Pathogenic Role of DNA-Damage Response Pathway in the Diabetic Retina

糖尿病视网膜病变与氧化应激、线粒体功能障碍和慢性炎症有关。 炎症和退行性通路的激活。大量证据表明视网膜 线粒体膜氧化应激轴作为一个主要的统一致病因素，几乎所有的糖尿病诱导 与视网膜并发症的发展有关的细胞变化。针对这些疾病的治疗 个别途径在人体临床试验中提供了令人失望的结果。同样，临床试验使用 抗氧化剂也产生了同样模棱两可的结果。总的来说，这些试验表明， 关于将氧化应激与促炎性细胞因子激活联系起来的潜在机制的知识差距 和糖尿病视网膜中的促变性途径。基于我们以前在脊髓小脑共济失调型中的工作， 3例患者，以及本修订申请中使用相关视网膜细胞提供的新数据，我们建议 糖尿病中ROS介导的DNA损伤慢性激活DNA损伤的新假说 ATM（共济失调-毛细血管扩张突变）途径。DNA含量的增加 损害积累和糖尿病并发症包括视网膜病变的发展。此外，还有一个 越来越多的人认为ATM不仅作为DNA损伤传感器协调受损位点的修复， 维持基因组的完整性，而且在调节细胞代谢传感器的活动中起关键作用 干扰线粒体功能、细胞能量稳态、炎症和凋亡。如何 DDR-ATM通路将各种信号传导组分相互连接以破坏细胞能量代谢， 增强促变性信号传导是深入研究的主题，但在视网膜中仍未探索。 我们最近的研究表明，DDR途径的慢性激活干扰线粒体 通过抑制PGC-1α活性发挥作用，PGC-1 α是一种调节线粒体 生物发生、氧化磷酸化和细胞能量稳态。我们新的初步数据 糖尿病视网膜中DNA损伤和ATM活化增加的证据支持了我们的假设。的 在本申请中提出的实验将检验糖尿病诱导的氧化 应激引起双链DNA损伤，导致ATM活化，导致PGC 1 α下调 影响糖尿病视网膜中观察到的多种致病途径。我们假设ATM激活 诱导糖尿病诱导的氧化应激的显着放大，通过线粒体破坏由多个 机制（目的1）、血管和神经元变性（目的2）和慢性炎症（目的3）。这些 目标有可能建立一个统一的分子机制，将增强的DNA损伤与 在糖尿病中观察到的慢性氧化、变性和炎性异常。的最大影响 我们的工作是提供一种调节机制，为高血糖如何影响 线粒体功能障碍放大视网膜中的氧化、炎症和退行性变化。 PHS 398/2590（Rev.06/09）

Diabetic retinopathy has been associated with oxidative stress, mitochondrial dysfunction, and chronic activation of inflammatory and degenerative pathways. Substantial evidence implicates the retinal mitochondrial ‒ oxidative stress axis as a major unifying pathogenic factor for virtually all diabetes-induced cellular changes implicated in the development of retinal complications. Therapies directed against these individual pathways have provided disappointing results in human clinical trials. Likewise, clinical trials utilizing antioxidants have produced equally ambiguous results. Taken together, these trials suggest a significant knowledge gap regarding underlying mechanism(s) linking oxidative stress to activation of pro-inflammatory and pro-degenerative pathways in diabetic retinas. Based on our previous work in Spinocerebellar ataxia type 3 patients, together with new data provided in this revised application using relevant retinal cells, we propose the novel hypothesis that ROS-mediated DNA damage in diabetes chronically activates the DNA damage response (DDR) ATM (ataxia-telangiectasia mutated) pathway. There is a strong link between increased DNA damage accumulation and development of diabetic complications including retinopathy. Also, there is a growing consensus that ATM not only acts as a DNA damage sensor to coordinate repair of damaged sites to maintain genome integrity but also plays a critical role in modulating the activities of cellular metabolic sensors to interfere with mitochondrial function, cellular energy homeostasis, inflammation, and apoptosis. How the DDR-ATM pathway interconnects various signaling components to disrupt cellular energy metabolism and enhance pro-degenerative signaling is the subject of intense investigation but remains unexplored in the retina. Our recent studies have shown that chronic activation of the DDR pathway interferes with mitochondrial function by suppressing PGC-1α activity, a key transcription co-activator that regulates mitochondrial biogenesis, oxidative phosphorylation, and cellular energy homeostasis. Our new preliminary data demonstrating increased DNA damage and ATM activation in diabetic retina supports our hypothesis. The experiments proposed in this application will test the central hypothesis that diabetes-induced oxidative stress causes double stranded DNA damage resulting in ATM activation, leading to downregulation of PGC1α that impacts multiple pathogenic pathways observed in diabetic retinas. We hypothesize that ATM activation induces a significant amplification of diabetes-induced oxidative stress via mitochondrial disruption by multiple mechanisms (aim 1), vascular and neuronal degeneration (aim 2), and chronic inflammation (aim 3). These aims have the potential to establish a unifying molecular mechanism that links enhanced DNA damage to chronic oxidative, degenerative, and inflammatory abnormalities observed in diabetes. The greatest impact of our work is to provide a regulatory mechanism offering a novel explanation for how hyperglycemia impacts mitochondrial dysfunction to amplify oxidative, inflammatory and degenerative changes in the retina. PHS 398/2590 (Rev. 06/09) Page Continuation Format Page