Fe-Radiation-Induced Alterations in Circulating Leukocyte Populations in the Apoe Mouse Atherosclerosis Model Are Temporary

Abstract

Radiation is associated with an increased risk of heart disease and stroke, likely due in part to vascular inflammation. One model used to understand this is the apoE mouse, where gamma irradiation accelerates development of atherosclerosis. Less is known, though, about the effects of high linear energy transfer (LET) radiation, such as 56Fe, likely to be encountered by astronauts in deep space. Radiation, however, also affects leukocyte numbers. For example, whole-body 56Fe irradiation has been shown to decrease circulating B-cells and T-cells, but whether this was due to radiation of the thymus, of the bone marrow, or both was not determined. We irradiated ApoE mice with 56Fe focused to the aorta and carotids to determine how irradiation of the thymus with 56Fe affects circulating lymphocyte number, and ultimately to determine the effect of iron ion irradiation on development of atherosclerosis. We found that only T-cells were affected at 13 weeks post-irradiation, but even these recovered at 40 weeks, suggesting that effects on the immune system are limited and temporary. Analysis of atherosclerosis development is pending sacrifice and histological analysis of irradiated mice.