Sensitivities of Leishmania species to hexadecylphosphocholine (miltefosine), ET-18-OCH(3) (edelfosine) and amphotericin B

Combination of the Topical Photodynamic Therapy of Chloroaluminum Phthalocyanine Liposomes with Fexinidazole Oral Self-Emulsifying System as a New Strategy for Cutaneous Leishmaniasis Treatment

Cutaneous leishmaniasis (CL) is a neglected tropical disease. The treatment is restricted to drugs, such as meglumine antimoniate and amphotericin B, that exhibit toxic effects, high cost, long-term treatment, and limited efficacy. The development of new alternative therapies, including the identification of effective drugs for the topical and oral treatment of CL, is of great interest. In this sense, a combination of topical photodynamic therapy (PDT) with chloroaluminum phthalocyanine liposomes (Lip-ClAlPc) and the oral administration of a self-emulsifying drug delivery system containing fexinidazole (SEDDS-FEX) emerges as a new strategy. The aim of the present study was to prepare, characterize, and evaluate the efficacy of combined therapy with Lip-ClAlPc and SEDDS-FEX in the experimental treatment of Leishmania (Leishmania) major. Lip-ClAlPc and SEDDS-FEX were prepared, and the antileishmanial efficacy study was conducted with the following groups: 1. Lip-ClAlPc (0.05 mL); 2. SEDDS-FEX (50 mg/kg/day); 3. Lip-ClAlPc (0.05 mL)+SEDDS-FEX (50 mg/kg/day) combination; 4. FEX suspension (50 mg/kg/day); and 5. control (untreated). BALB/c mice received 10 sessions of topical Lip-ClAlPc on alternate days and 20 consecutive days of SEDDS-FEX or FEX oral suspension. Therapeutical efficacy was evaluated via the parasite burden (limiting-dilution assay), lesion size (mm), healing of the lesion, and histological analyses. Lip-ClAlPc and SEDDS-FEX presented physicochemical characteristics that are compatible with the administration routes used in the treatments. Lip-ClAlPc+SEDDS-FEX led to a significant reduction in the parasitic burden in the lesion and spleen when compared to the control group (p < 0.05) and the complete healing of the lesion in 43% of animals. The Lip-ClAlPc+SEDDS-FEX combination may be promising for the treatment of CL caused by L. major.

Oliveria decumbens Vent. (Apiaceae): Biological screening and chemical compositions

ETHNOPHARMACOLOGICAL RELEVANCE

Oliveria decumbens Vent. (Apiaceae), a single aromatic species in Iran, is traditionally used for healing inflammation, gastrointestinal disorders, and infections.

AIM OF THE STUDY

Regarding the importance of O. decumbens in traditional medicine, we aimed to set out the plant's biological screening and analyze the chemical components of the active fractions.

MATERIALS AND METHODS

Air-dried O. decumbens aerial parts were macerated by ethanol:water (70:30). Using a liquid-liquid extraction (LLE) technique, n-hexane, dichloromethane (DCM), ethyl acetate (EtOAc), n-butanol (n-BuOH), and water were successively used to fractionate the crude extract into different portions. Various biological activities were performed on the crude extract, fractions, and some experiments on pure compounds. The bioassays were as follows: antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi (using microplate alamar blue assay; MABA), antifungal activity against Aspergillus niger, A. fumigatus, Candida albicans, C. glabarate, Fusarium lini, Microspurum canis, and Trichophyton rubrum (using agar tube dilution method), antileishmanial activity against Leishmania major and L. tropica using a 96-well serial dilution protocol, anti-inflammatory activity using the respiratory burst assay, cytotoxicity against HeLa (cervical cancer) and BJ (normal fibroblast) cells using MTT assay, insecticidal activity against Tribolium castaneum, Sitophilus oryzae, and Rhyzopertha dominica (using the contact toxicity method), larvicidal activity against Aedes aegypti, anti-DPPH• activity, and cytotoxicity against brine shrimp (Artemia salina) in a lethality assay. Eventually, the phytochemicals from the active fractions were studied by gas chromatography coupled with mass spectrometry (GC-MS).

RESULTS

Interestingly, the DCM fraction was the most active, followed by the n-hexane fraction in the biological assays, including antibacterial (>80% inhibition), leishmanicidal (IC50 (L.major) = 29.4 μg/mL, and IC50 (L.tropica) = 30.0 μg/mL), anti-inflammatory (IC50 = 15.8 μg/mL), insecticidal (>80% inhibition), and larvicidal (100% inhibition of A. aegypti) assays. Further GC-MS analysis of the DCM and n-hexane fractions resulted in the characterization of 12 and 14 phytoconstituents, respectively, compared with the NIST library. Thymol and carvacrol were abundant in both fractions. To lesser quantities, the presence of monoterpenoids (p-cymen-8-ol, thymoquinone, 3-hydroxy-β-damascone, and 3-hydroxy-7,8-dihydro-β-ionol), phenylpropanoids (methoxyeugenol, elemicin, and 4-[(1E)-3-hydroxy-1-propenyl]-2-methoxyphanol, simple phenolics (salicylic acid and 4-methoxy-2,3,6-trimethyl-phenol), and a coumarin (6,7-dimethoxy-coumarin) were detected in the DCM fraction. On the other hand, besides a coumarin and monoterpenoids, the fatty acids (tetradecanoid acid, n-hexadecanoic acid, and linolenic acid) and a sesquiterpene (spathulenol) were observed in the n-hexane fraction. The EtOAc fraction scavenged the DPPH• radicals better than other fractions (IC50 = 41.4 μg/mL), while in brine shrimp lethality assay, the crude extract was more active than n-hexane and DCM fractions with LD50 = 385.20, 660.28, and 699.74 μg/mL, respectively. Surprisingly, the crude extract and fractions were ineffective against assayed fungal strains and tested cancer and non-cancer cell lines.

CONCLUSIONS

Our findings showed that O. decumbens deserves to be a multi-bioactive medicinal plant, besides its ability for cereal protection against pests. To understand the principal mechanism of action, in silico, in vitro, and in vivo experiments may clarify the ambiguities and even figure out the synergistic behavior of the minor secondary metabolites.

Imidazo[1,2-a]pyrimidine as a New Antileishmanial Pharmacophore against Leishmania amazonensis Promastigotes and Amastigotes

Leishmania poses a substantial threat to the human population all over the globe because of its visceral and cutaneous spread engendered by all 20 species. Unfortunately, the available drugs against leishmania are already hobbled with toxicity, prolonged treatment, and increasing instances of acquirement of resistance. Under these grave circumstances, the development of new drugs has become imperative to keep these harmful microbes at bay. To this end, a Groebke-Blackburn-Bienaymé multicomponent reaction-based library of different imidazo-fused heterocycles has been synthesized and screened against Leishmania amazonensis promastigotes and amastigotes. Among the library compounds, the imidazo-pyrimidine 24 has been found to be the most effective (inhibitory concentration of 50% (IC50) < 10 μM), with selective antileishmanial activity on amastigote forms, a stage of the parasite related to human disease. The compound 24 has exhibited an IC50 value of 6.63 μM, being ∼two times more active than miltefosine, a reference drug. Furthermore, this compound is >10 times more destructive to the intracellular parasites than host cells. The observed in vitro antileishmanial activity along with suitable in silico physicochemical and absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of compound 24 reinforce the imidazo-pyrimidine scaffold as a new antileishmanial pharmacophore and encourage further murine experimental leishmaniasis studies.

