Proton therapy induces a local microglial neuroimmune response.

BACKGROUND AND PURPOSE: Although proton therapy is increasingly being used in the treatment of paediatric and adult brain tumours, there are still uncertainties surrounding the biological effect of protons on the normal brain. Microglia, the brain-resident macrophages, have been shown to play a role in the development of radiation-induced neurotoxicity. However, their molecular and hence functional response to proton irradiation remains unknown. This study investigates the effect of protons on microglia by comparing the effect of photons and protons as well as the influence of age and different irradiated volumes. MATERIALS AND METHODS: Rats were irradiated with 14 Gy to the whole brain with photons (X-rays), plateau protons, spread-out Bragg peak (SOBP) protons or to 50 % anterior, or 50 % posterior brain sub-volumes with plateau protons. RNA sequencing, validation of microglial priming gene expression using qPCR and high-content imaging analysis of microglial morphology were performed in the cortex at 12 weeks post irradiation. RESULTS: Photons and plateau protons induced a shared transcriptomic response associated with neuroinflammation. This response was associated with a similar microglial priming gene expression signature and distribution of microglial morphologies. Expression of the priming gene signature was less pronounced in juvenile rats compared to adults and slightly increased in rats irradiated with SOBP protons. High-precision partial brain irradiation with protons induced a local microglial priming response and morphological changes. CONCLUSION: Overall, our data indicate that the brain responds in a similar manner to photons and plateau protons with a shared local upregulation of microglial priming-associated genes, potentially enhancing the immune response to subsequent inflammatory challenges.

Shape of radiation dose response relationship for ischaemic heart disease mortality and its interpretation: analysis of the national registry for radiation workers (NRRW) cohort.

Statistically significant increases in ischemic heart disease (IHD) mortality with cumulative occupational external radiation dose were observed in the National Registry for Radiation Workers (NRRW) cohort. There were 174 541 subjects in the NRRW cohort. The start of follow up was 1955, and the end of the follow-up for each worker was chosen as the earliest date of death or emigration, their 85th birthday or 31 December 2011. The dose-response relationship showed a downward curvature at a higher dose level >0.4 Sv with the overall shape of the dose-response relationship best described by a linear-quadratic model. The smaller risk at dose >0.4 Sv appears to be primarily associated with workers who started employment at a younger age (<30 years old) and those who were employed for more than 30 years. We modelled the dose response by age-at-first exposure. For the age-at-first exposure of 30+ years old, a linear dose-response was the best fit. For age-at-first exposure <30 years old, there was no evidence of excess risk of IHD mortality for radiation doses below 0.1 Sv or above 0.4 Sv, excess risk was only observed for doses between 0.1-0.4 Sv. For this age-at-first exposure group, it was also found that the doses they received when they were less than 35 years old or greater than 50 years old did not contribute to any increased IHD risk.

Radiation exposure lymphocyte damage assessed by γ-H2AX level using flow cytometry.

DNA double-strand breaks (DSBs) are considered the most relevant lesions to the DNA damage of ionizing radiation (IR), and γ-H2AX foci in peripheral blood lymphocytes are regarded as an adequate marker for DSB quantitative studies. This study aimed to investigate IR-induced DNA damage in mice through γ-H2AX fluorescence analyses by flow cytometry (FCM). The levels of γ-H2AX in CD4/CD8/B220-positive lymphocytes were quantified by FCM through mean fluorescence intensity (MFI) values. Peripheral venous blood samples were collected for evaluation, and all the control groups were restrained from irradiation. For external irradiation experiments, the dose-dependency of MFI values and temporal alternations were assessed both in vitro and in vivo. External radiation exposure damage was positively correlated with the absorbed radiation dose, and the lymphocyte recovered from damage within 3 days. I-131 sodium iodide solution (74 MBq) was injected into the mice intraperitoneally for internal irradiation experiments. Gamma counting and γH2AX foci analyses were performed at 1 h and 24 h by the group. The blood-to-blood S values (Sblood←blood) were applied for the blood-absorbed dose estimation. Internal low-dose-irradiation-induced damage was proved to recover within 24 h. The FCM method was found to be an effective way of quantitatively assessing IR-induced DNA damage.

Interplay of immune modulation, adaptive response and hormesis: Suggestive of threshold for clinical manifestation of effects of ionizing radiation at low doses?

