The effect of intermittent high glucose on oxidative stress in human retinal pigment epithelial cells

Abstract

Objective To compare the effects of intermittent and constant high glucose on oxidative stress and inflammatory injury in human retinal pigment epithelial cells (HRPE).Methods HRPE cells were caltured and randomly divided into 4 groups:normal glucose control group (5.5 mmol/L of glucose,NG group),consistent high glucose group (33.0 mmol/L of glucose,HG group),intermittent high glucose group (33.0 mmol/l of glucose for 3 hours,at an interval of two hours of 5.5 mmol/Lof glucose; Such intermittent exposure was repeated 3 times a day and the cells were exposed to 33.0 mmol/L of glucose in the night,IHG group) and high mannitol group (33.0 mmol/L of mannitol,MG group).Each group had 6 duplicate vials.Samples were cultured in incubator of 37℃,5％ CO2,and the activity of total superoxide (T-SOD) and the levels of malondialdehyde,and glutathione (GSH) in supernatant were assayed using chromatometry in 24 hours,48 hours,and 72 hours.Results (1) The activity of T-SOD,GSH and malonaldehyde(MDA) in the HG were (12.1 ±3.0) U/ml,(68.5 ±3.8) mg/L and (17.5 ±3.0) μmol/L respectively,in IHG groups were (21.8 ± 1.6) U/ml,(90.8 ±4.8) mg/L and (12.9 ± 1.2) μmol/L respectively,in control group were (31.1 ± ±4.7) U/ml,(143.4 ± 8.3) mg/L and (3.1 ± 1.1) μmol/L respectively,in MG group were (32.4 ± 2.8) U/ml,(143.3 ± 12.8) mg/L and (2.8 ± 1.2) μmol/L respectively.(2) When cells were cultured for 48 hours,the levels of T-SOD,GSH and MDA in the IHG,HG,NG,and MG groups were (9.6 ± 1.8) U/ml,(72.5 ±4.3) mg/L,(19.1 ±1.7) μmol/L;(21.0±2.5) U/ml,(93.4 ±4.6) mg/L,(11.6±2.2) μmol/L;(31.0±2.5) U/ml,(145.5±6.6) mg/L,(3.9±1.0) μmol/L;(28.4±0.8) U/ml,(142.0±4.9) mg/L,and (2.9 ± 0.8) μmol/L respectively.(3) When cells were cultured for 72 hours,the levels of T-SOD,GSH and MDA in the IHG,HG,NG,and MG groups were (10.9 ± 1.7) U/ml,(70.9 ±7.3) mg/L,(19.5 ±0.5)μmol/L;(20.4± 1.7) U/ml,(91.6±7.2) mg/L,(11.2±3.3) μmol/L;(32.4±4.4) U/ml,(143.0 ± ±23.2) mg/L,(3.0±1.0) μmol/L;(29.5 ±2.6) U/ml,(134.5 ±11.1) mg/L,and (2.8 ±0.8) μmol/L respectively.(4) Compared with control group,the activity of T-SOD and the levels of GSH and MDA in IHG,HG group were significantly different after culture for 24 h,48 h,and 72 h (P ＜ 0.01).There was significant difference between the IHG group and the HG group in terms of the activity of T-SOD and the levels of GSH and MDA (P ＜ 0.01).The activity of T-SOD and the levels of GSH and MDA of the MG group were significant different from IHG and the HG groups (P ＜0.01).But no significant difference was seen in the NG group (P ＞ 0.05).Conclusion Intermittent high glucose causes a more significant damage in terms of oxidate stress and inflammatory injury to HRPE cells than that of consistent high glucose. Key words: Intermittent high glucose; Human retinal pigment epithelial cell; Oxidative stress