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Luo YS, Hsieh NH, Soldatow VY, Chiu WA, Rusyn I. Comparative analysis of metabolism of trichloroethylene and tetrachloroethylene among mouse tissues and strains. Toxicology 2018; 409:33-43. [PMID: 30053492 PMCID: PMC6186498 DOI: 10.1016/j.tox.2018.07.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 07/22/2018] [Accepted: 07/23/2018] [Indexed: 11/21/2022]
Abstract
Trichloroethylene (TCE) and tetrachloroethylene (PCE) are structurally similar chemicals that are metabolized through oxidation and glutathione conjugation pathways. Both chemicals have been shown to elicit liver and kidney toxicity in rodents and humans; however, TCE has been studied much more extensively in terms of both metabolism and toxicity. Despite their qualitative similarities, quantitative comparison of tissue- and strain-specific metabolism of TCE and PCE has not been performed. To fill this gap, we conducted a comparative toxicokinetic study where equimolar single oral doses of TCE (800 mg/kg) or PCE (1000 mg/kg) were administered to male mice of C57BL/6J, B6C3F1/J, and NZW/LacJ strains. Samples of liver, kidney, serum, brain, and lung were obtained for up to 36 h after dosing. For each tissue, concentrations of parent compounds, as well as their oxidative and glutathione conjugation metabolites were measured and concentration-time profiles constructed. A multi-compartment toxicokinetic model was developed to quantitatively compare TCE and PCE metabolism. As expected, the flux through oxidation metabolism pathway predominated over that through conjugation across all mouse strains examined, it is 1,200-3,800 fold higher for TCE and 26-34 fold higher for PCE. However, the flux through glutathione conjugation, albeit a minor metabolic pathway, was 21-fold higher for PCE as compared to TCE. The degree of inter-strain variability was greatest for oxidative metabolites in TCE-treated and for glutathione conjugation metabolites in PCE-treated mice. This study provides critical data for quantitative comparisons of TCE and PCE metabolism, and may explain the differences in organ-specific toxicity between these structurally similar chemicals.
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Affiliation(s)
- Yu-Syuan Luo
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, USA
| | - Nan-Hung Hsieh
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, USA
| | - Valerie Y Soldatow
- Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, NC, USA
| | - Weihsueh A Chiu
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, USA
| | - Ivan Rusyn
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, USA.
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Lee JH, Kim I, Seok H, Park I, Hwang J, Park JO, Won JU, Roh J. Case report of renal cell carcinoma in automobile manufacturing factory worker due to trichloroethylene exposure in Korea. Ann Occup Environ Med 2015; 27:19. [PMID: 26240754 PMCID: PMC4522957 DOI: 10.1186/s40557-015-0068-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 06/29/2015] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND The aim of this paper was report first case of renal cell carcinoma developed in a worker who worked in an automobile manufacture line which handles trichloroethylene in Korea. CASE PRESENTATION To clarify the relationship between the onset of renal cell carcinoma in 52-years old male worker and the exposure to trichloroethylene, document studies and work environment measurement were done. Past work environment exposure data were reviewed and medical history and surgery records of the worker were also reviewed. The patient had no personal risk factor related to renal cell carcinoma except for his smoking habit of quarter a pack per day for twenty years, and since trichloroethylene was not part of measurement criteria, past work environment risk assessment data could not verify the exposure. The exposure level is deduced by analyzing material exposure level of work environments which has similar processes in data from revised research of chemical exposure standard and work environment validity assessment. Evaluation Committee of Epidemiologic Survey decided that there are relevant relationship between the exposure and the disease, though we do not have exact data during that period, most experts agree that in every factories they used trichloroethylene without any direction. CONCLUSIONS From the relevant medical history and the results of the usage of trichloroethylene in the relevant industries, and initial discovery of renal cell carcinoma at health inspection sonogram in 2001, it can be concluded that suggests significant causal relationship between the exposure to trichloroethylene and renal cell carcinoma onset, thus reporting it to be the first domestic case declared to be occupational disease.
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Affiliation(s)
- June-Hee Lee
- Graduate School of Public Health, Yonsei University, 50 Seongsanno (134 Sinchon-dong), Seodaemun-gu, Seoul, South Korea ; The Institute for Occupational Health, Yonsei University College of Medicine, Seoul, South Korea
| | - Inah Kim
- Department of Occupational and Environmental Medicine, Hanyang University College of Medicine, Seoul, South Korea
| | - Hongdeok Seok
- Graduate School of Public Health, Yonsei University, 50 Seongsanno (134 Sinchon-dong), Seodaemun-gu, Seoul, South Korea ; The Institute for Occupational Health, Yonsei University College of Medicine, Seoul, South Korea
| | - Inhyo Park
- Graduate School of Public Health, Yonsei University, 50 Seongsanno (134 Sinchon-dong), Seodaemun-gu, Seoul, South Korea
| | - Jungho Hwang
- The Institute for Occupational Health, Yonsei University College of Medicine, Seoul, South Korea
| | - Jae-Oh Park
- Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency, Ulsan, South Korea
| | - Jong-Uk Won
- Graduate School of Public Health, Yonsei University, 50 Seongsanno (134 Sinchon-dong), Seodaemun-gu, Seoul, South Korea ; The Institute for Occupational Health, Yonsei University College of Medicine, Seoul, South Korea ; Department of Preventive Medicine and Public Health, Yonsei University College of Medicine, Seoul, South Korea
| | - Jaehoon Roh
- Graduate School of Public Health, Yonsei University, 50 Seongsanno (134 Sinchon-dong), Seodaemun-gu, Seoul, South Korea ; The Institute for Occupational Health, Yonsei University College of Medicine, Seoul, South Korea ; Department of Preventive Medicine and Public Health, Yonsei University College of Medicine, Seoul, South Korea
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3
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Lash LH, Chiu WA, Guyton KZ, Rusyn I. Trichloroethylene biotransformation and its role in mutagenicity, carcinogenicity and target organ toxicity. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2014; 762:22-36. [PMID: 25484616 PMCID: PMC4254735 DOI: 10.1016/j.mrrev.2014.04.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Metabolism is critical for the mutagenicity, carcinogenicity, and other adverse health effects of trichloroethylene (TCE). Despite the relatively small size and simple chemical structure of TCE, its metabolism is quite complex, yielding multiple intermediates and end-products. Experimental animal and human data indicate that TCE metabolism occurs through two major pathways: cytochrome P450 (CYP)-dependent oxidation and glutathione (GSH) conjugation catalyzed by GSH S-transferases (GSTs). Herein we review recent data characterizing TCE processing and flux through these pathways. We describe the catalytic enzymes, their regulation and tissue localization, as well as the evidence for transport and inter-organ processing of metabolites. We address the chemical reactivity of TCE metabolites, highlighting data on mutagenicity of these end-products. Identification in urine of key metabolites, particularly trichloroacetate (TCA), dichloroacetate (DCA), trichloroethanol and its glucuronide (TCOH and TCOG), and N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (NAcDCVC), in exposed humans and other species (mostly rats and mice) demonstrates function of the two metabolic pathways in vivo. The CYP pathway primarily yields chemically stable end-products. However, the GST pathway conjugate S-(1,2-dichlorovinyl)glutathione (DCVG) is further processed to multiple highly reactive species that are known to be mutagenic, especially in kidney where in situ metabolism occurs. TCE metabolism is highly variable across sexes, species, tissues and individuals. Genetic polymorphisms in several of the key enzymes metabolizing TCE and its intermediates contribute to variability in metabolic profiles and rates. In all, the evidence characterizing the complex metabolism of TCE can inform predictions of adverse responses including mutagenesis, carcinogenesis, and acute and chronic organ-specific toxicity.
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Affiliation(s)
- Lawrence H. Lash
- Department of Pharmacology, Wayne State University School of Medicine, 540 East Canfield Avenue, Detroit, MI, 48201 USA
| | - Weihsueh A. Chiu
- U.S. Environmental Protection Agency, 1200 Pennsylvania Avenue, NW, Washington, DC, 20460 USA; Chiu.Weihsueh@.epa.gov;
| | - Kathryn Z. Guyton
- U.S. Environmental Protection Agency, 1200 Pennsylvania Avenue, NW, Washington, DC, 20460 USA; Chiu.Weihsueh@.epa.gov;
| | - Ivan Rusyn
- Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, NC 27599 USA;
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Kim I, Ha J, Lee JH, Yoo KM, Rho J. The Relationship between the Occupational Exposure of Trichloroethylene and Kidney Cancer. Ann Occup Environ Med 2014; 26:12. [PMID: 24955246 PMCID: PMC4065577 DOI: 10.1186/2052-4374-26-12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 05/21/2014] [Indexed: 11/23/2022] Open
Abstract
Trichloroethylene (TCE) has been widely used as a degreasing agent in many manufacturing industries. Recently, the International Agency for Research on Cancer presented “sufficient evidence” for the causal relationship between TCE and kidney cancer. The aim of this study was to review the epidemiologic evidences regarding the relationship between TCE exposure and kidney cancer in Korean work environments. The results from the cohort studies were inconsistent, but according to the meta-analysis and case–control studies, an increased risk for kidney cancer was present in the exposure group and the dose–response relationship could be identified using various measures of exposure. In Korea, TCE is a commonly used chemical for cleaning or degreasing processes by various manufacturers; average exposure levels of TCE vary widely. When occupational physicians evaluate work-relatedness kidney cancers, they must consider past exposure levels, which could be very high (>100 ppm in some cases) and associated with jobs, such as plating, cleaning, or degreasing. The exposure levels at a manual job could be higher than an automated job. The peak level of TCE could also be considered an important exposure-related variable due to the possibility of carcinogenesis associated with high TCE doses. This review could be a comprehensive reference for assessing work-related TCE exposure and kidney cancer in Korea.
