High glucose attenuates protein S-nitrosylation in endothelial cells: role of oxidative stress

Abstract

Objective: Hyperglycemia-induced endothelial dysfunction, via a defect of nitric oxide (NO) bioactivity and overproduction of superoxide, is regarded as one of the most significant events contributing to the vascular lesions associated with diabetes mellitus. However, the mechanisms underlying such hyperglycemic injury remain undefined. We hypothesized that alterations in cellular protein S-nitrosylation may contribute to hyperglycemia-induced endothelial dysfunction.

Research Design and Methods: We exposed endothelial cells to high glucose in the presence and absence of reactive oxygen species inhibitors and used the biotin switch assay to analyze the alteration in the global pattern of protein S-nitrosylation, compared to cells cultured under normal glucose conditions. We identified endogenous S-nitrosylated proteins by mass spectrometry and/or immunoblotting with specific antibodies.

Results: High glucose treatment induced a significant reduction of endogenous S-nitrosylated proteins that include eNOS, β-actin, vinculin, diacylglycerol kinase α, GRP78, ERK-1 and transcription factor NF-κB. Interestingly, these changes were completely reversed by inhibition of superoxide production, suggesting a key role for oxidative stress in the regulation of S-nitrosylation under hyerglycemic conditions. In addition, we found that in parallel with the restoration of decreased S-nitrosylation of NF-κB, high glucose-induced NF-κB activation was blocked by the superoxide inhibitors.

Conclusions: The alterations in protein S-nitrosylation may underlie the adverse effect of hyperglycemia on the vasculature, such as endothelial dysfunction and the development of diabetic vascular complications.