Aneugenicity and clastogenicity in freshwater fish Oreochromis niloticus exposed to incipient safe concentration of tannery effluent

Conventional effluent bioassays mostly rely on overt responses or endpoints such as apical and Darwinian fitness. Beyond the empirical observation, laboratory toxicity testing needs to rely on effective detection of prognostic biomarkers such as genotoxicity. Indeed, characterization of tannery effluent requires slotting in of genotoxic responses in whole effluent toxicity testing procedures. Hence, the prime objective of the present experimental investigation is to apply the technique of biological assay as a tool of toxicity testing to evaluate the induction of micronuclei (MN) in peripheral erythrocytes, and exfoliated cells of gill and kidney of O.niloticus exposed to Maximum tolerable concentrations (MTCs) of composite Modjo tannery effluent (CMTE) and to compare the sensitivity of each cells origin to the induction of MN. After 72h of exposure, cellular aberrations were detected using MN and nuclear abnormality (NA) tests. The induction of MN was significantly higher in exposed groups (P<0.05) when compared to the control group; moreover the tissue specific MN response was in the order, gill cells>peripheral erythrocyte>kidney. Total NA was found to increase significantly (P<0.05), when compared to the non-exposed group. NA was also further ramified as blebbed (BL), bi-nucleated (BN), lobbed (LB) and notched (NT) abnormalities. The result of each endpoint measured has demonstrated that at a concentration of total chromium (0.1, 0.73 and 1.27mg/L), a perceptible amount cellular aberration was measured, further implicating somber treat of genotoxicity to fishes, if exposed to water contaminated with tannery effluent. This further highlight that conventional effluent monitoring alone cannot reveal the effects expressed at cellular and genetic levels further demanding the incorporation of effluent bioassays in risk assessment and risk management/abatement programs.

Frequencies of erythrocyte nuclear abnormalities and of leucocytes in the fish Barbus peloponnesius correlate with a pollution gradient in the River Bregalnica (Macedonia)

Integrated chemical and biomarker approaches were performed to estimate if there is ongoing toxicity in the River Bregalnica, namely connected with the presence of metals. The study was performed in water, sediment, and barbel (Barbus peloponnesius), collected in two seasons, from two suspected polluted and one reference zones. The water analyses revealed higher mean values in polluted sites for most of the examined physicochemical parameters. Metal concentrations (Zn, Cu, Cd, Mn, Pb, and Fe) in water were more or less constant, whereas in sediment, they were higher at the two polluted locations. Condition factor (CF), as a general health indicator, revealed better overall condition in barbel from the reference site. In general, blood parameters revealed higher values in the polluted localities. Irrespective of sex and/or season, the frequency of micronuclei (MN) and vacuolated nuclei (VN) were with higher rates in polluted sites. Similarly, the frequencies of the leucocytes (Le), binuclei (BN), and irregularly shaped nuclei (ISN) were also significantly increased in the polluted localities, but they seemed prone to be influenced by sex and/or season. However, strong positive correlations between blood biomarkers and most water physicochemical parameters and metal in sediment were estimated. Our data support that the River Bregalnica's lower course receives significant genotoxic pollution, likely via metal industry effluents, agricultural runoff, and domestic sewage, and reinforced the utility of MN and other nuclear abnormalities as sensitive and suitable biomarkers for genotoxicity when used in monitoring studies.

Toxicological effects of the waste of the sugarcane industry, used as agricultural fertilizer, on the test system Allium cepa

Sugarcane is cultivated in tropical countries for sugar and ethanol production. In Brazil, this culture is among the most profitable with a production of 658.7 million tons/harvest. Sugarcane filter cake (SCFC) is a waste rich in organic matter and micronutrients, but also contains toxic metals. As it has been used as fertilizer and there is not enough knowledge about its environmental impacts, this work assessed the genotoxicogenetic effects of raw SCFC and associations with soil and sugarcane bagasse (SCB), by Allium cepa tests. Six associations of SCFC + soil and five associations of SCFC + soil + SCB were tested at three moments of degradation: initial (T0), 3 and 6 months (T1 and T2). Genotoxicogenetic assays were performed with solid substrates of these associations and with their respective aqueous extracts. Chemical analysis showed a decrease in metals, total organic carbon and nitrogen after 6 months of biodegradation, complying with Brazilian laws. In general, the combination of SCFC + soil + SCB was better than using only SCFC. T0 solubilized samples of different associations composed by highest quantities of SCFC inhibited the MI and induced CA without presenting mutagenicity (except for 75%-SCFC + soil + SCB). T1 samples showed more cytotoxicity than T0 samples, and also presented genotoxic and mutagenic effects. Solid substrate and solubilized associations of SCFC + soil + SCB of T2 samples had no toxicity. These results suggest 6 months of biodegradation and the SCB adding as effective to reduce toxicogenetic effects induced by SCFC. Also, small proportions of SCFC interfered less on the A. cepa test-system when compared with those containing high quantities of residue.

