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Schleiff MA, Flynn NR, Payakachat S, Schleiff BM, Pinson AO, Province DW, Swamidass SJ, Boysen G, Miller GP. Significance of Multiple Bioactivation Pathways for Meclofenamate as Revealed through Modeling and Reaction Kinetics. Drug Metab Dispos 2020; 49:133-141. [PMID: 33239334 PMCID: PMC7841419 DOI: 10.1124/dmd.120.000254] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 11/05/2020] [Indexed: 12/20/2022] Open
Abstract
Meclofenamate is a nonsteroidal anti-inflammatory drug used in the treatment of mild-to-moderate pain yet poses a rare risk of hepatotoxicity through an unknown mechanism. Nonsteroidal anti-inflammatory drug (NSAID) bioactivation is a common molecular initiating event for hepatotoxicity. Thus, we hypothesized a similar mechanism for meclofenamate and leveraged computational and experimental approaches to identify and characterize its bioactivation. Analyses employing our XenoNet model indicated possible pathways to meclofenamate bioactivation into 19 reactive metabolites subsequently trapped into glutathione adducts. We describe the first reported bioactivation kinetics for meclofenamate and relative importance of those pathways using human liver microsomes. The findings validated only four of the many bioactivation pathways predicted by modeling. For experimental studies, dansyl glutathione was a critical trap for reactive quinone metabolites and provided a way to characterize adduct structures by mass spectrometry and quantitate yields during reactions. Of the four quinone adducts, we were able to characterize structures for three of them. Based on kinetics, the most efficient bioactivation pathway led to the monohydroxy para-quinone-imine followed by the dechloro-ortho-quinone-imine. Two very inefficient pathways led to the dihydroxy ortho-quinone and a likely multiply adducted quinone. When taken together, bioactivation pathways for meclofenamate accounted for approximately 13% of total metabolism. In sum, XenoNet facilitated prediction of reactive metabolite structures, whereas quantitative experimental studies provided a tractable approach to validate actual bioactivation pathways for meclofenamate. Our results provide a foundation for assessing reactive metabolite load more accurately for future comparative studies with other NSAIDs and drugs in general.
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Affiliation(s)
- Mary Alexandra Schleiff
- Departments of Biochemistry and Molecular Biology (M.A.S, G.P.M.) and Environmental and Occupational Health (G.B.), University of Arkansas for Medical Sciences, Little Rock, Arizona (M.A.S.); Department of Pathology and Immunology, Washington University, St. Louis, Missouri (N.R.F., S.J.S.); Department of Chemistry, Hendrix College, Conway, Arizona (S.P.); and Independent Researcher (B.M.S.) and Department of Chemistry and Biochemistry (A.O.P., D.W.P.), Harding University, Searcy, Arkansas
| | - Noah R Flynn
- Departments of Biochemistry and Molecular Biology (M.A.S, G.P.M.) and Environmental and Occupational Health (G.B.), University of Arkansas for Medical Sciences, Little Rock, Arizona (M.A.S.); Department of Pathology and Immunology, Washington University, St. Louis, Missouri (N.R.F., S.J.S.); Department of Chemistry, Hendrix College, Conway, Arizona (S.P.); and Independent Researcher (B.M.S.) and Department of Chemistry and Biochemistry (A.O.P., D.W.P.), Harding University, Searcy, Arkansas
| | - Sasin Payakachat
- Departments of Biochemistry and Molecular Biology (M.A.S, G.P.M.) and Environmental and Occupational Health (G.B.), University of Arkansas for Medical Sciences, Little Rock, Arizona (M.A.S.); Department of Pathology and Immunology, Washington University, St. Louis, Missouri (N.R.F., S.J.S.); Department of Chemistry, Hendrix College, Conway, Arizona (S.P.); and Independent Researcher (B.M.S.) and Department of Chemistry and Biochemistry (A.O.P., D.W.P.), Harding University, Searcy, Arkansas
| | - Benjamin Mark Schleiff
- Departments of Biochemistry and Molecular Biology (M.A.S, G.P.M.) and Environmental and Occupational Health (G.B.), University of Arkansas for Medical Sciences, Little Rock, Arizona (M.A.S.); Department of Pathology and Immunology, Washington University, St. Louis, Missouri (N.R.F., S.J.S.); Department of Chemistry, Hendrix College, Conway, Arizona (S.P.); and Independent Researcher (B.M.S.) and Department of Chemistry and Biochemistry (A.O.P., D.W.P.), Harding University, Searcy, Arkansas
| | - Anna O Pinson
- Departments of Biochemistry and Molecular Biology (M.A.S, G.P.M.) and Environmental and Occupational Health (G.B.), University of Arkansas for Medical Sciences, Little Rock, Arizona (M.A.S.); Department of Pathology and Immunology, Washington University, St. Louis, Missouri (N.R.F., S.J.S.); Department of Chemistry, Hendrix College, Conway, Arizona (S.P.); and Independent Researcher (B.M.S.) and Department of Chemistry and Biochemistry (A.O.P., D.W.P.), Harding University, Searcy, Arkansas
| | - Dennis W Province
