Ghrelin Therapy Decreases Incidents of Intracranial Hemorrhage in Mice after Whole-Body Ionizing Irradiation Combined with Burn Trauma

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.

Ciprofloxacin and pegylated G-CSF combined therapy mitigates brain hemorrhage and mortality induced by ionizing irradiation

Introduction

Brain hemorrhage was found between 13 and 16 days after acute whole-body 9.5 Gy 60Co-γ irradiation (IR). This study tested countermeasures mitigating brain hemorrhage and increasing survival from IR. Previously, we found that pegylated G-CSF therapy (PEG) (i.e., Neulasta®, an FDA-approved drug) improved survival post-IR by 20-40%. This study investigated whether Ciprofloxacin (CIP) could enhance PEG-induced survival and whether IR-induced brain hemorrhage could be mitigated by PEG alone or combined with CIP.

Methods

B6D2F1 female mice were exposed to 60Co-γ-radiation. CIP was fed to mice for 21 days. PEG was injected on days 1, 8, and 15. 30-day survival and weight loss were studied in mice treated with vehicles, CIP, PEG, or PEG + CIP. For the early time point study, blood and sternums on days 2, 4, 9, and 15 and brains on day 15 post-IR were collected. Platelet numbers, brain hemorrhage, and histopathology were analyzed. The cerebellum/pons/medulla oblongata were detected with glial fibrillary acidic protein (GFAP), p53, p16, interleukin-18 (IL-18), ICAM1, Claudin 2, ZO-1, and complement protein 3 (C3).

Results

CIP + PEG enhanced survival after IR by 85% vs. the 30% improvement by PEG alone. IR depleted platelets, which was mitigated by PEG or CIP + PEG. Brain hemorrhage, both surface and intracranial, was observed, whereas the sham mice displayed no hemorrhage. CIP or CIP + PEG significantly mitigated brain hemorrhage. IR reduced GFAP levels that were recovered by CIP or CIP + PEG, but not by PEG alone. IR increased IL-18 levels on day 4 only, which was inhibited by CIP alone, PEG alone, or PEG + CIP. IR increased C3 on day 4 and day 15 and that coincided with the occurrence of brain hemorrhage on day 15. IR increased phosphorylated p53 and p53 levels, which was mitigated by CIP, PEG or PEG + CIP. P16, Claudin 2, and ZO-1 were not altered; ICAM1 was increased.

Discussion

CIP + PEG enhanced survival post-IR more than PEG alone. The Concurrence of brain hemorrhage, C3 increases and p53 activation post-IR suggests their involvement in the IR-induced brain impairment. CIP + PEG effectively mitigated the brain lesions, suggesting effectiveness of CIP + PEG therapy for treating the IR-induced brain hemorrhage by recovering GFAP and platelets and reducing C3 and p53.

Injectable multifunctional chitosan/dextran-based hydrogel accelerates wound healing in combined radiation and burn injury

Clinical wound management of combined radiation and burn injury (CRBI) remains a huge challenge due to serious injuries induced by redundant reactive oxygen species (ROS), the accompanying hematopoietic, immunologic suppression and stem cell reduction. Herein, the injectable multifunctional Schiff base cross-linked with gallic acid modified chitosan (CSGA)/oxidized dextran (ODex) hydrogels were rationally designed to accelerate wound healing through elimination of ROS in CRBI. CSGA/ODex hydrogels, fabricated by mixing solutions of CSGA and Odex, displayed good self-healing ability, excellent injectability, strong antioxidant activity, and favorable biocompatibility. More importantly, CSGA/ODex hydrogels exhibited excellent antibacterial properties, which is facilitated for wound healing. Furthermore, CSGA/ODex hydrogels significantly suppressed the oxidative damage of L929 cells in an H₂O₂-induced ROS microenvironment. The recovery of mice with CRBI in mice demonstrated that CSGA/ODex hydrogels significantly reduced the hyperplasia of epithelial cells and the expression of proinflammatory cytokine, and accelerated wound healing which was superior to the treatment with commercial triethanolamine ointment. In conclusion, the CSGA/ODex hydrogels as a wound dressing could accelerate the wound healing and tissue regeneration of CRBI, which provides great potential in clinical treatment of CRBI.

