Eye Center, Medical Center, Medical Faculty, University of Freiburg, Freiburg, Germany.
Z Naturforsch C J Biosci. 2022 Jun 29;77(11-12):493-500. doi: 10.1515/znc-2022-0033. Print 2022 Nov 25.
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.
糖尿病的特征是高血糖和血管并发症的高风险。血管内皮生长因子 (VEGF) 及其主要受体 VEGFR2（KDR）在血管内皮细胞中高度表达，是血管维持和血管生成的重要介质。在高热量食物摄入后的糖酵解过程中，会形成甲基乙二醛 (MGO)，并且糖尿病患者的 MGO 血液水平升高。MGO 与精氨酸残基反应生成 MG-H1，或与赖氨酸残基反应生成羧乙基赖氨酸，它们都是晚期糖基化终产物的常见成分。因此，问题是高血糖条件是否会通过信号转导成分的非配体依赖性直接修饰来影响 VEGF 信号转导。作为第一步，通过 ELISA 测定 VEGF 刺激培养的人脐静脉内皮细胞中选定的酪氨酸残基处的 VEGFR2 磷酸化，并用磷酸化特异性抗体通过免疫印迹来研究 MGO 对 VEGFR2 激活的影响。VEGFR2-Y996、VEGFR2-Y1054 或 VEGFR2-Y1175 的磷酸化在 VEGF 刺激内皮细胞后 5 分钟达到最大值。100 µM MGO 和高葡萄糖处理显著抑制磷酸化，而 2,3-戊二酮和乙二醛的抑制作用较小。总之，VEGFR2 磷酸化对 MGO 或高葡萄糖浓度敏感，这可能与糖尿病中小血管疾病的病理生理学有关。
