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Hartwig A, Arand M, Epe B, Guth S, Jahnke G, Lampen A, Martus HJ, Monien B, Rietjens IMCM, Schmitz-Spanke S, Schriever-Schwemmer G, Steinberg P, Eisenbrand G. Mode of action-based risk assessment of genotoxic carcinogens. Arch Toxicol 2020; 94:1787-1877. [PMID: 32542409 PMCID: PMC7303094 DOI: 10.1007/s00204-020-02733-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 03/31/2020] [Indexed: 12/16/2022]
Abstract
The risk assessment of chemical carcinogens is one major task in toxicology. Even though exposure has been mitigated effectively during the last decades, low levels of carcinogenic substances in food and at the workplace are still present and often not completely avoidable. The distinction between genotoxic and non-genotoxic carcinogens has traditionally been regarded as particularly relevant for risk assessment, with the assumption of the existence of no-effect concentrations (threshold levels) in case of the latter group. In contrast, genotoxic carcinogens, their metabolic precursors and DNA reactive metabolites are considered to represent risk factors at all concentrations since even one or a few DNA lesions may in principle result in mutations and, thus, increase tumour risk. Within the current document, an updated risk evaluation for genotoxic carcinogens is proposed, based on mechanistic knowledge regarding the substance (group) under investigation, and taking into account recent improvements in analytical techniques used to quantify DNA lesions and mutations as well as "omics" approaches. Furthermore, wherever possible and appropriate, special attention is given to the integration of background levels of the same or comparable DNA lesions. Within part A, fundamental considerations highlight the terms hazard and risk with respect to DNA reactivity of genotoxic agents, as compared to non-genotoxic agents. Also, current methodologies used in genetic toxicology as well as in dosimetry of exposure are described. Special focus is given on the elucidation of modes of action (MOA) and on the relation between DNA damage and cancer risk. Part B addresses specific examples of genotoxic carcinogens, including those humans are exposed to exogenously and endogenously, such as formaldehyde, acetaldehyde and the corresponding alcohols as well as some alkylating agents, ethylene oxide, and acrylamide, but also examples resulting from exogenous sources like aflatoxin B1, allylalkoxybenzenes, 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx), benzo[a]pyrene and pyrrolizidine alkaloids. Additionally, special attention is given to some carcinogenic metal compounds, which are considered indirect genotoxins, by accelerating mutagenicity via interactions with the cellular response to DNA damage even at low exposure conditions. Part C finally encompasses conclusions and perspectives, suggesting a refined strategy for the assessment of the carcinogenic risk associated with an exposure to genotoxic compounds and addressing research needs.
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Affiliation(s)
- Andrea Hartwig
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany.
| | - Michael Arand
- Institute of Pharmacology and Toxicology, University of Zurich, 8057, Zurich, Switzerland
| | - Bernd Epe
- Institute of Pharmacy and Biochemistry, University of Mainz, 55099, Mainz, Germany
| | - Sabine Guth
- Department of Toxicology, IfADo-Leibniz Research Centre for Working Environment and Human Factors, TU Dortmund, Ardeystr. 67, 44139, Dortmund, Germany
| | - Gunnar Jahnke
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany
| | - Alfonso Lampen
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), 10589, Berlin, Germany
| | - Hans-Jörg Martus
- Novartis Institutes for BioMedical Research, 4002, Basel, Switzerland
| | - Bernhard Monien
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), 10589, Berlin, Germany
| | - Ivonne M C M Rietjens
- Division of Toxicology, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands
| | - Simone Schmitz-Spanke
- Institute and Outpatient Clinic of Occupational, Social and Environmental Medicine, University of Erlangen-Nuremberg, Henkestr. 9-11, 91054, Erlangen, Germany
| | - Gerlinde Schriever-Schwemmer
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany
| | - Pablo Steinberg
- Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Haid-und-Neu-Str. 9, 76131, Karlsruhe, Germany
| | - Gerhard Eisenbrand
- Retired Senior Professor for Food Chemistry and Toxicology, Kühler Grund 48/1, 69126, Heidelberg, Germany.