Combined radiation injury and its impacts on radiation countermeasures and biodosimetry

PURPOSE

Preparedness for medical responses to major radiation accidents and the increasing threat of nuclear warfare worldwide necessitates an understanding of the complexity of combined radiation injury (CI) and identifying drugs to treat CI is inevitably critical. The vital sign and survival after CI were presented. The molecular mechanisms, such as microRNA pathways, NF-κB-iNOS-IL-18 pathway, C3 production, the AKT-MAPK cross-talk, and TLR/MMP increases, underlying CI in relation to organ injury and mortality were analyzed. At present, no FDA-approved drug to protect, mitigate, or treat CI is available. The development of CI-specific medical countermeasures was reviewed. Because of the worsened acute radiation syndrome resulting from CI, diagnostic triage can be problematic. Therefore, biodosimetry and CI are bundled together with the need to establish effective triage methods with CI.

CONCLUSIONS

CI mouse model studies at AFRRI are reviewed addressing molecular responses, findings from medical countermeasures, and a proposed plasma proteomic biodosimetry approach based on a panel of radiation-responsive biomarkers (i.e., CD27, Flt-3L, GM-CSF, CD45, IL-12, TPO) negligibly influenced by wounding in an algorithm used for dose predictions is described.

Combined radiation burn injuries: A note

Combined radiation injury occurs when radiation is accompanied by any other form of trauma. The past experiences of Hiroshima, Nagasaki, and Chernobyl have revealed that a large number of victims of such nuclear accidents or attacks suffer from combined radiation injuries. The possibility of a nuclear attack seems very far-fetched, but the destruction that would occur in such an event would be massive, with a huge lossof lives. Therefore, preparedness for the same should be done beforehand. The severity of combined radiation depends upon various factors, such as radiation dose, type, tissues affected, and traumas. The article focuses on combined radiation burn injury (CRBI) which may arise due to the combination of ionising radiation with thermal burns. CRBI can have varied effects on different organs like the hematopoietic, digestive, lymphatic, cardiovascular, and respiratory systems. Some of the most profound lethal effects are hematopoietic dysfunction, gastrointestinal leakage, bacterial translocation to other organ sites, pulmonary fibrosis, and pneumonitis. In this article, we have attempted to accumulate the knowledge of ongoing research on the functioning of different organ systems, which are affected due to CRBI and possible countermeasures to minimize the effects, thus improving survival.

Autophagy inhibition facilitates wound closure partially dependent on the YAP/IL-33 signaling in a mouse model of skin wound healing

Autophagy is a self-phagocytic and highly evolutionarily conserved intracellular lysosomal catabolic system, which plays a vital role in a variety of trauma models, including skin wound healing (SWH). However, the roles and potential mechanisms of autophagy in SWH are still controversial. We firstly investigated the role of autophagy in SWH-induced wound closure rate, inflammatory response, and histopathology, utilizing an inhibitor of autophagy 3-methyladenine (3-MA) and its agonist rapamycin (RAP). As expected, we found 3-MA treatment remarkably increased the wound closure rate, combated inflammation response, and mitigated histopathological changes, while RAP delivery aggravated SWH-induced pathological damage. To further exploit the underlying mechanism of autophagy regulating inflammation, the specific inhibitors of yes-associated protein (YAP), Verteporfin, and Anti-IL-33 were applied. Herein, treating with 3-MA markedly suppressed the expression of tumor necrosis factor-α (TNF-α), IL-1β, and IL-6, promoted that of IL-10, IL-33, and ST2, while RAP administration reverted SWH-induced the up-regulation of these inflammatory cytokines mentioned above. Importantly, Verteporfin administration not only down-regulated the expression levels of YAP, TNF-α, and IL-6 but also up-regulated that of IL-33 and IL-10. Unexpectedly, 3-MA or RAP retreatment did not have any impact on the changes in IL-33 among these inflammatory indicators. Furthermore, elevated expression of IL-33 promoted wound closure and alleviated the pathological damage, whereas, its antagonist Anti-IL-33 treatment overtly reversed the above-mentioned effects of IL-33. Moreover, 3-MA in combination with anti-IL-33 treatment reversed the role of 3-MA alone in mitigated pathological changes, but they failed to revert the effect of anti-IL-33 alone on worsening pathological damage. In sum, emerging data support the novel contribution of the YAP/IL-33 pathway in autophagy inhibition against SWH-induced pathological damage, and highlight that the autophagy/YAP/IL-33 signal axis is expected to become a new therapeutic target for SWH.

