Treating leishmaniasis in Amazonia, part 2: Multi-target evaluation of widely used plants to understand medicinal practices

ETHNOPHARMACOLOGICAL RELEVANCE

Leishmaniasis are widely distributed among tropical and subtropical countries, and remains a crucial health issue in Amazonia. Indigenous groups across Amazonia have developed abundant knowledge about medicinal plants related to this pathology.

AIM OF THE STUDY

We intent to explore the weight of different pharmacological activities driving taxa selection for medicinal use in Amazonian communities. Our hypothesis is that specific activity against Leishmania parasites is only one factor along other (anti-inflammatory, wound healing, immunomodulating, antimicrobial) activities.

MATERIALS AND METHODS

The twelve most widespread plant species used against leishmaniasis in Amazonia, according to their cultural and biogeographical importance determined through a wide bibliographical survey (475 use reports), were selected for this study. Plant extracts were prepared to mimic their traditional preparations. Antiparasitic activity was evaluated against promastigotes of reference and clinical New-World strains of Leishmania (L. guyanensis, L. braziliensis and L. amazonensis) and L. amazonensis intracellular amastigotes. We concurrently assessed the extracts immunomodulatory properties on PHA-stimulated human PBMCs and RAW264.7 cells, and on L. guyanensis antigens-stimulated PBMCs obtained from Leishmania-infected patients, as well as antifungal activity and wound healing properties (human keratinocyte migration assay) of the selected extracts. The cytotoxicity of the extracts against various cell lines (HFF1, THP-1, HepG2, PBMCs, RAW264.7 and HaCaT cells) was also considered. The biological activity pattern of the extracts was represented through PCA analysis, and a correlation matrix was calculated.

RESULTS

Spondias mombin L. bark and Anacardium occidentale L. stem and leaves extracts displayed high anti-promatigotes activity, with IC₅₀ ≤ 32 μg/mL against L. guyanensis promastigotes for S. mombin and IC₅₀ of 67 and 47 μg/mL against L. braziliensis and L. guyanensis promastigotes, respectively, for A. occidentale. In addition to the antiparasitic effect, antifungal activity measured against C. albicans and T. rubrum (MIC in the 16-64 μg/mL range) was observed. However, in the case of Leishmania amastigotes, the most active species were Bixa orellana L. (seeds), Chelonantus alatus (Aubl.) Pulle (leaves), Jacaranda copaia (Aubl.) D. Don. (leaves) and Plantago major L. (leaves) with IC₅₀ < 20 μg/mL and infection rates of 14-25% compared to the control. Concerning immunomodulatory activity, P. major and B. orellana were highlighted as the most potent species for the wider range of cytokines in all tested conditions despite overall contrasting results depending on the model. Most of the species led to moderate to low cytotoxic extracts except for C. alatus, which exhibited strong cytotoxic activity in almost all models. None of the tested extracts displayed wound healing properties.

CONCLUSIONS

We highlighted pharmacologically active extracts either on the parasite or on associated pathophysiological aspects, thus supporting the hypothesis that antiparasitic activities are not the only biological factor useful for antileishmanial evaluation. This result should however be supplemented by in vivo studies, and attracts once again the attention on the importance of the choice of biological models for an ethnophamacologically consistent study. Moreover, plant cultural importance, ecological status and availability were discussed in relation with biological results, thus contributing to link ethnobotany, medical anthropology and biology.

Botryosphaeran, [(1 → 3)(1 → 6)-β-D-glucan], induces apoptosis-like death in promastigotes of Leishmania amazonensis, and exerts a leishmanicidal effect on infected macrophages by activating NF-kB and producing pro-inflammatory molecules

Leishmaniasis is an infectious-parasitic disease caused by the protozoan Leishmania spp. The available treatments are based upon expensive drugs bearing adverse side-effects. The search for new therapeutic alternatives that present a more effective action without causing adverse effects to the patient is therefore important. The objective of this study was to evaluate the in vitro effect of botryosphaeran, a (1 → 3)(1 → 6)-β-D-glucan, on the promastigote and intracellular amastigote forms of Leishmania amazonensis. The direct activity of botryosphaeran on promastigote forms was evaluated in vitro and inhibited proliferation, the IC50 7 μg/mL in 48 h was calculated. After 48 h treatment, botryosphaeran induced nitric oxide production (NO), caused mitochondrial membrane hyperpolarization, increased reactive oxygen species (ROS), and accumulation of lipid vesicles in promastigotes, resulting in apoptosis, necrosis and autophagy, and was accompanied by morphological and ultrastructural changes. The range of concentrations used did not alter the viability of peritoneal macrophages from BALB/c mice and erythrocytes of sheep. Botryosphaeran was able to reduce the number of infected macrophages and the number of amastigotes per macrophage at 12.5 μg/mL (50.75% ± 6.48), 25 μg/mL (55.66% ± 3.93) and 50 μg/mL (72.9% ± 6.98), and IC50 9.3 μg/mL (±0.66) for intracellular amastigotes forms. The leishmanicidal effect was due to activation of NF-κB and promoted an increase in pro-inflammatory cytokines (TNF-α and IL-6), iNOS and microbial-derived ROS and NO, in addition to decreasing the levels of SOD. Based upon the data obtained, we infer that botryosphaeran exerted an active leishmanicidal and immunomodulatory effect, acting on promastigotes through autophagic, apoptotic and necrosis processes, and in the intracellular amastigote form, through the action of ROS and NO.

Synthetic Perturbations in IL6 Biological Circuit Induces Dynamical Cellular Response

Macrophage phenotype plays a crucial role in the pathogenesis of Leishmanial infection. Pro-inflammatory cytokines signals through the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway that functions in parasite killing. Suppression of cytokine signaling (SOCS) is a well-known negative feedback regulator of the JAK/STAT pathway. However, change in the expression levels of SOCSs in correlation with the establishment of infection is not well understood. IL6 is a pleotropic cytokine that induces SOCS1 and SOCS3 expression through JAK-STAT signaling. Mathematical modeling of the TLR2 and IL6 signaling pathway has established the immune axis of SOCS1 and SOCS3 functioning in macrophage polarization during the early stage of Leishmania major infection. The ratio has been quantified both in silico and in vitro as 3:2 which is required to establish infection during the early stage. Furthermore, phosphorylated STAT1 and STAT3 have been established as an immunological cross talk between TLR2 and IL6 signaling pathways. Using synthetic biology approaches, peptide based immuno-regulatory circuits have been designed to target the activity of SOCS1 which can restore pro-inflammatory cytokine expression during infection. In a nutshell, we explored the potential of synthetic biology to address and rewire the immune response from Th2 to Th1 type during the early stage of leishmanial infection governed by SOCS1/SOCS3 immune axis.

In Vitro Antileishmanial and Antischistosomal Activities of Anemonin Isolated from the Fresh Leaves of Ranunculus multifidus Forsk

Leishmaniasis and schistosomiasis are neglected tropical diseases (NTDs) infecting the world’s poorest populations. Effectiveness of the current antileishmanial and antischistosomal therapies are significantly declining, which calls for an urgent need of new effective and safe drugs. In Ethiopia fresh leaves of Ranunculus multifidus Forsk. are traditionally used for the treatment of various ailments including leishmaniasis and eradication of intestinal worms. In the current study, anemonin isolated from the fresh leaves of R. multifidus was assessed for its in vitro antileishmanial and antischistosomal activities. Anemonin was isolated from the hydro-distilled extract of the leaves of R. multifidus. Antileishmanial activity was assessed on clinical isolates of the promastigote and amastigote forms of Leishmania aethiopica and L. donovani clinical isolates. Resazurin reduction assay was used to determine antipromastigote activity, while macrophages were employed for antiamastigote and cytotoxicity assays. Antischistosomal assays were performed against adult Schistosoma mansoni and newly transformed schistosomules (NTS). Anemonin displayed significant antileishmanial activity with IC₅₀ values of 1.33 nM and 1.58 nM against promastigotes and 1.24 nM and 1.91 nM against amastigotes of L. aethiopica and L. donovani, respectively. It also showed moderate activity against adult S. mansoni and NTS (49% activity against adult S. mansoni at 10 µM and 41% activity against NTS at 1 µM). The results obtained in this investigation indicate that anemonin has the potential to be used as a template for designing novel antileishmanial and antischistosomal pharmacophores.

Differential activity on trypanosomatid parasites of a novel recombinant defensin type 1 from the insect Triatoma (Meccus) pallidipennis

Defensins are one of the major families of antimicrobial peptides (AMPs) that are widely distributed in insects. In Triatomines (Hemiptera: Reduviidae) vectors of Trypanosoma cruzi the causative agent of Chagas disease, two large groups of defensin isoforms have been described: type 1 and type 4. The aim of this study was to analyze the trypanocidal activity of a type 1 recombinant defensin (rDef1.3) identified in Triatoma (Meccus) pallidipennis, an endemic specie from México. The trypanocidal activity of this defensin was evaluated in vitro, against the parasites T. cruzi, T. rangeli, and two species of Leishmania (L. mexicana and L. major) both causative agents of cutaneous leishmaniasis. Our data demonstrated that the defensin was active against all the parasites although in different degrees. The defensin altered the morphology, reduced the viability and inhibited the growth of T.cruzi. When tested against T. rangeli (a parasite that infects a variety of mammalian species), stronger morphological effects where observed. Surprisingly the greatest effects were observed against the two Leishmania species, of which L. major was the parasite most affected with 50% of dead cells or with damaged membranes, in addition of a reduction in its proliferative capacity in culture. These results suggest that rDef1.3 has an important antimicrobial effect against trypanosomatids which cause some of the more important neglected tropical diseases transmitted by insect vectors.

Outbreak of Cutaneous Leishmaniasis among military personnel in French Guiana, 2020: Clinical, phylogenetic, individual and environmental aspects

Background

Cutaneous Leishmaniasis (CL) is endemic in French Guiana but cases are usually sporadic. An outbreak signal was issued on May 15^th 2020 with 15 suspected cases after a military training course in the rainforest. An outbreak investigation was carried out.

