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In the last decades, the micronucleus assay has been recognized as a suitable biomarker for monitoring populations exposed to many different occupational factors, lifestyle, environmental conditions, radiation exposure, and deleterious effects of pesticides. The objective of this work is to direct the design of future field studies in the assessment of the risk of children exposed to environmental mutagens, radiation, and pesticides. This review sought available information on the analysis of micronuclei in oral cells in children. A literature search for papers investigating DNA damage, genetic damage, oral cells, buccal cells, genotoxicity, mutagenicity and micronucleus was begun in 2000 and is scheduled to be concluded in May, 2022. Briefly, a search of PubMed, MEDLINE, and Google Scholar for a variety of articles was performed. The results showed that there are still few studies that addressed micronuclei of oral cells in children exposed to the most diverse environmental conditions. Only environmental pollution was associated with damage to the genome of oral cells in children. Therefore, researchers need to be calibrated in cell analysis, standardization of field study protocols and the development of new research in the evaluation of children using the micronucleus test as a tool in child biomonitoring. [ABSTRACT FROM AUTHOR]

Abstract Background The human genome is constantly exposed to numerous environmental genotoxicants. To prevent the detrimental consequences induced by the expansion of damaged cells, cellular protective systems such as nucleotide excision repair (NER) exist and serve as a primary pathway for repairing the various helix-distorting DNA adducts induced by genotoxic agents. NER is further divided into two sub-pathways, namely, global genomic NER (GG-NER) and transcription-coupled NER (TC-NER). Both NER sub-pathways are reportedly involved in the damage response elicited by exposure to genotoxins. However, how disruption of these sub-pathways impacts the toxicity of different types of environmental mutagens in human cells is not well understood. Results To evaluate the role of NER sub-pathways on the cytotoxic effects of mutagens, we disrupted XPC and CSB to selectively inactivate GG-NER and TC-NER, respectively, in human lymphoblastoid TK6 cells, a standard cell line used in genotoxicity studies. Using these cells, we then comparatively assessed their respective sensitivities to representative genotoxic agents, including ultraviolet C (UVC) light, benzo [a] pyrene (B(a)P), 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline (MeIQx), 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP), γ-ray, and 2-acetylaminofluorene (2-AAF). CSB −/− cells exhibited a hyper-sensitivity to UVC, B(a)P, and MeIQx. On the other hand, XPC −/− cells were highly sensitive to UVC, but not to B(a)P and MeIQx, compared with wild-type cells. In contrast with other genotoxins, the sensitivity of XPC −/− cells against PhIP was significantly higher than CSB −/− cells. The toxicity of γ-ray and 2-AAF was not enhanced by disruption of either XPC or CSB in the cells. Conclusions Based on our findings, genetically modified TK6 cells appear to be a useful tool for elucidating the detailed roles of the various repair factors that exist to combat genotoxic agents, and should contribute to the improved risk assessment of environmental chemical contaminants.

Abstract Background Previously we found that DNA adducts were accumulated in the lungs of the rats exposed to ambient air in the Tokyo metropolitan area. To examine chronological change in in vivo mutagenicity of airborne particles, extracts produced from samples of total suspended particulates (TSP) collected from urban air in 1980, 1990, and 2010 in the Tokyo metropolitan area were intratracheally administered into the lungs of gpt delta mice, and differences in mutation and mutant frequency were determined by using the gpt assay. In vivo mutations induced by the extracts were characterized and mutation hotspots were identified by DNA sequencing of the mutated gpt gene. Results Administration of the 1990 extract at a dose of 0.3 mg/animal significantly elevated total mutant frequency to 3.3-times that in vehicle control, and the in vivo mutagenicity of the extract (induced mutation frequency per milligram extract) was estimated to be 2.0- and 2.4-times higher than that of the 2010 and 1980 extract, respectively. G-to-A transition was the most common base substitution in the vehicle control mice. However, administration of the 1990 extract increased the frequency of G-to-T transversion, which is a landmark base substitution induced by oxidative stress; furthermore, when the extract was administered at a dose of 0.15 mg, the mutant and mutation frequencies of G-to-T transversion were significantly increased to frequencies comparable with those of G-to-A transition. Similar increases in the mutant and mutation frequencies of G-to-T transversion were observed after administration of the 2010 extract. Hotspots (mutation foci identified in three or more mice) of G-to-A transition mutations at nucleotides 64 and 110 were induced by the 1980, 1990, and 2010 extracts; a hotspot of G-to-T transversions at nucleotide 406 was also induced by the 2010 extract. Previously, we showed that diesel exhaust particles or their extract, as well as 1,6-dinitropyrene, administered to mice induced these hotspots of G-to-A transitions. Conclusions The results of the present study suggested that mutagenesis induced by extracts produced from TSP collected in the Tokyo metropolitan area induced in vivo mutagenicity via the same mechanism underlying the induction of in vivo mutagenicity by components of diesel exhaust.

