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Salazar-González RA, Doll MA, Hein DW. N-acetyltransferase 2 genetic polymorphism modifies genotoxic and oxidative damage from new psychoactive substances. Arch Toxicol 2023; 97:189-199. [PMID: 36138126 PMCID: PMC10187882 DOI: 10.1007/s00204-022-03383-2] [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: 08/02/2022] [Accepted: 09/14/2022] [Indexed: 01/19/2023]
Abstract
The use of new psychoactive substances (NPS) as drugs of abuse is common and increasingly popular, particularly among youth and neglected communities. Recent studies have reported acute toxic effects from these chemicals; however, their long-term toxicity is unknown. Genetic differences between individuals likely affect the toxicity risk. Arylamine N-acetyltransferase 2 (NAT2) capacity differs among individuals due to genetic inheritance. The goal of the present study is to investigate the gene-environment interaction between NAT2 polymorphism and toxicity after exposure to these chemicals. We measured N-acetylation by human NAT1 and NAT2 and found that N-acetylation of NPS is carried out exclusively by NAT2. Differences in N-acetylation between NAT2*4 (reference allele) and NAT2*5B (common variant allele) were highly significant (p < 0.0001). Using DNA repair-deficient genetically engineered Chinese hamster ovary (CHO cells), expressing human CYP1A2 and either NAT2*4 or NAT2*5B, we measured the induction of DNA double-strand breaks ([Formula: see text]H2Ax) following treatment of the CHO cells with increasing concentrations of NPS. The induction of [Formula: see text]H2Ax showed a NAT2 allele-dependent response, higher in the NAT2*4 vs NAT2*5B alleles (p < 0.05). Induction of oxidative stress (ROS/RNS) was evaluated; we observed NAT2 allele-dependent response for all compounds in concentrations as low as 10 [Formula: see text]M, where NAT2*4 showed increased ROS/RNS vs NAT2*5B (p < 0.05). In summary, NPS are N-acetylated by NAT2 at rates higher in cells expressing NAT2*4 than NAT2*5B. Exposure to psychoactive chemicals results in genotoxic and oxidative damage that is modified by the NAT2 genetic polymorphism.
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Affiliation(s)
- 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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2
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Oladipupo I, Ali T, Hein DW, Pagidas K, Bohler H, Doll MA, Mann ML, Gentry A, Chiang JL, Pierson RC, Torres S, Reece E, Taylor KC. Association between cigarette smoking and ovarian reserve among women seeking fertility care. PLoS One 2022; 17:e0278998. [PMID: 36512605 PMCID: PMC9746951 DOI: 10.1371/journal.pone.0278998] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 11/28/2022] [Indexed: 12/15/2022] Open
Abstract
INTRODUCTION This study examined the association of smoking with ovarian reserve in a cross-sectional study of 207 women enrolled in the Louisville Tobacco Smoke Exposure, Genetic Susceptibility, and Infertility (LOUSSI) Study and assessed effect modification by NAT2 acetylator phenotype. METHODS Information on current smoking status was collected using a structured questionnaire and confirmed by cotinine assay. Serum anti-Müllerian hormone (AMH) levels were used to assess ovarian reserve. Diminished ovarian reserve (DOR) was defined as AMH <1ng/mL. Single nucleotide polymorphisms in the NAT2 gene, which metabolizes toxins found in cigarette smoke, were analyzed to determine NAT2 acetylator status. Linear and logistic regression were used to determine the effects of smoking on ovarian reserve and evaluate effect modification by NAT2. Regression analyses were stratified by polycystic ovary syndrome (PCOS) status and adjusted for age. RESULTS Current smoking status, either passive or active as measured by urinary cotinine assay, was not significantly associated with DOR. For dose-response assessed using self-report, the odds of DOR increased significantly for every additional cigarette currently smoked (Odds ratio, OR:1.08; 95% confidence interval, 95%CI:1.01-1.15); additionally, every 1 pack-year increase in lifetime exposure was associated with an increased odds of DOR among women without PCOS (OR: 1.08 95%CI: 0.99-1.18). These trends appear to be driven by the heavy or long-term smokers. Effect modification by NAT2 genotype was not established. CONCLUSION A history of heavy smoking may indicate increased risk of diminished ovarian reserve.
