Mitigation of radiation-induced lung injury with EUK-207 and genistein: effects in adolescent rats

Captopril reduces lung inflammation and accelerated senescence in response to thoracic radiation in mice

The lung is sensitive to radiation and exhibits several phases of injury, with an initial phase of radiation-induced pneumonitis followed by delayed and irreversible fibrosis. The angiotensin-converting enzyme inhibitor captopril has been demonstrated to mitigate radiation lung injury and to improve survival in animal models of thoracic irradiation, but the mechanism remains poorly understood. Here we investigated the effect of captopril on early inflammatory events in the lung in female CBA/J mice exposed to thoracic X-ray irradiation of 17-17.9 Gy (0.5-0.745 Gy min-1). For whole-body + thoracic irradiation, mice were exposed to 7.5 Gy (0.6 Gy min-1) total-body 60Co irradiation and 9.5 Gy thoracic irradiation. Captopril was administered orally (110 mg kg-1 day-1) in the drinking water, initiated 4 h through to150 days post-irradiation. Captopril treatment increased survival from thoracic irradiation to 75% at 150 days compared with 0% survival in vehicle-treated animals. Survival was characterized by a significant decrease in radiation-induced pneumonitis and fibrosis. Investigation of early inflammatory events showed that captopril significantly attenuated macrophage accumulation and decreased the synthesis of radiation-induced interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) pro-inflammatory cytokines in the lungs of irradiated mice. Suppression of IL-1β and TNF-α correlated with an increase of the anti-inflammatory cytokine IL-10 in the spleen with captopril treatment. We also found that captopril decreased markers for radiation-induced accelerated senescence in the lung tissue. Our data suggest that suppression of inflammation and senescence markers, combined with an increase of anti-inflammatory factors, are a part of the mechanism for captopril-induced survival in thoracic irradiated mice.

Mitigation of Radiation-induced Pneumonitis and Lung Fibrosis using Alpha-lipoic Acid and Resveratrol

BACKGROUND

Lung is a radiosensitive organ. Studies have shown that exposure of the lung to acute and high doses of radiation following inhalation of radioactive agents or an accidental radiological event may lead to pneumonitis and fibrosis, which are associated with a risk of death. So far, some agents have been studied for mitigation of pneumonitis and fibrosis following exposure of murine lung tissues to ionizing radiation. In this study, we aimed to detect the possible mitigatory effect of alpha-lipoic acid, resveratrol and their combination on mice pneumonitis and fibrosis markers following irradiation.

METHODS

25 mice were divided into 5 groups: control, radiation; radiation plus alpha-lipoic acid; radiation plus resveratrol; and radiation plus both resveratrol and alpha-lipoic acid. Mice chest regions were irradiated with 18 Gy using a cobalt-60 gamma rays source. Treatments started 24 h after irradiation and continued for two weeks. After 100 days, all mice were sacrificed and their lung tissues removed for histopathological evaluation.

RESULTS

Pathological study showed that exposure to radiation led to severe pneumonitis and moderate fibrosis after 100 days. Both resveratrol and alpha-lipoic acid, as well as their combination could mitigate pneumonitis and fibrosis markers. Although, resveratrol could not mitigate infiltration of most inflammatory cells as well as inflammation and vascular damage, alpha-lipoic acid and its combination were able to mitigate most damaged markers.

CONCLUSION

Alpha-lipoic acid and its combination with resveratrol were able to mitigate fibrosis and pneumonitis markers in mice lung tissues following lung irradiation. Although resveratrol has a protective effect on some markers, it has a weaker effect on lung injury. In conclusion, our results suggest that the combination of resveratrol and alpha-lipoic acid has a potent mitigatory effect compared to the single forms of these agents.

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.

Pursuing the Elixir of Life: In Vivo Antioxidative Effects of Manganosalen Complexes

Manganosalen complexes are coordination compounds that possess a chelating salen-type ligand, a class of bis-Schiff bases obtained by condensation of salicylaldehyde and a diamine. They may act as catalytic antioxidants mimicking both the structure and the reactivity of the native antioxidant enzymes active site. Thus, manganosalen complexes have been shown to exhibit superoxide dismutase, catalase, and glutathione peroxidase activities, and they could potentially facilitate the scavenging of excess reactive oxygen species (ROS), thereby restoring the redox balance in damaged cells and organs. Initial catalytic studies compared the potency of these compounds as antioxidants in terms of rate constants of the chemical reactivity against ROS, giving catalytic values approaching and even exceeding that of the native antioxidative enzymes. Although most of these catalytic studies lack of biological relevance, subsequent in vitro studies have confirmed the efficiency of many manganosalen complexes in oxidative stress models. These synthetic catalytic scavengers, cheaper than natural antioxidants, have accordingly attracted intensive attention for the therapy of ROS-mediated injuries. The aim of this review is to focus on in vivo studies performed on manganosalen complexes and their activity on the treatment of several pathological disorders associated with oxidative damage. These disorders, ranging from the prevention of fetal malformations to the extension of lifespan, include neurodegenerative, inflammatory, and cardiovascular diseases; tissue injury; and other damages related to the liver, kidney, or lungs.

