Morken Tora Sund, Sonnewald Ursula, Aschner Michael, Syversen Tore
Department of Neuroscience, Norwegian University of Science and Technology, N-7489 Trondheim, Norway.
Toxicol Sci. 2005 Sep;87(1):169-75. doi: 10.1093/toxsci/kfi227. Epub 2005 Jun 15.
We report on the uptake of MeHg in astrocytes and neurons, as well as specific indicators of neurotoxicity. Cerebellar granule neurons and astrocytes separately and in co-culture were cultured in the presence of MeHg and changes in 3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyltetrazolium bromide (MTT)-reduction, lactate dehydrogenase (LDH) leakage, and cellular content of glutathione and amino acids were used as indicators of MeHg toxicity. Mitochondria in cortical astrocytes were slightly more sensitive than those in cerebellar astrocytes to the toxic effects of MeHg; furthermore, cellular integrity was better preserved in cerebellar astrocytes. When neurons and astrocytes from cerebellum were incubated in separable co-cultures using inserts, the astrocytes showed cellular damage at lower exposure to MeHg while neurons showed less changes compared to respective cell types in mono-cultures. Mercury uptake studies at 25 microM MeHg (10% serum present) showed that for neurons in co-culture the uptake was 1/3 compared to mono-cultures. In contrast, for astrocytes in co-culture, uptake was increased by 75%. A MeHg concentration-dependent increase of glutamate content in mono-cultures was noted. When MeHg concentration was increased to 10, 25, or 50 microM, neurons in co-cultures decreased their glutamate content, whereas astrocytes showed an increase. Other amino acids, such as glutamine, serine, valine, isoleucine, taurine, and phenylalanine were unaffected by MeHg. Glutathione content showed MeHg concentration-dependent changes in astrocytes and was increased in neurons in co-culture incubated with 5 microM MeHg. In conclusion, astrocytes appear to increase neuronal resistance, indicating a possible protective role for astrocytes in MeHg neurotoxicity.
我们报告了甲基汞在星形胶质细胞和神经元中的摄取情况，以及神经毒性的特定指标。将小脑颗粒神经元和星形胶质细胞分别培养以及共培养，并置于甲基汞环境中，以3-[4,5-二甲基噻唑-2-基]-2,5-二苯基四氮唑溴盐（MTT）还原率、乳酸脱氢酶（LDH）泄漏率以及谷胱甘肽和氨基酸的细胞含量变化作为甲基汞毒性的指标。皮质星形胶质细胞中的线粒体对甲基汞毒性作用的敏感性略高于小脑星形胶质细胞中的线粒体；此外，小脑星形胶质细胞中的细胞完整性保存得更好。当使用插入物将来自小脑的神经元和星形胶质细胞在可分离的共培养体系中孵育时，与单培养中的相应细胞类型相比，星形胶质细胞在较低的甲基汞暴露水平下就出现了细胞损伤，而神经元的变化较小。在25微摩尔甲基汞（含10%血清）条件下进行的汞摄取研究表明，共培养中的神经元摄取量是单培养中的1/3。相比之下，共培养中的星形胶质细胞摄取量增加了75%。在单培养中，观察到甲基汞浓度依赖性地增加谷氨酸含量。当甲基汞浓度增加到10、25或50微摩尔时，共培养中的神经元谷氨酸含量降低，而星形胶质细胞则增加。其他氨基酸，如谷氨酰胺、丝氨酸、缬氨酸、异亮氨酸、牛磺酸和苯丙氨酸不受甲基汞影响。谷胱甘肽含量在星形胶质细胞中呈现甲基汞浓度依赖性变化，在与5微摩尔甲基汞共培养的神经元中增加。总之，星形胶质细胞似乎增强了神经元的抗性，表明星形胶质细胞在甲基汞神经毒性中可能起到保护作用。
