Health Effects of Ionizing Radiation on the Human Body

Radioactivity is a process in which the nuclei of unstable atoms spontaneously decay, producing other nuclei and releasing energy in the form of ionizing radiation in the form of alpha (α) and beta (β) particles as well as the emission of gamma (γ) electromagnetic waves. People may be exposed to radiation in various forms, as casualties of nuclear accidents, workers in power plants, or while working and using different radiation sources in medicine and health care. Acute radiation syndrome (ARS) occurs in subjects exposed to a very high dose of radiation in a very short period of time. Each form of radiation has a unique pathophysiological effect. Unfortunately, higher organisms-human beings-in the course of evolution have not acquired receptors for the direct "capture" of radiation energy, which is transferred at the level of DNA, cells, tissues, and organs. Radiation in biological systems depends on the amount of absorbed energy and its spatial distribution, particularly depending on the linear energy transfer (LET). Photon radiation with low LET leads to homogeneous energy deposition in the entire tissue volume. On the other hand, radiation with a high LET produces a fast Bragg peak, which generates a low input dose, whereby the penetration depth into the tissue increases with the radiation energy. The consequences are mutations, apoptosis, the development of cancer, and cell death. The most sensitive cells are those that divide intensively-bone marrow cells, digestive tract cells, reproductive cells, and skin cells. The health care system and the public should raise awareness of the consequences of ionizing radiation. Therefore, our aim is to identify the consequences of ARS taking into account radiation damage to the respiratory system, nervous system, hematopoietic system, gastrointestinal tract, and skin.

DAMPs and radiation injury

The heightened risk of ionizing radiation exposure, stemming from radiation accidents and potential acts of terrorism, has spurred growing interests in devising effective countermeasures against radiation injury. High-dose ionizing radiation exposure triggers acute radiation syndrome (ARS), manifesting as hematopoietic, gastrointestinal, and neurovascular ARS. Hematopoietic ARS typically presents with neutropenia and thrombocytopenia, while gastrointestinal ARS results in intestinal mucosal injury, often culminating in lethal sepsis and gastrointestinal bleeding. This deleterious impact can be attributed to radiation-induced DNA damage and oxidative stress, leading to various forms of cell death, such as apoptosis, necrosis and ferroptosis. Damage-associated molecular patterns (DAMPs) are intrinsic molecules released by cells undergoing injury or in the process of dying, either through passive or active pathways. These molecules then interact with pattern recognition receptors, triggering inflammatory responses. Such a cascade of events ultimately results in further tissue and organ damage, contributing to the elevated mortality rate. Notably, infection and sepsis often develop in ARS cases, further increasing the release of DAMPs. Given that lethal sepsis stands as a major contributor to the mortality in ARS, DAMPs hold the potential to function as mediators, exacerbating radiation-induced organ injury and consequently worsening overall survival. This review describes the intricate mechanisms underlying radiation-induced release of DAMPs. Furthermore, it discusses the detrimental effects of DAMPs on the immune system and explores potential DAMP-targeting therapeutic strategies to alleviate radiation-induced injury.

ACUTE RADIATION SICKNESS IN HUMAN: ETIOPATHOGENESIS, CLINIC, DIAGNOSIS AND TREATMENT (LECTURE)

Under the conditions of war in Ukraine, there remains a high probability that russia will use nuclear weapons or commit terrorist acts against nuclear power plants, which will lead to exposure of the population in doses that cause acute radiation sickness (ARS). In this regard, our medical service must be ready for the treatment of ARS of various degrees of severity under a mass influx of victims. In peacetime, ARS is a rather infrequent pathology, so most doctors lack experience in its treatment. This article, having the form of a lecture, presents material on the pathogenesis, classification, clinic, diagnosis and treatment of ARS, taking into account the modern achievements of radiation medicine. Treatment of ARS is based on the use of pharmaceutical drugs that are licensed in Ukraine. The article will be useful for doctors and medical workers of all branches and levels of health care, who will have to deal with irradiated persons in order to timely identify patients with ARS and provide them with effective treatment.

Assessment of uncertainties in threshold doses for tissue reactions following acute external radiation exposure

The study aimed to estimate threshold doses and their uncertainties for some human health effects after short-term high dose-rate radiation exposure by quantile technique and the effective dose threshold technique based on distribution functions. The relative uncertainty (U) of the threshold dose was estimated using the error propagation technique. The quantile technique provided statistically significant estimates of threshold doses for acute radiation syndrome onset (0.44 ± 0.12 Gy, U = 143%) and lethality (1.84 ± 0.44 Gy, U = 117%) but relative uncertainties were high. The effective threshold dose technique provided statistically significant and more precise threshold dose estimates for acute radiation syndrome onset (0.73 ± 0.02 Gy, U = 18%) and lethality (6.83 ± 0.08 Gy, U = 36%), as well as agranulocytosis (3.51 ± 0.03 Gy, U = 16%) and vomiting onset in the prodromal period (1.54 ± 0.02 Gy, U = 16%). Threshold doses estimated for the change in the peripheral blood neutrophil and leukocyte counts during the first days after short-term high dose-rate radiation exposure were not statistically significant.

Further Characterization of Multi-Organ DEARE and Protection by 16,16 Dimethyl Prostaglandin E2 in a Mouse Model of the Hematopoietic Acute Radiation Syndrome

Survivors of acute radiation exposure suffer from the delayed effects of acute radiation exposure (DEARE), a chronic condition affecting multiple organs, including lung, kidney, heart, gastrointestinal tract, eyes, and brain, and often causing cancer. While effective medical countermeasures (MCM) for the hematopoietic-acute radiation syndrome (H-ARS) have been identified and approved by the FDA, development of MCM for DEARE has not yet been successful. We previously documented residual bone marrow damage (RBMD) and progressive renal and cardiovascular DEARE in murine survivors of H-ARS, and significant survival efficacy of 16,16-dimethyl prostaglandin E2 (dmPGE2) given as a radioprotectant or radiomitigator for H-ARS. We now describe additional DEARE (physiological and neural function, progressive fur graying, ocular inflammation, and malignancy) developing after sub-threshold doses in our H-ARS model, and detailed analysis of the effects of dmPGE2 administered before (PGE-pre) or after (PGE-post) lethal total-body irradiation (TBI) on these DEARE. Administration of PGE-pre normalized the twofold reduction of white blood cells (WBC) and lymphocytes seen in vehicle-treated survivors (Veh), and increased the number of bone marrow (BM) cells, splenocytes, thymocytes, and phenotypically defined hematopoietic progenitor cells (HPC) and hematopoietic stem cells (HSC) to levels equivalent to those in non-irradiated age-matched controls. PGE-pre significantly protected HPC colony formation ex vivo by >twofold, long term-HSC in vivo engraftment potential up to ninefold, and significantly blunted TBI-induced myeloid skewing. Secondary transplantation documented continued production of LT-HSC with normal lineage differentiation. PGE-pre reduced development of DEARE cardiovascular pathologies and renal damage; prevented coronary artery rarefication, blunted progressive loss of coronary artery endothelia, reduced inflammation and coronary early senescence, and blunted radiation-induced increase in blood urea nitrogen (BUN). Ocular monocytes were significantly lower in PGE-pre mice, as was TBI-induced fur graying. Increased body weight and decreased frailty in male mice, and reduced incidence of thymic lymphoma were documented in PGE-pre mice. In assays measuring behavioral and cognitive functions, PGE-pre reduced anxiety in females, significantly blunted shock flinch response, and increased exploratory behavior in males. No effect of TBI was observed on memory in any group. PGE-post, despite significantly increasing 30-day survival in H-ARS and WBC and hematopoietic recovery, was not effective in reducing TBI-induced RBMD or any other DEARE. In summary, dmPGE2 administered as an H-ARS MCM before lethal TBI significantly increased 30-day survival and ameliorated RBMD and multi-organ and cognitive/behavioral DEARE to at least 12 months after TBI, whereas given after TBI, dmPGE2 enhances survival from H-ARS but has little impact on RBMD or other DEARE.

Establishing a Murine Model of the Hematopoietic Acute Radiation Syndrome

The hematopoietic system is one of the most sensitive tissues to ionizing radiation, and radiation doses from 2 to 10 gray can result in death from bleeding and infection if left untreated. Reviewing the range of radiation doses reported in the literature that result in similar lethality highlights the need for a more consistent model that would allow a better comparison of the hematopoietic acute radiation syndrome (H-ARS) studies carried out in different laboratories. Developing a murine model of H-ARS to provide a platform suited for efficacy testing of medical countermeasures (MCM) against radiation should include a review of the Food and Drug Administration requirements outlined in the Animal Rule. The various aspects of a murine H-ARS model found to affect consistent performance will be described in this chapter including strain, sex, radiation type and dose, mouse restraint, and husbandry.