Methodology/Principal findings

Thirty cases were confirmed. Leishmania guyanensis was the most frequent species (90%). The most frequent presentation was ulcerative (90%). Lesions on the face and hands were frequent (40% each). Eight cases (26%) presented a poor outcome after treatment with pentamidine and required a second line with amphotericin B. Three of them required further treatments with meglumine antimoniate or miltefosine. Two spots within the training area were deemed as likely sites of contamination, due to illegal logging. The isolated Leishmania strains did not form a separate cluster. Participation in Week 13 of year 2020 was associated with infection (OR = 4.59 [1.10–19.83]; p = 0.016) while undergoing only the “Fighting” exercise was protective (OR = 0.1 [0–0.74]; p = 0.021). There was no association between infection and other risk factors at the individual level. The attack rate of Regiment B (14/105 = 13.3%) was significantly higher (OR = 4.22 [1.84–9.53], p = 0.0001) compared to Regiment A (16/507 = 3.2%). The attack rate during this training course (30/858 = 3.5%) was significantly higher (OR 2.29 [1.28–4.13]; p = 0.002) than for other missions in French Guiana during the same period (22/1427 = 1.5%).

Conclusions

This outbreak could be explained by a combination of factors: climatic conditions around week 13, at-risk activities including night trainings, absence of impregnation, a lesser experience of rainforest duties in Regiment B and illegal logging attracting sandflies on military training grounds.

Cutaneous Leishmaniasis is caused by parasites of the Leishmania genus and infects humans after a sandfly bite. Outbreaks are rare and hard to investigate in isolated tropical areas. In this study, the authors explored the different possible origins of an outbreak of cutaneous leishmaniasis among soldiers training in the rainforest of French Guiana. The outbreak occurred in March 2020. Concerning the symptoms, several patients presented resistant infections and multiple lines of treatment, raising the issue of resistant Leishmania strains. The different strains isolated during the outbreak were not genetically closed, as far as routine PCR techniques would indicate. The authors looked for individual behaviours exposing soldiers to sandfly bites but none was significantly associated with infection. The authors found two spots in the military training areas where illegal logging probably increased the density of sandflies and put service members at risk. The 13^th week of 2020 was associated to a higher risk of infection due to climatic conditions. This study shows how interactions between humans and the rainforest can increase the risk of parasitic outbreaks.

Chalcones identify cTXNPx as a potential antileishmanial drug target

With current drug treatments failing due to toxicity, low efficacy and resistance; leishmaniasis is a major global health challenge that desperately needs new validated drug targets. Inspired by activity of the natural chalcone 2’,6’-dihydroxy-4’-methoxychalcone (DMC), the nitro-analogue, 3-nitro-2’,4’,6’- trimethoxychalcone (NAT22, 1c) was identified as potent broad spectrum antileishmanial drug lead. Structural modification provided an alkyne containing chemical probe that labelled a protein within the parasite that was confirmed as cytosolic tryparedoxin peroxidase (cTXNPx). Crucially, labelling is observed in both promastigote and intramacrophage amastigote life forms, with no evidence of host macrophage toxicity. Incubation of the chalcone in the parasite leads to ROS accumulation and parasite death. Deletion of cTXNPx, by CRISPR-Cas9, dramatically impacts upon the parasite phenotype and reduces the antileishmanial activity of the chalcone analogue. Molecular docking studies with a homology model of in-silico cTXNPx suggest that the chalcone is able to bind in the putative active site hindering access to the crucial cysteine residue. Collectively, this work identifies cTXNPx as an important target for antileishmanial chalcones.

Leishmaniasis is an insect vector-borne parasitic disease. With >350 million people world wide considered at risk, 12 million people currently infected and an economic cost that can be estimated in terms of >3.3 million working life years lost, leishmaniasis is a major global health challenge. The disease is of particular importance in Brazil. Current treatment of leishmaniasis is difficult requiring a long, costly course of drug treatment using old drugs with poor safety indications requiring close medical supervision. Moreover, resistance to current antileishmanials is growing, emphasising a major need for new drug targets. In earlier work we had identified a naturally inspired chalcone which had promising antileishmanial activity but with no known mode of action. In this work we use an analogue of this molecule as an activity based probe to identify a protein target of the chalcone. This protein, cTXNPx, has a major role in protecting the parasite against attack by reactive oxygen species in the host cell. By inhibiting this protein the parasite can no longer survive in the host. Collectively this work validates cTXNPx as a drug target with the chalcone as a lead structure for future drug discovery programmes.

An old drug and different ways to treat cutaneous leishmaniasis: Intralesional and intramuscular meglumine antimoniate in a reference center, Rio de Janeiro, Brazil

Background

Treatment of cutaneous leishmaniasis (CL) remains challenging since the drugs currently used are quite toxic, thus contributing to lethality unrelated to the disease itself but to adverse events (AE). The main objective was to evaluate different treatment regimens with meglumine antimoniate (MA), in a reference center in Rio de Janeiro, Brazil.

Methodology

A historical cohort of 592 patients that underwent physical and laboratory examination were enrolled between 2000 and 2017. The outcome measures of effectiveness were epithelialization and complete healing of cutaneous lesions. AE were graded using a standardized scale. Three groups were evaluated: Standard regimen (SR): intramuscular (IM) MA 10–20 mg Sb⁵⁺/kg/day during 20 days (n = 46); Alternative regimen (AR): IM MA 5 mg Sb⁵⁺/kg/day during 30 days (n = 456); Intralesional route (IL): MA infiltration in the lesion(s) through subcutaneous injections (n = 90). Statistical analysis was performed through Fisher exact and Pearson Chi-square tests, Kruskal-Wallis, Kaplan-Meier and log-rank tests.

Results

SR, AR and IL showed efficacy of 95.3%, 84.3% and 75.9%, with abandonment rate of 6.5%, 2.4% and 3.4%, respectively. IL patients had more comorbidities (58.9%; p = 0.001), were mostly over 50 years of age (55.6%), and had an evolution time longer than 2 months (65.6%; p = 0.02). Time for epithelialization and complete healing were similar in IL and IM MA groups (p = 0.9 and p = 0.5; respectively). Total AE and moderate to severe AE that frequently led to treatment interruption were more common in SR group, while AR and IL showed less toxicity.

Conclusions/Significance

AR and IL showed less toxicity and may be good options especially in CL cases with comorbidities, although SR treatment was more effective. IL treatment was an effective and safe strategy, and it may be used as first therapy option as well as a rescue scheme in patients initially treated with other drugs.

Treatment of cutaneous leishmaniasis remains a challenge since the drugs used are quite toxic. Currently, there is a global effort to reduce the morbidity associated with the treatment of this disease and life-threatening complications due to drugs or treatment approaches. Meglumine antimoniate (MA) in different regimens was evaluated in cutaneous leishmaniasis patients in the state of Rio de Janeiro, Brazil. Effectiveness and toxicity were compared among the groups: standard regimen (SR) [intramuscular (IM) MA in the dosage of 10 to 20 mg of pentavalent antimony (Sb5⁺)/kg/day]; alternative regimen (AR) [IM MA in the dosage of 5 mg Sb5⁺/kg/day]; and intralesional route (IL) [patients treated with MA through the infiltration of the lesion]. AR and IL regimens demonstrated good effectiveness, with reduced abandonment rate and toxicity. Total adverse events were higher in the SR group, which frequently led to treatment interruptions. AR and IL showed less toxicity especially in CL cases with comorbidities, although SR treatment was more effective than AR and IL regimens. IL was an effective and safe treatment and may be used as a first therapy option as well as a rescue scheme.

Dissection of phospholipases A2 reveals multifaceted peptides targeting cancer cells, Leishmania and bacteria

Cationic peptides bio-inspired by natural toxins have been recognized as an efficient strategy for the treatment of different health problems. Due to the specific interaction with substrates from biological membranes, snake venom phospholipases (PLA2s) represent valuable scaffolds for the research and development of short peptides targeting parasites, bacteria, and cancer cells. Considering this, we evaluated the in vitro therapeutic potential of three biomimetic peptides (pCergo, pBmTxJ and pBmje) based on three different amino acid sequences from Asp49 PLA2s. First, short amino acid sequences (12-17 in length) derived from these membranolytic toxins were selected using a combination of bioinformatics tools, including AntiCP, AMPA, PepDraw, ToxinPred, and HemoPI. The peptide, from each polypeptide sequence, with the greatest average antimicrobial index, no toxicity, and no hemolysis predicted was synthesized, purified, and characterized. According to in vitro assays performed, pBmje showed moderate cytotoxicity specifically against MCF-7 (breast cancer cells) with an EC50 of 464.85 µM, whereas pBmTxJ showed an antimicrobial effect against Staphylococcus aureus (ATCC 25923) with an MIC of 37.5 µM, and pCergo against E. coli (ATCC 25922) with an MIC of 75 µM. In addition, pCergo showed antileishmanial activity with an EC50 of 93.69 µM and 110.40 µM against promastigotes of Leishmania braziliensis and L. amazonensis, respectively. Altogether, these results confirmed the versatility of PLA2-derived synthetic peptides, highlighting the relevance of the use of these membrane-interacting toxins as specific archetypes for drug design focused on public health problems.

Amino-Substituted 3-Aryl- and 3-Heteroarylquinolines as Potential Antileishmanial Agents

Leishmaniasis, a disease caused by protozoa of the Leishmania species, afflicts roughly 12 million individuals worldwide. Most existing drugs for leishmaniasis are toxic, expensive, difficult to administer, and subject to drug resistance. We report a new class of antileishmanial leads, the 3-arylquinolines, that potently block proliferation of the intramacrophage amastigote form of Leishmania parasites with good selectivity relative to the host macrophages. Early lead 34 was rapidly acting and possessed good potency against L. mexicana (EC50 = 120 nM), 30-fold selectivity for the parasite relative to the macrophage (EC50 = 3.7 μM), and also blocked proliferation of Leishmania donovani parasites resistant to antimonial drugs. Finally, another early lead, 27, which exhibited reasonable in vivo tolerability, impaired disease progression during the dosing period in a murine model of cutaneous leishmaniasis. These results suggest that the arylquinolines provide a fruitful departure point for the development of new antileishmanial drugs.

