Pentavalent antimonials: new perspectives for old drugs

Increased thiol levels in antimony-resistant Leishmania infantum isolated from treatment-refractory visceral leishmaniasis in Brazil

BACKGROUND

Treatment-refractory visceral leishmaniasis (VL) has become an important problem in many countries.

OBJECTIVES

We evaluated the antimony-resistance mechanisms of Leishmania infantum isolated from VL patients refractory or responsive to treatment with pentavalent antimony.

METHODS

Strains isolated from antimony-refractory patients (in vitro antimony-resistant isolates) and antimony-responsive patients (in vitro antimony-sensitive isolates) were examined. Morphological changes were evaluated by transmission electron microscopy after trivalent antimony exposure. P-glycoprotein (P-gp) efflux pump activity was evaluated using the pump-specific inhibitor verapamil hydrochloride, and the role of thiol in trivalent antimony resistance was investigated using the enzymatic inhibitor L-buthionine sulfoximine.

FINDINGS

Antimony treatment induced fewer alterations in the cellular structure of L. infantum resistant isolates than in that of sensitive isolates. P-gp efflux activity was not involved in antimony resistance in these isolates. Importantly, the resistant isolates contained higher levels of thiol compared to the sensitive isolates, and inhibition of thiol synthesis in the resistant isolates recovered their sensitivity to trivalent antimony treatment, and enhanced the production of reactive oxygen species in promastigotes exposed to the drug.

MAIN CONCLUSIONS

Our results demonstrate that isolates from patients with antimony-refractory VL exhibited higher thiol levels than antimony-sensitive isolates. This indicates that redox metabolism plays an important role in the antimony-resistance of New World VL isolates.

Synthesis and leishmanicidal activity of eugenol derivatives bearing 1,2,3-triazole functionalities

In this paper, it is described the synthesis and the evaluation of the leishmanicidal activity of twenty-six eugenol derivatives bearing 1,2,3-triazole functionalities. The evaluation of the compounds on promastigotes of Leishmania amazonensis (WHOM/BR/75/Josefa) showed that eugenol derivatives present leishmanicidal activities with varying degrees of effectiveness. The most active compound, namely 4-(3-(4-allyl-2-methoxyphenoxy)propyl)-1-(4-methylbenzyl)-1H-1,2,3-triazole (7k) (IC₅₀ = 7.4 ± 0.8 μmol L^-1), also targeted Leishmania parasites inside peritoneal macrophages (IC₅₀ = 1.6 μmol L^-1) without interfering with cell viability. The cytotoxicity of 7k against macrophage cells presented IC₅₀ of 211.9 μmol L^-1 and the selective index was equal to 132.5. Under similar conditions, compound 7k was more effective than glucantime and pentamidine, two drugs currently in the clinic. In addition, theoretical calculations showed that this compound also presents most physicochemical and pharmacokinetic properties within the ranges expected for orally available drugs. It is believed that eugenol bearing 1,2,3-triazole functionalities may represent a scaffold to be explored toward the development of new agents to treat leishmaniasis.

Epidemiological Aspects of Cutaneous Leishmaniasis during 2009-2016 in Kashan City, Central Iran

Cutaneous leishmaniasis (CL) can be seen in 2 forms, zoonotic and anthroponotic, in Iran. In this study, epidemiological aspects of CL were studied during an 8-year period (2009-2016) in city of Kashan, central Iran. The demographic and epidemiological data, including age, sex, occupation, number and site of the lesions, treatment regimen, past history of CL, and season of all patients were gathered from the health centers. Descriptive statistics were used to describe features of the study data. Total 2,676 people with CL were identified. The highest annual incidence was estimated to be 182 per 100,000 population in 2009 and the least was in 2016 (47 per 100,000 population). The highest frequency affected age groups were observed in 20-29 year-old patients (20.9%). More than 51% of the patients were under 30 years old. The maximum frequency of the disease, 1,134 (43.3%), was seen in autumn. The most common location of lesions was hands (61.4%). Most of the patients (81.6%) were treated by systemic glucantime regimen. In the city of Kashan, the incidence rate of the CL disease is significantly higher than many other regions of Iran. To reduce the risk of disease, control of reservoir hosts and vectors of disease, and education of individual protection are strongly recommended.

Modulation of inflammation response to murine cutaneous Leishmaniasis by homeopathic medicines: Antimonium crudum 30cH

Background: Leishmaniasis is a zoonotic disease caused by protozoan parasites of the mononuclear phagocytic system. The modulation activity of these cells can interfere in the host/parasite relationship and influences the prognosis.

Methods: We evaluated the effects of the homeopathic preparation Antimonium crudum 30cH on experimental infection induced by Leishmania (L.) amazonensis. Male Balb/c mice were inoculated with 2 × 106 Leishmania (L.) amazonensis promastigotes into the footpad and, after 48 h (acute phase) or 60 days (chronic phase), cell population of lymphocytes and phagocytes present in the peritoneal washing fluid and spleen were analyzed by flow cytometry and histopathology, with histometry of the subcutaneous primary lesion, local lymph node and spleen. Immunohistochemistry was performed to quantify CD3 (T lymphocyte), CD45RA (B lymphocyte) and CD11b (phagocytes) positive cells.

Results: In treated mice, during the acute phase, there was significant increase of the macroscopic lesion, associated to inflammatory edema, as well increase in the number of free amastigotes and B lymphocytes inside the lesion. Increase of B lymphocytes (predominantly B-2 cells) was also seen in the local lymph node, spleen and peritoneum. In the chronic phase, the inflammatory process in the infection focus was reduced, with reduced phagocyte migration and peritoneal increase of B-1a cells (precursors of B-2 immunoglobulin producers cells) and T CD8+ cells.

Conclusion: The treatment of mice with Antimonium crudum 30cH induced a predominantly B cell pattern of immune response in Leishmania (L.) amazonensis experimental infection, alongside the increase of free amastigote forms number in the infection site. The clinical significance of this study is discussed, further studies are suggested.

