Examination of various biomarkers measuring genotoxic endpoints from Barcelona airport personnel

Genotoxicity associated to exposure to Prestige oil during autopsies and cleaning of oil-contaminated birds

After the accident involving the oil tanker Prestige in November 2002 near 63,000 tons of heavy oil reached Galician coast (Northwest of Spain). This unleashed a large movement of volunteers to collaborate in several cleaning tasks. The aim of this study was to determine whether handling of Prestige oil-contaminated birds during autopsies and cleaning may have resulted in genotoxic damage. We have also evaluated the possible influence of DNA repair genetic polymorphisms (XRCC1 codons 194 and 399, XRCC3 codon 241 and APE1 codon 148) on susceptibility to the genotoxic effects evaluated. Exposure levels were analysed by determining volatile organic compounds in air samples. Peripheral blood samples were obtained from 34 exposed and 35 controls, and comet assay and micronucleus (MN) test were carried out. Genotyping was performed following PCR-RFLP procedures. Results obtained have shown significantly higher DNA damage, but not cytogenetic damage, in exposed individuals than in controls, related to time of exposure. Among exposed individuals, carriers of the variant alleles XRCC1 399Gln and APE1 148Glu have shown altered DNA damage with regard to wild-type homozygotes, suggesting exposure-genotype interactions. No effect of the DNA repair genetic polymorphisms analysed was observed in the MN test.

Occupational exposure in airport personnel: characterization and evaluation of genotoxic and oxidative effects

Airport personnel can be exposed to several polycyclic aromatic hydrocarbons (PAHs) from jet fuel vapours, jet fuel combustion products and diesel exhaust. The aim of this study was to characterize the exposure and to evaluate genotoxic and oxidative effects in airport personnel (n=41) in comparison with a selected control group (n=31). Environmental monitoring of exposure was carried out analysing 23 PAHs on air samples collected from airport apron, airport building and terminal/office area during 5 working days. The urinary 1-hydroxy-pyrene (1-OHP) following 5 working days, was used as biomarker of exposure. Genotoxic effects and early direct-oxidative DNA damage were evaluated by micronucleus (MN) and Fpg-modified comet assay on lymphocytes and exfoliated buccal cells, and by chromosomal aberrations (CA) and sister chromatid exchange (SCE) analyses. For comet assay, tail moment (the product of comet relative tail intensity and length) values from Fpg-enzyme treated cells (TMenz) and from untreated cells (TM) were used as parameters of oxidative and direct DNA damage, respectively. We found 27,703 microg/m(3) total PAHs in airport apron, 17,275 microg/m(3) in airport building and 9,494 microg/m(3) in terminal/office area. Urinary OH-pyrene did not show differences between exposed and controls. The exposed group showed a higher mean value of SCE frequency in respect to controls (4.6 versus 3.8) and an increase (1.3-fold) of total structural CA in particular breaks (up to 2.0-fold) and fragments (0.32% versus 0.00%), whereas there were no differences of MN frequency in both cellular types. Comet assay evidenced in the exposed group a higher value in respect to controls of mean TM and TMenz in both exfoliated buccal cells (TM 118.87 versus 68.20, p=0.001; TMenz 146.11 versus 78.32, p<0.001) and lymphocytes (TM 43.01 versus 36.01, p=0.136; TMenz 55.86 versus 43.98, p=0.003). An oxidative DNA damage was found, for exfoliated buccal cells in the 9.7% and for lymphocytes in the 14.6% of exposed in respect to the absence in controls. Our findings furnish a useful contribution to the characterization of civil airport exposure and suggest the use of comet assay on exfoliated buccal cells to assess the occupational exposure to mixtures of inhalable pollutants at low doses since these cells represent the target tissue for this exposure and are obtained by non-invasive procedure.

The effect of smoking on DNA effects in the comet assay: a meta-analysis

The comet assay (alkaline single-cell gel electrophoresis, SCG or SCGE) is frequently used in biomonitoring to detect genotoxic effects in humans exposed at the workplace or in their environment. Because of its ready accessibility, blood is most frequently used in such studies. Many studies investigated cigarette smoking either as a genotoxic exposure itself or as a potential confounding factor in occupational studies. However, although smoking is considered to be a relevant exposure towards various genotoxins, conflicting results have been reported in the comet assay studies. The actual reasons for this discrepancy are not known. To further evaluate evidence for smoking-related DNA effects in the comet assay, we now used a meta-analysis approach based on a literature search. We identified 38 studies from 37 publications which were suited for a formal meta-analysis based on the standardized mean difference (SMD) between the study groups. The evaluation of these 38 studies indicated higher levels of DNA damage in smokers than in non-smokers [under a random effects model, SMD = 0.55, 95% confidence interval = (0.16-0.93)]. Subdividing these studies into studies investigating the effect of smoking as a genotoxic exposure (Type A studies, n = 12) and studies investigating smoking as a potential confounder in occupational studies (Type B, n = 26) indicated a significant difference only in Type A studies but not in Type B studies. Furthermore, studies using image analysis or image length measurements (n = 23) only indicated a tendency for a genotoxic effect of smoking, whereas studies using an arbitrary score (n = 15) found a significantly higher level of DNA damage in smokers.

