Nrf2 signaling and oxidative stress in Age-related macular degeneration

描述(由申请人提供)：老年性黄斑变性(AMD)是美国后天性失明的主要原因。早期疾病患者的预防和治疗选择有限且无效。为了解决这一缺陷，这项建议将重点放在早期疾病的机制上。吸烟是与AMD最密切的流行病学联系，但我们并不完全了解它在这种疾病的病理生理学中的作用。香烟烟雾是一种强大的化学氧化剂，也是补体激活的有力诱因。这两个因素都被认为在AMD的发展中很重要。AMD的一个关键早期事件是视网膜色素上皮(RPE)的凋亡，部分原因是没有充分中和氧化应激。核因子-红系2相关因子2(Nrf2)是一种碱性亮氨酸拉链氧化还原敏感的转录因子，通过与被称为抗氧化反应元件的顺式作用增强子序列结合来调节抗氧化剂和细胞保护基因的诱导表达。正常情况下，Nrf2水平很低，但在氧化刺激下，Nrf2从细胞质抑制物Keap1释放出来后，核积累增加，并激活其下游抗氧化酶的协调转录。Nrf2信号在衰老和疾病中减少，导致适应性应激反应不足。有趣的是，Nrf2活性的降低可以被合成的三萜类齐墩果酸的衍生物逆转，这代表了一类很有前途的细胞氧化损伤保护药物。在这项建议中，我们假设慢性吸烟导致眼底持续的氧化应激，并且随着AMD的发生，局部Nrf2信号变得不足。最近，我们发现慢性吸烟可引起小鼠视网膜色素上皮细胞氧化损伤和超微结构损伤，最终导致视网膜色素上皮细胞凋亡。我们将利用这一系统，使用转基因小鼠来解决我们的假设，目的如下：1)测试Nrf2信号对香烟烟雾诱导的氧化应激和眼底细胞凋亡具有保护作用的假设。2)探讨Nrf2信号对补体激活的调控决定了吸烟对眼底的损伤和细胞凋亡的假说。3)确定Nrf2的药理激活剂是否保护眼底免受氧化损伤和补体激活。 公共卫生相关性：老年性黄斑变性现在是美国老年人最常见的失明原因，但我们对早期疾病发展的了解有限。吸烟是与AMD相关的最强烈的危险因素，但我们还不知道它是如何导致疾病发生或发展的。这项研究将研究吸烟如何引发黄斑变性。实验将探索核因子-红系2相关因子2(Nrf2)，一种激活抗氧化剂和细胞保护酶的转录因子，是否对香烟烟雾诱导的氧化应激和补体激活具有保护作用。这项提案还将探索三萜类化合物或可以激活Nrf2的小分子是否会阻止AMD在小鼠模型中的发展。

DESCRIPTION (provided by applicant): Age-related macular degeneration (AMD) is the leading cause of acquired blindness in the United States. Patients with early disease suffer from limited and ineffective options for prevention and treatment. To address this shortcoming, this proposal focuses on the mechanisms underlying early disease. Cigarette smoking is the strongest epidemiological link with AMD, yet we do not fully understand its role in the pathophysiology of this disease. Cigarette smoke is a powerful chemical oxidant, and a potent inducer of complement activation. Both of these factors are thought to be important in AMD development. A key early event in AMD is apoptosis of the retinal pigmented epithelium (RPE), in part through inadequately neutralized oxidative stress. Nuclear factor- erythroid 2-related factor 2 (Nrf2), a basic leucine zipper redox-sensitive transcription factor, regulates the inducible expression of antioxidant and cytoprotective genes by binding to the cis-acting enhancer sequence known as the antioxidant response element. Normally, Nrf2 levels are low, but with an oxidative stimulus, nuclear accumulation of Nrf2 increases after it is released from its cytoplasmic inhibitor Keap1, and activates the coordinated transcription of its downstream antioxidant enzymes. Decreased Nrf2 signaling is seen in aging and disease, resulting in an inadequate adaptive stress response. Intriguingly, the decreased Nrf2 activity can be reversed by the synthetic triterpenoid derivatives of oleonolic acid, which represent a promising new class of agents for cytoprotection from oxidative injury. In this proposal, we hypothesize that chronic cigarette smoking induces persistent oxidative stress in the fundus, and that local Nrf2 signaling becomes inadequate with the onset of AMD. Recently, we showed that chronic cigarette smoke induces oxidative and ultrastructural damage, and eventually apoptosis to the RPE of mice. We will exploit this system using genetically modified mice to address our hypothesis with the following aims: 1) To test the hypothesis that Nrf2 signaling protects against cigarette smoke-induced oxidative stress and apoptosis in the fundus. 2) To investigate the hypothesis that regulation by Nrf2 signaling on complement activation determines the damage and apoptosis to the fundus that is induced by cigarette smoke. 3) To determine if a pharmacological activator of Nrf2 protects the fundus from oxidative damage and complement activation. PUBLIC HEALTH RELEVANCE: Age-related macular degeneration is now the most common cause of blindness among the elderly in the United States, yet our understanding of how early disease develops is limited. Cigarette smoking is the strongest risk factor associated with AMD yet we do not understand how it causes disease onset or progression. This proposal will study how cigarette smoking triggers the onset of macular degeneration. Experiments will explore if Nuclear factor-erythroid 2-related factor 2 (Nrf2), a transcription factor that activates antioxidant and cytoprotective enzymes, protects against cigarette smoke induced oxidative stress and complement activation. This proposal will also explore whether triterpenoids, or small molecules that can activate Nrf2, will prevent the development of AMD in mouse models.