Role of citrullination in pyroptotic cell death and rheumatoid arthritis

类风湿性关节炎(RA)是最常见的炎症性风湿病，其特征是对关节、关节外组织和其他器官产生免疫反应。高度促炎细胞因子IL-1的血浆浓度与RA疾病活动性相关，炎性小体控制其释放。由于炎性小体成分的多态与疾病的严重程度和治疗反应有关，因此炎性小体与类风湿关节炎有关。然而，现有的关于类风湿关节炎患者炎性小体的数据仅限于基因表达和相关性研究，而没有关于炎性小体是否在肺、关节内形成和/或释放到类风湿关节炎患者循环中的数据。此外，还没有数据表明哪些特定的炎性小体在RA中被激活，以及炎性小体是如何与这种疾病有关的。此外，是否有炎症体适配器蛋白ASC的细胞外炎症体复合体，称为ASC斑点，可以传播炎症，尚不清楚。我们已经通过实验证明，当ASC斑点被其他细胞摄取时，针对ASC斑点的自身抗体增强了炎症反应。我们的初步数据表明，当炎症小体被激活时，ASC斑点是瓜氨酸化的，我们在RA患者的关节中发现了瓜氨酸化的ASC斑点。瓜氨酸化是一种翻译后修饰，由钙依赖的多肽-精氨酸脱亚氨酶家族酶(PADS)催化为非必需的瓜氨酸氨基酸抗瓜氨酸自身抗体蛋白(ACPA)是RA的标志。我们的初步数据进一步表明，在小鼠和人的巨噬细胞中，炎性小体激活后蛋白质瓜氨酸化是常见的，PAD酶抑制会导致巨噬细胞释放活性的caspase-1和IL-1呈剂量依赖性的减少。因此，我们想要在分子水平上研究炎症体激活和蛋白质瓜氨酸化之间的生化联系。此外，我们希望解决炎症体激活是否在关节炎的发生和发展中起重要作用的问题，将利用RA的CIA和tgTNF-α小鼠模型来研究炎症体激活，并在这些实验模型中探讨炎症体抑制在疾病进展中的作用。

Rheumatoid arthritis (RA) is the most prevalent inflammatory rheumatic disease characterized by an immune reaction against joints, extraarticular tissues and other organs. Plasma concentrations of the highly proinflammatory cytokine IL-1ß correlate with RA disease activity and inflammasomes control its release. Inflammasomes have been implicated in RA, since polymorphisms of inflammasome components are associated with disease severity and response to treatment. However, existing data on inflammasomes in RA is limited to gene expression and association studies but no data exist, whether inflammasomes are formed within the lungs, joints and/or released into the circulation of RA patients. Moreover, there is no data, which particular inflammasome is activated in RA and how inflammasomes are implicated in this disease. Moreover, whether there is a role for extracellular inflammasome complexes of the inflammasome adaptor protein ASC, termed ASC specks, that can propagate inflammation, is unknown. We have shown experimentally that autoantibodies to ASC specks enhanced an inflammatory reaction when ASC specks were taken up by other cells. Our preliminary data suggest that ASC specks are citrullinated when inflammasomes are activated and we identified citrullinated ASC specks in the joints of RA patients. Citrullination is a post-translational modification catalyzed by calcium dependent peptidyl-arginine deiminase family enzymes (PADs) into non-essential citrulline amino acids Anti-citrullinated autoantibodies proteins (ACPA) are a hallmark in RA. Our preliminary data further suggest that protein citrullination is common following inflammasome activation in murine and human macrophages and PAD enzyme inhibition results in a dose-dependent reduction in the release of active caspase-1 and IL-1ß from macrophages. We therefore want to study the biochemical connection between inflammasome activation and protein citrullination on a molecular level. Further, we want to address the question whether inflammasome activation is important for the initiation and progression of arthritis, will make use of the CIA and tgTNF-alpha mouse model of RA to study inflammasome activation and investigate the effect of inflammasome inhibition in the context of disease progression in these experimental models.