Damage In Retinal Epithelial Cells Research Articles

α1-Microglobulin Binds Illuminated Flavins and Has a Protective Effect Against Sublethal Riboflavin-Induced Damage in Retinal Epithelial Cells.

Riboflavin (vitamin B2) is an important constituent of the prosthetic groups flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), which are utilized as electron-carriers in energy metabolism. Excitation by UV-light leads to the generation of riboflavin radicals and reactive oxygen species (ROS), which can oxidize a wide range of biomolecules. The human protein α1-microglobulin (A1M) is a reductase and a radical scavenger, which can protect cells and matrix against oxidative damage. Here, we provide evidence of a molecular interaction between illuminated riboflavin and A1M, similar to the radical scavenging reactions previously seen between A1M and other organic radicals. Binding between riboflavin and A1M was demonstrated by gel migration shift, UV-absorbance and fluorescence spectrum analysis. The reaction between A1M and UV-light illuminated riboflavin involved covalent modification of A1M and proteolytic release of an N-terminal part of the protein. Furthermore, A1M also inhibited the ROS-induced photoreduction reaction of riboflavin, in a reaction involving the free thiol group in position C34. Finally, the results show a protective effect of A1M, analyzed by gene expression rates of stress genes, against sublethal damage in retinal epithelial cells in culture. Together, our results suggest a new role of A1M as a scavenger of riboflavin radicals and ROS produced during illumination of riboflavin.

Effect of leptin on the oxidative damage in human retinal pigment epithelial cells

Objective To investigate the effects of leptin on the oxidative damage in human retinal pigment epithelial (RPE) cells.Methods Human RPE cells (ARPE-19) were cultured in vitro,and randomly divided into control group and insulin resistance group.RPE cells were treated with 0,10,100 ng/mL leptin for 24,48,72 hours respectively.Then the levels of reactive oxygen species (ROS) expression in RPE cells were detected by 2',7'-dichlorofluorescin-diacetate (DCFH-DA),and the levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG) expression in RPE cells were observed by immunocytochemistry (ICC),and the levels of human 8-oxoguanine DNA glycosylase 1 (hOGG1) expression in lysate were measured by Western blot.Results After 24,48,72 hours,the level of ROS (Control group:F=37.136,37.178,49.634; P＜0.05.Insulin resistance group:F=9.822,28.881,71.150;P＜0.05),8-OHdG (Control group:F =88.643,390.920,1039.276; P ＜ 0.05.Insulin resistance group:F =273.311,299.155,82.237;P＜0.05) and hOGGl (Control group:F=470.062,1073.113,295.456;P＜0.05.Insulin resistance group:F =240.032,592.389,527.760 ; P＜0.05) expression increased significantly with the increase of leptin concentration in control group and insulin resistance group.Under the same leptin concentration,the level of 8-OHdG has a trend that it was higher in the insulin resistance group than the control group.After 24 hours,the difference of hOGGl expression between control group and insulin resistance group was not significant (F=23.392,P＞0.05).After 72 hours,the level of hOGGl expression was significantly higher in the insulin resistance group than the control group (F=129.394,P＜0.05).The level of hOGGl expression was significantly higher at 48 hours than that at 24 hours and 72 hours (P＜ 0.05).Conclusion Leptin could induce the oxidative damage of RPE cells in normal and insulin resistance status.With the increase of leptin concentration and time extended,the degree of oxidative damage and its repair were both increased.The degree of oxidative repair increased with the increase of leptin concentration,but decreased with time extended. Key words: Retinal pigment epithelium/injuries; Leptin/poisoning; Reactive oxygen species/poisoning

Hypoxia induces cell damage via oxidative stress in retinal epithelial cells

Retinal diseases (RD), including diabetic retinopathy, are among the most important eye diseases in industrialized countries. RD is characterized by abnormal angiogenesis associated with an increase in cell proliferation and apoptosis. Hypoxia could be one of the triggers of the pathogenic mechanism of this disease. A key regulatory component of the cell's hypoxia response system is hypoxia-inducible factor 1 alpha (HIF-1α). It has been demonstrated that the induction of HIF-1α expression can be also achieved in vitro by exposure with cobalt chloride (CoCl2), leading to an intracellular hypoxia-like state. In this study we have investigated the effects of CoCl2 on human retinal epithelium cells (hRPE), which are an integral part of the blood–retinal barrier, with the aim to determine the possible role of oxidative stress in chemical hypoxia-induced damage in retinal epithelial cells. Our data showed that CoCl2 treatment is able to induce HIF-1α expression, that parallels with the formation of reactive oxygen species (ROS) and the increase of lipid 8-isoprostanes and 4-hydroxynonenal (4-HNE) protein adducts levels. In addition we observed the activation of the redox-sensitive transcription factor nuclear factor-kappaB (NFkB) by CoCl2 which can explain the increased levels of vascular endothelial growth factor (VEGF). The increased number of dead cells seems to be related to an apoptotic process. Taken together these evidences suggest that oxidative stress induced by hypoxia might be involved in RD development through the stimulation of two key-events of RD such as neo-angiogenesis and apoptosis.