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Nature Communications Jul 2020Macrophages are professional phagocytes known to play a vital role in controlling Mycobacterium tuberculosis (Mtb) infection and disease progression. Here we compare Mtb...
Macrophages are professional phagocytes known to play a vital role in controlling Mycobacterium tuberculosis (Mtb) infection and disease progression. Here we compare Mtb growth in mouse alveolar (AMs), peritoneal (PMs), and liver (Kupffer cells; KCs) macrophages and in bone marrow-derived monocytes (BDMs). KCs restrict Mtb growth more efficiently than all other macrophages and monocytes despite equivalent infections through enhanced autophagy. A metabolomics comparison of Mtb-infected macrophages indicates that ornithine and imidazole are two top-scoring metabolites in Mtb-infected KCs and that acetylcholine is the top-scoring in Mtb-infected AMs. Ornithine, imidazole and atropine (acetylcholine inhibitor) inhibit Mtb growth in AMs. Ornithine enhances AMPK mediated autophagy whereas imidazole directly kills Mtb by reducing cytochrome P450 activity. Intranasal delivery of ornithine or imidazole or the two together restricts Mtb growth. Our study demonstrates that the metabolic differences between Mtb-infected AMs and KCs lead to differences in the restriction of Mtb growth.
Topics: Ammonia; Animals; Apoptosis; Arginase; Atropine; Autophagy; Cell Proliferation; Disease Progression; Female; Imidazoles; Kupffer Cells; Macrophages, Alveolar; Macrophages, Peritoneal; Mice; Mice, Inbred C57BL; Nitric Oxide; Ornithine; Phosphatidylserines; RNA, Small Interfering; Reactive Oxygen Species; Tuberculosis; Urea
PubMed: 32669568
DOI: 10.1038/s41467-020-17310-5 -
The Plant Journal : For Cell and... May 2023Polyamines such as spermidine and spermine are essential regulators of cell growth, differentiation, maintenance of ion balance and abiotic stress tolerance. Their...
Polyamines such as spermidine and spermine are essential regulators of cell growth, differentiation, maintenance of ion balance and abiotic stress tolerance. Their levels are controlled by the spermidine/spermine N -acetyltransferase (SSAT) via acetylation to promote either their degradation or export outside the cell as shown in mammals. Plant genomes contain at least one gene coding for SSAT (also named NATA for N-AcetylTransferase Activity). Combining kinetics, HPLC-MS and crystallography, we show that three plant SSATs, one from the lower plant moss Physcomitrium patens and two from the higher plant Zea mays, acetylate various aliphatic polyamines and two amino acids lysine (Lys) and ornithine (Orn). Thus, plant SSATs exhibit a broad substrate specificity, unlike more specific human SSATs (hSSATs) as hSSAT1 targets polyamines, whereas hSSAT2 acetylates Lys and thiaLys. The crystal structures of two PpSSAT ternary complexes, one with Lys and CoA, the other with acetyl-CoA and polyethylene glycol (mimicking spermine), reveal a different binding mode for polyamine versus amino acid substrates accompanied by structural rearrangements of both the coenzyme and the enzyme. Two arginine residues, unique among plant SSATs, hold the carboxyl group of amino acid substrates. The most abundant acetylated compound accumulated in moss was N -acetyl-Lys, whereas N -acetyl-Orn, known to be toxic for aphids, was found in maize. Both plant species contain very low levels of acetylated polyamines. The present study provides a detailed biochemical and structural basis of plant SSAT enzymes that can acetylate a wide range of substrates and likely play various roles in planta.
Topics: Animals; Humans; Polyamines; Spermidine; Spermine; Zea mays; Lysine; Ornithine; Acetylation; Acetyltransferases; Catalysis; Mammals
PubMed: 36786691
DOI: 10.1111/tpj.16148 -
Biomolecules Jun 2022is an opportunistic pathogen that can cause acute and severe infections. Increasing resistance to antibiotics has given rise to the urgent need for an alternative...
is an opportunistic pathogen that can cause acute and severe infections. Increasing resistance to antibiotics has given rise to the urgent need for an alternative antimicrobial agent. A promising strategy is the inhibition of iron sequestration in the bacteria. The current work aimed to screen for inhibitors of pyoverdine-mediated iron sequestration in . As a drug target, we choose l-ornithine-N5-monooxygenase (PvdA), an enzyme involved in the biosynthesis of pyoverdine that catalyzes the FAD-dependent hydroxylation of the side chain amine of ornithine. As drug repurposing is a fast and cost-efficient way of discovering new applications for known drugs, the approach may help to solve emerging clinical problems. In this study, we use data about molecules from drug banks for screening. A total of 15 drugs that are similar in structure to l-ornithine, the substrate of PvdA, and 30 drugs that are sub-structures of l-ornithine were virtually docked against PvdA. N-2-succinyl ornithine and cilazapril were found to be the top binders with a binding energy of -12.8 and -9.1 kcal mol, respectively. As the drug-likeness and ADME properties of the drugs were also found to be promising, molecular dynamics studies were performed to further confirm the stability of the complexes. The results of this in silico study indicate that N-2-succinyl ornithine could potentially be explored as a drug for the treatment of infections.