PEG-G-CSF and L-Citrulline Combination Therapy for Mitigating Skin Wound Combined Radiation Injury in a Mouse Model

Radiation combined injury (RCI, radiation exposure coupled with other forms of injury, such as burn, wound, hemorrhage, blast, trauma and/or sepsis) comprises approximately 65% of injuries from a nuclear explosion, and greatly increases the risk of morbidity and mortality when compared to that of radiation injury alone. To date, no U.S. Food and Drug Administration (FDA)-approved countermeasures are available for RCI. Currently, three leukocyte growth factors (Neupogen®, Neulasta® and Leukine®) have been approved by the FDA for mitigating the hematopoietic acute radiation syndrome. However these granulocyte-colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) products have failed to increase 30-day survival of mice after RCI, suggesting a more complicated biological mechanism is in play for RCI than for radiation injury. In the current study, the mitigative efficacy of combination therapy using pegylated (PEG)-G-CSF (Neulasta) and -citrulline was evaluated in an RCI mouse model. L-citrulline is a neutral alpha-amino acid shown to improve vascular endothelial function in cardiovascular diseases. Three doses of PEG-G-CSF at 1 mg/kg, subcutaneously administered on days 1, 8 and 15 postirradiation, were supplemented with oral -citrulline (1 g/kg), once daily from day 1 to day 21 postirradiation. The combination treatment significantly improved the 30-day survival of mice after RCI from 15% (vehicle-treated) to 42%, and extended the median survival time by 4 days, as compared to vehicle controls. In addition, the combination therapy significantly increased body weight and bone marrow stem and progenitor cell clonogenicity in RCI mice, and accelerated recovery from RCI-induced intestinal injury, compared to animals treated with vehicle. Treatment with -citrulline alone also accelerated skin wound healing after RCI. In conclusion, these data indicate that the PEG-G-CSF and -citrulline combination therapy is a potentially effective countermeasure for mitigating RCI, likely by enhancing survival of the hematopoietic stem/progenitor cells and accelerating recovery from the RCI-induced intestinal injury and skin wounds.

Brain Damage and Patterns of Neurovascular Disorder after Ionizing Irradiation. Complications in Radiotherapy and Radiation Combined Injury

Exposure to ionizing radiation, mechanical trauma, toxic chemicals or infections, or combinations thereof (i.e., combined injury) can induce organic injury to brain tissues, the structural disarrangement of interactive networks of neurovascular and glial cells, as well as on arrays of the paracrine and systemic destruction. This leads to subsequent decline in cognitive capacity and decompensation of mental health. There is an ongoing need for improvement in mitigating and treating radiation- or combined injury-induced brain injury. Cranial irradiation per se can cause a multifactorial encephalopathy that occurs in a radiation dose- and time-dependent manner due to differences in radiosensitivity among the various constituents of brain parenchyma and vasculature. Of particular concern are the radiosensitivity and inflammation susceptibility of: 1. the neurogenic and oligodendrogenic niches in the subependymal and hippocampal domains; and 2. the microvascular endothelium. Thus, cranial or total-body irradiation can cause a plethora of biochemical and cellular disorders in brain tissues, including: 1. decline in neurogenesis and oligodendrogenesis; 2. impairment of the blood-brain barrier; and 3. ablation of vascular capillary. These changes, along with cerebrovascular inflammation, underlie different stages of encephalopathy, from the early protracted stage to the late delayed stage. It is evident that ionizing radiation combined with other traumatic insults such as penetrating wound, burn, blast, systemic infection and chemotherapy, among others, can exacerbate the radiation sequelae (and vice versa) with increasing severity of neurogenic and microvascular patterns of radiation brain damage.

