Chemotherapy Of Leishmaniasis Research Articles

PLGA Nanoparticles as New Drug Delivery Systems in Leishmaniasis Chemotherapy: A Review of Current Practices.

Although leishmaniasis is one of the most common parasitic diseases, its traditional treatments suffer from some serious problems. To solve such issues, we can take advantage of the effective nanoparticle-based approaches to deliver anti-leishmanial agents into leishmania-infected macrophages either using passive targeting or using macrophagerelated receptors. Despite the high potential of nanotechnology, Liposomal Amphotericin B (AmBisome®) is the only FDA-approved nanoparticle-based anti-leishmanial therapy. In an effort to find more anti-leishmanial nano-drugs, this 2011-2021 review study aimed to investigate the in-vivo and in-vitro effectiveness of poly (lactic-co-glycolic acid) nanoparticles (PLGA-NPs) in the delivery of some traditional anti-leishmanial drugs. Based on the results, PLGA-NPs could improve solubility, controlled release, trapping efficacy, bioavailability, selectivity, and mucosal penetration of the drugs, while they decreased resistance, dose/duration of administration and organotoxicity of the agents. However, none of these nano-formulations have been able to enter clinical trials so far. We summarized the data about the common problems of anti-leishmanial agents and the positive effects of various PLGA nano-formulations on reducing these drawbacks under both in-vitro and in-vivo conditions in three separate tables. Overall, this study proposes two AmB-loaded PLGA with a 99% reduction in parasite load as promising nanoparticles for further studies.

Anti-Leishmania compounds can be screened using Leishmania spp. expressing red fluorescence (tdTomato).

The main challenges associated with leishmaniasis chemotherapy are drug toxicity, the possible emergence of resistant parasites, and a limited choice of therapeutic agents. Therefore, new drugs and assays to screen and detect novel active compounds against leishmaniasis are urgently needed. We thus validated Leishmania braziliensis (Lb) and Leishmania infantum (Li) that constitutively express the tandem tomato red fluorescent protein (tdTomato) as a model for large-scale screens of anti-Leishmania compounds. Confocal microscopy of Lb and Li::tdTomato revealed red fluorescence distributed throughout the entire parasite, including the flagellum, and flow cytometry confirmed that the parasites emitted intense fluorescence. We evaluated the infectivity of cloned promastigotes and amastigotes constitutively expressing tdTomato, their growth profiles in THP-1 macrophages, and susceptibility to trivalent antimony, amphotericin, and miltefosine in vitro. The phenotypes of mutant and wild-type parasites were similar, indicating that the constitutive expression of tdTomato did not interfere with the evaluated parameters. We applied our validated model to a repositioning strategy and assessed the susceptibility of the parasites to eight commercially available drugs. We also screened 32 natural plant and fungal extracts and 10 pure substances to reveal new active compounds. The infectivity and Glucantime treatment efficacy of BALB/c mice and golden hamsters infected with Lb and Li::tdTomato mutant lines, respectively, were very similar compared to animals infected with wild-type parasites. Standardizing our methodology would offer more rapid, less expensive, and easier assays to screen of compounds against L. braziliensis and L. infantum in vitro and in vivo. Our method could also enhance the discovery of active compounds for treating leishmaniasis.

Organogold(III)-dithiocarbamate compounds and their coordination analogues as anti-tumor and anti-leishmanial metallodrugs

