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Zhang X, Felter SP, Api AM, Joshi K, Selechnik D. A Cautionary tale for using read-across for cancer hazard classification: Case study of isoeugenol and methyl eugenol. Regul Toxicol Pharmacol 2022; 136:105280. [DOI: 10.1016/j.yrtph.2022.105280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 09/16/2022] [Accepted: 10/19/2022] [Indexed: 11/06/2022]
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Kirkland D, Uno Y, Luijten M, Beevers C, van Benthem J, Burlinson B, Dertinger S, Douglas GR, Hamada S, Horibata K, Lovell DP, Manjanatha M, Martus HJ, Mei N, Morita T, Ohyama W, Williams A. In vivo genotoxicity testing strategies: Report from the 7th International workshop on genotoxicity testing (IWGT). MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2019; 847:403035. [PMID: 31699340 DOI: 10.1016/j.mrgentox.2019.03.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/13/2019] [Accepted: 03/23/2019] [Indexed: 12/14/2022]
Abstract
The working group reached complete or majority agreement on many issues. Results from TGR and in vivo comet assays for 91 chemicals showed they have similar ability to detect in vivo genotoxicity per se with bacterial mutagens and Ames-positive carcinogens. TGR and comet assay results were not significantly different when compared with IARC Group 1, 2 A, and unclassified carcinogens. There were significantly more comet assay positive responses for Group 2B chemicals, and for IARC classified and unclassified carcinogens combined, which may be expected since mutation is a sub-set of genotoxicity. A liver comet assay combined with the bone marrow/blood micronucleus (MNviv) test would detect in vivo genotoxins that do not exhibit tissue-specific or site-of-contact effects, and is appropriate for routine in vivo genotoxicity testing. Generally for orally administered substances, a comet assay at only one site-of-contact GI tract tissue (stomach or duodenum/jejunum) is required. In MNviv tests, evidence of target tissue exposure can be obtained in a number of different ways, as recommended by ICH S2(R1) and EFSA (Hardy et al., 2017). Except for special cases the i.p. route is inappropriate for in vivo testing; for risk evaluations more weight should be given to data from a physiologically relevant administration route. The liver MN test is sufficiently validated for the development of an OECD guideline. However, the impact of dosing animals >6 weeks of age needs to be evaluated. The GI tract MN test shows promise but needs more validation for an OECD guideline. The Pig-a assay detects systemically available mutagens and is a valuable follow-up to in vitro positive results. A new freeze-thaw protocol provides more flexibility. Mutant reticulocyte and erythrocyte frequencies should both be determined. Preliminary data are available for the Pig-a assay in male rat germ cells which require validation including germ cell DNA mutation origin.
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Affiliation(s)
- David Kirkland
- Kirkland Consulting, PO Box 79, Tadcaster, LS24 0AS, United Kingdom.
