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Environmental and Molecular Mutagenesis Jan 2020A mutagenesis moonshot addressing the influence of the environment on our genetic wellbeing was launched just 2 months before astronauts landed on the moon. Its impetus... (Review)
Review
A mutagenesis moonshot addressing the influence of the environment on our genetic wellbeing was launched just 2 months before astronauts landed on the moon. Its impetus included the discovery that X-rays (Muller HJ. [1927]: Science 64:84-87) and chemicals (Auerbach and Robson. [1946]: Nature 157:302) were germ-cell mutagens, the introduction of a growing number of untested chemicals into the environment after World War II, and an increasing awareness of the role of environmental pollution on human health. Due to mounting concern from influential scientists that germ-cell mutagens might be ubiquitous in the environment, Alexander Hollaender and colleagues founded in 1969 the Environmental Mutagen Society (EMS), now the Environmental Mutagenesis and Genomics Society (EMGS); Frits Sobels founded the European EMS in 1970. As Fred de Serres noted, such societies were necessary because protecting populations from environmental mutagens could not be addressed by existing scientific societies, and new multidisciplinary alliances were required to spearhead this movement. The nascent EMS gathered policy makers and scientists from government, industry, and academia who became advocates for laws requiring genetic toxicity testing of pesticides and drugs and helped implement those laws. They created an electronic database of the mutagenesis literature; established a peer-reviewed journal; promoted basic and applied research in DNA repair and mutagenesis; and established training programs that expanded the science worldwide. Despite these successes, one objective remains unfulfilled: identification of human germ-cell mutagens. After 50 years, the voyage continues, and a vibrant EMGS is needed to bring the mission to its intended target of protecting populations from genetic hazards. Environ. Mol. Mutagen. 61:8-24, 2020. © 2019 Wiley Periodicals, Inc.
Topics: Animals; Environmental Exposure; Genomics; Germ Cells; History, 20th Century; History, 21st Century; Humans; Mutagenesis; Mutagenicity Tests; Mutagens; Societies, Scientific; Ultraviolet Rays; X-Rays
PubMed: 31294870
DOI: 10.1002/em.22313 -
Mutagenesis Aug 2023Genotoxicity testing for nanomaterials remains challenging as standard testing approaches require some adaptation, and further development of nano-specific OECD Test...
Genotoxicity testing for nanomaterials remains challenging as standard testing approaches require some adaptation, and further development of nano-specific OECD Test Guidelines (TGs) and Guidance Documents (GDs) are needed. However, the field of genotoxicology continues to progress and new approach methodologies (NAMs) are being developed that could provide relevant information on the range of mechanisms of genotoxic action that may be imparted by nanomaterials. There is a recognition of the need for implementation of new and/or adapted OECD TGs, new OECD GDs, and utilization of NAMs within a genotoxicity testing framework for nanomaterials. As such, the requirements to apply new experimental approaches and data for genotoxicity assessment of nanomaterials in a regulatory context is neither clear, nor used in practice. Thus, an international workshop with representatives from regulatory agencies, industry, government, and academic scientists was convened to discuss these issues. The expert discussion highlighted the current deficiencies that exist in standard testing approaches within exposure regimes, insufficient physicochemical characterization, lack of demonstration of cell or tissue uptake and internalization, and limitations in the coverage of genotoxic modes of action. Regarding the latter aspect, a consensus was reached on the importance of using NAMs to support the genotoxicity assessment of nanomaterials. Also highlighted was the need for close engagement between scientists and regulators to (i) provide clarity on the regulatory needs, (ii) improve the acceptance and use of NAM-generated data, and (iii) define how NAMs may be used as part of weight of evidence approaches for use in regulatory risk assessments.
