Metabolomic applications in radiation biodosimetry: exploring radiation effects through small molecules

FAILLA MEMORIAL LECTURE How We Got Here: One Laboratory's Odyssey in the Field of Radiation-Inducible Genes

This review focuses on early discoveries that contributed to our understanding and the scope of transcriptional responses after radiation damage. Before the development of modern approaches to assess overall global transcriptomic responses, the idea that mammalian cells could respond to DNA-damaging agents in a manner analogous to bacteria was not generally accepted. To investigate this possibility, the development of technology to identify differentially expressed low-abundance transcripts substantially facilitated our appreciation that DNA damaging agents like UV radiation and subsequently ionizing radiation did in fact produce robust transcriptional responses. Here we focus on our identification and characterization of radiation-inducible genes, and how even early studies on stress gene signaling highlighted the broad scope of transcriptional responses to radiation damage. Since then, the central role of transcriptional responses to radiation injury in maintaining genome integrity has been highlighted in many processes, including cell cycle checkpoint control, resistance to cancer by p53 and other key factors, cell senescence, and metabolism.

Host microbiome depletion attenuates biofluid metabolite responses following radiation exposure

Development of novel biodosimetry assays and medical countermeasures is needed to obtain a level of radiation preparedness in the event of malicious or accidental mass exposures to ionizing radiation (IR). For biodosimetry, metabolic profiling with mass spectrometry (MS) platforms has identified several small molecules in easily accessible biofluids that are promising for dose reconstruction. As our microbiome has profound effects on biofluid metabolite composition, it is of interest how variation in the host microbiome may affect metabolomics based biodosimetry. Here, we 'knocked out' the microbiome of male and female C57BL/6 mice (Abx mice) using antibiotics and then irradiated (0, 3, or 8 Gy) them to determine the role of the host microbiome on biofluid radiation signatures (1 and 3 d urine, 3 d serum). Biofluid metabolite levels were compared to a sham and irradiated group of mice with a normal microbiome (Abx-con mice). To compare post-irradiation effects in urine, we calculated the Spearman's correlation coefficients of metabolite levels with radiation dose. For selected metabolites of interest, we performed more detailed analyses using linear mixed effect models to determine the effects of radiation dose, time, and microbiome depletion. Serum metabolite levels were compared using an ANOVA. Several metabolites were affected after antibiotic administration in the tryptophan and amino acid pathways, sterol hormone, xenobiotic and bile acid pathways (urine) and lipid metabolism (serum), with a post-irradiation attenuative effect observed for Abx mice. In urine, dose×time interactions were supported for a defined radiation metabolite panel (carnitine, hexosamine-valine-isoleucine [Hex-V-I], creatine, citric acid, and Nε,Nε,Nε-trimethyllysine [TML]) and dose for N1-acetylspermidine, which also provided excellent (AUROC ≥ 0.90) to good (AUROC ≥ 0.80) sensitivity and specificity according to the area under the receiver operator characteristic curve (AUROC) analysis. In serum, a panel consisting of carnitine, citric acid, lysophosphatidylcholine (LysoPC) (14:0), LysoPC (20:3), and LysoPC (22:5) also gave excellent to good sensitivity and specificity for identifying post-irradiated individuals at 3 d. Although the microbiome affected the basal levels and/or post-irradiation levels of these metabolites, their utility in dose reconstruction irrespective of microbiome status is encouraging for the use of metabolomics as a novel biodosimetry assay.

Metabolomic Profiles in Tissues of Nonhuman Primates Exposed to Either Total- or Partial-Body Radiation

A complex cascade of systemic and tissue-specific responses induced by exposure to ionizing radiation can lead to functional impairment over time in the surviving population. Current methods for management of survivors of unintentional radiation exposure episodes rely on monitoring individuals over time for the development of adverse clinical symptoms due to the lack of predictive biomarkers for tissue injury. In this study, we report on changes in metabolomic and lipidomic profiles in multiple tissues of nonhuman primates (NHPs) that received either 4.0 Gy or 5.8 Gy total-body irradiation (TBI) of 60Co gamma rays, and 4.0 or 5.8 Gy partial-body irradiation (PBI) from LINAC-derived photons and were treated with a promising radiation countermeasure, gamma-tocotrienol (GT3). These include small molecule alterations that correlate with radiation effects in the jejunum, lung, kidney, and spleen of animals that either survived or succumbed to radiation toxicities over a 30-day period. Radiation-induced metabolic changes in tissues were observed in animals exposed to both doses and types of radiation, but were partially alleviated in GT3-treated and irradiated animals, with lung and spleen being most responsive. The majority of the pathways protected by GT3 treatment in these tissues were related to glucose metabolism, inflammation, and aldarate metabolism, suggesting GT3 may exert radioprotective effects in part by sparing these pathways from radiation-induced dysregulation. Taken together, the results of our study demonstrate that the prophylactic administration of GT3 results in metabolic and lipidomic shifts that likely provide an overall advantage against radiation injury. This investigation is among the first to highlight the use of a molecular phenotyping approach in a highly translatable NHP model of partial- and total-body irradiation to determine the underlying physiological mechanisms involved in the radioprotective efficacy of GT3.

Global LC-MS/MS targeted metabolomics using a combination of HILIC and RP LC separation modes on an organic monolithic column based on 1-vinyl-1,2,4-triazole

The paper presents an LC-MS/MS-based approach to targeted screening of both polar and non-polar metabolites using a synthesized monolithic column which is a copolymer of styrene, divinylbenzene, and 1-vinyl-1,2,4-triazole. It was shown that this column in combination with eluents 20 mM (NH4)2CO3 + NH3 (pH = 9.8, eluent A) and ACN (eluent B) allows for separation of metabolites of different nature in two modes, HILIC and RP LC, and these methods are mutually complementary. A combination of analyses based on these two modes was proposed, allowing detection of about 400 metabolites in a total time of less than 30 min. Comparison of the developed method with those utilizing commercially available columns with sorbents of various types showed that it could provide a broader metabolite coverage. Using the developed approach, metabolomic screening of dried blood spots samples of mice exposed with X-ray was performed, and metabolites that could be considered as possible markers of irradiation exposure and organ tissue damage were detected. Analysis of marker metabolites revealed metabolic pathways that were altered by radiation exposure. Comparison of the results with literature data showed the effectiveness of the developed metabolomic screening approach.

Metabolomic Changes in Plasma of Preterminal Stage of Rhesus Nonhuman Primates Exposed to Lethal Dose of Radiation

Ionizing radiation exposure is known to induce molecular and cellular injury, inflicting a cascade of potentially catastrophic events leading to tissue and organ damage. Metabolomic analysis allows for the identification and quantification of small molecules downstream of genomic changes induced by radiation exposure. We aimed to characterize metabolomic changes that underscore the prefinal stage of lethally irradiated rhesus nonhuman primates (NHPs). Peripheral blood was drawn at baseline, post-exposure, as well as at the preterminal stage in NHPs (immediately prior to death in moribund NHPs) that did not survive exposure with 7.2 Gy total-body radiation (LD70/60). Herein, we analyzed global metabolomic changes using ultra-performance liquid chromatography (UPLC) quadrupole time-of-flight mass spectrometry (QTOF-MS) in plasma samples of NHPs collected at various timepoints in relation to irradiation. The overall goal was to identify metabolic shifts present immediately prior to death. Our findings showed radiation induced significant time-dependent metabolic perturbations when compared to pre-irradiation profiles, particularly in glycerophospholipid metabolism and steroid hormone biosynthesis and metabolism pathways. These findings provide valuable insights for identifying biomarkers for lethality, which may be helpful for triage during a mass casualty scenario.

Identification and validation of diagnostic biomarkers for intrahepatic cholestasis of pregnancy based on untargeted and targeted metabolomics analyses of urine metabolite profiles

BACKGROUND

Intrahepatic cholestasis of pregnancy (ICP) is a prevalent pregnancy-specific complication that presents with maternal itching and elevated serum bile acid levels. ICP is associated with unfavorable pregnancy outcomes, severely decreasing the pregnant woman's quality of life. Timely identification of ICP is crucial for effective management and improved outcomes.

METHODS

We collected urine samples from 8 patients with ICP and 8 healthy individuals. We used Liquid Chromatography-Mass Spectrometry (LC-MS) to detect metabolite expression levels, then conducted a series of bioinformatic analyses to explore the potential biological meanings of differentially expressed metabolites, and preliminarily discovered several candidate biomarkers. To validate these candidate biomarkers, we performed Gas Chromatography-Mass Spectrometry (GC-MS) detection and analyzed their diagnostic values using receiver operating characteristic (ROC) curve.

