The induction of micronuclei as a measure of genotoxicity. A report of the U.S. Environmental Protection Agency Gene-Tox Program

Cytogenetic monitoring of pharmaceutical staff working with cytostatic drug preparations: A 5-year follow-up

Introduction. Cytostatic drug preparation in hos pital pharmacies leads to a concentration of expo sure on a few people and requires considerable protective measures.

Methods. To prove the efficiency of those standards, 45 people who routinely prepare cyto static drugs were monitored with cytogenetic tests, Micronucleus-rate (MN), and Sister Chroma tid Exchange-rate (SCE), once a year over a period up to 5 years. All participants of the study received a physical examination before they began prepar ing cytostatic drugs. Baseline MN and SCE were performed at the time. Individual comparisons for the tests between pre- and post-exposure, and a comparison between an exposed and an unex posed group were then performed.

Results. During the 5-year follow-up there were no hints of genotoxic effects as a result of handling cytostatic drugs.

Conclusion. Thus, it appeared that the safety precautions employed at this Institute were ade quate.

An Evaluation of Genotoxicity Tests With Aquateric® Aqueous Enteric Coating

The genotoxic potential of Aquateric® Aqueous Enteric Coating was evaluated in the Ames test, the mouse lymphoma mutation assay, and the mouse micronucleus test. Aquateric was not mu-tagenic when tested in Salmonella typhimurium cell strains TA98, TA100, TA1535, TA1537, TA1538, with or without metabolic activation. A mouse lymphoma assay was conducted at concentrations ranging from 116 to 2000 μg/ml and 116 to 1250 μg/ml in the absence and presence of metabolic activation, respectively. No increased mutant frequencies were noted for any concentration tested. Aquateric was tested in the mouse micronucleus assay at a single oral dose of 7200 mg/kg Aquateric (equivalent to 5000 mg/kg cellulose acetate phthalate, the major ingredient) and bone marrow was harvested at 24, 48, and 72 hours after treatment. There was no significant increase in the number of mouse bone marrow mi-cronucleated polychromatic erythrocytes in Aquateric-treated animals at any of the harvest times. Based on the negative results in the Ames test, the mouse lymphoma mutation assay, and the mouse micronucleus test, it was concluded that Aquateric is not genotoxic.

In Vivo Effects of Vanadium Pentoxide and Antioxidants (Ascorbic Acid and Alpha-Tocopherol) on Apoptotic, Cytotoxic, and Genotoxic Damage in Peripheral Blood of Mice

This study was conducted to investigate the effects of vanadium pentoxide (V2O5), ascorbic acid (AA), and alpha-tocopherol (α-TOH) on apoptotic, cytotoxic, and genotoxic activity. Groups of five Hsd:ICR mice were treated with the following: (a) vehicle, distilled water; (b) vehicle, corn oil; (c) AA, 100 mg/kg intraperitoneally (ip); (d) α-TOH, 20 mg/kg by gavage; (e) V2O5, 40 mg/kg by ip injection; (f) AA + V2O5; and (g) α-TOH + V2O5. Genotoxic damage was evaluated by examining micronucleated polychromatic erythrocytes (MN-PCE) obtained from the caudal vein at 0, 24, 48, and 72 h after treatments. Induction of apoptosis and cell viability were assessed at 48 h after treatment in nucleated cells of peripheral blood. Treatment with AA alone reduced basal MN-PCE, while V2O5 treatment marginally increased MN-PCE at all times after injection. Antioxidants treatments prior to V2O5 administration decreased MN-PCE compared to the V2O5 group, with the most significant effect in the AA + V2O5 group. The apoptotic cells increased with all treatments, suggesting that this process may contribute to the elimination of the cells with V2O5-induced DNA damage (MN-PCE). The necrotic cells only increased in the V2O5 group. Therefore, antioxidants such as AA and α-TOH can be used effectively to protect or reduce the genotoxic effects induced by vanadium compounds like V2O5.

Comparative study of frequency of micronuclei in normal, potentially malignant diseases and oral squamous cell carcinoma

Context:

The assessment of micronuclei (MN) in exfoliated oral epithelial cells is a promising tool for the study of epithelial carcinogens and can be used to detect chromosome breakage or mitotic interference, thought to be relevant to carcinogenesis.

Aims:

To detect MN in exfoliated oral mucosal cells in individuals using various tobacco forms and also to detect frequency of MN in premalignant lesions and conditions (potentially malignant diseases [PMD's]) and oral squamous cell carcinoma (OSCC). To correlate frequency of MN in oral exfoliated cells in clinically diagnosed cases of OSCC followed by a histopathological grading.

Materials and Methods:

A total of 90 subjects (30 smokeless tobacco users, 30 smokers and 30 nontobacco users) consisted of clinically diagnosed cases of PMD's and OSCC were selected for the study. Cytosmears from the groups were stained with rapid Papanicolaou stain. MN was identified according to the Tolbert et al. criteria.

Results:

MN cells were found to be significantly higher in smokeless tobacco users than in smokers. The frequency of MN was three to four times higher in patients with OSCC as compared to patients in PMD's (P < 0.0001). The frequency of MN correlated with the histopathological grade was statistically significant.

Conclusion:

MN index can be used as a biomarker/screening test among the high-risk groups particularly the smokeless tobacco users and PMD's. MN can be a candidate to serve as a biomarker for prediction of the grade of OSCC.

