Psychosocial Stress and Age Influence Depression and Anxiety-Related Behavior, Drive Tumor Inflammatory Cytokines and Accelerate Prostate Cancer Growth in Mice.

Prostate cancer (PCa) prevalence is higher in older men and poorer coping with psychosocial stressors effect prognosis. Yet, interactions between age, stress and PCa progression are underexplored. Therefore, we characterized the effects of age and isolation combined with restraint (2 h/day) for 14 days post-tumor inoculation on behavior, tumor growth and host defense in the immunocompetent, orthotopic RM-9 murine PCa model. All mice were tumor inoculated. Isolation/restraint increased sympathetic and hypothalamic-pituitary-adrenal cortical activation, based on elevated serum 3-methoxy-4-hydroxyphenylglycol/norepinephrine ratios and corticosterone levels, respectively. Elevated zero maze testing revealed age-related differences in naïve C57Bl/6 mice, and increased anxiety-like behavior in tumor-bearing mice. In open field testing, old stressed mice were less active throughout the 30-min test than young non-stressed and stressed, and old non-stressed mice, suggesting greater anxiety in old stressed mice. Old (18 month) mice demonstrated more depression-like behavior than young mice with tail suspension testing, without effects of isolation/restraint stress. Old mice developed larger tumors, despite similar tumor expression of tumor vascular endothelial growth factor or transforming growth factor-beta1 across age. Tumor chemokine/cytokine expression, commonly prognostic for poorer outcomes, were uniquely age- and stress-dependent, underscoring the need for PCa research in old animals. Macrophages predominated in RM-9 tumors. Macrophages, and CD4+ and CD4+FoxP3+ T-cell tumor infiltration were greater in young mice than in old mice. Stress increased macrophage infiltration in old mice. Conversely, stress reduced intratumoral CD4+ and CD4+FoxP3+ T-cell numbers in young mice. CD8+ T-cell infiltration was similar across treatment groups. Our findings support that age- and psychological stress interacts to affect PCa outcomes by interfering with neural-immune mechanisms and affecting behavioral responses.

Proteomic Analysis of Mouse Brain Subjected to Spaceflight.

There is evidence that spaceflight poses acute and late risks to the central nervous system. To explore possible mechanisms, the proteomic changes following spaceflight in mouse brain were characterized. Space Shuttle Atlantis (STS-135) was launched from the Kennedy Space Center (KSC) on a 13-day mission. Within 3⁻5 h after landing, brain tissue was collected to evaluate protein expression profiles using quantitative proteomic analysis. Our results showed that there were 26 proteins that were significantly altered after spaceflight in the gray and/or white matter. While there was no overlap between the white and gray matter in terms of individual proteins, there was overlap in terms of function, synaptic plasticity, vesical activity, protein/organelle transport, and metabolism. Our data demonstrate that exposure to the spaceflight environment induces significant changes in protein expression related to neuronal structure and metabolic function. This might lead to a significant impact on brain structural and functional integrity that could affect the outcome of space missions.

Apoptosis and expression of apoptosis-related genes in mouse intestinal tissue after whole-body proton exposure.

Energetic protons are the most abundant particle type in space and can pose serious health risks to astronauts during long-duration missions. The health effects of proton exposure are also a concern for cancer patients undergoing radiation treatment with accelerated protons. To investigate the damage induced by energetic protons in vivo to radiosensitive organs, 6-week-old BALB/c male mice were subjected to 250 MeV proton radiation at whole-body doses of 0.1, 1, and 2 Gy. The gastrointestinal (GI) tract of each exposed animal was dissected 4 h post-irradiation, and the isolated small intestinal tissue was analyzed for histopathological and gene expression changes. Histopathologic observation of the tissue using standard hematoxylin and eosin (H&E) staining methods to screen for morphologic changes showed a marked increase in apoptotic lesions for even the lowest dose of 0.1 Gy, similar to X- or γ rays. The percentage of apoptotic cells increased dose-dependently, but the dose response appeared supralinear, indicating hypersensitivity at low doses. A significant decrease in surviving crypts and mucosal surface area, as well as in cell proliferation, was also observed in irradiated mice. Gene expression analysis of 84 genes involved in the apoptotic process showed that most of the genes affected by protons were common between the low (0.1 Gy) and high (1 and 2 Gy) doses. However, the genes that were distinctively responsive to the low or high doses suggest that high doses of protons may cause apoptosis in the small intestine by direct damage to the DNA, whereas low doses of protons may trigger apoptosis through a different stress response mechanism.

