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Wu KY, Wu CF, Luo YS, Huang YF, Uang SN, Lee YY, Chiang SY. Study of urinary mercapturic acids as biomarkers of human acrylonitrile exposure. Toxicol Lett 2022; 373:141-147. [PMID: 36402260 DOI: 10.1016/j.toxlet.2022.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 11/05/2022] [Accepted: 11/14/2022] [Indexed: 11/18/2022]
Abstract
Exposure to the vinyl monomer acrylonitrile (AN) is primarily occupational. AN is also found in cigarette smoke. AN can be detoxified to form N-acetyl-S-(2-cyanoethyl)-cysteine (CEMA) or activated to 2-cyanoethylene oxide (CEO) and detoxified to form N-acetyl-S-(1-cyano-2-hydroxyethyl)-cysteine (CHEMA) and N-acetyl-S-(2-hydroxyethyl)-cysteine (HEMA). These urinary mercapturic acids (MAs) are considered to be potential biomarkers of AN exposure. This study assessed personal AN exposure, urinary MAs (CEMA, CHEMA, and HEMA), and cotinine (a biomarker of cigarette smoke) in 80 AN-exposed and 23 non-exposed factory workers from urine samples provided before and after work shifts. Unambiguous linear correlations were observed between levels of urinary CEMA and CHEMA with personal AN exposures, indicating their potential as chemically-specific biomarkers for AN exposures. AN exposure was the dominant factor in MA formation for AN-exposed workers, whereas urinary cotinine used as a biomarker showed that cigarette smoke exposure was the primary factor for non-exposed workers. The CHEMA/CEMA and (CHEMA+HEMA)/CEMA ratios in this human study differ from those in similar studies of AN-treated rats and mice in literature, suggesting a possible dose- and species-dependent effect in AN metabolic activation and detoxification.
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Affiliation(s)
- Kuen-Yuh Wu
- Institute of Food Safety and Health, College of Public Health, National Taiwan University, Taipei, Taiwan; Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, Taipei, Taiwan; Department of Public Health, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Chia-Fang Wu
- Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Yu-Syuan Luo
- Institute of Food Safety and Health, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Yu-Fang Huang
- Department of Safety, Health, and Environmental Engineering, National United University, Miaoli, Taiwan
| | - Shi-Nian Uang
- Division of Analytical Chemistry, Institute of Occupational Safety and Health, Council of Labor Affairs, Executive Yuan, New Taipei, Taiwan
| | - Yen-Yi Lee
- Institute of Environmental Toxin and Emerging Contaminant, Cheng Shiu University, Kaohsiung, Taiwan; Department of Food and Beverage Management, Cheng Shiu University, Kaohsiung, Taiwan
| | - Su-Yin Chiang
- School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan.
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Yang B, Yin C, Zhang Y, Xing G, Wang S, Li F, Aschner M, Lu R. Differential effects of subchronic acrylonitrile exposure on hydrogen sulfide levels in rat blood, brain, and liver. Toxicol Res (Camb) 2022; 11:374-384. [PMID: 35510234 PMCID: PMC9052317 DOI: 10.1093/toxres/tfac011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 02/14/2022] [Accepted: 02/26/2022] [Indexed: 11/14/2022] Open
Abstract
Background Hydrogen sulfide (H2S), as the third gasotransmitter participates in both cellular physiological and pathological processes, including chemical-induced injuries. We recently reported acute acrylonitrile (AN) treatment inhibited endogenous H2S biosynthesis pathway in rat and astrocyte models. However, there is still no evidence to address the correlation between endogenous H2S and sub-chronic AN exposure. Objectives This study aims to explore the modulatory effects of prolonged AN exposure on endogenous H2S levels and its biosynthetic enzymes in rat blood, brain and liver. Methods A total of 50 male Sprague-Dawley rats were randomly divided into 5 groups, including the control group and AN-treated groups at dosages of 6.25, 12.5, 25 or 50 mg/kg. Rats received one exposure/day, 5 days/week, for 4 consecutive weeks. The rat bodyweight and brain/liver organ coefficient were detected, along with liver cytochrome P450 2E1(CYP2E1) expression. In addition, the H2S contents in rat serum and plasma, and in cerebral cortex and liver tissues were measured by methylene blue method. The expression of H2S-generating enzymes, including cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MPST) was also measured with Western blot both in rat cerebral cortex and liver. Results Subchronic exposure to AN significantly inhibited bodyweight-gain and increased the liver CYP2E1 expression compared with the control. In addition, AN significantly increased H2S levels in rat plasma and serum, but not in liver. The endogenous H2S level in rat cerebral cortex was also significantly increased upon AN treatment, when expression of the major H2S-generating enzymes, CBS and 3-MPST were significantly enhanced. However, hepatic protein levels of CBS and CSE were significantly increased, whereas hepatic levels of 3-MPST were significantly decreased. Conclusion This study showed that sub-chronic AN exposure increased endogenous H2S contents in rat blood and brain tissues, but not liver, which may be resulted from the distinct expression profile of H2S-producing enzymes in response to AN. The blood H2S contents may be applied as a potential novel biomarker for surveillance of chronically AN-exposed populations. Highlights Subchronic intraperitoneal exposure to acrylonitrile increased H2S content in rat blood and cerebral cortex, but not in liver.Distinct tissue expression profiles of H2S-producing enzymes contribute to the acrylonitrile-induced differential effects on the H2S level.Blood H2S level may be a biomarker for subchronic exposure to acrylonitrile.