Modulation of hexavalent chromium-induced genotoxic damage in peripheral blood of mice by epigallocatechin-3-gallate (EGCG) and its relationship to the apoptotic activity

This study was conducted to investigate the relationship between modulation of genotoxic damage and apoptotic activity in Hsd:ICR male mice treated with (-)-epigallocatechin-3-gallate (EGCG) and hexavalent chromium [Cr(VI)]. Four groups of 5 mice each were treated with (i) control vehicle only, (ii) EGCG (10 mg/kg) by gavage, (iii) Cr(VI) (20 mg/kg of CrO3) intraperitoneally (ip), and (iv) EGCG in addition to CrO3 (EGCG-CrO3). Genotoxic damage was evaluated by examining presence of micronucleated polychromatic erythrocytes (MN-PCE) obtained from peripheral blood of the caudal vein at 0, 24, 48, and 72 h after treatment. Induction of apoptosis and cell viability were assessed by differential acridine orange/ethidium bromide (AO/EB) staining. EGCG treatment produced no significant changes in frequency of MN-PCE. However, CrO3 treatment significantly increased number of MN-PCE at 24 and 48 h post injection. Treatment with EGCG prior to CrO3 injection decreased number of MN-PCE compared to CrO3 alone. The MN-PCE reduction was greater than when EGCG was administered ip. The frequency of early apoptotic cells was elevated at 48 h following EGCG, CrO3, or EGCG-CrO3 exposure, with highest levels observed in the combined treatment group, while the frequencies of late apoptotic cells and necrotic cells were increased only in EGCG-CrO3 exposure. Our findings support the view that EGCG is protective against genotoxic damage induced by Cr(VI) and that apoptosis may contribute to elimination of DNA-damaged cells (MN-PCE) when EGCG was administered prior to CrO3. Further, it was found that the route of administration of EGCG plays an important role in protection against CrO3-induced genotoxic damage.

Photolytic transformation products and biological stability of the hydrological tracer Uranine

Among many fluorescence tracers, Uranine (sodium fluorescein, UR) has most widely been used in hydrological research. Extensive use of UR for tracing experiments or commercial use might cause a potential risk of long-term environmental contamination. As any organic substance released to the environment, also UR is subjected to chemical and physical reactions that can be chemical, biological and photolysis processes. These processes transform the parent compound (PC) and have not been extensively investigated for UR. This study applies two OECDs (301 D and 301 F) tests and a screening water sediment test (WST) to investigate the biodegradability of the PC. Photolysis in water was explored by Xe lamp irradiation. Subsequently, the biodegradability of the photolysis mixtures was examined. The primary elimination of UR was monitored and structures of its transformation products (TPs) were elucidated by HPLC-FLD-MS/MS. UR was found not readily biodegradable, although small degradation rates could be observed in the OECD 301 D and WST. HPLC-FLD analysis showed high primary elimination of the tracer during photolysis. However, the low degree of mineralization found indicates that the UR was not fully degraded, instead transformed to TPs. A total of 5 photo-TPs were identified. According to MS/MS data, chemical structures could be proposed for all identified photo-TPs. Likewise the parent compound it was demonstrated that photo-TPs were largely recalcitrant to microbial degradation. Although we did not find indications for toxicity, target-oriented studies on the environmental impact of these photo-TPs are warranted. Results obtained in this study show that deeper investigations are necessary to fully understand fate and risk connected to the use of UR.

Ultraviolet Radiation-Induced Cytogenetic Damage in White, Hispanic and Black Skin Melanocytes: A Risk for Cutaneous Melanoma

Cutaneous Melanoma (CM) is a leading cause of cancer deaths, with reports indicating a rising trend in the incidence rate of melanoma among Hispanics in certain U.S. states. The level of melanin pigmentation in the skin is suggested to render photoprotection from the DNA-damaging effects of Ultraviolet Radiation (UVR). UVR-induced DNA damage leads to cytogenetic defects visualized as the formation of micronuclei, multinuclei and polymorphic nuclei in cells, and a hallmark of cancer risk. The causative relationship between Sun exposure and CM is controversial, especially in Hispanics and needs further evaluation. This study was initiated with melanocytes from White, Hispanic and Black neonatal foreskins which were exposed to UVR to assess their susceptibility to UVR-induced modulation of cellular growth, cytogenetic damage, intracellular and released melanin. Our results show that White and Hispanic skin melanocytes with similar levels of constitutive melanin are susceptible to UVR-induced cytogenetic damage, whereas Black skin melanocytes are not. Our data suggest that the risk of developing UVR-induced CM in a skin type is correlated with the level of cutaneous pigmentation and its ethnic background. This study provides a benchmark for further investigation on the damaging effects of UVR as risk for CM in Hispanics.

Genotoxic Evaluation of Mexican Welders Occupationally Exposed to Welding-Fumes Using the Micronucleus Test on Exfoliated Oral Mucosa Cells: A Cross-Sectional, Case-Control Study

BACKGROUND

An estimated 800,000 people worldwide are occupationally exposed to welding-fumes. Previous studies show that the exposure to such fumes is associated with damage to genetic material and increased cancer risk. In this study, we evaluate the genotoxic effect of welding-fumes using the Micronucleus Test on oral mucosa cells of Mexican welders.

MATERIAL AND METHODS

We conducted a cross-sectional, matched case-control study of n = 66 (33 exposed welders, and 33 healthy controls). Buccal mucosa smears were collected and stained with acridine orange, observed under 100x optical amplification with a fluorescence lamp, and a single-blinded observer counted the number of micronuclei and other nuclear abnormalities per 2,000 observed cells. We compared the frequencies of micronuclei and other nuclear abnormalities, and fitted generalised linear models to investigate the interactions between nuclear abnormalities and the exposure to welding-fumes, while controlling for smoking and age.

RESULTS

Binucleated cells and condensed-chromatin cells showed statistically significant differences between cases and controls. The frequency of micronuclei and the rest of nuclear abnormalities (lobed-nuclei, pyknosis, karyolysis, and karyorrhexis) did not differ significantly between the groups. After adjusting for smoking, the regression results showed that the occurrence of binucleated cells could be predicted by the exposure to welding-fumes plus the presence of tobacco consumption; for the condensed-chromatin cells, our model showed that the exposure to welding-fumes is the only reliable predictor.

CONCLUSIONS

Our findings suggest that Mexican welders who are occupationally exposed to welding-fumes have increased counts of binucleated and condensed-chromatin cells. Nevertheless, the frequencies of micronuclei and the rest of nuclear abnormalities did not differ between cases and controls. Further studies should shed more light on this subject.

