Improved Total-Body Irradiation Survival by Delivery of Two Radiation Mitigators that Target Distinct Cell Death Pathways

The acute lethality of total-body irradiation (TBI) involves damage to multiple organs, including bone marrow and intestine. Ionizing radiation mitigators that are effective when delivered 24 h or later after TBI include the anti-apoptotic drug, JP4-039 and the anti-necroptotic drug, necrostatin-1. In contrast to effective delivery of JP4-039 at 24 h after TBI, necrostatin-1 is most effective when delivery is delayed until 48 h, a time that correlates with the elevation of necroptosis-inducing inflammatory cytokines and necroptosis-induced serine phosphorylation of receptor-interacting serine/threonine-protein kinase-3 (RIP3) in tissues. The goal of this work was to determine whether administration of JP4-039 influenced the optimal delivery time for necrostatin-1. We measured daily levels of 33 proteins in plasma compared to intestine and bone marrow of C57BL/6NTac female mice over a 7-day time period after 9.25 Gy TBI (LD_50/30). Protein responses to TBI in plasma were different from those measured in intestine or bone marrow. In mice that were given JP4-039 at 24 h after TBI, we delayed necrostatin-1 delivery for 72 h after TBI based on measured delay in RIP-3 kinase elevation in marrow and intestine. Sequential delivery of these two radiation mitigator drugs significantly increased survival compared to single drug administration.