scholarly journals Breakdown in membrane asymmetry regulation leads to monocyte recognition of P. falciparum-infected red blood cells

2021 ◽  
Vol 17 (2) ◽  
pp. e1009259
Author(s):  
Merryn Fraser ◽  
Weidong Jing ◽  
Stefan Bröer ◽  
Florian Kurth ◽  
Leif-Erik Sander ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Fluorescent Dyes ◽  
Host Immune System ◽  
Enzymatic Reactions ◽  
Membrane Asymmetry ◽  
Outer Leaflet ◽  
Rbc Membrane ◽  
Infected Rbcs ◽  
Underlying Causes

The human malaria parasite Plasmodium falciparum relies on lipids to survive; this makes its lipid metabolism an attractive drug target. The lipid phosphatidylserine (PS) is usually confined to the inner leaflet of the red blood cell membrane (RBC) bilayer; however, some studies suggest that infection with the intracellular parasite results in the presence of this lipid in the RBC membrane outer leaflet, where it could act as a recognition signal to phagocytes. Here, we used fluorescent lipid analogues and probes to investigate the enzymatic reactions responsible for maintaining asymmetry between membrane leaflets, and found that in parasitised RBCs the maintenance of membrane asymmetry was partly disrupted, and PS was increased in the outer leaflet. We examined the underlying causes for the differences between uninfected and infected RBCs using fluorescent dyes and probes, and found that calcium levels increased in the infected RBC cytoplasm, whereas membrane cholesterol was depleted from the erythrocyte plasma membrane. We explored the resulting effect of PS exposure on enhanced phagocytosis by monocytes, and show that infected RBCs must expend energy to limit phagocyte recognition, and provide experimental evidence that PS exposure contributes to phagocytic recognition of P. falciparum-infected RBCs. Together, these findings underscore the pivotal role for PS exposure on the surface of Plasmodium falciparum-infected erythrocytes for in vivo interactions with the host immune system, and provide a rationale for targeted antimalarial drug design.

scholarly journals Plasmodium falciparum-infected erythrocyte receptor(s) for CD36 and thrombospondin are restricted to knobs on the erythrocyte surface.

1992 ◽  
Vol 40 (9) ◽  
pp. 1419-1422 ◽  
Author(s):  
K Nakamura ◽  
T Hasler ◽  
K Morehead ◽  
R J Howard ◽  
M Aikawa
Keyword(s):  
Endothelial Cells ◽  
Plasmodium Falciparum ◽  
Cerebral Malaria ◽  
Vascular Occlusion ◽  
Cerebral Microvessels ◽  
Erythrocyte Surface ◽  
Infected Rbcs ◽  
First Time

Adherence of Plasmodium falciparum-infected RBCs (PRBC) to endothelial cells causes PRBC sequestration in cerebral microvessels and is considered to be a major contributor to the pathogenesis of cerebral malaria. Both CD36 and thrombospondin (TSP) are glycoproteins that mediate PRBC adherence to endothelial cells in vitro. Because they are both expressed on the surface of endothelial cells, they probably contribute to PRBC sequestration and vascular occlusion in vivo. By applying affinity labeling of receptor binding sites with purified ligands, we showed for the first time that both CD36 and TSP can bind independently to the PRBC surface and that the PRBC receptor(s) for CD36 and TSP are localized specifically to the electron-dense knob protrusions of the PRBC surface. These findings may help in efforts to develop a malaria vaccine to prevent cerebral malaria.

scholarly journals Novel Antimalarial Aminoquinolines: Heme Binding and Effects on Normal or Plasmodium falciparum-Parasitized Human Erythrocytes

2009 ◽  
Vol 53 (10) ◽  
pp. 4339-4344 ◽  
Author(s):  
Fausta Omodeo-Salè ◽  
Lucia Cortelezzi ◽  
Nicoletta Basilico ◽  
Manolo Casagrande ◽  
Anna Sparatore ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Antimalarial Activity ◽  
Heme Binding ◽  
Human Red Blood Cells ◽  
Rbc Membrane ◽  
Alkyl Derivatives ◽  
Resistant Strains ◽  
Dose Dependent

