Establishment of Alzheimer model cell system and its application to therapeutics

阿尔茨海默病(AD)是以脑内大量神经元死亡导致的进行性痴呆为特征的疾病。阐明该病的发病机制是目前最紧迫的医学问题之一。淀粉样β蛋白(Abeta)是AD脑内沉积的淀粉样纤维的主要成分，因此Abeta可能与AD的发病机制密切相关。Abeta是由淀粉样前体蛋白(APP)衍生而来的。为了阐明APP在有丝分裂后神经元内积聚的病理意义，我们利用复制缺陷型腺病毒载体将APP基因转移到培养条件下的大鼠海马神经元中。积累膜结合形式的APP的神经元比不表达的对照神经元对外源谷氨酸的反应更强，这表明高钙水平可能导致神经退化。此外，我们还证明了同一表达APP的腺病毒载体过表达APP可以在几天内诱导人胚胎癌细胞来源的培养神经元死亡。当将表达APP的腺病毒注射到大鼠海马区时，海马结构中一些受感染的神经元在几天内经历了严重的变性，表现为核周膜缩小和突触异常。这些实验系统使我们能够研究APP诱导神经变性的详细分子机制，将有助于AD发病机制的研究和治疗药物的开发。

Alzheimer's disease (AD) is characterized by the progressive dementia as a result of massive neuronal death in the brain. Clarification of the pathogenesis of this disease is one of the most urgent medical problems. Amyloid beta protein (Abeta) is the principal component of amyloid fibrils that are deposited in the brain affected by AD.Thus Abeta might be closely associated with the pathogenesis of the disease. Abeta is derived from the precursor, termed the amyloid precursor protein (APP). In an attempt to elucidate the pathological implications of intracellular accumulation of APP in postmitotic neurons, we transferred APP cDNA into rat hippocampal neurons under cultured conditions by using a replication-defective adenovirus vector. Neurons accumulating the membrane-bound form of APP showed greater responsiveness to exogenous glutamate than non-expressing control neurons, suggesting that elevated calcium levels potentially cause neurodegeneration. Moreover, we demonstrated that overexpression of APP by the same APP-expressing adenovirus vector induces death of human cultured neurons derived from human embryonal carcinoma cells within several days. When an APP-expressing adenovirus wazs injected into a rat hippocampus, some of the infected neurons in the hippocampal formation underwent severe degeneration displaying shrunk perikarya along with synaptic abnormalities in a few days. These experimental systems enable us to study detailed molecular mechanisms of APP-induced neurodegeneration, and will be useful for studies on pathogenesis of AD and development of therapeutics.