Department of General Biochemistry, Institute of Biochemistry, University of Łódź, Banacha 12/16, 90-237 Łódź, Poland.
Platelets. 2010;21(7):533-40. doi: 10.3109/09537104.2010.501119.
The actions of homocysteine and its major metabolite, cyclic thioester, homocysteine thiolactone on endothelial cells, blood platelets, plasmatic fibrinogen and plasminogen--the important major components of haemostasis, regulating the flowing properties of blood--are complex and sometimes controversial. Homocysteine (Hcys) can promote apoptosis in endothelial cells, but the role of Hcys and its thiolactone in the apoptotic process in blood platelets is unknown. In order to study the appearance of apoptosis in platelets after treatment with the reduced form of Hcys or its thiolactone different markers were chosen: annexin V binding (phosphatidylserine exposure), platelet microparticle formation, mitochondrial membrane depolarization and αIIbβ3 expression in vitro. Apoptotic events and platelet activation were measured by a flow cytometer. In gel-filtered platelets treated with different concentrations of the reduced form of Hcys (25, 50 and 100 µM, 10 min) a significant increase of phosphatidylserine exposure (about 37% at the highest concentration, p < 0.001) and platelet microparticle formation were observed. Homocysteine caused also a dose-dependent depolarization of mitochondrial potential. The same apoptotic markers appeared in HTL-treated platelets (0.2 and 1 µM). Moreover, resveratrol (25 µM), a well known antioxidant, distinctly reduced the level of apoptotic markers. The obtained results indicate that Hcys and its thiolactone may promote in vitro apoptotic events in human gel-filtered platelets.
同型半胱氨酸及其主要代谢产物环状硫酯、同型半胱氨酸硫内酯对血管内皮细胞、血小板、血浆纤维蛋白原和纤溶酶原——这些重要的止血主要成分，调节血液的流动特性——的作用是复杂的，有时甚至是有争议的。同型半胱氨酸（Hcys）可以促进内皮细胞凋亡，但 Hcys 及其硫内酯在血小板凋亡过程中的作用尚不清楚。为了研究用 Hcys 的还原形式或其硫内酯处理后血小板中出现的凋亡，选择了不同的标记物：膜联蛋白 V 结合（磷脂酰丝氨酸暴露）、血小板微粒形成、线粒体膜去极化和αIIbβ3 表达。通过流式细胞仪测量凋亡事件和血小板激活。在用不同浓度的 Hcys 还原形式（25、50 和 100µM，10 分钟）处理的凝胶过滤血小板中，观察到磷脂酰丝氨酸暴露（最高浓度时约增加 37%，p<0.001）和血小板微粒形成显著增加。同型半胱氨酸还导致线粒体电位的去极化呈剂量依赖性。在 HTL 处理的血小板中也出现了相同的凋亡标记物（0.2 和 1µM）。此外，白藜芦醇（25µM），一种众所周知的抗氧化剂，明显降低了凋亡标记物的水平。所得结果表明，Hcys 和其硫内酯可能促进人凝胶过滤血小板中的体外凋亡事件。
