Protective effects of dietary antioxidants on proton total-body irradiation-mediated hematopoietic cell and animal survival

Evaluation of the Neuroprotective Effect of Organic Selenium Compounds: An in Vitro Model of Alzheimer's Disease

Selenium (Se) is an essential trace element for human health and plays an important role in the development and maintenance of central nervous system functions. Se deficiency has been associated with cognitive decline and increased oxidative stress. The increase in oxidative stress is one of the hypotheses for the emergence and worsening of neurodegenerative diseases, such as Alzheimer's disease (AD). To investigate the neuroprotective effects of organic Se compounds in human neuroblastoma cells (SH-SY5Y) differentiated into cholinergic neurons-like. The SH-SY5Y cells were differentiated into cholinergic neuron-like with retinoic acid (RA) and brain-derived neurotrophic factor (BDNF). AD was mimicked exposing the cells to okadaic acid (OA) and beta-amyloid protein (Aβ). The neuroprotective effect of organic Se compounds, selenomethionine (SeMet) and Ebselen, was evaluated through cell viability tests, acetylcholinesterase and antioxidant enzyme activities, and detection of reactive oxygen species (ROS). None of the SeMet concentrations tested protected against the toxic effect of OA + Aβ. On the other hand, previous exposure to 0.1 and 1 µM Ebselen protected cells from the toxic effect of OA + Aβ. Cell differentiation induced by RA and BDNF exposure was effective, showing characteristics of neuronal cells, and pointing to a promising model of AD. Ebselen showed a protective effect, but more studies are needed to identify the mechanism of action.

An Experimental Model of Proton-Beam-Induced Radiation Dermatitis In Vivo

Radiation dermatitis (RD) is one of the most common side effects of radiation therapy. However, to date, there is a lack of both specific treatments for RD and validated experimental animal models with the use of various sources of ionizing radiation (IR) applied in clinical practice. The aim of this study was to develop and validate a model of acute RD induced using proton radiation in mice. Acute RD (Grade 2-4) was obtained with doses of 30, 40, and 50 Gy, either with or without depilation. The developed model of RD was characterized by typical histological changes in the skin after irradiation. Moreover, the depilation contributed to a skin histology alteration of the irradiated mice. The assessment of animal vital signs indicated that there was no effect of proton irradiation on the well-being or general condition of the animals. This model can be used to develop effective therapeutic agents and study the pathogenesis of radiation-induced skin toxicity, including that caused by proton irradiation.

Ionized Radiation-Mediated Retinoid Oxidation in the Retina and Retinal Pigment Epithelium of the Murine Eye

The present study evaluated the effects of proton and gamma-ray ionizing radiation on the mouse eye. The aim of this work was to analyze radiation-mediated retinoid oxidation in the retina and retinal pigment epithelium (RPE). The findings from this analysis can be used to develop a noninvasive method for rapid assessment of the effects of ionizing radiation. Comparative fluorescence and chromatographic analyses of retinoids before and after irradiations were performed. The fluorescent properties of chloroform extracts from irradiated mouse retina and RPE exhibited an increase in fluorescence intensity in the short-wave region of the spectrum (λ < 550 nm). This change is due to increased retinal and RPE retinoid oxidation and degradation products after radiation exposure. Comparative analyses of radiation effects demonstrated that the effect of proton exposure on the retina and RPE was higher than that of gamma-ray exposure. The present study revealed a new approach to assessing the level of radiation exposure in ocular tissues.

The impact of deep space radiation on cognitive performance: From biological sex to biomarkers to countermeasures

In the coming decade, astronauts will travel back to the moon in preparation for future Mars missions. Exposure to galactic cosmic radiation (GCR) is a major obstacle for deep space travel. Using multivariate principal components analysis, we found sex-dimorphic responses in mice exposed to accelerated charged particles to simulate GCR (GCRsim); males displayed impaired spatial learning, whereas females did not. Mechanistically, these GCRsim-induced learning impairments corresponded with chronic microglia activation and synaptic alterations in the hippocampus. Temporary microglia depletion shortly after GCRsim exposure mitigated GCRsim-induced deficits measured months after the radiation exposure. Furthermore, blood monocyte levels measured early after GCRsim exposure were predictive of the late learning deficits and microglia activation measured in the male mice. Our findings (i) advance our understanding of charged particle–induced cognitive challenges, (ii) provide evidence for early peripheral biomarkers for identifying late cognitive deficits, and (iii) offer potential therapeutic strategies for mitigating GCR-induced cognitive loss.

Everything you wanted to know about space radiation but were afraid to ask

The space radiation environment is a complex combination of fast-moving ions derived from all atomic species found in the periodic table. The energy spectrum of each ion species varies widely but is prominently in the range of 400-600 MeV/n. The large dynamic range in ion energy is difficult to simulate in ground-based radiobiology experiments. Most ground-based irradiations with mono-energetic beams of a single one ion species are delivered at comparatively high dose rates. In some cases, sequences of such beams are delivered with various ion species and energies to crudely approximate the complex space radiation environment. This approximation may cause profound experimental bias in processes such as biologic repair of radiation damage, which are known to have strong temporal dependencies. It is possible that this experimental bias leads to an over-prediction of risks of radiation effects that have not been observed in the astronaut cohort. None of the primary health risks presumably attributed to space radiation exposure, such as radiation carcinogenesis, cardiovascular disease, cognitive deficits, etc., have been observed in astronaut or cosmonaut crews. This fundamentally and profoundly limits our understanding of the effects of GCR on humans and limits the development of effective radiation countermeasures.