Role of NADPH Oxidase as a Mediator of Oxidative Damage in Low-Dose Irradiated and Hindlimb-Unloaded Mice.

The purpose of this study was to determine whether nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-derived stress can account for unloading- and radiation-induced endothelial damage and neurovascular remodeling in a mouse model. Wild-type (WT, Nox2+/+) C57BL/6 mice or Nox2-/- (B6.129S6-CYBBM) knockout (KO) mice were placed into one of the following groups: age-matched control; hindlimb unloading (HLU); low-dose/low-dose-rate radiation (LDR); or HLU with LDR simultaneously for 21 days. The mice were then sacrificed one month later. Anti-orthostatic tail suspension was used to model the unloading, fluid shift and physiological stress aspects of microgravity. The LDR was delivered using 57Co plates (0.04 Gy at 0.01 cGy/h) to the simulate whole-body irradiation, similar to that experienced while in space. Brains were isolated for characterization of various oxidative stress markers and vascular topology. The level of 4-hydroxynonenal (4-HNE) protein, a specific marker for lipid peroxidation, was measured. Expression of aquaporin-4 (AQP4), a water channel protein expressed in astrocyte end-feet, was quantified. Thirty days after simulated spaceflight, KO mice showed decreased apoptosis (P < 0.05) in the brain compared to WT counterparts. The HLU-dependent increase in apoptosis in WT mice was not observed in KO mice. The level of 4-HNE protein was significantly elevated in the hippocampus of the LDR with HLU treatment group compared to WT controls (P < 0.05). However, there were no significant differences among groups of Nox2-KO mice at the one-month time point. In contrast to findings in the WT animals, superoxide dismutase (SOD) level and expression of AQP4 were similar among all KO groups. In summary, for most of the parameters, the oxidative response to HLU and LDR was suppressed in Nox2-KO mice. This suggests that Nox2-containing NADPH oxidase may contribute to spaceflight environment-induced oxidative stress.

Is spaceflight-induced immune dysfunction linked to systemic changes in metabolism?

The Space Shuttle Atlantis launched on its final mission (STS-135) on July 8, 2011. After just under 13 days, the shuttle landed safely at Kennedy Space Center (KSC) for the last time. Female C57BL/6J mice flew as part of the Commercial Biomedical Testing Module-3 (CBTM-3) payload. Ground controls were maintained at the KSC facility. Subsets of these mice were made available to investigators as part of NASA's Bio-specimen Sharing Program (BSP). Our group characterized cell phenotype distributions and phagocytic function in the spleen, catecholamine and corticosterone levels in the adrenal glands, and transcriptomics/metabolomics in the liver. Despite decreases in most splenic leukocyte subsets, there were increases in reactive oxygen species (ROS)-related activity. Although there were increases noted in corticosterone levels in both the adrenals and liver, there were no significant changes in catecholamine levels. Furthermore, functional analysis of gene expression and metabolomic profiles suggest that the functional changes are not due to oxidative or psychological stress. Despite changes in gene expression patterns indicative of increases in phagocytic activity (e.g. endocytosis and formation of peroxisomes), there was no corresponding increase in genes related to ROS metabolism. In contrast, there were increases in expression profiles related to fatty acid oxidation with decreases in glycolysis-related profiles. Given the clear link between immune function and metabolism in many ground-based diseases, we propose a similar link may be involved in spaceflight-induced decrements in immune and metabolic function.

Changes in the distribution and function of leukocytes after whole-body iron ion irradiation.

