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Penn T, Borza T, Liou JI, Jason Abel E, Shapiro DD, Jarrard DF, Ricke WA, Richards KA. Impact of Agent Orange Exposure on Non-muscle Invasive Bladder Cancer Outcomes. Urology 2023; 182:175-180. [PMID: 37730166 DOI: 10.1016/j.urology.2023.08.037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 08/28/2023] [Accepted: 08/30/2023] [Indexed: 09/22/2023]
Abstract
OBJECTIVE To explore the effect of Agent Orange (AO) exposure on bladder cancer (BCa) outcomes in patients receiving Bacillus Calmette-Guérin (BCG) for non-muscle invasive BCa (NMIBC). METHODS We retrospectively examined the association between AO exposure in patients with NMIBC in national veterans affairs databases who were being treated with BCG. Patients were diagnosed with NMIBC from 2000 to 2010 with follow-up through 2018. Clinical, pathological, and demographic variables were compared by AO exposure. Associations of AO exposure with recurrence, progression, and cancer-specific survival were performed using Cox proportional hazard models after inverse propensity score weighting and competing risks adjustments. We also assessed the association of AO exposure on grade and stage via multivariable logistic regression models. RESULTS A total of 7651 patients were identified of which 753 (9.8%) were exposed to AO. The median follow-up time was 130 months. The AO-exposed patients were younger (age 61 vs 71 years, P <.001), but had similar Charlson comorbidity scores and stage/grade distribution as the non-AO exposed patients. AO exposure was not associated with higher grade or stage. In our Cox multivariable analyses, AO exposure was not associated with worse recurrence (hazard ratio (HR) 0.89, 95% confidence interval (CI) 0.72-1.10, P = .29), progression (HR 1.08, 95% CI 0.86-1.36, P = .51), or cancer-specific survival (HR 1.31, 95% CI 0.92-1.87, P = .13). CONCLUSION AO exposure was not associated with worse oncologic outcomes in patients receiving BCG for NMIBC. While this is reassuring, additional research is needed in other patient populations and disease states to determine if the effect is consistent.
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Affiliation(s)
- Taylor Penn
- The University of Wisconsin-Madison, Department of Urology, Madison, WI
| | - Tudor Borza
- The University of Wisconsin-Madison, Department of Urology, Madison, WI
| | - Jinn-Ing Liou
- The University of Wisconsin-Madison, Department of Medicine, Madison, WI
| | - E Jason Abel
- The University of Wisconsin-Madison, Department of Urology, Madison, WI
| | - Daniel D Shapiro
- The University of Wisconsin-Madison, Department of Urology, Madison, WI; William S. Middleton Memorial Veterans Hospital, Division of Urology, Madison, WI
| | - David F Jarrard
- The University of Wisconsin-Madison, Department of Urology, Madison, WI
| | - William A Ricke
- The University of Wisconsin-Madison, Department of Urology, Madison, WI
| | - Kyle A Richards
- The University of Wisconsin-Madison, Department of Urology, Madison, WI; William S. Middleton Memorial Veterans Hospital, Division of Urology, Madison, WI.
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Hall A, Mattison D, Singh N, Chatzistamou I, Zhang J, Nagarkatti M, Nagarkatti P. Effect of TCDD exposure in adult female and male mice on the expression of miRNA in the ovaries and testes and associated reproductive functions. FRONTIERS IN TOXICOLOGY 2023; 5:1268293. [PMID: 37854252 PMCID: PMC10579805 DOI: 10.3389/ftox.2023.1268293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 09/12/2023] [Indexed: 10/20/2023] Open
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant found widely across the world. While animal and human studies have shown that exposure to TCDD may cause significant alterations in the reproductive tract, the effect of TCDD on the expression of miRNA in the reproductive organs has not been previously tested. In the current study, we exposed adult female or male mice to TCDD or vehicle and bred them to study the impact on reproduction. The data showed that while TCDD treatment of females caused no significant change in litter size, it did alter the survival of the pups. Also, TCDD exposure of either the male or female mice led to an increase in the gestational period. While TCDD did not alter the gross morphology of the ovaries and testes, it induced significant alterations in the miRNA expression. The ovaries showed the differential expression of 426 miRNAs, of which 315 miRNAs were upregulated and 111 miRNA that were downregulated after TCDD exposure when compared to the vehicle controls. In the testes, TCDD caused the differential expression of 433 miRNAs, with 247 miRNAs upregulated and 186 miRNAs downregulated. Pathway analysis showed that several of these dysregulated miRNAs targeted reproductive functions. The current study suggests that the reproductive toxicity of TCDD may result from alterations in the miRNA expression in the reproductive organs. Because miRNAs also represent one of the epigenetic pathways of gene expression, our studies suggest that the transgenerational toxicity of TCDD may also result from dysregulation in the miRNAs.
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Affiliation(s)
- Alina Hall
- Department of Pathology, Microbiology and Immunology, School of Medicine, University of South Carolina, Columbia, SC, United States
| | - Donald Mattison
- Arnold School of Public Health, University of South Carolina, Columbia, SC, United States
| | - Narendra Singh
- Department of Pathology, Microbiology and Immunology, School of Medicine, University of South Carolina, Columbia, SC, United States
| | - Ioulia Chatzistamou
- Department of Pathology, Microbiology and Immunology, School of Medicine, University of South Carolina, Columbia, SC, United States
| | - Jiajia Zhang
- Arnold School of Public Health, University of South Carolina, Columbia, SC, United States
| | - Mitzi Nagarkatti
- Department of Pathology, Microbiology and Immunology, School of Medicine, University of South Carolina, Columbia, SC, United States
| | - Prakash Nagarkatti
- Department of Pathology, Microbiology and Immunology, School of Medicine, University of South Carolina, Columbia, SC, United States
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3
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van Gerwen M, Vasan V, Genden E, Saul SR. Human 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure and thyroid cancer risk. Toxicology 2023; 488:153474. [PMID: 36868552 DOI: 10.1016/j.tox.2023.153474] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 02/27/2023] [Accepted: 03/01/2023] [Indexed: 03/05/2023]
Abstract
Thyroid cancer incidence has been steadily rising since the 1970s and exposure to environmental pollutants, including persistent organic pollutants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other dioxins, has emerged as a potential explanation for this increase. This study aimed to summarize available human studies on the association between TCDD exposure and thyroid cancer. A systematic review of the literature was performed searching the National Library of Medicine and National Institutes of Health PubMed, Embase, and Scopus databases, through January 2022, using the following keywords: "thyroid", "2,3,7,8-tetrachlorodibenzo-p-dioxin", "TCDD", "dioxin", and "Agent Orange". Six studies were included in this review. Three studies evaluated the acute exposure to the chemical factory accident in Seveso, Italy, and found a non-significant increase in the risk of thyroid cancer. Two studies investigating Agent Orange exposure among United States Vietnam War veterans found a significant risk of thyroid cancer following exposure. No association was found in one study evaluating TCDD exposure through herbicides. The current study highlights the limited information on the potential association between TCDD exposure and thyroid cancer and thus the need for future human studies, especially considering the persistent human exposure to dioxins in the environment.
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Affiliation(s)
- Maaike van Gerwen
- Department of Otolaryngology - Head and Neck Surgery, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Institute for Translational Epidemiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
| | - Vikram Vasan
- Department of Otolaryngology - Head and Neck Surgery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Eric Genden
- Department of Otolaryngology - Head and Neck Surgery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Shira R Saul
- Division of Endocrinology, Diabetes and Bone Diseases, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Division of Endocrinology, James J. Peters Veterans Affairs Medical Center, Bronx, NY, USA
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4
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Kobets T, Smith BPC, Williams GM. Food-Borne Chemical Carcinogens and the Evidence for Human Cancer Risk. Foods 2022; 11:foods11182828. [PMID: 36140952 PMCID: PMC9497933 DOI: 10.3390/foods11182828] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [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
- Correspondence: ; Tel.: +1-914-594-3105; Fax: +1-914-594-4163
| | - 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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Che X, Dai W. Aryl Hydrocarbon Receptor: Its Regulation and Roles in Transformation and Tumorigenesis. Curr Drug Targets 2020; 20:625-634. [PMID: 30411679 DOI: 10.2174/1389450120666181109092225] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Revised: 11/07/2018] [Accepted: 11/07/2018] [Indexed: 01/07/2023]
Abstract
AhR is an environmental response gene that mediates cellular responses to a variety of xenobiotic compounds that frequently function as AhR ligands. Many AhR ligands are classified as carcinogens or pro-carcinogens. Thus, AhR itself acts as a major mediator of the carcinogenic effect of many xenobiotics in vivo. In this concise review, mechanisms by which AhR trans-activates downstream target gene expression, modulates immune responses, and mediates malignant transformation and tumor development are discussed. Moreover, activation of AhR by post-translational modifications and crosstalk with other transcription factors or signaling pathways are also summarized.