Evaluating the Protective Effect of a Combination of Curcumin and Selenium-L-Methionine on Radiation Induced Dual Oxidase Upregulation

Background: Epidemiological studies have shown an increased incidence of heart diseases among survivors of Chernobyl disaster as well as Hiroshima and Nagasaki atomic bomb explosion. Similar results were observed for lung and left breast cancer patients. Experimental studies have proposed the chronic upregulation of some pro-inflammatory and pro-fibrotic cytokines. Recent studies have shown that upregulation of pro-oxidant enzymes play a key role in the development of late effects of ionizing radiation such as fibrosis. Interleukin-4 (IL-4) and Interleukin-13 (IL-13) are two important cytokines that have shown ability to induce production of free radicals through dual oxidases (Duox) i.e. Duox1 and Duox2. In this study, we aimed to detect the expression of IL-4 receptor-a1 (IL-4Ra1), IL-13 receptor-a2 (IL-13Ra2), Duox1 and Duox2 genes following irradiation of rat’s heart. In addition, we evaluated the possible role of the combination of curcumin and selenium-L-methionine on the regulation of these genes. Methods: Twenty rats were divided into 4 groups as follows; G1: control; G2: treatment with the combination of curcumin and selenium-L-methionine; G3: radiation; G4: radiation plus treatment with the combination of curcumin and selenium-L-methionine. Rats were sacrificed 10 weeks after irradiation for detecting the expression of IL-4Ra1, IL-13Ra2, Duox1 and Duox2. Results: Results showed that exposure to ionizing radiation caused upregulation of IL-4Ra1 by more than 4-fold as well as Duox1 and Duox2 by more than 5-fold. However, results showed no detectable expression for IL-13Ra2. Treatment with the combination of curcumin and selenium-L-methionine could attenuate the upregulation of all genes. Conclusion: This study has shown that exposing rat’s heart tissues to radiation leads to chronic upregulation of IL-4Ra1, Duox1 and Duox2 as well as pro-oxidant enzymes. Treatment with the combination of curcumin and selenium-L-methionine showed ability to attenuate the upregulation of these genes.

Limitations in predicting the space radiation health risk for exploration astronauts

Despite years of research, understanding of the space radiation environment and the risk it poses to long-duration astronauts remains limited. There is a disparity between research results and observed empirical effects seen in human astronaut crews, likely due to the numerous factors that limit terrestrial simulation of the complex space environment and extrapolation of human clinical consequences from varied animal models. Given the intended future of human spaceflight, with efforts now to rapidly expand capabilities for human missions to the moon and Mars, there is a pressing need to improve upon the understanding of the space radiation risk, predict likely clinical outcomes of interplanetary radiation exposure, and develop appropriate and effective mitigation strategies for future missions. To achieve this goal, the space radiation and aerospace community must recognize the historical limitations of radiation research and how such limitations could be addressed in future research endeavors. We have sought to highlight the numerous factors that limit understanding of the risk of space radiation for human crews and to identify ways in which these limitations could be addressed for improved understanding and appropriate risk posture regarding future human spaceflight.

Radioprotective Efficacy of Lutein in Ameliorating Electron Beam Radiation-induced Oxidative Injury in Swiss Albino Mice

BACKGROUND

Lutein, a carotenoid compound, has previously been studied for its antioxidant and medicinal properties as well as the moderate protection it confers against gamma radiation. This study aimed at evaluating the effects of lutein against radiation-induced hematological and biochemical changes in mice.

METHODS

The optimized dose of the compound was orally administered for 15 days, and the mice were irradiated (6 Gy) on day 15 after the administration of the compound. The groups were divided (6 mice in each group) into normal control, radiation control, gallic acid control, 10% DMSO control, lutein control, and irradiated groups pretreated with gallic acid, 10% DMSO, and lutein. Gallic acid was used to maintain a standard since it is a proven radioprotector. Within 24 hours post irradiation, the animals were anesthetized and sacrificed. The hematological, biochemical, and antioxidant changes were determined using suitable methods. Data were analyzed by the Kaplan-Meier curve (log-rank test) and ANOVA (the Tukey test). The independent t test was used to compare the independent groups. SPSS (ver. 16) was employed.

RESULTS

Maximum survival was observed with a dose of 250 mg/kg b.wt lutein. The total leukocyte count and the percentage lymphocyte count exhibited a significant decline in the irradiated groups pretreated with gallic acid and lutein in comparison to their controls, whereas the percentage granulocyte count showed a significant rise. Antioxidant activity had markedly declined in the irradiated groups, indicating oxidative stress. Lutein pretreatment reduced the damage and maintained the antioxidant system.

CONCLUSION

The present study suggests a protective role for lutein in palliating radiation-induced oxidative changes and maintaining the antioxidant system in vivo.

Pharmacological Modulation of Radiation Damage. Does It Exist a Chance for Other Substances than Hematopoietic Growth Factors and Cytokines?

In recent times, cytokines and hematopoietic growth factors have been at the center of attention for many researchers trying to establish pharmacological therapeutic procedures for the treatment of radiation accident victims. Two granulocyte colony-stimulating factor-based radiation countermeasures have been approved for the treatment of the hematopoietic acute radiation syndrome. However, at the same time, many different substances with varying effects have been tested in animal studies as potential radioprotectors and mitigators of radiation damage. A wide spectrum of these substances has been studied, comprising various immunomodulators, prostaglandins, inhibitors of prostaglandin synthesis, agonists of adenosine cell receptors, herbal extracts, flavonoids, vitamins, and others. These agents are often effective, relatively non-toxic, and cheap. This review summarizes the results of animal experiments, which show the potential for some of these untraditional or new radiation countermeasures to become a part of therapeutic procedures applicable in patients with the acute radiation syndrome. The authors consider β-glucan, 5-AED (5-androstenediol), meloxicam, γ-tocotrienol, genistein, IB-MECA (N⁶-(3-iodobezyl)adenosine-5'-N-methyluronamide), Ex-RAD (4-carboxystyryl-4-chlorobenzylsulfone), and entolimod the most promising agents, with regards to their contingent use in clinical practice.

