The micronucleus assay is one of the most common methods used to assess chromosomal damage (losses or breaks) in human peripheral blood lymphocytes (PBL) in genetic toxicology. Most studies have focused on analyzing total micronuclei (MN), but identifying the content of MN can provide more detailed information. The main aim of this study was to map the factors affecting the frequency and types of micronuclei in binucleated cells (BNC) in elderly population. Fluorescence in situ hybridization using Human Pan Centromeric Chromosome Paint was used to identify centromere positive (CEN+) or centromere negative (CEN-) MN. A group of 95 men from Southern Bohemia, Czech Republic (average age 68.0±6.8 years) was followed repeatedly, in spring and fall 2014. The study participants were former workers of the uranium plant "MAPE Mydlovary" (processing uranium ore from 1962 to 1991), and controls. The general profile of individual types of MN, and the effect of the season, former uranium exposure, age, smoking status, weight, and X-ray examination on the level and type of MN were analyzed. The results of this study showed: (i) a stable profile of BNC with MN based on the number of MN during two seasons; (ii) an increase of the number of CEN+ MN from spring to fall; (iii) a lower frequency of the total MN in the exposed group than in controls with a significant difference in the percentage of aberrant cells (%AB.C.) in the fall; (iv) no clear effect of age, smoking and BMI on DNA damage in this group; (v) lower DNA damage levels in former uranium workers who received X-ray examination later in life. In summary, the results indicate a trend of seasonal changes of individual types of MN and suggest that former exposure can have a protective effect on the level of DNA damage in case of future exposure.
Keywords: Environmental exposure; Micronuclei; Pan-centromeric FISH; Uranium exposure; X-ray.
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