Platelet glycoprotein VI dependent microparticle formation

描述(申请人提供)：(GP)VI是胶原蛋白的两种主要的血小板受体之一，胶原蛋白是流动的血液和受损的血管系统交界处的关键配体。GPVI与血小板功能的相关性已经通过抑制性抗体、转基因小鼠、人类基因多态和突变而得到证实。胶原纤维对血小板的刺激可导致血小板聚集和血小板微粒(小于1m的血小板碎片)的大量释放。我们将证明微粒的释放是通过与血小板GPVI的配体结合来实现的。除了胶原与止血和血栓形成的相关性外，GPVI和血小板微粒的存在最近被证明在小鼠模型中加剧了类风湿性关节炎。与人类疾病有关的是，在患病的滑液中，每个L体内存在多达400,000个血小板微粒。因此，血小板微粒是类风湿性关节炎患者滑液中的主要细胞成分。GPVI或其相关亚单位FCR-的基因缺失可以改善类风湿性关节炎小鼠模型的疾病。已经观察到在患病的人类滑液中存在的血小板微粒数量的变化，但这种变化的机制基础或生理相关性尚不清楚。我们建议解决GPVI生物学在我们对类风湿性关节炎的理解和治疗方面的一个主要差距。首先，已知的GPVI单倍型可以影响GPVI依赖的信号转导通路。对于血小板微粒是否以及如何受到特定GPVI单倍型的影响，我们的理解存在差距。其次，GPVI的表达和功能是否会影响类风湿关节炎的严重程度，这是一个主要的问题。为了解决这些问题，我们建议1)从定义的GPVI单倍型的正常人样本中表征血小板微粒子的产生，以及2)记录一组类风湿关节炎患者的GPVI单倍型，这些患者的疾病从轻微到极端严重。拟议的研究结果可能会影响治疗类风湿性关节炎的临床实践范例，这些机制可能与其他自身免疫依赖性炎症有关，如哮喘。因此，拟议的研究测试了寻求建立止血、血栓形成和炎症之间联系的新范式的新假设。 公共卫生相关性：这项提案寻求将已建立的血小板生物学概念应用于炎症性关节炎的发病机制。总体目标是定义血小板的“新生物学”，将其生理相关性扩大到一种本质上是自身免疫的疾病-类风湿性关节炎。拟议研究的结果可能会影响类风湿关节炎治疗的临床实践范例和治疗发展。

DESCRIPTION (provided by applicant): (GP) VI is one of two major primary platelet receptors for collagen, a critical ligand at the interface of flowing blood and damaged vasculature. The relevance of GPVI to platelet function has been established with inhibitory antibodies, genetically modified mice, human genetic polymorphisms, and mutations. Stimulation of platelets with fibrillar collagen leads to platelet aggregation and a dramatic release of platelet microparticles (platelet fragments of less than 1 m). We will demonstrate the release of microparticles is mediated by ligand binding to platelet GPVI. Beyond the relevance of collagen to hemostasis and thrombosis, GPVI and the presence of platelet microparticles has recently been shown to exacerbate rheumatoid arthritis in murine models. The link to human disease is the presence of up to 400,000 platelet microparticles per l in diseased synovial fluid. As such, the platelet microparticle represents the major cellular component in synovial fluid from rheumatoid arthritis patients. Genetic deletion of GPVI or its associated subunit, FcR- , ameliorates disease in mouse models of rheumatoid arthritis. Variation in the number of platelet microparticles present in diseased human synovial fluid has been observed but the mechanistic basis or physiologic relevance for this variation is unknown. We propose addressing a major gap in the translation of GPVI biology to our understanding and treatment of rheumatoid arthritis. First, known GPVI haplotypes exist that effect GPVI-dependent signal transduction pathways. A gap exists in our understanding for whether and how platelet microparticles are influenced by specific GPVI haplotypes. Secondly, a major question exists as to whether GPVI expression and function can influence the severity of rheumatoid arthritis. To address these issues, we propose 1) to characterize platelet microparticle production from normal human samples of defined GPVI haplotypes and 2) document GPVI haplotypes in a cohort of patients with rheumatoid arthritis patients exhibiting disease from minimal to extreme severity. The outcome of the proposed studies could impact clinical practice paradigms for the treatment of rheumatoid arthritis with the possibility these mechanisms are relevant to other autoimmune-dependent inflammations, such as asthma. Thus, the proposed studies test novel hypotheses seeking to establish new paradigms linking hemostasis, thrombosis and inflammation. PUBLIC HEALTH RELEVANCE: This proposal seeks to apply established concepts of platelet biology to mechanisms contributing to inflammatory arthritis. The overall objective is to define the "new biology" of platelets expanding their physiologic relevance to a disease that is autoimmune in nature - rheumatoid arthritis. The outcome of the proposed studies can impact clinical practice paradigms and therapeutic development for the treatment of rheumatoid arthritis.