Aurora-A, a serine/threonine kinase that is overexpressed in certain human cancer cell lines, plays an important role in mitotic progression. Aurora-A has also been reported to be involved in the activation of nuclear factor kappa B (NF-κ;B). The purpose of the present study was to identify the role of Aurora-A in the radiation-induced activation pathway of NF-κ;B. Wild-type and Aurora-A knockdown (Aurora-A^KD) HeLa cells were irradiated with 4 Gy of γ rays and the EMSA, luciferase reporter gene assay and immunoblot analysis were performed. The siRNA-based gene knockdown and overexpression system was adopted to elucidate the role of Aurora-A in radiation-induced NF-κ;B pathway activation. The clonogenic survival study indicated that Aurora-A^KD cells and the wild-type cells transfected with Aurora-A siRNA or RelA/p65 siRNA were more radiosensitive than the wild-type cells. In both the wild-type and Aurora-A^KD cells, radiation caused Iκ;B kinase-mediated phosphorylation, degradation of Iκ;Bα and phosphorylation of RelA/p65. The nuclear translocation of RelA/p65 was also similar in the wild-type and Aurora-A^KD cells. However, RelA/p65-DNA binding was markedly suppressed in Aurora-A^KD cells compared to that in wild-type cells. It was concluded that Aurora-A enhances the binding of NF-κ;B to DNA, thereby increasing the gene transcription by NF-κ;B and decreasing the radiosensitivity of the cells.

Previous work showed that in human nuclear extracts, double-strand break substrates bearing partially complementary (-ACG) 3′-phosphoglycolate (PG)-terminated 3′ overhangs are joined by a mechanism involving annealing of the terminal CG dinucleotides, PG removal, single-base gap filling and ligation. However, in these extracts only a minority of the breaks are rejoined, and most of the 3′-PG termini remain intact even after several hours. To determine whether the presence of a persistent 3′-PG prevents patching and ligation of the opposite strand, a substrate was constructed with two -ACG overhangs, one PG-terminated and one hydroxyl-terminated. after incubation in HeLa cell nuclear extracts, two major repair products of similar yield were formed: a fully repaired duplex and a nicked duplex in which the initial 3′-PG terminus remained intact. These results indicate that patching and ligation can proceed to completion in the unmodified strand despite persistence of the 3′-PG-terminated break in the opposite strand. The break in the PG-containing strand could then presumably be rejoined by a single-strand break repair pathway.

Cell-to-cell signaling has become a significant issue in radiation biology due to experimental evidence, accumulated primarily since the early 1990s, of radiation-induced bystander effects. Several candidate mediators involved in cell-to-cell communication have been investigated and proposed as being responsible for this phenomenon, but the current investigation techniques (both theoretical and experimental) of the mechanisms involved, due to the particular set-up of each experiment, result in experimental data that often are not directly comparable. In this study, a comprehensive approach was adopted to describe cell-to-cell communication (focusing on cytokine signaling) and its modulation by external agents such as ionizing radiation. The aim was also to provide integrated theoretical instruments and experimental data to help in understanding the peculiarities of in vitro experiments. Theoretical/modeling activities were integrated with experimental measurements by (1) redesigning a cybernetic model (proposed in its original form in the 1950s) to frame cell-to-cell communication processes, (2) implementing and developing a mathematical model, and (3) designing and carrying out experiments to quantify key parameters involved in intercellular signaling (focusing as a pilot study on the release and decay of IL-6 molecules and their modulation by radiation). This formalization provides an interpretative framework for understanding the intercellular signaling and in particular for focusing on the study of cell-to-cell communication in a “step-by-step” approach. Under this model, the complex phenomenon of signal transmission was reduced where possible into independent processes to investigate them separately, providing an evaluation of the role of cell communication to guarantee and maintain the robustness of the in vitro experimental systems against the effects of perturbations.

