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Walls KM, Joh JY, Hong KU, Hein DW. Heterocyclic Amines Disrupt Lipid Homeostasis in Cryopreserved Human Hepatocytes. Cardiovasc Toxicol 2024:10.1007/s12012-024-09874-1. [PMID: 38851663 DOI: 10.1007/s12012-024-09874-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 05/23/2024] [Indexed: 06/10/2024]
Abstract
Metabolic dysfunction associated-steatotic liver disease (MASLD)/metabolic dysfunction-associated steatohepatitis (MASH) is the liver manifestation of metabolic syndrome, which is characterized by insulin resistance, hyperglycemia, hypertension, dyslipidemia, and/or obesity. Environmental pollutant exposure has been recently identified as a risk factor for developing MASH. Heterocyclic amines (HCAs) are mutagens generated when cooking meat at high temperatures or until well-done. Recent epidemiological studies reported that dietary HCA exposure may be linked to insulin resistance and type II diabetes, and we recently reported that HCAs induce insulin resistance and glucose production in human hepatocytes. However, no previous studies have examined the effects of HCAs on hepatic lipid homeostasis. In the present study, we assessed the effects of two common HCAs, MeIQx (2-amino-3, 8-dimethylimidazo [4, 5-f] quinoxaline) and PhIP (2-amino-1-methyl-6-phenylimidazo[4, 5-b] pyridine), on lipid homeostasis in cryopreserved human hepatocytes. Exposure to a single concentration of 25 μM MeIQx or PhIP in human hepatocytes led to dysregulation of lipid homeostasis, typified by significant increases in lipid droplets and triglycerides. PhIP significantly increased expression of lipid droplet-associated genes, PNPLA3 and HSD17B13, and both HCAs significantly increased PLIN2. Exposure to MeIQx or PhIP also significantly increased expression of several key genes involved in lipid synthesis, transport and metabolism, including FASN, DGAT2, CPT1A, SCD, and CD36. Furthermore, both MeIQx and PhIP significantly increased intracellular cholesterol and decreased expression of PON1 which is involved in cholesterol efflux. Taken together, these results suggest that HCAs dysregulate lipid production, metabolism, and storage. The current study demonstrates, for the first time, that HCA exposure may lead to fat accumulation in hepatocytes, which may contribute to hepatic insulin resistance and MASH.
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Affiliation(s)
- Kennedy M Walls
- Department of Pharmacology and Toxicology and Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY, 40202, USA
- Environmental Justice, Community Health and Environmental Review Division, US Environmental Protection Agency, Chicago, USA
| | - Jonathan Y Joh
- Department of Pharmacology and Toxicology and Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY, 40202, USA
| | - Kyung U Hong
- Department of Pharmacology and Toxicology and Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY, 40202, USA
- Department of Pharmaceutical and Administrative Sciences, Western New England University, Springfield, USA
| | - David W Hein
- Department of Pharmacology and Toxicology and Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY, 40202, USA.
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Dolan M, St. John N, Zaidi F, Doyle F, Fasullo M. High-throughput screening of the Saccharomyces cerevisiae genome for 2-amino-3-methylimidazo [4,5-f] quinoline resistance identifies colon cancer-associated genes. G3 (BETHESDA, MD.) 2023; 13:jkad219. [PMID: 37738679 PMCID: PMC11025384 DOI: 10.1093/g3journal/jkad219] [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: 10/25/2022] [Revised: 10/25/2022] [Accepted: 09/15/2023] [Indexed: 09/24/2023]
Abstract
Heterocyclic aromatic amines (HAAs) are potent carcinogenic agents found in charred meats and cigarette smoke. However, few eukaryotic resistance genes have been identified. We used Saccharomyces cerevisiae (budding yeast) to identify genes that confer resistance to 2-amino-3-methylimidazo[4,5-f] quinoline (IQ). CYP1A2 and NAT2 activate IQ to become a mutagenic nitrenium compound. Deletion libraries expressing human CYP1A2 and NAT2 or no human genes were exposed to either 400 or 800 µM IQ for 5 or 10 generations. DNA barcodes were sequenced using the Illumina HiSeq 2500 platform and statistical significance was determined for exactly matched barcodes. We identified 424 ORFs, including 337 genes of known function, in duplicate screens of the "humanized" collection for IQ resistance; resistance was further validated for a select group of 51 genes by growth curves, competitive growth, or trypan blue assays. Screens of the library not expressing human genes identified 143 ORFs conferring resistance to IQ per se. Ribosomal protein and protein modification genes were identified as IQ resistance genes in both the original and "humanized" libraries, while nitrogen metabolism, DNA repair, and growth control genes were also prominent in the "humanized" library. Protein complexes identified included the casein kinase 2 (CK2) and histone chaperone (HIR) complex. Among DNA Repair and checkpoint genes, we identified those that function in postreplication repair (RAD18, UBC13, REV7), base excision repair (NTG1), and checkpoint signaling (CHK1, PSY2). These studies underscore the role of ribosomal protein genes in conferring IQ resistance, and illuminate DNA repair pathways for conferring resistance to activated IQ.
