Artemisinin activity against Plasmodium falciparum requires hemoglobin uptake and digestion

• Published in: Proceedings of the National Academy of Sciences - PNAS 2011-07, Vol.108 (28), p.11405-11410
• Main Authors: Klonis, Nectarios, Crespo-Ortiz, Maria P, Bottova, Iveta, Abu-Bakar, Nurhidanatasha, Kenny, Shannon, Rosenthal, Philip J, Tilley, Leann
• Format: Article
• Language: English
• Subjects: Animals; Antimalarials; Antimalarials - pharmacology; artemisinin; Artemisinins; Artemisinins - pharmacology; Bacteria; Biological Sciences; Biological Transport, Active; Cysteine Endopeptidases - deficiency; Cysteine Endopeptidases - genetics; Cysteine Endopeptidases - metabolism; cysteine proteinase inhibitors; cysteine proteinases; Cytometry; cytoplasm; digestion; Drug resistance; drug therapy; Endocytosis - drug effects; Enzyme kinetics; Erythrocytes - parasitology; Gene Deletion; Genes, Protozoan; half life; Hemoglobin; Hemoglobins; Hemoglobins - metabolism; Host-Parasite Interactions - drug effects; Humans; Malaria; Malaria, Falciparum - blood; Malaria, Falciparum - drug therapy; Malaria, Falciparum - parasitology; mechanism of action; new drugs; Oxidative stress; Parasitemia; Parasitemia - blood; Parasitemia - drug therapy; Parasitemia - parasitology; Parasites; Parasitism; Plasmodium falciparum; Plasmodium falciparum - drug effects; Plasmodium falciparum - genetics; Plasmodium falciparum - growth & development; Plasmodium falciparum - metabolism; Trophozoites
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1104063108

Combination regimens that include artemisinin derivatives are recommended as first line antimalarials in most countries where malaria is endemic. However, the mechanism of action of artemisinin is not fully understood and the usefulness of this drug class is threatened by reports of decreased parasite sensitivity. We treated Plasmodium falciparum for periods of a few hours to mimic clinical exposure to the short half-life artemisinins. We found that drug treatment retards parasite growth and inhibits uptake of hemoglobin, even at sublethal concentrations. We show that potent artemisinin activity is dependent on hemoglobin digestion by the parasite. Inhibition of hemoglobinase activity with cysteine protease inhibitors, knockout of the cysteine protease falcipain-2 by gene deletion, or direct deprivation of host cell lysate, significantly decreases artemisinin sensitivity. Hemoglobin digestion is also required for artemisinin-induced exacerbation of oxidative stress in the parasite cytoplasm. Arrest of hemoglobin digestion by early stage parasites provides a mechanism for surviving short-term artemisinin exposure. These insights will help in the design of new drugs and new treatment strategies to circumvent drug resistance.