Estimating the carcinogenic potency of chemicals from the in vivo micronucleus test

In this study, we investigated the applicability of using in vivo mouse micronucleus (MN) data to derive cancer potency information. We also present a new statistical methodology for correlating estimated potencies between in vivo MN tests and cancer studies, which could similarly be used for other systems (e.g. in vitro vs. in vivo genotoxicity tests). The dose-response modelling program PROAST was used to calculate benchmark doses (BMDs) for estimating the genotoxic and carcinogenic potency for 48 compounds in mice; most of the data were retrieved from the National Toxicology Program (NTP) database, while some additional data were retrieved from the Carcinogenic Potency Database and published studies. BMD05s (doses with 5% increase in MN frequency) were derived from MN data, and BMD10s (doses with 10% extra cancer risk) were derived from carcinogenicity data, along with their respective lower (BMDL) and upper (BMDU) confidence bounds. A clear correlation between the in vivo MN BMD05s and the cancer BMD10s was observed when the lowest BMD05 from the in vivo MN was plotted against the lowest BMD10 from the carcinogenicity data for each individual compound. By making a further selection of BMDs related to more or less equally severe cancer lesions, the correlation was considerably improved. Getting a general scientific consensus on how we can quantitatively compare different tumour lesion types and investigating the impact of MN study duration are needed to refine this correlation analysis. Nevertheless, our results suggest that a BMD derived from genotoxicity data might provide a prediction of the tumour potency (BMD10) with an uncertainty range spanning roughly a factor of 100.

Potent radioprotective effects of combined regimens of famotidine and vitamin C against radiation-induced micronuclei in mouse bone marrow erythrocytes

To investigate the radioprotective effect of the combination of famotidine and vitamin C against radiation-induced micronucleus formation in mouse bone marrow erythrocytes, various doses of famotidine or vitamin C or combinations thereof were administered intraperitoneally to adult male NMRI mice 2 h before 2 and 4 Gy γ-irradiation. The frequency of micronucleated polychromatic erythrocytes (MnPCEs) was scored in 5,000 polychromatic erythrocytes (PCEs), and the cell proliferation ratio [PCE/(PCE + NCE); NCE = normochromatic erythrocytes] was also calculated for each treatment group. Data were statistically evaluated using one-way ANOVA test. The results show that pretreatment with various doses of famotidine and vitamin C before γ-irradiation significantly reduced the frequency of MnPCEs with a protection factor (PF) of 2 and 1.7, respectively. Pretreatment with vitamin C also significantly increased the cell proliferation ratio, while famotidine had no effect. Combination of famotidine and vitamin C was more effective in reducing MnPCEs than each compound alone, leading to a PF of 4.3 after irradiation. Cell proliferation ratio was also significantly improved by the combination compared with the irradiated control groups. Both famotidine and vitamin C are potent scavengers of free radicals and reactive oxygen species, especially OH(·). The combination of the two compounds probably further enhances this activity, thus leading to high bone marrow protection.

Moving beyond classical markers of water quality: detection of enteric viruses and genotoxicity in water of the Sinos River

<p>It is well recognized that the classical biological and chemical markers of environmental pollution do not necessarily indicate the presence or absence of emerging threats to public health, such as waterborne viruses and genotoxicants. The purpose of this preliminary study was to evaluate the presence of material of enteroviruses (EV), rotavirus (RV) and adenovirus (AdV) and genotoxicity in water samples from points of routine monitoring of water quality in the main course of the Sinos River. The points are classified into different levels of pollution in accordance to the Brazilian federal regulations. Viral genomes from EV, AdV were detected in two of the 4 collection points regardless of the level of urbanisation of the surrounding areas. In contrast, genotoxicity was not observed in piava (<italic>Leporinus obtusidens</italic>) fingerlings cultivated on these same water samples. Results were compared with classical physical, chemical and microbiological parameters. There was no clear evidence of association between any of the classical markers and the presence of viral genomes in the water samples tested.</p>

Cytogenotoxicity assessment of monocrotophos and butachlor at single and combined chronic exposures in the fish Catla catla (Hamilton)

Cytogenotoxic effects in the form of micronuclei and deformed nucleus, nuclear buds, binucleated cells, vacuolated nucleus, vacuolated cytoplasm, echinocytes, and enucleus induced by two compounds belonging to two different chemical classes of agrochemicals (monocrotophos and butachlor) at sublethal concentrations (0.625, 1.3, and 2.3 ppm and 0.016, 0.032, and 0.064 ppm) in single and combined chronic exposures were studied under laboratory conditions for a period of 35 days in the economically important Indian fish Catla catla. Statistically significant duration-dependent increases in the frequencies of micronucleus (MN) and other cytological anomalies were observed. Compared to single exposures, a twofold increase in micronuclei frequency was noted at combined exposures indicating the synergistic phenomenon. Binucleated and enucleated cells appeared only in fishes exposed to sublethal concentrations of butachlor. The present study is the first of its kind in exploring a significant positive correlation between micronuclei and other nuclear anomalies suggesting them as new possible biomarkers of genotoxicity after agrochemical exposures. The study highlights the sensitivity of the assay in exploring various predictive biomarkers of genotoxic and cytotoxic events and also elicits the synergistic effects of agrochemicals in apparently healthy fishes. C. catla can be considered as a suitable aquatic biomonitoring sentinel species of contaminated water bodies.

PARP-2 sustains erythropoiesis in mice by limiting replicative stress in erythroid progenitors

Erythropoiesis is a tightly regulated process in which multipotential hematopoietic stem cells produce mature red blood cells. Here we show that deletion of poly(ADP-ribose) polymerase-2 (PARP-2) in mice leads to chronic anemia at steady state, despite increased erythropoietin plasma levels, a phenomenon not observed in mice lacking PARP-1. Loss of PARP-2 causes shortened lifespan of erythrocytes and impaired differentiation of erythroid progenitors. In erythroblasts, PARP-2 deficiency triggers replicative stress, as indicated by the presence of micronuclei, the accumulation of γ-H2AX (phospho-histone H2AX) in S-phase cells and constitutive CHK1 and replication protein A phosphorylation. Transcriptome analyses revealed the activation of the p53-dependent DNA-damage response pathways in PARP-2-deficient cells, culminating in the upregulation of cell-cycle and cell death regulators, concomitant with G2/M arrest and apoptosis. Strikingly, while loss of the proapoptotic p53 target gene Puma restored hematocrit levels in the PARP-2-deficient mice, loss of the cell-cycle regulator and CDK inhibitor p21 leads to perinatal death by exacerbating impaired fetal liver erythropoiesis in PARP-2-deficient embryos. Although the anemia displayed by PARP-2-deficient mice is compatible with life, mice die rapidly when exposed to stress-induced enhanced hemolysis. Our results pinpoint an essential role for PARP-2 in erythropoiesis by limiting replicative stress that becomes essential in the absence of p21 and in the context of enhanced hemolysis, highlighting the potential effect that might arise from the design and use of PARP inhibitors that specifically inactivate PARP proteins.