Recent Advances in Experimental Burn Models

Simple Summary

Human burns are diverse and the most difficult injuries to study in clinical settings. Numerous experimental burn models designed to study and compare different aspects of burns and their consequences and treatment are steadily progressing. This review summarizes the latest advances in experimental burn research as a guide to aid in the future design of studies.

Abstract

Experimental burn models are essential tools for simulating human burn injuries and exploring the consequences of burns or new treatment strategies. Unlike clinical studies, experimental models allow a direct comparison of different aspects of burns under controlled conditions and thereby provide relevant information on the molecular mechanisms of tissue damage and wound healing, as well as potential therapeutic targets. While most comparative burn studies are performed in animal models, a few human or humanized models have been successfully employed to study local events at the injury site. However, the consensus between animal and human studies regarding the cellular and molecular nature of systemic inflammatory response syndrome (SIRS), scarring, and neovascularization is limited. The many interspecies differences prohibit the outcomes of animal model studies from being fully translated into the human system. Thus, the development of more targeted, individualized treatments for burn injuries remains a major challenge in this field. This review focuses on the latest progress in experimental burn models achieved since 2016, and summarizes the outcomes regarding potential methodological improvements, assessments of molecular responses to injury, and therapeutic advances.

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.

Non-Human Primates Receiving High-Dose Total-Body Irradiation are at Risk of Developing Cerebrovascular Injury Years Postirradiation

Nuclear accidents and acts of terrorism have the potential to expose thousands of people to high-dose total-body iradiation (TBI). Those who survive the acute radiation syndrome are at risk of developing chronic, degenerative radiation-induced injuries [delayed effects of acute radiation (DEARE)] that may negatively affect quality of life. A growing body of literature suggests that the brain may be vulnerable to radiation injury at survivable doses, yet the long-term consequences of high-dose TBI on the adult brain are unclear. Herein we report the occurrence of lesions consistent with cerebrovascular injury, detected by susceptibility-weighted magnetic resonance imaging (MRI), in a cohort of non-human primate [(NHP); rhesus macaque, Macaca mulatta] long-term survivors of high-dose TBI (1.1-8.5 Gy). Animals were monitored longitudinally with brain MRI (approximately once every three years). Susceptibility-weighted images (SWI) were reviewed for hypointensities (cerebral microbleeds and/or focal necrosis). SWI hypointensities were noted in 13% of irradiated NHP; lesions were not observed in control animals. A prior history of exposure was correlated with an increased risk of developing a lesion detectable by MRI (P = 0.003). Twelve of 16 animals had at least one brain lesion present at the time of the first MRI evaluation; a subset of animals (n = 7) developed new lesions during the surveillance period (3.7-11.3 years postirradiation). Lesions occurred with a predilection for white matter and the gray-white matter junction. The majority of animals with lesions had one to three SWI hypointensities, but some animals had multifocal disease (n = 2). Histopathologic evaluation of deceased animals within the cohort (n = 3) revealed malformation of the cerebral vasculature and remodeling of the blood vessel walls. There was no association between comorbid diabetes mellitus or hypertension with SWI lesion status. These data suggest that long-term TBI survivors may be at risk of developing cerebrovascular injury years after irradiation.

