Pharmacogenomics studies of PAR4 regulation in human platelets

 描述（由申请人提供）：即使在调整社会经济和临床混杂因素后，与白人相比，黑人心肌梗死和中风的风险增加，这两种疾病具有强烈的血栓成分。我们组最近的研究表明，血栓形成事件风险的种族差异至少部分是由于凝血酶受体蛋白酶激活受体4（PAR 4）的基因多态性。我们的初步数据表明，与A120变异体纯合个体相比，PAR 4 T120变异体纯合个体的PAR 4介导的血小板反应性增加，这与种族无关。此外，PAR 4的这种变体依赖性活化在用考克斯和P2 Y12拮抗剂离体处理的血小板中持续存在。为了进一步描述PAR 4变异体如何影响血小板反应性，我们建议表征T120 A PAR 4变异体增加PAR 4介导的血小板反应性的机制，并确定该变异体是否在当前抗血小板治疗的存在下改变血小板反应性。为此，Ai 1将通过分析从表达任一变体的供体中分离的PAR 4刺激的血小板中的Gq和G12/13途径的生化组分来解决PAR 4 T120变体增加PAR 4介导的血小板反应性的机制。此外，PAR 4 T120 A置换是否增强接受双重抗血小板治疗的心脏病患者血小板中PAR 4介导的血小板反应性仍不清楚。因此，在目标2中，我们将招募接受双重抗血小板治疗的患者，这些患者对任一变体均为纯合子，以评估其血小板反应性，从而确定与来自表达A120的个体的血小板相比，从表达T120的个体分离的血小板是否具有PAR 4介导的血小板活化的增加。最后，我们的初步数据表明，PAR 4是减少T120 PAR 4变异患者血栓形成事件的新靶点。因此，在目的3中，我们将测试PAR 4拮抗剂抑制受试者血小板活化的功能，而不依赖于PAR 4变体。进一步了解PAR 4变体增强血小板反应性的机制将为靶向治疗PAR 4血小板反应性增加的患者提供证据。

 DESCRIPTION (provided by applicant): Blacks are at an increased risk of myocardial infarction and stroke, two diseases with strong thrombotic components, compared to whites even after adjusting for socioeconomic and clinical confounders. Recent work in our group suggests that racial differences in the risk for a thrombotic event is at least in part due to geneic polymorphisms in the thrombin receptor, protease-activated receptor 4 (PAR4). Our preliminary data demonstrates that independent of race individuals homozygous for the T120 variant of PAR4 have an increase in PAR4-mediated platelet reactivity compared to individuals homozygous for the A120 variant. Additionally, this variant dependent activation of PAR4 persists in platelets treated ex vivo with COX and P2Y12 antagonists. To further delineate how the PAR4 variant influences platelet reactivity we propose to characterize the mechanism by which the T120A PAR4 variant increases PAR4-mediated platelet reactivity and determine if this variant alters platelet reactivity in the presence of current antiplatelet therapy. To this end, Ai 1 will address the mechanism by which the PAR4 T120 variant increases PAR4-mediated platelet reactivity by analyzing the biochemical components of the Gq and G12/13 pathways in PAR4 stimulated platelets isolated from donors expressing either variant. Additionally, it remains unknown if the PAR4 T120A substitution enhances PAR4-mediated platelet reactivity in platelets from cardiac patients on dual antiplatelet therapy. Hence, in Aim 2 we will recruit patients on dual antiplatelet that are homozygous for either variant to assess their platelet reactivity to determine if platelets isolated from individuals expressing T120 have an increase in PAR4-mediated platelet activation compared to platelets from individuals expressing A120. Finally, our preliminary data suggests that PAR4 is a new target for decreasing thrombotic events in patients with the T120 PAR4 variant. Therefore, in Aim 3 we will test the function of PAR4 antagonists to inhibit platelet activation of subjects independent of PAR4 variant. A further understanding of the mechanism by which the PAR4 variants enhance platelet reactivity will provide evidence for targeted therapy to treat those with an increase in PAR4 platelet reactivity.