Targets for protection and mitigation of radiation injury

Protection of normal tissues against toxic effects of ionizing radiation is a critical issue in clinical and environmental radiobiology. Investigations in recent decades have suggested potential targets that are involved in the protection against radiation-induced damages to normal tissues and can be proposed for mitigation of radiation injury. Emerging evidences have been shown to be in contrast to an old dogma in radiation biology; a major amount of reactive oxygen species (ROS) production and cell toxicity occur during some hours to years after exposure to ionizing radiation. This can be attributed to upregulation of inflammatory and fibrosis mediators, epigenetic changes and disruption of the normal metabolism of oxygen. In the current review, we explain the cellular and molecular changes following exposure of normal tissues to ionizing radiation. Furthermore, we review potential targets that can be proposed for protection and mitigation of radiation toxicity.

Protective Effect of Selenium-L-methionine on Radiation-induced Acute Pneumonitis and Lung Fibrosis in Rat

BACKGROUND

In this study, we aimed to detect the changes in the level of interleukin (IL)-4 and IL-13 cytokines and their downstream genes including interleukin-13 receptor subunit alpha-2 (IL13Ra2), interleukin-4 receptor subunit alpha-1 (IL4Ra1), dual oxidase 1 (DUOX1) and dual oxidase 2 (DUOX2). The protective effects of Selenium-L-methionine on radiation-induced histopathological damages and changes in the level of these cytokines and genes were detected.

METHODS

Four groups of 20 rats (5 rats in each) namely, control; Selenium-L-methionine, radiation and radiation plus Selenium-L-methionine were used in this study. 4 mg/kg of Selenium-Lmethionine was administered 1 day before irradiation and five consecutive days after irradiation. Irradiation was done using a dose of 15 Gy 60Co gamma rays at 109 cGy/min. All rats were sacrificed 10 weeks after irradiation for detecting changes in IL-4 and IL-13 cytokines, the expressions of IL13Ra2, IL4Ra1, Duox1 and Duox2 and histopathological changes.

RESULTS

The level of IL-4 but not IL-13 increased after irradiation. This was associated with increased expression of IL4Ra1, Duox1 and Duox2, in addition to changes in morphological properties. Selenium-L-methionine could attenuate all injury markers following lung irradiation.

CONCLUSION

Selenium-L-methionine can protect lung tissues against toxic effects of ionizing radiation. It is possible that the modulation of immune responses and redox interactions are involved in the radioprotective effect of this agent.

Long-term Consequences of Pelvic Irradiation: Toxicities, Challenges, and Therapeutic Opportunities with Pharmacologic Mitigators

A percentage of long-term cancer survivors who receive pelvic irradiation will develop treatment-related late effects, collectively termed pelvic radiation disease. Thus, there is a need to prevent or ameliorate treatment-related late effects in these patients. Modern radiotherapy methods can preferentially protect normal tissues from radiation toxicities to permit higher doses to targets. However, concerns about chronic small bowel toxicity, for example, still constrain the prescription dose. This provides strong rationale for considering adding pharmacologic mitigators. Implementation of modern targeted radiotherapy methods enables delivery of focused radiation to target volumes, while minimizing dose to normal tissues. In prostate cancer, these technical advances enabled safe radiation dose escalation and better local tumor control without increasing normal tissue complications. In other pelvic diseases, these new radiotherapy methods have not resulted in the low probability of normal tissue damage achieved with prostate radiotherapy. The persistence of toxicity provides rationale for pharmacologic mitigators. Several new agents could be readily tested in clinical trials because they are being or have been studied in human patients already. Although there are promising preclinical data supporting mitigators, no clinically proven options to treat or prevent pelvic radiation disease currently exist. This review highlights therapeutic options for prevention and/or treatment of pelvic radiation disease, using pharmacologic mitigators. Successful development of mitigators would reduce the number of survivors who suffer from these devastating consequences of pelvic radiotherapy. It is important to note that pharmacologic mitigators to ameliorate pelvic radiation disease may be applicable to other irradiated sites in which chronic toxicity impairs quality of life.