Topics: Drug Repositioning; Humans; Iron; Mixed Function Oxygenases; Ornithine; Pseudomonas Infections; Pseudomonas aeruginosa
PubMed: 35883443
DOI: 10.3390/biom12070887 -
Familial Cancer Jan 2021Familial adenomatous polyposis (FAP) is a hereditary colorectal cancer syndrome characterized by colorectal adenomas and a near 100% lifetime risk of colorectal cancer... (Review)
Review
Familial adenomatous polyposis (FAP) is a hereditary colorectal cancer syndrome characterized by colorectal adenomas and a near 100% lifetime risk of colorectal cancer (CRC). Prophylactic colectomy, usually by age 40, is the gold-standard therapy to mitigate this risk. However, colectomy is associated with morbidity and fails to prevent extra-colonic disease manifestations, including gastric polyposis, duodenal polyposis and cancer, thyroid cancer, and desmoid disease. Substantial research has investigated chemoprevention medications in an aim to prevent disease progression, postponing the need for colectomy and temporizing the development of extracolonic disease. An ideal chemoprevention agent should have a biologically plausible mechanism of action, be safe and easily tolerated over a prolonged treatment period, and produce a durable and clinically meaningful effect. To date, no chemoprevention agent tested has fulfilled these criteria. New agents targeting novel pathways in FAP are needed. Substantial preclinical literature exists linking the molecular target of rapamycin (mTOR) pathway to FAP. A single case report of rapamycin, an mTOR inhibitor, used as chemoprevention in FAP patients exists, but no formal clinical studies have been conducted. Here, we review the prior literature on chemoprevention in FAP, discuss the rationale for rapamycin in FAP, and outline a proposed clinical trial testing rapamycin as a chemoprevention agent in patients with FAP.
Topics: Adenomatous Polyposis Coli; Anti-Inflammatory Agents, Non-Steroidal; Antibiotics, Antineoplastic; Ascorbic Acid; Aspirin; Capsules; Celecoxib; Chemoprevention; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Drug Therapy, Combination; Eflornithine; Erlotinib Hydrochloride; Fatty Acids, Nonesterified; Genes, APC; Humans; Sirolimus; Sulindac; TOR Serine-Threonine Kinases; Vitamins
PubMed: 32507936
DOI: 10.1007/s10689-020-00189-y -
CNS Oncology Apr 2018This review covers the literature between 1989 and 2007 on studies relevant to the neuro-oncology usage of eflornithine (α-difluoromethylornithine), an oral agent that... (Review)
Review
This review covers the literature between 1989 and 2007 on studies relevant to the neuro-oncology usage of eflornithine (α-difluoromethylornithine), an oral agent that irreversibly inhibits the enzyme ornithine decarboxylase. It covers the use of eflornithine, alone or in combination, to treat high-grade gliomas. In addition, we provide an update on overall survival from The University of Texas MD Anderson Cancer Center Community Clinical Oncology Program and Clinical Trials Data Office that demonstrates a meaningful benefit in overall survival for eflornithine as a single agent and in combination with nitrosourea-based therapies for anaplastic gliomas. We also provide a framework for understanding the basis and study design of the ongoing pivotal, registrational Phase III multicenter trial for recurrent/progressive anaplastic astrocytoma.
Topics: Animals; Antineoplastic Agents; Brain Neoplasms; Clinical Trials as Topic; Eflornithine; Glioma; Humans
PubMed: 29378419
DOI: 10.2217/cns-2017-0031 -
Case Reports in Gastroenterology 2014Ornithine transcarbamylase deficiency (OTCD) is the most common type urea cycle enzyme deficiencies. This syndrome results from a deficiency of the mitochondrial enzyme...