High-energy particle radiation could have a considerable impact on health during space missions. This study evaluated C57BL/6 mice on Day 40 after total-body 56Fe26+ irradiation at 0, 1, 2 and 3 gray (Gy). Radiation consistently increased thymus mass (one-way ANOVA: P < 0.005); spleen, liver and lung masses were similar among all groups. In the blood, there was no radiation effect on the white blood cell (WBC) count or major leukocyte types. However, the red blood cell count, hemoglobin, hematocrit and the CD8+ T cytotoxic (Tc) cell count and percentage all decreased, while both the CD4:CD8 (Th:Tc) cell ratio and spontaneous blastogenesis increased, in one or more irradiated groups compared with unirradiated controls (P < 0.05 vs 0 Gy). In contrast, splenic WBC, lymphocyte, B cell and T helper (Th) counts, %B cells and the CD4:CD8 ratio were all significantly elevated, while Tc percentages decreased, in one or more of the irradiated groups compared with controls (P < 0.05 vs 0 Gy). Although there were trends for minor, radiation-induced increases in %CD11b+ granulocytes in the spleen, cells double-labeled with adhesion markers (CD11b+CD54+, CD11b+CD62E+) were normal. Splenocyte spontaneous blastogenesis and that induced by mitogens (PHA, ConA, LPS) was equivalent to normal. In bone marrow, the percentage of cells expressing stem cell markers, Sca-1 and CD34/Sca-1, were low in one or more of the irradiated groups (P < 0.05 vs 0 Gy). Collectively, the data indicate that significant immunological abnormalities still exist more than a month after 56Fe irradiation and that there are differences dependent upon body compartment.

Simulated Microgravity and Low-Dose/Low-Dose-Rate Radiation Induces Oxidative Damage in the Mouse Brain.

Microgravity and radiation are stressors unique to the spaceflight environment that can have an impact on the central nervous system (CNS). These stressors could potentially lead to significant health risks to astronauts, both acutely during the course of a mission or chronically, leading to long-term, post-mission decrements in quality of life. The CNS is sensitive to oxidative injury due to high concentrations of oxidizable, unsaturated lipids and low levels of antioxidant defenses. The purpose of this study was to evaluate oxidative damage in the brain cortex and hippocampus in a ground-based model for spaceflight, which includes prolonged unloading and low-dose radiation. Whole-body low-dose/low-dose-rate (LDR) gamma radiation using (57)Co plates (0.04 Gy at 0.01 cGy/h) was delivered to 6 months old, mature, female C57BL/6 mice (n = 4-6/group) to simulate the radiation component. Anti-orthostatic tail suspension was used to model the unloading, fluid shift and physiological stress aspects of the microgravity component. Mice were hindlimb suspended and/or irradiated for 21 days. Brains were isolated 7 days or 9 months after irradiation and hindlimb unloading (HLU) for characterization of oxidative stress markers and microvessel changes. The level of 4-hydroxynonenal (4-HNE) protein, an oxidative specific marker for lipid peroxidation, was significantly elevated in the cortex and hippocampus after LDR + HLU compared to controls (P < 0.05). The combination group also had the highest level of nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) expression compared to controls (P < 0.05). There was a significant decrease in superoxide dismutase (SOD) expression in the animals that received HLU only or combined LDR + HLU compared to control (P < 0.05). In addition, 9 months after LDR and HLU exposure, microvessel densities were the lowest in the combination group, compared to age-matched controls in the cortex (P < 0.05). Our data provide the first evidence that prolonged exposure to simulated microgravity and LDR radiation is associated with increased oxidative stress biomarkers that may increase the likelihood of brain injury and reduced antioxidant defense. NOX2-containing nicotinamide adenosine dinucleotide phosphate (NADPH oxidase) may contribute to spaceflight environment-induced oxidative stress.

Correction: Spaceflight Activates Lipotoxic Pathways in Mouse Liver.

[This corrects the article DOI: 10.1371/journal.pone.0152877.].

Spaceflight Activates Lipotoxic Pathways in Mouse Liver.

