Increase In Micronucleus Frequency Research Articles

Size- and coating-dependent cytotoxicity and genotoxicity of silver nanoparticles evaluated using in vitro standard assays

The physicochemical characteristics of silver nanoparticles (AgNPs) may greatly alter their toxicological potential. To explore the effects of size and coating on the cytotoxicity and genotoxicity of AgNPs, six different types of AgNPs, having three different sizes and two different coatings, were investigated using the Ames test, mouse lymphoma assay (MLA) and in vitro micronucleus assay. The genotoxicities of silver acetate and silver nitrate were evaluated to compare the genotoxicity of nanosilver to that of ionic silver. The Ames test produced inconclusive results for all types of the silver materials due to the high toxicity of silver to the test bacteria and the lack of entry of the nanoparticles into the cells. Treatment of L5718Y cells with AgNPs and ionic silver resulted in concentration-dependent cytotoxicity, mutagenicity in the Tk gene and the induction of micronuclei from exposure to nearly every type of the silver materials. Treatment of TK6 cells with these silver materials also resulted in concentration-dependent cytotoxicity and significantly increased micronucleus frequency. With both the MLA and micronucleus assays, the smaller the AgNPs, the greater the cytotoxicity and genotoxicity. The coatings had less effect on the relative genotoxicity of AgNPs than the particle size. Loss of heterozygosity analysis of the induced Tk mutants indicated that the types of mutations induced by AgNPs were different from those of ionic silver. These results suggest that AgNPs induce cytotoxicity and genotoxicity in a size- and coating-dependent manner. Furthermore, while the MLA and in vitro micronucleus assay (in both types of cells) are useful to quantitatively measure the genotoxic potencies of AgNPs, the Ames test cannot.

Abstract 3596: KLLN protects genomic stability by maintaining H3K9 trimethylation (H3K9me3) at the pericentric heterochromatin

Abstract Dysregulation in the maintenance of chromatin organization resulting in genomic instability is a major driving force for inappropriate development and carcinogenesis. Tumor suppressor genes play a critical role in this regulation through the maintenance of epigenetic marks. Our study focuses on the role of KLLN in the maintenance of pericentric H3K9 trimethylation (H3K9me3) and genomic stability. Germline hypermethylation of KLLN resulting in decreased KLLN expression has been linked to Cowden cancer-predisposition syndrome (CS) in PTEN mutation negative patients. KLLN is a tumor suppressor gene necessary for p53-mediated apoptosis. The protein mediates S-phase arrest and is known to have DNA binding ability. Here, we first used chromatin immunoprecipitation-based sequencing (ChIP-seq) to investigate regions of KLLN binding on the genome and compared it to regions of H3K9me3 enrichment. We used H3K9 specific histone methyltransferase (HMT) activity assay and immunoblotting to measure levels of H3K9me3. Immunostaining was used to study the localization of KLLN, and micronuclei frequency and aberrations in chromosome number was used to assess chromosomal instability. Analysis of ChIP-seq shows enrichment of KLLN binding in regions of H3K9me3. Overexpression of KLLN using plasmid-based transfection correlates with increased H3K9 methyltransferase activity and increased global H3K9me3, while loss of KLLN expression through siRNA-mediated knockdown had an opposite effect. We also established that KLLN localizes to pericentric regions, and loss of KLLN results in dysregulation of pericentric heterochromatin, with consequent chromosomal instability manifested by increased micronuclei frequency and numerical chromosomal aberrations. KLLN regulation of H3K9me3 could be correlated with its interaction with deleted in breast cancer (DBC1). DBC1 is a known inhibitor of SUV39H1, a H3K9 specific histone methyltransferase responsible for maintenance of pericentric heterochromatin. We hypothesize that KLLN sequesters DBC1 through their interaction, thereby abrogating DBC1 inhibition of SUV39H1, resulting in maintenance of pericentric heterochromatin and genomic stability. Our study therefore suggests a critical role for KLLN in the deterrence of tumor initiation and progression. SIGNIFICANCE: Our study demonstrates a clear role for KLLN in maintenance of chromatin organization thereby maintaining genomic stability, which begins to uncover the basis of KLLN as a tumor suppressor and as a susceptibility gene for inherited cancers. Citation Format: Madhav Sankunny, Emily Nizialek, Farshad Niazi, Charis Eng. KLLN protects genomic stability by maintaining H3K9 trimethylation (H3K9me3) at the pericentric heterochromatin. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3596.