Saving normal tissues - a goal for the ages

Almost since the earliest utilization of ionizing radiation, many within the radiation community have worked toward either preventing (i.e. protecting) normal tissues from unwanted radiation injury or rescuing them from the downstream consequences of exposure. However, despite over a century of such investigations, only incremental gains have been made toward this goal and, with certainty, no outright panacea having been found. In celebration of the 60th anniversary of the International Journal of Radiation Biology and to chronicle the efforts that have been made to date, we undertook a non-rigorous survey of the articles published by normal tissue researchers in this area, using those that have appeared in the aforementioned journal as a road map. Three 'snapshots' of publications on normal tissue countermeasures were taken: the earliest (1959-1963) and most recent (2013-2018) 5-year of issues, as well as a 5-year intermediate span (1987-1991). Limiting the survey solely to articles appearing within International Journal of Radiation Biology likely reduced the number of translational studies interrogated given the basic science tenor of this particular publication. In addition, by taking 'snapshots' rather than considering the entire breadth of the journal's history in this field, important papers that were published during the interim periods were omitted, for which we apologize. Nonetheless, since the journal's inception, we observed that, during the chosen periods, the majority of studies undertaken in the field of normal tissue countermeasures, whether investigating radiation protectants, mitigators or treatments, have focused on agents that interfere with the physical, chemical and/or biological effects known to occur during the acute period following whole body/high single dose exposures. This relatively narrow approach to the reduction of normal tissue effects, especially those that can take months, if not years, to develop, seems to contradict our growing understanding of the progressive complexities of the microenvironmental disruption that follows the initial radiation injury. Given the analytical tools now at our disposal and the enormous benefits that may be reaped in terms of improving patient outcomes, as well as the potential for offering countermeasures to those affected by accidental or mass casualty exposures, it appears time to broaden our approaches to developing normal tissue countermeasures. We have no doubt that the contributors and readership of the International Journal of Radiation Biology will continue to contribute to this effort for the foreseeable future.

Intercellular communications-redox interactions in radiation toxicity; potential targets for radiation mitigation

Nowadays, using ionizing radiation (IR) is necessary for clinical, agricultural, nuclear energy or industrial applications. Accidental exposure to IR after a radiation terror or disaster poses a threat to human. In contrast to the old dogma of radiation toxicity, several experiments during the last two recent decades have revealed that intercellular signaling and communications play a key role in this procedure. Elevated level of cytokines and other intercellular signals increase oxidative damage and inflammatory responses via reduction/oxidation interactions (redox system). Intercellular signals induce production of free radicals and inflammatory mediators by some intermediate enzymes such as cyclooxygenase-2 (COX-2), nitric oxide synthase (NOS), NADPH oxidase, and also via triggering mitochondrial ROS. Furthermore, these signals facilitate cell to cell contact and increasing cell toxicity via cohort effect. Nitric oxide is a free radical with ability to act as an intercellular signal that induce DNA damage and changes in some signaling pathways in irradiated as well as non-irradiated adjacent cells. Targeting of these mediators by some anti-inflammatory agents or via antioxidants such as mitochondrial ROS scavengers opens a window to mitigate radiation toxicity after an accidental exposure. Experiments which have been done so far suggests that some cytokines such as IL-1β, TNF-α, TGF-β, IL-4 and IL-13 are some interesting targets that depend on irradiated organs and may help mitigate radiation toxicity. Moreover, animal experiments in recent years indicated that targeting of toll like receptors (TLRs) may be more useful for radioprotection and mitigation. In this review, we aimed to describe the role of intercellular interactions in oxidative injury, inflammation, cell death and killing effects of IR. Moreover, we described evidence on potential mitigation of radiation injury via targeting of these mediators.

Reactive Oxygen Species Drive Epigenetic Changes in Radiation-Induced Fibrosis

Radiation-induced fibrosis (RIF) develops months to years after initial radiation exposure. RIF occurs when normal fibroblasts differentiate into myofibroblasts and lay down aberrant amounts of extracellular matrix proteins. One of the main drivers for developing RIF is reactive oxygen species (ROS) generated immediately after radiation exposure. Generation of ROS is known to induce epigenetic changes and cause differentiation of fibroblasts to myofibroblasts. Several antioxidant compounds have been shown to prevent radiation-induced epigenetic changes and the development of RIF. Therefore, reviewing the ROS-linked epigenetic changes in irradiated fibroblast cells is essential to understand the development and prevention of RIF.

Metformin as a Radiation Modifier; Implications to Normal Tissue Protection and Tumor Sensitization

BACKGROUND

Nowadays, ionizing radiation is used for several applications in medicine, industry, agriculture, and nuclear power generation. Besides the beneficial roles of ionizing radiation, there are some concerns about accidental exposure to radioactive sources. The threat posed by its use in terrorism is of global concern. Furthermore, there are several side effects to normal organs for patients who had undergone radiation treatment for cancer. Hence, the modulation of radiation response in normal tissues was one of the most important aims of radiobiology. Although, so far, several agents have been investigated for protection and mitigation of radiation injury. Agents such as amifostine may lead to severe toxicity, while others may interfere with radiation therapy outcomes as a result of tumor protection. Metformin is a natural agent that is well known as an antidiabetic drug. It has shown some antioxidant effects and enhances DNA repair capacity, thereby ameliorating cell death following exposure to radiation. Moreover, through targeting endogenous ROS production within cells, it can mitigate radiation injury. This could potentially make it an effective radiation countermeasure. In contrast to other radioprotectors, metformin has shown modulatory effects through induction of several genes such as AMPK, which suppresses reduction/ oxidation (redox) reactions, protects cells from accumulation of unrepaired DNA, and attenuates initiation of inflammation as well as fibrotic pathways. Interestingly, these properties of metformin can sensitize cancer cells to radiotherapy.

