Challenges and Tools for In Vitro Leishmania Exploratory Screening in the Drug Development Process: An Updated Review

Eugenol-Rich Essential Oil from Pimenta dioica: In Vitro and In Vivo Potentialities against Leishmania amazonensis

Pimenta dioica L. is one the most recognized species with diverse biological activities. In this study, in vitro activity and in vivo efficacy of essential oil from P. dioica (EO-Pd) was evaluated. The main compound was also included in the animal studies and its in silico prediction related to biological activities, molecular ligands, drug likeness, and ADME (absorption, distribution, metabolism, and excretion) properties are listed. The chemical composition analyzed by GC-MS retrieved 45 components, which the most abundant compound was the eugenol (80.1%). The EO-Pd was able to inhibit the growth of L. amazonensis (IC50 = 9.7 ± 0.7 and 11.3 ± 2.1 µg/mL, promastigotes and amastigotes, respectively). The cytotoxicity assay showed a CC50 of 104.5 ± 0.9 µg/mL and a selectivity index of 9. In the model of cutaneous leishmaniasis in BALB/c mice, the effect of EO-Pd and eugenol was observed after treatment at 30 mg/kg by intralesional route with 5 administrations every 4 days. In the in silico predictions, some targets that justified the antileishmanial activity of eugenol and good drug like properties for this compound, were obtained. This study showed for first time the potential of EO-Pd to inhibit L. amazonensis, which could be linked to the activity of major compound eugenol.

Characterization of Leishmania Parasites Isolated from Naturally Infected Mammals

Leishmaniasis is spreading in Europe, especially in endemic countries such as Italy and Spain, in part due to ongoing climate change and the increase in travel and migration. Although Leishmania infantum is the main agent responsible for this disease in humans and animals, other species and hybrids have been detected. This highlights the need to continue isolating and characterizing Leishmania strains from biological samples of infected hosts. In this study, we characterized the recently isolated parasites L. infantum NAV and L. infantum TDL, obtained from naturally infected mammals (dogs), and we compared them with the widely distributed and studied strain L. infantum BCN 150. Both NAV and TDL promastigotes showed a slower growth rate than BCN 150 and were significantly more sensitive to amphotericin B and miltefosine. Furthermore, the expression of the CYCA gene (involved in cell cycle and proliferation) was significantly downregulated in NAV and TDL isolates. On the other hand, CYC6 (implicated in treatment resistance) and APG9 (related to the recycling of protein under stress conditions and/or while undergoing a differentiation process and treatment resistance) levels were upregulated, compared to those measured in BCN 150. Both isolates displayed a higher infection capacity (>3 amastigotes per macrophage and >70% of infected macrophages) compared to controls (<2 amastigotes/cells and <50% of infected macrophages). Finally, a higher susceptibility to miltefosine treatment was observed in intracellular NAV and TDL amastigotes. In conclusion, TDL and NAV are novel Leishmania isolates that might be useful for in vitro and in vivo assays that will allow a better understanding of the parasite biology in Mediterranean areas.

Flavonoid Derivatives as New Potent Inhibitors of Cysteine Proteases: An Important Step toward the Design of New Compounds for the Treatment of Leishmaniasis

Leishmaniasis is a neglected tropical disease, affecting more than 350 million people globally. However, there is currently no vaccine available against human leishmaniasis, and current treatment is hampered by high cost, side-effects, and painful administration routes. It has become a United Nations goal to end leishmaniasis epidemics by 2030, and multitarget drug strategy emerges as a promising alternative. Among the multitarget compounds, flavonoids are a renowned class of natural products, and a structurally diverse library can be prepared through organic synthesis, which can be tested for biological effectiveness. In this study, we synthesised 17 flavonoid analogues using a scalable, easy-to-reproduce, and inexpensive method. All synthesised compounds presented an impressive inhibition capacity against rCPB2.8, rCPB3, and rH84Y enzymes, which are highly expressed in the amastigote stage, the target form of the parasite. Compounds 3c, f12a, and f12b were found to be effective against all isoforms. Furthermore, their intermolecular interactions were also investigated through a molecular modelling study. These compounds were highly potent against the parasite and demonstrated low cytotoxic action against mammalian cells. These results are pioneering, representing an advance in the investigation of the mechanisms behind the antileishmanial action of flavonoid derivatives. Moreover, compounds have been shown to be promising leads for the design of other cysteine protease inhibitors for the treatment of leishmaniasis diseases.

Exploring direct and indirect targets of current antileishmanial drugs using a novel thermal proteomics profiling approach

Visceral leishmaniasis (VL), caused by Leishmania infantum, is an oft-fatal neglected tropical disease. In the absence of an effective vaccine, the control of leishmaniasis relies exclusively on chemotherapy. Due to the lack of established molecular/genetic markers denoting parasite resistance, clinical treatment failure is often used as an indicator. Antimony-based drugs have been the standard antileishmanial treatment for more than seven decades, leading to major drug resistance in certain regions. Likewise, drug resistance to miltefosine and amphotericin B continues to spread at alarming rates. In consequence, innovative approaches are needed to accelerate the identification of antimicrobial drug targets and resistance mechanisms. To this end, we have implemented a novel approach based on thermal proteome profiling (TPP) to further characterize the mode of action of antileishmanials antimony, miltefosine and amphotericin B, as well as to better understand the mechanisms of drug resistance deployed by Leishmania. Proteins become more resistant to heat-induced denaturation when complexed with a ligand. In this way, we used multiplexed quantitative mass spectrometry-based proteomics to monitor the melting profile of thousands of expressed soluble proteins in WT, antimony-resistant, miltefosine-resistant, and amphotericin B-resistant L. infantum parasites, in the presence (or absence) of the above-mentioned drugs. Bioinformatics analyses were performed, including data normalization, melting profile fitting, and identification of proteins that underwent changes (fold change &gt; 4) caused by complexation with a drug. With this unique approach, we were able to narrow down the regions of the L. infantum proteome that interact with antimony, miltefosine, and amphotericin B; validating previously-identified and unveiling novel drug targets. Moreover, analyses revealed candidate proteins potentially involved in drug resistance. Interestingly, we detected thermal proximity coaggregation for several proteins belonging to the same metabolic pathway (i.e., tryparedoxin peroxidase and aspartate aminotransferase in proteins exposed to antimony), highlighting the importance of these pathways. Collectively, our results could serve as a jumping-off point for the future development of innovative diagnostic tools for the detection and evaluation of antimicrobial-resistant Leishmania populations, as well as open the door for new on-target therapies.

Paving the Way: Contributions of Big Data to Apicomplexan and Kinetoplastid Research

In the age of big data an important question is how to ensure we make the most out of the resources we generate. In this review, we discuss the major methods used in Apicomplexan and Kinetoplastid research to produce big datasets and advance our understanding of Plasmodium, Toxoplasma, Cryptosporidium, Trypanosoma and Leishmania biology. We debate the benefits and limitations of the current technologies, and propose future advancements that may be key to improving our use of these techniques. Finally, we consider the difficulties the field faces when trying to make the most of the abundance of data that has already been, and will continue to be, generated.

Discovery of Novel Tubulin Polymerization Inhibitors by Utilizing 3D-QSAR, Molecular Docking and Molecular Dynamics Simulation

Tubulin is a potential therapeutic target for cancer. Compounds inhibit the polymerization of tubulin or promote the polymerization of tubulin to interfere with the mitotic process of cells, resulting in...