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Yamazoe Y, Murayama N, Yoshinari K. Refined CYP2E1 ∗ Template ∗∗ system to decipher the ligand-interactions. Drug Metab Pharmacokinet 2021; 41:100413. [PMID: 34673327 DOI: 10.1016/j.dmpk.2021.100413] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 05/16/2021] [Accepted: 06/23/2021] [Indexed: 10/20/2022]
Abstract
A Template system for a prediction of human CYP2E1-mediated reactions (Drug Metab Rev 2011) has been refined with the introduction of ideas of Trigger-residue and the residue-initiated movement of ligands in the active site. The refined system also includes ideas of bi-molecule binding and angled-placement, which allow to sit diverse types of ligands on Template. With the use of these ideas in common with other Template systems for human CYP1A1, CYP1A2 and CYP3A4 (Drug Metab Pharmacokinet 2016, 2017, 2019, and 2020), 349 reactions of 192 distinct chemicals published as CYP2E1 ligands were examined in the refined system. Verifications of good and poor substrates, regioselectivity and also inhibitory interaction were available faithfully for these ligands from their placements on the refined Template and rules for interaction modes, accompanied with their deciphering information to lead to the judgements. The refined CYP2E1 Template system will thus offer more reliable estimations of human CYP2E1 catalysis toward ligands of diverse structures.
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Affiliation(s)
- Yasushi Yamazoe
- Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, 980-8578, Japan; Division of Risk Assessment, National Institute of Health Sciences, Tonomachi 3-25-26, Kawasaki-ku, Kanagawa, 210-9501, Japan.
| | - Norie Murayama
- Laboratory of Drug Metabolism and Pharmacokinetics, Showa Pharmaceutical University, Machida, Tokyo, 194-8543, Japan
| | - Kouichi Yoshinari
- Laboratory of Molecular Toxicology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
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2
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Espiritu MJ, Chen J, Yadav J, Larkin M, Pelletier RD, Chan JM, Gc JB, Natesan S, Harrelson JP. Mechanisms of Herb-Drug Interactions Involving Cinnamon and CYP2A6: Focus on Time-Dependent Inhibition by Cinnamaldehyde and 2-Methoxycinnamaldehyde. Drug Metab Dispos 2020; 48:1028-1043. [PMID: 32788161 PMCID: PMC7543486 DOI: 10.1124/dmd.120.000087] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 07/15/2020] [Indexed: 12/21/2022] Open
Abstract
Information is scarce regarding pharmacokinetic-based herb-drug interactions (HDI) with trans-cinnamaldehyde (CA) and 2-methoxycinnamaldehyde (MCA), components of cinnamon. Given the presence of cinnamon in food and herbal treatments for various diseases, HDIs involving the CYP2A6 substrates nicotine and letrozole with MCA (KS = 1.58 µM; Hill slope = 1.16) and CA were investigated. The time-dependent inhibition (TDI) by MCA and CA of CYP2A6-mediated nicotine metabolism is a complex process involving multiple mechanisms. Molecular dynamic simulations showed that CYP2A6's active site accommodates two dynamic ligands. The preferred binding orientations for MCA and CA were consistent with the observed metabolism: epoxidation, O-demethylation, and aromatic hydroxylation of MCA and cinnamic acid formation from CA. The percent remaining activity plots for TDI by MCA and CA were curved, and they were analyzed with a numerical method using models of varying complexity. The best-fit models support multiple inactivator binding, inhibitor depletion, and partial inactivation. Deconvoluted mass spectra indicated that MCA and CA modified CYP2A6 apoprotein with mass additions of 156.79 (142.54-171.04) and 132.67 (123.37-141.98), respectively, and it was unaffected by glutathione. Heme degradation was observed in the presence of MCA (48.5% ± 13.4% loss; detected by liquid chromatography-tandem mass spectrometry). In the absence of clinical data, HDI predictions were made for nicotine and letrozole using inhibition parameters from the best-fit TDI models and parameters scaled from rats. Predicted area under the concentration-time curve fold changes were 4.29 (CA-nicotine), 4.92 (CA-letrozole), 4.35 (MCA-nicotine), and 5.00 (MCA-letrozole). These findings suggest that extensive exposure to cinnamon (corresponding to ≈ 275 mg CA) would lead to noteworthy interactions. SIGNIFICANCE STATEMENT: Human exposure to cinnamon is common because of its presence in food and cinnamon-based herbal treatments. Little is known about the risk for cinnamaldehyde and methoxycinnamaldehyde, two components of cinnamon, to interact with drugs that are eliminated by CYP2A6-mediated metabolism. The interactions with CYP2A6 are complex, involving multiple-ligand binding, time-dependent inhibition of nicotine metabolism, heme degradation, and apoprotein modification. An herb-drug interaction prediction suggests that extensive exposure to cinnamon would lead to noteworthy interactions with nicotine.
