Viable human buccal mucosa cells do not yield typical nucleoids: Impacts on the single-cell gel electrophoresis/comet assay

Buccal mucosa (BM) cells have been used in human biomonitoring studies for detecting DNA adducts and chromosomal damage in an epithelial cell population. In the present study, we have investigated if human BM cells are suitable for use in the single-cell gel electrophoresis (SCGE)/Comet assay as an approach for estimating the exposure of epithelial cells to DNA-damaging agents. Our results indicate that only a few cells from BM cell samples yield comets that can be analyzed by current methods, and that the yield of cells with comets is independent of the percentage of viable BM cells in the sample. Data generated after enzymatic enrichment of viable cells and immunomagnetic separation of epithelial cells suggest that most of the BM cells that do form comets are probably leukocytes. Moreover, by reevaluating specific cells after running the Comet assay, we found that viable epithelial BM cells give rise to atypical comets that are not included in the analysis. Comparing DNA migration patterns between small groups of smokers and nonsmokers indicated that long-term smoking had no effect on the subpopulation of cells that yield typical comets. Our results indicate that the SCGE assay, as it is commonly performed, may not be useful for genotoxicity monitoring in human epithelial BM cells.

Lack of genotoxicity induced by endogenous and synthetic female sex hormones in peripheral blood cells detected by alkaline Comet assay

The etiology of hormone-induced cancers has been considered to be a combination of genotoxic and epigenetic events. Currently, the Comet assay is widely used for detecting genotoxicity because it is relatively simple, sensitive, and capable of detecting various kinds of DNA damage. The present study evaluates the genotoxic potential of endogenous and synthetic sex hormones, as detected by the Comet assay. Blood cells were obtained from 12 nonsmoking and 12 smoking women with regular menstrual cycles and from 12 nonsmoking women taking low-dose oral contraceptives (OC). Peripheral blood samples were collected at three phases of the menstrual cycle (early follicular, mean follicular, and luteal phases), or at three different moments of oral contraceptive intake. Three blood samples were also collected from 12 healthy nonsmoking men, at the same time as oral contraceptive users. Results showed no significant difference in the level of DNA damage among the three moments of the menstrual cycle either in nonsmoking and smoking women, or between them. No significant difference in DNA damage was also observed among oral contraceptive users, nonusers, and men. Together, these data indicate lack of genotoxicity induced by the physiological level of the female sex hormones and OC as assessed by the alkaline Comet assay. In conclusion, normal fluctuation in endogenous sex hormones and use of low-doses of oral contraceptive should not interfere with Comet assay data when this technique is used for human biomonitoring.

Mercury and DDT exposure risk to fish-eating human populations in Amazon

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Genetic biomonitoring of an urban population exposed to mutagenic airborne pollutants

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)