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Recio L, Fowler J, Martin L, Swartz C. Genotoxicity assessment in HepaRG™ cells as a new approach methodology follow up to a positive response in the human TK6 cell micronucleus assay: Naphthalene case study. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2023; 64:458-465. [PMID: 37704589 DOI: 10.1002/em.22575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 09/06/2023] [Accepted: 09/07/2023] [Indexed: 09/15/2023]
Abstract
We are evaluating the use of metabolically competent HepaRG™ cells combined with CometChip® for DNA damage and the micronucleus (MN) assay as a New Approach Methodology (NAM) alternative to animals for follow up genotoxicity assessment to in vitro positive genotoxic response. Naphthalene is genotoxic in human TK6 cells inducing a nonlinear dose-response for the induction of micronuclei in the presence of rat liver S9. of naphthalene. In HepaRG™ cells, naphthalene genotoxicity was assessed using either 6 (CometChip™) or 12 concentrations of naphthalene (MN assay) with the top dose used for assessment of genotoxicity for the Comet and MN assay was 1.25 and 1.74 mM respectively, corresponding to approximately 45% cell survival. In contrast to human TK6 cell with S9, naphthalene was not genotoxic in either the HepaRG™ MN assay or the Comet assay using CometChip®. The lack of genotoxicity in both the MN and comet assays in HepaRG™ cells is likely due to Phase II enzymes removing phenols preventing further bioactivation to quinones and efficient detoxication of naphthalene quinones or epoxides by glutathione conjugation. In contrast to CYP450 mediated metabolism, these Phase II enzymes are inactive in rat liver S9 due to lack of appropriate cofactors causing a positive genotoxic response. Rat liver S9-derived BMD10 over-predicts naphthalene genotoxicity when compared to the negative genotoxic response observed in HepaRG™ cells. Metabolically competent hepatocyte models like HepaRG™ cells should be considered as human-relevant NAMs for use genotoxicity assessments to reduce reliance on rodents.
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Affiliation(s)
- Leslie Recio
- Integrated Laboratory Systems, an Inotiv Company, Morrisville, North Carolina, USA
| | - Jasmine Fowler
- Integrated Laboratory Systems, an Inotiv Company, Morrisville, North Carolina, USA
| | - Lincoln Martin
- Integrated Laboratory Systems, an Inotiv Company, Morrisville, North Carolina, USA
| | - Carol Swartz
- Integrated Laboratory Systems, an Inotiv Company, Morrisville, North Carolina, USA
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Habil MR, Salazar-González RA, Doll MA, Hein DW. N-acetyltransferase 2 acetylator genotype-dependent N-acetylation and toxicity of the arylamine carcinogen β-naphthylamine in cryopreserved human hepatocytes. Arch Toxicol 2022; 96:3257-3263. [PMID: 36112171 PMCID: PMC9641657 DOI: 10.1007/s00204-022-03381-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 09/08/2022] [Indexed: 11/02/2022]
Abstract
We used cryopreserved human hepatocytes that express rapid, intermediate, and slow acetylator N-acetyltransferase 2 (NAT2) genotypes to measure the N-acetylation of β-naphthylamine (BNA) which is one of the aromatic amines found in cigarette smoke including E-cigarettes. We investigated the role of NAT2 genetic polymorphism in genotoxicity and oxidative stress induced by BNA. In vitro BNA NAT2 activities in rapid acetylators was 1.6 and 3.5-fold higher than intermediate (p < 0.01) and slow acetylators (p < 0.0001). BNA N-acetylation in situ was 3 to 4- fold higher in rapid acetylators than slow acetylators, following incubation with 10 and 100 µM BNA (p < 0.01). DNA damage was two to threefold higher in the rapid versus slow acetylators (p < 0.0001) and 2.5-fold higher in intermediate versus slow acetylators following BNA treatment at 100 and 1000 μM, ROS/RNS level was the highest in rapid acetylators followed by intermediate and then slow acetylators (p < 0.0001). Our findings show that the N-acetylation of BNA is NAT2 genotype dependent in cryopreserved human hepatocytes and our data further document an important role for NAT2 genetic polymorphism in modifying BNA-induced genotoxicity and oxidative damage.
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Affiliation(s)
- Mariam R Habil
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, 505 S. Hancock Street, CTR Rm 303, Louisville, KY, 40202, USA
| | - Raúl A Salazar-González
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, 505 S. Hancock Street, CTR Rm 303, Louisville, KY, 40202, USA
| | - Mark A Doll
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, 505 S. Hancock Street, CTR Rm 303, Louisville, KY, 40202, USA
| | - David W Hein
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, 505 S. Hancock Street, CTR Rm 303, Louisville, KY, 40202, USA.