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Affiliation(s)
- Michael J Espiritu
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon (M.J.E., M.L., J.P.H.); College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (J.C., J.B.G., S.N.); Amgen, Cambridge, Massachusetts (J.Y.); Department of Medicinal Chemistry, University of Washington, Seattle, Washington (R.D.P.); and Chemistry Department, Pacific University Oregon, Forest Grove, Oregon (J.M.C.)
| | - Justin Chen
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon (M.J.E., M.L., J.P.H.); College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (J.C., J.B.G., S.N.); Amgen, Cambridge, Massachusetts (J.Y.); Department of Medicinal Chemistry, University of Washington, Seattle, Washington (R.D.P.); and Chemistry Department, Pacific University Oregon, Forest Grove, Oregon (J.M.C.)
| | - Jaydeep Yadav
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon (M.J.E., M.L., J.P.H.); College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (J.C., J.B.G., S.N.); Amgen, Cambridge, Massachusetts (J.Y.); Department of Medicinal Chemistry, University of Washington, Seattle, Washington (R.D.P.); and Chemistry Department, Pacific University Oregon, Forest Grove, Oregon (J.M.C.)
| | - Michael Larkin
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon (M.J.E., M.L., J.P.H.); College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (J.C., J.B.G., S.N.); Amgen, Cambridge, Massachusetts (J.Y.); Department of Medicinal Chemistry, University of Washington, Seattle, Washington (R.D.P.); and Chemistry Department, Pacific University Oregon, Forest Grove, Oregon (J.M.C.)
| | - Robert D Pelletier
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon (M.J.E., M.L., J.P.H.); College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (J.C., J.B.G., S.N.); Amgen, Cambridge, Massachusetts (J.Y.); Department of Medicinal Chemistry, University of Washington, Seattle, Washington (R.D.P.); and Chemistry Department, Pacific University Oregon, Forest Grove, Oregon (J.M.C.)
| | - Jeannine M Chan
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon (M.J.E., M.L., J.P.H.); College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (J.C., J.B.G., S.N.); Amgen, Cambridge, Massachusetts (J.Y.); Department of Medicinal Chemistry, University of Washington, Seattle, Washington (R.D.P.); and Chemistry Department, Pacific University Oregon, Forest Grove, Oregon (J.M.C.)
| | - Jeevan B Gc
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon (M.J.E., M.L., J.P.H.); College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (J.C., J.B.G., S.N.); Amgen, Cambridge, Massachusetts (J.Y.); Department of Medicinal Chemistry, University of Washington, Seattle, Washington (R.D.P.); and Chemistry Department, Pacific University Oregon, Forest Grove, Oregon (J.M.C.)
| | - Senthil Natesan
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon (M.J.E., M.L., J.P.H.); College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (J.C., J.B.G., S.N.); Amgen, Cambridge, Massachusetts (J.Y.); Department of Medicinal Chemistry, University of Washington, Seattle, Washington (R.D.P.); and Chemistry Department, Pacific University Oregon, Forest Grove, Oregon (J.M.C.)
| | - John P Harrelson
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon (M.J.E., M.L., J.P.H.); College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington (J.C., J.B.G., S.N.); Amgen, Cambridge, Massachusetts (J.Y.); Department of Medicinal Chemistry, University of Washington, Seattle, Washington (R.D.P.); and Chemistry Department, Pacific University Oregon, Forest Grove, Oregon (J.M.C.)
