1
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Thomas DN, Wills JW, Tracey H, Baldwin SJ, Burman M, Williams AN, Harte DSG, Buckley RA, Lynch AM. Ames test study designs for nitrosamine mutagenicity testing: qualitative and quantitative analysis of key assay parameters. Mutagenesis 2024; 39:78-95. [PMID: 38112628 DOI: 10.1093/mutage/gead033] [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] [Received: 08/31/2023] [Accepted: 12/15/2023] [Indexed: 12/21/2023] Open
Abstract
The robust control of genotoxic N-nitrosamine (NA) impurities is an important safety consideration for the pharmaceutical industry, especially considering recent drug product withdrawals. NAs belong to the 'cohort of concern' list of genotoxic impurities (ICH M7) because of the mutagenic and carcinogenic potency of this chemical class. In addition, regulatory concerns exist regarding the capacity of the Ames test to predict the carcinogenic potential of NAs because of historically discordant results. The reasons postulated to explain these discordant data generally point to aspects of Ames test study design. These include vehicle solvent choice, liver S9 species, bacterial strain, compound concentration, and use of pre-incubation versus plate incorporation methods. Many of these concerns have their roots in historical data generated prior to the harmonization of Ames test guidelines. Therefore, we investigated various Ames test assay parameters and used qualitative analysis and quantitative benchmark dose modelling to identify which combinations provided the most sensitive conditions in terms of mutagenic potency. Two alkyl-nitrosamines, N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) were studied. NDMA and NDEA mutagenicity was readily detected in the Ames test and key assay parameters were identified that contributed to assay sensitivity rankings. The pre-incubation method (30-min incubation), appropriate vehicle (water or methanol), and hamster-induced liver S9, alongside Salmonella typhimurium strains TA100 and TA1535 and Escherichia coli strain WP2uvrA(pKM101) provide the most sensitive combination of assay parameters in terms of NDMA and NDEA mutagenic potency in the Ames test. Using these parameters and further quantitative benchmark dose modelling, we show that N-nitrosomethylethylamine (NMEA) is positive in Ames test and therefore should no longer be considered a historically discordant NA. The results presented herein define a sensitive Ames test design that can be deployed for the assessment of NAs to support robust impurity qualifications.
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Affiliation(s)
- Dean N Thomas
- GSK Research & Development, Genetic Toxicology and Photosafety, Stevenage SG1 2NY, United Kingdom
| | - John W Wills
- GSK Research & Development, Genetic Toxicology and Photosafety, Stevenage SG1 2NY, United Kingdom
| | - Helen Tracey
- GSK Research & Development, Genetic Toxicology and Photosafety, Stevenage SG1 2NY, United Kingdom
| | - Sandy J Baldwin
- GSK Research & Development, Genetic Toxicology and Photosafety, Stevenage SG1 2NY, United Kingdom
| | - Mark Burman
- GSK Research & Development, Genetic Toxicology and Photosafety, Stevenage SG1 2NY, United Kingdom
| | - Abbie N Williams
- GSK Research & Development, Genetic Toxicology and Photosafety, Stevenage SG1 2NY, United Kingdom
| | - Danielle S G Harte
- GSK Research & Development, Genetic Toxicology and Photosafety, Stevenage SG1 2NY, United Kingdom
| | - Ruby A Buckley
- GSK Research & Development, Genetic Toxicology and Photosafety, Stevenage SG1 2NY, United Kingdom
| | - Anthony M Lynch
- GSK Research & Development, Genetic Toxicology and Photosafety, Stevenage SG1 2NY, United Kingdom
- School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom
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2
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Toma S, Omosebi A, Gao X, Abad K, Bhatnagar S, Qian D, Liu K, Thompson JG. Targeted electrochemical reduction of carcinogenic N-nitrosamines from emission control systems within CO 2 capture plants. CHEMOSPHERE 2023; 333:138915. [PMID: 37172623 DOI: 10.1016/j.chemosphere.2023.138915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 05/08/2023] [Accepted: 05/09/2023] [Indexed: 05/15/2023]
Abstract
N-Nitrosamines are one of the environmentally significant byproducts from aqueous amine-based post-combustion carbon capture systems (CCS) due to their potential risk to human health. Safely mitigating nitrosamines before they are emitted from these CO2 capture systems is therefore a key concern before widescale deployment of CCS can be used to address worldwide decarbonization goals. Electrochemical decomposition is one viable route to neutralize these harmful compounds. The circulating emission control waterwash system, commonly installed at the end of the flue gas treatment trains to minimize amine solvent emissions, plays an important role to capture N-nitrosamines and control their emission into the environment. The waterwash solution is the last point where these compounds can be properly neutralized before becoming an environmental hazard. In this study, the decomposition mechanisms of N-nitrosamines in a simulated CCS waterwash with residual alkanolamines was investigated using several laboratory-scale electrolyzers utilizing carbon xerogel (CX) electrodes. H-cell experiments revealed that N-nitrosamines were decomposed through a reduction reaction and are converted into their corresponding secondary amines thereby neutralizing their environmental impact. Batch-cell experiments statistically examined the kinetic models of N-nitrosamine removal by a combined adsorption and decomposition processes. The cathodic reduction of the N-nitrosamines statistically obeyed the first-order reaction model. Finally, a prototype flow-through reactor using an authentic waterwash was used to successfully target and decompose N-nitrosamines to below the detectable level without degrading the amine solvent compounds allowing them to be return to the CCS and lower the system operating costs. The developed electrolyzer was able to efficiently remove greater than 98% of N-nitrosamines from the waterwash solution without producing any additional environmentally harmful compounds and offers an effective and safe route to mitigate these compounds from CO2 capture systems.
