| objective: To observe the effects of ischemic postconditioning(IPO)on the expression of tumor necrosis factor-alpha(TNF-?)and supressor of cytokine signaling-3(SOCS-3)at different time points after focal cerebral ischemia/reperfusion in hyperlipidemic rats,and to probe into the neuroprotective effect and its possible mechanism.Methods:1.building model and grouping: One hundred and thirty adult healthy male Sprague-Dawley(SD)rats were randomly divided into normal diet group(n=10,fed with normal diet)and high fat diet group(n=120,fed with high fat diet),which was used to be made into the model of hyperlipidemic rats,then hyperlipidemic rats were randomly divided into sham operation group(sham group),ischemia/reperfusion group(I/R group),ischemic postconditioning group(IPO group),each group were 40 rats and could be divided into seven subgroups according to reperfusion time,which were 3,6,12,24,48,72 h and 7 day,except for 24 h time point were 10 rats(5rats were used for TTC staining among them),the remaining subgroups were respectively 5 rats.The focal cerebral ischemia/reperfusion model was created by the modified suture method,and the model of IPO adopted 15 s reperfusion,followed by 15 s ischemia,then repeated three times before reperfusion.2.the detection of indicators: the content of triglycerides(TG),total cholesterol(TC),low density lipoprotein cholesterol(LDL-C)and high density lipoproteincholesterol(HDL-C)were measured by automatic biochemical analyzer,the calcification of common carotid artery in rats were observed by Von Kossa staining,the volume of cerebral infarction was measured by TTC staining,nerve function score in rats were used for each group after reperfusion in each time point,the pathological changes of brain tissues in rats were observed by HE staining,the expression of TNF-? and SOCS-3 were detected by immunohistochemical method and the expression of apoptosis cells were measured by TUNEL method in brain tissues.Result:1.the establish of hyperlipidemic rat model: compared with normal diet group,the content of TC,TG,LDL-C in serum of rats were all higher in high fat group,but the content of HDL-C was lower,they differences were statistically significant,at the same time,the Von Kossa staining of common carotid artery showed the change of atherosclerosis,such as calcification,etc.2.the result of focal cerebral ischemia/reperfusion model building: after 90 minutes reperfusion,the vast majority of rats on nerve function score were in 1,2,3 points,and a few rats were 0,4 points or death.3.the result of rats in nerve functional scoring: the I/R group and IPO group in nerve functional scoring at each time point after reperfusion were lower than sham group(p<0.05),meanwhile,the two groups on nerve functional scoring were lowest in 24 h time point and compared with other time points in each group,the differences were statistically significant,when compared with I/R group,IPO group in never functional scoring were higher at the corresponding time points of 6,12,24,48,72h(p<0.05).4.pathological changes of brain tissuesin rats: the sham group had no pathological injury,the ischemic brain tissues of IPO group had obviously lower degree of pathological injury compared with the I/R group.5.the result of TTC staining and the measurement about volume of cerebral infarction: the brain tissues of Sham group showed uniform red stained at 24 h after reperfusion,but white infarction in ischemic brain tissues of IPO group were smaller than I/R group,and the measurement about volume of cerebral infarction did not show infarction in sham group,while,the infarction volume of IPO group reduced obviously compared with I/R group(p<0.05).6.the expression of TNF-? in brain tissues: TNF-? in brain tissues of ischemic hemisphere began to express at 3h after reperfusion in I/R group,increased at6 h,and reached its peak at 24 h,then started to decrease gradually at latter time points,and still had litter expression at 7d,the expression trend in each time point of IPO group was in keeping with I/R group,however,compared with I/R group,the expression of TNF-? obviously reduced at 6,12,24,48,72 h in IPO group(p<0.05),and the two groups were higher expression than sham group(p<0.05).7.the expression of SOCS-3in brain tissues: very small amount of SOCS-3 was found in sham group,SOCS-3 in brain tissues of ischemic hemisphere began to increase gradually at 3h,6h after reperfusion in I/R group,reached its peak at 24 h,then started to decrease gradually at latter time points,the expression trend in each time point of IPO group was in keeping with I/R group,however,compared with I/R group,the expression of SOCS-3 were obviously higher at 6,12,24,48,72 h in IPO group(p<0.05),and the two groupswere higher expression than sham group(p<0.05).8.the expression of apoptotic cells in brain tissues: sham group merely was seen a very few apoptotic cells,the I/R group and IPO group could found a small amount of apoptosis cells at3 h after reperfusion,began to increase at 6h,and reached peak at24-48 h,there was still a little expression to7 d,all of them were higher than sham group(p<0.05),and the expression of IPO group reduced at 12,24,48,72 h compared with I/R group(p<0.05).Conclusion: 1.We established hyperlipidemic rat model by free feeding with high fat diet and made cerebral ischemia/reperfusion model on the basis of improved line plug method,which could fully reflect the development process of human diseases,meanwhile,these methods also have simple operation and good repeatability,so they can be regarded as the ideal animal model to make cerebral ischemia/reperfusion injury.2.The rats occurred neurological impairment after cerebral ischemia/reperfusion,ischemic brain tissues happened pathological changes and the inflammatory cytokine of TNF-? and apoptosis cells increased,the expression of SOCS-3 increased at the same time,which suggested that SOCS-3 may play a role of endogenous brain protection by reducing inflammatory reaction and inhibiting cell apoptosis.3.Ischemic postconditioning could increase the expression of SOCS-3 in brain tissues after focal cerebral ischemia/reperfusion in rats and reduce the expression of TNF-? and apoptosis cells,which suppressed inflammatory damage and reduced the nerve cell apoptosis to alleviate cerebral ischemia/reperfusion injury,therefore,IPO plays a role of brain protection. |
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