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Luderer U, Eskenazi B, Hauser R, Korach KS, McHale CM, Moran F, Rieswijk L, Solomon G, Udagawa O, Zhang L, Zlatnik M, Zeise L, Smith MT. Proposed Key Characteristics of Female Reproductive Toxicants as an Approach for Organizing and Evaluating Mechanistic Data in Hazard Assessment. ENVIRONMENTAL HEALTH PERSPECTIVES 2019; 127:75001. [PMID: 31322437 PMCID: PMC6791466 DOI: 10.1289/ehp4971] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 06/17/2019] [Accepted: 06/24/2019] [Indexed: 05/13/2023]
Abstract
BACKGROUND Identification of female reproductive toxicants is currently based largely on integrated epidemiological and in vivo toxicology data and, to a lesser degree, on mechanistic data. A uniform approach to systematically search, organize, integrate, and evaluate mechanistic evidence of female reproductive toxicity from various data types is lacking. OBJECTIVE We sought to apply a key characteristics approach similar to that pioneered for carcinogen hazard identification to female reproductive toxicant hazard identification. METHODS A working group of international experts was convened to discuss mechanisms associated with chemical-induced female reproductive toxicity and identified 10 key characteristics of chemicals that cause female reproductive toxicity: 1) alters hormone receptor signaling; alters reproductive hormone production, secretion, or metabolism; 2) chemical or metabolite is genotoxic; 3) induces epigenetic alterations; 4) causes mitochondrial dysfunction; 5) induces oxidative stress; 6) alters immune function; 7) alters cell signal transduction; 8) alters direct cell–cell interactions; 9) alters survival, proliferation, cell death, or metabolic pathways; and 10) alters microtubules and associated structures. As proof of principle, cyclophosphamide and diethylstilbestrol (DES), for which both human and animal studies have demonstrated female reproductive toxicity, display at least 5 and 3 key characteristics, respectively. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), for which the epidemiological evidence is mixed, exhibits 5 key characteristics. DISCUSSION Future efforts should focus on evaluating the proposed key characteristics against additional known and suspected female reproductive toxicants. Chemicals that exhibit one or more of the key characteristics could be prioritized for additional evaluation and testing. A key characteristics approach has the potential to integrate with pathway-based toxicity testing to improve prediction of female reproductive toxicity in chemicals and potentially prevent some toxicants from entering common use. https://doi.org/10.1289/EHP4971.
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Affiliation(s)
- Ulrike Luderer
- Center for Occupational and Environmental Health, University of California, Irvine, Irvine, California, USA
| | - Brenda Eskenazi
- School of Public Health, University of California, Berkeley, Berkeley, California, USA
| | - Russ Hauser
- Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Kenneth S. Korach
- National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA
| | - Cliona M. McHale
- School of Public Health, University of California, Berkeley, Berkeley, California, USA
| | - Francisco Moran
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Linda Rieswijk
- School of Public Health, University of California, Berkeley, Berkeley, California, USA
- Institute of Data Science, Maastricht University, Maastricht, Netherlands
| | - Gina Solomon
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Osamu Udagawa
- Center for Health and Environmental Risk Research, National Institute of Environmental Studies, Tsukuba-City, Ibaraki, Japan
| | - Luoping Zhang
- School of Public Health, University of California, Berkeley, Berkeley, California, USA
| | - Marya Zlatnik
- Department of Obstetrics and Gynecology, University of California, San Francisco, San Francisco, California, USA
| | - Lauren Zeise
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Martyn T. Smith
- School of Public Health, University of California, Berkeley, Berkeley, California, USA
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Patrizi B, Siciliani de Cumis M. TCDD Toxicity Mediated by Epigenetic Mechanisms. Int J Mol Sci 2018; 19:ijms19124101. [PMID: 30567322 PMCID: PMC6320947 DOI: 10.3390/ijms19124101] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 12/11/2018] [Accepted: 12/14/2018] [Indexed: 12/27/2022] Open
Abstract
Dioxins are highly toxic and persistent halogenated organic pollutants belonging to two families i.e., Polychlorinated Dibenzo-p-Dioxins (PCDDs) and Polychlorinated Dibenzo Furans (PCDFs). They can cause cancer, reproductive and developmental issues, damage to the immune system, and can deeply interfere with the endocrine system. Dioxins toxicity is mediated by the Aryl-hydrocarbon Receptor (AhR) which mediates the cellular metabolic adaptation to these planar aromatic xenobiotics through the classical transcriptional regulation pathway, including AhR binding of ligand in the cytosol, translocation of the receptor to the nucleus, dimerization with the AhR nuclear translocator, and the binding of this heterodimeric transcription factor to dioxin-responsive elements which regulate the expression of genes involved in xenobiotic metabolism. 2,3,7,8-TCDD is the most toxic among dioxins showing the highest affinity toward the AhR receptor. Beside this classical and well-studied pathway, a number of papers are dealing with the role of epigenetic mechanisms in the response to environmental xenobiotics. In this review, we report on the potential role of epigenetic mechanisms in dioxins-induced cellular response by inspecting recent literature and focusing our attention on epigenetic mechanisms induced by the most toxic 2,3,7,8-TCDD.
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Affiliation(s)
- Barbara Patrizi
- National Institute of Optics-National Research Council (INO-CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy.
