Molecules in the bloodstream that might accurately gauge the likelihood of radiation illness after exposure to ionizing radiation have been identified. This animal study shows that X-rays or gamma rays alter the levels of certain molecules called microRNA (miRNA) in the blood in a predictable way. If verified in human subjects, the findings could lead to new methods for rapidly identifying people at risk for acute radiation syndrome after occupational exposures or accidents such as the recent Fukushima Daiichi nuclear reactor incident.

“Our paper reports the identification of a panel of miRNA markers in mice whose serum levels provide an estimate of radiation response and of the dose received after an exposure has occurred,” said senior author Arnab Chakravarti, MD, of The Ohio State University (OSU). “Accurate dose evaluation is critical for making medical decisions and for the timely administration of therapy to prevent or reduce acute and late effects.”

The findings might also one day allow doctors to evaluate radiation toxicity during the course of therapy based on a patient’s biology. “This would particularly benefit leukemia and lymphoma patients who receive total body irradiation in preparation for stem cell transplantation,” Chakravarti said.

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First author Naduparambil Jacob, PhD, also of OSU, noted that the study could be an important step in the development of biological dosimetry, or biodosimetry, a technology for identifying people at risk for acute radiation illnesses that develop within weeks of radiation exposure, and cancers and degenerative diseases that can occur months or years later. The study was published in PLOS ONE (2013; doi:10.1371/journal.pone.0057603).

“Biodosimetry is an emerging concept that could enable us to identify individuals who need immediate treatment after a radiation exposure and to better develop personalized radiation treatment plans for patients,” Jacob said.

For this study, Chakravarti, Jacob, and their colleagues evaluated dose-dependent changes in levels of 88 individual miRNAs in serum from mice after a single acute radiation exposure, and after fractionated doses of radiation that are typical of radiation treatment prior to stem cell transplantation. Samples were collected from exposed and control animals 24 or 48 hours after exposure.

After a one-time exposure, miRNA-150 showed a clear decrease over time with increasing radiation dose. It dropped 30% after 24 hours and 50% after 48 hours, even at the lowest exposure of 1 gray of radiation. Levels of both miRNA-200b and miRNA-762 increased after radiation exposure, and the changes were more pronounced in the animals that received the higher doses. Changes were similar for animals that received fractionated doses, such that miRNA-150 dropped about 50% after 24 hours in animals receiving 4 gray.