Sister chromatid exchanges (SCEs) and high frequency cells (HFCs) in human population studies: principles of their analysis

Environmental Tobacco Smoke in Occupational Settings: Effect and Susceptibility Biomarkers in Workers From Lisbon Restaurants and Bars

Environmental tobacco smoke (ETS) has been recognized as a major health hazard by environmental and public health authorities worldwide. In Portugal, smoke-free laws are in force for some years, banning smoking in most indoor public spaces. However, in hospitality venues such as restaurants and bars, owners can still choose between a total smoke-free policy or a partial smoking restriction with designated smoking areas, if adequate reinforced ventilation systems are implemented. Despite that, a previous study showed that workers remained continuously exposed to higher ETS pollution in Lisbon restaurants and bars where smoking was still allowed, comparatively to total smoke-free venues. This was assessed by measurements of indoor PM2.5 and urinary cotinine, a biomarkers of tobacco smoke exposure, demonstrating that partial smoking restrictions do not effectively protect workers from ETS. The aim of the present work was to characterize effect and susceptibility biomarkers in non-smokers from those hospitality venues occupationally exposed to ETS comparatively to non-exposed ones. A group of smokers was also included for comparison. The sister chromatid exchange (SCE), micronucleus (MN) and comet assays in whole peripheral blood lymphocytes (PBLs) and the micronucleus assay in exfoliated buccal cells, were used as biomarkers of genotoxicity. Furthermore, a comet assay after ex vivo challenge of leukocytes with an alkylating agent, ethyl methanesulfonate (EMS), was used to analyze the repair capacity of those cells. Genetic polymorphisms in genes associated with metabolism and DNA repair were also included. The results showed no clear association between occupational exposure to ETS and the induction of genotoxicity. Interestingly, the leukocytes from non-smoking ETS-exposed individuals displayed lower DNA damage levels in response to the ex vivo EMS challenge, in comparison to those from non-exposed workers, suggesting a possible adaptive response. The contribution of individual susceptibility to the effect biomarkers studied was unclear, deserving further investigation.

Cytogenetic monitoring of hospital staff exposed to ionizing radiation: optimize protocol considering DNA repair genes variability

PURPOSE

Chronic occupational exposure to ionizing radiation (IR) induces a wide spectrum of DNA damages. The aim of this study was to assess the frequencies of micronucleus (MN), sister chromatid exchanges (SCE) and to evaluate their association with XRCC1 399 Arg/Gln and XRCC3 241 Thr/Met polymorphisms in Hospital staff occupationally exposed to IR.

MATERIALS AND METHODS

A questionnaire followed by a cytogenetic analysis was concluded for each subject in our study. The exposed subjects were classified into two groups based on duration of employment (Group I < 15 years; Group II ≥15years). The genotypes of all individuals (subjects and controls) were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

DNA damage frequencies were significantly greater in IR workers compared with controls (p < .05). However, no association arised between XRCC1 399 Arg/Gln and XRCC3 241 Thr/Met polymorphisms, on one hand, and the severity of DNA damages in the studied cohort of Tunisian population, on the other hand.

CONCLUSION

Our data provide evidence for an obvious genotoxic effect associated with IR exposure and reinforce the high sensitivity of cytogenetic assays for biomonitoring of occupationally exposed populations. These results indicate that workers exposed to IR should have periodic monitoring, along their exposure. The variants, rs25487 and rs861539, of XRCC1 and XRCC3 genes have obvious functional effects. Paradoxically, these variants are not associated with the severity of damages, according to used assays, in the studied cohort of Tunisian population, unlike other studies.

Can consumption of raw vegetables decrease the count of sister chromatid exchange? Results from a cross-sectional study in Krakow, Poland

Background

Sister chromatid exchange (SCE) is a widely used sensitive cytogenetic biomarker of exposure to genotoxic and cancerogenic agents. Results of human monitoring studies and cytogenetic damage have revealed that biological effects of genotoxic exposures are influenced by confounding factors related to life-style. Vegetable and fruit consumption may play a role, but available results are not consistent. The purpose of the study was to investigate the effect of consumption of raw and cooked vegetables and fruits on SCE frequency.

