Digestion of the host erythrocyte by malaria parasites is the primary target for quinolinecontaining antimalarials

Zarchin, Sisi; Krugliak, Miriam; Ginsburg, Hagaï

doi:10.1016/0006-2952(86)90473-9

Cited by 105 publications

(55 citation statements)

References 46 publications

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“…However, to date, all drugs in clinical use for the treatment of malaria act primarily against the intraerythrocytic development of Plasmodium parasites. The most important drugs currently in use, or previously widely used, for the treatment of clinical P. falciparum malaria are focused either on the food vacuole of ring-stage and trophozoites of blood-stage malaria (2)(3)(4)(5) or on enzymes in the trophozoite folic acid biosynthesis pathway (6). Drugs that have been used clinically that have one of these two modes of action include chloroquine, amodiaquine, quinine, sulfadoxine-pyrimethamine, artemisinin derivatives (predominantly artemether and artesunate), and lumefantrine.…”

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confidence: 99%

Defining the Timing of Action of Antimalarial Drugs against Plasmodium falciparum

Wilson

Langer

Goodman

et al. 2013

Antimicrob Agents Chemother

129

135

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e Most current antimalarials for treatment of clinical Plasmodium falciparum malaria fall into two broad drug families and target the food vacuole of the trophozoite stage. No antimalarials have been shown to target the brief extracellular merozoite form of blood-stage malaria. We studied a panel of 12 drugs, 10 of which have been used extensively clinically, for their invasion, schizont rupture, and growth-inhibitory activity using high-throughput flow cytometry and new approaches for the study of merozoite invasion and early intraerythrocytic development. Not surprisingly, given reported mechanisms of action, none of the drugs inhibited merozoite invasion in vitro. Pretreatment of erythrocytes with drugs suggested that halofantrine, lumefantrine, piperaquine, amodiaquine, and mefloquine diffuse into and remain within the erythrocyte and inhibit downstream growth of parasites. Studying the inhibitory activity of the drugs on intraerythrocytic development, schizont rupture, and reinvasion enabled several different inhibitory phenotypes to be defined. All drugs inhibited parasite replication when added at ring stages, but only artesunate, artemisinin, cycloheximide, and trichostatin A appeared to have substantial activity against ring stages, whereas the other drugs acted later during intraerythrocytic development. When drugs were added to late schizonts, only artemisinin, cycloheximide, and trichostatin A were able to inhibit rupture and subsequent replication. Flow cytometry proved valuable for in vitro assays of antimalarial activity, with the free merozoite population acting as a clear marker for parasite growth inhibition. These studies have important implications for further understanding the mechanisms of action of antimalarials, studying and evaluating drug resistance, and developing new antimalarials.

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mentioning

confidence: 99%

Defining the Timing of Action of Antimalarial Drugs against Plasmodium falciparum

Wilson

Langer

Goodman

et al. 2013

Antimicrob Agents Chemother

129

135

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“…Second, the hemoglobin content of infected erythrocytes decreases 25-75% during the life cycle of erythrocytic parasites (2,3), and the concentration of free amino acids is greater in infected erythrocytes than in uninfected erythrocytes (4). Third, the composition of the amino acid pool of infected erythrocytes is similar to the amino acid composition of hemoglobin (5)(6)(7). Fourth, the infection of erythrocytes containing radiolabeled hemoglobin is followed by the appearance of labeled amino acids in parasite proteins (8)(9)(10).…”

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confidence: 99%

A malarial cysteine proteinase is necessary for hemoglobin degradation by Plasmodium falciparum.

Rosenthal

McKerrow²,

Aikawa³

et al. 1988

J. Clin. Invest.

317

231

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To obtain free amino acids for protein synthesis, trophozoite stage malaria parasites feed on the cytoplasm of host erythrocytes and degrade hemoglobin within an acid food vacuole. The food vacuole appears to be analogous to the secondary lysosomes of mammalian cells. To determine the enzymatic mechanism of hemoglobin degradation, we incubated trophozoite-infected erythrocytes with peptide inhibitors of different classes of proteinases. Leupeptin and L-transepoxy-succinyl-leucylamido-(4-guanidino)-butane (E-64) sufficient for the needs of the parasite (1). Second, the hemoglobin content of infected erythrocytes decreases 25-75% during the life cycle of erythrocytic parasites (2,3), and the concentration of free amino acids is greater in infected erythrocytes than in uninfected erythrocytes (4). Third, the composition of the amino acid pool of infected erythrocytes is similar to the amino acid composition of hemoglobin (5-7). Fourth, the infection of erythrocytes containing radiolabeled hemoglobin is followed by the appearance of labeled amino acids in parasite proteins (8-10).Hemoglobin degradation occurs predominantly during the trophozoite stage ofthe erythrocytic life cycle ofP. falciparum. Trophozoites ingest erythrocyte cytoplasm and transport it within vesicles to a large central food vacuole (1 1, 12), where the hemoglobin-rich cytoplasm is degraded. In the food vacuole the heme moiety precipitates and is a major component of malarial pigment (13), and globin is hydrolyzed to its constituent free amino acids. The food vacuole of P. falciparum is an acidic (14, 15), membrane-bound (1 1) compartment where proteins are degraded, and therefore it appears to be analogous to the secondary lysosomes of mammalian cells, where multiple proteinases hydrolyze proteins at acid pH (16,17).The enzymatic mechanism of globin degradation within the malarial food vacuole is unknown. In previous studies, aspartic proteinases that degraded denatured hemoglobin were isolated from malaria parasites (18-20). However, denatured hemoglobin is a nonspecific substrate that can be hydrolyzed by many proteinases, and the biological role of the aspartic proteinases cannot be determined from these studies. To determine the enzymatic mechanism of globin degradation in the trophozoite food vacuole we first studied the effects of class-specific proteinase inhibitors on intact parasites. We found that two peptide inhibitors of cysteine proteinases blocked globin degradation in the food vacuole of P. falciparum trophozoites. We also identified a cysteine proteinase of trophozoites that was inhibited by the same two proteinase inhibitors and had biochemical properties that were similar to those of the lysosomal cysteine proteinase cathepsin L. Our results suggest that the cysteine proteinase we identified has a critical role in hemoglobin degradation in the food vacuole of P. falciparum trophozoites.

