Influence of ozonation and UV/H2O2 on the genotoxicity of secondary wastewater effluents

The implementation of novel wastewater treatment technologies, including Advanced Oxidation Processes (AOPs) such as ozonation and ultraviolet radiation (UV) combined with hydrogen peroxide (H2O2), can be a promising strategy for enhancing the quality of these effluents. However, during effluent oxidation AOPs may produce toxic compounds that can compromise the water reuse and the receiving water body. Given this possibility, the aim of this study was to evaluate the genotoxic potential of secondary effluents from two different Wastewater Treatment Plants (WWTP) that were subjected to ozonation or UV/H2O2 for periods of 20 (T1) and 40 (T2) minutes. The genotoxic potential was carried out with the Comet assay (for clastogenic damage) and the Micronucleus assay (for clastogenic and aneugenic damage) in HepG2/C3A cell culture (metabolizing cell line). The results of the comet assay revealed a significant increase in tail intensity in the Municipal WWTP (dry period) effluents treated with UV/H2O2 (T1 and T2). MN occurrence was noted across all treatments in both Pilot and Municipal WWTP (dry period) effluents, whereas nuclear buds (NBs) were noted for all Pilot WWTP treatments and UV/H2O2 treatments of Municipal WWTP (dry period). Moreover, the UV/H2O2 (T1) treatment of Municipal WWTP (dry period) exhibited a noteworthy incidence of multiple alterations per cell (MN + NBs). These findings imply that UV/H2O2 treatment demonstrates higher genotoxic potential compared to ozonation. Furthermore, seasonal variations can have an impact on the genotoxicity of the samples. Results of the study emphasize the importance of conducting genotoxicological tests using human cell cultures, such as HepG2/C3A, to assess the final effluent quality from WWTP before its discharge or reuse. This precaution is essential to safeguard the integrity of the receiving water body and, by extension, the biotic components it contains.

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.

Guidance for the use and interpretation of assays for monitoring anti-genotoxicity

Since DNA damage can occur spontaneously or be produced by the environmental genotoxins in living cells, it is important to investigate compounds that can reverse or protect DNA damage. An appropriate methodology is essential for the responsive identification of protection offered against DNA damage. This review includes information on the current state of knowledge on prokaryotic cell-based assays (SOS chromotest, umu test, vitotox assay) and cytogenetic techniques (micronucleus assay, chromosome aberration test and sister chromatid exchange assay) with an emphasis on the possibility to explore genoprotective compounds. Throughout the last decade, studies have extrapolated the scientific methodologies utilized for genotoxicity to assess genoprotective compounds. Therefore, shortcomings of genotoxicity studies are also mirrored in antigenotoxicity studies. While regulatory authorities around the world (OECD, US-EPA and ICH) continue to update diverse genotoxic assay strategies, there are still no clear guidelines/approaches for efficient experimental design to screen genoprotective compounds. As a consequence, non-synergetic and inconsistent implementation of the test method by the researchers to execute such simulations has been adopted, which inevitably results in unreliable findings. The review has made the first attempt to collect various facets of experimentally verified approaches for evaluating genoprotective compounds, as well as to acknowledge potential significance and constraints, and further focus on the assessment of end points which are required to validate such action. Henceforth, the review makes an incredible commitment by permitting readers to equate several components of their test arrangement with the provided simplified information, allowing the selection of convenient technique for the predefined compound from a central repository.

Evaluation of cyto-genotoxicity biomarkers, changes in histology and antioxidant defense system of Oreochromis niloticus induced by the industrial effluents

Aquatic pollution mainly by industrial effluents has been a major concern since a few decades. The current study evaluated cyto-genotoxicity of industrial effluents on Oreochromis niloticus exposed to sublethal levels by hematotoxicity, blood biochemistry analysis, micronucleus assay, antioxidants and cerebral toxicity. The significant elevation in differential leukocytes of exposed fish was indicative of infections and compromised immune system. The acute and chronic industrial effluent exposure caused significant decline in aspartame transaminase (AST) and alanine transaminase (ALT) and renal function enzymes. Necrosis, hyperplastic growth, hypertrophy and toxicant accumulation exhibited cerebral toxicity potential of industrial toxicants. A significant decrease in antioxidants, GSH, SOD and catalase (0.14, 0.66 and 1549 unit/mg protein) in chronic exposure group in comparison to 0.18, 2.83, 7680 and 6200.8 values of GSH, SOD, GPx and CAT, respectively. Results showed that acute and chronic industrial effluent exposure caused genotoxicity with higher frequencies of formation of micronuclei and cytokaryotic fusion.

Exposure to nanoplastic particles and DNA damage in mammalian cells

There is concern about human exposure to nanoplastics from intentional use or degradation of plastics in the environment. This review assesses genotoxic effects of nanoplastics, defined as particles with a primary size of less than 1000 nm. The majority of results on genotoxicity come from studies on polystyrene (PS) particles in mammalian cell cultures. Most studies have measured DNA strand breaks (standard comet assay), oxidatively damaged DNA (Fpg-modified comet assay) and micronuclei. Twenty-nine out of 60 results have shown statistically significant genotoxic effects by PS exposure in cell cultures. A statistical analysis indicates that especially modified PS particles are genotoxic (odds ratio = 8.6, 95 % CI: 1.6, 46) and immune cells seems to be more sensitive to genotoxicity than other cell types such as epithelial cells (odds ratio = 8.0, 95 % CI: 1.6, 39). On the contrary, there is not a clear association between statistically significant effects in genotoxicity tests and the primary size of PS particles, (i.e. smaller versus larger than 100 nm) or between the type of genotoxic endpoint (i.e. repairable versus permanent DNA lesions). Three studies of PS particle exposure in animals have shown increased level of DNA strand breaks in leukocytes and prefrontal cortex cells. Nanoplastics from polyethylene, propylene, polyvinyl chloride and polyethylene terephthalate have been investigated in very few studies and it is currently not possible to draw conclusion about their genotoxic hazard. In summary, there is some evidence suggesting that PS particles may be genotoxic in mammalian cells.

Impact of DNA repair polymorphisms on DNA instability biomarkers induced by lead (Pb) in workers exposed to the metal

Although the mechanisms of Pb-induced genotoxicity are well established, a wide individual's variation response is seen in biomarkers related to Pb toxicity, despite similar levels of metal exposure. This may be related to intrinsic variations, such as genetic polymorphisms; moreover, very little is known about the impact of genetic variations related to DNA repair system on DNA instability induced by Pb. In this context, the present study aimed to assess the impact of SNPs in enzymes related to DNA repair system on biomarkers related to acute toxicity and DNA damage induced by Pb exposure, in individuals occupationally exposed to the metal. A cross-sectional study was run with 154 adults (males, >18 years) from an automotive batteries' factory, in Brazil. Blood lead levels (BLL) were determined by ICP-MS; biomarkers related to acute toxicity and DNA instability were monitored by the buccal micronucleus cytome (BMNCyt) assay and genotyping of polymorphisms of MLH1 (rs1799977), OGG1 (rs1052133), PARP1 (rs1136410), XPA (rs1800975), XPC (rs2228000) and XRCC1 (rs25487) were performed by TaqMan assays. BLL ranged from 2.0 to 51 μg dL^-1 (mean 20 ± 12 μg dL^-1) and significant associations between BLL and BMNCyt biomarkers related to cellular proliferation and cytokinetic, cell death and DNA damage were observed. Furthermore, SNPs from the OGG1, XPA and XPC genes were able to modulate interactions in nuclear bud formation (NBUDs) and micronucleus (MNi) events. Taken together, our data provide further evidence that polymorphisms related to DNA repair pathways may modulate Pb-induced DNA damage; studies that investigate the association between injuries to genetic material and susceptibilities in the workplace can provide additional information on the etiology of diseases and the determination of environmentally responsive genes.

Toxicogenic effects of the mushroom Ganoderma lucidum on human liver and kidney tumor cells and peripheral blood lymphocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Ganoderma lucidum (Curtis) P. Karst., a bioactive mushroom with medicinal properties, is known to exert immunomodulatory, anti-inflammatory, hypocholesterolemic, hypoglycemic, and hepatoprotective effects.

AIM OF THE STUDY

In this study, the effects of the G. lucidum fruiting body dry extract (GLE) on human liver (HepG2/C3A) and kidney (786-O) tumor cells and peripheral blood lymphocytes were evaluated.

MATERIALS AND METHODS

MTT-based cytotoxicity, trypan blue-based cell viability, comet, and cytokinesis-block micronucleus cytome assays were performed, and the production of reactive oxygen species was evaluated in vitro.

RESULTS

GLE was toxic to the tumor cells, decreasing their viability by increasing their production of reactive oxygen species and inducing damage to their DNA. By contrast, only high concentrations of GLE were toxic to lymphocytes and decreased their viability, whereas low concentrations increased lymphocyte viability. Moreover, primary DNA damage was induced by GLE only at the highest concentration tested.

CONCLUSIONS

G. lucidum shows potential antitumor effects against cancerous kidney and liver cells, exhibiting cytotoxic and genotoxic activity at low concentrations, whereas the same effects in lymphocytes are mediated only at high concentrations. This mushroom has the potential to be biotechnologically developed into a therapeutic agent for diseases, such as cancer.

