Changes in serum amylase and its isoenzymes after whole body irradiation

Improved radiation expression profiling in blood by sequential application of sensitive and specific gene signatures

PURPOSE

Combinations of expressed genes can discriminate radiation-exposed from normal control blood samples by machine learning (ML) based signatures (with 8-20% misclassification rates). These signatures can quantify therapeutically relevant as well as accidental radiation exposures. The prodromal symptoms of acute radiation syndrome (ARS) overlap those present in influenza and dengue fever infections. Surprisingly, these human radiation signatures misclassified gene expression profiles of virally infected samples as false positive exposures. The present study investigates these and other confounders, and then mitigates their impact on signature accuracy.

METHODS

This study investigated recall by previous and novel radiation signatures independently derived from multiple Gene Expression Omnibus datasets on common and rare non-neoplastic blood disorders and blood-borne infections (thromboembolism, S. aureus bacteremia, malaria, sickle cell disease, polycythemia vera, and aplastic anemia). Normalized expression levels of signature genes are used as input to ML-based classifiers to predict radiation exposure in other hematological conditions.

RESULTS

Except for aplastic anemia, these blood-borne disorders modify the normal baseline expression values of genes present in radiation signatures, leading to false-positive misclassification of radiation exposures in 8-54% of individuals. Shared changes, predominantly in DNA damage response and apoptosis-related gene transcripts in radiation and confounding hematological conditions, compromise the utility of these signatures for radiation assessment. These confounding conditions (sickle cell disease, thrombosis, S. aureus bacteremia, malaria) induce neutrophil extracellular traps, initiated by chromatin decondensation, DNA damage response and fragmentation followed by programmed cell death or extrusion of DNA fragments. Riboviral infections (e.g. influenza or dengue fever) have been proposed to bind and deplete host RNA binding proteins, inducing R-loops in chromatin. R-loops that collide with incoming replication forks can result in incompletely repaired DNA damage, inducing apoptosis and releasing mature virus. To mitigate the effects of confounders, we evaluated predicted radiation-positive samples with novel gene expression signatures derived from radiation-responsive transcripts encoding secreted blood plasma proteins whose expression levels are unperturbed by these conditions.

CONCLUSIONS

This approach identifies and eliminates misclassified samples with underlying hematological or infectious conditions, leaving only samples with true radiation exposures. Diagnostic accuracy is significantly improved by selecting genes that maximize both sensitivity and specificity in the appropriate tissue using combinations of the best signatures for each of these classes of signatures.

Development of a biodosimeter for radiation triage using novel blood protein biomarker panels in humans and non-human primates

Purpose: In a significant nuclear event, hundreds of thousands of individuals will require rapid triage for absorbed radiation to ensure effective medical treatment and efficient use of medical resources. We are developing a rapid screening method to assess whether an individual received an absorbed dose of ≥2 Gy based on the analysis of a specific panel of blood proteins in a fingerstick blood sample.Materials and methods: We studied a data set of 1051 human blood samples obtained from radiotherapy patients, normal healthy individuals, and several special population groups. We compared the findings in humans with those from irradiation studies in non-human primates (NHPs).Results: We identified a panel of three protein biomarkers, salivary alpha amylase (AMY1), Flt3 ligand (FLT3L), and monocyte chemotactic protein 1 (MCP1), which are upregulated in human patients receiving fractionated doses of total body irradiation (TBI) therapy as a treatment for cancer. These proteins exhibited a similar radiation response in NHPs after single acute or fractionated doses of ionizing radiation.Conclusion: Our work provides confidence in this biomarker panel for biodosimetry triage using fingerstick blood samples and in the use of NHPs as a model for irradiated humans.