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Affiliation(s)
- Michael Dolan
- College of Nanotechnology, Science, and Engineering, State University of NewYork at Albany, Albany, NY 12203, USA
| | - Nick St. John
- College of Nanotechnology, Science, and Engineering, State University of NewYork at Albany, Albany, NY 12203, USA
| | - Faizan Zaidi
- College of Nanotechnology, Science, and Engineering, State University of NewYork at Albany, Albany, NY 12203, USA
| | - Francis Doyle
- College of Nanotechnology, Science, and Engineering, State University of NewYork at Albany, Albany, NY 12203, USA
| | - Michael Fasullo
- College of Nanotechnology, Science, and Engineering, State University of NewYork at Albany, Albany, NY 12203, USA
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Walls KM, Hong KU, Hein DW. Induction of glucose production by heterocyclic amines is dependent on N-acetyltransferase 2 genetic polymorphism in cryopreserved human hepatocytes. Toxicol Lett 2023; 383:192-195. [PMID: 37423373 PMCID: PMC10528954 DOI: 10.1016/j.toxlet.2023.07.002] [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: 05/11/2023] [Revised: 06/20/2023] [Accepted: 07/04/2023] [Indexed: 07/11/2023]
Abstract
Heterocyclic amines (HCAs) are mutagenic compounds found in cooked meat. Recent epidemiological studies reported significant associations between dietary HCA exposure and insulin resistance and type II diabetes, and we recently reported that HCAs induce insulin resistance and glucose production in human hepatocytes. It is well known that HCAs require hepatic bioactivation by cytochrome P450 1A2 (CYP1A2) and N-acetyltransferase 2 (NAT2). NAT2 expresses a well-defined genetic polymorphism in humans that, depending on the combination of NAT2 alleles, correlates to rapid, intermediate, or slow acetylator phenotype that exhibits differential metabolism of aromatic amines and HCAs. No previous studies have examined the role of NAT2 genetic polymorphism in the context of HCA-mediated induction of glucose production. In the present study, we assessed the effect of three HCAs commonly found in cooked meat (2-amino-3,4-dimethylimidazo[4,5-f]quinoline [MeIQ], 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline [MeIQx], and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine [PhIP]) on glucose production in cryopreserved human hepatocytes with slow, intermediate, or rapid NAT2 acetylator phenotype. HCA treatment did not affect glucose production in slow NAT2 acetylator hepatocytes, while a slight increase in glucose production was observed in intermediate NAT2 acetylators treated with MeIQ or MeIQx. However, significant increases in glucose production were observed in rapid NAT2 acetylators following each HCA. The current findings suggest that individuals who are rapid NAT2 acetylators may be at a greater risk of developing hyperglycemia and insulin resistance following dietary exposure to HCAs.
