Search

Leishmania, a protozoan parasite that causes leishmaniasis, affects 1-2 million people every year worldwide. Leishmaniasis is a vector born disease and characterized by a diverse group of clinical syndromes. Current treatment is limited because of drug resistance, high cost, poor safety, and low efficacy. The urgent need for potent agents against Leishmania has led to significant advances in the development of novel antileishmanial drugs. β-galactofuranose (β-Galf) is an important component of Leishmanial cell surface matrix and plays a critical role in the pathogenesis of parasite. UDP-galactopyranose mutase (UGM) converts UDP-galactopyranose (UDP-Galp) to UDP-galactofuranose (UDP-Galf) which acts as the precursor for β-Galf synthesis. Due to its absence in human, this enzyme is selected as the potential target in search of new antileishmanial drugs. Three dimensional protein structure model of Leishmania major UGM (LmUGM) has been homology modeled using Trypanosoma cruzi UGM (TcUGM) as a template. The stereochemistry was validated further. We selected already reported active compounds from PubChem database to target the LmUGM. Three compounds (6064500, 44570814, and 6158954) among the top hit occupied the UDP binding site of UGM suggested to work as a possible inhibitor for it. In vitro antileishmanial activity assay was performed with the top ranked inhibitor, 6064500. The 6064500 molecule has inhibited the growth of Leishmania donovani promastigotes significantly. Further, at similar concentrations it has exhibited significantly lesser toxicity than standard drug miltefosine hydrate in mammalian cells., (© 2017 Wiley Periodicals, Inc.)

The trypanosomatid protozoa Leishmania is endemic in ~100 countries, with infections causing ~2 million new cases of leishmaniasis annually. Disease symptoms can include severe skin and mucosal ulcers, fever, anemia, splenomegaly, and death. Unfortunately, therapeutics approved to treat leishmaniasis are associated with potentially severe side effects, including death. Furthermore, drug-resistant Leishmania parasites have developed in most endemic countries. To address an urgent need for new, safe and inexpensive anti-leishmanial drugs, we utilized the IBM World Community Grid to complete computer-based drug discovery screens (Drug Search for Leishmaniasis) using unique leishmanial proteins and a database of 600,000 drug-like small molecules. Protein structures from different Leishmania species were selected for molecular dynamics (MD) simulations, and a series of conformational "snapshots" were chosen from each MD trajectory to simulate the protein's flexibility. A Relaxed Complex Scheme methodology was used to screen ~2000 MD conformations against the small molecule database, producing >1 billion protein-ligand structures. For each protein target, a binding spectrum was calculated to identify compounds predicted to bind with highest average affinity to all protein conformations. Significantly, four different Leishmania protein targets were predicted to strongly bind small molecules, with the strongest binding interactions predicted to occur for dihydroorotate dehydrogenase (LmDHODH; PDB:3MJY). A number of predicted tight-binding LmDHODH inhibitors were tested in vitro and potent selective inhibitors of Leishmania panamensis were identified. These promising small molecules are suitable for further development using iterative structure-based optimization and in vitro/in vivo validation assays.

The in vitro leishmanicidal activity and cytotoxicity of pyrazole-containing macrocyclic polyamines 1-4 was assayed on Leishmania infantum and Leishmania braziliensis species. Compounds 1-4 were more active and less toxic than glucantime and both infection rates and ultrastructural alterations confirmed that 1 and 2 were highly leishmanicidal and induced extensive parasite cell damage. Modifications in the excretion products of parasites treated with 1-3 were also consistent with substantial cytoplasm alterations. Compound 2 was highlighted as a potent inhibitor of Fe-SOD in both species, whereas its effect on human CuZn-SOD was poor. Molecular modelling suggested that 2 could deactivate Fe-SOD due to a sterically favoured enhanced ability to interact with the H-bonding net that supports the enzyme`s antioxidant features.

Background and Purpose: Identifying and characterizing potential new therapeutic agents to target cell proliferation may provide improved treatments for neoplastic disorders such as cancer and polycystic diseases., Experimental Approach: We used the simple, tractable biomedical model Dictyostelium to investigate the molecular mechanism of naringenin, a dietary flavonoid with antiproliferative and chemopreventive actions in vitro and in animal models of carcinogenesis. We then translated these results to a mammalian kidney model, Madin-Darby canine kidney (MDCK) tubule cells, grown in culture and as cysts in a collagen matrix., Key Results: Naringenin inhibited Dictyostelium growth, but not development. Screening of a library of random gene knockout mutants identified a mutant lacking TRPP2 (polycystin-2) that was resistant to the effect of naringenin on growth and random cell movement. TRPP2 is a divalent transient receptor potential cation channel, where mutations in the protein give rise to type 2 autosomal dominant polycystic kidney disease (ADPKD). Naringenin inhibited MDCK cell growth and inhibited cyst growth. Knockdown of TRPP2 levels by siRNA in this model conferred partial resistance to naringenin such that cysts treated with 3 and 10 μM naringenin were larger following TRPP2 knockdown compared with controls. Naringenin did not affect chloride secretion., Conclusions and Implications: The action of naringenin on cell growth in the phylogenetically diverse systems of Dictyostelium and mammalian kidney cells, suggests a conserved effect mediated by TRPP2 (polycystin-2). Further studies will investigate naringenin as a potential new therapeutic agent in ADPKD., (© 2013 The British Pharmacological Society.)

