Real-time quantitative RT-PCR assay of GADD45 gene expression changes as a biomarker for radiation biodosimetry

RNA N6-methyladenosine modification-based biomarkers for absorbed ionizing radiation dose estimation

Radiation triage and biological dosimetry are critical for the medical management of massive potentially exposed individuals following radiological accidents. Here, we performed a genome-wide screening of radiation-responding mRNAs, whose N6-methyladenosine (m6A) levels showed significant alteration after acute irradiation. The m6A levels of three genes, Ncoa4, Ate1 and Fgf22, in peripheral blood mononuclear cells (PBMCs) of mice showed excellent dose-response relationships and could serve as biomarkers of radiation exposure. Especially, the RNA m6A of Ncoa4 maintained a high level as long as 28 days after irradiation. We demonstrated its responsive specificity to radiation, conservation across the mice, monkeys and humans, and the dose-response relationship in PBMCs from cancer patients receiving radiation therapy. Finally, NOCA4 m6A-based biodosimetric models were constructed for estimating absorbed radiation doses in mice or humans. Collectively, this study demonstrated the potential feasibility of RNA m6A in radiation accidents management and clinical applications.

Profiling of gene expression in the brain associated with anxiety-related behaviors in the chronic phase following cranial irradiation

Although the brain is exposed to cranial irradiation in many clinical contexts, including malignant brain tumor therapy, such exposure can cause delayed neuropsychiatric disorders in the chronic phase. However, how specific molecular mechanisms are associated with irradiation-induced behavioral dysfunction, especially anxiety-like behaviors, is unclear. In the present study, we evaluated anxiety-like behaviors in adult C57BL/6 mice using the open-field (OF) and elevated plus maze (EPM) tests 3 months following single cranial irradiation (10 Gy). Additionally, by using RNA sequencing (RNA-seq), we analyzed gene expression profiles in the cortex and hippocampus of the adult brain to demonstrate the molecular mechanisms of radiation-induced brain dysfunction. In the OF and EPM tests, mice treated with radiation exhibited increased anxiety-like behaviors in the chronic phase. Gene expression analysis by RNA-seq revealed 89 and 106 differentially expressed genes in the cortex and hippocampus, respectively, following cranial irradiation. Subsequently, ClueGO and STRING analyses clustered these genes in pathways related to protein kinase activity, circadian behavior, and cell differentiation. Based on our expression analysis, we suggest that behavioral dysfunction following cranial irradiation is associated with altered expression of Cdkn1a, Ciart, Fos, Hspa5, Hspb1 and Klf10. These novel findings may provide potential genetic targets to investigate for the development of radioprotective agents.

Early molecular markers for retrospective biodosimetry and prediction of acute health effects

Radiation-induced biological changes occurring within hours and days after irradiation can be potentially used for either exposure reconstruction (retrospective dosimetry) or the prediction of consecutively occurring acute or chronic health effects. The advantage of molecular protein or gene expression (GE) (mRNA) marker lies in their capability for early (1-3 days after irradiation), high-throughput and point-of-care diagnosis, required for the prediction of the acute radiation syndrome (ARS) in radiological or nuclear scenarios. These molecular marker in most cases respond differently regarding exposure characteristics such as e.g. radiation quality, dose, dose rate and most importantly over time. Changes over time are in particular challenging and demand certain strategies to deal with. With this review, we provide an overview and will focus on already identified and used mRNA GE and protein markers of the peripheral blood related to the ARS. These molecules are examined in light of 'ideal' characteristics of a biomarkers (e.g. easy accessible, early response, signal persistency) and the validation degree. Finally, we present strategies on the use of these markers considering challenges as their variation over time and future developments regarding e.g. origin of samples, point of care and high-throughput diagnosis.

The Potential of Omics in Biological Dosimetry

Biological dosimetry is an internationally recognized method for quantifying and estimating radiation dose following suspected or verified excessive exposure to ionising radiation. In severe radiation accidents where a large number of people are potentially affected, it is possible to distinguish irradiated from non-irradiated people in order to initiate appropriate medical care if necessary. In addition to severe incidents caused by technical failure, environmental disasters, military actions, or criminal abuse, there are also radiation accidents in which only one or a few individuals are affected in the frame of occupational or medical exposure. The requirements for biological dosimetry are fundamentally different for these two scenarios. In particular, for large-scale radiation accidents, pre-screening methods are necessary to increase the throughput of samples for a rough first-dose categorization. The rapid development and increasing use of omics methods in research as well as in individual applications provides new opportunities for biological dosimetry. In addition to the discovery and search for new biomarkers, dosimetry assays based on omics technologies are becoming increasingly interesting and hold great potential, especially for large-scale dosimetry. In the following review, the different areas of biological dosimetry, the problems in finding suitable biomarkers, the current status of biomarker research based on omics, the potential applications of assays using omics technologies, and also the limitations for the different areas of biological dosimetry are discussed.

Does Gender Difference Effect Radiation-Induced Lung Toxicity? An Experimental Study by Genetic and Histopathological Predictors

Several studies have reported differences in radiation toxicity between the sexes, but these differences have not been tested with respect to histopathology and genes. This animal study aimed to show an association between histopathological findings of radiation-induced lung toxicity and the genes ATM, SOD2, TGF-β1, XRCC1, XRCC3 and HHR2. In all, 120 animals were randomly divided into 2 control groups (male and female) and experimental groups comprising fifteen rats stratified by sex, radiotherapy (0 Gy vs. 10 Gy), and time to sacrifice (6, 12, and 24 weeks postirradiation). Histopathological evaluations for lung injury, namely, intra-alveolar edema, alveolar neutrophils, intra-alveolar erythrocytes, activated macrophages, intra-alveolar fibrosis, hyaline arteriosclerosis, and collapse were performed under a light microscope using a grid system; the evaluations were semi quantitatively scored. Then, the alveolar wall thickness was measured. Real-time quantitative reverse transcription PCR (RT-qPCR) was used to determine gene expression differences in ATM, TGF-β1, XRCC1, XRCC3, SOD2 and HHR2L among the groups. Histopathological data showed that radiation-induced acute, subacute, and chronic lung toxicity were worse in male rats. The expression levels of the evaluated genes were significantly higher in females than males in the control group, but this difference was lost over time after radiotherapy. Less toxicity in females may be attributable to the fact that the expression of the evaluated genes was higher in normal lung tissue in females than in males and the changes in gene expression patterns in the postradiotherapy period played a protective role in females. Additional data related to pulmonary function, lung weights, imaging, or outcomes are needed to support this data that is based on histopathology alone.