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Affiliation(s)
- Shino Toma
- Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, KY, 40511, United States
| | - Ayokunle Omosebi
- Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, KY, 40511, United States
| | - Xin Gao
- Department of Mechanical Engineering, University of Kentucky, 151 Ralph G. Anderson Building, Lexington, KY, 40506, United States
| | - Keemia Abad
- Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, KY, 40511, United States; Department of Chemistry, University of Kentucky, 125 Chemistry/Physics Building, Lexington, KY, 40506, United States
| | - Saloni Bhatnagar
- Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, KY, 40511, United States
| | - Dali Qian
- Electron Microscopy Center, College of Engineering, University of Kentucky, ASTeCC Building - A004, Lexington, KY, 40502, United States
| | - Kunlei Liu
- Department of Mechanical Engineering, University of Kentucky, 151 Ralph G. Anderson Building, Lexington, KY, 40506, United States.
| | - Jesse G Thompson
- Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, KY, 40511, United States; Department of Chemistry, University of Kentucky, 125 Chemistry/Physics Building, Lexington, KY, 40506, United States.
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3
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Blum K, FitzGerald R, Wilks MF, Barle EL, Hopf NB. Use of the benchmark-dose (BMD) approach to derive occupational exposure limits (OELs) for genotoxic carcinogens: N-nitrosamines. J Appl Toxicol 2023. [PMID: 36840679 DOI: 10.1002/jat.4455] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 01/29/2023] [Accepted: 02/21/2023] [Indexed: 02/26/2023]
Abstract
N-Nitrosamines are potent carcinogens and considered non-threshold carcinogens in various regulatory domains. However, recent data indicate the existence of a threshold for genotoxicity, which can be adequately demonstrated. This aspect has a critical impact on selecting the methodology that is applied to derive occupational exposure limits (OELs). OELs are used to protect workers potentially exposed to various chemicals by supporting the selection of appropriate control measures and ultimately reducing the risk of occupational cancer. Occupational exposures to nitrosamines occur during manufacturing processes, mainly in the rubber and chemical industry. The present study derives OELs for inhaled N-nitrosamines, employing the benchmark dose (BMD) approach if data are adequate and read-across for nitrosamines without adequate data. Additionally, benchmark dose lower confidence limit (BMDL) is preferred and more suitable point-of-departure (PoD) to calculate human health guidance values, including OEL. The lowest OEL (0.2 μg/m3 ) was derived for nitrosodiethylamine (NDEA), and nitrosopiperidine (NPIP) (OEL = 0.2 μg/m3 ), followed by nitrosopyrrolidine (NPYR) (0.4 μg/m3 ), nitrosodimethylamine (NDMA), nitrosodimethylamine (NMEA), and nitrosodipropylamine (NDPA) (0.5 μg/m3 ), nitrosomorpholine (NMOR) (OEL = 1 μg/m3 ), and nitrosodibutylamine (NDBA) (OEL = 2.5 μg/m3 ). Limits based on "non-threshold" TD50 slope calculation were within a 10-fold range. These proposed OELs do not consider skin absorption of nitrosamines, which is also a possible route of entry into the body, nor oral or other environmental sources. Furthermore, we recommend setting a limit for total nitrosamines based on the occupational exposure scenario and potency of components.
