Role of DNA Repair in COPD

描述（由申请人提供）： 吸烟是肺气肿的主要危险因素，肺气肿是慢性阻塞性肺疾病（COPD）的重要表型。然而，目前还不清楚为什么戒烟后肺气肿仍然存在。新出现的证据表明，由于DNA修复不足，持续的DNA损伤可能发挥作用。我们的新的初步数据确定，DNA修复基因XRCC 5的蛋白质表达显着降低，并与COPD患者肺部小泛素相关修饰物缀合（SUMO化）增加有关。香烟烟雾提取物（CSE）显着降低XRCC 5蛋白，但不是mRNA，在原代人支气管上皮细胞（HBECs）。抑制XRCC 5表达增强CSE诱导的细胞毒性和DNA损伤（？）H2AX）。相比之下，XRCC 5过表达减弱了CSE效应。此外，XRCC 5的半合子缺陷增加了对香烟烟雾（CS）和流感病毒（IAV）感染的肺气肿。这些初步数据使我们得出一个总体假设，即CS诱导的关键修复蛋白XRCC 5的耗竭有助于持续的DNA损伤和肺气肿的形成。在目标1中，我们将确定与未患COPD的戒烟者相比，患有COPD的戒烟者的肺是否表现出XRCC 5丢失和DNA损伤。在目的2中，将研究CS诱导的XRCC 5体外耗竭的机制。在目的3中，为了确定XRCC 5蛋白表达是否调节CS诱导的DNA损伤和肺气肿，我们将分别使用XRCC 5 +/-和XRCC 5转基因小鼠进行XRCC 5的体内功能丧失和功能获得研究。通过实现这些目标，我们将加深我们对DNA修复在COPD发病机制中的作用的理解。这些发现可能导致通过增强DNA修复（例如，XRCC 5），可能调节CS诱导的肺气肿的易感性。

DESCRIPTION (provided by applicant): Cigarette smoking is the major risk factor for pulmonary emphysema, a critical phenotype of chronic obstructive pulmonary disease (COPD). However, it remains unclear why emphysema persists despite smoking cessation. Emerging evidence suggests a potential role of persistent DNA damage due to DNA repair insufficiency. Our novel preliminary data determined that protein expression of the DNA repair gene XRCC5 is markedly reduced and associated with increased small ubiquitin-related modifier conjugation (SUMOylation) in the lungs of patients with COPD. Cigarette smoke extract (CSE) significantly decreased XRCC5 protein, but not mRNA, in primary human bronchoepithelial cells (HBECs). Suppression of XRCC5 expression augmented CSE-induced cytotoxicity and DNA damage (?H2AX) in immortalized HBECs. By contrast, XRCC5 overexpression attenuated the CSE effects. Furthermore, the hemizygous deficiency of XRCC5 augmented emphysema in response to cigarette smoke (CS) and influenza virus (IAV) infection. These preliminary data led us to an overarching hypothesis that CS-induced depletion of the critical repair protein, XRCC5, contributes to persistent DNA damage and the formation of emphysema. In Aim 1, we will determine whether the lungs of ex-smokers with COPD exhibit XRCC5 loss and DNA damage compared with ex-smokers without COPD. In Aim 2, the mechanisms of CS-induced depletion of XRCC5 in vitro will be investigated. In Aim 3, to determine whether XRCC5 protein expression modulates CS-induced DNA damage and emphysema, we will execute loss-of-function and gain-of-function studies of XRCC5 in vivo using XRCC5+/- and XRCC5 transgenic mice, respectively. By achieving these aims, we will deepen our understanding of the role of DNA repair in COPD pathogenesis. These findings may lead to the development of novel therapeutics by augmenting DNA repair (e.g., XRCC5) that may modulate susceptibility to CS-induced emphysema.