Identification of novel inhibitors against UDP‐galactopyranose mutase to combat leishmaniasis

Spirocerca lupi draft genome, vaccine and anthelmintic targets

Spirocerca lupi is a parasitic nematode affecting predominantly domestic dogs. It causes spirocercosis, a disease that is often fatal. The assembled draft genome of S. lupi consists of 13,627 predicted protein-coding genes and is approximately 150 Mb in length. Several known anthelmintic gene targets such as for β-Tubulin, glutamate, and GABA receptors as well as known vaccine gene targets such as cysteine protease inhibitor and cytokines were identified in S. lupi by comparing orthologs of C. elegans anthelmintic gene targets as well as orthologs to known vaccine candidates. New anthelmintic targets were predicted through an inclusion-exclusion strategy and new vaccine targets were predicted through an immunoinformatics approach. New anthelminthic targets include DNA-directed RNA polymerases, chitin synthase, polymerases, and other enzymes. New vaccine targets include cuticle collagens. These gene targets provide a starting platform for new drug identification and vaccine design.

In silico prediction of CD8+ and CD4+ T cell epitopes in Leishmania major proteome: Using immunoinformatics

The leishmaniases are NDTs (neglected tropical diseases) that affect people all over the world. They are brought on by protozoans from the genus Leishmania and disseminated by phlebotomine flies that are afflicted with the disease. The best option to manage and lower the incidence of these diseases has been thought by the creation of a safe and effective vaccination. This research used an in silico based mining approach to look for high potential epitopes that might bind to MHC Class I and MHC Class II molecules (mainly; HLA-A*02:01 & HLA-DRB1*03:01) from human population in order to promote vaccine development. Based on the presence of signal peptides, GPI anchors, antigenicity predictions, and a subtractive proteomic technique, we have screened 17 putative antigenic proteins from the 8083 total proteins of L. major. After that thorough immunogenic epitope prediction were done using IEDB-AR tools. We isolated five immunogenic epitopes (three 9-mer & two 15-mer) from five antigenic proteins through docking and MD simulation analysis. Finally, these five anticipated epitopes, viz., TLPEIPVNV, ELMAPVFGL, TLAAAVALL, NSINIRLDGVTSAGF and NVPLVVDASSLFRVA have considerably stronger binding potential with their respective alleles and may trigger immunological responses. The goal of this work was to identify MHC restricted epitopes for CD8+ and CD4+ T cells activation using immunoinformatics in order to identify potential vaccine candidates against L. major parasites.

Molecular Docking and Molecular Dynamics Simulations in Related to Leishmania donovani: An Update and Literature Review

Leishmaniasis, a disease caused by Leishmania parasites and transmitted via sandflies, presents in two main forms: cutaneous and visceral, the latter being more severe. With 0.7 to 1 million new cases each year, primarily in Brazil, diagnosing remains challenging due to diverse disease manifestations. Traditionally, the identification of Leishmania species is inferred from clinical and epidemiological data. Advances in disease management depend on technological progress and the improvement of parasite identification programs. Current treatments, despite the high incidence, show limited efficacy due to factors like cost, toxicity, and lengthy regimens causing poor adherence and resistance development. Diagnostic techniques have improved but a significant gap remains between scientific progress and application in endemic areas. Complete genomic sequence knowledge of Leishmania allows for the identification of therapeutic targets. With the aid of computational tools, testing, searching, and detecting affinity in molecular docking are optimized, and strategies that assess advantages among different options are developed. The review focuses on the use of molecular docking and molecular dynamics (MD) simulation for drug development. It also discusses the limitations and advancements of current treatments, emphasizing the importance of new techniques in improving disease management.

Recent Advances in Chemotherapeutics for Leishmaniasis: Importance of the Cellular Biochemistry of the Parasite and Its Molecular Interaction with the Host