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Affiliation(s)
- Xun Che
- Department of Environmental Medicine, New York University Langone Health, New York, NY 10010, United States
| | - Wei Dai
- Department of Environmental Medicine, New York University Langone Health, New York, NY 10010, United States
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6
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In vitro toxicity and in silico docking analysis of two novel selective AH-receptor modulators. Toxicol In Vitro 2018; 52:178-188. [PMID: 29908305 DOI: 10.1016/j.tiv.2018.06.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 06/06/2018] [Accepted: 06/08/2018] [Indexed: 12/12/2022]
Abstract
The mediator of dioxin toxicity, aryl hydrocarbon receptor (AHR), has also important physiological functions. Selective AHR modulators (SAHRMs) share some effects of dioxins, except for their marked toxicity. We recently characterised toxicologically two novel SAHRMs, prodrugs IMA-08401 and IMA-07101 in rats, demonstrating that they are far less deleterious than the most toxic AHR-agonist, TCDD. Here, we analysed the in vitro toxicity and in silico AHR binding of the respective active, deacetylated metabolites, IMA-06201 (N-ethyl-N-phenyl-5-chloro-1,2-dihydro-4-hydroxy-1-methyl-2-oxo-quinoline-3-carboxamide) and IMA-06504 (N-(4-trifluoromethylphenyl)-1,2-dihydro-4-hydroxy-5-methoxy-1-methyl-2-oxo-quinoline-3-carboxamide). In H4IIE rat hepatoma cells, IMA-06201 and IMA-06504 induced CYP1A1 with comparable potencies and efficacies to those of TCDD. They had little effect on cell viability as assessed by LDH leakage and MTT reduction assays, and were not mutagenic in the Ames test, but IMA-06504 elicited a maximally 2.7-fold increase in micronuclei. Molecular docking simulations showed that similar to TCDD, they occupy the central region of AHR ligand binding cavity. Hence, while showing low to negligible in vitro toxicity, these novel SAHRMs bind to the AHR qualitatively in a similar fashion to TCDD, and appear comparably powerful AHR agonists. Combined with our earlier results demonstrating that they seem considerably less toxic in vivo than TCDD, these compounds are thus highly interesting new SAHRMs.
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7
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Taft JD, Colonnetta MM, Schafer RE, Plick N, Powell WH. Dioxin Exposure Alters Molecular and Morphological Responses to Thyroid Hormone in Xenopus laevis Cultured Cells and Prometamorphic Tadpoles. Toxicol Sci 2018; 161:196-206. [PMID: 29294139 PMCID: PMC5837452 DOI: 10.1093/toxsci/kfx213] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Amphibian metamorphosis is driven by thyroid hormone (TH). We used prometamorphic tadpoles and a cell line of the African clawed frog (Xenopus laevis) to examine immediate effects of dioxin exposure on TH. Gene expression patterns suggest cross-talk between the thyroid hormone receptor (TR) and aryl hydrocarbon receptor (AHR) signaling pathways. In XLK-WG cells, expression of Cytochrome P450 1A6 (cyp1A6), an AHR target, was induced 1000-fold by 100 nM TCDD (2, 3, 7, 8 tetrachlorodibenzo-p-dioxin). Krüppel-Like Factor 9 (klf9), the first gene induced in a cascade of TH responses tied to metamorphosis, was upregulated over 5-fold by 50 nM triiodothyronine (T3) and 2-fold by dioxin. Co-exposure to T3 and TCDD boosted both responses, further inducing cyp1A6 by 75% and klf9 about 60%. Additional canonical targets of each receptor, including trβa and trβb (TR) and udpgt1a (AHR) responded similarly. Induction of TH targets by TCDD in XLK-WG cells predicts that exposure could speed metamorphosis. We tested this hypothesis in two remodeling events: tail resorption and hind limb growth. Resorption of ex vivo cultured tails was accelerated by 10 nM T3, while a modest increase in resorption by 100 nM TCDD lacked statistical significance. Hind limbs doubled in length over four days following 1 nM T3 treatment, but limb length was unaffected by 100 nM TCDD. TCDD co-exposure reduced the T3 effect by nearly 40%, despite TCDD induction of klf9 in whole tadpoles, alone or with T3. These results suggest that tissue-specific TCDD effects limit or reverse the increased metamorphosis rate predicted by klf9 induction.
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Affiliation(s)
- Justin D Taft
- Biology Department, Kenyon College, Gambier, Ohio 43022
| | | | | | - Natalie Plick
- Biology Department, Kenyon College, Gambier, Ohio 43022
| | - Wade H Powell
- Biology Department, Kenyon College, Gambier, Ohio 43022
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8
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Pilsner JR, Parker M, Sergeyev O, Suvorov A. Spermatogenesis disruption by dioxins: Epigenetic reprograming and windows of susceptibility. Reprod Toxicol 2017; 69:221-229. [PMID: 28286111 DOI: 10.1016/j.reprotox.2017.03.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 02/24/2017] [Accepted: 03/02/2017] [Indexed: 02/06/2023]
Abstract
Dioxins are a group of highly persistent chemicals that are generated as by-products of industrial and natural processes. Reduction in sperm counts is among the most sensitive endpoints of dioxin toxicity. The exact mechanism by which dioxins reduce sperm counts is not known. Recent data implicate the role of epididymal factors rather than disruption of spermatogenesis. Studies reviewed here demonstrate that dioxins induce the transfer of environmental conditions to the next generation via male germline following exposures during the window of epigenetic reprogramming of primordial germ cells. Increased incidence of birth defects in offspring of male veterans exposed to dioxin containing, Agent Orange, suggest that dioxins may induce epigenomic changes in male germ cells of adults during spermatogenesis. This is supported by recent animal data that show that environmental conditions can cause epigenetic dysregulation in sperm in the context of specific windows of epigenetic reprogramming during spermatogenesis.
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Affiliation(s)
- J Richard Pilsner
- Department of Environmental Health Sciences, University of Massachusetts Amherst, 686 N. Pleasant St., 171 Goessmann, Amherst, MA 01003-9303, USA.
| | - Mikhail Parker
- Department of Environmental Health Sciences, University of Massachusetts Amherst, 686 N. Pleasant St., 171 Goessmann, Amherst, MA 01003-9303, USA.
| | - Oleg Sergeyev
- Department of Genomics and Human Genetics, Vavilov Institute of General Genetics, Russian Academy of Sciences, 3 Gubkina St., 119991 Moscow, Russia; Chapaevsk Medical Association, 3a Meditsinskaya St., 446100 Chapaevsk, Samara Region, Russia.
| | - Alexander Suvorov
- Department of Environmental Health Sciences, University of Massachusetts Amherst, 686 N. Pleasant St., 171 Goessmann, Amherst, MA 01003-9303, USA.
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9
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Martinez-Zamora MA, Mattioli L, Parera J, Abad E, Coloma JL, van Babel B, Galceran MT, Balasch J, Carmona F. Increased levels of dioxin-like substances in adipose tissue in patients with deep infiltrating endometriosis. Hum Reprod 2015; 30:1059-68. [DOI: 10.1093/humrep/dev026] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 01/26/2015] [Indexed: 12/20/2022] Open
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10
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Chen S, Han Z, Zhang D, Zhan J. Theoretical study of the inclusion complexation of TCDD with cucurbit[n]urils. RSC Adv 2014. [DOI: 10.1039/c4ra06011c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cucurbit[n]urils as a host are indicated to be capable of including TCDD guest and the formed inclusion complexes can be detected using IR and Raman techniques.
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Affiliation(s)
- Shunwei Chen
- Key Lab of Colloid and Interface Chemistry
- Ministry of Education
- Institute of Theoretical Chemistry
- Shandong University
- Jinan, P. R. China
| | - Zhe Han
- Key Lab of Colloid and Interface Chemistry
- Ministry of Education
- Institute of Theoretical Chemistry
- Shandong University
- Jinan, P. R. China
| | - Dongju Zhang
- Key Lab of Colloid and Interface Chemistry
- Ministry of Education
- Institute of Theoretical Chemistry
- Shandong University
- Jinan, P. R. China
| | - Jinhua Zhan
- Key Lab of Colloid and Interface Chemistry
- Ministry of Education
- Institute of Theoretical Chemistry
- Shandong University
- Jinan, P. R. China
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11
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Endocrine-disrupting chemicals: associated disorders and mechanisms of action. JOURNAL OF ENVIRONMENTAL AND PUBLIC HEALTH 2012; 2012:713696. [PMID: 22991565 PMCID: PMC3443608 DOI: 10.1155/2012/713696] [Citation(s) in RCA: 334] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 05/10/2012] [Accepted: 05/10/2012] [Indexed: 12/21/2022]
Abstract
The incidence and/or prevalence of health problems associated with endocrine-disruption have increased. Many chemicals have endocrine-disrupting properties, including bisphenol A, some organochlorines, polybrominated flame retardants, perfluorinated substances, alkylphenols, phthalates, pesticides, polycyclic aromatic hydrocarbons, alkylphenols, solvents, and some household products including some cleaning products, air fresheners, hair dyes, cosmetics, and sunscreens. Even some metals were shown to have endocrine-disrupting properties. Many observations suggesting that endocrine disruptors do contribute to cancer, diabetes, obesity, the metabolic syndrome, and infertility are listed in this paper. An overview is presented of mechanisms contributing to endocrine disruption. Endocrine disruptors can act through classical nuclear receptors, but also through estrogen-related receptors, membrane-bound estrogen-receptors, and interaction with targets in the cytosol resulting in activation of the Src/Ras/Erk pathway or modulation of nitric oxide. In addition, changes in metabolism of endogenous hormones, cross-talk between genomic and nongenomic pathways, cross talk with estrogen receptors after binding on other receptors, interference with feedback regulation and neuroendocrine cells, changes in DNA methylation or histone modifications, and genomic instability by interference with the spindle figure can play a role. Also it was found that effects of receptor activation can differ in function of the ligand.