Methods

A total of 62 participants included colorectal cancer (CRC) patients, hospital-based controls and healthy laboratory workers. SCE frequency was assessed in blood lymphocytes. Frequency of vegetable and fruit consumption was gathered by structured semi-quantitative food frequency questionnaire.

Results

SCE frequency was lowest among hospital-based controls (4.4 ± 1.1), a bit higher in CRC patients (4.5 ± 1.0) and highest among laboratory workers (7.4 ± 1.2) (p < 0.05). Multivariable linear regression showed a significant inverse effect (b = −0.20) of raw vegetable consumption, but not so for intake of cooked vegetables and fruits.

Conclusions

The results of the study have shown the beneficial effect of consumption of raw vegetables on disrupted replication of DNA measured by SCE frequency, implying protection against genotoxic agents. Further effort is required to verify the role of cooked vegetables and fruits.

Sister chromatid exchanges in smokers and smokers with alcohol habit

Aim:

Sister chromatid exchange (SCE) test is a sensitive, biomarker of genotoxic substances. The present study was conducted to observe the frequency of SCEs in peripheral blood lymphocytes of 30 males with and without the habit of cigarette smoking and alcohol consumption.

Materials and Methods:

Subjects for this study were males aged between 25-50 years and were selected from the students, employees and the patients attending the outpatient department of Ragas dental college and Hospital, Chennai.

Results:

Controls, smokers, and smokers with alcohol habit were divided into two age groups as ≤30 years and ≥30 years. In controls the mean frequency of SCEs/cell in ≤30 years and ≥30 year's age group was 5.80 and 6.05, respectively. In Smokers SCEs/cell in ≤30 years and ≥30 year's age group was 7.7 and 8.8, respectively. In Smokers with alcohol habit SCEs/cell in ≤30 years and ≥30 years age group was 10.1 and 12.8, respectively.

Conclusions:

In this study, the duration of the smoking habit has shown a positive correlation with the mean SCE frequency. Whereas, frequency of the habit did not show any influence on the SCE levels. In smokers with alcohol habit, both the duration and frequency of their smoking habit has shown a significant effect on the SCE levels suggesting a synergistic effect of alcohol and smoking leading to excessive DNA damage.

Differential radiation effects in smokers--culture time dependence of the yield of gamma ray-induced chromosome damage in first division metaphases

PURPOSE

Telomeric associations (TA) and unstable chromosomal aberration (CA) transmission through M1-M4 metphases (first to fourth division) in gamma-ray irradiated G0 lymphocytes in 2 smokers were examined, since TA in conventionally stained chromosomes were reported earlier as a sensitive cytogenetic marker in mutagen-exposed populations. The purpose of the present study is an extension of our earlier studies on unstable CA transmission through successive mitotic divisions.

MATERIALS AND METHODS

The bromodeoxyuridine (BrdU) incorporation and fluorescence plus giemsa (FPG) method for M1-M5 metaphase analysis was carried out at 50, 72, 96 h to analyse TA and CA in conventionally and FPG stained chromosomes after irradiation of human blood samples with 3 Gy of gamma-rays. In situ hybridization (ISH) with enzymatic/fluorescence detection was used to analyse radiation-induced aneuploidy and TA. Analysis was carried out on sister chromatid exchanges (SCE) in M2 cells at 72 h and micronuclei (MN) at 24, 50, 72, 96 h.

RESULTS

TA, corroborated by the absence of acentric fragments, were not detected in conventional/FPG stained/ISH chromosomes. Chromosome 21 aneuploidy was observed. Significant differences in mean frequencies of dicentrics/micronuclei (MN)/SCE with high frequency cells (HFC) were found in smokers after irradiation compared to non-smokers. Higher radiation induced CA in M1 cells were found with extended culture time. Induction of giant cells with mirror dicentrics, tricentrics and rings were found.

