Haptoglobin 2 variant and endothelial glycocalyx shedding in sepsis-induced ARDS

摘要 脓毒症引起的急性呼吸窘迫综合征（ARDS）是急性呼吸衰竭的主要原因， 病危发病率和死亡率很高，没有经过证实的药物治疗， 抗菌剂脓毒症相关的ARDS的特征是肺组织的病理性降解， 内皮糖萼-肺血管所必需的富含糖胺聚糖的血管内层 体内平衡迫切需要鉴定脓毒症中内皮糖萼降解的早期触发因素， 这不仅是为了增强我们对病理生理学的理解，而且关键是为了确定新的治疗靶点， 预防和早期治疗脓毒症引起的ARDS。我们公布的和初步的数据表明，（1） 无细胞血红蛋白（CFH）在脓毒症中被释放到循环中，并有助于氧化剂介导的器官损伤。 （2）CFH可直接损伤肺内皮糖萼，导致其降解， 脱落;（3）触珠蛋白，一种内源性无细胞血红蛋白清除剂，限制其引起 氧化损伤有一个共同的遗传变异，HP-2，它增加了人类和小鼠患ARDS的风险 （4）脓毒症和HP-2变体的患者和小鼠具有增加的 内皮糖萼和氧化应激增加的证据。本建议中的研究将建立在 这些初步的发现，以表征CFH介导的内皮糖萼的机制， 降解被HP-2基因型修饰。我们的主要目标是将这些发现转化为新的目标 这些疗法将在我们的新型分离人肺模型中进行测试，作为快速转化为 针对败血症的临床试验在目标1中，我们将使用最先进的质谱分析循环 糖胺聚糖片段，以确定内皮细胞糖萼脱落的程度和特征， HP-2变异患者，研究与ARDS的相关性，并确定 内皮损伤在目标2中，我们将使用基因操作的小鼠模型来确定以下因素的贡献： 乙酰肝素酶和氧化损伤与HP-2基因型小鼠的糖萼降解。在目标3中，我们 在HP-2基因型中测试靶向氧化剂介导的损伤的治疗潜力，以保持 内皮糖萼在离体灌注人肺作为一个翻译桥梁，以未来的病人研究。 这些目标中提议的研究有可能产生重大和持续的科学影响。由于HP-2是 HP基因最常见的等位基因，超过40%的欧洲或非洲血统的人是 对于该等位基因纯合子，针对具有HP 2基因型的患者进行治疗，以防止内皮 糖萼降解是一种新的方法，可能对临床结果产生重大影响。

ABSTRACT Sepsis-induced acute respiratory distress syndrome (ARDS) is a leading cause of acute respiratory failure in critical illness. Morbidity and mortality are high and there are no proven pharmacologic therapies other than antimicrobials. Sepsis-associated ARDS is characterized by pathologic degradation of the pulmonary endothelial glycocalyx—a glycosaminoglycan-enriched endovascular layer necessary for pulmonary vascular homeostasis. There is a vital need to identify early triggers of endothelial glycocalyx degradation in sepsis, both to enhance our understanding of pathophysiology, and critically, to identify new therapeutic targets for prevention and early treatment of sepsis-induced ARDS. Our published and preliminary data suggest that (1) cell-free hemoglobin (CFH) is released into the circulation in sepsis and contributes to oxidant-mediated organ dysfunction and death; (2) CFH can directly injure the lung endothelial glycocalyx, causing degradation and shedding; (3) haptoglobin, an endogenous scavenger for cell-free hemoglobin that limits its ability to cause oxidative injury has a common genetic variant, HP-2, that increases the risk of ARDS in both humans and mice with sepsis; and (4) patients and mice with sepsis and the HP-2 variant have increased degradation of the endothelial glycocalyx and evidence of increased oxidative stress. The studies in this proposal will build on these preliminary findings to characterize the mechanisms by which CFH-mediated endothelial glycocalyx degradation is modified by the HP-2 genotype. Our primary goal is to translate these findings to new targeted therapies that will be tested in our novel isolated human lung model as preparation for rapid translation to targeted clinical trials in sepsis. In Aim 1, we will use state-of-the-art mass spectrometry analyses of circulating glycosaminoglycan fragments to determine the extent and signature of endothelial glycocalyx shedding in patients with the HP-2 variant, study the association with ARDS and determine downstream mechanisms of endothelial injury. In Aim 2 we will use genetically manipulated mouse models to determine the contribution of heparanase and oxidative injury to glycocalyx degradation in mice with the HP-2 genotype. In Aim 3, we will test the therapeutic potential of targeting oxidant mediated injury in the HP-2 genotype to preserve the endothelial glycocalyx in the isolated perfused human lung as a translational bridge to future patient studies. The studies proposed in these aims have the potential for major and sustained scientific impact. Since HP-2 is the most common allele of the HP gene and over 40% of people of European or African ancestry are homozygous for this allele, targeting patients with the HP2 genotype with therapies to prevent endothelial glycocalyx degradation is a new approach that could have a major impact on clinical outcomes.