Copper salisylaldoxime (CuSAL) imparts protective efficacy against visceral leishmaniasis by targeting Leishmania donovani topoisomerase IB

Antileishmanial effects and drugability characteristics of a heterocyclic copper complex: An in silico, in vitro and molecular study

Leishmaniasis caused by the protozoan Leishmania presents a severe illness, principally in tropical and subtropical areas. Antileishmanial metal complexes, like Glucantime®️ with proven activity, are routinely studied to probe their potency. We investigated the effects of a Cu (II) homoleptic complex coordinated by two dimethyl-bipyridine ligands against Leishmania major stages in silico and in vitro. The affinity of this heterocyclic Cu (II) complex (CuDMBP) towards a parasitic metacaspase was studied by molecular docking. Key pharmacokinetic and pharmacodynamic properties of the complex were predicted using three web-based tools. CuDMBP was tested for in vitro antileishmanial activities using MTT assay, model murine macrophages, flow cytometry, and quantitative real-time polymerase chain reaction (qPCR). Molecular docking confirmed the tendency between the target macromolecule and the complex. ADMET evaluations highlighted CuDMBP's key pharmacological features, including P-glycoprotein-associated GI absorption and lack of trans-BBB permeability. MTT showed significant inhibitory effects against promastigotes. CuDMBP significantly increased the level of cellular IL-12 expression (p < 0.05), while the upregulation observed in the expression of iNOS was considered not significant (p > 0.05). It decreased the expression of IL-10 significantly (p < 0.05). Findings demonstrated that CuDMBP deserves to be introduced as a leishmanicidal candidate provided further studies are carried out.

Molecular-level strategic goals and repressors in Leishmaniasis - Integrated data to accelerate target-based heterocyclic scaffolds

Leishmaniasis is a complex of neglected tropical diseases caused by various species of leishmanial parasites that primarily affect the world's poorest people. A limited number of standard medications are available for this disease that has been used for several decades, these drugs have many drawbacks such as resistance, higher cost, and patient compliance, making it difficult to reach the poor. The search for novel chemical entities to treat leishmaniasis has led to target-based scaffold research. Among several identified potential molecular targets, enzymes involved in the purine salvage pathway include polyamine biosynthetic process, such as arginase, ornithine decarboxylase, S-adenosylmethionine decarboxylase, spermidine synthase, trypanothione reductase as well as enzymes in the DNA cell cycle, such as DNA topoisomerases I and II plays vital role in the life cycle survival of leishmanial parasite. This review mainly focuses on various heterocyclic scaffolds, and their specific inhibitory targets against leishmaniasis, particularly those from the polyamine biosynthesis pathway and DNA topoisomerases with estimated activity studies of various heterocyclic analogs in terms of their IC₅₀ or EC₅₀ value, reported molecular docking analysis from available published literatures.

Demystifying the potential of inhibitors targeting DNA topoisomerases in unicellular protozoan parasites

DNA topoisomerases are a group of enzymes omnipresent in all organisms. They maintain the DNA topology during replication, repair, recombination, and transcription. However, the structure of topoisomerase in protozoan parasites differs significantly from that of human topoisomerases; thus, this enzyme acts as a crucial target in drug development against parasitic diseases. Although the therapeutic potential of drugs targeting the parasitic topoisomerase is well known, to manage the shortcomings of currently available therapeutics and the emergence of drug resistance, the discovery of novel antiparasitic molecules is an urgent need. In this review, we describe various investigational and repurposed topoisomerase inhibitors developed against protozoan parasites over the past few years. Teaser: Fatal parasitic diseases are an increasing cause for concern; here, we provide a compilation of different inhibitors targeting DNA topoisomerases, enzymes that are essential for, and unique to, protozoan parasites; therefore, inhibitors are efficient and have few adverse effects.

Evaluation of scolicidal potential of salicylate coated zinc nanoparticles against Echinococcus granulosus protoscoleces

