scholarly journals Plasmodium falciparum-infected red blood cells depend on a functional glutathione de novo synthesis attributable to an enhanced loss of glutathione

2000 ◽  
Vol 346 (2) ◽  
pp. 545-552 ◽  
Author(s):  
Kai LÜERSEN ◽  
Rolf D. WALTER ◽  
Sylke MÜLLER
Keyword(s):  
Plasmodium Falciparum ◽  
Red Blood Cells ◽  
Blood Cells ◽  
De Novo ◽  
Specific Inhibitor ◽  
De Novo Synthesis ◽  
Glutamylcysteine Synthetase ◽  
Infected Rbcs ◽  
Erythrocytic Cycle ◽  
Gsh Metabolism

During the erythrocytic cycle, Plasmodium falciparum is highly dependent on an adequate thiol status for its survival. Glutathione reductase as well as de novo synthesis of GSH are responsible for the maintenance of the intracellular GSH level. The first and rate-limiting step of the synthetic pathway is catalysed by γ-glutamylcysteine synthetase (γ-GCS). Using L-buthionine-(S,R)-sulphoximine (BSO), a specific inhibitor of the γ-GCS, we show that the infection with P. falciparum causes drastic changes in the GSH metabolism of red blood cells (RBCs). Infected RBCs lose GSH at a rate 40-fold higher than non-infected RBCs. The de novo synthesis of the tripeptide was found to be essential for parasite survival. GSH depletion by BSO inhibits the development of P. falciparum with an IC50 of 73 μM. The effect of the drug is abolished by supplementation with GSH or GSH monoethyl ester. Our studies demonstrate that the plasmodicidal effect of the inhibitor BSO does not depend on its specificity towards its target enzyme in the parasite, but on the changed physiological needs for the metabolite GSH in the P. falciparum-infected RBCs. Therefore the depletion of GSH is proposed as a chemotherapeutic strategy for malaria, and γ-GCS is proposed as a potential drug target.

scholarly journals Stage-Dependent Topographical and Optical Properties of Plasmodium Falciparum-Infected Red Blood Cells

2021 ◽  
Author(s):  
Katharina Preißinger ◽  
Beáta Vértessy ◽  
István Kézsmárki ◽  
Miklós Kellermayer ◽  
Petra Molnár
Keyword(s):  
Plasmodium Falciparum ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Imaging Study ◽  
Close Correlation ◽  
Functional Changes ◽  
Force Microscopy ◽  
Atomic Force ◽  
Infected Rbcs ◽  
Bright Field Microscopy

Abstract Efficient malaria treatment is a major healthcare challenge. Addressing this challenge requires in-depth understanding of malaria parasite maturation during the intraerythrocytic cycle. Exploring the structural and functional changes of the parasite through the intraerythrocytic stages and their impact on red blood cells (RBCs) is a cornerstone of antimalarial drug development. In order to precisely trace such changes, we performed a thorough imaging study of RBCs infected by Plasmodium falciparum, by using atomic force microscopy (AFM) and total internal reflection fluorescence microscopy (TIRF) supplemented with bright field microscopy for stage assignment. This multifaceted imaging approach allows to reveal structure–function relations via correlations of the parasite maturation with morphological and fluorescence properties of the stages. We established diagnostic patterns characteristic to the parasite stages based on the topographical profile of infected RBCs, which show close correlation with their fluorescence (TIRF) map. Furthermore, we found that hemozoin crystals exhibit a strong optical contrast, possibly due to the quenching of fluorescence. The topographical and optical features provide a tool for locating the hemozoin crystals within the RBCs and following their growth.

scholarly journals No evidence for Ago2 translocation from the host erythrocyte into the Plasmodium parasite

2020 ◽  
Vol 5 ◽  
pp. 92 ◽  
Author(s):  
Franziska Hentzschel ◽  
Klara Obrova ◽  
Matthias Marti
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Specific Binding ◽  
Specific Inhibitor ◽  
Cross Reactivity ◽  
Host Protein ◽  
Parasite Development ◽  
Argonaute 2 ◽  
Infected Rbcs ◽  
Biochemical Fractionation

