低剂量X线照射幼鼠对海马神经元形态及微管相关蛋白2的影响
Effects of low-dose X-ray on morphology of neuron and expression of microtubule associated protein-2 in hippocampus of young rats
目的 探讨连续低剂量X线照射对幼年Sprague-Dawley (SD)大鼠海马神经元形态及微管相关蛋白2( MAP-2)表达的影响及其相互关系.方法 出生后35 d的SD大鼠18只随机分为照射组和对照组,照射组分别连续7d接受0.2、1.0 mGy剂量的X线照射(0.2 mGy组和1.0 mGy组)及对照组(接受假照射),通过HE染色观察海马CA1区锥体细胞形态学变化,通过免疫组织化学法对大鼠海马CA1区MAP-2表达进行检测,Western印迹检测海马总MAP-2表达,并通过电镜观察海马CA1区超微结构的变化.结果 (1)1.0 mGy组海马CA1区可见神经元核固缩,0.2 mGy组与对照组海马CA1区锥体细胞形态未见异常;(2)1.0 mGy组海马CA1区MAP-2阳性细胞平均吸光度(A)值(0.242±0.017)低于对照组(0.282±0.016),差异有统计学意义(F=14.419,P=0.005),0.2mGy组MAP-2阳性细胞平均A值(0.331±0.017)高于对照组,差异有统计学意义(F=21.700,P=0.002);1.0 mGy组海马总MAP-2表达(0.332±0.001)低于对照组(0.370±0.012),(F =28.055,P =0.000),而0.2 mGy组(0.455±0.018)高于对照组,(F =61.974,P=0.002);(3)电镜下1.0 mGy组海马CA1区微管减少,结构紊乱,部分突触后膜致密物(PSD)增多、不均匀,0.2 mGy组神经元结构完整,微管增生,排列整齐,PSD均匀.结论 幼年SD大鼠连续受低剂量X线照射后海马神经元形态改变与MAP-2表达强弱相关,其中1.0 mGy组神经元受损,导致MAP-2表达减弱,而0.2 mGy组通过低剂量X线兴奋效应促进微管增生,增生的微管结构正常,促使MAP-2表达增强.
更多Objective To explore the effects of a continuous low-dose of X-ray upon neuronal morphology and expression of microtubule associated protein-2 (MAP-2) in hippocampus of young rats.Methods A total of 18 Sprague-Dawley rats aged 35 days were randomly divided into two irradiated groups and one control group ( n =6 each).The irradiated groups received different doses of 0.2 mGy/d,1.0mGy/d for 7 consecutive days while the control group sham radiation.The hippocampal pyramidal cell was observed by HE staining,the expression of MAP-2 by immunohistochemistry and Western blot,and the morphologies of microtubule and synapse in CA1 by electron microscopy.Results ( 1 ) The phenomenon of neurodegeneration was observed in the 1.0 mGy group while the control and 0.2 mGy groups were normal;(2) the average optical density of positive MAP-2 protein significantly decreased in the 1.0 mGy group (0.242 ±0.017) in the region of CA1 versus the control group(0.282 ±0.016) (F =14.419,P =0.005).And the average optical density of positive MAP-2 significantly increased in the 0.2 mGy group (0.331 ±0.017) compared with the control group (F =21.700,P =0.002).The expression of total MAP-2 significantly decreased in the 1.0 mGy group (0.332 ± 0.001 ) versus the control group (0.370 ± 0.012)( F =28.055,P =0.000).And the expression of total MAP-2 significantly increased in the 0.2 mGy group (0.455 ±0.018) versus the control group (F =61.974,P =0.002); (3) there were the reduction of microtubule and the damage of postsynaptic density (PSD) in the 1.0 mGy group in hippocampal CA1.Increased microtubule and normal synapses were found in the 0.2 mGy group in hippocampal CA1.Conclusion The expression of MAP-2 is strongly associated with the integrity of hippocampal neurons in young rats.The 0.2 mGy group may promote the proliferation of hippocampal microtubule in hippocampus and further promote the expression of MAP-2.And the damage of microtubule and PSD on neuron could reduce the expression of MAP-2 in the 1.0 mGy group.
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