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A novel way to grow hemozoin-like crystals in vitro and its use to screen for hemozoin inhibiting antimalarial compounds.

Thomas V, Góis A, Ritts B, Burke P, Hänscheid T, McDonnell G - PLoS ONE (2012)

Bottom Line: Inhibition of hemozoin formation by various drugs results in free heme concentration toxic for the parasites.They were compared to synthetic hemozoin and to hemozoin obtained from Plasmodium falciparum.As already described by others, drugs that inhibit hemozoin crystal formation have also the potential to inhibit misfolded proteins assemblies formation.

View Article: PubMed Central - PubMed

Affiliation: STERIS SA R&D, Fontenay-aux-Roses, France.

ABSTRACT

Background: Hemozoin crystals are normally formed in vivo by Plasmodium parasites to detoxify free heme released after hemoglobin digestion during its intraerythrocytic stage. Inhibition of hemozoin formation by various drugs results in free heme concentration toxic for the parasites. As a consequence, in vitro assays have been developed to screen and select candidate antimalarial drugs based on their capacity to inhibit hemozoin formation. In this report we describe new ways to form hemozoin-like crystals that were incidentally discovered during research in the field of prion inactivation.

Methods: We investigated the use of a new assay based on naturally occurring "self-replicating" particles and previously described as presenting resistance to decontamination comparable to prions. The nature of these particles was determined using electron microscopy, Maldi-Tof analysis and X-ray diffraction. They were compared to synthetic hemozoin and to hemozoin obtained from Plasmodium falciparum. We then used the assay to evaluate the capacity of various antimalarial and anti-prion compounds to inhibit "self-replication" (crystallisation) of these particles.

Results: We identified these particles as being similar to ferriprotoporphyrin IX crystal and confirmed the ability of these particles to serve as nuclei for growth of new hemozoin-like crystals (HLC). HLC are morphologically similar to natural and synthetic hemozoin. Growth of HLC in a simple assay format confirmed inhibition by quinolines antimalarials at potencies described in the literature. Interestingly, artemisinins and tetracyclines also seemed to inhibit HLC growth.

Conclusions: The described HLC assay is simple and easy to perform and may have the potential to be used as an additional tool to screen antimalarial drugs for their hemozoin inhibiting activity. As already described by others, drugs that inhibit hemozoin crystal formation have also the potential to inhibit misfolded proteins assemblies formation.

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X-ray diffraction patterns of synthetic and natural hemozoin and hemozoin-like crystals.X-ray diffraction patterns of synthetic hemozoin (blue), natural hemozoin (green) and hemozoin-like crystals (red). The curves of natural and synthetic hemozoin are identical, while the curve of HLC shows additional peaks confirming that HLC are not identical to sHZ or nHz.
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pone-0041006-g006: X-ray diffraction patterns of synthetic and natural hemozoin and hemozoin-like crystals.X-ray diffraction patterns of synthetic hemozoin (blue), natural hemozoin (green) and hemozoin-like crystals (red). The curves of natural and synthetic hemozoin are identical, while the curve of HLC shows additional peaks confirming that HLC are not identical to sHZ or nHz.

Mentions: X-ray diffraction showed identical results for nHz and sHz (Figure 6). The results for HLC showed several additional peaks (Figure 6), confirming that HLC are indeed not identical to sHz or nHz.


A novel way to grow hemozoin-like crystals in vitro and its use to screen for hemozoin inhibiting antimalarial compounds.

Thomas V, Góis A, Ritts B, Burke P, Hänscheid T, McDonnell G - PLoS ONE (2012)

X-ray diffraction patterns of synthetic and natural hemozoin and hemozoin-like crystals.X-ray diffraction patterns of synthetic hemozoin (blue), natural hemozoin (green) and hemozoin-like crystals (red). The curves of natural and synthetic hemozoin are identical, while the curve of HLC shows additional peaks confirming that HLC are not identical to sHZ or nHz.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3399802&req=5

pone-0041006-g006: X-ray diffraction patterns of synthetic and natural hemozoin and hemozoin-like crystals.X-ray diffraction patterns of synthetic hemozoin (blue), natural hemozoin (green) and hemozoin-like crystals (red). The curves of natural and synthetic hemozoin are identical, while the curve of HLC shows additional peaks confirming that HLC are not identical to sHZ or nHz.
Mentions: X-ray diffraction showed identical results for nHz and sHz (Figure 6). The results for HLC showed several additional peaks (Figure 6), confirming that HLC are indeed not identical to sHz or nHz.

Bottom Line: Inhibition of hemozoin formation by various drugs results in free heme concentration toxic for the parasites.They were compared to synthetic hemozoin and to hemozoin obtained from Plasmodium falciparum.As already described by others, drugs that inhibit hemozoin crystal formation have also the potential to inhibit misfolded proteins assemblies formation.

View Article: PubMed Central - PubMed

Affiliation: STERIS SA R&D, Fontenay-aux-Roses, France.

ABSTRACT

Background: Hemozoin crystals are normally formed in vivo by Plasmodium parasites to detoxify free heme released after hemoglobin digestion during its intraerythrocytic stage. Inhibition of hemozoin formation by various drugs results in free heme concentration toxic for the parasites. As a consequence, in vitro assays have been developed to screen and select candidate antimalarial drugs based on their capacity to inhibit hemozoin formation. In this report we describe new ways to form hemozoin-like crystals that were incidentally discovered during research in the field of prion inactivation.

Methods: We investigated the use of a new assay based on naturally occurring "self-replicating" particles and previously described as presenting resistance to decontamination comparable to prions. The nature of these particles was determined using electron microscopy, Maldi-Tof analysis and X-ray diffraction. They were compared to synthetic hemozoin and to hemozoin obtained from Plasmodium falciparum. We then used the assay to evaluate the capacity of various antimalarial and anti-prion compounds to inhibit "self-replication" (crystallisation) of these particles.

Results: We identified these particles as being similar to ferriprotoporphyrin IX crystal and confirmed the ability of these particles to serve as nuclei for growth of new hemozoin-like crystals (HLC). HLC are morphologically similar to natural and synthetic hemozoin. Growth of HLC in a simple assay format confirmed inhibition by quinolines antimalarials at potencies described in the literature. Interestingly, artemisinins and tetracyclines also seemed to inhibit HLC growth.

Conclusions: The described HLC assay is simple and easy to perform and may have the potential to be used as an additional tool to screen antimalarial drugs for their hemozoin inhibiting activity. As already described by others, drugs that inhibit hemozoin crystal formation have also the potential to inhibit misfolded proteins assemblies formation.

Show MeSH