Effect Of RhEPO On Apoptosis Of Neonatal Rat Hippocampal Cell, Expression Of NF-κB MRNA And Long Term Effects Of Brain Damage On Learning And Memory Capacity During Hypoxia-ischemic Injury

Objective To study the effect of exogenous recombinant human erythropoietin(rhEP0) on apoptotic cells in hippocampal zone,expression of NF-κB mRNA and the long term effects on learning and memory capacity by hypoxia-ischemic brain damage(HIBD) model of neonatal rats.To explore the protective effect of rhEP0 on HIBD and the possible mechanisms.Methods One hundred and twenty postnatal 7-day Sprague-Dawley (SD) rats were randomly divided into 3 groups:control group,HIBD group,rhEPO-treated group,40 rats per group.The contrl group,left common carotid artery was not ligated and hypoxia on the seventh day.In HIBD group,rats received intra-peritoneal injection of the same dose of NS after the hypoxia period.In rhEPO-treated group,rats received intra-peritoneal injection of rhEP0(5000IU/kg·d) 15 min,once daily for consecutive 7 days.At 24h,48h,72h,7d,35d after HI,8 rats were randomly selected from each group for study of the apoptotic cells in hippocampal zone by HE straining and terminal deoxy- nucleotidyl transferase -mediated 2-deoxyuridine 5'-triphosphate-biotin nick end labeling(TUNEL) straining.The expression of NF-κB mRNA in the hipocampus was detected by RT-PCR technical.8 rats were randomly selected from in 35d-group tested the ability of learing and memory through Morris water maze.Results1.Very few number of TUNEL-positive cells was found in hippocampal zone by TUNEL staining in the control group,and there is no significantly difference between each time point(P＞0.05).In the HIBD group,the number of TUNEL-positive cells was increased at 24h,peaked at 48h(107.30±6.80),and lasted to 72h(85.39±5.88),then the cells were reduced at 7-day and 35-day,when compared with the control group(P＜0.05).In the rhEPO-treated group,the number of TUNEL-positive cells was significantly reduced comparing with the HIBD group. There were significantly differences between the control group,HIBD group and the rhEPO-treated group(P＜0.05).2.The expression of NF-κB mRNA in the hippocampal cells was observed in the control group.There was no difference between each time point(P＞0.05).The expression was increased at 24h after HIBD by RT-PCR technical,peaked at 48h(NF-κB/β-actin:0.605±0.024),and lasted to 72h(NF-κB/β-actin:0.290±0.018),then the expression was reduced to 7-day and 35-day,when compared with the control group (P＜0.05).In the rhEPO-treated group,the expression of the NF-κB mRNA was significantly reduced when compared with the control group and HIBD group(P＜0.05).3.Comparison of the learning and memory ability:the escape latency of the HIBD group was significantly longer than that of the control group and rhEPO-treated group at 35 days.There were significantly differences between three groups(P＜0.01).The escape latency of the rhEPO group was longer than the control group.There was difference between two groups(P＜0.05).Conclusion1.Exogenous rhEPO could reduce apoptisis of the nerve cell of the neonatal rats after HIBD,and maybe inhibit the expression of NF-κB mRNA.2.rhEPO reduce the brain damage and improve learning and memory capacity of the neonatal rats.