Assessment of DNA damage in peripheral blood lymphocytes of individuals susceptible to arsenic induced toxicity in West Bengal, India

Assessment of DNA damage was carried out using alkaline comet assay in lymphocytes of 30 individuals exposed to high levels of arsenic (247.12+/-18.93 microg/l) through contaminated groundwater in North 24 Parganas district, West Bengal, India. All of them exhibited high arsenic contents in nail (4.20+/-0.67 microg/g), hair (2.06+/-0.20 microg/g) and urine (259.75+/-33.89 microg/l) samples and manifested various arsenical skin lesions. Unexposed samples were collected from 30 residents of the unaffected East Midnapur district with very little or no exposure to arsenic (7.69+/-0.49 microg/l) in drinking water. The results were evaluated principally by manual analysis of comets and partly by computerized image analysis. Both the analytical methods exhibited a high degree of agreement in results. The exposed participants expressed significantly higher DNA damage (p < 0.01) in their lymphocytes than the unexposed participants. Alkaline comet assay was also combined with formamidopyrimidine-DNA glycosylase enzyme digestion to confirm that arsenic induced oxidative base damage in the lymphocytes. Significant positive trend effects of comet lengths in relation to arsenic levels in water prove that DNA damage can be used as a sensitive biomarker of arsenic exposure. This study demonstrates that arsenic induced significant DNA damage in the exposed participants, which could correspond to a higher susceptibility to arsenic induced toxicity and carcinogenicity.

Differential induction of micronuclei in peripheral lymphocytes and exfoliated urothelial cells of workers exposed to 4,4'-methylenebis-(2-chloroaniline) (MOCA) and bitumen fumes

Cytogenetic end-points used to estimate risk of genotoxic events in workers include the measurement of micronuclei (MN) in exfoliated cells, lymphocytes, and other tissues. Micronuclei are chromatin-containing bodies outside the cell nucleus resulting from contaminant-induced DNA damage. A review of 71 reports of human genotoxic responses to chemical or physical agents published between 1999 and 2001 revealed that 14% of such studies measured genotoxicity endpoints in specific target tissues relevant to the site of disease for the agent examined; 18% used endpoints in surrogate or non-target tissues but considered the relations between endpoints in surrogate and disease target tissues, and 68% measured genotoxicity endpoints in accessible tissues without reference to specific targets for disease. Methylenebis-(2-chloroaniline) (MOCA), used in polyurethane manufacture, is a suspected bladder carcinogen. Bitumen, used in road surfacing, contains skin and lung carcinogens. In this study, we aimed to compare genotoxicity in urothelial cells and in lymphocytes of workers exposed to these materials. Twelve men employed in polyurethane manufacture, twelve bitumen road layers, and eighteen hospital stores personnel (controls) were recruited and all provided blood and urine samples on the same day. Blood cultures were prepared using a cytochalasin B-block method. Exfoliated urothelial cells were collected from urine and stained for light microscopy. The number of MN in urothelial cells was higher in MOCA-exposed (14.27 +/- 0.56 MN/1000, 9.69 +/- 0.32 MN cells/1000) than in bitumen exposed workers (11.99 +/- 0.65 MN/1000, 8.66 +/- 0.46 MN cells/1000) or in control subjects (6.88 +/- 0.18 MN/1000, 5.17 +/- 0.11 MN cells/1000). Conversely, in lymphocytes, MN were higher in bitumen-exposed (16.24 +/- 0.63 MN/1000, 10.65 +/- 0.24 MN cells/1000) than in MOCA-exposed workers (13.25 +/- 0.48 MN/1000, 8.54 +/- 0.14 MN cells/1000) or in control subjects (9.24 +/- 0.29 MN/ 1000, 5.93 +/- 0.13 MN cells/1000). The results of this study suggest that genotoxins can cause different rates of micronuclei formation in different tissues. Thus, the sensitivity and relevance to cancer risk may be greater if the tissues selected for genotoxicity studies reflect the target tissue for the chemicals concerned.

