1
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Kobets T, Smith BPC, Williams GM. Food-Borne Chemical Carcinogens and the Evidence for Human Cancer Risk. Foods 2022; 11:2828. [PMID: 36140952 PMCID: PMC9497933 DOI: 10.3390/foods11182828] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 09/07/2022] [Accepted: 09/08/2022] [Indexed: 11/16/2022] Open
Abstract
Commonly consumed foods and beverages can contain chemicals with reported carcinogenic activity in rodent models. Moreover, exposures to some of these substances have been associated with increased cancer risks in humans. Food-borne carcinogens span a range of chemical classes and can arise from natural or anthropogenic sources, as well as form endogenously. Important considerations include the mechanism(s) of action (MoA), their relevance to human biology, and the level of exposure in diet. The MoAs of carcinogens have been classified as either DNA-reactive (genotoxic), involving covalent reaction with nuclear DNA, or epigenetic, involving molecular and cellular effects other than DNA reactivity. Carcinogens are generally present in food at low levels, resulting in low daily intakes, although there are some exceptions. Carcinogens of the DNA-reactive type produce effects at lower dosages than epigenetic carcinogens. Several food-related DNA-reactive carcinogens, including aflatoxins, aristolochic acid, benzene, benzo[a]pyrene and ethylene oxide, are recognized by the International Agency for Research on Cancer (IARC) as causes of human cancer. Of the epigenetic type, the only carcinogen considered to be associated with increased cancer in humans, although not from low-level food exposure, is dioxin (TCDD). Thus, DNA-reactive carcinogens in food represent a much greater risk than epigenetic carcinogens.
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Affiliation(s)
- Tetyana Kobets
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA
| | - Benjamin P. C. Smith
- Future Ready Food Safety Hub, Nanyang Technological University, Singapore 639798, Singapore
| | - Gary M. Williams
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA
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2
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Lowery RL, Latchney SE, Peer RP, Lamantia CE, Opanashuk L, McCall M, Majewska AK. Acute 2,3,7,8-Tetrachlorodibenzo-p-dioxin exposure in adult mice does not alter the morphology or inflammatory response of cortical microglia. Neurosci Lett 2020; 742:135516. [PMID: 33227371 DOI: 10.1016/j.neulet.2020.135516] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 10/15/2020] [Accepted: 11/16/2020] [Indexed: 10/23/2022]
Abstract
Microglia, the immune cells of the brain, have a canonical role in regulating responses to neurological disease or injury, but have also recently been implicated as regulators of neurophysiological processes such as learning and memory. Given these dual immune and physiological roles, microglia are a likely mechanism by which external toxic stimuli are converted into deficits in neuronal circuitry and subsequently function. However, while it is well established that exposure to environmental toxicants negatively affects the peripheral immune system, it remains unknown whether and how such exposure causes neuroinflammation which, in turn, may negatively impact microglial functions in vivo. Here, we examined how acute 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure in adulthood, which negatively impacts immune cells in the periphery, affects microglial characteristics in the cortex of the mouse. We found that microglia density, distribution, morphology, inflammatory signaling, and response to a secondary, pathological activation were unaffected by acute TCDD exposure. These results suggest that acute, peripheral TCDD exposure in adulthood is not sufficient to induce an overt inflammatory phenotype in cortical microglia.
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Affiliation(s)
- R L Lowery
- Department of Neuroscience, Center for Visual Science, University of Rochester, Rochester, NY, 14642, United States
| | - S E Latchney
- Biology Department, St. Mary's College of Maryland, St. Mary's City, MD, 20686, United States
| | - R P Peer
- Department of Neuroscience, Center for Visual Science, University of Rochester, Rochester, NY, 14642, United States
| | - C E Lamantia
- Department of Neuroscience, Center for Visual Science, University of Rochester, Rochester, NY, 14642, United States
| | - L Opanashuk
- National Institute on Aging, Bethesda, MD, 20892, United States
| | - M McCall
- Department of Biostatistics and Computational Biology, University of Rochester, NY, 14642, United States; Department of Biomedical Genetics, University of Rochester, NY, 14642, United States
| | - A K Majewska
- Department of Neuroscience, Center for Visual Science, University of Rochester, Rochester, NY, 14642, United States.
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3
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Prokopec SD, Viluksela M, Miettinen HM, Boutros PC, Pohjanvirta R. Transgenerational epigenetic and transcriptomic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure in rat. Arch Toxicol 2020; 94:1613-1624. [PMID: 32277265 DOI: 10.1007/s00204-020-02730-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 03/26/2020] [Indexed: 12/30/2022]
Abstract
In rats, direct exposure to TCDD causes myriad toxicities. Exposed rats experience hepatotoxicity, wasting syndrome and immune suppression, amongst others. "Inherited exposure", as occurs in the F3 generation of directly exposed F0 animals, has also been shown to cause toxicity: both male and female F3 rats demonstrate an increased incidence of adult onset disease, females also display reproductive abnormalities and increased incidence of ovarian diseases while males show increased incidence of kidney disease and an altered sperm epigenome. Here, we explore the hepatic transcriptomic profile of male and female F3 Sprague-Dawley rats bred through the paternal germ line from F0 dams exposed to a single dose of TCDD (0, 30, 100, 300 or 1000 ng/kg body weight) by oral gavage. We hypothesize that RNA transcripts with altered abundance in livers of unexposed F3 progeny of treated F0 Sprague-Dawley rats may result from epigenetic modifications to the genome. We further survey patterns of differential methylation within male F3 rat testis. Female F3 rats demonstrated more TCDD-mediated hepatic transcriptomic changes than males, with differences primarily in the lowest dose group. In testis from male F3 rats, multiple olfactory receptors displayed patterns of differential methylation. Hypermethylation of Egfr and Mc5r among testes from TCDD lineage rats was observed, but without corresponding changes in hepatic mRNA abundance. Further studies examining these differences in other tissue types are warranted.
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Affiliation(s)
| | - Matti Viluksela
- Department of Environmental and Biological Sciences, School of Pharmacy (Toxicology), University of Eastern Finland, Kuopio, Finland.,Environmental Health Unit, Finnish Institute for Health and Welfare (THL), Kuopio, Finland
| | - Hanna M Miettinen
- Environmental Health Unit, Finnish Institute for Health and Welfare (THL), Kuopio, Finland.,A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Paul C Boutros
- Department of Medical Biophysics, University of Toronto, Toronto, Canada. .,Department of Pharmacology and Toxicology, Universally of Toronto, Toronto, Canada. .,Department of Human Genetics, University of California, Los Angeles, 12-109 CHS, 10833 Le Conte Avenue, Los Angeles, CA, 90095, USA. .,Department of Urology, University of California, Los Angeles, Los Angeles, USA. .,Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, USA. .,Institute for Precision Health, University of California, Los Angeles, Los Angeles, USA. .,Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, USA.
| | - Raimo Pohjanvirta
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014, Helsinki, Finland.
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4
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Erdemli ME, Yigitcan B, Erdemli Z, Gul M, Bag HG, Gul S. Thymoquinone protection against 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin induced nephrotoxicity in rats. Biotech Histochem 2020; 95:567-574. [PMID: 32207631 DOI: 10.1080/10520295.2020.1735520] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We investigated the effects of thymoquinone (TQ) on kidney tissues of Wistar rats with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced nephrotoxicity. We used 50 rats divided into five groups; control, corn oil, TCDD, TQ, TCDD + TQ. We found that malondialdehyde (MDA), total oxidant status (TOS), blood urea nitrogen (BUN), creatinine, interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α) levels in the TCDD treated group increased significantly compared to the other groups, while reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and total antioxidant status (TAS) levels decreased in the TCDD group. In the TQ treated group, we found that GSH, SOD, CAT, TAS levels increased and MDA, TOS, IL-6 and TNF-α levels decreased compared to the other groups. The effects of TCDD on oxidative stress parameters, inflammatory markers and histological changes were ameliorated by TQ treatment.
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Affiliation(s)
- Mehmet Erman Erdemli
- Department of Medical Biochemistry, Medical Faculty, Inonu University , Malatya, Turkey
| | - Birgul Yigitcan
- Department of Histology and Embryology, Medical Faculty, Inonu University , Malatya, Turkey
| | - Zeynep Erdemli
- Department of Medical Biochemistry, Medical Faculty, Inonu University , Malatya, Turkey
| | - Mehmet Gul
- Department of Histology and Embryology, Medical Faculty, Inonu University , Malatya, Turkey
| | - Harika Gozukara Bag
- Department of Biostatistics, Medical Faculty, Inonu University , Malatya, Turkey
| | - Semir Gul
- Department of Histology and Embryology, Medical Faculty, Inonu University , Malatya, Turkey
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5
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Prokopec SD, Pohjanvirta R, Mahiout S, Pettersson L, Boutros PC. Transcriptomic Impact of IMA-08401, a Novel AHR Agonist Resembling Laquinimod, on Rat Liver. Int J Mol Sci 2019; 20:ijms20061370. [PMID: 30893768 PMCID: PMC6471016 DOI: 10.3390/ijms20061370] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 03/13/2019] [Accepted: 03/15/2019] [Indexed: 02/06/2023] Open
Abstract
IMA-08401 (C2) is a novel aryl hydrocarbon receptor (AHR) agonist and selective AHR modulator (SAHRM) that is structurally similar to laquinimod (LAQ). Both compounds are converted to the AHR-active metabolite DELAQ (IMA-06201) in vivo. SAHRMs have been proposed as therapeutic options for various autoimmune disorders. Clinical trials on LAQ have not reported any significant toxic outcomes and C2 has shown low toxicity in rats; however, their functional resemblance to the highly toxic AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) raises questions. Here, we characterize the hepatic transcriptomic changes induced by acute (single-dose) and subacute exposure (repeated dosing for 5 days followed by a 5-day recovery period) to C2 in Sprague-Dawley rats. Exposure to C2 leads to activation of the AHR, as shown by altered transcription of Cyp1a1. We identify a heightened response early after exposure that drops off by day 10. Acute exposure to C2 leads to changes to transcription of genes involved in antiviral and antibacterial responses, which highlights the immunomodulator effects of this AHR agonist. Subacute exposure causes an oxidative stress response in the liver, the consequences of which require further study on target tissues such as the CNS and immune system, both of which may be compromised in this patient population.
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Affiliation(s)
| | - Raimo Pohjanvirta
- Laboratory of Toxicology, National Institute for Health and Welfare, FI-70210 Kuopio, Finland.
