Pulmonary endothelial glycocalyx degradation causes ARDS during sepsis

描述（由申请人提供）：急性呼吸窘迫综合征（ARDS）是一种严重的（死亡率> 30%）危重疾病，在美国每年影响超过190，000例患者。尽管研究了40多年，但对这种疾病的发展知之甚少，也没有具体的治疗方法。虽然脓毒症是ARDS的一个众所周知的原因，但脓毒症ARDS发展的潜在机制尚不确定。 在ARDS发展过程中的关键步骤是肺内皮屏障功能障碍，其将血液与肺动脉分隔开。对全身（非肺）血管系统的研究表明，适当的内皮屏障功能依赖于完整的糖萼--衬在血管腔内的蛋白多糖、糖蛋白和糖胺聚糖的薄层。新出现的数据表明，脓毒症的炎症介质降解系统性内皮糖萼，导致屏障功能障碍。然而，肺内皮糖萼在脓毒症和ARDS中的作用尚未研究。 我们推测脓毒症诱导肺内皮糖萼降解，导致屏障功能障碍和ARDS。由于糖萼结构在体外通常是异常的，因此将使用离体和体内模型探索该假设：分离的灌注小鼠肺和闭胸的活体小鼠肺显微镜。将确定脂多糖（LPS，脓毒症模型）诱导的肺糖萼降解的剂量-反应和时间过程。将使用多光子活体显微镜绘制糖萼损失的血管节段性（动脉vs.微血管vs.静脉）模式，并与脓毒症期间内皮高通透性的节段性模式进行比较。肿瘤坏死因子1和乙酰肝素酶的作用将探讨作为介导的脂多糖诱导的糖萼损失，使用药理学抑制剂和转基因小鼠模型。将探讨肝素酶抑制剂肝素的治疗益处。 总之，这项研究有望通过结合生理（分离，灌注小鼠肺）和专门的显微镜（多光子活体显微镜）方法，更好地了解与常见临床疾病（脓毒症相关的ARDS）相关的一个不太清楚的结构（肺内皮糖萼）。此外，这项调查确定乙酰肝素酶作为一个有吸引力的治疗目标的疾病，但缺乏具体的治疗。 公共卫生相关性：脓毒症是一种常见的严重疾病，由身体对压倒性感染的反应引起。败血症通常会导致肺部血管渗漏，血液和液体充斥肺部（一种称为急性呼吸窘迫综合征或ARDS的致命疾病）。我们正在研究如何预防急性呼吸窘迫综合征，特别是通过试图保护一层薄薄的，但非常重要的，排列在肺血管中的糖层。

DESCRIPTION (provided by applicant): The acute respiratory distress syndrome (ARDS) is a severe (> 30% mortality) critical illness that affects over 190,000 patients in the United States each year. Despite over 40 years of study, little is known about how this disease develops, and no specific treatment exists. While sepsis is a well-known cause of ARDS, the mechanisms underlying the development of septic ARDS are uncertain. A key step in the development of ARDS is dysfunction of the pulmonary endothelial barrier, which separates blood from the lung interstitium. Studies of the systemic (non-pulmonary) vasculature have revealed that proper endothelial barrier function is dependent on an intact glycocalyx-a thin layer of proteoglycans, glycoproteins, and glycosaminoglycans lining the vascular lumen. Emerging data suggest that inflammatory mediators of sepsis degrade the systemic endothelial glycocalyx, causing barrier dysfunction. The role of the pulmonary endothelial glycocalyx in sepsis and ARDS, however, has been unexplored. We hypothesize that sepsis induces pulmonary endothelial glycocalyx degradation, leading to barrier dysfunction and ARDS. As glycocalyx structure is often aberrant in-vitro, this hypothesis will be explored using ex-vivo and in-vivo models: the isolated, perfused mouse lung and closed-chest, intravital mouse lung microscopy. The dose-response and time course of lipopolysaccharide (LPS, a model of sepsis) induced pulmonary glycocalyx degradation will be determined. The vascular segmental (arterial vs. microvascular vs. venous) pattern of glycocalyx loss will be mapped using multiphoton intravital microscopy and compared to the segmental pattern of endothelial hyperpermeability during sepsis. The role of tumor necrosis factor 1 and heparanase will be explored as mediators of LPS-induced glycocalyx loss, using pharmacologic inhibitors and transgenic mouse models. The therapeutic benefit of heparin, an inhibitor of heparanase, will be explored. In summary, this investigation promises a better understanding of a poorly-understood structure (the pulmonary endothelial glycocalyx) with relevance to a common clinical condition (sepsis-associated ARDS) via a combined physiologic (isolated, perfused mouse lung) and specialized microscopic (multiphoton intravital microscopy) approach. Furthermore, this investigation identifies heparanase as an attractive therapeutic target in a disease that yet lacks specific treatment. PUBLIC HEALTH RELEVANCE: Sepsis is a common, severe condition caused by the body's response to an overwhelming infection. Sepsis often causes blood vessels in the lungs to become leaky, flooding the lungs with blood and fluid (an often-fatal condition called the acute respiratory distress syndrome or ARDS). We are studying how to prevent ARDS, specifically by trying to protect a thin, yet very important, layer of sugars lining the blood vessels in the lung.