DNA Repair and Replication in Oxidant Lung Injury

描述（由申请人提供）：补充氧气对于减少患有呼吸窘迫的患者的组织缺氧的有益作用是众所周知的。不幸的是，氧气会被还原成具有细胞毒性的活性氧，从而损害 DNA、蛋白质和脂质，导致细胞损伤、死亡和炎症。 DNA 修复和复制发生在室内空气恢复过程中，因为受伤和死亡的细胞被替换。未能适当修复和增殖可能导致细胞死亡、炎症、纤维化和慢性肺部疾病。因此，识别调节 DNA 修复和复制的分子对于改善高氧治疗患者的临床结果非常重要。最近的研究表明，高氧会激活涉及 p53 肿瘤抑制因子的 DNA 损伤依赖性途径。 P53 在 DNA 受损的细胞中积累，并增加细胞周期蛋白依赖性激酶抑制剂 p21Cip1/WAF1（以下简称 p21）或促凋亡基因 bax 的表达。使用 p21 缺陷小鼠和细胞系的研究表明，p21 抑制增殖，从而减少细胞死亡、炎症和死亡率。令人惊讶的是，当 p21 被诱导时，高氧也会抑制 DNA 修复蛋白 AP 核酸内切酶的表达，但当 p21 不存在时则不会。 APE 也是氧化还原因子 (Ref)-1，可还原氧化形式的转录因子，例如 p53。这表明，当 DNA 受损时，p21 通过阻止 DNA 修复承诺来保护细胞免受氧化损伤，并调节 p53 依赖性转录。目标 1 中提出的研究将确定 p21 缺陷细胞在高氧期间是否由于修复活性增加而产生更多 DNA 碎片，目标 2 将确定 APE/Ref-1 是否调节 DNA 修复和 p53 活性，目标 3 将确定 p53 依赖性细胞凋亡是否在 p21 缺失的情况下促进组织修复。更好地了解 p21 如何保护细胞免受氧诱导的损伤对于治疗由高氧以及其他产生氧化自由基的吸入污染物引起的肺损伤具有治疗价值。

DESCRIPTION (provided by applicant): The beneficial effects of supplemental oxygen to reduce tissue hypoxia in patients suffering from respiratory distress are well known. Unfortunately, oxygen is reduced to cytotoxic reactive oxygen species that damage DNA, proteins and lipids resulting in cell injury, death and inflammation. DNA repair and replication occur during recovery in room air as injured and dead cells are replaced. Failure to appropriately repair and proliferate can lead to cell death, inflammation, fibrosis and chronic lung disease. Therefore, identifying molecules that regulate DNA repair and replication is important for improving clinical outcomes for patients treated with hyperoxia. Recent studies have shown that hyperoxia activates the DNA damage-dependent pathway involving the p53 tumor suppressor. P53 accumulates in cells with damaged DNA and increases the expression of the cyclin-dependent kinase inhibitor p21Cip1/WAF1 (hereafter p21) or the proapoptotic gene bax. Studies using p21-deficient mice and cell lines reveal that p21 inhibits proliferation, thereby reducing cell death, inflammation and mortality. Surprisingly, hyperoxia also inhibited the expression of the DNA repair protein AP-endonuclease when p21 was induced, but not when it was absent. APE is also redox factor (Ref)-1, which reduces oxidized forms of transcription factors, such as p53. This suggests that p21 protects cells from oxidant damage by preventing DNA repair commitment when DNA is being damaged and regulates p53-dependent transcription. The studies proposed in Aim 1 will determine whether p21-deficient cells have more DNA fragmentation during hyperoxia due to increased repair activity, Aim 2 will determine whether APE/Ref-1 regulates DNA repair and p53 activity, and Aim 3 will determine whether p53-dependent apoptosis promotes tissue repair in the absence of p21. A better understanding of how p21 protects cells from oxygen-induced damage has therapeutic value for treatment of lung injury caused by hyperoxia as well as other as other inhaled pollutants that produce oxidant free radicals.