Collagen Gene Expression and Atherosclerosis

胶原蛋白基因表达与动脉粥样硬化

• 批准号: 6781659
• 负责人: BARBARA Davis SMITH
• 金额: $ 24.34万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-12-01 至 2008-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6781659
• 关键词: antihypercholesterolemic agent; atherosclerotic plaque; cell proliferation; clinical research; collagen; gene induction /repression; genetic transcription; genetically modified animals; histocompatibility gene; interferon gamma; laboratory mouse; methylation; protein metabolism; transcription factor; vascular smooth muscle

Atherosclerotic lesions are characterized by infiltrating monocytes/macrophages, lymphocytes and smooth muscle cells (SMC). SMCs migrate from the medial layer to the vessel's intima, where they proliferate and deposit extracellular matrix components with collagen as the major component. Lipid infiltration at the site of lesion formation is prominent extracellularly and intracellularly. SMC and monocyte/macrophage lipid accumulation results in characteristic "foam cell" formation, which contributes to lesion formation. The collagen cap in a fibrous lesion is critical to stabilization of the plaque. Decreased collagen synthesis and/or increased collagen degradation by matrix metalloproteinases (MMPs) compromises the stable plaque, leading to rupture. This proposal will address factors that might influence SMC collagen gene expression in the lesion. Interferon-gamma (IFN-gamma), which is secreted by T lymphocytes, decreases collagen gene transcription and activates major histocompatibility class II (MHC II) gene transcription by inducing synthesis of the class II transcriptional activator, CIITA. The statins are a class of drugs used to decrease hypercholesterolemia via their ability to inhibit the enzyme, 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Recent studies suggest that these agents have a greater beneficial effect in cardiovascular disease beyond their cholesterol lowering activity, in part, through their anti-inflammatory properties. Interestingly, they block IFN-gamma induced activation of MHC-II by inhibiting CIITA. We have recently demonstrated that CIITA interacts with an RFX5-complex at an RFX binding site located within the transcription start site of the collagen alpha2(I) gene leading to repression of collagen gene transcription by CIITA. Since statins also increase collagen gene expression, we hypothesize that the statins cause increased collagen synthesis in plaques by blocking IFN-gamma induction of CIITA. In addition, c-Abl interacts with RFX-1 and represses collagen synthesis when cells are not stimulated by IFN-gamma. RFX1 binds with high affinity to the collagen gene transcription start site when the DNA is methylated, and it can repress collagen gene transcription. The collagen gene is methylated at the RFX site in highly proliferating cancer cells that make low amounts of collagen. Therefore, we hypothesize that RFX1 interaction with c-Abl in the nucleus represses collagen gene transcription during SMC proliferation associated with plaque formation. In order to test our hypotheses, our specific aims are to 1. Investigate CIITA-mediated- regulation of collagen type I gene transcription by SMCs 2. Examine whether statins increase collagen type I gene expression by blocking IFN-gamma, induction of CIITA. 3. Determine if changes in proliferation by statins alter the interaction of c-Abl with RFX1 or collagen gene methylation status and expression and 4. Study collagen type I expression and accumulation in vascular lesions in vivo.

动脉粥样硬化病变的特征在于浸润的单核细胞/巨噬细胞、淋巴细胞和平滑肌细胞（SMC）。SMC从中层迁移到血管内膜，在那里它们增殖并存款细胞外基质成分，胶原蛋白作为主要成分。脂质浸润在病变形成的网站是突出的细胞外和细胞内。SMC和单核细胞/巨噬细胞脂质积聚导致特征性“泡沫细胞”形成，这有助于病变形成。纤维病变中的胶原帽对斑块的稳定至关重要。胶原蛋白合成减少和/或增加 基质金属蛋白酶（MMPs）引起的胶原降解损害了稳定的斑块，导致破裂。该建议将解决可能影响病变中SMC胶原基因表达的因素。由T淋巴细胞分泌的干扰素-γ（IFN-γ）通过诱导II类转录激活因子CIITA的合成来降低胶原基因转录并激活主要组织相容性II类（MHC II）基因转录。他汀类药物是一类用于降低高胆固醇血症的药物， 抑制酶，3-羟基-3-甲基戊二酰辅酶A（HMG-CoA）还原酶。最近的研究表明，这些药物在心血管疾病中具有更大的有益作用，而不仅仅是降低胆固醇的活性，部分是通过其抗炎特性。有趣的是，它们通过抑制CIITA阻断IFN-γ诱导的MHC-II活化。我们最近证明，CIITA在位于胶原蛋白α 2（I）基因转录起始位点内的RFX结合位点与RFX 5复合物相互作用，导致抑制 胶原基因转录。由于他汀类药物也增加胶原基因的表达，我们假设，他汀类药物通过阻断IFN-γ诱导CIITA导致斑块中胶原合成增加。此外，c-Abl与RFX-1相互作用，并在细胞不受IFN-γ刺激时抑制胶原合成。当DNA甲基化时，RFX 1以高亲和力结合胶原基因转录起始位点，并且其可抑制胶原基因转录。胶原基因在高度增殖的细胞中的RFX位点被甲基化， 产生少量胶原蛋白的癌细胞。因此，我们假设RFX 1与c-Abl在细胞核中的相互作用抑制了与斑块形成相关的SMC增殖过程中胶原基因的转录。为了验证我们的假设，我们的具体目标是1。研究CIITA介导的SMC I型胶原基因转录的调控2.检查他汀类药物是否通过阻断IFN-γ诱导CIITA来增加I型胶原基因表达。3.确定他汀类药物引起的增殖变化是否改变了c-Abl 与RFX 1或胶原基因甲基化状态和表达有关;研究I型胶原在体内血管病变中的表达和积聚。