Efficacy of oleylphosphocholine in experimental cutaneous leishmaniasis

OBJECTIVES

Cutaneous leishmaniasis (CL) is a neglected tropical disease causing a range of skin lesions for which safe and efficacious drugs are lacking. Oleylphosphocholine (OLPC) is structurally similar to miltefosine and has previously demonstrated potent activity against visceral leishmaniasis. We here present the in vitro and in vivo efficacy of OLPC against CL-causing Leishmania species.

METHODS

The antileishmanial activities of OLPC were evaluated and compared with miltefosine in vitro against intracellular amastigotes of seven CL-causing species. Following the confirmation of significant in vitro activity, the performance of the maximum tolerated dose of OLPC was evaluated in an experimental murine model of CL followed by a dose-response titration and the efficacy evaluation of four OLPC formulations (two with a fast-release and two with a slow-release profile) using bioluminescent Leishmania major parasites.

RESULTS

OLPC demonstrated potent in vitro activity of the same order as miltefosine in the intracellular macrophage model against a range of CL-causing species. A dose of 35 mg of OLPC/kg/day administered orally for 10 days was well-tolerated and able to reduce the parasite load in the skin of L. major-infected mice to a similar extent as the positive control paromomycin (50 mg/kg/day, intraperitoneally) in both in vivo studies. Reducing the dose of OLPC resulted in inactivity and modifying the release profile using mesoporous silica nanoparticles led to a decrease in activity when solvent-based loading was used in contrast to extrusion-based loading, which had no impact on its antileishmanial efficacy.

CONCLUSIONS

Together, these data suggest that OLPC could be a promising alternative to miltefosine treatment for CL. Further investigations exploring experimental models with additional Leishmania species and skin pharmacokinetic and dynamic analyses are required.

Exploring the repositioning of the amodiaquine as potential drug against visceral leishmaniasis: The in vitro effect against Leishmania infantum is associated with multiple mechanisms, involving mitochondria dysfunction, oxidative stress and loss of cell cycle control

Visceral leishmaniasis (VL) is a progressive, debilitating, and potentially fatal disease if left untreated. As a neglected tropical disease (NTD), the available treatment is restricted to a few drugs, which typically must be administered over a long period but are associated with serious adverse effects and have variability in efficacy. In this sense, drug repositioning has been considered an excellent strategy in the search for alternative treatments, especially in reducing the time and cost of the research. In this work, the repositioning potential of amodiaquine (AQ), a well-known antimalarial drug, was investigated for the treatment of VL. AQ showed significant and selective activity against promastigotes (IC₅₀ = 11.6 μg/mL) and intracellular amastigotes (IC₅₀ = 2.4 μg/mL) of L. infantum, being 10 times more destructive to the intracellular parasites than the host cell. In addition, pre-treatment of macrophages with AQ caused a significant reduction in the infection index, indicating a prophylactic effect of this drug. SEM images showed that AQ induces strong shape alterations of the promastigotes with an increase in cell volume with rounding and ribbing (vertical ridges), as well as a shortened flagellum. In addition, AQ induced depolarization of the ΔΨm, an increase in ROS and neutral lipids levels, and changes in the cell cycle in promastigotes, without alterations to the permeability of the parasite plasma membrane. L. infantum-infected macrophages treated with AQ induced the activation of oxidative mechanisms by infected host cells, with an increase in ROS and NO levels. Finally, in vitro interactions between AQ and miltefosine were found to have an additive effect in both biological stages of the parasite, with the ∑FIC₅₀ values ranging from 0.74 to 1.16 μg/mL and 0.54-1.11 μg/mL for promastigotes and intracellular amastigotes, respectively. Overall, these data highlight the utility of drug repurposing and indicate future preclinical testing for AQ itself or in combination as a potential VL treatment.

Antileishmanial Activities of ( Z )-2-(Nitroimidazolylmethylene)-3( 2H )-Benzofuranones: Synthesis, In Vitro Assessment, and Bioactivation by NTR 1 and 2

The antileishmanial activity of a series of ( Z )-2-(heteroarylmethylene)-3(2 H )-benzofuranone derivatives, possessing 5-nitroimidazole or 4-nitroimidazole moieties, was investigated against Leishmania major promastigotes and some analogues exhibited prominent activities. Compounds with IC 50 values lower than 20 μM were further examined against L. donovani axenic amastigotes.

Cutaneous Leishmaniasis: A 2022 Updated Narrative Review into Diagnosis and Management Developments

This review is an update of an earlier narrative review published in 2015 on developments in the clinical management of cutaneous leishmaniasis (CL) including diagnosis, treatment, prevention and control measurements. CL is a vector-borne infection caused by the protozoan parasite Leishmania. The vector is the female sandfly. Globally, CL affects 12 million cases and annually 2 million new cases occur. CL is endemic in almost 100 countries and the total risk population is approximately 350 million people. WHO lists CL an emerging and uncontrolled disease and a neglected tropical disease. Local experience-based evidence remains the mainstay for the management of CL. Whereas intralesional therapeutic options are the first treatment option for most CL patients, those with mucocutaneous and disseminated involvement require a systemic therapeutic approach. Moreover, different Leishmania species can vary in their treatment outcomes. Therefore, species determination is critical for optimal CL clinical management. New DNA techniques allow for relatively easy Leishmania species determination, yet they are not easily implemented in resource-limited settings. There is a desperate need for novel, less toxic, and less painful treatment options, especially for children with CL. Yet, the large and well conducted studies required to provide the necessary evidence are lacking. To further control and potentially eliminate CL, we urgently need to improve vector control, and diagnostics, and we require efficient and safe vaccines. Alas, since CL primarily affects poor people, biotechnical companies dedicate little investment into the research programs that could lead to diagnostic, pharmaceutical, and vaccine innovations.

In Vitro Antiparasitic Activities of Monovalent Ionophore Compounds for Human and Canine Leishmaniases

The leishmaniases are vector-borne parasitic diseases affecting humans and animals, with high mortality rates in endemic countries. Infected dogs represent the main reservoir of infection. Disease control is mainly based on chemotherapy, which, at present, shows serious drawbacks both in humans and dogs. Therefore, the discovery or repurposing of new treatments is mandatory. Here, three monovalent ionophores (salinomycin, monensin, nigericin) were tested against promastigotes of Leishmania (L.) infantum, Leishmania tropica, and Leishmania braziliensis, and against amastigotes of L. infantum within human and, for the first time, canine macrophages. All three drugs were leishmanicidal against all Leishmania spp. promastigotes with IC50 values between 7.98 and 0.23 µM. Monensin and nigericin showed IC50 values < 1 µM, whereas salinomycin was the least active compound (IC50 > 4 µM). Notably, the ionophores killed L. infantum amastigotes within human THP-1 cells with IC50 values ranging from 1.67 to 1.93 µM, but they only reduced by 27−37% the parasite burden in L. infantum-infected canine macrophages, showing a host-specific efficacy. Moreover, a selective higher toxicity against canine macrophages was observed. Overall, repurposed ionophores have the potential to be further investigated as anti-Leishmania agents, but different drug options may be required to tackle human or canine leishmaniases.