Effect of diterpenoid kaurenoic acid on genotoxicity and cell cycle progression in gastric cancer cell lines

The goal of our study was to evaluate the effect of kaurenoic acid, obtained from copaiba oil resin, in gastric cancer (GC) and a normal mucosa of stomach (MNP01) cell lines. The compound was tested at concentrations of 2.5, 5, 10, 30 and 60μg/mL. Comet and micronucleus assays were used to access its potential genotoxicity in vitro. Moreover, we evaluated the effect of kaurenoic acid in cell cycle progression and in the transcription of genes involved in the control of the cell cycle: MYC, CCND1, BCL2, CASP3, ATM, CHK2 and TP53. Kaurenoic acid induced an increase on cell DNA damage or micronucleus frequencies on GC cell lines in a dose-dependent manner. The GC and MNP01 cell lines entering DNA synthesis and mitosis decreased significantly with kaurenoic acid treatment, and had an increased growth phase compared with non-treated cells. The treatment induced apoptosis (or necrosis) even at a concentration of 2.5μg/mL in relation to non-treated cells. GC cell lines presented reduced MYC, CCND1, BCL2 and CASP3 transcription while ATM, CHK2 and TP53 increased in transcription in relation to non-treated cells, especially at a concentration above 10μg/mL. The gene transcription in the MNP01 (non-treated non-cancer cell line) was designated as a calibrator for all the GC cell lines. In conclusion, our results showed that kaurenoic acid obtained from Copaifera induces DNA damage and increases the micronuclei frequency in a dose-dependent manner in GC cells, with a significant genotoxicity observed above the concentration of 5μg/mL. Moreover, this compound seems to be able to induce cell cycle arrest and apoptosis in GC cells.

Fate of micronuclei and micronucleated cells

The present review describes available evidence about the fate of micronuclei and micronucleated cells. Micronuclei are small, extranuclear chromatin bodies surrounded by a nuclear envelope. The mechanisms underlying the formation of micronuclei are well understood but not much is known about the potential fate of micronuclei and micronucleated cells. Many studies with different experimental approaches addressed the various aspects of the post-mitotic fate of micronuclei and micronucleated cells. These studies are reviewed here considering four basic possibilities for potential fates of micronuclei: degradation of the micronucleus or the micronucleated cell, reincorporation into the main nucleus, extrusion from the cell, and persistence in the cytoplasm. Two additional fates need to be considered: premature chromosome condensation/chromothripsis and the elimination of micronucleated cells by apoptosis, yielding six potential fates for micronuclei and/or micronucleated cells. The available data is still limited, but it can be concluded that degradation and extrusion of micronuclei might occur in rare cases under specific conditions, reincorporation during the next mitosis occurs more frequently, and the majority of the micronuclei persist without alteration at least until the next mitosis, possibly much longer. Overall, the consequences of micronucleus formation on the cellular level are still far from clear, but they should be investigated further because micronucleus formation may contribute to the initial and later steps of malignant cell transformation, by causing gain or loss of genetic material in the daughter cells and by the possibility of massive chromosome rearrangement in chromosomes entrapped within a micronucleus by the mechanisms of chromothripsis and chromoanagenesis.

Evaluation of cytological and genetic effects of Tribulus terrestris fruit aqueous extract on cultured human lymphocytes

The current study was carried out to evaluate the genotoxic aspects of the aqueous extracts of the Tribulus terrestris fruits by comet assay and cytogenetic procedures conditions on cultured human peripheral blood lymphocyte. After the treatment of the lymphocytes with four concentrations of the aqueous fruit extract of T. terrestris (10, 20, 40 and 80 mg/L) for 24 h it was noticed that, the presence of micronuclei and/or chromosomal aberration were monitored and a significant increase of comet cells at high concentration of T. terrestris extract 80 mg/L. Also, this study showed that the presence of micronuclei, chromosomal aberration as a chromosomal gap, fragmentation, stickiness and necrotic cells were appeared and increased with high concentrations of T. terrestris fruits extract (40–80 mg/L). On the other hand, no significant difference was observed with the low concentration of the extract (10–20 mg/L) as compared with control. The current study refers to the ability of the extract of T. terrestris fruits to do damage in the target DNA at the higher concentrations. Thus, it could be considered that the aqueous extracts of the T. terrestris fruits have genotoxic effect in the therapeutic protocols if it used in high doses.

