Hemozoin production by Plasmodium falciparum: variation with strain and exposure to chloroquine

Orjih, Augustine U.; Fitch, Coy D.

doi:10.1016/0304-4165(93)90109-l

Cited by 93 publications

(71 citation statements)

References 18 publications

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“…Briefly, by reference to standard hematological measurements and assuming that 1) a 70-kg adult has a 1% synchronized Pf parasitemia (a relatively mild parasite load), 2) 50% of the hemoglobin in an infected cell is degraded, and 3) all heme in the degraded hemoglobin is converted into HZ, it has been estimated that as much as 200 mol of HZ (ϳ3 mol/kg) is released into the circulation of a Pf-infected human patient at schizogeny (12). In addition, it was calculated that 10 6 Pf trophozoite-infected RBC contain between 339 and 652 ng of HZ (equal to 0.5-1.0 nmol of heme content) (19,20). According to these data, the concentrations of HZ used in the current study (ϳ26 -29 nmol/ml heme content) could be easily released by a patient with a mild parasitemia load.…”

Section: Heme Quantitationmentioning

confidence: 83%

“…Twenty-five micrograms of sHZ equals 26 nmol of heme content, and 25 g of Pf HZ equals 29 nmol of heme content. It should be noted that the concentrations of HZ used to stimulate M (25-75 g/ml) were chosen based on reported estimates of the HZ concentrations encountered during malaria infection (12,19,20) as well as on previous studies in which these amounts of HZ were shown to be effective both in vitro and in vivo (12,21). Briefly, by reference to standard hematological measurements and assuming that 1) a 70-kg adult has a 1% synchronized Pf parasitemia (a relatively mild parasite load), 2) 50% of the hemoglobin in an infected cell is degraded, and 3) all heme in the degraded hemoglobin is converted into HZ, it has been estimated that as much as 200 mol of HZ (ϳ3 mol/kg) is released into the circulation of a Pf-infected human patient at schizogeny (12).…”

Section: Heme Quantitationmentioning

confidence: 99%

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Hemozoin Induces Macrophage Chemokine Expression through Oxidative Stress-Dependent and -Independent Mechanisms

Jaramillo

Godbout

Olivier

2005

The Journal of Immunology

121

100

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Chemokine production has been associated with the immunopathology related to malaria. Previous findings indicated that hemozoin (HZ), a parasite metabolite released during schizogeny, might be an important source of these proinflammatory mediators. In this study we investigated the molecular mechanisms underlying HZ-inducible macrophage (Mφ) chemokine mRNA expression. We found that both Plasmodium falciparum HZ and synthetic HZ increase mRNA levels of various chemokine transcripts (MIP-1α/CCL3, MIP-1β/CCL4, MIP-2/CXCL2, and MCP-1/CCL2) in murine B10R Mφ. The cellular response to HZ involved ERK1/2 phosphorylation, NF-κB activation, reactive oxygen species (ROS) generation, and ROS-dependent protein-tyrosine phosphatase down-regulation. Selective inhibition of either IκBα or the ERK1/2 pathway abolished both NF-κB activation and chemokine up-regulation. Similarly, blockage of HZ-inducible Mφ ROS with superoxide dismutase suppressed chemokine induction, strongly reduced NF-κB activation, and restored HZ-mediated Mφ protein-tyrosine phosphatase inactivation. In contrast, superoxide dismutase had no effect on EKR1/2 phosphorylation by HZ. Collectively, these data indicate that HZ triggers ROS-dependent and -independent signals, leading to increased chemokine mRNA expression in Mφ. Overall, our findings may help to better understand the molecular mechanisms through which parasite components, such as HZ, modulate the immune response during malaria infection.