Topics: Organisation for Economic Co-Operation and Development; Mutagenicity Tests; Nanostructures; Risk Assessment
PubMed: 37234002
DOI: 10.1093/mutage/gead017 -
Basic & Clinical Pharmacology &... Sep 2017Changes in paradigm contribute to advances in research. The current paradigms for the evaluation of toxicity of chemicals refer to linear or curvilinear dose-response... (Review)
Review
Changes in paradigm contribute to advances in research. The current paradigms for the evaluation of toxicity of chemicals refer to linear or curvilinear dose-response curves with or without threshold and to surface-dependent induction of oxidative damage for particles. The unique physicochemical properties and biological/genotoxic activity of engineered nanomaterials (NMs) require the development of a new paradigm. Because of their unusual dosimetry and their multiple interactions at NM level (agglomeration/aggregation) and at different cellular and extracellular levels, NMs are likely to have complex modes of action (multiple hits at multiple targets) leading to complex thresholded-non-thresholded dose-response curves. Understanding their cellular targets and their modes of action will contribute to the production of safe-by-design NMs. An integrative, cell-by-cell approach for genotoxic effects should be applied to tackle this emerging paradigm in nano-genotoxicology.
Topics: Cell Communication; DNA Damage; Humans; Mutagenicity Tests; Nanostructures; Neoplasms; Particle Size; Reactive Oxygen Species; Surface Properties
PubMed: 27813321
DOI: 10.1111/bcpt.12698 -
Cytotherapy Nov 2019Pluripotent stem cells offer the potential for an unlimited source for cell therapy products. However, there is concern regarding the tumorigenicity of these products in... (Review)
Review
Pluripotent stem cells offer the potential for an unlimited source for cell therapy products. However, there is concern regarding the tumorigenicity of these products in humans, mainly due to the possible unintended contamination of undifferentiated cells or transformed cells. Because of the complex nature of these new therapies and the lack of a globally accepted consensus on the strategy for tumorigenicity evaluation, a case-by-case approach is recommended for the risk assessment of each cell therapy product. In general, therapeutic products need to be qualified using available technologies, which ideally should be fully validated. In such circumstances, the developers of cell therapy products may have conducted various tumorigenicity tests and consulted with regulators in respective countries. Here, we critically review currently available in vivo and in vitro testing methods for tumorigenicity evaluation against expectations in international regulatory guidelines. We discuss the value of those approaches, in particular the limitations of in vivo methods, and comment on challenges and future directions. In addition, we note the need for an internationally harmonized procedure for tumorigenicity assessment of cell therapy products from both regulatory and technological perspectives.
Topics: Animals; Carcinogenesis; Cell- and Tissue-Based Therapy; Consensus; Health Services Needs and Demand; Humans; In Vitro Techniques; Mutagenicity Tests; Pluripotent Stem Cells; Practice Guidelines as Topic
PubMed: 31711733
DOI: 10.1016/j.jcyt.2019.10.001 -
Journal of Ethnopharmacology Apr 2023Asarum heterotropoides var. seoulense (Nakai) Kitag is a traditional herbal medicine used in Korea and China. It is effective in aphthous stomatitis, local anesthesia,...
ETHNOPHARMACOLOGICAL RELEVANCE
Asarum heterotropoides var. seoulense (Nakai) Kitag is a traditional herbal medicine used in Korea and China. It is effective in aphthous stomatitis, local anesthesia, headache, toothache, gingivitis, and inflammatory diseases. However, information on the toxicity of the root of Asarum heterotropoides var. seoulense (Nakai) Kitag (AR) is limited. Therefore, preclinical toxicity studies on AR are needed to reduce the risk of excessive intake.
AIM OF THE STUDY
We aimed to evaluate genotoxicity and the potential toxicity due to repeated administration of AR powder.
MATERIALS AND METHODS
In vitro bacterial reverse mutation assay (Ames), in vitro chromosomal aberration assay (CA), and in vivo micronucleus (MN) assay in ICR mice were conducted. As positive results were obtained in Ames and CA assays, alkaline comet assay and pig-a gene mutation test were conducted for confirmation. For evaluating the general toxicity of AR powder, a 13-week subchronic toxicity test was conducted, after determining the dose by performing a single and a 4-week dose range finding (DRF) test. A total of 152 Sprague-Dawley (SD) rats were orally administered AR powder at doses of 0, 150, 350, 500, 1000, and 2000 mg/kg/day in the 13-week subchronic toxicity test. Hematology, clinical chemistry, urinalysis, organ weight, macro-, and microscopic examination were conducted after rat necropsy.