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Affiliation(s)
- Bobo Yang
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Changsheng Yin
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Yu Zhang
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Guangwei Xing
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Suhua Wang
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Fang Li
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Rongzhu Lu
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
- Center for Experimental Research, Affiliated Kunshan Hospital to Jiangsu University School of Medicine, Kunshan, Suzhou, Jiangsu 215300, China
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Acrylonitrile induction of rodent neoplasia: Potential mechanism of action and relevance to humans. TOXICOLOGY RESEARCH AND APPLICATION 2022. [DOI: 10.1177/23978473211055363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Acrylonitrile, an industrial chemical, is a multisite carcinogen in rats and mice, producing tumors in four tissues with barrier function, that is, brain, forestomach, Zymbal’s gland, and Harderian gland. To assess mechanism(s) of action (MoA) for induction of neoplasia and to evaluate whether the findings in rodents are indicative of human hazard, data on the potential key effects produced by acrylonitrile in the four rodent target tissues of carcinogenicity were evaluated. A notable finding was depletion of glutathione in various organs, including two target tissues, the brain, and forestomach, suggesting that this effect could be a critical initiating event. An additional combination of oxidative DNA damage and cytotoxic effects of acrylonitrile and its metabolites, cyanide, and 2-cyanoethylene oxide, could initiate pro-inflammatory signaling and sustained cell and tissue injury, leading to compensatory cell proliferation and neoplastic development. The in vivo DNA-binding and genotoxicity of acrylonitrile has been studied in several target tissues with no compelling positive results. Thus, while some mutagenic effects were reported in acrylonitrile-exposed rodents, data to determine whether this mutagenicity stems from direct DNA reactivity of acrylonitrile are insufficient. Accordingly, the induction of tumors in rodents is consistent primarily with a non-genotoxic MoA, although a contribution from weak mutagenicity cannot be ruled out. Mechanistic data to support conclusions regarding human hazard from acrylonitrile exposure is weak. Comparison of metabolism of acrylonitrile between rodents and humans provide little support for human hazard. Three of the tissues affected in bioassays (forestomach, Zymbal’s gland, and Harderian gland) are present only in rodents, while the brain is anatomically different between rodents and humans, diminishing relevance of tumor induction in these tissues to human hazard. Extensive epidemiological data has not revealed causation of human cancer by acrylonitrile.
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Bhandari D, Zhang L, Zhu W, De Jesús VR, Blount BC. Optimal Cutoff Concentration of Urinary Cyanoethyl Mercapturic Acid for Differentiating Cigarette Smokers from Nonsmokers. Nicotine Tob Res 2021; 24:761-767. [PMID: 34718769 DOI: 10.1093/ntr/ntab224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 10/21/2021] [Indexed: 11/13/2022]
Abstract
BACKGROUND Cotinine is a widely used biomarker for classifying cigarette smoking status. However, cotinine does not differentiate between the use of combustible and noncombustible tobacco products. The increasing use of noncombustible tobacco drives the need for a complementary biomarker for distinguishing cigarette smokers from users of noncombustible tobacco products. METHODS We evaluated the urinary acrylonitrile metabolite, 2CyEMA, as a biomarker of exposure to cigarette smoke in the U.S. population-representative data from the National Health and Nutritional Examination Survey (NHANES). Smoking status was categorized based on the recent tobacco use questionnaire. The receiver operating characteristic (ROC) curve analysis was performed to identify optimal cutoff concentrations by maximizing Youden's J index. The area under the curve (AUC) was used to compare 2CyEMA effectiveness with respect to serum cotinine. RESULTS The overall cutoff concentration for the classification of cigarette smokers from nonsmokers was 7.32 ng/mL with high sensitivity and specificity (≥0.925). When stratified by demographic variables, the cutoff concentrations varied among subgroups based on age, sex, and race/Hispanic origin. Non-Hispanic Blacks had the highest cutoff concentration (15.3 ng/mL), and Hispanics had the lowest (4.63 ng/mL). Females had higher cutoff concentrations (8.80 ng/mL) compared to males (6.10 ng/mL). Among different age groups, the cutoff concentrations varied between 4.63 ng/mL (21 - 39 years old) and 10.6 ng/mL (for ≥60 years old). We also explored the creatinine adjusted cutoff values. CONCLUSIONS 2CyEMA is an effective biomarker for distinguishing cigarette smokers from nonsmokers (users of noncombustible tobacco products or nonusers). IMPACT Increasing use of noncombustible tobacco products, including e-cigarettes, complicates differentiating smokers from nonsmokers; we document that urinary 2CyEMA accurately differentiates cigarette smokers from the noncombustible tobacco product users and nonusers. Also, it is the first paper to report urinary 2CyEMA cutoff values based on U.S. representative population data.
