Radiation-induced biomarkers for the detection and assessment of absorbed radiation doses

Proteomic analysis of plasma at the preterminal stage of rhesus nonhuman primates exposed to a lethal total-body dose of gamma-radiation

The identification and validation of radiation biomarkers is critical for assessing the radiation dose received in exposed individuals and for developing radiation medical countermeasures that can be used to treat acute radiation syndrome (ARS). Additionally, a fundamental understanding of the effects of radiation injury could further aid in the identification and development of therapeutic targets for mitigating radiation damage. In this study, blood samples were collected from fourteen male nonhuman primates (NHPs) that were exposed to 7.2 Gy ionizing radiation at various time points (seven days prior to irradiation; 1, 13, and 25 days post-irradiation; and immediately prior to the euthanasia of moribund (preterminal) animals). Plasma was isolated from these samples and was analyzed using a liquid chromatography tandem mass spectrometry approach in an effort to determine the effects of radiation on plasma proteomic profiles. The primary objective was to determine if the radiation-induced expression of specific proteins could serve as an early predictor for health decline leading to a preterminal phenotype. Our results suggest that radiation induced a complex temporal response in which some features exhibit upregulation while others trend downward. These statistically significantly altered features varied from pre-irradiation levels by as much as tenfold. Specifically, we found the expression of integrin alpha and thrombospondin correlated in peripheral blood with the preterminal stage. The differential expression of these proteins implicates dysregulation of biological processes such as hemostasis, inflammation, and immune response that could be leveraged for mitigating radiation-induced adverse effects.

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.

DDB2 and MDM2 genes are promising markers for radiation diagnosis and estimation of radiation dose independent of trauma and burns

In the field of biodosimetry, the current accepted method for evaluating radiation dose fails to meet the need of rapid, large-scale screening, and most RNA marker-related studies of biodosimetry are concentrating on a single type of ray, while some other potential factors, such as trauma and burns, have not been covered. Microarray datasets that contain the data of human peripheral blood samples exposed to X-ray, neutron, and γ-ray radiation were obtained from the GEO database. Totally, 33 multi-type ray co-induced genes were obtained at first from the differentially expressed genes (DEGs) and key genes identified by weighted gene co-expression network analysis (WGCNA), and these genes were mainly enriched in DNA damage, cellular apoptosis, and p53 signaling pathway. Following transcriptome sequencing of blood samples from 11 healthy volunteers, 13 patients with severe burns, and 37 patients with severe trauma, 6635 trauma-related DEGs and 7703 burn-related DEGs were obtained. Through the exclusion method, a total of 12 radiation-specific genes independent of trauma and burns were identified. ROC curve analysis revealed that the DDB2 gene performed the best in diagnosis of all three types of ray radiation, while correlation analysis showed that the MDM2 gene was the best in assessment of radiation dose. The results of multiple-linear regression analysis indicated that such analysis could improve the accuracy in assessment of radiation dose. Moreover, the DDB2 and MDM2 genes remained effective in radiation diagnosis and assessment of radiation dose in an external dataset. In general, the study brings new insights into radiation biodosimetry.

-Omics potential of in vitro skin models for radiation exposure

There is a growing need to uncover biomarkers of ionizing radiation exposure that leads to a better understanding of how exposures take place, including dose type, rate, and time since exposure. As one of the first organs to be exposed to external sources of ionizing radiation, skin is uniquely positioned in terms of model systems for radiation exposure study. The simultaneous evolution of both MS-based -omics studies, as well as in vitro 3D skin models, has created the ability to develop a far more holistic understanding of how ionizing radiation affects the many interconnected biomolecular processes that occur in human skin. However, there are a limited number of studies describing the biomolecular consequences of low-dose ionizing radiation to the skin. This review will seek to explore the current state-of-the-art technology in terms of in vitro 3D skin models, as well as track the trajectory of MS-based -omics techniques and their application to ionizing radiation research, specifically, the search for biomarkers within the low-dose range.

Alteration of physiological and biochemical properties in leaves and fruits of pomegranate in response to gamma irradiation

Pomegranate breeding to improve the marketability requires the production of large and high quality fruits. Gamma radiation on pomegranate can be used to generate genetic diversity that allows the breeder to screen the mutants for superior quality and quantity. For this purpose, dormant buds on 1-year-old shoots of pomegranate cultivar "Malase Saveh" were subjected to 36 Gy (Gy) of gamma irradiation from a cobalt (⁶⁰CO) source. Shoot cuttings were taken from the mutated shoots and generate M₁V₂. The number of 11 mutants were selected from M₁V₂ plants based on their winter survival and disease resistance. After a period of 3–4 years, leaf and fruit samples were harvested from the M₁V₅. Results showed that physiological and biochemical parameters of leaves were altered unevenly, some clones showed no alterations from the control, while others revealed considerable differences. Irradiation altered various aspects related to fruit, such as the number and weight of ripe and unripe fruits, number of cracked, sunburn, worm-eaten fruits, and fruit size. In general, mutant clones 5, 8, and 10 had higher fruit sizes and weight of ripe fruits and less number and weight of unripe fruits. The stability of the detected mutants will be evaluated and new commercial field trials using selected materials will be established.