RESULTS

Untargeted metabolomics data showed that 6129 positive peaks and 6218 negative peaks were extracted from each specimen. OPLS-DA analysis and the heat map for cluster analysis showed satisfactory capability in discriminating ICP specimens from controls. Subsequent analysis extracted 64 significantly differentially expressed metabolites, which could be potential biomarkers for diagnosis of ICP. Based on the KEGG enrichment analyses, six candidate biomarkers were preliminarily identified. Two most promising biomarkers (3-hydroxypropionic acid and uracil) were validated by targeted metabolomics analyses with the area under the curve (AUC) of 0.920 and 0.850 respectively.

CONCLUSION

Based on preliminary screening from untargeted metabolomics and subsequent validation through targeted metabolomics, 3-hydroxypropionic acid and uracil were identified as promising diagnostic biomarkers for ICP.

Novel biomarkers for acute radiation injury and countermeasures using large and small animal models and multi-omics approach

Threats of radiological or nuclear disasters are of serious concern and a top priority for government agencies involved in domestic security and public health preparedness. There is a need for sensitive bioassays for biodosimetric assessments of radiation exposures originating from unanticipated nuclear/radiological events. The Food and Drug Administration Animal Rule approval pathway requires an in-depth understanding of the mechanisms of radiation injury, drug efficacy and biomarkers for radiation medical countermeasure approval. Biomarkers can be helpful for extrapolating the efficacious countermeasure dose in animals to humans. We summarised here our studies to identify candidate biomarkers for the acute radiation injury using various omic platforms (metabolomics/lipidomics, proteomics, microbiome and transcriptomics/microRNA) using murine and non-human primate models conducted in our laboratory. Multi-omic platforms appear to be highly useful in assessing radiation exposure levels and for identifying biomarkers of radiation injury and countermeasure efficacy, which can expedite the regulatory approval of countermeasures.

Metabolomic Signatures Associated with Radiation-Induced Lung Injury by Correlating Lung Tissue to Plasma in a Rat Model

The lung has raised significant concerns because of its radiosensitivity. Radiation-induced lung injury (RILI) has a serious impact on the quality of patients' lives and limits the effect of radiotherapy on chest tumors. In clinical practice, effective drug intervention for RILI remains to be fully elucidated. Therefore, an in-depth understanding of the biological characteristics is essential to reveal the mechanisms underlying the complex biological processes and discover novel therapeutic targets in RILI. In this study, Wistar rats received 0, 10, 20 or 35 Gy whole-thorax irradiation (WTI). Lung and plasma samples were collected within 5 days post-irradiation. Then, these samples were processed using liquid chromatography-mass spectrometry (LC-MS). A panel of potential plasma metabolic markers was selected by correlation analysis between the lung tissue and plasma metabolic features, followed by the evaluation of radiation injury levels within 5 days following whole-thorax irradiation (WTI). In addition, the multiple metabolic dysregulations primarily involved amino acids, bile acids and lipid and fatty acid β-oxidation-related metabolites, implying disturbances in the urea cycle, intestinal flora metabolism and mitochondrial dysfunction. In particular, the accumulation of long-chain acylcarnitines (ACs) was observed as early as 2 d post-WTI by dynamic plasma metabolic data analysis. Our findings indicate that plasma metabolic markers have the potential for RILI assessment. These results reveal metabolic characteristics following WTI and provide new insights into therapeutic interventions for RILI.

Variable Dose Rates in Realistic Radiation Exposures: Effects on Small Molecule Markers of Ionizing Radiation in the Murine Model

Novel biodosimetry assays for use in preparedness and response to potential malicious attacks or nuclear accidents would ideally provide accurate dose reconstruction independent of the idiosyncrasies of a complex exposure to ionizing radiation. Complex exposures will consist of dose rates spanning the low dose rates (LDR) to very high-dose rates (VHDR) that need to be tested for assay validation. Here, we investigate how a range of relevant dose rates affect metabolomic dose reconstruction at potentially lethal radiation exposures (8 Gy in mice) from an initial blast or subsequent fallout exposures compared to zero or sublethal exposures (0 or 3 Gy in mice) in the first 2 days, which corresponds to an integral time individuals will reach medical facilities after a radiological emergency. Biofluids (urine and serum) were collected from both male and female 9-10-week-old C57BL/6 mice at 1 and 2 days postirradiation (total doses of 0, 3 or 8 Gy) after a VHDR of 7 Gy/s. Additionally, samples were collected after a 2-day exposure consisting of a declining dose rate (1 to 0.004 Gy/min) recapitulating the 7:10 rule-of-thumb time dependency of nuclear fallout. Overall similar perturbations were observed in both urine and serum metabolite concentrations irrespective of sex or dose rate, with the exception of xanthurenic acid in urine (female specific) and taurine in serum (VHDR specific). In urine, we developed identical multiplex metabolite panels (N6, N6,N6-trimethyllysine, carnitine, propionylcarnitine, hexosamine-valine-isoleucine, and taurine) that could identify individuals receiving potentially lethal levels of radiation from the zero or sublethal cohorts with excellent sensitivity and specificity, with creatine increasing model performance at day 1. In serum, individuals receiving a 3 or 8 Gy exposure could be identified from their pre-irradiation samples with excellent sensitivity and specificity, however, due to a lower dose response the 3 vs. 8 Gy groups could not be distinguished from each other. Together with previous results, these data indicate that dose-rate-independent small molecule fingerprints have potential in novel biodosimetry assays.

Protein biomarkers for radiation injury and testing of medical countermeasure efficacy: promises, pitfalls, and future directions

INTRODUCTION

Radiological/nuclear accidents, hostile military activity, or terrorist strikes have the potential to expose a large number of civilians and military personnel to high doses of radiation resulting in the development of acute radiation syndrome and delayed effects of exposure. Thus, there is an urgent need for sensitive and specific assays to assess the levels of radiation exposure to individuals. Such radiation exposures are expected to alter primary cellular proteomic processes, resulting in multifaceted biological responses.

AREAS COVERED

This article covers the application of proteomics, a promising and fast developing technology based on quantitative and qualitative measurements of protein molecules for possible rapid measurement of radiation exposure levels. Recent advancements in high-resolution chromatography, mass spectrometry, high-throughput, and bioinformatics have resulted in comprehensive (relative quantitation) and precise (absolute quantitation) approaches for the discovery and accuracy of key protein biomarkers of radiation exposure. Such proteome biomarkers might prove useful for assessing radiation exposure levels as well as for extrapolating the pharmaceutical dose of countermeasures for humans based on efficacy data generated using animal models.

EXPERT OPINION

The field of proteomics promises to be a valuable asset in evaluating levels of radiation exposure and characterizing radiation injury biomarkers.

Paper-Based Vertical Flow Immunoassay for the Point-of-Care Multiplex Detection of Radiation Dosimetry Genes

In a nuclear or radiological incident, first responders must quickly and accurately measure radiation exposure among civilians as medical countermeasures are radiation dose-dependent and time-sensitive. Although several approaches have been explored to measure absorbed radiation dose, there is an important need to develop point-of-care (POC) bioassay devices that can be used immediately to triage thousands of individuals potentially exposed to radiation. Here we present a proof-of-concept study showing the use of a paper-based vertical flow immunoassay (VFI) to detect radiation dosimetry genes. Using labeled primers during amplification and a multiplex membrane, our results showed that the nucleic acid VFI can simultaneously detect two biodosimetry genes, CDKN1A and DDB2, as well as one housekeeping gene MRPS5. The assay demonstrated good linearity and precision with an inter- and intra-assay coefficient of variance <20% and <10%, respectively. Moreover, the assay showed its ability to discriminate non-irradiated controls (0 Gy) from irradiated samples (1 + 2 Gy) with an overall sensitivity of 62.5% and specificity of 100% (AUC = 0.8672, 95% CI: 0.723-1.000; p = 0.004). Interestingly, the gene combination also showed a dose-dependent response for 0, 1, and 2 Gy, similar to data obtained by real-time PCR benchmark. These preliminary results suggest that a VFI platform can be used to detect simultaneously multiple genes that can be then quantified, thus offering a new approach for a POC biodosimetry assay that could be rapidly deployed on-site to test a large population and help triage and medical management after radiological event.

