Characterization of γ-H2AX foci formation under alpha particle and X-ray exposures for dose estimation

DNA double-strand break (DSB) induction is one of the phenotypes of cellular damage from radiation exposure and is commonly quantified by gamma-H2AX assay with the number of excess fluorescent foci per cell as the main component. However, the number of foci alone may not fully characterize the state of DNA damage following exposures to different radiation qualities. This study investigated the feasibility of utilizing the focus size distribution and dephosphorylation rate of gamma-H2AX to identify the type of causative radiation and dose. Human lung epithelial cells and mouse vascular endothelial cells were used to observe the expression changes of gamma-H2AX foci due to alpha particle and X-ray exposures. Results showed that the average number of excess foci per cell linearly increased with the dose. The focus size distribution showed a consistent pattern depending on the causative radiation type. Three criteria for the identification of causative radiation type were derived from experimental focus size distributions and were validated in blind testing with correct identification of 27 out of 32 samples. The dose could be estimated based on the proportionality constant specific to the identified radiation type with a difference of less than 15% from the actual value. The different dephosphorylation rates of gamma-H2AX produced from alpha particle and X-ray exposures were effectively utilized to determine the individual dose contributions of alpha particles and X-rays under mixed beam exposure. Individual doses were estimated to have differences of less than similar to 12% from actual values.

Automated summary

This study investigates the feasibility of utilizing the focus size distribution and dephosphorylation rate of gamma-H2AX to identify the type of causative radiation and dose. The results show a linear relationship between the average number of foci and the dose, and the focus size distribution can identify the type of causative radiation. The dose can be estimated with a small difference from the actual value using these methods.