Abstract The open symposium of the Japanese Environmental Mutagen Society (JEMS), under the title of “Comprehensive framework between environment and genomic stability,” was held in the Main Conference Room of the Foundation for Promotion of Cancer Research, Tokyo, on June 8, 2019. To understand the relationship between genes and environmental mutagens, the symposium highlights the research activities in the fields of cancer, carcinogenesis and related diseases caused by genomic instabilities, including epigenetic and metabolomic alterations. The symposium was planned to help familiarize attendees with the current trends in research on genome safety. The organizers herein present a summary of the symposium.

Abstract Various kind of chemical substances, including man-made chemical products and unintended products, are emitted to ambient air. Some of these substances have been shown to be mutagenic and therefore to act as a carcinogen in humans. National pollutant inventories (e.g., Pollutant Release and Transfer Registration in Japan) have estimated release amounts of man-made chemical products, but a major concern is the release of suspended particulate matter containing potent mutagens, for example, polycyclic aromatic hydrocarbons and related compounds generated by the combustion of fossil fuel, which are not estimated by PRTR system. In situ exposure studies have revealed that DNA adducts in the lung, and possibly mutations in germline cells are induced in rodents by inhalation of ambient air, indicating that evaluating in vivo mutations is important for assessing environmental health risks. Transgenic rodent systems (Muta, Big Blue, and gpt delta) are good tools for analyzing in vivo mutations induced by a mixture of chemical substances present in the environment. Following inhalation of diesel exhaust (used as a model mixture), mutation frequency was increased in the lung of gpt delta mice and base substitutions were induced at specific guanine residues (mutation hotspots) on the target transgenes. Mutation hotspots induced by diesel exhaust were different from those induced by benzo[a]pyrene, a typical mutagen in ambient air, but nearly identical to those induced by 1,6-dinitropyrene contained in diesel exhaust. Comparison between mutation hotspots in the TP53 (p53) gene in human lung cancer (data extracted from the IARC TP53 database) and mutations we identified in gpt delta mice showed that G to A transitions centered in CGT and CGG trinucleotides were mutation hotspots on both TP53 genes in human lung cancers and gpt genes in transgenic mice that inhaled diesel exhaust. The carcinogenic potency (TD50 value) of genotoxic carcinogen was shown to be correlated with the in vivo mutagenicity (total dose per increased mutant frequency). These results suggest that the mutations identified in transgenic rodents can help identify environmental mutagens that cause cancer.

Abstract The Open Symposium of the Japanese Environmental Mutagen Society (JEMS) entitled “Challenges of Young Scientists at the Cutting-edge of Genotoxicity Research” was held in the Main Conference Room of the Foundation for Promotion of Cancer Research, Tokyo, on June 9th, 2018. This year, the symposium aimed to provide an opportunity to highlight the cutting-edge research activities of young scientists who are continuing to expand frontiers of the fields of environmental mutagenesis and genetic toxicology; it also aimed to inform JEMS activities to the participants. Through this report, the organizers present a summary of the symposium.

Abstract The open symposium of the Japanese Environmental Mutagen Society (JEMS) titled, “Research on Environmental Mutagenesis from Young Scientists,” was held at Kokusai Kenkyu Koryu Kaikan, the Foundation for Promotion of Cancer Research, in Tokyo on June 10, 2017. The aim of this symposium was to provide an opportunity to present the research activities of young scientists in the important field of environmental mutagenesis and genetic toxicology and inform JEMS activities to the participants. The organizers reported the symposium summary.

