Juliann G. Kiang

Background:Exposure to ionizing radiation (IR), particularly when combined with additional trauma such as skin wounding (referred to as radiation combined injury, RCI), results in a synergistic pathology that significantly increases morbidity and mortality compared to isolated radiation injury (RI). While Nplate (romiplostim), a thrombopoietin (TPO) receptor agonist, is a Food and Drug Administration (FDA)-approved medical countermeasure for haematopoietic acute radiation syndrome (H-ARS), its efficacy on RCI is unclear. This study evaluated the mitigative effects of Nplate on 30-day survival, wound healing, and haematopoietic recovery following RCI.Methods:Fourteen-week-old female B6D2F1/J mice were exposed to 60Co γ-radiation (9.0 or 9.5 Gy at 0.4 Gy/min) followed by a full-thickness skin wound within one to two h. A single dose of Nplate (30 µg/kg) or vehicle was administered subcutaneously 24 h post-IR. Survival, body weight, and wound closure were monitored for 30 days. On day 30, survivors were euthanized for blood and tissue analysis, including bone marrow histology, colony-forming unit (CFU) assays, complete blood count (CBC), and splenic assessment.Results:Nplate significantly improved 30-day survival following 9.5 Gy RI, increasing survival from 30% to 75% (p = 0.0071). In contrast, Nplate provided no significant survival improvement in the RCI groups, with 30-day survival rates of 65% at 9.0 Gy (p = 0.5485) and 15% at 9.5 Gy (p = 0.6044) compared to 75% and 20% in their respective vehicle controls. Despite the lack of survival improvement after RCI, Nplate significantly accelerated wound closure on day 14 after RCI at 9.5 Gy. During the acute phase (Days 1–14), Nplate treatment significantly accelerated healing kinetics, increasing the linear wound healing rate by 54% from 0.124 mm/day to 0.192 mm/day (p = 0.0205). Histological analysis revealed that Nplate enhanced bone marrow cellularity, increased megakaryocyte counts, and suppressed IR-induced adipocyte formation. Furthermore, Nplate treatment significantly strengthened functional haematopoiesis, particularly after 9.0 Gy RCI, and stimulated recovery of the splenic lymphoid compartment after both RI and RCI at 9.5 Gy.Conclusions:Nplate is a potent mitigator of H-ARS and a stimulator of multi-lineage haematopoietic and tissue regeneration. However, its efficacy in improving survival is limited in RCI, potentially due to exacerbated systemic physiological stress. These results suggest that while Nplate promotes haematopoietic recovery, managing RCI may require a multi-modal approach to address the unique complexities of combined injury, including gastrointestinal (GI)-ARS, systemic inflammation and endothelial dysfunction.

No US Food and Drug Administration (FDA)-approved prophylaxis is currently available for Acute Radiation Syndrome (ARS), which remains a significant threat to military and civilian populations. In this study, we investigated Vasculotide (VT), a Tie2 receptor agonist mimic, as a novel pre-exposure prophylaxis designed to stabilize the vascular endothelium, one of primary targets of radiation-induced damage. To evaluate its efficacy, female B6D2F1/J mice were exposed to 9.5 Gy total body irradiation (TBI), with VT administered subcutaneously at 12 and 2 h prior to exposure. Assessments included 30-day survival, biomarkers of vascular injury, proinflammatory cytokine/chemokine profiling, and evaluation of hematopoietic (H) and gastrointestinal (GI) recovery. Our findings demonstrate that VT significantly increased 30-day survival in a dose-dependent manner, achieving a 30% survival advantage at the 20 μg/kg dose. Furthermore, VT provided robust protection against radiation-induced vascular activation and injury, effectively alleviating damage to the bone marrow (BM) and GI tract. Taken together, these results identify VT as a promising prophylactic countermeasure for ARS. By targeting the Tie2 pathway to preserve vascular integrity, VT addresses a critical gap in medical countermeasures, offering a viable strategy to enhance survival and accelerate multi-organ recovery in radiological mass-casualty scenarios.

Immunogenic cell death (ICD) is a programmed pathway leading to cell death and promotion of immunological responses. Melanoma is resistant to chemotherapy and radiotherapy (RT). Disulfiram (DSF), which forms complexes with copper (Cu), has been shown to induce ICD of many tumor types. Here, we aim to investigate whether DSF/Cu combined with irradiation (IR) can induce ICD and exert anti-cancer effects in melanoma. In vitro experiments, treatment of MV3 and B16F10 melanoma cells with DSF/Cu + IR significantly increased the cellular apoptosis and increased ICD markers: damage-associated molecular pattern molecule (DAMP) exposure and release, including calreticulin cell surface expression, high-mobility group box 1 (HMGB1) release, and decreased intracellular ATP levels. In addition, DSF/Cu combined with IR treatment inhibited tumor growth and enhanced tumor-infiltrating immune cells in the B16F10-bearing C57BL/6 model. Our findings reveal that combining IR with DSF/Cu induces ICD and inhibits tumor growth in melanoma, providing a promising strategy to overcome the inherent resistance of RT in melanoma.

