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Dekant W, Jean P, Arts J. Evaluation of the carcinogenicity of dichloromethane in rats, mice, hamsters and humans. Regul Toxicol Pharmacol 2021; 120:104858. [PMID: 33387565 DOI: 10.1016/j.yrtph.2020.104858] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 12/23/2020] [Accepted: 12/24/2020] [Indexed: 12/26/2022]
Abstract
Dichloromethane (DCM) is a high production volume chemical (>1000 t/a) mainly used as an industrial solvent. Carcinogenicity studies in rats, mice and hamsters have demonstrated a malignant tumor inducing potential of DCM only in the mouse (lung and liver) at 1000-4000 ppm whereas human data do not support a conclusion of cancer risk. Based on this, DCM has been classified as a cat. 2 carcinogen. Dose-dependent toxicokinetics of DCM suggest that DCM is a threshold carcinogen in mice, initiating carcinogenicity via the low affinity/high capacity GSTT1 pathway; a biotransformation pathway that becomes relevant only at high exposure concentrations. Rats and hamsters have very low activities of this DCM-metabolizing GST and humans have even lower activities of this enzyme. Based on the induction of specific tumors selectively in the mouse, the dose- and species-specific toxicokinetics in this species, and the absence of a malignant tumor response by DCM in rats and hamsters having a closer relationship to DCM toxicokinetics in humans and thus being a more relevant animal model, the current classification of DCM as human carcinogen cat. 2 remains appropriate.
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Affiliation(s)
- Wolfgang Dekant
- Department of Pharmacology and Toxicology, Universität Würzburg, Versbacherstr. 9, 97078 Würzburg, Germany
| | - Paul Jean
- Olin Corporation, 2205 Ridgewood Dr., Midland, MI, 48642 USA
| | - Josje Arts
- Nouryon Industrial Chemicals, PO Box 60192, 6800 JD Arnhem, the Netherlands.
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2
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Evans MV, Eklund CR, Williams DN, Sey YM, Simmons JE. Global optimization of the Michaelis-Menten parameters using physiologically-based pharmacokinetic (PBPK) modeling and chloroform vapor uptake data in F344 rats. Inhal Toxicol 2020; 32:97-109. [PMID: 32241199 DOI: 10.1080/08958378.2020.1742818] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Objective: To quantify metabolism, a physiologically based pharmacokinetic (PBPK) model for a volatile compound can be calibrated with the closed chamber (i.e. vapor uptake) inhalation data. Here, we introduce global optimization as a novel component of the predictive process and use it to illustrate a procedure for metabolic parameter estimation.Materials and methods: Male F344 rats were exposed in vapor uptake chambers to initial concentrations of 100, 500, 1000, and 3000 ppm chloroform. Chamber time-course data from these experiments, in combination with optimization using a chemical-specific PBPK model, were used to estimate Michaelis-Menten metabolic constants. Matlab® simulation software was used to integrate the mass balance equations and to perform the global optimizations using MEIGO (MEtaheuristics for systems biology and bIoinformatics Global Optimization - Version 64 bit, R2016A), a toolbox written for Matlab®. The cost function used the chamber time-course data and least squares to minimize the difference between data and simulation values.Results and discussion: The final values estimated for Vmax (maximum metabolic rate) and Km (affinity constant) were 1.2 mg/h and a range between 0.0005 and 0.6 mg/L, respectively. Also, cost function plots were used to analyze the dose-dependent capacity to estimate Vmax and Km within the experimental range used. Sensitivity analysis was used to assess identifiability for both parameters and show these kinetic data may not be sufficient to identify Km.Conclusion: In summary, this work should help toxicologists interested in optimization techniques understand the overall process employed when calibrating metabolic parameters in a PBPK model with inhalation data.
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Affiliation(s)
- Marina V Evans
- ORD, National Health and Environmental Effects Research Laboratory, ISTD, US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Christopher R Eklund
- ORD, National Health and Environmental Effects Research Laboratory, ISTD, US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - David N Williams
- ORISE, Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA
| | - Yusupha M Sey
- ORD, National Health and Environmental Effects Research Laboratory, ISTD, US Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Jane Ellen Simmons
- ORD, National Health and Environmental Effects Research Laboratory, ISTD, US Environmental Protection Agency, Research Triangle Park, NC, USA
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Zhang K, Chen TT, Shen YJ, Yang ZR, Huang Y, Zhang S, Xue J, Li B. An N-linked disalicylaldehyde together with its caesium ion and dichloromethane sensing performances: ‘dual key & lock’ LMCT-enhanced fluorescence strategy. Analyst 2020; 145:5826-5835. [DOI: 10.1039/d0an00475h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The disalicylaldehyde-Cs+sensing system, a novel approach for quick and reusable detection of Cs+together with convenient CH2Cl2monitoring.
