The Role of IL-17 in Monocyte Migration

描述(由申请人提供)： 已有研究表明，白介素17在类风湿关节炎动物模型的发病机制中起重要作用。然而，IL-17促进疾病的机制还不完全清楚。TH-17细胞是一种新的CD4+T细胞谱系，不同于TH1和TH2，其特征是产生IL-17。与正常外周血(PB)相比，RA滑液(SF)中TH-17细胞的数量增加。腺病毒将IL-17诱导的单核细胞体内募集转移到腹膜腔内。在没有其他介质的情况下，IL-17在RA SF中检测到的浓度下对单核细胞具有趋化作用。通过中和IL-17受体(R)，IL-17诱导的单核细胞迁移被取消。我们还证明，与假免疫耗竭相比，IL-17免疫耗竭显著降低了RA SF诱导的单核细胞趋化能力。同时检测IL-17对单核细胞趋化的间接影响。IL-17激活的RA滑膜组织(ST)成纤维细胞和体外分化的巨噬细胞(IVDM$S)同时产生MCP-1和CCL20，而CXCL16仅在M$S中被诱导。根据我们的初步数据，我们推测IL-17可以通过改变单核细胞表面整合素的构象，从而增加其与内皮上同源配体的结合亲和力，直接诱导单核细胞向RA滑膜组织内皮细胞迁移。此外，我们假设IL-17通过诱导内皮细胞产生单核细胞趋化蛋白-1而介导单核细胞重新聚集到滑膜。本研究的目的是研究IL-17诱导的单核细胞向RA ST的迁移是通过IL-17对单核细胞的直接作用，还是通过由内皮细胞产生的趋化因子和/或整合素介导的IL-17的间接作用，或者两者兼而有之。本方案的具体目的是：a.确定IL-17是否促进严重联合免疫缺陷(SCID)小鼠移植的RA ST的单核细胞募集；b.研究IL-17R阻断单核细胞是否能阻止其对IL-17的应答而归巢至SCID小鼠植入的RA ST；2：a.检测IL-17是否能诱导内皮细胞产生单核细胞趋化因子；b.研究IL-17是否诱导单核细胞和内皮细胞(ICAM1和VCAM1)的黏附分子激活和表达(LFA1，VLA4)；C.研究IL-17诱导的单核细胞在层流中的跨内皮细胞迁移是否依赖于其对单核细胞、内皮细胞或两者表达的黏附分子的影响。这项拟议研究的成功完成将阐明IL-17介导单核细胞重新聚集到RA ST的机制。这些调节IL-17诱导的单核细胞迁移的因子可能是RA的潜在治疗靶点。 公共卫生相关性： 项目叙事。在类风湿性关节炎(RA)中，一种名为单核细胞的免疫细胞迁移到关节内会导致炎症。在这项提案中，我们展示了新的数据显示，一种名为IL-17的促炎细胞信号蛋白在单核细胞的迁移中起重要作用，并且这种作用发生在RA关节液中存在的IL-17浓度时。这项拟议研究的成功完成将阐明IL-17介导单核细胞在RA关节组织中迁移的机制。这些调节IL-17诱导的单核细胞迁移的因子可能是RA的潜在治疗靶点。

DESCRIPTION (provided by applicant): Project Summary It has been shown that interleukin (IL)-17 is important in the pathogenesis of animal models of Rheumatoid Arthritis (RA). However, the mechanism by which IL-17 promotes disease is incompletely understood. The TH- 17 cell, a new lineage of CD4+ T cells distinct from TH1 and TH2 is characterized by the production of IL-17. We identified increased numbers of TH-17 cells in RA synovial fluid (SF) compared to normal peripheral blood (PB). Adenovirally transferred IL-17 induced in vivo monocyte recruitment into the peritoneal cavity. IL-17, in the absence of other mediators, was chemotactic for monocytes at the concentrations detected in the RA SF. IL-17-induced monocyte migration was abrogated by neutralizing IL-17 receptor (R). We also demonstrated that IL-17 immunodepletion significantly reduced monocyte chemotaxis induced by RA SF compared to sham immunodepletion. The indirect effects of IL-17 on monocyte chemotaxis were also examined. RA synovial tissue (ST) fibroblasts and in vitro differentiated macrophages (IVD M$s) activated by IL-17 produced both MCP-1 and CCL20 while CXCL16 was only induced in M$s. Based on our preliminary data we hypothesize that IL-17 can induce monocyte transendothelial migration into the RA ST directly by altering integrin conformation on monocytes and thereby increasing their binding affinity to their cognate ligands on endothelium. Further, we hypothesize that IL-17 mediates monocyte recruitment into the synovium by inducing MCP-1 production by endothelial cells. The goal of this proposal is to examine whether IL-17-induced monocyte migration into the RA ST is through direct effects of IL-17 on monocytes or through the indirect effects of IL-17 mediated by chemokines and/or integrins produced by endothelial cells or perhaps both. The specific aims of this proposal are 1: a. Determine whether IL-17 promotes monocyte recruitment into RA ST engrafted in the severe combined immune deficiency (SCID) mice; b. Investigating whether IL-17R blockade on monocytes prevents their homing to engrafted RA ST in SCID mice in response to IL-17; 2: a. Examine whether IL-17 can induce monocyte chemoattractant chemokines from the endothelial cells; b. Investigate whether IL-17 induces adhesion molecule activation (LFA1, VLA4) and expression (LFA1, VLA4) on monocytes, and endothelial cells (ICAM1 and VCAM1) or both; c. Investigate whether IL-17-induced monocyte transendothelial migration in laminar flow depends on its effect on adhesion molecules expressed on monocytes, endothelial cells or both. Successful completion of the proposed research will elucidate the mechanism by which IL-17 mediates monocyte recruitment into the RA ST. Those factors that regulate IL-17- induced monocyte migration may be potential therapeutic targets in RA. PUBLIC HEALTH RELEVANCE: Project Narrative. In rheumatoid arthritis (RA), migration of a type of immune cells called monocytes into the joint contributes to inflammation. In this proposal we demonstrate novel data showing that a pro-inflammatory cell signaling protein called IL-17 is important in the migration of monocytes, and that this effect occurs at the concentrations of IL-17 present in RA joint fluid. Successful completion of the proposed research will elucidate the mechanism by which IL-17 mediates monocyte migration in RA joint tissue. Those factors that regulate IL- 17-induced monocyte migration may be potential therapeutic targets in RA.