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12
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Sankpal UT, Pius H, Khan M, Shukoor MI, Maliakal P, Lee CM, Abdelrahim M, Connelly SF, Basha R. Environmental factors in causing human cancers: emphasis on tumorigenesis. Tumour Biol 2012; 33:1265-74. [PMID: 22614680 DOI: 10.1007/s13277-012-0413-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 04/30/2012] [Indexed: 01/22/2023] Open
Abstract
The environment and dietary factors play an essential role in the etiology of cancer. Environmental component is implicated in ~80 % of all cancers; however, the causes for certain cancers are still unknown. The potential players associated with various cancers include chemicals, heavy metals, diet, radiation, and smoking. Lifestyle habits such as smoking and alcohol consumption, exposure to certain chemicals (e.g., polycyclic aromatic hydrocarbons, organochlorines), metals and pesticides also pose risk in causing human cancers. Several studies indicated a strong association of lung cancer with the exposure to tobacco products and asbestos. The contribution of excessive sunlight, radiation, occupational exposure (e.g., painting, coal, and certain metals) is also well established in cancer. Smoking, excessive alcohol intake, consumption of an unhealthy diet, and lack of physical activity can act as risk factors for cancer and also impact the prognosis. Even though the environmental disposition is linked to cancer, the level and duration of carcinogen-exposure and associated cellular and biochemical aspects determine the actual risk. Modulations in metabolism and DNA adduct formation are considered central mechanisms in environmental carcinogenesis. This review describes the major environmental contributors in causing cancer with an emphasis on molecular aspects associated with environmental disposition in carcinogenesis.
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Affiliation(s)
- Umesh T Sankpal
- Cancer Research Institute, MD Anderson Cancer Center Orlando, 6900 Lake Nona Blvd, Orlando, FL 32827, USA
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13
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Jin KS, Park CM, Lee YW. Identification of differentially expressed genes by 2,3,7,8-tetrachlorodibenzo-p-dioxin in human bronchial epithelial cells. Hum Exp Toxicol 2011; 31:107-12. [DOI: 10.1177/0960327111417266] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- K-S Jin
- Department of Biomedical Laboratory Science, Inje University, Gimhae, Gyeongnam, Korea
- Blue-Bio Industry Regional Innovation Center, Dongeui University, Busan, Korea
| | - CM Park
- Department of Biomedical Laboratory Science, Inje University, Gimhae, Gyeongnam, Korea
- Department of Pathology, College of Medicine, Inje University, Busan, Korea
| | - Y-W Lee
- Department of Biomedical Laboratory Science, Inje University, Gimhae, Gyeongnam, Korea
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Yoshizawa K, Walker NJ, Nyska A, Kissling GE, Jokinen MP, Brix AE, Sells DM, Wyde ME. Thyroid follicular lesions induced by oral treatment for 2 years with 2,3,7,8-tetrachlorodibenzo-p-dioxin and dioxin-like compounds in female Harlan Sprague-Dawley rats. Toxicol Pathol 2010; 38:1037-50. [PMID: 20924081 DOI: 10.1177/0192623310382560] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and structurally-similar dioxin-like compounds affect thyroid function and morphology and thyroid hormone metabolism in animals and humans. The National Toxicology Program conducted eight 2-year gavage studies in female Harlan Sprague-Dawley rats to determine the relative potency of chronic toxicity and carcinogenicity of TCDD, 3,3',4,4',5-pentachlorobiphenyl (PCB126), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), 2,3',4,4',5-pentachlorobiphenyl (PCB118), 2,2',4,4',5,5'-hexachloro-biphenyl (PCB153), a tertiary mixture of TCDD/PCB126/PeCDF, and two binary mixtures (PCB126/PCB153 and PCB126/PCB118). Administration of these compounds was associated with increased incidences of thyroid follicular cell hypertrophy, variably observed in the 14-, 31-, and 53-week interim and 2-year sacrifice groups. In all studies, the incidences of follicular cell adenoma and carcinoma were not increased. Decreased levels of serum thyroxine were primarily noted in the 14-or-later -week interim groups of all chemicals. Serum triiodothyronine (T3) levels were increased in the TCDD, PCB126, PeCDF, TCDD/PCB126/PeCDF, and PCB126/PCB153 studies, while decreased levels were noted in the PCB153 and PCB126/PCB118 studies. TCDD, PCB126, PCB126/PCB153, and PCB126/PCB118 increased levels of serum thyroid-stimulating hormone almost in a dose-dependent manner in the 14-week groups. These data suggest that although dioxin-like compounds alter thyroid hormones and increase follicular cell hyperplasia, there is not an increase in thyroid adenoma or carcinoma in female Sprague-Dawley rats.
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15
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Pesatori AC, Consonni D, Rubagotti M, Grillo P, Bertazzi PA. Cancer incidence in the population exposed to dioxin after the "Seveso accident": twenty years of follow-up. Environ Health 2009; 8:39. [PMID: 19754930 PMCID: PMC2754980 DOI: 10.1186/1476-069x-8-39] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Accepted: 09/15/2009] [Indexed: 05/18/2023]
Abstract
BACKGROUND The Seveso, Italy accident in 1976 caused the contamination of a large population by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Possible long-term effects have been examined through mortality and cancer incidence studies. We have updated the cancer incidence study which now covers the period 1977-96. METHODS The study population includes subjects resident at the time of the accident in three contaminated zones with decreasing TCDD soil levels (zone A, very high; zone B, high; zone R, low) and in a surrounding non-contaminated reference territory. Gender-, age-, and period-adjusted rate ratios (RR) and 95% confidence intervals (95% CI) were calculated by using Poisson regression for subjects aged 0-74 years. RESULTS All cancer incidence did not differ from expectations in any of the contaminated zones. An excess of lymphatic and hematopoietic tissue neoplasms was observed in zones A (four cases; RR, 1.39; 95% CI, 0.52-3.71) and B (29 cases; RR, 1.56; 95% CI, 1.07-2.27) consistent with the findings of the concurrent mortality study. An increased risk of breast cancer was detected in zone A females after 15 years since the accident (five cases, RR, 2.57; 95% CI, 1.07-6.20). No cases of soft tissue sarcomas occurred in the most exposed zones (A and B, 1.17 expected). No cancer cases were observed among subjects diagnosed with chloracne early after the accident. CONCLUSION The extension of the Seveso cancer incidence study confirmed an excess risk of lymphatic and hematopoietic tissue neoplasms in the most exposed zones. No clear pattern by time since the accident and zones was evident partly because of the low number of cases. The elevated risk of breast cancer in zone A females after 15 years since the accident deserves further and thorough investigation. The follow-up is continuing in order to cover the long time period (even decades) usually elapsing from exposure to carcinogenic chemicals and disease occurrence.
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Affiliation(s)
- Angela Cecilia Pesatori
- Unit of Epidemiology, Department of Preventive Medicine, Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Via San Barnaba 8, 20122 Milano, Italy
- EPOCA Research Center, Department of Occupational and Environmental Health, Università degli Studi di Milano, Milan, Via San Barnaba 8, 20122 Milano, Italy
| | - Dario Consonni
- Unit of Epidemiology, Department of Preventive Medicine, Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Via San Barnaba 8, 20122 Milano, Italy
- EPOCA Research Center, Department of Occupational and Environmental Health, Università degli Studi di Milano, Milan, Via San Barnaba 8, 20122 Milano, Italy
| | - Maurizia Rubagotti
- Unit of Epidemiology, Department of Preventive Medicine, Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Via San Barnaba 8, 20122 Milano, Italy
| | - Paolo Grillo
- Unit of Epidemiology, Department of Preventive Medicine, Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Via San Barnaba 8, 20122 Milano, Italy
| | - Pier Alberto Bertazzi
- Unit of Epidemiology, Department of Preventive Medicine, Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Via San Barnaba 8, 20122 Milano, Italy
- EPOCA Research Center, Department of Occupational and Environmental Health, Università degli Studi di Milano, Milan, Via San Barnaba 8, 20122 Milano, Italy
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T. BERBNER, N. RAHMAN, T. BRAUNBECK. Induction of cytochrome P450 1A and DNA damage in isolated rainbow trout (Oncorhynchus mykiss) hepatocytes by 2,3,7,8 tetrachlorodibenzo-p-dioxin. Biomarkers 2008; 4:214-28. [DOI: 10.1080/135475099230886] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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17
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Miyazaki W, Iwasaki T, Takeshita A, Tohyama C, Koibuchi N. Identification of the functional domain of thyroid hormone receptor responsible for polychlorinated biphenyl-mediated suppression of its action in vitro. ENVIRONMENTAL HEALTH PERSPECTIVES 2008; 116:1231-6. [PMID: 18795168 PMCID: PMC2535627 DOI: 10.1289/ehp.11176] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2007] [Accepted: 05/13/2008] [Indexed: 05/03/2023]
Abstract
BACKGROUND Polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins, and poly-chlorinated dibenzofurans adversely affect the health of humans and various animals. Such effects might be partially exerted through the thyroid hormone (TH) system. We previously reported that one of the hydroxylated PCB congeners suppresses TH receptor (TR)-mediated transcription by dissociating TR from the TH response element (TRE). However, the binding site of PCB within TR has not yet been identified. OBJECTIVES We aimed to identify the functional TR domain responsible for the PCB-mediated suppression of TR action by comparing the magnitude of suppression using several representative PCB/dioxin congeners. MATERIALS AND METHODS We generated chimeric receptors by combining TR and glucocorticoid receptor (GR) and determined receptor-mediated transcription using transient transfection-based reporter gene assays, and TR-TRE binding using electrophoretic mobility shift assays. RESULTS Although several PCB congeners, including the hydroxylated forms, suppressed TR-mediated transcription to various degrees, 2,3,7,8-tetrachlorodibenzo-p-dioxin did not alter TR action, but 2,3,4,7,8-pentachlorodibenzofuran weakly suppressed it. The magnitude of suppression correlated with that of TR-TRE dissociation. The suppression by PCB congeners was evident from experiments using chimeric receptors containing a TR DNA-binding domain (DBD) but not a GR-DBD. CONCLUSIONS Several nondioxin-like PCB congeners and hydroxylated PCB compounds suppress TR action by dissociating TR from TRE through interaction with TR-DBD.
