Linking Doses with Clinical Scores of Hematopoietic Acute Radiation Syndrome

Blocking TRAIL-DR5 signaling pathway with soluble death receptor 5 fusion protein mitigates radiation-induced injury

The increasing application of nuclear technology, the high fatality of acute radiation syndrome (ARS) and its complex mechanism make ARS a global difficulty that requires urgent attention. Here we reported that the death receptor 5 (DR5), as well as its ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), were both significantly upregulated after irradiation in mice with 6 Gy γ-ray single radiation. And by intravenously administrated with soluble DR5 fusion protein (sDR5-Fc), the competitive antagonist of DR5, the excessive apoptosis in the radiation-sensitive tissues such as spleen and thymus were significantly inhibited and the radiation-induced damage of spleen and thymus were mitigated, while the expression of apoptosis-inhibiting proteins such as Bcl-2 was also significantly upregulated. The biochemical indicators such as serum ALP, AST, ALT, TBIL, K, and Cl levels that affected by radiation, were improved by sDR5-Fc administration. sDR5-Fc can also regulate the number of immune cells and reduce blood cell death. For in vitro studies, it had been found that sDR5-Fc effectively inhibited apoptosis of human small intestinal mucosal epithelial cells and IEC-6 cells using flow cytometry. Finally, survival studies showed that mice administrated with sDR5-Fc after 9 Gy γ-ray single whole body radiation effectively increased the 30-day survival and was in a significant dose-dependent manner. Overall, the findings revealed that DR5/TRAIL-mediated apoptosis pathway had played important roles in the injury of ARS mice, and DR5 probably be a potential target for ARS therapeutics. And the DR5 apoptosis antagonist, sDR5 fusion protein, probably is a promising anti-ARS drug candidate which deserves further investigation.

Nuclear and Radiological Emergencies: Biological Effects, Countermeasures and Biodosimetry

Atomic and radiological crises can be caused by accidents, military activities, terrorist assaults involving atomic installations, the explosion of nuclear devices, or the utilization of concealed radiation exposure devices. Direct damage is caused when radiation interacts directly with cellular components. Indirect effects are mainly caused by the generation of reactive oxygen species due to radiolysis of water molecules. Acute and persistent oxidative stress associates to radiation-induced biological damages. Biological impacts of atomic radiation exposure can be deterministic (in a period range a posteriori of the event and because of destructive tissue/organ harm) or stochastic (irregular, for example cell mutation related pathologies and heritable infections). Potential countermeasures according to a specific scenario require considering basic issues, e.g., the type of radiation, people directly affected and first responders, range of doses received and whether the exposure or contamination has affected the total body or is partial. This review focuses on available medical countermeasures (radioprotectors, radiomitigators, radionuclide scavengers), biodosimetry (biological and biophysical techniques that can be quantitatively correlated with the magnitude of the radiation dose received), and strategies to implement the response to an accidental radiation exposure. In the case of large-scale atomic or radiological events, the most ideal choice for triage, dose assessment and victim classification, is the utilization of global biodosimetry networks, in combination with the automation of strategies based on modular platforms.

Early-response multiple-parameter biodosimetry and dosimetry: risk predictions

The accepted generic multiple-parameter and early-response biodosimetry and dosimetry assessment approach for suspected high-dose radiation (i.e. life-threatening) exposure includes measuring radioactivity associated with the exposed individual (if appropriate); observing and recording prodromal signs/symptoms; obtaining serial complete blood counts with white-blood-cell differential; sampling blood for the chromosome-aberration cytogenetic bioassay using the 'gold standard' dicentric assay (premature chromosome condensation assay for exposures >5 Gy photon acute doses equivalent), measurement of proteomic biomarkers and gene expression assays for dose assessment; bioassay sampling, if appropriate, to determine radioactive internal contamination; physical dose reconstruction, and using other available opportunistic dosimetry approaches. Biodosimetry and dosimetry resources are identified and should be setup in advance along with agreements to access additional national, regional, and international resources. This multifaceted capability needs to be integrated into a biodosimetry/dosimetry 'concept of operations' for use in a radiological emergency. The combined use of traditional biological-, clinical-, and physical-dosimetry should be use in an integrated approach to provide: (a) early-phase diagnostics to guide the development of initial medical-management strategy, and (b) intermediate and definitive assessment of radiation dose and injury. Use of early-phase (a) clinical signs and symptoms, (b) blood chemistry biomarkers, and (c) triage cytogenetics shows diagnostic utility to predict acute radiation injury severity.