Chemical characterisation of the constituents of Eugenia protenta McVaugh and leishmanicidal activity of dimethylxanthoxylin

The chemical study of Eugenia protenta McVaugh extracts performed by classical and high-performance liquid chromatography techniques and spectral methods has led to the identification of known triterpenoids, flavonoids and an acetophenone derivative (dimethylxanthoxylin). The effect of dimethylxanthoxylin on Leishmania (Leishmania) amazonensis was evaluated against the promastigotes forms after 96 h of treatment. Dimethylxanthoxylin reduced 57 and 59% of the promastigotes growth when treated with 50 and 100 μg/mL solutions, respectively (IC₅₀ 117.35 μg/mL or 52.3 μM). Cytotoxicity experiments using MTT assays showed that this substance did not promote cell death after 24 h of treatment. Dimethylxanthoxylin was active on the promastigotes and could be a promising agent for treating leishmaniasis.

Mixed Formulation of Conventional and Pegylated Meglumine Antimoniate-Containing Liposomes Reduces Inflammatory Process and Parasite Burden in Leishmania infantum-Infected BALB/c Mice

Pentavalent antimonial has been the first choice treatment for visceral leishmaniasis; however, it has several side effects that leads to low adherence to treatment. Liposome-encapsulated meglumine antimoniate (MA) arises as an important strategy for chemotherapy enhancement. We evaluated the immunopathological changes using the mixture of conventional and pegylated liposomes with MA. The mice were infected with Leishmania infantum and a single-dose treatment regimen. Comparison was made with groups treated with saline, empty liposomes, free MA, and a liposomal formulation of MA (Lipo MA). Histopathological analyses demonstrated that animals treated with Lipo MA showed a significant decrease in the inflammatory process and the absence of granulomas. The in vitro stimulation of splenocytes showed a significant increase of gamma interferon (IFN-γ) produced by CD8⁺ T cells and a decrease in interleukin-10 (IL-10) produced by CD4⁺ and CD8⁺ T cells in the Lipo MA. Furthermore, the Lipo MA group showed an increase in the IFN-γ/IL-10 ratio in both CD4⁺ and CD8⁺ T cell subsets. According to the parasite load evaluation using quantitative PCR, the Lipo MA group showed no L. infantum DNA in the spleen (0.0%) and 41.4% in the liver. In addition, we detected a low positive correlation between parasitism and histopathology findings (inflammatory process and granuloma formation). Thus, our results confirmed that Lipo MA is a promising antileishmanial formulation able to reduce the inflammatory response and induce a type 1 immune response, accompanied by a significant reduction of the parasite burden into hepatic and splenic compartments in treated animals.

Leishmania and other intracellular pathogens: selectivity, drug distribution and PK-PD

New drugs and treatments for diseases caused by intracellular pathogens, such as leishmaniasis and the Leishmania species, have proved to be some of the most difficult to discover and develop. The focus of discovery research has been on the identification of potent and selective compounds that inhibit target enzymes (or other essential molecules) or are active against the causative pathogen in phenotypic in vitro assays. Although these discovery paradigms remain an essential part of the early stages of the drug R & D pathway, over the past two decades additional emphasis has been given to the challenges needed to ensure that the potential anti-infective drugs distribute to infected tissues, reach the target pathogen within the host cell and exert the appropriate pharmacodynamic effect at these sites. This review will focus on how these challenges are being met in relation to Leishmania and the leishmaniases with lessons learned from drug R & D for other intracellular pathogens.

Antimonene Quantum Dots: Synthesis and Application as Near-Infrared Photothermal Agents for Effective Cancer Therapy

Photothermal therapy (PTT) has shown significant potential for cancer therapy. However, developing nanomaterials (NMs)-based photothermal agents (PTAs) with satisfactory photothermal conversion efficacy (PTCE) and biocompatibility remains a key challenge. Herein, a new generation of PTAs based on two-dimensional (2D) antimonene quantum dots (AMQDs) was developed by a novel liquid exfoliation method. Surface modification of AMQDs with polyethylene glycol (PEG) significantly enhanced both biocompatibility and stability in physiological medium. The PEG-coated AMQDs showed a PTCE of 45.5 %, which is higher than many other NMs-based PTAs such as graphene, Au, MoS2 , and black phosphorus (BP). The AMQDs-based PTAs also exhibited a unique feature of NIR-induced rapid degradability. Through both in vitro and in vivo studies, the PEG-coated AMQDs demonstrated notable NIR-induced tumor ablation ability. This work is expected to expand the utility of 2D antimonene (AM) to biomedical applications through the development of an entirely novel PTA platform.

Lipidomics and anti-trypanosomatid chemotherapy

BACKGROUND

Trypanosomatids such as Leishmania, Trypanosoma brucei and Trypanosoma cruzi belong to the order Kinetoplastida and are the source of many significant human and animal diseases. Current treatment is unsatisfactory and is compromised by the rising appearance of drug resistant parasites. Novel and more effective chemotherapeutics are urgently needed to treat and prevent these devastating diseases, which relies on the identification of essential, parasite specific targets that are absent in the host. Lipids constitute essential components of the cell and carry out multiple critical functions from building blocks of biological membranes to regulatory roles in signal transduction, organellar biogenesis, energy storage, and virulence. The recent technological advances of lipidomics has facilitated the broadening of our knowledge in the field of cellular lipid content, structure, functions, and metabolic pathways.

MAIN BODY

This review highlights the application of lipidomics (i) in the characterization of the lipidome of kinetoplastid parasites or of their subcellular structure(s), (ii) in the identification of unique lipid species or metabolic pathways that can be targeted for novel drug therapies, (iii) as an analytic tool to gain a deeper insight into the roles of specific enzymes in lipid metabolism using genetically modified microorganisms, and (iv) in deciphering the mechanism of action of anti-microbial drugs on lipid metabolism. Lastly, an outlook stating where the field is evolving is presented.

