Collagen Gene Expression and Atherosclerosis

描述（由申请方提供）：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）、坏死核心和含细胞外基质成分的纤维帽组成。在肩部和富含脂质的核心上的纤维帽变薄部位的斑块破裂可能是心肌梗死的原因。这一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-γ）。IFN-γ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，我们已经证明，I型胶原基因在I型胶原转录起始位点具有RFX结合位点，并且RFX 5仅在IFN-7刺激后与CIITA相互作用。胶原蛋白合成被CIITA下调，IFN-7通过CIITA降低胶原蛋白基因转录。我们的假设是，胶原抑制发生在RFX网站通过协同相互作用与CIITA和INF-γ刺激SMC导致降低纤维帽稳定性。HMG-CoA还原酶抑制剂辛伐他汀通过抑制CIITA的合成来阻断IFN γ诱导的MHC-II活化。他汀类药物除了在减少脂质合成方面的作用外，还可增加胶原基因表达，减少炎症，抑制细胞增殖，并减少MMP在动脉粥样硬化中的积聚。我们认为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诱导CIITA而导致胶原合成增加。RFX 1以高亲和力结合于甲基化胶原基因转录起始位点，并且当过度表达时可以抑制胶原基因转录。在增殖的SMC中，胶原基因在RFX位点甲基化。因此，我们推测，在SMC增殖伴随着发展的动脉粥样硬化病变，胶原基因甲基化，增加结合RFXI。我们的具体目标是1.研究CIITA介导的SMC对I型胶原基因转录的调节。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型胶原基因表达。3.使用转基因小鼠模型研究I型胶原蛋白在体内血管病变中的表达和积聚。

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.