The effect of pigment epithelium-derived factor on glutamate metabolism in diabetic rat retina

Abstract

Objective To observe the effect of pigment epithelium-derived factor(PEDF)on glutamate metabolism in diabetic rat retina.Methods 78 Sprague-Dawley rats were randomly divided into the model group,model control group,PEDF intervention group and intervention control group.There were some dead and euglycemia rats at the end of experiment,so only 12 rats in each group were included in the statistical analysis.The diabetic retinopathy rat model of the model,PEDF intervention and intervention control group were induced with streptozotocin injection.The rats in the model group were not intervened.The monthly-age matched normal rats of model group were in the model control group.The left eyes of rats were received intravitreal injection with 5μl(0.1μg/μl)PEDF(PEDF intervention group)or 5μlphosphate buffer solution(intervention control group).The expressions of L-glutamate/L-aspartate transporter in retina were analyzed by western blot and real time RT-PCR techniques and glutamate content in retina was analyzed by high-pressure liquid chromatography(HPLC).Cultured rat Mailer cells were divided into the control,experimental,PEDF intervention and intervention control group,GLAST expressions were detected by fluorescence immunofluorescence and real-time RT-PCR techniques.The glutamate up-take activity of Muller cells was determined by intracellular[3H] labeled D,L-glutamate concentration with scintillation counting.Results Western blot and real-time RT-PCR showed that GLAST expression decreased(real-time RT-PCR:t=8.86,P＜0.01;Western blot:t=3.42,P＜0.05).glutamate content increased(t=4.01,P＜0.05)in model group compared with the model control group:GLAST expression increased(real-time RT-PCR:t=3.56,P＜0.05;Western blot:t=3.52,P＜0.05),glutamate content decreased(y=4.36,P＜0.05)in the PEDF intervention group compared with the intervention control group.Real-time RT-PCR and fluorescence immunofluorescenee showed that high glucose down-regulate GLAST expressions in Muller cells(real-time RT-PCR:t=3.48,P＜0.05;fluorescence immunofluoreseence:t=4.72,P＜0.05)and impair glutamate up-take activity of Muller cells(t=3.81,P＜0.05).Under high glucose conditions,PEDF up-regulated GLAST expression significantly(real-time RT-PCR:t=6.82,P＜0.01;fluorescence immunofluorescence:t=3.72,P＜0.05)and ameliorated the glutamate up-take activitv of Mailer cells(t=4.14,P＜0.05).Conclusions In diabetic rats,PEDF may improve the activitv of GLAST in Muller cells,thus ameliorate retinal glutamate metabolism and inhibit death of retinal ganglion cells. Key words: Diabetic retinopathy/pathophysiology; Cytokines/physiology; Glutamic acid/metabolism; Diabetes mellitus,experimental