Antioxidant vitamins in models of Alzheimer's Disease

描述(申请人提供)：阿尔茨海默病是老年人最常见的痴呆症，但其病因尚不清楚。人们一致认为，这在一定程度上与淀粉样前体蛋白的β-淀粉样蛋白片段的毒性和沉积有关。甚至在疾病的临床病程早期，β-淀粉样蛋白毒性的一个关键发现就是氧化应激。这表现为选定皮质区域的脂质过氧化和DNA损伤，随后是神经细胞死亡。由此得出的结论是，抗氧化剂，特别是抗氧化维生素，如抗坏血酸和α-生育酚，应该延缓或防止与β-淀粉样蛋白毒性相关的氧化剂损伤。然而，这一假说几乎没有得到研究。我们建议在培养的神经细胞水平和阿尔茨海默病的动物模型中测试它。由于神经元的抗坏血酸含量是体内所有细胞中最高的，而且抗坏血酸既是一种神经调节剂，也是一种抗氧化剂，我们将重点介绍它在防止皮层神经元氧化损伤方面的作用。第一个目的是利用培养的SHSY5Y神经元建立抗坏血酸摄取和循环的机制，测试抗坏血酸是否可以防止脂质过氧化和节省α-生育酚，并确定细胞内抗坏血酸是减轻β-淀粉样蛋白诱导的氧化应激还是改变β-淀粉样蛋白的分泌。第二个目的是评估氧化应激在携带与人类阿尔茨海默病有关的关键蛋白突变的转基因小鼠的组织损伤和记忆缺陷中的作用。我们希望发现，在这些动物中，氧化应激降低了皮质神经元中抗坏血酸的浓度，抗坏血酸通过逆转局部的“坏疽”来补充认知缺陷的缓慢进展。我们还将把阿尔茨海默病的转基因小鼠模型与不能合成抗坏血酸的基因敲除小鼠杂交。如果抗坏血酸可以防止神经细胞氧化损伤，那么饮食限制导致的中度抗坏血酸缺乏应该会加速氧化应激和认知缺陷的发生并加重其严重程度。在第三个目标中，我们将使用新生转基因小鼠的皮质神经元培养在细胞水平上确定抗氧化维生素减轻脂质过氧化损伤的机制。如果抗氧化维生素可以减轻阿尔茨海默病细胞和动物模型的毒性，那么氧化应激参与了疾病的进展，而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.