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Affiliation(s)
- Inah Kim
- Department of occupational health, Yonsei University Graduate School of Public Health, Seoul, Korea ; Institutes for Occupational Health, Yonsei University College of Medicine, Seoul, Korea
| | - Jaehyeok Ha
- Department of occupational health, Seoul National University Graduate School of Public Health, Seoul, Korea
| | - June-Hee Lee
- Department of occupational health, Yonsei University Graduate School of Public Health, Seoul, Korea ; Institutes for Occupational Health, Yonsei University College of Medicine, Seoul, Korea
| | - Kye-Mook Yoo
- Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency, Ulsan, Korea
| | - Jaehoon Rho
- Department of occupational health, Yonsei University Graduate School of Public Health, Seoul, Korea ; Institutes for Occupational Health, Yonsei University College of Medicine, Seoul, Korea ; Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Korea
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5
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Cheikh Rouhou M, Haddad S. Modulation of trichloroethylene in vitro metabolism by different drugs in human. Toxicol In Vitro 2014; 28:732-41. [PMID: 24632077 DOI: 10.1016/j.tiv.2014.03.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Revised: 03/03/2014] [Accepted: 03/05/2014] [Indexed: 11/16/2022]
Abstract
Toxicological interactions with drugs have the potential to modulate the toxicity of trichloroethylene (TCE). Our objective is to identify metabolic interactions between TCE and 14 widely used drugs in human suspended hepatocytes and characterize the strongest using microsomal assays. Changes in concentrations of TCE and its metabolites were measured by headspace GC-MS. Results with hepatocytes show that amoxicillin, cimetidine, ibuprofen, mefenamic acid and ranitidine caused no significant interactions. Naproxen and salicylic acid showed to increase both TCE metabolites levels, whereas acetaminophen, carbamazepine and erythromycin rather decreased them. Finally, diclofenac, gliclazide, sulphasalazine and valproic acid had an impact on the levels of only one metabolite. Among the 14 tested drugs, 5 presented the most potent interactions and were selected for confirmation with microsomes, namely naproxen, salicylic acid, acetaminophen, carbamazepine and valproic acid. Characterization in human microsomes confirmed interaction with naproxen by competitively inhibiting trichloroethanol (TCOH) glucuronidation (Ki=2.329 mM). Inhibition of TCOH formation was also confirmed for carbamazepine (partial non-competitive with Ki=70 μM). Interactions with human microsomes were not observed with salicylic acid and acetaminophen, similar to prior results in rat material. For valproic acid, interactions with microsomes were observed in rat but not in human. Inhibition patterns were shown to be similar in human and rat hepatocytes, but some differences in mechanisms were noted in microsomal material between species. Next research efforts will focus on determining the adequacy between in vitro observations and the in vivo situation.
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Affiliation(s)
- Mouna Cheikh Rouhou
- TOXEN, Département des sciences biologiques, Université du Québec à Montréal, C.P. 8888 Succ. Centre-ville, Montreal, Qc. H3C 3P8, Canada
| | - Sami Haddad
- Département de Santé environnementale et santé au travail, IRSPUM, Faculté de Médecine, Université de Montréal, C.P. 6128 Succ. Centre-ville, Montreal, Qc. H3C 3J7, Canada.
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Hassoun E, Cearfoss J. Do Antioxidant Enzymes and Glutathione Play Roles in the Induction of Hepatic Oxidative Stress in Mice upon Subchronic Exposure to Mixtures of Dichloroacetate and Trichloroacetate? TOXICOLOGICAL AND ENVIRONMENTAL CHEMISTRY 2014; 96:482-490. [PMID: 25530655 PMCID: PMC4267469 DOI: 10.1080/02772248.2014.947988] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Dichloroacetate (DCA) and trichloroacetate (TCA) are water chlorination byproducts, and their mixtures were previously found to induce additive to greater than additive effects on hepatic oxidative stress (OS) induction in mice after subchronic exposure. To investigate the roles of antioxidant enzymes and glutathione (GSH) in those effects, livers of B6C3F1 mice treated by gavage with 7.5, 15, or 30 mg DCA/kg/day, 12.5, 25, or 50 mg TCA/kg/day, and mixtures (Mix I, Mix II and Mix III) at DCA:TCA ratios corresponding to 7.5:12.5, 15:25 and 25:50 mg/kg/day, respectively, for 13 weeks. Livers were assayed for superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), as well as for GSH levels. In general, DCA suppressed SOD and GSH-Px activities and GSH levels but caused no changes in CAT activity; TCA increased SOD and CAT activities, suppressed GSH-Px activity, but did not change GSH levels; mixtures of DCA and TCA increased SOD and CAT activities and suppressed GSH-Px activity and GSH levels. In conclusion, antioxidant enzymes contribute to DCA-, TCA- and mixtures-induced OS, but not to changes from additive to greater than additive effects produced by different mixture compositions of the compounds. GSH on the hand may contribute to these changes.
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Affiliation(s)
- Ezdihar Hassoun
- The University of Toledo, College of Pharmacy and Pharmaceutical
Sciences, HSC 3000 Arlington Ave., Toledo, OH 43614-2598, USA
| | - Jacquelyn Cearfoss
- The University of Toledo, College of Pharmacy and Pharmaceutical
Sciences, HSC 3000 Arlington Ave., Toledo, OH 43614-2598, USA
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7
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Hassoun E, Cearfoss J, Mamada S, Al-Hassan N, Brown M, Heimberger K, Liu MC. The effects of mixtures of dichloroacetate and trichloroacetate on induction of oxidative stress in livers of mice after subchronic exposure. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2014; 77:313-23. [PMID: 24593144 PMCID: PMC4100325 DOI: 10.1080/15287394.2013.864576] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Dichloroacetate (DCA) and trichloroacetate (TCA) are drinking-water chlorination by-products previously found to induce oxidative stress (OS) in hepatic tissues of B6C3F1 male mice. To assess the effects of mixtures of the compounds on OS, groups of male B6C3F1 mice were treated daily by gavage with DCA at doses of 7.5, 15, or 30 mg/kg/d, TCA at doses of 12.5, 25, or 50 mg/kg/d, and 3 mixtures of DCA and TCA (Mix I, Mix II, and Mix III), for 13 wk. The concentrations of the compounds in Mix I, Mix II, and Mix III corresponded to those producing approximately 15, 25, and 35%, respectively, of maximal induction of OS by individual compounds. Livers were assayed for production of superoxide anion (SA), lipid peroxidation (LP), and DNA single-strand breaks (SSB). DCA, TCA, and the mixtures produced dose-dependent increases in the three tested biomarkers. Mix I and II effects on the three biomarkers, and Mix III effect on SA production were found to be additive, while Mix III effects on LP and DNA-SSB were shown to be greater than additive. Induction of OS in livers of B6C3F1 mice after subchronic exposure to DCA and TCA was previously suggested as an important mechanism in chronic hepatotoxicity/hepatocarcinogenicity induced by these compounds. Hence, there may be rise in exposure risk to these compounds as these agents coexist in drinking water.
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Affiliation(s)
- Ezdihar Hassoun
- The University of Toledo, College of Pharmacy and Pharmaceutical Sciences, HSC 3000 Arlington Ave., Toledo, OH 43614-2598, USA
- Author to whom correspondence should be addressed, Telephone: 419-383-1917, Fax: 419-383-1909,
| | - Jacquelyn Cearfoss
- The University of Toledo, College of Pharmacy and Pharmaceutical Sciences, HSC 3000 Arlington Ave., Toledo, OH 43614-2598, USA
| | - Sukamto Mamada
- The University of Toledo, College of Pharmacy and Pharmaceutical Sciences, HSC 3000 Arlington Ave., Toledo, OH 43614-2598, USA
| | - Noor Al-Hassan
- College of Natural Sciences and Mathematics, MC, 2801 W. Bancroft Street, Toledo, OH 43606
| | - Michael Brown
- The University of Toledo, College of Pharmacy and Pharmaceutical Sciences, HSC 3000 Arlington Ave., Toledo, OH 43614-2598, USA
| | - Kevin Heimberger
- The University of Toledo, College of Pharmacy and Pharmaceutical Sciences, HSC 3000 Arlington Ave., Toledo, OH 43614-2598, USA
| | - Ming-Cheh Liu
- The University of Toledo, College of Pharmacy and Pharmaceutical Sciences, HSC 3000 Arlington Ave., Toledo, OH 43614-2598, USA
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Rusyn I, Chiu WA, Lash LH, Kromhout H, Hansen J, Guyton KZ. Trichloroethylene: Mechanistic, epidemiologic and other supporting evidence of carcinogenic hazard. Pharmacol Ther 2013; 141:55-68. [PMID: 23973663 DOI: 10.1016/j.pharmthera.2013.08.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 07/31/2013] [Indexed: 02/09/2023]
Abstract
The chlorinated solvent trichloroethylene (TCE) is a ubiquitous environmental pollutant. The carcinogenic hazard of TCE was the subject of a 2012 evaluation by a Working Group of the International Agency for Research on Cancer (IARC). Information on exposures, relevant data from epidemiologic studies, bioassays in experimental animals, and toxicity and mechanism of action studies was used to conclude that TCE is carcinogenic to humans (Group 1). This article summarizes the key evidence forming the scientific bases for the IARC classification. Exposure to TCE from environmental sources (including hazardous waste sites and contaminated water) is common throughout the world. While workplace use of TCE has been declining, occupational exposures remain of concern, especially in developing countries. The strongest human evidence is from studies of occupational TCE exposure and kidney cancer. Positive, although less consistent, associations were reported for liver cancer and non-Hodgkin lymphoma. TCE is carcinogenic at multiple sites in multiple species and strains of experimental animals. The mechanistic evidence includes extensive data on the toxicokinetics and genotoxicity of TCE and its metabolites. Together, available evidence provided a cohesive database supporting the human cancer hazard of TCE, particularly in the kidney. For other target sites of carcinogenicity, mechanistic and other data were found to be more limited. Important sources of susceptibility to TCE toxicity and carcinogenicity were also reviewed by the Working Group. In all, consideration of the multiple evidence streams presented herein informed the IARC conclusions regarding the carcinogenicity of TCE.
