Acute Proteomic Changes in the Lung After WTLI in a Mouse Model: Identification of Potential Initiating Events for Delayed Effects of Acute Radiation Exposure

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

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

A human lung alveolus-on-a-chip model of acute radiation-induced lung injury

Acute exposure to high-dose gamma radiation due to radiological disasters or cancer radiotherapy can result in radiation-induced lung injury (RILI), characterized by acute pneumonitis and subsequent lung fibrosis. A microfluidic organ-on-a-chip lined by human lung alveolar epithelium interfaced with pulmonary endothelium (Lung Alveolus Chip) is used to model acute RILI in vitro. Both lung epithelium and endothelium exhibit DNA damage, cellular hypertrophy, upregulation of inflammatory cytokines, and loss of barrier function within 6 h of radiation exposure, although greater damage is observed in the endothelium. The radiation dose sensitivity observed on-chip is more like the human lung than animal preclinical models. The Alveolus Chip is also used to evaluate the potential ability of two drugs - lovastatin and prednisolone - to suppress the effects of acute RILI. These data demonstrate that the Lung Alveolus Chip provides a human relevant alternative for studying the molecular basis of acute RILI and may be useful for evaluation of new radiation countermeasure therapeutics.

VNLG-152R and its deuterated analogs potently inhibit/repress triple/quadruple negative breast cancer of diverse racial origins in vitro and in vivo by upregulating E3 Ligase Synoviolin 1 (SYVN1) and inducing proteasomal degradation of MNK1/2

Triple-negative breast cancer (TNBC) and its recently identified subtype, quadruple negative breast cancer (QNBC), collectively account for approximately 13% of reported breast cancer cases in the United States. These aggressive forms of breast cancer are associated with poor prognoses, limited treatment options, and lower overall survival rates. In previous studies, our research demonstrated that VNLG-152R exhibits inhibitory effects on TNBC cells both in vitro and in vivo and the deuterated analogs were more potent inhibitors of TNBC cells in vitro. Building upon these findings, our current study delves into the molecular mechanisms underlying this inhibitory action. Through transcriptome and proteome analyses, we discovered that VNLG-152R upregulates the expression of E3 ligase Synoviolin 1 (SYVN1), also called 3-hydroxy-3-methylglutaryl reductase degradation (HRD1) in TNBC cells. Moreover, we provide genetic and pharmacological evidence to demonstrate that SYVN1 mediates the ubiquitination and subsequent proteasomal degradation of MNK1/2, the only known kinases responsible for phosphorylating eIF4E. Phosphorylation of eIF4E being a rate-limiting step in the formation of the eIF4F translation initiation complex, the degradation of MNK1/2 by VNLG-152R and its analogs impedes dysregulated translation in TNBC cells, resulting in the inhibition of tumor growth. Importantly, our findings were validated in vivo using TNBC xenograft models derived from MDA-MB-231, MDA-MB-468, and MDA-MB-453 cell lines, representing different racial origins and genetic backgrounds. These xenograft models, which encompass TNBCs with varying androgen receptor (AR) expression levels, were effectively inhibited by oral administration of VNLG-152R and its deuterated analogs in NRG mice. Importantly, in direct comparison, our compounds are more effective than enzalutamide and docetaxel in achieving tumor growth inhibition/repression in the AR+ MDA-MD-453 xenograft model in mice. Collectively, our study sheds light on the involvement of SYVN1 E3 ligase in the VNLG-152R-induced degradation of MNK1/2 and the therapeutic potential of VNLG-152R and its more potent deuterated analogs as promising agents for the treatment of TNBC across diverse patient populations.

Protein biomarkers for radiation injury and testing of medical countermeasure efficacy: promises, pitfalls, and future directions

INTRODUCTION

Radiological/nuclear accidents, hostile military activity, or terrorist strikes have the potential to expose a large number of civilians and military personnel to high doses of radiation resulting in the development of acute radiation syndrome and delayed effects of exposure. Thus, there is an urgent need for sensitive and specific assays to assess the levels of radiation exposure to individuals. Such radiation exposures are expected to alter primary cellular proteomic processes, resulting in multifaceted biological responses.

