Food vacuole‐associated lipid bodies and heterogeneous lipid environments in the malaria parasite, Plasmodium falciparum

Abstract

SummaryThe malaria parasite Plasmodium falciparum induces a sixfold increase in the phospholipid content of infected erythrocytes during its intraerythrocytic growth. We have characterized the lipid environments in parasitized erythrocyte using the hydrophobic probe, Nile Red. Spectral imaging with a confocal microscope revealed heterogeneous lipid environments in parasite-infected erythrocytes. An insight into the nature of these environments was gained by comparing these spectra with those of triacylglycerol/ phospholipid emulsions and phospholipid membranes. Using this approach, we identified a population of intensely stained particles of a few hundred nanometers in size that are closely associated with the digestive vacuole of the parasite and appear to be composed of neutral lipids. Electron microscopy and isolation of food vacuoles confirmed the size of these particles and their intimate association respectively. Lipid analysis suggests that these neutral lipid bodies are composed of di-and triacylgycerols and may represent storage organelles for lipid intermediates that are generated during digestion of phospholipids in the food vacuole. Mono-, di-and triacylglycerol suspensions promote b b b b -haematin formation, suggesting that these neutral lipid bodies, or their precursors, may also be involved in haem detoxification. We also characterized other compartments of the infected erythrocyte that were stained less intensely with the Nile Red probe. Both the erythrocyte membrane and the parasite membrane network exhibit red shifts compared with the neutral lipid bodies that are consistent with cholesterol-rich and cholesterol-poor membranes respectively. Ratiometric imaging revealed more subtle variations in the lipid environments within the parasite membrane network.

The mechanism of antimalarial action of the ruthenium(II)–chloroquine complex [RuCl2(CQ)]2

“…This means that the metal complex probably accumulates near water-lipid interface regions within the digestive vacuole of the parasite, rather than deeply inside the aqueous regions where CQ concentrates. This observation, together with the idea that lipids catalyze heme aggregation within plasmodium food vacuoles [47,48] and with the findings of Egan et al [36] that β-hematin spontaneously forms by rapid self-assembly near octanol-water or lipid-water interfaces can explain the enhanced antimalarial activity of complex 1 both in vitro and in vivo, when compared with CQ. Furthermore, the fact that the complex is active against CQ-resistant strains of P. falciparum may also be related to its greater lipophilicity, in line with previous reports indicating a lowered ability of the mutated transmembrane transporter PfCRT to promote the efflux of highly lipophilic drugs [40,51].…”

“…2b), indicating that in the pH region corresponding to the acidity of the food vacuole of the malaria parasite CQ will be concentrated strongly in the aqueous regions, whereas the effective concentration of complex 1 will be greater at or near water-lipid interfaces. This is important in connection with the proposal that lipids catalyze heme aggregation, probably by increasing heme solubility in acidic environments [47]; neutral lipids that catalyze the formation of hemozoin in vitro have been shown to form lipid bodies associated with plasmodium food vacuoles [48]. Egan et al [36] recently demonstrated that under acidic physiologically realistic conditions β-hematin spontaneously forms by rapid selfassembly near octanol-water, pentanol-water, or lipid-water interfaces.…”

Phospholipases during membrane dynamics in malaria parasites

“…TAG and DAG increase by 2-to 5-fold in the parasite during the 48-hours RBC infection (Gulati et al, 2015). These NLs accumulate mostly in the FV, where they appear to be involved in heme detoxification (Gulati et al, 2015;Jackson et al, 2004).…”

A phosphatidylcholine‐BODIPY 581/591 conjugate allows mapping of oxidative stress in P. falciparum‐infected erythrocytes

“…4Avi), BODIPY 581/591-PC molecules located in a punctate structure adjacent to the digestive vacuole (marked by the presence of hemozoin in the DIC image) appear to be relatively protected from oxidation (i.e., this structure appears purple in the ratiometric image). This structure may be a neutral lipid body (44).…”