Proatherogenic properties of platelet factor 4

描述(申请人提供)：动脉粥样硬化是一种复杂的血管疾病，涉及炎症、凝血和脂类代谢之间的相互作用。越来越多的证据表明，血小板活化可能在动脉粥样硬化病变的启动和/或扩展中发挥重要作用。由于血小板含有多种炎症、细胞黏附和内皮激活的调节因子，阐明血小板促进动脉粥样硬化形成的机制可能为干预提供新的机会。我的团队主要关注血小板特异性趋化因子--血小板第4因子(PF4)在动脉粥样硬化中的作用。我们已经在体内产生了初步数据，支持PF4是致动脉粥样硬化的概念。我们实验室以前的工作已经定义了两个可能与PF4致动脉粥样硬化有关的受体依赖途径。首先，PF4抑制依赖低密度脂蛋白受体(LDLR)的低密度脂蛋白(LDL)的降解。这导致低密度脂蛋白滞留在细胞表面，容易被修饰为氧化型低密度脂蛋白(ox-LDL)。其次，PF4通过低密度脂蛋白受体相关蛋白(LRP)激活了核因子-kB(一种参与动脉粥样硬化和炎症的转录因子)。这一建议的压倒一切的假设是，PF4激活了这两条途径中的一条或两条，以促进动脉粥样硬化病变的形成。我们进一步假设，在LDLR和/或LRP通路激活之前，PF4四聚体在细胞表面糖胺聚糖(GAG)存在的情况下进行寡聚。为了验证这一假说，我们将通过三个相关的具体目标来研究PF4在体内动脉粥样硬化中的作用，并利用体外模型系统阐明其在体内和体外对血管细胞的作用机制：SA I：《有助于前动脉粥样硬化的PF4的结构特征》将在体外进一步剖析这些途径的细节，重点是PF4的结构特征。SA II：《表征pF4对apoE-/-小鼠脂蛋白代谢和动脉粥样硬化的影响》将扩大我们对缺乏pF4的apoE-/-小鼠的表征，并了解pF4在apoE-/-小鼠中过表达的意义。SA III：《体内PF4致动脉粥样硬化的机制》将研究LDLR和LRP通路在PF4介导的动脉粥样硬化形成中的重要性。这些研究将对活化的血小板释放的最丰富的蛋白pf4在动脉粥样硬化的发展中的作用提供新的见解，描绘体内发生这种情况的途径，并提出潜在的干预动脉粥样硬化的方法。

DESCRIPTION (provided by applicant): Atherosclerosis is complex vascular disorder involving the interplay between inflammation, coagulation and lipid metabolism. There is increasing evidence that platelet activation but may play important roles in the initiation and/or expansion of atherosclerotic lesions. As platelets contain diverse modulators of inflammation, cell adhesion and endothelial activation, elucidating the mechanisms by which platelets promote atherogenesis may offer novel opportunities for intervention. My group has focused on the involvement of the platelet specific chemokine platelet factor 4 (PF4) in atherosclerosis. We have generated preliminary data in vivo that support the notion that PF4 is proatherogenic. Previous work from our laboratory has defined two receptor dependent pathways that may be responsible for PF4 atherogenicity. First, PF4 inhibits low density lipoprotein receptor (LDLR) dependent low density lipoprotein (LDL) degradation. This results in retention of LDL on the cell surface, which is prone to modification into oxidized LDL (ox-LDL). Second, PF4 activated NF-kB (a transcription factor involved in atherosclerosis and inflammation) via the LDL receptor related protein (LRP). The overriding hypothesis of this proposal is that PF4 activates one or both of these pathways to promote atherosclerotic lesion formation. We further posit that PF4 tetramers oligomerize in the presence of cell surface glycosaminoglycans (GAGs) before activation of the LDLR and/or LRP pathways. To test this hypothesis, we will study the effect of PF4 on atherosclerosis in vivo and elucidate its mechanism of action both in vivo and on vascular cells using in vitro model systems through three related Specific Aims: SA I: "Structural features of PF4 that contribute to proatherogenicity" will further dissect the details of these pathways in vitro, focusing on structural characteristics of PF4. SA II: "Characterize the effects of PF4 on lipoprotein metabolism and atherosclerosis in apoE-/- mice" will expand our characterization of apoE-/- mice lacking PF4, as well as to understand the implications of PF4 overexpression in apoE-/- mice. SA III: "Mechanism of PF4 proatherogenicity in vivo" will examine the importance of both the LDLR and LRP pathways for PF4 mediated atherogenesis. These studies will provide novel insights into the role of PF4, the most abundant protein released by activated platelets, on the development of atherosclerosis, delineate the pathways by which this occurs in vivo, and suggest potential methods to intervene in atherogenesis