Effects of High-Linear-Energy-Transfer Heavy Ion Radiation on Intestinal Stem Cells: Implications for Gut Health and Tumorigenesis.

Simple Summary: Heavy ion radiation, found in outer space and used in some cancer treatments, can damage vital cells in the intestines. Studies using mice show that this type of radiation causes long-lasting stress, accelerated aging, and harmful changes in these cells, which can perturb gut function and increase the risk of developing cancer. Specialized mouse models were employed to monitor how these intestinal stem cells are affected over time after exposure to this radiation. We found that particle radiation caused more stress-induced damage and tumor incidence compared to photon radiation. Intestinal stem cells showed signs of aging and inflammation, which persisted for up to a year. This ongoing stress and damage also disrupt the gut barrier's function and ability to absorb nutrients properly. The findings suggest that astronauts exposed to this radiation during deep space missions might face increased risks of gut dysfunction as well as increased cancer risk. Heavy ion radiation, prevalent in outer space and relevant for radiotherapy, is densely ionizing and poses a risk to intestinal stem cells (ISCs), which are vital for maintaining intestinal homeostasis. Earlier studies have shown that heavy-ion radiation can cause chronic oxidative stress, persistent DNA damage, cellular senescence, and the development of a senescence-associated secretory phenotype (SASP) in mouse intestinal mucosa. However, the specific impact on different cell types, particularly Lgr5+ intestinal stem cells (ISCs), which are crucial for maintaining cellular homeostasis, GI function, and tumor initiation under genomic stress, remains understudied. Using an ISCs-relevant mouse model (Lgr5+ mice) and its GI tumor surrogate (Lgr5+Apc1638N/+ mice), we investigated ISCs-specific molecular alterations after high-LET radiation exposure. Tissue sections were assessed for senescence and SASP signaling at 2, 5 and 12 months post-exposure. Lgr5+ cells exhibited significantly greater oxidative stress following 28Si irradiation compared to γ-ray or controls. Both Lgr5+ cells and Paneth cells showed signs of senescence and developed a senescence-associated secretory phenotype (SASP) after 28Si exposure. Moreover, gene expression of pro-inflammatory and pro-growth SASP factors remained persistently elevated for up to a year post-28Si irradiation. Additionally, p38 MAPK and NF-κB signaling pathways, which are critical for stress responses and inflammation, were also upregulated after 28Si radiation. Transcripts involved in nutrient absorption and barrier function were also altered following irradiation. In Lgr5+Apc1638N/+ mice, tumor incidence was significantly higher in those exposed to 28Si radiation compared to the spontaneous tumorigenesis observed in control mice. Our results indicate that high-LET 28Si exposure induces persistent DNA damage, oxidative stress, senescence, and SASP in Lgr5+ ISCs, potentially predisposing astronauts to altered nutrient absorption, barrier function, and GI carcinogenesis during and after a long-duration outer space mission. [ABSTRACT FROM AUTHOR]