Combining Pharmacological Countermeasures to Attenuate the Acute Radiation Syndrome-A Concise Review

The goal of combined pharmacological approaches in the treatment of the acute radiation syndrome (ARS) is to obtain an effective therapy producing a minimum of undesirable side effects. This review summarizes important data from studies evaluating the efficacy of combining radioprotective agents developed for administration prior to irradiation and therapeutic agents administered in a post-irradiation treatment regimen. Many of the evaluated results show additivity, or even synergism, of the combined treatments in comparison with the effects of the individual component administrations. It can be deduced from these findings that the research in which combined treatments with radioprotectors/radiomitigators are explored, tested, and evaluated is well-founded. The requirement for studies highly emphasizing the need to minimize undesirable side effects of the radioprotective/radiomitigating therapies is stressed.

Radioprotective and Apoptotic Properties of a Combination of α-Tocopherol Acetate and Ascorbic Acid

We studied radioprotective and apoptotic properties of a combination of α-tocopherol acetate and ascorbic acid. α-Tocopherol acetate (10 mg/kg body weight) or ascorbic acid (20 mg/kg) or combination of these agents in the same doses was orally administered to male rats at various terms before and after single whole-body exposure to γ-irradiation in the doses of 2 and 8 Gy. Irradiation increased the frequency of chromosome aberrations in bone marrow cells and plasma level of low-molecular-weight DNA. Vitamin combination administered before or after irradiation significantly reduced the frequency of chromosome aberrations by 2-2.5 times. Administration of this combination 10 min before irradiation 1.5-fold increased the content of low-molecular-weight DNA in blood plasma in comparison with the control animals exposed to radiation. The combination of α-tocopherol acetate and ascorbic acid produced radioprotective effects and enhanced apoptosis in irradiated cells.

Radioprotective combination of α-tocopherol and ascorbic acid promotes apoptosis that is evident by release of low-molecular weight DNA fragments into circulation

PURPOSE

Genotoxic stresses, including irradiation, lead to the apoptosis of damaged cells and the release of DNA fragments into circulation. Both α-tocopherol acetate and ascorbic acid possess antioxidant and radioprotective properties. Interestingly, depending on a particular experimental system, the treatment with vitamins may demonstrate either apoptosis-promoting or apoptosis-suppressing effects.

MATERIALS AND METHODS

Adult Wistar male rats received total body irradiation with 2-100 Gy doses, while non-irradiated rats served as controls. Oral gavages with vitamins were administered either 10 min or 1 h before irradiation. Control groups were similarly treated with water. Blood samples were collected at 5 h post irradiation. The levels and the composition of circulating DNA were profiled. Chromosomal aberrations were assessed 24 h after irradiation.

RESULTS

A substantial dose-dependent increase in circulating low-molecular weight (LMW) DNA levels was observed after whole body irradiation. An order-of-magnitude increase in the proportion of bone marrow cells with chromosomal abnormalities was observed after irradiation at 2 Gy. Single vitamin preparations were not protective, while the combination of α-tocopherol (10 mg/kg) and ascorbic acid (20 mg/kg) displayed a protective effect evident from marked decrease in chromosomal aberrations. In animals treated with a combination of the vitamins only, substantial increases in the release of LMW DNA were observed.

CONCLUSIONS

Radioprotective combination of α-tocopherol and ascorbic acid promotes apoptosis that is evident by release of low-molecular weight DNA into circulation. We hypothesize that the pretreatment with vitamins provides radioprotection, at least in part, by aiding non-inflammatory, apoptotic elimination of most damaged cells. The microevolutionary nature of observed adaptive response provides mechanistic foundation for the phenomenon of hormesis.

Whole-body proton irradiation causes long-term damage to hematopoietic stem cells in mice

Space flight poses certain health risks to astronauts, including exposure to space radiation, with protons accounting for more than 80% of deep-space radiation. Proton radiation is also now being used with increasing frequency in the clinical setting to treat cancer. For these reasons, there is an urgent need to better understand the biological effects of proton radiation on the body. Such improved understanding could also lead to more accurate assessment of the potential health risks of proton radiation, as well as the development of improved strategies to prevent and mitigate its adverse effects. Previous studies have shown that exposure to low doses of protons is detrimental to mature leukocyte populations in peripheral blood, however, the underlying mechanisms are not known. Some of these detriments may be attributable to damage to hematopoietic stem cells (HSCs) that have the ability to self-renew, proliferate and differentiate into different lineages of blood cells through hematopoietic progenitor cells (HPCs). The goal of this study was to investigate the long-term effects of low-dose proton irradiation on HSCs. We exposed C57BL/6J mice to 1.0 Gy whole-body proton irradiation (150 MeV) and then studied the effects of proton radiation on HSCs and HPCs in the bone marrow (BM) 22 weeks after the exposure. The results showed that mice exposed to 1.0 Gy whole-body proton irradiation had a significant and persistent reduction of BM HSCs compared to unirradiated controls. In contrast, no significant changes were observed in BM HPCs after proton irradiation. Furthermore, irradiated HSCs and their progeny exhibited a significant impairment in clonogenic function, as revealed by the cobblestone area-forming cell (CAFC) and colony-forming cell assays, respectively. These long-term effects of proton irradiation on HSCs may be attributable to the induction of chronic oxidative stress in HSCs, because HSCs from irradiated mice exhibited a significant increase in NADPH oxidase 4 (NOX4) mRNA expression and reactive oxygen species (ROS) production. In addition, the increased production of ROS in HSCs was associated with a significant reduction in HSC quiescence and an increase in DNA damage. These findings indicate that exposure to proton radiation can lead to long-term HSC injury, probably in part by radiation-induced oxidative stress.