- Department of Food Hygiene and Environmental Health, University of Helsinki, FI-00790 Helsinki, Finland.
| | - Selma Mahiout
- Department of Food Hygiene and Environmental Health, University of Helsinki, FI-00790 Helsinki, Finland.
| | | | - Paul C Boutros
- Ontario Institute for Cancer Research, Toronto, ON M5G 0A3, Canada.
- Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada.
- Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada.
- Department of Human Genetics, University of California, Los Angeles, CA 90095, USA.
- Department of Urology, University of California, Los Angeles, CA 90095, USA.
- Institute for Precision Health, University of California, Los Angeles, CA 90095, USA.
- Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA 90095, USA.
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6
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Knutsen HK, Alexander J, Barregård L, Bignami M, Brüschweiler B, Ceccatelli S, Cottrill B, Dinovi M, Edler L, Grasl-Kraupp B, Hogstrand C, Nebbia CS, Oswald IP, Petersen A, Rose M, Roudot AC, Schwerdtle T, Vleminckx C, Vollmer G, Wallace H, Fürst P, Håkansson H, Halldorsson T, Lundebye AK, Pohjanvirta R, Rylander L, Smith A, van Loveren H, Waalkens-Berendsen I, Zeilmaker M, Binaglia M, Gómez Ruiz JÁ, Horváth Z, Christoph E, Ciccolallo L, Ramos Bordajandi L, Steinkellner H, Hoogenboom LR. Risk for animal and human health related to the presence of dioxins and dioxin-like PCBs in feed and food. EFSA J 2018; 16:e05333. [PMID: 32625737 PMCID: PMC7009407 DOI: 10.2903/j.efsa.2018.5333] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of dioxins (PCDD/Fs) and DL-PCBs in feed and food. The data from experimental animal and epidemiological studies were reviewed and it was decided to base the human risk assessment on effects observed in humans and to use animal data as supportive evidence. The critical effect was on semen quality, following pre- and postnatal exposure. The critical study showed a NOAEL of 7.0 pg WHO2005-TEQ/g fat in blood sampled at age 9 years based on PCDD/F-TEQs. No association was observed when including DL-PCB-TEQs. Using toxicokinetic modelling and taking into account the exposure from breastfeeding and a twofold higher intake during childhood, it was estimated that daily exposure in adolescents and adults should be below 0.25 pg TEQ/kg bw/day. The CONTAM Panel established a TWI of 2 pg TEQ/kg bw/week. With occurrence and consumption data from European countries, the mean and P95 intake of total TEQ by Adolescents, Adults, Elderly and Very Elderly varied between, respectively, 2.1 to 10.5, and 5.3 to 30.4 pg TEQ/kg bw/week, implying a considerable exceedance of the TWI. Toddlers and Other Children showed a higher exposure than older age groups, but this was accounted for when deriving the TWI. Exposure to PCDD/F-TEQ only was on average 2.4- and 2.7-fold lower for mean and P95 exposure than for total TEQ. PCDD/Fs and DL-PCBs are transferred to milk and eggs, and accumulate in fatty tissues and liver. Transfer rates and bioconcentration factors were identified for various species. The CONTAM Panel was not able to identify reference values in most farm and companion animals with the exception of NOAELs for mink, chicken and some fish species. The estimated exposure from feed for these species does not imply a risk.
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7
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Mahiout S, Lindén J, Esteban J, Sánchez-Pérez I, Sankari S, Pettersson L, Håkansson H, Pohjanvirta R. Toxicological characterisation of two novel selective aryl hydrocarbon receptor modulators in Sprague-Dawley rats. Toxicol Appl Pharmacol 2017; 326:54-65. [PMID: 28433708 DOI: 10.1016/j.taap.2017.04.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/20/2017] [Accepted: 04/18/2017] [Indexed: 12/11/2022]
Abstract
The aryl hydrocarbon receptor (AHR) mediates the toxicity of dioxins, but also plays important physiological roles. Selective AHR modulators, which elicit some effects imparted by this receptor without causing the marked toxicity of dioxins, are presently under intense scrutiny. Two novel such compounds are IMA-08401 (N-acetyl-N-phenyl-4-acetoxy-5-chloro-1,2-dihydro-1-methyl-2-oxo-quinoline-3-carboxamide) and IMA-07101 (N-acetyl-N-(4-trifluoromethylphenyl)-4-acetoxy-1,2-dihydro-5-methoxy-1-methyl-2-oxo-quinoline-3-carboxamide). They represent, as diacetyl prodrugs, AHR-active metabolites of the drug compounds laquinimod and tasquinimod, respectively, which are intended for the treatment of autoimmune diseases and cancer. Here, we toxicologically assessed the novel compounds in Sprague-Dawley rats, after a single dose (8.75-92.5mg/kg) and 5-day repeated dosing at the highest doses achievable (IMA-08401: 100mg/kg/day; and IMA-07101: 75mg/kg/day). There were no overt clinical signs of toxicity, but body weight gain was marginally retarded, and the treatments induced minimal hepatic extramedullary haematopoiesis. Further, both the absolute and relative weights of the thymus were significantly decreased. Cyp1a1 gene expression was substantially increased in all tissues examined. The hepatic induction profile of other AHR battery genes was distinct from that caused by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The only marked alterations in serum clinical chemistry variables were a reduction in triglycerides and an increase in 3-hydroxybutyrate. Liver and kidney retinol and retinyl palmitate concentrations were affected largely in the same manner as reported for TCDD. In vitro, the novel compounds activated CYP1A1 effectively in H4IIE cells. Altogether, these novel compounds appear to act as potent activators of the AHR, but lack some major characteristic toxicities of dioxins. They therefore represent promising new selective AHR modulators.
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Affiliation(s)
- Selma Mahiout
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Finland.
| | - Jere Lindén
- Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, University of Helsinki, Finland
| | - Javier Esteban
- Instituto de Bioingeniería, Universidad Miguel Hernández de Elche, Elche, Alicante, Spain
| | - Ismael Sánchez-Pérez
- Instituto de Bioingeniería, Universidad Miguel Hernández de Elche, Elche, Alicante, Spain
| | - Satu Sankari
- Central Laboratory of the Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Finland
| | | | - Helen Håkansson
- Institute of Environmental Medicine (IMM), Karolinska Institutet, Stockholm, Sweden
| | - Raimo Pohjanvirta
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Finland
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8
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Prokopec SD, Houlahan KE, Sun RX, Watson JD, Yao CQ, Lee J, P'ng C, Pang R, Wu AH, Chong LC, Smith AB, Harding NJ, Moffat ID, Lindén J, Lensu S, Okey AB, Pohjanvirta R, Boutros PC. Compendium of TCDD-mediated transcriptomic response datasets in mammalian model systems. BMC Genomics 2017; 18:78. [PMID: 28086803 PMCID: PMC5237151 DOI: 10.1186/s12864-016-3446-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Accepted: 12/20/2016] [Indexed: 02/04/2023] Open
Abstract
Background 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent congener of the dioxin class of environmental contaminants. Exposure to TCDD causes a wide range of toxic outcomes, ranging from chloracne to acute lethality. The severity of toxicity is highly dependent on the aryl hydrocarbon receptor (AHR). Binding of TCDD to the AHR leads to changes in transcription of numerous genes. Studies evaluating the transcriptional changes brought on by TCDD may provide valuable insight into the role of the AHR in human health and disease. We therefore compiled a collection of transcriptomic datasets that can be used to aid the scientific community in better understanding the transcriptional effects of ligand-activated AHR. Results Specifically, we have created a datasets package – TCDD.Transcriptomics – for the R statistical environment, consisting of 63 unique experiments comprising 377 samples, including various combinations of 3 species (human derived cell lines, mouse and rat), 4 tissue types (liver, kidney, white adipose tissue and hypothalamus) and a wide range of TCDD exposure times and doses. These datasets have been fully standardized using consistent preprocessing and annotation packages (available as of September 14, 2015). To demonstrate the utility of this R package, a subset of “AHR-core” genes were evaluated across the included datasets. Ahrr, Nqo1 and members of the Cyp family were significantly induced following exposure to TCDD across the studies as expected while Aldh3a1 was induced specifically in rat liver. Inmt was altered only in liver tissue and primarily by rat-AHR. Conclusions Analysis of the “AHR-core” genes demonstrates a continued need for studies surrounding the impact of AHR-activity on the transcriptome; genes believed to be consistently regulated by ligand-activated AHR show surprisingly little overlap across species and tissues. Until now, a comprehensive assessment of the transcriptome across these studies was challenging due to differences in array platforms, processing methods and annotation versions. We believe that this package, which is freely available for download (http://labs.oicr.on.ca/boutros-lab/tcdd-transcriptomics) will prove to be a highly beneficial resource to the scientific community evaluating the effects of TCDD exposure as well as the variety of functions of the AHR. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3446-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Stephenie D Prokopec
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Kathleen E Houlahan
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Ren X Sun
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada.,Department of Pharmacology & Toxicology, University of Toronto, Toronto, Canada
| | - John D Watson
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Cindy Q Yao
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Jamie Lee
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Christine P'ng
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Renee Pang
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Alexander H Wu
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Lauren C Chong
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Ashley B Smith
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Nicholas J Harding
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Ivy D Moffat
- Department of Pharmacology & Toxicology, University of Toronto, Toronto, Canada
| | - Jere Lindén
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
| | - Sanna Lensu
- Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.,Department of Environmental Health, National Institute for Health and Welfare, Kuopio, Finland
| | - Allan B Okey
- Department of Pharmacology & Toxicology, University of Toronto, Toronto, Canada
| | - Raimo Pohjanvirta
- Laboratory of Toxicology, National Institute for Health and Welfare, Kuopio, Finland.,Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland
| | - Paul C Boutros
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, 661 University Avenue, Suite 510, Toronto, ON, M5G 0A3, Canada. .,Department of Pharmacology & Toxicology, University of Toronto, Toronto, Canada. .,Department of Medical Biophysics, University of Toronto, Toronto, Canada.
