Micronuclei assessment in the urothelial cells of women using hair dyes and its modulation by genetic polymorphisms

Micronuclei and other nuclear anomalies in exfoliated urothelial cells and urinary 8-hydroxy-deoxyguanosine levels among Turkish hairdressers

Hairdressers are constantly occupationally exposed to many chemicals have the potential to cause allergies and carcinogenic effects, act as skin and eye irritants and induce oxidative stress and DNA damage. This study aimed to evaluate occupation-induced genotoxicity based on the presence of micronucleus (MN) and other nuclear anomalies in urothelial cells and measure oxidative DNA damage based on the 8-hydroxy-2'-deoxyguanosine level in the urine of Turkish hairdressers. Originality of this study comes from that there was no study on MN and other nuclear anomalies frequencies and oxidative DNA damage in urine samples of hairdressers in the literature. The mean±standard deviation frequency (‰) of micronucleated (MNed) cells was higher in the hairdresser group (n=56) (4.81±7.87, p<0.001) than in the control group (n=56) (0.93±1.85). Nuclear buds were not observed in either group. While the frequency of basal cells was higher in the control group (446.6±106.21) than in the hairdresser group (367.78±101.51, p<0.001), the frequency of binuclear, karyolytic, pycnotic and karyorrhectic cells were higher in the hairdresser group (0.41±0.80, p<0.001; 438.02±118.27, p<0.001; 0.43±0.76, p<0.001; and 47.27±28.40, p<0.001) than in the control group (0.04±0.27, 358.57±95.71, 0.05±0.23 and 24.41±14.50). Condensed chromatins were observed only in the hairdresser group. Specific gravity adjusted 8-hydroxy-2'-deoxyguanosine level was statistically lower in the hairdresser group (908.21±403.25 ng/mL-SG) compared to the control group (1003.09±327.09 ng/mL-SG) (p=0.024). No significant correlation was found between the 8-hydroxy-2'-deoxyguanosine level and the frequency MN. The amount of formaldehyde released during Brazilian keratin treatment was higher than the American Conference of Governmental Industrial Hygienists -Threshold Limit Value (ACGIH-TLV; 0.1 ppm). Similarly, the amount of ethyl acetate released in three salons was above the recommended limit (400 ppm). These findings suggest that hairdressers have an increased risk of genotoxicity and cytotoxicity owing to occupational exposure, regardless of age, working hours, smoking and alcohol consumption.

Do hairdressers comprise a high risk group for genotoxicity? A systematic review

BACKGROUND AND OBJECTIVES

Nowadays, hair dye products are widely used for aesthetic purposes, in which it generates chemical exposure to customers and, mainly, hairdressers. The aim of this systematic review was designed to elucidate the following question: are hair dye products able to induce DNA damage in hairdressers?

METHODS

Studies were included in our analyses if they met the following criteria: (1) studies measuring genetic damage in vivo; (2) studies published in English; (3) studies that provided data clearly presented in scientific standards.

RESULTS

Full manuscripts from 13 studies were carefully selected in this setting. Our results demonstrate that hair dye products may contain chemical agents able to induce DNA strand breaks or chromosome damage since the majority of studies demonstrated positive findings for genotoxicity. A total of 7 studies (out of 13) had strong or moderate rates in the quality assessment. The type of genotoxicity assay and sample selection criteria time influenced the outcome.

CONCLUSION

In summary, our results reveal that hairdressers are occupationally exposed to genotoxic agents. Such findings are very important for protecting these professionals who are continuously exposed to chemicals for long periods.

