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

Exosomes: A new perspective for radiation combined injury as biomarker and therapeutics

Radiation Combined Injuries (RCI) pose formidable public health risks, particularly in the context of nuclear incidents, necessitating specialized treatments and development of biomarkers. RCI encompasses instances where ionizing radiation exposure coincides with burns, wounds, or trauma. However, the limited understanding of cellular responses hinders progress in developing effective therapies. This article underscores the pivotal role of exosomes, nano-sized particles (30-120 nm) actively secreted by cells, in addressing the intricate challenges posed by RCI. Exosomes serve as vehicles for the transportation of bioactive molecules, including proteins, lipids, and miRNA, thereby facilitating processes critical to radiotherapy, burn injury, and wound healing. Exosomes hold significant promise for the transformation of RCI management by reducing inflammation, promoting wound healing, managing sepsis, altering immunological responses, and modulating signal transduction pathways. Moreover, exosomes are also being explored as biomarker for various diseases and stress conditions including radiation exposure and associated injuries. This comprehensive review highlights the burgeoning potential of exosomes in advancing the management of RCI, thereby enhancing public health preparedness and response.

Nicotinamide mononucleotide ameliorates ionizing radiation-induced spermatogenic dysfunction in mice by modulating the glycolytic pathway

Radiotherapy, a common cancer treatment, leads to infertility in male cancer survivors, particularly young and middle-aged patients. Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD +), plays crucial roles in energy metabolism, DNA repair, and gene expression. The purpose of this study is to investigate the protective effects and underlying mechanisms of NMN against ionizing radiation (IR)-induced testicular injury and spermatogenic dysfunction in an adult male mouse model. To assess the effects of NMN, single whole-body γ-ray irradiation is used to induce testicular injury and spermatogenic dysfunction in adult male mice. NMN is orally administered at 500 mg/kg before and after IR exposure. The structural and cellular damage to the testes caused by 5 Gy γ-ray irradiation, as well as the protective effect of NMN on testicular spermatogenic dysfunction, are evaluated. The serum hormone testosterone, LH, and FSH levels, as well as testicular NAD +, lactate, and pyruvate levels, are detected. Furthermore, the expressions of the apoptosis-related genes Bcl-2, Bax, and Caspase-3 and the rate-limiting enzymes HK2, PKM2, and LDHA, which are potentially associated with the mechanism of injury, are examined. The results demonstrate that 5 Gy γ-ray irradiation exposure causes a decrease in the serum testosterone, LH, and FSH levels in adult male mice, as well as in the testicular NAD +, lactate, and pyruvate levels, and causes damage to the testicular structure and cells. Morphometric analysis reveal a decrease in the testis mass, seminiferous tubule diameter, and height of the germinal epithelium. The sperm quantity, motility, and testicular volume are reduced in the 5 Gy group but are restored by NMN supplementation. NMN intervention downregulates the expressions of proapoptotic genes ( Bax and Caspase-3) and upregulates the expression of an antiapoptotic gene ( Bcl- 2). Sertoli cells marker genes ( WT-1, GATA-4, SOX9, and vimentin) and glycolysis rate-limiting enzyme-encoding genes ( HK2, PKM2, LDHA) are significantly upregulated. In summary, NMN has a positive regulatory effect on testicular spermatogenic dysfunction in male mice induced by ionizing radiation. This positive effect is likely achieved by promoting the proliferation of spermatogenic cells and activating glycolytic pathways. These findings suggest that NMN supplementation may be a potential protective strategy to prevent reproductive damage to male subjects from ionizing radiation.

Mitigating the Effects of 1-Palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol on Gastrointestinal Acute Radiation Syndrome after Total-Body Irradiation in Mice

Total-body irradiation (TBI) with gamma rays can damage organisms in various unexpected ways and trigger several organ dysfunction syndromes, such as acute radiation syndrome (ARS). Hematopoietic cells and enterocytes are particularly sensitive to radiation due to their self-renewal ability and rapid division, which leads to hematopoietic ARS (H-ARS) and gastrointestinal ARS (GI-ARS). We previously showed that a lipid-based small molecule, 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG), improved 30-day survival and alleviated H-ARS symptoms in BALB/c mice after a lethal dose (LD70/30) of gamma-ray TBI. In this study, we investigated the mitigating effects of PLAG on radiation-induced GI damage that occurs under the same conditions as H-ARS in BALB/c mice. Our study showed that PLAG facilitated the structural restoration of intestinal tissues by increasing villus height, crypt depth, crypt number, mucin-producing goblet cells, and proliferating cell nuclear antigen (PCNA)-positive crypt cells. PLAG significantly improved intestinal absorptive capacity and reduced intestinal injury-induced bacterial translocation. In addition, PLAG effectively inhibited radiation-induced necroptosis signaling activation in the intestinal crypt cells, which was responsible for sustained tissue damage and the release of high mobility group box 1 (HMGB1), a typical damage-associated molecular pattern. Overall, our findings support the radiation-mitigating potential of PLAG against GI-ARS after accidental radiation exposure.

BAX and DDB2 as biomarkers for acute radiation exposure in the human blood ex vivo and non-human primate models

There are currently no available FDA-cleared biodosimetry tools for rapid and accurate assessment of absorbed radiation dose following a radiation/nuclear incident. Previously we developed a protein biomarker-based FAST-DOSE bioassay system for biodosimetry. The aim of this study was to integrate an ELISA platform with two high-performing FAST-DOSE biomarkers, BAX and DDB2, and to construct machine learning models that employ a multiparametric biomarker strategy for enhancing the accuracy of exposure classification and radiation dose prediction. The bioassay showed 97.92% and 96% accuracy in classifying samples in human and non-human primate (NHP) blood samples exposed ex vivo to 0-5 Gy X-rays, respectively up to 48 h after exposure, and an adequate correlation between reconstructed and actual dose in the human samples (R2 = 0.79, RMSE = 0.80 Gy, and MAE = 0.63 Gy) and NHP (R2 = 0.80, RMSE = 0.78 Gy, and MAE = 0.61 Gy). Biomarker measurements in vivo from four NHPs exposed to a single 2.5 Gy total body dose showed a persistent upregulation in blood samples collected on days 2 and 5 after irradiation. The data indicates that using a combined approach of targeted proteins can increase bioassay sensitivity and provide a more accurate dose prediction.

BIO 300 Attenuates Whole Blood Transcriptome Changes in Mice Exposed to Total-Body Radiation

Development of radiation medical countermeasures under the U.S. Food and Drug Administration Animal Rule requires the capability to translate an effective animal-to-human drug dose. One method of human dose translation is using a biomarker and determining drug doses that modulate the biomarker to the desired level. BIO 300 Oral Powder (BIO 300) is a prophylactic radiation medical countermeasure that is currently being developed following the Animal Rule. The present study aimed to identify biomarkers that can be used for human dose conversion by conducting transcriptomics of whole blood collected from BIO 300-treated CD2F1 mice in the presence and absence of total-body irradiation (TBI). Unirradiated mice were treated with vehicle or 50, 100, or 200 mg/kg BIO 300, and irradiated mice were treated with 200 mg/kg or BIO 300 or vehicle prior to TBI. Whole-blood samples were collected after the last dose of the drug and after irradiation. RNA sequencing demonstrated 100 and 200 mg/kg of BIO 300 doses caused significantly more differential gene expression at 48 h after drug dose compared to 50 mg/kg of BIO 300 (7648, 7680, and 55 significantly differently expressed genes, respectively). Interestingly, following TBI, there were no significantly differentially expressed genes between vehicle- and BIO 300-treated mice. Despite the lack of significant changes in gene expression, the transcriptomic profiles in both groups indicated differential changes in signaling pathways. Pathway analysis of the transcriptome profile from vehicle-treated/TBI mice revealed that many inflammatory signaling pathways were activated in these animals. Signaling pathways enriched in BIO 300-treated/TBI mice were involved in cellular stress and immune response and were predicted to be inhibited. In all, four signaling pathways of interest were identified that were differentially enriched in irradiated animals treated with BIO 300: pathogen-induced cytokine storm signaling, S100 family signaling, pulmonary fibrosis idiopathic signaling, and wound-healing signaling. These pathways should be explored to identify potential biomarkers of BIO 300 that can be used for human dose translation.

An Overview of Radiation Countermeasure Development in Radiation Research from 1954 to 2024

Preparation for medical responses to major radiation accidents, further driven by increases in the threat of nuclear warfare, has led to a pressing need to understand the underlying mechanisms of radiation injury (RI) alone or in combination with other trauma (combined injury, CI). The identification of these mechanisms suggests molecules and signaling pathways that can be targeted to develop radiation medical countermeasures. Thus far, the United States Food and Drug Administration (U.S. FDA) has approved seven countermeasures to mitigate hematopoietic acute radiation syndrome (H-ARS), but no drugs are available for prophylaxis and no agents have been approved to combat the other sub-syndromes of ARS, let alone delayed effects of acute radiation exposure or the effects of combined injury. From its inception, Radiation Research has significantly contributed to the understanding of the underlying mechanisms of radiation injury and combined injury, and to the development of radiation medical countermeasures for these indications through the publication of peer-reviewed research and review articles.