RESULTS
AR powder induced genotoxicity evidenced in the Ames test at 187.5, 750, 375, and 1500 μg/plate of TA100, TA98, TA1537, and E. coli WP2uvrA in the presence and absence of S9, respectively; CA test at 790 μg/mL for 6 h in the presence of S-9; 75 μg/mL for 6 h in the absence of S-9, and 70 μg/mL for 22 h in the absence of S-9 in the stomach in the comet assay but not in MN and pig-a assays. In the 13-week subchronic toxicity study, clinical signs including irregular respiration, noisy respiration, salivation, and decreased body weight or food consumption were observed in males and females in the 2000 mg/kg/day group. In hematology tests, clinical chemistry, urinalysis, organ weight, and macroscopic examination, changes were observed in the dose groups of 500 mg/kg/day and above. Microscopic examination revealed hyperplasia of the stomach as a test-related change. Hepatocellular adenoma and changes in liver-related clinical chemistry parameters were observed. The rat No Observed Adverse Effect Level (NOAEL) was 150 mg/kg/day in males and <150 mg/kg/day in females.
CONCLUSIONS
AR powder is potentially toxic to the liver and stomach and should be used with caution in humans. A long-term study on carcinogenicity is necessitated because DNA damage or changes in tissue lesions were observed in SD rats.
Topics: Mice; Humans; Male; Female; Rats; Animals; Rats, Sprague-Dawley; Mutagenicity Tests; Asarum; Escherichia coli; Powders; Mice, Inbred ICR; DNA Damage; Chromosome Aberrations
PubMed: 36567041
DOI: 10.1016/j.jep.2022.116012 -
Mutation Research. Genetic Toxicology... Aug 2018The Organisation for Economic Co-operation and Development Test Guideline 488 (TG 488) provides recommendations for assessing germ cell and somatic cell mutagenicity...
The Organisation for Economic Co-operation and Development Test Guideline 488 (TG 488) provides recommendations for assessing germ cell and somatic cell mutagenicity using transgenic rodent (TGR) models. However, important data gaps exist for selecting an optimal approach for simultaneously evaluating mutagenicity in both cell types. It is uncertain whether analysis of germ cells from seminiferous tubules (hereafter, tubule germ cells) or caudal sperm within the recommended design for somatic tissues (i.e., 28 days of exposure plus three days of fixation time, 28 + 3d) has enough sensitivity to detect an effect as compared with the analysis of sperm within the recommended design for germ cells (i.e., 28 + 49d and 28 + 70d for mouse and rat, respectively). To address these data gaps, the Germ Cell workgroup of the Genetic Toxicology Technical Committee of the Health and Environmental Sciences Institute reviewed the available TGR mutagenicity data in male germ cells, and, characterized the exposure history of tubule germ cells for different sampling times to evaluate its impact on germ cell mutagenicity testing using TG 488. Our analyses suggest that evaluating mutant frequencies in: i) sperm from the cauda epididymis at 28 + 3d does not provide meaningful mutagenicity data; ii), tubule germ cells at 28 + 3d provides reliable mutagenicity data only if the results are positive; and iii) tubule germ cells at 28 + 28d produces reliable positive and negative results in both mice and rats. Thus, the 28 + 28d regimen may provide an approach for simultaneously assessing mutagenicity in somatic tissues and germ cells from the same animals. Further work is required to support the 28 + 28d protocol for tissues other than slowly proliferating tissues as per current TG 488. Finally, recommendations are provided to guide the experimental design for germ cell mutagenicity data for regulatory submission, as well as other possible approaches to increase the reliability of the TGR assay.
