Processing Of Oxidative Stress In Alzheimer

我们正在利用转基因小鼠、培养细胞和线虫等多种模型系统来验证这一假设，即氧化DNA损伤的积累导致神经退行性疾病中出现的神经元功能障碍。我们将重点放在阿尔茨海默病(AD)上，因为这是65岁或以上人群中最常见的痴呆症。碱基切除修复(BER)途径修复氧化DNA损伤，如碱基修饰，这是自发发生的或由于活性氧物种(ROS)的攻击而发生的。DNA聚合酶Beta(PolB)负责BER途径中的DNA合成步骤，这可能是速率限制。我们观察到AD患者中PolB的表达降低，因此我们将3xTg AD小鼠与我们的DNA聚合酶β杂合子小鼠(PolB)杂交，创建了一个新的小鼠模型3xTgAD/PolB+/-。这种新的AD品系显示了亲代AD小鼠模型所没有的几个重要的新特征。我们观察到细胞死亡标志物升高，ABeta沉积改变，线粒体功能障碍加剧，记忆力、学习和嗅觉缺陷恶化。这些新增的功能使新的老鼠模型更类似于人类的AD表现。综上所述，我们的工作和其他研究表明，BER酶的缺陷可能有助于AD患者核和线粒体DNA氧化损伤的积累，并有助于疾病的进展。 在我们的3xTg/PolB模型中，我们已经表明NAD补充使关键的AD特征正常化，如磷酸化tau、记忆和学习缺陷。在一定程度上，我们认为这是由于DNA修复增加以及线粒体功能和有丝分裂能力的改善。我们已经证明，人类AD患者的脑细胞和培养的神经元显示出线粒体功能障碍。因此，我们试图评估吞丝分裂增强剂，如NAD补充剂、尿毒素A或放线菌素是否也能改善AD模型中的AD特征。在这里，我们使用了APP/PS1小鼠和A或tau线虫AD模型。有丝分裂刺激剂能有效地改善蠕虫和小鼠的记忆。重要的是，我们观察到小胶质细胞吞噬活性增加，APP/PS1小鼠的神经炎症减轻。我们之前在3xTgAD小鼠中观察到了补充NAD的类似结果。在过度表达tau的人类神经细胞和3xTgAD小鼠中，有丝分裂诱导特异性地减少了过度磷酸化的tau的出现，tau是AD病理的主要标志。受到这些结果的鼓舞，我们正在继续研究在AD模型和其他神经退行性疾病中诱导有丝分裂的益处。

We are testing the hypothesis that the accumulation of oxidative DNA damage contributes to neuronal dysfunction seen in neurodegenerative diseases by utilizing multiple model systems like transgenic mice, cultured cells and C. elegans. We are focusing on Alzheimer's disease (AD) since this is the most prevalent form of dementia in people 65 years or older. The base excision repair (BER) pathway repairs oxidative DNA damage, such as base modifications, which occur spontaneously or from attack by reactive oxygen species (ROS). DNA polymerase Beta (PolB) is responsible for the DNA synthesis step in the BER pathway, which can be rate limiting. We observed decreased expression of PolB in AD patients so we bred the 3xTg AD mouse to our DNA Polymerase Beta heterozygous mouse (PolB) to create a new mouse model, 3xTgAD/PolB+/-. This new AD strain displayed several important new features that the parental AD mouse model did not. We observed elevated cell death markers, altered ABeta deposition, greater mitochondrial dysfunction, worse memory, learning, and smelling defects. These added features make the new mouse model more similar to the AD presentation seen in humans. Together, our work and others suggest that deficiencies in BER enzymes might contribute to the accumulation of oxidative damage in both nuclear and mitochondria DNA of AD patients and contribute to disease progression. In our 3xTg/PolB model, we have shown that NAD supplementation normalized key AD features like phospho-tau, memory and learning deficits. In part, we believed this is due to increased DNA repair and improved mitochondrial function and mitophagy. We have shown that human AD patient brain cells and cultured neurons display mitochondrial disfunction. Thus, we sought to evaluate whether mitophagy enhancers like NAD supplementation, urolithin A or actinonin could also improve AD features in AD models. Here we used APP/PS1 mice and A or tau C. elegans AD models. Mitophagy stimulators were effective at improving memory in worms and mice. Importantly, we observed increased phagocytic activity of microglia and reduced neuroinflammation in APP/PS1 mice following administration of urolithin A or actinonin. We had previously observed similar findings with NAD supplementation in 3xTgAD mice. In both tau overexpressing human neuronal cells and 3xTgAD mice, mitophagy induction specifically decreased the appearance of hyperphosphorylated tau, a major marker of AD pathology. Encouraged by these results we are continuing to characterize the benefits of mitophagy induction in AD models and other neurodegenerative diseases.