VEGF Increases Permeability of the Endothelial Cell Monolayer by Activation of PKB/akt, Endothelial Nitric-Oxide Synthase, and MAP Kinase Pathways

VEGF is a key regulator of vascular permeability. However, its signaling pathways are incompletely understood. We tested the hypothesis that VEGF regulates endothelial cell (EC) permeability by activating PKB/akt, NOS, and MAP kinase dependent pathways using human umbilical vein EC (HUVEC). Permeability was measured from FITC–dextran 70-kDa flux across the EC monolayer at baseline and after VEGF at 0.034, 0.068, 1, 10, and 100 nM. VEGF increased HUVEC permeability to FITC–dextran in a dose-dependent manner. VEGF (1 nM) increased permeability from 3.9 × 10−6 ± 0.7 × 10−6 to 14.0 × 10−6 ± 1.7 × 10−6 cm/s (mean ± SEM; P < 0.001). Permeability changes were also assessed after treatment with 1, 10, and 100 nM wortmannin (PI 3-kinase inhibitor); 0.01, 0.1, and 1.0 nM LY294002 (PI 3-kinase inhibitor); 200 μM l-NMMA (NOS inhibitor); 2.7 μM AG126 (p42/44MAPK inhibitor); and 0.006, 0.06, and 0.6 μM SB203580 (p38MAPK inhibitor). All inhibitors blocked VEGF-induced permeability changes. Our data demonstrate that (1) VEGF increases permeability of EC monolayers in a dose-dependent fashion, and (2) VEGF-induced permeability is mediated through PI-3 kinase-PKB, NOS, and MAP-kinase signaling cascades. These observations suggest that microvascular hyperpermeability associated with inflammation and vascular disease is mediated by activation of these EC signaling pathways.