Partial-body Irradiation Research Articles

Evaluation of sodium orthovanadate as a radioprotective agent under total-body irradiation and partial-body irradiation conditions in mice

Purpose Our previous study indicated that sodium orthovanadate (vanadate), a strong inhibitor of p53, effectively suppressed the lethality from the hematopoietic (HP) and gastrointestinal (GI) syndromes after 12 Gy total-body irradiation (TBI) in mice. This conclusion, however, was inconsistent with the fact that p53 plays a radioprotective role in the intestinal epithelium. The death after TBI of around 12 Gy was attributed to a combined effect of HP and GI syndromes. To verify the effect from prophylactic administration of p53 inhibitor on protection of HP and GI syndromes, in this study, the radioprotective effects from vanadate were investigated in TBI and lower half-body irradiation (partial-body irradiation: PBI) mouse models. Methods Female ICR mice were given a single injection of vanadate or vehicle, followed by a lethal dose of TBI or PBI. Radioprotective effects of vanadate against the irradiations were evaluated by analyzing survival rate, body weight, hematopoietic parameters, and histological changes in the bone marrow and intestinal epithelium. Results TBI-induced HP syndrome was effectively suppressed by vanadate treatment. After TBI, the vanadate-treated mice retained better bone marrow cellularity and showed markedly higher survival rate compared to the vehicle-treated animals. In contrast, vanadate did not relieve loss of intestinal crypts and failed to rescue mice from GI death after PBI. Conclusion Vanadate is a p53 inhibitor that has been shown to be beneficial as a radiation protective agent against HP but was not effective in protecting against acute GI radiation injury.

Acute Radiation-Induced Hematopoietic Depletion Does Not Alter the Onset or Severity of Pneumonitis in Mice.

Survival from partial-body irradiation (PBI) may be limited by the development of the late lung injury response of pneumonitis. Herein we investigated the hypothesis that acute hematopoietic depletion alters the onset and severity of lung disease in a mouse model. To establish depletion, C3H/HeJ mice received 8 Gy PBI with shielding of only the tibiae, ankles and feet. One week after irradiation, blood lymphocyte and neutrophil counts were each significantly reduced (P < 0.04) in these mice compared to levels in untreated controls or in mice receiving 16 Gy to the whole thorax only. All 8 Gy PBI mice survived to the experimental end point of 16 weeks postirradiation. To determine whether the hematopoietic depletion affects lung disease, groups of mice received 8 Gy PBI plus 8 Gy whole-thorax irradiation (total lung dose of 16 Gy) or 16 Gy whole-thorax irradiation only. The weight loss, survival to onset of respiratory distress (P = 0.17) and pneumonitis score (P = 0.96) of mice that received 8 Gy PBI plus 8 Gy whole-thorax irradiation were not significantly different from those of mice receiving 16 Gy whole-thorax irradiation only. Mice in respiratory distress from PBI plus whole-thorax irradiation had significantly reduced (P = 0.02) blood monocyte counts compared to levels in distressed, whole-thorax irradiated mice, and symptomatic pneumonitis was associated with increased blood neutrophil counts (P = 0.04) relative to measures from irradiated, non-distressed mice. In conclusion, survivable acute hematopoietic depletion by partial-body irradiation did not alter the onset or severity of lethal pneumonitis in the C3H/HeJ mouse model.

Differential Recovery of Small Intestinal Segments after Partial-Body Irradiation in Non-Human Primates.

In the event of a radiological attack or accident, it is more likely that the absorbed radiation dose will be heterogeneous, rather than uniformly distributed throughout the body. This type of uneven dose distribution is known as partial-body irradiation (PBI). Partial exposure of the vital organs, specifically the highly radiosensitive intestines, may cause death, if the injury is significant and the post-exposure recovery is considerably compromised. Here we investigated the recovery rate and extent of recovery from PBI-induced intestinal damage in large animals. Rhesus macaques (Macaca mulatta) were randomly divided into four groups: sham-irradiated (0 Gy), 8 Gy PBI, 11 Gy PBI and 14 Gy PBI. A single dose of ionizing radiation was delivered in the abdominal region using a uniform bilateral anteroposterior and posteroanterior technique. Irradiated animals were scheduled for euthanasia on days 10, 28 or 60 postirradiation, and sham-irradiated animals on day 60. Intestinal structural injuries were assessed via crypt depth, villus height, and mucosal surface length in the four different intestinal regions (duodenum, proximal jejunum, distal jejunum and ileum) using H&E staining. Higher radiation doses corresponded with more injury at 10 days post-PBI and a faster recovery rate. However, at 60 days post-PBI, damage was still evident in all regions of the intestine. The proximal and distal ends (duodenum and ileum, respectively) sustained less damage and recovered more fully than the jejunum.

