Environmental and Molecular Mutagenesis

p‐Aminophenol (PAP), a metabolite of aniline and acetaminophen, has been reported to be mutagenic in the L5178Y mouse lymphoma assay, but not in the CHO/HGPRT assay. In the present study, the effects of PAP in these two cells lines were examined to determine if the difference in activity is related to an intrinsic difference in the cell lines. CHO and L5178Y ^+/− mouse lymphoma cells were treated with PAP for 4 hr and assayed for 3 genetic endpoints: gene mutation at the HGPRT or TK locus, respectively; chromosomal aberrations at approximately 20 hr after initiation of treatment; and single‐stand DNA breaks as detected by the single cell electrophoresis assay immediately after treatment. All treatments were conducted in the absence of S9. There was a dose‐related, significant increase in TFT‐resistant mouse lymphoma cells at dose levels that reduced survival to ⩽=50% of concurrent controls. In CHO cells, however, there was no increase in thioguanine‐resistant cells at dose levels that reduced cell survival to < 20%. These results are consistent with published reports on PAP. While the CHO cells were slightly more resistant to the toxic effects of PAP, the dose levels used in the two cell lines did not differ by more than 2‐fold. At equivalent survival levels, PAP induced a significant (up to 20% aberrant cells) number of aberrations, primarily complex rearrangements, in both cell lines. In the single cell electrophoresis assay, there was a reproducible dose‐related increase in cells with single‐strand DNA breaks with both the L5178Y cells and the CHO cells. The induction of single‐strand breaks and chromosome aberrations by PAP suggests that, mechanistically, PAP produces similar genetic damage in both CHO and L5178Y cell lines, but intrinsic differences between assay systems are responsible for the divergent gene mutation results. © 1995 Wiley‐liss, Inc.

Increased intake of selenium (Se) may reduce the risk of degenerative diseases including cancer but excessive intake may be toxic. Wheat is a major source of dietary Se in humans. However, the effect of Se from wheat that is agronomically biofortified with Se on biomarkers of human health status is unknown. This study aimed to investigate whether improving Se status, by increased dietary intake of Se‐biofortified wheat, affects biomarkers of cancer risk, cardiovascular disease risk, oxidative stress, and immune function in healthy South Australian men. A 24‐week placebo‐controlled double‐blind intervention was performed in healthy older men (n = 62), with increased dose of Se intake every 8 weeks. Wheat was provided as 1, 2, and 3 puffed wheat biscuits, during weeks 1–8, 9–16, and 17–24, respectively. Blood was collected to measure a wide range of disease risk biomarkers. Consumption of Se‐biofortified wheat was found to increase plasma Se concentration from a baseline level of 122 to 192 μg/L following intake of three biscuits/day, which provided 267 μg Se. Platelet glutathione peroxidase, chromosome aberrations, and DNA damage in lymphocytes measured using the cytokinesis‐block micronucleus cytome assay and with the Comet assay, plasma F2‐isoprostanes, protein carbonyls, plasma C‐reactive protein, and leukocyte number were unaffected by the improved Se status. Improvement of Se status by consumption of Se‐biofortified wheat did not substantially modify the selected biomarkers of degenerative disease risk and health status in this apparently selenium‐replete cohort of healthy older men in South Australia. Environ. Mol. Mutagen. 2009. © 2009 Wiley‐Liss, Inc.

Twenty chemicals were tested for their ability to induce sister chromatid exchanges (SCEs) and chromosomal aberrations (ABs) in cultured Chinese hamster ovary cells (CHO). These chemicals were tested with and without an added metabolic activation system (rat liver S9 fraction). Four chemicals were negative in both assays, 1 induced ABs only, and 15 were positive for SCEs; 6 of these 15 also induced ABs.

