表没食子儿茶素没食子酸酯对大鼠视神经钳夹伤后胶质纤维酸性蛋白表达的影响

背景先前的研究已证实，绿茶提取物表没食子儿茶素没食子酸酯（EGCG）能提高大鼠视神经钳夹伤后视网膜神经节细胞（RGCs）的生存率。星形胶质细胞（AS）在神经系统损伤中对神经元的修复起重要作用，而EGCG对视神经钳夹伤后AS反应活性的影响尚有待证实。胶质纤维酸性蛋白（GFAP）是AS的特异性标记物。目的观察EGCG对大鼠视神经钳夹伤后视神经GFAP表达的影响。方法将72只Wistar大鼠随机分为正常对照组、假手术＋EGCG组、视神经钳夹伤＋生理盐水组、视神经钳夹伤＋EGCG组，每组18只。于大鼠球后2mm处用夹持力dOg的微型视神经夹垂直视神经钳夹60s建立视神经钳夹伤模型，似手术大鼠仅切开眼外软组织，不损伤视神经。假手术＋EGCG组和视神经钳夹伤＋EGCG组大鼠术前2d起每日给予25mg／kgEGCG腹腔注射至术后2d，随后改为每日2mg／kg口服。采用免疫组织化学染色及Westernblot法检测并比较各组大鼠造模后7、1d、28d视神经组织中GFAP的表达。结果免疫组织化学染色显示，正常对照组和假手术＋EGCG组视神经组织中GFAP呈弱表达；造模后7、14、28d，视神经钳夹伤＋生理盐水组GFAP表达明显增强，视神经钳夹伤＋EGCG组GFAP的表达强于正常对照组，弱于视神经钳夹伤＋生理盐水组。Westernblot检测表明，造模后视神经组织GFAP的表达量较正常对照组明显增高，差异有统计学意义（P〈0．01）；造模后7d、14d，视神经钳夹伤＋EGCG组GFAP的表达量明显低于视神经钳夹伤＋生理盐水组，差异均有统计学意义（P〈0．05）。结论全身应用EGCG可以下调大鼠视神经钳夹伤后视神经组织中GFAP的表达，降低AS的增生活性，提示EGCG可以抑制视神经创伤修复过程中的瘢痕形成。

Effects of epigallocatechin-3-gallate on expression of glial fibrillary acidic protein in optic nerve crush model

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.