Lagoa Ricardo, Graziani Ilaria, Lopez-Sanchez Carmen, Garcia-Martinez Virginio, Gutierrez-Merino Carlos
Department of Biochemistry and Molecular Biology, Faculty of Sciences, University of Extremadura, Badajoz, Spain.
Biochim Biophys Acta. 2011 Dec;1807(12):1562-72. doi: 10.1016/j.bbabio.2011.09.022. Epub 2011 Oct 12.
Flavonoids can protect cells from different insults that lead to mitochondria-mediated cell death, and epidemiological data show that some of these compounds attenuate the progression of diseases associated with oxidative stress and mitochondrial dysfunction. In this work, a screening of 5 flavonoids representing major subclasses showed that they display different effects on H₂O₂ production by mitochondria isolated from rat brain and heart. Quercetin, kaempferol and epicatechin are potent inhibitors of H₂O₂ production by mitochondria from both tissues (IC₅₀ approximately 1-2 μM), even when H₂O₂ production rate was stimulated by the mitochondrial inhibitors rotenone and antimycin A. Although the rate of oxygen consumption was unaffected by concentrations up to 10 μM of these flavonoids, quercetin, kaempferol and apigenin inhibited complex I activity, while up to 100 μM epicatechin produced less than 20% inhibition. The extent of this inhibition was found to be dependent on the concentration of coenzyme Q in the medium, suggesting competition between the flavonoids and ubiquinone for close binding sites in the complex. In contrast, these flavonoids did not significantly inhibit the activity of complexes II and III, and did not affect the redox state of complex IV. However, we have found that epicatechin, quercetin and kaempferol are able to stoichiometrically reduce purified cytochrome c. Our results reveal that mitochondria are a plausible main target of flavonoids mediating, at least in part, their reported preventive actions against oxidative stress and mitochondrial dysfunction-associated pathologies.
黄酮类化合物可以保护细胞免受导致线粒体介导的细胞死亡的各种损伤，流行病学数据表明，其中一些化合物可减缓与氧化应激和线粒体功能障碍相关疾病的进展。在这项研究中，对代表主要亚类的5种黄酮类化合物进行的筛选表明，它们对从大鼠脑和心脏分离的线粒体产生H₂O₂具有不同的影响。槲皮素、山奈酚和表儿茶素是这两种组织中线粒体产生H₂O₂的有效抑制剂（IC₅₀约为1 - 2 μM），即使H₂O₂产生速率受到线粒体抑制剂鱼藤酮和抗霉素A的刺激也是如此。尽管高达10 μM的这些黄酮类化合物浓度对氧消耗速率没有影响，但槲皮素、山奈酚和芹菜素抑制了复合物I的活性，而高达100 μM的表儿茶素产生的抑制作用小于20%。发现这种抑制程度取决于培养基中辅酶Q的浓度，表明黄酮类化合物与泛醌在复合物中紧密结合位点存在竞争。相比之下，这些黄酮类化合物对复合物II和III的活性没有显著抑制作用，也不影响复合物IV的氧化还原状态。然而，我们发现表儿茶素、槲皮素和山奈酚能够化学计量地还原纯化的细胞色素c。我们的结果表明，线粒体是黄酮类化合物可能的主要作用靶点，至少部分介导了它们对氧化应激和线粒体功能障碍相关疾病的预防作用。