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Affiliation(s)
- Ivan Rusyn
- University of North Carolina, Chapel Hill, NC, USA.
| | | | | | | | - Johnni Hansen
- Danish Cancer Society Research Center, Copenhagen, Denmark
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Hassoun EA, Cearfoss J, Musser B, Krispinsky S, Al-Hassan N, Liu MC. The induction of phagocytic activation by mixtures of the water chlorination by-products, dichloroacetate- and trichloroacetate, in mice after subchronic exposure. J Biochem Mol Toxicol 2013; 27:237-42. [PMID: 23436740 DOI: 10.1002/jbt.21476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 01/15/2013] [Accepted: 01/22/2013] [Indexed: 11/05/2022]
Abstract
In this study, groups of B6C3F1 male mice were treated with dichloroacetate (DCA), trichloroacetate (TCA), and mixtures of the compounds (Mix I, II, and III) daily by gavage, for 13 weeks. The tested doses were 7.5, 15, and 30 mg DCA/kg/day and 12.5, 25, and 50 mg TCA/kg/day. The DCA: TCA ratios in Mix I, II, and III were 7.5:12.5, 15:25, and 30:50 mg/kg/day, respectively. Peritoneal lavage cells were collected at the end of the treatment period and assayed for the biomarkers of phagocytic activation, including superoxide anion and tumor necrosis factor-alpha production, and myeloperoxidase activity. The mixtures produced nonlinear effects on the biomarkers of phagocytic activation, with Mix I and II effects were found to be additive, but Mix III effects were found to be less than additive.
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Affiliation(s)
- Ezdihar A Hassoun
- College of Pharmacy and Pharmaceutical Sciences, The University of Toledo, Toledo, OH 43614-2598, USA.
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Cheikh Rouhou M, Rheault I, Haddad S. Modulation of trichloroethylene in vitro metabolism by different drugs in rats. Toxicol In Vitro 2013; 27:34-43. [DOI: 10.1016/j.tiv.2012.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Revised: 09/10/2012] [Accepted: 10/08/2012] [Indexed: 11/26/2022]
Affiliation(s)
- Mouna Cheikh Rouhou
- TOXEN, Département des Sciences Biologiques, Université du Québec à Montréal, CP 8888 Succ Centre-ville, Montreal, Canada H3C 3P8
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Hassoun EA, Al-Dieri A. Vitamin E restriction in the diet enhances phagocytic activation by dichloroacetate and trichloroacetate in mice. Food Chem Toxicol 2011; 50:701-6. [PMID: 22178223 DOI: 10.1016/j.fct.2011.11.055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 11/07/2011] [Accepted: 11/29/2011] [Indexed: 11/26/2022]
Abstract
The effects of a vitamin E-restricted diet on the induction of phagocytic activation by dichloroacetate (DCA) and trichloroacetate (TCA) was investigated. Groups of B6C3F1 male mice were either kept on standard diet (Std diet group) or diet that had the vitamin provided only by its natural ingredients (Low-E diet group). The animals in each diet group were administered 77 mg of DCA or TCA/ kg/day, or 5 ml/kg water (controls), by gavage, for 13 weeks. Thereafter, peritoneal lavage cells (PLC) were assayed for superoxide anion (SA), tumor necrosis factor (TNF)-α, and myeloperoxidase (MPO), as well as for the activities of the anti-oxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). SA and TNFα production, as well as MPO, SOD, CAT and GSH-Px activities were significantly increased in the cells from the Low-E diet group treated with the compounds as compared with cells from hosts in the Std-diet group that received the corresponding treatments. The results indicate that consumption of a Vitamin E-restricted diet enhances the induction of phagocytic activation by DCA and TCA, a mechanism that was previously suggested to be an initial adaptive/protective response against the compounds long-term effects.
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Affiliation(s)
- Ezdihar A Hassoun
- The University of Toledo, College of Pharmacy and Pharmaceutical Sciences, HSC, 3000 Arlington Avenue, Toledo, OH 43614-2598, USA.
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12
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Hassoun EA, Cearfoss J. Dichloroacetate- and Trichloroacetate-Induced Modulation of Superoxide Dismutase, Catalase, and Glutathione Peroxidase Activities and Glutathione Level in the livers of Mice after Subacute and Subchronic exposure. TOXICOLOGICAL AND ENVIRONMENTAL CHEMISTRY 2011; 93:332-344. [PMID: 21170174 PMCID: PMC3002262 DOI: 10.1080/02772248.2010.509602] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Dichloroacetate (DCA) and trichloroacetate (TCA) were previously found to induce various levels of oxidative stress in the hepatic tissues of mice after subacute and subchronic exposure. The cells are known to have several protective mechansims against production of oxidative stress by different xenobiotics. To assess the roles of the antioxidant enzymes and glutathione (GSH) in DCA- and TCA-induced oxidative stress, groups of B6C3F1 mice were administered either DCA or TCA at doses of 7.7, 77, 154 and 410 mg/kg/day, by gavage for 4 weeks (4-W) and 13 weeks (13-W), and superoxide dismutase (SOD) catalase (CAT) and glutathione peroxidase (GSH-Px) activities, as well as GSH were determined in the hepatic tissues. DCA at doses ranging between 7.7-410, and 7.7-77 mg/kg/day, given for 4-W and 13-W, respectively, resulted in either suppression or no change in SOD, CAT and GSH-Px activities, but doses of 154-410 mg DCA/kg/day administered for 13-W were found to result in significant induction of the three enzyme activities. TCA administration on the other hand, resulted in increases in SOD and CAT activities, and suppression of GSH-Px activity in both periods. Except for the DCA doses of 77-154 mg/kg/day administered for 13-W that resulted in significant reduction in GSH levels, all other DCA, as well as TCA treatments produced no changes in GSH. Since these enzymes are involved in the detoxification of the reactive oxygen species (ROS), superoxide anion (SA) and H(2)O(2), it is concluded that SA is the main contributor to DCA-induced oxidative stress while both ROS contribute to that of TCA. The increases in the enzyme activities associated with 154-410 mg DCA/kg/day in the 13-W period suggest their role as protective mechanisms contributing to the survival of cells modified in response to those treatments.
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Hassoun EA, Cearfoss J, Spildener J. Dichloroacetate- and trichloroacetate-induced oxidative stress in the hepatic tissues of mice after long-term exposure. J Appl Toxicol 2010; 30:450-6. [PMID: 20222146 DOI: 10.1002/jat.1516] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Dichoroacetate (DCA) and trichloroacetate (TCA) were found to be hepatotoxic and hepatocarcinogenic in rodents. To investigate the role of oxidative stress in the long-term hepatotoxicity of the compounds, groups of mice were administered 7.7, 77, 154 and 410 mg kg(-1) per day, of either DCA or TCA, by gavage, for 4 weeks (4-W) and 13 weeks (13-W), and superoxide anion (SA), lipid peroxidation (LP) and DNA-single strand breaks (SSBs) were determined in the hepatic tissues. Significant increases in all of the biomarkers were observed in response to the tested doses of both compounds in the two test periods, with significantly greater increases observed in the 13-W, as compared with the 4-W, period. Hepatomegaly was only observed with a DCA dose of 410 mg kg(-1) per day in the 13-W treatment period, and that was associated with significant declines in the biomarkers, when compared with the immediately lower dose. With the exception of LP production in the 13-W treatment period that was similarly induced by the two compounds, the DCA-induced increases in all of the biomarkers were significantly greater than those of TCA. Since those biomarkers were significantly induced by the compounds' doses that were shown to be carcinogenic but at earlier periods than those demonstrating hepatotoxicity/haptocarcinogencity, they can be considered as initial events that may lead to later production of those long-term effects. The results also suggest LP to be a more significant contributing mechanism than SA and DNA damage to the long-term hepatotoxicity of TCA.