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Hu K, Cai L, Li Z, Glatt H, Shi M, Liu Y. Human CYP2E1-dependent mutagenicity of benzene and its hydroxylated metabolites in V79-derived cells: Suppression and enhancement by ethanol pretreatment. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:622-634. [PMID: 32285472 DOI: 10.1002/em.22375] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 03/25/2020] [Accepted: 04/03/2020] [Indexed: 06/11/2023]
Abstract
Benzene is a human carcinogen that requires metabolic activation. We previously observed that benzene and its hydroxylated metabolites induce micronuclei in mammalian cells expressing human CYP2E1. This study was initially aimed to study another endpoint, the induction of gene mutations by those compounds in the same cell models. A V79-derived cell line expressing human CYP2E1 and sulfotransferase (SULT) 1A1 (V79-hCYP2E1-hSULT1A1) pretreated with ethanol (a CYP2E1 stabilizer) was used in the hprt gene mutagenicity assay. Phenol, hydroquinone, catechol, and 1,2,4-trihydroxybenzene all induced gene mutations, while they were inactive, or only weakly positive (hydroquinone), in parental V79-Mz cells. Unexpectedly, benzene was non-mutagenic in both cell lines, but it became positive in V79-hCYP2E1-hSULT1A1 cells using regimes of short exposure/long recovery without ethanol pretreatment, for both gene mutations and micronuclei formation. In silico molecular simulation showed binding energies and positions favorable for each compound to be oxidized by human CYP2E1, benzene demonstrating the highest affinity. By tunnel analysis, ethanol binding did not limit benzene to pass tunnel S, which was specifically active for benzene. However, its end product, acetic acid, decreased the occurrence of tunnel S from 5.4 to 2.2% and extended the length of its bottleneck from 5.5 to 9.0 Å. With residual ethanol molecules still being present in CYP2E1 for a period of time after benzene exposure, the acetic acid formed could limit the entrance of benzene, thus inhibit its metabolic activation. In summary, ethanol may interfere with the activation of benzene to mutagenic metabolites, at least in cultured cells.
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Affiliation(s)
- Keqi Hu
- Department of Toxicology, School of Public Health, Southern Medical University, Guangzhou, China
| | - Lu Cai
- Department of Toxicology, School of Public Health, Southern Medical University, Guangzhou, China
| | - Zihuan Li
- Department of Toxicology, School of Public Health, Southern Medical University, Guangzhou, China
| | - Hansruedi Glatt
- Department of Nutritional Toxicology, German Institute of Human Nutrition (DIfE), Nuthetal, Germany
- Department of Food Safety, Federal Institute for Risk Assessment (BfR), Berlin, Germany
| | - Ming Shi
- Department of Environmental and Occupational Health, School of Public Health, Guangdong Medical University, Dongguan, China
| | - Yungang Liu
- Department of Toxicology, School of Public Health, Southern Medical University, Guangzhou, China
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Chen J, Jiang S, Wang J, Renukuntla J, Sirimulla S, Chen J. A comprehensive review of cytochrome P450 2E1 for xenobiotic metabolism. Drug Metab Rev 2019; 51:178-195. [PMID: 31203697 DOI: 10.1080/03602532.2019.1632889] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cytochrome P450 2E1 (CYP2E1) plays a vital role in drug-induced hepatotoxicity and cancers (e.g. lung and bladder cancer), since it is responsible for metabolizing a number of medications and environmental toxins to reactive intermediate metabolites. CYP2E1 was recently found to be the highest expressed CYP enzyme in human livers using a proteomics approach, and CYP2E1-related toxicity is strongly associated with its protein level that shows significant inter-individual variability related to ethnicity, age, and sex. Furthermore, the expression of CYP2E1 demonstrates regulation by extensive genetic polymorphism, endogenous hormones, cytokines, xenobiotics, and varying pathological states. Over the past decade, the knowledge of pharmacology, toxicology, and biology about CYP2E1 has grown remarkably, but the research progress has yet to be summarized. This study presents a timely systematic review on CYP2E1's xenobiotic metabolism, genetic polymorphism, and inhibitors, with the focus on their clinical relevance for the efficacy and toxicity of various CYP2E1 substrates. Moreover, several knowledge gaps have been identified towards fully understanding the potential interactions among different CYP2E1 substrates in clinical settings. Through in-depth analyses of these knowns and unknowns, we expect this review will aid in future drug development and improve management of CYP2E1 related clinical toxicity.