Development of a point-of-care radiation biodosimeter: studies using novel protein biomarker panels in non-human primates

Purpose: There is a need to rapidly triage individuals for absorbed radiation dose following a significant nuclear event. Since most exposed individuals will not have physical dosimeters, we are developing a method to assess exposure dose based on the analysis of a specific panel of blood proteins that can be easily obtained from a fingerstick blood sample.Materials and methods: In three large non-human primate (NHP) studies, animals were exposed to single acute total body doses of x-ray or gamma radiation. A total of 895 blood samples were obtained at baseline and for 7 days after exposure, to evaluate the temporal progression of markers in each of 10 animals (5M/5F) in six dose groups receiving 0-10 Gy. We used tandem mass spectrometry and immunoassay techniques to identify radiation-responsive proteins in blood plasma samples.Results: A blood protein biomarker panel was developed based on analysis of blood plasma samples obtained from several irradiation studies in NHPs that aimed to simulate acute radiation injury in humans from a nuclear exposure event. Panels of several subsets of proteins were shown to accurately classify plasma samples into two exposure groups either above or below a critical dose threshold with sensitivities and specificities exceeding 90%.Conclusion: This study lays the groundwork for developing a radiation biodosimetry triage tool. Our results in NHPs must be compared with those in human patients undergoing radiotherapy to determine if the biomarker panel proteins exhibit a similar radiation response and allow adequate classification power in humans.

Radiation therapy and serum salivary amylase in head and neck cancer

Radiation therapy (RT) is a valid treatment option for head and neck cancer (HNC). The risk of RT-induced toxicities is significant, especially due to extended treatment fields. The raise in amylase activity is strictly dependent on the volume of salivary glands included in the irradiated target volume and it is firmly related to the dose. The aim of this review is to report the effects on salivary amylase activity after radiation exposure of salivary glands, in patients with HNC.

Intestinal microbiota-derived metabolomic blood plasma markers for prior radiation injury

PURPOSE

Assessing whole-body radiation injury and absorbed dose is essential for remediation efforts following accidental or deliberate exposure in medical, industrial, military, or terrorist incidents. We hypothesize that variations in specific metabolite concentrations extracted from blood plasma would correlate with whole-body radiation injury and dose.

METHODS AND MATERIALS

Groups of C57BL/6 mice (n=12 per group) were exposed to 0, 2, 4, 8, and 10.4 Gy of whole-body gamma radiation. At 24 hours after treatment, all animals were euthanized, and both plasma and liver biopsy samples were obtained, the latter being used to identify a distinct hepatic radiation injury response within plasma. A semiquantitative, untargeted metabolite/lipid profile was developed using gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry, which identified 354 biochemical compounds. A second set of C57BL/6 mice (n=6 per group) were used to assess a subset of identified plasma markers beyond 24 hours.

RESULTS

We identified a cohort of 37 biochemical compounds in plasma that yielded the optimal separation of the irradiated sample groups, with the most correlated metabolites associated with pyrimidine (positively correlated) and tryptophan (negatively correlated) metabolism. The latter were predominantly associated with indole compounds, and there was evidence that these were also correlated between liver and plasma. No evidence of saturation as a function of dose was observed, as has been noted for studies involving metabolite analysis of urine.

CONCLUSIONS

Plasma profiling of specific metabolites related to pyrimidine and tryptophan pathways can be used to differentiate whole-body radiation injury and dose response. As the tryptophan-associated indole compounds have their origin in the intestinal microbiome and subsequently the liver, these metabolites particularly represent an attractive marker for radiation injury within blood plasma.

Proteomics in radiation research: present status and future perspectives

Rapidly developing postgenome research has made proteins an attractive target for biological analysis. The well-established term of proteome is defined as the complete set of proteins expressed in a given cell, tissue or organism. Unlike the genome, a proteome is rapidly changing as it tends to adapt to microenvironmental signals. The systematic analysis of the proteome at a given time and state is referred to as proteomics. This technique provides information on the molecular and cellular mechanisms that regulate physiology and pathophysiology of the cell. Applications of proteome profiling in radiation research are increasing. However, the large-scale proteomics data sets generated need to be integrated into other fields of radiation biology to facilitate the interpretation of radiation-induced cellular and tissue effects. The aim of this review is to introduce the most recent developments in the field of radiation proteomics.