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Affiliation(s)
- Wataru Miyazaki
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Toshiharu Iwasaki
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
- Address correspondence to T. Iwasaki, Department of Integrative Physiology, Division of Biological Regulation, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan. Telephone: 81-27-220-7923. Fax: 81-27-220-7926. E-mail:
| | - Akira Takeshita
- Endocrine Center, Toranomon Hospital and Okinaka Memorial Institute for Medical Research, Tokyo, Japan
| | - Chiharu Tohyama
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
| | - Noriyuki Koibuchi
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
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18
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Reichard JF, Dalton TP, Shertzer HG, Puga A. Induction of oxidative stress responses by dioxin and other ligands of the aryl hydrocarbon receptor. Dose Response 2006; 3:306-31. [PMID: 18648615 DOI: 10.2203/dose-response.003.03.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
TCDD and other polyhalogenated aromatic hydrocarbon ligands of the aryl hydrocarbon receptor (AHR) have been classically considered as non-genotoxic compounds because they fail to be directly mutagenic in either bacteria or most in vitro assay systems. They do so in spite of having repeatedly been linked to oxidative stress and to mutagenic and carcinogenic outcomes. Oxidative stress, on the other hand, has been used as a marker for the toxicity of dioxin and its congeners. We have focused this review on the connection between oxidative stress induction and the toxic effects of fetal and adult dioxin exposure, with emphasis on the large species difference in sensitivity to this agent. We examine the roles that the dioxin-inducible cytochromes P450s play in the cellular and toxicological consequences of dioxin exposure with emphasis on oxidative stress involvement. Many components of the health consequences resulting from dioxin exposure may be attributable to epigenetic mechanisms arising from prolonged reactive oxygen generation.
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Affiliation(s)
- John F Reichard
- Center for Environmental Genetics and Department of Environmental Health, University of Cincinnati Medical Center, Cincinnati, OH 45267, USA
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19
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Thornton AS, Oda Y, Stuart GR, Holcroft J, de Boer JG. The dioxin TCDD protects against aflatoxin-induced mutation in female rats, but not in male rats. Mutat Res 2004; 561:147-52. [PMID: 15238239 DOI: 10.1016/j.mrgentox.2004.05.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2003] [Revised: 04/30/2004] [Accepted: 05/04/2004] [Indexed: 04/30/2023]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant and a potent carcinogen in laboratory rodents. When combined with other environmental toxins, it has been shown to increase the (geno)toxicity of some compounds. In this study, the effect of TCDD on the mutagenicity of aflatoxin-B1 (AFB1) was examined in the rat liver using a lacI transgenic rodent mutation assay. AFB1 induces GC-->TA transversions. Since TCDD is known to have a differential effect in male and female rodents, both sexes were studied. The data showed that a 6-week pre-exposure to TCDD had no significant effect on the frequency of aflatoxin-induced mutation in the liver of male rats. However, the TCDD treatment completely prevented the aflatoxin-induced transversion mutations in female animals.
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Affiliation(s)
- A S Thornton
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada V8W 3N5
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20
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Akhtar FZ, Garabrant DH, Ketchum NS, Michalek JE. Cancer in US Air Force Veterans of the Vietnam War. J Occup Environ Med 2004; 46:123-36. [PMID: 14767215 DOI: 10.1097/01.jom.0000111603.84316.0f] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cancer incidence and mortality were summarized in Air Force veterans of the Vietnam War. The index subjects were Operation Ranch Hand veterans who sprayed 2,3,7,8 tetrachlorodibenzo-p-dioxin (dioxin)-contaminated herbicides in Vietnam. Comparisons served in Southeast Asia during the same period but did not spray herbicides. We assessed cancer incidence and mortality using national rates and contrasted cancer risk in each of three Ranch Hand dioxin exposure categories relative to comparisons. The incidence of melanoma and prostate cancer was increased among white Ranch Hand veterans relative to national rates. Among veterans who spent at most 2 years in Southeast Asia, the risk of cancer at any site, of prostate cancer and of melanoma was increased in the highest dioxin exposure category. These results appear consistent with an association between cancer and dioxin exposure.
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21
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Choi SM, Yoo SD, Lee BM. Toxicological characteristics of endocrine-disrupting chemicals: developmental toxicity, carcinogenicity, and mutagenicity. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2004; 7:1-24. [PMID: 14681080 DOI: 10.1080/10937400490253229] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
It is generally accepted that endocrine-disrupting chemicals (EDCs) play a role in a variety of adverse health effects in an intact organism or its progeny as a consequence of changes in the endocrine system. Primary toxic effects of EDCs were reported to be related to infertility, reduction in sperm count, and teratogenicity, but other important toxic effects of EDCs such as carcinogenicity and mutagenicity have also been demonstrated. The aim of the present study was to systematically analyze the toxicological characteristics of EDCs in pesticides, industrial chemicals, and metals. A comprehensive literature survey on the 48 EDCs classified by the Centers for Disease Control and Prevention (CDC) was conducted using a number of databases which included Medline, Toxline, and Toxnet. The survey results revealed that toxicological characteristics of EDCs were shown to produce developmental toxicity (81%), carcinogenicity (79%, when positive in at least one animal species; 48%, when classified based on IARC evaluation), mutagenicity (79%), immunotoxicity (52%), and neurotoxicity (50%). Regarding the hormone-modulating effects of the 48 EDCs, estrogenic effects were the most predominant in pesticides, while effects on thyroid hormone were found for heavy metals. EDCs showing estrogen-modulating effects were closely related to carcinogenicity or mutagenicity with a high degree of sensitivity. Systematic information on the toxicological characteristics of the EDCs will be useful for future research directions on EDCs, the development of new screening methods, legal regulation, and for investigations of their mechanism of action.
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Affiliation(s)
- Seul Min Choi
- Division of Toxicology/Pharmacokinetics, College of Pharmacy, Sungkyunkwan University, Suwon, Kyonggi-do, South Korea
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22
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Zeytun A, McKallip RJ, Fisher M, Camacho I, Nagarkatti M, Nagarkatti PS. Analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced gene expression profile in vivo using pathway-specific cDNA arrays. Toxicology 2002; 178:241-60. [PMID: 12167310 DOI: 10.1016/s0300-483x(02)00230-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In the current study, we used pathway-specific cDNA arrays to detect the transcriptional signature induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in vivo by studying simultaneously the expression profiles of 83 genes involved in apoptosis, cytokine production and angiogenesis. To this end, C57BL/6 mice were injected i.p. with 50 microg/kg body weight of TCDD and 1 or 3 days later, the thymus was analyzed for gene expression profiles. In the thymus, 23 out of 37 apoptotic genes screened were up-regulated by TCDD by a factor of two or more when compared to the vehicle-treated controls. In contrast, in the spleen, 20 out of 22 and in the liver, 16 out of 37 apoptotic genes were up-regulated. In the thymus, several genes encoding caspases, and members of the TNF family, including Fas ligand, were induced. Also, in the thymus, eight out of 23, and in the spleen, six out of 23 cytokine genes were up-regulated. In the liver and to a lesser extent in the thymus, certain angiogenesis genes were induced while others were repressed. When mice were injected with 0.1, 1, 10 or 50 microg/kg body weight of TCDD and the thymus was analyzed for apoptotic genes 1 day later, a dose-dependent response was not seen with most apoptotic genes. However, certain apoptotic genes were induced in the thymus even at low doses of 0.1 microg/kg body weight of TCDD. These data demonstrate that TCDD alters the expression of a large array of genes involved in apoptosis, cytokine production and angiogenesis. Thus, pathway-specific cDNA arrays may help in the identification of specific gene expression profiles induced by xenobiotics and to delineate the molecular mechanisms of toxicity.
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Affiliation(s)
- Ahmet Zeytun
- Department of Microbiology and Immunology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23113, USA
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23
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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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24
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Mitrou PI, Dimitriadis G, Raptis SA. Toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds. Eur J Intern Med 2001; 12:406-411. [PMID: 11557325 DOI: 10.1016/s0953-6205(01)00146-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Dioxin-type chemicals produce a variety of toxic and biochemical changes, some of which occur at very low doses and last for long periods of time. The most consistent toxin effect is body weight loss. In animals, the histopathologic changes, which are hyperplastic and hypertrophic, affect the gastrointestinal mucosa and the urinary track epithelium. In contrast, atrophic responses are seen in the thymus. Both hyperplasia and necrosis are observed in the liver. The administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin also produces endocrine effects and changes in carbohydrate and lipid metabolism. The most serious toxic effects and the biochemical background of the lesions are reviewed.
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Affiliation(s)
- P I. Mitrou
- Second Department of Internal Medicine, Research Institute and Diabetes Center, Athens University Medical School, 'Evangelismos' Hospital, P.O. Box 171 51, GR-100 24, Athens, Greece
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25
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Thornton AS, Oda Y, Stuart GR, Glickman BW, de Boer JG. Mutagenicity of TCDD in Big Blue transgenic rats. Mutat Res 2001; 478:45-50. [PMID: 11406168 DOI: 10.1016/s0027-5107(01)00105-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a significant environmental contaminant resulting from such industrial processes as pulp and paper production. TCDD is a suspected human carcinogen and its ability to induce cancer in laboratory rodents is well documented. Its mechanism of tumor initiation, however, is not well understood and in vitro mutagenicity studies have yielded inconsistent results. In this study, Big Blue lacI transgenic rats were used to assess the mutagenicity of TCDD in both male and female animals. After 6 weeks of exposure to 2 microg/kg TCDD neither an increase in mutation frequency nor any change in mutation spectrum was observed in either male or female animals.
