Minimum Information for Reporting on the Comet Assay (MIRCA): recommendations for describing comet assay procedures and results

Short communication: The boring sponge (Pione vastifica, Hancock, 1849) induces oxidative stress in the Pacific oyster (Magallana gigas, Thunberg, 1793)

Boring sponge infection affects growth, development and reduces the soft tissue weight of oysters. In this study, we investigated the effects of boring sponge on the activity of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GP)) in the mantle, and the production of reactive oxygen species (ROS) and potential genotoxicity in hemocytes of the Pacific oyster Magallana gigas. Our results showed a significant increase in ROS production and DNA damage in hemocytes. Notably, the activity of SOD, CAT, and GP in the mantle was not significantly affected by boring sponge infection. Collectively, these results suggest that sponge invasion may cause oxidative stress in Pacific oyster hemocytes through ROS overproduction.

SUMOylation modification of FTO facilitates oxidative damage response of arsenic by IGF2BP3 in an m6A-dependent manner

N6-methyladenosine (m6A) is the most common form of internal post-transcriptional methylation observed in eukaryotic mRNAs. The abnormally increased level of m6A within the cells can be catalyzed by specific demethylase fat mass and obesity-associated protein (FTO) and stay in a dynamic and reversible state. However, whether and how FTO regulates oxidative damage via m6A modification remain largely unclear. Herein, by using both in vitro and in vivo models of oxidative damage induced by arsenic, we demonstrated for the first time that exposure to arsenic caused a significant increase in SUMOylation of FTO protein, and FTO SUMOylation at lysine (K)- 216 site promoted the down-regulation of FTO expression in arsenic target organ lung, and therefore, remarkably elevating the oxidative damage via an m6A-dependent pathway by its specific m6A reader insulin-like growth factor-2 mRNA-binding protein-3 (IGF2BP3). Consequently, these findings not only reveal a novel mechanism underlying FTO-mediated oxidative damage from the perspective of m6A, but also imply that regulation of FTO SUMOylation may serve as potential approach for treatment of oxidative damage.

How water acidification influences the organism antioxidant capacity and gill structure of Mediterranean mussel (Mytilus galloprovincialis, Lamarck, 1819) at normoxia and hypoxia

The effect of water acidification in combination with normoxia or hypoxia on the antioxidant capacity and oxidative stress markers in gills and hemolymph of the Mediterranean mussel (Mytilus galloprovincialis), as well as on gill microstructure, has been evaluated through an in vivo experiment. Mussels were exposed to a low pH (7.3) under normal dissolved oxygen (DO) conditions (8 mg/L), and hypoxia (2 mg/L) for 8 days, and samples were collected on days 1, 3, 6, and 8 to evaluate dynamic changes of physiological responses. Cytoplasmic concentrations of reactive oxygen species (ROS) and levels of DNA damage were measured in hemocytes, while the activity of catalase (CAT) and superoxide dismutase (SOD) and histopathological changes were assessed in gills. The results revealed that while water acidification did not significantly affect the activity of SOD and CAT in gills under normoxic and hypoxic conditions, there was a trend towards suppression of CAT activity at the end of the experimental period (day 8). Similarly, we did not observe increased formation of ROS in hemocytes or changes in the levels of DNA damage during the experimental period. These results strongly suggest that the oxidative stress response system in mussels is relatively stable to experimental conditions of acidification and hypoxia. Experimental acidification under normoxia and hypoxia caused changes to the structure of the gills, leading to various histopathological alterations, including dilation, hemocyte infiltration into the hemal sinuses, intercellular edema, vacuolization of epithelial cells in gill filaments, lipofuscin accumulation, changes in the shape and adjacent gill filaments, hyperplasia, exfoliation of the epithelial layer, necrosis, swelling, and destruction of chitinous layers (chitinous rods). Most of these alterations were reversible, non-specific changes that represent a general inflammatory response and changes in the morphology of the gill filaments. The dynamics of histopathological alterations suggests an active adaptive response of gills to environmental stresses. Taken together, our data indicate that Mediterranean mussels have a relative tolerance to water acidification and hypoxia at tissue and cellular levels.

Assessment of genotoxic damage induced by exposure to binary mixtures of polycyclic aromatic hydrocarbons and three heavy metals in male mice

INTRODUCTION

Heavy metals (HM) and polycyclic aromatic hydrocarbons (PAHs) exposition has been associated with health problems. Therefore, this research evaluated genotoxicity induced in male mice strain CD-1 exposed to benzo[a]anthracene (B[a]A) and benzo[a]pyrene (B[a]P) and their interaction with Fe, Pb, and Al.

METHODS

Groups of animals were exposed intraperitoneally to HM, PAHs, and mixtures of both. Peripheral blood samples were taken from 0 to 96 h at 24 h intervals; genotoxicity was determined by micronucleus tests and comet assay. Additionally, toxicity and viability were evaluated.

RESULTS

HM and PAHs individually were genotoxic. About toxicity, only Al altered polychromatic erythrocytes number and did not change leukocytes viability. Concerning mixtures, Fe + B[a]P, Fe + B[a]A, Pb + B[a]P increased genotoxicity. There were no changes with Pb + B[a]A. Finally, Al mixtures with both PAHs damage was decreased.

CONCLUSIONS

Exposure to HM and PAH caused genetic damage. Fe, Al, and B[a]A, established a genotoxic potential. Every metal can interact with PAHs in different ways. Also, the micronucleus test and the comet assay demonstrated their high capacity and reliability to determine the genotoxic potential of the compounds evaluated in this work.

Toxicity of particulate emissions from residential biomass combustion: An overview of in vitro studies using cell models

This article aims to critically review the current state of knowledge on in vitro toxicological assessments of particulate emissions from residential biomass heating systems. The review covers various aspects of particulate matter (PM) toxicity, including oxidative stress, inflammation, genotoxicity, and cytotoxicity, all of which have important implications for understanding the development of diseases. Studies in this field have highlighted the different mechanisms that biomass combustion particles activate, which vary depending on the combustion appliances and fuels. In general, particles from conventional combustion appliances are more potent in inducing cytotoxicity, DNA damage, inflammatory responses, and oxidative stress than those from modern appliances. The sensitivity of different cell lines to the toxic effects of biomass combustion particles is also influenced by cell type and culture conditions. One of the main challenges in this field is the considerable variation in sampling strategies, sample processing, experimental conditions, assays, and extraction techniques used in biomass burning PM studies. Advanced culture systems, such as co-cultures and air-liquid interface exposures, can provide more accurate insights into the effects of biomass combustion particles compared to simpler submerged monocultures. This review provides critical insights into the complex field of toxicity from residential biomass combustion emissions, underscoring the importance of continued research and standardisation of methodologies to better understand the associated health hazards and to inform targeted interventions.

Safety assessment of high fructose corn syrup and fructose used as sweeteners in foods

High Fructose Corn Syrup (HFCS) and Fructose (FR) are widely used sweeteners in many foods and beverages. This study aimed at investigating the cytotoxic effects of HFCS (5%-30%) and FR (62.5-2000 μg/mL) using MTT assay in Human Hepatocellular Carcinoma (HepG2) cells, and genotoxic effects of using Chromosome Aberrations (CAs), Sister Chromatid Exchanges (SCEs), Micronuclei (MN) and comet assays in human lymphocytes. HFCS significantly reduced the cell viability in HepG2 cells at between 7.5% and 30% for 24 and 48 h. 30% HFCS caused a very significant toxic effect. FR had a cytotoxic effect in HepG2 cells at all treatments. However, as fructose concentration decreased, the cell viability decreased. HFCS (10%-20%) and FR (250-2000 μg/mL) decreased the mitotic index at higher concentrations. IC50 value was found to be a 15% for 48 h. IC50 value of FR was detected as 62.5 μg/mL for 24 h and 48 h. HFCS significantly increased CAs frequency at 15% and 20%. FR significantly increased the frequency of CAs at 250, 1000, and 2000 μg/mL for 48 h. Both sweeteners increased the frequency of SCEs at all concentrations. HFCS (15% and 20%) and FR (250, 1000, and 2000 μg/mL) induced MN frequency at higher concentrations. HFCS caused DNA damage in comet assay at 10% -30%. FR increased tail intensity and moment at 125-2000 μg/mL and tail length at 62.5, 250 and 500 μg/mL. Therefore, HFCS and FR are clearly seen to be cytotoxic and genotoxic, especially at higher concentrations.