Quantitative monitoring of experimental and human leishmaniasis employing amastigote-specific genes

The gold standard for diagnosis of leishmaniasis is the microscopic detection of amastigotes/Leishman Donovan (LD) bodies, but its moderate sensitivity necessitates the development of molecular approaches. This study aimed to quantify in experimental animal models and human leishmaniasis the expression of amastigote-specific virulence genes, A2 and amastin by droplet digital polymerase chain reaction (ddPCR). Total RNA was isolated from L. donovani-infected hamsters or murine peritoneal macrophages and lesional biopsies from patients with post kala-azar dermal leishmaniasis (PKDL). Following cDNA conversion, EvaGreen-based ddPCR was performed using specific primers for A2 or amastin and parasite load expressed in copies per μL. Assay was optimized and the specificity of amastigote-specific A2 and amastin was confirmed. In hepatic and splenic tissues of L. donovani-infected hamsters and peritoneal macrophages, ddPCR demonstrated a greater abundance of A2 than amastin. Treatment of L. donovani-infected peritoneal macrophages with conventional anti-leishmanials, miltefosine and amphotericin B translated into a dose-dependent reduction in copies per μL of A2 and amastin, and the extrapolated IC50 was comparable with results obtained by counting LD bodies in Giemsa-stained macrophages. Similarly, in dermal biopsies of patients with PKDL, A2 and amastin were detected. Overall, monitoring of A2 by ddPCR can be an objective measure of parasite burden and potentially adaptable into a high throughput approach necessary for drug development and monitoring disease progression when the causative species is L. donovani.

Tackling Drug Resistance and Other Causes of Treatment Failure in Leishmaniasis

Leishmaniasis is a tropical infectious disease caused by the protozoan Leishmania parasite. The disease is transmitted by female sand flies and, depending on the infecting parasite species, causes either cutaneous (stigmatizing skin lesions), mucocutaneous (destruction of mucous membranes of nose, mouth and throat) or visceral disease (a potentially fatal infection of liver, spleen and bone marrow). Although more than 1 million new cases occur annually, chemotherapeutic options are limited and their efficacy is jeopardized by increasing treatment failure rates and growing drug resistance. To delay the emergence of resistance to existing and new drugs, elucidating the currently unknown causes of variable drug efficacy (related to parasite susceptibility, host immunity and drug pharmacokinetics) and improved use of genotypic and phenotypic tools to define, measure and monitor resistance in the field are critical. This review highlights recent progress in our understanding of drug action and resistance in Leishmania, ongoing challenges (including setbacks related to the COVID-19 pandemic) and provides an overview of possible strategies to tackle this public health challenge.

Treatment of Cutaneous Leishmaniasis and Insights into Species-Specific Responses: A Narrative Review

Cutaneous leishmaniasis (CL) is a complex skin infection that has imposed a heavy burden on many developing countries and is caused by more than 20 Leishmania species. This disease is predominantly associated with disfiguring scars and major social stigma upon infection. The severity of the disease seemingly depends on many factors including the species of parasite, the host, region of endemicity, socio-economic status and the accessibility to health facilities. Despite myriad studies that have been performed on current and novel therapies, the treatment outcomes of CL remain contentious, possibly because of the knowledge gaps that still exist. The differential responses to the current CL therapies have become a major drawback in disease control, and the dearth of information on critical analyses of outcomes of such studies is a hindrance to the overall understanding. On the basis of currently available literature on treatment outcomes, we discuss the most effective doses, drug susceptibilities/resistance and treatment failures of the Leishmania genus for both monotherapy and combination therapy. This review focuses on the available treatment modalities for CL caused by different Leishmania species, with insights into their species-specific efficacies, which would inform the selection of appropriate drugs for the treatment and control of leishmaniasis.

Fatty Acid Profiles of Leishmania major Derived from Human and Rodent Hosts in Endemic Cutaneous Leishmaniasis Areas of Tunisia and Algeria

Leishmaniasis is a protozoal vector-borne disease that affects both humans and animals. In the Mediterranean Basin, the primary reservoir hosts of Leishmania spp. are mainly rodents and canids. Lipidomic approaches have allowed scientists to establish Leishmania spp. lipid profiles for the identification of cell stage specific biomarkers, drug mechanisms of action, and host immune response. Using an in silico approach of global network interaction between genes involved in fatty acid (FA) synthesis followed by the GC-MS approach, we were able to characterize the fatty acid profiles of L. major derived from human and rodent hosts. Our results revealed that the lipid profile of L. major showed similarities and differences with those already reported for other Leishmania species. Phospholipids are the predominant lipid class. FA composition of rodent parasites was characterized by a lower abundance of the precursor C18:2(n-6). One of the rodent clones, which also expressed the lowest lipid abundance in PL and TAG, was the least sensitive clone to the miltefosine drug and has the lowest infection efficiency. Our findings suggest that the lipid composition variation may explain the response of the parasite toward treatment and their ability to infect their host.

Potency and preclinical evidence of synergy of oral azole drugs and miltefosine in an ex vivo model of Leishmania (Viannia) panamensis infection

Failure of treatment of cutaneous leishmaniasis with antimonial drugs and miltefosine is frequent. Use of oral combination therapy represents an attractive strategy to increase efficacy of treatment and reduce the risk of drug resistance. We evaluated the potency of posaconazole, itraconazole, voriconazole and fluconazole, and the potential synergy of those demonstrating the highest potency, in combination with miltefosine (HePC), against infection with Leishmania (Viannia) panamensis. Synergistic activity was determined by isobolograms and calculation of Fractional Inhibitory Concentration Index (FICI), based on parasite quantification using an ex vivo model of human PBMCs infected with a luciferase-transfected, antimony and miltefosine sensitive line of L. panamensis. The drug combination and concentrations that displayed synergy were then evaluated for anti-leishmanial effect in 10 clinical strains of L. panamensis by qRT-PCR of Leishmania 7SLRNA. High potency was substantiated for posaconazole and itraconazole against sensitive as well as HePC and antimony resistant lines of L. panamensis, whereas fluconazole and voriconazole displayed low potency. HePC combined with posaconazole (Poz) demonstrated evidence of synergy at free drug concentrations achieved in plasma during treatment (2 μM HePC + 4 μM Poz). FICI, based on 70% and 90% reduction of infection, was 0.5 for the sensitive line. Combination of 2 μM HePC + 4 μM Poz effected significantly greater reduction of infection by clinical strains of L. panamensis than individual drugs. Orally administrable miltefosine/posaconazole combinations demonstrated synergistic anti-leishmanial capacity ex vivo against L. panamensis, supporting their potential as a novel therapeutic strategy to improve efficacy, and effectiveness of treatment.

