Pharmacogenomics studies of PAR4 regulation in human platelets

 描述(申请人提供)：与白人相比，黑人患心肌梗死和中风的风险更高，这两种疾病的血栓成分都很强，即使在调整了社会经济和临床因素后也是如此。我们小组最近的工作表明，血栓事件风险的种族差异至少部分是由于凝血酶受体，即蛋白酶激活受体4(PAR4)的遗传多态性。我们的初步数据表明，与A120变异的纯合子相比，PAR4的T120纯合子个体的PAR4介导的血小板反应性增加，这与种族无关。此外，在用COX和P2Y12拮抗剂体外处理的血小板中，PAR4的这种变异体依赖的激活持续存在。为了进一步阐明PAR4变异体如何影响血小板反应性，我们建议对T120A PAR4变异体增加PAR4介导的血小板反应性的机制进行表征，并确定该变异体在当前抗血小板治疗的存在下是否改变了血小板的反应性。为此，AI 1将通过分析PAR4刺激的血小板中GQ和G12/13途径的生化成分来阐述PAR4 T120变体增加PAR4介导的血小板反应性的机制，这些途径是从表达这两种变体的供体中分离出来的。此外，目前尚不清楚PAR4 T120A替代是否增强了接受双重抗血小板治疗的心脏病患者的血小板中PAR4介导的血小板反应性。因此，在目标2中，我们将招募使用双重抗血小板药物的患者来评估他们的血小板反应性，以确定从表达T120的个体分离的血小板是否比表达A120的个体的血小板有更多的PAR4介导的血小板激活。最后，我们的初步数据表明，PAR4是减少T120 PAR4变异患者血栓事件的新靶点。因此，在目标3中，我们将测试PAR4拮抗剂抑制受试者血小板激活的功能，这些受试者不受PAR4变体的影响。进一步了解PAR4变异体增强血小板反应性的机制将为靶向治疗那些PAR4血小板反应性增强的患者提供证据。

 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.