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Affiliation(s)
- Jingxuan Chen
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Screening, Southern Medical University , Guangzhou , China
| | - Sibo Jiang
- Department of Pharmaceutics, University of Florida , Orlando , FL , USA
| | - Jin Wang
- AbbVie Inc , North Chicago , IL , USA
| | - Jwala Renukuntla
- School of Pharmacy, The University of Texas at El Paso , El Paso , TX , USA
| | - Suman Sirimulla
- School of Pharmacy, The University of Texas at El Paso , El Paso , TX , USA
| | - Jianjun Chen
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Screening, Southern Medical University , Guangzhou , China
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5
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Miura T, Uehara S, Nakazato M, Kusama T, Toda A, Kamiya Y, Murayama N, Shimizu M, Suemizu H, Yamazaki H. Human plasma and liver concentrations of styrene estimated by combining a simple physiologically based pharmacokinetic model with rodent data. J Toxicol Sci 2019; 44:543-548. [DOI: 10.2131/jts.44.543] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
| | | | | | | | - Akiko Toda
- Shin Nippon Biomedical Laboratories, Ltd
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6
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Mak PJ, Denisov IG. Spectroscopic studies of the cytochrome P450 reaction mechanisms. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2018; 1866:178-204. [PMID: 28668640 PMCID: PMC5709052 DOI: 10.1016/j.bbapap.2017.06.021] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 06/22/2017] [Indexed: 10/19/2022]
Abstract
The cytochrome P450 monooxygenases (P450s) are thiolate heme proteins that can, often under physiological conditions, catalyze many distinct oxidative transformations on a wide variety of molecules, including relatively simple alkanes or fatty acids, as well as more complex compounds such as steroids and exogenous pollutants. They perform such impressive chemistry utilizing a sophisticated catalytic cycle that involves a series of consecutive chemical transformations of heme prosthetic group. Each of these steps provides a unique spectral signature that reflects changes in oxidation or spin states, deformation of the porphyrin ring or alteration of dioxygen moieties. For a long time, the focus of cytochrome P450 research was to understand the underlying reaction mechanism of each enzymatic step, with the biggest challenge being identification and characterization of the powerful oxidizing intermediates. Spectroscopic methods, such as electronic absorption (UV-Vis), electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), electron nuclear double resonance (ENDOR), Mössbauer, X-ray absorption (XAS), and resonance Raman (rR), have been useful tools in providing multifaceted and detailed mechanistic insights into the biophysics and biochemistry of these fascinating enzymes. The combination of spectroscopic techniques with novel approaches, such as cryoreduction and Nanodisc technology, allowed for generation, trapping and characterizing long sought transient intermediates, a task that has been difficult to achieve using other methods. Results obtained from the UV-Vis, rR and EPR spectroscopies are the main focus of this review, while the remaining spectroscopic techniques are briefly summarized. This article is part of a Special Issue entitled: Cytochrome P450 biodiversity and biotechnology, edited by Erika Plettner, Gianfranco Gilardi, Luet Wong, Vlada Urlacher, Jared Goldstone.
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Affiliation(s)
- Piotr J Mak
- Department of Chemistry, Saint Louis University, St. Louis, MO, United States.
| | - Ilia G Denisov
- Department of Biochemistry, University of Illinois Urbana-Champaign, Urbana, IL, United States.
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7
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Hartman JH, Miller GP, Meyer JN. Toxicological Implications of Mitochondrial Localization of CYP2E1. Toxicol Res (Camb) 2017; 6:273-289. [PMID: 28989700 DOI: 10.1039/c7tx00020k] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Cytochrome P450 2E1 (CYP2E1) metabolizes an extensive array of pollutants, drugs, and other small molecules, often resulting in bioactivation to reactive metabolites. Therefore, it is unsurprising that it has been the subject of decades of research publications and reviews. However, while CYP2E1 has historically been studied in the endoplasmic reticulum (erCYP2E1), active CYP2E1 is also present in mitochondria (mtCYP2E1). Relatively few studies have specifically focused on mtCYP2E1, but there is growing interest in this form of the enzyme as a driver in toxicological mechanisms given its activity and location. Many previous studies have linked total CYP2E1 to conditions that involve mitochondrial dysfunction (fasting, diabetes, non-alcoholic steatohepatitis, and obesity). Furthermore, a large number of reactive metabolites that are formed by CYP2E1 through metabolism of drugs and pollutants have been demonstrated to cause mitochondrial dysfunction. Finally, there appears to be significant inter-individual variability in targeting to the mitochondria, which could constitute a source of variability in individual response to exposures. This review discusses those outcomes, the biochemical properties and toxicological consequences of mtCYP2E1, and highlights important knowledge gaps and future directions. Overall, we feel that this exciting area of research is rich with new and important questions about the relationship between mtCYP2E1, mitochondrial dysfunction, and pathology.