Polypharmacy to Mitigate Acute and Delayed Radiation Syndromes.

There is a need for countermeasures to mitigate lethal acute radiation syndrome (ARS) and delayed effects of acute radiation exposure (DEARE). In WAG/RijCmcr rats, ARS occurs by 30-days following total body irradiation (TBI), and manifests as potentially lethal gastrointestinal (GI) and hematopoietic (H-ARS) toxicities after >12.5 and >7 Gy, respectively. DEARE, which includes potentially lethal lung and kidney injuries, is observed after partial body irradiation >12.5 Gy, with one hind limb shielded (leg-out PBI). The goal of this study is to enhance survival from ARS and DEARE by polypharmacy, since no monotherapy has demonstrated efficacy to mitigate both sets of injuries. For mitigation of ARS following 7.5 Gy TBI, a combination of three hematopoietic growth factors (polyethylene glycol (PEG) human granulocyte colony-stimulating factor (hG-CSF), PEG murine granulocyte-macrophage-CSF (mGM-CSF), and PEG human Interleukin (hIL)-11), which have shown survival efficacy in murine models of H-ARS were tested. This triple combination (TC) enhanced survival by 30-days from ∼25% to >60%. The TC was then combined with proven medical countermeasures for GI-ARS and DEARE, namely enrofloxacin, saline and the angiotensin converting enzyme inhibitor, lisinopril. This combination of ARS and DEARE mitigators improved survival from GI-ARS, H-ARS, and DEARE after 7.5 Gy TBI or 13 Gy PBI. Circulating blood cell recovery as well as lung and kidney function were also improved by TC + lisinopril. Taken together these results demonstrate an efficacious polypharmacy to mitigate radiation-induced ARS and DEARE in rats.

Radiation Increases Bioavailability of Lisinopril, a Mitigator of Radiation-Induced Toxicities.

There are no FDA-approved drugs to mitigate the delayed effects of radiation exposure that may occur after a radiological attack or nuclear accident. To date, angiotensin-converting enzyme inhibitors are one of the most successful candidates for mitigation of hematopoietic, lung, kidney, and brain injuries in rodent models and may mitigate delayed radiation injuries after radiotherapy. Rat models of partial body irradiation sparing part of one hind leg (leg-out PBI) have been developed to simultaneously expose multiple organs to high doses of ionizing radiation and avoid lethal hematological toxicity to study the late effects of radiation. Exposures between 9 and 14 Gy damage the gut and bone marrow (acute radiation syndrome), followed by delayed injuries to the lung, heart, and kidney. The goal of the current study is to compare the pharmacokinetics (PK) of a lead angiotensin converting enzyme (ACE) inhibitor, lisinopril, in irradiated vs. nonirradiated rats, as a step toward licensure by the FDA. Methods: Female WAG/RijCmcr rats were irradiated with 12.5–13 Gy leg-out PBI. At day 35 after irradiation, during a latent period for injury, irradiated and nonirradiated siblings received a single gavage (0.3 mg, 0.6 mg) or intravenous injection (0.06 mg) of lisinopril. Plasma, urine, lung, liver and kidney levels of lisinopril were measured at different times. PK modeling (R package) was performed to track distribution of lisinopril in different compartments. Results: A two-compartment (central plasma and periphery) PK model best fit lisinopril measurements, with two additional components, the gavage and urine. The absorption and renal clearance rates were similar between nonirradiated and irradiated animals (respectively: ratios 0.883, p = 0.527; 0.943, p = 0.605). Inter-compartmental clearance (from plasma to periphery) for the irradiated rats was lower than for the nonirradiated rats (ratio 0.615, p = 0.003), while the bioavailability of the drug was 33% higher (ratio = 1.326, p < 0.001). Interpretation: Since receptors for lisinopril are present in endothelial cells lining blood vessels, and radiation induces vascular regression, it is possible that less lisinopril remains bound in irradiated rats, increasing circulating levels of the drug. However, this study cannot rule out changes in total amount of lisinopril absorbed or excreted long-term, after irradiation in rats.

