Thrombin-triggered platelet apoptosis
Thrombin-triggered platelet apoptosis
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DOI：
10.1111/j.1538-7836.2006.02200.x
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发表时间：
2006-12-01
影响因子：
10.4
通讯作者：
Freedman, J.
中科院分区：
文献类型：
--
作者：
Leytin, V.;Allen, D. J.;Freedman, J.
背景：凝血酶主要被认为是一种凝血因子和血小板活化和聚集的诱导剂。有报道称凝血酶可调节有核细胞的凋亡。目的：研究凝血酶是否能影响人无核血小板的凋亡。方法：采用流式细胞术在单细胞水平上研究血小板凋亡，分析线粒体和细胞质凋亡标志物。除流式细胞术外，还采用Western blotting检测Bcl-2家族蛋白的表达。结果：我们发现人α -凝血酶诱导人血小板凋亡的四个关键表现：(1)线粒体内跨膜电位（Delta Psi m）去极化；（ii）促凋亡Bax和Bak蛋白强表达，抗凋亡Bcl-2蛋白弱表达；（iii） caspase-3激活；（iv）磷脂酰丝氨酸（PS）暴露。结论：本研究表明，凝血酶除了具有诱导血小板活化的“经典”功能外，还可以引发血小板凋亡，并作为死亡配体发挥作用。这些数据表明凝血酶通过影响几个细胞内凋亡靶点触发血小板凋亡，包括将Bcl-2调节蛋白之间的平衡向促凋亡方向转移，使线粒体内膜去极化，激活刽子手caspase-3，以及刺激血小板表面PS的异常暴露。
Background: Thrombin is primarily known as a coagulation factor and as an inducer of platelet activation and aggregation. It has been reported that thrombin modulates apoptosis of nucleated cells. Objectives: The current study investigated whether thrombin can affect apoptosis in anucleated human platelets. Methods: Using flow cytometry, we studied platelet apoptosis at the single-cell level, analyzing markers of mitochondrial and cytoplasmic apoptosis. Western blotting was also employed, in addition to flow cytometry, for determining the expression of Bcl-2 family proteins. Results: We found that human alpha-thrombin induced four key manifestations of apoptosis in human platelets: (i) mitochondrial inner transmembrane potential (Delta Psi m) depolarization; (ii) strong expression of pro-apoptotic Bax and Bak proteins but only weak expression of anti-apoptotic Bcl-2 protein; (iii) caspase-3 activation; and (iv) phosphatidylserine (PS) exposure. Conclusions: This study demonstrates that, aside from its 'classical' function as an inducer of platelet activation, thrombin can trigger platelet apoptosis, where it acts as a death ligand. These data indicate that thrombin triggers platelet apoptosis by impacting on several intracellular apoptotic targets, including shifting the balance between Bcl-2 regulatory proteins in a pro-apoptotic direction, depolarizing the inner mitochondrial membrane, activating the executioner caspase-3, and stimulating aberrant exposure of PS on the platelet surface.