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Affiliation(s)
| | - Grover P Miller
- Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR
| | - Joel N Meyer
- Nicholas School of the Environment, Duke University, Durham, NC
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Burkina V, Rasmussen MK, Pilipenko N, Zamaratskaia G. Comparison of xenobiotic-metabolising human, porcine, rodent, and piscine cytochrome P450. Toxicology 2017; 375:10-27. [DOI: 10.1016/j.tox.2016.11.014] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 11/16/2016] [Accepted: 11/20/2016] [Indexed: 12/25/2022]
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9
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Nair PC, McKinnon RA, Miners JO. Cytochrome P450 structure–function: insights from molecular dynamics simulations. Drug Metab Rev 2016; 48:434-52. [DOI: 10.1080/03602532.2016.1178771] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Hartman JH, Martin HC, Caro AA, Pearce AR, Miller GP. Subcellular localization of rat CYP2E1 impacts metabolic efficiency toward common substrates. Toxicology 2015; 338:47-58. [PMID: 26463279 DOI: 10.1016/j.tox.2015.10.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/22/2015] [Accepted: 10/06/2015] [Indexed: 01/12/2023]
Abstract
Cytochrome P450 2E1 (CYP2E1) detoxifies or bioactivates many low molecular-weight compounds. Most knowledge about CYP2E1 activity relies on studies of the enzyme localized to endoplasmic reticulum (erCYP2E1); however, CYP2E1 undergoes transport to mitochondria (mtCYP2E1) and becomes metabolically active. We report the first comparison of in vitro steady-state kinetic profiles for erCYP2E1 and mtCYP2E1 oxidation of probe substrate 4-nitrophenol and pollutants styrene and aniline using subcellular fractions from rat liver. For all substrates, metabolic efficiency changed with substrate concentration for erCYP2E1 reflected in non-hyperbolic kinetic profiles but not for mtCYP2E1. Hyperbolic kinetic profiles for the mitochondrial enzyme were consistent with Michaelis-Menten mechanism in which metabolic efficiency was constant. By contrast, erCYP2E1 metabolism of 4-nitrophenol led to a loss of enzyme efficiency at high substrate concentrations when substrate inhibited the reaction. Similarly, aniline metabolism by erCYP2E1 demonstrated negative cooperativity as metabolic efficiency decreased with increasing substrate concentration. The opposite was observed for erCYP2E1 oxidation of styrene; the sigmoidal kinetic profile indicated increased efficiency at higher substrate concentrations. These mechanisms and CYP2E1 levels in mitochondria and endoplasmic reticulum were used to estimate the impact of CYP2E1 subcellular localization on metabolic flux of pollutants. Those models showed that erCYP2E1 mainly carries out aniline metabolism at all aniline concentrations. Conversely, mtCYP2E1 dominates styrene oxidation at low styrene concentrations and erCYP2E1 at higher concentrations. Taken together, subcellular localization of CYP2E1 results in distinctly different enzyme activities that could impact overall metabolic clearance and/or activation of substrates and thus impact the interpretation and prediction of toxicological outcomes.
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Affiliation(s)
- Jessica H Hartman
- Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - H Cass Martin
- Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States; Department of Chemistry, University of Central Arkansas, Conway, AR, United States
| | - Andres A Caro
- Department of Chemistry, Hendrix College, Conway, AR, United States
| | - Amy R Pearce
- Arkansas Biosciences Institute, United States; Psychology & Counseling, Arkansas State University, Jonesboro, AR, United States
| | - Grover P Miller
- Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States.