The protective role of antioxidants in the defence against ROS/RNS-mediated environmental pollution

Overproduction of reactive oxygen and nitrogen species can result from exposure to environmental pollutants, such as ionising and nonionising radiation, ultraviolet radiation, elevated concentrations of ozone, nitrogen oxides, sulphur dioxide, cigarette smoke, asbestos, particulate matter, pesticides, dioxins and furans, polycyclic aromatic hydrocarbons, and many other compounds present in the environment. It appears that increased oxidative/nitrosative stress is often neglected mechanism by which environmental pollutants affect human health. Oxidation of and oxidative damage to cellular components and biomolecules have been suggested to be involved in the aetiology of several chronic diseases, including cancer, cardiovascular disease, cataracts, age-related macular degeneration, and aging. Several studies have demonstrated that the human body can alleviate oxidative stress using exogenous antioxidants. However, not all dietary antioxidant supplements display protective effects, for example, β-carotene for lung cancer prevention in smokers or tocopherols for photooxidative stress. In this review, we explore the increases in oxidative stress caused by exposure to environmental pollutants and the protective effects of antioxidants.

Acute Hematological Effects in Mice Exposed to the Expected Doses, Dose-rates, and Energies of Solar Particle Event-like Proton Radiation

NASA has funded several projects that have provided evidence for the radiation risk in space. One radiation concern arises from solar particle event (SPE) radiation, which is composed of energetic electrons, protons, alpha particles and heavier particles. SPEs are unpredictable and the accompanying SPE radiation can place astronauts at risk of blood cell death, contributing to a weakened immune system and increased susceptibility to infection. The doses, dose rates, and energies of the proton radiation expected to occur during a SPE have been simulated at the NASA Space Radiation Laboratory, Brookhaven National Laboratory, delivering total body doses to mice. Hematological values were evaluated at acute time points, up to 24 hrs. post-radiation exposure.

Biological Effects of Space Radiation and Development of Effective Countermeasures

As part of a program to assess the adverse biological effects expected from astronaut exposure to space radiation, numerous different biological effects relating to astronaut health have been evaluated. There has been major focus recently on the assessment of risks related to exposure to solar particle event (SPE) radiation. The effects related to various types of space radiation exposure that have been evaluated are: gene expression changes (primarily associated with programmed cell death and extracellular matrix (ECM) remodeling), oxidative stress, gastrointestinal tract bacterial translocation and immune system activation, peripheral hematopoietic cell counts, emesis, blood coagulation, skin, behavior/fatigue (including social exploration, submaximal exercise treadmill and spontaneous locomotor activity), heart functions, alterations in biological endpoints related to astronaut vision problems (lumbar puncture/intracranial pressure, ocular ultrasound and histopathology studies), and survival, as well as long-term effects such as cancer and cataract development. A number of different countermeasures have been identified that can potentially mitigate or prevent the adverse biological effects resulting from exposure to space radiation.

Evidence for radiation-induced disseminated intravascular coagulation as a major cause of radiation-induced death in ferrets

PURPOSE

The studies reported here were performed as part of a program in space radiation biology in which proton radiation like that present in solar particle events, as well as conventional gamma radiation, were being evaluated in terms of the ability to affect hemostasis.

METHODS AND MATERIALS

Ferrets were exposed to 0 to 2 Gy of whole-body proton or gamma radiation and monitored for 30 days. Blood was analyzed for blood cell counts, platelet clumping, thromboelastometry, and fibrin clot formation.

RESULTS

The lethal dose of radiation to 50% of the population (LD50) of the ferrets was established at ∼ 1.5 Gy, with 100% mortality at 2 Gy. Hypocoagulability was present as early as day 7 postirradiation, with animals unable to generate a stable clot and exhibiting signs of platelet aggregation, thrombocytopenia, and fibrin clots in blood vessels of organs. Platelet counts were at normal levels during the early time points postirradiation when coagulopathies were present and becoming progressively more severe; platelet counts were greatly reduced at the time of the white blood cell nadir of 13 days.

CONCLUSIONS

Data presented here provide evidence that death at the LD50 in ferrets is most likely due to disseminated intravascular coagulation (DIC). These data question the current hypothesis that death at relatively low doses of radiation is due solely to the cell-killing effects of hematopoietic cells. The recognition that radiation-induced DIC is the most likely mechanism of death in ferrets raises the question of whether DIC is a contributing mechanism to radiation-induced death at relatively low doses in large mammals.

Flaxseed Mitigates Acute Oxidative Lung Damage in a Mouse Model of Repeated Radiation and Hyperoxia Exposure Associated with Space Exploration

BACKGROUND

Spaceflight missions may require crewmembers to conduct extravehicular activities (EVA). Pre-breathe protocols in preparation for an EVA entail 100% hyperoxia exposure that may last for a few hours and be repeated 2-3 times weekly. Each EVA is associated with additional challenges such as low levels of total body cosmic/galactic radiation exposure that may present a threat to crewmember health. We have developed a mouse model of total body radiation and hyperoxia exposure and identified acute damage of lung tissues. In the current study we evaluated the usefulness of dietary flaxseed (FS) as a countermeasure agent for such double-hit exposures.

METHODS

We evaluated lung tissue changes 2 weeks post-initiation of exposure challenges. Mouse cohorts (n=5/group) were pre-fed diets containing either 0% FS or 10% FS for 3 weeks and exposed to: a) normoxia (Untreated); b) >95% O₂ (O₂); c) 0.25Gy single fraction gamma radiation (IR); or d) a combination of O₂ and IR (O₂+IR) 3 times per week for 2 consecutive weeks, where 8-hour hyperoxia treatments were spanned by normoxic intervals.