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9
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Mahiout S, Pohjanvirta R. Aryl hydrocarbon receptor agonists trigger avoidance of novel food in rats. Physiol Behav 2016; 167:49-59. [DOI: 10.1016/j.physbeh.2016.08.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 08/08/2016] [Accepted: 08/31/2016] [Indexed: 12/22/2022]
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10
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Regulations and Advisories. Toxicol Ind Health 2016. [DOI: 10.1177/074823370001600312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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11
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AhR-dependent 2,3,7,8-tetrachlorodibenzo- p -dioxin toxicity in human neuronal cell line SHSY5Y. Neurotoxicology 2016; 56:55-63. [DOI: 10.1016/j.neuro.2016.07.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 07/04/2016] [Accepted: 07/04/2016] [Indexed: 11/21/2022]
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12
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El-Barbary MI. Detoxification and antioxidant effects of garlic and curcumin in Oreochromis niloticus injected with aflatoxin B₁ with reference to gene expression of glutathione peroxidase (GPx) by RT-PCR. FISH PHYSIOLOGY AND BIOCHEMISTRY 2016; 42:617-629. [PMID: 26590820 DOI: 10.1007/s10695-015-0164-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 11/08/2015] [Indexed: 06/05/2023]
Abstract
The present study aims to investigate the effects of both garlic and curcumin through evaluating their therapeutic properties as antioxidants on liver and kidney functions, hepatic antioxidants and GPx gene expression against aflatoxicosis of O. niloticus. In total, 180 of tilapia were divided into ten groups; T1 represented the negative control fed on a basal diet, and T2 was injected with a single intraperitoneal (i.p.) dose of AFB1 (6 mg/kg b.w.). Fish in T3-T6 were fed on a basal diet supplemented with both garlic (T3 and T4) and curcumin (T5 and T6) at the two concentrations of 10 and 20 g/kg diet, respectively. Fish in T7-T10 groups were injected with AFB1 and fed on the garlic (T7 and T8) and curcumin (T9 and T10) dietaries. The results showed that AFB1 has significant potency for increasing the activity of plasma AST, ALT, creatinine and uric acid values, and hepatic MDA as well as for reducing the concentrations of plasma TP, AL, GL and hepatic activity of TAC, while AFB1 led to up-regulated GPx gene expression when compared to the control (T1). These harmful effects of AFB1 were alleviated due to the garlic and curcumin dietaries in some studied parameters. Garlic reflected the highest induction of gene expression (T7); however, curcumin showed significant down-regulated (T9). These results concluded that the effects of garlic were better than curcumin at the two concentrations and the low concentration of them is more beneficial than the high concentration when it used against AFB1 in O. niloticus.
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Affiliation(s)
- Manal I El-Barbary
- Fish Diseases Laboratory, National Institute of Oceanography and Fisheries (NIOF), Cairo, Egypt.
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Sholts SB, Korkalainen M, Simanainen U, Miettinen HM, Håkansson H, Viluksela M. In utero/lactational and adult exposures to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) show differential effects on craniofacial development and growth in rats. Toxicology 2015; 337:30-8. [DOI: 10.1016/j.tox.2015.08.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/18/2015] [Accepted: 08/24/2015] [Indexed: 12/27/2022]
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14
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Developmental origin of abnormal dendritic growth in the mouse brain induced by in utero disruption of aryl hydrocarbon receptor signaling. Neurotoxicol Teratol 2015; 52:42-50. [PMID: 26526904 DOI: 10.1016/j.ntt.2015.10.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Revised: 09/26/2015] [Accepted: 10/21/2015] [Indexed: 11/20/2022]
Abstract
Increased prevalence of mental disorders cannot be solely attributed to genetic factors and is considered at least partly attributable to chemical exposure. Among various environmental chemicals, in utero and lactational dioxin exposure has been extensively studied and is known to induce higher brain function abnormalities in both humans and laboratory animals. However, how the perinatal dioxin exposure affects neuromorphological alterations has remained largely unknown. Therefore, in this study, we initially studied whether and how the over-expression of aryl hydrocarbon receptor (AhR), a dioxin receptor, would affect the dendritic growth in the hippocampus of the developing brain. Transfecting a constitutively active AhR plasmid into the hippocampus via in utero electroporation on gestational day (GD) 14 induced abnormal dendritic branch growth. Further, we observed that 14-day-old mice born to dams administered with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dose: 0, 0.6, or 3.0 μg/kg) on GD 12.5 exhibited disrupted dendritic branch growth in both the hippocampus and amygdala. Finally, we observed that 16-month-old mice born to dams exposed to perinatal TCDD as described above exhibited significantly reduced spine densities. These results indicated that abnormal micromorphology observed in the developing brain may persist until adulthood and may induce abnormal higher brain function later in life.
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Houlahan KE, Prokopec SD, Sun RX, Moffat ID, Lindén J, Lensu S, Okey AB, Pohjanvirta R, Boutros PC. Transcriptional profiling of rat white adipose tissue response to 2,3,7,8-tetrachlorodibenzo-ρ-dioxin. Toxicol Appl Pharmacol 2015; 288:223-31. [PMID: 26232522 DOI: 10.1016/j.taap.2015.07.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 07/18/2015] [Accepted: 07/21/2015] [Indexed: 12/21/2022]
Abstract
Polychlorinated dibenzodioxins are environmental contaminants commonly produced as a by-product of industrial processes. The most potent of these, 2,3,7,8-tetrachlorodibenzo-ρ-dioxin (TCDD), is highly lipophilic, leading to bioaccumulation. White adipose tissue (WAT) is a major site for energy storage, and is one of the organs in which TCDD accumulates. In laboratory animals, exposure to TCDD causes numerous metabolic abnormalities, including a wasting syndrome. We therefore investigated the molecular effects of TCDD exposure on WAT by profiling the transcriptomic response of WAT to 100μg/kg of TCDD at 1 or 4days in TCDD-sensitive Long-Evans (Turku/AB; L-E) rats. A comparative analysis was conducted simultaneously in identically treated TCDD-resistant Han/Wistar (Kuopio; H/W) rats one day after exposure to the same dose. We sought to identify transcriptomic changes coinciding with the onset of toxicity, while gaining additional insight into later responses. More transcriptional responses to TCDD were observed at 4days than at 1day post-exposure, suggesting WAT shows mostly secondary responses. Two classic AHR-regulated genes, Cyp1a1 and Nqo1, were significantly induced by TCDD in both strains, while several genes involved in the immune response, including Ms4a7 and F13a1 were altered in L-E rats alone. We compared genes affected by TCDD in rat WAT and human adipose cells, and observed little overlap. Interestingly, very few genes involved in lipid metabolism exhibited altered expression levels despite the pronounced lipid mobilization from peripheral fat pads by TCDD in L-E rats. Of these genes, the lipolysis-associated Lpin1 was induced slightly over 2-fold in L-E rat WAT on day 4.
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Affiliation(s)
- Kathleen E Houlahan
- Informatics and Bio-Computing Program, Ontario Institute for Cancer Research, Toronto, Canada
| | - Stephenie D Prokopec
- Informatics and Bio-Computing Program, Ontario Institute for Cancer Research, Toronto, Canada
| | - Ren X Sun
- Informatics and Bio-Computing Program, Ontario Institute for Cancer Research, Toronto, Canada
| | - Ivy D Moffat
- Department of Pharmacology & Toxicology, University of Toronto, Toronto, Canada
| | - Jere Lindén
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
| | - Sanna Lensu
- Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland; Department of Environmental Health, National Institute for Health and Welfare, Kuopio, Finland
| | - Allan B Okey
- Department of Pharmacology & Toxicology, University of Toronto, Toronto, Canada
| | - Raimo Pohjanvirta
- Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland.
| | - Paul C Boutros
- Informatics and Bio-Computing Program, Ontario Institute for Cancer Research, Toronto, Canada; Department of Pharmacology & Toxicology, University of Toronto, Toronto, Canada; Department of Medical Biophysics, University of Toronto, Toronto, Canada.
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Prokopec SD, Watson JD, Lee J, Pohjanvirta R, Boutros PC. Sex-related differences in murine hepatic transcriptional and proteomic responses to TCDD. Toxicol Appl Pharmacol 2015; 284:188-96. [PMID: 25703434 DOI: 10.1016/j.taap.2015.02.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 02/06/2015] [Accepted: 02/10/2015] [Indexed: 12/14/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant that produces myriad toxicities in most mammals. In rodents alone, there is a huge divergence in the toxicological response across species, as well as among different strains within a species. But there are also significant differences between males and females animals of a single strain. These differences are inconsistent across model systems: the severity of toxicity is greater in female rats than males, while male mice and guinea pigs are more sensitive than females. Because the specific events that underlie this difference remain unclear, we characterized the hepatic transcriptional response of adult male and female C57BL/6 mice to 500μg/kg TCDD at multiple time-points. The transcriptional profile diverged significantly between the sexes. Female mice demonstrated a large number of altered transcripts as early as 6h following treatment, suggesting a large primary response. Conversely, male animals showed the greatest TCDD-mediated response 144h following exposure, potentially implicating significant secondary responses. Nr1i3 was statistically significantly induced at all time-points in the sensitive male animals. This mRNA encodes the constitutive androstane receptor (CAR), a transcription factor involved in the regulation of xenobiotic metabolism, lipid metabolism, cell cycle and apoptosis. Surprisingly though, changes at the protein level (aside from the positive control, CYP1A1) were modest, with only FMO3 showing clear induction, and no genes with sex-differences. Thus, while male and female mice show transcriptional differences in their response to TCDD, their association with TCDD-induced toxicities remains unclear.
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Affiliation(s)
- Stephenie D Prokopec
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, Toronto, Canada
| | - John D Watson
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, Toronto, Canada
| | - Jamie Lee
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, Toronto, Canada; Department of Pharmacology & Toxicology, University of Toronto, Toronto, Canada
| | - Raimo Pohjanvirta
- Laboratory of Toxicology, National Institute for Health and Welfare, Kuopio Finland; Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland
| | - Paul C Boutros
- Informatics and Bio-computing Program, Ontario Institute for Cancer Research, Toronto, Canada; Department of Pharmacology & Toxicology, University of Toronto, Toronto, Canada; Department of Medical Biophysics, University of Toronto, Toronto, Canada.