Transcriptome profile changes in the jejunum of nonhuman primates exposed to supralethal dose of total- or partial-body radiation

The risk of exposure of the general public or military personnel to high levels of ionizing radiation from nuclear weapons or radiological accidents is a dire national security matter. The development of advanced molecular biodosimetry methods, those that measure biological response, such as transcriptomics, to screen large populations of radiation-exposed victims is key to improving survival outcomes during radiological mass casualty scenarios. In this study, nonhuman primates were exposed to either 12.0 Gy cobalt-60 gamma (total-body irradiation, TBI) or X-ray (partial-body irradiation, PBI) 24 h after administration of a potential radiation medical countermeasure, gamma-tocotrienol (GT3). Changes in the jejunal transcriptomic profiles in GT3-treated and irradiated animals were compared to healthy controls to assess the extent of radiation damage. No major effect of GT3 on radiation-induced transcriptome at this radiation dose was identified. About 80% of the pathways with a known activation or repression state were commonly observed between both exposures. Several common pathways activated due to irradiation include FAK signaling, CREB signaling in the neurons, phagosome formation, and G-protein coupled signaling pathway. Sex-specific differences associated with excessive mortality among irradiated females were identified in this study, including Estrogen receptor signaling. Differential pathway activation was also identified across PBI and TBI, pointing towards altered molecular response for different degrees of bone marrow sparing and radiation doses. This study provides insight into radiation-induced changes in jejunal transcriptional profiles, supporting the investigation for the identification of biomarkers for radiation injury and countermeasure efficacy.

Radiation biology workforce in the United States

In recent decades, the principal goals of participants in the field of radiation biologists have included defining dose thresholds for cancer and non-cancer endpoints to be used by regulators, clinicians and industry, as well as informing on best practice radiation utilization and protection applications. Importantly, much of this work has required an intimate relationship between "bench" radiation biology scientists and their target audiences (such as physicists, medical practitioners and epidemiologists) in order to ensure that the requisite gaps in knowledge are adequately addressed. However, despite the growing risk for public exposure to higher-than-background levels of radiation, e.g. from long-distance travel, the increasing use of ionizing radiation during medical procedures, the threat from geopolitical instability, and so forth, there has been a dramatic decline in the number of qualified radiation biologists in the U.S. Contributing factors are thought to include the loss of applicable training programs, loss of jobs, and declining opportunities for advancement. This report was undertaken in order to begin addressing this situation since inaction may threaten the viability of radiation biology as a scientific discipline.

Fatty acid metabolism and radiation-induced anti-tumor immunity

Fatty acid metabolic reprogramming has emerged as a major regulator of anti-tumor immune responses with large body of evidence that demonstrate its ability to impact the differentiation and function of immune cells. Therefore, depending on the metabolic cues that stem in the tumor microenvironment, the tumor fatty acid metabolism can tilt the balance of inflammatory signals to either promote or impair anti-tumor immune responses. Oxidative stressors such as reactive oxygen species generated from radiation therapy can rewire the tumor energy supply, suggesting that radiation therapy can further perturb the energy metabolism of a tumor by promoting fatty acid production. In this review, we critically discuss the network of fatty acid metabolism and how it regulates immune response especially in the context of radiation therapy.

ESTABLISHMENT OF THE IN VITRO DOSE-RESPONSE CALIBRATION CURVE FOR X-RAY-INDUCED MICRONUCLEI IN HUMAN LYMPHOCYTES

The cytokinesis-block micronucleus assay has proven to be a reliable technique for biological dosimetry. This study aimed to establish the dose-response curve for X-ray-induced micronucleus. Peripheral blood samples from three healthy donors were irradiated with various doses and scoring criteria by the micronuclei (MN) in binucleated cells. The results showed that the frequency of MN increased with the elevation of radiation dose. CABAS and Dose Estimate software were used to fit the MN and dose into a linear quadratic model, and the results were compared. The linear and quadratic coefficients obtained by the two software were basically the same and were comparable with published curves of similar radiation quality and dose rates by other studies. The dose-response curve established in this study can be used as an alternative method for in vitro dose reconstruction and provides a reliable tool for biological dosimetry in accidental or occupational radiation exposures.

Lung transcriptome of nonhuman primates exposed to total- and partial-body irradiation

The focus of radiation biodosimetry has changed recently, and a paradigm shift for using molecular technologies of omic platforms in addition to cytogenetic techniques has been observed. In our study, we have used a nonhuman primate model to investigate the impact of a supralethal dose of 12 Gy radiation on alterations in the lung transcriptome. We used 6 healthy and 32 irradiated animal samples to delineate radiation-induced changes. We also used a medical countermeasure, γ-tocotrienol (GT3), to observe any changes. We demonstrate significant radiation-induced changes in the lung transcriptome for total-body irradiation (TBI) and partial-body irradiation (PBI). However, no major influence of GT3 on radiation was noted in either comparison. Several common signaling pathways, including PI3K/AKT, GADD45, and p53, were upregulated in both exposures. TBI activated DNA-damage-related pathways in the lungs, whereas PTEN signaling was activated after PBI. Our study highlights the various transcriptional profiles associated with γ- and X-ray exposures, and the associated pathways include LXR/RXR activation in TBI, whereas pulmonary wound-healing and pulmonary fibrosis signaling was repressed in PBI. Our study provides important insights into the molecular pathways associated with irradiation that can be further investigated for biomarker discovery.

Transcriptomes of Wet Skin Biopsies Predict Outcomes after Ionizing Radiation Exposure with Potential Dosimetric Applications in a Mouse Model

Countermeasures for radiation diagnosis, prognosis, and treatment are trailing behind the proliferation of nuclear energy and weaponry. Radiation injury mechanisms at the systems biology level are not fully understood. Here, mice skin biopsies at h2, d4, d7, d21, and d28 after exposure to 1, 3, 6, or 20 Gy whole-body ionizing radiation were evaluated for the potential application of transcriptional alterations in radiation diagnosis and prognosis. Exposure to 20 Gy was lethal by d7, while mice who received 1, 3, or 6 Gy survived the 28-day time course. A Sammon plot separated samples based on survival and time points (TPs) within lethal (20 Gy) and sublethal doses. The differences in the numbers, regulation mode, and fold change of significantly differentially transcribed genes (SDTGs, p < 0.05 and FC > 2) were identified between lethal and sublethal doses, and down and upregulation dominated transcriptomes during the first post-exposure week, respectively. The numbers of SDTGs and the percentages of upregulated ones revealed stationary downregulation post-lethal dose in contrast to responses to sublethal doses which were dynamic and largely upregulated. Longitudinal up/downregulated SDTGs ratios suggested delayed and extended responses with increasing IR doses in the sublethal range and lethal-like responses in late TPs. This was supported by the distributions of common and unique genes across TPs within each dose. Several genes with potential dosimetric marker applications were identified. Immune, fibrosis, detoxification, hematological, neurological, gastric, cell survival, migration, and proliferation radiation response pathways were identified, with the majority predicted to be activated after sublethal and inactivated after lethal exposures, particularly during the first post-exposure week.

Application of radiation omics in the development of adverse outcome pathway networks: an example of radiation-induced cardiovascular disease

BACKGROUND

Epidemiological studies have indicated that exposure of the heart to doses of ionizing radiation as low as 0.5 Gy increases the risk of cardiac morbidity and mortality with a latency period of decades. The damaging effects of radiation to myocardial and endothelial structures and functions have been confirmed radiobiologically at high dose, but much less is known at low dose. Integration of radiation biology and epidemiology data is a recommended approach to improve the radiation risk assessment process. The adverse outcome pathway (AOP) framework offers a comprehensive tool to compile and translate mechanistic information into pathological endpoints which may be relevant for risk assessment at the different levels of a biological system. Omics technologies enable the generation of large volumes of biological data at various levels of complexity, from molecular pathways to functional organisms. Given the quality and quantity of available data across levels of biology, omics data can be attractive sources of information for use within the AOP framework. It is anticipated that radiation omics studies could improve our understanding of the molecular mechanisms behind the adverse effects of radiation on the cardiovascular system. In this review, we explored the available omics studies on radiation-induced cardiovascular disease (CVD) and their applicability to the proposed AOP for CVD.

RESULTS

The results of 80 omics studies published on radiation-induced CVD over the past 20 years have been discussed in the context of the AOP of CVD proposed by Chauhan et al. Most of the available omics data on radiation-induced CVD are from proteomics, transcriptomics, and metabolomics, whereas few datasets were available from epigenomics and multi-omics. The omics data presented here show great promise in providing information for several key events of the proposed AOP of CVD, particularly oxidative stress, alterations of energy metabolism, extracellular matrix and vascular remodeling.

CONCLUSIONS

The omics data presented here shows promise to inform the various levels of the proposed AOP of CVD. However, the data highlight the urgent need of designing omics studies to address the knowledge gap concerning different radiation scenarios, time after exposure and experimental models. This review presents the evidence to build a qualitative omics-informed AOP and provides views on the potential benefits and challenges in using omics data to assess risk-related outcomes.

Identification of novel biomarkers for acute radiation injury using multi-omics approach and nonhuman primate model

PURPOSE

The availability of validated biomarkers to assess radiation exposure and to assist in developing medical countermeasures remains an unmet need.

METHODS AND MATERIALS

We used a cobalt-60 gamma-irradiated nonhuman primate (NHP) model to delineate a multi-omics-based serum probability index of radiation exposure. Both male and female NHPs were irradiated with different doses ranging from 6.0 to 8.5 Gy, with 0.5 Gy increments between doses. We leveraged high-resolution mass spectrometry for analysis of metabolites, lipids, and proteins at 1, 2, and 6 days post-irradiation in NHP serum.