Comparative analysis of the transcriptional responses of five Leishmania species to trivalent antimony

BACKGROUND

Leishmaniasis is a neglected tropical disease caused by several species of Leishmania. The resistance phenotype of these parasites depends on the characteristics of each species, which contributes to increased therapeutic failures. Understanding the mechanism used by the parasite to survive under treatment pressure in order to identify potential common and specific therapeutic targets is essential for the control of leishmaniasis. The aim of this study was to investigate the expression profiles and potential shared and specific resistance markers of the main Leishmania species of medical importance [subgenus L. (Leishmania): L. donovani, L. infantum and L. amazonensis; subgenus L. (Viannia): L. panamensis and L. braziliensis)] resistant and sensitive to trivalent stibogluconate (SbIII).

METHODS

We conducted comparative analysis of the transcriptomic profiles (only coding sequences) of lines with experimentally induced resistance to SbIII from biological replicates of five Leishmania species available in the databases of four articles based on ortholog attribution. Simultaneously, we carried out functional analysis of ontology and reconstruction of metabolic pathways of the resulting differentially expressed genes (DEGs).

RESULTS

Resistant lines for each species had differential responses in metabolic processes, compound binding, and membrane components concerning their sensitive counterpart. One hundred and thirty-nine metabolic pathways were found, with the three main pathways comprising cysteine and methionine metabolism, glycolysis, and the ribosome. Differentially expressed orthologous genes assigned to species-specific responses predominated, with 899 self-genes. No differentially expressed genes were found in common among the five species. Two common upregulated orthologous genes were found among four species (L. donovani, L. braziliensis, L. amazonensis, and L. panamensis) related to an RNA-binding protein and the NAD(P)H cytochrome-B5-oxidoreductase complex, associated with transcriptional control and de novo synthesis of linoleic acid, critical mechanisms in resistance to antimonials.

CONCLUSION

Herein, we identified potential species-specific genes related to resistance to SbIII. Therefore, we suggest that future studies consider a treatment scheme that is species-specific. Despite the limitations of our study, this is the first approach toward unraveling the pan-genus genetic mechanisms of resistance in leishmaniasis.

Toll-like receptor-7/8 agonist kill Leishmania amazonensis by acting as pro-oxidant and pro-inflammatory agent

OBJECTIVES

Evaluation of the anti-Leishmanial activity of imidazoquinoline-based TLR7/8 agonists.

METHODS

TLR7/8-active imidazoquinolines (2 and 3) were synthesized and assessed for activity against Leishmania amazonensis-intracellular amastigotes using mouse peritoneal macrophages. The production of reactive oxygen species (ROS), nitric oxide (NO) and cytokines was determined in infected and non-infected macrophages.

KEY FINDINGS

The imidazoquinolines, 2 and 3, were primarily agonists of TLR7 with compound 3 also showing modest TLR8 activity. Docking studies showed them to occupy the same binding pocket on TLR7 and 8 as the known agonists, imiquimod and resiquimod. Compounds 2 and 3 inhibited the growth of L. amazonensis-intracellular amastigotes with the most potent compound (3, IC50 = 5.93 µM) having an IC50 value close to miltefosine (IC50 = 4.05 µM), a known anti-Leishmanial drug. Compound 3 induced macrophages to produce ROS, NO and inflammatory cytokines that likely explain the anti-Leishmanial effects.

CONCLUSIONS

This study shows that activating TLR7 using compounds 2 or 3 induces anti-Leishmanial activity associated with induction of free radicals and inflammatory cytokines able to kill the parasites. While 2 and 3 had a very narrow cytotoxicity window for macrophages, this identifies the possibility to further develop this chemical scaffold to less cytotoxic TLR7/8 agonist for potential use as anti-Leishmanial drug.

An Overview on Target-Based Drug Design against Kinetoplastid Protozoan Infections: Human African Trypanosomiasis, Chagas Disease and Leishmaniases

The protozoan diseases Human African Trypanosomiasis (HAT), Chagas disease (CD), and leishmaniases span worldwide and therefore their impact is a universal concern. The present regimen against kinetoplastid protozoan infections is poor and insufficient. Target-based design expands the horizon of drug design and development and offers novel chemical entities and potential drug candidates to the therapeutic arsenal against the aforementioned neglected diseases. In this review, we report the most promising targets of the main kinetoplastid parasites, as well as their corresponding inhibitors. This overview is part of the Special Issue, entitled "Advances of Medicinal Chemistry against Kinetoplastid Protozoa (Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp.) Infections: Drug Design, Synthesis and Pharmacology".

Current status of nanoscale drug delivery and the future of nano-vaccine development for leishmaniasis - A review

The study of tropical diseases like leishmaniasis, a parasitic disease, has not received much attention even though it is the second-largest infectious disease after malaria. As per the WHO report, a total of 0.7-1.0 million new leishmaniasis cases, which are spread by 23 Leishmania species in more than 98 countries, are estimated with an alarming 26,000-65,000 death toll every year. Lack of potential vaccines along with the cost and toxicity of amphotericin B (AmB), the most common drug for the treatment of leishmaniasis, has raised the interest significantly for new formulations and drug delivery systems including nanoparticle-based delivery as anti-leishmanial agents. The size, shape, and high surface area to volume ratio of different NPs make them ideal for many biological applications. The delivery of drugs through liposome, polymeric, and solid-lipid NPs provides the advantage of high biocomatibilty of the carrier with reduced toxicity. Importantly, NP-based delivery has shown improved efficacy due to targeted delivery of the payload and synergistic action of NP and payload on the target. This review analyses the advantage of NP-based delivery over standard chemotherapy and natural product-based delivery system. The role of different physicochemical properties of a nanoscale delivery system is discussed. Further, different ways of nanoformulation delivery ranging from liposome, niosomes, polymeric, metallic, solid-lipid NPs were updated along with the possible mechanisms of action against the parasite. The status of current nano-vaccines and the future potential of NP-based vaccine are elaborated here.

Identification of Potential Kinase Inhibitors within the PI3K/AKT Pathway of Leishmania Species

Leishmaniasis is a public health disease that requires the development of more effective treatments and the identification of novel molecular targets. Since blocking the PI3K/AKT pathway has been successfully studied as an effective anticancer strategy for decades, we examined whether the same approach would also be feasible in Leishmania due to their high amount and diverse set of annotated proteins. Here, we used a best reciprocal hits protocol to identify potential protein kinase homologues in an annotated human PI3K/AKT pathway. We calculated their ligandibility based on available bioactivity data of the reported homologues and modelled their 3D structures to estimate the druggability of their binding pockets. The models were used to run a virtual screening method with molecular docking. We found and studied five protein kinases in five different Leishmania species, which are AKT, CDK, AMPK, mTOR and GSK3 homologues from the studied pathways. The compounds found for different enzymes and species were analysed and suggested as starting point scaffolds for the design of inhibitors. We studied the kinases’ participation in protein–protein interaction networks, and the potential deleterious effects, if inhibited, were supported with the literature. In the case of Leishmania GSK3, an inhibitor of its human counterpart, prioritized by our method, was validated in vitro to test its anti-Leishmania activity and indirectly infer the presence of the enzyme in the parasite. The analysis contributes to improving the knowledge about the presence of similar signalling pathways in Leishmania, as well as the discovery of compounds acting against any of these kinases as potential molecular targets in the parasite.

Design, Synthesis and Antiparasitic Evaluation of Click Phospholipids

A library of seventeen novel ether phospholipid analogues, containing 5-membered heterocyclic rings (1,2,3-triazolyl, isoxazolyl, 1,3,4-oxadiazolyl and 1,2,4-oxadiazolyl) in the lipid portion were designed and synthesized aiming to identify optimised miltefosine analogues. The compounds were evaluated for their in vitro antiparasitic activity against Leishmania infantum and Leishmania donovani intracellular amastigotes, against Trypanosoma brucei brucei and against different developmental stages of Trypanosoma cruzi. The nature of the substituents of the heterocyclic ring (tail) and the oligomethylene spacer between the head group and the heterocyclic ring was found to affect the activity and toxicity of these compounds leading to a significantly improved understanding of their structure-activity relationships. The early ADMET profile of the new derivatives did not reveal major liabilities for the potent compounds. The 1,2,3-triazole derivative 27 substituted by a decyl tail, an undecyl spacer and a choline head group exhibited broad spectrum antiparasitic activity. It possessed low micromolar activity against the intracellular amastigotes of two L. infantum strains and T. cruzi Y strain epimastigotes, intracellular amastigotes and trypomastigotes, while its cytotoxicity concentration (CC50) against THP-1 macrophages ranged between 50 and 100 μM. Altogether, our work paves the way for the development of improved ether phospholipid derivatives to control neglected tropical diseases.

Mechanistic Insights into the Leishmanicidal and Bactericidal Activities of Batroxicidin, a Cathelicidin-Related Peptide from a South American Viper (Bothrops atrox)

Snake venoms are important sources of bioactive molecules, including those with antiparasitic activity. Cathelicidins form a class of such molecules, which are produced by a variety of organisms. Batroxicidin (BatxC) is a cathelicidin found in the venom of the common lancehead (Bothrops atrox). In the present work, BatxC and two synthetic analogues, BatxC(C-2.15Phe) and BatxC(C-2.14Phe)des-Phe1, were assessed for their microbicidal activity. All three peptides showed a broad-spectrum activity on Gram-positive and -negative bacteria, as well as promastigote and amastigote forms of Leishmania (Leishmania) amazonensis. Circular dichroism (CD) and nuclear magnetic resonance (NMR) data indicated that the three peptides changed their structure upon interaction with membranes. Biomimetic membrane model studies demonstrated that the peptides exert a permeabilization effect in prokaryotic membranes, leading to cell morphology distortion, which was confirmed by atomic force microscopy (AFM). The molecules considered in this work exhibited bactericidal and leishmanicidal activity at low concentrations, with the AFM data suggesting membrane pore formation as their mechanism of action. These peptides stand as valuable prototype drugs to be further investigated and eventually used to treat bacterial and protozoal infections.