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Houlahan KE, Prokopec SD, Moffat ID, Lindén J, Lensu S, Okey AB, Pohjanvirta R, Boutros PC. Transcriptional profiling of rat hypothalamus response to 2,3,7,8-tetrachlorodibenzo- ρ -dioxin. Toxicology 2015; 328:93-101. [DOI: 10.1016/j.tox.2014.12.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 12/12/2014] [Accepted: 12/16/2014] [Indexed: 12/21/2022]
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18
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Wan C, Liu J, Nie X, Zhao J, Zhou S, Duan Z, Tang C, Liang L, Xu G. 2, 3, 7, 8-Tetrachlorodibenzo-P-dioxin (TCDD) induces premature senescence in human and rodent neuronal cells via ROS-dependent mechanisms. PLoS One 2014; 9:e89811. [PMID: 24587053 PMCID: PMC3933666 DOI: 10.1371/journal.pone.0089811] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 01/27/2014] [Indexed: 11/30/2022] Open
Abstract
The widespread environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent toxicant that causes significant neurotoxicity. However, the biological events that participate in this process remain largely elusive. In the present study, we demonstrated that TCDD exposure triggered apparent premature senescence in rat pheochromocytoma (PC12) and human neuroblastoma SH-SY5Y cells. Senescence-associated β-galactosidase (SA-β-Gal) assay revealed that TCDD induced senescence in PC12 neuronal cells at doses as low as 10 nM. TCDD led to F-actin reorganization and the appearance of an alternative senescence marker, γ-H2AX foci, both of which are important features of cellular senescence. In addition, TCDD exposure altered the expression of senescence marker proteins, such as p16, p21 and p-Rb, in both dose- and time-dependent manners. Furthermore, we demonstrated that TCDD promotes mitochondrial dysfunction and the accumulation of cellular reactive oxygen species (ROS) in PC12 cells, leading to the activation of signaling pathways that are involved in ROS metabolism and senescence. TCDD-induced ROS generation promoted significant oxidative DNA damage and lipid peroxidation. Notably, treatment with the ROS scavenger N-acetylcysteine (NAC) markedly attenuated TCDD-induced ROS production, cellular oxidative damage and neuronal senescence. Moreover, we found that TCDD induced a similar ROS-mediated senescence response in human neuroblastoma SH-SY5Y cells. In sum, these results demonstrate for the first time that TCDD induces premature senescence in neuronal cells by promoting intracellular ROS production, supporting the idea that accelerating the onset of neuronal senescence may be an important mechanism underlying TCDD-induced neurotoxic effects.
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Affiliation(s)
- Chunhua Wan
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, People's Republic of China
| | - Jiao Liu
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, People's Republic of China
| | - Xiaoke Nie
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, People's Republic of China
| | - Jianya Zhao
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, People's Republic of China
| | - Songlin Zhou
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, People's Republic of China
| | - Zhiqing Duan
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, People's Republic of China
| | - Cuiying Tang
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, People's Republic of China
| | - Lingwei Liang
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, People's Republic of China
| | - Guangfei Xu
- Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, Jiangsu, People's Republic of China
- * E-mail: .
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2,3,7,8-Tetrachlorodibenzo-p-dioxin induces apoptosis by disruption of intracellular calcium homeostasis in human neuronal cell line SHSY5Y. Apoptosis 2014; 17:1170-81. [PMID: 22986482 DOI: 10.1007/s10495-012-0760-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The persistent xenobiotic agent 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces neurotoxic effects that alters neurodevelopment and behavior both during development and adulthood. There are many ongoing efforts to determine the molecular mechanisms of TCDD-mediated neurotoxicity, the signaling pathways involved and its molecular targets in neurons. In this work, we have used SHSY5Y human neuroblastoma cells to characterize the TCDD-induced toxicity. TCDD produces a loss of viability linked to an increased caspase-3 activity, PARP-1 fragmentation, DNA laddering, nuclear fragmentation and hypodiploid (apoptotic) DNA content, in a similar way than staurosporine, a prototypical molecule of apoptosis induction. In addition, TCDD produces a decrease of mitochondrial membrane potential and an increase of intracellular calcium concentration (P < 0.05). Finally, based on the high lipophilic properties of the dioxin, we test the TCDD effect on the membrane integrity using sarcoplasmic reticulum vesicles as a model. TCDD produces calcium efflux through the membrane and an anisotropy decrease (P < 0.05) that reflects an increase in membrane fluidity. Altogether these results support the hypothesis that TCDD toxicity in SHSY5Y neuroblastoma cells provokes the disruption of calcium homeostasis, probably affecting membrane structural integrity, leading to an apoptotic process.
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20
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Nault R, Forgacs AL, Dere E, Zacharewski TR. Comparisons of differential gene expression elicited by TCDD, PCB126, βNF, or ICZ in mouse hepatoma Hepa1c1c7 cells and C57BL/6 mouse liver. Toxicol Lett 2013; 223:52-9. [PMID: 23994337 DOI: 10.1016/j.toxlet.2013.08.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 08/17/2013] [Accepted: 08/19/2013] [Indexed: 12/21/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a promiscuous receptor activated by structurally diverse synthetic and natural compounds. AhR activation may lead to ligand-specific changes in gene expression despite similarities in mode of action. Therefore, differential gene expression elicited by four structurally diverse, high affinity AhR ligands (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 10nM, 30 μg/kg), 3,3',4,4',5-pentachlorobiphenyl (PCB126; 100nM, 300μg/kg), β-naphthoflavone (βNF; 10 μM, 90 mg/kg), and indolo[3,2-b]carbazole (ICZ; 1μM)) in mouse Hepa1c1c7 hepatoma cells and C57BL/6 mouse liver samples were compared. A total of 288, 183, 119, and 131 Hepa1c1c7 genes were differentially expressed (|fold-change|≥ 1.5, P1(t)≥ 0.9999) by TCDD, βNF, PCB126, and ICZ, respectively. Only ∼35% were differentially expressed by all 4 ligands in Hepa1c1c7 cells. In vivo, 661, 479, and 265 hepatic genes were differentially expressed following treatment with TCDD, βNF, and PCB126, respectively. Similar to Hepa1c1c7 cells, ≤ 34% of gene expression changes were common across all ligands. Principal components analysis identified time-dependent gene expression divergence. Comparisons of ligand-elicited expression between Hepa1c1c7 cells and mouse liver identified only 11 common gene expression changes across all ligands. Although metabolism may explain some ligand-specific gene expression changes, PCB126, βNF, and ICZ also elicited divergent expression compared to TCDD, suggestive of selective AhR modulation.
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Affiliation(s)
- Rance Nault
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA; Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824, USA
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Kopec AK, Boverhof DR, Nault R, Harkema JR, Tashiro C, Potter D, Sharratt B, Chittim B, Zacharewski TR. Toxicogenomic evaluation of long-term hepatic effects of TCDD in immature, ovariectomized C57BL/6 mice. Toxicol Sci 2013; 135:465-75. [PMID: 23864506 DOI: 10.1093/toxsci/kft156] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Acute exposure to hepatotoxic doses of 2,3,7,8-tetrachloro- dibenzo-p-dioxin (TCDD) in mice is characterized by differential gene expression that can be phenotypically anchored to elevated levels of serum alanine aminotransferase, increased relative liver weights, hepatic steatosis, inflammation, and hepatocellular necrosis. Unlike most studies that focus on acute exposure effects, this study evaluated the long-term effects of a single oral gavage of 30 μg/kg TCDD at 1, 4, 12, 24, 36, and 72 weeks postdose in ovariectomized C57BL/6 mice. Hepatic TCDD levels were almost completely eliminated by 24 weeks with a calculated half-life of 12 days. Hepatic gene expression analysis identified 395 unique differentially expressed genes between 1 and 12 weeks that decreased to ≤ 8 by 72 weeks, consistent with the minimal hepatic TCDD levels. Hepatic vacuolization, characteristic of short-term exposure, subsided by 4 weeks. Similarly, TCDD-elicited hepatic necrosis and inflammation dissipated by 1 week. Collectively, these results suggest that TCDD-elicited histologic and gene expression responses can be correlated to elevated hepatic TCDD levels, which, once eliminated, elicit minimal hepatic gene expression and histologic alterations.
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Affiliation(s)
- Anna K Kopec
- * Department of Biochemistry & Molecular Biology
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22
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Abstract
Bone microenvironment is a complex dynamic equilibrium between osteoclasts and osteoblasts and is modulated by a wide variety of hormones and osteocyte mediators secreted in response to physiological and pathological conditions. The rate of remodeling involves tight coupling and regulation of both cells population and is regulated by a wide variety of hormones and mediators such as parathyroid hormone, prostaglandins, thyroid hormone, sex steroids, etc. It is also well documented that bone formation is easily influenced by the exposure of osteoblasts and osteoclasts to chemical compounds. Currently, humans and wildlife animals are exposed to various environmental xenoestrogens typically at low doses. These compounds, known as endocrine disruptor chemicals (EDCs), can alter the systemic hormonal regulation of the bone remodeling process and the skeletal formation. This review highlights the effects of the EDCs on mammalian bone turnover and development providing a macro and molecular view of their action.
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Affiliation(s)
- Dimitrios Agas
- School of Biosciences and Biotechnology, University of Camerino, Via Gentile III da Varano, 62032 Camerino, MC, Italy.
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Lensu S, Tiittanen P, Lindén J, Tuomisto J, Pohjanvirta R. Effects of a single exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on macro- and microstructures of feeding and drinking in two differently TCDD-sensitive rat strains. Pharmacol Biochem Behav 2011; 99:487-99. [DOI: 10.1016/j.pbb.2011.04.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 04/19/2011] [Accepted: 04/27/2011] [Indexed: 11/25/2022]
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Sánchez-Martín FJ, Fernández-Salguero PM, Merino JM. Aryl hydrocarbon receptor-dependent induction of apoptosis by 2,3,7,8-tetrachlorodibenzo-p-dioxin in cerebellar granule cells from mouse. J Neurochem 2011; 118:153-62. [PMID: 21534955 DOI: 10.1111/j.1471-4159.2011.07291.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a prototypical environmental contaminant with neurotoxic properties that alters neurodevelopment and behavior. TCDD is a ligand of the aryl hydrocarbon receptor (AhR), which is a key signaling molecule to fully understand the toxic and carcinogenic properties of dioxin. Much effort is underway to unravel the molecular mechanisms and the signaling pathways involved in TCDD-induced neurotoxicity, and to define its molecular targets in neurons. We have used cerebellar granule cells (CGC) from wild-type (AhR+/+) and AhR-null (AhR-/-) mice to characterize the cell death that takes place in neurons after TCDD toxicity. TCDD induced cell death in CGC cultures from wild-type mice with an EC(50) of 127±21 nM. On the contrary, when CGC neurons from AhR-null mice were treated with TCDD no significant cell death was observed. The role of AhR in TCDD-induced death was further assessed by using the antagonists resveratrol and α-naphtoflavone, which readily protected against TCDD toxicity in AhR+/+ CGC cultures. AhR+/+ CGC cultures treated with TCDD showed nuclear fragmentation, DNA laddering, and increased caspase 3 activity, similarly to what was found by the use of staurosporine, a well-established inducer of apoptosis. Finally, the AhR pathway was active in CGC because TCDD could induce the expression of the target gene cytochrome P450 1A2 in AhR+/+ CGC cultures. All together these results support the hypothesis that TCDD toxicity in CGC neurons involves the AhR and that it takes place mainly through an apoptotic process. AhR could be then considered a novel target in neurotoxicity and neurodegeneration whose down-modulation could block certain xenobiotic-related adverse effects in CNS.
