抑制胶质细胞增生对创伤性癫癎大鼠神经胶质细胞谷氨酸转运的影响

Effects of the inhibition of gliosis on glutamate transport of neuroglia in post-traumatic epileptic rats

目的 探讨海马胶质细胞增生和谷氨酸转运异常在铁离子诱发创伤性癫痫大鼠发病机制中的作用，以及胶质细胞增生对谷氨酸转运体表达的影响。方法 36只SD大鼠随机分3组，A组单侧杏仁核内注射生理盐水，B组仅注射氯化铁，C组注射氯化铁后，静脉注射含7β-羟基胆固醇的脂质包被微泡。动态观察大鼠脑电图和行为改变，并用免疫组化、免疫印迹方法观察鼠脑海马胶质纤维酸性蛋白(glial fibrillary acidic protein，GFlAP)在注射氯化铁后15d的表达，同时应用逆转录-聚合酶链反应(RT-PCR)检测双侧海马谷氨酸天门冬氨酸转运体(GLAST)、谷氨酸转运体1(GLT1)和兴奋性氨基酸载体1(EAAC1)mRNA的表达。结果 A组大鼠行为学和脑电图表现无明显改变；B组大鼠致痫成功92％，致病潜伏期为(6．09±0，37)d；C组致痫比例降低到67％，致痫潜伏期延长至(10．07±0，56)d。致痫大鼠抽搐发作的同时记录到阵发的节律性的高幅棘波和尖波。B组大鼠双侧海马GFAP表达均比A组明显增高(P<0.05)，C组双侧海马GFAP表达比B组低50％～60％。与A组比较，B组大鼠双侧海马GLAST mRNA表达显著降低(P<0．05)，而EAAC1 mRNA表达增高(P<0．05)；C组双侧海马GLAST mRNA表达与A组无明显差异，而GLT1和EAAC1均比A组明显增高(P<0．05)。结论 胶质细胞的增生和GLAST的下调可能参与铁离子诱发创伤性癫痫的发生发展；抑制胶质细胞的增生，有利于调节兴奋性氨基酸的转运，一定程度上延缓和降低癫痫的发生。

Objective To investigate the role of gliosis and abnormal glutamate transport of hippocampi in post-traumatic epileptogenesis induced by iron, and the effect of gliosis on expressions of glutamate transporters.Methods Sprague-Dawley rats were randomly divided into groups A, B and C. Rats of group A were given an amygdalar injection of 0.9% NaCl, group B given an injection of FeCl3 instead, and group C received i.v. injection of lipid-coated microbubbles containing 7β-hydroxycholesterol after the injection of FeCl_3. Behavior and electroencephalography (EEG) were recorded over the 15 days following injection. Expression of glial fibrillary acidic protein (GFAP) was detected with immunohistochemistry and Western blots at 15 days following injection, levels of glutamate-aspartate transporter (GLAST), glutamate transporter subtype 1 (GLT1), and excitatory amino-acid carrier 1 (EAAC1) mRNA were measured by RT-PCR for both hippocampi at the same time.Results None of the group A rats had behavioral seizures and EEG discharges. Among the group B rats, 92% developed seizures by (6.09±0.37) days, while just 67% of the group C developed by (10.07±0.56) days. Epileptiform discharges were recorded when behavioral seizures were observed. GFAP expression in both hippocampi of the group B increased significantly compared with the group A (P<0.05), while that of the group C decreased to 50%-60% of the group B. Compared with the group A, GLAST mRNA expression of the group B decreased significantly in both hippocampi (P<0.05), while EAAC1 mRNA elevated bilaterally (P<0.05). GLAST mRNA expression of the group C was no significant difference compared with the group A, while GLT1 and EAAC1 elevated significantly (P<0.05) in both hippocampi.Conclusions The gliosis and the down-regulation of GLAST might probably be involved in the iron-induced epileptogenesis. Inhibition of the gliosis is benefit for modulating the transportation of excitatory amino acid, and to some extent, postpones and decreases the incidence of epilepsy.