RESULTS

At 2 weeks post challenge, while control-diet fed mice developed significant lung injury and inflammation across all challenges, FS protected lung tissues by decreasing bronchoalveolar lavage fluid (BALF) neutrophils (p<0.003) and protein levels, oxidative tissue damage, as determined by levels of malondialdehyde (MDA) (p<0.008) and nitrosative stress as determined by nitrite levels. Lung hydroxyproline levels, a measure of lung fibrosis, were significantly elevated in mice fed 0% FS (p<0.01) and exposed to hyperoxia/radiation or the combination treatment, but not in FS-fed mice. FS also decreased levels of a pro-inflammatory, pro-fibrogenic cytokine (TGF-β1) gene expression levels in lung.

CONCLUSION

Flaxseed mitigated adverse effects in lung of repeat exposures to radiation/hyperoxia. This data will provide useful information in the design of countermeasures to early tissue oxidative damage associated with space exploration.

The Effects of Gamma and Proton Radiation Exposure on Hematopoietic Cell Counts in the Ferret Model

Exposure to total-body radiation induces hematological changes, which can detriment one's immune response to wounds and infection. Here, the decreases in blood cell counts after acute radiation doses of γ-ray or proton radiation exposure, at the doses and dose-rates expected during a solar particle event (SPE), are reported in the ferret model system. Following the exposure to γ-ray or proton radiation, the ferret peripheral total white blood cell (WBC) and lymphocyte counts decreased whereas neutrophil count increased within 3 hours. At 48 hours after irradiation, the WBC, neutrophil, and lymphocyte counts decreased in a dose-dependent manner but were not significantly affected by the radiation type (γ-rays verses protons) or dose rate (0.5 Gy/minute verses 0.5 Gy/hour). The loss of these blood cells could accompany and contribute to the physiological symptoms of the acute radiation syndrome (ARS).

Radioprotective effects of oral 17-dimethylaminoethylamino-17-demethoxygeldanamycin in mice: bone marrow and small intestine

Background

Our previous research demonstrated that one subcutaneous injection of 17-Dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) 24 hours (h) before irradiation (8.75 Gy) increased mouse survival by 75%. However, the protective mechanism of 17-DMAG is currently unknown. The present study aimed to investigate whether oral administration of 17-DMAG was also radioprotective and the potential role it may play in radioprotection.

Results

A single dose of orally pre-administered (24, 48, or 72 h) 17-DMAG (10 mg/kg) increased irradiated mouse survival, reduced body weight loss, improved water consumption, and decreased facial dropsy, whereas orally post-administered 17-DMAG failed. Additional oral doses of pre-treatment did not improve 30-day survival. The protective effect of multiple pre-administrations (2−3 times) of 17-DMAG at 10 mg/kg was equal to the outcome of a single pre-treatment. In 17-DMAG-pretreated mice, attenuation of bone marrow aplasia in femurs 30 days after irradiation with recovered expressions of cluster of differentiation 34, 44 (CD34, CD44), and survivin in bone marrow cells were observed. 17-DMAG also elevated serum granulocyte-colony stimulating factor (G-CSF), decreased serum fms-related tyrosine kinase 3 ligand, and reduced white blood cell depletion. 17-DMAG ameliorated small intestinal histological damage, promoted recovery of villus heights and intestinal crypts including stem cells, where increased leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5) was found 30 days after irradiation.

Conclusions

17-DMAG is a potential radioprotectant for bone marrow and small intestine that results in survival improvement.

Preventive or potential therapeutic value of nutraceuticals against ionizing radiation-induced oxidative stress in exposed subjects and frequent fliers

Humans are constantly exposed to ionizing radiation deriving from outer space sources or activities related to medical care. Absorption of ionizing radiation doses over a prolonged period of time can result in oxidative damage and cellular dysfunction inducing several diseases, especially in ageing subjects. In this report, we analyze the effects of ionizing radiation, particularly at low doses, in relation to a variety of human pathologies, including cancer, and cardiovascular and retinal diseases. We discuss scientific data in support of protection strategies by safe antioxidant formulations that can provide preventive or potential therapeutic value in response to long-term diseases that may develop following exposure.

Leukocyte activity is altered in a ground based murine model of microgravity and proton radiation exposure

Immune system adaptation during spaceflight is a concern in space medicine. Decreased circulating leukocytes observed during and after space flight infer suppressed immune responses and susceptibility to infection. The microgravity aspect of the space environment has been simulated on Earth to study adverse biological effects in astronauts. In this report, the hindlimb unloading (HU) model was employed to investigate the combined effects of solar particle event-like proton radiation and simulated microgravity on immune cell parameters including lymphocyte subtype populations and activity. Lymphocytes are a type of white blood cell critical for adaptive immune responses and T lymphocytes are regulators of cell-mediated immunity, controlling the entire immune response. Mice were suspended prior to and after proton radiation exposure (2 Gy dose) and total leukocyte numbers and splenic lymphocyte functionality were evaluated on days 4 or 21 after combined HU and radiation exposure. Total white blood cell (WBC), lymphocyte, neutrophil, and monocyte counts are reduced by approximately 65%, 70%, 55%, and 70%, respectively, compared to the non-treated control group at 4 days after combined exposure. Splenic lymphocyte subpopulations are altered at both time points investigated. At 21 days post-exposure to combined HU and proton radiation, T cell activation and proliferation were assessed in isolated lymphocytes. Cell surface expression of the Early Activation Marker, CD69, is decreased by 30% in the combined treatment group, compared to the non-treated control group and cell proliferation was suppressed by approximately 50%, compared to the non-treated control group. These findings reveal that the combined stressors (HU and proton radiation exposure) result in decreased leukocyte numbers and function, which could contribute to immune system dysfunction in crew members. This investigation is one of the first to report on combined proton radiation and simulated microgravity effects on hematopoietic, specifically immune cells.