The health impacts of low-dose ionizing radiation exposures have been a subject of debate over the last three to four decades. While there has been enough evidence of "no adverse observable" health effects at low doses and low dose rates, the hypothesis of "Linear No Threshold" continues to rule and govern the principles of radiation protection and the formulation of regulations and public policies. In adopting this conservative approach, the role of the biological processes underway in the human body is kept at abeyance. This review consolidates the available studies that discuss all related biological pathways and repair mechanisms that inhibit the progression of deleterious effects at low doses and low dose rates of ionizing radiation. It is pertinent that, taking cognizance of these processes, there is a need to have a relook at policies of radiation protection, which as of now are too stringent, leading to undue economic losses and negative public perception about radiation.

CXCL10 upregulation in radiation-exposed human peripheral blood mononuclear cells as a candidate biomarker for rapid triage after radiation exposure.

PURPOSE: In case of a nuclear accident, individuals with high-dose radiation exposure (>1-2 Gy) should be rapidly identified. While ferredoxin reductase (FDXR) was recently suggested as a radiation-responsive gene, the use of a single gene biomarker limits radiation dose assessment. To overcome this limitation, we sought to identify reliable radiation-responsive gene biomarkers. MATERIALS AND METHODS: Peripheral blood mononuclear cells (PBMCs) were isolated from mice after total body irradiation, and gene expression was analyzed using a microarray approach to identify radiation-responsive genes. RESULTS: In light of the essential role of the immune response following radiation exposure, we selected several immune-related candidate genes upregulated by radiation exposure in both mouse and human PBMCs. In particular, the expression of ACOD1 and CXCL10 increased in a radiation dose-dependent manner, while remaining unchanged following lipopolysaccharide (LPS) stimulation in human PBMCs. The expression of both genes was further evaluated in the blood of cancer patients before and after radiotherapy. CXCL10 expression exhibited a distinct increase after radiotherapy and was positively correlated with FDXR expression. CONCLUSIONS: CXCL10 expression in irradiated PBMCs represents a potential biomarker for radiation exposure.

Phenotypic and transcriptional changes in lens epithelial cells following acute and fractionated ionizing radiation exposure.

PURPOSE: Exposure to ionizing radiation is one of the known risk factors for the development of lens opacities. It is believed that radiation interactions with lens epithelial cells (LEC) are the underlying cause of cataract development, however, the exact mechanisms have yet to be identified. The aim of this study was to investigate how different radiation dose and fractionation impact normal LEC function. MATERIALS AND METHODS: A human derived LEC cell line (HLE-B3) was exposed to a single acute x-ray dose (0.25 Gy) and 6 fractionated doses (total dose of 0.05, 0.1, 0.25, 0.5, 1, and 2 Gy divided over 5 equal fractions). LEC were examined for proliferation using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and migration using a Boyden chamber assay at various time points (0.25, 0.5, 1, 2, 4, 7, 9, 11, and 14 d) post-irradiation. Transcriptomic analysis through RNA sequencing was also performed to identify differentially expressed genes and regulatory networks in cells following 4 different acute exposures and 1 fractionated exposure. RESULTS: Exposure to an acute dose of 0.25 Gy significantly increased proliferation and migration rates, peaking at 7 d post irradiation (20% and 240% greater than controls, respectively), before returning to baseline levels by day 14. Fractionated exposures had minimal effects up to a dose of 0.5 Gy, but significantly reduced proliferation and migration after 1 and 2 Gy by up to 50%. The largest transcriptional response occurred 12 h after an acute 0.25 Gy dose, with 362 genes up-regulated and 288 genes down-regulated. A unique panel of differentially expressed genes was observed between moderate versus high dose exposures, suggesting a dose-dependent transcriptional response in LEC that is more pronounced at lower doses. Gene ontology and upstream regulator analysis identified multiple biological processes and molecular functions implicated in the radiation response, in particular differentiation, motility, receptor/ligand binding, cell signaling and epithelial-mesenchymal cell transition. CONCLUSIONS: Overall, this research provides novel insights into the dose and fractionation effects on functional changes and transcriptional regulatory networks in LEC, furthering our understanding of the mechanisms behind radiation induced cataracts.

Radiation cataract in Heterogeneous Stock mice after γ-ray or HZE ion exposure.

