Amyloid β protein inhibits cellular MTT reduction not by suppression of mitochondrial succinate dehydrogenase but by acceleration of MTT formazan exocytosis in cultured rat cortical astrocytes

被引:74
作者
Abe, K [1 ]
Saito, H [1 ]
机构
[1] Univ Tokyo, Fac Pharmaceut Sci, Dept Chem Pharmacol, Tokyo 1130033, Japan
关键词
amyloid beta protein; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; 3-nitropropionic acid; cholesterol; lysophosphatidic acid; astrocyte; neuron;
D O I
10.1016/S0168-0102(98)00055-8
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Alzheimer's disease amyloid beta protein (A beta) inhibits cellular reduction of the dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Kaneko et al. have previously hypothesized that AP works by suppressing mitochondrial succinate dehydrogenase (SDH), but Liu and Schubert have recently demonstrated that A beta decreases cellular MTT reduction by accelerating the exocytosis of MTT formazan in neuronal cells. To ask which is the case in astrocytes, we compared the effects of A beta and 3-nitropropionic acid (3-NP), a specific SDH inhibitor, on MTT reduction in cultured rat cortical astrocytes. Treatment with 3-NP (10 mM) decreased cellular activity of MTT reduction, regardless of the time of incubation with MTT. On the other hand, A beta-induced inhibition of cellular MTT reduction was dependent on the time of incubation with MTT. The cells treated with A beta (0.1-1000 nM) exhibited normal capacity for MTT reduction at an early stage of incubation (< 30 min), but ceased to reduce MTT at the late stage (> 1 h). Microscopic examination revealed that A beta treatment accelerated the appearance of needle-like MTT formazan crystals at the cell surface. These observations support that A beta accelerates the exocytosis of MTT formazan in astrocytes. In addition to inhibition of MTT reduction, A beta is known to induce morphological changes in astrocytes. Following addition of A beta (20 mu M), polygonal astrocytes changed into process-bearing stellate cells. To explore a possible linkage between these two effects of A beta, we tested if astrocyte stellation is induced by agents that mimic the effect of A beta on MTT reduction. Cholesterol (5-5000 nM) and lysophosphatidic acid (0.2-20 mu g/ml) were found to accelerate the exocytosis of MTT formazan in a similar manner to A beta, but failed to induce astrocyte stellation. Therefore, A beta-induced inhibition of MTT reduction is unlikely to be directly linked to its effect on astrocyte morphology. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.
引用
收藏
页码:295 / 305
页数:11
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