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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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Rannug A, Rannug U. The tryptophan derivative 6-formylindolo[3,2-b]carbazole, FICZ, a dynamic mediator of endogenous aryl hydrocarbon receptor signaling, balances cell growth and differentiation. Crit Rev Toxicol 2018; 48:555-574. [PMID: 30226107 DOI: 10.1080/10408444.2018.1493086] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The aryl hydrocarbon receptor (AHR) is not essential to survival, but does act as a key regulator of many normal physiological events. The role of this receptor in toxicological processes has been studied extensively, primarily employing the high-affinity ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, regulation of physiological responses by endogenous AHR ligands remains to be elucidated. Here, we review developments in this field, with a focus on 6-formylindolo[3,2-b]carbazole (FICZ), the endogenous ligand with the highest affinity to the receptor reported to date. The binding of FICZ to different isoforms of the AHR seems to be evolutionarily well conserved and there is a feedback loop that controls AHR activity through metabolic degradation of FICZ via the highly inducible cytochrome P450 1A1. Several investigations provide strong evidence that FICZ plays a critical role in normal physiological processes and can ameliorate immune diseases with remarkable efficiency. Low levels of FICZ are pro-inflammatory, providing resistance to pathogenic bacteria, stimulating the anti-tumor functions, and promoting the differentiation of cancer cells by repressing genes in cancer stem cells. In contrast, at high concentrations FICZ behaves in a manner similar to TCDD, exhibiting toxicity toward fish and bird embryos, immune suppression, and activation of cancer progression. The findings are indicative of a dual role for endogenously activated AHR in barrier tissues, aiding clearance of infections and suppressing immunity to terminate a vicious cycle that might otherwise lead to disease. There is not much support for the AHR ligand-specific immune responses proposed, the differences between FICZ and TCDD in this context appear to be explained by the rapid metabolism of FICZ.
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Affiliation(s)
- Agneta Rannug
- a Karolinska Institutet, Institute of Environmental Medicine , Stockholm , Sweden
| | - Ulf Rannug
- b Department of Molecular Biosciences , The Wenner-Gren Institute, Stockholm University , Stockholm , Sweden
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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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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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Lensu S, Tuomisto JT, Tuomisto J, Viluksela M, Niittynen M, Pohjanvirta R. Immediate and highly sensitive aversion response to a novel food item linked to AH receptor stimulation. Toxicol Lett 2011; 203:252-7. [PMID: 21458548 DOI: 10.1016/j.toxlet.2011.03.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 03/17/2011] [Accepted: 03/21/2011] [Indexed: 10/18/2022]
Abstract
Aversion to novel food items was studied in male rats and mice after 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure using chocolate consumption as an indicator. The correlation of this phenomenon with susceptibility to acute toxicity and CYP1A1 induction was examined by determining the dose-response of chocolate aversion in differently dioxin-sensitive rat lines after TCDD (0.01-10 μg/kg). Furthermore, the dependence of this behavioral alteration on the AH receptor (AHR) was studied employing AHR-deficient and wild-type mice. We offered chocolate for both species as a novel food item immediately after the exposure, and it was available with standard rodent chow for 3 days. The ED₅₀ value for the extremely resistant rat line A (LD₅₀) value > 10,000 μg/kg) was 0.36 μg/kg, for the semi-resistant line B (LD₅₀) value 830 μg/kg) 1.07 μg/kg and for the TCDD-sensitive line C (LD₅₀ value 40 μg/kg) 0.34 μg/kg. Interestingly, the ED₅₀ values for chocolate aversion were very similar to those for CYP1A1 induction in these rat lines. Findings on AHR-deficient and wild-type mice implied the involvement of the AHR in this intriguing response, which may thus represent a mechanism to restrict exposure to potentially toxic dietary substances causing hepatic induction of drug-metabolizing enzymes.
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Affiliation(s)
- Sanna Lensu
- Department of Environmental Health, National Institute for Health and Welfare (THL), P.O.B. 95, FI-70701 Kuopio, Finland.
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