Showing papers in "Mutation Research-genetic Toxicology and Environmental Mutagenesis in 2009"
TL;DR: Evidence of organ-specific antioxidant responses elicited by environmental pollutants in humans and animal models is reviewed and it is suggested that in complex organisms such as mammals, organs and tissues contain distinct antioxidant systems, and this may form the basis for differential susceptibility to environmental toxic agents.
Abstract: In aerobic organisms, oxygen is essential for efficient energy production but paradoxically, produces chronic toxic stress in cells. Diverse protective systems must exist to enable adaptation to oxidative environments. Oxidative stress (OS) results when production of reactive oxidative species (ROS) exceeds the capacity of cellular antioxidant defenses to remove these toxic species. Epidemiological and clinical studies have linked environmental factors such as diet and lifestyle to cancer, diabetes, atherosclerosis, and neurodegenerative disorders. All of these conditions, as well as the aging process, are associated with OS due to elevation of ROS or insufficient ROS detoxification. Many environmental pollutants engage signaling pathways that are activated in response to OS. The same sequences of events are also associated with the etiology and early pathology of many chronic diseases. Investigations of oxidative responses in different in vivo models suggest that, in complex organisms such as mammals, organs and tissues contain distinct antioxidant systems, and this may form the basis for differential susceptibility to environmental toxic agents Thus, understanding the pathways leading to the induction of antioxidant responses will enable development of strategies to protect against oxidative damage. We shall review evidence of organ-specific antioxidant responses elicited by environmental pollutants in humans and animal models.
698 citations
TL;DR: The established mechanisms by which oxidative stress and environmental stressors regulate the apoptotic machinery are reviewed with the aim of underscore the relevance of apoptosis as a component in environmental toxicity and human disease progression.
Abstract: Apoptosis is an evolutionary conserved homeostatic process involved in distinct physiological processes including organ and tissue morphogenesis, development and senescence. Its deregulation is also known to participate in the etiology of several human diseases including cancer, neurodegenerative and autoimmune disorders. Environmental stressors (cytotoxic agents, pollutants or toxicants) are well known to induce apoptotic cell death and to contribute to a variety of pathological conditions. Oxidative stress seems to be the central element in the regulation of the apoptotic pathways triggered by environmental stressors. In this work, we review the established mechanisms by which oxidative stress and environmental stressors regulate the apoptotic machinery with the aim to underscore the relevance of apoptosis as a component in environmental toxicity and human disease progression.
470 citations
TL;DR: It is important to remark that, in agreement with present knowledge, oxidative/nitrosative/metabolic stress, inflammation, senescence, and cancer are linked concepts that must be discussed in a coordinated manner.
Abstract: Reactive oxygen species (ROS) are the more abundant free radicals in nature and have been related with a number of tissue/organ injuries induced by xenobiotics, ischemia, activation of leucocytes, UV exposition, etc. Oxidative stress is caused by an imbalance between ROS production and a biological system's ability to readily detoxify these reactive intermediates or easily repair the resulting damage. Thus, oxidative stress is accepted as a critical pathophysiological mechanism in different frequent human pathologies, including cancer. In fact ROS can cause protein, lipid, and DNA damage, and malignant tumors often show increased levels of DNA base oxidation and mutations. Different lifestyle- and environmental-related factors (including, e.g., tobacco smoking, diet, alcohol, ionizing radiations, biocides, pesticides, viral infections) and other health-related factors (e.g. obesity or the aging process) may be procarcinogenic. In all these cases oxidative stress acts as a critical pathophysiological mechanism. Nevertheless it is important to remark that, in agreement with present knowledge, oxidative/nitrosative/metabolic stress, inflammation, senescence, and cancer are linked concepts that must be discussed in a coordinated manner.
310 citations
TL;DR: In this brief review, some insight is provided into what the authors currently know about the health problems associated with various air pollutants and their relationship in promoting chronic diseases through changes in oxidative stress and modulation of gene expression.
Abstract: Air pollutants have, and continue to be, major contributing factors to chronic diseases and mortality, subsequently impacting public health. Chronic diseases include: chronic obstructive pulmonary diseases (COPD), cardiovascular diseases (CVD), asthma, and cancer. Byproducts of oxidative stress found in air pollutants are common initiators or promoters of the damage produced in such chronic diseases. Such air pollutants include: ozone, sulfur oxides, carbon monoxide, nitrogen oxides, and particulate matter. Interaction between oxidative stress byproducts and certain genes within our population may modulate the expression of specific chronic diseases. In this brief review we attempt to provide some insight into what we currently know about the health problems associated with various air pollutants and their relationship in promoting chronic diseases through changes in oxidative stress and modulation of gene expression. Such insight eventually may direct the means for effective public health prevention and treatment of diseases associated with air pollution and treatment of diseases associated with air pollution.
267 citations
TL;DR: Arsenite activates several pathways involved in MCF-7 cell proliferation suggesting that arsenite exposure may pose a risk for breast cancer in human exposed populations notwithstanding that most studies to date have not yet implicated this metalloid as a cofactor in the etiology of this disease.
Abstract: Epidemiological evidence has associated exposure to arsenic (As) in drinking water with an increased incidence of human cancers in the skin, bladder, liver, kidney and lung. Sodium arsenite mimics the effects of estradiol and induces cell proliferation in the estrogen responsive breast cancer cell line MCF-7. Therefore, our aim was to further explore the ability of sodium arsenite to induce MCF-7 epithelial breast cell proliferation and some of its underlying mechanisms by studying ROS production, c-Myc and HO-1 protein levels, 8-OHdG formation and NF-kappaB activation. Low arsenite concentrations (0.5-5 microM) induced ROS production and ROS-related depolarization of the mitochondrial membrane suggesting that mitochondria played an important role in the oxidative effects of As. ROS-mediated DNA damage as measured by the presence of 8-OHdG DNA-adducts in their nuclei, IkappaB phosphorylation, NF-kappaB activation and increases in c-Myc and HO-1 protein levels were also observed, suggesting that these factors play a relevant role in the arsenite induced MCF-7 cell recruitment into the S-phase of the cell cycle and cell proliferation observed. In conclusion, arsenite activates several pathways involved in MCF-7 cell proliferation suggesting that arsenite exposure may pose a risk for breast cancer in human exposed populations notwithstanding that most studies to date have not yet implicated this metalloid as a cofactor in the etiology of this disease.
189 citations
TL;DR: There is insufficient evidence that N7-guanine adducts can be used beyond confirmation of exposure to the target tissue and demonstration of the molecular dose, and it was concluded that there is little to no evidence that they are the cause of mutations in cells and tissues.
