Synthesis and activity of novel tetrazole compounds and their pyrazole-4-carbonitrile precursors against Leishmania spp.

A new series of 5-(1-aryl-3-methyl-1H-pyrazol-4-yl)-1H-tetrazole derivatives (4a-m) and their precursor 1-aryl-3-methyl-1H-pyrazole-4-carbonitriles (3a-m) were synthesized and evaluated as antileishmanials against Leishmania braziliensis and Leishmania amazonensis promastigotes in vitro. In parallel, the cytotoxicity of these compounds was evaluated on the RAW 264.7 cell line. The results showed that among the assayed compounds the substituted 3-chlorophenyl (4a) (IC50/24h=15±0.14 µM) and 3,4-dichlorophenyl tetrazoles (4d) (IC50/24h=26±0.09 µM) were the most potent against L. braziliensis promastigotes, as compared the reference drug pentamidine, which presented IC50=13±0.04 µM. In addition, 4a and 4d derivatives were less cytotoxic than pentamidine. However, these tetrazole derivatives (4) and pyrazole-4-carbonitriles precursors (3) differ against each of the tested species and were more effective against L.braziliensis than on L. amazonensis.

The histopathological and immunological pattern of CBA mice infected with Leishmania amazonensis after treatment with pyrazole carbohydrazide derivatives.

Because there is no vaccine in clinical use, control of Leishmaniasis relies almost exclusively on chemotherapy and the conventional treatments exhibit high toxicity for patients and emerging drug resistance. Recently, we showed that oral treatment with synthetic pyrazole carbohydrazide compounds induced lower parasite load in draining lymph nodes and reduced skin lesion size without causing any toxic effects in an experimental murine infection model with Leishmania amazonensis. In this study, CBA mice were infected in the footpad with L. amazonensis and then orally treated with pyrazole carbohydrazides derivatives, such as BrNO(2), NO(2)Cl and NO(2)Br and their histopathological and immunological effects were then investigated. Epidermis and dermis had lower levels of inflammatory infiltration compared to the infected untreated control mice. In the dermis of treated animals, the numbers of vacuolated macrophages containing intracellular parasites were far lower than in infected untreated animals. In addition to dermal macrophages, we also observed a mixed inflammatory infiltrate containing lymphocytes and granulocyte cells. Lower numbers of B cells (B220+) and T lymphocytes (CD3+) were identified in the lesions of treated mice compared with the untreated, infected mice. In draining lymph node cells, the number of T lymphocytes (CD3+) was decreased, and the numbers of B cells (CD19+) and CD8+ T cells were increased in infected mice, when compared with the non-infected control group. In additional, we have shown that infected treated and untreated lymph node cells had similar levels of TGF-ß and IFN-γ mRNA expression, whereas IL-4 was expressed at a lower level in the treated group. Increased levels of the specific anti-Leishmania IgG2a or IgG3 antibody subclass were observed in NO(2)Cl or BrNO(2)-treated group, respectively. Overall, our experimental findings suggest that pyrazole carbohydrazides exert modulation of IL-4 expression and B cell levels; however, further evaluation is required to determine the optimal treatment regime.

Investigation of trypanothione reductase inhibitory activity by 1,3,4-thiadiazolium-2-aminide derivatives and molecular docking studies.

The biological activities of a series of mesoionic 1,3,4-thiadiazolium-2-aminide derivatives have been studied. The most active compounds (MI-HH; MI-3-OCH(3); MI-4-OCH(3) and MI-4-NO(2)) were evaluated to determine their effect on trypanothione reductase (TryR) activity in Leishmania sp. and Trypanosoma cruzi. Among the assayed compounds, only MI-4-NO(2) showed enzyme inhibition effect on extracts from different cultures of parasites, which was confirmed using the recombinant enzyme from T. cruzi (TcTryR) and Leishmania infantum (LiTryR). The enzyme kinetics determined with LiTryR demonstrated a non-competitive inhibition profile of MI-4-NO(2). A molecular docking study showed that the mesoionic compounds could effectively dock into the substrate binding site together with the substrate molecule. The mesoionic compounds were also effective ligands of the NADPH and FAD binding sites and the NADPH binding site was predicted as the best of all three binding sites. Based on the theoretical results, an explanation at the molecular level is proposed for the MI-4-NO(2) enzyme inhibition effect. Given TryR as a molecular target, it is important to continue the study of mesoionic compounds as part of a drug discovery campaign against Leishmaniasis or Chagas' disease.