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Affiliation(s)
- Kamila Blum
- Environment, Health & Safety Department, GlaxoSmithKline, Munich, Germany.,Faculty of Science and Medicine, University of Geneva, Switzerland
| | - Rex FitzGerald
- Swiss Centre for Applied Human Toxicology (SCAHT) & Department of Pharmaceutical Sciences, University of Basel, Switzerland
| | - Martin F Wilks
- Swiss Centre for Applied Human Toxicology (SCAHT) & Department of Pharmaceutical Sciences, University of Basel, Switzerland
| | | | - Nancy B Hopf
- Swiss Centre for Applied Human Toxicology (SCAHT) & Department of Pharmaceutical Sciences, University of Basel, Switzerland.,Department for Occupational and Environmental Health, Centre for Primary Care and Public Health (Unisanté), University of Lausanne, Lausanne, Switzerland
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4
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Kostal J, Voutchkova-Kostal A. Quantum-Mechanical Approach to Predicting the Carcinogenic Potency of N-Nitroso Impurities in Pharmaceuticals. Chem Res Toxicol 2023; 36:291-304. [PMID: 36745540 DOI: 10.1021/acs.chemrestox.2c00380] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
N-Nitroso contaminants in medicinal products are of concern due to their high carcinogenic potency; however, not all these compounds are created equal, and some are relatively benign chemicals. Understanding the structure-activity relationships (SARs) that drive hazards in one molecule versus another is key to both protecting human health and alleviating costly and sometimes inaccurate animal testing. Here, we report on an extension of the CADRE (computer-aided discovery and REdesign) platform, which is used broadly by the pharmaceutical and personal care industries to assess environmental and human health endpoints, to predict the carcinogenic potency of N-nitroso compounds. The model distinguishes compounds in three potency categories with 77% accuracy in external testing, which surpasses the reproducibility of rodent cancer bioassays and constraints imposed by limited (high-quality) data. The robustness of predictions for more complex pharmaceuticals is maximized by capturing key SARs using quantum mechanics, that is, by hinging the model on the underlying chemistry versus chemicals in the training set. To this end, the present approach can be leveraged in a quantitative hazard assessment and to offer qualitative guidance using electronic structure comparisons between well-studied analogues and unknown contaminants.
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Affiliation(s)
- Jakub Kostal
- Designing Out Toxicity (DOT) Consulting LLC, 2121 Eisenhower Avenue, Alexandria, Virginia22314, United States.,The George Washington University, 800 22nd Street NW, Washington, D.C.20052, United States
| | - Adelina Voutchkova-Kostal
- Designing Out Toxicity (DOT) Consulting LLC, 2121 Eisenhower Avenue, Alexandria, Virginia22314, United States.,The George Washington University, 800 22nd Street NW, Washington, D.C.20052, United States
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5
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Thomas R, Tennant RE, Oliveira AAF, Ponting DJ. What Makes a Potent Nitrosamine? Statistical Validation of Expert-Derived Structure-Activity Relationships. Chem Res Toxicol 2022; 35:1997-2013. [PMID: 36302501 PMCID: PMC9682520 DOI: 10.1021/acs.chemrestox.2c00199] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The discovery of carcinogenic nitrosamine impurities above the safe limits in pharmaceuticals has led to an urgent need to develop methods for extending structure-activity relationship (SAR) analyses from relatively limited datasets, while the level of confidence required in that SAR indicates that there is significant value in investigating the effect of individual substructural features in a statistically robust manner. This is a challenging exercise to perform on a small dataset, since in practice, compounds contain a mixture of different features, which may confound both expert SAR and statistical quantitative structure-activity relationship (QSAR) methods. Isolating the effects of a single structural feature is made difficult due to the confounding effects of other functionality as well as issues relating to determining statistical significance in cases of concurrent statistical tests of a large number of potential variables with a small dataset; a naïve QSAR model does not predict any features to be significant after correction for multiple testing. We propose a variation on Bayesian multiple linear regression to estimate the effects of each feature simultaneously yet independently, taking into account the combinations of features present in the dataset and reducing the impact of multiple testing, showing that some features have a statistically significant impact. This method can be used to provide statistically robust validation of expert SAR approaches to the differences in potency between different structural groupings of nitrosamines. Structural features that lead to the highest and lowest carcinogenic potency can be isolated using this method, and novel nitrosamine compounds can be assigned into potency categories with high accuracy.