| | - Yoshifumi Uno
- Mitsubishi Tanabe Pharma Corporation, 2-2-50, Kawagishi, Toda, Saitama, 335-8505, Japan
| | - Mirjam Luijten
- National Institute for Public Health and the Environment (RIVM), Centre for Health Protection, Bilthoven, the Netherlands
| | - Carol Beevers
- Exponent International Ltd., The Lenz, Hornbeam Park, Harrogate, HG2 8RE, United Kingdom
| | - Jan van Benthem
- National Institute for Public Health and the Environment (RIVM), Centre for Health Protection, Bilthoven, the Netherlands
| | - Brian Burlinson
- Envigo, Huntingdon, Cambridgeshire, PE28 4HS, United Kingdom
| | | | - George R Douglas
- Environmental Health Science Research Bureau, Health Canada, Ottawa, K1A 0K9, Canada
| | - Shuichi Hamada
- LSI Medience Corporation, 14-1 Sunayama, Kamisu-shi, Ibaraki, 314-0255, Japan
| | - Katsuyoshi Horibata
- National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki, Kanagawa, 210-9501, Japan
| | - David P Lovell
- St George's Medical School, University of London, London, SW17 0RE, United Kingdom
| | | | | | - Nan Mei
- US FDA, National Center for Toxicological Research, Jefferson, AR, USA
| | - Takeshi Morita
- National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki, Kanagawa, 210-9501, Japan
| | - Wakako Ohyama
- Yakult Honsha Co., Ltd., 5-11, Izumi, Kunitachi-shi, Tokyo, 186-8650, Japan
| | - Andrew Williams
- Environmental Health Science Research Bureau, Health Canada, Ottawa, K1A 0K9, Canada
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Zeller A, Pfuhler S, Albertini S, Bringezu F, Czich A, Dietz Y, Fautz R, Hewitt NJ, Kirst A, Kasper P. A critical appraisal of the sensitivity of in vivo genotoxicity assays in detecting human carcinogens. Mutagenesis 2018; 33:179-193. [DOI: 10.1093/mutage/gey005] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 03/20/2018] [Indexed: 11/13/2022] Open
Affiliation(s)
- Andreas Zeller
- Pharmaceutical Sciences, pRED Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse, Basel, Switzerland
| | - Stefan Pfuhler
- Procter & Gamble, Global Product Stewardship, Human Safety, Mason Business Centre, Mason, OH, USA
| | - Silvio Albertini
- Pharmaceutical Sciences, pRED Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse, Basel, Switzerland
| | | | - Andreas Czich
- Sanofi-Aventis Deutschland GmbH, Industriepark Hoechst, Frankfurt, Germany
| | - Yasmin Dietz
- Sanofi-Aventis Deutschland GmbH, Industriepark Hoechst, Frankfurt, Germany
| | | | | | | | - Peter Kasper
- Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee, Bonn, Germany
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Xiang L, Wang Q, Zhou Y, Yin L, Zhang G, Ma Y. High-level expression of a ZEN-detoxifying gene by codon optimization and biobrick in Pichia pastoris. Microbiol Res 2016; 193:48-56. [PMID: 27825486 DOI: 10.1016/j.micres.2016.09.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 09/13/2016] [Accepted: 09/23/2016] [Indexed: 11/16/2022]
Abstract
The mycotoxin zearalenone (ZEN) can be degraded by a lactone hydrolase ZHD, which was derived from Gliocladium roseum. Here, based on the native ZHD encoding gene zhd101, a codon optimized zhd gene was synthesized, which was used for high expression of ZHD in Pichia pastoris GS115. Meanwhile, to further improve the expression of recombinant ZHD, the plasmids containing 1 to 4 copies of the zhd expression cassette were constructed, respectively, using the biobrick method. The protein expression in the recombinant P. pastoris X3c, which was transformed with the plasmid containing 3 copies of zhd expression cassette, was the highest. In addition, the enzymatic activity of ZHD against ZEN was defined for the first time based on a standard curve of peak area vs ZEN concentration. The ZEN degradation activity of ZHD from shake flask fermentation was calculated as 22.5U/mL with the specific activity of 4976.5U/mg. Furthermore, the high-density fermentation of P. pastoris X3c strain was also performed in 5L fermenter. The maximum enzyme activity of the supernatant was 150.1U/mL, which were 6.7-fold higher than that of the shake flask fermentation.
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Affiliation(s)
- La Xiang
- Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, The College of Life Sciences, Hubei University, Wuhan 430062, China
| | - Qinhong Wang
- Tianjin institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China
| | - Yuling Zhou
- Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, The College of Life Sciences, Hubei University, Wuhan 430062, China
| | - Lifeng Yin
- Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, The College of Life Sciences, Hubei University, Wuhan 430062, China
| | - Guimin Zhang
- Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, The College of Life Sciences, Hubei University, Wuhan 430062, China.