CONCLUSION

In this article, we aimed to review the interesting properties of metformin such as radioprotection, radiomitigation and radiosensitization, which could make it an interesting adjuvant for clinical radiotherapy, as well as an interesting candidate for mitigation of radiation injury after a radiation disaster.

Soy Isoflavones Protect Normal Tissues While Enhancing Radiation Responses

Soy isoflavones have demonstrated chemopreventive and anticancer properties in epidemiology and biological studies, in addition to their function as antioxidants in prevention of cardiovascular disease. We have explored the potential of soy isoflavones, as a safe biological approach, to enhance the efficacy of radiotherapy for local tumor control and limit normal tissue damage in solid tumors. This review presents studies investigating the interaction between soy isoflavones and radiation in different malignancies, including prostate cancer, renal cell carcinoma, and nonsmall cell lung cancer. Soy isoflavones were found to be potent sensitizers of cancer cells to radiation causing increased cell killing in vitro in human tumor cell lines and greater tumor inhibition in vivo in preclinical orthotopic murine tumor models. In the course of these studies, radioprotection of normal tissues and organs in the field of radiation was observed both in a clinical trial for prostate cancer and in preclinical models. The mechanisms of radiosensitization and radioprotection mediated by soy isoflavones are discussed and emphasize the role of soy isoflavones in increasing radiation effect on tumor and mitigating inflammatory responses induced by radiation in normal tissues. Soy isoflavones could be used as a safe, nontoxic complementary strategy that simultaneously increases radiation effectiveness on the malignancy while reducing damage in normal tissues in the field of radiation.

Recurrent DNA damage is associated with persistent injury in progressive radiation-induced pulmonary fibrosis

PURPOSE

Radiation-induced lung injuries (RILI), namely radiation pneumonitis and/or fibrosis, are dose-limiting outcomes following treatment for thoracic cancers. As part of a search for mitigation targets, we sought to determine if persistent DNA damage is a characteristic of this progressive injury.

METHODS

C57BL/6J female mice were sacrificed at 24 h, 1, 4, 12, 16, 24 and 32 weeks following a single dose of 12.5 Gy thorax only gamma radiation; their lungs were compared to age-matched unirradiated animals. Tissues were examined for DNA double-strand breaks (DSBs) (γ-H2A.X and p53bp1), cellular senescence (senescence-associated beta-galactosidase and p21) and oxidative stress (malondialdehyde).

RESULTS

Data revealed consistently higher numbers of DSBs compared to age-matched controls, with increases in γ-H2A.X positivity beyond 24 h post-exposure, particularly during the pathological phases, suggesting periods of recurrent DNA damage. Additional intermittent increases in both cellular senescence and oxidative stress also appeared to coincide with pneumonitis and fibrosis.

CONCLUSIONS

These novel, long-term data indicate (a) increased and persistent levels of DSBs, oxidative stress and cellular senescence may serve as bioindicators of RILI, and (b) prevention of genotoxicity, via mitigation of free radical production, continues to be a potential strategy for the prevention of pulmonary radiation injury.

Modeling radiation-induced lung injury: lessons learned from whole thorax irradiation

Models of thoracic irradiation have been developed as clinicians and scientists have attempted to decipher the events that led up to the pulmonary toxicity seen in human subjects following radiation treatment. The most common model is that of whole thorax irradiation (WTI), applied in a single dose. Mice, particularly the C57BL/6J strain, has been frequently used in these investigations, and has greatly informed our current understanding of the initiation and progression of radiation-induced lung injury (RILI). In this review, we highlight the sequential progression and dynamic nature of RILI, focusing primarily on the vast array of information that has been gleaned from the murine model. Ample evidence indicates a wide array of biological responses that can be seen following irradiation, including DNA damage, oxidative stress, cellular senescence and inflammation, all triggered by the initial exposure to ionizing radiation (IR) and heterogeneously maintained throughout the temporal progression of injury, which manifests as acute pneumonitis and later fibrosis. It appears that the early responses of specific cell types may promote further injury, disrupting the microenvironment and preventing a return to homeostasis, although the exact mechanisms driving these responses remains somewhat unclear. Attempts to either prevent or treat RILI in preclinical models have shown some success by targeting these disparate radiobiological processes. As our understanding of the dynamic cellular responses to radiation improves through the use of such models, so does the likelihood of preventing or treating RILI.

Mechanisms of Normal Tissue Injury From Irradiation

Normal tissue injury from irradiation is an unfortunate consequence of radiotherapy. Technologic improvements have reduced the risk of normal tissue injury; however, toxicity causing treatment breaks or long-term side effects continues to occur in a subset of patients. The molecular events that lead to normal tissue injury are complex and span a variety of biologic processes, including oxidative stress, inflammation, depletion of injured cells, senescence, and elaboration of proinflammatory and profibrogenic cytokines. This article describes selected recent advances in normal tissue radiobiology.

