Avaliação da atividade Antileishmanial de Cardenolídeos para uso no tratamento da Leishmaniose Visceral

Abstract

Leishmaniasis is a complex of diseases caused by protozoan parasites of the genus Leishmania, and can be divided into two major groups, cutaneous leishmaniasis and visceral leishmaniasis. The current treatment of visceral leishmaniasis (VL) has limitations due to drug toxicity and/or high cost, along with the emergence of parasite resistance. Drug development is a long and expensive process and, therefore, drug repositioning may represent an alternative. Cardenolides are used in the treatment of heart disease, especially those obtained from species of the genus Digitalis. In the present study, β-acetyl-digitoxin (b-AD) and digitoxigenin (DIGI), obtained from the methanolic extract of leaves of Digitalis lanata, were evaluated in vitro and in vivo against Leishmania infantum. The results showed direct action of b-AD and DIGI against the parasites, as well as efficacy in the treatment of infected macrophages. The investigation of the mechanism of action showed that b-AD and DIGI induced changes in the potential of the mitochondrial membrane, increased the levels of reactive oxygen species and caused the accumulation of lipid bodies in the parasites. DIGI and b-AD were incorporated into a polymeric micelle system based on Pluronic® F127 (DIGI/Mic and b-AD/Mic, respectively) and were used to treat mice infected with L. infantum. Miltefosine was used as a control. Animals treated with miltefosine, b-AD or b-AD/Mic and DIGI or DIGI/Mic showed significant reductions in parasitic load on the spleen, liver, bone marrow (BM) and draining lymph nodes (dLN), as well as the development of a specific Th1-type response, attested by the high levels of IFN-, IL 12, TNF-α, GM-CSF, nitrite and IgG2a isotype antibodies, in addition to low IL-4 and IL-10 contents, along with higher IFN--producing CD4+ and CD8+ T-cell frequency, when compared to controls. The results obtained one day after the treatment were corroborated with the data found 15 days after the treatment. In conclusion, the results suggest that b-AD/Mic and DIGI/Mic could be considered for additional studies for the treatment against VL.