In Silico Insights into the Mechanism of Action of Epoxy-α-Lapachone and Epoxymethyl-Lawsone in Leishmania spp

Epoxy-α-lapachone (Lap) and Epoxymethyl-lawsone (Law) are oxiranes derived from Lapachol and have been shown to be promising drugs for Leishmaniases treatment. Although, it is known the action spectrum of both compounds affect the Leishmania spp. multiplication, there are gaps in the molecular binding details of target enzymes related to the parasite’s physiology. Molecular docking assays simulations were performed using DockThor server to predict the preferred orientation of both compounds to form stable complexes with key enzymes of metabolic pathway, electron transport chain, and lipids metabolism of Leishmania spp. This study showed the hit rates of both compounds interacting with lanosterol C-14 demethylase (−8.4 kcal/mol to −7.4 kcal/mol), cytochrome c (−10.2 kcal/mol to −8.8 kcal/mol), and glyceraldehyde-3-phosphate dehydrogenase (−8.5 kcal/mol to −7.5 kcal/mol) according to Leishmania spp. and assessed compounds. The set of molecular evidence reinforces the potential of both compounds as multi-target drugs for interrupt the network interactions between parasite enzymes, which can lead to a better efficacy of drugs for the treatment of leishmaniases.

Miltefosine for the treatment of cutaneous leishmaniasis-A pilot study from Ethiopia

Background

Cutaneous leishmaniasis (CL) in Ethiopia, caused by Leishmania aethiopica, is often severe and hard to treat compared to CL caused by other species elsewhere. Miltefosine is the only oral anti-leishmanial drug, with a favorable side-effect profile compared to routinely available sodium stibogluconate (SSG), but evidence about its use for L. aethiopica is lacking.

Methodology and principal findings

In an observational cohort study, treatment outcomes, safety and adherence among CL patients who required systemic treatment and received miltefosine for 28 days in Boru Meda Hospital and University of Gondar Hospital were studied. Patient cure was defined as 100% flattening for non-ulcerated lesions and 100% flattening and 100% re-epithelization for ulcerated lesions. Outcomes were documented for day 28, 90 and 180, both per site, and pooled, adjusting for site as a fixed effect with effect coding. Among 94 included patients (32 in Gondar, 62 in Boru Meda), median lesion duration was 12 months, median size six cm, and mucosal involvement (46.8%) and diffuse (30.9%) lesions were common. Adherence to miltefosine was good, and side-effects were tolerable. Initial outcomes at day 28 were promising, with 68.8% and 94.0% of patients having good improvement or cure in Gondar and Boru Meda respectively. In Boru Meda, outcomes were good with 72.7% and 72.9% cure at day 90 and day 180 respectively. In Gondar, results were less promising, with only 12.5% and 26.7% cure at day 90 and day 180, although confidence intervals were wide. In pooled estimates, 48.7% of patients reached cure at day 180, and 32.3% relapsed. Outcomes were better in Boru Meda Hospital, for smaller lesions and for mucosal lesions.

Conclusions/Significance

Based on miltefosine’s good initial response, tolerable side-effects, tablet-form, we propose to include miltefosine for future clinical trials using extended treatment schedules, combination therapy, or targeting specific subgroups.

Trial registration

ClinicalTrials.gov NCT04004754.

Cutaneous leishmaniasis (CL) in Ethiopia is caused by Leishmania aethiopica, resulting in relatively severe lesions, which are hard to treat. Currently, most patients are treated with pentavalent antimonials, although effectiveness seems poor, with many patients requiring repeated treatment cycles before good response is seen. Miltefosine is the only oral drug available for leishmaniasis treatment and has a good safety profile compared to other treatment options. Although evidence on the use of miltefosine for CL in other regions looks promising, reports from Ethiopia are lacking.

We systematically recorded outcomes and side-effects for patients with CL lesions that required systemic treatment and who were treated with 28 days of miltefosine in a prospective study in two hospitals in Ethiopia. Side-effects were common but generally mild. Although all patients showed improvement after 28 days, overall, around half of patients were cured after six months, with relapse being common. Therefore, we propose to include miltefosine in future clinical trials, but to adapt the treatment regimen using combination therapy or treatment extension to improve overall outcomes and reduce relapse.

Anti-Leishmania activity of extracts from Piper cabralanum C.DC. (Piperaceae)

Species of Piperaceae are known by biological properties, including antiparasitic such as leishmanicidal, antimalarial and in the treatment of schistosomiasis. The aim of this work was to evaluate the antileishmania activity, cytotoxic effect, and macrophage activation patterns of the methanol (MeOH), hexane (HEX), dichloromethane (DCM) and ethyl acetate (EtOAc) extract fractions from the leaves of Piper cabralanum C.DC. The MeOH, HEX and DCM fractions inhibited Leishmanina amazonensis promastigote-like forms growth with a half maximal inhibitory concentration (IC₅₀) of 144.54, 59.92, and 64.87 μg/mL, respectively. The EtOAc fraction did not show any relevant activity. The half maximal cytotoxic concentration (CC₅₀) for macrophages were determined as 370.70, 83.99, 113.68 and 607 μg/mL for the MeOH, HEX and DCM fractions, respectively. The macrophage infectivity was concentration-dependent, especially for HEX and DCM. MeOH, HEX and DCM fractions showed activity against L. amazonensis with low cytotoxicity to murine macrophages and lowering infectivity by the parasite. Our results provide support for in vivo studies related to a potential application of P. cabralanum extract and fractions as a promising natural resource in the treatment of leishmaniasis.

Trichilones A-E: New Limonoids from Trichilia adolfi

In addition to the trichilianones A-D recently reported from Trichilia adolfi, a continuing investigation of the chemical constituents of the ethanol extract of the bark of this medicinal plant yielded the five new limonoids 1-5. They are characterized by having four fused rings and are new examples of prieurianin-type limonoids, having a ε-lactone which in 4 and 5 is α, β- unsaturated. The structures of the isolated metabolites were determined by high field NMR spectroscopy and HR mass spectrometry. The new metabolites were shown to have the ε-lactone fused with a tetrahydrofuran ring which is connected to an oxidized hexane ring joined with a cyclo-pentanone having a 3-furanyl substituent. As the crude extract possesses antileishmanial activity, the compounds were assayed for cytotoxic and antiparasitic activities in vitro in murine macrophage cells (raw 264.7 cells) and in Leishmania amazoniensis as well as L. braziliensis promastigotes. Metabolites 1-3 and 5 showed moderate cytotoxicity (between 30-94 µg/mL) but are not responsible for the antileishmanial effect of the extract.

Identification of Kaurane-Type Diterpenes as Inhibitors of Leishmania Pteridine Reductase I

The current treatments against Leishmania parasites present high toxicity and multiple side effects, which makes the control and elimination of leishmaniasis challenging. Natural products constitute an interesting and diverse chemical space for the identification of new antileishmanial drugs. To identify new drug options, an in-house database of 360 kauranes (tetracyclic diterpenes) was generated, and a combined ligand- and structure-based virtual screening (VS) approach was performed to select potential inhibitors of Leishmania major (Lm) pteridine reductase I (PTR1). The best-ranked kauranes were employed to verify the validity of the VS approach through LmPTR1 enzyme inhibition assay. The half-maximal inhibitory concentration (IC₅₀) values of selected bioactive compounds were examined using the random forest (RF) model (i.e., 2β-hydroxy-menth-6-en-5β-yl ent-kaurenoate (135) and 3α-cinnamoyloxy-ent-kaur-16-en-19-oic acid (302)) were below 10 μM. A compound similar to 302, 3α-p-coumaroyloxy-ent-kaur-16-en-19-oic acid (302a), was also synthesized and showed the highest activity against LmPTR1. Finally, molecular docking calculations and molecular dynamics simulations were performed for the VS-selected, most-active kauranes within the active sites of PTR1 hybrid models, generated from three Leishmania species that are known to cause cutaneous leishmaniasis in the new world (i.e., L. braziliensis, L. panamensis, and L. amazonensis) to explore the targeting potential of these kauranes to other species-dependent variants of this enzyme.

Solidagenone acts on promastigotes of L. amazonensis by inducing apoptosis-like processes on intracellular amastigotes by IL-12p70/ROS/NO pathway activation

BACKGROUND

Leishmaniasis is a neglected tropical disease caused by protozoan parasites of the Leishmania genus. Currently, the treatment has limited effectiveness and high toxicity, is expensive, requires long-term treatment, induces significant side effects, and promotes drug resistance. Thus, new therapeutic strategies must be developed to find alternative compounds with high efficiency and low cost. Solidagenone (SOL), one of the main constituents of Solidago chilensis, has shown gastroprotective, anti-inflammatory and immunomodulatory effects.

PURPOSE

This study assessed the in vitro effect of SOL on promastigotes and Leishmania amazonensis-infected macrophages, as well its microbicide and immunomodulatory mechanisms.

METHODS

SOL was isolated from the roots of S. chilensis, 98% purity, and identified by chromatographic methods, and the effect of SOL on leishmanicidal activity against promastigotes in vitro, SOL-induced cytotoxicity in THP-1, J774 cells, sheep erythrocytes, and L. amazonensis-infected J774 macrophages, and the mechanisms of death involved in this action were evaluated.

RESULTS

In silico predictions showed good drug-likeness potential for SOL with high oral bioavailability and intestinal absorption. SOL treatment (10-160 μM) inhibited promastigote proliferation 24, 48, and 72 h after treatment. After 24 h of treatment, SOL at the IC₅₀ (34.5 μM) and 2 × the IC₅₀ (69 μM) induced several morphological and ultrastructural changes in promastigotes, altered the cell cycle and cellular volume, increased phosphatidylserine exposure on the cell surface, induced the loss of plasma membrane integrity, increased the reactive oxygen species (ROS) level, induced loss of mitochondrial integrity (characterized by an apoptosis-like process), and increased the number of lipid droplets and autophagic vacuoles. Additionally, SOL induced low cytotoxicity in J774 murine macrophages (CC₅₀ of 1587 μM), THP-1 human monocytes (CC₅₀ of 1321 μM), and sheep erythrocytes. SOL treatment reduced the percentage of L. amazonensis-infected macrophages and the number of amastigotes per macrophage (IC₅₀ 9.5 μM), reduced TNF-α production and increased IL-12p70, ROS and nitric oxide (NO) levels.