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Affiliation(s)
- Deepak Bhandari
- Centers for Disease Control and Prevention, Division of Laboratory Sciences, Tobacco and Volatiles Branch, Atlanta, GA
| | - Luyu Zhang
- Centers for Disease Control and Prevention, Division of Laboratory Sciences, Tobacco and Volatiles Branch, Atlanta, GA
| | - Wanzhe Zhu
- Centers for Disease Control and Prevention, Division of Laboratory Sciences, Tobacco and Volatiles Branch, Atlanta, GA
| | - Víctor R De Jesús
- Centers for Disease Control and Prevention, Division of Laboratory Sciences, Tobacco and Volatiles Branch, Atlanta, GA
| | - Benjamin C Blount
- Centers for Disease Control and Prevention, Division of Laboratory Sciences, Tobacco and Volatiles Branch, Atlanta, GA
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Yang B, Zhao W, Yin C, Bai Y, Wang S, Xing G, Li F, Bian J, Aschner M, Cai J, Shi H, Lu R. Acute acrylonitrile exposure inhibits endogenous H 2S biosynthesis in rat brain and liver: The role of CBS/3-MPST-H 2S pathway in its astrocytic toxicity. Toxicology 2021; 451:152685. [PMID: 33486070 DOI: 10.1016/j.tox.2021.152685] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/12/2020] [Accepted: 01/15/2021] [Indexed: 12/11/2022]
Abstract
Hydrogen sulfide (H2S) as the third gasotransmitter molecule serves various biological regulatory roles in health and disease. Acrylonitrile (AN) is a common occupational toxicant and environmental pollutant, causing brain and liver damage in mammals. The biotransformation of AN is dependent-upon reduced glutathione (GSH), cysteine and other sulfur-containing compounds. However, the effects of AN on the endogenous H2S biosynthesis pathway have yet to be determined. Herein, we demonstrated that a single exposure to AN (at 25, 50, or 75 mg/kg for 1, 6 or 24 h) decreased the endogenous H2S content and H2S-producing capacity in a dose-dependent manner, both in the cerebral cortex and liver of rats in vivo. In addition, the inhibitory effects of AN (1, 2.5, 5, 10 mM for 12 h) on the H2S content and/or the expression of H2S-producing enzymes were also found both in primary rat astrocytes and rat liver cell line (BRL cells). Impairment in the H2S biosynthesis pathway was also assessed in primary rat astrocytes treated with AN. It was found that inhibition of the cystathionine-β-synthase (CBS)/3-mercaptopyruvate sulfurtransferase (3-MPST)-H2S pathway with the CBS inhibitor or 3-MPST-targeted siRNA significantly increased the AN-induced (5 mM for 12 h) cytotoxicity in astrocytes. In turn, CBS activation or 3-MPST overexpression as well as exogenous NaHS supplementation significantly attenuated AN-induced cytotoxicity. Taken together, endogenous H2S biosynthesis pathway was disrupted in rats acutely exposed to AN, which contributes to acute AN neurotoxicity in primary rat astrocytes.
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Affiliation(s)
- Bobo Yang
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China
| | - Wenjun Zhao
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China; Department of Clinical Laboratory, Affiliated People's Hospital to Jiangsu University School of Medicine, Zhenjiang, Jiangsu, 212002, China
| | - Changsheng Yin
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China
| | - Yu Bai
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China
| | - Suhua Wang
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China
| | - Guangwei Xing
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China
| | - Fang Li
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China
| | - Jinsong Bian
- Department of Pharmacology, School of Medicine, National Singapore University, 117597, Singapore
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Jiyang Cai
- Department of Physiology, College of Medicine, University of Oklahoma Health Science Center, Lindsay, Oklahoma City, OK, 73104, USA
| | - Haifeng Shi
- School of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu, 212013, China
| | - Rongzhu Lu
- Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China; Center for Experimental Research, Affiliated Kunshan Hospital to Jiangsu University School of Medicine, Kunshan, Suzhou, Jiangsu, 215132, China.
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6
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Review of the evidence for thresholds for DNA-Reactive and epigenetic experimental chemical carcinogens. Chem Biol Interact 2019; 301:88-111. [DOI: 10.1016/j.cbi.2018.11.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 11/06/2018] [Accepted: 11/22/2018] [Indexed: 01/01/2023]
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Williams GM, Kobets T, Duan JD, Iatropoulos MJ. Assessment of DNA Binding and Oxidative DNA Damage by Acrylonitrile in Two Rat Target Tissues of Carcinogenicity: Implications for the Mechanism of Action. Chem Res Toxicol 2017; 30:1470-1480. [DOI: 10.1021/acs.chemrestox.7b00105] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gary M. Williams
- Chemical Safety Program,
Department of Pathology, New York Medical College, Valhalla, New York 10595, United States
| | - Tetyana Kobets
- Chemical Safety Program,
Department of Pathology, New York Medical College, Valhalla, New York 10595, United States
| | - Jian-Dong Duan
- Chemical Safety Program,
Department of Pathology, New York Medical College, Valhalla, New York 10595, United States
| | - Michael J. Iatropoulos
- Chemical Safety Program,
Department of Pathology, New York Medical College, Valhalla, New York 10595, United States
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8
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Pu X, Wang Z, Zhou S, Klaunig JE. Protective effects of antioxidants on acrylonitrile-induced oxidative stress in female F344 rats. ENVIRONMENTAL TOXICOLOGY 2016; 31:1808-1818. [PMID: 26332274 DOI: 10.1002/tox.22182] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 07/30/2015] [Accepted: 08/05/2015] [Indexed: 06/05/2023]
Abstract
