In silico screening, molecular dynamic simulations, and in vitro activity of selected natural compounds as an inhibitor of Leishmania donovani 3-mercaptopyruvate sulfurtransferase.

In Leishmania sp., the enzymes of de novo cysteine biosynthesis pathway require sulfide. Other organisms utilize sulfide through the sulfide reduction pathway, but Leishmania lacks the gene that encodes these enzymes. Hence, the major source of sulfide for Leishmania is believed to be from the action of 3-mercaptopyruvate sulfurtransferase (3MST) on 3-mercapto-pyruvate (3MP). There has been no effort reported in the past to screen inhibitors against L. donovani 3MST (Ld3MST). As a result, this study examines natural compounds that are potent against Ld3MST and validates it by in vitro activity and cytotoxicity tests. Initially, a library of ~ 5000 natural compounds was subjected to molecular docking approach for screening, and the best hit was validated using a long-term molecular dynamic simulation (MD). Among the docking results, quercetine-3-rutinoside (Rutin) was deemed the best hit. The results of the MD indicated that Rutin was highly capable of interacting with the varied active site segments, possibly blocking substrate access. Additionally, promastigotes and amastigotes were tested for Rutin activity and the IC50 was found to be 40.95 and 90.09 µM, respectively. Similarly, the cytotoxicity assay revealed that Rutin was not toxic even at a concentration of 819.00 µM to THP-1 cell lines. Additionally, the Ld3MST was cloned, purified, and evaluated for enzyme activity in the presence of Rutin. Reduction in the enzyme activity (~ 85%) was observed in the presence of ~ 40 µM Rutin. Thus, this study suggests that Rutin may act as a potent inhibitor of Ld3MST. With further in vivo investigations, Rutin could be a small molecule of choice for combating leishmaniasis.

Current status of nanoscale drug delivery and the future of nano-vaccine development for leishmaniasis - A review.

The study of tropical diseases like leishmaniasis, a parasitic disease, has not received much attention even though it is the second-largest infectious disease after malaria. As per the WHO report, a total of 0.7-1.0 million new leishmaniasis cases, which are spread by 23 Leishmania species in more than 98 countries, are estimated with an alarming 26,000-65,000 death toll every year. Lack of potential vaccines along with the cost and toxicity of amphotericin B (AmB), the most common drug for the treatment of leishmaniasis, has raised the interest significantly for new formulations and drug delivery systems including nanoparticle-based delivery as anti-leishmanial agents. The size, shape, and high surface area to volume ratio of different NPs make them ideal for many biological applications. The delivery of drugs through liposome, polymeric, and solid-lipid NPs provides the advantage of high biocomatibilty of the carrier with reduced toxicity. Importantly, NP-based delivery has shown improved efficacy due to targeted delivery of the payload and synergistic action of NP and payload on the target. This review analyses the advantage of NP-based delivery over standard chemotherapy and natural product-based delivery system. The role of different physicochemical properties of a nanoscale delivery system is discussed. Further, different ways of nanoformulation delivery ranging from liposome, niosomes, polymeric, metallic, solid-lipid NPs were updated along with the possible mechanisms of action against the parasite. The status of current nano-vaccines and the future potential of NP-based vaccine are elaborated here.

In-silico screening and validation of high-affinity tetra-peptide inhibitor of Leishmania donovani O-acetyl serine sulfhydrylase (OASS).

OASS is a specific enzyme that helps Leishmania parasite to survive the oxidative stress condition in human macrophages. SAT C-terminal peptides in several organisms, including Leishmania, were reported to inhibit or reduce the activity of OASS. Small peptide and small molecules mimicking the SAT C-terminal residues are designed and tested for the inhibition of OASS in different organisms. Hence, in this study, all the possible tetra-peptide combinations were designed and screened based on the docking ability with Leishmania donovani OASS (Ld-OASS). The top ranked peptides were further validated for the stability using 50 ns molecular dynamic simulation. In order to identify the better binding capability of the peptides, the top peptides complexed with Ld-OASS were also subjected to molecular dynamic simulation. The docking and simulation results favored the peptide EWSI to possess greater advantage than previously reported peptide (DWSI) in binding with Ld-OASS active site. Also, screening of non-peptide inhibitor of Asinex Biodesign library based on the shape similarity of EWSI and DWSI was performed. The top similar molecules of each peptides were docked on to Ld-OASS active site and subsequently simulated for 20 ns. The results suggested that the ligand that shares high shape similarity with EWSI possess better binding capability than the ligand that shares high shape similarity with DWSI. This study revealed that the tetra-peptide EWSI had marginal advantage over DWSI in binding with Ld-OASS, thereby providing basis for defining a pharmacophoric scaffold for the design of peptidomimetic inhibitors as well as non-peptide inhibitors of Ld-OASS. Communicated by Ramaswamy H. Sarma.

LeishInDB: A web-accessible resource for small molecule inhibitors against Leishmania sp.

Despite the availability of drugs to treat Leishmaniasis, various other factors including drug resistance and adverse side effects encourage the researchers to search for new strategies and alternatives for treating Leishmaniasis. Repurposing and devising combination therapy with the existing small molecules would serve as an alternative strategy to address the issue, especially the drug resistance. Hence, here we report LeishInDB, a web-accessible resource of small molecule inhibitors having a varying degree of activity towards Leishmania sp. The database includes searchable information of >7000 small molecules collected from >600 literature. The comprehensive information of inhibitors mainly include the activity details (IC50, EC50, Ki, binding energy etc., if any); information on species and form of Leishmania the inhibitor is active against; and the details about their protein target (actively linked to TriTrypDB). In addition, chemical properties including the log P-value, number of rotatable bonds, number of hydrogen bond donors and acceptors, molecular weight, 2D/3D structural information etc., were also included. Toxicity prediction for each molecule was performed using admetSAR and their corresponding results were available to perform the filtered search. In addition, facility to perform sub-structure search, facility to perform the dynamic search on various fields, and facility to download all the structure of molecules that match the search criteria were also included. We believe that the scope of LeishInDB allows the researchers to utilize the available information for repurposing the inhibitors as well as for the investigation of new therapeutics. Database URL:http://leishindb.biomedinformri.com/.