Trypanothione is a unique diglutathionyl-spermidine conjugate found in abundance in trypanosomes but not in other eukaryotes. Because trypanothione is a naturally occurring polyamine thiol reminiscent of the synthetic drug amifostine, it may be a useful protector against radiation and oxidative stress. For these reasons we hypothesized that trypanothione might serve as a radioprotective agent when produced in bacteria. To accomplish this objective, the trypanothione synthetase and reductase genes from T. cruzi were introduced into E. coli and their expression was verified by qPCR and immunoblotting. Trypanothione synthesis in bacteria, detected by HPLC, resulted in decreased intracellular levels of reactive oxygen species as determined by H₂DCFDA oxidation. Moreover, E. coli genomic DNA was protected from radiation-induced DNA damage by 4.6-fold in the presence of trypanothione compared to control bacteria. Concordantly, the transgenic E. coli expressing trypanothione were 4.3-fold more resistant to killing by ¹³⁷Cs γ radiation compared to E. coli devoid of trypanothione expression. Thus we have shown for the first time that E. coli can be genetically engineered to express the trypanothione biosynthetic pathway and produce trypanothione, which results in their radioresistance. These results warrant further research to explore the possibility of developing trypanothione as a novel radioprotective agent.

The effect of deletion of the nitric oxide synthase 1 gene (NOS1^−/−) on radiosensitivity was determined. In vitro, long-term cultures of bone marrow stromal cells derived from NOS1^−/− were more radioresistant than cells from C57BL/6NHsd (wild-type), NOS2^−/− or NOS3^−/− mice. Mice from each strain received 20 Gy thoracic irradiation or 9.5 Gy total-body irradiation (TBI), and NOS1^−/− mice were more sensitive to both. To determine the etiology of radiosensitivity, studies of histopathology, lower esophageal contractility, gastrointestinal transit, blood counts, electrolytes and inflammatory markers were performed; no significant differences between irradiated NOS1^−/− and control mice were found. Video camera surveillance revealed the cause of death in NOS1^−/− mice to be grand mal seizures; control mice died with fatigue and listlessness associated with low blood counts after TBI. NOS1^−/− mice were not sensitive to brain-only irradiation. MnSOD-PL therapy delivered to the esophagus of wild-type and NOS1^−/− mice resulted in equivalent biochemical levels in both; however, in NOS1^−/− mice, MnSOD-PL significantly increased survival after both thoracic and total-body irradiation. The mechanism of radiosensitivity of NOS1^−/− mice and its reversal by MnSOD-PL may be related to the developmental esophageal enteric neuronal innervation abnormalities described in these mice.

We recently reported that repeated 0.5-Gy γ irradiation attenuates the pathology of collagen-induced arthritis. In this study, to investigate the mechanism further, we focused on changes in Treg/Th17 cells and changes in the production of antibody against an external antigen in response to γ irradiation as well as on the radiosensitivity of Treg cells. DBA/1J mice were immunized with type II collagen to induce arthritis and exposed to low-dose γ rays (0.5 Gy/week for 5 weeks). Production of IL6 and IL17 as well as autoantibody was suppressed by irradiation in the early phase of collagen-induced arthritis. The percentage of Treg cells was significantly increased by irradiation at 4, 6 and 8 weeks after the immunization. We also investigated the effect of repeated γ radiation on the production of antibodies against an external antigen in ovalbumin-immunized BALB/c mice. We found that repeated 0.5-Gy γ irradiation enhanced antibody production, accompanied by an increase of the antibody-producing plasma cell population and increased Th2-type cytokine secretion. We also found that the radiosensitivity of Treg cells did not differ from that of other T cells. These results suggest that a major mechanism of attenuation of the pathology of collagen-induced arthritis by repeated 0.5-Gy γ irradiation is up-regulation of Treg cells concomitantly with suppression of IL6 and IL17 production.

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.

