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PLoS Neglected Tropical Diseases Dec 2021Studies of drug resistance in the protozoan parasites of the genus Leishmania have been helpful in revealing biochemical pathways as potential drug targets. The...
Studies of drug resistance in the protozoan parasites of the genus Leishmania have been helpful in revealing biochemical pathways as potential drug targets. The chlorinated glutamine analogue acivicin has shown good activity against Leishmania cells and was shown to target several enzymes containing amidotransferase domains. We selected a Leishmania tarentolae clone for acivicin resistance. The genome of this resistant strain was sequenced and the gene coding for the amidotransferase domain-containing GMP synthase was found to be amplified. Episomal expression of this gene in wild-type L. tarentolae revealed a modest role in acivicin resistance. The most prominent defect observed in the resistant mutant was reduced uptake of glutamate, and through competition experiments we determined that glutamate and acivicin, but not glutamine, share the same transporter. Several amino acid transporters (AATs) were either deleted or mutated in the resistant cells. Some contributed to the acivicin resistance phenotype although none corresponded to the main glutamate transporter. Through sequence analysis one AAT on chromosome 22 corresponded to the main glutamate transporter. Episomal expression of the gene coding for this transporter in the resistant mutant restored glutamate transport and acivicin susceptibility. Its genetic knockout led to reduced glutamate transport and acivicin resistance. We propose that acivicin binds covalently to this transporter and as such leads to decreased transport of glutamate and acivicin thus leading to acivicin resistance.
Topics: Amino Acid Transport Systems; Antiprotozoal Agents; Biological Transport; Drug Resistance; Glutamic Acid; Humans; Isoxazoles; Leishmania; Leishmaniasis; Protozoan Proteins
PubMed: 34914690
DOI: 10.1371/journal.pntd.0010046 -
Nature Immunology May 2020Oxidative stress is a central part of innate immune-induced neurodegeneration. However, the transcriptomic landscape of central nervous system (CNS) innate immune cells...
Oxidative stress is a central part of innate immune-induced neurodegeneration. However, the transcriptomic landscape of central nervous system (CNS) innate immune cells contributing to oxidative stress is unknown, and therapies to target their neurotoxic functions are not widely available. Here, we provide the oxidative stress innate immune cell atlas in neuroinflammatory disease and report the discovery of new druggable pathways. Transcriptional profiling of oxidative stress-producing CNS innate immune cells identified a core oxidative stress gene signature coupled to coagulation and glutathione-pathway genes shared between a microglia cluster and infiltrating macrophages. Tox-seq followed by a microglia high-throughput screen and oxidative stress gene network analysis identified the glutathione-regulating compound acivicin, with potent therapeutic effects that decrease oxidative stress and axonal damage in chronic and relapsing multiple sclerosis models. Thus, oxidative stress transcriptomics identified neurotoxic CNS innate immune populations and may enable discovery of selective neuroprotective strategies.
Topics: Animals; Antioxidants; Disease Models, Animal; Encephalomyelitis, Autoimmune, Experimental; Female; Gene Expression Profiling; Gene Regulatory Networks; High-Throughput Screening Assays; Humans; Immunity, Innate; Isoxazoles; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Microglia; Multiple Sclerosis; Neurogenic Inflammation; Oxidative Stress; Sequence Analysis, RNA; Single-Cell Analysis
PubMed: 32284594
DOI: 10.1038/s41590-020-0654-0 -
Molecules (Basel, Switzerland) Apr 2023Chiral natural compounds are often biosynthesized in an enantiomerically pure fashion, and stereochemistry plays a pivotal role in biological activity. Herein, we...
Chiral natural compounds are often biosynthesized in an enantiomerically pure fashion, and stereochemistry plays a pivotal role in biological activity. Herein, we investigated the significance of chirality for nature-inspired 3-Br-acivicin (3-BA) and its derivatives. The three unnatural isomers of 3-BA and its ester and amide derivatives were prepared and characterized for their antimalarial activity. Only the (5, α) isomers displayed significant antiplasmodial activity, revealing that their uptake might be mediated by the L-amino acid transport system, which is known to mediate the acivicin membrane's permeability. In addition, we investigated the inhibitory activity towards glyceraldehyde 3-phosphate dehydrogenase (GAPDH) since it is involved in the multitarget mechanism of action of 3-BA. Molecular modeling has shed light on the structural and stereochemical requirements for an efficient interaction with GAPDH, leading to covalent irreversible binding and enzyme inactivation. While stereochemistry affects the target binding only for two subclasses (- and -), it leads to significant differences in the antimalarial activity for all subclasses, suggesting that a stereoselective uptake might be responsible for the enhanced biological activity of the (5, α) isomers.
