Recombinant thrombomodulin protects mice against histone-induced lethal thromboembolism.

Recent studies have shown that histones, the chief protein component of chromatin, are released into the extracellular space during sepsis, trauma, and ischemia-reperfusion injury, and act as major mediators of the death of an organism. This study was designed to elucidate the cellular and molecular basis of histone-induced lethality and to assess the protective effects of recombinant thrombomodulin (rTM). rTM has been approved for the treatment of disseminated intravascular coagulation (DIC) in Japan, and is currently undergoing a phase III clinical trial in the United States. Histone H3 levels in plasma of healthy volunteers and patients with sepsis and DIC were measured using enzyme-linked immunosorbent assay. Male C57BL/6 mice were injected intravenously with purified histones, and pathological examinations were performed. The protective effects of rTM against histone toxicity were analyzed both in vitro and in mice. Histone H3 was not detectable in plasma of healthy volunteers, but significant levels were observed in patients with sepsis and DIC. These levels were higher in non-survivors than in survivors. Extracellular histones triggered platelet aggregation, leading to thrombotic occlusion of pulmonary capillaries and subsequent right-sided heart failure in mice. These mice displayed symptoms of DIC, including thrombocytopenia, prolonged prothrombin time, decreased fibrinogen, fibrin deposition in capillaries, and bleeding. Platelet depletion protected mice from histone-induced death in the first 30 minutes, suggesting that vessel occlusion by platelet-rich thrombi might be responsible for death during the early phase. Furthermore, rTM bound to extracellular histones, suppressed histone-induced platelet aggregation, thrombotic occlusion of pulmonary capillaries, and dilatation of the right ventricle, and rescued mice from lethal thromboembolism. Extracellular histones cause massive thromboembolism associated with consumptive coagulopathy, which is diagnostically indistinguishable from DIC. rTM binds to histones and neutralizes the prothrombotic action of histones. This may contribute to the effectiveness of rTM against DIC.

近期研究表明，组蛋白（染色质的主要蛋白质成分）在脓毒症、创伤以及缺血 - 再灌注损伤期间会释放到细胞外空间，并作为生物体死亡的主要介质。本研究旨在阐明组蛋白诱导致死的细胞和分子基础，并评估重组血栓调节蛋白（rTM）的保护作用。rTM已在日本被批准用于治疗弥散性血管内凝血（DIC），目前正在美国进行III期临床试验。 采用酶联免疫吸附测定法测量健康志愿者以及脓毒症和DIC患者血浆中的组蛋白H3水平。给雄性C57BL/6小鼠静脉注射纯化的组蛋白，并进行病理检查。在体外和小鼠体内分析rTM对组蛋白毒性的保护作用。 在健康志愿者的血浆中未检测到组蛋白H3，但在脓毒症和DIC患者中观察到显著水平。这些水平在死亡患者中高于存活患者。细胞外组蛋白引发血小板聚集，导致小鼠肺毛细血管血栓性闭塞以及随后的右侧心力衰竭。这些小鼠表现出DIC的症状，包括血小板减少、凝血酶原时间延长、纤维蛋白原减少、毛细血管内纤维蛋白沉积以及出血。血小板耗竭在最初30分钟内保护小鼠免受组蛋白诱导的死亡，这表明富含血小板的血栓造成的血管闭塞可能是早期死亡的原因。此外，rTM与细胞外组蛋白结合，抑制组蛋白诱导的血小板聚集、肺毛细血管血栓性闭塞以及右心室扩张，并将小鼠从致命的血栓栓塞中解救出来。 细胞外组蛋白导致与消耗性凝血病相关的大量血栓栓塞，这在诊断上与DIC无法区分。rTM与组蛋白结合并中和组蛋白的促凝血作用。这可能有助于rTM对DIC的疗效。