The limited chemical stability of gold(III)-based compounds in physiological environment has been a challenge in drug discovery, and organometallic chemistry might provide the solution to overcome this issue. In this work, four novel cationic organogold(III)-dithiocarbamate complexes of general structure [(C^N)AuIIIDTC]PF6 (C1a – C4a, DTC = dithiocarbamate, L1 – L4, C^N = 2-anilinopyridine) are presented, and compared to their coordination gold(III)-dithiocarbamate analogues [AuIIIDTCCl2] (C1b – C4b), as potential anti-cancer and anti-leishmanial drugs. Most of the complexes effectively inhibited cancer cell growth, notably C3a presented anti-proliferative effect in the nanomolar range against breast cancer (MCF-7 and MDA-MB-231 cells with moderate selectivity. Pro-apoptotic studies on treated MCF-7 cells showed a high population of cells in early apoptosis. Reactivity studies of C3a towards model thiols (N-acetyl-L-cysteine) refer to a possible mode of action involving bonding between the organogold(III)-core and the thiolate. In the scope of neglected diseases, gold complexes are emerging as promising therapeutic alternatives against leishmaniasis. In this regard, all gold(III)-dithiocarbamate complexes presented anti-leishmanial activity against at least one Leishmania species. Complexes C1a, C4a, C1b, C4b were active against all tested parasites with IC50 values varying between 0.12 and 42 μM, and, overall, organometallic compounds presented more intriguing inhibition profiles. For C4a selectivity over 500-fold for L. braziliensis; even higher than the reference anti-leishmanial drug amphotericin B. Overall, our findings revealed that the organogold(III) moiety significantly amplified the anti-cancer and anti-leishmanial effects with respect to the coordination analogues; thus, showing the great potential of organometallic chemistry in metallodrug-based chemotherapy for cancer and leishmaniasis.

In Vitro Drug Susceptibility of a Leishmania (Leishmania) infantum Isolate from a Visceral Leishmaniasis Pediatric Patient after Multiple Relapses.

The parasitic protozoan Leishmania (Leishmania) infantum is the etiological agent of human visceral leishmaniasis in South America, an infectious disease associated with malnutrition, anemia, and hepatosplenomegaly. In Brazil alone, around 2700 cases are reported each year. Treatment failure can occur as a result of drug, host, and/or parasite-related factors. Here, we isolated a Leishmania species from a pediatric patient with visceral leishmaniasis that did not respond to chemotherapy, experiencing a total of nine therapeutic relapses and undergoing a splenectomy. The parasite was confirmed as L. (L.) infantum after sequencing of the ribosomal DNA internal transcribed spacer, and the clinical isolate, in both promastigote and amastigote forms, was submitted to in vitro susceptibility assays with all the drugs currently used in the chemotherapy of leishmaniasis. The isolate was susceptible to meglumine antimoniate, amphotericin B, pentamidine, miltefosine, and paromomycin, similarly to another strain of this species that had previously been characterized. These findings indicate that the multiples relapses observed in this pediatric patient were not due to a decrease in the drug susceptibility of this isolate; therefore, immunophysiological aspects of the patient should be further investigated to understand the basis of treatment failure in this case.

High Selectivity of 8-Hydroxyquinoline on Leishmania (Leishmania) and Leishmania (Viannia) Species Correlates with a Potent Therapeutic Activity In Vivo.

Leishmaniasis is a neglected disease caused by protozoa of the genus Leishmania, which causes different clinical manifestations. Drugs currently used in the treatment such as pentavalent antimonial and amphotericin B cause severe side effects in patients, and parasite resistance has been reported. Thus, it is necessary and urgent to characterize new and effective alternative drugs to replace the current chemotherapy of leishmaniasis. In this regard, it has been experimentally demonstrated that quinoline derivatives present significative pharmacological and parasitic properties. Thus, the aim of this work was to demonstrate the leishmanicidal activity of 8-hydroxyquinoline (8-HQ) in vitro and in vivo. The leishmanicidal activity (in vitro) of 8-HQ was assayed on promastigote and intracellular amastigote forms of L. (L.) amazonensis, L. (L.) infantum chagasi, L. (V.) guyanensis L. (V.) naiffi, L. (V.) lainsoni, and L. (V.) shawi. Additionally, the levels of nitric oxide and hydrogen peroxide were analyzed. The therapeutic potential of 8-HQ was analyzed in BALB/c mice infected with a strain of L. (L.) amazonensis that causes anergic cutaneous diffuse leishmaniasis. In vitro data showed that at 24 and 72 h, 8-HQ eliminated promastigote and intracellular amastigote forms of all studied species and this effect may be potentialized by nitric oxide. Furthermore, 8-HQ was more selective than miltefosine. Infected animals treated with 8-HQ by the intralesional route dramatically reduced the number of tissue parasites in the skin, and it was associated with an increase in IFN-γ and decrease in IL-4, which correlated with a reduction in inflammatory reaction in the skin. These results strongly support the idea that 8-HQ is an alternative molecule that can be employed in the treatment of leishmaniasis, given its selectivity and multispectral action in parasites from the Leishmania genus.

