The majority of circulating platelet-derived microparticles fail to bind annexin V, lack phospholipid-dependent procoagulant activity and demonstrate greater expression of glycoprotein Ib
The majority of circulating platelet-derived microparticles fail to bind annexin V, lack phospholipid-dependent procoagulant activity and demonstrate greater expression of glycoprotein Ib
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DOI：
10.1160/th09-09-0644
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发表时间：
2010-05-01
影响因子：
6.7
通讯作者：
Joseph, Joanne Emily
中科院分区：
文献类型：
--
作者：
Connor, David Ewan;Exner, Thomas;Joseph, Joanne Emily
它已被广泛接受的微粒暴露磷脂酰丝氨酸，进而结合膜联蛋白V。这是本研究的目的是比较抗原特性和磷脂依赖性促凝血活性的膜联蛋白V阳性和阴性亚群的血小板衍生的微粒。膜联蛋白V阳性和阴性的微粒进行了鉴定，并采用流式细胞术和促凝血活性测定磷脂依赖性试验（XACT）。在未受刺激的血小板贫乏的血浆中，80%的血小板衍生的微粒未能结合膜联蛋白V。改变测定成分（缓冲液，钙和膜联蛋白V浓度）没有改变膜联蛋白V结合。结合膜联蛋白V的微粒的比例取决于激动剂，其中生理激动剂如胶原蛋白导致比非生理激动剂如离子载体更少的膜联蛋白V结合微粒。与膜联蛋白V阴性亚群相比，膜联蛋白V阳性亚群中CD42 b（糖蛋白Ib）表达显著降低，CD62 p和CD63表达显著增加。Annexin V阳性和阴性亚群之间的CD 41、CD 61、CD 42a和CD 40L表达无显著差异。发现膜联蛋白V结合与XACT之间存在显著相关性（p=0.033）。膜联蛋白V抑制大于95%的磷脂活性，表明膜联蛋白V结合是促凝血活性的真实反映。未刺激血浆中的大多数血小板衍生微粒未能结合膜联蛋白V，并且与膜联蛋白V阳性事件相比显示出显著增加的CD42b水平。磷脂依赖性促凝血活性仅限于膜联蛋白V阳性亚群，并且是激动剂依赖性的。膜联蛋白V阴性微粒的意义尚不清楚，然而，它们可能具有除促凝血磷脂活性之外的其他活性。
It has been widely accepted that microparticles expose phosphatidylserine which in turn binds annexin V. It was the objective of this study to compare the antigenic characteristics and phospholipid-dependent procoagulant activity of annexin V positive and -negative subpopulations of platelet-derived microparticles. Annexin V positive and -negative microparticles were identified and characterised using flow cytometry and procoagulant activity was measured by a phospholipid-dependent assay (XACT). In unstimulated platelet-poor plasma, 80% of platelet-derived microparticles failed to bind annexin V. Varying the assay constituents (buffer, calcium and annexin V concentration) did not alter annexin V binding. The proportion of microparticles that bound annexin V was dependent upon the agonist, with physiological agonists such as collagen resulting in fewer annexin V binding microparticles than non-physiological agonists such as ionophore. CD42b (glycoprotein Ib) expression was significantly decreased and CD62p and CD63 expression were significantly increased in annexin V positive compared to annexin V negative subpopulations. There was no significant difference in CD41, CD61, CD42a and CD40L expression between annexin V positive and -negative subpopulations. A significant correlation between annexin V binding and XACT was found (p=0.033). Annexin V inhibited greater than 95% of phospholipid activity, suggesting that annexin V binding was a true reflection of procoagulant activity. The majority of platelet-derived microparticles in unstimulated plasma failed to bind annexin V and showed significantly increased levels of CD42b compared to annexin V positive events. Phospholipid-dependent procoagulant activity is limited to the annexin V positive subpopulation and is agonist-dependent. The significance of annexin V negative microparticles is unclear, however, it is possible that they possess other activities aside from procoagulant phospholipid activity.