Platelet hyperactivity and abnormal Ca2+ homeostasis in diabetes mellitus
Platelet hyperactivity and abnormal Ca2+ homeostasis in diabetes mellitus
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DOI：
10.1152/ajpheart.2001.280.4.h1480
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发表时间：
2001-04-01
影响因子：
4.8
通讯作者：
Bose, R
中科院分区：
文献类型：
--
作者：
Li, Y;Woo, V;Bose, R
我们试图确定糖尿病患者过度活跃和异常血小板Ca2+稳态的机制。糖化血红蛋白（HbA(1c)）水平作为血糖控制的指标。人血小板装载Ca-green- fura - red，同时测量胞质Ca2+ ([Ca2+](i))和聚集。在第一个系列的实验中，比较了糖尿病患者和正常人的血小板释放Ca2+或促进Ca2+内流的能力。一种有效且相对特异性的Na+/Ca2+交换抑制剂5-（4-氯苯基）-2'，4-二甲苯甲胺（CB-DMB）增加了凝血酶诱导的第二阶段Ca2+反应，表明Na+/Ca2+交换剂以正向模式介导Ca2+外排。相反，在糖尿病患者的血小板中，CB-DMB降低了Ca2+反应，表明Na+/Ca2+交换器以相反的方式介导Ca2+内流。在第二组实验中，我们在体外评估了高血糖对血小板的直接影响。我们发现凝血酶和胶原诱导的[Ca2+](i)和聚集的增加并没有受到45 mM高葡萄糖浓度的急性影响。然而，当富含血小板的血浆在37℃的高葡萄糖浓度下孵育24小时时，凝血酶激活后的第二阶段被CB- DMB抑制。此外，胶原刺激的[Ca2+](i)反应和聚集也增加。因此，在糖尿病中，Na+/Ca2+交换器的方向和活性发生改变，这可能是血小板[Ca2+](i)增加和过度活跃的机制之一。长期的体外高血糖可以诱导类似的变化，提示高血糖本身可能是导致糖尿病血小板过度活跃的因素。
We sought to determine the mechanisms for hyperactivity and abnormal platelet Ca2+ homeostasis in diabetes. The glycosylated Hb (HbA(1c)) level was used as an index of glycemic control. Human platelets were loaded with Ca-green- fura red, and cytosolic Ca2+ ([Ca2+](i)) and aggregation were simultaneously measured. In the first series of experiments, the platelets from diabetic and normal subjects were compared for the ability to release Ca2+ or to promote Ca2+ influx. A potent and relatively specific inhibitor of Na+/Ca2+ exchange, 5-(4- chlorobenzyl)-2',4-dimethylbenzamil (CB-DMB), increased the second phase of thrombin-induced Ca2+ response, suggesting that the Na+/Ca2+ exchanger works in the forward mode to mediate Ca2+ efflux. In contrast, in the platelets from diabetics, CB-DMB decreased the Ca2+ response, indicating that the Na+/Ca2+ exchanger works in the reverse mode to mediate Ca2+ influx. In the second series of experiments we evaluated the direct effect of hyperglycemia on platelets in vitro. We found that thrombin- and collagen-induced increases in [Ca2+](i) and aggregation were not acutely affected by high glucose concentrations of 45 mM. However, when the platelet- rich plasma was incubated with a high glucose concentration at 37 degrees C for 24 h, the second phase after thrombin activation was inhibited by CB- DMB. In addition, collagen-stimulated [Ca2+](i) response and aggregation were also increased. Thus in diabetes the direction and activity of the Na+/Ca2+ exchanger is changed, which may be one of the mechanisms for the increased platelet [Ca2+](i) and hyperactivity. Prolonged hyperglycemia in vitro can induce similar changes, suggesting hyperglycemia per se may be the factor responsible for the platelet hyperactivity in diabetes.