ABSTRACT
We have reported that two endoperoxides, N-89 and N-251, synthesized in 2001, possess potent antimalarial activities. Aiming at their eventual use for curing malaria in humans, we have been investigating various aspects of their antimalarial actions. Here we show that N-89 and N-251 inhibit the growth of Plasmodium falciparum within human erythrocytes in vitro at its lifecycle stage 'trophozoite' specifically. It is known that artemisinin compounds, which are currently used for curing malaria, have other stage-specificities. Therefore, it is likely that the antimalarial mechanism of N-89 and N-251 differs from those of artemisinin compounds. As malaria parasites resistant to artemisinin-based combination therapy are currently emerging in some tropical regions, N-89 and N-251 are candidates for overcoming these new problems.
Subject(s)
Antimalarials/pharmacology , Heterocyclic Compounds, 2-Ring/pharmacology , Plasmodium falciparum/drug effects , Spiro Compounds/pharmacology , Tetraoxanes/pharmacology , Animals , Antimalarials/chemical synthesis , Artemisinins/pharmacology , Drug Resistance, Multiple , Erythrocytes/parasitology , Humans , Malaria/parasitology , Parasitic Sensitivity Tests , Plasmodium falciparum/growth & development , Trophozoites/drug effects , Trophozoites/ultrastructureABSTRACT
The endoperoxide artemisinin is a current first-line antimalarial and a critical component of the artemisinin-based combination therapies (ACT) recommended by WHO for treatment of Plasmodium falciparum, the deadliest of malaria parasites. However, recent emergence of the artemisinin-resistant P. falciparum urged us to develop new antimalarial drugs. We have shown that synthetic endoperoxides N-89 and its hydroxyl derivative N-251 had high antimalarial activities both in vivo and in vitro. However, the mechanisms including the cellular targets of the endoperoxide antimalarials are not well understood. Thus, in this study, we employed chemical proteomics to survey potential molecular targets of endoperoxides by evaluating P. falciparum proteins capable to associate with endoperoxide structure (N-346, a carboxyamino derivative of N-89). We also analyzed the protein expression profiles of malaria parasites treated with N-89 or N-251 to explore possible changes associated with the drug action. From these experiments, we found that P. falciparum endoplasmic reticulum-resident calcium binding protein (PfERC) had high affinity to the endoperoxide structure (N-346) and was decreased by treatment with N-89 or N-251. PfERC is a member of CREC protein family, a potential disease marker and also a potential target for therapeutic intervention. We propose that the PfERC is a strong candidate of the endoperoxide antimalarial's target.
Subject(s)
Antimalarials/pharmacology , Calcium-Binding Proteins/chemistry , Endoplasmic Reticulum/chemistry , Peroxides/pharmacology , Plasmodium falciparum/chemistry , Protozoan Proteins/chemistry , Antimalarials/chemistry , Chromatography, Affinity , Electrophoresis, Polyacrylamide Gel , Erythrocytes/parasitology , Heterocyclic Compounds, 2-Ring/pharmacology , Humans , Peroxides/chemistry , Plasmodium falciparum/drug effects , Plasmodium falciparum/pathogenicity , Proteomics/methods , Recombinant Proteins/chemistry , Spiro Compounds/pharmacology , Tetraoxanes/pharmacology , Trophozoites/chemistry , Trophozoites/drug effectsABSTRACT
N-89, a new antimalarial endoperoxide, was selected as a promising antimalarial compound showing high activity and selectivity. To study the mechanism of N-89 action, N-89 resistant strain (NRC10) was obtained by intermittent drug pressure. NRC10 had a tenfold increase in the EC(50) value of N-89. No cross-resistance was obtained with other antimalarial compounds. Comparative proteome analysis of N-89 sensitive and NRC10 strains revealed over-expression of 12 spots and down-regulation of 14 spots in NRC10. Fifteen proteins were identified of Plasmodium falciparum origin. The identified proteins representing several functions, mainly related to the glycolytic pathway, and metabolism of protein and lipid. Our results suggest that identified proteins may be candidates of antimalarial endoperoxide targets.