A peripherally restricted P2Y12 receptor antagonist altered rat tumor incidences with no human relevance: Mode of action consistent with dopamine agonism

Background

Ticagrelor is an orally available, direct acting and reversible P2Y₁₂ receptor antagonist approved for treatment of acute coronary syndrome. The objectives of these studies were to (1) evaluate the Ticagrelor 2-year rat carcinogenicity bioassay data; (2) investigate potential mode of action (MOA) and (3) interpret human relevance.

Methods

The following studies were done (1) rat two-year carcinogenicity study in male and female rats, (2) in vitro and in vivo genotoxicity assays, (3) quantitative whole body autoradiography (QWBA; male and female rats), (4) in vitro pharmacological profiling for more than 300 assays, and (5) in vivo ovariectomized rat assay.

Results

The carcinogenicity study indicated Ticagrelor increased uterine tumor incidence while decreasing mammary and pituitary tumors/hyperplasia incidences in only high dose female rats. However, this altered tumor incidences were not P2Y₁₂ target related since marketed non-reversible P2Y₁₂ receptor antagonists were not associated with alter tumor incidences. MOA studies determined Ticagrelor exposure in the anterior pituitary and Ticagrelor was (1) non-genotoxic, (2) peripherally-restricted, (3) a dopamine transport (DAT) inhibitor with an IC₅₀ lower than systemic free exposure in the rat carcinogenic study and more than a log higher than the free systemic exposure seen in clinical trials and (4) an inhibitor of estradiol-induced prolactin secretion.

Discussion

Similar to Ticagrelor, centrally active dopamine agonists induce the same altered tumor incidence patterns that according to literature do not translate into the clinical setting, with a MOA involving decreased prolactin secretion. The Ticagrelor MOA data and literature suggest that altered dopamine levels in the hypophyseal part of the hypothalamus–hypophyseal axis (by Ticagrelor) will result in similar altered tumor incidences in rat that do not translate into the clinical setting, based on qualitative species differences. In conclusion Ticagrelor increased uterine tumors in the rat carcinogenesis study by a MOA consistent with reduced dopamine inhibition of prolactin, which is not a patient safety risk.

Assessment of genotoxic induction and deterioration of fish quality in commercial species due to heavy-metal exposure in an urban reservoir

The aim of the study was to evaluate the effect of heavy-metal contamination on two fish species (Channa striatus and Heteropneustes fossilis) inhabiting a small freshwater body of northern India. After being captured, each specimen was weighed, measured, and analyzed for heavy metals (chromium [Cr], nickel [Ni], and lead [Pb]). Accumulation of heavy metals was found to be significantly greater (p < 0.05) in different tissues (gill, liver, kidney, and muscle) of fishes captured from the reservoir than from the reference site. Levels of heavy-metal contamination in Shah jamal water was Cr (1.51 mg/l) > Ni (1.22 mg/l) > Pb (0.38 mg/l), which is significantly greater than World Health Organization standards. Bioaccumulation factor was calculated, and it was observed that Pb was most detrimental heavy metal. Condition factor was also influenced. Micronucleus test of fish erythrocytes and comet assay of liver cells confirmed genotoxicity induced by heavy-metal contamination in fishes. Heavy metals (Cr, Ni, and Pb) were increased in both fish species as determined using recommended values of Federal Environmental Protection Agency for edible fishes. This raises a serious concern because these fishes are consumed by the local populations and hence would ultimately affect human health.

Safety evaluation of phytase 50104 enzyme preparation (also known as VR003), expressed in Pseudomonas fluorescens, intended for increasing digestibility of phytate in monogastrics

Phytase 50104 enzyme (also known as VR003) can be added to swine and poultry diets to catalyze the hydrolysis of phosphate from phytic acid, thereby increasing phosphorus bioavailability in these animals. This enzyme was produced from a Pseudomonas fluorescens (P. fluorescens) production strain and was tested in acute, subchronic and genotoxicity studies. Dosages of the test article preparation ranged from 5000μg/plate for in vitro toxicity studies to 2000mg/kg/day for in vivo toxicity studies. The highest oral dose tested in vivo (NOAEL of 2000mg/kg/day) resulted in a safety margin of 5870 based on TOS and a conservative estimate of total poultry consumption at the highest inclusion rate. There was no toxicity reported for any of these studies or in the following additional safety studies: eye irritation, dermal irritation, and delayed hypersensitivity studies. A review of the public literature indicated that P. fluorescens fulfilled the recognized safety criteria pertinent to microbial production strains used in the manufacture of food/feed enzyme preparations. The results of the toxicity studies presented herein attest to the safety of phytase 50104 enzyme for its intended use.

Evaluation of perfluorooctanoate for potential genotoxicity

Perfluorooctanoate (PFOA) is a fully fluorinated eight-carbon fatty acid analog with exceptional stability toward degradation that has been used as an industrial surfactant and has been detected in environmental and biological matrices. Exposures to PFOA in the workplace and in the environment have continuously stimulated investigations into its potential human health hazards. In this article, the results of fifteen unpublished genotoxicity assays conducted with perfluorooctanoate (as either the linear or linear/branched ammonium salt (APFO) or the linear/branched sodium salt) are reported and include: seven mutation assays (three in vitro reverse mutation assays with histidine auxotrophic strains of Salmonella typhimurium, two in vitro reverse mutation assays with the tryptophan auxotrophic Escherichia coli WP2uvr strain, one in vitro mitotic recombination (gene conversion) assay with Saccharomyces cerevisiae D4, and an in vitro Chinese hamster ovary (CHO) HGPRT forward mutation assay); seven studies to assess potential for chromosomal damage (three in vitro CHO chromosomal aberration studies, an in vitro human whole blood lymphocyte chromosomal aberration study, and three in vivo mouse micronucleus assays); and an in vitro C3H 10T1/2 cell transformation assay. Although PFOA has not been demonstrated to be metabolized, all in vitro assays were conducted both in the presence and in the absence of a mammalian hepatic microsomal activation system. These assays were originally described in twelve contract laboratory reports which have been available via the United States Environmental Protection Agency public docket (Administrative Record 226) for over a decade; however, the details of these assays have not been published previously in the open scientific literature. With the exception of limited positive findings at high and cytotoxic concentrations in some assay trials which reflected the likely consequence of cytotoxic disruption of normal cellular processes and not a specific genotoxic effect, the results of the studies presented in this paper and other published results clearly demonstrate the absence of direct mutagenic or genotoxic risk associated with PFOA. This finding is consistent with the physical/chemical characteristics of PFOA and is supported by other published genotoxicity studies.

