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Shiver AL, Sun J, Culver R, Violette A, Wynter C, Nieckarz M, Mattiello SP, Sekhon PK, Friess L, Carlson HK, Wong D, Higginbottom S, Weglarz M, Wang W, Knapp BD, Guiberson E, Sanchez J, Huang PH, Garcia PA, Buie CR, Good B, DeFelice B, Cava F, Scaria J, Sonnenburg J, Sinderen DV, Deutschbauer AM, Huang KC. A mutant fitness compendium in Bifidobacteria reveals molecular determinants of colonization and host-microbe interactions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.29.555234. [PMID: 37693407 PMCID: PMC10491234 DOI: 10.1101/2023.08.29.555234] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Bifidobacteria commonly represent a dominant constituent of human gut microbiomes during infancy, influencing nutrition, immune development, and resistance to infection. Despite interest as a probiotic therapy, predicting the nutritional requirements and health-promoting effects of Bifidobacteria is challenging due to major knowledge gaps. To overcome these deficiencies, we used large-scale genetics to create a compendium of mutant fitness in Bifidobacterium breve (Bb). We generated a high density, randomly barcoded transposon insertion pool in Bb, and used this pool to determine Bb fitness requirements during colonization of germ-free mice and chickens with multiple diets and in response to hundreds of in vitro perturbations. To enable mechanistic investigation, we constructed an ordered collection of insertion strains covering 1462 genes. We leveraged these tools to improve models of metabolic pathways, reveal unexpected host- and diet-specific requirements for colonization, and connect the production of immunomodulatory molecules to growth benefits. These resources will greatly reduce the barrier to future investigations of this important beneficial microbe.
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Affiliation(s)
- Anthony L. Shiver
- Department of Bioengineering, Stanford University, Stanford CA 94305, USA
| | - Jiawei Sun
- Department of Bioengineering, Stanford University, Stanford CA 94305, USA
| | - Rebecca Culver
- Department of Genetics, Stanford University, Stanford CA 94305, USA
| | - Arvie Violette
- Department of Bioengineering, Stanford University, Stanford CA 94305, USA
| | - Charles Wynter
- Department of Bioengineering, Stanford University, Stanford CA 94305, USA
| | - Marta Nieckarz
- Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, SE-90187, Sweden
| | - Samara Paula Mattiello
- Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD, 57007, USA
- College of Mathematics and Science, The University of Tennessee Southern, Pulaski TN 38478, USA
| | - Prabhjot Kaur Sekhon
- Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD, 57007, USA
- Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK, 74074, USA
| | - Lisa Friess
- School of Microbiology, University College Cork, Ireland
- APC Microbiome Ireland, University College Cork, Ireland
| | - Hans K. Carlson
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Daniel Wong
- Department of Applied Physics, Stanford University, Stanford CA 94305, USA
| | - Steven Higginbottom
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | - Meredith Weglarz
- Stanford Shared FACS Facility, Center for Molecular and Genetic Medicine, Stanford University, Stanford, California, USA
| | - Weigao Wang
- Department of Chemical Engineering, Stanford University, Stanford CA 94305, USA
| | | | - Emma Guiberson
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | | | - Po-Hsun Huang
- Department of Mechanical Engineering, Laboratory for Energy and Microsystems Innovation, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, 02139, MA, USA
| | - Paulo A. Garcia
- Department of Mechanical Engineering, Laboratory for Energy and Microsystems Innovation, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, 02139, MA, USA
| | - Cullen R. Buie
- Department of Mechanical Engineering, Laboratory for Energy and Microsystems Innovation, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, 02139, MA, USA
| | - Benjamin Good
- Department of Applied Physics, Stanford University, Stanford CA 94305, USA
| | | | - Felipe Cava
- Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, SE-90187, Sweden
| | - Joy Scaria
- Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD, 57007, USA
- Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK, 74074, USA
| | - Justin Sonnenburg
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | - Douwe Van Sinderen
- School of Microbiology, University College Cork, Ireland
- APC Microbiome Ireland, University College Cork, Ireland
| | - Adam M. Deutschbauer
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
| | - Kerwyn Casey Huang
- Department of Bioengineering, Stanford University, Stanford CA 94305, USA