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Affiliation(s)
- Islamiat Oladipupo
- Department of Epidemiology and Population Health, School of Public Health and Information Sciences, University of Louisville, Louisville, KY, United States of America
- * E-mail:
| | - T’shura Ali
- Department of Epidemiology and Population Health, School of Public Health and Information Sciences, University of Louisville, Louisville, KY, United States of America
| | - David W. Hein
- Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Kelly Pagidas
- Department of Obstetrics, Gynecology, and Women’s Health, Division of Reproductive Endocrinology, and Infertility, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Henry Bohler
- Department of Obstetrics, Gynecology, and Women’s Health, Division of Reproductive Endocrinology, and Infertility, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Mark A. Doll
- Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Merry Lynn Mann
- Department of Obstetrics, Gynecology, and Women’s Health, Division of Reproductive Endocrinology, and Infertility, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Adrienne Gentry
- Department of Obstetrics, Gynecology, and Women’s Health, Division of Reproductive Endocrinology, and Infertility, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Jasmine L. Chiang
- Department of Obstetrics, Gynecology, and Women’s Health, Division of Reproductive Endocrinology, and Infertility, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Rebecca C. Pierson
- Department of Obstetrics, Gynecology, and Women’s Health, Division of Reproductive Endocrinology, and Infertility, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Sashia Torres
- Department of Epidemiology and Population Health, School of Public Health and Information Sciences, University of Louisville, Louisville, KY, United States of America
| | - Emily Reece
- Department of Epidemiology and Population Health, School of Public Health and Information Sciences, University of Louisville, Louisville, KY, United States of America
| | - Kira C. Taylor
- Department of Epidemiology and Population Health, School of Public Health and Information Sciences, University of Louisville, Louisville, KY, United States of America
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3
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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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4
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Hernández-González O, Herrera-Vargas DJ, Martínez-Leija ME, Zavala-Reyes D, Portales-Pérez DP. The role of arylamine N-acetyltransferases in chronic degenerative diseases: Their possible function in the immune system. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119297. [PMID: 35588943 DOI: 10.1016/j.bbamcr.2022.119297] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 05/11/2022] [Accepted: 05/12/2022] [Indexed: 06/15/2023]
Abstract
Since their discovery, arylamine N-acetyltransferases 1 and 2 (NAT1 and NAT2, respectively) have been associated with the metabolism of xenobiotics. NAT2 is the main factor in the therapeutic success of tuberculosis treatment due to its role in the biotransformation of isoniazid. However, researchers have started to investigate the possible participation of NAT1 and NAT2 (NATs) in carcinogenesis, although the mechanisms have not been elucidated fully. NATs enzymatic activity is essential in some types of cancer, such as breast cancer and acute lymphoblastic leukemia. Whether NAT1 and/or NAT2 participate in insulin resistance level in diabetes mellitus or in the immune system remains to be explored. Therefore, it is clear that its role in cell physiology has more implications than just metabolizing compounds.
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Affiliation(s)
| | | | - Miguel Ernesto Martínez-Leija
- Faculty of Chemical Sciences, Autonomous University of San Luis Potosí, Mexico; Research Center for Health Sciences and Biomedicine, Autonomous University of San Luis Potosí, Mexico
| | - Daniel Zavala-Reyes
- Research Center for Health Sciences and Biomedicine, Autonomous University of San Luis Potosí, Mexico
| | - Diana Patricia Portales-Pérez
- Faculty of Chemical Sciences, Autonomous University of San Luis Potosí, Mexico; Research Center for Health Sciences and Biomedicine, Autonomous University of San Luis Potosí, Mexico.
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5
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Hein DW, Doll MA, Habil MR. Human N-Acetyltransferase 1 and 2 Differ in Affinity Towards Acetyl-Coenzyme A Cofactor and N-Hydroxy-Arylamine Carcinogens. Front Pharmacol 2022; 13:821133. [PMID: 35281898 PMCID: PMC8914035 DOI: 10.3389/fphar.2022.821133] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 01/24/2022] [Indexed: 02/01/2023] Open
Abstract
Arylamine N-acetyltransferases catalyze the transfer of acetyl groups from the endogenous cofactor acetyl coenzyme A (AcCoA) to arylamine (N-acetylation) and N-hydroxy-arylamine (O-acetylation) acceptors. Humans express two arylamine N-acetyltransferase isozymes (NAT1 and NAT2) which catalyze both N- and O-acetylation but differ in genetic regulation, substrate selectivity, and expression in human tissues. We investigated recombinant human NAT1 and NAT2 expressed in an Escherichia coli JM105 and Schizosaccharomyces pombe expression systems as well as in Chinese hamster ovary (CHO) cells to assess the relative affinity of AcCoA for human NAT1 and NAT2. NAT1 and NAT2 affinity for AcCoA was higher for recombinant human NAT1 than NAT2 when catalyzing N-acetylation of aromatic amine carcinogens 2-aminofluroene (AF), 4-aminobiphenyl (ABP), and β-naphthylamine (BNA) and the metabolic activation of N-hydroxy-2-aminofluorene (N-OH-AF) and N-hydroxy-4-aminobiphenyl (N-OH-ABP) via O-acetylation. These results suggest that AcCoA level may influence differential rates of arylamine carcinogen metabolism catalyzed by NAT1 and NAT2 in human tissues. Affinity was higher for NAT2 than for NAT1 using N-OH-AF and N-OH-ABP as substrate consistent with a larger active site for NAT2. In conclusion, following recombinant expression in bacteria, yeast, and CHO cells, we report significant differences in affinity between human NAT1 and NAT2 for its required co-factor AcCoA, as well as for N-hydroxy-arylamines activated via O-acetylation. The findings provide important information to understand the relative contribution of human NAT1 vs NAT2 towards N-acetylation and O-acetylation reactions in human hepatic and extrahepatic tissues.