Leishmaniasis, a category 1 neglected protozoan disease caused by a kinetoplastid pathogen called Leishmania, is transmitted through dipteran insect vectors (phlebotomine, sand flies) in three main clinical forms: fatal visceral leishmaniasis, self-healing cutaneous leishmaniasis, and mucocutaneous leishmaniasis. Generic pentavalent antimonials have long been the drug of choice against leishmaniasis; however, their success is plagued with limitations such as drug resistance and severe side effects, which makes them redundant as frontline therapy for endemic visceral leishmaniasis. Alternative therapeutic regimens based on amphotericin B, miltefosine, and paromomycin have also been approved. Due to the unavailability of human vaccines, first-line chemotherapies such as pentavalent antimonials, pentamidine, and amphotericin B are the only options to treat infected individuals. The higher toxicity, adverse effects, and perceived cost of these pharmaceutics, coupled with the emergence of parasite resistance and disease relapse, makes it urgent to identify new, rationalized drug targets for the improvement in disease management and palliative care for patients. This has become an emergent need and more relevant due to the lack of information on validated molecular resistance markers for the monitoring and surveillance of changes in drug sensitivity and resistance. The present study reviewed the recent advances in chemotherapeutic regimens by targeting novel drugs using several strategies including bioinformatics to gain new insight into leishmaniasis. Leishmania has unique enzymes and biochemical pathways that are distinct from those of its mammalian hosts. In light of the limited number of available antileishmanial drugs, the identification of novel drug targets and studying the molecular and cellular aspects of these drugs in the parasite and its host is critical to design specific inhibitors targeting and controlling the parasite. The biochemical characterization of unique Leishmania-specific enzymes can be used as tools to read through possible drug targets. In this review, we discuss relevant metabolic pathways and novel drugs that are unique, essential, and linked to the survival of the parasite based on bioinformatics and cellular and biochemical analyses.

Identification of the furanose ring conformations and the factors driving their adoption

Three groups of furanoses with restricted freedom of rotation on the C3-C4, C2-C3, and C1-C2 bonds, respectively, are presented. Conformational analysis of these furanoses is conducted based on the proton nuclear magnetic resonance (¹H NMR) spectroscopy, density functional theory (DFT) calculations, and X-ray analysis. It is shown that the particular group of the presented furanoses is locked in the specific conformation. These are the ¹T₂-like, the ⁰E-like, and the ³T₄-like conformation, respectively. Characteristic ¹H NMR spectra of these three conformations are presented and the factors influencing the conformational preferences of the analyzed furanoses are discussed.

Identification of potential novel inhibitors against glutamine synthetase enzyme of Leishmania major by using computational tools

Glutamine Synthetase (GS) is functionally important in many pathogens, so its viability as a drug target has been widely investigated. We identified Leishmania major glutamine synthetase (Lm-GS) as an appealing target for developing potential leishmaniasis inhibitors. Comparative modeling, virtual screening, MD simulations along with MM-PBSA analyses were performed and two FDA approved compounds namely Chlortalidone (id ZINC00020253) and Ciprofloxacin (id ZINC00020220) were identified as potential inhibitor among the screened library. These compounds may be used as a lead molecule, although additional in vitro and in vivo testing is required to establish its anti-leishmanial effect. Hence, the goal of this study was to locate and identify certain medications that were previously FDA-approved for definite disorders and that might show anti-leishmanial effect. Due to GS's presence in additional Leishmania species, a novel medication docked with Lm-GS may have broad anti-leishmania efficacy.Communicated by Ramaswamy H. Sarma.

Immunoinformatics based design and prediction of proteome-wide killer cell epitopes of Leishmania donovani: Potential application in vaccine development

Despite several extensive and exhaustive efforts, search for potential therapy against leishmaniasis has not made much progress. In the present work, we have employed mining strategy to screen Leishmania donovani proteome for identification of promising vaccine candidate. We have screened 21 potential antigenic proteins from 7960 total protein of L. donovani, based on the presence of signal peptide, GPI anchor, antigenicity prediction and substractive proteomic approach. Secondly, we have also performed comprehensive immunogenic epitope prediction from the screened 21 proteins, using IEDB-AR tools. Out of the 21 antigenic proteins, we obtained 11 immunogenic epitopes from 9 proteins. The final results revealed that four predicted epitopes namely; YPAFAALVF, VAVAATVAY, AAAPTEAAL and MYPLVAVVF, have significantly better binding potential with respective alleles and could elicits immune responses. Docking analysis using PATCHDOCK server and molecular dynamic simulation using GROMACS revealed the potential of the sequences as immunogenic epitopes. In silico studies also suggested that the epitopes occupied almost same binding cleft with the respective alleles, when compared with the reference peptides. It is also suggested from the molecular dynamic simulation data that the peptides were intact in the pocket for longer periods of time. Our study was designed to select MHC class I restricted epitopes for the activation of CD8 T cells using immunoinformatics for the prediction of probable vaccine candidate against L. donovani parasites. Communicated by Ramaswamy H. Sarma.