Celebrating 60 Years of Accomplishments of the Armed Forces Radiobiology Research Institute1

Chartered by the U.S. Congress in 1961, the Armed Forces Radiobiology Research Institute (AFRRI) is a Joint Department of Defense (DoD) entity with the mission of carrying out the Medical Radiological Defense Research Program in support of our military forces around the globe. In the last 60 years, the investigators at AFRRI have conducted exploratory and developmental research with broad application to the field of radiation sciences. As the only DoD facility dedicated to radiation research, AFRRI's Medical Radiobiology Advisory Team provides deployable medical and radiobiological subject matter expertise, advising commanders in the response to a U.S. nuclear weapon incident and other nuclear or radiological material incidents. AFRRI received the DoD Joint Meritorious Unit Award on February 17, 2004, for its exceptionally meritorious achievements from September 11, 2001 to June 20, 2003, in response to acts of terrorism and nuclear/radiological threats at home and abroad. In August 2009, the American Nuclear Society designated the institute a nuclear historic landmark as the U.S.'s primary source of medical nuclear and radiological research, preparedness and training. Since then, research has continued, and core areas of study include prevention, assessment and treatment of radiological injuries that may occur from exposure to a wide range of doses (low to high). AFRRI collaborates with other government entities, academic institutions, civilian laboratories and other countries to research the biological effects of ionizing radiation. Notable early research contributions were the establishment of dose limits for major acute radiation syndromes in primates, applicable to human exposures, followed by the subsequent evolution of radiobiology concepts, particularly the importance of immune collapse and combined injury. In this century, the program has been essential in the development and validation of prophylactic and therapeutic drugs, such as Amifostine, Neupogen®, Neulasta®, Nplate® and Leukine®, all of which are used to prevent and treat radiation injuries. Moreover, AFRRI has helped develop rapid, high-precision, biodosimetry tools ranging from novel assays to software decision support. New drug candidates and biological dose assessment technologies are currently being developed. Such efforts are supported by unique and unmatched radiation sources and generators that allow for comprehensive analyses across the various types and qualities of radiation. These include but are not limited to both 60Co facilities, a TRIGA® reactor providing variable mixed neutron and γ-ray fields, a clinical linear accelerator, and a small animal radiation research platform with low-energy photons. There are five major research areas at AFRRI that encompass the prevention, assessment and treatment of injuries resulting from the effects of ionizing radiation: 1. biodosimetry; 2. low-level and low-dose-rate radiation; 3. internal contamination and metal toxicity; 4. radiation combined injury; and 5. radiation medical countermeasures. These research areas are bolstered by an educational component to broadcast and increase awareness of the medical effects of ionizing radiation, in the mass-casualty scenario after a nuclear detonation or radiological accidents. This work provides a description of the military medical operations as well as the radiation facilities and capabilities present at AFRRI, followed by a review and discussion of each of the research areas.

Assessment of absorbed dose of gamma rays using the simultaneous determination of inactive hemoglobin derivatives as a biological dosimeter

Biological dosimetry based on sulfhemoglobin (SHb), methemoglobin (MetHb), and carboxyhemoglobin (HbCO) levels was evaluated. SHb, MetHb and HbCO levels were estimated in erythrocytes of mice irradiated by γ rays from a ⁶⁰Co source using the method of multi-component spectrophotometric analysis developed recently. In this method, absorption measurements of diluted aqueous Hb-solution were made at λ = 500, 569, 577 and 620 nm, and using the mathematical formulas based on multi-component spectrophotometric analysis and the mathematical Gaussian elimination method for matrix calculation, the concentrations of various Hb-derivatives and total Hb in mice blood were estimated. The dose range of γ rays was from 0.5 to 8 Gy and the dose rate was 0.5 Gy min^-1. Among all Hb-derivatives, MetHb, SHb and HbCO demonstrated an unambiguous dose-dependent response. For SHb and MetHb, the detection limits were about 0.5 Gy and 1 Gy, respectively. After irradiation, high levels of MetHb, SHb and HbCO persisted for at least 10 days, and the maximal increase of MetHb, SHb and HbCO occurred up to 24 h following γ irradiation. The use of this "MetHb + SHb + HbCO"-derivatives-based absorbed dose relationship showed a high accuracy. It is concluded that simultaneous determination of MetHb, SHb and HbCO, by multi-component spectrophotometry provides a quick, simple, sensitive, accurate, stable and inexpensive biological indicator for the early assessment of the absorbed dose in mice.

Identification of Potential Biomarkers of Radiation Exposure in Blood Cells by Capillary Electrophoresis Time-of-Flight Mass Spectrometry

Biodosimetry is a useful method for estimating personal exposure doses to ionizing radiation. Studies have identified metabolites in non-cellular biofluids that can be used as markers in biodosimetry. Levels of metabolites in blood cells may reflect health status or environmental stresses differentially. Here, we report changes in the levels of murine blood cell metabolites following exposure to X-rays in vivo. Levels of blood cell metabolites were measured by capillary electrophoresis time-of-flight mass spectrometry. The levels of 100 metabolites were altered substantially following exposure. We identified 2-aminobutyric acid, 2'-deoxycytidine, and choline as potentially useful markers of radiation exposure and established a potential prediction panel of the exposure dose using stepwise regression. Levels of blood cell metabolites may be useful biomarkers in estimating exposure doses during unexpected radiation incidents.

Impact of Inter-Individual Variance in the Expression of a Radiation-Responsive Gene Panel Used for Triage

In previous studies we determined a gene expression signature in baboons for predicting the severity of hematological acute radiation syndrome. We subsequently validated a set of eight of these genes in leukemia patients undergoing total-body irradiation. In the current study, we addressed the effect of intra-individual variability on the basal level of expression of those eight radiation-responsive genes identified previously, by examining baseline levels in 200 unexposed healthy human donors (122 males and 88 females with an average age of 46 years) using real-time PCR. In addition to the eight candidate genes ( DAGLA, WNT3, CD177, PLA2G16, WLS, POU2AF1, STAT4 and PRF1), we examined two more genes ( FDXR and DDB2) widely used in ex vivo whole blood experiments. Although significant sex- (seven genes) and age-dependent (two genes) differences in expression were found, the fold changes ranged only between 1.1-1.6. These were well within the twofold differences in gene expression generally considered to represent control values. Age and sex contributed less than 20-30% to the complete inter-individual variance, which is calculated as the fold change between the lowest (reference) and the highest Ct value minimum-maximum fold change (min-max FC). Min-max FCs ranging between 10-17 were observed for most genes; however, for three genes, min-max FCs of complete inter-individual variance were found to be 37.1 ( WNT3), 51.4 ( WLS) and 1,627.8 ( CD177). In addition, to determine whether discrimination between healthy and diseased baboons might be altered by replacing the published gene expression data of the 18 healthy baboons with that of the 200 healthy humans, we employed logistic regression analysis and calculated the area under the receiver operating characteristic (ROC) curve. The additional inter-individual variance of the human data set had either no impact or marginal impact on the ROC area, since up to 32-fold change gene expression differences between healthy and diseased baboons were observed.

GDF-15 gene expression alterations in human lymphoblastoid cells and peripheral blood lymphocytes following exposure to ionizing radiation

The identification of rapid, sensitive and high‑throughput biomarkers is imperative in order to identify individuals harmed by radiation accidents, and accurately evaluate the absorbed doses of radiation. DNA microarrays have previously been used to evaluate the alterations in growth/differentiation factor 15 (GDF15) gene expression in AHH‑1 human lymphoblastoid cells, following exposure to γ‑rays. The present study aimed to characterize the relationship between the dose of ionizing radiation and the produced effects in GDF‑15 gene expression in AHH‑1 cells and human peripheral blood lymphocytes (HPBLs). GDF‑15 mRNA and protein expression levels following exposure to γ‑rays and neutron radiation were assessed by reverse transcription‑quantitative polymerase chain reaction and western blot analysis in AHH‑1 cells. In addition, alterations in GDF‑15 gene expression in HPBLs following ex vivo irradiation were evaluated. The present results demonstrated that GDF‑15 mRNA and protein expression levels in AHH‑1 cells were significantly upregulated following exposure to γ‑ray doses ranging between 1 and 10 Gy, regardless of the dose rate. A total of 48 h following exposure to neutron radiation, a dose‑response relationship was identified in AHH‑1 cells at γ‑ray doses between 0.4 and 1.6 Gy. GDF‑15 mRNA levels in HPBLs were significantly upregulated following exposure to γ‑ray doses between 1 and 8 Gy, within 4‑48 h following irradiation. These results suggested that significant time‑ and dose‑dependent alterations in GDF‑15 mRNA and protein expression occur in AHH‑1 cells and HPBLs in the early phases following exposure to ionizing radiation. In conclusion, alterations in GDF‑15 gene expression may have potential as a biomarker to evaluate radiation exposure.