USP11 Exacerbates Radiation-Induced Pneumonitis by Activating Endothelial Cell Inflammatory Response via OTUD5-STING Signaling

PURPOSE

Radiation-induced pneumonitis (RIP) seriously limits the application of radiation therapy in the treatment of thoracic tumors, and its etiology and pathogenesis remain elusive. This study aimed to elucidate the role of ubiquitin-specific peptidase 11 (USP11) in the progression of RIP and the associated underlying mechanisms.

METHODS AND MATERIALS

Changes in cytokines and infiltrated immune cells were detected by enzyme-linked immunosorbent assays and immunohistochemistry after exposure to 20 Gy x-ray with whole-thorax irradiation. The effects of USP11 expression on endothelial cell proliferation and apoptosis were analyzed by costaining of CD31/Ki67 and CD31/caspase-3 in vivo, and the production of cytokines and reactive oxygen species was confirmed by reverse-transcription polymerase chain reaction and flow cytometry in vitro. Comprehensive proteome and ubiquitinome analyses were used for USP11 substrate screening after radiation. Results were verified by Western blotting and coimmunoprecipitation experiments. Recombinant adeno-associated virus lung vectors expressing OTUD5 were used for localized overexpression of OTUD5 in mouse pulmonary tissue, and immunohistochemistry was conducted to analyze cytokine expression.

RESULTS

The progression of RIP was significantly alleviated by reduced expression of proinflammatory cytokines in both Usp11-knockout (Usp11-/-) mice and in mice treated with the USP11 inhibitor mitoxantrone. Likewise, the absence of USP11 resulted in decreased permeability of pulmonary vessels and neutrophils and macrophage infiltration. The proliferation rates of endothelial cells were prominently increased in the Usp11-/- lung, whereas apoptosis in Usp11-/- lungs decreased after irradiation compared with that observed in Usp11+/+ lungs. Conversely, USP11 overexpression increased proinflammatory cytokine expression and reactive oxygen species production in endothelial cells after radiation. Comprehensive proteome and ubiquitinome analyses indicated that USP11 overexpression upregulates the expression of several deubiquitinating enzymes, including USP22, USP33, and OTUD5. We demonstrate that USP11 deubiquitinates OTUD5 and implicates the OTUD5-STING signaling pathway in the progression of the inflammatory response in endothelial cells.

CONCLUSIONS

USP11 exacerbates RIP by triggering an inflammatory response in endothelial cells both in vitro and in vivo, and the OTUD5-STING pathway is involved in the USP11-dependent promotion of RIP. This study provides experimental support for the development of precision intervention strategies targeting USP11 to mitigate RIP.

Single-dose Administration of Recombinant Human Thrombopoietin Enhances Survival and Hematopoietic Reconstruction in Canines Irradiated with 3 Gy Gamma Radiation

We conducted this study to investigate the radioprotective effects of recombinant human thrombopoietin (rhTPO) on beagle dogs irradiated with 3.0 Gy 60Co gamma rays. Fifteen healthy adult beagles were randomly assigned to a control group with alleviating care, and 5 and 10 μg/kg rhTPO treatment group. All animals received total-body irradiation using 60Co γ-ray source at a dose of 3.0 Gy (dose rate was 69.1 cGy/min). The treatment group received intramuscular injection of rhTPO 5 and 10 μg/kg at 2 h postirradiation, and the control group was administrated the same volume of normal saline. The survival rate, clinical signs, peripheral hemogram, serum biochemistry, and histopathological examination of animals in each group were assessed. Single administration of 10 μg/kg rhTPO at 2 h postirradiation promoted the recovery of multilineage hematopoiesis and improved the survival rate of beagles irradiated with 3 Gy 60Co γ rays. The administration of 10 μg/kg rhTPO alleviated fever and bleeding, reduced the requirement for supportive care, and may have mitigated multiple organ damage.

Pharmacokinetic and Metabolomic Studies with a Promising Radiation Countermeasure, BBT-059 (PEGylated interleukin-11), in Rhesus Nonhuman Primates

BBT-059, a long-acting PEGylated interleukin-11 (IL-11) analog that is believed to have hematopoietic promoting and anti-apoptotic properties, is being developed as a potential radiation medical countermeasure (MCM) for hematopoietic acute radiation syndrome (H-ARS). This agent has been shown to improve survival in lethally irradiated mice. To further evaluate the drug's toxicity and safety profile, 12 naïve nonhuman primates (NHPs, rhesus macaques) were administered one of three doses of BBT-059 subcutaneously and were monitored for the next 21 days. Blood samples were collected throughout the study to assess the pharmacokinetics (PK) and pharmacodynamics (PD) of the drug as well as its effects on complete blood counts, cytokines, vital signs, and to conduct metabolomic studies. No adverse effects were detected in any treatment group during the study. Short-term changes in metabolomic profiles were present in all groups treated with BBT-059 beginning immediately after drug administration and reverting to near normal levels by the end of the study period. Several pathways and metabolites, particularly those related to inflammation and steroid hormone biosynthesis, were activated by BBT-059 administration. Taken together, these observations suggest that BBT-059 has a good safety profile for further development as a radiation MCM for regulatory approval for human use.

Disrupted gut microecology after high-dose 131I therapy and radioprotective effects of arachidonic acid supplementation

BACKGROUND

Despite the potential radiotoxicity in differentiated thyroid cancer (DTC) patients with high-dose 131I therapy, the alterations and regulatory mechanisms dependent on intestinal microecology remain poorly understood. We aimed to identify the characteristics of the gut microbiota and metabolites in DTC patients suffering from high-dose 131I therapy and explore the radioprotective mechanisms underlying arachidonic acid (ARA) treatment.

METHODS

A total of 102 patients with DTC were recruited, with fecal samples collected before and after 131I therapy for microbiome and untargeted and targeted metabolomic analyses. Mice were exposed to total body irradiation with ARA replenishment and antibiotic pretreatment and were subjected to metagenomic, metabolomic, and proteomic analyses.

RESULTS

131I therapy significantly changed the structure of gut microbiota and metabolite composition in patients with DTC. Lachnospiraceae were the most dominant bacteria after 131I treatment, and metabolites with decreased levels and pathways related to ARA and linoleic acid were observed. In an irradiation mouse model, ARA supplementation not only improved quality of life and recovered hematopoietic and gastrointestinal systems but also ameliorated oxidative stress and inflammation and preserved enteric microecology composition. Additionally, antibiotic intervention eliminated the radioprotective effects of ARA. Proteomic analysis and ursolic acid pretreatment showed that ARA therapy greatly influenced intestinal lipid metabolism in mice subjected to irradiation by upregulating the expression of hydroxy-3-methylglutaryl-coenzyme A synthase 1.

CONCLUSION

These findings highlight that ARA, as a key metabolite, substantially contributes to radioprotection. Our study provides novel insights into the pivotal role that the microbiota-metabolite axis plays in radionuclide protection and offers effective biological targets for treating radiation-induced adverse effects.

Cell Therapies for Acute Radiation Syndrome

The risks of severe ionizing radiation exposure are increasing due to the involvement of nuclear powers in combat operations, the increasing use of nuclear power, and the existence of terrorist threats. Exposure to a whole-body radiation dose above about 0.7 Gy results in H-ARS (hematopoietic acute radiation syndrome), which is characterized by damage to the hematopoietic system; higher doses result in further damage to the gastrointestinal and nervous systems. Only a few medical countermeasures for ARS are currently available and approved for use, although others are in development. Cell therapies (cells or products produced by cells) are complex therapeutics that show promise for the treatment of radiation injury and have been shown to reduce mortality and morbidity in animal models. Since clinical trials for ARS cannot be ethically conducted, animal testing is extremely important. Here, we describe cell therapies that have been tested in animal models. Both cells and cell products appear to promote survival and lessen tissue damage after whole-body irradiation, although the mechanisms are not clear. Because radiation exposure often occurs in conjunction with other traumatic injuries, animal models of combined injury involving radiation and future countermeasure testing for these complex medical problems are also discussed.

