Reactive gamma-Ketoaldehydes in Dementia

描述（由申请人提供）：痴呆的许多已知危险因素可诱发氧化损伤，包括年龄、淀粉样蛋白β、高同型半胱氨酸血症和ApoE4。我们通过证明自由基诱导花生四烯酸和二十二碳六烯酸氧化产生过量的异前列腺素（IsoPs）和神经前列腺素（NPs）产物，确定了神经退行性疾病，特别是阿尔茨海默病（AD）中氧化损伤的发生。IsoKs和neuroketals是分别由IsoP和NP途径产生的高活性γ -酮醛。isok和NKs迅速加合到蛋白质上，并表现出独特的交联蛋白倾向。最近，我们发现pyridoxamine在体外有效地捕获和阻止isok内合到蛋白质上。阿尔茨海默病的一个主要特征是聚集蛋白的积累。蛋白酶体活性在阿尔茨海默病中也受损，这可以诱导细胞凋亡。蛋白质聚集、蛋白酶体抑制的原因以及这些现象之间的关系尚不清楚。最近，我们在AD大脑的海马神经元中发现了强烈的IsoK免疫反应性，而在年龄匹配的对照组中则没有。在神经胶质细胞中，IsoK内合蛋白被20S蛋白酶体降解较差，并抑制蛋白酶体功能，在nM浓度下，IsoK抑制蛋白酶体功能并诱导细胞死亡。这些发现提出了一种假设，即阿尔茨海默病和其他形式的痴呆症中的氧化损伤产生isok和NKs，它们加合到蛋白质上，改变神经元功能，抑制蛋白酶体功能，并诱导神经元细胞死亡。为了验证这一假设，我们将确定阿尔茨海默病患者死后大脑中IsoK/NK加合物的水平和分布，并确定AD患者脑脊液中是否存在IsoK/NK加合物。我们最近在一个与严重记忆缺陷相关的痴呆动物模型中建立了氧化损伤的发生，老年ApoE缺失小鼠过度表达人类ApoE4。我们将确定记忆缺陷的发展和进展的时间进程；这些动物中IsoPs、NPs、IsoK/NK加合物的形成增加，蛋白酶活性发生变化。我们将在阿尔茨海默病大脑海马和痴呆小鼠模型大脑中鉴定IsoK/NK内合蛋白。我们还将确定两种抗氧化剂Tempol和硫辛酸在抑制氧化应激、IsoK/NK加合物形成和减轻小鼠记忆缺陷方面的功效。我们还将探索一种新的药理学干预，pyridoxamine选择性地阻止IsoK/NK内合并减轻小鼠模型中的记忆缺陷的能力。

DESCRIPTION (provided by applicant): Many established risk factors for dementia induce oxidative injury including age, amyloid Beta, hyperhomocysteinemia, and ApoE4. We have established the occurrence of oxidant injury in neurodegenerative diseases, in particular Alzheimer's disease (AD), by demonstrating overproduction of isoprostanes (IsoPs), neuroprostanes (NPs) products of free radical induced oxidation of arachidonic acid and docosahexaenoic acid, respectively. Isoketals (IsoKs) and neuroketals (NKs) are highly reactive gamma-ketoaldehydes produced by the IsoP and NP pathways, respectively. IsoKs and NKs rapidly adduct to proteins and exhibit a unique proclivity to cross link proteins. Recently, we found that pyridoxamine effectively traps and prevents IsoKs from adducting to proteins in vitro. A dominant feature of Alzheimer's disease is the accumulation of aggregated proteins. Proteasome activity is also impaired in Alzheimer's disease, which can induce apoptosis. The cause of protein aggregation, proteasome inhibition, and the relationship between these phenomena is poorly understood. Recently, we found intense IsoK immunoreactivity in hippocampal neurons in AD brains, which was absent in brains from aged-matched controls. IsoK adducted proteins are poorly degraded by the 20S proteasome and also inhibit proteasome function, lsoKs inhibit proteasome function and induce cell death at nM concentrations in neuroglial cells. These findings have engendered the hypothesis that oxidative injury in Alzheimer's disease and likely other forms of dementia produces IsoKs and NKs, which adduct to proteins and alter neuronal function, inhibit proteasome function, and induce neuronal cell death. To test this hypothesis, we will determine the levels and distribution of IsoK/NK adducts in post-mortem brains from patients with Alzheimer's disease and determine whether IsoK/NK adducts are present in CSF from AD patients. We recently established the occurrence of oxidant injury in an animal model of dementia that is associated with severe memory deficit, aged ApoE null mice overexpressing human ApoE4. We will determine the time-course of development and progression of memory deficit; increased formation of IsoPs, NPs, IsoK/NK adducts, and changes in protease activity in these animals. We will identify IsoK/NK adducted proteins in the hippocampus of AD brains and in brains of the mouse model of dementia. We will also determine the efficacy of 2 antioxidants, Tempol and lipoic acid, to suppress oxidative stress, IsoK/NK adduct formation, and mitigate the memory deficit in the mouse model. We will also explore a novel pharmacologic intervention, the ability of pyridoxamine to selectively prevent IsoK/NK adduction and mitigate the memory deficit in the mouse model.