- European Laboratory for Non-Linear Spectroscopy (LENS), Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
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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: 85] [Impact Index Per Article: 14.2] [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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Sahlberg C, Peltonen E, Lukinmaa PL, Alaluusua S. Dioxin Alters Gene Expression in Mouse Embryonic Tooth Explants. J Dent Res 2016; 86:600-5. [PMID: 17586704 DOI: 10.1177/154405910708600704] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Dioxins are ubiquitous environmental poisons that cause disturbances in developing organs, including the teeth. Exposure to 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) at the cap stage leads to reduced tooth size and deformation of cuspal morphology. Our hypothesis was that TCDD affects the expression of genes specific for tooth development, which leads to these aberrations. Mouse embryonic E14 tooth germs were cultured for 24 hrs with/without 1 μM TCDD. Analysis of total RNA on Affymetrix arrays showed that TCDD altered the expression of 31 known genes by a fold factor of at least 2. Genes implied in tooth development expressed only slight changes. Genes active at the cap stage were selected for quantitative PCR analysis. Of these, the most highly up-regulated were Follistatin and Runx2, while TGFβ 1 and p21 were the most down-regulated genes. Incomplete tooth morphogenesis caused by TCDD may thus result from modified expression of developmentally regulated genes.
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Affiliation(s)
- C Sahlberg
- Department of Pediatric and Preventive Dentistry, Institute of Dentistry, Biomedicum Helsinki, FIN-00014 UNiversity of Helsinki, Helsinki, Finland.
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Inhibition of CK2 Activity by TCDD via binding to ATP-competitive binding site of catalytic subunit: Insight from computational studies. Chem Res Chin Univ 2013. [DOI: 10.1007/s40242-013-2384-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Chopra M, Schrenk D. Dioxin toxicity, aryl hydrocarbon receptor signaling, and apoptosis-persistent pollutants affect programmed cell death. Crit Rev Toxicol 2011; 41:292-320. [PMID: 21323611 DOI: 10.3109/10408444.2010.524635] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Exogenous ligands of the aryl hydrocarbon receptor (AhR) such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related substances are highly toxic pollutants ubiquitously present in the environment. They cause a variety of toxic effects to different organs and tissues. Among other effects, TCDD exposure to laboratory animals leads to thymus atrophy and immunosuppression on the one hand, and to tumor formation on the other. Apoptosis appears to be involved in both these toxic effects: AhR activation by TCDD was discussed to induce apoptosis of immune cells, leading to the depletion of thymocytes and ultimately immunosuppression. This mechanism could help to explain the highly immunotoxic actions of TCDD but it is nevertheless under debate whether this is the mode of action for immunosuppression by this class of chemical substances. In other cell types, especially liver cells, TCDD inhibits apoptosis induced by genotoxic treatment. In initiation-promotion studies, TCDD was shown to be a potent liver tumor promoter. Among other theories it was hypothesized that TCDD acts as a tumor promoter by preventing initiated cells from undergoing apoptosis. The exact mechanisms of apoptosis inhibition by TCDD are not fully understood, but both in vivo and in vitro studies consistently showed an involvement of the tumor suppressor p53 in this effect. Various strings of evidence have been established linking apoptosis to the detrimental effects of exogenous activation of the AhR. Within this article, studies elucidating the effects of TCDD and related substances on apoptosis signaling, be it inducing or repressing, is to be reviewed.
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Affiliation(s)
- Martin Chopra
- Institute of Food Chemistry and Toxicology, University of Kaiserslautern, Kaiserslautern, Germany
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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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8
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Pedersen M, Halldorsson TI, Mathiesen L, Mose T, Brouwer A, Hedegaard M, Loft S, Kleinjans JCS, Besselink H, Knudsen LE. Dioxin-like exposures and effects on estrogenic and androgenic exposures and micronuclei frequency in mother-newborn pairs. ENVIRONMENT INTERNATIONAL 2010; 36:344-351. [PMID: 20189248 DOI: 10.1016/j.envint.2010.02.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 01/12/2010] [Accepted: 02/05/2010] [Indexed: 05/23/2023]
Abstract
In utero exposure to environmental dioxin-like, estrogen and androgen compounds can cause adverse health effects. Little is known about potential interactions in vivo between dioxin-like compounds, estrogens and androgens during fetal development in humans. Therefore we explored the potential interactions in vivo between dioxin-like compounds, estrogens, androgens using chemical-activated luciferase expression (CALUX)(R) bioassays in maternal and umbilical cord blood plasma concurrently collected at the time of planned Caesarean section from 98 healthy pregnancies. The dioxin-like activity was also determined after placental transfer of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the ex vivo human placenta perfusion system. Similar dioxin-like activity in maternal and cord blood (37 versus 33pg CALUX(R)-TEQ/g plasma lipids, P>0.05) was detected and it demonstrates transplacental transfer. Increased dioxin-like activity in the perfused placenta tissue after ex vivo TCDD perfusions (from 17 to 280pg CALUX(R)-TEQ/g plasma lipids) suggest that accumulation in the placenta prevents immediate transplacental transfer of TCDD. Androgenic activity were also similar in the paired mother-newborns (0.10 versus 0.18ng CALUX(R)-AEQ/mL plasma), whereas cord blood plasma estrogenic activity was higher than maternal levels (22.6 versus 18.5ng CALUX(R)-EEQ/mL plasma). In cord blood plasma androgenic activity was strongly positively associated with maternal levels (Rs=0.8, P<0.001) whereas dioxin-like and estrogenic activities were modestly associated with maternal levels (Rs</=0.4, P<0.001). The micronuclei frequency, an indicator of genetic instability was significantly associated with dioxin-like activity in cord blood, independently of other recorded factors (Rs=0.4, P<0.003). This study demonstrated interactions in vivo between dioxin-like, estrogenic and androgenic exposures during fetal development of humans.