Radiotherapy-Associated Long-term Modification of Expression of the Inflammatory Biomarker Genes ARG1, BCL2L1, and MYC

Ionizing radiation (IR) exposure of cells in vitro and in vivo triggers a complex cellular response among which modifications of gene expression have been consistently reported. Nevertheless, little is currently known about the transcriptionally responsive genes which play a role in the inflammation response. In order to improve our understanding of such transcriptional response to radiation in vivo, we simultaneously monitored the expression of 249 genes associated with the inflammation response over the course of the radiotherapy treatment in blood of patients treated for endometrial or head and neck cancer. We have identified genes whose transcriptional expression is either upregulated (ARG1, BCL2L1) or downregulated (MYC) several fold in vivo. These modifications were consistently detected across patients and further confirmed by quantitative real-time polymerase chain reaction (QRT-PCR); they were specifically significant toward the end of the radiotherapy treatment, 5 weeks following the first radiation fraction and more pronounced in endometrial patients (respectively, 2.9, 4.1, and 1.8 times). Importantly, in an attempt to correlate expression levels with normal tissue reaction to IR, we also identified three other genes CD40, OAS2, and CXCR1 whose expression level fluctuations during radiotherapy were more pronounced in patients developing late normal tissue responses to curative radiotherapy after the end of the radiotherapy treatment. Overall, we identified inflammation-associated genes which are promising biomarkers of IR exposure and susceptibility to radiation-induced toxicity.

Gene expression in Catla catla (Hamilton) subjected to acute and protracted doses of gamma radiation

Studies on transcriptional modulation after gamma radiation exposure in fish are limited. Cell cycle perturbations and expression of apoptotic genes were investigated in the fish, Catla catla after acute and protracted exposures to gamma radiation over a 90day period. Significant changes in gene expression were observed between day 1 and 90 post-exposure. Gamma radiation induced a significant down-regulation of target genes gadd45α, cdk1 and bcl-2 from day 1 to day 3 after protracted exposure, whereas it persists till day 6 upon acute exposure. From day 12 onwards, Gadd45α, cdk1 and bcl-2 genes were up-regulated following protracted exposure, indicating DNA repair, cell-cycle arrest and apoptosis. There exists a linear correlation between these genes (gadd45α - r=0.85, p=0.0073; cdk1 - r=0.86, p=0.0053; bcl-2 - r=0.89, p=0.0026) at protracted exposures. This is the first report on the dual role of bcl-2 gene in fish exposed to acute and protracted radiation and correlation among the aforementioned genes that work in concert to promote 'repair' and 'death' circuitries in fish blood cells.

Hepatic transcriptional responses in Atlantic salmon (Salmo salar) exposed to gamma radiation and depleted uranium singly and in combination

Radionuclides are a special group of substances posing both radiological and chemical hazards to organisms. As a preliminary approach to understand the combined effects of radionuclides, exposure studies were designed using gamma radiation (Gamma) and depleted uranium (DU) as stressors, representing a combination of radiological (radiation) and chemical (metal) exposure. Juvenile Atlantic salmon (Salmo salar) were exposed to 70mGy external Gamma dose delivered over the first 5h of a 48h period (14mGy/h), 0.25mg/L DU were exposed continuously for 48h and the combination of the two stressors (Combi). Water and tissue concentrations of U were determined to assess the exposure quality and DU bioaccumulation. Hepatic gene expression changes were determined using microarrays in combination with quantitative real-time reverse transcription polymerase chain reaction (qPCR). Effects at the higher physiological levels were determined as plasma glucose (general stress) and hepatic histological changes. The results show that bioaccumulation of DU was observed after both single DU and the combined exposure. Global transcriptional analysis showed that 3122, 2303 and 3460 differentially expressed genes (DEGs) were significantly regulated by exposure to gamma, DU and Combi, respectively. Among these, 349 genes were commonly regulated by all treatments, while the majority was found to be treatment-specific. Functional analysis of DEGs revealed that the stressors displayed similar mode of action (MoA) across treatments such as induction of oxidative stress, DNA damage and disturbance of oxidative phosphorylation, but also stressor-specific mechanisms such as cellular stress and injury, metabolic disorder, programmed cell death, immune response. No changes in plasma glucose level as an indicator of general stress and hepatic histological changes were observed. Although no direct linkage was successfully established between molecular responses and adverse effects at the organism level, the study has enhanced the understanding of the MoA of single radionuclides and mixtures of these.

Methemoglobin-Based Biological Dose Assessment for Human Blood

Methemoglobin is an oxidative form of hemoglobin in erythrocytes. The authors' aim was to develop a new biological dosimeter based on a methemoglobin assay. Methemoglobin in peripheral blood (of females or males) that was exposed to a Co source (0.20 Gy min) was quantified using an enzyme-linked immunosorbent assay. The dose range was 0.5-8.0 Gy. In a time-course experiment, the time points 0, 0.02, 1, 2, 3, 7, 15, 21, and 30 d after 4-Gy irradiation of heparinized peripheral blood were used. Methemoglobin levels in a lysed erythrocyte pellet from the irradiated blood of females and males increased with the increasing dose. Methemoglobin levels in female blood irradiated with γ-doses more than 4 Gy were significantly higher than those in male samples at the same doses. Two dose-response relations were fitted to the straight line: one is with the correlation coefficient of 0.98 for females, and the other is with the correlation coefficient of 0.99 for males. The lower limit of dose assessment based on methemoglobin is about 1 Gy. Methemoglobin levels in blood as a result of auto-oxidation increase after 7-d storage at -20 °C. The upregulation of methemoglobin induced by γ-radiation persists for ∼3 d. The absorbed doses that were estimated using the two dose-response relations were close to the actual doses. The results suggest that methemoglobin can be used as a rapid and accurate biological dosimeter for early assessment of absorbed γ-dose in human blood.

Hormetic effect induced by depleted uranium in zebrafish embryos

The present work studied the hormetic effect induced by uranium (U) in embryos of zebrafish (Danio rerio) using apoptosis as the biological endpoint. Hormetic effect is characterized by biphasic dose-response relationships showing a low-dose stimulation and a high-dose inhibition. Embryos were dechorionated at 4h post fertilization (hpf), and were then exposed to 10 or 100μg/l depleted uranium (DU) in uranyl acetate solutions from 5 to 6 hpf. For exposures to 10μg/l DU, the amounts of apoptotic signals in the embryos were significantly increased at 20 hpf but were significantly decreased at 24 hpf, which demonstrated the presence of U-induced hormesis. For exposures to 100μg/l DU, the amounts of apoptotic signals in the embryos were significantly increased at 20, 24 and 30 hpf. Hormetic effect was not shown but its occurrence between 30 and 48 hpf could not be ruled out. In conclusion, hormetic effect could be induced in zebrafish embryos in a concentration- and time-dependent manner.