Abstract: DNA alkylation or adduct formation occurs at nucleophilic sites in DNA, mainly the N7-position of guanine. Ever since identification of the first N7-guanine adduct, several hundred studies on DNA adducts have been reported. Major issues addressed include the relationships between N7-guanine adducts and exposure, mutagenesis, and other biological endpoints. It became quickly apparent that N7-guanine adducts are frequently formed, but may have minimal biological relevance, since they are chemically unstable and do not participate in Watson Crick base pairing. However, N7-guanine adducts have been shown to be excellent biomarkers for internal exposure to direct acting and metabolically activated carcinogens. Questions arise, however, regarding the biological significance of N7-guanine adducts that are readily formed, do not persist, and are not likely to be mutagenic. Thus, we set out to review the current literature to evaluate their formation and the mechanistic evidence for the involvement of N7-guanine adducts in mutagenesis or other biological processes. It was concluded that there is insufficient evidence that N7-guanine adducts can be used beyond confirmation of exposure to the target tissue and demonstration of the molecular dose. There is little to no evidence that N7-guanine adducts or their depurination product, apurinic sites, are the cause of mutations in cells and tissues, since increases in AP sites have not been shown unless toxicity is extant. However, more research is needed to define the extent of chemical depurination versus removal by DNA repair proteins. Interestingly, N7-guanine adducts are clearly present as endogenous background adducts and the endogenous background amounts appear to increase with age. Furthermore, the N7-guanine adducts have been shown to convert to ring opened lesions (FAPy), which are much more persistent and have higher mutagenic potency. Studies in humans are limited in sample size and differences between controls and study groups are small. Future investigations should involve human studies with larger numbers of individuals and analysis should include the corresponding ring opened FAPy derivatives.
186 citations
TL;DR: The most useful application is in biomonitoring of human population groups suffering actual exposure to environmental or occupational mutagens, and the potential use of this technique to monitor effects of contaminants in the natural environment has yet to be fully exploited.
Abstract: DNA oxidation, which can have potentially serious mutagenic consequences, commonly accompanies exposure to environmental mutagens. Oxidised bases can be measured chromatographically, but spurious oxidation during sample preparation leads to serious over-estimation of low levels of damage. A more reliable approach is to employ endonucleases specific for oxidised bases, to introduce breaks in cellular DNA that are then most commonly measured using the comet assay (alkaline single cell gel electrophoresis). The two enzymes in general use are formamidopyrimidine DNA glycosylase, which detects primarily 8-oxo-7,8-dihydroguanine (8-oxoGua), and endonuclease III which recognises oxidised pyrimidines. We give a brief account of the recommended experimental procedures, and then describe applications in various areas of environmental research. Cultured cell lines or white blood cells have been exposed to a range of environmental mutagens, including natural products, industrial chemicals, radiation and nanoparticles. In vivo exposure of animals and humans to pollutants is more challenging but can give particularly valuable information in relation to real life exposure. Possibly the most useful application is in biomonitoring of human population groups suffering actual exposure to environmental or occupational mutagens. Finally, the potential use of this technique to monitor effects of contaminants in the natural environment has yet to be fully exploited.
184 citations
TL;DR: A mini-review summarizes the literature describing the molecular mechanisms affected by As, as well as the most used biomarkers of oxidative stress and damage in human populations and how microarray-based gene expression analysis can provide better insights of the underlying mechanisms involved in As-induced diseases.
Abstract: Arsenic (As) is an ubiquitous element in the environment for which the main route of human exposure is through consumption of drinking water. Reactive oxygen species generation (ROS) associated with As exposure is known to play a fundamental role in the induction of adverse health effects and disease (cancer, diabetes, hypertension, and cardiovascular and neurological diseases). However, the precise mechanisms of oxidative stress and damage from As exposure are not fully understood and moreover the use of non-invasive methods of measuring ROS generation and oxidative damage footprints in humans is no easy task. Although As induces adverse health effects not all exposed individuals develop degenerative chronic diseases or even manifest adverse effects or symptoms, suggesting that genetic susceptibility is an important factor involved in the human response to As exposure. This mini-review summarizes the literature describing the molecular mechanisms affected by As, as well as the most used biomarkers of oxidative stress and damage in human populations. The most reported biomarkers of oxidative DNA damage are the urinary excretion of 8-OHdG and the comet assay in lymphocytes, and more recently DNA repair mechanism markers from the base and nuclear excision repair pathways (BER and NER). Genetic heterogeneity in the oxidative stress pathways involved in As metabolism are important causative factors of disease. Thus further refinement of human exposure assessment is needed to reinforce study design to evaluate exposure–response relationships and study gene–environment interactions. The use of microarray-based gene expression analysis can provide better insights of the underlying mechanisms involved in As-induced diseases and could help to identify target genes that can be modulated to prevent disease.
151 citations
TL;DR: WSPM generated more DNA damage than traffic-generated PM per unit mass in human cell lines, possibly due to the high level of polycyclic aromatic hydrocarbons in WSPM.
Abstract: Genotoxic effects of traffic-generated particulate matter (PM) are well described, whereas little data are available on PM from combustion of biomass and wood, which contributes substantially to air pollution world wide. The aim of this study was to compare the genotoxicity of wood smoke particulate matter (WSPM), authentic traffic-generated particles, mineral PM and standard reference material (SRM2975) of diesel exhaust particles in human A549 lung epithelial and THP-1 monocytic cell lines. DNA damage was measured as strand breaks (SB) and formamidopyrimidine DNA glycosylase (FPG) sites by the comet assay, whereas cell cytotoxicity was determined as lactate dehydrogenase release. The exposure to WSPM generated SB and FPG sites in both cell lines at concentrations from 2.5 or 25 microg/ml, which were not cytotoxic. Compared to all other studied particles, WSPM generated greater responses in terms of both SB and FPG sites. Organic extracts of WSPM and SRM2975 elicited higher levels of SB than native and washed PM at 25 and 100 microg/ml, whereas assay saturation precluded reliable assessment of FPG sites. During a 6h post-exposure period, in which the medium with PM had been replaced by fresh medium, 60% of the DNA lesions generated by WSPM were removed. In conclusion, WSPM generated more DNA damage than traffic-generated PM per unit mass in human cell lines, possibly due to the high level of polycyclic aromatic hydrocarbons in WSPM. This suggests that exposure to WSPM might be more hazardous than PM collected from vehicle exhaust with respect to development of lung cancer.
