Development of ELISA system for plasma EDL and its clinical application for atherosclerosis

我们和另一个团队独立克隆了LPL基因家族的一个新成员--血管内皮细胞产生的内皮细胞衍生脂肪酶(EDL)。我们已经建立了检测人血浆EDL水平的酶联免疫吸附试验系统，并正在检测正常志愿者和缺血性心脏病患者的血浆EDL水平。相反，EDL基因敲除小鼠的高密度脂蛋白胆固醇水平显著升高。这些数据表明，EDL可能在高密度脂蛋白代谢中发挥生理学作用。免疫组织化学分析显示，EDL在非动脉粥样硬化冠状动脉内皮细胞和中膜平滑肌细胞中均有表达。此外，在动脉粥样硬化斑块内的浸润性细胞以及血管内皮细胞和平滑肌细胞中也检测到EDL。为了研究脂肪酶活性和血管壁脂代谢的局部调控，我们检测了HCAECs和HCAECs中EDL表达的调节。在两种类型的细胞中，EDL mRNA水平不受与血管疾病病因有关的炎性细胞因子的调节，包括肿瘤坏死因子-α和白介素1-β。此外，流体剪切力和循环拉伸均可增加培养细胞中EDL基因的表达水平。为了更好地了解EDL在体内的功能，我们培育了缺乏EDL基因的小鼠。EDL-/-小鼠是可存活和有生育能力的，没有表现出任何明显的缺陷或体重差异。与野生型(WT)小鼠相比，杂合突变(EDL+/-)小鼠的空腹血浆高密度脂蛋白胆固醇水平升高。相反，这些基因型之间的甘油三酯水平没有显著差异。综上所述，EDL是体内高密度脂蛋白代谢的重要调节因子，可能介导内皮-脂蛋白的相互作用，而血管细胞中的EDL可能参与调节血管壁脂代谢，并可能在动脉粥样硬化等血管疾病中发挥作用。

We and another group have cloned independently a new member of the LPL gene family, endothelial cell-derived lipase (EDL) that is produced by vascular endothelial cells. We have established ELISA system to measure the plasma EDL level in humans and are measuring the plasma EDL levels in normal volunteers and patients with ischemic heart diseases. Conversely, EDL knockout mice showed a marked elevation in HDL cholesterol levels. These data suggest that EDL may play a physiologic role in HDL metabolism. Immunohistochemical analysis revealed that EDL was expressed in endothelial cells and medial smooth muscle cells in non-atherosclerotic coronary arteries. In addition, EDL was detected in infiltrating cells within atheromatous plaques as well as endothelial and smooth muscle cells. To investigate local control of lipase activity and lipid metabolism in the blood vessel wall, we have examined the regulation of EDL expression in HCAECs and HCAECs. EDL mRNA levels were unregulated in both cell types by inflammatory cytokines implicated in vascular disease etiology, including TNF-α and IL-1β. Moreover, both fluid shear stress and cyclic stretch were found to increase the EDL mRNA levels in these cultured cells. To gain better understanding of the function of EDL in vivo, we have generated mice that lack EDL gene. EDL-/- mice are viable and fertile and do not exhibit any overt defects or body weight differences. Fasting plasma HDL cholesterol was increased in heterozygous mutant (EDL+/-) mice, compared with wild type (WT) mice. In contrast, there was no significant difference in triglyceride levels among these genotypes. In conclusion, EDL is an important regulator of HDL metabolism in vivo and likely mediates endothelium-lipoprotein interactions, and EDL in vascular cells may be involved in modulating vessel wall lipid metabolism and may play a role in vascular diseases such as atherosclerosis.