In Vitro and In Vivo Activities of 2,3-Diarylsubstituted Quinoxaline Derivatives against Leishmania amazonensis

The fungicidal effectiveness of 2-Chloro-3-hydrazinylquinoxaline, a newly developed quinoxaline derivative, against Candida species

BACKGROUND

Candida represents a prevalent fungal infection, notable for its substantial implications on morbidity and mortality rates. In the landscape of prospective treatments, quinoxaline derivatives emerge as a category of compact compounds exhibiting notable potential in addressing infections. These derivatives showcase promising antimicrobial efficacy coupled with favorable pharmacokinetic and safety characteristics.

AIMS

The central aim of this investigation was to examine the antifungal characteristics of 2-Chloro-3-hydrazinylquinoxaline against diverse strains of Candida and Aspergillus in vitro. Additionally, we endeavored to assess the in vivo efficacy of 2-Chloro-3-hydrazinylquinoxaline using a murine model for oral candidiasis induced by C. albicans cells ATCC 10231.

RESULTS

2-Chloro-3-hydrazinylquinoxaline demonstrated noteworthy effectiveness when tested against various reference strains of Candida species. It exhibited heightened efficacy, particularly against Candida krusei isolates. However, its performance against Candida albicans, Candida tropicalis, Candida glabrata, Candida parapsilosis, and Candida auris isolates exhibited variability. Notably, 2-Chloro-3-hydrazinylquinoxaline manifests variable efficacy against Aspergillus fumigatus, Aspergillus niger, Aspergillus terreus and Aspergillus flavus and no effect against Aspergillus brasiliensis. In a murine model, 2-Chloro-3-hydrazinylquinoxaline exhibited significant efficacy in combating the C. albicans cells ATCC 10231 strain, underscoring its potential as a viable treatment option.

CONCLUSION

2-Chloro-3-hydrazinylquinoxaline has demonstrated substantial potential in effectively addressing various Candida and Aspergillus species, showcasing dual attributes of antifungal and anti-inflammatory properties. However, to attain a more comprehensive understanding of its therapeutic capabilities, further investigations, incorporating additional tests and experiments, are imperative.

Characterization of the Effect of N-(2-Methoxyphenyl)-1-methyl-1H-benzimidazol-2-amine, Compound 8, against Leishmania mexicana and Its In Vivo Leishmanicidal Activity

Chemotherapy currently available for leishmaniasis treatment has many adverse side effects and drug resistance. Therefore, the identification of new targets and the development of new drugs are urgently needed. Previously, we reported the synthesis of a N-(2-methoxyphenyl)-1-methyl-1H-benzimidazol-2-amine, named compound 8, with an IC50 value in the micromolar range against L. mexicana, it also inhibited 68.27% the activity of recombinant L. mexicana arginase. Herein, we report studies carried out to characterize the mechanism of action of compound 8, as well as its in vivo leishmanicidal activity. It was shown in our ultrastructural studies that compound 8 induces several changes, such as membrane blebbing, the presence of autophagosomes, membrane detachment and mitochondrial and kinetoplast disorganization, among others. Compound 8 triggers the production of ROS and parasite apoptosis. It reduced 71% of the parasite load of L. mexicana in an experimental model of cutaneous leishmaniasis in comparison with a control. Altogether, the data obtained suggest the potential use of compound 8 in the treatment of cutaneous leishmaniasis.

Ionized alkaline water reduces injury in BALB/c mice infected with Leishmania amazonensis

Ionized water has been reported to contribute to the tissue repair process and wound healing. Water purifiers can generate ionized water by means of activated charcoal with silver and minerals, the main purpose of which are to reduce microbiological and physicochemical contaminants. Moreover, when water is subjected to a magnetic field an organization of water molecules occurs due to the presence of mineral salts. The resulting water is thus more alkaline, which has been shown to be non-toxic to mice and can actually prolong survival. Cutaneous leishmaniasis is a neglected tropical disease, caused by obligate uni- and intracellular protozoa belonging to the genus Leishmania, that can manifest in the form of skin lesions. Thus, the objective of this study was to compare the evolution of disease in L. amazonensis-infected BALB/c mice that received tap water (TW) or ionized alkaline water (IAW). As a control, additional groups of mice receiving TW or IAW were also treated with the antileishmanial miltefosine. All mouse groups received either TW or IAW as drinking water 30 days prior to infection and the groups continued to receive the respective drinking water for 4 weeks, after which the blood and plasma were collected. Biochemical assays of aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, creatinine, urea, glucose, triglycerides, and cholesterol were performed, in addition to hematology tests. There was a significant decrease in the volume of the lesion for groups that received IAW, in which the ingestion of ionized alkaline water favored the non-evolution of the lesion in the footpads of the animals. The results of the blood count and leukogram tests were within the normal values for BALB/c mice demonstrating that ionized water has no toxic effects on blood factors.