Mathematical complexities in radionuclide metabolic modelling: a review of ordinary differential equation kinetics solvers in biokinetic modelling

Biokinetic models have been employed in internal dosimetry (ID) to model the human body's time-dependent retention and excretion of radionuclides. Consequently, biokinetic models have become instrumental in modelling the body burden from biological processes from internalized radionuclides for prospective and retrospective dose assessment. Solutions to biokinetic equations have been modelled as a system of coupled ordinary differential equations (ODEs) representing the time-dependent distribution of materials deposited within the body. In parallel, several mathematical algorithms were developed for solving general kinetic problems, upon which biokinetic solution tools were constructed. This paper provides a comprehensive review of mathematical solving methods adopted by some known internal dose computer codes for modelling the distribution and dosimetry for internal emitters, highlighting the mathematical frameworks, capabilities, and limitations. Further discussion details the mathematical underpinnings of biokinetic solutions in a unique approach paralleling advancements in ID. The capabilities of available mathematical solvers in computational systems were also emphasized. A survey of ODE forms, methods, and solvers was conducted to highlight capabilities for advancing the utilization of modern toolkits in ID. This review is the first of its kind in framing the development of biokinetic solving methods as the juxtaposition of mathematical solving schemes and computational capabilities, highlighting the evolution in biokinetic solving for radiation dose assessment.

Metabolomic Profiles in Tissues of Nonhuman Primates Exposed to Either Total- or Partial-Body Radiation

A complex cascade of systemic and tissue-specific responses induced by exposure to ionizing radiation can lead to functional impairment over time in the surviving population. Current methods for management of survivors of unintentional radiation exposure episodes rely on monitoring individuals over time for the development of adverse clinical symptoms due to the lack of predictive biomarkers for tissue injury. In this study, we report on changes in metabolomic and lipidomic profiles in multiple tissues of nonhuman primates (NHPs) that received either 4.0 Gy or 5.8 Gy total-body irradiation (TBI) of 60Co gamma rays, and 4.0 or 5.8 Gy partial-body irradiation (PBI) from LINAC-derived photons and were treated with a promising radiation countermeasure, gamma-tocotrienol (GT3). These include small molecule alterations that correlate with radiation effects in the jejunum, lung, kidney, and spleen of animals that either survived or succumbed to radiation toxicities over a 30-day period. Radiation-induced metabolic changes in tissues were observed in animals exposed to both doses and types of radiation, but were partially alleviated in GT3-treated and irradiated animals, with lung and spleen being most responsive. The majority of the pathways protected by GT3 treatment in these tissues were related to glucose metabolism, inflammation, and aldarate metabolism, suggesting GT3 may exert radioprotective effects in part by sparing these pathways from radiation-induced dysregulation. Taken together, the results of our study demonstrate that the prophylactic administration of GT3 results in metabolic and lipidomic shifts that likely provide an overall advantage against radiation injury. This investigation is among the first to highlight the use of a molecular phenotyping approach in a highly translatable NHP model of partial- and total-body irradiation to determine the underlying physiological mechanisms involved in the radioprotective efficacy of GT3.

Thrombopoietin mimetic stimulates bone marrow vascular and stromal niches to mitigate acute radiation syndrome

BACKGROUND

Acute radiation syndrome (ARS) manifests after exposure to high doses of radiation in the instances of radiologic accidents or incidents. Facilitating regeneration of the bone marrow (BM), namely the hematopoietic stem and progenitor cells (HSPCs), is key in mitigating ARS and multi-organ failure. JNJ-26366821, a PEGylated thrombopoietin mimetic (TPOm) peptide, has been shown as an effective medical countermeasure (MCM) to treat hematopoietic-ARS (H-ARS) in mice. However, the activity of TPOm on regulating BM vascular and stromal niches to support HSPC regeneration has yet to be elucidated.

METHODS

C57BL/6J mice (9-14 weeks old) received sublethal or lethal total body irradiation (TBI), a model for H-ARS, by 137Cs or X-rays. At 24 h post-irradiation, mice were subcutaneously injected with a single dose of TPOm (0.3 mg/kg or 1.0 mg/kg) or PBS (vehicle). At homeostasis and on days 4, 7, 10, 14, 18, and 21 post-TBI with and without TPOm treatment, BM was harvested for histology, BM flow cytometry of HSPCs, endothelial (EC) and mesenchymal stromal cells (MSC), and whole-mount confocal microscopy. For survival, irradiated mice were monitored and weighed for 30 days. Lastly, BM triple negative cells (TNC; CD45-, TER-119-, CD31-) were sorted for single-cell RNA-sequencing to examine transcriptomics after TBI with or without TPOm treatment.

RESULTS

At homeostasis, TPOm expanded the number of circulating platelets and HSPCs, ECs, and MSCs in the BM. Following sublethal TBI, TPOm improved BM architecture and promoted recovery of HSPCs, ECs, and MSCs. Furthermore, TPOm elevated VEGF-C levels in normal and irradiated mice. Following lethal irradiation, mice improved body weight recovery and 30-day survival when treated with TPOm after 137Cs and X-ray exposure. Additionally, TPOm reduced vascular dilation and permeability. Finally, single-cell RNA-seq analysis indicated that TPOm increased the expression of collagens in MSCs to enhance their interaction with other progenitors in BM and upregulated the regeneration pathway in MSCs.

CONCLUSIONS

TPOm interacts with BM vascular and stromal niches to locally support hematopoietic reconstitution and systemically improve survival in mice after TBI. Therefore, this work warrants the development of TPOm as a potent radiation MCM for the treatment of ARS.

Radioprotective effectiveness of a novel delta-tocotrienol prodrug on mouse hematopoietic system against 60Co gamma-ray irradiation through inducing granulocyte-colony stimulating factor production

Considering the increasing risk of nuclear attacks worldwide, the development of develop potent and safe radioprotective agents for nuclear emergencies is urgently needed. γ-tocotrienol (GT3) and δ-tocotrienol (DT3) have demonstrated a potent radioprotective effect by inducing the production of granulocyte-colony stimulating factor (G-CSF) in vivo. However, their application is limited because of their low bioavailability. The utilization of ester prodrugs can be an effective strategy for modifying the pharmacokinetic properties of drug molecules. In this study, we initially confirmed that DT3 exhibited the most significant potential for inducing G-CSF effects among eight natural vitamin E homologs. Consequently, we designed and synthesized a series of DT3 ester and ether derivatives, leading to improved radioprotective effects. The metabolic study conducted in vitro and in vivo has identified DT3 succinate 5b as a prodrug of DT3 with an approximately seven-fold higher bioavailability compared to DT3 alone. And DT3 ether derivative 8a were relatively stable and approximately 4 times more bioavailable than DT3 prototype. Furthermore, 5b exhibited superior ability to mitigate radiation-induced pancytopenia, enhance the recovery of bone marrow hematopoietic stem and progenitor cells, and promote splenic extramedullary hematopoiesis in sublethal irradiated mice. Similarly, 8a shown potential radiation protection, but its radiation protection is less than DT3. Based on these findings, we identified 5b as a DT3 prodrug, and providing an attractive candidate for further drug development.

Advances in the regulation of radiation-induced apoptosis by polysaccharides: A review

Polysaccharides are biomolecules composed of monosaccharides that are widely found in animals, plants and microorganisms and are of interest for their various health benefits. Cumulative studies have shown that the modulation of radiation-induced apoptosis by polysaccharides can be effective in preventing and treating a wide range of radiation injuries with safety and few side effects. Therefore, this paper summarizes the monosaccharide compositions, molecular weights, and structure-activity relationships of natural polysaccharides that regulate radiation-induced apoptosis, and also reviews the molecular mechanisms by which these polysaccharides modulate radiation-induced apoptosis, primarily focusing on promoting cancer cell apoptosis to enhance radiotherapy efficacy, reducing radiation damage to normal tissues, and inhibiting apoptosis in normal cells. Additionally, the role of gut microbiota in mediating the interaction between polysaccharides and radiation is discussed, providing innovative ideas for various radiation injuries, including hematopoiesis, immunity, and organ damage. This review will contribute to a better understanding of the value of natural polysaccharides in the field of radiation and provide guidance for the development of natural radioprotective agents and radiosensitizers.

Histopathological studies of nonhuman primates exposed to supralethal doses of total- or partial-body radiation: influence of a medical countermeasure, gamma-tocotrienol

Despite remarkable scientific progress over the past six decades within the medical arts and in radiobiology in general, limited radiation medical countermeasures (MCMs) have been approved by the United States Food and Drug Administration for the acute radiation syndrome (ARS). Additional effort is needed to develop large animal models for improving the prediction of clinical safety and effectiveness of MCMs for acute and delayed effects of radiation in humans. Nonhuman primates (NHPs) are considered the animal models that reproduce the most appropriate representation of human disease and are considered the gold standard for drug development and regulatory approval. The clinical and histopathological effects of supralethal, total- or partial-body irradiations (12 Gy) of NHPs were assessed, along with possible protective actions of a promising radiation MCM, gamma-tocotrienol (GT3). Results show that these supralethal radiation exposures induce severe injuries that manifest both clinically as well as pathologically, as evidenced by the noted functionally crippling lesions within various major organ systems of experimental NHPs. The MCM, GT3, has limited radioprotective efficacy against such supralethal radiation doses.