The induction of oxidative stress and damage appears to be involved in acrylonitrile induction of brain astrocytomas in rat. The present study examined the effects of dietary antioxidant supplementation on acrylonitrile-induced oxidative stress and oxidative damage in rats in vivo. To assess the effects of antioxidants on biomarkers of acrylonitrile-induced oxidative stress, female F344 rats were provided with diets containing vitamin E (0.05%), green tea polyphenols (GTP, 0.4%), N-acetyl cysteine (NAC, 0.3%), sodium selenite (0.1mg/kg), and taurine (10g/kg) for 7 days, and then co-administered with 0 and 100 ppm acrylonitrile in drinking water for 28 days. Significant increase in oxidative DNA damage in brain, evidenced by elevated 8OHdG levels, was seen in acrylonitrile-exposed rats. Supplementation with vitamin E, GTP, and NAC reduced acrylonitrile-induced oxidative DNA damage in brain while no protective effects were seen with the selenium or taurine supplementation. Acrylonitrile increased oxidative DNA damage, measured by the fpg-modified alkaline Comet assay in rat WBCs, which was reduced by supplementation of Vitamin E, GTP, NAC, selenium, and taurine. In addition to stimulation of oxidative DNA damage, acrylonitrile triggered induction of pro-inflammatory cytokines Tnfα, Il-1β, and Ccl2, and the growth stimulatory cyclin D1 and cyclin D2 genes, which were effectively down-regulated with antioxidant treatment. Antioxidant treatment also was able to stimulate the pro-apoptotic genes Bad, Bax, and FasL and DNA repair genes Xrcc6 and Gadd45α. The results of this study support the involvement of oxidative stress in the development of acrylonitrile-induced astrocytomas and suggest that antioxidants block acrylonitrile-mediated damage through mechanisms that may involve in the suppression of inflammatory responses, inhibition of cell proliferation and stimulation of apoptosis. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1808-1818, 2016.
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Affiliation(s)
- Xinzhu Pu
- Biomolecular Research Center, Boise State University, Idaho, USA, 47408
| | - Zemin Wang
- Department of Environmental Health, Indiana University School of Public Health, Bloomington, Indiana, 47408
| | - Shaoyu Zhou
- Department of Environmental Health, Indiana University School of Public Health, Bloomington, Indiana, 47408
- Department of Pharmacology, Zunyi Medical College, Zunyi, 563000, China
| | - James E Klaunig
- Department of Environmental Health, Indiana University School of Public Health, Bloomington, Indiana, 47408
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Kesarwala AH, Krishna MC, Mitchell JB. Oxidative stress in oral diseases. Oral Dis 2016; 22:9-18. [PMID: 25417961 PMCID: PMC4442080 DOI: 10.1111/odi.12300] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 11/14/2014] [Accepted: 11/14/2014] [Indexed: 01/10/2023]
Abstract
Oxidative species, including reactive oxygen species (ROS), are components of normal cellular metabolism and are required for intracellular processes as varied as proliferation, signal transduction, and apoptosis. In the situation of chronic oxidative stress, however, ROS contribute to various pathophysiologies and are involved in multiple stages of carcinogenesis. In head and neck cancers specifically, many common risk factors contribute to carcinogenesis via ROS-based mechanisms, including tobacco, areca quid, alcohol, and viruses. Given their widespread influence on the process of carcinogenesis, ROS and their related pathways are attractive targets for intervention. The effects of radiation therapy, a central component of treatment for nearly all head and neck cancers, can also be altered via interfering with oxidative pathways. These pathways are also relevant to the development of many benign oral diseases. In this review, we outline how ROS contribute to pathophysiology with a focus toward head and neck cancers and benign oral diseases, describing potential targets and pathways for intervention that exploit the role of oxidative species in these pathologic processes.
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Affiliation(s)
- Aparna H. Kesarwala
- Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Murali C. Krishna
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - James B. Mitchell
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
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Kolenda-Roberts HM, Harris N, Singletary E, Hardisty JF. Immunohistochemical characterization of spontaneous and acrylonitrile-induced brain tumors in the rat. Toxicol Pathol 2012; 41:98-108. [PMID: 22821367 DOI: 10.1177/0192623312452492] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Twenty-eight spontaneously occurring glial tumors (previously diagnosed as astrocytomas, oligodendrogliomas, and gliomas) and eleven granular cell tumors (GCTs) were selected for evaluation using a panel of immunohistochemistry (IHC) stains (Ricinus communis agglutinin type 1 [RCA-1], ionized calcium-binding adapter molecule 1 [Iba-1], OX-6/major immunohistocompatibility complex class II, oligodendrocytes transcription factor 2 [Olig2], glial fibrillary acidic protein [GFAP], S100 beta, glutamine synthetase, neurofilament, proliferating cell nuclear antigen). In addition, nine brain tumors from a 2-year drinking water study for acrylonitrile were obtained from the Acrylonitrile Group, Inc. Based on IHC staining characteristics, Olig2+ oligodendrogliomas were the most commonly diagnosed spontaneous tumor in these animals. Many of the spontaneous tumors previously diagnosed as astrocytomas were RCA-1+, Iba-1+ and negative for GFAP, S100beta, and glutamine synthetase; the diagnosis of malignant microglial tumor is proposed for these neoplasms. Three mixed tumors were identified with Olig2+ (oligodendrocytes) and Iba-1+ (macrophage/microglia) cell populations. The term mixed glioma is not recommended for these tumors, as it is generally used to refer to oligoastrocytomas, which were not observed in this study. GCT were positive for RCA-1 and Iba-1. All acrylonitrile tumors were identified as malignant microglial tumors. These results may indicate that oligodendrogliomas are more common as spontaneous tumors, while acrylonitrile-induced neoplasms are microglial/histiocytic in origin. No astrocytomas (GFAP, S100 beta, and/or glutamine synthetase-positive neoplasms) were observed.