AREAS COVERED

This article covers the application of proteomics, a promising and fast developing technology based on quantitative and qualitative measurements of protein molecules for possible rapid measurement of radiation exposure levels. Recent advancements in high-resolution chromatography, mass spectrometry, high-throughput, and bioinformatics have resulted in comprehensive (relative quantitation) and precise (absolute quantitation) approaches for the discovery and accuracy of key protein biomarkers of radiation exposure. Such proteome biomarkers might prove useful for assessing radiation exposure levels as well as for extrapolating the pharmaceutical dose of countermeasures for humans based on efficacy data generated using animal models.

EXPERT OPINION

The field of proteomics promises to be a valuable asset in evaluating levels of radiation exposure and characterizing radiation injury biomarkers.

Alterations in cytoskeletal and Ca2+ cycling regulators in atria lacking the obscurin Ig58/59 module

Introduction

Obscurin (720-870 kDa) is a giant cytoskeletal and signaling protein that possesses both structural and regulatory functions in striated muscles. Immunoglobulin domains 58/59 (Ig58/59) of obscurin bind to a diverse set of proteins that are essential for the proper structure and function of the heart, including giant titin, novex-3, and phospholamban (PLN). Importantly, the pathophysiological significance of the Ig58/59 module has been further underscored by the discovery of several mutations within Ig58/59 that are linked to various forms of myopathy in humans. We previously generated a constitutive deletion mouse model, Obscn-ΔIg58/59, that expresses obscurin lacking Ig58/59, and characterized the effects of this deletion on cardiac morphology and function through aging. Our findings demonstrated that Obscn-ΔIg58/59 male animals develop severe arrhythmia, primarily manifesting as episodes of junctional escape and spontaneous loss of regular p-waves, reminiscent of human atrial fibrillation, accompanied by significant atrial enlargement that progresses in severity with aging.

Methods and Results

To comprehensively characterize the molecular alterations responsible for these pathologies, we performed proteomic and phospho-proteomic analyses in aging Obscn-ΔIg58/59 atria. Our studies revealed extensive and novel alterations in the expression and phosphorylation profile of major cytoskeletal proteins, Ca2+ regulators, and Z-disk associated protein complexes in the Obscn-ΔIg58/59 atria through aging.

Discussion

These studies implicate obscurin, particularly the Ig58/59 module, as an essential regulator of the Z-disk associated cytoskeleton and Ca2+ cycling in the atria and provide new molecular insights into the development of atrial fibrillation and remodeling.

Targeted Inhibition of Select Extracellular Signal-regulated Kinases 1 and 2 Functions Mitigates Pathological Features of Asthma in Mice

ERK1/2 (extracellular signal-regulated kinases 1 and 2) regulate the activity of various transcription factors that contribute to asthma pathogenesis. Although an attractive drug target, broadly inhibiting ERK1/2 is challenging because of unwanted cellular toxicities. We have identified small molecule inhibitors with a benzenesulfonate scaffold that selectively inhibit ERK1/2-mediated activation of AP-1 (activator protein-1). Herein, we describe the findings of targeting ERK1/2-mediated substrate-specific signaling with the small molecule inhibitor SF-3-030 in a murine model of house dust mite (HDM)-induced asthma. In 8- to 10-week-old BALB/c mice, allergic asthma was established by repeated intranasal HDM (25 μg/mouse) instillation for 3 weeks (5 days/week). A subgroup of mice was prophylactically dosed with 10 mg/kg SF-3-030/DMSO intranasally 30 minutes before the HDM challenge. Following the dosing schedule, mice were evaluated for alterations in airway mechanics, inflammation, and markers of airway remodeling. SF-3-030 treatment significantly attenuated HDM-induced elevation of distinct inflammatory cell types and cytokine concentrations in BAL and IgE concentrations in the lungs. Histopathological analysis of lung tissue sections revealed diminished HDM-induced pleocellular peribronchial inflammation, mucus cell metaplasia, collagen accumulation, thickening of airway smooth muscle mass, and expression of markers of cell proliferation (Ki-67 and cyclin D1) in mice treated with SF-3-030. Furthermore, SF-3-030 treatment attenuated HDM-induced airway hyperresponsiveness in mice. Finally, mechanistic studies using transcriptome and proteome analyses suggest inhibition of HDM-induced genes involved in inflammation, cell proliferation, and tissue remodeling by SF-3-030. These preclinical findings demonstrate that function-selective inhibition of ERK1/2 signaling mitigates multiple features of asthma in a murine model.