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Affiliation(s)
- Francisco J Sánchez-Martín
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
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Ishida T, Matsumoto Y, Takeda T, Koga T, Ishii Y, Yamada H. Distribution of 14C-2,3,7,8-tetrachlorodibenzo-p-dioxin to the brain and peripheral tissues of fetal rats and its comparison with adults. J Toxicol Sci 2011; 35:563-9. [PMID: 20686343 DOI: 10.2131/jts.35.563] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Some forms of reproductive and developmental toxicity by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) occur via initial damage to the pituitary synthesis of gonadotropins followed by the reduced expression of gonadal steroidogenic proteins. Defects in gonadotropin synthesis are highly specific to the periods from late fetal to early newborn stages. The reason for this specificity remains unknown. To address this issue, we compared the tissue distribution of 14C-TCDD between fetal and adult rats. In adult male rats, the major portion of TCDD given orally (approximately 33-42% dose) accumulated in the liver during day 1 and 5 after treatment. Very little TCDD (approximately 0.01% of the dose) distributed into the brain. A similar picture was also observed in TCDD-treated pregnant rats. The amount of TCDD transferred from a dam to the fetuses was extremely low (around 0.02% of the maternal dose/fetus) after 1 day of treatment. Male and female fetuses showed the same pattern in the brain distribution of TCDD. The rate of TCDD distribution to fetal brain, which was calculated on the basis of body burden to a fetus, was 100 times or more than that in adults. However, the brain content of TCDD (ng/g tissue) was comparable in fetuses and their dams, and adult males exposed to TCDD. These results suggest that although TCDD easily translocates to fetal brain, this is not a major mechanism for a fetal age-specific reduction in gonadotropin synthesis.
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Dioxins, the aryl hydrocarbon receptor and the central regulation of energy balance. Front Neuroendocrinol 2010; 31:452-78. [PMID: 20624415 DOI: 10.1016/j.yfrne.2010.07.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 06/15/2010] [Accepted: 07/05/2010] [Indexed: 01/03/2023]
Abstract
Dioxins are ubiquitous environmental contaminants that have attracted toxicological interest not only for the potential risk they pose to human health but also because of their unique mechanism of action. This mechanism involves a specific, phylogenetically old intracellular receptor (the aryl hydrocarbon receptor, AHR) which has recently proven to have an integral regulatory role in a number of physiological processes, but whose endogenous ligand is still elusive. A major acute impact of dioxins in laboratory animals is the wasting syndrome, which represents a puzzling and dramatic perturbation of the regulatory systems for energy balance. A single dose of the most potent dioxin, TCDD, can permanently readjust the defended body weight set-point level thus providing a potentially useful tool and model for physiological research. Recent evidence of response-selective modulation of AHR action by alternative ligands suggests further that even therapeutic implications might be possible in the future.
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Quantitative and statistical analysis of differences in sensitivity between Long–Evans and Han/Wistar rats following long-term exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Regul Toxicol Pharmacol 2010; 57:136-45. [DOI: 10.1016/j.yrtph.2010.01.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 01/21/2010] [Accepted: 01/21/2010] [Indexed: 01/27/2023]
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2,3,7,8-Tetrachlorodibenzo-p-dioxin induces apoptosis in neural growth factor (NGF)-differentiated pheochromocytoma PC12 cells. Neurotoxicology 2010; 31:267-76. [PMID: 20302886 DOI: 10.1016/j.neuro.2010.03.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 03/10/2010] [Accepted: 03/10/2010] [Indexed: 01/01/2023]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent toxicant that alters normal brain development and produces cognitive disability and motor dysfunction. However, after decades of intense study, the molecular mechanisms of TCDD-induced neurotoxicity, the signaling pathways involved and its molecular targets in neurons still remain unknown. TCDD acts as an exogenous ligand of the aryl hydrocarbon receptor (AhR) that becomes a key signaling molecule in the regulation of the toxic and carcinogenic properties of TCDD. We have used NGF-differentiated pheochromocytoma (dPC12) cells to determine the type of cell death that takes place by TCDD toxicity. TCDD induced cell death in dPC12 cultures with an EC(50) of 218+/-24 nM, similar to that obtained in undifferentiated PC12 cells, 171+/-31 nM. Nuclear fragmentation was observed after TCDD incubation in parallel to an increase in caspase-3 activity. Staurosporine, which readily induced apoptosis in dPC12 cells, showed a similar increase in caspase-3 activity and the characteristic pattern of nuclear fragmentation. Flow cytometry measurements showed that dPC12 cells in the presence of TCDD were positive for annexin V labeling but negative for propidium iodide staining. In addition, TCDD increased the area of the peak corresponding to hypodiploid (apoptotic) DNA content. All together these results support the hypothesis that TCDD toxicity in dPC12 cells takes place mainly through an apoptotic process.
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Sorg O, Zennegg M, Schmid P, Fedosyuk R, Valikhnovskyi R, Gaide O, Kniazevych V, Saurat JH. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) poisoning in Victor Yushchenko: identification and measurement of TCDD metabolites. Lancet 2009; 374:1179-85. [PMID: 19660807 DOI: 10.1016/s0140-6736(09)60912-0] [Citation(s) in RCA: 127] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BACKGROUND 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has a long half-life of 5-10 years in human beings as a result of its high lipophilicity, and little or no metabolism. We monitored TCDD, its form, distribution, and elimination in Victor Yushchenko after he presented with severe poisoning. METHODS In late December, 2004, a patient presented with TCDD poisoning; the levels in his blood serum (108000 pg/g lipid weight) were more than 50 000-fold greater than those in the general population. We identified TCDD and its metabolites, and monitored their levels for 3 years using gas chromatography and high-resolution mass spectrometry in samples of blood serum, adipose tissue, faeces, skin, urine, and sweat, after they were extracted and cleaned with different organic solvents. FINDINGS The amount of unmodified TCDD in the samples that were analysed accounted for about 60% of TCDD eliminated from the body during the same period. Two TCDD metabolites-2,3,7-trichloro-8-hydroxydibenzo-p-dioxin and 1,3,7,8-tetrachloro-2-hydroxydibenzo-p-dioxin-were identified in the faeces, blood serum, and urine. The faeces contained the highest concentration of TCDD metabolites, and were the main route of elimination. Altogether, the different routes of elimination of TCDD and its metabolites accounted for 98% of the loss of the toxin from the body. The half-life of TCDD in our patient was 15.4 months. INTERPRETATION This case of poisoning with TCDD suggests that the design of methods for routine assessment of TCDD metabolites in human beings should be a main aim of TCDD research in the metabolomic era. FUNDING University of Geneva Dermatology Fund, and Swiss Centre for Applied Human Toxicology.
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Affiliation(s)
- O Sorg
- Dermato-Toxicology, Swiss Centre for Applied Human Toxicology, and Department of Dermatology, University Hospital, Geneva, Switzerland
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Pohjanvirta R. Transgenic mouse lines expressing rat AH receptor variants — A new animal model for research on AH receptor function and dioxin toxicity mechanisms. Toxicol Appl Pharmacol 2009; 236:166-82. [DOI: 10.1016/j.taap.2009.01.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Revised: 01/09/2009] [Accepted: 01/12/2009] [Indexed: 11/25/2022]
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31
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Shimba S, Watabe Y. Crosstalk between the AHR signaling pathway and circadian rhythm. Biochem Pharmacol 2009; 77:560-5. [DOI: 10.1016/j.bcp.2008.09.040] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 09/25/2008] [Accepted: 09/26/2008] [Indexed: 01/28/2023]
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2,3,7,8-TCDD neurotoxicity in neuroblastoma cells is caused by increased oxidative stress, intracellular calcium levels, and tau phosphorylation. Toxicology 2009; 255:65-71. [DOI: 10.1016/j.tox.2008.10.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 10/07/2008] [Accepted: 10/07/2008] [Indexed: 12/22/2022]
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Mukai M, Lin TM, Peterson RE, Cooke PS, Tischkau SA. Behavioral rhythmicity of mice lacking AhR and attenuation of light-induced phase shift by 2,3,7,8-tetrachlorodibenzo-p-dioxin. J Biol Rhythms 2008; 23:200-10. [PMID: 18487412 DOI: 10.1177/0748730408316022] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Transcription factors belonging to the Per/Arnt/Sim (PAS) domain family are highly conserved and many are involved in circadian rhythm regulation. One member of this family, aryl hydrocarbon receptor (AhR), is an orphan receptor whose physiological role is unknown. Recent findings have led to the hypothesis that AhR has a role in circadian rhythm, which is the focus of the present investigation. First, time-of-day-dependent mRNA expression of AhR and its signaling target, cytochrome p4501A1 (Cyp1a1), was determined in C57BL/6J mice by quantitative RT-PCR. Circadian expression of AhR and Cyp1a1 was observed both in the suprachiasmatic nucleus (SCN) and liver. Next, the circadian phenotype of mice lacking AhR (AhRKO) was investigated using behavioral monitoring. Intact AhRKO mice had robust circadian rhythmicity with a similar tau under constant conditions compared to wild-type mice, but a significant difference in tau was observed between genotypes in ovariectomized female mice. Time to reentrainment following 6-h advances or delays of the light/dark cycle was not significantly different between genotypes. However, mice exposed to the AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 1 microg/kg of body weight) displayed decreased phase shifts in response to light and had altered expression of Per1 and Bmal1. These results suggest that chronic activation of AhR may affect the ability of the circadian timekeeping system to adjust to alterations in environmental lighting by affecting canonical clock genes. Further studies are necessary to decipher the mechanism of how AhR agonists could disrupt light-induced phase shifts. If AhR does have a role in circadian rhythm, it may share redundant roles with other PAS domain proteins and/or the role of AhR may not be exhibited in the behavioral activity rhythm, but could be important elsewhere in the peripheral circadian system.