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6
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Leggett CS, Doll MA, Salazar-González RA, Habil MR, Trent JO, Hein DW. Identification and characterization of potent, selective, and efficacious inhibitors of human arylamine N-acetyltransferase 1. Arch Toxicol 2022; 96:511-524. [PMID: 34783865 PMCID: PMC8837702 DOI: 10.1007/s00204-021-03194-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Accepted: 11/04/2021] [Indexed: 02/03/2023]
Abstract
Arylamine N-acetyltransferase 1 (NAT1) plays a pivotal role in the metabolism of carcinogens and is a drug target for cancer prevention and/or treatment. A protein-ligand virtual screening of 2 million chemicals was ranked for predicted binding affinity towards the inhibition of human NAT1. Sixty of the five hundred top-ranked compounds were tested experimentally for inhibition of recombinant human NAT1 and N-acetyltransferase 2 (NAT2). The most promising compound 9,10-dihydro-9,10-dioxo-1,2-anthracenediyl diethyl ester (compound 10) was found to be a potent and selective NAT1 inhibitor with an in vitro IC50 of 0.75 µM. Two structural analogs of this compound were selective but less potent for inhibition of NAT1 whereas a third structural analog 1,2-dihydroxyanthraquinone (a compound 10 hydrolysis product also known as Alizarin) showed comparable potency and efficacy for human NAT1 inhibition. Compound 10 inhibited N-acetylation of the arylamine carcinogen 4-aminobiphenyl (ABP) both in vitro and in DNA repair-deficient Chinese hamster ovary (CHO) cells in situ stably expressing human NAT1 and CYP1A1. Compound 10 and Alizarin effectively inhibited NAT1 in cryopreserved human hepatocytes whereas inhibition of NAT2 was not observed. Compound 10 caused concentration-dependent reductions in DNA adduct formation and DNA double-strand breaks following metabolism of aromatic amine carcinogens beta-naphthylamine and/or ABP in CHO cells. Compound 10 inhibited proliferation and invasion in human breast cancer cells and showed selectivity towards tumorigenic versus non-tumorigenic cells. In conclusion, our study identifies potent, selective, and efficacious inhibitors of human NAT1. Alizarin's ability to inhibit NAT1 could reduce breast cancer metastasis particularly to bone.
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Affiliation(s)
- Carmine S. Leggett
- Department of Pharmacology and Toxicology, University of
Louisville, Louisville, KY USA,UofL Health Brown Cancer Center, University of Louisville,
Louisville, KY USA
| | - Mark A. Doll
- Department of Pharmacology and Toxicology, University of
Louisville, Louisville, KY USA,UofL Health Brown Cancer Center, University of Louisville,
Louisville, KY USA
| | - Raúl A. Salazar-González
- Department of Pharmacology and Toxicology, University of
Louisville, Louisville, KY USA,UofL Health Brown Cancer Center, University of Louisville,
Louisville, KY USA
| | - Mariam R. Habil
- Department of Pharmacology and Toxicology, University of
Louisville, Louisville, KY USA,UofL Health Brown Cancer Center, University of Louisville,
Louisville, KY USA
| | - John O. Trent
- UofL Health Brown Cancer Center, University of Louisville,
Louisville, KY USA,Department of Medicine, University of Louisville,
Louisville, KY USA
| | - David W. Hein
- Department of Pharmacology and Toxicology, University of
Louisville, Louisville, KY USA,UofL Health Brown Cancer Center, University of Louisville,
Louisville, KY USA,Department of Medicine, University of Louisville,
Louisville, KY USA,Corresponding author: David W. Hein, University of
Louisville Health Science Center, Kosair Charities Clinical and Translational
Research Building Room 303, 505 South Hancock Street, Louisville, KY USA
40202-1617. . Telephone:
502-852-6252
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7
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Wendt FR, Koller D, Pathak GA, Jacoby D, Miller EJ, Polimanti R. Biobank Scale Pharmacogenomics Informs the Genetic Underpinnings of Simvastatin Use. Clin Pharmacol Ther 2021; 110:777-785. [PMID: 33837531 DOI: 10.1002/cpt.2260] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 04/01/2021] [Indexed: 12/31/2022]
Abstract
Studying drug-metabolizing enzymes, encoded by pharmacogenes, may inform biological mechanisms underlying the diseases for which a medication is prescribed. Until recently, pharmacogenes could not be studied at biobank scale. In 7,649 unrelated African-ancestry (AFR) and 326,214 unrelated European-ancestry (EUR) participants from the UK Biobank, we associated pharmacogene haplotypes from 50 genes with 265 (EUR) and 17 (AFR) medication use phenotypes using generalized linear models. In EUR, N-acetyltransferase 2 (NAT2) metabolizer phenotype and activity score were associated with simvastatin use. The dose of NAT2*1 was associated with simvastatin use when compared with NAT2*5 (the most common haplotype). This association was robust to effects of low-density lipoprotein cholesterol (LDL-C) concentration (NAT2*1 odds ratio (OR) = 1.07, 95% CI: 1.05-1.09, P = 1.14 × 10-8 ) and polygenic risk for LDL-C concentration (NAT2*1 OR = 1.09, 95% CI: 1.04-1.14, P = 2.26 × 10-4 ). Interactive effects between NAT2*1 and simvastatin use on LDL-C concentration (OR = 0.957, 95% CI: 0.916-0.998, P = 0.045) were replicated in the electronic Medical Records and Genomics Pharmacogenetic Sequencing Pilot (eMERGE-PGx) cohort (OR = 0.987, 95% CI: 0.976-0.998, P = 0.029). We used biobank-scale data to uncover and replicate an association between NAT2 locus variation and better response to statin therapy. Testing NAT2 alleles may be useful for making clinical decisions regarding the potential benefit (e.g., absolute risk reduction) in LDL-C concentration prior to statin treatment.