Household cooking oil type and risk of oral micronucleus frequency in Chinese nonsmokers

Household animal fat has been linked to increased incidence of cancers compared with vegetable fat. However, few epidemiological studies have associated these two cooking oil types with precancerous genotoxic effects, such as occurrence of micronuclei (MN). This study aimed to explore the association between oral MN frequency and household cooking oil type and whether the association can be attributed to polycyclic aromatic hydrocarbons (PAHs). We collected information about individual cooking oil use, measured genotoxic effects by MN tests and urinary PAHs metabolites (OHPAHs) in 245 nonsmokers. The associations between household cooking oil type and MN frequency and OHPAHs were analyzed using generalized linear models (GLMs) and logistic regression models, evaluating odds ratios and coefficient (95% confidence intervals) (ORs, 95% Cls; β, 95% Cls). The odds of animal fat consumers, rather than vegetable fat consumers, was positively associated with higher MN frequency (OR = 1.94, P < 0.05). The associations were discovered in participants only using kitchen ventilation (OR = 2.04, P < 0.05). Animal fat consumers had higher total OHPAHs than vegetable fat consumers (1.58 ± 0.22 mg/mol, Cr vs 1.20 ± 0.12 mg/mol, Cr; P = 0.028). Significant correlations were observed between total OHPAHs quartiles and increased MN frequency (β = 0.38, P-trend = 0.026). After stratifying by household cooking oil type, sensitivity analyses showed that the positive association between total OHPAHs quartiles and increased MN frequency was only observed in animal fat consumers (β = 0.61, P-trend = 0.030). In conclusion, usage of household animal fat was associated with an increased odds of oral MN frequency in Chinese nonsmokers and the odds correlated with increased PAHs exposure. This finding supplemented evidence associating cooking oil type with genotoxic effects and explained its association with PAHs exposure.

Micronuclei as biomarkers of DNA damage, aneuploidy, inducers of chromosomal hypermutation and as sources of pro-inflammatory DNA in humans

Micronuclei (MNi) are among the most widely studied biomarkers of DNA damage and chromosomal instability in humans. They originate from chromosome fragments or intact chromosomes that are not included in daughter nuclei during mitosis. The main reasons for their formation are a lack of functional centromere in the chromosome fragments or whole chromosomes or defects in one or more of the proteins of the mitotic system that, consequently, fails to segregate chromosomes properly. Assays have been developed to measure MNi in peripheral blood lymphocytes, red blood cells as well as various types of epithelial cells such as buccal, nasal, urothelial and cervical cells. Some of the assays have been further developed into micronucleus (MN) cytome assays to include additional nuclear anomalies, cell death and nuclear division biomarkers. In addition, the use of molecular probes has been adopted widely for the purpose of understanding the mechanistic origin of MNi. MN assays in humans are used for the purpose of investigating the genotoxic effects of adverse environmental, life-style and occupational factors, genetic susceptibility to DNA damage, and for determining risk of accelerated aging and diseases affected by genomic instability such as developmental defects and cancer. The emerging new knowledge showing that chromosomes trapped in MNi can undergo a high rate of fragmentation and become massively re-arranged have highlighted the possibility that MN formation is not only a biomarker of induced DNA damage but also a mechanism that drives hypermutation. Furthermore, another line of recent research showed that DNA and chromatin leaking from disrupted MNi triggers the innate immune cGAS-STING mechanism that promotes inflammation which can cause a wide-range of age-related diseases if left unresolved. For these reasons, MN assays in humans have become an increasingly important biomarker of disease initiation and progression across all life-stages.

Environmental chemical exposures in the urine of dogs and people sharing the same households

Introduction:

Urothelial carcinoma (UCC) develops in both humans and dogs and tracks to regions of high industrial activity. We hypothesize that dogs with UCC may act as sentinels for human urothelial carcinogen exposures. The aim of this pilot study was to determine whether healthy people and dogs in the same households share urinary exposures to potentially mutagenic chemical carcinogens.

Methods:

We measured urinary concentrations of acrolein (as its metabolite 3-HPMA), arsenic species, 4-aminobiphenyl, and 4-chlorophenol (a metabolite of the phenoxyherbicide 2,4-D) in healthy dogs and their owners. We assessed possible chemical sources through questionnaires and screened for urothelial DNA damage using the micronucleus assay.

