Cell Survival and Death in Oxidant Lung Injury

描述（由申请人提供）：当患者出现呼吸窘迫时，高氧通常用于增强组织氧合。不幸的是，它的治疗效果受到肺细胞氧化损伤和死亡的限制。修复氧化损伤或启动细胞死亡的决定是由基因决定的，比如控制细胞命运的肿瘤抑制因子p53。p53介导的细胞存活的主要决定因素是细胞周期蛋白依赖性激酶抑制剂p21。与p21是重要的促生存分子一致，缺乏p21的小鼠和细胞系很快就会死于高氧。在寻找p21抗高氧的机制时，发现p21可以防止高氧暴露细胞中Bcl-XL的丢失。细胞系的功能增益和损失研究提供了实验证明，Bcl-XL是Bcl-2基因家族的抗凋亡成员，是p21介导的抗高氧保护的相关靶点。初步研究表明p21还能调控Bcl-2家族其他抗凋亡成员的表达。相反，p21不改变促凋亡蛋白Bax或Bak的表达。基于这些观察结果，我们提出验证p21通过调节抗凋亡Bcl-2家族成员的表达来防止高氧的假设。利用转基因细胞系和小鼠模型，Aim 1将鉴定高氧状态下受p21调控表达的所有抗凋亡Bcl-2家族成员，Aim 2将确定高氧和p21如何调节其表达，Aim 3将确定它们是否介导p21的细胞保护作用。这些研究的成功完成将阐明p21如何促进高氧损伤细胞的存活，并为氧化肺中细胞命运的决定提供新的见解。公共卫生研究的相关性。由于持续的氧化应激是哮喘、慢性炎症、缺血/再灌注损伤、癌症、衰老过程和许多其他疾病的潜在原因，了解p21如何在高氧条件下控制细胞生长和存活可以为促进公众健康提供新的机会。

DESCRIPTION (provided by applicant): Hyperoxia is often used to enhance tissue oxygenation when patients are suffering from respiratory distress. Unfortunately, its therapeutic benefits are limited by oxidative cell injury and death to pulmonary cells. The decision to repair oxidative damage or initiate cell death is dictated by genes, such as the tumor suppressor p53, that control cell fate. The major determinant of p53- mediated cell survival is the cyclin-dependent kinase inhibitor p21. Consistent with p21 being an important pro-survival molecule, mice and cell lines lacking p21 quickly succumb to hyperoxia. While searching for mechanisms by which p21 protects against hyperoxia, p21 was discovered to prevent the loss of Bcl-XL in cells exposed to hyperoxia. Gain and loss of function studies in cell lines provided experimental proof that Bcl-XL, an anti-apoptotic member of the Bcl-2 gene family, is a relevant target of p21-mediated protection against hyperoxia. Preliminary studies indicate p21 also regulates expression of other anti-apoptotic members of the Bcl-2 family. In contrast, p21 does not alter expression of the pro-apoptotic proteins Bax or Bak. Based upon these observations, we propose to test the hypothesis that p21 protects against hyperoxia by regulating expression of anti- apoptotic members of the Bcl-2 family. Using genetically modified cell line and mouse models, Aim 1 will identify all anti-apoptotic members of the Bcl-2 family whose expression is regulated by p21 during hyperoxia, Aim 2 will determine how hyperoxia and p21 regulates their expression, and Aim 3 will determine whether they mediate the cytoprotective effects of p21. Successful completion of these studies will clarify how p21 promotes survival of cells damaged by hyperoxia and provide new insight into how cell fate decisions are made in the oxidized lung. Relevance of Research for Public Health. Because persistent oxidative stress is an underlying cause of asthma, chronic inflammation, ischemia/reperfusion injury, cancer, the aging process, and many other diseases, understanding how p21 controls cell growth and survival during hyperoxia could provide new opportunities for promoting public health.