缺氧缺血性脑损伤新生大鼠脑Nogo受体水平及NEP1-40的神经保护作用

Expression of Nogo receptor in brain and neuroprotective effect of NEP1-40 on hypoxic ischemic brain damage in newborn rats

目的探讨缺氧缺血性脑损伤（HIBI）新生大鼠脑Nogo受体表达及Nogo受体拮抗剂NEP1-40的脑保护作用。方法采用随机数字表法将80只7日龄大鼠随机分为对照组、HIBD组、GM-1组和NEP1-40组。正常对照组及HIBD模型组腹腔注射生理盐水0．25ml／kg，NEP1—40组、GM-1组分别注射5g／LNEP1-40、2．5μl／d，40g／LGM-1 0．25ml／（kg·d），视分组情况连用3d或7d。采用原位杂交法检测各组大鼠脑组织24h、72h及7dNsR-mRNA表达水平，透射电镜观测其脑神经元与轴突的变化。多个样本率总体比较采用Χ^2检验，组间均数多重比较采用LSD—t检验，数据均采用SPSS10．0统计软件包处理，以P〈0．05有统计学意义。结果HIBD组、GM-1组和NEP1-40组各时期脑组织NgR水平均低于对照组（t值分别为5．48、6．11、6．96、8．24、5．99和5．34，均P〈0．05），三组间24hNgR水平差异无统计学意义（t值分别为1．48、2．76和1．29，均P〉0．05），而NEP1-40组72h与7dNgR水平低于同时期HIBD组、GM-1组；GM-1治疗后脑组织神经元得到不同程度的修复，而NEP1-40治疗后神经元修复良好，轴突再生明显。结论缺氧缺血性脑损伤后脑NgR水平下调，NEP1-40可促进脑损伤的修复，发挥脑保护作用。

Objective The hypoxic-ischemic encephalopathy caused by asphyxia in peripartum is a serious disease in newborn infants, with a high disability and mortality rate. Lack of regenerative ability in central nervous system after injury is considered as the fundamental cause. However, in recent years many studies have revealed that there are myelin-associated neurite growth inhibitory factors that exert inhibiting effect through the Nogo receptor （NgR）. This study aimed to investigate the expression level of NgR and the possible neuroprotective effect of NEP1-40 in newborn rats with hypoxic ischemic brain damage （ HIBD ）. Method Eighty healthy Wistar rats aged 7 days were randomly divided into 4 groups ;8 in control group, 24 in HIBD model group,24 in GM-I group and 24 in NEP1-40 group. The rats of the control group and HIBD group were injected with normal saline （0. 25 ml/kg） intraperitoneally, while those in NEP1-40 group and GM-1 group with NEP1-40 12. 5 μg/d, GM-1 10 mg/（kg - d） for continuous 3 days of 72-hour group or 7 days of 168-hour group, respectively. In situ hybridization was adopted for detecting the expression of NgR in the brain of the rats at the time point of 24 hours, 72 hours and 7 days. Meanwhile histopatholagical changes of neurons and axon were detected by transmission electron microscopy （TEM）. The SPSS statistical software package for Windows, version 10. 0, was used to run Chi-square tests and least significance difference（ISD-t） on the data presented, and P value of less than 0.05 was regarded as statistically significant. Result The expression level of Nogo-A receptor in the control group was higher than that of the other groups at different time point （ t value was 5.48, 6. 11,6. 96, 8. 24, 5.99 and 5. 34, respectively, and all P values were less than 0. 05 ）. There were no significant differences in Nogo-A receptor level among the HIBD group,the GM-1 group and the NEP1-40 at 24 hours （t was 1.48, 2. 76 and 1.29, respectively,and all P 〉 0.05 ）, while the expression of Nogo-A receptor of NEP1-40 at 72 hours and 7 days was lower than that of the HIBD group and the GM-1 group at the same time point, respectively （ all P 〈 0. 05 ）. Repair of neurons in damaged brain to some extent was found after GM-1 treatment and satisfactory repair of neurons and axon regeneration was obtained with NEP1-40 administration as shown by TEM. Conclusion Hypoxic ischemic brain damage can down-regulate the expression of Nogo-A receptor in the central nervous system. NEP1-40 contributes to the regeneration of axon and repair of brain damage, thus exerts neuroprotective effect.