RESULTS

A logistic regression model was implemented to develop a 4-analyte panel to stratify irradiated NHPs from unirradiated with high accuracy that was agnostic for all doses of gamma-rays tested in the study, up to six days after exposure. This panel was comprised of Serpin Family A9, acetylcarnitine, PC (16:0/22:6), and suberylglycine, which showed 2 - 4-fold elevation in serum abundance upon irradiation in NHPs and can potentially be translated as a molecular diagnostic for human use following larger validation studies.

CONCLUSIONS

Taken together, this study, for the first time, demonstrates the utility of a combinatorial molecular characterization approach using an NHP model for developing minimally invasive assays from small volumes of blood that can be effectively used for radiation exposure assessments.

Biofluid Metabolomics and Lipidomics of Mice Exposed to External Very High-Dose Rate Radiation

High-throughput biodosimetry methods to determine exposure to ionizing radiation (IR) that can also be easily scaled to multiple testing sites in emergency situations are needed in the event of malicious attacks or nuclear accidents that may involve a substantial number of civilians. In the event of an improvised nuclear device (IND), a complex IR exposure will have a very high-dose rate (VHDR) component from an initial blast. We have previously addressed low-dose rate (LDR, ≤1 Gy/day) exposures from internal emitters on biofluid small molecule signatures, but further research on the VHDR component of the initial blast is required. Here, we exposed 8- to 10-week-old male C57BL/6 mice to an acute dose of 3 Gy using a reference dose rate of 0.7 Gy/min or a VHDR of 7 Gy/s, collected urine and serum at 1 and 7 d, then compared the metabolite signatures using either untargeted (urine) or targeted (serum) approaches with liquid chromatography mass spectrometry platforms. A Random Forest classification approach showed strikingly similar changes in urinary signatures at 1 d post-irradiation with VHDR samples grouping closer to control samples at 7 d. Identical metabolite panels (carnitine, trigonelline, xanthurenic acid, N6,N6,N6-trimethyllysine, spermine, and hexosamine-valine-isoleucine-OH) could differentiate IR exposed individuals with high sensitivity and specificity (area under the receiver operating characteristic (AUROC) curves 0.89–1.00) irrespective of dose rate at both days. For serum, the top 25 significant lipids affected by IR exposure showed slightly higher perturbations at 0.7 Gy/min vs. 7 Gy/s; however, identical panels showed excellent sensitivity and specificity at 1 d (three hexosylceramides (16:0), (18:0), (24:0), sphingomyelin [26:1], lysophosphatidylethanolamine [22:1]). Mice could not be differentiated from control samples at 7 d for a 3 Gy exposure based on serum lipid signatures. As with LDR exposures, we found that identical biofluid small molecule signatures can identify IR exposed individuals irrespective of dose rate, which shows promise for more universal applications of metabolomics for biodosimetry.

Metabolomics as a valid analytical technique in environmental exposure research: application and progress

BACKGROUND

In recent years, studies have shown that exposure to environmental pollutants (e.g., radiation, heavy metal substances, air pollutants, organic pollutants) is a leading cause of human non-communicable diseases. The key to disease prevention is to clarify the harmful mechanisms and toxic effects of environmental pollutants on the body. Metabolomics is a high-sensitivity, high-throughput omics technology that can obtain detailed metabolite information of an organism. It is a crucial tool for gaining a comprehensive understanding of the pathway network regulation mechanism of the organism. Its application is widespread in many research fields such as environmental exposure assessment, medicine, systems biology, and biomarker discovery.

AIM OF REVIEW

Recent findings show that metabolomics can be used to obtain molecular snapshots of organisms after environmental exposure, to help understand the interaction between environmental exposure and organisms, and to identify potential biomarkers and biological mechanisms.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review focuses on the application of metabolomics to understand the biological effects of radiation, heavy metals, air pollution, and persistent organic pollutants exposure, and examines some potential biomarkers and toxicity mechanisms.

An optimized method for the isolation of urinary extracellular vesicles for molecular phenotyping: detection of biomarkers for radiation exposure

Background

Urinary extracellular vesicles (EVs) are a source of biomarkers with broad potential applications across clinical research, including monitoring radiation exposure. A key limitation to their implementation is minimal standardization in EV isolation and analytical methods. Further, most urinary EV isolation protocols necessitate large volumes of sample. This study aimed to compare and optimize isolation and analytical methods for EVs from small volumes of urine.

Methods

3 EV isolation methods were compared: ultracentrifugation, magnetic bead-based, and size-exclusion chromatography from 0.5 mL or 1 mL of rat and human urine. EV yield and mass spectrometry signals (Q-ToF and Triple Quad) were evaluated from each method. Metabolomic profiling was performed on EVs isolated from the urine of rats exposed to ionizing radiation 1-, 14-, 30- or 90-days post-exposure, and human urine from patients receiving thoracic radiotherapy for the treatment of lung cancer pre- and post-treatment.

Results

Size-exclusion chromatography is the preferred method for EV isolation from 0.5 mL of urine. Mass spectrometry-based metabolomic analyses of EV cargo identified biochemical changes induced by radiation, including altered nucleotide, folate, and lipid metabolism. We have provided standard operating procedures for implementation of these methods in other laboratories.

Conclusions

We demonstrate that EVs can be isolated from small volumes of urine and analytically investigated for their biochemical contents to detect radiation induced metabolomic changes. These findings lay a groundwork for future development of methods to monitor response to radiotherapy and can be extended to an array of molecular phenotyping studies aimed at characterizing EV cargo.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03414-7.

Screening of radiation gastrointestinal injury biomarkers in rat plasma by high-coverage targeted lipidomics

INTRODUCTION

In the event of radiological accidents and cancer radiotherapies in clinic, the gastrointestinal (GI) system is vulnerable to ionizing radiation and shows GI injury. Accessible biomarkers may provide means to predict, evaluate, and treat GI tissue damage. The current study investigated radiation GI injury biomarkers in rat plasma.

MATERIAL AND METHODS

High-coverage targeted lipidomics was employed to profile lipidome perturbations at 72 h after 0, 1, 2, 3, 5 and 8 Gy (⁶⁰Co γ-rays at 1 Gy/min) total-body irradiation in male rat jejunum. The results were correlated with previous plasma screening outcomes.

RESULTS

In total, 93 differential metabolites and 28 linear dose-responsive metabolites were screened in the jejunum. Moreover, 52 lipid species with significant differences both in jejunum and plasma were obtained. Three lipid species with linear dose-response relationship both in jejunum and plasma were put forth, which exhibited good to excellent sensitivity and specificity in triaging different exposure levels.

DISCUSSION

The linear dose-effect relationship of lipid metabolites in the jejunum and the triage performance of radiation GI injury biomarkers in plasma were studied for the first time.

CONCLUSION

The present study can provide insights into expanded biomarkers of IR-mediated GI injury and minimally invasive assays for evaluation.

An Analysis of the Serum Metabolomic Profile for the Radiomitigative Effect of the Thrombopoietin Receptor Agonist Romiplostim in Lethally Whole-Body-Irradiated Mice

The thrombopoietin receptor agonist romiplostim (RP) was recently approved by the US Food and Drug Administration for improving survival in patients acutely exposed to myelosuppressive doses of radiation. Our previous studies with mice have shown that RP administration after lethal irradiation not only completely rescues irradiated mice but also shows mitigative effects on their hematopoiesis and multiple organ injury, including that of the lung, bone marrow, small intestine, and liver. However, the mechanism by which RP functions as a radiomitigator remains unclear. In the present study, we applied a metabolomics approach, which has the ability to reflect the status of an organism directly and accurately, helping to elucidate the biology of treatment responses. Our results showed that the disruption of several metabolites and pathways in response to total body irradiation was partially corrected by RP administration. Notably, RP-corrected metabolites and pathways have been reported to be indicators of DNA damage and lung, bone marrow, small intestine, and liver injury. Taken together, the present findings suggested that the radiomitigative effect of RP is partially involved in the recovery of organ injury, and the identified metabolites may be a useful biomarker of the survival likelihood following radiation exposure.

Metabolic response to radiation therapy in cancer

Tumor metabolism has emerged as a hallmark of cancer and is involved in carcinogenesis and tumor growth. Reprogramming of tumor metabolism is necessary for cancer cells to sustain high proliferation rates and enhanced demands for nutrients. Recent studies suggest that metabolic plasticity in cancer cells can decrease the efficacy of anticancer therapies by enhancing antioxidant defenses and DNA repair mechanisms. Studying radiation-induced metabolic changes will lead to a better understanding of radiation response mechanisms as well as the identification of new therapeutic targets, but there are few robust studies characterizing the metabolic changes induced by radiation therapy in cancer. In this review, we will highlight studies that provide information on the metabolic changes induced by radiation and oxidative stress in cancer cells and the associated underlying mechanisms.