| | - Yanhe Ma
- Tianjin institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China
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Combes RD. Is Phenylbutazone a Genotoxic Carcinogen? A Weight-of-Evidence Assessment. Altern Lab Anim 2013; 41:235-48. [DOI: 10.1177/026119291304100307] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Published in silico, in vitro, in vivo laboratory animal and human data, together with information on biotransformation and data from structure-activity analyses with two decision-tree systems (ACToR and Toxtree), have been used in a weight-of-evidence (WoE) assessment to determine whether phenylbutazone (PBZ) is a genotoxic or a non-genotoxic carcinogen. This was undertaken to facilitate the risk assessment of human exposure to this veterinary drug via the consumption of horsemeat from treated animals. Despite problems with data interpretation at all tiers of the database, it was concluded that PBZ behaves like a genotoxic carcinogen with a threshold dose. This conclusion is based mainly on the results of a definitive rodent bioassay, and on the following observations: a) that PBZ has weak in vitro activity only at high concentrations in some genotoxicity assays, accompanied by high levels of cytotoxicity; b) that it (and a major metabolite) is able to cause sister chromatid exchanges in vivo in rodents; and c) that it can induce cytogenetic effects in vivo in humans. It also takes into account the known and predicted activities of the parent drug, some of its metabolites and two structural analogues, and, importantly, several of the drug's other biochemical effects that are unrelated to toxicity. However, this conclusion is not fully supported by all the evidence, and much of the information is based on old papers. Therefore, more studies are required to establish whether the concentration thresholds seen in vitro would translate to dose thresholds for carcinogenicity, such that a safe dose-level could be defined for the purposes of assessing risk. It was disappointing that a WoE approach to evaluating all of the available hazard data, as is increasingly being advocated to improve the hazard identification paradigm, was unable to provide definitive answers in this case, particularly in view of the large numbers of animals that had been used to provide much of the information.
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Li S, Jin X, Chen J. Effects of piperidine and piperideine alkaloids from the venom of red imported fire ants, Solenopsis invicta Buren, on Pythium ultimum Trow growth in vitro and the application of piperideine alkaloids to control cucumber damping-off in the greenhouse. PEST MANAGEMENT SCIENCE 2012; 68:1546-1552. [PMID: 22685059 DOI: 10.1002/ps.3337] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 03/22/2012] [Accepted: 05/02/2012] [Indexed: 06/01/2023]
Abstract
BACKGROUND Pythium ultimum is a plant pathogen that causes significant yield losses on many economically important crops. Chemical treatment has been used for disease control. In searching for alternatives, venom piperidine and piperideine alkaloids from red imported fire ants were tested against P. ultimum in vitro, and piperideines were employed to control cucumber damping-off in the greenhouse as drench treatments. Results Piperidine and piperideine alkaloids of the red imported fire ant significantly inhibited mycelium growth of P. ultimum. Piperidine alkaloids were stable at both room and elevated temperatures. The inhibitory activity positively correlated with the concentrations of piperidine alkaloids in the medium, and the EC(50) = 17.0 µg ml(-1). Germination of sporangia of P. ultimum was negatively correlated with the concentrations of piperidine alkaloids in the medium, and the EC(50) = 12.3 µg ml(-1). The piperideine alkaloid drenching treatment significantly improved seedling emergence and seedling height of cucumber. CONCLUSION This is the first report describing the use of venom alkaloids from the red imported fire ant to inhibit P. ultimum in the laboratory and the application of piperideine alkaloids to control damping-off disease caused by P. ultimum in the greenhouse. These findings may lead to the development of a new group of fungicides.