Apigenin is a promising molecule for treatment of visceral leishmaniasis.

Current treatment for visceral leishmaniasis is based on drugs such as pentavalent antimony and amphotericin B. However, this treatment remains mostly ineffective and expensive, resulting in several side effects and generating resistance. Apigenin, a flavonoid present in fruits and vegetables, has demonstrated several biological functions. In the present study, we observed a concentration-dependent inhibition of the L. infantum promastigote in the presence of apigenin, exhibiting an IC50 value of 29.9 µM. Its effect was also evaluated in L. infantum-infected murine peritoneal macrophages, presenting an C50 value against intracellular amastigotes of 2.3 µM and a selectivity index of 34.3. In a murine model of visceral leishmaniasis, the in vivo effect of apigenin was measured using short-term and long-term treatment schemes. Treatment with apigenin demonstrated 99.7% and 94% reductions in the liver parasite load in the short-term and long-term treatment schemes, respectively. Furthermore, no alterations in serological and hematological parameters were observed. Taken together, these results suggest that apigenin is a potential candidate for visceral leishmaniasis chemotherapy by oral administration.

In Vivo Safety and Efficacy of Chalcone-Loaded Microparticles with Modified Polymeric Matrix against Cutaneous Leishmaniasis.

Current chemotherapy of cutaneous leishmaniasis (CL) is based on repeated systemic or intralesional administration of drugs that often cause severe toxicity. Previously, we demonstrated the therapeutic potential of biodegradable poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) loaded with 8% of the nitrochalcone CH8 (CH8/PLGA) prepared by a conventional bench method. Aiming at an industrially scalable process and increased drug loading, new MPs were prepared by spray drying: CH8/PDE with PLGA matrix and CH8/PVDE with PLGA + polyvinylpyrrolidone (PVP) matrix, both with narrower size distribution and higher drug loading (18%) than CH8/PLGA. Animal studies were conducted to evaluate their clinical feasibility. Both MP types induced transient local swelling and inflammation, peaking at 1-2 days, following a single intralesional injection. Different from CH8/PDE that released 90% of the drug in the ear tissue in 60 days, CH8/PVDE achieved that in 30 days. The therapeutic efficacy of a single intralesional injection was evaluated in BALB/c mice infected with Leishmania (Leishmania) amazonensis and golden hamsters infected with L. (Viannia) braziliensis. CH8/PVDE promoted greater reduction in parasite burden than CH8/PDE or CH8/PLGA, measured at one month and two months after the treatment. Thus, addition of PVP to PLGA MP matrix accelerates drug release in vivo and increases its therapeutic effect against CL.

Current Applications of Plant-Based Drug Delivery Nano Systems for Leishmaniasis Treatment.

Leishmania is a trypanosomatid that causes leishmaniasis. It is transmitted to vertebrate hosts during the blood meal of phlebotomine sandflies. The clinical manifestations of the disease are associated with several factors, such as the Leishmania species, virulence and pathogenicity, the host-parasite relationship, and the host's immune system. Although its causative agents have been known and studied for decades, there have been few advances in the chemotherapy of leishmaniasis. The urgency of more selective and less toxic alternatives for the treatment of leishmaniasis leads to research focused on the study of new pharmaceuticals, improvement of existing drugs, and new routes of drug administration. Natural resources of plant origin are promising sources of bioactive substances, and the use of ethnopharmacology and folk medicine leads to interest in studying new medications from phytocomplexes. However, the intrinsic low water solubility of plant derivatives is an obstacle to developing a therapeutic product. Nanotechnology could help overcome these obstacles by improving the availability of common substances in water. To contribute to this scenario, this article provides a review of nanocarriers developed for delivering plant-extracted compounds to treat clinical forms of leishmaniasis and critically analyzing them and pointing out the future perspectives for their application.

