1
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Frank EA, Meek MEB. Procedural application of mode-of-action and human relevance analysis: styrene-induced lung tumors in mice. Crit Rev Toxicol 2024; 54:134-151. [PMID: 38440945 DOI: 10.1080/10408444.2024.2310600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 01/18/2024] [Indexed: 03/06/2024]
Abstract
Risk assessment of human health hazards has traditionally relied on experiments that use animal models. Although exposure studies in rats and mice are a major basis for determining risk in many cases, observations made in animals do not always reflect health hazards in humans due to differences in biology. In this critical review, we use the mode-of-action (MOA) human relevance framework to assess the likelihood that bronchiolar lung tumors observed in mice chronically exposed to styrene represent a plausible tumor risk in humans. Using available datasets, we analyze the weight-of-evidence 1) that styrene-induced tumors in mice occur through a MOA based on metabolism of styrene by Cyp2F2; and 2) whether the hypothesized key event relationships are likely to occur in humans. This assessment describes how the five modified Hill causality considerations support that a Cyp2F2-dependent MOA causing lung tumors is active in mice, but only results in tumorigenicity in susceptible strains. Comparison of the key event relationships assessed in the mouse was compared to an analogous MOA hypothesis staged in the human lung. While some biological concordance was recognized between key events in mice and humans, the MOA as hypothesized in the mouse appears unlikely in humans due to quantitative differences in the metabolic capacity of the airways and qualitative uncertainties in the toxicological and prognostic concordance of pre-neoplastic and neoplastic lesions arising in either species. This analysis serves as a rigorous demonstration of the framework's utility in increasing transparency and consistency in evidence-based assessment of MOA hypotheses in toxicological models and determining relevance to human health.
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Affiliation(s)
- Evan A Frank
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
| | - M E Bette Meek
- School of Epidemiology and Public Health in the Faculty of Medicine, University of Ottawa, Ottawa, Canada
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2
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Borgert CJ. Hypothesis-driven weight of evidence evaluation indicates styrene lacks endocrine disruption potential. Crit Rev Toxicol 2023:1-16. [PMID: 37216681 DOI: 10.1080/10408444.2022.2112652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 08/01/2022] [Accepted: 08/02/2022] [Indexed: 05/24/2023]
Abstract
Styrene is among the U.S. EPA's List 2 chemicals for Tier 1 endocrine screening subject to the agency's two-tiered Endocrine Disruptor Screening Program (EDSP). Both U.S. EPA and OECD guidelines require a Weight of Evidence (WoE) to evaluate a chemical's potential for disrupting the endocrine system. Styrene was evaluated for its potential to disrupt estrogen, androgen, thyroid, and steroidogenic (EATS) pathways using a rigorous WoE methodology that included problem formulation, systematic literature search and selection, data quality evaluation, relevance weighting of endpoint data, and application of specific interpretive criteria. Sufficient data were available to assess the endocrine disruptive potential of styrene based on endpoints that would respond to EATS modes of action in some Tier 1-type and many Tier 2-type reproductive, developmental, and repeat dose toxicity studies. Responses to styrene were inconsistent with patterns of responses expected for chemicals and hormones known to operate via EATS MoAs, and thus, styrene cannot be deemed an endocrine disruptor, a potential endocrine disruptor, or to exhibit endocrine disruptive properties. Because Tier 1 EDSP screening results would trigger Tier 2 studies, like those evaluated here, subjecting styrene to further endocrine screening would produce no additional useful information and would be unjustified from animal welfare perspectives.
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Affiliation(s)
- Christopher J Borgert
- Applied Pharmacology and Toxicology Inc, Gainesville, FL, USA
- Department of Physiological Sciences, University of Florida College of Veterinary Medicine, Gainesville, FL, USA
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3
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Api AM, Belsito D, Botelho D, Bruze M, Burton GA, Cancellieri MA, Chon H, Dagli ML, Date M, Dekant W, Deodhar C, Fryer AD, Jones L, Joshi K, Kumar M, Lapczynski A, Lavelle M, Lee I, Liebler DC, Moustakas H, Na M, Penning TM, Ritacco G, Romine J, Sadekar N, Schultz TW, Selechnik D, Siddiqi F, Sipes IG, Sullivan G, Thakkar Y, Tokura Y. RIFM fragrance ingredient safety assessment, p,α-dimethylstyrene, CAS Registry Number 1195-32-0. Food Chem Toxicol 2022; 169 Suppl 1:113390. [PMID: 36031161 DOI: 10.1016/j.fct.2022.113390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 08/15/2022] [Accepted: 08/20/2022] [Indexed: 01/18/2023]
Affiliation(s)
- A M Api
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - D Belsito
- Member Expert Panel for Fragrance Safety, Columbia University Medical Center, Department of Dermatology, 161 Fort Washington Ave., New York, NY, 10032, USA
| | - D Botelho
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Bruze
- Member Expert Panel for Fragrance Safety, Malmo University Hospital, Department of Occupational & Environmental Dermatology, Sodra Forstadsgatan 101, Entrance 47, Malmo, SE, 20502, Sweden
| | - G A Burton
- Member Expert Panel for Fragrance Safety, School of Natural Resources & Environment, University of Michigan, Dana Building G110, 440 Church St., Ann Arbor, MI, 58109, USA
| | - M A Cancellieri
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - H Chon
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M L Dagli
- Member Expert Panel for Fragrance Safety, University of Sao Paulo, School of Veterinary Medicine and Animal Science, Department of Pathology, Av. Prof. dr. Orlando Marques de Paiva, 87, Sao Paulo, CEP 05508-900, Brazil
| | - M Date
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - W Dekant
- Member Expert Panel for Fragrance Safety, University of Wuerzburg, Department of Toxicology, Versbacher Str. 9, 97078, Würzburg, Germany
| | - C Deodhar
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - A D Fryer
- Member Expert Panel for Fragrance Safety, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - L Jones
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - K Joshi
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Kumar
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - A Lapczynski
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Lavelle
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - I Lee
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - D C Liebler
- Member Expert Panel for Fragrance Safety, Vanderbilt University School of Medicine, Department of Biochemistry, Center in Molecular Toxicology, 638 Robinson Research Building, 2200 Pierce Avenue, Nashville, TN, 37232-0146, USA
| | - H Moustakas
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Na
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - T M Penning
- Member of Expert Panel for Fragrance Safety, University of Pennsylvania, Perelman School of Medicine, Center of Excellence in Environmental Toxicology, 1316 Biomedical Research Building (BRB) II/III, 421 Curie Boulevard, Philadelphia, PA, 19104-3083, USA
| | - G Ritacco
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - J Romine
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - N Sadekar
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - T W Schultz
- Member Expert Panel for Fragrance Safety, The University of Tennessee, College of Veterinary Medicine, Department of Comparative Medicine, 2407 River Dr., Knoxville, TN, 37996- 4500, USA
| | - D Selechnik
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - F Siddiqi
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - I G Sipes
- Member Expert Panel for Fragrance Safety, Department of Pharmacology, University of Arizona, College of Medicine, 1501 North Campbell Avenue, P.O. Box 245050, Tucson, AZ, 85724-5050, USA
| | - G Sullivan
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA.
| | - Y Thakkar
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - Y Tokura
- Member Expert Panel for Fragrance Safety, The Journal of Dermatological Science (JDS), Department of Dermatology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan
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4
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Api AM, Belsito D, Botelho D, Bruze M, Burton GA, Cancellieri MA, Chon H, Dagli ML, Date M, Dekant W, Deodhar C, Fryer AD, Jones L, Joshi K, Kumar M, Lapczynski A, Lavelle M, Lee I, Liebler DC, Moustakas H, Na M, Penning TM, Ritacco G, Romine J, Sadekar N, Schultz TW, Selechnik D, Siddiqi F, Sipes IG, Sullivan G, Thakkar Y, Tokura Y. RIFM fragrance ingredient safety assessment, styrene, CAS Registry Number 100-42-5. Food Chem Toxicol 2022; 165 Suppl 1:113138. [PMID: 35595040 DOI: 10.1016/j.fct.2022.113138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 05/06/2022] [Accepted: 05/12/2022] [Indexed: 11/18/2022]
Affiliation(s)
- A M Api
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - D Belsito
- Member Expert Panel for Fragrance Safety, Columbia University Medical Center, Department of Dermatology, 161 Fort Washington Ave., New York, NY, 10032, USA
| | - D Botelho
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Bruze
- Member Expert Panel for Fragrance Safety, Malmo University Hospital, Department of Occupational & Environmental Dermatology, Sodra Forstadsgatan 101, Entrance 47, Malmo, SE-20502, Sweden
| | - G A Burton
- Member Expert Panel for Fragrance Safety, School of Natural Resources & Environment, University of Michigan, Dana Building G110, 440 Church St., Ann Arbor, MI, 58109, USA
| | - M A Cancellieri
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - H Chon
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M L Dagli
- Member Expert Panel for Fragrance Safety, University of Sao Paulo, School of Veterinary Medicine and Animal Science, Department of Pathology, Av. Prof. dr. Orlando Marques de Paiva, 87, Sao Paulo, CEP 05508-900, Brazil
| | - M Date
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - W Dekant
- Member Expert Panel for Fragrance Safety, University of Wuerzburg, Department of Toxicology, Versbacher Str. 9, 97078, Würzburg, Germany
| | - C Deodhar
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - A D Fryer
- Member Expert Panel for Fragrance Safety, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - L Jones
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - K Joshi
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Kumar
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - A Lapczynski
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Lavelle
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - I Lee
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - D C Liebler
- Member Expert Panel for Fragrance Safety, Vanderbilt University School of Medicine, Department of Biochemistry, Center in Molecular Toxicology, 638 Robinson Research Building, 2200 Pierce Avenue, Nashville, TN, 37232-0146, USA
| | - H Moustakas
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Na
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - T M Penning
- Member of Expert Panel for Fragrance Safety, University of Pennsylvania, Perelman School of Medicine, Center of Excellence in Environmental Toxicology, 1316 Biomedical Research Building (BRB) II/III, 421 Curie Boulevard, Philadelphia, PA, 19104-3083, USA
| | - G Ritacco
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - J Romine
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - N Sadekar
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - T W Schultz
- Member Expert Panel for Fragrance Safety, The University of Tennessee, College of Veterinary Medicine, Department of Comparative Medicine, 2407 River Dr., Knoxville, TN, 37996- 4500, USA
| | - D Selechnik
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - F Siddiqi
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - I G Sipes
- Member Expert Panel for Fragrance Safety, Department of Pharmacology, University of Arizona, College of Medicine, 1501 North Campbell Avenue, P.O. Box 245050, Tucson, AZ, 85724-5050, USA
| | - G Sullivan
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA.