Aberrant Meiotic Modulation Partially Contributes to the Lower Germination Rate of Pollen Grains in Maize (Zea mays L.) Under Low Nitrogen Supply

Pollen germination is an essential step towards successful pollination during maize reproduction. How low niutrogen (N) affects pollen germination remains an interesting biological question to be addressed. We found that only low N resulted in a significantly lower germination rate of pollen grains after 4 weeks of low N, phosphorus or potassium treatment in maize production. Importantly, cytological analysis showed 7-fold more micronuclei in male meiocytes under the low N treatment than in the control, indicating that the lower germination rate of pollen grains was partially due to numerous chromosome loss events resulting from preceding meiosis. The appearance of 10 bivalents in the control and low N cells at diakinesis suggested that chromosome pairing and recombination in meiosis I was not affected by low N. Further gene expression analysis revealed dramatic down-regulation of Nuclear Division Cycle 80 (Ndc80) and Regulator of Chromosome Condensation 1 (Rcc1-1) expression and up-regulation of Cell Division Cycle 20 (Cdc20-1) expression, although no significant difference in the expression level of kinetochore foundation proteins Centromeric Histone H3 (Cenh3) and Centromere Protein C (Cenpc) and cohesion regulators Recombination 8 (Rec8) and Shugoshin (Sgo1) was observed. Aberrant modulation of three key meiotic regulators presumably resulted in a high likelihood of erroneous chromosome segregation, as testified by pronounced lagging chromosomes at anaphase I or cell cycle disruption at meiosis II. Thus, we proposed a cytogenetic mechanism whereby low N affects male meiosis and causes a higher chromosome loss frequency and eventually a lower germination rate of pollen grains in a staple crop plant.

Photodegradation of 2-chloropyridine in aqueous solution: Reaction pathways and genotoxicity of intermediate products

2-Chloropyridine, an important precursor of the chemical industry is also a persistent water pollutant. The genotoxicity of photolytically treated 2-chloropyridine aqueous solution to human lymphocytes initially increases and fluctuates during treatment finally reaching the control values after prolonged treatment. Intermediate products formed were identified; a kinetic scheme for their formation is presented. To identify the source of genotoxicity variations and the potential in vitro effects on human lymphocytes of the partially photo-treated aqueous solution, the genotoxicity of four (the only) commercially available intermediates, i.e., 1H-pyrrole-2-carboxaldehyde, 6-chloro-2-pyridinecarboxylic acid, 2,3-dichloropyridine and 2-pyridinecarbonitrile was measured; the obtained results were used for the reasoning on the variation of the solution genotoxic (including clastogenic as well as aneugenic) events and cytotoxic activity. It was found that 1H-pyrrole-2-carboxaldehyde and 6-chloro-2-pyridinecarboxylic acid were highly genotoxic even at the very low concentration measured here. Thus, they likely had a significant contribution to the photolytically treated solution genotoxicity. 2,3-Dichloropyridine was found to be genotoxic but only at concentrations higher than the ones measured in this work. Thus, it was not likely to have contributed to the solution genotoxicity. Finally, at the concentrations measured in this work 2-pyridinecarbonitrile was found to be only cytotoxic.

Radioprotective effects of cimetidine on rats irradiated by long-term, low-dose-rate neutrons and 60Co γ-rays

BACKGROUND

Cimetidine, an antagonist of histamine type II receptors, has shown protective effects against γ-rays or neutrons. However, there have been no reports on the effects of cimetidine against neutrons combined with γ-rays. This study was carried out to evaluate the protective effects of cimetidine on rats exposed to long-term, low-dose-rate neutron and γ-ray combined irradiation (n-γ LDR).