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Affiliation(s)
- Shezeng Li
- Institute of Plant Protection, Hebei Academy of Agricultural and Forestry Sciences, Baoding, Hebei Province, China
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Andersen FA. Annual Review of Cosmetic Ingredient Safety Assessments: 2007-2010. Int J Toxicol 2011; 30:73S-127S. [DOI: 10.1177/1091581811412618] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Kirkland D, Fowler P. Further analysis of Ames-negative rodent carcinogens that are only genotoxic in mammalian cells in vitro at concentrations exceeding 1 mM, including retesting of compounds of concern. Mutagenesis 2010; 25:539-53. [DOI: 10.1093/mutage/geq041] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Combes R, Grindon C, Cronin MTD, Roberts DW, Garrod JF. Integrated decision-tree testing strategies for mutagenicity and carcinogenicity with respect to the requirements of the EU REACH legislation. Altern Lab Anim 2009; 36 Suppl 1:43-63. [PMID: 19025331 DOI: 10.1177/026119290803601s05] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Liverpool John Moores University and FRAME recently conducted a research project sponsored by Defra, on the status of alternatives to animal testing with regard to the European Union REACH (Registration, Evaluation and Authorisation of Chemicals) system for the safety testing and risk assessment of chemicals. The project covered all the main toxicity endpoints associated with the REACH system. This paper focuses on the prospects for using alternative methods (both in vitro and in silico) for mutagenicity (genotoxicity) and carcinogenicity testing--two toxicity endpoints, which, together with reproductive toxicity, are of pivotal importance for the REACH system. The manuscript critically discusses well-established testing approaches, and in particular, the requirement for short-term in vivo tests for confirming positive mutagenicity, and the need for the rodent bioassay for detecting non-genotoxic carcinogens. Recently-proposed testing strategies focusing on non-animal approaches are also considered, and our own testing scheme is presented and supported with background information. This scheme makes maximum use of pre-existing data, computer (in silico) and in vitro methods, with weight-of-evidence assessments at each major stage. The need for the improvement of in vitro methods, to reduce the generation of false-positive results, is also discussed. Lastly, ways in which reduction and refinement measures can be used are also considered, and some recommendations are made for future research to facilitate the implementation of the proposed testing scheme.
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Combes R, Grindon C, Cronin MTD, Roberts DW, Garrod J. Proposed integrated decision-tree testing strategies for mutagenicity and carcinogenicity in relation to the EU REACH legislation. Altern Lab Anim 2007; 35:267-87. [PMID: 17559315 DOI: 10.1177/026119290703500201] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Liverpool John Moores University and FRAME recently conducted a research project sponsored by Defra, on the status of alternatives to animal testing with regard to the European Union REACH (Registration, Evaluation and Authorisation of Chemicals) system for the safety testing and risk assessment of chemicals. The project covered all the main toxicity endpoints associated with the REACH system. This paper focuses on the prospects for using alternative methods (both in vitro and in silico) for mutagenicity (genotoxicity) and carcinogenicity testing - two toxicity endpoints, which, together with reproductive toxicity, are of pivotal importance for the REACH system. The manuscript critically discusses well-established testing approaches, and in particular, the requirement for short-term in vivo tests for confirming positive mutagenicity, and the need for the rodent bioassay for detecting non-genotoxic carcinogens. Recently-proposed testing strategies focusing on non-animal approaches are also considered, and our own testing scheme is presented and supported with background information. This scheme makes maximum use of pre-existing data, computer (in silico) and in vitro methods, with weight-of-evidence assessments at each major stage. The need for the improvement of in vitro methods, to reduce the generation of false-positive results, is also discussed. Lastly, ways in which reduction and refinement measures can be used are also considered, and some recommendations are made for future research to facilitate the implementation of the proposed testing scheme.
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Affiliation(s)
- Robert Combes
- FRAME, Russell & Burch House, 96-98 North Sherwood Street, Nottingham, NG1 4EE, UK.