Photodynamic therapy (PDT) with low light fluence rate has rarely been studied in protocols that use short drug–light intervals and thus deliver illumination while plasma concentrations of photosensitizer are high, creating a prominent vascular response. In this study, the effects of light fluence rate on PDT response were investigated using motexafin lutetium (10 mg/kg) in combination with 730 nm light and a 180-min drug–light interval. At 180 min, the plasma level of photosensitizer was 5.7 ng/μl compared to 3.1 ng/mg in RIF tumor, and PDT-mediated vascular effects were confirmed by a spasmodic decrease in blood flow during illumination. Light delivery at 25 mW/cm² significantly improved long-term tumor responses over that at 75 mW/cm². This effect could not be attributed to oxygen conservation at low fluence rate, because 25 mW/cm² PDT provided little benefit to tumor hemoglobin oxygen saturation. However, 25 mW/cm² PDT did prolong the duration of ischemic insult during illumination and was correspondingly associated with greater decreases in perfusion immediately after PDT, followed by smaller increases in total hemoglobin concentration in the hours after PDT. Increases in blood volume suggest blood pooling from suboptimal vascular damage; thus the smaller increases after 25 mW/cm² PDT provide evidence of more widespread vascular damage, which was accompanied by greater decreases in clonogenic survival. Further study of low fluence rate as a means to improve responses to PDT under conditions designed to predominantly damage vasculature is warranted.

To evaluate the effect of low-dose-rate radiation on cancer incidence, we housed AKR/J mice in a long-term low-dose-rate irradiation facility (¹³⁷Cs, 0.07 cGy/h). We compared the thymic lymphoma incidence and life span with those of mice irradiated at a high dose rate (¹³⁷Cs, 0.8 Gy/min, total dose of 4.5 Gy) and nonirradiated mice. The average life span of the low-dose-rate irradiated mice (243 days) was longer than those of the high-dose-rate irradiated mice (208 days) and nonirradiated mice (230 days) (P  =  0.02). The incidence of thymic lymphoma in low-dose-rate irradiated mice was lower than that in nonirradiated mice and high-dose-rate irradiated mice by 10 and 20%, respectively (P < 0.01). Normal-sized thymuses were collected 130 days after irradiation, and whole genome microarray analysis was performed. A total of 17,625 genes were assessed. Up- and down-regulated genes in low-dose-rate irradiated mice were 1.7 and 9 times less frequent than in high-dose-rate irradiated mice. We profiled expressed genes associated with carcinogenesis pathways (DNA repair, DNA damage signaling pathway, cell cycle, cancer pathway finder, p53 signaling pathway, apoptosis and T-cell and B-cell activation). Apoptosis- (Cd5l, Fcgr3 and Pycard) and immune- (Pycard, Lilrb3, Igh-6, Fcgr2b and MGC60843) related genes were commonly activated in both high- and low-dose-rate irradiated mice. The results suggest that carcinogenic cells have been removed by activated apoptosis and immune mechanisms, contributing to decreased thymic lymphoma and elongated life span. Functional studies for expressed genes associated with thymic lymphoma incidence in low-dose-rate exposed mice are currently under way.

The aim of this cross-sectional study was to investigate the association between exposure to various sources of radiofrequency electromagnetic fields (RF EMFs) in the everyday environment and sleep quality, which is a common public health concern. We assessed self-reported sleep disturbances and daytime sleepiness in a random population sample of 1,375 inhabitants from the area of Basel, Switzerland. Exposure to environmental far-field RF EMFs was predicted for each individual using a prediction model that had been developed and validated previously. Self-reported cordless and mobile phone use as well as objective mobile phone operator data for the previous 6 months were also considered in the analyses. In multivariable regression models, adjusted for relevant confounders, no associations between environmental far-field RF EMF exposure and sleep disturbances or excessive daytime sleepiness were observed. The 10% most exposed participants had an estimated risk for sleep disturbances of 1.11 (95% CI: 0.50 to 2.44) and for excessive daytime sleepiness of 0.58 (95% CI: 0.31 to 1.05). Neither mobile phone use nor cordless phone use was associated with decreased sleep quality. The results of this large cross-sectional study did not indicate an impairment of subjective sleep quality due to exposure from various sources of RF EMFs in everyday life

Studies of radiation carcinogenesis in animals allow detailed investigation of how the risk depends on age at exposure and time since exposure and of the mechanisms that determine this risk, e.g., induction of new pre-malignant cells (initiation) and enhanced proliferation of already existing pre-malignant cells (promotion). To assist the interpretation of these patterns, we apply a newly developed biologically based mathematical model to data on several types of solid tumors induced by acute whole-body radiation in mice. The model includes both initiation and promotion and analyzes pre-malignant cell dynamics on two different time scales: comparatively short-term during irradiation and long-term during the entire life span. Our results suggest general mechanistic similarities between radiation carcinogenesis in mice and in human atomic bomb survivors. The excess relative risk (ERR) in mice decreases with age at exposure up to an exposure age of 1 year, which corresponds to mid-adulthood in humans; the pattern for older ages at exposure, for which there is some evidence of increasing ERRs in atomic bomb survivors, cannot be evaluated using the data set analyzed here. Also similar to findings in humans, initiation dominates the ERR at young ages in mice, when there are few background pre-malignant cells, and promotion becomes important at older ages.

