Endotoxin, Vascular Inflammation and Atherosclerosis

描述（由申请人提供）：动脉粥样硬化是美国最常见的死亡原因，是一种慢性炎症性疾病。然而，炎症的来源以及炎症导致血管疾病的机制仍有待阐明。循环内毒素（革兰氏阴性菌外膜的糖脂组分）的水平在革兰氏阴性菌败血症期间显著升高，并导致急性血管炎性损伤。最近，内毒素血症在低得多的水平（即，>50 pg/ml）已被确定为动脉粥样硬化的强危险因素，特别是在吸烟者中。内毒素血症在表面上健康的受试者中可能由慢性或复发性感染、牙周炎或上皮屏障功能破坏引起。然而，低水平内毒素引起的内皮功能障碍的程度及其在动脉粥样硬化发病机制中的潜在作用仍有待确定。来自我们实验室的初步数据表明，相对低水平的内毒素（即，1 ng/ml）增加活性氧（ROS）水平，诱导促炎细胞因子白细胞介素-8和单核细胞趋化肽-1，促进U-937单核细胞与人冠状动脉内皮细胞结合。类似地，非常低水平的内毒素（等于约30 pg/ml）在人冠状动脉平滑肌细胞和人血管外植体中诱导炎症反应。这些内毒素介导的促炎作用可通过HMG-CoA还原酶抑制剂（他汀类药物）和环氧二十碳三烯酸（Epoxyeicosatrienoic acids，ESTs）（多不饱和脂肪酸花生四烯酸的内皮衍生代谢物）预处理来阻断，这对动脉粥样硬化及其治疗具有潜在的重要意义。我们的假设是，亚临床水平的内毒素导致人冠状动脉内皮细胞和平滑肌细胞以及完整的人血管的促炎性激活，并且这些作用可以通过他汀类药物、雌二醇和脂肪酸来调节。本文提出了四个具体目标，即研究内毒素在血管细胞中的信号转导机制，内毒素诱导的ROS产生的来源和后果，特异性结合蛋白和酶降解对内毒素的调节，以及他汀类药物、雌二醇和其他脂肪酸调节内毒素生物活性的能力。拟议的研究将为内毒素介导的血管炎症可能导致动脉粥样硬化的机制提供新的见解。

DESCRIPTION (provided by applicant): Atherosclerosis, the most common cause of death in the United States, is a chronic inflammatory disorder. The sources of inflammation, and the mechanisms by which the inflammation leads to vascular disease, however, remain to be elucidated. Levels of circulating endotoxin, a glycolipid component of the outer membrane of Gram-negative bacteria, are markedly elevated during Gram-negative septicemia and lead to acute vascular inflammatory injury. Very recently, endotoxemia at much lower levels (i.e., >50 pg/ml) has been identified as a strong risk factor for atherosclerosis, particularly among smokers. Endotoxemia in apparently healthy subjects may result from chronic or recurrent infection, periodontitis, or breaching of epithelial barrier function. However, the extent of endothelial dysfunction caused by low levels of endotoxin, and its potential role in the pathogenesis of atherosclerosis, remain to be determined. Preliminary data from our laboratocy indicate that relatively low levels of endotoxin (i.e., 1 ng/ml) increase the levels of reactive oxygen species (ROS), induce the pro-inflammatory cytokines interleukin-8 and monocyte chemoattractant peptide-1, and promote U-937 monocyte binding to human coronary artery endothelial cells. Similarly, very low levels of endotoxin ( equal to approximately 30 pg/ml) induce inflammatory responses in human coronary artery smooth muscle cells and human blood vessel explants. These endotoxin-mediated pro-inflammatory effects are blocked by pre-treatment with HMG-CoA reductase inhibitors (statins) and epoxyeicosatrienoic acids (EETs), endothelium-derived metabolites of the polyunsaturated fatty acid arachidonic acid, which has potentially important implications for atherosclerosis and its treatment. Our hypothesis is that subclinical levels of endotoxin cause pro-inflammatory activation of human coronary artery endothelial and smooth muscle cells, and intact human blood vessels, and that these effects can be modulated by statins, EETs and fatty acids. Four specific aims are proposed, in which we will investigate the mechanisms of endotoxin signaling in vascular cells, the sources and consequences of endotoxin-induced ROS production, the regulation of endotoxin by specific binding proteins and enzymatic degradation, and the capacity of statins, EETs and other fatty acids to modulate endotoxin bioactivity. The proposed studies will provide novel insight into the mechanisms by which endotoxin-mediated vascular inflammation may contribute to atherosclerosis.