Evaluation for substitution of stem bark with small branches of Cassia fistula Linn for traditional medicinal uses: A comparative chemical profiling studies by HPLC, LC-MS, GC-MS

Background

The Aim of the present research article is to proposing a conservative approach for the Cassia fistula by using of small branches instead of stem bark because of plant has many important chemical constituents which show different medicinal activity so consumption of plant is high. We studied here Comparative preliminary phytochemical screening test of the ethanol extract and aqueous extract of the stem bark and small branches of Cassia fistula obtained by cold maceration process. Physicochemical analysis of Cassia fistula was done to ascertain the quality of the raw material used in the study. Successive soxhlet extraction method used for the successive extraction of stem bark and small branches with different solvents for comparative chemical profile study by HPLC, LCMS, and GCMS. Molecular Docking Interaction of Abundant Medicinal Phytochemicals in the Liquid Chromatography−Mass Spectrometry (LC−MS) Analysis Data of C. fistula with the L. donovani Drug Target Proteins and Pancreatic lipase colipase target protein.

Result

The pH of the small branches was found slightly higher as compared to stem bark and the percentage of other parameters like total ash content, acid insoluble ash, loss on drying at 105 °C, water soluble extractive and alcohol soluble extractive values were found fewer in the small branches as compare to stem bark of the plant. It was observed that the number of peaks in stem bark and small branches of the plant sample were almost similar and the retention time of each peak in stem bark was coincide with the retention of small branches of the sample. Therefore, similarity was observed in stem bark and small branches of the Cassia fistula plant in HPLC, LC-MS and GC-MS. The results obtained from HPLC analysis shows that stem bark contains 0.0084% and small branches having 0.0257% of rhein in Cassia fistula. Compounds 3, 9 and 12 are present in Stem bark as well as small branches of C. fistula and Compounds 22, 32 and 37 are present in small branches only. All the compounds have very good binding energy (Kcal/mol) with the respective target proteins.

Conclusion

The small branches have more active chemical constituents than stem bark against particular target proteins.

Exploration of potential inhibitors for autophagy-related protein 8 as antileishmanial agents

Leishmaniasis is considered a tropical neglected disease, which is caused by an intra-macrophagicparasite, Leishmania. It is endemic in 89 different countries. Autophagy-related protein 8 (Ldatg8) is responsible for the transformation of parasites from promastigote to amastigote differentiation. Ldatg8 is one of the key drug targets of Leishmania donovani (L. donovani) responsible for the defense of parasites during stress conditions. Virtual screening of natural ligands library hadbeen performed against Ldatg8 to identify novel and potent inhibitors. Molecular-docking and molecular dynamics simulation studies showed that urolithin A stably blocked Ldatg8. Urolithins are combinations of coumarin and isocoumarin. Further, we evaluated the antileishmanial effects of urolithin A by antileishmanial assays. Urolithin A inhibited the growth and proliferation of L. donovani promastigotes with an IC₅₀ value of 90.3 ± 6.014 μM. It also inhibited the intra-macrophagic parasite significantly with an IC₅₀ value of 78.67±4.62 μM. It showed limited cytotoxicity to the human THP-1 differentiated macrophages with a CC₅₀ value of 190.80 ± 16.89 μM. Further, we assayed reactive oxygen species (ROS) generation and annexin V/PI staining upon Urolithin A treatment of parasites to have an insight into the mechanism of its action. It induced ROS significantly in a dose-dependent manner which caused apoptosis partially in parasites. The potential inhibitors for Ldatg8, identified in this study would provide the platform for the development of an effective and affordable antileishmanial drug.