Synthesis, characterization, antioxidant and antiparasitic activities new naphthyl-thiazole derivatives

In this work, 13 thiosemicarbazones (1a - m) and 16 thiazoles (2a - p) were obtained, which were properly characterized by spectroscopic and spectrometric techniques. The pharmacokinetic properties obtained in silico revealed that the derivatives are in accordance with the parameters established by lipinski and veber, showing that such compounds have good bioavailability or permeability when administered orally. In assays of antioxidant activity, thiosemicarbazones showed moderate to high antioxidant potential when compared to thiazoles. In addition, they were able to interact with albumin and DNA. Screening assays to assess the toxicity of compounds to mammalian cells revealed that thiosemicarbazones were less toxic when compared to thiazoles. In relation to in vitro antiparasitic activity, thiosemicarbazones and thiazoles showed cytotoxic potential against the parasites Leishmania amazonensis and Trypanosoma cruzi. Among the compounds, 1b, 1j and 2l stood out, showing inhibition potential for the amastigote forms of the two parasites. As for the in vitro antimalarial activity, thiosemicarbazones did not inhibit Plasmodium falciparum growth. In contrast, thiazoles promoted growth inhibition. This study shows in a preliminary way that the synthesized compounds have antiparasitic potential in vitro.

In vitro anti-Leishmania activity of new isomeric cobalt(II)complexes and in silico insights: Mitochondria impairment and apoptosis-like cell death of the parasite

The synthesis, physico-chemical characterization and in vitro antiproliferative activity against the promastigote form of Leishmania amazonensis of two new cobalt(II) coordination compounds (i.e. [Co(HL1)Cl₂]0.4,2H₂O (1) and [Co(HL2)(Cl)(CH₃OH)](ClO₄).2H₂O (2)) are reported, where HL1 = 4-{3-[bis(pyridin-2-ylmethyl)amino]-2-hydroxypropoxy}-2H-chromen-2-one and HL2 = 7-{3-[bis(pyridin-2-ylmethyl)amino]-2-hydroxypropoxy}-2H-chromen-2-one. X-ray diffraction studies were performed for complex (2) and the structure of complex (1) was built through Density Functional Theory (DFT) calculations. Complex (1) presented no cytotoxicity to LLC-MK2, but complex (2) was toxic. IC₅₀ against promastigotes of L. amazonensis for complex (1) were 4.90 (24 h), 3.50 (48 h) and 3. 80 μmol L^-1 (72 h), and for complex (2) were 2.09, 4.20 and 2.80 μmol L^-1, respectively. Due to the high toxicity presented by complex (2) against LLC-MK2 host cells, mechanistic studies, to shed light on the probable mode of leishmanicidal activity, were carried out only for the non-cytotoxic complex. Complex (1) was able to elevate mitochondrial membrane potential of the parasites after treatment. Transmission electron microscopy revealed typical apoptotic condensation of chromatin, altered kinetoplast and mitochondria structures, suggesting that apoptosis-like cell death of the protozoa is probably mediated by an apoptotic mechanism associated with mitochondrial dysfunction (intrinsic pathway). Molecular docking studies with complex (1) upon protein tyrosine phosphatase (LmPRL-1) suggests a plausible positive complex anchoring mainly by hydrophobic and hydrogen bond forces close to the enzyme's catalytic site. These promising results for complex 1 will prompt future investigations against amastigote form of L. amazonensis.

Exploring Synthetic Dihydrobenzofuran and Benzofuran Neolignans as Antiprotozoal Agents against Trypanosoma cruzi

Chagas disease is a neglected tropical disease that affects more than 8 million people. Although there are therapies against this disease, the search for new drugs is important because the current treatments show limited effectiveness and high toxicity. In this work, eighteen dihydrobenzofuran-type neolignans (DBNs) and two benzofuran-type neolignans (BNs) were synthesized and evaluated against amastigote forms of two Trypanosoma cruzi strains. The in vitro cytotoxicity and hemolytic activity of the most active compounds were also evaluated and their relationships with T. cruzi tubulin DBNs were investigated by an in silico approach. Four DBNs demonstrated activity against the T. cruzi Tulahuen lac-Z strain (IC₅₀ from 7.96 to 21.12 µM), and DBN 1 exhibited the highest activity against the amastigote forms of the T. cruzi Y strain (IC₅₀ 3.26 μM). Compounds 1-4 showed CC₅₀ values higher than antitrypanosomal activities, except for DBN 3. All DBNs with antitrypanosomal activity demonstrated CH₅₀ higher than 100 µM. The in silico results indicated that DBNs 1, 2, and 4 are capable of destabilizing the dynamics of the tubulin-microtubule from the vinca site. These compounds displayed promising in vitro activity against T. cruzi, especially compound 1, and can be considered molecular prototypes for the development of new antiparasitic drugs.

