Lipoxin A4 protects diabetic rats against focal cerebral ischemia-reperfusion by downregulating tumor necrosis factor-α and nuclear factor-κB

Objective To investigate the protective effect of lipoxin A4 on diabetic rats with focal cerebral ischemia-reperfusion and its mechanisms.Methods Thirty-six adult male Sprague-Dawley rats were randomly divided into a sham operation group,a cerebral ischemia-reperfusion group,and a lipoxin A4 group (n=12 in each group).Diabetes was induced by repeated intraperitoneal injection of low-dose streptozotocin.A model of middle cerebral artery occlusion and reperfusion was induced by the intraluminal suture method.Five minutes after cerebral ischemia,lipoxin A4 0.03 nmol/5 μ1 was injected via intracerebroventricular in the lipoxin A4 group.The other groups were injected equal volume of saline.Two hours after ischemia,the suture was pulled out and reperfusion was achieved.Neurological deficit scores were performed at 24 hours.Then the rats were decapitated and their brains were taken out.2,3,5-triphenyl tetrazolium chloride (TTC) staining was used to detect infarct size.Western blotting was used to detect the expression of cortical tumor necrosis factor-α (TNF-α) and nuclear factor-κB (NF-κB).Results The neurological deficit score showed that no neurological deficit was observed in the sham operation group (score 0).The neurological deficit score in the lipoxin A4 group was significantly lower than that in the cerebral ischemia-reperfusion group (2.20 ± 1.03 vs.3.20 ± 1.03; P ＜0.05).TTC staining showed that no infarct was observed in the sham operation group.The infarct size in the lipoxin A4 group was significantly lower than that in the cerebral ischemia-reperfusion group (27.52％ ± 5.71％ vs.55.45％ ± 9.29％ ; P ＜0.05).Western blotting showed that the expression levels of TNF-α in the sham operation,cerebral ischemiareperfusion,and lipoxin A4 groups were 0.64 ± 0.16,1.85 ± 0.52,and 1.40 ± 0.34,respectively.There were significant differences among the 3 groups (F =18.868,P ＜0.001).The expression level of TNF-α in the lipoxin A4 group was significantly lower than that in the cerebral ischemia-reperfusion group (P ＜0.05).The expression levels of NF-κB in the sham operation,cerebral ischemia-reperfusion and lipoxin A4 groups were 0.79 ±0.24,2.09 ± 0.47,and 1.27 ± 0.35,respectively.There were significant differences among the 3 groups (F =16.736,P ＜ 0.001).The expression level of NF-κB in the lipoxin A4 group was significantly lower than that in the cerebral ischemia-reperfusion group (P ＜0.05).Conclusions Lipoxin A4 has certain protective effect on focal cerebral ischemia-reperfusion injury in diabetic rats,its mechanism may be associated with the inhibition of the expression of TNF-α and NF-κB. Key words: Lipoxins;  Diabetes Mellitus, Experimental;  Brain Ischemia;  Infarction, Middle Cerebral Artery;  Tumor Necrosis Factor-α;  NF-κB;  Inflammation;  Rats