High-throughput micronucleus assay using three-dimensional HepaRG spheroids for in vitro genotoxicity testing

The in vitro micronucleus (MN) assay is a component of most test batteries used in assessing potential genotoxicity. Our previous study adapted metabolically competent HepaRG cells to the high-throughput (HT) flow-cytometry-based MN assay for genotoxicity assessment (Guo et al. in J Toxicol Environ Health A 83:702-717, 2020b, https://doi.org/10.1080/15287394.2020.1822972 ). We also demonstrated that, compared to HepaRG cells grown as two-dimensional (2D) cultures, 3D HepaRG spheroids have increased metabolic capacity and improved sensitivity in detecting DNA damage induced by genotoxicants using the comet assay (Seo et al. in ALTEX 39:583-604, 2022, https://doi.org/10.14573/altex.22011212022 ). In the present study, we have compared the performance of the HT flow-cytometry-based MN assay in HepaRG spheroids and 2D HepaRG cells by testing 34 compounds, including 19 genotoxicants or carcinogens and 15 compounds that show different genotoxic responses in vitro and in vivo. 2D HepaRG cells and spheroids were exposed to the test compounds for 24 h, followed by an additional 3- or 6-day incubation with human epidermal growth factor to stimulate cell division. The results demonstrated that HepaRG spheroids showed generally higher sensitivity in detecting several indirect-acting genotoxicants (require metabolic activation) compared to 2D cultures, with 7,12-dimethylbenzanthracene and N-nitrosodimethylamine inducing higher % MN formation along with having significantly lower benchmark dose values for MN induction in 3D spheroids. These data suggest that 3D HepaRG spheroids can be adapted to the HT flow-cytometry-based MN assay for genotoxicity testing. Our findings also indicate that integration of the MN and comet assays improved the sensitivity for detecting genotoxicants that require metabolic activation. These results suggest that HepaRG spheroids may contribute to New Approach Methodologies for genotoxicity assessment.

Is micronucleus assay a suitable method for biomonitoring children exposed to X-ray? A systematic review with meta-analysis

PURPOSE

The aim of this study was to evaluate if the micronucleus test using oral epithelial cells is a suitable biomarker for biomonitoring children exposed to X-ray.

MATERIAL AND METHODS

A search was performed through the electronic databases PubMed/Medline, Scopus, and Web of Science, all studies published up to February 2022 that examined the relationship between exposure of children to radiographic examinations and micronucleus.

RESULTS

A total of 17 full-text manuscripts were screened for eligibility. Only two studies found a difference in micronucleus labeling. On the other hand, all studies showed that X-ray was able to induce cellular death in oral mucosa cells. Following the parameters of the Effective Practices in Public Health Project (EPHPP), five manuscripts reached moderate and strong scores, and four studies were categorized as weak at final rating. In the meta-analysis, statistically significant difference was detected in micronucleated cells in children before and after radiographic examinations (SMD = 0.96, 95% CI, 0.07-1.84, p = .04), with τ2=1.09; χ2=53.37, and p < .001.

CONCLUSION

Radiographic examinations in children can cause genotoxic and cytotoxic damage in the oral epithelium with a large effect size.

Genotoxic effects of particulate matter on larvae of a common and widespread butterfly along an urbanization gradient

Biodiversity is currently declining worldwide. Several threats have been identified such as habitat loss and climate change. It is unknown if and how air pollution can work in addition or in synergy to these threats, contributing to the decline of current species and/or local extinction. Few studies have investigated the effects of particulate matter (PM), the main component of air pollution, on insects, and no studies have investigated its genotoxic effects through Micronucleus assay. Butterflies play an important role in the environment, as herbivores during larval stages, and as pollinators as adults. The aim of this study was to evaluate the genotoxic effects of PM₁₀ from different sites along a gradient of population urbanization, on a common cabbage butterfly species (Pieris brassicae). PM₁₀ was collected from April to September in an urban (Turin, Italy), a suburban (Druento, Italy) and a mountain site (Ceresole Reale, Italy) with different urbanization levels. P. brassicae larvae (n = 218) were reared in the laboratory under controlled conditions (26 °C, L:D 15:9) on cabbage plants (average 9.2 days), and they were exposed to PM₁₀ organic extracts (20 and 40 m³/mL) or dimethyl sulfoxide (controls) through vaporization. After exposure, larvae were dissected and cells were used for the Micronucleus (MN) assay. Results showed that all PM extracts induced significant DNA damage in exposed larvae compared to controls, and that increasing the PM dose (from 20 to 40 m³/mL) increased genotoxic effects. However, we did not detect any significant differences between sites with different urbanization levels. In conclusion, PM at different concentrations induced genotoxic effects on larvae of a common butterfly species. More alarmingly, PM could work in addition to and/or in synergy with other compounds (e.g. pesticides) and, especially on species already threatened by other factors (e.g. fragmentation), thus affecting the vitality of populations, leading to local extinctions.

PEGylation of genistein-loaded bovine serum albumin nanoparticles and its effect on in vitro cell viability and genotoxicity properties

Self-assembled bovine serum albumin nanoparticles loaded with the isoflavone genistein have shown apoptosis-mediated cytotoxicity against murine mammary adenocarcinoma F3II cells. Due to their protein nature and small particle size (13-15 nm), their parenteral administration could be affected by possible immunogenic reactions and rapid clearance from the bloodstream. To avoid these problems, PEGylation of the systems was achieved in this work by using a 30 kDa methoxy-polyethylene glycol carbonyl imidazole derivative through the reaction between the carbonyl imidazole group and the amino groups of Lys residues on the protein surface, which was confirmed by a 17% reduction in the available amino groups content measured by the o-phthaldialdehyde method. PEGylated isoforms were obtained, showing an increase of particle size from 13 to 15 nm to around 260 nm, and were purified by SEC-FPLC and characterized by SDS-PAGE, DLS and AFM techniques. The effect of PEGylation on BSAnp-Gen cytotoxicity and genotoxicity against F3II cells was evaluated in vitro by MTT assay, flow cytometry analysis and micronucleus assay. From the results, PEGylation produced an improvement of the biological properties of genistein-loaded nanoparticles in terms of cytotoxicity (lower IC₅₀), not affecting the induction of apoptosis, decreasing the genotoxicity of the systems (less induction of micronucleus formation).

Evaluation of genetic instability, oxidative stress, and metabolism-related gene polymorphisms in workers exposed to waste anesthetic gases

Professionals who work in operating rooms (ORs) may be exposed daily to waste anesthetic gases (WAGs) due to the use of inhalational anesthetics. Considering the controversial findings related to genetic damage and redox status in addition to a lack of knowledge about the effect of polymorphisms in genes related to phase I and II detoxification upon occupational exposure to WAGs, this cross-sectional study is the first to jointly evaluate biomarkers of genetic instability, oxidative stress, and susceptibility genes in professionals occupationally exposed to high trace amounts of halogenated (≥ 7 ppm) and nitrous oxide (165 ppm) anesthetics in ORs and in individuals not exposed to WAGs (control group). Elevated rates of buccal micronucleus (MN) and nuclear bud (NBUD) were observed in the exposure group and in professionals exposed aged more than 30 years. Exposed males showed a higher antioxidant capacity, as determined by the ferric reducing antioxidant power (FRAP), than exposed females; exposed females had higher frequencies of MN and NBUD than nonexposed females. Genetic instability (MN) was observed in professionals with greater weekly WAG exposure, and those exposed for longer durations (years) exhibited oxidative stress (increased lipid peroxidation and decreased FRAP). Polymorphisms in metabolic genes (cytochrome P450 2E1 (CYP2E1) and glutathione S-transferases (GSTs)) did not exert an effect, except for the effects of the GSTP1 (rs1695) AG/GG polymorphism on FRAP (both groups) and GSTP1 AG/GG and GSTT1 null polymorphisms, which were associated with greater FRAP values in exposed males. Minimizing WAG exposure is necessary to reduce impacts on healthcare workers.

Determination of potential thresholds for N-ethyl-N-nitrosourea and ethyl methanesulfonate based on a multi-endpoint genotoxicity assessment platform in rats

The main goal of the study was to investigate the genotoxic response of N-ethyl-N-nitrosourea (ENU) and ethyl methanesulfonate (EMS) at low doses in a multi-endpoint genotoxicity assessment platform in rats and to derive potential thresholds and related metrics. Male Sprague-Dawley rats were treated by daily oral gavage for 28 consecutive days with ENU (0.25 ~ 8 mg/kg bw) and EMS (5 ~ 160 mg/kg bw), both with six closely spaced dose levels. Pig-a gene mutation assay, micronucleus test, and comet assay were performed in several timepoints. Then, the dose-response relationships were analyzed for possible points of departure (PoD) using the no observed genotoxic effect level and benchmark dose (BMD) protocols with different critical effect sizes (CES, 0.05, 0.1, 0.5, and 1SD). Overall, dose-dependent increases in all investigated endpoints were found for ENU and EMS. PoDs varied across genetic endpoints, timepoints, and statistical methods, and selecting an appropriate lower 95% confidence limit of BMD needs a comprehensive consideration of the mode of action of chemicals, the characteristics of tests, and the model fitting methods. Under the experimental conditions, the PoDs of ENU and EMS were 0.0036 mg/kg bw and 1.7 mg/kg bw, respectively.

