Viral infections have been associated with exacerbation of disease in human cases of idiopathic pulmonary fibrosis. Since pulmonary fibrosis is a common outcome after irradiation to the lung, we hypothesized that viral infection after radiation exposure would exacerbate radiation-induced lung injury. Epithelial injury, a frequent outcome after infection, has been hypothesized to contribute to the pathogenesis of pulmonary fibrosis and bronchiolar epithelial Clara cells participate in epithelial repair. Therefore, it was further hypothesized that altered responses after irradiation involve the bronchiolar epithelial Clara cells. C57BL/6J or CCSP^–/– mice were irradiated with 0 (sham), 5, 10 or 15 Gy to the whole thorax. At ten weeks post-irradiation, animals were mock infected or infected with influenza A virus and body weight and survival were monitored. Pulmonary function was assessed by whole-body plethysmography. The Clara cell markers, CCSP and Cyp2f2, were measured in the lung by qRT-PCR, and protein expression was visualized in the lung by immunofluorescence. Following pulmonary function tests, mice were sacrificed and tissues were collected for pathological analysis. In 15 Gy irradiated animals infected with influenza A virus, accelerated respiratory rates, reduced pulmonary function, and exacerbated lung pathology occurred earlier post-irradiation than previously observed after irradiation alone, suggesting infection accelerates the development of radiation injury. After irradiation alone, CCSP and Cyp2f2 mRNA levels were reduced, correlating with reductions in the number of Clara cells lining the airways. When combined with infection, these markers further declined and an apparent delay in recovery of mRNA expression was observed, suggesting that radiation injury leads to a chronic reduction in the number of Clara cells that may potentiate the epithelial injury observed after influenza A virus infection. This novel finding may have considerable therapeutic implications with respect to both thoracic tumor patients and recipients of bone marrow transplants.

Neurons are essential components of neural circuits and provide brain function organization. We previously reported that X irradiation induces apoptosis in immature neurons. To the best of our knowledge, there have been few reports investigating the effects of X irradiation on mature neurons. We analyzed the effects of X irradiation on the morphology, density and cytoskeletal proteins in dendritic spines on mature neurons. We prepared developing hippocampal neurons from 18 days embryo by using Banker's method. Neurons at 21 days in vitro were X irradiated at several doses and were immediately fixed. To evaluate the dendritic spine morphology and density, the neurons were transfected with a reporter plasmid for enhanced green fluorescent protein (GFP). Changes in the dendritic spines as a result of X irradiation were evaluated using electron microscopy. To analyze the cytoskeletal proteins within the dendritic spines, we performed immunocytochemistry to detect filamentous actin (F-actin), drebrin and PSD-95. X irradiation immediately changed the dendritic spine morphology, and the irradiated spines were significantly thinner and longer than the nonirradiated spines. X irradiation decreased the dendritic spine density in a dose-dependent manner. Electron microscopy confirmed these changes of dendritic spines by X irradiation. Immunohistochemical studies showed that X irradiation decreased the accumulation of drebrin and F-actin, but not PSD-95, within the dendritic spines. These results suggest that X irradiation immediately decreases the dendritic spine density and changes the morphology of mature neurons by reducing the abundance of cytoskeletal proteins. The abnormal dendritic spines may be associated with acute adverse effects after X irradiation in a clinical setting, although further investigations are warranted to validate these findings.

Tissue stem cells have self-renewal capability throughout their whole life, which is high enough to lead to the accumulation of DNA damage in a stem cell pool. Whether radiation-induced damage accumulates in tissue stem cells remains unknown, but could be investigated if the fate of tissue stem cells could be followed after irradiation. To realize this goal, we used an Lgr5-dependent lineage tracing system that allows the conditional in vivo labeling of Lgr5 intestinal stem cells and their progeny. We found that radiation induced loss of Lgr5 stem cells in the colon, but not in the duodenum. Interestingly, the loss of colonic Lgr5 cells was compensated by de novo production of Lgr5 cells, which increased after irradiation. These findings show that ionizing radiation effectively stimulates the turnover of colonic Lgr5 stem cells, implying that radiation-induced damage does not accumulate in the colonic Lgr5 stem cells by this mechanism.

Radiation-induced DNA damage initiates a series of overlapping responses that include DNA damage recognition and repair, induction of cell cycle checkpoints, senescence and/or apoptosis. This study assessed the DNA damage response and whole genome expression profile in two mammalian cell lines (HEK and U87) in response to (5-{4-methylpiperazin-1-yl}-2-[2′-(3,4-dimethoxyphenyl)-5′-benzimidazolyl] benzimidazole) DMA and ionizing radiation. DMA has been shown to act as a potent radiation protector, yielding significant levels of protection, i.e., 20.9% in HEK cells and 21.2% in U87 cells. Our findings revealed treatment with DMA significantly reduced γ-H2AX, 53BP1 and Rad51 foci formation after irradiation. MAP kinase, WNT signaling and p53 pathways were found to be activated in DMA-treated cells. In addition, the DNA damage response genes, HSP70, HSPD1, PRDX1, PRX, CALR, NPM, UBC, and SET showed differential regulation in DMA, DMA radiation and radiation-treated cells. The data suggest that DMA-influenced repertoire of repair proteins, which are an indispensable part of the cell, interplay with each other to reduce DNA damage and maintain the genomic integrity of the cell.

