Epidemiological studies suggested that diabetic patients are susceptible to develop cardiovascular complications along with having endothelial dysfunction. It has been suggested that methylglyoxal (MGO), a glycolytic metabolite, has more detrimental effects on endothelial dysfunction rather than glucose itself. Here, we investigated the molecular mechanism by which MGO induces endothelial dysfunction via the regulation of ER stress. Biochemical data showed that 4-PBA significantly inhibited MGO-induced protein cleavages of PARP-1 and caspase-3. In addition, it was found that high glucose induced endothelial apoptosis was enhanced in the presence of GLO1 inhibitor, suggesting the role of endogenous MGO in high glucose-induced endothelial dysfunction. MGO-induced endothelial apoptosis was significantly diminished by the depletion of CHOP with si-RNA against human CHOP, but not by SP600125, a specific inhibitor of JNK. The physiological relevance of this signaling pathway was demonstrated in CHOP deficiency mouse model, in which instillation of osmotic pump containing MGO led to aortic endothelial dysfunction. Notably, the aortic endothelial dysfunction response to MGO infusion was significantly improved in CHOP deficiency mice compared to littermate control. Taken together, these findings indicate that MGO specifically induces endothelial dysfunction in a CHOP dependent manner, suggesting the therapeutic potential of CHOP inhibition in diabetic cardiovascular complications. (C) 2016 Elsevier Inc. All rights reserved.