Regulatory Pathways in Osteoclasts and Immune Cells during Inflammatory Arthritis

描述（由申请人提供）：在类风湿关节炎（RA）期间，免疫细胞激活增加导致局灶性骨侵蚀和系统性骨质流失，两者都是由破骨细胞（OCs）介导的。树突状细胞（dc）是与RA相关的炎症反应的关键组成部分，因为它们负责T淋巴细胞的激活，由于自身抗原的异常呈现。中性粒细胞可以通过募集更多的树突状细胞来进一步改善炎症状况，并通过积极分泌炎症和促破骨细胞因子来促进局部骨侵蚀。不幸的是，传统的阻断炎症细胞因子活性的药物治疗可能不足以控制症状和疾病进展。我们的总体目标是确定对类风湿关节炎炎症和溶骨成分调节至关重要的信号分子，并可能为新的更有效的治疗方法奠定基础。我们之前发现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与更普遍表达的PLC？1，从而使其具体的针对性变得困难。二酰基甘油（DAG）是PLC？催化活性和我们组和其他人的数据表明，它介导PLC？2在OCs和免疫细胞中的功能。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）来降低细胞DAG水平的酶。因此,DGK吗?-缺乏会导致DAG的积累。我们的初步数据表明DGK？在oc、中性粒细胞和dc中高度表达。我们还发现缺乏DGK？具有明显的骨质疏松表型，其特征是小梁数量和厚度减少，OC形成和功能增强。因此，我们的数据表明DGK？是破骨细胞激活的负调节因子。基于这些信息，我们的中心假设是DGK？通过DAG的调节，是PLC?2下游骨细胞和免疫细胞的常见调节因子。因此，我们建议：具体目标1：研究DGK？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？血清性关节炎的发生、消退及其对中性粒细胞活化的影响。具体目标3：确定DGK的作用？抗原诱导的关节炎及其在DC介导的T细胞活化中的作用。本应用程序的目标是证明DGK？OCs、中性粒细胞和dc的激活和功能，作为一种针对RA的溶骨和炎症成分的方法。这种新方法可能为类风湿关节炎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.