The effect of cell harvest time on the ability to detect the induction of chromosomal aberrations was examined for six chemicals. Five of these had caused at least one of the following: cell cycle delay, aberrations observed in first division metaphase cells in the SCE assay, or a weak response in the standard AB assay (10–12‐hr growth period). Three chemicals, chlorinated tri‐sodium phosphate, 1, 2‐dibromo‐3‐chloropro‐pane, and tetrakis(hydroxymethyl)phosphonium chloride, were positive using both the standard and extended harvest times. N‐Nitrosodimethyl‐amine and diphenhydramine HCI were only positive using an extended harvest time, and malo‐naldehyde was negative using both standard and extended harvest times.

Chromosome damage was studied in female B6C3F1 mice exposed to dichloromethane (DCM) by subcutaneous or inhalation treatments. No increase in the frequency of either sister chromatid exchanges (SCEs) or chromosome aberrations (CAs) in bone marrow cells was observed after a single subcutaneous injection of 2,500 or 5,000 mg/kg DCM. Inhalation exposure to DCM for 10 days at concentrations of 4,000 or 8,000 ppm resulted in significant increases in frequencies of SCEs in lung cells and peripheral blood lymphocytes, CAs in lung and bone marrow cells, and micronuclei (MN) in peripheral blood erythrocytes. Lung cell CAs and blood erythrocyte MN reached frequencies of approximately two times control levels. Following a 3‐month inhalation exposure to 2,000 ppm DCM, mice showed small but significant increases in lung cell SCEs and peripheral blood erythrocyte MN. These findings suggest that genotoxicity may play a role in the carcinogenicity of DCM in the lungs of B6C3F1 female mice.

Bisphenol A (BPA) has become a target of intense public scrutiny since concerns about its association with human diseases such as obesity, diabetes, reproductive disorders, and cancer have emerged. BPA is a highly prevalent chemical in consumer products, and human exposure is thought to be ubiquitous. Numerous studies have demonstrated its endocrine disrupting properties and attributed exposure with cytotoxic, genotoxic, and carcinogenic effects; however, the results of these studies are still highly debated and a consensus about BPA's safety and its role in human disease has not been reached. One of the contributing factors is a lack of molecular mechanisms or modes of action that explain the diverse and pleiotropic effects observed after BPA exposure. The increase in BPA research seen over the last ten years has resulted in more studies that examine molecular mechanisms and revealed links between BPA‐induced oxidative stress and human disease. Here, a review of the current literature examining BPA exposure and the induction of reactive oxygen species (ROS) or oxidative stress will be provided to examine the landscape of the current BPA literature and provide a framework for understanding how induction of oxidative stress by BPA may contribute to the pleiotropic effects observed after exposure. Environ. Mol. Mutagen. 58:60–71, 2017. © 2017 Wiley Periodicals, Inc.

The National Toxicology Program has undertaken a study to assess the ability of four genetic toxicology assays to predict the carcinogenicity of chemicals in 2‐year rodent studies [Tennant et al.: Science 236:933–941, 1987]. Two of the assays, used for evaluating in vitro cytogenetic damage, were the SCE and chromosome aberration assays in Chinese hamster ovary cells. The results and data for 15 of the chemicals tested in these two assays are presented here. Each chemical was tested with and without exogenous metabolic activation. The chemicals tested were bisphenol A, 2‐chloroethanol, C.I. acid orange 10, C.I. disperse yellow 3, C.I. solvent yellow 14, cytembena, D&C red 9, 1,2‐dibromoethane, FD&C yellow 6, malaoxon, D, L‐menthol, phenol, sulfisoxazole, titanium dioxide, and tris(2‐ethylhexyl)phosphate. In vitro cytogenetic results from the other chemicals presented by Tennant et al. (Science 236:933–941, 1987) have been published by Galloway et al. (Environmental and Molecular Mutagenesis 10(Suppl 10):1–175, 1987 ), Gulati et al. (Environmental and Molecular Mutagenesis 13:133–193, 1989), and Loveday et al. (Environmental Mutagenesis 13:60–94).