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Affiliation(s)
- Marie Pedersen
- Section of Environmental Health, Department of Public Health, University of Copenhagen, Oester Farimagsgade 5A, 1353 Copenhagen K, Denmark.
| | - Thorhallur I Halldorsson
- Faculty of Food Science and Nutrition, School of Health Sciences, University of Iceland, Hjarðarhagi 2-6, 107 Reykjavík, Iceland; Maternal Nutrition Group, Department of Epidemiology, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen S, Denmark.
| | - Line Mathiesen
- Section of Environmental Health, Department of Public Health, University of Copenhagen, Oester Farimagsgade 5A, 1353 Copenhagen K, Denmark.
| | - Tina Mose
- Section of Environmental Health, Department of Public Health, University of Copenhagen, Oester Farimagsgade 5A, 1353 Copenhagen K, Denmark.
| | - Abraham Brouwer
- BioDetection Systems B.V., Science Park 406, 1098 XH Amsterdam, The Netherlands.
| | - Morten Hedegaard
- Department of Obstetrics, University Hospital of Copenhagen, Blegdamsvej 9, 2100 Copenhagen Oe, Denmark.
| | - Steffen Loft
- Section of Environmental Health, Department of Public Health, University of Copenhagen, Oester Farimagsgade 5A, 1353 Copenhagen K, Denmark.
| | - Jos C S Kleinjans
- Department of Health Risk Analysis and Toxicology, University of Maastricht, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands.
| | - Harrie Besselink
- BioDetection Systems B.V., Science Park 406, 1098 XH Amsterdam, The Netherlands.
| | - Lisbeth E Knudsen
- Section of Environmental Health, Department of Public Health, University of Copenhagen, Oester Farimagsgade 5A, 1353 Copenhagen K, Denmark.
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9
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Jin MH, Hong CH, Lee HY, Kang HJ, Han SW. Toxic effects of lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on development of male reproductive system: involvement of antioxidants, oxidants, and p53 protein. ENVIRONMENTAL TOXICOLOGY 2010; 25:1-8. [PMID: 19085997 DOI: 10.1002/tox.20466] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent endocrine disruptor compound and induces multiple organ dysfunctions. The effect of TCDD exposure both in adults and in utero has been well established. However, little is known about the effects of TCDD acquired through mother's milk on the development of the male reproductive system. The aim of this study was to investigate the effects and mechanisms of TCDD from lactational exposure. TCDD (1 microg/kg) was administered to C57BL/6 mouse mothers for 4 days from the day of delivery. On postnatal day 30 (PND 30) and postnatal day 60 (PND 60), body weight, body length, and anogenital distance (AGD) of male offspring were measured. The weights of the testes and epididymides were also measured. Epididymides were used for sperm counts, and testes were used to measure the activity of antioxidant enzymes (SOD, CAT, GPX, GR), the parameters of oxidative stress (hydrogen peroxide, MDA), and testosterone. In addition, expression of p53 and the proapoptotic protein, Bax, were analyzed by Western blot. TCDD exposure decreased body weight, body length, and AGD in both PND 30 and PND 60 groups compared with the control group. The activity of all antioxidant enzymes at PND 60 was decreased after TCDD treatment. TCDD treatment decreased testicular testosterone levels in both the PND 30 and PND 60 groups. The expression of p53 and Bax were also upregulated by TCDD and did not return to normal levels by PND 60. These data suggest that TCDD affects development of male offspring when the mother is exposed to TCDD during lactation. In addition, oxidative stress is a major mediator of TCDD-induced adverse effects, and p53 may play an important role in this mechanism.
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Affiliation(s)
- Mei Hua Jin
- Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea
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Liu P, Pazin DE, Merson RR, Albrecht KH, Vaziri C. The developmentally-regulated Smoc2 gene is repressed by Aryl-hydrocarbon receptor (Ahr) signaling. Gene 2008; 433:72-80. [PMID: 19146932 DOI: 10.1016/j.gene.2008.12.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Revised: 12/08/2008] [Accepted: 12/08/2008] [Indexed: 12/11/2022]
Abstract
SPARC-Related Modular Calcium Binding Protein-2 (Smoc-2) is a broadly-expressed matricellular protein which contributes to mitogenesis via activation of Integrin-Linked Kinase (ILK). Here we show that expression of Smoc2 is repressed in cultured cells following treatment with Aryl-hydrocarbon receptor (Ahr) ligands including the ubiquitous environmental pollutants Benzo[a]pyrene (B[a]P) and 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD). The Smoc2 promoter contains two consensus putative Ahr-binding sites and Smoc2 promoter-driven reporter genes are repressed in response to B[a]P in an Ahr-dependent manner in cultured cells. Using organ culture experiments we show that TCDD also represses Smoc2 mRNA expression in testes from Ahr(+/+) but not Ahr(-/-) mice. Therefore, exposure to Ahr ligands is likely to affect Smoc2 expression in vivo. Taken together our results indicate that Smoc2 is a novel transcriptional target of activated Ahr. Perturbation of Smoc2 expression may mediate the adverse developmental effects of environmental aryl-hydrocarbon exposure.
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Affiliation(s)
- Peijun Liu
- Department of Pathology, Boston University School of Medicine, Boston, MA 02118, USA
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11
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Fritsche E, Schäfer C, Calles C, Bernsmann T, Bernshausen T, Wurm M, Hübenthal U, Cline JE, Hajimiragha H, Schroeder P, Klotz LO, Rannug A, Fürst P, Hanenberg H, Abel J, Krutmann J. Lightening up the UV response by identification of the arylhydrocarbon receptor as a cytoplasmatic target for ultraviolet B radiation. Proc Natl Acad Sci U S A 2007; 104:8851-6. [PMID: 17502624 PMCID: PMC1885591 DOI: 10.1073/pnas.0701764104] [Citation(s) in RCA: 327] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
UVB radiation-induced signaling in mammalian cells involves two major pathways: one that is initiated through the generation of DNA photoproducts in the nucleus and a second one that occurs independently of DNA damage and is characterized by cell surface receptor activation. The chromophore for the latter one has been unknown. Here, we report that the UVB response involves tryptophan as a chromophore. We show that through the intracellular generation of photoproducts, such as the arylhydrocarbon receptor (AhR) ligand 6-formylindolo[3,2-b]carbazole, signaling events are initiated, which are transferred to the nucleus and the cell membrane via activation of the cytoplasmatic AhR. Specifically, AhR activation by UVB leads to (i) transcriptional induction of cytochrome P450 1A1 and (ii) EGF receptor internalization with activation of the EGF receptor downstream target ERK1/2 and subsequent induction of cyclooxygenase-2. The role of the AhR in the UVB stress response was confirmed in vivo by studies employing AhR KO mice.
