新的活性分子组织因子途径抑制物C端小肽促动脉粥样硬化斑块消退的机制研究

Although atherosclerotic lesion can be regressed, there is no available approach to regress it. Since aggregation of macrophages plays a critical role in atherosclerosis, the reduction of lesion macrophage content may be exploited as a potential strategy for the treatment of this disease. Our previous study found that tissue factor pathway inhibitor (TFPI) inhibited TF activity and reduced the development of atherosclerosis. One of our recent publications shows that a tethered human TFPI expressed on vascular smooth muscle cells attenuates atherosclerosis. Although we have shown that a 32-amino acid human TFPIct fragment (TFPIct32) can promote the regression of atherosclerosis, the underlying mechanism is still unclear. Based on the literatures and our previous studies, we postulated the hypothesis that TFPIct32 promotes the regression of atherosclerosis possibly by a combination of mechanisms including inhibition of inflammation and reduction of lesion macrophage content. In this study, using raw264.7 cells, atherosclerosis-prone apolipoprotein E deficient (ApoE-/-) mice and ApoE-/- mice transplanted with atherosclerotic plaques (aortic segment with atherosclerotic plaques from different donors), we will clarify the molecular mechanism by which TFPIct32 reverses atherosclerotic plaques through evaluating its role on the regression of atherosclerotic plaques, inflammation, macrophage recruitment and reverse emigration of macrophages, and expression of CCR7 and UNC5b. This work should establish the foundations for a novel approach to reverse atherosclerosis for clinical translation to reduce and prevent cardiovascular disease events, based on the ability of TFPIct32 to inhibit inflammation and macrophage recruitment, and promote reverse emigration of macrophages.

动脉粥样硬化（As）可以消退，而目前尚无有效的消退手段。巨噬细胞聚集是As的发生发展中的关键因素之一，减少斑块内巨噬细胞数量是促斑块消退的有效途径。前期研究表明，组织因子途径抑制物（TFPI）能阻止As的发生与发展。我们最新的研究发现，人TFPI的C端一段由32个氨基酸序列构成的小片段（TFPIct32）可促As病变消退，而机制不清。基于最新文献和前期研究基础，我们认为TFPIct32通过减少斑块内巨噬细胞数量与抑制炎症，进而促进斑块消退。据此，本研究将在细胞、As小鼠及移植As斑块的ApoE-/-小鼠模型来观察TFPIct3对As病变消退，巨噬细胞募集与外迁，炎症及诱导巨噬细胞移出斑块的受体 CCR7 及抑制巨噬细胞移出的受体 UNC5b表达等的影响；证实TFPIct32对斑块的消退作用，揭示其通过减少斑块内巨噬细胞聚集和抑制炎症而促斑块消退的新机制，为As斑块的消退治疗提供新策略。

动脉粥样硬化（Atherosclerosis，As）是动脉的慢性炎症过程，其特征是修饰的低密度脂蛋白在血管壁沉积，导致动脉粥样硬化斑块的形成。它是脑卒中、心肌梗塞等急性心脑血管事件的主要原因。尽管动脉粥样硬化的临床诊断和治疗取得很大进展，但斑块形成的复杂过程给有效的诊断和治疗带来了巨大的挑战。特异性的诊断方法及高效的治疗手段成为动脉粥样硬化的研究热点。大量研究表明，巨噬细胞作为斑块中的重要成分，是影响斑块发展的重要调控靶点。巨噬细胞在吞噬大量修饰的低密度脂蛋白后转变为巨噬细胞源性泡沫细胞。泡沫细胞的迁移能力较低，大量滞留在内膜下，进而驱动粥样斑块和坏死核心形成，炎症状态加剧，斑块持续发展。因此，促进泡沫细胞迁出有助于抑制斑块进展。组织因子途径抑制物（Tissue factor pathway inhibitor，TFPI）是组织因子介导的外源性凝血途径的生理性抑制剂。研究证实，TFPI对斑块发展的抑制作用与其下调血管内皮细胞激活、血管平滑肌细胞的增殖和迁移以及炎症因子的表达有关。研究显示，TFPIct32作为TFPI的C端由32个氨基酸序列构成的肽段，具有类似TFPI抗动脉粥样硬化的作用，但是其具体作用机制未明。本课题组实验结果表明：TFPIct32处理后，ApoE-/-小鼠主动脉窦处斑块面积缩小，且斑块内巨噬细胞数量减少。其作用机制可能与通过上调泡沫细胞表面趋化因子受体CCR7表达来促进泡沫细胞的迁移有关。并且TFPIct32对平滑肌细胞增殖与迁移也表现出抑制作用，其具体机制还有待进一步探讨研究。为抑制As斑块的进展或促进其消退提供了有前景的干预策略。