Fractionated whole-brain irradiation for the treatment of intracranial neoplasia causes progressive neurodegeneration and neuroinflammation. The long-term consequences of single-fraction high-dose irradiation to the brain are unknown. To assess the late effects of brain irradiation we compared transcriptomic gene expression profiles from nonhuman primates (NHP; rhesus macaques Macaca mulatta) receiving single-fraction total-body irradiation (TBI; n = 5, 6.75–8.05 Gy, 6–9 years prior to necropsy) to those receiving fractionated whole-brain irradiation (fWBI; n = 5, 40 Gy, 8 × 5 Gy fractions; 12 months prior to necropsy) and control comparators (n = 5). Gene expression profiles from the dorsolateral prefrontal cortex (DLPFC), hippocampus (HC) and deep white matter (WM; centrum semiovale) were compared. Stratified analyses by treatment and region revealed that radiation-induced transcriptomic alterations were most prominent in animals receiving fWBI, and primarily affected white matter in both TBI and fWBI groups. Unsupervised canonical and ontologic analysis revealed that TBI or fWBI animals demonstrated shared patterns of injury, including white matter neuroinflammation, increased expression of complement factors and T-cell activation. Both irradiated groups also showed evidence of impaired glutamatergic neurotransmission and signal transduction within white matter, but not within the dorsolateral prefrontal cortex or hippocampus. Signaling pathways and structural elements involved in extracellular matrix (ECM) deposition and remodeling were noted within the white matter of animals receiving fWBI, but not of those receiving TBI. These findings indicate that those animals receiving TBI are susceptible to neurological injury similar to that observed after fWBI, and these changes persist for years postirradiation. Transcriptomic profiling reaffirmed that macrophage/ microglial-mediated neuroinflammation is present in radiation-induced brain injury (RIBI), and our data provide novel evidence that the complement system may contribute to the pathogenesis of RIBI. Finally, these data challenge the assumption that the hippocampus is the predilection site of injury in RIBI, and indicate that impaired glutamatergic neurotransmission may occur in white matter injury.

In this work, we describe a fully automated cytokinesis-block micronucleus (CBMN) assay with a significantly shortened time to result, motivated by the need for rapid high-throughput biodosimetric estimation of radiation doses from small-volume human blood samples. The Rapid Automated Biodosimetry Tool (RABiT-II) currently consists of two commercial automated systems: a PerkinElmer cell: :explorer Workstation and a GE Healthcare IN Cell Analyzer 2000 Imager. Blood samples (30 ll) from eight healthy volunteers were gamma-ray irradiated ex vivo with 0 (control), 0.5, 1.5, 2.5, 3.5 or 4.5 Gy and processed with full automation in 96-well plates on the RABiT-II system. The total cell culture time was 54 h and total assay time was 3 days. DAPI-stained fixed samples were imaged on an IN Cell Analyzer 2000 with fully-automated image analysis using the GE Healthcare IN Cell Developer Toolbox version 1.9. A CBMN dose-response calibration curve was established, after which the capability of the system to predict known doses was assessed. Various radiation doses for irradiated samples from two donors were estimated within 20% of the true dose (±0.5 Gy below 2 Gy) in 97% of the samples, with the doses in some 5 Gy irradiated samples being underestimated by up to 25%. In summary, the findings from this work demonstrate that the accelerated CBMN assay can be automated in a high-throughput format, using commercial biotech robotic systems, in 96-well plates, providing a rapid and reliable bioassay for radiation exposure.