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Hassoun EA, Spildener J, Cearfoss J. The induction of tumor necrosis factor-alpha, superoxide anion, myeloperoxidase, and superoxide dismutase in the peritoneal lavage cells of mice after prolonged exposure to dichloroacetate and trichloroacetate. J Biochem Mol Toxicol 2010; 24:136-44. [PMID: 20391627 DOI: 10.1002/jbt.20322] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The induction of phagocytic activation in response to prolonged treatment with different doses of dichloroacetate (DCA) and trichloroacetate (TCA) has been investigated in mice. Groups of B6C3F1 male mice were administered 7.7, 77, 154, and 410 mg of DCA or TCA/kg/day, postorally, for 4- and 13-weeks. Peritoneal lavage cells (PLCs) were isolated and assayed for the different biomarkers of phagocytic activation, including superoxide anion (SA), tumor necrosis factor-alpha (TNF-alpha), and myeloperoxidase (MPO). In addition, the role of superoxide dismutase (SOD) in the SA production was also assessed. DCA and TCA produced significant and dose-dependent increases in SA and TNF-alpha production and in MPO activity, but the increases in response to the high doses of the compounds (>77 mg/kg/day) in the 13-week treatment period were less significant than those produced in the 4-week treatment period. Also, dose-dependent increases in SOD activity were observed in both periods of treatments. In general, the results demonstrate significant induction of the biomarkers of phagocytic activation by doses of DCA and TCA that were previously shown to be noncarcinogenic, with significantly greater increases observed at the earlier period of exposure, as compared with later period. These findings may argue against the contribution of those mechanisms to the hepatotoxicity/hepatocarcinogenicity of the compounds and suggest them to be early adaptive/ protective mechanisms against their long-term effects.
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Affiliation(s)
- Ezdihar A Hassoun
- College of Pharmacy, The University of Toledo, 2801 W. Bancroft Street, Toledo, OH 43606, USA.
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15
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Hassoun EA, Mehta J. Dichloroacetate-induced modulation of cellular antioxidant enzyme activities and glutathione level in the J774A.1 cells. J Appl Toxicol 2009; 28:931-7. [PMID: 18493934 DOI: 10.1002/jat.1356] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Dichloroacetate (DCA) is used for different medical and industrial purposes and has been found to be a toxic by-product produced during the process of water chlorination. The DCA effects on superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) activities and glutathione (GSH) level were assessed and correlated with each other and also with cellular viabilities in J774A.1 macrophage cells. A concentration of 24 mm of DCA resulted in time-dependent decreases in cellular viability and glutathione level, and time-dependent increases in SOD activity when incubated with the cells for 24-48 h. DCA also resulted in significant increases in CAT and GSH-Px activities of the viable cells when incubated with the cells for 36 and 48 h. The changes in antioxidant enzyme activities and GSH levels were found to be strongly correlated with each other, and with cellular viabilities at different time points. While GSH did not result in any significant effects when added to the cells at concentrations ranging between 15 and 60 nmol ml(-1), it resulted in concentration-dependent increases in cellular viability when added to the DCA-treated cells, with maximal effects achieved at 45-60 nmol GSH ml(-1). However, cellular viability of the GSH + DCA treated cells remained below that of the control. Since viable cells from the DCA-treated cultures displayed significantly higher antioxidant enzyme activities compared with the control, it is concluded that those increases may have contributed to the cellular protection against DCA-induced cell death. Also, glutathione depletion has a major contribution to the observed cellular death induced by DCA.
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Affiliation(s)
- Ezdihar A Hassoun
- The University of Toledo, College of Pharmacy, Toledo, OH 43606, USA.
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16
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Biotransformation of 2,3,3,3-tetrafluoropropene (HFO-1234yf). Toxicol Appl Pharmacol 2008; 233:323-32. [DOI: 10.1016/j.taap.2008.08.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Revised: 08/25/2008] [Accepted: 08/28/2008] [Indexed: 11/23/2022]
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17
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Clewell HJ, Andersen ME. Applying Mode-of-Action and Pharmacokinetic Considerations in Contemporary Cancer Risk Assessments: An Example with Trichloroethylene. Crit Rev Toxicol 2008; 34:385-445. [PMID: 15560567 DOI: 10.1080/10408440490500795] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The guidelines for carcinogen risk assessment recently proposed by the U.S. Environmental Protection Agency (U.S. EPA) provide an increased opportunity for the consideration of pharmacokinetic and mechanistic data in the risk assessment process. However, the greater flexibility of the new guidelines can also make their actual implementation for a particular chemical highly problematic. To illuminate the process of performing a cancer risk assessment under the new guidelines, the rationale for a state-of-the-science risk assessment for trichloroethylene (TCE) is presented. For TCE, there is evidence of increased cell proliferation due to receptor interaction or cytotoxicity in every instance in which tumors are observed, and most tumors represent an increase in the incidence of a commonly observed, species-specific lesion. A physiologically based pharmacokinetic (PBPK) model was applied to estimate target tissue doses for the three principal animal tumors associated with TCE exposure: liver, lung, and kidney. The lowest points of departure (lower bound estimates of the exposure associated with 10% tumor incidence) for lifetime human exposure to TCE were obtained for mouse liver tumors, assuming a mode of action primarily involving the mitogenicity of the metabolite trichloroacetic acid (TCA). The associated linear unit risk estimates for mouse liver tumors are 1.5 x 10(-6) for lifetime exposure to 1 microg TCE per cubic meter in air and 0.4 x 10(-6) for lifetime exposure to 1 microg TCE per liter in drinking water. However, these risk estimates ignore the evidence that the human is likely to be much less responsive than the mouse to the carcinogenic effects of TCA in the liver and that the carcinogenic effects of TCE are unlikely to occur at low environmental exposures. Based on consideration of the most plausible carcinogenic modes of action of TCE, a margin-of-exposure (MOE) approach would appear to be more appropriate. Applying an MOE of 1000, environmental exposures below 66 microg TCE per cubic meter in air and 265 microg TCE per liter in drinking water are considered unlikely to present a carcinogenic hazard to human health.
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18
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König R, Cai P, Guo X, Ansari GAS. Transcriptomic analysis reveals early signs of liver toxicity in female MRL +/+ mice exposed to the acylating chemicals dichloroacetyl chloride and dichloroacetic anhydride. Chem Res Toxicol 2008; 21:572-82. [PMID: 18293905 DOI: 10.1021/tx7002728] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Dichloroacetyl chloride (DCAC) is a reactive metabolite of trichloroethene (TCE). TCE and its metabolites have been implicated in the induction of organ-specific and systemic autoimmunity, in the acceleration of autoimmune responses, and in the development of liver toxicity and hepatocellular carcinoma. In humans, effects of environmental toxicants are often multifactorial and detected only after long-term exposure. Therefore, we developed a mouse model to determine mechanisms by which DCAC and related acylating agents affect the liver. Autoimmune-prone female MRL +/+ mice were injected intraperitoneally with 0.2 mmol/kg of DCAC or dichloroacetic anhydride (DCAA) in corn oil twice weekly for six weeks. No overt liver pathology was detectable. Using microarray gene expression analysis, we detected changes in the liver transcriptome consistent with inflammatory processes. Both acylating toxicants up-regulated the expression of acute phase response and inflammatory genes. Furthermore, metallothionein genes were strongly up-regulated, indicating effects of the toxicants on zinc ion homeostasis and stress responses. In addition, DCAC and DCAA induced the up-regulation of several genes indicative of tumorigenesis. Our data provide novel insight into early mechanisms for the induction of liver disease by acylating agents. The data also demonstrate the power of microarray analysis in detecting early changes in liver function following exposure to environmental toxicants.
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Affiliation(s)
- Rolf König
- Department of Microbiology & Immunology, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
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19
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Hassoun EA, Dey S. Dichloroacetate- and trichloroacetate-induced phagocytic activation and production of oxidative stress in the hepatic tissues of mice after acute exposure. J Biochem Mol Toxicol 2008; 22:27-34. [DOI: 10.1002/jbt.20210] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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20
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Green T. Trichloroethylene Induced Cancer in Animals and Its Relevance to Humans. J Occup Health 2006. [DOI: 10.1539/joh.39.261] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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21
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Abstract
Glutathione conjugation has been identified as an important detoxication reaction. However, several glutathione-dependent bioactivation reactions have been identified. Current knowledge on the mechanisms and the possible biological importance of these reactions is discussed in this article. Vicinal dihaloalkanes are transformed by glutathione S-transferase-catalyzed reactions to mutagenic and nephrotoxic S-(2-haloethyl) glutathione S-conjugates. Electrophilic episulphonium ions are the ultimate reactive intermediates formed and interact with nucleic acids. Several polychlorinated alkenes are bioactivated in a complex, glutathione-dependent pathway. The first step is hepatic glutathione S-conjugate formation followed by cleavage to the corresponding cysteine S-conjugates, and, after translocation to the kidney, metabolism by renal cystein conjugate beta-lyase. Beta-Lyase-dependent metabolism of halovinyl cysteine S-conjugates yields electrophilic thioketenes, whose covalent binding to cellular macromolecules is likely to be responsible for the observed nephrotoxicity of the parent compounds. Finally, hepatic glutathione conjugate formation with hydroquinones and aminophenols yields conjugates that are directed to gamma-glutamyltransferase-rich tissues, such as the kidney, where they cause alkylation or redox cycling reactions, or both, that cause organ-selective damage.
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Affiliation(s)
- W Dekant
- Department of Toxicology, University of Würzburg, Versbacher Street 9, 97078 Würzburg, Germany.