141 citations
TL;DR: The association of circadian disruption with chronic DEN exposure suggests that circadian clocks actively control the mechanisms of liver carcinogenesis in mice and may further be critical for slowing down and/or reverting cancer development after carcinogen exposure.
Abstract: Background The circadian timing system rhythmically controls behavior, physiology, cellular proliferation and xenobiotic metabolism over the 24-h period. The suprachiasmatic nuclei in the hypothalamus coordinate the molecular clocks in most mammalian cells through an array of circadian physiological rhythms including rest-activity, body temperature, feeding patterns and hormonal secretions. As a result, shift work that involves circadian disruption is probably carcinogenic in humans. In experimental models, chronic jet-lag (CJL) suppresses rest-activity and body temperature rhythms and accelerates growth of two transplantable tumors in mice. CJL also suppresses or significantly alters the expression rhythms of clock genes in liver and tumors. Circadian clock disruption from CJL downregulates p53 and upregulates c-Myc, thus favoring cellular proliferation. Here, we investigate the role of CJL as a tumor promoter in mice exposed to the hepatic carcinogen, diethylnitrosamine (DEN). Methods In experiment 1 (Exp 1), the dose-dependent carcinogenicity of chronic intraperitoneal (i.p.) administration of DEN was explored in mice. In Exp 2, mice received DEN at 10 mg/kg/day (cumulative dose: 243 mg/kg), then were randomized to remain in a photoperiodic regimen where 12 h of light alternates with 12 h of darkness (LD 12:12) or to be submitted to CJL (8-h advance of light onset every 2 days). Rest-activity and body temperature were monitored. Serum liver enzymes were determined repeatedly. Mice were sacrificed and examined for neoplastic lesions at 10 months. Results In Exp 1, DEN produced liver cancers in all the mice receiving 10 mg/kg/day. In Exp 2, mice on CJL had increased mean plasma levels of aspartate aminotransferase and more liver tumors as compared to LD mice at ∼10 months (p = 0.005 and 0.028, respectively). The mean diameter of the largest liver tumor was twice as large in CJL vs LD mice (8.5 vs 4.4 mm, p = 0.027). In LD, a single histologic tumor type per liver was observed. In CJL, up to four different types were associated in the same liver (hepatocellular- or cholangio-carcinomas, sarcomas or mixed tumors). DEN itself markedly disrupted the circadian rhythms in rest-activity and body temperature in all the mice. DEN-induced disruption was prolonged for ≥3 months by CJL exposure. Conclusions The association of circadian disruption with chronic DEN exposure suggests that circadian clocks actively control the mechanisms of liver carcinogenesis in mice. Persistent circadian coordination may further be critical for slowing down and/or reverting cancer development after carcinogen exposure.
133 citations
TL;DR: The current data indicate that H2AX phosphorylation could be used as a biomarker of genot toxicity, which could predict the outcome of in vitro mammalian cell genotoxicity assays.
Abstract: The gammaH2AX focus assay, based on phosphorylation of the variant histone protein H2AX, was evaluated as a genotoxicity test in immortalised wild-type mouse embryonic fibroblasts (MEFs) treated for 4h with a panel of reference compounds routinely used in genotoxicity testing. The topoisomerase II poison etoposide (0.006-60 microg/ml), the alkylating agent methyl methanesulfonate (1.3-65 microg/ml) and the direct DNA-damaging agent bleomycin (0.1-10 microg/ml) all produced a positive concentration-response relationship. The non-genotoxic compounds ampicillin (0.035-3500 microg/ml) and sodium chloride (0.058-580 microg/ml) showed no such response with increased concentrations. The H2AX phosphorylation results were compared with the outcome of two standard in vitro genotoxicity tests, namely the micronucleus and comet assays. Compounds that produced measurable DNA damage in the focus assay generated micronuclei at comparable concentrations. In this study, the focus assay identified genotoxic agents with the same specificity as the comet assay. These results were substantiated when H2AX phosphorylation was analysed using flow cytometry in the murine cell line L5178Y, growing in suspension. The data were in concordance with the manual scoring focus assay. To further this investigation, the gammaH2AX flow cytometry was compared to the in vitro micronucleus flow cytometry and mouse lymphoma assay using the same cell population after MMS treatment. The median gammaH2AX value increased significantly above the control at all four MMS concentrations tested. The percentage of micronucleus events in the in vitro micronucleus flow test and the mutation frequency in the mouse lymphoma assay were also significantly increased at each MMS concentration. The current data indicate that H2AX phosphorylation could be used as a biomarker of genotoxicity, which could predict the outcome of in vitro mammalian cell genotoxicity assays.
TL;DR: This study demonstrated adverse effects of Roundup on DNA of C. latirostris and confirmed that the Comet assay and the MN test applied on caiman erythrocytes are useful tools in determining potential genotoxicity of pesticides.
Abstract: The genotoxicity of pesticides is an issue of worldwide concern. The present study was undertaken to evaluate the genotoxic potential of a widely used herbicide formulation, Roundup (glyphosate), in erythrocytes of broad-snouted caiman (Caiman latirostris) after in ovo exposure. Caiman embryos were exposed at early embryonic stage to different sub-lethal concentrations of Roundup (50, 100, 200, 300, 400, 500, 750, 1000, 1250 and 1750microg/egg). At time of hatching, blood samples were obtained from each animal and two short-term tests, the Comet assay and the Micronucleus (MN) test, were performed on erythrocytes to assess DNA damage. A significant increase in DNA damage was observed at a concentration of 500microg/egg or higher, compared to untreated control animals (p<0.05). Results from both the Comet assay and the MN test revealed a concentration-dependent effect. This study demonstrated adverse effects of Roundup on DNA of C. latirostris and confirmed that the Comet assay and the MN test applied on caiman erythrocytes are useful tools in determining potential genotoxicity of pesticides. The identification of sentinel species as well as sensitive biomarkers among the natural biota is imperative to thoroughly evaluate genetic damage, which has significant consequences for short- and long-term survival of the natural species.
TL;DR: Results show that non-thermal exposure to the radiofrequency fields investigated here can induce mitotic aberrations in root meristematic cells of A. cepa.
