Effect Of Recombinant Human Erythropoietin On XIAP And Smac/DIABLO Expression In Brain Tissues After Traumatic Brain Injury In Rats

Apoptosis is a main way of neurocyte death after traumatic brain injury(TBI),but the certain mechanism of apoptosis after TBI still remain enigmatic.We designed an animal experiment in an effort to determine if there were correlation between XIAP and Smac/DIABLO expression and apoptotic cells after TBI and to explore the effect of recombinant human erythropoietin(r-HuEpo) on the expression of XIAP and Smac/DIABLO after TBI in rats and the mechanisms of anti-apoptotic by r-HuEPO.Objective:1.To investigate the dynamic change and correlation of XIAP and Smac/DIABLO expression and apoptosis following TBI;2.To explore the effect of r-HuEpo on the expression of XIAP and Smac/DIABLO after TBI in rats and the mechanisms of anti-apoptotic by r-HuEPO.Method:Sixty-six healthy male Wistar rats were randomly divided into sham operation group(n=6),TBI group(n=30) and r-HuEPO group(n=30).The experimental TBI model was established by Feeney's method.The injuried cerebral cortex tissues were obtained at different time points(2,6,24,72h,7d ) after TBI for determining apoptosis of cells by TUNEL and inspecting the expression of XIAP and Smac/DIABLO by immunochemicalmethod.All values were expressed as means±SD.One-way analysis of variance was used to assess group means,and two groups of the same point in time were compared using Independent-Samples t test.P＜0.05 was considered statistically significant.Statistics were using SPSS 11.5.Result:1.Compared to the sham group,the number of apoptotic cells in TBI groups was increased significantly at 2h after injury,reached its peak at 24h,remained a higher level and still increased significantly at 7d;the number of apoptotic cells were significantly decreased from 6h to 7d after TBI in r-HuEPO groups compared to TBI group;2.Compared with sham group,the expression of XIAP and Smac/DIABLO increased significantly in the surronding zone of injury after TBI,the expression of XIAP and Smac/DIABLO in neurons increased at 2h after TBI,and not still returned to nomal at 7d,XIAP reached the highest level at 6h,but the expression of Smac/DIABLO peaked at 24h after TBI;3.The expression of XIAP in r-HuEPO groups from 2h to 72h after TBI was more increased than that in TBI groups;compared to the the TBI groups,the expression of Smac/DIABLO in r-HuEPO groups from 6h to 7d reduced significantly.Conclusion:1.Apoptosis occurred generally and distributed mainly in the brain tissue perimeter traumatic cortex after TBI.R-HuEPO can inhibit neuronal apoptosis after brain injury to play a role in the neuroprotection after TBI;2.The expression of XIAP increased early after TBI,and may dcrease apoptosis damage following TBI by inhibitting activity of Caspase-3,Caspase-7 and Caspase-9 protein and ubiquitination and degradation of caspases via RING finger domain of XIAP;3.TBI induces the increased expression of Smac/DIABLO and its translocation from mitochondria to promote apoptosis following TBI.The expression of Smac/DIABLO increased significantly at 2h after TBI,which reached its peak at 24h when apoptosis reached the highest level,and contributed to apoptosis by inhibiting activity of XIAP and other IAPs.This result proves the dependences of time and space about its expression;4.R-HuEPO can inhibit neuronal apoptosis after TBI through promotion of XIAP expression and suppression of Smac / DIABLO expression,to play a role in the neuroprotection after TBI.