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)的关键表型。然而，尽管戒烟，肺气肿仍然存在的原因仍不清楚。新出现的证据表明，由于DNA修复不足，持续的DNA损伤可能起到了作用。我们新的初步数据确定，在COPD患者的肺中，DNA修复基因XRCC5的蛋白表达显著减少，并与小泛素相关修饰结合(SUMO化)增加有关。香烟烟雾提取物(CSE)能显著降低原代培养的人支气管上皮细胞(HBECs)中XRCC5蛋白的表达，但不能降低HBECs中XRCC5的表达。抑制XRCC5的表达可增强CSE对永生化HBECs的细胞毒作用和DNA损伤。相反，XRCC5的过表达减弱了CSE的影响。此外，XRCC5基因的半合子缺陷增加了对香烟烟雾(CS)和流感病毒(IAV)感染的肺气肿的反应。这些初步数据使我们得出了一个重要的假设，即CS诱导的关键修复蛋白XRCC5的枯竭导致持续的DNA损伤和肺气肿的形成。在目标1中，我们将确定与没有COPD的既往吸烟者相比，患有COPD的既往吸烟者的肺是否表现出XRCC5缺失和DNA损伤。在目的2中，我们将在体外研究CS诱导XRCC5耗竭的机制。在目的3中，为了确定XRCC5蛋白的表达是否调节了CS诱导的DNA损伤和肺气肿，我们将分别使用XRCC5+/-和XRCC5转基因小鼠进行体内XRCC5功能丧失和功能获得的研究。通过这些目标的实现，我们将加深对DNA修复在COPD发病机制中作用的理解。这些发现可能导致通过增强DNA修复(例如，XRCC5)来调节CS诱导的肺气肿的易感性，从而开发新的治疗方法。

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.