Investigating the Multi-Faceted Nature of Radiation-Induced Coagulopathies in a Göttingen Minipig Model of Hematopoietic Acute Radiation Syndrome

Coagulopathies are well documented after acute radiation exposure at hematopoietic doses, and radiation-induced bleeding is notably one of the two main causes of mortality in the hematopoietic acute radiation syndrome. Despite this, understanding of the mechanisms by which radiation alters hemostasis and induces bleeding is still lacking. Here, male Göttingen minipigs received hematopoietic doses of 60Co gamma irradiation (total body) and coagulopathies were characterized by assessing bleeding, blood cytopenia, fibrin deposition, changes in hemostatic properties, coagulant/anticoagulant enzyme levels, and markers of inflammation, endothelial dysfunction, and barrier integrity to understand if a relationship exists between bleeding, hemostatic defects, bone marrow aplasia, inflammation, endothelial dysfunction and loss of barrier integrity. Acute radiation exposure induced coagulopathies in the Göttingen minipig model of hematopoietic acute radiation syndrome; instances of bleeding were not dependent upon thrombocytopenia. Neutropenia, alterations in hemostatic parameters and damage to the glycocalyx occurred in all animals irrespective of occurrence of bleeding. Radiation-induced bleeding was concurrent with simultaneous thrombocytopenia, anemia, neutropenia, inflammation, increased heart rate, decreased nitric oxide bioavailability and endothelial dysfunction; bleeding was not observed with the sole occurrence of a single aforementioned parameter in the absence of the others. Alteration of barrier function or clotting proteins was not observed in all cases of bleeding. Additionally, fibrin deposition was observed in the heart and lungs of decedent animals but no evidence of DIC was noted, suggesting a unique pathophysiology of radiation-induced coagulopathies. These findings suggest radiation-induced coagulopathies are the result of simultaneous damage to several key organs and biological functions, including the immune system, the inflammatory response, the bone marrow and the cardiovasculature.

Acute radiation risk assessment and mitigation strategies in near future exploration spaceflights

As more exploration spaceflights are planned to travel beyond the protective Earth magnetosphere to deep space destinations, acute health risks due to possible high radiation doses during severe Solar Particle Events (SPEs) are of greater concern to mission planners and management teams. It is expected that some degree of Acute Radiation Syndromes (ARS) symptoms may be observed, but the specific list of health risks that are relevant to exploration missions has been ambiguous and debatable in the past. This mini-review gives a brief summary of the features of radiation exposure if astronauts encounter severe SPEs beyond Low Earth Orbit (LEO), the evidence of ARS radiobiological studies at exposure levels close to recommended limits, and the shortcomings of previous dose projection approaches for ARS risk assessment. Some ARS biomathematical models, particularly those pertinent to the dose ranges that severe SPEs beyond LEO could generate, are reviewed and evaluated, focusing on their capability to predict the incidence of performance incapacitation and time-phased health effects with subsequent medical care recommendations. Using onboard active dosimeter input for estimating organ doses and likely clinical outcomes for SPEs in real time, a new strategy for ARS assessment and mitigation is described to cope with the potential threats of severe SPEs for planned deep space missions.

Gamma and Beta Absorbed Dose Conversion Coefficients in the Range from 10 keV to 10 MeV for Accidental Exposures From Point Sources Placed in Clothing in Proximity to the Body

Retrospective dose assessment following acute radiation exposures during radiological incidents can be difficult and inaccurate due to the large uncertainties associated with dose estimation. However, rapid and accurate dose assessment is critical following an incident so that appropriate treatment can be provided to the patient as early as possible. Incident dose assessment relies heavily on biological dosimetry with corresponding large uncertainties for inhomogeneous exposures, resulting from the estimates of whole-body doses, while the assessment of absorbed doses to individual tissues might actually be more appropriate for acute radiation exposures. Incident exposure scenarios for orphan sources placed in a breast or back pants pocket were modeled using the International Commission on Radiological Protection computational reference male and female and the Monte Carlo N-particle code MCNP6 to compute absorbed dose conversion coefficients for organs of interest for monoenergetic photon and beta sources. The absorbed dose conversion coefficients are intended for use in conjunction with source information to rapidly estimate absorbed doses to organs of interest from radiological sources in one of the two pocket geometries. Absorbed dose conversion coefficients also have been calculated specifically for Co, Cs, and Ir. Those absorbed dose conversion coefficients were applied to data from a radiological incident in Yanango, Peru, for comparison with published dose assessments; the results agree within 20%. The conversion coefficients are expected to provide an accurate tool for assessing doses for the modeled geometries, provided uncertainties due to the exact source-body geometry and exposure time are considered.