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Affiliation(s)
- Ellen Fritsche
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Claudia Schäfer
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Christian Calles
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Thorsten Bernsmann
- Chemical and Veterinary Control Laboratory, Josef-König-Strasse 40, 48147 Münster, Germany
| | - Thorsten Bernshausen
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Melanie Wurm
- Department of Pediatric Oncology, Hematology, and Immunology, Children's Hospital, Heinrich Heine University Medical Center, Moorenstrasse 5, 40225 Düsseldorf, Germany
| | - Ulrike Hübenthal
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Jason E. Cline
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Hossein Hajimiragha
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Peter Schroeder
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Lars-Oliver Klotz
- Institute for Biochemistry und Molecular Biology I, Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Agneta Rannug
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, S-171 77 Stockholm, Sweden; and
| | - Peter Fürst
- Chemical and Veterinary Control Laboratory, Josef-König-Strasse 40, 48147 Münster, Germany
| | - Helmut Hanenberg
- Department of Pediatric Oncology, Hematology, and Immunology, Children's Hospital, Heinrich Heine University Medical Center, Moorenstrasse 5, 40225 Düsseldorf, Germany
| | - Josef Abel
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Jean Krutmann
- *Institut für Umweltmedizinische Forschung (IUF), Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
- To whom correspondence should be addressed. E-mail:
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Barnett KR, Tomic D, Gupta RK, Miller KP, Meachum S, Paulose T, Flaws JA. The aryl hydrocarbon receptor affects mouse ovarian follicle growth via mechanisms involving estradiol regulation and responsiveness. Biol Reprod 2007; 76:1062-70. [PMID: 17329597 DOI: 10.1095/biolreprod.106.057687] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) is a known transcription factor. Although studies indicate that Ahr-deficient (AhRKO) mice have defects in female reproduction, only a few studies have examined the role of AHR in the ovary. Previous studies have suggested, without directly testing, that AhRKO mice have slower follicular growth than wild-type (WT) mice. Therefore, the first objective of the present study was to examine whether AhRKO follicles grow slower than WT follicles and if so, to determine whether the mechanism by which Ahr affects follicular growth is through effects on antrum size, granulosa cell proliferation, and regulators of cell cycle progression. Since estradiol (E(2)) is critical for the normal growth of ovarian follicles, the second objective of the present study was to determine the role of Ahr in regulating E(2) production and responsiveness. The third objective of the present study was to determine whether E(2) replacement restores follicular growth of AhRKO follicles to WT levels in vitro. We found that AhRKO follicles grew slower than WT follicles in vitro. While AhRKO and WT follicles had similar antrum sizes, AhRKO follicles showed decreased granulosa cell proliferation and reduced mRNA and protein levels of cell cycle regulators, as compared to WT follicles. Furthermore, the AhRKO mice had lower serum and follicle-produced E(2) levels and showed decreased Esr1 and Esr2 mRNA levels compared to WT mice. Finally, E(2) treatment of AhRKO follicles restored follicular growth to WT levels in vitro. Collectively, these findings suggest that the AHR affects follicular growth via mechanisms that involve E(2) regulation and responsiveness.
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Affiliation(s)
- Kimberly R Barnett
- Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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Garrett RW, Gasiewicz TA. The aryl hydrocarbon receptor agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin alters the circadian rhythms, quiescence, and expression of clock genes in murine hematopoietic stem and progenitor cells. Mol Pharmacol 2006; 69:2076-83. [PMID: 16556773 DOI: 10.1124/mol.105.021006] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR) agonist, has been identified as a potent immunohematopoietic toxicant with the ability to alter the number of Lin(-) Sca-1(+) cKit(+) (LSK) bone marrow cells, a population enriched for murine hematopoietic stem cells. The biology of these cells is governed by circadian rhythms and TCDD has been shown to disrupt circadian rhythms of other biological endpoints. We investigated the effect of TCDD on the circadian rhythms of hematopoietic precursors. Female C57BL/6 mice were treated with a single oral dose of 10 mug/kg TCDD. Five days later, bone marrow was harvested every 4 h for 24 h and stained for specific hematopoietic populations using fluorescently labeled antibodies. In addition, cells were placed into semisolid culture to measure different functionally defined populations. Activation of the AhR by TCDD elicited disruptions in the rhythms of LSK cell numbers and phenotypically defined myeloid and erythroid precursors. Simultaneous DNA and RNA staining revealed an abnormal in vivo rhythm of percentage of total number of LSK cells in G(0) phase of the cell cycle, suggesting disruption of stem cell quiescence. Finally, quantitative reverse transcription-polymerase chain reaction revealed that expression of AhR and Arnt mRNA within enriched hematopoietic precursors oscillates with a circadian period. Modest changes in the 24-h expression of mPer1 and mPer2 mRNA and increased AhR repressor mRNA after TCDD exposure suggest a direct effect on the molecular machinery responsible for these rhythms. Together, these data demonstrate that activation of the AhR by TCDD disrupts the circadian rhythms associated with murine hematopoietic precursors.
