Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Universitat de Barcelona, Barcelona, Spain.
CIBER of Hepatic and Digestive Diseases (CIBEREHD) and Metabolomics Node at Spanish National Bioinformatics Institute (INB-ISCIII-ES- ELIXIR), Institute of Health Carlos III (ISCIII), Madrid, Spain.
PLoS One. 2021 Aug 3;16(8):e0255164. doi: 10.1371/journal.pone.0255164. eCollection 2021.
Glutamate plays diverse roles in neuronal cells, affecting cell energetics and reactive oxygen species (ROS) generation. These roles are especially vital for neuronal cells, which deal with high amounts of glutamate as a neurotransmitter. Our analysis explored neuronal glutamate implication in cellular energy metabolism and ROS generation, using a kinetic model that simulates electron transport details in respiratory complexes, linked ROS generation and metabolic reactions. The analysis focused on the fact that glutamate attenuates complex II inhibition by oxaloacetate, stimulating the latter's transformation into aspartate. Such a mechanism of complex II activation by glutamate could cause almost complete reduction of ubiquinone and deficiency of oxidized form (Q), which closes the main stream of electron transport and opens a way to massive ROS generating transfer in complex III from semiquinone radicals to molecular oxygen. In this way, under low workload, glutamate triggers the respiratory chain (RC) into a different steady state characterized by high ROS generation rate. The observed stepwise dependence of ROS generation on glutamate concentration experimentally validated this prediction. However, glutamate's attenuation of oxaloacetate's inhibition accelerates electron transport under high workload. Glutamate-oxaloacetate interaction in complex II regulation underlies the observed effects of uncouplers and inhibitors and acceleration of Ca2+ uptake. Thus, this theoretical analysis uncovered the previously unknown roles of oxaloacetate as a regulator of ROS generation and glutamate as a modifier of this regulation. The model predicted that this mechanism of complex II activation by glutamate might be operative in situ and responsible for excitotoxicity. Spatial-time gradients of synthesized hydrogen peroxide concentration, calculated in the reaction-diffusion model with convection under a non-uniform local approximation of nervous tissue, have shown that overproduction of H2O2 in a cell causes excess of its level in neighbor cells.
谷氨酸在神经元细胞中发挥多种作用，影响细胞能量代谢和活性氧（ROS）的产生。这些作用对于神经元细胞尤为重要，因为神经元细胞作为神经递质会处理大量的谷氨酸。我们的分析使用模拟呼吸复合物电子传递细节的动力学模型，研究了神经元谷氨酸对细胞能量代谢和 ROS 产生的影响，该模型将 ROS 产生与代谢反应联系起来。分析集中于以下事实：谷氨酸通过抑制草酰乙酸来减弱复合物 II 的抑制作用，从而刺激后者转化为天冬氨酸。谷氨酸激活复合物 II 的这种机制可能导致泛醌几乎完全还原和氧化形式（Q）缺乏，从而关闭电子传递的主流并为从半醌自由基到分子氧的大量 ROS 产生转移在复合物 III 中开辟途径。通过这种方式，在低工作负载下，谷氨酸会使呼吸链（RC）进入以高 ROS 产生速率为特征的不同稳定状态。实验上观察到的 ROS 产生对谷氨酸浓度的逐步依赖性验证了这一预测。然而，谷氨酸对草酰乙酸抑制作用的减弱加速了高工作负载下的电子传递。复合物 II 中谷氨酸-草酰乙酸相互作用的调节是观察到解偶联剂和抑制剂的作用以及 Ca2+摄取加速的基础。因此，这种理论分析揭示了以前未知的草酰乙酸作为 ROS 产生调节剂和谷氨酸作为这种调节修饰剂的作用。该模型预测，这种由谷氨酸激活复合物 II 的机制可能在原位起作用，并导致兴奋毒性。在非均匀局部神经组织近似下的反应-扩散模型中计算出的合成过氧化氢浓度的时空梯度表明，细胞中 H2O2 的过度产生会导致相邻细胞中 H2O2 水平的过量。