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6
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Trejo-Martin A, Bercu JP, Thresher A, Tennant RE, Thomas RF, Cross K, Czich A, Waese K, Nicolette JJ, Murray J, Sonders P, Kondratiuk A, Cheung JR, Thomas D, Lynch A, Harvey J, Glowienke S, Custer L, Escobar PA. Use of the bacterial reverse mutation assay to predict carcinogenicity of N-nitrosamines. Regul Toxicol Pharmacol 2022; 135:105247. [PMID: 35998738 DOI: 10.1016/j.yrtph.2022.105247] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 08/08/2022] [Accepted: 08/12/2022] [Indexed: 11/29/2022]
Abstract
Under ICH M7, impurities are assessed using the bacterial reverse mutation assay (i.e., Ames test) when predicted positive using in silico methodologies followed by expert review. N-Nitrosamines (NAs) have been of recent concern as impurities in pharmaceuticals, mainly because of their potential to be highly potent mutagenic carcinogens in rodent bioassays. The purpose of this analysis was to determine the sensitivity of the Ames assay to predict the carcinogenic outcome with curated proprietary Vitic (n = 131) and Leadscope (n = 70) databases. NAs were selected if they had corresponding rodent carcinogenicity assays. Overall, the sensitivity/specificity of the Ames assay was 93-97% and 55-86%, respectively. The sensitivity of the Ames assay was not significantly impacted by plate incorporation (84-89%) versus preincubation (82-89%). Sensitivity was not significantly different between use of rat and hamster liver induced S9 (80-93% versus 77-96%). The sensitivity of the Ames is high when using DMSO as a solvent (87-88%). Based on the analysis of these databases, the Ames assay conducted under OECD 471 guidelines is highly sensitive for detecting the carcinogenic hazards of NAs.
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Affiliation(s)
- Alejandra Trejo-Martin
- Gilead Sciences, Inc., Nonclinical Safety and Pathobiology (NSP), Foster City, CA, 94404, USA.
| | - Joel P Bercu
- Gilead Sciences, Inc., Nonclinical Safety and Pathobiology (NSP), Foster City, CA, 94404, USA
| | - Andrew Thresher
- Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Leeds, West Yorkshire, LS11 5PS, UK
| | - Rachael E Tennant
- Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Leeds, West Yorkshire, LS11 5PS, UK
| | - Robert F Thomas
- Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Leeds, West Yorkshire, LS11 5PS, UK
| | - Kevin Cross
- Leadscope, Inc., an Instem Company, Columbus, OH, 43215, USA
| | - Andreas Czich
- Sanofi, R&D Preclinical Safety, D-65926, Frankfurt, Germany
| | - Kerstin Waese
- Sanofi, R&D Preclinical Safety, D-65926, Frankfurt, Germany
| | - John J Nicolette
- Janssen Pharmaceuticals, Global Toxicology, Raritan, New Jersey, USA
| | - Joel Murray
- AbbVie, Inc., Pre-clinical Safety, North Chicago, IL, USA
| | - Paul Sonders
- AbbVie, Inc., Pre-clinical Safety, North Chicago, IL, USA
| | | | - Jennifer R Cheung
- Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, Groton, CT, USA
| | - Dean Thomas
- GlaxoSmithKline R&D, Park Road, Ware, Hertfordshire, SG12 0DP, UK
| | - Anthony Lynch
- GlaxoSmithKline R&D, Park Road, Ware, Hertfordshire, SG12 0DP, UK
| | - James Harvey
- GlaxoSmithKline R&D, Park Road, Ware, Hertfordshire, SG12 0DP, UK
| | - Susanne Glowienke
- Novartis AG, NIBR, Pre-clinical Safety, WSJ-340, CH-4002 Basel, Switzerland
| | - Laura Custer
- Bristol-Myers Squibb, Nonclinical Safety, 1 Squibb Dr, New Brunswick, NJ, 08903, USA
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7
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Sood A, Thakur A, Ahuja SM. Recent advancements in ionic liquid based carbon capture technologies. CHEM ENG COMMUN 2021. [DOI: 10.1080/00986445.2021.1990886] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Akash Sood
- Research Laboratory-III, Department of Chemical Engineering, Sant Longowal Institute of Engineering and Technology, Longowal, Punjab, India
| | - Avinash Thakur
- Research Laboratory-III, Department of Chemical Engineering, Sant Longowal Institute of Engineering and Technology, Longowal, Punjab, India
| | - Sandeep Mohan Ahuja
- Research Laboratory-III, Department of Chemical Engineering, Sant Longowal Institute of Engineering and Technology, Longowal, Punjab, India
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8