Is micronucleus assay in oral exfoliated cells a useful biomarker for biomonitoring populations exposed to pesticides? A systematic review with meta-analysis

The systematic review (SR) with meta-analysis aimed to infer if micronucleus assay using oral mucosal cells a useful biomarker for biomonitoring populations continuously exposed to pesticides (EP). The SR has been made in accordance with the PRISMA-P guidelines. The PICOS strategy has focused to answer the following question: "Does exposure to pesticides cause genetic damage in oral cells?" The literature search was made in the following scientific databases: Web of Science, PubMed/Medline, and Scopus. The approach was defined as follows: standardized mean difference (SMD) and 95% confidence intervals (CI). The quality assessment of manuscripts was obtained by the EPHPP (Effective Public Health Practice Project). The GRADE tool was chosen for assessing the quality of evidence. A total of 108 articles were selected in this setting. After screening abstracts and titles, 23 manuscripts were evaluated for eligibility. After reviewing the studies, two were considered weak and 22 were classified as moderate or strong. The meta-analysis data pointed out statistically significant differences in volunteers exposed to EP (SMD = 1.23, 95% CI, 0.69 to 1.77, p < 0.001), with a Tau2 = 1.44; Chi2 = 566.38, and p < 0.001, so that the selected manuscripts were considered heterogeneous and the I2 of 97% indicated high heterogeneity. Taken together, this review was able to validate the micronucleus assay in oral exfoliated cells as a useful biomarker in individuals continuously exposed to EP because the studies categorized as moderate and strong have demonstrated positive response related to mutagenesis.

Susceptibility to chromosome instability and occurrence of the regular form of Down syndrome in young couples

Although the risk of pregnancy with Down syndrome (DS) increases with age, conceptions with trisomy 21 can occur in mothers aged 35 or less. The micronucleus test on peripheral blood lymphocytes is a well-recognized method for studying chromosomal instability. The aim of this study was to evaluate the application of the micronucleus assay and fluorescence in situ hybridization (FISH) for estimation of chromosome instability and occurrence of trisomy 21 in young parents having pregnancy or a child with the regular form of Down syndrome. The study included 54 parents (27 couples) who had previous pregnancy with trisomy 21 at age 35 or less. The control group consisted of 30 couples with two healthy children and no previous spontaneous abortions. Parents with trisomy 21 pregnancy had significantly higher frequencies of micronuclei in binucleated cells. There was no statistically significant difference between the study and control groups in the frequencies of micronuclei in mononuclear cells, nuclear buds, or nucleoplasmic bridges. FISH analysis showed higher percentages of micronuclei containing whole chromosomes as well as statistically significant higher numbers of micronuclei containing chromosome 21 in the peripheral blood of DS parents. There was no statistically significant difference between the two groups in the responses of peripheral blood lymphocytes to treatment with the mutagen mitomycin C. Our results suggest that young parents with a history of the regular form of Down syndrome have a higher susceptibility to chromosome nondisjunction in peripheral blood lymphocytes. The micronucleus assay showed high specificity, but moderate sensitivity, for risk assessment of trisomy 21 pregnancy.

The effect of aging on the repeated-dose liver micronucleus assay using diethylnitrosamine

Background

The repeated-dose liver micronucleus (RDLMN) assay has been well-developed and applied because of its simplicity and the ease of integration into general toxicity studies which is the preferred method from the 3R’s point of view. In this assay, we observed micronucleated hepatocytes which accumulated during a rather long-term dosing period. When considering integration into general toxicity studies, the effects of age of the animals used in the micronucleus assay becomes a major issue. The effect of age on the micronucleus induction rate has been reported in bone marrow micronucleus assays, and it is considered that the decrease in cell proliferation rate due to aging is the cause of the decrease in sensitivity. A decrease in sensitivity due to aging was also reported in a liver micronucleus assay using clofibrate and the cause is considered to be a decrease in hepatocyte proliferation activity due to aging. However, no actual decrease in hepatocyte proliferation rate due to aging has been reported. In addition, there are no reports, so far, on whether similar effects of aging appear when other substances were administered. To investigate the effects of aging in the RDLMN assay, this study focused on the effects of 14-day repeated administration of DEN, a well-known genotoxic hepatocarcinogen with the hepatocyte toxicity which should cause an elevation of cell proliferation rate as a reflective regeneration.

Results

The liver micronuclei induced by DEN were equivalent between the two age groups (i.e., six and eight weeks of age at the start of dosing). In the histopathological examination for the liver, single cell necrosis, karyomegaly, and increased mitosis were observed in the hepatocytes, and the frequency and severity were increased dose-dependently. Ki-67 immunohistochemical analysis which can detect all cells in the cell cycle other than those in the G0 phase revealed dose-dependent increase of cell proliferation activity, and the difference between ages was not observed.

Conclusion

The effect of aging on the RDLMN assay could not be recognized when DEN was administered for 14 days in rats. Meanwhile, it was supported by the histopathological examination and Ki-67 immunohistochemical analysis that such an effect of aging was masked by the compensatory hepatocyte proliferation which was induced by the hepatocyte toxicity of DEN.

Cytogenetic Biomonitoring in Buccal Mucosa Cells from Seaport Dockers

BACKGROUND/AIM

Dockers of seaport working as stevedores are self-employed workers who carry out arduous and dangerous activities. To date, few studies have investigated the human health risks in these professionals. The aim of this study was to evaluate cytogenetic damage in oral cells of dockers of seaports working as stevedores by micronucleus assay in buccal cells.

PATIENTS AND METHODS

For this study, a total of 26 seaport dockers working as stevedores aged 51.2±8.4 years (all men) were included in this study. All volunteers had worked for at least 3 years. The control group consisted of 25 participants aged 55.2±9.9 years (all men), who did not work in the Port of Santos city.

RESULTS

The results showed statistically significant differences (p<0.05) of micronucleated cells in buccal mucosa cells of seaport dockers. Pyknosis, karyolysis and karrhyorexis did not show statistically significant differences (p>0.05) between groups.

CONCLUSION

The results of the present study suggest that seaport dockers present mutagenicity in oral cells.

The chemical structure impairs the intensity of genotoxic effects promoted by 1,2-unsaturated pyrrolizidine alkaloids in vitro

1,2-unsaturated pyrrolizidine alkaloids (PAs) represent a large group of secondary plant metabolites exhibiting hepatotoxic, genotoxic, and carcinogenic properties upon bioactivation. To examine how the degree of esterification affects the genotoxic profile of PA we investigated cytotoxicity, histone H2AX phosphorylation, DNA strand break induction, cell cycle perturbation, micronuclei formation, and aneugenic effects in different cell models. Analysis of cytotoxicity and phosphorylation of histone H2AX was structure- and concentration-dependent: diester-type PAs (except monocrotaline) showed more pronounced effects than monoester-type PAs. Cell cycle analysis identified that diester-type PAs induced a S-phase arrest and a decrease in the occurrence of cells in the G1-phase. The same structure-dependency was observed by flow-cytometric analysis of PA-induced micronuclei in CYP3A4-overexpressing V79 cells. Analysis of centromeres induced by lasiocarpine in the micronuclei by fluorescence in situ hybridization indicated an aneugenic effect in V79_h3A4 cells. Comet assays revealed no significant induction of DNA strand breaks for all investigated PAs. Overall, diester-type PAs induced more pronounced effects than monoester-type PAs. Furthermore, our results indicate aneugenic effects upon exposure towards lasiocarpine in vitro. These data improve our understanding how structural features of PA influence the genotoxic profile. Especially, the monoester-type PAs seem to induce less severe effects than other PAs.

Assessment of the mutagenic potential of the water of an urban river by means of two Tradescantia-based test systems

River pollution can be caused by anthropogenic or natural factors. When testing water quality for the presence of toxic substances, higher plants as bioindicators for the genotoxic effects of complex mixtures are effective and appropriate. Hence, in this work the Tradescantia (clone 02) stamen hair mutations (Trad-SHM) and Tradescantia micronuclei (Trad-MCN) were used to determine mutagenic and clastogenic potential of an urban river. A significant increase in the level of all studied endpoints as well as morphological changes, including pink cells (PC) and colorless cells (CC) in stamen hairs, stunted hairs (SH), tetrads with micronuclei (MN) and MN in tetrads of pollen microspores in the Tradescantia was observed compared to the negative control (tap water). As an example riverine system, part of the River Hrazdan (Armenia) flowing through a highly urbanized and industrial area was studied. The positive control (10 mM CrO₃) showed the highest genotoxicity for the SHM assay (PC: 5.1 / 1000, CC: 17.9 / 1000) and for the MCN assay (12 MN / 100 tetrads and 9.4 ± 0.53 tetrads with MN). Genetic responses were analyzed in conjunction with the concentrations of select elements in the riverine water. Reasons for observing such a high level of genetic markers in the riverine water and applicability of the Tradescantia (clone 02) test-systems in environmental risk assessment and biomonitoring are discussed.

