Effects of melatonin on retinal oxidative stress in short-term diabetic retina / 中华实验眼科杂志

ABSTRACT

Background Oxidative stress is one of the pathogenesis mechanisms of diabetic complications.Melatonin is the most powerful antioxidant in living organism.Seldom study on the effects of melatonin on diabetic complications is found in China now.Objective This study aimed to detect the expression and alteration of malonadehyde(MDA),glutathione(GSH)and glial fibrillary acidic protein(GFAP)in retina with experimental diabetes and explore the effects of melatonin on retinal oxidative stress in diabetic rats. Methods The animal models of diabetes were established by injection of 2％ streptozocin via caudal vein(STZ,45 mS/kg)in 48 6-week-old clean SD rats.Isometric citric acid buffer solution wag injected in 24 normal.rats as control group.Seven days after injection of STZ,melatonin(10 mg/kg)was injected into the abdominal cavity of 24 diabetic rats in melatonin group dailv,and the equal volume of normal saline was injected in other 24 diabetic rats(model rats)and 24 rats in normal control group.The animals were sacrificed and retinas were obtained in three groups in 4,6 and 8 weeks respectively.Immunohistochemistry and Western blot were used to detect the expression of GFAP in rat retina.The levels of MDA and GSH in retina homogenate were assayed by spectrophotometer.This experiment complied the Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.Results The expression of GSH in model group was lower than that in melatonin group or control group at 4,6 and 8 weeks (all P<0.05).However,no statistically significant difference was seen in the expression level of GSH between melatonin group and normal control group at 4 and 6 weeks(P>0.05),and in the eighth week,expression of GSH in melatonin group was lower than that in control group(P<0.05).The expressions of MDA and GFAP were more prominent in the model group than in melatonin group and control group in 4,6 and 8 weeks(P<0.05),but no significant difference was found between melatonin group and control group at 4 and 6 weeks(P>0.05).The expressions of MDA and GFAP in melatonin group were higher than those in control group at 8 weeks(P<0.05).Conclusion Melatonin plays a powerful effect in protecting the retina from oxidative stress in diabetes retina by downregulating the MDA level,upregulating GSH level and inhibiting GFAP expression.