Interventional radiologists have a higher rate of chromosomal damage due to occupational radiation exposure: a dicentric chromosome assay.

There are growing concerns regarding radiation exposure in medical workers who perform interventional fluoroscopy procedures. Owing to the nature of certain interventional procedures, workers may be subjected to partial-body radiation exposure that is high enough to cause local damage. We aimed to investigate the level of radiation exposure in interventional radiologists in South Korea by performing cytogenetic biodosimetry, particularly focusing on partial-body exposure. Interventional radiologists (n = 52) completed a questionnaire, providing information about their work history and practices. Blood samples were collected and processed for a dicentric chromosome assay. We determined Papworth's U-value to assess the conformity of dicentrics with the Poisson distribution to estimate the partial-body exposures of the radiologists. Radiologists had a higher number of dicentrics than the normal population and industrial radiographers. Indeed, subjects with a U-value of > 1.96, an indicator of heterogeneous exposure, were observed more frequently; 4.67 ± 0.81% of their body was irradiated at an average dose of 4.64 ± 0.67 Gy. Logistic regression analysis revealed that the total duration of all interventional procedures per week was associated with partial-body exposure levels. Our findings suggest that interventional radiologists had greater chromosomal damages than those in other occupational groups, and their partial-body exposure levels might be high enough to cause local damage. Use of special dosimeters to monitor partial-body exposure, as well as restricting the time and frequency of interventional procedures, could help reduce occupational radiation exposure. • Interventional radiologists had a higher number of dicentrics than the normal population and industrial radiographers. • The level of partial-body exposure of interventional radiologists might be high enough to cause occupational local damage such as a skin cancer in fingers. • Restricting the duration and frequency of interventional procedures might be helpful in reducing occupational radiation exposure.

Abstract PO-081: LR-IL-22 protects the intestine to facilitate whole abdomen irradiation in ovarian cancer

Abstract Ovarian cancer is the most lethal gynecological cancer worldwide with an estimated 152,000 deaths per year. Despite optimal management with radical cytoreductive surgery and subsequent platinum/taxane-based chemotherapy, most patients, will suffer recurrence within 18 months. Our laboratory has recently discovered a new therapeutic agent for intestinal radiation protection, namely the novel second-generation probiotic Lactobacillus reuteri (LR) genetically engineered to produce the radioprotective cytokine Interleukin-22 (IL-22) (Zhang et al. In Vivo, 34(1):39-50, 2020 Jan-Feb). To demonstrate that LR-IL-22 could protect the intestines from irradiation, we used three mouse models (total body irradiation (TBI), whole abdomen irradiation (WAI) and partial body irradiation (PBI)). For TBI, C57BL/6 mice were irradiated to 9.25 Gy to the entire body. For WAI, C57BL/6 mice were irradiated using a linear accelerator so that only the abdomen was irradiated to 19.75 Gy with the remainder of the body shielded from the irradiation. PBI was performed with the right rear leg shielded with the rest of the body irradiated to 15 Gy. In all three models the mice were gavaged 24 hours after irradiation with 1 × 109 LR-IL-22 cells. The mice were followed for development of either the hematopoietic syndrome (TBI) or gastrointestinal syndrome (WAI or PBI). In separate experiments we determined if mice irradiated as above had decreased irradiation induced inflammation using a Luminex assay on the intestine and blood plasma from mice sacrificed on days 0, 1, 2, 3, 5 and 7 following irradiation. We also determined whether intraoral gavage of LR-IL-22 24 hours prior to irradiation might protect the tumor in a mouse ovarian tumor model. Murine ovarian tumor cells 2F8-cis were injected intraperitoneally into Muc1 transgenic mice. Seventy-two hours later the mice were irradiated to 16 Gy WAI and followed for tumor growth. In the TBI model, mice treated with LR-IL-22 24 hours prior to irradiation had an increased survival of 80% compared to 0% in control irradiated mice (p = 0.0001). In the WAI model, mice treated with LR-IL-22 had a 40% survival following 19.75 Gy compared to 0% in the control irradiated group (p = 0. 0100). Following the PBI dose of 15 Gy, mice treated with LR-IL-22 had a 70% survival compared to 0% for the control irradiation only mice (p = 0.0006). Decreased expression of several inflammatory proteins such as TNF-α, IL-6 and IFN-γ (p = 0.0423, 0.0473 and 0.0024, respectively) was also detected in mice treated with LR-IL-22 24 hours prior to WAI compared to control irradiated mice. Furthermore, two weeks after injecting Muc1 transgenic mice with tumors, the nonirradiated mice had more than 200 small tumor nodules disseminated throughout the peritoneum while control WAI mice or mice treated with intraoral LR-IL-22 prior to WAI had no more than 10 tumor nodules. Hence, intraoral LR-IL-22 prior to chemoradiation may protect the intestines and result in increased survival of ovarian cancer patients. Citation Format: Diala Fatima Hamade, Renee Fisher, Wen Hou, Donna Shields, Michael W. Epperly, Joel S. Greenberger. LR-IL-22 protects the intestine to facilitate whole abdomen irradiation in ovarian cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-081.