MASM, a Matrine Derivative, Offers Radioprotection by Modulating Lethal Total-Body Irradiation-Induced Multiple Signaling Pathways in Wistar Rats

Matrine is an alkaloid extracted from Sophora flavescens Ait and has many biological activities, such as anti-inflammatory, antitumor, anti-fibrosis, and immunosuppressive properties. In our previous studies, the matrine derivative MASM was synthesized and exhibited potent inhibitory activity against liver fibrosis. In this study, we mainly investigated its protection against lethal total-body irradiation (TBI) in rats. Administration of MASM reduced the radiation sickness characteristics and increased the 30-day survival of rats before or after lethal TBI. Ultrastructural observation illustrated that pretreatment of rats with MASM significantly attenuated the TBI-induced morphological changes in the different organs of irradiated rats. Gene expression profiles revealed that pretreatment with MASM had a dramatic effect on gene expression changes caused by TBI. Pretreatment with MASM prevented differential expression of 53% (765 genes) of 1445 differentially expressed genes induced by TBI. Pathway enrichment analysis indicated that these genes were mainly involved in a total of 21 pathways, such as metabolic pathways, pathways in cancer, and mitogen-activated protein kinase (MAPK) pathways. Our data indicated that pretreatment of rats with MASM modulated these pathways induced by TBI, suggesting that the pretreatment with MASM might provide the protective effects on lethal TBI mainly or partially through the modulation of these pathways, such as multiple MAPK pathways. Therefore, MASM has the potential to be used as an effective therapeutic or radioprotective agent to minimize irradiation damages and in combination with radiotherapy to improve the efficacy of cancer therapy.

Up-regulation of Bcl-2 expression in cultured human lymphocytes after exposure to low doses of gamma radiation

Lymphocytes have demonstrated complex molecular responses to induced stress by ionizing radiation. Many of these reactions are mediated through modifications in gene expressions, including the genes involved in apoptosis. The primary aim of this study was to assess the effects of low doses of ionizing radiation on the apoptotic genes, expression levels. The secondary goal was to estimate the time-effect on the modified gene expression caused by low doses of ionizing radiation. Mononuclear cells in culture were exposed to various dose values ranged from 20 to 100 mGy by gamma rays from a Cobalt-60 source. Samples were taken for gene expression analysis at hours 4, 24, 48, 72, and 168 following to exposure. Expression level of two apoptotic genes; BAX (pro-apoptotic) and Bcl-2 (anti-apoptotic) were examined by relative quantitative real-time polymerase chain reaction (PCR), at different time intervals. Radio-sensitivity of peripheral blood mononucleated cells (PBMCs) was measured by the Bcl-2/BAX ratio (as a predictive marker for radio-sensitivity). The non-parametric two independent samples Mann-Whitney U-test were performed to compare means of gene expression. The results of this study revealed that low doses of gamma radiation can induce early down-regulation of the BAX gene of freshly isolated human PBMCs; however, these changes were restored to near normal levels after 168 hours. In most cases, expression of the Bcl-2 anti-apoptotic gene was up-regulated. Four hours following to exposure to low doses of gamma radiation, apoptotic gene expression is modified, this is manifested as adaptive response. Modification of these gene expressions seems to be a principle pathway in the early radioresistance response. In our study, we found that these changes were temporary and faded completely within a week.

Quantifying murine bone marrow and blood radiation dose response following (18)F-FDG PET with DNA damage biomarkers

The purpose of this study was to quantify the poorly understood radiation doses to murine bone marrow and blood from whole-body fluorine 18 ((18)F)-fluorodeoxyglucose (FDG) positron emission tomography (PET), by using specific biomarkers and comparing with whole body external low dose exposures. Groups of 3-5 mice were randomly assigned to 10 groups, each receiving either a different activity of (18)F-FDG: 0-37MBq or whole body irradiated with corresponding doses of 0-300mGy X-rays. Blood samples were collected at 24h and at 43h for reticulocyte micronucleus assays and QPCR analysis of gene expression in peripheral blood leukocytes. Blood and bone marrow dose estimates were calculated from injected activities of (18)F-FDG and were based on a recommended ICRP model. Doses to the bone marrow corresponding to 33.43mGy and above for internal (18)F-FDG exposure and to 25mGy and above for external X-ray exposure, showed significant increases in radiation-induced MN-RET formation relative to controls (P<0.05). Regression analysis showed that both types of exposure produced a linear response with linear regression analysis giving R(2) of 0.992 and 0.999 for respectively internal and external exposure. No significant difference between the two data sets was found with a P-value of 0.493. In vivo gene expression dose-responses at 24h for Bbc3 and Cdkn1 were similar for (18)F-FDG and X-ray exposures, with significant modifications occurring for doses over 300mGy for Bbc3 and at the lower dose of 150mGy for Cdkn1a. Both leucocyte gene expression and quantification of MN-RET are highly sensitive biomarkers for reliable estimation of the low doses delivered in vivo to, respectively, blood and bone marrow, following (18)F-FDG PET.

Development of serum zinc as a biological dosimeter in mice

PURPOSE

To develop a new biological dosimeter based on serum zinc concentration.

MATERIALS AND METHODS

Male mice (8 weeks old) were exposed to different doses (0, 1.0, 2.0, 4.0, or 8.0 Gy) of gamma rays from a (60)Co source. Blood was then collected from the orbital area of these mice, and the serum zinc concentration was detected using the 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol colorimetric method. The data were analyzed using one-way analysis of variance.

RESULTS

The serum zinc concentration in the irradiated mice decreased with increasing dose. Two dose-response relationships fitted to the linear quadratic curve were obtained: One immediately after exposure (y = 0.010x(2) - 0.133x + 0.663, r = 0.983) and the other on the seventh day after exposure (y = 0.008x(2) - 0.127x + 0.695, r = 0.990). The serum zinc concentration continued to decrease until 21 days after exposure. The absorbed doses estimated using both dose-response relationships were close to the actual doses.

CONCLUSIONS

Serum zinc is a quick, effective, and sensitive biomarker for early biological doses assessment of mice irradiated by gamma radiation.

Assessment of ER Stress and autophagy induced by ionizing radiation in both radiotherapy patients and ex vivo irradiated samples

Acute radiation leads to several toxic clinical states and triggers some molecular pathways. To shed light on molecular mechanisms triggered by ionizing radiation (IR), we examined the expression profiles of endoplasmic reticulum (ER) stress and autophagy-related genes in individuals who were exposed to IR. Blood samples were collected from 50 cancer patients before radiotherapy and on the 5th, 15th, and 25th days of the treatment. Peripheral blood samples from 10 healthy volunteers were also obtained for ex vivo irradiation, divided into five and irradiated at a rate of 373 kGy/h to 0, 0.1, 0.5, 1, and 3Gy γ-rays using a constant gamma source. GRP78, ATG5, LC3, ATF4, XBP1, and GADD153 genes were analyzed by quantitative real-time polymerase chain reaction (QRT-PCR) using beta 2 microglobulin (B2M) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as references. In both groups, expressions of the selected genes have increased. It can be concluded that IR induces ER stress and related authophagy pathway in the peripheral lymphocyte cells proportionally by dose.

Assessment of biodosimetry methods for a mass-casualty radiological incident: medical response and management considerations

Following a mass-casualty nuclear disaster, effective medical triage has the potential to save tens of thousands of lives. In order to best use the available scarce resources, there is an urgent need for biodosimetry tools to determine an individual's radiation dose. Initial triage for radiation exposure will include location during the incident, symptoms, and physical examination. Stepwise triage will include point of care assessment of less than or greater than 2 Gy, followed by secondary assessment, possibly with high throughput screening, to further define an individual's dose. Given the multisystem nature of radiation injury, it is unlikely that any single biodosimetry assay can be used as a standalone tool to meet the surge in capacity with the timeliness and accuracy needed. As part of the national preparedness and planning for a nuclear or radiological incident, the authors reviewed the primary literature to determine the capabilities and limitations of a number of biodosimetry assays currently available or under development for use in the initial and secondary triage of patients. Understanding the requirements from a response standpoint and the capability and logistics for the various assays will help inform future biodosimetry technology development and acquisition. Factors considered include: type of sample required, dose detection limit, time interval when the assay is feasible biologically, time for sample preparation and analysis, ease of use, logistical requirements, potential throughput, point-of-care capability, and the ability to support patient diagnosis and treatment within a therapeutically relevant time point.

