ISCHEMIC POSTCONDITIONING ON EXPRESSIONS OF TLR4 AND NF-κB DURING FOCAL CEREBRAL ISCHEMIA/REPERFUSION IN RATS

Objective To investigate ischemic postconditioning(IP) on the expressions of Toll-like receptor 4(TLR4) and nuclear factor-κB(NF-κB) in rats during focal cerebral ischemic reperfusion,and explore the role of TLR4-NF-κB signaling pathway in IP.Methods This study consisted of 110 adult healthy male Sprague-Dawley rats,which were randomized to sham group(n=10),ischemic reperfusion group(I-R group,n=50) and IP group(IP group,n=50).The latter two groups were divided into five subgroups according to different time points of I-R(6,12,24,48 and 72 h)(n=10).In I-R group: a model of focal cerebral I-R was created by blocking middle cerebral artery with intraluminal thread for 120 min,then the thread was removed and reperfusion lasted;In IP group: the middle cerebral artery was blocked for two hours,and subjected to three cycles of 15 s reperfusion interspersed by 15 s ischemia immediately after onset of reperfusion;those in the sham group,no ischemia and reperfusion were offered.Neurobehavioral score was carried out for rats in each group,the volume of cerebral infarction was detected by using TTC staining,TLR4 protein and NF-κB protein by immunohistochemistry,and TLR4 mRNA and NF-κB mRNA by In Situ Hybridization(ISH).Results The neurobehavioral function deficit and cerebral infarction were observed in the I-R group.Compared with the I-R group,the volume of cerebral infarction in rats in the IP group was decreased,the score of neurobehavioral function improved,the difference between the two groups was significant(t=2.683-5.657,P0.05).In the sham group,slight expressions of TLR4 protein,NF-κB protein,TLR4 mRNA and NF-κB mRNA could be found in the frontoparietal cortex;In I-R group and IP group,the expressions began to rise at six hours of reperfusion,and reached the peak at 24 h(F=7.995-11.704;q=4.770-9.001;P0.05);Compared with subgroups of I-R group,the expressions of TLR4,NF-κB protein and NF-κB mRNA decreased dramatically,with a significant difference among them(t=2.333-6.916,P0.05).Conclusion IP can down-regulate the expressions of TLR4 and NF-κB,and thus reduce ischemic reperfusion injury and improve neurobehavioral function in the rats.