ELECTRON TRANSPORT ENZYMES IN ALZHEIMERS DISEASE

(1)神经元的动态平衡依赖于正常的线粒体功能 提供能量以维持膜的极化、隔离和 排出钙，并驱动离子泵。线粒体中的酶 电子传递(ET)链在一定程度上受 细胞的生物能量学需求。兴奋性的相对密度 对大脑区域的输入有助于确定局部神经元活动， 反过来，调节代谢需求，从而调节ET酶水平 和活动。我们假设，通过检查酶在体内的状态 线粒体ET链的近端和远端，它将 在体外评估局部神经元激活的一个指标是可能的 (近期代谢需求)在AD中的控制和阿尔茨海默氏症状态。这个 ET链上的第一个酶，复合体I，将在对照和 AD脑切片，使用定量放射自显影结合 [H]二氢烯酮标记酶的ND-1亚基。航站楼 ET链酶，即复合体IV或细胞色素氧化酶，将用 定量组织化学染色。土壤水分的数量分布 将复合体I和复合体IV进行比较，以确定是否存在 AD中的关系会发生变化。初步数据显示， 阿尔茨海默病患者齿状回内复合体I和IV显著减少。我们 假设这一下降反映了 这个区域，是由于失去了从 内嗅皮层。我们将在大鼠身上验证这一假说 7天和30天评估复合体I和IV的内嗅皮层损害 损伤后数天。人类大脑的其他区域将在未来进行检查 研究包括内嗅皮层、下丘脑、颞上回， 初级运动皮质、初级感觉皮质、纹状体、黑质 还有小脑。(2)电子传递功能受损易患 减少膜极化和细胞毒性引起的兴奋性神经元变性 解除对NMDA受体离子通道的镁离子通道的阻断。在 存在生物能量缺陷，正常浓度的 细胞外的谷氨酸可能会变得致命。有间接证据表明 兴奋性毒性可能在阿尔茨海默病的神经元死亡中起次要作用， 在体外和体内都有证据表明存在生物能量学缺陷 广告。我们假设，生物能量状态(ET)之间的不匹配 酶活性)和兴奋性毒性潜力(NMDA受体密度)可以 帮助确定有选择地易受伤害的大脑区域。例如，CA1 和齿状回有相似的高密度NMDA受体，但CA1 选择性地易受兴奋性毒性和神经退行性变的影响 精神障碍，包括阿尔茨海默病。我们的初步数据显示，复杂的 CA1区的水平和复合体IV活性远低于齿状回。 N-甲基-D-天冬氨酸高密度地区ET酶的相对缺乏 受体可能是神经元变性的诱因。我们将在 N-甲基-D-天冬氨酸受体复合体I和IV的串联分布 人脑多个区域的切片。

(1) Neuronal homeostasis depends on normal mitochondrial function to provide 4 the energy to maintain membrane polarization, sequester and extrude calcium, and drive ion pumps. Enzymes of the mitochondrial electron transport (ET) chain are regulated, in part, by the bioenergetics needs of the cell. The relative density of excitatory input to a brain region helps to determine local neuronal activity which, in turn, regulates metabolic demand and, consequently, ET enzyme levels and activity. We hypothesize that by examining the status of enzymes in the proximal and distal portions of the mitochondrial ET chain, it will be possible to assess in vitro one index of regional neuronal activation (recent metabolic demand) in control and Alzheimer's status in AD. The first enzyme in the ET chain, complex I, will be assayed in control and AD brain sections, using quantitative autoradiographic binding of [H]dihydrotenone to label the ND-1 subunit of the enzyme. The terminal ET chain enzyme, complex IV or cytochrome oxidase, will be assayed using quantitative histochemical staining. The quantitative distributions of complex I and complex IV will be compared to determine whether there is relationship changes in AD. Preliminary data indicate that both complexes I and IV are substantially reduced in dentate gyrus in AD. We hypothesize that this decrease reflects a reduced metabolic demand in this region, resulting from loss of perforans pathway input from entorhinal cortex. We will test this hypothesis in rats after unilateral entorhinal cortex lesions by assessing complex I and IV 7 days and 30 days postlesion. Other regions of human brain to be examined in future studies include entorhinal cortex, subiculum, superior temporal gyrus, primary motor cortex, primary sensory cortex, striatum, substantia nigra and cerebellum. (2) Impaired electron transport function predisposes to excitotoxic neuronal degeneration by reducing membrane polization and relieving the Mg** blockade of the NMDA receptor ion channel. In the presence of a bioenergetics defect, normal concentrations of extracellular glutamate may become lethal. There is indirect evidence that excitotoxicity may play a secondary role in neuronal death in AD, and there is in vitro and in vivo evidence for bioenergetics defects in AD. We hypothesize that mismatches between bioenergetics status (ET enzyme activity) and excitotoxic potential (NMDA receptor density) may help to define selectively vulnerable brain regions. For example, CA1 and dentate gyrus have similar high densities of NMDA receptors, but CA1 is selectively vulnerable to excitotoxicity and neurodegenerative disorders, including AD. Our preliminary data indicate the complex I levels and complex IV activity are much lower in CA1 than dentate gyrus. The relative lack of ET enzymes in a region with a high density of NMDA receptors may predispose to neuronal degeneration. We will compare in detail the distributions of complexes I & IV to NMDA receptors in serial sections in multiple regions of human brain.