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11
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Hartman JH, Letzig LG, Roberts DW, James LP, Fifer EK, Miller GP. Cooperativity in CYP2E1 metabolism of acetaminophen and styrene mixtures. Biochem Pharmacol 2015. [PMID: 26225832 DOI: 10.1016/j.bcp.2015.07.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Risk assessment for exposure to mixtures of drugs and pollutants relies heavily on in vitro characterization of their bioactivation and/or metabolism individually and extrapolation to mixtures assuming no interaction. Herein, we demonstrated that in vitro CYP2E1 metabolic activation of acetaminophen and styrene mixtures could not be explained through the Michaelis-Menten mechanism or any models relying on that premise. As a baseline for mixture studies with styrene, steady-state analysis of acetaminophen oxidation revealed a biphasic kinetic profile that was best described by negative cooperativity (Hill coefficient=0.72). The best-fit mechanism for this relationship involved two binding sites with differing affinities (Ks=830μM and Kss=32mM). Introduction of styrene inhibited that reaction less than predicted by simple competition and thus provided evidence for a cooperative mechanism within the mixture. Likewise, acetaminophen acted through a mixed-type inhibition mechanism to impact styrene epoxidation. In this case, acetaminophen competed with styrene for CYP2E1 (Ki=830μM and Ksi=180μM for catalytic and effector sites, respectively) and resulted in cooperative impacts on binding and catalysis. Based on modeling of in vivo clearance, cooperative interactions between acetaminophen and styrene resulted in profoundly increased styrene activation at low styrene exposure levels and therapeutic acetaminophen levels. Current Michaelis-Menten based toxicological models for mixtures such as styrene and acetaminophen would fail to detect this concentration-dependent relationship. Hence, future studies must assess the role of alternate CYP2E1 mechanisms in bioactivation of compounds to improve the accuracy of interpretations and predictions of toxicity.
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Affiliation(s)
- Jessica H Hartman
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Lynda G Letzig
- Department of Pediatrics, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Dean W Roberts
- Department of Pediatrics, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Laura P James
- Department of Pediatrics, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - E Kim Fifer
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Grover P Miller
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, United States.
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12
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Katen AL, Roman SD. The genetic consequences of paternal acrylamide exposure and potential for amelioration. Mutat Res 2015; 777:91-100. [PMID: 25989052 DOI: 10.1016/j.mrfmmm.2015.04.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Revised: 03/31/2015] [Accepted: 04/08/2015] [Indexed: 06/04/2023]
Abstract
Acrylamide is a toxin that humans are readily exposed to due to its formation in many carbohydrate rich foods cooked at high temperatures. Acrylamide is carcinogenic, neurotoxic and causes reproductive toxicity when high levels of exposure are reached in mice and rats. Acrylamide induced effects on fertility occur predominantly in males. Acrylamide exerts its reproductive toxicity via its metabolite glycidamide, a product which is only formed via the cytochrome P450 detoxifying enzyme CYP2E1. Glycidamide is highly reactive and forms adducts with DNA. Chronic low dose acrylamide exposure in mice relevant to human exposure levels results in significantly increased levels of DNA damage in terms of glycidamide adducts in spermatocytes, the specific germ cell stage where Cyp2e1 is expressed. Since cells in the later stages of spermatogenesis are unable to undergo DNA repair, and this level of acrylamide exposure causes no reduction in fertility, there is potential for this damage to persist until sperm maturation and fertilisation. Cyp2e1 is also present within epididymal cells, allowing for transiting spermatozoa to be exposed to glycidamide. This could have consequences for future generations in terms of predisposition to diseases such as cancer, with growing indications that paternal DNA damage can be propagated across multiple generations. Since glycidamide is the major contributor to DNA damage, a mechanism for preventing these effects is inhibiting the function of Cyp2e1. Resveratrol is an example of an inhibitor of Cyp2e1 which has shown success in reducing damage caused by acrylamide treatment in mice.
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Affiliation(s)
- Aimee L Katen
- Reproductive Science Group, School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Shaun D Roman
- Reproductive Science Group, School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia; The Australian Research Council Centre of Excellence in Biotechnology and Development, Callaghan, New South Wales 2308, Australia; The Priority Research Centres for Reproductive Sciences and Chemical Biology, University of Newcastle, Callaghan, New South Wales 2308, Australia.