Evaluation of genotoxic damage, production reactive oxygen and nitrogen species in Plasmodium yoelii yoelii exposed to sodium metavanadate

Malaria represents the greatest global health burden among all parasitic diseases, with drug resistance representing the primary obstacle to control efforts. Sodium metavanadate (NaVO3) exhibits antimalarial activity against the Plasmodium yoelii yoelii (Pyy), yet its precise antimalarial mechanism remains elusive. This study aimed to assess the antimalarial potential of NaVO3, evaluate its genotoxicity, and determine the production of reactive oxygen and nitrogen species (ROS/RNS) in Pyy. CD-1 mice were infected and divided into two groups: one treated orally with NaVO3 (10 mg/kg/day for 4 days) and the other untreated. A 50% decrease in parasitemia was observed in treated mice. All experimental days demonstrated DNA damage in exposed parasites, along with an increase in ROS and RNS on the fifth day, suggesting a possible parasitostatic effect. The results indicate that DNA is a target of NaVO3, but further studies are necessary to fully elucidate the mechanisms underlying its antimalarial activity.

DNA modifications: Biomarkers for the exposome?

The concept of the exposome is the encompassing of all the environmental exposures, both exogenous and endogenous, across the life course. Many, if not all, of these exposures can result in the generation of reactive species, and/or the modulation of cellular processes, that can lead to a breadth of modifications of DNA, the nature of which may be used to infer their origin. Because of their role in cell function, such modifications have been associated with various major human diseases, including cancer, and so their assessment is crucial. Historically, most methods have been able to only measure one or a few DNA modifications at a time, limiting the information available. With the development of DNA adductomics, which aims to determine the totality of DNA modifications, a far more comprehensive picture of the DNA adduct burden can be gained. Importantly, DNA adductomics can facilitate a "top-down" investigative approach whereby patterns of adducts may be used to trace and identify the originating exposure source. This, together with other 'omic approaches, represents a major tool for unraveling the complexities of the exposome and hence allow a better a understanding of the environmental origins of disease.

The HOCl dry fog-is it safe for human cells?

This study aims to investigate if high-concentration HOCl fogging disinfection causes cytotoxicity and genotoxicity to cultured primary human skin fibroblasts. The cells were exposed to a dry fog of HOCl produced from solutions with a concentration of 300 ppm (5.72 mM) or 500 ppm (9.53 mM). After four times when fibroblasts were exposed to aerosolized HOCl at a concentration of 500 ppm for 9 minutes, significant cytotoxicity and genotoxicity effects were observed. Significant changes in the morphology of fibroblasts and cell death due to membrane disruption were observed, independent of the number of exposures. Flow cytometry analyses performed under these experimental conditions indicated a decrease in the number of cells with an intact cell membrane in the exposed samples compared to the sham samples, dropping to 49.1% of the total cells. Additionally, under the same conditions, the neutral comet assay results demonstrated significant DNA damage in the exposed cells. However, no analogous damages were found when the cells were exposed to aerosolized HOCl generated from a 300-ppm solution for 3 minutes, whether once or four times. Therefore, we have concluded that aerosolized HOCl in dry fog, with a concentration exceeding 300 ppm, can cause cytotoxic and genotoxic effects on human skin fibroblasts.

Impact of indoor air pollution on DNA damage and chromosome stability: a systematic review

Indoor air pollution is becoming a rising public health problem and is largely resulting from the burning of solid fuels and heating in households. Burning these fuels produces harmful compounds, such as particulate matter regarded as a major health risk, particularly affecting the onset and exacerbation of respiratory diseases. As exposure to polluted indoor air can cause DNA damage including DNA sd breaks as well as chromosomal damage, in this paper, we aim to provide an overview of the impact of indoor air pollution on DNA damage and genome stability by reviewing the scientific papers that have used the comet, micronucleus, and γ-H2AX assays. These methods are valuable tools in human biomonitoring and for studying the mechanisms of action of various pollutants, and are readily used for the assessment of primary DNA damage and genome instability induced by air pollutants by measuring different aspects of DNA and chromosomal damage. Based on our search, in selected studies (in vitro, animal models, and human biomonitoring), we found generally higher levels of DNA strand breaks and chromosomal damage due to indoor air pollutants compared to matched control or unexposed groups. In summary, our systematic review reveals the importance of the comet, micronucleus, and γ-H2AX assays as sensitive tools for the evaluation of DNA and genome damaging potential of different indoor air pollutants. Additionally, research in this particular direction is warranted since little is still known about the level of indoor air pollution in households or public buildings and its impact on genetic material. Future studies should focus on research investigating the possible impact of indoor air pollutants in complex mixtures on the genome and relate pollutants to possible health outcomes.

A template wizard for the cocreation of machine-readable data-reporting to harmonize the evaluation of (nano)materials

Making research data findable, accessible, interoperable and reusable (FAIR) is typically hampered by a lack of skills in technical aspects of data management by data generators and a lack of resources. We developed a Template Wizard for researchers to easily create templates suitable for consistently capturing data and metadata from their experiments. The templates are easy to use and enable the compilation of machine-readable metadata to accompany data generation and align them to existing community standards and databases, such as eNanoMapper, streamlining the adoption of the FAIR principles. These templates are citable objects and are available as online tools. The Template Wizard is designed to be user friendly and facilitates using and reusing existing templates for new projects or project extensions. The wizard is accompanied by an online template validator, which allows self-evaluation of the template (to ensure mapping to the data schema and machine readability of the captured data) and transformation by an open-source parser into machine-readable formats, compliant with the FAIR principles. The templates are based on extensive collective experience in nanosafety data collection and include over 60 harmonized data entry templates for physicochemical characterization and hazard assessment (cell viability, genotoxicity, environmental organism dose-response tests, omics), as well as exposure and release studies. The templates are generalizable across fields and have already been extended and adapted for microplastics and advanced materials research. The harmonized templates improve the reliability of interlaboratory comparisons, data reuse and meta-analyses and can facilitate the safety evaluation and regulation process for (nano) materials.

Systemic DNA Damage and Repair Activity Vary by Race in Breast Cancer Survivors

Non-Hispanic Black breast cancer survivors have poorer outcomes and higher mortality rates than White survivors, but systemic biological mechanisms underlying these disparities are unclear. We used circulating leukocytes as a surrogate for measuring systemic mechanisms, which might be different from processes in the target tissue (e.g., breast). We investigated race-based differences in DNA damage and repair, using a novel CometChip assay, in circulating leukocytes from breast cancer survivors who had completed primary cancer therapy and were cancer free. We observed novel race-based differences in systemic DNA damage and repair activity in cancer survivors, but not in cells from healthy volunteers. Basal DNA damage in leukocytes was higher in White survivors, but Black survivors showed a much higher induction after bleomycin treatment. Double-strand break repair activity was also significantly different between the races, with cells from White survivors showing more sustained repair activity compared to Black leukocytes. These results suggest that cancer and cancer therapy might have long-lasting effects on systemic DNA damage and repair mechanisms that differ in White survivors and Black survivors. Findings from our preliminary study in non-cancer cells (circulating leukocytes) suggest systemic effects beyond the target site, with implications for accelerated aging-related cancer survivorship disparities.

Agricultural exposures and DNA damage in PBMC of female farmers measured using the alkaline comet assay

OBJECTIVE

Several studies investigated the link between agricultural occupational exposures and DNA damage, in an attempt to bring elements of biological plausibility to the increased cancer risk associated with them. However, only a few of these studies focused on females.

METHODS

The comet assay was performed on PBMC (Peripheral Blood Mononuclear Cells) samples from 245 females working in open field farming and cattle raising, located in the Normandy area of France. Individual questionnaires on tasks performed were administered at the time of sampling to directly assess exposures. Environmental exposures were issued from a questionnaire assessing the farm productions. Linear regression analyses were done using the DNA damage scores.

RESULTS

Regarding direct exposures, several tasks associated with exposure to potentially harmful chemicals were not associated with DNA damage, but a longer duration of use of herbicide on meadows (p = 0.05) or of cleaning and upkeep of agricultural equipment (p = 0.06) revealed higher DNA damage levels, although the number of exposed women was low. Several indirect and/or environmental exposures were associated with DNA damage in multivariate analyses: a larger surface of meadows (p = 0.006) or the presence of poultry (p = 0.03) was associated with less DNA damage, while the presence of swine (p = 0.01) was associated with higher DNA damage. Smokers and former smokers had less DNA damage than non-smokers (p = 0.0008 and p = 0.03).

