RESUMO
The paper analyzes the effects of spontaneous level of yH2AX and 53BP1 foci on a frequency of radiation-induced centromere-negative and centromere-positive micronuclei in peripheral blood lymphocytes of 54 healthy individuals after exposure to 2 Gy of ionizing radiation in vitro. An inverse correlation was found between the level of spontaneous yH2AX foci and the frequency of centromere-negative micronuclei after irradiation. The corresponding correlations between the spontaneous level of protein 53BP1 foci and the frequency of centromere-negative micronuclei were not statistically significant. In addition, cells of the individuals with a high frequency of radiation-induced micronuclei were also characterized by a low proliferative activity. It was suggested that DNA double strand break repair works less efficiently in cells of the individuals with low levels of spontaneous yH2AX foci, and a greater number of DNA double strand breaks after exposure to ionizing radiation remains unrepaired, thus leading to a cell cycle block and an increase of the frequency of centromere-negative micronuclei.
Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA , Histonas/genética , Linfócitos/efeitos da radiação , Micronúcleos com Defeito Cromossômico/efeitos da radiação , Tolerância a Radiação/genética , Adulto , Idoso , Células Cultivadas , Raios gama/efeitos adversos , Humanos , Linfócitos/patologia , Masculino , Testes para Micronúcleos , Pessoa de Meia-Idade , Adulto JovemRESUMO
Effects of ionizing radiation registered in cells after low dose irradiation are still poorly understood. A pulsed mode of irradiation is even more problematic in terms of predicting the radiation-induced response in cells. Thus, the aim of this paper was to study and analyze the effects of dose and frequency of pulsed X-rays on the frequency of radiation-induced DNA double-strand breaks and their repair kinetics in human peripheral blood lymphocytes in vitro. Analysis of radiation-induced gammaH2AX and 53BP1 repair foci was used to assess the DNA damage in these cells. The dose-response curve of radiation-induced foci of both proteins has shown deviations from linearity to a higher effect in the 12-32 mGy dose range and a lower effect at 72 mGy. The dose-response curve was linear at doses higher than 100 mGy. The number of radiation-induced gammaH2AX and 53BP1 foci depended on the frequency of X-ray pulses: the highest effect was registered at 13 pulses per second. Moreover, slower repair kinetics was observed for those foci induced by very low doses with a nonlinear dose-response relationship.