Models for cytotoxicity screening of antileishmanial drugs: what has been done so far?

A growing number of studies have demonstrated the in vitro potential of an impressive number of antileishmanial candidates in the past years. However, the lack of uniformity regarding the choice of cell types for cytotoxicity assays may lead to uncomparable and inconclusive data. In vitro assays relying solely on non-phagocytic cell models may not represent a realistic result as the effect of an antileishmanial agent should ideally be presented based on its cytotoxicity profile against reticuloendothelial system cells. In the present review, we have assembled studies published in the scientific literature from 2015 to 2021 that explored leishmanicidal candidates, emphasising the main host cell models used for cytotoxicity assays. The pros and cons of different host cell types as well as primary cells and cell lines are discussed in order to draw attention to the need to establish standardised protocols for preclinical testing when assessing new antileishmanial candidates.

Proteomic and Functional Analysis of the Effects of Quinoxaline Derivatives on Entamoeba histolytica

Quinoxalines are heterocyclic compounds that contain a benzene ring and a pyrazine ring. The oxidation of both nitrogen of the pyrazine ring results in quinoxaline derivatives (QdNO), which exhibit a variety of biological properties, including antiparasitic activity. However, its activity against Entamoeba histolytica, the protozoan that causes human amebiasis, is poorly understood. Recently, our group reported that various QdNOs produce morphological changes in E. histolytica trophozoites, increase reactive oxygen species, and inhibit thioredoxin reductase activity. Notably, T-001 and T-017 derivatives were among the QdNOs with the best activity. In order to contribute to the characterization of the antiamebic effect of QdNOs, in this work we analyzed the proteomic profile of E. histolytica trophozoites treated with the QdNOs T-001 and T-017, and the results were correlated with functional assays. A total number of 163 deregulated proteins were found in trophozoites treated with T-001, and 131 in those treated with T-017. A set of 21 overexpressed and 24 under-expressed proteins was identified, which were mainly related to cytoskeleton and intracellular traffic, nucleic acid transcription, translation and binding, and redox homeostasis. Furthermore, T-001 and T-017 modified the virulence of trophozoites, since they altered their erythrophagocytosis, migration, adhesion and cytolytic capacity. Our results show that in addition to alter reactive oxygen species, and thioredoxin reductase activity, T-001 and T-017 affect essential functions related to the actin cytoskeleton, which eventually affects E. histolytica virulence and survival.

Functionalized 1,2,3-triazolium salts as potential agents against visceral leishmaniasis

Visceral leishmaniasis (VL) is the most severe clinical form of leishmaniasis, being fatal if untreated. In search of a more effective treatment for VL, one of the main strategies is the development and screening of new antileishmanial compounds. Here, we reported the synthesis of seven new acetyl functionalized 1,2,3-triazolium salts, together with four 1,2,3-triazole precursors, and investigated their effect against different strains of L. infantum from dogs and humans. The 1,2,3-triazolium salts exhibited better activity than the 1,2,3-triazole derivatives with IC₅₀ range from 0.12 to 8.66 μM and, among them, compound 5 showed significant activity against promastigotes (IC₅₀ from 4.55 to 5.28 μM) and intracellular amastigotes (IC₅₀ from 5.36 to 7.92 μM), with the best selective index (SI ~ 6-9) and reduced toxicity. Our findings, using biochemical and ultrastructural approaches, demonstrated that compound 5 targets the mitochondrion of L. infantum promastigotes, leading to the formation of reactive oxygen species (ROS), increase of the mitochondrial membrane potential, and mitochondrial alteration. Moreover, quantitative transmission electron microscopy (TEM) revealed that compound 5 induces the reduction of promastigote size and cytoplasmic vacuolization. Interestingly, the effect of compound 5 was not associated with apoptosis or necrosis of the parasites but, instead, seems to be mediated through a pathway involving autophagy, with a clear detection of autophagic vacuoles in the cytoplasm by using both a fluorescent marker and TEM. As for the in vivo studies, compound 5 showed activity in a mouse model of VL at 20 mg/kg, reducing the parasite load in both spleen and liver (59.80% and 26.88%, respectively). Finally, this compound did not induce hepatoxicity or nephrotoxicity and was able to normalize the altered biochemical parameters in the infected mice. Thus, our findings support the use of 1,2,3-triazolium salts as potential agents against visceral leishmaniasis.