Information on early internal radiation doses in Fukushima after the nuclear power plant accident on March 11, 2011, is quite limited due to initial organizational difficulties, high background radiation and contamination of radiation measuring devices. In Nagasaki, approximately 1,200 km away from Fukushima, the internal radioactivity in evacuees and short-term visitors to Fukushima has been measured by a whole body counter (WBC) since March 15, 2011. A horizontal bed-type scanning WBC equipped with two NaI(Tl) scintillation detectors was used for 173 people who stayed in the Fukushima prefecture between March 11 and April 10, 2011. The average length of stay was 4.8 days. The internal radioactivity was converted to an estimated amount of intake according to the scenario of acute inhalation, and then the committed effective dose and the thyroid dose were evaluated. ¹³¹I, ¹³⁴Cs and ¹³⁷Cs were detected in more than 30% of examined individuals. In subjects who stayed in Fukushima from March 12 to March 18, the detection rate was approximately 50% higher for each radionuclide and 44% higher for all three nuclides. The maximum committed effective dose and thyroid equivalent dose were 1 mSv and 20 mSv, respectively. Although the number of subjects and settlements in the study are limited, the results suggest that the internal radiation exposure in Fukushima due to the intake of radioactive materials shortly after the accident will probably not result in any deterministic or stochastic health effects.

The aim of the present study is to determine the deoxyribonucleic acid (DNA) damage by cells exposed to atmospheric pressure non-thermal plasma (APNTP). Mouse leukocytes embedded in agarose were exposed to the plasma at two different distances from a helium plasma needle outlet and during three different exposure periods. Damage was assessed by the single cell gel electrophoresis assay. The results indicate that, at 0.1 cm from the plasma needle, the exposure caused complete DNA fragmentation determined by the presence of so called “clouds”. Samples exposed at 0.5 cm from the slide sample surface presented damage proportional to the exposure periods in terms of tail intensity, tail moment and “clouds” frequency. Studies performed with alkaline single cell gel electrophoresis assay to determine DNA breaks and alkali-labile sites, indicates that DNA damage produced by exposure to APNTP was caused mainly by oxidative radicals, rather than by UV light which causes cyclobutane pyrimidine dimers. These results allow us to conclude that plasma needle induced DNA breaks in mice leukocytes proportionally to exposure time.

Ataxia telangiectasia (AT) is a human genetic disease characterized by radiation sensitivity, impaired neuronal development and predisposition to cancer. Using a genetically defined model cell system consisting of cells expressing a kinase dead or a kinase proficient ATM gene product, we previously reported systemic alterations in major metabolic pathways that translate at the gene expression, protein and small molecule metabolite levels. Here, we report ionizing radiation induced stress response signaling arising from perturbations in the ATM gene, by employing a functional proteomics approach. Functional pathway analysis shows robust translational and post-translational responses under ATM proficient conditions, which include enrichment of proteins in the Ephrin receptor and axonal guidance signaling pathways. These molecular networks offer a hypothesis generating function for further investigations of cellular stress responses.

Even though serum iron is a commonly used parameter in iron metabolism, it has not yet been applied for biological dosimetry purpose. A new biological dosimeter based on serum iron has been developed in this work. Serum iron levels in mice subjected to gamma rays from a ⁶⁰Co source were detected with the use of ferrous. The doses are from 0.2–7 Gy with a dose rate of 0.2 Gy/min. The results demonstrate that serum iron level increases with increasing dose. The detection limit based on serum iron has a lower limit of dose detection of about 0.5 Gy and the maximal increase of serum iron observed is maintained 4 h after γ irradiation. Therefore the best suggested time for blood collection is within 4 h after γ irradiation. Two dose-response relationships were observed with both according to degrees of the increase of serum iron levels and different intervals after γ irradiation. The first is a linear relationship of y = 0.98x 6.76 (r = 0.98) obtained 10 min after γ irradiation; the second is the linear quadratic relationship of y = −0.07x² 1.02x 6.45 (r = 0.99) obtained 7 days after γ irradiation. The absorbed doses of mice estimated with the use of both these two dose-response relationships were close to the actual dose of 1 Gy. It is concluded that serum iron is a quick, simple and sensitive biomarker for early assessment of the absorbed dose of mice.