Cytotoxic and oxidative effects induced by man-made vitreous fibers (MMVFs) in a human mesothelial cell line

The introduction of man-made vitreous fibers (MMVFs) as a substitute for asbestos in industrial and residential applications raises concerns about their potential health hazards. The aim of our study was to assess cytotoxic and oxidative effects induced on a human mesothelial cell line (MeT-5A) by exposure to glass wool (GW), rock wool (RW) and refractory ceramic fibers (RCF) in comparison with crocidolite asbestos (CR). MeT-5A cells were exposed for 24 h to 2, 5 and 10 microg/cm2 of MMVF and crocidolite fibers and analysed by scanning electron microscope (SEM) for cell surface alterations. Cells were exposed for 2 h to 1, 2, 5 and 10 microg/cm2 of the same fibers and analysed by enzyme Fpg-modified comet test for direct and oxidative DNA damage. SEM revealed loss of microvilli in cells exposed to RCF and numerous blebs in cells exposed to higher doses of RW. Comet test showed significant direct DNA damage in cells exposed to RCF even at the lowest dose. Comet test with Fpg, that permits the detection of oxided DNA bases, showed significant oxidative DNA damage in cells exposed to higher doses of RW. The presence of DNA damage and alterations of cell surface induced by low doses of RCF and the presence of oxidative DNA damage and blebs on cell surface in cells exposed to higher dose of RW suggest possible cytotoxic, oxidative and genotoxic effects for these MMVFs.

DNA single strand breaks in peripheral lymphocytes associated with urinary thiodiglycolic acid levels in polyvinyl chloride workers

The association between vinyl chloride monomer (VCM) exposure and DNA damage has been established. However, the relationship between individual exposure and DNA single strand breaks was limited. Since environmental monitoring may not reflect the actual exposure, a useful marker of exposure is needed to assess the individual exposure. In our previous study, we have found a high correlation between air VCM level and urinary thiodiglycolic acid (TdGA) at the commencement of the next shift. Here, we further used comet assay to evaluate the relationship between urinary TdGA levels and DNA single strand breaks in polyvinyl chloride monomer (PVC) workers. Urinary TdGA levels (n=26) at the commencement of the following shift were analyzed. Ten of the 26 workers also had personal air sampling for air VCM exposure. Questionnaires were administered to obtain epidemiological information including detailed history of occupation and lifestyles. Workers experiencing air VCM level greater than 5 ppm had higher tail moment and tail intensity (%) than those experiencing VCM exposure between 1 and 5, or <1 ppm, respectively (P < 0.05). The results also revealed that level of DNA single strand breaks, including tail moment and tail intensity, were increased with urinary TdGA level. The dose-response relationship of urinary TdGA level and DNA single strand breaks was particularly significant among the workers with 4 mg/g Cr of urinary TdGA level, which is equivalent to 5 ppm air VCM level. We concluded that air VCM exposure greater than 5 ppm could induce DNA damage. Further sensitive assay should be developed for the diction of DNA damage when air VCM exposure below 5 ppm.

Use of primary blood cells for the assessment of exposure to occupational genotoxicants in human biomonitoring studies

The Comet assay is an often used approach for the assessment of genetic damage in primary cells of exposed populations. In the majority of these studies lymphocytes are used. Therefore, we reviewed human biomonitoring studies of occupational exposure using the Comet assay with lymphocytes. We also tried to elucidate the strengths of the studies, which were that (i) data could be obtained in a fast and cost-effective manner, (ii) the ease at which these cells can be collected and (iii) a remarkable concordance between Comet assay and cytogenetic assays. However, the analysis also revealed some shortcomings: (i) the low number of study participants, (ii) the bias in the distribution of gender, (iii) lack of qualitative and quantitative exposure data, (iv) omission to consider differences in physical activity and diet between control and exposed groups, (v) lack of uniformity in the Comet assay procedures, and (vi) controversy in the sensitivity of Comet assay since it picked up DNA damage caused by agents which were found to be weak genotoxicants or non-genotoxicants in other tests, but gave inconsistent results with known mutagens/carcinogens such as cigarette smoke.

