Frequency of gamma H2AX foci in healthy volunteers and health workers occupationally exposed to X-irradiation and its relevance in biological dosimetry.

Abstract

Gamma-H2AX (γ-H2AX) assay is a marker to measure double-strand breaks in the deoxyribonucleic acid. Variables such as age, oxidative stress, temperature, genetic factors and inter-individual variation have been reported to influence the baseline γ-H2AX focus levels. Therefore, knowledge on baseline frequency of γ-H2AX foci in a targeted population would facilitate reliable radiation triage and dose estimation. The objective of the present study was to establish the baseline data using blood samples from healthy volunteers (n=130) differing in age, occupation and lifestyle as well as from occupationally exposed health workers (n=20). The γ-H2AX focus assay was performed using epifluorescence microscopy. In vitro dose-response curve for γ-H2AX foci was constructed in blood samples (n=3) exposed to X-rays (30min post-exposure). The mean γ-H2AX focus frequency obtained in healthy volunteers was 0.042±0.001 and showed an age-related increase (p<0.001). Significantly higher (p<0.005) focus frequencies were observed in health workers (0.066±0.005) than in healthy volunteers. A sub-group analysis did not show a significant (p>0.1) difference in γ-H2AX focus frequency among sexes. Blood exposed in vitro to X-rays showed dose-dependent increase in γ-H2AX foci frequency (Y=0.1902±0.1363+2.9020±0.3240*D). Baseline frequency of γ-H2AX foci obtained from different age groups showed a significant (p<0.01) influence on the dose-response coefficients. The overall results demonstrated that the γ-H2AX assay can be used as a reliable biomarker for radiation triage and estimating the radiation absorbed dose by considering variables such as age, occupation and lifestyle factors.