Background: Plasmodium parasites rely on various host factors to grow and replicate within red blood cells (RBC). While many host proteins are known that mediate parasite adhesion and invasion, few examples of host enzymes co-opted by the parasite during intracellular development have been described. Recent studies suggested that the host protein Argonaute 2 (Ago2), which is involved in RNA interference, can translocate into the parasite and affect its development. Here, we investigated this hypothesis. Methods: We used several different monoclonal antibodies to test for Ago2 localisation in the human malaria parasite, P. falciparum and rodent P. berghei parasites. In addition, we biochemically fractionated infected red blood cells to localize Ago2. We also quantified parasite growth and sexual commitment in the presence of the Ago2 inhibitor BCI-137. Results: Ago2 localization by fluorescence microscopy produced inconclusive results across the three different antibodies, suggesting cross-reactivity with parasite targets. Biochemical separation of parasite and RBC cytoplasm detected Ago2 only in the RBC cytoplasm and not in the parasite. Inhibition of Ago2 using BCl-137 did not result in altered parasite development. Conclusion: Ago2 localization in infected RBCs by microscopy is confounded by non-specific binding of antibodies. Complementary results using biochemical fractionation and Ago2 detection by western blot did not detect the protein in the parasite cytosol, and growth assays using a specific inhibitor demonstrated that its catalytical activity is not required for parasite development. We therefore conclude that previous data localising Ago2 to parasite ring stages are due to antibody cross reactivity, and that Ago2 is not required for intracellular Plasmodium development.

scholarly journals Local Hematocrit Fluctuation Induced by Malaria-Infected Red Blood Cells and Its Effect on Microflow

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Tong Wang ◽  
Zhongwen Xing
Keyword(s):  
Blood Flow ◽  
Plasmodium Falciparum ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Volume Fraction ◽  
Numerical Approach ◽  
Infected Rbcs ◽  
Infected Cells ◽  
Slow Moving ◽  
Cell Free Layer

We investigate numerically the microscale blood flow in which red blood cells (RBCs) are partially infected byPlasmodium falciparum, the malaria parasite. The infected RBCs are modeled as more rigid cells with less deformability than healthy ones. Our study illustrates that, in a 10 μm microvessel in low-hematocrit conditions (18% and 27%), thePlasmodium falciparum-infected red blood cells (Pf-IRBCs) and healthy ones first form a train of cells. Because of the slow moving of thePf-IRBCs, the local hematocrit (Hct) near thePf-IRBCs is then increased, to approximately40%or even higher values. This increase of the local hematocrit is temporary and is kept for a longer length of time because of the long RBC train formed in 27%-Hctcondition. Similar hematocrit elevation at the downstream region with 45%-Hctin the same 10 μm microvessel is also observed with the cells randomly located. In 20 μm microvessels with 45%-Hct, thePf-IRBCs slow down the velocity of the healthy red blood cells (HRBCs) around them and then locally elevate the volume fraction and result in the accumulation of the RBCs at the center of the vessels, thus leaving a thicker cell free layer (CFL) near the vessel wall than normal. Variation of wall shear stress (WSS) is caused by the fluctuation of localHctand the distance between the wall and the RBCs. Moreover, in high-hematocrit condition (45%), malaria-infected cells have a tendency to migrate to the edge of the aggregates which is due to the uninterrupted hydrodynamic interaction between the HRBCs andPf-IRBC. Our results suggest that the existence of Pf-IRBCs is a nonnegligible factor for the fluctuation of hematocrit and WSS and also contributes to the increase of CFL of pathological blood flow in microvessels. The numerical approach presented has the potential to be utilized to RBC disorders and other hematologic diseases.

scholarly journals No evidence for Ago2 translocation from the host erythrocyte into the Plasmodium parasite

