脑白质损伤新生大鼠脑白质P75NTR蛋白与RhoA mRNA的表达及意义

目的：最近研究发现NgR-P75NTR- RhoA信号通路在神经损伤和重塑方面发挥关键作用,但其确切传导机制及在缺氧缺血后新生动物P75NTR对下游分子RhoA调控变化尚不清楚。该实验在建立新生大鼠缺氧缺血性脑白质损伤(WMD)模型基础上，观察WMD新生大鼠脑白质P75NTR和RhoA mRNA表达变化, 探讨WMD时两者的关系及意义，为临床治疗早产儿WMD提供新思路和实验依据。方法：制备新生大鼠WMD模型，光镜及电镜观察脑组织形态学改变。应用免疫组织化学方法及荧光定量RT-PCR检测对照组及WMD 12，24，48，72 h和7 d组病变侧脑白质P75NTR蛋白及RhoA mRNA表达变化。结果：光镜和电镜形态学发现WMD组缺氧缺血48 h后即有显著的脑室周围脑白质损伤。WMD组大鼠纹状体和胼胝体P75NTR蛋白水平12 h开始升高，48 h达峰值，至72 h略有下降，与对照组比较差异有显著性，均P<0.01，之后下降明显，第7天与对照组比较差异无统计学意义（P>0.05）。WMD组大鼠脑白质RhoA mRNA 表达12 h开始升高，48 h达到峰值，与对照组比较，差异有显著性，均P<0.05。72 h仍高于对照组水平，之后开始下降，第7天与对照组比较差异无显著性（P>0.05）。结论：WMD新生大鼠脑白质中P75NTR蛋白水平呈现先上升后下降的趋势。其升高与介导神经细胞凋亡和抑制神经轴突再生可能有关，表达下降则与缺氧缺血性损伤加重神经细胞坏死相关。RhoA mRNA的表达变化趋势与P75NTR一致，提示P75NTR水平升高可促使RhoA mRNA高表达。［中国当代儿科杂志，2007，9（4）：317-320］

Expression of P75NTR protein and RhoA mRNA in the brain of neonatal rats with white matter damage

Objective Recent studies have indicated that the signal pathway of NgR-P75NTR-RhoA plays a key role in nerve injury and remodeling,but its exact mechanism and the role of the downstream molecule RhoA regulated by P75NTR remain unclear in hypoxia-ischemia(HI)neonatal animals.The present study was designed to assess the expression of P75NTR protein and RhoA mRNA in neonatal white matter and to investigate their relationship in newborn rats with white matter damage(WMD).Methods The rat WMD model was established by the ligation of right common carotid artery,followed by 6% hypoxia exposure for 4 hrs.The control group was sham-operated,without HI treatment.The histological changes of brain tissue were observed under light and electron microscopes.Expression of P75NTR protein and RhoA mRNA in the brain white matter after 12,24,48 and 72 hrs and 7 days of HI were detected by RT-PCR and immunohistochemistry,respectively.Results Periventricular white matter damage was observed by 48 hrs of HI.Expression of P75NTR protein increased in the striatum and callosum zones at 12 hrs,peaked at 48 hrs,and remained at a higher level than control until 72 hrs of HI in the WMD group(P<0.01).After 7 days of HI expression of P75NTR protein was no longer statistically different from controls.The RhoA mRNA was higher in the WMD group for the first 72 hrs and then declined to control values.Conclusions Increased P75NTR protein might mediate apoptosis of nerve cells and inhibit the regeneration of neuron axons.The subsequent decline back to control value may be correlated with the aggregation of necrosis of nerve cells after HI.The patterns of RhoA mRNA expression were consistent with those of P75NTR protein,suggesting that the increased P75NTR level may promote RhoA mRNA expression.