DNA repair and DNA damage response for the maintenance of endothelial cell function during genotoxic stress

一些常染色体隐性遗传性疾病的特征是基因组不稳定增加，这是由于DNA修复不足和肿瘤发病率的相关增加引起的。沃纳综合征是这些疾病之一，其特征不仅是修复缺陷，而且在受影响的患者(成人)中还会加速衰老过程。与其他已知的遗传不稳定综合征相反，青春期后的Werner患者会迅速出现明显的老年症状，如骨质疏松症、糖尿病(II型)和动脉硬化。动脉硬化改变(心肌梗塞、中风)，除了肿瘤的发展外，是Werner患者寿命相对较短(40至50岁)的最重要原因。这些患者的缺陷基因编码RecQ解旋酶(WRN)。这种DNA解旋酶主要参与DNA修复和依赖DNA损伤的应激反应，这些应激反应是由活性氧(ROS)或烷化剂等引起的。ROS诱导的DNA损伤损害内皮细胞的生理功能(内皮功能障碍)，因此与动脉硬化的发病机制有关。亚硝胺的内源性形成所导致的DNA甲基化是否会影响内皮细胞的功能，目前还没有得到很好的研究。我们假设WRN相关DNA修复和应激反应的损害影响内皮细胞相关功能，最终导致在Werner患者中观察到的已知心血管并发症。此外，我们假设，DNA修复通常也独立于WRN，是保存内皮细胞功能的主要决定因素。利用原代人内皮细胞，我们将研究RNAi介导的WRN、WRN相关和WRN非依赖DNA修复因子的下调在多大程度上影响氧化剂和烷化剂引发的遗传毒性应激后内皮细胞的功能。考虑到他汀类药物是众所周知的血管保护性疗法，我们的目标是研究它们在遗传毒性应激后即使在DNA修复受损的情况下仍能维持内皮功能和生存能力的有效性。

A number of autosomally recessive hereditary disorders is characterized by increased genomic instability, caused by insufficient DNA repair and a related increase of tumor incidence. One of these disorders is the Werner syndrome, which is characterized not only by a repair defect but also by an accelerated ageing process in affected patients (adult progerie). Contrary to other known genetic instability syndromes, post-pubescent Werner patients develop rapid and pronounced geriatric symptoms such as osteoporosis, diabetes mellitus (type II) and arteriosclerosis. Arteriosclerical changes (myocardial infarction, apoplexis) are, besides tumor development, the most significant reason for the relatively short lifespan (40 to 50 yrs) of Werner patients. The defective gene in these patiens encodes the RecQ helicase (WRN). This DNA helicase is essentially involved in DNA repair and DNA damage-dependent stress responses, caused by, among others, reactive oxygen species (ROS) or alkylating agents. ROS-induced DNA damage compromises the physiological function of endothelial cells (endothelial dysfunction), hence being relevant for the pathogenesis of arteriosclerosis. Whether DNA methylation, which can result from endogenous formation of nitrosamines, impacts endothelial cell functions is poorly investigated. We posit that impairment of WRN associated DNA repair and stress responses impacts the endothel cell-related functions, which eventually result in the known cardiovascular complications observed in Werner patients. In addition, we hypothesize that DNA repair in general, also independent of WRN, is a major determinant for the preservation of endothel cell function. Using primary human endothelial cells we will address the question to which extent an RNAi mediated downregulation of WRN, WRN associated and WRN independent DNA repair factors influences endothelial cell function following genotoxic stress provoked by oxidants and alkylating agents. Bearing in mind that statins are well known vessel protective therapeutics, we aim to investigate their potency for maintaining endothelial function and viability following genotoxic stress even under conditions of compromised DNA repair.