RUSH and CRUSH: a rapid and conditional RNA interference method in mice

RNA interference (RNAi) is a powerful approach to phenocopy mutations in many organisms. Gold standard conventional knock-out mouse technology is labor- and time-intensive; however, off-target effects may confound transgenic RNAi approaches. Here, we describe a rapid method for conditional and reversible gene silencing in RNAi transgenic mouse models and embryonic stem (ES) cells. RUSH and CRUSH RNAi vectors were designed for reversible or conditional knockdown, respectively, demonstrated using targeted replacement in an engineered ROSA26(lacZ) ES cell line and wildtype V6.5 ES cells. RUSH was validated by reversible knockdown of Dnmt1 in vitro. Conditional mouse model production using CRUSH was expedited by deriving ES cell lines from Cre transgenic mouse strains (nestin, cTnnT, and Isl1) and generating all-ES G0 transgenic founders by tetraploid complementation. A control CRUSH(GFP) RNAi mouse strain showed quantitative knockdown of GFP fluorescence as observed in compound CRUSH(GFP) , Ds-Red Cre-reporter transgenic mice, and confirmed by Western blotting. The capability to turn RUSH and CRUSH alleles off or on using Cre recombinase enables this method to rapidly address questions of tissue-specificity and cell autonomy of gene function in development.

Development of serum copper-based biological dosimetry in whole body gamma irradiation of mice

A new biological dosimeter based on serum copper has been developed. Serum copper in mice subjected to a 60Co source at a dose rate of 0.5 Gy min-1 was detected using the bis(cyclohexanone) oxaldihydrazone colorimetric method. The dose range was from 0.5–7 Gy. The results demonstrate that serum copper decreases with increasing dose. A linear dose response is obtained. The detection limit based on serum copper is the same as that with the lower limit of dose assessment; i.e., about 1 Gy. The decrease in serum copper continues until the 28th day after gamma radiation. The absorbed doses in mice assessed using the linear curve are close to “blind” doses of 4 and 6 Gy. Therefore, serum copper is a quick, simple, and accurate biomarker for early assessment of radiation exposure of mice in the range of 0.5–7 Gy.

Laboratory intercomparison of gene expression assays

The possibility of a large-scale acute radiation exposure necessitates the development of new methods that could provide rapid individual dose estimates with high sample throughput. The focus of the study was an intercomparison of laboratories' dose-assessment performances using gene expression assays. Lithium-heparinized whole blood from one healthy donor was irradiated (240 kVp, 1 Gy/min) immediately after venipuncture at approximately 37°C using single X-ray doses. Blood samples to establish calibration curves (0.25-4 Gy) as well as 10 blinded test samples (0.1-6.4 Gy) were incubated for 24 h at 37°C supplemented with an equal volume of medium and 10% fetal calf serum. For quantitative reverse transcription polymerase chain reaction (qRT-PCR), samples were lysed, stored at -20°C and shipped on ice. For the Chemical Ligation Dependent Probe Amplification methodology (CLPA), aliquots were incubated in 2 ml CLPA reaction buffer (DxTerity), mixed and shipped at room temperature. Assays were run in each laboratory according to locally established protocols. The mean absolute difference (MAD) of estimated doses relative to the true doses (in Gy) was calculated. We also merged doses into binary categories reflecting aspects of clinical/diagnostic relevance and examined accuracy, sensitivity and specificity. The earliest reported time on dose estimates was <8 h. The standard deviation of technical replicate measurements in 75% of all measurements was below 11%. MAD values of 0.3-0.5 Gy and 0.8-1.3 Gy divided the laboratories contributions into two groups. These fourfold differences in accuracy could be primarily explained by unexpected variances of the housekeeping gene (P = 0.0008) and performance differences in processing of calibration and blinded test samples by half of the contributing laboratories. Reported gene expression dose estimates aggregated into binary categories in general showed an accuracies and sensitivities of 93-100% and 76-100% for the groups, with low MAD and high MAD, respectively. In conclusion, gene expression-based dose estimates were reported quickly, and for laboratories with MAD between 0.3-0.5 Gy binary dose categories of clinical significance could be discriminated with an accuracy and sensitivity comparable to established cytogenetic assays.

Dose-dependent and gender-related radiation-induced transcription alterations of Gadd45a and Ier5 inhuman lymphocytes exposed to gamma ray emitted by (60)Co

Growth arrest DNA damage-inducible 45a gene (Gadd45a) and immediate early response gene 5 (Ier5) have been emphasised as ideal radiation biomarkers in several reports. However, some aspects of radiation-induced transcriptional alterations of these genes are unknown. In this study, gender-dependency and dose-dependency as two factors that may affect radiation-induced transcription of Gadd45a and Ier5 genes were investigated. Human lymphocyte cells from six healthy voluntary blood donors (three women and three men) were irradiated in vitro with doses of 0.5-4.0 Gy from a (60)Co source and RNA isolated 4 h later using the High Pure RNA Isolation Kit. Dose and gender dependency of radiation-induced transcriptional alterations of Gadd45a and Ier5 genes were studied by quantitative real-time polymerase chain reaction. The results showed that as a whole, Gadd45a and Ier5 gave responses to gamma rays, while the responses were independent of radiation doses. Therefore, regardless of radiation dose, Gadd45a and Ier5 can be considered potential radiation biomarkers. Besides, although radiation-induced transcriptional alterations of Gadd45a in female and male lymphocyte samples were insignificant at 0.5 Gy, at other doses, their quantities in female samples were at a significantly higher level than in male samples. Radiation-induced transcription of Ier5 of females samples had a reduction in comparison with male samples at 1 and 2 Gy, but at doses of 0.5 and 4 Gy, females were significantly more susceptible to radiation-induced transcriptional alteration of Ier5.

High and low dose responses of transcriptional biomarkers in ex vivo X-irradiated human blood

PURPOSE

Modifications of gene expression following ionizing radiation (IR) exposure of cells in vitro and in vivo are well documented. However, little is known about the dose-responses of transcriptionally responsive genes, especially at low doses. In this study, we investigated these dose-responses and assessed inter-individual variability.

MATERIALS AND METHODS

High dose (0.5-4 Gy) and low dose (5-100 mGy) gene expression responses at 2 h and 24 h using 13 biomarkers transcriptionally regulated through the DNA damage response by the tumor suppressor p53 were investigated. Inter-individual variation was also examined.

RESULTS

High dose-response curves were best constructed using a polynomial fit while the low dose-response curves used a linear fit with linear R(2) values of 0.841-0.985. Individual variation was evident in the high and low dose ranges. The FDXR, DDB2 high dose gene combination produced a mean dose estimate of 0.7 Gy for 1 Gy irradiated 'unknown' samples (95% CIs of 0.3-1.1 Gy) and 1.4 Gy for 2 Gy exposure (95% CIs of 0.6-2.1 Gy). The FDXR, DDB2, CCNG1 low dose gene combination estimated 98 mGy (95% CIs of 27-169 mGy) for 100 mGy exposure.

CONCLUSIONS

These findings identify genes that fulfill some of the requirements of a good exposure biomarker even at low doses, such as sensitivity, reproducibility and simple proportionality with dose.