Determination of mutagenicity and genotoxicity of indium tin oxide nanoparticles using the Ames test and micronucleus assay

In this study, the mutagenicity and genotoxicity of indium tin oxide (ITO) nanomaterial were assessed using two standard genotoxicity assays, the Salmonella reverse mutation assay (Ames test) and the in vitro micronucleus (MN) assay. Seven different concentrations (12.5, 25, 50, 75, 100, 125, and 150 µg/plate) of this nanomaterial were tested using the Ames test on the TA98 and TA100 strains in the presence and absence of the S9 mixture. At all the concentrations tested, this substance did not significantly increase the number of revertant colonies compared with the control with or without S9 mixture. The genotoxic effects of ITO were investigated in human peripheral lymphocytes treated with 125, 250, 500, and 750 µg/ml concentrations of this substance for 24- and 48-h treatment periods using an MN test. Nuclear division index (NDI) was also calculated in order to determine the cytotoxicity of ITO. It was determined that ITO increased MN frequency in the 750 µg/ml concentration in 24- and 48-h treatments. In addition, ITO dose dependently decreased the NDI significantly for two treatment periods.

Modulatory role of GSTM1 null genotype on the frequency of micronuclei in pesticide-exposed agricultural workers.

In this study, we aimed to investigate the extent of genotoxic risk and the association between null GSTM1/GSTT1 and GSTP1 Ile105Val variants and cellular DNA damage, as measured by micronucleus (MN) assay in a group of agricultural workers from Denizli, Turkey. Peripheral blood samples were collected from 116 subjects, including 58 workers who were occupationally exposed to pesticides and 58 healthy unexposed controls. The MN frequencies of each individual were assessed by cytokinesis-blocked micronuclei assays on lymphocytes. Genotypes for different GST variants were determined using polymerase chain reaction-based methods. A significant 3.4-fold increase in MN frequency was observed in workers compared with the controls (p < 0.001). Among the GST genotypes, only the GSTM1 null genotype was found to be significantly associated with an increased MN frequency in workers (p = 0.01). Individuals with a concomitant null GSTM1/GSTT1 genotype demonstrated a significant (p = 0.01) increase in MN frequency compared with those with functional isozymes in the exposed worker group. The association of the GSTM1 null genotype with higher MN frequency suggests that it may be a modifier of genotoxic risk in individuals exposed to pesticides and may thus be a candidate susceptibility biomarker for human biomonitoring studies.

The cytokinesis-block micronucleus (CBMN) assay in human populations exposed to styrene: A systematic review and meta-analysis.

Styrene is a building-block of several compounds used in a wide array of materials and products. The most important human exposure to this substance occurs in industrial settings, especially among reinforced-plastics industry workers. The effect of occupational exposure to styrene on cytogenetics biomarkers has been previously reviewed with positive association observed for chromosomal aberrations, and inconclusive data for the micronucleus assay. Some limitations were noted in those studies, including inadequate exposure assessment and poor epidemiological design. Furthermore, in earlier studies micronuclei frequency was measured with protocols not as reliable as cytokinesis-block micronucleus (CBMN) assay. Aim of the present systematic review and meta-analysis is to investigate genomic instability and DNA damage as measured by the CBMN assay in lymphocytes of subjects exposed to styrene. A total of 11 studies published between 2004 and 2012 were included in the meta-analysis encompassing 479 styrene-exposed workers and 510 controls. The quality of each study was estimated by a quality scoring system which ranked studies according to the consideration of major confounders, exposure characterization, and technical parameters. An overall increase of micronuclei frequencies was found in styrene-exposure workers when compared to referents (meta-MR 1.34; 95% CI 1.18-1.52), with significant increases achieved in six individual studies. The consistency of results in individual studies, the independence of this result from major confounding factors and from the quality of the study strengthens the reliability of risk estimates and supports the use of the CBMN assay in monitoring genetic risk in styrene workers.