Detection of hepatocarcinogens by combination of liver micronucleus assay and histopathological examination in 2-week or 4-week repeated dose studies

Background

Currently, revisions to the ICH S1 guidance on rodent carcinogenicity testing are being proposed. Application of this approach would reduce the use of animals in accordance with the 3Rs principles (reduce/refine/replace). The method would also shift resources to focus on more scientific mechanism-based carcinogenicity assessments and promote safe and ethical development of new small molecule pharmaceuticals. In the revised draft, findings such as cellular hypertrophy, diffuse and/or focal cellular hyperplasia, persistent tissue injury and/or chronic inflammation, preneoplastic changes, and tumors are listed as histopathology findings of particular interest for identifying carcinogenic potential. In order to predict hepatocarcinogenicity of test chemicals based on the results from 2- or 4-week repeated dose studies, we retrospectively reanalyzed the results of a previous collaborative study on the liver micronucleus assay. We focused on liver micronucleus induction in combination with histopathological changes including hypertrophy, proliferation of oval cells or bile duct epithelial cells, tissue injuries, regenerative changes, and inflammatory changes as the early responses of hepatocarcinogenesis. For these early responses, A total of 20 carcinogens, including 14 genotoxic hepatocarcinogens (Group A) and 6 non-liver-targeted genotoxic carcinogens (Group B) were evaluated.

Results

In the Group A chemicals, 5 chemicals (NPYR, MDA, NDPA, 2,6-DNT, and NMOR) showed all of the 6 early responses in hepatocarcinogenesis. Five chemicals (DMN, 2,4-DNT, QUN, 2-AAF, and TAA) showed 4 responses, and 4 chemicals (DAB, 2-NP, MCT, and Sudan I) showed 3 responses. All chemicals exhibited at least 3 early responses.

Contrarily, in the Group B chemicals (6 chemicals), 3 of the 6 early responses were observed in 1 chemical (MNNG). No more than two responses were observed in 3 chemicals (MMC, MMS, and KA), and no responses were observed in 2 chemicals (CP and KBrO3).

Conclusion

Evaluation of liver micronucleus induction in combination with histopathological examination is useful for detecting hepatocarcinogens. This assay takes much less time than routine long-term carcinogenicity studies.

Is micronucleus assay in oral exfoliated cells a suitable tool for biomonitoring children exposed to environmental pollutants? A systematic review

The aim of this review was to evaluate if micronucleus assay in oral exfoliated cells is a suitable tool for biomonitoring children exposed to environmental pollutants. Through the electronic databases PubMed/Medline, Scopus, and Web of Science, all published studies until April 2021 that examined the relationship between exposure to environmental pollutants and micronucleus frequency in oral cells were searched. All relevant articles using a combination of the following keywords-"children," "micronucleus," "oral cells," and "environmental pollution"-were considered. A total of 20 papers met the criteria for inclusion in the systematic review. The results regarding the cytogenetic damage induced by environmental pollutants are conflicting. Some authors have demonstrated that environmental pollution induces mutagenesis in oral cells while others did not. Following the parameters of the Project for Effective Public Health Practices (EPHPP) and after extensive reading of all the articles included, a total of 12 articles had moderate and strong scores and 8 had a classification considered weak. Taken together, this review was able to demonstrate the association between micronucleus frequency and exposure to environmental pollutants in oral exfoliated cells of children.

Cytogenetic Biomonitoring in Buccal Mucosa Cells of COVID-19 Patients: Preliminary Findings

BACKGROUND/AIM

COVID-19 may lead to progressive respiratory failure as a consequence of alveolar damage, resulting in death. The aim of this study was to evaluate cytogenetic damage in oral cells of COVID-19 patients by micronucleus assay.

PATIENTS AND METHODS

A total of 11 COVID-19 patients aged 40.7±9.3 years (5 men and 6 women) were included in this study. For the control group, a total of 15 participants not infected with SARS-CoV-2 virus were included. The mean age was 41.6±6.2 years (5 men and 10 women).

RESULTS

The results showed statistically significant differences (p<0.05) in micronucleated buccal mucosa cells of COVID-19 patients. In addittion, a statistically significant increase in karyolysis and karrhyorexis (p<0.05) was observed in COVID-19 patients compared to control.

CONCLUSION

SARS-CoV-2 virus can induce mutagenesis and cytotoxicity in oral cells.

Appropriate in vivo follow-up assays to an in vitro bacterial reverse mutation (Ames) test positive investigational drug candidate (active pharmaceutical ingredient), drug-related metabolite, or drug-related impurity

Kirkland et al. [Mutation Research/Genetic Toxicology and Environmental Mutagenesis 847 (2019) 403035, https://doi.org/10.1016/j.mrgentox.2019.03.008; Mutation Research/Genetic Toxicology and Environmental Mutagenesis 839 (2019): 21-35, https://doi.org/10.1016/j.mrgentox.2019.01.007] made recommendations on the use of the in vivo comet and transgenic rodent (TGR) gene mutation assays to screen for in vivo mutagenicity. Although it is not directly stated in either of these publications, we are concerned that the reports could potentially be used to support assertions that it is equally acceptable to follow up a positive bacterial reverse mutation (Ames) finding for an investigational drug with either the in vivo TGR mutation assay or an in vivo comet assay. For regulatory genotoxicity assessment, the in vivo follow-up for an in vitro bacterial mutation-positive drug, drug-related metabolite, or impurity should be based upon evaluating a similar endpoint (i.e., mutagenicity) as the intent is to determine if the findings of in vitro gene mutation correlate with findings of in vivo gene mutation (i.e., biologically relevant to the in vitro results). Thus, the most scientifically appropriate in vivo assays would be the TGR mutation assay or, in some circumstances, the in vivo Pig-a assay. An in vivo rodent comet assay or combination of the in vivo micronucleus and in vivo rodent comet assays would generally not be an appropriate follow-up test.

From environmental bioavailability of metal(loid)s to their ecogenotoxicological effects in land snails

To date, no study has linked the environmental and the ecogenotoxicological bioavailability of contaminants to land snails. Yet, understanding the specific ecotoxicological mechanisms from bioaccumulation to genotoxicity is necessary e.g., to build an adverse outcome pathway relevant to risk assessment. Consequently, the aim of our study is to look for relationships between accumulated concentrations of As, Cd and Hg in sub-adult snails and ecotoxicological effects at the individual (survival and growth) and molecular (genomic stability) levels. This study combines random amplified polymorphic DNA (RAPD) coupled with high-resolution capillary electrophoresis system (HRS) and micronucleus (MN) assay on haemocytes to consider various types of cytogenomic damage, such as chromosomal aberrations, breakages, adducts and mutations. The results showed alteration of the individual endpoints at higher accumulation quotients (AQs) that reflect the excess of transfers to snails, especially with decreased survival for As. In addition, genotoxic effects were observed with an increased occurrence of MN in haemocytes for the three meta(loid)s considered (R² from 0.57 to 0.61 as a function of the meta(loid)s). No concentration-dependent decrease in genome stability was highlighted by RAPD-HRS in snails exposed to As and Cd but not Hg. Our results demonstrate the complementarity of the RAPD-HRS and the MN assay for understanding the different genotoxic mechanisms of the three metal(loid)s studied in land snails. They show a way to better assess environmental risks of contaminated soils by associating ecotoxicity, genotoxicity and bioaccumulation assays (ISO 24032), i.e., ecogenotoxicological bioavailability. Convergences highlighted here between the bioaccumulation of metal(loid)s in viscera and genotoxic effects in haemocytes constitute a way to better assess the bioavailability of contaminants in soils to the land snail and the subsequent environmental risk.

Aristolochic acid IVa forms DNA adducts in vitro but is non-genotoxic in vivo

Aristolochic acids (AAs) are a family of natural compounds with AA I and AA II being known carcinogens, whose bioactivation causes DNA adducts formation. However, other congeners have rarely been investigated. This study aimed to investigate genotoxicity of AA IVa, which differs from AA I by a hydroxyl group, abundant in Aristolochiaceae plants. AA IVa reacted with 2'-deoxyadenosine (dA) and 2'-deoxyguanosine (dG) to form three dA and five dG adducts as identified by high-resolution mass spectrometry, among which two dA and three dG adducts were detected in reactions of AA IVa with calf thymus DNA (CT DNA). However, no DNA adducts were detected in the kidney, liver, and forestomach of orally dosed mice at 40 mg/kg/day for 2 days, and bone marrow micronucleus assay also yielded negative results. Pharmacokinetic analyses of metabolites in plasma indicated that AA IVa was mainly O-demethylated to produce a metabolite with two hydroxyl groups, probably facilitating its excretion. Meanwhile, no reduced metabolites were detected. The competitive reaction of AA I and AA IVa with CT DNA, with adducts levels varying with pH of reaction revealed that AA IVa was significantly less reactive than AA I, probably by hydroxyl deprotonation of AA IVa, which was explained by theoretical calculations for reaction barriers, energy levels of the molecular orbits, and charges at the reaction sites. In brief, although it could form DNA adducts in vitro, AA IVa was non-genotoxic in vivo, which was attributed to its low reactivity and biotransformation into an easily excreted metabolite rather than bioactivation.