Effects of chronic exposure to low levels of IR on Medaka (Oryzias latipes): a proteomic and bioinformatic approach

PURPOSE

Chronic exposure to ionizing radiation (IR) at low doses (<100 mGy) has been insufficiently studied to understand fully the risk to health. Relatively little knowledge exists regarding how species and healthy tissues respond at the protein level to chronic exposure to low doses of IR, and mass spectrometric-based profiling of protein expression is a powerful tool for studying changes in protein abundance.

MATERIALS AND METHODS

SDS gel electrophoresis, LC-MS/MS mass spectrometry-based approaches and bioinformatic data analytics were used to detect proteomic changes following chronic exposure to moderate/low doses of radiation in adults and normally developed Medaka fish (Oryzias latipes).

RESULTS

Significant variations in the abundance of proteins involved in thyroid hormone signaling and lipid metabolism were detected, which could be related to the gonadal regression phenotype observed after 21.04 mGy and 204.3 mGy/day exposure. The global proteomic change was towards overexpression of proteins in muscle and skin, while the opposite effect was observed in internal organs.

CONCLUSION

The present study provides information on the impacts of biologically relevant low doses of IR, which will be useful in future research for the identification of potential biomarkers of IR exposure and allow for a better assessment of radiation biosafety regulations.

Investigation of Chromosome 1 Aberrations in the Lymphocytes of Prostate Cancer and Benign Prostatic Hyperplasia Patients by Fluorescence in situ Hybridization

Purpose

Radiotherapy is one of the most common treatments for prostate cancer. Finding a useful predictor of the therapeutic outcome is crucial as it increases the efficacy of treatment planning. This study investigated the individual susceptibility to radiation based on chromosome 1 aberration frequency measured by the FISH (fluorescence in situ hybridization) method.

Patients and Methods

Whole blood samples were collected from 27 prostate cancer (PCa) patients and 32 subjects with benign prostatic hyperplasia (BPH), who were considered as a control group. Samples were irradiated with 2 Gy of x-rays, cultured, harvested, and used in the FISH procedure.

Results

After irradiation, significantly higher levels of all studied chromosome 1 aberrations (except for deletions) in the group of PCa patients were revealed. Furthermore, in the lymphocytes of cancer patients, nearly five-fold higher frequencies of acentric fragments were observed compared to the BPH group. The highest individual radiosensitivities for all estimated biomarkers were seen in PCa patient cells who reported cancer incidence in the immediate family (CIF+).

Conclusion

The differences in chromosome 1 aberrations between PCa and BPH demonstrate that lymphocytes taken from patients with prostate cancer have higher radiosensitivity which might be related to hereditary or familiar inclinations. Therefore, this technique may find future application in searching biomarkers of the cellular radiotherapy response in prostate cancer patients.

Chronic exposure to low doses of ionizing radiation impacts the processing of glycoprotein N-linked glycans in Medaka (Oryzias latipes)

PURPOSE

Ionizing radiation is found naturally in the environment. Low doses of IR may have beneficial applications, yet there is also potential for detrimental long-term health effects. Impacts following exposure to low levels of IR have been refractory to identification and quantification. Glycoprotein glycosylation is vital to cell-cell communication and organismal function, and sensitive to changes in an organism's macro- and cellular environment. We investigated whether accumulated low doses of IR (LoDIR) affect the N-linked glycoprotein glycans using Medaka fish (Oryzias latipes).

MATERIALS AND METHODS

State-of-the-art methods in radiation exposure and glycan analysis were applied to study N-glycan changes after 190 day exposure at three different rates of gamma irradiation (2.25, 21.01, and 204.3 mGy/day) in wild-type adult Medaka. Tissue N-glycans were analyzed following enzymatic release from extracted proteins.

RESULTS

N-linked glycan profiles are dominated by complex type N-glycans modified with terminal sialic acid and core fucose. Fucosylation and sialylation of N-linked glycoprotein glycans are affected by LoDIR and a subset of N-glycans are involved in the organismal radio-response.

CONCLUSION

This is the first indication that the glycome can be interrogated for biomarkers that report the impact of chronic exposure to environmental stressors, such as low-level IR.

