Eckstein-Ludwig U, Webb R J, Van Goethem I D A, East J M, Lee A G, Kimura M, O'Neill P M, Bray P G, Ward S A, Krishna S
Department of Cellular and Molecular Medicine, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK.
Nature. 2003 Aug 21;424(6951):957-61. doi: 10.1038/nature01813.
Artemisinins are extracted from sweet wormwood (Artemisia annua) and are the most potent antimalarials available, rapidly killing all asexual stages of Plasmodium falciparum. Artemisinins are sesquiterpene lactones widely used to treat multidrug-resistant malaria, a disease that annually claims 1 million lives. Despite extensive clinical and laboratory experience their molecular target is not yet identified. Activated artemisinins form adducts with a variety of biological macromolecules, including haem, translationally controlled tumour protein (TCTP) and other higher-molecular-weight proteins. Here we show that artemisinins, but not quinine or chloroquine, inhibit the SERCA orthologue (PfATP6) of Plasmodium falciparum in Xenopus oocytes with similar potency to thapsigargin (another sesquiterpene lactone and highly specific SERCA inhibitor). As predicted, thapsigargin also antagonizes the parasiticidal activity of artemisinin. Desoxyartemisinin lacks an endoperoxide bridge and is ineffective both as an inhibitor of PfATP6 and as an antimalarial. Chelation of iron by desferrioxamine abrogates the antiparasitic activity of artemisinins and correspondingly attenuates inhibition of PfATP6. Imaging of parasites with BODIPY-thapsigargin labels the cytosolic compartment and is competed by artemisinin. Fluorescent artemisinin labels parasites similarly and irreversibly in an Fe2+-dependent manner. These data provide compelling evidence that artemisinins act by inhibiting PfATP6 outside the food vacuole after activation by iron.
青蒿素是从青蒿（黄花蒿）中提取的，是目前最有效的抗疟药物，能迅速杀死恶性疟原虫的所有无性阶段。青蒿素是倍半萜内酯，广泛用于治疗耐多药疟疾，这种疾病每年导致100万人死亡。尽管有广泛的临床和实验室经验，但它们的分子靶点尚未确定。活化的青蒿素与多种生物大分子形成加合物，包括血红素、翻译控制肿瘤蛋白（TCTP）和其他高分子量蛋白质。在这里，我们表明，青蒿素而非奎宁或氯喹，在非洲爪蟾卵母细胞中抑制恶性疟原虫的SERCA同源物（PfATP6），其效力与毒胡萝卜素（另一种倍半萜内酯和高度特异性的SERCA抑制剂）相似。正如预期的那样，毒胡萝卜素也拮抗青蒿素的杀寄生虫活性。脱氧青蒿素缺乏内过氧化物桥，作为PfATP6的抑制剂和抗疟药均无效。去铁胺对铁的螯合消除了青蒿素的抗寄生虫活性，并相应减弱了对PfATP6的抑制。用BODIPY-毒胡萝卜素对寄生虫进行成像标记了胞质区室，并被青蒿素竞争。荧光青蒿素以类似的方式并以Fe2+依赖的方式不可逆地标记寄生虫。这些数据提供了令人信服的证据，表明青蒿素在被铁激活后通过抑制食物泡外的PfATP6发挥作用。