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Affiliation(s)
- A S Thornton
- Centre for Environmental Health, University of Victoria, P.O. Box 3020, Victoria, BC, Canada V8W 3N5
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26
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Kohn MC, Walker NJ, Kim AH, Portier CJ. Physiological modeling of a proposed mechanism of enzyme induction by TCDD. Toxicology 2001; 162:193-208. [PMID: 11369115 DOI: 10.1016/s0300-483x(01)00363-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A physiological model was previously constructed to facilitate extrapolation of surrogates for the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rat liver to doses comparable to human environmental exposures. The model included induction of P450 isozymes and suggested the presence of multiple binding sites with different affinities for the TCDD-liganded Ah receptor at CYP1A1 dioxin responsive elements. The model also indicated that protein synthesis on the mRNA template exhibited saturation kinetics with respect to message levels. In the present work the earlier model was revised to include the increased proteolysis of the Ah receptor on binding TCDD, more realistic representations of gene transcription and mRNA translation, and different stability for each mRNA. The revised model includes multiple TCDD-liganded Ah receptor binding sites for CYP1A1 and CYP1B1 genes, a lag of 0.2 day for production of mRNA and induced proteins, and stabilization of mRNA by a poly(A) tail. The model reproduced the transient depletion of the Ah receptor subsequent to binding ligand and the dose-response of the receptor in rats treated with biweekly oral doses of TCDD in corn oil. The model reproduced tissue TCDD concentrations observed for several dosing scenarios. Such robustness indicates the utility of the model in estimating internal dose. The model also reproduced the observed dose-response patterns for mRNA and protein for CYP1A1, CYP1A2, and CYP1B1 after repeated dosing. Neither of the two dissociation constants for the Ah receptor bound to the CYP1B1 gene is negligible, supporting the assumption of multiple response elements for this gene. The poorer induction of CYP1B1 was predicted to be due to lower affinity of the dioxin responsive elements for binding the liganded Ah receptor, suggesting the involvement of other regulatory factors, and a shorter poly(A) tail on CYP1B1 mRNA, leading to a shorter lifetime. Saturation in the kinetics of protein synthesis was linked to the limited number of ribosomes that could bind to each message molecule, resulting in fewer ribosomes bound per message at higher doses. Predicted induction at low doses was found to vary widely with the assumptions used in the construction of a model. More detailed descriptions of biological processes might provide more reliable predictions of enzyme induction.
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Affiliation(s)
- M C Kohn
- Laboratory of Computational Biology and Risk Analysis, National Institute of Environmental Health Sciences, PO Box 12233, Research Triangle Park, NC 27709, USA.
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27
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Abstract
A physiological dosimetric model was constructed to describe the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on circulating thyroid hormones in the rat and to test the hypothesis that these hormonal changes cause chronically elevated serum thyrotropin (thyroid stimulating hormone, TSH), which mediates growth promotion and may lead to thyroid tumors in TCDD-treated rats. The model included diffusion restricted distribution of TCDD among compartments for liver, kidney, white fat, slowly and rapidly perfused tissues, and the thyroxine-sensitive tissues brown fat, pituitary, and thyroid. Blood was distributed among major vessels and the capillary beds of the tissues. Metabolism of TCDD was limited to the liver. Secretion of 3,5,3'-triiodothyronine (T3) and thyroxine (3,5,3',5'-tetraiodothyronine, T4) from the thyroid was modeled as stimulated by circulating TSH, whose release from the pituitary was regulated by the hypothalamic peptides thyrotropin releasing hormone (activating) and somatostatin (inhibiting). Release of these peptides was represented as inhibited and activated, respectively, by circulating T4. Binding proteins for T3 and T4 and metabolism of the hormones by deiodination were included in thyroxine-sensitive tissues. Induction of hepatic UDP-glucuronosyltransferase-1*6 (UGT), the enzyme which glucuronidates T4, was modeled as induced by the complex formed between TCDD and the aryl hydrocarbon receptor. The computed extent of deiodination, primacy of the thyroid in generating T3 from T4, dependence of liver and kidney on locally produced T3, and export of T3 formed in the pituitary agreed with experimental observations. The model reproduced the observed decrease in circulating T4 and elevated serum TSH following chronic administration of TCDD. The altered levels were attributed to the increased clearance of T4 by the induced UGT and the consequent modification of feedback control of hormone releases. These results are consistent with the hypothesis of growth stimulation by elevated TSH, but measured values of this hormone in blood of rats vary over a large range, and the change induced by TCDD is often small. Measured UGT levels are less variable and the increase in this protein is much greater, suggesting that this response may be a more reliable biomarker for effects of TCDD on the thyroid.
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Affiliation(s)
- M C Kohn
- Laboratory of Computational Biology and Risk Analysis, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
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Schümann J, Tiegs G. Pathophysiological mechanisms of TNF during intoxication with natural or man-made toxins. Toxicology 1999; 138:103-26. [PMID: 10576587 DOI: 10.1016/s0300-483x(99)00087-6] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intoxication with different natural toxins or man-made toxicants has been associated with the induction of tumor necrosis factor alpha (TNF). These include endotoxin, superantigens, Pseudomonas aeruginosa exotoxin A, bacterial DNA, T cell stimulatory agents such as agonistic anti-CD3 mAbs or concanavalin A, alpha-amanitin, paracetamol, ethanol, carbon tetrachloride, dioxin, and dimethylnitrosamine. In this paper we compile and discuss the current knowledge on the pathophysiological role of TNF during intoxication with all mentioned toxins and toxicants. A possible role of gut-derived endotoxin in several TNF-dependent toxic events has been considered. The development of pharmaceuticals that selectively interfere with the detrimental pathways induced by TNF during intoxication with bacteria, viruses, drugs, or other chemicals requires detailed knowledge of the signaling pathways originating from the two TNF receptors (TNFR1 and TNFR2). Major characteristics of these signaling pathways are described and put together.
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Affiliation(s)
- J Schümann
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Erlangen-Nürnberg, Erlangen, Germany
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Hengstler JG, Van der Burg B, Steinberg P, Oesch F. Interspecies differences in cancer susceptibility and toxicity. Drug Metab Rev 1999; 31:917-70. [PMID: 10575555 DOI: 10.1081/dmr-100101946] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
One of the most complex challenges to the toxicologist represents extrapolation from laboratory animals to humans. In this article, we review interspecies differences in metabolism and toxicity of heterocyclic amines, aflatoxin B1, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and related compounds, endocrine disrupters, polycyclic aromatic hydrocarbons, tamoxifen, and digitoxin. As far as possible, extrapolations to human toxicity and carcinogenicity are performed. Humans may be more susceptible to the carcinogenic effect of heterocyclic amines than monkeys, rats, and mice. Especially, individuals with high CYP1A2 and 3A4 activities and the rapid acetylator phenotype may be expected to have an increased risk. Striking interspecies variation in susceptibility to aflatoxin B1 carcinogenesis is known, with rats representing the most sensitive and mice the most resistant species, refractory to dietary levels three orders of magnitude higher than rats. An efficient conjugation with glutathione, catalyzed by glutathione S-transferase mYc, confers aflatoxin B1 resistance to mice. Extremely large interspecies differences in TCDD-induced toxicity are known. The guinea pig is the most susceptible mammal known, with an LD50 in the range 1-2 micrograms TCDD/kg, whereas the hamster is the most resistant species with an LD50 greater than 3000 micrograms/kg. A number of experts have pointed out to the fact that humans appear to be less sensitive to TCDD than most laboratory animals. Human exposure to background levels of TCDD is not likely to cause an incremental cancer risk. A clear cause--effect relationship has been shown between environmental endocrine-disrupting contaminants and adverse health effects in wildlife, whereas the effects seem to be less critical for humans. Studies on DNA adduct formation and metabolism of the nonsteroidal antiestrogen tamoxifen indicate that rats and mice are orders of magnitude more susceptible than humans.
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Affiliation(s)
- J G Hengstler
- Institute of Toxicology, University of Mainz, Germany
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Walker NJ, Portier CJ, Lax SF, Crofts FG, Li Y, Lucier GW, Sutter TR. Characterization of the dose-response of CYP1B1, CYP1A1, and CYP1A2 in the liver of female Sprague-Dawley rats following chronic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Toxicol Appl Pharmacol 1999; 154:279-86. [PMID: 9931287 DOI: 10.1006/taap.1998.8595] [Citation(s) in RCA: 68] [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]
Abstract
One of the current knowledge gaps in the evaluation of risk for human exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the relationship between gene expression induced by TCDDmore complex biological responses such as altered growth, differentiation, and neoplasia. This study investigates the dose-dependent expression of CYP1A1, CYP1A2,CYP1B1 in the livers of female Sprague-Dawley rats chronically exposed to TCDD. Animals were treated biweekly for 30 weeks with daily averaged doses of 0 to 125 ng TCDD/kg/day. Immunoblot analysis showed that protein levels for CYP1B1, CYP1A1, CYP1A2 exhibited a dose-dependent induction by TCDD. However, CYP1A1 and CYP1A2 protein levels were approximately 100-fold higher than CYP1B1, which could not be detected by either immunoblot analysis or immunohistochemistry in the livers of rats treated with TCDD for 30 weeks at a dose-equivalent less than 35.7 ng/kg/day. In control animals, CYP1A1CYP1A2 RNA levels, measured by quantitative RT-PCR, were 1100-15,000-fold higher than that of CYP1B1, respectively. TCDD induced CYP1B1 RNA levels at all doses, although absolute TCDD-induced levels of CYP1A1CYP1A2 at the highest dose (125 ng/kg/day) were more than 40-fold higher than that of CYP1B1. While the liver concentration of TCDD required for half-maximal induction of CYP1A1, CYP1A2,CYP1B1 RNA levels was similar, the shaping parameter (Hill coefficient) of the dose-response curve for CYP1B1 was significantly higher than that for CYP1A1 or CYP1A2. The low level of TCDD-induced CYP1B1 expression in the liver relative to that of the CYP1A1CYP1A2 suggest that, if CYP1B1 is involved in TCDD-induced hepatocarcinogenesis, its endogenous function is likely to be uniquenot overlapping with that of CYP1A1 or CYP1A2.