Deviation from Mendelian transmission of autosomal SNPs can be used to estimate germline mutations in humans exposed to ionizing radiation

We aimed to estimate the rate of germline mutations in the offspring of individuals accidentally exposed to Cesium-137 ionizing radiation. The study included two distinct groups: one of cases, consisting of males and females accidentally exposed to low doses of ionizing radiation of Cs137, and a control group of non-exposed participants. The cases included 37 people representing 11 families and 15 children conceived after the accident. Exposed families incurred radiation absorbed doses in the range of 0.2 to 0.5 Gray. The control group included 15 families and 15 children also conceived after 1987 in Goiânia with no history of radiation exposure. DNA samples from peripheral blood were analyzed with the Affymetrix GeneChip® CytoScanHD™ to estimate point mutations in autosomal SNPs. A set of scripts previously developed was used to detect de novo mutations by comparing parent and offspring genotypes at the level of each SNP marker. Overall numbers of observed Mendelian deviations were statistically significant between the exposed and control groups. Our retrospective transgenerational DNA analysis showed a 44.0% increase in the burden of SNP mutations in the offspring of cases when compared to controls, based on the average of MFMD for the two groups. Parent-of-origin and type of nucleotide substitution were also inferred. This proved useful in a retrospective estimation of the rate of de novo germline mutations in a human population accidentally exposed to low doses of radiation from Cesium-137. Our results suggested that observed burden of germline mutations identified in offspring was a potentially useful biomarker of effect to estimate parental exposure to low doses of IR and could become an important marker suitable for biomonitoring human population exposed to environmental mutagens.

Lipidomic Profiling for Serum Biomarkers in Mice Exposed to Ionizing Radiation

Radiation biodosimeters are required urgently for fast and accurate evaluation of absorbed dose for irradiated individuals. Lipidomics has appeared as a credible technique for identification and quantification of lipid for researching biomarker of diseases. We performed a lipidomic profile on mice serum at time points of 6, 24, and 72 hours after 0, 2, 5.5, 7, and 8 Gy irradiation to select radiation-responsive lipids and conducted Kyoto Encyclopedia of Genes and Genome pathway enrichment analysis to recognize the pathways and network changes. Then, Pearson correlation analysis was performed to evaluate the feasibility of radiation-responsive lipids to estimate radiation dose. Seven radiation-responsive lipids including PC (18:2/18:2), PC (18:0/18:2), Lyso PC 18:1, PC (18:0/20:4), SM (D18:0/24:1), PC (16:0/18:1), and Lyso PC 18:2 were identified in which glycerophospholipid metabolism presented as the most significant pathway, and they all presented good linear correlation with the irradiated dose. This study identified 7 radiation-responsive lipids in mice serum and certificate their feasibility of dose estimation as biodosimeters.

The hunt for radiation biomarkers: current situation

Purpose: The possibility of a large-scale acute radiation exposure necessitates the development of new methods that could provide a rapid assessment of the doses received by individuals using high-throughput technologies. There is also a great interest in developing new biomarkers of dose exposure, which could be used in large molecular epidemiological studies in order to correlate estimated doses received and health effects. The goal of this review was to summarize current literature focused on biological dosimetry, namely radiation-responsive biomarkers.Methods: The studies involved in this review were thoroughly selected according to the determined criteria and PRISMA guidelines.Results: We described briefly recent advances in radiation genomics and metabolomics, giving particular emphasis to proteomic analysis. The majority of studies were performed on animal models (rats, mice, and non-human primates). They have provided much beneficial information, but the most relevant tests have been done on human (oncological) patients. By inspecting the radiaiton biodosimetry literate of the last 10 years, we identified a panel of candidate markers for each -omic approach involved.Conslusions: We reviewed different methodological approaches and various biological materials, which can be exploited for dose-effect prediction. The protein biomarkers from human plasma are ideal for this specific purpose. From a plethora of candidate markers, FDXR is a very promising transcriptomic candidate, and importantly this biomarker was also confirmed by some studies at protein level in humans.

The FDA NIH Biomarkers, EndpointS, and other Tools (BEST) resource in neuro-oncology

In early 2016, the FDA and the National Institutes of Health (NIH) published the first version of the glossary included in the Biomarkers, EndpointS, and other Tools (BEST) resource.1 The BEST glossary was constructed to harmonize and clarify terms used in translational science and medical product development and to provide a common language used for communication by those agencies. It is considered a "living" document that will be updated in the future. This review will discuss the main biomarker and clinical outcome categories contained in the BEST glossary as they apply to neuro-oncology, as well as the overlapping and hierarchical relationships among them.

Fabric Phase Sorptive Extraction-A Metabolomic Preprocessing Approach for Ionizing Radiation Exposure Assessment

The modern application of mass spectrometry-based metabolomics to the field of radiation assessment and biodosimetry has allowed for the development of prompt biomarker screenings for radiation exposure. Our previous work on radiation assessment, in easily accessible biofluids (such as urine, blood, saliva), has revealed unique metabolic perturbations in response to radiation quality, dose, and dose rate. Nevertheless, the employment of swift injury assessment in the case of a radiological disaster still remains a challenge as current sample processing can be time consuming and cause sample degradation. To address these concerns, we report a metabolomics workflow using a mass spectrometry-compatible fabric phase sorptive extraction (FPSE) technique. FPSE employs a matrix coated with sol-gel poly(caprolactone-b-dimethylsiloxane-b-caprolactone) that binds both polar and nonpolar metabolites in whole blood, eliminating serum processing steps. We confirm that the FPSE preparation technique combined with liquid chromatography-mass spectrometry can distinguish radiation exposure markers such as taurine, carnitine, arachidonic acid, α-linolenic acid, and oleic acid found 24 h after 8 Gy irradiation. We also note the effect of different membrane fibers on both metabolite extraction efficiency and the temporal stabilization of metabolites in whole blood at room temperature. These findings suggest that the FPSE approach could work in future technology to triage irradiated individuals accurately, via biomarker screening, by providing a novel method to stabilize biofluids between collection and sample analysis.