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Klaunig JE, Kamendulis LM, Hocevar BA. Oxidative stress and oxidative damage in carcinogenesis. Toxicol Pathol 2009; 38:96-109. [PMID: 20019356 DOI: 10.1177/0192623309356453] [Citation(s) in RCA: 609] [Impact Index Per Article: 40.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Carcinogenesis is a multistep process involving mutation and the subsequent selective clonal expansion of the mutated cell. Chemical and physical agents including those that induce reative oxygen species can induce and/or modulate this multistep process. Several modes of action by which carcinogens induce cancer have been identified, including through production of reactive oxygen species (ROS). Oxidative damage to cellular macromolecules can arise through overproduction of ROS and faulty antioxidant and/or DNA repair mechanisms. In addition, ROS can stimulate signal transduction pathways and lead to activation of key transcription factors such as Nrf2 and NF-kappaB. The resultant altered gene expression patterns evoked by ROS contribute to the carcinogenesis process. Recent evidence demonstrates an association between a number of single nucleotide polymorphisms (SNPs) in oxidative DNA repair genes and antioxidant genes with human cancer susceptibility. These aspects of ROS biology will be discussed in the context of their relationship to carcinogenesis.
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Affiliation(s)
- James E Klaunig
- Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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12
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Pu X, Kamendulis LM, Klaunig JE. Acrylonitrile-induced oxidative stress and oxidative DNA damage in male Sprague-Dawley rats. Toxicol Sci 2009; 111:64-71. [PMID: 19546159 PMCID: PMC2726299 DOI: 10.1093/toxsci/kfp133] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Accepted: 06/16/2009] [Indexed: 11/12/2022] Open
Abstract
Studies have demonstrated that the induction of oxidative stress may be involved in brain tumor induction in rats by acrylonitrile. The present study examined whether acrylonitrile induces oxidative stress and DNA damage in rats and whether blood can serve as a valid surrogate for the biomonitoring of oxidative stress induced by acrylonitrile in the exposed population. Male Sprague-Dawley rats were treated with 0, 3, 30, 100, and 200 ppm acrylonitrile in drinking water for 28 days. One group of rats were also coadministered N-acetyl cysteine (NAC) (0.3% in diet) with acrylonitrile (200 ppm in drinking water) to examine whether antioxidant supplementation was protective against acrylonitrile-induced oxidative stress. Direct DNA strand breakage in white blood cells (WBC) and brain was measured using the alkaline comet assay. Oxidative DNA damage in WBC and brain was evaluated using formamidopyrimidine DNA glycosylase (fpg)-modified comet assay and with high-performance liquid chromatography-electrochemical detection. No significant increase in direct DNA strand breaks was observed in brain and WBC from acrylonitrile-treated rats. However, oxidative DNA damage (fpg comet and 8'hydroxyl-2-deoxyguanosine) in brain and WBC was increased in a dose-dependent manner. In addition, plasma levels of reactive oxygen species (ROS) increased in rats administered acrylonitrile. Dietary supplementation with NAC prevented acrylonitrile-induced oxidative DNA damage in brain and WBC. A slight, but significant, decrease in the GSH:GSSG ratio was seen in brain at acrylonitrile doses > 30 ppm. These results provide additional support that the mode of action for acrylonitrile-induced astrocytomas involves the induction of oxidative stress and damage. Significant associations were seen between oxidative DNA damage in WBC and brain, ROS formation in plasma, and the reported tumor incidences. Since oxidative DNA damage in brain correlated with oxidative damage in WBC, these results suggest that monitoring WBC DNA damage maybe a useful tool to assess acrylonitrile-induced oxidative stress in humans.
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Affiliation(s)
| | | | - James E. Klaunig
- Department of Pharmacology and Toxicology, Center for Environmental Health, Indiana University School of Medicine, Indianapolis, Indiana 46202
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Nagatani M, Ando R, Yamakawa S, Saito T, Tamura K. Histological and immunohistochemical studies on spontaneous rat astrocytomas and malignant reticulosis. Toxicol Pathol 2009; 37:599-605. [PMID: 19487256 DOI: 10.1177/0192623309338385] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Among spontaneous neoplasms of the rat central nervous system, the discrimination between astrocytoma and malignant reticulosis (MR) is sometimes difficult because of their similar cell morphology and infiltration patterns. In the present study, we carried out histological and immunohistochemical analyses on a total of sixty-four cases in Sprague-Dawley and F344 rats. These cases were diagnosed as benign/malignant astrocytoma containing no neoplastic oligodendroglial elements or MR according to the diagnostic criteria of the World Health Organization International Classification of Rodent Tumors (Mohr et al. 1994). Astrocytomas were divided into three types and MR into two types based on the number of lesions, cellularity and infiltration patterns, and so on. Although the neoplastic cells from all types showed various immunoreactivities for RM-4 (anti-rat macrophages and dendritic cells), ED-1, and/or vimentin, there were no distinctive differences among these types, and most cells that were positive for RM-4 were also positive for ED-1. None of the tumor types showed any reactivity for GFAP or S-100 protein. From the results of morphological and immunohistochemical examinations, it was indicated that there are no distinctive differences between spontaneous astrocytomas and MR in rats, and they are probably derived from the same cell lineage, that is, microglia, macrophage, or radial glia.