Animal Care in Radiation Medical Countermeasures Studies

Animal models are necessary to demonstrate the efficacy of medical countermeasures (MCM) to mitigate/treat acute radiation syndrome and the delayed effects of acute radiation exposure and develop biodosimetry signatures for use in triage and to guide medical management. The use of animal models in radiation research allows for the simulation of the biological effects of exposure in humans. Robust and well-controlled animal studies provide a platform to address basic mechanistic and safety questions that cannot be conducted in humans. The U.S. Department of Health and Human Services has tasked the National Institute of Allergy and Infectious Diseases (NIAID) with identifying and funding early- through advanced-stage MCM development for radiation-induced injuries; and advancement of biodosimetry platforms and exploration of biomarkers for triage, definitive dose, and predictive purposes. Some of these NIAID-funded projects may transition to the Biomedical Advanced Research and Development Authority (BARDA), a component of the Office of the Assistant Secretary for Preparedness and Response in the U.S. Department of Health and Human Services, which is tasked with the advanced development of MCMs to include pharmacokinetic, exposure, and safety assessments in humans. Guided by the U.S. Food and Drug Administration's (FDA) Animal Rule, both NIAID and BARDA work closely with researchers to advance product and device development, setting them on a course for eventual licensure/approval/clearance of their approaches by the FDA. In August 2020, NIAID partnered with BARDA to conduct a workshop to discuss currently accepted animal care protocols and examine aspects of animal models that can influence outcomes of studies to explore MCM efficacy for potential harmonization. This report provides an overview of the two-day workshop, which includes a series of special topic presentations followed by panel discussions with subject-matter experts from academia, industry partners, and select governmental agencies.

Dysregulated retinoic acid signaling in airway smooth muscle cells in asthma

Vitamin A deficiency has been shown to exacerbate allergic asthma. Previous studies have postulated that retinoic acid (RA), an active metabolite of vitamin A and high-affinity ligand for RA receptor (RAR), is reduced in airway inflammatory condition and contributes to multiple features of asthma including airway hyperresponsiveness and excessive accumulation of airway smooth muscle (ASM) cells. In this study, we directly quantified RA and examined the molecular basis for reduced RA levels and RA-mediated signaling in lungs and ASM cells obtained from asthmatic donors and in lungs from allergen-challenged mice. Levels of RA and retinol were significantly lower in lung tissues from asthmatic donors and house dust mite (HDM)-challenged mice compared to non-asthmatic human lungs and PBS-challenged mice, respectively. Quantification of mRNA and protein expression revealed dysregulation in the first step of RA biosynthesis consistent with reduced RA including decreased protein expression of retinol dehydrogenase (RDH)-10 and increased protein expression of RDH11 and dehydrogenase/reductase (DHRS)-4 in asthmatic lung. Proteomic profiling of non-asthmatic and asthmatic lungs also showed significant changes in the protein expression of AP-1 targets consistent with increased AP-1 activity. Further, basal RA levels and RA biosynthetic capabilities were decreased in asthmatic human ASM cells. Treatment of human ASM cells with all-trans RA (ATRA) or the RARγ-specific agonist (CD1530) resulted in the inhibition of mitogen-induced cell proliferation and AP-1-dependent transcription. These data suggest that RA metabolism is decreased in asthmatic lung and that enhancing RAR signaling using ATRA or RARγ agonists may mitigate airway remodeling associated with asthma.

Effect of Radiation on the Essential Nutrient Homeostasis and Signaling of Retinoids in a Non-human Primate Model with Minimal Bone Marrow Sparing

ABSTRACT

High-dose radiation exposure results in hematopoietic (H) and gastrointestinal (GI) acute radiation syndromes (ARS) followed by delayed effects of acute radiation exposure (DEARE), which include damage to lung, heart, and GI. Whereas DEARE includes inflammation and fibrosis in multiple tissues, the molecular mechanisms contributing to inflammation and to the development of fibrosis remain incompletely understood. Reports that radiation dysregulates retinoids and proteins within the retinoid pathway indicate that radiation disrupts essential nutrient homeostasis. An active metabolite of vitamin A, retinoic acid (RA), is a master regulator of cell proliferation, differentiation, and apoptosis roles in inflammatory signaling and the development of fibrosis. As facets of inflammation and fibrosis are regulated by RA, we surveyed radiation-induced changes in retinoids as well as proteins related to and targets of the retinoid pathway in the non-human primate after high dose radiation with minimal bone marrow sparing (12 Gy PBI/BM2.5). Retinoic acid was decreased in plasma as well as in lung, heart, and jejunum over time, indicating a global disruption of RA homeostasis after IR. A number of proteins associated with fibrosis and with RA were significantly altered after radiation. Together these data indicate that a local deficiency of endogenous RA presents a permissive environment for fibrotic transformation.

