Abstract
In the aftermath of 9/11, the radiobiology community sought novel radiation mitigators capable of preventing death when administered 24 hours or later after exposure to lethal ionizing radiation. The survival and expansion of normal stem cells are crucial for restoring tissue integrity in time to prevent mortality. While FDA-approved drugs for acute radiation syndrome primarily target the hematopoietic system, restoring the integrity of the intestinal lining is equally important for survival. However, the radiation response of the intestinal stem cell (ISC) population and its niche environment is not as well understood as that of the bone marrow. The aim of this study was to explore early transcriptomic changes in the small intestine after a lethal dose of total body irradiation (TBI), and during subsequent recovery. C3H/Sed/Kam mice were irradiated with a TBI dose of 16 Gy, the published LD (70/10) . The compound 1-[(4-Nitrophenyl)sulfonyl]-4-phenylpiperazine (NSPP) was administered 24 hours post-irradiation. RNAs from the proximal duodenum were extracted at 28, 72, and 96 hours post-irradiation and subjected to RNA-sequencing. Differentially expressed genes were analyzed using gene-set enrichment analysis. Radiation induced significant transcriptomic changes known to precede the death of lymphatic endothelial and epithelial cells. Upregulation of Lgr5+ ISC gene signature was observed during recovery. NSPP treatment further amplified the activation of ISC-associated genes and other regenerative markers. Notably, gene Psrc1 showed strong activation throughout the recovery process, highlighting its potential role in this regenerative response. These findings suggest additional points of intervention for radiation mitigation in the intestines beyond targeting programmed cell death.