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Affiliation(s)
- Russell W Garrett
- Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester Medical Center, 601 Elmwood Avenue, Box EHSC, Rochester, NY 14642, USA
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Liu G, Shang Y, Yu Y. Induced endoplasmic reticulum (ER) stress and binding of over-expressed ER specific chaperone GRP78/BiP with dimerized epidermal growth factor receptor in mammalian cells exposed to low concentration of N-methyl-N'-nitro-N-nitrosoguanidine. Mutat Res 2006; 596:12-21. [PMID: 16488447 DOI: 10.1016/j.mrfmmm.2005.10.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2005] [Revised: 10/18/2005] [Accepted: 10/27/2005] [Indexed: 11/16/2022]
Abstract
Previously we have shown that alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) can induce the clustering of epidermal growth factor receptor (EGFR) in human amnion FL cells. However, the biological consequence of MNNG-induced clustering is different from that of epidermal growth factor (EGF)-induced clustering. In addition, MNNG strongly blocks the autophosphorylation of EGFR in response to its ligand, we speculate it might be due to the altered conformation of EGFR by MNNG alkylation, or the binding of some unknown suppressive molecules to EGFR, which could lead to the down-regulation of EGFR pathway. In this study, we further demonstrated that EGFR could not be phosphorylated by EGF in lysates prepared from MNNG-pretreated cell. In addition, it was found that the clustering of EGFR induced by low concentration (<or=1 microM) of MNNG on cell surface was indeed the dimerization of EGFR; however, unlike EGF treatment, the dimerization initiated by MNNG was irreversible upon mild-acid washing. Besides, in accordance with our previous results, the recruitment of adaptor proteins Grb-2/Sos1, which play key roles in activating ensuing RAS-MAPK pathway, was also suppressed. Interestingly, we found that endoplasmic reticulum (ER) stress participates in MNNG-induced down-regulation of EGFR signaling. It was demonstrated that the ER specific chaperone, glucose-regulated protein 78 (GRP78/BiP) formed a stable complex with EGFR in MNNG-treated cell. However, in the presence of 1mM ATP, EGF induced phosphorylation of tyrosine residues of EGFR can be revitalized in lysates prepared from MNNG pretreated cells. We also found that MNNG can induce ER stress or unfolded protein response (UPR) which is characterized by induced expression of ER-stress response proteins, such as GRP78/BiP, GADD153/CHOP, and activation of ER-localized caspase-12. Therefore, it is concluded MNNG is also an ER stress inducer. In MNNG-exposed cells, ER stress plays an important role in the blockage of EGFR-signaling pathway by forming a stable complex of EGFR/BiP.
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Affiliation(s)
- Geng Liu
- Department of Pathology and Pathophysiology, Zhejiang University School of Medicine, Hangzhou 310031, China
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Popp JA, Crouch E, McConnell EE. A Weight-of-Evidence Analysis of the Cancer Dose-Response Characteristics of 2,3,7,8-Tetrachlorodibenzodioxin (TCDD). Toxicol Sci 2005; 89:361-9. [PMID: 16267338 DOI: 10.1093/toxsci/kfj016] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cancer risk assessment for TCDD and other compounds must focus on the cancer dose-response relationship and corresponding potency for the range of human doses before it can have relevance to the human exposure environment. Major differences of opinion exist over whether the dose-response curve for TCDD and other dioxin congeners is non-linear (incorporating a threshold dose region below which tumors are unlikely to be elicited) or linear (implying that any exposure has a statistical likelihood of causing cancer). The World Health Organization and others strongly support a non-linear dose-response relationship for TCDD and cancer, whereas USEPA characterizes the dose-response function as linear. This review critically summarizes the available information on TCDD dose-response relationship for cancer utilizing a weight-of-evidence approach. This assessment concludes that the available data support a non-linear dose-response relationship as being most likely and appropriate for human cancer risk assessment, i.e., the evidence suggests that a biological threshold exists in the dose-response. While proof of a threshold is not absolute, and never can be, the level of certainty for TCDD is substantial because of the concordance of many lines of evidence and the consistency of repeated observations pointing to non-linearity.
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Affiliation(s)
- James A Popp
- Stratoxon, LLC, 1853 William Penn Way, PO Box 10368, Lancaster, Pennsylvania 17601, USA.
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Nyska A, Yoshizawa K, Jokinen MP, Brix AE, Sells DM, Wyde ME, Orzech DP, Kissling GE, Walker NJ. Olfactory epithelial metaplasia and hyperplasia in female Harlan Sprague-Dawley rats following chronic treatment with polychlorinated biphenyls. Toxicol Pathol 2005; 33:371-7. [PMID: 15805076 DOI: 10.1080/01926230590930209] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The National Toxicology Program recently completed a series of studies to evaluate the relative potency for toxicity and carcinogenicity of several polyhalogenated aromatic hydrocarbons including dioxin-like compounds (DLCs) and polychlorinated biphenyls. Female Sprague-Dawley rats were administered by gavage for up to 2 years with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD); 3,3',4,4',5-pentachlorobiphenyl (PCB126); 2,3,4,7,8-pentachlorodibenzofuran (PeCDF); 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153); a tertiary mixture of TCDD, PCB126, and PeCDF; a binary mixture of PCB126 and 153; or a binary mixture of PCB126 and 2,3',4,4',5-pentachlorobiphenyl (PCB118); control animals received corn oil-acetone vehicle (99:1) alone. Nasal epithelial changes were observed only in animals exposed for 2 years to the higher doses of the binary mixtures of PCB126 + PCB153 (1000 ng/kg and 1000 microg/kg) and PCB126 + PCB118 (216 and 360 ng TCDD equivalents/kg). In both studies, the changes were of the same nonneoplastic nature, localized to nasal sections II and III located, respectively, at the level of the incisive papilla anterior to the first palatial ridge (section II) and through the middle of the second molar teeth (section III). The changes consisted of hyperplasia of the respiratory epithelium (level II) and metaplasia of olfactory epithelium to respiratory epithelium with further hyperplasia of the metaplastic respiratory epithelium (levels II and III). Variable amounts of acute inflammatory exudate appeared within the lumen of the nasal cavity, overlying the affected epithelium. Occasionally, the inflammation eroded through the skull and into the adjacent olfactory bulbs.