Abstract: The effects of exposure to radiofrequency electromagnetic fields (RF-EMFs) on seed germination, primary root growth as well as mitotic activity and mitotic aberrations in root meristematic cells were examined in Allium cepa L. cv. Srebrnjak Majski. Seeds were exposed for 2h to EMFs of 400 and 900MHz at field strengths of 10, 23, 41 and 120Vm(-1). The effect of longer exposure time (4h) and field modulation was investigated at 23Vm(-1) as well. Germination rate and root length did not change significantly after exposure to radiofrequency fields under any of the treatment conditions. At 900MHz, exposures to EMFs of higher field strengths (41 and 120Vm(-1)) or to modulated fields showed a significant increase of the mitotic index compared with corresponding controls, while the percentage of mitotic abnormalities increased after all exposure treatments. On the other hand, at 400MHz the mitotic index increased only after exposure to modulated EMF. At this frequency, compared with the control higher numbers of mitotic abnormalities were found after exposure to modulated EMF as well as after exposure to EMFs of higher strengths (41 and 120Vm(-1)). The types of aberration induced by the EMFs of both frequencies were quite similar, mainly consisting of lagging chromosomes, vagrants, disturbed anaphases and chromosome stickiness. Our results show that non-thermal exposure to the radiofrequency fields investigated here can induce mitotic aberrations in root meristematic cells of A. cepa. The observed effects were markedly dependent on the field frequencies applied as well as on field strength and modulation. Our findings also indicate that mitotic effects of RF-EMF could be due to impairment of the mitotic spindle.
TL;DR: Results do not indicate any correlation between the DNA-protective and the anti-oxidative capacities of eugenol and borneol.
Abstract: Plant volatiles, which can get into the human organism in food, medicines, or cosmetic preparations, frequently manifest antibacterial, antifungal, antiviral and other effects. We studied anti-oxidative, cytotoxic, genotoxic and possible DNA-protective effects of eugenol and borneol. Anti-oxidative activities of aqueous and ethanolic solutions of these two volatile compounds of plants were determined by a spectrophotometric method by the use of the stable DPPH radical. Borneol did not show any anti-oxidative activity even at the highest concentrations soluble in water or ethanol (<1000mM), while eugenol did manifest anti-oxidative activity, and at much lower concentrations (5-100 microM). The cytotoxicity of eugenol and borneol as well as their DNA-damaging effects and their influence on sensitivity of cells against the DNA-damaging effects of H(2)O(2) were investigated in three different cell lines, i.e. malignant HepG2 hepatoma cells, malignant Caco-2 colon cells, and nonmalignant human VH10 fibroblasts. The trypan-blue exclusion assay showed that in the three cell lines the cytotoxicity of eugenol was significantly higher than that of borneol. Single-cell gel electrophoresis revealed that borneol did not cause any DNA strand-breaks at the concentrations studied, but showed that all concentrations of eugenol (<600 microM) significantly increased the level of DNA breaks in human VH10 fibroblasts and to a lower degree in Caco-2 colon cells. The DNA-damaging effects of eugenol were not observed in metabolically active HepG2 hepatoma cells. Borneol and eugenol differed also with respect to their DNA-protective effects. While borneol protected HepG2 and, to a lesser extent, VH10 cells (but not Caco-2) against H(2)O(2)-induced DNA damage, eugenol either did not change the cellular sensitivity to H(2)O(2) (HepG2 cells) or it even increased the sensitivity (Caco-2 and VH10 cells). These results do not indicate any correlation between the DNA-protective and the anti-oxidative capacities of eugenol and borneol.
TL;DR: Evaluating the mutagenic activity of Disperse Red 1 and Disperse Orange 1 using the micronucleus (MN) assay in human lymphocytes and in HepG2 cells found that the number of MN induced by the lowest concentration of each dye was similar to that of the negative control.
Abstract: The use of azo dyes by different industries can cause direct and/or indirect effects on human and environmental health due to the discharge of industrial effluents that contain these toxic compounds. Several studies have demonstrated the genotoxic effects of various azo dyes, but information on the DNA damage caused by Disperse Red 1 and Disperse Orange 1 is unavailable, although these dyes are used in dyeing processes in many countries. The aim of the present study was to evaluate the mutagenic activity of Disperse Red 1 and Disperse Orange 1 using the micronucleus (MN) assay in human lymphocytes and in HepG2 cells. In the lymphocyte assay, it was found that the number of MN induced by the lowest concentration of each dye (0.2 microg/mL) was similar to that of the negative control. At the other concentrations, a dose response MN formation was observed up to 1.0 microg/mL. At higher dose levels, the number of MN decreased. For the HepG2 cells the results were similar. With both dyes a dose dependent increase in the frequency of MN was detected. However for the HepG2, the threshold for this increase was 2.0 microg/mL, while at higher doses a reduction in the MN number was observed. The proliferation index was also calculated in order to evaluate acute toxicity during the test. No differences were detected between the different concentrations tested and the negative control.
TL;DR: The mechanisms of carcinogenesis caused by heavy metals are reviewed emphasizing on the involvement of the hypoxia signalling pathway by metal-induced generation of reactive oxygen species and oxidative stress generation in cancer progression.
Abstract: Heavy metal-induced carcinogenesis is well documented by epidemiological studies. Several diverse mechanisms of cancer induction may be involved, depending on the form of every metal and the tissue that is exposed. Over the recent years, induction of signalling pathways that regulate key cellular responses related to cancer growth and progression by metals has been the focus of many studies. The unravelling of these pathways and the deciphering of their interplay with metals should allow a better understanding of metal toxicity and hopefully will enable development of prophylactic strategies and therapeutic approaches. In this work, we review the mechanisms of carcinogenesis caused by heavy metals emphasizing on the involvement of the hypoxia signalling pathway by metal-induced generation of reactive oxygen species and oxidative stress generation in cancer progression.
TL;DR: Assessing the sensitivity threshold of DNA-adduct detection by 32P-postlabelling in an acellular system and evaluating the formation of DNA adducts in both liver and mammary cells of female CD-1 mice receiving BPA in their drinking water for eight consecutive days found new evidence that DNAAdducts are formed in target Mammary cells.
Abstract: Endocrine disruptors (EDs) represent a major toxicological and public health issue, and the xenoestrogen bisphenol A (BPA) has received much attention due to its high production volume and widespread human exposure. Also, due to its similarity to diethylstilbestrol, a known human carcinogen, BPA has been investigated for its genotoxic and carcinogenic properties, but the results have been either inconclusive or controversial. Metabolically activated BPA has previously been shown to form DNA adducts both in vitro and in rat liver. The present study was designed (a) to assess the sensitivity threshold of DNA-adduct detection by 32P-postlabelling in an acellular system and (b) to evaluate the formation of DNA adducts in both liver and mammary cells of female CD-1 mice receiving BPA in their drinking water (200 mg/kg body weight) for eight consecutive days. The reaction of BPA with calf thymus DNA, in the presence of S9 mix, resulted in a dose-dependent formation of multiple DNA adducts, with a detection limit of approximately 10 ng of this ED under our experimental conditions. Administration of BPA to mice confirmed that DNA adducts are formed in liver (3.4-fold higher levels than in controls). In addition, new evidence is provided that DNA adducts are formed in target mammary cells (4.7-fold higher than in controls). Although DNA adducts do not necessarily evolve into tumours or other chronic degenerative diseases, the formation of these molecular lesions in target mammary cells may bear relevance for the potential involvement of BPA in breast carcinogenesis.
