Peri-operative factors that drive cell-free hemoglobin-mediated primary graft dysfunction

原发性移植物功能障碍是一种严重的急性肺损伤，发生在20-30%的肺移植受者中 并且是短期和长期结果的主要决定因素。PGD风险受临床特征影响 捐赠者和接受者以及运营管理。然而，细胞机制， PGD的潜在风险还不完全清楚，对PGD机制的新研究 对于开发和测试特定疗法以减轻PGD风险至关重要。我们已公布的和初步的 数据表明无细胞血红蛋白（CFH）是肺泡毛细血管破裂的主要原因， 导致PGD中肺水肿的特征性发展。在一项试点病例对照研究中，我们发现 受体术前血浆CFH升高与PGD风险增加独立相关。中 在人离体肺灌注模型中，灌注液中的CFH通过 肺内皮的氧化损伤。同样，肺泡内CFH水平升高与 重症患者的严重肺损伤和CFH支气管内滴注到离体人肺损伤中 肺上皮屏障并损害肺泡液体清除。新的初步数据显示， 供体肺同种异体移植物的空气空间。在本建议中，我们将确定如何围手术期管理， 放大CFH对PGD的影响。体外循环（CPB）和体外膜 氧合（ECMO）增加溶血和CFH释放。尽管ECMO与 PGD风险低于CPB，尚不清楚这是否是由CFH的改变解释的。更高的驱动压力 在机械通气期间也可能增加CFH和肺泡-毛细血管屏障功能障碍。此外，委员会认为， 再灌注时FiO 2增加增强了CFH和PGD之间的相关性，高氧加重了 CFH诱导的离体人肺损伤。这一强有力的初步数据支持了这一概念，即： 手术处理通过调节CFH的积累和氧化影响PGD。在本提案中，我们 将建立一个三点联盟来检验CFH通过氧化损伤引起PGD的假设 肺内皮和上皮屏障。我们还将确定如何改变风险因素 包括机械支持和再灌注时的高氧增加了 CFH，从而增加PGD的风险。具体目标有三：1）检验 血管内和肺泡内CFH对PGD风险以及内皮和上皮屏障损伤的影响，2） 确定围手术期因素如何影响血管内和肺泡内CFH积聚，以及3）测试如何 术中高氧导致CFH氧化增加PGD风险。完成该大型多中心队列 对肺移植受者的研究将提供新的见解， 肺泡内CFH到PGD，并确定可改变CFH积累和氧化的因素， 开发临床试验以减轻CFH靶向干预的PGD的必要基础。

Primary graft dysfunction, a severe form of acute lung injury, occurs in 20-30% of lung transplant recipients and is a major determinant of both short- and long-term outcomes. Risk of PGD is affected by clinical features of both the donor and recipient as well as by operative management. However, the cellular mechanisms that underlie risk of PGD are incompletely understood and new studies of mechanisms contributing to PGD are essential to development and testing of specific therapies to mitigate PGD risk. Our published and preliminary data suggest that cell-free hemoglobin (CFH) is a major causal factor in the alveolar-capillary disruption that leads to the characteristic development of pulmonary edema in PGD. In a pilot case-control study, we showed that elevated recipient pre-operative plasma CFH is independently associated with increased PGD risk. In a human ex vivo lung perfusion model, CFH in the perfusate caused increased microvascular permeability by oxidative injury to the lung endothelium. Similarly, elevated levels of intra-alveolar CFH are associated with severe lung injury in critically ill patients and intra-bronchial instillation of CFH into ex vivo human lungs injures the lung epithelial barrier and impairs alveolar fluid clearance. New preliminary data show increased CFH in the airspace of donor lung allografts. In this proposal, we will determine how peri-operative management may magnify the impact of CFH on PGD. Cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO) increase hemolysis and release of CFH. Although ECMO has been associated with lower PGD risk than CPB, it is unclear whether this is explained by alterations in CFH. Higher driving pressure during mechanical ventilation may also increase CFH and alveolar-capillary barrier dysfunction. Furthermore, increased FiO2 at reperfusion augments the association between CFH and PGD and hyperoxia exacerbates CFH-induced lung injury in ex vivo human lungs. This strong preliminary data supports the concept that peri- operative management affects PGD by modulating accumulation and oxidation of CFH. In this proposal, we will establish a three-site consortium to test the hypothesis that CFH causes PGD via oxidative injury to the lung endothelial and epithelial barriers. We will also determine how modifiable risk factors including mechanical support and hyperoxia at reperfusion increase accumulation and oxidation of CFH, thereby increasing risk of PGD. There are three specific aims: 1) test the independent effects of intravascular and intra-alveolar CFH on risk of PGD and injury to the endothelial and epithelial barriers, 2) determine how peri-operative factors affect intravascular and intra-alveolar CFH accumulation, and 3) test how CFH oxidation by intra-operative hyperoxia increases risk of PGD. Completion of this large multicenter cohort study of lung transplant recipients will provide novel insight into the relative contributions of intravascular and intra-alveolar CFH to PGD and identify modifiable factors that alter CFH accumulation and oxidation, providing the necessary foundation for development of clinical trials to mitigate PGD with CFH-targeted interventions.