CONCLUSION

Lipidomics has contributed to the expanding knowledge related to lipid metabolism, mechanism of drug action and resistance, and pathogen-host interaction of trypanosomatids, which provides a solid basis for the development of better anti-parasitic pharmaceuticals.

Evaluation of Boldine Activity against Intracellular Amastigotes of Leishmania amazonensis

Leishmaniasis is a neglected and endemic disease that affects poorest population mainly in developing countries. A lack of adequate and definitive chemotherapeutic agents to fight against this infection has led to the investigation of numerous compounds. The aim of this study was to investigate in vitro activity of boldine against Leishmania amazonensis murine cell infection. Boldine ((S)-2,9-dihydroxy-1,10-dimethoxy-aporphine) is an aporphine alkaloid found abundantly in the leaves/bark of boldo (Peumus boldus Molina), a widely distributed tree native to Chile. The in vitro system consisted of murine macrophage infection with amastigotes of L. amazonensis treated with different concentrations from 50 to 600 μg/ml of boldine for 24 hr. Intracellular parasite destruction was assessed by morphological examination and boldine cytotoxicity to macrophages was tested by the MTT viability assay. When cells were treated with 100 μg/ml of boldine the reduction of parasite infection was 81% compared with untreated cultures cells. Interestingly, boldine-treatment caused a concentration-dependent decrease of macrophage infection that culminated with 96% of reduction when cells were submitted to 600 μg/ml of boldine. Cell cultures exposed to 100 μg/ml of boldine and 300 μg/ml of Glucantime^® during 24 hr showed a significant reduction of 50% in parasitized cells compared with cell cultures exposed just to Glucantime^®. The study showed that treatment with boldine produces a better effect than treatment with the reference antimonial drug, glucantime, in L. amazonensis infected macrophage. Our results suggest that boldine is a potentially useful agent for the treatment of leishmaniasis.

A Computational Methodology to Overcome the Challenges Associated With the Search for Specific Enzyme Targets to Develop Drugs Against Leishmania major

We present an approach for detecting enzymes that are specific of Leishmania major compared with Homo sapiens and provide targets that may assist research in drug development. This approach is based on traditional techniques of sequence homology comparison by similarity search and Markov modeling; it integrates the characterization of enzymatic functionality, secondary and tertiary protein structures, protein domain architecture, and metabolic environment. From 67 enzymes represented by 42 enzymatic activities classified by AnEnPi (Analogous Enzymes Pipeline) as specific for L major compared with H sapiens, only 40 (23 Enzyme Commission [EC] numbers) could actually be considered as strictly specific of L major and 27 enzymes (19 EC numbers) were disregarded for having ambiguous homologies or analogies with H sapiens. Among the 40 strictly specific enzymes, we identified sterol 24-C-methyltransferase, pyruvate phosphate dikinase, trypanothione synthetase, and RNA-editing ligase as 4 essential enzymes for L major that may serve as targets for drug development.

Meglumine Antimoniate (Glucantime) Causes Oxidative Stress-Derived DNA Damage in BALB/c Mice Infected by Leishmania (Leishmania) infantum

Leishmaniasis is a neglected tropical disease caused by >20 species of the protozoan parasite Leishmania Meglumine antimoniate (Glucantime) is the first-choice drug recommended by the World Health Organization for the treatment of all types of leishmaniasis. However, the mechanisms of action and toxicity of pentavalent antimonials, including genotoxic effects, remain unclear. Therefore, the mechanism by which meglumine antimoniate causes DNA damage was investigated for BALB/c mice infected by Leishmania (Leishmania) infantum and treated with meglumine antimoniate (20 mg/kg for 20 days). DNA damage was analyzed by a comet assay using mouse leukocytes. Furthermore, comet assays were followed by treatment with formamidopyrimidine-DNA glycosylase and endonuclease III, which remove oxidized DNA bases. In addition, the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in the animals' sera were assessed. To investigate mutagenicity, we carried out a micronucleus test. Our data demonstrate that meglumine antimoniate, as well as L. infantum infection, induces DNA damage in mammalian cells by the oxidation of nitrogenous bases. Additionally, the antileishmanial increased the frequency of micronucleated cells, confirming its mutagenic potential. According to our data, both meglumine antimoniate treatment and L. infantum infection promote oxidative stress-derived DNA damage, which promotes overactivation of the SOD-CAT axis, whereas the SOD-GPx axis is inhibited as a probable consequence of glutathione (GSH) depletion. Finally, our data enable us to suggest that a meglumine antimoniate regimen, as recommended by the World Health Organization, would compromise GPx activity, leading to the saturation of antioxidant defense systems that use thiol groups, and might be harmful to patients under treatment.

An overview of azoles targeting sterol 14α-demethylase for antileishmanial therapy

The azole antifungal drugs are an important class of chemotherapeutic agents with broad-spectrum of activity against yeasts and filamentous fungi, act in the ergosterol biosynthetic pathway through inhibition of the cytochrome P450-dependent enzyme sterol 14α-demethylase. Azole antifungals have also been repurposed for treatment of tropical protozoan infections including human leishmaniasis. Recent advances in molecular biology and computational chemistry areas have increased our knowledge about sterol biochemical pathway in Leishmania parasites. Based on the importance of sterol biosynthetic pathway in Leishmania parasites, we reviewed all studies reported on azoles for potential antileishmanial therapy along their structural and biological aspects. This review may help medicinal chemists for design of new azole-derived antileishmanial drugs.