Paraquat (1,1′-dimethyl, 4,4′-bipyridinium dichloride; PQ), a widely used herbicide, is toxic to mammals through ingestion, inhalation and skin contact. Epidemiological data suggest that PQ is also mutagenic and carcinogenic, especially in high doses. The toxic and mutagenic properties of PQ are attributed to the ability of the molecule to redox-cycle, which generates reactive oxygen species (ROS) and subsequent oxidative stress. ROS also cause oxidative DNA damage such as 8-oxoguanine (8OG), a mutagenic base that, when replicated, causes G to T transversion mutations. The present study employed the CHO-derived cell line AS52 to quantify the mutagenic properties of low doses of PQ. By containing a functional, chromosomally-integrated copy of the bacterial gpt gene, AS52 cells a facile system for evaluating the mutagenic properties of genotoxicants. To bolster the sensitivity of this system for detecting mutagenesis of weak mutagens like PQ, and to provide a tool for mechanistic evaluation of the mutagenic process, we constructed a new AS52-derived cell line defective for 8OG DNA repair. Specifically, we employed CRISPR-Cas9 technology to knock out 8-oxoguanine DNA glycosylase (OGG1) and MUTYH glycosylase, two key enzymes involved in the base excision repair of 8OG. The double knock-out (DKO) AS52 cells were found to be more sensitive to PQ toxicity than the parental (WT) AS52 cell line. They experienced higher levels of ROS, which translated into more DNA double-strand breaks, which explained the PQ toxicity. The increased ROS levels also led to more 8OG genomic accumulation, and a higher level of mutations in the DKO cells, suggesting that PQ mutagenesis is mediated primarily by 8OG genomic accumulation. Consistent with this view, antioxidant co-treatment lowered induced cellular ROS and PQ-induced mutagenesis. Taken together, our data demonstrate the strong protective role of OGG1 and MUTYH against PQ-induced mutagenesis. Moreover, our experiments establish the engineered OGG1 -/- MUTYH -/- AS52 cell line and associated methods as a versatile cellular system for studying in quantitative terms the mutagenesis of other agents, environmental or endogenous, that induce oxidative stress. [ABSTRACT FROM AUTHOR]

Mutational signatures associated with specific forms of DNA damage have been identified in several forms of human cancer. Such signatures provide information regarding mechanisms of tumor induction which, in turn, can reduce exposure to carcinogens by shaping public health policy. Using a molecular epidemiologic approach that takes advantage of recent advances in genome sequencing while applying sensitive and specific analytical methods to characterize DNA damage, it has become increasingly possible to establish causative linkages between certain environmental mutagens and disease risk. In this perspective, we use aristolochic acid, a human carcinogen and nephrotoxin found in Aristolochia herbs, to illustrate the power and effectiveness of this multidisciplinary approach. The genome-wide mutational signature for this toxin, detected initially in cancers of the upper urinary tract, has subsequently been associated with cancers of the liver and kidney. These findings have significant implications for global public health, especially in China, where millions of individuals have used Aristolochia herbal remedies as part of traditional Chinese medicine and, thus, are at risk of developing aristolochic acid nephropathy and/or upper urinary tract carcinomas. The studies reported here set the stage for research into prevention and early detection, both of which will be required to manage a potentially devastating global disease. [ABSTRACT FROM AUTHOR]

In the last decades, the micronucleus assay has been recognized as a suitable biomarker for monitoring populations exposed to many different occupational factors, lifestyle, environmental conditions, radiation exposure, and deleterious effects of pesticides. The objective of this work is to direct the design of future field studies in the assessment of the risk of children exposed to environmental mutagens, radiation, and pesticides. This review sought available information on the analysis of micronuclei in oral cells in children. A literature search for papers investigating DNA damage, genetic damage, oral cells, buccal cells, genotoxicity, mutagenicity and micronucleus was begun in 2000 and is scheduled to be concluded in May, 2022. Briefly, a search of PubMed, MEDLINE, and Google Scholar for a variety of articles was performed. The results showed that there are still few studies that addressed micronuclei of oral cells in children exposed to the most diverse environmental conditions. Only environmental pollution was associated with damage to the genome of oral cells in children. Therefore, researchers need to be calibrated in cell analysis, standardization of field study protocols and the development of new research in the evaluation of children using the micronucleus test as a tool in child biomonitoring., (© 2022 Walter de Gruyter GmbH, Berlin/Boston.)