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Affiliation(s)
- Mariko Nagatani
- Hamamatsu Branch of Pathology Department, Biology and Zoology Research Center Inc., Hamamatsu, Shizuoka 435-0016, Japan.
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Kirman CR, Sweeney LM, Gargas ML, Strother DE, Collins JJ, Deskin R. Derivation of noncancer reference values for acrylonitrile. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2008; 28:1375-1394. [PMID: 18761732 DOI: 10.1111/j.1539-6924.2008.01101.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Dose-response assessments were conducted for the noncancer effects of acrylonitrile (AN) for the purposes of deriving subchronic and chronic oral reference dose (RfD) and inhalation reference concentration (RfC) values. Based upon an evaluation of available toxicity data, the irritation and neurological effects of AN were determined to be appropriate bases for deriving reference values. A PBPK model, which describes the toxicokinetics of AN and its metabolite 2-cyanoethylene oxide (CEO) in both rats and humans, was used to assess the dose-response data in terms of an internal dose measure for the oral RfD values, but could not be used in deriving the inhalation RfC values. Benchmark dose (BMD) methods were used to derive all reference values. Where sufficient information was available, data-derived uncertainty factors were applied to the points of departure determined by BMD methods. From this assessment, subchronic and chronic oral RfD values of 0.5 and 0.05 mg/kg/day, respectively, were derived. Similarly, subchronic and chronic inhalation RfC values of 0.1 and 0.06 mg/m(3), respectively, were derived. Confidence in the reference values derived for AN was considered to be medium to high, based upon a consideration of the confidence in the key studies, the toxicity database, dosimetry, and dose-response modeling.
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Affiliation(s)
- C R Kirman
- The Sapphire Group, Inc., Beachwood, OH 44122, USA.
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15
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Csanády GA, Filser JG. A physiological toxicokinetic model for inhaled propylene oxide in rat and human with special emphasis on the nose. Toxicol Sci 2006; 95:37-62. [PMID: 17062723 DOI: 10.1093/toxsci/kfl140] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Chronic exposure to high concentrations of PO induced inflammation in the respiratory nasal mucosa (RNM) of rodents and, for concentrations >or= 300 ppm, caused nasal tumors. Considering the nose to be the most relevant target organ for PO-induced tumorigenicity, we developed a physiological toxicokinetic model for PO in rats and humans. It includes compartments for arterial, venous, and pulmonary blood, liver, muscle, fat, richly perfused tissues, lung, and nose. It simulates inhalation of PO, its distribution into tissues by blood flow, and its elimination by exhalation and metabolism. In nose, lung, and liver of rats, PO conjugation with glutathione (GSH), PO-induced GSH depletion, and formation of PO adducts to DNA are described. Also modeled are PO adducts to hemoglobin of rats and humans. Required partition coefficients and metabolic parameters were derived experimentally or from publications. In rats, simulated PO concentrations in blood and GSH levels in tissues agreed with measured data. If compared with reported values, levels of adducts with hemoglobin were underpredicted up to a factor of about 2. Adducts with DNA differed up to a factor of 3. Hemoglobin adducts predicted for PO-exposed workers were 1.5-1.9 times higher than the reported ones. Considering identical conditions of PO exposure, similar PO concentrations in RNM were modeled for rats and humans. Also, PO concentrations in blood, about 1/30th of those in RNM, were similar in both species. Since the model was evaluated on all available data in rats and humans, we consider it to be useful for estimating the risk from inhalation exposure to PO.
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Affiliation(s)
- György A Csanády
- Institute of Toxicology, GSF National Research Center for Environment and Health, D-85764 Neuherberg, Germany
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16
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Pu X, Kamendulis LM, Klaunig JE. Acrylonitrile-induced oxidative DNA damage in rat astrocytes. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2006; 47:631-8. [PMID: 16917936 DOI: 10.1002/em.20249] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Chronic administration of acrylonitrile results in a dose-related increase in astrocytomas in rat brain, but the mechanism of acrylonitrile carcinogenicity is not fully understood. The potential of acrylonitrile or its metabolites to induce direct DNA damage as a mechanism for acrylonitrile carcinogenicity has been questioned, and recent studies indicate that the mechanism involves the induction of oxidative stress in rat brain. The present study examined the ability of acrylonitrile to induce DNA damage in the DI TNC1 rat astrocyte cell line using the alkaline Comet assay. Oxidized DNA damage also was evaluated using formamidopyrimidine DNA glycosylase treatment in the modified Comet assay. No increase in direct DNA damage was seen in astrocytes exposed to sublethal concentrations of acrylonitrile (0-1.0 mM) for 24 hr. However, acrylonitrile treatment resulted in a concentration-related increase in oxidative DNA damage after 24 hr. Antioxidant supplementation in the culture media (alpha-tocopherol, (-)-epigallocathechin-3 gallate, or trolox) reduced acrylonitrile-induced oxidative DNA damage. Depletion of glutathione using 0.1 mM DL-buthionine-[S,R]-sulfoximine increased acrylonitrile-induced oxidative DNA damage (22-46%), while cotreatment of acrylonitrile with 2.5 mM L-2-oxothiazolidine-4-carboxylic acid, a precursor for glutathione biosynthesis, significantly reduced acrylonitrile-induced oxidative DNA damage (7-47%). Cotreatment of acrylonitrile with 0.5 mM 1-aminobenzotriazole, a suicidal inhibitor of cytochrome P450, prevented the oxidative DNA damage produced by acrylonitrile. Cyanide (0.1-0.5 mM) increased oxidative DNA damage (44-160%) in astrocytes. These studies demonstrate that while acrylonitrile does not directly damage astrocyte DNA, it does increase oxidative DNA damage. The oxidative DNA damage following acrylonitrile exposure appears to arise mainly through the P450 metabolic pathway; moreover, glutathione depletion may contribute to the induction of oxidative DNA damage by acrylonitrile.