| | - Y Thakkar
- Research Institute for Fragrance Materials Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - Y Tokura
- Member Expert Panel for Fragrance Safety, The Journal of Dermatological Science (JDS), Editor-in-Chief, Professor and Chairman, Department of Dermatology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan
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5
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Andersen ME, Guerrero T. Assessing Modes of Action, Measures of Tissue Dose and Human Relevance of Rodent Toxicity Endpoints with Octamethylcyclotetrasiloxane (D4). Toxicol Lett 2022; 357:57-72. [PMID: 34995712 DOI: 10.1016/j.toxlet.2021.12.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 12/07/2021] [Accepted: 12/30/2021] [Indexed: 10/19/2022]
Abstract
Octamethylcyclotetrasiloxane (D4), a highly lipophilic, volatile compound with low water solubility, is metabolized to lower molecular weight, linear silanols. Toxicity has been documented in several tissues in animals following mixed vapor/aerosol exposures by inhalation at near saturating vapor concentrations or with gavage dosing in vegetable oil vehicles. These results, together with more mechanism-based studies and detailed pharmacokinetic information, were used to assess likely modes of action (MOAs) and the tissue dose measures of D4 and metabolites that would serve as key events leading to these biological responses. This MOA analysis indicates that pulmonary effects arise from direct epithelial contact with mixed vapor/aerosol atmospheres of D4; liver hypertrophy and hepatocyte proliferation arise from adaptive, rodent-specific actions of D4 with nuclear receptor signaling pathways; and, nephropathy results from silanol metabolites binding with alpha-2μ globulin (a rat specific protein). At this time, the MOAs of other liver effects - pigment accumulation and bile duct hyperplasia (BDH) preferentially observed in Sprague-Dawley (SD) rats- are not known. Hypothalamic actions of D4 delaying the rat mid-cycle gonadotrophin releasing hormone (GnRH) surge that result in reproductive effects and subsequent vaginal/uterine/ovarian tissue responses, including small increases in incidence of benign endometrial adenomas, are associated with prolongation of endogenous estrogen exposures due to delays in ovulation. Human reproduction is not controlled by a mid-cycle GnRH surge. Since the rodent-specific reproductive and the vaginal/uterine/ovarian tissue responses are not relevant for risk assessments in human populations, D4 should neither be classified as a CMR (i.e., carcinogenic, mutagenic, or toxic for reproduction) substance nor be regarded as an endocrine disruptor. Bile duct hyperplasia (BDH) and pigment accumulation in liver seen in SD rats are endpoints that could serve to define a Benchmark Dose or No-Observed-Effect-Level (NOEL) for D4.
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Affiliation(s)
- Melvin E Andersen
- Andersen ToxConsulting LLC, 424 Granite Lake Ct., Denver, NC 28037, United States.
| | - Tracy Guerrero
- American Chemistry Council Director, Silicones, Environmental, Health, and Safety Center, 700 2nd Street, NE, Washington, DC, 20002, United States.
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6
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Digumarti R, Dhara VR, Sridhar GR, Gassert T. The styrene gas disaster – lessons to learn and the way forward. JOURNAL OF DR. NTR UNIVERSITY OF HEALTH SCIENCES 2021. [DOI: 10.4103/jdrntruhs.jdrntruhs_32_21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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7
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Hill T, Conolly RB. Development of a Novel AOP for Cyp2F2-Mediated Lung Cancer in Mice. Toxicol Sci 2019; 172:1-10. [PMID: 31407013 DOI: 10.1093/toxsci/kfz185] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 06/26/2019] [Accepted: 08/07/2019] [Indexed: 12/14/2022] Open
Abstract
Abstract
Traditional methods for carcinogenicity testing rely heavily on the rodent bioassay as the standard for identification of tumorigenic risk. As such, identification of species-specific outcomes and/or metabolism are a frequent argument for regulatory exemption. One example is the association of tumor formation in the mouse lung after exposure to Cyp2F2 ligands. The adverse outcome pathway (AOP) framework offers a theoretical platform to address issues of species specificity that is consistent, transparent, and capable of integrating data from new approach methodologies as well as traditional data streams. A central premise of the AOP concept is that pathway progression from the molecular initiating event (MIE) implies a definable “response-response” (R-R) relationship between each key event (KE) that drives the pathway towards a specific adverse outcome (AO). This article describes an AOP for lung cancer in the mouse from an MIE of Cyp2F2-specific reactive metabolite formation, advancing through KE that include protein and/or nucleic acid adducts, diminished Club Cell 10 kDa (CC10) protein expression, hyperplasia of CC10 deficient Club cells, and culminating in the AO of mixed-cell tumor formation in the distal airways. This tumor formation is independent of route of exposure and our AOP construct is based on overlapping mechanistic events for naphthalene, styrene, ethyl benzene, isoniazid, and fluensulfone in the mouse. This AOP is intended to accelerate the explication of an apparent mouse-specific outcome and serve as a starting point for a quantitative analysis of mouse-human differences in susceptibility to the tumorigenic effects of Cyp2F2 ligands.
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Affiliation(s)
- Thomas Hill
- Oak Ridge Institute for Science and Education Fellow at the National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27709
| | - Rory B Conolly
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27709
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8
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Deaths from Nonmalignant Respiratory Disease in Styrene-Exposed Workers: Does Obliterative Bronchiolitis Contribute to Mortality? Ann Am Thorac Soc 2019; 14:810-811. [PMID: 28345967 DOI: 10.1513/annalsats.201612-1026le] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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9
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Banton MI, Bus JS, Collins JJ, Delzell E, Gelbke HP, Kester JE, Moore MM, Waites R, Sarang SS. Evaluation of potential health effects associated with occupational and environmental exposure to styrene - an update. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2019; 22:1-130. [PMID: 31284836 DOI: 10.1080/10937404.2019.1633718] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The potential chronic health risks of occupational and environmental exposure to styrene were evaluated to update health hazard and exposure information developed since the Harvard Center for Risk Analysis risk assessment for styrene was performed in 2002. The updated hazard assessment of styrene's health effects indicates human cancers and ototoxicity remain potential concerns. However, mechanistic research on mouse lung tumors demonstrates these tumors are mouse-specific and of low relevance to human cancer risk. The updated toxicity database supports toxicity reference levels of 20 ppm (equates to 400 mg urinary metabolites mandelic acid + phenylglyoxylic acid/g creatinine) for worker inhalation exposure and 3.7 ppm and 2.5 mg/kg bw/day, respectively, for general population inhalation and oral exposure. No cancer risk value estimates are proposed given the established lack of relevance of mouse lung tumors and inconsistent epidemiology evidence. The updated exposure assessment supports inhalation and ingestion routes as important. The updated risk assessment found estimated risks within acceptable ranges for all age groups of the general population and workers with occupational exposures in non-fiber-reinforced polymer composites industries and fiber-reinforced polymer composites (FRP) workers using closed-mold operations or open-mold operations with respiratory protection. Only FRP workers using open-mold operations not using respiratory protection have risk exceedances for styrene and should be considered for risk management measures. In addition, given the reported interaction of styrene exposure with noise, noise reduction to sustain levels below 85 dB(A) needs be in place.
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Affiliation(s)
- M I Banton
- a Gorge View Consulting LLC , Hood River , OR , USA
| | - J S Bus
- b Health Sciences , Exponent , Midland , MI , USA
| | - J J Collins
- c Health Sciences , Saginaw Valley State University , Saginaw , MI , USA
| | - E Delzell
- d Private consultant , Birmingham , AL , USA
| | | | - J E Kester
- f Kester Consulting LLC , Wentzville , MO , USA
| | | | - R Waites
- h Sabic , Innovative Plastics US LLC , Mount Vernon , IN , USA
| | - S S Sarang
- i Shell Health , Shell International , Houston , TX , USA
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10
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Abstract
This review addresses the adverse influences of neurotoxic exposures on the ability to smell and taste. These chemical senses largely determine the flavor of foods and beverages, impact food intake, and ultimately nutrition, and provide a warning for spoiled or poisonous food, leaking natural gas, smoke, airborne pollutants, and other hazards. Hence, toxicants that damage these senses have a significant impact on everyday function. As noted in detail, a large number of toxicants encountered in urban and industrial air pollution, including smoke, solvents, metals, and particulate matter can alter the ability to smell. Their influence on taste, i.e., sweet, sour, bitter, salty, and savory (umami) sensations, is not well documented. Given the rather direct exposure of olfactory receptors to the outside environment, olfaction is particularly vulnerable to damage from toxicants. Some toxicants, such as nanoparticles, have the potential to damage not only the olfactory receptor cells, but also the central nervous system structures by their entrance into the brain through the olfactory mucosa.
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Affiliation(s)
- Mary Beth Genter
- Department of Environmental Health, University of Cincinnati, Cincinnati, OH, United States
| | - Richard L Doty
- Smell and Taste Center and Department of Otorhinolaryngology: Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
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11
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Werner S, Nies E. Olfactory dysfunction revisited: a reappraisal of work-related olfactory dysfunction caused by chemicals. J Occup Med Toxicol 2018. [PMID: 30202422 DOI: 10.1186/s12995‐018‐0209‐6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Occupational exposure to numerous individual chemicals has been associated with olfactory dysfunction, mainly in individual case descriptions. Comprehensive epidemiological investigations into the olfactotoxic effect of working substances show that the human sense of smell may be impaired by exposure to metal compounds involving cadmium, chromium and nickel, and to formaldehyde. This conclusion is supported by the results of animal experiments. The level of evidence for a relationship between olfactory dysfunction and workplace exposure to other substances is relatively weak.
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Affiliation(s)
- Sabine Werner
- Institute for Occupational Safety and Health of the German Social Accident Insurance, Unit Toxicology of Industrial Chemicals, Alte Heerstrasse 111, 53757 Sankt Augustin, Germany
| | - Eberhard Nies
- Institute for Occupational Safety and Health of the German Social Accident Insurance, Unit Toxicology of Industrial Chemicals, Alte Heerstrasse 111, 53757 Sankt Augustin, Germany
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12
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Werner S, Nies E. Olfactory dysfunction revisited: a reappraisal of work-related olfactory dysfunction caused by chemicals. J Occup Med Toxicol 2018; 13:28. [PMID: 30202422 PMCID: PMC6124006 DOI: 10.1186/s12995-018-0209-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 07/30/2018] [Indexed: 11/10/2022] Open
Abstract
Occupational exposure to numerous individual chemicals has been associated with olfactory dysfunction, mainly in individual case descriptions. Comprehensive epidemiological investigations into the olfactotoxic effect of working substances show that the human sense of smell may be impaired by exposure to metal compounds involving cadmium, chromium and nickel, and to formaldehyde. This conclusion is supported by the results of animal experiments. The level of evidence for a relationship between olfactory dysfunction and workplace exposure to other substances is relatively weak.