Topics: Antimalarials; Isoxazoles; Plasmodium falciparum; Models, Molecular
PubMed: 37049935
DOI: 10.3390/molecules28073172 -
Letters in Applied Microbiology Oct 2014Acivicin is an inhibitor of γ-glutamyl transpeptidase and glutamine amidotransferase. When grown on a synthetic minimal agar medium, acivicin strongly inhibited the...
Acivicin is an inhibitor of γ-glutamyl transpeptidase and glutamine amidotransferase. When grown on a synthetic minimal agar medium, acivicin strongly inhibited the growth of Magnaporthe oryzae and Alternaria brassicicola, and to a lesser extent, Botrytis cinerea. However, only partial or marginal growth inhibition was observed with regard to Fusarium sporotrichioides and Fusarium graminearum. The growth retardation caused by acivicin was significantly alleviated by cultivating the fungus on a nutrient-rich medium. The inhibition of M. oryzae growth caused by 1 μmol l(-1) of acivicin on minimal agar medium was subdued by the addition of specific single amino acids, including His, a branched-chain amino acid (Leu, Ile or Val), an aromatic amino acid (Trp, Tyr or Phe), Met or Gln, at a concentration of 0·4 mmol l(-1). Trichothecene production by F. graminearum in trichothecene-inducing liquid medium was reduced significantly in the presence of acivicin despite its inability to inhibit growth in the trichothecene-inducing liquid medium. Foliar application of conidia in the presence of acivicin reduced the severity of rice blast disease caused by M. oryzae. These results suggest the usefulness of this modified amino acid natural product to mitigate agricultural problems caused by some phytopathogenic fungi. Significance and impact of the study: Fusarium head blight or scab disease and rice blast, caused by Fusarium graminearum and Magnaporthe oryzae, respectively, are major diseases of cereal crops that cause a significant loss of yield and deterioration in the quality of the grain. The present study investigated the effects of acivicin, a glutamine amino acid analog, on the physiology of various phytopathogenic fungi. Application of acivicin to a fungal culture and conidial suspension reduced mycotoxin production by the wheat scab fungus and the severity of rice blast, respectively. These results suggest the possibility that acivicin may serve as a lead compound to develop agricultural chemicals for the control of some plant diseases.
Topics: Fusarium; Isoxazoles; Magnaporthe; Mycotoxins; Oryza; Plant Diseases; Spores, Fungal; Triticum; Virulence
PubMed: 24863673
DOI: 10.1111/lam.12289 -
Proceedings of the National Academy of... Feb 2019Glutamate is the most abundant excitatory neurotransmitter, present at the bulk of cortical synapses, and participating in many physiologic and pathologic processes...
Glutamate is the most abundant excitatory neurotransmitter, present at the bulk of cortical synapses, and participating in many physiologic and pathologic processes ranging from learning and memory to stroke. The tripeptide, glutathione, is one-third glutamate and present at up to low millimolar intracellular concentrations in brain, mediating antioxidant defenses and drug detoxification. Because of the substantial amounts of brain glutathione and its rapid turnover under homeostatic control, we hypothesized that glutathione is a relevant reservoir of glutamate and could influence synaptic excitability. We find that drugs that inhibit generation of glutamate by the glutathione cycle elicit decreases in cytosolic glutamate and decreased miniature excitatory postsynaptic potential (mEPSC) frequency. In contrast, pharmacologically decreasing the biosynthesis of glutathione leads to increases in cytosolic glutamate and enhanced mEPSC frequency. The glutathione cycle can compensate for decreased excitatory neurotransmission when the glutamate-glutamine shuttle is inhibited. Glutathione may be a physiologic reservoir of glutamate neurotransmitter.
Topics: Animals; Cells, Cultured; Excitatory Postsynaptic Potentials; Glutamic Acid; Glutathione; Homeostasis; Neurons; Rats, Sprague-Dawley; Synapses; Synaptic Transmission
PubMed: 30692251
DOI: 10.1073/pnas.1817885116 -
Translational Vision Science &... Jul 2020To investigate whether human donor lenses are capable of exporting reduced glutathione.
PURPOSE
To investigate whether human donor lenses are capable of exporting reduced glutathione.
METHODS
Human lenses of varying ages were cultured in artificial aqueous humor for 1 hour under hypoxic conditions to mimic the physiologic environment and reduced glutathione (GSH) and oxidized glutathione (GSSG) levels measured in the media and in the lens.
