小剂量谷氨酸预先给药对谷氨酸致大鼠大脑皮质神经元神经毒性作用的影响

Effects of low-dose glutamate pretreatment on glutamate-induced neurotoxicity in primary rat cerebral cortical neurons

目的探讨小剂量谷氨酸预先给药对谷氨酸致大鼠大脑皮质神经元（CCNs）神经毒性作用的影响及其信号转导机制。方法出生24h内健康SD大鼠8只，雌雄不拘，原代培养CCNs，随机分为7组（n=4），对照组（C组）不加任何处理因素；G50组加入50μmol／L谷氨酸孵育24h；G10＋G50组：先加入10μmol／L谷氨酸孵育1h，再加入50μmol／L谷氨酸孵育24h；U＋G10＋G50组：加入细胞外信号调节激酶1/2（ERK1/ERK2）上游的激酶抑制剂U0126 10μmol／L孵育1h后，按G10＋G50组处理；U＋G50组：10μmol／L U0126孵育2h后，按G50组处理；U组：10μmol／L U0126孵育26h；G10组加入10μmol／L谷氨酸孵育25h。计算CCNs存活率。结果与C组比较，G50组CCNs存活率降低（P〈0．01），G10组差异无统计学意义（P〉0．05）；与G50组比较，G10＋G50组CCNs存活率增高（P〈0．01）；与G10＋G50组比较，U＋G10＋G50组CCNs存活率减低（P〈0．01）。结论小剂量谷氨酸（10μmol／L）预先给药可减轻50μmol／L谷氨酸致大鼠CCNs的神经毒性作用，其机制与激活ERK1／ERK2信号转导通路有关。

Objective To investigate the effects of low-dose glutamate pretreatment on neurotoxicity induced by glutamate in primary rat cerebral cortical neurons （CCNs） and its possible signal transduction pathway. Methods CCNs obtained from newborn SD rats of either sex were randomly divided into 7 groups： （1） control group （C） ; （2） G50 group-glutamate 50 μmol/L was added to CCNs and the CCNs were incubated for 24 h; （3） G10 ＋ G50 group-glutamate 10 μmol/L was added to CCNs and the CCNs were incubated 1 h and then treated as in group Gso ; （4） U ＋ G10 ＋ G50 group-CCNs were pretreated with 130126 10 μmol/L [ a specific mitogen activated protein kinase/extracellular signal-regulated kinase inhibitor] and incubated for 1 h and then treated as in group Gl0 ＋ Gso ; （5） U ＋ G50 group-CCNs were pretreated with U0126 and incubated for 2 h and then treated as in G50 group; （6） U group-CCNs were treated with U0126 for 26 h and （7） G10 group-CCNs were treated with glutamate 10 μmol/L for 25 h. The neuronal viability was determined by MTT method. Results Glutamate 10 μmol/L had no significant effect on neuronal viability but pretreatment with glutamate 10 μmol/L attenuated neurotoxicity induced by glutamate 50 μmol/L . 130126 10 μmol/L affected neither neuronal viability nor neurotoxicity induced by glutamate 50 μmol/L , but partially abolished neuroprotection provided by pretreatment with glutamate 10 μmol/L. Conclusion Low-dose glutamate pretreatment can protect CCNs from neurotoxicity induced by glutamate 50 μmol/ L. Extracellular signal-regulated kinase （ERK1/ERK2） pathway may be involved in the process.