The complexity of adverse responses from radiation injury (RI) followed by physical trauma, namely, radiation combined injury (RCI), is unique and more pronounced than either insult alone due to a poor understanding of the integration of these insults at the molecular/cellular/tissue and/or organ levels. It was shown that mice receiving ⁶⁰Co γ-photon RCI with wounding had a lower LD_50/30 than RI alone. This survival synergism was observed in bone marrow and the gastrointestinal system, as evidenced by an increase in γ-H2AX expression in bone marrow cell DNA, loss of circulatory blood cells, elevation of serum cytokine concentration, and activation of nuclear factor-κB/inducible nitric oxide synthase, and an earlier onset of bacterial infection and sepsis after RCI than after RI was detected. Dysbiosis (imbalance of the gut microbiota) was observed. There remains a pressing need for both prophylactic countermeasures and therapeutic remedies to deal with RCI threats. Investigations of how RCI can affect this important network of communication between the gut microbiota and other organs, including the brain, lung, heart, liver, kidney, and skin, could lead to new and critical interventions and prevention strategies. This review provides an update on new RCI animal models, dynamic changes in cytokine expression, dysbiosis, as well as links between the gut microbiome and other organs after RCI.

Ciprofloxacin (CIP) was found to enhance pegylated G-CSF therapy (PEG, Neulasta®)-induced survival from 30% to 85% after ionizing radiation exposure. This combined therapy significantly mitigated radiation-induced brain hemorrhage through its capability to improve platelet recovery. This study tested whether this combined treatment also mitigated gastrointestinal damage from radiation. B6D2F1 female mice were exposed to 60Co c radiation. CIP was fed daily to mice for up to 14 days. PEG was injected on day 1, and then weekly up to day 14. For the early time point study, blood, femurs, spleen, and ileum were collected on days 2, 4, 9, and 15 postirradiation. Bone marrow cells were counted; spleen weights and splenocyte counts were measured; and ileum histopathology was examined and analyzed. AKT, ERK, JNK, p38, claudin 2, NF-kB, Bax, Bcl-2, and gasdermin D were measured in ileum lysates using Western blotting while miR-34a was measured by reverse transcription followed by real-time-PCR, and citrulline was measured by colorimetric assay. In serum, interleukin-18 (IL-18) was measured by Luminex assay and complement protein 3 (C3) was detected by ELISA. The bacterial DNA load in livers was measured by real-time PCR. Radiation depleted bone marrow cells in femurs beginning day 2 through day 15 postirradiation, which was mitigated by PEG or CIP1PEG on day 9 through day 15 and by CIP on day 15, respectively. Radiation exposure led to decreased spleen weight on day 2 through day 15, while PEG or CIP1PEG significantly mitigated the reduction on day 9 through day 15. Radiation exposure reduced splenocyte counts on day 2 through day 15 postirradiation, but that was mitigated by PEG or CIP1PEG on day 15. Ileum histology showed that radiation decreased villus height on day 2 through day 15; CIP mitigated the reduction on day 15, whereas PEG1CIP mitigated it on day 2 through 15. Villus widths were increased on day 2 through day 15, while PEG1CIP effectively decreased them on day 4 through day 15. Crypt depth was reduced by radiation on day 2, but returned to the baseline on day 4 through 15. CIP or CIP1PEG transiently increased the depth only on day 4. Crypt counts were reduced by radiation on days 2 and 4, but returned to the baseline on days 9 and 15, regardless of individual drugs or combinations. Citrulline data confirmed the villus height recovery. Radiation significantly increased pro-inflammatory cytokine IL-18 on days 4 and 9, which was mitigated by PEG alone or PEG1CIP, but not by CIP alone. Radiation increased C3 on day 9 in ileum and serum. The serum C3 was positively associated with the serum IL-18 levels and negatively correlated with the crypt depth. Radiation-induced decreases in claudin 2 (a tight junction marker) in ileum and increases in bacterial DNA in livers were mitigated by PEG1CIP. Radiation did not reduce NF-kB and its activation but reduced Bcl-2 expression, which was not significantly recovered by any individual drug or combination. However, the PEG and CIP combination significantly decreased NF- kB and BAX. In contrast, radiation increased miR-34a and cleaved gasdermin D, which CIP1PEG effectively mitigated. This was confirmed by immunohistochemistry. The results taken together suggest that PEG1CIP combined treatment was effective in mitigating the radiation-induced bone marrow, spleen, and ileum injury. The mitigative effect of this combined treatment was mediated by increases in G-CSF levels that suppress miR-34a, thereby probably leading to decreased gasdermin D-mediated pyroptosis.