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Affiliation(s)
- Abraham Nyska
- Laboratory of Experimental Pathology National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709-9998, USA.
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Drukteinis JS, Medrano T, Ablordeppey EA, Kitzman JM, Shiverick KT. Benzo[a]pyrene, but Not 2,3,7,8-TCDD, Induces G2/M Cell Cycle Arrest, p21CIP1 and p53 Phosphorylation in Human Choriocarcinoma JEG-3 Cells: A Distinct Signaling Pathway. Placenta 2005; 26 Suppl A:S87-95. [PMID: 15837074 DOI: 10.1016/j.placenta.2005.01.013] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/26/2005] [Indexed: 12/13/2022]
Abstract
Maternal cigarette smoking is known to disrupt placental growth and function. The polyaromatic hydrocarbon benzo[a]pyrene (BaP) is a major toxicant in cigarette smoke that has been shown to alter placental cell function. This study compared the effects of the benzo[a]pyrene (BaP) with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the prototype ligand for the aryl hydrocarbon (Ah) receptor, on proliferation and cell cycle progression in the human trophoblastic JEG-3 cell line. BaP, but not TCDD, significantly inhibited proliferation in a dose-dependent manner characterized by G2/M cell cycle phase arrest. No evidence of apoptosis was detected following BaP or TCDD exposure. Immunocytochemistry and Western blot analysis showed that BaP induced expression of nuclear p21CIP1 protein, the major inhibitor of cyclin-dependent kinases. In contrast, CDK1 expression, the main G2 cyclin-dependent kinase, was significantly reduced by 50% with a shift in localization from the nucleus to cytoplasm. Although BaP had no effect on total cellular p53 levels, phosphorylation of p53 at serine 15 (p53 ser-15phos) was markedly increased. The presence of Wortmannin, an inhibitor of PI-3 kinases, decreased BaP-induced p53 ser-15phos, as did the presence of the antioxidant vitamin E. In addition, vitamin E suppressed BaP-induced G2/M arrest without altering the level of induced CYP1A1 protein. Thus, the anti-proliferative effect of BaP involves activation of a p53-dependent pathway involving cell cycle arrest at G2/M, providing evidence of oxidative stress and activation of a DNA damage response pathway in JEG-3 cells.
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Affiliation(s)
- J S Drukteinis
- University of Florida, Department of Pharmacology and Therapeutics, 1600 SW Archer Road, P.O. Box 100267, Gainesville, FL 32610-0267, USA
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Marlowe JL, Puga A. Aryl hydrocarbon receptor, cell cycle regulation, toxicity, and tumorigenesis. J Cell Biochem 2005; 96:1174-84. [PMID: 16211578 DOI: 10.1002/jcb.20656] [Citation(s) in RCA: 237] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Most effects of exposure to halogenated and polycyclic aromatic hydrocarbons are mediated by the aryl hydrocarbon receptor (AHR). It has long been recognized that the AHR is a ligand-activated transcription factor that plays a central role in the induction of drug-metabolizing enzymes and hence in xenobiotic detoxification. Of late, it has become evident that outside this well-characterized role, the AHR also functions as a modulator of cellular signaling pathways. In this Prospect, we discuss the involvement of the AHR in pathways critical to cell cycle regulation, mitogen-activated protein kinase cascades, immediate-early gene induction, and the functions of the RB protein. Ultimately, the toxicity of AHR xenobiotic ligands may be intrinsically connected with the perturbation of these pathways and depend on the many critical signaling pathways and effectors with which the AHR itself interacts.
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Affiliation(s)
- Jennifer L Marlowe
- Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati Medical Center, Cincinnati, Ohio 45267-0056, USA
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Dhulipala VC, Maddali KK, Welshons WV, Reddy CS. Secalonic acid D blocks embryonic palatal mesenchymal cell-cycle by altering the activity of CDK2 and the expression of p21 and cyclin E. ACTA ACUST UNITED AC 2005; 74:233-42. [PMID: 15880679 DOI: 10.1002/bdrb.20043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The mycotoxin, secalonic acid D (SAD), a known animal and potential human cleft palate (CP)-inducing agent, is produced by Pencillium oxalicum in corn. SAD selectively inhibits proliferation of murine embryonic palatal mesenchymal (MEPM) cells leading to a reduction in cell numbers. These effects can explain the reduction in shelf size and the resulting CP seen in the offspring of SAD-exposed mice. Ability of SAD to inhibit proliferation as well as to block the progression of cells from G1- to S-phase of the cell-cycle were also shown in the human embryonic palatal mesenchymal (HEPM) cells suggesting the potential CP-inducing effect of SAD in human beings METHODS Gestation day (GD) 12 mouse embryos and HEPM cells were used to test the hypothesis that the cell-cycle block induced by SAD results from a disruption of stage-specific regulatory components both in vivo and in vitro. The effects of SAD on the activity of various cyclin dependent kinases (CDK) and on the levels of various positive (cyclins and CDK) and negative (CDK inhibitors p15, 16, 18, 19, 21, 27, 57) cell-cycle regulators were assessed by performing kinase assays and immunoblots, respectively. RESULTS In the murine embryonic palates, SAD specifically inhibited G1/S-phase-specific CDK2 activity, reduced the level of cyclin E and tended to increase the level of the CIP/kip CDK inhibitor, p21. In the HEPM cell cultures, exposure to IC50 of SAD significantly affected all of the above targets. In addition, a reduction in the levels/activity of CDK 4/6, a reduction in the levels of cyclins D1, D2, D3, E, A, and all INK4 family proteins, and an increase in the level of the CIP/kip CDK inhibitor, p57, were also seen. CONCLUSIONS These results suggest that the S-phase-specific cell-cycle proteins CDK2, cyclin E and possibly p21 are the common targets of SAD in murine palatal shelves in vivo and in human embryonic palatal mesenchymal cells in vitro and may be relevant to the pathogenesis of SAD-induced CP.
