16, 16 dimethyl-Prostaglandin E₂ (dmPGE₂) administered prior to lethal irradiation protects against mortality from the hematopoietic acute radiation syndrome (H-ARS). It protects hematopoietic stem (HSC) and progenitor (HPC) cells and accelerates hematopoietic recovery by attenuating mitochondrial compromise, epigenetic downregulation of p53, and inhibition of histone acetylation at the promoters of genes involved in cell cycle, DNA repair and apoptosis. Since PGE₂ mediates it effects through 4 conserved G-protein coupled receptors (EP1-4) we utilized highly selective EP receptor agonists to identify the EP receptors mediating radioprotection in H-ARS and evaluated the genes, cellular pathways and biological functions downstream of the EP receptors involved in HSC radioprotection. Radioprotection of mice from lethal radiation exposure was observed for the EP3 agonist sulprostone (65% survival) and the EP4 agonist rivenprost (50% survival), with the combination of EP3 + EP4 agonists providing 100% survival. Misoprostol, a PGE₁ analog with similar EP receptor affinities as dmPGE₂ also provided >90% survival. The combination of EP3 and EP4 agonists was highly efficacious in accelerating recovery of all peripheral blood cell counts. Analysis of bone marrow HSPC populations from lethally irradiated mice by flow cytometry indicated that the EP3 + EP4 agonist combination trended closest to dmPGE₂ in protecting total HSC and HPC, preventing early entry of these cells into cell cycle, and attenuating radiation-induced upregulation of the proapoptotic death receptor Fas, with similar activity also shown by misoprostol. Several genes involved in cell cycle and/or apoptosis control were upregulated (s1pr1, arrdc3, osm) or downregulated (hcar2 and cxcl10) in HSCs by all efficacious agonist treatments. Analysis of gene expression profiles and functional pathway analysis in HSC suggests that the EP4 receptor signals primarily through cAMP/PKA/CREB1, while EP3 signals primarily through a PI3K/Akt pathway initiated through activation of the Ras/Rho GTPases. In the combination setting, EP4 signaling appears dominant. Co-stimulation of EP3 and EP4 gave a stronger z-score for CREB1 activation with EP3 signaling augmenting/enhancing gene expression downstream of EP4 predominantly through CREB1. Comparison of KEGG pathways regulated by dmPGE₂ and those regulated by the combination of EP3 + EP4 agonists indicate that both groups' TNF signaling pathways may be key functional components for radioprotection by dmPGE₂ in HSC. Differentially expressed genes (DEG) associated with GTPase activity were observed in HSCs from mice treated with both EP3 and EP4 agonists likely contributing to their enhanced radioprotective effect mediated through the PI3K/Akt pathways downstream of both receptors. Some upstream regulators most strongly activated by dmPGE₂ in bone marrow stromal cells overlapped with those observed in HSCs, with the most striking similarity being inhibition of p53 activation. In summary, these studies show that signaling through both the EP3 and EP4 PGE receptors recapitulates maximal radioprotection of mice from H-ARS by dmPGE₂ via inhibition of cell cycle progression and apoptosis.

The hydroxypyridinone ligand 3,4,3-LI(1,2-HOPO) (HOPO), has been previously characterized as a promising chelating agent for in vivo decorporation of actinides, with decorporation being the removal of internally deposited contaminants from the body after exposure. The large majority of relevant literature reports have detailed the efficacy profile of HOPO as a decorporation agent in rodent models, where controlled radionuclide contamination is conducted via intravenous injection. However, this method of contamination does not necessarily reflect an accurate predictive model of the most probable biodistribution of free metal in the body. In the event of a radiological dispersal device or nuclear power plant accident scenario, it is most likely that first responders, military personnel, and victims of the event will be contaminated via air and water transmission. Therefore, research into the efficacy of chelating agents to treat lung-contaminated in vivo models needs to be carried out. Here, we establish a murine model with controlled, reproducible lung contamination using two different radionuclides, ⁸⁹Zr and ²⁴¹Am, for orthogonal biodistribution validation by positron emission tomography and ex vivo radioanalysis, respectively. In addition, we report effective chelation treatment of ²⁴¹Am-contaminated lungs using HOPO, which improves decorporation by up to 40% compared to Ca-DTPA, the current standard of care.