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Affiliation(s)
- Sabine Werner
- Institute for Occupational Safety and Health of the German Social Accident Insurance, Unit Toxicology of Industrial Chemicals, Alte Heerstrasse 111, 53757 Sankt Augustin, Germany
| | - Eberhard Nies
- Institute for Occupational Safety and Health of the German Social Accident Insurance, Unit Toxicology of Industrial Chemicals, Alte Heerstrasse 111, 53757 Sankt Augustin, Germany
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13
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Cruzan G, Bus JS, Andersen ME, Carlson GP, Banton MI, Sarang SS, Waites R. Based on an analysis of mode of action, styrene-induced mouse lung tumors are not a human cancer concern. Regul Toxicol Pharmacol 2018; 95:17-28. [DOI: 10.1016/j.yrtph.2018.02.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 02/14/2018] [Accepted: 02/15/2018] [Indexed: 02/06/2023]
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Cancer Incidence in Workers Exposed to Styrene in the Danish-reinforced Plastics Industry, 1968-2012. Epidemiology 2018; 28:300-310. [PMID: 27984421 DOI: 10.1097/ede.0000000000000608] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Occupational exposure to styrene is widespread and has been suggested to be carcinogenic. The aim of this study was to investigate whether occupational exposure to styrene increases the risk of cancer, in particular lymphohematopoietic cancers. METHODS We established a study population of 72,292 workers employed in 443 small and medium-sized companies producing reinforced plastics 1964-2007 by utilizing several national registries, expert assessment, and worker survey data. We identified incident cancer cases from 1968 to 2012 in the national Danish cancer registry and computed standardized incidence rate ratios (SIRs) with 95% confidence intervals (95% CI) based on national rates. RESULTS Increasing SIRs of Hodgkin lymphoma, myeloid leukemia, and cancer of nasal cavities and sinuses were inconsistently associated with increasing duration of employment, early year of first employment, or styrene exposure probability. No such trends were observed for cancer of the esophagus, pancreas, lung, kidney, or urinary bladder, which have previously been associated with styrene exposure. Lung cancer showed an overall increased risk that decreased by duration of employment. CONCLUSION Occupational styrene exposure may be associated with Hodgkin lymphoma, myeloid leukemia, and cancer of nasal cavities and sinuses. Further studies are needed to evaluate if the observed associations are likely to be causal.
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Andersen ME, Cruzan G, Black MB, Pendse SN, Dodd D, Bus JS, Sarang SS, Banton MI, Waites R, McMullen PD. Assessing molecular initiating events (MIEs), key events (KEs) and modulating factors (MFs) for styrene responses in mouse lungs using whole genome gene expression profiling following 1-day and multi-week exposures. Toxicol Appl Pharmacol 2017; 335:28-40. [DOI: 10.1016/j.taap.2017.09.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 09/06/2017] [Accepted: 09/18/2017] [Indexed: 02/08/2023]
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16
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Nett RJ, Cox-Ganser JM, Hubbs AF, Ruder AM, Cummings KJ, Huang YCT, Kreiss K. Non-malignant respiratory disease among workers in industries using styrene-A review of the evidence. Am J Ind Med 2017; 60:163-180. [PMID: 28079275 DOI: 10.1002/ajim.22655] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2016] [Indexed: 11/12/2022]
Abstract
BACKGROUND Asthma and obliterative bronchiolitis (OB) cases have occurred among styrene-exposed workers. We aimed to investigate styrene as a risk factor for non-malignant respiratory disease (NMRD). METHODS From a literature review, we identified case reports and assessed cross-sectional and mortality studies for strength of evidence of positive association (i.e., strong, intermediate, suggestive, none) between styrene exposure and NMRD-related morbidity and mortality. RESULTS We analyzed 55 articles and two unpublished case reports. Ten OB cases and eight asthma cases were identified. Six (75%) asthma cases had abnormal styrene inhalation challenges. Thirteen (87%) of 15 cross-sectional studies and 12 (50%) of 24 mortality studies provided at least suggestive evidence that styrene was associated with NMRD-related morbidity or mortality. Six (66%) of nine mortality studies assessing chronic obstructive pulmonary disease-related mortality indicated excess mortality. CONCLUSIONS Available evidence suggests styrene exposure is a potential risk factor for NMRD. Additional studies of styrene-exposed workers are warranted. Am. J. Ind. Med. 60:163-180, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Randall J. Nett
- Respiratory Health Division; Centers for Disease Control and Prevention (CDC); National Institute for Occupational Safety and Health (NIOSH); Morgantown West Virginia
| | - Jean M. Cox-Ganser
- Respiratory Health Division; Centers for Disease Control and Prevention (CDC); National Institute for Occupational Safety and Health (NIOSH); Morgantown West Virginia
| | - Ann F. Hubbs
- Health Effects Laboratory Division; National Institute for Occupational Safety and Health (NIOSH), CDC; Morgantown West Virginia
| | - Avima M. Ruder
- Division of Surveillance, Hazard Evaluations, and Field Studies; National Institute for Occupational Safety and Health (NIOSH), CDC; Cincinnati Ohio
| | - Kristin J. Cummings
- Respiratory Health Division; Centers for Disease Control and Prevention (CDC); National Institute for Occupational Safety and Health (NIOSH); Morgantown West Virginia
| | - Yuh-Chin T. Huang
- Division of Pulmonary and Critical Care Medicine; Duke University Medical Center; Durham North Carolina
| | - Kathleen Kreiss
- Respiratory Health Division; Centers for Disease Control and Prevention (CDC); National Institute for Occupational Safety and Health (NIOSH); Morgantown West Virginia
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Gelbke HP, Banton M, Leibold E, Pemberton M, Samson SL. A critical review finds styrene lacks direct endocrine disruptor activity. Crit Rev Toxicol 2015; 45:727-64. [PMID: 26406562 DOI: 10.3109/10408444.2015.1064091] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The European Commission lists styrene (S) as an endocrine disruptor based primarily on reports of increased prolactin (PRL) levels in S-exposed workers. The US Environmental Protection Agency included S in its list of chemicals to be tested for endocrine activity. Therefore, the database of S for potential endocrine activity is assessed. In vitro and in vivo screening studies, as well as non-guideline and guideline investigations in experimental animals indicate that S is not associated with (anti)estrogenic, (anti)androgenic, or thyroid-modulating activity or with an endocrine activity that may be relevant for the environment. Studies in exposed workers have suggested elevated PRL levels that have been further examined in a series of human and animal investigations. While there is only one definitively known physiological function of PRL, namely stimulation of milk production, many normal stress situations may lead to elevations without any chemical exposure. Animal studies on various aspects of dopamine (DA), the PRL-regulating neurotransmitter, in the central nervous system did not give mechanistic explanations on how S may affect PRL levels. Overall, a neuroendocrine disruption of PRL regulation cannot be deduced from a large experimental database. The effects in workers could not consistently be reproduced in experimental animals and the findings in humans represented acute reversible effects clearly below clinical and pathological levels. Therefore, unspecific acute workplace-related stress is proposed as an alternative mode of action for elevated PRL levels in workers.
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Affiliation(s)
| | - Marcy Banton
- b Lyondell Chemical Company , Houston, Texas , USA
| | | | | | - Susan Leanne Samson
- e Division of Endocrinology, Department of Medicine , Baylor College of Medicine , Houston, Texas , USA
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18
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Doty RL. Neurotoxic exposure and impairment of the chemical senses of taste and smell. HANDBOOK OF CLINICAL NEUROLOGY 2015; 131:299-324. [PMID: 26563795 DOI: 10.1016/b978-0-444-62627-1.00016-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The chemical senses of taste and smell determine the flavor of foods and beverages, guide appropriate food intake, and warn of such environmental hazards as spoiled or poisonous food, leaking natural gas, smoke, and airborne pollutants. This chapter addresses the influences of neurotoxic exposures on human chemoreception and provides basic information on the adverse influences of such exposures on rodent epithelia. The focus of the chapter is in olfaction, given dearth of empiric research on the effects of neurotoxic chemical exposures on the sense of taste, i.e., sweet, sour, bitter, salty, and savory sensations. As will be apparent from the chapter, numerous neurotoxins--many of which are encountered in industrial workplaces--alter the ability to smell, including solvents, metals, and particulate matter. The olfactory system is particularly vulnerable to such agents since its receptors are more or less directly exposed to the outside environment. Importantly, some such agents can enter the brain via the olfactory nerve or surrounding perineural spaces, bypassing the blood-brain barrier and damaging central nervous system structures and inducing pathologic processes that appear to be similar to those seen in neurodegenerative diseases such as Alzheimer's and Parkinson's.
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Affiliation(s)
- Richard L Doty
- Smell and Taste Center, Department of Otorhinolaryngology; Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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19
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Gelbke HP, Banton M, Faes E, Leibold E, Pemberton M, Duhayon S. Derivation of safe health-based exposure limits for potential consumer exposure to styrene migrating into food from food containers. Food Chem Toxicol 2014; 64:258-69. [DOI: 10.1016/j.fct.2013.11.039] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2013] [Revised: 11/25/2013] [Accepted: 11/26/2013] [Indexed: 11/30/2022]
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20
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Rhomberg LR, Goodman JE, Prueitt RL. The Weight of Evidence Does Not Support the Listing of Styrene as "Reasonably Anticipated to be a Human Carcinogen" in NTP's Twelfth Report on Carcinogens. HUMAN AND ECOLOGICAL RISK ASSESSMENT : HERA 2013; 19:4-27. [PMID: 23335843 PMCID: PMC3545489 DOI: 10.1080/10807039.2012.650577] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 09/24/2011] [Indexed: 06/01/2023]
Abstract
Styrene was listed as "reasonably anticipated to be a human carcinogen" in the twelfth edition of the National Toxicology Program's Report on Carcinogens based on what we contend are erroneous findings of limited evidence of carcinogenicity in humans, sufficient evidence of carcinogenicity in experimental animals, and supporting mechanistic data. The epidemiology studies show no consistent increased incidence of, or mortality from, any type of cancer. In animal studies, increased incidence rates of mostly benign tumors have been observed only in certain strains of one species (mice) and at one tissue site (lung). The lack of concordance of tumor incidence and tumor type among animals (even within the same species) and humans indicates that there has been no particular cancer consistently observed among all available studies. The only plausible mechanism for styrene-induced carcinogenesis-a non-genotoxic mode of action that is specific to the mouse lung-is not relevant to humans. As a whole, the evidence does not support the characterization of styrene as "reasonably anticipated to be a human carcinogen," and styrene should not be listed in the Report on Carcinogens.