CONCLUSIONS

We report modified levels of DNA damage for those environmentally exposed to meadows, poultry and pig farming, underlining the need for a better knowledge of the potential health risks experienced by females in this setting.

Evaluation of imidacloprid (Confidor OD®) genotoxicity in Chrysoperla externa eggs (Neuroptera: Chrysopidae) through comet assay

The comet assay allows the analysis of DNA damage caused by different genotoxins. This assay has recently gained interest because of its ease of studying the interactions of xenobiotics with different organisms. Chrysoperla externa (Hagen, 1861) is a species of great economic relevance because it is a predator of major agricultural pests during its larval stage. Neonicotinoids are the most important chemical class of insecticides introduced into markets. A previous imidacloprid toxicity assessment on C. externa showed that this neonicotinoid insecticide reduced the egg viability. The objective of this study was to analyze the genotoxicity of Confidor OD® (imidacloprid 20% a.i., LS, Bayer CropScience) on the biological control agent C. externa at DNA level using the comet assay as an ecotoxicological biomarker. A comet assay protocol has been developed for this species at first time. For the bioassays, the commercial product formulated Confidor OD® was used at two concentrations: 100 and 180 mg/l of the active ingredient. Selected eggs were dipped in a Confidor OD® solution for 15 s. Descriptors evaluated in the comet assay were damage index, % DNA damage, and tail length. The damage index did not show any significant differences between the different concentrations evaluated, but differences were observed for tail length, because at higher concentrations of Confidor OD®, there were greater DNA breaks. The DNA of the cells from treated eggs analyzed at 48 h and 96 h of development showed the same % DNA damage; that is, they had no recovery capacity. Application of Confidor OD® to C. externa eggs produced irreparable breaks at the DNA level. The technique adjusted for C. externa can be used in other beneficial insects to study pesticide genotoxicity using a comet assay.

Genotoxicity and heating Performance of VxFe3-xO4 nanoparticles in Health applications

The applications of magnetic nanoparticles (MNPs) as biocatalysts in different biomedical areas have been evolved very recently. One of the main challenges in this field is to design affective MNPs surfaces with catalytically active atomic centres, while producing minimal toxicological side effects on the hosting cell or tissues. MNPs of vanadium spinel ferrite (VFe2O4) are a promising material for mimicking the action of natural enzymes in degrading harmful substrates due to the presence of active V5+ centres. However, the toxicity of this material has not been yet studied in detail enough to grant biomedical safety. In this work, we have extensively measured the structural, compositional, and magnetic properties of a series of VxFe3-xO4 spinel ferrite MNPs to assess the surface composition and oxidation state of V atoms, and also performed systematic and extensive in vitro cytotoxicity and genotoxicity testing required to assess their safety in potential clinical applications. We could establish the presence of V5+ at the particle surface even in water-based colloidal samples at pH 7, as well as different amounts of V2+ and V3+ substitution at the A and B sites of the spinel structure. All samples showed large heating efficiency with Specific Loss Power values up to 400 W/g (H0 = 30 kA/m; f = 700 kHz). Samples analysed for safety in human hepatocellular carcinoma (HepG2) cell line with up to 24h of exposure showed that these MNPs did not induce major genomic abnormalities such as micronuclei, nuclear buds, or nucleoplasmic bridges (MNIs, NBUDs, and NPBs), nor did they cause DNA double-strand breaks (DSBs) or aneugenic effects-types of damage considered most harmful to cellular genetic material. The present study is an essential step towards the use of these type of nanomaterials in any biomedical or clinical application.

Viability of Human Arterial Grafts Monitored by Comet Assay

An analytical method for studying DNA degradation by electrophoresis after cell lysis and visualization of DNA fragments with fluorescent dye, comet assay, was used to evaluate the viability of the endothelial layer of human arterial grafts with the aim of identifying the procedure that will least damage the tissue before cryopreservation. Four groups of samples were studied: cryopreserved arterial grafts that were thawed in two different ways, slowly lasting 2 hours or rapidly for approx. 7 minutes. Arterial grafts that were collected as part of multiorgan procurement with minimal warm ischemia time. Cadaveric grafts were taken as part of the autopsy, so they have a more extended period of warm ischemia. The HeadDNA (%) parameter and others commonly used parameters like TailDNA (%). TailMoment, TailLength, OliveMoment, TailMoment to characterize the comet were used to assess viability in this study. The ratio of non-decayed to decayed nuclei was determined from the values found. This ratio for cadaveric grafts was 0.63, for slowly thawed cryopreserved grafts 2.9, for rapidly thawed cryopreserved grafts 1.9, and for multi-organ procurement grafts 0.68. The results of the study confirmed the assumption that the allografts obtained from cadaveric donors are the least suitable. On the other hand, grafts obtained from multiorgan donors are better in terms of viability monitored by comet assay. Keywords: Arterial grafts, Cryopreservation, Cadaveric, Multiorgan procurement, Viability, Comet assay.

The Comet Assay as a Tool in Human Biomonitoring Studies of Environmental and Occupational Exposure to Chemicals-A Systematic Scoping Review

Biomonitoring of human populations exposed to chemical substances that can act as potential mutagens or carcinogens, may enable the detection of damage and early disease prevention. In recent years, the comet assay has become an important tool for assessing DNA damage, both in environmental and occupational exposure contexts. To evidence the role of the comet assay in human biomonitoring, we have analysed original research studies of environmental or occupational exposure that used the comet assay in their assessments, following the PRISMA-ScR method (preferred reporting items for systematic reviews and meta-analyses extension for scoping reviews). Groups of chemicals were designated according to a broad classification, and the results obtained from over 300 original studies (n = 123 on air pollutants, n = 14 on anaesthetics, n = 18 on antineoplastic drugs, n = 57 on heavy metals, n = 59 on pesticides, and n = 49 on solvents) showed overall higher values of DNA strand breaks in the exposed subjects in comparison with the unexposed. In summary, our systematic scoping review strengthens the relevance of the use of the comet assay in assessing DNA damage in human biomonitoring studies.

Genotoxicity and cytotoxicity of antineoplastic drugs at environmentally relevant concentrations after long-term exposure

Introduction

5-fluorouracil (5-FU) and methotrexate (MTX) are the antineoplastic drugs most commonly used worldwide. Considered cytotoxic, these pharmaceuticals exhibit low specificity, causing damage not only to cancer cells but also to healthy cells in organisms. After being consumed and metabolized, these drugs are excreted through urine and feces, followed by wastewater treatment. However, conventional treatments do not have the capacity to completely remove these substances, risking their introduction into freshwater systems. This could pose a risk to human health even at low concentrations.

Aims

Thus, the present study aimed to investigate the genotoxicity, cytotoxicity, and mutagenicity of 5-FU and MTX at environmentally relevant concentrations after a long-term exposure, using adult male rats as an experimental model.

Methods

Male Wistar rats (70 days old) were distributed into 4 groups (n = 10/group): control, received only vehicle; MTX, received methotrexate at 10ngL-1; 5-FU received 5-fluorouracil at 10ngL-1; and MTX + 5-FU, received a combination of MTX and 5-FU at 10ngL-1 each. The period of exposure was from postnatal day (PND) 70 to PND 160, through drinking water. After that, the animals were euthanized and the samples (liver, testis, femoral bone marrow, and peripheral blood) were obtained.

Results

Increased DNA fragmentation was observed in the peripheral blood, liver, and testis, altering the parameters of the tail moment and tail intensity in the Comet assay. Besides, the change in the ratio between PCE and NCE indicates bone marrow suppression.

Conclusion

These findings warn the adverse effects for the general population worldwide chronically exposed to these drugs at trace concentration unintentionally.

SIRT7 sustains tumor development and radioresistance by repressing endoplasmic reticulum stress-induced apoptosis in cutaneous melanoma

Cutaneous melanoma is one of the most malignant human tumors and possesses strong resistance to radiotherapy. However, the mechanisms contribute to such radioresistance of melanoma is unclear. In this study, SIRT7 is identified to be higher-expressed in melanoma and positively correlated with melanoma staging. Under ionizing radiation (IR)-treatment condition, loss of SIRT7 compromised the survivability of melanoma cells showed by decreased proliferation, colony formation, migration, but enhancing apoptosis. Transcriptomic sequencing analysis indicated the apoptosis induced after SIRT7 knockdown is tightly related with the induction of endoplasmic reticulum stress (ER stress) by IR treatment. Loss of SIRT7 enhanced EIF2α acetylation and activated its phosphorylation to induce the expression of ER stress proteins including DDIT3, XBP1 and GRP78, among which DDIT3 is responsible for apoptosis induction. SIRT7 depletion enriched ER stress-activated transcription factor ATF4 at the promoter region of DDIT3 gene to transactivate its expression and induces apoptotic cascade in both mock- and IR-treatment conditions. Consistently, SIRT7 is highly upregulated in radioresistant melanoma cell strain and still modulates the ER-stress responsive genes to maintain the homeostasis of melanoma. Collectively, SIRT7 negatively regulates ER stress-activated apoptosis to enhance the survivability of melanoma cells in both non-IR- and IR-treatment conditions. Our study highlights the role of SIRT7 in repressing ER stress and the following apoptosis to sustain tumor development and mediate radioresistance in melanoma, which may suggest a novel intervention target for melanoma therapy.

