Мета. Визначити біологічні маркери радіаційного ураження у віддаленому періоді після опромінення у широ кому інтервалі доз.

Low-dose radiation effects were studied in Ukrainian personnel of the Chernobyl exclusion zone. The aim of this study was to determine the influence of borderline exposure to annual professional limits and age on expression of molecular markers. Study groups included 300 radiation workers performing construction work on the New Safe Confinement (Arch) upon the Chernobyl “Shelter” [external dose, 26.1 ± 18.1 mSv; age, 43.1 ± 10.3 y overall and 48.7 ± 5.9 y for 69 control persons]. Methods included gene expression using RT-PCR, flow cytometry of lymphocyte antigens, gamma-H2AX, Cyclin D1 expression, and relative telomere length using flow-FISH. A statistically significant upregulation of VEGFA BAX, DDB2, NFKB1 was shown at doses below 35 mSv. In workers aged under 40 y with doses higher than 35 mSv, an upregulation of 16 genes was revealed—VEGFA, TERF2, TERF1, BIRC5, BAX, TP53, DDB2, CDKN1B, CDKN2A, NFKB2, MAPK14, TGFBR1, MKNK2, CDKN1A, NFKB1, TP53I3; and four genes were downregulated—MADD, FASL, CSF2, and TERT. In workers older than 40 y, 8 genes were upregulated and 12 were downregulated. All groups showed an increased and dose-dependent gamma-H2AX expression. Downregulation of CCND1 genes in older groups was accompanied by lower numbers of Cyclin D1 protein expression and lower CD3+ and CD4+ cell counts. Upregulation of CSF2 in those over 40 y old positively correlated with B-cell and NK-cell counts. A non-linear type of gene expression response was demonstrated: in doses over 35 mSv for those over 40 y, the increased expression of gamma-H2AX is associated with upregulation of cell survival positive regulators—BIRC5, BRCA1, DDB2, CCND1, TERT genes, and longer telomeres; the younger age group was characterized by TERF1 and TERF2 upregulation and telomere shortening.

This study confirms the presence of radiation-induced changes in gene regulation of cell proliferation, telomere function and apoptosis in radiation workers exposed to external and internal exposure at doses above professional limits and increase of compensatory changes.

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Objective. To study proliferative potential of peripheral blood lymphocytes of Chornobyl clean-up workers by level of expression of cyclin D1 and quantitative parameters of cell cycle at a remote period after radiation exposure. Materials and methods. The research subject was the peripheral blood lymphocytes (PB) of Chornobyl clean-up workers 30–33 years after radiation exposure. A total of 207 men were surveyed, 164 of them were clean-up workers exposed in the dose range 10.43–3623.31 mSv and 43 persons of the control group. Analysis of proliferation potential (cell cycle initiation) and cyclin D1 expression in PB lymphocytes were performed in vitro by a micro method of whole blood leukocytes culture with phytohemagglutinine-P (PHA). Sample preparation was performed by a standard immunofluorescent assay for intracellular proteins using the FITC labelled Mouse Anti-Human Cyclin D1 Antibody Set. Cell distribution by cell cycle phases studied by propidium iodide DNA staining and analysis on FACSCalibur laser flow cytometer in histogram mode with separation of G0/G1-, S- and G2/M-regions and Sub-G0/G1- region (apoptotic cells). Results and conclusions. An increase in the level of spontaneous сyclin D1 expression and disturbance of сyclin D1-dependent regulation of cell cycle of PB lymphocytes after mitogen activation were determined in a remote period after radiation exposure. An increase in the level of cyclin D1 expression was accompanied by increase in pool of cells in the S- and G2/M-phases of cell cycle which characterizes the high proliferative potential of PB lymphocytes. Mitogen-induced delay of cell cycle of lymphocytes in G1/S check point and reduction of S-phase was revealed. These changes are a manifestation of genomic instability caused by the effect of radiation and depend on the radiation dose. The results confirm the hypothesis about the significance of levels of cyclin D1 expression, as a criterion for manifestations of genome instability and risks of oncogenesis in a remote period after irradiation. Key words: cell cycle, cell proliferation, cyclin D1, genome instability, radiation exposure, Chornobyl clean-up workers.