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Affiliation(s)
- Kennedy M Walls
- Department of Pharmacology & Toxicology, University of Louisville School of Medicine, Louisville, KY 40202, USA
| | - Kyung U Hong
- Department of Pharmacology & Toxicology, University of Louisville School of Medicine, Louisville, KY 40202, USA
| | - David W Hein
- Department of Pharmacology & Toxicology, University of Louisville School of Medicine, Louisville, KY 40202, USA
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4
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Walls KM, Hong KU, Hein DW. Heterocyclic amines reduce insulin-induced AKT phosphorylation and induce gluconeogenic gene expression in human hepatocytes. Arch Toxicol 2023; 97:1613-1626. [PMID: 37005939 PMCID: PMC10192068 DOI: 10.1007/s00204-023-03488-2] [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: 09/23/2022] [Accepted: 03/21/2023] [Indexed: 04/04/2023]
Abstract
Heterocyclic amines (HCAs) are well-known for their mutagenic properties. One of the major routes of human exposure is through consumption of cooked meat, as certain cooking methods favor formation of HCAs. Recent epidemiological studies reported significant associations between dietary HCA exposure and insulin resistance and type II diabetes. However, no previous studies have examined if HCAs, independent of meat consumption, contributes to pathogenesis of insulin resistance or metabolic disease. In the present study, we have assessed the effect of three HCAs commonly found in cooked meat (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline [MeIQ], 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline [MeIQx], and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine [PhIP]) on insulin signaling and glucose production. HepG2 or cryopreserved human hepatocytes were treated with 0-50 μM of MeIQ, MeIQx, or PhIP for 3 days. Treatment of HepG2 cells and hepatocytes with MeIQ and MeIQx resulted in a significant reduction in insulin-induced AKT phosphorylation, suggesting that HCA exposure decreases hepatic insulin signaling. HCA treatment also led to significant increases in expression of gluconeogenic genes, G6PC and PCK1, in both HepG2 and cryopreserved human hepatocytes. Additionally, the level of phosphorylated FOXO1, a transcriptional regulator of gluconeogenesis, was significantly reduced by HCA treatment in hepatocytes. Importantly, HCA treatment of human hepatocytes led to increases in extracellular glucose level in the presence of gluconeogenic substrates, suggesting that HCAs induce hepatic glucose production. The current findings suggest that HCAs induce insulin resistance and promote hepatic glucose production in human hepatocytes. This implicates that exposure to HCAs may lead to the development of type II diabetes or metabolic syndrome.
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Affiliation(s)
- Kennedy M. Walls
- Department of Pharmacology & Toxicology and Brown Cancer Center,
University of Louisville School of Medicine, Louisville, KY. U.S.A
| | - Kyung U. Hong
- Department of Pharmacology & Toxicology and Brown Cancer Center,
University of Louisville School of Medicine, Louisville, KY. U.S.A
| | - David W. Hein
- Department of Pharmacology & Toxicology and Brown Cancer Center,
University of Louisville School of Medicine, Louisville, KY. U.S.A
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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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Bellamri M, Walmsley SJ, Turesky RJ. Metabolism and biomarkers of heterocyclic aromatic amines in humans. Genes Environ 2021; 43:29. [PMID: 34271992 PMCID: PMC8284014 DOI: 10.1186/s41021-021-00200-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 06/27/2021] [Indexed: 12/15/2022] Open
Abstract
Heterocyclic aromatic amines (HAAs) form during the high-temperature cooking of meats, poultry, and fish. Some HAAs also arise during the combustion of tobacco. HAAs are multisite carcinogens in rodents, inducing cancer of the liver, gastrointestinal tract, pancreas, mammary, and prostate glands. HAAs undergo metabolic activation by N-hydroxylation of the exocyclic amine groups to produce the proposed reactive intermediate, the heteroaryl nitrenium ion, which is the critical metabolite implicated in DNA damage and genotoxicity. Humans efficiently convert HAAs to these reactive intermediates, resulting in HAA protein and DNA adduct formation. Some epidemiologic studies have reported an association between frequent consumption of well-done cooked meats and elevated cancer risk of the colorectum, pancreas, and prostate. However, other studies have reported no associations between cooked meat and these cancer sites. A significant limitation in epidemiology studies assessing the role of HAAs and cooked meat in cancer risk is their reliance on food frequency questionnaires (FFQ) to gauge HAA exposure. FFQs are problematic because of limitations in self-reported dietary history accuracy, and estimating HAA intake formed in cooked meats at the parts-per-billion level is challenging. There is a critical need to establish long-lived biomarkers of HAAs for implementation in molecular epidemiology studies designed to assess the role of HAAs in health risk. This review article highlights the mechanisms of HAA formation, mutagenesis and carcinogenesis, the metabolism of several prominent HAAs, and the impact of critical xenobiotic-metabolizing enzymes on biological effects. The analytical approaches that have successfully biomonitored HAAs and their biomarkers for molecular epidemiology studies are presented.