CONCLUSION

SOL showed in vitro leishmanicidal effects against the promastigotes by apoptosis-like mechanism and amastigotes by reducing TNF-α and increasing IL-12p70, ROS, and NO levels, suggesting their potential as a candidate for use in further studies on the design of antileishmanial drugs.

Peptides to Tackle Leishmaniasis: Current Status and Future Directions

Peptide-based drugs are an attractive class of therapeutic agents, recently recognized by the pharmaceutical industry. These molecules are currently being used in the development of innovative therapies for diverse health conditions, including tropical diseases such as leishmaniasis. Despite its socioeconomic influence on public health, leishmaniasis remains long-neglected and categorized as a poverty-related disease, with limited treatment options. Peptides with antileishmanial effects encountered to date are a structurally heterogeneous group, which can be found in different natural sources—amphibians, reptiles, insects, bacteria, marine organisms, mammals, plants, and others—or inspired by natural toxins or proteins. This review details the biochemical and structural characteristics of over one hundred peptides and their potential use as molecular frameworks for the design of antileishmanial drug leads. Additionally, we detail the main chemical modifications or substitutions of amino acid residues carried out in the peptide sequence, and their implications in the development of antileishmanial candidates for clinical trials. Our bibliographic research highlights that the action of leishmanicidal peptides has been evaluated mainly using in vitro assays, with a special emphasis on the promastigote stage. In light of these findings, and considering the advances in the successful application of peptides in leishmaniasis chemotherapy, possible approaches and future directions are discussed here.

Nanotechnology based solutions for anti-leishmanial impediments: a detailed insight

As a neglected tropical disease, Leishmaniasis is significantly instigating morbidity and mortality across the globe. Its clinical spectrum varies from ulcerative cutaneous lesions to systemic immersion causing hyperthermic hepato-splenomegaly. Curbing leishmanial parasite is toughly attributable to the myriad obstacles in existing chemotherapy and immunization. Since the 1990s, extensive research has been conducted for ameliorating disease prognosis, by resolving certain obstacles of conventional therapeutics viz. poor efficacy, systemic toxicity, inadequate drug accumulation inside the macrophage, scarce antigenic presentation to body's immune cells, protracted length and cost of the treatment. Mentioned hurdles can be restricted by designing nano-drug delivery system (nano-DDS) of extant anti-leishmanials, phyto-nano-DDS, surface modified-mannosylated and thiolated nano-DDS. Likewise, antigen delivery with co-transportation of suitable adjuvants would be achievable through nano-vaccines. In the past decade, researchers have engineered nano-DDS to improve the safety profile of existing drugs by restricting their release parameters. Polymerically-derived nano-DDS were found as a suitable option for oral delivery as well as SLNs due to pharmacokinetic re-modeling of drugs. Mannosylated nano-DDS have upgraded macrophage internalizing of nanosystem and the entrapped drug, provided with minimal toxicity. Cutaneous Leishmaniasis (CL) was tackling by the utilization of nano-DDS designed for topical delivery including niosomes, liposomes, and transfersomes. Transfersomes, however, appears to be superior for this purpose. The nanotechnology-based solution to prevent parasitic resistance is the use of Thiolated drug-loaded and multiple drugs loaded nano-DDS. These surfaces amended nano-DDS possess augmented IC50 values in comparison to conventional drugs and un-modified nano-DDS. Phyto-nano-DDS, another obscure horizon, have also been evaluated for their anti-leishmanial response, however, more intense assessment is a prerequisite. Impoverished Cytotoxic T-cells response followed by Leishmanial antigen proteins delivery have also been vanquished using nano-adjuvants. The eminence of nano-DDS for curtailment of anti-leishmanial chemotherapy and immunization associated challenges are extensively summed up in this review. This expedited approach is ameliorating the Leishmaniasis management successfully. Alongside, total to partial eradication of this disease can be sought along with associated co-morbidities.

Apoptosis-like cell death upon kinetoplastid induction by compounds isolated from the brown algae Dictyota spiralis

BACKGROUND

The in vitro activity of the brown seaweed Dictyota spiralis against both Leishmania amazonensis and Trypanosoma cruzi was evaluated in a previous study. Processing by bio-guided fractionation resulted in the isolation of three active compounds, classified as diterpenes. In the present study, we performed several assays to detect clinical features associated to cell death in L. amazonensis and T. cruzi with the aim to elucidate the mechanism of action of these compounds on parasitic cells.

METHODS

The aims of the experiments were to detect and evaluate specific events involved in apoptosis-like cell death in the kinetoplastid, including DNA condensation, accumulation of reactive oxygen species and changes in ATP concentration, cell permeability and mitochondrial membrane potential, respectively, in treated cells.

RESULTS

The results demonstrated that the three isolated diterpenes could inhibit the tested parasites by inducing an apoptosis-like cell death.

CONCLUSIONS

These results encourage further investigation on the isolated compounds as potential drug candidates against both L. amazonensis and T. cruzi.

Safety and efficacy of allylamines in the treatment of cutaneous and mucocutaneous leishmaniasis: A systematic review

Cutaneous and mucocutaneous leishmaniasis affect a million people yearly, leading to skin lesions and potentially disfiguring mucosal disease. Current treatments can have severe side effects. Allylamine drugs, like terbinafine, are safe, including during pregnancy. This review assesses efficacy and safety of allylamines for the treatment of cutaneous and mucocutaneous leishmaniasis. It followed the PRISMA statement for reporting and was preregistered in PROSPERO(CRD4201809068). MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, the Global Health Library, Web of Science, Google Scholar, and clinical trial registers were searched from their creation to May 24^th, 2020. All original human, animal, and in vitro studies concerning allylamines and cutaneous or mucocutaneous leishmaniasis were eligible for inclusion. Comparators—if any—included both placebo or alternative cutaneous or mucocutaneous leishmaniasis treatments. Complete cure, growth inhibition, or adverse events served as outcomes. The search identified 312 publications, of which 22 were included in this systematic review. There were one uncontrolled and two randomised controlled trials. The only well-designed randomised controlled trial that compared the treatment efficacy of oral terbinafine versus intramuscular meglumine antimoniate in 80 Leismania tropica infected patients showed a non-significant lower cure rate for terbinafine vs meglumine antimoniate (38% vs 53%). A meta-analysis could not be performed due to the small number of studies, their heterogeneity, and low quality. This systematic review shows that there is no evidence of efficacy of allylamine monotherapy against cutaneous and mucocutaneous leishmaniasis. Further trials of allylamines should be carefully considered as the outcomes of an adequately designed trial were disappointing and in vitro studies indicate minimal effective concentrations that are not achieved in the skin during standard doses. However, the in vitro synergistic effects of allylamines combined with triazole drugs warrant further exploration.

Therapeutic advances in the topical treatment of cutaneous leishmaniasis: A review

Cutaneous leishmaniasis has been endemic since decades. Millions of cases are reported worldwide specially in developing and underdeveloped countries. There are 2 major types of cutaneous leishmaniasis based on the causating species found in different regions of the world. These include New and Old World cutaneous leishmaniasis, which are self-healing, but if not treated, these may cause severe scars and many other complications like mucosal involvement. The conventional gold standard treatment for both types is mainly intralesional or parenteral administration of antimonial. Lately, a great deal of research has been done on development of topical treatment based on single agent or combination therapy. This review summarizes the current state of literature regarding therapeutic outcome of topical treatment against cutaneous leishmaniasis caused by different species in different regions.

Susceptibility to paromomycin in clinical isolates and reference strains of Leishmania species responsible for tegumentary leishmaniasis in Brazil

Treatment of tegumentary leishmaniasis in Brazil is limited to pentavalent antimonial, amphotericin B and pentamidine. These drugs, administered parenterally, cause several side effects and have a varied clinical response, depending on the species of Leishmania. Urgent expansion of the therapeutic arsenal against the disease is therefore necessary. Paromomycin is an aminoglycoside antibiotic that has already been approved for the treatment of visceral leishmaniasis in Southeast Asia. Here, we provide an in vitro evaluation of the activity of paromomycin in fifteen clinical isolates from patients with tegumentary leishmaniasis at a reference center for the treatment of the disease. Furthermore, the in vitro susceptibility to this drug in reference strains of Leishmania species that are endemic in Brazil has also been evaluated. Among the clinical isolates, nine were typed as Leishmania (Viannia) braziliensis, five as L. (Leishmania) amazonensis and one as L. (V.) guyanensis. Although never exposed to paromomycin, we found variable susceptibility among these isolates and reference strains in promastigotes and intracellular amastigotes, with the drug being more active in the amastigote form of the parasite. This study provides a preclinical dataset that is useful for the evaluation of paromomycin in the treatment of tegumentary leishmaniasis caused by species that are endemic in Brazil.

Chemical and Bioinformatics Analyses of the Anti-Leishmanial and Anti-Oxidant Activities of Hemp Essential Oil

Industrial hemp is a multiuse crop that has been widely cultivated to produce fibers and nutrients. The capability of the essential oil (EO) from inflorescences as antimicrobial agent has been reported. However, literature data are still lacking about the hemp EO antiprotozoal efficacy in vivo. The present study aims to unravel this concern through the evaluation of the efficacy of hemp EOs (2.5 mL/kg, intraperitoneally) of three different cultivars, namely Futura 75, Carmagnola selezionata and Eletta campana, in mice intraperitoneally infected with Leishmania tropica. A detailed description of EO composition and targets-components analysis is reported. Myrcene, α-pinene and E-caryophyllene were the main components of the EOs, as indicated by the gas-chromatographic analysis. However, a prominent position in the scenario of the theoretical interactions underlying the bio-pharmacological activity was also occupied by selina-3,7(11)-diene, which displayed affinities in the micromolar range (5.4–28.9) towards proliferator-activated receptor α, cannabinoid CB2 receptor and acetylcholinesterase. The content of this compound was higher in Futura 75 and Eletta campana, in accordance with their higher scavenging/reducing properties and efficacy against the tissue wound, induced by L. tropica. Overall, the present study recommends hemp female inflorescences, as sources of biomolecules with potential pharmacological applications, especially towards infective diseases.