The use of the alkaline comet assay with lymphocytes in human biomonitoring studies

We reviewed the data of 45 alkaline comet assay studies with lymphocytes published during the last three years with the objective of monitoring human exposure to genotoxic agents as a result of occupation, drug treatment, diseases or environmental pollution. The strengths of the studies were that: (i) a lot of data could be obtained within a relatively short period of time in a cost-effective manner, (ii) lymphocytes could be easily collected in a non-invasive way and proved to be good surrogate cells in that they picked up effects caused by agents with different cancer target organs and (iii) a remarkable concordance between comet assay and cytogenetic assay data was proved. However, our analysis revealed some shortcomings of the studies such as: (i) the inclusion of low number of study participants and bias in the number and gender of subjects between control and exposed groups, (ii) lack of qualitative and quantitative exposure data, (iii) lack of consideration of differences in physical activity and diet between control and exposed groups, (iv) difficulty in comparison of the studies due to lack of uniformity in the comet assay procedures such as duration of alkali unwinding and electrophoresis, slide scoring method and the metrics used to assess the extent of DNA damage and (v) controversy in the sensitivity of comet assay since it picked up DNA damage caused by agents such as wood dust, pesticides and hormone preparations which were found to be weak genotoxins or non-genotoxins in other tests, but gave inconsistent results with known mutagens/carcinogens such as tobacco smoke. We feel that for the alkaline comet assay to be an important tool in human biomonitoring studies, serious consideration should be given to the flaws in the design and performance of the assay.

DDT induces DNA damage in blood cells. Studies in vitro and in women chronically exposed to this insecticide

In this study, DDT-induced DNA damage on blood cells was analyzed both in vitro and in vivo. Peripheral blood mononuclear cells (PBMC) were isolated from healthy donors and incubated in the presence of three different concentrations (40, 80, and 100 microg/mL) of p,p'-DDT, p,p'-DDE, and p,p'-DDD at three different treatment times (24, 48, and 72 h). Then, DNA damage was assessed by the single-cell electrophoresis assay (comet assay) as well as by flow cytometry detection of hypodiploid cells (DNA content assay). All compounds induced significant DNA damage as shown by the comet assay. Accordingly, cells exposed to DDT, DDE, and DDD showed a significant increase in the percentage of hypodiploid cells compared with untreated PBMC. In agreement with the in vitro data, a significant correlation between blood levels of DDT, DDD, and DDE and DNA damage (comet assay) was found in women with different amounts of environmental exposure. This association remained significant after controlling for nutritional status, smoking habits, alcohol ingestion, and reported exposure to other pesticides. Although the precise biological importance remains to be explained, our results strongly suggest that DDT and its metabolites are able to induce DNA damage in PBMC both in vitro and in vivo.

Sister chromatid exchanges and micronuclei analysis in lymphocytes of men exposed to simazine through drinking water

In some cities of the autonomous community of Extremadura (south-west of Spain), levels of simazine from 10 to 30 ppm were detected in tap water. To analyse the possible effect of this herbicide, two biomarkers, sister chromatid exchanges (SCE) and micronuclei (MN), were used in peripheral blood lymphocytes from males exposed to simazine through drinking water. SCE and MN analysis failed to detect any statistically significant increase in the people exposed to simazine when compared with the controls. With respect to high frequency cells (HFC), a statistically significant difference was detected between exposed and control groups.

Effect of smoking habit on the frequency of micronuclei in human lymphocytes: results from the Human MicroNucleus project

The effect of tobacco smoking on the frequency of micronuclei (MN) in human lymphocytes has been the object of many population studies. In most reports, the results were unexpectedly negative, and in many instances smokers had lower frequencies of MN than non-smokers. A pooled re-analysis of 24 databases from the HUMN international collaborative project has been performed with the aim of understanding the impact of smoking habits on MN frequency. The complete database included 5710 subjects, with 3501 non-smokers, 1409 current smokers, and 800 former smokers, among subjects in occupational and environmental surveys. The overall result of the re-analysis confirmed the small decrease of MN frequencies in current smokers (frequency ratio (FR) = 0.97, 95% confidence interval (CI) = 0.93-1.01) and in former smokers (FR = 0.96, 95% CI = 0.91-1.01), when compared to non-smokers. MN frequency was not influenced by the number of cigarettes smoked per day among subjects occupationally exposed to genotoxic agents, whereas a typical U-shaped curve is observed for non-exposed smokers, showing a significant increase of MN frequency in individuals smoking 30 cigarettes or more per day (FR = 1.59, 95% CI = 1.35-1.88). This analysis confirmed that smokers do not experience an overall increase in MN frequency, although when the interaction with occupational exposure is taken into account, heavy smokers were the only group showing a significant increase in genotoxic damage as measured by the micronucleus assay in lymphocytes. From these results some general recommendations for the design of biomonitoring studies involving smokers can be formulated. Quantitative data about smoking habit should always be collected because, in the absence of such data, the simple comparison of smokers versus non-smokers could be misleading. The sub-group of heavy smokers (> or =30 cigarettes per day) should be specifically evaluated whenever it is large enough to satisfy statistical requirements. The presence of an interaction between smoking habit and occupational exposure to genotoxic agents should be always tested.