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
- Chan-Zuckerberg Biohub, San Francisco, CA 94158
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2
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Tang X, Du X, Yu Y, Qin M, Qian L, Zhang M, Yang Y, Yu Q, Gan Z. Deep-Penetrating Triple-Responsive Prodrug Nanosensitizer Actuates Efficient Chemoradiotherapy in Pancreatic Ductal Adenocarcinoma Models. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2202834. [PMID: 35808966 DOI: 10.1002/smll.202202834] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 06/24/2022] [Indexed: 06/15/2023]
Abstract
Chemoradiotherapy (CRT) is the most accepted treatment for locally advanced pancreatic ductal adenocarcinoma (PDAC) and can significantly improve the R0 resection rate. However, there are few long-term survivors after CRT. Although some polymer nanoparticles have shown potential in alleviating the dose-limiting toxicity and assisting the chemotherapy of PDAC, there are few efficient nanosensitizers (NS) available for CRT of this malignancy, especially in the context of its hypoxic nature. Herein, based on the biological features of PDAC, a γ-glutamyl transpeptidase (GGT)/glutathione (GSH)/hypoxia triple-responsive prodrug NS to overcome the biological barrier and microenvironmental limitations confronted by CRT in PDAC is developed. Due to triple-responsiveness, deep tumor penetration, GSH/hypoxia-responsive drug release/activation, and hypoxia-induced chemoradio-sensitization can be simultaneously achieved with this NS. As a result, tumor shrinkage after CRT with this NS can be observed in both subcutaneous and orthotopic PDAC models, foreshadowing its potential in clinical neoadjuvant CRT.
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Affiliation(s)
- Xiaohu Tang
- Beijing Laboratory of Biomedical Materials, The State Key Laboratory of Organic-Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Xiaomeng Du
- Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Beijing, 100026, P. R. China
| | - Yanting Yu
- Beijing Laboratory of Biomedical Materials, The State Key Laboratory of Organic-Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Meng Qin
- Beijing Laboratory of Biomedical Materials, The State Key Laboratory of Organic-Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Lili Qian
- Beijing Laboratory of Biomedical Materials, The State Key Laboratory of Organic-Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Meng Zhang
- Beijing Laboratory of Biomedical Materials, The State Key Laboratory of Organic-Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Yan Yang
- Beijing Laboratory of Biomedical Materials, The State Key Laboratory of Organic-Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Qingsong Yu
- Beijing Laboratory of Biomedical Materials, The State Key Laboratory of Organic-Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Zhihua Gan
- Beijing Laboratory of Biomedical Materials, The State Key Laboratory of Organic-Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
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3
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Leitsch D, Kolarich D, Wilson IBH, Altmann F, Duchêne M. Nitroimidazole action in Entamoeba histolytica: a central role for thioredoxin reductase. PLoS Biol 2008; 5:e211. [PMID: 17676992 PMCID: PMC1933457 DOI: 10.1371/journal.pbio.0050211] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Accepted: 06/07/2007] [Indexed: 02/06/2023] Open
Abstract
Metronidazole, a 5-nitroimidazole drug, has been the gold standard for several decades in the treatment of infections with microaerophilic protist parasites, including Entamoeba histolytica. For activation, the drug must be chemically reduced, but little is known about the targets of the active metabolites. Applying two-dimensional gel electrophoresis and mass spectrometry, we searched for protein targets in E. histolytica. Of all proteins visualized, only five were found to form adducts with metronidazole metabolites: thioredoxin, thioredoxin reductase, superoxide dismutase, purine nucleoside phosphorylase, and a previously unknown protein. Recombinant thioredoxin reductase carrying the modification displayed reduced enzymatic activity. In treated cells, essential non-protein thiols such as free cysteine were also affected by covalent adduct formation, their levels being drastically reduced. Accordingly, addition of cysteine allowed E. histolytica to survive in the presence of otherwise lethal metronidazole concentrations and reduced protein adduct formation. Finally, we discovered that thioredoxin reductase reduces metronidazole and other nitro compounds, suggesting a new model of metronidazole activation in E. histolytica