In Vitro and In Silico Approaches for the Antileishmanial Activity Evaluations of Actinomycins Isolated from Novel Streptomyces smyrnaeus Strain UKAQ_23

Leishmaniasis, a Neglected Tropical Parasitic Disease (NTPD), is induced by several Leishmania species and is disseminated through sandfly (Lutzomyia longipalpis) bites. The parasite has developed resistance to currently prescribed antileishmanial drugs, and it has become pertinent to the search for new antileishmanial agents. The current study aimed to investigate the in vitro and in silico antileishmanial activity of two newly sourced actinomycins, X₂ and D, produced by the novel Streptomyces smyrnaeus strain UKAQ_23. The antileishmanial activity conducted on promastigotes and amastigotes of Leishmania major showed actinomycin X₂ having half-maximal effective concentrations (EC₅₀), at 2.10 ± 0.10 μg/mL and 0.10 ± 0.0 μg/mL, and selectivity index (SI) values of 0.048 and 1, respectively, while the actinomycin D exhibited EC₅₀ at 1.90 ± 0.10 μg/mL and 0.10 ± 0.0 μg/mL, and SI values of 0.052 and 1. The molecular docking studies demonstrated squalene synthase as the most favorable antileishmanial target protein for both the actinomycins X₂ and D, while the xanthine phosphoribosyltransferase was the least favorable target protein. The molecular dynamics simulations confirmed that both the actinomycins remained stable in the binding pocket during the simulations. Furthermore, the MMPBSA (Molecular Mechanics Poisson-Boltzmann Surface Area) binding energy calculations established that the actinomycin X₂ is a better binder than the actinomycin D. In conclusion, both actinomycins X₂ and D from Streptomyces smyrnaeus strain UKAQ_23 are promising antileishmanial drug candidates and have strong potential to be used for treating the currently drug-resistant leishmaniasis.

Current status of quinoxaline and quinoxaline 1,4-di-N-oxides derivatives as potential antiparasitic agents

Parasitic diseases are a public health problem, especially in developing countries where millions of people are affected every year. Current treatments have several drawbacks: emerging resistance to the existing drugs, lack of efficacy, and toxic side effects. Therefore, new antiparasitic drugs are urgently needed to treat and control diseases that affect human health, such as malaria, Chagas disease, leishmaniasis, amebiasis, giardiasis schistosomiasis, and filariasis, among others. Quinoxaline is a compound containing a benzene ring and a pyrazine ring. The oxidation of both pyrazine ring nitrogens allows the obtention of quinoxaline 1,4-di-N-oxides (QdNOs) derivatives. By modifying the chemical structure of these compounds, it is possible to obtain a wide variety of biological properties. This review investigated the activity of quinoxaline derivatives and QdNOs against different protozoan parasites and helminths. We also cover the structure-activity relationship (SAR) and summarize the main findings related to their mechanisms of action from published works in recent years. However, further studies are needed to determine specific molecular targets. This review aims to highlight the new development of antiparasitic drugs with better pharmacological profiles than current treatments.

Epigallocathechin-O-3-Gallate Inhibits Trypanothione Reductase of Leishmania infantum, Causing Alterations in Redox Balance and Leading to Parasite Death

Leishmania infantum is a protozoan parasite that causes a vector borne infectious disease in humans known as visceral leishmaniasis (VL). This pathology, also caused by L. donovani, presently impacts the health of 500,000 people worldwide, and is treated with outdated anti-parasitic drugs that suffer from poor treatment regimens, severe side effects, high cost and/or emergence of resistant parasites. In previous works we have disclosed the anti-Leishmania activity of (-)-Epigallocatechin 3-O-gallate (EGCG), a flavonoid compound present in green tea leaves. To date, the mechanism of action of EGCG against Leishmania remains unknown. This work aims to shed new light into the leishmanicidal mode of action of EGCG. Towards this goal, we first confirmed that EGCG inhibits L. infantum promastigote proliferation in a concentration-dependent manner. Second, we established that the leishmanicidal effect of EGCG was associated with i) mitochondria depolarization and ii) decreased concentration of intracellular ATP, and iii) increased concentration of intracellular H₂O₂. Third, we found that the leishmanicidal effect and the elevated H₂O₂ levels induced by of EGCG can be abolished by PEG-catalase, strongly suggesting that this flavonoid kills L. infantum promastigotes by disturbing their intracellular redox balance. Finally, we gathered in silico and in vitro evidence that EGCG binds to trypanothione reductase (TR), a central enzyme of the redox homeostasis of Leishmania, acting as a competitive inhibitor of its trypanothione substrate.

Liposome-based nanocarrier loaded with a new quinoxaline derivative for the treatment of cutaneous leishmaniasis

The use of nanocarriers for drug delivery is a strategy aimed to improve therapeutic indices through changes in their pharmacokinetic and pharmacodynamic characteristics. Liposomes are well-investigated nanocarriers for drug delivery to macrophage-targeted therapy, the main hosts of intracellular pathogens of some infectious diseases, such as leishmaniasis. In this study, we developed hyaluronic acid (HA)-coated liposomes by different methods that can encapsulate a new quinoxaline derivative, the LSPN331, to increase its solubility and improve its bioavailability. The surface modification of liposomes and their physicochemical characteristics may depend on the coating method, which may be a critical parameter with regard to the route of administration of the antileishmanial drug. Liposomes with identical phospholipid composition containing the same drug were developed, and different biological responses were verified, and our hypothesis is that it is related to the type of modification of the surface. Different physicochemical characterization techniques (dynamic light scattering, transmission electron microscopy and UV-vis quantification of labeled-HA) were used to confirm the successful modification of liposomes as well as their stability upon storage. The encapsulation of LSPN331 was performed using HPLC method, and the entrapment efficiency (EE%) was satisfatory in all formulations, considering results of similar formulations in the literature. Furthermore, in vitro and in vivo studies were carried out to evaluate the efficacy against the parasite Leishmania amazonensis. The in vitro activity was maintained or even improved and HA-coated liposomes showed the ability to target to the site of action by the proposed routes of administration, topically and intravenously. Both formulations are promising for future tests of antileishmania activity in vivo.

N-acetyl-L-cysteine reduces Leishmania amazonensis-induced inflammation in BALB/c mice

Background

Leishmaniasis is a emergent disease characterized by different clinical manifestations in both humans and dogs. Predominant clinical features of cutaneous leishmaniasis are ulcerative painless skin lesions. Several data reported that pain is associated with human and dog leishmaniasis, out with areas of painless ulcerative lesions per se. Actually, current medications used for leishmaniasis management are characterized by several side effects and, in addition, some cases of the disease are refractory to the treatment. On this background it is mandatory the identification of new and safe candidates for designing less toxic and low-cost remedies. Therefore, the search for new leishmanicidal compounds is indispensable.

Methods

In the present paper we investigated the effect of orally N-acetyl-L-cysteine (NAC) supplementation at dose of 200 mg/Kg for 10 weeks, in subcutaneous Leishmania (L). amazonensis infected BALB/c mice. And evaluating the effect of NAC on inflammatory response such as TNF-α, IL-6, IL-1β levels, and on thermal and mechanical hyperalgesia.

Results

In the present paper we showed how NAC supplementation affected parameters of oxidative stress (GSH, MDA, SOD), inflammation such as cytokines levels (IL-1β, IL-6, TNFα) and mast cell activation and consequently on induced pain, during leishmaniosis in BALB\c mice.

Conclusions

The findings of our study provided the scientific data demonstrating that L. amazonensis infection induces inflammation and pain in BALB/c mice that are reversed by administration of NAC.

Biological activity of esters of quinoxaline-7-carboxylate 1,4-di-N-oxide against E. histolytica and their analysis as potential thioredoxin reductase inhibitors

Amoebiasis is caused by the protozoan Entamoeba histolytica that affects millions of people throughout the world. The standard treatment is metronidazole, however, this drug causes several side effects, and is also mutagenic and carcinogenic. Therefore, the search for therapeutic alternatives is necessary. Quinoxaline 1,4-di-N-oxides (QdNOs) derivatives have been shown to exhibit activity against different protozoan. In the present study, the effects of esters of quinoxaline-7-carboxylate 1,4-di-N-oxide (7-carboxylate QdNOs) derivatives on E. histolytica proliferation, morphology, ultrastructure, and oxidative stress were evaluated, also their potential as E. histolytica thioredoxin reductase (EhTrxR) inhibitors was analyzed. In vitro tests showed that 12 compounds from n-propyl and isopropyl series, were more active (IC₅₀ = 0.331 to 3.56 μM) than metronidazole (IC₅₀ = 4.5 μM). The compounds with better biological activity have a bulky, trifluoromethyl and isopropyl group at R1-, R2-, and R3-position, respectively. The main alterations found in trophozoites treated with some of these compounds included changes in chromatin, cell granularity, redistribution of vacuoles with cellular debris, and an increase in reactive oxygen species. Interestingly, docking studies suggested that 7-carboxylate QdNOs derivatives could interact with amino acid residues of the NADPH-binding domain and/or the redox-active site of EhTrxR. Enzymatic assays demonstrated that selected 7-carboxylate QdNOs inhibits EhTrxR disulfide reductase activity, and diaphorase activity shows that these compounds could act as electron acceptor substrates for the enzyme. Taken together, these data indicate that among the mechanisms involved in the antiamoebic effect of the 7-carboxylate QdNOs derivatives studied, is the induction of oxidative stress and the inhibition of EhTrxR activity.

Activity and Cell-Death Pathway in Leishmania infantum Induced by Sugiol: Vectorization Using Yeast Cell Wall Particles Obtained From Saccharomyces cerevisiae

Visceral leishmaniasis, caused by Leishmania infantum, is a neglected tropical disease, to which efforts in the innovation of effective and affordable treatments remain limited, despite the rising incidence in several regions of the world. In this work, the antileishmanial effects of sugiol were investigated in vitro. This compound was isolated from the bark of Cupressus lusitanica and showed promising activity against L. infantum. In spite of the positive results, it is known that the compound is a poorly water-soluble diterpene molecule, which hinders further investigation, especially in preclinical animal studies. Thus, in an alternative delivery method, sugiol was entrapped in glucan-rich particles obtained from Saccharomyces cerevisiae yeast cell walls (YCWPs). To evaluate the activity of sugiol, the experiments were divided into two parts: (i) the in vitro investigation of antileishmanial activity of free sugiol against L. infantum promastigotes after 24, 48, and 72 h of treatment and (ii) the evaluation of antileishmanial activity of sugiol entrapped in glucan-rich particles against intracellular L. infantum amastigotes. Free sugiol induced the cell-death process in promastigotes, which was triggered by enhancing cytosolic calcium level and promoting the autophagy up to the first 24 h. Over time, the presence of autophagic vacuoles became rarer, especially after treatment with lower concentrations of sugiol, but other cellular events intensified, like ROS production, cell shrinkage, and phosphatidylserine exposure. Hyperpolarization of mitochondrial membrane potential was found at 72 h, induced by the mitochondria calcium uptake, causing an increase in ROS production and lipid peroxidation as a consequence. These events resulted in the cell death of promastigotes by secondary necrosis. Sugiol entrapped in glucan-rich particles was specifically recognized by dectin-1 receptor on the plasma membrane of macrophages, the main host cell of Leishmania spp. Electron micrographs revealed particles containing sugiol within the infected macrophages and these particles were active against the intracellular L. infantum amastigotes without affecting the host cell. Therefore, the YCWPs act like a Trojan horse to successfully deliver sugiol into the macrophage, presenting an interesting strategy to deliver water-insoluble drugs to parasitized cells.

Synthesis of pyrazolo-1,2,4-triazolo[4,3-a]quinoxalines as antimicrobial agents with potential inhibition of DHPS enzyme

AIM

The development of a new class of antimicrobial agents is the optimal lifeline to scrap the escalating jeopardy of drug resistance.

EXPERIMENTAL

This study aims to design and synthesize a series of pyrazolo-1,2,4-triazolo[4,3-a]quinoxalines, to develop agents having antimicrobial activity through potential inhibition of dihyropteroate synthase enzyme. The target compounds have been evaluated for their in-vitro antimicrobial activity.

RESULTS & DISCUSSION

Compounds 5b, 5c were equipotent (minimal inhibitory concentration = 12.5 μg/ml) to ampicillin. The docking patterns of 5b and 5c demonstrated that both fit into Bacillus Anthracis dihydropteroate synthase pterin and p-amino benzoic acid-binding pockets. Moreover, their physicochemical properties and pharmacokinetic profiles recommend that they can be considered drug-like candidates. The results highlight some significant information for the future design of lead compounds as antimicrobial agents.

In vitro anti-Leishmania activity of T6 synthetic compound encapsulated in yeast-derived β-(1,3)-d-glucan particles

The objective of this study was to encapsulate a synthetic compound, the 4-[(2E)-N'-(2,2'-bithienyl-5-methylene)hydra-zinecarbonyl]-6,7-dihydro-1-phenyl-1H-pyrazolo[3,4-d]pyridazin-7-one (T6) in glucan-rich particles mainly composed by the cell wall of Saccharomyces cerevisiae (GPs) and to study their individual and combined activity on Leishmania infantum. The possible mechanism of action of T6 was also investigated. Our results showed the activity of T6 compound in both promastigote (IC₅₀ = 2.5 μg/mL) and intracellular amastigote (IC₅₀ = 1.23 μg/mL) forms. We also found activity against intracellular amastigote forms (IC₅₀ = 8.20 μg/mL) when the T6 compound was encapsulated in GPs. Another interesting finding was the fact that T6 encapsulated in GPs showed a significant decrease in J774A1 macrophage toxicity (CC₅₀ ≥ 18.53 μg/mL) compared to the T6 compound alone (IC₅₀ = 2.27 μg/mL). Through electron microscopy and biochemical methodologies, we verified that the activity of T6 in promastigote forms of L. infantum was characterized by events of cell death by apoptosis like increased ROS production, cell shrinkage, phosphatidylserine exposure and DNA fragmentation. We conclude that T6 can be considered a promising anti-Leishmania compound, and that the use of GPs for drug encapsulation is an interesting approach to the development of new effective and less toxic formulations.