Results:

Biomarkers of urinary exposure to acrolein, arsenic, and 4-chlorophenol were found in the urine of 42 pet dogs and 42 owners, with 4-aminobiphenyl detected sporadically. Creatinine-adjusted urinary chemical concentrations were significantly higher, by 2.8- to 6.2-fold, in dogs compared to humans. Correlations were found for 3-HPMA (r = 0.32, P = 0.04) and monomethylarsonic acid (r = 0.37, P = 0.02) between people and their dogs. Voided urothelial cell yields were inadequate to quantify DNA damage, and questionnaires did not reveal significant associations with urinary chemical concentrations.

Conclusions:

Healthy humans and pet dogs have shared urinary exposures to known mutagenic chemicals, with significantly higher levels in dogs. Higher urinary exposures to acrolein and arsenic in dogs correlate to higher exposures in their owners. Follow-up studies will assess the mutagenic potential of these levels in vitro and measure these biomarkers in owners of dogs with UCC.

Micronucleus Assay of Buccal Mucosal Cells in Hairdressers: The Importance of Occupational Exposure

Background and objective: Today, the chemical materials available in hair dyes are considered risk factors for many cancers, particularly oral cancer. This study was performed to study the effect of occupational exposure on micronucleus (MN) frequency of buccal mucosa cells in hairdressers. Materials and methods: This historical cohort study was performed on 28 hairdressers and 28 control samples. To eliminate the gender variable, all the samples were women and they were matched by age. Buccal mucosa cells were removed using a wet spatula and after fixation, Papanicolaou staining method was applied. The percentage of the cells containing MN was registered. T-test was used to compare the results between the two groups. Results: The mean percentages of MN in buccal mucosa cells of hairdresser’s and control sample were 16.61±4.95 and 8.84±4.74, respectively, with a significant difference (P<0.001). In addition, higher MN mean percentage was reported in subjects working more than 60 hours weekly compared with those working 60 hours and less; however, the difference was not statistically significant (P=0.14). Conclusion: In the present study, hairdressers demonstrate significantly higher average of MN in buccal mucosa cells. Also, it seems increment in their working time can increase MN frequency in these studied samples.

Evaluation of Pb-210 in urine and frequency of micronuclei in exfoliated cells as indicators of exposure to cigarettes

This study aimed at analyzing the frequency of micronuclei (MN) in exfoliated cells as well as the levels of Pb-210 in urine samples to evaluate the association between the smoking habit and toxic stress of transitional epithelial cells. The frequency of MN was scored from Giemsa-stained slides while exchange resin and beta counting techniques were employed to measure the concentrations of this radioisotope. Urine samples of smokers had levels of Pb-210 up to 158.65 mBq L^-1. For nonsmokers, the median was below the detection limit (45 mBq L^-1). The analyses of mononucleated cells showed a significant increase of the frequency of MN in smokers when compared to nonsmokers. Statistical tests showed a tight relation between the cigarette consumption and the increase of the frequency of MN, rather than with the levels of Pb-210 present in smoke particles. The results indicate the usefulness of the methodology for the evaluation of human health risks related to chronic contamination with Pb-210.

Genotoxic risk assessment in professionals working hairdressers area using buccal micronucleus assay, in Aydın City, Turkey

The aim of this study was to determine the genotoxic risk of professional hairdressers in Aydın City, Turkey, through investigating the micronucleus frequencies in buccal mucosa epithelial cells. All the hairdresser working hairdresser area were included in the genotoxic risk group (GRG = 20) in Aydın City, Turkey. The control group (CG = 20) comprised healthy individuals matching the gender and age of the GRG. Buccal mucosal scraping from all the 40 subjects of GRG (10 women and 10 men) and CG (10 women and 10 men) was stained with Giemsa stain and observed under light microscope (×40) for the presence of micronuclei (M 10 N) and karyolysis, pyknosis, condensed chromatin, karyorrhexis, nuclear bud, and binucleates in the exfoliated epithelial cells. There are significance between the incidence of MN in GRG and CG (P = <0.005) using one-way ANOVA, Kolmogorov-Smirnov Z test, and Spearman Rank Correlation Tests.

