[DNA double-strand breaks in human lymphocytes after single irradiation by low doses of pulsed X-rays: non-linear dose-response relationship]

Abstract

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.