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Tucker JD. Reflections on the development and application of FISH whole chromosome painting. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2015; 763:2-14. [DOI: 10.1016/j.mrrev.2014.11.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/11/2014] [Indexed: 11/28/2022]
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Albertini RJ, Sweeney LM. Propylene oxide: genotoxicity profile of a rodent nasal carcinogen. Crit Rev Toxicol 2007; 37:489-520. [PMID: 17661214 DOI: 10.1080/10408440701382959] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Propylene oxide (PO) is a DNA-reactive genotoxic agent; that is, it reacts with DNA to produce lesions in the genetic material. PO also induces tumors in rodents, although only at high concentrations and at portals of entry. This review of PO's genotoxicity profile is organized according to endpoints measured, that is, nonmutational or mutational endpoints, and as to whether the results were from in vitro or in vivo studies. In addition to results of experimental studies, PO's genotoxicity for humans is assessed by reviewing results of published biomarker studies. The weight of evidence indicates that although it is genotoxic, PO's potency as a DNA-reactive mutagen is weak. Other aspects of PO's overall tissue toxicities are also reviewed, with attention to glutathione (GSH) depletion and its consequences, that is, cell proliferation, death, and necrosis. These toxic tissue responses occur in the same anatomical regions in rodents as do the PO-induced tumors. Furthermore, some of these tissue toxicities can produce effects that may either augment PO's DNA-reactive mutagenicity or be genotoxic in themselves, not dependent on PO's DNA reactivity. Although its DNA reactivity may be a necessary component of PO's overall genotoxicity and rodent carcinogenicity, it is likely not sufficient, and the associated tissue toxicities, which are rate-limiting, also seem to be required. This complex mode of action has implications for estimations of PO's cancer potential in humans, especially at low exposure concentrations.
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Affiliation(s)
- Richard J Albertini
- Department of Pathology, University of Vermont, Burlington, Vermont 05401, USA.
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Ríos-Blanco MN, Plna K, Faller T, Kessler W, Håkansson K, Kreuzer PE, Ranasinghe A, Filser JG, Segerbäck D, Swenberg JA. Propylene oxide: mutagenesis, carcinogenesis and molecular dose. Mutat Res 1997; 380:179-97. [PMID: 9385398 DOI: 10.1016/s0027-5107(97)00135-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The results from mutagenic and carcinogenic studies of propylene oxide (PO) and the current efforts to develop molecular dosimetry methods for PO-DNA adducts are reviewed. PO has been shown to be active in several bacterial and mammalian mutagenicity tests and induces site of contact tumors in rodents after long-term administration. Quantitation of N7-(2-hydroxypropyl)guanine (7-HPG) in nasal and hepatic tissues of male F344 rats exposed to 500 ppm PO (6 h/day; 5 days/week for 4 weeks) by inhalation was performed to evaluate the potential of high concentrations of PO to produce adducts in the DNA of rodent tissues and to obtain information necessary for the design of molecular dosimetry studies. The persistence of 7-HPG in nasal and hepatic tissues was studied in rats killed three days after cessation of a 4-week exposure period. DNA samples from exposed and untreated animals were analyzed for 7-HPG by two different methods. The first method consisted of separation of the adduct from DNA by neutral thermal hydrolysis, followed by electrophoretic derivatization of the adduct and gas chromatography-high resolution mass spectrometry (GC-HRMS) analysis. The second method utilized 32P-postlabeling to quantitate the amount of this adduct in rat tissues. Adducts present in tissues from rats killed immediately after cessation of exposure were 835.4 +/- 80.1 (respiratory), 396.8 +/- 53.1 (olfactory) and 34.6 +/- 3.0 (liver) pmol adduct/mumol guanine using GC-HRMS. Lower values, 592.7 +/- 53.3, 296.5 +/- 32.6 and 23.2 +/- 0.6 pmol adduct/mumol guanine were found in respiratory, olfactory and hepatic tissues of rats killed after three days of recovery. Analysis of the tissues by 32P-postlabeling yielded the following values: 445.7 +/- 8.0 (respiratory), 301.6 +/- 49.2 (olfactory) and 20.6 +/- 1.8 (liver) pmol adduct/mumol guanine in DNA of rats killed immediately after exposure cessation and 327.1 +/- 21.7 (respiratory), 185.3 +/- 29.2 (olfactory) and 15.7 +/- 0.9 (liver) pmol adduct/mumol guanine after recovery. Current methods of quantitation did not provide evidence for the endogenous formation of this adduct in control animals. These studies demonstrated that the target tissue for carcinogenesis has much greater alkylation of DNA than liver, a tissue that did not exhibit a carcinogenic response.