Effects of Low-dose Gamma Radiation on Expression of Apoptotic Genes in Rat Peripheral Blood Lymphocyte

Background:

Exposure to high-dose ionizing radiation is known as a human carcinogen factor, but our information about the effects of low-dose ionizing radiation such as occupational exposures is limited. The main concern of scientific community is biological consequences due to low-dose radiations.

Objective:

This study aims to evaluate the effects of low-dose γ-radiation on expression changes of apoptotic genes (bax and bcl-2) in the rat peripheral blood lymphocytes.

Material and Methods:

In this experimental study, 42 adult male rats were classified into 6 groups, which was exposed to various doses values ranged from 20 mGy to 1000 mGy by γ-rays from a Co-60 source. Blood samples were provided for analysis of gene expression 24 h after gamma radiation by relative quantitative Reverse Transcription - Polymerase Chain Reaction (RT-PCR). Radiation sensitivity of rat lymphocytes was measured by the bax/bcl-2 ratio as a predictive marker for radio-sensitivity.

Results:

The results of this study showed that low dose of gamma radiation can induce down-regulation of bax in rat peripheral blood lymphocytes. Despite other mechanisms of cellular radio-protection, changes in expression of these apoptotic genes can be the primary pathway in responses of the lymphocytes radio-protection to the exposure. Our study revealed a significant decrease in the bax/bcl-2 ratio at 50 mGy dose compare to control and the other irradiated groups (p < 0.05).

Conclusion:

These results suggest that changes in the bax/bcl-2 ratio especially in radiation workers, as a key factor in apoptosis, can be considered as a biological marker in low-dose gamma radiation.

Clinical Applications of Biological Dosimetry in Patients Exposed to Low Dose Radiation Due to Radiological, Imaging or Nuclear Medicine Procedures

Radiation dosimetric biomarkers have found applications beyond radiation protection area and now are actively introduced into clinical practice. Cytogenetic assays appeared to be a valuable tool for individualized quantifying radiation effects in patients, with high capability for assessing genotoxicity of various medical exposure modalities and providing meaningful radiation dose estimates for prognoses of radiation-related cancer risk. This review summarized current data on the use of biological dosimetry methods in patients undergoing various medical irradiations to low doses. The highlighted topics include basic aspects of biological dosimetry and its limitations in the range of low radiation doses, and main patterns of in vivo induction of radiation biomarkers in clinical exposure scenarios, occurring in X-ray diagnostics, computed tomography, interventional radiology, low dose radiotherapy, and nuclear medicine (internally administered ¹³¹I and other radiopharmaceuticals). Additionally, several specific issues, examined by biodosimetry techniques, are analysed, such as contrast media effect, radiation response in pediatric patients, impact of magnetic resonance imaging, evaluation of radioprotectors, detection of patients' abnormal intrinsic radiosensitivity and dose estimation in persons involved in medical radiation incidents. A prognosis of possible directions for further improvements in this area includes the automation of cytogenetic analysis, introduction of molecular biodosimeters and development of multiparametric biodosimetry platforms. A potential approach to the advanced biodosimetry of internal exposure and/or low dose external irradiation is suggested; this can be a multiparametric platform based on the combination of the γ-H2AX foci, dicentric, and translocation assays, each applied in the optimum postexposure time range, with the amalgamation of the dose estimates. The study revealed the necessity of further research, which might clarify medical radiation safety concerns for patients via using stringent biodosimetry methodology.

Comprehensive Analysis of Serum Metabolites Profiles in Acute Radiation Enteritis Rats by Untargeted Metabolomics

Acute radiation enteritis is a common complication occurring in patients with pelvic and abdominal tumors who receive radiotherapy. Acute radiation enteritis seriously reduces the life quality, even threatens the lives of patients. Untargeted metabolomics is an emerging strategy to explore the novel biomarkers and uncover potential pathogenesis of acute radiation enteritis. Acute radiation enteritis rat model was established by single abdominal irradiation with a gamma-ray dose of 10 Gy. Serum from 15 acute radiation enteritis rats and 10 controls was extracted for metabolomics analysis by UHPLC-Q-TOF/MS. Clinical manifestations and morphological alterations of intestine confirmed the successful establishment of acute radiation enteritis. According to the metabolomics data, 6,044 positive peaks and 4,241 negative peaks were extracted from each specimen. OPLS-DA analysis and the heat map for cluster analysis showed satisfactory discriminatory power between acute radiation enteritis rats and controls. Subsequent analysis extracted 66 significantly differentially expressed metabolites, which might be potential biomarkers for acute radiation enteritis diagnosis. Moreover, Kyoto Encyclopedia of Genes and Genomes enrichment analyses uncovered the potential mechanisms through which differentially expressed metabolites participated in acute radiation enteritis pathogenesis. To sum up, we summarized several differentially expressed serum metabolites as potential biomarkers for diagnosis of acute radiation enteritis and provide latent clues for elucidating acute radiation enteritis pathology.

Biofluid Metabolomics of Mice Exposed to External Low-Dose Rate Radiation in a Novel Irradiation System, the Variable Dose-Rate External 137Cs Irradiator

An important component of ionizing radiation (IR) exposure after a radiological incident may include low-dose rate (LDR) exposures either externally or internally, such as from ¹³⁷Cs deposition. In this study, a novel irradiation system, VAriable Dose-rate External ¹³⁷Cs irradiatoR (VADER), was used to expose male and female mice to a variable LDR irradiation over a 30 d time span to simulate fall-out-type exposures in addition to biofluid collection from a reference dose rate (0.8 Gy/min). Radiation markers were identified by untargeted metabolomics and random forests. Mice exposed to LDR exposures were successfully identified from control groups based on their urine and serum metabolite profiles. In addition to metabolites commonly perturbed after IR exposure, we identified and validated a novel metabolite (hexosamine-valine-isoleucine-OH) that increased up to 150-fold after LDR and 80-fold after conventional exposures in urine. A multiplex panel consisting of hexosamine-valine-isoleucine-OH with other urinary metabolites (N6,N6,N6-trimethyllysine, carnitine, 1-methylnicotinamide, and α-ketoglutaric acid) achieved robust classification performance using receiver operating characteristic curve analysis, irrespective of the dose rate or sex. These results show that in terms of biodosimetry, dysregulated energy metabolism is associated with IR exposure for both LDR and conventional IR exposures. These mass spectrometry data have been deposited to the NIH data repository via Metabolomics Workbench with study IDs ST001790, ST001791, ST001792, ST001793, and ST001806.

Cytogenetic biological dosimetry assays: recent developments and updates

Biological dosimetry is the measurement of radiation-induced changes in the human to measure short and long-term health risks. Biodosimetry offers an independent means of obtaining dose information and also provides diagnostic information on the potential for “partial-body” exposure information using biological indicators and otherwise based on computer modeling, dose reconstruction, and physical dosimetry. A variety of biodosimetry tools are available and some features make some more valuable than others. Among the available biodosimetry tool, cytogenetic biodosimetry methods occupy an exclusive and advantageous position. The cytogenetic analysis can complement physical dosimetry by confirming or ruling out an accidental radiological exposure or overexposures. We are discussing the recent developments and adaptability of currently available cytogenetic biological dosimetry assays.

The future of biological dosimetry in mass casualty radiation emergency response, personalized radiation risk estimation and space radiation protection

PURPOSE

The aim of this brief personal, high level review is to consider the state of the art for biological dosimetry for radiation routine and emergency response, and the potential future progress in this fascinating and active field. Four areas in which biomarkers may contribute to scientific advancement through improved dose and exposure characterization, as well as potential contributions to personalized risk estimation, are considered: emergency dosimetry, molecular epidemiology, personalized medical dosimetry, and space travel.

CONCLUSION

Ionizing radiation biodosimetry is an exciting field which will continue to benefit from active networking and collaboration with the wider fields of radiation research and radiation emergency response to ensure effective, joined up approaches to triage; radiation epidemiology to assess long term, low dose, radiation risk; radiation protection of workers, optimization and justification of radiation for diagnosis or treatment of patients in clinical uses, and protection of individuals traveling to space.