Development of a Fluorescent Assay to Search New Drugs Using Stable tdTomato-Leishmania, and the Selection of Galangin as a Candidate With Anti-Leishmanial Activity

Antimonials continue to be considered the first-line treatment for leishmaniases, but its use entails a wide range of side effects and serious reactions. The search of new drugs requires the development of methods more sensitive and faster than the conventional ones. We developed and validated a fluorescence assay based in the expression of tdTomato protein by Leishmania, and we applied this method to evaluate the activity in vitro of flavonoids and reference drugs. The pIR1SAT/tdTomato was constructed and integrated into the genome of Leishmania (Leishmania) amazonensis. Parasites were selected with nourseothricin (NTC). The relation of L. amaz/tc3 fluorescence and the number of parasites was determined; then the growth in vitro and infectivity in BALB/c mice was characterized. To validate the fluorescence assay, the efficacy of miltefosine and meglumine antimoniate was compared with the conventional methods. After that, the method was used to assess in vitro the activity of flavonoids; and the mechanism of action of the most active compound was evaluated by transmission electron microscopy and ELISA. A linear correlation was observed between the emission of fluorescence of L. amaz/tc3 and the number of parasites (r2 = 0.98), and the fluorescence was stable in the absence of NTC. No differences were observed in terms of infectivity between L. amaz/tc3 and wild strain. The efficacy of miltefosine and meglumine antimoniate determined by the fluorescence assay and the microscopic test showed no differences, however, in vivo the fluorescence assay was more sensitive than limiting dilution assay. Screening assay revealed that the flavonoid galangin (GAL) was the most active compound with IC50 values of 53.09 µM and 20.59 µM in promastigotes and intracellular amastigotes, respectively. Furthermore, GAL induced mitochondrial swelling, lipid inclusion bodies and vacuolization in promastigotes; and up-modulated the production of IL-12 p70 in infected macrophages. The fluorescence assay is a useful tool to assess the anti-leishmanial activity of new compounds. However, the assay has some limitations in the macrophage-amastigote model that might be related with an interfere of flavanol aglycones with the fluorescence readout of tdTomato. Finally, GAL is a promising candidate for the development of new treatment against the leishmaniasis.

Overcoming the Challenge; In Vivo Efficacy of Miltefosine for Chronic Cutaneous Leishmaniasis

BACKGROUND

Cutaneous Leishmaniasis (CL) is the most common form of leishmaniasis. CL can be divided into two major groups: acute CL (ACL) and chronic CL (CCL). The aim of this study is to compare the efficacy of miltefosin and pentavalent antimony compounds in vivo with the CCL patient samples.

MATERIALS

Three study groups were formed, each consisting of five male Mus musculus (Balb/C) mice. In this model, promastigotes from the culture of a CCL patient were utilized. 100 μL L. tropica promastigote suspension with a density of 10⁸ promastigotes/ml were injected into the hint-right footpad of each experimental animal intradermally. Footpads of the mice were measured every two weeks until 24th week. From the 13th week, miltefosin 50 mg/kg/day was administered orally using gavage for 21 days, Meglumin antimoniate (MA) was administered by intramuscular (IM) injection daily for 21 days at 50 mg/kg/day and saline was administered IM for 21 days for the miltefosine, MA and control group, respectively.

RESULTS

The footpad measurements of the miltefosine group were lower than the control group statistically. Between the MA group and the miltefosine group and MA group and the control group, there was no statistically significant difference. Giemsa stained slides revealed amastigotes in one, two and all of the slides for the miltefosine, MA and control group, respectively. Molecular tests were performed with the Rotor-Gene device and L. tropica consistent peaks were obtained in one of the miltefosine group, four in the MA group and all mice in the control group.

CONCLUSIONS

Demonstration of both clinical and laboratory improvement in four of the five experimental animals provides strong evidence that miltefosine is an effective drug in the treatment of CCL. In the literature, no clinical or laboratory studies using miltefosine have been performed with CCL patients only.

Methods for Identifying Microbial Natural Product Compounds that Target Kinetoplastid RNA Structural Motifs by Homology and De Novo Modeled 18S rRNA

The development of novel anti-infectives against Kinetoplastids pathogens targeting proteins is a big problem occasioned by the antigenic variation in these parasites. This is also a global concern due to the zoonosis of these parasites, as they infect both humans and animals. Therefore, we need not only to create novel antibiotics, but also to speed up the development pipeline for these antibiotics. This may be achieved by using novel drug targets for Kinetoplastids drug discovery. In this study, we focused our attention on motifs of rRNA molecules that have been created using homology modeling. The RNA is the most ambiguous biopolymer in the kinetoplatid, which carries many different functions. For instance, tRNAs, rRNAs, and mRNAs are essential for gene expression both in the pro-and eukaryotes. However, all these types of RNAs have sequences with unique 3D structures that are specific for kinetoplastids only and can be used to shut down essential biochemical processes in kinetoplastids only. All these features make RNA very potent targets for antibacterial drug development. Here, we combine in silico methods combined with both computational biology and structure prediction tools to address our hypothesis. In this study, we outline a systematic approach for identifying kinetoplastid rRNA-ligand interactions and, more specifically, techniques that can be used to identify small molecules that target particular RNA. The high-resolution optimized model structures of these kineoplastids were generated using RNA 123, where all the stereochemical conflicts were solved and energies minimized to attain the best biological qualities. The high-resolution optimized model's structures of these kinetoplastids were generated using RNA 123 where all the stereochemical conflicts were solved and energies minimized to attain the best biological qualities. These models were further analyzed to give their docking assessment reliability. Docking strategies, virtual screening, and fishing approaches successfully recognized novel and myriad macromolecular targets for the myxobacterial natural products with high binding affinities to exploit the unmet therapeutic needs. We demonstrate a sensible exploitation of virtual screening strategies to 18S rRNA using natural products interfaced with classical maximization of their efficacy in phamacognosy strategies that are well established. Integration of these virtual screening strategies in natural products chemistry and biochemistry research will spur the development of potential interventions to these tropical neglected diseases.

Pharmacokinetics and pharmacodynamics in the treatment of cutaneous leishmaniasis - challenges and opportunities

Pharmacological efficacy is obtained when adequate concentrations of a potent drug reach the target site. In cutaneous leishmaniasis, a heterogeneous disease characterised by a variety of skin manifestations from simple nodules, skin discoloration, plaques to extensive disseminated forms, the parasites are found in the dermal layers of the skin. Treatment thus involves the release of the active compound from the formulation (administered either topically or systemically), it's permeation into the skin, accumulation by the local macrophages and further transport into the phagolysosome of the macrophage. The pharmacodynamic activity of a drug against the parasite is relatively straight forward to evaluate both in vivo and in vitro. The pharmacokinetic processes taking place inside the skin are more complex to elucidate due to the multi-lamellar structure of the skin, heterogeneous distribution of drugs within the tissue, the difficulty of accessing the site of infection complicating sampling and the lack of surrogate markers reflecting the activity of a drug in the skin. This review will discuss the difficulties encountered when investigating drug distribution, PK PD relationships and efficacy in the skin with a focus on cutaneous leishmaniasis treatment.