Health effects of space radiation are a serious concern for astronauts on long-duration missions. The lens of the eye is one of the most radiosensitive tissues in the body and, therefore, ocular health risks for astronauts is a significant concern. Studies in humans and animals indicate that ionizing radiation exposure to the eye produces characteristic lens changes, termed "radiation cataract," that can affect visual function. Animal models of radiation cataractogenesis have previously utilized inbred mouse or rat strains. These studies were essential for determining morphological changes and dose-response relationships between radiation exposure and cataract. However, the relevance of these studies to human radiosensitivity is limited by the narrow phenotypic range of genetically homogeneous animal models. To model radiation cataract in genetically diverse populations, longitudinal cataract phenotyping was nested within a lifetime carcinogenesis study in male and female heterogeneous stock (HS/Npt) mice exposed to 0.4 Gy HZE ions (n = 609) or 3.0 Gy γ-rays (n = 602) and in unirradiated controls (n = 603). Cataractous change was quantified in each eye for up to 2 years using Merriam-Focht grading criteria by dilated slit lamp examination. Virtual Optomotry™ measurement of visual acuity and contrast sensitivity was utilized to assess visual function in a subgroup of mice. Prevalence and severity of posterior lens opacifications were 2.6-fold higher in HZE ion and 2.3-fold higher in γ-ray irradiated mice compared to unirradiated controls. Male mice were at greater risk for spontaneous and radiation associated cataracts. Risk for cataractogenesis was associated with family structure, demonstrating that HS/Npt mice are well-suited to evaluate genetic determinants of ocular radiosensitivity. Last, mice were extensively evaluated for cataract and tumor formation, which revealed an overlap between individual susceptibility to both cancer and cataract.

Acute Large Dose Irradiation Sensitizes Surviving Cells to Subsequent Irradiation; Implications for Stereotactic Body Radiation Therapy.

To determine if the radiation sensitivity of cells that survive acute high-dose radiation exposure used in stereotactic body radiation therapy (SBRT), differs from the sensitivity of non-irradiated cells and cells that survive multiple 2 Gy doses of radiation. Isogenic rodent and two human tumor cell lines were exposed to 14 × 2 Gy of radiation, or a single acute dose of 12 Gy. The most resistant cell line was also exposed to an acute dose of 15 Gy. One week after 12 Gy, and 4 days after 14 × 2 Gy, surviving cells were exposed to 0-8 Gy in 2 Gy doses and cell survival was assessed by colony formation. In addition, the colony forming efficiency of 12 Gy survivors was evaluated for 1 month postirradiation. For cells exposed to 15 Gy, the response of surviving cells to 6 Gy was determined for up to 35 days postirradiation and compared to the 6 Gy surviving fraction of control cells. The radiation sensitivity of cells that survived 12 Gy exposure, and cells that survived 14 fractions of 2 Gy irradiation did not differ from the response of unirradiated control cells. However, the growth rate and colony forming efficiency of 12 Gy survivors was transiently reduced for greater than 2 weeks postirradiation. In contrast to the unchanged sensitivity of 12 Gy surviving cells at day 7 postirradiation, 15 Gy survivors exhibited enhanced sensitivity to radiation for up to 21 days postirradiation and suggests a biological basis for SBRT.

Enhanced RBE of Particle Radiation Depends on Beam Size in the Micrometer Range.