Transcriptional Profiling of Non-Human Primate Lymphoid Organ Responses to Total-Body Irradiation

The global threat of exposure to radiation and its subsequent outcomes require the development of effective strategies to mitigate immune cell injury. In this study we explored transcriptional and immunophenotypic characteristics of lymphoid organs of a non-human primate model after total-body irradiation (TBI). Fifteen middle-aged adult, ovariectomized, female cynomolgus macaques received a single dose of 0, 2 or 5 Gy gamma radiation. Thymus, spleen and lymph node from three controls and 2 Gy (n = 2) and 5 Gy (n = 2) exposed animals were assessed for molecular responses to TBI through microarray-based transcriptional profiling at day 5 postirradiation, and cellular changes through immunohistochemical (IHC) characterization of markers for B and T lymphocytes and macrophages across all 15 animals at time points up to 6 months postirradiation. Irradiated macaques developed acute hematopoietic syndrome. Analysis of array data at day 5 postirradiation identified transcripts with ≥2-fold difference from control and a false discovery rate (FDR) of Padj < 0.05 in lymph node (n = 666), spleen (n = 493) and thymus (n=3,014). Increasing stringency of the FDR to P < 0.001 reduced the number of genes to 71 for spleen and 379 for thymus. IHC and gene expression data demonstrated that irradiated animals had reduced numbers of T and B lymphocytes along with relative elevations of macrophages. Transcriptional analysis revealed unique patterns in primary and secondary lymphoid organs of cynomolgus macaques. Among the many differentially regulated transcripts, upregulation of noncoding RNAs [MIR34A for spleen and thymus and NEAT1 (NCRNA00084) for thymus] showed potential as biomarkers of radiation injury and targets for mitigating the effects of radiation-induced hematopoietic syndrome-impaired lymphoid reconstitution.

Delineating the Effects of Ionizing Radiation on Erythropoietic Lineage-Implications for Radiation Biodosimetry

The overall lethality/morbidity of ionizing radiation exposure involves multiple forms of inhibitory or cytotoxic effects that may manifest in different tissues with a varying dose and time response. One of the major systemic effects leading to lethality of radiation includes its suppressive effect on hematopoiesis, which could be observed even at doses as low as 1-2 Gy, whereas effects on gastrointestinal and nervous systems appear at relatively higher doses in the same order. This article reviews the effects of radiation on the three distinct stages of erythropoiesis-formation of erythroid progenitor cells, differentiation of erythroid precursor cells, and terminal maturation. During these stepwise developmental processes, erythroid progenitor cells undergo rapid expansion to form terminally differentiated red blood cells that are continuously replenished from bone marrow into the circulating peripheral blood stream. Cellular radiation response depends upon many factors such as cell lineage, rate of proliferation, and differentiation status. Therefore, we discuss radiation-induced alterations during the progenitor, precursor, and terminal maturation stages and the implications thereof. Since biomarkers of ionizing radiation exposure in human populations are of great interest for assessing normal tissue injury as well as for biodosimetry in the event of accidental or incidental radiation exposures, we also highlight blood-based biomarkers that have potential utility for medical management.

The devastating effect of exposure to high irradiation dose on liver and the performance of synthesized nano-Hap in relieve the associated symptoms in rats

Ionizing radiation is one of the environmental factors that may contribute to liver dysfunction through a mechanism involving oxidative stress. This investigation studied the possible therapeutic effects of nano-HAp on hepatotoxicity in rats induced with gamma (γ) radiation. The study was carried out using 3 groups with 10 rats in each. Group 1 comprised the non-irradiated control rats, whereas the rats in groups 2 and 3 received a single dose of 10 Gy γ-radiation. The rats in group 3 were treated with nano-HAp [100 mg·(kg body mass)−1] once a week for 2 weeks starting the day after irradiation. The results showed that the rats exposed to γ-radiation had fragmented DNA, and significantly decreased levels of liver tissue enzymes such as paraoxonase 1, gamma glutamyl, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Pro-inflammatory factors such as interleukin (IL)-2, IL-6, tumor necrosis factor alpha (TNF-α), and interferon gamma (IFN-γ) in tissue were significantly increased compared with the controls. Also, exposure to γ-radiation significantly decreased the activity of superoxide dismutase and glutathione oxidase and increased lipid peroxidation in liver tissue. These effects were accompanied by severe histopathological changes to the hepatocytes. Intravenous injection of nano-HAp after irradiation has significant therapeutic potential against irradiation-induced liver damage because the treatment with nano-HAp restored antioxidant activity in the liver, antagonized the significant changes in the levels of IL-2, IL-6, TNF-α, IFN-γ, and restored the tissue level of paraoxonase 1, gamma glutamyl, ALT, and AST. Administering nano-HAp seemed to relieve the pathological changes induced by γ-radiation. Based on these results, it could be concluded that nano-HAp may have a therapeutic effect against liver dysfunction induced by γ-radiation through antagonizing the generation of free radicals and enhancing the antioxidant defense mechanisms.