METHODS

Fifty male Sprague-Dawley (SD) rats were randomly divided into 5 groups: the normal control group, radiation model group, 20 mg/(kg · d) cimetidine group, 80 mg/(kg · d) cimetidine group and 160 mg/(kg · d) cimetidine group (10 rats per group). Except for the normal control group, 40 rats were simultaneously exposed to fission neutrons (²⁵²Cf, 0.085 mGy/h) for 22 h every day and γ-rays (⁶⁰Co, 0.097 Gy/h) for 1.03 h once every three days, and the cimetidine groups were administered intragastrically with cimetidine at doses of 20, 80 and 160 mg/kg each day. Peripheral blood WBC of the rats was counted the day following exposure to γ-rays. The rats were anesthetized and sacrificed on the day following exposure to ²⁵²Cf for 28 days. The spleen, thymus, testicle, liver and intestinal tract indexes were evaluated. The DNA content of bone marrow cells and concanavalin A (ConA)-induced lymphocyte proliferation were measured. The frequency of micronuclei in polychromatic erythrocytes (fMNPCEs), superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) in the serum and liver tissues were detected.

RESULTS

The peripheral blood WBC in the cimetidine groups was increased significantly on the 8th day and the 26th day compared with those in the radiation model group. The spleen, thymus and testicle indexes of the cimetidine groups were higher than those of the radiation model group. The DNA content of bone marrow cells and lymphocyte proliferation in the cimetidine groups were increased significantly, and fMNPCE was reduced 1.41-1.77 fold in cimetidine treated groups. The activities of SOD and GSH-Px in the cimetidine groups were increased significantly, and the content of MDA in the cimetidine groups was decreased significantly.

CONCLUSIONS

The results suggested that cimetidine alleviated damage induced by long-term, low-dose-rate neutron and γ combined irradiation via antioxidation and immunomodulation. Cimetidine might be useful as a potent radioprotector for radiotherapy patients as well as for occupational exposure workers.

Micronuclei and dyskaryosis of erythrocytes and oxidative stress response with endosulfan exposure in topmouth gudgeon Pseudorasbora parva

Endosulfan is a chlorinated and genotoxic insecticide extensively used worldwide in agriculture. However, residues of endosulfan can be detected in farmland soil and natural water. In this study, toxic effects of endosulfan were studied by measuring micronuclei and dyskaryosis in peripheral erythrocytes of topmouth gudgeon (Pseudorasbora parva). In addition, liver antioxidant enzyme activity and lipid peroxidation level were measured. P. parva were exposed to control and 5 doses (0.12, 0.16, 0.21, 0.31 and 0.62μg/L) of endosulfan for 48h and 96h. The frequencies of micronuclei and dyskaryosis, antioxidant enzyme activity, contents of ROS and lipid peroxidation increased by endosulfan exposure. Compared to controls, frequencies of micronuclei and dyskaryosis were significantly increased with endosulfan exposure, and an obvious dose-response relationship was found. Endosulfan has potential genotoxicity by inducing the oxidative stress and lipid peroxidation, which probably lead to the occurrence of micronuclei and dyskaryosis in erythrocytes.

Erythrocyte micronucleus cytome assay of 17 wild bird species from the central Monte desert, Argentina

Birds have the potential to be considered valuable bioindicators of the quality of ecosystems and the environmental impact of pollutants. The aims of this study were to determine the micronuclei frequency and other nuclear abnormalities in erythrocytes by analyzing a wild bird community from central Monte desert (Argentina) and to clarify if there were any differences among certain species. Frequencies of nuclear abnormalities were determined in 73 wild birds belonging to 17 species and two orders (Passeriformes and Columbiformes). A high proportion of individuals, 90.4 and 80.9 %, had erythrocytes with micronuclei and nuclear buds, respectively. Notched nuclei, binucleated cells, nuclear tails, and nucleoplasmic bridges were also recorded. Certain species appeared to be more informative than others with regard to the possibility of being used as bioindicators of genetic damage. Saltator aurantiirostris and Columbina picui were the only species that showed significantly different frequencies of nuclear alterations, in comparison with the other species. The frequencies here presented are the first reported for these bird species from the orders Passeriformes and Columbiformes. This research supports the notion that the use of these biomarkers could be effectively applied to evaluate spontaneous or induced genetic instability in wild birds.

DNA replication after mutagenic treatment in Hordeum vulgare

The temporal and spatial properties of DNA replication in plants related to DNA damage and mutagenesis is poorly understood. Experiments were carried out to explore the relationships between DNA replication, chromatin structure and DNA damage in nuclei from barley root tips. We quantitavely analysed the topological organisation of replication foci using pulse EdU labelling during the S phase and its relationship with the DNA damage induced by mutagenic treatment with maleic hydrazide (MH), nitroso-N-methyl-urea (MNU) and gamma ray. Treatment with mutagens did not change the characteristic S-phase patterns in the nuclei; however, the frequencies of the S-phase-labelled cells after treatment differed from those observed in the control cells. The analyses of DNA replication in barley nuclei were extended to the micronuclei induced by mutagens. Replication in the chromatin of the micronuclei was rare. The results of simultanous TUNEL reaction to identify cells with DNA strand breaks and the labelling of the S-phase cells with EdU revealed the possibility of DNA replication occurring in damaged nuclei. For the first time, the intensity of EdU fluorescence to study the rate of DNA replication was analysed.