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Knight A, Bailey J, Balcombe J. Animal carcinogenicity studies: 3. Alternatives to the bioassay. Altern Lab Anim 2006; 34:39-48. [PMID: 16522149 DOI: 10.1177/026119290603400119] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Conventional animal carcinogenicity tests take around three years to design, conduct and interpret. Consequently, only a tiny fraction of the thousands of industrial chemicals currently in use have been tested for carcinogenicity. Despite the costs of hundreds of millions of dollars and millions of skilled personnel hours, as well as millions of animal lives, several investigations have revealed that animal carcinogenicity data lack human specificity (i.e. the ability to identify human non-carcinogens), which severely limits the human predictivity of the bioassay. This is due to the scientific inadequacies of many carcinogenicity bioassays, and numerous serious biological obstacles, which render profoundly difficult any attempts to accurately extrapolate animal data in order to predict carcinogenic hazards to humans. Proposed modifications to the conventional bioassays have included the elimination of mice as a second species, and the use of genetically-altered or neonatal mice, decreased study durations, initiation-promotion models, the greater incorporation of toxicokinetic and toxicodynamic assessments, structure-activity relationship (computerised) systems, in vitro assays, cDNA microarrays for detecting changes in gene expression, limited human clinical trials, and epidemiological research. The potential advantages of non-animal assays when compared to bioassays include the superior human specificity of the results, substantially reduced time-frames, and greatly reduced demands on financial, personnel and animal resources. Inexplicably, however, the regulatory agencies have been frustratingly slow to adopt alternative protocols. In order to decrease the enormous cost of cancer to society, a substantial redirection of resources away from excessively slow and resource-intensive rodent bioassays, into the further development and implementation of non-animal assays, is both strongly justified and urgently required.
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Affiliation(s)
- Andrew Knight
- Animal Consultants International, London SE11 4NR, UK.
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Combes RD, Gaunt I, Balls M. A Scientific and Animal Welfare Assessment of the OECD Health Effects Test Guidelines for the Safety Testing of Chemicals under the European Union REACH System. Altern Lab Anim 2004; 32:163-208. [PMID: 15588165 DOI: 10.1177/026119290403200304] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We have assessed each of the OECD Health Effects Test Guidelines (TGs) that were included in an annex to the Internet consultation issued by the European Commission relating to the Registration, Evaluation and Authorisation of Chemicals (REACH) legislation for the testing of new and existing chemical substances. Each guideline has been analysed with respect to its design and its scientific and animal welfare implications, the extent to which it makes use of modern techniques, and its suitability to be used in the REACH system for the testing of large numbers of chemicals. The scientific basis of the test and its justification are considered, as well as the numbers of animals required, and the potential adverse effects on them. The prospects and possibilities for applying the Three Rs ( reduction, refinement and replacement) to each of the TGs are also discussed. We have proposed an overall testing strategy for how these TGs and other methods could best be deployed for chemicals testing, should it be necessary to fill data gaps. Certain TGs have been omitted from the strategy, when we have considered them to be unnecessary for chemicals testing. A series of recommendations has been made for improving the TGs with regard to both their scientific content and ways in which they could be better designed in relation to optimising the use of the animals concerned, and minimising adverse welfare consequences to them. Our investigations show that there is an urgent need to update the TGs to reflect modern techniques and methods, and to use current approaches for applying refinement strategies to improve the scientific and animal welfare aspects of the procedures used. Improvements can and should be made in all aspects of toxicity testing, from sample preparation, and animal housing, care and feeding, to dose formulation, test material administration, and the histopathological and clinical analysis of tissue samples. Opportunities for streamlining individual assays are very limited, but testing could be made more efficient by: a) only undertaking studies that provide relevant data; b) making greater use of screens and preliminary testing; c) applying some tests simultaneously to the same animals; d) using one sex; and e) eliminating redundant tests. In conclusion, it is clear that, as they stand, the OECD Health Effects TGs are unsuitable for use in the European Union REACH system, for which potentially very large numbers of laboratory animals will be needed for the testing of a very large number of chemicals.
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Affiliation(s)
- Robert D Combes
- FRAME, Russell & Burch House, 96-98 North Sherwood Street, Nottingham NG1 4EE, UK.
