Mechanisms of Thrombus Instability

描述（由申请人提供）：血栓栓塞性疾病是西方社会猝死和灾难性残疾的主要原因。这项拨款将采用小鼠肥胖模型来描述潜在的机制。初步研究表明，ob/ob（瘦素缺乏）和db/db（功能性瘦素受体缺乏）小鼠对动脉损伤（FeCI3）的反应形成的血栓是不稳定的，并且经常栓塞。瘦素可稳定ob/ob小鼠而非db/db小鼠形成的血栓，并可促进ob/ob而非db/db小鼠的血小板聚集。本研究的主要假设是瘦素与血小板上的受体结合，引起血小板信号和功能的生化变化，这是血栓稳定所必需的。在Aim 1中，将进行骨髓移植研究以及瘦素和瘦素抑制剂（如中和抗体）输注研究，以确定稳定瘦素在血栓中的起源、靶点和作用动力学，并验证瘦素减少会导致野生型小鼠不稳定血栓形成的假设。瘦素促进血栓稳定性和增强血小板活化的机制将在Aim 2中进行研究。瘦素是最佳血小板所需的可能性：血小板和/或血小板血管壁相互作用将被检查，瘦素和瘦素抑制剂对小鼠血小板聚集、分泌和信号传导的影响将被确定。初步研究表明，瘦素能增强来自某些供体的血小板聚集，而不是来自其他供体的。在Aim 3中，将检查无反应血小板缺陷的性质（例如，瘦素受体异常）。瘦素抑制剂对反应性和非反应性血小板聚集的影响，以及对稳定“血栓”形成的影响将被测试。这些研究将为瘦素在血小板功能以及血栓形成和稳定性中的意想不到的作用提供新的见解。

DESCRIPTION (provided by applicant): Thromboembolic disease is a major cause of sudden death and catastrophic disability in Western societies. This grant will employ murine models of obesity to delineate underlying mechanisms. Preliminary Studies indicate that thrombi formed in ob/ob (leptin-deficient) and db/db (functional leptin receptor-deficient) mice in response to arterial injury (FeCI3) are unstable and frequently embolize. Administration of leptin stabilizes the thrombi formed in ob/ob but not in db/db mice, and promotes the aggregation of platelets from ob/ob but not db/db mice. The primary hypothesis of this grant is that leptin binds to its receptors on platelets, causing biochemical changes in platelet signaling and function that are necessary for thrombus stability. In Aim 1, bone marrow transplantation studies and leptin and leptin inhibitor (e.g., neutralizing antibodies) infusion studies, will be performed to determine the origin, target, and kinetics of action of the stabilizing leptin in thrombi, and to test the hypothesis that decrease in leptin will lead to the formation of unstable thrombi in wild-type mice. The mechanism(s) by which leptin promotes thrombus stability and enhances platelet activation will be studied in Aim 2. The possibility that leptin is required for optimal platelet: platelet and/or platelet vessel wall interactions will be examined, and the effects of leptin and leptin inhibitors on the aggregation, secretion and signaling of murine platelets will be determined. Preliminary Studies show that leptin potentiates the aggregation of human platelets from some donors but not from others. In Aim 3, the nature of the defect in non-responsive platelets (e.g., abnormalities in the leptin receptor) will be examined. The effects of leptin inhibitors on the aggregation of responsive and non-responsive platelets, and on the formation of stable "thrombi" will be tested. These studies will provide novel insights into the unexpected role of leptin in platelet function, and in the formation and stability of thrombi.