High-linear energy transfer (LET) radiation, such as heavy ions is associated with a higher relative biological effectiveness (RBE) than low-LET radiation, such as photons. Irradiation with low- and high-LET particles differ in the interaction with the cellular matter and therefore in the spatial dose distribution. When a single high-LET particle interacts with matter, it results in doses of up to thousands of gray (Gy) locally concentrated around the ion trajectory, whereas the mean dose averaged over the target, such as a cell nucleus is only in the range of a Gy. DNA damage therefore accumulates in this small volume. In contrast, up to hundreds of low-LET particle hits are required to achieve the same mean dose, resulting in a quasi-homogeneous damage distribution throughout the cell nucleus. In this study, we investigated the dependence of RBE from different spatial dose depositions using different focused beam spot sizes of proton radiation with respect to the induction of chromosome aberrations and clonogenic cell survival. Human-hamster hybrid (AL) as well as Chinese hamster ovary cells (CHO-K1) were irradiated with focused low LET protons of 20 MeV (LET = 2.6 keV/µm) beam energy with a mean dose of 1.7 Gy in a quadratic matrix pattern with point spacing of 5.4 × 5.4 µm2 and 117 protons per matrix point at the ion microbeam SNAKE using different beam spot sizes between 0.8 µm and 2.8 µm (full width at half maximum). The dose-response curves of X-ray reference radiation were used to determine the RBE after a 1.7 Gy dose of radiation. The RBE for the induction of dicentric chromosomes and cell inactivation was increased after irradiation with the smallest beam spot diameter (0.8 µm for chromosome aberration experiments and 1.0 µm for cell survival experiments) compared to homogeneous proton radiation but was still below the RBE of a corresponding high LET single ion hit. By increasing the spot size to 1.6-1.8 µm, the RBE decreased but was still higher than for homogeneously distributed protons. By further increasing the spot size to 2.7-2.8 µm, the RBE was no longer different from the homogeneous radiation. Our experiments demonstrate that varying spot size of low-LET radiation gradually modifies the RBE. This underlines that a substantial fraction of enhanced RBE originates from inhomogeneous energy concentrations on the µm scale (mean intertrack distances of low-LET particles below 0.1 µm) and quantifies the link between such energy concentration and RBE. The missing fraction of RBE enhancement when comparing with high-LET ions is attributed to the high inner track energy deposition on the nanometer scale. The results are compared with model results of PARTRAC and LEM for chromosomal aberration and cell survival, respectively, which suggest mechanistic interpretations of the observed radiation effects.

Optimizing chemical-induced premature chromosome condensation assay for rapid estimation of high-radiation doses.

In the event of exposure to high doses of radiation, prompt dose estimation is crucial for selecting appropriate treatment modalities, such as cytokine therapy or stem cell transplantation. The chemical-induced premature chromosome condensation (PCC) method offers a simple approach for such dose estimation with significant radiation exposure, but its 48-h incubation time poses challenges for early dose assessment. In this study, we optimized the chemical-induced PCC assay for more rapid dose assessment. A sufficient number of PCC and G2/M-PCC cells were obtained after 40 h of culture for irradiated human peripheral blood up to 20 Gy. By adding caffeine (final concentration of 1 mM) at 34 h from the start of culture, G2/M-PCC index increased by 1.4-fold in 10 Gy cultures. There was also no significant difference in the G2/M-PCC ring frequency induced for doses 0 to 15 Gy between our 40-h caffeine-supplemented chemical-induced PCC method and the conventional 48-h PCC assay.

Generalized methods for predicting biological response to mixed radiation types and calculating equieffective doses (EQDX).

BACKGROUND: Predicting biological responses to mixed radiation types is of considerable importance when combining radiation therapies that use multiple radiation types and delivery regimens. These may include the use of both low- and high-linear energy transfer (LET) radiations. A number of theoretical models have been developed to address this issue. However, model predictions do not consistently match published experimental data for mixed radiation exposures. Furthermore, the models are often computationally intensive. Accordingly, there is a need for efficient analytical models that can predict responses to mixtures of low- and high-LET radiations. Additionally, a general formalism to calculate equieffective dose (EQDX) for mixed radiations is needed. PURPOSE: To develop a computationally efficient analytical model that can predict responses to complex mixtures of low- and high-LET radiations as a function of either absorbed dose or EQDX. METHODS: The Zaider-Rossi model (ZRM) was modified by replacing the geometric mean of the quadratic coefficients in the interaction term with the arithmetic mean. This modified ZRM model (mZRM) was then further generalized to any number of radiation types and its validity was tested against published experimental observations. Comparisons between the predictions of the ZRM and mZRM, and other models, were made using two and three radiation types. In addition, a generalized formalism for calculating EQDX for mixed radiations was developed within the context of mZRM and validated with published experimental results. RESULTS: The predictions of biological responses to mixed-LET radiations calculated with the mZRM are in better agreement with experimental observations than ZRM, especially when high- and low-LET radiations are mixed. In these situations, the ZRM overestimated the surviving fraction. Furthermore, the EQDX calculated with mZRM are in better agreement with experimental observations. CONCLUSION: The mZRM is a computationally efficient model that can be used to predict biological response to mixed radiations that have low- and high-LET characteristics. Importantly, interaction terms are retained in the calculation of EQDX for mixed radiation exposures within the mZRM framework. The mZRM has application in a wide range of radiation therapies, including radiopharmaceutical therapy.

Response of Cancer Stem Cells and Human Skin Fibroblasts to Picosecond-Scale Electron Irradiation at 1010 to 1011 Gy/s.

