title: Angiotensin II-induced process of angiogenesis is mediated by spleen tyrosine kinase via VEGF receptor-1 phosphorylation.
abstract: Spleen tyrosine kinase (Syk), expressed in endothelial cells, has been implicated in migration and proliferation and in vasculogenesis. This study was conducted to determine the contribution of Syk and the underlying mechanism to the angiogenic effect of ANG II and VEGF. Angiogenesis was determined by tube formation from the endothelial cell line EA.hy926 (EA) and human umbilical vein endothelial cells (HUVECs) and microvessel sprouting in rat aortic rings. ANG II (10 nM), EGF (30 ng/ml), and VEGF (50 ng/ml) stimulated EA cells and HUVECs to form tubular networks and increased aortic sprouting; these effects were blocked by VEGF receptor-1 and Flt-1 antibody (Flt-1/Fc) but not by the VEGF receptor-2 (Flk-1) antagonist SU-1498. ANG II increased the phosphorylation of Flt-1 but not Flk-1, whereas VEGF increased the phosphorylation of both receptors in EA cells and HUVECs. VEGF expression elicited by ANG II was not altered by Flt-1/Fc or SU-1498. EGF stimulated tube formation from EA cells and HUVECs and Flt-1 phosphorylation and aortic sprouting, which were blocked by the EGF receptor antagonist AG-1478 and Flt-1/Fc but not by SU-1498. ANG II-, EGF-, and VEGF-induced tube formation and aortic sprouting were attenuated by the Syk inhibitor piceatannol and by Syk short hairpin interfering (sh)RNA and small interfering RNA, respectively. ANG II, EGF, and VEGF increased Syk phosphorylation, which was inhibited by piceatannol and Syk shRNA in EA cells and HUVECs. Neither piceatannol nor Syk shRNA altered ANG II-, EGF-, or VEGF-induced phosphorylation of Flt-1. These data suggest that ANG II stimulates angiogenesis via transactivation of the EGF receptor, which promotes the phosphorylation of Flt-1 and activation of Syk independent of VEGF expression.
authors.affiliation: Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
authors.forename: Cuneyt K
authors.initials: CK
authors.lastname: Buharalioglu
authors.forename: Chi Young
authors.initials: CY
authors.lastname: Song
authors.forename: Fariborz A
authors.initials: FA
authors.lastname: Yaghini
authors.forename: Hafiz U B
authors.initials: HU
authors.lastname: Ghafoor
authors.forename: Mustafa
authors.initials: M
authors.lastname: Motiwala
authors.forename: Tusita
authors.initials: T
authors.lastname: Adris
authors.forename: Anne M
authors.initials: AM
authors.lastname: Estes
authors.forename: Kafait U
authors.initials: KU
authors.lastname: Malik
mesh_terms: D000704:Analysis of Variance; D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000804:Angiotensin II / Q000378:metabolism*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018919:Neovascularization, Physiologic / Q000187:drug effects; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D000072377:Syk Kinase; D013997:Time Factors; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism
chemical_list: D020533:Angiogenesis Inhibitors; D047228:Angiotensin II Type 1 Receptor Blockers; D047908:Intracellular Signaling Peptides and Proteins; D047428:Protein Kinase Inhibitors; D042461:Vascular Endothelial Growth Factor A; D000804:Angiotensin II; D004815:Epidermal Growth Factor; C512478:EGFR protein, human; C483803:Egfr protein, rat; D066246:ErbB Receptors; C501162:FLT1 protein, human; C501164:Flt1 protein, rat; D011505:Protein-Tyrosine Kinases; D040281:Vascular Endothelial Growth Factor Receptor-1; D040301:Vascular Endothelial Growth Factor Receptor-2; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606898:Syk protein, rat