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Affiliation(s)
- N J Walker
- National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA.
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31
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Hardell L, Eriksson M, Axelson O. Agent Orange in war medicine: an aftermath myth. INTERNATIONAL JOURNAL OF HEALTH SERVICES 1998; 28:715-24. [PMID: 9842495 DOI: 10.2190/l940-b8fk-3y5e-rg86] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Since the late 1970s several epidemiological studies have appeared linking exposure to phenoxy herbicides or chlorophenols to some malignant tumors. Most of these compounds are contaminated with dioxins and dibenzofurans; for example, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a contaminant of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), a component of Agent Orange which was sprayed in Vietnam during the war. The results of some of the epidemiological studies on cancer risks associated with exposure to these compounds have been manipulated and misinterpreted, particularly by the Australian Royal Commission on the Use and Effects of Chemical Agents on Australian Personnel in Vietnam. Furthermore, a book on Australian war history entitled Medicine at War, commissioned by the Federal Government, reiterates several of these misinterpretations, despite available contrary evaluations from Australian and U.S. authorities. These remarkable and confusing circumstances in the scientific process are considered also in the light of the recent classification of TCDD as carcinogenic to humans, Group 1, by a Working Group at the International Agency for Research on Cancer in Lyon, France.
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Affiliation(s)
- L Hardell
- Department of Oncology, Orebro Medical Centre, Sweden
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Abstract
Synthetic chemicals are released into the environment by design (pesticides) or as a result of industrial activity. It is well known that natural environmental chemicals can cause goiter or thyroid imbalance. However, the effects of synthetic chemicals on thyroid function have received little attention, and there is much controversy over their potential clinical impact, because few studies have been conducted in humans. This article reviews the literature on possible thyroid disruption in wildlife, humans, and experimental animals and focuses on the most studied chemicals: the pesticides DDT, amitrole, and the thiocarbamate family, including ethylenethiourea, and the industrial chemicals polyhalogenated hydrocarbons, phenol derivatives, and phthalates. Wildlife observations in polluted areas clearly demonstrate a significant incidence of goiter and/or thyroid imbalance in several species. Experimental evidence in rodents, fish, and primates confirms the potentiality for thyroid disruption of several chemicals and illustrates the mechanisms involved. In adult humans, however, exposure to background levels of chemicals does not seem to have a significant negative effect on thyroid function, while exposure at higher levels, occupational or accidental, may produce mild thyroid changes. The impact of transgenerational, background exposure in utero on fetal neurodevelopment and later childhood cognitive function is now under scrutiny. There are several studies linking a lack of optimal neurological function in infants and children with high background levels of exposure to polychlorinated biphenyls (PCBs), dioxins, and/or co-contaminants, but it is unclear if the effects are caused by thyroid disruption in utero or direct neurotoxicity.
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Affiliation(s)
- F Brucker-Davis
- Wildlife and Contaminants Program, World Wildlife Fund, Washington, DC 20037, USA
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Puga A, Hoffer A, Zhou S, Bohm JM, Leikauf GD, Shertzer HG. Sustained increase in intracellular free calcium and activation of cyclooxygenase-2 expression in mouse hepatoma cells treated with dioxin. Biochem Pharmacol 1997; 54:1287-96. [PMID: 9393671 DOI: 10.1016/s0006-2952(97)00417-6] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a non-genotoxic environmental pollutant that causes multiple adverse effects in experimental animals and in humans. We show here that TCDD treatment of mouse hepatoma cells causes a rapid mobilization of intracellular calcium both in wild type Hepa-1 cells and in its c2 variant, a cell line that has highly reduced levels of functional aromatic hydrocarbon (Ah) receptor (AHR). In wild type cells, but not in the c2 variant, TCDD treatment leads to a sustained elevation of cytosolic free calcium. TCDD also induces elevated levels of cyclooxygenase-2 (COX-2) mRNA in wild type and in c37, a CYP1A1-deficient cell line, but not in c2 cells. Induction of Cox-2 is in fact dependent on the presence of a functional Ah receptor, since it can be blocked by antisense oligonucleotides to Ah receptor mRNA. Most likely as a consequence of Cox-2 induction, we find a significant increase in the level of 12-hydroxyheptadecatrienoic acid (12-HHT) secreted from TCDD-treated Hepa-1 cells. In addition, we observe elevated levels of 6-keto prostaglandin F1alpha in c2 cells and high levels of secreted prostaglandin F2alpha in c2, c37 and c4, the variant cell line lacking aromatic hydrocarbon nuclear translocator protein. These data suggest that Cox-2 activation by TCDD leads to the release of prostaglandins, eicosanoids and other mediators which may have an important role in the biological and toxic effects of TCDD.
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Affiliation(s)
- A Puga
- Center for Environmental Genetics and Department of Environmental Health, University of Cincinnati Medical Center, Ohio 45267-0056, USA
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34
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Van Beneden RJ. Environmental effects and aquatic organisms: investigations of molecular mechanisms of carcinogenesis. ENVIRONMENTAL HEALTH PERSPECTIVES 1997; 105 Suppl 3:669-74. [PMID: 9168012 PMCID: PMC1469911 DOI: 10.1289/ehp.97105s3669] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Cancers of the reproductive system are among the leading causes of mortality in women in the United States. While both genetic and environmental factors have been implicated in their etiology, the extent of the contribution of environmental factors to human diseases remains controversial. To better address the role of environmental exposures in cancer etiology, there has been an increasing focus on the development of nontraditional, environmentally relevant models. Our research involves the development of one such model. Gonadal tumors have been described in the softshell clam (Mya arenaria) in Maine and the hardshell clam (Mercenaria spp.) from Florida. Prevalence of these tumors is as high as 40% in some populations in eastern Maine and 60% in some areas along the Indian River in Florida. The average tumor prevalence in Maine and Florida is approximately 20 and 11%, respectively. An association has been suggested between the use of herbicides and the incidence of gonadal tumors in the softshell clam in Maine. The role of environmental exposures in the development of the tumors in Mercenaria in Florida is unknown; however, there is evidence that genetic factors may contribute to its etiology. Epidemiologic studies of human populations in these same areas show a higher than average mortality rate due to cancers of the reproductive system in women, including both ovarian and breast cancer. The relationship, if any, among these observations is unknown. Our studies on the molecular basis of this disease in clams may provide additional information on environmental exposures and their possible link to cancer in clams and other organisms, including humans.
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Affiliation(s)
- R J Van Beneden
- Department of Zoology, University of Maine, Orono 04469-5751, USA.
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Wingren GB, Axelson O. Occupational and Environmental Determinants for Benign Thyroid Disease and Follicular Thyroid Cancer. INTERNATIONAL JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HEALTH 1997; 3:89-94. [PMID: 9891105 DOI: 10.1179/107735297800407703] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Occupational and environmental determinants of benign thyroid disease and follicular thyroid cancer were evaluated in a series of cases in 1977-1987. Of the cases initially diagnosed as follicular thyroid cancer, only 31 remained after a reclassification, whereas 44 were found to be benign thyroid disease. Both series were compared with 387 randomly selected population controls. Occupational solvent exposure was strongly associated with benign thyroid disease (odds ratio, OR, 2.8; 95% confidence interval, 95% CI, 0.9-9.0 for women and OR 18.9; 95% CI 2.2-161 for men). Eight of the nine men found to have benign disease had been exposed to solvents, and six of them to trichloroethylene. For both types of cases, a private well at the birth address increased the risk, OR 2.0; 95% CI 0.9-4.0 and OR 3.0; 95% CI 1.2-7.2, respectively, whereas the risk was lower for those living in coastal areas. Less fish and shellfish in the diet increased the risk for malignant thyroid disease only. Although based on small numbers, the study indicates etiologic roles of occupational and environmental factors for both conditions studied. The influences of occupation and diet differ, however, for the two outcomes.
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Affiliation(s)
- GB Wingren
- Department of Occupational and Environmental Medicine, Faculty of Health Sciences, Linköping University, S-581 85 Linköping, Sweden
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Abstract
Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin) has been the subject of intensive investigations in laboratory animals during the last 2 decades. Toxicity studies have been conducted in several species of rodents and include several carcinogenicity studies as well as numerous mechanistic studies initiated to elucidate dioxin's mode of action, as both a carcinogen and a toxicant. Hepatotoxicity is a primary effect of dioxin. There has been an increase in hepatocellular tumors reported in both rats and mice exposed to dioxin. In addition to neoplastic changes, dioxin causes a spectrum of toxic changes in the liver. Additional neoplastic changes include subcutaneous fibrosarcomas and thyroid follicular cell tumors in both rats and mice and histiocytic sarcomas in mice. Dioxin causes developmental effects in the palate and kidney of mice. Changes in the female reproductive tract include ovarian atrophy, sertoliform hyperplasia, and Sertoli cell tumors. Dosing in utero results in gross malformations of the external genetalia. The effects of dioxin on the rodent model of endometriosis are described. In males, there are lowered sperm counts in the epididymis and minor testicular effects following gestational administration of dioxin. Both estrogenic and antiestrogenic-like effects have been ascribed to dioxin in laboratory animals; these activities are the result of dioxin-specific pathways resulting in the same end points as classic reproductive toxicants.
