Platelets and microvascular thrombosis in inflammation

 描述(由申请人提供)： 微血管血栓形成和炎症在包括败血症在内的各种疾病中都是相互关联的，败血症是身体对感染的炎症反应。败血症是退伍军人管理局系统中重症监护病房最常见的入院诊断，也是美国成人重症监护病房的主要死亡原因。患有脓毒症和器官功能障碍的退伍军人有50%的死亡率，微血管血栓与脓毒症的器官功能障碍有关。因此，了解微血管血栓形成的机制对退伍军人保健系统具有重要的临床意义。血小板除了在止血和血栓形成中的作用外，还被越来越多地认为是炎症反应的重要介质。本实验室最近的工作表明，内毒素是革兰氏阴性菌细胞壁的主要成分，通过血小板上的Toll样受体4(TLR4)促进体内微血管血小板血栓的形成。内毒素和血小板TLR4促进组蛋白的释放，这是一种核蛋白，也可能与炎症、血小板激活和血栓形成有关。我们的初步数据显示，组蛋白促进微血管血栓形成，它们激活血小板，并诱导内皮细胞释放von Willebrand因子(VWF)。这项建议将阐述血小板TLR4和组蛋白促进微血管血栓形成的机制。中心假说是，血小板TLR4通过微粒和组蛋白诱导的VWF释放，介导内毒素血症时的微血管血栓形成。该提案将利用体内和体外技术；在体内，它将利用我们实验室和其他实验室建立的两个活体显微镜模型。这些模型可以实时评估微血管血栓形成和血小板-内皮黏附相互作用的动力学。体外实验包括在流动和血小板聚集条件下评估血小板与培养的内皮细胞和固定化底物的粘附性。提出了两个目标：目标1将确定血小板TLR4促进内毒素血症微血管血栓形成的机制。目的2将确定组蛋白促进微血管血栓形成的机制。拟议实验的完成将扩大对炎症和脓毒症微血管血栓形成之间联系的了解，并将为未来旨在预防炎症微血管血栓形成的工作提供基础。长期目标是为脓毒症和其他炎症性疾病患者开发最佳治疗方法。

 DESCRIPTION (provided by applicant): Microvascular thrombosis and inflammation are interrelated in a variety of illnesses including sepsis, the body's inflammatory response to an infection. Sepsis is the most common admission diagnosis in intensive care units in the VA system and the leading cause of death in adult intensive care units in the United States. Veterans with sepsis and organ dysfunction have >50% mortality and microvascular thrombosis is implicated in organ dysfunction in sepsis. Thus, understanding the mechanisms responsible for microvascular thrombosis has major clinical significance to the VA health care system. Platelets are increasingly recognized to be important mediators of the inflammatory response, in addition to their well-established role in hemostasis and thrombosis. Recent work from this laboratory demonstrates that endotoxin, a major component of the cell wall of gram-negative bacteria, promotes microvascular platelet thrombus formation in vivo via toll-like receptor 4 (TLR4) on platelets. Endotoxin and platelet TLR4 promote release of histones, nuclear proteins that may also link inflammation, platelet activation and thrombosis. Our preliminary data show that histones promote microvascular thrombosis, they activate platelets and they induce endothelial cells to release von Willebrand factor (VWF). This proposal will address the mechanisms by which platelet TLR4 and histones promote microvascular thrombosis. The central hypothesis is that platelet TLR4 mediates microvascular thrombosis in endotoxemia via microparticles and histone-induced VWF release. The proposal will utilize in vivo and in vitro techniques; in vivo it will utilize two intravital microscopy modls well established in our lab and others. These models allow assessment of the kinetics of microvascular thrombosis and platelet- endothelial adhesive interactions in real-time. In vitro experiments involve assessment of platelet adhesion to cultured endothelial cells and immobilized substrates under flow and platelet aggregation. Two aims are proposed: Aim 1 will determine the mechanisms by which platelet TLR4 promotes microvascular thrombosis in endotoxemia. Aim 2 will determine the mechanisms by which histones promote microvascular thrombosis. Completion of the proposed experiments will broaden understanding of the links between inflammation and microvascular thrombosis in sepsis, and will provide the basis for future work aimed at preventing microvascular thrombosis in inflammation. The long-term goal is to develop optimal therapeutic approaches for patients with sepsis and other inflammatory diseases.