Ischemic Postconditioning On Cerebral Ischemia-reperfusion Rats Il - 1 Beta, And The Influence Of Tnf Alpha Expression

Part I:Optimal protocol of ischemic postconditioning against focal cerebral ischemia/reperfusion injury in ratsObjective:To establish a model of focal cerebral ischemia/reperfusion(I/R) in rats and investigate the optimal protocol of ischemic postconditioning(IP) against focal cerebral ischemia/reperfusion ingury.Methods:Sixty adult male Sprague-Dawley rats were randomized into six groups (n=10each): sham surgery group, I/R group and IP group with different time intervals(15s,30s,45s and60s). Focal cerebral ischemia was established by an intraluminal thread middle cerebral artery occlusion(MCAO) for2h. For IP, the rats were subjected to3cycles of reperfusion/reocclusion at different time intervals(15s,30s,45s and60s). Each group was evaluated with examinating neurologic deficit scores,infarct volume and nerve cell apoptosis after reperfusion for24hours.Results:The ischemia/reperfusion model in the rats were successfully established by intraluminal suture method. Neurobehavioral function deficit and cerebral infarction were seen in the I/R group and IP group. Compared with the I/R group, the neurologic deficit scores decreased significantly in IP-15s,IP-30s and IP-45s groups, and the neurologic deficit scores in IP15s group were lower than those of IP-30s and IP-45s groups. The infarct volume and the numbers of apoptosis cell significantly decreased in IP-15s,IP-30s and IP-45s groups as compared with I/R group, particularly in IP-15s group(P<0.05). There were no significant difference between IP-60s group and I/R group(P>0.05).Conclusions:The modified MCAO model is a cerebral ischemic tolerance model with favorable stability. IP may be a promising neuroprotective approach for focal cerebral ischemia/reperfusion injury. The optimal protocol of IP to induce ischemic tolerance in brain is3cycles of15-second/15-second reperfusion/reocclusion. Part II:Ischemic postconditioning down-regulate IL-1β and TNF-a expression in rat model of cerebral ischemia/reperfusionObjective:To investigate the effects of ischemic postconditioning on interleukin-1β (IL-1(3) and tumor necrosis factor-a (TNF-a) expression in rat model of focal cerebral ischemia/reperfusion.Methods:One hundred and ten adult healthy male Sprague-Dawley rats were randomized into sham surgery group(n=10), ischemia/reperfusion group(I/R group, n=50) and ischemic postconditioning group(IP group, n=50). The latter two groups were equally divided into five subgroups according to different time points of ischemia-reperfusion (6,12,24,48and72h)(n=10, respectively). Focal cerebral ischemia was established by an intraluminal thread middle cerebral artery occlusion(MCAO) for2h. For IP, the rats were subjected to3cycles of15-second/15-second reperfusion/reocclusion after2h MCAO. Each group was evaluated with examinating neurologic deficit scores and infarct volume. The immunohistochemistry stain was used to determine expression of TNF-a and IL-1β protein. Expression of TNF-a and IL-1β mRNA were examined by In Situ Hybridization.Results:(1) Intergroup comparison:neurobehavioral function deficit and cerebral infarction were seen in the I/R group and IP group. Compared with I/R group, cerebral infarct volume and neurologic deficit scores significantly decreased in IP group (P<0.05). IL-1β protein and mRNA expression were found in the frontoparietal cortex in I/R group and IP group, the positive products in IP group were lower than those in I/R group at each time point after reperfusion (P<0.05). TNF-aprotein and mRNA expression was consistent with IL-1βexpression.(2) In I/R group, the expression of IL-1β and TNF-a were found at6h, peaking at24h after reperfusion. IL-1β and TNF-a expression in24h subgroup significantly increased compared with other subgroups (P<0.05). In IP group, the dynamic change of IL-1β and TNF-amRNA expression was consistent with I/R group.Conclusions:IP could down-regulate the expression of IL-1β and TNF-a and reduce infarct volume. These findings indicated that IP may be a promising neuroprotective approach for focal cerebral I/R injury by inhibiting inflammation.