Luteolin, an emerging anti-cancer flavonold, poisons eukaryotic DNA topoisomerase I
Luteolin, an emerging anti-cancer flavonold, poisons eukaryotic DNA topoisomerase I
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DOI：
10.1042/bj20020098
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发表时间：
2002-09-01
影响因子：
4.1
通讯作者：
Majumder, HK
中科院分区：
文献类型：
--
作者：
Chowdhury, AR;Sharma, S;Majumder, HK
木犀草素是一种天然存在的类黄酮，在我们的日常饮食摄入量丰富。它具有广泛的药理学特性，但除了它诱导拓扑异构酶II介导的细胞凋亡之外，对其生化靶点知之甚少。在本研究中，我们发现，木犀草素完全抑制真核DNA拓扑异构酶I的催化活性，在40 μ M的浓度，与5 μ M的IC 50。在加入DNA底物之前用木犀草素预孵育酶增加了对催化活性的抑制（IC 50 = 0.66 μ M）。在加入拓扑异构酶I之前用木犀草素处理DNA会降低这种抑制作用。随后的荧光测试表明，毛地黄黄酮不仅直接与酶相互作用，而且与底物DNA相互作用，并以非常高的浓度（> 250 μ M）嵌入，而不与小沟结合。毛地黄黄酮和DNA之间的直接相互作用并不影响组装的酶-DNA复合物，从电泳迁移率变化测定明显。在这里，我们表明，抑制拓扑异构酶I的木犀草素是由于稳定的拓扑异构酶-I的DNA可切割的复合物。因此，就其形成拓扑异构酶I介导的“可裂解复合物”的能力而言，毛地黄黄酮与喜树碱（I类抑制剂）相似。但是，与喜树碱不同，毛地黄黄酮与游离酶和底物DNA相互作用。毛地黄黄酮的抑制作用被转化为伴刀豆球蛋白A刺激的小鼠脾细胞，该化合物诱导SDS-K+-可沉淀的DNA-拓扑异构酶复合物。这是第一份关于木犀草素作为拓扑异构酶1催化活性抑制剂的报告，我们的研究结果进一步支持其作为一种毒性拓扑异构酶的领先抗癌化合物的治疗潜力。
Luteolin, a naturally occurring flavonoid, is abundant in our daily dietary intake. It exhibits a wide spectrum of pharmacological properties, but little is known about its biochemical targets other than the fact that it induces topoisomerase II-mediated apoptosis. In the present study, we show that luteolin completely inhibits the catalytic activity of eukaryotic DNA topoisomerase I at a concentration of 40 muM, with an IC50 of 5 muM. Preincubation of enzyme with luteolin before adding a DNA substrate increases the inhibition of the catalytic activity (IC50 = 0.66 muM). Treatment of DNA with luteolin before addition of topoisomerase I reduces this inhibitory effect. Subsequent fluorescence tests show that luteolin not only interacts directly with the enzyme but also with the substrate DNA, and intercalates at a very high concentration (> 250 muM) without binding to the minor groove. Direct interaction between luteolin and DNA does not affect the assembly of the enzyme-DNA complex, as evident from the electrophoretic mobility-shift assays. Here we show that the inhibition of topoisomerase I by luteolin is due to the stabilization of topoisomerase-I DNA-cleavable complexes. Hence, luteolin is similar to camptothecin, a class I inhibitor, with respect to its ability to form the topoisomerase I-mediated 'cleavable complex'. But, unlike camptothecin, luteolin interacts with both free enzyme and substrate DNA. The inhibitory effect of luteolin is translated into concanavalin A-stimulated mouse splenocytes, with the compound inducing SDS-K+-precipitable DNA-topoisomerase complexes. This is the first report on luteolin as an inhibitor of the catalytic activity of topoisomerase 1, and our results further support its therapeutic potential as a lead anti-cancer compound that poisons topoisomerases.