Complementary Lipidomic, Proteomic, and Mass Spectrometry Imaging Approach to the Characterization of the Acute Effects of Radiation in the Non-human Primate Mesenteric Lymph Node after Partial-body Irradiation with Minimal Bone Marrow Sparing

ABSTRACT

Radiation sequelae is complex and characterized by multiple pathologies, which occur over time and nonuniformly throughout different organs. The study of the mesenteric lymph node (MLN) due to its importance in the gastrointestinal system is of particular interest. Other studies have shown an immediate post-irradiation reduction in cellularity due to the known effects of irradiation on lymphoid cell populations, but the molecular and functional mechanisms that lead to these cellular alterations remain limited. In this work, we show the use of lipidomic, proteomic, and mass spectrometry imaging in the characterization of the effects of acute radiation exposure on the MLN at different time points after ionizing radiation (IR) from 4 d to 21 d after 12 Gy partial body irradiation with 2.5% bone marrow sparing. The combined analyses showed a dysregulation of the lipid and protein composition in the MLN after IR. Protein expression was affected in numerous pathways, including pathways regulating lipids such as LXR/RXR activation and acute phase response. Lipid distribution and abundance was also affected by IR in the MLN, including an accumulation of triacylglycerides, a decrease in polyunsaturated glycerophospholipids, and changes in polyunsaturated fatty acids. Those changes were observed as early as 4 d after IR and were more pronounced for lipids with a higher concentration in the nodules and the medulla of the MLN. These results provide molecular insight into the MLN that can inform on injury mechanism in a non-human primate model of the acute radiation syndrome of the gastrointestinal tract. Those findings may contribute to the identification of therapeutic targets and the development of new medical countermeasures.

Multi-omic Analysis of Non-human Primate Heart after Partial-body Radiation with Minimal Bone Marrow Sparing

ABSTRACT

High-dose radiation exposure results in hematopoietic and gastrointestinal acute radiation syndromes followed by delayed effects of acute radiation exposure, which encompasses multiple organs, including heart, kidney, and lung. Here we sought to further characterize the natural history of radiation-induced heart injury via determination of differential protein and metabolite expression in the heart. We quantitatively profiled the proteome and metabolome of left and right ventricle from non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing over a time period of 3 wk. Global proteome profiling identified more than 2,200 unique proteins, with 220 and 286 in the left and right ventricles, respectively, showing significant responses across at least three time points compared to baseline levels. High-throughput targeted metabolomics analyzed a total of 229 metabolites and metabolite combinations, with 18 and 22 in the left and right ventricles, respectively, showing significant responses compared to baseline levels. Bioinformatic analysis performed on metabolomic and proteomic data revealed pathways related to inflammation, energy metabolism, and myocardial remodeling were dysregulated. Additionally, we observed dysregulation of the retinoid homeostasis pathway, including significant post-radiation decreases in retinoic acid, an active metabolite of vitamin A. Significant differences between left and right ventricles in the pathology of radiation-induced injury were identified. This multi-omic study characterizes the natural history and molecular mechanisms of radiation-induced heart injury in NHP exposed to PBI with minimal bone marrow sparing.

Acute Proteomic Changes in Non-human Primate Kidney after Partial-body Radiation with Minimal Bone Marrow Sparing

Near total body exposure to high-dose ionizing radiation results in organ-specific sequelae, including acute radiation syndromes and delayed effects of acute radiation exposure. Among these sequelae are acute kidney injury and chronic kidney injury. Reports that neither oxidative stress nor inflammation are dominant mechanisms defining radiation nephropathy inspired an unbiased, discovery-based proteomic interrogation in order to identify mechanistic pathways of injury. We quantitatively profiled the proteome of kidney from non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing over a time period of 3 wk. Kidney was analyzed by liquid chromatography-tandem mass spectrometry. Out of the 3,432 unique proteins that were identified, we found that 265 proteins showed significant and consistent responses across at least three time points post-irradiation, of which 230 proteins showed strong upregulation while 35 proteins showed downregulation. Bioinformatics analysis revealed significant pathway and upstream regulator perturbations post-high dose irradiation and shed light on underlying mechanisms of radiation damage. These data will be useful for a greater understanding of the molecular mechanisms of injury in well-characterized animal models of partial body irradiation with minimal bone marrow sparing. These data may be potentially useful in the future development of medical countermeasures.

