3D skin bioprinting as promising therapeutic strategy for radiation-associated skin injuries

Both cutaneous radiation injury and radiation combined injury (RCI) could have serious skin traumas, which are collectively referred to as radiation-associated skin injuries in this paper. These two types of skin injuries require special managements of wounds, and the therapeutic effects still need to be further improved. Cutaneous radiation injuries are common in both radiotherapy patients and victims of radioactive source accidents, which could lead to skin necrosis and ulcers in serious conditions. At present, there are still many challenges in management of cutaneous radiation injuries including early diagnosis, lesion assessment, and treatment prognosis. Radiation combined injuries are special and important issues in severe nuclear accidents, which often accompanied by serious skin traumas. Mass victims of RCI would be the focus of public health concern. Three-dimensional (3D) bioprinting, as a versatile and favourable technique, offers effective approaches to fabricate biomimetic architectures with bioactivity, which provides potentials for resolve the challenges in treating radiation-associated skin injuries. Combining with the cutting-edge advances in 3D skin bioprinting, the authors analyse the damage characteristics of skin wounds in both cutaneous radiation injury and RCI and look forward to the potential value of 3D skin bioprinting for the treatments of radiation-associated skin injuries.

NEAR-INFRARED DYE IR-780 ALLEVIATES HEMATOPOIETIC SYSTEM DAMAGE BY PROMOTING HEMATOPOIETIC STEM CELLS INTO QUIESCENCE

ABSTRACT

Potential radiation exposure is a general concern, but there still lacks radioprotective countermeasures. Here, we found a small molecular near-infrared dye IR-780, which promoted hematopoietic stem cells (HSCs) into quiescence to resist stress. When mice were treated with IR-780 before stress, increased HSC quiescence and better hematopoietic recovery were observed in mice in stress conditions. However, when given after radiation, IR-780 did not show obvious benefit. Transplantation assay and colony-forming assay were carried out to determine self-renewal ability and repopulation capacity of HSCs. Furthermore, IR-780 pretreatment reduced the generation of reactive oxygen species (ROS) and DNA damage in HSCs after radiation. In homeostasis, the percentage of Lineage - , Sca-1 + , and c-Kit + cells and long-term HSCs (LT-HSCs) were improved, and more HSCs were in G0 state after administration of IR-780. Further investigations showed that IR-780 selectively accumulated in mitochondria membrane potential high LT-HSCs (MMP-high LT-HSCs). Finally, IR-780 promoted human CD34 + HSC reconstruction ability in NOD-Prkdc scid Il2rg null mice after transplantation and improved repopulation capacity in vitro culture. Our research showed that IR-780 selectively entered MMP-high LT-HSCs and promoted them into dormancy, thus reducing hematopoietic injury and improving regeneration capacity. This novel approach might hold promise as a potential countermeasure for radiation injury.

Medical countermeasures for the hematopoietic-subsyndrome of acute radiation syndrome in space

More than 50 years after the Apollo missions ended, the National Aeronautical and Space Administration (NASA) and other international space agencies are preparing a return to the moon as a step towards deep space exploration. At doses ranging from a fraction of a Gray (Gy) to a few Gy, crew will be at risk for developing bone marrow failure associated with the hematopoietic subsyndrome of acute radiation syndrome (H-ARS) requiring pharmacological intervention to reduce risk to life and mission completion. Four medical countermeasures (MCM) in the colony stimulating factor class of drugs are now approved for treatment of myelosuppression associated with ARS. When taken in conjunction with antibiotics, fluids, antidiarrheals, antiemetics, antipyretics, and other treatments for symptomatic illness, the likelihood for recovery and mission completion can be greatly improved. The current review describes the performance and health risks of deep space flight, ionizing radiation exposure during crewed missions to the moon and Mars, and U.S. Food and Drug Administration (FDA)-approved medical interventions to treat ARS. With an expansion of human exploration missions beyond low Earth orbit (LEO), including near-term Lunar and future Mars missions, inclusion of MCMs to counteract ARS in the spaceflight kit will be critical for preserving crew health and performance.

Female Mice are More Resistant to the Mixed-Field (67% Neutron + 33% Gamma) Radiation-Induced Injury in Bone Marrow and Small Intestine than Male Mice due to Sustained Increases in G-CSF and the Bcl-2/Bax Ratio and Lower miR-34a and MAPK Activation