Alterations of telomere length and DNA methylation in hairdressers: A cross-sectional study

Working as hairdressers has been associated with increased risk for cancer, particularly bladder cancer. To evaluate if current hairdressers have elevated risks of adverse health effects, we measured several biomarkers related to cancer-related DNA alterations. We enrolled 295 hairdressers and 92 non-hairdressers (all female non-smokers) from Stockholm and southern Sweden. Questionnaire data were collected for each participant, including work tasks for the hairdressers. We measured telomere length in peripheral blood leucocytes using quantitative PCR and DNA methylation status of genes relevant for bladder cancer using methylation sensitive high resolution melting analysis. The hairdressers had shorter telomeres (β = -0.069, P = 0.019) compared with non-hairdressers. Shorter telomeres were found in hairdressers up to 32 years old performing hair waving more than once per week as compared with hairdressers in the same age group performing hair waving less often (β = -0.12, P = 0.037). Hair waving was associated with less frequent CDKN2A methylation (odds ratio, OR = 0.19, P = 0.033). Shorter telomeres in hairdressers may indicate a genotoxic effect. Performing hair waving was associated with short telomere length, although the effect was only observed in young hairdressers. No clear patterns were discerned with regard to DNA methylation of bladder cancer-related genes. The observed changes of methylation were not all in the expected direction and warrant further investigation.

Exposure of hairdressers to ortho- and meta-toluidine in hair dyes

BACKGROUND

Carcinogenic aromatic amines derived from hair dyes have recently received new attention. One of these is ortho (o)-toluidine, which is classified as carcinogenic to humans.

OBJECTIVES

To clarify exposure of hairdressers to potentially carcinogenic aromatic amines, including o-toluidine.

METHODS

We measured eight potentially carcinogenic aromatic amines in the blood of 295 hairdressers, 32 users of hair dyes and 60 controls. The study was restricted to female non-smokers. Lifestyle data were collected for all participants using self-administered questionnaires. Blood samples were taken for analysis of ortho-, meta (m)- and para (p)-toluidine; 2-, 3- and 4-ethylaniline, 2,3- and 3,4-dimethylaniline as haemoglobin adducts. The samples were analysed with gas chromatography-tandem mass spectrometry.

RESULTS

Generally, adduct concentrations were in the range of 0-200 pg/g haemoglobin. A comparison of the adduct concentrations found in hairdressers, consumers and controls showed no statistically significant differences. However, for hairdressers, o- and m-toluidine concentrations increased significantly with the weekly number of hair waving (p=0.020) and permanent hair dyeing treatments (p=0.026), respectively. o-Toluidine and m-Toluidine concentrations also tended (p=0.076 and 0.080, respectively) to increase with the frequency of light-colour permanent hair dye treatments.

CONCLUSIONS

Hairdressers who use light-colour permanent hair dyes, other permanent hair dyes and hair waving treatments seem to be exposed to o- and m-toluidine as indicated by associations with the number of treatments performed. Analyses of hair waving and hair dye products should be performed to identify the possible sources of exposure to o- and m-toluidine.