ABSTRACT Two new quinolizidinyl-alkyl derivatives of 7-chloro-4-aminoquinoline, named AM-1 and AP4b, which are highly effective in vitro against both the D10 (chloroquine [CQ] susceptible) and W2 (CQ resistant) strains of Plasmodium falciparum and in vivo in the rodent malaria model, have been studied for their ability to bind to and be internalized by normal or parasitized human red blood cells (RBC) and for their effects on RBC membrane stability. In addition, an analysis of the heme binding properties of these compounds and of their ability to inhibit beta-hematin formation in vitro has been performed. Binding of AM1 or AP4b to RBC is rapid, dose dependent, and linearly related to RBC density. Their accumulation in parasitized RBC (pRBC) is increased twofold compared to levels in normal RBC. Binding of AM1 or AP4b to both normal and pRBC is higher than that of CQ, in agreement with the lower pKa and higher lipophilicity of the compounds. AM1 or AP4b is not hemolytic per se and is less hemolytic than CQ when hemolysis is accelerated (induced) by hematin. Moreover, AM-1 and AP4b bind heme with a stoichiometry of interaction similar to that of CQ (about 1:1.7) but with a lower affinity. They both inhibit dose dependently the formation of beta-hematin in vitro with a 50% inhibitory concentration comparable to that of CQ. Taken together, these results suggest that the antimalarial activity of AM1 or AP4b is likely due to inhibition of hemozoin formation and that the efficacy of these compounds against the CQ-resistant strains can be ascribed to their hydrophobicity and capacity to accumulate in the vacuolar lipid (elevated lipid accumulation ratios).

scholarly journals Carrier-Mediated Partitioning of Artemisinin into Plasmodium falciparum-Infected Erythrocytes

2002 ◽  
Vol 46 (1) ◽  
pp. 105-109 ◽  
Author(s):  
Nehal Vyas ◽  
Bonnie A. Avery ◽  
Mitchell A. Avery ◽  
Christy M. Wyandt
Keyword(s):  
Plasmodium Falciparum ◽  
Drug Concentration ◽  
Blood Cells ◽  
Competitive Inhibition ◽  
Temperature Dependent ◽  
Optimum Time ◽  
Rbc Membrane ◽  
Drug Concentrations ◽  
Infected Rbcs ◽  
Time Periods

ABSTRACT The purpose of the present study was to characterize the partitioning of artemisinin into both uninfected and Plasmodium falciparum-infected red blood cells (RBCs). The partitioning of [14C](+)-artemisinin into RBCs was studied at four different hematocrit levels and eight time periods. At the optimum time of 2 h, the partitioning process was investigated with eight different drug concentrations ranging from 0.88 to 3.52 μM at 37 and 4°C. The effect of the presence of unlabeled artemisinin on the partitioning of the same concentration of [14C]artemisinin was studied. About 35 to 40% of the drug was seen to partition into uninfected RBCs at a hematocrit of 33%, irrespective of the incubation period or the drug concentration used. In contrast, infected RBCs showed an increase in partitioning of the drug with time until saturation was achieved at 1 h. While the partitioning of artemisinin into parasitized RBCs at 37°C was found to be significantly higher than that in nonparasitized RBCs, at 4°C both parasitized and nonparasitized RBCs showed identical partitioning of the drug. The partitioning of [14C]artemisinin into parasitized RBCs was completely inhibited in the presence of the same concentration of unlabeled artemisinin. However, no such effect was observed in nonparasitized cells, and no evidence suggesting that binding of the drug in parasitized RBCs is reversible was found. The partitioning of artemisinin into parasitized RBCs was found to be rapid, saturable, temperature dependent, irreversible, and subject to competitive inhibition with unlabeled artemisinin. The results obtained suggest the involvement of carrier mediation in the partitioning of artemisinin across the parasitized RBC membrane. In contrast, simple passive diffusion of artemisinin was seen in nonparasitized RBCs.

scholarly journals Hemolysis-associated phosphatidylserine exposure promotes polyclonal plasmablast differentiation

2021 ◽  
Vol 218 (6) ◽  
Author(s):  
Rahul Vijay ◽  
Jenna J. Guthmiller ◽  
Alexandria J. Sturtz ◽  
Sequoia Crooks ◽  
Jordan T. Johnson ◽  
...  
Keyword(s):  
Cell Activation ◽  
Parasite Burden ◽  
B Cell Activation ◽  
Plasmodium Parasite ◽  
Rbc Membrane ◽  
Phosphatidylserine Exposure ◽  
Phosphatidylserine Receptor ◽  
Infected Rbcs ◽  
And Function