Characterization of Leishmania (L.) amazonensis oligopeptidase B and its role in macrophage infection.

Leishmania spp. are parasitic protozoa that cause leishmaniasis, a disease endemic in 98 countries. Leishmania promastigotes are transmitted by the vector and differentiate into amastigotes within phagocytic cells of the vertebrate host. To survive in multiple and hostile environments, the parasite has several virulence factors. Oligopeptidase B (OPB) is a serine peptidase present in prokaryotes, some eukaryotes and some higher plants. It has been considered a virulence factor in trypanosomatids, but only a few studies, performed with Old World species, analysed its role in Leishmania virulence or infectivity.L. (L.) amazonensis is an important agent of cutaneous leishmaniasis in Brazil. The L. (L.) amazonensis OPB encoding gene has been sequenced and analysed in silico but has never been expressed. In this work, we produced recombinant L. (L.) amazonensis OPB and showed that its pH preferences, Km and inhibition patterns are similar to those reported for L. (L.) major and L. (L.) donovani OPBs. Since Leishmania is known to secrete OPB, we performed in vitro infection assays using the recombinant enzyme. Our results showed that active OPB increased in vitro infection by L. (L.) amazonensis when present before and throughout infection. Our findings suggest that OPB is relevant to L. (L.) amazonensis infection, and that potential drugs acting through OPB will probably be effective for Old and New World Leishmania species. OPB inhibitors may eventually be explored for leishmaniasis chemotherapy.

Antileishmanial Efficacy of the Calpain Inhibitor MDL28170 in Combination with Amphotericin B.

The necessity of drug combinations to treat leishmaniasis came to the surface mainly because of the toxicity of current treatments and the emergence of resistant strains. The calpain inhibitor MDL28170 has previously shown anti-Leishmania activity, therefore its use in association with standard drugs could provide a new alternative for the treatment strategy against leishmaniasis. In this study, we analyzed the potential of the combination of MDL28170 and the antileishmanial drug amphotericin B against Leishmania amazonensis and Leishmania chagasi. The compounds were tested in the combination of the ½ × IC50 value of MDL28170 plus the ¼ × IC50 value of amphotericin B, which led to an increment in the anti-promastigote activity when compared to the single drug treatments. This drug association revealed several and severe morphophysiological changes on parasite cells, such as loss of plasma membrane integrity, reduced size of flagellum, and depolarization of mitochondrial membrane potential besides increased reactive oxygen species production. In addition, the combination of both drugs had a deleterious effect on the Leishmania–macrophage interaction, reflecting in a significant anti-amastigote action, which achieved a reduction of 50% in the association index. These results indicate that the combination treatment proposed here may represent a new alternative for leishmaniasis chemotherapy.

Amentoflavone isolated from Selaginella sellowii Hieron induces mitochondrial dysfunction in Leishmania amazonensis promastigotes.

Leishmaniasis chemotherapy is a bottleneck in disease treatment. Although available, chemotherapy is limited, toxic, painful, and does not lead to parasite clearance, with parasite resistance also being reported. Therefore, new therapeutic options are being investigated, such as plant-derived anti-parasitic compounds. Amentoflavone is the most common biflavonoid in the Selaginella genus, and its antileishmanial activity has already been described on Leishmania amazonensis intracellular amastigotes but its direct action on the parasite is controversial. In this work we demonstrate that amentoflavone is active on L. amazonensis promastigotes (IC50=28.5±2.0μM) and amastigotes. Transmission electron microscopy of amentoflavone-treated promastigotes showed myelin-like figures, autophagosomes as well as enlarged mitochondria. Treated parasites also presented multiple lipid droplets and altered basal body organization. Similarly, intracellular amastigotes presented swollen mitochondria, membrane fragments in the lumen of the flagellar pocket as well as autophagic vacuoles. Flow cytometric analysis after TMRE staining showed that amentoflavone strongly decreased mitochondrial membrane potential. In silico analysis shows that amentoflavone physic-chemical, drug-likeness and bioavailability characteristics suggest it might be suitable for oral administration. We concluded that amentoflavone presents a direct effect on L. amazonensis parasites, causing mitochondrial dysfunction and parasite killing. Therefore, all results point for the potential of amentoflavone as a promising candidate for conducting advanced studies for the development of drugs against leishmaniasis.