Gene expression comparisons performed for biodosimetry purposes on in vitro peripheral blood cellular subsets and irradiated individuals

We examined the benefit of gene expression analysis on peripheral blood cellular subsets of different radiosensitivity to elucidate their utility as biodosimeters for estimation of dose in irradiated individuals. Peripheral mononucleated cells were isolated from 18 healthy volunteers employing density separation in a CPT-NH tube. Peripheral mononucleated cells were cultured in RPMI 1640 medium containing 10% autologous serum and were irradiated with 0.1-1 Gy (240 kV, 13 mA, X rays at 1 Gy/min). A low-dose study was performed with isolated peripheral mononucleated cells from one healthy donor in three independent experiments. Peripheral mononucleated cells were irradiated at 0 (sham), 1, 2.5 and 5 cGy (70 kV, 13 mA X rays at 1 cGy/min) and gene expression was measured 24 and 48 h after irradiation. After irradiation, CD4(+) or CD8(+) cells were isolated by magnetic beads in independent experiments. RNA from lymphocyte subsets and peripheral mononucleated cells was isolated after 24 and 48 h and converted into cDNA. Gene expression of GADD45, CDKN1A, DDB2, PCNA, BAX and ATF3 were determined using RTQ-PCR. Data were analyzed employing linear and logistic regression analysis. The same examinations were performed in 5 individuals either diagnosed using CT scans (up to 4.3 cGy) or by administering (F-18)-fluoro-2-deoxy-d-glucose (F-18 FDG, 0.6 cGy). Methodological, intra- and inter-individual variability in 90-95% of measurements did not exceed the introduced twofold change over sham-irradiated control values in peripheral mononucleated cells and CD4(+) cells, and therefore no false positive results were observed. Dose reconstruction in peripheral mononucleated cells in opposite to CD4(+) lymphocytes required fewer genes and appeared more efficient (R-square = 84.8% compared to 51.8%). In vitro samples exposed to 10 cGy could be completely discriminated from sham-irradiated samples without individual pre-exposure controls, which coincided with our preliminary in vivo results. However, in vitro differential gene expression was measured relative to control values and did not differ significantly at 24 and 48 h after irradiation in contrast to our preliminary in vivo data. In addition, below 5 cGy in vitro data did not show reproducible significant changes in gene expression, which was opposite to our preliminary in vivo data. Therefore a twofold change in gene expression over control sufficiently controls for different sources of variance, and measuring gene expression in peripheral mononucleated cell for biological dosimetry purposes appears superior over measurements in lymphocyte subsets. The increased gene expression measured after low absorbed doses in vivo and in vitro might indicate a particular applicability of this method for a low-level radiation scenario in the absence of individual pre-exposure controls. However, the constant gene expression values measured up to 48 h in our in vitro model at doses >10 cGy, and the absence of reproducible and statistically significant gene expression changes below 5 cGy contrast to the preliminary in vivo results performed at similar doses. Therefore, measurements with our in vitro models should be interpreted cautiously.

Gene expression signatures of radiation exposure in peripheral white blood cells of smokers and non-smokers

PURPOSE

The issue of potential confounding factors is critical to the development of any approach to radiation biodosimetry, and has not been fully addressed for gene expression-based approaches.

MATERIALS AND METHODS

As a step in this direction, we have investigated the effect of smoking on the global radiation gene expression response in ex vivo-irradiated peripheral blood cells using microarray analysis. We also evaluated the ability of gene expression signatures to predict the radiation exposure level of ex vivo-exposed samples from smokers and non-smokers of both genders.

RESULTS

We identified eight genes with a radiation response that was significantly affected by smoking status, and confirmed an effect of smoking on the radiation response of the four and a half LIM domains 2 (FHL2) gene using quantitative real-time polymerase chain reaction. The performance of our previously defined 74-gene signature in predicting the radiation dose to samples in this study was unaffected by differences in gender or smoking status, however, giving 98% correct prediction of dose category. This is the same accuracy as that found in the original study from which the signature was derived, using different donors.

CONCLUSION

The results support the development of peripheral blood gene expression as a viable strategy for radiation biodosimetry.

Radiation dose effect of DNA repair-related gene expression in mouse white blood cells

Background

The aim of this study was to screen molecular biomarkers for biodosimetry from DNA repair-related gene expression profiles.

Material/Methods

Mice were subjected to whole-body exposure with ⁶⁰Co γ rays with a dose range of 0–8 Gy at a dose rate of 0.80 Gy/min. RNA was extracted from the peripheral blood of irradiated mice at 4, 8, 12, 24 and 48hrs post-irradiation. The mRNA transcriptional changes of 11 genes related to DNA damage and repair were detected using real-time quantitative polymerase chain reaction (RT-PCR).

Results

Of the 11 genes examined, CDKN1A (cyclin-dependent kinase inhibitor 1A or p21, Cip1) and ATM (ataxia telangiectasia mutated) expression levels were found to be heavily up- and down-regulated, respectively, with exposure dose increasing at different post-irradiation times. RAD50 (RAD50 homolog), PLK3 (polo-like kinase 3), GADD45A (growth arrest and DNA damage-inducible, alpha), DDB2 (damage-specific DNA-binding protein 2), BBC3 (BCL2-binding component 3) and IER5 (immediate early response 5) gene expression levels were found to undergo significant oscillating changes over a broad dose range of 2–8 Gy at post-exposure time points observed. Three of the genes were found not to change within the observed exposure dose and post-radiation time ranges.

Conclusions

The results of this study add to the biodosimetry with biomarker data pool and will be helpful for constructing appropriate gene expression biomarker systems to evaluate radiation exposure doses.

Characterization of invading glioma cells using molecular analysis of leading-edge tissue

OBJECTIVE

We have introduced a method of characterization of invading glioma cells by using molecular analysis of marginal invading tumor cells and molecular profiles of glioma tumor margin.

METHODS

Each of tumor core and marginal tissues was obtained in 22 glioma patients. Tumor core cells and marginal cells from each glial tumor were collected by laser capture microdissection or intraoperative microdissection under the operating microscope. Expression of MMP-2, MMP-9, CD44 and RHAMM mRNA by invading glioma cells compared with tumor core was confirmed by realtime-PCR of twenty-four glioma specimens. Clinical data also were reviewed for invasion and recurrence pattern of the gliomas radiologically and invasive rim pattern microscopically.

RESULTS

Overall results of the molecular analysis showed that relative overexpression of MMP-2, MMP-9 and RHAMM were noted at the invasive edge of human glioma specimens comparing to the tumor core but CD44 was highly expressed in the tumor core comparing to the margin. High marginal expression of MMP-2 and MMP-9 were noted in poorly ill-defined margin on the pathological finding. High marginal expression of CD44 and MMP-2 were demonstrated in the midline cross group on the radiological review, and that of RHAMM and MMP-2 were showed in the aggressive recurrence group. High expression of MMP-2 seems to be involved in the various invasion-related phenomenons.

CONCLUSION

Up-regulation of MMP-2, MMP-9, CD44 and RHAMM was noted in invasive edge of gliomas according to the various clinical situations.

Gene expression analysis in radiotherapy patients and C57BL/6 mice as a measure of exposure to ionizing radiation

Dose assessment after radiological disasters is imperative to decrease mortality through rationally directed medical intervention. Our goal was to identify biomarkers capable of qualitative (nonirradiated/irradiated) and/or quantitative (dose) assessment of radiation exposure. Using real-time quantitative PCR, biodosimetry genes were identified in blood samples from cancer patients undergoing total-body irradiation. Time- (5, 12, 23, 48 h) and dose- (0-8 Gy) dependent changes in gene expression were examined in C57BL/6 mice. A training set was used to derive weighted voting classification algorithms (nonirradiated/irradiated) and continuous regression (dose assessment) models that were tested in a separate validation set of mice. Of eight biodosimetry genes identified in cancer patients ( ACTA2 , BBC3 , CCNG1 , CDKN1A , GADD45A , MDK , SERPINE1 , Tnfrsf10b ), expression of BBC3 , CCNG1 , CDKN1A , SERPINE1 and Tnfrsf10b was significantly (P < 0.05) increased in irradiated mice. CCNG1 and CDKN1A expression segregated irradiated mice from controls with an accuracy, specificity and sensitivity of 96.3, 100.0 and 94.4%, respectively, at 48 h. Multiple linear regression analysis predicted doses for the 0-, 1-, 2-, 4-, 6- and 8-Gy treatment groups as 0.0 ± 0.2, 1.6 ± 1.0, 2.9 ± 1.4, 5.1 ± 2.0, 5.3 ± 0.7 and 10.5 ± 5.6 Gy, respectively. These results suggest that gene expression analysis could be incorporated into biodosimetry protocols for qualitative and quantitative assessment of radiation exposure.