with a central role for thioredoxin reductase. By reducing metronidazole, the enzyme renders itself and associated thiol-containing proteins vulnerable to adduct formation. Because thioredoxin reductase is a ubiquitous enzyme, similar processes could occur in other eukaryotic or prokaryotic organisms. The protist parasites Entamoeba histolytica, Trichomonas vaginalis, and Giardia intestinalis grow in environments with low oxygen concentration. Infections with these parasites are commonly treated with metronidazole, a nitroimidazole drug that must be reduced for activation, resulting in several toxic metabolites. We examined the soluble proteome of metronidazole-treated E. histolytica cells for target proteins of these metabolites, applying two-dimensional gel electrophoresis and mass spectrometry. Of about 1,500 proteins visualized, only five formed covalent adducts with metronidazole metabolites, including thioredoxin, thioredoxin reductase, and superoxide dismutase. Metronidazole-bound thioredoxin reductase displayed diminished activity. In addition to these proteins, small thiol molecules, including cysteine, formed adducts with metronidazole. Supplementation with cysteine allowed the cells to survive otherwise lethal metronidazole concentrations. Finally, we discovered that one of the modified proteins, thioredoxin reductase, reduces metronidazole, suggesting a central role for this enzyme with regard to metronidazole toxicity. Taken together, our work reveals a new area of molecular interactions of activated metronidazole with cellular components. Because thioredoxin reductase is a ubiquitous enzyme, similar processes could also occur in other eukaryotic or prokaryotic organisms. Metronidazole is used for treatment of infections with microaerophilic protist parasites. Here, a new model of metronidazole activation is proposed, with a central role for thioredoxin reductase.
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Affiliation(s)
- David Leitsch
- Department of Specific Prophylaxis and Tropical Medicine, Center for Physiology and Pathophysiology, Medical University of Vienna, Vienna, Austria
| | - Daniel Kolarich
- Department of Chemistry, University of Natural Resources and Applied Life Sciences, Vienna, Austria
| | - Iain B. H Wilson
- Department of Chemistry, University of Natural Resources and Applied Life Sciences, Vienna, Austria
| | - Friedrich Altmann
- Department of Chemistry, University of Natural Resources and Applied Life Sciences, Vienna, Austria
| | - Michael Duchêne
- Department of Specific Prophylaxis and Tropical Medicine, Center for Physiology and Pathophysiology, Medical University of Vienna, Vienna, Austria
- * To whom correspondence should be addressed. E-mail:
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4
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Chaignon P, Cortial S, Ventura A, Lopes P, Halgand F, Laprevote O, Ouazzani J. Purification and identification of a Bacillus nitroreductase: Potential use in 3,5-DNBTF biosensoring system. Enzyme Microb Technol 2006. [DOI: 10.1016/j.enzmictec.2006.04.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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5
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Lu AY. Covalent binding of chemical residues: health impact. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 500:657-61. [PMID: 11765012 DOI: 10.1007/978-1-4615-0667-6_98] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A Y Lu
- Department of Chemical Biology, College of Pharmacy, Rutgers, The State University of NJ, Piscataway 08854, USA
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6
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Alvaro RF, Wislocki PG, Miwa GT, Lu AY. Drug residue formation from ronidazole, a 5-nitroimidazole. VIII. Identification of the 2-methylene position as a site of protein alkylation. Chem Biol Interact 1992; 82:21-30. [PMID: 1547514 DOI: 10.1016/0009-2797(92)90011-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Ronidazole protein-bound adducts were generated by the in vitro anaerobic incubation of [2-methylene-14C]ronidazole with microsomes from the livers of male rats. Acid hydrolysis of the protein adducts yielded an imidazole ring fragment bearing the radiolabel and an amino acid residue derived from the proteins. This fragment has been identified as carboxymethylcysteine by co-chromatography of the amino acid and its dansyl derivative with known standards under a variety of conditions. The carboxymethylcysteine was estimated to represent at least 15% of the radioactivity derived from the protein-bound adducts and provides unequivocal evidence that nucleophilic attack by protein cysteine thiols occurred at the 2-methylene position of ronidazole.