In nuclear and radiological incidents, overexposure to ionizing radiation is life-threatening. It is evident that radiation depletes blood cells and increases circulating cytokine/chemokine concentrations as well as mortality. While microglia cells of female mice have been observed to be less damaged by radiation than in male mice, it is unclear whether sex affects physio-pathological responses in the bone marrow (BM) and gastrointestinal system (GI). We exposed B6D2F1 male and female mice to 0, 1.5, 3, or 6 Gy with mixed-field radiation containing 67% neutron and 33% gamma at a dose rate of 0.6 Gy/min. Blood and tissues were collected on days 1, 4, and 7 postirradiation. Radiation increased cytokines/chemokines in the femurs and ilea of female and male mice in a dose-dependent manner. Cytokines and chemokines reached a peak on day 4 and declined on day 7 with the exception of G-CSF which continued to increase on day 7 in female mice but not in male mice. MiR-34a (a Bcl-2 inhibitor), G-CSF (a miR-34a inhibitor), MAPK activation (pro-cell death), and citrulline (a biomarker of entro-epithelial proliferation), active caspase-3 (a biomarker of apoptosis) and caspase-1activated gasdermin D (a pyroptosis biomarker) were measured in the sternum, femur BM and ileum. Sternum histopathology analysis with H&E staining and femur BM cell counts as well as Flt-3L showed that BM cellularity was not as diminished in females, with males showing a 50% greater decline on day 7 postirradiation, mainly mediated by pyroptosis as indicated by increased gasdermin D in femur BM samples. Ileum injury, such as villus height and crypt depth, was also 43% and 30%, respectively, less damaged in females than in males. The severity of injury in both sexes was consistent with the citrulline and active caspase-3 measurements as well as active caspase-1 and gasdermin D measurements, suggesting apoptosis and pyroptosis occurred. On day 7, G-CSF in the ileum of female mice continued to be elevated by sevenfold, whereas G-CSF in the ileum of male mice returned to baseline. Furthermore, G-CSF is known to inhibit miR-34a expression, which in ileum on day 1 displayed a 3- to 4-fold increase in female mice after mixed-field (67% neutron + 33% gamma) irradiation, as compared to a 5- to 9-fold increase in male mice. Moreover, miR-34a blocked Bcl-2 expression. Mixed-field (60% neutron + 33% gamma) radiation induced more Bcl-2 in females than in males. On day 7, AKT activation was found in the ileums of females and males. However, MAPK activation including ERK, JNK, and p38 showed no changes in the ileum of females (by 0-fold; P > 0.05), whereas the MAPK activation was increased in the ileum of males (by 100-fold; P < 0.05). Taken together, the results suggest that organ injury from mixed-field (67% neutron + 33% gamma) radiation is less severe in females than in males, likely due to increased G-CSF, less MAPK activation, low miR-34a and increased Bcl-2/Bax ratio.

Small Molecule Responses to Sequential Irradiation with Neutrons and Photons for Biodosimetry Applications: An Initial Assessment

Mass casualty exposure scenarios from an improvised nuclear device are expected to be far more complex than simple photons. Based on the proximity to the explosion and potential shielding, a mixed field of neutrons and photons comprised of up to approximately 30% neutrons of the total dose is anticipated. This presents significant challenges for biodosimetry and for short-term and long-term medical treatment of exposed populations. In this study we employed untargeted metabolomic methods to develop a biosignature in urine and serum from C57BL/6 mice to address radiation quality issues. The signature was developed in males and applied to samples from female mice to identify potential sex differences. Thirteen urinary (primarily amino acids, vitamin products, nucleotides) and 18 serum biomarkers (primarily mitochondrial and fatty acid β oxidation intermediates) were selected and evaluated in samples from day 1 and day 7 postirradiation. Sham-irradiated groups (controls) were compared to an equitoxic dose (3 Gy X-ray equivalent) from X rays (1.2 Gy/min), neutrons (∼1 Gy/h), or neutrons-photons. Results showed a time-dependent increase in the efficiency of the signatures, with serum providing the highest levels of accuracy in distinguishing not only between exposed from non-exposed populations, but also between radiation quality (photon exposures vs. exposures with a neutron component) and in between neutron-photon exposures (5, 15 or 25% of neutrons in the total dose) for evaluating the neutron contribution. A group of metabolites known as acylcarnitines was only responsive in males, indicating the potential for different mechanisms of action in baseline levels and of neutron-photon responses between the two sexes. Our findings highlight the potential of metabolomics in developing biodosimetric methods to evaluate mixed exposures with high sensitivity and specificity.

Cytogenetic Damage of Human Lymphocytes in Humanized Mice Exposed to Neutrons and X Rays 24 h After Exposure

Detonation of an improvised nuclear device highlights the need to understand the risk of mixed radiation exposure as prompt radiation exposure could produce significant neutron and gamma exposures. Although the neutron component may be a relatively small percentage of the total absorbed dose, the large relative biological effectiveness (RBE) can induce larger biological DNA damage and cell killing. The objective of this study was to use a hematopoietically humanized mouse model to measure chromosomal DNA damage in human lymphocytes 24 h after in vivo exposure to neutrons (0.3 Gy) and X rays (1 Gy). The human dicentric and cytokinesis-block micronucleus assays were performed to measure chromosomal aberrations in human lymphocytes in vivo from the blood and spleen, respectively. The mBAND assay based on fluorescent in situ hybridization labeling was used to detect neutron-induced chromosome 1 inversions in the blood lymphocytes of the neutron-irradiated mice. Cytogenetics endpoints, dicentrics and micronuclei showed that there was no significant difference in yields between the 2 irradiation types at the doses tested, indicating that neutron-induced chromosomal DNA damage in vivo was more biologically effective (RBE ∼3.3) compared to X rays. The mBAND assay, which is considered a specific biomarker of high-LET neutron exposure, confirmed the presence of clustered DNA damage in the neutron-irradiated mice but not in the X-irradiated mice, 24 h after exposure.

Radiation countermeasures for hematopoietic acute radiation syndrome: growth factors, cytokines and beyond

PURPOSE

The intent of this article is to report the status of some of the pharmaceuticals currently in late stage development for possible use for individuals unwantedly and acutely injured as a result of radiological/nuclear exposures. The two major questions we attempt to address here are: (a) What medicinals are currently deemed by regulatory authorities (US FDA) to be safe and effective and are being stockpiled? (b) What additional agents might be needed to make the federal/state/local medicinal repositories more robust and useful in effectively managing contingencies involving radiation overexposures?