Analysis of qPCR data by converting exponentially related Ct values into linearly related X0 values

A common method for calculating results from qPCR experiments is the comparative Ct method, also called the 2(-ΔΔCt) method. However, several assumptions are included in the 2(-ΔΔCt) method and standard statistical analyses are not directly applicable. Here, we describe a different method, the X(0) method, for result calculations and statistical analysis from qPCR experiments. The X(0) method differs from the 2(-ΔΔCt) method by introducing a conversion of the exponentially related Ct values into linearly related X(0) values, which represent the amount of starting material in a qPCR experiment. Results calculated by the X(0) method are illustrated for qPCR experiments with technical and biological replicates, including procedures to calculate standard deviations. Incorporation of primer efficiencies in calculations by the X(0) method is also described. Altogether, the X(0) method constitutes a very simple and accurate alternative to the 2(-ΔΔCt) method for result calculations from qPCR data.

Dcr3 inhibit p53-dependent apoptosis in gamma-irradiated lung cancer cells

PURPOSE

To identify genes responsible for the radiosensitivity, we investigated the role of the differential gene expression profiles by comparing radioresistant H1299 with radiosensitive H460 lung cancer cell lines.

MATERIALS AND METHODS

mRNA profiles of lung cancer cell lines were assessed using microarray, and subsequent validation was performed with qRT-PCR (Quantitative real time-polymerase chain reaction). The expression levels of differentially expressed genes were determined by Western blot and the radioresistance of lung cancer cell lines was measured by clonogenic assay.

RESULTS

From the differentially expressed apoptosis-related genes between H1299 and H460, we found Dcr3 (Decoy receptor 3, also known as TNFRSF6B; Tumour necrosis factor receptor super family member 6B) expression was significantly (P = 4.38 x 10(-7)) higher in H1299 cells than H460 cells. Moreover, the Dcr3 mRNA expression level in the radioresistant cell lines (H1299, A549, DLD1, MB231, MB157) was increased in comparison to the radiosensitive cell lines (ME180, Caski, U87MG, MCF7, H460). Overexpression of Dcr3 increased the survival rate of radiosensitive H460, MCF7, and U87MG cells, and knockdown of Dcr3 abolished the radioresistance of A549 cells. The survival rate of p53 (Tumour protein 53)-deficient H1299 after gamma-irradiation was not affected by the suppression of Dcr3 expression. However, when we introduced p53 into H1299 cells, siDcr3 (siRNA of Dcr3) suppressed the radioresistance of H1299 cells by inducing p53-dependent Fas (Fas receptor, also known as TNFRSF6; Tumour necrosis factor receptor super family member 6)-mediated apoptosis pathway.

CONCLUSION

Characterisation of gene expression profiles in two lung cancer cell lines revealed that Dcr3 expression and p53-dependent apoptosis signalling pathway regulate cellular response to ionising radiation.

Diagnosis of partial body radiation exposure in mice using peripheral blood gene expression profiles

In the event of a terrorist-mediated attack in the United States using radiological or improvised nuclear weapons, it is expected that hundreds of thousands of people could be exposed to life-threatening levels of ionizing radiation. We have recently shown that genome-wide expression analysis of the peripheral blood (PB) can generate gene expression profiles that can predict radiation exposure and distinguish the dose level of exposure following total body irradiation (TBI). However, in the event a radiation-mass casualty scenario, many victims will have heterogeneous exposure due to partial shielding and it is unknown whether PB gene expression profiles would be useful in predicting the status of partially irradiated individuals. Here, we identified gene expression profiles in the PB that were characteristic of anterior hemibody-, posterior hemibody- and single limb-irradiation at 0.5 Gy, 2 Gy and 10 Gy in C57Bl6 mice. These PB signatures predicted the radiation status of partially irradiated mice with a high level of accuracy (range 79-100%) compared to non-irradiated mice. Interestingly, PB signatures of partial body irradiation were poorly predictive of radiation status by site of injury (range 16-43%), suggesting that the PB molecular response to partial body irradiation was anatomic site specific. Importantly, PB gene signatures generated from TBI-treated mice failed completely to predict the radiation status of partially irradiated animals or non-irradiated controls. These data demonstrate that partial body irradiation, even to a single limb, generates a characteristic PB signature of radiation injury and thus may necessitate the use of multiple signatures, both partial body and total body, to accurately assess the status of an individual exposed to radiation.

Assessment of radiation damage-the need for a multiparametric and integrative approach with the help of both clinical and biological dosimetry

Accidental exposure to ionizing radiation leads to damage on different levels of the biological organization of an organism. Depending on exposure conditions, such as the nature of radiation, time and affected organs and organ systems, the clinical endpoint of radiation damage and the resulting acute and chronic radiation syndromes may vary to a great extent. Exposure situations range from purely localized radiation scenarios and partial-body exposures to whole-body exposures. Therefore, clinical pictures vary from localized radiation injuries up to the extreme situation of radiation-induced multi-organ involvement and failure requiring immediate, intensive, and interdisciplinary medical treatment. These totally different and complex clinical situations not only appear most different in clinical diagnostic and therapeutic aspects, but also, due to different levels of underlying biological damage, biological indicators of effects may vary to a wide extent. This fact means that an exact assessment of the extent of radiation damage within individual patients can only be performed when taking into consideration clinical as well as different biological indicators. Among the clinical indicators, routine laboratory parameters such as blood counts and the documentation of clinical signs and symptoms (using such methods as the METREPOL system) are the key parameters, but dicentric assay, the gold standard for biological dosimetry, and other methods under development, such as the gamma-H2AX focus assay or gene expression analysis of radiosensitive genes, must also be taken into account. Each method provides best results in different situations, or, in other words, there are methods that work better in a specific exposure condition or at a given time of examination (e.g., time after exposure) than others. Some methods show results immediately; others require days to weeks until results are available for clinical decision-making. Therefore, to provide the best basis for triage and planning and to provide medical treatment after accidental radiation exposure, different and independent diagnostic procedures integrating all clinical aspects as well as different biological indicators have to be applied. This multiparametric approach has been suggested after recent radiation accidents but needs to be adopted and standardized worldwide. A new integrative concept is shown and discussed.

Rapid radiation dose assessment for radiological public health emergencies: roles of NIAID and BARDA

A large-scale radiological incident would result in an immediate critical need to assess the radiation doses received by thousands of individuals to allow for prompt triage and appropriate medical treatment. Measuring absorbed doses of ionizing radiation will require a system architecture or a system of platforms that contains diverse, integrated diagnostic and dosimetric tools that are accurate and precise. For large-scale incidents, rapidity and ease of screening are essential. The National Institute of Allergy and Infectious Diseases of the National Institutes of Health is the focal point within the Department of Health and Human Services (HHS) for basic research and development of medical countermeasures for radiation injuries. The Biomedical Advanced Research and Development Authority within the HHS Office of the Assistant Secretary for Preparedness and Response coordinates and administers programs for the advanced development and acquisition of emergency medical countermeasures for the Strategic National Stockpile. Using a combination of funding mechanisms, including funds authorized by the Project BioShield Act of 2004 and those authorized by the Pandemic and All-Hazards Preparedness Act of 2006, HHS is enhancing the nation's preparedness by supporting the radiation dose assessment capabilities that will ensure effective and appropriate use of medical countermeasures in the aftermath of a radiological or nuclear incident.