- Departments of Biochemistry and Molecular Biology (M.A.S, G.P.M.) and Environmental and Occupational Health (G.B.), University of Arkansas for Medical Sciences, Little Rock, Arizona (M.A.S.); Department of Pathology and Immunology, Washington University, St. Louis, Missouri (N.R.F., S.J.S.); Department of Chemistry, Hendrix College, Conway, Arizona (S.P.); and Independent Researcher (B.M.S.) and Department of Chemistry and Biochemistry (A.O.P., D.W.P.), Harding University, Searcy, Arkansas
| | - S Joshua Swamidass
- Departments of Biochemistry and Molecular Biology (M.A.S, G.P.M.) and Environmental and Occupational Health (G.B.), University of Arkansas for Medical Sciences, Little Rock, Arizona (M.A.S.); Department of Pathology and Immunology, Washington University, St. Louis, Missouri (N.R.F., S.J.S.); Department of Chemistry, Hendrix College, Conway, Arizona (S.P.); and Independent Researcher (B.M.S.) and Department of Chemistry and Biochemistry (A.O.P., D.W.P.), Harding University, Searcy, Arkansas
| | - Gunnar Boysen
- Departments of Biochemistry and Molecular Biology (M.A.S, G.P.M.) and Environmental and Occupational Health (G.B.), University of Arkansas for Medical Sciences, Little Rock, Arizona (M.A.S.); Department of Pathology and Immunology, Washington University, St. Louis, Missouri (N.R.F., S.J.S.); Department of Chemistry, Hendrix College, Conway, Arizona (S.P.); and Independent Researcher (B.M.S.) and Department of Chemistry and Biochemistry (A.O.P., D.W.P.), Harding University, Searcy, Arkansas
| | - Grover P Miller
- Departments of Biochemistry and Molecular Biology (M.A.S, G.P.M.) and Environmental and Occupational Health (G.B.), University of Arkansas for Medical Sciences, Little Rock, Arizona (M.A.S.); Department of Pathology and Immunology, Washington University, St. Louis, Missouri (N.R.F., S.J.S.); Department of Chemistry, Hendrix College, Conway, Arizona (S.P.); and Independent Researcher (B.M.S.) and Department of Chemistry and Biochemistry (A.O.P., D.W.P.), Harding University, Searcy, Arkansas
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Breadmore MC, Shallan AI, Rabanes HR, Gstoettenmayr D, Abdul Keyon AS, Gaspar A, Dawod M, Quirino JP. Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2010-2012). Electrophoresis 2013; 34:29-54. [PMID: 23161056 DOI: 10.1002/elps.201200396] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 09/03/2012] [Accepted: 09/04/2012] [Indexed: 12/21/2022]
Abstract
CE has been alive for over two decades now, yet its sensitivity is still regarded as being inferior to that of more traditional methods of separation such as HPLC. As such, it is unsurprising that overcoming this issue still generates much scientific interest. This review continues to update this series of reviews, first published in Electrophoresis in 2007, with updates published in 2009 and 2011 and covers material published through to June 2012. It includes developments in the field of stacking, covering all methods from field amplified sample stacking and large volume sample stacking, through to isotachophoresis, dynamic pH junction and sweeping. Attention is also given to online or inline extraction methods that have been used for electrophoresis.
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Affiliation(s)
- Michael C Breadmore
- Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania, Hobart, Tasmania, Australia.
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Hartman JH, Boysen G, Miller GP. Cooperative effects for CYP2E1 differ between styrene and its metabolites. Xenobiotica 2013; 43:755-64. [PMID: 23327532 DOI: 10.3109/00498254.2012.760764] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Cooperative interactions are frequently observed in the metabolism of drugs and pollutants by cytochrome P450s; nevertheless, the molecular determinants for cooperativity remain elusive. Previously, we demonstrated that steady-state styrene metabolism by CYP2E1 exhibits positive cooperativity. We hypothesized that styrene metabolites have lower affinity than styrene toward CYP2E1 and limited ability to induce cooperative effects during metabolism. To test the hypothesis, we determined the potency and mechanism of inhibition for styrene and its metabolites toward oxidation of 4-nitrophenol using CYP2E1 Supersomes® and human liver microsomes. Styrene inhibited the reaction through a mixed cooperative mechanism with high affinity for the catalytic site (67 µM) and lower affinity for the cooperative site (1100 µM), while increasing substrate turnover at high concentrations. Styrene oxide and 4-vinylphenol possessed similar affinity for CYP2E1. Styrene oxide behaved cooperatively like styrene, but 4-vinylphenol decreased turnover at high concentrations. Styrene glycol was a very poor competitive inhibitor. Among all compounds, there was a positive correlation with binding and hydrophobicity. Taken together, these findings for CYP2E1 further validate contributions of cooperative mechanisms to metabolic processes, demonstrate the role of molecular structure on those mechanisms and underscore the potential for heterotropic cooperative effects between different compounds.
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Affiliation(s)
- Jessica H Hartman
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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