Repurposing of FDA-approved drugs as inhibitors of sterol C-24 methyltransferase of Leishmania donovani to fight against leishmaniasis

Leishmaniasis is a vector-borne disease caused by around 20 species of Leishmania. The main clinical forms of leishmaniasis are cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL). VL is caused by Leishmania infantum in Central and South America, Mediterranean Basin, Middle East, and by L. donovani in Asia and Africa. Sterol C-24 methyltransferase (LdSMT) of L. donovani is a transferase enzyme of the sterol biosynthesis pathway. This pathway is one of the major targets for drug developments in Leishmania. Due to insufficient evidence about the exact function of SMT inside the cell and the uniqueness of the SMT enzyme in the Leishmania parasites made it a significant target for an effective drug development approach. We performed virtual screening of the Food and Drug Administration (FDA)-approved drug library against LdSMT and found simeprevir, an antiviral drug on top in the binding score. It showed a significant binding affinity with LdSMT. The binding was supported by hydrogen bonds and several other interactions. Simeprevir inhibited L. donovani growth of promastigotes with 50% inhibitory concentration (IC₅₀ ) of 51.49 ± 5.87 μM. Further studies showed that simeprevir induced ROS generation in 44.7% of parasites at 125-μM concentration. Here, we for the first time reported simeprevir as an antileishmanial lead molecule using a drug repurposing approach.

Antileishmanial Evaluation of Bark Methanolic Extract of Acacia nilotica: In Vitro and In Silico Studies

Acacia nilotica (A. nilotica) is an important medicinal plant, found in Africa, the Middle East, and the Indian subcontinent. Every part of the plant possesses a wide array of biologically active and therapeutically important compounds. We reported the antileishmanial activity of A. nilotica bark methanolic extract through in vitro antileishmanial assays and dissected the mechanism of its action through in silico studies. Bark methanolic extract exhibited antipromastigote and antiamastigote potential in a time and dose-dependent manner with IC₅₀ values of 19.6 ± 0.9037 and 77.52 ± 5.167 μg/mL, respectively. It showed cytotoxicity on THP-1-derived human macrophages at very high dose with a CC₅₀ value of 432.7 ± 7.71 μg/mL. The major constituents identified by gas chromatography-mass spectrometry (GC-MS) analysis, 13-docosenoic acid, lupeol, 9,12-octadecadienoic acid, and 6-octadecanoic acid, showed effective binding with the potential drug targets of Leishmania donovani (L. donovani) including sterol 24-c-methyltransferase, trypanothione reductase, pteridine reductase, and adenine phosphoribosyltransferase, suggesting the possible mechanism of its antileishmanial action. Pharmacokinetic studies on major phytoconstituents analyzed by GC-MS supported their use as safe antileishmanial drug candidates. This study proved the antileishmanial potential of bark methanolic extract A. nilotica and its mechanism of action through the inhibition of potential drug targets of L. donovani.

Hesperidin Targets Leishmania donovani Sterol C-24 Reductase to Fight against Leishmaniasis

Hesperidin, a naturally occurring flavanoid, is present in citrus family of fruits. It was found effective against an array of pathogens including fungi, bacteria, viruses, and protozoa. Here, we evaluated its antileishmanial activity and possible mechanism of action through different in vitro and in silico experiments. It inhibited the growth and proliferation of the parasites significantly with a IC50 value of 1.019 ± 0.116 mM in vitro. It also reduced the growth of intra-macrophagic amastigotes with a IC50 value of 0.2858 ± 0.01398 mM. It induced the reactive oxygen species (ROS) in parasites in a dose-dependent manner. Through 2,7-dichloro dihydro fluorescein diacetate (H₂DCFDA) staining, it was observed that around 96.9% parasites were ROS positive at 2.0 mM concentration of hesperidin. The ROS generated led to the apoptosis of parasites in a dose-dependent manner as observed by annexin/PI staining. Molecular docking with one of the very important and unique drug-targets of Leishmania donovani sterol C-24 reductase resulted in its significant inhibition. Here, we for the first time showed that hesperidin induced the antileishmanial response through the induction of apoptosis and inhibition of sterol C-24 reductase. Our study will be helpful in the development of a cost-effective antileishmanial lead with higher efficacy.

Molecular docking analysis of rutin reveals possible inhibition of SARS-CoV-2 vital proteins

BACKGROUND AND AIM

COVID-19 emerged by the end of 2019 in Wuhan, China. It spreaded and became a public health emergency all over the world by mid of April 2020. Flavonoids are specialized metabolites that have antimicrobial properties including anti-viral activity. Rutin, a medicinally important flavonoid belongs to one of the best natural antioxidant classes. It has antiprotozoal, antibacterial, and antiviral properties. Keeping the antimicrobial potential of rutin in mind, we studied its role in the inhibition of essential proteins of SARS-CoV-2 including main protease (Mpro), RNA-dependent RNA polymerase (RdRp), papain-like protease (PLpro), and spike (S)-protein through different in silico approaches.