Genotoxicity of multi-walled carbon nanotube reference materials in mammalian cells and animals

Carbon nanotubes (CNTs) were the first nanomaterials to be evaluated by the International Agency for Research on Cancer (IARC). The categorization as possibly carcinogenic agent to humans was only applicable to multi-walled carbon nanotubes called MWCNT-7. Other types of CNTs were not classifiable because of missing data and it was not possible to pinpoint unique CNT characteristics that cause cancer. Importantly, the European Commission's Joint Research Centre (JRC) has established a repository of industrially manufactured nanomaterials that encompasses at least four well-characterized MWCNTs called NM-400 to NM-403 (original JRC code). This review summarizes the genotoxic effects of these JRC materials and MWCNT-7. The review consists of 36 publications with results on cell culture experiments (22 publications), animal models (9 publications) or both (5 publications). As compared to the publications in the IARC monograph on CNTs, the current database represents a significant increase as there is only an overlap of 8 publications. However, the results come mainly from cell cultures and/or measurements of DNA strand breaks by the comet assay and the micronucleus assay (82 out of 97 outcomes). A meta-analysis of cell culture studies on DNA strand breaks showed a genotoxic response by MWCNT-7, less consistent effect by NM-400 and NM-402, and least consistent effect by NM-401 and NM-403. Results from other in vitro tests indicate strongest evidence of genotoxicity for MWCNT-7. There are too few observations from animal models and humans to make general conclusions about genotoxicity.

Roadmap for translating results from the micronucleus assay into clinical practice: From observational studies to randomized controlled trials

According to the definition delivred by the WHO, a biomarker, independently from its role that may be indicative of exposure, response or effect, is inevitably linked to a clinical outcome or to a disease. The presence of a continuum from early biological events to therapy, and prognosis is the unifying mechanism that justifies this conclusion. Traditionally, the technical and inter-individual variability of the assays, together with the long duration between early pathogenetic events and the disease, prevented clinical applications to these biomarkers. These limitations became less important with the emerging of personalized preventive medicine because of the focus on disease prediction and prevention, and the recommended use of all data concerning measurable patient's features. Several papers have been published on the best validation procedures for translating biomarkers to real life. The history of cholesterol concentration is extensively discussed as a reliable example of a biomarker that - after a long and controversial validation process - is currently used in clinical practice. The frequency of micronucleated cells is a reliable biomarker for the pathogenesis of cancer and other non-communicable diseases, and the link with clinical outcomes is substantiated by epidemiological evidence and strong mechanistic basis. Available literature concerning the use of the micronucleus assay in clinical studies is discussed, and a suitable three-levels road-map driving this biomarker towards clinical practice is presented. Under the perspective of personalized medicine, the use of the micronucleus assays can play a decisive role in addressing preventive and therapeutic strategies of chronic diseases. In many cases the MN assay is either currently used in clinical practice or classified as adequate to consider translation into practice. The roadmap to clinical validation of the micronucleus assay finds inspiration from the history of biomarkers such as cholesterol, which clearly showed that the evidence from prospective studies or RCTs is critical to achieve the required level of trust from the healthcare profession. (307 words).

ASSESSMENT OF CYTOGENETIC DAMAGE TO EXFOLIATED GINGIVAL CELLS IN PATIENTS WITH CHRONIC GENERALIZED PERIODONTITIS

The aim of this cross-sectional study was to investigate the occurrence of chromosomal abnormalities through the frequency of micronuclei and other genomic damage markers in patients with chronic generalized periodontitis and without periodontal disease. Micronucleus assay was performed in exfoliated gingival epithelial cells of 35 patients with generalized chronic periodontitis and 30 control subjects with healthy periodontium. Full mouth clinical examination was performed to define periodontal condition. The mean number of cells with micronuclei observed in chronic periodontitis and control groups was 1.8 (±1.49) and 2.0 (±1.34), respectively. Differences between the groups were not significant (p=0.574). Compared to control subjects, patients with chronic periodontitis showed a significant increase in the number of binucleated cells (p≤0.001) and number of cells with nucleoplasmic bridges (p=0.042). Study results indicated that chronic periodontitis was not associated with higher occurrence of chromosomal damage in gingival cells compared to individuals with healthy periodontium.

Evaluating the radioprotective effect of Cimetidine, IMOD, and hybrid radioprotectors agents: An in-vitro study

INTRODUCTION

There are various radioprotective agents with different mechanisms that help to decrease ionizing radiation side effects. The radioprotective effect of Cimetidine and IMOD was assessed individually and compared with the hybrid radioprotectors agents (HRPAs-IMOD and Cimetidine) on human lymphocyte cells.

METHODS

Twenty healthy volunteers (ten men and ten women) participated in the present study. About 75 mL peripheral blood lymphocytes from each individual were collected, and they were divided into 36 groups. Briefly, the blood samples were treated with different concentrations of Cimetidine (12.6 and 25.2 μg/mL) and IMOD (0.04, 0.08, and 0.12 mg/mL), and also a combination of these agents, namely hybrid radioprotectors agents (HRPAs). Besides, the irradiated groups were exposed to 2 and 4 Gy of Co-60 gamma irradiation. The amount of cellular damage was assessed using the micronucleus assay. The repeated measurements and paired T-test statistical analysis were used to compare the micronucleus frequencies in different groups.

RESULTS

The micronucleus frequencies were significantly reduced (p < 0.05) in irradiated groups when the non-toxic concentrations of Cimetidine, IMOD, and HRPAs have been used. The reduction in micronucleus frequency was obtained 5-29% for Cimetidine and 40-51% for IMOD in peripheral blood lymphocytes irradiated with 2 Gy. This reduction in 4 Gy irradiation was 8-17% for Cimetidine and 27-37% for IMOD. The HRPAs resulted in a higher radioprotective effect, in a way that they cause up to 58% and 43% micronucleus frequency reduction in 2 and 4 Gy, respectively.

CONCLUSION

In conclusion, the HRPAs showed the highest level of radioprotective. In addition, IMOD was remarkably higher radioprotective than Cimetidine, which may be related to its greater non-toxic concentrations.

Micronucleus Formation in Primary Oropharyngeal Epithelial Cells Reveals Mutagenicity of Cement Dusts

BACKGROUND/AIM

Epidemiological studies showed an increased risk of developing laryngeal head and neck squamous cell carcinoma (HNSCC) for employees working in the construction business. This suggested a causal link between exposure to cement particles and development of HNSCC but data were missing.

MATERIALS AND METHODS

We established an Organisation for Economic Co-operation and Development (OECD) guideline 487-conform micronucleus assay (MNA) using oropharyngeal mucosa-derived primary epithelial cells (OPCs) ex vivo. OPCs from healthy mucosa of 52 donors were cultured in vitro and incubated with serial concentrations of two common cement particles. Mitomycin C was used as a soluble positive control, and TiO₂ and DQ12 were used as negative and positive particle controls. Bi-nucleated cells were counted and the mitotic index (MI) was determined. Subsequently, micronuclei-containing bi-nucleated cells (MN+) were counted.

RESULTS

Cement particles, in concentrations not significantly reducing ex vivo proliferation according to mitotic index, dose-dependently increased micronuclei formation.

CONCLUSION

Through the establishment of an OECD guideline 487 conform MNA, we demonstrate the mutagenic effects of cement on human OPCs.

Evaluation of genoprotection against malathion induced toxicity by Orthosiphon thymiflorus Sleesen

BACKGROUND

Pesticide toxicity is considered to be one of the significant reason for increased incidence of cancer. Plants are treasure troves of active phytochemical compounds which are used as herbal medicine as well as nutraceuticals.

OBJECTIVE

To evaluate the genoprotective potential of Orthosiphon thymiflorus (Roth) Sleesen, (Lamiaceae) against the toxicity induced by malathion by a battery of four in vivo assays in Swiss albino mice.

MATERIALS AND METHODS

Micronucleus assay was performed for analyzing the micronuclei induction and ratio of polychromatic and normochromatic erythrocytes (PCE/NCE). Anticlastogenic and mito depressive effect of the methanol and hexane extracts of O.thymiflorus were evaluated by chromosome aberration assay. Alkali comet assay was performed to assess double strand DNA repair. DNA damage sensing ability of the bone marrow cells were assessed by γ-H2AX foci formation. Phytochemical screening of hexane and methanol extract was done by GC-MS analysis.

RESULT

O. thymiflorus extracts showed a dose dependant protective effect in all assays. It significantly decreased the frequency of micronuclei and improved PCE/NCE value in post treated groups of animals. Malathion induced clastogenic aberrations were effectively attenuated by methanol and hexane extracts. DNA comet assay showed that malathion induced damage can be protected by O. thymiflorus extracts. Multiple foci formation in γ-H2AX assay confirmed the activation of DNA repair proteins in post treated animals.