Development of oral mucositis represents a rate-limiting factor in radiation therapy for the treatment of head and neck, as well as other cancers. In this work, we investigated the treatment effect of ecdysterone (a steroid derived from the dry root of Achyranthes bidentate) on radiation-induced oral mucositis, and examined possible underlying mechanisms. Male Sprague-Dawley rats were exposed to 20 Gy X-ray irradiation (single dose, cranial localization) to induce oral mucositis. Possible therapeutic effects of ecdysterone on radiation-induced oral mucositis were investigated by monitoring weights, direct observations, visual scoring method and evaluation of hematoxylin and eosin staining. Assessments of leukocyte common antigen and proliferating cell nuclear antigen staining were also performed in the damaged areas of tongues harvested after irradiation, and changes in signaling pathways were investigated using Western blotting. The development and progression of radiation-induced oral mucositis in this model was similar to that observed in clinic patients. Ecdysterone effectively improved radiation-induced oral mucositis as assessed by direct observation and histopathology, and also increased proliferation of matrix cells, since the Ras-Raf-ERK signal pathway was found to be activated by its use. It was concluded that orally administered ecdysterone accelerated the healing process in a rat model of radiation-induced oral mucositis by upregulating the Ras-Raf-ERK signal pathway.

Although the risk of breast cancer after high-dose-rate irradiation has been firmly established, however, the risk incurred for low-dose-rate irradiation is not well understood. Here we provide experimental evidence for dose rate and age dependencies induced by continuous γ-ray irradiation on mammary carcinogenesis. Female rats received continuous whole-body irradiation at one of the following time points: at 7 weeks of age (denoted adults) at a dose rate of 3–60 mGy/h (4 Gy total); or at either 3 weeks (denoted juveniles) or 7 weeks of age at a dose rate of 6 mGy/h (1–8 Gy total). Additional rats were acutely irradiated at 13 weeks of age at a dose rate of 30 Gy/h (0.5–4 Gy total). We observed the incidence of mammary tumors by weekly palpation until they were 90 weeks old and after pathological inspection upon autopsy. The tumor incidence rate for each group was characterized by Cox regression analysis. When adult rats were irradiated at 60 mGy/h for a total of 4 Gy, their hazard ratio for mammary carcinoma significantly increased relative to nonirradiated controls; however, for adult rats irradiated at 3–24 mGy/h, even though they also received a total of 4 Gy, their hazard ratio for carcinoma incidence did not significantly increase. A larger increase in the incidence rate of carcinoma per dose was found for the juveniles than for the adults irradiated at 6 mGy/h, whereas age did not influence the effect of acute irradiation at 30 Gy/h; a threshold-like dose response was observed for irradiation at 6 mGy/h (threshold, ∼2.5 and ∼4 Gy for juveniles and adults, respectively). Regarding benign tumors of the mammary gland, a significant increase in their incidence was observed for irradiation down to 6 mGy/h, but not at 3 mGy/h and there was no evidence of age-dependent induction. Thus, induction of female rat mammary carcinogenesis by continuous γ-ray exposure was age dependent and drastically increased for adult rats that received between 24 and 60 mGy/h irradiation.

It has been hypothesized that species with holocentric chromosomes have a selective evolutionary advantage for developmental and reproductive success because holocentric chromosomes are less susceptible to chromosome breakage than monocentric chromosomes. We analyzed data on sterilizing doses of ionizing radiation for more than 250 species of arthropods to test whether the minimal dose for reproductive sterilization is higher for species with holocentric chromosomes than for species with monocentric chromosomes. Using linear mixed models that account for phylogeny, we show that holocentric arthropods are more tolerant of sterilizing radiation than monocentrics. Moreover, higher dose rates correlate with lower sterilizing doses in monocentrics, but not in holocentrics, which is a novel finding that may be of importance for radiosanitation practice. Under the dose rate of 1 Gy/min, holocentric arthropods are sterilized on average with a 2.9 times higher minimal dose than monocentrics. Life stage and sex have significant but considerably weaker effects on sterilizing dose than chromosome type. Adults and males require 1.2 and 1.4 times higher sterilizing doses than juveniles and females, respectively. These results support the hypothesis that holocentric lineages may originate and thrive better in times of increased exposure to chromosome-breaking factors.

