新生大鼠缺氧缺血性损伤致脑白质自噬体形成增多

Autophagosomes in cerebral white matter increase after hypoxic-ischemic injury in neonatal rats

目的:探讨缺氧缺血对新生大鼠脑白质自噬体形成及髓鞘生成的影响。方法:3日龄的SD大鼠随机分为假手术组(sham)和缺氧组(HI),每组又分为24 h、48 h、72 h、5 d、7 d 5个时间点,透射电镜观察脑白质自噬发生情况及髓鞘生成情况,免疫印迹检测自噬相关蛋白LC3和髓鞘碱性蛋白(MBP)的表达情况。结果:HI 24 h组自噬体增多,散在分布;HI 48 h组自噬体增多更明显,较多细胞突起内可见成堆聚集的自噬体;HI 72 h组自噬体和HI 48 h组比较略少,与sham组比较差异均有统计学意义。MBP表达下调,其中HI 7 d组与sham组比较,差异有统计学意义,HI 7 d组髓鞘形成疏松,板层结构紊乱。结论:新生大鼠脑缺氧缺血可诱导脑白质发生自噬,在缺氧缺血后48 h达到高峰;新生大鼠缺氧缺血后不仅MBP合成减少,新生髓鞘结构也异常。

Objectives:To investigate the formation of autophagosomes in cerebral white matter after hypoxiaischemia damage in neonatal rats.Methods:Postnatal day(P)3 SD rats were randomly divided into sham group and hypoxia-ischemia(HI)group.Each group was divided into 5 time points as 24 h,48 h,72 h,5 d and 7 d.The autophagosome and myelin changes were observed by transmission electron microscopy and the expressions of myelin basic protein(MBP)and LC3Ⅱwere studied by Western blotting.Results:A few autophagy bodies could be found in HI 24 h group,while autophagy bodies increased and could be easily found in HI 48 h group.Autophagy bodies in the HI 72 h group were slightly less than those in HI 48 h group.The expression of LC3Ⅱin HI groups was higher than sham groups.The differenee between HI groups and sham groups were statistically significant in each time point.MBP was down-regulat in HI 7 d group.The difference between HI 7 d and sham 7 d was statistically significant.The loosed and disordered myelin sheaths were observed in In HI 7 d group.Conclusion:Cerebral hypoxia-ischemia damage in P3 neonatal rats could induce autophagy in white matter,and the peak was found at HI 48 h,not only MBP synthesis is reduced after cerebral hypoxia-ischemia,but also the structure of new myelin sheath is abnormal.