Echinococcosis is a zoonotic disease caused by larval stages of the Echinococcus genus (metastasis). In this study, salicylate-coated Zinc oxide nanoparticles (SA-ZnO-NPs) were fabricated and characterized by SEM, FTIR and XRD analytical techniques. After that, different doses of SA-ZnO-NPs, SA and ZnO-NPs were taken to assess scolicidal potency. Scanning electron microscopy (SEM) micrographs were also used to evaluate the morphological deformities of treated protoscoleces. Furthermore, Caspase-3&7 inductions were examined in protoscoleces cysts treated with all formulations. Based on SEM and DLS analyses, the size of SA-ZnO-NPs was between 30 and 40 nm, with a spherical shape. The FTIR spectrum verified the presence of SA functional groups on the ZnO coating. At 20 min, SA-ZnO-NPs at 2000 μg/ml exhibited the greatest activity on protoscolices with 100% mortality, followed by ZnO-NPs at 1500 μg/ml at 10 min and SA alone at 2000 μg/ml at 30 min. The activation of Caspase-3&7 apoptotic enzyme was determined for 2000 μg/ml of SA-ZnO-NPs, ZnO-NPs and SA to be 16.4, 31.4, and 35.7%, respectively. The SEM image revealed apoptogenic alterations and the induction of tegument surface wrinkles, as well as abnormalities in rostellum protoscolices. According to the current study, SA-ZnO-NPs have a high mortality rate against hydatid cyst protoscolices. As a result, further studies on the qualitative assessment of these nanoformulations in vivo and preclinical animal trials seem to be required. Furthermore, the adoption of nano-drugs potentially offers alternative therapeutic approaches to combat hydatid cysts.

The Anti-Leishmania amazonensis and Anti-Leishmania chagasi Action of Copper(II) and Silver(I) 1,10-Phenanthroline-5,6-dione Coordination Compounds

Leishmaniasis is a neglected disease caused by protozoa belonging to the Leishmania genus. Notably, the search for new, promising and potent anti-Leishmania compounds remains a major goal due to the inefficacy of the available drugs used nowadays. In the present work, we evaluated the effects of 1,10-phenanthroline-5,6-dione (phendione) coordinated to silver(I), [Ag(phendione)₂]ClO₄ (Ag-phendione), and copper(II), [Cu(phendione)₃](ClO₄)₂·4H₂O (Cu-phendione), as potential drugs to be used in the chemotherapy against Leishmania amazonensis and Leishmania chagasi. The results showed that promastigotes treated with Ag-phendione and Cu-phendione presented a significant reduction in the proliferation rate. The IC₅₀ values calculated to Ag-phendione and Cu-phendione, respectively, were 7.8 nM and 7.5 nM for L. amazonensis and 24.5 nM and 20.0 nM for L. chagasi. Microscopical analyses revealed several relevant morphological changes in promastigotes, such as a rounding of the cell body and a shortening/loss of the single flagellum. Moreover, the treatment promoted alterations in the unique mitochondrion of these parasites, inducing significant reductions on both metabolic activity and membrane potential parameters. All these cellular perturbations induced the triggering of apoptosis-like death in these parasites, as judged by the (i) increased percentage of annexin-positive/propidium iodide negative cells, (ii) augmentation in the proportion of parasites in the sub-G₀/G₁ phase and (iii) DNA fragmentation. Finally, the test compounds showed potent effects against intracellular amastigotes; contrarily, these molecules were well tolerated by THP-1 macrophages, which resulted in excellent selective index values. Overall, the results highlight new selective and effective drugs against Leishmania species, which are important etiological agents of both cutaneous (L. amazonensis) and visceral (L. chagasi) leishmaniasis in a global perspective.

DNA Topoisomerases in the Unicellular Protozoan Parasites: Unwinding the Mystery

DNA topoisomerases are a group of enzymes present ubiquitously in all organisms from unicellular protozoan parasites to humans. These enzymes control the topological problems caused by DNA double helix in the cell during nucleic acid metabolism. Certain types of topoisomerases present in unicellular parasites are quite different from human topoisomerases (hTop) concerning structure, expression, and function. Many protozoan parasites causing fatal diseases have DNA topoisomerases, which play vital roles in their survival. Given the fact that the structures of the protozoan parasite topoisomerases are different from humans, DNA topoisomerase acts as an essential target for potent drug development for parasitic diseases. Moreover, various studies revealed the therapeutic potential of these drugs targeting the parasitic topoisomerases. Therefore, the characterization of parasitic topoisomerases is pivotal for the development of future potential drug targets. Considering the importance of this ubiquitous enzyme as a potential drug target, we describe in detail all the reported protozoan topoisomerases in an organized manner including Leishmania, Trypanosoma, Plasmodium, Giardia, Entamoeba, Babesia, Theileria, Crithidia, Cryptosporidium, Toxoplasma, etc. This review highlights the unique attributes associated with the structure and function of different types of DNA topoisomerases from the unicellular protozoan parasites. So, it would be beneficial for researchers to obtain awareness about the currently characterized topoisomerases and the ones that need better characterization, understand the structure-function relationship of parasitic topoisomerases, to develop the potent anti-parasitic drugs, and also provides a future platform for therapeutic development.