Genotoxicity in Astyanax bimaculatus (Twospot Astyanax) exposed to the waters of Engano River (Brazil) as determined by micronucleus tests in erythrocytes

Changes in aquatic environments are potentially large, and effects on biota are highly variable. In Santa Catarina State, Brazil, the main sources of pollution in headwaters are wastewater, pesticides, and animal waste, which contain chemical and organic additives, and there is little knowledge about their effects on aquatic organisms. This study was aimed at investigating the possible genotoxic effects of the waters of the Engano River through the micronucleus (MN) test in Astyanax bimaculatus erythrocytes. Samplings were performed at two sites on the river, and there were six temporal repetitions with collection of blood from six individuals per site/repetition. For the negative-control treatment, we used fish from organic culture; cyclophosphamide was inoculated to constitute the positive-control treatment. MN was obtained in 3,000 erythrocytes/individual. Kruskal-Wallis analysis of variance, Scott-Knott test, and Spearman correlation were employed for data analysis. We found 124 MN in fish from the river, with 70 and 54 MN, respectively, for each site and 16 and 59 MN in negative and positive controls, respectively. The results showed a statistical difference for the formation of MN between river fish and fish in the positive-control treatment. Considering the average MN, we found the formation of three distinct groups: (1) fish from site no. 1 and those in the negative-control group, (2) fish from site no. 2, and (3) fish in the positive-control group. The greater values of chromosomal damage were found during periods of lower rainfall. The test used indicated the presence in the water of substances likely to cause clastogenic and aneugenic effects.

Evaluation of potential genotoxicity of HIV entry inhibitors derived from natural sources

AIDS is a global pandemic that has seen the development of novel and effective treatments to improve the quality of life of those infected and reduction of spread of the disease. Palmitic Acid (PA), which we identified and isolated from Sargassum fusiforme, is a naturally occurring fatty acid that specifically inhibits HIV entry by binding to a novel pocket on the CD4 receptor. We also identified a structural analogue, 2-bromopalmitate (2-BP), as a more effective HIV entry inhibitor with a 20-fold increase in efficacy. We have used the structure-activity relationship (SAR) of 2-BP as a platform to identify new small chemical molecules that fit into the various identified active sites in an effort to identify more potent CD4 entry inhibitors. To validate further drug development, we tested the PA and 2-BP scaffold molecules for genotoxic potential. The FDA and International Conference on Harmonisation (ICH) recommends using a standardized 3-test battery for testing compound genotoxicity consisting of the bacterial reverse mutation assay, mouse lymphoma assay, and rat micronucleus assay. PA and 2-BP and their metabolites tested negative in all three genotoxicty tests. 2-BP is the first derivative of PA to undergo pre-clinical screening, which will enable us to now test multiple simultaneous small chemical structures based on activity in scaffold modeling across the dimension of pre-clinical testing to enable transition to human testing.

Mutagenicity and genotoxicity studies of arruva, an R,R-monatin salt isomer

Arruva, the R,R-isomer of monatin (sodium/potassium 2R,4R-2-amino-4-carboxy-4-hydroxy-5-(3-indolyl) pentanoate), an intense sweetener originally identified in root bark of the South African shrub Schlerochitin ilicifolius, was examined for its mutagenic and genotoxic potential via bacterial reverse mutation, mouse lymphoma and in vivo mouse micronucleus assays, all accomplished in the presence and absence of S9 metabolic activation. In the bacterial reverse mutation assay, arruva was determined to not cause reverse mutations in four Salmonella typhimurium strains and one Escherichia coli strain at concentrations up-cells did not exhibit concentration-related increases in mutant frequency at test concentrations up to 3200μg/ml. In the in vivo micronucleus test, arruva was administered to male mice via single gavage doses at 500, 1000 or 2000mg/kg bw. At 24 or 48h post-dose, the mice were euthanized and femoral bone marrow cells were collected for evaluation of micronucleated polychromatic erythrocyte (MPCE) presence. No statistically significant increases of MPEs were observed relative to the respective vehicle control groups. Under the conditions of these studies, arruva was concluded to be negative in all three assays, thereby indicating the absence of its potential mutagenicity or genotoxicity under the conditions tested.

Antigenotoxic and apoptotic activity of green tea polyphenol extracts on hexavalent chromium-induced DNA damage in peripheral blood of CD-1 mice: analysis with differential acridine orange/ethidium bromide staining

This study was conducted to investigate the modulating effects of green tea polyphenols on genotoxic damage and apoptotic activity induced by hexavalent chromium [Cr (VI)] in CD-1 mice. Animals were divided into the following groups: (i) injected with vehicle; (ii) treated with green tea polyphenols (30 mg/kg) via gavage; (iii) injected with CrO₃ (20 mg/kg) intraperitoneally; (iv) treated with green tea polyphenols in addition to CrO₃. Genotoxic damage was evaluated by examining micronucleated polychromatic erythrocytes (MN-PCEs) obtained from peripheral blood at 0, 24, 48, and 72 h after treatment. Induction of apoptosis and cell viability were assessed by differential acridine orange/ethidium bromide (AO/EB) staining. Treatment of green tea polyphenols led to no significant changes in the MN-PCEs. However, CrO₃ treatment significantly increased MN-PCEs at 24 and 48 h after injection. Green tea polyphenols treatment prior to CrO₃ injection led to a decrease in MN-PCEs compared to the group treated with CrO₃ only. The average of apoptotic cells was increased at 48 h after treatment compared to control mice, suggesting that apoptosis could contribute to eliminate the DNA damaged cells induced by Cr (VI). Our findings support the proposed protective effects of green tea polyphenols against the genotoxic damage induced by Cr (VI).

