Assessment of radiation induced bystander effect in peripheral blood lymphocytes
Bulgarian Medical Journal, 2025, 19(2), 54-59.
L. Hadjiiska1, К. Коstadinova2, N. Kostova1, A. Staynova1, D. Georgieva1, E. Nasonova3, P. Kutsalo3, R. Hristova1
1 National Center of Radiobiology and Radiation Protection ‒ Sofia
2 Biology Faculty, Department of Biophysics and Radiobiology ‒ Sofia
3 Joint Institute for Nuclear Research ‒ Dubna, Russia
Abstract. The bystander effect is defined as the occurrence of damage in unirradiated cells, similar to that observed in their irradiated neighbors. From the point of view of radiotherapy, the bystander effect can be a potentially harmful or beneficial event. The study of the pathways for the realization of the bystander effect is of particular interest in the assessment of radiation risk. Despite the conducted studies, the mechanisms of the bystander effect are not sufficiently elucidated. The aim of the present study is to clarify the early cellular and molecular mechanisms responsible for the bystander effect and the radioadaptive response in peripheral blood lymphocytes by assessing the frequency of DNA double-strand breaks. For the quantitative assessment of DNA double-strand breaks, the cytokinesis-block micronucleus test was applied. The frequency of micronuclei was assessed in peripheral blood lymphocytes. For the purpose of the experiment, the influence of irradiated medium on unirradiated cells and of unirradiated medium on irradiated cells was studied. The medium was changed immediately and 22 hours after irradiation. Two doses were applied – 1 and 2 Gy of γ-rays. Our results show a statistically significant decrease in the frequency of micronuclei in cells irradiated with 1 or 2 Gy, placed in unirradiated medium immediately after irradiation (p = 0,000). A significant increase in the frequency of micronuclei was observed in unirradiated cells placed in medium from irradiated with 1 (p = 0,000) or 2 Gy (p = 0,001) cultures. Transferring non-irradiated cells to irradiated medium immediately after irradiation had no similar effect.
Key words: bystander effect, cytokinesis-block micronucleus test, peripheral blood lymphocytes