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Bercu JP, Masuda-Herrera M, Johnson G, Czich A, Glowienke S, Kenyon M, Thomas R, Ponting DJ, White A, Cross K, Waechter F, Rodrigues MAC. Use of less-than-lifetime (LTL) durational limits for nitrosamines: Case study of N-Nitrosodiethylamine (NDEA). Regul Toxicol Pharmacol 2021; 123:104926. [PMID: 33862169 DOI: 10.1016/j.yrtph.2021.104926] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 04/02/2021] [Accepted: 04/06/2021] [Indexed: 11/30/2022]
Abstract
The ICH M7(R1) guideline describes a framework to assess the carcinogenic risk of mutagenic and carcinogenic pharmaceutical impurities following less-than-lifetime (LTL) exposures. This LTL framework is important as many pharmaceuticals are not administered for a patient's lifetime and as clinical trials typically involve LTL exposures. While there has been regulatory caution about applying LTL concepts to cohort of concern (COC) impurities such as N-nitrosamines, ICH M7 does not preclude this and indeed literature data suggests that the LTL framework will be protective of patient safety for N-nitrosamines. The goal was to investigate if applying the LTL framework in ICH M7 would control exposure to an acceptable excess cancer risk in humans. Using N-nitrosodiethylamine as a case study, empirical data correlating exposure duration (as a percentage of lifespan) and cancer incidence in rodent bioassays indicate that the LTL acceptable intake (AI) as derived using the ICH M7 framework would not exceed a negligible additional risk of cancer. Therefore, controlling N-nitrosamines to an LTL AI based on the ICH M7 framework is thus demonstrated to be protective for potential carcinogenic risk to patients over the exposure durations typical of clinical trials and many prescribed medicines.
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Affiliation(s)
- Joel P Bercu
- Gilead Sciences, Nonclinical Safety and Pathobiology (NSP), Foster City, CA, USA.
| | | | - George Johnson
- Institute of Life Science, Swansea University Medical School, Singleton Park, Swansea, SA3 5DE, UK
| | - Andreas Czich
- Sanofi, R&D Preclinical Safety, D-65926, Frankfurt, Germany
| | | | - Michelle Kenyon
- Pfizer Worldwide Research and Development, Genetic Toxicology, Eastern Point Road, Groton, CT, USA
| | - Rob Thomas
- Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Leeds, LS11 5PS, UK
| | - David J Ponting
- Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Leeds, LS11 5PS, UK
| | - Angela White
- GlaxoSmithKline R&D, Park Road, Ware, Hertfordshire, SG12 0DP, UK
| | - Kevin Cross
- Leadscope Inc. an Instem Company, Columbus, OH, 43215, USA
| | - Fernanda Waechter
- Aché Laboratórios Farmacêuticos S.A., Rodovia Presidente Dutra, km 222,2, Porto da Igreja, 07034-904, Guarulhos, SP, Brazil
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9
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Liu J, Xie B, Mai B, Cai Q, He R, Guo D, Zhang Z, Fan J, Zhang W. Development of a sensitive and stable GC-MS/MS method for simultaneous determination of four N-nitrosamine genotoxic impurities in sartan substances. J Anal Sci Technol 2021. [DOI: 10.1186/s40543-020-00254-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
AbstractRecently, N-nitrosamines have been unexpectedly found in generic sartan products. Herein, we developed a sensitive and stable GC-MS/MS method with multiple reactions monitoring mode for the simultaneous determination of four N-nitrosamines in sartan substances, namely, N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine, and N-nitrosodiisopropylamine. The conditions of gas chromatography and mass spectrometry were optimized. The method was validated according to the International Council for Harmonization guidelines in terms of sensitivity, linearity, accuracy, precision, specificity, and stability. The limits of detection of N-nitrosamines in sartan substances ranged from 0.002 to 0.150 ppm, and the corresponding limits of quantification were in the range of 0.008-0.500 ppm, which met the sensitivity requirements for the limits set by the Food and Drug Administration of the United States. The internal standard curve of four N-nitrosamines showed good linearity of regression coefficients over 0.99. The recoveries of N-nitrosamines in selected sartan drugs ranged from 87.68 to 123.76%. The intraday and interday relative standard deviation values were less than 9.15%. Therefore, this proposed method exhibited good sensitivity and precision, high accuracy, and fast analysis speed, which provide a reliable method for quality control of N-nitrosamines in sartan products.
