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目的探讨长期低剂量微波辐射后大鼠海马组织中Occludin的表达及其在微波辐射致血脑屏障损伤中的作用。方法 156只二级雄性Wistar大鼠随机分为对照组及2.5、5、10mW/cm2辐射组(每组39只),分别采用0、2.5、5、10mW/cm2微波辐射,5次/周,6min/次,持续1个月。于辐射后6h及7、14、30、60、180d活杀大鼠(每组每个时间点5只),取海马组织,光镜和透射电镜观察海马血脑屏障结构改变;另取各组动物分别于6h及7、30d(每组每时间点3只)用2%伊文思蓝灌注后活杀大鼠,取海马组织,于激光共聚焦扫描显微镜下观察血脑屏障通透性变化;Western blotting、Real-time PCR和图像分析技术检测Occludin基因及蛋白表达的改变。结果 2.5、5、10mW/cm2微波辐射后7、14、30d,大鼠海马组织内血管周间隙增宽,内皮细胞间紧密连接结构模糊、增宽,星形胶质细胞肿胀。对照组海马组织中伊文思蓝局限于血管腔内,5、10mW/cm2组于辐射后6h均可见伊文思蓝弥散至血管外周,辐射后7d时更加显著,30d内未见恢复,且病变随辐射剂量增加呈加重趋势。5、10mW/cm2组大鼠海马中Occludin蛋白表达分别于第14天(P<0.05)和第7天(P<0.01)时开始降低,第30天时表达显著降低(P<0.01),而第60天时恢复至对照组水平(P>0.05)。2.5、5、10mW/cm2组海马中Occludin mRNA表达在辐射后6h和7d时无明显改变,14d时显著下降(P<0.01),30d时降至最低值(P<0.01),60d时恢复至对照组水平(P>0.05)。结论 2.5、5、10mW/cm2微波长期辐射可导致大鼠海马血脑屏障结构破坏,通透性增加,病变程度与辐射剂量有关;海马组织中Occludin表达减少可能参与了微波辐射致血脑屏障通透性升高的病理生理过程。
Objective To investigate the expression of Occludin in rat hippocampus after long-term low-dose microwave irradiation and its role in the damage of blood-brain barrier induced by microwave radiation. Methods Two hundred and fifty-two male Wistar rats were randomly divided into control group and 2.5, 5, 10mW / cm2 radiation group (39 rats in each group). The rats were anesthetized with 0,2.5,5,10 mW / 6min / time for 1 month. The rats were sacrificed at 6h, 7h, 14h, 30h, 60h and 180d after radiation (5 rats at each time point). The structure of hippocampal blood-brain barrier was observed with light microscopy and transmission electron microscopy. The animals were sacrificed at 6h and 7d, 3d respectively. Each group was infused with 2% Evans blue to kill the rats. The hippocampus was harvested and the permeability of the blood-brain barrier was observed under laser scanning confocal microscope. Western blotting, Real-time PCR and image analysis were used to detect the changes of Occludin gene and protein expression. Results After perfused with 2.5, 5 and 10mW / cm2 of microwave for 7, 14, and 30 days, the perivascular space in the hippocampus of rats was broadened. The tight junctions between endothelial cells were vague and broadened, and astrocytes became swollen. Evans blue in the control group was confined to the lumen of the vessel. In the 5 and 10 mW / cm2 groups, Evans blue diffused to the periphery of the blood vessel 6 h after irradiation, and became more prominent at 7 d after irradiation, and no recovery was found within 30 d Radiation dose increased aggravating trend. The expression of Occludin protein in hippocampus of rats in 5 and 10 mW / cm2 groups decreased at day 14 (P <0.05) and day 7 (P <0.01), and decreased significantly at day 30 (P <0.01) 60 days to return to the control group level (P> 0.05). Occludin mRNA expression in hippocampus of 2.5, 5, 10mW / cm2 group had no significant change at 6h and 7d after radiation, but decreased significantly at 14d (P <0.01), then decreased to the lowest at 30d (P <0.01) Control group level (P> 0.05). Conclusion Long-term exposure to 2.5, 5 and 10mW / cm2 of microwave radiation can cause the destruction of the blood-brain barrier in the hippocampus of rats. The permeability increases with the dose dependent. The decreased Occludin expression in hippocampus may be involved in the blood- Permeability of the pathophysiological process.