Post-Irradiation Treatment with a Superoxide Dismutase Mimic, MnTnHex-2-PyP5+, Mitigates Radiation Injury in the Lungs of Non-Human Primates after Whole-Thorax Exposure to Ionizing Radiation

Radiation injury to the lung is the result of acute and chronic free radical formation, and there are currently few effective means of mitigating such injury. Studies in rodents indicate that superoxide dismutase mimetics may be effective in this regard; however, studies in humans or large animals are lacking. We hypothesized that post-exposure treatment with the lipophilic mitochondrial superoxide dismutase mimetic, MnTnHex-2-PyP⁵⁺ (hexyl), would reduce radiation-induced pneumonitis and fibrosis in the lungs of nonhuman primates. Rhesus monkeys (Macaca mulatta) received 10 Gy whole thorax irradiation, 10 Gy + hexyl treatment, sham irradiation, or sham irradiation + hexyl. Hexyl was given twice daily, subcutaneously, at 0.05 mg/kg, for 2 months. Animals were monitored daily, and respiratory rates, pulse oximetry, hematology and serum chemistry panels were performed weekly. Computed tomography scans were performed at 0, 2, and 4 months after irradiation. Supportive fluid therapy, corticosteroids, analgesics, and antibiotics were given as needed. All animals were humanely euthanized 4.5 months after irradiation, and pathologic assessments were made. Multifocal, progressive lung lesions were seen at 2 and 4 months in both irradiated groups. Hexyl treatment delayed the onset of radiation-induced lung lesions, reduced elevations of respiratory rate, and reduced pathologic increases in lung weight. No adverse effects of hexyl treatment were found. These results demonstrate (1) development of a nonhuman primate model of radiation-induced lung injury, (2) a significant mitigating effect of hexyl treatment on lung pathology in this model, and (3) no evidence for toxicity of hexyl at the dose studied.

BIO 300, a nanosuspension of genistein, mitigates pneumonitis/fibrosis following high-dose radiation exposure in the C57L/J murine model

BACKGROUND AND PURPOSE

BIO 300 nanosuspension (Humanetics Corporation) is being developed as a medical countermeasure (MCM) for the mitigation of the delayed effects of acute radiation exposure, specifically pneumonitis and fibrosis of the lung. The objective of this study was to determine the best dose and treatment duration of BIO 300 to mitigate lung injury and improve the likelihood for survival in C57L/J mice exposed to whole thorax lung irradiation (WTLI).

EXPERIMENTAL APPROACH

Age- and sex-matched C57L/J mice received a single dose of 11.0 or 12.5 Gy WTLI. BIO 300 (200 or 400 mg·kg^-1 , oral gavage) was administered daily starting 24 h post-exposure for a duration of 2, 4, 6 or, in some cases, 10 weeks. Non-treated controls were included for comparison in both sexes. Animals were observed daily for signs of major morbidity. Respiratory function was assessed biweekly. Lungs were collected, weighed and paraffin embedded for histological evaluation post mortem.

KEY RESULTS

BIO 300 administered at an oral dose of 400 mg·kg^-1 for 4 to 6 weeks starting 24 h post-WTLI reduced morbidity associated with WTLI. The improvement in survival correlated with reduced respiratory frequency and enhanced pause. The irradiated lungs of mice treated with BIO 300 (400 mg·kg^-1 ) for 4 to 6 weeks displayed less morphological damage and airway loss due to oedema, congestion and fibrotic scarring than the untreated, irradiated controls.

CONCLUSIONS AND IMPLICATIONS

BIO 300 is a promising MCM candidate to mitigate pneumonitis/fibrosis when administered daily for 4-6 weeks starting 24 h post-exposure.

Radiation exposure and lung disease in today's nuclear world

PURPOSE OF REVIEW

Ionizing radiation poses important health risks. The per capita annual dose rate has increased in the United States and there is increasing concern for the risks posed by low-dose occupational exposure among workers in nuclear industries and healthcare. Recent nuclear accidents and concern for terrorism have heightened concern for catastrophic, high-dose ionizing radiation exposure. This review will highlight recent research into the risks to lung health posed by ionizing radiation exposure and into potential treatments.

RECENT FINDINGS

Angiotensin-converting enzyme inhibitors and some antioxidants have shown promise as mitigators, to decrease pneumonitis and fibrosis when given after exposure. Studies of survivors of nuclear catastrophes have shown increased risk for lung cancer, especially in nonsmokers. There is evidence for increased lung cancer risk in industrial radiation workers, especially those who process plutonium and may inhale radioactive particles. There does not seem to be an increased risk of lung cancer in healthcare workers who perform fluoroscopic procedures.

SUMMARY

High-dose ionizing radiation exposure causes pneumonitis and fibrosis, and more research is needed to develop mitigators to improve outcomes in nuclear catastrophes. Long-term, low-dose occupational radiation may increase lung cancer risk. More research to better define this risk could lead to improved safety protocols and screening programs.

