title: Intracellular pathways triggered by the selective FLT-1-agonist placental growth factor in vascular smooth muscle cells exposed to hypoxia.
abstract: We have previously shown that hypoxia makes vascular smooth muscle cells (VSMCs) responsive to placental growth factor (PlGF) through the induction of functional fms-like tyrosine kinase (Flt-1) receptors. The aim of this study was to investigate the molecular mechanisms involved in the PlGF effects on proliferation and contraction of VSMCs previously exposed to hypoxia (3% O2). In cultured rat VSMCs exposed to hypoxia, PlGF increased the phosphorylation of protein kinase B (Akt), p38 and STAT3; activation of STAT3 was higher than that of other kinases. In agreement with this finding, the proliferation of hypoxia-treated VSMCs in response to PlGF was significantly impaired by the p38 and the phosphatidylinositol 3-kinase inhibitors SB202190 and LY294002, respectively, and was almost completely prevented by AG490, a janus tyrosine kinase (JAK)/signal transducer and activator of transcription (STAT) inhibitor. Since hypoxia was able to reverse the vasorelaxant effect of PlGF into a vasoconstrictor response, the mechanism of this latter effect was also investigated. Significant Flt-1 activity was measured in isolated preparations from rat aorta exposed to hypoxia. Inhibitors of mitogen-activated protein kinase kinase, Akt and STAT3 induced a modest inhibition of the vasoconstrictor response to PlGF, while the p38 inhibitor SB202190 markedly impaired the PlGF-induced contractile response. These effects were selectively mediated by Flt-1 without any involvement of foetal liver kinase-1 receptors. These data are the first evidence that different intracellular pathways activated by Flt-1 receptor in VSMCs are involved in diverse biological effects of PlGF: while mitogen activated protein kinase kinase/extracellular signal regulated kinase(1/2) and JAK/STAT play a role in VSMC proliferation, p38 is involved in VSMC contraction. These findings may highlight the role of PlGF in vascular pathology.
authors.affiliation: Laboratory of Vascular Pharmacology, Department of Preclinical and Clinical Pharmacology, University of Florence, Viale G. Pieraccini, 50139, Florence, Italy.
authors.forename: Lydia
authors.initials: L
authors.lastname: Bellik
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Vinci
authors.forename: Sandra
authors.initials: S
authors.lastname: Filippi
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Ledda
authors.forename: Astrid
authors.initials: A
authors.lastname: Parenti
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015687:Cell Hypoxia; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D000072483:Placenta Growth Factor; D011257:Pregnancy Proteins / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D020032:Tyrphostins / Q000494:pharmacology; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000187:drug effects* / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D002867:Chromones; D007093:Imidazoles; D009025:Morpholines; C000608038:Pgf protein, rat; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011257:Pregnancy Proteins; D011725:Pyridines; D050796:STAT3 Transcription Factor; C494088:Stat3 protein, rat; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D000072483:Placenta Growth Factor; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C501164:Flt1 protein, rat; D040281:Vascular Endothelial Growth Factor Receptor-1; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole