Search Results (191)

Background/Objectives: Leishmaniasis constitutes one of the most fatal parasitic diseases globally, adversely impacting the health of individuals residing in both intertropical and temperate zones. In these geographical areas, the administration of treatment is often inconsistent and largely ineffective with the available pharmaceuticals, as these exhibit more pronounced side effects than the therapeutic advantages they purport to provide. Methods: Consequently, the current investigation seeks to engage in molecular modeling of novel pharmacological candidates incorporating 1,2,3 disubstituted triazole moieties, coordinated with Cu^II metal centers, in pursuit of promising bioactive properties. Results: Two complexes were prepared and X-ray analysis revealed a comparable structural configuration surrounding the copper (II) atom. The planar square coordination geometry was elucidated through the assessment of the ${\tau }_4=0$ (tau four) parameters. The comprehensive characterization encompasses HRMS-ESI (+), NMR, elemental analyses, mid-infrared, and UV-vis spectroscopic techniques. Time-dependent density functional theory (TD-DFT) analyses will substantiate the findings obtained through UV-vis spectroscopy. Crucially, the biological assays against Leishmania (L.) amazonensis revealed that Complex 1 exhibited outstanding potency against the intracellular amastigote form, demonstrating a half-maximal inhibitory concentration (IC₅₀) of 0.4 µM. This activity was 6-fold higher than that of amphotericin B (IC₅₀ = 2.5 µM) and 33-fold higher than pentamidine (IC₅₀ = 13.3 µM). Furthermore, Complex 1 showed a promising selectivity index (SI = 9.7) against amastigotes, surpassing the reference drugs and meeting the criteria for a lead compound. While less active on promastigotes, both complexes demonstrated high stability in DMSO solution, a prerequisite for biological testing. Conclusions: These results unequivocally identify Complex 1 as a highly promising candidate for the development of new antileishmanial therapies, warranting further in vivo studies. Full article

Leishmaniasis is a severe parasitic disease transmitted by sandflies that affects both humans and animals, with clinical manifestations ranging from cutaneous lesions to life-threatening visceral involvement. Current treatments are limited by toxicity, high cost, and the emergence of drug-resistant strains, underscoring the need for safer and more effective therapeutic strategies. In this study, we investigated the antiparasitic potential of combining Amphotericin B, a drug commonly used for leishmaniasis treatment, with 1,10-phenanthroline-5,6-dione (phendione) coordinated to copper (Cu²⁺-phendione), an experimental coordination compound, against Leishmania amazonensis promastigotes. The combination markedly impaired parasite proliferation, disrupted ultrastructural integrity, and interfered with metabolic activity. Mechanistic analyses revealed the presence of autophagosomes and pronounced mitochondrial alterations in treated parasites, suggesting the induction of cellular stress and the disruption of essential survival pathways. In addition, the treatment reduced the association index with THP-1 cells, indicating a decrease in parasite infectivity. Collectively, these findings demonstrate that the combination of Cu²⁺-phendione and Amphotericin B exerts potent antiparasitic effects through multiple mechanisms. Our results also showed that Cu²⁺-phendione combined with AmB displayed an additive effect, although the isobologram suggested that certain ratios approached synergy. The results support the potential of this combination as a novel chemotherapeutic approach against leishmaniasis and provide a basis for future in vivo studies to evaluate safety, efficacy, and optimal dosing strategies. Full article

Background/Objectives: Leishmaniasis is a neglected parasitic disease with significant global impact and limited therapeutic options due to the toxicity and cost of current treatments. Antimicrobial peptides (AMPs) derived from amphibians, such as Ocellatin-PT4 and Ocellatin-PT6, have emerged as promising bioactive molecules due to their antimicrobial properties and low toxicity to mammalian cells. This study evaluated the leishmanicidal and immunomodulatory effects of Ocellatin-PT4 and Ocellatin-PT6 against Leishmania amazonensis amastigotes. Methods: Peptides were tested on axenic amastigotes and macrophages infected with amastigotes. Cytotoxicity was assessed using MTT (0.4–197 µM for Ocellatin-PT4 and 0.3–152.1 µM for Ocellatin-PT6) and vital dye exclusion assays. Reactive oxygen species (ROS), nitric oxide (NO), and lipid droplet (LD) production were quantified to assess immunomodulatory responses. Results: Ocellatin-PT4 and Ocellatin-PT6 significantly reduced the viability of free and intracellular amastigotes at concentrations ≥ 24.7 µM and ≥19 µM, respectively, without affecting J774 macrophage viability. Infected macrophages treated with the peptides showed reduced parasite load and decreased infection index (≥12.3 µM for Ocellatin-PT4 and ≥2.4 µM for Ocellatin-PT6). Both peptides modulated the oxidative stress response: they reduced ROS levels in infected macrophages while only slightly increasing NO production at higher concentrations. Additionally, lipid droplet accumulation, which was increased during infection, was downregulated by both peptides—particularly by Ocellatin-PT6. Conclusions: Ocellatin-PT4 and Ocellatin-PT6 exert leishmanicidal effects and modulate key macrophage functions without cytotoxicity. These peptides represent promising candidates for the development of novel therapies against cutaneous leishmaniasis. Full article

Photodynamic therapy (PDT), which combines light and dyes, has emerged as a cost-effective, selective, and less toxic alternative to conventional chemotherapy for cutaneous leishmaniasis (CL), offering potential benefits for millions, especially those who are socioeconomically vulnerable. Therefore, this study investigated the in vitro effects of methylene blue (MB), a widely used photosensitizer with proven clinical efficacy, along with its derivatives—new methylene blue—NMB, NMB-B, and NMB-P—in PDT against L. amazonensis promastigotes, using a red LED device. Inhibitory concentrations (ICs) and 168 h proliferation curves were obtained. The production of reactive oxygen species (ROS) and the mechanism of cell death induction were analyzed by flow cytometry. PDT enhanced leishmanicidal effects compared to non-PDT conditions, reducing ICs by up to 85% and outperforming miltefosine, reaching the submicromolar range (IC_25NMB-P = 0.73 ± 0.16 µM, p < 0.05). The proliferation curve showed a consistent inhibitory effect, with MB exhibiting a greater decline than miltefosine, a pattern also observed with MB derivatives. PDT also increased ROS production by up to 5-fold and induced apoptosis-like cell death, characterized by AV⁺ parasites (up to 51.49 ± 2.90%, p < 0.0001). The results demonstrated that the tested dyes effectively eliminated L. amazonensis promastigotes, highlighting the potential of the NMB derivatives as photosensitizers and supporting further investigations. Full article

Chemotherapy for cutaneous leishmaniasis is hindered by high toxicity, adverse effects, and increasing drug resistance. Thus, safer and more selective therapies are urgently required. Here, we evaluated the antiparasitic efficacy of methylene blue (MB) and new MB, as well as novel ruthenium complex derivatives (NMB-B and NMB-P) against promastigote and amastigote forms of Leishmania amazonensis. Their cytotoxicity and selectivity on L929, HepG2, VERO, J774.G8 cells, and murine peritoneal macrophages were measured. Mechanisms of action were explored via flow cytometry, assessing morphological changes, mitochondrial depolarization, ROS production, and cell death. The compounds inhibited parasite proliferation in a dose and time-dependent manner, achieving submicromolar efficacy against amastigotes (NMB-P = 0.46 μM). No cytotoxicity was observed on L929, J774.G8, and VERO cells (except NMB), while HepG2 and murine peritoneal macrophages showed low to moderate toxicity. Selective indexes reached 84 for promastigotes and over 500 for amastigotes. The compounds induced mitochondrial depolarization by up to 61% and a five-fold increase in ROS levels, leading to structural damage and parasite death via late apoptosis/necrosis-like mechanisms. These findings indicate that the compounds act selectively and trigger the release of oxidative species, exerting leishmanicidal activity and warranting further investigation. Full article

Phytochemical investigation of Radula voluta, a liverwort species collected in the Ecuadorian Amazon, led to the isolation of four known bibenzyl derivatives: 2-prenyl-3,5-dihydroxy-bibenzyl (1), 2-geranyl-3,5-dihydroxybibenzyl (2), 2,2-dimethyl-5-phenethyl-2H-chromen-7-ol (3), and radulanin L (4). Structural elucidation was achieved through extensive NMR and MS analyses, supported by comparison with previously reported data. Compounds 1 and 4 are reported for the first time in R. voluta. The crude extract and isolated compounds were evaluated for their in vitro antiprotozoal activity against Trypanosoma cruzi, Leishmania amazonensis, Leishmania donovani, Naegleria fowleri, and Acanthamoeba castellanii Neff. Among the isolated compounds, bibenzyls 2 and 4 exhibited the most potent activity across multiple protozoan strains. Cytotoxicity was assessed against murine macrophages (J774A.1), obtaining moderate–low toxicities against compounds 1 and 3. These findings highlight the pharmacological value of liverwort-derived bibenzyls and support further research on R. voluta as a promising source of antiparasitic leads. Full article

Background/Objective: American tegumentary leishmaniasis is a neglected tropical disease with limited therapeutic options characterized by high toxicity and poor tolerability. Drug repurpose offers a pragmatic strategy to accelerate the development of safer treatments. This study evaluated the antileishmanial activity of three clinically approved acetylcholinesterase (AChE) inhibitors—donepezil hydrochloride (DH), rivastigmine tartrate (RT), and galantamine hydrobromide (GH), tested individually and in combination with amphotericin B (AmpB) against Leishmania species relevant to tegumentary leishmaniasis. Methods: Antileishmanial activity was assessed against Leishmania (Leishmania) amazonensis promastigotes and intracellular amastigotes and Leishmania (Viannia) braziliensis promastigotes and axenic amastigotes. Cytotoxicity was evaluated in mammalian cell lines. The synergy with AmpB was analyzed at different proportions. Mechanistic studies included morphological analysis using light and scanning electron microscopy, flow cytometry, AChE activity assays, choline supplementation experiments, and membrane fluidity measurements. Results: All three AChE inhibitors demonstrated antileishmanial activity with selectivity indices > 1. DH emerged as the most promising candidate (IC₅₀ = 16.82 μM against promastigotes; SI = 10.25), with superior potency compared to other repurposed drugs. Strong synergistic interactions with AmpB were observed for all inhibitors (χΣFIC ≤ 0.17), with DH-AmpB displaying the most robust synergy (χΣFIC = 0.09), reducing the IC ₅₀ of AmpB by nearly 90-fold. DH induced distinct morphological alterations and acted through non-cholinergic mechanisms. The DH-AmpB combination retained maximal efficacy against L. (V.) braziliensis, with enhanced activity against clinically relevant amastigotes. Conclusions: Repurposed AChE inhibitors, particularly donepezil hydrochloride, are highly promising therapeutic candidates for tegumentary leishmaniasis. The robust synergistic effect with amphotericin B, together with their favorable safety profiles and non-antimicrobial mechanisms, positions these drugs as viable partners in dose-sparing combination regimens that could improve treatment adherence and reduce toxicity in endemic areas. Full article

Calcineurin (CaN), a Ca²⁺-dependent phosphatase, plays key roles in eukaryotic cell signaling. We investigated whether Leishmania amazonensis’ two infective forms—promastigotes and amastigotes—exhibit differences in CaN expression, localization, and functional impact, using two canonical inhibitors (cyclosporin A, CsA; tracolimus, FK506). At high 40 µM CsA, promastigotes showed reduced viability, whereas amastigotes remained resistant. FK506 had no effect on either form. At a sub-lethal 25 µM CsA, parasite proliferation remained unaffected. In parasite–macrophage co-incubation assays, phosphorylation patterns differed: amastigotes—but not promastigotes—showed increased serine/threonine phosphorylation upon CaN inhibition. Western blotting and in silico data revealed higher CaN catalytic (CaNA2) and regulatory (CaNB) subunit expression in amastigotes than promastigotes. Immunofluorescence localized CaNA prominently in both cytoplasm and nucleus of promastigotes, but predominantly cytoplasmic in amastigotes; CaNB was largely cytoplasmic in both. In silico localization predictions suggested strong membrane associations for CaNA in Leishmania, contrasting with mammalian models. Subcellular fractionation confirmed CaNA enrichment in membrane fractions, with CaNB in cytoplasmic and nuclear fractions. Collectively, these findings reveal form-specific differences in expression, subcellular distribution, and inhibitor responses of CaN in L. amazonensis, highlighting its potential as a stage-specific therapeutic target in leishmaniasis. Full article

Background: Leishmania amazonensis, one of the causative agents of cutaneous leishmaniasis, is responsible for a neglected tropical disease affecting nearly one million individuals worldwide. Although clinical treatments are available, their effectiveness is often compromised by high toxicity and limited selectivity. Methods: From a database, 64 chalcone derivatives were studied using Comparative Molecular Similarity Indices Analysis (CoMSIA) and Hansch analysis (2D-QSAR) to construct predictive computational models. Internal and external validation criteria were applied to identify structural determinants associated with antileishmanial activity. Based on these insights, twelve novel quinoline–chalcone hybrids were designed, synthesized, and biologically evaluated against L. amazonensis. Results: The most robust CoMSIA model combined steric and hydrogen-bond acceptor fields (CoMSIA-SA), while Hansch analysis highlighted electronic descriptors—specifically LUMO energy and the global electrophilicity index—as critical for parasite growth inhibition. Guided by these computational findings, a new series of 12 hybrid quinoline–chalcone derivatives (E001–E012) was synthesized through a two-step procedure, achieving overall yields of 43–71%. Biological assays demonstrated that four compounds displayed inhibitory activity comparable to amphotericin B. Furthermore, physicochemical profiling and in silico pharmacokinetic predictions for the most active compounds (E003, E005, E006, and E011) indicated favorable biocompatibility and drug-like properties. Conclusions: These results underscore the value of an integrative computational–experimental approach in the rational design of next-generation L. amazonensis inhibitors, reinforcing chalcone-based scaffolds as promising pharmacophoric frameworks for antileishmanial drug discovery. Full article

Antibody-free nucleic acid lateral flow assays (AF-NALFA) are an established approach for rapid detection of amplified pathogens DNA but can yield inconsistent signals across targets. Since AF-NALFA depends on dual hybridization of probes to single-stranded amplicons (ssDNA), site-specific thermodynamic (Gibbs free energy-ΔG) at probe-binding regions may be crucial for performance. This study investigated how site-specific-ΔG and sequence complementarity at probe-binding regions determine Test-line signal generation, comparing native and synthetic amplicons and assessing the effects of local secondary structures and mismatches. Asymmetric PCR-generated ssDNA amplicons of Listeria monocytogenes, Mycobacterium leprae, and Leishmania amazonensis were analyzed in silico and tested in AF-NALFA prototypes with gold-labeled thiol probes and biotinylated capture probes. T-line signals were photographed, quantified (ImageJ version 1.4k), and statistically correlated with site-specific-ΔG. While native ssDNA from M. leprae and L. amazonensis failed to produce AF-NALFA T-line signals, L. monocytogenes yielded strong detection. Site-specific-ΔG below −10 kcal/mol correlated with reduced hybridization. Synthetic oligos preserved signals despite structural constraints, whereas ~3–4 mismatches, especially at capture probe regions, markedly impaired T-line intensity. The performance of AF-NALFA depends on the synergism between thermodynamic accessibility, site-specific-ΔG-induced site constraints, and sequence complementarity. Because genomic context affects hybridization, target-specific thermodynamic in silico evaluation is necessary for reliable pathogen DNA detection. Full article

Cell membranes and the cytoskeleton play crucial roles in the regulation of cellular responses by mediating mechanical forces and physical stimuli from the microenvironment through their viscoelastic properties. Investigating these properties provides valuable insights into disease mechanisms and therapeutic strategies. Gold nanorods (GNRs), especially under irradiation, exhibit lethal effects against Leishmania parasites through plasmonic photothermal conversion. In this study, we focus on evaluating the effects of non-irradiated GNRs on macrophage properties to better understand their intrinsic interactions with cells and support the development of future phototherapy applications. Here, defocusing microscopy (DM), a quantitative phase microscopy technique, was used to analyze membrane fluctuations in macrophages ($M\varnothing s$) exposed to GNRs (average length of $43\pm 8 \mathrm{n}\mathrm{m}$ and diameter of $20\pm 4 \mathrm{n}\mathrm{m}$) and infected with Leishmania amazonensis. By quantifying membrane–cytoskeleton fluctuation from defocused images, we extracted viscoelastic parameters, including bending modulus ($k_c$) and viscosity ($\eta$), to characterize membrane behavior in detail. Our results show that infection increases both $k_c$ and $\eta$, while treatment at IC₅₀ reduces infection and selectively increases $k_c$ without affecting $\eta$. In healthy macrophages, exposure to GNRs resulted in a reduction in both parameters, indicative of increased membrane fluidity and cytoskeletal rearrangement. These findings provide new insights into the biomechanical effects of GNRs on macrophages and may enlighten the design of future phototherapeutic approaches. Full article

Background/Objectives: Canine visceral leishmaniasis (CVL) is one of the main neglected protozoan diseases in the world. Dogs play a fundamental role in the maintenance of Leishmania infantum in the Americas, and we have already encountered resistance problems with drugs currently used in these animals. Methods: In view of this, two new immunotherapeutic protocols were tested in 48 dogs, using L. amazonensis antigens plus saponin (LaSap) and only L. amazonensis antigens (La) as a control group. Dogs naturally infected with L. infantum were divided into four groups, according to clinical staging. A total of 24 dogs (stages 1 and 2) received a four-dose protocol, and another 24 dogs (stages 3 to 5) received six doses. All animals received a booster dose every three months until they were one year old. Results: Our results showed that dogs in the early stages of the disease respond better and are able to remain stable for longer, maintaining baseline laboratory biomarkers, in addition to having a lower parasite load. Conclusions: On the other hand, dogs in more advanced stages have a poor response, with stage 3 being a key point in clinical progression or regression. Full article

Background/Objectives: Leishmaniasis is a zoonotic and anthropozoonotic disease with significant public health impact worldwide and is classified as a neglected tropical disease. The search for new affordable treatments, particularly oral and/or topical ones that are easy to administer and have fewer side effects, remains a priority for the scientific community in this field of research. In previous investigations, 3-alkoxy-1-benzyl-5-nitroindazole derivatives showed remarkable in vitro results against Leishmania species, and predictions of absorption, distribution, metabolism, excretion, and toxicity properties, as well as pharmacological scores, of the compounds classified as active were superior to those of amphotericin B, indicating their potential as candidates for in vivo studies. Therefore, the aim of the present study was to evaluate the in vivo antileishmanial activity of the indazole derivatives NV6 and NV16. Methods: The compounds were administered intralesionally at concentrations of 10 and 5 mg/kg in a BALB/c mouse model of cutaneous leishmaniasis caused by Leishmania amazonensis. To evaluate the efficacy of the compounds, indicators such as lesion size, ulcer area, lesion weight, and parasitic load were determined. Amphotericin B was used as a positive control. Results: The compound NV6 showed leishmanicidal activity comparable to that observed with amphotericin B, with a significant reduction in lesion development and parasite load, while NV16 caused a reduction in ulcer area. Conclusions: These results provide strong evidence for the antileishmanial activity of NV6 and support future studies to improve its pharmacokinetic profile, as well as the investigation of combination therapies with other chemotherapeutic agents currently in use. Full article

Leishmaniasis is a significant public health concern, affecting millions and causing substantial mortality, thus urgently requiring more effective and safer treatments. This study explored the potential of 33 novel N-acylhydrazone-derived compounds against Leishmania amazonensis parasites, focusing on their inhibition of the Leishmania arginase enzyme and promastigote growth. Compounds 8 and 18 showed over 90% inhibitory activity against promastigote cultures after 72 h of treatment. Compound 8 showed an IC₅₀ of 10.5 µM (9.4–11.8 µM), while compound 18 exhibited an IC₅₀ of 42.8 µM (41.3–44.4 µM). The antipromastigote effects of these compounds highlight their potential for further new drug design. These findings offer a promising starting point for addressing the pressing need for new therapeutic options against leishmaniasis. In addition, we used web-based tools to predict the compounds’ toxicity and pharmacokinetic parameters. Despite the lack of inhibition against the L. amazonensis arginase enzyme, further investigation into the mechanisms of action of these compounds and in vivo efficacy could contribute to the development of safer and more effective treatments for this neglected tropical disease. Full article

Natural products have long been recognized as invaluable resources in drug discovery. Essential oils have attracted widespread attention due to their broad spectrum of biological activities. Herein, we report the anti-kinetoplastid activity of Aloysia citrodora leaf essential oil through a bioassay-guided fractionation method against the etiological agents of Chagas disease and leishmaniasis. This approach has led to the isolation and structural identification of compound 1 (citral) as the main active constituent, with IC₅₀ values of 8.47 μM against Leishmania amazonensis and 12.90 μM against Trypanosoma cruzi. In addition, eight compounds (2–9) were synthesized and evaluated. Among these, citral 2,4-dinitrophenylhydrazone (9) exhibited the highest anti-kinetoplastid activity, with an IC₅₀ value of 10.62 μM against L. amazonensis, displaying a similar biological profile to citral and the reference drug. Structure–activity relationship studies revealed that the type of Schiff base and acylating agent played a crucial role in the activity. Mechanism of action studies demonstrated that compound 9 directly targets the apoptotic pathway, inducing programmed cell death through selective pathway inhibition. This work underscores the potential of A. citrodora essential oil and its compounds as prospective therapeutic leads against neglected tropical diseases. Full article