Modulation of genotoxicity and endocrine disruptive effects of malathion by dietary honeybee pollen and propolis in Nile tilapia (Oreochromis niloticus)

The present study aimed at verifying the usefulness of dietary 2.5% bee-pollen (BP) or propolis (PROP) to overcome the genotoxic and endocrine disruptive effects of malathion polluted water in Oreochromis niloticus (O. niloticus). The acute toxicity test was conducted in O. niloticus in various concentrations (0–8 ppm); mortality rate was assessed daily for 96 h. The 96 h-LC₅₀ was 5 ppm and therefore 1/5 of the median lethal concentration (1 ppm) was used for chronic toxicity assessment. In experiment (1), fish (n = 8/group) were kept on a diet (BP/PROP or without additive (control)) and exposed daily to malathion in water at concentration of 5 ppm for 96 h “acute toxicity experiment”. Protective efficiency against the malathion was verified through chromosomal aberrations (CA), micronucleus (MN) and DNA-fragmentation assessment. Survival rate in control, BP and PROP groups was 37.5%, 50.0% and 100.0%, respectively. Fish in BP and PROP groups showed a significant (P < 0.05) reduction in the frequency of CA (57.14% and 40.66%), MN (53.13% and 40.63%) and DNA-fragmentation (53.08% and 30.00%). In experiment (2), fish (10 males and 5 females/group) were kept on a diet with/without BP for 21 days before malathion-exposure in water at concentration of 0 ppm (control) or 1 ppm (Exposed) for further 10 days “chronic toxicity experiment”. BP significantly (P < 0.05) reduced CA (86.33%), MN (82.22%) and DNA-fragmentation (93.11%), prolonged the sperm motility when exposed to 0.01 ppm of pollutant in vitro and increased the estradiol level in females comparing to control. In conclusion, BP can be used as a feed additive for fish prone to be raised in integrated fish farms or cage culture due to its potency to chemo-protect against genotoxicity and sperm-teratogenicity persuaded by malathion-exposure.

Protective effect of dietary curcumin in Anabas testudineus (Bloch) with a special note on DNA fragmentation assay on hepatocytes and micronucleus assay on erythrocytes in vivo

The present study was conducted to evaluate the safety of long-term dietary curcumin at doses 0.5 and 1% in Anabas testudineus employing hematological and cytological techniques. The fish were fed with curcumin-supplemented feed for 6 months. Fine blood smears were prepared and subjected to three different staining techniques. The erythrocyte micronucleus frequency (MN) and the cytometric measurements of erythrocytes were determined. Blood from the control and treated fish was subjected to the assessment of several hematological parameters. Also, DNA fragmentation assay on hepatocytes was conducted. The results showed that hemoglobin content, RBC count and hematocrit increased in the curcumin-fed fish compared to control, whereas WBC count, platelet count, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration were unaffected. WBC/RBC ratio was lower in the case of curcumin-treated fish. The cytometric measurements revealed no change in the erythrocytes and their nuclei after curcumin treatment. DNA fragmentation assay revealed intact DNA in curcumin-fed group, ruling out the possibility of curcumin-induced DNA damage. The positive control group showed a significant increase in MN frequency compared to negative control and curcumin-fed groups. In fact, the MN frequency decreased in 1% curcumin-fed group compared to the negative control and 0.5% curcumin groups. All these indicated a state of well-being of the curcumin-treated fish. Therefore, it is concluded that curcumin could be used as a safe feed ingredient to improve the growth of finfish in aquaculture.

In vivo genotoxicity assessment of sertraline by using alkaline comet assay and the cytokinesis-block micronucleus assay

Sertraline, a leading antidepressant in the selective serotonin reuptake inhibitor (SSRI) group of medicine, is the most frequently prescribed drug. In this study, the alkaline comet assay and the cytokinesis-block micronucleus (CBMN) assay were used to investigate genotoxicity potential of sertraline in the peripheral blood lymphocytes (PBLs) of acute and chronic sertraline-treated Wistar albino rats. Male Wistar albino rats (n = 48) were administered low, medium and high doses of sertraline (10, 40, 80 mg/kg) for acute and chronic treatment by employing the gavage method to investigate genotoxicity of the administered drug. The data (tail length, tail intensity and tail moment) were analysed and indicated that there was no statistically significant difference between sertraline-treated groups and the negative control group with respect to DNA damage (p > 0.05). However, it was observed that acute sertraline administration had caused much more DNA damage in comparison with chronic treatment (p < 0.05). According to the data obtained from the CBMN test, an increase in the micronucleus (MN) frequency was detected at chronic and high-dose acute sertraline treatment. Based on the outcome of comet assay, detection of statistically insignificant DNA damage may be due to the fact that sertraline did not cause damage on DNA. Also, increase in frequency of MN in chronic sertraline treatment suggests that chronic sertraline administration might influence some mechanisms of cell division. Therefore, dose adjustment in depressed patients seems significant as it may help prevent further prognosis of the diseases.

Micronuclei in genotoxicity assessment: from genetics to epigenetics and beyond

Micronuclei (MN) are extra-nuclear bodies that contain damaged chromosome fragments and/or whole chromosomes that were not incorporated into the nucleus after cell division. MN can be induced by defects in the cell repair machinery and accumulation of DNA damages and chromosomal aberrations. A variety of genotoxic agents may induce MN formation leading to cell death, genomic instability, or cancer development. In this review, the genetic and epigenetic mechanisms of MN formation after various clastogenic and aneugenic effects on cell division and cell cycle are described. The knowledge accumulated in literature on cytotoxicity of various genotoxins is precisely reflected and individual sensitivity to MN formation due to single gene polymorphisms is discussed. The importance of rapid MN scoring with respect to the cytokinesis-block micronucleus assay is also evaluated.

