Antiproliferative and ultrastructural effects of phenethylamine derivatives on promastigotes and amastigotes of Leishmania ( Leishmania ) infantum chagasi

The Natural Alkaloid Tryptanthrin Induces Apoptosis-like Death in Leishmania spp

Leishmaniasis is a vector-borne disease against which there are no approved vaccines, and the treatment is based on highly toxic drugs. The alkaloids consist of a chemical class of natural nitrogen-containing substances with a long history of antileishmanial activity. The present study aimed at determining the antileishmanial activity and in silico pharmacokinetic and toxicological potentials of tryptanthrin alkaloid. The anti-Leishmania amazonensis and anti-L. infantum assays were performed against both promastigotes and intracellular amastigotes. Cellular viability was determined by parasites’ ability to grow (promastigotes) or differentiate (amastigotes) after incubation with tryptanthrin. The mechanisms of action were explored by mitochondrion dysfunction and apoptosis-like death evaluation. For the computational pharmacokinetics and toxicological analysis (ADMET), tryptanthrin was submitted to the PreADMET webserver. The alkaloid displayed anti-promastigote activity against L. amazonensis and L. infantum (IC₅₀ = 11 and 8.0 μM, respectively). Tryptanthrin was active against intracellular amastigotes with IC₅₀ values of 75 and 115 μM, respectively. Mitochondrial membrane depolarization was observed in tryptanthrin-treated promastigotes. In addition, parasites undergoing apoptosis-like death were detected after 18 h of exposure. In silico ADMET predictions revealed that tryptanthrin has pharmacokinetic and toxicological properties similar to miltefosine. The results presented herein demonstrate that tryptanthrin is an interesting drug candidate against leishmaniasis.

Novel indol-3-yl-thiosemicarbazone derivatives: Obtaining, evaluation of in vitro leishmanicidal activity and ultrastructural studies

Parasitic diseases still represent serious public health problems, since the high and steady emergence of resistant strains is evident. Because parasitic infections are distributed predominantly in developing countries, less toxic, more efficient, safer and more accessible drugs have become desirable in the treatment of the infected population. This is the case of leishmaniasis, an infectious disease caused by a protozoan of the genus Leishmania sp., responsible for triggering pathological processes from the simplest to the most severe forms leading to high rates of morbidity and mortality throughout the world. In the search for new leishmanicidal drugs, the thiosemicarbazones and the indole fragments have been identified as promising structures for leishmanicidal activity. The present study proposes the synthesis and structural characterization of new indole-thiosemicarbazone derivatives (2a-j), in addition to performing in vitro evaluations through cytotoxicity assays using macrophages (J774) activity against forms of Leishmania infantum and Leishmania amazonensis promastigote as well as ultrastructural analyzes in promastigotes of L. infantum. Results show that the indole-thiosemicarbazone derivatives were obtained with yield values varying from 32.09 to 94.64%. In the evaluation of cytotoxicity, the indole-thiosemicarbazone compounds presented CC₅₀ values between 53.23 and 357.97 μM. Concerning the evaluation against L. amazonensis promastigote forms, IC₅₀ values ranged between 12.31 and  > 481.52 μM, while the activity against L. infantum promastigotes obtained IC₅₀ values between 4.36 and 23.35 μM. The compounds 2d and 2i tested against L. infantum were the most promising in the series, as they showed the lowest IC₅₀ values: 5.60 and 4.36 respectively. The parasites treated with the compounds 2d and 2i showed several structural alterations, such as shrinkage of the cell body, shortening and loss of the flagellum, intense mitochondrial swelling and vacuolization of the cytoplasm leading the parasite to cellular unviability. Therefore, the indole-thiosemicarbazone compounds are promising because they yield considerable synthesis, have low cytotoxicity to mammalian cells and act as leishmanicidal agents.

Ascorbic acid reduces the genetic damage caused by miltefosine (hexadecylphosphocholine) in animals infected by Leishmania (Leishamnia) infantum without decreasing its antileishmanial activity

Leishamaniasis is a neglected disease caused by over 20 Leishmania species, occurring in more than a hundred countries. Miltefosine (hexadecylphosphocholine) is the single oral drug used in treatment for leshmaniases, including cases of infections resistant to pentavalent antimony. Our group has recently demonstrated the ability of miltefosine to cause genomic lesions by DNA oxidation. Acknowledging that antioxidant compounds can potentially modulate Reactive Oxygen Species (ROS), our study verified whether ascorbic acid reduces the genotoxic and mutagenic effects caused by miltefosine, and whether it interferes with drug efficacy. For this purpose, uninfected Swiss mice received simultaneous (single dose treatment) miltefosine and ascorbic acid (gavage and intraperitoneally), besides pre and post treatments (ascorbic acid 24 h before and after drug administration); furthermore, Balb/c mice infected with Leishmania infantum received miltefosine plus ascorbic acid (repeated doses treatment). We conducted comet assays, micronucleus tests, dosages of superoxide dismutase enzyme and parasitic burden by the limiting dilution assay. We observed that ascorbic acid administered intraperitoneally displayed a protective effect over damage caused by miltefosine. However, this effect was not not observed when the same doses were administered via gavage, possibly due to low serum levels of this antioxidant. Ascorbic acid's protective effect reinforces that miltefosine damages DNA by oxidizing its nitrogenous bases, which is reduced by ascorbic acid due to its ability of protecting genetic material from the action of ROS. Therefore, our results show that this drug is efficient in reducing parasitic burden of L. infantum.