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Affiliation(s)
- R F Alvaro
- Department of Animal and Exploratory Drug Metabolism, Merck Sharp and Dohme Research Laboratories, Rahway, NJ 07065
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7
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Abstract
Most chemical carcinogens are not active in themselves but require bioactivation to electrophiles that bind covalently to DNA and often act by producing mutations. In recent years it has been realized that mutations can be important at many stages of carcinogenesis. A variety of different enzymes are involved in bioactivation reactions, which include oxidation, reduction, thiol conjugation, acetyl transfer, sulfur transfer, methyl transfer, glucuronosyl transfer, and epoxide hydrolysis. These processes often occur in concert with a single carcinogen. Humans vary considerably in activities of these enzymes and this variation may contribute to differences in risk.
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Affiliation(s)
- F P Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146
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8
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Bryant C, DeLuca M. Purification and characterization of an oxygen-insensitive NAD(P)H nitroreductase from Enterobacter cloacae. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(20)64294-6] [Citation(s) in RCA: 159] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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9
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Girard M, Carignan G, Mousseau N, Dawson BA. Chromatographic and spectroscopic characterization of sulphur-bound dimetridazole and ranidazole derivatives. J Pharm Biomed Anal 1991; 9:151-7. [PMID: 1873306 DOI: 10.1016/0731-7085(91)80138-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The 5-nitroimidazoles, dimetridazole and ronidazole, two important veterinary drugs, were reacted under reductive conditions with the sulfhydryl-containing substrates cysteine and glutathione to yield 5-amino-4-S-substituted imidazoles. After purification by reversed-phase liquid chromatography (RP-LC), the four adducts were characterized by RP-LC with photodiode array detection using conditions where their parent drugs were not eluted from the column. Structural identification was conducted by spectroscopic techniques, mainly 1-dimensional and 2-dimensional NMR. While the dimetridazole adducts were found to be monosubstituted at the C-4 position, the two ronidazole products contained two units of the sulfhydryl substrate, located at the C-4 and C-6 positions.
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Affiliation(s)
- M Girard
- Bureau of Drug Research, Health and Welfare Canada, Ottawa, Ontario
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10
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Affiliation(s)
- P G Wislocki
- Department of Animal and Exploratory Drug Metabolism, Merck Sharp & Dohme Research Laboratories, Rahway, New Jersey 07065-0900
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11
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Abstract
Azathioprine, an immunosuppressive drug, has been used for 25 years. Azathioprine is rapidly converted into a number of metabolites after absorption. Maximum blood levels in experimental animals (mice) were 11.3 micrograms/ml after a dosage of 33.3 mg/kg. Generally, levels of less than 1 microgram/ml are found. As azathioprine is ineffective in hypoxanthine guanine phosphoribosyltransferase (HPRT)-deficient patients, it will be clear that for immunosuppressive activity azathioprine must be metabolised. Regarding mutagenic activity, its mutagenicity for bacteria seems irrelevant for man because the nitroimidazole moiety can be reduced by bacteria but not or hardly at all by mammalian tissues. So 6-mercaptopurine (a metabolite of azathioprine) and its metabolites should be regarded as the active compounds. In vitro azathioprine can induce chromosome aberrations and other cytogenetic events at high, non-physiological doses. However, in view of the low blood levels it is unlikely that azathioprine can induce chromosome aberrations in kidney transplant patients. It is more probable that azathioprine inhibits the elimination of such aberrant cells through its immunosuppressive activity. It should be pointed out that in microbial mutagenicity systems also, azathioprine concentrations that are not reached in patients are needed to obtain an increased mutation rate.
