Effects of oxidized low density lipoprotein on vascular endothelial and smooth muscle cells

溶血磷脂酰胆碱（LPC）从氧化修饰的低密度脂蛋白（Ox-LDL）转移到内皮表面膜，在兔主动脉和猪冠状动脉中对细胞表面受体调节的内皮依赖性松弛（EDR）产生选择性不反应。为了确定其机制，研究了LPC或Ox-LDL对内皮细胞内信号的影响。本实验结果表明，LPC抑制内皮细胞早期跨膜信号通路，蛋白激酶C （PKC）的激活可能至少部分参与了LPC的负调控。LPC的这些细胞内作用可能在LPC诱导EDR损伤响应细胞表面受体介导的刺激的机制中发挥作用。为了确定Ox-LDL是否调节内皮纤维蛋白溶解系统，采用ELISA法测定条件培养基中纤溶酶原激活物抑制剂-1 （PAI-1）和组织型纤溶酶原激活物（t-PA） a的水平。结果表明，Ox-LDL通过Ox-LDL中可转移的亲水脂质(s)刺激PAI-1释放，尤其是LPC，而Ox-LDL抑制25-羟基胆固醇和7-酮胆固醇或其他可转移的脂质(s)从Ox-LDL到白蛋白而不是LPC释放t-PA。因此，Ox-LDL中的脂质产物可能损害内皮纤维蛋白溶解。我们进一步研究了Ox-LDL对培养血管内皮细胞（猪主动脉内皮细胞和人脐静脉内皮细胞）分泌内皮素-1样免疫反应性（ET-1- li）的影响，考虑ET-1与动脉粥样硬化和高胆固醇血症的可能相关性。结果表明，Ox-LDL中的LPC会抑制ET-1-LI的释放，这可能会抵消动脉粥样硬化的血管收缩特性。此外，Ox-LDL中的LPC导致内皮对多形核白细胞（PMNs）的粘附性增加，从而增加了PMNs诱导的猪冠状动脉EDR损伤。这是由于猪冠状动脉内皮细胞间粘附分子-1的表达增加，而LPC在Ox-LDL中激活PKC可能至少部分参与了这些机制。少

Lysophosphatidylcholine (LPC) transferred from oxidatively modified low density lipoprotein (Ox-LDL) to the endothelial surface membrane has been shown to produce a selective unresponsiveness to cell surface receptor-regulated endothelium-dependent relaxation (EDR) in the rabbit aorta and porcine coronary artery. To determine its mechanism, the effects of LPC or Ox-LDL on intracellular signals in endothelial cells were examined. The results from this experiment indicate that LPC inhibits the early transmembrane signaling pathway in endothelial cells, and Protein Kinase C (PKC) activation could at least partially be involved in the negative regulation by LPC. These intracellular actions of LPC may play a role in the mechanism of the LPC-induced impairment of EDR in response to cell surface receptor-mediated stimulations.To determine whether Ox-LDL modulates endothelial fibrinolytic system, levels of plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) a … More ntigens in the conditioned medium were measured by ELISA. The results indicate that Ox-LDL stimulates PAI-1 release by the transferable hydrophilic lipid(s) in Ox-LDL, especially LPC, while Ox-LDL inhibits t-PA release by 25-hydroxycholesterol and 7-ketocholesterol or other transferable lipid(s) from Ox-LDL to albumin rather than LPC. Thus, lipid products in Ox-LDL may impair endothelial fibrinolysis. We further examined the effects of Ox-LDL on the secretion of endothelin-1-like immunoreactivity (ET-1-LI) by the cultured vascular endothelial cells (porcine aortic endothelial cells and human umbilical vein endothelial cells), considering the possible relevance of ET-1 to the atherosclerosis and hypercholesterolemia. The results show that LPC in Ox-LDL causes suppression of ET-1-LI release, which may counteract the vasoconstricitve properties of atherosclerotic arteries. Furthermore, LPC in Ox-LDL causes the increase of the endothelial adhesiveness to polymorphonuclear leukocytes (PMNs), which augments PMNs-induced impairment of EDR in porcine coronary artery. This is due to increased expression of intercellular adhesion molecule-1 in endothelium of the porcine coronary artery, and the activation of PKC by LPC in Ox-LDL may at least in part be involved in these mechanisms. Less