Cell survival and death in oxidant lung injury

描述（由申请人提供）：过早暴露于氧气是支气管肺发育不良（BPD）的主要风险因素，BPD是一种常见于新生儿的慢性肺部疾病，其特征是肺部发育停滞。尽管外源性表面活性剂和温和通气策略的治疗性使用降低了死亡率，但早产的儿童和青少年肺功能降低，呼吸道病毒感染的易感性增加，以及与年龄相关的血压升高。因此，迫切需要了解氧气是如何永久地破坏发育中的肺的生长的。最近的研究表明，线粒体损伤是氧诱导的新生儿肺病的一个组成部分，因为氧水平升高（高氧）抑制线粒体呼吸并损伤线粒体DNA。为了确定细胞是否激活逆行信号回到细胞核以响应线粒体DNA损伤来控制基因表达，用逆转录病毒感染上皮细胞，所述逆转录病毒表达引起线粒体或核DNA中的链断裂的酶。像高氧一样，线粒体或核DNA的损伤刺激了肿瘤抑制蛋白p53的表达。相比之下，线粒体靶向一种只切割核DNA的酶未能激活p53，但当靶向细胞核时却能激活。当被线粒体DNA损伤激活时，p53刺激核基因的表达，从而抑制细胞生长并提高细胞存活率。这些发现表明细胞对线粒体DNA损伤的反应是典型的核DNA损伤反应，并且这种反应抑制细胞生长，可能是预期即将发生的线粒体功能障碍和能量耗尽。基于这些发现，我们现在提出测试的假设，线粒体DNA损伤是如何高氧激活p53信号和破坏出生后肺发育的一个组成部分。我们将使用新型逆转录病毒和能够有条件地破坏呼吸道上皮细胞线粒体DNA的转基因小鼠来验证这一假设。了解细胞如何特异性地对氧诱导的线粒体DNA损伤做出反应是非常重要的，因为它可能导致新的治疗机会，以减少对发育中的肺的氧毒性以及归因于氧毒性的年龄相关疾病。

DESCRIPTION (provided by applicant): Premature exposure to oxygen is a major risk factor for bronchopulmonary dysplasia (BPD), a chronic form of lung disease frequently seen in neonates that is characterized as an arrest in lung development. Although the therapeutic use of exogenous surfactant and milder ventilation strategies has reduced mortality, children and adolescents born prematurely have reduced lung function, increased susceptibility to respiratory viral infections, and age-associated increases in blood pressure. Hence there is an urgent need to understand how oxygen permanently disrupts growth of the developing lung. Recent studies suggest damage to mitochondria is a component of oxygen-induced newborn lung disease because elevated levels of oxygen (hyperoxia) suppress mitochondrial respiration and damage mitochondrial DNA. To determine whether cells activate retrograde signaling back to the nucleus to control gene expression in response to mitochondrial DNA damage, epithelial cells were infected with retroviruses expressing enzymes that cause strand breaks in mitochondrial or nuclear DNA. Like hyperoxia, damage to mitochondrial or nuclear DNA stimulated expression of the tumor suppressor protein p53. In contrast, mitochondrial targeting of an enzyme that only cuts nuclear DNA failed to activate p53, but did so when targeted to the nucleus. When activated by mitochondrial DNA damage, p53 stimulated expression of nuclear genes that inhibited cell growth and enhanced cell survival. These findings suggest the cell reacts to mitochondrial DNA damage with a classic nuclear DNA damage response, and that this response inhibits cell growth, perhaps in anticipation of impending mitochondrial dysfunction and energy depletion. Based upon these findings, we now propose to test the hypothesis that mitochondrial DNA damage is a component of how hyperoxia activates p53 signaling and disrupts postnatal lung development. We will test this hypothesis using novel retroviruses and transgenic mice capable of conditionally damaging mitochondrial DNA in respiratory epithelial cells. Understanding how cells respond specifically to oxygen-induced mitochondrial DNA damage is highly significant because it could lead to new therapeutic opportunities for reducing oxygen-toxicity to the developing lung as well as age-related diseases attributed to oxygen toxicity.