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Affiliation(s)
- Motoko Mukai
- Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois, Urbana, Illinois, USA
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de Waard WJ, Aarts JMMJG, Peijnenburg AACM, Baykus H, Talsma E, Punt A, de Kok TMCM, van Schooten FJ, Hoogenboom LAP. Gene expression profiling in Caco-2 human colon cells exposed to TCDD, benzo[a]pyrene, and natural Ah receptor agonists from cruciferous vegetables and citrus fruits. Toxicol In Vitro 2007; 22:396-410. [PMID: 18061397 DOI: 10.1016/j.tiv.2007.10.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Revised: 10/18/2007] [Accepted: 10/18/2007] [Indexed: 10/22/2022]
Abstract
Cruciferous vegetables and citrus fruits are reported to possess health-beneficial properties, but also have been shown to contain natural aryl hydrocarbon receptor (AhR) agonists (NAhRAs). Binding to the AhR is widely assumed to activate the main pathway by which dioxins, like 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exert their toxicity. To establish whether or not activation of the AhR pathway by NAhRAs and dioxin-like substances results in similar cellular responses, gene expression profiles induced in Caco-2 cells were studied using microarray analysis. Cells were exposed to indolo[3,2-b]carbazole (ICZ), an acid reaction product from cruciferous vegetables, and to extracts of citrus pulp and grapefruit juice. Gene expression profiles induced by these NAhRAs were compared to those of the xenobiotic AhR agonists TCDD and benzo[a]pyrene (B[a]P). Over 20 genes were found more than 1.5 times up- or down-regulated by TCDD, and the expression of most of these genes was modulated in the same direction and to a similar extent by B[a]P and the NAhRAs. Results were confirmed by RT-PCR, and many of these genes may be involved in dioxin-related toxic effects. In conclusion, this in vitro study showed similar effects induced by NAhRAs, TCDD and B[a]P at the transcriptome level in a human intestinal cell line.
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Affiliation(s)
- W J de Waard
- Department of Health Risk Analysis and Toxicology, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
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Lensu S, Miettinen R, Pohjanvirta R, Lindén J, Tuomisto J. Assessment by c-Fos immunostaining of changes in brain neural activity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and leptin in rats. Basic Clin Pharmacol Toxicol 2006; 98:363-71. [PMID: 16623859 DOI: 10.1111/j.1742-7843.2006.pto_276.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes multiple effects in laboratory animals. One of these is a wasting syndrome (a dramatic loss of body weight over 2-5 weeks) whose mechanism is still largely unknown. We exploited the over 1000 times difference in TCDD sensitivity between Long-Evans (Turku/AB); (L-E) and Han/Wistar (Kuopio); (H/W) rats to reveal brain areas that might be activated by a single dose of TCDD (50 microg/kg) given 24 hr previously. Leptin (1.3 mg/kg intraperitoneally 2 hr before tissue harvest) was used as a reference compound, as its neural pathway for decreasing food intake in the control of energy homeostasis is fairly well known. Serial sections of the brains were immunostained with an antibody for the activity marker c-Fos, and selected areas -- primarily in the hypothalamus -- were analysed with a computer-assisted microscope. Given alone, TCDD did not elicit any major alterations in c-Fos protein levels in the hypothalamic nuclei at the early time-point studied (24 hr after administration), neither in pooled data nor in individual strains. The control substance leptin proved that the method is valid as it increased the number of c-Fos-immunopositive cells in the hypothalamic ventromedial and arcuate nuclei. Although the present findings are not suggestive of a primary role for the hypothalamus in the wasting syndrome, a time-course study covering also the feeding-active dark hours is warranted for their verification.
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Affiliation(s)
- Sanna Lensu
- National Public Health Institute, Department of Environmental Health, P.O.B. 95, FI-70701 Kuopio, Finland.
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Emond C, Birnbaum LS, DeVito MJ. Use of a physiologically based pharmacokinetic model for rats to study the influence of body fat mass and induction of CYP1A2 on the pharmacokinetics of TCDD. ENVIRONMENTAL HEALTH PERSPECTIVES 2006; 114:1394-400. [PMID: 16966094 PMCID: PMC1570044 DOI: 10.1289/ehp.8805] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly lipophilic chemical that distributes into adipose tissue, especially at low doses. However, at high doses TCDD sequesters in liver because it induces cytochrome P450 1A2 (CYP1A2) that binds TCDD. A physiologically based pharmacokinetic (PBPK) model was developed that included an inducible elimination rate of TCDD in the Sprague-Dawley rat. Objectives of this work were to characterize the influence of induction of CYP1A2 and adipose tissue mass fraction on the terminal elimination half-life (t1/2) of TCDD using this PBPK model. When the model assumes a fixed elimination of TCDD, t1/2 increases with dose, due to hepatic sequestration. Because experimental data indicate that the t1/2 of TCDD decreases with dose, the model was modified to include an inducible elimination rate. The PBPK model was then used to compare the t1/2 after an increase of adipose tissue mass fraction from 6.9 to 70%. The model suggests that at low exposures, increasing adipose tissue mass increases the terminal t1/2. However, at higher exposures, as CYP1A2 is induced, the relationship between adipose tissue mass and t1/2 reaches a plateau. This demonstrates that an inducible elimination rate is needed in a PBPK model in order to describe the pharmacokinetics of TCDD. At low exposures these models are more sensitive to parameters related to partitioning into adipose tissue.
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Affiliation(s)
- Claude Emond
- National Research Council, National Academy of Sciences, Washington, DC, USA
- National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
- Environmental and Occupational Health Department, Medicine Faculty, University of Montreal, Montreal, Quebec, Canada
| | - Linda S. Birnbaum
- National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
| | - Michael J. DeVito
- National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
- Address correspondence to M.J. DeVito, U.S. EPA, National Health and Environmental Effects Research Laboratory, Environmental Toxicology Division, Pharmacokinetics Branch, Mail Drop B143-05, Research Triangle Park, NC 27711 USA. Telephone: (919) 541-0061. Fax: (919) 541-4284. E-mail:
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Haavisto TE, Myllymäki SA, Adamsson NA, Brokken LJS, Viluksela M, Toppari J, Paranko J. The effects of maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin on testicular steroidogenesis in infantile male rats. ACTA ACUST UNITED AC 2006; 29:313-22. [PMID: 16533353 DOI: 10.1111/j.1365-2605.2005.00568.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Exposure of adult male animals to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) decreases serum androgen concentrations. Reduction in androgen levels after maternal exposure has also been reported, but these results have not been reproduced. We have earlier shown that TCDD stimulates rather than inhibits testosterone synthesis in the prenatal rat testis. The aim of the present study was to elucidate in utero-induced effects of TCDD on testicular steroidogenesis in the 14-day-old infant rats. At that time the foetal Leydig cell population is still the prevailing source of androgens. Pregnant Sprague-Dawley dams were given a single oral dose of TCDD (0, 0.04, 0.2, or 1.0 microg/kg) on day 13 of pregnancy. On postnatal day 14, the body weight of male offspring was reduced after exposure to 1.0 microg/kg TCDD (from 33.9 +/- 1.66 g to 31.6 +/- 2.67 g). Relative testis weight, plasma testosterone, luteinizing hormone and follicle-stimulating hormone levels remained unaltered in all exposure groups. Moreover, in ex vivo incubations, testosterone and cAMP production was not affected. StAR protein level in the freshly isolated testes was increased in the 0.2 microg/kg group, and seminiferous cord diameter in the 0.04 microg/kg group. The present study confirms our earlier findings in in utero TCDD-exposed foetal testis indicating that maternal TCDD exposure does not negatively influence the developmental testosterone production of foetal type Leydig cells in rats.
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Affiliation(s)
- T E Haavisto
- Department of Biology, Laboratory of Animal Physiology, University of Turku, Turku, Finland
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38
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Hassoun EA, Vodhanel J, Holden B, Abushaban A. The effects of ellagic acid and vitamin E succinate on antioxidant enzymes activities and glutathione levels in different brain regions of rats after subchronic exposure to TCDD. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2006; 69:381-93. [PMID: 16455616 DOI: 10.1080/15287390500246431] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Ellagic acid (EA) and vitamin E succinate (VES) were previously shown to protect against 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD)-induced reactive oxygen species (ROS) overproduction in certain brain regions of rats after subchronic exposure. The current study was designed to assess the modulation of antioxidant enzyme activities and glutathione (GSH) levels as protective measures for VES and EA against TCDD-induced ROS overproduction in four regions of rat brain. TCDD was administered to groups of rats at a daily dose of 46 ng/kg for 90 d. EA and VES were administered to some other groups of rats either alone or simultaneously with TCDD, every other day for 90 d. At the end of the treatment period, animals were sacrificed and brain regions were dissected, including cerebral cortex (Cc), hippocampus (H), cerebellum (C), and brainstem (Bs), for assay of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities, as well as GSH levels. While treatment of rats with VES alone or in combination with TCDD resulted in significant increases in SOD and CAT activities in different brain regions, treatment with EA resulted in a significant rise in total GSH levels and GSH-Px activity in those regions. Results may suggest antioxidant modulation by VES and EA as a mechanism for the previously observed protection by these compounds against TCDD-induced ROS overproduction in brain. Data also indicate there are two different pathways in the protection provided by the two antioxidants.
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Affiliation(s)
- Ezdihar A Hassoun
- College of Pharmacy, University of Toledo, Toledo, Ohio 43606,, USA.