A Review of Radiation-Induced Alterations of Multi-Omic Profiles, Radiation Injury Biomarkers, and Countermeasures

Increasing utilization of nuclear power enhances the risks associated with industrial accidents, occupational hazards, and the threat of nuclear terrorism. Exposure to ionizing radiation interferes with genomic stability and gene expression resulting in the disruption of normal metabolic processes in cells and organs by inducing complex biological responses. Exposure to high-dose radiation causes acute radiation syndrome, which leads to hematopoietic, gastrointestinal, cerebrovascular, and many other organ-specific injuries. Altered genomic variations, gene expression, metabolite concentrations, and microbiota profiles in blood plasma or tissue samples reflect the whole-body radiation injuries. Hence, multi-omic profiles obtained from high-resolution omics platforms offer a holistic approach for identifying reliable biomarkers to predict the radiation injury of organs and tissues resulting from radiation exposures. In this review, we performed a literature search to systematically catalog the radiation-induced alterations from multi-omic studies and radiation countermeasures. We covered radiation-induced changes in the genomic, transcriptomic, proteomic, metabolomic, lipidomic, and microbiome profiles. Furthermore, we have covered promising multi-omic biomarkers, FDA-approved countermeasure drugs, and other radiation countermeasures that include radioprotectors and radiomitigators. This review presents an overview of radiation-induced alterations of multi-omics profiles and biomarkers, and associated radiation countermeasures.

Cutaneous and local radiation injuries

The threat of a large-scale radiological or nuclear (R/N) incident looms in the present-day climate, as noted most recently in an editorial in Scientific American (March 2021). These large-scale incidents are infrequent but affect large numbers of people. Smaller-scale R/N incidents occur more often, affecting smaller numbers of people. There is more awareness of acute radiation syndrome (ARS) in the medical community; however, ionising radiation-induced injuries to the skin are much less understood. This article will provide an overview of radiation-induced injuries to the skin, deeper tissues, and organs. The history and nomenclature; types and causes of injuries; pathophysiology; evaluation and diagnosis; current medical management; and current research of the evaluation and management are presented. Cutaneous radiation injuries (CRI) or local radiation injuries (LRI) may lead to cutaneous radiation syndrome, a sub-syndrome of ARS. These injuries may occur from exposure to radioactive particles suspended in the environment (air, soil, water) after a nuclear detonation or an improvised nuclear detonation (IND), a nuclear power plant incident, or an encounter with a radioactive dispersal or exposure device. These incidents may also result in a radiation-combined injury; a chemical, thermal, or traumatic injury, with radiation exposure. Skin injuries from medical diagnostic and therapeutic imaging, medical misadministration of nuclear medicine or radiotherapy, occupational exposures (including research) to radioactive sources are more common but are not the focus of this manuscript. Diagnosis and evaluation of injuries are based on the scenario, clinical picture, and dosimetry, and may be assisted through advanced imaging techniques. Research-based multidisciplinary therapies, both in the laboratory and clinical trial environments, hold promise for future medical management. Great progress is being made in recognising the extent of injuries, understanding their pathophysiology, as well as diagnosis and management; however, research gaps still exist.

Acute Radiation Effects, the H-ARS in the Non-human Primate: A Review and New Data for the Cynomolgus Macaque with Reference to the Rhesus Macaque

ABSTRACT

Medical countermeasure development under the US Food and Drug Administration animal rule requires validated animal models of acute radiation effects. The key large animal model is the non-human primate, rhesus macaque. To date, only the rhesus macaque has been used for both critical supportive data and pivotal efficacy trials seeking US Food and Drug Administration approval. The potential for use of the rhesus for other high priority studies such as vaccine development underscores the need to identify another non-human primate model to account for the current lack of rhesus for medical countermeasure development. The cynomolgus macaque, Macaca fascicularis, has an existing database of medical countermeasure development against the hematopoietic acute radiation syndrome, as well as the use of radiation exposure protocols that mimic the likely nonuniform and heterogenous exposure consequent to a nuclear terrorist event. The review herein describes published studies of adult male cynomolgus macaques that used two exposure protocols-unilateral, nonuniform total-body irradiation and partial-body irradiation with bone marrow sparing-with the administration of subject-based medical management to assess mitigation against the hematopoietic acute radiation syndrome. These studies assessed the efficacy of cytokine combinations and cell-based therapy to mitigate acute radiation-induced myelosuppression. Both therapeutics were shown to mitigate the myelosuppression of the hematopoietic acute radiation syndrome. Additional studies being presented herein further defined the dose-dependent hematopoietic acute radiation syndrome of cynomolgus and rhesus macaques and a differential dose-dependent effect with young male and female cynomolgus macaques. The database supports the investigation of the cynomolgus macaque as a comparable non-human primate for efficacy testing under the US Food and Drug Administration animal rule. Critical gaps in knowledge required to validate the models and exposure protocols are also identified.

Rat Models of Partial-body Irradiation with Bone Marrow-sparing (Leg-out PBI) Designed for FDA Approval of Countermeasures for Mitigation of Acute and Delayed Injuries by Radiation

ABSTRACT

The goal of this study was to develop rat models of partial body irradiation with bone-marrow sparing (leg-out PBI) to test medical countermeasures (MCM) of both acute radiation syndrome (ARS) and delayed effects of acute radiation exposure (DEARE) under the FDA animal rule. The leg-out PBI models were developed in female and male WAG/RijCmcr rats at doses of 12.5-14.5 Gy. Rats received supportive care consisting of fluids and antibiotics. Gastrointestinal ARS (GI-ARS) was assessed by lethality to d 7 and diarrhea scoring to d 10. Differential blood counts were analyzed between d 1-42 for the natural history of hematopoietic ARS (H-ARS). Lethality and breathing intervals (BI) were measured between d 28-110 to assess delayed injury to the lung (L-DEARE). Kidney injury (K-DEARE) was evaluated by measuring elevation of blood urea nitrogen (BUN) between d 90-180. The LD50/30, including both lethality from GI-ARS and H-ARS, for female and male rats are 14.0 Gy and 13.5 Gy, respectively, while the LD50/7 for only GI-ARS are 14.3 Gy and 13.6 Gy, respectively. The all-cause mortalities, including ARS and L-DEARE, through 120 d (LD50/120) are 13.5 Gy and 12.9 Gy, respectively. Secondary end points confirmed occurrence of four distinct sequelae representing GI, hematopoietic, lung, and kidney toxicities after leg-out PBI. Adult rat models of leg-out PBI showed the acute and long-term sequelae of radiation damage that has been reported in human radiation exposure case studies. Sex-specific differences were observed in the DRR between females and males. These rat models are among the most useful for the development and approval of countermeasures for mitigation of radiation injuries under the FDA animal rule.

Acute Proteomic Changes in Non-human Primate Kidney after Partial-body Radiation with Minimal Bone Marrow Sparing

Near total body exposure to high-dose ionizing radiation results in organ-specific sequelae, including acute radiation syndromes and delayed effects of acute radiation exposure. Among these sequelae are acute kidney injury and chronic kidney injury. Reports that neither oxidative stress nor inflammation are dominant mechanisms defining radiation nephropathy inspired an unbiased, discovery-based proteomic interrogation in order to identify mechanistic pathways of injury. We quantitatively profiled the proteome of kidney from non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing over a time period of 3 wk. Kidney was analyzed by liquid chromatography-tandem mass spectrometry. Out of the 3,432 unique proteins that were identified, we found that 265 proteins showed significant and consistent responses across at least three time points post-irradiation, of which 230 proteins showed strong upregulation while 35 proteins showed downregulation. Bioinformatics analysis revealed significant pathway and upstream regulator perturbations post-high dose irradiation and shed light on underlying mechanisms of radiation damage. These data will be useful for a greater understanding of the molecular mechanisms of injury in well-characterized animal models of partial body irradiation with minimal bone marrow sparing. These data may be potentially useful in the future development of medical countermeasures.

Metabolomics of Multiorgan Radiation Injury in Non-human Primate Model Reveals System-wide Metabolic Perturbations

ABSTRACT

Exposure to ionizing radiation following a nuclear or radiological incident results in potential acute radiation syndromes causing sequelae of multi-organ injury in a dose- and time-dependent manner. Currently, medical countermeasures against radiation injury are limited, and no biomarkers have been approved by regulatory authorities. Identification of circulating plasma biomarkers indicative of radiation injury can be useful for early triage and injury assessment and in the development of novel therapies (medical countermeasures). Aims of this study are to (1) identify metabolites and lipids with consensus signatures that can inform on mechanism of injury in radiation-induced multi-organ injury and (2) identify plasma biomarkers in non-human primate (NHP) that correlate with tissues (kidney, liver, lung, left and right heart, jejunum) indicative of radiation injury, assessing samples collected over 3 wk post-exposure to 12 Gy partial body irradiation with 2.5% bone marrow sparing. About 180 plasma and tissue metabolites and lipids were quantified through Biocrates AbsoluteIDQ p180 kit using liquid chromatography and mass spectrometry. System-wide perturbations of specific metabolites and lipid levels and pathway alterations were identified. Citrulline, Serotonin, PC ae 38:2, PC ae 36:2, and sum of branched chain amino acids were identified as potential biomarkers of radiation injury. Pathway analysis revealed consistent changes in fatty acid oxidation and metabolism and perturbations in multiple other pathways.