Progression of Notch signaling regulation of B cells under radiation exposure

With the continuous development of nuclear technology, the radiation exposure caused by radiation therapy is a serious health hazard. It is of great significance to further develop effective radiation countermeasures. B cells easily succumb to irradiation exposure along with immunosuppressive response. The approach to ameliorate radiation-induced B cell damage is rarely studied, implying that the underlying mechanisms of B cell damage after exposure are eager to be revealed. Recent studies suggest that Notch signaling plays an important role in B cell-mediated immune response. Notch signaling is a critical regulator for B cells to maintain immune function. Although accumulating studies reported that Notch signaling contributes to the functionality of hematopoietic stem cells and T cells, its role in B cells is scarcely appreciated. Presently, we discussed the regulation of Notch signaling on B cells under radiation exposure to provide a scientific basis to prevent radiation-induced B cell damage.

Serum microRNA profile of rhesus macaques following ionizing radiation exposure and treatment with a medical countermeasure, Ex-Rad

Exposure to ionizing radiation (IR) presents a formidable clinical challenge. Total-body or significant partial-body exposure at a high dose and dose rate leads to acute radiation syndrome (ARS), the complex pathologic effects that arise following IR exposure over a short period of time. Early and accurate diagnosis of ARS is critical for assessing the exposure dose and determining the proper treatment. Serum microRNAs (miRNAs) may effectively predict the impact of irradiation and assess cell viability/senescence changes and inflammation. We used a nonhuman primate (NHP) model-rhesus macaques (Macaca mulatta)-to identify the serum miRNA landscape 96 h prior to and following 7.2 Gy total-body irradiation (TBI) at four timepoints: 24, 36, 48, and 96 h. To assess whether the miRNA profile reflects the therapeutic effect of a small molecule ON01210, commonly known as Ex-Rad, that has demonstrated radioprotective efficacy in a rodent model, we administered Ex-Rad at two different schedules of NHPs; either 36 and 48 h post-irradiation or 48 and 60 h post-irradiation. Results of this study corroborated our previous findings obtained using a qPCR array for several miRNAs and their modulation in response to irradiation: some miRNAs demonstrated a temporary increased serum concentration within the first 24-36 h (miR-375, miR-185-5p), whereas others displayed either a prolonged decline (miR-423-5p) or a long-term increase (miR-30a-5p, miR-27b-3p). In agreement with these time-dependent changes, hierarchical clustering of differentially expressed miRNAs showed that the profiles of the top six miRNA that most strongly correlated with radiation exposure were inconsistent between the 24 and 96 h timepoints following exposure, suggesting that different biodosimetry miRNA markers might be required depending on the time that has elapsed. Finally, Ex-Rad treatment restored the level of several miRNAs whose expression was significantly changed after radiation exposure, including miR-16-2, an miRNA previously associated with radiation survival. Taken together, our findings support the use of miRNA expression as an indicator of radiation exposure and the use of Ex-Rad as a potential radioprotectant.

Thrombopoietin mimetic stimulates bone marrow vascular and stromal niches to mitigate acute radiation syndrome

Background

Acute radiation syndrome (ARS) manifests after exposure to high doses of radiation in the instances of radiologic accidents or incidents. Facilitating the regeneration of the bone marrow (BM), namely the hematopoietic stem and progenitor cells (HSPCs), is a key in mitigating ARS and multi-organ failure. JNJ-26366821, a PEGylated thrombopoietin mimetic (TPOm) peptide, has been shown as an effective medical countermeasure (MCM) to treat hematopoietic-ARS (H-ARS) in mice. However, the activity of TPOm on regulating BM vascular and stromal niches to support HSPC regeneration has not yet been elucidated.

Methods

C57BL/6J mice (9-14 weeks old) received sublethal or lethal total body irradiation (TBI), a model for H-ARS, by 137Cs or X-rays. At 24 hours post-irradiation, mice were subcutaneously injected with a single dose of TPOm (0.3 mg/kg or 1.0 mg/kg) or PBS (vehicle). At homeostasis and on days 4, 7, 10, 14, 18, and 21 post-TBI with and without TPOm treatment, BM was harvested for histology, BM flow cytometry of HSPCs, endothelial (EC) and mesenchymal stromal cells (MSC), and whole-mount confocal microscopy. For survival, irradiated mice were monitored and weighed for 30 days. Lastly, BM triple negative cells (TNC; CD45-, TER-119-, CD31-) were sorted for single-cell RNA-sequencing to examine transcriptomics after TBI with or without TPOm treatment.

Results

At homeostasis, TPOm expanded the number of circulating platelets and HSPCs, ECs, and MSCs in the BM. Following sublethal TBI, TPOm improved BM architecture and promoted recovery of HSPCs, ECs, and MSCs. Furthermore, TPOm elevated VEGF-C levels in normal and irradiated mice. Following lethal irradiation, mice improved body weight recovery and 30-day survival when treated with TPOm after 137Cs and X-ray exposure. Additionally, TPOm reduced vascular dilation and permeability. Finally, single-cell RNA-seq analysis indicated that TPOm increased the expression of collagens in MSCs to enhance their interaction with other progenitors in BM and upregulated the regeneration pathway in MSCs.

Conclusions

TPOm interacts with BM vascular and stromal niches to locally support hematopoietic reconstitution and systemically improve survival in mice after TBI. Therefore, this work warrants the development of TPOm as a potent radiation MCM for the treatment of ARS.

Fluacrypyrim Protects Hematopoietic Stem and Progenitor Cells against Irradiation via Apoptosis Prevention

Ionizing radiation (IR)-induced hematopoietic injury has become a global concern in the past decade. The underlying cause of this condition is a compromised hematopoietic reserve, and this kind of hematopoietic injury could result in infection or bleeding, in addition to lethal mishaps. Therefore, developing an effective treatment for this condition is imperative. Fluacrypyrim (FAPM) is a recognized effective inhibitor of STAT3, which exhibits anti-inflammation and anti-tumor effects in hematopoietic disorders. In this context, the present study aimed to determine whether FAPM could serve as a curative agent in hematopoietic-acute radiation syndrome (H-ARS) after total body irradiation (TBI). The results revealed that the peritoneally injection of FAPM could effectively promote mice survival after lethal dose irradiation. In addition, promising recovery of peripheral blood, bone marrow (BM) cell counts, hematopoietic stem cell (HSC) cellularity, BM colony-forming ability, and HSC reconstituting ability upon FAPM treatment after sublethal dose irradiation was noted. Furthermore, FAPM could reduce IR-induced apoptosis in hematopoietic stem and progenitor cells (HSPCs) both in vitro and in vivo. Specifically, FAPM could downregulate the expressions of p53-PUMA pathway target genes, such as Puma, Bax, and Noxa. These results suggested that FAPM played a protective role in IR-induced hematopoietic damage and that the possible underlying mechanism was the modulation of apoptotic activities in HSCs.

The potential value of 5-androstenediol in countering acute radiation syndrome

Moderate-to-high doses of ionizing irradiation can lead to potentially life-threatening morbidities and increase mortality risk. In preclinical testing, 5-androstenediol has been shown to be effective in protecting against hematopoietic acute radiation syndrome. This agent is important for innate immunity, serves to modulate cell cycle progression, reduces radiation-induced apoptosis, and regulates DNA repair. The drug has been evaluated clinically for its pharmacokinetics and safety. The United States Food and Drug Administration granted investigational new drug status to its injectable depot formulation (NEUMUNE). Its safety and efficacy profiles make it an attractive candidate for further development as a radiation countermeasure.

A 3D In Vitro Cortical Tissue Model Based on Dense Collagen to Study the Effects of Gamma Radiation on Neuronal Function

Studies on gamma radiation-induced injury have long been focused on hematopoietic, gastrointestinal, and cardiovascular systems, yet little is known about the effects of gamma radiation on the function of human cortical tissue. The challenge in studying radiation-induced cortical injury is, in part, due to a lack of human tissue models and physiologically relevant readouts. Here, a physiologically relevant 3D collagen-based cortical tissue model (CTM) is developed for studying the functional response of human iPSC-derived neurons and astrocytes to a sub-lethal radiation exposure (5 Gy). Cytotoxicity, DNA damage, morphology, and extracellular electrophysiology are quantified. It is reported that 5 Gy exposure significantly increases cytotoxicity, DNA damage, and astrocyte reactivity while significantly decreasing neurite length and neuronal network activity. Additionally, it is found that clinically deployed radioprotectant amifostine ameliorates the DNA damage, cytotoxicity, and astrocyte reactivity. The CTM provides a critical experimental platform to understand cell-level mechanisms by which gamma radiation (GR) affects human cortical tissue and to screen prospective radioprotectant compounds.