Topics: Animals; Animals, Genetically Modified; DNA Damage; Genes, Reporter; Germ Cells; Male; Mice; Mutagenicity Tests; Mutagens; Mutation; Organisation for Economic Co-Operation and Development; Rats
PubMed: 30057023
DOI: 10.1016/j.mrgentox.2018.05.021 -
Mutagenesis Mar 2024The two-test in vitro battery for genotoxicity testing (Ames and micronucleus) has in the majority of cases replaced the three-test battery (as two-test plus mammalian...
The two-test in vitro battery for genotoxicity testing (Ames and micronucleus) has in the majority of cases replaced the three-test battery (as two-test plus mammalian cell gene mutation assay) for the routine testing of chemicals, pharmaceuticals, cosmetics, and agrochemical metabolites originating from food and feed as well as from water treatment. The guidance for testing agrochemical groundwater metabolites, however, still relies on the three-test battery. Data collated in this study from 18 plant protection and related materials highlights the disparity between the often negative Ames and in vitro chromosome aberration data and frequently positive in vitro mammalian cell gene mutation assays. Sixteen of the 18 collated materials with complete datasets were Ames negative, and overall had negative outcomes in in vitro chromosome damage tests (weight of evidence from multiple tests). Mammalian cell gene mutation assays (HPRT and/or mouse lymphoma assay (MLA)) were positive in at least one test for every material with this data. Where both MLA and HPRT tests were performed on the same material, the HPRT seemed to give fewer positive responses. In vivo follow-up tests included combinations of comet assays, unscheduled DNA synthesis, and transgenic rodent gene mutation assays, all gave negative outcomes. The inclusion of mammalian cell gene mutation assays in a three-test battery for groundwater metabolites is therefore not justified and leads to unnecessary in vivo follow-up testing.
Topics: Mice; Animals; Hypoxanthine Phosphoribosyltransferase; Mutagenicity Tests; Comet Assay; Rodentia; Lymphoma; Agrochemicals; Micronucleus Tests; DNA Damage
PubMed: 38183270
DOI: 10.1093/mutage/gead037 -
Regulatory Toxicology and Pharmacology... Jun 2021In 2019, the California Office of Environmental Health Hazard Assessment initiated a review of the carcinogenic hazard potential of acetaminophen, including an... (Review)
Review
In 2019, the California Office of Environmental Health Hazard Assessment initiated a review of the carcinogenic hazard potential of acetaminophen, including an assessment of its genotoxicity. The objective of this analysis was to inform this review process with a weight-of-evidence assessment of more than 65 acetaminophen genetic toxicology studies that are of widely varying quality and conformance to accepted standards and relevance to humans. In these studies, acetaminophen showed no evidence of induction of point or gene mutations in bacterial and mammalian cell systems or in in vivo studies. In reliable, well-controlled test systems, clastogenic effects were only observed in unstable, p53-deficient cell systems or at toxic and/or excessively high concentrations that adversely affect cellular processes (e.g., mitochondrial respiration) and cause cytotoxicity. Across the studies, there was no clear evidence that acetaminophen causes DNA damage in the absence of toxicity. In well-controlled clinical studies, there was no meaningful evidence of chromosomal damage. Based on this weight-of-evidence assessment, acetaminophen overwhelmingly produces negative results (i.e., is not a genotoxic hazard) in reliable, robust high-weight studies. Its mode of action produces cytotoxic effects before it can induce the stable, genetic damage that would be indicative of a genotoxic or carcinogenic hazard.
