Methylglyoxal and high glucose inhibit VEGFR2 phosphorylation at specific tyrosine residues.

Diabetes is characterized by hyperglycemia and a significant risk of vascular complications. Vascular endothelial growth factor (VEGF) and its main receptor VEGFR2 (KDR), which is highly expressed in vascular endothelial cells, are essential mediators of vascular maintenance and angiogenesis. During glycolysis after high calorie food intake, methylglyoxal (MGO) is formed and MGO blood levels are elevated in diabetes. MGO reacts with arginine residues to generate MG-H1 or with lysine residues to carboxyethyl lysine which are common components of advanced glycation end-products. Therefore, the question arises whether hyperglycemic conditions affect VEGF signaling via a ligand-independent direct modification of signaling components. As a first step, the effect of MGO on VEGFR2 activation was investigated in cultured endothelial cells from human umbilical vein by determination of VEGFR2 phosphorylation at selected tyrosine residues by ELISA and immunoblotting using phospho-specific antibodies. Phosphorylation of VEGFR2-Y996, VEGFR2-Y1054, or VEGFR2-Y1175 reached a maximum 5 min after stimulation of endothelial cells with VEGF. Phosphorylation was significantly inhibited by 100 µM MGO and to a lesser extent by high glucose treatment. 2,3-Pentanedione and glyoxal were investigated for comparison. In summary, VEGFR2 phosphorylation is sensitive to MGO or high glucose concentrations which may be relevant in the pathophysiology of microvascular disease in diabetes.