Identification and quantitation of biomarkers for radiation-induced injury via mass spectrometry

Biomarker identification and validation for radiation exposure is a rapidly expanding field encompassing the need for well defined animal models and advanced analytical techniques. The resources within the consortium, Medical Countermeasures Against Radiological Threats (MCART), provide a unique opportunity for accessing well defined animal models that simulate the key sequelae of the acute radiation syndrome and the delayed effects of acute radiation exposure. Likewise, the use of mass spectrometry-based analytical techniques for biomarker discovery and validation enables a robust analytical platform that is amenable to a variety of sample matrices and considered the benchmark for biomolecular identification and quantitation. Herein, the authors demonstrate the use of two targeted mass spectrometry approaches to link established MCART animal models to identified metabolite biomarkers. Circulating citrulline concentration was correlated to gross histological gastrointestinal tissue damage, and retinoic acid production in lung tissue was established to be reduced at early and late time points post high dose irradiation. Going forward, the use of mass spectrometry-based metabolomics coupled to well defined animal models provides the unique opportunity for comprehensive biomarker discovery.

Serum and plasma proteomics and its possible use as detector and predictor of radiation diseases

All tissues can be damaged by ionizing radiation. Early biomarkers of radiation injury are critical for triage, treatment and follow-up of large numbers of people exposed to ionizing radiation after terrorist attacks or radiological accident, and for prediction of normal tissue toxicity before, during and after a treatment by radiotherapy. The comparative proteomic approach is a promising and powerful tool for the discovery of new radiation biomarkers. In association with multivariate statistics, proteomics enables measurement of the level of hundreds or thousands of proteins at the same time and identifies set of proteins that can discriminate between different groups of individuals. Human serum and plasma are the preferred samples for the study of normal and disease-associated proteins. Extreme complexity, extensive dynamic range, genetic and physiological variations, protein modifications and incompleteness of sampling by two-dimensional electrophoresis and mass spectrometry represent key challenges to reproducible, high-resolution, and high-throughput analyses of serum and plasma proteomes. The future of radiation research will possibly lie in molecular networks that link genome, transcriptome, proteome and metabolome variations to radiation pathophysiology and serve as sensors of radiation disease. This chapter reviews recent advances in proteome analysis of serum and plasma as well as its applications to radiation biology and radiation biomarker discovery for both radiation exposure and radiation tissue toxicity.

Influence of Radiation Dose Rate and Lung Dose on Interstitial Pneumonitis after Fractionated Total Body Irradiation: Acute Parotitis May Predict Interstitial Pneumonitis

This study evaluated patients for the influence of the dose rate and lung dose of fractionated total body irradiation (TBI) in preparation for allogeneic bone marrow transplantation (BMT) on the subsequent development of interstitial pneumonitis (IP). Sixty-six patients at our institute were treated with TBI followed by BMT. All of the patients received a total TBI dose of 12 Gy given in 6 fractions over 3 days and were divided into 3 groups according to the radiation dose rate and lung dose: group A, lung dose of 8 Gy (n = 18); group B, lung dose of 12 Gy at 8 cGy/min (n = 25); and group C, lung dose of 12 Gy at 19 cGy/min (n = 23). The overall survival rate, the cumulative incidence of relapse, and the cumulative incidence of IP were evaluated in relation to various potential indicators of future IP. There were no significant differences in survival and relapse rates between patient group A and combined groups B and C. Clinically significant IP occurred in 13 patients. The cumulative incidence of IP was significantly higher in patients who developed acute parotitis as indicated by either an elevation in the serum amylase level or parotid pain of grade 1 to 2. There was no difference in IP incidence among groups A, B, and C. There was no significant difference in IP incidence between lung dose values of 8 Gy (with lung shielding) and 12 Gy (without lung shielding) and between dose rate values of 8 cGy/min and 19 cGy/ min, at least when TBI was given in 6 fractions. The presence of acute parotitis during or just after TBI may be a predictor of IP.

