Insights into the drug screening approaches in leishmaniasis

Anhydroparthenin as a dual-target inhibitor against Sterol C-24 methyltransferase and Sterol 14-α demethylase of Leishmania donovani: A comprehensive in vitro and in silico study

Parthenium hysterophorus plant has a diverse chemical profile and immense bioactive potential. It exhibits excellent pharmacological properties such as anti-cancer, anti-inflammatory, anti-malarial, microbicidal, and anti-trypanosomal. The present study aims to evaluate the anti-leishmanial potential and toxicological safety of anhydroparthenin isolated from P. hysterophorus. Anydroparthenin was extracted from the leaves of P. hysterophorus and characterized through detailed analysis of 1H, 13C NMR, and HRMS. Dye-based in vitro and ex vivo assays confirmed that anhydroparthenin significantly inhibited both promastigote and amastigote forms of the Leishmania donovani parasites. Both the cytotoxicity experiment and hemolytic assay revealed its non-toxic nature and safety index in the range of 10 to 15. Further, various mechanistic assays suggested that anhydroparthenin led to the generation of oxidative stress, intracellular ATP depletion, alterations in morphology and mitochondrial membrane potential, formation of intracellular lipid bodies, and acidic vesicles, ultimately leading to parasite death. As a dual targeting approach, computational studies and sterol quantification assays confirmed that anhydroparthenin inhibits the Sterol C-24 methyl transferase and Sterol 14-α demethylase proteins involved in the ergosterol biosynthesis in Leishmania parasites. These results suggest that anhydroparthenin could be a promising anti-leishmanial molecule and can be developed as a novel therapeutic stratagem against leishmaniasis.

Genomic Insight of Leishmania Parasite: In-Depth Review of Drug Resistance Mechanisms and Genetic Mutations

Leishmaniasis, which is caused by a parasitic protozoan of the genus Leishmania, is still a major threat to global health, impacting millions of individuals worldwide in endemic areas. Chemotherapy has been the principal method for managing leishmaniasis; nevertheless, the evolution of drug resistance offers a significant obstacle to therapeutic success. Drug-resistant behavior in these parasites is a complex phenomenon including both innate and acquired mechanisms. Resistance is frequently related to changes in drug transportation, drug target alterations, and enhanced efflux of the drug from the pathogen. This review has revealed specific genetic mutations in Leishmania parasites that are associated with resistance to commonly used antileishmanial drugs such as pentavalent antimonials, miltefosine, amphotericin B, and paromomycin, resulting in changes in gene expression along with the functioning of various proteins involved in drug uptake, metabolism, and efflux. Understanding the genetic changes linked to drug resistance in Leishmania parasites is essential for creating approaches for tackling and avoiding the spread of drug-resistant variants. Based on which specific treatments focus on mutations and pathways could potentially improve treatment efficacy and help long-term leishmaniasis control. More study is needed to uncover the complete range of genetic changes generating medication resistance and to develop new therapies based on available information.

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

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

Curcumin-loaded nanostructured systems for treatment of leishmaniasis: a review

Leishmaniasis is a neglected tropical disease that has affected more than 350 million people worldwide and can manifest itself in three different forms: cutaneous, mucocutaneous, or visceral. Furthermore, the current treatment options have drawbacks which compromise efficacy and patient compliance. To face this global health concern, new alternatives for the treatment of leishmaniasis have been explored. Curcumin, a polyphenol obtained from the rhizome of turmeric, exhibits leishmanicidal activity against different species of Leishmania spp. Although its mechanism of action has not yet been fully elucidated, its leishmanicidal potential may be associated with its antioxidant and anti-inflammatory properties. However, it has limitations that compromise its clinical use. Conversely, nanotechnology has been used as a tool for solving biopharmaceutical challenges associated with drugs, such as curcumin. From a drug delivery standpoint, nanocarriers (1-1000 nm) can improve stability, increase solubility, promote intracellular delivery, and increase biological activity. Thus, this review offers a deep look into curcumin-loaded nanocarriers intended for the treatment of leishmaniasis.

