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Currently, there are no U.S. Food and Drug Administration (FDA)-approved medical countermeasures (MCMs) for radiation combined injury (RCI), partially due to limited understanding of its mechanisms. Our previous research suggests that endothelial dysfunction may contribute to a poor prognosis of RCI. In this study, we demonstrated an increased risk of mortality, body weight loss, and delayed skin wound healing in RCI mice compared to mice with skin wounds alone or radiation injury (RI) 30 days post-insult. Furthermore, we evaluated biomarkers of endothelial dysfunction, inflammation, and impaired wound healing in mice at early time points after RCI. Mice were exposed to 9.0 Gy total-body irradiation (TBI) followed by skin wound. Samples were collected on days 3, 7, and 14 post-TBI. Endothelial dysfunction markers were measured by ELISA, and skin wound healing was assessed histologically. Our results show that endothelial damage and inflammation are more severe and persistent in the RCI compared to the wound-alone group. Additionally, RCI impairs granulation tissue formation, reduces myofibroblast presence, and delays collagen deposition, correlating with more severe endothelial damage. TGF signaling may play a key role in this impaired healing. These findings suggest that targeting the endothelial dysfunction and TGF-β pathways may provide potential therapeutic strategies for improving delayed wound healing in RCI, which could subsequently influence outcomes such as survival after RCI. [ABSTRACT FROM AUTHOR]

IL-18 has been shown to play important roles in response to total body irradiation. However, homogenous total body irradiation is not a realistic model to reflect the radiation exposure in a real nuclear event. To further study the roles of IL-18 in a real nuclear scenario, we developed a mouse partial body irradiation with 5% bone marrow sparing (PBI/BM5) model to mimic the inhomogeneous radiation exposure. We established the dose response curves of PBI/BM5 using different radiation doses ranging from 12 to 16 Gy. Using the PBI/BM5 model, we showed that IL-18 knockout mice were significantly more radiation resistant than the wild-type mice at 14.73 Gy. We further studied the hematopoietic changes using a complete blood count, bone marrow colony-forming assays, and serum cytokine assays on the mice exposed to PBI/BM5 with IL-18BP treatment and wild-type/IL-18 knockout mice. In conclusion, our data suggest that IL-18 plays important roles in mouse survival in a realistic nuclear exposure model, potentially through the IL-18/IFNγ pathway. [ABSTRACT FROM AUTHOR]