Mammography screening is an accepted procedure for early detection of breast tumors among asymptomatic women. Since this procedure involves the use of X rays, it is itself potentially carcinogenic. Although there is general consensus about the benefit of screening for older women, screening practices differ between countries. In this paper radiation risks for these different practices are estimated using a new approach. We model breast cancer induction by ionizing radiation in a cohort of patients exposed to frequent X-ray examinations. The biologically based, mechanistic model provides a better foundation for the extrapolation of risks to different mammography screening practices than empirical models do. The model predicts that the excess relative risk (ERR) doubles when screening starts at age 40 instead of 50 and that a continuation of screening at ages 75 and higher carries little extra risk. The number of induced fatal breast cancers is estimated to be considerably lower than derived from epidemiological studies and from internationally accepted radiation protection risks. The present findings, if used in a risk-benefit analysis for mammography screening, would be more favorable to screening than estimates currently recommended for radiation protection. This has implications for the screening ages that are currently being reconsidered in several countries.

The “Spiess study” follows the health of 899 persons who received multiple injections of the short-lived α-particle emitter ²²⁴Ra mainly between 1945 and 1955 for the treatment of tuberculosis, ankylosing spondylitis and some other diseases. In December 2007, 124 persons were still alive. The most striking health effect, observed shortly after ²²⁴Ra injections, was a temporal wave of 57 malignant bone tumors. During the two most recent decades of observation, a significant excess of non-skeletal malignant diseases has become evident. Expected numbers of cases were computed from the age, gender and calendar year distribution of person years at risk and incidence rates from the German Saarland Cancer Registry. Poisson statistics were applied to test for statistical significance of the standardized incidence ratios. Up to the end of December 2007, the total number of observed malignant non-skeletal diseases was 270 (248 specified cases of non-skeletal solid cancers and 22 other malignant diseases, among these 16 malignant neoplasms of lymphatic and hematopoietic tissue, six without specification of site) compared to 192 expected cases. Accounting for a 5-year minimum latent period and excluding 13 cases of non-melanoma skin cancer, 231 non-skeletal solid cancers were observed compared to 151 expected cases. Significantly increased cancer rates were observed for breast (32 compared to 9.7), soft and connective tissue (11 compared to 1.0), thyroid (7 compared to 1.0), liver (10 compared to 2.4), kidney (13 compared to 5.0), pancreas (9 compared to 4.1), bladder (16 compared to 8.0), and female genital organs (15 compared to 7.8).

The etiology of childhood leukemia remains generally unknown, although risk models based on the Japanese A-bomb survivors imply that the dose accumulated from protracted exposure to low-level natural background ionizing radiation materially raises the risk of leukemia in children. In this paper a novel Monte Carlo score-test methodology is used to assess the statistical power of cohort, ecological and case-control study designs, using the linear low-dose part of the BEIR V model derived from the Japanese data. With 10 (or 20) years of follow-up of childhood leukemias in Great Britain, giving about 4600 (or 9200) cases, under an individual-based cohort design there is 67.9% (or 90.9%) chance of detecting an excess (at 5% significance level, one-sided test); little difference is made by extreme heterogeneity in risk. For an ecological design these figures reduce to 57.9% (or 83.2%). Case-control studies with five controls per case achieve much of the power of a cohort design, 61.1% (or 86.0%). However, participation bias may seriously affect studies that require individual consent, and area-based studies are subject to severe interpretational problems. For this reason register-based studies, in particular those that make use of predicted doses that avoid the need for interviews, have considerable advantages. We argue that previous studies have been underpowered (all have power <80%), and some are also subject to unquantifiable biases and confounding. Sufficiently large studies should be capable of detecting the predicted risk attributable to natural background radiation.