DNA Repair and Replication in Oxidant Lung Injury

描述（由申请人提供）：补充氧气对呼吸窘迫患者减少组织缺氧的有益作用是众所周知的。不幸的是，氧气被还原成细胞毒性活性氧，破坏DNA、蛋白质和脂质，导致细胞损伤、死亡和炎症。DNA修复和复制发生在恢复期间，在室内空气中受伤和死亡的细胞被替换。不能适当地修复和增殖可导致细胞死亡、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患者的临床结果非常重要。最近的研究表明，高氧激活了包括p53肿瘤抑制因子在内的DNA损伤依赖通路。P53在DNA受损的细胞中积累，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。对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诱导时，高氧也会抑制DNA修复蛋白ap -内切酶的表达，而当p21缺失时则不会。APE也是一种氧化还原因子(Ref)-1，它可以减少氧化形式的转录因子，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。Aim 1中提出的研究将确定p21缺陷细胞在高氧状态下是否会由于修复活性增加而产生更多的DNA碎片，Aim 2将确定APE/Ref-1是否调节DNA修复和p53活性，Aim 3将确定p53依赖性凋亡是否会促进p21缺失时的组织修复。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吸入污染物引起的产生氧化自由基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.