Bovine serum albumin nanoparticles containing amphotericin B were effective in treating murine cutaneous leishmaniasis and reduced the drug toxicity

Cutaneous leishmaniasis is the most common form of leishmaniasis and the available chemotherapy causes serious side effects, justifying the search for new therapies. This study investigated the antileishmanial activity of bovine serum albumin (BSA) nanoparticles containing amphotericin B (AmB) against Leishmania amazonensis. The antiproliferative activity against promastigotes and amastigotes was assessed and the cytotoxicity was determined and compared to commercial AmB-deoxycholate (AmB-D). In vivo antileishmania activity was evaluated in murine cutaneous leishmaniasis model. BSA nanoparticles showed spherical shape, mean size about 180 nm, zeta potential of ≈ -45 mV and AmB encapsulation efficiency >95%. AmB-D was effective in promastigote and amastigote forms, while AmB-loaded BSA nanoparticles were more effective against amastigotes than promastigotes. AmB-D was more effective than AmB-loaded BSA nanoparticles in both forms, however, the lowest cytotoxicity against macrophages was achieved by AmB-nanoparticles. BALB/c mice treated with AmB-D or AmB-loaded BSA nanoparticles showed a significant decrease in the lesion thickness at the infected footpad. Histopathological analysis after 3 weeks of treatment revealed AmB-D-related toxicity in heart, spleen, lung, liver and kidneys, while treatment with AmB-loaded BSA nanoparticles did not reveal tissue toxicity. The antileishmanial efficacy and the reduced toxicity become BSA nanoparticles containing AmB a potential candidate for treating cutaneous leishmaniasis.

Isopropyl quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives induce regulated necrosis-like cell death on Leishmania (Leishmania) mexicana

Leishmaniasis is a neglected tropical disease caused by the parasite of the genus Leishmania. About 13 million people are infected worldwide, and it is estimated that 350 million are at risk of infection. Clinical manifestations depend on the parasite species and factors related to the host such as the immune system, nutrition, housing, and financial resources. Available treatments have severe side effects; therefore, research currently focuses on finding more active and less toxic compounds. Quinoxalines have been described as promising alternatives. In this context, 17 isopropyl quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives were evaluated as potential leishmanicidal agents. Their effect on the cell metabolism of Leishmania mexicana promastigotes and their cytotoxic effects on the J774.A1 cell line and on erythrocytes were evaluated, and their selectivity index was calculated. Compounds T-069 (IC₅₀ = 1.49 μg/mL), T-070 (IC₅₀ = 1.71 μg/mL), T-072 (IC₅₀ = 6.62 μg/mL), T-073 (IC₅₀ = 1.25 μg/mL), T-085 (IC₅₀ = 0.74 μg/mL), and T-116 (IC₅₀ = 0.88 μg/mL) were the most active against L. mexicana promastigotes and their mechanism of action was characterized by flow cytometry and microscopy. Compound T-073, the most selective quinoxaline derivative, induced cell membrane damage, phosphatidylserine exposition, reactive oxygen species production, disruption of the mitochondrion membrane potential, and DNA fragmentation, all in a dose-dependent manner, indicating the induction of regulated necrosis. Light and transmission electron microscopy showed the drastic morphological changes induced and the mitochondrion as the most sensitive organelle in response to T-073. This study describes the mechanism by which active isopropyl quinoxaline-7-carboxylate 1,4-di-N-oxide quinoxalines affect the parasite.

Acyclic Sesquiterpenes from the Fruit Pericarp of Sapindus saponaria Induce Ultrastructural Alterations and Cell Death in Leishmania amazonensis

Previous studies reported antiprotozoal activities of Sapindus saponaria L. The aim of this work was the evaluation of antileishmanial activity and mechanism of action of extract and fractions of S. saponaria L. Hydroethanolic extract (EHA) obtained from fruit pericarps was fractionated using solid-phase extraction in a reversed phase, resulting in fractions enriched with saponins (SAP fraction) and acyclic sesquiterpene oligoglycosides (OGSA fraction). The activities of EHA, SAP, and OGSA were evaluated by antiproliferative assays with promastigote and intracellular amastigote forms. Cytotoxicity on macrophages and hemolytic activity were also analyzed. Morphological and ultrastructural changes in Leishmania amazonensis promastigotes were evaluated by electron microscopy. Flow cytometry was used to investigate mitochondrial dysfunction and phosphatidylserine exposure. OGSA was more selective for parasites than mammalian J774A1 macrophage cells, with selectivity indices of 3.79 and 7.35, respectively. Our results showed that only the OGSA fraction did not present hemolytic activity at its IC₅₀ for promastigote growth. Electron microscopy revealed changes in parasite flagellum, cell body shape, and organelle size, mainly mitochondria. Flow cytometry analysis indicated mitochondrial membrane and cell membrane dysfunction. OGSA showed antileishmanial activity, resulting in several changes to protozoa cells, including mitochondrial depolarization and early phosphatidylserine exposure, suggesting a possible apoptotic induction.

N-acetyl-cysteine inhibits liver oxidative stress markers in BALB/c mice infected with Leishmania amazonensis

BACKGROUND

Leishmaniasis is a parasitosis caused by several species of the genus Leishmania. These parasites present high resistance against oxidative stress generated by inflammatory cells.

OBJECTIVES

To investigate oxidative stress and molecular inflammatory markers in BALB/c mice infected with L. amazonensis and the effect of antioxidant treatment on these parameters.

