VWF Activity: Molecular Biology, Ethnic Diversity and Disease Associations

项目摘要von Willebrand因子(VWF)通过将血小板拴在血管损伤部位来启动止血，并通过保护凝血因子VIII(FVIII)免受蛋白质降解而参与凝血。低VWF抗原和/或缺乏大的多聚体可能导致出血，而高水平和/或超大的VWF多聚体的存在与血栓形成有关。这种双向活性表明，VWF的表达和黏附活性受到高度调控，以维持主动止血而不促进血栓形成。血浆VWF水平在健康受试者中差异很大，越来越多的证据表明，这种差异具有种族多样性。已知环境和遗传因素导致VWF的合成、稳定性、粘附性和清除性的变化，但关键问题仍然存在。首先，在健康人中，VWF抗原和黏附活性之间有什么关系？第二，遗传变异如何与环境因素相互作用来改变VWF的合成和活性，VWF是一种已知的急性相反应物？第三，种族和年龄如何影响VWF基因变异与VWF黏附活性和血栓性疾病的发展的关联？我们假设：1)VWF基因的变异不仅影响VWF的表达，而且影响VWF的黏附活性；2)存在强烈的基因-环境交互作用，影响VWF的黏附活性，这种交互作用通过种族、年龄和FVIII等协变量表现出来；以及3)与单独模拟VWF抗原相比，评估VWF的黏附活性可以改善血栓性疾病的风险评估。我们广泛的、长期的目标是了解VWF的生物学活性及其对种族、老龄化和FVIII疾病关联的修饰。这项提议有三个具体目标。首先是研究来自社区动脉粥样硬化风险中心和日本水田队列的受试者的vwf黏附活性，在25年来收集的样本中，vwf抗原一直被测量为低(≤50%)或高(≥200%)。VWF黏附活性和VWF合成和清除速率的测定将确定1)VWF水平和黏附活性之间的内在关系，以及2)衰老和种族对这种关系的影响。第二，1)在欧洲裔美国人、非裔美国人和日本人三个民族的受试者中鉴定与VWF抗原和黏附活性相关的遗传变异；2)检测这些关联的种族修饰；以及3)检测调节VWF抗原和黏附活性的遗传上位性和新的分子相互作用。第三是确定1)测量VWF活性和VWF合成-清除速率是否比单独测量VWF抗原更能改善心肌梗死、缺血性中风和外周动脉疾病的风险预测；2)VWF和/或黏附活性低的受试者是否免受这些疾病的保护；以及3)种族和年龄如何改变风险。这项研究与美国国立卫生研究院在抗击与衰老相关的血栓和出血障碍以改善美国公共健康方面的使命高度相关。

Project Summary von Willebrand factor (VWF) initiates hemostasis by tethering platelets to sites of vascular injury and participates in the coagulation by protecting the coagulation factor VIII (FVIII) against proteolytic degradation. A low VWF antigen and/or lack of large multimers can result in bleeding, whereas high levels and/or the presence of ultra‐large VWF multimers are associated with thrombosis. This bidirectional activity suggests that VWF expression and adhesive activity are highly regulated to maintain active hemostasis without promoting thrombosis. Plasma VWF levels vary significantly among healthy subjects and there is increasing evidence that this variation is ethnically diverse. Environmental and genetic factors are known to contribute to variations in VWF synthesis, stability, adhesiveness, and clearance, but crucial questions remain. First, what is the relationship between VWF antigen and adhesive activity in healthy individuals? Second, how do genetic variations interact with environmental factors to modify the synthesis and activity of VWF, a known acute phase reactant? Third, how do ethnicity and aging influence the association of variants in the VWF gene with VWF adhesive activity and the development of thrombotic diseases? We hypothesize that 1) variation in the VWF gene influences not only VWF expression, but also adhesive activity; 2) there is a strong gene‐ environment interaction that influences VWF adhesive activity and this interaction is manifested through covariates as ethnicity, age and FVIII; and 3) evaluating VWF adhesive activity can improve risk assessments for thrombotic diseases compared to modeling VWF antigen alone. Our broad, long‐term objective is to understand VWF biological activity and its modification of disease associations by ethnicity, aging and FVIII. There are three specific aims in this proposal. First is to characterize VWF adhesive activity in subjects from the Atherosclerosis Risk in Communities (ARIC) and the Japanese Suita cohorts, whose VWF antigen was consistently measured as low (≤ 50%) or high (≥ 200%) in samples collected over 25 years. VWF adhesive activity and rates of VWF synthesis and clearance will be determined to define 1) an intrinsic relationship between VWF levels and adhesive activity and 2) the impact of aging and ethnicity on this relationship. Second is to 1) identify genetic variants associated with VWF antigen and adhesive activity in subjects from three ethnic groups of European American, African Americans, and Japanese; 2) detect ethnic modifications of these associations; and 3) detect the genetic epistasis and novel molecular interactions that regulate the VWF antigen and adhesive activity. Third is to determine 1) if measuring VWF activity and rates of VWF synthesis‐ clearance improve risk predictions for myocardial infarction, ischemic stroke, and peripheral arterial disease than VWF antigen alone; 2) if subjects with low VWF and/or adhesive activity are protected from these diseases; and 3) how ethnicity and aging modify the risk. The research is highly relevant to the mission of NIH in combating aging‐associated thrombotic and bleeding disorders to improve public health in the US.