Ornithine transcarbamylase deficiency (OTCD) is the most common type urea cycle enzyme deficiencies. This syndrome results from a deficiency of the mitochondrial enzyme ornithine transcarbamylase, which catalyzes the conversion of ornithine and carbamoyl phosphate to citrullin. Our case was a 28-year-old female diagnosed with OTCD following neurocognitive deficit during her first pregnancy. Although hyperammonemia was suspected as the cause of the patient's mental changes, there was no evidence of chronic liver disease. Plasma amino acid and urine organic acid analysis revealed OTCD. After combined modality treatment with arginine, sodium benzoate and hemodialysis, the patient's plasma ammonia level stabilized and her mental status returned to normal. At last she recovered without any damage left.
PubMed: 25759629
DOI: 10.1159/000369131 -
Protein Science : a Publication of the... Jun 2022DcsB, an enzyme produced from the d-cycloserine biosynthetic gene cluster, displays moderate similarity to arginase in the sequence and three-dimensional structure....
DcsB, an enzyme produced from the d-cycloserine biosynthetic gene cluster, displays moderate similarity to arginase in the sequence and three-dimensional structure. Arginase is a ubiquitous enzyme hydrolyzing l-arginine to generate l-ornithine and urea, whereas DcsB hydrolyzes N -hydroxy-l-arginine (l-NOHA), an arginase inhibitor, to generate l-ornithine and hydroxyurea. We determined the crystal structure of DcsB associated with l-ornithine and that with the tetrahedral derivative of 2(S)-amino-6-boronohexanoic acid, whose boron atom forms a covalent bond with an oxygen atom bridging two manganese ions at the active center. The substrate-binding pocket of DcsB is narrower than that of arginase, suggesting that DcsB is unsuitable for the binding of l-NOHA in an inhibitory manner. The transition state-like structure demonstrated that Asp210 and Glu241 have a role to trap a positively charged ion near the dimanganese cluster. Kinetic analysis using the mutated DcsB showed that the enzyme employs different catalytic mechanisms under the neutral and alkaline pH conditions. Glu241 in DcsB is likely involved in the recognition of the hydroxyguanidino group of l-NOHA, whereas Asp210, in cooperation with Glu241, seems to contribute to the reactivity toward the protonated l-NOHA, which is a preferable species under the neutral pH conditions. After entering of the protonated l-NOHA to the substrate-binding pocket of DcsB, a hydronium ion may be trapped at the positive ion-binding site. Then, the ion serves as a specific acid catalyst to facilitate the collapse of the tetrahedral intermediate of l-NOHA.
Topics: Amino Acids; Arginase; Arginine; Catalysis; Kinetics; Ornithine
PubMed: 35634777
DOI: 10.1002/pro.4338 -
FASEB Journal : Official Publication of... Oct 2017, protozoan parasites that cause human African trypanosomiasis (HAT), depend on ornithine uptake and metabolism by ornithine decarboxylase (ODC) for survival. Indeed,...
, protozoan parasites that cause human African trypanosomiasis (HAT), depend on ornithine uptake and metabolism by ornithine decarboxylase (ODC) for survival. Indeed, ODC is the target of the WHO "essential medicine" eflornithine, which is antagonistic to another anti-HAT drug, suramin. Thus, ornithine uptake has important consequences in , but the transporters have not been identified. We describe these amino acid transporters (AATs). In a heterologous expression system, TbAAT10-1 is selective for ornithine, whereas TbAAT2-4 transports both ornithine and histidine. These AATs are also necessary to maintain intracellular ornithine and polyamine levels in , thereby decreasing sensitivity to eflornithine and increasing sensitivity to suramin. Consistent with competition for histidine, high extracellular concentrations of this amino acid phenocopied a TbAAT2-4 genetic defect. Our findings established TbAAT10-1 and TbAAT2-4 as the parasite ornithine transporters, one of which can be modulated by histidine, but both of which affect sensitivity to important anti-HAT drugs.-Macedo, J. P., Currier, R. B., Wirdnam, C., Horn, D., Alsford, S., Rentsch, D. Ornithine uptake and the modulation of drug sensitivity in .
Topics: Animals; Antineoplastic Agents; Eflornithine; Humans; Ornithine; Ornithine Decarboxylase; Polyamines; Trypanosoma brucei brucei; Trypanosomiasis, African
PubMed: 28679527
DOI: 10.1096/fj.201700311R -
Molecular Genetics and Metabolism Sep 2017Propionic acidemia is a rare metabolic disorder caused by a deficiency of propionyl- CoA carboxylase, the enzyme converting propionyl-CoA to methylmalonyl-CoA that... (Clinical Trial)
Clinical Trial
BACKGROUND
Propionic acidemia is a rare metabolic disorder caused by a deficiency of propionyl- CoA carboxylase, the enzyme converting propionyl-CoA to methylmalonyl-CoA that subsequently enters the citric acid cycle as succinyl-CoA. Patients with propionic acidemia cannot metabolize propionic acid, which combines with oxaloacetate to form methylcitric acid. This, with the defective supply of succinyl-CoA, may lead to a deficiency in citric acid cycle intermediates.