CONCLUSION

Genoprotective effect of O. thymiflorus against malathion induced toxicity was confirmed. This study would be helpful to initiate more research including clinical using O. thymiflorus extract against pesticide induced toxicity.

Assessment of Cytotoxic and Genotoxic Effect of Fissure Sealants in Buccal Epithelial Cells

Aim

The main purpose of this study was to assess the genotoxic and cytotoxic effect of fissure sealants on buccal epithelial cells.

Material and methods

The study was conducted on 45 patients (27 girls and 18 boys), seven to 16 years of age (age mean 12.09 ± 2.20). Buccal swabs were collected before (T0), seven (T1), 30 (T2) and 90 days (T3) consequently after fissure sealant placement (Helioseal F®, Equia Fil®, Constic®). Patients or legal guardians filled in the questionnaire regarding the demographic data (age, gender), dietary habits, health status, medication usage, and recent X-ray exposure. DNA damage was analyzed using the micronucleus test.

Results

Statistically significant difference in the number of buccal cells with condensed chromatin was found between T0 (time before fissure sealant placement) and T3 (90 days after fissure sealant placement) period for Helioseal F® (P = 0.025). For the other two analyzed materials, no difference was observed during the tested period. There was no difference between materials in the same sampling time.

Conclusion

Apart from an increase in cells with condensed chromatin 90 days after the placement of Helioseal F®, no other nuclear abnormalities were observed for tested fissure sealants. Although these sealants have now largely been used, it is of high importance that their biocompatibility is checked continuously, especially in in vivo clinical studies.

Genotoxic effect of meat consumption: A mini review

In 2015, the International Agency for Research on Cancer classified the consumption of processed meat as carcinogenic to humans (Group 1) and red meat as probably carcinogenic to humans (Group 2A) based on sufficient data from animal models and epidemiological studies. However, research characterising the mechanisms underlying this carcinogenic process in humans are limited, particularly with respect to measures of direct DNA damage. The current review sought to evaluate and summarize the recent literature, published since 2000, regarding the associations of meat consumption and three biomarkers of genotoxicity in humans: DNA strand breaks (measured using the comet assay), DNA adducts, and micronucleus formation. After screening 230 potential articles, 35 were included, and then were classified as experimental or observational in design, the latter of which were further categorized according to their dietary assessment approach. Among the 30 observational studies, 4 of which used two different assays, 3 of 5 comet assay studies, 13 of 20 DNA adduct studies, and 7 of 9 micronucleus studies reported a positive association between meat consumption and DNA damage. Among the 5 experimental studies, 1 of 1 using the comet assay, 3 of 3 measuring DNA adducts and 0 of 1 measuring micronuclei reported significant positive associations with meat consumption. Nevertheless, common limitations among the selected publications included small sample size, and poor methodological reporting of both exposure and outcome measures. Moreover, the vast majority of studies only measured DNA damage in one biological sample using a single assay and we cannot exclude the possibility of publication bias. Ultimately, our review of the literature, published since 2000, revealed a preponderance of studies that support mechanisms of genotoxicity in playing an important role in the meat-cancer association.

Dietary exposure to mercury and its relation to cytogenetic instability in populations from "La Mojana" region, northern Colombia

Fish consumption and chronic exposure to low doses of mercury (Hg) seems to activate several molecular mechanisms leading to carcinogenic and/or teratogenic processes. However, Hg genotoxic effects on humans are not completely described. In the present study, we assessed cytogenetic damage in isolated human peripheral lymphocytes using the cytokinesis-block micronucleus cytome assay (CBMN-Cyt), micronucleus formation with anti-kinetochore antibody (CREST staining), levels of total Hg in hair (T-Hg), fish consumption, and estimated Hg dose. The study comprised 39 non-exposed, and 73 residents from La Mojana region, an area with a well-documented Hg contamination. Data showed a significant increase in micronuclei (MNBN), nucleoplasmic bridges (NPB), and necrotic and apoptotic cell frequencies in residents of "La Mojana." The overall mean T-Hg level in hair for exposed residents was 1.12 ± 0.94 mg kg^-1 and 0.15 ± 0.05 in individuals from the reference area. Approximately 40% of analyzed individuals showed T-Hg levels that exceeded US Environmental Protection Agency (USEPA) reference dose. Increased T-Hg levels in hair were related to increased MNBN frequencies and high fish consumption. Other cellular markers, such as necrotic and apoptotic cell frequencies, were also correlated with high fish intake and T-Hg contents. Results of the CREST staining demonstrated that in vivo exposure to Hg induces genetic instability by chromosome fragment loss (clastogenic). Additionally, a high average intake of some fish species, particularly with carnivorous habits like Caquetaia kraussii, Hoplias malabaricus, and Sorubin cuspicaudus, seems to increase MNBN frequencies significantly.

Laser Responsive Cisplatin-Gold Nano-Assembly Synergizes the Effect of Cisplatin With Compliance

Cisplatin therapy faces low bioavailability and clastogenic potential limitations. Early payload leakage of nanocarriers may impair adequate therapeutic efficacy. We propose encapsulation of cisplatin in such nanocarrier that can be externally stimulated for high payload release and enhanced toxicity at site of action. Cisplatin conjugated gold nanorods (Pt-AuNRs) have been synthesized and characterized through UV visible spectroscopy, dynamic light scattering and transmission electron microscopy. Physico-chemical characterization through X-ray photon spectrometry confirms the covalent linkage between linker and aquated cisplatin with AuNRs. Laser exposure (850 nm, CW) enabled ~15-fold payload release from Pt-AuNRs nano-assembly, which is quite high (P < 0.0001) compared to non-stimulated conditions. The median growth inhibitory concentration (GI₅₀) after laser exposure of Pt-AuNRs was ~11- and 13-fold low compared to corresponding Pt-AuNRs without laser exposure and cisplatin respectively, in sarcoma cells. Synergistic therapeutic difference is more significant (P < 0.01), at lower concentrations of Pt-AuNRs (0.5-10 μg/mL). Pt-AuNRs photothermal therapy indicates a convincible association of over-production of reactive oxygen species (P < 0.0001) and synergistic therapeutic efficacy. Clastogenic potential is found non-significant for Pt-AuNRs (10 μg/mL). Cisplatin nanoconjugate shows biocompatibility against blood cells. In conclusion, laser-stimulated Pt-AuNRs appear a promising drug delivery with synergistic toxic potential against cancer while attenuating cisplatin toxicity.

Using a high-throughput method in the micronucleus assay to compare animal-free with rat-derived S9

This study presents a high-throughput (HTP) micronucleus assay in multi-well plates with an automated evaluation for risk assessment applications. The evaluation of genotoxicity via the micronucleus assays according to international guidelines ISO 21427-2 with Chinese hamster (Cricetulus griseus) V79 cells was the starting point to develop our methodology. A drawback of this assay is that it is very time consuming and cost intensive. Our HTP micronucleus assay in a 48-well plate format allows for the simultaneous assessment of five different sample-concentrations with additional positive, negative and solvent controls with six technical replicates each within a quarter of the time required for the equivalent evaluation using the traditional slide method. In accordance with the 3R principle, animal compounds should be replaced with animal-free alternatives. However, traditional cell culture-based methods still require animal derived compounds like rat-liver derived S9-fraction, which is used to simulate the mammalian metabolism in in vitro assays that do show intrinsic metabolization capabilities. In the present study, a recently developed animal-free biotechnological alternative (ewoS9R) was investigated in the new high-throughput micronucleus assay. In total, 12 different mutagenic or genotoxic chemicals were investigated to assess the potential use of the animal-free metabolization system (ewoS9R) in comparison to a common rat-derived product. Out of the 12 compounds, one compound did not induce micronuclei in any treatment and 2 substances showed a genotoxic potential without the need for a metabolization system. EwoS9R demonstrated promising potential for future applications as it shows comparable results to the rat-derived S9 for 6 of the 9 pro-genotoxic substances tested. The remaining 3 substances (2-Acetamidofluorene, Benzo[a]pyrene, Cyclophosphamide) were only metabolized by rat-derived S9. A potential explanation is that ewoS9R was investigated with an approx. 10-fold lower enzyme concentration and was only optimized for CYP1A metabolization that may be improved with a modified production procedure. Future applications of ewoS9R go beyond the micronucleus assay, but further research is necessary.