CONCLUSIONS

A limited number (precisely four) of medicinals have been deemed safe and effective, and are approved by the US FDA for the 'hematopoietic acute radiation syndrome (H-ARS).' These agents are largely recombinant growth factors (e.g. rhuG-CSF/filgrastim, rhuGM-CSF/sargramostim) that target and stimulate myeloid progenitors within bone marrow. Romiplostim, a small molecular agonist that enhances platelet production via stimulation of bone marrow megakaryocytes, has been recently approved and indicated for H-ARS. It is critical that additional agents for other major sub-syndromes of ARS (gastrointestinal-ARS) be approved. Future success in developing such medicinals will undoubtedly entail some form of a polypharmaceutical strategy, or perhaps novel, bioengineered chimeric agents with multiple, radioprotective/radiomitigative functionalities.

Neutron Radiobiology and Dosimetry

As the U.S. prepares for the possibility of a radiological or nuclear incident, or anticipated lunar and Mars missions, the exposure of individuals to neutron radiation must be considered. More information is needed on how to determine the neutron dose to better estimate the true biological effects of neutrons and mixed-field (i.e., neutron and photon) radiation exposures. While exposure to gamma-ray radiation will cause significant health issues, the addition of neutrons will likely exacerbate the biological effects already anticipated after radiation exposure. To begin to understand the issues and knowledge gaps in these areas, the National Institute of Allergy and Infectious Diseases (NIAID), Radiation Nuclear Countermeasures Program (RNCP), Department of Defense (DoD), Defense Threat Reduction Agency (DTRA), and National Aeronautics and Space Administration (NASA) formed an inter-agency working group to host a Neutron Radiobiology and Dosimetry Workshop on March 7, 2019 in Rockville, MD. Stakeholder interests were clearly positioned, given the differences in the missions of each agency. An overview of neutron dosimetry and neutron radiobiology was included, as well as a historical overview of neutron exposure research. In addition, current research in the fields of biodosimetry and diagnostics, medical countermeasures (MCMs) and treatment, long-term health effects, and computational studies were presented and discussed.

Celebrating 60 Years of Accomplishments of the Armed Forces Radiobiology Research Institute1

Chartered by the U.S. Congress in 1961, the Armed Forces Radiobiology Research Institute (AFRRI) is a Joint Department of Defense (DoD) entity with the mission of carrying out the Medical Radiological Defense Research Program in support of our military forces around the globe. In the last 60 years, the investigators at AFRRI have conducted exploratory and developmental research with broad application to the field of radiation sciences. As the only DoD facility dedicated to radiation research, AFRRI's Medical Radiobiology Advisory Team provides deployable medical and radiobiological subject matter expertise, advising commanders in the response to a U.S. nuclear weapon incident and other nuclear or radiological material incidents. AFRRI received the DoD Joint Meritorious Unit Award on February 17, 2004, for its exceptionally meritorious achievements from September 11, 2001 to June 20, 2003, in response to acts of terrorism and nuclear/radiological threats at home and abroad. In August 2009, the American Nuclear Society designated the institute a nuclear historic landmark as the U.S.'s primary source of medical nuclear and radiological research, preparedness and training. Since then, research has continued, and core areas of study include prevention, assessment and treatment of radiological injuries that may occur from exposure to a wide range of doses (low to high). AFRRI collaborates with other government entities, academic institutions, civilian laboratories and other countries to research the biological effects of ionizing radiation. Notable early research contributions were the establishment of dose limits for major acute radiation syndromes in primates, applicable to human exposures, followed by the subsequent evolution of radiobiology concepts, particularly the importance of immune collapse and combined injury. In this century, the program has been essential in the development and validation of prophylactic and therapeutic drugs, such as Amifostine, Neupogen®, Neulasta®, Nplate® and Leukine®, all of which are used to prevent and treat radiation injuries. Moreover, AFRRI has helped develop rapid, high-precision, biodosimetry tools ranging from novel assays to software decision support. New drug candidates and biological dose assessment technologies are currently being developed. Such efforts are supported by unique and unmatched radiation sources and generators that allow for comprehensive analyses across the various types and qualities of radiation. These include but are not limited to both 60Co facilities, a TRIGA® reactor providing variable mixed neutron and γ-ray fields, a clinical linear accelerator, and a small animal radiation research platform with low-energy photons. There are five major research areas at AFRRI that encompass the prevention, assessment and treatment of injuries resulting from the effects of ionizing radiation: 1. biodosimetry; 2. low-level and low-dose-rate radiation; 3. internal contamination and metal toxicity; 4. radiation combined injury; and 5. radiation medical countermeasures. These research areas are bolstered by an educational component to broadcast and increase awareness of the medical effects of ionizing radiation, in the mass-casualty scenario after a nuclear detonation or radiological accidents. This work provides a description of the military medical operations as well as the radiation facilities and capabilities present at AFRRI, followed by a review and discussion of each of the research areas.

Repurposing Pharmaceuticals Previously Approved by Regulatory Agencies to Medically Counter Injuries Arising Either Early or Late Following Radiation Exposure

The increasing risks of radiological or nuclear attacks or associated accidents have served to renew interest in developing radiation medical countermeasures. The development of prospective countermeasures and the subsequent gain of Food and Drug Administration (FDA) approval are invariably time consuming and expensive processes, especially in terms of generating essential human data. Due to the limited resources for drug development and the need for expedited drug approval, drug developers have turned, in part, to the strategy of repurposing agents for which safety and clinical data are already available. Approval of drugs that are already in clinical use for one indication and are being repurposed for another indication is inherently faster and more cost effective than for new agents that lack regulatory approval of any sort. There are four known growth factors which have been repurposed in the recent past as radiomitigators following the FDA Animal Rule: Neupogen, Neulasta, Leukine, and Nplate. These four drugs were in clinic for several decades for other indications and were repurposed. A large number of additional agents approved by various regulatory authorities for given indications are currently under investigation for dual use for acute radiation syndrome or for delayed pathological effects of acute radiation exposure. The process of drug repurposing, however, is not without its own set of challenges and limitations.