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Abstract
The organic solvent trichloroethylene has been used in dry cleaning, as an industrial degreasing agent and as a solvent for oils and resins; large numbers of workers have been exposed to trichloroethylene, mainly by inhalation. Trichloroethylene has been categorised as a Group 2A carcinogen (probably carcinogenic to humans) by the International Agency for Research on Cancer (World Health Organization) and a Category 2 carcinogen (to be regarded as carcinogenic to humans) by the Australian National Industrial Chemicals Notification and Assessment Scheme. The Administrative Appeals Tribunal was asked to determine the validity of classifying trichloroethylene as a Category 2 rather than a Category 3 (data inadequate for making a satisfactory assessment) carcinogen. In the AAT's determination, relevant epidemiological evidence was not taken into account because such evidence concerned tumour sites apart from the kidney (the site of tumour induction by trichloroethylene in rats). This mode of evaluation is fundamentally different from that used by the International Agency for Research on Cancer. The precedent set by the consideration of carcinogenicity data in this case could have significant implications for classification of other putative carcinogens
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Affiliation(s)
- B W Stewart
- South Eastern Sydney Public Health Unit, Randwick, NSW.
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23
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Nakajima T, Kamijo Y, Usuda N, Liang Y, Fukushima Y, Kametani K, Gonzalez FJ, Aoyama T. Sex-dependent regulation of hepatic peroxisome proliferation in mice by trichloroethylene via peroxisome proliferator-activated receptor alpha (PPARalpha). Carcinogenesis 2000; 21:677-82. [PMID: 10753203 DOI: 10.1093/carcin/21.4.677] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The mechanism of trichloroethylene-induced liver peroxisome proliferation and the sex difference in response was investigated using wild-type Sv/129 and peroxisome proliferator-activated receptor alpha (PPARalpha)-null mice. Trichloroethylene treatment (0.75 g/kg for 2 weeks by gavage) resulted in liver peroxisome proliferation in wild-type mice, but not in PPARalpha-null mice, suggesting that trichloroethylene-induced peroxisome proliferation is primarily mediated by PPARalpha. No remarkable sex difference was observed in induction of peroxisome proliferation, as measured morphologically, but a markedly higher induction of several enzymes and PPARalpha protein and mRNA was found in males. On the other hand, trichloroethylene induced liver cytochrome P450 2E1, the principal enzyme responsible for metabolizing trichloroethylene to chloral hydrate, only in males, which resulted in similar expression levels in both sexes after the treatment. Trichloroethylene influenced neither the level of catalase, an enzyme involved in the reduction of oxidative stress, nor aldehyde dehydrogenase, the main enzyme catalyzing the conversion to trichloroacetic acid. These results suggest that trichloroethylene treatment causes a male-specific PPARalpha-dependent increase in cellular oxidative stress.
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Affiliation(s)
- T Nakajima
- Department of Hygiene, Shinshu University School of Medicine, Matsumoto, Nagano 390-8621, Japan.
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24
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Wempe MF, Anderson WB, Tzeng HF, Board PG, Anders MW. Glutathione transferase zeta-catalyzed biotransformation of deuterated dihaloacetic acids. Biochem Biophys Res Commun 1999; 261:779-83. [PMID: 10441501 DOI: 10.1006/bbrc.1999.1127] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glutathione transferase zeta (GSTZ) catalyzes the biotransformation of alpha-haloalkanoic acids. Treatment of rats or humans with dichloroacetic acid prolongs its elimination half-life, and preliminary studies in this laboratory show that fluorine-lacking, but not fluorine-containing dihaloacetic acids inactivate GSTZ. In the present study, the GSTZ-catalyzed biotransformation of unlabeled and deuterated dihaloacetic acids was investigated. With [(2)H]dichloroacetic acid and [(2)H]chlorofluoroacetic acid as substrates, the deuterium present in the [(2)H]dihaloacetic acid was retained in the [(2)H]glyoxylic acid formed. This finding indicates that the enol of the dihaloacetic acid does not serve as the substrate for the enzyme. The data afford an explanation of the failure of fluorine-containing dihaloacetic acids to inactivate GSTZ: dichloroacetic acid is converted to glyoxylic acid and inactivates GSTZ, whereas chlorofluoroacetic acid is biotransformed to glyoxylic acid, but produces negligible inactivation. Mechanisms are presented indicating that this difference may be attributed to the nucleofugicity of the leaving group.
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Affiliation(s)
- M F Wempe
- Department of Pharmacology and Physiology, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, New York, 14642, USA
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25
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Brondeau MT, Hesbert A, Beausoleil C, Schneider O. To what extent are biomonitoring data available in chemical risk assessment? Hum Exp Toxicol 1999; 18:322-6. [PMID: 10372754 DOI: 10.1191/096032799678840147] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
1. Chemical risk assessment integrates the identification of hazards and the human exposure levels which can be established from external and/or internal exposure data. 2. The availability of biomonitoring and metabolism animal data, the skin penetration ability, and the existence of atmospheric threshold limit values were examined for twelve substances of the European first list of priority existing substances. This investigation was focused on workplace exposures and on urinary biomarkers of exposure. Appropriate biomonitoring data appeared to be available for two substances: styrene and trichloroethylene. Some biomonitoring research has been conducted on acrylonitrile, buta-1,3-diene, cyclohexane, 1,4-dichlorobenzene, hydrogen fluoride, 2-(2-methoxyethoxy)ethanol, however additional studies could be usefully carried out. No biomonitoring data are available for alkanes, C10-13, chloro; benzene, C10-13-alkyl derivatives; bis(pentabromophenyl)ether; diphenylether, octabromo-derivative. 3. It was concluded that in some cases, biomonitoring data are either lacking or scarce. This is rather surprising since the selection of the substances of the priority list was based on high tonnage, widespread use, extent of human exposure, and toxicological concern. The development of biomonitoring information could be helpful in assessing individual or population chemical exposure whatever the source and route, and would result in both more realistic and more accurate risk assessments.
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Affiliation(s)
- M T Brondeau
- Institut National de Recherche et de Sécurité, Vandoeuvre, France
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26
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Yan Z, Henderson GN, James MO, Stacpoole PW. Determination of chloral hydrate metabolites in human plasma by gas chromatography-mass spectrometry. J Pharm Biomed Anal 1999; 19:309-18. [PMID: 10704096 DOI: 10.1016/s0731-7085(98)00123-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Chloral hydrate (CH) is a widely used sedative. Its pharmacological and toxicological effects are directly related to its metabolism. Prior investigations of CH metabolism have been limited by the lack of analytical techniques sufficiently sensitive to identify and quantify metabolites of CH in biological fluids. In this study a gas chromatography mass spectrometry (GC/MS) method was developed and validated for determining CH and its metabolites, monochloroacetate (MCA), dichloroacetate (DCA), trichloroacetate (TCA) and total trichloroethanol (free and glucuronidated form, TCE and TCE-Glu) in human plasma. Of these, DCA and MCA are newly identified metabolites in humans. The drug, its plasma metabolites and an internal standard, 4-chlorobutyric acid (CBA), were derivatized to their methyl esters by reacting with 12% boron trifluoride-methanol complex (12% BF3-MeOH). The reaction mixture was extracted with methylene chloride and analyzed by GC/MS, using a selected ion monitoring (SIM) mode. The quantitation limits of MCA, DCA, TCA, and TCE were between 0.12 and 7.83 microM. The coefficients of variation were between 0.58 and 14.58% and the bias values ranged between -10.03 and 14.37%. The coefficients of linear regression were between 0.9970 and 0.9996.
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Affiliation(s)
- Z Yan
- Department of Medicine, University of Florida, Gainesville 32610, USA
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27
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Kim H, Haltmeier P, Klotz JB, Weisel CP. Evaluation of biomarkers of environmental exposures: urinary haloacetic acids associated with ingestion of chlorinated drinking water. ENVIRONMENTAL RESEARCH 1999; 80:187-195. [PMID: 10092412 DOI: 10.1006/enrs.1998.3896] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A study was conducted to determine if DCAA and TCAA urinary excretion rates are valid biomarkers of chronic ingestion exposure to these disinfection by-products of chlorination of drinking water. Entire first morning urine voids, time-of-visit urine samples, and tap water samples were collected from 47 female subjects. In addition, a 48-h recall questionnaire was administered to determine the amounts and types of liquids ingested by each subject as well as other exposures that could lead to DCAA and TCAA urinary excretion. The TCAA excretion rate for the first morning urine samples was significantly correlated with the estimated 48-h TCAA ingestion exposure for 25 subjects whose ingestion exposures primarily occurred at home, while the DCAA excretion rate was not correlated with the DCAA ingestion exposure. Thus, urinary TCAA appears to be a valid biomarker of chronic ingestion exposure to TCAA from chlorinated water, while urinary DCAA is not. It is proposed that the difference in the biological half-lives between these two compounds is the rationale for this finding. The biological half-life of TCAA is longer than successive exposure intervals; thus TCAA accumulates until it reaches a steady state. The half-life of DCAA is shorter than successive exposure intervals; thus DCAA is almost completely metabolized following an exposure and is eliminated from the body. This study suggests that biological half-life, exposure interval, and sample collection interval should be considered in selecting biomarkers and designing studies to validate them.
