trans-Resveratrol Inhibits Hyperglycemia-Induced Inflammation and Connexin Downregulation in Retinal Pigment Epithelial Cells

The purpose of this study was to determine the inhibitory activity of trans-resveratrol against hyperglycemia-induced inflammation and degradation of gap junction intercellular communication in retinal pigment epithelial cells. Retinal (ARPE-19) cells were incubated with 5.5 mM glucose, 5.5 mM glucose and 10 mu M resveratrol, 33 mM glucose, or 33 mM glucose and 0-10 mu M transresveratrol at 37 degrees C and 5% CO2 for 9 days. Cell viability was determined by the crystal violet assay. The levels of low-grade inflammation biomarkers interleukin-6 and interleukin-8 (IL-6 and IL-8), angiogenic factors, and vascular endothelial growth factor (VEGF) were determined by the enzyme-linked immunosorbent assay (ELISA). Gap junction intercellular communication (GJIC) was determined by the scrape-load/dye transfer method. The expression levels of protein kinase C beta (PKC beta), connexin 43 (Cx43), transforming growth factor-beta 1 (TGF-beta 1), and cyclooxygenase-2 (COX-2) were determined by Western blot. Incubation of retinal cells with 10 mu M trans-resveratrol in the presence of 5.5 mM glucose did not affect any of the biomarkers investigated. Incubation of ARPE-19 cells with 33 mM glucose for 9 days significantly induced the accumulation of VEGF, IL-6, IL-8, TGF-beta, and COX-2, activation of PKC beta, and reduction of Cx43 and GJIC. Incubation of ARPE-19 cells with 33 mM glucose in the presence of 0-10 mu M trans-resveratrol dose-dependently inhibited VEGF, TGF-beta 1, COX-2, IL-6, and IL-8 accumulation, PKC beta activation, and Cx43 degradation and enhanced GJIC. These data suggest that trans-resveratrol can protect the retinal pigment epithelial cells against hyperglycemia-induced low-grade inflammation and GJIC degradation.