Metabolomic Response of the Creeping Wood Sorrel Oxalis corniculata to Low-Dose Radiation Exposure from Fukushima's Contaminated Soil

The biological consequences of the Fukushima nuclear accident have been intensively studied using the pale grass blue butterfly Zizeeria maha and its host plant, the creeping wood sorrel Oxalis corniculata. Here, we performed metabolomic analyses of Oxalis leaves from Okinawa to examine the plant metabolites that were upregulated or downregulated in response to low-dose radiation exposure from Fukushima's contaminated soil. The cumulative dose of radiation to the plants was 5.7 mGy (34 μGy/h for 7 days). The GC-MS analysis revealed a systematic tendency of downregulation among the metabolites, some of which were annotated as caproic acid, nonanoic acid, azelaic acid, and oleic acid. Others were annotated as fructose, glucose, and citric acid, involved in the carbohydrate metabolic pathways. Notably, the peak annotated as lauric acid was upregulated. In contrast, the LC-MS analysis detected many upregulated metabolites, some of which were annotated as either antioxidants or stress-related chemicals involved in defense pathways. Among them, only three metabolite peaks had a single annotation, one of which was alfuzosin, an antagonist of the α₁-adrenergic receptor. We conclude that this Oxalis plant responded metabolically to low-dose radiation exposure from Fukushima's contaminated soil, which may mediate the ecological "field effects" of the developmental deterioration of butterflies in Fukushima.

Identification of odor biomarkers in irradiation injury urine based on headspace SPME-GC-MS

PURPOSE

The threat of population exposure to ionizing radiation is increasing rapidly worldwide. Such exposure, especially at high-dose, is known to cause acute radiation syndrome (ARS). Hence, it is necessary to develop specific and sensitive biomarkers to accurately diagnose radiation injury and evaluate medical countermeasures.

MATERIALS AND METHODS

Caenorhabditis elegans (C. elegans), a model organism with a fine and sound olfactory system, was used to examine the odor of urine samples collected from irradiation-injured rats, and compared with those from un-irradiated control rats to investigate the 'special odor' of radiation injury. Subsequently, headspace SPME-GC-MS was applied for non-targeted metabolomic analysis of volatile organic compounds (VOCs) in urine, with the aim to discover changes of small molecule metabolites and identify odor biomarkers of irradiation injury.

RESULTS

C. elegans showed significant attraction to the urine of total body irradiation (TBI) rats compared with control rats, indicating that irradiation injury can emit 'special odor' and the metabolites in urine VOCs were changed. Using metabolomics based on headspace SPME-GC-MS for metabolic profiles analysis, we screened 63 differentially expressed metabolites. Among them, 10 metabolites including p-Cresol with excellent diagnostic ability were identified as odor biomarkers according to receiver operating characteristic (ROC) curve analysis.

CONCLUSIONS

This study confirmed the 'special odor' induced by irradiation injury, and identified biomarkers through urine VOCs analysis for the first time, which can provide a novel approach and insight to evaluate irradiation injury noninvasively, accurately and conveniently.[Figure: see text].

Radiation exposure induces cross-species temporal metabolic changes that are mitigated in mice by amifostine

Exposure to acute, damaging radiation may occur through a variety of events from cancer therapy and industrial accidents to terrorist attacks and military actions. Our understanding of how to protect individuals and mitigate the effects of radiation injury or Acute Radiation Syndrome (ARS) is still limited. There are only a few Food and Drug Administration-approved therapies for ARS; whereas, amifostine is limited to treating low dose (0.7-6 Gy) radiation poisoning arising from cancer radiotherapy. An early intervention is critical to treat ARS, which necessitates identifying diagnostic biomarkers to quickly characterize radiation exposure. Towards this end, a multiplatform metabolomics study was performed to comprehensively characterize the temporal changes in metabolite levels from mice and non-human primate serum samples following γ-irradiation. The metabolomic signature of amifostine was also evaluated in mice as a model for radioprotection. The NMR and mass spectrometry metabolomics analysis identified 23 dysregulated pathways resulting from the radiation exposure. These metabolomic alterations exhibited distinct trajectories within glucose metabolism, phospholipid biosynthesis, and nucleotide metabolism. A return to baseline levels with amifostine treatment occurred for these pathways within a week of radiation exposure. Together, our data suggests a unique physiological change that is independent of radiation dose or species. Furthermore, a metabolic signature of radioprotection was observed through the use of amifostine prophylaxis of ARS.

Two-miRNA-based finger-stick assay for estimation of absorbed ionizing radiation dose

Nuclear radiation and radioactive fallouts resulting from a nuclear weapon detonation or reactor accidents could result in injuries affecting multiple sensitive organs, defined as acute radiation syndrome (ARS). Rapid and early estimation of injuries to sensitive organs using markers of radiation response is critical for identifying individuals who could potentially exhibit ARS; however, there are currently no biodosimetry assays approved for human use. We developed a sensitive microRNA (miRNA)-based blood test for radiation dose reconstruction with ±0.5 Gy resolution at critical dose range. Radiation dose-dependent changes in miR-150-5p in blood were internally normalized by a miRNA, miR-23a-3p, that was nonresponsive to radiation. miR-23a-3p was not highly expressed in blood cells but was abundant in circulation and was released primarily from the lung. Our assay showed the capability for dose estimation within hours to 1 week after exposure using a drop of blood from mice. We tested this biodosimetry assay for estimation of absorbed ionizing radiation dose in mice of varying ages and after exposure to both improvised nuclear device (IND)-spectrum neutrons and gamma rays. Leukemia specimens from patients exposed to fractionated radiation showed depletion of miR-150-5p in blood. We bridged the exposure of these patients to fractionated radiation by comparing responses after fractionated versus single acute exposure in mice. Although validation in nonhuman primates is needed, this proof-of-concept study suggests the potential utility of this assay in radiation disaster management and clinical applications.

Metabolomics-based predictive biomarkers of radiation injury and countermeasure efficacy: current status and future perspectives

INTRODUCTION

There is an urgent need for specific and sensitive bioassays to augment biodosimetric assessments of unwanted and excessive radiation exposures that originate from unexpected nuclear/radiological events, including nuclear accidents, acts of terrorism, or the use of a radiological dispersal device. If sufficiently intense, such ionizing radiation exposures are likely to impact normal metabolic processes within the cells and organs of the body, thus inducing multifaceted biological responses.

AREAS COVERED

This review covers the application of metabolomics, an emerging and promising technology based on quantitative and qualitative determinations of small molecules in biological samples for the rapid assessment of an individual's exposure to ionizing radiation. Recent advancements in the analytics of high-resolution chromatography, mass spectrometry, and bioinformatics have led to untargeted (global) and targeted (quantitative phase) approaches to identify biomarkers of radiation injury and countermeasure efficacy. Biomarkers are deemed essential for both assessing the radiation exposure levels and for extrapolative processes involved in determining scaling factors of a given radiation countering medicinal between experimental animals and humans.

EXPERT OPINION

The discipline of metabolomics appears to be highly informative in assessing radiation exposure levels and for identifying biomarkers of radiation injury and countermeasure efficacy.

Small Molecule Responses to Sequential Irradiation with Neutrons and Photons for Biodosimetry Applications: An Initial Assessment

Mass casualty exposure scenarios from an improvised nuclear device are expected to be far more complex than simple photons. Based on the proximity to the explosion and potential shielding, a mixed field of neutrons and photons comprised of up to approximately 30% neutrons of the total dose is anticipated. This presents significant challenges for biodosimetry and for short-term and long-term medical treatment of exposed populations. In this study we employed untargeted metabolomic methods to develop a biosignature in urine and serum from C57BL/6 mice to address radiation quality issues. The signature was developed in males and applied to samples from female mice to identify potential sex differences. Thirteen urinary (primarily amino acids, vitamin products, nucleotides) and 18 serum biomarkers (primarily mitochondrial and fatty acid β oxidation intermediates) were selected and evaluated in samples from day 1 and day 7 postirradiation. Sham-irradiated groups (controls) were compared to an equitoxic dose (3 Gy X-ray equivalent) from X rays (1.2 Gy/min), neutrons (∼1 Gy/h), or neutrons-photons. Results showed a time-dependent increase in the efficiency of the signatures, with serum providing the highest levels of accuracy in distinguishing not only between exposed from non-exposed populations, but also between radiation quality (photon exposures vs. exposures with a neutron component) and in between neutron-photon exposures (5, 15 or 25% of neutrons in the total dose) for evaluating the neutron contribution. A group of metabolites known as acylcarnitines was only responsive in males, indicating the potential for different mechanisms of action in baseline levels and of neutron-photon responses between the two sexes. Our findings highlight the potential of metabolomics in developing biodosimetric methods to evaluate mixed exposures with high sensitivity and specificity.

Exploring the differentially expressed genes in human lymphocytes upon response to ionizing radiation: a network biology approach

Purpose

The integration of large-scale gene data and their functional analysis needs the effective application of various computational tools. Here we attempted to unravel the biological processes and cellular pathways in response to ionizing radiation using a systems biology approach.

Materials and Methods

Analysis of gene ontology shows that 80, 42, 25, and 35 genes have roles in the biological process, molecular function, the cellular process, and immune system pathways, respectively. Therefore, our study emphasizes gene/protein network analysis on various differentially expressed genes (DEGs) to reveal the interactions between those proteins and their functional contribution upon radiation exposure.