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Affiliation(s)
- H Kim
- Graduate Program in Human Exposure Assessment, Rutgers, The State University of New Jersey and UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey, 08855, USA
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28
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Greenberg MS, Burton GA, Fisher JW. Physiologically based pharmacokinetic modeling of inhaled trichloroethylene and its oxidative metabolites in B6C3F1 mice. Toxicol Appl Pharmacol 1999; 154:264-78. [PMID: 9931286 DOI: 10.1006/taap.1998.8594] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A physiologically based pharmacokinetic (PBPK) model for inhaled trichloroethylene (TCE) was developed for B6C3F1 mice. Submodels described four P450-mediated metabolites of TCE, which included chloral hydrate (CH), free and glucuronide-bound trichloroethanol (TCOH-f and TCOH-b), trichloroacetic acid (TCA), and dichloroacetic acid (DCA). Inhalation time course studies were carried out for calibration of the model by exposing mice to TCE vapor concentrations of either 100 or 600 ppm for 4 h. At several time points, mice were euthanized and blood, liver, kidney, lung, and fat were collected and analyzed for TCE and its oxidative metabolites. Peak blood TCE concentrations were 0.86 and 7.32 microgram/mL, respectively, in mice exposed to 100 and 600 ppm TCE. The model overpredicted the mixed venous blood and tissue concentrations of TCE for mice of both exposure groups. Fractional absorption of inhaled TCE was proposed to explain the discrepancy between the model predictions and the TCE blood time course data. When fractional absorption (53%) of inhaled TCE was incorporated into the model, a comprehensive description of the uptake, distribution, and clearance of TCE in the blood was obtained. Fractional uptake of inhaled TCE was further verified by collecting TCE in exhaled breath following a 4-h constant concentration exposure to TCE and validation was provided by testing the model against TCE blood concentrations from an independent data set. The submodels adequately simulated the distribution and clearance kinetics of CH and TCOH-f in blood and the lungs, TCOH-b in the blood, and TCA and DCA, which were respectively detected for up to 43 and 14 h postexposure in blood and livers of mice exposed to 600 ppm TCE. This is the first extensive tissue time course study of the major metabolites of TCE following an inhalation exposure to TCE and the PBPK model predictions were in good general agreement with the observed kinetics of the oxidative metabolites formed in mice exposed to TCE concentrations of 100 and 600 ppm.
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Affiliation(s)
- M S Greenberg
- Operational Toxicology Branch (AFRL/HEST), Air Force Research Laboratory, Wright-Patterson AFB, Ohio, USA
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Zamudio Rivera LS, Carrillo L, Mancilla T. Syntheses and characterization of 2-hydroxy-N-(2?-hydroxyalkyl)acetamides. HETEROATOM CHEMISTRY 1999. [DOI: 10.1002/(sici)1098-1071(1999)10:2<153::aid-hc9>3.0.co;2-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Channel SR, Pravecek TL. Metabolism of trichloroethylene in B6C3F1 mouse and human liver slices. Drug Chem Toxicol 1998; 21:275-89. [PMID: 9706461 DOI: 10.3109/01480549809002205] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Human and B6C3F1 mouse liver tissue was exposed to trichloroethylene (TCE) to determine metabolic rate constants. Using a novel volatile exposure system based on precision-cut tissue explants, TCE biometabolism was measured by appearance of a major oxidative product trichloroacetic acid (TCA). TCE metabolic rate was linear in this system to 150 minutes, allowing calculation of Michaelis-Menten kinetic parameters, Km and Vmax. Both human and mouse liver explants tolerated exposure to TCE up to 750 microM without evidence of cytotoxicity. Km values for mouse and human tissue were 215 and 30.6 microM TCE, respectively, and Vmax estimates were 6.14 and 0.47 ng TCA produced per mg protein*min-1, mouse and human, respectively. These results are consistent with other reports in describing the greater capacity of mice to metabolize TCE. Metabolic differences such as these must be considered when interpreting the implications of TCE-induced toxicity in rodent models for human health assessment.
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Affiliation(s)
- S R Channel
- Operational Toxicology Branch, Air Force Research Laboratory, Wright-Patterson AFB, OH 45433-7400, USA.
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31
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Tong Z, Board PG, Anders MW. Glutathione transferase zeta catalyses the oxygenation of the carcinogen dichloroacetic acid to glyoxylic acid. Biochem J 1998; 331 ( Pt 2):371-4. [PMID: 9531472 PMCID: PMC1219363 DOI: 10.1042/bj3310371] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Dichloroacetic acid (DCA), a common drinking-water contaminant, is hepatocarcinogenic in rats and mice, and is a therapeutic agent used clinically in the management of lactic acidosis. DCA is biotransformed to glyoxylic acid by glutathione-dependent cytosolic enzymes in vitro and is metabolized to glyoxylic acid in vivo. The enzymes that catalyse the oxygenation of DCA to glyoxylic acid have not, however, been identified or characterized. In the present investigation, an enzyme that catalyses the glutathione-dependent oxygenation of DCA was purified to homogeneity (587-fold) from rat liver cytosol. SDS/PAGE and HPLC gel-filtration chromatography showed that the purified enzyme had a molecular mass of 27-28 kDa. Sequence analysis showed that the N-terminus of the purified protein was blocked. An internal sequence of 30 amino acid residues was obtained that matched the recently discovered human glutathione transferase Zeta well [Board, Baker, Chelvanayagam and Jermiin (1997) Biochem. J. 328, 929-935]. Western-blot analysis showed that the purified rat-liver enzyme cross-reacted with rabbit antiserum raised against recombinant human glutathione transferase Zeta. The apparent Km and Vmax values of the purified enzyme with DCA as the variable substrate were 71.4 microM and 1334 nmol/min per mg of protein, respectively; the Km for glutathione was 59 microM. Both the purified rat-liver enzyme and the recombinant human enzyme showed high activity with DCA as the substrate. These results demonstrate that the glutathione-dependent oxygenation of DCA to glyoxylic acid is catalysed by a Zeta-class glutathione transferase.
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Affiliation(s)
- Z Tong
- Department of Pharmacology and Physiology, University of Rochester Medical Center, 601 Elmwood Avenue, Box 711, Rochester, NY 14642, USA
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Yan Z, Henderson GN, James MO, Stacpoole PW. Determination of dichloroacetate and its metabolites in human plasma by gas chromatography-mass spectrometry. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1997; 703:75-84. [PMID: 9448064 DOI: 10.1016/s0378-4347(97)00404-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Sodium dichloroacetate (DCA) is an investigational drug for the treatment of lactic acidosis, and is also a putative environmental toxicant. We developed and validated a gas chromatography-mass spectrometry (GC-MS) technique that simultaneously measures lactate, DCA and its metabolites, monochloroacetate (MCA), glyoxylate, glycolate and oxalate in human plasma. Following administration of [13C1,2]DCA to healthy volunteers, blood samples were collected at various time points and the drug and its metabolites present in plasma were derivatized to their methyl esters by reacting with 12% boron trifluoride-methanol complex. The methyl esters were extracted with methylene chloride and analyzed by GC-MS. The quantitation limits of DCA and metabolites ranged between 0.3 and 1.5 microM. The coefficients of variation of the standards within the entire calibration range were between 0.3 and 14.5%. The bias values ranged between -16.3% and 18.7%. Total recoveries from derivatization and extraction were between 46.9% and 78.5%. The coefficients (r2) of linear regression of the calibration curves were 0.9882 to 0.9996.
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Affiliation(s)
- Z Yan
- Department of Medicine (Division of Endocrinology and Metabolism), College of Medicine, University of Florida, Gainesville 32610, USA
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Simon TW. Combining physiologically based pharmacokinetic modeling with Monte Carlo simulation to derive an acute inhalation guidance value for trichloroethylene. Regul Toxicol Pharmacol 1997; 26:257-70. [PMID: 9441916 DOI: 10.1006/rtph.1997.1168] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Using the Monte Carlo method and physiologically based pharmacokinetic modeling, an occupational inhalation exposure to trichloroethylene consisting of 7 h of exposure per day for 5 days was simulated in populations of men and women of 5000 individuals each. The endpoint of concern for occupational exposure was drowsiness. The toxicologic condition leading to drowsiness was assumed to be high levels of both trichloroethanol and trichloroethylene. Therefore, the output of the simulation or dose metric was the maximum value of the sum of the concentration of trichloroethylene in blood and the concentration of trichloroethanol within its volume of distribution occurring within 1 week of exposure. The distributions of the dose metric in the simulated populations were lognormal. To protect 99% of a worker population, a concentration of 30 ppm over a 7-h period of the work day should not be exceeded. Subjecting a susceptible individual (the 99th percentile of the dose metric) to 200 ppm (the ACGIH short-term exposure limit or STEL) for 15 min twice a day over a work week necessitates a 2.5-h rest in fresh air following the STEL exposure to allow the blood concentrations of trichloroethylene and trichloroethanol to drop to levels that would not cause drowsiness. Both the OSHA PEL and the ACGIH TLV are greater than the value of 30 ppm derived here. As well as suggesting a new occupational guidance value, this study provides an example of this method of guidance value derivation.
