Regulatory Pathways in Osteoclasts and Immune Cells during Inflammatory Arthritis

描述（由申请方提供）：在风湿性关节炎（RA）期间，免疫细胞活化增加导致局灶性骨侵蚀以及全身性骨丢失，两者均由破骨细胞（OC）介导。树突状细胞（DC）是与RA相关的炎症反应的关键组分，因为它们负责由于自身抗原的异常呈递而激活T淋巴细胞。中性粒细胞可以通过募集更多的DC来进一步增强炎症状况，并通过主动分泌炎性细胞因子和促破骨细胞生成细胞因子来促进局部骨侵蚀。不幸的是，阻断炎性细胞因子活性的传统药物疗法可能不足以控制症状和疾病进展。我们的总体目标是识别对调节RA的炎症和溶骨性成分至关重要的信号分子，并为新的更有效的治疗方法奠定基础。我们以前发现PLC？2是与RA相关的骨稳态和炎症反应的关键调节剂。然而，PLC？2股高同源性更普遍表达PLC？1，从而使其具体目标难以确定。甘油二酯（DAG）是PLC的下游产物。2催化活性和数据从我们的小组和其他人表明，它介导PLC？2在OC和免疫细胞中起作用。为了研究DAG的作用，我们现在将注意力转向DGK？，一种通过将DAG转化为磷脂酸（PA）来降低DAG细胞水平的酶。因此，DGK？缺乏引起DAG的积累。我们的初步数据显示DGK？在OC、中性粒细胞和DC中高度表达。我们还发现，小鼠缺乏DGK？具有显著的骨小梁表型，其特征为骨小梁数量和厚度减少以及OC形成和功能增强。因此，我们的数据表明，DGK？是破骨细胞活化的负调节剂。基于这些信息，我们的中心假设是DGK？，通过调节DAG，是PLC下游骨和免疫细胞的常见调节因子？2.因此，我们建议：具体目标1：调查的机制，DGK？在体外和体内调节破骨细胞形成和骨吸收。具体目标2：检查DGK的作用？血清诱导性关节炎的发生和消退以及对中性粒细胞活化的影响。具体目标3：确定DGK的作用？及其在DC介导的T细胞活化中的作用。这个应用程序的目标是证明DGK的重要性？在OC、中性粒细胞和DC的激活和功能中作为靶向RA的溶骨性和炎性组分的一种方式。这种新方法可能为RA的新治疗干预奠定基础。 公共卫生相关性：考虑到西方人群中炎性关节炎和相关骨丢失的影响，我们研究的意义在于鉴定DGK6作为骨稳态的新调节剂。本申请的目的是证明DGK6在OC、嗜中性粒细胞和DC的活化和功能中的重要性，作为靶向风湿性关节炎的溶骨性和炎性组分的一种方式。这种新方法可能为风湿性关节炎和炎性骨丢失的新治疗干预奠定基础。

DESCRIPTION (provided by applicant): During Rheumatoid Arthritis (RA), increased immune cell activation leads to focal bone erosion as well as systemic bone loss, both mediated by osteoclasts (OCs). Dendritic cells (DCs) are critical components of the inflammatory response associated with RA as they are responsible for the activation of T lymphocytes, due to abnormal presentation of self-antigens. Neutrophils can further enhance the inflammatory condition by recruiting more DCs and contribute to local bone erosion by actively secreting inflammatory and pro-osteoclastogenic cytokines. Unfortunately, traditional pharmacotherapy to block the activity of inflammatory cytokines can be inadequate in controlling symptoms and disease progression. Our overall goal is to identify signaling molecules that are critical to modulate the inflammatory and osteolytic components of RA and that may lay the groundwork for novel and more effective therapeutic approaches. We have previously found that PLC?2 is a critical modulator of bone homeostasis and inflammatory responses associated with RA. However, PLC?2 shares high homology with the more ubiquitously expressed PLC?1, thus rendering its specific targeting difficult. Diacylglycerol (DAG) is a downstream product of PLC?2 catalytic activity and data from our group and others indicate that it mediates PLC?2 function in OCs and immune cells. In order to study the role of DAG, we now turned our attention to DGK?, an enzyme that decreases cellular levels of DAG by converting it to phosphatidic acid (PA). Thus, DGK?-deficiency causes accumulation of DAG. Our preliminary data indicate that DGK? is highly expressed in OCs, neutrophils and DCs. We also found that mice lacking DGK? have a substantial osteoporotic phenotype, characterized by reduced trabecular number and thickness and enhanced OC formation and function. Thus, our data indicate that DGK? is a negative modulator of osteoclast activation. Based on this information, our central hypothesis is that DGK?, via modulation of DAG, is a common regulator of bone and immune cells downstream of PLC?2. Thus, we propose to: Specific Aim 1: Investigate the mechanism by which DGK? modulates osteoclast formation and bone resorption in vitro and in vivo. Specific Aim 2: Examine the role of DGK? in development and resolution of serum induced arthritis and its effect on neutrophil activation. Specific Aim 3: Determine the role of DGK? in antigen-induced arthritis and its effect in DC- mediated T cell activation. The goal of this application is to demonstrate the importance of DGK? in the activation and functionality of OCs, neutrophils and DCs as a way to target both the osteolytic and inflammatory components of RA. This novel approach might lay the basis for new therapeutic interventions for RA. PUBLIC HEALTH RELEVANCE: Considering the impact of inflammatory arthritis and associated bone loss in the western population, the significance of our study consists in having identified DGK6 as a novel regulator of bone homeostasis. The goal of this application is to demonstrate the importance of DGK6 in the activation and functionality of OCs, neutrophils and DCs as a way to target both the osteolytic and inflammatory components of Rheumatoid Arthritis. This novel approach might lay the basis for new therapeutic interventions for Rheumatoid Arthritis and inflammatory bone loss.