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Affiliation(s)
- C E Voogd
- National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands
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12
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Mikalsen A, Alexander J, Ryberg D. Microsomal metabolism of hexavalent chromium. Inhibitory effect of oxygen and involvement of cytochrome P-450. Chem Biol Interact 1989; 69:175-92. [PMID: 2495190 DOI: 10.1016/0009-2797(89)90076-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The reduction of hexavalent chromium (Cr(VI] by rat liver microsomes was studied. With 15-120 microM Na2CrO4 microsomes (0.5 mg protein/ml) effectively reduced Cr(VI) in the presence of NADPH provided anaerobic conditions. Phenobarbital (PB) and Aroclor 1254 (PCB) pretreatment increased microsomal Cr(VI) reduction while CoCl2 reduced the rate. The rates with 30 microM Na2CrO4 were: 6.4 +/- 0.1, 7.8 +/- 0.7, 13.4 +/- 0.5, 2.95 +/- 0.09 nmol Cr.mg prot.-1 min-1 for control, PB, PCB and cobalt pretreated microsomes respectively. Kinetic studies gave a Michaeli-Menten like first-order kinetics with increases both in Km and Vmax values after pretreatment with PB or PCB. CO partly inhibited the microsomal Cr(VI) reduction. The CO-sensitive reduction rate was directly correlated to the cyt. P-450 content of the different microsomal preparations. Substituting NADH for NADPH gave approximately 27% lower activity with 30 microM Na2CrO4. This activity was neither inducible by cyt. P-450 inducers nor influenced by CO. Oxygen 1.0% and 0.10% gave approximately 100% and 30% inhibition of Cr(VI) reduction (30 microM Na2CrO4) respectively, and an uncompetitive like inhibitory pattern was found. No redox cycling of Cr(VI) was seen. 51Cr binding to the microsomes was approximately 10% after complete reduction of 30 microM Na2CrO4. Externally added FMN, Fe3+-ADP and nitrobenzen stimulated microsomal Cr(VI) reduction. A 60% higher reduction rate of Cr(VI) by isolated hepatocytes was found during anaerobic in comparison with aerobic conditions.
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Affiliation(s)
- A Mikalsen
- National Institute of Public Health, Dept. of Toxiology, Geitmyrsveien, Oslo, Norway
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13
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Kedderis GL, Argenbright LS, Miwa GT. Mechanism of reductive activation of a 5-nitroimidazole by flavoproteins: model studies with dithionite. Arch Biochem Biophys 1988; 262:40-8. [PMID: 3128179 DOI: 10.1016/0003-9861(88)90166-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The flavoprotein nitroreductases NADPH:cytochrome P-450 reductase and xanthine oxidase catalyzed the cofactor-dependent anaerobic nitro group reduction and covalent binding to protein sulfhydryl groups of the 5-nitroimidazole substrate ronidazole [1-methyl-5-nitroimidazole-2-yl)-methyl carbamate). Studies with variously radiolabeled ronidazole molecules demonstrated that the imidazole ring was intact while greater than 80% of the C-4 3H and 2-carbamoyl group were lost from the covalently bound product. The stoichiometry of cofactor consumption during the enzyme-catalyzed reduction of the substrate could not be determined, so a model nitroreductase system which utilized dithionite as the reductant and agarose-immobilized cysteine as the target for alkylation was developed. Two moles of dithionite was consumed per mole of substrate for maximal reduction of uv absorbance due to the nitro group, for maximal release of C-4 3H, and for maximal covalent binding to agarose-immobilized cysteine. These results indicate that four electrons are required for the reductive activation of the substrate, consistent with formation of a hydroxylamine reactive intermediate. Covalent binding of variously radiolabeled substrate molecules after dithionite reduction exhibited the same labeling pattern as flavoprotein-catalyzed covalent binding, suggesting that covalent binding is mediated by the same species in both chemical and biological systems. The data are consistent with a mechanism where the substrate undergoes four-electron reduction to form a hydroxylamine, which is susceptible to nucleophilic attack at C-4. When water attacks C-4, the 2-carbamoyl group can eliminate to form a Michael-like acceptor which adds thiols at the 2-methylene position.
