Nitro-Heterocyclic compounds induce apoptosis-like effects in Leishmania (L). amazonensis promastigotes

Abstract Background: Three drugs - pentavalent antimonials, amphotericin B and pentamidine - are currently used for leishmaniasis treatment. They are administered for long periods, only parenterally, and have high cardiac, renal and hepatic toxicities. Therefore, the investigation of new compounds is required. Nitro-heterocyclic derivatives have been used as possible drug candidates to treat diseases caused by trypanosomatids. Methods: Leishmania (L.) amazonensis promastigotes (MHO/BR/73/M2269), maintained in the Laboratório de Soroepidemiologia - Instituto de Medicina Tropical- USP, were exposed to five nitroheterocyclic derivatives, with differences at phenyl-ring position 4: BSF-C4H9, BSF-H, BSF-NO2, BSF-CH3 and BSF-Cl, for 48 hours. After analyzing viability (MTT assay), we evaluated cellular-morphology activity of compounds by transmission electron microscopy (TEM) and measurement of apoptosis (phosphatidylserine expression) by flow cytometry. Results: EC50 of amphotericin B and BSF-CH3 were 0.50 (M and 0.39 (M respective. Other nitro-heterocyclic compounds presented EC50 higher than amphotericin B. All compounds showed greater AV- and PI-positive expression than amphotericin B at 100 (M, except BSF-NO2. TEM showed complete nuclear disfigurement with 100 (M of BSF-NO2, 25 and 6.25 (M of BSF-H, and 6.25 (M BSF-Cl; presence of vesicles within the flagellar pocket with 25 (M BSF-H; alteration of the kinetoplast with 25 (M BSF-C4H9, 25 (M of BSF-H, 6.25 (M BSF-CH3 and 6.25 (M of BSF-Cl. Conclusions: Nitro-heterocyclic compounds have shown activity against promastigotes of L. amazonensis, at lower concentrations. However, improvement of compound scaffolds are needed to assist the elucidation of the mechanism of action and to achieve greater activity.

Effects of nitro-heterocyclic derivatives against Leishmania (Leishmania) infantum promastigotes and intracellular amastigotes

Leishmaniasis is an overlooked tropical disease affecting approximately 1 million people in several countries. Clinical manifestation depends on the interaction between Leishmania and the host's immune response. Currently available treatment options for leishmaniasis are limited and induce severe side effects. In this research, we tested nitro-heterocyclic compounds (BSF series) as a new alternative against Leishmania. Its activity was measured in Leishmania (Leishmania) infantum promastigotes and intracellular amastigotes using MTT colorimetric assay. Additionally, we assessed the phosphatidylserine exposure by promastigotes, measured by flow cytometry, as well as nitric oxide production, measured by Griess' method. The nitro-heterocyclic compounds (BSF series) showed activity against L. (L.) infantum promastigotes, inducting the phosphatidylserine exposition by promastigotes, decreasing intracellular amastigotes and increasing oxide nitric production. The selectivity index was more prominent to Leishmania than to macrophages. Compared to amphotericin b, our compounds presented higher IC50, however the selectivity index was more specific to parasite than to amphotericin b. In conclusion, these nitro-heterocyclic compounds showed to be promising as an anti-Leishmania drug, in in vitro studies