Comparison of radiosensitivity response to acute and chronic gamma irradiation in colored wheat

We aimed to investigate the biological responses induced by acute and chronic gamma irradiation in colored wheat seeds rich in natural antioxidants. After acute and chronic irradiation, the phenotypic effects on plant growth, germination rate, seedling height, and root length were examined, and the biochemical changes were investigated by analyzing the expression of antioxidant enzyme-related genes, antioxidant enzyme activities, and total antioxidant capacity. High dosages of chronic radiation reduced plant growth compared with the controls. Electron spin resonance measurement and 2,2-diphenyl-1-picrylhydrazyl activity analysis showed lower amount of free radicals in colored wheat seeds on chronic irradiation with low dosage of gamma rays compared to seeds subjected to acute irradiation. Expression levels of anthocyanin biosynthesis genes, antioxidant-related genes, and antioxidant enzyme activity in seeds and young leaves of seedling showed diverse effects in response to different dosages and types of gamma irradiation. This suggests that phenotype is affected by the dosage and type of gamma radiation, and the phytochemicals in colored wheat seeds involved in antioxidant activity to scavenge free radicals respond differently to irradiation types. This provides evidence that acute and chronic exposure to radiation have different effects on seeds and young leaves after germination.

Small de novo CNVs as biomarkers of parental exposure to low doses of ionizing radiation of caesium-137

The radiological accident in Goiania in 1987 caused a trail of human contamination, animal, plant and environmental by a radionuclide. Exposure to ionizing radiation results in different types of DNA lesions. The mutagenic effects of ionizing radiation on the germline are special concern because they can endures for several generations, leading to an increase in the rate of mutations in children of irradiated parents. Thus, to evaluate the biological mechanisms of ionizing radiation in somatic and germline cells, with consequent determination of the rate mutations, is extremely important for the estimation of genetic risks. Recently it was established that Chromosomal Microarray Analysis is an important tool for detecting wide spectra of gains or losses in the human genome. Here we present the results of the effect of accidental exposure to low doses of ionizing radiation on the formation of CNVs in the progeny of a human population accidentally exposed to Caesium-137 during the radiological accident in Goiânia, Brazil.

DNA Topoisomerase IB as a Potential Ionizing Radiation Exposure and Dose Biomarker

In radiation exposure scenarios where physical dosimetry is absent or inefficient, dose estimation must rely on biological markers. A reliable biomarker is of utmost importance in correlating biological system changes with radiation exposure. Human DNA topoisomerase ІB (topo І) is a ubiquitous nuclear enzyme, which is involved in essential cellular processes, including transcription, DNA replication and DNA repair, and is the target of anti-cancer drugs. It has been shown that the cellular activity of this enzyme is significantly sensitive to various DNA lesions, including radiation-induced DNA damages. Therefore, we investigated the potential of topo I as a biomarker of radiation exposure and dose. We examined the effect of exposure of different human cells to beta, X-ray and gamma radiation on the cellular catalytic activity of topo I. The results demonstrate a significant reduction in the DNA relaxation activity of topo I after irradiation and the level of the reduction was correlated with radiation dose. In normal human peripheral blood lymphocytes, exposure for 3 h to an integral dose of 0.065 mGy from tritium reduced the enzyme activity to less than 25%. In MG-63 osteoblast-like cells and in human pulmonary fibroblast (HPF) cells exposed to gamma radiation from a ⁶⁰Co source (up to 2 Gy) or to X rays (up to 2.8 Gy), a significant decrease in topo I catalytic activity was also observed. We observed that the enzyme-protein level was not altered but was partially posttranslational modified by ADP-ribosylation of the enzyme protein that is known to reduce topo I activity. The results of this study suggest that the decrease in the cellular topo I catalytic activity after low-dose exposure to different radiation types may be considered as a novel biomarker of ionizing radiation exposure and dose. For this purpose, a suitable ELISA-based method for large-scale analysis of radiation-induced topo I modification is under development.

Radiation Exposure in Endovascular Infra-Renal Aortic Aneurysm Repair and Factors that Influence It

Objective

The endovascular repair of aortic abdominal aneurysms exposes the patients and surgical team to ionizing radiation with risk of direct tissue damage and induction of gene mutation. This study aims to describe our standard of radiation exposure in endovascular aortic aneurysm repair and the factors that influence it.

Methods

Retrospective analysis of a prospective database of patients with abdominal infra-renal aortic aneurysms submitted to endovascular repair. This study evaluated the radiation doses (dose area product (DAP)), fluoroscopy durations and their relationships to the patients, aneurysms, and stent-graft characteristics.

