Steffen Yvonne, Schewe Tankred, Sies Helmut
Institut für Biochemie und Molekularbiologie I, Heinrich-Heine-Universität Düsseldorf, D-40001 Düsseldorf, Germany.
Biochem Biophys Res Commun. 2007 Aug 3;359(3):828-33. doi: 10.1016/j.bbrc.2007.05.200. Epub 2007 Jun 6.
Dietary (-)-epicatechin is known to improve bioactivity of ()NO in arterial endothelium of humans, but the mode of action is unclear. We used the fluorophore 4,5-diaminofluorescein diacetate to visualize the ()NO level in living human umbilical vein endothelial cells (HUVEC). Untreated cells showed only a weak signal, whereas pretreatment with (-)-epicatechin (10 microM) or apocynin (100 microM) elevated the ()NO level. The effects were more pronounced when the cells were treated with angiotensin II with or without preloading of the cells with ()NO via PAPA-NONOate. While (-)-epicatechin scavenged O2(-), its O-methylated metabolites prevented O2(-) generation through inhibition of endothelial NADPH oxidase activity, even more strongly than apocynin. From the effect of 3,5-dinitrocatechol, an inhibitor of catechol-O-methyltransferase (COMT), on HUVEC it is concluded that (-)-epicatechin serves as 'prodrug' for conversion to apocynin-like NADPH oxidase inhibitors. These data indicate an ()NO-preserving effect of (-)-epicatechin via suppression of O2(-)-mediated loss of (*)NO.
已知膳食（-）-表儿茶素可改善人体动脉内皮中（）一氧化氮的生物活性，但其作用方式尚不清楚。我们使用荧光团4,5-二氨基荧光素二乙酸酯来可视化活的人脐静脉内皮细胞（HUVEC）中的（）一氧化氮水平。未处理的细胞仅显示微弱信号，而用（-）-表儿茶素（10微摩尔）或夹竹桃麻素（100微摩尔）预处理可提高（）一氧化氮水平。当细胞用血管紧张素II处理时，无论是否通过PAPA- NONOate对细胞进行（）一氧化氮预加载，效果都更明显。虽然（-）-表儿茶素清除超氧阴离子（），但其O-甲基化代谢产物通过抑制内皮NADPH氧化酶活性来阻止超氧阴离子（）的产生，甚至比夹竹桃麻素更强。从儿茶酚-O-甲基转移酶（COMT）抑制剂3,5-二硝基儿茶酚对HUVEC的作用可以得出结论，（-）-表儿茶素作为“前药”转化为类似夹竹桃麻素的NADPH氧化酶抑制剂。这些数据表明（-）-表儿茶素通过抑制超氧阴离子（）介导的一氧化氮（）损失而具有一氧化氮（*）保护作用。
