Electrical Membrane Properties in the Model Leishmania-Macrophage (original) (raw)
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Experimental Parasitology, 2010
Understanding the impact of intracellular pathogens on the behavior of their host cells is key to designing new interventions. We are interested in how Leishmania alters the electrical function of the plasma membrane of the macrophage it infects. The specific question addressed here is the impact of Leishmania infection on macrophage membrane properties during the first 12 h post-infection. A decrease of 29% in macrophage membrane capacitance at 3 h post-infection indicates that the phagolysosome membrane is donated on entry by the macrophage plasma membrane. Macrophage membrane potential depolarized during the first 12 h post-infection, which associated with a decreased inward potassium current density, changed in inward rectifier conductance and increased outward potassium current density. Decreased membrane capacitance and membrane potential, with no changes in ion current density, were found in macrophages after phagocytosis of latex beads. Therefore we suggest that the macrophage membrane changes observed during early Leishmania infection appear to be associated with the phagocytic and activation processes.
Journal of Cellular Biochemistry, 1983
Species of the parasitic protozoan genus Leishmania are the causative agents of a wide variety of human cutaneous, mucocutaneous, and visceral diseases. These organisms reside throughout their digenetic life cycles in hydrolytic environs, ie, as extracellular, flagellated promastigote forms in the alimentary tract of their sandfly vector hosts and as obligate intracellular amastigote forms within the phagolysosomal system of macrophages in their mammalian hosts. In the latter hosts, cutaneous (eg L tropica, L major, and L mexicana) and mucocutaneous (eg, L braziliensis) species reside within, and are generally restricted to, macrophages of the skin and/or the mucous membranes, whereas viscerotropic species (eg, L donovani, L aethiopica, L infantum, and L chagasi) inhabit tissue macrophages of the spleen, liver (ie, Kupffer cells), and bone marrow [l-141. How these organisms transform, survive, and respond to signals within their infected hosts is unknown. However, considering that all physiologic and biochemical interactions between host and parasite occur, at least temporally, at or across such membranes (eg, they are in direct confrontation with both host immune and nonimmune responses, and all of an organism's nutrient requirements, as well as its secretory and metabolic excretory products, must traverse them), they must obviously play a central role in the survival and maintenance of the parasite within the infected host. Therefore, knowledge of the chemical, enzymatic, and antigenic composition of surface membranes are of import in defining the mechanisms by which Leishmania survive. Further, the identification of unique parasite surface membrane constituents may prove useful as adjuncts in the clinical diagnosis of leishmania1 infections in addition to serving as potential targets for the design of new and more effective chemotherapeutic agents and/or immunoprophylactic therapies.
Anionic site behavior in Leishmania and its role in the parasite-macrophage interaction
Journal of cell science, 1989
The behavior of cationized ferritin (CF) binding sites on the surface of Leishmania mexicana amazonensis (amastigotes, infective and non-infective promastigotes) and their participation in the interaction with macrophages were evaluated. Glutaral-dehyde-fixed parasites treated with CF present a uniform labelling over the whole cell surface. However, living parasites displayed CF patches and caps. Capping was usually seen towards the anterior (flagellated) portion of the cells, where shedding phenomena took place. These processes were inhibited by sodium azide but not by low temperature (4 degrees C). CF treatment of non-infective promastigotes led to an increase in their uptake by macrophages, whereas the uptake of amastigotes or infective promastigotes was not significantly altered. The effect of CF on the parasite surface charge was analyzed by whole-cell microelectrophoresis. The mean electrophoretic mobility (EPM) of non-infective promastigotes was decreased by 26%, while once a...
Parasitophorous vacuoles of Leishmania amazonensis-infected macrophages maintain an acidic pH
Infection and immunity, 1990
Leishmania amastigotes are intracellular protozoan parasites of mononuclear phagocytes which reside within parasitophorous vacuoles of phagolysosomal origin. The pH of these compartments was studied with the aim of elucidating strategies used by these microorganisms to evade the microbicidal mechanisms of their host cells. For this purpose, rat bone marrow-derived macrophages were infected with L. amazonensis amastigotes. Intracellular acidic compartments were localized by using the weak base 3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine as a probe. This indicator, which can be detected by light microscopy by using immunocytochemical methods, mainly accumulated in perinuclear lysosomes of uninfected cells, whereas in infected cells, it was essentially localized in parasitophorous vacuoles, which thus appeared acidified. Phagolysosomal pH was estimated quantitatively in living cells loaded with the pH-sensitive endocytic tracer fluoresceinated dextran. After a 15- to 20-h...
PubMed, 1988
To facilitate studies on the effect of chemotherapeutic agents on the host-parasite interaction in leishmaniasis, we have developed an experimental model for infecting mouse peritoneal macrophages in culture with recently-isolated Leishmania donovani promastigotes. As the drug action is often dependent on concentration, the distribution of sodium stibogluconate, which is the commonly used drug for treatment of leishmaniasis, was studied in various parts of the macrophages by energy dispersive X-ray microanalysis. The drug was found to accumulate in secondary lysosomes. The ultrastructural examination, using TEM and SEM, of macrophages, whose secondary lysosomes had been preloaded with gold particles, showed that leishmania parasites are phagocytosed and finally located in secondary lysosomes. Using flameless atomic absorption spectrophotometry, the concentration of Mn, Fe and Cu in promastigotes of Leishmania donovani, Leishmania aethiopica, Leishmania crithidia, Leishmania major and their culture media was estimated. Of the three transition metals, the parasites accumulated only Mn from the medium, which they may use in a primitive defense mechanism against reactive oxygen metabolites produced by macrophages during the respiratory burst associated with phagocytosis.
Journal of Cell Science, 1992
The continued success of Leishmania as an intramacrophage parasite is dependent on its ability to survive within an acidic intracellular compartment, resist degradation by lysosomal hydrolases, exploit the host cell as a source of nutrients, and avoid the macrophage's antigen-presenting capabilities. All these requirements are dependent on the properties of the parasitophorous vacuole in which Leishmania resides. This study shows that the vacuole possesses membrane proteins characteristic of a lysosome, and has MHC class II molecules. The trafficking of a variety of endocytic markers supports this finding. However, a temporal study up to 14 days post-infection indicates that, as it matures, the vacuole gains mannose 6-phosphate receptor, and becomes more accessible to endocytosed ligand, suggesting that the vacuole has functionally translocated from a lysosomal to late endosomal compartment. Endocytosed material was detected in the flagellar pocket and inside the amastigote, dem...
THE ULTRASTRUCTURE OF THE PARASITOPHOROUS VACUOLE FORMED BY LEISHMANIA MAJOR
Journal of Parasitology, 2006
Protozoan parasites of Leishmania spp. invade macrophages as promastigotes and differentiate into replicative amastigotes within parasitophorous vacuoles. Infection of inbred strains of mice with Leishmania major is a well-studied model of the mammalian immune response to Leishmania species, but the ultrastructure and biochemical properties of the parasitophorous vacuole occupied by this parasite have been best characterized for other species of Leishmania. We examined the parasitophorous vacuole occupied by L. major in lymph nodes of infected mice and in bone marrow-derived macrophages infected in vitro. At all time points after infection, single L. major amastigotes were wrapped tightly by host membrane, suggesting that amastigotes segregate into separate vacuoles during replication. This small, individual vacuole contrasts sharply with the large, communal vacuoles occupied by Leishmania amazonensis. An extensive survey of the literature revealed that the single vacuoles occupied by L. major are characteristic of those formed by Old World species of Leishmania, while New World species of Leishmania form large vacuoles occupied by many amastigotes.