DNA topoisomerases as a drug target in Leishmaniasis: Structural and mechanistic insights

Leishmaniasis, caused by a protozoan parasite, is among humanity's costliest banes, owing to the high mortality and morbidity ratio in poverty-stricken areas. To date, no vaccine is available for the complete cure of the disease. Current chemotherapy is expensive, has undesirable side effects, and faces drug resistance limitations and toxicity concerns. The substantial differences in homology between leishmanial DNA topoisomerase IB compared with the human counterparts provided a new lead in the study of the structural determinants that can be targeted. Several research groups explored this molecular target, trying to fill the therapeutic gap, and came forward with various anti-leishmanial scaffolds. This article is a comprehensive review of knowledge about topoisomerases as an anti-leishmanial drug target and their inhibitors collected over the years. In addition to information on molecular targets and reported scaffolds, the review details the structure-activity relationship of described compounds with leishmanial Topoisomerase IB. Moreover, the work also includes information about the structure of the inhibitors, showing common interacting residues with leishmanial topoisomerases that drive their mode of action towards them. Finally, in search of topoisomerase inhibitors at the stage of clinical trials, we have listed all the drugs that have been in clinical trials against leishmaniasis.

Detergent-free parasite transformation and replication assay for drug screening against intracellular Leishmania amastigotes

Leishmaniasis is an infectious disease caused by protozoan species in the genera Leishmania and Endotrypanum. Current antileishmanial drugs are limited due to adverse effects, variable efficacy, the development of resistant parasites, high cost, parenteral administration and lack of availability in endemic areas. Therefore, active searching for new antileishmanial drugs has been done for years, mainly by academia. Drug screening techniques have been a challenge since the intracellular localization of Leishmania amastigotes implies that the host cell may interfere with the quantification of the parasites and the final estimation of the effect. One of the procedures to avoid host cell interference is based on its detergent-mediated lysis and subsequent transformation of viable amastigotes into promastigotes, their proliferation and eventual quantification as an axenic culture of promastigotes. However, the use of detergent involves additional handling of cultures and variability. In the present work, cultures of intracellular amastigotes were incubated for 72 h at 26 °C after exposure to the test compounds and the transformation and proliferation of parasites took place without need of adding any detergent. The assay demonstrated clear differentiation of negative and positive controls (average Z´ = 0.75) and 50% inhibitory concentrations of compounds tested by this method and by the gold standard enumeration of Giemsa-stained cultures were similar (p = 0.5002) and highly correlated (r = 0.9707). This simplified procedure is less labor intensive, the probability of contamination and the experimental error are reduced, and it is appropriate for the automated high throughput screening of compounds.

Design, synthesis, and biological evaluation of 3,3'-diindolylmethane N-linked glycoconjugate as a leishmanial topoisomerase IB inhibitor with reduced cytotoxicity

Leishmaniasis, one of the neglected diseases, ranks second to malaria in the cause of parasitic mortality and morbidity. The present chemotherapeutic regimen faces the limitations of drug resistance and toxicity concerns, raising a great need to develop new chemotherapeutic leads that are orally administrable, potent, non-toxic, and cost-effective. Several research groups came forward to fill this therapeutic gap with new classes of active compounds against leishmaniasis, one such being 3,3'-diindolylmethane (DIM) derivatives. We tried to link this concept with another promising approach of glycoconjugation to study how glycosylated groups work differently from non-glycosylated ones. In the present study, a series of 3,3'-DIM derivatives have been synthesized and screened for their anti-leishmanial potency on Leishmania donovani promastigotes. Next, we synthesized the β-N,N' glycoside of potent compound 3d using indole-indoline conversion, Fischer-type glycosylation, 2,3-dichloro-5,6-dicyano-1,4-benzoquionone (DDQ) oxidation, and molecular iodine catalyzed coupling with a suitable aldehyde in reasonable overall yield. The biological evaluation revealed that glycosides had reduced cytotoxic effects on the J774A.1 macrophage cell line. The enzyme inhibition study confirms that the glycoside derivatives have significant inhibitory activity against the leishmanial topoisomerase IB enzyme. Molecular docking further displayed the better binding efficiency of glycoside 13 with the target enzyme, suggesting the involvement of more H-bond interactions in the case of glycosides as compared to free drugs. Therefore, this work helps in proposing the fact that the addition of sugar moieties adds some favorable characteristics to free inhibitors, making it a promising approach for future clinical diagnostic and therapeutic applications, which can prove to be a valuable arsenal in combating such neglected diseases.