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Affiliation(s)
- M N Ríos-Blanco
- Curriculum in Toxicology, University of North Carolina at Chapel Hill 27599, USA
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Garnier R, Rambourg-Schepens MO, Müller A, Hallier E. Glutathione transferase activity and formation of macromolecular adducts in two cases of acute methyl bromide poisoning. Occup Environ Med 1996; 53:211-15. [PMID: 8704864 PMCID: PMC1128446 DOI: 10.1136/oem.53.3.211] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVES To determine the activity of glutathione transferase and to measure the S-methylcysteine adducts in blood proteins, after acute inhalation exposure to methyl bromide. To examine the influence of the polymorphism of glutathione-S-transferase theta (GSTT1) on the neurotoxicity of methyl bromide. METHODS Two workers acutely exposed to methyl bromide with inadequate respiratory protective devices were poisoned. Seven weeks after the accident, blood samples were drawn from both patients, for measurement of glutathione transferase activity in erythrocytes (conjugator status--that is, GSTT1 phenotype) and measurement of binding products of methyl bromide with blood proteins. Conjugator status was determined by a standard procedure. The binding product of methyl bromide, S-methylcysteine, was measured in globin and albumin. RESULTS Duration and intensity of exposure were identical for both patients as they worked together with the same protective devices and with similar physical effort. However, one patient had very severe poisoning, whereas the other only developed mild neurotoxic symptoms. The first patient was a "conjugator" with normal glutathone transferase activity, whereas this activity was undetectable in the erythrocytes of the second patient, who consequently had higher concentrations of S-methylcysteine adduct in albumin (149 v 91 nmol/g protein) and in globin (77 v 30 nmol/g protein). CONCLUSIONS Methyl bromide is genotoxic and neurotoxic. Its genotoxicity seems to be the consequence of the alkylating activity of the parent compound, and conjugation to glutathione has a protective effect. The data presented here suggest a different mechanism for methyl bromide neurotoxicity which could be related to the transformation of methylglutathione into toxic metabolites such as methanethiol and formaldehyde. If such metabolites are the ultimate toxic species, N-acetylcysteine treatment could have a toxifying rather than a detoxifying effect.
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Affiliation(s)
- R Garnier
- Centre Anti-poisons, Clinique, Interuniversitaire de Médicine du Travail, Paris, France
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Yang RS, Witt KL, Alden CJ, Cockerham LG. Toxicology of methyl bromide. REVIEWS OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 1995; 142:65-85. [PMID: 7652197 DOI: 10.1007/978-1-4612-4252-9_3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Methyl bromide is widely used as an insecticidal fumigant in food supplies, warehouses, barges, buildings, and furniture. Its popularity as a fumigant is largely attributable to its high toxicity to many pests, the variety of settings in which it can be applied, its ability to penetrate the fumigated substances, and its rapid dissipation following application. Because of its frequent use around humans and human-related activities and its high acute toxicity, methyl bromide-related fatal accidents have occurred. The primary route for human exposure to methyl bromide is inhalation. In California, the most frequent cause of death from methyl bromide exposure in recent years has been unauthorized entry into structures under fumigation. The most frequently reported lesions included pulmonary edema, congestion, and hemorrhage. In recent years, a great deal of effort has been given to the characterization of the toxicity of methyl bromide because of its commercial value and its direct and indirect economic importance. Methyl bromide is acutely very toxic. Subchronically and chronically, the principal target site for methyl bromide appears to be the central nervous system. However, there was no evidence for carcinogenic activity of methyl bromide following the normal environmental exposure routes of inhalation or oral intake through residue on foods. Methyl bromide is clearly genotoxic in vitro and in vivo, as evidenced by the positive results from various tests. The mechanism of toxicity for methyl bromide is currently uncertain, although its alkylating property as well as the possibility of forming a reactive intermediate through metabolic transformation remain attractive hypotheses.