RESULTS
Human donor lenses released both GSH and GSSG into the media. Donor lenses cultured in the presence of acivicin, a γ-glutamyltranspeptidase inhibitor, exhibited a significant increase in GSSG levels ( < 0.05), indicating that GSSG undergoes degradation into its constituent amino acids. Screening of GSH/GSSG efflux transporters revealed Mrp1, Mrp4, and Mrp5 to be present at the transcript level, but only Mrp5 was expressed at the protein level. Blocking Mrp5 function with the Mrp inhibitor MK571 led to a significant decrease in GSSG efflux ( < 0.05), indicating that Mrp5 is likely to be involved in mediating GSSG efflux. Measurements of efflux from the anterior and posterior surface of the lens revealed that GSH and GSSG efflux occurs at both surfaces but predominantly at the anterior surface.
CONCLUSIONS
Human lenses export GSH and GSSG into the surrounding ocular humors, which can be recycled by the lens to maintain intracellular GSH homeostasis or used by neighboring tissues to maintain GSH levels.
TRANSLATIONAL RELEVANCE
Early removal of a clear lens, as occurs to treat myopia and presbyopia, would eliminate this GSH reservoir and reduce the supply of GSH to other tissues, which, over time, may have clinical implications for the progression of other ocular diseases associated with oxidative stress.
Topics: Biological Transport; Glutathione; Glutathione Disulfide; Humans; Lens, Crystalline; Oxidative Stress
PubMed: 32855883
DOI: 10.1167/tvst.9.8.37 -
Pharmaceuticals (Basel, Switzerland) Aug 2021Glaucoma is a leading cause of permanent vision loss and current drugs do not halt disease progression. Thus, new therapies targeting different drug targets with novel...
Glaucoma is a leading cause of permanent vision loss and current drugs do not halt disease progression. Thus, new therapies targeting different drug targets with novel mechanisms of action are urgently needed. Previously, we identified CACNA2D1 as a novel modulator of intraocular pressure (IOP) and demonstrated that a topically applied CACNA2D1 antagonist-pregabalin (PRG)-lowered IOP in a dose-dependent manner. To further validate this novel IOP modulator as a drug target for IOP-lowering pharmaceutics, a homology model of CACNA2D1 was built and docked against the NCI library, which is one of the world's largest and most diverse compound libraries of natural products. Acivicin and zoledronic acid were identified using this method and together with PRG were tested for their plausible IOP-lowering effect on Dutch belted rabbits. Although they have inferior potency to PRG, both of the other compounds lower IOP, which in turn validates CACNA2D1 as a valuable drug target in treating glaucoma.
PubMed: 34577587
DOI: 10.3390/ph14090887 -
Acta Crystallographica. Section D,... Feb 2022Purine biosynthesis is a fundamental cellular process that sustains life by maintaining the intracellular pool of purines for DNA/RNA synthesis and signal transduction....
Purine biosynthesis is a fundamental cellular process that sustains life by maintaining the intracellular pool of purines for DNA/RNA synthesis and signal transduction. As an integral determinant of fungal survival and virulence, the enzymes in this metabolic pathway have been pursued as potential antifungal targets. Guanosine monophosphate (GMP) synthase has been identified as an attractive target as it is essential for virulence in the clinically prominent fungal pathogens Aspergillus fumigatus, Candida albicans and Cryptococcus neoformans. However, a lack of structural information on GMP synthase has hindered drug-design efforts. Here, the first structure of a GMP synthase of fungal origin, that from A. fumigatus (at 2.3 Å resolution), is presented. Structural analysis of GMP synthase shows a distinct absence of the D1 dimerization domain that is present in the human homologue. Interestingly, A. fumigatus GMP synthase adopts a dimeric state, as determined by native mass spectrometry and gel-filtration chromatography, in contrast to the monomeric human homologue. Analysis of the substrate-binding pockets of A. fumigatus GMP synthase reveals key differences in the ATP- and XMP-binding sites that can be exploited for species-specific inhibitor drug design. Furthermore, the inhibitory activities of the glutamine analogues acivicin (IC = 16.6 ± 2.4 µM) and 6-diazo-5-oxo-L-norleucine (IC = 29.6 ± 5.6 µM) against A. fumigatus GMP synthase are demonstrated. Together, these data provide crucial structural information required for specifically targeting A. fumigatus GMP synthase for future antifungal drug-discovery endeavours.
Topics: Antifungal Agents; Aspergillus fumigatus; Candida albicans; Carbon-Nitrogen Ligases; Fungal Proteins; Guanosine Monophosphate; Humans
PubMed: 35102890
DOI: 10.1107/S2059798321012031 -
Nucleosides, Nucleotides & Nucleic Acids 2018The pyrimidine de novo nucleotide synthesis consists of 6 sequential steps. Various inhibitors against these enzymes have been developed and evaluated in the clinic for...
