Department of Pharmacology & Toxicology, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia.
Department of Biochemistry, Faculty of Sciences, King Abdulaziz University, Jeddah, Saudi Arabia.
Biochem Biophys Res Commun. 2018 Dec 2;506(4):1013-1018. doi: 10.1016/j.bbrc.2018.10.171. Epub 2018 Nov 4.
Advanced glycation end-products (AGEs) play a pivotal role in macro- and micro-vascular diabetic complications. We investigated the mechanism by which methylglyoxal (an endogenous generator of AGEs) affects vascular contractility using the isolated artery technique. Contractile responses to vasoconstrictors phenylephrine (PE), angiotensin II (Ang II), vasopressin (VP) and KCl were measured in the isolated rat aorta following one-our exposure to methylglyoxal (50-200 μM). The perfused rat kidney was employed to confirm the effect of methylglyoxal on microvessels. Methylglyoxal-induced changes in cytosolic calcium were measured in the smooth muscle layer of the aorta with the calcium-sensing fluorophore Fluo-4 AM. Methylglyoxal significantly increased maximal contraction of the rat aorta to PE, Ang II and VP. Similar results were seen in response to the depolarizing vasoconstrictor KCl in macro and micro vessels. The methylglyoxal-induced increases in aortic contraction mediated by the agonist and KCl were endothelium independent. Methylglyoxal-induced increases in KCl-dependent aortic contraction were abolished after the removal of extracellular calcium or in the presence of the calcium channel blocker nifedipine. Incubation with the antioxidant N-acetyl-l-cysteine (NAC), apocynin (a nonselective NADPH oxidase (NOX) inhibitor) or chelerythrine (a protein kinase C (PKC) inhibitor) prior to methylglyoxal pre-treatment reversed the methylglyoxal-induced increases in the rat aortic contractility. In conclusion, the formation of AGEs increases vasoconstriction of both macro- and micro-vessels by increasing the voltage-activated calcium entry in vascular smooth muscles in a NOX and PKC dependent manner.
晚期糖基化终产物（AGEs）在大血管和微血管糖尿病并发症中起关键作用。我们使用离体动脉技术研究了甲基乙二醛（AGEs 的内源性生成物）影响血管收缩性的机制。在离体大鼠主动脉中，将其暴露于甲基乙二醛（50-200μM）1 小时后，测量血管收缩剂苯肾上腺素（PE）、血管紧张素 II（Ang II）、血管加压素（VP）和 KCl 引起的收缩反应。使用灌注大鼠肾脏来确认甲基乙二醛对微血管的影响。使用钙敏荧光染料 Fluo-4 AM 测量主动脉平滑肌层中甲基乙二醛引起的细胞浆钙离子变化。甲基乙二醛显著增加了大鼠主动脉对 PE、Ang II 和 VP 的最大收缩。在大血管和微血管中，对去极化血管收缩剂 KCl 的反应也观察到了类似的结果。激动剂和 KCl 介导的主动脉收缩增加与甲基乙二醛诱导的主动脉收缩增加是内皮细胞独立的。在去除细胞外钙或存在钙通道阻滞剂硝苯地平的情况下，甲基乙二醛诱导的 KCl 依赖性主动脉收缩增加被消除。在用抗氧化剂 N-乙酰-L-半胱氨酸（NAC）、阿朴肉桂醇（一种非选择性 NADPH 氧化酶（NOX）抑制剂）或Chelerythrine（一种蛋白激酶 C（PKC）抑制剂）孵育之前，用甲基乙二醛预处理可以逆转甲基乙二醛引起的大鼠主动脉收缩性增加。总之，AGEs 的形成通过增加血管平滑肌中电压激活的钙内流，以 NOX 和 PKC 依赖性方式增加了大血管和微血管的血管收缩。