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Affiliation(s)
- Frank R Wendt
- Division of Human Genetics, Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, USA
- Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Dora Koller
- Division of Human Genetics, Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, USA
- Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Gita A Pathak
- Division of Human Genetics, Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, USA
- Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Daniel Jacoby
- Section of Cardiovascular Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Edward J Miller
- Section of Cardiovascular Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Renato Polimanti
- Division of Human Genetics, Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, USA
- Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
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8
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Dumouchel JL, Kramlinger VM. Case Study 10: A Case to Investigate Acetyl Transferase Kinetics. Methods Mol Biol 2021; 2342:781-808. [PMID: 34272717 DOI: 10.1007/978-1-0716-1554-6_29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Major routes of metabolism for marketed drugs are predominately driven by enzyme families such as cytochromes P450 and UDP-glucuronosyltransferases. Less studied conjugative enzymes, like N-acetyltransferases (NATs), are commonly associated with detoxification pathways. However, in the clinic, the high occurrence of NAT polymorphism that leads to slow and fast acetylator phenotypes in patient populations has been linked to toxicity for a multitude of drugs. A key example of this is the observed clinical toxicity in patients who exhibit the slow acetylator phenotype and were treated with isoniazid. Toxicity in patients has led to detailed characterization of the two NAT isoforms and their polymorphic genotypes. Investigation in recombinant enzymes, genotyped hepatocytes, and in vivo transgenic models coupled with acetylator status-driven clinical studies have helped understand the role of NATs in drug development, clinical study design and outcomes, and potential roles in human disease models. The selected case studies herein document NAT enzyme kinetics to explore substrate overlap from two human isoforms, preclinical species considerations, and clinical genotype population concerns.
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Affiliation(s)
- Jennifer L Dumouchel
- Molecular Pharmacology and Physiology Graduate Training Program, Brown University, Providence, RI, USA.
| | - Valerie M Kramlinger
- Translational Medicine, Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA
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9
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Hein DW, Millner LM. Arylamine N-acetyltransferase acetylation polymorphisms: paradigm for pharmacogenomic-guided therapy- a focused review. Expert Opin Drug Metab Toxicol 2021; 17:9-21. [PMID: 33094670 PMCID: PMC7790970 DOI: 10.1080/17425255.2021.1840551] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 10/19/2020] [Indexed: 01/10/2023]
Abstract
INTRODUCTION The N-acetylation polymorphism has been the subject of comprehensive reviews describing the role of arylamine N-acetyltransferase 2 (NAT2) in the metabolism of numerous aromatic amine and hydrazine drugs. AREAS COVERED We describe and review data that more clearly defines the effects of NAT2 haplotypes and genotypes on the expression of acetylator phenotype towards selected drugs within human hepatocytes in vitro, within human hepatocyte cultures in situ, and clinical measures such as bioavailability, plasma metabolic ratios of parent to N-acetyl metabolite, elimination rate constants and plasma half-life, and/or clearance determinations in human subjects. We review several drugs (isoniazid, hydralazine, sulfamethazine, amifampridine, procainamide, sulfasalazine, amonafide and metamizole) for which NAT2 phenotype-guided therapy may be important. The value of pharmacogenomics-guided isoniazid therapy for the prevention and treatment of tuberculosis is presented as a paradigm for NAT2 phenotype-dependent dosing strategies. EXPERT OPINION Studies in human subjects and cryopreserved human hepatocytes show evidence for rapid, intermediate and slow acetylator phenotypes, with further data suggesting genetic heterogeneity within the slow acetylator phenotype. Incorporation of more robust NAT2 genotype/phenotypes relationships, including genetic heterogeneity within the slow acetylator phenotype, should lead to further advancements in both health outcomes and cost benefit for prevention and treatment of tuberculosis.
