Role of Retroelements in Environmental Atherogenesis

描述(申请人提供)：动脉粥样硬化是工业化国家发病率和死亡率的主要原因，是一种纤维增生性疾病，与血管内皮细胞损伤、炎性细胞(巨噬细胞和T细胞)募集、血管平滑肌细胞(VSMCs)扩张以及动脉内层内胆固醇和细胞外基质的积聚有关。临床疾病是心脏、大脑或四肢供血的血管闭塞所致。动脉粥样硬化(AS)的早期阶段包括对血管壁的炎性损伤、巨噬细胞的渗透和血管平滑肌细胞的失控增殖。血管壁的氧化损伤是动脉粥样硬化反应的共同特征，血胆固醇水平升高、高血压、糖尿病和吸烟被认为是主要的危险因素。长期接触空气颗粒物和与颗粒物有关的化学品，如多环芳烃，与啮齿动物和灵长类动物动脉粥样硬化的发展或恶化有关。相关的是苯并(A)芘(BaP)的生物效应，这是一种存在于各种形式的污染中的致癌物质，由细胞色素P450代谢成破坏DNA并引起氧化应激的中间产物。在体内或体外反复暴露于BaP可引起血管壁内动脉粥样硬化的改变。BaP动脉粥样硬化形成的分子机制涉及基因表达的转录失控和DNA损伤。令人感兴趣的是涉及c-Ha-ras基因激活的反应和人和小鼠血管平滑肌细胞中长时间散布的核元素(行1或L1)。自从L1家族的成员通过一种涉及RNA中间体、逆转录酶和内切酶的“复制粘贴”机制来修改体细胞中的遗传程序以来，L1已经成为环境动脉粥样硬化发生中有趣的基因组靶标。为了继续以往的研究，本研究拟在Apoetm1Unc小鼠模型中评估L1在动脉粥样硬化疾病进展过程中的表达，评估L1的血管特异性表达对动脉粥样硬化病变发生和严重程度的影响，并阐明L1在动脉粥样硬化的两种主要细胞类型--血管平滑肌细胞和巨噬细胞中激活的分子机制。需要检验的中心假设是，斑块形成的进展与动脉粥样硬化斑块内细胞中L1的过度表达和基因组不稳定性有关。此外，假设L1激活是通过表观遗传机制介导的，该机制增加了启动子的活性和RNA聚合酶II的效率。这些研究首次系统地研究了L1和逆转位在血管壁疾病中的作用。公共卫生相关性：动脉粥样硬化仍然是美国大多数心血管死亡病例的原因。最近的研究表明，环境污染会加速这种疾病的发生，但调节这种关系的遗传机制并不完全清楚。在这一应用中，建议进行研究，以研究病毒样序列在实验系统中环境诱导的动脉粥样硬化的发生和发展中所起的作用。

DESCRIPTION (provided by applicant): Atherosclerosis, the leading cause of morbidity and mortality in industrialized nations, is a fibro-proliferative disease associated with endothelial injury, recruitment of inflammatory cells (macrophages and T cells), expansion of vascular smooth muscle cells (vSMCs) and buildup of cholesterol and extracellular matrix within the inner lining of arteries. Clinical disease results from occlusion of vessels that feed the heart, brain, or extremities. The early stages of atherosclerosis (atherogenesis) involve inflammatory injury to the vessel wall, infiltration of macrophages and uncontrolled proliferation of vSMCs. Oxidative injury to the vessel wall is a common denominator of the atherogenic response, with elevated levels of blood cholesterol, high blood pressure, diabetes, and smoking recognized as primary risk factors. Chronic exposures to air particulates and chemicals associated with particulate matter, such as polycyclic aromatic hydrocarbons, have been associated with development or exacerbation of atherosclerosis in rodents and primates. Of relevance are the biological effects of benzo(a)pyrene (BaP), a carcinogen present in various forms of pollution and metabolized by cytochromes P450 to intermediates that damage DNA and cause oxidative stress. Repeated exposure of vSMCs to BaP in vivo or in vitro induces atherosclerotic changes within the vascular wall. The molecular mechanisms responsible for BaP atherogenesis involve transcriptional deregulation of gene expression and DNA damage. Of interest are responses involving activation of the c-Ha-ras gene and long interspersed nuclear elements (LINE 1 or L1) in human and murine vSMCs. L1s have emerged as interesting genomic targets in environmental atherogenesis since members of this family modify genetic programs in somatic cells through a "copy and paste" mechanism involving RNA intermediates, reverse transcriptase and endonuclease. To continue previous investigations, studies are proposed in this application to evaluate the expression of L1 during the course of atherosclerotic disease progression in the Apoetm1Unc mouse model, to evaluate the impact of vascular specific expression of L1 on atherosclerotic lesion occurrence and severity, and to elucidate molecular mechanisms of L1 activation in vSMCs and macrophages, two of the principal cell types in atherosclerosis. The central hypothesis to be tested is that progression of plaque formation is associated with L1 overexpression and genomic instability in cells within the atherosclerotic plaque. Further, it is hypothesized that L1 activation is mediated via epigenetic mechanisms that increase promoter activity and RNA polymerase II efficiency. These studies are the first to systematically examine the role of L1 and retrotransposition in diseases of the vascular wall. PUBLIC HEALTH RELEVANCE: Atherosclerosis continues to be responsible for most cases of cardiovascular mortality in the US. Recent studies have shown that the incidence of this disease is accelerated by environmental contaminants, but the genetic mechanisms that mediate this relationship are not fully understood. Studies are proposed in this application to study the role of virus-like sequences in the onset and progression of environmentally-induced atherosclerosis in experimental systems.