Toxicity and genotoxic evaluations in African catfish Clarias gariepinus (Burchell 1822) exposed to Act Force Gold®, Butaforce®, and Atraforce®

Act Force Gold^®, Butaforce^®, and Atraforce^® are among the most commonly used pesticides in Nigeria. The lethal concentrations and the respective toxic units for the three pesticides were determined. The genotoxic effects of the three pesticides were investigated in the red blood cells of Clarias gariepinus using micronucleus (MN) assay. The 96 h LC₅₀ was 4.75, 4.84, and 54.74 mg L^-1 for Act Force Gold^®, Butaforce^®, and Atraforce^®, respectively. The toxic units in ascending order of toxicity were 1.83, 20.66, and 21.05 for Act Force Gold^®, Butaforce^®, and Atraforce^® respectively. The estimated safe levels based on NAS/NAE varied from 4.75 × 10^-1-4.75 × 10^-5 in Act Force Gold^® through 4.64 × 10^-1-4.85 × 10^-5 in Butaforce^® to 5.74-5.74 × 10^-5 in Atraforce^®. Fish specimens were exposed to the pesticides and sampling was done at regular intervals at days 1, 7, 14, and 21 and after another 7-day recovery period. The results obtained indicated concentration- and duration-dependent increase in % MN formation with maximum values of 3.40 ± 0.25 for Act Force Gold^® on day 14 and 3.05 ± 0.36 and 2.35 ± 0.14 for Butaforce^® and Atraforce^® respectively on day 7 of exposure. The 7-day recovery period could not reverse the trend as the % MN values obtained were significantly different from the control. The results further support the use of MN assay in assessing the toxicity of aquatic pollutants and can be used in the monitoring of aquatic ecosystems.

Ex vivo/in vitro effects of aspirin and ibuprofen, bulk and nano forms, in peripheral lymphocytes of prostate cancer patients and healthy individuals

Inhibiting inflammatory processes or eliminating inflammation represents a logical role in the suppression and treatment strategy of cancer. Several studies have shown that anti-inflammatory drugs (NSAIDs) act as anticancer agents while reducing metastases and mortality rate. NSAIDs are seriously limited by their side effects and toxicity, which can become cumulative with their long-term administration for chemoprevention. In the current ex vivo / in vitro study, the genotoxicity mechanisms of NSAIDS in bulk and nanoparticle forms allowed a strategy to prevent and minimise the damage in human lymphocytes. When compared to their bulk forms, acetylsalicylic acid (Aspirin) nano and ibuprofen nano (IBU N), both NSAIDs in 500 μg/mL concentration significantly decreased DNA damage measured by alkaline comet assay. Micronuclei (MNi) frequency also decreased after ASP N (500 μg/mL), ASP B (500 μg/mL) and IBU N (200 μg/mL) in prostate cancer patients and healthy individuals, however, the ibuprofen bulk (200 μg/mL) showed a significant increase in MNi formation in lymphocytes from healthy and prostate cancer patients when compared to the respective untreated lymphocytes. These findings suggest that a reduction in particle size had an impact on the reactivity of the drug, further emphasising the potential of nanoparticles to improve the current treatment options.

Micronuclei and upper body cancers (head, neck, breast cancers) a systematic review and meta-analysis

A systematic review and a meta-analysis were performed on 19 studies on head and neck cancer (HNC) and 21 studies on breast cancer (BC) to evaluate the application of micronucleus (MN) assay as a predictive and prognostic test for cancer risk. In these studies the MN test was applied in peripheral lymphocytes and buccal cells of patients and healthy subjects with family history of cancer. The meta-analysis on MN applied in buccal cells of HNC patients was performed on two subgroups of studies. A significant increase of MN frequency in patients compared to healthy controls was observed for the subgroup on oral cancer (243 cases/370 controls, meta-MR = 4.71 95 %CI:2.75-8.06) and HNC (204 patients/163 controls metaMR=2.28 95 %CI:2.02-2.58). A metaMR = 3.27 (95 %CI:1.41-7.59) was obtained for MN applied in peripheral lymphocytes on HNC (160 cases/160 controls). For BC, the analysis of MN in peripheral lymphocytes showed significantly higher values in patients (n = 761) than in controls (n = 788) (meta-MR1.90 95 % CI:1.44-2.49). No statistically significant increase of baseline MN was detected in studies on groups of healthy subjects with BC family history (n = 224) or with BRCA1/2 mutations (n = 101) with respect to the controls. After ex-vivo challenge with ionizing radiation, the meta-analysis revealed a slightly statistically significant increase in MN only in BC patients (n = 614) compared to controls (n = 622)(meta-MR = 1.11 95 %CI:1.02-1.21); no increase was observed in healthy subjects with BC family history carrying or not BRCA1/2 mutations. Significant difference between BC patients (n = 183) and controls (n = 165) was observed by the meta-analysis of data on MN in buccal cells (MR = 3.89 95 %CI:1.54-9.78). The MN assay in buccal cells has some perspective of clinical application in HNC.

Toxicity associated with long term use of aluminum cookware in mice: A systemic, genetic and reproductive perspective

Studies on the toxic effects of cooking with aluminum pots are limited and none of them have explored its impact on the genetic material in germ and somatic cells. Therefore, this study investigated the cytogenotoxic effect of boiled water from new, 3- and 6-year old aluminum pots in germ and somatic cells viz-a-vis mouse sperm morphology test and sperm count; and the bone marrow micronucleus test. The mice were allowed to freely drink the boiled water from the different aluminum pots for 3, 4, and 5 weeks. The heavy metal analysis showed that As, Pb, Cd, and Al were present in the boiled water samples at different concentrations with the 6-year old pot having the highest concentrations of Pb, Cd, and Al. There were duration of exposure and age of pot-dependent significant increase in abnormal sperm cells and a significant decrease total mean sperm count of exposed mice. Similarly, there was a statistically significant increase in micronucleated polychromatic erythrocytes and nuclear abnormalities in the exposed mice that increased dependently upon the age of the cookware. Finally there were significantly increased activities of serum AST and ALT; and the liver concentrations of MDA, SOD and CAT in boiled water exposed mice. The findings of this study revealed that boiled water from aluminum pots is capable of inducing cytotoxic and genotoxic effects, especially as the pot ages.

Performance of HepaRG and HepG2 cells in the high-throughput micronucleus assay for in vitro genotoxicity assessment

The micronucleus (MN) assay is a core test used to evaluate genotoxic potential of xenobiotics. The traditional in vitro MN assay is usually conducted in cells lacking metabolic competency or by supplementing cultures with an exogenous rat S9 metabolic system, which creates a significant assay limitation for detecting genotoxic metabolites. Our previous study demonstrated that compared to HepG2, HepaRG cells exhibited a significantly higher level of CYP450 enzyme activities and detected a greater portion of genotoxic carcinogens requiring metabolic activation using the Comet assay. The aim of this study was to assess the performance of HepaRG cells in the flow cytometry-based MN assay by testing 28 compounds with known genotoxic or carcinogenic modes of action (MoA). HepaRG cells exhibited higher sensitivity (83%) than HepG2 cells (67%) in detecting 12 indirect-acting genotoxicants or carcinogens. The HepaRG MN assay was 100% specific and 93% accurate in detecting genotoxic potential of the 28 compounds. Quantitative comparison of the MN concentration-response data using benchmark dose analysis showed that most of the tested compounds induced higher % MN in HepaRG than HepG2 cells. In addition, HepaRG cells were compatible with the Multiflow DNA damage assay, which predicts the genotoxic MoA of compounds tested. These results suggest that high-throughput flow cytometry-based MN assay may be adapted using HepaRG cells for genotoxicity assessment, and that HepaRG cells appear to be more sensitive than HepG2 cells in detecting genotoxicants or carcinogens that require metabolic activation.

Genomic instability in chronic obstructive pulmonary disease and lung cancer: A systematic review and meta-analysis of studies using the micronucleus assay

Respiratory tissues are highly susceptible to diseases due to the constant exposure to physical and chemical airborne pollutants. Chronic obstructive pulmonary disease (COPD) and lung cancer are among the most common causes of serious illness and death worldwide. The inflammatory environment associated with these respiratory diseases has long been accepted as the major player in the development of airway abnormalities. The presence and relevance of DNA damage and genomic instability makes the micronucleus assay a suitable candidate to quantitatively estimate these early pathogenetic events. A systematic review and meta-analysis were planned to determine underlying common mechanisms that can explain the relationships between COPD and lung cancer. A total of 17 studies from Jan 1999 to Dec 2019 comparing micronucleus frequency in patients affected by respiratory diseases vs healthy controls were analysed. Our results confirmed the presence of significant association between MN frequency and the diseases investigated, and suggested a circle of events linking inflammation induced oxidative stress to the risk of disease through genomic instability and hypoxia. Therefore, using non-invasive, robust and cost effective genomic instability assays such as the micronucleus assay, would allow us to capture unique phenotypic and biological changes that would allow the identification of subjects at high risk of developing lung diseases and improve early detection strategies.

Pooled analysis of genotoxicity markers in relation to exposure in the Flemish Environment and Health Studies (FLEHS) between 1999 and 2018

BACKGROUND

The Flemish Environment and Health Studies (FLEHS) are human biomonitoring surveys running in Flanders since 1999. Additionally to biomarkers of exposure, markers of genotoxicity and oxidative stress have been measured, including the alkaline comet and micronucleus assay in peripheral whole blood cells, and urinary concentrations of 8-oxo-2'-deoxyguanosine (8-oxodG).

AIM

Exposure-effect associations were explored in a pooled dataset of nine different cross-sectional FLEHS surveys. Data of adolescents collected in a time frame of about 20 years (1999-2018) were compiled. The aim of the study was to examine whether increased variation in exposure, lifestyle and environmental factors would lead to more powerful and robust exposure-effect associations.