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Affiliation(s)
- G L Kedderis
- Department of Animal Drug Metabolism, Merck Sharp & Dohme Research Laboratories, Rahway, New Jersey 07065
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14
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Affiliation(s)
- G L Kedderis
- Department of Animal Drug Metabolism, Merck Sharp & Dohme Research Laboratories, Rahway, New Jersey 07065
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15
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Lu AY, Wislocki PG, Chiu SH, Miwa GT. Tissue drug residues and their toxicological significance. Drug Metab Rev 1987; 18:363-78. [PMID: 3330522 DOI: 10.3109/03602538708998313] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- A Y Lu
- Department of Animal Drug Metabolism, Merck Sharp & Dohme Research Laboratories, Rahway, New Jersey 07065
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16
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Miwa GT, Wang R, Alvaro R, Walsh JS, Lu AY. The metabolic activation of ronidazole [(1-methyl-5-nitroimidazole-2-yl)-methyl carbamate] to reactive metabolites by mammalian, cecal bacterial and T. foetus enzymes. Biochem Pharmacol 1986; 35:33-6. [PMID: 3940524 DOI: 10.1016/0006-2952(86)90551-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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17
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Miwa GT, Wislocki P, Bagan E, Wang R, Walsh JS, Lu AY. Studies on the mechanism of activation and the mutagenicity of ronidazole, a 5-nitroimidazole. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1986; 197:527-35. [PMID: 3766278 DOI: 10.1007/978-1-4684-5134-4_50] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Substantial evidence implicates the obligatory nucleophilic attack by water at C4 for the elimination of the carbamate and subsequent immobilization by electrophilic attack on protein thiols. Consequently, the strong correlation between the structural requirements for protein alkylation and for mutagenicity in TA100 suggests a possible role of nucleophilic addition at C4 or at the 2-methylene carbon for the expression of mutagenicity. Further studies directed at evaluating this possibility are currently in progress.
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18
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Abstract
A variety of enzymes function in the oxygenation, oxidation-reduction, conjugation, and hydrolysis of drugs and other foreign chemicals. Often these enzymes detoxicate chemicals to prevent detrimental effects. In this review we will, however, concentrate on cases in which metabolism activates chemicals to reactive species which cause cellular damage. Particular attention will be given to mixed-function oxidases, which carry out a variety of oxygenations, as well as other reactions. (We will focus on cellular toxicity as opposed to initiation of tumorigenesis in this review.) In many cases, considerable circumstantial evidence exists linking these enzymes to enhanced toxicity of chemicals, although causal relationships have seldom been demonstrated. Further, in very few cases is the explicit cause of toxicity known. Modification of critical protein residues is suspected, although oxidative stress may also be involved in some cases. We discuss general aspects of mechanisms of toxic action, briefly list all cases in which metabolism is suspected to play a role in enhancing toxicity, and review a few examples in detail where substantial chemical and enzymatic information is available. The latter instances would involve knowledge of the enzymes involved, chemical evidence on the structures of the reactive metabolites, identification of adducts, and some inference into the biological processes which are effected to elicit toxicity. We consider, in this regard, vinyl halides (which have been a focus in our own laboratory), acetaminophen, pyrrolizidine alkaloids, and fluoroxene.