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Affiliation(s)
- Kun Zhang
- Department of Chemistry
- Zhejiang Sci-Tech University
- Xiasha Higher Education District
- Hangzhou 310018
- P. R. China
| | - Ting-Ting Chen
- Department of Chemistry
- Zhejiang Sci-Tech University
- Xiasha Higher Education District
- Hangzhou 310018
- P. R. China
| | - Yin-Jing Shen
- Department of Chemistry
- Zhejiang Sci-Tech University
- Xiasha Higher Education District
- Hangzhou 310018
- P. R. China
| | - Zhuo-Ran Yang
- Department of Chemistry
- Zhejiang Sci-Tech University
- Xiasha Higher Education District
- Hangzhou 310018
- P. R. China
| | - Yan Huang
- Department of Chemistry
- Zhejiang Sci-Tech University
- Xiasha Higher Education District
- Hangzhou 310018
- P. R. China
| | - Shishen Zhang
- Department of Chemistry
- Zhejiang Sci-Tech University
- Xiasha Higher Education District
- Hangzhou 310018
- P. R. China
| | - Jiadan Xue
- Department of Chemistry
- Zhejiang Sci-Tech University
- Xiasha Higher Education District
- Hangzhou 310018
- P. R. China
| | - Benxia Li
- Department of Chemistry
- Zhejiang Sci-Tech University
- Xiasha Higher Education District
- Hangzhou 310018
- P. R. China
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4
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Kim EB, Abdullah, Ameen S, Akhtar MS, Shin HS. Environment-friendly and highly sensitive dichloromethane chemical sensor fabricated with ZnO nanopyramids-modified electrode. J Taiwan Inst Chem Eng 2019. [DOI: 10.1016/j.jtice.2019.05.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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5
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Spun films of perylene diimide derivative for the detection of organic vapors with host–guest principle. J INCL PHENOM MACRO 2018. [DOI: 10.1007/s10847-018-0823-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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6
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Huang Z, Chen X, Fu H, Wen X, Ma C, Zhang J, Wu C, Huang Y, Pan X, Wu C. Formation Mechanism and In Vitro Evaluation of Risperidone-Containing PLGA Microspheres Fabricated by Ultrafine Particle Processing System. J Pharm Sci 2017; 106:3363-3371. [PMID: 28736289 DOI: 10.1016/j.xphs.2017.07.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Revised: 07/06/2017] [Accepted: 07/13/2017] [Indexed: 10/19/2022]
Abstract
Ultrafine particle processing system (UPPS) was developed previously by our group to provide a new solution to microsphere fabrication. The UPPS was supposed to possess many featured advantages, but the microsphere formation mechanism during UPPS processing was still unknown. The objective of this study was to perform the formation mechanism investigation and in vitro evaluation on risperidone-containing poly(d, l-lactic-co-glycolic acid) microspheres (RIS-PLGA MS) fabricated by UPPS. Evaporation profile and viscosity of the PLGA-containing solutions were considered as the critical factors for the microsphere formation mechanism and were determined in present study. The formation mechanism of RIS-PLGA MS was put forward by semiquantitative analysis on the basis of the evaporation profile, viscosity, and scanning electron microscopy results. It was established that the evaporation profile and viscosity would have an impact on the evaporation velocity and PLGA molecular diffusion velocity during solidification process, resulting in different appearance of the microspheres. Furthermore, comprehensive in vitro evaluations of RIS-PLGA MS were conducted, including particle size distribution, micromeritics, morphology, drug loading, encapsulation efficiency, residual organic solvent, syringeability, and in vitro release behavior. The results revealed that RIS-PLGA MS was a promising candidate for intramuscular administration, and meanwhile UPPS was a qualified technology for microsphere production.
