Vascular Protective Effect Of Pretreatment With Candesartan On Cerebral Ischemia-reperfusion In Rats

Objective:To investigate the vascular protective effect of pretreatment with Candesartan on Cerebral ischemia in rats,we observed the change and relationship between endothelial nitric oxide synthase(eNOS) and vascular endothelial growth factor(VEGF) in the ischemia penumbra,with middle cerebral artery occlusion (MCAO) by intraluminal suture method in rats.Methods:72 male SD rats,12 weeks,were randomly divided into sham operation group,ischemia-reperfusion group,candesartan low-dose group[0.1mg/(kg.d)],and candesartan high-dose group[1mg/(kg.d)],there were 18 rats in each group,each group was randomly divided into two sub-groups (n=9 in each group):reperfusion 24 hour and 72 hour. Normal sodium was delivered by intragastric administration with 2ml/d in sham operation group and ischemia-reperfusion group,Candesartan was delivered by intragastric administration with 0.1mg/(kg.d) and 1mg/(kg.d) in candesartan low- dose group,candesartan high-dose group,respectively.A model of middle cerebral artery occlusion was induced by intraluminal suture method after four weeks of drug gavage. Blood pressure was measured preoperatively.Cerebral blood flow of ischemic region was quantified by laser-Doppler flowmetry after MCAO. Neurological scores were performed after 24 and 72 hours of reperfusion,then the rats were decapitated and the brains were removed.The Infarct volume was measured using TTC staining. The expression of vascular endothelial growth factor and endothelial nitric oxide synthase protein in ischemic penumbra was detected by Immunohistochemical staining and Western blot analysis.Results:(1) In the second week after medication,the blood pressure was decreased significantly in the high-dose candesartan group,maintaining at 85mmHg,and there was no significant antihypertensive effect in the low-dose group.(2)The neurological scores of the low-dose and high-dose candesartan groups at 24 hour and 72 hour after reperfusion were significantly better than those of the ischemia-reperfusion group (P<0.05,respectively).(3)Infarct volume in low-dose and high-dose candesartan group reduced to [(34±4)%,(30±3)%],there is no significant difference between the two groups(P>0.05).Ischemia-reperfusion group decreased to (52±6)%,the infarct volume of ischemia-reperfusion group is significantly higher than those of the two groups (P<0.05,respectively).(4)After 2 hour occlusion,in ischemia-reperfusion group cerebral blood flow of the ischemic region in right middle cerebral artery decreased to(32±3)%,cerebral blood flow in candesartan low-dose group and high-dose group were decreased to[(55±5)%,(64±7)%],respectively(P<0.05).(5)The positive express- ion of eNOS and VEGF mainly distributed in vascular endothelial cells around ischemic penumbra.The Immunohistochemical staining is yellow.The expression of eNOS protein in the low-dose and high-dose candesartan group was upregulated at 24 and 72 hour after reperfusion,it reached the peak after 24-hour reperfusion (P<0.05) , and then down-regulation.The expression of VEGF was further upregulated with time, it reached the peak after 72-hour reperfusion.The result of Western blot analysis was consistent with that of Immunohistochemical staining.Conclusion:Candesartan may not only reduce the infarct volume, but improve the neurological scores and cerebral blood flow by upregulating the expression of eNOS and VEGF protein in the ischemia region.