METHODS

Four months after infection, oxidative and inflammatory parameters of liver, kidneys, spleen, heart and lungs from BALB/c mice were assessed.

FINDINGS

In liver, L. amazonensis caused thiol oxidation and nitrotyrosine formation; SOD activity and SOD2 protein content were increased while SOD1 protein content decreased. The content of the cytokines IL-1β, IL-6, TNF-α, and the receptor of advanced glycation endproducts (RAGE) increased in liver. Treatment with the antioxidant N-acetyl-cysteine (20 mg/kg b.w) for five days inhibited oxidative stress parameters.

MAIN CONCLUSIONS

L. amazonensis induces significant alterations in the redox status of liver but not in other organs. Acute antioxidant treatment alleviates oxidative stress in liver, but it had no effect on pro-inflammatory markers. These results indicate that the pathobiology of leishmaniasis is not restricted to the cutaneous manifestations and open perspectives for the development of new therapeutic approaches to the disease, especially for liver function.

Induction of Early Autophagic Process on Leishmania amazonensis by Synergistic Effect of Miltefosine and Innovative Semi-synthetic Thiosemicarbazone

Drug combination therapy is a current trend to treat complex diseases. Many benefits are expected from this strategy, such as cytotoxicity decrease, retardation of resistant strains development, and activity increment. This study evaluated in vitro combination between an innovative thiosemicarbazone molecule – BZTS with miltefosine, a drug already consolidated in the leishmaniasis treatment, against Leishmania amazonensis. Cytotoxicity effects were also evaluated on macrophages and erythrocytes. Synergistic antileishmania effect and antagonist cytotoxicity were revealed from this combination therapy. Mechanisms of action assays were performed in order to investigate the main cell pathways induced by this treatment. Mitochondrial dysfunction generated a significant increase of reactive oxygen and nitrogen species production, causing severe cell injuries and promoting intense autophagy process and consequent apoptosis cell death. However, this phenomenon was not strong enough to promote dead in mammalian cell, providing the potential selective effect of the tested combination for the protozoa. Thus, the results confirmed that drugs involved in distinct metabolic routes are promising agents for drug combination therapy, promoting a synergistic effect.

Anti-Leishmania amazonensis activity of Serjania lethalis A. St.-Hil

Extracts of Serjania lethalis A. St.-Hil leaves and stems were tested in order to identify potential agents against Leishmania amazonensis. The hexane fraction (HF) and dichloromethane subfractions (DDF and MDF) showed leishmanicidal effect. The anti-promastigote IC₅₀ values were 10.29 (HF), 11.41 (DDF) and 28.33μg⁄mL (MDF); whereas those against amastigote were 7.2 (HF), 8.1 (DDF) and 6.5μg⁄mL (MDF). Among the fractions and subfractions assayed, only HF altered the cell cycle of the parasite, increasing 3-fold the number of cells in the sub-G0/G1 phase. HF also changed the parasite mitochondrial membrane potential (ΔΨm) and the percentage of annexin-V-propidium iodide positive promastigotes. Our evaluations of the IC₅₀ values showed that HF, DDF and MDF decreased NO production in infected macrophages stimulated with IFN-γ and LPS. Moreover, HF increased the production of TNF-α in Leishmania infected macrophages. This paper reports for the first time the leishmanicidal activity of extracts and fractions of Serjania lethalis leaves and also characterizes its leishmanicidal and immunomodulatory properties.

Antileishmanial activity of antiretroviral drugs combined with miltefosine

Co-infection of Leishmaniasis, a neglected tropical disease, with human immunodeficiency virus (HIV) has hindered treatment efficacy. In this study, we aim to evaluate the antileishmanial activity of two protease inhibitors (darunavir and atazanavir) and four reverse transcriptase inhibitors (tenofovir, efavirenz, neviraprine, and delavirdine mesylate) on Leishmania infantum. The activity of different antiretrovirals combinations and of antiretroviral with miltefosine, a drug used on leishmaniasis treatment, was also evaluated. Only two non-nucleoside reverse transcriptase inhibitors (NNRTIs) were active on L. infantum. Efavirenz showed the best antileishmanial activity on promastigotes cells with IC50 value of 26.1 μM followed by delavirdine mesylate with an IC50 value of 136.2 μM. Neviraprine, tenofovir, atazanavir, and darunavir were not active at the concentrations tested (IC50 > 200 μM). The efavirenz also showed high antileishmanial activity on intramacrophage amastigotes with IC50 of 12.59 μM. The interaction of efavirenz with miltefosine improved antileishmanial activity on promastigotes and intracellular amastigotes (IC50 values of 11. 8 μM and 8.89 μM, respectively). These results suggest that combined-therapy including efavirenz and miltefosine could be alternative options for treating Leishmaniasis and Leishmania/HIV co-infections.