A High Throughput Approach to Reconstruct Partial-Body and Neutron Radiation Exposures on an Individual Basis

Biodosimetry-based individualized reconstruction of complex irradiation scenarios (partial-body shielding and/or neutron + photon mixtures) can improve treatment decisions after mass-casualty radiation-related incidents. We used a high-throughput micronucleus assay with automated scanning and imaging software on ex-vivo irradiated human lymphocytes to: a) reconstruct partial-body and/or neutron exposure, and b) estimate separately the photon and neutron doses in a mixed exposure. The mechanistic background is that, compared with total-body photon irradiations, neutrons produce more heavily-damaged lymphocytes with multiple micronuclei/binucleated cell, whereas partial-body exposures produce fewer such lymphocytes. To utilize these differences for biodosimetry, we developed metrics that describe micronuclei distributions in binucleated cells and serve as predictors in machine learning or parametric analyses of the following scenarios: (A) Homogeneous gamma-irradiation, mimicking total-body exposures, vs. mixtures of irradiated blood with unirradiated blood, mimicking partial-body exposures. (B) X rays vs. various neutron + photon mixtures. The results showed high accuracies of scenario and dose reconstructions. Specifically, receiver operating characteristic curve areas (AUC) for sample classification by exposure type reached 0.931 and 0.916 in scenarios A and B, respectively. R² for actual vs. reconstructed doses in these scenarios reached 0.87 and 0.77, respectively. These encouraging findings demonstrate a proof-of-principle for the proposed approach of high-throughput reconstruction of clinically-relevant complex radiation exposure scenarios.

Pharmacological management of ionizing radiation injuries: current and prospective agents and targeted organ systems

Introduction: There is a limited array of currently available medicinals that are useful for either the prevention, mitigation or treatment of bodily injuries arising from ionizing radiation exposure.Area covered: In this brief article, the authors review those pharmacologic agents that either are currently being used to counter the injurious effects of radiation exposure, or those that show promise and are currently under development.Expert opinion: Although significant, but limited progress has been made in the development and fielding of safe and effective pharmacotherapeutics for select types of acute radiation-associated injuries, additional effort is needed to broaden the scope of drug development so that overall health risks associated with both short- and long-term injuries in various organ systems can be reduced and effectively managed. There are several promising radiation countermeasures that may gain regulatory approval from the government in the near future for use in clinical settings and in the aftermath of nuclear/radiological exposure contingencies.

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.

Use of Growth Factors and Other Cytokines for Treatment of Injuries During a Radiation Public Health Emergency

Due to the threat of a radiological or nuclear incident that could impact citizens, the U.S. Department of Health and Human Services tasked the National Institute of Allergy and Infectious Diseases (NIAID) with identifying and funding early- to mid-stage medical countermeasure (MCM) development to treat radiation-induced injuries. Given that the body's natural response to radiation exposure includes production of growth factors and cytokines, and that the only drugs approved by the U.S. Food and Drug Administration to treat acute radiation syndrome are growth factors targeting either the granulocyte (Neupogen^® or Neulasta^®) or granulocyte and macrophage (Leukine^®) hematopoietic cell lineages, there is interest in understanding the role that these factors play in responding to and/or ameliorating radiation damage. Furthermore, in an environment where resources are scarce, such as what might be expected during a radiation public health emergency, availability of growth factor or other treatments may be limited. For these reasons, the NIAID partnered with the Radiation Injury Treatment Network (RITN), whose membership includes medical centers with expertise in the management of bone marrow failure, to explore the use of growth factors and other cytokines as MCMs to mitigate/treat radiation injuries. A workshop was convened that included government, industry and academic subject matter experts, with presentations covering the anticipated concept of operations during a mass casualty incident including triage and treatment, growth factors under development for a radiation indication, and how the practice of medicine can inform other potential approaches, as well as considerations for administration of these products to diverse civilian populations. This report reviews the information presented, and provides an overview of the discussions from a guided breakout session.

Serum lipidomic analysis from mixed neutron/X-ray radiation fields reveals a hyperlipidemic and pro-inflammatory phenotype

Heightened threats for nuclear terrorism using improvised nuclear devices (IND) necessitate the development of biodosimetry assays that could rapidly assess thousands of individuals. However, the radiation exposures from an IND may be complex due to mixed fields of neutrons and photons (γ-rays), shielding from buildings, and proximity to the epicenter among others. In this study we utilized lipidomics to analyze serum samples from mice exposed to various percentages of neutrons and X-rays to a total dose of 3 Gy. Triacylglycerides, phosphatidylserines, lysophosphatidylethanolamines, lysophosphatidylcholines (LPCs), sphingolipids, and cholesteryl esters all showed delayed increases at day 7 compared to day 1 after irradiation, while diacylglycerides decreased in mixed field exposures and phosphatidylcholines (PCs) remained largely unchanged. Individual lipid molecules with a high degree of unsaturation exhibited the highest fold changes in mixed fields compared to photons alone. More importantly, the increased ratio of LPCs to PCs of each irradiation group compared to control could be used as a radiation biomarker and highlights the existence of a pro-inflammatory phenotype. The results showed that even a small percentage of neutrons in a mixed field can lead to high biological responses with implications for accurate biodosimetry, triage and medical managements of exposed populations.