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Cytolyse hépatique et exposition au styrène. ARCH MAL PROF ENVIRO 2012. [DOI: 10.1016/j.admp.2012.10.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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22
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Chung JK, Shen S, Jiang Z, Yuan W, Zheng J. Structure-toxicity relationship study of para-halogenated styrene analogues in CYP2E1 transgenic cells. Toxicol Lett 2012; 210:353-9. [PMID: 22366341 PMCID: PMC3463238 DOI: 10.1016/j.toxlet.2012.02.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 02/07/2012] [Accepted: 02/08/2012] [Indexed: 01/16/2023]
Abstract
Styrene is one of the most important industrial intermediates consumed in the world and is mainly used as a monomer for reinforced plastics and rubber. Styrene has been found to be hepatotoxic and pneumotoxic in humans and experimental animals. The toxicity of styrene is suggested to be metabolism-dependent. Styrene-7,8-oxide has been considered as the major metabolite responsible for styrene-induced cytotoxicity. The objective of the study was to investigate the correlation between cytotoxicity of styrene and chemical and biochemical properties of the vinyl group of styrene by development of structure activity relationships (SAR). 4-Fluorostyrene, 4-chlorostyrene and 4-bromostyrene were selected for the SAR study. Cytotoxicity of styrene and the halogenated styrene derivatives with an order of 4-bromostyrene>4-chlorostyrene>4-fluorostyrene≈styrene was observed in CYP2E1 transgenic cells. Similar orders in the efficiency of the metabolism of styrene and the halogenated styrene analogues to their oxides and in the electrophilicity of the corresponding oxides were observed. Additionally, the order of the potency of cellular glutathione depletion and the degree of protein adduction induced by styrene and the halogenated styrenes were consistent with that of their cytotoxicities. The wild-type cells were less susceptible to the toxicity of the corresponding model compounds than CYP2E1 cells. The present study provided insight into the roles of the biochemical and chemical properties of styrene in its cytotoxicity.
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Affiliation(s)
- Jou-Ku Chung
- Department of Drug Metabolism and Pharmacokinetics, Archemix Corp., Cambridge, MA 02142
| | - Shuijie Shen
- Center for Developmental Therapeutics, Seattle Children’s Research Institute; Division of Gastroenterology and Hepatology, Department of Pediatrics, University of Washington, Seattle, Washington 98101
| | - Zhiteng Jiang
- Center for Developmental Therapeutics, Seattle Children’s Research Institute; Division of Gastroenterology and Hepatology, Department of Pediatrics, University of Washington, Seattle, Washington 98101
| | - Wei Yuan
- Department of Medicine, University of Washington, Seattle, Washington 98195
| | - Jiang Zheng
- Center for Developmental Therapeutics, Seattle Children’s Research Institute; Division of Gastroenterology and Hepatology, Department of Pediatrics, University of Washington, Seattle, Washington 98101
- Department of Medicine, University of Washington, Seattle, Washington 98195
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Interpreting REACH guidance in the determination of the derived no effect level (DNEL). Regul Toxicol Pharmacol 2010; 58:323-9. [DOI: 10.1016/j.yrtph.2010.07.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 06/15/2010] [Accepted: 07/17/2010] [Indexed: 11/16/2022]
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24
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Yuan W, Jin H, Chung JK, Zheng J. Evidence for cellular protein covalent binding derived from styrene metabolite. Chem Biol Interact 2010; 186:323-30. [PMID: 20470765 PMCID: PMC3463232 DOI: 10.1016/j.cbi.2010.05.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 05/06/2010] [Accepted: 05/06/2010] [Indexed: 12/13/2022]
Abstract
Styrene is one of the most important industrial intermediates consumed in the world. Human exposure to styrene occurs mainly in the reinforced plastics industry, particularly in developing countries. Styrene has been found to be hepatotoxic and pneumotoxic in humans and animals. The biochemical mechanisms of styrene-induced toxicities remain unknown. Albumin and hemoglobin adduction derived from styrene oxide, a major reactive metabolite of styrene, has been reported in blood samples obtained from styrene-exposed workers. The objectives of the current study focused on cellular protein covalent binding of styrene metabolite and its correlation with cytotoxicity induced by styrene. We found that radioactivity was bound to cellular proteins obtained from mouse airway trees after incubation with (14)C-styrene. Microsomal incubation studies showed that the observed protein covalent binding required the metabolic activation of styrene. The observed radioactivity binding in protein samples obtained from the cultured airways and microsomal incubations was significantly suppressed by co-incubation with disulfiram, a CYP2E1 inhibitor, although disulfiram apparently did not show a protective effect against the cytotoxicity of styrene. A 2-fold increase in radioactivity bound to cellular proteins was detected in cells stably transfected with CYP2E1 compared to the wild-type cells after (14)C-styrene exposure. With the polyclonal antibody developed in our lab, we detected cellular protein adduction derived from styrene oxide at cysteinyl residues in cells treated with styrene. Competitive immunoblot studies confirmed the modification of cysteine residues by styrene oxide. Cell culture studies showed that the styrene-induced protein modification and cell death increased with the increasing concentration of styrene exposure. In conclusion, we detected cellular protein covalent modification by styrene oxide in microsomal incubations, cultured cells, and mouse airways after exposure to styrene and found a good correlation between styrene-induced cytotoxicity and styrene oxide-derived cellular protein adduction.
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Affiliation(s)
- Wei Yuan
- Department of Medicine, University of Washington, Seattle, WA 98195
| | - Hua Jin
- Center for Developmental Therapeutics, Seattle Children’s Research Institute, Division of Gastroenterology, Department of Pediatrics, University of Washington, Seattle, WA 98101
| | - Jou-Ku Chung
- Department of Drug Metabolism and Pharmacokinetics, Archemix Corp., Cambridge, MA 02142
| | - Jiang Zheng
- Center for Developmental Therapeutics, Seattle Children’s Research Institute, Division of Gastroenterology, Department of Pediatrics, University of Washington, Seattle, WA 98101
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25
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Vassallo JD, Kaetzel RS, Born SL, Lewis CL, Lehman-McKeeman LD, Reed DJ. Gamma-glutamyl transpeptidase null mice fail to develop tolerance to coumarin-induced Clara cell toxicity. Food Chem Toxicol 2010; 48:1612-8. [PMID: 20347914 DOI: 10.1016/j.fct.2010.03.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Revised: 03/15/2010] [Accepted: 03/22/2010] [Indexed: 01/22/2023]
Abstract
Coumarin was used as a model Clara cell toxicant to test the hypothesis that tolerance to injury requires increased gamma-glutamyl transpeptidase (GGT) activity. Wildtype (GGT(+/+)) and GGT-deficient (GGT(-/-)) mice on a C57BL/6/129SvEv hybrid background were dosed orally with corn oil (vehicle) or coumarin (200 mg/kg). In vehicle-treated mice, Clara cell secretory protein (CC10) expression was distributed throughout the bronchiolar epithelium. After one dose of coumarin, CC10 expression was dramatically reduced and the bronchiolar epithelium was devoid of Clara cells in GGT(+/+) and GGT(-/-) mice. In wildtype mice, 9 doses of coumarin produced tolerance, characterized as a renewed bronchiolar epithelium with Clara cells expressing CC10 along with a 40% increase in total glutathione (GSH) and a 7-fold increase in GGT activity in the lung. In contrast, tolerance was not observed in GGT(-/-) mice. To assess whether changes in whole lung levels of GSH and GGT activity reflect Clara cell specific changes an enriched population of cells was isolated from female wildtype B6C3F1 mice made tolerant to coumarin. Compared to Clara cells from control mice, GSH and GGT activity increased 3- and 13-fold, respectively. Collectively, these data suggest Clara cell tolerance to coumarin toxicity requires increased GGT activity favoring enhanced GSH synthesis.
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Affiliation(s)
- Jeffrey D Vassallo
- Miami Valley Innovation Center, The Procter and Gamble Company, Cincinnati, OH 45252, USA.
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26
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Cruzan G, Bus J, Banton M, Gingell R, Carlson G. Mouse specific lung tumors from CYP2F2-mediated cytotoxic metabolism: An endpoint/toxic response where data from multiple chemicals converge to support a mode of action. Regul Toxicol Pharmacol 2009; 55:205-18. [DOI: 10.1016/j.yrtph.2009.07.002] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Revised: 07/01/2009] [Accepted: 07/02/2009] [Indexed: 11/28/2022]
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27
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Harvilchuck JA, Pu X, Klaunig JE, Carlson GP. Indicators of oxidative stress and apoptosis in mouse whole lung and Clara cells following exposure to styrene and its metabolites. Toxicology 2009; 264:171-8. [PMID: 19666080 DOI: 10.1016/j.tox.2009.08.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Revised: 07/24/2009] [Accepted: 08/02/2009] [Indexed: 11/25/2022]
Abstract
In mice, styrene is hepatotoxic, pneumotoxic, and causes lung tumors. One explanation for the mechanism of toxicity is oxidative stress/damage. Previous studies have shown decreased glutathione levels, linked to increased apoptosis, in lung homogenates and isolated Clara cells 3 h following styrene or styrene oxide (SO) administration or in vitro exposure. The objective of the current studies was to determine what effects styrene and its active metabolites, primarily styrene oxide, had on indicators of oxidative stress and attendant apoptosis in order to understand better the mechanism of styrene-induced toxicity. Three hours following in vitro exposure of Clara cells to styrene or SO there were increases in reactive oxygen species (ROS). Following administration of styrene or styrene oxide ip, increases in ROS, superoxide dismutase (SOD), and 8-hydroxydeoxyguanosine (8-OHdG) formation were observed. Since increases in ROS have been linked to increases in apoptosis ratios of bax/bcl-2, mRNA and protein expression were determined 3-240 h following the administration of styrene and R-styrene oxide (RSO). The bax/bcl-2 mRNA ratio increased 12 and 24 h following R-SO and 120 h following styrene administration. However, the bax/bcl-2 protein ratio was not increased until 240 h following R-SO, and 24 and 240 h following styrene administration. However, only a slight increase in caspase 3 was observed. These results indicated that oxidative stress occurred 3h following styrene or styrene oxide as evidenced by increased ROS and SOD. This increased ROS may be responsible for the increased 8-OHdG formation. Our findings of limited apoptosis in Clara cells following acute exposure to styrene or SO are in agreement with others and may reflect the minimal extent to which apoptosis plays a role in acute styrene toxicity. It is clear, however, that oxidative stress and oxidative effects on DNA are increased following exposure to styrene or styrene oxide, and these may play a role in the lung tumorigenesis in mice.