Topics: Acetaminophen; Animals; Carcinogenesis; Cell Cycle; Chromosome Aberrations; DNA Damage; Humans; Mutagenicity Tests; Mutagens
PubMed: 33592196
DOI: 10.1016/j.yrtph.2021.104892 -
Environmental and Molecular Mutagenesis Dec 2022The OECD Test Guideline 488 (TG 488) for the Transgenic Rodent Gene Mutation Assay has undergone several revisions to update the recommended design for studying... (Review)
Review
The OECD Test Guideline 488 (TG 488) for the Transgenic Rodent Gene Mutation Assay has undergone several revisions to update the recommended design for studying mutations in somatic tissues and male germ cells. The recently revised TG recommends a single sampling time of 28 days following 28 days of exposure (i.e., 28 + 28 days) for all tissues, irrespective of proliferation rates. An alternative design (i.e., 28 + 3 days) is appropriate when germ cell data is not required, nor considered. While the 28 + 28 days design is clearly preferable for slowly proliferating somatic tissues and germ cells, there is still uncertainty about the impact of extending the sampling time to 28 days for rapidly somatic tissues. Here, we searched the available literature for evidence supporting the applicability and utility of the 28 + 28 days design for rapidly proliferating tissues. A total of 79 tests were identified. When directly comparing results from both designs in the same study, there was no evidence that the 28 + 28 days regimen resulted in a qualitatively different outcome from the 28 + 3 days design. Studies with a diverse range of agents that employed only a 28 + 28 days protocol provide further evidence that this design is appropriate for rapidly proliferating tissues. Benchmark dose analyses demonstrate high quantitative concordance between the 28 + 3 and 28 + 28 days designs for rapidly proliferating tissues. Accordingly, our review confirms that the 28 + 28 days design is appropriate to assess mutagenicity in both slowly and rapidly proliferating somatic tissues, and germ cells, and provides further support for the recommended design in the recently adopted TG 488.
Topics: Animals; Male; Rodentia; Animals, Genetically Modified; Mutation; Mutagens; Germ Cells; Mutagenicity Tests
PubMed: 36271823
DOI: 10.1002/em.22514 -
BMC Complementary and Alternative... Jan 2019Opuntia ficus-indica var. saboten (OFIS) is used widely in Korea to treat constipation due to its diuretic effects and its enhancement of bowel function and appetite....
BACKGROUND
Opuntia ficus-indica var. saboten (OFIS) is used widely in Korea to treat constipation due to its diuretic effects and its enhancement of bowel function and appetite. However, its safety has not yet been established. The aim of this study was to evaluate the repeated oral toxicity and genotoxicity of OFIS extract (OE).
METHODS
White female and male Sprague Dawley rats (n = 6) were divided into 4 groups, and OE was administered to them orally (0, 500, 1000, and 2000 mg/kg/day, respectively) for one week. The Ames test, the chromosomal aberration assay, and the mammalian micronucleus test were performed to determine the OE genotoxicity. The Ames test was conducted using Salmonella typhimurium (S. typhimurium) strains TA100, TA1535, TA98, and TA153 and Escherichia coli (E. coli) WP2 urvA, and Chinese hamster lung (CHL) cells were used for the chromosomal aberration assay. The mammalian micronucleus test was performed using mouse bone marrow cells.
RESULTS
This study revealed that OE administration did not alter the normal rat behavior, body weight gain, and food and water consumption with respect to the normal controls. In addition, there were no toxic effects observed during the ophthalmological test. The biochemical hematological and serum values as well as urinalysis parameters and organ weights were all similar to those of the normal control group. In addition, no mutagenicity effects from the OE were found in S. typhimurium or E. coli with or without S9 activation according to the Ames test. The OE did not significantly alter the number of structural aberrations in the CHL cells in the presence or absence of S9 activation. The oral administration of OE also caused no significant increase in the number of micronucleated polychromatic erythrocytes or in the mean ratio of polychromatic to total erythrocytes.
CONCLUSIONS
In conclusion, OE could be considered as a reliable and safe herbal medicine or functional food since no toxicity was found under the conditions of this study.
Topics: Administration, Oral; Animals; Bone Marrow Cells; Cells, Cultured; Chromosome Aberrations; Eating; Escherichia coli; Female; Male; Mice; Micronucleus Tests; Mutagenicity Tests; Mutagens; Opuntia; Plant Extracts; Plant Stems; Rats; Rats, Sprague-Dawley; Salmonella typhimurium
PubMed: 30691445
DOI: 10.1186/s12906-019-2442-7