血小板活化在抗中性粒细胞胞浆抗体相关小血管炎发病机制中的作用

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of autoimmune disease with rapid progression and poor prognosis. The pathogenesis of AAV is not fully clear yet. Our previous study found that complement activation via the alternative pathway plays an important role. The product of complement activation, C5a, in combination with ANCA, can activate neutrophils, leading to inflammation as well as the formation of thrombin, which can activates platelets. Activated platelets can subsequently further activate the complement system. We further found that up-regulation of proteins in platelets from patients with active AAV are associated with cellular signaling activation, leukocyte chemotaxis, cellular adhesion and damage. Therefore, we raised the hypothesis of this project: in AAV, platelets can be activated as the consequence of the interaction among ANCA, neutrophils and complements; activated platelets can further active neutrophils and leads to the injury of endothelial cells, forming the self-amplification loop, and thus plays an important role in the pathogenesis of AAV. We will investigate the pathogenesis and the pathogenic role of platelets activation in AAV via clinical, in vitro and in vivo study. Our study will help to find new clue for the investigation of the pathogenesis, as well as the potential target of treatment of AAV.

抗中性粒细胞胞浆抗体（ANCA）相关小血管炎（AAV）是进展迅速、预后凶险的自身免疫病，发病机制不清，申请者前期研究发现补体旁路途径活化在其中发挥了重要作用，补体活化所产生的C5a与ANCA激活中性粒细胞导致炎症反应，并促进凝血酶的生成，后者可以激活血小板，而血小板活化后会进一步激活补体旁路途径；AAV患者血小板中高表达的活性蛋白质与细胞信号激活、白细胞趋化及细胞粘附、损伤相关，并集中在细胞粘附及炎症等信号通路。因此我们提出进一步的科学假说：在AAV中，血小板被由ANCA、中性粒细胞和补体三者组成的炎症反应环路激活，并发挥一系列致病作用包括激活补体、激活中性粒细胞和损伤内皮细胞等，从而形成ANCA-中性粒细胞-补体-血小板的正反馈环路，导致疾病发生。本项目将从临床、体外和在体三个层面研究AAV中血小板活化的机制和血小板活化后的病生理作用，以期深入揭示本病的发病机制，并为治疗提供潜在靶点。

抗中性粒细胞胞浆抗体（ANCA）相关小血管炎（AAV）是进展迅速、预后凶险的自身免疫病，发病机制不清，申请者前期研究发现补体旁路途径活化所产生的C5a与ANCA激活中性粒细胞导致炎症反应，并促进凝血酶的生成从而激活血小板，而血小板活化后会进一步激活补体旁路途径；AAV患者血小板中高表达的活性蛋白质与细胞信号激活、白细胞趋化及细胞粘附、损伤相关，并集中在细胞粘附及炎症等信号通路。因此我们提出进一步的科学假说：在AAV中，血小板被由ANCA、中性粒细胞和补体三者组成的炎症反应环路激活，并发挥一系列致病作用包括激活补体、激活中性粒细胞和损伤内皮细胞等，从而形成ANCA-中性粒细胞-补体-血小板的正反馈环路，导致疾病发生。本项目得主要研究内容包括：(1) 利用临床标本，进一步验证血小板活化与疾病活动性的关系，(2) AAV中血小板的活化机制和活化后的致病机制等。主要发现包括：(1) AAV患者外周血中血小板微颗粒的水平与疾病活动度密切相关，血小板在本病中可能参与了趋化、凋亡、生长和黏附的生物学过程；(2) 抗髓过氧化物酶抗体（MPO-ANCA）可在低剂量凝血酶的刺激下使血小板活化，血小板中存在MPO；凝血酶启动后，血小板不仅以激活依赖的方式在表面表达MPO，而且还将MPO释放到细胞外，这些作用显著增强了血小板的活化。(3) 应用S1P受体调节剂FTY720对大鼠ANCA相关小血管炎疾病模型进行干预，研究发现FTY720治疗能显著减轻血管炎大鼠病情严重程度，进一步的体外研究表明，FTY720孵育可显著抑制T细胞的增殖、粘附和迁移，增加T细胞凋亡。本项目发表SCI论文6篇，研究成果不仅对揭示AAV发病机制提供了新的理论，也为寻找有效的治疗靶点进行了有益的探索。