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Affiliation(s)
- R S Yang
- Department of Environmental Health, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins 80523, USA
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Tucker JD, Lee DA, Ramsey MJ, Briner J, Olsen L, Moore DH. On the frequency of chromosome exchanges in a control population measured by chromosome painting. Mutat Res 1994; 313:193-202. [PMID: 7523904 DOI: 10.1016/0165-1161(94)90049-3] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Chromosome painting has been shown to be a valid and rapid method for quantifying structural chromosome rearrangements in human lymphocytes. The method is particularly useful for detecting stable aberrations which are difficult and expensive to quantify with classical methods. The inherent stability of translocations has enabled them to be used as a biodosimeter for chronic and temporally displaced exposure to radiation. Translocations may also be useful for quantifying chronic exposure to other environmental agents which may result in an accumulation of cytogenetic damage with age. Most exposures are chronic and occur at low rates, and conventional cytogenetic methods such as dicentric analysis are not expected to be informative. To understand the extent to which age and lifestyle factors impact the frequency of stable aberrations, we have performed chromosome painting on metaphase-arrested lymphocytes cultured from 47 healthy adults ranging in age from 19 to 77 years, and from umbilical cord blood obtained from eight healthy full-term infants. All subjects had previously been screened to eliminate those who had received significant occupational or accidental exposure to radiation or chemicals, and none had received chemo- or radiotherapy. Due to the infrequent occurrence of stable aberrations in peripheral lymphocytes, we analyzed the equivalent of more than 1100 metaphase cells from each of these 55 people. An average of one cell in 130 (0.77%) was observed to have a translocation or a stable insertion. A significant relationship between stable aberrations and the square of the age is apparent (R2 = 0.69, Y = 0.0615 + 0.000304 age2; p < 0.00001). These results support the hypothesis that stable aberrations accumulate with time, and are likely to integrate adverse environmental exposure.
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Affiliation(s)
- J D Tucker
- Biology and Biotechnology Research Program, L-452 Lawrence Livermore National Laboratory, Livermore, CA 94551
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Farooqi Z, Törnqvist M, Ehrenberg L, Natarajan AT. Genotoxic effects of ethylene oxide and propylene oxide in mouse bone marrow cells. Mutat Res 1993; 288:223-8. [PMID: 7688081 DOI: 10.1016/0027-5107(93)90088-w] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Ethylene oxide and propylene oxide are high-volume reactive alkylating agents used primarily as intermediates in the chemical industry. Studies were undertaken to investigate the ability of these alkylating agents to induce chromosomal aberrations, micronuclei and sister-chromatid exchanges in mouse bone marrow cells. The mice were exposed to these chemicals by intraperitoneal injection. The data show that both compounds are effective in inducing chromosomal alterations. Our studies confirm the findings reported by different investigators that ethylene oxide is more cytotoxic than propylene oxide. This difference is to a large extent due to a faster detoxification of propylene oxide than of ethylene oxide.
