Vascular permeability induced by VEGF family members in vivo: role of endogenous PAF and NO synthesis.
We previously reported that vascular endothelial growth factor (VEGF) increases vascular permeability through the synthesis of endothelial platelet-activating factor (PAF), while others reported the contribution of nitric oxide (NO). Herein, we addressed the contribution of VEGF receptors and the role played by PAF and NO in VEGF-induced plasma protein extravasation. Using a modified Miles assay, intradermal injection in mice ears of VEGF-A(165), VEGF-A(121), and VEGF-C (1 microM) which activate VEGFR-2 (Flk-1) receptor increased vascular permeability, whereas a treatment with VEGFR-1 (Flt-1) analogs; PlGF and VEGF-B (1 microM) had no such effect. Pretreatment of mice with PAF receptor antagonist (LAU8080) or endothelial nitric oxide synthase (eNOS) inhibitor (L-NAME) abrogated protein extravasation mediated by VEGF-A(165). As opposed to PAF (0.01-1 microM), treatment with acetylcholine (ACh; up to 100 microM; inducer of NO synthesis) or sodium nitroprusside (SNP; up to 1 microM; NO donor) did not induce protein leakage. Simultaneous pretreatment of mice with eNOS and protein kinase A (PKA) inhibitors restored VEGF-A(165) vascular hyperpermeability suggesting that endogenous NO synthesis leads to PKA inhibition, which support maintenance of vascular integrity. Our data demonstrate that VEGF analogs increase vascular permeability through VEGFR-2 activation, and that both endogenous PAF and NO synthesis contribute to VEGF-A(165)-mediated vascular permeability. However, PAF but not NO directly increases vascular permeability per se, thereby, suggesting that PAF is a direct inflammatory mediator, whereas NO serves as a cofactor in VEGF-A(165) proinflammatory activities.
Brkovic
Alexandre
A
Research Center, Montreal Heart Institute, Department of Pharmacology, Université de Montréal, Montreal, QC, Canada.
Sirois
Martin G
MG
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D002199:Capillary Permeability / Q000187:drug effects*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D051379:Mice; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000737:chemistry / Q000494:pharmacology*; D000099152:Cadherin 5
D015703:Antigens, CD; D015820:Cadherins; D004791:Enzyme Inhibitors; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide; D010972:Platelet Activating Factor; D042461:Vascular Endothelial Growth Factor A; D000099152:Cadherin 5