2020 ◽  
Vol 5 ◽  
pp. 92
Author(s):  
Franziska Hentzschel ◽  
Klara Obrova ◽  
Matthias Marti
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Specific Binding ◽  
Specific Inhibitor ◽  
Cross Reactivity ◽  
Host Protein ◽  
Parasite Development ◽  
Argonaute 2 ◽  
Infected Rbcs ◽  
Biochemical Fractionation

Background: Plasmodium parasites rely on various host factors to grow and replicate within red blood cells (RBC). While many host proteins are known that mediate parasite adhesion and invasion, few examples of host enzymes co-opted by the parasite during intracellular development have been described. Recent studies suggested that the host protein Argonaute 2 (Ago2), which is involved in RNA interference, can translocate into the parasite and affect its development. Here, we investigated this hypothesis. Methods: We used several different monoclonal antibodies to test for Ago2 localisation in the human malaria parasite, P. falciparum and rodent P. berghei parasites. In addition, we biochemically fractionated infected red blood cells to localize Ago2. We also quantified parasite growth and sexual commitment in the presence of the Ago2 inhibitor BCI-137. Results: Ago2 localization by fluorescence microscopy produced inconclusive results across the three different antibodies, suggesting cross-reactivity with parasite targets. Biochemical separation of parasite and RBC cytoplasm detected Ago2 only in the RBC cytoplasm and not in the parasite. Inhibition of Ago2 using BCl-137 did not result in altered parasite development. Conclusion: Ago2 localization in infected RBCs by microscopy is confounded by non-specific binding of antibodies. Complementary results using biochemical fractionation and Ago2 detection by western blot did not detect the protein in the parasite cytosol, and growth assays using a specific inhibitor demonstrated that its catalytical activity is not required for parasite development. We therefore conclude that previous data localising Ago2 to parasite ring stages are due to antibody cross reactivity, and that Ago2 is not required for intracellular Plasmodium development.

scholarly journals De Novo Generated Human Red Blood Cells in Humanized Mice Support Plasmodium falciparum Infection

PLoS ONE ◽  
2015 ◽  
Vol 10 (6) ◽  
pp. e0129825 ◽  
Author(s):  
Anburaj Amaladoss ◽  
Qingfeng Chen ◽  
Min Liu ◽  
Sara K. Dummler ◽  
Ming Dao ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Red Blood Cells ◽  
Blood Cells ◽  
De Novo ◽  
Falciparum Infection ◽  
Humanized Mice ◽  
Plasmodium Falciparum Infection ◽  
Human Red Blood Cells

scholarly journals Selective permeabilization of the host cell membrane of Plasmodium falciparum-infected red blood cells with streptolysin O and equinatoxin II

2007 ◽  
Vol 403 (1) ◽  
pp. 167-175 ◽  
Author(s):  
Katherine E. Jackson ◽  
Tobias Spielmann ◽  
Eric Hanssen ◽  
Akinola Adisa ◽  
Frances Separovic ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Cell Membrane ◽  
Red Blood Cells ◽  
Host Cell ◽  
Blood Cells ◽  
Parasitophorous Vacuole ◽  
Host Cell Membrane ◽  
Streptolysin O ◽  
Infected Rbcs ◽  
Equinatoxin Ii

Plasmodium falciparum develops within the mature RBCs (red blood cells) of its human host in a PV (parasitophorous vacuole) that separates the host cell cytoplasm from the parasite surface. The pore-forming toxin, SLO (streptolysin O), binds to cholesterol-containing membranes and can be used to selectively permeabilize the host cell membrane while leaving the PV membrane intact. We found that in mixtures of infected and uninfected RBCs, SLO preferentially lyses uninfected RBCs rather than infected RBCs, presumably because of differences in cholesterol content of the limiting membrane. This provides a means of generating pure preparations of viable ring stage infected RBCs. As an alternative permeabilizing agent we have characterized EqtII (equinatoxin II), a eukaryotic pore-forming toxin that binds preferentially to sphingomyelin-containing membranes. EqtII lyses the limiting membrane of infected and uninfected RBCs with similar efficiency but does not disrupt the PV membrane. It generates pores of up to 100 nm, which allow entry of antibodies for immunofluorescence and immunogold labelling. The present study provides novel tools for the analysis of this important human pathogen and highlights differences between Plasmodium-infected and uninfected RBCs.