PURPOSE: This study aimed to demonstrate for the first time the possibility of irradiating biological cells with gray (Gy)-scale doses delivered over single bursts of picosecond-scale electron beams, resulting in unprecedented dose rates of 1010 to 1011 Gy/s. METHODS AND MATERIALS: Cancer stem cells and human skin fibroblasts were irradiated with MeV-scale electron beams from a laser-driven source. Doses up to 3 Gy per pulse with a high spatial uniformity (coefficient of variance, 3%-6%) and within a timescale range of 10 to 20 picoseconds were delivered. Doses were characterized during irradiation and were found to be in agreement with Monte Carlo simulations. Cell survival and DNA double-strand break repair dynamics were studied for both cell lines using clonogenic assay and 53BP1 foci formation. The results were compared with reference x-rays at a dose rate of 0.49 Gy/min. RESULTS: Results from clonogenic assays of both cell lines up to 3 Gy were well fitted by a linear quadratic model with α = (0.68 ± 0.08) Gy-1 and ß = (0.01 ± 0.01) Gy-2 for human skin fibroblasts and α = (0.51 ± 0.14) Gy-1 and ß = (0.01 ± 0.01) Gy-2 for cancer stem cells. Compared with irradiation at 0.49 Gy/min, our experimental results indicate no statistically significant difference in cell survival rate for doses up to 3 Gy despite a significant increase in the α parameter, which may reflect more complex damage. Foci measurements showed no significant difference between irradiation at 1011 Gy/s and at 0.49 Gy/min. CONCLUSIONS: This study demonstrates the possibility of performing radiobiological studies with picosecond-scale laser-generated electron beams at ultrahigh dose rates of 1010 to1011 Gy/s. Preliminary results indicate, within statistical uncertainties, a significant increase of the α parameter, a possible indication of more complex damage induced by a higher density of ionizing tracks.

Sparing and enhancing dose protraction effects for radiation damage to the aorta of wild-type mice.

PURPOSE: Our previous work indicated the greater magnitude of damage to the thoracic aorta at 6 months after starting 5 Gy irradiation in descending order of exposure to X-rays in 25 fractions > acute X-rays > acute γ-rays > X-rays in 100 fractions ≫ chronic γ-rays, in which the limitations of the study included a lack of data for fractionated γ-ray exposure. To better understand effects of dose protraction and radiation quality, the present study examined changes after exposure to γ-rays in 25 fractions, and compared its biological effectiveness with five other irradiation regimens. MATERIALS AND METHODS: Male C57BL/6J mice received 5 Gy of 137Cs γ-rays delivered in 25 fractions spread over six weeks. At 6 months after starting irradiation, mice were subjected to echocardiography, followed by tissue sampling. The descending thoracic aorta underwent scanning electron microscopy, immunofluorescence staining and histochemical staining. The integrative analysis of multiple aortic endpoints was conducted for inter-regimen comparisons. RESULTS: Exposure to γ-rays in 25 fractions induced vascular damage (evidenced by increases in endothelial detachment and vascular endothelial cell death, decreases in endothelial waviness, CD31, endothelial nitric oxide synthase and vascular endothelial cadherin), inflammation (evidenced by increases in tumor necrosis factor α, CD68 and F4/80) and fibrosis (evidenced by increases in transforming growth factor ß1, alanine blue stain and intima-media thickness). The integrative analysis revealed biological effectiveness in descending order of exposure to X-rays in 25 fractions > acute X-rays > γ-rays in 25 fractions > acute γ-rays > X-rays in 100 fractions ≫ chronic γ-rays. CONCLUSIONS: The results suggest that dose protraction effects on aortic damage depend on radiation quality, and are not a simple function of dose rate and the number of fractions.

A mathematical model for radiation-induced life-shortening attributed to cancer.

PURPOSE: In this paper, we described our mathematical model for radiation-induced life shortening in detail and applied the model to the experimental data on mice to investigate the effect of radiation on cancer-related life-shortening. MATERIALS AND METHODS: Our mathematical model incorporates the following components: (i) occurrence of cancer, (ii) progression of cancer over time, and (iii) death from cancer. We evaluated the progression of cancer over time by analyzing the cancer incidence data and cumulative mortalities data obtained from mice experiments conducted at the Institute for Environmental Sciences (IES). RESULTS: We analyzed non-irradiated control and 20 mGy/day × 400 days irradiated groups. In the analysis, all malignant neoplasms were lumped together and referred to as 'cancer'. Our analysis showed that the reduction in lifespan (104 days in median) was the result of the early onset of cancer (68 days in median) and the shortening of the cancer progression period (48 days in median). CONCLUSIONS: We described in detail our mathematical model for radiation-induced life-shortening attributed to cancer. We analyzed the mice data obtained from the experiment conducted at the IES using our model. We decomposed radiation-induced life-shortening into the early onset of cancer and the shortening of the cancer progression period.

