细胞外组蛋白在急性呼吸窘迫综合征（ARDS）发病中的作用及分子机制研究

Acute respiratory distress syndrome (ARDS) is an important cause of acute respiratory failure that is often associated with multiple organ failure. Several clinical disorders can precipitate ARDS, including pneumonia, sepsis, aspiration of gastric contents, and major trauma. ARDS is physiologically characterized by enhanced alveolar-capillary permeability, hypoxemia, accumulation and activation of leukocytes within the lungs, and uncontrolled overwhelming inflammatory responses. It is noticeable that systemic inflammation is a common pathological feature shared by different etiologies-caused ARDS, as demonstrated by a rapid influx of leukocytes and releases of proinflammatory cytokines. However, the factors or mechanisms that trigger systemic inflammation in ARDS are largely unclear. Recently, extracellular histones have been identified as a new DAMP (Damage Associated Molecular Pattern) molecule and exhibited to be a major mediator of death in sepsis. In our pilot study, we found that extracellular histones were significantly released in the circulation of LPS-induced ARDS mice in a time-dependent manner, which likely contributed to the increase of inflammatory cytokines and the death of mice. Neutralization of histones by specific anti-histones antibodies strikingly improved the survival rate of ARDS mice. It thus indicated a dual role of extracellular histones either as a cell death marker for ARDS or as a new therapeutic target in the treatment of ARDS. In the present study, we aim to investigate the profile of extracellular histones levels following LPS-induced or acid aspiration-induced ARDS models as well as in clinical patients with ARDS. Moreover, the molecular pathways of extracellular histones involved in activation of innate immunity and inflammatory events will be examined. Most importantly, we will explore the protective effects and the potential therapeutic significance of specific anti-histones antibodies, which may serve as a new strategy in the treatment of ARDS. Our study will shed light on the pathogenesis of ARDS and provide valuable information for exploring its biomarker and therapeutic potential.

急性呼吸窘迫综合征（ARDS）是一种多病因导致的临床危急重症，死亡率高。失控的炎症反应和促炎介质大量释放是ARDS的共同发病途径，但目前对其诱发机制尚不清楚。我们前期研究发现，一种新的炎症分子—细胞外组蛋白与ARDS的发生发展密切相关，并可能是激活异常免疫反应的关键介质，这为探索ARDS的发病机制和治疗靶点等开辟了新的视角。本项目拟制备感染性(脂多糖注射)和盐酸吸入性的小鼠ARDS模型，并结合临床病人资料，研究细胞外组蛋白的动态变化规律，探讨细胞外组蛋白对氧化应激、细胞凋亡、免疫细胞活化和炎症信号通路激活等事件的影响作用，从上游的早期损伤事件、中游的信号传导通路和下游的炎性因子等不同层面，阐释细胞外组蛋白在ARDS发病中的具体功能及分子机制，并通过给予特异性抗组蛋白中和抗体等干预措施验证假说。本研究有望在新的层面揭示ARDS发病的关键问题或核心关节，为临床早期预警和干预治疗等提供科学线索。

本项目以新近发现的一种炎症DAMPs分子-细胞外组蛋白为切入点，从ARDS动物模型和临床患者两个层面进行全面探索，观察细胞外组蛋白在不同病因所致ARDS发病过程中的变化规律，以及与氧化应激、免疫细胞活化和炎症信号通路激活等相关性，并通过给与相应的干预手段，深入探究ARDS发生发展的共同规律及调控途径，为临床上最终攻克这一临床难题奠定科学基础。同时，又进一步探究细胞外组蛋白在肺移植和急性肝损伤等炎症相关性疾病中的作用，为炎症相关性疾病的治疗提供了参考。研究结果显示在盐酸吸入诱导的小鼠ARDS模型中，小鼠血浆和BALF中细胞外组蛋白水平均显著增高，并且升高程度与ARDS的严重程度密切相关。特异性的组蛋白中和抗体和肝素能发挥细胞保护作用，验证了细胞外组蛋白的毒性效应。同时收集不同病因ARDS患者的血标本和BALF样本，建立ARDS患者全病程的纵向队列，检测细胞外组蛋白水平，并以正常人、重症肺炎、休克等患者作为对照，发现ARDS患者血浆和BALF中的细胞外组蛋白水平明显增高，并且与ARDS患者的严重程度和预后相一致。在前面研究的基础上，又进一步探索细胞外组蛋白在ARDS中的分子机制以及细胞外组蛋白在肺移植、急性肝损伤等其他炎症相关性疾病中的作用。本课题表明细胞外组蛋白可以作为ARDS、急性肝损伤等炎症相关性疾病早期诊断的一种标志物，并且细胞外组蛋白的水平和变化趋势有助于帮助判断临床患者的严重程度和预后,针对细胞外组蛋白的治疗措施有望成为治疗炎症相关性疾病的新靶点。