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Affiliation(s)
- Medjda Bellamri
- Masonic Cancer Center and Department of Medicinal Chemistry, Cancer and Cardiovascular Research Building, University of Minnesota, 2231 6th Street, Minneapolis, MN, 55455, USA.,Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Scott J Walmsley
- Masonic Cancer Center and Department of Medicinal Chemistry, Cancer and Cardiovascular Research Building, University of Minnesota, 2231 6th Street, Minneapolis, MN, 55455, USA.,Institute of Health Informatics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Robert J Turesky
- Masonic Cancer Center and Department of Medicinal Chemistry, Cancer and Cardiovascular Research Building, University of Minnesota, 2231 6th Street, Minneapolis, MN, 55455, USA. .,Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, MN, 55455, USA.
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Baldauf KJ, Salazar-González RA, Doll MA, Pierce WM, States JC, Hein DW. Role of Human N-Acetyltransferase 2 Genetic Polymorphism on Aromatic Amine Carcinogen-Induced DNA Damage and Mutagenicity in a Chinese Hamster Ovary Cell Mutation Assay. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:235-245. [PMID: 31490564 PMCID: PMC7017392 DOI: 10.1002/em.22331] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/27/2019] [Accepted: 08/30/2019] [Indexed: 05/10/2023]
Abstract
Carcinogenic aromatic amines such as 4-aminobiphenyl (ABP) and 2-aminofluorene (AF) require metabolic activation to form electrophilic intermediates that mutate DNA leading to carcinogenesis. Bioactivation of these carcinogens includes N-hydroxylation catalyzed by CYP1A2 followed by O-acetylation catalyzed by arylamine N-acetyltransferase 2 (NAT2). To better understand the role of NAT2 genetic polymorphism in ABP- and AF-induced mutagenesis and DNA damage, nucleotide excision repair-deficient (UV5) Chinese hamster ovary (CHO) cells were stably transfected with human CYP1A2 and either NAT2*4 (rapid acetylator) or NAT2*5B (slow acetylator) alleles. ABP and AF both caused significantly (P < 0.001) greater mutagenesis measured at the hypoxanthine phosphoribosyl transferase (hprt) locus in the UV5/CYP1A2/NAT2*4 acetylator cell line compared to the UV5, UV5/CYP1A2, and UV5/CYP1A2/NAT2*5B cell lines. ABP- and AF-induced hprt mutant cDNAs were sequenced and over 80% of the single-base substitutions were at G:C base pairs. DNA damage also was quantified by γH2AX in-cell western assays and by identification and quantification of the two predominant DNA adducts, N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-ABP) and N-(deoxyguanosin-8-yl)-2-aminofluorene (dG-C8-AF) by liquid chromatography-mass spectrometry. DNA damage and adduct levels were dose-dependent, correlated highly with levels of hprt mutants, and were significantly (P < 0.0001) greater in the UV5/CYP1A2/NAT2*4 rapid acetylator cell line following treatment with ABP or AF as compared to all other cell lines. Our findings provide further clarity on the importance of O-acetylation in CHO mutagenesis assays for aromatic amines. They provide evidence that NAT2 genetic polymorphism modifies aromatic amine-induced DNA damage and mutagenesis that should be considered in human risk assessments following aromatic amine exposures. Environ. Mol. Mutagen. 61:235-245, 2020. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
| | | | | | | | | | - David W. Hein
- Correspondence to: David W. Hein, Kosair Charities CTR-Room 303, 505 South Hancock Street, Louisville, Kentucky 40202.