Results

A gene/protein interaction network was constructed, which comprises 79 interactors with 718 interactions and TP53, MAPK8, MAPK1, CASP3, MAPK14, ATM, NOTCH1, VEGFA, SIRT1, and PRKDC are the top 10 proteins in the network with high betweenness centrality values. Further, molecular complex detection was used to cluster these associated partners in the network, which produced three effective clusters based on the Molecular Complex Detection (MCODE) score. Interestingly, we found a high functional similarity from the associated genes/proteins in the network with known radiation response genes.

Conclusion

This network-based approach on DEGs of human lymphocytes upon response to ionizing radiation provides clues for an opportunity to improve therapeutic efficacy.

Transcriptome of rhesus macaque (Macaca mulatta) exposed to total-body irradiation

The field of biodosimetry has seen a paradigm shift towards an increased use of molecular phenotyping technologies including omics and miRNA, in addition to conventional cytogenetic techniques. Here, we have used a nonhuman primate (NHP) model to study the impact of gamma-irradiation on alterations in blood-based gene expression. With a goal to delineate radiation induced changes in gene expression, we followed eight NHPs for 60 days after exposure to 6.5 Gy gamma-radiation for survival outcomes. Analysis of differential gene expression in response to radiation exposure yielded 26,944 dysregulated genes that were not significantly impacted by sex. Further analysis showed an increased association of several pathways including IL-3 signaling, ephrin receptor signaling, ErbB signaling, nitric oxide signaling in the cardiovascular system, Wnt/β-catenin signaling, and inflammasome pathway, which were associated with positive survival outcomes in NHPs after acute exposure to radiation. This study provides novel insights into major pathways and networks involved in radiation-induced injuries that may identify biomarkers for radiation injury.

BIO 300: a promising radiation countermeasure under advanced development for acute radiation syndrome and the delayed effects of acute radiation exposure

INTRODUCTION

There are no radioprotectors currently approved by the United States Food and Drug Administration (US FDA) for either the hematopoietic acute radiation syndrome (H-ARS) or for the acute radiation gastrointestinal syndrome (GI-ARS). There are currently, however, three US FDA-approved medicinals that serve to mitigate acute irradiation-associated hematopoietic injury.

AREA COVERED

We present the current status of a promising radiation countermeasure, BIO 300 (a genistein-based agent), that has been extensively investigated in murine models of H-ARS and models of the delayed effects of acute radiation exposure (DEARE) and is currently being evaluated in large animal models. It is also being developed for the prevention of radiation-induced toxicities associated with solid tumor radiotherapy and is the subject of two active Investigational New Drug (IND) applications. We have included a listing and brief review of significant investigations of this promising medical countermeasure.

EXPERT OPINION

BIO 300 is a leading radioprotector under advanced development for H-ARS and DEARE, as well as for select oncologic indication(s). Efficacy following oral administration (po), lack of clinical side effects, storage at ambient temperature, and intended dual use makes BIO 300 an ideal candidate for military and civilian use as well as for storage in the Strategic National Stockpile.

Longitudinal metabolic alterations in plasma of rats exposed to low doses of high linear energy transfer radiation

Astronauts embarking on deep space missions are at high risk of long-term exposure to low doses of high linear energy transfer (LET) radiation, which can contribute to the development of cancer and multiple degenerative diseases. However, long term effects of exposure to low doses of high LET radiation in plasma metabolite profiles have not been elucidated. We utilized an untargeted metabolomics and lipidomics approach to analyze plasma obtained from adult male Long Evans rats to determine the longitudinal effects of low-dose proton and low-dose oxygen ion whole-body irradiation on metabolic pathways. Our findings reveal that radiation exposure induced modest changes in the metabolic profiles in plasma, 7 months after exposure. Furthermore, we identified some common metabolite dysregulations between protons and oxygen ions, which may indicate a similar mechanism of action for both radiation types.

Screening of Lipids for Early Triage and Dose Estimation after Acute Radiation Exposure in Rat Plasma Based on Targeted Lipidomics Analysis

Rapid early triage and dose estimation is vital for limited medical resource allocation and treatment of a large number of the wounded after radiological accidents. Lipidomics has been utilized to delineate biofluid lipid signatures after irradiation. Here, high-coverage targeted lipidomics was employed to screen radiosensitive lipids after 0, 1, 2, 3, 5, and 8 Gy total body irradiation at 4, 24, and 72 h postirradiation in rat plasma. Ultra-performance liquid chromatography-tandem mass spectrometry with a multiple reaction monitoring method was utilized. In total, 416 individual lipids from 18 major classes were quantified and those biomarkers altered in a dose-dependent manner constituted panel A-panel D. Receiver operator characteristic curve analysis using combined lipids showed good to excellent sensitivity and specificity in triaging different radiation exposure levels (area under curve = 0.814-1.000). The equations for dose estimation were established by stepwise regression analysis for three time points. A novel strategy for radiation early triage and dose estimation was first established and validated using panels of lipids. Our study suggests that it is feasible to acquire quantitative lipid biomarker panels using targeted lipidomics platforms for rapid, high-throughput triage, which can provide further insights in developing lipidomics strategies for radiation biodosimetry in humans.

Radioprotection and Radiomitigation: From the Bench to Clinical Practice

The development of protective agents against harmful radiations has been a subject of investigation for decades. However, effective (ideal) radioprotectors and radiomitigators remain an unsolved problem. Because ionizing radiation-induced cellular damage is primarily attributed to free radicals, radical scavengers are promising as potential radioprotectors. Early development of such agents focused on thiol synthetic compounds, e.g., amifostine (2-(3-aminopropylamino) ethylsulfanylphosphonic acid), approved as a radioprotector by the Food and Drug Administration (FDA, USA) but for limited clinical indications and not for nonclinical uses. To date, no new chemical entity has been approved by the FDA as a radiation countermeasure for acute radiation syndrome (ARS). All FDA-approved radiation countermeasures (filgrastim, a recombinant DNA form of the naturally occurring granulocyte colony-stimulating factor, G-CSF; pegfilgrastim, a PEGylated form of the recombinant human G-CSF; sargramostim, a recombinant granulocyte macrophage colony-stimulating factor, GM-CSF) are classified as radiomitigators. No radioprotector that can be administered prior to exposure has been approved for ARS. This differentiates radioprotectors (reduce direct damage caused by radiation) and radiomitigators (minimize toxicity even after radiation has been delivered). Molecules under development with the aim of reaching clinical practice and other nonclinical applications are discussed. Assays to evaluate the biological effects of ionizing radiations are also analyzed.

Urine metabolomics based prediction model approach for radiation exposure

The radiological incidents and terrorism have demanded the need for the development of rapid, precise, and non-invasive technique for detection and quantification of exposed dose of radiation. Though radiation induced metabolic markers have been thoroughly investigated, but reproducibility still needs to be elucidated. The present study aims at assessing the reliability and reproducibility of markers using nuclear magnetic resonance (NMR) spectroscopy and further deriving a logistic regression model based on these markers. C57BL/6 male mice (8–10 weeks) whole body γ-irradiated and sham irradiated controls were used. Urine samples collected at 24 h post dose were investigated using high resolution NMR spectroscopy and the datasets were analyzed using multivariate analysis. Fifteen distinguishable metabolites and 3 metabolic pathways (TCA cycle, taurine and hypotaurine metabolism, primary bile acid biosynthesis) were found to be amended. ROC curve and logistic regression was used to establish a diagnostic model as Logit (p) = log (p/1 − p) = −0.498 + 13.771 (tau) − 3.412 (citrate) − 34.461 (α-KG) + 515.183 (fumarate) with a sensitivity and specificity of 1.00 and 0.964 respectively. The findings demonstrate the proof of concept and the potential of NMR based metabolomics to establish a prediction model that can be implemented as a promising mass screening tool during triage.

