Reactive gamma-Ketoaldehydes in Dementia

描述（由申请方提供）：许多已确定的痴呆风险因素可诱导氧化损伤，包括年龄、β淀粉样蛋白、高同型半胱氨酸血症和ApoE 4。我们已经确定了在神经退行性疾病，特别是阿尔茨海默氏病（AD）中氧化损伤的发生，通过证明异前列烷（IsoPs），神经前列烷（NP）产品的自由基诱导的花生四烯酸和二十二碳六烯酸的氧化，分别过量生产。异缩酮（IsoKs）和神经缩酮（NKs）是分别由IsoP和NP途径产生的高反应性γ-酮醛。IsoK和NK迅速加合到蛋白质上，并表现出独特的交联蛋白质的倾向。最近，我们发现吡哆胺在体外有效地捕获并阻止IsoKs加合到蛋白质上。阿尔茨海默病的一个主要特征是聚集蛋白的积累。阿尔茨海默病中蛋白酶体活性也会受损，从而诱导细胞凋亡。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知之甚少。最近，我们在AD脑的海马神经元中发现了强烈的IsoK免疫反应，这在年龄匹配的对照组中是不存在的。IsoK加合蛋白被20 S蛋白酶体降解很差，并且还抑制蛋白酶体功能，IsoK在神经胶质细胞中以nM浓度抑制蛋白酶体功能并诱导细胞死亡。这些发现产生了这样的假设，即阿尔茨海默病和可能的其他形式的痴呆中的氧化损伤产生IsoKs和NK，其加合到蛋白质并改变神经元功能，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IsoK/NK加合物在阿尔茨海默病患者死后大脑中的水平和分布，并确定IsoK/NK加合物是否存在于AD患者的CSF中。我们最近建立了氧化损伤的发生在痴呆症的动物模型，这是与严重的记忆缺陷，老年ApoE基因敲除小鼠过表达人ApoE 4。我们将确定这些动物中记忆缺陷的发展和进展的时间过程; IsoPs，NPs，IsoK/NK加合物的形成增加以及蛋白酶活性的变化。我们将确定IsoK/NK加合蛋白在AD脑海马和痴呆小鼠模型的脑中。我们还将确定2种抗氧化剂Tempol和硫辛酸抑制氧化应激、IsoK/NK加合物形成和减轻小鼠模型中记忆缺陷的功效。我们还将探索一种新的药理学干预，吡哆胺选择性地阻止IsoK/NK内收和减轻小鼠模型记忆缺陷的能力。

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.