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Affiliation(s)
- V C Dhulipala
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri 65211, USA
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20
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Hoelper P, Faust D, Oesch F, Dietrich C. Evaluation of the role of c-Src and ERK in TCDD-dependent release from contact-inhibition in WB-F344 cells. Arch Toxicol 2004; 79:201-7. [PMID: 15592923 DOI: 10.1007/s00204-004-0624-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2004] [Accepted: 09/24/2004] [Indexed: 10/25/2022]
Abstract
TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is the most potent tumor promoter ever tested in rodents. Although it is known that most of the effects of TCDD are mediated by binding to the aryl hydrocarbon receptor (AhR), the mechanisms leading to tumor promotion remain to be elucidated. Loss of contact-inhibition is one characteristic hallmark in tumorigenesis. In WB-F344 cells, TCDD induces a release from contact-inhibition which is manifested by a twofold increase in DNA-synthesis and cell number when TCDD (1 nmol L-1) is given to confluent cells. Because TCDD leads to phosphorylation of the epidermal growth factor receptor and an increase in c-Src-activation in WB-F344 cells, we investigated the functional relevance of this observation. Pharmacological inhibition of c-Src using PP1 (10 micromol L-1) or genistein (10 micromol L-1) did not prevent TCDD-dependent release from contact-inhibition. In accordance, elevation of cyclin A-a previously identified target of TCDD and marker of S-phase entry-was not reduced in the presence of PP1 or genistein. Western blot analysis revealed that phosphorylation of the EGF-receptor downstream target ERK was not induced in response to TCDD. Furthermore, TCDD-dependent increase in DNA-synthesis was not inhibited by the MEK1/2 inhibitor U0126 (10 micromol L-1). Our data show that neither c-Src-activation, nor ERK-activation are required for TCDD-dependent release from contact-inhibition arguing against a functional role of EGF-receptor activation in response to TCDD in WB-F344 cells.
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Affiliation(s)
- Peter Hoelper
- Institute of Toxicology, Johannes Gutenberg-University, Obere Zahlbacherstr. 67, 55131, Mainz, Germany
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Steenland K, Bertazzi P, Baccarelli A, Kogevinas M. Dioxin revisited: developments since the 1997 IARC classification of dioxin as a human carcinogen. ENVIRONMENTAL HEALTH PERSPECTIVES 2004; 112:1265-8. [PMID: 15345337 PMCID: PMC1247514 DOI: 10.1289/ehp.7219] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Accepted: 06/10/2004] [Indexed: 05/02/2023]
Abstract
In 1997 the International Agency for Research on Cancer (IARC) classified 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; the most potent dioxin congener) as a group 1 carcinogen based on limited evidence in humans, sufficient evidence in experimental animals, and extensive mechanistic information indicating that TCDD acts through a mechanism involving the aryl hydrocarbon receptor (AhR), which is present in both humans and animals. The judgment of limited evidence in humans was based primarily on an elevation of all cancers combined in four industrial cohorts. The group 1 classification has been somewhat controversial and has been challenged in the literature in recent years. In this article we review the epidemiologic and mechanistic evidence that has emerged since 1997. New epidemiologic evidence consists primarily of positive exposure-response analyses in several of the industrial cohorts, as well as evidence of excesses of several specific cancers in the Seveso accident cohort. There are also new data regarding how the AhR functions in mediating the carcinogenic response to TCDD. The new evidence generally supports the 1997 IARC classification.
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Affiliation(s)
- Kyle Steenland
- Rollins School of Public Health, Emory University, Atlanta, Georgia 30306, USA.
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22
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Tan Z, Huang M, Puga A, Xia Y. A critical role for MAP kinases in the control of Ah receptor complex activity. Toxicol Sci 2004; 82:80-7. [PMID: 15272135 DOI: 10.1093/toxsci/kfh228] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The heterodimeric complex of aromatic hydrocarbon receptor (AHR) and Ah receptor nuclear translocator (ARNT) plays a pivotal role in controlling the expression of drug metabolism genes, such as the cytochromes p450 (Cyp) 1a1 and 1b1, believed to be responsible for most toxic effects of the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In this study, we show that activation of Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) modulates ARNT transcription activity and potentiates the transcriptional activity of AHR/ARNT complexes. Inhibition of ERK by chemical compounds and ablation of JNK caused significant decreases in CYP1A1 induction by TCDD. Compared to wild type, JNK2 ablation significantly reduced TCDD-stimulated CYP1A1 expression in mouse thymus and testis, but not in liver. In contrast, CYP1B1 expression was unaffected in all three tissues of the knockout mice. These data suggest that JNK and ERK modulate ARNT activity and AHR/ARNT-dependent gene expression, contributing to the gene-specific and tissue-specific toxicity of environmental contaminants.