An Update on Natural Antileishmanial Treatment Options from Plants, Fungi and Algae

Efficient drugs for the treatment of leishmaniasis, which is classified as a neglected tropical disease, are sought for. This review covers potential drug candidates from natural plant, fungus and algae sources, which were described over the last six years. The identification of these natural antileishmanials often based on the knowledge of traditional medicines. Crucial insights into the activities of these natural remedies against Leishmania parasites and against infections caused by these parasites in laboratory animals or patients are provided and compared with selected former active examples published more than six years ago. In addition, immuno-modulatory natural antileishmanials and recent developments on combination therapies including natural products and approved antileishmanials are discussed. The described natural products revealed promising data warranting further efforts on the discovery and development of new antileishmanials based on patterns from nature.

Effect of Silica Based Nanoparticles against Plasmodium falciparum and Leishmania infantum parasites

Malaria and Leishmaniasis are two major parasitic diseases, endemic in large areas of tropical countries with high morbidity and mortality across the world. Nanoparticles in small sizes are specifically considered in medicine due to their ability to enter the cells, control the distribution of the administered drug and carry the drug specifically to the place of action. The present study aims to introduce the application of silica nanoparticles as new promising nanotools in malaria and leishmaniasis treatment. Ion doped silica nanomaterials revealed antileishmanial activities indicating the positive role of calcium, magnesium and copper to the surface of the particles against Leishmania parasites. Artemisinin-loaded nanoparticles presented the most promising antiparasitic properties with a sustained release able to overcome the parasite invasion. The sustainable release of artemisinin guarantee both the maintenance of its potential efficacy and also introduce an administration of drug to avoid subsequent drug resistance.

Investigation of the antileishmanial activity and mechanisms of action of acetyl-thiohydantoins

The currently available treatment options for leishmaniasis are associated with high costs, severe side effects, and high toxicity. In previous studies, thiohydantoins demonstrated some pharmacological activities and were shown to be potential hit compounds with antileishmanial properties. The present study further explored the antileishmanial effect of acetyl-thiohydantoins against Leishmania amazonensis and determined the main processes involved in parasite death. We observed that compared to thiohydantoin nuclei, acetyl-thiohydantoin treatment inhibited the proliferation of promastigotes. This treatment caused alterations in cell cycle progression and parasite size and caused morphological and ultrastructural changes. We then investigated the mechanisms involved in the death of the protozoan; there was an increase in ROS production, phosphatidylserine exposure, and plasma membrane permeabilization and a loss of mitochondrial membrane potential, resulting in an accumulation of lipid bodies and the formation of autophagic vacuoles on these parasites and confirming an apoptosis-like process. In intracellular amastigotes, selected acetyl-thiohydantoins reduced the percentage of infected macrophages and the number of amastigotes/macrophages by increasing ROS production and reducing TNF-α levels. Moreover, thiohydantoins did not induce cytotoxicity in murine macrophages (J774A.1), human monocytes (THP-1), or sheep erythrocytes. In silico and in vitro analyses showed that acetyl-thiohydantoins exerted in vitro antileishmanial effects on L. amazonensis promastigotes in apoptosis-like and amastigote forms by inducing ROS production and reducing TNF-α levels, indicating that they are good candidates for drug discovery studies in leishmaniasis treatment. Additionally, we carried out molecular docking analyses of acetyl-thiohydantoins on two important targets of Leishmania amazonensis: arginase and TNF-alpha converting enzyme. The results suggested that the acetyl groups in the N1-position of the thiohydantoin ring and the ring itself could be pharmacophoric groups due to their affinity for binding amino acid residues at the active site of both enzymes via hydrogen bond interactions. These results demonstrate that thiohydantoins are promising hit compounds that could be used as antileishmanial agents.

Metallodrugs for the Treatment of Trypanosomatid Diseases: Recent Advances and New Insights

Trypanosomatid parasites are responsible for many Neglected Tropical Diseases (NTDs). NTDs are a group of illnesses that prevail in low-income populations, such as in tropical and subtropical areas of Africa, Asia, and the Americas. The three major human diseases caused by trypanosomatids are African trypanosomiasis, Chagas disease and leishmaniasis. There are known drugs for the treatment of these diseases that are used extensively and are affordable; however, the use of these medicines is limited by several drawbacks such as the development of chemo-resistance, side effects such as cardiotoxicity, low selectivity, and others. Therefore, there is a need to develop new chemotherapeutic against these tropical parasitic diseases. Metal-based drugs against NTDs have been discussed over the years as alternative ways to overcome the difficulties presented by approved antiparasitic agents. The study of late transition metal-based drugs as chemotherapeutics is an exciting research field in chemistry, biology, and medicine due to the ability to develop multitarget antiparasitic agents. The evaluation of the late transition metal complexes for the treatment of trypanosomatid diseases is provided here, as well as some insights about their mechanism of action.