Modulation of Hematopoietic Injury by a Promising Radioprotector, Gamma-Tocotrienol, in Rhesus Macaques Exposed to Partial-Body Radiation

Currently, no radioprotectors have been approved to mitigate hematopoietic injury after exposure to ionizing radiation. Acute ionizing radiation results in damage to both hematopoietic and immune system cells. Pre-exposure prophylactic agents are needed for first responders and military personnel. In this study, the ability of gamma-tocotrienol (GT3), a promising radioprotector and antioxidant, to ameliorate partial-body radiation-induced damage to the hematopoietic compartment was evaluated in a nonhuman primate (NHP) model. A total of 15 rhesus NHPs were divided into two groups, and were administered either GT3 or vehicle 24 h prior to 4 or 5.8 Gy partial-body irradiation (PBI), with 5% bone marrow (BM) sparing. Each group consisted of four NHPs, apart from the vehicle-treated group exposed to 5.8 Gy, which had only three NHPs. BM samples were collected 8 days prior to irradiation in addition to 2, 7, 14, and 30 days postirradiation. To assess the clonogenic ability of hematopoietic stem and progenitor cells (HSPCs), colony forming unit (CFU) assays were performed, and lymphoid cells were immunophenotyped using flow cytometry. As a result of GT3 treatment, an increase in HSPC function was evident by an increased recovery of CFU-granulocyte macrophages (CFU-GM). Additionally, GT3 treatment was shown to increase the percentage of CD34+ cells, including T and NK-cell subsets. Our data further affirm GT3's role in hematopoietic recovery and suggest the need for its further development as a prophylactic radiation medical countermeasure.

Sulforaphane attenuates irradiation induced testis injury in mice

OBJECTIVE

The testis is vulnerable to ionizing radiation, sexual dysfunction and male infertility are common problems after local radiation or whole-body exposure. Currently, there are no approved drugs for the prevention or treatment of radiation testicular injury. Sulforaphane (SFN) is an indirect antioxidant that induces phase II detoxification enzymes and antioxidant genes. Herein, we investigated the radiation protective effect of SFN on testicular injury in mice and its potential mechanism.

MATERIALS AND METHODS

Mice were randomly divided into blank control group (Ctrl), radiation + no pretreatment group (IR), and radiation + SFN groups (IRS). In the radiation + SFN groups, starting from 72 h before radiation, SFN solution was intraperitoneally injected once a day until they were sacrificed. Mice in the blank control group and the radiation + no pretreatment group were simultaneously injected intraperitoneally with an equal volume of the solvent used to dissolve SFN (PBS with a final concentration of 0.1%DMSO) until they were sacrificed. They were subjected to 6Mev-ray radiation to the lower abdominal testis area (total dose 2Gy). Twenty-four hours after radiation, six mice in each group were randomly sacrificed. Seventy-two hours after radiation, the remaining mice were sacrificed.

RESULTS

The results showed that the harmful effects of ionizing radiation on testes were manifested as damage to histoarchitecture, increased oxidative stress, and apoptosis, and thus impaired male fertility. SFN injections can reverse these symptoms.

CONCLUSIONS

The results showed that SFN can improve the damage of mouse testis caused by irradiation. Furthermore, SFN prevents spermatogenesis dysfunction caused by ionizing radiation by activating Nrf2 and its downstream antioxidant gene.

Development of radiation countermeasure agents for acute radiation syndromes

The risk of internal and external exposure to ionizing radiation (IR) has increased alongside the development and implementation of nuclear technology. Therefore, serious security issues have emerged globally, and there has been an increase in the number of studies focusing on radiological prevention and medical countermeasures. Radioprotective drugs are particularly important components of emergency medical preparedness strategies for the clinical management of IR-induced injuries. However, a few drugs have been approved to date to treat such injuries, and the related mechanisms are not entirely understood. Thus, the aim of the present review was to provide a brief overview of the World Health Organization's updated list of essential medicines for 2023 for the proper management of national stockpiles and the treatment of radiological emergencies. This review also discusses the types of radiation-induced health injuries and the related mechanisms, as well as the development of various radioprotective agents, including Chinese herbal medicines, for which significant survival benefits have been demonstrated in animal models of acute radiation syndrome.

Radiosensitivity of rhesus nonhuman primates: consideration of sex, supportive care, body weight, and age at time of exposure

BACKGROUND

Animal models are vital for the development of radiation medical countermeasures for the prophylaxis or treatment of acute radiation syndrome and for the delayed effects of acute radiation exposure. Nonhuman primates (NHPs) play an important role in the regulatory approval of such agents by the United States Food and Drug Administration following the Animal Rule. Reliance on such animal models requires that such models are well characterized.

METHODS

Data gathered from both male and female animals under the same conditions and gathered concurrently are limited; therefore, the authors compared and contrasted here the radiosensitivity of both male and female NHPs provided different levels of clinical support over a range of acute, total-body gamma irradiation, as well as the influence of age and body weight.

RESULTS

Under matched experimental conditions, the authors observed only marginal, but clearly evident differences between acutely irradiated male and female NHPs relative to the measured response endpoints (rates of survival, blood cell changes, and cytokine fluctuations). These differences appeared to be accentuated by the level of exposure as well as by the nature of clinical support.

CONCLUSION

Additional studies with both sexes under various experimental conditions and different radiation qualities run concurrently are needed.

The Acute Radiation Syndrome-Mitigator Romiplostim and Secreted Extracellular Vesicles Improved Survival in Mice Acutely Exposed to Myelosuppressive Doses of Ionizing Radiation

In cases of accidental high-dose total-body irradiation (TBI), acute radiation syndrome (ARS) can cause death. We reported that the thrombopoietin receptor agonist romiplostim (RP) has the potential to completely rescue mice exposed to lethal TBI. Extracellular vesicles (EVs) are involved in cell-to-cell communication, and the mechanism of RP action may be related to EVs that reflect the radio-mitigative information. We investigated the radio-mitigative effects of EVs on mice with severe ARS. C57BL/6 mice exposed to lethal TBI were treated with RP, and the EVs were isolated from the serum and intraperitoneally injected into other mice with severe ARS. The 30-day survival rate of lethal TBI mice drastically improved by 50-100% with the administration of EVs in the sera collected weekly from the mice in which radiation damage was alleviated and mortality was avoided by the administration of RP. Four responsive miRNAs, namely, miR-144-5p, miR-3620-5p, miR-6354, and miR-7686-5p showed significant expression changes in an array analysis. In particular, miR-144-5p was expressed only in the EVs of RP-treated TBI mice. Specific EVs may exist in the circulating blood of mice that escaped mortality with an ARS mitigator, and their membrane surface and endogenous molecules may be the key to the survival of mice with severe ARS.

Nanodrugs with intrinsic radioprotective exertion: Turning the double-edged sword into a single-edged knife

Ionizing radiation (IR) poses a growing threat to human health, and thus ideal radioprotectors with high efficacy and low toxicity still receive widespread attention in radiation medicine. Despite significant progress made in conventional radioprotectants, high toxicity, and low bioavailability still discourage their application. Fortunately, the rapidly evolving nanomaterial technology furnishes reliable tools to address these bottlenecks, opening up the cutting-edge nano-radioprotective medicine, among which the intrinsic nano-radioprotectants characterized by high efficacy, low toxicity, and prolonged blood retention duration, represent the most extensively studied class in this area. Herein, we made the systematic review on this topic, and discussed more specific types of radioprotective nanomaterials and more general clusters of the extensive nano-radioprotectants. In this review, we mainly focused on the development, design innovations, applications, challenges, and prospects of the intrinsic antiradiation nanomedicines, and presented a comprehensive overview, in-depth analysis as well as an updated understanding of the latest advances in this topic. We hope that this review will promote the interdisciplinarity across radiation medicine and nanotechnology and stimulate further valuable studies in this promising field.

Analysis of the Proteomic Profile in Serum of Irradiated Nonhuman Primates Treated with Ex-Rad, a Radiation Medical Countermeasure

There are currently four radiation medical countermeasures that have been approved by the United States Food and Drug Administration to mitigate hematopoietic acute radiation syndrome, all of which are repurposed radiomitigators. The evaluation of additional candidate drugs that may also be helpful for use during a radiological/nuclear emergency is ongoing. A chlorobenzyl sulfone derivative (organosulfur compound) known as Ex-Rad, or ON01210, is one such candidate medical countermeasure, being a novel, small-molecule kinase inhibitor that has demonstrated efficacy in the murine model. In this study, nonhuman primates exposed to ionizing radiation were subsequently administered Ex-Rad as two treatment schedules (Ex-Rad I administered 24 and 36 h post-irradiation, and Ex-Rad II administered 48 and 60 h post-irradiation) and the proteomic profiles of serum using a global molecular profiling approach were assessed. We observed that administration of Ex-Rad post-irradiation is capable of mitigating radiation-induced perturbations in protein abundance, particularly in restoring protein homeostasis, immune response, and mitigating hematopoietic damage, at least in part after acute exposure. Taken together, restoration of functionally significant pathway perturbations may serve to protect damage to vital organs and provide long-term survival benefits to the afflicted population.