Antimalarial antibody responses are essential for mediating the clearance of Plasmodium parasite–infected RBCs from infected hosts. However, the rapid appearance of large numbers of plasmablasts in Plasmodium-infected hosts can suppress the development and function of durable humoral immunity. Here, we identify that the formation of plasmablast populations in Plasmodium-infected mice is mechanistically linked to both hemolysis-induced exposure of phosphatidylserine on damaged RBCs and inflammatory cues. We also show that virus and Trypanosoma infections known to trigger hemolytic anemia and high-grade inflammation also induce exuberant plasmablast responses. The induction of hemolysis or administration of RBC membrane ghosts increases plasmablast differentiation. The phosphatidylserine receptor Axl is critical for optimal plasmablast formation, and blocking phosphatidylserine limits plasmablast expansions and reduces Plasmodium parasite burden in vivo. Our findings support that strategies aimed at modulating polyclonal B cell activation and phosphatidylserine exposure may improve immune responses against Plasmodium parasites and potentially other infectious diseases that are associated with anemia.

scholarly journals CD47-SIRPα Interactions Regulate Macrophage Uptake of Plasmodium falciparum-Infected Erythrocytes and Clearance of MalariaIn Vivo

2016 ◽  
Vol 84 (7) ◽  
pp. 2002-2011 ◽  
Author(s):  
Kodjo Ayi ◽  
Ziyue Lu ◽  
Lena Serghides ◽  
Jenny M. Ho ◽  
Constance Finney ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Fusion Protein ◽  
Regulatory Protein ◽  
Content Type ◽  
Fc Fusion Protein ◽  
Infected Rbcs ◽  
Deficient Mice ◽  
Macrophage Uptake

CD47 engagement by the macrophage signal regulatory protein alpha (SIRPα) inhibits phagocytic activity and protects red blood cells (RBCs) from erythrophagocytosis. The role of CD47-SIRPα in the innate immune response toPlasmodium falciparuminfection is unknown. We hypothesized that disruption of SIRPα signaling may enhance macrophage uptake of malaria parasite-infected RBCs. To test this hypothesis, we examinedin vivoclearance in CD47-deficient mice infected withPlasmodium bergheiANKA andin vitrophagocytosis ofP. falciparum-infected RBCs by macrophages from SHP-1-deficient (Shp-1−/−) mice and NOD.NOR-Idd13.Prkdcscid(NS-Idd13) mice, as well as human macrophages, following disruption of CD47-SIRPα interactions with anti-SIRPα antibodies or recombinant SIRPα-Fc fusion protein. Compared to their wild-type counterparts,Cd47−/−mice displayed significantly lower parasitemia, decreased endothelial activation, and enhanced survival. Using macrophages from SHP-1-deficient mice or from NS-Idd13mice, which express a SIRPα variant that does not bind human CD47, we showed that altered SIRPα signaling resulted in enhanced phagocytosis ofP. falciparum-infected RBCs. Moreover, disrupting CD47-SIRPα engagement using anti-SIRPα antibodies or SIRPα-Fc fusion protein also increased phagocytosis ofP. falciparum-infected RBCs. These results indicate an important role for CD47-SIRPα interactions in innate control of malaria and suggest novel targets for intervention.

scholarly journals Biophysical and biomolecular interactions of malaria-infected erythrocytes in engineered human capillaries

2020 ◽  
Vol 6 (3) ◽  
pp. eaay7243 ◽  
Author(s):  
Christopher Arakawa ◽  
Celina Gunnarsson ◽  
Caitlin Howard ◽  
Maria Bernabeu ◽  
Kiet Phong ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Blood Cell ◽  
Vessel Wall ◽  
Three Dimensional ◽  
Wild Type ◽  
Infected Rbcs ◽  
Kinetics Of ◽  
Microvascular Diseases ◽  
Shed Light

Microcirculatory obstruction is a hallmark of severe malaria, but mechanisms of parasite sequestration are only partially understood. Here, we developed a robust three-dimensional microvessel model that mimics the arteriole-capillary-venule (ACV) transition consisting of a narrow 5- to 10-μm-diameter capillary region flanked by arteriole- or venule-sized vessels. Using this platform, we investigated red blood cell (RBC) transit at the single cell and at physiological hematocrits. We showed normal RBCs deformed via in vivo–like stretching and tumbling with negligible interactions with the vessel wall. By comparison, Plasmodium falciparum–infected RBCs exhibited virtually no deformation and rapidly accumulated in the capillary-sized region. Comparison of wild-type parasites to those lacking either cytoadhesion ligands or membrane-stiffening knobs showed highly distinctive spatial and temporal kinetics of accumulation, linked to velocity transition in ACVs. Our findings shed light on mechanisms of microcirculatory obstruction in malaria and establish a new platform to study hematologic and microvascular diseases.