Neutrons are forever! Historical perspectives

Purpose: Neutrons were an active field of radiobiology at the time of publication of the first issues of the International Journal of Radiation Biology in 1959. Three back-to-back papers published by Neary and his colleagues contain key elements of interest at the time. The present article aims to put these papers into context with the discovery of the neutron 27 years previously and then give a feel for how the field has progressed to the present day. It does not intend to provide a comprehensive review of this enormous field, but rather to provide selective summaries of main driving forces and developments. Conclusions: Neutron radiobiology has continued as a vigorous field of study throughout the past 84 years. Main driving forces have included concern for protection from the harmful effects of neutrons, exploitation and optimization for cancer therapy (fast beam therapy, brachytherapy and boron capture therapy), and scientific curiosity about the mechanisms of radiation action. Effort has fluctuated as the emphasis has shifted from time to time, but all three areas remain active today. Whatever the future holds for the various types of neutron therapy, the health protection aspects will remain with us permanently because of natural environmental exposure to neutrons as well as increased additional exposures from a variety of human activities.

Biomarkers for Radiation Biodosimetry and Injury Assessment after Mixed-field (Neutron and Gamma) Radiation in the Mouse Total-body Irradiation Model

The risk of potential radiation exposure scenarios that include detonation of nuclear weapons, terrorist attacks on nuclear reactors, and the use of conventional explosives to disperse radioactive substances has increased in recent years. The majority of radiation biodosimetry and countermeasure studies have been performed using photon radiation even though many exposure scenarios predict mixed-field (neutron and photon) radiation. Hence, there is a need to evaluate biomarkers and accurately determine exposure levels of mixed-field combinations of neutrons and photons for an individual. These biomarkers will be critical for biodosimetry triage, treatment, and follow-up visits with such individuals. We evaluated the utility of multiple blood biomarkers for early response assessment of radiation exposure using a mouse (B6D2F1, males and females) total-body irradiation model exposed to a mixed-field (neutrons and gamma rays) using the Armed Forces Radiobiology Research Institute's Mark F nuclear research reactor. Total-body irradiation was given as a single exposure over a dose range from 1.5 to 6 Gy, dose rates of 0.6 and 1.9 Gy min, and different proportions of neutrons and gammas: either (67% neutrons + 33% gammas) or (30% neutrons + 70% gammas). Blood was collected 1, 2, 4, and 7 d after total-body irradiation. Radiation-responsive protein biomarkers were measured using the Meso Scale Diagnostics' high-throughput MULTI-ARRAY plate-format platform (QuickPlex 120 Imager) and enzyme-linked immunosorbent assay kits. Results demonstrate (1) dose- and time-dependent changes in fms-related tyrosine kinase 3 ligand, interleukins IL-5, IL-10, IL-12, and IL-18, granulocyte and granulocyte-macrophage colony-stimulating factors, thrombopoietin, erythropoietin, acute-phase proteins (serum amyloid A and lipopolysaccharide binding protein), surface plasma neutrophil (CD45) and lymphocyte (CD27) markers, ratio of CD45 to CD27, and procalcitonin; (2) dose- and time-dependent changes in blood cell counts (lymphocytes, neutrophils, platelets, red blood cells, and ratio of neutrophils to lymphocytes); (3) levels of IL-18, granulocyte and granulocyte-macrophage colony-stimulating factors, serum amyloid A, and procalcitonin were significantly higher in animals irradiated with 67% neutrons + 33% gammas compared to those irradiated with 30% neutrons + 70% gammas (p < 0.015), while no significant differences (p > 0.114) were observed in hematological biomarker counts; (4) exposure with 3-fold difference in dose rate (0.6 or 1.9 Gy min) revealed no significant differences in hematological and protein biomarker levels (p > 0.154); and (5) no significant differences in hematological and protein biomarker levels were observed in the sex-comparison study for any radiation dose at any time after exposure (p > 0.088). Results show that the dynamic changes in the levels of selected hematopoietic cytokines, organ-specific biomarkers, and acute-phase protein biomarkers reflect the time course and severity of acute radiation syndrome and may function as prognostic indicators of acute radiation syndrome outcome. These studies supplement an ongoing effort to deliver U.S. Federal Drug Administration-approved biodosimetry capabilities, which assess mixed-field radiation exposure.

Comparison of Biodosimetry Biomarkers for Radiation Dose and Injury Assessment After Mixed-Field (Neutron and Gamma) and Pure Gamma Radiation in the Mouse Total-Body Irradiation Model