This review constitutes an overview of our investigations of aristolochic acid nephropathy, a chronic kidney disease associated with carcinomas of the upper urinary tract. Our studies began by confirming the hypothesis that chronic dietary poisoning by aristolochic acid was responsible for endemic (Balkan) nephropathy. A unique TP53 mutational signature in urothelial tumors and the presence of aristolactam-DNA adducts in the renal cortex, defined in the course of this research, proved to be robust biomarkers of exposure to this potent nephrotoxin and human carcinogen. Armed with this information, we used molecular epidemiologic approaches and novel mechanistic information to establish the causative role of aristolochic acid in upper urinary tract carcinoma in Taiwan, where one-third of the population had been prescribed herbal remedies containing Aristolochia, and the recorded incidence of upper urinary tract cancers is the highest in the world. As traditional Chinese medicine is practiced similarly in Taiwan and China, it is likely that upper urinary tract carcinomas and their attendant aristolochic acid nephropathy are prevalent in China and other Asian countries where Aristolochia herbs have been used for centuries in the treatment and prevention of disease, creating a potential public health problem of considerable magnitude. Environ. Mol. Mutagen., 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Endemic (Balkan) nephropathy (EN), a devastating renal disease affecting men and women living in rural areas of Bosnia, Bulgaria, Croatia, Romania, and Serbia, is characterized by its insidious onset, invariable progression to chronic renal failure and a strong association with transitional cell (urothelial) carcinoma of the upper urinary tract. Significant epidemiologic features of EN include its focal occurrence in certain villages and a familial, but not inherited, pattern of disease. Our experiments test the hypothesis that chronic dietary poisoning by aristolochic acid is responsible for EN and its associated urothelial cancer. Using 32P-postlabeling/ PAGE and authentic standards, we identified dA-aristolactam (AL) and dG-AL DNA adducts in the renal cortex of patients with EN but not in patients with other chronic renal diseases. In addition, urothelial cancer tissue was obtained from residents of endemic villages with upper urinary tract malignancies. The AmpliChip p53 microarray was then used to sequence exons 2-11 of the p53 gene where we identified 19 base substitutions. Mutations at A:T pairs accounted for 89% of all p53 mutations, with 78% of these being A:T → T:A transversions. Our experimental results, namely, that (i) DNA adducts derived from aristolochic acid (AA) are present in renal tissues of patients with documented EN, (ii) these adducts can be detected in transitional cell cancers, and (iii) A:T → T:A transversions dominate the p53 mutational spectrum in the upper urinary tract malignancies found in this population lead to the conclusion that dietary exposure to AA is a significant risk factor for EN and its attendant transitional cell cancer. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various topics in the issue which includes the effects of environmental pollutants on human beings, plant allergy to children and the third on allergic rhinitis.

Paraquat (1,1'-dimethyl, 4,4'-bipyridinium dichloride; PQ), a commonly used herbicide worldwide, is both toxic and mutagenic. The mutagenic effect of PQ stems from its ability to redox-cycle, generating oxidative stress and subsequently oxidative DNA damage, which miscodes when replication is attempted. Andrographolide (AP1), the major constituent in the leaves of the herbaceous plant Andrographis paniculata, is a diterpenoid with reported antioxidant activity. The present study employed the mammalian cell line AS52 to investigate the protective effect of AP1 against PQ-induced mutagenesis. AP1 induced cytotoxicity in AS52 cells in a dose-dependent manner (IC50 = 15.7 µM), which allowed the selection of a non-lethal dose for the mutagenesis studies. While PQ was mutagenic in AS52 cells as evidenced by the increased levels of 6-TGr mutants, AP1 by itself did not increase the mutation frequency. However, co-treatment with AP1 (1-5 µM) or the antioxidant N-acetylcysteine (2 mM) almost completely counteracted the mutagenicity of PQ (10-100 µM) in AS52 cells. Taken together, these findings suggest that AP1, and likely by extension, A. paniculata extracts, are effective antioxidants that can protect against PQ-induced mutations, and thus could be a promising alternative treatment for PQ poisoning.

Various kind of chemical substances, including man-made chemical products and unintended products, are emitted to ambient air. Some of these substances have been shown to be mutagenic and therefore to act as a carcinogen in humans. National pollutant inventories (e.g., Pollutant Release and Transfer Registration in Japan) have estimated release amounts of man-made chemical products, but a major concern is the release of suspended particulate matter containing potent mutagens, for example, polycyclic aromatic hydrocarbons and related compounds generated by the combustion of fossil fuel, which are not estimated by PRTR system. In situ exposure studies have revealed that DNA adducts in the lung, and possibly mutations in germline cells are induced in rodents by inhalation of ambient air, indicating that evaluating in vivo mutations is important for assessing environmental health risks. Transgenic rodent systems (Muta, Big Blue, and gpt delta) are good tools for analyzing in vivo mutations induced by a mixture of chemical substances present in the environment. Following inhalation of diesel exhaust (used as a model mixture), mutation frequency was increased in the lung of gpt delta mice and base substitutions were induced at specific guanine residues (mutation hotspots) on the target transgenes. Mutation hotspots induced by diesel exhaust were different from those induced by benzo[ a ]pyrene, a typical mutagen in ambient air, but nearly identical to those induced by 1,6-dinitropyrene contained in diesel exhaust. Comparison between mutation hotspots in the TP53 (p53) gene in human lung cancer (data extracted from the IARC TP53 database) and mutations we identified in gpt delta mice showed that G to A transitions centered in CGT and CGG trinucleotides were mutation hotspots on both TP53 genes in human lung cancers and gpt genes in transgenic mice that inhaled diesel exhaust. The carcinogenic potency (TD 50 value) of genotoxic carcinogen was shown to be correlated with the in vivo mutagenicity (total dose per increased mutant frequency). These results suggest that the mutations identified in transgenic rodents can help identify environmental mutagens that cause cancer.