Stretch and Hyperoxia in Ventilator-induced Lung Injury

描述(由申请人提供)：机械通气和高氧血症，虽然是必要的支持性干预措施，但已经独立地与肺损伤的发生有关。尽管患有低氧性呼吸衰竭的患者经常接受这两种干预措施，但对它们潜在的不良相互作用知之甚少。我们假设，机械通气引起的肺泡上皮细胞的周期性伸展，在中度高氧存在的情况下，导致活性氧物种(ROS)的产生增加，这比单独使用任何一种刺激产生的ROS都要大。这些过量的ROS通过改变氧化信号，导致肺泡上皮细胞凋亡增加。由此导致的细胞丢失导致肺泡上皮屏障完整性的破坏，导致肺对液体、细胞和炎症介质的渗透性变得更强。这种液体和细胞的流入导致了肺力学和气体交换的不利紊乱，并加速了肺损伤的发展。在拟议的研究中，我们将使用大潮气量机械通气和中度高氧联合作用造成的肺损伤的体内模型，这是一个体外系统，允许在高氧条件下对分离的肺泡上皮细胞单层进行周期性机械拉伸，并分离暴露于机械通风和高氧后的大鼠肺泡II型上皮细胞。我们将使用这些系统来实现以下特定目标：特定目标1：证明机械拉伸和中度高氧相结合会导致肺泡-毛细血管屏障完整性的早期丧失和肺损伤的加速发展。目的2：探讨机械牵张和高氧条件下培养的肺泡上皮细胞产生ROS的机制。具体目的3：证实机械牵张联合中度高氧通过激活凋亡信号调节蛋白-1(ASK-1)促进肺泡II型上皮细胞的凋亡，并探讨ASK-1介导的细胞凋亡对肺泡上皮屏障完整性的影响。由于接受机械通气的ALI患者获得了不同程度的补充氧气，因此拟议的工作可能具有重要的临床适用性，包括确定预防和/或治疗急性肺损伤的潜在治疗靶点。

DESCRIPTION (provided by applicant): Both mechanical ventilation and hyperoxia, although necessary supportive interventions, have been independently implicated in the genesis of lung injury. Although patients with hypoxemic respiratory failure are routinely exposed to both of these interventions, little is known about their potential adverse interaction. We hypothesize that cyclic stretch of alveolar epithelial cells caused by mechanical ventilation, in the presence of moderate hyperoxia, causes an increase in production of reactive oxygen species (ROS) that is greater than that produced by either stimulus alone. These excess ROS, through altered oxidative signaling, result in increased apoptotic cell death of alveolar epithelial cells. The resulting cell loss leads to the breakdown of alveolar-epithelial barrier integrity causing the lungs to become more permeable to fluid, cells, and inflammatory mediators. This influx of fluid and cells causes adverse derangement in lung mechanics and gas exchange, and the accelerated development of lung injury. In the proposed studies, we will use an in vivo model of lung injury caused by the combined effect of large tidal volume mechanical ventilation and moderate hyperoxia, an in vitro system that allows cyclic mechanical stretch of isolated alveolar epithelial cell monolayers in hyperoxic conditions as well as isolation of alveolar type II epithelial cells from rats after exposure to mechanical ventilation and hyperoxia. We will use these systems to accomplish the following specific aims: Specific Aim 1: To demonstrate that the combination of mechanical stretch and moderate hyperoxia leads to early loss of alveolar-capillary barrier integrity and accelerated development of lung injury. Specific Aim 2: To determine the mechanisms by which ROS are produced during mechanical stretch and hyperoxia in cultured alveolar epithelial cells. Specific Aim 3: To demonstrate that COMBINED mechanical stretch and moderate hyperoxia increases alveolar type II epithelial cell apoptosis via activation of apoptosis signal-regulating kinase-1 (ASK-1) and to determine the effect of ASK-1 mediated apoptosis on alveolar epithelial barrier integrity. Because ALI patients supported with mechanical ventilation receive varied levels of supplemental oxygen, the proposed work could have significant clinical applicability, including the identification of potential therapeutic targets for the prevention and/or treatment of acute lung injury.