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.

The delayed effects of radiation alone and combined with skin injury on the kidney are poorly understood. We aimed to unravel and compare the inflammatory, oxidative stress, and survival signaling pathways in the kidney cortex before mice manifested renal dysfunction after these two injuries. Mice were analyzed 30 days post irradiation (9.5 Gy for radiation alone, 9.0 Gy for radiation combined with a skin wound). Radiation alone did not significantly alter BUN, NGAL, or KIM-1 protein levels, indicating preserved kidney function. However, the combined injury had increased KIM-1 protein levels, indicating a nuanced effect on renal health. Radiation and combined injury activated distinct inflammatory pathways. Radiation increased STAT3-Y705 phosphorylation, while combined injury boosted STAT1-Y701 phosphorylation. Additionally, radiation increased mRNA abundance of IFNγR1, IFNγR2, heparanase and IL-10, while combined injury tended to increase heparanase mRNA levels and reduced IL-4 mRNA levels. Both injuries increased the abundance of HO-1 protein, indicating oxidative stress, but radiation alone also reduced MnSOD and catalase proteins. Both injuries promoted AKT1-S473 phosphorylation and diminished p53 protein levels, suggesting inhibition of apoptosis. In summary, despite the distinct activation of inflammatory and oxidative stress pathways, both radiation alone and combined injury activated protective mechanisms such as HO-1 and AKT1, offering insights into molecular events before manifesting renal dysfunction.

Combined radiation with hemorrhage (combined injury, CI) exacerbates hematopoietic acute radiation syndrome and mortality compared to radiation alone (RI). We evaluated the effects of RI or CI on blood cell depletion as a biomarker to differentiate the two. Male CD2F1 mice were exposed to 8.75 Gy γ-radiation (⁶⁰Co). Within 2 h of RI, animals were bled under anesthesia 0% (RI) or 20% (CI) of total blood volume. Blood samples were collected at 4–5 h and days 1, 2, 3, 7, and 15 after RI. CI decreased WBC at 4–5 h and continued to decrease it until day 3; counts then stayed at the nadir up to day 15. CI decreased neutrophils, lymphocytes, monocytes, eosinophils, and basophils more than RI on day 1 or day 2. CI decreased RBCs, hemoglobin, and hematocrit on days 7 and 15 more than RI, whereas hemorrhage alone returned to the baseline on days 7 and 15. RBCs depleted after CI faster than post-RI. Hemorrhage alone increased platelet counts on days 2, 3, and 7, which returned to the baseline on day 15. Our data suggest that WBC depletion may be a potential biomarker within 2 days post-RI and post-CI and RBC depletion after 3 days post-RI and post-CI. For hemorrhage alone, neutrophil counts at 4–5 h and platelets for day 2 through day 7 can be used as a tool for confirmation.

Combined radiation with hemorrhage (combined injury, CI), exacerbates hematopoietic acute radiation syndrome and mortality compared to radiation alone (RI). We evaluated the effects of RI or CI on blood cell depletion as a biomarker to differentiate the two. Male CD2F1 mice were exposed to 8.75 Gy γ- radiation (60Co). Within 2 h of RI, animals were bled under anesthesia 0% (RI) or 20% (CI) of total blood volume. Blood samples were collected at 4-5 h and days 1, 2, 3, 7, and 15 after RI. CI decreased WBC at 4-5 h and continued to decrease them until day 3; counts then stayed at the nadir up to day 15. CI decreased neutrophils, lymphocytes, monocytes, eosinophils and basophils more than RI on day 1 or day 2. CI decreased RBCs, hemoglobin and hematocrit on days 7 and 15 compared to RI, whereas Hemorrhage alone returned to the baseline on days 7 and 15. RBCs depleted after CI faster than post RI. Hemorrhage alone increased platelet counts on days 2, 3, and 7, which returned to the baseline on day 15. Our data suggest that WBC depletion may be a biomarker within 2 days post-CI and RBC depletion after 3 days post-CI.

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.