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Affiliation(s)
- David W. Hein
- Department of Pharmacology & Toxicology, University of Louisville School of Medicine, Louisville, Kentucky, USA
| | - Lori M. Millner
- Bluewater Diagnostic Laboratory, Mount Washington, Kentucky, USA
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10
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Nicoletti P, Devarbhavi H, Goel A, Venkatesan R, Eapen CE, Grove JI, Zafer S, Bjornsson E, Lucena MI, Andrade RJ, Pirmohamed M, Wadelius M, Larrey D, Maitland-van der Zee AH, Ibanez L, Watkins PB, Daly AK, Aithal GP. Genetic Risk Factors in Drug-Induced Liver Injury Due to Isoniazid-Containing Antituberculosis Drug Regimens. Clin Pharmacol Ther 2020; 109:1125-1135. [PMID: 33135175 DOI: 10.1002/cpt.2100] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 10/15/2020] [Indexed: 12/11/2022]
Abstract
Drug-induced liver injury (DILI) is a complication of treatment with antituberculosis (TB) drugs, especially in isoniazid (INH)-containing regimens. To investigate genetic risk factors, we performed a genomewide association study (GWAS) involving anti-TB DILI cases (55 Indian and 70 European) and controls (1,199 Indian and 10,397 European). Most cases were treated with a standard anti-TB drug regimen; all received INH. We imputed single nucleotide polymorphism and HLA genotypes and performed trans-ethnic meta-analysis on GWAS and candidate gene genotypes. GWAS found one significant association (rs117491755) in Europeans only. For HLA, HLA-B*52:01 was significant (meta-analysis odds ratio (OR) 2.67, 95% confidence interval (CI) 1.63-4.37, P = 9.4 × 10-5 ). For N-acetyltransferase 2 (NAT2), NAT2*5 frequency was lower in cases (OR 0.69, 95% CI 0.57-0.83, P = 0.01). NAT2*6 and NAT2*7 were more common, with homozygotes for NAT2*6 and/or NAT2*7 enriched among cases (OR 1.89, 95% CI 0.84-4.22, P = 0.004). We conclude HLA genotype makes a small contribution to TB drug-related DILI and that the NAT2 contribution is complex, but consistent with previous reports when differences in the metabolic effect of NAT2*5 compared with those of NAT2*6 and NAT2*7 are considered.
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Affiliation(s)
- Paola Nicoletti
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Harshad Devarbhavi
- Department of Gastroenterology, St John's Medical College Hospital, Bangalore, India
| | | | - Radha Venkatesan
- Department of Molecular Genetics, Madras Diabetes Research Foundation, Chennai, India
| | | | - Jane I Grove
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, University of Nottingham, UK.,Nottingham Digestive Diseases Centre, School of Medicine, University of Nottingham, Nottingham, UK
| | - Samreen Zafer
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Einar Bjornsson
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, The National University Hospital of Iceland, Reykjavik, Iceland.,Faculty of Medicine, University of Iceland, Reykjavik, Iceland
| | - M Isabel Lucena
- UGC Digestivo y Servicio de Farmacología Clínica, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Universitario Virgen de la Victoria, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Madrid, Spain
| | - Raul J Andrade
- UGC Digestivo y Servicio de Farmacología Clínica, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Universitario Virgen de la Victoria, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Madrid, Spain
| | - Munir Pirmohamed
- Department of Pharmacology and Therapeutics, Liverpool University Hospitals and Liverpool Health Partners, University of Liverpool, Liverpool, UK
| | - Mia Wadelius
- Department of Medical Sciences and Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | | | - Anke-Hilse Maitland-van der Zee
- Department of Respiratory Medicine, Academic Medical Center (AMC), University of Amsterdam, Amsterdam, Netherlands.,Division of Pharmacoepidemiology and Clinical Pharmacology, Department of Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands
| | - Luisa Ibanez
- Fundació Institut Català de Farmacologia, Hospital Universitari Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Paul B Watkins
- Eshelman School of Pharmacy, University of North Carolina Institute for Drug Safety Sciences, Chapel Hill, North Carolina, USA
| | - Ann K Daly
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Guruprasad P Aithal
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, University of Nottingham, UK.,Nottingham Digestive Diseases Centre, School of Medicine, University of Nottingham, Nottingham, UK
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11
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Human arylamine N-acetyltransferase 2 genotype-dependent protein expression in cryopreserved human hepatocytes. Sci Rep 2020; 10:7566. [PMID: 32372066 PMCID: PMC7200704 DOI: 10.1038/s41598-020-64508-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 04/16/2020] [Indexed: 01/08/2023] Open
Abstract
Human N-acetyltransferases (NAT; EC 2.3.1.5) catalyze the N-acetylation of arylamine and hydrazine drugs and the O-acetylation of N-hydroxylated metabolites of aromatic and heterocyclic amines. Two different isoforms of this protein, N-acetyltransferase 1 (NAT1) and N-acetyltransferase 2 (NAT2), are expressed in human hepatocytes. Both are encoded by a single 870-bp open reading frame that exhibits genetic polymorphisms in human populations. NAT1 and NAT2 share more than 85% gene and protein sequence, making it challenging to produce antibodies with high specificity for NAT1 or NAT2. In the present study, we compared methods for the quantification of immunoreactive NAT1 and NAT2 with seven different antibodies and investigated the relationship of NAT2 genotype to NAT2 mRNA and protein expression in cryopreserved human hepatocytes. Sulfamethazine (NAT2-selective substrate) and NAT2 protein expression differed significantly with NAT2 acetylator genotype (p < 0.0001). NAT2 protein expression and sulfamethazine NAT2 catalytic activity correlated highly across the cryopreserved human hepatocytes of rapid, intermediate, and slow acetylator NAT2 genotypes. In conclusion, our data describe a specific analytical method for the quantification of NAT1 and NAT2 protein expression. We showed that the NAT2 activity in human hepatocytes is directly correlated to expression levels of NAT2 protein but not mRNA.