Association between cancer and contact allergy: a linkage study

Background Contact allergy is a prevalent disorder. It is estimated that about 20% of the general population are allergic to one or more of the chemicals that constitute the European baseline patch test panel. While many studies have investigated associations between type I allergic disorders and cancer, few have looked into the association between cancer and contact allergy, a type IV allergy. By linking two clinical databases, the authors investigate the possible association between contact allergy and cancer. Methods Record linkage of two different registers was performed: (1) a tertiary hospital register of dermatitis patients patch tested for contact allergy and (2) a nationwide cancer register (the Danish Cancer Register). After linking the two registers, only cancer subtypes with 40 or more patients registered were included in the analysis. The final associations were evaluated by logistic regression analysis. Results An inverse association between contact allergy and non-melanoma skin- and breast cancer, respectively, was identified in both sexes, and an inverse trend for brain cancer was found in women with contact allergy. Additionally, a positive association between contact allergy and bladder cancer was found. Conclusion The inverse associations support the immunosurveillance hypothesis (ie, individuals with an allergy are less likely to get cancer due to a triggered immune system), while the positive association with bladder cancer could be due to accumulations of chemical metabolites in the bladder. The authors' findings add to the limited knowledge about contact allergy and the risk of cancer.

Genotoxic effects in swimmers exposed to disinfection by-products in indoor swimming pools

BACKGROUND

Exposure to disinfection by-products (DBPs) in drinking water has been associated with cancer risk. A recent study (Villanueva et al. 2007; Am J Epidemiol 165:148-156) found an increased bladder cancer risk among subjects attending swimming pools relative to those not attending.

OBJECTIVES

We evaluated adults who swam in chlorinated pools to determine whether exposure to DBPs in pool water is associated with biomarkers of genotoxicity.

METHODS

We collected blood, urine, and exhaled air samples from 49 nonsmoking adult volunteers before and after they swam for 40 min in an indoor chlorinated pool. We estimated associations between the concentrations of four trihalomethanes (THMs) in exhaled breath and changes in micronuclei (MN) and DNA damage (comet assay) in peripheral blood lymphocytes before and 1 hr after swimming; urine mutagenicity (Ames assay) before and 2 hr after swimming; and MN in exfoliated urothelial cells before and 2 weeks after swimming. We also estimated associations and interactions with polymorphisms in genes related to DNA repair or to DBP metabolism.

RESULTS

After swimming, the total concentration of the four THMs in exhaled breath was seven times higher than before swimming. The change in the frequency of micronucleated lymphocytes after swimming increased in association with higher exhaled concentrations of the brominated THMs (p = 0.03 for bromodichloromethane, p = 0.05 for chlorodibromomethane, p = 0.01 for bromoform) but not chloroform. Swimming was not associated with DNA damage detectable by the comet assay. Urine mutagenicity increased significantly after swimming, in association with the higher concentration of exhaled bromoform (p = 0.004). We found no significant associations with changes in micronucleated urothelial cells.

CONCLUSIONS

Our findings support potential genotoxic effects of exposure to DBPs from swimming pools. The positive health effects gained by swimming could be increased by reducing the potential health risks of pool water.

Optimizing urothelial cell preparation for the human urinary micronucleus assay

Biological monitoring of early genotoxic effects in urothelial cells using the urinary micronucleus (MNu) assay is promising for early detection of cancer, such as bladder carcinoma. But many problems are encountered, the major being the poorly differential staining of cells, particularly in women having an important amount of squamous cells. We have optimized the protocol and obtained a differential staining of the cell types present in urine on 10 subjects. Following Carnoy I fixation and Papanicolaou staining, urothelial cells were blue while most squamous cells were pink. This differential staining allowed for optimization of the MNu assay on a single urine void, for both females and males. Even if our MNu means were comparable to the literature, the great variation in reported MNu results could reside in the ability of scorers to distinguish correctly between urothelial and squamous cells. When monitoring exposed populations, this erroneous distinction could largely influence the results, even more in women's urine samples. Given a situation where exposure would not increase micronuclei frequency in vaginal squamous cells, their erroneous analysis in the MNu assay could mask an early genotoxic effect. Therefore, as transitional cell carcinoma of the bladder originates from transformed urothelial cells, restricting micronuclei analysis to urothelial cells could yield a more precise estimate of cancer risk in exposed populations. Moreover, it is hoped that the improvements proposed in this paper will allow for an easier implementation of the MNu assay in various set-ups and enhance its specificity, since MNu are considered a suitable biomarker.