Abstract
Purpose: :
Progression of diabetic retinopathy may be mediated by the presence of specific reactive metabolites such as Advanced Glycation End products that accumulate due to high glucose concentration. Accumulation of AGE causes retinal endothelial cell dysfunction by impairing the barrier functions. However the direct effect of AGE-BSA on glucose uptake has not been reported. The deleterious effects of AGEs on diabetic retinopathy are reported to be at least in part, due to inhibition of PEDF and VEGF mediated BREC proliferation. Therefore, the aim of our study was to determine the effect of AGE-BSA on glucose uptake in BREC and determine the VEGF and PEDF levels
Methods: :
BREC was isolated from bovine retinal capillary using CD31 coated dynabeads and cultured in endothelium specific media. (Endopan) BREC was characterized using Von Willebrand factor and VE-Cadherin as cell specific markers. AGE-BSA was prepared by the method of Hammes et al. BREC (1500cells) were grown in gelatin coated petridishes (till 50% confluence) and exposed to either 100µg/ml of AGE-BSA, BSA (100µg/ml) alone, or control for 6 days. Modified method of Hirohito et al using radio labeled U14Cglucose was used for glucose uptake. Immunohistochemical localization of VEGF and PEDF was also done.
Results: :
There was a significant 2.5 fold increase in the glucose uptake in AGE-BSA exposed cells on the 6th day when compared to control (n=3,p=0.017). VEGF expression was seen only on the 6th day on AGE exposed endothelial cells along with decreased levels of PEDF. In contrast VEGF expression in control and BSA treated cells was absent. PEDF expression was decreased in BREC treated with AGE relative to control.
Conclusions: :
AGE is reported to up regulate VEGF through its interaction with RAGE leading to endothelial cell proliferation. This study is the first to show a significant increase in glucose uptake in BREC after exposure to AGE-BSA This data is consistent with the endothelial cell proliferation observed in diabetic retinopathy.
Keywords: diabetic retinopathy • growth factors/growth factor receptors • proliferation