A large portion of the astrocyte proteome is dedicated to perivascular endfeet, including critical components of the electron transport chain

The perivascular astrocyte endfoot is a specialized and diffusion-limited subcellular compartment that fully ensheathes the cerebral vasculature. Despite their ubiquitous presence, a detailed understanding of endfoot physiology remains elusive, in part due to a limited understanding of the proteins that distinguish the endfoot from the greater astrocyte body. Here, we developed a technique to isolate astrocyte endfeet from brain tissue, which was used to study the endfoot proteome in comparison to the astrocyte somata. In our approach, brain microvessels, which retain their endfoot processes, were isolated from mouse brain and dissociated, whereupon endfeet were recovered using an antibody-based column astrocyte isolation kit. Our findings expand the known set of proteins enriched at the endfoot from 10 to 516, which comprised more than 1/5th of the entire detected astrocyte proteome. Numerous critical electron transport chain proteins were expressed only at the endfeet, while enzymes involved in glycogen storage were distributed to the somata, indicating subcellular metabolic compartmentalization. The endfoot proteome also included numerous proteins that, while known to have important contributions to blood-brain barrier function, were not previously known to localize to the endfoot. Our findings highlight the importance of the endfoot and suggest new routes of investigation into endfoot function.

Acute Proteomic Changes in Lung after Radiation: Toward Identifying Initiating Events of Delayed Effects of Acute Radiation Exposure in Non-human Primate after Partial Body Irradiation with Minimal Bone Marrow Sparing

ABSTRACT

Radiation-induced lung injury is a delayed effect of acute radiation exposure resulting in pulmonary pneumonitis and fibrosis. Molecular mechanisms that lead to radiation-induced lung injury remain incompletely understood. Using a non-human primate model of partial body irradiation with minimal bone marrow sparing, lung was analyzed from animals irradiated with 12 Gy at timepoints every 4 d up to 21 d after irradiation and compared to non-irradiated (sham) controls. Tryptic digests of lung tissues were analyzed by liquid chromatography-tandem mass spectrometry followed by pathway analysis. Out of the 3,101 unique proteins that were identified, we found that 252 proteins showed significant and consistent responses across at least three time points post-irradiation, of which 215 proteins showed strong up-regulation while 37 proteins showed down-regulation. Canonical pathways affected by irradiation, changes in proteins that serve as upstream regulators, and proteins involved in key processes including inflammation, fibrosis, and retinoic acid signaling were identified. The proteomic profiling of lung conducted here represents an untargeted systems biology approach to identify acute molecular events in the non-human primate lung that could potentially be initiating events for radiation-induced lung injury.

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.

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.

A Systematic Review of the Hematopoietic Acute Radiation Syndrome (H-ARS) in Canines and Non-human Primates: Acute Mixed Neutron/Gamma vs. Reference Quality Radiations

A systematic review of relevant studies that determined the dose response relationship (DRR) for the hematopoietic (H) acute radiation syndrome (ARS) in the canine relative to radiation quality of mixed neutron:gamma radiations, dose rate, and exposure uniformity relative to selected reference radiation exposure has not been performed. The datasets for rhesus macaques exposure to mixed neutron:gamma radiation are used herein as a species comparative reference to the canine database. The selection of data cohorts was made from the following sources: Ovid Medline (1957-present), PubMed (1954-present), AGRICOLA (1976-present), Web of Science (1954-present), and US HHS RePORT (2002-present). The total number of hits across all search sites was 3,077. Several referenced, unpublished, non-peer reviewed government reports were unavailable for review. Primary published studies using canines, beagles, and mongrels were evaluated to provide an informative and consistent review of mixed neutron:gamma radiation effects to establish the DRRs for the H-ARS. Secondary and tertiary studies provided additional information on the hematologic response or the effects on hematopoietic progenitor cells, radiation dosimetry, absorbed dose, and organ dose. The LD50/30 values varied with neutron quality, exposure aspect, and mixed neutron:gamma ratio. The reference radiation quality varied from 250 kVp or 1-2 MeV x radiation and Co gamma radiation. A summary of a published review of a data set describing the DRR in rhesus macaques for mixed neutron:gamma radiation exposure in the H-ARS is included for a comparative reference to the canine dataset. The available evidence provided a reliable and extensive database that characterized the DRR for the H-ARS in canines and young rhesus macaques exposed to mixed neutron:gamma radiations of variable energy relative to 250 kVp, 1-2 MeV x radiation and Co gamma, and uniform and non-uniform total-body irradiation without the benefit of medical management. The mixed neutron:gamma radiation showed an energy-dependent RBE of ~ 1.0 to 2.0 relative to reference radiation exposure within both species. A marginal database described the DRR for the gastrointestinal (GI)-ARS. Medical management showed benefit in both species relative to the mixed neutron:gamma as well as exposure to reference radiation. The DRR for the H-ARS was characterized by steep slopes and relative LD50/30 values that reflected the radiation quality, exposure aspect, and dose rate over a range in time from 1956-2012.