The detonation of a nuclear weapon and the occurrence of a nuclear accident represent possible mass-casualty events with significant exposure to mixed neutron and gamma radiation fields in the first few minutes after the event with the ensuing fallout, extending for miles from the epicenter, that would result primarily in photon (gamma- and/or x-ray) exposure. Circulating biomarkers represent a crucial source of information in a mass-casualty radiation exposure triage scenario. We evaluated multiple blood biodosimetry and organ-specific biomarkers for early-response assessment of radiation exposure using a mouse (B6D2F1, males and females) total-body irradiation model exposed to Co gamma rays over a broad dose range (3-12 Gy) and dose rates of either 0.6 or 1.9 Gy min and compared the results with those obtained after exposure of mice to a mixed field (neutrons and gamma rays) using the Armed Forces Radiobiology Research Institute Co gamma-ray source and TRIGA Mark F nuclear research reactor. The mixed-field studies were performed previously over a broad dose range (1.5-6 Gy), with dose rates of either 0.6 or 1.9 Gy min, and using different proportions of neutrons and gammas: either (67% neutrons + 33% gammas) or (30% neutrons + 70% gammas). Blood was collected 1, 2, 4, and 7 d after total-body irradiation. Results from Co gamma-ray studies demonstrate: (1) significant dose- and time-dependent reductions in circulating mature hematopoietic cells; (2) dose- and time-dependent changes in fms-related tyrosine kinase 3 ligand, interleukins IL-5, IL-10, IL-12, and IL-18, granulocyte colony-stimulating factors, thrombopoietin, erythropoietin, acute-phase proteins (serum amyloid A and lipopolysaccharide binding protein), surface plasma neutrophil (CD45) and lymphocyte (CD27) markers, ratio of CD45 to CD27, procalcitonin but not in intestinal fatty acid binding protein; (3) no significant differences were observed between dose-rate groups in hematological and protein profiles (fms-related tyrosine kinase 3 ligand, IL-5, IL-12, IL-18, erythropoietin, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, CD27, CD45, and ratio of CD45 to CD27) for any radiation dose at any time after exposure (p > 0.148); (4) no significant differences were observed between sex groups in hematological and protein profiles (fms-related tyrosine kinase 3 ligand, IL-18, erythropoietin, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, serum amyloid A, CD45) for any radiation dose at any time after exposure (p > 0.114); and (5) PCT level significantly increased (p < 0.008) in mice irradiated with 12 Gy on day 7 post-total-body irradiation without significant differences between groups irradiated at dose rates of either 0.6 or 1.9 Gy min (p > 0.287). Radiation-quality comparison results demonstrate that: (1) equivalent doses of pure gamma rays and mixed-field radiation do not produce equivalent biological effects, and hematopoietic syndrome occurs at lower doses of mixed-field radiation; (2) ratios of hematological and protein biomarker means in the Co study compared to mixed-field studies using 2× Co doses vs. 1× TRIGA radiation doses (i.e., 3 Gy Co vs. 1.5 Gy TRIGA) ranged from roughly 0.2 to as high as 26.5 but 57% of all ratios fell within 0.7 and 1.3; and (3) in general, biomarker results are in agreement with the relative biological effectiveness = 1.95 (Dn/Dt = 0.67) reported earlier by Armed Forces Radiobiology Research Institute scientists in mouse survival countermeasure studies.

Identification of differentially expressed genes and pathways in mice exposed to mixed field neutron/photon radiation

Background

Radiation exposure due to the detonation of an improvised nuclear device remains a major security concern. Radiation from such a device involves a combination of photons and neutrons. Although photons will make the greater contribution to the total dose, neutrons will certainly have an impact on the severity of the exposure as they have high relative biological effectiveness.

Results

We investigated the gene expression signatures in the blood of mice exposed to 3 Gy x-rays, 0.75 Gy of neutrons, or to mixed field photon/neutron with the neutron fraction contributing 5, 15%, or 25% of a total 3 Gy radiation dose. Gene ontology and pathway analysis revealed that genes involved in protein ubiquitination pathways were significantly overrepresented in all radiation doses and qualities. On the other hand, eukaryotic initiation factor 2 (EIF2) signaling pathway was identified as one of the top 10 ranked canonical pathways in neutron, but not pure x-ray, exposures. In addition, the related mTOR and regulation of EIF4/p70S6K pathways were also significantly underrepresented in the exposures with a neutron component, but not in x-ray radiation. The majority of the changed genes in these pathways belonged to the ribosome biogenesis and translation machinery and included several translation initiation factors (e.g. Eif2ak4, Eif3f), as well as 40S and 60S ribosomal subunits (e.g. Rsp19, Rpl19, Rpl27). Many of the differentially downregulated ribosomal genes (e.g. RPS19, RPS28) have been causally associated with human bone marrow failure syndromes and hematologic malignancies. We also observed downregulation of transfer RNA processes, in the neutron-only exposure (p < 0.005). Ingenuity Pathway Analysis (p < 0.05) of differentially expressed genes predicted significantly suppressed activity of the upstream regulators c-Myc and Mycn, transcription factors known to control ribosome biogenesis.

Conclusions

We describe the gene expression profile of mouse blood following exposure to mixed field neutron/photon irradiation. We have discovered that pathways related to protein translation are significantly underrepresented in the exposures containing a neutron component. Our results highlight the significance of neutron exposures that even the smallest percentage can have profound biological effects that will affect medical management and treatment decisions in case of a radiological emergency.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4884-6) contains supplementary material, which is available to authorized users.

Novel Indications for Commonly Used Medications as Radiation Protectants in Spaceflight

BACKGROUND

In the space environment, the traditional radioprotective principles of time, distance, and shielding become difficult to implement. Additionally, the complex radiation environment inherent in space, the chronic exposure timeframe, and the presence of numerous confounding variables complicate the process of creating appropriate risk models for astronaut exposure. Pharmaceutical options hold tremendous promise to attenuate acute and late effects of radiation exposure in the astronaut population. Pharmaceuticals currently approved for other indications may also offer radiation protection, modulation, or mitigation properties along with a well-established safety profile. Currently there are only three agents which have been clinically approved to be employed for radiation exposure, and these only for very narrow indications. This review identifies a number of agents currently approved by the U.S. Food and Drug Administration (FDA) which could warrant further investigation for use in astronauts. Specifically, we examine preclinical and clinical evidence for statins, nonsteroidal anti-inflammatory drugs (NSAIDs), angiotensin converting enzyme inhibitors (ACEIs), angiotensin II receptor blockers (ARBs), metformin, calcium channel blockers, β adrenergic receptor blockers, fingolimod, N-acetylcysteine, and pentoxifylline as potential radiation countermeasures.McLaughlin MF, Donoviel DB, Jones JA. Novel indications for commonly used medications as radiation protectants in spaceflight. Aerosp Med Hum Perform. 2017; 88(7):665-676.