Late Health Effects of Partial Body Irradiation Injury in a Minipig Model Are Associated with Changes in Systemic and Cardiac IGF-1 Signaling

Clinical, epidemiological, and experimental evidence demonstrate non-cancer, cardiovascular, and endocrine effects of ionizing radiation exposure including growth hormone deficiency, obesity, metabolic syndrome, diabetes, and hyperinsulinemia. Insulin-like growth factor-1 (IGF-1) signaling perturbations are implicated in development of cardiovascular disease and metabolic syndrome. The minipig is an emerging model for studying radiation effects given its high analogy to human anatomy and physiology. Here we use a minipig model to study late health effects of radiation by exposing male Göttingen minipigs to 1.9–2.0 Gy X-rays (lower limb tibias spared). Animals were monitored for 120 days following irradiation and blood counts, body weight, heart rate, clinical chemistry parameters, and circulating biomarkers were assessed longitudinally. Collagen deposition, histolopathology, IGF-1 signaling, and mRNA sequencing were evaluated in tissues. Our findings indicate a single exposure induced histopathological changes, attenuated circulating IGF-1, and disrupted cardiac IGF-1 signaling. Electrolytes, lipid profiles, liver and kidney markers, and heart rate and rhythm were also affected. In the heart, collagen deposition was significantly increased and transforming growth factor beta-1 (TGF-beta-1) was induced following irradiation; collagen deposition and fibrosis were also observed in the kidney of irradiated animals. Our findings show Göttingen minipigs are a suitable large animal model to study long-term effects of radiation exposure and radiation-induced inhibition of IGF-1 signaling may play a role in development of late organ injuries.

Prognostic value of the micronucleus assay for clinical endpoints in neoadjuvant radiochemotherapy for rectal cancer

BackgroundThe question whether lymphocyte radiosensitivity is representative of patients’ response to radiotherapy (RT) remains unsolved. We analyzed lymphocyte cytogenetic damage in patients who were homogeneously treated with preoperative radiochemotherapy (RCT) for rectal cancer within clinical trials. We tested for interindividual variation and consistent radiosensitivity after in-vivo and in-vitro irradiation, analyzed the effect of patients’ and RCT characteristics on cytogenetic damage, and tested for correlations with patients’ outcome in terms of tumor response, survival and treatment-related toxicity.MethodsThe cytokinesis-block micronucleus cytome (CBMNcyt) assay was performed on the peripheral blood lymphocytes (PBLCs) of 134 patients obtained before, during, at the end of RCT, and during the 2-year follow-up. A subset of PBLCs obtained before RCT was irradiated in-vitro with 3 Gy. RCT included 50.4 Gy of pelvic RT with 5-fluorouracil (5-FU) alone (n = 78) or 5-FU plus oxaliplatin (n = 56). The analyzed variables included patients’ age, gender, RT characteristics (planning target volume size [PTV size], RT technique), and chemotherapy characteristics (5-FU plasma levels, addition of oxaliplatin). Outcome was analyzed as tumor regression, patient survival, and acute and late toxicity.ResultsCytogenetic damage increased significantly with the radiation dose and varied substantially between individuals. Women were more sensitive than men; no significant age-dependent differences were observed. There was a significant correlation between the cytogenetic damage after in-vitro irradiation and in-vivo RCT. We found a significant effect of the PTV size on the yields of cytogenetic damage after RCT, while the RT technique had no effect. Neither the addition of oxaliplatin nor the 5-FU levels influenced cytogenetic damage. We found no correlation between patient outcome and the cytogenetic damage.ConclusionsWe found consistent cytogenetic damage in lymphocytes after in-vivo RCT and in-vitro irradiation. Gender was confirmed as a well-known, and the PTV size was identified as a less well-known influencing variable on lymphocyte cytogenetic damage after partial-body irradiation. A consistent level of cytogenetic damage after in-vivo and in-vitro irradiation may indicate the importance of genetic factors for individual radiosensitivity. However, we found no evidence that in-vivo or in-vitro irradiation-induced cytogenetic damage is an adequate biomarker for the response to RCT in rectal cancer patients.