Anti-leishmanial and anti-trypanosomal natural products from endophytes

Leishmania spp. and Trypanosoma cruzi are parasites belonging to the Trypanosomatidae family and the causative agents for two very important neglected tropical diseases (NTDs), namely leishmaniasis and trypanosomiasis, respectively. Together, they affect millions of people worldwide and the number of cases is constantly rising; thus, further effort on identifying and developing non-toxic, affordable and effective new drug is urgently needed to overcome this alarming situation. Exploring natural products from fungal and bacterial origin remains hitherto a valuable approach to find new hits and candidates for the development of new drugs against these protozoal human infections. Endophytes, which are microorganisms (fungal and bacterial) inhabiting plant tissues, represent a promising source, as they hold potential to produce a high number of distinct chemical scaffolds. These structurally diverse natural products have previously been successfully tested against a wide range of pathogenic microorganisms. The present review provides an update of endophytic compounds exerting anti-trypanosomal and anti-leishmanial effects and their predicted pharmacokinetic properties.

Drug screening using shape-based virtual screening and in vitro experimental models of cutaneous Leishmaniasis

Cutaneous leishmaniasis (CL) is one of the most disregarded tropical neglected disease with the occurrence of self-limiting ulcers and triggering mucosal damage and stigmatizing scars, leading to huge public health problems and social negative impacts. Pentavalent antimonials are the first-line drug for CL treatment for over 70 years and present several drawbacks in terms of safety and efficacy. Thus, there is an urgent need to search for non-invasive, non-toxic and potent drug candidates for CL. In this sense, we have implemented a shape-based virtual screening approach and identified a set of 32 hit compounds. In vitro phenotypic screenings were conducted using these hit compounds to check their potential leishmanicidal effect towards Leishmania amazonensis (L. amazonensis). Two (Cp1 and Cp2) out of the 32 compounds revealed promising antiparasitic activities, exhibiting considerable potency against intracellular amastigotes present in peritoneal macrophages (IC50 values of 9.35 and 7.25 μm, respectively). Also, a sterile cidality profile was reached at 20 μm after 48 h of incubation, besides a reasonable selectivity (≈8), quite similarly to pentamidine, a diamidine still in use clinically for leishmaniasis. Cp1 with an oxazolo[4,5-b]pyridine scaffold and Cp2 with benzimidazole scaffold could be developed by lead optimization studies to enhance their leishmanicidal potency.

Total Phenolic Fraction (TPF) from Extra Virgin Olive Oil: Induction of apoptotic-like cell death in Leishmania spp. promastigotes and in vivo potential of therapeutic immunomodulation

BACKGROUND

Leishmaniasis is a serious multifactorial parasitic disease with limited treatment options. Current chemotherapy is mainly consisted of drugs with serious drawbacks such as toxicity, variable efficacy and resistance. Alternative bioactive phytocompounds may provide a promising source for discovering new anti-leishmanial drugs. Extra Virgin Olive Oil (EVOO), a key-product in the Mediterranean diet, is rich in phenols which are associated with anti-inflammatory, anti-cancer and anti-microbial effects. In this study, we investigate the anti-leishmanial effect of Total Phenolic Fraction (TPF) derived from EVOO in both in vitro and in vivo systems by investigating the contributing mechanism of action.

METHODOLOGY/PRINCIPAL FINDINGS

We tested the ability of TPF to cause apoptotic-like programmed cell death in L. infantum and L. major exponential-phase promastigotes by evaluating several apoptotic indices, such as reduction of proliferation rate, sub-G0/G1 phase cell cycle arrest, phosphatidylserine externalization, mitochondrial transmembrane potential disruption and increased ROS production, by using flow cytometry and microscopy techniques. Moreover, we assessed the therapeutic effect of TPF in L. major-infected BALB/c mice by determining skin lesions, parasite burden in popliteal lymph nodes, Leishmania-specific antibodies and biomarkers of tissue site cellular immune response, five weeks post-treatment termination. Our results show that TPF triggers cell-cycle arrest and apoptotic-like changes in Leishmania spp. promastigotes. Moreover, TPF treatment induces significant reduction of parasite burden in draining lymph nodes together with an antibody profile indicative of the polarization of Th1/Th2 immune balance towards the protective Th1-type response, characterized by the presence of IFN-γ-producing CD4+ T-cells and increased Tbx21/GATA-3 gene expression ratio in splenocytes.

CONCLUSIONS/SIGNIFICANCE

TPF exhibits chemotherapeutic anti-leishmanial activity by inducing programmed cell death on cell-free promastigotes and immunomodulatory properties that induce in vivo T cell-mediated responses towards the protective Th1 response in experimental cutaneous leishmaniasis. These findings enable deeper understanding of TPF's dual mode of action that encourages further studies.

Colombian Contributions Fighting Leishmaniasis: A Systematic Review on Antileishmanials Combined with Chemoinformatics Analysis

Leishmaniasis is a parasitic morbid/fatal disease caused by Leishmania protozoa. Twelve million people worldwide are appraised to be currently infected, including ca. two million infections each year, and 350 million people in 88 countries are at risk of becoming infected. In Colombia, cutaneous leishmaniasis (CL) is a public health problem in some tropical areas. Therapeutics is based on traditional antileishmanial drugs, but this practice has several drawbacks for patients. Thus, the search for new antileishmanial agents is a serious need, but the lack of adequately funded research programs on drug discovery has hampered its progress. Some Colombian researchers have conducted different research projects focused on the assessment of the antileishmanial activity of naturally occurring and synthetic compounds against promastigotes and/or amastigotes. Results of such studies have separately demonstrated important hits and reasonable potential, but a holistic view of them is lacking. Hence, we present the outcome from a systematic review of the literature (under PRISMA guidelines) on those Colombian studies investigating antileishmanials during the last thirty-two years. In order to combine the general efforts aiming at finding a lead against Leishmania panamensis (one of the most studied and incident parasites in Colombia causing CL) and to recognize structural features of representative compounds, fingerprint-based analyses using conventional machine learning algorithms and clustering methods are shown. Abstraction from such a meta-description led to describe some function-determining molecular features and simplify the clustering of plausible isofunctional hits. This systematic review indicated that the Colombian efforts for the antileishmanials discovery are increasingly intensified, though improvements in the followed pathways must be definitively pursued. In this context, a brief discussion about scope, strengths and limitations of such advances and relationships is addressed.

Comparing the Antileishmanial Activity of Gold(I) and Gold(III) Compounds in L. amazonensis and L. braziliensis in Vitro

A series of mononuclear coordination or organometallic AuI /AuIII complexes (1-9) have been comparatively studied in vitro for their antileishmanial activity against promastigotes and amastigotes, the clinically relevant parasite form, of Leishmania amazonensis and Leishmania braziliensis. One of the cationic AuI bis-N-heterocyclic carbenes (3) has low EC50 values (ca. 4 μM) in promastigotes cells and no toxicity in host macrophages. Together with two other AuIII complexes (6 and 7), the compound is also extremely effective in intracellular amastigotes from L. amazonensis. Initial mechanistic studies include an evaluation of the gold complexes' effect on L. amazonensis' plasma membrane integrity.

The Strong Anti-Kinetoplastid Properties of Bee Propolis: Composition and Identification of the Active Agents and Their Biochemical Targets

The kinetoplastids are protozoa characterized by the presence of a distinctive organelle, called the kinetoplast, which contains a large amount of DNA (kinetoplast DNA (kDNA)) inside their single mitochondrion. Kinetoplastids of medical and veterinary importance include Trypanosoma spp. (the causative agents of human and animal African Trypanosomiasis and of Chagas disease) and Leishmania spp. (the causative agents of the various forms of leishmaniasis). These neglected diseases affect millions of people across the globe, but drug treatment is hampered by the challenges of toxicity and drug resistance, among others. Propolis (a natural product made by bees) and compounds isolated from it are now being investigated as novel treatments of kinetoplastid infections. The anti-kinetoplastid efficacy of propolis is probably a consequence of its reported activity against kinetoplastid parasites of bees. This article presents a review of the reported anti-kinetoplastid potential of propolis, highlighting its anti-kinetoplastid activity in vitro and in vivo regardless of geographical origin. The mode of action of propolis depends on the organism it is acting on and includes growth inhibition, immunomodulation, macrophage activation, perturbation of the cell membrane architecture, phospholipid disturbances, and mitochondrial targets. This gives ample scope for further investigations toward the rational development of sustainable anti-kinetoplastid drugs.

Exploring the ability of dihydropyrimidine-5-carboxamide and 5-benzyl-2,4-diaminopyrimidine-based analogues for the selective inhibition of L. major dihydrofolate reductase

To tackle leishmaniasis, search for efficient therapeutic drug targets should be pursued. Dihydrofolate reductase (DHFR) is considered as a key target for the treatment of leishmaniasis. In current study, we are interested in the design and synthesis of selective antifolates targeting DHFR from L. major. We focused on the development of new antifolates based on 3,4-dihydropyrimidine-2-one and 5-(3,5-dimethoxybenzyl)pyrimidine-2,4-diamine motif. Structure activity relationship (SAR) studies were performed on 4-phenyl ring of dihydropyrimidine (26-30) template. While for 5-(3,5-dimethoxybenzyl)pyrimidine-2,4-diamine, the impact of different amino acids (valine, tryptophan, phenylalanine, and glutamic acid) and two carbon linkers were explored (52-59). The synthesized compounds were assayed against LmDHFR. Compound 59 with the IC₅₀ value of 0.10 μM appeared as potent inhibitors of L. major. Selectivity for parasite DHFR over human DHFR was also determined. Derivatives 55-59 demonstrated excellent selectivity for LmDHFR. Highest selectivity for LmDHFR was shown by compounds 56 (SI = 84.5) and 58 (SI = 87.5). Compounds Antileishmanial activity against L. major and L. donovani promastigotes was also performed. To explore the interaction pattern of the synthesized compounds with biological macromolecules, the docking studies were carried out against homology modelled LmDHFR and hDHFR targets.

