Protective effect of astragalus polysaccharides on retinal ganglion cell in acute ocular hypertension rat model / 中华实验眼科杂志

ABSTRACT

Background More efforts have been made in the functional protection of the glaucoma ganglion cells (RGCs) nowadays.As main ingredient,astragalus polysaccharides (APS) enhances neuron regeneration protein expression and promotes peripheral nerve recovery.But whether APS has a protecting effect on RGCs is incompletely clear.Objective The purpose of this study was to evaluate the neuroprotective effect of APS on the RGCs in a rat model of experimental glaucoma.Methods Forty-four SPF SD rats were divided into 4 groups randomly as followsnormal control group,negative control group,low dose APS group and high dose APS group,with 10 rats for each group.APS of 500 mg/kg or 2000 mg/kg (2.5 ml) was administered by gavage feeding once daily for 2 weeks in low dose or high dose of APS group,respectively,and the same volume of normal saline solution was applied instead of APS in the model control group.Two weeks later,aspirate 0.2 ml aqueous followed by methylcellulose injected into the anterior chamber to create the acute ocular hypertension model in the three groups above.No any intervention was performed in the normal control group.The rats were sacrificed on the fifth day after model established to take a retinal section.Ocular hypertension-induced damage was evaluated by regular retina histopathologic examination.Immunolhistochemistry for caspase-3 and TUNEL kits were used to determine the expression of caspase-3 protein in retina and apoptosis rate of RGCs.Retinal cross-sections were analyzed by Image Pro Plus 5.1 software to determine the thickness of various retinal layers and the positive staining cell density in the retinal ganglion cell layer (RGCL).Results On the fifth day after establishment of models,intraocular pressure (IOP) was significantly elevated in the model control group,low dose APS group and high dose APS group in comparison with the normal control group (t=-8.900,-10.700,-11.300,P＜0.01).Retinal morphology was normal in the rats of the normal control group,but in the model control group,rat retina was significantly thickened from severe retinal edema and cell arrangement disorder.Mild retinal abnormality was seen in the low dose APS group;while obvious retina edema was in high dose APS group.The entire retinal thickness,outer nuclear layer thickness and retinal nerve fiber thickness values were lower in the low dose APS group than those of model control group (t =-23.700,-14.770,-11.640,P＜0.01).However,no difference was found in outer nuclear layer thickness and retinal nerve fiber thickness values between high dose APS group and normal control group (t =-0.780,-0.460,P ＞ 0.05).Percentage of positive RGCs for caspase-3 protein and rate of apoptotic RGCs were significantly reduced in low dose APS group compared with model control group (caspase-3F=87.710,P=0.001;RGCs apoptosisF=272.840,P＜0.01).Conclusions 500 mg/kg APS can protect retina and RGCs against ocular hypertension-induced damage.The protection of APS is non-dosedependent.