Spaceflight affects numerous organ systems in the body, leading to metabolic dysfunction that may have long-term consequences. Microgravity-induced alterations in liver metabolism, particularly with respect to lipids, remain largely unexplored. Here we utilize a novel systems biology approach, combining metabolomics and transcriptomics with advanced Raman microscopy, to investigate altered hepatic lipid metabolism in mice following short duration spaceflight. Mice flown aboard Space Transportation System -135, the last Shuttle mission, lose weight but redistribute lipids, particularly to the liver. Intriguingly, spaceflight mice lose retinol from lipid droplets. Both mRNA and metabolite changes suggest the retinol loss is linked to activation of PPARα-mediated pathways and potentially to hepatic stellate cell activation, both of which may be coincident with increased bile acids and early signs of liver injury. Although the 13-day flight duration is too short for frank fibrosis to develop, the retinol loss plus changes in markers of extracellular matrix remodeling raise the concern that longer duration exposure to the space environment may result in progressive liver damage, increasing the risk for nonalcoholic fatty liver disease.

Effects of Targeted Proton Radiation on Spinal Cord in a Porcine Model: A Pilot Study.

AIM: To determine whether proton radiation can be used to treat chronic intractable pain. The focus of this study was on the biological effects of spinal cord irradiation. MATERIALS AND METHODS: Proton radiation (0-25 Gy, single fraction) was applied to the spinal cord within L3-L5 of Yucatan mini-pigs (n=20). Skin reaction, body mass and behavior were monitored. At euthanasia, blood and spinal cord were analyzed. RESULTS: Skin morbidity was mild and overall health for the 5-20 Gy-treated groups was good based on behavior and weight gain up to 8.5-9 months post-exposure. The 25 Gy-treated animals developed hind limb weakness at 2.5-3 months and were euthanized. Radiation had a significant effect on white blood cell count (p<0.05), with the 25 Gy-treated mini-pigs having the highest number of all three major leukocyte populations. A few differences were also noted for erythrocyte parameters, but the blood chemistry panel was normal. Apoptosis in the targeted portion of the spinal cord was elevated in the 20- and 25 Gy-treated groups versus 0 Gy (p<0.05) based on the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. There was a trend (p<0.1) for a radiation effect on glial fibrillary acidic protein expression, with the highest value being found after 25 Gy. Histology showed no difference between 0 versus 25 Gy. CONCLUSION: The data demonstrated that a small segment of the spinal cord can be readily targeted using proton radiation; doses ranging from 5-20 Gy were well-tolerated in an animal model with radiosensitivity similar to humans. Future studies with a pain model should use ≤15 Gy.

Chlorisondamine, a sympathetic ganglionic blocker, moderates the effects of whole-body irradiation (WBI) on early host defense to a live bacterial challenge.

There is a growing consensus that long-term deficits in the brain are due to dynamic interactions between multiple neural and immune cell types. Specifically, radiation induces an inflammatory response, including changes in neuromodulatory pro- and anti-inflammatory cytokine secretion. The purpose of this study was to establish that there is sympathetic involvement in radiation-induced decrements early in in vivo immune function host defense. Female, 8-9 week-old C57BL/6J mice were exposed to whole-body irradiation (WBI). There were 8 groups with radiation (0 vs. 3 Gy protons), immune challenge (Escherichia coli) and exposure to the sympathetic ganglionic blocker, chlorisondamine (1 mg/kg weight, i.p.), as independent variables. Ten days post-irradiation, mice were inoculated with E. coli intraperitoneally and sacrificed 90-120 min later. The data suggest that radiation-induced changes in immune function may in part be mediated by the sympathetic nervous system. Briefly, we found that radiation augments the bacteria-induced inflammatory cytokine response, particularly those cytokines involved in innate immunity. However, this augmentation can be reduced by the ganglionic blockade.

Dermatopathology effects of simulated solar particle event radiation exposure in the porcine model.

