Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, 14665-1157, Tehran, Iran.
Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Science, Tehran, Iran.
J Thromb Thrombolysis. 2020 Jul;50(1):123-134. doi: 10.1007/s11239-020-02137-0.
Thrombosis involves different stages including platelet adhesion to the site of injury, aggregatory events governed by integrin activation, pro-inflammatory responses recruiting leukocytes and finally, pro-coagulant activity which results in fibrin generation and clot formation. As important signaling agents, reactive oxygen species (ROS) reduce thrombus volume and growth, however given such a multistage mechanism, it is not well-elucidated how ROS inhibition modulates thrombosis. PRP-platelet concentrates (PCs) were either treated with ROS-reducing agents (1 mM NAC or 30 μM NOX inhibitor, VAS2870) or kept untreated during storage. Shedding and expression of platelet adhesion receptors in presence of inhibitors, agonists and CCCP (as controls) were analyzed by flow cytometery and western blot respectively. Besides above parameters, platelet adhesion to collagen in stored platelets was examined in presence of ROS inhibitors using fluorescence-microscopy. Highest levels of adhesion receptors shedding were achieved by ionophore and CCCP while collagen induces much more GPVI shedding than that of GPIbα. ROS inhibition reduced receptors shedding from day 3 of storage while enhanced their expressions. ROS inhibition not only did not reduce platelet adhesion capacity but it also enhanced platelets adhesion (in presence of NAC) or spreading (in presence of VAS2870) in 5 days-stored PCs. While reducing state significantly inhibits platelet aggregation and thrombus growth, our results indicated that as a first stage of thrombosis, platelet adhesion is resistance to such inhibitory effects. These findings highlight the fact that integrin-dependent platelet activation is much more vulnerable to the inhibition of ROS generation than GPVI-dependent platelet adhesion. Presumably, inhibition of platelet activating signals by ROS inhibitors preserves platelet adhesiveness to collagen due to lessening GPVI shedding.
血栓形成涉及多个阶段,包括血小板黏附到损伤部位、整合素激活介导的聚集事件、募集白细胞的促炎反应,以及最终导致纤维蛋白生成和血栓形成的促凝活性。作为重要的信号分子,活性氧(ROS)可减少血栓体积和生长,但鉴于这种多阶段机制,ROS 抑制如何调节血栓形成尚不清楚。富血小板血浆(PRP)-血小板浓缩物(PCs)在储存过程中要么用 ROS 还原剂(1 mM NAC 或 30 μM NOX 抑制剂 VAS2870)处理,要么不处理。用流式细胞术和 Western blot 分别分析抑制剂、激动剂和 CCCP(作为对照)存在下血小板黏附受体的脱落和表达。除了上述参数外,还在 ROS 抑制剂存在下使用荧光显微镜检查储存血小板中对胶原的黏附。离子载体和 CCCP 可实现最高水平的黏附受体脱落,而胶原诱导的 GPVI 脱落比 GPIbα 多得多。ROS 抑制不仅在储存第 3 天减少了受体脱落,还增强了它们的表达。ROS 抑制不仅没有降低血小板黏附能力,反而增强了血小板在储存 5 天的 PCs 中的黏附(在 NAC 存在下)或铺展(在 VAS2870 存在下)。虽然还原状态显著抑制血小板聚集和血栓生长,但我们的结果表明,作为血栓形成的第一阶段,血小板黏附对这种抑制作用具有抵抗力。这些发现强调了这样一个事实,即与依赖于 GPVI 的血小板黏附相比,整合素依赖性血小板激活对 ROS 生成的抑制更为敏感。推测 ROS 抑制剂通过减少 GPVI 脱落,从而抑制血小板激活信号,来维持血小板对胶原的黏附能力。