Brazil nut consumption reduces DNA damage in overweight type 2 diabetes mellitus patients

Type 2 diabetes mellitus (T2D) is a metabolic disease, which occurs largely due to unhealthy lifestyle. As oxidative stress is believed to promote T2D, by inducing damage to lipids, proteins, and DNA, appropriate dietary interventions seem critical to prevent, manage, and even reverse this condition. Brazil nuts (Bertholletia excelsa, H.B.K.) are nature's richest source of selenium, a mineral that has shown several health benefits. Therefore, this study aims to assess the effects of selenium consumption, through Brazil nuts, on biochemical and oxidative stress parameters, and genomic instability in T2D patients. We recruited 133 patients with T2D, registered in the Integrated Clinics of the University of Southern Santa Catarina (Brazil). Participants consumed one Brazil nut a day for six months. Blood samples and exfoliated buccal cells were collected at the beginning and the end of the intervention. The glycemic profile, lipid profile, renal profile and hepatic profile, DNA damage and selenium content were evaluated. A total of 74 participants completed the intervention. Brazil nut consumption increased selenium and GSH levels, GPx, and CAT activity while DCF and nitrites levels decreased. Total thiols increased, and protein carbonyl and MDA levels decreased. Levels of baseline and oxidative DNA damage in T2D patients were significantly decreased, as well as the frequency of micronuclei and nuclear buds. The fasting glucose levels, HDL and LDL cholesterol, and GGT levels that increased significantly in patients with type 2 diabetes were significantly reduced with nut consumption. Our results show an increase in antioxidant activity, along with reductions of protein and lipid oxidation as well as DNA damage, suggesting that Brazil nut consumption could be an ally in reducing oxidative stress and modulating the genomic instability in T2D patients.

Exploring cytokinesis block micronucleus assay in Croatia: A journey through the past, present, and future in biomonitoring of the general population

In this study, we used the cytokinesis-block micronucleus (CBMN) assay to evaluate the background frequency of cytogenetic damage in peripheral blood lymphocytes of the general population concerning different anthropometric data and lifestyle factors. The background frequency of CBMN assay parameters was analysed in 850 healthy, occupationally non-exposed male and female subjects (average age, 38±11 years) gathered from the general Croatian population from 2000 to 2023. The mean background values for micronuclei (MNi) in the whole population were 5.3±4.3 per 1000 binucleated cells, while the mean frequency of nucleoplasmic bridges (NPBs) was 0.7±1.3 and of nuclear buds (NBUDs) 3.1±3.2. The cut-off value, which corresponds to the 95th percentile of the distribution of 850 individual values, was 14 MNi, 3 NPBs, and 9 NBUDs. Results from our database also showed an association of the tested genomic instability parameters with age and sex but also with other lifestyle factors. These findings underscore the importance of considering several anthropometric and lifestyle factors when conducting biomonitoring studies. Overall, the normal and cut-off values attained here present normal values for the general population that can later serve as baseline values for further human biomonitoring studies either in Croatia or worldwide.

Trypanosoma cruzi infection induces DNA double-strand breaks and activates DNA damage response pathway in host epithelial cells

Trypanosoma cruzi, the etiological agent of Chagas disease, invades many cell types affecting numerous host-signalling pathways. During the T. cruzi infection, we demonstrated modulations in the host RNA polymerase II activity with the downregulation of ribonucleoproteins affecting host transcription and splicing machinery. These alterations could be a result of the initial damage to the host DNA caused by the presence of the parasite, however, the mechanisms are not well understood. Herein, we examined whether infection by T. cruzi coincided with enhanced DNA damage in the host cell. We studied the engagement of the DNA damage response (DDR) pathways at the different time points (0-24 h post-infection, hpi) by T. cruzi in LLC-MK2 cells. In response to double-strand breaks (DSB), maximum phosphorylation of the histone variant H2AX is observed at 2hpi and promotes recruitment of the DDR p53-binding protein (53BP1). During T. cruzi infection, Ataxia-telangiectasia mutated protein (ATM) and DNA-PK protein kinases remained active in a time-dependent manner and played roles in regulating the host response to DSB. The host DNA lesions caused by the infection are likely orchestrated by the non-homologous end joining (NHEJ) pathway to maintain the host genome integrity.

Are hydroxyapatite-based biomaterials free of genotoxicity? A systematic review

Hydroxyapatite (HA) is a biomaterial widely used in clinical applications and pharmaceuticals. The literature on HA-based materials studies is focused on chemical characterization and biocompatibility. Generally, biocompatibility is analyzed through adhesion, proliferation, and differentiation assays. Fewer studies are looking for genotoxic events. Thus, although HA-based biomaterials are widely used as biomedical devices, there is a lack of literature regarding their genotoxicity. This systematic review was carried out following the PRISMA statement. Specific search strategies were developed and performed in four electronic databases (PubMed, Science Direct, Scopus, and Web of Science). The search used "Hydroxyapatite OR Calcium Hydroxyapatite OR durapatite AND genotoxicity OR genotoxic OR DNA damage" and "Hydroxyapatite OR Calcium Hydroxyapatite OR durapatite AND mutagenicity OR mutagenic OR DNA damage" as keywords and articles published from 2000 to 2022, after removing duplicate studies and apply include and exclusion criteria, 53 articles were identified and submitted to a qualitative descriptive analysis. Most of the assays were in vitro and most of the studies did not show genotoxicity. In fact, a protective effect was observed for hydroxyapatites. Only 20 out of 71 tests performed were positive for genotoxicity. However, no point mutation-related mutagenicity was observed. As the genotoxicity of HA-based biomaterials observed was correlated with its nanostructured forms as needles or rods, it is important to follow their effect in chronic exposure to guarantee safe usage in humans.

In vivo alkaline comet assay: Statistical considerations on historical negative and positive control data

The alkaline comet assay is frequently used as in vivo follow-up test within different regulatory environments to characterize the DNA-damaging potential of different test items. The corresponding OECD Test guideline 489 highlights the importance of statistical analyses and historical control data (HCD) but does not provide detailed procedures. Therefore, the working group "Statistics" of the German-speaking Society for Environmental Mutation Research (GUM) collected HCD from five laboratories and >200 comet assay studies and performed several statistical analyses. Key results included that (I) observed large inter-laboratory effects argue against the use of absolute quality thresholds, (II) > 50% zero values on a slide are considered problematic, due to their influence on slide or animal summary statistics, (III) the type of summarizing measure for single-cell data (e.g., median, arithmetic and geometric mean) may lead to extreme differences in resulting animal tail intensities and study outcome in the HCD. These summarizing values increase the reliability of analysis results by better meeting statistical model assumptions, but at the cost of information loss. Furthermore, the relation between negative and positive control groups in the data set was always satisfactorily (or sufficiently) based on ratio, difference and quantile analyses.

Chromosomal single-strand break repair and neurological disease: Implications on transcription and emerging genomic tools

Cells are constantly exposed to various sources of DNA damage that pose a threat to their genomic integrity. One of the most common types of DNA breaks are single-strand breaks (SSBs). Mutations in the repair proteins that are important for repairing SSBs have been reported in several neurological disorders. While several tools have been utilised to investigate SSBs in cells, it was only through recent advances in genomics that we are now beginning to understand the architecture of the non-random distribution of SSBs and their impact on key cellular processes such as transcription and epigenetic remodelling. Here, we discuss our current understanding of the genome-wide distribution of SSBs, their link to neurological disorders and summarise recent technologies to investigate SSBs at the genomic level.