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Affiliation(s)
- P C Mann
- Experimental Pathology Laboratories, Inc., Research Triangle Park, North Carolina 27709, USA
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37
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De Haan LH, Halfwerk S, Hovens SE, De Roos B, Koeman JH, Brouwer A. Inhibition of intercellular communication and induction of ethoxyresorufin-O-deethylase activity by polychlorobiphenyls, -dibenzo-p-dioxins and -dibenzofurans in mouse hepa1c1c7 cells. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 1996; 1:27-37. [PMID: 21781660 DOI: 10.1016/1382-6689(95)00006-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Inhibition of intercellular communication (IC) between hepa1c1c7 cells was used as a possible bioassay to predict tumor promoting potency of polyhalogenated aromatic hydrocarbons (PAHs). Relative potencies with regard to 2,3,7,8-TCDD to inhibit IC and to induce cytochrome P450IA1/2 (EROD) in these hepa1c1c7 cells were compared in order to investigate the possible role of the Ah receptor (AhR). For the PCDD/F and the co-planar PCB congeners relative potencies of both responses were within the same range. However, the mono-ortho PCBs, 2,3,3',4,4'-PeCB, 2,3,4,4',5-PeCB, 2,3',4,4',5-PeCB and 2,3,3',4,4',5,5'-HxCB showed a 30-1300 times higher potency to inhibit IC compared to EROD induction activity. These potency differences were even more pronounced for the di-ortho PCBs, 2,2',5,5'-TeCB and 2,2',3,3',4,4'-HxCB. The data presented here indicate that for IC inhibition by these non-planar PCBs a non-AhR mediated mechanism, with a different structure-activity relationship may be responsible. Given the high IC inhibition potency of mono- and di-ortho PCBs and their abundancy in environmental mixtures, the mono- and di-ortho PCBs may contribute for a major part to the total tumor promoting potency of complex mixtures relevant to human exposure. Using the traditional TEF values, these compounds do not account for much toxic potency in a mixture, which may imply that the tumor promotion potential is not covered by the commonly derived TEF values.
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Affiliation(s)
- L H De Haan
- Department of Toxicology, Agricultural University Wageningen, P.O. Box 8000, 6700 EA Wageningen, Netherlands
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38
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Abstract
Biologically realistic mechanistic models of carcinogenesis by TCDD are composed of equations representing biochemical events leading to altered expression of proteins involved in the response or equations representing the kinetics of proliferation of clones of mutant cells. A biochemically augmented physiological dosimetry model reproduces the observed altered expression of liver proteins in female rats exposed to dioxin. The model suggests that oxidation of estradiol to DNA reactive quinones or semiquinones by CYP1A2 protein induced by TCDD may contribute to an increased mutational rate. It suggests that TCDD-stimulated production of a peptide ligand of the epidermal growth factor (EGF) receptor and subsequent activation of the receptor's tyrosine kinase activity may increase the rate of proliferation of susceptible cells. These calculated quantities can serve as indices of toxicity and can be used to predict tumor incidence as a function of exposure.
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Affiliation(s)
- M C Kohn
- Laboratory of Quantitative and Computational Biology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
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39
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Yang JH, Rhim JS. 2,3,7,8-Tetrachlorodibenzo-p-dioxin: molecular mechanism of carcinogenesis and its implication in human in vitro model. Crit Rev Oncol Hematol 1995; 18:111-27. [PMID: 7695826 DOI: 10.1016/1040-8428(94)00125-d] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Affiliation(s)
- J H Yang
- Department of Preventive Medicine, Taegu Catholic University, School of Medicine, Republic of Korea
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40
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Hanioka N, Jinno H, Toyo'oka T, Ando M. The effect of 1,2,3,4-tetrachlorodibenzo-p-dioxin on drug-metabolizing enzymes in the rat liver. CHEMOSPHERE 1994; 29:2477-2491. [PMID: 7866751 DOI: 10.1016/0045-6535(94)90051-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The effects of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) on drug-metabolizing enzymes were studied in male and female rats. 1,2,3,4-TCDD (25, 50, 100 and 200 mumol/kg) was administered by i.p. injection once. Among the cytochrome P-450 (P450)-mediated monooxygenase activities tested, 7-ethoxyresorufin O-deethylase (EROD) activities in both male and female rats, which are associated with CYP1A1, were remarkably induced by all doses of 1,2,3,4-TCDD. The relative induction to each control activity were from 3.0- to 24.5-fold and from 2.2- to 16.5-fold, respectively. Also, 1,2,3,4-TCDD increased other CYP1A-mediated monooxygenase activities such as 7-ethoxycoumarin O-deethylase (ECOD) and 7-methoxyresorufin O-demethylase (MROD) in male and female rats dose-dependently (1.4- to 4.3-fold). Western immunoblotting showed that the levels of CYP1A1 and CYP1A2 proteins in liver microsomes were increased by 1,2,3,4-TCDD. Although the activities of other P450-mediated monooxygenases, namely 7-pentoxyresorufin O-depentylase (PROD), 7-benzyloxyresorufin O-debenzylase (BROD), aminopyrine N-demethylase (APND) and nitrosodimethylamine N-demethylase (NDAND) in both male and female rats were induced at high doses (> or = 50 mumol/kg) of 1,2,3,4-TCDD, the relative level was low compared with those of the CYP1A-mediated monooxygenase such as EROD, ECOD or MROD. In addition to P450-mediated monooxygenase, there was significant induction in the activities of the Phase II drug-metabolizing enzymes, UDP-glucuronyltransferase (UGT) activities towards 4-nitrophenol (4-NP) and 7-hydroxycoumarin (7-HC) and glutathione S-transferase (GST) towards 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB) and DT-diaphorase. These results indicate that 1,2,3,4-TCDD induces both Phase I (CYP1A-mediated monooxygenase) and Phase II drug-metabolizing enzymes (UGT, GST, DT-diaphorase) in the male and female rat liver, and that the alterations of drug-metabolizing enzyme are characteristic of PCDD toxicity.
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Affiliation(s)
- N Hanioka
- Division of Environmental Chemistry, National Institute of Health Sciences, Tokyo, Japan
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41
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Kohn MC, Lucier GW, Portier CJ. The importance of biological realism in dioxin risk assessment models. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 1994; 14:993-1000. [PMID: 7846331 DOI: 10.1111/j.1539-6924.1994.tb00068.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Mechanistic mathematical models of hepatocarcinogenesis in the female rat were constructed to investigate possible relationships among the Ah, estrogen, and EGF receptors in TCDD hepatocarcinogenicity. Each model generates dose-response curves for the expression of biomarker liver proteins CYP1A1, CYP1A2, and residual plasma membrane EGF receptor consequent to exposure to TCDD. The shapes of the response curves were strongly dependent on the assumed mechanisms of constitutive expression of these proteins. Assuming a constant level of the hepatic Ah receptor, a sigmoidal dose-response of hepatic CYP1A1 to total liver TCDD was computed. However, inclusion of induction of the Ah receptor by TCDD in a physiologically realistic dosimetric model produced a linear low-dose response of CYP1A1. This behavior was computed to arise from the net effect of sublinear response of CYP1A1 mRNA to the concentration of the Ah-TCDD complex and supralinear response of the protein concentration to the mRNA level, illustrating the importance of biological realism in dose-response modeling. The dosimetric model also computed effects of TCDD on the hepatic estradiol concentration and consequent effects on the binding capacity of the EGF receptor and suggests plausible mechanisms for tumor promotion by TCDD. Setting circulating estradiol levels in the model to values typical of the male rat indicated possible sources of the differences in the responses of the EGF receptor and in development of tumors in the two sexes.
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Affiliation(s)
- M C Kohn
- Laboratory of Quantitative and Computational Biology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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Legator MS, Au WW. Application of integrated genetic monitoring: the optimal approach for detecting environmental carcinogens. ENVIRONMENTAL HEALTH PERSPECTIVES 1994; 102 Suppl 9:125-32. [PMID: 7698074 PMCID: PMC1566778 DOI: 10.1289/ehp.94102s9125] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Short-term in vitro genetic toxicity assays have not fulfilled their anticipated role in predicting the carcinogenicity of environmental agents reliably and economically. A reduction in emphasis from nonanimal systems to relevant animal assays and population monitoring will help to reestablish the credibility of this field. An analysis of the various steps in the carcinogenic process indicates the biological responses occurring during these stages can be utilized for early detection of environmental carcinogens. Emphasis should be placed on using the earliest significant response that indicates genetic damage (e.g., gene mutations and chromosome alterations). Assays that detect pregenomic damage (e.g., adduct formation), without evidence of subsequent heritable genetic alterations, may produce misleading results for risk assessment and should not be considered as stand-alone monitoring procedures. Late biological responses may occur in tissues or organs where genetic damage may be difficult to measure, and the opportunity for intervention diminishes as we approach the clinical outcome. For example, analyzing localized cells that contain activated protooncogenes and inactivated tumor suppressor genes, although they further document adverse response from exposure to carcinogens, may be of greater value for indicating clinical outcome than for genetic monitoring. With few notable exceptions, the window of opportunity for genetic monitoring is the period after exposure where genetic damage is evident and where circulating lymphocytes can faithfully record this damage. An ongoing study of butadiene-exposed workers illustrates an optimum protocol, where multiple assays can be carried out and correlated with both external and internal measurements of exposure.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M S Legator
- Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston 77555-1010
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Hanioka N, Jinno H, Toyo'oka T, Ando M. Effect of 1,2,4-trichlorodibenzo-p-dioxin on drug-metabolizing enzymes in the rat liver. CHEMOSPHERE 1994; 29:1313-1324. [PMID: 7953469 DOI: 10.1016/0045-6535(94)90261-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The effects of 1,2,4-trichlorodibenzo-p-dioxin (1,2,4-TrCDD) on drug-metabolizing-enzymes have been studied in male Wistar rats. 1,2,4-TrCDD (0.1 mmol/kg per day) was administered by i.p. injection for 3 days. Among the cytochrome P-450 (P450)-mediated monooxygenase activities tested, 7-ethoxyresorufin O-deethylase, which is associated with CYP1A1, was remarkably induced by 1,2,4-TrCDD (0.1 mmol/kg). The relative induction to control activity was 32.9-fold. Also, 1,2,4-TrCDD increased other CYP1A-mediated monooxygenase activities such as 7-ethoxycoumarin O-deethylase, 4-nitroanisole O-demethylase, 7-methoxyresorufin O-demethylase and caffeine N-demethylase from 5.7- to 1.9-fold. Western immunoblotting showed that the levels of CYP1A1 and CYP1A2 proteins in liver microsomes were increased by 1,2,4-TrCDD. On the other hand, 7-pentoxyresorufin O-depentylase activity was induced 2.6-fold whereas aniline 4-hydroxylase, nitrosodimethylamine N-demethylase and erythromycin N-demethylase activities were increased slightly (1.3-, 1.6- and 1.3-fold, respectively) by 1,2,4-TrCDD. However, aminopyrine N-demethylase was not significantly induced by 1,2,4-TrCDD. Of the Phase II drug-metabolizing enzymes, DT-diaphorase and glutathione S-transferase (GST) activities towards 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene, and those of UDP-glucuronyltransferase (UGT) towards 4-nitrophenol and 7-hydroxycoumarin were increased from 2.7 to 1.4-fold by 1,2,4-TrCDD. These results indicate that 1,2,4-TrCDD induces both Phase I and Phase II drug-metabolizing enzymes in the rat liver.
