forename: Basil O
authors.initials: BO
authors.lastname: Ibe
authors.forename: J Usha
authors.initials: JU
authors.lastname: Raj
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism*; D066246:ErbB Receptors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D009154:Mutation; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000378:metabolism* / Q000494:pharmacology; D011667:Pulmonary Veins / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D011799:Quinazolines; D012756:Sheep; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D020032:Tyrphostins / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004151:Dipeptides; D004791:Enzyme Inhibitors; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D061965:Matrix Metalloproteinase Inhibitors; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D010972:Platelet Activating Factor; D011799:Quinazolines; D020032:Tyrphostins; C028581:CRM197 (non-toxic variant of diphtheria toxin); C101044:RTKI cpd; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9