Self-Assembling Peptide Scaffold Carrying Neural-Cell Adhesion Molecule-Derived Mimetic-Peptide Transplantation Promotes Proliferation and Stimulates Neurite Extension by Modulating Tau Phosphorylation and Calpain/Glycogen Synthase Kinase 3 beta (GSK-3β) in Neurons

BACKGROUND Self-assembling peptide scaffolds have been extensively applied in tissue engineering. Many investigations have modified self-assembling peptide scaffolds by integrating functional motifs, with promising applications. This study aimed to generate a novel RADA16 self-assembling peptide scaffold integrating a neural-cell adhesion molecule-derived mimetic-peptide (SIDRVEPYSSTAQ) and evaluated the effects on neuron proliferation. MATERIAL AND METHODS A 37-amino-acids peptide of RADA16-activation motif containing neural-cell adhesion molecule-derived mimetic-peptide (SIDRVEPYSSTAQ) was synthesized and self-assembled into a scaffold. Dorsal root ganglion (DRG) and spinal cord motor neurons (SCMN) were primarily isolated and identified. Neurons (DRG and SCMN) were divided into FRM, FRM-MP, and FRM-MP-LiCl groups. The adherence ability of neurons was evaluated using toluidine blue staining. Proliferation and apoptosis of neurons were assessed using CCK-8 and flow cytometry assay, respectively. Immunofluorescence assay was used to measure neurite extension. Western blot assay was used to assess GSK-3ß/p-GSK-3ß, Tau/p-Tau, and calpain expression in neurons. RESULTS FRM-MP-LiCl released multiple-peptide with higher efficiency. FRM-MP-LiCl significantly enhanced proliferation and inhibited apoptosis compared to FRM and FRM-MP groups (p.

Ghrelin, a novel therapy, corrects cytokine and NF-κB-AKT-MAPK network and mitigates intestinal injury induced by combined radiation and skin-wound trauma

BACKGROUND

Compared to radiation injury alone (RI), radiation injury combined wound (CI) further enhances acute radiation syndrome and subsequently mortality. We previously reported that therapy with Ghrelin, the 28-amino-acid-peptide secreted from the stomach, significantly increased 30-day survival and mitigated hematopoietic death by enhancing and sustaining granulocyte-colony stimulating factor (G-CSF) and keratinocyte chemoattractant (KC) in the blood and bone marrow; increasing circulating white blood cell depletion; inhibiting splenocytopenia; and accelerating skin-wound healing on day 30 after CI. Herein, we aimed to study the efficacy of Ghrelin on intestinal injury at early time points after CI.

METHODS

B6D2F1/J female mice were exposed to 60Co-γ-photon radiation (9.5 Gy, 0.4 Gy/min, bilateral), followed by 15% total-body-surface-area skin wounds. Several endpoints were measured: at 4-5 h and on days 1, 3, 7, and 15.

RESULTS

Ghrelin therapy mitigated CI-induced increases in IL-1β, IL-6, IL-17A, IL-18, KC, and TNF-α in serum but sustained G-CSF, KC and MIP-1α increases in ileum. Histological analysis of ileum on day 15 showed that Ghrelin treatment mitigated ileum injury by increasing villus height, crypt depth and counts, as well as decreasing villus width and mucosal injury score. Ghrelin therapy increased AKT activation and ERK activation; suppressed JNK activation and caspase-3 activation in ileum; and reduced NF-κB, iNOS, BAX and Bcl-2 in ileum. This therapy recovered the tight junction protein and mitigated bacterial translocation and lipopolysaccharides levels. The results suggest that the capacity of Ghrelin therapy to reduce CI-induced ileum injury is mediated by a balanced NF-κB-AKT-MAPK network that leads to homeostasis of pro-inflammatory and anti-inflammatory cytokines.

CONCLUSIONS

Our novel results are the first to suggest that Ghrelin therapy effectively decreases intestinal injury after CI.

A novel therapy, using Ghrelin with pegylated G-CSF, inhibits brain hemorrhage from ionizing radiation or combined radiation injury

