ELECTRON TRANSPORT ENZYMES IN ALZHEMIERS DISEASE

(1)神经元的稳态依赖于正常的线粒体功能， 提供4能量以维持膜极化，隔离和 挤出钙，驱动离子泵 线粒体酶 电子传递（ET）链的调节，部分是由 细胞的能量需求。 兴奋性神经元的相对密度 对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，通过检查酶的状态， 线粒体ET链的近端和远端部分， 有可能在体外评估局部神经元激活的一个指标 （最近的代谢需求）的控制和阿尔茨海默氏症的状态。 的 ET链中的第一个酶，复合物I，将在对照中测定， 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。 终端 ET链酶、复合物IV或细胞色素氧化酶将使用 定量组织化学染色。 的数量分布 将比较复合物I和复合物IV以确定是否存在 AD中的关系变化。 初步数据显示， 复合物I和IV在AD的齿状回中显著减少。 我们 假设这种减少反映了代谢需求的减少， 这一区域，由于穿通途径输入的损失， 内嗅皮层 我们将在大鼠中测试这一假设， 通过评估复合物I和IV 7天和30天的内嗅皮质病变 d。 人类大脑的其他区域将在未来进行研究 研究包括内嗅皮层，下托，上级颞回， 初级运动皮层，初级感觉皮层，纹状体，黑质 和小脑 (2)电子传递功能受损易导致 通过减少膜极化引起兴奋性毒性神经元变性， 解除NMDA受体离子通道的Mg** 阻断。 在 存在生物能量学缺陷，正常浓度的 细胞外谷氨酸盐可能变得致命。 有间接证据表明 兴奋性毒性可能在AD的神经元死亡中起次要作用， 有体外和体内的证据表明， AD. 我们假设生物能量状态（ET）之间的不匹配 酶活性）和兴奋性毒性电位（NMDA受体密度）可能 帮助确定有选择性的脆弱大脑区域。 例如，CA 1 海马和齿状回也有类似的高密度NMDA受体，但CA 1 选择性地易受兴奋性毒性和神经变性的影响， 疾病，包括AD。 我们的初步数据表明复合物I 水平和复合物IV活性在CA 1中比齿状回低得多。 在NMDA密度高的区域，ET酶相对缺乏， 受体可能易患神经元变性。 我们将在 详细描述了复合物I和IV对NMDA受体的连续分布 大脑的多个区域。

(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.