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Affiliation(s)
- Xinzhu Pu
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Kirman CR, Gargas ML, Marsh GM, Strother DE, Klaunig JE, Collins JJ, Deskin R. Cancer dose–response assessment for acrylonitrile based upon rodent brain tumor incidence: Use of epidemiologic, mechanistic, and pharmacokinetic support for nonlinearity. Regul Toxicol Pharmacol 2005; 43:85-103. [PMID: 16099568 DOI: 10.1016/j.yrtph.2005.06.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Indexed: 11/19/2022]
Abstract
A cancer dose-response assessment was conducted for acrylonitrile (AN) using updated information on mechanism of action, epidemiology, toxicity, and pharmacokinetics. Although more than 10 chronic bioassays indicate that AN produces multiple tumors in rats and mice, a number of large, well-conducted epidemiology studies provide no evidence of a causal association between AN exposure and cancer mortality of any type. The epidemiological data include early industry exposures that are far higher than occur today and that approach or exceed levels found to be tumorigenic in animals. Despite the absence of positive findings in the epidemiology data, a dose-response assessment was conducted for AN based on brain tumors in rats. Mechanistic studies implicate the involvement of oxidative stress in rat brain due to a metabolite (2-cyanoethylene oxide or CEO, cyanide), but do not conclusively rule out a potential role for the direct genotoxicity of CEO. A PBPK model was used to predict internal doses (peak CEO in brain) for 12 data sets, which were pooled together to provide a consistent characterization of the dose-response relationship for brain tumor incidence in the rat. The internal dose corresponding to a 5% increase in extra risk (ED 05=0.017 mg/L brain) and its lower confidence limit (LED 05=0.014 mg/L brain) was used as the point of departure. The weight-of-evidence supports the use of a nonlinear extrapolation for the cancer dose-response assessment. A quantitative comparison of the epidemiology exposure-response data (lung and brain cancer mortality) to the rat brain tumor data in terms of internal dose adds to the confidence in the nonlinear extrapolation. Uncertainty factors of 200 and 220 (for the oral and inhalation routes, respectively) were applied to the LED 05 to account for interspecies variation, intraspecies variation, and the severity of the response measure. Accordingly, oral doses below 0.009 mg/kg-day and air concentrations below 0.1mg/m(3) are not expected to pose an appreciable risk to human populations exposed to AN.
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Affiliation(s)
- C R Kirman
- The Sapphire Group, Inc., Beachwood, OH, USA.
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18
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Quast JF. Two-year toxicity and oncogenicity study with acrylonitrile incorporated in the drinking water of rats. Toxicol Lett 2002; 132:153-96. [PMID: 12044703 DOI: 10.1016/s0378-4274(02)00072-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Sprague-Dawley rats (80 per sex per control and 48 per sex in each treatment group) were given drinking water formulated to contain 0, 35, 100, or 300 ppm acrylonitrile (AN) for up to 2-years. An additional ten rats per sex per group were added for a 1-year interim necropsy. The equivalent doses of AN consumed were 0, 3.4, 8.5, and 21.3 mg/kg per day for males and 0, 4.4, 10.8, and 25.0 for females. Rats were closely monitored clinically with body weight, feed and water consumption measured at numerous intervals. Hematology, clinical chemistry, and urinalysis were evaluated six times. All rats were necropsied when moribund, found dead, or at scheduled termination, with extensive histopathology of all rats. Numerous adverse toxic and oncogenic effects were observed in both sexes of all AN treatment groups. Decreased water consumption, feed consumption, and concomitant body weight suppression occurred within days of study initiation and persisted throughout the study in all treatment groups. An early onset of Zymbal gland tumors in high dose male and female rats, and in the mammary gland of all treated groups of females, was detected in-life. Hematology, clinical chemistry, and urinalysis, repeatedly evaluated, were without significant biological effects, except for an increased urine specific gravity due to the rats lower water intake. Organ weights at study termination were not significantly affected. Mortality was high in all female treated groups, with no surviving male or female 300 ppm rats during the last 2 months of the study. The most significant findings in this study were detected following gross and microscopic examination of an extensive list of tissues from all rats in the study. Nontumorous and tumorous lesions were found at an increased and/or decreased rate in a number of tissues of both sexes at all treatment levels. The primary nontumorous histopathologic effects of AN exposure occurred in the forestomach and the central nervous system of rats of both sexes and involved all treatment groups. A statistically significant increased incidence of tumors in one or more dose levels of either sex occurred in the central nervous system, Zymbal gland, forestomach, tongue, small instestine, and mammary gland. A no-observed-effect level (NOEL) was not identified in this study for toxicity or oncogenicity in either sex.