Association between XRCC1 polymorphisms and chromosome damage in workers exposed to benzene in jewelcrafting industry

To investigate the association between the gene polymorphisms of the DNA damage repair gene X-ray repair cross-complementing gene 1 (XRCC1) and susceptibility to chromosome damage in workers exposed to low-concentration benzene in the jewelcrafting industry. A total of 286 workers exposed to benzene in jewelcrafting enterprises were enrolled as study subjects from January 2013 to December 2014. Gas chromatography was used to measure benzene concentration in workplace, cytokinesis-block micronucleus test was used to analyze the level of chromosome damage in peripheral blood, and the Sequenom technique was used to determine the single nucleotide polymorphisms of XRCC1. The time-weighted average concentration of benzene in workplace was <0.6~1.8 mg/m(3), lower than the national occupational exposure limit (6 mg/m(3)). The distribution of allele frequencies met the Hardy-Weinberg equilibrium in genetics (P>0.05). Increase in age (RR=1.38, 95%CI 1.06~3.75) and increase in working years (RR=1.45, 95%CI 1.18~2.58) were risk factors for the increase in micronucleus frequency. Compared with those with the wild-type homozygous genotype, the individuals with XRCC1 rs25487 CT genotype showed a significantly higher risk of increase in micronucleus frequency (RR=1.51, 95% CI 1.28~3.87, P<0.05) , and the individuals with XRCC1 rs1799782 AA genotype also showed a significantly higher risk of increase in micronucleus frequency (RR=1.65, 95% CI 1.30~3.12, P<0.05). There was no clear association between XRCC1 rs25489 polymorphisms and micronucleus frequency (P>0.05). Exposure to low-concentration benzene may cause chromosome damage in workers exposed to benzene, and the XRCC1 polymorphisms rs 25487 and rs1799782 may be associated with chromosome damage induced by benzene.

Lethal and sub-lethal effects on the Asian common toad Duttaphrynus melanostictus from exposure to hexavalent chromium

Chromium discharged in industrial effluents frequently occurs as an environmental pollutant, but the lethal and sub-lethal effects the heavy metal might cause in animals exposed to it have been insufficiently investigated. Selecting the amphibian Duttaphrynus melanostictus, we carried out laboratory tests to investigate the effects of short and long term exposure to hexavalent chromium (Cr(VI)) in both tadpoles and adult toads. The concentrations used were 0.002, 0.02, 0.2, 1.0 and 2.0mg/L, the first three corresponding to field levels. In vitro exposures were also carried out using toad erythrocytes and Cr(VI) concentrations of 0.0015, 0.003, 0.015, 0.03, 0.15mg/L. Mortality, growth retardation, developmental delays and structural aberrations were noted in the metal-treated tadpoles, with increasing incidence corresponding to increase in Cr(VI) level and duration of exposure. Many of the sub-lethal effects were evident with long term exposure to environmentally relevant levels of the toxicant. Changes in selected blood parameters and erythrocyte morphometry were also detected in Cr(VI) exposed toads, indicating anaemic and leucopenic conditions. In the genotoxicity study, DNA damage indicated by comet assay and increased micronuclei frequency, occurred at the low Cr(VI) concentrations tested. The multiple deleterious effects of exposure to chromium signal the need for monitoring and controlling the discharge of chromium to the environment. The dose-dependency and genotoxic effects observed in this widely distributed Asian toad indicates its suitability for monitoring heavy metal pollution in aquatic systems.

Study of the genotoxic and cytotoxic effects of the α-, β-, and γ- Hexachlorocyclohexane isomers in human lymphocyte cells using the cytokinesis-block micronucleus assay

The genotoxic potential of hexachlorocyclohexane (HCH) isomers (α-, β-, and γ-) which are organochlorine pesticides was tested in peripheral blood lymphocyte cultures from two donors by using the cytokinesis-block micronucleus assay. Micronucleus (MN) frequency, binucleated cells with micronucleus (BNMN), and cytokinesis-blocked proliferation index (CBPI) were determined as genotoxic and cytotoxic endpoints. At the concentration ranges tested (12.5–100 μg.L −1), all HCH isomers induced dose-dependent cytotoxic effects, γ-HCH being the most toxic. This isomer was also able to induce significant increase in MN frequency and BNMN cells indicating a genotoxic potential at 50 and 100 μg.L −1. The genotoxic test of β-HCH showed a positive induction of MN and BNMN cells at the highest concentration of 100 μg.L −1 and a significant cytotoxicity at 50 μg.L −1. Under the experimental condition used, α-HCH was unable to induce any significant increase in MN frequency confirming that α-HCH is a non-genotoxic agent.

