Zyśk Marlena, Bielarczyk Hanna, Gul-Hinc Sylwia, Dyś Aleksandra, Gapys Beata, Ronowska Anna, Sakowicz-Burkiewicz Monika, Szutowicz Andrzej
Department of Laboratory Medicine, Medical University of Gdańsk, Gdańsk, Poland.
Department of Molecular Medicine, Medical University of Gdańsk, Gdańsk, Poland.
J Alzheimers Dis. 2017;56(3):1145-1158. doi: 10.3233/JAD-160693.
Pyruvate dehydrogenase reaction utilizing glucose-derived pyruvate is an almost exclusive source of acetyl-CoA in different cell mitochondrial compartments of the brain. In neuronal mitochondria, the largest fraction of acetyl-CoA is utilized for energy production and the much smaller one for N-acetyl-L-aspartate (NAA) synthesis. Cholinergic neurons, unlike others, require additional amounts of acetyl-CoA for acetylcholine synthesis. Therefore, several neurotoxic signals, which inhibit pyruvate dehydrogenase, generate deeper shortages of acetyl-CoA and greater mortality of cholinergic neurons than noncholinergic ones. NAA is considered to be a marker of neuronal energy status in neuropathic brains. However, there is no data on putative differential fractional distribution of the acetyl-CoA pool between energy producing and NAA or acetylcholine synthesizing pathways in noncholinergic and cholinergic neurons, respectively. Therefore, the aim of this study was to investigate whether zinc-excess, a common excitotoxic signal, may evoke differential effects on the NAA metabolism in neuronal cells with low and high expression of the cholinergic phenotype. Differentiated SN56 neuronal cells, displaying a high activity of choline acetyltransferase and rates of acetylcholine synthesis, contained lower levels of acetyl-CoA and NAA, being more susceptible to ZnCl2 exposition that the nondifferentiated SN56 or differentiated dopaminergic SHSY5Y neuronal and astroglial C6 cells. Differentiated SN56 accumulated greater amounts of Zn2 + from extracellular space than the other ones, and displayed a stronger suppression of pyruvate dehydrogenase complex activity and acetyl-CoA, NAA, ATP, acetylcholine levels, and loss of viability. These data indicate that the acetyl-CoA synthesizing system in neurons constitutes functional unity with energy generating and NAA or acetylcholine pathways of its utilization, which are uniformly affected by neurotoxic conditions.
利用源自葡萄糖的丙酮酸的丙酮酸脱氢酶反应，几乎是大脑不同细胞线粒体区室中乙酰辅酶A的唯一来源。在神经元线粒体中，大部分乙酰辅酶A用于能量产生，而小得多的一部分用于N-乙酰-L-天冬氨酸（NAA）的合成。与其他神经元不同，胆碱能神经元需要额外的乙酰辅酶A来合成乙酰胆碱。因此，几种抑制丙酮酸脱氢酶的神经毒性信号，会导致乙酰辅酶A的短缺更严重，胆碱能神经元的死亡率也比非胆碱能神经元更高。NAA被认为是神经病变大脑中神经元能量状态的标志物。然而，目前尚无数据表明非胆碱能和胆碱能神经元中，乙酰辅酶A池在能量产生途径与NAA或乙酰胆碱合成途径之间的假定差异分布情况。因此，本研究的目的是调查过量锌这种常见的兴奋性毒性信号，是否可能对胆碱能表型低表达和高表达的神经元细胞中的NAA代谢产生不同影响。分化后的SN56神经元细胞表现出高胆碱乙酰转移酶活性和乙酰胆碱合成速率，其乙酰辅酶A和NAA水平较低，比未分化的SN56细胞、分化后的多巴胺能SHSY5Y神经元细胞和星形胶质细胞C6更易受到ZnCl2暴露的影响。与其他细胞相比，分化后的SN56从细胞外空间积累了更多的Zn2 +，并表现出对丙酮酸脱氢酶复合体活性以及乙酰辅酶A、NAA、ATP、乙酰胆碱水平的更强抑制，且细胞活力丧失。这些数据表明，神经元中的乙酰辅酶A合成系统与其能量产生途径以及NAA或乙酰胆碱利用途径构成功能统一体，这些途径均受到神经毒性条件的一致影响。