In the event of a mass casualty radiation scenario, biodosimetry has the potential to quantify individual exposures for triaging and providing dose-appropriate medical intervention. Structural maintenance of chromosomes 1 (SMC1) is phosphorylated in response to ionizing radiation. The goal of this study was to develop a new biodosimetry method using SMC1 phosphorylation as a measure of exposure to radiation. In the initial experiments, two normal human cell lines (WI-38VA-13 and HaCaT) and four lymphoblastoid cell lines were irradiated, and the levels of SMC1 phosphorylation at Ser-360 and Ser-957 were assessed using Western blotting. Subsequently, similar experiments were performed using peripheral blood mononuclear cells (PBMCs) obtained from 20 healthy adults. Phosphorylation of SMC1 at Ser-957 and Ser-360 was increased by exposure in a dose-dependent manner, peaked at 1–3 h postirradiation and then decreased gradually. Ser-360 was identified as a new phosphorylation site and was more sensitive to radiation than Ser-957, especially at doses below 1 Gy. Our results demonstrate a robust ex vivo response of phospho-SMC1-(Ser-360) to ionizing radiation in human PBMCs. Detection of phosphorylation at Ser-360 in SMC1 could be used as a marker of radiation exposure. Our findings suggest that it is feasible to measure blood cell-based changes in the phosphorylation level of a protein as an ex vivo radiation exposure detection method, even after low-dose exposure.

Pneumonitis is a common adverse effect found in non-small cell lung cancer patients after radiotherapy or immune checkpoint inhibitor treatment. We investigated the effects of these two therapies, combined, in the lung tissue of an orthotopic tumor-bearing mouse model. The mice received an 8 Gy dose three times with or without 200 µg anti-programmed death-1 (anti-PD-1) antibody intraperitoneal injection every three days. Lung tissues were H&E stained to determine histological changes. The serum levels of cytokines, such as interferon-γ, tumor necrosis factor and interleukin-5, were detected by cytometric bead array. The neutrophil infiltration was evaluated by immunohistochemical staining for myeloperoxidase. The lung injury score was higher in the treated groups than the control group, especially in the combined treatment group, in which the proportion of neutrophils in lung tissues was significantly higher compared to any other groups. Similarly, the CD4/CD8 ratio of the lung tissues in the combined treatment group, as well as the serum levels of interferon-γ, tumor necrosis factor and interleukin-5, were significantly higher than the other groups. These findings indicate that radiation combined with anti-PD-1 treatment leads to more severe lung injury in the orthotopic tumor-bearing mouse model, accompanied by increased neutrophil infiltration and increased inflammatory response.

The radiation environment in space remains a major concern for manned space exploration, as there is currently no shielding material capable of fully protecting flight crews. Additionally, there is growing concern for the social and cognitive welfare of astronauts, due to prolonged radiation exposure and confinement they will experience on a mission to Mars. In this artice, we report on the late effects of ¹⁶O-particle radiation on social and cognitive behavior and neuronal morphology in the hippocampus of adult female mice. Six-month-old mice received ¹⁶O-particle whole-body irradiation at doses of either 0.25 or 0.1 Gy (600 MeV/n; 18–33 cGy/min) at the NASA's Space Radiation Laboratory in Upton, NY. At nine months postirradiation, the animals underwent behavioral testing in the three-chamber sociability, novel object recognition and Y-maze paradigms. Exposure to 0.1 or 0.25 Gy ¹⁶O significantly impaired object memory, a 0.25 Gy dose impaired social novelty learning, but neither dosage impaired short-term spatial memory. We observed significant decreases in mushroom spine density and dendrite morphology in the dentate gyrus, cornu ammonis 3, 2 and 1 of the hippocampus, which are critical areas for object novelty and sociability processing. Our data suggest exposure to ¹⁶O modulates hippocampal pyramidal and granular neurons and induces behavioral deficits at a time point of nine months after exposure in females.