High-resolution inhibition profiling and ligand fishing for screening of nucleoside hydrolase ligands in Moringa oleifera Lamarck

In Leishmania donovani, the causative protozoan of visceral leishmaniasis, nucleoside hydrolase enzyme (NH) is fundamental for the biosynthesis of its DNA and RNA. Therefore, LdNH is considered a potential target for the development of new leishmaniasis chemotherapy. Moringa oleifera Lamarck is a medicinal plant native to northeastern India with numerous pharmacological properties, including antileishmanial activity. Thus, this study aimed to explore the inhibitory activity of different extracts from M. oleifera leaves and flowers on LdNH. Using LdNH covalently immobilized on magnetic particles (LdNH-MPs), a novel activity assay was developed based on the direct quantification of the formed product by HPLC-DAD. This study screened 12 extracts from leaves and flowers of M. oleifera using different extraction methods. The hydroethanolic (70% ethanol) extract from flowers, obtained by infusion (FIEH) or ultrasound-assisted extraction (FUEH), exhibited respectively IC50 values of 26.2 ± 4.63 µg/mL and 4.96 ± 0.52 µg/mL. The most promising extract (FUEH) was investigated by high-resolution LdNH inhibition profiling, which showed different regions of inhibition in the biochromatogram. A ligand fishing assay was attempted to pinpoint the bioactive compounds. Experimental conditions employed in the elution step of the ligand fishing assay did not result in ligands isolation. However, the analyses of the crude extract solution and the supernatants after the incubation with the active and inactive LdNH-MPs indicated missing peaks referring to compounds selectively retained in the active LdNH-MPs incubation. The missing peaks eluted in the same region that exhibits inhibition in the high-resolution LdNH inhibition profiling. The ligands were identified by UHPLC-MS/MS as palatinose, adenosine, 3-p-coumaroylquinic acid, 4-p-coumaroylquinic acid, hyperoside, quercetin-3-O-malonyl glycoside, and kaempferol-3-O-galactoside.

Antioxidant defence system as a rational target for Chagas disease and Leishmaniasis chemotherapy

Chagas disease and leishmaniasis are neglected tropical diseases caused by the protozoan parasites Trypanosoma cruzi and Leishmania spp., respectively. They are among the most important parasitic diseases, affecting millions of people worldwide, being a considerable global challenge. However, there is no human vaccine available against T. cruzi and Leishmania infections, and their control is based mainly on chemotherapy. Treatments for Chagas disease and leishmaniasis have multiple limitations, mainly due to the high toxicity of the available drugs, long-term treatment protocols, and the occurrence of drug-resistant parasite strains. In the case of Chagas disease, there is still the problem of low cure rates in the chronic stage of the disease. Therefore, new therapeutic agents and novel targets for drug development are urgently needed. Antioxidant defence in Trypanosomatidae is a potential target for chemotherapy because the organisms present a unique mechanism for trypanothione-dependent detoxification of peroxides, which differs from that found in vertebrates. Cellular thiol redox homeostasis is maintained by the biosynthesis and reduction of trypanothione, involving different enzymes that act in concert. This study provides an overview of the antioxidant defence focusing on iron superoxide dismutase A, tryparedoxin peroxidase, and ascorbate peroxidase and how the enzymes play an important role in the defence against oxidative stress and their involvement in drug resistance mechanisms in T. cruzi and Leishmania spp.

