RESUMO
Malaria is caused by apicomplexan parasites of the Plasmodium genus. Plasmodium chabaudi is an excellent animal model for the study of human malaria caused by P. falciparum. Merozoites invade erythrocytes but are also found in other host cells including macrophages from the spleen and liver. Methodologies for obtaining merozoites usually involve treatment with protease inhibitors. However, merozoites obtained in this way may have their enzymatic profile altered and, therefore, are not ideal for cell-interaction assays. We report the obtainment of P. chabaudi merozoites naturally egressed from a synchronous erythrocyte population infected with schizonts forms. Merozoites had their infectivity and ultrastructure analyzed. Interaction assays were performed with mice erythrocytes and classically activated mice peritoneal macrophages, a very well-established classic model. Obtained merozoites were able to kill mice and efficiently infect erythrocytes. Interestingly, a lower merozoite:erythrocyte ratio resulted in a higher percentage of infected erythrocytes. We describe a simpler method for obtaining viable and infective merozoites. Classically activated macrophages killed merozoites, suggesting that these host cells may not serve as reservoirs for these parasites. These findings have implications for our understanding of P. chabaudi merozoite biology and may improve the comprehension of their host-parasite relationship.
RESUMO
BACKGROUND: Infections and inflammation lead to a downregulation of drug metabolism and kinetics in experimental animals. These changes in the expression and activities of drug-metabolizing enzymes may affect the effectiveness and safety of pharmacotherapy of infections and inflammatory conditions. OBJECTIVE: In this review, we addressed the available evidence on the effects of malaria on drug metabolism activity and kinetics in rodents and humans. RESULTS: An extensive literature review indicated that infection by Plasmodium spp consistently decreased the activity of hepatic Cytochrome P450s and phase-2 enzymes as well as the clearance of a variety of drugs in mice (lethal and non-lethal) and rat models of malaria. Malaria-induced CYP2A5 activity in the mouse liver was an exception. Except for paracetamol, pharmacokinetic trials in patients during acute malaria and in convalescence corroborated rodent findings. Trials showed that, in acute malaria, clearance of quinine, primaquine, caffeine, metoprolol, omeprazole, and antipyrine is slower and that AUCs are greater than in convalescent individuals. CONCLUSION: Notwithstanding the differences between rodent models and human malaria, studies in P. falciparum and P. vivax patients confirmed rodent data showing that CYP-mediated clearance of antimalarials and other drugs is depressed during the symptomatic disease when rises in levels of acute-phase proteins and inflammatory cytokines occur. Evidence suggests that inflammatory cytokines and the interplay between malaria-activated NF-kB-signaling and cell pathways controlling phase 1/2 enzyme genes transcription mediate drug metabolism changes. The malaria-induced decrease in drug clearance may exacerbate drug-drug interactions, and the occurrence of adverse drug events, particularly when patients are treated with narrow-margin-of-safety medicines.
Assuntos
Antimaláricos/farmacocinética , Sistema Enzimático do Citocromo P-450/metabolismo , Vias de Eliminação de Fármacos , Malária , Animais , Humanos , Inativação Metabólica , Malária/tratamento farmacológico , Malária/metabolismo , Taxa de Depuração Metabólica , RoedoresRESUMO
Malaria is caused by protozoan parasites of the genus Plasmodium, which is transmitted by Anopheline mosquitoes. Experimental murine models using rodent malaria are useful for studying pathologic aspects of severe malaria. We evaluated histopathologic lesions of TLR-2-/-, TLR-4-/-, TLR-6-/-, TLR-9-/-, CD14-/- and MyD88-/- mice experimentally infected with Plasmodium chabaudi. Frequencies and severity of microscopic lesions in the spleen and liver at one and four weeks post infection (wpi) were determined. At one wpi, adherence of macrophages to the endothelial surface was the most evident change, whereas at four wpi there was marked accumulation of cytoplasmic pigment in macrophages in the liver and spleen. Lesions were not markedly influenced by the absence of TLRs, MyD88 or CD14. Our findings suggest that acute and chronic phases of murine infection with P. chabaudi are characterized by distinct lesions. In addition, TLRs and MyD88 are not essential to promote these lesions during P. chabaudi infection.(AU)
Assuntos
Animais , Camundongos , Reações Bioquímicas , Malária , Plasmodium chabaudi/fisiologia , Receptores de Lipopolissacarídeos/análise , Receptor Toll-Like 9 , Receptor 2 Toll-Like/análise , Receptor 4 Toll-Like/análise , Receptor 6 Toll-Like/análise , Fator 88 de Diferenciação Mieloide/análiseRESUMO
Malaria is caused by protozoan parasites of the genus Plasmodium, which is transmitted by Anopheline mosquitoes. Experimental murine models using rodent malaria are useful for studying pathologic aspects of severe malaria. We evaluated histopathologic lesions of TLR-2-/-, TLR-4-/-, TLR-6-/-, TLR-9-/-, CD14-/-, and MyD-88-/- mice experimentally infected with Plasmodium chabaudi. Frequencies and severity of microscopic lesions in the spleen and liver at one and four weeks post infection (wpi) were determined. At one wpi, adherence of macrophages to the endothelial surface was the most evident change, whereas at four wpi there was marked accumulation of cytoplasmic pigment in macrophages in the liver and spleen. Lesions were not markedly influenced by the absence of TLRs, MyD88 or CD14. Our findings suggest that acute and chronic phases of murine infection with P. chabaudi are characterized by distinct lesions. In addition, TLRs and MyD88 are not essential to promote these lesions during P. chabaudi infection.
RESUMO
Plasmodium chabaudi malaria parasite organelles are major elements for ion homeostasis and cellular signaling and also target for antimalarial drugs. By using confocal imaging of intraerythrocytic parasites we demonstrated that the dye acridine orange (AO) is accumulated into P. chabaudi subcellular compartments. The AO could be released from the parasite organelles by collapsing the pH gradient with the K+/H+ ionophore nigericin (20 µM), or by inhibiting the H+-pump with bafilomycin (4 µM). Similarly, in isolated parasites loaded with calcium indicator Fluo 3-AM, bafilomycin caused calcium mobilization of the acidic calcium pool that could also be release with nigericin. Interestingly after complete release of the acidic compartments, addition of thapsigargin at 10 µM was still effective in releasing parasite intracellular calcium stores in parasites at trophozoite stage. The addition of antimalarial drugs chloroquine and artemisinin resulted in AO release from acidic compartments and also affected maintenance of calcium in ER store by using different drug concentrations.