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12
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Expression and genotype-dependent catalytic activity of N-acetyltransferase 2 (NAT2) in human peripheral blood mononuclear cells and its modulation by Sirtuin 1. Biochem Pharmacol 2018; 156:340-347. [PMID: 30149019 DOI: 10.1016/j.bcp.2018.08.034] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 08/21/2018] [Indexed: 01/15/2023]
Abstract
N-acetyltransferase 2 (NAT2) catalyzes the biotransformation of numerous arylamine and hydrazine drugs and carcinogens. Genetic polymorphisms of NAT2 modify drug efficacy and toxicity and susceptibility to diseases such as cancer and type 2 diabetes. Expression of NAT2 has been documented in the liver and gastrointestinal tract but not in other tissues. Deacetylation of cytosolic proteins by sirtuins is a post-translational modification important in regulatory networks of diverse cellular processes. The aim of the present study was to investigate NAT2 expression in peripheral blood mononuclear cells (PBMC) and the effects of NAT2 genotype and Sirtuin 1 (SIRT1). Both NAT2 and SIRT1 proteins were expressed on PBMC. Their expression was more prevalent on CD3+ compared to CD19+ and CD56+ cell populations. N-acetylation capacity of PBMC exhibited a NAT2 gene-dose response toward the N-acetylation of isoniazid. Subjects with rapid NAT2 genotype showed an apparent Vmax of 42.1 ± 2.4; intermediate NAT2 genotypes an apparent Vmax of 22.6 ± 2.2; and slow acetylator NAT2 genotypes an apparent Vmax of 19.9 ± 1.7 nM acetyl-isoniazid/24 h/million cells. The N-acetylation capacity of NAT2 in the presence of SIRT1 enhancer was significantly decreased (p < 0.001), conversely, the transient silencing of SIRT1 resulted in an increase of N-acetylation capacity (p < 0.001). These findings are the first report of NAT2 genotype-dependent expression on PBMC and post-translational modification by SIRT1. These findings constitute a substantial advance in our understanding of human N-acetyltransferase expression and a new much less invasive method for measurement of human NAT2 expression and phenotype.
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13
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Highlight report: quality control of stem cell-derived hepatocytes. Arch Toxicol 2018; 92:2409-2410. [PMID: 29968160 DOI: 10.1007/s00204-018-2253-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 06/25/2018] [Indexed: 10/28/2022]
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14
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Turiján-Espinoza E, Salazar-González RA, Uresti-Rivera EE, Hernández-Hernández GE, Ortega-Juárez M, Milán R, Portales-Pérez D. A pilot study of the modulation of sirtuins on arylamine N-acetyltransferase 1 and 2 enzymatic activity. Acta Pharm Sin B 2018; 8:188-199. [PMID: 29719779 PMCID: PMC5926248 DOI: 10.1016/j.apsb.2017.11.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/15/2017] [Accepted: 11/17/2017] [Indexed: 11/25/2022] Open
Abstract
Arylamine N-acetyltransferase (NAT; E.C. 2.3.1.5) enzymes are responsible for the biotransformation of several arylamine and hydrazine drugs by acetylation. In this process, the acetyl group transferred to the acceptor substrate produces NAT deacetylation and, in consequence, it is susceptible of degradation. Sirtuins are protein deacetylases, dependent on nicotine adenine dinucleotide, which perform post-translational modifications on cytosolic proteins. To explore possible sirtuin participation in the enzymatic activity of arylamine NATs, the expression levels of NAT1, NAT2, SIRT1 and SIRT6 in peripheral blood mononuclear cells (PBMC) from healthy subjects were examined by flow cytometry and Western blot. The in situ activity of the sirtuins on NAT enzymatic activity was analyzed by HPLC, in the presence or absence of an agonist (resveratrol) and inhibitor (nicotinamide) of sirtuins. We detected a higher percentage of positive cells for NAT2 in comparison with NAT1, and higher numbers of SIRT1+ cells compared to SIRT6 in lymphocytes. In situ NAT2 activity in the presence of NAM inhibitors was higher than in the presence of its substrate, but not in the presence of resveratrol. In contrast, the activity of NAT1 was not affected by sirtuins. These results showed that NAT2 activity might be modified by sirtuins.