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Affiliation(s)
- T W Simon
- U.S. Environmental Protection Agency, Atlanta Federal Center, Georgia 30303-3104, USA
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Abbas R, Fisher JW. A physiologically based pharmacokinetic model for trichloroethylene and its metabolites, chloral hydrate, trichloroacetate, dichloroacetate, trichloroethanol, and trichloroethanol glucuronide in B6C3F1 mice. Toxicol Appl Pharmacol 1997; 147:15-30. [PMID: 9356303 DOI: 10.1006/taap.1997.8190] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A six-compartment physiologically based pharmacokinetic (PBPK) model for the B6C3F1 mouse was developed for trichloroethylene (TCE) and was linked with five metabolite submodels consisting of four compartments each. The PBPK model for TCE and the metabolite submodels described oral uptake and metabolism of TCE to chloral hydrate (CH). CH was further metabolized to trichloroethanol (TCOH) and trichloroacetic acid (TCA). TCA was excreted in urine and, to a lesser degree, metabolized to dichloroacetic acid (DCA). DCA was further metabolized. The majority of TCOH was glucuronidated (TCOG) and excreted in the urine and feces. TCOH was also excreted in urine or converted back to CH. Partition coefficient (PC) values for TCE were determined by vial equilibrium, and PC values for nonvolatile metabolites were determined by centrifugation. The largest PC values for TCE were the fat/blood (36.4) and the blood/air (15.9) values. Tissue/blood PC values for the water-soluble metabolites were low, with all PC values under 2.0. Mice were given bolus oral doses of 300, 600, 1200, and 2000 mg/kg TCE dissolved in corn oil. At various time points, mice were sacrificed, and blood, liver, lung, fat, and urine were collected and assayed for TCE and metabolites. The 1200 mg/kg dose group was used to calibrate the PBPK model for TCE and its metabolites. Urinary excretion rate constant values were 0. 06/hr/kg for CH, 1.14/hr/kg for TCOH, 32.8/hr/kg for TCOG, and 1. 55/hr/kg for TCA. A fecal excretion rate constant value for TCOG was 4.61/hr/kg. For oral bolus dosing of TCE with 300, 600, and 2000 mg/kg, model predictions of TCE and several metabolites were in general agreement with observations. This PBPK model for TCE and metabolites is the most comprehensive PBPK model constructed for P450-mediated metabolism of TCE in the B6C3F1 mouse.
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Affiliation(s)
- R Abbas
- Toxicology Division, Geo-Centers, Inc., Wright-Patterson Air Force Base, Ohio 45433-7400, USA
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Latendresse JR, Pereira MA. Dissimilar characteristics of N-methyl-N-nitrosourea-initiated foci and tumors promoted by dichloroacetic acid or trichloroacetic acid in the liver of female B6C3F1 mice. Toxicol Pathol 1997; 25:433-40. [PMID: 9323830 DOI: 10.1177/019262339702500501] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Dichloroacetic acid (DCA) and trichloroacetic acid (TCA) are metabolites of the industrial solvent and environmental contaminant trichloroethylene (TCE), as well as contaminants of chlorinated drinking water. Human exposure to these chemicals is of concern as all three have been shown to increase liver tumor incidence in mice. Differences in dose-response curves, progression to cancer, and postexposure regression of lesions suggest that TCA and DCA work through different mechanisms. The purpose of this study was to further characterize the proliferative hepatocellular lesions promoted by TCA and DCA using biomarkers of cell growth, differentiation, and metabolism in liver sections to better delineate the distinctions in the mechanism of the two chloroacetates. Fifteen-day-old female mice were initiated with 25 mg/kg N-methyl-N-nitrosourea. The initiated mice were administered DCA or TCA (20.0 mmol/L) in drinking water from age 49 days until euthanasia at age 413 days. The pathologic assessment showed that the foci of altered hepatocytes and tumors occurring in the animals promoted with DCA were eosinophilic and positive immunohistochemically for TGF-alpha, c-jun, c-myc, CYP 2E1, CYP 4A1, and glutathione S-transferase-pi (GST-pi). The DCA lesions also were essentially negative for c-fos and TGF-beta, but nontumor hepatocytes were consistently TGF-beta-positive. In contrast, tumors promoted by TCA were predominantly basophilic, lacked GST-pi, and stained variably; usually, more than 50% of the tumor hepatocytes were essentially negative for the other biomarkers. This study demonstrates some striking differences in certain molecular biomarkers of cell growth, differentiation, and metabolism between DCA and TCA. The results also suggest some potential growth signal transduction pathways that may contribute to the DCA promotion of tumors, further support the premise that these two chloroacetates promote hepatocarcinogenesis in different ways, and provide a rational basis for a similar comparison with TCE. Such a comparison should give some insight as to whether DCA, TCA, or both are playing a significant role in the murine liver carcinogenesis of the parent compound, TCE.
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Affiliation(s)
- J R Latendresse
- ManTech Environmental Technology, Toxicology Division, Armstrong Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA
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Henderson GN, Yan Z, James MO, Davydova N, Stacpoole PW. Kinetics and metabolism of chloral hydrate in children: identification of dichloroacetate as a metabolite. Biochem Biophys Res Commun 1997; 235:695-8. [PMID: 9207222 DOI: 10.1006/bbrc.1997.6868] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Chloral hydrate was introduced into therapeutics more than 100 years ago, and since then a number of kinetic and metabolic studies have been conducted on this drug. Trichloroethanol, its glucuronide and trichloroacetic acid have been identified as the metabolites of chloral hydrate. We now report the identification of dichloroacetate as a major product of chloral hydrate metabolism in children, in addition to trichloroethanol and trichloroacetic acid. Furthermore, pretreatment of children with chloral hydrate appears to retard the plasma clearance of dichloroacetate.
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Affiliation(s)
- G N Henderson
- Department of Medicine, University of Florida, Gainesville 32610, USA
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Pereira MA, Li K, Kramer PM. Promotion by mixtures of dichloroacetic acid and trichloroacetic acid of N-methyl-N-nitrosourea-initiated cancer in the liver of female B6C3F1 mice. Cancer Lett 1997; 115:15-23. [PMID: 9097974 DOI: 10.1016/s0304-3835(97)04699-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Hepatic tumor promoting activity was determined for mixtures of dichloroacetic acid (DCA) and trichloroacetic acid (TCA) in female B6C3F1 mice initiated on day 15 of age with 25 mg/kg N-methyl-N-nitrosourea. The mice received in their drinking water from 6 to 50 weeks of age either DCA (7.8, 15.6, or 25 mmol/l) with/without 6.0 mmol/l TCA or TCA (6.0 or 25 mmol/l) with/without 15.6 mmol/l DCA. Proliferative lesions (foci of altered hepatocytes and hepatocellular adenomas) promoted by TCA increased linearly with its concentration and were predominantly basophilic and negative for glutathione S-transferase-pi (GST-pi), while those promoted by DCA increased exponentially with its concentration and were eosinophilic and positive for GST-pi. The promoting activity of DCA and TCA in mixtures was at least additive. The proliferative lesions resulting from exposure to the mixtures were predominately similar to those promoted by DCA, i.e. contained eosinophilic and GST-pi-positive hepatocytes.
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Affiliation(s)
- M A Pereira
- Medical College of Ohio, Department of Pathology, Toledo 43614, USA
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Bogen KT, Gold LS. Trichloroethylene cancer risk: simplified calculation of PBPK-based MCLs for cytotoxic end points. Regul Toxicol Pharmacol 1997; 25:26-42. [PMID: 9056499 DOI: 10.1006/rtph.1996.1070] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Cancer risk assessments for trichloroethylene (TCE) based on linear extrapolation from bioassay results are questionable in light of new data on TCE's likely mechanism of action involving induced cytotoxicity, for which a threshold-type dose-response model may be more appropriate. Previous studies have shown that if a genotoxic mechanism for TCE is assumed, algebraic methods can considerably simplify the use of physiologically based pharmacokinetic (PBPK) models to estimate virtually safe environmental concentrations for humans based on rodent cancer-bioassay data. We show here how such methods can be extended to the case in which TCE is assumed to induce cancer via cytotoxicity, to estimate environmentally safe concentrations based on rodent toxicity data. These methods can be substituted for the numerical methods typically used to calculate PBPK-effective doses when these are defined as peak concentrations. We selected liver and kidney as plausible target tissues, based on an analysis of rodent TCE-bioassay data and on a review of related data bearing on mechanism. Tumor patterns in rodent bioassays are shown to be consistent with our estimates of PBPK-based, effective cytotoxic doses to mice and rats used in these studies. When used with a margin of exposure of 1000, our method yielded maximum concentration levels for TCE of 16 ppb (87 micrograms/m3) for TCE in air respired 24 hr/day, 700 ppb (3.8 mg/m3) for TCE in air respired for relatively brief daily periods (e.g., 0.5 hr while showering/bathing), and 210 micrograms/liter for TCE in drinking water assuming a daily 2-liter ingestion. Cytotoxic effective doses were also estimated for occupational respiratory exposures. These estimates indicate that the current OSHA permissible exposure limit for TCE would produce metabolite concentrations that exceed an acute no observed adverse effect level for hepatotoxicity in mice. On this basis, the OSHA TCE limit is not expected to be protective.