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Lavender N, Hein DW, Brock G, Kidd LCR. Evaluation of Oxidative Stress Response Related Genetic Variants, Pro-oxidants, Antioxidants and Prostate Cancer. AIMS MEDICAL SCIENCE 2015; 2:271-294. [PMID: 26636131 PMCID: PMC4664461 DOI: 10.3934/medsci.2015.4.271] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Background Oxidative stress and detoxification mechanisms have been commonly studied in Prostate Cancer (PCa) due to their function in the detoxification of potentially damaging reactive oxygen species (ROS) and carcinogens. However, findings have been either inconsistent or inconclusive. These mixed findings may, in part, relate to failure to consider interactions among oxidative stress response related genetic variants along with pro- and antioxidant factors. Methods We examined the effects of 33 genetic and 26 environmental oxidative stress and defense factors on PCa risk and disease aggressiveness among 2,286 men from the Cancer Genetic Markers of Susceptibility project (1,175 cases, 1,111 controls). Single and joint effects were analyzed using a comprehensive statistical approach involving logistic regression, multi-dimensionality reduction, and entropy graphs. Results Inheritance of one CYP2C8 rs7909236 T or two SOD2 rs2758331 A alleles was linked to a 1.3- and 1.4-fold increase in risk of developing PCa, respectively (p-value = 0.006–0.013). Carriers of CYP1B1 rs1800440GG, CYP2C8 rs1058932TC and, NAT2 (rs1208GG, rs1390358CC, rs7832071TT) genotypes were associated with a 1.3 to 2.2-fold increase in aggressive PCa [p-value = 0.04–0.001, FDR 0.088–0.939]. We observed a 23% reduction in aggressive disease linked to inheritance of one or more NAT2 rs4646247 A alleles (p = 0.04, FDR = 0.405). Only three NAT2 sequence variants remained significant after adjusting for multiple hypotheses testing, namely NAT2 rs1208, rs1390358, and rs7832071. Lastly, there were no significant gene-environment or gene-gene interactions associated with PCa outcomes. Conclusions Variations in genes involved in oxidative stress and defense pathways may modify PCa. Our findings do not firmly support the role of oxidative stress genetic variants combined with lifestyle/environmental factors as modifiers of PCa and disease progression. However, additional multi-center studies poised to pool genetic and environmental data are needed to make strong conclusions.
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Affiliation(s)
- Nicole Lavender
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville, Louisville, KY
| | - David W Hein
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville, Louisville, KY
| | - Guy Brock
- Department of Bioinformatics and Biostatistics, University of Louisville, Louisville, KY
| | - La Creis R Kidd
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville, Louisville, KY
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Stavros KM, Hawkins EK, Rizzo CJ, Stone MP. Base-Displaced Intercalated Conformation of the 2-Amino-3-methylimidazo[4,5-f]quinoline N(2)-dG DNA Adduct Positioned at the Nonreiterated G(1) in the NarI Restriction Site. Chem Res Toxicol 2015; 28:1455-68. [PMID: 26083477 PMCID: PMC4511292 DOI: 10.1021/acs.chemrestox.5b00140] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
![]()
The
conformation of an N2-dG adduct
arising from the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a potent food mutagen, was determined
in 5′-d(C1T2C3X4G5C6G7C8C9A10T11C12)-3′:5′-d(G13A14T15G16G17C18G19C20C21G22A23G24)-3′; X = N2-dG-IQ, in which the modified nucleotide X4 corresponds to G1 in the 5′-d(G1G2CG3CC)-3′ NarI restriction endonuclease site. Circular dichroism (CD) revealed
blue shifts relative to the unmodified duplex, consistent with adduct-induced
twisting, and a hypochromic effect for the IQ absorbance in the near
UV region. NMR revealed that the N2-dG-IQ
adduct adopted a base-displaced intercalated conformation in which
the modified guanine remained in the anti conformation
about the glycosidic bond, the IQ moiety intercalated into the duplex,
and the complementary base C21 was displaced into the major
groove. The processing of the N2-dG-IQ
lesion by hpol η is sequence-dependent; when placed at the reiterated
G3 position, but not at the G1 position, this
lesion exhibits a propensity for frameshift replication [Choi, J.
Y., et al. (2006) J. Biol. Chem., 281, 25297–25306]. The structure of the N2-dG-IQ adduct at the nonreiterated G1 position
was compared to that of the same adduct placed at the G3 position [Stavros, K. M., et al. (2014) Nucleic Acids Res., 42, 3450–3463]. CD indicted minimal spectral
differences between the G1 vs G3N2-dG-IQ adducts. NMR indicated that the N2-dG-IQ adduct exhibited similar base-displaced intercalated
conformations at both the G1 and G3 positions.
This result differed as compared to the corresponding C8-dG-IQ adducts
placed at the same positions. The C8-dG-IQ adduct adopted a minor
groove conformation when placed at position G1 but a base-displaced
intercalated conformation when placed at position G3 in
the NarI sequence. The present studies suggest that
differences in lesion bypass by hpol η may be mediated by differences
in the 3′-flanking sequences, perhaps modulating the ability
to accommodate transient strand slippage intermediates.