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Key Words
- APC, allophycocyanin
- Ac-INH, acetyl-Isoniazid
- Ac-PABA, acetyl-p-aminobenzoic acid
- Arylamine N-acetyltransferase
- CHO, Chinese hamster ovary cells
- DMEM, Dulbecco's modified Eagle's medium
- E2F1, E2F transctriptios factor 1
- ER81, ETS-related protein 81
- FITC, fluorescein IsoTioCyanate
- FOXO1, forkhead box protein O1
- HPLC, high performance liquid chromatography
- HeLa, adenocarcinoma epithelial cells
- INH, isoniazid
- NAD, nicotinamide adenine dinucleotide
- NAM, nicotinamide
- NAT
- NAT, arylamine N-acetyltranferase
- Nicotinamide
- PABA, p-aminobenzoic acid
- PAS, p-aminosalicilic acid
- PBMC, peripheral blood mononuclear cells
- PBS, phosphate-buffered saline
- PGAM1, phosphoglycerate mutase 1
- PGC-1α, peroxisome proliferator-activated receptor-gamma coactivator 1α
- Peripheral blood mononuclear cells
- RSV, resveratrol
- RUNX3, runt-related transcription factor 3
- Resveratrol
- SIRT, sirtuin
- SMZ, sulfamethazine
- SREBP1a, sterol regulatory element-binding protein 1a
- SREBP2, sterol regulatory element-binding protein 2
- Sirtuins
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Affiliation(s)
- Eneida Turiján-Espinoza
- Laboratory of Immunology and Cellular and Molecular Biology, Faculty of Chemical Science, UASLP, San Luis Potosi, Mexico
- Laboratory of Biopharmacy and Pharmacokinetics, Faculty of Chemical Science, UASLP, San Luis Potosi, Mexico
- Corresponding authors. Tel.: (52-44) 82624-40, ext. 6465 and 6594.
| | - Rául Alejandro Salazar-González
- Laboratory of Immunology and Cellular and Molecular Biology, Faculty of Chemical Science, UASLP, San Luis Potosi, Mexico
- Laboratory of Biopharmacy and Pharmacokinetics, Faculty of Chemical Science, UASLP, San Luis Potosi, Mexico
| | - Edith Elena Uresti-Rivera
- Laboratory of Immunology and Cellular and Molecular Biology, Faculty of Chemical Science, UASLP, San Luis Potosi, Mexico
| | | | - Montserrat Ortega-Juárez
- Laboratory of Immunology and Cellular and Molecular Biology, Faculty of Chemical Science, UASLP, San Luis Potosi, Mexico
| | - Rosa Milán
- Laboratory of Biopharmacy and Pharmacokinetics, Faculty of Chemical Science, UASLP, San Luis Potosi, Mexico
| | - Diana Portales-Pérez
- Laboratory of Immunology and Cellular and Molecular Biology, Faculty of Chemical Science, UASLP, San Luis Potosi, Mexico
- Corresponding authors. Tel.: (52-44) 82624-40, ext. 6465 and 6594.
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15
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Selinski S. Highlight report: gene dose response in N-acetylation capacity. Arch Toxicol 2017; 91:4019-4020. [PMID: 29185025 DOI: 10.1007/s00204-017-2131-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 11/22/2017] [Indexed: 10/18/2022]
Affiliation(s)
- Silvia Selinski
- IfADo-Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund, Ardeystr. 67, 44139, Dortmund, Germany.
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16
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Arylamine N-acetyltransferase 1 in situ N-acetylation on CD3+ peripheral blood mononuclear cells correlate with NATb mRNA and NAT1 haplotype. Arch Toxicol 2017; 92:661-668. [PMID: 29043425 DOI: 10.1007/s00204-017-2082-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 09/25/2017] [Indexed: 12/19/2022]
Abstract
Human arylamine N-acetyltransferase 1 (NAT1) is responsible for the activation and elimination of xenobiotic compounds and carcinogens. Genetic polymorphisms in NAT1 modify both drug efficacy and toxicity. Previous studies have suggested a role for NAT1 in the development of several diseases. The aim of the present study was to evaluate NAT1 protein expression and in situ N-acetylation capacity in peripheral blood mononuclear cells (PBMC), as well as their possible associations with the expression of NAT1 transcript and NAT1 genotype. We report NAT1 protein, mRNA levels, and N-acetylation in situ activity for PBMC obtained from healthy donors. NAT1-specific protein expression was higher in CD3+ cells than other major immune cell subtypes (CD19 or CD56 cells). N-acetylation of pABA varied markedly among the PBMC of participants, but correlated very significantly with levels of NAT1 transcripts. NAT1*4 subjects showed significantly (p = 0.017) higher apparent pABA V max of 71.3 ± 3.7 versus the NAT1*14B subjects apparent V max of 58.5 ± 2.5 nmoles Ac-pABA/24 h/million cells. Levels of pABA N-acetylation activity at each concentration of substrate evaluated also significantly correlated with NAT1 mRNA levels for all samples (p < 0.0001). This highly significant correlation was maintained for samples with the NAT1*4 (p = 0.002) and NAT1*14B haplotypes (p = 0.0106). These results provide the first documentation that NAT1-catalyzed N-acetylation in PBMC is higher in T cell than in other immune cell subtypes and that individual variation in N-acetylation capacity is dependent upon NAT1 mRNA and NAT1 haplotype.