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Affiliation(s)
- K T Bogen
- Health and Ecological Assessment Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
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39
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Dekant W. Glutathione-dependent bioactivation and renal toxicity of xenobiotics. Recent Results Cancer Res 1997; 143:77-87. [PMID: 8912413 DOI: 10.1007/978-3-642-60393-8_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Affiliation(s)
- W Dekant
- Department of Toxicology, University of Würzburg, Germany
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40
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Physiologically based pharmacodynamic modeling of an interaction threshold between trichloroethylene and 1,1-dichloroethylene in fischer 344 rats. Toxicol Appl Pharmacol 1996. [DOI: 10.1016/s0041-008x(96)80017-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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41
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el-Masri HA, Tessari JD, Yang RS. Exploration of an interaction threshold for the joint toxicity of trichloroethylene and 1,1-dichloroethylene: utilization of a PBPK model. Arch Toxicol 1996; 70:527-39. [PMID: 8831903 DOI: 10.1007/s002040050310] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Physiologically based pharmacokinetic (PBPK) modeling and gas uptake experiments were utilized to verify the competitive inhibition mechanism of interaction between trichloroethylene (TCE) and 1,1-dichloroethylene (DCE) and to investigate the presence of an interaction threshold between the two chemicals. Initially, gas uptake experiments were conducted on Fischer 344 rats where the initial concentrations of both DCE and TCE were 2000:0, 0:2000, 2000:2000, 1000:0, 1000:1000, and 500:500 ppm, respectively. When the different modes of inhibition interactions (competitive, uncompetitive and noncompetitive) were employed in the PBPK model, the model description of the competitive inhibition provided the best description of the declining concentrations in the gas uptake chamber. Furthermore, to predict the range at which the interaction threshold would be found, the PBPK model included a mathematical description of the percentage of enzyme sites occupied by either chemical in the presence or the absence of the other. By comparing the percentage of occupied sites by one chemical, in the presence of the other, to those sites occupied in the absence of the latter, the PBPK model predicted a range of concentrations (100 ppm or less) of either chemical where the competitive inhibition interaction would not be observed. Consequently, gas uptake experiments were designed where the initial concentration was selected at 2000 ppm for one chemical while the other chemical was set at 100 in one experiment and 50 ppm in another. Under these conditions, the best stimulation to the concentration depletion curves in the gas uptake system of the chemical in the higher concentration was obtained when the PBPK model was run under the assumption of no-interaction. This substantiated the model predictions of the presence of observable interaction only at concentrations higher than 100 ppm.
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Affiliation(s)
- H A el-Masri
- Center for Environmental Toxicology and Technology, Colorado State University, Fort Collins 80523, USA
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Abstract
The kidney is a frequent target organ for toxic effects of xenobiotics. In recent years, the molecular mechanisms responsible for the selective renal toxicity of many nephrotoxic xenobiotics have been elucidated. Accumulation by renal transport mechanisms, and thus aspects of renal physiology, plays an important role in the renal toxicity of some antibiotics, metals, and agents binding to low molecular weight proteins such as alpha(2u)-globulin. The accumulation by active transport of metabolites formed in other organs is involved in the kidney-specific toxicity of certain polyhaloalkanes, polyhaloalkenes, hydroquinones, and aminophenols. Other xenobiotics are selectively metabolized to reactive electrophiles by enzymes expressed in the kidney. This review summarizes the present knowledge on the mechanistic basis of target organ selectivity of these compounds.
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Affiliation(s)
- W Dekant
- Institut für Toxikologie, Universität Würzburg, FRG
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43
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Pereira MA, Phelps JB. Promotion by dichloroacetic acid and trichloroacetic acid of N-methyl-N-nitrosourea-initiated cancer in the liver of female B6C3F1 mice. Cancer Lett 1996; 102:133-41. [PMID: 8603361 DOI: 10.1016/0304-3835(96)04156-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hepatic tumor promoting activity was determined for dichloroacetic acid (DCA) and trichloroacetic acid (TCA) in female B6C3F1 mice initiated on day 15 of age with 25m/kg N-methyl-N-nitrosourea (MNU). The mice were administered the chloroacetic acids in drinking water starting at 7 weeks of age and continuing until sacrificed 31 or 52 weeks later. Both chloroacetic acids promoted MNU-initiated foci and tumors, however their concentration-response relationships differed being exponential and linear for DCA or TCA, respectively. Lesions promoted by DCA but not by TCA, regressed upon termination of exposure at 31 weeks. Foci and tumors promoted by DCA were eosinophilic and contained glutathione S-transferase-pi(GST-pi), while TCA promoted basophilic tumors lacking GST-pi. Hence, tumor promotion by DCA and TCA appeared to differ both with respect to their concentration-response relationships and to the characteristics of precancerous lesions and tumors.
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Affiliation(s)
- M A Pereira
- Environmental Health Research and Testing, Inc., Lexington, KY 40503, USA
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44
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Dekant W. Biosynthesis and cellular effects of toxic glutathione S-conjugates. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1996; 387:297-312. [PMID: 8794224 DOI: 10.1007/978-1-4757-9480-9_38] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- W Dekant
- Institut für Toxikologie und Pharmakologie, Universität Würzburg, Germany
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45
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Saillenfait AM, Langonné I, Sabaté JP. Developmental toxicity of trichloroethylene, tetrachloroethylene and four of their metabolites in rat whole embryo culture. Arch Toxicol 1995; 70:71-82. [PMID: 8773178 DOI: 10.1007/bf02733666] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The embryotoxicity of trichloroethylene (TRI), tetrachloroethylene (PER), and of four of their oxidative metabolites i.e. trichloroacetic acid, dichloroacetic acid, chloral hydrate, and trichloroacetyl chloride, was studied in vitro, using the rat whole embryo culture system. Embryos from Sprague-Dawley rats were explanted on gestational day 10 (plug day = day 0) and cultured for 46 h in the presence of the test chemical. All of the tested chemicals produced concentration-dependent decreases in growth and differentiation and increases in the incidence of morphologically abnormal embryos. TRI and PER produced qualitatively similar patterns of abnormalities, while TRI and/or PER metabolites, each elicited clearly distinguishable dysmorphogenic profiles. The presence of hepatic microsomal fractions in the culture medium produced marked decreases in TRI- and PER-induced embryotoxic effects, including mortality, severity of malformations, and delayed growth and differentiation.
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Affiliation(s)
- A M Saillenfait
- Institut National de Recherche et de Sécurité, Vandoeuvre, France
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46
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Gist GL, Burg JR. Trichloroethylene--a review of the literature from a health effects perspective. Toxicol Ind Health 1995; 11:253-307. [PMID: 7482570 DOI: 10.1177/074823379501100301] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
This report reviews the literature on the impact of exposure to trichloroethylene (TCE) on human health. Special emphasis is given to the health effects reported in excess of national norms by participants in the TCE Subregistry of the Volatile Organic Compounds Registry of the National Exposure Registries--persons with documented exposure to TCE through drinking and use of contaminated water. The health effects reported in excess by some or all of the sex and age groups studied were speech and hearing impairments, effects of stroke, liver problems, anemia and other blood disorders, diabetes, kidney disease, urinary tract disorders, and skin rashes.
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Affiliation(s)
- G L Gist
- Exposure and Disease Registry Branch, Agency for Toxic Substances and Disease Registry, Atlanta, Georgia 30333, USA
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47
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Austin EW, Okita JR, Okita RT, Larson JL, Bull RJ. Modification of lipoperoxidative effects of dichloroacetate and trichloroacetate is associated with peroxisome proliferation. Toxicology 1995; 97:59-69. [PMID: 7716793 DOI: 10.1016/0300-483x(94)02926-l] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Pretreatment of male B6C3F1 mice with clofibric acid (CFA) or trichloroacetic acid (TCA) in the drinking water results in a marked decrease in the lipoperoxidative response as measured by the production of thiobarbituric acid reactive substances (TBARS) in mouse liver homogenates following acute dosing with TCA or dichloroacetic acid (DCA). Pretreatment with TCA or CFA also increased palmitoyl-CoA oxidase activity, microsomal 12-(omega) hydroxylation of lauric acid and expression of P450 4A isoforms. At the doses utilized, DCA-pretreatment did not increase the level of P450 4A protein, or markers of peroxisome proliferation. However, DCA-pretreatment did result in enhanced levels of TBARS, following acute dosing with DCA, compared to controls. Pretreatment with DCA, TCA, or CFA did not alter p-nitrophenol hydroxylation (an assay specific for P450 2E1), and no increases in immunodetectable P450 2E1, 4A, 1A1/2, 2B1/2 or 3A1 protein were observed. Assays from CFA- and TCA-pretreated mice suggest that the reduction in the TBARS response seen in TCA-pretreated animals results from activities associated with peroxisome proliferation. This might result from the induction of systems efficient in scavenging of peroxide intermediates or detoxification of aldehyde by-products of lipid peroxidation.
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Affiliation(s)
- E W Austin
- Pharmacology/Toxicology Graduate Program, College of Pharmacy, Washington State University, Pullman 99164-6510, USA
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48
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Dodds PF. Xenobiotic lipids: the inclusion of xenobiotic compounds in pathways of lipid biosynthesis. Prog Lipid Res 1995; 34:219-47. [PMID: 8685240 DOI: 10.1016/0163-7827(95)00007-m] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- P F Dodds
- Department of Biological Sciences, University of London, Ashford, Kent, U.K
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49
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Appendix I: Chlorinated aldehydes. Regul Toxicol Pharmacol 1994. [DOI: 10.1016/s0273-2300(05)80034-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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50
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