The in vivo activity of 1,3,4-thiadiazolium-2-aminide compounds in the treatment of cutaneous and visceral leishmaniasis.

OBJECTIVES: Researchers have recently investigated the biological activities of mesoionic (MI) compounds, which have shown in vitro activity against many species of Leishmania, as well as Trypanosoma cruzi. The main goal of this study was to evaluate and compare the activity of three MI compounds against Leishmania amazonensis and Leishmania infantum infection in vivo. METHODS: The experiments were carried out using BALB/c mice infected with L. amazonensis or L. infantum as a highly sensitive murine model. The infected mice were treated with MI-HH, MI-4-OCH(3), MI-4-NO(2) or meglumine antimoniate by different routes (intralesional, topical or intraperitoneal). RESULTS: Treatment with MI-4-OCH(3) and MI-4-NO(2) efficiently contained the progression of cutaneous and visceral leishmaniasis in comparison with the control group or mice treated with meglumine antimoniate. Interestingly, these MI compounds did not produce toxicological effects after treatment. Furthermore, treatment with these compounds led to a modulation of the immune response that was correlated with disease control. In this study, MI compounds, and MI-4-NO(2) in particular, exhibited high activity in the L. infantum murine model. In the L. amazonensis model, intralesional treatment with MI-4-OCH(3) or MI-4-NO(2) showed greater therapeutic efficacy than treatment with meglumine antimoniate, and the new topical formulations of these compounds also displayed great activity in the cutaneous leishmaniasis model. CONCLUSIONS: Upon comparison of each MI compound, MI-4-NO(2) was clearly the compound with the greatest activity in these two in vivo infection models by each administration route tested.

Effect of oral treatment with pyrazole carbohydrazide derivatives against murine infection by Leishmania amazonensis.

Newly synthesized pyrazole carbohydrazide derivatives with substituents X = Br/Y = NO(2) and X = NO(2)/Y = Cl were independently investigated in the CBA mouse model of cutaneous leishmaniasis. Animals were infected with Leishmania amazonensis and treated two weeks after the parasitic infection with the pyrazole carbohydrazides for 45 days. Oral treatment with both compounds controlled evolution of footpad cutaneous lesions and dissemination of parasites to draining lymph nodes. Nitric oxide generation was observed in supernatants of lymph node cells from infected CBA mice that were treated with these compounds. The pyrazole carbohydrazide derivatives did not show any toxicity or cause alterations in body weight, plasma concentrations of alanine aminotransferase and aspartate aminotransferase, and urinary creatinine levels, but promoted a small decrease in blood neutrophils. These results provide new perspectives on the development of drugs with activities against leishmaniasis.

Antileishmanial activity of 1,3,4-thiadiazolium-2-aminide in mice infected with Leishmania amazonensis.

The efficacy of two mesoionic derivatives (MI-H-H and MI-4-OCH(3)) was evaluated in CBA/J mice infected with Leishmania amazonensis. Treatment with these compounds demonstrated that the MI-4-OCH(3) derivative and the reference drug meglumine antimoniate (Glucantime) presented significant activity relative to an untreated control. No apparent hepatic or renal toxicity due to these mesoionic compounds was found.

A comparative study of mesoionic compounds in Leishmania sp. and toxicity evaluation.

In this first study, a series of mesoionic compounds like 1,3,4-thiadiazolium-2-phenylamine derivatives were synthesized and studied in Leishmania amazonensis. The cytotoxic effects of these compounds on the host cells were investigated and the antileishmanial in vitro activity was compared with other species of Leishmania (Leishmania chagasi and Leishmania braziliensis). The compounds presented lower toxicity in murine macrophages than the reference drug pentamidine. The halogen derivatives 5, 6, 8 and 13 (4-F, 4-Cl, 4-Br and 3-Cl) were the most active compounds among all the species tested.