Medical treatment becomes challenging when complicated injuries arise from secondary reactive metabolic and inflammatory products induced by initial acute ionizing radiation injury (RI) or when combined with subsequent trauma insult(s) (CI). With such detrimental effects on many organs, CI exacerbates the severity of primary injuries and decreases survival. Previously, in a novel study, we reported that ghrelin therapy significantly improved survival after CI. This study aimed to investigate whether brain hemorrhage induced by RI and CI could be inhibited by ghrelin therapy with pegylated G-CSF (i.e., Neulasta®, an FDA-approved drug). B6D2F1 female mice were exposed to 9.5 Gy 60Co-γ-radiation followed by 15% total-skin surface wound. Several endpoints were measured at several days. Brain hemorrhage and platelet depletion were observed in RI and CI mice. Brain hemorrhage severity was significantly higher in CI mice than in RI mice. Ghrelin therapy with pegylated G-CSF reduced the severity in brains of both RI and CI mice. RI and CI did not alter PARP and NF-κB but did significantly reduce PGC-1α and ghrelin receptors; the therapy, however, was able to partially recover ghrelin receptors. RI and CI significantly increased IL-6, KC, Eotaxin, G-CSF, MIP-2, MCP-1, MIP-1α, but significantly decreased IL-2, IL-9, IL-10, MIG, IFN-γ, and PDGF-bb; the therapy inhibited these changes. RI and CI significantly reduced platelet numbers, cellular ATP levels, NRF1/2, and AKT phosphorylation. The therapy significantly mitigated these CI-induced changes and reduced p53-mdm2 mediated caspase-3 activation. Our data are the first to support the view that Ghrelin therapy with pegylated G-CSF is potentially a novel therapy for treating brain hemorrhage after RI and CI.

Radiation: a poly-traumatic hit leading to multi-organ injury

The range of radiation threats we face today includes everything from individual radiation exposures to mass casualties resulting from a terrorist incident, and many of these exposure scenarios include the likelihood of additional traumatic injury as well. Radiation injury is defined as an ionizing radiation exposure inducing a series of organ injury within a specified time. Severity of organ injury depends on the radiation dose and the duration of radiation exposure. Organs and cells with high sensitivity to radiation injury are the skin, the hematopoietic system, the gastrointestinal (GI) tract, spermatogenic cells, and the vascular system. In general, acute radiation syndrome (ARS) includes DNA double strand breaks (DSB), hematopoietic syndrome (bone marrow cells and circulatory cells depletion), cutaneous injury, GI death, brain hemorrhage, and splenomegaly within 30 days after radiation exposure. Radiation injury sensitizes target organs and cells resulting in ARS. Among its many effects on tissue integrity at various levels, radiation exposure results in activation of the iNOS/NF-kB/NF-IL6 and p53/Bax pathways; and increases DNA single and double strand breaks, TLR signaling, cytokine concentrations, bacterial infection, cytochrome c release from mitochondria to cytoplasm, and possible PARP-dependent NAD and ATP-pool depletion. These alterations lead to apoptosis and autophagy and, as a result, increased mortality. In this review, we summarize what is known about how radiation exposure leads to the radiation response with time. We also describe current and prospective countermeasures relevant to the treatment and prevention of radiation injury.

Delayed Captopril Administration Mitigates Hematopoietic Injury in a Murine Model of Total Body Irradiation

The increasing potential for accidental radiation exposure from either nuclear accidents or terrorist activities has escalated the need for radiation countermeasure development. We previously showed that a 30-day course of high-dose captopril, an ACE inhibitor, initiated 1–4 h after total body irradiation (TBI), improved Hematopoietic Acute Radiation Syndrome (H-ARS) and increased survival in mice. However, because of the time likely required for the deployment of a stockpiled radiation countermeasure to a radiation mass casualty site, there is a need for therapies that can be administered 24–48 hours after initial exposure. Using C57BL/6 mice exposed to an LD_50-80/30 of ⁶⁰Co TBI (7.75–7.9 Gy, 0.615 Gy/min), we show that low-dose captopril administration, initiated as late as 48 h post-TBI and continued for 14 days, significantly enhanced overall survival similarly to high-dose, rapid administration. Captopril treatment did not affect radiation-induced cell cycle arrest genes or the immediate loss of hematopoietic precursors. Reduced mortality was associated with the recovery of bone marrow cellularity and mature blood cell recovery at 21–30 days post-irradiation. Captopril reduced radiation-induced cytokines EPO, G-CSF, and SAA in the plasma. Finally, delayed captopril administration mitigated brain micro-hemorrhage at 21 days post-irradiation. These data indicate that low dose captopril administered as late as 48 h post-TBI for only two weeks improves survival that is associated with hematopoietic recovery and reduced inflammatory response. These data suggest that captopril may be an ideal countermeasure to mitigate H-ARS following accidental radiation exposure.