Biophysical and Pharmacological Characterization of Energy-Dependent Efflux of Sb in Laboratory-Selected Resistant Strains of Leishmania (Viannia) Subgenus

The growing resistance of leishmaniasis to first-line drugs like antimonials in some regions limits the control of this parasitic disease. The precise mechanisms involved in Leishmania antimony resistance are still subject to debate. The reduction of intracellular Sb^III accumulation is a common change observed in both laboratory-selected and field isolated resistant Leishmania strains, but the exact transport pathways involved in antimony resistance have not yet been elucidated. In order to functionally characterize the antimony transport routes responsible for resistance, we performed systematic transport studies of Sb^III in wild-type and resistant strains of L. (Viannia) guyanensis and L. (V.) braziliensis. Those include influx and efflux assays and the influence of ABC transporters and metabolism inhibitors: prochlorperazine, probenecid, verapamil, BSO, and sodium azide. The mRNA levels of genes associated with antimony resistance (MRPA, GSH1, ODC, AQP1, ABCI4, and ARM58) were also investigated in addition to intracellular thiol levels. A strong reduction of Sb influx was observed in L. guyanensis resistant mutant (LgSbR), but not in L. braziliensis (LbSbR). Both mutants showed increased energy-dependent efflux of Sb^III, when compared to their respective parental strains. In LgSbR, BSO and prochlorperazine inhibited antimony efflux and resistance was associated with increased MRPA and GSH1 mRNA levels, while in LbSbR antimony efflux was inhibited by probenicid and prochlorperazine in absence of resistance-associated gene modulation. Intracellular thiol levels were increased in both Sb-resistant mutants. An energy-dependent Sb^III efflux pathway sensitive to prochlorperazine was clearly evidenced in both Sb-resistant mutants. In conclusion, the present study allowed the biophysical and pharmacological characterization of energy-dependent Sb efflux pathway apparently independent of MRPA, ABCI4, and ARM58 upregulation, in Leishmania (Vianna) mutant selected in vitro for resistance to Sb^III. Prochlorperazine has also been identified as an effective chemosensitizer in both Sb resistant mutants, which acts through inhibition of the active efflux of Sb.

Carboxylate derivatives of tributyltin (IV) complexes as anticancer and antileishmanial agents

Background

Tributyltin (IV) compounds are promising candidates for drug development. In the current study, we evaluated in-vitro and in-silico profile of carboxylate derivatives of tributyltin (IV) complexes.

Methods

ADMET and drug-likeliness properties were predicted using MetaPrint2D React, preADMET, SwissADME and Molsoft tools. SwissTargetPrediction predicted molecular targets for compounds. In-vitro bioactivity was evaluated by quantifying cytotoxicity against HepG2, THP-1 cell lines, isolated lymphocytes and leishmania promastigotes as well as measuring protein kinase (PK) inhibition activity.

Results

Results indicate partial compliance of compounds with drug-likeliness rules. Ch-409 complies with WDI and Lipinski rules. ADMET profile prediction shows strong plasma protein binding except for Ch-409, low to high GI absorption and BBB penetration (C_brain/C_blood = 0.942–11; caco-2 cells permeability 20.13–26.75 nm/sec), potential efflux by P-glycoprotein, metabolism by CYP3A4, medium inhibition of hERG, mutagenicity and capacity to be detoxified by glutathionation and glucuronidation. Molecular targets include proteases, enzymes, membrane receptors, transporters and ion channels where Ch-409 targets membrane receptors only. Compounds are significantly (p < 0.05) cytotoxic against HepG2 cell line and leishmania as compared with normal isolated lymphocytes. Ch-459 indicates highest toxicity against leishmania (mortality 97.9 ± 3.99%; LC50 0.323 ± 0.002 μg/mL) whereas Ch-409 possesses maximum cytotoxicity against HepG2 cell line (IC50 0.08 ± 0.001 μg/mL) as well as 97.5 ± 1.98% (LC50 0.954 ± 0.158 μg/mL) mortality of leishmania promastigotes. It was observed that antileishmanial effect was reduced by 16.38%–34.38% and 15–38.2% in the presence of NaN₃ and mannitol respectively. PK inhibition and reactive oxygen species production are possible mechanisms for cytotoxicity.

Conclusions

Selected carboxylate derivatives of tributyltin (IV) complexes possess significant antileishmanial and cytotoxic potential. These are promising compounds for the development of antileishmanial and anticancer drugs.

Graphical Abstract

Thermodynamics, functional and structural characterization of inosine–uridine nucleoside hydrolase from Leishmania braziliensis

Inosine–uridine nucleoside hydrolase fromLeishmania braziliensisis a nonspecific enzyme that contains a disulfide bond not needed for tetramer stabilization.

Nanoscaled hydrated antimony (V) oxide as a new approach to first-line antileishmanial drugs

Background

Coordination compounds of pentavalent antimony have been, and remain, the first-line drugs in leishmaniasis treatment for >70 years. Molecular forms of Sb (V) complexes are commercialized as sodium stibogluconate (Pentostam^®) and meglumine antimoniate (MA) (Glucantime^®). Ever-increasing drug resistance in the parasites limits the use of antimonials, due to the low drug concentrations being administered against high parasitic counts. Sb⁵⁺ toxicity provokes severe side effects during treatment. To enhance therapeutic potency and to increase Sb (V) concentration within the target cells, we decided to try a new active substance form, a hydrosol of Sb₂O₅·nH₂O nanoparticles (NPs), instead of molecular drugs.

Methodology/principal findings

Sb₂O₅·nH₂O NPs were synthesized by controlled SbCl₅ hydrolysis in a great excess of water. Sb₂O₅·nH₂O phase formation was confirmed by X-ray diffraction. The surface of Sb (V) NPs was treated with ligands with a high affinity for target cell membrane receptors. The mean particle size determined by dynamic light scattering and transmission electron microscopy was ~35–45 nm. In vitro tests demonstrated a 2.5–3 times higher antiparasitic activity of Sb (V) nanohybrid hydrosols, when compared to MA solution. A similar comparison for in vivo treatment of experimental cutaneous leishmaniasis with Sb⁵⁺ nanohybrids showed a 1.75–1.85 times more effective decrease in the lesions. Microimages of tissue fragments confirmed the presence of NPs inside the cytoplasm of infected macrophages.