Results

This study included 127 patients with a mean age of 73 years. The mean DAP was 4.8 mGy.m², and the fluoroscopy time was 21.8 minutes. Aortic bilateral iliac aneurysms, higher body mass index, aneurysms with diameters larger than 60 mm, necks with diameters larger than 28 mm, common iliac arteries with diameters larger than 20 mm, and neck angulations superior to 50 degrees were associated with an increased radiation dose. The number of anatomic risk factors present was associated with increased radiation exposure and fluoroscopy time, regardless of the anatomical risk factors.

Conclusion

The radiation exposure during endovascular aortic aneurysm repair is significant (mean DAP 4.8 mGy.m²) with potential hazards to the surgical team and the patients. The anatomical characteristics of the aneurysm, patient characteristics, and the procedure's technical difficulty were all related to increased radiation exposure during endovascular aortic aneurysm repair procedures. Approximately 40% of radiation exposure can be explained by body mass index, neck angulation, aneurysm diameter, neck diameter, and aneurysm type.

Nonhuman primates as models for the discovery and development of radiation countermeasures

INTRODUCTION

Despite significant scientific advances over the past six decades toward the development of safe and effective radiation countermeasures for humans using animal models, only two pharmaceutical agents have been approved by United States Food and Drug Administration (US FDA) for hematopoietic acute radiation syndrome (H-ARS). Additional research efforts are needed to further develop large animal models for improving the prediction of clinical safety and effectiveness of radiation countermeasures for ARS and delayed effects of acute radiation exposure (DEARE) in humans. Area covered: The authors review the suitability of animal models for the development of radiation countermeasures for ARS following the FDA Animal Rule with a special focus on nonhuman primate (NHP) models of ARS. There are seven centers in the United States currently conducting studies with irradiated NHPs, with the majority of studies being conducted with rhesus monkeys. Expert opinion: The NHP model is considered the gold standard animal model for drug development and approval by the FDA. The lack of suitable substitutes for NHP models for predicting response in humans serves as a bottleneck for the development of radiation countermeasures. Additional large animal models need to be characterized to support the development and FDA-approval of new radiation countermeasures.

Generalized multiple indicators, multiple causes measurement error models

Generalized Multiple Indicators, Multiple Causes Measurement Error Models (G-MIMIC ME) can be used to study the effects of an unobservable latent variable on a set of outcomes when the causes of the latent variables are unobserved. The errors associated with the unobserved causal variables can be due to either bias recall or day-to-day variability. Another potential source of error, the Berkson error, is due to individual variations that arise from the assignment of group data to individual subjects. In this article, we accomplish the following: (a) extend the classical linear MIMIC models to allow both Berkson and classical measurement errors where the distributions of the outcome variables belong in the exponential family, (b) develop likelihood based estimation methods using the MC-EM algorithm and (c) estimate the variance of the classical measurement error associated with the approximation of the amount of radiation dose received by atomic bomb survivors at the time of their exposure. The G-MIMIC ME model is applied to study the effect of genetic damage, a latent construct based on exposure to radiation, and the effect of radiation dose on physical indicators of genetic damage.

Microfluidics as a new tool in radiation biology

Ionizing radiations interact with molecules at the cellular and molecular levels leading to several biochemical modifications that may be responsible for biological effects on tissue or whole organisms. The study of these changes is difficult because of the complexity of the biological response(s) to radiations and the lack of reliable models able to mimic the whole molecular phenomenon and different communications between the various cell networks, from the cell activation to the macroscopic effect at the tissue or organismal level. Microfluidics, the science and technology of systems that can handle small amounts of fluids in confined and controlled environment, has been an emerging field for several years. Some microfluidic devices, even at early stages of development, may already help radiobiological research by proposing new approaches to study cellular, tissue and total-body behavior upon irradiation. These devices may also be used in clinical biodosimetry since microfluidic technology is frequently developed for integrating complex bioassay chemistries into automated user-friendly, reproducible and sensitive analyses. In this review, we discuss the use, numerous advantages, and possible future of microfluidic technology in the field of radiobiology. We will also examine the disadvantages and required improvements for microfluidics to be fully practical in radiation research and to become an enabling tool for radiobiologists and radiation oncologists.

Use of biomarkers for assessing radiation injury and efficacy of countermeasures

Several candidate drugs for acute radiation syndrome (ARS) have been identified that have low toxicity and significant radioprotective and radiomitigative efficacy. Inasmuch as exposing healthy human volunteers to injurious levels of radiation is unethical, development and approval of new radiation countermeasures for ARS are therefore presently based on animal studies and Phase I safety study in healthy volunteers. The Animal Efficacy Rule, which underlies the Food and Drug Administration approval pathway, requires a sound understanding of the mechanisms of injury, drug efficacy, and efficacy biomarkers. In this context, it is important to identify biomarkers for radiation injury and drug efficacy that can extrapolate animal efficacy results, and can be used to convert drug doses deduced from animal studies to those that can be efficacious when used in humans. Here, we summarize the progress of studies to identify candidate biomarkers for the extent of radiation injury and for evaluation of countermeasure efficacy.