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Affiliation(s)
- N Hanioka
- Division of Environmental Chemistry, National Institute of Health Sciences, Tokyo, Japan
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Marsman DS, Barrett JC. Apoptosis and chemical carcinogenesis. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 1994; 14:321-326. [PMID: 8029504 DOI: 10.1111/j.1539-6924.1994.tb00247.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Long recognized as a normal component of organogenesis during development, apoptosis (programmed cell death) has recently been implicated in alterations of cell growth and differentiation. Tissue homeostasis is normally maintained by a balance between cell division and cell death, with apoptosis often functioning in complement to cell growth. Thus, antithetical parallels in chemical carcinogenesis can be drawn between apoptosis and the proliferative events more commonly addressed. While enhanced cell replication may contribute to an increased frequency of mutation, apoptosis within a tissue may counteract chemical carcinogenesis through loss of mutated cells. Many strong carcinogens act as tumor promoters, selectively expanding an initiated cell population advantageously over surrounding cells. Similarly, chemicals with a selective inhibition of apoptosis within an initiated population would offer a growth advantage. In contrast, chemicals causing selective apoptosis of initiated cells would be expected to have an anticarcinogenic effect. Selective apoptosis, in concert with cell-specific replication, may explain the unique promoting effects of different carcinogens such as the peroxisome-proliferating chemicals, phenobarbital, and 2, 3, 7, 8-tetrachloro-dibenzo-p-dioxin (TCDD). Cell turnover, both cell growth and cell death, is central to the process of chemically induced carcinogenesis in animals and understanding its impact is a critical determinant of the relevance of chemically induced effects to man.
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Affiliation(s)
- D S Marsman
- Environmental Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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45
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Hardell L, Eriksson M, Axelson O. On the misinterpretation of epidemiological evidence. New Solut 1994; 4:49-56. [PMID: 22910923 DOI: 10.2190/ns4.3.h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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46
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MacDonald JS, Lankas GR, Morrissey RE. Toxicokinetic and mechanistic considerations in the interpretation of the rodent bioassay. Toxicol Pathol 1994; 22:124-40. [PMID: 7973360 DOI: 10.1177/019262339402200206] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
When chemicals that are nongenotoxic in conventional assays produce increases in tumor incidence in rodents in chronic bioassays, the determination of the significance of these data for human safety is a challenging task. An important first step in this process is consideration of available data on the mechanism of action and biological properties of the chemical as well as pharmacokinetic and metabolism data in the species showing the response. In recent years, there has been an increase in the understanding of so-called "secondary mechanisms" of carcinogenesis (e.g., thyroid tumors in rats following exposure to enzyme inducers). Application of these data may assist in determination of human risk. There are 2 important questions that will be explored and developed: Are there biological effects produced in the test species that could explain the increase in tumor incidence, and will these effects be reproduced in humans? What is the exposure to the chemical that is associated with the increase in tumors, and how does this relate to exposure in humans?
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Affiliation(s)
- J S MacDonald
- Merck Research Laboratories, West Point, Pennsylvania 19486
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47
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Kogevinas M, Saracci R, Winkelmann R, Johnson ES, Bertazzi PA, Bueno de Mesquita BH, Kauppinen T, Littorin M, Lynge E, Neuberger M. Cancer incidence and mortality in women occupationally exposed to chlorophenoxy herbicides, chlorophenols, and dioxins. Cancer Causes Control 1993; 4:547-53. [PMID: 8280832 DOI: 10.1007/bf00052430] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The association between exposure to chlorophenoxy herbicides contaminated with dioxins and occurrence of cancer has been studied mainly in male populations. In animal experiments, gender differences have been recorded in the cancer response to administered 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Mortality and cancer incidence in an international cohort of 701 women from an International Register of Workers occupationally exposed to chlorophenoxy herbicides, chlorophenols, and dioxins is examined. Cause-specific, national death rates and cancer incidence rates were used as referents. Cancer risk was not increased overall, with a standardized incidence ratio (SIR) of 96 and 95 percent confidence interval (CI) of 64-137, based on 29 cases. Among workers exposed to those chlorophenoxy herbicides contaminated with TCDD, excess cancer incidence (for all sites) was observed (SIR = 222, CI = 102-422, 9 cases); this was highest in the first 10 years after exposure. No excess was observed for breast cancer, the most common cancer in this cohort. Results on cancer mortality were consistent with those on incidence.
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Affiliation(s)
- M Kogevinas
- Unit of Analytical Epidemiology, International Agency for Research on Cancer, Lyon, France
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48
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Zober A, Ott MG, Fleig I, Heidemann A. Cytogenetic studies in lymphocytes of workers exposed to 2,3,7,8-TCDD. Int Arch Occup Environ Health 1993; 65:157-61. [PMID: 8282413 DOI: 10.1007/bf00381151] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Chromosome aberrations and sister chromatid exchanges (SCEs) were evaluated in 27 workers with current 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) blood lipid concentrations exceeding 40 parts per trillion (ppt) and in 28 unexposed referents of similar age. No statistical differences were found between the two groups in the percentages of gaps, chromatid or chromosome exchanges, chromatid or chromosome breaks/fragments/deletions, multiple aberrations, or the overall percentage of aberrations including gaps (1.33% in the exposed group vs 1.75% in the referent group) or excluding gaps (0.54% in each group). There was an increased rate of SCEs per cell (P = 0.051) and a higher percentage of cells with more than 10 SCEs (P = 0.064) in the exposed group; however, these associations were no longer significant when smoking status was included as covariate. Additionally, neither current nor back-calculated TCDD concentration was a significant predictor of these parameters based on multiple linear and rank regression analyses.
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Affiliation(s)
- A Zober
- Occupational Medical and Health Protection Department, BASF Aktiengesellschaft, Ludwigshafen, Germany
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49
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Lucier G, Clark G, Hiermath C, Tritscher A, Sewall C, Huff J. Carcinogenicity of TCDD in laboratory animals: implications for risk assessment. Toxicol Ind Health 1993; 9:631-68. [PMID: 8296316 DOI: 10.1177/074823379300900406] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- G Lucier
- Laboratory of Biochemical Risk Analysis, N.I.E.H.S., Research Triangle Park, NC 27709
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50
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Huff J. Issues and controversies surrounding qualitative strategies for identifying and forecasting cancer causing agents in the human environment. PHARMACOLOGY & TOXICOLOGY 1993; 72 Suppl 1:12-27. [PMID: 8474975 DOI: 10.1111/j.1600-0773.1993.tb01664.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Certain chemicals, mixtures of chemicals, exposure circumstances, life-styles and personal or cultural habits, occupations, viruses, living conditions, and physical agents have been causally associated with cancers in humans. Most however are not considered potentially carcinogenic, and the proportion of 'agents' eventually identified to cause cancer is projected to be relatively low. Current methods to identify carcinogenic potential of chemicals rely largely on short-term in vitro and in vivo tests, mid- & long-term in vivo assays, molecular mechanisms, epidemiological investigations, and structural-activity-effect-relationships. Thus, the scientific and public health communities must continue to utilize available means and concomitantly strive to develop newer methods and tools to more easily, quickly, cheaply, and reliably identify carcinogens in the human milieu. Since adequate human studies are typically absent, the most useful method for identifying potential human carcinogens continues to be long-term carcinogenesis experiments. Agents identified as causing cancers in humans have been shown to cause cancer in animals, and this knowledge, together with similarities in mechanisms of carcinogenesis across species, led to the scientific logic and public health strategy that chemicals shown clearly to be carcinogenic in animals should be considered as being likely and anticipated to present cancer risks to humans. The quest of hazard identification efforts is cancer prevention, largely by reducing or eliminating exposures to chemicals that cause cancer and other diseases.
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Affiliation(s)
- J Huff
- National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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