Antioxidant vitamins in models of Alzheimer's Disease

描述（由申请人提供）：阿尔茨海默病是老年人中最常见的痴呆症，但其病因学知之甚少。有共识认为，它部分涉及淀粉样前体蛋白的β-淀粉样片段的毒性和沉积。β-淀粉样蛋白毒性的一个关键发现，即使在疾病的临床过程的早期，是氧化应激。这表现为选择皮质区域的脂质过氧化和DNA损伤，随后是神经元细胞死亡。因此，抗氧化剂，特别是抗氧化维生素，如抗坏血酸和α-生育酚，应该延迟或预防与β-淀粉样蛋白毒性相关的氧化损伤。然而，这一假设很少得到研究。我们建议在培养的神经元细胞水平和阿尔茨海默病的动物模型中对其进行测试。由于神经元具有体内任何细胞中最高的抗坏血酸含量，并且由于抗坏血酸作为神经调节剂和抗氧化剂都很重要，因此我们将重点关注其在防止氧化剂损伤皮质神经元中的作用。第一个目的是使用培养的SHSY 5 Y神经元建立抗坏血酸摄取和再循环的机制，以测试抗坏血酸是否防止脂质过氧化和备用α-生育酚，并确定细胞内抗坏血酸是否减少β-淀粉样蛋白诱导的氧化应激或修改β-淀粉样蛋白分泌。第二个目标是评估氧化应激在转基因小鼠组织损伤和记忆缺陷中的作用，转基因小鼠携带与人类阿尔茨海默病有关的关键蛋白质突变。我们期望发现这些动物的氧化应激降低了皮质神经元中抗坏血酸的浓度，并且抗坏血酸补充剂通过逆转局部“坏血病”来减缓认知缺陷的进展。“我们还将使阿尔茨海默病的转基因小鼠模型与不能合成抗坏血酸的敲除小鼠杂交。如果抗坏血酸防止神经细胞氧化损伤，由于饮食限制导致的中度抗坏血酸缺乏应加速氧化应激和认知缺陷的发作并使其严重程度恶化。在第三个目标中，我们将使用从新生转基因小鼠培养的皮层神经元，以确定在细胞水平的抗氧化维生素减少脂质过氧化损伤的机制。如果抗氧化维生素改善阿尔茨海默病细胞和动物模型的毒性，那么氧化应激参与疾病进展，抗氧化维生素补充剂可能是有益的。

DESCRIPTION (provided by applicant): Alzheimer's disease is the most common dementia in aging humans, but its etiology is poorly understood. There is consensus that it relates in part to the toxicity and deposition of beta-amyloid fragments of the amyloid precursor protein. A key finding of beta-amyloid toxicity, even early in the clinical course of the disease, is oxidant stress. This manifests as lipid peroxidation and DNA damage in select cortical areas, followed by neuronal cell death. It follows that antioxidants, and particularly antioxidant vitamins such as ascorbic acid and alpha-tocopherol, should delay or prevent oxidant damage associated with beta-amyloid toxicity. However, this hypothesis has received little study. We propose to test it at the level of cultured neuronal cells and in animal models of Alzheimer's disease. Since neurons have the highest ascorbate content of any cell in the body, and since ascorbate is important as both a neuromodulator and antioxidant, we will focus on its role in preventing oxidant injury to cortical neurons. The first aim uses cultured SHSY5Y neurons to establish mechanisms of ascorbate uptake and recycling, to test whether ascorbate prevents lipid peroxidation and spares alpha-tocopherol, and to determine whether intracellular ascorbate either lessens beta-amyloid-induced oxidant stress or modifies beta-amyloid secretion. The second aim assesses the role of oxidant stress in the tissue damage and memory deficits in transgenic mice carrying mutations in key proteins implicated in human Alzheimer's disease. We expect to find that oxidant stress in these animals decreases cortical neuron concentrations of ascorbate, and that ascorbate supplements slow progression of cognitive defects by reversing local "scurvy." We will also crossbreed the transgenic mouse model of Alzheimer's disease with a knockout mouse that cannot synthesize ascorbate. If ascorbate prevents neuronal cell oxidant damage, moderate ascorbate deficiency due to dietary restriction should hasten the onset and worsen the severity of oxidant stress and cognitive deficits. In the third aim, we will use cortical neurons cultured from neonatal transgenic mice to determine at the cell level the mechanisms by which antioxidant vitamins lessen lipid peroxidative damage. If antioxidant vitamins ameliorate toxicity in cell and animal models of Alzheimer's disease, then oxidant stress is involved in disease progression, and antioxidant vitamin supplements may be beneficial.