Investigation of 8-methoxy-3-(4-nitrobenzoyl)-6-propyl-2H-chromen-2-one as a promising coumarin compound for the development of a new and orally effective antileishmanial agent

Changes in host immunity and parasite resistance to drugs are among the factors that contribute to decreased efficacy of antiparasitic drugs such as the antimonial compounds pentamidine, amphotericin (AMP B) and miltefosine. Bioactive natural products could be alternatives for the development of new drugs to treat neglected human diseases such as leishmaniasis. Natural coumarins and synthetic analogues have shown leishmanicidal activity, mainly in vitro. This study investigated the in vitro and in vivo leishmanicidal activity of synthetic coumarin compounds (C1-C5) in parasites Leishmania (L.) amazonensis and L. (L.) infantum chagasi. The cytotoxicity of these compounds in mammalian cells and their influence on production of reactive oxygen species was also investigated. In vitro assays showed that 8-methoxy-3-(4-nitrobenzoyl)-6-propyl-2H-chromen-2-one (C4) was as active as AMP B mainly in the amastigote form (p < 0.05); C4 presented a selectivity index (65.43) four times higher than C2 (15.4) in L. amazonensis and six times higher (33.94) than C1 (5.46) in L. infantum chagasi. Additionally, coumarin C4 reduced the H₂O₂ concentration 32.5% more than the control group in L. amazonensis promastigotes during the lag phase of proliferation. No interference of C4 was observed on the mitochondrial membrane potential of the parasites. In vivo, coumarin C4 in corn oil (oral route) led to a reduction in the number of amastigotes from L. infantum chagasi to 1.31 × 10⁶ and 4.09 × 10⁴ in the spleen and liver, respectively (p < 0.05). Thus, C4 represents a candidate for further studies aiming at new treatments of leishmaniasis.

β-Cyclodextrin/Isopentyl Caffeate Inclusion Complex: Synthesis, Characterization and Antileishmanial Activity

Isopentyl caffeate (ICaf) is a bioactive ester widely distributed in nature. Our patented work has shown promising results of this molecule against Leishmania. However, ICaf shows poor solubility, which limits its usage in clinical settings. In this work, we have proposed the development of an inclusion complex of ICaf in β-cyclodextrin (β-CD), with the aim to improve the drug solubility, and thus, its bioavailability. The inclusion complex (ICaf:β-CD) was developed applying three distinct methods, i.e., physical mixture (PM), kneading (KN) or co-evaporation (CO) in different molar proportions (0.25:1, 1:1 and 2:1). Characterization of the complexes was carried out by thermal analysis, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and molecular docking. The ICaf:β-CD complex in a molar ratio of 1:1 obtained by CO showed the best complexation and, therefore, was selected for further analysis. Solubility assay showed a marked improvement in the ICaf:β-CD (CO, 1:1) solubility profile when compared to the pure ICaf compound. Cell proliferation assay using ICaf:β-CD complex showed an IC50 of 3.8 and 2.7 µg/mL against L. amazonesis and L. chagasi promastigotes, respectively. These results demonstrate the great potential of the inclusion complex to improve the treatment options for visceral and cutaneous leishmaniases.

Physicochemical characterization and in vitro biological evaluation of solid compounds from furazolidone-based cyclodextrins for use as leishmanicidal agents

The discovery of new drugs and dosage forms for the treatment of neglected tropical diseases, such as human and animal leishmaniasis, is gaining interest in the chemical, biological, pharmaceutical, and medical fields. Many pharmaceutical companies are exploring the use of old drugs to establishing new drug dosage forms and drug delivery systems, in particular for use in neglected diseases. The formation of complexes with cyclodextrins is widely used to improve the stability, solubility, and bioavailability of pharmaceutical drugs, as well as reduce both the toxicity and side effects of many of these drugs. The aim of this study was to characterize solid compounds obtained from the association between furazolidone (FZD) and β-cyclodextrin (β-CD) or hydroxypropyl-β-cyclodextrin (HP-β-CD). The solid compounds were prepared in molar ratios of 1:1 and 1:2 (drug:CD) by kneading and lyophilization. Molecular docking was used to predict the preferred relative orientation of FZD when bound in both studied cyclodextrins. The resulting solid compounds were qualitatively characterized by scanning electron microscopy (SEM), thermal analysis (DSC and TG/DTG), X-ray diffraction (XRD), Raman spectroscopy with image mapping (Raman mapping), and ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR) in the solid state. The cytotoxicity of the compounds against THP-1 macrophages and the 50% growth inhibition (IC₅₀) against Leishmania amazonensis promastigote forms were subsequently investigated using in vitro techniques. For all of the solid compounds obtained, the existence of an association between FZD and CD were confirmed by one or more characterization techniques (TG/DTG, DSC, SEM, XRD, RAMAN, and ¹³C NMR), particularly by a significant decrease in the crystallinity of these materials and a reduction in the melting enthalpy associated with furazolidone thermal events. The formation of more effective interactions occurred in the compounds prepared by lyophilization, in a 1:2 molar ratio of the two CDs studied. However, the formation of an inclusion complex was confirmed only for the solid compound obtained from HP-β-CD prepared by lyophilization (LHFZD1:2). The absence of cytotoxicity on the THP-1 macrophage lineages and the leishmanicidal activity were confirmed for all compounds. MHFZD1:2 and LHFZD1:2 were found to be very active against promastigote forms of L. amazonensis, while all others were considered only active. These results are in line with the literature, demonstrating the existence of biological activity for associations between drugs and CDs in the form of complexes and non-complexes. All solid compounds obtained were found to be promising for use as leishmanicidal agents against promastigote forms of L. amazonensis.

Molecular modeling and simulation study of homoserine kinase as an effective leishmanial drug target

Leishmaniasis is a tropical neglected disease that imposes major health concerns in many endemic countries worldwide and requires urgent attention to the identification of new drug targets as well as drug candidates. In the current study, we propose homoserine kinase (HSK) inhibition as a strategy to induce pathogen mortality via generating threonine deficiency. We introduce a homology-based molecular model of leishmanial HSK that appears to possess all conserved structural as well as functional features in the GHMP kinase family. Furthermore, 200 ns molecular dynamics data of the enzyme in open and closed state attempts to provide the mechanistic details involved in the substrate as well as phosphate binding to this enzyme. We discuss the structural and functional significance of movements involved in various loops (motif 1, 2, 3) and lips (upper and lower) in the transition of leishmanial HSK from closed to open state. Virtual screening data of more than 40,000 compounds from the present investigation tries to identify a few potential HSK inhibitors that possess important features to act as efficient HSK inhibitors. These compounds can be considered an effective starting point for the identification of novel drug-like scaffolds. We hope the structural wealth that is offered in this report will be utilized in designing competent experimental and therapeutic interventions for leishmaniasis management. Graphical abstract.

Tibouchina granulosa (Vell.) Cogn (Melastomataceae) as source of endophytic fungi: isolation, identification, and antiprotozoal activity of metabolites from Phyllosticta capitalensis

Endophytes are microorganisms that form symbiotic relationships with their own host. Included in this group are the species Phyllosticta capitalensis, a group of fungi that include saprobes that produce bioactive metabolites. The present study aimed to identify the cultivable endophytic fungal microbiota present in healthy leaves of Tibouchina granulosa (Desr.) Cogn. (Melastomataceae) and investigate secondary metabolites produced by a strain of P. capitalensis and their effects against both Leishmania species and Trypanossoma cruzi. Identification of the strains was accomplished through multilocus sequencing analysis (MLSA), followed by phylogenetic analysis. The frequency of colonization was 73.66% and identified fungi belonged to the genus Diaporthe, Colletotrichum, Phyllosticta, Xylaria, Hypoxylon, Fusarium, Nigrospora, and Cercospora. A total of 18 compounds were identified by high-resolution mass spectrum analysis (UHPLC-HRMS), including fatty acids based on linoleic acid and derivatives, from P. capitalensis. Crude extracts had activity against Leishmania amazonensis, L. infantum, and Trypanosoma cruzi, with inhibitory concentration (IC50) values of 17.2 μg/mL, 82.0 μg/mL, and 50.13 μg/mL, respectively. This is the first report of the production of these compounds by the endophytic P. capitalensis isolated from T. granulosa.

A Multi-Species Phenotypic Screening Assay for Leishmaniasis Drug Discovery Shows That Active Compounds Display a High Degree of Species-Specificity

High genetic and phenotypic variability between Leishmania species and strains within species make the development of broad-spectrum antileishmanial drugs challenging. Thus, screening panels consisting of several diverse Leishmania species can be useful in enabling compound prioritization based on their spectrum of activity. In this study, a robust and reproducible high content assay was developed, and 1280 small molecules were simultaneously screened against clinically relevant cutaneous and visceral species: L. amazonensis, L. braziliensis, and L. donovani. The assay is based on THP-1 macrophages infected with stationary phase promastigotes and posterior evaluation of both compound antileishmanial activity and host cell toxicity. The profile of compound activity was species-specific, and out of 51 active compounds, only 14 presented broad-spectrum activity against the three species, with activities ranging from 52% to 100%. Notably, the compounds CB1954, Clomipramine, Maprotiline, Protriptyline, and ML-9 presented pan-leishmanial activity, with efficacy greater than 70%. The results highlight the reduced number of compound classes with pan-leishmanial activity that might be available from diversity libraries, emphasizing the need to screen active compounds against a panel of species and strains. The assay reported here can be adapted to virtually any Leishmania species without the need for genetic modification of parasites, providing the basis for the discovery of broad spectrum anti-leishmanial agents.