Could fluoride be considered a genotoxic chemical agent in vivo? A systematic review with meta-analysis

The goal of this study was to perform systematic review (SR) to investigate the scientific literature regarding the genotoxicity effects of fluoride exposure (FE). The search of databases used for this study was PubMed/Medline, SCOPUS and Web of Science. The quality of included studies was assessed using the EPHPP (Effective Public Health Practice Project). A total of 20 potentially relevant studies were selected for evaluating the genotoxicity induced by fluoride. Few studies have revealed that FE induces genotoxicity. A total of 14 studies demonstrated negative results whereas 6 studies did not. After reviewing the twenty studies, 1 was classified as weak, 10 were considered moderate and 9 were considered strong, according to the EPHPP. Taken together, it has been established that genotoxicity of fluoride is limited.

Comparison between inhalational anesthetics in terms of DNA damage and immunological markers

This study compared genetic damage and immunological markers between surgical patients who underwent inhalational anesthesia with isoflurane or sevoflurane. Blood samples were collected from surgical patients (n = 18 in the isoflurane group and n = 17 in the sevoflurane group) at baseline (before the anesthesia procedure) and the day after anesthesia. DNA damage was detected using an alkaline comet assay; proinflammatory interleukin (IL)-6 was detected by flow cytometry, and white blood cells were detected via an automatic hematology analyzer. The characteristics of both groups were similar, and neither of the two anesthetics induced DNA damage. Similarly, mild neutrophilia was observed after anesthesia in both groups. Increased IL-6 levels were observed 1 day after anesthesia regardless of the type of anesthetic, but this increase was greater in the isoflurane group. Our study suggested that isoflurane and sevoflurane administration may contribute to changes in the immune parameters measured, though no genotoxic hazard was identified, in healthy adult patients who undergo low-stress surgery.

The uses of zebrafish (Danio rerio) as an in vivo model for toxicological studies: A review based on bibliometrics

An in vivo model is necessary for toxicology. This review analyzed the uses of zebrafish (Danio rerio) in toxicology based on bibliometrics. Totally 56,816 publications about zebrafish from 2002 to 2023 were found in Web of Science Core Collection, with Toxicology as the top 6 among all disciplines. Accordingly, the bibliometric map reveals that "toxicity" has become a hot keyword. It further reveals that the most common exposure types include acute, chronic, and combined exposure. The toxicological effects include behavioral, intestinal, cardiovascular, hepatic, endocrine toxicity, neurotoxicity, immunotoxicity, genotoxicity, and reproductive and transgenerational toxicity. The mechanisms include oxidative stress, inflammation, autophagy, and dysbiosis of gut microbiota. The toxicants commonly evaluated by using zebrafish model include nanomaterials, arsenic, metals, bisphenol, and dioxin. Overall, zebrafish provide a unique and well-accepted model to investigate the toxicological effects and mechanisms. We also discussed the possible ways to address some of the limitations of zebrafish model, such as the combination of human organoids to avoid species differences.

Protective effects of Pt-N-C single-atom nanozymes against myocardial ischemia-reperfusion injury

Effective therapeutic strategies for myocardial ischemia/reperfusion (I/R) injury remain elusive. Targeting reactive oxygen species (ROS) provides a practical approach to mitigate myocardial damage following reperfusion. In this study, we synthesize an antioxidant nanozyme, equipped with a single-Platinum (Pt)-atom (PtsaN-C), for protecting against I/R injury. PtsaN-C exhibits multiple enzyme-mimicking activities for ROS scavenging with high efficiency and stability. Mechanistic studies demonstrate that the excellent ROS-elimination performance of the single Pt atom center precedes that of the Pt cluster center, owing to its better synergistic effect and metallic electronic property. Systematic in vitro and in vivo studies confirm that PtsaN-C efficiently counteracts ROS, restores cellular homeostasis and prevents apoptotic progression after I/R injury. PtsaN-C also demonstrates good biocompatibility, making it a promising candidate for clinical applications. Our study expands the scope of single-atom nanozyme in combating ROS-induced damage and offers a promising therapeutic avenue for the treatment of I/R injury.

DNA base oxidation in relation to TNM stages and chemotherapy treatment in colorectal cancer patients 2-9 months post-surgery

Accumulation of DNA damage is a critical feature of genomic instability, which is a hallmark of various cancers. The enzyme-modified comet assay is a recognized method to detect specific DNA lesions at the level of individual cells. In this cross-sectional investigation, we explore possible links between clinicopathological and treatment related factors, nutritional status, physical activity and function, and DNA damage in a cohort of colorectal cancer (CRC) patients with non-metastatic disease. Levels of DNA damage in peripheral mononuclear blood cells (PBMCs) assessed 2-9 months post-surgery, were compared across tumour stage (localized (stage I-II) vs. regional (stage III) disease), localization (colon vs. rectosigmoid/rectum cancer), and adjuvant chemotherapy usage, with the last dosage administrated 2-191 days prior to sampling. Associations between DNA damage and indicators of nutritional status, physical activity and function were also explored. In PBMCs, DNA base oxidation was higher in patients diagnosed with regional compared with localized tumours (P = 0.03), but no difference was seen for DNA strand breaks (P > 0.05). Number of days since last chemotherapy dosage was negatively associated with DNA base oxidation (P < 0.01), and patients recently receiving chemotherapy (<15 days before blood collection) had higher levels of DNA base oxidation than those not receiving chemotherapy (P = 0.03). In the chemotherapy group, higher fat mass (in kg and %) as well as lower physical activity were associated with greater DNA base oxidation (P < 0.05). In conclusion, DNA base oxidation measured with the enzyme-modified comet assay varies according to tumour and lifestyle related factors in CRC patients treated for non-metastatic disease.

Long-term suboptimal dietary trace element supply does not affect trace element homeostasis in murine cerebellum

The ageing process is associated with alterations of systemic trace element (TE) homeostasis increasing the risk, e.g. neurodegenerative diseases. Here, the impact of long-term modulation of dietary intake of copper, iron, selenium, and zinc was investigated in murine cerebellum. Four- and 40-wk-old mice of both sexes were supplied with different amounts of those TEs for 26 wk. In an adequate supply group, TE concentrations were in accordance with recommendations for laboratory mice while suboptimally supplied animals received only limited amounts of copper, iron, selenium, and zinc. An additional age-adjusted group was fed selenium and zinc in amounts exceeding recommendations. Cerebellar TE concentrations were measured by inductively coupled plasma-tandem mass spectrometry. Furthermore, the expression of genes involved in TE transport, DNA damage response, and DNA repair as well as selected markers of genomic stability [8-oxoguanine, incision efficiency toward 8-oxoguanine, 5-hydroxyuracil, and apurinic/apyrimidinic sites and global DNA (hydroxy)methylation] were analysed. Ageing resulted in a mild increase of iron and copper concentrations in the cerebellum, which was most pronounced in the suboptimally supplied groups. Thus, TE changes in the cerebellum were predominantly driven by age and less by nutritional intervention. Interestingly, deviation from adequate TE supply resulted in higher manganese concentrations of female mice even though the manganese supply itself was not modulated. Parameters of genomic stability were neither affected by age, sex, nor diet. Overall, this study revealed that suboptimal dietary TE supply does not substantially affect TE homeostasis in the murine cerebellum.

Tissue-specific toxic effects of nano-copper on zebrafish

Understanding the behavior and potential toxicity of copper nanoparticles (nano-Cu) in the aquatic environment is a primary way to assess their environmental risks. In this study, RNA-seq was performed on three different tissues (gills, intestines, and muscles) of zebrafish exposed to nano-Cu, to explore the potential toxic mechanism of nano-Cu on zebrafish. The results indicated that the toxic mechanism of nano-Cu on zebrafish was tissue-specific. Nano-Cu enables the CB1 receptor of the presynaptic membrane of gill cells to affect short-term synaptic plasticity or long-term synaptic changes (ECB-LTD) through DSI and DSE, causing dysfunction of intercellular signal transmission. Imbalance of de novo synthesis of UMP in intestinal cells and its transformation to UDP, UTP, uridine, and uracil, resulted in many functions involved in the pyrimidine metabolic pathway being blocked. Meanwhile, the toxicity of nano-Cu caused abnormal expression of RAD51 gene in muscle cells, which affects the repair of damaged DNA through Fanconi anemia and homologous recombination pathway, thus causing cell cycle disorder. These results provide insights for us to better understand the differences in toxicity of nano-Cu on zebrafish tissues and are helpful for a comprehensive assessment of nano-Cu's effects on aquatic organisms.

