P286	Vascular endothelial growth factor does not upregulate endothelial cell adhesion molecules, but synergistically enhances induction of E-selectin by tumor necrosis factor-alpha.
A.Stannard, R.Khurana, V.Sofra, D.Holmes, S.Sultan, I.Zachary
British Heart Foundation Laboratories, Centre for Cardiovascular Biology and Medicine, Department of Medicine, University College London, London, GB.

It was recently reported that the potent angiogenic factor vascular endothelial growth factor (VEGF) might act as a pro-inflammatory cytokine to induce endothelial cell adhesion molecule (CAM) expression. We investigated whether VEGF could upregulate cell surface vascular cell adhesion molecule-1 (VCAM-1/CD106), intercellular cell adhesion molecule-1 (ICAM-1/CD54) or E-selectin (CD62E) on human umbilical vein endothelial cells (HUVECs). VEGF alone failed to cause any significant induction of VCAM-1, ICAM-1 or E-selectin, although CAMs were strongly upregulated by tumor necrosis factor-α (TNF-α). VEGF also induced negligible changes in CAM mRNA compared to TNF-α. In addition, adenoviral overexpression of VEGF in a model of atherogenic neointima formation and macrophage accumulation also had no significant effect on endothelial VCAM-1 expression in vivo. Although VEGF alone had no significant effect on CAM expression, we tested whether VEGF could modulate endothelial CAM upregulation by TNF-α. When HUVECs were pre-incubated with VEGF prior to adding TNF-α, E-selectin expression was significantly increased by 67±17% (n=4, p<0.005) as compared to TNF-α alone, whilst VCAM-1 or ICAM-1 were not. VEGF also synergistically increased TNF-α-induced E-selectin mRNA expression and shedding of soluble E-selectin. VEGF pre-treatment also synergistically enhanced interleukin-1β-induced upregulation of E-selectin. Placental growth factor (PlGF), a ligand for Flt-1 failed to synergise with TNF-α to enhance E-selectin while a specific inhibitor of KDR/Flk-1, SU5614, blocked the effect, indicating that this response was mediated via KDR. The calcineurin/NFAT signalling pathway was also implicated as cyclosporin A inhibited the synergism, whereas inhibiting the MAP kinase pathway using U0126 had no effect. We conclude that VEGF alone is unable to activate endothelium to induce CAM expression, but hypothesize that VEGF may prime endothelial cells to increase their sensitivity to cytokines leading to heightened selective pro-inflammatory responses, including the upregulation of E-selectin. This work was sponsored by a grant from the British Heart Foundation.

Copyright © 2005 S. Karger AG, Basel. Any further use of this abstract requires written permission from the publisher.