Enhanced antibacterial and antiparasitic activity of multifunctional polymeric nanoparticles

Due to the resistance to drugs, studies involving the combination and controlled release of different agents are gradually increasing. In this study, two different active ingredients, known to have antibacterial and antiparasitic activities, were encapsulated into single polymeric nanoparticles. After co-encapsulation their antibacterial and antileishmanial activity was enhanced approximately 5 and 250 times, respectively. Antibacterial and antileishmanial activities of caffeic acid phenethyl ester and juglone loaded, multifunctional nanoformulations (CJ4-CJ6-CJ8) were also evaluated for the first time in the literature comparatively with their combined free formulations. The antibacterial activity of the multifunctional nanoformulation (CJ8) were found to have a much higher activity (MIC values 6.25 and 12.5 μg ml^-1 for S. aureus and E. coli, respectively) than all other formulations. Similar efficacy for CJ8 was obtained in the antiparasitic study against the Leishmania promastigotes and the IC₅₀ was reduced to 0.1263 μg ml^-1. The high activity of multifunctional nanoparticles is not only due to the synergistic effect of the active molecules but also by the encapsulation into polymeric nanoparticles. Therefore, it has been shown in the literature for the first time that the biological activity of molecules whose activity is increased by the synergistic effect can be improved with nanosystems.

Targeting Trypanothione Reductase, a Key Enzyme in the Redox Trypanosomatid Metabolism, to Develop New Drugs against Leishmaniasis and Trypanosomiases

The protozoans Leishmania and Trypanosoma, belonging to the same Trypanosomatidae family, are the causative agents of Leishmaniasis, Chagas disease, and human African trypanosomiasis. Overall, these infections affect millions of people worldwide, posing a serious health issue as well as socio-economical concern. Current treatments are inadequate, mainly due to poor efficacy, toxicity, and emerging resistance; therefore, there is an urgent need for new drugs.

Antimicrobial activity of RP-1 peptide conjugate with ferrocene group

Parasitic diseases are a neglected and serious problem, especially in underdeveloped countries. Among the major parasitic diseases, Leishmaniasis figures as an urgent challenge due to its high incidence and severity. At the same time, the indiscriminate use of antibiotics by the population is increasing together with resistance to medicines. To address this problem, new antibiotic-like molecules that directly kill or inhibit the growth of microorganisms are necessary, where antimicrobial peptides (AMPs) can be of great help. In this work, the ferrocene molecule, one active compound with low levels of in vivo toxicity, was coupled to the N-terminus of the RP1 peptide (derived from the human chemokine CXCL4), aiming to evaluate how this change modifies the structure, biological activity, and toxicity of the peptide. The peptide and the conjugate were synthesized using the solid phase peptide synthesis (SPPS). Circular dichroism assays in PBS showed that the RP1 peptide and its conjugate had a typical spectrum for disordered structures. The Fc-RP1 presented anti-amastigote activity against Leishmania amazonensis (IC₅₀ = 0.25 μmol L^–1). In comparison with amphotericin B, a second-line drug approved for leishmaniasis treatment, (IC₅₀ = 0.63 μmol L^-1), Fc-RP1 was more active and showed a 2.5-fold higher selectivity index. The RP1 peptide presented a MIC of 4.3 μmol L^-1 against S. agalactiae, whilst Fc-RP1 was four times more active (MIC = 0.96 μmol L^-1), indicating that ferrocene improved the antimicrobial activity against Gram-positive bacteria. The Fc-RP1 peptide also decreased the minimum inhibitory concentration (MIC) in the assays against E. faecalis (MIC = 7.9 μmol L^-1), E. coli (MIC = 3.9 μmol L^-1) and S. aureus (MIC = 3.9 μmol L^-1). The cytotoxicity of the compounds was tested against HaCaT cells, and no significant activity at the highest concentration tested (500 μg. mL^-1) was observed, showing the high potential of this new compound as a possible new drug. The coupling of ferrocene also increased the vesicle permeabilization of the peptide, showing a direct relation between high peptide concentration and high carboxyfluorescein release, which indicates the action mechanism by pore formation on the vesicles. Several studies have shown that ferrocene destabilizes cell membranes through lipid peroxidation, leading to cell lysis. It is noteworthy that the Fc-RP1 peptide synthesized here is a prototype of a bioconjugation strategy, but it still is a compound with great biological activity against neglected and fish diseases.

Comparison of in vitro Resistance of Wild Leishmania İsolates, Which are Resistant to Pentavalent Antimonial Compounds, Against Drugs Used in the Treatment of Leishmaniasis

OBJECTIVE

Meglumine antimoniate (Glucantime^®) and Sodium stibogluconate (Pentostam^®) are used for the treatment of cutaneous leismaniasis in Turkey. There is a reported resistance to these drugs in recent years. The aim of the present study was to compare the in vitro sensitivities of resistant Leishmania isolates against Amphotericin B, Miltefosine, Meglumine Antimoniate, Paromomycin and Sodium Stibogluconate.

METHODS

Five Leishmania isolates of patients with cutaneous leishmaniasis, who showed no clinical recovery despite two consecutive meglumine antimoniate treatments, which were stored in the Parasite Bank in Manisa Celal Bayar University Medical Faculty were selected. They were genotyped with Real-Time PCR using specific primers and probes to ITS1 region. Drug resistance levels of each Leishmania isolate were analysed for Amphotericin B, Miltefosine, Meglumine Antimoniate, Paromomycin, and Sodium Stibogluconate at concentrations of 500, 250, 125, 50, 25 μg/mL with XTT method and hemocytometer.

RESULTS

It was observed that the resistant Leishmania tropica isolates showed no resistance to Amphotericin B, and were sensitive to Miltefosine, Sodium Stibogluconate, Paromomycin and Meglumin Antimonate, respectively. In addition, Leishmania tropica (MHOM/AZ/1974/SAF-K27) isolate of the control group could stay viable in none of the drug concentrations of five agents in the study.

CONCLUSION

It was determined that none of the selected resistant L. tropica isolates showed resistance to Amphotericin B and that was also shown statistically (p<0.05). The results of this study are important in guiding clinicians and researchers who conduct studies on drugs and search for new drug molecules.

Targeting tRNA-synthetase interactions towards novel therapeutic discovery against eukaryotic pathogens

The development of chemotherapies against eukaryotic pathogens is especially challenging because of both the evolutionary conservation of drug targets between host and parasite, and the evolution of strain-dependent drug resistance. There is a strong need for new nontoxic drugs with broad-spectrum activity against trypanosome parasites such as Leishmania and Trypanosoma. A relatively untested approach is to target macromolecular interactions in parasites rather than small molecular interactions, under the hypothesis that the features specifying macromolecular interactions diverge more rapidly through coevolution. We computed tRNA Class-Informative Features in humans and independently in eight distinct clades of trypanosomes, identifying parasite-specific informative features, including base pairs and base mis-pairs, that are broadly conserved over approximately 250 million years of trypanosome evolution. Validating these observations, we demonstrated biochemically that tRNA:aminoacyl-tRNA synthetase (aaRS) interactions are a promising target for anti-trypanosomal drug discovery. From a marine natural products extract library, we identified several fractions with inhibitory activity toward Leishmania major alanyl-tRNA synthetase (AlaRS) but no activity against the human homolog. These marine natural products extracts showed cross-reactivity towards Trypanosoma cruzi AlaRS indicating the broad-spectrum potential of our network predictions. We also identified Leishmania major threonyl-tRNA synthetase (ThrRS) inhibitors from the same library. We discuss why chemotherapies targeting multiple aaRSs should be less prone to the evolution of resistance than monotherapeutic or synergistic combination chemotherapies targeting only one aaRS.

Trypanosome parasites pose a significant health risk worldwide. Conventional drug development strategies have proven challenging given the high conservation between humans and pathogens, with off-target toxicity being a common problem. Protein synthesis inhibitors have historically been an attractive target for antimicrobial discovery against bacteria, and more recently for eukaryotic pathogens. Here we propose that exploiting pathogen-specific tRNA-synthetase interactions offers the potential for highly targeted drug discovery. To this end, we improved tRNA gene annotations in trypanosome genomes, identified functionally informative trypanosome-specific tRNA features, and showed that these features are highly conserved over approximately 250 million years of trypanosome evolution. Highlighting the species-specific and broad-spectrum potential of our approach, we identified natural product inhibitors against the parasite translational machinery that have no effect on the homologous human enzyme.

Synthesis and Evaluation of Antileishmanial and Cytotoxic Activity of Benzothiopyrane Derivatives

In continuation of our efforts to identify promising antileishmanial agents based on the chroman scaffold, we synthesized several substituted 2H-thiochroman derivatives, including thiochromenes, thichromanones and hydrazones substituted in C-2 or C-3 with carbonyl or carboxyl groups. Thirty-two compounds were thus obtained, characterized, and evaluated against intracellular amastigotes of Leishmania (V)panamensis. Twelve compounds were active, with EC₅₀ values lower than 40 µM, but only four compounds displayed the highest antileishmanial activity, with EC₅₀ values below 10 µM; these all compounds possess a good Selectivity Index > 2.6. Although two active compounds were thiochromenes, a clear structure-activity relationship was not detected since each active compound has a different substitution pattern.

In vivo antileishmanial activity of Annona mucosa extracts

INTRODUCTION

Leishmaniasis, a disease caused by a parasite endemic to large areas of tropical and subtropical countries, is a growing public health problem.

METHODS

Male BALB/c mice were infected with Leishmania amazonensis and treated with extracts isolated from Annona mucosa.

RESULTS

Treated groups had significantly reduced footpad swelling. The group treated intraperitoneally with hexane extract showed footpad swelling similar to groups treated with Pentamidine® and Glucantime®. Groups treated with dichloromethane extract and hexane extract presented the recovering phenotype associated with reduced parasite levels.

CONCLUSIONS

Extracts of A. mucosa are promising sources of novel antileishmanial compounds.