Joachim Kohn (1912–1987) and the Origin of Cellulose Acetate Electrophoresis

The year 2006 marks the 50th anniversary of the discovery of cellulose acetate (CA) electrophoresis by Joachim Kohn, a pathologist at Queen Mary’s Hospital in Roehampton, London. During a career in pathology that began in 1950 and spanned 37 years, Kohn published more than 50 papers in clinical laboratory medicine. He was the first to report the use of CA microbiology filters as solid supports for zone electrophoresis and the separation of hemoglobin phenotypes on CA membranes. Kohn also invented a new electrophoresis chamber and an 8-position stamp applicator especially for use with CA membranes. Beginning in 1957, Kohn pioneered the development of CA techniques for immunoelectrophoresis, counter immunoelectrophoresis, radial immunodiffusion, protein blotting, and immunofixation. He also designed a transport dressing for burn patients and was the first person to describe the use of an enzyme-based dipstick for measuring fingerstick blood glucose concentrations. This short review highlights Kohn’s discovery of CA electrophoresis and his contributions to the development of this procedure.

Initial medical management of patients severely irradiated in the Tokai-mura criticality accident

A nuclear criticality accident occurred in Japan on September 30, 1999, which resulted in severe exposure of three victims to mixed flux of neutrons and gamma-rays. Estimated average doses for the three victims were 5.4 Gy of neutrons and 8.5 Gy of gamma-rays for Patient A, 2.9 Gy of neutrons and 4.5 Gy of gamma-rays for Patient B, and 0.81 Gy of neutrons and 1.3 Gy of gamma-rays for Patient C. They then suffered the consequences of the effects of ionizing radiation resulting in acute radiation syndrome. In Patients A and B, bone marrow failure was so severe that they received haematopoietic stem cell transplantation. The graft initially took successfully in both patients, although in Patient B it was later taken over by his own haematopoietic cells. They also suffered from severe skin lesions, later exhibited gastrointestinal bleeding and eventually died of multiple organ failure 82 and 210 days after the accident, respectively. The survival of these patients beyond the period of agranulocytosis means that bone marrow failure per se caused by exposure to ionizing radiation may now be overcome. Patient C also developed bone marrow failure and was treated with granulocyte colony-stimulating factor as well as supportive care. He recovered without major complications and is now under periodical follow-up. Remarkably, during the prodromal phase, all the patients exhibited hypoxaemia, two of whom also showed interstitial oedema of the lungs. In Patient C these manifestations improved within a week. The circumstances of the accident and the initial medical treatment of the victims are described.

Biological and biophysical techniques to assess radiation exposure: a perspective