A review of radiation countermeasures focusing on injury-specific medicinals and regulatory approval status: part III. Countermeasures under early stages of development along with 'standard of care' medicinal and procedures not requiring regulatory approval for use

PURPOSE

Terrorist attacks, with their intent to maximize psychological and economic damage as well as inflicting sickness and death on given targeted populations, are an ever-growing worldwide concern in government and public sectors as they become more frequent, violent, and sensational. If given the chance, it is likely that terrorists will use radiological or nuclear weapons. To thwart these sinister efforts, both physical and medical countermeasures against these weapons are currently being researched and developed so that they can be utilized by the first responders, military, and medical providers alike. This is the third article of a three-part series in which we have reviewed additional radiation countermeasures that are currently under early preclinical phases of development using largely animal models and have listed and discussed clinical support measures, including agents used for radiation-induced emesis, as well as countermeasures not requiring Food and Drug Administration approval.

CONCLUSIONS

Despite the significant progress that has been made in this area during the last several years, additional effort is needed in order to push promising new agents, currently under development, through the regulatory pipeline. This pipeline for new promising drugs appears to be unreasonably slow and cumbersome; possible reasons for this inefficiency are briefly discussed. Significant and continued effort needs to be afforded to this research and development area, as to date, there is no approved radioprotector that can be administered prior to high dose radiation exposure. This represents a very significant, unmet medical need and a significant security issue. A large number of agents with potential to interact with different biological targets are under development. In the next few years, several additional radiation countermeasures will likely receive Food and Drug Administration approval, increasing treatment options for victims exposed to unwanted ionizing irradiation.

A review of radiation countermeasures focusing on injury-specific medicinals and regulatory approval status: part I. Radiation sub-syndromes, animal models and FDA-approved countermeasures

PURPOSE

The increasing global risk of nuclear and radiological accidents or attacks has driven renewed research interest in developing medical countermeasures to potentially injurious exposures to acute irradiation. Clinical symptoms and signs of a developing acute radiation injury, i.e. the acute radiation syndrome, are grouped into three sub-syndromes named after the dominant organ system affected, namely the hematopoietic, gastrointestinal, and neurovascular systems. The availability of safe and effective countermeasures against the above threats currently represents a significant unmet medical need. This is the first article within a three-part series covering the nature of the radiation sub-syndromes, various animal models for radiation countermeasure development, and the agents currently approved by the United States Food and Drug Administration for countering the medical consequences of several of these prominent radiation exposure-associated syndromes.

CONCLUSIONS

From the U.S. and global perspectives, biomedical research concerning medical countermeasure development is quite robust, largely due to increased government funding following the 9/11 incidence and subsequent rise of terrorist-associated threats. A wide spectrum of radiation countermeasures for specific types of radiation injuries is currently under investigation. However, only a few radiation countermeasures have been fully approved by regulatory agencies for human use during radiological/nuclear contingencies. Additional research effort, with additional funding, clearly will be needed in order to fill this significant, unmet medical health problem.

Modeling Hematopoiesis and Responses to Radiation Countermeasures in a Bone Marrow-on-a-Chip

Studies on hematopoiesis currently rely on animal models because in vitro culture methods do not accurately recapitulate complex bone marrow physiology. We recently described a bone marrow-on-a-chip microfluidic device that enables the culture of living hematopoietic bone marrow and mimics radiation toxicity in vitro. In the present study, we used this microdevice to demonstrate continuous blood cell production in vitro and model bone marrow responses to potential radiation countermeasure drugs. The device maintained mouse hematopoietic stem and progenitor cells in normal proportions for at least 2 weeks in culture. Increases in the number of leukocytes and red blood cells into the microfluidic circulation also could be detected over time, and addition of erythropoietin induced a significant increase in erythrocyte production. Exposure of the bone marrow chip to gamma radiation resulted in reduction of leukocyte production, and treatment of the chips with two potential therapeutics, granulocyte-colony stimulating factor or bactericidal/permeability-increasing protein (BPI), induced significant increases in the number of hematopoietic stem cells and myeloid cells in the fluidic outflow. In contrast, BPI was not found to have any effect when analyzed using static marrow cultures, even though it has been previously shown to accelerate recovery from radiation-induced toxicity in vivo. These findings demonstrate the potential value of the bone marrow-on-a-chip for modeling blood cell production, monitoring responses to hematopoiesis-modulating drugs, and testing radiation countermeasures in vitro.

Colony-stimulating factors for the treatment of the hematopoietic component of the acute radiation syndrome (H-ARS): a review

One of the greatest national security threats to the United States is the detonation of an improvised nuclear device or a radiological dispersal device in a heavily populated area. As such, this type of security threat is considered to be of relatively low risk, but one that would have an extraordinary high impact on health and well-being of the US citizenry. Psychological counseling and medical assessments would be necessary for all those significantly impacted by the nuclear/radiological event. Direct medical interventions would be necessary for all those individuals who had received substantial radiation exposures (e.g., >1 Gy). Although no drugs or products have yet been specifically approved by the United States Food and Drug Administration (US FDA) to treat the effects of acute radiation syndrome (ARS), granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), and pegylated G-CSF have been used off label for treating radiation accident victims. Recent threats of terrorist attacks using nuclear or radiologic devices makes it imperative that the medical community have up-to-date information and a clear understanding of treatment protocols using therapeutically effective recombinant growth factors and cytokines such as G-CSF and GM-CSF for patients exposed to injurious doses of ionizing radiation. Based on limited human studies with underlying biology, we see that the recombinants, G-CSF and GM-CSF appear to have modest, but significant medicinal value in treating radiation accident victims. In the near future, the US FDA may approve G-CSF and GM-CSF as ‘Emergency Use Authorization’ (EUA) for managing radiation-induced aplasia, an ARS-related pathology. In this article, we review the status of growth factors for the treatment of radiological/nuclear accident victims.