The Natural History of Acute Radiation-induced H-ARS and Concomitant Multi-organ Injury in the Non-human Primate: The MCART Experience

ABSTRACT

The dose response relationship and corresponding values for mid-lethal dose and slope are used to define the dose- and time-dependent parameters of the hematopoietic acute radiation syndrome. The characteristic time course of mortality, morbidity, and secondary endpoints are well defined. The concomitant comorbidities, potential mortality, and other multi-organ injuries that are similarly dose- and time-dependent are less defined. Determination of the natural history or pathophysiology associated with the lethal hematopoietic acute radiation syndrome is a significant gap in knowledge, especially when considered in the context of a nuclear weapon scenario. In this regard, the exposure is likely ill-defined, heterogenous, and nonuniform. These conditions forecast sparing of bone marrow and increased survival from the acute radiation syndrome consequent to threshold doses for the delayed effects of acute radiation exposure due to marrow sparing, medical management, and use of approved medical countermeasures. The intent herein is to provide a composite natural history of the pathophysiology concomitant with the evolution of the potentially lethal hematopoietic acute radiation syndrome derived from studies that focused on total body irradiation and partial body irradiation with bone marrow sparing. The marked differential in estimated LD50/60 from 7.5 Gy to 10.88 Gy for the total body irradiation and partial body irradiation with 5% bone marrow sparing models, respectively, provided a clear distinction between the attendant multiple organ injury and natural history of the two models that included medical management. Total body irradiation was focused on equivalent LD50/60 exposures. The 10 Gy and 11 Gy partial body with 5% bone marrow sparing exposures bracketed the LD50/60 (10.88 Gy). The incidence, progression, and duration of multiple organ injury was described for each exposure protocol within the hematopoietic acute radiation syndrome. The higher threshold doses for the partial body irradiation with bone marrow sparing protocol induced a marked degree of multiple organ injury to include lethal gastrointestinal acute radiation syndrome, prolonged crypt loss and mucosal damage, immune suppression, acute kidney injury, body weight loss, and added clinical comorbidities that defined a complex timeline of organ injury through the acute hematopoietic acute radiation syndrome. The natural history of the acute radiation syndrome presents a 60-d time segment of multi-organ sequelae that is concomitant with the latent period or time to onset of the evolving multi-organ injury of the delayed effects of acute radiation exposure.

Scientific research and product development in the United States to address injuries from a radiation public health emergency

The USA has experienced one large-scale nuclear incident in its history. Lessons learned during the Three-Mile Island nuclear accident provided government planners with insight into property damage resulting from a low-level release of radiation, and an awareness concerning how to prepare for future occurrences. However, if there is an incident resulting from detonation of an improvised nuclear device or state-sponsored device/weapon, resulting casualties and the need for medical treatment could overwhelm the nation's public health system. After the Cold War ended, government investments in radiation preparedness declined; however, the attacks on 9/11 led to re-establishment of research programs to plan for the possibility of a nuclear incident. Funding began in earnest in 2004, to address unmet research needs for radiation biomarkers, devices and products to triage and treat potentially large numbers of injured civilians. There are many biodosimetry approaches and medical countermeasures (MCMs) under study and in advanced development, including those to address radiation-induced injuries to organ systems including bone marrow, the gastrointestinal (GI) tract, lungs, skin, vasculature and kidneys. Biomarkers of interest in determining level of radiation exposure and susceptibility of injury include cytogenetic changes, 'omics' technologies and other approaches. Four drugs have been approved by the US Food and Drug Administration (FDA) for the treatment of acute radiation syndrome (ARS), with other licensures being sought; however, there are still no cleared devices to identify radiation-exposed individuals in need of treatment. Although many breakthroughs have been made in the efforts to expand availability of medical products, there is still work to be done.

Case review of severe acute radiation syndrome from whole body exposure: concepts of radiation-induced multi-organ dysfunction and failure

Acute radiation syndrome (ARS) due to whole body exposure (WBE) presents various clinical pictures, occasionally leading to fatal consequences. In this report, the literature providing details of the clinical course of severe ARS owing to WBE is reviewed and the lessons learned from recent accidents are discussed, to better prepare for another radiological event. Studies investigating radiological accidents that provided details of medical care for severe ARS were searched in official reports from the International Atomic Energy Agency and through the databases of PubMed, Medline, CiNii and Google Scholar and reviewed. Four fatal cases of severe ARS due to WBE in Soreq 1990 and Nesvizh 1992, and two cases in JCO Tokaimura 1999 were reviewed. A common set of medical interventions was carried out, that put a focus on medical management assuming the occurrence of hematopoietic disorders. However, clinicians were faced with a mixture of chronic hematological and non-hematological events including persistent gastrointestinal disorders, gradual and progressive skin disorders, liver and renal dysfunction and respiratory failure. Clinical pictures following high-dose WBE have become more complicated as treatment modalities improve. To address these issues, a concept of severe ARS due to WBE has been proposed with respect to radiation-induced multi-organ dysfunction syndrome (RI-MODS) and failure (RI-MOF). These patients need to be managed at institutions where multidisciplinary, resource-intensive therapy can be provided.

Software Tools for the Evaluation of Clinical Signs and Symptoms in the Medical Management of Acute Radiation Syndrome-A Five-year Experience

A suite of software tools has been developed for dose estimation (BAT, WinFRAT) and prediction of acute health effects (WinFRAT, H-Module) using clinical symptoms and/or changes in blood cell counts. We constructed a database of 191 ARS cases using the METREPOL (n = 167) and the SEARCH-database (n = 24). The cases ranged from unexposed (RC0), to mild (RC1), moderate (RC2), severe (RC3), and lethal ARS (RC4). From 2015-2019, radiobiology students and participants of two NATO meetings predicted clinical outcomes (RC, H-ARS, and hospitalization) based on clinical symptoms. We evaluated the prediction outcomes using the same input datasets with a total of 32 teams and 94 participants. We found that: (1) unexposed (RC0) and mildly exposed individuals (RC1) could not be discriminated; (2) the severity of RC2 and RC3 were systematically overestimated, but almost all lethal cases (RC4) were correctly predicted; (3) introducing a prior education component for non-physicians significantly increased the correct predictions of RC, ARS, and hospitalization by around 10% (p<0.005) with a threefold reduction in variance and a halving of the evaluation time per case; (4) correct outcome prediction was independent of the software tools used; and (5) comparing the dose estimates generated by the teams with H-ARS severity reflected known limitations of dose alone as a surrogate for H-ARS severity. We found inexperienced personnel can use software tools to make accurate diagnostic and treatment recommendations with up to 98% accuracy. Educational training improved the quality of decision making and enabled participants lacking a medical background to perform comparably to experts.

Development of a Model of the Acute and Delayed Effects of High Dose Radiation Exposure in Jackson Diversity Outbred Mice; Comparison to Inbred C57BL/6 Mice

Development of medical countermeasures against radiation relies on robust animal models for efficacy testing. Mouse models have advantages over larger species due to economics, ease of conducting aging studies, existence of historical databases, and research tools allowing for sophisticated mechanistic studies. However, the radiation dose-response relationship of inbred strains is inherently steep and sensitive to experimental variables, and inbred models have been criticized for lacking genetic diversity. Jackson Diversity Outbred (JDO) mice are the most genetically diverse strain available, developed by the Collaborative Cross Consortium using eight founder strains, and may represent a more accurate model of humans than inbred strains. Herein, models of the Hematopoietic-Acute Radiation Syndrome and the Delayed Effects of Acute Radiation Exposure were developed in JDO mice and compared to inbred C57BL/6. The dose response relationship curve in JDO mice mirrored the more shallow curves of primates and humans, characteristic of genetic diversity. JDO mice were more radioresistant than C57BL/6 and differed in sensitivity to antibiotic countermeasures. The model was validated with pegylated-G-CSF, which provided significantly enhanced 30-d survival and accelerated blood recovery. Long-term JDO survivors exhibited increased recovery of blood cells and functional bone marrow hematopoietic progenitors compared to C57BL/6. While JDO hematopoietic stem cells declined more in number, they maintained a greater degree of quiescence compared to C57BL/6, which is essential for maintaining function. These JDO radiation models offer many of the advantages of small animals with the genetic diversity of large animals, providing an attractive alternative to currently available radiation animal models.

