Docking-based screening of natural product database in quest for dual site inhibitors of Trypanosoma cruzi trypanothione reductase (TcTR)

Molecular Docking-Based Virtual Screening of FDA-Approved Drugs Using Trypanothione Reductase Identified New Trypanocidal Agents

American trypanosomiasis or Chagas disease, caused by Trypanosoma cruzi (T. cruzi), affects approximately 6-7 million people worldwide. However, its pharmacological treatment causes several uncomfortable side effects, causing patients' treatment abandonment. Therefore, there is a need for new and better treatments. In this work, the molecular docking of nine hundred twenty-four FDA-approved drugs on three different sites of trypanothione reductase of T. cruzi (TcTR) was carried out to find potential trypanocidal agents. Finally, biological evaluations in vitro and in vivo were conducted with the selected FDA-approved drugs. Digoxin, alendronate, flucytosine, and dihydroergotamine showed better trypanocidal activity than the reference drugs benznidazole and nifurtimox in the in vitro evaluation against the trypomastigotes form. Further, these FDA-approved drugs were able to reduce 20-50% parasitemia in a short time in an in vivo model, although with less efficiency than benznidazole. Therefore, the results suggest a combined therapy of repurposed and canonical drugs against T. cruzi infection.

In Vitro, In Vivo, and In Silico Studies of Cumanin Diacetate as a Potential Drug against Trypanosoma cruzi Infection

The sesquiterpene lactones cumanin, helenalin, and hymenin and their semisynthetic derivatives were evaluated against Trypanosoma cruzi epimastigotes. The cytotoxicity of the compounds was evaluated on murine splenocytes. Cumanin diacetate was one of the most active and selective compounds [IC₅₀ = 3.20 ± 0.52 μg/mL, selectivity index (SI) = 26.0]. This sesquiterpene lactone was selected for its evaluation on trypomastigote and amastigote forms of the parasite. The diacetylated derivative of cumanin showed moderate activity on trypomastigotes (IC₅₀ = 32.4 ± 5.8 μg/mL). However, this compound was able to efficiently inhibit parasite replication with an IC₅₀ value of 2.2 ± 0.05 μg/mL against the amastigote forms. Cumanin diacetate showed selectivity against the intracellular forms of Trypanosoma cruzi with an SI value of 52.7. This cumanin analogue was also active on an in vivo model of Chagas disease, leading to a reduction in the parasitemia levels in comparison with nontreated animals. Histopathological analysis of skeletal muscular tissues from treated mice showed only focal interstitial lymphocyte inflammatory infiltrates with slight myocyte necrosis; in contrast, nontreated animals showed severe lymphocyte inflammatory infiltrates with necrosis of the myocytes. A molecular docking study of cumanin and its derivatives on trypanothione reductase from T. cruzi (TcTR) was performed. The results of ΔG docking achieved let the identification of diacetylated and O-alkylated derivatives of cumanin as good inhibitors of TcTR. Cumanin diacetate could be considered a potential candidate for further studies for the development of new therapies against Chagas disease.

Identification of novel thiadiazin derivatives as potentially selective inhibitors towards trypanothione reductase from Trypanosoma cruzi by molecular docking using the numerical index poses ratio Pr and the binding mode analysis

Abstract

Chagas disease is a serious health problem in Central and South America for which effective treatment is not currently available. This illness is caused by the protozoa Trypanosoma cruzi, a species that relies on a thiol-based metabolism to regulate oxidative stress. Trypanothione reductase enzyme plays a central role in the metabolic pathway of the parasite. In this work, a virtual screening of a library of novel thiadiazine derivatives against trypanothione reductase using molecular docking was performed. Four different series of hybrid ligands having in the structure one or two peptoid moieties (series I and II) or the tetrazole ring (series III and IV) were considered. An ad hoc numerical index called poses ratio was introduced to interpret the results of the docking analysis and to establish relevant structure-interaction relationships. In addition, six binding modes were found for the ligands with the highest populated conformational clusters after applying contact-based analysis. The most regular and relevant were binding modes I and II, found mainly for ligands from series I. A subsequent molecular docking on human glutathione reductase enzyme allowed to assess the possible cytotoxicity of the ligands towards human cells. A selective binding profile was found for ligands with interactions in the Hydrophobic cleft, the spermidine and the Z subsites inside the active site of trypanothione reductase. At the end of the study, new thiadiazine-based compounds were identified as plausible candidates to selectively inhibit the parasitic enzyme.

Graphic abstract

The Potential of Secondary Metabolites from Plants as Drugs or Leads against Protozoan Neglected Diseases-Part III: In-Silico Molecular Docking Investigations

Malaria, leishmaniasis, Chagas disease, and human African trypanosomiasis continue to cause considerable suffering and death in developing countries. Current treatment options for these parasitic protozoal diseases generally have severe side effects, may be ineffective or unavailable, and resistance is emerging. There is a constant need to discover new chemotherapeutic agents for these parasitic infections, and natural products continue to serve as a potential source. This review presents molecular docking studies of potential phytochemicals that target key protein targets in Leishmania spp., Trypanosoma spp., and Plasmodium spp.

Molecular Docking and Binding Mode Analysis of Plant Alkaloids as in Vitro and in silico Inhibitors of Trypanothione Reductase from Trypanosoma cruzi

Trypanothione reductase (TryR) is a key enzyme in the metabolism of Trypanosoma cruzi, the parasite responsible for Chagas disease. The available repertoire of TryR inhibitors relies heavily on synthetic substrates of limited structural diversity, and less on plant-derived natural products. In this study, a molecular docking procedure using a Lamarckian Genetic Algorithm was implemented to examine the protein-ligand binding interactions of strong in vitro inhibitors for which no X-ray data is available. In addition, a small, skeletally diverse, set of natural alkaloids was assessed computationally against T. cruzi TryR in search of new scaffolds for lead development. The preferential binding mode (low number of clusters, high cluster population), together with the deduced binding interactions were used to discriminate among the virtual inhibitors. This study confirms the prior in vitro data and proposes quebrachamine, cephalotaxine, cryptolepine, (22 S,25 S)-tomatidine, (22 R,25 S)-solanidine, and (22 R,25 R)-solasodine as new alkaloid scaffold leads in the search for more potent and selective TryR inhibitors.