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Affiliation(s)
- Zongqing Tan
- Center for Environmental Genetics and Department of Environmental Health, University of Cincinnati Medical Center, 123 E. Shields Street, Cincinnati, OH 45267-0056, USA
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Abstract
Traditionally, the aryl hydrocarbon receptor (AHR) is considered to be a ligand-activated receptor and transcription factor responsible for the induction of drug-metabolizing enzymes. Its role in the combinatorial matrix of cell functions was neatly established long before the first report of an AHR cDNA sequence was published. Only recently, other functions of this protein have begun to be recognized. This review addresses novel findings relating to AHR functions that have resulted from experimental approaches markedly outside traditional receptor analyses. Here we examine the aspects of AHR biology relevant to its role in cell cycle regulation, from the activation of mitogen-activated protein kinases to the cross-talk between AHR and the RAS pathway and the functional significance of the interaction between AHR and the retinoblastoma protein. We have attempted to provide the reader with a balanced interpretation of the evidence, highlighting areas of consensus as well as areas still being contested.
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Affiliation(s)
- Alvaro Puga
- Center for Environmental Genetics and Department of Environmental Health, University of Cincinnati Medical Center, P.O. Box 670056, OH 45267-0056, USA.
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Ramakrishna G, Perella C, Birely L, Diwan BA, Fornwald LW, Anderson LM. Decrease in K-ras p21 and increase in Raf1 and activated Erk 1 and 2 in murine lung tumors initiated by N-nitrosodimethylamine and promoted by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Toxicol Appl Pharmacol 2002; 179:21-34. [PMID: 11884234 DOI: 10.1006/taap.2001.9344] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent evidence suggests that K-ras protooncogene protein p21 may have a tumor-suppressive role in the context of development of lung adenocarcinoma. Levels of K-ras p21, raf-1, mitogen-activated protein kinases Erk 1 and 2, the phosphorylated-activated forms of Erk 1 and 2 (Erk 1P and 2P), and proliferating cell nuclear antigen (PCNA) were measured by immunoblotting in mouse lung tumors (5 to 9 mm in size) caused by N-nitrosodimethylamine (NDMA) and in control lungs. In tumors compared with normal lung, cell membrane-associated K-ras p21 was significantly decreased and cytosolic K-ras p21 increased. Total, membrane, and cytosolic raf-1 and Erk 1P and 2P were increased in tumors compared with normal lung. A single dose of 5 nmol/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) given after NDMA resulted in a significant 2.4-fold increase in tumor multiplicity. A significantly greater decrease in membrane-associated K-ras p21 and increase in total and membrane associated raf-1 occurred in the NDMA/TCDD tumors compared with the NDMA-only tumors. PCNA levels increased in tumors, a finding confirmed by immunohistochemistry, and correlated with tumor size after NDMA/TCDD treatment but not after NDMA only. The increase in raf-1 in the tumors was confirmed by immunohistochemistry, which also revealed an increase in raf-1-positive alveolar macrophages specifically associating with tumors from the earliest stages. These results suggest a possible tumor-suppressive function for K-ras p21 in lung and a positive role for raf-1 and Erk 1/2 in lung tumorigenesis. TCDD may promote tumors by contributing to downregulation of K-ras and stimulation of raf-1.
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Affiliation(s)
- Gayatri Ramakrishna
- Laboratory of Comparative Carcinogenesis, National Cancer Institute at Frederick, Frederick, Maryland 21702, USA
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25
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Bagchi D, Balmoori J, Bagchi M, Ye X, Williams CB, Stohs SJ. Role of p53 tumor suppressor gene in the toxicity of TCDD, endrin, naphthalene, and chromium (VI) in liver and brain tissues of mice. Free Radic Biol Med 2000; 28:895-903. [PMID: 10802220 DOI: 10.1016/s0891-5849(00)00173-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
It has been postulated that tumor suppressor genes are involved in the cascade of events leading to the toxicity of diverse xenobiotics. Therefore, we have assessed the comparative effects of 0.01, 0.10, and 0.50 median lethal doses (LD(50)) of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD), endrin, naphthalene, and sodium dichromate (VI) [Cr(VI)] on lipid peroxidation, DNA fragmentation, and enhanced production of superoxide anion (cytochrome c reduction) in liver and brain tissues of p53-deficient and standard C57BL/6NTac mice to determine the role of p53 gene in the toxic manifestations produced by these diverse xenobiotics. In general, p53-deficient mice are more susceptible to all four xenobiotics than C57BL/6NTac mice, with dose-dependent effects being observed. Specifically, at a 0.50 LD(50) dose, naphthalene and Cr(VI) induced the greatest toxicity in the liver tissue of mice, and naphthalene and endrin exhibited the greatest effect in the brain tissue. At this dose, TCDD, endrin, naphthalene, and Cr(VI) induced 2.3- to 3.7-fold higher increases in hepatic lipid peroxidation and 1.8- to 3.0-fold higher increases in brain lipid peroxidation in p53-deficient mice than in C57BL/6NTac mice. At a 0. 10 LD(50) dose, TCDD, endrin, naphthalene, and Cr(VI) induced 1.3- to 1.8-fold higher increases in hepatic lipid peroxidation and 1.4- to 1.9-fold higher increases in brain lipid peroxidation in p53-deficient mice than in C57BL/6NTac mice. Similar results were observed with respect to DNA fragmentation and cytochrome c reduction (superoxide anion production). For example, at the 0.10 LD(50) dose, the four xenobiotics induced increases of 1.6- to 3. 0-fold and 1.5- to 2.1-fold in brain and liver DNA fragmentation, respectively, and increases of 1.5- to 2.3-fold and 1.4- to 2.5-fold in brain and liver cytochrome c reduction (superoxide anion production), respectively, in p53-deficient mice compared with control C57BL/6NTac mice. These results suggest that the p53 tumor suppressor gene may play a role in the toxicity of structurally diverse xenobiotics.
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Affiliation(s)
- D Bagchi
- Creighton University School of Pharmacy and Allied Health Professions, Omaha, NE 68178, USA
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