内皮抗衰老蛋白SIRT1调控组织因子在巨细胞病毒隐性感染协同高脂血症加速脑小血管血栓形成中的作用

Thrombosis in cerebral microvasculature is the main reason for cognitive dysfunction in elderly population. At present, a large number of "healthy" people have been infected by CMV along with hyperlipidemia. We demonstrated in a mouse model that CMV-HC synergistically accelerated light/dye induced thrombosis in cerebral microvasculature. But the mechanism remains unclear. SIRT1 (silent mating type information regulation 2 homolog 1) has been shown to decrease tissue factor expression, and subsequently aortic thrombosis through deacetylation of the p65 subunit of NF-kB resulting in the reduction of the inflammatory responses mediated by this transcription factor. Our preliminary results showed that CMV persistent infection reduced the SIRT1 protein level of the microvessels and CMV-HC changed fibrinolytic system. Additionally, we exhibited that microvascular dysfunction induced by CMV-HC was dependent on the Toll-like receptor-2 signaling pathway, which is essential in NF-κB transcription. Therefore, we speculate that SIRT1 plays an important role in the microvascular thrombosis induced by CMV-HC. CMV reduces endothelial SIRT1 protein leading to increased transcription of NF-kB , which promotes endothelial inflammation and increases tissue factor expression and activity, thereby accelerating microvascular thrombosis. The study can elucidate the mechanisms that acceleration of microvascular thrombosis in CMV-HC patients and provide molecular targets for early intervention.

脑部小血管血栓是老年人群认知功能障碍的罪魁祸首。目前大量“健康”人群同时存在巨细胞病毒感染（CMV）和高脂血症（HC）。我们在小鼠模型中证实：CMV协同HC加速荧光/染料诱导的脑软脑膜小血管血栓形成，但机制尚不清楚。沉默信息调节因子2相关酶1(SIRT1)是抗衰老蛋白，通过去乙酰化NF-kB/p65，减少内皮炎症及组织因子表达，从而降低大动脉血栓。我们研究显示①CMV隐性感染降低小血管SIRT1蛋白水平；②CMV-HC诱导纤溶系统改变；③CMV-HC诱导的小血管功能不全依赖于Toll样受体2通路，其是NF-kB转录的重要上游通路。因此，我们推测CMV-HC减少脑小血管内皮SIRT1蛋白，促进NF-kB转录，促进内皮炎症，增加组织因子表达及活性，最终加速氧化损伤诱导的脑小血管血栓形成。本研究的完成，可阐明CMV-HC加速氧化损伤诱导的脑小血管血栓的主要机制，并为早期干预提供分子靶标。

脑部小血管血栓是老年人群认知功能障碍的罪魁祸首。目前大量“健康”人群同时存在巨细胞病毒感染（CMV）和高脂血症（HC）。我们在小鼠模型中证实：CMV协同HC加速荧光/染料诱导的脑软脑膜小血管血栓形成，但机制尚不清楚。本课题基于CMV诱导细胞的衰老机制，以CMV-HC诱导的脑小血管内皮沉默信息调节因子2相关酶1(SIRT1)降低为切入点探讨其下游经典炎症启动通路NF-kB或其反馈通路变化，最终造成炎症因子及其凝血相关组织因子等变化，从而阐明衰老蛋白SIRT1蛋白在CMV协同HC诱导脑小血管血栓形成的机制。本课题首先发现与无CMV感染及正常饮食组小鼠相比，CMV感染及高脂血症喂养的小鼠脑组织特点：① 脑血管数增多及形态异常；② SIRT1表达明显降低；③p65蛋白表达升高，核转位现象; ④PGC1α和PPARα蛋白表达降低；炎症因子IL-6、TNF-α、AngII及vWF、组织因子（TF）的含量明显上升，而组织因子抑制因子（TFPI）显著降低。随之，我们通过细胞试验应用helenalin抑制NF-KB通路，发现CMV-氧化低密度脂蛋白（ox-LDL）诱导的脑微血管内皮细胞的炎症因子及TF表达降低，TFPI升高；PGC1α和PPARα蛋白表达升高。进一步，我们应用SRT1720促进SIRT1表达，也能减少NF-KB的激活并达到与应用helenalin同样的效果。以上研究提示CMV-HC降低脑小血管内皮SIRT1蛋白表达，一方面通过促进NF-kB转录，增加内皮炎症因子，上调VWF及TF表达及活性，降低TFPI；该过程也可能反馈降低PGC1α和PPARα；另一方面，SIRT1降低可能直接降低PGC1α和PPARα，最终加速损伤脑小血管诱导血栓形成。本研为从衰老机制阐明CMV-HC加速氧化损伤诱导的脑小血管血栓的机制，为早期干预提供分子靶标。