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Affiliation(s)
- Jill A Harvilchuck
- School of Health Sciences, Purdue University, West Lafayette, IN 47907-2051, USA
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28
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Harvilchuck JA, Carlson GP. Effect of multiple doses of styrene and R-styrene oxide on CC10, bax, and bcl-2 expression in isolated Clara cells of CD-1 mice. Toxicology 2009; 259:149-52. [DOI: 10.1016/j.tox.2009.02.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 02/16/2009] [Accepted: 02/25/2009] [Indexed: 10/21/2022]
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Meszka-Jordan A, Mahlapuu R, Soomets U, Carlson GP. Oxidative stress due to (R)-styrene oxide exposure and the role of antioxidants in non-Swiss albino (NSA) mice. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2009; 72:642-650. [PMID: 19308849 DOI: 10.1080/15287390902769436] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Styrene produces lung and liver damage that may be related to oxidative stress. The purpose of this study was to investigate the toxicity of (R)-styrene oxide (R-SO), the more active enantiomeric metabolite of styrene, and the protective properties of the antioxidants glutathione (GSH), N-acetylcysteine (NAC), and 4-methoxy-L-tyrosinyl-gamma-L-glutamyl-L-cysteinyl-glycine (UPF1) against R-SO-induced toxicity in non-Swiss Albino (NSA) mice. UPF1 is a synthetic GSH analog that was shown to have 60 times the ability to scavenge reactive oxygen species (ROS) in comparison to GSH. R-SO toxicity to the lung was measured by elevations in the activity of lactate dehydrogenase (LDH), protein concentration, and number of cells in bronchoalveolar lavage fluid (BALF). Toxicity to the liver was measured by increases in serum sorbitol dehydrogenase (SDH) activity. Antioxidants were not able to decrease the adverse effects of R-SO on lung. However, NAC (200 mg/kg) ip and GSH (600 mg/kg), administered orally prior to R-SO (300 mg/kg) ip, showed significant protection against liver toxicity as measured by SDH activity. Unexpectedly, a synthetic GSH analog, UPF1 (0.8 mg/kg), administered intravenously (iv) prior to R-SO, produced a synergistic effect with regard to liver and lung toxicity. Treatment with UPF1 (0.8 mg/kg) iv every other day for 1 wk for preconditioning prior to R-SO ip did not result in any protection against liver and lung toxicity, but rather enhanced the toxicity when administered prior R-SO. The results of the present study demonstrated protection against R-SO toxicity in liver but not lung by the administration of the antioxidants NAC and GSH.
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Dalton P, Lees PSJ, Gould M, Dilks D, Stefaniak A, Bader M, Ihrig A, Triebig G. Evaluation of Long-Term Occupational Exposure to Styrene Vapor on Olfactory Function. Chem Senses 2007; 32:739-47. [PMID: 17602142 DOI: 10.1093/chemse/bjm041] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The primary sensory neurons of the olfactory system are chronically exposed to the ambient environment and may therefore be susceptible to damage from occupational exposure to many volatile chemicals. To investigate whether occupational exposure to styrene was associated with olfactory impairment, we examined olfactory function in 2 groups: workers in a German reinforced-plastics boat-manufacturing facility having a minimum of 2 years of styrene exposure (15-25 ppm as calculated from urinary metabolite concentrations, with historical exposures up to 85 ppm) and a group of age-matched workers from the same facility with lower styrene exposures. The results were also compared with normative data previously collected from healthy, unexposed individuals. Multiple measures of olfactory function were evaluated using a standardized battery of clinical assessments from the Monell-Jefferson Chemosensory Clinical Research Center that included tests of threshold sensitivity for phenylethyl alcohol (PEA) and odor identification ability. Thresholds for styrene were also obtained as a measure of occupational olfactory adaptation. Styrene exposure history was calculated through the use of past biological monitoring results for urinary metabolites of styrene (mandelic acid [MA], phenylglyoxylic acid [PGA]); current exposure was determined for each individual using passive air sampling for styrene and biological monitoring for styrene urinary metabolites. Current mean effective styrene exposure during the day of olfactory testing for the group of workers who worked directly with styrene resins was 18 ppm styrene (standard deviation [SD] = 14), 371 g/g creatinine MA + PGA (SD = 289) and that of the group of workers with lower exposures was 4.8 ppm (SD = 5.2), 93 g/g creatinine MA+PGA (SD = 100). Historic annual average exposures for all workers were greater by a factor of up to 6x. No differences unequivocally attributable to exposure status were observed between the Exposed and Comparison groups or between performance of either group and normative population values on thresholds for PEA or odor identification. Although odor identification performance was lower among workers with higher ongoing exposures, performance on this test is not a pure measure of olfactory ability and is influenced by familiarity with the stimuli and their sources. Consistent with exposure-induced sensory adaptation, however, elevated styrene thresholds were significantly associated with higher occupational exposures to styrene. In summary, the present study found no evidence among a cross-section of reinforced-plastics workers that current or historical exposure to styrene was associated with a general impairment of olfactory function. When taken together with prior studies of styrene-exposed workers, these results suggest that styrene is not a significant olfactory toxicant in humans at current exposure levels.
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Affiliation(s)
- Pamela Dalton
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104-3308, USA.
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31
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Carlson GP, Turner M, Mantick NA. Effects of styrene and styrene oxide on glutathione-related antioxidant enzymes. Toxicology 2006; 227:217-26. [PMID: 16971035 DOI: 10.1016/j.tox.2006.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Revised: 08/01/2006] [Accepted: 08/03/2006] [Indexed: 11/22/2022]
Abstract
Styrene is both hepatotoxic and pneumotoxic in mice. Its mode of action is not clear, but it may be related to oxidative stress including a very large decrease in reduced glutathione (GSH). The current studies evaluated if: (1) the more toxic R-styrene oxide had a greater effect on reduced GSH levels than the less toxic S-styrene oxide, (2) the ratio of reduced to oxidized forms of glutathione was altered by styrene or styrene oxide, (3) other enzymes involved in the oxidant status of the cell, namely glutathione reductase, glutathione peroxidase and gamma-glutamylcysteine synthetase were altered, and (4) lipid peroxidation, as measured by the determination of malondialdehyde, increased. R-Styrene oxide (300mg/kg, ip) caused greater decreases in mouse liver and lung GSH than did S-styrene oxide (300mg/kg, ip). Styrene (600mg/kg, ip) caused decreases in both GSH and GSSG in both liver and lung. Styrene and styrene oxide did not cause significant increases in lipid peroxidation in either liver or lung. Styrene and styrene oxide had minimal effects on glutathione reductase and glutathione peroxidase in liver and lung. Styrene increased gamma-glutamylcysteine synthetase activity. The results suggest that while styrene and its metabolite styrene oxide cause significant decreases in GSH levels, they have little effect on the enzymes glutathione reductase and glutathione peroxidase and that in response to decreased glutathione levels there is an increase in its synthesis via induction of gamma-glutamylcysteine synthetase activity.
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Affiliation(s)
- Gary P Carlson
- School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA.
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Chung JK, Yuan W, Liu G, Zheng J. Investigation of bioactivation and toxicity of styrene in CYP2E1 transgenic cells. Toxicology 2006; 226:99-106. [PMID: 16872732 DOI: 10.1016/j.tox.2006.06.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2006] [Revised: 05/17/2006] [Accepted: 06/03/2006] [Indexed: 10/24/2022]
Abstract
Styrene has been found to be toxic to the respiratory system, and the toxicity of styrene is metabolism-dependent. CYP2E1 is suggested to be one of the cytochrome P450 enzymes responsible for the bioactivation of styrene. Our work focused on the roles of CYP2E1 and epoxide, a metabolite of styrene epoxidation, in the cytotoxicity of styrene. Styrene was found to be more toxic to h2E1 cells than to the wild type, while there was no difference found when styrene oxide was administered. Both soluble and microsomal epoxide hydrolase inhibitors dramatically enhanced styrene toxicity. Glutathione and glutathione ethyl ester showed protection against styrene cytotoxicity. Cytotoxicity of a selection of styrene analogues, such as ethylbenzene, vinylcyclohexane, and ethylcyclohexane, was assessed to determine if unsaturation is required for styrene toxicity. Ethylbenzene and vinylcyclohexane were found to be as toxic as styrene to h2E1 cells, whereas little toxicity of ethylcyclohexane to h2E1 cells was observed. This indicates the importance of vinyl group of styrene in its cytotoxicity, but saturation of the vinyl group does not necessarily eliminate styrene toxicity. An N-acetylcysteine conjugate derived from styrene oxide was identified by LC/MS/MS in the sample obtained from the incubation of h2E1 cell lysate with styrene in the presence of N-acetylcysteine. Formation of the N-acetylcysteine conjugate was found to be NADPH-dependent. These studies provided strong evidence in support of toxic role of styrene epoxide metabolite in styrene toxicity.
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Affiliation(s)
- Jou-Ku Chung
- Department of Pharmaceutical Sciences, School of Pharmacy, Northeastern University, Boston, MA 02115, USA
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Felter SP, Vassallo JD, Carlton BD, Daston GP. A safety assessment of coumarin taking into account species-specificity of toxicokinetics. Food Chem Toxicol 2006; 44:462-75. [PMID: 16203076 DOI: 10.1016/j.fct.2005.08.019] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 08/19/2005] [Accepted: 08/22/2005] [Indexed: 11/16/2022]
Abstract
Coumarin (1,2-benzopyrone) is a naturally occurring fragrant compound found in a variety of plants and spices. Exposure to the general public is through the diet and from its use as a perfume raw material in personal care products. High doses of coumarin by the oral route are known to be associated with liver toxicity in rodents. Chronic oral bioassays conducted in the 1990s reported liver tumors in rats and mice and lung tumors in mice, raising concerns regarding the safety of coumarin. Since then, an extensive body of research has focused on understanding the etiology of these tumors. The data support a conclusion that coumarin is not DNA-reactive and that the induction of tumors at high doses in rodents is attributed to cytotoxicity and regenerative hyperplasia. The species-specific target organ toxicity is shown to be related to the pharmacokinetics of coumarin metabolism, with data showing rats to be particularly susceptible to liver effects and mice to be particularly susceptible to lung effects. A quantitative human health risk assessment that integrates both cancer and non-cancer effects is presented, confirming the safety of coumarin exposure from natural dietary sources as well as from its use as a perfume in personal care products.
