Estimation of the magnitude of nuclear DNA damage in coal thermal power plant workers using a micronucleus test with a cytokinetic block in connection with individual variants of the genes of the DNA repair system XRCC1, XRCC3, XRCC4

Employees of coal-fired thermal power plants are exposed to high concentrations of coal dust containing suspended particles, polycyclic aromatic hydrocarbons, and heavy metals, which can contribute to oxidative stress, leading to DNA damage, adduct formation, and chromosomal abnormalities. Production conditions cause adverse effects that are dangerous for the human genome, thus, one of the directions of genetic toxicology tracks their effects. Workers of coal-fired thermal power plants have to have a professional contact with high level of concentrations of coal dust, food both organic and inorganic compounds, including suspended particles, polycyclic aromatic hydrocarbons, and heavy metals. An important risk factor for pathological changes in the genome is hereditary predisposition. In view of the goal, the analysis of coal-fired thermal power plants workers with an increased frequency of cytogenetic damage, detected using a micronucleus test with a cytochalasin block, began to work in connection with inherited variations of DNA repair enzymes: XRCC1, XRCC3, and XRCC4. In this work, we assessed nuclear DNA damage in 222 employees of coal-fired thermal power plants in Kemerovo, whose average age was 52. The control group included 219 residents of the same area who were not employed in production, with their average age of 50. To analyze the genotoxic load, a micronucleus test on blood lymphocytes with a cytochalasin block was used. To take into account the contribution of genetic factors to the formation of disorders using the polymerase chain reaction, we analyzed the genes for DNA repair enzymes: XRCC1 rs254S9, XRCC3 rsS61539,XRCC4 rs2075686, and rs2075685. An increase in the frequency of occurrence of binuclear lymphocytes with micronuclei, bridges and protrusions and the occurrence of cells in apoptosis was established. Proliferative parameters (mitosis frequency and replication index) were lower in workers compared to the control group (see Fig. 1). It was found that smoking did not have a statistically significant effect on the performance both in the working and control groups (differences were not observed when comparing smokers and nonsmokers). Most often, the cells with micronuclei and protrusions were registered in workers performing the main production operations in the fuel and transportation workshops (on average, 2,3% and 2,9%, respectively). The workers with genotypes AA XRCC1 rs25489, CT, TT XRCC4 rs2075686, TT XRCC4 rs2075685, and TT rs861539 XRCC3 (see Table 1) were proved to be the most sensitive to the damaging effects of the production environment factors. The owners of these genotypic variants should become a priority group for the implementation of preventive measures. The accumulation of cytogenetic damage the immune system cells can lead to an increased risk of various (including cancer) diseases. In this study, the results obtained indicate a significant contribution of not only environmental, but also genetic factors to the formation of cytogenetic effects in workers at coal-fired thermal power plants. Understanding the complexity of relations at the genomic, epigenomic, proteomic, and metabolomic levels requires further large-scale studies using additional biomarkers of sensitivity and the effect of working environment factors on the body of the working population. The article contains 3 Tables, 2 Figures, 37 References. The Authors declare no conflict of interest.

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