The GS-nitroxide JP4-039 improves intestinal barrier and stem cell recovery in irradiated mice

Abstract

Total body irradiation (TBI) leads to dose- and tissue-specific lethality. In the current study, we demonstrate that a mitochondrion-targeted nitroxide JP4-039 given once 24 hours after 9–10 Gy TBI significantly improves mouse survival, and the recovery of intestinal barrier, differentiation and stem cell functions. The GI-protective effects are associated with rapid and selective induction of tight junction proteins and cytokines including TGF-β, IL-10, IL-17a, IL-22 and Notch signaling long before bone marrow depletion. However, no change was observed in crypt death or the expression of prototypic pro-inflammatory cytokines such as TNF-α, IL-6 or IL-1β. Surprisingly, bone marrow transplantation (BMT) performed 24 hours after TBI improves intestinal barrier and stem cell recovery with induction of IL-10, IL-17a, IL-22, and Notch signaling. Further, BMT-rescued TBI survivors display increased intestinal permeability, impaired ISC function and proliferation, but not obvious intestinal inflammation or increased epithelial death. These findings identify intestinal epithelium as a novel target of radiation mitigation, and potential strategies to enhance ISC recovery and regeneration after accidental or medical exposures.

Second-generation Probiotics Producing IL-22 Increase Survival of Mice After Total Body Irradiation

“…Radiation mitigators that are delivered 24 h or later after total body irradiation (TBI) are needed as countermeasures against a radiation terrorist event or nuclear reactor accidents (1,2). Ionizing irradiation damages the intestine and leads to the gastrointestinal syndrome (3)(4)(5)(6). TBI at levels that exceed the dose that can be rescued by bone marrow transplantation (hematopoietic syndrome) kills intestinal crypt cells, damages villi, and results in a systemic increase in gut bacteria, which leads to sepsis, and, ultimately, death (4)(5)(6).…”

“…Ionizing irradiation damages the intestine and leads to the gastrointestinal syndrome (3)(4)(5)(6). TBI at levels that exceed the dose that can be rescued by bone marrow transplantation (hematopoietic syndrome) kills intestinal crypt cells, damages villi, and results in a systemic increase in gut bacteria, which leads to sepsis, and, ultimately, death (4)(5)(6). A distinct gastrointestinal syndrome is observed after TBI at higher doses, and kills mice 5-10 days after exposure to doses in excess of 12 Gy.…”

“…Animals receiving 15 Gy total abdominal irradiation die within 10 days associated with shrinkage of antimicrobial intestinal Paneth cells that, naturally, produce defensins, lysozyme and other antimicrobial factors (7)(8)(9)(10)(11)(12)(13)(14)(15)(16). Loss of intestinal crypt cells, principally leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5+) stem cells (17), is also detected after doses that produce death from gastrointestinal syndrome (4)(5)(6). Following irradiation, there is rapid depletion of intestinal immunocytes, prominently, γδT-cells and helper T-cells, which are known to produce interleukin-22 (IL-22) and other anti-inflammatory cytokines (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28).…”

“…IL-22 produced by anti-inflammatory immunocytes helps to stabilize both intestinal Paneth cells and Lgr5+ intestinal stem cells (17). Other differentiated cell populations within intestinal villi include goblet cells that produce mucin (6), which protects the intestinal epithelium, has a barrier function and prevents entry of bacteria. In addition to production of anti-microbial defensins and lysozyme, Paneth cells are critical for support of Lgr5+ stem cells.…”

“…Assays for intestinal paneth, goblet, and Lgr5+ stem cells. These assays were carried out using antibodies and assay conditions according to published methods (5,6).…”