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Habil MR, Salazar-González RA, Doll MA, Hein DW. Differences in β-naphthylamine metabolism and toxicity in Chinese hamster ovary cell lines transfected with human CYP1A2 and NAT2*4, NAT2*5B or NAT2*7B N-acetyltransferase 2 haplotypes. Arch Toxicol 2022; 96:2999-3012. [PMID: 36040704 PMCID: PMC10187863 DOI: 10.1007/s00204-022-03367-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 08/17/2022] [Indexed: 02/01/2023]
Abstract
β-naphthylamine (BNA) is an important aromatic amine carcinogen. Current exposures derive primarily from cigarette smoking including e-cigarettes. Occupational and environmental exposure to BNA is associated with urinary bladder cancer which is the fourth most frequent cancer in the United States. N-acetyltransferase 2 (NAT2) is an important metabolizing enzyme for aromatic amines. Previous studies investigated mutagenicity and genotoxicity of BNA in bacteria and in rabbit or rat hepatocytes. However, the effects of human NAT2 genetic polymorphism on N-acetylation and genotoxicity induced by BNA still need to be clarified. We used nucleotide excision repair-deficient Chinese hamster ovary (CHO) cells that were stably transfected with human CYP1A2 and NAT2 alleles: NAT2*4 (reference allele), NAT2*5B (variant slow acetylator allele common in Europe) or NAT2*7B (variant slow acetylator allele common in Asia). BNA N-acetylation was measured both in vitro and in situ via high-performance liquid chromatography (HPLC). Hypoxanthine phosphoribosyl transferase (HPRT) mutations, double-strand DNA breaks, and reactive oxygen species (ROS) were measured as indices of toxicity. NAT2*4 cells showed significantly higher BNA N-acetylation rates followed by NAT2*7B and NAT2*5B. BNA caused concentration-dependent increases in DNA damage and ROS levels. NAT2*7B showed significantly higher levels of HPRT mutants, DNA damage and ROS than NAT2*5B (p < 0.001, p < 0.0001, p < 0.0001 respectively) although both are slow alleles. Our findings suggest that BNA N-acetylation and toxicity are modified by NAT2 polymorphism. Furthermore, they confirm heterogeneity among slow acetylator alleles for BNA metabolism and toxicity supporting differential risk for individuals carrying NAT2*7B allele.
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Affiliation(s)
- Mariam R Habil
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, 505 S. Hancock Street, CTR Rm 303, Louisville, KY, 40202, USA
| | - Raúl A Salazar-González
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, 505 S. Hancock Street, CTR Rm 303, Louisville, KY, 40202, USA
| | - Mark A Doll
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, 505 S. Hancock Street, CTR Rm 303, Louisville, KY, 40202, USA
| | - David W Hein
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, 505 S. Hancock Street, CTR Rm 303, Louisville, KY, 40202, USA.
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Kobets T, Duan JD, Vock E, Deschl U, Williams GM. Evaluation of Pharmaceuticals for DNA Damage in the Chicken Egg Genotoxicity Assay (CEGA). Int J Toxicol 2022; 41:297-311. [PMID: 35658642 DOI: 10.1177/10915818221093583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
DNA damage is an established initiating event in the mutagenicity and carcinogenicity of genotoxic chemicals. Accordingly, assessment of this endpoint is critical for chemicals which are being developed for use in humans. To assess the ability of the Chicken Egg Genotoxicity Assay (CEGA) to detect genotoxic pharmaceuticals, a set of 23 compounds with different pharmacological and reported genotoxic effects was tested for the potential to produce nuclear DNA adducts and strand breaks in the embryo-fetal livers using the 32P-nucleotide postlabeling (NPL) and comet assays, respectively. Due to high toxicity, two aneugens, colchicine and vinblastine, and an autophagy inhibitor, hydroxychloroquine, could not be evaluated. Out of the 20 remaining pharmaceuticals, 10 including estrogen modulators, diethylstilbestrol and tamoxifen, antineoplastics cyclophosphamide, etoposide, and mitomycin C, antifungal griseofulvin, local anesthetics lidocaine and prilocaine, and antihistamines diphenhydramine and doxylamine, yielded clear positive outcomes in at least one of the assays. The antihypertensive vasodilator hydralazine and antineoplastics streptozotocin and teniposide, produced only DNA strand breaks, which were not dose-dependent, and thus, the results with these 3 pharmaceuticals were considered equivocal. No DNA damage was detected for 7 compounds, including the purine antagonist 6-thioguanine, antipyretic analgesics acetaminophen and phenacetin, antibiotic ciprofloxacin, antilipidemic clofibrate, anti-inflammatory ibuprofen, and sedative phenobarbital. However, low solubility of these compounds limited dosages tested in CEGA. Overall, results in CEGA were largely in concordance with the outcomes in other systems in vitro and in vivo, indicating that CEGA provides reliable detection of DNA damaging activity of genotoxic compounds. Further evaluations with a broader set of compounds would support this conclusion.