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Affiliation(s)
- Zhengwei Huang
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, Guangdong, P. R. China
| | - Xiaona Chen
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, Guangdong, P. R. China
| | - Han Fu
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, Guangdong, P. R. China
| | - Xinguo Wen
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, Guangdong, P. R. China
| | - Cheng Ma
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, Guangdong, P. R. China
| | - Jiwen Zhang
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, P. R. China
| | - Chuanyu Wu
- Department of Chemical and Process Engineering, University of Surrey, Guildford, Surrey GU2 7XH, UK
| | - Ying Huang
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, Guangdong, P. R. China.
| | - Xin Pan
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, Guangdong, P. R. China.
| | - Chuanbin Wu
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, Guangdong, P. R. China
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7
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Huang R, McPhedran KN, Sun N, Chelme-Ayala P, Gamal El-Din M. Investigation of the impact of organic solvent type and solution pH on the extraction efficiency of naphthenic acids from oil sands process-affected water. CHEMOSPHERE 2016; 146:472-477. [PMID: 26741553 DOI: 10.1016/j.chemosphere.2015.12.054] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 11/26/2015] [Accepted: 12/15/2015] [Indexed: 06/05/2023]
Abstract
Naphthenic acids (NAs) from oil sand process-affected water (OSPW) were liquid-liquid extracted using six organic solvents (n-pentane, n-hexane, cyclohexane, dichloromethane, ethyl ether, and ethyl acetate) at three pHs (2.0, 8.5, and 12.0). The NAs exist in ionic (ions) and non-ionic (molecules) forms in the water phase depending on their dissociation constants and the solution pH. Results showed the extractability of NA molecules depends on the solvent polarity and the extractability of NA ions on the water solubility in solvent. The organic solvent type and solution pH were found to not only impact the extracted amounts of each NA species, but also the NAs distribution in terms of molecule carbon number and hydrogen deficiency. Overall, it is concluded that ethyl ether can be used as an alternative to dichloromethane (DCM) given their similar extraction efficiencies and extracted NA profiles. This is important since DCM is known to have metabolic toxicity and transitioning to the safer ethyl ether would eliminate laboratory DCM exposures and risk to human health. Despite the higher extraction efficiency of NAs at pH 2.0, extraction at pH 12.0 could be useful for targeted extraction of low-concentration nonpolar organic compounds in OSPW. This knowledge may assist in the determination of the specific NAs species that are known to have chronic, sub-chronic and acute toxicity to various organisms, and the potential targeting of treatment to these NAs species.
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Affiliation(s)
- Rongfu Huang
- Department of Civil and Environmental Engineering, 7-285 Donadeo Innovation Centre for Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada
| | - Kerry N McPhedran
- Department of Civil and Geological Engineering, College of Engineering, University of Saskatchewan, Engineering Building, 57 Campus Dr., Saskatoon, SK, S7N 5A9, Canada
| | - Nian Sun
- Department of Civil and Environmental Engineering, 7-285 Donadeo Innovation Centre for Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada
| | - Pamela Chelme-Ayala
- Department of Civil and Environmental Engineering, 7-285 Donadeo Innovation Centre for Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada
| | - Mohamed Gamal El-Din
- Department of Civil and Environmental Engineering, 7-285 Donadeo Innovation Centre for Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada.
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8
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Hartman JH, Martin HC, Caro AA, Pearce AR, Miller GP. Subcellular localization of rat CYP2E1 impacts metabolic efficiency toward common substrates. Toxicology 2015; 338:47-58. [PMID: 26463279 DOI: 10.1016/j.tox.2015.10.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/22/2015] [Accepted: 10/06/2015] [Indexed: 01/12/2023]
Abstract
Cytochrome P450 2E1 (CYP2E1) detoxifies or bioactivates many low molecular-weight compounds. Most knowledge about CYP2E1 activity relies on studies of the enzyme localized to endoplasmic reticulum (erCYP2E1); however, CYP2E1 undergoes transport to mitochondria (mtCYP2E1) and becomes metabolically active. We report the first comparison of in vitro steady-state kinetic profiles for erCYP2E1 and mtCYP2E1 oxidation of probe substrate 4-nitrophenol and pollutants styrene and aniline using subcellular fractions from rat liver. For all substrates, metabolic efficiency changed with substrate concentration for erCYP2E1 reflected in non-hyperbolic kinetic profiles but not for mtCYP2E1. Hyperbolic kinetic profiles for the mitochondrial enzyme were consistent with Michaelis-Menten mechanism in which metabolic efficiency was constant. By contrast, erCYP2E1 metabolism of 4-nitrophenol led to a loss of enzyme efficiency at high substrate concentrations when substrate inhibited the reaction. Similarly, aniline metabolism by erCYP2E1 demonstrated negative cooperativity as metabolic efficiency decreased with increasing substrate concentration. The opposite was observed for erCYP2E1 oxidation of styrene; the sigmoidal kinetic profile indicated increased efficiency at higher substrate concentrations. These mechanisms and CYP2E1 levels in mitochondria and endoplasmic reticulum were used to estimate the impact of CYP2E1 subcellular localization on metabolic flux of pollutants. Those models showed that erCYP2E1 mainly carries out aniline metabolism at all aniline concentrations. Conversely, mtCYP2E1 dominates styrene oxidation at low styrene concentrations and erCYP2E1 at higher concentrations. Taken together, subcellular localization of CYP2E1 results in distinctly different enzyme activities that could impact overall metabolic clearance and/or activation of substrates and thus impact the interpretation and prediction of toxicological outcomes.
