Initial radiation DNA damage observed in prematurely condensed chromosomes of G2-phase human lymphocytes and analytical model of ion tracks

Agata Kowalska,Polina Kutsalo,Eugene Krasavin,Elena Nasonova,Konrad Czerski

doi:10.1140/epjd/e2019-100113-3

Abstract

In the present work, we have adopted the premature chromosome condensation (PCC) technique to study the initial DNA damage in order to distinguish between the biological and physical components of the dose-effect curves. We have studied G2-chromatid breaks in human lymphocytes, isochromatid-type breaks as well as chromatid exchanges at two different sampling times: directly after irradiation (t0) and 12 hours later (t12). The lymphocyte samples have been exposed to 150 MeV and spread out Bragg peak (SOBP) proton beams, 22 MeV/u 11B ions and for comparison to 60Co γ rays. Dose-response curves for both types of breaks have been determined. We have shown that t0 G2-chromatid breaks follow linear-quadratic dependence for all studied cases and could be used for estimation of the effective ion track radius. A comparison to the expected physical track radii leads to the conclusion that the biological repair mechanism considerably prevails the physical effect of the overlapping ion tracks even at the time t0. The results have been also compared to the dose-effect curves previously obtained in our chromosome aberrations study.Graphical abstract

Highlights

Knowledge of the biological response of single cells to different radiation quality is of fundamental importance for protection against radiation, and for the use of heavy charged particles in radiation therapy [1].Differences in the response of investigated cells or tissues exposed to ionizing radiation depend on physical properties of chosen particle flux, absorbed dose and dose rate resulting from formation of ion track structures
The lymphocytes were isolated by gradient centrifugation and seeded with a density of 0.5 × 106 cell/ml in the in RPMI medium supplemented by 20% fetal calf serum, 2 mM L-glutamine, 100 U/ml penicillin, 100 μg/ml streptomycin and 1% phytohaemagglutinin (PHA)
The main aim of the present work was to look for the contribution to the dose-effect curves resulting from the overlapping of ion tracks produced by charge particle irradiation in peripheral blood lymphocytes

Summary

Introduction

Knowledge of the biological response of single cells to different radiation quality is of fundamental importance for protection against radiation, and for the use of heavy charged particles in radiation therapy [1]. Differences in the response of investigated cells or tissues exposed to ionizing radiation depend on physical properties of chosen particle flux, absorbed dose and dose rate resulting from formation of ion track structures. Rely on the observation of chromosome aberrations (CA) induced in peripheral blood lymphocytes (PBL) [2] which are preferable for several reasons. The assessment of chromosome damage in human lymphocytes is considered to be the only reliable method in human biodosimetry since half a century [3].

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