EXPERIMENTAL PROCEDURE

Molecular docking, inhibition constant, hydrogen bond calculations, and ADMET-properties prediction were performed using different softwares.

RESULTS AND CONCLUSION

Molecular docking study showed significant binding of rutin with Mpro, RdRp, PLpro, and S-proteins of SARS-CoV-2. Out of these four proteins, Mpro exhibited the strongest binding affinity with the least binding energy (-8.9 kcal/mol) and stabilized through hydrogen bonds with bond lengths ranging from 1.18 Å to 3.17 Å as well as hydrophobic interactions. The predicted ADMET and bioactivity showed its optimal solubility, non-toxic, and non-carcinogenic properties. The values of the predicted inhibitory constant of the rutin with SARS-CoV-2 vital proteins ranged between 5.66 μM and 6.54 μM which suggested its promising drug candidature. This study suggested rutin alone or in combination as a dietary supplement may be used to fight against COVID-19 after detailed in vitro and in vivo studies.

Unveiling the Targets Involved in the Quest of Antileishmanial Leads Using In silico Methods

BACKGROUND

Leishmaniasis is a neglected tropical disease associated with several clinical manifestations, including cutaneous, mucocutaneous, and visceral forms. As currently available drugs have some limitations (toxicity, resistance, among others), the target-based identification has been an important approach to develop new leads against leishmaniasis. The present study aims to identify targets involved in the pharmacological action of potent antileishmanial compounds.

METHODS

The literature information regarding molecular interactions of antileishmanial compounds studied over the past half-decade is discussed. The information was obtained from databases such as Wiley, SciFinder, Science Direct, National Library of Medicine, American Chemical Society, Scientific Electronic Library Online, Scopus, Springer, Google Scholar, Web of Science, etc. Results: Numerous in vitro antileishmanial compounds showed affinity and selective interactions with enzymes such as arginase, pteridine reductase 1, trypanothione reductase, pyruvate kinase, among others, which are crucial for the survival and virulence of the Leishmania parasite.

CONCLUSION

The in-silico activity of small molecules (enzymes, proteins, among others) might be used as pharmacological tools to develop candidate compounds for the treatment of leishmaniasis. As some pharmacologically active compounds may act on more than one target, additional studies of the mechanism (s) of action of potent antileishmanial compounds might help to better understand their pharmacological action. Also, the optimization of promising antileishmanial compounds might improve their biological activity.

Assessment of the Antileishmanial Potential of Cassia fistula Leaf Extract

Cassia fistula has a wide array of biologically active and therapeutically important class of compounds. Leishmania donovani important drug targets, sterol 24-c methyltransferase (LdSMT), trypanothione reductase (LdTR), pteridine reductase (LdPTR1), and nucleoside hydrolase (LdNH), were modelled, and molecular docking was performed against the abundant phytochemicals of its leaf extract. Molecular docking results provided the significant prima facie evidence of the leaf extract to have antileishmanial potential. To confirm this, we performed in vitro antileishmanial and cytotoxicity assays. Methanolic extract of C. fistula leaves showed growth inhibition and proliferation of L. donovani promastigote with an IC50 value of 43.31 ± 4.202 μg/mL. It also inhibited the growth of intra-macrophagic amastigotes with an IC50 value of 80.76 ± 3.626 μg/mL. C. fistula extract was found cytotoxic at a very high concentration on human macrophages (CC50 = 626 ± 39 μg/mL). Annexin V/propidium iodide (PI) staining assay suggested partial apoptosis induction in parasites by C. fistula to exert its antileishmanial activity. Here, for the first time, we have shown the antileishmanial potential of C. fistula leaves. Overall, our results could open new insight for an affordable and natural antileishmanial with high efficacy and less toxicity.

