Effects of ginkgo biloba extract on the expression of inducible nitric oxide synthase and glial fibrillary acidic protein after local cerebral ischemia/reperfusion in rats

Abstract

Objective To explore the protective effect and mechanism of ginkgo biloba extract on brain tissue after local cerebral ischemia and reperfusion in rats.Methods Eighty male Sprague-Dawley rats were randomly divided into two groups:control group (group A,normal saline injected,n =40),and ginkgo biloba extract intervention group (group B,ginkgo biloba extract injected,n =40),which were then subdivided into 4 subgrouops:post-reperfusion 1,3,6 and 24 h groups,10 in each sub-group.The model of right middle cerebral artery occlusion (MCAO) and reperfusion was made.Pathological changes in brain morphology were observed by hematoxylin and eosin (HE) staining.Immunohitochemistry was used to detect the inducible nitric oxide synthase (iNOS) changes.The expression of glial fibrillary acidic protein (GFAP) was examined by using enzyme linked immunosorbent assay (ELISA).Results (1) Necrosis,apoptosis and cytoplasmic vacuolatin of nerve cells were observed in group A,neuronal shape was difficult to be identified,and most of the cell structure disappeared.However,the injury was relieved at the same time points in group B as compared with that in group A; (2) Immunohitochemical results showed that there were a few iNOS expression positive cells 1 h after reperfusion,iNOS expression positive cells were obviously increased at 3 h after referfusion,and nucler translocation appeared.Analysis by Image-pro plus 5.0 showed that iNOS expression levels in group B (1851.38 ±242.12,2005.41 ± 290.52,2625.28 ±385.21,3142.5 ±425.72 respectively at 1,3,6 and 24 h) were significantly lower than those in group A (1950.25 ± 298.26,2232.45 ± 305.28,3251.22 ± 425.26,3965.36 ± 521.62 respectively at 1,3,6and 24 h) (P ＜ 0.05) ; (3) ELISA results showed that serum GFAP levels were increased after ischemiareperfusion,and those in group B [(275.29 ± 112.72),(308.72 ±124.11),(372.56 ± 185.62),(452.12 ± 145.26) ng/L respectively at 1,3,6 and 24 h] were significantly lower than those in group A [(437.17 ± 152.26),(490.27 ± 198.37),(583.45 ± 201.42),(656.26 ± 256.36) ng/L respectively at 1,3,6 and 24 h] (P ＜ 0.05).Conclusion iNOS and GFAP were significantly increased after the cerebral ischemia-reperfusion in rats.ginkgo biloba extract can significantly reduce the cerebral injury by down-regulating the expression of iNOS and GFAP,suggesting the protective effects of ginkgo biloba extract on the ischemic cerebral tissues. Key words: Ginkgo biloba extract; Ischemia/reperfusion injury; Apoptosis; Inducible nitric oxide synthase