Proteomics of Non-human Primate Plasma after Partial-body Radiation with Minimal Bone Marrow Sparing

High-dose radiation exposure results in organ-specific sequelae that occurs in a time- and dose-dependent manner. The partial body irradiation with minimal bone marrow sparing model was developed to mimic intentional or accidental radiation exposures in humans where bone marrow sparing is likely and permits the concurrent analysis of coincident short- and long-term damage to organ systems. To help inform on the natural history of the radiation-induced injury of the partial body irradiation model, we quantitatively profiled the plasma proteome of non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing with 6 MV LINAC-derived photons at 0.80 Gy min over a time period of 3 wk. The plasma proteome was analyzed by liquid chromatography-tandem mass spectrometry. A number of trends were identified in the proteomic data including pronounced protein changes as well as protein changes that were consistently upregulated or downregulated at all time points and dose levels interrogated. Pathway and gene ontology analysis were performed; bioinformatic analysis revealed significant pathway and biological process perturbations post high-dose irradiation and shed light on underlying mechanisms of radiation damage. Additionally, proteins were identified that had the greatest potential to serve as biomarkers for radiation exposure.

Lack of Cellular Inflammation in a Non-human Primate Model of Radiation Nephropathy

Inflammation is commonly cited as a mechanism of delayed effects of acute radiation exposure (DEARE). Confirmation of its presence could provide significant insight to targeted use of treatments or mitigators of DEARE. We sought to quantify the presence of cellular inflammation in kidneys of non-human primates that developed acute and chronic kidney injury after a partial body irradiation exposure. We show herein that cellular inflammation is not found as a component of either acute or chronic kidney injury. Other mechanistic pathways of injury must be sought.

Proteomic Evaluation of the Natural History of the Acute Radiation Syndrome of the Gastrointestinal Tract in a Non-human Primate Model of Partial-body Irradiation with Minimal Bone Marrow Sparing Includes Dysregulation of the Retinoid Pathway

Exposure to ionizing radiation results in injuries of the hematopoietic, gastrointestinal, and respiratory systems, which are the leading causes responsible for morbidity and mortality. Gastrointestinal injury occurs as an acute radiation syndrome. To help inform on the natural history of the radiation-induced injury of the partial body irradiation model, we quantitatively profiled the proteome of jejunum from non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing over a time period of 3 wk. Jejunum was analyzed by liquid chromatography-tandem mass spectrometry, and pathway and gene ontology analysis were performed. A total of 3,245 unique proteins were quantified out of more than 3,700 proteins identified in this study. Also a total of 289 proteins of the quantified proteins showed significant and consistent responses across at least three time points post-irradiation, of which 263 proteins showed strong upregulations while 26 proteins showed downregulations. Bioinformatic analysis suggests significant pathway and upstream regulator perturbations post-high dose irradiation and shed light on underlying mechanisms of radiation damage. Canonical pathways altered by radiation included GP6 signaling pathway, acute phase response signaling, LXR/RXR activation, and intrinsic prothrombin activation pathway. Additionally, we observed dysregulation of proteins of the retinoid pathway and retinoic acid, an active metabolite of vitamin A, as quantified by liquid chromatography-tandem mass spectrometry. Correlation of changes in protein abundance with a well-characterized histological endpoint, corrected crypt number, was used to evaluate biomarker potential. These data further define the natural history of the gastrointestinal acute radiation syndrome in a non-human primate model of partial body irradiation with minimal bone marrow sparing.

Immune Reconstitution and Thymic Involution in the Acute and Delayed Hematopoietic Radiation Syndromes

Lymphoid lineage recovery and involution after exposure to potentially lethal doses of ionizing radiation have not been well defined, especially the long-term effects in aged survivors and with regard to male/female differences. To examine these questions, male and female C57BL/6 mice were exposed to lethal radiation at 12 wk of age in a model of the Hematopoietic-Acute Radiation Syndrome, and bone marrow, thymus, spleen, and peripheral blood examined up to 24 mo of age for the lymphopoietic delayed effects of acute radiation exposure. Aged mice showed myeloid skewing and incomplete lymphocyte recovery in all lymphoid tissues. Spleen and peripheral blood both exhibited a monophasic recovery pattern, while thymus demonstrated a biphasic pattern. Naïve T cells in blood and spleen and all subsets of thymocytes were decreased in aged irradiated mice compared to age-matched non-irradiated controls. Of interest, irradiated males experienced significantly improved reconstitution of thymocyte subsets and peripheral blood elements compared to females. Bone marrow from aged irradiated survivors was significantly deficient in the primitive lymphoid-primed multipotent progenitors and common lymphoid progenitors, which were only 8-10% of levels in aged-matched non-irradiated controls. Taken together, these analyses define significant age- and sex-related deficiencies at all levels of lymphopoiesis throughout the lifespan of survivors of the Hematopoietic-Acute Radiation Syndrome and may provide a murine model suitable for assessing the efficacy of potential medical countermeasures and therapeutic strategies to alleviate the severe immune suppression that occurs after radiation exposure.

Evaluation of Plasma Biomarker Utility for the Gastrointestinal Acute Radiation Syndrome in Non-human Primates after Partial Body Irradiation with Minimal Bone Marrow Sparing through Correlation with Tissue and Histological Analyses

Exposure to total- and partial-body irradiation following a nuclear or radiological incident result in the potentially lethal acute radiation syndromes of the gastrointestinal and hematopoietic systems in a dose- and time-dependent manner. Radiation-induced damage to the gastrointestinal tract is observed within days to weeks post-irradiation. Our objective in this study was to evaluate plasma biomarker utility for the gastrointestinal acute radiation syndrome in non-human primates after partial body irradiation with minimal bone marrow sparing through correlation with tissue and histological analyses. Plasma and jejunum samples from non-human primates exposed to partial body irradiation of 12 Gy with bone marrow sparing of 2.5% were evaluated at various time points from day 0 to day 21 as part of a natural history study. Additionally, longitudinal plasma samples from non-human primates exposed to 10 Gy partial body irradiation with 2.5% bone marrow sparing were evaluated at timepoints out to 180 d post-irradiation. Plasma and jejunum metabolites were quantified via liquid chromatography-tandem mass spectrometry and histological analysis consisted of corrected crypt number, an established metric to assess radiation-induced gastrointestinal damage. A positive correlation of metabolite levels in jejunum and plasma was observed for citrulline, serotonin, acylcarnitine, and multiple species of phosphatidylcholines. Citrulline levels also correlated with injury and regeneration of crypts in the small intestine. These results expand the characterization of the natural history of gastrointestinal acute radiation syndrome in non-human primates exposed to partial body irradiation with minimal bone marrow sparing and also provide additional data toward the correlation of citrulline with histological endpoints.

A Systematic Review of the Hematopoietic Acute Radiation Syndrome (H-ARS) in Canines and Non-human Primates: Acute Mixed Neutron/Gamma vs. Reference Quality Radiations

A systematic review of relevant studies that determined the dose response relationship (DRR) for the hematopoietic (H) acute radiation syndrome (ARS) in the canine relative to radiation quality of mixed neutron:gamma radiations, dose rate, and exposure uniformity relative to selected reference radiation exposure has not been performed. The datasets for rhesus macaques exposure to mixed neutron:gamma radiation are used herein as a species comparative reference to the canine database. The selection of data cohorts was made from the following sources: Ovid Medline (1957-present), PubMed (1954-present), AGRICOLA (1976-present), Web of Science (1954-present), and US HHS RePORT (2002-present). The total number of hits across all search sites was 3,077. Several referenced, unpublished, non-peer reviewed government reports were unavailable for review. Primary published studies using canines, beagles, and mongrels were evaluated to provide an informative and consistent review of mixed neutron:gamma radiation effects to establish the DRRs for the H-ARS. Secondary and tertiary studies provided additional information on the hematologic response or the effects on hematopoietic progenitor cells, radiation dosimetry, absorbed dose, and organ dose. The LD50/30 values varied with neutron quality, exposure aspect, and mixed neutron:gamma ratio. The reference radiation quality varied from 250 kVp or 1-2 MeV x radiation and Co gamma radiation. A summary of a published review of a data set describing the DRR in rhesus macaques for mixed neutron:gamma radiation exposure in the H-ARS is included for a comparative reference to the canine dataset. The available evidence provided a reliable and extensive database that characterized the DRR for the H-ARS in canines and young rhesus macaques exposed to mixed neutron:gamma radiations of variable energy relative to 250 kVp, 1-2 MeV x radiation and Co gamma, and uniform and non-uniform total-body irradiation without the benefit of medical management. The mixed neutron:gamma radiation showed an energy-dependent RBE of ~ 1.0 to 2.0 relative to reference radiation exposure within both species. A marginal database described the DRR for the gastrointestinal (GI)-ARS. Medical management showed benefit in both species relative to the mixed neutron:gamma as well as exposure to reference radiation. The DRR for the H-ARS was characterized by steep slopes and relative LD50/30 values that reflected the radiation quality, exposure aspect, and dose rate over a range in time from 1956-2012.