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13
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Structural basis for cooperative binding of azoles to CYP2E1 as interpreted through guided molecular dynamics simulations. J Mol Graph Model 2014; 56:43-52. [PMID: 25544389 DOI: 10.1016/j.jmgm.2014.11.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 10/21/2014] [Accepted: 11/30/2014] [Indexed: 01/20/2023]
Abstract
CYP2E1 metabolizes a wide array of small, hydrophobic molecules, resulting in their detoxification or activation into carcinogens through Michaelis-Menten as well as cooperative mechanisms. Nevertheless, the molecular determinants for CYP2E1 specificity and metabolic efficiency toward these compounds are still unknown. Herein, we employed computational docking studies coupled to molecular dynamics simulations to provide a critical perspective for understanding a structural basis for cooperativity observed for an array of azoles from our previous binding and catalytic studies (Hartman et al., 2014). The resulting 28 CYP2E1 complexes in this study revealed a common passageway for azoles that included a hydrophobic steric barrier causing a pause in movement toward the active site. The entrance to the active site acted like a second sieve to restrict access to the inner chamber. Collectively, these interactions impacted the final orientation of azoles reaching the active site and hence could explain differences in their biochemical properties observed in our previous studies, such as the consequences of methylation at position 5 of the azole ring. The association of a second azole demonstrated significant differences in interactions stabilizing the bound complex than observed for the first binding event. Intermolecular interactions occurred between the two azoles as well as CYP2E1 residue side chains and backbone and involved both hydrophobic contacts and hydrogen bonds. The relative importance of these interactions depended on the structure of the respective azoles indicating the absence of specific defining criteria for binding unlike the well-characterized dominant role of hydrophobicity in active site binding. Consequently, the structure activity relationships described here and elsewhere are necessary to more accurately identify factors impacting the observation and significance of cooperativity in CYP2E1 binding and catalysis toward drugs, dietary compounds, and pollutants.
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Hartman JH, Knott K, Miller GP. CYP2E1 hydroxylation of aniline involves negative cooperativity. Biochem Pharmacol 2014; 87:523-33. [DOI: 10.1016/j.bcp.2013.12.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 11/28/2013] [Accepted: 12/02/2013] [Indexed: 11/24/2022]
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Pianalto KM, Hartman JH, Boysen G, Miller GP. Differences in butadiene adduct formation between rats and mice not due to selective inhibition of CYP2E1 by butadiene metabolites. Toxicol Lett 2013; 223:221-7. [PMID: 24021170 PMCID: PMC3831829 DOI: 10.1016/j.toxlet.2013.08.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 08/29/2013] [Accepted: 08/30/2013] [Indexed: 10/26/2022]
Abstract
CYP2E1 metabolizes 1,3-butadiene (BD) into genotoxic and possibly carcinogenic 1,2-epoxy-3-butene (EB), 1,2:3,4-diepoxybutane (DEB), and 1,2-epoxy-3,4-butanediol (EB-diol). The dose response of DNA and protein adducts derived from BD metabolites increases linearly at low BD exposures and then saturates at higher exposures in rats, but not mice. It was hypothesized that differences in adduct formation between rodents reflect more efficient BD oxidation in mice than rats. Herein, we assessed whether BD-derived metabolites selectively inhibit rat but not mouse CYP2E1 activity using B6C3F1 mouse and Fisher 344 rat liver microsomes. Basal CYP2E1 activities toward 4-nitrophenol were similar between rodents. Through IC50 studies, EB was the strongest inhibitor (IC50 54μM, mouse; 98μM, rat), BD-diol considerably weaker (IC50 1200μM, mouse; 1000μM, rat), and DEB inhibition nonexistent (IC50>25mM). Kinetic studies showed that in both species EB and BD-diol inhibited 4-nitrophenol oxidation through two-site mechanisms in which inhibition constants reflected trends observed in IC50 studies. None of the reactive epoxide metabolites inactivated CYP2E1 irreversibly. Thus, there was no selective inhibition or inactivation of rat CYP2E1 by BD metabolites relative to mouse Cyp2e1, and it can be inferred that CYP2E1 activity toward BD between rodent species would similarly not be impacted by the presence of BD metabolites. Inhibition of CYP2E1 by BD metabolites is then not responsible for the reported species difference in BD metabolism, formation of BD-derived DNA and protein adducts, mutagenicity and tumorigenesis.
