Limits...
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.

Show MeSH

Related in: MedlinePlus

Comparing the effects of continuous and washout BBMQ treatment on P. falciparum growth.Percentage growth inhibition of P. falciparum 3D7 (A) and K1 (B) using continuous or washout BBMQ treatment. Data represent the mean (± SEM) of at least two independent experiments performed in duplicate. * indicates p<0.01.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3974718&req=5

pone-0092411-g003: Comparing the effects of continuous and washout BBMQ treatment on P. falciparum growth.Percentage growth inhibition of P. falciparum 3D7 (A) and K1 (B) using continuous or washout BBMQ treatment. Data represent the mean (± SEM) of at least two independent experiments performed in duplicate. * indicates p<0.01.

Mentions: Continuously treating the parasite cultures with BBMQ in the above experiments meant that we could not distinguish between effects of BBMQ on host versus parasite proteins. We therefore exploited the irreversible action of BBMQ to determine if specific exposure of the host cell to BBMQ subsequently affected parasite viability. Red cells were pretreated with increasing concentrations of BBMQ and then washed (as described in Methods) prior to parasite infection (called washout). Following addition of purified trophozoites to the washout cells, identical proportions of ring-stage cells were observed after 12 hours incubation, indicating that parasite invasion was unaffected. BBMQ concentrations up to 25 µM were tested without any observable differences on invasion (data not shown). After 48 hours incubation in the washout cells, we noted the appearance of parasites exhibiting signs of growth arrest (at the ring stage), and condensed and pyknotic appearing nuclei similar to observations in the continuously treated cultures. Analysis of cultures after 72 hours also revealed a concentration dependent reduction in the proportion of second-generation rings (and overall parasite growth) (Figures 3A and B). This occurred for both the 3D7 and K1 strains, with similar IC50 values (2.2 and 3.9 µM, respectively). Compared to continuous BBMQ treatment, the potency of BBMQ in the washout experiments was reduced three to five fold, suggesting the inhibitory effect may be partly due to BBMQ inhibition of parasite proteins. Taken together, the data indicate that intraerythrocytic development of parasites is prevented by treatment of the red cell with BBMQ. We hypothesize that the compound targets and inactivates host proteins that are normally required by the parasite for its growth.


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)

Comparing the effects of continuous and washout BBMQ treatment on P. falciparum growth.Percentage growth inhibition of P. falciparum 3D7 (A) and K1 (B) using continuous or washout BBMQ treatment. Data represent the mean (± SEM) of at least two independent experiments performed in duplicate. * indicates p<0.01.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0092411-g003: Comparing the effects of continuous and washout BBMQ treatment on P. falciparum growth.Percentage growth inhibition of P. falciparum 3D7 (A) and K1 (B) using continuous or washout BBMQ treatment. Data represent the mean (± SEM) of at least two independent experiments performed in duplicate. * indicates p<0.01.
Mentions: Continuously treating the parasite cultures with BBMQ in the above experiments meant that we could not distinguish between effects of BBMQ on host versus parasite proteins. We therefore exploited the irreversible action of BBMQ to determine if specific exposure of the host cell to BBMQ subsequently affected parasite viability. Red cells were pretreated with increasing concentrations of BBMQ and then washed (as described in Methods) prior to parasite infection (called washout). Following addition of purified trophozoites to the washout cells, identical proportions of ring-stage cells were observed after 12 hours incubation, indicating that parasite invasion was unaffected. BBMQ concentrations up to 25 µM were tested without any observable differences on invasion (data not shown). After 48 hours incubation in the washout cells, we noted the appearance of parasites exhibiting signs of growth arrest (at the ring stage), and condensed and pyknotic appearing nuclei similar to observations in the continuously treated cultures. Analysis of cultures after 72 hours also revealed a concentration dependent reduction in the proportion of second-generation rings (and overall parasite growth) (Figures 3A and B). This occurred for both the 3D7 and K1 strains, with similar IC50 values (2.2 and 3.9 µM, respectively). Compared to continuous BBMQ treatment, the potency of BBMQ in the washout experiments was reduced three to five fold, suggesting the inhibitory effect may be partly due to BBMQ inhibition of parasite proteins. Taken together, the data indicate that intraerythrocytic development of parasites is prevented by treatment of the red cell with BBMQ. We hypothesize that the compound targets and inactivates host proteins that are normally required by the parasite for its growth.

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