Genistein suppresses retinoblastoma cell viability and growth and induces apoptosis by upregulating miR-145 and inhibiting its target ABCE1

PURPOSE

Retinoblastoma is a rare malignancy in developing retina tissue in children with limited therapeutic options. Here we sought to investigate the potential clinical value of genistein, the phytoestrogen derived from the soybean with antioxidant activity, in this disease.

METHODS

Retinoblastoma cells were treated with genistein. Colony formation capacity was measured with soft agar assay. MiRNA was identified with microarray. Post-transcriptional regulation of gene expression was determined with dual-luciferase reporter assay. Cell proliferation and apoptosis were measured with the Cell Counting Kit-8 (CCK-8) method and annexin V-propidium iodide (PI) staining. The xenograft model was administered with genistein, and tumor growth was monitored.

RESULTS

The results showed that genistein treatment significantly suppressed proliferation and anchorage-independent growth of the human retinoblastoma cell line Y79 in vitro, which partially attributed to apoptosis induction. MicroRNA array screening identified that miR-145 was upregulated by genistein. Through post-transcriptional regulation of ABCE1, miR-145 functioned as a key downstream effector in genistein-mediated tumor suppression in retinoblastoma. Moreover, the in vivo data consolidated the inhibitory effect of genistein against retinoblastoma xenograft via upregulation of miR-145.

CONCLUSIONS

The data highlighted the therapeutic potency of genistein in this disease and showed that further clinical investigation is warranted.

Extracellular superoxide dismutase increased the therapeutic potential of human mesenchymal stromal cells in radiation pulmonary fibrosis

BACKGROUND AIMS

Pulmonary fibrosis induced by irradiation is a significant problem of radiotherapy in cancer patients. Extracellular superoxide dismutase (SOD3) is found to be predominantly and highly expressed in the extracellular matrix of lung and plays a pivotal role against oxidative damage. Early administration of mesenchymal stromal cells (MSCs) has been demonstrated to reduce fibrosis of damaged lung. However, injection of MSCs at a later stage would be involved in fibrosis development. The present study aimed to determine whether injection of human umbilical cord-derived MSCs (UC-MSCs) over-expressing SOD3 at the established fibrosis stage would have beneficial effects in a mice model of radiation pulmonary fibrosis.

METHODS

Herein, pulmonary fibrosis in mice was induced using Cobalt-60 (⁶⁰Co) irradiator with 20 Gy, followed by intravenous injection of UC-MSCs, transduced or not to express SOD3 at 2 h (early delivery) and 60 day (late delivery) post-irradiation, respectively.

RESULTS

Our results demonstrated that the early administration of UC-MSCs could attenuate the microscopic damage, reduce collagen deposition, inhibit (myo)fibroblast proliferation, reduce inflammatory cell infiltration, protect alveolar type II (AE2) cell injury, prevent oxidative stress and increase antioxidant status, and reduce pro-fibrotic cytokine level in serum. Furthermore, the early treatment with SOD3-infected UC-MSCs resulted in better improvement. However, we failed to observe the therapeutic effects of UC-MSCs, transduced to express SOD3, during established fibrosis.

CONCLUSION

Altogether, our results demonstrated that the early treatment with UC-MSCs alone significantly reduced radiation pulmonary fibrosis in mice through paracrine effects, with further improvement by administration of SOD3-infected UC-MSCs, suggesting that SOD3-infected UC-MSCs may be a potential cell-based gene therapy to treat clinical radiation pulmonary fibrosis.

Subcutaneous administration of bovine superoxide dismutase protects lungs from radiation-induced lung injury

BACKGROUND

The objective of the present study was to determine whether single administration of the antioxidant enzyme bovine superoxide dismutase (bSOD) after radiation therapy (RT) mitigates development of pulmonary toxicity in rats.

METHODS

Female F344 rats (n = 60) were divided among six experimental groups: (1) RT, single dose of 21 Gy to the right hemithorax; (2) RT + 5 mg/kg bSOD; (3) RT + 15 mg/kg bSOD; (4) No RT; (5) sham RT + 5 mg/kg bSOD; and (6) sham RT + 15 mg/kg bSOD. A single subcutaneous injection of bSOD (5 or 15 mg/kg) was administered 24 h post-radiation. The effects of bSOD on radiation-induced lung injury were assessed by measurement of body weight, breathing frequency, and histopathological changes. Immunohistochemistry was used to evaluate oxidative stress (8-OHdG(+), NOX4(+), nitrotyrosine(+), and 4HNE(+) cells), macrophage activation (ED1(+)), and expression of profibrotic transforming growth factor-β or TGF-β in irradiated tissue.

RESULTS

Radiation led to an increase in all the evaluated parameters. Treatment with 15 mg/kg bSOD significantly decreased levels of all the evaluated parameters including tissue damage and breathing frequency starting 6 weeks post-radiation. Animals treated with 5 mg/kg bSOD trended toward a suppression of radiation-induced lung damage but did not reach statistical significance.