The space environment exposes astronauts to risks of acute and chronic exposure to ionizing radiation. Of particular concern is possible exposure to ionizing radiation from a solar particle event (SPE). During an SPE, magnetic disturbances in specific regions of the Sun result in the release of intense bursts of ionizing radiation, primarily consisting of protons that have a highly variable energy spectrum. Thus, SPE events can lead to significant total body radiation exposures to astronauts in space vehicles and especially while performing extravehicular activities. Simulated energy profiles suggest that SPE radiation exposures are likely to be highest in the skin. In the current report, we have used our established miniature pig model system to evaluate the skin toxicity of simulated SPE radiation exposures that closely resemble the energy and fluence profile of the September, 1989 SPE using either conventional radiation (electrons) or proton simulated SPE radiation. Exposure of animals to electron or proton radiation led to dose-dependent increases in epidermal pigmentation, the presence of necrotic keratinocytes at the dermal-epidermal boundary and pigment incontinence, manifested by the presence of melanophages in the derm is upon histological examination. We also observed epidermal hyperplasia and a reduction in vascular density at 30 days following exposure to electron or proton simulated SPE radiation. These results suggest that the doses of electron or proton simulated SPE radiation results in significant skin toxicity that is quantitatively and qualitatively similar. Radiation-induced skin damage is often one of the first clinical signs of both acute and non-acute radiation injury where infection may occur, if not treated. In this report, histopathology analyses of acute radiation-induced skin injury are discussed.

Genetic and Apoptotic Changes in Lungs of Mice Flown on the STS-135 Mission in Space.

AIM: The goal of the study was to evaluate changes in lung status due to spaceflight stressors that include radiation above levels found on Earth. MATERIALS AND METHODS: Within hours after return from a 13-day mission in space onboard the Space Shuttle Atlantis, C57BL/6 mice (FLT group) were euthanized; mice housed on the ground in similar animal enclosure modules served as controls (AEM group). Lung tissue was collected to evaluate the expression of genes related to extracellular matrix (ECM)/adhesion and stem cell signaling. Pathway analysis was also performed. In addition, immunohistochemistry for stem cell antigen-1 (SCA-1), the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay for apoptosis, and staining for histological characteristics were performed. RESULTS: There were 18/168 genes significantly modulated in lungs from the FLT group (p<0.05 vs. AEM); 17 of these were up-regulated and one was down-regulated. The greatest effect, namely a 5.14-fold increase, was observed on Spock1 (also known as Spark/osteonectin), encoding a multi-functional protein that has anti-adhesive effects, inhibits cell proliferation and regulates activity of certain growth factors. Additional genes with increased expression were cadherin 3 (Cdh3), collagen, type V, alpha 1 (Col5a1), integrin alpha 5 (Itga5), laminin, gamma 1 (Lamc1), matrix metallopeptidase 14 (Mmp14), neural cell adhesion molecule 1 (Ncam1), transforming growth factor, beta induced (Tgfbi), thrombospondin 1 (Thbs1), Thbs2, versican (Vcan), fibroblast growth factor receptor 1 (Fgfr1), frizzled homolog 6 (Fzd6), nicastrin (Ncstn), nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 4 (Nfatc4), notch gene homolog 4 (Notch4) and vang-like 2 (Vangl2). The down-regulated gene was Mmp13. Staining for SCA-1 protein showed strong signal intensity in bronchiolar epithelial cells of FLT mice (p<0.05 vs. AEM). TUNEL positivity was also significantly higher in the FLT mice (p<0.05 vs. AEM), but no consistent histological differences were noted. CONCLUSION: The results demonstrate that spaceflight-related stress had a significant impact on lung integrity, indicative of tissue injury and remodeling.

pKC modulates integrin expression that contributes to fibrotic changes in irradiated thyroid tissue.

AIM: We hypothesized that radiation-induced fibrosis was, in part, a result of altered signal transduction that directly modulates integrin expression and may indirectly affect the extracellular matrix (ECM). Major focus was given on protein kinase C (pKC). MATERIALS AND METHODS: Rat FRTL-5 and primary thyroid cells were exposed to proton radiation (5 and 10 Gy). Hours to days after exposure, a series of assays were performed. In addition, the neck region of Lewis rats was proton-irradiated to 40 Gy (5 Gy/day or 10 Gy/day). At 11 weeks after exposure, thyroid tissue was evaluated. RESULTS: Accumulation of ECM in irradiated FRTL-5 and primary thyroid cells was coincident with loss of tissue organization and follicularization at one or more doses and time points. Several pKC isoforms increased post-irradiation, which coincided with modulated integrin expression; fibronectin, laminin and collagen were also altered (p<0.05 vs. 0 Gy). Modulation of thyroid cells in culture with 12-O-tetradecanoylphorbol-13-acetate (TPA)±calphostin C supported a direct role of pKC in these altered properties. Thyroid tissue from irradiated rats had significantly more fibrotic lesions and increases in several pKC isoforms, integrins and fibronectin compared to 0-Gy (p<0.05). CONCLUSION: pKC is a likely contributor to alteration of key players associated with radiation-induced fibrosis.

