Department of Biochemistry, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, 88040-900, Brazil.
Laboratório de Neurociências, Programa de Pós-Graduação em Ciências da Saúde, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil.
Mol Neurobiol. 2018 Feb;55(2):1580-1589. doi: 10.1007/s12035-017-0425-6. Epub 2017 Feb 10.
Folic acid (folate) is a vitamin of the B-complex group crucial for neurological function. Considering that excitotoxicity and cell death induced by glutamate are involved in many disorders, the potential protective effect of folic acid on glutamate-induced cell damage in rat hippocampal slices and the possible intracellular signaling pathway involved in such effect were investigated. The treatment of hippocampal slices with folic acid (100 μM) significantly abrogated glutamate (1 mM)-induced reduction of cell viability measured by MTT reduction assay and inhibited glutamate-induced D-[H]-aspartate release. To investigate the putative intracellular signaling pathways implicated in the protective effect of folic acid, we used a PI3K inhibitor, LY294002, which abolished the protective effects of folic acid against glutamate-induced cell damage and D-[H] aspartate release. Moreover, hippocampal slices incubated with folic acid alone for 30 min presented increased phosphorylation of GSK-3β at Ser9, indicating an inhibition of the activity of this enzyme. Furthermore, folic acid in the presence of glutamate insult in hippocampal slices maintained for an additional period of 6 h in fresh culture medium without glutamate and/or folic acid induced phosphorylation of GSK-3β and β-catenin expression. In addition, glutamate-treated hippocampal slices showed increased iNOS expression that was reversed by folic acid. In conclusion, the results of this study show that the protective effect of folic acid against glutamate-induced excitotoxicity may involve the modulation of PI3K/GSK-3β/β-catenin pathway and iNOS inhibition.
叶酸（folate）是 B 族维生素复合物中的一种，对神经系统功能至关重要。鉴于谷氨酸引起的兴奋毒性和细胞死亡与许多疾病有关，本研究旨在探讨叶酸对谷氨酸诱导的大鼠海马切片细胞损伤的潜在保护作用及其可能涉及的细胞内信号通路。MTT 还原实验结果表明，叶酸（100 μM）处理可显著减轻谷氨酸（1 mM）诱导的细胞活力降低，并抑制谷氨酸诱导的 D-[H]-天冬氨酸释放。为了研究参与叶酸保护作用的潜在细胞内信号通路，我们使用了 PI3K 抑制剂 LY294002，其可消除叶酸对谷氨酸诱导的细胞损伤和 D-[H]天冬氨酸释放的保护作用。此外，单独孵育叶酸 30 分钟可使海马切片中 GSK-3β 磷酸化增加（Ser9），表明该酶活性受到抑制。进一步研究发现，在无谷氨酸和/或叶酸的新鲜培养基中培养 6 小时后，孵育有叶酸和谷氨酸的海马切片仍可诱导 GSK-3β和 β-连环蛋白表达的磷酸化。此外，谷氨酸处理的海马切片中 iNOS 表达增加，而叶酸可逆转这一现象。综上，本研究结果表明，叶酸对谷氨酸诱导的兴奋毒性的保护作用可能涉及 PI3K/GSK-3β/β-连环蛋白通路的调节和 iNOS 抑制。