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10
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Thongararm P, Fedeles BI, Khumsubdee S, Armijo AL, Kim L, Thiantanawat A, Promvijit J, Navasumrit P, Ruchirawat M, Croy RG, Essigmann JM. Modulation of N-Methyl- N-nitrosourea Mutagenesis in Mouse Embryo Fibroblasts Derived from the gpt Delta Mouse by an Inhibitor of the O6-Methylguanine Methyltransferase, MGMT. Chem Res Toxicol 2019; 33:625-633. [PMID: 31841318 DOI: 10.1021/acs.chemrestox.9b00444] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
DNA methylating agents are abundant in the environment and are sometimes used in cancer chemotherapy. They react with DNA to form methyl-DNA adducts and byproduct lesions that can be both toxic and mutagenic. Foremost among the mutagenic lesions is O6-methylguanine (m6G), which base pairs with thymine during replication to cause GC → AT mutations. The gpt delta C57BL/6J mouse strain of Nohmi et al. (Mol. Mutagen 1996, 28, 465-70) reliably produces mutational spectra of many DNA damaging agents. In this work, mouse embryo fibroblasts (MEFs) were made from gpt delta C57BL/6J mice and evaluated as a screening tool to determine the qualitative and quantitative features of mutagenesis by N-methyl-N-nitrosourea (MNU), a direct-acting DNA alkylator that serves as a model for environmental N-nitrosamines, such as N-nitrosodimethylamine and therapeutic agents such as Temozolomide. The DNA repair protein MGMT (O6-methylguanine DNA methyltransferase) protects against environmental mutagenesis by DNA methylating agents and, by removing m6G, limits the therapeutic potential of Temozolomide in cancer therapy. The gpt delta MEFs were treated with MNU to establish dose-dependent toxicity. In parallel, MNU mutagenicity was determined in the presence and absence of the MGMT inhibitor AA-CW236 (4-(2-(5-(chloromethyl)-4-(4-(trifluoromethoxy)phenyl)-1H-1,2,3-triazol-1-yl)ethyl)-3,5-dimethylisoxazole). With and without the inhibitor, the principal mutagenic event of MNU was GC → AT, but more mutations were observed when the inhibitor was present. Evidence that the mutagenic lesion was m6G was based on mass spectral data collected using O6-methyl-d3-guanine as an internal standard; m6G levels were higher in AA-CW236 treated MEFs by an amount proportional to the higher mutation frequency seen in the same cells. This work establishes gpt delta MEFs as a versatile tool for probing mutagenesis by environmental and therapeutic agents and as a cell culture model in which chemical genetics can be used to determine the impact of DNA repair on biological responses to DNA damaging agents.
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Affiliation(s)
- Pennapa Thongararm
- Departments of Biological Engineering and Chemistry, and Center for Environmental Health Sciences , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.,Chulabhorn Research Institute , Bangkok 10210 , Thailand
| | - Bogdan I Fedeles
- Departments of Biological Engineering and Chemistry, and Center for Environmental Health Sciences , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Sakunchai Khumsubdee
- Departments of Biological Engineering and Chemistry, and Center for Environmental Health Sciences , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.,Chulabhorn Research Institute , Bangkok 10210 , Thailand
| | - Amanda L Armijo
- Departments of Biological Engineering and Chemistry, and Center for Environmental Health Sciences , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Lina Kim
- Departments of Biological Engineering and Chemistry, and Center for Environmental Health Sciences , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | | | | | | | | | - Robert G Croy
- Departments of Biological Engineering and Chemistry, and Center for Environmental Health Sciences , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - John M Essigmann
- Departments of Biological Engineering and Chemistry, and Center for Environmental Health Sciences , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
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11
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Colantuono G, Cockerill T. Selective strategy for solid sorbent replacement in CCS. Chem Eng Res Des 2017. [DOI: 10.1016/j.cherd.2017.01.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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12
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Safe Synthesis of Alkylhydroxy and Alkylamino Nitramines. Molecules 2016; 21:molecules21121738. [PMID: 27999297 PMCID: PMC6274293 DOI: 10.3390/molecules21121738] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 12/06/2016] [Accepted: 12/12/2016] [Indexed: 12/05/2022] Open
Abstract
Three different protocols for the syntheses of hydroxyalkylnitramines are presented and compared. Safety issues regarding the synthesis of nitramines are also discussed.
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