大鼠弥漫性轴索损伤后氧化应激对谷氨酸兴奋性毒性的影响及其机制
The effect and its mechanism of oxidative stress on glutamate excitotoxicity after diffuse axonal injury in rats

摘要：目的 探讨大鼠弥漫性轴索损伤(diffuse axonal injury, DAI)后脑内氧化应激对谷氨酸兴奋性毒性的影响及其作用机制。方法 采用大鼠头部瞬间旋转损伤装置制备DAI模型，通过促氧化剂SIN-1及抗氧化剂GSH干预控制DAI大鼠脑内氧化应激水平，对大鼠进行神经功能缺损评分(modified neurological severity scores, mNSS)，检测脑干组织内超氧化物歧化酶(superoxide dismutase, SOD)活力、丙二醛(malondialdehyde, MDA)含量和谷氨酸(glutamate, Glu)含量，Western blot法测定谷氨酸转运体-1(glutamate transporter-1, GLT-1)的表达水平。结果 损伤组在6、24、72h的mNSS评分值均高于假损伤组(P<0.05)。与假损伤组相比，损伤组大鼠在各时间点脑干SOD活力均降低，MDA含量均升高(P<0.05)；与DAI+NS组相比，DAI+SIN-1组24h及72h SOD活力均降低、MDA含量均升高(P<0.05)，而DAI+GSH组变化相反(P<0.05)。与假损伤组相比，损伤组在各时间点脑干细胞内Glu含量均有所降低(P<0.05)；与DAI+NS组相比，DAI+SIN-1组在各时间点细胞内Glu含量明显降低(P<0.05)，DAI+GSH组在24h细胞内Glu含量有所升高(P<0.05)。DAI后24h及72h损伤组GLT-1表达水平较假损伤组均降低(P<0.05)，同时DAI+SIN-1组GLT-1表达水平均低于DAI+NS组(P<0.05)，而DAI+GSH组在72h时GLT-1表达高于DAI+NS组(P<0.05)。结论 大鼠DAI后脑内氧化应激可降低神经细胞膜GLT-1的表达水平，抑制Glu的回摄取，从而加重细胞外Glu堆积，增强谷氨酸兴奋性毒性作用。
ABSTRACT: Objective To explore the potential effect and its mechanism of oxidative stress on glutamate excitotoxicity after diffuse axonal injury (DAI) in rats. Methods An instantaneous rotation head damage device was used to build the rat DAI model. 3-morpholino-sydnonimine (SIN-1) and glutathione (GSH) were respectively administered as pro-oxidant and anti-oxidant to induce different levels of oxidative stress. Rats were scored by the modified neurological severity scores (mNSS); the concentration of superoxide dismutase (SOD), malondialdehyde (MDA) and glutamate (Glu) in rats？？ brain stem were respectively determined, and the expression level of GLT-1 was detected by Western blot. Results The mNSS scores in all DAI groups were higher than those in sham group at 6h, 24h and 72h after DAI (P<0.05). Compared with sham group, all DAI groups had a lower SOD content and a higher MDA content at each time point (P<0.05); at 24h and 72h, there was less SOD and more MDA in DAI+SIN-1 group than in DAI+NS group (P<0.05) while for DAI+GSH group the result was just the opposite(P<0.05). Compared with that in sham group, the intracellular Glu content in the brain stem of all DAI groups was lower (P<0.05) at all time points, which was the same for DAI+SIN-1 group compared with DAI+NS group. For DAI+GSH group, the intracellular Glu content was higher than that of DAI+NS group at 24h (P<0.05). At 24h and 72h, the GLT-1 level showed a decrease (P<0.05) and DAI+SIN-1 group had a lower GLT-1 level than DAI+NS group (P<0.05); at 72h the GLT-1 level in DAI+GSH group was higher than that in DAI+NS group (P<0.05). Conclusion The oxidative stress, which occurs after DAI in rats, can reduce the level of GLT-1