Multi-organ failure in a radiation accident: the Chinese experience of 1990

A survey of changing trends in modelling radiation lung injury in mice: bringing out the good, the bad, and the uncertain

Within this millennium there has been resurgence in funding and research dealing with animal models of radiation-induced lung injury to identify and establish predictive biomarkers and effective mitigating agents that are applicable to humans. Most have been performed on mice but there needs to be assurance that the emphasis on such models is not misplaced. We therefore considered it timely to perform a comprehensive appraisal of the literature dealing with radiation lung injury of mice and to critically evaluate the validity and clinical relevance of the research. A total of 357 research papers covering the period of 1970-2015 were extensively reviewed. Whole thorax irradiation (WTI) has become the most common treatment for studying lung injury in mice and distinct trends were seen with regard to the murine strain, radiation dose, intended pathology investigated, length of study, and assays. Recently, the C57BL/6 strain has been increasingly used in the majority of these studies with the notion that they are susceptible to pulmonary fibrosis. Nonetheless, many of these investigations depend on animal survival as the primary end point and neglect the importance of radiation pneumonitis and the anomaly of lethal pleural effusions. A relatively large variation in survival times of C5BL/6 mice is also seen among different institutions pointing to the need for standardization of radiation treatments and environmental conditions. An analysis of mitigating drug treatments is complicated by the fact that the majority of studies are limited to the C57BL/6 strain with a premature termination of the experiments and do not establish whether the treatment actually prevents or simply delays the progression of radiation injury. This survey of the literature has pointed to several improvements that need to be considered in establishing a reliable preclinical murine model of radiation lung injury. The lethality end point should also be used cautiously and with greater emphasis on other assays such as non-invasive lung functional and imaging monitoring in order to quantify specific pulmonary injury that can be better extrapolated to radiation toxicity encountered in our own species.

Accelerated hematopoietic syndrome after radiation doses bridging hematopoietic (H-ARS) and gastrointestinal (GI-ARS) acute radiation syndrome: early hematological changes and systemic inflammatory response syndrome in minipig

PURPOSE

To characterize acute radiation syndrome (ARS) sequelae at doses intermediate between the bone marrow (H-ARS) and full gastrointestinal (GI-ARS) syndrome.

METHODS

Male minipigs, approximately 5 months old, 9-12 kg in weight, were irradiated with Cobalt-60 (total body, bilateral gamma irradiation, 0.6 Gy/min). Endpoints were 10-day survival, gastrointestinal histology, plasma citrulline, bacterial translocation, vomiting, diarrhea, vital signs, systemic inflammatory response syndrome (SIRS), febrile neutropenia (FN).

RESULTS

We exposed animals to doses (2.2-5.0 Gy) above those causing H-ARS (1.6-2.0 Gy), and evaluated development of ARS. Compared to what was observed during H-ARS (historical data: Moroni et al. 2011a , 2011c ), doses above 2 Gy produced signs of increasingly severe pulmonary damage, faster deterioration of clinical conditions, and faster increases in levels of C-reactive protein (CRP). In the range of 4.6-5.0 Gy, animals died by day 9-10; signs of the classic GI syndrome, as measured by diarrhea, vomiting and bacterial translocation, did not occur. At doses above 2 Gy we observed transient reduction in circulating citrulline levels, and animals exhibited earlier depletion of blood elements and faster onset of SIRS and FN.

CONCLUSIONS

An accelerated hematopoietic subsyndrome (AH-ARS) is observed at radiation doses between those producing H-ARS and GI-ARS. It is characterized by early onset of SIRS and FN, and greater lung damage, compared to H-ARS.

Animal models and medical countermeasures development for radiation-induced lung damage: report from an NIAID Workshop

Since 9/11, there have been concerns that terrorists may detonate a radiological or nuclear device in an American city. Aside from several decorporation and blocking agents for use against internal radionuclide contamination, there are currently no medications within the Strategic National Stockpile that are approved to treat the immediate or delayed complications resulting from accidental exposure to radiation. Although the majority of research attention has focused on developing countermeasures that target the bone marrow and gastrointestinal tract, since they represent the most acutely radiosensitive organs, individuals who survive early radiation syndromes will likely suffer late effects in the months that follow. Of particular concern are the delayed effects seen in the lung that play a major role in late mortality seen in radiation-exposed patients and accident victims. To address these concerns, the National Institute of Allergy and Infectious Diseases convened a workshop to discuss pulmonary model development, mechanisms of radiation-induced lung injury, targets for medical countermeasures development, and end points to evaluate treatment efficacy. Other topics covered included guidance on the challenges of developing and licensing drugs and treatments specific to a radiation lung damage indication. This report reviews the data presented, as well as key points from the ensuing discussion.

Radiation damage to the lung: mitigation by angiotensin-converting enzyme (ACE) inhibitors

Concern regarding accidental overexposure to radiation has been raised after the devastating Tohuku earthquake and tsunami which initiated the Fukushima Daiichi nuclear disaster in Japan in March 2011. Radiation exposure is toxic and can be fatal depending on the dose received. Injury to the lung is often reported as part of multi-organ failure in victims of accidental exposures. Doses of radiation >8 Gray to the chest can induce pneumonitis with right ventricular hypertrophy starting after ∼2 months. Higher doses may be followed by pulmonary fibrosis that presents months to years after exposure. Though the exact mechanisms of radiation lung damage are not known, experimental animal models have been widely used to study this injury. Rodent models for pneumonitis and fibrosis exhibit vascular, parenchymal and pleural injuries to the lung. Inflammation is a part of the injuries suggesting involvement of the immune system. Researchers worldwide have tested a number of interventions to prevent or mitigate radiation lung injury. One of the first and most successful class of mitigators are inhibitors of angiotensin-converting enzyme (ACE), an enzyme that is abundant in the lung. These results offer hope that lung injury from radiation accidents may be mitigated, since the ACE inhibitor captopril was effective when started up to 1 week after irradiation.

Identifying the high radiosensitivity of the lungs of C57L mice in a model of total-body irradiation and bone marrow transplantation

Pulmonary tissue is sensitive and often treatment-limiting in patients exposed to total-body irradiation (TBI) in preparation for hematopoietic stem cell transplantation. Many rodent strains, however, exhibit a relatively high resistance to radiation lung damage that often requires extra radiation doses to be delivered locally to the thorax to generate significant levels of pulmonary injury. The present study compared the effects of TBI and bone marrow transplantation (BMT) on two mouse strains that are known to differ in lung radiosensitivity after whole-thorax irradiation, namely the relatively resistant CBA mice and the sensitive C57L mice. Evaluation by survival, microcomputerized tomography (micro-CT), lung tissue weights and histopathology showed that the C57L mice responded with severe lethal radiation pneumonitis at 4 months after 12.5 Gy while CBA mice showed only minimal sublethal damage at this dose. C57L mice receiving 10 Gy TBI also had focal fibrotic lesions in the lungs out to 8 months. The manifestation of both pneumonitis and focal fibrosis in the lungs of C57L mice at relatively low radiation doses points to the merits of using this strain in further studies aimed at exploring and ameliorating the high susceptibility of the lung as encountered in clinical TBI.