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ABSTRACT
Objective To investigate the effect of intravitreal injection of 7, 8-dihydroxyflavone (DHF) on N-methyl-D-aspartate (NMDA)-induced apoptosis of retinal ganglion cells (RGCs).
Methods A total of 138 male Sprague-Dawley rats aged 6-8 weeks were randomly divided into normal control group (30 rats), model control group (36 rats), DHF treatment group (36 rats), and brain-derived neurotrophic factor (BDNF) control group (36 rats) using the random number table method, which received intravitreal injections of 5 μl 0.1 mmol/L phosphate buffered saline, 10 mmol/L NMDA, 10 mmol/L NMDA+ 100 mmol/L DHF, and 10 mmol/L NMDA+ 100 mmol/L BDNF, according to the group.The right eye was taken as the experimental eye.At 12 hours, 1 day, 3 days, 7 days, 14 days, and 28 days after modeling, RGCs were observed and counted by immunofluorescence staining.The apoptosis rate of peripapillary cells was assessed by TUNEL staining.At 12 hours, 3 days, 14 days, and 28 days after treatment, the expression of caspase-3, B-cell lymphoma-2 (bcl-2), bcl-2 associated X protein (bax), and tyrosine kinase receptor B (TrkB) were detected by real-time quantitative fluorescence PCR.The use and feeding of experimental animals in this study followed the Regulations on the Management of Laboratory Animals issued by the Ministry of Science and Technology.This research protocol was reviewed and approved by the Medical Ethics Committee of Southwest Jiaotong University (No.SWJTU-2303-NSFC[066]).
Results The RGCs count and the apoptosis rates in the normal control group, DHF treatment group, and BDNF control group were significantly higher than those in the model control group at each time point after treatment (all P<0.05).There was no significant difference in the apoptosis rate of peripapillary cells between the DHF treatment group and the BDNF control group at different time points after treatment (all P>0.05).Compared with the model control group, the TrkB mRNA expressions were significantly increased in the DHF treatment group at 12 hours, 3 days, and 14 days after treatment and in the BDNF control group at 3, 14, and 28 days after treatment (all P<0.05).At 12 hours and 3 days after treatment, the expression of caspase-3 mRNA was significantly decreased in the DHF treatment group and BDNF control group compared with the model control group (all P<0.05).At 12 hours after treatment, the relative expressions of bax and bcl-2 mRNA were significantly higher in the DHF treatment group than in the normal control group (both P<0.05).Compared with normal control group, the relative expression of bax mRNA at 14 days after treatment and the relative expression of bcl-2 mRNA in the BDNF control group were significantly increased at 12 hours and 3 days (all P<0.05).
Conclusions Intravitreal injection of DHF effectively alleviates NMDA-induced RGCs damage in the rat model.Its neuroprotective mechanism may be achieved by promoting TrkB expression and inhibiting related apoptotic factors.