College of Korean Medicine, Gachon University, Seongnam 13120, Korea.
Department of Food Science and Biotechnology, Kyonggi University, Suwon 16227, Korea.
Molecules. 2021 Mar 4;26(5):1387. doi: 10.3390/molecules26051387.
Oxidative stress leads to protein degeneration or mitochondrial dysfunction, causing neuronal cell death. Glutamate is a neurotransmitter that nerve cells use to send signals. However, the excess accumulation of glutamate can cause excitotoxicity in the central nervous system. In this study, we deciphered the molecular mechanism of catechin-mediated neuroprotective effect on glutamate-induced oxidative stress in mouse hippocampal neuronal HT22 cells. Cellular antioxidant activity was determined using the 1,1-diphenyl-picryl hydrazyl (DPPH) assay and 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) staining. Furthermore, the levels of intracellular calcium (Ca) as well as nuclear condensation and protein expression related to neuronal damage were assessed. All five catechins (epigallocatechin gallate, gallocatechin gallate (GCG), gallocatechin, epicatechin gallate, and epicatechin) showed strong antioxidant effects. Among them, GCG exhibited the highest neuroprotective effect against glutamate excitotoxicity and was used for further mechanistic studies. The glutamate-induced increase in intracellular Ca was reduced after GCG treatment. Moreover, GCG reduced nuclear condensation and the phosphorylation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinases (JNK) involved in cell death. The neuroprotective effect of GCG against glutamate-induced oxidative stress in HT22 cells was attributed to the reduction in intracellular free radicals and Ca influx and also the inhibition of phosphorylation of ERK and JNK. Furthermore, the antioxidant effect of GCG was found to be likely due to the inhibition of phosphorylation of ERK and JNK that led to the effective suppression of neurocytotoxicity caused by glutamate in HT22 cells.
氧化应激导致蛋白质变性或线粒体功能障碍，从而引起神经元细胞死亡。谷氨酸是一种神经递质，神经细胞用它来传递信号。然而，谷氨酸的过度积累会导致中枢神经系统的兴奋性毒性。在这项研究中，我们揭示了儿茶素介导的神经保护作用对谷氨酸诱导的小鼠海马神经元 HT22 细胞氧化应激的分子机制。使用 1,1-二苯基-2-苦基肼（DPPH）测定法和 2'，7'-二氯二氢荧光素二乙酸酯（DCFDA）染色来测定细胞抗氧化活性。此外，评估了与神经元损伤相关的细胞内钙（Ca）水平以及核浓缩和蛋白质表达。五种儿茶素（表没食子儿茶素没食子酸酯、没食子儿茶素没食子酸酯（GCG）、儿茶素、表儿茶素没食子酸酯和表儿茶素）均表现出很强的抗氧化作用。其中，GCG 对谷氨酸兴奋性毒性表现出最强的神经保护作用，并用于进一步的机制研究。GCG 处理后，谷氨酸诱导的细胞内 Ca 增加减少。此外，GCG 减少了核浓缩以及与细胞死亡相关的细胞外信号调节激酶（ERK）和 c-Jun N-末端激酶（JNK）的磷酸化。GCG 对 HT22 细胞中谷氨酸诱导的氧化应激的神经保护作用归因于细胞内自由基和 Ca 内流的减少，以及 ERK 和 JNK 磷酸化的抑制。此外，发现 GCG 的抗氧化作用可能归因于 ERK 和 JNK 磷酸化的抑制，从而有效抑制了 HT22 细胞中谷氨酸引起的神经细胞毒性。