Mapping the factors affecting the frequency and types of micronuclei in an elderly population from Southern Bohemia

The micronucleus assay is one of the most common methods used to assess chromosomal damage (losses or breaks) in human peripheral blood lymphocytes (PBL) in genetic toxicology. Most studies have focused on analyzing total micronuclei (MN), but identifying the content of MN can provide more detailed information. The main aim of this study was to map the factors affecting the frequency and types of micronuclei in binucleated cells (BNC) in elderly population. Fluorescence in situ hybridization using Human Pan Centromeric Chromosome Paint was used to identify centromere positive (CEN+) or centromere negative (CEN-) MN. A group of 95 men from Southern Bohemia, Czech Republic (average age 68.0±6.8 years) was followed repeatedly, in spring and fall 2014. The study participants were former workers of the uranium plant "MAPE Mydlovary" (processing uranium ore from 1962 to 1991), and controls. The general profile of individual types of MN, and the effect of the season, former uranium exposure, age, smoking status, weight, and X-ray examination on the level and type of MN were analyzed. The results of this study showed: (i) a stable profile of BNC with MN based on the number of MN during two seasons; (ii) an increase of the number of CEN+ MN from spring to fall; (iii) a lower frequency of the total MN in the exposed group than in controls with a significant difference in the percentage of aberrant cells (%AB.C.) in the fall; (iv) no clear effect of age, smoking and BMI on DNA damage in this group; (v) lower DNA damage levels in former uranium workers who received X-ray examination later in life. In summary, the results indicate a trend of seasonal changes of individual types of MN and suggest that former exposure can have a protective effect on the level of DNA damage in case of future exposure.

Cytogenetic biomarkers in detection of genotoxic effects of gestagens in peripheral blood lymphocytes in vitro and in vivo

Gestagens are the most frequently used steroid hormones in hormone-replacement therapy in the treatment of threatened miscarriage during the first trimester of pregnancy. This therapy has been applied in a large number of women with threatened abortion, despite various degrees of success of its efficacy. Genetic factors play a key role in miscarriages, especially in the initial stages. Cytogenetic biomarkers such as micronucleus (MN) test, chromosomal aberrations (CAs), and sister chromatid exchanges (SCEs) provide information on DNA damage. Cytogenetic markers detecting DNA damage have become very popular and useful in analysing genetic risk associated with hormone-replacement therapy. Cytogenetic studies presented heterogenous information. In many in vitro studies synthetic gestagens have been shown to induce genotoxic effects, and it was evaluated using three cytogenetic biomarkers. Genotoxic effects of gestagens have also been confirmed in in vivo studies that were conducted involving patients who received gestagen therapy during pregnancy and their newborns. However, some studies have shown that hormone-replacement therapy does not have genotoxic effects. In this paper, we summarize the results from previous studies. We also describe the usefulness of these biomarkers in the detection of genotoxic effects of hormone-replacement therapy.

Micronucleated erythrocytes in newborns rats exposed to three different types of ultraviolet-A (UVA) lamps from commonly uses devices

Exposure to ultraviolet-A (UVA) light can accidentally cause adverse effects in the skin and eyes. UVA induces DNA damage directly by creating pyrimidine dimers or by the formation of reactive oxygen species that can indirectly affect DNA integrity. UVA radiation is emitted by lamps from everyday devices. In adult rats, micronucleated erythrocytes (MNE) are removed from the circulation by the spleen. However, in newborn rats, MNE have been observed in peripheral blood erythrocytes. The objective of this study was to use micronucleus tests to evaluate the DNA damage caused in newborn rats exposed to UVA light from three different types of UVA lamps obtained from commonly used devices: counterfeit detectors, insecticide devices, and equipment used to harden resins for artificial nails. Rat neonates were exposed to UVA lamps for 20min daily for 6days. The neonates were sampled every third day, and the numbers of MNE and micronucleated polychromatic erythrocytes (MNPCE) in the peripheral blood were determined. The rat neonates exposed to the three types of UVA lamps showed increased numbers of MNE and MNPCE from 48h to 144h (P<0.05 and P<0.001 respectively). However, no relationship was observed between the number of MNE and the wattage of the lamps. In conclusion, under these conditions, UVA light exposure induced an increase in MNE without causing any apparent damage to the skin.