Conclusion/significance

Sb₂O₅·nH₂O hydrosols are proposed as a new form of treatment for cutaneous leishmaniasis caused by Leishmania amazonensis. The NPs penetrate directly into the affected cells, creating a high local concentration of the drug, a precondition to overcoming the parasite resistance to molecular forms of pentavalent antimonials. The nanohybrids are more effective at a lower dose, when compared to MA, the molecular drug. Our data suggest that the new form of treatment has the potential to reduce and simplify the course of cutaneous leishmaniasis treatment. At the same time, Sb₂O₅·nH₂O hydrosols provide an opportunity to avoid toxic antimony (V) spreading throughout the body.

Quinoline derivatives: Synthesis, leishmanicidal activity and involvement of mitochondrial oxidative stress as mechanism of action

Leishmaniasis comprise a spectrum of diseases caused by protozoa parasites from the genus Leishmania, affecting millions of people worldwide, mainly in subtropical countries. Most antileishmanial drugs are highly toxic, present resistance issues or require long-term treatment. Consequently, new drugs are urgently needed. Quinoline-containing compounds have displayed an impressive array of biological properties over the years, including antileishmanial activity. In the present study, we report the synthesis and evaluation of novel quinoline derivatives (QuinDer) against Leishmania species and cytotoxic effect on mammalian cells. The ROS production and mitochondrial membrane potential analyses were also studied. The compound QuinDer1 showed activity on L. amazonensis and L. braziliensis promastigotes and this compound exhibited a strong inhibition of the proliferation of L. amazonensis amastigotes at nM concentration (IC₅₀ of 0.0911 μM), being 139 times more active than miltefosine (IC₅₀ of 12.7 μM), used as reference drug. This compound presents low cytotoxicity toward murine macrophages and human erythrocytes. In addition, promastigotes of L. amazonensis treated with the compound QuinDer1 present high generation of ROS levels with low alterations in mitochondrial membrane potential and maintenance of parasite membrane integrity. No substantial NO production in infected-macrophages treated with this compound was detected. These results suggest that the compound QuinDer 1 is a potent and selective antileishmanial agent by mitochondrial oxidative stress.

Highly potent anti-leishmanial derivatives of hederagenin, a triperpenoid from Sapindus saponaria L

Leishmaniasis is a neglected tropical disease (NTDs), endemic in 88 countries that affect more than 12 million people. Current drugs are limited due to their toxicity, development of biological resistance, length of treatment and high cost. Thus, the search for new effective and less toxic treatments is an urgent need. In this study, we report the synthesis of 3 new amide derivatives of hederagenin (22-24) with yields between 70% and 90%, along with 57 other derivatives of hederagenin (1-21, 25-60) carrying different groups at C-28 previously reported by our group, and the results of their in vitro ability to inhibit the growth of Leishmania infantum. Some derivatives (3, 4, 44, 49 and 52), showed activity at micromolar level and low toxicity against BGM and HepG2 cells. Moreover, the ability of hederagenin derivatives 3 (IC₅₀ = 9.7 μM), 4 (12 μM), 44 (11 μM) and 49 (2 μM), to prevent proliferation of intracellular amastigote forms of L. infantum and their higher selectivity index and low toxicity compared to commercial positive drug control of choice (potassium antimonyl tartrate trihydrate) (IC₅₀ = 80 μM, SI = 0.1), make these compounds promising candidates for the treatment of leishmaniasis.

Current status on prevention and treatment of canine leishmaniasis

Canine leishmaniasis (CanL) is a parasite-borne disease mainly induced by Leishmania infantum in the Old World and Leishmania chagasi (infantum) in the New World. CanL is a zoonosis transmitted by the bite of infected Phlebotominae flies that act as vectors. CanL is a very serious disease that usually produces death when remains untreated and can be a focus of transmission to other dogs or humans. Infected dogs and other domestic and wild animals act as reservoirs and are a real threat to uninfected/healthy dogs and humans in endemic areas where the sand flies are present. Prevention of new infections in dogs can help to stop the current increase of the disease in humans, reinforcing the concept of "One Health" approach. The management of CanL is being performed using prophylactic measures in healthy dogs - insecticides impregnated in collars or immunostimulants applied by spot-on devices - and chemotherapy in animals that suffer from the disease. Antimonials as first-line monotherapy have proven efficacy in reducing most of the clinical signs of CanL, but they need to be administered during several days, and no complete parasite clearance is achieved, favouring the presence of relapses among treated dogs. Therefore, new drugs, such as miltefosine, or combinations of this drug or antimonials with allopurinol are in the pipeline of clinical treatment of CanL. Recently, there has been an emergence of protective - prophylactic - and curative - autogenous vaccines - immunotherapy tools to face CanL, whose results are still under study. This review highlights the current use of preventive and eradicative weapons to fight against this disease, which is a scourge for dogs and a continuous threat to human beings.