Genotoxic effects of X-rays in buccal mucosal cells in children subjected to dental radiographs.

Objectives/Aims:Bitewing and digital dental panoramic radiographs have become important adjuvants for successful dental practice in pediatric dentistry. Both methods lead to genetic changes in the oral buccal epithelium that have not yet been satisfactorily explored. The aim of the present study was to evaluate the genotoxic effects induced by X-ray radiation from bitewing and panoramic dental radiography in exfoliated buccal epithelial cells of children, using the Buccal Micronucleus Cytome assay.Materials and Methods:Children (n=40) who met the inclusion criteria and provided signed informed consent were included in the study. Children were selected for undergoing bitewing radiographs (group 1; n=20) or digital dental panoramic radiographs (group 2; n=20). Exfoliated buccal mucosal cells were obtained by scraping the right/left buccal mucosa with a wooden spatula immediately before the X-ray exposure and 10±2 days after exposure.Results:The frequency of micronuclei increases significantly post exposure to both bitewing and digital dental panoramic radiography in children, but the frequency was higher in bitewing radiographs.Conclusion:It was concluded that the frequency of micronuclei increases post exposure to both bitewing and digital panoramic radiographs. Increased radiation exposure results in an increase in micronuclei frequency.

Peripheral blood lymphocyte micronucleus frequencies in men from areas of Kerala, India, with high vs normal levels of natural background ionizing radiation

We have measured the frequencies of micronuclei (MN) in adult male individuals living in areas of the Kerala coast, southwest India, with either high (HLNRA, >1.5mGy/year) or normal levels of natural ionizing radiation (NLNRA, ≤1.5mGy/year). Blood samples were obtained from 141 individuals, 94 from HLNRA and 47 from NLNRA, aged 18–72, and were subjected to the cytokinesis-block micronucleus (CBMN) assay. An average of 1835 binucleated (BN) cells per individual were scored. The overall frequency of MN (mean±SD) was 11.7±6.7 per 1000 BN cells. The frequencies of MN in the HLNRA (11.7±6.6) and NLNRA (11.6±6.7) were not statistically significantly different (P=0.59). However, a statistically significant (P<0.001) age-dependent increase in MN frequency was observed among individuals from both HLNRA and NLNRA. No natural background radiation dose-dependent increase in MN frequency was seen. MN frequency was not influenced by tobacco smoking or chewing but it was increased among individuals consuming alcohol. Chronic low-dose radiation in the Kerala coast did not have a significant effect on MN frequency among adult men.

Sugarcane Vinasse, a Residue of Ethanol Industry: Toxic, Cytotoxic and Genotoxic Potential Using the &amp;lt;i&amp;gt;Allium cepa&amp;lt;/i&amp;gt; Test

The search for fuels to replace petroleum consumption has caused an increase in the production of biofuels worldwide. The ethanol, which comes from sugarcane, is an energy resource with low polluting potential, but its production generates other environmental problems. On average, 10 to 15 liters of vinasse are generated while preparing each liter of ethanol. Vinasse is the final by-product of the biomass distillation, mainly for the production of ethanol, from different cultures such as sugarcane. Because excessive quantities of vinasse are produced, alternatives have been required for use, for example as fertilizer, in a process known as fertigation. These excessive amounts of vinasse applied in soils have generated adverse effects on soil properties and to the organisms. This study carried out the toxic, cytotoxic and genotoxic potential of sugarcane vinasse obtained from two different harvests (Samples I and II), using the Allium cepa organism test. A. cepa seeds were exposed to raw vinasse (RV) and diluted in different concentrations: control soil + raw vinasse (SV); vinasse diluted in water at 50% + control soil (V 50%); vinasse diluted in water at 25% + control soil (V 25%); vinasse diluted in water at 12.5% + control soil (V 12.5%). The chemical characterization of vinasse samples showed a low pH and high concentration of potassium. The results demonstrate that the two RV samples tested are toxic, since no seeds germination was observed. The cytotoxic potential was observed in the sample II of SV and V (50%). All groups evaluated in samples I and II, induced chromosomal alterations, statistically significant compared with negative control. An increase in frequency of micronuclei in meristematic cells was observed in the SV (Sample I) and all groups evaluated in samples II. Based on the results it is concluded that the genetic material of the test-system was damaged when exposed to sugarcane vinasse, suggesting that one should be very careful in the use of this waste that has been used sometimes indiscriminately in soils.