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Affiliation(s)
- Kallie M Stavros
- †Department of Chemistry, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235-1822, United States
| | | | - Carmelo J Rizzo
- †Department of Chemistry, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235-1822, United States
| | - Michael P Stone
- †Department of Chemistry, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235-1822, United States
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Present status of quinoxaline motifs: Excellent pathfinders in therapeutic medicine. Eur J Med Chem 2014; 85:688-715. [DOI: 10.1016/j.ejmech.2014.08.034] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Revised: 08/07/2014] [Accepted: 08/08/2014] [Indexed: 11/18/2022]
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Stavros KM, Hawkins EK, Rizzo CJ, Stone MP. Base-displaced intercalation of the 2-amino-3-methylimidazo[4,5-f]quinolone N2-dG adduct in the NarI DNA recognition sequence. Nucleic Acids Res 2014; 42:3450-63. [PMID: 24366876 PMCID: PMC3950664 DOI: 10.1093/nar/gkt1109] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 10/18/2013] [Accepted: 10/21/2013] [Indexed: 12/14/2022] Open
Abstract
2-Amino-3-methylimidazo[4,5-f]quinolone (IQ), a heterocyclic amine found in cooked meats, undergoes bioactivation to a nitrenium ion, which alkylates guanines at both the C8-dG and N2-dG positions. The conformation of a site-specific N2-dG-IQ adduct in an oligodeoxynucleotide duplex containing the iterated CG repeat restriction site of the NarI endonuclease has been determined. The IQ moiety intercalates, with the IQ H4a and CH3 protons facing the minor groove, and the IQ H7a, H8a and H9a protons facing the major groove. The adducted dG maintains the anti-conformation about the glycosyl bond. The complementary dC is extruded into the major groove. The duplex maintains its thermal stability, which is attributed to stacking between the IQ moiety and the 5'- and 3'-neighboring base pairs. This conformation is compared to that of the C8-dG-IQ adduct in the same sequence, which also formed a 'base-displaced intercalated' conformation. However, the C8-dG-IQ adopted the syn conformation placing the Watson-Crick edge of the modified dG into the major groove. In addition, the C8-dG-IQ adduct was oriented with the IQ CH3 group and H4a and H5a facing the major groove. These differences may lead to differential processing during DNA repair and replication.
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Affiliation(s)
| | | | | | - Michael P. Stone
- Department of Chemistry, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37235-1822, USA
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Fu Z, Shrubsole MJ, Li G, Smalley WE, Hein DW, Cai Q, Ness RM, Zheng W. Interaction of cigarette smoking and carcinogen-metabolizing polymorphisms in the risk of colorectal polyps. Carcinogenesis 2013; 34:779-86. [PMID: 23299405 PMCID: PMC3616674 DOI: 10.1093/carcin/bgs410] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 11/28/2012] [Accepted: 12/18/2012] [Indexed: 12/20/2022] Open
Abstract
The causal role of cigarette smoking in the risk of colorectal neoplasm has been suggested but not established. In a case-control study including 2060 colorectal polyp patients and 3336 polyp-free controls, we evaluated 21 functional genetic variants to construct a tobacco-carcinogen-metabolizing genetic risk score. Data regarding cigarette smoking were obtained through telephone interviews. Cigarette smoking was associated with an elevated risk of both adenomas and hyperplastic polyps. The association with smoking was stronger in participants with a high carcinogen-metabolizing risk score than those with a low risk score. Smoking 30 or more cigarettes per day was associated with a 1.7-fold elevated risk of any polyps (95% confidence interval = 1.3-2.2) among those with a low genetic risk score and 2.9-fold elevated risk (95% confidence interval = 1.8-4.8) among those with a high genetic risk score (P interaction = 0.025). A similar pattern of interaction was observed in analyses conducted separately for those with adenomas only (P interaction = 0.039) and hyperplastic polyps only (P interaction = 0.024). Interaction between carcinogen-metabolizing genetic risk and cigarette smoking was found in relation to high-risk adenomas (P interaction = 0.010) but not low-risk adenomas (P interaction = 0.791). No apparent interaction was found for duration of smoking. This study shows that the association between cigarette smoking and colorectal polyp risk is modified by tobacco-carcinogen-metabolizing polymorphisms, providing support for a causal role of cigarette smoking in the etiology of colorectal tumors.
