AMPA受体亚单位GluR2在大鼠局灶性脑缺血不同时期表达及其机制研究

目的通过研究大鼠局灶性脑缺血不同时期缺血中心区与半暗带α-氨基羟甲基异恶唑丙酸（AMPA）受体亚单位GluR2蛋白表达，并同时观察凋亡指数，以进一步阐述GluR2在缺血性脑卒中的作用机制。方法采用免疫组化和Tunnel染色分别检测大脑中动脉梗塞（MCAO）2h再灌后1h、1d、3d、7d、15d、30d大鼠GluR2蛋白和凋亡细胞的表达。结果再灌1h，缺血侧中心区（ischemia core IC）与缺血半暗带区（ischernia penumbra，IP）GluR2蛋白表达与对照组无差异。在缺血中心区，再灌后1dGluR2蛋白表达开始减少（F=1.104，P〈0．05），3d表达达到最低（F=3．252，P〈0．01），7、15d表达回升（F=1．878，P〈0.01；F=1．185，P〈0．05），30d基本上与对照组相同。在缺血半暗带，GluR2蛋白表达在再灌后1、3、7d与健侧无明显差异，但在15d可见表达明显增强（F=27.166，P〈0．01），在30d表达呈更强（F=28．515，P〈0.01），且阳性细胞数目也稍有所增多。在缺血中心区，再灌1h即检测到表达非常弱但数目较多的凋亡细胞，再灌1d后更为明显，3d和7d凋亡细胞在数量上和表达程度上达到高峰，15d凋亡细胞减少，1个月后只见中心区少许凋亡细胞。在半暗带区，MCAO再灌后3d，7d和15d仅见少许TUNNEL阳性细胞。结论再灌后细胞凋亡出现时间先于GluR2蛋白表达下调时间提示GluR2不是早期凋亡的启动因子。再灌后1-30d，GluR2蛋白表达变化与凋亡阳性细胞几乎平行，提示GluR2虽不启动早期凋亡，但可能导致神经元进一步凋亡，或参与迟发性神经元死亡。缺血侧半暗带区GluR2蛋白在再灌后15-30d表达明显增强，且数目也稍有增多，提示GluR2与突触的可塑性有关。

Study on AMPA receptor gluR2 expression and mechanisms at various recirculation times following focal ischemia in rats

[Objective] To explore molecular mechanism following focal ischemia, the glutamate receptor subunit 2 (GluR2) protein expression and apoptosis measured in ischemia core (IC)and ischemia penumbra (IP)of adult rats at various recirculation times (1h, 1, 3, 7, 15 and 30 day) following a 120-min period of middle cerebral artery occlusion (MCAO). [Methods] Immunohistochemistry and terminal dUTP nick-end labeling (TUNEL) assay were performed to detect the GluR2 protein expression and apoptotic cell death of adult rats respectively. [Results] At 1h recirculation, Immunohistochemistry results showed that the GluR2 protein expression retained control levels in both IC and IP regions. In IC regions, GluR2 protein expression reduced at 1-day recirculation, remarkablely reduced at 3-day recirculation, persisted at 7 to 15 day recirculation and unaltered at 30day recirculation relative to the control level. In IP regions, GluR2 protein expressions were unaltered at 1, 3, 7day recirculation, however, the most intense expressions of GluR2 protein were found at 15 and 30 day recirculation with a slightly increased GluR2 immunopositive cells compared to the contralateral side. In IC regions, weak but definite positive apoptotic cells were detected at 1 hour recirculation. The apoptotic cells increased at 1 day recirculation, peaked in expression level and extensity at 3 to 7-day recirculation, persisted at 15 day recirculation, and expressed slightly at 30day recirculation. In IP regions, few scattered apoptotic cells were detected in the margin of the IC regions at 3, 7 and 15 recirculation. [Conclusions] Apoptotic cells expression occurs prior to GluR2 protein expression in IC regions of adult rat after MCAO. This finding indicates that GluR2 might not induce early neuronal death. At 1 to 30 day recirculation, the decreased GluR2 protein expression parallel with the apoptotic cells indicates that GluR2 might result in the further neuronal apoptosis or or induce delayed neuronal death. The intense expression of the GluR2 protein and the slightly increased GluR2 immunopositive cells in IP regions at 15 and 30day recirculation suggest that GluR2 might contribute to the synaptic plasticity.