Utilization of cytogenetic biomarkers as a tool for assessment of radiation injury and evaluation of radiomodulatory effects of various medicinal plants - a review

Systematic biological measurement of “cytogenetic endpoints” has helped phenomenally in assessment of risks associated with radiation exposure. There has been a surge in recent times for the usage of radioactive materials in health care, agriculture, industrial, and nuclear power sectors. The likelihood of radiation exposure from accidental or occupational means is always higher in an overburdened ecosystem that is continuously challenged to meet the population demands. Risks associated with radiation exposure in this era of modern industrial growth are minimal as international regulations for maintaining the safety standards are stringent and strictly adhered to, however, a recent disaster like “Fukushima” impels us to think beyond. The major objective of radiobiology is the development of an orally effective radio-modifier that provides protection from radiation exposure. Once available for mass usage, these compounds will not only be useful for providing selective protection against accidental and occupational radiation exposure but also help to permit use of higher doses of radiation during treatment of various malignancies curtailing unwarranted adverse effects imposed on normal tissues. Bio-active compounds isolated from natural sources enriched with antioxidants possess unique immune-modulating properties, thus providing a double edged benefit over synthetic radioprotectors. We aim to provide here a comprehensive overview of the various agents originating from plant sources that portrayed promising radioprotection in various experimental models with special emphasis on studies that used cytogenetic biomarkers. The agents will include crude extracts of various medicinal plants, purified fractions, and herbal preparations.

Modulation of Radiation Response by the Tetrahydrobiopterin Pathway

Ionizing radiation (IR) is an integral component of our lives due to highly prevalent sources such as medical, environmental, and/or accidental. Thus, understanding of the mechanisms by which radiation toxicity develops is crucial to address acute and chronic health problems that occur following IR exposure. Immediate formation of IR-induced free radicals as well as their persistent effects on metabolism through subsequent alterations in redox mediated inter- and intracellular processes are globally accepted as significant contributors to early and late effects of IR exposure. This includes but is not limited to cytotoxicity, genomic instability, fibrosis and inflammation. Damage to the critical biomolecules leading to detrimental long-term alterations in metabolic redox homeostasis following IR exposure has been the focus of various independent investigations over last several decades. The growth of the "omics" technologies during the past decade has enabled integration of "data from traditional radiobiology research", with data from metabolomics studies. This review will focus on the role of tetrahydrobiopterin (BH4), an understudied redox-sensitive metabolite, plays in the pathogenesis of post-irradiation normal tissue injury as well as how the metabolomic readout of BH4 metabolism fits in the overall picture of disrupted oxidative metabolism following IR exposure.

Biological dose assessment after low-dose overexposures in nuclear medicine

This paper focuses on the application of dicentric chromosome assay biodosimetry in cases of low-dose overexposures to professionals working in nuclear medicine and discusses how to present the results and associated uncertainties, to make possible a better understanding of biodosimetric reports. Five examples are presented of low or possibly zero exposure dose that are illustrative of typical problems that arise in occupational settings, in this instance in nuclear medicine departments. This is a scenario of minor concern in terms of health consequences but it is relevant in legal terms. They pose dilemmas for investigators but biological dosimetry can make a valuable contribution to resolving the cases.

Overview of the principles and practice of biodosimetry

The principle of biodosimetry is to utilize changes induced in the individual by ionizing radiation to estimate the dose and, if possible, to predict or reflect the clinically relevant response, i.e., the biological consequences of the dose. Ideally, the changes should be specific for ionizing radiation, and the response should be unaffected by prior medical or physiological variations among subjects, including changes that might be caused by the stress and trauma from a radiation event. There are two basic types of biodosimetry with different and often complementary characteristics: those based on changes in biological parameters such as gene activation or chromosomal abnormalities and those based on physical changes in tissues (detected by techniques such as EPR). In this paper, we consider the applicability of the various techniques for different scenarios: small- and large-scale exposures to levels of radiation that could lead to the acute radiation syndrome and exposures with lower doses that do not need immediate care, but should be followed for evidence of long-term consequences. The development of biodosimetry has been especially stimulated by the needs after a large-scale event where it is essential to have a means to identify those individuals who would benefit from being brought into the medical care system. Analyses of the conventional methods officially recommended for responding to such events indicate that these methods are unlikely to achieve the results needed for timely triage of thousands of victims. Emerging biodosimetric methods can fill this critically important gap.

Method for validating radiobiological samples using a linear accelerator

There is an immediate need for rapid triage of the population in case of a large scale exposure to ionizing radiation. Knowing the dose absorbed by the body will allow clinicians to administer medical treatment for the best chance of recovery for the victim. In addition, today's radiotherapy treatment could benefit from additional information regarding the patient's sensitivity to radiation before starting the treatment. As of today, there is no system in place to respond to this demand. This paper will describe specific procedures to mimic the effects of human exposure to ionizing radiation creating the tools for optimization of administered radiation dosimetry for radiotherapy and/or to estimate the doses of radiation received accidentally during a radiation event that could pose a danger to the public. In order to obtain irradiated biological samples to study ionizing radiation absorbed by the body, we performed ex-vivo irradiation of human blood samples using the linear accelerator (LINAC). The LINAC was implemented and calibrated for irradiating human whole blood samples. To test the calibration, a 2 Gy test run was successfully performed on a tube filled with water with an accuracy of 3% in dose distribution. To validate our technique the blood samples were ex-vivo irradiated and the results were analyzed using a gene expression assay to follow the effect of the ionizing irradiation by characterizing dose responsive biomarkers from radiobiological assays. The response of 5 genes was monitored resulting in expression increase with the dose of radiation received. The blood samples treated with the LINAC can provide effective irradiated blood samples suitable for molecular profiling to validate radiobiological measurements via the gene-expression based biodosimetry tools.