Acute Radiation-induced GI-ARS and H-ARS in a Canine Model of Mixed Neutron/Gamma Relative to Reference Co-60 Gamma Radiation: A Retrospective Study

Studies performed decades ago in the canine and nonhuman primate established the dose response relationships for the hematopoietic acute radiation syndrome in response to mixed neutron/gamma, x-radiation, and Co gamma radiation. There were no published studies that determined the dose response relationships for the gastrointestinal acute radiation syndrome in response to either noted radiation quality. This analysis of a retrospective, unpublished study provided the dose response relationships in a canine model for the acute gastrointestinal syndrome relative to the acute hematopoietic syndrome due to mixed neutron/gamma radiation. Canines were exposed to total-body, steady state, bilateral, 0.40 Gy min, mixed neutron/gamma (5.4:1) radiation from a TRIGA reactor. The average neutron/gamma energy (MeV) was 0.85/0.9, and exposure was reported as midline tissue dose. Medical management was not administered. The mixed neutron/gamma exposure resulted in an estimated LD50/6 of 2.83 Gy [2.76, 2.94] and LD50/30 of 2.16 Gy [2.01, 2.24] for the GI- and H-ARS respectively. The mean survival times for decedents after mixed neutron/gamma exposure approximate to the LD50/6 were 8.5 d, 10.5 d, and 4 d for 2.75 Gy, 2.80 Gy, 3.00, and 3.12 Gy exposures, respectively. The mean survival times for decedents for mixed neutron/gamma exposure approximate to the LD50/30 were 21.3 d and 15.6 d for 2.00 Gy and 2.25 Gy, respectively. Furthermore, the dose response relationships for the acute hematopoietic syndrome due to mixed neutron/gamma exposure (0.85/0.9 MeV; 5.4:1) resulted in an estimated relative biological effectiveness of 1.2 as compared with reference Co gamma radiation.

Radiation-induced tissue damage and response

Normal tissue responses to ionizing radiation have been a major subject for study since the discovery of X-rays at the end of the 19th century. Shortly thereafter, time-dose relationships were established for some normal tissue endpoints that led to investigations into how the size of dose per fraction and the quality of radiation affected outcome. The assessment of the radiosensitivity of bone marrow stem cells using colony-forming assays by Till and McCulloch prompted the establishment of in situ clonogenic assays for other tissues that added to the radiobiology toolbox. These clonogenic and functional endpoints enabled mathematical modeling to be performed that elucidated how tissue structure, and in particular turnover time, impacted clinically relevant fractionated radiation schedules. More recently, lineage tracing technology, advanced imaging and single cell sequencing have shed further light on the behavior of cells within stem, and other, cellular compartments, both in homeostasis and after radiation damage. The discovery of heterogeneity within the stem cell compartment and plasticity in response to injury have added new dimensions to the consideration of radiation-induced tissue damage. Clinically, radiobiology of the 20th century garnered wisdom relevant to photon treatments delivered to a fairly wide field at around 2 Gy per fraction, 5 days per week, for 5-7 weeks. Recently, the scope of radiobiology has been extended by advances in technology, imaging and computing, as well as by the use of charged particles. These allow radiation to be delivered more precisely to tumors while minimizing the amount of normal tissue receiving high doses. One result has been an increase in the use of schedules with higher doses per fraction given in a shorter time frame (hypofractionation). We are unable to cover these new technologies in detail in this review, just as we must omit low-dose stochastic effects, and many aspects of dose, dose rate and radiation quality. We argue that structural diversity and plasticity within tissue compartments provides a general context for discussion of most radiation responses, while acknowledging many omissions. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Acute radiation risk assessment and mitigation strategies in near future exploration spaceflights

As more exploration spaceflights are planned to travel beyond the protective Earth magnetosphere to deep space destinations, acute health risks due to possible high radiation doses during severe Solar Particle Events (SPEs) are of greater concern to mission planners and management teams. It is expected that some degree of Acute Radiation Syndromes (ARS) symptoms may be observed, but the specific list of health risks that are relevant to exploration missions has been ambiguous and debatable in the past. This mini-review gives a brief summary of the features of radiation exposure if astronauts encounter severe SPEs beyond Low Earth Orbit (LEO), the evidence of ARS radiobiological studies at exposure levels close to recommended limits, and the shortcomings of previous dose projection approaches for ARS risk assessment. Some ARS biomathematical models, particularly those pertinent to the dose ranges that severe SPEs beyond LEO could generate, are reviewed and evaluated, focusing on their capability to predict the incidence of performance incapacitation and time-phased health effects with subsequent medical care recommendations. Using onboard active dosimeter input for estimating organ doses and likely clinical outcomes for SPEs in real time, a new strategy for ARS assessment and mitigation is described to cope with the potential threats of severe SPEs for planned deep space missions.

RADIATION DOSE IS OF LIMITED CLINICAL USEFULNESS IN PERSONS WITH ACUTE RADIATION SYNDROME

The relation of radiation exposure (dose) with acute radiation syndrome (ARS) depends on many factors. In this overview, we reconsider (1) radiation exposure characteristics (e.g. radiation quality, fractionation, dose rate, partial/total body irradiation) and (2) biological processes (e.g. radiosensitivity, cell cycle dependency, oxygenation) affecting acute health effects after exposure. Furthermore we include evidence from recently published work that examined the relationship of absorbed dose and risk of clinically relevant ARS in persons exposed after a radiation accident. We introduce the concept of radiation-related bioindicators for effect prediction. Bioindicators are considered here to be factors that integrate multiple radiation exposure characteristics and cell- and molecular-based processes to improve clinical prediction in persons with ARS.

CONTRIBUTION OF BIODOSIMETRY TO DIFFERENT MEDICAL ISSUES

Biodosimetry is a well-established field in science as well as diagnostics and is essential in various areas of application such as dose reconstruction after an accidental radiation exposure. However, depending on the medical issue the purpose of biodosimetry might differ. In this presentation, we will discuss about the contribution of biodosimetry regarding three medical subjects such as (i) diagnosis of acute effects after ionising radiation (Acute Radiation Syndrome), (ii) impact in the field of conventional and molecular epidemiology and (iii) occupational medicine.

CYTOGENETIC BIODOSIMETRY OF ACCIDENTAL EXPOSURES IN THE LONG TERMS AFTER IRRADIATION

The group of radiation victims who had received radiation injures similar to those of Chernobyl accident victims was evaluated in terms of retrospective cytogenetic biodosimetry in the long term period of from 17 y up to 50 y after irradiation. Based on the existing results of the long-term cytogenetic examination of the victims injured after the Chernobyl accident, an original method was developed. This method of retrospective dose recovery was based on the use of a special computer program, the time elapsed after irradiation and the frequency of atypical chromosomes. Both patient groups were examined using conventional cytogenetic analysis. The new method of a retrospective biodosimetry was tested on the non-Chernobyl group. As a result the multiple regression equations which included frequency atypical chromosomes produced better results because the majority of the estimates of the retrospective doses fell into the 95%-prediction intervals for the reference group of the Chernobyl victims.

BABOON RADIATION QUALITY (MIXED-FIELD NEUTRON AND GAMMA, GAMMA ALONE) DOSE-RESPONSE MODEL SYSTEMS: ASSESSMENT OF H-ARS SEVERITY USING HAEMATOLOGIC BIOMARKERS

Results from archived (1986 and 1996) experiments were used to establish a baboon radiation-quality dose-response database with haematology biomarker time-course data following exposure to mixed-fields (i.e. neutron to gamma ratio: 5.5; dose: 0-8 Gy) and 60Co gamma-ray exposures (0-15 Gy). Time-course (i.e. 0-40 d) haematology changes for relevant blood-cell types for both mixed-field (neutron to gamma ratio = 5.5) and gamma ray alone were compared and models developed that showed significant differences using the maximum likehood ratio test. A consensus METREPOL-like haematology ARS (H-ARS) severity scoring system for baboons was established using these results. The data for mixed-field and the gamma only cohorts appeared similar, and so the cohorts were pooled into a single consensus H-ARS severity scoring system. These findings provide proof-of-concept for the use of a METREPOL H-ARS severity scoring system following mixed-field and gamma exposures.

Brief Story on Prostaglandins, Inhibitors of their Synthesis, Hematopoiesis, and Acute Radiation Syndrome

Prostaglandins and inhibitors of their synthesis (cyclooxygenase (COX) inhibitors, non-steroidal anti-inflammatory drugs) were shown to play a significant role in the regulation of hematopoiesis. Partly due to their hematopoiesis-modulating effects, both prostaglandins and COX inhibitors were reported to act positively in radiation-exposed mammalian organisms at various pre- and post-irradiation therapeutical settings. Experimental efforts were targeted at finding pharmacological procedures leading to optimization of therapeutical outcomes by minimizing undesirable side effects of the treatments. Progress in these efforts was obtained after discovery of selective inhibitors of inducible selective cyclooxygenase-2 (COX-2) inhibitors. Recent studies have been able to suggest the possibility to find combined therapeutical approaches utilizing joint administration of prostaglandins and inhibitors of their synthesis at optimized timing and dosing of the drugs which could be incorporated into the therapy of patients with acute radiation syndrome.