Effect of radiation and repeated sub-culturing on the transforming growth factor-ß1 signaling pathway in FRTL-5 cells.

BACKGROUND/AIM: Fisher rat thyroid cells (FRTL-5) display increased proliferation, reduced follicularization and decreased thyroxin release with repeated sub-culturing. These changes occur earlier and more rapidly following exposure to ionizing radiation. We hypothesized that altered transforming growth factor-ß1 (TGF-ß1) signaling contributes to these differences. MATERIALS AND METHODS: Assessments included FRTL-5 cell growth rate and quantification of TGF-ß1 ligand and receptors. The levels and activity of Smads2, 3 and 4 were measured by western blotting and the ability of TGF-ß1 to regulate cyclin A and plasminogen activator inhibitor type 1 (PAI-1) activity was assessed using transfection assays. RESULTS: TGF-ß1 production increased after radiation but returned to control levels after repeated sub-culturing. There was no difference in TGF-ß1 levels between un-irradiated cells at low versus high-passage number. TGF-ß1 receptors and basal levels of Smads2, 3 and 4 remained unchanged. However, there were significant changes in cell proliferation, TGF-ß1-mediated Smads2 and 3 activation and in TGF-ß1's ability to regulate cyclin A and PAI-1 transcription in irradiated and repeatedly sub-cultured cells (p<0.05). CONCLUSION: Collectively, these results support the conclusion that alterations in the TGF-ß1 pathway contribute to phenotypic changes in FRTL-5 cells as a function of passage number and radiation.

Biological effects of passive versus active scanning proton beams on human lung epithelial cells.

The goal was to characterize differences in cell response after exposure to active beam scanning (ABS) protons compared to a passive delivery system. Human lung epithelial (HLE) cells were evaluated at various locations along the proton depth dose profile. The dose delivered at the Bragg peak position was essentially identical (∼4 Gy) with the two techniques, but depth dose data showed that ABS resulted in lower doses at entry and more rapid drop-off after the peak. Average dose rates for the passive and ABS beams were 1.1 Gy/min and 5.1 Gy/min, respectively; instantaneous dose rates were 19.2 Gy/min and 2,300 Gy/min (to a 0.5 × 0.5 mm(2) voxel). Analysis of DNA synthesis was based on (3)H-TdR incorporation. Quantitative real-time polymerase chain reaction (RT-PCR) was done to determine expression of genes related to p53 signaling and DNA damage; a total of 152 genes were assessed. Spectral karyotyping and analyses of the Golgi apparatus and cytokines produced by the HLE cells were also performed. At or near the Bragg peak position, ABS protons resulted in a greater decrease in DNA synthesis compared to passively delivered protons. Genes with >2-fold change (P < 0.05 vs. 0 Gy) after passive proton irradiation at one or more locations within the Bragg curve were BTG2, CDKN1A, IFNB1 and SIAH1. In contrast, many more genes had >2-fold difference with ABS protons: BRCA1, BRCA2, CDC25A, CDC25C, CCNB2, CDK1, DMC1, DNMT1, E2F1, EXO1, FEN1, GADD45A, GTSE1, IL-6, JUN, KRAS, MDM4, PRC1, PTTG1, RAD51, RPA1, TNF, WT1, XRCC2, XRCC3 and XRCC6BP1. Spectral karyotyping revealed numerous differences in chromosomal abnormalities between the two delivery systems, especially at or near the Bragg peak. Percentage of cells staining for the Golgi apparatus was low after exposure to passive and active proton beams. Studies such as this are needed to ensure patient safety and make modifications in ABS delivery, if necessary.

Impact of total-body irradiation on the response to a live bacterial challenge.

