Collagen Gene Expression and Atherosclerosis

描述(申请人提供)：动脉粥样硬化病变始于脂肪条纹，可发展为成熟病变，由单核/巨噬细胞、T淋巴细胞和平滑肌细胞(SMCs)、坏死核和含有细胞外基质成分的纤维帽组成。肩部斑块破裂和富脂核心上纤维帽变薄的部位可能是心肌梗死的原因。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(干扰素-γ)。干扰素通过诱导II类转录激活物(CIITA)的转录来激活主要组织相容性II类(MHC II)基因转录。最近，我们已经证明了I型胶原基因在I型胶原转录起始点有一个RFX结合位点，并且RFX5只有在干扰素-7刺激后才与CIITA相互作用。CIITA下调胶原合成，而干扰素-7通过CIITA减少胶原基因转录。我们的假设是，通过与CIITA的协同作用，胶原抑制发生在RFX部位，并且对SMC的INF-y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IFNy诱导的MHC-II的激活。除了众所周知的减少脂质合成的作用外，他汀类药物还可以增加胶原基因的表达，减轻炎症，抑制细胞增殖，并减少动脉粥样硬化中基质金属蛋白酶的积聚。我们认为，这些过程是通过阻断CIITA诱导而发生的。我们推测，他汀类药物通过脂类中间体阻断干扰素-γ对CIITA的诱导，从而导致胶原合成增加。RFX1与甲基化的胶原基因转录起始点高度结合，过表达时可抑制胶原基因的转录。在增殖的SMC中，胶原基因在RFX位置发生甲基化。因此，我们推测，随着动脉硬化病变的发展，在SMC增殖过程中，胶原基因甲基化，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型胶原基因转录的调控。2.检测他汀类药物是否通过阻断干扰素-7对CIITA的诱导和/或通过阻断增殖来增加I型胶原基因的表达。3.利用转基因小鼠模型研究I型胶原在体内血管病变中的表达和蓄积。

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.