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Takahashi-Ando N, Kimura M, Kakeya H, Osada H, Yamaguchi I. A novel lactonohydrolase responsible for the detoxification of zearalenone: enzyme purification and gene cloning. Biochem J 2002; 365:1-6. [PMID: 11978180 PMCID: PMC1222652 DOI: 10.1042/bj20020450] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2002] [Revised: 04/22/2002] [Accepted: 04/26/2002] [Indexed: 11/17/2022]
Abstract
Zearalenone (ZEN) is converted into a far less oestrogenic product by incubation with Clonostachys rosea IFO 7063. An alkaline hydrolase responsible for the detoxification was purified to homogeneity from the fungus by a combination of salt precipitation and column chromatography methods. The purified enzyme was homodimeric with a subunit molecular mass of 30 kDa and contained an intra-subunit disulphide bridge. On the basis of the internal peptide sequences of the purified protein, we cloned the entire coding region of the gene (designated as zhd101) by PCR techniques. The ZEN degradation activity was detected in heterologous hosts (Schizosaccharomyces pombe and Escherichia coli) carrying the cloned gene. Zhd101 could be a promising genetic resource for in planta detoxification of the mycotoxin in important crops.
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Affiliation(s)
- Naoko Takahashi-Ando
- Laboratory for Remediation Research, Plant Science Centre, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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McCann J, Kavet R, Rafferty CN. Assessing the potential carcinogenic activity of magnetic fields using animal models. ENVIRONMENTAL HEALTH PERSPECTIVES 2000; 108 Suppl 1:79-100. [PMID: 10698725 PMCID: PMC1637772 DOI: 10.1289/ehp.00108s179] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
We update our 1997 publication by reviewing 29 new reports of tests of magnetic fields (MFs) in six different in vivo animal models of carcinogenesis: 2-year, lifetime, or multigeneration exposure studies in rats or mice; and promotion/progression models (rat mammary carcinoma, rat liver focus, mouse skin, several models of human leukemia/lymphoma in rats and mice, and brain cancer in rats). Individual experiments are evaluated using a set of data quality criteria, and summary judgments are made across multiple experiments by applying a criterion of rough reproducibility. The potential for carcinogenicity of MFs is discussed in light of the significant body of carcinogenesis data from animal bioassays that now exists. Excluding abstracts, approximately 80% of the 41 completed studies identified in this and our previous review roughly satisfy data quality criteria. Among these studies, the criterion for independent reproducibility is not satisfied for any positive results but is satisfied for negative results in chronic bioassays in rats and mice and for negative results in both promotion and co-promotion assays using the SENCAR mouse skin model. Results of independent replication studies using the rat mammary carcinoma model were conflicting. We conclude that long-term exposure to continuous 50- or 60-Hz MFs in the range of 0.002-5 mT is unlikely to result in carcinogenesis in rats or mice. Though results of most promotion/progression assays are negative, a weak promoting effect of MFs under certain exposure conditions cannot be ruled out based on available data.
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Affiliation(s)
- J McCann
- Electric Power Research Institute, Palo Alto, California, USA.
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Abstract
Enzymatic inactivation of fungal toxins is an attractive strategy for the decontamination of agricultural commodities and for the protection of crops from phytotoxic effects of fungal metabolites. This review summarizes research on the biological detoxification of fungal toxins by microorganisms and plants and its practical applications. Some mycotoxins are detoxified during ensiling and other fermentation processes (aflatoxins, alternariol, mycophenolic acid, patulin, PR toxin) while others are transformed into toxic products or survive fermentation unchanged. Plants can detoxify fomannoxin, fusaric acid, HC-toxin, ochratoxin A and oxalate but the degradation of deoxynivalenol has yet to be proven. Microflora of the digestive tract of vertebrates and invertebrates exhibit detoxification activities towards aflatoxins, ochratoxin A, oxalate and trichothecenes. Some toxin-producing fungi are able to degrade or transform their own products under suitable conditions. Pure cultures of bacteria and fungi which detoxify mycotoxins have been isolated from complex microbial populations by screening and enrichment culture techniques. Genes responsible for some of the detoxification activities have been cloned and expressed in heterologous hosts. The detoxification of aflatoxins, cercosporin, fumonisins, fusaric acid, ochratoxin A, oxalic acid, patulin, trichothecenes and zearalenone by pure cultures is reviewed. Finally, current application of these results in food and feed production and plant breeding is summarized and expected future developments are outlined.
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Affiliation(s)
- P Karlovsky
- University of Hohenheim, Stuttgart, Germany.
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