Modulatory Effect of Betulinic Acid on the Genotoxicity Induced by Different Mutagens in V79 Cells.

Betulinic acid (BA) is a pentacyclic triterpene that can be isolated from many medicinal plants around the world. The aim of this study was to evaluate the genotoxic potential of BA and its effect on the genotoxicity induced by different mutagens in V79 cells using the cytokinesis-block micronucleus assay. Different BA concentrations were combined with methyl methanesulfonate (MMS), doxorubicin (DXR), camptothecin (CPT), and etoposide (VP-16). The frequencies of micronuclei in cultures treated with different BA concentrations did not differ from those of the negative control. Treatment with BA and MMS resulted in lower micronucleus frequencies than those observed for cultures treated with MMS alone. On the other hand, a significant increase in micronucleus frequencies was observed in cultures treated with BA combined with DXR or VP-16 when compared to these mutagens alone. The results showed no effect of BA on CPT-induced genotoxicity. Therefore, BA was not genotoxic under the present experimental conditions and exerted a different influence on the genotoxicity induced by different mutagens. The modulatory effect of BA depends on the type of mutagen and concentrations used.

Genotoxicity Evaluation of Dipotassium -Trioxohydroxytetrafluorotriborate, K2(B3O3F4OH), in Human Lymphocyte Cultures and Mice Reticulocytes

Genotoxic effects of inorganic molecule dipotassium-trioxohydroxytetrafluorotriborate, K2(B3O3F4OH), a promising new therapeutic for the epidermal changes treatment, have been evaluated. In vitro analysis included evaluation of genotoxic and cytotoxic potential of K2(B3O3F4OH) in concentrations of 0.01, 0.02, 0.05 and 0.06 mg/mL applying cytokinesis-block micronucleus cytome assay in human lymphocyte culture. With the increase of concentration the frequency of micronuclei elevated but the differences were not significant. Also, there were no significant differences among the frequencies of nuclear buds and nucleoplasmic bridges between controls and treated cultures. Nuclear division index and nuclear division cytotoxycity index values did not reveal significant cytotoxic effect of K2(B3O3F4OH). In vivo genotoxic effects were analyzed on BALB/c mice applying reticulocytes micronucleus assay. K2(B3O3F4OH) was administrated intraperitoneally in final concentrations of 10, 20, 50 and 55 mg/kg. Significant decrease of reticulocytes ratio and increase of micronuclei frequencies against pre-treatments were found for both sampling periods of 48 and 72 hours of the highest applied concentration. This study confirmed that K2(B3O3F4OH) is not genotoxic in tested concentrations in vitro as well as in concentrations lower than 55 mg/kg in vivo. This study presents a reliable basis for further pre-clinical and potential clinical investigations.

