Abstract
The aim of our study was to determine whether phosphorylation of histone H2AX can be used as an indicator of received dose of gamma radiation after whole-body irradiation of rats. Wistar rats were irradiated by 1-10 Gy of gamma radiation by60Co source. Value LD50/60 was 7.37 (4.68-8.05) Gy. Histone H2AX is phosphorylated by ATM kinase on serine 139 (γH2AX) quickly after the irradiation. It forms microscopically visible foci in the site of double strand breaks of DNA. Flow-cytometric method was used for quantitative detection. This study is the first one that evaluated dose-dependency of H2AX phosphorylation in peripheral lymphocytes of rats irradiated by whole-body dose 1-10 Gy. Our data show a dose-dependent increase in γH2AX in rat peripheral blood lymphocytes 1 h after whole-body irradiation by the dose of 1-10 Gy. We proved that phosphorylation of histone H2AX is a prompt and reliable indicator of the received radiation dose suitable for rapid measurement before the number of lymphocytes in peripheral blood starts to decrease. It can be used already 1 h after the irradiation for an estimation of the received dose of radiation. Blood samples can be stored in 4 °C for 23 h without significantly affecting the result.
Highlights
High doses of radiation induce apoptosis of lymphocytes in peripheral blood and these are, after in vivo irradiation, quickly phagocytised
We proved that phosphorylation of histone H2AX is a prompt and reliable indicator of the received radiation dose suitable for rapid measurement before the number of lymphocytes in peripheral blood starts to decrease
High amount of endogenous γH2AX foci was detected in many tumour cell lines, and it seems to be linked with telomere damage (Nakamura et al 2009)
Summary
High doses of radiation induce apoptosis of lymphocytes in peripheral blood and these are, after in vivo irradiation, quickly phagocytised. Biodosimetric method based on detection of chromosomal aberrations is more precise but requires phytohaemagglutinin (PHA) stimulation of lymphocytes and manual counting of dicentric chromosomes This method has its limitations, is time-consuming and after high doses it is not possible to find enough mitotic cells; new methods are intensively studied (Blakely 2002). Rogakou et al (1998) performed a study on human glioblastoma cell line SF268 using two-dimensional electrophoresis and they were the first ones who reported that H2AX becomes phosphorylated on serine residue 139 in the cells with gamma-radiation-induced DSBs. With IMR90 and MCF7 cells, foci were apparent 3 min after irradiation with 0.6 Gy still persisting at 15–60 min and decreasing in number at 180 min (Rogakou et al 1999)
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