Peripheral blood lymphocytes differ in DNA damage response after exposure to X-rays with different physical properties.

Introduction: In radiology, low X-ray energies (<140 keV) are used to obtain an optimal image while in radiotherapy, higher X-ray energies (MeV) are used to eradicate tumor tissue. In radiation research, both these X-ray energies being used to extrapolate in vitro research to clinical practice. However, the energy deposition of X-rays depends on their energy spectrum, which might lead to changes in biological response. Therefore, this study compared the DNA damage response (DDR) in peripheral blood lymphocytes (PBLs) exposed to X-rays with varying beam quality, mean photon energy (MPE) and dose rate.Methods: The DDR was evaluated in peripheral blood lymphocytes (PBLs) by the É£-H2AX foci assay, the cytokinesis-block micronucleus assay and an SYTOX-based cell death assay, combined with specific cell death inhibitors. Cell cultures were irradiated with a 220 kV X-ray research cabinet (SARRP, X-Strahl) or a 6 MV X-ray linear accelerator (Elekta Synergy). Three main physical parameters were investigated: beam quality (V), MPE (eV) and dose rate (Gy/min). Additional copper (Cu) filtration caused variation in the MPE (78 keV, 94 keV, 118 keV) at SARRP; dose rates were varied by adjusting tube current for 220 kV X-rays (0.33-3 Gy/min) or water-phantom depth in the 6 MV set-up (3-6 Gy/min).Results: The induction of chromosomal damage and initial (30 min) DNA double-stranded breaks (DSBs) were significantly higher for 220 kV X-rays compared to 6 MV X-rays, while cell death induction was similar. Specific cell death inhibitors for apoptosis, necroptosis and ferroptosis were not capable of blocking cell death after irradiation using low or high-energy X-rays. Additional Cu filtration increased the MPE, which significantly decreased the amount of chromosomal damage and DSBs. Within the tested ranges no specific effects of dose rate variation were observed.Conclusion: The DDR in PBLs is influenced by the beam quality and MPE. This study reinforces the need for consideration and inclusion of all physical parameters in radiation-related studies.

Low-dose radiation from CT examination induces DNA double-strand breaks and detectable changes of DNA methylation in peripheral blood cells.

BACKGROUND: Radiation burden from CT examinations increases rapidly with the increased clinical use frequency. Previous studies have disclosed the association between radiation exposure and increased double-strand breaks (DSBs) and changes in DNA methylation. However, whether the induced DSBs by CT examination recover within 24h and whether a CT examination induces detectable gene-specific methylation changes are still unclear. The aim of the present study was to analyze γ-H2AX in the peripheral blood lymphocyte (PBL) of healthy adults before and after CT examination and to discover the differentially methylated positions (DMPs) along with an analysis of DNA methylation changes caused by CT examination. MATERIALS AND METHODS: Peripheral blood samples of 4 ml were drawn from 20 healthy volunteers at three time points: before CT examination, after CT examination 1h, and after CT examination 24h. γ-H2AX immunofluorescence and Illumina Infinium Human Methylation EPIC BeadChip (850k BeadChip) were used respectively for the test of DSBs and the epigenome-wide DNA methylation analysis. Linear mixed-effect (LME) models were used to evaluate the impacts of doses represented by different parameters and foci on genome-wide DNA methylation. RESULTS: The number of γ-H2AX foci per cell at 1h showed linear dose-responses for the radiation doses represented by CT index volume (CTDIvol), dose length product (DLP), and blood absorbed dose, respectively. Residual γ-H2AX foci was observed after CT examination at 24h (p < .001). DMPs and γ-H2AX foci changes could be found within 1h. One CpG site related to PAX5 was significantly changed by using most of the parameters in LME models and did not recover till 24h. CONCLUSIONS: Residual γ-H2AX foci exist after CT examination at 24h. The DNA methylation changes induced by CT examination may not recover within 24h. The DNA methylation had been changed as early as at 1h. The PAX5-related CpG site may be a potential biomarker of low-dose radiation. CLINICAL RELEVANCE: The biological effects and the cancer risks of CT examination are still unclear. The present study is an effort to document the CT scan-induced events in 24h in vivo. The CT scanning area should be strictly limited, and non-essential repeated operations shouldn't be performed within 24h.