Effect of (211)At alpha-particle irradiation on expression of selected radiation responsive genes in human lymphocytes

PURPOSE

Analysis of the relative expression of radiation responsive genes (previously shown to respond to gamma-radiations) after exposure of human lymphocytes to (211)At alpha-particles and the suitability of these genes as potential markers for alpha-biodosimetry.

MATERIALS AND METHODS

Lymphocytes isolated from the peripheral blood of two healthy human donors were exposed in triplicate for 30 min to different concentrations of Na(211)At at 37 degrees C (absorbed doses: 0.05-1.6 Gy). Following an incubation period (2 h), the total RNA was isolated from the irradiated lymphocytes and the relative expression of the following 18 genes was tested for change using TaqMan probes based upon the real-time quantitative polymerase chain reaction.

METHOD

BBC3 (B-cell lymphoma 2 binding component 3), CD69 (cluster of differentiation 69), CDKN1A (cyclin-dependent kinase inhibitor 1A), DUSP8 (dual specificity phosphatase 8) EGR1 (early growth response 1), EGR4 (early growth response 4), GADD45A (growth arrest and DNA-damage-inducible, alpha), GRAP (growth factor receptor-bound protein 2-related adaptor protein), LAP1B (TOR1AIP1; torsin A interacting protein 1), IFNG (interferon gamma), ISG20L1 (interferon-stimulated exonuclease gene 20kDa - like 1), c-JUN (jun oncogene), MDM2 (mouse double minute 2), PCNA (proliferating cell nuclear antigen), PLK2 (polo-like kinase 2), RND1 (rho family GTPase 1), TNFSF9 (tumour necrosis factor superfamily member 9) and TRAF4 (tumour necrosis factor receptor-associated factor 4).

RESULTS

The expressions of the 18 genes, except GRAP, were up-regulated following exposure to alpha-radiation. A comparison of the results of two individuals tested here showed great variability. Dependence of gene expression upon alpha-dose was observed in certain dose intervals for BBC3 (R(2) = 0.61 [individual 1] / 0.81 [individual 2], significance 0.2-1.6 Gy [1] / 0.05-0.1 Gy [2]) and MDM2 (R(2) = 0.78/0.54; 0.8-1.6 Gy [1], 0.05-0.1 Gy [2]) genes in both individuals. Additionally, for individual 1 the dose dependence was found for the following genes: ISG20L1 (R(2) = 0.69, 0.05-0.1 Gy), PCNA (R(2) = 0.59, 0.8-1.6 Gy) and IFNG (R(2) = 0.74 up to 0.4 Gy, 0.05-0.1 Gy).

CONCLUSION

Candidate genes for a possible role in future early-phase (2 h) alpha-biodosimetry are BBC3, ISG20L1, MDM2, PCNA and IFNG.

Candidate protein biodosimeters of human exposure to ionizing radiation

PURPOSE

To conduct a literature review of candidate protein biomarkers for individual radiation biodosimetry of exposure to ionizing radiation.

MATERIALS AND METHODS

Reviewed approximately 300 publications (1973 - April 2006) that reported protein effects in mammalian systems after either in vivo or in vitro radiation exposure.

RESULTS

We found 261 radiation-responsive proteins including 173 human proteins. Most of the studies used high doses of ionizing radiation (>4 Gy) and had no information on dose- or time-responses. The majority of the proteins showed increased amounts or changes in phosphorylation states within 24 h after exposure (range: 1.5- to 10-fold). Of the 47 proteins that are responsive at doses of 1 Gy and below, 6 showed phosphorylation changes at doses below 10 cGy. Proteins were assigned to 9 groups based on consistency of response across species, dose- and time-response information and known role in the radiation damage response.

CONCLUSIONS

ATM (Ataxia telengiectasia mutated), H2AX (histone 2AX), CDKN1A (Cyclin-dependent kinase inhibitor 1A), and TP53 (tumor protein 53) are top candidate radiation protein biomarkers. Furthermore, we recommend a panel of protein biomarkers, each with different dose and time optima, to improve individual radiation biodosimetry for discriminating between low-, moderate-, and high-dose exposures. Our findings have applications for early triage and follow-up medical assessments.

Another formula for calculating the gene change rate in real-time RT-PCR

Relative quantification real-time PCR has become a routine method in molecular biology research to study the small amount gene expression. There are a few mathematical models for relative quantification data analysis in real-time PCR, and the formula 2(-DDCT ) is one of the most frequently used method. In this paper, we are to present another equation which directly calculates the change rate (R (c)) of gene expression, and give a example to compare the application of this model with 2(-DDCT).

Broad modulation of gene expression in CD4+ lymphocyte subpopulations in response to low doses of ionizing radiation

To compare the responses of the different lymphocyte subtypes after an exposure of whole blood to low doses of ionizing radiation, we examined variations in gene expression in different lymphocyte subpopulations using microarray technology. Blood samples from five healthy donors were independently exposed to 0 (sham irradiation), 0.05 and 0.5 Gy of ionizing radiation. Three and 24 h after exposure, CD56+, CD4+ and CD8+ cells were negatively isolated. RNA from each set of experimental conditions was competitively hybridized on 25k oligonucleotide microarrays. Modifications of gene expression were measured after both intervals and in all cell types. Twenty-four hours after exposure to 0.5 Gy, we observed an induction of the expression of BAX, PCNA, GADD45, DDB2 and CDKN1A. However, the numbers of modulated genes greatly differed between cell types. In particular, 3 h after exposure to doses as low as 0.05 Gy, the number of down-modulated genes was 10 times greater for CD4+ cells than for all other cell types. Moreover, most of these repressed genes were taking part in the cell processes of protein biosynthesis and oxidative phosphorylation. The results suggest that several biological pathways in CD4+ cells could be sensitive to low doses of radiation. Therefore, specifically studying CD4+ cells could help to understand the mechanisms involved in low-dose response and allow their detection.

Development of gene expression signatures for practical radiation biodosimetry

PURPOSE

In a large-scale radiologic emergency, estimates of exposure doses and radiation injury would be required for individuals without physical dosimeters. Current methods are inadequate for the task, so we are developing gene expression profiles for radiation biodosimetry. This approach could provide both an estimate of physical radiation dose and an indication of the extent of individual injury or future risk.

METHODS AND MATERIALS

We used whole genome microarray expression profiling as a discovery platform to identify genes with the potential to predict radiation dose across an exposure range relevant for medical decision making in a radiologic emergency. Human peripheral blood from 10 healthy donors was irradiated ex vivo, and global gene expression was measured both 6 and 24 h after exposure.

RESULTS

A 74-gene signature was identified that distinguishes between four radiation doses (0.5, 2, 5, and 8 Gy) and controls. More than one third of these genes are regulated by TP53. A nearest centroid classifier using these same 74 genes correctly predicted 98% of samples taken either 6 h or 24 h after treatment as unexposed, exposed to 0.5, 2, or > or =5 Gy. Expression patterns of five genes (CDKN1A, FDXR, SESN1, BBC3, and PHPT1) from this signature were also confirmed by real-time polymerase chain reaction.

CONCLUSION

The ability of a single gene set to predict radiation dose throughout a window of time without need for individual pre-exposure controls represents an important advance in the development of gene expression for biodosimetry.