Molecular biological study for mechanism of intraplaque hemorrhage in carotid stenosis

最近研究发现，血管内皮生长因子(VEGF)及其受体(Flt-1)可改变动脉粥样硬化斑块的形成，抗FIT-1抗体可抑制动脉粥样硬化的形成。由于血管内皮生长因子是血管生成/通透性因子，它可以促进血管生成，并可能导致斑块内出血。此外，低氧诱导因子(HIF)上调血管内皮细胞生长因子(VEGF)，而VHL蛋白下调HIF的表达。本研究的目的是阐明这些因素在颈动脉狭窄病变中的作用。我们对症状性颈动脉狭窄患者行颈动脉内膜切除术时获得的颈动脉斑块样本进行了检测。用血管内皮生长因子、Flt-1、缺氧诱导因子-1α、血管内皮生长因子、α-肌动蛋白和巨噬细胞CD68进行免疫组织化学研究。血管内皮生长因子在颈动脉粥样硬化斑块深层纤维帽和斑块肩部的泡沫细胞中有明显表达。泡沫细胞主要来源于巨噬细胞，但也有一部分来源于平滑肌细胞。在大部分VEGF阳性细胞中可见Flt-1阳性细胞。低氧诱导因子-1α阳性细胞在大多数血管内皮生长因子阳性细胞中表达，而血管内皮生长因子阳性细胞在少数血管生长因子阳性细胞中表达，尤其是在颈动脉斑块新生血管中。综上所述，颈动脉斑块中血管内皮生长因子的表达主要来源于颈动脉斑块深层的巨噬细胞。提示缺氧诱导因子-1α可上调血管内皮生长因子的表达，而缺氧诱导因子-1可部分下调血管内皮细胞生长因子的表达。已有研究表明，血管内皮生长因子的表达受氧化低密度脂蛋白的调节，因此，血管内皮生长因子相关途径可能在动脉粥样硬化性颈动脉斑块的进展和斑块内出血的发生发展中起关键作用。

Recently it is reported that vascular endothelial growth factor (VEGF) and its receptor (Flt-1) may exert effects to alter the role of atherosclerotic plaque development and that atherosclerosis is inhibited by anti-Fit-1 antibody. Since VEGF is angiogenesis/permeable factor, it can promote angiogenesis and may lead to intraplaque hemorrhage. In addition, VEGF is up-regulated by hypoxia-inducible factor (HIF) which is down-regulated by von Hippel-Lindau (VHL) protein. The object of the study is elucidate the roles of these factors in cervical carotid stenotic lesion. We examined specimens of carotid plaques obtained at carotid endarterectomy for patients with symtptomatic carotid stenosis. Immunohistochemical study was performed with antibodies against VEGF, Flt-1,HIF-1α,VHL,α-actin for smooth muscle cell, and CD68 for macrophage. VEGF was expressed distinctly at foamy cells in fibrous cap and plaque shoulder in the deep layer of atherosclerotic carotid plaques. Most of foamy cells were derived from macrophages, but a part of them from smooth muscle cells. Flt-1 positive cells were identified at most of VEGF positive cells. HIF-1α -positive cells were identified at a majority of VEGF-positive cells while VHL-positive cells at a minority of VEGF-positive cells, particularly at newly formed vessels in carotid plaques. In conclusion, VEGF expression in carotid plaque is identified at foamy cells mostly derived from macrophages in the deep layer of carotid plaque. It is suggested that VEGF expression is up-regulated by HIF-1α which is partially down-regulated by VHL. Since it is reported that VEGF expression is regulated by oxidated LDL, VEGF-related pathway might play critical role in the advancement of atherosclerotic carotid plaque and the development of intraplaque hemorrhage.