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Affiliation(s)
- S P Felter
- The Procter & Gamble Company, Miami Valley Innovation Center, 11810 E. Miami River Road, Cincinnati, OH 45252, USA.
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Jacquot L, Pourie G, Buron G, Monnin J, Brand G. Effects of toluene inhalation exposure on olfactory functioning: behavioral and histological assessment. Toxicol Lett 2006; 165:57-65. [PMID: 16567067 DOI: 10.1016/j.toxlet.2006.01.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 01/24/2006] [Accepted: 01/24/2006] [Indexed: 11/21/2022]
Abstract
Exposure to pollutant or toxic substances is known to induce adverse health effects but few studies have been devoted to study the impact on olfactory functioning although neuroreceptors in the nasal cavity are directly in contact with volatile molecules. Thus, this work was designed to evaluate in mice the potential modifications of the olfactory functioning during (1 month) and after (1 month) a prolonged toluene exposure at both sensitive/perceptive and cellular levels. Mice were exposed to 1000ppm of toluene for 5h/day, 5days/week for 4 weeks. Firstly, behavioral evaluation (T-maze test) to toluene sensitivity showed a constant decrease during all the 4 weeks of exposure (W1-W4) which continued during 2 weeks after the exposure (W5, W6). In contrast, during the last 2 weeks of the experiment (W7, W8), the sensitivity of mice to toluene went back to normal. Secondly, structural modifications, i.e. density of cells and thickness of olfactory epithelium were observed soon after the outset of exposure. The number of cells did not change at the beginning of exposure (W1, W2), decreased markedly later (W3, W4), increased significantly the first week of the recovery period (W5) and stayed stable during the following weeks (W6-W8). Concerning the thickness of neuroepithelium, the results at W1 showed a decrease followed by an increase suggesting an inflammatory process (W2, W3). In contrast, the results of W4 revealed an abrupt decrease of the thickness whereas the return to normal arose immediately at the outset of recovery period.
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Affiliation(s)
- L Jacquot
- Laboratoire de Neurosciences, Université de Franche-Comté-Place Leclerc, 25000 Besançon, France
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Luderer U, Collins TFX, Daston GP, Fischer LJ, Gray RH, Mirer FE, Olshan AF, Setzer RW, Treinen KA, Vermeulen R. NTP-CERHR Expert Panel Report on the reproductive and developmental toxicity of styrene. ACTA ACUST UNITED AC 2006; 77:110-93. [PMID: 16345075 DOI: 10.1002/bdrb.20061] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Kaufmann W, Mellert W, van Ravenzwaay B, Landsiedel R, Poole A. Effects of styrene and its metabolites on different lung compartments of the mouse—cell proliferation and histomorphology. Regul Toxicol Pharmacol 2005; 42:24-36. [PMID: 15896440 DOI: 10.1016/j.yrtph.2005.01.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2004] [Revised: 12/23/2004] [Accepted: 01/01/2005] [Indexed: 11/24/2022]
Abstract
Styrene is not carcinogenic in rats but has caused pneumotoxicity and increased lung tumors after inhalation in mice. This study investigated whether styrene-7,8-oxide, ring-oxidized, and side-chain hydroxylated styrene metabolites induce cell proliferation, apoptosis, pathological changes, and glutathione depletion in mice lungs. Intraperitoneal treatment with phenylacetaldehyde and phenylacetic acid (3 x 100 mg/kg b.w./day) increased the levels of apoptosis and cell proliferation in the alveoli without producing any effects in the terminal bronchioli, the target site of tumor formation in mice. Only styrene-oxide (SO) at 3 x 100 mg/kg b.w./day and 4-vinyl-phenol (4-VP) at 3 x 35 and 3 x 20 mg/kg b.w./day, respectively, caused up to 19-fold increases in cell proliferation in the large/medium bronchi and terminal bronchioles; marginal increases in alveolar cell proliferation were noted with SO (1.6-fold) but not with 4-VP. These compounds also caused glutathione depletion in the bronchiolar epithelium and histomorphological changes of the bronchiolar epithelium in large and medium bronchi and terminal bronchioles. Changes were characterized by flattened cells and a loss of the typical bulging of the "dome-shaped" Clara cells, suggesting that Clara cells were primary target cells. The specific reactions of mouse lung to SO and 4-VP could serve as a verifiable hypothesis for the different response of rats and mice with regard to tumor formation.
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Affiliation(s)
- W Kaufmann
- BASF Aktiengesellschaft, Experimental Toxicology and Ecology, Z 470, 67056 Ludwigshafen, Germany
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Carlson GP. Comparison of the susceptibility of wild-type and CYP2E1 knockout mice to the hepatotoxic and pneumotoxic effects of styrene and styrene oxide. Toxicol Lett 2005; 150:335-9. [PMID: 15110085 DOI: 10.1016/j.toxlet.2004.02.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2003] [Revised: 02/09/2004] [Accepted: 02/09/2004] [Indexed: 10/26/2022]
Abstract
Styrene causes both liver and lung damage in non-Swiss albino, CD-1, and other strains of mice. This is considered to be due to the bioactivation of styrene to styrene oxide by cytochromes P450, principally CYP2E1 and CYP2F2. If so, one would expect CYP2E1 knockout mice to be less susceptible to styrene-induced toxicity than wild-type mice. However, previous in vitro and in vivo studies demonstrated little difference in the metabolism of styrene to styrene oxide between wild-type and CYP2E1 knockout mice. These findings would suggest that there should be no difference in the toxic responses to styrene between these two strains. To determine which of these possibilities was correct, styrene (600 mg/kg) or styrene oxide (300 mg/kg) was administered i.p. 24 h prior to measurement of serum sorbitol dehydrogenase as a biomarker of hepatotoxicity or lactate dehydrogenase activity, protein, and cells in bronchoalveolar lavage fluid as biomarkers for pneumotoxicity. Styrene was more hepatotoxic in the wild-type mice than in the knockout mice suggesting CYP2E1 activity is important. Strain differences were not observed with styrene oxide indicating no difference in intrinsic susceptibility. For lung, the response was similar in both strains to both styrene and styrene oxide supporting the idea that CYP2F2 is important in the bioactivation of styrene in this tissue and that there is no strain difference in susceptibility to the active metabolite.
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Affiliation(s)
- Gary P Carlson
- School of Health Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907-2051, USA.
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Cruzan G, Carlson GP, Turner M, Mellert W. Ring-oxidized metabolites of styrene contribute to styrene-induced Clara-cell toxicity in mice. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2005; 68:229-237. [PMID: 15762181 DOI: 10.1080/15287390590890464] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Styrene produced cytotoxicity in the terminal bronchioles of mice, but not rats, due to metabolites produced in situ by CYP2F2 metabolism. It has generally been presumed that styrene toxicity is mediated by styrene 7,8-oxide, but styrene oxide is not much more toxic than styrene. In contrast, ring-oxidized metabolites (4-vinylphenol or its metabolites) induce much greater toxicity. Administration of 4-vinylphenol results in pneumotoxicity, based on analysis of bronchoalveolar lavage fluid (BALF) at a 5- to 10 fold lower dose than does styrene oxide. In the current research, studies demonstrated that ip administration of 4-vinylphenol for 14 consecutive days at dosages of 6, 20, or 60 mg/kg/d (split into 3 doses) produced cytotoxicity in the terminal bronchioles of mice, but not rats. While higher doses of 4-vinylphenol produced adverse effects in both liver and lung, no liver toxicity was seen in mice exposed to 60 mg/kg/d for 14 d. Approximately 4 d was required for BALF parameters to return to normal following a single administration of 4-vinylphenol. These studies add further support for the role of ring-oxidized metabolites in the pneumotoxicity induced by styrene in mice and the lack thereof in rats.
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Cruzan G, Faber WD, Johnson KA, Roberts LS, Hellwig J, Maurissen J, Beck MJ, Radovsky A, Stump DG. Developmental neurotoxicity study of styrene by inhalation in Crl-CD rats. ACTA ACUST UNITED AC 2005; 74:221-32. [PMID: 15880801 DOI: 10.1002/bdrb.20042] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This study was conducted to assess potential adverse functional and/or morphological effects of styrene on the neurological system in the F2 offspring following F0 and F1 generation whole-body inhalation exposures. Four groups of male and female Crl:CD (SD)IGS BR rats (25/sex/group) were exposed to 0, 50, 150, and 500 ppm styrene for 6 hr daily for at least 70 consecutive days prior to mating for the F0 and F1 generations. Inhalation exposure continued for the F0 and F1 females throughout mating and through gestation day 20. On lactation days 1 through 4, the F0 and F1 females received styrene in virgin olive oil via oral gavage at dose levels of 66, 117, and 300 mg/kg/day (divided into three equal doses, approximately 2 hr apart). Inhalation exposure of the F0 and F1 females was re-initiated on lactation day 5 and continued through weaning of the F1 or F2 pups on postnatal day (PND) 21. Developmental landmarks were assessed in F1 and F2 offspring. The neurological development of randomly selected pups from the F2 generation was assessed by functional observational battery, locomotor activity, acoustic startle response, learning and memory evaluations, brain weights and dimension measurements, and brain morphometric and histologic evaluation. Styrene exposure did not affect survival or the clinical condition of the animals. As expected from previous studies, slight body weight and histopathologic effects on the nasal olfactory epithelium were found in F0 and F1 rats exposed to 500 ppm and, to a lesser extent, 150 ppm. There were no indications of adverse effects on reproductive performance in either the F0 or F1 generation. There were exposure-related reductions in mean body weights of the F1 and F2 offspring from the mid and high-exposure groups and an overall pattern of slightly delayed development evident in the F2 offspring only from the 500-ppm group. This developmental delay included reduced body weight (which continued through day 70) and slightly delayed acquisition of some physical landmarks of development. Styrene exposure of the F0 and F1 animals had no effect on survival, the clinical condition or necropsy findings of the F2 animals. Functional observational battery evaluations conducted for all F1 dams during the gestation and lactation periods and for the F2 offspring were unaffected by styrene exposure. Swimming ability as determined by straight channel escape times measured on PND 24 were increased, and reduced grip strength values were evident for both sexes on PND 45 and 60 in the 500-ppm group compared to controls. There were no other parental exposure-related findings in the F2 pre-weaning and post-weaning functional observational battery assessments, the PND 20 and PND 60 auditory startle habituation parameters, in endpoints of learning and memory performance (escape times and errors) in the Biel water maze task at either testing age, or in activity levels measured on PND 61 in the 500-ppm group. Taken together, the exposure-related developmental and neuromotor changes identified in F2 pups from dams exposed to 500 ppm occurred in endpoints known to be both age- and weight-sensitive parameters, and were observed in the absence of any other remarkable indicators of neurobehavioral toxicity. Based on the results of this study, an exposure level of 50 ppm was considered to be the NOAEL for growth of F2 offspring; an exposure level of 500 ppm was considered to be the NOAEL for F2 developmental neurotoxicity.
