BDNF对兔急性高眼压玻璃体谷氨酸浓度和视网膜兴奋性谷氨酸转运体表达的影响

Effect of BDNF on the vitreous glutamate concentration and the expression of excitatory amino acid transporter in the retina in rabbits with acute intraocular hypertension

目的探讨脑源性神经营养因子（brain derived neurotrophic factor，BDNF）对急性高眼压兔眼玻璃体谷氨酸浓度以及视网膜兴奋性谷氨酸转运体1（excitatory amino acid transporter 1，EAAT1）、转运体2（EAAT2）表达的影响；探讨BDNF抑制青光眼视神经损害可能的作用机制。方法将24只兔随机分为正常对照组、平衡盐溶液（BSS）组和BDNF组（每组n=8）。采用前房灌注法建立兔急性高眼压模型，BSS组和BDNF组在玻璃体内分别注射BSS或BDNF；正常对照组不做处理。用高效液相色谱分析检测玻璃体谷氨酸浓度。分别用Western blot和免疫组化染色检测视网膜EAAT1和EAAT2的表达。结果①BSS组的玻璃体谷氨酸浓度明显高于正常对照组和BDNF组（P〈0．05）；BDNF组与正常对照组相比，玻璃体谷氨酸浓度差异无统计学意义（P〉0．05）。②Western blot分析显示，BSS组与正常对照组相比，EAAT1的表达无明显变化（P〉0．05）；BDNF组与正常对照组以及BSS组相比，EAAT1的表达明显升高（P〈0．05）。BSS组和BDNF组与正常对照组相比，EAAT2的表达降低（P〈0．05）；BSS组下降明显，与BDNF组相比，差异有统计学意义（P〈0．05）。③免疫组化染色显示，与正常对照组相比，BDNF组和BSS组EAAT1染色明显增强；BSS组EAAT2染色明显减弱，BDNF组EAAT2染色介于正常对照组和BSS组之间。结论急性高眼压模型兔眼玻璃体谷氨酸浓度明显升高；BDNF可通过上调EAAT1表达和抑制EAAT2表达的下降降低玻璃体谷氨酸浓度，从而减少谷氨酸对视网膜神经节细胞（RGCs）的兴奋性毒性作用。

Objective To investigate the effects of brain derived neurotrophic factor （BDNF） on the vitreous glutamate concentration and the expression of excitatory amino acid transporter 1 （ EAAT1 ） and excitatory amino acid transporter 2 （EAAT2） in the retina in rabbits with acute intraocular hypertension. Methods 24 rabbits were divided into the normal control group, balanced salt solution （BBS） group and BDNF group （n = 8 each）. Acute intraocular hypertension model was established by irrigating the anterior chamber. The rabbits received intravitreal injection of BSS （ BSS group） or BDNF（ BDNF group）. Normal control group received no treatment. Vitreous glutamate concentrations in each group were detected by high - performance liquid chromatography. Western blot and immunohistochemistry staining were used to observe the expression of EAAT1 and EAAT2 in the retina. Results （1） Vitreous glutamate concentration in BSS group was higher than that in normal control group and BDNF group （ P 〈 0.05） ; There was no significant difference in vitreous glutamate concentrations between normal control group and BDNF group （ P 〉 0.05 ）. （2） Western blot analysis showed that there was no significant difference in the expression level of EAAT1 between normal control group and BSS group （ P 〉 0.05 ） ; the expression level of EAAT1 in BDNF group was higher than that in normal control group and BSS group （ P 〈 0.05 ）. The expression level of EAAT2 in BSS group and BDNF group was lower than that in normal control group （ P 〈0.05 ） ; The level of EAAT2 in BSS group was lower than that in BDNF group （ P 〈0. 05 ）. （3） Immunohistochemistry staining showed that compared with normal control group, EAAT1 staining level increased significantly in BDNF group and BSS group; EAAT2 staining level decreased significantly in BSS group, while the EAAT2 staining level in BDNF group was between BSS group and normal control group. Conclusions Vitreous glutamate concentration in rabbit model with acute experimental intraocular hypertension is elevated significantly. BDNF can reduce the vitreious glutamate concentration through up - regulating the expression of EAAT1 and inhibiting down - regulation of the expression of EAAT2, which can inhibit the excitotoxic effect of glutamate on retinal ganglion cells （ RGCs）.