Polarity-sensitive nanocarrier for oral delivery of Sb(V) and treatment of cutaneous leishmaniasis

There is a great need for orally active drugs for the treatment of the neglected tropical disease leishmaniasis. Amphiphilic Sb(V) complexes, such as 1:3 Sb–N-octanoyl-N-methylglucamide complex (SbL8), are promising drug candidates. It has been previously reported that SbL8 forms kinetically stabilized nanoassemblies in water and that this simple dispersion exhibits antileishmanial activity when given by oral route to a murine model of visceral leishmaniasis. The main objective of the present work was to interfere in the structural organization of these nanoassemblies so as to investigate their influence on the oral bioavailability of Sb, and ultimately, optimize an oral formulation of SbL8 for the treatment of cutaneous leishmaniasis. The structural organization of SbL8 nanoassemblies was manipulated through addition of propylene glycol (PG) to the aqueous dispersion of SbL8. The presence of 50% (v/v) PG resulted in the loss of hydrophobic microenvironment, as evidenced by fluorescence probing. However, nanostructures were still present, as demonstrated by dynamic light scattering, small-angle X-ray scattering, and atomic force microscopy (AFM). A remarkable property of these nanoassemblies, as revealed by AFM analysis, is the flexibility of their supramolecular organization, which showed changes as a function of the solvent and substrate polarities. The formulation of SbL8 in 1:1 water:PG given orally to mice promoted significantly higher and more sustained serum levels of Sb, when compared to SbL8 in water. The new formulation, when given as repeated doses (200 mg Sb/kg/day) to BALB/c mice infected with Leishmania amazonensis, was significantly more effective in reducing the lesion parasite burden, compared to SbL8 in water, and even, the conventional drug Glucantime^® given intraperitoneally at the same dose. In conclusion, this work introduces a new concept of polarity-sensitive nanocarrier that was successfully applied to optimize an oral formulation of Sb(V) for treating cutaneous leishmaniasis.

Leishmania cell wall as a potent target for antiparasitic drugs. A focus on the glycoconjugates

Although leishmaniasis has been studied for over a century, the fight against cutaneous, mucocutaneous and visceral forms of the disease remains a hot topic. This review refers to the parasitic cell wall and more particularly to the constitutive glycoconjugates. The structures of the main glycolipids and glycoproteins, which are species-dependent, are described. The focus is on the disturbance of the lipid membrane by existing drugs and possible new ones, in order to develop future therapeutic agents.

Abietane-Type Diterpenoid Amides with Highly Potent and Selective Activity against Leishmania donovani and Trypanosoma cruzi

Dehydroabietylamine (1) was used as a starting material to synthesize a small library of dehydroabietyl amides by simple and facile methods, and their activities against two disease-causing trypanosomatids, namely, Leishmania donovani and Trypanosoma cruzi, were assayed. The most potent compound, 10, an amide of dehydroabietylamine and acrylic acid, was found to be highly potent against these parasites, displaying an IC50 value of 0.37 μM against L. donovani axenic amastigotes and an outstanding selectivity index of 63. Moreover, compound 10 fully inhibited the growth of intracellular amastigotes in Leishmania donovani-infected human macrophages with a low IC50 value of 0.06 μM. This compound was also highly effective against T. cruzi amastigotes residing in L6 cells with an IC50 value of 0.6 μM and high selectivity index of 58, being 3.5 times more potent than the reference compound benznidazole. The potent activity of this compound and its relatively low cytotoxicity make it attractive for further development in pursuit of better drugs for patients suffering from leishmaniasis and Chagas disease.

Leishmanicidal, cytotoxicity and wound healing potential of Arrabidaea chica Verlot

BACKGROUND

Leishmaniasis includes a wide complex of diseases that affect humans and other mammals, and can range from a mild cutaneous form to a severe visceral type. The safety of the standard treatment using pentavalent antimony is a concern due to its toxic effects. The search for alternative, effective and less toxic treatments has led to the testing of natural products. The present study aimed to evaluate the cytotoxic, leishmanicidal and healing potential of Arrabidaea chica.

METHODS

The crude ethanolic extract, as well as the chloroform, methanol and ethyl acetate fractions of A. chica were prepared and phytochemical analysis was performed. Cytotoxic evaluation was carried out through MTT colorimetric assay, and the 50% cellular cytotoxicity was determined. After that, the effect of the extract and fractions against Leishmania amazonensis promastigotes, at intervals of 24, 48 and 72 h, was analyzed, and 50% inhibitory concentration was determined. The healing effect of the plant was also tested in surgical lesions in Swiss mice skin.

RESULTS

Phytochemical screening showed that the crude extracts contained flavonoids, tannins, anthocyanidins and chalcones. The leishmanicidal potential of A. chica produced satisfactory results in concentrations of between 60 and 155.9 μg/mL. Cytotoxic assay revealed a 50% reduction in viable cells at a concentration of 189.9 μg/mL. The healing results indicated that the treated group exhibited more pronounced signs of lesion resolution in the early period, but this pattern did not persist throughout the treatment.

CONCLUSIONS

The results of the present study demonstrate that A. chica has cytotoxic and leishmanicidal potential but its healing effect must be better studied.

Antiprotozoal activity of dehydroabietic acid derivatives against Leishmania donovani and Trypanosoma cruzi

Dehydroabietic acid derivatives have potent antiprotozoal activity and selectivity against L. donovani and T. cruzi.

Improvement of Asthma and Gastroesophageal Reflux Disease With Oral Pulvis stomachicus cum Belladonna, a Combination of Matricaria recutita, Atropa belladonna, Bismuth, and Antimonite: A Pediatric Case Report

The association between gastroesophageal reflux disease (GERD) and asthma, although well established in adults, is less strong in the pediatric age group. Benefits of proton pump therapy are limited across age ranges. While there is a growing body of literature on the use of complementary treatments for both asthma and GERD, few studies have focused on treatment benefits for the GERD-asthma association. We present the case of a 2-year-old boy with asthma and GERD who was not responding to inhaled, low-dose corticosteroids, beta-mimetic therapy, and a 6-week course of proton pump inhibitor treatment. We noted a gradual disappearance of symptoms when he was given an oral preparation of Pulvis stomachicuscum Belladonna, an anthroposophic medication containing Matricaria recutita, Atropa belladonna, bismuth, and antimonite. Matricaria recutita and bismuth have known gastric protective properties, and Atropa belladonna contains anticholinergic agents that have a bronchodilatory effect. These complementary medications appear promising in terms of relieving the symptoms of GERD-associated asthma.