Effect of Sex on Biomarker Response in a Mouse Model of the Hematopoietic Acute Radiation Syndrome

Sex is an important confounding variable in biomarker development that must be incorporated into biomarker discovery and validation. Additionally, understanding of sex as a biological variable is essential for effective translation of biomarkers in animal models to human populations. Toward these ends, we conducted high-throughput targeted metabolomics using liquid chromatography tandem mass spectrometry and multiplexed immunoassay analyses using a Luminex-based system in both male and female mice in a model of total-body irradiation at a radiation dose consistent with the hematopoietic acute radiation syndrome. Metabolomic and immunoassay analyses identified metabolites and cytokines that were significantly different in plasma from naive and irradiated C57BL/6 mice consisting of equal numbers of female and male mice at 3 d after 8.0 or 8.72 Gy, an approximate LD60-70/30 dose of total-body irradiation. An additional number of metabolites and cytokines had sex-specific responses after radiation. Analyses of sham-irradiated mice illustrate the presence of stress-related changes in several cytokines due simply to undergoing the irradiation procedure, absent actual radiation exposure. Basal differences in metabolite levels between female and male were also identified as well as time-dependent changes in cytokines up to 9 d postexposure. These studies provide data toward defining the influence of sex on plasma-based biomarker candidates in a well-defined mouse model of acute radiation syndrome.

The Gastrointestinal Subsyndrome of the Acute Radiation Syndrome in Rhesus Macaques: A Systematic Review of the Lethal Dose-response Relationship With and Without Medical Management

Well-characterized animal models that mimic the human response to potentially lethal doses of radiation are required to assess the efficacy of medical countermeasures under the criteria of the US Food and Drug Administration's Animal Rule. Development of a model for the gastrointestinal acute radiation syndrome requires knowledge of the radiation dose-response relationship and time course of mortality and morbidity across the acute and prolonged gastrointestinal radiation syndrome. The nonhuman primate, rhesus macaque, is a relevant animal model that has been used to determine the efficacy of medical countermeasures to mitigate major signs of morbidity and mortality relative to the hematopoietic acute radiation syndrome, gastrointestinal acute radiation syndrome, and lung injury. It can be used to assess the natural history of gastrointestinal damage, concurrent multiple organ injury, and aspects of the mechanism of action for acute radiation exposure and treatment. A systematic review of relevant studies that determined the dose-response relationship for the gastrointestinal acute and prolonged radiation syndrome in the rhesus macaque relative to radiation dose, quality, dose rate, exposure uniformity, and use of medical management has never been performed.

Modeling the Optimum Prussian Blue Treatment for Acute Radiation Syndrome Following 137Cs Ingestion

Accidents or radiological attacks may lead to ingestion of Cs by large numbers of the public. This work models the efficacy of Prussian blue, the medical countermeasure for internal contamination with Cs, to prevent acute radiation syndrome as a function of the duration of treatment and the time that treatment starts after uptake. Risk of acute radiation syndrome is modeled using the International Commission on Radiological Protection's acute radiation hazard model. Dose rates to target organs from Cs ingestion were based on the data published by the US Environmental Protection Agency and the retention of Cs in the reference man. Modeling found that treatment is most effective if begun within 15 d of ingestion, and the course length should be at least 75 d to mitigate cancer risk and 290 d to mitigate fatalities due to acute radiation syndrome. Both of these course lengths are much longer than the minimum Prussian blue treatment regimen of 30 d. Extending the treatment time for contaminated individuals would increase demand for Prussian blue following an accident or attack and in turn, would require a larger stockpile of Prussian blue to meet demand. Not enough data is available to determine if this longer treatment time would lead to adverse medical outcomes due to the toxicity of the treatment itself.

COORDINATION OF MANAGEMENT OF THE ACUTE RADIATION SYNDROME

The acute radiation syndrome (ARS) constitutes the most challenging, immediate medical consequence of exposure to high doses of ionizing radiation in an emergency situation. This report highlights some of the currently available medical guidelines and recommendations on the clinical management of ARS, comments recent trends regarding the approval of targeted pharmaceuticals for ARS, and suggests further initiatives for international collaboration aiming at continuously updating the medical knowledge base of this syndrome.

CLINICAL TRIAGE OF RADIATION CASUALTIES-THE HEMATOLOGICAL MODULE OF THE BUNDESWEHR INSTITUTE OF RADIOBIOLOGY

Novel treatment regimens for therapy of the acute radiation syndrome (ARS) were developed over the last years. Their application relies on an early and high-throughput diagnosis. Based on the database SEARCH a new scientific triage tool (called H-module) was developed for early prediction of the later developing ARS. Based on peripheral blood cell counts measured within the first three days after a radiation exposure a prediction of the H-ARS severity (as well as therapeutic recommendations) can be performed with this tool. The H-module was tested within two table top exercises. Contributors were either radiation experts or radiobiology students and the required patient data were generated from real case histories. The H-module proved to be an easy to train and easy to use precise and promising new tool to assist and guide the treating physician in a large-scale radiation scenario. An introduction into this new tool and other diagnostic tools will be provided in the context of a NATO-teaching class in October/November 2019 in Paris.

ACUTE MYELOID LEUKEMIA, PROSTATE AND SKIN CANCER IN ACUTE RADIATION SYNDROME SURVIVOR AFTER THE 1986 CHERNOBYL NUCLEAR ACCIDENT: CASE REPORT

The development of hemoblastosis is often associated with the influence of various genotoxic unfavorable factors, in particular, with the effect of ionizing radiation. This article presents a case report of acute myeloid leukemia (AML) in a patient who was involved in the 1986 accident at the Chernobyl Nuclear Power Plant and suffered an acute radiation syndrome of degree II severity. Based on clinical and cytogenetic dosimetry, the average absorbed radiation dose to the whole body was estimated to be 4.3 Gy. During long-term clinical follow-up (27 years), moderate transient instability of hematological parameters was observed: lymphocytosis, leukopenia and thrombocytopenia, which was associated with chronic viral hepatitis C. Further cytogenetic investigations demonstrated a very high frequency of translocations, up to 50 times background values, that persisted over 3 decades. In 2014, the patient was diagnosed and operated on for prostate cancer and received a course of radiotherapy (total fractionated local dose of 35 Gy) in May 2015. From December 2015 through April 2016, the patient experienced general weakness and developed progressive cytopenia. A diagnosis of AML, resulting from a myelodysplastic syndrome, was confirmed by abnormal complex clones detected in 38% of metaphases by the mFISH-method, along with other chromosomal rearrangements. The patient underwent several chemotherapy treatments for AML but eventually died of bilateral pneumonia in March 2017.

A comparative analysis of gut microbiota disturbances in the Gottingen minipig and rhesus macaque models of acute radiation syndrome following bioequivalent radiation exposures

In rodent studies, the gut microbiota has been implicated in facilitating both radioresistance, by protecting the epithelium from apoptotic responses and radiosensitivity, inducing endothelial apoptotic responses. Despite the observation that large animal models, such as the Chinese Rhesus macaque and the Gottingen Minipig, demonstrate similarity to human physiologic responses to radiation, little is known about radiation-induced changes of the gut microbiome in these models. To compare the two models, we used bioequivalent radiation doses which resulted in an LD50 for Gottingen Minipigs and Chinese Rhesus macaques, 1.9 Gy and 6.8 Gy, respectively. Fecal samples taken prior and 3 days post-radiation were used for 16S rRNA gene sequence amplicon high throughput sequencing (Illumina MiSeq). Baseline gut microbiota profiles were dissimilar between minipigs and rhesus macaques. Irradiation profoundly impacted gut microbiota profiles in both animals. Significant increases of intracellular symbionts were common to both models and to reported changes in rodents suggesting universality of these findings post-radiation. Remarkably, opposite dynamics were observed for the main phyla, with increase of Firmicutes and decrease of Bacteroidetes and Proteobacteria in minipigs but with enrichment of Bacteroidetes in rhesus macaques. Minipig changes in magnitude and in variety of species affected were more extensive than those observed in rhesus macaques. This pilot study provides an important first step in comparing the radiosensitive pig model to the comparatively more radioresistant macaque model, for the identification of microbial elements which may influence radiosensitivity.