Computationally designed synthetic peptides for transporter proteins imparts allostericity in Miltefosine resistant L. major

The emergence of drug resistance is a major concern for combating against Cutaneous Leishmaniasis, a neglected tropical disease affecting 98 countries including India. Miltefosine is the only oral drug available for the disease and Miltefosine transporter proteins play a pivotal role in the emergence of drug-resistant Leishmania major. The cause of resistance is less accumulation of drug inside the parasite either by less uptake of the drug due to a decrease in the activity of P4ATPase-CDC50 complex or by increased efflux of the drug by P-glycoprotein (P-gp, an ABC transporter). In this paper, we are trying to allosterically modulate the behavior of resistant parasite (L. major) towards its sensitivity for the existing drug (Miltefosine, a phosphatidylcholine analog). We have used computational approaches to deal with the conservedness of the proteins and apparently its three-dimensional structure prediction through ab initio modeling. Long scale membrane-embedded molecular dynamics simulations were carried out to study the structural interaction and stability. Parasite-specific motifs of these proteins were identified based on the machine learning technique, against which a peptide library was designed. The protein-peptide docking shows good binding energy of peptides Pg5F, Pg8F and PC2 with specific binding to the motifs. These peptides were tested both in vitro and in vivo, where Pg5F in combination with PC2 showed 50-60% inhibition in resistant L. major's promastigote and amastigote forms and 80-90% decrease in parasite load in mice. We posit a model system wherein the data provide sufficient impetus for being novel therapeutics in order to counteract the drug resistance phenotype in Leishmania parasites.

Bioassay-based Corchorus capsularis L. leaf-derived β-sitosterol exerts antileishmanial effects against Leishmania donovani by targeting trypanothione reductase

Leishmaniasis, a major neglected tropical disease, affects millions of individuals worldwide. Among the various clinical forms, visceral leishmaniasis (VL) is the deadliest. Current antileishmanial drugs exhibit toxicity- and resistance-related issues. Therefore, advanced chemotherapeutic alternatives are in demand, and currently, plant sources are considered preferable choices. Our previous report has shown that the chloroform extract of Corchorus capsularis L. leaves exhibits a significant effect against Leishmania donovani promastigotes. In the current study, bioassay-guided fractionation results for Corchorus capsularis L. leaf-derived β-sitosterol (β-sitosterol_CCL) were observed by spectroscopic analysis (FTIR, ¹H NMR, ¹³C NMR and GC–MS). The inhibitory efficacy of this β-sitosterol_CCL against L. donovani promastigotes was measured (IC₅₀ = 17.7 ± 0.43 µg/ml). β-Sitosterol_CCL significantly disrupts the redox balance via intracellular ROS production, which triggers various apoptotic events, such as structural alteration, increased storage of lipid bodies, mitochondrial membrane depolarization, externalization of phosphatidylserine and non-protein thiol depletion, in promastigotes. Additionally, the antileishmanial activity of β-sitosterol_CCL was validated by enzyme inhibition and an in silico study in which β-sitosterol_CCL was found to inhibit Leishmania donovani trypanothione reductase (LdTryR). Overall, β-sitosterol_CCL appears to be a novel inhibitor of LdTryR and might represent a successful approach for treatment of VL in the future.

In vitro activity and in vivo efficacy of fexinidazole against New World Leishmania species

OBJECTIVES

To evaluate the in vitro activity and in vivo efficacy of fexinidazole against the main species that cause visceral and cutaneous New World leishmaniasis.

METHODS

The inhibitory concentrations of fexinidazole against Leishmania (Leishmania) infantum chagasi, Leishmania (Leishmania) amazonensis and Leishmania (Viannia) braziliensis in amastigotes were determined by in vitro activity assays. For the in vivo evaluation, animals were infected with L. (L.) infantum chagasi, L. (L.) amazonensis, L. (V.) braziliensis or Leishmania (Viannia) guyanensis and divided into groups: (i) control; and (ii) treated with oral fexinidazole, from 50 to 300 mg/kg/day. For cutaneous leishmaniasis, the size of the lesion was determined weekly after the beginning of the treatment. Upon completion, parasites were recovered from the spleen and liver, or skin lesion and spleen, and evaluated by a limiting dilution assay.

RESULTS

All Leishmania isolates were susceptible to fexinidazole in the in vitro assays. The viable parasites in the liver and spleen were reduced with 100 and 300 mg/kg/day, respectively, for L. (L.) infantum chagasi. For the species causing cutaneous leishmaniasis, the viable parasites in lesions and the size of the lesions were reduced, starting from 200 mg/kg/day. The viable parasites in the spleen were also reduced with 200 and 300 mg/kg/day for L. (V.) braziliensis and L. (L.) amazonensis.

CONCLUSIONS

Considering the defined parameters, fexinidazole showed in vitro and in vivo activity against all tested species. This drug may represent an alternative treatment for the New World species.

In vitro and in silico analysis of L. donovani enoyl acyl carrier protein reductase - A possible drug target

The emergence of increased resistance to the available drugs has created a situation that demands to find out more specific molecular drug targets for Leishmaniasis. The enoyl acyl carrier protein reductase (ENR), a regulatory enzyme in type II fatty acid synthesis, was confirmed as a novel drug target and triclosan as its specific inhibitor in many microorganisms. In this study, the triclosan was tested for the leishmanicidal property against Leishmania donovani (L. donovani) and the results of in vitro and ex vivo drug assays on promastigotes and amastigotes showed that triclosan possessed antileishmanial activity with a half minimal inhibitory concentration (IC₅₀) of 30 µM. Consequently, adopting in silico approach, we have tested the triclosan's ability to bind with the L. donovani enoyl acyl carrier protein reductase (LdENR). The 3D structure of LdENR was modelled, triclosan and cofactors were docked in LdENR model and molecular dynamic simulations were performed to observe the protein-ligands interactions, stability, compactness and binding energy calculation of the ligands-LdENR complexes. The observation showed that triclosan stably interacted with LdENR in presence of both the cofactors (NADPH and NADH), however, simulation results favor NADH as a preferred co-factor for LdENR. These results support that the reduction of L. donovani growth in the in vitro and ex vivo drug assays may be due to the interaction of triclosan with LdENR, which should be confirmed through enzymatic assays. The results of this study suggest that LdENR could be a potential drug target and triclosan as a lead for Leishmaniasis.Communicated by Ramaswamy H. Sarma.

Miltefosine as an alternative strategy in the treatment of the emerging fungus Candida auris

OBJECTIVES

Candida auris (C. auris) is an emerging fungal species that is able to develop multidrug resistance and outbreaks of invasive infections worldwide with high mortality rates. To increase the treatment options for C. auris infection this study assessed the efficacy of miltefosine (MFS), that has demonstrated a broad-spectrum antifungal action in vitro. This study aimed to: (i) evaluate the in vitro antifungal activity of MFS against C. auris clinical isolates in the planktonic and biofilm lifestyles; and (ii) compare the activity of MFS in its free form and encapsulated in alginate nanoparticles (MFS-AN) in Galleria mellonella larvae infected by C. auris.

METHODS

The antifungal susceptibility test was performed using broth microdilution method and the in vivo treatment in Galleria mellonella larval infection model.

RESULTS

MFS exhibited in vitro inhibitory effects at MICs ranging 1-4 µg/mL and fungicidal activity against planktonic cells of C. auris clinical isolates. MFS antibiofilm activity was observed during biofilm formation (0.25-4 µg/mL) and on pre-formed biofilms (16-32 µg/mL). Moreover, the dispersed cells from C. auris biofilms had a similar susceptibility to those obtained for planktonic cells. Treatment with free MFS or MFS-AN resulted in significant improvements in the survival and morbidity rates of Galleria mellonella larvae infected by C. auris. In addition, reduction of fungal burden (0.5-1 log CFU/g) and granuloma formation were observed when compared with the untreated group.

CONCLUSIONS

The findings suggest that both the free MFS and MFS-AN have potential for the treatment of fungal infections caused by the emerging C. auris.

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.