The aim of the present study was to evaluate the effects of crude extracts from Handroanthus impetiginosa, Ageratum conyzoides, and Ruta graveolens on Leishmania amazonensis and Trypanosoma cruzi infection in vitro. The results showed that the extracts caused significant toxicity in promastigotes and trypomastigotes. A significant decrease in the rate of cell invasion by pretreated trypomastigotes and promastigotes was also observed. The extracts caused a significant reduction of the multiplication of intracellular amastigotes of both parasites. Therefore, these herbal extracts may be potential candidates for the development of drugs for the treatment of leishmaniasis and Chagas disease.

Current treatments for the parasitic disease leishmaniasis are unsatisfactory due to their route of administration, toxicity and expense. Resistance is also developing to first-line antimonial drugs. Fortunately, a handful of antileishmanial agents, such as the orally available compound miltefosine, are currently in clinical trials. In addition, several promising drug targets and lead molecules are being studied with the goal of developing new antileishmanial agents. Drug candidates have been identified through the continued investigation of parasite sterol metabolism and parasite proteases. New antileishmanial molecules have also been discovered through the study of novel targets and pathways, such as the bisphosphonate inhibitors of isoprenoid biosynthesis. This review presents a synopsis of the drug targets and lead compounds that have been investigated over the last few years against leishmaniasis, gives a perspective on the chemotherapeutic potential of each and discusses some of the obstacles to antileishmanial drug development.

The capacity of flow-cytometric techniques to detect drug-specific biochemical targets and side effects in Leishmania infantum promastigotes was estimated by assessing the effects of three antileishmanial drugs (pentamidine, allopurinol, and amphotericin B) on parasite metabolism. Cell cycle and total protein content were estimated by staining cells with propidium iodide and fluorescein isothiocyanate, nonprotein thiols were stained by mercury orange, and membrane potential was measured by the accumulation of 3,3'-dipenthyloxacarbocyanine iodide inside the cell. Results showed that dynamic studies in parasites treated with subtoxic concentrations of drugs allowed the detection of drug-specific targets: pentamidine primarily affected nonprotein thiol contents and DNA synthesis, allopurinol primarily affected intracellular protein contents, and amphotericin B primarily affected membrane potential. Moreover, the assessment of cellular functions in parasites treated with increasing concentrations of drugs certified the capacity of these techniques to establish dose-response curves and to permit the detection of side effects.

A number of bis(benzyl)polyamine analogs were found to be potent inhibitors of Leishmania donovani growth in vitro (IC50 = 4.3-25 microM). Structural variations appear to have important effects on the biological functions of these analogs. Subinhibitory concentration of all of the analogs with the exception of MDL 27994 could rescue the cells from DL-alpha-difluoromethylornithine toxicity. The analogs inhibited macromolecular synthesis as evaluated by [3H]thymidine, [14C]uracil, and [35S]methionine incorporation. They inhibited the activity of the two enzymes, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC), involved in the biosynthesis of polyamines. These analogs depleted intracellular levels of natural polyamines. We conclude, therefore, that the major mechanism by which these analogs act may be by disruption of macromolecular biosynthesis and cell death. Repression of polyamines by these analogs may be yet another factor involved in slowing the growth of the parasite.

Sinefungin and its cyclic analog were evaluated in vitro for activity against the multiplication of Trypanosoma cruzi. When either drug was tested for eight days on twelve T. cruzi epimastigote isolates, an 800-fold difference in drug sensitivity was found. Both drugs were trypanostatics at a concentration range from 0.1 micrograms/ml to 300 micrograms/ml. The 50% effective concentration (EC50) of sinefungin and its cyclic analog at which the growth of a given isolate was inhibited was 0.38 micrograms/ml for sinefungin and 0.31 micrograms/ml for the cyclic analog against the Ma, Marin, OPS-86, Y, and Ya isolates, and > 300 micrograms/ml for sinefungin and 217 micrograms/ml for the cyclic analog against the A-35, Bertoldo, DS, EP, ES, OPS-58, and FL isolates. Incubation of drug-sensitive isolates for more than 10 days in glucose-saline (GS) medium, but not in minimal essential medium, in the presence of a 30-fold EC50 concentration of the drug induced an increase in the drug-resistant population, which maintained this phenotype for several passages in drug-free culture medium. Growth curves were analyzed as a function of parasite inoculum; it was observed that with sinefungin-sensitive T. cruzi epimastigote isolates grown in GS medium in the presence of 10 micrograms/ml of the drug, the inhibitory effects of the drug were dependent on the initial inoculum: 1 x 10(3)-1 x 10(4) parasites/ml were strongly inhibited even after 16 days. Significant impairment of thymidine incorporation into the DNA of parasites by both drugs was observed only in drug-sensitive epimastigote isolates.(ABSTRACT TRUNCATED AT 250 WORDS)