Baseline and oxidatively damaged DNA in end-stage renal disease patients on varied hemodialysis regimens: a comet assay assessment

Global estimates exhibit that one million people have end-stage renal disease, a disease-state characterized by irreversible loss of kidney structure and function, thus necessitating renal replacement therapy. The disease-state, oxidative stress, inflammatory responses, as well as the treatment procedure can have damaging effects on the genetic material. Therefore, the present study was carried out to investigate DNA damage (basal and oxidative) using the comet assay in peripheral blood leukocytes of patients (n = 200) with stage V Chronic Kidney Disease (on dialysis and those recommended but yet to initiate dialysis) and compare it to that in controls (n = 210). Basal DNA damage was significantly elevated (1.13x, p ≤ 0.001) in patients (46.23 ± 0.58% DNA in tail) compared to controls (40.85 ± 0.61% DNA in tail). Oxidative DNA damage was also significantly (p ≤ 0.001) higher in patients (9.18 ± 0.49 vs. 2.59 ± 0.19% tail DNA) compared to controls. Twice-a-week dialysis regimen patients had significantly elevated % tail DNA and Damage Index compared to the non-dialyzed and to the once-a-week dialysis group implying dialysis- induced mechanical stress and blood-dialyzer membrane interactions as probable contributors to elevated DNA damage. The present study with a statistically significant power implies higher disease-associated as well as maintenance therapy (hemodialysis)-induced basal and oxidatively damaged DNA, which if not repaired has the potential to initiate carcinogenesis. These findings mark the need for improvement and development of interventional therapies for delaying disease progression and associated co-morbidities so as to improve life expectancy of patients with kidney disease.

Impacts of high-dose riboflavin on cytotoxicity, antioxidant, growth, reproductive gene expressions, and genotoxicity in the rainbow trout gonadal cells

Riboflavin (vitamin B2 found in food) is a precursor of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which study as coenzymes for a variety of cellular processes including biosynthesis, homocysteine metabolism, detoxification, and various oxidation and reduction reactions. Although studies on the symptoms resulting from riboflavin deficiency are intense, studies on the effects of high doses of riboflavin are almost absent. This report aimed to examine the actions of riboflavin on cell viability, the transcriptional expressions of antioxidant enzyme (gsr and gpx1a), growth (gh1, igf1, and igf2), the reproductive (bol) genes and DNA damage in the rainbow trout gonad cells (RTG-2) for 48 h. All concentrations of riboflavin (3.125, 6.25, 12.5, 25, 50, and 100 μM) significantly reduced the RTG-2 cell viability. Riboflavin (LD50: 12.5 μM) significantly downregulated the transcriptional expressions of gpx1a, igf1, and bol genes, while it non-significantly upregulated or downregulated the transcriptional expression of gsr, igf2, and gh1 genes in the RTG-2 cells in comparison to the control group for 48 h. The comet assay demonstrated that riboflavin significantly raised tail DNA% >10% DMSO (positive control). Based on the outcomes, high doses of riboflavin exhibit the potential to have a role in cellular mechanisms, including especially reproduction, DNA damage, and cell death.

Hazard characterization of Alternaria toxins to identify data gaps and improve risk assessment for human health

Fungi of the genus Alternaria are ubiquitous plant pathogens and saprophytes which are able to grow under varying temperature and moisture conditions as well as on a large range of substrates. A spectrum of structurally diverse secondary metabolites with toxic potential has been identified, but occurrence and relative proportion of the different metabolites in complex mixtures depend on strain, substrate, and growth conditions. This review compiles the available knowledge on hazard identification and characterization of Alternaria toxins. Alternariol (AOH), its monomethylether AME and the perylene quinones altertoxin I (ATX-I), ATX-II, ATX-III, alterperylenol (ALP), and stemphyltoxin III (STTX-III) showed in vitro genotoxic and mutagenic properties. Of all identified Alternaria toxins, the epoxide-bearing analogs ATX-II, ATX-III, and STTX-III show the highest cytotoxic, genotoxic, and mutagenic potential in vitro. Under hormone-sensitive conditions, AOH and AME act as moderate xenoestrogens, but in silico modeling predicts further Alternaria toxins as potential estrogenic factors. Recent studies indicate also an immunosuppressive role of AOH and ATX-II; however, no data are available for the majority of Alternaria toxins. Overall, hazard characterization of Alternaria toxins focused, so far, primarily on the commercially available dibenzo-α-pyrones AOH and AME and tenuazonic acid (TeA). Limited data sets are available for altersetin (ALS), altenuene (ALT), and tentoxin (TEN). The occurrence and toxicological relevance of perylene quinone-based Alternaria toxins still remain to be fully elucidated. We identified data gaps on hazard identification and characterization crucial to improve risk assessment of Alternaria mycotoxins for consumers and occupationally exposed workers.

Genotoxicity induced by endodontic sealers: A systematic review

Introduction

This systematic review aimed to help further elucidate the following question: are endodontics sealers able to induce DNA damage in vitro or in vivo?

Methods

This study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement 2020 criteria. A total of 23 studies were carefully selected by the authors.

Results

Regarding the general characteristics, most studies evaluated, on average, 3-5 types of sealers (resin epoxy, salicylate, salicylate + MTA, zinc oxide-eugenol, bioceramic products, calcium hydroxide), performing comparisons between them. Our results demonstrate that endodontic sealers may be a genotoxic agent since most studies demonstrated positive findings, with the resin-based ones being the most potentially genotoxic.

Conclusion

The type of genotoxicity assay, material evaluated, and dilution concentration levels influenced the outcome. This study clarifies whether and to what extent endodontic sealers are capable of inducing DNA injury in oral tissues.

Alkaline Comet Assay to Assess Genotoxicity in Zebrafish Larvae

The zebrafish (Danio rerio) is a model organism widely used in several research fields due to its characteristics and numerous advantages, such as optical embryo transparency, fully sequenced genome, orthologous genes to humans, small size, high reproductive rate, easy gene editing and relatively low costs. Thus, a number of protocols have been developed that allow the use of this vertebrate model for toxic effect evaluation at various biological levels, including genotoxicity, using the comet assay technique.The comet assay or single-cell gel electrophoresis is a popular and sensitive method to study DNA damage in cells, which is described in this chapter. Briefly, cells suspended in agarose on a microscope slide are lysed, denatured, electrophoresed, neutralized, and stained to study the migration of DNA strand breaks. As a result, cells with increased DNA damage present a high fluorescence intensity and an increase of comet tail length. For the visual score, comets are classified according to the head integrity, tail intensity, and tail length into five classes, namely, class 0 until class 4 (comets with high damage and with almost all the DNA in the tail). These data are used to calculate the Genetic Damage Index (GDI) expressed as Arbitrary Units (AU).

Further development of CometChip technology to measure DNA damage in vitro and in vivo: Comparison with the 2 gels/slide format of the standard and enzyme-modified comet assay

DNA damage plays a pivotal role in carcinogenesis and other diseases. The comet assay has been used for more than three decades to measure DNA damages. The 1-2 gels/slide format is the most used version of the assay. In 2010, a high throughput 96 macrowell format with a spatially encoded array of microwells patterned in agarose was developed, called the CometChip. The commercial version (CometChip®) has been used for the in vitro standard version of the comet assay (following the manufacturer's protocol), although it has not been compared directly with the 2 gels/slide format. The aim of this work is to developed new protocols to allow use of DNA repair enzymes as well as the analysis of in vivo frozen tissue samples in the CometChip®, to increase the throughput, and to compare its performance with the classic 2 gels/slide format. We adapted the manufacturer's protocol to allow the use of snap frozen tissue samples, using male Wistar rats orally dosed with methyl methanesulfonate (MMS, 200 mg/kg b.w.), and to detect altered nucleobases using DNA repair enzymes, with TK6 cells treated with potassium bromate (KBrO3, 0-4 mM, 3 h) and formamidopyrimidine DNA glycosylase (Fpg) as the enzyme. Regarding the standard version of the comet, we performed thee comparison of the 2 gel/slide and CometChip® format (using the the manufacturer's protocol), using TK6 cells with MMS (100-800 µM, 1 h) and hydrogen peroxide (H2O2, 7.7-122.5 µM, 5 min) as testing compounds. In all cases the CometChip® was performed along with the 2 gels/slide format. Results obtained were comparable and the CometChip® is a good alternative to the 2 gels/slide format when a higher throughput is required.

