Collagen Gene Expression and Atherosclerosis

胶原蛋白基因表达与动脉粥样硬化

基本信息

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
项目类别：
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

项目摘要

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是浸润单核细胞/巨噬细胞、淋巴细胞和平滑肌细胞(SMC)。 SMC从血管内层迁移至血管内膜，在那里增殖并沉积以胶原蛋白为主要成分的细胞外基质成分。病变形成部位的脂质浸润在细胞外和细胞内都很明显。 SMC 和单核细胞/巨噬细胞脂质积累导致特征性“泡沫细胞”形成，从而导致病变形成。纤维病变中的胶原蛋白帽对于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 (MMP) 导致的胶原蛋白降解会损害稳定的斑块，导致斑块破裂。该提案将解决可能影响病变中 SMC 胶原蛋白基因表达的因素。 T 淋巴细胞分泌的干扰素-γ (IFN-gamma) 可减少胶原蛋白基因转录，并通过诱导 II 类转录激活剂 CIITA 的合成来激活主要组织相容性 II 类 (MHC II) 基因转录。他汀类药物是一类通过其能力来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，除了降低胆固醇的活性外，这些药物对心血管疾病还有更大的有益作用，部分原因是它们的抗炎特性。有趣的是，它们通过抑制 CIITA 来阻断 IFN-γ 诱导的 MHC-II 激活。我们最近证明 CIITA 与位于胶原蛋白 alpha2(I) 基因转录起始位点内的 RFX 结合位点处的 RFX5 复合物相互作用，从而抑制 CIITA 的胶原蛋白基因转录。由于他汀类药物也会增加胶原蛋白基因表达，因此我们假设他汀类药物通过阻断 CIITA 的 IFN-γ 诱导来增加斑块中的胶原蛋白合成。此外，当细胞不受 IFN-γ 刺激时，c-Abl 与 RFX-1 相互作用并抑制胶原蛋白合成。当DNA甲基化时，RFX1与胶原蛋白基因转录起始位点高亲和力结合，可以抑制胶原蛋白基因转录。高度增殖的胶原蛋白基因在 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 RFX1 与细胞核中的 c-Abl 相互作用会抑制与斑块形成相关的 SMC 增殖过程中的胶原蛋白基因转录。为了检验我们的假设，我们的具体目标是 1. 研究 CIITA 介导的 SMC 对 I 型胶原蛋白基因转录的调节 2. 检查他汀类药物是否通过阻断 IFN-γ 和 CIITA 的诱导来增加 I 型胶原蛋白基因表达。 3. 确定他汀类药物引起的增殖变化是否会改变 c-Abl 的相互作用 4.研究体内血管病变中I型胶原蛋白的表达和积累。