Antileishmanial metallodrugs and the elucidation of new drug targets linked to post-translational modifications machinery: pitfalls and progress

Despite the increasing number of manuscripts describing potential alternative antileishmanial compounds, little is advancing on translating these knowledges to new products to treat leishmaniasis. This is in part due to the lack of standardisations during pre-clinical drug discovery stage and also depends on the alignment of goals among universities/research centers, government and pharmaceutical industry. Inspired or not by drug repurposing, metal-based antileishmanial drugs represent a class that deserves more attention on its use for leishmaniasis chemotherapy. Together with new chemical entities, progresses have been made on the knowledge of parasite-specific drug targets specially after using CRISPR/Cas system for functional studies. In this regard, Leishmania parasites undergoe post-translational modification as key regulators in several cellular processes, which represents an entire new field for drug target elucidation, once this is poorly explored. This perspective review describes the advances on antileishmanial metallodrugs and the elucidation of drug targets based on post-translational modifications, highlighting the limitations on the drug discovery/development process and suggesting standardisations focused on products addressed to who need it most.

Antileishmanial metallodrugs and the elucidation of new drug targets linked to post-translational modifications machinery: pitfalls and progress.

Despite the increasing number of manuscripts describing potential alternative antileishmanial compounds, little is advancing on translating these knowledges to new products to treat leishmaniasis. This is in part due to the lack of standardisations during pre-clinical drug discovery stage and also depends on the alignment of goals among universities/research centers, government and pharmaceutical industry. Inspired or not by drug repurposing, metal-based antileishmanial drugs represent a class that deserves more attention on its use for leishmaniasis chemotherapy. Together with new chemical entities, progresses have been made on the knowledge of parasite-specific drug targets specially after using CRISPR/Cas system for functional studies. In this regard, Leishmania parasites undergoe post-translational modification as key regulators in several cellular processes, which represents an entire new field for drug target elucidation, once this is poorly explored. This perspective review describes the advances on antileishmanial metallodrugs and the elucidation of drug targets based on post-translational modifications, highlighting the limitations on the drug discovery/development process and suggesting standardisations focused on products addressed to who need it most.

Antileishmanial Drug Discovery and Development: Time to Reset the Model?

Leishmaniasis is a vector-borne parasitic disease caused by Leishmania species. The disease affects humans and animals, particularly dogs, provoking cutaneous, mucocutaneous, or visceral processes depending on the Leishmania sp. and the host immune response. No vaccine for humans is available, and the control relies mainly on chemotherapy. However, currently used drugs are old, some are toxic, and the safer presentations are largely unaffordable by the most severely affected human populations. Moreover, its efficacy has shortcomings, and it has been challenged by the growing reports of resistance and therapeutic failure. This manuscript presents an overview of the currently used drugs, the prevailing model to develop new antileishmanial drugs and its low efficiency, and the impact of deconstruction of the drug pipeline on the high failure rate of potential drugs. To improve the predictive value of preclinical research in the chemotherapy of leishmaniasis, several proposals are presented to circumvent critical hurdles—namely, lack of common goals of collaborative research, particularly in public–private partnership; fragmented efforts; use of inadequate surrogate models, especially for in vivo trials; shortcomings of target product profile (TPP) guides.

Heterocyclic Diamines with Leishmanicidal Activity.

Leishmaniasis is one of the world's most neglected diseases with a worldwide prevalence of 12 million people. There are no effective human vaccines for its prevention, and outdated drugs hamper treatment. Therefore, research aimed at developing new therapeutic tools to fight leishmaniasis remains a crucial goal today. With this purpose in mind, here, we present 10 new compounds made up by linking alkylated ethylenediamine units to pyridine or quinoline heterocycles with promising in vitro and in vivo efficacy against promastigote and amastigote forms of Leishmania infantum, Leishmania donovani, and Leishmania braziliensis species. Three compounds (2, 4, and 5) showed a selectivity index much higher in the amastigote form than the reference drug glucantime. These three derivatives affected the parasite infectivity rates; the result was lower parasite infectivity rates than glucantime tested at an IC25 dose. In addition, these derivatives were substantially more active against the three Leishmania species tested than glucantime. The mechanism of action of these compounds has been studied, showing alterations in glucose catabolism and leading to greater levels of iron superoxide dismutase inhibition. These molecules could be potential candidates for leishmaniasis chemotherapy due to their effectiveness and their ready synthesis.