Comparative metabolic profiles of total and partial body radiation exposure in mice using an untargeted metabolomics approach.

A large scale population exposure to ionizing radiation during intentional or unintentional nuclear accidents undoubtedly generates a complex scenario with partial-body as well as total-body irradiated victims. A high throughput technique based rapid assessment method is an urgent necessity for stratification of exposed subjects independent of whether exposure is uniform total-body or non-homogenous partial-body. Here, we used Nuclear Magnetic Resonance (NMR) based metabolomics approach to compare and identify candidate metabolites differentially expressed in total and partially irradiated mice model. C57BL/6 male mice (8-10weeks) were irradiated total-body or locally to thoracic, hind limbor abdominal regions with 10Gy of gamma radiation. Urine samples collected at 24h post irradiation were examined using high resolution NMR spectroscopy and the datasets were analysed using multivariate analysis. Multivariate and metabolic pathway analysis in urine samples collected at 24h post-radiation exhibited segregation of all irradiated groups from controls. Metabolites associated with energy metabolism, gut flora metabolism and taurine were common to partial and total-body irradiation, thus making them potential candidates for radiation exposure. Nevertheless, a distinct metabolic pattern was observed in partial-body exposed groups with maximum changes observed in the hind limb region indicating differential tissue associated radiation sensitivity. The organ-specific changes may provide an early warning regarding the physiological system at risk after radiation injury. The study affirms potentiality of metabolite markers and comparative analysis could be an important piece of information for an integrated solution to a complex research question in terms of radiation biomarkers.

Gamma Tocotrienol Protects Mice From Targeted Thoracic Radiation Injury.

Radiation injury will result in multiorgan dysfuntion leading to multiorgan failure. In addition to many factors such as radiation dose, dose rate, the severity of the injury will also depend on organ systems which are exposed. Here, we report the protective property of gamma tocotrienol (GT3) in total as well as partial body irradiation (PBI) model in C3H/HeN male mice. We have carried out PBI by targeting thoracic region (lung-PBI) using Small Animal Radiation Research Platform, an X-ray irradiator with capabilities of an image guided irradiation with a variable collimator with minimized exposure to non-targeted tissues and organs. Precise and accurate irradiation of lungs was carried out at either 14 or 16 Gy at an approximate dose rate of 2.6 Gy/min. Though a low throughput model, it is amenable to change the field size on the spot. No damage to other non-targeted organs was observed in histopathological evaluation. There was no significant change in peripheral blood counts of irradiated mice in comparison to naïve mice. Femoral bone marrow cells had no damage in irradiated mice. As expected, damage to the targeted tissue was observed in the histopathological evaluation and non-targeted tissue was found normal. Regeneration and increase of cellularity and megakaryocytes on GT3 treatment was compared to significant loss of cellularity in saline group. Peak alveolitis was observed on day 14 post-PBI and protection from alveolitis by GT3 was noted. In irradiated lung tissue, thirty proteins were found to be differentially expressed but modulated by GT3 to reverse the effects of irradiation. We propose that possible mode of action of GT3 could be Angiopoietin 2-Tie2 pathway leading to AKT/ERK pathways resulting in disruption in cell survival/angiogenesis.

Phenotypic and Functional Characteristics of Exosomes Derived from Irradiated Mouse Organs and Their Role in the Mechanisms Driving Non-Targeted Effects.