Gastrointestinal tract exposure to particles and DNA damage in animals: A review of studies before, during and after the peak of nanotoxicology

Humans ingest particles and fibers on daily basis. Non-digestible carbohydrates are beneficial to health and food additives are considered safe. However, titanium dioxide (E171) has been banned in the European Union because the European Food Safety Authority no longer considers it non-genotoxic. Ingestion of microplastics and nanoplastics are novel exposures; their potential hazardous effects to humans have been under the radar for many years. In this review, we have assessed the association between oral exposure to man-made particles/fibers and genotoxicity in gastrointestinal tract cells and secondary tissues. We identified a total of 137 studies on oral exposure to particles and fibers. This was reduced to 49 papers with sufficient quality and relevance, including exposures to asbestos, diesel exhaust particles, titanium dioxide, silver nanoparticles, zinc oxide, synthetic amorphous silica and certain other nanomaterials. Nineteen studies show positive results, 25 studies show null results, and 5 papers show equivocal results on genotoxicity. Recent studies seem to show null effects, whereas there is a higher proportion of positive genotoxicity results in early studies. Genotoxic effects seem to cluster in studies on diesel exhaust particles and titanium dioxide, whereas studies on silver nanoparticles, zinc oxide and synthetic amorphous silica seem to show mainly null effects. The most widely used genotoxic tests are the alkaline comet assay and micronucleus assay. There are relatively few results on genotoxicity using reliable measurements of oxidatively damaged DNA, DNA double strand breaks (γH2AX assay) and mutations. In general, evidence suggest that oral exposure to particles and fibers is associated with genotoxicity in animals.

Exploring the Antioxidant and Genoprotective Potential of Salicornia ramosissima Incorporation in the Diet of the European Seabass (Dicentrarchus labrax)

The identification of novel feed materials as a source of functional ingredients is a topical priority in the finfish aquaculture sector. Due to the agrotechnical practices associated and phytochemical profiling, halophytes emerge as a new source of feedstuff for aquafeeds, with the potential to boost productivity and environmental sustainability. Therefore, the present study aimed to assess the potential of Salicornia ramosissima incorporation (2.5, 5, and 10%), for 2 months, in the diet of juvenile European seabass, seeking antioxidant (in the liver, gills, and blood) and genoprotective (DNA and chromosomal integrity in blood) benefits. Halophyte inclusion showed no impairments on growth performance. Moreover, a tissue-specific antioxidant improvement was apparent, namely through the GSH-related defense subsystem, but revealing multiple and complex mechanisms. A genotoxic trigger (regarded as a pro-genoprotective mechanism) was identified in the first month of supplementation. A clear protection of DNA integrity was detected in the second month, for all the supplementation levels (and the most prominent melioration at 10%). Overall, these results pointed out a functionality of S. ramosissima-supplemented diets and a promising way to improve aquaculture practices, also unraveling a complementary novel, low-value raw material, and a path to its valorization.

Accessing the Health Risk of Ingestion of Surface Water from Lucrécia and Parelhas Dams in Northeast Brazil Using the Sentinel Organism Drosophila melanogaster

This study investigated the genotoxic risk of chronic exposure of hemolymph's cells of Drosophila melanogaster (Insecta, Diptera) to water samples from Boqueirão de Parelhas Dam and from Lucrécia Dam in the semiarid region of Brazil. The dams are located over the Pegmatite Province of Borborema, with rocks rich in uranium and thorium. Water samples hydrated a culture medium composed of mashed potatoes, where larvae of D. melanogaster fed for 24 h, before be underwent to the Comet assay. The same water was evaluated for the presence of dissolved Radon gas (222Rn) and concentrations of 11 toxic metals (Ag, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn). The results indicated a genotoxic effect resulting from exposure to the waters of the Parelhas dam, in the samples of August 2018; and in Lucrécia dam, in January 2019. D. melanogaster stood out for its high sensitivity to monitor the genotoxic effects of compounds dissolved in public dams. And unlike to other essentially aquatic sentinel organisms, this species stood out as a model to concomitant studies of air and water possible contaminated, in a scenario of natural environmental radioactivity present in semiarid of Brazil.

Comet assay as a suitable biomarker for in vivo oral carcinogenesis: a systematic review

BACKGROUND AND OBJECTIVES

In order to detect genetic damage, different methods have been developed, such as micronuclei and comet assay. The comet assay presents some advantages when compared to the other aforementioned methods, including wide versatility, as any eukaryotic cell can be evaluated at an individual cellular level. In this context, the aim of this systematic review was designed to help further elucidate the following question: is the comet assay a suitable biomarker of in vivo oral carcinogenesis?

MATERIAL AND METHODS

The present systematic review was performed in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Full manuscripts from 18 studies were carefully selected in this setting.

RESULTS

A total of 15 studies demonstrated positive findings for genotoxicity in peripheral blood or oral cells in patients with pre-malignant lesions or oral cancer. In the quality assessment of studies, 1 was classified as Strong, 5 were considered as Moderate, and 12 were classified as Weak.

CONCLUSION

In summary, the comet assay can be a useful biomarker for oral carcinogenesis. However, further studies with more strict parameters are suggested (with less uncontrolled confounders) in order to increase findings reliability for diagnosis of oral potentially malignant lesions.

Application of the Fpg-modified comet assay on three-spined stickleback in freshwater biomonitoring: toward a multi-biomarker approach of genotoxicity

Aquatic species are exposed to a wide spectrum of substances, which can compromise their genomic integrity by inducing DNA damage or oxidative stress. Genotoxicity biomarkers as DNA strand breaks and chromosomal damages developed on sentinel species have already proved to be relevant in aquatic biomonitoring. However, these biomarkers do not reflect DNA oxidative lesions, i.e., the 8-oxodG, recognized as pre-mutagenic lesion if not or mis-repaired in human biomonitoring. The relevance to include the measure of these lesions by using the Fpg-modified comet assay on erythrocytes of the three-spined stickleback was investigated. An optimization step of the Fpg-modified comet assay considering enzyme buffer impact, Fpg concentration, and incubation time has been performed. Then, this measure was integrated in a battery of genotoxicity and cytotoxicity biomarkers (considering DNA strand breaks, DNA content variation, and cell apoptosis/necrosis and density) and applied in a freshwater monitoring program on six stations of the Artois Picardie watershed (3-week caging of control fish). These biomarkers allowed to discriminate the stations regarding the genotoxic potential of water bodies and specifically by the measure of oxidative DNA lesions, which seem to be a promising tool in environmental genotoxicity risk assessment.

Pleural inflammatory response, mesothelin content and DNA damage in mice at one-year after intra-pleural carbon nanotube administration

Many in vitro and in vivo studies have shown that exposure to carbon nanotubes (CNTs) is associated with inflammation, oxidative stress and genotoxicity, although there is a paucity of studies on these effects in the pleural cavity. In the present study, we investigated adverse outcomes of pleural exposure to multi-walled CNTs (MWCNT-7, NM-401 and NM-403) and single-walled CNTs (NM-411). Female C57BL/6 mice were exposed to 0.2 or 5 µg of CNTs by intra-pleural injection and sacrificed one-year post-exposure. Exposure to long and straight types of MWCNTs (i.e. MWCNT-7 and NM-401) was associated with decreased number of macrophages and increased number of neutrophils and eosinophils in pleural lavage fluid. Increased protein content in the pleural lavage fluid was also observed in mice exposed to MWCNT-7 and NM-401. The concentration of mesothelin was increased in mice exposed to MWCNT-7 and NM-411. Levels of DNA strand breaks and DNA oxidation damage, measured by the comet assay, were unaltered in cells from pleural scrape. Extra-pleural effects were seen in CNT exposed mice, including enlarged and pigmented mediastinal lymph nodes (all four types of CNTs), pericardial plaques (MWCNT-7 and NM-401), macroscopic abnormalities on the liver (MWCNT-7) and ovaries/uterus (NM-411). In conclusion, the results demonstrate that intra-pleural exposure to long and straight MWCNTs is associated with adverse outcomes. Certain observations such as increased content of mesothelin in pleural lavage fluid and ovarian/uterine abnormalities in mice exposed to NM-411 suggests that exposure to SWCNTs may also be associated with some adverse outcomes.

