Microvesicles (MVs) have previously been shown to exert profibrinolytic capacity, which is increased in patients with septic shock (SS) with a favorable outcome. We, therefore, hypothesized that the plasmin generation capacity (PGC) could confer to MVs a protective effect supported by their capacity to lyse a thrombus, and we investigated the mechanisms involved. Using an MV-PGC kinetic assay, ELISA, and flow cytometry, we found that granulocyte MVs (Gran-MVs) from SS patients display a heterogeneous PGC profile driven by the uPA (urokinase)/uPAR system. In vitro, these MVs lyse a thrombus according to their MV-PGC levels in a uPA/uPAR-dependent manner, as shown in a fluorescent clot lysis test and a lysis front retraction assay. Fibrinolytic activators conveyed by MVs contribute to approximately 30% of the plasma plasminogenolytic capacity of SS patients. In a murine model of SS, the injection of high PGC Gran-MVs significantly improved mouse survival and reduced the number of thrombi in vital organs. This was associated with a modification of the mouse coagulation and fibrinolysis properties toward a more fibrinolytic profile. Interestingly, mouse survival was not improved when soluble uPA was injected. Finally, using a multiplex array on plasma from SS patients, we found that neutrophil elastase correlates with the effect of high-PGC-capacity plasma and modulates the Gran-MV plasmin generation capacity by cleaving uPA-PAI-1 complexes. In conclusion, we show that the high PGC level displayed by Gran-MVs reduces thrombus formation and improves survival, conferring to Gran-MVs a protective role in a murine model of sepsis.

中文翻译：

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具有高纤溶酶生成能力的粒细胞微泡促进凝块溶解并改善感染性休克的结果。

先前已显示微泡 (MV) 发挥纤溶能力，这在感染性休克 (SS) 患者中增加，并具有良好的结果。因此，我们假设纤溶酶生成能力 (PGC) 可以赋予 MV 一种由它们溶解血栓的能力支持的保护作用，并且我们研究了所涉及的机制。使用 MV-PGC 动力学测定、ELISA 和流式细胞术，我们发现来自 SS 患者的粒细胞 MV (Gran-MV) 显示出由 uPA（尿激酶）/uPAR 系统驱动的异质 PGC 谱。在体外，这些 MV 根据其 MV-PGC 水平以 uPA/uPAR 依赖性方式裂解血栓，如荧光凝块裂解试验和裂解前沿收缩试验所示。MVs 传递的纤溶激活剂对 SS 患者血浆纤溶酶原溶解能力的贡献约为 30%。在 SS 的小鼠模型中，注射高 PGC Gran-MVs 显着提高了小鼠的存活率并减少了重要器官中的血栓数量。这与小鼠凝血和纤维蛋白溶解特性向更纤维蛋白溶解特性的改变有关。有趣的是，当注射可溶性 uPA 时，小鼠的存活率并没有提高。最后，在 SS 患者血浆上使用多重阵列，我们发现中性粒细胞弹性蛋白酶与高 PGC 容量血浆的作用相关，并通过切割 uPA-PAI-1 复合物调节 Gran-MV 纤溶酶生成能力。总之，我们表明 Gran-MV 显示的高 PGC 水平减少了血栓形成并提高了存活率，