Biological dosimeters measure biologically relevant effects of radiation exposure that are in some sense an estimate of effective dose, whereas biophysical indicators serve as surrogates of absorbed dose in a manner analogous to conventional thermoluminescent dosimeters (TLD). The biological and biophysical dosimeters have the potential to play an important role in assessing unanticipated or occupational radiation exposures. For example, where the exposure is large and uncertain (i.e. radiation accidents), accurate dose information can help in deciding the most appropriate therapy and medical treatment. Another useful area is that of lifetime accumulated dose determination, and the ability to distinguish between and integrate the exposures from natural and anthropogenic (medical X-rays, indoor radon, natural background radiation, occupational and non-occupational exposures). Also, the possibility to monitor individual response and differences in inherent or induced radiation sensitivity may have important implications for radiation protection. More commonly, this type of dosimetry could be used for routine monitoring to detect and quantify unsuspected exposure, for regulatory purposes or for epidemiological studies of the long-term effects of radiation exposure (e.g. in Japanese A-bomb survivors or in the population surrounding Chernobyl). This review is a comparative study of the existing techniques and their future prospects. It summarizes the sensitivity, reproducibility, limiting dose, dose-rate, energy, LET response, sources of variability and uncertainty, and other practical aspects of each bio-indicator. The strengths and weaknesses of each approach are evaluated on the basis of common criteria for particular applications, and are summarized for each assay both in the text and in tabular form, for convenience. It is clear that no single indicator qualifies to reliably measure occupational exposures at the current levels of sensitivity conventional dosimetry services provide. Most of the bio-techniques are applicable to the detection of relatively high radiation exposures at relatively short times after exposure. Some of the bio-indicators have been identified that are, or offer future prospects for becoming, appropriate bio-indicators for dosimetry needs. However, all methods are subject to biological and other variables that are presently uncontrolled, and represent a major source of uncertainty. These include variations in background signals not directly associated with radiation exposure, inter- and intra-individual variability of radiation response, and genetic and environmental effects. Although these factors contribute to the lack of confidence in biological dosimetry, promising bio-indicators may be applied to large populations to establish the inherent variability and confounding factors that limit quantitative data collection and analysis, and reduce reliability and reproducibility.

Post-irradiation hyperamylasemia as a biological dosimeter

Serum alpha-amylase was measured before and 24 h after either total body (31 patients) or localized irradiation including the salivary glands (40 patients) or the pancreatic area (22 patients). A significant increase in amylasemia was observed for doses to the parotid glands larger than 0.5 Gy. A sigmoid function of dose was fitted to the data and predicted a maximum amylasemia level for doses larger than 4 Gy and smaller than 10 Gy. The raw data from other published series were adequately described by the same model. However, the confidence limits of the parameters remained wide, because of a considerable interindividual variability. Post-irradiation hyperamylasemia appears to provide a good criterion for triage of accidentally irradiated patients: 24 h after a dose larger than 2 Gy to the parotid glands, 91% of the patients had an amylasemia level higher than 2.5-fold the upper normal value (sensitivity). Conversely, 96% had their serum amylasemia lower than 2.5-fold the upper normal value when dose was smaller than 2 Gy (specificity). However, a retrospective estimation of the absorbed dose (dosimetry) is not likely to be very precise because of the large interindividual variability.

Isoamylase levels in bone marrow transplant patients are affected by total body irradiation and not by graft-versus-host disease

The mean total serum amylase levels in patients was 3.2 +/- 0.5 mukat/l (+/-SE) before total body irradiation (TBI) prior to bone marrow transplantation of which 50% was due to pancreatic isoamylase and 50% salivary isoamylase. Total serum amylase increased to a maximum of 100.3 +/- 12.3 mukat/l on the first day after TBI and most of this increase was due to an increase in salivary isoamylase (90.0 +/- 12.1 mukat/l). In association with this, all patients had clinical symptoms of parotitis. An increase in pancreatic isoamylase was found in 27% of the patients; however, none of them had clinical symptoms of pancreatitis. Serum amylase levels returned to normal within 5 days after TBI but then decreased to subnormal values, remaining below the normal range for 3 weeks. Pancreatic isoamylase returned to pre-irradiation levels 1.5 months after TBI, while salivary isoamylase remained low for the rest of the observation time. TBI of 7.5 Gy at 26 cGy/min gave significantly lower salivary amylase at 2 days after TBI compared with 10 Gy at 4 cGy/min: 32 +/- 4 versus 76 +/- 13 mukat/l (P less than 0.05). At 2.5 and 6 months after TBI significantly higher total amylase levels were recorded for patients treated with 7.5 Gy of TBI compared with 10 Gy: 2.5 +/- 0.4 and 2.7 +/- 0.3 versus 2.0 +/- 0.5 and 0.8 +/- 0.3 mukat/l, respectively (P less than 0.01, P less than 0.05, respectively). Acute or chronic GVHD did not affect acinar cells in this investigation.