Neutrophil Accumulation in the Small Intestine Contributes to Local Tissue Destruction Following Combined Radiation and Burn Injury.

The threat of nuclear disaster makes combined radiation and burn injury (CRI) a relevant topic when discussing modern trauma, as burn injuries are likely to occur with detonation of a conventional nuclear weapon. Previous studies in a murine model have shown that there is a breakdown of the gut epithelium and subsequent bacterial translocation into mesenteric lymph nodes after CRI. This study examines the early innate immune response of the small intestine after CRI. Using a previously established murine model of 5 to 5.5 Gy total body irradiation combined with 15% TBSA burn, the injury response of the small intestine was examined at 24, 48, and 72 hours by visual assessment, myeloperoxidase, and cytokine measurement. At 24 hours, intestinal damage as measured by villus blunting, crypt debris, and decreased mitosis, was apparent in all injury groups but the derangements persisted out to 72 hours only with CRI. The prolonged intestinal damage in CRI was accompanied by a 2-fold (P < .05) elevation in myeloperoxidase activity over sham animals at 48 hours and persisted as a 3-fold (P < .05) elevation at 72 hours after injury. Corresponding levels of KC were 8-fold (P < .05) higher than sham at 48 hours with persistent elevation at 72 hours. An enhanced innate immune response, partially mediated by the influx of neutrophils into the gastrointestinal tract is contributing to the hyperinflammatory state seen after CRI. Attenuation of the local gastrointestinal inflammatory response may play a major role in managing victims after nuclear disaster.