Hexavalent chromium [Cr(VI)] is a recognized environmental toxin with ubiquitous distribution in industrialized societies. Its concentration in ambient air derives from several sources including but not limited to chemical processes, the burning of fossil fuels and the production of cement. It is a food contaminant because of its deposition into bodies of water. The majority of published studies on the effects of Cr(VI) concern animal models and these studies have shown that it can induce a variety of cytotoxic and genotoxic reactions that affect the immune system. In order to identify the specific cellular impact of Cr(VI) on humans, we studied its effect on protein production and gene expression in human peripheral blood mononuclear cells (PBMC) obtained from both men and women of each major ethnic group including Caucasians, Hispanics, Asians and African‐Americans. High‐throughput protein profiling using bead‐based protein arrays showed a concentration‐dependent biphasic effect of Cr(VI) on the expression of many cytokines and chemokines by activated PBMC. High‐density oligonucleotide microarray analysis identified several functional families of genes including those involved in immune response, intracellular signaling, cell cycle, apoptosis, RNA transport and binding, organelle organization and biogenesis that were strongly affected by Cr(VI). Cr(VI) suppressed many cellular receptor genes involved in immune response and activated many cell cycle‐related and proapoptotic genes. These results defined responses that were unique to Cr(VI). This methodology defined an effective manner for identifying injurious/toxic human exposures to Cr(VI) at the cellular level that may facilitate the identification and monitoring of efficacious treatments for Cr(VI)‐related maladies. Environ. Mol. Mutagen., 2007. © 2007 Wiley‐Liss, Inc.

The mutagenesis of metals in bacteria, as reported in the literature, can best be described as inconsistent. We report that cobalt chloride (Co⁺⁺), ferrous sulfate (Fe⁺⁺), manganese sulfate (Mn⁺⁺), cadmium chloride (Cd⁺⁺), and zinc chloride (Zn⁺⁺) could be reproducibly detected as mutagens in Salmonella strain TA97 when preincubation exposures were made in sterile, distilled, deionized water, or in Hepes buffer in NaCl₂/KCl₂, rather than the standard sodium phosphate buffer. Co⁺⁺ was also mutagenic under standard preincubation conditions. The individual components of Vogel‐Bonner medium, i.e., potassium and ammonium phosphates, citrate, and magnesium sulfate, inhibit mutagenesis by these metals. The phosphates and the citrate probably inhibit by chelating the metals, while data are presented to suggest that Mg⁺⁺ inhibition of metal mutagenesis is due to competitive inhibition for active transport via the magnesium active transport system in Salmonella. The chelator, diethyldithiocarbamate, inhibited the mutagenicity of Co⁺⁺, Fe⁺⁺, Zn⁺⁺, and Mn⁺⁺, but enhanced the mutagenicity of Cd⁺⁺. The results presented show that divalent metals can be detected as mutagens in Salmonella, and that their lack of detection as mutagens is not due to an inherent insensitivity of Salmonella but to their interaction with media components and/or passive and active transport processes.

The Microscreen phage‐induction assay, which quantitatively measures the induction of prophage λ in Escherichia coli WP2_s(λ), was used to test 14 crude (unfractionated) hazardous industrial waste samples for genotoxic activity in the presence and absence of metabolic activation. Eleven of the 14 wastes induced prophage, and induction was observed at concentrations as low as 0.4 pg per ml. Comparisons between the ability of these waste samples to induce prophage and their mutagenicity in the Salmonella reverse mutation assay indicate that the phage‐induction assay detected genotoxic activity in all but one of the wastes that were mutagenic in Salmonella. Moreover, the Microscreen assay detected as genotoxic five additional wastes that were not detected in the Salmonella assay. The applicability of the Microscreen phage‐induction assay for screening hazardous wastes for genotoxic activity is discussed, as are some of the problems associated with screening highly toxic wastes containing toxic volatile compounds.