Institut für Kardiovaskuläre Physiologie, Goethe-Universität, Frankfurt, Germany.
Hypertension. 2013 Jul;62(1):140-6. doi: 10.1161/HYPERTENSIONAHA.113.01314. Epub 2013 May 13.
Monoamine oxidases (MAOs) generate H(2)O(2) as a by-product of their catalytic cycle. Whether MAOs are mediators of endothelial dysfunction is unknown and was determined here in the angiotensin II and lipopolysaccharide-models of vascular dysfunction in mice. Quantitative real-time polymerase chain reaction revealed that mouse aortas contain enzymes involved in catecholamine generation and MAO-A and MAO-B mRNA. MAO-A and -B proteins could be detected by Western blot not only in mouse aortas but also in human umbilical vein endothelial cells. Ex vivo incubation of mouse aorta with recombinant MAO-A increased H(2)O(2) formation and induced endothelial dysfunction that was attenuated by polyethylene glycol-catalase and MAO inhibitors. In vivo lipopolysaccharide (8 mg/kg IP overnight) or angiotensin II (1 mg/kg per day, 2 weeks, minipump) treatment induced vascular MAO-A and -B expressions and resulted in attenuated endothelium-dependent relaxation of the aorta in response to acetylcholine. MAO inhibitors reduced the lipopolysaccharide- and angiotensin II-induced aortic reactive oxygen species formation by 50% (ferrous oxidation xylenol orange assay) and partially normalized endothelium-dependent relaxation. MAO-A and MAO-B inhibitors had an additive effect; combined application completely restored endothelium-dependent relaxation. To determine how MAO-dependent H(2)O(2) formation induces endothelial dysfunction, cyclic GMP was measured. Histamine stimulation of human umbilical vein endothelial cells to activate endothelial NO synthase resulted in an increase in cyclic GMP, which was almost abrogated by MAO-A exposure. MAO inhibition prevented this effect, suggesting that MAO-induced H(2)O(2) formation is sufficient to attenuate endothelial NO release. Thus, MAO-A and MAO-B are both expressed in the mouse aorta, induced by in vivo lipopolysaccharide and angiotensin II treatment and contribute via the generation of H(2)O(2) to endothelial dysfunction in vascular disease models.
单胺氧化酶（MAO）在其催化循环中产生 H₂O₂作为副产物。MAO 是否是内皮功能障碍的介质尚不清楚，本研究在血管功能障碍的血管紧张素 II 和脂多糖模型中确定了这一点。定量实时聚合酶链反应显示，小鼠主动脉含有参与儿茶酚胺生成的酶以及 MAO-A 和 MAO-B mRNA。Western blot 不仅可以检测到小鼠主动脉中的 MAO-A 和 -B 蛋白，还可以检测到人脐静脉内皮细胞中的 MAO-A 和 -B 蛋白。体外孵育重组 MAO-A 可增加 H₂O₂的形成并诱导内皮功能障碍，而聚乙二醇-过氧化氢酶和 MAO 抑制剂可减轻这种功能障碍。体内脂多糖（8 mg/kg IP 过夜）或血管紧张素 II（1 mg/kg/天，2 周，微泵）处理诱导血管 MAO-A 和 -B 表达，并导致对乙酰胆碱反应的主动脉内皮依赖性舒张减弱。MAO 抑制剂可使脂多糖和血管紧张素 II 诱导的主动脉活性氧形成减少 50%（亚铁氧化二甲氧唑橙测定法），并部分使内皮依赖性舒张正常化。MAO-A 和 MAO-B 抑制剂具有相加作用；联合应用可完全恢复内皮依赖性舒张。为了确定 MAO 依赖性 H₂O₂形成如何诱导内皮功能障碍，测量了环鸟苷酸。组胺刺激人脐静脉内皮细胞激活内皮型一氧化氮合酶导致环鸟苷酸增加，而 MAO-A 暴露几乎消除了这种增加。MAO 抑制可防止这种作用，表明 MAO 诱导的 H₂O₂形成足以减弱内皮型一氧化氮释放。因此，MAO-A 和 MAO-B 均在小鼠主动脉中表达，由体内脂多糖和血管紧张素 II 处理诱导，并通过产生 H₂O₂对血管疾病模型中的内皮功能障碍产生影响。
