Flavonoids as substrates and inhibitors of myeloperoxidase: Molecular actions of aglycone and metabolites
Flavonoids as substrates and inhibitors of myeloperoxidase: Molecular actions of aglycone and metabolites
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DOI：
10.1021/tx8000835
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发表时间：
2008-08-01
影响因子：
4.1
通讯作者：
Kawai, Yoshichika
中科院分区：
文献类型：
--
作者：
Shiba, Yuko;Kinoshita, Takashi;Kawai, Yoshichika
髓过氧化物酶(MPO)由炎症部位活化的中性粒细胞和巨噬细胞分泌，可能与心血管疾病发生发展过程中蛋白质/脂蛋白的氧化有关。黄酮类化合物已被认为在体内具有抗氧化和抗炎作用，但其分子作用尚不完全清楚。在这项研究中，我们采用生物测定和理论计算相结合的方法，研究了食物中的黄酮类化合物，如槲皮素，及其代谢产物对MPO催化反应的抑制作用的分子基础。免疫组织化学染色显示，在人动脉粥样硬化的动脉中，一种栎素代谢物与巨噬细胞、MPO以及MPO衍生的酪氨酸氧化产物Dityroine共存。槲皮素及其血浆代谢物对MPO酶和HL-60细胞催化的二羟甲基丙氨酸的生成有抑制作用，且呈剂量依赖关系。光谱分析表明，槲皮素可能是MPO的辅助底物，使氧化后的槲皮素更加坚固。定量构效关系研究表明，黄酮类化合物的抑制作用不仅依赖于自由基清除活性，还依赖于疏水性(LogP)。提出了抑制作用需要3、5、4‘位上的一组羟基和C-2-C-3双键。通过计算机对接模拟，还提出了在MPO的远端血红素口袋入口处的疏水区域与栎素及其代谢物的结合。本研究针对体内MPO引发的氧化反应，提供了作为抗炎饮食成分的类黄酮类化合物的构效关系。
Myeloperoxidase (MPO), secreted by activated neutrophils and macrophages at the site of inflammation, may be implicated in the oxidation of protein/lipoprotein during the development of cardiovascular diseases. Flavonoids have been suggested to act as antioxidative and anti-inflammatory agents in vivo; however, their molecular actions have not yet been fully understood. In this study, we examined the molecular basis of the inhibitory effects of dietary flavonoids, such as quercetin, and their metabolites on the catalytic reaction of MPO using a combination of biological assays and theoretical calculation studies. Immunohistochemical staining showed that a quercetin metabolite was colocalized with macrophages, MPO, and dityrosine, an MPO-derived oxidation product of tyrosine, in human atherosclerotic aorta. Quercetin and the plasma metabolites inhibited the formation of dityrosine catalyzed by the MPO enzyme and HL-60 cells in a dose-dependent manner. Spectrometric analysis indicated that quercetin might act as a cosubstrate of MPO resulting in the fort-nation of the oxidized quercetin. Quantitative structure-activity relationship studies showed that the inhibitory actions of flavonoids strongly depended not only on radical scavenging activity but also on hydrophobicity (log P). The requirement of a set of hydroxyl groups at the 3, 5, and 4'-positions and C-2-C-3 double bond was suggested for the inhibitory effect. The binding of quercetin and the metabolites to a hydrophobic region at the entrance to the distal heme pocket of MPO was also proposed by a computer docking simulation. The current study provides the structure- activity relationships for flavonoids as the anti-inflammatory dietary constituents targeting the MPO-derived oxidative reactions in vivo.