The number of small radiation-induced DNA fragments can be heavily underestimated when determined from measurements of DNA mass fractions by gel electrophoresis, leading to a consequent underestimation of the initial DNA damage induction. In this study we reanalyzed the experimental results for DNA fragmentation and DNA double-strand break (DSB) yields in human fibroblasts irradiated with γ rays and nitrogen ion beams with linear energy transfer (LET) equal to 80, 125, 175 and 225 keV/μm, originally measured by Höglund et al. (Radiat Res 155, 818–825, 2001 and Int J Radiat Biol 76, 539–547, 2000). In that study the authors converted the measured distributions of fragment masses into DNA fragment distributions using mid-range values of the measured fragment length intervals, in particular they assumed fragments with lengths in the interval of 0–48 kbp had the mid-range value of 24 kbp. However, our recent detailed simulations with the Monte Carlo code PARTRAC, while reasonably in agreement with the mass distributions, indicate significantly increased yields of very short fragments by high-LET radiation, so that the actual average fragment lengths, in the interval 0–48 kbp, 2.4 kbp for 225 keV/μm nitrogen ions were much shorter than the assumed mid-range value of 24 kbp. When the measured distributions of fragment masses are converted into fragment distributions using the average fragment lengths calculated by PARTRAC, significantly higher yields of DSB related to short fragments were obtained and resulted in a constant relative biological effectiveness (RBE) for DSB induction yield of 2.3 for nitrogen ions at 125–225 keV/μm LET. The previously reported downward trend of the RBE values over this LET range for DSB induction appears to be an artifact of an inadequate average fragment length in the smallest interval.

We used sequentially transformed mesenchymal stem cells to investigate how the events that lead to tumorigenicity influence the cellular response to radiation. Bone marrow derived SH2 , SH4 , Stro-1 mesenchymal stem cells (MSC) were transformed stepwise by retroviral transfection of hTERT, HPV-16 E6 and E7, SV40 small T antigen and oncogenic H-ras. Cells at three different stages of transformation were irradiated and compared using assays for cytotoxicity, apoptosis, DNA double-strand break (DSB) repair and checkpoint signaling. The effects of inhibition of cell cycle checkpoint signaling on radiosensitivity were investigated using RNA interference. During stepwise transformation, specifically after HPV-16 E6 and E7 transduction, MSCs became more sensitive to radiation. This was associated with increased residual DNA DSB at 24 h and increased apoptosis. Enhanced checkpoint signaling occurred during transformation and there was a differential effect of checkpoint targeting in cells at different stages; Chk1 knockdown enhanced radiosensitivity in all cells while Chk2 knockdown only affected non-transformed cells. These data show that transformation of MSC is associated with a reduction in DNA DSB repair capacity and increased radiosensitivity. Up-regulation of checkpoint signaling does not overcome this and the effect of checkpoint inhibition may change with transformation status.

The bioeffects of exposure to Wireless High-Fidelity (WiFi) signals on the developing nervous systems of young rodents was investigated by assessing the in vivo and in situ expression levels of three stress markers: 3-Nitrotyrosine (3-NT), an oxidative stress marker and two heat-shock proteins (Hsp25 and Hsp70). These biomarkers were measured in the brains of young rats exposed to a 2450 MHz WiFi signal by immunohistochemistry. Pregnant rats were first exposed or sham exposed to WiFi from day 6 to day 21 of gestation. In addition three newborns per litter were further exposed up to 5 weeks old. Daily 2-h exposures were performed blind in a reverberation chamber and whole-body specific absorption rate levels were 0, 0.08, 0.4 and 4 W/kg. 3-NT and stress protein expression was assayed in different areas of the hippocampus and cortex. No significant difference was observed among exposed and sham-exposed groups. These results suggest that repeated exposure to WiFi during gestation and early life has no deleterious effects on the brains of young rats.

While lifespan studies provide basic information for estimating the risk of ionizing radiation, findings on the effect of low-dose/low-dose-rate irradiation on the lifespan of mammals are controversial. Here we evaluate the effect of continuous exposure to low-dose-rate γ radiation on the lifespan of mice with accelerated aging caused by mutation of the klotho gene. While control mice died within 80 days after birth, more than 10% of mice exposed continuously to 0.35 or 0.7 or mGy/h γ radiation from 40 days after birth survived for more than 80 days. Two of 50 mice survived for more than 100 days. Low-dose-rate irradiation significantly increased plasma calcium concentration in mutant mice, and concomitantly increased hepatic catalase activity. Although hepatic activity of superoxide dismutase in mutant mice decreased significantly compared to wild-type mice, continuous γ irradiation decreased the activity in mutant mice significantly. These results suggest that low-dose-rate ionizing radiation can prolong the lifespan of mice in certain settings.

Radiation simultaneously activate Fas and JNK pathway in lymphocytes but their precise interaction is not clearly understood. Activation of Fas pathway is required for radiation induced apoptosis, however induction of JNK pathway may or may not contribute in apoptosis. Here we report that Fas, Fas associated death domain and total JNK are activated in a dose- and time-dependent radiation exposure. A biphasic pattern of phospho-JNK was found at lower doses (1 and 2 Gy), however at higher doses of radiation phospho-JNK was continuously activated. Interestingly, Fas ligand expression remained biphasic at all the doses of radiation. Our results suggest that the Fas pathway is the major player in radiation-induced apoptosis, with JNK playing a contributory role. We also observed that Fas ligand expression by radiation is dependent on JNK activation. We also propose that radiation activates JNK pathway, but sustained activation is required for maximal induction of apoptosis at later times. Our findings define a mechanism for crosstalk between JNK and Fas pathway in radiation-induced apoptosis, which may lead to the development of new therapeutic strategies.