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19
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Miwa GT, Alvaro RF, Walsh JS, Wang R, Lu AY. Drug residue formation from ronidazole, a 5-nitroimidazole. VII. Comparison of protein-bound products formed in vitro and in vivo. Chem Biol Interact 1984; 50:189-202. [PMID: 6744464 DOI: 10.1016/0009-2797(84)90095-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
In vivo experiments were conducted with ronidazole radiolabelled in the 2-14CH2-, 4,5-14C-, N-14CH3- and 4-3H-positions. The hepatic protein-bound residues, assessed by the radioactivity of exhaustively washed protein samples, were independent of the radiolabel position and occurred with 4-3H loss (greater than 80%) in excellent agreement to previous results obtained in vitro with anaerobic incubations of liver microsomes (Miwa et al., Chem. Biol. Interact., 41 (1982) 297). HPLC analysis of acid hydrolyzed in vivo protein-bound residues, obtained from [2-14CH2] ronidazole, produced a radiochromatographic profile which was virtually identical to that obtained from a similarly treated in vitro sample. Moreover, almost quantitative (76-96%) liberation of radiolabelled methylamine was obtained from hydrolysates of in vivo and in vitro residue samples formed from [N-14CH3] ronidazole. With 4,5-ring labeled ronidazole the distribution of total radioactivity of the protein hydrolysate on cation exchange resin and the fraction of the residue recovered as oxalic acid were nearly identical for the in vivo and in vitro products. We interpret these data to indicate that ronidazole alkylates proteins with retention of most of the carbon framework of the molecule, in vivo. It is also concluded that the in vitro model, previously used to examine the mechanism of protein alkylation, accurately reflects the salient process initially occurring in the intact animal during the formation of protein-bound residues of this drug.
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Wislocki PG, Bagan ES, Cook MM, Bradley MO, Wolf FJ, Lu AY. Drug residue formation from ronidazole, a 5-nitroimidazole. VI. Lack of mutagenic activity of reduced metabolites and derivatives of ronidazole. Chem Biol Interact 1984; 49:27-38. [PMID: 6722938 DOI: 10.1016/0009-2797(84)90050-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The potential toxicity of ronidazole residues present in the tissues of food-producing animals was assessed using the Ames mutagenicity test. Since ronidazole is activated by reduction, reduced derivatives of ronidazole and metabolites formed by enzymatic reduction of ronidazole were tested for mutagenicity. When tested at levels several orders of magnitude higher than that at which ronidazole was mutagenic, 5-amino-4-S-cysteinyl-1,2- dimethylimidazole , a product of the dithionite reduction of ronidazole in the presence of cysteine, the 5-N-acetylamino derivative of ronidazole and 5-amino-1,2- dimethylimidazole all lacked mutagenic activity in Ames strain TA100. The metabolites of ronidazole formed by the incubation of ronidazole with microsomes under anaerobic conditions were also not mutagenic. These data demonstrate that although ronidazole is a potent mutagen, residues from it which may be present in the tissues of food-producing animals lack any mutagenic activity.
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Abstract
Benznidazole (Bz) (N-benzyl-2-nitro-1-imidazole-acetamide) is a drug used against Chagas' disease. Rat liver microsomal and cytosolic fractions, but not mitochondria, exhibited Bz nitroreductase activity under anaerobic conditions in the presence of NADPH. Microsomal nitroreductase activity was enhanced by FAD and was inhibited totally by oxygen and partially by carbon monoxide. Liver cystosol fraction was able to reduce Bz nitrogroups in the presence of either N-methylnicotinamide or hypoxanthine as substrates. These enzyme activities were inhibited by menadione or allopurinol respectively. Under every experimental condition leading to enzymatic reduction of Bz nitrogroups and its inhibition or enhancement, reactive metabolites that bind covalently to proteins were also produced. This covalent binding was effectively prevented by reduced glutathione. Results suggest the participation of cytochrome P-450 and cytochrome c reductase in liver microsomal processes and of xanthine oxidase and aldehyde oxidase in liver cytosolic processes of Bz nitroreduction and activation to reactive metabolites that bind covalently to proteins. Possible pharmacological and toxicological implications of the described observations were discussed.
