Effects of epigallocatechin-3-gallate on expression of glial fibrillary acidic protein in optic nerve crush model / 中华实验眼科杂志

ABSTRACT

Background Our previous study demonstrated that epigallocateehin-gallate(EGCG),an active ingredient of green tea,has protective effect on optical nerve after optic nerve crush.Astrocyte was proved to play key role in the repair of nerve tissue,but the influence of EGCG on astrocyte is unclear.Glial flbrillary acidic protein (GFAP) is a special marker for astrocyte. Objective The aim of this study was to investigate the effect of EGCG on the expression of GFAP in optic nerve tissue after optic nerve crush. Methods Seventy-two clean Wistar rats were randomly divided into normal control group,sham+EGCG group,optic nerve crush+normal saline group(vehicle group),optic nerve crush+EGCG group.Optic nerve crush models were established by clamping optical nerve for 60 seconds by minitype optic nerve clipper with the force of 40 gram.Only ocular tissue was cut in the rats in sham group.Normal saline solution or EGCG(25 mg/kg)was intraperitoneally injected daily for 5 days consecutively and orally administered(2 mg/kg)daily afterwards.The expression of GFAP in optic nerve was detected by immunohistochemistry and quantified by Western blotting analysis on day 7,14 and 28 after modeling. Results lmmunochemistry showed that GFAP were weakly expressed in the rats of both normal group and sham+EGCG group with the sliSht brown staining in optic nerve tissue.The deeply brown staining for GFAP was seen in vehicle group,and the staining intensity weakened in optic nerve crush+EGCG group compared to vehicle group on days 7,14 and 28 after modeling.Western blotting analysis revealed that the expression level of GFAP in rat optic nerve tissue of vehicle group was significantly enhanced in comparison with normal control group(P＜0.01).On day 7 and 14 after optic nerve modeling,the expression levels of GFAP were evidently decreased in optic nerve crush+EGCG group in comparison with vehicle group(P＜0.05).However,on day 28 after modeling,no significant difference wag found in the expression levels of GFAP between vehicle group and optic nerve erush+EGCG group(P＞0.05). Conclusion EGCG down-regulates optic nerve crush-induced of GFAP in the optic nerve and therefore attenuates the activity of astrocytes,suggesting that EGCG might reduce the formation of glial scar.