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Affiliation(s)
- Jessica H Hartman
- Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - H Cass Martin
- Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States; Department of Chemistry, University of Central Arkansas, Conway, AR, United States
| | - Andres A Caro
- Department of Chemistry, Hendrix College, Conway, AR, United States
| | - Amy R Pearce
- Arkansas Biosciences Institute, United States; Psychology & Counseling, Arkansas State University, Jonesboro, AR, United States
| | - Grover P Miller
- Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States.
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9
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Schlosser PM, Bale AS, Gibbons CF, Wilkins A, Cooper GS. Human health effects of dichloromethane: key findings and scientific issues. ENVIRONMENTAL HEALTH PERSPECTIVES 2015; 123:114-9. [PMID: 25325283 PMCID: PMC4314245 DOI: 10.1289/ehp.1308030] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 10/16/2014] [Indexed: 05/19/2023]
Abstract
BACKGROUND The U.S. EPA's Integrated Risk Information System (IRIS) completed an updated toxicological review of dichloromethane in November 2011. OBJECTIVES In this commentary we summarize key results and issues of this review, including exposure sources, identification of potential health effects, and updated physiologically based pharmacokinetic (PBPK) modeling. METHODS We performed a comprehensive review of primary research studies and evaluation of PBPK models. DISCUSSION Hepatotoxicity was observed in oral and inhalation exposure studies in several studies in animals; neurological effects were also identified as a potential area of concern. Dichloromethane was classified as likely to be carcinogenic in humans based primarily on evidence of carcinogenicity at two sites (liver and lung) in male and female B6C3F1 mice (inhalation exposure) and at one site (liver) in male B6C3F1 mice (drinking-water exposure). Recent epidemiologic studies of dichloromethane (seven studies of hematopoietic cancers published since 2000) provide additional data raising concerns about associations with non-Hodgkin lymphoma and multiple myeloma. Although there are gaps in the database for dichloromethane genotoxicity (i.e., DNA adduct formation and gene mutations in target tissues in vivo), the positive DNA damage assays correlated with tissue and/or species availability of functional glutathione S-transferase (GST) metabolic activity, the key activation pathway for dichloromethane-induced cancer. Innovations in the IRIS assessment include estimation of cancer risk specifically for a presumed sensitive genotype (GST-theta-1+/+), and PBPK modeling accounting for human physiological distributions based on the expected distribution for all individuals 6 months to 80 years of age. CONCLUSION The 2011 IRIS assessment of dichloromethane provides insights into the toxicity of a commonly used solvent.
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Affiliation(s)
- Paul M Schlosser
- National Center for Environmental Assessment, U.S. Environmental Protection Agency, Washington, DC, USA
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10
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Kuempel ED, Sweeney LM, Morris JB, Jarabek AM. Advances in Inhalation Dosimetry Models and Methods for Occupational Risk Assessment and Exposure Limit Derivation. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2015; 12 Suppl 1:S18-40. [PMID: 26551218 PMCID: PMC4685615 DOI: 10.1080/15459624.2015.1060328] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The purpose of this article is to provide an overview and practical guide to occupational health professionals concerning the derivation and use of dose estimates in risk assessment for development of occupational exposure limits (OELs) for inhaled substances. Dosimetry is the study and practice of measuring or estimating the internal dose of a substance in individuals or a population. Dosimetry thus provides an essential link to understanding the relationship between an external exposure and a biological response. Use of dosimetry principles and tools can improve the accuracy of risk assessment, and reduce the uncertainty, by providing reliable estimates of the internal dose at the target tissue. This is accomplished through specific measurement data or predictive models, when available, or the use of basic dosimetry principles for broad classes of materials. Accurate dose estimation is essential not only for dose-response assessment, but also for interspecies extrapolation and for risk characterization at given exposures. Inhalation dosimetry is the focus of this paper since it is a major route of exposure in the workplace. Practical examples of dose estimation and OEL derivation are provided for inhaled gases and particulates.
