Identification of O-GlcNAcylation Modification in Diabetic Retinopathy and Crosstalk with Phosphorylation of STAT3 in Retina Vascular Endothelium Cells.

BACKGROUND/AIMS: Recently, we observed an increase in O-GlcNAc (O-linked-ß-N-acetylglucosamine) modification, and signal transducer and activator of transcription proteins 3 (STAT3) expression in primary retinal vascular endothelial cells (RVECs) under high glucose conditions and tissues altered by diabetic retinopathy (DR). In this study, we focused on the correlations between O-GlcNAcylation and STAT3 phosphorylation, and their potential effects with regards to DR.
METHODS: Expression of O-GlcNAcylation and STAT3 were detected in DR-affected tissues and primary RVECs. The relationship between O-GlcNAcylation and STAT3 was further delineated by immunoprecipitation and Western blot analysis. Effects of O-GlcNAcylation on human RVEC apoptosis and involved protein expression were assayed with flow cytometry and Western blot.
RESULTS: Global O-GlcNAcylation and pSTAT3 levels were significantly elevated in diabetic rat retina and primary RVECs under high glucose conditions. In vitro assays demonstrated that the Tyr705 site was sensitive to high glucose. While O-GlcNAcylation inhibited p727STAT3 expression, augmented O-GlcNAcylation could balance p705STAT3 expression within relatively high levels corresponding to vascular endothelial growth factor (VEGF) changes. Immunoprecipitation revealed that STAT3 was modified by O-GlcNAcylation and phosphorylation simultaneously. Next, we observed that overexpression of O-GlcNAcylation could relieve human RVEC apoptosis related to the JAK2-Tyr705STAT3-VEGF pathway.
CONCLUSION: O-GlcNAcylation could relieve RVECs apoptosis through the STAT3 pathway in DR, and O-GlcNAcylation combined with STAT3 phosphorylation might open up new insights into the mechanisms of DR and other diabetic complications.