EphA5/ephrinA5在癫癎大鼠海马CA3区的表达变化及作用

Changes in the expression of EphA5/ephrinA5 in the CA3 region of the hippocampus in rats with epilepsy and their role in the pathogenesis of temporal lobe epilepsy

探讨EphA5及其配体ephrinA5在癫癎大鼠模型海马内表达变化及其在颞叶癫癎发病中的作用。方法将240只Sprague-Dawley(SD)大鼠随机分为对照组(n=120)和癫癎组(n=120),建立氯化锂-匹罗卡品颞叶癫癎大鼠模型。致癎后分别选取12 h、24 h、7 d、15 d、30 d和60 d 6个时间点为亚组(n=20),采用原位杂交法检测各亚组大鼠海马CA3区和齿状回(DG)ephrinA5 m RNA表达水平(n=9);采用免疫组化法检测各亚组大鼠海马CA3区和DG EphA5蛋白的表达水平(n=9);采用Neo-Timm银染法观察各亚组大鼠海马CA3区的苔藓纤维出芽情况(n=2)。结果原位杂交结果显示:ephrinA5 m RNA在海马CA3区可见表达,但在DG无表达;与同时间点对照组相比,致癎后7 d、15 d,癫癎组大鼠海马CA3区ephrinA5 m RNA表达明显下调(P<0.05),在致癎后30 d、60 d,癫癎组大鼠海马CA3区ephrinA5 m RNA表达逐渐上调(P<0.05),且与对照组相比差异无统计学意义(P>0.05)。免疫组化结果显示:EphA5蛋白在大鼠海马CA3区及DG区均有表达,其水平变化趋势与ephrinA5 m RNA相一致。Neo-Timm银染法结果显示:致癎后7 d、15 d,癫癎组大鼠海马CA3区存在明显苔藓纤维出芽。结论配体ephrinA5协同受体EphA5在海马CA3区的表达下调,可能共同参与了CA3区的苔藓纤维出芽作用机制,并与癫癎的发生、发展关系密切。

Objective To investigate the changes in the expression of EphA5 and its ligand ephrinA5 in the hippocampus of rats with epilepsy and their role in the pathogenesis of temporal lobe epilepsy（TLE）. MethodsA total of 240 Sprague-Dawley rats were randomly divided into control group and TLE group, with 120 rats in each group.A rat model of lithium-pilocarpine TLE was established, and then the rats were divided into subgroups at 12 and 24 hours and 7, 15, 30, and 60 days after epilepsy was induced. In-situ hybridization was used to measure the m RNA expression of ephrinA5 in the CA3 region and the dentate gyrus of the hippocampus in 9 rats; immunohistochemistry was used to measure the protein expression of EphA5 in the CA3 region and the dentate gyrus of the hippocampus in 9 rats; NeoTimm silver staining was used to observe mossy fiber sprouting in the CA3 region of the hippocampus in 2 rats. Results In-situ hybridization showed m RNA expression of ephrinA5 in the CA3 region of the hippocampus, but this was not found in the dentate gyrus. Compared with the control group at the same time point, the TLE group had a significant reduction in the m RNA expression of ephrinA5 in the CA3 region of the hippocampus at 7 and 15 days after epilepsy was induced（P〈0.05）; at 30 and 60 days after epilepsy was induced, the TLE group had a gradual increase in the m RNA expression of ephrinA5 in the CA3 region of the hippocampus, and there was no significant difference between the TLE and control groups（P〉0.05）. Immunohistochemistry showed that EphA5 protein was expressed in the CA3 region andthe dentate gyrus of the hippocampus and had a similar trend of change as ephrinA5 m RNA. Neo-Timm silver staining showed that the TLE group developed marked mossy fiber sprouting in the CA3 region of the hippocampus at 7 and 15 days after epilepsy was induced. Conclusions Downregulation of ephrinA5 and EphA5 in the CA3 region of the hippocampus may participate in the mechanism of mossy fiber sprouting and is closely associated with the development and progression of epilepsy.