Epidemiology of Late Health Effects in Ukrainian Chornobyl Cleanup Workers

This article summarizes the results of 30 y of follow-up of cancer and noncancer effects in Ukrainian cleanup workers after the Chornobyl accident. The number of power plant employees and first responders with acute radiation syndrome under follow-up by the National Research Center for Radiation Medicine decreased from 179 in 1986-1991 to 105 in 2011-2015. Cancers and leukemia (19) and cardiovascular diseases (21) were the main causes of deaths among acute radiation syndrome survivors (54) during the postaccident period. Increased radiation risks of leukemia in the Ukrainian cohort of 110,645 cleanup workers exposed to low doses are comparable to those among survivors of the atomic bomb explosions in Japan in 1945. Additionally, an excess of chronic lymphocytic leukemia was demonstrated in the cleanup workers cohort for 26 y after the exposure. A significant excess of multiple myeloma incidence [standardized incidence rate (SIR) 1.61 %, 95% confidence interval (CI) 1.01-2.21], thyroid cancer (SIR 4.18, 95% CI 3.76-4.59), female breast cancer (SIR 1.57 CI 1.40-1.73), and all cancers combined (SIR 1.07; 95% CI 1.05-1.09) was registered. High prevalence was demonstrated for cardio- and cerebrovascular diseases and mental health changes. However, the reasons for the increases require further investigation. To monitor other possible late effects of radiation exposure in Chornobyl cleanup workers, analytical cohort and case-control studies need to include cardiovascular pathology, specifically types of potentially radiogenic cancers using a molecular epidemiology approach. Possible effects for further study include increased rates of thyroid, breast, and lung cancers and multiple myeloma; reduction of radiation risks of leukemia to population levels; and increased morbidity and mortality of cleanup workers from cardio- and cerebrovascular pathology.

PEGylated IL-11 (BBT-059): A Novel Radiation Countermeasure for Hematopoietic Acute Radiation Syndrome

Interleukin-11 was developed to reduce chemotherapy-induced thrombocytopenia; however, its clinical use was limited by severe adverse effects in humans. PEGylated interleukin-11 (BBT-059), developed by Bolder Biotechnology, Inc., exhibited a longer half-life in rodents and induced longer-lasting increases in hematopoietic cells than interleukin-11. A single dose of 1.2 mg kg of BBT-059, administered subcutaneously to CD2F1 mice (12-14 wk, male) was found to be safe in a 14 d toxicity study. The drug demonstrated its efficacy both as a prophylactic countermeasure and a mitigator in CD2F1 mice exposed to Co gamma total-body irradiation. A single dose of 0.3 mg kg, administered either 24 h pre-, 4 h post-, or 24 h postirradiation increased the survival of mice to 70-100% from lethal doses of radiation. Preadministration (-24 h) of the drug conferred a significantly (p < 0.05) higher survival compared to 24 h post-total-body irradiation. There was significantly accelerated recovery from radiation-induced peripheral blood neutropenia and thrombocytopenia in animals pretreated with BBT-059. The drug also increased bone marrow cellularity and megakaryocytes and accelerated multilineage hematopoietic recovery. In addition, BBT-059 inhibited the induction of radiation-induced hematopoietic biomarkers, thrombopoietin, erythropoietin, and Flt-3 ligand. These results indicate that BBT-059 is a promising radiation countermeasure, demonstrating its potential to be used both pre- and postirradiation for hematopoietic acute radiation syndrome with a broad window for medical management in a radiological or nuclear event.

Use of Proteomic and Hematology Biomarkers for Prediction of Hematopoietic Acute Radiation Syndrome Severity in Baboon Radiation Models

Use of plasma proteomic and hematological biomarkers represents a promising approach to provide useful diagnostic information for assessment of the severity of hematopoietic acute radiation syndrome. Eighteen baboons were evaluated in a radiation model that underwent total-body and partial-body irradiations at doses of Co gamma rays from 2.5 to 15 Gy at dose rates of 6.25 cGy min and 32 cGy min. Hematopoietic acute radiation syndrome severity levels determined by an analysis of blood count changes measured up to 60 d after irradiation were used to gauge overall hematopoietic acute radiation syndrome severity classifications. A panel of protein biomarkers was measured on plasma samples collected at 0 to 28 d after exposure using electrochemiluminescence-detection technology. The database was split into two distinct groups (i.e., "calibration," n = 11; "validation," n = 7). The calibration database was used in an initial stepwise regression multivariate model-fitting approach followed by down selection of biomarkers for identification of subpanels of hematopoietic acute radiation syndrome-responsive biomarkers for three time windows (i.e., 0-2 d, 2-7 d, 7-28 d). Model 1 (0-2 d) includes log C-reactive protein (p < 0.0001), log interleukin-13 (p < 0.0054), and procalcitonin (p < 0.0316) biomarkers; model 2 (2-7 d) includes log CD27 (p < 0.0001), log FMS-related tyrosine kinase 3 ligand (p < 0.0001), log serum amyloid A (p < 0.0007), and log interleukin-6 (p < 0.0002); and model 3 (7-28 d) includes log CD27 (p < 0.0012), log serum amyloid A (p < 0.0002), log erythropoietin (p < 0.0001), and log CD177 (p < 0.0001). The predicted risk of radiation injury categorization values, representing the hematopoietic acute radiation syndrome severity outcome for the three models, produced least squares multiple regression fit confidences of R = 0.73, 0.82, and 0.75, respectively. The resultant algorithms support the proof of concept that plasma proteomic biomarkers can supplement clinical signs and symptoms to assess hematopoietic acute radiation syndrome risk severity.

A Metabolomic Serum Signature from Nonhuman Primates Treated with a Radiation Countermeasure, Gamma-tocotrienol, and Exposed to Ionizing Radiation

The search for and development of radiation countermeasures to treat acute lethal radiation injury has been underway for the past six decades, resulting in the identification of multiple classes of radiation countermeasures. However, to date only granulocyte colony-stimulating factor (Neupogen) and PEGylated granulocyte colony-stimulating factor (Neulasta) have been approved by the U.S. Food and Drug Administration for the treatment of hematopoietic acute radiation syndrome. Gamma-tocotrienol has demonstrated radioprotective efficacy in murine and nonhuman primate models. Currently, this agent is under advanced development as a radioprotector, and the authors are trying to identify its efficacy biomarkers. In this study, global metabolomic changes were analyzed using ultraperformance liquid chromatography quadrupole time-of-flight mass spectrometry. The pilot study using 16 nonhuman primates (8 nonhuman primates each in gamma-tocotrienol- and vehicle-treated groups), with samples obtained from gamma-tocotrienol-treated and irradiated nonhuman primates, demonstrates several metabolites that are altered after irradiation, including compounds involved in fatty acid beta-oxidation, purine catabolism, and amino acid metabolism. The machine-learning algorithm, Random Forest, separated control, irradiated gamma-tocotrienol-treated, and irradiated vehicle-treated nonhuman primates at 12 h and 24 h as evident in a multidimensional scaling plot. Primary metabolites validated included carnitine/acylcarnitines, amino acids, creatine, and xanthine. Overall, gamma-tocotrienol administration reduced high fluctuations in serum metabolite levels, suggesting an overall beneficial effect on animals exposed to radiation. This initial assessment also highlights the utility of metabolomics in determining underlying physiological mechanisms responsible for the radioprotective efficacy of gamma-tocotrienol.

Successful Teaching of Radiobiology Students in the Medical Management of Acute Radiation Effects From Real Case Histories Using Clinical Signs and Symptoms and Taking Advantage of Recently Developed Software Tools

In 2015, the Bundeswehr Institute of Radiobiology organized a North Atlantic Treaty Organization exercise to examine the significance of clinical signs and symptoms for the prediction of late-occurring acute radiation syndrome. Cases were generated using either the Medical Treatment Protocols for Radiation Accident Victims (METREPOL, n = 167) system or using real-case descriptions extracted from a database system for evaluation and archiving of radiation accidents based on case histories (SEARCH, n = 24). The cases ranged from unexposed [response category 0 (RC 0, n = 89)] to mild (RC 1, n = 45), moderate (RC 2, n = 19), severe (RC 3, n = 20), and lethal (RC 4, n = 18) acute radiation syndrome. During the previous exercise, expert teams successfully predicted hematological acute radiation syndrome severity, determined whether hospitalization was required, and gave treatment recommendations, taking advantage of different software tools developed by the North Atlantic Treaty Organization teams. The authors provided the same data set to radiobiology students who were introduced to the medical management of acute effects after radiation exposure and the software tools during a class lasting 15 h. Corresponding to the previous results, difficulties in the discrimination between RC 0/RC 1 and RC 3/RC 4, as well as a systematic underestimation of RC 1 and RC 2, were observed. Nevertheless, after merging reported response categories into clinically relevant groups (RC 0-1, RC 2-3, and RC 3-4), it was found that the majority of cases (95.2% ± 2.2 standard deviations) were correctly identified and that 94.7% (±2.6 standard deviations) developing acute radiation syndrome and z96.4% (±1.6 standard deviations) requiring hospitalization were identified correctly. Two out of three student teams also provided a dose estimate. These results are comparable to the best-performing team of the 2015 North Atlantic Treaty Organization exercise (response category: 92.5%; acute radiation syndrome: 95.8%; hospitalization: 96.3%).

