A Novel Immune Stimulatory Ligand in Autoimmunity-Associated Angiogenesis

描述(申请人提供)：“共同表位”(SE)--一个由人类白细胞抗原DRB1编码的5氨基酸序列基序，由绝大多数类风湿关节炎(RA)患者携带--与严重疾病有关。RA-SE相关性的机制基础尚不清楚。在以前的研究中，该实验室已经证明SE作为信号转导配体激活其他细胞中一氧化氮(NO)的产生。细胞表面钙网蛋白(CRT)是一种已知的天然免疫受体，参与免疫调节、自身免疫和血管生成。为了更好地了解SE在RA中的致病作用，我们已经开始表征RA相关细胞中的SE信号事件。初步研究表明，在树突状细胞(DC)中，SE是调节性T(Treg)细胞的有效抑制因子，也是促血管生成、产生IL-17的T(Th17)细胞的增强子。在内皮细胞(ECs)中，SE触发促血管生成因子IL-8、IL-6和单核细胞趋化蛋白-1(MCP-1)的产生。此外，研究还发现，在RA患者的滑膜中，CRT被过度瓜氨酸化，而且瓜氨酸化的CRT与SE的亲和力显著高于未修饰的蛋白，并且传递的信号也比未经修饰的蛋白更强。因此，SE触发了与血管生成相关的功能事件，这可能是其对RA的影响的原因。这项研究的主要目的是描述SE在血管生成中的作用，这是包括RA在内的几种自身免疫疾病的关键致病机制。具体地说，我们建议：1.利用小鼠耐受和胶原诱导性关节炎(CIA)模型来表征SE介导的Th17极化的功能效应；2.在实验性血管生成和CIA模型中确定SE-CRT对EC激活的影响；3.确定CRT瓜氨酸化在SE激活的小鼠内皮细胞促血管生成效应中的作用。这些研究共同检验了一种新的范式，为RA的几个重要机制提供了统一的解释。从长远来看，在这个项目中获得的新知识可以为设计新的治疗策略提供基础。

DESCRIPTION (provided by applicant): The "shared epitope" (SE) - a HLA-DRB1-encoded 5-amino acid sequence motif carried by the vast majority of rheumatoid arthritis (RA) patients - is associated with severe disease. The mechanistic basis of RA-SE association is unknown. In prior studies, this laboratory has demonstrated that the SE acts as a signal transduction ligand that activates nitric oxide (NO) production in other cells. SE signaling is transduced by cell surface calreticulin (CRT), a known innate immunity receptor previously implicated in immune regulation, autoimmunity and angiogenesis. To better understand the pathogenic role of the SE in RA, we have begun characterizing SE signaling events in RA-related cells. Preliminary data demonstrate that in dendritic cells (DCs) the SE is a potent inhibitor of regulatory T (Treg) cells and enhancer of pro-angiogenic, IL-17- producing T (Th17) cells. In endothelial cells (ECs), the SE triggers production of the pro-angiogenic factors, IL-8, IL-6 and monocyte chemotactic protein-1 (MCP-1). Additionally, it was found the CRT is over- citrullinated in the synovium of RA patients and citrullinated CRT showed markedly higher affinity to the SE and transduced much more potent signals than the unmodified protein. Thus, the SE triggers angiogenesis- relevant functional events that could account for its effect in RA. The main goal of the research proposed here is to characterize the effect of the SE in angiogenesis, a key pathgenetic mechanism in several autoimmune conditions, including RA. Specifically, we propose to: 1. Characterize the functional effect of SE-mediated Th17 polarization using mouse models of tolerance and collagen-induced arthritis (CIA); 2. Determine the effect of the SE-CRT on EC activation in experimental mouse models of angiogenesis and CIA; 3. Determine the role of CRT citrullination in SE-activated pro- angiogenic effect in mouse ECs Collectively, these studies offer an examination of a novel paradigm that provides a unifying explanation for several important mechanistic aspects of RA. In the long run, the new knowledge gained in this project could provide a basis for designing novel therapeutic strategies.