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“…The parasite ingests and digests about 70% of the host cell hemoglobin (Hb) 1 but uses only up to 16% of the released amino acids for protein biosynthesis. 2 The excess is discharged out of the infected red blood cells (IRBCs) to the surrounding plasma 3 mainly through new permeation pathways (NPPs) of broad solute selectivity induced by the parasite in the host cell membrane. [4][5][6] The reason why parasites expend so much energy ingesting and digesting excess hemoglobin [7][8][9][10] and detoxifying the cell from toxic ferriprotoporphyrin IX [11][12][13] remains puzzling.…”

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confidence: 99%

Excess hemoglobin digestion and the osmotic stability ofPlasmodium falciparum–infected red blood cells

Lew

Tiffert

Ginsburg

2003

Blood

Self Cite

236

192

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During their asexual reproduction cycle (about 48 hours) in human red cells, Plasmodium falciparum parasites consume most of the host cell hemoglobin, far more than they require for protein biosynthesis. They also induce a large increase in the permeability of the host cell plasma membrane to allow for an increased traffic of nutrients and waste products. IntroductionDuring their intraerythrocytic phase, Plasmodium falciparum parasites grow and divide within the red blood cells to occupy about 16-to 20-fold the volume of the invading merozoite. The parasite ingests and digests about 70% of the host cell hemoglobin (Hb) 1 but uses only up to 16% of the released amino acids for protein biosynthesis. 2 The excess is discharged out of the infected red blood cells (IRBCs) to the surrounding plasma 3 mainly through new permeation pathways (NPPs) of broad solute selectivity induced by the parasite in the host cell membrane. [4][5][6] The reason why parasites expend so much energy ingesting and digesting excess hemoglobin [7][8][9][10] and detoxifying the cell from toxic ferriprotoporphyrin IX 11-13 remains puzzling.Another unresolved puzzle concerns the mechanism by which parasitized red cells are able to retain their osmotic stability for the approximately 48-hour reproductive cycle of the parasite despite the rapid NPP-mediated dissipation of the Na ϩ and K ϩ gradients. 14 A recent study by Staines et al 15 demonstrated that if NPPs were induced in uninfected cells as they are in infected cells, the uninfected cells would hemolyse by approximately 44 hours. Since the additional volume of the parasite was excluded from their computations, their estimates make the lysis resistance of IRBCs with large internal parasites even harder to comprehend.To investigate these issues we developed a mathematical model of the homeostasis of a parasitized red cell, formulated critical predictions on the stage-related volume changes of IRBCs, and carried out experimental tests to determine the validity of the model. The experimental results confirmed the predicted stagerelated volume changes, and validated the model-based suggestion that NPP-mediated permeability and excess Hb consumption are fine-tuned to ensure the osmotic stability and integrity of the parasitized cell for the duration of its asexual cycle. Materials and methods Preparation of cells and determination of the osmotic fragility distribution of infected red cell populationsRed cells infected with P falciparum A4 clone (kind gift from B. C. Elford, Institute of Molecular Medicine, Oxford, United Kingdom), derived from the ITO4 line 16 were cultured under a low oxygen atmosphere by standard methods. 17 The culture medium, changed daily, was RPMI 1640 supplemented with 40 mM HEPES (N-2-hydroxyethylpiperazine-NЈ-2-ethanesulfonic acid), 25 mg/L gentamicin sulfate, 10 mM D-glucose, 2 mM glutamine, and 8.5% vol/vol pooled human serum. There were 9 experiments carried out, 6 with IRBCs harvested from nonsynchronized cultures and 3 from synchronized cultures. Synchronization w...

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Digestion of the host erythrocyte by malaria parasites is the primary target for quinolinecontaining antimalarials

Cited by 105 publications

References 46 publications

Defining the Timing of Action of Antimalarial Drugs against Plasmodium falciparum

Defining the Timing of Action of Antimalarial Drugs against Plasmodium falciparum

A malarial cysteine proteinase is necessary for hemoglobin degradation by Plasmodium falciparum.

Excess hemoglobin digestion and the osmotic stability ofPlasmodium falciparum–infected red blood cells

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