CONCLUSIONS

The single application of bSOD (15 mg/kg) ameliorates radiation-induced lung injury through suppression of reactive oxygen species/reactive nitrogen species or ROS/RNS-dependent tissue damage.

Radioprotective effects of genistein on HL-7702 cells via the inhibition of apoptosis and DNA damage

Radiation induced normal tissue damage is the most important limitation for the delivery of a high potentially curative radiation dose. Genistein (GEN), one of the main soy isoflavone components, has drawn wide attention for its bioactivity in alleviating radiation damage. However, the effects and molecular mechanisms underlying the radioprotective effects of GEN remain unclear. In the present study, we showed that low concentration of GEN (1.5 µM) protected L-02 cells against radiation damage via inhibition of apoptosis, alleviation of DNA damage and chromosome aberration, down-regulation of GRP78 and up-regulation of HERP, HUS1 and hHR23A. In contrast, high concentration of GEN (20 µM) demonstrated radiosensitizing characteristics through the promotion of apoptosis and chromosome aberration, impairment of DNA repair, up-regulation of GRP78, and down-regulation of HUS1, SIRT1, RAD17, RAD51 and RNF8. These findings shed light on using low, but not high-concentration GEN, as a potential candidate for adjuvant therapy to alleviate radiation-induced injuries to human recipients of ionizing radiation.

Model development and use of ACE inhibitors for preclinical mitigation of radiation-induced injury to multiple organs

The NIH/NIAID initiated a countermeasure program to develop mitigators for radiation-induced injuries from a radiological attack or nuclear accident. We have previously characterized and demonstrated mitigation of single organ injuries, such as radiation pneumonitis, pulmonary fibrosis or nephropathy by angiotensin converting enzyme (ACE) inhibitors. Our current work extends this research to examine the potential for mitigating multiple organ dysfunctions occurring in the same irradiated rats. Using total body irradiation (TBI) followed by bone marrow transplant, we tested four doses of X radiation (11, 11.25, 11.5 and 12 Gy) to develop lethal late effects. We identified three of these doses (11, 11.25 and 11.5 Gy TBI) that were lethal to all irradiated rats by 160 days to test mitigation by ACE inhibitors of injury to the lungs and kidneys. In this study we tested three ACE inhibitors at doses: captopril (88 and 176 mg/m(2)/day), enalapril (18, 24 and 36 mg/m(2)/day) and fosinopril (60 mg/m(2)/day) for mitigation. Our primary end point was survival or criteria for euthanization of morbid animals. Secondary end points included breathing intervals, other assays for lung structure and function and blood urea nitrogen (BUN) to assess renal damage. We found that captopril at 176 mg/m(2)/day increased survival after 11 or 11.5 Gy TBI. Enalapril at 18-36 mg/m(2)/day improved survival at all three doses (TBI). Fosinopril at 60 mg/m(2)/day enhanced survival at a dose of 11 Gy, although no improvement was observed for pneumonitis. These results demonstrate the use of a single countermeasure to mitigate the lethal late effects in the same animal after TBI.

2013 Dade W. Moeller lecture: medical countermeasures against radiological terrorism

Soon after the 9-11 attacks, politicians and scientists began to question our ability to cope with a large-scale radiological terrorism incident. The outline of what was needed was fairly obvious: the ability to prevent such an attack, methods to cope with the medical consequences, the ability to clean up afterward, and the tools to figure out who perpetrated the attack and bring them to justice. The medical response needed three components: the technology to determine rapidly the radiation doses received by a large number of people, methods for alleviating acute hematological radiation injuries, and therapies for mitigation and treatment of chronic radiation injuries. Research done to date has shown that a realistic medical response plan is scientifically possible, but the regulatory and financial barriers to achieving this may currently be insurmountable.

Targeting the Renin-angiotensin system combined with an antioxidant is highly effective in mitigating radiation-induced lung damage

PURPOSE

To investigate the outcome of suppression of the renin angiotensin system using captopril combined with an antioxidant (Eukarion [EUK]-207) for mitigation of radiation-induced lung damage in rats.

METHODS AND MATERIALS

The thoracic cavity of female Sprague-Dawley rats was irradiated with a single dose of 11 Gy. Treatment with captopril at a dose of 40 mg/kg/d in drinking water and EUK-207 given by subcutaneous injection (8 mg/kg daily) was started 1 week after irradiation (PI) and continuing until 14 weeks PI. Breathing rate was monitored until the rats were killed at 32 weeks PI, when lung fibrosis was assessed by lung hydroxyproline content. Lung levels of the cytokine transforming growth factor-β1 and macrophage activation were analyzed by immunohistochemistry. Oxidative DNA damage was assessed by 8-hydroxy-2-deoxyguanosine levels, and lipid peroxidation was measured by a T-BARS assay.