The effects of antioxidants on gene expression following gamma-radiation (GR) and proton radiation (PR) in mice in vivo

Ionizing radiation (IR) generates free radicals that interact randomly with a range of intracellular biomolecules that can result in lethal cellular injury. Therefore, IR-inflicted damage is a highly complex interplay of vastly different pathophysiological processes, including inflammation, epithelial regeneration, tissue remodeling, and fibrosis. The development of safe and effective radioprotectors that protect normal tissues following IR exposure is highly desirable. It was previously shown that dietary supplementation with an antioxidant (AOX) diet containing SeM (0.06 μg/g diet), α-lipoic acid (85.7 μg/g diet), NAC (171.4 μg/g diet), sodium ascorbate (142.8 μg/g diet), and vitamin E succinate (71.4μg/ g diet) was an effective countermeasure to lethality in mice following γ-radiation (GR) and proton radiation (PR). ( 1) (,) ( 2) Here we are examining the effect of the AOX diet on global gene expression following RBE-weighted doses of GR (7.0 Gy) and PR (6.4 Gy) in an attempt to gain further insight into the molecular mechanism of action of AOX diet in the context of radiation exposure. The AOX diet altered the expression pattern of several pro- and anti-apoptotic genes. Our data suggest that the AOX diet may alter IL6 signaling following GR and completely block the expression of the prokineticin PROK2, the ligand to the G protein-coupled receptors PROKR1 and PROKR2, which are involved in a number of pathophysiological processes.

Reactive oxygen species and x-ray disrupted spontaneous [Ca²⁺]I oscillation in alveolar macrophages

Radiation leads to a rapid burst of reactive oxygen species (ROS), which is considered to be one of the major causes of radiation-induced injury. ROS have previously been shown to induce changes in cytosolic Ca²⁺ ([Ca²⁺]i) including [Ca²⁺]i oscillation. However, the role of radiation in [Ca²⁺]i oscillation is poorly understood. The purpose of this study was to identify the effect of ROS and X ray on [Ca²⁺]i oscillation, as well as their role in radiation-induced lung injury. Alveolar macrophages were cultured in the absence and presence of different doses of hydrogen peroxide (H₂O₂) or exposed to X-ray irradiation with or without pretreatment of diphenyleneiodonium chloride (DPI, an inhibitor of NADPH oxidases) or tetrandrine (TET, a calcium entry blocker) and cytosolic Ca²⁺ concentration was detected by fluorescent Ca²⁺ indicator Fura-2. Rat radiation lung injury was induced in vivo by using 40 Gy X ray and DPI or TET was used to prevent radiation-induced lung injury. The results showed that there was spontaneous [Ca²⁺]i oscillation in alveolar macrophages under normal conditions, and treatment of H₂O₂ (100-500 μM) or 2 Gy X ray inhibited the spontaneous [Ca²⁺]i oscillation and induced [Ca²⁺]i rise. TET abolished H₂O₂ or X ray induced [Ca²⁺]i rise in alveolar macrophages, and attenuated X ray- induced rat alveolitis in vivo. DPI prevented X-ray-induced inhibition of [Ca²⁺]i oscillation in alveolar macrophages and prevented X-ray-induced rat alveolitis. Taken together, the data suggest that the disruption of [Ca²⁺]i oscillation and induction of [Ca²⁺]i rise through ROS is involved in the mechanism of radiation-induced lung injury.

Mitigating effects of hUCB-MSCs on the hematopoietic syndrome resulting from total body irradiation

This study evaluated the clinical and pathologic effects of human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) in the recovery from total body irradiation by comparing it with the effects of granulocyte-colony stimulating factor (G-CSF), an efficacious drug in the treatment of acute bone marrow radiation syndrome. BALB/c mice were treated with G-CSF or hUCB-MSCs after they were irradiated with 7 Gy cobalt-60 γ-rays. Circulating blood counts, histopathologic changes in the bone marrow, and plasma level of Flt-3L and transforming growth factor (TGF-β1) were monitored in the postirradiation period. Hematologic analysis revealed that the peripheral leukocyte counts were markedly increased in the hUCB-MSCs-treated group, whereas G-CSF-treated mice did not recover significantly. Moreover, differential counts showed that hUCB-MSC treatment has regenerative effects on white blood cells, lymphocytes, and monocytes compared with the irradiated group. Treatment with hUCB-MSCs or G-CSF significantly increased immunoreactivity of Ki-67 until 3 weeks after total body irradiation. However, at 3 weeks, the number of Ki-67 immunoreactive cells significantly increased in the hUCB-MSCs-treated group compared with the G-CSF-treated group. Furthermore, hUCB-MSC treatment significantly modulated plasma levels of the hematopoietic cytokines Flt-3L and TGF-β1, whereas G-CSF treatment failed to decrease the plasma Flt-3L levels at 2 weeks after irradiation. Based on the differences in circulating blood cell reconstitution and cell density of bone marrow, the authors suggest that MSC treatment is superior to G-CSF treatment for hematopoietic reconstitution following sublethal dose radiation exposure.

Adaptive radiation-induced epigenetic alterations mitigated by antioxidants

Humans are exposed to low-dose ionizing radiation (LDIR) from a number of environmental and medical sources. In addition to inducing genetic mutations, there is concern that LDIR may also alter the epigenome. Such heritable effects early in life can either be positively adaptive or result in the enhanced formation of diseases, including cancer, diabetes, and obesity. Herein, we show that LDIR significantly increased DNA methylation at the viable yellow agouti (A(vy)) locus in a sex-specific manner (P=0.004). Average DNA methylation was significantly increased in male offspring exposed to doses between 0.7 and 7.6 cGy, with maximum effects at 1.4 and 3.0 cGy (P<0.01). Offspring coat color was concomitantly shifted toward pseudoagouti (P<0.01). Maternal dietary antioxidant supplementation mitigated both the DNA methylation changes and coat color shift in the irradiated offspring. Thus, LDIR exposure during gestation elicits epigenetic alterations that lead to positive adaptive phenotypic changes that are negated with antioxidants, indicating they are mediated in part by oxidative stress. These findings provide evidence that in the isogenic A(vy) mouse model, epigenetic alterations resulting from LDIR play a role in radiation hormesis, bringing into question the assumption that every dose of radiation is harmful.