Where are the medical countermeasures against the ARS and DEARE? A current topic relative to an animal model research platform, radiation exposure context, the acute and delayed effects of acute exposure, and the FDA animal rule

PURPOSE

A question echoed by the National Biodefense Science Board (NBSB) in 2010, remains a reasonable question in 2023; 'Where are the Countermeasures?'. A critical path for development of medical countermeasures (MCM) against acute, radiation-induced organ-specific injury within the acute radiation syndrome (ARS) and the delayed effects of acute radiation exposure (DEARE) requires the recognition of problems and solutions inherent in the path to FDA approval under the Animal Rule. Keep Rule number one in mind, It's not easy.

CONSIDERATIONS

The current topic herein is focused on defining the nonhuman primate model(s) for efficient MCM development relative to consideration of prompt and delayed exposure in the context of the nuclear scenario. The rhesus macaque is a predictive model for human exposure of partial-body irradiation with marginal bone marrow sparing that allows definition of the multiple organ injury in the acute radiation syndrome (ARS) and the delayed effects of acute radiation exposure (DEARE). The continued definition of natural history is required to delineate an associative or causal interaction within the concurrent multi-organ injury characteristic of the ARS and DEARE. A more efficient development of organ specific MCM for both pre-exposure and post-exposure prophylaxis to include acute radiation-induced combined injury requires closing critical gaps in knowledge and urgent support to rectify the national shortage of nonhuman primates. The rhesus macaque is a validated, predictive model of the human response to prompt and delayed radiation exposure, medical management and MCM treatment. A rational approach to further development of the cynomolgus macaque as a comparable model is urgently required for continued development of MCM for FDA approval.

CONCLUSION

It is imperative to examine the key variables relative to animal model development and validation, The pharmacokinetics, pharmacodynamics and exposure profiles, of candidate MCM relative to route, administration schedule and optimal efficacy define the fully effective dose. The conduct of adequate and well-controlled pivotal efficacy studies as well as safety and toxicity studies support approval under the FDA Animal Rule and label definition for human use.

Research Progress with Membrane Shielding Materials for Electromagnetic/Radiation Contamination

As technology develops at a rapid pace, electromagnetic and radiation pollution have become significant issues. These forms of pollution can cause many important environmental issues. If they are not properly managed and addressed, they will be everywhere in the global biosphere, and they will have devastating impacts on human health. In addition to minimizing sources of electromagnetic radiation, the development of lightweight composite shielding materials to address interference from radiation has become an important area of research. A suitable shielding material can effectively reduce the harm caused by electromagnetic interference/radiation. However, membrane shielding materials with general functions cannot effectively exert their shielding performance in all fields, and membrane shielding materials used in different fields must have specific functions under their use conditions. The aim of this review was to provide a comprehensive review of these issues. Firstly, the causes of electromagnetic/radiation pollution were briefly introduced and comprehensively identified and analyzed. Secondly, the strategic solutions offered by membrane shielding materials to address electromagnetic/radiation problems were discussed. Then, the design concept, technical innovation, and related mechanisms of the existing membrane shielding materials were expounded, the treatment methods adopted by scholars to study the environment and performance change laws were introduced, and the main difficulties encountered in this area of research were summarized. Finally, on the basis of a comprehensive analysis of the protection provided by membrane shielding materials against electromagnetic/radiation pollution, the action mechanism of membrane shielding materials was expounded in detail, and the research progress, structural design and performance characterization techniques for these materials were summarized. In addition, the future challenges were prospected. This review will help universities, research institutes, as well as scientific and technological enterprises engaged in related fields to fully understand the design concept and research progress of electromagnetic/radiation-contaminated membrane shielding materials. In addition, it is hoped that this review will facilitate efforts to accelerate the research and development of membrane shielding materials and offer potential applications in areas such as electronics, nuclear medicine, agriculture, and other areas of industry.

Analysis of the urinary metabolic profiles in irradiated rats treated with Activated Protein C (APC), a potential mitigator of radiation toxicity

PURPOSE

The goal of the current study was to identify longitudinal changes in urinary metabolites following IR exposure and to determine potential alleviation of radiation toxicities by administration of recombinant APC formulations.

MATERIALS AND METHODS

Female adult WAG/RijCmcr rats were irradiated with 13.0 Gy leg-out partial body X-rays; longitudinally collected urine samples were subject to LC-MS based metabolomic profiling. Sub-cohorts of rats were treated with three variants of recombinant APC namely, rat wildtype (WT) APC, rat 3K3A mutant form of APC, and human WT APC as two bolus injections at 24 and 48 hours post IR.

RESULTS

Radiation induced robust changes in the urinary profiles leading to oxidative stress, severe dyslipidemia, and altered biosynthesis of PUFAs, glycerophospholipids, sphingolipids, and steroids. Alterations were observed in multiple metabolic pathways related to energy metabolism, nucleotide biosynthesis and metabolism that were indicative of disrupted mitochondrial function and DNA damage. On the other hand, sub-cohorts of rats that were treated with rat wildtype-APC showed alleviation of radiation toxicities, in part, at the 90-day time point, while rat 3K3A-APC showed partial alleviation of radiation induced metabolic alterations 14 days after irradiation.

CONCLUSIONS

Taken together, these results show that augmenting the Protein C pathway and activity via administration of recombinant APC may be an effective approach for mitigation of radiation induced normal tissue toxicity.

Withaferin A, a steroidal lactone, selectively protects normal lymphocytes against ionizing radiation induced apoptosis and genotoxicity via activation of ERK/Nrf-2/HO-1 axis

Increasing use of ionizing radiation (IR) in medicine, industry, agriculture and research ensues potential health hazards if not used properly or contained effectively. However, radioprotectors which are effective in clinical and/or accidental radiation exposures are still elusive. In this direction, we have explored the radioprotective potential of Withaferin A, a plant withanolide, which was recently shown to be safe and well tolerated in cancer patients in a clinical trial and is also known to be a radio-sensitizer in cancer cells. Our results show that, Withaferin A (WA) protected only normal lymphocytes, but not cancer cells, against IR-induced apoptosis and offered radioprotection even when added post-radiation exposure. WA treatment led to significant inhibition of IR-induced caspase-3 activation and decreased IR-induced DNA damage to lymphocytes and bone-marrow cells. WA reduced intracellular ROS and GSH levels and only thiol based anti-oxidants could abrogate the radio-protective effects of WA, indicating a crucial role of cellular/protein thiols in its biological activity. The inability of WA-glutathione adduct to offer radioprotection further underscored the role of cellular thiols. WA induced pro-survival transcription factor, Nrf-2, and expression of cytoprotective genes HO-1, catalase, SOD, peroxiredoxin-2 via ERK. Further, WA administration could rescue mice against radiation induced mortality, DNA damage, increase in micro-nucleated polychromatic erythrocytes (mn-PCEs) and increased ratio of polychromatic erythrocytes (PCEs) to Normochromatic Erythrocytes (NCEs) in bone-marrow, demonstrating its potent in vivo the radio-protective efficacy. In conclusion, WA selectively protects normal cells against IR-induced apoptosis via activation of cytoprotective Nrf-2 pathway.

Looking for the phoenix: the current research on radiation countermeasures

PURPOSE

Ionizing radiation (IR) is widely applied in radiotherapy for the treatment of over 50% of cancer patients. IR is also intensively used in medical diagnostics on a daily basis in imaging. Moreover, recent geopolitical events have re-ignited the real threat of the use of nuclear weapons. Medical radiation countermeasures represent one of the effective protection strategies against the effects of IR. The aim of this review was to summarize the most commonly used strategies and procedures in the development of radiation countermeasures and to evaluate the current state of their research, with a focus on those in the clinical trial phase.

METHODS

Clinical trials for this review were selected in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement. The search was performed in the clinicaltrials.gov database as of May 2022.

RESULTS

Our search returned 263 studies, which were screened and of which 25 were included in the review. 10 of these studies had been completed, 3 with promising results: KMRC011 increased G-CSF, IL-6, and neutrophil counts suggesting potential for the treatment of hematopoietic acute radiation syndrome (H-ARS); GC4419 reduced the number of patients with severe oral mucositis and its duration; the combination of enoxaparin, pentoxifylline, and ursodeoxycholic acid reduced the incidence of focal radiation-induced liver injury.

