同型半胱氨酸通过调控Smad7甲基化致动脉粥样硬化的研究

Homocysteine (Hcy) is an independent risk factor for atherosclerosis (AS), the pathogenic mechanisms may include inflammation, extracellular matrix remodeling, DNA methylation, and so on. Angiotensin Ⅱ (AngⅡ) is also an important factor for AS. Our series of studies have shown that AngⅡ induces fibrosis and inflammation through TGF-b/Smad and NF-Kb signaling pathways, in which reduced Smad7- the negative regulator of these two pathways plays a key role. Since Hcy and AngⅡ have similar pathogenic mechanisms, we hypothesize that Hcy may induce vascular fibrosis and inflammation in AS via reducing levels of Smad7, thereby enhancing TGF-b/Smad and NF-Kb signaling pathways. We will test the hypothesis in vitro and investigate the effects of angiotensin converting enzyme inhibitor on it. Hcy may lead to AS by enhancing methylation in the promoter region of Smad7 gene and reducing its expression. In this study, nested methylation-specific PCR will be used to examine the DNA methylation status of Smad7 gene from cells, tissues and the whole body levels in order to explore the epigenetic mechanisms of Hcy-induced AS and provide a theoretical basis for drug treatment...

同型半胱氨酸(Hcy)是动脉粥样硬化(AS)独立的危险因素，其致病机制可能包括促进炎症反应、细胞外基质重构、干扰甲基化反应等。血管紧张素Ⅱ（AngⅡ）也是致AS的重要因素。课题组系列研究显示AngⅡ通过TGF-b/Smad及NF-Kb信号传导途径导致纤维化炎症病变，其中两条通路的负调节者—Smad7的减少在病变的发展进程中起到关键作用。Hcy与AngⅡ有相似的致病机制。以此假设，在Hcy诱导的AS血管纤维化炎症病变中,同样存在Smad7水平的降低，从而增强两条信号通路。本项目在体外对此机制进行研究，并探索血管紧张素转换酶抑制剂对其的影响。Hcy可能通过促使Smad7基因启动子区高甲基化而降低其表达从而导致AS病变。本研究采用巢式甲基化特异性PCR检测Smad7基因甲基化水平，从细胞、组织及人体层面明确Smad7的甲基化改变以探讨Hcy致AS的表观调控机制，为药物治疗提供理论依据。

同型半胱氨酸(Hcy)是动脉粥样硬化(AS)独立重要的危险因素，其致病机制可能包括促进炎症反应、细胞外基质重构、干扰甲基化反应等。Smad7在炎症、纤维化等过程中起着重要作用。以往对Smad7的研究主要集中在肾脏疾病、心脏重构、肝纤维化及肿瘤等方面，而在AS上鲜见报道。Smad7启动子区可受甲基化调控，因此本项目从组织及人体层面明确AS病变中Smad7甲基化的改变，此改变与血Hcy水平的关系，并从细胞层面进一步探讨Hcy致AS的表观调控机制。结果显示，Smad7在AS组织及AS患者外周血中都呈现高甲基化状态，且外周血Smad7启动子区甲基化程度与血Hcy水平及颈动脉斑块积分呈正相关。此人体研究提示甲基化的Smad7可能是临床上AS病变程度的预测指标和AS新的治疗靶点。在体外研究中，我们发现Hcy引起人脐静脉血管平滑肌细胞（HUVSMCs）内Smad7启动子区甲基化水平呈浓度和时间依赖性增加，从而导致Smad7表达降低，进而激活NF-kB炎症通路。此体外细胞实验补充了我们体内临床研究,并进一步阐明了Hcy致AS的表观调控的血管炎症机制。