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Cruzan G, Faber WD, Johnson KA, Roberts LS, Hellwig J, Carney E, Yarrington JT, Stump DG. Two generation reproduction study of styrene by inhalation in Crl-CD rats. ACTA ACUST UNITED AC 2005; 74:211-20. [PMID: 15880800 DOI: 10.1002/bdrb.20041] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This study was conducted to evaluate the potential adverse effects of styrene on reproductive capability from whole-body inhalation exposure of F0 and F1 parental animals. Assessments included gonadal function, estrous cyclicity, mating behavior, conception rate, gestation, parturition, lactation, and weaning in the F0 and F1 generations, and F1 generation offspring growth and development. Four groups of male and female Crl:CD(SD)IGS BR rats (25/sex/group) were exposed to 0, 50, 150, and 500 ppm styrene for 6 hr daily for at least 70 consecutive days prior to mating for the F0 and F1 generations. Inhalation exposure for the F0 and F1 females continued throughout mating and gestation through gestation day 20. Inhalation exposure of the F0 and F1 females was suspended from gestation day 21 through lactation day 4. On lactation days 1 through 4, the F0 and F1 females received styrene in virgin olive oil via oral gavage at dose levels of 66, 117, and 300 mg/kg/day (divided into three equal doses, approximately 2 hr apart). These oral dosages were calculated to provide similar maternal blood peak concentrations as provided by the inhalation exposures. Inhalation exposure of the F0 and F1 females was re-initiated on lactation day 5. Styrene exposure did not affect survival or clinical observations. Rats in the 150- and 500-ppm groups in both parental generations gained weight more slowly than the controls. There were no indications of adverse effects on reproductive performance in either the F0 or F1 generation. Male and female mating and fertility indices, pre-coital intervals, spermatogenic endpoints, reproductive organ weights, lengths of estrous cycle and gestation, live litter size and postnatal survival were similar in all exposure groups. Additionally, ovarian follicle counts and corpora lutea counts for the F1 females in the high-exposure group were similar to the control values. No adverse exposure-related macroscopic pathology was noted at any exposure level in the F0 and F1 generations. A previously characterized pattern of degeneration of the olfactory epithelium that lines the dorsal septum and dorsal and medial aspects of the nasal turbinates occurred in the F0 and F1 generation animals from the 500-ppm group. In the 500-ppm group, F2 birthweights were reduced compared to the control and F2 offspring from both the 150- and 500-ppm exposure groups gained weight more slowly than the controls. Based on the results of this study, an exposure level of 50 ppm was considered to be the NOAEL for F0 and F1 parental systemic toxicity; the NOAEL for F0 and F1 reproductive toxicity was 500 ppm or greater.
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Gamer AO, Leibold E, Deckardt K, Kittel B, Kaufmann W, Tennekes HA, van Ravenzwaay B. The effects of styrene on lung cells in female mice and rats. Food Chem Toxicol 2004; 42:1655-67. [PMID: 15304312 DOI: 10.1016/j.fct.2004.06.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2003] [Accepted: 06/01/2004] [Indexed: 11/19/2022]
Abstract
Styrene has been shown to cause an increase in the incidence of lung tumors in CD-1 mice following chronic exposure at 40 and 160 ppm, whereas no treatment-related increase in tumors in any organ was seen in rats chronically exposed to up to 1000 ppm styrene. So far most of the mechanistic studies have been performed with male animals. The aim of the present study was to further elucidate the target cell population in mouse lungs exposed to styrene, and to investigate possible differential in vivo effects (e.g., glutathione depletion, increased lipid peroxidation, and oxidative DNA damage). Groups of female CD-1 mice were exposed to styrene at concentrations of 0, 172 or 688 mg/m3 (0, 40 or 160 ppm) for 6 h per day on 1 day, 5 consecutive days or for 20 days during a 4 week period. Groups of female Crl:CD rats were exposed to styrene at concentrations of 0, 688 or 2150 mg/m3 (0, 160 or 500 ppm) for a single 6 h period or for 6 h per day on 5 consecutive days. No signs of lung toxicity were observed in rats. The cytology of cells in lung lavage fluid provided no signs of an inflammatory response in either rats or mice. In mice, both exposure levels caused decreased CC16 protein concentrations in lung lavage fluid after 1 and 5 exposures and in mouse blood serum throughout the study, suggesting that styrene may cause destruction of Clara cells in mice. Degenerative lesions in mouse Clara cells (vacuolar cell degeneration, cell necrosis) were revealed by electronmicroscopy. After 5 and 20 exposures of mice at 160 ppm, cellular crowding, expressed as an irregular epithelial lining and indicative of a very early hyperplasia was noted. Although a depletion of glutathione was noted in mouse lung homogenates after 20 exposures, there was no evidence of oxidative stress as indicated by unchanged concentrations of 8-OH-deoxyguanosine. Malondialdehyde, an indicator of lipid peroxidation, was slightly increased in mice after 1 exposure at 160 ppm only.
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Affiliation(s)
- A O Gamer
- BASF Aktiengesellschaft, Department of Product Safety, Z 470, D-67056 Ludwigshafen, Germany
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Dalton P, Cowart B, Dilks D, Gould M, Lees PSJ, Stefaniak A, Emmett E. Olfactory function in workers exposed to styrene in the reinforced-plastics industry. Am J Ind Med 2003; 44:1-11. [PMID: 12822130 DOI: 10.1002/ajim.10102] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Impairment of olfactory function in humans has been associated with occupational exposure to volatile chemicals. To investigate whether exposure to styrene was associated with olfactory impairment, olfactory function was examined in workers with a minimum of 4 years exposure to styrene in the reinforced-plastics industry (current mean exposure: 26 ppm, range: 10-60 ppm; historic mean dose: 156 ppm-years, range: 13.8-328 ppm-years) and in a group of age- and gender-matched, unexposed controls. METHODS Olfactory function was assessed using a standardized battery that included tests of threshold sensitivity for phenylethyl alcohol (PEA), odor identification ability, and retronasal odor perception. Odor detection thresholds for styrene were also obtained as a measure of specific adaptation to the work environment. RESULTS No differences were observed between exposed workers and controls on tests of olfactory function. Elevation of styrene odor detection thresholds among exposed workers indicated exposure-induced adaptation. CONCLUSIONS The present study found no evidence among a cross-section of reinforced-plastics industry workers that current or historical exposure to styrene was associated with impairment of olfactory function. Taken together with anatomical differences between rodent and human airways and the lack of evidence for styrene metabolism in human nasal tissue, the results strongly suggest that at these concentrations, styrene is not an olfactory toxicant in humans.
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Affiliation(s)
- Pamela Dalton
- Monell Chemical Senses Center, Philadelphia, Pennsylvania 19104-3308, USA.
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43
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Carlson G. In vitro metabolism of styrene to styrene oxide in liver and lung of Cyp2E1 knockout mice. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2003; 66:861-869. [PMID: 12746132 DOI: 10.1080/15287390306386] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Styrene is a widely used chemical. In mice it is both hepatotoxic and pneumotoxic, and this toxicity is thought to be associated with its metabolism to styrene oxide. In vitro studies by several investigators suggest that this bioactivation in mice is primarily due to CYP2E1 and CYP2F2. However, in vivo studies demonstrate that CYP2E1 knockout mice can metabolize styrene to a similar extent as the wild-type mice. The current studies compared the in vitro metabolism of styrene by hepatic and pulmonary microsomes from CYP2E1 knockout and wild-type mice. There was no difference in the hepatic microsomal metabolism of styrene to styrene oxide between the two strains. The metabolism of styrene was lower in the lungs of the knockout mice than in the wild-type. Chemical inhibitors were used to ascertain the contributions made by various cytochromes P-450: imipramine for CYP2C, alpha -methylbenzylaminobenzotriazole for CYP2B, alpha -naphthoflavone for CYP1A, 5-phenyl-1-pentyne for CYP2F2, and diethyldithiocar-bamate for CYP2E1. The data indicate that CYP2E1 and CYP2F2 may be important in wild-type mice, but they do not clearly indicate what cytochromes P-450 are responsible for the metab-olism in the knockout mice. Inhibition of styrene metabolism in the knockout mice by diethyl-dithiocarbamate indicates this inhibitor is not completely selective for CYP2E1. These in vitro data support the in vivo finding of styrene metabolism in CYP2E1 knockout mice and indicate that other enzymes are contributing to styrene metabolism in these mice.
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Affiliation(s)
- Gary Carlson
- School of Health Sciences, Purdue University, West Lafayette, Indiana 47907-1338, USA.
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Andersen ME, Green T, Frederick CB, Bogdanffy MS. Physiologically based pharmacokinetic (PBPK) models for nasal tissue dosimetry of organic esters: assessing the state-of-knowledge and risk assessment applications with methyl methacrylate and vinyl acetate. Regul Toxicol Pharmacol 2002; 36:234-45. [PMID: 12473408 DOI: 10.1006/rtph.2002.1576] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mathematical models have been developed to describe nasal epithelial tissue dosimetry with two compounds, vinyl acetate (VA) and methyl methacrylate (MMA), that cause toxicity in these tissues These models couple computational fluid dynamics (CFD) calculations that map airflow patterns within the nose with physiologically based pharmacokinetic (PBPK) models that integrate diffusion, metabolism, and tissue interactions of these compounds. Dose metrics estimated in these models for MMA and VA, respectively, were rates of MMA metabolism per volume of tissue and alterations in pH in target tissues associated with VA hydrolysis and metabolism. In this article, four scientists who have contributed significantly to development of these models describe the many similarities and relatively few differences between the MMA and VA models. Some differences arise naturally because of differences in target tissues, in the calculated measures of tissue dose, and in the modes of action for highly extracted vapors (VA) compared with poorly extracted vapors (MMA). A difference in the approach used to estimate metabolic parameters from human tissues provides insights into interindividual extrapolation and identifies opportunities for studies with human nasal tissues to enhance current risk assessments. In general, the differences in model structure for these two esters were essential for describing the biology of the observed responses and in accounting for the different measures of target tissue dose. This article is intended to serve as a guide for understanding issues of optimum model structure and optimal data sources for these nasal tissue dosimetry models. We also hope that it leads to greater international acceptance of these hybrid CFD/PBPK modeling approaches for improving risk assessment for many nasal toxicants. In general, these models predict either equivalent (VA) or lower (MMA) nasal tissue doses in humans compared with tissue doses at equivalent exposure concentrations in rats.