Molecular communication between irradiated and unirradiated neighbouring cells initiates radiation-induced bystander effects (RIBE) and out-of-field (abscopal) effects which are both an example of the non-targeted effects (NTE) of ionising radiation (IR). Exosomes are small membrane vesicles of endosomal origin and newly identified mediators of NTE. Although exosome-mediated changes are well documented in radiation therapy and oncology, there is a lack of knowledge regarding the role of exosomes derived from inside and outside the radiation field in the early and delayed induction of NTE following IR. Therefore, here we investigated the changes in exosome profile and the role of exosomes as possible molecular signalling mediators of radiation damage. Exosomes derived from organs of whole body irradiated (WBI) or partial body irradiated (PBI) mice after 24 h and 15 days post-irradiation were transferred to recipient mouse embryonic fibroblast (MEF) cells and changes in cellular viability, DNA damage and calcium, reactive oxygen species and nitric oxide signalling were evaluated compared to that of MEF cells treated with exosomes derived from unirradiated mice. Taken together, our results show that whole and partial-body irradiation increases the number of exosomes, instigating changes in exosome-treated MEF cells, depending on the source organ and time after exposure.

Acute Radiation-induced Lung Injury in the Non-human Primate: A Review and Comparison of Mortality and Co-morbidities Using Models of Partial-body Irradiation with Marginal Bone Marrow Sparing and Whole Thorax Lung Irradiation

The nonhuman primate, rhesus macaque, is a relevant animal model that has been used to determine the efficacy of medical countermeasures to mitigate major signs of morbidity and mortality of radiation-induced lung injury. Herein, a literature review of published studies showing the evolution of lethal lung injury characteristic of the delayed effects of acute radiation exposure between the two significantly different exposure protocols, whole thorax lung irradiation and partial-body irradiation with bone marrow sparing in the nonhuman primate, is provided. The selection of published data was made from the open literature. The primary studies conducted at two research sites benefitted from the similarity of major variables; namely, both sites used rhesus macaques of approximate age and body weight and radiation exposure by LINAC-derived 6 MV photons at dose rates of 0.80 Gy min and 1.00 Gy min delivered to the midline tissue via bilateral, anterior/posterior, posterior/anterior geometry. An advantage relative to sex difference resulted from the use of male and female macaques by the Maryland and the Washington sites, respectively. Subject-based medical management was used for all macaques. The primary studies (6) provided adequate data to establish dose response relationships within 180 d for the radiation-induced lung injury consequent to whole thorax lung irradiation (male vs. female) and partial-body irradiation with bone marrow sparing exposure protocols (male). The dose response relationships established by probit analyses vs. linear dose relationships were characterized by two main parameters or dependent variables, a slope and LD50/180. Respective LD50/180 values for the primary studies that used whole thorax lung irradiation for respective male and female nonhuman primates were 10.24 Gy [9.87, 10.52] (n = 76, male) and 10.28 Gy [9.68, 10.92] (n = 40, female) at two different research sites. The respective slopes were steep at 1.73 [0.841, 2.604] and 1.15 [0.65, 1.65] probits per linear dose. The LD50/180 value and slope derived from the dose response relationships for the partial-body irradiation with bone marrow sparing exposure was 9.94 Gy [9.35, 10.29] (n = 87) and 1.21 [0.70, 1.73] probits per linear dose. A secondary study (1) provided data on limited control cohort of nonhuman primates exposed to whole thorax lung irradiation. The data supported the incidence of clinical, radiographic, and histological indices of the dose-dependent lung injury in the nonhuman primates. Tertiary studies (6) provided data derived from collaboration with the noted primary and secondary studies on control cohorts of nonhuman primates exposed to whole thorax lung irradiation and partial-body irradiation with bone marrow sparing exposure. These studies provided a summary of histological evidence of fibrosis, inflammation and reactive/proliferative changes in pneumonocytes characteristic of lung injury and data on biomarkers for radiation-induced lung injury based on matrix-assisted laser desorption ionization-mass spectrometry imaging and gene expression approaches. The available database in young rhesus macaques exposed to whole thorax lung irradiation or partial-body irradiation with bone marrow sparing using 6 MV LINAC-derived radiation with medical management showed that the dose response relationships were equivalent relative to the primary endpoint all-cause mortality. Additionally, the latency, incidence, severity, and progression of the clinical, radiographic, and histological indices of lung injury were comparable. However, the differences between the exposure protocols are remarkable relative to the demonstrated time course between the multiple organ injury of the acute radiation syndrome and that of the delayed effects of acute radiation exposure, respectively.