Combination of tacrolimus and mycophenolate mofetil induces oxidative stress and genotoxicity in spleen and bone marrow of Wistar rats

Tacrolimus (TAC) and mycophenolate mofetil (MMF) are common immunosuppressive drugs used to avoid immunological rejection of transplanted organs. The risk of developing cancer is the most critical complication in organ transplant recipients undergoing immunosuppressive therapy. This study aims to explore the cytotoxic and genotoxic effects of TAC and MMF alone or combined orally administrated on spleen and bone marrow of Wistar rats. Our results showed that TAC (2.4; 24 and 60mg/kg) and MMF (5; 50 and 125mg/kg) induced a genotoxic effect on rat bone marrow. Moreover, the co-treatment with the TAC/MMF (2.4/5mg/kg b.w.; 2.4/50mg/kg b.w. and 60/50mg/kg b.w.) produce a genotoxicity as measured by micronuclei (MN) frequencies, chromosomal aberrations (CA) rates and DNA damage levels. Furthermore, the TAC and MMF-treated animals developed oxidative stress in spleen, indicated by a significant increase of malondialdehyde (MDA), protein oxidation and decrease of anti-oxidant enzymes levels such as catalase (CAT) and superoxide dismutase (SOD). This damage was associated with an increase of DNA fragmentation. Co-treatment with TAC/MMF synergistically induced markers of oxidative stress in rat splenic tissue. In conclusion, TAC/MMF associated induction in oxidative stress plays a role in the splenic and bone marrow toxicity and enhances the different endpoints of genotoxicity, suggesting its mutagenic action in vivo.

Surface-modified magnetite nanoparticles act as aneugen-like spindle poison

Iron oxide nanoparticles are one of the most promising types of nanoparticles for biomedical applications, primarily in the context of nanomedicine-based diagnostics and therapy; hence, great attention should be paid to their bio-safety. Here, we investigate the ability of surface-modified magnetite nanoparticles (MNPs) to produce chromosome damage in human alveolar A549 cells. Compared to control cells, all the applied MNPs increased the level of micronuclei moderately but did not cause structural chromosomal aberrations in exposed cells. A rise in endoreplication, polyploid and multinuclear cells along with disruption of tubulin filaments, downregulation of Aurora protein kinases and p53 protein activation indicated the capacity of these MNPs to impair the chromosomal passenger complex and/or centrosome maturation. We suppose that surface-modified MNPs may act as aneugen-like spindle poisons via interference with tubulin polymerization. Further studies on experimental animals revealing mechanisms of therapeutic-aimed MNPs are required to confirm their suitability as potential anti-cancer drugs.

Mutagenic properties of linuron and chlorbromuron evaluated by means of cytogenetic biomarkers in mammalian cell lines

Agricultural practices are usually supported by several chemical substances, such as herbicides. Linuron and chlorbromuron are phenylurea herbicides largely used to protect crops from weeds, blocking photosynthesis by inhibition of the photosystem II complex. The former, also commercially known as lorox or afalon, is selectively used to protect bean and French bean plants, fennels, and celeriacs; the second, commercially known as maloran, is selectively used for carrots, peas, potatoes, soy sprouts, and sunflowers. Considering the widespread use of herbicides and, more generally, pesticides, it is important to clarify their involvement on human health, one of them concerning the possible direct or indirect effect on the genome of exposed populations. Here, we show that these herbicides are endowed by mutagenic properties, as demonstrated by an increased number of chromosomal aberrations (CAs) in two exposed Chinese hamster cell lines derived from ovary and epithelial liver, respectively. This was also confirmed by sister chromatid exchange (SCE) and micronucleus (MN) assays. Our present and previously obtained data clearly indicate that phenylurea herbicides must be used with great caution, especially for agricultural workers who use large amounts of herbicides during their work, and particular attention should be given to residues of these herbicides and their involvement in environmental pollution.