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Affiliation(s)
- Melvin E Andersen
- Department of Environmental Health, Colorado State University, Ft. Collins, Colorado, USA.
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Carlson GP. Effect of the inhibition of the metabolism of 4-vinylphenol on its hepatotoxicity and pneumotoxicity in rats and mice. Toxicology 2002; 179:129-36. [PMID: 12204549 DOI: 10.1016/s0300-483x(02)00340-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Styrene is known to be both hepatotoxic and pneumotoxic in rodents. 4-Vinylphenol (4-VP) has been shown to be a minor metabolite of styrene in some studies and is a more potent toxicant in mice than either styrene or styrene oxide. 4-VP is metabolized primarily by CYP2E1 and CYP2F2 to an unknown metabolite. The purpose of this study was to use inhibitors of these cytochromes P450 to address the question of whether the parent compound or a metabolite is responsible for 4-VP induced toxicity. Rats as well as mice were found to be susceptible to the toxicity of 4-VP. Prior treatment with either diethyldithiocarbamate or 5-phenyl-1-pentyne as inhibitors of CYP2E1 and CYP2F2 prevented or greatly decreased the hepatotoxicity of 4-VP as assessed by measuring serum sorbitol dehydrogenase and its pneumotoxicity as determined by measurements of cells, protein and lactate dehydrogenase (LDH) activity in bronchoalveolar lavage fluid. Thus the hepatotoxicity and pneumotoxicity of 4-VP are due to a metabolite(s) and not the parent compound.
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Affiliation(s)
- Gary P Carlson
- School of Health Sciences, Purdue University, West Lafayette, IN 47907-1338, USA.
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46
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Carlson GP, Ullman M, Mantick NA, Snyder PW. 4-Vinylphenol-induced pneumotoxicity and hepatotoxicity in mice. Toxicol Pathol 2002; 30:565-9. [PMID: 12371665 DOI: 10.1080/01926230290105866] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
4-Vinylphenol (4-hydroxystyrene, 4-ethenylphenol, 4-VP) occurs naturally in some foods and has been used as a flavoring agent in food products. It is used synthetically in the production of polymers and resins. It has also been reported to be a minor metabolite of styrene in rats and humans. Varying doses of 4-vinylphenol were administered ip to mice. Hepatotoxicity was assessed by measuring serum sorbitol dehydrogenase (SDH) and by light microscopy. Pneumotoxicity was assessed by measuring proteins, cells, and lactate dehydrogenase activity in bronchoalveolar lavage fluid (BALF) and by light microscopy. 4-VP caused a dose-dependent increase in serum SDH and mild hepatocellular swelling. It caused an increase in cell number and lactate dehydrogenase activity in BALF. Microscopically, there was widespread and severe necrosis of the bronchioles by 12 hours. Re-epithelialzation of the bronchioles was evident by 48 hours. These studies indicate that 4-vinylphenol is both hepatotoxic and pneumotoxic.
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Affiliation(s)
- Gary P Carlson
- School of Health Sciences, Purdue University, West Lafayette, Indiana 47907-1338, USA.
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47
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Cruzan G, Carlson GP, Johnson KA, Andrews LS, Banton MI, Bevan C, Cushman JR. Styrene respiratory tract toxicity and mouse lung tumors are mediated by CYP2F-generated metabolites. Regul Toxicol Pharmacol 2002; 35:308-19. [PMID: 12202046 DOI: 10.1006/rtph.2002.1545] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mice are particularly sensitive to respiratory tract toxicity following styrene exposure. Inhalation of styrene by mice results in cytotoxicity in terminal bronchioles, followed by increased incidence of bronchioloalveolar tumors, as well as degeneration and atrophy of nasal olfactory epithelium. In rats, no effects on terminal bronchioles are seen, but effects in the nasal olfactory epithelium do occur, although to a lesser degree and from higher exposure concentrations. In addition, cytotoxicity and tumor formation are not related to blood levels of styrene or styrene oxide (SO) as measured in chronic studies. Whole-body metabolism studies have indicated major differences in styrene metabolism between rats and mice. The major differences are 4- to 10-fold more ring-oxidation and phenylacetaldehyde pathways in mice compared to rats. The data indicate that local metabolism of styrene is responsible for cytotoxicity in the respiratory tract. Cytotoxicity is seen in tissues that are high in CYP2F P450 isoforms. These tissues have been demonstrated to produce a high ratio of R-SO compared to S-SO (at least 2.4 : 1). In other rat tissues the ratio is less than 1, while in mouse liver the ratio is about 1.1. Inhibition of CYP2F with 5-phenyl-1-pentyne prevents the styrene-induced cytotoxicity in mouse terminal bronchioles and nasal olfactory epithelium. R-SO has been shown to be more toxic to mouse terminal bronchioles than S-SO. In addition, 4-vinylphenol (ring oxidation of styrene) has been shown to be highly toxic to mouse terminal bronchioles and is also metabolized by CYP2F. In human nasal and lung tissues, styrene metabolism to SO is below the limit of detection in nearly all samples, and the most active sample of lung was approximately 100-fold less active than mouse lung tissue. We conclude that styrene respiratory tract toxicity in mice and rats, including mouse lung tumors, are mediated by CYP2F-generated metabolites. The PBPK model predicts that humans do not generate sufficient levels of these metabolites in the terminal bronchioles to reach a toxic level. Therefore, the postulated mode of action for these effects indicates that respiratory tract effects in rodents are not relevant for human risk assessment.
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48
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Cohen JT, Carlson G, Charnley G, Coggon D, Delzell E, Graham JD, Greim H, Krewski D, Medinsky M, Monson R, Paustenbach D, Petersen B, Rappaport S, Rhomberg L, Ryan PB, Thompson K. A comprehensive evaluation of the potential health risks associated with occupational and environmental exposure to styrene. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2002; 5:1-265. [PMID: 12012775 DOI: 10.1080/10937400252972162] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Affiliation(s)
- Joshua T Cohen
- Harvard Center for Risk Analysis, Harvard School of Public Health, Boston, Massachusetts, USA
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49
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Green T, Toghill A, Foster JR. The role of cytochromes P-450 in styrene induced pulmonary toxicity and carcinogenicity. Toxicology 2001; 169:107-17. [PMID: 11718952 DOI: 10.1016/s0300-483x(01)00488-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Exposure of CD-1 mice to atmospheres of 40 and 160 ppm styrene, daily for up to 10 days, caused pulmonary toxicity characterised by focal loss of cytoplasm and focal crowding of non-ciliated Clara cells, particularly in the terminal bronchiolar region. The toxicity was accompanied by an increase in cell replication rates in terminal and large bronchioles of mice exposed for 3 days or longer. The toxicity and increased cell replication were no longer apparent after a 2-day break in exposure, but re-occurred when exposure was resumed. Similar effects were seen in mice given oral doses of 10, 100 or 200 mg/kg styrene, daily for 5 days. Increases in cell replication rates were seen in the terminal bronchioles in mice dosed with 100 and 200 mg/kg styrene, but not 10 mg/kg. Toxicity was limited to 3 to 10 animals in the 200 mg/kg group. Neither morphological nor cell proliferation effects were seen in the alveolar region of the mouse lung in any of these studies, nor were any effects observed in the lungs of CD rats exposed to 500 ppm styrene for up to 10 days. The pulmonary toxicity and increased cell division seen in mice, but not rats, correlates with the known species differences in pulmonary carcinogenicity of styrene, suggesting that the acute and chronic responses are causally related. 5-Phenyl-1-pentyne was shown to inhibit the pulmonary cytochrome P-450 metabolism of styrene in vivo. Cell replication rates in the lungs of mice treated with this inhibitor and exposed to styrene were comparable with controls demonstrating that the pulmonary effects of styrene on the mouse lung are caused by a metabolite of styrene, probably styrene oxide. The risks associated with exposure to styrene appear to correlate well with the metabolic capacity of the lung.
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Affiliation(s)
- T Green
- Syngenta Central Toxicology Laboratory, Alderley Park, Macclesfield, SK10 4TJ, Cheshire, UK.
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50
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Green T, Lee R, Toghill A, Meadowcroft S, Lund V, Foster J. The toxicity of styrene to the nasal epithelium of mice and rats: studies on the mode of action and relevance to humans. Chem Biol Interact 2001; 137:185-202. [PMID: 11551533 DOI: 10.1016/s0009-2797(01)00236-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Inhaled styrene is known to be toxic to the nasal olfactory epithelium of both mice and rats, although mice are markedly more sensitive. In this study, the nasal tissues of mice exposed to 40 and 160 ppm styrene 6 h/day for 3 days had a number of degenerative changes including atrophy of the olfactory mucosa and loss of normal cellular organisation. Pretreatment of mice with 5-phenyl-1-pentyne, an inhibitor of both CYP2F2 and CYP2E1 completely prevented the development of a nasal lesion on exposure to styrene establishing that a metabolite of styrene, probably styrene oxide, is responsible for the observed nasal toxicity. Comparisons of the cytochrome P-450 mediated metabolism of styrene to its oxide, and subsequent metabolism of the oxide by epoxide hydrolases and glutathione S-transferases in nasal tissues in vitro, have provided an explanation for the increased sensitivity of the mouse to styrene. Whereas cytochrome P-450 metabolism of styrene is similar in rats and mice, the rat is able to metabolise styrene oxide at higher rates than the mouse thus rapidly detoxifying this electrophilic metabolite. Metabolism of styrene to its oxide could not be detected in human nasal tissues in vitro, but the same tissues did have epoxide hydrolase and glutathione S-transferase activities, and were able to metabolise styrene oxide efficiently, indicating that styrene is unlikely to be toxic to the human nasal epithelium.
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Affiliation(s)
- T Green
- Syngenta Central Toxicology Laboratory, Alderley Park, Macclesfield, SK10 4TJ, Cheshire, UK.
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