Radiation-induced changes in serum lipidome of head and neck cancer patients

Cancer radiotherapy (RT) induces response of the whole patient’s body that could be detected at the blood level. We aimed to identify changes induced in serum lipidome during RT and characterize their association with doses and volumes of irradiated tissue. Sixty-six patients treated with conformal RT because of head and neck cancer were enrolled in the study. Blood samples were collected before, during and about one month after the end of RT. Lipid extracts were analyzed using MALDI-oa-ToF mass spectrometry in positive ionization mode. The major changes were observed when pre-treatment and within-treatment samples were compared. Levels of several identified phosphatidylcholines, including (PC34), (PC36) and (PC38) variants, and lysophosphatidylcholines, including (LPC16) and (LPC18) variants, were first significantly decreased and then increased in post-treatment samples. Intensities of changes were correlated with doses of radiation received by patients. Of note, such correlations were more frequent when low-to-medium doses of radiation delivered during conformal RT to large volumes of normal tissues were analyzed. Additionally, some radiation-induced changes in serum lipidome were associated with toxicity of the treatment. Obtained results indicated the involvement of choline-related signaling and potential biological importance of exposure to clinically low/medium doses of radiation in patient’s body response to radiation.

Intragenic controls utilizing radiation-induced alternative transcript regions improves gene expression biodosimetry

Ionizing-radiation exposure can be life threatening if given to the whole body. In addition, whole body radiation exposure can affect large numbers of people such as after a nuclear reactor accident, a nuclear explosion or a radiological terrorist attack. In these cases, an accurate biodosimeter is essential for triage management. One of the problems for biodosimetry in general is the interindividual variation before and after exposure, which can make it challenging to assign an accurate dose. To begin to address this challenge, lymphocyte cell lines were exposed to 0, 1, 2 and 5 Gy ionizing radiation from a ¹³⁷Cs source at a dose rate of 0.6 Gy/min. Alternative transcripts with regions showing large differential responses to ionizing radiation were determined from exon array data. Gene expression analysis was then performed on isolated mRNA using qRT-PCR with normalization to intergenic (PGK1, GAPDH) and novel intragenic regions for candidate radiation-responsive genes, PPM1D and MDM2. Our studies show that the use of a cis-associated expression reference improved the potential dose prediction approximately 2.3-8.3 fold and provided an advantage for dose prediction compared to distantly or trans-located control ionizing radiation nonresponsive genes. This approach also provides an alternative gene expression normalization method to potentially reduce interindividual variations when untreated basal gene expression levels are unavailable. Using associated noninduced regions of ionizing radiation-induced genes provides a way to estimate basal gene expression in the irradiated sample. This strategy can be utilized as a biodosimeter on its own or to enhance other gene expression candidates for biodosimetry. This normalization strategy may also be generally applicable for other quantitative PCR strategies where normalization is required for a particular response.

Electron paramagnetic resonance dosimetry for a large-scale radiation incident

With possibilities for radiation terrorism and intensified concerns about nuclear accidents since the recent Fukushima Daiichi event, the potential exposure of large numbers of individuals to radiation that could lead to acute clinical effects has become a major concern. For the medical community to cope with such an event and avoid overwhelming the medical care system, it is essential to identify not only individuals who have received clinically significant exposures and need medical intervention but also those who do not need treatment. The ability of electron paramagnetic resonance to measure radiation-induced paramagnetic species, which persist in certain tissues (e.g., teeth, fingernails, toenails, bone, and hair), has led to this technique becoming a prominent method for screening significantly exposed individuals. Although the technical requirements needed to develop this method for effective application in a radiation event are daunting, remarkable progress has been made. In collaboration with General Electric and through funding committed by the Biomedical Advanced Research and Development Authority, electron paramagnetic resonance tooth dosimetry of the upper incisors is being developed to become a Food and Drug Administration-approved and manufacturable device designed to carry out triage for a threshold dose of 2 Gy. Significant progress has also been made in the development of electron paramagnetic resonance nail dosimetry based on measurements of nails in situ under point-of-care conditions, and in the near future this may become a second field-ready technique. Based on recent progress in measurements of nail clippings, it is anticipated that this technique may be implementable at remotely located laboratories to provide additional information when the measurements of dose on-site need to be supplemented. The authors conclude that electron paramagnetic resonance dosimetry is likely to be a useful part of triage for a large-scale radiation incident.