Mooberry M J, Bradford R, Hobl E L, Lin F C, Jilma B, Key N S
Department of Medicine, University of North Carolina, Chapel Hill, NC, USA.
McAllister Heart Institute, University of North Carolina, Chapel Hill, NC, USA.
J Thromb Haemost. 2016 May;14(5):1031-42. doi: 10.1111/jth.13285. Epub 2016 Apr 5.
Essentials The procoagulant effects of microparticles (MPs) on coagulation in endotoxemia are not known. MPs from endotoxemia volunteers were evaluated for procoagulant activity in a plasma milieu. MPs from endotoxemia volunteers shortened clotting times and enhanced thrombin generation. MP procoagulant effects were mediated in a factor XI-dependent manner.
Background Human endotoxemia is characterized by acute inflammation and activation of coagulation, as well as increased numbers of circulating microparticles (MPs). Whether these MPs directly promote coagulation and through which pathway their actions are mediated, however, has not been fully explored. Objectives In this study, we aimed to further characterize endotoxin-induced MPs and their procoagulant properties using several approaches. Methods Enumeration and characterization of MPs were performed using a new-generation flow cytometer. Relative contributions of the extrinsic and intrinsic pathways in MP-mediated procoagulant activity were assessed using plasmas deficient in factor (F) VII or FXI or with blocking antibodies to tissue factor (TF) or FXIa. Results Total MPs and platelet MPs were significantly elevated in plasma at 6 h after infusion of endotoxin in healthy human subjects. MPs isolated from plasma following endotoxin infusion also demonstrated increased TF activity in a reconstituted buffer system. When added to recalcified platelet-poor plasma, these MPs also promoted coagulation, as judged by a decreased clotting time with shortening of the lag time and time to peak thrombin using calibrated automated thrombography (CAT). However, the use of FVII-deficient plasma or blocking antibody to TF did not inhibit these procoagulant effects. In contrast, plasma clotting time was prolonged in FXI-deficient plasma and a blocking antibody to FXIa inhibited all MP-mediated parameters in the CAT assay. Conclusions The initiation of coagulation by cellular TF in endotoxemia is in contrast to (and presumably complemented by) the intrinsic pathway-mediated procoagulant effects of circulating MPs.
要点 微粒（MPs）在内毒素血症中对凝血的促凝作用尚不清楚。对内毒素血症志愿者的MPs在血浆环境中的促凝活性进行了评估。内毒素血症志愿者的MPs缩短了凝血时间并增强了凝血酶生成。MP的促凝作用以因子XI依赖性方式介导。
背景 人类内毒素血症的特征是急性炎症和凝血激活，以及循环微粒（MPs）数量增加。然而，这些MPs是否直接促进凝血以及其作用通过何种途径介导尚未得到充分探索。目的 在本研究中，我们旨在使用几种方法进一步表征内毒素诱导的MPs及其促凝特性。方法 使用新一代流式细胞仪对MPs进行计数和表征。使用缺乏因子（F）VII或FXI的血浆或针对组织因子（TF）或FXIa的阻断抗体评估外在和内在途径在MP介导的促凝活性中的相对贡献。结果 在健康人类受试者输注内毒素后6小时，血浆中的总MPs和血小板MPs显著升高。在内毒素输注后从血浆中分离的MPs在重组缓冲系统中也显示出TF活性增加。当添加到重新钙化的少血小板血浆中时，这些MPs也促进了凝血，通过校准自动血栓形成测定法（CAT）判断，凝血时间缩短，滞后时间和凝血酶峰值时间缩短。然而，使用缺乏FVII的血浆或针对TF的阻断抗体并未抑制这些促凝作用。相反，在缺乏FXI的血浆中血浆凝血时间延长，并且针对FXIa的阻断抗体抑制了CAT测定中所有MP介导的参数。结论 内毒素血症中细胞TF引发的凝血与循环MPs的内在途径介导的促凝作用形成对比（并且可能相互补充）。