MATERIALS & METHODS

The biomarkers were measured in 2283 adolescents in the age range of 14-18 years. Exposure to polycyclic aromatic hydrocarbons [1-hydroxypyrene (1-OHP)], benzene (tt'-muconic acid), metals (arsenic, cadmium, copper, nickel, thallium, lead, chromium), persistent organochlorines and phthalates were assessed in blood or urine. Furthermore, outdoor air levels of particulate matter (PM₁₀ and PM_2.5) at the residences of the youngsters were calculated. Pooled statistical analysis was done using mixed models. Study-specific differences in the genotoxicity markers and in the strength/direction of the association were accounted for. This was done by incorporating the random factor 'study' and a random study slope (if possible). The exposure markers were centered around the study-specific mean in order to correct for protocol changes over time.

RESULTS

A significant association was observed for the urinary oxidative stress marker 8-oxodG, which was positively associated with 1-OHP (5% increase for doubling of 1-OHP levels, p = 0.001), and with urinary copper (26% increase for doubling of copper levels, p = 0.001), a metal involved in the Fenton reaction in biological systems. 8-oxodG was also associated with the sum of the metabolites of the phthalate di(2-ethylhexyl) phthalate (DEHP) (3% increase for doubling of the DEHP levels, p = 0.02). For those associations, data pooling increased the statistical power. However, some of the associations in the individual surveys, were not confirmed in the pooled analysis (such as comet assay and 8-oxodG vs. atmospheric PM; and 8-oxodG vs. urinary nickel). This may be due to inconsistencies in exposure-effect relations and/or variations in the pollutant mix over time and regions.

CONCLUSION

Pooled analysis including a large population of 2283 Flemish adolescents showed that 8-oxodG, a marker of oxidative DNA damage is a valuable marker to assess impact of daily life pollutants, such as PAHs, Cu and the phthalate DEHP.

Triterpenoid CDDO-Me induces ROS generation and up-regulates cellular levels of antioxidative enzymes without induction of DSBs in human peripheral blood mononuclear cells

Ionizing radiation produces reactive oxygen species (ROS) leading to cellular DNA damage. Therefore, patients undergoing radiation therapy or first responders in radiological accident scenarios could both benefit from the identification of specifically acting pharmacological radiomitigators. The synthetic triterpenoid bardoxolone-methyl (CDDO-Me) has previously been shown to exert antioxidant, anti-inflammatory and anticancer activities in several cell lines, in part by enhancing the DNA damage response. In our study, we examined the effect of nanomolar concentrations of CDDO-Me in human peripheral blood mononuclear cells (PBMC). We observed increased cellular levels of the antioxidative enzymes heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase (quinone1) and mitochondrial superoxide dismutase 2 by immunoblotting. Surprisingly, we found increased intracellular ROS-levels using imaging flow-cytometry. However, the radiation-induced DNA double-strand break (DSB) formation using the γ-H2AX + 53BP1 DSB focus assay and the cytokinesis-block micronucleus assay both revealed, that nanomolar CDDO-Me pre-treatment of PBMC for 2 h or 6 h ahead of X irradiation with 2 Gy did neither significantly affect γ-H2AX + 53BP1 DSB foci formation nor the frequency of micronuclei. CDDO-Me treatment also failed to alter the nuclear division index and the frequency of IR-induced PBMC apoptosis as investigated by Annexin V-labeled live-cell imaging. Our results indicate that pharmacologically increased cellular concentrations of antioxidative enzymes might not necessarily exert radiomitigating short-term effects in IR-exposed PBMC. However, the increase of antioxidative enzymes could also be a result of a defensive cellular mechanism towards elevated ROS levels.

In vivo and in vitro analysis of cytogenotoxicity in populations living in abnormal conditions from Santos-Sao Vicente estuary

The aim of the study was to evaluate cyto- and genotoxic effects in populations living in subnormal clusters in Santos São Vicente estuary. For in vivo study, samples of buccal mucosa and peripheral blood cells were collected. Micronucleus assay and single-cell gel (comet) assay were performed. For in vitro study, Chinese ovary hamster (CHO) cells were exposed to contaminated water. The results showed that people living in the contaminated estuary have increased DNA damage in oral mucosa and peripheral blood cells, as detected in the micronucleus and comet assays respectively. In addition, estuarine water was able to promote cytotoxicity at the highest concentrations, as well as decrease the number of cells in the G1 phase. In summary, our results indicate that water from the Santos-São Vicente estuary is capable of inducing cytogenotoxicity in mammalian cells in vivo and in vitro.

LiCoO2 particles used in Li-ion batteries induce primary mutagenicity in lung cells via their capacity to generate hydroxyl radicals

BACKGROUND

Li-ion batteries (LIB) are used in most portable electronics. Among a wide variety of materials, LiCoO₂ (LCO) is one of the most used for the cathode of LIB. LCO particles induce oxidative stress in mouse lungs due to their Co content, and have a strong inflammatory potential. In this study, we assessed the mutagenic potential of LCO particles in lung cells in comparison to another particulate material used in LIB, LTO (Li₄Ti₅O₁₂), which has a low inflammatory potential compared to LCO particles.

RESULTS

We assessed the mutagenic potential of LCO and LTO particles in vitro by performing a cytokinesis-block micronucleus (MN) assay with rat lung epithelial cells (RLE), as well as in vivo in alveolar type II epithelial (AT-II) cells. LCO particles induced MN in vitro at non-cytotoxic concentrations and in vivo at non-inflammatory doses, indicating a primary genotoxic mechanism. LTO particles did not induce MN. Electron paramagnetic resonance and terephthalate assays showed that LCO particles produce hydroxyl radicals (•OH). Catalase inhibits this •OH production. In an alkaline comet assay with the oxidative DNA damage repair enzyme human 8-oxoguanine DNA glycosylase 1, LCO particles induced DNA strand breaks and oxidative lesions. The addition of catalase reduced the frequency of MN induced by LCO particles in vitro.

CONCLUSIONS

We report the mutagenic activity of LCO particles used in LIB in vitro and in vivo. Our data support the role of Co(II) ions released from these particles in their primary genotoxic activity which includes the formation of •OH by a Fenton-like reaction, oxidative DNA lesions and strand breaks, thus leading to chromosomal breaks and the formation of MN. Documenting the genotoxic potential of the other LIB particles, especially those containing Co and/or Ni, is therefore needed to guarantee a safe and sustainable development of LIB.

[In vitro exposure of human nasal mucous membrane cells and lymphocytes to snuff]

BACKGROUND

While an abundant number of studies concerning tobacco smoke and chewing tobacco show carcinogenic potential, there is little data on the consequences of snuff, especially on the cellular level. Therefore, the mutagenic effect of snuff is difficult to estimate and the WHO assessment of snuff being not carcinogenic is based on very limited data.

OBJECTIVES

This paper investigates the potential cytotoxic and genotoxic effects of snuff on human lymphocytes and nasal mucosa cells.

MATERIALS AND METHODS

Two types of snuff were used: one without menthol and one with a high degree of menthol. The necessary nasal mucosa cells and lymphocytes were collected from 10 subjects undergoing nasal obstruction surgery and incubated for one hour with a snuff-DMSO mixture (range 0.01-2000 µg/ml). Methods included the trypan blue test, the comet assay, and the micronucleus test.

RESULTS

The trypan blue test showed no decrease in cell viability for either cell type. The comet assay revealed a significant increase in the Olive Tail Moment for lymphocytes starting at 100 µg/ml and at 1000 µg/ml for nasal mucosa cells. There was no significant increase in micronuclei according to the micronucleus test. No differences between these two types of tobacco were observed.

CONCLUSION

The present study demonstrated genotoxic damage, such as DNA strand breaks, which may be repaired, but no non-repairable elevated micronuclei. The present findings cast doubts on the WHO assessment that snuff is not carcinogenic. However, for a sound assessment of the risk potential of snuff, further research on various genotoxic endpoints in human cells is warranted.

Age related micronuclei frequency ranges in buccal and nasal cells in a healthy population

BACKGROUND

Micronuclei (MNs) are extranuclear DNA-containing bodies and determining MN frequencies is a measure of genomic instability. An age-related increase in MN frequencies in lymphocytes has been quantified, but this effect has not yet been measured in nasal and buccal cells.

METHODS

We determined the effect of age on the MN frequency distributions in buccal and nasal cells among a sample of a general adult population in Switzerland. To maximize the power to detect an effect of age in our population study, we recruited preferentially younger and older working age adults. We harvested buccal and nasal cells from 32 young (19-36 year) and 33 working age (47-71 years) participants. The collected cells were washed, centrifuged, and stained (Feulgen) before microscopic manual counting in 2000 cells. Based on these results, we developed an age-dependent background MN frequency chart to help interpret an individual's MN frequency score as an early signal for the effect of genotoxic exposure.

RESULTS

MN frequencies were respectively 0.53‰ and 0.47‰ for buccal and nasal among the younger and 0.87‰ and 1.03‰ in the older working age group. This corresponded to a multiplicative slope of 14% and 20% per 10 years of age for buccal and nasal cells, respectively.

CONCLUSION

Based on our study results, we are able to propose an approach for interpreting an individual's MN screening results.