Gender-related differences in basal DNA damage in lymphocytes of a healthy Indian population using the alkaline Comet assay

The Comet assay, a sensitive, rapid and non-invasive technique, measures DNA damage in individual cells and has found wide acceptance in epidemiological and biomonitoring studies to determine the DNA damage resulting from lifestyle, occupational and environmental exposure. The present study was undertaken to measure the basal level of DNA damage in a normal, healthy Indian male and female population. Out of the 230 volunteers included in this study, 124 were male and 106 were female. All the individuals belonged to a comparable socio-economic background and aged between 20 and 30 years. They were also matched for their smoking and dietary habits. The period of sample collection was also matched. The results revealed a statistically significant higher level of DNA damage in males when compared to females as evident by an increase in the Olive tail moment [3.76+/-1.21 (arbitrary units) for males as compared to 3.37+/-1.47 for females (P<0.05)], tail DNA (%) [10.2+/-2.96 for males as compared to 9.40+/-2.83 for females (P<0.05)] and tail length (microm) [59.65+/-9.23 for males and 49.57+/-14.68 for females (P<0.001)]. To our knowledge, this report has, for the first time demonstrated significant differences in the basal level of DNA damage between males and females in a normal healthy Indian population.

DNA damage assessment by comet assay of human lymphocytes exposed to jet propulsion fuels

Exposure to jet fuel damages DNA and results in a number of physiological changes in liver, lung, immune, and neurological tissue. In this study the single-cell gel electrophoresis assay or comet assay was used to compare the DNA damage in human peripheral lymphocytes produced by three jet propulsion fuels: JP-8, JP-5, and JP-8+100. These fuels consist of complex mixtures of aliphatic, aromatic, and substituted naphthalene hydrocarbons. Two exposure times were investigated which correspond to estimated occupational exposure times and concentrations of fuels were used that were based on previous fuel toxicity studies. Analysis of samples for the extent of DNA damage as determined by tail moment and percent tail DNA was performed on exposed cells following a brief recovery time. All fuels produced significant increases in DNA damage; however, only JP-8+100 was genotoxic at the lowest exposure concentration (1:500). At the highest exposure concentration (1:75), the mean tail moments for JP-8 and JP-8+100 (32.041 +/- 2.599 and 45.774 +/- 4.743, respectively) were significantly greater than for JP-5 (1.314 +/- 0.474). These results indicate that JP-8+100 is the most potent inducer of DNA damage in human peripheral lymphocytes and that both JP-8+100 and JP-8 are capable of damaging lymphocyte DNA to a greater extent than JP-5.

JP-8 jet fuel-induced DNA damage in H4IIE rat hepatoma cells

We investigated the genotoxicity of middle distillate jet fuel, Jet Propulsion 8 (JP-8), on H4IIE rat hepatoma cells in vitro. DNA damage was evaluated using the comet (single cell gel electrophoresis) assay. Cells were exposed for 4h to JP-8 (solubilized in ethanol (EtOH) at 0.1% (v/v)) to concentrations ranging from 1 to 20microg/ml. Exposure to JP-8 resulted in an overall increase in mean comet tail moments ranging from 0.74+/-0.065 (0.1% EtOH control) to 3.13+/-0.018,4.36+/-0.32,5.40+/-0.29,7.70+/-0.52 and 11.23+/-0.77 for JP-8 concentrations 3, 5, 10, 15 and 20microg/ml, respectively. Addition of DNA repair inhibitors hydroxyurea (HU) and cytosine arabinoside (Ara-C) to cell culture with JP-8 resulted in accumulation of DNA damage strand breaks and increase in comet tail length. Inclusion of 4mM HU and 40microM Ara-C with 3, 5, 10 and 20microg/ml JP-8 concentrations resulted in increased mean tail moments to 5.94+/-0.43,10.12+/-0.72,17.03+/-0.96,and29.25+/-1.55. JP-8, in the concentrations used in this study, did not result in cytotoxicity or significant apoptosis, as measured using the terminal deoxynucleotidyl transferase (TDT)-mediated dUTP-X nick end labeling (TUNEL) assay. These results demonstrate that relevant exposures to JP-8 result in DNA damage to H4IIE cells, and suggest that DNA repair is involved in mitigating these effects.