Increased micronucleus, nucleoplasmic bridge, nuclear bud frequency and oxidative DNA damage associated with prolactin levels and pituitary adenoma diameters in patients with prolactinoma

Prolactinoma is the most common pituitary tumor. Most pituitary tumors are benign, but they often are clinically significant. We investigated cytokinesis-block micronucleus cytome (CBMN cyt) assay parameters and oxidative DNA damage in patients with prolactinoma to assess the relations among age, prolactin level, pituitary adenoma diameter and 8-hydroxy-2’-deoxyguanosine (8-OHdG) level in patients with prolactinoma. We investigated 27 patients diagnosed with prolactinoma and 20 age- and sex-matched healthy controls. We measured CBMN cyt parameters and plasma 8-OHdG levels in peripheral blood lymphocytes of patients with prolactinoma and controls. The frequencies of micronucleus (MN), nucleoplasmic bridge, nuclear bud, apoptotic and necrotic cells, and plasma 8-OHdG levels in patients with prolactinoma were significantly greater than controls. MN frequency was correlated positively with age, prolactin levels and pituitary adenoma diameters in patients with prolactinoma. The increased chromosomal and oxidative DNA damage, and the positive correlation between MN frequency, prolactin levels and pituitary adenoma diameters may be associated with increased risk of cancer in patients with prolactinoma, because increased MN frequency is a predictor of cancer risk.

The impact of water pollution on fish species in southeast region of Goiás, Brazil

ABSTRACTThe rivers from the region of Catalão, Southeast Goiás State, Brazil, are exposed to intense anthropogenic influences including agricultural activities, industry, and urban waste. The aim of this study was to determine the severity of water pollution by conducting an experiment involving in situ biomonitoring of water constituents on genotoxicity in fish inhabiting these sites. The genotoxicity of three sites of the region were analyzed utilizing the micronucleus (MN) test. It was of interest to determine whether there were differences between sampling sites such as urban perimeter, agriculture, and fertilizer industry in control, and monitored species including Astyanax fasciatus, Astyanax altiparanae, and Characidium fasciatum. Data demonstrated that the species at sites 1, 2, and 3 exhibited a marked increase in frequency of MN compared to fish from site 4. Significant elevation in frequency of MN occurred in erythrocytes of A. fasciatus and A. altiparanae at sites 1 and 2. At site 3 higher frequencies of MN were observed in C. fasciatum. MN induction in C. fasciatum was correlated with chromium levels in water and sediment, while A. fasciatum and A. altiparanae showed an association with zinc in water and sediment. Data suggest that benthic and nektonic fish species display different sensitivities in relation to anthropogenic contaminant influences.

Measuring biological responses at different levels of organisation to assess the effects of diffuse contamination derived from harbour and industrial activities in estuarine areas

To evaluate the effects of diffuse contamination, biological measurements were applied in a scrap cargo harbour, a marina and an industrial area. Metal accumulation and biomarkers (survival in air, digestive gland and gonad histopathology, lysosomal membrane stability, intralysosomal metal accumulation, transcription of vitellogenin and MT20, peroxisome proliferation and micronuclei formation) were measured in transplanted mussels, together with metrics of benthic invertebrates. Benthic species were classified into ecological groups and univariate indexes were calculated. The marina showed high richness (16) and percentage of opportunistic species (55.1%) and low metal accumulation. Mussels in the scrap cargo harbour showed high metal accumulation, up-regulation of MT20 transcription, reduced health status (LP<6min) and increased micronuclei frequencies (up to 11.3‰). At the industrial area, low species richness (4) and badly organised assemblages were detected and chemical analyses indicated significant amounts of bioavailable metals. Overall, selected biological measurements showed potential for the assessment of diffuse contamination.

Genotoxic evaluation of the River Paranaíba hydrographic basin in Monte Carmelo, MG, Brazil, by the Tradescantia micronucleus.

Pollutants have adverse effects on human health and on other organisms that inhabit or use water resources. The aim of the present study was to assess the environmental quality of three watercourses in Monte Carmelo, MG, Brazil, using the micronucleus test on Tradescantia. For each treatment, 15 plants were exposed to water samples for 24 h. The control group was exposed to formaldehyde (0.2%) and the negative control to Hoagland solution. Subsequently the plants were placed in Hoagland solution for 24 h to recover. Cells were stained with 2% acetic carmine and examined by light microscopy. Three hundred tetrads were analyzed per slide. The frequency of genotoxic alterations was expressed as the number of micronuclei per 100 tetrads, and the groups were compared by ANOVA. At all sample sites for each watercourse significant genotoxicity indices were observed. The results suggest that in the Mumbuca creek, the current situation of effluent discharge should be reconsidered by the municipal environmental authorities. The increase in micronucleus frequency denoted for water samples of the Mumbuca creek, Lambari river and Perdizes river emphasizes the need to adopt environmental vigilance strategies, such as biological monitoring.