Cynaroside inhibits Leishmania donovani UDP-galactopyranose mutase and induces reactive oxygen species to exert antileishmanial response

Cynaroside, a flavonoid, has been shown to have antibacterial, antifungal and anticancer activities. Here, we evaluated its antileishmanial properties and its mechanism of action through different in silico and in vitro assays. Cynaroside exhibited antileishmanial activity in time- and dose-dependent manner with 50% of inhibitory concentration (IC₅₀) value of 49.49 ± 3.515 µM in vitro. It inhibited the growth of parasite significantly at only 20 µM concentration when used in combination with miltefosine, a standard drug which has very high toxicity. It also inhibited the intra-macrophagic parasite significantly at low doses when used in combination with miltefosine. It showed less toxicity than the existing antileishmanial drug, miltefosine at similar doses. Propidium iodide staining showed that cynaroside inhibited the parasites in G₀/G₁ phase of cell cycle. 2,7-dichloro dihydro fluorescein diacetate (H₂DCFDA) staining showed cynaroside induced antileishmanial activity through reactive oxygen species (ROS) generation in parasites. Molecular-docking studies with key drug targets of Leishmania donovani showed significant inhibition. Out of these targets, cynaroside showed strongest affinity with uridine diphosphate (UDP)-galactopyranose mutase with −10.4 kcal/mol which was further validated by molecular dynamics (MD) simulation. The bioactivity, ADMET (absorption, distribution, metabolism, excretion and toxicity) properties, Organisation for Economic Co-operation and Development (OECD) chemical classification and toxicity risk prediction showed cynaroside as an enzyme inhibitor having sufficient solubility and non-toxic properties. In conclusion, cynaroside may be used alone or in combination with existing drug, miltefosine to control leishmaniasis with less cytotoxicity.

N5 Is the New C4a: Biochemical Functionalization of Reduced Flavins at the N5 Position

For three decades the C4a-position of reduced flavins was the known site for covalency within flavoenzymes. The reactivity of this position of the reduced isoalloxazine ring with the dioxygen ground-state triplet established the C4a as a site capable of one-electron chemistry. Within the last two decades new types of reduced flavin reactivity have been documented. These studies reveal that the N5 position is also a protean site of reactivity, that is capable of nucleophilic attack to form covalent bonds with substrates. In addition, though the precise mechanism of dioxygen reactivity is yet to be definitively demonstrated, it is clear that the N5 position is directly involved in substrate oxygenation in some enzymes. In this review we document the lineage of discoveries that identified five unique modes of N5 reactivity that collectively illustrate the versatility of this position of the reduced isoalloxazine ring.

Leishmanicidal Activity of an In Silico-Screened Novel Inhibitor against Ascorbate Peroxidase of Leishmania donovani

Peroxidases are a heterogeneous family of enzymes that have diverse biological functions. Ascorbate peroxidase is a redox enzyme that is reduced by trypanothione, which plays a central role in the redox defense system of Leishmania In view of developing new and novel therapeutics, we performed in silico studies in order to search for a ligand library and identify new drug candidates and their physiological roles against promastigotes and intracellular amastigotes of Leishmania donovani Our results demonstrated that the selected inhibitor ZINC96021026 has significant antileishmanial effect and effectively killed both free and intracellular forms of the parasite. ZINC96021026 was found to be identical to ML-240, a selective inhibitor of valosin-containing protein (VCP), or p97, a member of the AAA-ATPase protein family which was derived from the scaffold of N ²,N ⁴-dibenzylquinazoline-2,4-diamine (DBeQ), targeting the D2-ATPase domain of the enzyme. ZINC96021026 (ML-240) thus has a broad range of cellular functions, thought to be derived from its ability to unfold proteins or disassemble protein complexes, besides inhibiting the ascorbate peroxidase activity. ML-240 may inhibit the parasite's ascorbate peroxidase, leading to extensive apoptosis and inducing generation of reactive oxygen species. Taken together, our results demonstrated that ML-240 could be an attractive therapeutic option for treatment against leishmaniasis.

Targeting Trypanothione Reductase of Leishmanial major to Fight Against Cutaneous Leishmaniasis

BACKGROUND

1.2-2.0 million cases of leishmaniasis occur annually throughout the world. The available drugs like Amphotericin B, antimonials and miltefosine are unable to fulfill the need due to less effectiveness, high toxicity, resistance, high cost and complex route of administration. Leishmania survives inside the macrophages through different evasion mechanisms; one of that is activation of its trypanothione reductase enzyme which neutralizes the reactive oxygen species generated inside the macrophages to kill the parasites. This enzyme is unique and absent in human, therefore in this study I targeted it for screening of new inhibitors to fight against leishmaniasis.