Efficacy and mechanisms underlying the effects of allogeneic umbilical cord mesenchymal stem cell transplantation on acute radiation injury in tree shrews

Umbilical cord mesenchymal stem cells (UC-MSCs) exert strong immunomodulatory effects and can repair organs. However, their roles in radiation injury remain unclear. We show that in tree shrews with acute radiation injury, injected UC-MSCs significantly improved survival rates, reduced lung inflammation and apoptosis, prevented pulmonary fibrotic processes, recovered hematopoiesis, and increased blood counts. A protein microarray analysis showed that serum levels of the anti-inflammatory cytokines IL-10 and IL-13 and the growth factors BMP-5, BMP-7, HGF, insulin, NT-4, VEGFR3, and SCF were significantly higher, while those of the inflammatory cytokines IL-2, TIMP-2, TNF-α, IFN-γ, IL-1ra, and IL-8 and the fibrosis-related factors PDGF-BB, PDGF-AA, TGF-β1, IGFBP-2, and IGFBP-4 were significantly lower in UC-MSC-injected animals. A transcriptome analysis of PBMCs showed that the mRNA expression of C1q was upregulated, while that of HLA-DP was downregulated after UC-MSC injection. These results confirm the immunohistochemistry results. eGFP-labeled UC-MSCs were traced in vivo and found in the heart, liver, spleen, lungs, kidneys, thymus, small intestine and bone marrow. Our findings suggest that UC-MSC transplantation may be a novel therapeutic approach for treating acute radiation injury.

Ghrelin therapy mitigates bone marrow injury and splenocytopenia by sustaining circulating G-CSF and KC increases after irradiation combined with wound

Background

Radiation injury combined wound (CI) enhances acute radiation syndrome and subsequently mortality as compared to radiation injury alone (RI). We previously reported that ghrelin (a 28-amino-acid-peptide secreted from the stomach) treatment significantly increased a 30-day survival, mitigated hematopoietic death, circulating white blood cell (WBC) depletion and splenocytopenia and accelerated skin-wound healing on day 30 after CI. Herein, we aimed to study the ghrelin efficacy at early time points after CI.

Methods

B6D2F1/J female mice were exposed to ⁶⁰Co-γ-photon radiation at 9.5 Gy (LD_50/30) followed by a 15% total-body-surface-area skin wound. Several endpoints were measured at 4-5 h, days 1, 3, 7 and 15.

Results

Histological analysis of sternums on day 15 showed that CI induced more adipocytes and less megakaryocytes than RI. Bone marrow cell counts from femurs also indicated CI resulted in lower bone marrow cell counts on days 1, 7 and 15 than RI. Ghrelin treatment mitigated these CI-induced adverse effects. RI and CI decreased WBCs within 4-5 h and continued to decrease to day 15. Ghrelin treatment mitigated decreases in CI mice, mainly from all types of WBCs, but not RBCs, hemoglobin levels and hematocrit values. Ghrelin mitigated the CI-induced thrombocytopenia and splenocytopenia. CI increased granulocyte-colony stimulating factor (G-CSF) and keratinocyte chemoattractant (KC) in blood and bone marrow. Ghrelin therapy was able to enhance and sustain the increases in serum on day 15, probably contributed by spleen and ileum, suggesting the correlation between G-CSF and KC increases and the neutropenia mitigation. Activated caspase-3 levels in bone marrow cells were significantly mitigated by ghrelin therapy on days 3 and 15.

Conclusions

Our novel results are the first to suggest that ghrelin therapy effectively decreases hematopoietic death and splenocytopenia by sustaining circulating G-CSF and KC increases after CI. These results demonstrate efficacy of ghrelin as a radio-mitigator/therapy agent for CI.