The pyrimidine de novo nucleotide synthesis consists of 6 sequential steps. Various inhibitors against these enzymes have been developed and evaluated in the clinic for their potential anticancer activity: acivicin inhibits carbamoyl-phosphate-synthase-II, N-(phosphonacetyl)-L- aspartate (PALA) inhibits aspartate-transcarbamylase, Brequinar sodium and dichloroallyl-lawsone (DCL) inhibit dihydroorotate-dehydrogenase, and pyrazofurin (PF) inhibits orotate-phosphoribosyltransferase. We compared their growth inhibition against 3 cell lines from head-and-neck-cancer (HEP-2, UMSCC-14B and UMSCC-14C) and related the sensitivity to their effects on nucleotide pools. In all cell lines Brequinar and PF were the most active compounds with IC50 (50% growth inhibition) values between 0.06-0.37 µM, Acivicin was as potent (IC50s 0.26-1 µM), but DCL was 20-31-fold less active. PALA was most inactive (24-128 µM). At equitoxic concentrations, all pure antipyrimidine de novo inhibitors depleted UTP and CTP after 24 hr exposure, which was most pronounced for Brequinar (between 6-10% of UTP left, and 12-36% CTP), followed by DCL and PF, which were almost similar (6-16% UTP and 12-27% CTP), while PALA was the least active compound (10-70% UTP and 13-68% CTP). Acivicin is a multi-target inhibitor of more glutamine requiring enzymes (including GMP synthetase) and no decrease of UTP was found, but a pronounced decrease in GTP (31-72% left). In conclusion, these 5 inhibitors of the pyrimidine de novo nucleotide synthesis varied considerably in their efficacy and effect on pyrimidine nucleotide pools. Inhibitors of DHO-DH were most effective suggesting a primary role of this enzyme in controlling pyrimidine nucleotide pools.
Topics: Amides; Antineoplastic Agents; Aspartate Carbamoyltransferase; Aspartic Acid; Biphenyl Compounds; Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing); Carcinoma, Squamous Cell; Cell Line, Tumor; Dihydroorotate Dehydrogenase; Head and Neck Neoplasms; Humans; Isoxazoles; Naphthoquinones; Orotate Phosphoribosyltransferase; Oxidoreductases Acting on CH-CH Group Donors; Phosphonoacetic Acid; Purine Nucleotides; Pyrazoles; Pyrimidine Nucleotides; Ribonucleosides; Ribose
PubMed: 29723133
DOI: 10.1080/15257770.2018.1460479 -
Journal of Cellular Physiology May 2019Excess reactive oxygen species (ROS) generated in embryos during in vitro culture damage cellular macromolecules and embryo development. Glutathione (GSH) scavenges ROS...
Excess reactive oxygen species (ROS) generated in embryos during in vitro culture damage cellular macromolecules and embryo development. Glutathione (GSH) scavenges ROS and optimizes the culture system. However, how exogenous GSH influences intracellular GSH and improves the embryo developmental rate is poorly understood. In this study, GSH or GSX (a stable GSH isotope) was added to the culture media of bovine in vitro fertilization embryos for 7 days. The cleavage rate, blastocyst rate, and total cell number of blastocysts were calculated. Similarly to GSH, GSX increased the in vitro development rate and embryo quality. We measured intracellular ROS, GSX, and GSH for 0-32-hr postinsemination (hpi) in embryos (including zygotes at G1, S, and G2 phases and cleaved embryos) cultured in medium containing GSX. Intracellular ROS significantly decreased with increasing intracellular GSH in S-stage zygotes (18 hpi) and cleaved embryos (32 hpi). γ-Glutamyltranspeptidase ( GGT) and glutathione synthetase ( GSS) messenger RNA expression increased in zygotes (18 hpi) and cleaved embryos treated with GSH, consistent with the tendency of overall GSH content. GGT activity increased significantly in 18 hpi zygotes. GGT and GCL enzyme inhibition with acivicin and buthionine sulfoximine, respectively, decreased cleavage rate, blastocyst rate, total cell number, and GSH and GSX content. All results indicated that exogenous GSH affects intracellular GSH levels through the γ-glutamyl cycle and improves early embryo development, enhancing our understanding of the redox regulation effects and transport of GSH during embryo culture in vitro.
Topics: Animals; Cattle; Cleavage Stage, Ovum; Embryo Culture Techniques; Enzyme Inhibitors; Female; Fertilization in Vitro; Gene Expression Regulation, Developmental; Gene Expression Regulation, Enzymologic; Glutathione; Glutathione Synthase; Male; Oxidation-Reduction; Oxidative Stress; Reactive Oxygen Species; Time Factors; Zygote; gamma-Glutamyltransferase
PubMed: 30362550
DOI: 10.1002/jcp.27497