Greene J G, Sheu S S, Gross R A, Greenamyre J T
Department of Neurobiology and Anatomy, University of Rochester Medical Center, NY 14642, USA.
Neuroscience. 1998 May;84(2):503-10. doi: 10.1016/s0306-4522(97)00389-8.
We examined the effects of 3-nitropropionic acid-induced succinate dehydrogenase inhibition on neuronal ATP content, N-methyl-D-aspartate-induced neuronal death, resting membrane potential, and N-methyl-D-aspartate-induced changes in cytosolic calcium concentration ([Ca2+]c) in cultured rat striatal neurons. Exposure of cultures to 3 mM 3-nitropropionic acid for 3 h did not cause overt toxicity, but reduced ATP content by 35%. Treatment with 3-nitropropionic, or removal of Mg2+ from the medium, enhanced subsequent N-methyl-D-aspartate toxicity, reducing the LC50 from 250 microM to 12 microM or 30 microM, respectively. Even after Mg2+ removal, enhancement of N-methyl-D-aspartate toxicity by 3-nitropropionic acid remained pronounced, with the LC50 further decreasing to 3 microM. The mean resting membrane potential of neurons treated with 3-nitropropionic acid was -37 mV, while that in control neurons was -61 mV. Treatment with 3-nitropropionic did not affect baseline [Ca2+]c as determined by fura-2 microfluorimetry. N-methyl-D-aspartate (30 microM) caused a rapid rise in [Ca2+]c, the initial magnitude of which was not affected by 3-nitropropionic acid. However, after a 1-h treatment, [Ca2+]c was dramatically higher in 3-nitropropionic acid-treated neurons. This increased calcium load was washed out slowly and only partially, although calcium in control neurons washed out rapidly and almost completely. These results suggest that in striatal neurons, the enhancement of N-methyl-D-aspartate toxicity caused by succinate dehydrogenase inhibition may be due to synergism between partial relief of the Mg2+ blockade of the N-methyl-D-aspartate receptor and other mechanisms, including disruption of neuronal calcium regulation. This synergism may be relevant to the neuronal death observed in neurodegenerative disorders.
我们研究了3-硝基丙酸诱导的琥珀酸脱氢酶抑制对培养的大鼠纹状体神经元的神经元ATP含量、N-甲基-D-天冬氨酸诱导的神经元死亡、静息膜电位以及N-甲基-D-天冬氨酸诱导的胞质钙浓度（[Ca2+]c）变化的影响。将培养物暴露于3 mM 3-硝基丙酸3小时未引起明显毒性，但ATP含量降低了35%。用3-硝基丙酸处理或从培养基中去除Mg2+，增强了随后的N-甲基-D-天冬氨酸毒性，使半数致死浓度（LC50）分别从250 microM降至12 microM或30 microM。即使去除Mg2+后，3-硝基丙酸对N-甲基-D-天冬氨酸毒性的增强作用仍然显著，LC50进一步降至3 microM。用3-硝基丙酸处理的神经元的平均静息膜电位为-37 mV，而对照神经元为-61 mV。用3-硝基丙酸处理不影响用fura-2显微荧光测定法测定的基线[Ca2+]c。N-甲基-D-天冬氨酸（30 microM）引起[Ca2+]c迅速升高，其初始幅度不受3-硝基丙酸影响。然而，处理1小时后，用3-硝基丙酸处理的神经元中的[Ca2+]c显著更高。这种增加的钙负荷缓慢且仅部分被洗脱，而对照神经元中的钙迅速且几乎完全被洗脱。这些结果表明，在纹状体神经元中，琥珀酸脱氢酶抑制引起的N-甲基-D-天冬氨酸毒性增强可能是由于N-甲基-D-天冬氨酸受体Mg2+阻断的部分解除与其他机制（包括神经元钙调节的破坏）之间的协同作用。这种协同作用可能与神经退行性疾病中观察到的神经元死亡有关。
