NEURODEGENERATION MEDIATED BY GLUTAMATE AND BETA-AMYLOID PEPTIDE - A COMPARISON AND POSSIBLE INTERACTION
NEURODEGENERATION MEDIATED BY GLUTAMATE AND BETA-AMYLOID PEPTIDE - A COMPARISON AND POSSIBLE INTERACTION
复制标题
谷氨酸和β-淀粉样蛋白肽介导的神经变性--比较和可能的相互作用
DOI：
10.1016/0006-8993(95)00669-h
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发表时间：
1995-09-11
期刊：
影响因子：
2.9
通讯作者：
PATEL, AJ
中科院分区：
文献类型：
--
作者：
GRAY, CW;PATEL, AJ
在阿尔茨海默病中，P-淀粉样蛋白(老年斑的主要成分)和兴奋性氨基酸谷氨酸在细胞外的异常堆积都被认为与神经细胞的退化有关。本研究以体外培养的大脑皮层或海马神经元为模型，比较了谷氨酸或β-淀粉样蛋白(Aβ)等多种因素对神经元退行性变的影响。我们还提出了一个问题：亚致死剂量的Aβ(25-35)长期治疗是否会增强谷氨酸介导的兴奋性毒性？用乳酸脱氢酶(LDH)法测定神经细胞死亡。由于细胞外LDH在几天内保持稳定，LDH的相对流入的大小与培养中受损神经元的数量呈线性相关。当单独应用谷氨酸(15分钟)和Aβ-(25-35)或其母肽A-β-(1-40)(持续)时，均可引起剂量依赖性的神经元变性。在谷氨酸的情况下，约0.08 mM的谷氨酸对大脑皮层和海马神经元(体外培养13天，DIV)都有半最大作用。Aβ-(25-35)的作用也是时间依赖的，而生长在化学定义的培养液中的神经元比培养在含血清的培养液中的神经元对Aβ-(25-35)的敏感性相对更高。这些差异效应与培养物中不同数量的神经胶质细胞无关。用不同剂量的阿糖胞苷处理24小时(6-7DIV)，用星形胶质细胞特异性酶谷氨酰胺合成酶测定，13DIV培养的皮质神经元产生不同数量的星形胶质细胞。星形胶质细胞的存在降低了谷氨酸对神经元的毒性。这种调节是由于星形胶质细胞摄取谷氨酸，从而降低了其有效浓度，因为这种影响在0.1 mM时显现，而不是在10 mM谷氨酸时出现。NMDA受体介导的钙离子通道阻断剂MK-801与谷氨酸共同作用可完全抑制皮质神经元的变性，碱性成纤维细胞生长因子处理2d可部分抑制神经元的变性。然而，这些化合物对Aβ-(25-35)介导的神经毒性没有影响。最后，谷氨酸的作用与Aβ-(25-35)的作用相互作用。10 mU M Aβ-(25-35)单独处理皮质神经元2d无明显作用，但可明显增强谷氨酸介导的神经元变性。基于这些发现，我们认为无症状个体谷氨酸代谢的微小异常可能会加强与阿尔茨海默病病程中选择性脆弱神经元中β-淀粉样蛋白积聚有关的病理生理后果。
In Alzheimer's disease, abnormal extracellular accumulations of P-amyloid (a major component of the senile plaques) and of the excitatory amino acid glutamate are both thought to be associated with degeneration of nerve cells. In the present study, using cultured cortical or hippocampal neurons as an in vitro model, we compared the effects of various factors influencing neurodegeneration mediated by glutamate or by beta-amyloid peptide (A beta). We also asked the question: does long-term treatment with sublethal doses of A beta-(25-35) potentiate glutamate-mediated excitotoxicity? Neuronal cell death was quantified using the lactate dehydrogenase (LDH) method. Since extracellular LDH remains stable for days, the magnitude of relative afflux of LDH correlates in a linear fashion with the number of damaged neurons in cultures. When applied singly, both glutamate (for 15 min) and A beta-(25-35) or its parent peptide A beta-(1-40) (continuously) produced a dose-dependent neuronal degeneration. In the case of glutamate, the half-maximal effects were observed at about 0.08 mM glutamate for both cerebral cortical and hippocampal neurons (cultured for 13 days in vitro, DIV). The effect of A beta-(25-35) was also time-dependent, while neurons grown in a chemically defined medium showed relatively greater susceptibility to A beta-(25-35) than those cultured in a serum-containing medium. These differential effects were not related to the presence of different numbers of glial cells in the cultures. Treatment with different doses of the antimitotic inhibitor, cytosine arabinoside, for 24 h (6-7 DIV) produced at 13 DIV cortical neuronal cultures with varying numbers of astrocytes, as determined by the astrocyte-specific enzyme glutamine synthetase. The presence of astrocytes decreased the toxicity of glutamate for neurons. The modulation was due to uptake of glutamate by astrocytes, thereby reducing its effective concentration, as the effect was seen at 0.1 mM and not at 10 mM glutamate. Incorporation of an NMDA receptor mediated Ca2+ ion channel blocker, MK-801, together with glutamate completely inhibited degeneration of cortical neurons, and pretreatment of cultures with basic fibroblast growth factor for 2 days did so partially. However, these compounds had no effect on neurotoxicity mediated by A beta-(25-35). Lastly, the effect of glutamate interacted with that of A beta-(25-35). Pretreatment of cortical neurons for 2 days with 10 mu M A beta-(25-35) by itself had no appreciable effect, but it potentiated significantly the degeneration of these neurons mediated by glutamate. On the basis of these findings, we propose that a subtle abnormality in glutamate metabolism in asymptomatic individuals may potentiate the pathophysiological consequences related to the accumulation of beta-amyloid in selectively vulnerable neurons during the course of Alzheimer's disease.