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Affiliation(s)
- Z Farooqi
- Department of Radiation Genetics and Chemical Mutagenesis, State University of Leiden, The Netherlands
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Gansewendt B, Foest U, Xu D, Hallier E, Bolt HM, Peter H. Formation of DNA adducts in F-344 rats after oral administration or inhalation of [14C]methyl bromide. Food Chem Toxicol 1991; 29:557-63. [PMID: 1894222 DOI: 10.1016/0278-6915(91)90048-c] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The genotoxic effects of methyl bromide were investigated in a DNA-binding study. [14C]Methyl bromide was administered to male and female F-344 rats orally, or by inhalation from a closed exposure system. DNA adducts were detected in the liver, lung, stomach and forestomach. [14C]3-Methyladenine, [14C]7-methylguanine and [14C]O6-methylguanine were identified using a combination of three different methods of hydrolysing DNA, followed by HPLC or gas chromatography-mass spectrometry. After both oral and inhalation exposure, the highest levels of methylated guanines, especially those of [14C]O6-methylguanine, were found in the stomach and forestomach of the rats. These results clearly demonstrate a systemic DNA-alkylating potential of methyl bromide.
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Affiliation(s)
- B Gansewendt
- Institut für Arbeitsphysiologie, Universität Dortmund, Germany
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Garry VF, Nelson RL, Griffith J, Harkins M. Preparation for human study of pesticide applicators: sister chromatid exchanges and chromosome aberrations in cultured human lymphocytes exposed to selected fumigants. TERATOGENESIS, CARCINOGENESIS, AND MUTAGENESIS 1990; 10:21-9. [PMID: 1971966 DOI: 10.1002/tcm.1770100104] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In preparation for a human study of worker exposure to grain fumigants and pesticides, we decided to screen commonly used fumigants for genotoxic effects in vitro. This research strategy was employed to test the possibility that structurally simple chemicals might have similar genotoxic properties in vivo and in vitro. As a first step, we designed our in vitro protocol to mimic to the extent possible, a single in vivo exposure of lymphocytes to fumigants. Go lymphocytes were treated with different doses of carbon tetrachloride, carbon disulfide, methyl bromide, chloropicrin, and melathion with and without addition of rat liver homogenate for 1/2 hour, washed free of toxicant, and stimulated with PHA. After culture, the prepared slides were studied for chromosome aberrations and SCEs. Malathion, methyl bromide, and chloropicrin significantly induced SCEs without S-9. Carbon disulfide alone required S-9 for significant SCE induction. Chromosome aberrations were significantly increased by malathion and methyl bromide. Carbon tetrachloride failed to induce SCEs or chromosome aberrations with or without S-9. We concluded from these preliminary studies and other comparable work that the fumigants studied here may be less likely to express genotoxicity in terms of SCEs or chromosome aberrations than ethylene oxide or phosphine given a single short-term in vivo exposure. The final design of our human study was altered to focus on seasonal worker exposure rather than on a single exposure event.
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Affiliation(s)
- V F Garry
- Laboratory of Environmental Medicine Pathology, University of Minnesota, Minneapolis
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Ong TM, Stewart J, Wen YF, Whong WZ. Application of SOS umu-test for the detection of genotoxic volatile chemicals and air pollutants. ENVIRONMENTAL MUTAGENESIS 1987; 9:171-6. [PMID: 2434323 DOI: 10.1002/em.2860090207] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The SOS umu-test has been used for the detection of DNA-damaging agents. In this system the plasmid pSK1002 carrying a fused gene umuC-lacZ was introduced into Salmonella typhimurium TA1535. The SOS function induced by genotoxic agents is detected by a colorimetric measurement of beta-galactosidase activity encoded by the lacZ gene, which is regulated by the Umu operon. This system was used with modifications to study the SOS function inducibility of volatile chemicals (propylene oxide, methyl bromide, and ethylene dibromide) and air pollutants (diesel emission, welding fumes, and cigarette smoke). Tester cells were exposed directly to the test material. The enzyme activity of the treated cells was measured according to the established procedure. Results of the study showed that all chemicals and pollutants tested induced SOS function in a dose-related manner. These results indicate that the SOS umu-test is potentially useful for the in situ detection of genotoxic agents in occupational settings.
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