Galactic cosmic ray simulation at the NASA Space Radiation Laboratory

Most accelerator-based space radiation experiments have been performed with single ion beams at fixed energies. However, the space radiation environment consists of a wide variety of ion species with a continuous range of energies. Due to recent developments in beam switching technology implemented at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL), it is now possible to rapidly switch ion species and energies, allowing for the possibility to more realistically simulate the actual radiation environment found in space. The present paper discusses a variety of issues related to implementation of galactic cosmic ray (GCR) simulation at NSRL, especially for experiments in radiobiology. Advantages and disadvantages of different approaches to developing a GCR simulator are presented. In addition, issues common to both GCR simulation and single beam experiments are compared to issues unique to GCR simulation studies. A set of conclusions is presented as well as a discussion of the technical implementation of GCR simulation.

Radiation countermeasure agents: an update (2011-2014)

INTRODUCTION

Despite significant scientific advances over the past 60 years towards the development of a safe, nontoxic and effective radiation countermeasure for the acute radiation syndrome (ARS), no drug has been approved by the US FDA. A radiation countermeasure to protect the population at large from the effects of lethal radiation exposure remains a significant unmet medical need of the US citizenry and, thus, has been recognized as a high priority area by the government.

AREA COVERED

This article reviews relevant publications and patents for recent developments and progress for potential ARS treatments in the area of radiation countermeasures. Emphasis is placed on the advanced development of existing agents since 2011 and new agents identified as radiation countermeasure for ARS during this period.

EXPERT OPINION

A number of promising radiation countermeasures are currently under development, seven of which have received US FDA investigational new drug status for clinical investigation. Four of these agents, CBLB502, Ex-RAD, HemaMax and OrbeShield, are progressing with large animal studies and clinical trials. G-CSF has high potential and well-documented therapeutic effects in countering myelosuppression and may receive full licensing approval by the US FDA in the future.

Radioprotective effects of dragon's blood and its extracts on radiation-induced myelosuppressive mice

ETHNOPHARMACOLOGICAL RELEVANCE

Dragon׳s blood, a traditional Chinese herb, has been used to "panacea of blood activating" and its major biological activity appears to be from phenolic compounds. In this study, our research aims to examine the effects of Dragon׳s blood (DB) and its extracts (DBE) on radiation-induced myelosuppressive mice.

MATERIALS AND METHODS

Adult BALB/C mice were exposed to the whole body irradiation with 4 Gy (60)Co γ-rays. DB and DBE were respectively administered orally for 5 constitutive days prior to irradiation treatment. The radioprotective effects and relevant mechanisms of DB and DBE in radiation-induced bone marrow injury were investigated by ex vivo examination.

RESULTS

We found that the administration of DB and DBE significantly increased the numbers of peripheral blood cells and colony forming unit of bone marrow-derived stem/progenitor cells. Interestingly, compared with the irradiation group, the administration of DB and DBE significantly decreased the levels of the inflammatory cytokines such as IL-6, TNF-α and IFN-γ and oxidative stress injury such as SOD, CAT, GSH, MDA in serum of mice. Furthermore, DBE markedly improved the morphology of bone marrow histopathology.

CONCLUSIONS

Our data suggest that DB and DBE effectively attenuate radiation-induced damage in bone marrow, which is likely associated with the anti-oxidative and anti-inflammatory properties of DB and DBE.

Overview of use of G-CSF and GM-CSF in the treatment of acute radiation injury

Depression of hematopoietic elements due to significant levels of whole-body or partial-body irradiation due to radiation-induced suppression of mitosis in the stem and progenitor cells can result in life-threatening injury. Successful administration of intensive care of patients experiencing acute radiation sickness (ARS; also called acute radiation syndrome) is dependent upon the ability to stimulate the recovery of surviving hematopoietic stem cells (HSC), assuming the non-hematopoietic injuries are also survivable with treatment. To date, there have been a number of studies involving radiation accidents where patients were treated with cytokines. Although the data overall seem to indicate that the period of neutropenia is shortened and survival prolonged, so far there is no statistically significant proof that cytokine administration actually decreases mortality in radiation-injured humans. Some studies have shown no improved survival when used in a mouse model; however, studies in canines and primates have shown improved survival. CSF therapy is considered a valuable adjunct to treatment with antibiotics and strict hygiene controls in certain irradiated patients. It appears that these drugs do shorten the periods of neutropenia in irradiated patients and must be considered part of the therapeutic armamentarium in the treatment of ARS in a mass casualty situation. Based on review of the human experience with G-CSF and GM-CSF, as well as some animal studies, current consensus opinions support the prompt administration of these materials to patients suffering significant bone marrow depression from exposure to ionizing radiation.

Bone marrow-on-a-chip replicates hematopoietic niche physiology in vitro

Current in vitro hematopoiesis models fail to demonstrate the cellular diversity and complex functions of living bone marrow; hence, most translational studies relevant to the hematologic system are conducted in live animals. Here we describe a method for fabricating 'bone marrow-on-a-chip' that permits culture of living marrow with a functional hematopoietic niche in vitro by first engineering new bone in vivo, removing it whole and perfusing it with culture medium in a microfluidic device. The engineered bone marrow (eBM) retains hematopoietic stem and progenitor cells in normal in vivo-like proportions for at least 1 week in culture. eBM models organ-level marrow toxicity responses and protective effects of radiation countermeasure drugs, whereas conventional bone marrow culture methods do not. This biomimetic microdevice offers a new approach for analysis of drug responses and toxicities in bone marrow as well as for study of hematopoiesis and hematologic diseases in vitro.