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Treatment of erythrocytes with the 2-cys peroxiredoxin inhibitor, Conoidin A, prevents the growth of Plasmodium falciparum and enhances parasite sensitivity to chloroquine.

Brizuela M, Huang HM, Smith C, Burgio G, Foote SJ, McMorran BJ - PLoS ONE (2014)

Bottom Line: These cells remained susceptible to merozoite invasion, but failed to support normal intraerythrocytic development.CQ IC50 values decreased an order of magnitude when parasites were either co-incubated with BBMQ, or introduced into BBMQ-pretreated cells; these effects were equivalent for both drug-resistant and drug-sensitive parasite lines.Together these results indicate that treatment of red cells with BBMQ renders them incapable of supporting parasite growth and increases parasite sensitivity to CQ.

View Article: PubMed Central - PubMed

Affiliation: The Menzies Research Institute Tasmania, University of Tasmania, Hobart, Tasmania, Australia.

ABSTRACT
The human erythrocyte contains an abundance of the thiol-dependant peroxidase Peroxiredoxin-2 (Prx2), which protects the cell from the pro-oxidant environment it encounters during its 120 days of life in the blood stream. In malarial infections, the Plasmodium parasite invades red cells and imports Prx2 during intraerythrocytic development, presumably to supplement in its own degradation of peroxides generated during cell metabolism, especially hemoglobin (Hb) digestion. Here we demonstrate that an irreversible Prx2 inhibitor, Conoidin A (2,3-bis(bromomethyl)-1,4-dioxide-quinoxaline; BBMQ), has potent cytocidal activity against cultured P. falciparum. Parasite growth was also inhibited in red cells that were treated with BBMQ and then washed prior to parasite infection. These cells remained susceptible to merozoite invasion, but failed to support normal intraerythrocytic development. In addition the potency of chloroquine (CQ), an antimalarial drug that prevents the detoxification of Hb-derived heme, was significantly enhanced in the presence of BBMQ. CQ IC50 values decreased an order of magnitude when parasites were either co-incubated with BBMQ, or introduced into BBMQ-pretreated cells; these effects were equivalent for both drug-resistant and drug-sensitive parasite lines. Together these results indicate that treatment of red cells with BBMQ renders them incapable of supporting parasite growth and increases parasite sensitivity to CQ. We also propose that molecules such as BBMQ that target host cell proteins may constitute a novel host-directed therapeutic approach for treating malaria.

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Related in: MedlinePlus

BBMQ-CQ isobologram analysis.Growth inhibition curves for 3D7 (A and B) and K1 parasites (C and D) after 48 hours culture in the indicated concentrations and proportions of CQ and BBMQ. Data represent mean of triplicate wells analyzed in one experiment. The calculated IC50 for each compound at each mixture fraction is indicated in the figure keys (nM).
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pone-0092411-g005: BBMQ-CQ isobologram analysis.Growth inhibition curves for 3D7 (A and B) and K1 parasites (C and D) after 48 hours culture in the indicated concentrations and proportions of CQ and BBMQ. Data represent mean of triplicate wells analyzed in one experiment. The calculated IC50 for each compound at each mixture fraction is indicated in the figure keys (nM).

Mentions: In a second set of experiments we conducted an isobologram analysis of the 3D7 and K1 strains to determine the type of interaction between BBMQ and CQ. Increasing proportions of CQ had little effect on BBMQ IC50 values for both strains (Figure 5A and C). However, IC50 values for CQ decreased markedly (and in proportion) with increasing ratios of BBMQ (Figure 5B and D). For example, the CQ IC50 for 3D7 decreased from 21 nM in the absence of BBMQ to 1.2 nM in the presence of BBMQ added at a 4∶1 ratio. The same 4∶1 BBMQ∶CQ ratio reduced the CQ IC50 of the K1 strain more than thirty-fold, and effectively rendered the strain as sensitive to CQ as 3D7. The sum of the fractional IC50 values for each strain were approximately one (3D7: 1.01+/−0.18; K1: 1.11+/−0.09), indicating that the growth inhibitory effects of the two compounds were additive. However the additive effect occurred exclusively via the enhancement of BBMQ on CQ activity, and not the reverse. We speculate that this is due to differences in parasite stages most sensitive to each compound. Our observations (Figure 4A) and those made previously [23] show that the cytocidal effects of CQ are not apparent until the later trophozoite stages of development, while BBMQ is cytocidal against early ring-stage parasites (Figure 2C).


