(673.4) Iron Deposition in the Spleen in a Murine Model of Acute Radiation Syndrome

Poster Board Number: A398

Bradley Rittase (Uniformed Services University of the Health Sciences), John Slaven (Uniformed Services University of the Health Sciences), Jeannie Muir (Uniformed Services University of the Health Sciences), Sang-Ho Lee (Uniformed Services University of the Health Sciences), Milan Rusnak (Uniformed Services University of the Health Sciences), Grace Brehm (Uniformed Services University of the Health Sciences), Aviva Symes (Uniformed Services University of the Health Sciences), Regina Day (Uniformed Services University of the Health Sciences)

Total body radiation (TBI) can result in death associated with hematopoietic insufficiency. Although radiation causes apoptosis of white blood cells, red blood cells (RBC) undergo hemolysis due to hemoglobin denaturation. RBC lysis post-irradiation results in the release of iron into the plasma, producing a secondary toxic event following TBI. We investigated the impact of radiation-induced iron release on the spleen following TBI and the effects of the radiation mitigator captopril. RBC and HCT were reduced within 7 days, with the nadir at ~14 days post-TBI. Prussian blue staining revealed ~20-60-fold increased Fe3+ in the spleen 7-14 days post-irradiation. Increased iron was associated with altered expression of iron binding and transport proteins, determined by qPCR, western blotting, and immunohistochemistry. Captopril did not prevent iron deposition in the spleen, and did not significantly modulate most iron-binding proteins. Spleen volumes were markedly decreased 7-14 days post-irradiation, correlating high Fe3+ levels. At this time point,  caspase-3 was activated and we identified four additional markers of ferroptosis, an iron-dependent programmed cell death. Interestingly, we did not observe increased expression of p21/Waf1, a marker of accelerated senescence. We investigated the effects of radiation and Fe3+ on the J774.A1 murine macrophage cell line in culture. Radiation induced p21/Waf1 and ferritin within 24 h. Radiation alone and with iron upregulated several markers of M1; radiation + iron also modulated a marker of M2 polarization. Our data indicate that following TBI, iron is deposited in the spleen where it modulates the expression of iron binding proteins and triggers ferroptosis.

This work was supported by a JPC7 grant (CDMRP grant to RMD and additional grant to AS).