OX40/OX40L介导滤泡辅助性T细胞激活促进动脉粥样硬化进展的作用及机制研究

Dysfunction of the immune system plays a critical role in the initiation and progression of atherosclerosis (AS). Follicular helper T cell (Tfh) is a novel T cell subtype, which has been proved to modulate maturation and differentiation of B cells. Our preliminary data have presented that the level of Tfh and IL-21 in peripheral blood was significantly increased in patients with coronary heart disease, and was correlated with the severity of lesions, but the inside mechanism was still unclear. Based on these, we hypothesize that important etiological factor of AS, OX40L activate Tfh via OX40, which would induce dysfunction of B cells and accelerate AS progression. In order to verify it, the maturation, activation and OX40 expression of Tfh in patients and healthy controls will be firstly detected and analyzed to confirm the relationship with AS in a clinical trial with large amount of samples, secondly the potential signal pathway responsible for activation of Tfh by OX40/OX40L will be explored and verified with combination of chip screening and techniques including siRNA and et al; and at last such mechanism will be proved in vivo animal models by transplantation of Tfh pre-treated with different interventions, which are based on the results of in vitro experiments. Results of this project will help to uncover the mechanism how OX40/OX40L-activated Tfh induce hyper-function of B cells in and promote AS progression, and provide potential targets for clinical intervention in future.

动脉粥样硬化（AS）发生与免疫异常密切相关。新发现的滤泡辅助性T细胞（Tfh）是调控B细胞成熟分化的关键。前期研究发现：冠心病患者外周血Tfh数量及其效应分子IL-21显著升高，并与冠脉病变程度正相关，但导致Tfh功能异常的机制尚不清楚，故此推测：AS的致病因素OX40L经表面受体OX40激活Tfh，致其辅助B细胞活化的功能亢进促AS进展。为验证该假说，拟首先在大样本临床研究中，检测并分析外周血Tfh的成熟度、活性、OX40表达及其辅助B细胞功能的变化，进一步明确Tfh功能和OX40表达与AS相关性；再于体外培养的Tfh中，经芯片结合siRNA等手段，筛选并初步验证OX40/OX40L激活Tfh的分子机制；最后在回输小鼠模型中明确上述信号通路介导Tfh激活促AS进展的作用，本研究将有助于阐明OX40/OX40L介导Tfh辅助B细胞功能亢进促AS进展的作用机制，并为未来临床干预提供潜在靶标。

动脉粥样硬化（AS）是由于脂肪、血栓、结缔组织和碳酸钙在血管（主要是动脉）沉积所造成的一种对人体有害的状态，其中冠状动脉粥样硬化是导致冠心病的主要因素。AS的发生机理错综复杂。近期研究显示，AS与免疫异常密切相关。滤泡辅助性T细胞（Tfh）一种新发现的辅助性CD4+T细胞亚型，在免疫反应中发挥重要功能。课题组推测Tfh与AS导致的CAD密切相关。本课题的研究结果显示，Tfh在AS导致的CAD患者中的绝对数量和在CD4+T细胞中的比例都有显著的上升，亚型比例失调，并且患者血液循环中的Tfh细胞多为PD-1+CCR7-表型。Tfh的功能研究显示，AS患者Tfh-Th1亚型和Th17亚型细胞因子分泌升高，而Th2亚型细胞因子分泌减少。并且，AS导致的CAD患者中Tfh促使幼稚B细胞向浆母细胞方向分化。课题组进一步检测了Tfh对于肠道B细胞功能的影响，发现AS导致的CAD患者中存在肠道低级别炎症状态， 且这种状态以B细胞/浆母细胞增加为特征。而外周血Tfh 细胞在可以肠道中浸润增加以协同B 细胞IgG 的产生。另外，课题组研究数据表明AS导致的CAD患者外周血中的Tfh细胞具有更强的促炎功能。课题组深入探讨了Tfh的调控机制，发现OX40通路对于介导Tfh细胞对于B细胞的细胞因子分泌发挥重要的调控作用。除此以外，PD-1通路是调控Tfh细胞本身的细胞因子产生的重要途径。而发挥这些作用的重要一环是STAT1和STAT3的磷酸化。最后，课题组通过小鼠模型验证了Tfh与AS发生发展的关系。结果显示，过继回输Tfh可以促进小鼠AS的发展。本研究从一个崭新的方向揭示了AS形成发展机制，为将来开发新型治疗方法提供理论依据。