ABSTRACT
Artermisinin and its derivatives are now the mainstays of antimalarial treatment; however, their mechanism of action is only poorly understood. We report on the synthesis of a novel series of epoxy-endoperoxides that can be prepared in high yields from simple starting materials. Endoperoxides that are disubstituted with alkyl or benzyl side chains show efficient inhibition of the growth of both chloroquine-sensitive and -resistant strains of
Plasmodium falciparum
. A
trans
-epoxide with respect to the peroxide linkage increases the activity compared to that of its
cis
-epoxy counterpart or the parent endoperoxide. The novel endoperoxides do not show a strong interaction with artemisinin. We have compared the mechanism of action of the novel endoperoxides with that of artemisinin. Electron microscopy reveals that the novel endoperoxides cause the early accumulation of endocytic vesicles, while artemisinin causes the disruption of the digestive vacuole membrane. At longer incubation times artemisinin causes extensive loss of organellar structures, while the novel endoperoxides cause myelin body formation as well as the accumulation of endocytic vesicles. An early event following endoperoxide treatment is the redistribution of the pH-sensitive probe LysoSensor Blue from the digestive vacuole to punctate structures. By contrast, neither artemisinin nor the novel endoperoxides caused alterations in the morphology of the endoplasmic reticulum nor showed antagonistic antimalarial activity when they were used with thapsigargin. Analysis of rhodamine 123 uptake by
P. falciparum
suggests that disruption of the mitochondrial membrane potential occurs as a downstream effect rather than as an initiator of parasite killing. The data suggest that the digestive vacuole is an important initial site of endoperoxide antimalarial activity.
摘要
目前,蒿甲素及其衍生物已成为抗疟治疗的主要药物;然而,人们对它们的作用机制却知之甚少。我们报告了一系列新型环氧内过氧化物的合成过程,这些化合物可以用简单的起始原料高产率地制备。用烷基或苄基侧链二取代的内过氧化物对恶性疟原虫的氯喹敏感菌株和耐药菌株的生长都有有效的抑制作用。
恶性疟原虫
.A
反式
-过氧化物连接的反式环氧化物比其顺式环氧化物的活性更强。
顺式
-环氧化物或母体内过氧化物的活性。新型内过氧化物不会与青蒿素产生强烈的相互作用。我们比较了新型内过氧化物与青蒿素的作用机制。电子显微镜显示,新型内过氧化物会导致内囊泡的早期积聚,而青蒿素则会导致消化泡膜的破坏。在较长的培养时间内,青蒿素会导致细胞器结构的广泛丧失,而新型内过氧化物则会导致髓鞘体的形成以及内囊泡的积累。内过氧化物处理后的一个早期现象是 pH 敏感探针 LysoSensor Blue 从消化泡重新分布到点状结构。相比之下,青蒿素和新型内过氧化物既不会引起内质网形态的改变,也不会在与硫糖苷一起使用时显示出拮抗抗疟活性。分析恶性疟原虫对罗丹明 123 的吸收
恶性疟原虫
分析表明,线粒体膜电位的破坏是一种下游效应,而不是杀死寄生虫的始作俑者。数据表明,消化泡是内过氧化物抗疟活性的重要初始场所。