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Dunnick JK, Pandiri AR, Merrick BA, Kissling GE, Cunny H, Mutlu E, Waidyanatha S, Sills R, Hong HL, Ton TV, Maynor T, Recio L, Phillips SL, Devito MJ, Brix A. Carcinogenic activity of pentabrominated diphenyl ether mixture (DE-71) in rats and mice. Toxicol Rep 2018; 5:615-624. [PMID: 29868454 PMCID: PMC5984199 DOI: 10.1016/j.toxrep.2018.05.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 05/11/2018] [Accepted: 05/14/2018] [Indexed: 01/19/2023] Open
Abstract
Pentabrominated diphenyl ether (PBDE) mixture was a multispecies carcinogen causing liver tumors in male and female rats and mice. Hras or Ctnnb1 mutations characterized the PBDE-induced liver tumors. PBDE-induced liver tumors increased with increasing PBDE exposure.
Pentabrominated diphenyl ether (PBDE) flame retardants have been phased out in Europe and in the United States, but these lipid soluble chemicals persist in the environment and are found human and animal tissues. PBDEs have limited genotoxic activity. However, in a 2-year cancer study of a PBDE mixture (DE-71) (0, 3, 15, or 50 mg/kg (rats); 0, 3, 30, or 100 mg/kg (mice)) there were treatment-related liver tumors in male and female Wistar Han rats [Crl:WI(Han) after in utero/postnatal/adult exposure, and in male and female B6C3F1 mice, after adult exposure. In addition, there was evidence for a treatment-related carcinogenic effect in the thyroid and pituitary gland tumor in male rats, and in the uterus (stromal polyps/stromal sarcomas) in female rats. The treatment-related liver tumors in female rats were unrelated to the AhR genotype status, and occurred in animals with wild, mutant, or heterozygous Ah receptor. The liver tumors in rats and mice had treatment-related Hras and Ctnnb mutations, respectively. The PBDE carcinogenic activity could be related to oxidative damage, disruption of hormone homeostasis, and molecular and epigenetic changes in target tissue. Further work is needed to compare the PBDE toxic effects in rodents and humans.
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Affiliation(s)
- J K Dunnick
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - A R Pandiri
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - B A Merrick
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - G E Kissling
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - H Cunny
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - E Mutlu
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - S Waidyanatha
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - R Sills
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - H L Hong
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - T V Ton
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - T Maynor
- Integrated Laboratory Systems, Research Triangle Park, NC 27709, USA
| | - L Recio
- Integrated Laboratory Systems, Research Triangle Park, NC 27709, USA
| | - S L Phillips
- Integrated Laboratory Systems, Research Triangle Park, NC 27709, USA
| | - M J Devito
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - A Brix
- EPL, Inc., Research Triangle Park, NC 27709, USA
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Abstract
Dioxins have been shown to bind and induce rodent CYP1A2, producing a dose-dependent hepatic sequestration in vivo. The induction of CYP1A2 activity has been used as a noninvasive biomarker for human exposure to dioxins; while there is a consistent relationship between exposure and hepatic CYP1A2 induction in rodents, this relationship has only been observed in some of the highest exposed human populations. This may be explained by inhibition of CYP1A2 activity by dioxins as some rodent studies demonstrate that rodent CYP1A2 activity can in fact be inhibited by dioxins in vitro. CYP1A2 activity was examined using a series of dioxins to inhibit human and rat CYP1A2 activity in species-specific CYP1A2 SUPERSOMES using three common CYP1A2 substrates. Methoxyresorufin was a more efficient substrate than acetanalide or caffeine in this in vitro system. Rat and human CYP1A2 enzymatic activity is inhibited by TCDD, PCDD, TCDF, 4-PeCDF, and PCBs 126, 169, 105, 118, and 156 in a concentration-dependent manner. These data demonstrate that the in vitro metabolism of prototype substrates is similar between the rat and human CYP1A2 SUPERSOME preparations and that dioxins inhibit CYP1A2 activity in both species. Because of the potential for inhibition of CYP1A2 activity by TCDD and other dioxins, studies examining CYP1A2 induction in dioxin-exposed populations using these substrates should be viewed cautiously.
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Affiliation(s)
- D F Staskal
- UNC Curriculum in Toxicology, US EPA, MD B143-01, 109 TW Alexander Dr., Research Triangle Park, North Carolina 27711, USA.
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Hassoun EA, Wilt SC, Devito MJ, Van Birgelen A, Alsharif NZ, Birnbaum LS, Stohs SJ. Induction of oxidative stress in brain tissues of mice after subchronic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Toxicol Sci 1998; 42:23-7. [PMID: 9538044 DOI: 10.1006/toxs.1997.2411] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ability of single doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to induce oxidative stress in hepatic and some extrahepatic tissues of animals is well documented. However, no previous study has examined the ability of TCDD to induce oxidative stress and tissue damage in brain in vivo. In this study the ability of TCDD to induce oxidative stress in brain tissues of mice was studied after subchronic exposures. Groups of female B6C3F1 mice were treated orally with TCDD (0, 0.45, 1.5, 15, and 150 ng/kg/day) for 13 weeks, 5 days/week. The animals were euthanized 3 days after the last treatment and brain tissues were collected. Biomarkers of oxidative stress including production of superoxide anion, lipid peroxidation, and DNA-single-strand breaks (SSB) were determined. TCDD treatment resulted in significant and dose-dependent increases in the production of superoxide anion as assessed by reduction of cytochrome c. Significant increases were also observed in lipid peroxidation and DNA-SSB in those tissues, as assessed by the presence of thiobarbituric acid-reactive substances and the alkaline elution technique, respectively. These results clearly indicate that subchronic exposure to low doses of TCDD can induce oxidative tissue damage in brain tissues which may at least in part play a role in the effects of TCDD on the central nervous system.
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Affiliation(s)
- E A Hassoun
- College of Pharmacy, University of Toledo, Toledo, Ohio, 43606, USA
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