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Korkalainen M, Lindén J, Tuomisto J, Pohjanvirta R. Effect of TCDD on mRNA expression of genes encoding bHLH/PAS proteins in rat hypothalamus. Toxicology 2005; 208:1-11. [PMID: 15664428 DOI: 10.1016/j.tox.2004.11.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Revised: 11/01/2004] [Accepted: 11/01/2004] [Indexed: 10/26/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) brings about a wide variety of toxic and biochemical effects via an AH receptor (AHR)-mediated signalling pathway. Wasting syndrome and acute lethality are TCDD-induced endpoints showing a striking sensitivity difference between two rat strains, TCDD-sensitive Long-Evans (Turku/AB) (L-E) and TCDD-resistant Han/Wistar (Kuopio) (H/W). These rat strains were used to study hypothalamic effects of TCDD on expression of genes encoding AHR-regulated bHLH/PAS proteins potentially involved in molecular pathogenesis of the wasting syndrome. In addition, two well-established target genes of TCDD, CYP1A1 and CYP1A2 were also examined. Quantitative RT-PCR was used to measure mRNA levels in hypothalamus, which is a major center of food intake and body weight regulation. At both 6 and 96 h after a single dose of 50 microg/kg TCDD, significant elevations were found in mRNA levels of AHR repressor (AHRR), CYP1A1 and CYP1A2, but not those of AHR, ARNT or ARNT2. Likewise, TCDD (100 microg/kg) did not alter the expression of SIM1, implicated in the suppressive impact of TCDD on food intake, nor that of PER2, involved in regulation of circadian rhythms. Differences between H/W and L-E rats appeared in constitutive levels of AHR and ARNT and in TCDD-induced levels of CYP1A2, AHRR, AHR and ARNT, which all were about two- to four-fold lower in H/W rats. Thus, although the changes found do not account for the wasting syndrome, expression of all principal genes of the AHR-signalling pathway in rat hypothalamus make it a candidate target for TCDD.
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Affiliation(s)
- Merja Korkalainen
- National Public Health Institute, Department of Environmental Health, P.O. Box 95, FIN-70701 Kuopio, Finland.
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Li LA, Wang PW. PCB126 induces differential changes in androgen, cortisol, and aldosterone biosynthesis in human adrenocortical H295R cells. Toxicol Sci 2005; 85:530-40. [PMID: 15703266 DOI: 10.1093/toxsci/kfi105] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dioxins and polychlorinated biphenyls (PCBs) have been shown to accumulate in the adrenal glands when incorporated into the body. However, the impacts of exposure on adrenal steroidogenesis have not been thoroughly investigated. In this study, we demonstrated that dioxin-like PCB126 altered androgen, cortisol, and aldosterone biosynthesis differentially in human adrenocortical H295R cells. PCB126 diminished basal and cAMP-induced androstenedione production as well as CYP17 mRNA expression in a dose-dependent and time-dependent manner. The CYP17 repression was accompanied with decreases in the encoded 17 alpha-hydroxylase and 17,20-lyase activities, particularly the latter. In contrast, high concentrations of PCB126 stimulated basal cortisol and aldosterone biosynthesis, including induction of CYP21B, CYP11B1, and CYP11B2 mRNA expression and elevation of the conversion of cortisol from 17-OH-progesterone and aldosterone from progesterone. cAMP abolished the positive effect of PCB126 on cortisol synthesis, while it synergistically enhanced PCB126 stimulation on CYP11B2 expression and aldosterone production. It seemed likely that the downregulation of CYP21B caused by the combination of PCB126 and cAMP counteracted the CYP11B1 induction stimulated by the co-treatment. In addition, high concentrations of PCB126 might sensitize the regulation of adrenocorticotropin (ACTH) on the adrenocortical cells by increasing ACTH receptor levels. Because adrenal steroids have profound influences on glucose tolerance, insulin sensitivity, lipid metabolism, obesity, vascular function, and cardiac remodeling, this article also discusses the potential association of the detected adrenocortical alterations with increased diabetic and cardiovascular risk found among highly exposed people.
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Affiliation(s)
- Lih-Ann Li
- Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Kaohsiung 807, Taiwan, Republic of China.
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Fetissov SO, Huang P, Zhang Q, Mimura J, Fujii-Kuriyama Y, Rannug A, Hökfelt T, Ceccatelli S. Expression of hypothalamic neuropeptides after acute TCDD treatment and distribution of Ah receptor repressor. ACTA ACUST UNITED AC 2004; 119:113-24. [PMID: 15093705 DOI: 10.1016/j.regpep.2004.01.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2003] [Revised: 01/20/2004] [Accepted: 01/29/2004] [Indexed: 11/21/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant originating from industrial waste. At sublethal concentrations it induces anorexia and weight loss as part of the so-called wasting syndrome. To gain insight into its possible underlying mechanisms, mRNA expression of some key hypothalamic neuropeptides involved in the regulation of body weight was studied using in situ hybridization histochemistry in adult male Sprague-Dawley rats 6 days after single oral administration of TCDD (15 microg/kg) and in age-paired control rats. In TCDD-treated rats which displayed a decrease in body weight gain vs. controls, arcuate nucleus expression of neuropeptide Y (NPY), proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) mRNA was increased. In the lateral hypothalamic area, melanin-concentrating hormone (MCH) mRNA expression was also increased, while levels of CART and orexin/hypocretin mRNA were not significantly changed. Since TCDD is known to bind to the aryl hydrocarbon receptor (AhR), the distribution of the AhR repressor (AhRR), which is co-expressed with AhR in the same cells, was studied by immunohistochemistry in the mouse hypothalamus using mouse AhRR specific antiserum. AhRR immunoreactivity was present in the nuclei of neurons found in all main hypothalamic groups including NPY, CART, MCH and orexin/hypocretin neurons. Xenobiotic response elements were found in these neuropeptide genes with the exception of MCH. Thus changes in expression of orexigenic and anorexigenic neuropeptides after TCDD treatment may help to explain the occurrence of the TCDD-induced weight loss, which may be either directly or indirectly related to the effects of TCDD on neuropeptide expression.
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Affiliation(s)
- Sergueï O Fetissov
- Department of Neuroscience B3:4, Karolinska Institutet, Retzius väg. 8, S-171 77 Stockholm, Sweden.
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Simanainen U, Tuomisto JT, Pohjanvirta R, Syrjälä P, Tuomisto J, Viluksela M. Postnatal development of resistance to short-term high-dose toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in TCDD-resistant and -semiresistant rats. Toxicol Appl Pharmacol 2004; 196:11-9. [PMID: 15050403 DOI: 10.1016/j.taap.2003.11.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2003] [Accepted: 11/17/2003] [Indexed: 11/22/2022]
Abstract
Despite great interspecies differences in adult 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) sensitivity, the toxic potency of TCDD is similar across species in fetal mortality. Han/Wistar (Kuopio; H/W) rats are exceptionally resistant to acute toxicity of TCDD, but show sensitivity to embryotoxicity and teratogenicity. The resistance of adult H/W rats to acute TCDD toxicity is based on a point mutation in the transactivation domain of the aryl hydrocarbon receptor (AHR) and to an unknown gene "B". This study investigated the time course of postnatal development of resistance to TCDD and the significance of genotypic variation in resistance development. H/W, line A (a new line with the H/W-type mutated AHR), and line B rats (a line with normal AHR but moderately resistant because of gene "B") were exposed to a single dose of TCDD 2-56 days after birth. H/W and line A rats received 1000 microg/kg; male and female B rats received 200 and 100 microg/kg, respectively. Survival was monitored for 42 days. Interestingly, although TCDD ceased growth and weight gain in all TCDD groups, the younger dosed animals did not seem to reach the body weight of the older dosed animals even in 100 days. The survival results after 42 days showed that line A rats are fairly resistant to TCDD immediately after birth, and their full TCDD resistance develops during the first week of life. The moderate resistance of line B rats develops approximately at the time of weaning. This difference in the time course of resistance development suggests that there are basic differences in pathways mediating resistance in lines A and B rats.
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Affiliation(s)
- Ulla Simanainen
- Laboratory of Toxicology, Department of Environmental Health, National Public Health Institute, FIN-70701 Kuopio, Finland.
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Hassoun EA, Vodhanel J, Abushaban A. The modulatory effects of ellagic acid and vitamin E succinate on TCDD-induced oxidative stress in different brain regions of rats after subchronic exposure. J Biochem Mol Toxicol 2004; 18:196-203. [PMID: 15452880 DOI: 10.1002/jbt.20030] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The effects of ellagic acid (EA) and vitamin E succinate (VES) on 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced oxidative stress in different brain regions of rats have been studied after subchronic exposure to the compounds. TCDD was administered to groups of rats at a dose of 46 ng/kg/day for 90 days. EA and VES were administered to groups of rats, either separately or simultaneously with TCDD, every other day for 90 days. At the end of the treatment period, animals were sacrificed and brains were dissected to cerebral cortex (Cc), hippocampus (H), cerebellum (C), and brain stem (Bs), and were assayed for production of superoxide anion (SA), lipid peroxidation (LP), and DNA single-strand breaks (SSBs). While TCDD administration to rats resulted in significant production of SA, LP, and DNA SSBs in Cc and H, simultaneous administration of VES or EA with the xenobiotics resulted in significant protection against those effects. The results also indicate that VES provided a better protyection against TCDD-induced effects in brains when compared with EA.
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Hassoun EA, Al-Ghafri M, Abushaban A. The role of antioxidant enzymes in TCDD-induced oxidative stress in various brain regions of rats after subchronic exposure. Free Radic Biol Med 2003; 35:1028-36. [PMID: 14572606 DOI: 10.1016/s0891-5849(03)00458-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The induction of oxidative stress by TCDD in various brain regions of rats has been investigated after subchronic exposure. TCDD was administered by gavage to female Sprague-Dawley rats at daily doses of 0, 10, 22, and 46 ng/kg for 13 weeks. The brains were dissected to cerebral cortex (Cc), hippocampus (H), cerebellum (C), and brain stem (Bs); the production of superoxide anion (SA) and lipid peroxides and the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase, and glutathione peroxidase (GSH-Px) were determined in those regions. TCDD caused dose-dependent increases in the production of SA and lipid peroxidation in Cc and H and those were associated with dose-dependent suppressions of SOD. While a TCDD dose of 10 ng/kg/d resulted in significant increases in catalase and GSH-Px activities in Cc and H, doses of 22 and 46 ng/kg/d resulted in dose-dependent suppressions of these two enzymes in the same regions. In the C and Bs, TCDD treatment did not result in significant production of SA and lipid peroxidation but it resulted in dose-dependent increases in the activities of various antioxidant enzymes. These results suggest that Cc and H are vulnerable to TCDD-induced oxidative stress after subchronic exposure, and that C and Bs are protected against that effect.
