ABSTRACT
Diabetic retinopathy is a common complication of diabetes mellitus (DM). The oxidative damage inflicted on retinal pigment epithelial (RPE) cells by high glucose closely approximates the molecular basis for the loss of vision associated with this disease. We investigate a novel algae-derived polysaccharide compound for its role in protecting ARPE-19 cells from high glucose-induced oxidative damage. ARPE-19 cells were cultured for 4 d with normal concentration of D-glucose, and exposed to either normal or high concentrations of D-glucose in the presence or absence of the polysaccharide compound at variety of concentrations for another 48 h. Taurine was used as a positive control. Activity of super oxide dismutase (SOD) and concentration of glutathione (GSH) were measured as well as cytotoxicity of high glucose and the polysaccharide compound. To analyse cellular damage by high glucose, activation of Annexin V and p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) were examined. Our results showed that a significant cellular damage on ARPE-19 cells after 48 h treatment with high glucose, accompanied by a decrease in SOD activity and GSH concentration; high glucose also caused ARPE-19 cell apoptosis and activation of p38MAPK and ERK. As the non-toxic polysaccharide compound protected ARPE-19 cells from high glucose-induced cellular damage, the compound recovered SOD activity and concentration of GSH in the cells. The compound also abrogated the cell apoptosis and activation of p38MAPK and ERK. Therefore, the polysaccharide compound derived from algae extracts could be unique candidate for a new class of anti-DM and anti-oxidative damage.
Subject(s)
Antioxidants/pharmacology , Diabetic Retinopathy/metabolism , Glucose/adverse effects , Oxidative Stress/drug effects , Phaeophyceae/chemistry , Polysaccharides/pharmacology , Retinal Pigment Epithelium/drug effects , Antioxidants/metabolism , Apoptosis/drug effects , Cell Line , Diabetic Retinopathy/chemically induced , Enzyme Activation/drug effects , Epithelial Cells/drug effects , Epithelial Cells/metabolism , Extracellular Signal-Regulated MAP Kinases/metabolism , Glutathione/metabolism , Humans , Phytotherapy , Plant Extracts/pharmacology , Retinal Pigment Epithelium/cytology , Retinal Pigment Epithelium/metabolism , Superoxide Dismutase/metabolism , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
The aim of this study was to investigate the change of Integrin-linked kinase (ILK) expression of human retinal pigment epithelium (RPE) cells in response to high glucose, and the effect of targeting ILK with small interference RNA (siRNA) on the high glucose-induced expression of vascular endothelial growth factor (VEGF) and intercellular adhesion molecule-1 (ICAM-1). The ILK mRNA and protein expression in human RPE cells were analyzed with RT-PCR and western blot after exposure to 5.5, 30, 40, 50 mM glucose, or 5.5 mM glucose+45.5 mM mannitol for 48 h. The expression of VEGF and ICAM-1 was also determined. Cells were treated with ILK siRNA, to determine the effect of ILK on VEGF and ICAM-1 expression following treatment with high glucose. High concentrations of glucose significantly up-regulated ILK mRNA and protein expression, and the ILK expression increased along with the glucose concentration. The changes of VEGF and ICAM-1 expression were similar to that of ILK expression. Knocking down ILK gene expression with siRNA inhibited the elevation of VEGF and ICAM-1 induced by high glucose treatment. These results suggested that ILK was involved in the response of RPE cells to high glucose and may therefore play a role in the pathogenesis of diabetic ophthalmology.
Subject(s)
Gene Expression Regulation/genetics , Glucose/pharmacology , Intercellular Adhesion Molecule-1/metabolism , Protein Serine-Threonine Kinases/metabolism , Retinal Pigment Epithelium/metabolism , Vascular Endothelial Growth Factor A/metabolism , Analysis of Variance , Blotting, Western , Cells, Cultured , DNA Primers/genetics , Dose-Response Relationship, Drug , Gene Expression Regulation/drug effects , Gene Knockout Techniques , Glucose/administration & dosage , Humans , Protein Serine-Threonine Kinases/genetics , RNA, Small Interfering/genetics , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
We prepared two series of polysaccharide compounds derived from algae extracts and investigated their stimulatory activity on insulin secretion in vitro using the rat pancreatic cell line, RIN-5F. Several of the compounds exhibited significant stimulatory activity in a dose-dependent manner without apparent cytotoxicity at concentrations above 10 microM. Glybenclamide, a commonly prescribed sulfonylurea (SU) against diabetes mellitus type II, was used as a positive control and showed moderate cytotoxicity in the cell culture assay system. Amylin (IAPP; islet amyloid polypeptide), an inhibitor for glybenclamide, did not inhibit the activity of the isolated compounds, suggesting that they act through a mechanism(s) different from glybenclamide. Algae-derived extracts could be candidates for a new class of anti-diabetic drugs.