Plasmodium falciparum likely encodes the principal anion channel on infected human erythrocytes

Blood ◽  
2004 ◽  
Vol 104 (13) ◽  
pp. 4279-4286 ◽  
Author(s):  
Abdulnaser Alkhalil ◽  
Jamieson V. Cohn ◽  
Marissa A. Wagner ◽  
Jennifer S. Cabrera ◽  
Thavamani Rajapandi ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Ion Channel ◽  
Anion Channel ◽  
Host Protein ◽  
Single Donor ◽  
Rbc Membrane ◽  
Parasite Plasmodium ◽  
Voltage Dependent ◽  
Parasite Plasmodium Falciparum ◽  
Infected Rbcs

Abstract Invasion by the human malaria parasite, Plasmodium falciparum, is associated with marked yet selective increases in red blood cell (RBC) membrane permeability. We previously identified an unusual voltage-dependent ion channel, the plasmodial surface anion channel (PSAC), which may account for these increases. Since then, controversy has arisen about whether there are additional parasite-induced anion channels on the RBC membrane and whether these channels are parasite-encoded proteins or the result of modifications of an endogenous host protein. Here, we used genetically divergent parasite isolates and quantitative transport measurements to examine these questions. Our studies indicate that PSAC alone can adequately account for the increased permeability of infected RBCs to key solutes. Two distinct parasite isolates, grown in RBCs from a single donor, exhibit channel activity with measurably different voltage-dependent gating, a finding difficult to reconcile with simple activation or modification of a host protein. Instead, this difference in channel gating can be conservatively explained by a small number of polymorphisms in a parasite gene that encodes PSAC. The absence of known eukaryotic ion channel homologues in the completed P falciparum genome suggests a novel channel gene, and substantiates PSAC as a target for antimalarial development.

scholarly journals Multiple stiffening effects of nanoscale knobs on human red blood cells infected with Plasmodium falciparum malaria parasite

2015 ◽  
Vol 112 (19) ◽  
pp. 6068-6073 ◽  
Author(s):  
Yao Zhang ◽  
Changjin Huang ◽  
Sangtae Kim ◽  
Mahdi Golkaram ◽  
Matthew W. A. Dixon ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Strain Hardening ◽  
Malaria Parasite ◽  
Molecular Mechanisms ◽  
Molecular Structures ◽  
Coarse Grained ◽  
Cell Stiffness ◽  
Rbc Membrane ◽  
Infected Rbcs ◽  
Spectrin Network

During its asexual development within the red blood cell (RBC), Plasmodium falciparum (Pf), the most virulent human malaria parasite, exports proteins that modify the host RBC membrane. The attendant increase in cell stiffness and cytoadherence leads to sequestration of infected RBCs in microvasculature, which enables the parasite to evade the spleen, and leads to organ dysfunction in severe cases of malaria. Despite progress in understanding malaria pathogenesis, the molecular mechanisms responsible for the dramatic loss of deformability of Pf-infected RBCs have remained elusive. By recourse to a coarse-grained (CG) model that captures the molecular structures of Pf-infected RBC membrane, here we show that nanoscale surface protrusions, known as “knobs,” introduce multiple stiffening mechanisms through composite strengthening, strain hardening, and knob density-dependent vertical coupling. On one hand, the knobs act as structural strengtheners for the spectrin network; on the other, the presence of knobs results in strain inhomogeneity in the spectrin network with elevated shear strain in the knob-free regions, which, given its strain-hardening property, effectively stiffens the network. From the trophozoite to the schizont stage that ensues within 24–48 h of parasite invasion into the RBC, the rise in the knob density results in the increased number of vertical constraints between the spectrin network and the lipid bilayer, which further stiffens the membrane. The shear moduli of Pf-infected RBCs predicted by the CG model at different stages of parasite maturation are in agreement with experimental results. In addition to providing a fundamental understanding of the stiffening mechanisms of Pf-infected RBCs, our simulation results suggest potential targets for antimalarial therapies.

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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