A "Golden Age" for the discovery of new antileishmanial agents: Current status of leishmanicidal gold complexes and prospective targets beyond the trypanothione system

Leishmaniasis is one of the most neglected diseases worldwide and is considered a serious public health issue. The current therapeutic options have several disadvantages that make the search for new therapeutics urgent. Gold compounds are emerging as promising candidates based on encouraging in vitro and limited in vivo results for several Au^I and Au^III complexes. The antiparasitic mechanisms of these molecules remain only partially understood. However, a few studies have proposed the trypanothione redox system as a target, similar to the mammalian thioredoxin system, pointed out as the main target for several gold compounds with significant antitumor activity. In this review, we present the current status of the investigation and design of gold compounds directed at treating leishmaniasis. In addition, we explore potential targets in Leishmania parasites beyond the trypanothione system, taking into account previous studies and structure modulation performed for gold-based compounds.

The HIV - 1 protease inhibitor Amprenavir targets Leishmania donovani topoisomerase I and induces oxidative stress-mediated programmed cell death

The global prevalence of HIV is a major challenge for the control of visceral leishmaniasis. Although the effectiveness and usefulness of amprenavir (APV) are well studied in anti-retroviral regimens, very little is known on HIV/VL-co-infected patients. In the present study, we report for the first time the protective efficacy of APV against visceral leishmaniasis by inhibition of DNA Topoisomerase I (LdTOP1LS) and APV-induced downstream pathway in programmed cell death (PCD). During the early phase of activation, reactive oxygen species (ROS) is increased inside the cells, which causes subsequent elevation of lipid peroxidation. Endogenous ROS formation and lipid peroxidation cause eventual depolarization of mitochondrial membrane potential (ΔΨ_m). Furthermore, the release of cytochrome c and activation of CED3/CPP32 group of proteases lead to the formation of oxidative DNA lesions followed by DNA fragmentation. The promising in vitro and ex vivo results promoted to substantiate further by in vivo animal experiment, which showed a significant reduction of splenic and hepatic parasites burden compared to infected controls. Interestingly, APV selectively targets LdTOPILS and does not inhibit the catalytic activity of human topoisomerase I (hTopI). Moreover, based on the cytotoxicity test APV is not toxic for host macrophage cells, which is correlated with non-responsiveness of inhibition of catalytic activity of hTopI. Taken together, this study provides the opportunity for discovering and evaluating newer potential molecular therapeutic targets for drug designing. The present study might be exploited in future as important therapeutics, which will be useful for treatment of VL as well as HIV-VL co-infection.

Semicarbazone derivatives as promising therapeutic alternatives in leishmaniasis

In the present study, we investigated the in vitro and in vivo leishmanicidal activity of synthetic compounds, containing a semicarbazone scaffold as a peptide mimetic framework. The leishmanicidal effect against amastigotes of Leishmania amazonensis was also evaluated at concentration of 100 μM-0.01 nM. The derivatives 2e, 2f, 2g and 1g, beyond the standards miltefosine and pentamidine, significantly diminished the number of L. amazonensis amastigotes in macrophages. These derivatives were also active against amastigotes of L. braziliensis. As 2g presented potent leishmanicidal activity against the amastigotes of L. amazonensis in macrophages, we also investigated the in vivo leishmanicidal activity of this compound against L. amazonensis. Approximately 10⁵L. amazonensis promastigotes were subcutaneously inoculated into the dermis of the right ear of BALB/c mice, which were subsequently treated with 2g (p.o. or i.p.), miltefosine (p.o.) or glucantime (i.p.) at 30 μmol/kg/day x 28 days. Thus, a similar reduction in the lesion size was observed after the administration of 2g through oral (63.7 ± 10.1%) and intraperitoneal (61.8 ± 3.7%) routes. A larger effect was observed after treatment with miltefosine (97.7 ± 0.4%), and glucantime did not exhibit activity at the dose administered. With respect to the ear parasite load, 2g diminished the number of parasites by p.o. (30.5 ± 5.1%) and i.p. (33.3 ± 4.3%) administration. In addition, 2g induced in vitro apoptosis, autophagy and cell cycle alterations on L. amazonensis promastigotes. In summary, the derivative 2g might represent a lead candidate for antileishmanial drugs, as this compound displayed pronounced leishmanicidal activity.