Blood RNA Integrity is a Direct and Simple Reporter of Radiation Exposure and Prognosis: A Pilot Study

In the event of a mass casualty radiation scenario, rapid assessment of patients' health and triage is required for optimal resource utilization. Identifying the level and extent of exposure as well as prioritization of care is extremely challenging under such disaster conditions. Blood-based biomarkers, such as RNA integrity numbers (RIN), could help healthcare personnel quickly and efficiently determine the extent and effect of multiple injuries on patients' health. Evaluation of the effect of different radiation doses, alone or in combination with burn injury, on total RNA integrity over multiple time points was performed. Total RNA integrity was tallied in blood samples for potential application as a marker of radiation exposure and survival. Groups of aged mice (3-6 mice/group, 13-18 months old) received 0.5, 1, 5, 10 or 20 Gy ionizing radiation. Two additional mouse groups received low-dose irradiation (0.5 or 1 Gy) with a 15% total body surface area (TBSA) burn injury. Animals were euthanized at 2 or 12 h and at day 1, 2, 3, 7 or 14 postirradiation, or when injury-mediated mortality occurred. Total RNA was isolated from blood. The quality of RNA was evaluated and RNA RIN were obtained. Analysis of RIN indicated that blood showed the clearest radiation effect. There was a time- and radiation-dose-dependent reduction in RIN that was first detectable at 12 h postirradiation for all doses in animals receiving irradiation alone. This effect was reversible in lower-dose groups (i.e., 0.5, 1 and 5 Gy) that survived to the end of the study (14 days). In contrast, the effect persisted for 10 and 20 Gy groups, which showed suppression of RIN values <4.5 with high mortalities. Radiation doses of 20 Gy were lethal and required euthanasia by day 6. A low RIN (<2.5) at any time point was associated with 100% mortality. Combined radiation-burn injury produced significantly increased mortality such that no dually-injured animals survived beyond day 3, and no radiation dose >1 Gy resulted in survival past day 1. More modest suppression of RIN was observed in the surviving dually challenged mice, and no statistically significant changes were identified in RIN values of burn-only mice at any time point. In this study of an animal model, a proof of concept is presented for a simple and accurate method of assessing radiation dose exposure in blood which potentially predicts lethality. RIN assessment of blood-derived RNA could form the basis for a clinical decision-support tool to guide healthcare providers under the strenuous conditions of a radiation-based mass casualty event.

Radiation Exposure Biomarkers in the Practice of Medical Radiology: Cooperative Research and the Role of the International Atomic Energy Agency (IAEA) Biodosimetry/Radiobiology Laboratory

The strategy toward personalized medicine in radiation oncology, nuclear medicine, and diagnostic and interventional radiology demands a specific set of assays for individualized estimation of radiation load for safety concerns and prognosis of normal tissue reactions caused by ionizing radiation. Apparently, it seems reasonable to use validated radiation dosimetric biomarkers for these purposes. However, a number of gaps in knowledge and methodological limitations still have to be resolved until dosimetric biomarkers will start to play a valuable role in clinical practice beyond radiation protection and radiation medicine. An extensive international multicenter research is necessary to improve the methodology of clinical applications of biodosimetry. That became a rationale for launching the IAEA Coordinated Research Project E35010 MEDBIODOSE: "Applications of Biological Dosimetry Methods in Radiation Oncology, Nuclear Medicine, and Diagnostic and Interventional Radiology." At the 2 Coordination Meeting on MEDBIODOSE (18-22 February 2019, Recife, Brazil), participants reported progress in the usage of biological dosimetry for genotoxicity assessment and/or individualization of radiotherapy treatment plans. Another avenue of research was the prognosis of normal tissue toxicity and cancer risk prediction using biomarkers' yield measured in vivo or after ex vivo irradiation of patients' cells. Other important areas are mechanisms of cytogenetic radiation response, validation of new radiation biomarkers, development of innovative techniques, automated and high-throughput assays for biodosimetry, and the overall improvement of biodosimetry service. An important aspect of clinical application of biodosimetry is standardization of techniques and unification of approaches to data interpretation. The new IAEA Biodosimetry/Radiobiology Laboratory, which is being established, will provide support for this activity. The declared lab's mission includes, among other tasks, a harmonization of the biodosimetry applications with relevant international standards, guidelines on good laboratory practice, and the IAEA EPR-Biodosimetry manual.

Biomarkers of Brain Damage Induced by Radiotherapy

Radiotherapy remains currently a critical component for both primary and metastatic brain tumors either alone or in combination with surgery, chemotherapy, and molecularly targeted agents, while it could cause simultaneously normal brain tissue injury leading to serious health consequences, that is, development of cognitive impairments following cranial radiotherapy is considered as a critical clinical disadvantage especially for the whole brain radiotherapy. Biomarkers can help to detect the accurate physiology or conditions of patients with brain tumor and develop effective treatment procedures for these patients. In the near future, biomarkers will become one of the prime driving forces of cancer treatment. In this minireview, we analyze the documented work on the acute brain damage and late consequences induced by radiotherapy, identify the biomarkers, in particular, the predictive biomarkers for the damage, and summarize the biological significance of the biomarkers. It is expected that translation of these research advance to radiotherapy would assist stratifying patients for optimized treatment and improving therapeutic efficacy and the quality of life.

Serum Metabolomic Alterations Associated with Cesium-137 Internal Emitter Delivered in Various Dose Rates

Our laboratory and others have use radiation metabolomics to assess responses in order to develop biomarkers reflecting exposure and level of injury. To expand the types of exposure and compare to previously published results, metabolomic analysis has been carried out using serum samples from mice exposed to ¹³⁷Cs internal emitters. Animals were injected intraperitoneally with ¹³⁷CsCl solutions of varying radioactivity, and the absorbed doses were calculated. To determine the dose rate effect, serum samples were collected at 2, 3, 5, 7, and 14 days after injection. Based on the time for each group receiving the cumulative dose of 4 Gy, the dose rate for each group was determined. The dose rates analyzed were 0.16 Gy/day (low), 0.69 Gy/day (medium), and 1.25 Gy/day (high). The results indicated that at a cumulative dose of 4 Gy, the low dose rate group had the least number of statistically significantly differential spectral features. Some identified metabolites showed common changes for different dose rates. For example, significantly altered levels of oleamide and sphingosine 1-phosphate were seen in all three groups. On the other hand, the intensity of three amino acids, Isoleucine, Phenylalanine and Arginine, significantly decreased only in the medium dose rate group. These findings have the potential to be used in assessing the exposure and the biological effects of internal emitters.

A Systematic Review of Metabolomic and Lipidomic Candidates for Biomarkers in Radiation Injury

A large-scale nuclear event has the ability to inflict mass casualties requiring point-of-care and laboratory-based diagnostic and prognostic biomarkers to inform victim triage and appropriate medical intervention. Extensive progress has been made to develop post-exposure point-of-care biodosimetry assays and to identify biomarkers that may be used in early phase testing to predict the course of the disease. Screening for biomarkers has recently extended to identify specific metabolomic and lipidomic responses to radiation using animal models. The objective of this review was to determine which metabolites or lipids most frequently experienced perturbations post-ionizing irradiation (IR) in preclinical studies using animal models of acute radiation sickness (ARS) and delayed effects of acute radiation exposure (DEARE). Upon review of approximately 65 manuscripts published in the peer-reviewed literature, the most frequently referenced metabolites showing clear changes in IR induced injury were found to be citrulline, citric acid, creatine, taurine, carnitine, xanthine, creatinine, hypoxanthine, uric acid, and threonine. Each metabolite was evaluated by specific study parameters to determine whether trends were in agreement across several studies. A select few show agreement across variable animal models, IR doses and timepoints, indicating that they may be ubiquitous and appropriate for use in diagnostic or prognostic biomarker panels.

Effects of Genetic Variation on Urinary Small Molecule Signatures of Mice after Exposure to Ionizing Radiation: A Study of p53 Deficiency

Due to risks from potential exposures to ionizing radiation (IR), improved radiological countermeasures are required, as well as rapid high-throughput biodosimetry. Genotypic variation in the general population contributes to differences in radiosensitivity that may affect biodosimetry accuracy. Previous studies utilized radiosensitive mutant mouse models (Parp1^−/− and Atm^−/−) to determine the effects of genotypic deficiency on radiation signatures. Here, we extend this approach by examining changes in the urinary metabolome in a hematopoietic (HP) resistant mouse model (p53^−/−) after IR exposure. As p53 is a primary regulator in radiation response and apoptosis, limited hematopoietic stem cell apoptosis leads to reduced mortality at doses of ~8–10 Gy but increased mortality at higher doses (>15 Gy) due to mitotic catastrophe in gastrointestinal (GI) crypt cells. Urine was collected from mice (wild-type (WT), p53^+/−, and p53^−/−) pre-irradiation and at 4 and 24 h after total body irradiation (TBI) (WT: 8 and 10 Gy; p53^−/−: 10 Gy) for metabolic phenotyping using an ultra-performance liquid chromatography mass spectrometry (UPLC-MS) platform. Minimal differences were detected between unirradiated WT, p53^+/−, and p53^−/− mice. While similar perturbations were observed for metabolites involved in tryptophan, vitamin B6, and histamine pathways, glycine conjugation, and redox metabolism for WT and p53^−/− mice after TBI, an overall dampened response was observed in p53-deficient mice. Despite comparable metabolite patterns between genotypes, differentiation was achieved through receiver operating characteristic curve analysis with high specificity and sensitivity for carnitine, N1-acetylspermidine, and creatine. These studies highlight that both attenuated and dampened metabolic responses due to genetic variability in the general population need to be addressed in biodosimetry frameworks.