CONCLUSION

The agents discovered so far show significant side effects or low efficacy, and hence most of the tested agents terminate in the early stages of development. In addition, the low profitability of this type of drug demotivates the private sector to invest in such research. To overcome this problem, there is a need to involve more public resources in funding. Among the technological opportunities, a deeper use of in silico approaches seems to be prospective.

Protective mechanism of a novel aminothiol compound on radiation-induced intestinal injury

PURPOSE

With the development of nuclear technology and radiotherapy, the risk of radiation injury has been increasing. Therefore, it is important to find an effective radiation-protective agent. In this study, we designed and synthesized a novel compound called compound 8, of which the radioprotective effect and mechanism were studied.

MATERIALS AND METHODS

Before being exposed to ionizing radiation, mice were pretreated with compound 8. The 30-day mortality assay, hematoxylin-eosin staining, and immunohistochemistry staining assay were performed to evaluate the anti-radiation effect of the compound 8. TUNEL and immunofluorescence assays were conducted to study the anti-radiation mechanism of compound 8.

RESULTS

Compared to the IR + vehicle group, the 30-day survival rate of mice treated with 25 mg/kg of compound 8 was significantly improved after 8 Gy total body irradiation. In the morphological study of the small intestine, we found that compound 8 could maintain crypt-villus structures in the irradiated mice. Further immunohistochemical staining displayed that compound 8 could improve the survival of Lgr5⁺ cells, ki67⁺ cells, and lysozyme⁺ cells. The results of TUNEL and immunofluorescence assays showed that compound 8 could decrease the expression of apoptosis-related caspase-8/-9, γ-H2AX, Bax, and p53.

CONCLUSIONS

These results indicate that compound 8 exerts its effects by maintaining structure and function of small intestine. It also reduces DNA damage, promotes crypt proliferation and differentiation. Moreover, it may enhance the anti-apoptotic ability of small intestinal tissue by inhibiting the activation of p53 and blocking the caspase cascade reaction. Compound 8 can protect the intestinal tract from post-radiation damage, it is thus a new and effective protective agent of radiation.

Safety, Pharmacokinetics, and Biomarkers of an Amorphous Solid Dispersion of Genistein, a Radioprotectant, in Healthy Volunteers

A pharmaceutical formulation of genistein, produced as an amorphous solid dispersion by hot melt extrusion (genistein HME), has been developed that can be administered prophylactically to improve outcomes and survival following radiation exposure. Here, genistein HME was evaluated in a phase 1, open-label, single ascending dose (SAD) and multiple single dose (MSD) study enrolling 34 healthy volunteers. In the SAD study, participants were administered a single dose (500, 1000, 2000, or 3000 mg) and in the MSD study, participants were administered a single daily dose for six consecutive days (3000 mg/day). The overall adverse event profile and pharmacokinetics of genistein HME were determined. Additionally, biomarkers of genistein HME were evaluated by profiling whole blood for changes in gene expression by RNA sequencing. Genistein HME was found to be safe at doses up to 3000 mg. Most toxicities were mild to moderate gastrointestinal events, and no dose-limiting toxicities were reported. The maximum tolerated dose was not determined and the no observable adverse effect level was 500 mg. Genistein HME bioavailability greatly increased between the 2000 mg and 3000 mg doses. RNA sequencing analysis revealed that the majority of drug-related changes in gene expression occurred 8-12 hours after the sixth dose in the MSD study. Based on these results, the putative effective dose in humans is 3000 mg.

Host antibacterial defense of 6-10 Gy γ-irradiated mice subjected to lentiviral vector-based Gas5 gene therapy

Gut bacteria-associated sepsis is a serious concern in patients with gastrointestinal acute radiation syndrome (GIARS). In our previous studies, all mice exposed to 8 Gy of whole body γ-irradiation (8 Gy GIARS-mice) died by sepsis stemming from bacterial translocation. M1Mϕ located in the bacterial translocation site (i.e., the mesenteric lymph nodes, MLNs) have been characterized as major antibacterial effector cells. However, M2bMϕ, inhibitor cells for M1Mϕ polarization, predominated in the MLNs of these mice. The reduced expression of long noncoding RNA Gas5 was associated with M2bMϕ polarization. In this study, we tried to reduce the mortality rate of 8 Gy GIARS-mice through Gas5 gene transduction using lentivirus (Gas5 lentivirus). After Gas5 lentivirus injection, Gas5 RNA was overexpressed in MLN-F4/80⁺ cells of 8 Gy GIARS-mice, and these cells were identified as non-M2bMϕ. All of the 8 Gy GIARS-mice injected with Gas5 lentivirus survived 30 days or more after irradiation, and bacterial translocation and subsequent sepsis were shown to be minimal in these mice. These results indicate that the antibacterial resistance of 8 Gy GIASR-mice can be restored through the modulation of M2bMϕ located in the bacterial translocation site by Gas5 transduction.

Development of gamma-tocotrienol as a radiation medical countermeasure for the acute radiation syndrome: current status and future perspectives

INTRODUCTION

The possibility of exposure to high doses of total- or partial-body ionizing radiation at a high dose rate due to radiological/nuclear accidents or terrorist attacks is increasing. Despite research and development during the last six decades, there is a shortage of nontoxic, safe, and effective radiation medical countermeasures (MCMs) for radiological and nuclear emergencies. To date, the US Food and Drug Administration (US FDA) has approved only four agents for the mitigation of hematopoietic acute radiation syndrome (H-ARS).

AREA COVERED

We present the current status of a promising radiation countermeasure, gamma-tocotrienol (GT3; a component of vitamin E) as a radiation MCM that has been investigated in murine and nonhuman primate models of H-ARS. There is significant work with this agent using various omic platforms during the last few years to identify its efficacy biomarkers.

EXPERT OPINION

GT3 is a newer type of radioprotector having significant injury-countering potential and is currently under advanced development for H-ARS. As a pre-exposure drug, it requires only single doses, lacks significant toxicity, and has minimal, ambient temperature storage requirements; thus, GT3 appears to be an ideal MCM for military and first responders as well as for storage in the Strategic National Stockpile.

Gamma-Tocotrienol Modulates Total-Body Irradiation-Induced Hematopoietic Injury in a Nonhuman Primate Model

Radiation exposure causes acute damage to hematopoietic and immune cells. To date, there are no radioprotectors available to mitigate hematopoietic injury after radiation exposure. Gamma-tocotrienol (GT3) has demonstrated promising radioprotective efficacy in the mouse and nonhuman primate (NHP) models. We determined GT3-mediated hematopoietic recovery in total-body irradiated (TBI) NHPs. Sixteen rhesus macaques divided into two groups received either vehicle or GT3, 24 h prior to TBI. Four animals in each treatment group were exposed to either 4 or 5.8 Gy TBI. Flow cytometry was used to immunophenotype the bone marrow (BM) lymphoid cell populations, while clonogenic ability of hematopoietic stem cells (HSCs) was assessed by colony forming unit (CFU) assays on day 8 prior to irradiation and days 2, 7, 14, and 30 post-irradiation. Both radiation doses showed significant changes in the frequencies of B and T-cell subsets, including the self-renewable capacity of HSCs. Importantly, GT3 accelerated the recovery in CD34⁺ cells, increased HSC function as shown by improved recovery of CFU-granulocyte macrophages (CFU-GM) and burst-forming units erythroid (B-FUE), and aided the recovery of circulating neutrophils and platelets. These data elucidate the role of GT3 in hematopoietic recovery, which should be explored as a potential medical countermeasure to mitigate radiation-induced injury to the hematopoietic system.

Armed Forces Radiobiology Research Institute/Uniformed Services University of the Health Sciences perspective on space radiation countermeasure discovery

There is a need to develop and deploy medical countermeasures (MCMs) in order to support astronauts during space missions against excessive exposures to ionizing radiation exposure. The radiation environment of extraterrestrial space is complex and is characterized by nearly constant fluences of elemental atomic particles (protons being a dominant particle type) with widely different energies and ionization potentials. Chronic exposure to such ionizing radiation carries both near- and long-term health risks, which are generally related to the relative intensity and duration of exposure. These radiation-associated health risks can be managed only to a limited extent by physical means, but perhaps they might be more effectively managed biomedically. The Armed Forces Radiobiology Research Institute/Uniformed Services University of the Health Sciences has a long history of researching and developing MCMs specifically designed to support terrestrial-based military missions involving a radiation-threat component. The development of MCMs for both low and high doses of radiation are major aims of current research, and as such can provide lessons learned for the development of countermeasures applicable to future space missions and its extraterrestrial radiation environment.