TL;DR: FA and FNA are reported to ameliorate the germ cell toxicity of MTX in mice as evident from the decreased sperm head abnormalities, seminiferous tubule damage, sperm DNA damage, TUNEL positive cells and increased sperm counts.
Abstract: Methotrexate (MTX) is an anti-metabolite widely used in the treatment of neoplastic disorders, rheumatoid arthritis and psoriasis. The basis for its therapeutic efficacy is the inhibition of dihydrofolate reductase (DHFR), a key enzyme in the folic acid (FA) metabolism. FA is a water-soluble vitamin which is involved in the synthesis of purines and pyrimidines, the essential precursors of DNA. Folinic acid (FNA) is the reduced form of FA that circumvents the inhibition of DHFR. Folate supplementation during MTX therapy for psoriasis and inflammatory arthritis reduces both toxicity and side effects without compromising the efficacy. Further, FNA supplementation reduces the common side effects of MTX in the treatment of juvenile idiopathic arthritis. FA and FNA are reported to have protective effects on MTX-induced genotoxicity in the somatic cells; however their protective effects on the germ cells have not been much explored. Previously, we evaluated the cytotoxic and genotoxic effects of MTX in the germ cells of mice. In the present study, we have intervened FA and FNA for the protection of germ cell toxicity induced by MTX in male swiss mice. The animals were pre-treated with FA at the doses of 50, 100 and 200 microg/kg for 4 consecutive days per week and on day five; MTX was administered at the dose of 20mg/kg once. FNA was administered at the doses of 2.5, 5 and 10 mg/kg, 6 h (h) after single administration of MTX at the dose of 20 mg/kg. The dosing regimen was continued up to 10 weeks. The germ cell toxicity was evaluated using testes weight (wt), sperm count, sperm head morphology, sperm comet assay, histology, TUNEL and halo assay in testis. The results clearly demonstrate that prior administration of FA and post-treatment with FNA reduces the germ cell toxicity induced by MTX as evident from the decreased sperm head abnormalities, seminiferous tubule damage, sperm DNA damage, TUNEL positive cells and increased sperm counts. In the present study, we report that FA and FNA ameliorate the germ cell toxicity of MTX in mice.
TL;DR: The presence of ethyl methanesulfonate in tablets of a HIV medication triggered non-clinical studies into the dose response for mutation analysis after chronic dosing, and the existence of a threshold for mutagenic and clastogenic activity in vivo was verified using the micronucleus test (MNT) and gene mutationtest (MutaMouse).
Abstract: The presence of ethyl methanesulfonate (EMS) in tablets of a HIV medication triggered non-clinical studies into the dose response for mutation analysis after chronic dosing. Although there are a multitude of in vitro and in vivo studies on the genotoxic activity of EMS, no lifetime carcinogenicity studies, repeat dose mutation data or exposure analysis are available to serve as a solid basis for risk assessment. For alkylators like EMS it is generally assumed that the dose response for mutagenicity (and by default for carcinogenicity) is linear - indicating that no 'safe' dose does exist. A recent in vitro genotoxicity study [S.H. Doak, G.J. Jenkins, G.E. Johnson, E. Quick, E.M. Parry, J.M. Parry, Mechanistic influences for mutation induction curves after exposure to DNA-reactive carcinogens, Cancer Res. 67 (2007) 3904-3911] provided evidence, however, that the dose-response curve for mutagenic and clastogenic activity of EMS was thresholded - in contrast to ethylnitrosourea (ENU) tested in parallel. For risk assessment we sought to verify the existence of a threshold for mutagenic and clastogenic activity in vivo using the micronucleus test (MNT) and gene mutation test (MutaMouse), with the aim to provide reassurance to the patients that their exposure to EMS did not carry a toxicological risk. Dose levels ranging from 1.25 to 260mg/(kgday) were applied for up to 28 days. As reference we included ENU at doses of 1.1-22mg/(kgday). Our studies showed that daily doses of EMS up to 25mg/(kgday) (bone marrow, GI tract) and 50mg/(kgday) (liver) did not induce mutations in the lacZ gene in the three organs tested. Doses of EMS up to 80mg/(kgday) did not induce micronuclei in mouse bone marrow. Only at higher dose levels the genotoxic activity of EMS became apparent. Dose fractionation of EMS (28 times 12.5mg/kg versus a single high dose 380mg/kg) in the MutaMouse study provided further convincing evidence for the thresholded dose response of EMS and showed that no accumulation below the threshold was occurring. For ENU no threshold was apparent and dose fractionation indicated additivity. However, there are arguments that a threshold in the dose region of about 0.4mg/(kgday) ENU might exist.
TL;DR: The participants concluded that these options for reduction have not been sufficiently utilized to date, and encouraged the use and promotion of these options as well as the dissemination of data related to reduction opportunities by the scientific community in order to boost the acceptance level of these approaches.
Abstract: In vivo genetic toxicology tests measure direct DNA damage or the formation of gene or chromosomal mutations, and are used to predict the mutagenic and carcinogenic potential of compounds for regulatory purposes and/or to follow-up positive results from in vitro testing. These tests are widely used and consume large numbers of animals, with a foreseeable marked increase as a result of the EU chemicals legislation (REACH), which may require follow-up of any positive outcome in the in vitro standard battery with appropriate in vivo tests, regardless of the tonnage level of the chemical. A 2-day workshop with genotoxicity experts from academia, regulatory agencies and industry was hosted by the European Centre for the Validation of Alternative Methods (ECVAM) in Ranco, Italy from 24 to 25 June 2008. The objectives of the workshop were to discuss how to reduce the number of animals in standard genotoxicity tests, whether the application of smarter test strategies can lead to lower animal numbers, and how the possibilities for reduction can be promoted and implemented. The workshop agreed that there are many reduction options available that are scientifically credible and therefore ready for use. Most of these are compliant with regulatory guidelines, i.e. the use of one sex only, one administration and two sampling times versus two or three administrations and one sampling time for micronucleus (MN), chromosomal aberration (CA) and Comet assays; and the integration of the MN endpoint into repeat-dose toxicity studies. The omission of a concurrent positive control in routine CA and MN tests has been proven to be scientifically acceptable, although the OECD guidelines still require this; also the combination of acute MN and Comet assay studies are compliant with guidelines, except for sampling times. Based on the data presented at the workshop, the participants concluded that these options have not been sufficiently utilized to date. Key factors for this seem to be the uncertainty regarding regulatory compliance/acceptance, lack of awareness, and an in many cases unjustified uncertainty regarding the scientific acceptance of reduction options. The workshop therefore encourages the use and promotion of these options as well as the dissemination of data related to reduction opportunities by the scientific community in order to boost the acceptance level of these approaches. Furthermore, experimental proof is needed and under way to demonstrate the credibility of additional options for reduction of the number of animals, such as the integration of the Comet assay into repeat-dose toxicity studies. © 2009 Elsevier B.V.
