ABSTRACT
Background Oxydative stress is an important pathogenesis of age-related macular degeneration.Resent evidences indicate that docosahexaenoic acid (DHA) plays an important role during the development of retinal photoreceptor cells and protect the cells against oxydative stress by inducing the expression of heme oxygenase-1 (HO-1).However,whether DHA can induce the expression of HO-1 in human retinal pigment epithelium (RPE) cells is unelucidated.Objective This study was to investigate the effect of DHA on the expression of HO-1 in RPE cells and its molecular mechanism.Methods Human RPE cell line ARPE-19 was cultured in vitro and treated with 30,50,100 and 120 μmol/L DHA for 4 to 24 hours,respectively,and the cells were cultured without DHA as the control group.The cytotoxicity of DHA was detected by lactate dehydrogenase(LDH),and the expression of HO-1 mRNA and protein were detected by real-time PCR and Western blot assay,respectively.The enzymatic activity of HO-1 was detected by colorimetry.The reactive oxygen species (ROS) proportion in the cells was detected using fluorescence probe H2 DCFDA,and immunofluorescence technology was adopted to detect the nuclear translocation of nuclear facotor-E2-related factor 2 (Nrf2).The expression of Nrt2 protein in the cells was detected by Western blot after intervention of ROS inhibitor N-acetylcysteine (NAC) and transfection of Nrf2 small interfering RNA (siRNA).Results The LDH leakage rate was significantly different after 0,3,50,100 and 120 μmol/L DHA treated the cells for 24 hours (F=8.14,P＜0.05),and the LDH leakage rate in the 120 μmol/L DHA group was significantly higher than that of 0,30,50 and 100 μmol/L DHA group (all at P＜0.05).The relative expression levels of HO-1 mRNA and HO-1 protein or HO-1 enzymatic activity in the cells were significantly different among different concentrations of DHA group in 8 hours after treatment (F=16.24,P＜0.05;F=11.34,P＜0.05;F=11.81,P＜0.05),and the expressions of these factors were considerably higher in the 30,50 and 100 μ mol/L DHA group than those in the 0 μmol/L DHA group (all at P＜0.05).The ROS relative fluorescence intensity and nuclear Nrf2 positive cells proportion were statistically significant among different concentrations of DHA groups (F =11.08,P ＜ 0.05;F=16.42,P＜0.05),and the ROS relative fluorescence intensity and nuclear Nrf2 positive cells proportion were evidently higher in the 30,50 and 100 μmol/L DHA group than those in the 0 μmol/L DHA group (all at P＜0.05).The relative expression levels of HO-1 protein and the proportion of nuclear Nrf2 positive cells were significantly lower in the NAC pretreated 100 μmol/L DHA group than those in the 100 μmol/L DHA group.In addition,the HO-1 relative expression level and the positive cells proportion of nuclear Nrf2 were significantly lower in the of Nrf2 siRNA transfection group than those in the blank siRNA transfection group (both at P＜0.05).Conclusions DHA with concentration below 100 μ mol/L can protect RPE cells from oxidative stress by inducting the expression of HO-1 in the cells via ROS/Nrf2 pathway.
ABSTRACT
Background Oxidative stress is a main cause of age-related macular degeneration (AMD).Lutein has a preventive role for AMD, but its antioxidant mechanism remains unclear.Objective Present study was to investigate the effect of lutein on oxidative stress of Müller cells and its signaling pathway.Methods Human Müller cells (human Müller cell strain) were cultured, and the cells at logarithmimic growth phase were incubated in 96 well plate overnightly.Oxidative stress cell models were established by adding 160 μmol/L H2O2, a median lethal dose for Müller cells.The models were divided into the model control group and 12.5,25.0,50.0 mg/L lutein groups,and the different concentrations of lutein were used to culture the cells for 24 hours, respectively.The routine cultured cells served as the blank control group.Growth of the cells was assayed by MTT method (absorbancy);the reactive oxygen species (ROS) content in the cells was assayed by flow cytometry;the mRNA and protein levels of nuclear factor-E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) in the cells were detected by quantitative real-time PCR and Western blot, respectively.Results The inhibitory effects on the cells were gradually enhanced with the increase of H2O2 concentrations,showing a significant difference among the groups (F =43.890,P＜0.01).A significant difference was found in apoptotic rate of the cells among the blank control group,model control group and 12.5,25.0,50.0 mg/L lutein groups (F =346.770, P =0.000) , and the apoptosis rate was significant elevated with the increase of lutein dose (all at P＜0.05).The ROS contents in the cells were 1.92±0.18,64.89±2.86,52.70±2.80,32.61 ±4.20 and 5.68 ± 1.35 in the blank control group, model control group and 12.5,25.0,50.0 mg/L group, respectively, with significant difference among the groups (F =324.900, P =0.000), and the ROS content was gradually reduced as the increase of lutein dose (all at P＜0.05).The relative mRNA and protein expressions of Nrf2 and HO-1 were remarkedly higher in the 12.5,25.0,50.0 mg/L lutein groups than those in the model control group (F =236.960,242.620,186.830,263.120, all at P =0.000) , and no significant difference was seen in the relative expression level of nuclear Nrf2 protein among the groups (F =1.790, P =0.210).Conclusions Lutein can induce the expression of antioxidant enzymes by inducing the expression of nuclear translocation of Nrf2 and consequently inhibit the oxidative stress status.