Estimating partial-body ionizing radiation exposure by automated cytogenetic biodosimetry

Purpose Inhomogeneous exposures to ionizing radiation can be detected and quantified with the dicentric chromosome assay (DCA) of metaphase cells. Complete automation of interpretation of the DCA for whole-body irradiation has significantly improved throughput without compromising accuracy, however, low levels of residual false positive dicentric chromosomes (DCs) have confounded its application for partial-body exposure determination. Materials and methods We describe a method of estimating and correcting for false positive DCs in digitally processed images of metaphase cells. Nearly all DCs detected in unirradiated calibration samples are introduced by digital image processing. DC frequencies of irradiated calibration samples and those exposed to unknown radiation levels are corrected subtracting this false positive fraction from each. In partial-body exposures, the fraction of cells exposed, and radiation dose can be quantified after applying this modification of the contaminated Poisson method. Results Dose estimates of three partially irradiated samples diverged 0.2–2.5 Gy from physical doses and irradiated cell fractions deviated by 2.3%–15.8% from the known levels. Synthetic partial-body samples comprised of unirradiated and 3 Gy samples from 4 laboratories were correctly discriminated as inhomogeneous by multiple criteria. Root mean squared errors of these dose estimates ranged from 0.52 to 1.14 Gy2 and from 8.1 to 33.3%2 for the fraction of cells irradiated. Conclusions Automated DCA can differentiate whole- from partial-body radiation exposures and provides timely quantification of estimated whole-body equivalent dose.

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

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

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

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

LPAR2 receptor activation attenuates radiation-induced disruption of apical junctional complexes and mucosal barrier dysfunction in mouse colon.

The tight junction (TJ) and barrier function of colonic epithelium is highly sensitive to ionizing radiation. We evaluated the effect of lysophosphatidic acid (LPA) and its analog, Radioprotein-1, on γ-radiation-induced colonic epithelial barrier dysfunction using Caco-2 and m-ICC12 cell monolayers in vitro and mice in vivo. Mice were subjected to either total body irradiation (TBI) or partial body irradiation (PBI-BM5). Intestinal barrier function was assessed by analyzing immunofluorescence localization of TJ proteins, mucosal inulin permeability, and plasma lipopolysaccharide (LPS) levels. Oxidative stress was analyzed by measuring protein thiol oxidation and antioxidant mRNA. In Caco-2 and m-ICC12 cell monolayers, LPA attenuated radiation-induced redistribution of TJ proteins, which was blocked by a Rho-kinase inhibitor. In mice, TBI and PBI-BM5 disrupted colonic epithelial tight junction and adherens junction, increased mucosal permeability, and elevated plasma LPS; TJ disruption by TBI was more severe in Lpar2-/- mice compared to wild-type mice. RP1, administered before or after irradiation, alleviated TBI and PBI-BM5-induced TJ disruption, barrier dysfunction, and endotoxemia accompanied by protein thiol oxidation and downregulation of antioxidant gene expression, cofilin activation, and remodeling of the actin cytoskeleton. These data demonstrate that LPAR2 receptor activation prevents and mitigates γ-irradiation-induced colonic mucosal barrier dysfunction and endotoxemia.

Methionine dietary supplementation potentiates ionizing radiation-induced gastrointestinal syndrome.

Methionine is an essential amino acid needed for a variety of processes in living organisms. Ionizing radiation depletes tissue methionine concentrations and leads to the loss of DNA methylation and decreased synthesis of glutathione. In this study, we aimed to investigate the effects of methionine dietary supplementation in CBA/CaJ mice after exposure to doses ranging from 3 to 8.5 Gy of 137Cs of total body irradiation. We report that mice fed a methionine-supplemented diet (MSD; 19.5 vs. 6.5 mg/kg in a methionine-adequate diet, MAD) developed acute radiation toxicity at doses as low as 3 Gy. Partial body irradiation performed with hindlimb shielding resulted in a 50% mortality rate in MSD-fed mice exposed to 8.5 Gy, suggesting prevalence of radiation-induced gastrointestinal syndrome in the development of acute radiation toxicity. Analysis of the intestinal microbiome demonstrated shifts in the gut ecology, observed along with the development of leaky gut syndrome and bacterial translocation into the liver. Normal gut physiology impairment was facilitated by alterations in the one-carbon metabolism pathway and was exhibited as decreases in circulating citrulline levels mirrored by decreased intestinal mucosal surface area and the number of surviving crypts. In conclusion, we demonstrate that a relevant excess of methionine dietary intake exacerbates the detrimental effects of exposure to ionizing radiation in the small intestine.NEW & NOTEWORTHY Methionine supplementation, instead of an anticipated health-promoting effect, sensitizes mice to gastrointestinal radiation syndrome. Mechanistically, excess of methionine negatively affects intestinal ecology, leading to a cascade of physiological, biochemical, and molecular alterations that impair normal gut response to a clinically relevant genotoxic stressor. These findings speak toward increasing the role of registered dietitians during cancer therapy and the necessity of a solid scientific background behind the sales of dietary supplements and claims regarding their benefits.

