危险预警分子HMGB1对血小板活化的影响及其作用机制

Thrombotic diseases are a group of prevalent and life-threatening diseases. Inflammation plays a critical role in pathogenic thrombosis. Damage-Associated Molecular Patterns (DAMPs), a group of endogenous molecules that are released by necrotic or damaged cells, are the major mediators of sterile inflammation. The effect of DAMPs in thrombosis is not fully understood, and drew a lot of attentions in the field. High mobility group box 1 protein (HMGB1) is a prototypical DAMP. We recently investigated the role of HMGB1 in platelet aggregation and obtained following observations. 1. Highly purified HMGB1 recombinant protein induces platelet aggregation in a dose-dependent manner in the presence of serum. 2. Extracellular HMGB1 could synergistically promote platelet aggregation with collagen, which is a well-known activator of platelets. In this context, HMGB1 and collagen could effectively initiate platelet aggregation at very low levels. 3. Extracellular HMGB1 promoted platelet aggregation in a platelet-expressed GPⅡb/Ⅲa-dependent manner. Together with the fact that platelets express TLR4, a well-known receptors of HMGB1, here we proposed that extracellular HMGB1 promotes platelet activation and aggregation via TLR4-GPⅡb/Ⅲa signaling. Based on this working hypothesis, we will investigate the role of HMGB1 in thrombosis formation and the molecular mechanisms by which HMGB1 activates platelets. This project might provide a new avenue for the treatment of thrombotic diseases in the future.

血栓性疾病是一类威胁人类健康的重大疾病。炎症反应是促进病理性血栓形成的重要因素。危险预警分子为一类由坏死或损伤细胞释放的内源性分子，是引起非感染性炎症反应的主要介质。该类分子对血栓形成的影响尚不完全清楚。高迁移率蛋白-1 (HMGB1) 是一种典型的危险预警分子。我们在前期工作中探讨了HMGB1对血小板活化的影响，并有以下发现：1. 活化的血小板能大量释放内源性的HMGB1。2. HMGB1蛋白能直接引发血小板的聚集和活化。3. HMGB1能与胶原发生协同作用。4. HMGB1促进血小板的聚集依赖血小板膜糖蛋白Ⅱb/Ⅲa。基于血小板表面存在HMGB1的受体TLR4，我们提出HMGB1可能对血小板活化具有重要的调控作用，并通过TLR4-GPⅡb/Ⅲa途径促进血小板的聚集。围绕该科学假设，我们将深入探讨HMGB1在血小板血栓形成中的作用及其机制。本项目的开展可能为血栓性疾病的防治提供新的方向。

血栓性疾病是一类威胁人类健康的重大疾病。炎症反应是促进病理性血栓形成的重要因素。病理性血栓可以有组织坏死或失调的炎症诱发，然而血栓形成的具体机制不明确。高迁移率蛋白-1 (HMGB1)是一种典型的危险预警分子，是重要的坏死性炎症介质。前期实验研究发现血小板和病理性血栓表达大量HMGB1，活化的血小板能释放内源性的HMGB1至胞浆外。上述结果提示HMGB1可能在生理性止血及病理性血栓形成过程中发挥重要作用。基于以上发现，我们研究探讨了HMGB1对血小板活化的作用及其机制。结果提示：①血小板和病理性血栓组织表达丰富的HMGB1；②HMGB1剂量依赖性的刺激血小板活化；③HMGB1刺激血小板聚集依赖血小板整合素GPIIb-GPIII受体及血小板TLR4受体。由于HMGB1在脓毒症病理生理过程中发挥重要作用，同时脓毒症患者并发凝血功能障碍，严重者脓毒症患者导致弥散性血管内凝血（disseminated intravascular coagulation；DIC），通过本课题研究我们进一步探讨HMGB1在脓毒症凝血活化中的作用机制，结果提示：①我们发现了HMGB1通过加速Caspase-11活化促进磷脂酰丝氨酸外翻、组织因子活性提升并最终导致凝血活化的关键分子机制。②脓毒症过程中细菌内毒素（LPS）活化血小板与TLR4介导ROS生成导致线粒体损伤。③我们阐述了丙酮酸乙酯（脓毒症保护药物）对血小板活化以及磷脂酰丝氨酸外翻的抑制作用及其机制；④我们阐述了ROS抑制PI3K/AKT/mTOR和上调自噬在血小板活化中的机制。