神经生长因子对兔急性高眼压视神经节细胞Bcl-2和Bax表达的影响

目的研究神经生长因子(nerve growth factor,NGF)对兔眼急性高眼压视网膜神经节细胞(retinal ganglion cells,RGCs)损伤的保护作用。方法健康成年新西兰大耳白兔30只,随机分为5组,每组6只,均一眼为高眼压模型眼,另一眼为自身对照眼,每组3只兔于术后每日肌肉注射NGF2000BU,5组兔分别于制造模型眼后第1天、第3天、第7天、第15天和第30天处死,用透射电镜观察线粒体的变化,免疫组织化学SABC法检测RGCs的Bcl-2、Bax蛋白表达,定量分析NGF的药物疗效。结果急性高眼压3d后,RGCs轴突中线粒体肿胀,空泡化,Bcl-2蛋白表达减少,Bax蛋白表达增多,Bcl-2/Bax比值下降,实验组与对照组相比差异有显著性(t=3.09,P<0.05);应用NGF7d后,治疗组线粒体肿胀程度减轻,Bcl-2表达增多,Bax表达减少,Bcl-2/Bax比值开始上升,治疗组与实验组相比差异有显著性(t=2.79,P<0.05),15d后,轴突中线粒体增多,30d后,线粒体形态、数量基本恢复正常,治疗组与实验组相比差异有极显著性(t=4.23,P<0.01)。结论NGF可改善急性高眼压RGCs的营养状况,保护线粒体,上调Bcl-2/Bax比值,促进RGCs功能的恢复,减轻急性高眼压后视网膜神经节细胞的损伤。

Effects of NGF on optic nerves injured by acute ocular hypertension and its Bcl-2/Bax expression

Objective To observe in vitro the protective effect of nerve growth factor(NGF) on the retinal ganglion cells(RGCs) of rabbits injured by acute ocular hypertension. Methods Thirty healthy adult New Zealand white rabbits were randomly divided into five groups. An injury model was established in six rabbits in each group by forcing a perfusion of normal saline solution into the anterior chamber until the intraocular pressure(IOP) reached 50 mmHg and was sustained for 6 hours in one eye. The contralateral eye of each rabbit was used as a control. Three rabbits in each group were then treated daily with NGF 2000BU intramuscularly. The optic nerve and retina were surgically removed at five different time points (1st, 3rd, 7th, 15th and 30th day) after the operation, six rabbits for each point in time. With the HRP orthograde tracing technique and transmission electron microscopy, the effect of NGF on the optic nerve was observed by detecting the changes in the ultrastructure of the optic nerve. Results from the SABC method labeling of positive Bcl-2 and Bax RGCs were statistically analyzed to detect NGF's effect. Results Compared with the controls, the expression of the Bcl-2 gene protein had decreased and Bax was over-expressed three days after the operation. The ratio of Bcl-2/Bax decreased significantly (t=3.09, P<0.05). Swollen mitochondria were vacuolated. Compared with the experimental groups, the ratio of Bcl-2/Bax significantly increased (t=2.79, P<0.05) after using NGF for seven days and swelling was reduced in the mitochondria. There was less degeneration of mitochondria in the treated groups after fifteen days and some mitochondria recovered after using NGF for thirty days. Compared with the experimental groups, the ratio of Bcl-2/Bax markedly increased (t=4.23, P<0.01). Conclusion NGF can improve the nutriture of RGCs, protect the mitochondria and increase the ratio of Bcl-2/Bax. NGF might prompt the recovery of RGCs after optic nerve injury induced by acute ocular hypertension.