The Effects of High Glucose on Paraquat-induced Cell Injury in Human Retinal Pigment Epithelial Cells

ABSTRACT

PURPOSE: Functional and structural alterations of retinal pigment epithelial cells were observed in experimental and clinical diabetes. To investigate the effects of high glucose on free radical-induced injury in retinal pigment epithelial cells, we determined the effects of high glucose on activities of antioxidant enzymes and paraquat-induced cytotoxicity in cultured human retinal pigment epithelial (HRPE) cells. METHODS: Human retinal pigment epithelial (HRPE) cell line (ATCCCRL-2302) was cultured with high glucose (22.4 mM)-and normoglucose (5.6 mM)-contained DMEM for 3 days. The activities of superoxide dismutase (SOD), catalase and GSHPx were assayed by Crapo's method, Aebi's method and GUnzler's method, respectively. Paraquat-induced cytotoxicity was determined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) method. RESULTS: CuZn-SOD activity of HRPE cells was decreased by 32% in high glucose (25.4 mM) media compared to normoglucose (5.6 mM) media. But the activities of catalase and GSHPx were not changed by high glucose. The paraquat-induced HRPE cells toxicity was increased by high glucose. Diethydithiocarbamate (DDC), as inhibitor of CuZn-SOD, also potentiated paraquat-induced HRPE cell CONCLUSIONS: Paraquat-induced HEPE cells injury was potentiated by high glucose and decreased CuZn-SOD activity by high glucose may be some roles in free radical-induced HRPE cell injury.