ROLE OF VEGF IN ATHEROGENESIS

免疫组织化学研究显示，人早期动脉粥样硬化病变增厚的内膜内皮下巨噬细胞丰富的区域显示出强烈的血管内皮生长因子(VEGF)免疫反应。在动脉粥样硬化斑块中，邻近脂质核心的泡沫细胞富集区或以平滑肌细胞为主的新生血管斑块基底区也可观察到VEGF染色。高倍视野观察发现，血管内皮生长因子定位于细胞外间隙和巨噬细胞表面。这些观察结果提示，氧化低密度脂蛋白(Ox-LDL)可能通过诱导巨噬细胞中的血管内皮生长因子参与动脉粥样硬化的发展。我们还证明了氧化低密度脂蛋白以时间和浓度依赖的方式上调单核细胞系RAU264细胞中血管内皮生长因子的表达，并刺激细胞分泌血管内皮生长因子蛋白。我们推测血管内皮生长因子在内皮下巨噬细胞丰富的…中管腔表面与内皮细胞相邻的更多区域可能参与管腔内皮细胞的维持和修复。为了验证我们的假设，我们检验了血管内皮生长因子是否保护氧化低密度脂蛋白对培养的牛主动脉内皮细胞的毒性。血管内皮细胞与血管内皮细胞共同孵育可抑制Ox-LDL的毒性，且呈时间和浓度依赖关系。血管内皮细胞与血管内皮细胞共同孵育后，细胞内谷胱甘肽(GSH)含量呈时间依赖性增加。联合应用血管内皮细胞生长因子和谷胱甘肽合成抑制剂L丁硫氨酸亚磺胺可逆转GSH水平及血管内皮生长因子对氧化低密度脂蛋白诱导的细胞毒性的保护作用。胎盘生长因子与血管内皮生长因子Fit-1受体结合，但不与KDR/Flk-1结合，不能预防氧化低密度脂蛋白毒性，对细胞内GSH水平无影响。抗KDR/Flk-1抗体可完全阻断血管内皮细胞的上述活性。这些结果表明，VEGF通过KDR/Flk-1受体，通过细胞内GSH依赖机制来拮抗Ox-LDL诱导的内皮细胞损伤。较少

Immunohistochemical studies showed that human early atherosclerotic lesions exhibited intensive vascular endothelial growth factor (VEGF) immunoreactivity in subendothelial macrophage-rich regions of thickened intima. In atherosclerotic plaques, VEGF staining was also observed in foam cell-rich regions adjacent to lipid core or neovascularized basal regions of plaque consisting predominantly of smooth muscle cells. High powered field observation revealed that VEGF was localized in extracellular space as well as macrophage cell surface. These observations suggest the possible involvement of oxidized loe density lipoprtein (Ox-LDL) in the development of human atherosclerosis through VEGF induction in macrophages. We also demonstrated that Ox-LDL upregulated VEGF mRNA expression in RAW 264 cells, monocytic cell line, in a time and concentration dependent manner, and that Ox-LDL stimulated the VEGF protein secretion from the cells.We hypothesized that VEGF in subendothelial macrophage-rich … More regions adjacent to endothelial cells at the luminal surface may participate in the maintenance and repair of the lumen endothelium. To test our hypothesis we examined whether VEGF protects the toxicity of Ox-LDL to cultured endothelial cells derived from bovine aorta (BAECs). BAECs preincubation with VEGF prevented Ox-LDL toxicity in a preincubation time- and VEGF concentration-dependent manner. Incubation of BAECs with VEGF increased intracellular glutathione (GSH) in a time-dependent manner. Combined addition of VEGF and L-buthionine sulfoximine, a GSH synthesis inhibitor, reversed GSH level and the protective effect of VEGF on Ox-LDL-induced cytotoxicity. Placenta growth factor, which ligates to VEGF Fit-1 receptor but not KDR/Flk-1, failed to prevent Ox-LDL toxicity and had no effect on intracellular GSH level. Anti- KDR/Flk-1 antibody completely blocked these activities of VEGF.These results suggest that VEGF prevents Ox-LDL-induced endothelial cell damage via intracellular GSH-dependent mechanism through KDR/Flk-1 receptor. Less