REGULATORY PATHWAYS IN OSTEOCLAST FORMATION AND FUNCTION

儿童或成人关节炎的确切发病机制尚不清楚，但有几种细胞参与自身免疫性关节炎的发展，包括T淋巴细胞和B淋巴细胞、滑膜细胞、巨噬细胞、中性粒细胞和破骨细胞（OC）[1-3]。识别影响骨免疫系统的常见信号分子及其对正常和病理性骨质流失的影响可能为未来治疗各种疾病（如风湿性关节炎）奠定基础。我们发现PLC32就是这样的候选者。除了B细胞发育缺陷外，PLC32-/-小鼠由于破骨细胞募集和功能[4][5]异常而发生骨变。PLC32影响破骨细胞发生过程中rankl诱导的两大信号通路，即NF:B和NFAT的激活，以及再吸收细胞中1v23整合素粘附结构的激活和适当定位。出乎意料的是，我们还发现PLC32 -/-小鼠可以免受与两种不同关节炎模型相关的炎症的侵袭，一种是严格依赖中性粒细胞[6]的血清诱导关节炎，另一种是依赖T细胞激活的抗原诱导关节炎。虽然PLC32不在T细胞中表达，但PLC32控制树突状细胞（DC）激活T细胞的能力。抗原脉冲PLC32-/- DC，而不是WT DC，在局部膝关节注射抗原后注射到WT小鼠体内，不能引发炎症反应。相反，向PLC32-/-小鼠注射抗原脉冲WT DC完全恢复炎症反应，而不引起破骨细胞募集和局灶性骨溶解。这些有趣的数据表明，PLC32是炎症性关节炎期间骨完整性和免疫反应的关键调节剂。基于这一观察，我们假设PLC32是炎症性关节炎中dc介导的T细胞激活所必需的。因此，我们的目的是研究PLC32在炎症性关节炎期间抗原呈递和DC运动中的作用。我们相信，将我们最初提议的重点从理解PLC32在OCs中的作用扩展到研究其在DC中的作用，可能会导致针对类风湿关节炎炎症和溶骨成分的新治疗途径。本申请是为了响应通知no - od -09-058: NIH宣布恢复法案基金可用于竞争性修订。

DESCRIPTION (provided by applicant): Project Summary/Abstract The exact pathogenesis of arthritis in children or adults is not known, but several cells contribute to the development of autoimmune arthritis including T and B lymphocytes, synovial cells, macrophages, neutrophils and osteoclasts (OC) [1-3]. Identifying common signaling molecules affecting the osteo-immune system and their impact on normal and pathological bone loss may lay the groundwork for future therapies for the variety of diseases such as rheumatoid arthritis. We have found PLC32 to be such candidate. In addition to defective B cell development, PLC32-/- mice are osteopetrotic due to aberrant osteoclast recruitment and function [4] [5]. PLC32 affects the two major RANKL-induced signaling pathways during osteoclastogenesis, namely NF:B and NFAT activation, as well as activation and proper localization of 1v23 integrin adhesive structure in the resorbing cell. Unexpectedly, we also found that PLC32 -/- mice are protected from the insurgence of inflammation associated with two different models of arthritis, the serum induced arthritis which is strictly dependent on neutrophils [6], and the antigen induced arthritis which relays on T cell activation. Although PLC32 is not expressed in T cells, PLC32 controls the ability of dendritic cells (DC) to activate T cells. Antigen pulsed PLC32-/- DC, but not WT DC, fail to initiate an inflammatory reaction when injected into WT mice following a local knee injection of the antigen. Conversely, injection of antigen pulsed WT DC into PLC32-/- mice completely restores the inflammatory response without eliciting osteoclast recruitment and focal osteolysis. These intriguing data position PLC32 as a critical modulator of bone integrity and immune responses during inflammatory arthritis. Based on this observation, we hypothesize that PLC32 is required for DC-mediated T cell activation during inflammatory arthritis. Thus, we aim to study the role of PLC32 in antigen presentation and in DC motility during inflammatory arthritis. We believe that expanding the focus of our original proposal from understanding the role of PLC32 in the OCs to study its effects in DC, may lead to new therapeutic avenues aimed at targeting the inflammatory and osteolytic components of rheumatoid arthritis. This application is in response to Notice NOT-OD-09-058: NIH Announces the Availability of Recovery Act Funds for Competitive Revision. PUBLIC HEALTH RELEVANCE: The overall goal of this proposal is to expand the goals of our original R01 proposal from studying PLC32- mediated regulation of osteoclast differentiation and function to examining the role of PLC32 in DC-mediated T cell activation. Specifically, we aim to investigate the role of PLC32 in antigen presentation and in the recruitment of DCs to the lymph nodes, both critical events required for T cell activation, during inflammatory arthritis. Since the interaction between immune cells and osteoclast is increasingly recognized, identifying common signaling molecules affecting the osteo-immune system and their impact on normal and pathological bone loss may lay the groundwork for future therapies for the variety of diseases such as inflammatory arthritis. .