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Affiliation(s)
- Tetyana Kobets
- Department of Pathology, Immunology and Microbiology, 8137New York Medical College, Valhalla, NY, USA
| | - Jian-Dong Duan
- Department of Pathology, Immunology and Microbiology, 8137New York Medical College, Valhalla, NY, USA
| | - Esther Vock
- Boehringer Ingelheim Pharma GmbH&Co. KG, Biberach an der Riss, Germany
| | - Ulrich Deschl
- Boehringer Ingelheim Pharma GmbH&Co. KG, Biberach an der Riss, Germany
| | - Gary M Williams
- Department of Pathology, Immunology and Microbiology, 8137New York Medical College, Valhalla, NY, USA
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Sleight TW, Sexton CN, Mpourmpakis G, Gilbertson LM, Ng CA. A Classification Model to Identify Direct-Acting Mutagenic Polycyclic Aromatic Hydrocarbon Transformation Products. Chem Res Toxicol 2021; 34:2273-2286. [PMID: 34662518 DOI: 10.1021/acs.chemrestox.1c00187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are a complex group of environmental contaminants, many having long environmental half-lives. As these compounds degrade, the changes in their structure can result in a substantial increase in mutagenicity compared to the parent compound. Over time, each individual PAH can potentially degrade into several thousand unique transformation products, creating a complex, constantly evolving set of intermediates. Microbial degradation is the primary mechanism of their transformation and ultimate removal from the environment, and this process can result in mutagenic activation similar to the metabolic activation that can occur in multicellular organisms. The diversity of the potential intermediate structures in PAH-contaminated environments renders hazard assessment difficult for both remediation professionals and regulators. A mixture of structural and energetic descriptors has proven effective in existing studies for classifying which PAH transformation products will be mutagenic. However, most existing studies of environmental PAH mutagens primarily focus on nitrogenated derivatives, which are prevalent in the atmosphere and not as relevant in soil. Additionally, PAH products commonly found in the environment can range from as large as five rings to as small as a single ring, requiring a broadly inclusive methodology to comprehensively evaluate mutagenic potential. We developed a combination of supervised and unsupervised machine learning methods to predict environmentally induced PAH mutagenicity with improved performance over currently available tools. K-means clustering with principal component analysis allows us to identify molecular clusters that we hypothesize to have similar mechanisms of action. Recursive feature elimination identifies the most influential descriptors. The cluster-specific regression outperforms available classifiers in predicting direct-acting mutagens resulting from the microbial biodegradation of PAHs and provides direction for future studies evaluating the environmental hazards resulting from PAH biodegradation.
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Affiliation(s)
- Trevor W Sleight
- Civil & Environmental Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Caitlin N Sexton
- Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Giannis Mpourmpakis
- Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Leanne M Gilbertson
- Civil & Environmental Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States.,Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Carla A Ng
- Civil & Environmental Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States.,Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
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Leggett CS, Doll MA, States JC, Hein DW. Acetylation of putative arylamine and alkylaniline carcinogens in immortalized human fibroblasts transfected with rapid and slow acetylator N-acetyltransferase 2 haplotypes. Arch Toxicol 2021; 95:311-319. [PMID: 33136180 PMCID: PMC7855884 DOI: 10.1007/s00204-020-02901-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 09/02/2020] [Indexed: 10/23/2022]
Abstract
Exposure to alkylanilines found in tobacco smoke and indoor air is associated with risk of bladder cancer. Genetic factors significantly influence the metabolism of arylamine carcinogens and the toxicological outcomes that result from exposure. We utilized nucleotide excision repair (NER)-deficient immortalized human fibroblasts to examine the effects of human N-acetyltransferase 1 (NAT1), CYP1A2, and common rapid (NAT2*4) and slow (NAT2*5B or NAT2*7B) acetylator human N-acetyltransferase 2 (NAT2) haplotypes on environmental arylamine and alkylaniline metabolism. We constructed SV40-transformed human fibroblast cells that stably express human NAT2 alleles (NAT2*4, NAT2*5B, or NAT2*7B) and human CYP1A2. Human NAT1 and NAT2 apparent kinetic constants were determined following recombinant expression of human NAT1 and NAT2 in yeast for the arylamines benzidine, 4-aminobiphenyl (ABP), and 2-aminofluorene (2-AF), and the alkylanilines 2,5-dimethylaniline (DMA), 3,4-DMA, 3,5-DMA, 2-6-DMA, and 3-ethylaniline (EA) compared with those of the prototype NAT1-selective substrate p-aminobenzoic acid and NAT2-selective substrate sulfamethazine. Benzidine, 3,4-DMA, and 2-AF were preferential human NAT1 substrates, while 3,5-DMA, 2,5-DMA, 3-EA, and ABP were preferential human NAT2 substrates. Neither recombinant human NAT1 or NAT2 catalyzed the N-acetylation of 2,6-DMA. Among the alkylanilines, N-acetylation of 3,5-DMA was substantially higher in human fibroblasts stably expressing NAT2*4 versus NAT2*5B and NAT2*7B. The results provide important insight into the role of the NAT2 acetylator polymorphism (in the presence of competing NAT1 and CYP1A2-catalyzed N-acetylation and N-hydroxylation) on the metabolism of putative alkyaniline carcinogens. The N-acetylation of two alkylanilines associated with urinary bladder cancer (3-EA and 3,5-DMA) was modified by NAT2 acetylator polymorphism.