Prediction of potential cysteine synthase inhibitors of Leishmania braziliensis and Leishmania major parasites by computational screening

Leishmaniasis is a neglected tropical disease considered a public health problem that requires innovative strategies for its chemotherapeutic control. In the present investigation, a molecular docking approach was carried out using the protein cysteine synthase (CS) of Leishmania braziliensis (CSLb) and Leishmania major (CSLm) parasites to identify new compounds as potential candidates for the development of selective leishmaniasis therapy. CS protein sequence similarity, active site, structural modeling, molecular docking, and ADMET properties of compounds were analyzed using bioinformatics tools. Molecular docking analyses identified 1000 ligands with highly promising binding affinity scores for both CS proteins. A total of 182 compounds for CSLb and 173 for CSLm were selected for more detailed characterization based on the binding energy and frequency values and ADMET properties. Based on Principal Component Analysis (PCA) and K-means clusterization for both CS proteins, we classified compounds into 5 clusters for CSLb and 7 for CSLm, thus providing an excellent starting point for verification of enzyme inhibition in in vitro studies. We found the ZINC16524774 compound predicted to have a high affinity and stability for both CSLb and CSLm proteins, which was also evaluated through molecular dynamics simulations. Compounds within each of the five clusters also displayed pharmacological and structural properties that make them attractive drug candidates for the development of selective cutaneous leishmaniasis chemotherapy.

In vitro biological activity of liposomal-containing antimony trioxide

Antimonials are used as chemotherapy for leishmaniasis, but have limited results due to their toxicity and broad resistance already acquired by the parasites. Nanotechnology offers an alternative to reduce these effects through the use of biocompatible nanocarriers, which can be vectorized to the target site. In addition, the redirection of molecules, already developed for the treatment of other pathologies, has the advantage of being already approved for therapy by regulatory agencies. The present study addresses the production of liposomal vesicles containing antimony trioxide (LC Sb2O3), as well as the evaluation of activity against tumor and bacterial cells. We produce liposomes in order of nanometric size, polydispersity index (PDI <0.3), pH value close to physiological (7.2), and zeta potential (anionic). Cytotoxicity was evaluated in 24 and 72 hours, in the HepG2, T98G, and U87MG tumor cell lines, by the method (3-4.5 dimethylthiazole-2.5 diphenyltetrazolium bromide) (MTT). The minimum inhibitory concentration (MIC) was tested on three bacterial strains (American Type Culture Collection – ATCC-Escherichia coli ATCC 35218, Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212) and mandatory (Staphylococcus aureus and Klebsiella pneumoniae). The liposomes were more cytotoxic than Sb2O3 in the free form, for all tested cell lines. This effect was stronger after 72 hours incubation. Antimony trioxide in both free and liposomal forms showed low antibacterial activity. Based on our results, we suggest that liposomes containing antimony trioxide have the potential for the repositioning of drugs addressing anticancer therapy.

7,8-dihydroxyflavone-functionalized gold nanoparticles target thearginase enzyme of Leishmania donovani.

Aim: To analyze the efficacy and possible mechanism of action of 7,8-dihydroxyflavone (DHF) and DHF synthesized gold nanoparticles (GNPs) against theparasite Leishmania donovani. Methods: GNPs were synthesized using DHF and characterized by dynamic light scattering, ζpotential, Fourier transforminfrared spectroscopy, transmission electron microscopy andx-ray diffraction. The efficacy of DHF and DHF-GNP were tested against sensitive and drug-resistant parasites. GNP uptake was measured on macrophages by atomic absorption spectroscopy. Results: DHF and DHF-GNP (∼35nm) were equally effective against sensitive and drug-resistant strains and inhibited the arginase activity of parasites. Increased IFN-γ and reduced IL-12 cytokine response showed a Th1/Th2-mediated cell death in macrophages. Conclusion: The low cytotoxicity and high biological activity of DHF-GNP may be useful for chemotherapy of leishmaniasis.