Collagen Gene Expression and Atherosclerosis

胶原蛋白基因表达与动脉粥样硬化

• 批准号: 6599673
• 负责人: BARBARA Davis SMITH
• 金额: $ 9.39万
• 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: 2003-05-01 至 2003-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6599673
• 关键词: apolipoprotein E; atherosclerosis; binding sites; cell proliferation; collagen; gene expression; genetic regulation; genetically modified animals; immunoprecipitation; interferon gamma; laboratory mouse; methylation; muscle cells; pathologic process; protein biosynthesis; protein isoforms; protein protein interaction; protein structure function; simvastatin; smooth muscle; tissue /cell culture; transcription factor

DESCRIPTION (provided by applicant): Atherosclerotic lesions begin as fatty streaks that can develop into mature lesions consisting of monocytes/macrophages, T lymphocytes and smooth muscle cells (SMCs), a necrotic core and a fibrous cap containing extracellular matrix components. Plaque rupture at the shoulder region and at sites of thinning in the fibrous cap overlying the lipid-rich core is a likely cause of myocardial infarction. This process is the result of chronic inflammation and is accompanied by cytokines, including interferon-gamma (IFN-y). IFN-y activates major histocompatibility class II (MHC II) gene transcription by inducing transcription of the class II transcriptional activator (CIITA). Recently, we have demonstrated that the collagen type I genes have an RFX binding site at the collagen type I transcription start sites and that RFX5 interacts with CIITA only after IFN-7 stimulation. Collagen synthesis is down regulated by CIITA and IFN-7 decreases collagen gene transcription through CIITA. Our hypotheses are that collagen repression occurs at the RFX site through cooperative interactions with CIITA and that INF-y stimulation of SMCs leads to lowered fibrous cap stability. An HMG-CoA reductase inhibitor, simvastatin, blocks IFNy-induced activation of MHC-II by inhibiting synthesis of CIITA. In addition to their well-known role in reducing lipid synthesis, statins increase collagen gene expression, reduce inflammation, inhibit cell proliferation, and decrease MMP accumulation in atheromas. We propose that these processes occur through the blocking of CIITA induction. We hypothesize that the statins lead to increased collagen synthesis by blocking IFN-gamma induction of CIITA through a lipid intermediate. RFX1 binds with high affinity to the methylated collagen gene transcription start site and can repress collagen gene transcription when over-expressed. The collagen gene is methylated at the RFX site in proliferating SMCs. Therefore, we hypothesize that, during SMC proliferation accompanying the development of aterhosclerotic lesions, the collagen gene is methylated, increasing binding of RFXI. 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-7 induction of CIITA and/or by blocking proliferation. 3. Study collagen type I expression and accumulation in vascular lesions in vivo using transgenic mice models.

描述（由申请人提供）：动脉粥样硬化病变开始为脂肪条纹，可发展为成熟病变，由单核细胞/巨噬细胞、T淋巴细胞和平滑肌细胞（SMC）、坏死核心和含有细胞外基质成分的纤维帽组成。肩部区域和覆盖富含脂质的核心的纤维帽变薄部位的斑块破裂可能是心肌梗塞的原因。这个过程是慢性炎症的结果，并伴随着细胞因子，包括干扰素-γ (IFN-y)。 IFN-y 通过诱导 II 类转录激活因子 (CIITA) 的转录来激活主要组织相容性 II 类 (MHC II) 基因转录。最近，我们证明I型胶原蛋白基因在I型胶原蛋白转录起始位点有一个RFX结合位点，并且RFX5仅在IFN-7刺激后才与CIITA相互作用。 CIITA 下调胶原蛋白合成，并且 IFN-7 通过 CIITA 减少胶原蛋白基因转录。我们的假设是，胶原蛋白抑制通过与 CIITA 的相互作用发生在 RFX 位点，并且 INF-y 对 SMC 的刺激导致纤维帽稳定性降低。 HMG-CoA 还原酶抑制剂辛伐他汀通过抑制 CIITA 的合成来阻断 IFNγ 诱导的 MHC-II 激活。他汀类药物除了众所周知的减少脂质合成作用外，还能增加胶原蛋白基因表达、减少炎症、抑制细胞增殖并减少动脉粥样硬化中 MMP 的积累。我们建议这些过程是通过阻断 CIITA 诱导而发生的。我们假设他汀类药物通过脂质中间体阻断 IFN-γ 对 CIITA 的诱导，从而导致胶原蛋白合成增加。 RFX1 以高亲和力与甲基化胶原蛋白基因转录起始位点结合，并且在过度表达时可以抑制胶原蛋白基因转录。在增殖的 SMC 中，胶原蛋白基因在 RFX 位点甲基化。因此，我们假设，在伴随动脉粥样硬化病变发展的 SMC 增殖过程中，胶原蛋白基因被甲基化，从而增加了 RFXI 的结合。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-7 诱导 CIITA 和/或阻断增殖来增加 I 型胶原蛋白基因表达。 3.使用转基因小鼠模型研究体内血管病变中I型胶原蛋白的表达和积累。