The combined effects of reduced weightbearing and ionizing radiation on splenic lymphocyte population and function

PURPOSE

The effects of radiation +/- hypogravity on immunologic function were investigated using the Partial Weight Suspension (PWS) model ( Wagner et al. 2010 ).

MATERIALS AND METHODS

Mice were exposed to 0.5, 1, or 2 Gray (Gy) dose of gamma radiation and then placed in the PWS system for 4, 24, 48 hours, or 4 days. Spleens were excised and white blood cells were prepared for flow cytometry analyses.

RESULTS

The combination of PWS + radiation (1 and 2 Gy doses only) resulted in decreased cell viability at the 24 h (∼16% decrease), 48 h (∼20% decrease), and 4 day (∼20% decrease) time points, compared to the PWS (no radiation) and no treatment (non-suspended, non-irradiated) groups. The T lymphocyte (thymus-derived) population increased by ∼10% (24 h, 48 h, and 4 day time points), while the B lymphocyte (bursal or bone marrow-derived) population decreased by ∼10% (at all time points examined), when mice were exposed to PWS + radiation (2 Gy dose only), compared to the PWS or no treatment groups. T cell activation was observed in the PWS group and the 0.5 Gy +/- PWS groups at the 4 and 24 h time points, compared to the no treatment group. However, T cell activation was significantly suppressed (∼85%) at the acute time points in the 2 Gy +/- PWS groups, comparable to the no treatment group.

CONCLUSIONS

Ionizing radiation in the absence and presence of simulated hypogravity results in acute lymphocyte dysfunction and compromised immune response.

Nutrient-enhanced diet reduces noise-induced damage to the inner ear and hearing loss

Oxidative stress has been implicated broadly as a cause of cell death and neural degeneration in multiple disease conditions; however, the evidence for successful intervention with dietary antioxidant manipulations has been mixed. In this study, we investigated the potential for protection of cells in the inner ear using a dietary supplement with multiple antioxidant components, which were selected for their potential interactive effectiveness. Protection against permanent threshold shift (PTS) was observed in CBA/J mice maintained on a diet supplemented with a combination of β-carotene, vitamins C and E, and magnesium when compared with PTS in control mice maintained on a nutritionally complete control diet. Although hair cell survival was not enhanced, noise-induced loss of type II fibrocytes in the lateral wall was significantly reduced (P < 0.05), and there was a trend toward less noise-induced loss in strial cell density in animals maintained on the supplemented diet. Taken together, our data suggest that prenoise oral treatment with the high-nutrient diet can protect cells in the inner ear and reduce PTS in mice. The demonstration of functional and morphologic preservation of cells in the inner ear with oral administration of this antioxidant supplemented diet supports the possibility of translation to human patients and suggests an opportunity to evaluate antioxidant protection in mouse models of oxidative stress-related disease and pathology.

Antioxidant-chemoprevention diet ameliorates late effects of total-body irradiation and supplements radioprotection by MnSOD-plasmid liposome administration

Abstract Many acute and chronic effects of ionizing radiation are mediated by reactive oxygen species and reactive nitrogen species, which deplete antioxidant stores, leading to cellular apoptosis, stem cell depletion and accelerated aging. C57BL/6NHsd mice receiving intravenous MnSOD-PL prior to 9.5 Gy total-body irradiation (TBI) show increased survival from the acute hematopoietic syndrome, and males demonstrated improved long-term survival (Epperly et al., Radiat. Res. 170, 437-444, 2008). We evaluated the effect of an antioxidant-chemopreventive diet compared to a regular diet on long-term survival in female mice. Twenty-four hours before the LD(50/30) dose of 9.5 Gy TBI, subgroups of mice were injected intravenously with MnSOD-PL (100 μg plasmid DNA in 100 μl of liposomes). Mice on either diet treated with MnSOD-PL showed decreased death after irradiation compared to irradiated mice on the house diet alone (P = 0.031 for the house diet plus MnSOD-PL or 0.015 for antioxidant diet plus MnSOD-PL). The mice on the antioxidant-chemoprevention diet alone or with MnSOD-PL that survived 30 days after irradiation had a significant increase in survival compared to mice on the regular diet (P = 0.04 or 0.01, respectively). In addition, mice treated with MnSOD-PL only and surviving 30 days after radiation also had increased survival compared to those on the regular diet alone (P = 0.02). Survivors of acute ionizing radiation damage have ameliorated life shortening if they are fed an antioxidant-chemopreventive diet.

Antioxidant dietary supplementation in mice exposed to proton radiation attenuates expression of programmed cell death-associated genes

Dietary antioxidants have radioprotective effects after ionizing radiation exposure that limit hematopoietic cell depletion. We sought to determine the mechanism of proton-induced hematopoietic cell death in animals receiving a moderate dose of whole-body proton radiation. In addition, animals were maintained on diets supplemented with or without dietary antioxidants. In the presence of the dietary antioxidants, total bone marrow mRNA and protein expression of apoptosis-related genes were decreased compared to the expression profiles in the irradiated mice not receiving the antioxidant formulation. These data confirm high-energy proton-induced gene expression of classical apoptosis markers including BAX, caspase-3 and PARP-1. Antioxidant supplementation resulted in decreased expression of these genes in addition to increased protein expression of the anti-apoptosis markers Bcl2 and Bcl-xL. In conclusion, oral supplementation with antioxidants appears to be an effective approach for radioprotection against hematopoietic cell death.