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Affiliation(s)
- Carmine S Leggett
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY, USA
- American Association for Cancer Research, Washington, DC, USA
| | - Mark A Doll
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY, USA
| | - J Christopher States
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY, USA
| | - David W Hein
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY, USA.
- University of Louisville Superfund Research Program, Louisville, KY, USA.
- University of Louisville Health Sciences Center, Kosair Charities CTR Room 303, 505 South Hancock Street, Louisville, KY, 40202, USA.
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Li Y, Yin W, Zhan Y, Jia Y, Cui D, Zhang W, Chang Y. Comparative metabolome analysis provides new insights into increased larval mortality under seawater acidification in the sea urchin Strongylocentrotus intermedius. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 747:141206. [PMID: 32777501 DOI: 10.1016/j.scitotenv.2020.141206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 07/20/2020] [Accepted: 07/21/2020] [Indexed: 06/11/2023]
Abstract
Mortality and metabolic responses of four-armed larvae of Strongylocentrotus intermedius under CO2-induced seawater acidification were investigated. Gametes of S. intermedius were fertilized and developed to the four-armed larval stage in either current natural seawater pH levels (as Control; pH = 7.99 ± 0.01) or laboratory-controlled acidified conditions (OA1: ΔpH = -0.3 units; OA2: ΔpH = -0.4 units; OA3: ΔpH = -0.5 units) according to the predictions of the Intergovernmental Panel on Climate Change (IPCC). The degrees of spicule exposure and asymmetry and mortality of four-armed larvae of S. intermedius were observed; each had a significant linearly increasing trend as the seawater pH level decreased. Comparative metabolome analysis identified a total of 87 significantly differentially expressed metabolites (SDMs, UP: 57, DOWN: 30) in OA-treated groups compared with the control group. Twenty-three SDMs, including carnitine, lysophosphatidylcholine (LPC) 18:3, lysophosphatidyl ethanolamine (LPE) 16:1, glutathione (GSH) and L-ascorbate, exhibited a linear increasing trend with decreasing seawater pH. Nine SDMs exhibited a linear decreasing trend as the seawater pH declined, including hypoxanthine, guanine and thymidine. Among all SDMs, we further mined 48 potential metabolite biomarkers responding to seawater acidification in four-armed larvae of S. intermedius. These potential metabolite biomarkers were mainly enriched in five pathways: glycerophospholipid metabolism, glutathione metabolism, purine metabolism, pyrimidine metabolism and the tricarboxylic acid cycle (TCA cycle). Our results will enrich our knowledge of the molecular mechanisms employed by sea urchins in response to CO2-induced seawater acidification.
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Affiliation(s)
- Yingying Li
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture and Rural Affairs, Dalian Ocean University, Dalian, Liaoning 116023, PR China
| | - Wenlu Yin
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture and Rural Affairs, Dalian Ocean University, Dalian, Liaoning 116023, PR China
| | - Yaoyao Zhan
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture and Rural Affairs, Dalian Ocean University, Dalian, Liaoning 116023, PR China.
| | - Yujie Jia
- College of Basic Medical Science, Dalian Medical University, Dalian, Liaoning 116044, PR China
| | - Dongyao Cui
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture and Rural Affairs, Dalian Ocean University, Dalian, Liaoning 116023, PR China
| | - Weijie Zhang
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture and Rural Affairs, Dalian Ocean University, Dalian, Liaoning 116023, PR China
| | - Yaqing Chang
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture and Rural Affairs, Dalian Ocean University, Dalian, Liaoning 116023, PR China.
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