An altered redox balance and increased genetic instability characterize primary fibroblasts derived from xeroderma pigmentosum group A patients

Xeroderma pigmentosum (XP)-A patients are characterized by increased solar skin carcinogenesis and present also neurodegeneration. XPA deficiency is associated with defective nucleotide excision repair (NER) and increased basal levels of oxidatively induced DNA damage. In this study we search for the origin of increased levels of oxidatively generated DNA lesions in XP-A cell genome and then address the question of whether increased oxidative stress might drive genetic instability. We show that XP-A human primary fibroblasts present increased levels and different types of intracellular reactive oxygen species (ROS) as compared to normal fibroblasts, with O2− and H2O2 being the major reactive species. Moreover, XP-A cells are characterized by decreased reduced glutathione (GSH)/oxidized glutathione (GSSG) ratios as compared to normal fibroblasts. The significant increase of ROS levels and the alteration of the glutathione redox state following silencing of XPA confirmed the causal relationship between a functional XPA and the control of redox balance. Proton nuclear magnetic resonance (1H NMR) analysis of the metabolic profile revealed a more glycolytic metabolism and higher ATP levels in XP-A than in normal primary fibroblasts. This perturbation of bioenergetics is associated with different morphology and response of mitochondria to targeted toxicants. In line with cancer susceptibility, XP-A primary fibroblasts showed increased spontaneous micronuclei (MN) frequency, a hallmark of cancer risk. The increased MN frequency was not affected by inhibition of ROS to normal levels by N-acetyl-l-cysteine.

Exposure to 915 MHz radiation induces micronuclei in Vicia faba root tips.

The increasing use of mobile phones and wireless networks raised a great debate about the real carcinogenic potential of radiofrequency-electromagnetic field (RF-EMF) exposure associated with these devices. Conflicting results are reported by the great majority of in vivo and in vitro studies on the capability of RF-EMF exposure to induce DNA damage and mutations in mammalian systems. Aimed at understanding whether less ambiguous responses to RF-EMF exposure might be evidenced in plant systems with respect to mammalian ones, in the present work the mutagenic effect of RF-EMF has been studied through the micronucleus (MN) test in secondary roots of Vicia faba seedlings exposed to mobile phone transmission in controlled conditions, inside a transverse electro magnetic (TEM) cell. Exposure of roots was carried out for 72h using a continuous wave (CW) of 915 MHz radiation at three values of equivalent plane wave power densities (23, 35 and 46W/m(2)). The specific absorption rate (SAR) was measured with a calorimetric method and the corresponding values were found to fall in the range of 0.4-1.5W/kg. Results of three independent experiments show the induction of a significant increase of MN frequency after exposure, ranging from a 2.3-fold increase above the sham value, at the lowest SAR level, up to a 7-fold increase at the highest SAR. These findings are in agreement with the limited number of data on cytogenetic effects detected in other plant systems exposed to mobile phone RF-EMF frequencies and clearly show the capability of radiofrequency exposure to induce DNA damage in this eukaryotic cell system.

Cytogenetic evaluation for the genotoxicity of bisphenol-A in Chinese hamster ovary cells

Bisphenol A (BPA), identified as an endocrine disruptor, is an important man-made compound used in a wide range of consumer products. The MTT assay, comet assay, micronucleus test, chromosome aberration test, and Ames assay were conducted to assess the cytotoxic, genotoxic, cytogenetic effects, and mutagenic activity of BPA. After BPA exposure, we showed significant increases in cytotoxicity and level of DNA damage indicated by Olive tail moment, tail length, and % tail DNA in a similar dose- and time-dependent manner. Significant increases in micronucleus frequency and conventional chromosome aberrations were also observed after BPA treatment. The major types of structural aberrations were breaks, gaps, and fragments. However, no positive mutagenic activity of BPA was observed in any of the tester strains. Taken together, the data obtained in this study clearly demonstrated that BPA is not mutagenic but could exhibit significant genotoxic and cytogenetic effects in Chinese hamster ovary cells.