Induction and disappearance of γH2AX foci and formation of micronuclei after exposure of human lymphocytes to ⁶⁰Co γ-rays and p(66)+ Be(40) neutrons

Abstract

Purpose: To investigate both the formation of micronuclei (MN) and the induction and subsequent loss of phosphorylated histone H2AX foci (γH2AX foci) after in vitro exposure of human lymphocytes to either ⁶⁰Co γ-rays or p(66)+ Be(40) neutrons.

Materials and methods: MN dose response (DR) curves were obtained by exposing isolated lymphocytes of 10 different donors to doses ranging from 0–4 Gy γ-rays or 0–2 Gy neutrons. Also, γH2AX foci DR curves were obtained following exposure to doses ranging from 0–0.5 Gy of either γ-rays or neutrons. Foci kinetics for lymphocytes for a single donor exposed to 0.5 Gy γ-rays or neutrons were studied up to 24 hours post-irradiation.

Results: Micronuclei yields following neutron exposure were consistently higher compared to that from ⁶⁰Co γ-rays. All MN yields were over-dispersed compared to a Poisson distribution. Over-dispersion was higher after neutron irradiation for all doses > 0.1 Gy. Up to 4 hours post-irradiation lower yields of neutron-induced γH2AX foci were observed. Between 4 and 24 hours the numbers of foci from neutrons were consistently higher than that from γ-rays. The half-live of foci disappearance is only marginally longer for neutrons compared to that from γ-rays. Foci formations were more likely to be over-dispersed for neutron irradiations.

Conclusion: Although neutrons are more effective to induce MN, the absolute number of induced γH2AX foci are less at first compared to γ-rays. With time neutron-induced foci are more persistent. These findings are helpful for using γH2AX foci in biodosimetry and to understand the repair of neutron-induced cellular damage.

Keywords::

• Micronucleus
• γH2AX foci
• neutrons

Acknowledgements

The work was supported by a University Development Cooperation ‘VLIR Own Initiative Programme’ between Belgium and South Africa (ZEIN 2005PR309, ZEIN2011PR387) and the National Research Foundation of South Africa. The authors would like to thank all the volunteers who donated blood samples.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.