Role of Retroelements in Environmental Atherogenesis

描述（由申请人提供）：动脉粥样硬化是工业化国家发病率和死亡率的主要原因，是一种与内皮损伤、炎症细胞（巨噬细胞和T细胞）募集、血管平滑肌细胞（vSMC）扩增以及动脉内衬内胆固醇和细胞外基质积聚相关的纤维增生性疾病。临床疾病是由供给心脏、大脑或四肢的血管闭塞引起的。动脉粥样硬化（动脉粥样硬化形成）的早期阶段涉及对血管壁的炎性损伤、巨噬细胞的浸润和vSMC的不受控制的增殖。血管壁的氧化损伤是致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风险因素。长期暴露于空气颗粒物和与颗粒物相关的化学物质，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。与此相关的是苯并（a）芘（BaP）的生物效应，这是一种存在于各种形式污染中的致癌物，并通过细胞色素P450代谢为损害DNA和引起氧化应激的中间体。vSMC在体内或体外反复暴露于BaP诱导血管壁内的动脉粥样硬化变化。BaP致动脉粥样硬化的分子机制涉及基因表达的转录失调和DNA损伤。感兴趣的是涉及人和鼠vSMC中c-Ha-ras基因和长散布核元件（LINE 1或L1）的活化的应答。L1已经成为环境动脉粥样硬化形成中有趣的基因组靶点，因为该家族的成员通过涉及RNA中间体、逆转录酶和核酸内切酶的“复制和粘贴”机制来修改体细胞中的遗传程序。为了继续先前的研究，本申请中提出了研究来评估Apoetm 1Unc小鼠模型中动脉粥样硬化疾病进展过程中L1的表达，以评估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，并阐明动脉粥样硬化中两种主要细胞类型vSMC和巨噬细胞中L1活化的分子机制。待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过表达和基因组不稳定性相关。此外，据推测，L1激活介导的表观遗传机制，增加启动子活性和RNA聚合酶II的效率。这些研究是第一次系统地研究L1和逆转录在血管壁疾病中的作用。公共卫生相关性：在美国，动脉粥样硬化仍然是大多数心血管死亡病例的原因。最近的研究表明，环境污染物加速了这种疾病的发病率，但介导这种关系的遗传机制尚未完全了解。在本申请中提出了在实验系统中研究病毒样序列在环境诱导的动脉粥样硬化的发作和进展中的作用的研究。

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.