TL;DR: It was proposed in 1987 that increasing use of electricity to light the night accounts in part for the rising risk of breast cancer globally and predictions from the theory include: non-day shift work increases risk, blindness reduces risk, long sleep duration lowers risk, and population level community nighttime light level co-distributes with breast cancer incidence.
Abstract: Breast cancer incidence increases rapidly as societies industrialize. Many changes occur during the industrialization process, one of which is a dramatic alteration in the lighted environment from a sun-based system to an electricity-based system. Increasingly, the natural dark period at night is being seriously eroded for the bulk of humanity. Based on the fact that light during the night can suppress melatonin, and also disrupt the circadian rhythm, it was proposed in 1987 that increasing use of electricity to light the night accounts in part for the rising risk of breast cancer globally. Predictions from the theory include: non-day shift work increases risk, blindness lowers risk, long sleep duration lowers risk, and population level community nighttime light level co-distributes with breast cancer incidence. Thus far, studies of these predictions are consistent in support of the theory. A new avenue of research has been on function of circadian genes and whether these are related to breast cancer risk. In particular, a length variant of Per3 (5-VNTR) has been associated with increased risk in young women, and this same 5-VNTR variant has also been found to predict morning diurnal type and shorter sleep duration compared to the 4-VNTR variant. An important question is how an effect of light-at-night (LAN) exposure on breast cancer risk might be modified by polymorphisms and/or epigenetic alterations in the circadian genes, and conversely whether light-at-night exposure (e.g., shift work) can induce deleterious epigenetic changes in these genes.
TL;DR: Assessment of the levels of endogenous OCDLs in several human tumor and adjacent normal tissues from patients with liver, ovary, kidney, breast and colon cancer suggests for the first time the importance of endogenous non-DSB clusters in human cancer and their potential use as cancer biomarkers.
Abstract: Increased levels of oxidatively induced DNA damage have been reported in various cases of human pathogenesis like age-related and chronic diseases. Advances in experimental carcinogenesis associate high oxidative stress with genome instability and oncogenic transformation. Cancer biomarkers are helpful for early tumor diagnostics, prediction of tumor development, and analysis of individual tumors’ response to therapy as well as recurrence. The repair resistant oxidatively induced clustered DNA lesions (OCDLs) could serve as a common indicator of oxidative stress in human malignant cells or tissues. To test this hypothesis, we assessed the levels of endogenous OCDLs in several human tumor and adjacent normal tissues from patients with liver, ovary, kidney, breast and colon cancer. These tumor tissues have already been shown to accumulate higher endogenous levels of γ-H2AX foci. For the detection of clustered DNA lesions we used the human repair enzymes APE1, OGG1 and NTH1 as well as the Escherichia coli homologue Endonuclease III. In the majority of cases we detected higher levels of OCDLs in tumor vs. normal tissues but not always with a statistically significant difference and not with uniform tissue dependence. These data suggest for the first time the importance of endogenous non-DSB clusters in human cancer and their potential use as cancer biomarkers.
TL;DR: It is suggested that at concentrations<20 μM imidacloprid is not genotoxic to human lymphocytes in vitro, Nonetheless, the presence of co-formulants in the commercial product and occupational exposure, along with poor safety procedures, may present an increased risk for DNA fragmentation and chromosomal aberrations.
Abstract: Imidacloprid is a neonicotinoid insecticide combining excellent efficiency against parasites with low toxicity for mammals. Commercially, it is co-formulated with dimethyl sulfoxide, methylpyrrolidone, propylene carbonate and mineral oil, which can modify its bioavailability and toxicological profile for humans following occupational exposure. A combined in vitro approach employing the comet assay and the micronucleus test was used to assess the genotoxicity of imidacloprid in relation to formulation, metabolic activation and exposure level. Human peripheral blood lymphocytes from unexposed healthy volunteers were treated with imidacloprid (0.2, 2 and 20 μM) and with equimolar concentrations of a commercial product, with and without addition of S9 fraction. Imidacloprid significantly increased the comet score and the frequency of micronuclei only at the highest concentration tested. DNA damage was slightly more severe with the commercial product, and was increased, though not significantly, by metabolic activation. Formation of reactive oxygen species (ROS) does not seem to be involved as a mechanism of genotoxicity, but this result may be explained by the insufficient sensitivity of the 2',7'-dichlorofluorescein diacetate assay at the test concentrations of imidacloprid. These results suggest that at concentrations<20 μM imidacloprid is not genotoxic to human lymphocytes in vitro. Nonetheless, the presence of co-formulants in the commercial product and occupational exposure, along with poor safety procedures, may present an increased risk for DNA fragmentation and chromosomal aberrations.
TL;DR: A statistical model is offered to analyze continuous response data and estimate a threshold dose together with its confidence limits, thereby taking data quality and degree of sublinearity into account and the question of biological relevance of the resulting slope is discussed.
Abstract: Strongly sublinear dose-response relationships (slope increasing with dose) raise the question about a putative threshold dose below which no biologically relevant effect would be expected. A mathematical threshold with a break in the curve at the threshold dose is generally rejected for consequences of genotoxicity such as mutation, because proportionality between low dose and the rate of DNA-adduct formation is a reasonable hypothesis. In view of an increasing database for distinct deviation from linearity for mutagenicity, we offer a statistical model to analyze continuous response data and estimate a threshold dose together with its confidence limits, thereby taking data quality and degree of sublinearity into account. The simplest mathematical threshold model is a hockey stick defined by a low-dose part with slope zero at background level a to a theoretical break point at threshold dose td, followed by a linear increase above td with slope b. The function is y (dose d)=a+bx(d-td)x1([d>td]). Using the free statistics software package "R", we make a procedure available to estimate the parameters a, b, and td. Confidence intervals are calculated for all parameters at a significance level that can be defined by the user. If the lower limit of the confidence interval for td is >0, linearity is rejected. The procedure is illustrated by two examples. A small data set with three replicates per dose group, indicating a threshold for the induction of thymidine kinase mutants in L5178Y tk(+/-) mouse lymphoma cells treated with methyl methanesulfonate, did not achieve significance. On the other hand, the large data set reported in this issue (Gocke et al.) on lacZ mutants in bone marrow cells of transgenic mice treated with ethyl methanesulfonate strongly favoured the hockey stick model. The question of a theoretically expected linear dose-related increase below the threshold dose is addressed by linear regression of the data below the break point and estimation of an upper limit of the slope. The question of biological relevance of the resulting slope is discussed against the normal variation of background measures in the control group.