RESULTS

The increase in breathing rate in the irradiated rats was significantly reduced by the drug treatments. The drug treatment also significantly decreased the hydroxyproline content, 8-hydroxy-2-deoxyguanosine and malondialdehyde levels, and levels of activated macrophages and the cytokine transforming growth factor-β1 at 32 weeks. Almost complete mitigation of these radiation effects was observed by combining captopril and EUK-207.

CONCLUSION

Captopril and EUK-207 can provide mitigation of radiation-induced lung damage out to at least 32 weeks PI after treatment given 1-14 weeks PI. Overall the combination of captopril and EUK-207 was more effective than the individual drugs used alone.

Antioxidant therapeutics: Pandora's box

Evolution has favored the utilization of dioxygen (O2) in the development of complex multicellular organisms. O2 is actually a toxic mutagenic gas that is highly oxidizing and combustible. It is thought that plants are largely to blame for polluting the earth's atmosphere with O2 owing to the development of photosynthesis by blue-green algae over 2 billion years ago. The rise of the plants and atmospheric O2 levels placed evolutionary stress on organisms to adapt or become extinct. This implies that all the surviving creatures on our planet are mutants that have adapted to the "abnormal biology" of O2. Much of the adaptation to the presence of O2 in biological systems comes from well-coordinated antioxidant and repair systems that focus on converting O2 to its most reduced form, water (H2O), and the repair and replacement of damaged cellular macromolecules. Biological systems have also harnessed O2's reactive properties for energy production, xenobiotic metabolism, and host defense and as a signaling messenger and redox modulator of a number of cell signaling pathways. Many of these systems involve electron transport systems and offer many different mechanisms by which antioxidant therapeutics can alternatively produce an antioxidant effect without directly scavenging oxygen-derived reactive species. It is likely that each agent will have a different set of mechanisms that may change depending on the model of oxidative stress, organ system, or disease state. An important point is that all biological processes of aerobes have coevolved with O2 and this creates a Pandora's box for trying to understand the mechanism(s) of action of antioxidants being developed as therapeutic agents.

Radioprotection of lung tissue by soy isoflavones

INTRODUCTION

Radiation-induced pneumonitis and fibrosis have restricted radiotherapy for lung cancer. In a preclinical lung tumor model, soy isoflavones showed the potential to enhance radiation damage in tumor nodules and simultaneously protect normal lung from radiation injury. We have further dissected the role of soy isoflavones in the radioprotection of lung tissue.

METHODS

Naive Balb/c mice were treated with oral soy isoflavones for 3 days before and up to 4 months after radiation. Radiation was administered to the left lung at 12 Gy. Mice were monitored for toxicity and breathing rates at 2, 3, and 4 months after radiation. Lung tissues were processed for histology for in situ evaluation of response.

RESULTS

Radiation caused damage to normal hair follicles, leading to hair loss in the irradiated left thoracic area. Supplementation with soy isoflavones protected mice against radiation-induced skin injury and hair loss. Lung irradiation also caused an increase in mouse breathing rate that was more pronounced by 4 months after radiation, probably because of the late effects of radiation-induced injury to normal lung tissue. However, this effect was mitigated by soy isoflavones. Histological examination of irradiated lungs revealed a chronic inflammatory infiltration involving alveoli and bronchioles and a progressive increase in fibrosis. These adverse effects of radiation were alleviated by soy isoflavones.

CONCLUSION

Soy isoflavones given pre- and postradiation protected the lungs against adverse effects of radiation including skin injury, hair loss, increased breathing rates, inflammation, pneumonitis and fibrosis, providing evidence for a radioprotective effect of soy.

Differential effect of soy isoflavones in enhancing high intensity radiotherapy and protecting lung tissue in a pre-clinical model of lung carcinoma

BACKGROUND

Radiotherapy of locally-advanced non-small cell lung cancer is limited by radiation-induced pneumonitis and fibrosis. We have further investigated the role of soy isoflavones to improve the effect of a high intensity radiation and reduce lung damage in a pre-clinical lung tumor model.

METHODS

Human A549 NSCLC cells were injected i.v. in nude mice to generate a large tumor burden in the lungs. Mice were treated with lung irradiation at 10 Gy and with oral soy. The therapy effect on the tumor cells and surrounding lung tissue was analyzed on lung sections stained with H&E, Ki-67 and Masson's Trichrome. Pneumonitis and vascular damage were evaluated by measurements of alveolar septa and immunofluorescent staining of vessel walls.

RESULTS

Combined soy and radiation caused a significantly stronger inhibition of tumor progression compared to each modality alone in contrast to large invasive tumor nodules seen in control mice. At the same time, soy reduced radiation injury in lung tissue by decreasing pneumonitis, fibrosis and protecting alveolar septa, bronchioles and vessels.

CONCLUSIONS

These studies demonstrate a differential effect of soy isoflavones on augmenting tumor destruction induced by radiation while radioprotecting the normal lung tissue and support using soy to alleviate radiotoxicity in lung cancer.