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Affiliation(s)
- John F Quast
- The Toxicology Research Laboratory, Health and Environmental Sciences, Dow Chemical Company, Midland, MI 48674, USA.
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Johannsen FR, Levinskas GJ. Comparative chronic toxicity and carcinogenicity of acrylonitrile by drinking water and oral intubation to Spartan Sprague-Dawley rats. Toxicol Lett 2002; 132:197-219. [PMID: 12044704 DOI: 10.1016/s0378-4274(02)00073-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Groups of 100 male and 100 female Spartan Sprague-Dawley rats were administered lifetime oral doses of Acrylonitrile (AN) by one of two routes of dosing, either at 0.1 or 10 mg/kg per day, 7 day per week by intubation or continually at 1 or 100 ppm AN in their drinking water. The doses selected were designed to approximate the same daily intake of AN in each of two separate studies, whether by a single bolus dose (intubation) or a more continuous dosing regimen in drinking water. Each study had its own untreated control group of 100 rats per sex. In the drinking water study, the equivalent mean dosage of AN administered to males and females were 0, 0.09, and 0.15 mg/kg per day, respectively, at the 1 ppm level, and 0, 8.0 and 10.7 mg/kg per day, respectively, for 100 ppm dose groups. In both studies, groups of ten rats per sex were sacrificed at 6, 12 and 18 months and at study term. Ophthalmoscopic, hematological, clinical biochemistry, urinalysis and full histopathological exams were performed on control and high dose groups of rats in each study. Similar tests were done in lower dose groups, as required, to define dose-responses of observed effects. All animals were necropsied and underwent microscopic examination of target tissues, including brain, ear canal, stomach, spinal cord and any observable tissue masses. High dose male and female rats in both studies exhibited statistically decreased body weights. Food consumption and water intake were reduced only in the drinking water study. Due to increased deaths in groups of high dose rats of both studies receiving AN, all intubation test groups were terminated after 20 months of treatment. Surviving males and females in the drinking water study were terminated after 22 and 19 months, respectively. Small, sometimes statistically significant, reductions in hemoglobin, hematocrit and erythrocyte count were observed in male and female rats in both high dose (10 mg/kg per day intubation and 100 ppm drinking water) groups from both studies. There were increases in absolute or relative organ weight ratios for liver and adrenal in the high dose intubation study groups, but could not be correlated with AN toxicity in the absence of adverse clinical biochemistry or microscopic findings. Similar organ weight findings were not observed in the drinking water study. Again, there were no changes in clinical biochemistry or microscopic findings in these tissues. Absolute kidney weights were increased in high dose male and female rats in the intubation study and high dose female rats only in the drinking water study. Male and female rats from high dose groups in each study had a higher incidence of palpable masses of the head and the nonglandular stomach and, in females only, the mammary region. In both sexes, treatment-related tumors of the central nervous system (brain, spinal cord), ear canal, and gastrointestinal tract, and in females only, the mammary gland (intubation only) were observed in rats administered either 10 mg/kg per day by intubation or 100 ppm in drinking water. Animals from the intubation study had a substantially higher incidence of AN-related site-specific tumors than did their drinking water study counterparts. While a similar spectrum of tumors was produced by both oral dosing regimens, there were some notable differences in organ-specific incidence of tumors. Astrocytomas of the brain and spinal cord were found at a higher incidence in those rats exposed continuously to AN administered in the drinking water versus bolus dosing by intubation. Conversely, a higher incidence of squamous cell carcinomas/papillomas of the forestomach and adenocarcinomas of the intestine and, in females only, carcinomas of the mammary gland were observed in high dose rats receiving AN by intubation. An increase in the degree of severity of forestomach hyperplasia was observed in all high dose groups of animals, irrespective of mode of administration. These effects were more pronounced, were correlated with a much higher incidence of forestomach tumors, and were identified earlier (12 months) in the intubation study in which there was direct tissue contact with a more concentrated AN solution. Elevations in epidermal cysts in high dose males and females in the intubation study and renal hyperplasia in high dose animals of both sexes in both studies may have a treatment relationship. All other clinical and microscopic findings were considered unremarkable. There were no discernable non-neoplastic effects attributable to treatment in groups of low dose male and female rats given AN by intubation at 0.1 mg/kg per day or 1 ppm in drinking water. The results of this study indicate a consistent spectrum of neoplastic and non-neoplastic effects produced by AN in the same rat strain, whether administered orally by bolus or by continuous dosing in the drinking water. While the spectrum of tumors and target organ toxicity produced was similar, bolus dosing clearly increased tumors associated with the gastrointestinal tract. Neoplasms found in several other tissues were most prominently displayed in groups of more continuously dosed rats.
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Affiliation(s)
- Frederick R Johannsen
- Environmental, Safety and Health, Solutia Inc., 575 Maryville Center Drive, St. Louis, MO 63141, USA.
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