The current drug discovery landscape for trypanosomiasis and leishmaniasis: Challenges and strategies to identify drug targets

Human trypanosomiasis and leishmaniasis are vector-borne neglected tropical diseases caused by infection with the protozoan parasites Trypanosoma spp. and Leishmania spp., respectively. Once restricted to endemic areas, these diseases are now distributed worldwide due to human migration, climate change, and anthropogenic disturbance, causing significant health and economic burden globally. The current chemotherapy used to treat these diseases has limited efficacy, and drug resistance is spreading. Hence, new drugs are urgently needed. Phenotypic compound screenings have prevailed as the leading method to discover new drug candidates against these diseases. However, the publication of the complete genome sequences of multiple strains, advances in the application of CRISPR/Cas9 technology, and in vivo bioluminescence-based imaging have set the stage for advancing target-based drug discovery. This review analyses the limitations of the narrow pool of available drugs presently used for treating these diseases. It describes the current drug-based clinical trials highlighting the most promising leads. Furthermore, the review presents a focused discussion on the most important biological and pharmacological challenges that target-based drug discovery programs must overcome to advance drug candidates. Finally, it examines the advantages and limitations of modern research tools designed to identify and validate essential genes as drug targets, including genomic editing applications and in vivo imaging.

The preclinical discovery and development of oral miltefosine for the treatment of visceral leishmaniasis: a case history

INTRODUCTION

Visceral leishmaniasis (VL) is a vector-borne disease caused by Leishmania donovani or Leishmania infantum. Closely related to poverty, VL is fatal and represents one of the main burdens on public health in developing countries. Treatment of VL relies exclusively on chemotherapy, a strategy still experiencing numerous limitations. Miltefosine (MF) has been used in the chemotherapy of VL in some endemic areas, and has been expanded to other regions, being considered crucial in eradication programs.

AREAS COVERED

This article reviews the most relevant preclinical and clinical aspects of MF, its mechanism of action and resistance to Leishmania parasites, as well as its limitations. The authors also give their perspectives on the treatment of VL.

EXPERT OPINION

The discovery of MF represented an enormous advance in the chemotherapy of VL, since it was the first oral drug for this neglected disease. Beyond selection of resistant parasites due to drug pressure, several other factors can lead to treatment failure such as, for example, factors intrinsic to the host, parasite and the drug itself. Although its efficacy as a monotherapy has reduced over recent years, MF is still an important alternative in VL chemotherapy, especially when used in combination with other drugs.

Development of dextrin-amphotericin B formulations for the treatment of Leishmaniasis

The most effective medicines available for the treatment of leishmaniasis, a life-threatening disease, exhibit serious toxicological issues. To achieve better therapeutic efficiency while decreasing toxicity associated with amphotericin B (AmB), water-soluble dextrin-AmB (Dex-AmB) formulations were developed. Self-assembled nanocomplexes were formed by dissolving Dex and AmB in alkaline borate buffer, followed by dialysis and either freeze-drying (FD) or nano spray-drying (SD), yielding water dispersible particles with a diameter of 214 nm and 347 nm, respectively. The very simple production process allowed the formation of amorphous inclusion complexes containing 14% of AmB in the form of monomers and water-soluble aggregates. Nanocomplexes were effective against parasites in axenic culture (IC₅₀ of 0.056 and 0.096 μM for L. amazonensis and 0.030 and 0.044 μM for L. infantum, respectively for Dex-AmB FD and Dex-AmB SD) and in decreasing the intramacrophagic infection with L. infantum (IC₅₀ of 0.017 and 0.023 μM, respectively for Dex-AmB FD and Dex-AmB SD). Also, the formulations were able to significantly reduce the cytotoxicity of AmB. Overall, this study demonstrates the suitability of dextrin as an AmB carrier and the facile and inexpensive development of a delivery system for the treatment of leishmaniasis.

Outwitting an Old Neglected Nemesis: A Review on Leveraging Integrated Data-Driven Approaches to Aid in Unraveling of Leishmanicides of Therapeutic Potential

The global prevalence of leishmaniasis has increased with skyrocketed mortality in the past decade. The causative agent of leishmaniasis is Leishmania species, which infects populations in almost all the continents. Prevailing treatment regimens are consistently inefficient with reported side effects, toxicity and drug resistance. This review complements existing ones by discussing the current state of treatment options, therapeutic bottlenecks including chemoresistance and toxicity, as well as drug targets. It further highlights innovative applications of nanotherapeutics-based formulations, inhibitory potential of leishmanicides, anti-microbial peptides and organometallic compounds on leishmanial species. Moreover, it provides essential insights into recent machine learning-based models that have been used to predict novel leishmanicides and also discusses other new models that could be adopted to develop fast, efficient, robust and novel algorithms to aid in unraveling the next generation of anti-leishmanial drugs. A plethora of enriched functional genomic, proteomic, structural biology, high throughput bioassay and drug-related datasets are currently warehoused in both general and leishmania-specific databases. The warehoused datasets are essential inputs for training and testing algorithms to augment the prediction of biotherapeutic entities. In addition, we demonstrate how pharmacoinformatics techniques including ligand-, structure- and pharmacophore-based virtual screening approaches have been utilized to screen ligand libraries against both modeled and experimentally solved 3D structures of essential drug targets. In the era of data-driven decision-making, we believe that highlighting intricately linked topical issues relevant to leishmanial drug discovery offers a one-stop-shop opportunity to decipher critical literature with the potential to unlock implicit breakthroughs.

The effect of edelfosine on GRA1 and MIC3 expressions in acute toxoplasmosis

Phosphoinositide-dependent phospholipase-C (PI-PLC) triggers the calcium signaling pathway which plays an important role in dense granule and microneme secretion and pathogenesis of Toxoplasma gondii (T. gondii). There are limited data about the effects of phospholipid analogues against T. gondii. The current study assessed the effect of edelfosine, as a phospholipid analogue, on GRA1 and MIC3 expressions using in vitro and in vivo models of acute toxoplasmosis. Infected Vero cells were treated by edelfosine in two subgroups: 24 h following the cell infection and treatment at the same time of cell infection. Animal study was performed on forty mice in four groups including non-infected, infected untreated, infected edelfosine-treated, and infected pyrimethamine-treated. Gene and protein expression analyses were done using quantitative real-time PCR and western blot, respectively. Edelfosine significantly reduced the GRA1 (P < 0.01) and MIC3 (P < 0.01) mRNA and protein expressions in 24 h following the cell infection and at the same time of cell infection groups. In vivo study showed that the edelfosine significantly reduced the GRA1 expression in eye, and MIC3 expression in brain and liver. Moreover, the edelfosine-treated infected mice had significant higher survival rate compared with uninfected mice. The reducing effect of edelfosine on GRA1 and MIC3 mRNA and protein levels 24 h following the cell infection was more than treatment at the same time of cell infection group. Moreover, the effect of edelfosine on GRA1 and MIC3 expression in animal tissues was variable. These data showed that the edelfosine may decrease the T. gondii excretory/secretory antigens through inhibition of PI-PLC.