METHODS

Homology modeling of Leishmania major trypanothione reductase was performed using Phyre2 server. The homology based modelled protein was validated with PROCHECK analysis. Ligplot analysis was performed to predict the active residues inside the binding pocket. Further, virtual screening of ligand library containing 113 ligands from PubChem Bioassay was performed against the target using AutoDock Vina Tool.

RESULTS

Top five ligands showed best binding affinity. The molecule having PubChem CID: 10553746 showed highest binding affinity of -11.3 kcal/mol. Over all this molecule showed highest binding affinity and moderate number of hydrogen bonds. Hopefully, this molecule will be able to block the activity of target enzyme, trypanothione reductase of Leishmania major effectively and may work as new molecules to fight against cutaneous leishmanaisis.

CONCLUSION

This study will help the researchers to identify the new molecules which can block the activity of leishmanial-trypanothione reductase, a novel enzyme of trypanosomatids. These screened inhibitors may also be effective not only in leishmaniasis but also other trypanosomatid-mediated infectious diseases.

Repurposing Glyburide as Antileishmanial Agent to Fight Against Leishmaniasis

BACKGROUND

Leishmaniasis is caused by a protozoan parasite, Leishmania. It is common in more than 98 countries throughout the world. Due to insufficient availability of antileishmanial chemotherapeutics, it is an urgent need to search for new molecules which have better efficacy, low toxicity and are available at low cost.

OBJECTIVES

There is a high rate of diabetic cases throughout the world that is why we planned to test the antileishmanial activity of glyburide, an effective sugar lowering drug used for the treatment of diabetes. In this study, glyburide showed a significant decrease in the parasite growth and survival in vitro in a dose-dependent manner.

METHODS

Anti-leishmanial activity of glyburide was checked by culturing Leishmania donovani promastigotes in the presence of glyburide in a dose and time dependent manner. Docking study against Leishmania donovani-Trypanothione synthetase (LdTrySyn) protein was performed using Autodock Vina tool.

RESULTS

Growth reversibility assay shows that growth of treated parasite was not reversed when transferred to fresh culture media after 7 days. Moreover, docking studies show efficient interactions of glyburide with key residues in the catalytic site of Leishmania donovani- Trypanothione synthetase (LdTrySyn), a very important leishmanial enzyme involved in parasite's survival by detoxification of Nitric Oxide (NO) species, generated by the mammalian host as a defense molecule. Thus this study proves that the drug-repurposing is a beneficial strategy for identification of new and potent antileishmanial molecules.

CONCLUSION

The results suggest that glyburide binds to LdTrySyn and inhibits its activity which further leads to the altered parasite morphology and inhibition of parasite growth. Glyburide may also be used in combination with other anti-leishmanial drugs to potentiate the response of the chemotherapy. Overall this study provides information about combination therapy as well as a single drug treatment for the infected patients suffering from diabetes. This study also provides raw information for further in vivo disease model studies to confirm the hypothesis.

Leishmania donovani infection differentially regulates small G-proteins

Leishmania is a protozoan parasite that resides and replicates in macrophages and causes leishmaniasis. The parasite alters the signaling cascade in host macrophages and evades the host machinery. Small G-proteins are GTPases, grouped in 5 different families that play a crucial role in the regulation of cell proliferation, cell survival, apoptosis, intracellular trafficking, and transport. In particular, the Ras family of small G-proteins has been identified to play a significant role in the cellular functions mentioned before. Here, we studied the differential expression of the most important small G-proteins during Leishmania infection. We found major changes in the expression of different isoforms of Ras, mainly in N-Ras. We observed that Leishmania donovani infection led to enhanced N-Ras expression, whereas it inhibited K-Ras and H-Ras expression. Furthermore, an active N-Ras pull-down assay showed enhanced N-Ras activity. L donovani infection also increased extracellular signal-regulated kinase 1/2 phosphorylation and simultaneously decreased p38 phosphorylation. In contrast, pharmacological inhibition of Ras led to reduction in the phosphorylation of extracellular signal-regulated kinase 1/2 and enhanced the phosphorylation of p38 in Leishmania-infected cells, which could lead to increased interleukin-12 expression and decreased interleukin-10 expression. Indeed, farnesylthiosalicyclic acid (a Ras inhibitor), when used at the effective level in L donovani-infected macrophages, reduced amastigotes in the host macrophages. Thus, upregulated N-Ras expression during L donovani infection could be a novel immune evasion strategy of Leishmania and would be a potential target for antileishmanial immunotherapy.