Title: Molecular evidence of radiation hormesis at occupational exposure

Authors: Radostina Georgieva, Ilona Guleva, Ivanka Rupova, Jana Djunova, Anna Acheva, Mircho Vukov, Borislav D. Dimitrov

Addresses: Department of Radiobiology, National Centre of Radiobiology and Radiation Protection, Ministry of Health, 132 Kliment Ohridski Blvd., Sofia 1756, Bulgaria. ' Department of Radiation Medicine, National Centre of Radiobiology and Radiation Protection, Ministry of Health, 132 Kliment Ohridski Blvd., Sofia 1756, Bulgaria. ' Department of Radiobiology, National Centre of Radiobiology and Radiation Protection, Ministry of Health, 132 Kliment Ohridski Blvd., Sofia 1756, Bulgaria. ' Department of Radiation Medicine, National Centre of Radiobiology and Radiation Protection, Ministry of Health, 132 Kliment Ohridski Blvd., Sofia 1756, Bulgaria. ' Department of Radiobiology, National Centre of Radiobiology and Radiation Protection, Ministry of Health, 132 Kliment Ohridski Blvd., Sofia 1756, Bulgaria. ' Department of Information Systems and Technologies, National Centre of Health Informatics, Ministry of Health, Sofia 1000, Bulgaria. ' Department of Patient Information, Computing, and Network Support Services, University Hospital 'St. George', Plovdiv 4000, Bulgaria; Bordani, Alzano Lombardo (BG) 24022, Italy

Abstract: The idea of favourable effects of low dose ionising radiation in biological systems has existed for many years and is the basis of radiation hormesis hypothesis. New evidence at subcellular levels might contribute to further clarify this problem. We used molecular epidemiological biomarkers (DNA/protein changes in peripheral blood; immunological changes in lymphocytes) in occupationally-exposed individuals (400 Nuclear Power Plant (NPP) workers). Two levels of investigations were studied: molecular (spontaneous and induced DNA repair by unscheduled DNA synthesis, induced protein synthesis, DNA damage) and cellular (lymphocyte subsets, immunofluorescent-stained mouse monoclonal antibodies). Potentially lethal damage is decreased in persons with mean annual dose ≤5 mSv. The highest repair capacity (after 2 Gy γ-rays) was also evaluated. Significant decreases of CD3+4+, CD4+25+, CD4+62L+ lymphocytes and CD4/CD8 ratio were observed at <200 mSv. Simultaneously, increased natural killer cells, CD57+8+, CD8+28+ and CD8+38 were recorded. Our study showed DNA repair capacity elevation following high dose irradiation and increased cellular resistance at annual doses twice lower than natural radiation background. We postulated that the positive dose correlation with CD4+25+ and CD57+8+ as well as the negative one with CD4+62L+, CD8+28+ and CD8+38+ could reflect adaptive processes and compensatory activated immune system due to the low dose irradiation.

Keywords: radiation hormesis; occupational exposure; NPP workers; low dose radiation; DNA repair capacity; DNA damage; protein response; immune response; nuclear power plants; nuclear energy; nuclear power; low radiation; ionising radiation; biomarkers; irradiation.

DOI: 10.1504/IJLR.2009.028903

International Journal of Low Radiation, 2009 Vol.6 No.3, pp.263 - 282

Published online: 11 Oct 2009 *

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