Estimating Risk of Hematopoietic Acute Radiation Syndrome in Children

Following a radiological terrorist attack or radiation accident, the general public may be exposed to radiation. Historically, modeling efforts have focused on radiation effects on a "reference man"-a 70-kg, 180-cm-tall, 20- to 30-y-old male-which does not adequately reflect radiation hazard to special populations, particularly children. This work examines the radiosensitivity of children with respect to reference man to develop a set of parameters for modeling hematopoetic acute radiation syndrome in children. This analysis was performed using animal studies and the results verified using data from medical studies. Overall, the hematopoietic system in children is much more radiosensitive than that in adults, with the LD50 for children being 56% to 91% of the LD50 of adults, depending on age.

Combined Therapy of Pegylated G-CSF and Alxn4100TPO Improves Survival and Mitigates Acute Radiation Syndrome after Whole-Body Ionizing Irradiation Alone and Followed by Wound Trauma

Exposure to ionizing radiation alone or combined with traumatic tissue injury is a crucial life-threatening factor in nuclear and radiological incidents. Radiation injuries occur at the molecular, cellular, tissue and systemic levels; their mechanisms, however, remain largely unclear. Exposure to radiation combined with skin wounding, bacterial infection or burns results in greater mortality than radiation exposure alone in dogs, pigs, rats, guinea pigs and mice. In the current study we observed that B6D2F1/J female mice exposed to 60Co gamma-photon radiation followed by 15% total-body-surface-area skin wounds experienced an increment of 25% higher mortality over a 30-day observation period compared to those subjected to radiation alone. Radiation exposure delayed wound healing by approximately 14 days. On day 30 post-injury, bone marrow and ileum in animals from both groups (radiation alone or combined injury) still displayed low cellularity and structural damage. White blood cell counts, e.g., neutrophils, lymphocytes, monocytes, eosinophils, basophils and platelets, still remained very low in surviving irradiated alone animals, whereas only the lymphocyte count was low in surviving combined injury animals. Likewise, in surviving animals from radiation alone and combined injury groups, the RBCs, hemoglobin, hematocrit and platelets remained low. We observed, that animals treated with both pegylated G-CSF (a cytokine for neutrophil maturation and mobilization) and Alxn4100TPO (a thrombopoietin receptor agonist) at 4 h postirradiation, a 95% survival (vehicle: 60%) over the 30-day period, along with mitigated body-weight loss and significantly reduced acute radiation syndrome. In animals that received combined treatment of radiation and injury that received pegylated G-CSF and Alxn4100TPO, survival was increased from 35% to 55%, but did not accelerate wound healing. Hematopoiesis and ileum showed significant improvement in animals from both groups (irradiation alone and combined injury) when treated with pegylated G-CSF and Alxn4100TPO. Treatment with pegylated G-CSF alone increased survival after irradiation alone and combined injury by 33% and 15%, respectively, and further delayed wound healing, but increased WBC, RBC and platelet counts after irradiation alone, and only RBCs and platelets after combined injury. Treatment with Alxn4100TPO alone increased survival after both irradiation alone and combined injury by 4 and 23%, respectively, and delayed wound healing after combined injury, but increased RBCs, hemoglobin concentrations, hematocrit values and platelets after irradiation alone and only platelets after combined injury. Taken together, the results suggest that combined treatment with pegylated G-CSF and Alxn4100TPO is effective for mitigating effects of both radiation alone and in combination with injury.

Acute Radiation Syndrome Severity Score System in Mouse Total-Body Irradiation Model

Radiation accidents or terrorist attacks can result in serious consequences for the civilian population and for military personnel responding to such emergencies. The early medical management situation requires quantitative indications for early initiation of cytokine therapy in individuals exposed to life-threatening radiation doses and effective triage tools for first responders in mass-casualty radiological incidents. Previously established animal (Mus musculus, Macaca mulatta) total-body irradiation (γ-exposure) models have evaluated a panel of radiation-responsive proteins that, together with peripheral blood cell counts, create a multiparametic dose-predictive algorithm with a threshold for detection of ~1 Gy from 1 to 7 d after exposure as well as demonstrate the acute radiation syndrome severity score systems created similar to the Medical Treatment Protocols for Radiation Accident Victims developed by Fliedner and colleagues. The authors present a further demonstration of the acute radiation sickness severity score system in a mouse (CD2F1, males) TBI model (1-14 Gy, Co γ-rays at 0.6 Gy min) based on multiple biodosimetric endpoints. This includes the acute radiation sickness severity Observational Grading System, survival rate, weight changes, temperature, peripheral blood cell counts and radiation-responsive protein expression profile: Flt-3 ligand, interleukin 6, granulocyte-colony stimulating factor, thrombopoietin, erythropoietin, and serum amyloid A. Results show that use of the multiple-parameter severity score system facilitates identification of animals requiring enhanced monitoring after irradiation and that proteomics are a complementary approach to conventional biodosimetry for early assessment of radiation exposure, enhancing accuracy and discrimination index for acute radiation sickness response categories and early prediction of outcome.

Mean Organ Doses Resulting From Non-Human Primate Whole Thorax Lung Irradiation Prescribed to Mid-Line Tissue

Multi-organ dose evaluations and the effects of heterogeneous tissue dose calculations have been retrospectively evaluated following irradiation to the whole thorax and lung in non-human primates (NHP). A clinical-based approach was established to evaluate actual doses received in the heart and lungs during whole thorax lung irradiation. Anatomical structure and organ densities have been introduced in the calculations to show the effects of dose distribution through heterogeneous tissue. Mean organ doses received by non-human primates undergoing whole thorax lung irradiations were calculated using a treatment planning system that is routinely used in clinical radiation oncology. The doses received by non-human primates irradiated following conventional dose calculations have been retrospectively reconstructed using computerized tomography-based, heterogeneity-corrected dose calculations. The use of dose volume descriptors for irradiation to organs at risk and tissue exposed to radiation is introduced. Mean and partial-volume doses to lung and heart are presented and contrasted. The importance of exact dose definitions is highlighted, and the relevance of precise dosimetry to establish organ-specific dose response relationships in NHP models of acute and delayed effects of acute radiation exposure is emphasized.

The H-ARS Dose Response Relationship (DRR): Validation and Variables

Manipulations of lethally-irradiated animals, such as for administration of pharmaceuticals, blood sampling, or other laboratory procedures, have the potential to induce stress effects that may negatively affect morbidity and mortality. To investigate this in a murine model of the hematopoietic acute radiation syndrome, 20 individual survival efficacy studies were grouped based on the severity of the administration (Admn) schedules of their medical countermeasure (MCM) into Admn 1 (no injections), Admn 2 (1-3 injections), or Admn 3 (29 injections or 6-9 oral gavages). Radiation doses ranged from LD30/30 to LD95/30. Thirty-day survival of vehicle controls in each group was used to construct radiation dose lethality response relationship (DRR) probit plots, which were compared statistically to the original DRR from which all LDXX/30 for the studies were obtained. The slope of the Admn 3 probit was found to be significantly steeper (5.190) than that of the original DRR (2.842) or Admn 2 (2.009), which were not significantly different. The LD50/30 for Admn 3 (8.43 Gy) was less than that of the original DRR (8.53 Gy, p < 0.050), whereas the LD50/30 of other groups were similar. Kaplan-Meier survival curves showed significantly worse survival of Admn 3 mice compared to the three other groups (p = 0.007). Taken together, these results show that stressful administration schedules of MCM can negatively impact survival and that dosing regimens should be considered when constructing DRR to use in survival studies.

Delayed Effects of Acute Radiation Exposure in a Murine Model of the H-ARS: Multiple-Organ Injury Consequent to <10 Gy Total Body Irradiation

The threat of radiation exposure from warfare or radiation accidents raises the need for appropriate animal models to study the acute and chronic effects of high dose rate radiation exposure. The goal of this study was to assess the late development of fibrosis in multiple organs (kidney, heart, and lung) in survivors of the C57BL/6 mouse model of the hematopoietic-acute radiation syndrome (H-ARS). Separate groups of mice for histological and functional studies were exposed to a single uniform total body dose between 8.53 and 8.72 Gy of gamma radiation from a Cs radiation source and studied 1-21 mo later. Blood urea nitrogen levels were elevated significantly in the irradiated mice at 9 and 21 mo (from ∼22 to 34 ± 3.8 and 69 ± 6.0 mg dL, p < 0.01 vs. non-irradiated controls) and correlated with glomerosclerosis (29 ± 1.8% vs. 64 ± 9.7% of total glomeruli, p < 0.01 vs. non-irradiated controls). Glomerular tubularization and hypertrophy and tubular atrophy were also observed at 21 mo post-total body irradiation (TBI). An increase in interstitial, perivascular, pericardial and peribronchial fibrosis/collagen deposition was observed from ∼9-21 mo post-TBI in kidney, heart, and lung of irradiated mice relative to age-matched controls. Echocardiography suggested decreased ventricular volumes with a compensatory increase in the left ventricular ejection fraction. The results indicate that significant delayed effects of acute radiation exposure occur in kidney, heart, and lung in survivors of the murine H-ARS TBI model, which mirrors pathology detected in larger species and humans at higher radiation doses focused on specific organs.