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

原发移植物功能障碍是急性肺损伤的一种严重形式，发生在20%-30%的肺移植受者中。 它是短期和长期结果的主要决定因素。PGD的风险受临床特征的影响 捐赠者和受赠者以及手术管理。然而，细胞机制 PGD的潜在风险还不完全清楚，关于PGD发病机制的新研究 对于开发和测试降低PGD风险的特定疗法至关重要。我们已出版的和初步的 数据表明，无细胞血红蛋白(CFH)是导致肺泡-毛细血管破裂的主要原因 导致PGD肺水肿的特征性发展。在一项试点病例对照研究中，我们展示了 受者术前血浆CFH升高与PGD风险增加独立相关。在一个 人体外肺灌流模型，CFH在灌流液中引起微血管通透性增加 对肺内皮细胞的氧化损伤。同样，肺泡内CFH水平升高与 危重病患者严重肺损伤及体外人肺损伤支气管内滴注CFH 肺上皮屏障，损害肺泡液清除。新的初步数据显示CFH在 供体肺移植的空隙。在这份提案中，我们将确定围手术期管理如何 放大CFH对PGD的影响。体外循环与体外循环膜 氧合(ECMO)可增加CFH的溶血和释放。尽管ECMO一直被认为与 尽管PGD风险低于CPB，但尚不清楚这是否由CFH的改变所解释。较高的驾驶压力 机械通气时还可增加CFH和肺泡-毛细血管屏障功能障碍。此外， 再灌流时FiO2增加增加CFH和PGD之间的联系，并加剧高氧 CFH致人肺损伤的实验研究。这一强劲的初步数据支持这样一种观点，即 手术治疗通过调节CFH的积聚和氧化来影响PGD。在这项提案中，我们 将建立一个由三个部位组成的联合体来测试CFH通过氧化损伤导致PGD的假设 至肺内皮细胞和上皮性屏障。我们还将确定可更改的风险因素如何 包括机械支持和再灌流时的高氧增加蓄积和氧化 CFH，从而增加了PGD的风险。有三个具体目标：1)检验独立效应 血管内和肺泡内CFH对PGD风险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 术中高氧性CFH氧化增加了PGD的风险。完成这一大型多中心队列 对肺移植受者的研究将为血管内和肺移植受者的相对贡献提供新的见解 肺泡内CFH到PGD，并确定改变CFH积累和氧化的可修改因素，提供 为通过CFH靶向干预缓解PGD的临床试验的开发奠定了必要的基础。

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.