PURPOSE
The objective of this study was to determine whether supplements with glutamine (400mg/kg per day), citrate (7.5mEq/kg per day), or ornithine α-ketoglutarate (400mg/kg per day) (anaplerotic agents that could fill up the citric acid cycle) would affect plasma levels of glutamine and ammonia, the urinary excretion of Krebs cycle intermediates, and the clinical outcome in 3 patients with propionic acidemia.
METHODS
Each supplement was administered daily for four weeks with a two week washout period between supplements. The supplement that produced the most favorable changes was supplemented for 30 weeks following the initial study period and then for a 2 year extension.
RESULTS
The urinary excretion of the Krebs cycle intermediates, α-ketoglutarate, succinate, and fumarate increased significantly compared to baseline during citrate supplementation, but not with the other two supplements. For this reason, citrate supplements were continued in the second part of the study. The urinary excretion of methylcitric acid and 3-hydroxypropionic acid did not change with any intervention. No significant changes in ammonia or glutamine levels were observed with any supplement. However, supplementation with any anaplerotic agents normalized the physiological buffering of ammonia by glutamate, with plasma glutamate and alanine levels significantly increasing, rather than decreasing with increasing ammonia levels. No significant side effects were observed with any therapy and safety labs (blood counts, chemistry and thyroid profile) remained unchanged. Motor and cognitive development was severely delayed before the trial and did not change significantly with therapy. Hospitalizations per year did not change during the trial period, but decreased significantly (p<0.05) in the 2years following the study (when citrate was continued) compared to the 2years before and during the study.
CONCLUSIONS
These results indicate that citrate entered the Krebs cycle providing successful anaplerotic therapy by increasing levels of the downstream intermediates of the Krebs cycle: α-ketoglutarate, succinate and fumarate. Citrate supplements were safe and might have contributed to reduce hospitalizations in patients with propionic acidemia.
Topics: Amino Acids; Ammonia; Carbon-Carbon Ligases; Child; Child, Preschool; Citrates; Citric Acid; Citric Acid Cycle; Dietary Supplements; Female; Glutamine; Humans; Lactic Acid; Male; Ornithine; Propionic Acidemia; Treatment Outcome
PubMed: 28712602
DOI: 10.1016/j.ymgme.2017.07.003 -
Scientific Reports Jul 2022Polyamines are small cationic molecules that have been linked to various cellular processes including replication, translation, stress response and recently, capsule...
Polyamines are small cationic molecules that have been linked to various cellular processes including replication, translation, stress response and recently, capsule regulation in Streptococcus pneumoniae (Spn, pneumococcus). Pneumococcal-associated diseases such as pneumonia, meningitis, and sepsis are some of the leading causes of death worldwide and capsule remains the principal virulence factor of this versatile pathogen. α-Difluoromethyl-ornithine (DFMO) is an irreversible inhibitor of the polyamine biosynthesis pathway catalyzed by ornithine decarboxylase and has a long history in modulating cell growth, polyamine levels, and disease outcomes in eukaryotic systems. Recent evidence shows that DFMO can also target arginine decarboxylation. Interestingly, DFMO-treated cells often escape polyamine depletion via increased polyamine uptake from extracellular sources. Here, we examined the potential capsule-crippling ability of DFMO and the possible synergistic effects of the polyamine transport inhibitor, AMXT 1501, on pneumococci. We characterized the changes in pneumococcal metabolites in response to DFMO and AMXT 1501, and also measured the impact of DFMO on amino acid decarboxylase activities. Our findings show that DFMO inhibited pneumococcal polyamine and capsule biosynthesis as well as decarboxylase activities, albeit, at a high concentration. AMXT 1501 at physiologically relevant concentration could inhibit both polyamine and capsule biosynthesis, however, in a serotype-dependent manner. In summary, this study demonstrates the utility of targeting polyamine biosynthesis and transport for pneumococcal capsule inhibition. Since targeting capsule biosynthesis is a promising way for the eradication of the diverse and pathogenic pneumococcal strains, future work will identify small molecules similar to DFMO/AMXT 1501, which act in a serotype-independent manner.
Topics: Antineoplastic Agents; Eflornithine; Ornithine Decarboxylase; Ornithine Decarboxylase Inhibitors; Polyamines; Streptococcus pneumoniae
PubMed: 35821246
DOI: 10.1038/s41598-022-16007-7