TFPI, Protein S, and Plasma FIXa in Hormone-Induced Hypercoagulability

服用口服避孕药的女性发生静脉血栓栓塞症(VTE)是一个广泛的临床问题。 至少部分地由雌激素对凝血蛋白表达的影响所介导的意义 肝脏或血管系统的蛋白质。我们的总体目标是识别和描述潜在的凝血 导致OC诱导的高凝状态的途径和确定个体中普遍存在的遗传因素 VTE的风险最高。使用OC可降低血浆中两种内源性抗凝蛋白的浓度， 组织因子途径抑制物(TFP I)和调节血浆FixA产生和活性的蛋白S(PS)。 我们开发了一种高灵敏度和高特异度(&lt；10pmol/L)的血浆固定物测定技术 使用增强的凝血酶生成试验的活性，该试验通过 FIX缺陷血浆中凝血酶的产生。在献血者的血浆样本中使用这种分析方法，我们发现 OC诱导的TFPI和PS的变化与血浆IXA(FixA)活性升高有关 服用OC的女性比例约为30%。我们的中心假设是OC的使用改变了促凝剂的抑制 天然抗凝剂TFPI和PS的反应，导致血浆因子IXa(FIXA)大幅增加 活跃性和全身高凝状态。这一假说将被探索以确定生化和 OC诱导的高凝状态的遗传相关性。利用重组FIX变异体进行生化研究 对抗凝血酶或PS结合的抵抗力将被用来定义TFPI和PS如何在 基于人体血浆的系统。生化结果的临床影响将通过以下方式进行检查 血浆TFPI、PS和FixA水平的测定、GWAS分析和血栓形成史问卷调查 在两组绝经前妇女中：1)约1000名绝经前献血者的横断面队列； 2)一个纵向队列，约45名青春期女孩，在OC治疗开始后进行一年的跟踪调查。 在横断面队列中收集的数据将被建模，以识别非遗传和遗传因素， 与OC相关的血浆TFPI、PS和FixA的差异以及血栓病史相关。数据 收集的纵向队列将被用来检查OC诱导的时间进程和稳定性 重复测量分析个体内血浆高凝状态。这些发现将被用于 在横断面队列中验证血浆蛋白的变化和GWAS确定的SNPs的作用。 拟议的实验将确定OC诱导的高密度脂蛋白的生化和遗传基础。 凝聚状态主要集中在我们发现血浆中激活的凝血因子FixA的数量增加 约30%的女性使用OC。这些结果也将为进一步的临床研究奠定基础，以确定 血浆FixA及相关遗传标志物对OC诱导血栓形成的预测价值 考虑使用OC和相关激素治疗的女性的循证决策。

Venous thromboembolism (VTE) in women taking oral contraceptives (OC) is a problem of broad clinical significance that is mediated, at least in part, by estrogen effects on the expression of blood coagulation proteins by the liver or vasculature. Our overall goal is to identify and characterize the underlying coagulation pathways leading to OC-induced hypercoagulability and to identify genetic factors prevalent in individuals at highest risk for VTE. OC use decreases the plasma concentration of two endogenous anticoagulant proteins, tissue factor pathway inhibitor (TFPI) and protein S (PS) that modulate plasma FIXa production and activity. We have developed a highly sensitive and specific (<10 pmol/L) technique for measurement of plasma FIXa activity using an enhanced thrombin generation assay, which amplifies the FIXa signal from subject plasma via thrombin generation in FIX-deficient plasma. Using this assay in plasma samples from blood donors we found that OC-induced changes in TFPI and PS are associated with elevated plasma factor IXa (FIXa) activity in ~30% of women taking OC. Our central hypothesis is that OC use alters the inhibition of procoagulant responses by the natural anticoagulants TFPI and PS, producing large increases in plasma factor IXa (FIXa) activity and a systemic hypercoagulable state. This hypothesis will be probed to identify biochemical and genetic correlates of OC-induced hypercoagulability. Biochemical studies using recombinant FIX variants resistant to antithrombin or PS binding will be used to define how TFPI and PS modulate FIXa generation in human plasma-based systems. The clinical impact of the biochemical findings will be examined by measurement of plasma levels of TFPI, PS, and FIXa, GWAS analysis, and a thrombosis history questionnaire in two cohorts of pre-menopausal women: 1) a cross-sectional cohort of ~1000 pre-menopausal blood donors; and 2) a longitudinal cohort of ~45 adolescent girls to be followed for one year after initiation of OC-therapy. The data collected in the cross-sectional cohort will be modeled to identify non-genetic and genetic factors that correlate with OC-associated differences in plasma TFPI, PS and FIXa and thrombosis history. The data collected in the longitudinal cohort will be used to examine the time course and stability of the OC-induced plasma hypercoagulable state within individuals using repeated measures analysis. These findings will be used to validate plasma protein changes and the effect of SNPs identified by GWAS in the cross-sectional cohorts. The proposed experiments will define the biochemical and genetic underpinnings of the OC-induced hyper- coaguable state focused on our finding of elevated amounts of an activated clotting factor, FIXa, in the plasma of about 30% of women using OC. These results will also establish rationale for further clinical studies to define the predictive value of plasma FIXa and associated genetic markers for OC-induced thrombosis and facilitate evidence-based decision-making for women considering use of OC and related hormonal therapies.