Mitigation of ionizing radiation-induced bone marrow suppression by p38 inhibition and G-CSF administration

p38 mitogen-activated protein kinases (p38) has been shown to be activated in hematopoietic stem and progenitors cells after exposure to ionizing radiation (IR) and its activation has been implicated in bone marrow (BM) suppression under various pathological conditions. Therefore, in the present study we investigated whether inhibition of p38 activity alone with SB203580 (SB, a specific p38 inhibitor) or in combination with granulocyte colony-stimulating factor (G-CSF) can mitigate total body irradiation (TBI)-induced BM damage and lethality. Our results showed that p38 inhibition with SB had no significant effect on the 30-day survival rates of the mice exposed to 7.2 Gy TBI when it was used alone but increased the survival of the mice when it was combined with G-CSF. This combined effect may be attributable to a better preservation or stimulation of hematopoietic stem and progenitor cells, because BM cells from SB and G-CSF-treated mice produced more colony forming units-granulocyte-macrophage (CFU-GM) and 4-week cobblestone area forming cells (CAFCs) than the cells from either SB or G-CSF-treated mice after TBI in a colony forming cell assay and a CAFC assay, respectively. These findings suggest that the combined therapy with SB and G-GSF is more effective in mitigating TBI-induced acute BM injury than either agent alone.

Using electron beam radiation to simulate the dose distribution for whole body solar particle event proton exposure

As a part of the near solar system exploration program, astronauts may receive significant total body proton radiation exposures during a solar particle event (SPE). In the Center for Acute Radiation Research (CARR), symptoms of the acute radiation sickness syndrome induced by conventional radiation are being compared to those induced by SPE-like proton radiation, to determine the relative biological effectiveness (RBE) of SPE protons. In an SPE, the astronaut's whole body will be exposed to radiation consisting mainly of protons with energies below 50 MeV. In addition to providing for a potentially higher RBE than conventional radiation, the energy distribution for an SPE will produce a relatively inhomogeneous total body dose distribution, with a significantly higher dose delivered to the skin and subcutaneous tissues than to the internal organs. These factors make it difficult to use a (60)Co standard for RBE comparisons in our experiments. Here, the novel concept of using megavoltage electron beam radiation to more accurately reproduce both the total dose and the dose distribution of SPE protons and make meaningful RBE comparisons between protons and conventional radiation is described. In these studies, Monte Carlo simulation was used to determine the dose distribution of electron beam radiation in small mammals such as mice and ferrets as well as large mammals such as pigs. These studies will help to better define the topography of the time-dose-fractionation versus biological response landscape for astronaut exposure to an SPE.

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Heavy ions, radioprotectors and genomic instability: implications for human space exploration

The risk associated with space radiation exposure is unique from terrestrial radiation exposures due to differences in radiation quality, including linear energy transfer (LET). Both high- and low-LET radiations are capable of inducing genomic instability in mammalian cells, and this instability is thought to be a driving force underlying radiation carcinogenesis. Unfortunately, during space exploration, flight crews cannot entirely avoid radiation exposure. As a result, chemical and biological countermeasures will be an important component of successful extended missions such as the exploration of Mars. There are currently several radioprotective agents (radioprotectors) in use; however, scientists continue to search for ideal radioprotective compounds-safe to use and effective in preventing and/or reducing acute and delayed effects of irradiation. This review discusses the agents that are currently available or being evaluated for their potential as radioprotectors. Further, this review discusses some implications of radioprotection for the induction and/or propagation of genomic instability in the progeny of irradiated cells.

Silymarin modulates doxorubicin-induced oxidative stress, Bcl-xL and p53 expression while preventing apoptotic and necrotic cell death in the liver

The emergence of silymarin (SMN) as a natural remedy for liver diseases, coupled with its entry into NIH clinical trial, signifies its hepatoprotective potential. SMN is noted for its ability to interfere with apoptotic signaling while acting as an antioxidant. This in vivo study was designed to explore the hepatotoxic potential of Doxorubicin (Dox), the well-known cardiotoxin, and in particular whether pre-exposures to SMN can prevent hepatotoxicity by reducing Dox-induced free radical mediated oxidative stress, by modulating expression of apoptotic signaling proteins like Bcl-xL, and by minimizing liver cell death occurring by apoptosis or necrosis. Groups of male ICR mice included Control, Dox alone, SMN alone, and Dox with SMN pre/co-treatment. Control and Dox groups received saline i.p. for 14 days. SMN was administered p.o. for 14 days at 16 mg/kg/day. An approximate LD(50) dose of Dox, 60 mg/kg, was administered i.p. on day 12 to animals receiving saline or SMN. Animals were euthanized 48 h later. Dox alone induced frank liver injury (>50-fold increase in serum ALT) and oxidative stress (>20-fold increase in malondialdehyde [MDA]), as well as direct damage to DNA (>15-fold increase in DNA fragmentation). Coincident genomic damage and oxidative stress influenced genomic stability, reflected in increased PARP activity and p53 expression. Decreases in Bcl-xL protein coupled with enhanced accumulation of cytochrome c in the cytosol accompanied elevated indexes of apoptotic and necrotic cell death. Significantly, SMN exposure reduced Dox hepatotoxicity and associated apoptotic and necrotic cell death. The effects of SMN on Dox were broad, including the ability to modulate changes in both Bcl-xL and p53 expression. In animals treated with SMN, tissue Bcl-xL expression exceeded control values after Dox treatment. Taken together, these results demonstrated that SMN (i) reduced, delayed onset, or prevented toxic effects of Dox which are typically associated with hydroxyl radical production, (ii) performed as an antioxidant limiting oxidative stress, (iii) protected the integrity of the genome, and (iv) antagonized apoptotic and necrotic cell death while increasing antiapoptotic Bcl-xL protein levels and minimizing the leakage of proapoptotic cytochrome c from liver mitochondria. These observations demonstrate the protective actions of SMN in liver, and raise the possibility that such protection may extend to other organs during Dox treatment including the heart.