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Section: Heme Quantitationmentioning

confidence: 83%

Section: Heme Quantitationmentioning

confidence: 99%

Hemozoin Induces Macrophage Chemokine Expression through Oxidative Stress-Dependent and -Independent Mechanisms

Jaramillo

Godbout

Olivier

2005

The Journal of Immunology

121

100

View full text Add to dashboard Cite

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“…Beta-hematin, the principal pigment in parasite hemozoin, was measured as described previously (20). Briefly, parasites were synchronized, adjusted to 10% parasitemia, and cultured with 50 M leupeptin for 18 h to allow maturation to the trophozoite stage and minimize the effects of leupeptin on later stages.…”

Section: Methodsmentioning

confidence: 99%

Changes in the Plasmodial Surface Anion Channel Reduce Leupeptin Uptake and Can Confer Drug Resistance in Plasmodium falciparum -Infected Erythrocytes

Lisk

Pain

Gluzman

et al. 2008

Antimicrob Agents Chemother

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Cysteine protease inhibitors kill malaria parasites and are being pursued for development as antimalarial agents. Because they have multiple targets within bloodstream-stage parasites, workers have assumed that resistance to these inhibitors would not be acquired easily. In the present study, we used in vitro selection to generate a parasite resistant to growth inhibition by leupeptin, a broad-profile cysteine and serine protease inhibitor. Resistance was not associated with upregulation of cysteine protease activity, reduced leupeptin sensitivity of this activity, or expression level changes for putative cysteine or serine proteases in the parasite genome. Instead, it was associated with marked changes in the plasmodial surface anion channel (PSAC), an ion channel on infected erythrocytes that functions in nutrient and bulky organic solute uptake. Osmotic fragility measurements, electrophysiological recordings, and leupeptin uptake studies revealed selective reductions in organic solute permeability via PSAC, altered single-channel gating, and reduced inhibitor affinity. These changes yielded significantly reduced leupeptin uptake and could fully account for the acquired resistance. PSAC represents a novel route for the uptake of bulky hydrophilic compounds acting against intraerythrocytic parasite targets. Drug development based on such compounds should proceed cautiously in light of possible resistance development though the selection of PSAC mutants.

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“…Importantly, Orjih and Fitch found that mid-stage trophozoites with fully formed DV accumulate more CQ than any other stage [13]. Morever, recently, CQR was shown to segregate with mutations in the pfcrt gene which encodes a protein found in the DV membrane, which is only fully developed during the early trophozoite stage [14].…”

Section: Introductionmentioning

confidence: 99%

Stage independent chloroquine resistance and chloroquine toxicity revealed via spinning disk confocal microscopy

Gligorijevic

Purdy

Elliott

et al. 2008

Molecular and Biochemical Parasitology

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We previously customized a Nipkow spinning disk confocal microscope (SDCM) to acquire 4D data for live, intraerythrocytic malarial parasites (Gligorijevic, B. et al., Biochemistry 45, 12400). We reported that chloroquine (CQ) treatment did not appear to affect progress through the cell cycle, and suggested that toxicity may be manifested post-schizogony. We now use SDCM, synchronized cell culture and continuous vs. bolus drug dosing to investigate stage specific CQ effects in detail. We develop a novel, extremely rapid method for counting schizont nuclei in 3D. We then quantify schizont nuclei and hemozoin (Hz) production for live parasite cultures pulsed with CQ at different stages in the cell cycle and find that bolus treatment of rings affects the multiplicity of nuclear division. We quantify parasitemia and merozoite development in subsequent cycles following bolus CQ exposure and find that a portion of CQ toxicity is manifested post schizogony as "delayed death". Using these methods and others we compare CQ sensitive (CQS) vs. resistant (CQR) strains as well as transfectants that are CQR via introduction of mutant PfCRT. Surprisingly, we find that PfCRT confers resistance to CQ administered at the very early ring stage of development, wherein a digestive vacuole is not yet formed, as well as at the schizont stage, wherein Hz production is thought to plateau. Taken together, these data force a rethinking of CQ pharmacology and the mechanism of CQR.

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Hemozoin production by Plasmodium falciparum: variation with strain and exposure to chloroquine

Cited by 93 publications

References 18 publications

Hemozoin Induces Macrophage Chemokine Expression through Oxidative Stress-Dependent and -Independent Mechanisms

Hemozoin Induces Macrophage Chemokine Expression through Oxidative Stress-Dependent and -Independent Mechanisms

Changes in the Plasmodial Surface Anion Channel Reduce Leupeptin Uptake and Can Confer Drug Resistance in Plasmodium falciparum -Infected Erythrocytes

Stage independent chloroquine resistance and chloroquine toxicity revealed via spinning disk confocal microscopy

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