Abstract
Insoluble radioactive microparticles emitted by the incident at the Fukushima nuclear power plant have drawn keen interests from the viewpoint of radiation protection. Cs-bearing particles have been assumed to adhere in the long term to trachea after aspirated into respiratory system, leading to heterogeneous dose distribution within healthy tissue around the particles. However, the biological effects posed by an insoluble radioactive particle remain unclear. Here, we show cumulative DNA damage in normal human lung cells proximal and distal to the particle (β-ray and γ-ray-dominant areas, respectively) under localized chronic exposure in comparison with uniform exposure. We put a Cs-bearing particle into a microcapillary tip and placed it onto a glass-base dish containing fibroblast or epithelial cells cultured in vitro. A Monte Carlo simulation with PHITS code provides the radial distribution of absorbed dose-rate around the particle, and subsequently we observed a significant change in nuclear γ-H2AX foci after 24 h or 48 h exposure to the particle. The nuclear foci in the cells distal to the particle increased even under low-dose-rate exposure compared with uniform exposure to 137Cs γ-rays, which was suppressed by a treatment with a scavenger of reactive oxygen species. In contrast, such focus formation was less manifested in the exposed cells proximal to the particle compared with uniform exposure. These data suggest that the localized exposure to a Cs-bearing particle leads to not only disadvantage to distal cells but also advantage to proximal cells. This study is the first to provide quantitative evaluation for the spatial distribution of DNA double strand breaks after the heterogeneous chronic exposure to a Cs-bearing particle in comparison with uniform Cs exposure.
Highlights
Large amounts of artificial radionuclides were released after the incident at the Fukushima Dai-ichi Nuclear Power Station (F1NPS) in 20111,2, which have drawn keen interest of public in terms of radiation safety[3]
To test whether reactive oxygen species (ROS) through intercellular communication contributes to this effect or not, we examined the effect of 1% DMSO
Given that a Cs-bearing radioactive particle chronically adheres to trachea after entry into the respiratory system, we investigated the spatial characteristics of cumulative DNA damage during the localized energy deposition by a Cs-bearing particle in comparison with uniform exposure
Summary
Large amounts of artificial radionuclides were released after the incident at the Fukushima Dai-ichi Nuclear Power Station (F1NPS) in 20111,2, which have drawn keen interest of public in terms of radiation safety[3]. Microenvironment of cells would heavily rely on the energy deposition which is concentrated in the region close to Cs-bearing particles[5]. Www.nature.com/scientificreports confirmed that micron scale is not necessarily needed for estimating the biological effects by soluble 134Cs and 137Cs10, those by insoluble Cs-bearing particle have not yet been evaluated. For localized chronic energy deposition by a Cs-bearing particle, the DNA damage arising from intercellular communication is suspected to accumulate[26,27]. There is no report of the effects on cells in the vicinity of a Cs-bearing particle after the long-term exposure. We evaluated the DNA damage responses under heterogeneous exposure by a Cs-bearing particle, compared with conventional uniform Cs exposure
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