CONCLUSION

TA in conventional or FPG stained metaphase chromosomes is not a sensitive cytogenetic marker for mutagen exposed population screening. Higher radiation induced CA frequencies in M1 cells with extended culture time were indicative of a delay in cell cycle progression of aberrant cells or different lymphocyte subset populations. Bridge-breakage-fusion (BBF) events due to dicentrics may be instrumental in the perpetuation of chromosomal instability. Differential effects were noted in radiation-induced dicentric, SCE and MN frequencies in smokers compared to non-smokers. Heavy smoking could be a confounding variable in chromosome-based biodosimetry and biomonitoring studies. Giant cells may denote a switch to amitotic modes of cell survival, providing additional mechanisms of genotoxic resistance.

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.

Microplate enzyme-linked immunosorbent assay for the detection of primary DNA alterations based on the interaction with UvrA/UvrB

An enzyme-linked microplate immunoassay for the analysis of primary DNA lesions is described. The assay principle is based on the interaction of the bacterial DNA repair proteins UvrA and UvrB with DNA and on the immunodetection of UvrB forming a stable complex with covalently modified nucleotides. Using this technique we were able to detect damages in genomic DNA induced by uv light and by several different genotoxic agents. The detection sensitivity of the method reaches down to the nanomolar range of the mutagenic compound depending on the type of the DNA alteration. The method might be used in automated high-throughput studies.

Analysis of correlated data in human biomonitoring studies. The case of high sister chromatid exchange frequency cells

Sister chromatid exchange (SCE) analysis in peripheral blood lymphocytes is a well established technique that aims to evaluate human exposure to toxic agents. The individual mean value of SCE per cell had been the only recommended index to measure the extent of this cytogenetic damage until the early 1980's, when the concept of high frequency cells (HFC) was introduced to increase the sensitivity of the assay. All statistical analyses proposed thus far to handle these data are based on measures which refer to the individual mean values and not to the single cell. Although this approach allows the use of simple statistical methods, part of the information provided by the distribution of SCE per single cell within the individual is lost. Using the appropriate methods developed for the analysis of correlated data, it is possible to exploit all the available information. In particular, the use of random-effects models seems to be very promising for the analysis of clustered binary data such as HFC. Logistic normal random-effects models, which allow modelling of the correlation among cells within individuals, have been applied to data from a large study population to highlight the advantages of using this methodology in human biomonitoring studies. The inclusion of random-effects terms in a regression model could explain a significant amount of variability, and accordingly change point and/or interval estimates of the corresponding coefficients. Examples of coefficients that change across different regression models and their interpretation are discussed in detail. One model that seems particularly appropriate is the random intercepts and random slopes model.

Cytogenetic biomonitoring of workers exposed to bitumen fumes

Bitumen samples and fumes consist essentially of polycyclic hydrocarbons (PAH) and their derivatives, some of which are known to be carcinogenic or co-carcinogenic in animals. The level of total PAH is low when compared with coal-tar products. There is very limited data on possible health risk from exposure to bitumen fumes in workers. In this study, sister-chromatid exchange (SCE), micronuclei (MN) and high frequency of SCE cells (HFCs) were determined for 28 workers exposed to bitumen fumes and 28 control subjects. Urinary 1-hydroxypyrene (1-OHP) excretion was used as a biomarker of occupational exposure to PAH. The mean value of 1-OHP excretion of workers was 0.78+/-0.46 micromol/mol creatinine and for controls 0.52+/-0.44 micromol/mol creatinine (p<0.05). The mean values of SCE per cell and the frequency ( per thousand) of MN in peripheral lymphocytes from the workers and controls were 5.13+/-0. 64, 4.71+/-0.67, and 2.25+/-0.42, 1.79+/-0.32 respectively (p<0.05, p<0.0001). The mean value of HFCs for workers and controls were 7. 85+/-2.3 and 7.05+/-3.16, respectively (p>0.05). Our data reveal that bitumen fumes during road paving operations are absorbed by workers and that bitumen fume exposure is able to significantly induce cytogenetic damage in peripheral lymphocytes of workers after controlling some possible confounding factors, such as age, sex and smoking habits.