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17
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Allen CE, Doll MA, Hein DW. N-Acetyltransferase 2 Genotype-Dependent N-Acetylation of Hydralazine in Human Hepatocytes. Drug Metab Dispos 2017; 45:1276-1281. [PMID: 29018032 DOI: 10.1124/dmd.117.078543] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 10/06/2017] [Indexed: 11/22/2022] Open
Abstract
Hydralazine is used in the treatment of essential hypertension and is under investigation for epigenetic therapy in the treatment of neoplastic and renal diseases. N-acetyltransferase (NAT) 2 exhibits a common genetic polymorphism in human populations. After recombinant expression in yeast, human NAT2 exhibited an apparent Lineweaver-Burk constant (K-m) value (20.1 ± 8.8 μM) for hydralazine over 20-fold lower than the apparent K-m value (456 ± 57 μM) for recombinant human NAT1 (P = 0.0016). The apparent Vmax value for recombinant human NAT1 (72.2 ± 17.9 nmol acetylated/min/mg protein) was significantly (P = 0.0245) lower than recombinant human NAT2 (153 ± 15 nmol acetylated/min/mg protein), reflecting 50-fold higher clearance for recombinant human NAT2. Hydralazine NAT activities exhibited a robust acetylator gene dose response in cryopreserved human hepatocytes both in vitro and in situ. Hydralazine NAT activities in vitro differed significantly with respect to NAT2 genotype at 1000 (P = 0.0319), 100 (P = 0.002), and 10 μM hydralazine (P = 0.0029). Hydralazine NAT activities differed significantly (P < 0.001) among slow acetylator hepatocytes, (NAT2*5B/*5B > NAT2*5B/*6A > NAT2*6A/*6A). The in situ hydralazine N-acetylation rates differed significantly with respect to NAT2 genotype after incubation with 10 (P = 0.002) or 100 µM (P = 0.0015) hydralazine and were higher after incubation with 100 μM (10-fold) than with 10 μM (4.5-fold) hydralazine. Our results clearly document NAT2 genotype-dependent N-acetylation of hydralazine in human hepatocytes, suggesting that hydralazine efficacy and safety could be improved by NAT2 genotype-dependent dosing strategies.
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Affiliation(s)
- Cecily E Allen
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, Kentucky
| | - Mark A Doll
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, Kentucky
| | - David W Hein
- Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, Kentucky
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18
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Catalytic properties and heat stabilities of novel recombinant human N-acetyltransferase 2 allozymes support existence of genetic heterogeneity within the slow acetylator phenotype. Arch Toxicol 2017; 91:2827-2835. [PMID: 28523442 DOI: 10.1007/s00204-017-1989-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/11/2017] [Indexed: 01/25/2023]
Abstract
Human N-acetyltransferase 2 (NAT2) catalyzes the N-acetylation of numerous aromatic amine drugs such as sulfamethazine (SMZ) and hydrazine drugs such as isoniazid (INH). NAT2 also catalyzes the N-acetylation of aromatic amine carcinogens such as 2-aminofluorene and the O- and N,O-acetylation of aromatic amine and heterocyclic amine metabolites. Genetic polymorphism in NAT2 modifies drug efficacy and toxicity as well as cancer risk. Acetyltransferase catalytic activities and heat stability associated with six novel NAT2 haplotypes (NAT2*6C, NAT2*14C, NAT2*14D, NAT2*14E, NAT2*17, and NAT2*18) were compared with that of the reference NAT2*4 haplotype following recombinant expression in Escherichia coli. N-acetyltransferase activities towards SMZ and INH were significantly (p < 0.0001) lower when catalyzed by the novel recombinant human NAT2 allozymes compared to NAT2 4. SMZ and INH N-acetyltransferase activities catalyzed by NAT2 14C and NAT2 14D were significantly lower (p < 0.001) than catalyzed by NAT2 6C and NAT2 14E. N-Acetylation catalyzed by recombinant human NAT2 17 was over several hundred-fold lower than by recombinant NAT2 4 precluding measurement of its kinetic or heat inactivation constants. Similar results were observed for the O-acetylation of N-hydroxy-2-aminofluorene and N-hydroxy-2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine and the intramolecular N,O-acetylation of N-hydroxy-N-acetyl-2-aminofluorene. The apparent V max of the novel recombinant NAT2 allozymes NAT2 6C, NAT2 14C, NAT2 14D, and NAT2 14E towards AF, 4-aminobiphenyl (ABP), and 3,2'-dimethyl-4-aminobiphenyl (DMABP) were each significantly (p < 0.001) lower while their apparent K m values did not differ significantly (p > 0.05) from recombinant NAT2 4. The apparent V max catalyzed by NAT2 14C and NAT2 14D were significantly lower (p < 0.05) than the apparent V max catalyzed by NAT2 6C and NAT2 14E towards AF, ABP, and DMABP. Heat inactivation rate constants for recombinant human NAT2 14C, 14D, 14E, and 18 were significantly (p < 0.05) higher than NAT2 4. These results provide further evidence of genetic heterogeneity within the NAT2 slow acetylator phenotype.
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