Fish liver and gill cells as cytogenotoxic indicators in assessment of water quality

The present study was aimed to evaluate the effect of municipal wastewater of Tung Dhab drain to freshwater fish Labeo rohita through genotoxicity assays. The idea is to explore and standardize procedures for assessment of toxic impact of pollutant at the cellular level in aquatic species. Hence, chronic, non-renewal toxicity tests were performed with sublethal concentrations (17.7, 26.6 and 35.4 %) of wastewater for exposure durations of 15, 30 and 60 days. Recovery experiments were also performed for duration of 60 days. Higher micronuclei (MN) and binuclei (BN) frequencies were recorded in fluorescently stained liver cells as compared to frequencies obtained for gill cells and erythrocytes. The induced frequencies of MN, BN and nuclear abnormalities (NA) were found in the following order: MN (liver cells) > BN (liver cells) > BN (gill cells) > MN (gill cells) > NA (erythrocytes) > MN (erythrocytes). The results pointed towards the mutagenic nature of water quality of Tung Dhab drain and recommend the incorporation of the liver and gill cells as biomarkers of cytotoxicity over erythrocytes in chronic experiments during water monitoring programs.

Impaired nuclear functions in micronuclei results in genome instability and chromothripsis

Micronuclei (MN) have generally been considered a consequence of DNA damage and, as such, have been used as markers of exposure to genotoxic agents. However, advances in DNA sequencing methods and the development of high-resolution microscopy with which to analyse chromosome dynamics in live cells have been fundamental in building a more refined view of the existing links between DNA damage and micronuclei. Here, we review recent progress indicating that defects of micronuclei affect basic nuclear functions, such as DNA repair and replication, generating massive damage in the chromatin of the MN. In addition, the physical isolation of chromosomes within MN offers an attractive mechanistic explanation for chromothripsis, a massive local DNA fragmentation that produces complex rearrangements restricted to only one or a few chromosomes. When micronuclear chromatin is reincorporated in the daughter cell nuclei, the under-replicated, damaged or rearranged micronuclear chromatin might contribute to genome instability. The traditional conception of micronuclei has been overturned, as they have evolved from passive indicators of DNA damage to active players in the formation of DNA lesions, thus unravelling previously unforeseen roles of micronuclei in the origins of chromosome instability.

Micronuclei as a marker for medical screening of subjects continuously occupationally exposed to low doses of ionizing radiation

CONTEXT

Genotoxicity assays are widely employed in human biomonitoring studies to assess genetic damage inflicted by genotoxic agents.

OBJECTIVE

Evaluation of micronuclei (MN) as a screening marker of occupational ionizing radiation (IR) exposure.

MATERIALS AND METHODS

Using micronucleus test, peripheral blood lymphocytes (PBL) of 402 control and exposed subjects were screened for genetic damage.

RESULTS

The mean frequencies of micronucleus test parameters were significantly higher in exposed persons. Increase of micronucleus yield with duration of exposure (DOE) by 0.303MN/year was revealed.

DISCUSSION AND CONCLUSION

The obtained data encourage us to consider MN as valuable markers for preventive medical screening of occupationally exposed groups.

A Genome-Wide Association Study for Regulators of Micronucleus Formation in Mice

In mammals the regulation of genomic instability plays a key role in tumor suppression and also controls genome plasticity, which is important for recombination during the processes of immunity and meiosis. Most studies to identify regulators of genomic instability have been performed in cells in culture or in systems that report on gross rearrangements of the genome, yet subtle differences in the level of genomic instability can contribute to whole organism phenotypes such as tumor predisposition. Here we performed a genome-wide association study in a population of 1379 outbred Crl:CFW(SW)-US_P08 mice to dissect the genetic landscape of micronucleus formation, a biomarker of chromosomal breaks, whole chromosome loss, and extranuclear DNA. Variation in micronucleus levels is a complex trait with a genome-wide heritability of 53.1%. We identify seven loci influencing micronucleus formation (false discovery rate <5%), and define candidate genes at each locus. Intriguingly at several loci we find evidence for sexual dimorphism in micronucleus formation, with a locus on chromosome 11 being specific to males.