Comparison of cellular responses to ionizing radiation in keratinocytes isolated from healthy donors and type II diabetes patients.

PURPOSE: Due to the expanding repertoire of treatment devices that use radiation, the possibility of exposure to both low-dose and high-dose radiation continues to increase. Skin is the outermost part of the body and thus directly exposed to radiation-induced damage. In particular, the skin of diabetes patients is fragile and easily damaged by external stimuli, such as radiation. However, damage and cellular responses induced by ionizing irradiation in diabetic skin have not been explored in detail. In this study, we investigated the effects of several irradiation dose on normal keratinocytes and those from type II diabetes patients, with particular focus on DNA damage. MATERIALS AND METHODS: Cellular responses to low-dose radiation (0.1 Gy) and high-dose radiation (0.5 and 2 Gy) were evaluated. Cell cycle analysis was conducted via flow cytometry and cell viability analyzed using the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. Proteins related to the DNA damage response (DDR) and repair signaling pathways and apoptosis were detected via immunoblot analysis. Apoptosis and cell differentiation were additionally examined in 3D skin organoids using immunohistochemistry. RESULTS: Compared to respective control groups, no significant changes were observed in cell cycle, DDR and repair mechanisms, cell survival, and differentiation in response to 0.1 Gy irradiation in both normal and diabetes type II keratinocytes. On the other hand, the cell cycle showed an increase in the G2/M phase in both cell types following exposure to 2 Gy irradiation. At radiation doses 2 Gy, activation of the DDR and repair signaling pathways, apoptosis, and cell differentiation were increased and viability was decreased in both cell types. Notably, these differences were more pronounced in normal than diabetes type II keratinocytes. CONCLUSIONS: Normal keratinocytes respond more strongly to radiation-induced damage and recovery than diabetes type II keratinocytes.

Muller misled the Pugwash Conference on radiation risks.

The Pugwash Conferences have been a highly visible attempt to create profoundly important discussions on matters related to global safety and security at the highest levels, starting in 1957 at the height of the Cold War. This paper assesses, for the first time, the formal comments offered at this first Pugwash Conference by the Nobel Prize-winning radiation geneticist, Hermann J. Muller, on the effects of ionizing radiation on the human genome. This analysis shows that the presentation by Muller was highly biased and contained scientific errors and misrepresentations of the scientific record that resulted in seriously misleading the attendees. The presentation of Muller at Pugwash served to promote, on a very visible global scale, continued misrepresentations of the state of the science and had a significant impact on policies and practices internationally and both scientific and personal belief systems concerning the effects of low dose radiation on human health. These misrepresentations would come to affect the adoption and use of nuclear technologies and the science of radiological and chemical carcinogen health risk assessment, ultimately having a profound effect on global environmental health.

Side effects of different head and neck radiotherapy doses on wistar rat's behavior.

Radiotherapy (RT) is a common treatment for head and neck tumors. However, it causes several physical and behavioral side effects, and no study has assessed the emotional effects in rats. Therefore, the present study evaluated the influence of head and neck RT on the behavior and body weight gain in Wistar rats. Fifty-four male Wistar rats were allocated into six groups (n = 9) according to the irradiation dose, which was applied at the first day of the experiment: RT-7.5 (single dose of 7.5 Gy); RT-10 (single dose of 10 Gy); RT-15 (single dose of 15 Gy); RT-30 (single dose of 30 Gy); Control (without RT). The animals were irradiated in the region of the right face, and behavioral tests and weighing were performed on days one, seven, and 28. The open field and Y-maze tests were undertaken to analyze the animal's behavior. The dose of 30 Gy was lethal when applied to the head and neck region. The irradiated animals had less weight gain when compared to the control ones, but there was no statistical difference. In the open field and Y-maze tests, lower mobility of animals in the RT groups was observed both on day seven and at the end of the experiment (day 28) when compared to the control rats (p < 0.05). It was possible to conclude that the different doses of radiation induced depressive behavior in the animals, and that the weight gain tended to be lower in the irradiated groups, however, without statistical difference.