The Antileishmanial Potential of C-3 Functionalized Isobenzofuranones against Leishmania (Leishmania) Infantum Chagasi

Leishmaniases are diseases caused by protozoan parasites of the genus Leishmania. Clinically, leishmaniases range from cutaneous to visceral forms, with estimated global incidences of 1.2 and 0.4 million cases per year, respectively. The treatment of these diseases relies on multiple parenteral injections with pentavalent antimonials or amphotericin B. However, these pharmaceuticals are either too toxic or expensive for routine use in developing countries. These facts call for safer, cheaper, and more effective new antileishmanial drugs. In this investigation, we describe the results of the assessment of the activities of a series of isobenzofuran-1(3H)-ones (phtalides) against Leishmania (Leishmania) infantum chagasi, which is the main causative agent of visceral leishmaniasis in the New World. The compounds were tested at concentrations of 100, 75, 50, 25 and 6.25 µM over 24, 48, and 72 h. After 48 h of treatment at the 100 µM concentration, compounds 7 and 8 decreased parasite viability to 4% and 6%, respectively. The concentration that gives half-maximal responses (LC50) for the antileishmanial activities of compounds 7 and 8 against promastigotes after 24 h were 60.48 and 65.93 µM, respectively. Additionally, compounds 7 and 8 significantly reduced parasite infection in macrophages.

Leishmanicidal Activity of (+)-Phyllanthidine and the Phytochemical Profile of Margaritaria nobilis (Phyllanthaceae)

The effects of the Securinega alkaloid (+)-phyllanthidine on Leishmania (L.) amazonensis and the first chemical investigation of Margaritaria nobilis L.f. (Phyllanthaceae) are described. Treating the parasites with this alkaloid caused a dose-dependent reduction in promastigote growth of 67.68% (IC₅₀ 82.37 μg/mL or 353 µM) and in amastigote growth of 83.96% (IC₅₀ 49.11 μg/mL or 210 µM), together with ultrastructural alterations in the promastigotes. No cytotoxic effect was detected in mammalian cells (CC₅₀ 1727.48 µg/mL or CC₅₀ 5268 µM). Classical chromatographic techniques and spectral methods led to the isolation and identification of betulinic acid, kaempferol, corilagin, gallic acid and its methyl ester, besides (+)-phyllanthidine from M. nobilis leaves and stems. Margaritaria nobilis is another source of the small group of Securinega alkaloids, together with other Phyllanthaceae (Euphorbiaceae s.l.) species. The low toxicity to macrophages and the effects against promastigotes and amastigotes are suggestive that (+)-phyllanthidine could be a promising antileishmanial agent for treating cutaneous leishmaniasis.

Identification of Th1/Th2 regulatory switch to promote healing response during leishmaniasis: a computational approach

Leishmania devices its survival strategy by suppressing the host's immune functions. The antigen molecules produced by Leishmania interferes with the host's cell signaling cascades and consequently changes the protein expression pattern of the antigen-presenting cell (APC). This creates an environment suitable for the switching of the T-cell responses from a healing Th1 response to a non-healing Th2 response that is favorable for the continued survival of the parasite inside the host APC. Using a reconstructed signaling network of the intracellular and intercellular reactions between a Leishmania infected APC and T-cell, we propose a computational model to predict the inhibitory effect of the Leishmania infected APC on the T-cell and to identify the regulators of this Th1-/Th2-switching behavior as observed during Leishmania infection. In this work, we hypothesize that a complete removal of the parasite could only be achieved with a simultaneous up-regulation of the healing Th1 response and stimulation of nitric oxide (NO) production from the APCs, and downregulation of the non-healing Th2 response and thereby propose several unique combinations of protein molecules that could elicit this anti-Leishmania immune response. Our results indicate that TLR3 may play a positive role in eliciting NO synthesis, while TLR2 may be responsible for inhibiting an anti-Leishmania immune response. Also, TLR3 overexpression (in the APC), when combined with SHP2 inhibition (in the T cell), produces an anti-Leishmania response that is better than the conventional IFN-gamma or IL12 treatment. A similar anti-Leishmania response is also obtained in another combination where TLR3 (in APC) is overexpressed, and SHC and MKP (of T cell) are inhibited and activated, respectively. Through our study, we also observe that Leishmania infection may induce an upregulation of IFN-beta production from the APC that may lead to an upregulation of the RAP1 and SOCS3 proteins inside the T cell, the potential inhibitors of MAPK and JAK-STAT signaling pathways, respectively, via the TYK2-mediated pathway. This study not only enhances our knowledge in understanding the Th1/Th2 regulatory switch to promote healing response during leishmaniasis but also helps to identify novel combinations of proteins as potential immunomodulators.

IFN-γ-induced macrophage antileishmanial mechanisms in mice: A role for immunity-related GTPases, Irgm1 and Irgm3, in Leishmania donovani infection in the liver

In C57BL/6 mice, Leishmania donovani infection in the liver provoked IFN-γ-induced expression of the immunity-related GTPases (IRG), Irgm1 and Irgm3. To gauge the antileishmanial effects of these macrophage factors in the liver, intracellular infection was analyzed in IRG-deficient mice. In early- (but not late-) stage infection, Irgm3(-/-) mice failed to properly control parasite replication, generated little tissue inflammation and were hyporesponsive to pentavalent antimony (Sb) chemotherapy. Observations limited to early-stage infection in Irgm1(-/-) mice demonstrated increased susceptibility and virtually no inflammatory cell recruitment to heavily-parasitized parenchymal foci but an intact response to chemotherapy. In L. donovani infection in the liver, the absence of either Irgm1 or Irgm3 impairs early inflammation and initial resistance; the absence of Irgm3, but not Irgm1, also appears to impair the intracellular efficacy of Sb chemotherapy.