Obesity is a growing global health concern, and the Western diet characterized by its high-calorie and high-fat content, is widely acknowledged as a major contributor. Obesity is closely linked to the onset of various metabolic syndromes in affected individuals. Furthermore, maternal obesity has been revealed to have persistent effects on the long-term health of offspring, a phenomenon widely recognized as the developmental origins of health and disease (DOHaD). In this study, we aimed to explore the potential modifying effects of maternal exposure to a high-fat diet (HFD) on the health outcomes of offspring after exposure to ionizing radiation. C57BL/6J female mice were fed either an HFD or a standard diet (STD) immediately after weaning at 3 weeks of age. At 10 weeks of age, they were mated with C3H/He male mice raised on an STD. The resulting pups were nursed by their dams and were subjected to a total body X-ray dose of 3.8 Gy at 7 days after birth. All pups were weaned onto an STD at 4 weeks of age, irrespective of their experimental group. Lifelong observation of these pups demonstrated that maternal exposure to HFD reduced the lifespan of male offspring postirradiation, whereas maternal HFD alone did not significantly impact the lifespan of both male and female offspring. Pathological analysis revealed that the lifespan shortening by maternal HFD after X irradiation was primarily attributed to early deaths associated with depletion of bone marrow cells and thymic lymphoma within 6 months after X irradiation. To the best of our knowledge, this is the first report showcasing the modifying effects of maternal HFD on the radiosensitivity of offspring.

Ionizing radiation exposure induces DNA damage and chromosome aberrations through both direct and indirect effect. The indirect effects are primarily mediated by the generation of hydroxyl radicals, a process attributed to radiation. Dimethyl sulfoxide (DMSO) and ascorbic acid (AA) are known as radical scavengers and have radioprotective effects. Radiation therapy is widely employed in the treatment of malignant tumors such as glioblastoma; however, its side effects, including cognitive impairments resulting from damage to healthy neurons, pose significant challenges. To ameliorate these effects, radioprotective reagents have been sought. In this study, we used cerebral organoids derived from human-induced pluripotent stem cells to address the radioprotective effect of radical scavengers, DMSO and AA in brain exposure. Although exposure to radiation for 20-day-old cerebral organoids results in DNA double-strand breaks and apoptosis leading to microcephaly phenotype, treatment with DMSO or AA not only before but also after radiation alleviated DNA damage, cell death, and the microcephaly phenotype. Our results suggest that DMSO and AA are candidates for the radioprotective reagents for brain tumor therapy.

The target theory is the most classical hypothesis explaining radiation-induced cell death, yet the physical or biological nature of the target remains ambiguous. This study hypothesizes that the distribution of DNA double-strand breaks (DSBs) within the 3D genome is a pivotal factor affecting the probability of radiation-induced cell death. We propose that clustered DSBs in DNA segments with high-interaction frequencies are more susceptible to leading to cell death than isolated DSBs. Topologically associating domains (TAD) can be regarded as the reference unit for evaluating the impact of DSB clustering in the 3D genome. To quantify this correlation between the DSB distribution in 3D genome and radiation-induced effect, we developed a simplified model considering the DSB distribution across TADs. Utilizing track-structure Monte Carlo codes to simulate the electron and carbon ion irradiation, and we calculated the incidence of each DSB case across a variety of radiation doses and linear energy transfers (LETs). Our simulation results indicate that DSBs in TADs with frequent interactions (case 3) are significantly more likely to induce cell death than clustered DSBs within a single TAD (case 2). Moreover, case 2 is significantly more likely to induce cell death than isolated DSBs (case 1). The curves of the incidence of cases 2 and 3 compared with LETs have a similar shape to the radiation quality factor (Q) used in radiation protection. This indicates that these two cases are also associated with the stochastic effects induced by high-LET radiation. Our study underscores the crucial significance of the 3D genome structure in the fundamental mechanisms of radiobiological effects. The hypothesis in our research offers novel perspectives on the mechanisms that regulate radiobiological effects. Moreover, it serves as a valuable reference for the establishment of mechanistic models that can predict cell survival under different doses and LETs.

High doses of radiation can cause irreversible bone marrow hematopoietic damage and even death. No effective strategies have been developed to protect against radiation effects in hematopoietic stem cells (HSCs). A total-body irradiation model was used to determine damage to HSCs. HSCs were sorted for transcriptome sequencing, and gene function analysis showed that Octamer-Binding Transcription Factor 4 (Oct4) increased significantly after irradiation. Oct4 deletion or inhibition of nuclear factor kappa-B (NF-jB) significantly reversed HSC apoptosis, promoted HSC colony formation, reduced cellular DNA damage, and promoted bone marrow regeneration after irradiation. ChIP assays showed that Oct4 binds to the IjB kinase (IKK) promoter region and increases the level of IKK. Overexpression of Oct4 significantly increased the entry of NF-jB into the nucleus after irradiation. NF-jB activators reversed the protective roles of knocking out Oct4. In vivo, the knockout of Oct4 and inhibition of NF-jB significantly improved the survival rate of mice after irradiation. We further found that the expression level of Oct4 decreased significantly in human leukemia cells, while the overexpression of Oct4 significantly increased the level of apoptosis in leukemia cells after irradiation. This study demonstrated a novel role of Oct4 in mediating apoptosis of HSCs after irradiation through the NF-jB pathway, providing an important biomedical strategy for the functional protection of HSCs in bone marrow after irradiation.