PURPOSE: Concern regarding radiation effects on human health continues to increase worldwide. Given that infection is a major cause of morbidity and mortality after exposure, the aim of this study was to evaluate decrements in immune cell populations using a mammalian model subjected to a live bacterial infection. MATERIALS AND METHODS: C57BL/6 mice were exposed to total-body irradiation (TBI) with 3 Gy protons (70 cGy/min). One, 2, 4, 8 or 16 days later, subsets of mice were injected intraperitoneally with live Escherichia coli [055:K59(B5)]. Control groups received no radiation and vehicle (no bacteria). The mice were euthanized for analyses 90-120 min after injection of the bacteria. RESULTS: There were no unexpected effects of radiation or E. coli alone. Despite dramatic radiation-induced decreases in all leukocyte populations in both the blood and spleen, irradiated mice were still able to respond to an immune challenge based on capacity to generate an oxidative burst and secrete inflammatory cytokines, i.e., tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). However, these responses were generally elevated above control values. CONCLUSIONS: Together, these results suggest the possibility for enhanced inflammation-associated tissue injury and increased risk for chronic inflammation.

Minocycline modulates cytokine and gene expression profiles in the brain after whole-body exposure to radiation.

An effective countermeasure against radiation damage to normal tissues is urgently needed. The major goal of the present study was to determine if minocycline could modify the immunomodulatory effects of radiation on the brain. C57BL/6 mice were treated with minocycline intraperitoneally for 5 days beginning immediately before total-body exposure to 0, 1, 2 and 3 Gray (Gy) (60)Co γ-rays. Brains were collected on days 4 and 32 post-irradiation for cytokine and gene analyses. Minocycline treatment significantly increased the levels of interleukin (IL)-10, IL-15 and vascular endothelial growth factor (VEGF) in the brain on day 4 in one or more irradiated groups compared to radiation-alone (p<0.05). IL-10 is anti-inflammatory, IL-15 can prevent apoptosis and VEGF is nuroprotective. On day 32, the drug decreased IL-1ß in the 2- Gy group (p<0.05 vs. 2-Gy alone); this cytokine is implicated in immune-related central nervous system pathologies. Microarray analysis of brains on day 32 showed that while radiation increased expression of inflammatory genes such as Il1f10, Il17, Tnfrsf11b, Tnfsf12, Il12b and Il1f8, these were no longer up-regulated in the minocycline-treated groups. Similarly, the pro-apoptotic gene Bik and nitric oxide synthase producer (Nostrin) were no longer up-regulated in the drug-treated groups. Pathway analysis based on gene data suggested that catenin-ß1 and tumor suppressor-related transcription regulation were significantly activated by radiation and/or minocycline (activation z-score >2.0). Overall, the data warrant further testing of minocycline as a potential neuroprotectant against radiation-induced damage.

Low-dose radiation modifies skin response to acute gamma-rays and protons.

The goal of the present study was to obtain pilot data on the effects of protracted low-dose/low-dose-rate (LDR) γ-rays on the skin, both with and without acute gamma or proton irradiation (IR). Six groups of C57BL/6 mice were examined: a) 0 Gy control, b) LDR, c) Gamma, d) LDR+Gamma, e) Proton, and f) LDR+Proton. LDR radiation was delivered to a total dose of 0.01 Gy (0.03 cGy/h), whereas the Gamma and Proton groups received 2 Gy (0.9 Gy/min and 1.0 Gy/min, respectively). Assays were performed 56 days after exposure. Skin samples from all irradiated groups had activated caspase-3, indicative of apoptosis. The significant (p<0.05) increases in immunoreactivity in the Gamma and Proton groups were not present when LDR pre-exposure was included. However, the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay for DNA fragmentation and histological examination of hematoxylin and eosin-stained sections revealed no significant differences among groups, regardless of radiation regimen. The data demonstrate that caspase-3 activation initially triggered by both forms of acute radiation was greatly elevated in the skin nearly two months after whole-body exposure. In addition, LDR γ-ray priming ameliorated this response.

Correction: Changes in Mouse Thymus and Spleen after Return from the STS-135 Mission in Space.

[This corrects the article on p. e75097 in vol. 8.].