Intracellular reactive oxygen species1 level in blood cells of atomic
bomb survivors is increased due to aging and radiation exposureWith increased age and radiation dose in atomic bomb survivors more than 60 years
after the bombings, decreased immune function and increased inflammation-related
biomarkers have been observed. However, the association of reactive oxygen species(ROS) levels in immune-related cells with age and radiation dose is still unclear. In thisstudy, RERF investigated the association between ROS levels in blood cells and serum
iron,2 ferritin,3 and C-reactive protein4 (CRP) levels in 2,495 Hiroshima A-bomb
survivors who underwent health examinations in the RERF Adult Health Study during
2007–2012, in an attempt to examine the relationship between such changes and age
and radiation dose.
After adjusting for the effects of gender, age at examination, smoking and drinking
habits, body mass index, and blood sampling time, RERF carried out analysis usingsophisticated statistical techniques. As a result, superoxide anion5 (one kind of ROS)
levels in monocytes, granulocytes, and T cells6 (intracellular) tended to be higher insurvivors exposed to higher radiation doses. In addition, serum iron, ferritin, and CRP
levels were suggestively associated with intracellular ROS levels. CRP levels were also
higher in older and more heavily exposed study participants, as observed in previous
RERF studies.
When divided into three groups according to blood CRP level, the intracellularsuperoxide anion levels in blood cells were higher in survivors exposed to higher
radiation doses, and this was most prominently observed in the group with the highest
CRP levels. The results suggest that increased intracellular ROS levels might beassociated with inflammatory conditions such as increased CRP levels and decreased
serum iron, especially after radiation exposure. In this study, RERF observed a tendency
toward higher levels of oxidative stress7 — a situation marked by decreased immune
function and increased inflammation — in the blood cells of older A-bomb survivors
who had been exposed to higher doses of radiation.
Notes1
Reactive oxygen species (ROS):A type of oxygen molecule in the atmosphere that has been converted into a more reactivecompound. These highly reactive oxygen molecules play important roles in immune
responses. Excessive ROS production and accumulation might enhance the risk ofdevelopment of cancer and lifestyle-related diseases.
2Serum iron:
An iron component that binds to proteins and is transported in serum, a liquid component ofblood. This component is involved in the production and breakdown of free radicals (one typeof ROS).
3
Ferritin:A type of protein that binds to iron and is stored in the cells of living organisms. This protein
plays a role in preventing the production of iron-induced free radicals.

4C-reactive protein (CRP):
A relatively large protein synthesized by liver cells that appears in the blood when aninflammatory reaction or tissue destruction occurs in the body.
5Superoxide anion:
One type of ROS. This negatively charged molecule contains an oxygen molecule with an excessof one electron and is highly reactive.
6T cells:
Immune cells are activated in the body to fight infection, and T cells, a type of white blood cell,
act to manage the immune response to such disease. T cells are mainly produced in the thymus,
from which the letter “T” is derived.
7
Oxidative stress:
Production of active oxygen and antioxidant defense mechanisms are ordinarily balanced in
the body. Oxidative stress occurs when the production of active oxygen becomes excessive andthe antioxidant defense mechanism is overwhelmed.
doi.10.1126/science.abg2365(Doi are permanent, content-specific numbers assigned to most digital information and, in this case, canbe used to link to published abstracts and/or full papers.)

RERF’s objective with this brief outline is to succinctly explain our research for the laypublic. Much of the technical content of the original paper has been omitted. For furtherdetails about the study, please refer to the full paper published by the journal.