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Hilscherova K, Blankenship AL, Nie M, Coady KK, Upham BL, Trosko JE, Giesy JP. Oxidative stress in liver and brain of the hatchling chicken (Gallus domesticus) following in ovo injection with TCDD. Comp Biochem Physiol C Toxicol Pharmacol 2003; 136:29-45. [PMID: 14522597 DOI: 10.1016/s1532-0456(03)00167-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was injected into chicken eggs prior to incubation to study possible mechanisms of toxicity and teratogenicity. One of the suggested mechanisms of teratogenicity is oxidative stress. Eggs were injected simultaneously with TCDD and cotreatment compounds in an attempt to prevent oxidative stress or to block cytochrome P450 activity. Indicators of oxidative stress were assessed in livers and brains of hatchling chicks. In ovo, exposure to TCDD caused significant effects on indicators of oxidative stress in liver, but not in the brain of the hatchling chicks. TCDD did not significantly affect superoxide production. In liver, TCDD treatment caused a decrease in glutathione content and glutathione peroxidase activity and an increase in the ratio of oxidized to reduced glutathione. TCDD increased the susceptibility to lipid peroxidation and oxidative DNA damage in liver. Administration of the antioxidants vitamin E and vitamin A provided partial protection against TCDD-induced oxidative stress in liver. The lack of effect of TCDD in chicken brain could be due to the low cytochrome P4501A activity in this tissue and little accumulation of TCDD in brain compared to liver. Phenytoin, a known inducer of oxidative stress, caused a decrease in glutathione content and an increase in susceptibility to lipid peroxidation in both liver and brain and increased oxidative DNA damage in brain. Responsiveness varied among individual animals, but measures of the oxidative stress were correlated.
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Affiliation(s)
- K Hilscherova
- Department of Environmental Chemistry and Ecotoxicology, Faculty of Science, Masaryk University, Brno, Czech Republic
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46
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Hassoun EA, Wang H, Abushaban A, Stohs SJ. Induction of oxidative stress in the tissues of rats after chronic exposure to TCDD, 2,3,4,7,8-pentachlorodibenzofuran, and 3,3',4,4',5-pentachlorobiphenyl. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2002; 65:825-42. [PMID: 12079609 DOI: 10.1080/00984100290071054] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The abilities of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), 3,3',4,4',5-pentachlorobiphenyl (PCB126), and mixtures of these xenobiotics (toxic equivalents, TEQs) to induce oxidative stress in hepatic and brain tissues of rats have been investigated after chronic (30 wk) exposure to these congeners. TCDD, PeCDF, PCB126, and TEQs were administered daily to groups of rats at doses that corresponded to their toxic equivalency factors (TEFs), and the biomarkers of oxidative stress, including the production of superoxide anion, lipid peroxidation, and DNA single-strand breaks (SSBs), were determined in hepatic and brain tissues at the end of the exposure period. The three chemicals caused similar dose-dependent increases in the production of superoxide anion, lipid peroxidation, and DNA SSBs, which plateaued at certain dose ranges, followed by secondary increases at the higher dose levels. Similar effects were also produced by the TEQs; however, the dose-dependent increases in the biomarkers of oxidative stress were continuous and never achieved plateau levels. Except for PCB126, where statistical analyses revealed greater productions of superoxide anion and lipid peroxidation in brain tissues as compared with hepatic tissues, no significant differences were revealed between the two tissues in response to the other xenobiotics or the TEQs. Nonsignificant differences were also revealed when comparing the effects induced by the TEQs with those induced by the individual chemicals.
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Cheng SB, Kuchiiwa S, Nagatomo I, Akasaki Y, Uchida M, Tominaga M, Hashiguchi W, Kuchiiwa T, Nakagawa S. 2,3,7,8-Tetrachlorodibenzo-p-dioxin treatment induces c-Fos expression in the forebrain of the Long-Evans rat. Brain Res 2002; 931:176-80. [PMID: 11897103 DOI: 10.1016/s0006-8993(02)02257-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is one of the most toxic environmental pollutants. In the present study, we examined c-Fos expression in the central nervous system (CNS) after administration of a lethal dose of TCDD to the adult Long-Evans rat to clarify if the CNS participates in TCDD-induced intoxication. A single dose of TCDD (dissolved in olive oil, 50 microg/kg) or olive oil alone was administered to the rats by gavage. Animals were allowed to survive for 1 day to 5 weeks. Three days after the administration, a significantly large number of Fos-immunopositive cells were found in the hypothalamus (i.e. dorsomedial hypothalamic nucleus, paraventricular hypothalamic nucleus, medial preoptic nucleus), central amygdaloid nucleus and bed nucleus of the stria terminalis. These results suggest that some TCDD toxicity may be induced by its direct action on the CNS.
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Affiliation(s)
- Shi-Bin Cheng
- Department of Anatomy, Faculty of Medicine, Kagoshima University, Sakuragaoka 8-35-1, 890-8520, Japan
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Jämsä T, Viluksela M, Tuomisto JT, Tuomisto J, Tuukkanen J. Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on bone in two rat strains with different aryl hydrocarbon receptor structures. J Bone Miner Res 2001; 16:1812-20. [PMID: 11585345 DOI: 10.1359/jbmr.2001.16.10.1812] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Polychlorinated dibenzo-p-dioxins (PCDDs) are highly toxic environmental contaminants, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent dioxin. Here, we studied the effects of TCDD on bone. Two rat strains, Han/Wistar (H/W) and Long-Evans (L-E), were used because they exhibit a 1000-fold sensitivity difference in acute lethality of TCDD, which difference is related to the aryl hydrocarbon receptor (AHR). TCDD inhibited the tibial growth dose dependently, the effect being manifested at lower doses in the more sensitive L-E strain. In H/W rats the effect of TCDD was seen only at the high dose of 170 microg/kg (p < 0.05), whereas in the sensitive L-E rats a significant reduction of bone growth was already seen at 1.7 microg/kg (p < 0.01). This reduction was caused by the smaller tibial size because the diaphyseal bone mineral density (BMD) did not change. The three-point bending breaking force of the tibia was significantly reduced in H/W rats at 170 microg/kg (p < 0.05), but tibial stiffness was lower already at the dose of 17 microg/kg (p < 0.05). In the sensitive L-E strain, both breaking force and stiffness were reduced at the dose of 17 microg/kg (p < 0.001). These results indicate that TCDD dose-dependently interferes with bone growth, modeling, and mechanical strength. The altered transactivation domain of AHR is associated with a lower sensitivity of bone to TCDD in H/W rats, suggesting that AHR plays a role in modulating the effects of dioxins on bone.
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Affiliation(s)
- T Jämsä
- Department of Medical Technology, University of Oulu, Finland
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Michalek JE, Ketchum NS, Longnecker MP. Serum dioxin and hepatic abnormalities in veterans of Operation Ranch Hand. Ann Epidemiol 2001; 11:304-11. [PMID: 11399444 DOI: 10.1016/s1047-2797(00)00218-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE We studied hepatic abnormalities and indices of hepatic function in relation to exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) in veterans of Operation Ranch Hand, the Air Force unit responsible for the aerial spraying of herbicides in Vietnam from 1962 to 1971. METHODS The prevalence of ever having liver disease through March 1993, and level of alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltransferase (GGT), lactic dehydrogenase (LDH), alkaline phosphatase, and total bilirubin were examined according to serum dioxin levels. RESULTS We found an increased risk of "other liver disorders" among veterans with the highest dioxin levels [adjusted odds ratio (OR) = 1.6, 95% confidence interval (CI) 1.2 to 2.1], due primarily to increased transaminases or LDH (adjusted OR = 2.7, 95% CI 1.4 to 5.1) and to other nonspecific liver abnormalities (adjusted OR = 1.4, 95% CI 1.0 to 2.0). CONCLUSIONS Whether the associations observed were causal is unclear from these data.
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Affiliation(s)
- J E Michalek
- Air Force Research Laboratory, Brooks AFB, TX, USA
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Haavisto T, Nurmela K, Pohjanvirta R, Huuskonen H, El-Gehani F, Paranko J. Prenatal testosterone and luteinizing hormone levels in male rats exposed during pregnancy to 2,3,7,8-tetrachlorodibenzo-p-dioxin and diethylstilbestrol. Mol Cell Endocrinol 2001; 178:169-79. [PMID: 11403907 DOI: 10.1016/s0303-7207(01)00425-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Changes in the perinatal testosterone surge have been related to demasculinization of the central nervous system and androgen-dependent growth of the reproductive organs in male mammals. Earlier reports suggest that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) interferes with androgen production, but the perinatal effects have remained elusive. In the present study we explored in utero-effects of TCDD (0.05, 0.1, 0.5, and 1.0 microg/kg), introduced on day 13.5 of pregnancy, on prenatal (day 19.5 post-conception [p.c.]) testosterone (T) surge and pituitary luteinizing hormone (LH) production in TCDD-resistant Han/Wistar (H/W) and TCDD-sensitive Long-Evans (L-E) rats. To elucidate estrogenic effects on T and LH production, Sprague-Dawley (S-D) fetuses with previously known DES-sensitivity were exposed in utero to diethylstilbestrol (DES, 100-300 microg/kg) on days 13.5, 15.5, and 17.5 p.c. For comparison, H/W fetuses that responded to TCDD treatments were exposed to DES at concentration of 100 microg/kg. It was found that TCDD has a stimulatory effect on testicular T synthesis in the H/W fetuses and that their circulating T concentrations increased significantly. The effect was not seen in the inbred L-E fetuses, which throughout the study showed considerably low testicular T levels. Pituitary LH concentrations also increased in the H/W fetuses exposed to TCDD. Effects of TCDD (1.0 microg/kg) in the H/W fetuses could be confirmed in vitro by human chorionic gonadotropin (hCG) stimulation assay showing the highest response rate in the TCDD exposed testes. Stimulation of cyclic AMP (adenosine-3', 5'-cyclic monophosphate[cAMP]) production was not considerably altered by in utero TCDD exposure. A significant depression in testicular and plasma T content was seen in the DES-exposed S-D and H/W fetuses, but pituitary LH levels did not alter considerably. In the presence of hCG, DES-exposed testes showed lower in vitro T and cAMP production rates compared to the untreated testes. TCDD (1.0 microg/kg) increased and DES decreased the male body weight gain, but the changes were not sex-dependent. It is concluded that TCDD may increase the amplitude of the prenatal testosterone surge in male rats by stimulating pituitary LH production and enhancing the sensitivity of the fetal testis to LH. DES, on the contrary, apparently impairs testicular steroidogenesis and pituitary function.
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Affiliation(s)
- T Haavisto
- Laboratory of Animal Physiology, Department of Biology, University of Turku, 20014, Turku, Finland
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