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Affiliation(s)
- Eileen D. Kuempel
- National Institute for Occupational Safety and Health, Education and Information Division, Cincinnati, Ohio
| | - Lisa M. Sweeney
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Naval Medical Research Unit Dayton, Wright-Patterson Air Force Base, Ohio
| | - John B. Morris
- School of Pharmacy, University of Connecticut, Storrs, Connecticut
| | - Annie M. Jarabek
- U.S. Environmental Protection Agency, National Center for Environmental Assessment, Research Triangle Park, North Carolina
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Huang B, Lei C, Wei C, Zeng G. Chlorinated volatile organic compounds (Cl-VOCs) in environment - sources, potential human health impacts, and current remediation technologies. ENVIRONMENT INTERNATIONAL 2014; 71:118-38. [PMID: 25016450 DOI: 10.1016/j.envint.2014.06.013] [Citation(s) in RCA: 332] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 06/20/2014] [Accepted: 06/24/2014] [Indexed: 05/03/2023]
Abstract
Chlorinated volatile organic compounds (Cl-VOCs), including polychloromethanes, polychloroethanes and polychloroethylenes, are widely used as solvents, degreasing agents and a variety of commercial products. These compounds belong to a group of ubiquitous contaminants that can be found in contaminated soil, air and any kind of fluvial mediums such as groundwater, rivers and lakes. This review presents a summary of the research concerning the production levels and sources of Cl-VOCs, their potential impacts on human health as well as state-of-the-art remediation technologies. Important sources of Cl-VOCs principally include the emissions from industrial processes, the consumption of Cl-VOC-containing products, the disinfection process, as well as improper storage and disposal methods. Human exposure to Cl-VOCs can occur through different routes, including ingestion, inhalation and dermal contact. The toxicological impacts of these compounds have been carefully assessed, and the results demonstrate the potential associations of cancer incidence with exposure to Cl-VOCs. Most Cl-VOCs thus have been listed as priority pollutants by the Ministry of Environmental Protection (MEP) of China, Environmental Protection Agency of the U.S. (U.S. EPA) and European Commission (EC), and are under close monitor and strict control. Yet, more efforts will be put into the epidemiological studies for the risk of human exposure to Cl-VOCs and the exposure level measurements in contaminated sites in the future. State-of-the-art remediation technologies for Cl-VOCs employ non-destructive methods and destructive methods (e.g. thermal incineration, phytoremediation, biodegradation, advanced oxidation processes (AOPs) and reductive dechlorination), whose advantages, drawbacks and future developments are thoroughly discussed in the later sections.
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Affiliation(s)
- Binbin Huang
- College of Environment Science and Engineering, Hunan University, Changsha 410082, P.R. China
| | - Chao Lei
- School of Hydraulic Engineering, Changsha University of Science & Technology, Changsha 410114, P.R. China
| | - Chaohai Wei
- Key Laboratory of Environmental Protection and Eco-Remediation of Guangdong Regular Higher Education Institutions, South China University of Technology, Guangzhou 510006, P.R. China
| | - Guangming Zeng
- College of Environment Science and Engineering, Hunan University, Changsha 410082, P.R. China
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Cutting Edge PBPK Models and Analyses: Providing the Basis for Future Modeling Efforts and Bridges to Emerging Toxicology Paradigms. J Toxicol 2012; 2012:852384. [PMID: 22899915 PMCID: PMC3413973 DOI: 10.1155/2012/852384] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 06/21/2012] [Indexed: 12/16/2022] Open
Abstract
Physiologically based Pharmacokinetic (PBPK) models are used for predictions of internal or target dose from environmental and pharmacologic chemical exposures. Their use in human risk assessment is dependent on the nature of databases (animal or human) used to develop and test them, and includes extrapolations across species, experimental paradigms, and determination of variability of response within human populations. Integration of state-of-the science PBPK modeling with emerging computational toxicology models is critical for extrapolation between in vitro exposures, in vivo physiologic exposure, whole organism responses, and long-term health outcomes. This special issue contains papers that can provide the basis for future modeling efforts and provide bridges to emerging toxicology paradigms. In this overview paper, we present an overview of the field and introduction for these papers that includes discussions of model development, best practices, risk-assessment applications of PBPK models, and limitations and bridges of modeling approaches for future applications. Specifically, issues addressed include: (a) increased understanding of human variability of pharmacokinetics and pharmacodynamics in the population, (b) exploration of mode of action hypotheses (MOA), (c) application of biological modeling in the risk assessment of individual chemicals and chemical mixtures, and (d) identification and discussion of uncertainties in the modeling process.