In Vitro Schistosomicidal Activity of the Alkaloid-Rich Fraction from Ruta graveolens L. (Rutaceae) and Its Characterization by UPLC-QTOF-MS

Schistosomiasis is a neglected tropical disease that affects million people worldwide, mostly in developing countries. Ruta graveolens (Rutaceae) is a plant used in folk medicine to treat several diseases, including parasitic infections. In this study, we reported the in vitro schistosomicidal activity of the R. graveolens extract (Rg) and its active fraction (Rg-FAE). Also, the characterization of Rg-FAE by UPLC-ESI-QTOF-MS analysis and its in vitro antileishmanial activity against Leishmania braziliensis were also performed. In vitro schistosomicidal assays were assessed against adult worms of S. mansoni, while cell viability against peritoneal macrophages was measured by MTT assay. Rg (100 μg/mL) exhibited noticeable schistosomicidal activity, causing 100% mortality and decreasing motor activity of all adult male and female schistosomes, but with low activity against L. braziliensis. After chromatographic fractionation of Rg, fraction Rg-FAE was obtained, showing high activity against adult schistosomes. UPLC-ESI-QTOF-MS analysis of Rg-FAE revealed the presence of eleven alkaloids and one furanocoumarin. No significant antileishmanial activity was found for Rg, while Rg-FAE exhibited activity against L. braziliensis promastigotes. We demonstrated, for the first time, that the R. graveolens extract (Rg) and its alkaloid-rich fraction (Rg-FAE) are active against adult worms of S. mansoni, with no significant cytotoxicity on macrophages. Our findings open the route to further antiparasitic studies with the active fraction of R. graveolens and its identified compounds, especially alkaloids.

Novel benzoxaborole, nitroimidazole and aminopyrazoles with activity against experimental cutaneous leishmaniasis

OBJECTIVES

Drugs for Neglected Diseases initiative (DNDi) has identified three chemical lead series, the nitroimidazoles, benzoxaboroles and aminopyrazoles, as innovative treatments for visceral leishmaniasis. The leads discovered using phenotypic screening, were optimised following disease- and compound-specific criteria. Several leads of each series were progressed and preclinical drug candidates have been nominated. Here we evaluate the efficacy of the lead compounds of each of these three chemical classes in in vitro and in vivo models of cutaneous leishmaniasis.

METHODS

The in vitro activity of fifty-five compounds was evaluated against the intracellular amastigotes of L. major, L. aethiopica, L. amazonensis, L. panamensis, L. mexicana and L. tropica. The drugs demonstrating potent activity (EC50 < 5 μM) against at least 4 of 6 species were subsequently evaluated in vivo in different L. major - BALB/c mouse models using a 5 or 10-day treatment with either the oral or topical formulations. Efficacy was expressed as lesion size (measured daily using callipers), parasite load (by quantitative PCR - DNA) and bioluminescence signal reduction relative to the untreated controls.

RESULTS

The selected drug compounds (3 nitroimidazoles, 1 benzoxaborole and 3 aminopyrazoles) showed consistent and potent activity across a range of Leishmania species that are known to cause CL with EC50 values ranging from 0.29 to 18.3 μM. In all cases, this potent in vitro antileishmanial activity translated into high levels of efficacy with a linear dose-response against murine CL. When administered at 50 mg/kg/day, DNDI-0690 (nitroimidazole), DNDI-1047 (aminopyrazole) and DNDI-6148 (benzoxaborole) all resulted in a significant lesion size reduction (no visible nodule) and an approximate 2-log-fold reduction of the parasite load as measured by qPCR compared to the untreated control.

CONCLUSIONS

The lead compounds DNDI-0690, DNDI-1047 and DNDI-6148 showed excellent activity across a range of Leishmania species in vitro and against L. major in mice. These compounds offer novel potential drugs for the treatment of CL.

Development of topical liposomes containing miltefosine for the treatment of Leishmania major infection in susceptible BALB/c mice

Herein, we investigated the efficacy of liposomes for the topical delivery of miltefosine (ML) to treat cutaneous leishmaniasis (CL). Liposomes containing varying concentrations of ML (0.5, 1, 2 and 4%) were prepared and characterized by their size and entrapment efficiency. The liposome diameters were between 100-150 nm. The penetration of ML from liposomal formulations through and in the skin was assessed using ex-vivo Franz diffusion cells fitted with mouse skin at 37 °C for 24 h. Data indicated that Lip-ML-4% showed the highest percent of retention across mouse skin (82%). in vitro promastigote and amastigote assays showed that ML and Lip-ML inhibit the growth of parasites either in the culture medium or intracellularly. Lip-ML formulations were topically applied twice a day for 4 weeks to the skin of BALB/c mice infected with L. major. Results showed a significantly (p < 0.001) smaller lesion size in Lip-ML-2 and 4% when compared to controls. At week 8 post-infection, the number of parasites was higher in Lip-ML-0.5% compared to Lip-ML-2 and 4%, however, the difference was not significant. At week 12, the splenic parasite burden was significantly (p < 0.001) lower in mice treated with different Lip-ML formulations when compared to controls. The lesion parasite burden was significantly (p < 0.001) lower in mice treated with either Lip-ML-2 and 4% compared to Lip-ML-0.5% at week 12 post-infection. The results suggested that topical Lip-ML-4% showed optimal ex-vivo penetration and in vivo anti-leishmanial activity against CL caused by L. major when compared to ML cream and other liposomes and thus, merits further investigation.

A Functional Wound Dressing as a Potential Treatment for Cutaneous Leishmaniasis

Cutaneous leishmaniasis (CL) is a parasitic disease characterized by progressive skin sores. Currently, treatments for CL are limited to parenteral administration of the drug, which presents severe adverse effects and low cure rates. Therefore, this study aimed to develop poly(vinyl-alcohol) (PVA) hydrogels containing Amphotericin B (AmB) intended for topical treatment of CL. Hydrogels were evaluated in vitro for their potential to eliminate promastigote forms of Leishmania spp., to prevent secondary infections, to maintain appropriate healing conditions, and to offer suitable biocompatibility. AmB was incorporated into the system in its non-crystalline state, allowing it to swell more and faster than the system without the drug. Furthermore, the AmB release profile showed a continuous and controlled behavior following Higuchi´s kinetic model. AmB-loaded-PVA-hydrogels (PVA-AmB) also showed efficient antifungal and leishmanicidal activity, no cytotoxic potential for VERO cells, microbial impermeability and water vapor permeability compatible with the healthy skin's physiological needs. Indeed, these results revealed the potential of PVA-AmB to prevent secondary infections and to maintain a favorable environment for the healing process. Hence, these results suggest that PVA-AmB could be a suitable and efficient new therapeutic approach for the topical treatment of CL.

Validation of NAD synthase inhibitors for inhibiting the cell viability of Leishmania donovani: In silico and in vitro approach

NAD (nicotinamide adenine dinucleotide) synthase catalyses the biochemical synthesis of NAD, from nicotinic acid adenine dinucleotide (NAAD). NAD may be synthesized through the de novo pathways and/or the salvage pathways in cells. However, in Leishmania parasite, the synthesis of NAD solely depends on the salvage pathways. NAD synthetase is widely explored as a drug target in various microorganisms. In Bacillus anthracis, a group of sulphonamides 5599, 5617 and 5824 and complex amide 5833 were reported to have activity at micromolar range against NAD synthetase. Hence, in the present study, the same group of sulphonamides and complex amide were validated through in silico and in vitro studies for its efficiency towards Leishmania donovani NAD synthase. In silico study revealed the ligands 5824 and 5833 to have better docking score. Molecular dynamics simulation for a duration of 50 ns of all the ligand-protein complexes suggested that the complexes with the ligands 5824 and 5833 were stable and interacting. In vitro and ex vivo studies have shown that 5824 and 5833 inhibit the cell viability of the organism at a lower concentration than 5599 and 5617. Hence, with further in vivo validation, 5824 (or its synthetic analogues) and 5833 could be the choice that may work synergistically with other potential drugs in treating drug-resistant cases of leishmaniasis. Communicated by Ramaswamy H. Sarma.