scholarly journals Functional alteration of red blood cells by a megadalton protein of Plasmodium falciparum

Blood ◽  
2009 ◽  
Vol 113 (4) ◽  
pp. 919-928 ◽  
Author(s):  
Fiona K. Glenister ◽  
Kate M. Fernandez ◽  
Lev M. Kats ◽  
Eric Hanssen ◽  
Narla Mohandas ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Membrane Skeleton ◽  
Membrane Structures ◽  
Rbc Membrane ◽  
Infected Rbcs ◽  
Membrane Rigidity ◽  
Transgenic Parasites ◽  
Normal Adhesion

AbstractProteins exported from Plasmodium falciparum parasites into red blood cells (RBCs) interact with the membrane skeleton and contribute to the pathogenesis of malaria. Specifically, exported proteins increase RBC membrane rigidity, decrease deformability, and increase adhesiveness, culminating in intravascular sequestration of infected RBCs (iRBCs). Pf332 is the largest (>1 MDa) known malaria protein exported to the RBC membrane, but its function has not previously been determined. To determine the role of Pf332 in iRBCs, we have engineered and analyzed transgenic parasites with Pf332 either deleted or truncated. Compared with RBCs infected with wild-type parasites, mutants lacking Pf332 were more rigid, were significantly less adhesive to CD36, and showed decreased expression of the major cytoadherence ligand, PfEMP1, on the iRBC surface. These abnormalities were associated with dramatic morphologic changes in Maurer clefts (MCs), which are membrane structures that transport malaria proteins to the RBC membrane. In contrast, RBCs infected with parasites expressing truncated forms of Pf332, although still hyperrigid, showed a normal adhesion profile and morphologically normal MCs. Our results suggest that Pf332 both modulates the level of increased RBC rigidity induced by P falciparum and plays a significant role in adhesion by assisting transport of PfEMP1 to the iRBC surface.

Ultrastructural observations on the in vitro cytoadherence of Plasmodium falciparum infected red blood cells

1990 ◽  
Vol 48 (3) ◽  
pp. 914-915
Author(s):  
D.J.P. Ferguson ◽  
A.R. Berendt ◽  
J. Tansey ◽  
K. Marsh ◽  
C.I. Newbold
Keyword(s):  
Plasmodium Falciparum ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Umbilical Vein ◽  
Cell Types ◽  
Amelanotic Melanoma ◽  
Cytoplasmic Process ◽  
Umbilical Vein Endothelial Cells

In human malaria, the most serious clinical manifestation is cerebral malaria (CM) due to infection with Plasmodium falciparum. The pathology of CM is thought to relate to the fact that red blood cells containing mature forms of the parasite (PRBC) cytoadhere or sequester to post capillary venules of various tissues including the brain. This in vivo phenomenon has been studied in vitro by examining the cytoadherence of PRBCs to various cell types and purified proteins. To date, three Ijiost receptor molecules have been identified; CD36, ICAM-1 and thrombospondin. The specific changes in the PRBC membrane which mediate cytoadherence are less well understood, but they include the sub-membranous deposition of electron-dense material resulting in surface deformations called knobs. Knobs were thought to be essential for cytoadherence, lput recent work has shown that certain knob-negative (K-) lines can cytoadhere. In the present study, we have used electron microscopy to re-examine the interactions between K+ PRBCs and both C32 amelanotic melanoma cells and human umbilical vein endothelial cells (HUVEC).We confirm previous data demonstrating that C32 cells possess numerous microvilli which adhere to the PRBC, mainly via the knobs (Fig. 1). In contrast, the HUVEC were relatively smooth and the PRBCs appeared partially flattened onto the cell surface (Fig. 2). Furthermore, many of the PRBCs exhibited an invagination of the limiting membrane in the attachment zone, often containing a cytoplasmic process from the endothelial cell (Fig. 2).

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