Genetic toxicity of high-boiling petroleum substances

There are several specific types of high-boiling petroleum substances (HBPS) having final boiling points >343°C), in which genetic toxicity can be related to the content of polycyclic aromatic compounds (PACs), specifically crude oils, gas oils, heavy fuel oils, lubricant base oils, waxes and aromatic extracts. Evaluation of optimized Salmonella tests covering over 250 samples from 43 types of HBPS revealed that gene mutation can be determined for these substances using a protocol optimized for the detection of mutagenic PAC. The outcomes of modified Salmonella assays can be predicted using HBPS compositional information as input to a newly developed statistical model. The general outcome of the optimized Salmonella assay can be predicted for an untested substance based on its Aromatic Ring Class (ARC) profile. Review of the results from numerous cytogenetic tests showed that although a few positive study results have been reported, most HBPS do not produce chromosomal effects when tested in rodent bone marrow assays or in in vitro chromosomal aberration assays. Results of both bacterial and cytogenetic studies can be used to satisfy genetic toxicity endpoints for the HBPS category substances.

Mouse micronucleus assay as a surrogate to assess genotoxic potential of arsenic at its human reference dose

Exposure to high contents of arsenic (a genotoxic carcinogen) in humans through drinking water is one of the most serious concerns in many parts of the world including India. The United States Environmental Protection Agency (USEPA) has recommended a permissible limit of daily exposure in humans to arsenic as its reference dose (0.3 μg kg(-1) d(-1)) with almost no likelihood of any adverse effect. The present work was a quantitative assessment of the genotoxic potential of arsenic at the exposure level of its human reference dose through micronucleus (MN) assay in mice. The animals were exposed to various doses of arsenic through oral gavaging for 15 consecutive days. Significant increases in the frequency of micronucleated erythrocytes were observed in mice upon exposure to arsenic which occurred even at its human reference dose and in a dose-dependent manner. The study of the genotoxic potential of arsenic in humans at lower exposure levels (including its human reference dose) is, therefore, highly desirable for risk assessment and hazard identification.

Transient nuclear envelope rupturing during interphase in human cancer cells

Neoplastic cells are often characterized by specific morphological abnormalities of the nuclear envelope (NE), which have been used for cancer diagnosis for more than a century. The NE is a double phospholipid bilayer that encapsulates the nuclear genome, regulates all nuclear trafficking of RNAs and proteins and prevents the passive diffusion of macromolecules between the nucleoplasm and the cytoplasm. Whether there is a consequence to the proper functioning of the cell and loss of structural integrity of the nucleus remains unclear. Using live cell imaging, we characterize a phenomenon wherein nuclei of several proliferating human cancer cell lines become temporarily ruptured during interphase. Strikingly, NE rupturing was associated with the mislocalization of nucleoplasmic and cytoplasmic proteins and, in the most extreme cases, the entrapment of cytoplasmic organelles in the nuclear interior. In addition, we observed the formation of micronuclei-like structures during interphase and the movement of chromatin out of the nuclear space. The frequency of these NE rupturing events was higher in cells in which the nuclear lamina, a network of intermediate filaments providing mechanical support to the NE, was not properly formed. Our data uncover the existence of a NE instability that has the potential to change the genomic landscape of cancer cells.

Genotoxic effects of N-nitrosoketamine and ketamine as assessed by in vitro micronucleus test in Chinese hamster lung fibroblast cell line

OBJECTIVES

Ketamine hydrochloride (KT) is a secondary amine that has been safely used as an injectable anesthetic and analgesic to avoid the production of nitroso compounds in the stomach. However, ketamine in the tablet form has recently become an abused, recreational drug. The aim of this study was to investigate the genotoxic effects of N-nitrosoketamine (NKT) and KT on the basis of an in vitro micronucleus (MN) test using a Chinese hamster lung fibroblast cell line (CHL/IU).

METHODS

NKT was synthesized from KT in our laboratory. In the MN tests, CHL/IU cells were continuously treated with either NKT or KT for 24, 48, or 72 hours without the S9 mix. The cells were also treated with NKT or KT with or without the S9 mix for 6 hours, followed by a recovery period of 18, 42, or 66 hours (short-term treatment). The results were considered to be statistically significant when the p-values of both Fisher's exact test and the trend test were less than 0.05.

RESULTS

After the short-term treatment with either NKT or KT with and without the S9 mix, the frequency of micronuclei significantly increased. However, the frequency of micronuclei did not significantly increase after the continuous treatment with either NKT or KT. Both NKT and KT were determined to be genotoxic in the short-term treatment with or without the S9 mix, but they were determined to be nongenotoxic in continuous treatment.

CONCLUSION

Our findings suggest that NKT has a stronger genotoxic effect than KT.

Evaluation of micronuclei in tobacco users: A study in Punjabi population

Introduction:

The assessment of micronuclei in exfoliated cells is a promising tool for the study of epithelial carcinogens and can be used to detect chromosome breakage or mitotic interference, thought to be relevant to carcinogenesis.

Aim:

The present study aimed to detect micronuclei in exfoliated oral mucosal cells in individuals using various tobacco forms from the last 5 years.

Materials and Methods:

A total of 75 healthy male subjects (25 smokeless tobacco users, 25 smokers, and 25 non–tobacco users) were selected for the study. Smears were obtained with moistened wooden spatula from buccal mucosa and fixed with 95% alcohol. All the cytologic smears were stained by Papanicolaou technique. From each slide, ~1000 cells were examined under the 400× magnification and where micronucleated (MN) cells were located, they were examined under the 1000× magnification.

Result:

MN cells were found to be significantly higher in smokeless tobacco users than in smokers and controls.

Conclusion:

A positive correlation is found between increased micronucleus frequency and tobacco-using habits. So micronucleus assay can be used as a biomarker of genotoxicity.