Insights about resveratrol analogs against trypanothione reductase of Leishmania braziliensis: Molecular modeling, computational docking and in vitro antileishmanial studies

In this work, we combined molecular modeling, computational docking and in vitro analysis to explore the antileishmanial effect of some resveratrol analogs (ResAn), focusing on their pro-oxidant effect. The molecular target was the trypanothione reductase of Leishmania braziliensis (LbTryR), an essential component of the antioxidant defenses in trypanosomatid parasites. Three-dimensional structures of LbTryR were modeled and molecular docking studies of ResAn1-5 compounds showed the following affinity: ResAn1 > ResAn2 > ResAn4 > ResAn5 > ResAn3. Positive correlation was observed between these compounds' affinity to the LbTryR and the IC₅₀ values against Leishmania sp (ResAn1 < ResAn2 < ResAn4), which allows for TryR being considered an important target for them. As the compound ResAn1 showed the best antileishmanial activity, and docking studies showed its high affinity for NADP binding site (NS) of TryR, plus having been able to induce ROS production in L. braziliensis promastigotes treated, ResAn1 probably occupies NS interfering in the electron transfer processes responsible for the catalytic reaction. The in silico prediction of ADMET properties suggests that ResAn1 may be a promising drug candidate with properties to cross biological membranes and high gastrointestinal absorption, not violating Lipinski's rules. Ultimately, the antileishmanial effect of ResAn can be associated with a pro-oxidant effect which, in turn, can be exploited as an antimicrobial agent. Communicated by Ramaswamy H. Sarma.

Lipase Precursor-Like Protein Promotes Miltefosine Tolerance in Leishmania donovani by Enhancing Parasite Infectivity and Eliciting Anti-inflammatory Responses in Host Macrophages

The oral drug miltefosine (MIL) was introduced in the Indian subcontinent in the year 2002 for the treatment of visceral leishmaniasis (VL). However, recent reports on its declining efficacy and increasing relapse rates pose a serious concern. An understanding of the factors contributing to MIL tolerance in Leishmania parasites is critical. In the present study, we assessed the role of the lipase precursor-like protein (Lip) in conferring tolerance to miltefosine by episomally overexpressing Lip in Leishmania donovani (LdLip⁺⁺). We observed a significant increase (∼3-fold) in the MIL 50% inhibitory concentration (IC₅₀) at both the promastigote (3.90 ± 0.68 µM; P < 0.05) and intracellular amastigote (9.10 ± 0.60 µM; P < 0.05) stages compared to the wild-type counterpart (LdNeo) (MIL IC₅₀s of 1.49 ± 0.20 µM at the promastigote stage and 3.95 ± 0.45 µM at the amastigote stage). LdLip⁺⁺ parasites exhibited significantly (P < 0.05) increased infectivity to host macrophages and increased metacyclogenesis and tolerance to MIL-induced oxidative stress. The susceptibility of LdLip⁺⁺ to other antileishmanial drugs (sodium antimony gluconate and amphotericin B) remained unchanged. In comparison to LdNeo, the LdLip⁺⁺ parasites elicited high host interleukin-10 (IL-10) cytokine expression levels (1.6-fold; P < 0.05) with reduced expression of the cytokine tumor necrosis factor alpha (TNF-α) (1.5-fold; P < 0.05), leading to a significantly (P < 0.01) increased ratio of IL-10/TNF-α. The above-described findings suggest a role of lipase precursor-like protein in conferring tolerance to the oral antileishmanial drug MIL in L. donovani parasites.

Evaluation of total phenolic fraction derived from extra virgin olive oil for its antileishmanial activity

BACKGROUND

Leishmaniasis is a neglected and emerging disease with varying clinical manifestations. The current treatment options rely on limited chemotherapy with serious drawbacks. Thus, there is an increasing interest in the identification of new candidates for designing potent, less toxic and low-cost drugs.

PURPOSE

The purpose of this study was to evaluate the potential antileishmanial activity of the total phenolic fraction (TPF) derived from extra virgin olive oil (EVOO) when added in in vitro and in vivo experimental models of Leishmania infection.

STUDY DESIGN

We investigated the in vitro antileishmanial activity of TPF against two Leishmania species: a viscerotropic (L. infantum) and a dermotropic (L. major) strain. The antileishmanial effect was also tested in vivo in a murine cutaneous leishmaniasis model using L. major-infected BALB/c mice.

METHODS

Separation and analytical methodologies were applied in order to extract the olive oil phenols (TPF) and determine the concentration of the major ones, respectively. The in vitro antileishmanial activity of TPF against promastigotes and intracellular amastigotes was determined by the resazurin cell viability assay. The TPF-induced nitric oxide synthesis by L. infantum and L. major -infected J774A.1 macrophages was determined using the Griess reaction, while the respective generation of reactive oxygen species was assessed by flow cytometry. Moreover, L. major-infected BALB/c mice were treated with TPF and its in vivo therapeutic effect was determined as reduction of the footpad swelling.

RESULTS

Our data showed that TPF exhibits inhibitory effect against cell free promastigotes and intracellular amastigotes of both L. infantum and L. major parasite strains. TPF demonstrated to be selectively active against Leishmania amastigotes and its antileishmanial activity was possibly mediated by reactive nitrogen and oxygen intermediates generated from the infected J774A.1 macrophages. Furthermore, administration of TPF in BALB/c mice infected with L. major caused significant reduction of footpad swelling demonstrating in vivo its antileishmanial effect. Based on HPLC-DAD analysis the major components of TPF are tyrosol, hydroxytyrosol, oleacein and oleocanthal.

CONCLUSION

This study brings a new low-cost candidate to the leishmaniasis drug discovery pipeline, upon further pharmacological investigation.

Leishmania parasitophorous vacuole membranes display phosphoinositides that create conditions for continuous Akt activation and a target for miltefosine in Leishmania infections

Miltefosine is an important drug for the treatment of leishmaniasis; however, its mechanism of action is still poorly understood. In these studies, we tested the hypothesis that like in cancer cells, miltefosine's efficacy in leishmaniasis is due to its inhibition of Akt activation in host cells. We show using pharmacologic agents that block Akt activation by different mechanisms and also using an inducible knockdown approach that miltefosine loses its efficacy when its access to Akt1 is limited. Interestingly, limitation of Akt activation results in clearance of established Leishmania infections. We then show, using fluorophore-tagged probes that bind to phosphoinositides, that Leishmania parasitophorous vacuole membranes (LPVMs) display the relevant phosphoinositides to which Akt can be recruited and activated continuously. Taken together, we propose that the acquisition of PI(4) P and the display of PI (3,4)P2 on LPVMs initiate the machinery that supports continuous Akt activation and sensitivity to miltefosine.