Advances in Development of New Treatment for Leishmaniasis

Leishmaniasis is a neglected infectious disease caused by several different species of protozoan parasites of the genus Leishmania. Current strategies to control this disease are mainly based on chemotherapy. Despite being available for the last 70 years, leishmanial chemotherapy has lack of efficiency, since its route of administration is difficult and it can cause serious side effects, which results in the emergence of resistant cases. The medical-scientific community is facing difficulties to overcome these problems with new suitable and efficient drugs, as well as the identification of new drug targets. The availability of the complete genome sequence of Leishmania has given the scientific community the possibility of large-scale analysis, which may lead to better understanding of parasite biology and consequent identification of novel drug targets. In this review we focus on how high-throughput analysis is helping us and other groups to identify novel targets for chemotherapeutic interventions. We further discuss recent data produced by our group regarding the use of the high-throughput techniques and how this helped us to identify and assess the potential of new identified targets.

Immunomodulatory and Antileishmanial Activity of Phenylpropanoid Dimers Isolated from Nectandra leucantha

Three phenylpropanoid dimers (1-3) including two new metabolites were isolated from the extract of the twigs of Nectandra leucantha using antileishmanial bioassay-guided fractionation. The in vitro antiparasitic activity of the isolated compounds against Leishmania donovani parasites and mammalian cytotoxicity and immunomodulatory effects were evaluated. Compounds 1-3 were effective against the intracellular amastigotes within macrophages, with IC50 values of 26.7, 17.8, and 101.9 μM, respectively. The mammalian cytotoxicity, given by the 50% cytotoxic concentration (CC50), was evaluated against peritoneal macrophages. Compounds 1 and 3 were not toxic up to 290 μM, whereas compound 2 demonstrated a CC50 value of 111.2 μM. Compounds 1-3 also suppressed production of disease exacerbatory cytokines IL-6 and IL-10 but had minimal effect on nitric oxide production in L. donovani-infected macrophages, indicating that antileishmanial activity of these compounds is mediated via an NO-independent mechanism. Therefore, these new natural products could represent promising scaffolds for drug design studies for leishmaniasis.

Immunohistochemical evidence of stress and inflammatory markers in mouse models of cutaneous leishmaniosis

Leishmanioses are chronic parasitic diseases and host responses are associated with pro- or anti-inflammatory cytokines involved, respectively, in the control or exacerbation of infection. The relevance of other inflammatory mediators and stress markers has not been widely studied and there is a need to search for biomarkers to leishmaniasis. In this work, the stress and inflammatory molecules p38 mitogen-activated protein kinase, cyclooxygenase-2, migration inhibitory factor, macrophage inflammatory protein 2, heat shock protein 70 kDa, vascular endothelial factor (VEGF), hypoxia-inducible factors (HIF-1α and HIF-2α), heme oxygenase and galectin-3 expression were assessed immunohistochemically in self-controlled lesions in C57BL/6 mice and severe lesions in Balb/c mice infected with Leishmania amazonensis. The results indicated that the majority of molecules were expressed in the cutaneous lesions of both C57BL/6 and Balb/c mice during various phases of infection, suggesting no obvious correlation between the stress and inflammatory molecule expression and the control/exacerbation of leishmanial lesions. However, the cytokine VEGF was only detected in C57BL/6 footpad lesions and small lesions in Balb/c mice treated with antimonial pentavalent. These findings suggest that VEGF expression could be a predictive factor for murine leishmanial control, a hypothesis that should be tested in human leishmaniosis.

Chemical and bioassay techniques to authenticate quality of the anti-leishmanial drug miltefosine

Miltefosine, an effective oral treatment of visceral leishmaniasis (VL), was selected in May 2005, by the governments of India, Nepal, and Bangladesh for the elimination of VL. However, abnormally high treatment failure rates reported in patients in Bangladesh, given a miltefosine generic product (“Miltefos”, Popular Pharmaceuticals Ltd.) during 2008, led the World Health Organization (WHO) to procure this formulation for quality testing. Proton (¹H) and phosphorous (³¹P) nuclear magnetic resonance (NMR) analyses of the Miltefos™ capsules did not give the peaks defined for Impavido^®, the quality assured VL treatment product from Aeterna Zentaris. Contents of capsules of Impavido^® yielded expected peaks for miltefosine (m/z 408.33 for the protonated parent ion and m/z 183.99 plus m/z 124.8 the fragment ions) that were absent in the Miltefos™ capsules. Furthermore, testing using an in vitro Leishmania donovani intracellular amastigote—macrophage model, yielded EC₅₀ values of between 2.55 and 4.06 μg/mL and 3.02 to 5.92 μg/mL for extracts from the Impavido^® capsules and the miltefosine standard, respectively. Lack of significant anti-leishmanial activity of Miltefos™ capsules was identified in this assay even at concentrations up to 100 μg/mL. Capsules of Miltefos™ were classified as falsified (absence of stated active pharmaceutical ingredient) by three methods—NMR and mass spectrometry analysis and bioassay.

The elements of life and medicines

Which elements are essential for human life? Here we make an element-by-element journey through the periodic table and attempt to assess whether elements are essential or not, and if they are, whether there is a relevant code for them in the human genome. There are many difficulties such as the human biochemistry of several so-called essential elements is not well understood, and it is not clear how we should classify elements that are involved in the destruction of invading microorganisms, or elements which are essential for microorganisms with which we live in symbiosis. In general, genes do not code for the elements themselves, but for specific chemical species, i.e. for the element, its oxidation state, type and number of coordinated ligands, and the coordination geometry. Today, the biological periodic table is in a position somewhat similar to Mendeleev's chemical periodic table of 1869: there are gaps and we need to do more research to fill them. The periodic table also offers potential for novel therapeutic and diagnostic agents, based on not only essential elements, but also non-essential elements, and on radionuclides. Although the potential for inorganic chemistry in medicine was realized more than 2000 years ago, this area of research is still in its infancy. Future advances in the design of inorganic drugs require more knowledge of their mechanism of action, including target sites and metabolism. Temporal speciation of elements in their biological environments at the atomic level is a major challenge, for which new methods are urgently needed.