Long-term cryopreservation of potassium bromate positive assay controls for measurement of oxidatively damaged DNA by the Fpg-modified comet assay: results from the hCOMET ring trial

The formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay is widely used for the measurement of oxidatively generated damage to DNA. However, there has not been a recommended long-term positive control for this version of the comet assay. We have investigated potassium bromate as a positive control for the Fpg-modified comet assay because it generates many Fpg-sensitive sites with a little concurrent generation of DNA strand breaks. Eight laboratories used the same procedure for the treatment of monocytic THP-1 cells with potassium bromate (0, 0.5, 1.5, and 4.5 mM) and subsequent cryopreservation in a freezing medium consisting of 50% foetal bovine serum, 40% RPMI-1640 medium, and 10% dimethyl sulphoxide. The samples were analysed by the Fpg-modified comet assay three times over a 3-year period. All laboratories obtained a positive concentration-response relationship in cryopreserved samples (linear regression coefficients ranging from 0.79 to 0.99). However, there was a wide difference in the levels of Fpg-sensitive sites between the laboratory with the lowest (4.2% Tail DNA) and highest (74% Tail DNA) values in THP-1 cells after exposure to 4.5 mM KBrO3. In an attempt to assess sources of inter-laboratory variation in Fpg-sensitive sites, comet images from one experiment in each laboratory were forwarded to a central laboratory for visual scoring. There was high consistency between measurements of %Tail DNA values in each laboratory and the visual score of the same comets done in the central laboratory (r = 0.98, P < 0.001, linear regression). In conclusion, the results show that potassium bromate is a suitable positive comet assay control.

DNA strand break levels in cryopreserved mononuclear blood cell lines measured by the alkaline comet assay: results from the hCOMET ring trial

The comet assay is widely used in biomonitoring studies for the analysis of DNA damage in leukocytes and peripheral blood mononuclear cells. Rather than processing blood samples directly, it can be desirable to cryopreserve whole blood or isolated cells for later analysis by the comet assay. However, this creates concern about artificial accumulation of DNA damage during cryopreservation. In this study, 10 laboratories used standardized cryopreservation and thawing procedures of monocytic (THP-1) or lymphocytic (TK6) cells. Samples were cryopreserved in small aliquots in 50% foetal bovine serum, 40% cell culture medium, and 10% dimethyl sulphoxide. Subsequently, cryopreserved samples were analysed by the standard comet assay on three occasions over a 3-year period. Levels of DNA strand breaks in THP-1 cells were increased (four laboratories), unaltered (four laboratories), or decreased (two laboratories) by long-term storage. Pooled analysis indicates only a modest positive association between storage time and levels of DNA strand breaks in THP-1 cells (0.37% Tail DNA per year, 95% confidence interval: -0.05, 0.78). In contrast, DNA strand break levels were not increased by cryopreservation in TK6 cells. There was inter-laboratory variation in levels of DNA strand breaks in THP-1 cells (SD = 3.7% Tail DNA) and TK6 reference sample cells (SD = 9.4% Tail DNA), whereas the intra-laboratory residual variation was substantially smaller (i.e. SD = 0.4%-2.2% Tail DNA in laboratories with the smallest and largest variation). In conclusion, the study shows that accumulation of DNA strand breaks in cryopreserved mononuclear blood cell lines is not a matter of concern.

Inter-laboratory variation in measurement of DNA damage by the alkaline comet assay in the hCOMET ring trial

The comet assay is a simple and versatile method for measurement of DNA damage in eukaryotic cells. More specifically, the assay detects DNA migration from agarose gel-embedded nucleoids, which depends on assay conditions and the level of DNA damage. Certain steps in the comet assay procedure have substantial impact on the magnitude of DNA migration (e.g. electric potential and time of electrophoresis). Inter-laboratory variation in DNA migration levels occurs because there is no agreement on optimal assay conditions or suitable assay controls. The purpose of the hCOMET ring trial was to test potassium bromate (KBrO3) as a positive control for the formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay. To this end, participating laboratories used semi-standardized protocols for cell culture (i.e. cell culture, KBrO3 exposure, and cryopreservation of cells) and comet assay procedures, whereas the data acquisition was not standardized (i.e. staining of comets and image analysis). Segregation of the total variation into partial standard deviation (SD) in % Tail DNA units indicates the importance of cell culture procedures (SD = 10.9), comet assay procedures (SD = 12.3), staining (SD = 7.9) and image analysis (SD = 0.5) on the overall inter-laboratory variation of DNA migration (SD = 18.2). Future studies should assess sources of variation in each of these steps. On the positive side, the hCOMET ring trial demonstrates that KBrO3 is a robust positive control for the Fpg-modified comet assay. In conclusion, the hCOMET ring trial has demonstrated a high reproducibility of detecting genotoxic effects by the comet assay, but inter-laboratory variation of DNA migration levels is a concern.

Visual comet scoring revisited: a guide to scoring comet assay slides and obtaining reliable results

Measurement of DNA migration in the comet assay can be done by image analysis or visual scoring. The latter accounts for 20%-25% of the published comet assay results. Here we assess the intra- and inter-investigator variability in visual scoring of comets. We include three training sets of comet images, which can be used as reference for researchers who wish to use visual scoring of comets. Investigators in 11 different laboratories scored the comet images using a five-class scoring system. There is inter-investigator variation in the three training sets of comets (i.e. coefficient of variation (CV) = 9.7%, 19.8%, and 15.2% in training sets I-III, respectively). However, there is also a positive correlation of inter-investigator scoring in the three training sets (r = 0.60). Overall, 36% of the variation is attributed to inter-investigator variation and 64% stems from intra-investigator variation in scoring between comets (i.e. the comets in training sets I-III look slightly different and this gives rise to heterogeneity in scoring). Intra-investigator variation in scoring was also assessed by repeated analysis of the training sets by the same investigator. There was larger variation when the training sets were scored over a period of six months (CV = 5.9%-9.6%) as compared to 1 week (CV = 1.3%-6.1%). A subsequent study revealed a high inter-investigator variation when premade slides, prepared in a central laboratory, were stained and scored by investigators in different laboratories (CV = 105% and 18%-20% in premade slides with comets from unexposed and hydrogen peroxide-exposed cells, respectively). The results indicate that further standardization of visual scoring is desirable. Nevertheless, the analysis demonstrates that visual scoring is a reliable way of analysing DNA migration in comets.

Gaining insight into genotoxicity with the comet assay in inhomogenoeous exposure scenarios: The effects of tritiated steel and cement particles on human lung cells in an inhalation perspective

The comet assay was recently applied for the first time to test the genotoxicity of micrometric stainless steel and cement particles, representative of those produced in the dismantling of nuclear power plants. A large dataset was obtained from in vitro exposure of BEAS-2B lung cells to different concentrations of hydrogenated (non-radiative control) and tritiated particles, to assess the impact of accidental inhalation. Starting from the distributions of the number of nuclei scored at different extent of DNA damage (% tail DNA values), we propose a new comet data treatment designed to consider the inhomogeneity of the action of such particles. Indeed, due to particle behavior in biological media and concentration, a large fraction of cells remains undamaged, and standard averaging of genotoxicity indicators leads to a misinterpretation of experimental results. The analysis we propose reaches the following goals: genotoxicity in human lung cells is assessed for stainless steel and cement microparticles; the role of radiative damage due to tritium is disentangled from particulate stress; the fraction of damaged cells and their average level of DNA damage are assessed separately, which is essential for carcinogenesis implications and sets the basis for a better-informed risk management for human exposure to radioactive particles.

In vitro evaluation of the cytotoxic and genotoxic effects of Al and Mn in ambient concentrations detected in groundwater intended for human consumption

Environmental exposure to metals can induce cytotoxic and genotoxic effects in cells and affect the health of the exposed population. To investigate the effects of aluminum (Al) and manganese (Mn), we evaluated their cytogenotoxicity using peripheral blood mononuclear cells (PBMCs) exposed to these metals at previously quantified concentrations in groundwater intended for human consumption. The cell viability, membrane integrity, nuclear division index (NDI), oxidative stress, cell death, cell cycle, and DNA damage were analyzed in PBMCs exposed to Al (0.2, 0.6, and 0.8 mg/L) and Mn (0.1, 0.3, 1.0, and 1.5 for 48 h. We found that Al induced late apoptosis; decreased cell viability, NDI, membrane integrity; and increased DNA damage. However, no significant alterations in the early apoptosis, cell cycle, and reactive oxygen species levels were observed. In contrast, exposure to Mn altered all evaluated parameters related to cytogenotoxicity. Our data show that even concentrations allowed by the Brazilian legislation for Al and Mn in groundwater intended for human consumption cause cytotoxic and genotoxic effects in PBMCs. Therefore, in view of the results found, a comprehensive approach through in vivo investigations is needed to give robustness and validity to the results obtained, thus broadening the understanding of the impacts of metals on the health of environmentally exposed people.