Treatment of erythrocytes with the 2-cys peroxiredoxin inhibitor, Conoidin A, prevents the growth of Plasmodium falciparum and enhances parasite sensitivity to chloroquine.

Brizuela M, Huang HM, Smith C, Burgio G, Foote SJ, McMorran BJ - PLoS ONE (2014)

BBMQ-CQ isobologram analysis.Growth inhibition curves for 3D7 (A and B) and K1 parasites (C and D) after 48 hours culture in the indicated concentrations and proportions of CQ and BBMQ. Data represent mean of triplicate wells analyzed in one experiment. The calculated IC50 for each compound at each mixture fraction is indicated in the figure keys (nM).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3974718&req=5

pone-0092411-g005: BBMQ-CQ isobologram analysis.Growth inhibition curves for 3D7 (A and B) and K1 parasites (C and D) after 48 hours culture in the indicated concentrations and proportions of CQ and BBMQ. Data represent mean of triplicate wells analyzed in one experiment. The calculated IC50 for each compound at each mixture fraction is indicated in the figure keys (nM).
Mentions: In a second set of experiments we conducted an isobologram analysis of the 3D7 and K1 strains to determine the type of interaction between BBMQ and CQ. Increasing proportions of CQ had little effect on BBMQ IC50 values for both strains (Figure 5A and C). However, IC50 values for CQ decreased markedly (and in proportion) with increasing ratios of BBMQ (Figure 5B and D). For example, the CQ IC50 for 3D7 decreased from 21 nM in the absence of BBMQ to 1.2 nM in the presence of BBMQ added at a 4∶1 ratio. The same 4∶1 BBMQ∶CQ ratio reduced the CQ IC50 of the K1 strain more than thirty-fold, and effectively rendered the strain as sensitive to CQ as 3D7. The sum of the fractional IC50 values for each strain were approximately one (3D7: 1.01+/−0.18; K1: 1.11+/−0.09), indicating that the growth inhibitory effects of the two compounds were additive. However the additive effect occurred exclusively via the enhancement of BBMQ on CQ activity, and not the reverse. We speculate that this is due to differences in parasite stages most sensitive to each compound. Our observations (Figure 4A) and those made previously [23] show that the cytocidal effects of CQ are not apparent until the later trophozoite stages of development, while BBMQ is cytocidal against early ring-stage parasites (Figure 2C).

Bottom Line: These cells remained susceptible to merozoite invasion, but failed to support normal intraerythrocytic development.CQ IC50 values decreased an order of magnitude when parasites were either co-incubated with BBMQ, or introduced into BBMQ-pretreated cells; these effects were equivalent for both drug-resistant and drug-sensitive parasite lines.Together these results indicate that treatment of red cells with BBMQ renders them incapable of supporting parasite growth and increases parasite sensitivity to CQ.

View Article: PubMed Central - PubMed

Affiliation: The Menzies Research Institute Tasmania, University of Tasmania, Hobart, Tasmania, Australia.

ABSTRACT
The human erythrocyte contains an abundance of the thiol-dependant peroxidase Peroxiredoxin-2 (Prx2), which protects the cell from the pro-oxidant environment it encounters during its 120 days of life in the blood stream. In malarial infections, the Plasmodium parasite invades red cells and imports Prx2 during intraerythrocytic development, presumably to supplement in its own degradation of peroxides generated during cell metabolism, especially hemoglobin (Hb) digestion. Here we demonstrate that an irreversible Prx2 inhibitor, Conoidin A (2,3-bis(bromomethyl)-1,4-dioxide-quinoxaline; BBMQ), has potent cytocidal activity against cultured P. falciparum. Parasite growth was also inhibited in red cells that were treated with BBMQ and then washed prior to parasite infection. These cells remained susceptible to merozoite invasion, but failed to support normal intraerythrocytic development. In addition the potency of chloroquine (CQ), an antimalarial drug that prevents the detoxification of Hb-derived heme, was significantly enhanced in the presence of BBMQ. CQ IC50 values decreased an order of magnitude when parasites were either co-incubated with BBMQ, or introduced into BBMQ-pretreated cells; these effects were equivalent for both drug-resistant and drug-sensitive parasite lines. Together these results indicate that treatment of red cells with BBMQ renders them incapable of supporting parasite growth and increases parasite sensitivity to CQ. We also propose that molecules such as BBMQ that target host cell proteins may constitute a novel host-directed therapeutic approach for treating malaria.

Show MeSH
Related in: MedlinePlus