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Wislocki PG, Bagan ES, Vandenheuvel WJ, Walker RW, Alvaro RF, Arison BH, Lu AY, Wolf FJ. Drug residue formation from ronidazole, a 5-nitroimidazole. V. Cysteine adducts formed upon reduction of ronidazole by dithionite or rat liver enzymes in the presence of cysteine. Chem Biol Interact 1984; 49:13-25. [PMID: 6722933 DOI: 10.1016/0009-2797(84)90049-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
When ronidazole (1-methyl-5-nitroimidazole-2-methanol carbamate) is reduced by either dithionite or rat liver microsomal enzymes in the presence of cysteine, ronidazole-cysteine adducts can be isolated. Upon reduction with dithionite ronidazole can react with either one or two molecules of cysteine to yield either a monosubstituted ronidazole-cysteine adduct substituted at the 4-position or a disubstituted ronidazole-cysteine adduct substituted at both the 4-position and the 2-methylene position. In both products the carbamoyl group of ronidazole has been lost. The use of rat liver microsomes to reduce ronidazole led to the formation of the disubstituted ronidazole-cysteine adduct. These data indicate that upon the reduction of ronidazole one or more reactive species can be formed which can bind covalently to cysteine. The proposed reactive intermediates formed under these conditions may account for the observed binding of ronidazole to microsomal protein and the presence of intractable drug residues in the tissues of animals treated with this compound. They may also account for the mutagenicity of this compound in bacteria.
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Involvement of FMN and phenobarbital cytochrome P-450 in stimulating a one-electron reductive denitrosation of 1-(2-chloroethyl)-3-(cyclohexyl)-1-nitrosourea catalyzed by NADPH-cytochrome P-450 reductase. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)32309-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Miwa GT, West SB, Walsh JS, Wolf FJ, Lu AY. Drug residue formation from ronidazole, a 5-nitroimidazole. III. Studies on the mechanism of protein alkylation in vitro. Chem Biol Interact 1982; 41:297-312. [PMID: 6809347 DOI: 10.1016/0009-2797(82)90107-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Ronidazole (1-methyl-5-nitroimidazole-2-methanol carbamate) is reductively metabolized by liver microsomal and purified NADPH-cytochrome P-450 reductase preparations to reactive metabolites that covalently bind to tissue proteins. Kinetic experiments and studies employing immobilized cysteine or blocked cysteine thiols have shown that the principal targets of protein alkylation ara cysteine thiols. Furthermore, ronidazole specifically radiolabelled with 14C in the 4,5-ring, N-methyl or 2-methylene positions give rise to equivalent apparent covalent binding suggesting that the imidazole nucleus is retained in the bound residue. In contrast, the carbonyl-14C-labeled ronidazole gives approx. 6--15-fold less apparent covalent binding indicating that the carbamoyl group is lost during the reaction leading to the covalently bound metabolite. The conversion of ronidazole to reactive metabolite(s) is quantitative and reflects the amazing efficiency by which this compound is activated by microsomal enzymes. However, only about 5% of this metabolite can be accounted for as protein-bound products under the conditions employed in these studies. Consequently, approx. 95% of the reactive ronidazole metabolite(s) can react with other constituents in the reaction media such as other thiols or water. Based on these results, a mechanism is proposed for the metabolic activation of ronidazole.
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West SB, Wislocki PG, Fiorentini KM, Alvaro R, Wolf FJ, Lu AY. Drug residue formation from ronidazole, a 5-nitroimidazole. I. Characterization of in vitro protein alkylation. Chem Biol Interact 1982; 41:265-79. [PMID: 6809345 DOI: 10.1016/0009-2797(82)90105-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The metabolic activation of [14C]ronidazole by rat liver enzymes to metabolite(s) bound to macromolecules was investigated. The alkylation of protein by [14C]ronidazole metabolite(s) was catalyzed most efficiently by rat liver microsomes, in the absence of oxygen utilizing NADPH as a source of reducing equivalents. Based on a comparison of total ronidazole metabolized versus the amount bound to microsomal protein, approximately one molecule alkylates microsomal protein for every 20 molecules of ronidazole metabolized. Protein alkylation was strongly inhibited by sulfhydryl-containing compounds such as cysteine and glutathione whereas methionine had no effect. Based on HPLC analysis of ronidazole, cysteine was found not to inhibit microsomal metabolism of ronidazole ruling out a decrease in the rate of production of the reactive metabolite(s) as the mechanism of cysteine inhibition.
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