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Physiologically Based Pharmacokinetic (PBPK) Modeling of Metabolic Pathways of Bromochloromethane in Rats. J Toxicol 2012; 2012:629781. [PMID: 22719758 PMCID: PMC3377357 DOI: 10.1155/2012/629781] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 03/27/2012] [Accepted: 03/30/2012] [Indexed: 11/18/2022] Open
Abstract
Bromochloromethane (BCM) is a volatile compound and a by-product of disinfection of water by chlorination. Physiologically based pharmacokinetic (PBPK) models are used in risk assessment applications. An updated PBPK model for BCM is generated and applied to hypotheses testing calibrated using vapor uptake data. The two different metabolic hypotheses examined are (1) a two-pathway model using both CYP2E1 and glutathione transferase enzymes and (2) a two-binding site model where metabolism can occur on one enzyme, CYP2E1. Our computer simulations show that both hypotheses describe the experimental data in a similar manner. The two pathway results were comparable to previously reported values (Vmax = 3.8 mg/hour, Km = 0.35 mg/liter, and kGST = 4.7 /hour). The two binding site results were Vmax1 = 3.7 mg/hour, Km1 = 0.3 mg/hour, CL2 = 0.047 liter/hour. In addition, we explore the sensitivity of different parameters for each model using our obtained optimized values.
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Lopes N, Hawkins SA, Jegier P, Menn FM, Sayler GS, Ripp S. Detection of dichloromethane with a bioluminescent (lux) bacterial bioreporter. J Ind Microbiol Biotechnol 2011; 39:45-53. [PMID: 21688172 DOI: 10.1007/s10295-011-0997-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 06/06/2011] [Indexed: 11/26/2022]
Abstract
The focus of this research effort was to develop an autonomous, inducible, lux-based bioluminescent bioreporter for the real-time detection of dichloromethane. Dichloromethane (DCM), also known as methylene chloride, is a volatile organic compound and one of the most commonly used halogenated solvents in the U.S., with applications ranging from grease and paint stripping to aerosol propellants and pharmaceutical tablet coatings. Predictably, it is released into the environment where it contaminates air and water resources. Due to its classification as a probable human carcinogen, hepatic toxin, and central nervous system effector, DCM must be carefully monitored and controlled. Methods for DCM detection usually rely on analytical techniques such as solid-phase microextraction (SPME) and capillary gas chromatography or photoacoustic environmental monitors, all of which require trained personnel and/or expensive equipment. To complement conventional monitoring practices, we have created a bioreporter for the self-directed detection of DCM by taking advantage of the evolutionary adaptation of bacteria to recognize and metabolize chemical agents. This bioreporter, Methylobacterium extorquens DCM( lux ), was engineered to contain a bioluminescent luxCDABE gene cassette derived from Photorhabdus luminescens fused downstream to the dcm dehalogenase operon, which causes the organism to generate visible light when exposed to DCM. We have demonstrated detection limits down to 1.0 ppm under vapor phase exposures and 0.1 ppm under liquid phase exposures with response times of 2.3 and 1.3 h, respectively, and with specificity towards DCM under relevant industrial environmental monitoring conditions.
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Affiliation(s)
- Nicholas Lopes
- The Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN 37996, USA
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15
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Susceptibility to the cytogenetic effects of dichloromethane is related to the glutathione S-transferase theta phenotype. Toxicol Lett 2010; 199:218-24. [DOI: 10.1016/j.toxlet.2010.09.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 09/01/2010] [Accepted: 09/02/2010] [Indexed: 11/22/2022]
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