Vascular Endothelial Growth Factor Synergistically Enhances Induction of E-Selectin by Tumor Necrosis Factor-α

Abstract

Objective— The regulation of endothelial cell adhesion molecules (CAMs) by vascular endothelial growth factor (VEGF) was investigated in cell cultures and in a rabbit model of atherogenic neointima formation. Methods and Results— VEGF regulation of vascular CAM-1 (vascular cell adhesion molecule), intercellular CAM-1 (intercellular adhesion molecule), and E-selectin were investigated in human umbilical vein endothelial cells using quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and flow cytometry, and in the rabbit collar model of atherogenic macrophage accumulation by immunostaining. VEGF alone caused no significant induction of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, or E-selectin compared with tumor necrosis factor-α. In both hypercholesterolemic and normal rabbits, adenoviral VEGF-A 165 expression caused no increase in endothelial vascular cell adhesion molecule-1 or E-selectin. In contrast, pretreatment of human umbilical vein endothelial cells with VEGF significantly increased E-selectin expression induced by tumor necrosis factor-α, compared with tumor necrosis factor-α alone, whereas vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 were unaffected. VEGF similarly enhanced IL-1β–induced E-selectin upregulation. VEGF also synergistically increased tumor necrosis factor-α–induced E-selectin mRNA and shedding of soluble E-selectin. Synergistic upregulation of E-selectin expression by VEGF was mediated via VEGF receptor-2 and calcineurin signaling. Conclusions— VEGF alone does not activate endothelium to induce CAM expression; instead, VEGF “primes” endothelial cells, sensitizing them to cytokines leading to heightened selective pro-inflammatory responses, including upregulation of E-selectin.