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Affiliation(s)
- Kaila M. Pianalto
- Department of Chemistry and Biochemistry, University of Arkansas at Fayetteville, Fayetteville, AR 72701, USA
| | - Jessica H. Hartman
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Gunnar Boysen
- Department of Environmental and Occupational Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Grover P. Miller
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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Hartman JH, Bradley AM, Laddusaw RM, Perry MD, Miller GP. Structure of pyrazole derivatives impact their affinity, stoichiometry, and cooperative interactions for CYP2E1 complexes. Arch Biochem Biophys 2013; 537:12-20. [PMID: 23811196 DOI: 10.1016/j.abb.2013.06.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 06/14/2013] [Accepted: 06/17/2013] [Indexed: 12/18/2022]
Abstract
CYP2E1 plays a critical role in detoxification and carcinogenic activation of drugs, pollutants, and dietary compounds; however, these metabolic processes can involve poorly characterized cooperative interactions that compromise the ability to understand and predict CYP2E1 metabolism. Herein, we employed an array of ten azoles with an emphasis on pyrazoles to establish the selectivity of catalytic and cooperative CYP2E1 sites through binding and catalytic studies. Spectral binding studies for monocyclic azoles suggested two binding events, while bicyclic azoles suggested one. Pyrazole had moderate affinity toward the CYP2E1 catalytic site that improved when a methyl group was introduced at either position 3 or 4. The presence of methyl groups simultaneously at positions 3 and 5 blocked binding, and a phenyl group at position 3 did not improve binding affinity. In contrast, pyrazole fusion to a benzene or cyclohexane ring greatly increased affinity. The consequences of these binding events on CYP2E1 catalysis were studied through inhibition studies with 4-nitrophenol, a substrate known to bind both sites. Most pyrazoles shared a common mixed cooperative inhibition mechanism in which pyrazole binding rescued CYP2E1 from substrate inhibition. Overall, inhibitor affinities toward the CYP2E1 catalytic site were similar to those reported in binding studies, and the same trend was observed for binding at the cooperative site. Taken together, these studies identified key structural determinants in the affinity and stoichiometry of azole interactions with CYP2E1 and consequences on catalysis that further advance an understanding of the relationship between structure and function for this enzyme.
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Affiliation(s)
- Jessica H Hartman
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, USA
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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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Zhang H, Gay SC, Shah M, Foroozesh M, Liu J, Osawa Y, Zhang Q, Stout CD, Halpert JR, Hollenberg PF. Potent mechanism-based inactivation of cytochrome P450 2B4 by 9-ethynylphenanthrene: implications for allosteric modulation of cytochrome P450 catalysis. Biochemistry 2013; 52:355-64. [PMID: 23276288 DOI: 10.1021/bi301567z] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mechanism-based inactivation of cytochrome P450 2B4 (CYP2B4) by 9-ethynylphenanthrene (9EP) has been investigated. The partition ratio and k(inact) are 0.2 and 0.25 min(-1), respectively. Intriguingly, the inactivation exhibits sigmoidal kinetics with a Hill coefficient of 2.5 and an S(50) of 4.5 μM indicative of homotropic cooperativity. Enzyme inactivation led to an increase in mass of the apo-CYP2B4 by 218 Da as determined by electrospray ionization liquid chromatography and mass spectrometry, consistent with covalent protein modification. The modified CYP2B4 was purified to homogeneity and its structure determined by X-ray crystallography. The structure showed that 9EP is covalently attached to Oγ of Thr 302 via an ester bond, which is consistent with the increased mass of the protein. The presence of the bulky phenanthrenyl ring resulted in inward rotations of Phe 297 and Phe 206, leading to a compact active site. Thus, binding of another molecule of 9EP in the active site is prohibited. However, results from the quenching of 9EP fluorescence by unmodified or 9EP-modified CYP2B4 revealed at least two binding sites with distinct affinities, with the low-affinity site being the catalytic site and the high-affinity site on the protein periphery. Computer-aided docking and molecular dynamics simulations with one or two ligands bound revealed that the high-affinity site is situated at the entrance of a substrate access channel surrounded by the F' helix, β1-β2 loop, and β4 loop and functions as an allosteric site to enhance the efficiency of activation of the acetylenic group of 9EP and subsequent covalent modification of Thr 302.
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Affiliation(s)
- Haoming Zhang
- Department of Pharmacology, The University of Michigan Medical School , Ann Arbor, Michigan 48109, USA
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