TL;DR: Exposure to Aluminum oxide nanomaterials has the potential to cause genetic damage, as suggested by the results of the study.
Abstract: Nanomaterials have novel properties and functions because of their small size The unique nature of nanomaterials may be associated with potentially toxic effects The aim of this study was to evaluate the in vivo genotoxicity of rats exposed with Aluminum oxide nanomaterials Hence in the present study, the genotoxicity of Aluminum oxide nanomaterials (30 and 40 nm) and its bulk material was studied in bone marrow of female Wistar rats using chromosomal aberration and micronucleus assays The rats were administered orally with the doses of 500, 1000 and 2000 mg/kg bw Statistically significant genotoxicity was observed with Aluminum oxide 30 and 40 nm with micronucleus as well as chromosomal aberration assays Significantly (p < 005 or p < 0001) increased frequency of MN was observed with 1000 and 2000 mg/kg bw dose levels of Aluminum oxide 30 nm (94 ± 187 and 152 ± 23, respectively) and Aluminum oxide 40 nm (81 ± 18 and 139 ± 221, respectively) over control (25 ± 07) at 30 h Likewise, at 48 h sampling time a significant (p < 005 or p < 0001) increase in frequency of MN was evident at 1000 and 2000 mg/kg bw dose levels of Aluminum oxide 30 nm (106 ± 168 and 166 ± 266, respectively) and Aluminum oxide 40 nm (90 ± 138 and 147 ± 168, respectively) compared to control (18 ± 075) Significantly increased frequencies (p < 005 or p < 0001) of chromosomal aberrations were observed with Aluminum oxide 30 nm (1000 and 2000 mg/kg bw) and Aluminum oxide 40 nm (2000 mg/kg bw) in comparison to control at 18 and 24 h Further, since there is need for information on the toxicokinetics of nanomaterials, determination of these properties of the nanomaterials was carried out in different tissues, urine and feces using inductively coupled plasma mass spectrometry (ICP–MS) A significant size dependent accumulation of Aluminum oxide nanomaterials occurred in different tissues, urine and feces of rats as shown by ICP–MS data The results of our study suggest that exposure to Aluminum oxide nanomaterials has the potential to cause genetic damage
TL;DR: To the authors' knowledge, this is the first report to describe the use of B. bufo gargarizans for genotoxicity assessment of chlorpyrifos, and the significant (P < 0.05 concentration-dependent increase in DNA damage) were observed in erythrocytes and liver cells of tadpoles exposed to the sublethal concentrations of chlorine and MMS by Comet assay.
Abstract: In the present study, the genotoxicity of chlorpyrifos was evaluated in the Chinese toad by using Comet assay and Micronucleus test (MN), as the potential tools for the assessment of genotoxicity. The first step was determined by the acute toxicity of chlorpyrifos. Tadpoles were exposed to the series of relatively high concentrations of chlorpyrifos for 96 h. LC(50) values at 24, 48, 72, and 96 h were 3.63, 1.17, 0.82, and 0.80 mgl(-1), respectively. Secondly, the Micronucleus test was used for detecting chromosome damage in Chinese toad tadpoles exposed to the sublethal concentrations of chlorpyrifos and methyl methane sulfonate (MMS), which indicated that they induced chromosomal lesion in erythrocytes of Bufo bufo gargarizans tadpoles. Thirdly, the significant (P < 0.05 concentration-dependent increase in DNA damage (as indicated by Tail DNA%, Tail length, Olive tail moment)) were observed in erythrocytes and liver cells of tadpoles exposed to the sublethal concentrations of chlorpyrifos and MMS by Comet assay. To our knowledge, this is the first report to describe the use of B. bufo gargarizans for genotoxicity assessment of chlorpyrifos.
TL;DR: The Vitotox and RadarScreen assays were evaluated as early screens for mutagenicity and clastogenicity and validated with respect to a list of genotoxic and non-genotoxic chemicals that can be used for the validation and/or optimization of in vitro genotoxicity assays.
Abstract: The Vitotox and RadarScreen assays were evaluated as early screens for mutagenicity and clastogenicity, respectively. The Vitotox assay is a bacterial reporter assay in Salmonella typhimurium based on the SOS-response, and it contains a luciferase gene under control of the recN promoter. The RadarScreen assay is a RAD54 promoter-linked beta-galactosidase reporter assay in yeast. The expression of this beta-galactosidase can easily be quantified by use of the substrate d-luciferin-o-beta-galactopyranoside, which is converted into galactose and luciferin that can be measured luminometrically. Recently, an ECVAM workgroup defined a list of 20 genotoxic and 42 non-genotoxic compounds [D. Kirkland, P. Kasper, L. Muller, R. Corvi, G. Speit, Recommended lists of genotoxic and non-genotoxic chemicals for assessment of the performance of new or improved genotoxicity tests: a follow-up to an ECVAM workshop, Mutat. Res. 653 (2008) 99-108.] that can be used for the validation and/or optimization of in vitro genotoxicity assays. In the present study, this compound set was used for the validation of the assays. Moreover, an additional set of 192 compounds was used to broaden this validation study. The compounds of this additional set can be classified as non-genotoxins and genotoxins and consists of both in-house and reference compounds. In case of the ECVAM compound list, the results from the Vitotox and RadarScreen assays were compared to the genotoxic/non-genotoxic classification of the compounds in this list. In case of the additionally tested compounds, the results of the Vitotox and RadarScreen assays were compared, respectively, with bacterial mutagenicity (Ames) results or in vitro clastogenicity data obtained in-house or from the literature. The validation with respect to the ECVAM compound list resulted in a sensitivity for both the Vitotox and RadarScreen assay of 70% (14/20). If both assays were combined the sensitivity increased to 85% (17/20). Both tests also gave a low number of false positive results. The specificity of the Vitotox and RadarScreen assays was 93% (39/42) and 83% (35/42), respectively. This resulted in a predictivity of the Vitotox and RadarScreen assay of 85% (53/62) and 79% (49/62), respectively. In case both tests were combined the specificity and the predictivity of the Vitotox and RadarScreen assay turned out to be 81% (34/42) and 82% (51/62), respectively. The results from the additional list of 192 compounds confirmed the results found with the ECVAM compound list. The results from the Vitotox assay showed a high correlation with Ames test of 91% (132/145). Subsequently, the RadarScreen assay had a correlation with in vitro clastogenicity of 76% (93/123). The specificity of the Vitotox assay was 94% (90/96) for Ames test results and that of the RadarScreen assay was 74% (34/46) for clastogenicity. Moreover, the sensitivities of the Vitotox and RadarScreen assays were 86% (42/49) and 77% (59/77), respectively. Implementation of the Vitotox and RadarScreen assays in the early research phase of drug development can lead to fast de-selection for genotoxicity. It is expected that this application will reduce the number of compounds that have a positive score in the regulatory Ames and clastogenicity tests. Moreover, problems with a complete compound class can be foreseen at an early time point in the research phase, which gives more time for issue resolution than late detection of these problems with the regulatory tests.
