Effects of lycium barbarum polysaccharides on retinal pathological change and expression of VEGF in retina of diabetic rats / 中华实验眼科杂志

ABSTRACT

Background The primary pathological basis of diabetic retinopathy (DR) is new blood formation due to anoxia and inflammation,which results in breakdown of blood-retinal barrier (BRB).Vascular endothelial growth factor (VEGF) is a key factor promoting neovascularization.Researches determined that lycium barbarum polysaccharides (LBP) can protect cells against oxidative damage.However,the study of LBP in ophthalmology is lack.Objective This study was to investigate the effects of LBP on the dynamic pathological change of retinal vessels and expression of VEGF in retina of diabetic rats.Methods One hundred and seventeen SPF male SD rats were randomly divided into the normal control group,the diabetic mellitus (DM) group and the LBP group according to random number table.Type 1 DM models were induced by intraperitoneal injection of streptozotocin (STZ,55 mg/kg) in the rats of the DM group and the LBP group,and then 250 mg/kg LBP was intragastically administered in the rats of the LBP group.The morphological change of retinal vessels was dynamically observed by retinal stretched preparation with Evans blue (EB) in 4,10 and 16 weeks after modeling.E B (45 mg/kg) was slowly injection via jugular vein,and 1％ polyoxymethylene was infused into the left ventricule.The eyeballs were extracted and retina were isolated.EB content in the retinas (mg/g) was calculated using retinal stretched preparation method at the time points mentioned above.Expressions of VEGF protein and mRNA in the retinas were detected by immunohistochemistry and real-time quantitative PCR at various time points,respectively.Results Retinal stretched preparation with EB exhibited that the abnormal degree in the shape,diameter of vessels and leakage of the retinal blood vessels were significantly slighter in the LBP group than those of the DM group in 4,10,16 weeks after modeling.At 4,10,16 weeks,EB content in the retinas was (12.17±1.55),(16.46±1.60) and (19.55±1.49) mg/g,which was significantly lower than (15.76± 1.90),(21.61 ±2.05) and (26.30±2.28) mg/g of the DM group (P＜0.05).Immunochemistry showed that the expression of VEGF protein primarily located at retinal ganglion cells (RGCs) layer.The staining intensity for VEGF protein was weaker in the LBP group than that of the DM group.The expression levels of VEGF protein (A value) in the LBP group were 0.234±0.011,0.331±0.023 and 0.536±0.031at various time points,with significant decline in comparison with 0.281±0.018,0.533±0.055 and 0.765±0.075 of the DM group (all at P＜0.05).Real-time quantitative PCR revealed that the expression levels of VEGF mRNA were 0.157±0.013,0.505 ±0.114 and 1.577±0.074 in the LBP group at various time points,which were significantly lower than 0.235±0.209,1.043±0.084 and 2.446±0.061 of the DM group (all at P＜0.05).Conclusions LBP can alleviate the DM-induced retinal vasculopathy,lessen the leakage of vessels well,and further protect the BRB.