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Affiliation(s)
- Zhenming Fu
- Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Martha J. Shrubsole
- Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt University School of Medicine, Nashville, TN, USA
- Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Guoliang Li
- Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Walter E. Smalley
- VA Tennessee Valley Geriatric Research, Education and Clinical Center, Nashville, TN, USA
- Division of Gastroenterology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA and
| | - David W. Hein
- Department of Pharmacology & Toxicology, James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY, USA
| | - Qiuyin Cai
- Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Reid M. Ness
- VA Tennessee Valley Geriatric Research, Education and Clinical Center, Nashville, TN, USA
- Division of Gastroenterology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA and
| | - Wei Zheng
- Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt University School of Medicine, Nashville, TN, USA
- Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN, USA
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Fu Z, Shrubsole MJ, Li G, Smalley WE, Hein DW, Chen Z, Shyr Y, Cai Q, Ness RM, Zheng W. Using gene-environment interaction analyses to clarify the role of well-done meat and heterocyclic amine exposure in the etiology of colorectal polyps. Am J Clin Nutr 2012; 96:1119-28. [PMID: 23015320 PMCID: PMC3471199 DOI: 10.3945/ajcn.112.040345] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND The role of well-done meat intake and meat-derived mutagen heterocyclic amine (HCA) exposure in the risk of colorectal neoplasm has been suggested but not yet established. OBJECTIVE With the use of gene-environment interaction analyses, we sought to clarify the association of HCA exposure with colorectal polyp risk. DESIGN In a case-control study including 2057 colorectal polyp patients and 3329 controls, we evaluated 16 functional genetic variants to construct an HCA-metabolizing score. To derive dietary HCA-exposure amount, data were collected regarding dietary intake of meat by cooking method and degree of doneness. RESULTS A 2-fold elevated risk associated with high red meat intake was found for colorectal polyps or adenomas in subjects with a high HCA-metabolizing risk score, whereas the risk was 1.3- to 1.4-fold among those with a low risk score (P-interaction ≤ 0.05). The interaction was stronger for the risk of advanced or multiple adenomas, in which an OR of 2.8 (95% CI: 1.8, 4.6) was observed for those with both a high HCA-risk score and high red meat intake (P-interaction = 0.01). No statistically significant interaction was found in analyses that used specific HCA exposure derived from dietary data. CONCLUSION High red meat intake is associated with an elevated risk of colorectal polyps, and this association may be synergistically modified by genetic factors involved in HCA metabolism.
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Affiliation(s)
- Zhenming Fu
- Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt University School of Medicine, Nashville, TN 37203, USA
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Doll MA, Zang Y, Moeller T, Hein DW. Codominant expression of N-acetylation and O-acetylation activities catalyzed by N-acetyltransferase 2 in human hepatocytes. J Pharmacol Exp Ther 2010; 334:540-4. [PMID: 20430842 DOI: 10.1124/jpet.110.168567] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Human populations exhibit genetic polymorphism in N-acetylation capacity, catalyzed by N-acetyltransferase 2 (NAT2). We investigated the relationship between NAT2 acetylator genotype and phenotype in cryopreserved human hepatocytes. NAT2 genotypes determined in 256 human samples were assigned as rapid (two rapid alleles), intermediate (one rapid and one slow allele), or slow (two slow alleles) acetylator phenotypes based on functional characterization of the NAT2 alleles reported previously in recombinant expression systems. A robust and significant relationship was observed between deduced NAT2 phenotype (rapid, intermediate, or slow) and N-acetyltransferase activity toward sulfamethazine (p < 0.0001) and 4-aminobiphenyl (p < 0.0001) and for O-acetyltransferase-catalyzed metabolic activation of N-hydroxy-4-aminobiphenyl (p < 0.0001), N-hydroxy-2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (p < 0.01), and N-hydroxy-2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (p < 0.0001). NAT2-specific protein levels also significantly associated with the rapid, intermediate, and slow NAT2 acetylator phenotypes (p < 0.0001). As a negative control, p-aminobenzoic acid (an N-acetyltransferase 1-selective substrate) N-acetyltransferase activities from the same samples did not correlate with the three NAT2 acetylator phenotypes (p > 0.05). These results clearly document codominant expression of human NAT2 alleles resulting in rapid, intermediate, and slow acetylator phenotypes. The three phenotypes reflect levels of NAT2 protein catalyzing both N- and O-acetylation. Our results suggest a significant role of NAT2 acetylation polymorphism in arylamine-induced cancers and are consistent with differential cancer risk and/or drug efficacy/toxicity in intermediate compared with rapid or slow NAT2 acetylator phenotypes.
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Affiliation(s)
- Mark A Doll
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, Kentucky 40202-1617, USA
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