TL;DR: HN is found to be an effective radioprotector against gamma-radiation induced in-vitro cellular damage in lymphocytes and shows optimum protection by effectively decreasing the MN frequencies, dicentric aberrations and comet attributes.
Abstract: The present study was aimed to evaluate the radioprotective efficacy of hesperidin (HN), a flavonone glycoside against gamma-radiation-induced cellular damage in cultured human peripheral blood lymphocytes Different concentrations of HN (327, 655, 983, 1310, 1638 and 1965 microM) were pre-incubated with lymphocytes for 30 min prior to gamma-irradiation [4 Gy] and the micronuclei (MN) scoring, dicentric aberration and comet assay were performed to fix the effective dose of HN against gamma-irradiation induced cellular damage The results indicated that among all the concentrations, 1638 microM concentration of HN showed optimum protection by effectively decreasing the MN frequencies, dicentric aberrations and comet attributes Based on the above results, 1638 microM concentration of HN was fixed as the effective dose to further investigate its radioprotective efficacy which was then carried out by pre-incubating lymphocytes with 1638 microM concentration of HN, exposing the lymphocytes to different doses (1, 2, 3 and 4 Gy) of radiation and investigating radiation induced genetic damage (MN, dicentric aberration, comet assay, DNA fragmentation assay) and biochemical changes (changes in the level of enzymic and non-enzymic antioxidants, lipid peroxidation) The results indicated a dose dependent increase in both genetic damage and thiobarbituric acid reactive substances (TBARS), accompanied by a significant decrease in the antioxidant status compared to HN treated groups which modulated the toxic effects through its antioxidant potential Thus the current study shows HN to be an effective radioprotector against gamma-radiation induced in-vitro cellular damage in lymphocytes
TL;DR: It is shown that the 3beta-hydroxy-lanosta-8, 24-dien-21-al and inotodiol components of Inonotus obliquus bear antimutagenic and antioxidative activities.
Abstract: Inonotus obliquus is a mushroom commonly known as Chaga that is widely used in folk medicine in Siberia, North America, and North Europe. Here, we evaluated the antimutagenic and antioxidant capacities of subfractions of Inonotus obliquus extract. The ethyl acetate extract was separated by vacuum chromatography into three fractions, and the fraction bearing the highest antimutagenic activity was subsequently separated into four fractions by reversed phase (ODS-C18) column chromatography. The most antimutagenic fraction was then separated into two subfractions (subfractions 1 and 2) by normal phase silica gel column chromatography. Ames test analysis revealed that the subfractions were not mutagenic. At 50 μg/plate, subfractions 1 and 2 strongly inhibited the mutagenesis induced in Salmonella typhimurium strain TA100 by the directly acting mutagen MNNG (0.4 μg/plate) by 80.0% and 77.3%, respectively. They also inhibited 0.15 μg/plate 4NQO-induced mutagenesis in TA98 and TA100 by 52.6–62.0%. The mutagenesis in TA98 induced by the indirectly acting mutagens Trp-P-1 (0.15 μg/plate) and B(α)P (10 μg/plate) was reduced by 47.0–68.2% by the subfractions, while the mutagenesis in TA100 by Trp-P-1 and B(α)P was reduced by 70.5–87.2%. Subfraction 1 was more inhibitory than subfraction 2 with regard to the mutagenic effects of 4NQO, Trp-P-1, and B(α)P. Subfractions 1 and 2 also had a strong antioxidant activity against DPPH radicals and were identified by MS, 1H NMR and 13C NMR analyses as 3β-hydroxy-lanosta-8, 24-dien-21-al and inotodiol, respectively. Thus, we show that the 3β-hydroxy-lanosta-8, 24-dien-21-al and inotodiol components of Inonotus obliquus bear antimutagenic and antioxidative activities.
TL;DR: NPBs and NBUDs are more sensitive and reliable biomarkers for genetic damages induced by PAHs and could potentially be used for the biomonitoring of genotoxin-exposed populations.
Abstract: Coke oven workers are regularly exposed to polycyclic aromatic hydrocarbons (PAHs) and have a high risk for lung cancer. Limited evidence has demonstrated a direct link between exposure to PAHs and early genetic damage in exposed workers. The cytokinesis-block micronucleus (CBMN) cytome assay is a comprehensive system for measuring DNA damage and cytotoxicity. In the current study, we investigated different chromosomal damage endpoints including micronuclei (MN), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs), in 141 PAH-exposed subjects and 66 unexposed controls. The frequencies of MN, NPBs and NBUDs were all significantly higher in PAH-exposed workers than in controls (2.4-, 5-, and 3-fold, respectively). We further classified the PAH-exposed workers into different PAHs exposure groups based on their work positions on the oven and their urinary 1-hydroxypyrene and found that the frequencies of NPBs and NBUDs increased with the increasing level of both external and internal PAHs exposure levels. Similar trend was not found for MN due to the reduced MN frequency in the highest PAHs exposure group compared with the second highest PAHs exposure group. Using principal component analysis, we confirmed that the frequencies of NPBs and NBUDs are more sensitive to reflect the external or internal levels of PAHs exposure. In PAH-exposed subjects, NPB and NBUD frequencies were influenced by gender and females have lower frequencies of NPB and NBUD. Taken together, our observations indicate that NPBs and NBUDs are more sensitive and reliable biomarkers for genetic damages induced by PAHs and could potentially be used for the biomonitoring of genotoxin-exposed populations.