Differentiation of Heterogeneous Radiation Exposure Using Hematology and Blood Chemistry.

In the aftermath of a nuclear incident, survivors will suffer the deleterious effects from acute radiation exposure. The majority of those affected would have received heterogeneous radiation exposure, reflected in hematological metrics and blood chemistry. Here, we investigated the acute and long-term changes in kinetics and magnitude of pancytopenia and blood chemistry in rats irradiated using varying degrees of body shielding. We hypothesized that, although a single blood count may not be able to differentiate the degree of radiation exposure, a combination of measurements from complete blood cell counts (CBCs) and blood chemistry tests is able to do so. Male Sprague Dawley rats, 8-10 weeks of age, received single-dose 7.5 Gy (160 kVp, 25 mA, 1.16 Gy/min) whole-body irradiation (WBI, LD100/30) or partial-body irradiation (PBI), as follows: one leg shielded (1LS, LD0/30), two legs shielded (2LS, LD0/30) or the upper half of the body shielded (UHS, LD0/30). Animal morbidity and weights were measured. Blood was drawn at 1, 5, 10, 20 and 30 days postirradiation (n = 4-11). For kidney and liver function measurements, CBC and blood chemistry analyses were performed. WBI animals on average survived 9 ± 0.4 days postirradiation. In contrast, all PBI animals survived the 30-day study period. CBC analysis revealed that both white blood cell (WBC) and platelet counts were most affected after irradiation. While WBC counts were significantly lower in all irradiated groups on days 1, 5 and 10, platelets were only significantly lower on days 5 and 10 postirradiation. In addition, on day 5 postirradiation both WBC and platelet counts were able to differentiate WBI (non-survivors) from PBI 2LS and UHS animals (survivors). Using four blood parameters (platelets, percentage lymphocytes, percentage neutrophils and percentage monocytes) on day 5 after 7.5 Gy irradiation and a linear discrimination analysis (LDA), we were able to predict the degree of body exposure in animals with a 95.8% accuracy. Alkaline phosphatase (ALP) was significantly lower in all groups on days 5 and 10 postirradiation compared to baseline. Furthermore, ALP was significantly higher in the UHS than WBI animals. The AST:ALT ratio was significantly higher than baseline in all irradiated groups on day 1 postirradiation. In conclusion, four CBC parameters, on day 5 after receiving a 7.5 Gy dose of radiation, can be employed in a LDA to differentiate various degrees of exposure (shielding). The characterization presented in this work paves the way for further studies in differences caused by heterogeneous body exposure to radiation and a new metric for biodosimetry.

Sex-Specific Effects of a Wartime-Like Radiation Exposure on Cognitive Function.

Evaluating the risk for central nervous system (CNS) effects after whole-body or partial-body irradiation presents challenges due in part to the varied exposure scenarios in the context of occupational, accidental or wartime releases. Risk estimations are further complicated by the fact that robust changes in brain function are unlikely to manifest until significantly late post exposure times. Collectively, the current data regarding CNS radiation risk are conflicting in humans and a survey of the animal model data shows that it is similarly inconsistent. Due to the sparseness of such data, the current study was conducted using male and female mice to evaluate the brain for the delayed effects of a 2 Gy whole-body exposure to c rays starting six months postirradiation. Behavioral testing indicated sex-specific differences in the induction of anxiety-like behaviors and in the ability to abolish fear memories. Molecular analyses showed alterations in post-synaptic protein levels that might affect synaptic plasticity and increased levels of global DNA methylation, suggesting a potential epigenetic mechanism that might contribute to radiation-induced cognitive dysfunction. These data add to the understanding of the CNS response to whole-body irradiation and may lead to improved risk assessment and provide guidance in the development of effective radiation countermeasures to protect military personnel and civilians alike.