Analyses of combined effects of cytostatic drugs on micronucleus formation in the Tradescantia

Recent experiments showed that 5-fluorouracil (5FU), cisplatin (CDDP), etoposide (ET), and imatinib mesylate (IM), which are currently among the most widely used anticancer drugs, cause damage of the genetic material in higher plants. The aim of the present study was to determine whether mixtures of these drugs cause synergistic or antagonistic effects which may have an impact on their environmental safety. Therefore, the effects of binary mixtures of these anticancer drugs on the induction of micronuclei (MN) which reflect structural and numerical chromosomal aberrations were assessed in Tradescantia tetrads. Synergistic/antagonistic effects were determined by comparison with single exposures that would be equally effective in a reference model of independent action. This comparison was performed at two distinct effect sizes. We found clear evidence for synergisms in combination experiments with IM and antagonism in a high-dose experiment with ET and 5FU. Our findings indicate that IM increases the genotoxic effects of other anticancer drugs. The maximal effects which we found were in the range between 19 and 38 % in the excess of effect sizes predicted under independent action. These effects may have an impact on the overall genotoxic activities of untreated hospital waste waters but not on the environment in general as the predicted environmental concentrations of the studied drugs are several orders of magnitude lower as the levels which are required to cause induction of MN in higher plants.

Vincristine-induced bystander effect in human lymphocytes

Bystander effect is a known radiobiological effect, widely described using ionizing radiations and which, more recently, has also been related to chemical mutagens. In this study, we aimed to assess whether or not a bystander response can be induced in cultured human peripheral lymphocytes by vincristine, a chemotherapeutic mutagen acting as spindle poison, and by mitomycin-C, an alkylating agent already known to induce this response in human lymphoblastoid cells. Designing a modified ad hoc protocol for the cytokinesis blocked micronucleus (MN) assay, we detected the presence of a dose-dependent bystander response in untreated cultures receiving the conditioned medium (CM) from mitomycin-C (MMC) or vincristine (VCR) treated cultures. In the case of MMC, MN frequencies, expressed as micronucleated binucleates, were: 13.5±1.41 at 6μM, 22±2.12 at 12μM or 28.25±5.13 at 15μM vs. a control value of 4.75±1.59. MN levels for VCR, expressed as micronucleated mononucleates were: 2.75±0.88 at 0.0μM, 27.25±2.30 at 0.4μM, 46.25±1.94 at 0.8μM, 98.25±7.25 at 1.6μM. To verify that no mutagen residual was transferred to recipient cultures together with the CM, we evaluated MN levels in cultures receiving the medium immediately after three washings following the chemical treatment (unconditioned medium). We further confirmed these results using a cell-mixing approach where untreated lymphocytes were co-cultured with donor cells treated with an effect-inducing dose of MMC or VCR. A distinct production pattern of both reactive oxygen species and soluble mediator proteins by treated cells may account for the differences observed in the manifestation of the bystander effect induced by VCR. In fact, we observed an increased level of ROS, IL-32 and TGF-β in the CM from VCR treated cultures, not present in MMC treated cultures.

Vitamin D insufficient levels during pregnancy and micronuclei frequency in peripheral blood T lymphocytes mothers and newborns (Rhea cohort, Crete)

BACKGROUND & AIMS

Vitamin D deficiency is common among pregnant women and may be associated with several adverse health outcomes including cancer. Micronuclei frequency is a biomarker of early genetic effects and has been used to examine the association between genotoxic exposures and cancer. We examined maternal vitamin D levels during pregnancy in associations with micronuclei frequency in maternal blood and in cord blood.

METHODS

173 mothers and 171 newborns born between 2007 and 2008 in Heraklion (Crete, Greece) were included in the study. Between 14th and 18th weeks of gestation we collected information on maternal diet using food frequency questionnaires (FFQs). We measured maternal serum concentrations of 25-hydroxyvitamin D [25(OH)D] between the first and second trimester of pregnancy. We estimated dietary vitamin D intake using information from FFQ. After delivery we collected cord blood and maternal peripheral blood. We used the cytokinesis-block micronucleus (CBMN) assay to assess the frequencies of micronucleated cells in binucleated T lymphocytes (MNBN).

RESULTS

Maternal insufficient serum levels of 25(OH)D (<50 nmol/L) during pregnancy were associated with increased MNBN frequency in cord blood [IRR = 1.32 (95%CI: 1.00, 1.72)]. This increase was higher for newborns with birth weight above the third quartile [≥3.500 kg; IRR = 2.21 (1.26, 3.89)]. Similarly, low levels of dietary vitamin D were associated with increased MNBN frequency in cord blood [middle tertile IRR = 1.08 (0.78, 1.47), lower tertile IRR = 1.51 (1.06, 2.14)]. Insufficient levels of vitamin D were not associated with MNBN in mothers.

CONCLUSION

Our results suggest that vitamin D deficiency during pregnancy increases genotoxic risks in newborns. The prevalence of vitamin D deficiency globally is high and it is important to further investigate whether vitamin D supplementation or similar interventions during pregnancy could prevent DNA damage at early stages of life.