Pharmacokinetic and metabolomic studies with a BIO 300 Oral Powder formulation in nonhuman primates

BIO 300, a pharmaceutical formulation of genistein, is being developed as a radiation countermeasure to treat hematopoietic acute radiation syndrome (H-ARS) and the delayed effects of acute radiation exposure (DEARE). Several studies have affirmed its safety and efficacy in alleviating the damaging effects of ionizing radiation. However, dose optimization of any drug has always been an important area of research because unnecessarily high drug doses may result in serious complications. In this study, we assessed the pharmacokinetics (PK) and metabolic profiles of two different doses of a novel solid-dosage formulation of BIO 300 (BIO 300 Oral Powder; 100 mg/kg and 200 mg/kg), when administered orally to nonhuman primates (NHPs). While the T_max values of both doses remained the same, the area under the curve at 48 h (AUC_0-48) was tripled by doubling the dose. Additionally, we monitored serum samples for global metabolomic/lipidomic changes using high resolution mass spectrometry followed by functional pathway analysis prior to and at various time points up to 48 h post drug administration. Interestingly, the metabolomic profiles of sera from NHPs that received the lower dose demonstrated a transient perturbation in numerous metabolites between the 4 and 12 h time points. Eventually, the metabolite abundance reverted to near-normal by 48 h. These study results are consistent with our previous studies focused on the PK and metabolomic analysis for parenteral and oral aqueous nanosuspension formulations of BIO 300. This study affirms that administration of a single dose of up to 200 mg/kg of BIO 300 Oral Powder is safe in NHPs and conferred no metabolomic-mediated safety features.

Acute radiation syndrome drug discovery using organ-on-chip platforms

INTRODUCTION

: The high attrition rate during drug development remains a challenge that costs a significant amount of time and money. Improving the probabilities of success during the early stages of radiation medical countermeasure (MCM) development for approval by the United States Food and Drug Administration (US FDA) following the Animal Rule will reduce this burden. For optimal development of MCMs, we need suitable and efficient radiation injury models with high biological relevance for evaluating drug efficacy as well as biomarker discovery and validation.

AREA COVERED

This article focuses on new technologies involving various organs-on-chip platforms. Of late, there have been rapid development of these technologies, especially in terms of mimicking both normal and abnormal physiological conditions. Here, we suggest possible applications of these novel systems for the discovery and development of radiation MCMs for the acute radiation syndrome (ARS). We offer preliminary information on the utility of one such system for MCM research and discovery for the ARS condition.

EXPERT OPINION

: Each organ-on-a-chip system has its own strengths and shortcomings. As such, the system selected for MCM discovery, development, and regulatory approval should be carefully considered and optimized to the fullest extent in order to augment successful drug testing and the minimization of attrition rates of candidate agents. The recent encouraging progress with organ-on-a-chip technology will likely lead to additional radiation MCMs for ARS approved by the US FDA. The acceptance of organ-on-a-chip technology may be a promising step toward improving the success rate of pharmaceuticals in MCM development.

Dimethyl Sulfoxide Attenuates Radiation-Induced Testicular Injury through Facilitating DNA Double-Strand Break Repair

The testis is susceptible to ionizing radiation, and male infertility and sexual dysfunction are prevalent problems after whole-body or local radiation exposure. Currently, there is no approved agent for the prevention or treatment of radiation-induced testicular injury. Herein, we investigated the radioprotective effect of dimethyl sulfoxide (DMSO), an organosulfur compound that acts as a free radical scavenger, on testicular injury. Treatment of mice with a single dose of DMSO prior to 5 Gy irradiation restored sex hormones and attenuated the reduction in testis weight. Histological analyses revealed that DMSO alleviated the distorted architecture of seminiferous tubules and promoted seminiferous epithelium regeneration following irradiation. Moreover, DMSO provided quantitative and qualitative protection for sperm and preserved spermatogenesis and fertility in male mice. Mechanistically, DMSO treatment enhanced GFRα-1⁺ spermatogonial stem cell and c-Kit⁺ spermatogonial survival and regeneration after radiation. DMSO also alleviated radiation-induced oxidative stress and suppressed radiation-induced germ cell apoptosis in vivo and in vitro. Additionally, DMSO efficiently reduced DNA damage accumulation and induced the expression of phosph-BRCA1, BRCA1, and RAD51 proteins, indicating that DMSO facilitates DNA damage repair with a bias toward homologous recombination. In summary, our findings demonstrate the radioprotective efficacy of DMSO on the male reproductive system, which warrants further studies for future application in the preservation of male fertility during conventional radiotherapy and nuclear accidents.

The Protective Effects of Apigenin Against Radiation-Induced Intestinal Injury

Radiation-induced intestinal injury (RIII) restricts the therapeutic efficacy of radiotherapy in abdominal or pelvic malignancies. Also, intestinal injury is a major cause of death following exposure to high doses of radiation in nuclear accidents. No safe and effective prophylactics or therapeutics for RIII are currently available. Here, we reported that the apigenin, a natural dietary flavone, prolonged the survival in c57 mice after lethal irradiation. Apigenin pretreatment brought about accelerated restoration of crypt-villus structure, including enhanced regenerated crypts, more differentiated epithelium cells, and increased villus length. In addition, intestinal crypt cells in the apigenin-treated group exhibited more proliferation and less apoptosis. Furthermore, apigenin increased the expression of Nrf2 and its downstream target gene HO-1, and decreased oxidative stress after irradiation. In conclusion, our findings demonstrate the radioprotective efficacy of apigenin. Apigenin has the potential to be used as a radioprotectant in cancer therapy and nuclear accidents.

The injuries of spleen and intestinal immune system induced by 2-Gy 60Co -ray whole-body irradiation

PURPOSE

The aim of the present study was to investigate the injuries of spleen and intestinal immune system induced by 2 Gy ⁶⁰Co γ ray in mice.

MATERIALS AND METHODS

A total of 120 Balb/c mice were randomly divided into two groups: blank control (Ctrl) and model (IR). The IR mice were exposed to a single dose of total body irradiation (2 Gy, dose rate: 1 Gy/min) and sacrificed on 1st, 3rd, 7th, 14th and 21st day after irradiation. The indicators including general observations and body weight, the changes in peripheral hemogram, spleen index, histopathology examination and lymphocyte subsets of spleen. As well as the count and subsets of lymphocyte in gut-associated lymphoid tissue.

RESULTS

Compared with the Ctrl group, the body weight, spleen index, peripheral blood cell and splenocyte amounts, intraepithelial lymphocytes number decreased significantly after exposure, accompanied by a notable decreased count of lymphocytes in Peyer's patch and mesenteric lymph nodes. Moreover, ionizing radiation also broke the balance of CD4+/CD8+ and increased the Treg proportion in spleen, which then triggered immune imbalance and immunosuppression. In general, the spleen injuries occurred on 1st day after exposure, worse on 3rd day, and were relieved on 7th day. The intestinal immune injuries were observed on 1st day, and attenuated on 3rd day. On 21st day after exposure, the spleen volume and index have returned to normal, except for the distribution of lymphocyte subpopulations. Furthermore, all indicators of gut-associated lymphoid tissue, except for mesenteric lymph nodes lymphocyte count, had returned to normal levels on 21st day.

CONCLUSION

In conclusion, our data showed the injuries of spleen and intestinal immune system induced by 2 Gy ⁶⁰Co γ ray whole-body irradiation. These findings may provide the bases for further radiation protection in the immunity.

Identification of novel biomarkers for acute radiation injury using multi-omics approach and nonhuman primate model

PURPOSE

The availability of validated biomarkers to assess radiation exposure and to assist in developing medical countermeasures remains an unmet need.

METHODS AND MATERIALS

We used a cobalt-60 gamma-irradiated nonhuman primate (NHP) model to delineate a multi-omics-based serum probability index of radiation exposure. Both male and female NHPs were irradiated with different doses ranging from 6.0 to 8.5 Gy, with 0.5 Gy increments between doses. We leveraged high-resolution mass spectrometry for analysis of metabolites, lipids, and proteins at 1, 2, and 6 days post-irradiation in NHP serum.

RESULTS

A logistic regression model was implemented to develop a 4-analyte panel to stratify irradiated NHPs from unirradiated with high accuracy that was agnostic for all doses of gamma-rays tested in the study, up to six days after exposure. This panel was comprised of Serpin Family A9, acetylcarnitine, PC (16:0/22:6), and suberylglycine, which showed 2 - 4-fold elevation in serum abundance upon irradiation in NHPs and can potentially be translated as a molecular diagnostic for human use following larger validation studies.

CONCLUSIONS

Taken together, this study, for the first time, demonstrates the utility of a combinatorial molecular characterization approach using an NHP model for developing minimally invasive assays from small volumes of blood that can be effectively used for radiation exposure assessments.