The protective role of vitamin E on gill and liver tissue histopathology and micronucleus frequencies in peripheral erythrocytes of Oreochromis niloticus exposed to deltamethrin

Deltamethrin, is a commonly used pyrethroid pesticide. Vitamin E is a antioxidant that plays an important role in protecting cells against toxicity by inactivating free radicals generated following pesticides exposure. Therefore, it was evaluated whether deltamethrin induced histopathological changes and nuclear abnormalities using micronucleus test in Oreochromis niloticus, and the possible protective effect of vitamin E against deltamethrin inducing adverse effects in O. niloticus were investigated. Fish was fed with no pesticide+control diet, no pesticide+vitamin E-supplemented diet, 1.45μg/l deltamethrin+control diet, 1.45μg/l deltamethrin+vitamin E-supplemented diet for 30 days. Pesticide and diet quality made an impact on histopathological lesions. In treatments of deltamethrin, group fed with control diet showed much greater damage in comparison with group fed with vitamin E supplemented diet. Vitamin E decreased some histopathological changes induced by deltamethrin, but did not confer complete protection. Deltamethrin treatment has been shown to results in a significant increase in the frequency of micronucleus. However, coadministration of deltamethrin and vitamin E showed decrease in the frequency of micronucleus as compared to deltamethrin treated fish. Our results indicate that, the MN assay and histopathology can be used as bioassays for monitoring pollution in aquatic medium. On the other hand, it was observed that vitamin E decreased the genotoxicity and histopathological changes induced by deltamethrin.

Micronucleus investigation in human buccal epithelial cells of gutkha users

BACKGROUND

Gutkha is a cheap and convenient betel quid substitute, which is popular among all age groups. Various studies reveal its carcinogenic nature that leads to oral submucosus fibrosis and increases the chances of oral cancer. The micronucleus (MN) assay in exfoliated mucosal cells is a useful method for observing genetic damage in humans.

AIM

To observe the genotoxic effect of gutkha on human buccal epithelial cells.

MATERIALS AND METHODS

The MN assay was performed to assess the frequency of MN in human buccal epithelial cells. The study comprises 60 individuals of which 30 individuals were gutkha chewers and another 30 were nonusers (control). The MN frequency was scored to estimate the genotoxic damage.

RESULTS

In gutkha users, the frequency of MN was highly significant (17.4 ± 0.944) as compared with nonusers (control) groups (4.53 ± 0.331) (P < 0.001).

CONCLUSIONS

The MN assay in human buccal epithelial cells is a useful and minimally invasive method for monitoring genetic damage in humans. Asignificantly higher frequency of micronucleated cells are found among gutkha users.

Safety evaluation of a lipase enzyme (BD29241 Palmitase) preparation, expressed in Pseudomonas fluorescens, intended for removing palmitic acid from triacylglycerol

The lipase enzyme, BD29241 Palmitase, can be used as a processing aid for removing palmitic acid from triacylglycerol in the production of refined oil. This enzyme was produced from a Pseudomonas fluorescens (P. fluorescens) production strain and was tested in acute, inhalation, and subchronic toxicity studies. In addition, this enzyme was also tested for its potential to induce genotoxicity. Dosages of the test article preparation ranged from 5000μg/plate for in vitro toxicity studies to 2000mg/kg/day for in vivo toxicity studies. The highest oral dose tested in vivo (NOAEL of 2000mg/kg/day) resulted in a safety margin of 2.442×10(3) based on a conservative estimate of the total human consumption of BD29241 Palmitase of 0.819mg/kg/day. There was no toxicity reported for any of these studies including additional safety studies. A review of the literature indicates that P. fluorescens fulfills recognized safety criteria pertinent to microbial production strains used in the manufacture of food enzyme preparations. The results of the toxicity studies presented herein attest to the safety of BD29241 Palmitase for its above-stated intended use.

Effects of hexavalent chromium on microtubule organization, ER distribution and callose deposition in root tip cells of Allium cepa L

The subcellular targets of hexavalent chromium [Cr(VI)] were examined in Allium cepa root tips with confocal laser scanning microscopy. Cr(VI) exerted dose- and time-dependent negative effects on root growth rate, the mitotic index and microtubule (MT) organization during cell division cycle. Interphase MTs were more resistant than the mitotic ones, but when affected they were shorter, sparse and disoriented. The preprophase band of MTs became poorly organized, branched or with fragmented MTs, whilst neither a perinuclear array nor a prophase spindle was formed. Metaphase spindles converged to eccentric mini poles or consisted of dissimilar halves and were unable to correctly orient the chromosomes. Anaphase spindles were less disturbed, but chromatids failed to separate; neither did they move to the poles. At telophase, projecting, lagging or bridging chromosomes and micronuclei also occurred. Phragmoplasts were unilaterally developed, split, located at unexpected sites and frequently dissociated from the branched and misaligned cell plates. Chromosomal aberrations were directly correlated with MT disturbance. The morphology and distribution of endoplasmic reticulum was severely perturbed and presumably contributed to MT disassembly. Heavy callose apposition was also induced by Cr(VI), maybe in the context of a cellular defence reaction. Results indicate that MTs are one of the main subcellular targets of Cr(VI), MT impairment underlies chromosomal and mitotic aberrations, and MTs may constitute a reliable biomonitoring system for Cr(VI) toxicity in plants.

Genotoxicity testing of low molecular weight fucoidan from brown seaweeds

Fucoidan extracts from brown seaweed have anticoagulant, antithrombotic, and antiviral activities. Low molecular weight fucoidan (LMF) obtained by acid hydrolysis of high molecular weight fucoidan showed more favorable bioactivity. Despite extensive work on LMF bioactivities, detailed studies on the genotoxicity of LMF have not been conducted. As part of a safety evaluation, the potential genotoxicity of LMF was evaluated using a standard battery of tests (bacterial reverse mutation assay, chromosomal aberrations assay, and mouse micronucleus assay). The LMF was determined not to be genotoxic under the conditions of the reverse mutation assay, chromosomal aberrations assay, or mouse micronucleus assay. In a reverse mutation assay using four Salmonella typhimurium strains and Escherichia coli, LMF did not increase the number of revertant colonies in any tester strain regardless of metabolic activation by S9 mix, and did not cause chromosomal aberration in short tests with the S9 mix or in the continuous (24 h) test. A bone marrow micronucleus test in ICR mice dosed by oral gavage at doses up to 2000 mg/kg body weight/day showed no significant or dose-dependent increases in the frequency of micronucleated polychromatic erythrocytes. Use of LMF is presently expected to be safe, as anticipated intake is small compared to doses administered in the genotoxicity assays and may prove to be a useful bioactive agent after further toxicity research.