细胞外组蛋白介导的炎症反应对重型肝炎发病的影响及机制研究

Acute liver failure occurs in a variety of medical conditions and causes higher mortalities. It has been suggested that secondary inflammation and immunological disorders, following primary hepatocyte damage caused by viruses (HBV), alcohol, drug or chemical toxins, play a vital role in the initiation of acute hepatic failure. But the underlying molecular mechanisms remain largely unclear. Recently, extracellular histones have been identified as a new DAMP (Damage Associated Molecular Pattern) molecule and shown to be a major mediator in a variety of inflammatory diseases. In our previous study, we found that extracellular histones were significantly released in the circulation of GalN/LPS-treated mice in a time-dependent manner, which likely contributed to the increase of inflammatory cytokines and the death of mice. Neutralization of circulating histones by specific anti-histones antibodies strikingly improved the survival rate of GalN/LPS-treated mice and reduced the inflammation markedly. It thus indicated a dual role of extracellular histones either as a cell death marker for acute liver failure or as a new therapeutic target in the treatment of hepatic injury. In the present study, we aim to investigate the changes of extracellular histones levels following acute liver damage in in vivo and in vitro models as well as in clinical patients with severe liver failure. Moreover, the molecular pathways of extracellular histones involved with the activation of innate immunity and inflammatory events will be examined. Most importantly, we will explore the protective effects and the potential therapeutic significance of anti-histones antibodies, which may serve as a new strategy in the treatment of acute liver failure. Our study will shed light on the pathogenesis of severe liver damage and provide valuable information for exploring its biomarker and therapeutic potential.

重型肝炎病因复杂，病死率极高；继发性炎症反应和免疫功能紊乱在肝炎重症化转变中可能起关键作用，但具体机制不明。我们前一年研究发现，一种新的"损伤相关分子模式"（DAMP）分子- - 细胞外组蛋白与肝脏炎症损伤反应有着密切相关，并可能是激活天然免疫细胞、诱发异常免疫反应的关键介质，抗组蛋白中和抗体能显著减轻小鼠肝损伤，这为探索重肝的发病机制和治疗靶点等拓开了新的视野。本项目是前一国自然主任基金（1年期项目）的延续和扩大，此次拟通过建立多病因重肝动物和细胞模型，并结合临床病人资料，重点研究细胞外组蛋白的变化规律及干预效果，及其与细胞凋亡、免疫细胞活化和炎症信号通路激活等事件的关系，从上游损伤事件、信号传导通路和下游代谢产物（炎性因子TNF-a等）等不同层面，深入探讨细胞外组蛋白介导的炎症反应在重肝发病中的一些关键问题或核心关节，以为临床早期预警和干预治疗等提供科学线索。

重肝病因复杂、病死率极高；研究发现，继发性炎症反应和免疫功能紊乱在肝炎重症化转变中可能起关键作用，但其具体作用机制不明。我们前面研究发现，一种新发现的损伤相关分子模式-细胞外组蛋白与肝脏炎症损伤反应密切相关，并可能是激活天然免疫细胞、诱发异常免疫反应的关键介质，这为探索重肝的发病机制和治疗靶点等开辟了新的研究视角。因此，本项目通过建立不同病因（感染、免疫和药物性）诱导的重肝动物和细胞模型，并收集临床病人（重肝、慢加急肝衰竭）资料，系统探讨细胞外组蛋白的变化规律及干预效果。我们的研究发现，细胞外组蛋白在重肝病人中水平显著升高，与病情严重程度、预后等密切相关，是预示疾病进展的重要因子。切断组蛋白从细胞内向细胞外的释放途径或以组蛋白为靶标进行干预，能有效抑制炎症反应。我们还发现，细胞外组蛋白在不同病因导致的小鼠急性肝损伤中均明显升高，提示细胞外组蛋白是启动和维持肝脏炎性损伤反应的共性分子，其具体损伤机制可能是激活天然免疫细胞活化和直接损伤细胞膜，上调钙离子内流等。本项目另一重要发现是揭示了肝素的抗炎机制是通过直接中和细胞外组蛋白实现的，这为临床应用肝素提供了重要的科学依据，同时也验证了以细胞外组蛋白为靶点进行干预可有效抑制炎症反应。本项目基于这一发现，陆续探索了其它中和或降解组蛋白的药物的抗炎作用。