Delayed effects of acute whole body lethal radiation exposure in mice pre-treated with BBT-059

The threat of nuclear exposure is heightened and it is imperative to identify potential countermeasures for acute radiation syndrome. Currently no countermeasures have been approved for prophylactic administration. Effective countermeasures should function to increase survival in the short term as well as to increase the overall prognosis of an exposed individual long term. Here we describe the use of a promising radiation countermeasure, BBT-059, and the results of a long term mouse study (up to 12 months) in the male CD2F1 strain using ⁶⁰Co gamma irradiation (~0.6 Gy/min, 7.5-12.5 Gy). We report the dose reduction factor of 1.28 for BBT-059 (0.3 mg/kg) compared to control administered 24 h prior to irradiation. In the long term study animals showed accelerated recovery in peripheral blood cell counts, bone marrow colony forming units, sternal cellularity and megakaryocyte numbers in drug treated mice compared to formulation buffer. In addition, increased senescence was observed in the kidneys of animals administered control or drug and exposed to the highest doses of radiation. Decreased levels of E-cadherin, LaminB1 and increased levels of Cyc-D and p21 in spleen lysates were observed in animals administered control. Taken together the results indicate a high level of protection following BBT-059 administration in mice exposed to lethal and supralethal doses of total body gamma-radiation.

Modulation of retinoid signaling: therapeutic opportunities in organ fibrosis and repair

The vitamin A metabolite, retinoic acid, is an important signaling molecule during embryonic development serving critical roles in morphogenesis, organ patterning and skeletal and neural development. Retinoic acid is also important in postnatal life in the maintenance of tissue homeostasis, while retinoid-based therapies have long been used in the treatment of a variety of cancers and skin disorders. As the number of people living with chronic disorders continues to increase, there is great interest in extending the use of retinoid therapies in promoting the maintenance and repair of adult tissues. However, there are still many conflicting results as we struggle to understand the role of retinoic acid in the multitude of processes that contribute to tissue injury and repair. This review will assess our current knowledge of the role retinoic acid signaling in the development of fibroblasts, and their transformation to myofibroblasts, and of the potential use of retinoid therapies in the treatment of organ fibrosis.

Proteomic Evaluation of the Acute Radiation Syndrome of the Gastrointestinal Tract in a Murine Total-body Irradiation Model

Radiation exposure to the gastrointestinal system contributes to the acute radiation syndrome in a dose- and time-dependent manner. Molecular mechanisms that lead to the gastrointestinal acute radiation syndrome remain incompletely understood. Using a murine model of total-body irradiation, C57BL/6J male mice were irradiated at 8, 10, 12, and 14 Gy and assayed at day 1, 3, and 6 after exposure and compared to nonirradiated (sham) controls. Tryptic digests of gastrointestinal tissues (upper ileum) were analyzed by liquid chromatography-tandem mass spectrometry on a Waters nanoLC coupled to a Thermo Scientific Q Exactive hybrid quadrupole-orbitrap mass spectrometer. Pathway and gene ontology analysis were performed with Qiagen Ingenuity, Panther GO, and DAVID databases. A number of trends were identified in our proteomic data including pronounced protein changes as well as protein changes that were consistently up regulated or down regulated at all time points and dose levels interrogated. Time- and dose-dependent protein changes, canonical pathways affected by irradiation, and changes in proteins that serve as upstream regulators were also identified. Additionally, proteins involved in key processes including inflammation, radiation, and retinoic acid signaling were identified. The proteomic profiling conducted here represents an untargeted systems biology approach to identify acute molecular events that will be useful for a greater understanding of animal models and may be potentially useful toward the development of medical countermeasures and/or biomarkers.