RENEB Inter-Laboratory Comparison 2021: Inter-Assay Comparison of Eight Dosimetry Assays

Tools for radiation exposure reconstruction are required to support the medical management of radiation victims in radiological or nuclear incidents. Different biological and physical dosimetry assays can be used for various exposure scenarios to estimate the dose of ionizing radiation a person has absorbed. Regular validation of the techniques through inter-laboratory comparisons (ILC) is essential to guarantee high quality results. In the current RENEB inter-laboratory comparison, the performance quality of established cytogenetic assays [dicentric chromosome assay (DCA), cytokinesis-block micronucleus assay (CBMN), stable chromosomal translocation assay (FISH) and premature chromosome condensation assay (PCC)] was tested in comparison to molecular biological assays [gamma-H2AX foci (gH2AX), gene expression (GE)] and physical dosimetry-based assays [electron paramagnetic resonance (EPR), optically or thermally stimulated luminescence (LUM)]. Three blinded coded samples (e.g., blood, enamel or mobiles) were exposed to 0, 1.2 or 3.5 Gy X-ray reference doses (240 kVp, 1 Gy/min). These doses roughly correspond to clinically relevant groups of unexposed to low exposed (0-1 Gy), moderately exposed (1-2 Gy, no severe acute health effects expected) and highly exposed individuals (>2 Gy, requiring early intensive medical care). In the frame of the current RENEB inter-laboratory comparison, samples were sent to 86 specialized teams in 46 organizations from 27 nations for dose estimation and identification of three clinically relevant groups. The time for sending early crude reports and more precise reports was documented for each laboratory and assay where possible. The quality of dose estimates was analyzed with three different levels of granularity, 1. by calculating the frequency of correctly reported clinically relevant dose categories, 2. by determining the number of dose estimates within the uncertainty intervals recommended for triage dosimetry (±0.5 Gy or ±1.0 Gy for doses <2.5 Gy or >2.5 Gy), and 3. by calculating the absolute difference (AD) of estimated doses relative to the reference doses. In total, 554 dose estimates were submitted within the 6-week period given before the exercise was closed. For samples processed with the highest priority, earliest dose estimates/categories were reported within 5-10 h of receipt for GE, gH2AX, LUM, EPR, 2-3 days for DCA, CBMN and within 6-7 days for the FISH assay. For the unirradiated control sample, the categorization in the correct clinically relevant group (0-1 Gy) as well as the allocation to the triage uncertainty interval was, with the exception of a few outliers, successfully performed for all assays. For the 3.5 Gy sample the percentage of correct classifications to the clinically relevant group (≥2 Gy) was between 89-100% for all assays, with the exception of gH2AX. For the 1.2 Gy sample, an exact allocation to the clinically relevant group was more difficult and 0-50% or 0-48% of the estimates were wrongly classified into the lowest or highest dose categories, respectively. For the irradiated samples, the correct allocation to the triage uncertainty intervals varied considerably between assays for the 1.2 Gy (29-76%) and 3.5 Gy (17-100%) samples. While a systematic shift towards higher doses was observed for the cytogenetic-based assays, extreme outliers exceeding the reference doses 2-6 fold were observed for EPR, FISH and GE assays. These outliers were related to a particular material examined (tooth enamel for EPR assay, reported as kerma in enamel, but when converted into the proper quantity, i.e. to kerma in air, expected dose estimates could be recalculated in most cases), the level of experience of the teams (FISH) and methodological uncertainties (GE). This was the first RENEB ILC where everything, from blood sampling to irradiation and shipment of the samples, was organized and realized at the same institution, for several biological and physical retrospective dosimetry assays. Almost all assays appeared comparably applicable for the identification of unexposed and highly exposed individuals and the allocation of medical relevant groups, with the latter requiring medical support for the acute radiation scenario simulated in this exercise. However, extreme outliers or a systematic shift of dose estimates have been observed for some assays. Possible reasons will be discussed in the assay specific papers of this special issue. In summary, this ILC clearly demonstrates the need to conduct regular exercises to identify research needs, but also to identify technical problems and to optimize the design of future ILCs.

RENEB Inter-Laboratory Comparison 2021: The Gene Expression Assay

Early and high-throughput individual dose estimates are essential following large-scale radiation exposure events. In the context of the Running the European Network for Biodosimetry and Physical Dosimetry (RENEB) 2021 exercise, gene expression assays were conducted and their corresponding performance for dose-assessment is presented in this publication. Three blinded, coded whole blood samples from healthy donors were exposed to 0, 1.2 and 3.5 Gy X-ray doses (240 kVp, 1 Gy/min) using the X-ray source Yxlon. These exposures correspond to clinically relevant groups of unexposed, low dose (no severe acute health effects expected) and high dose exposed individuals (requiring early intensive medical health care). Samples were sent to eight teams for dose estimation and identification of clinically relevant groups. For quantitative reverse transcription polymerase chain reaction (qRT-PCR) and microarray analyses, samples were lysed, stored at 20°C and shipped on wet ice. RNA isolations and assays were run in each laboratory according to locally established protocols. The time-to-result for both rough early and more precise later reports has been documented where possible. Accuracy of dose estimates was calculated as the difference between estimated and reference doses for all doses (summed absolute difference, SAD) and by determining the number of correctly reported dose estimates that were defined as ±0.5 Gy for reference doses <2.5 Gy and ±1.0 Gy for reference doses >3 Gy, as recommended for triage dosimetry. We also examined the allocation of dose estimates to clinically/diagnostically relevant exposure groups. Altogether, 105 dose estimates were reported by the eight teams, and the earliest report times on dose categories and estimates were 5 h and 9 h, respectively. The coefficient of variation for 85% of all 436 qRT-PCR measurements did not exceed 10%. One team reported dose estimates that systematically deviated several-fold from reported dose estimates, and these outliers were excluded from further analysis. Teams employing a combination of several genes generated about two-times lower median SADs (0.8 Gy) compared to dose estimates based on single genes only (1.7 Gy). When considering the uncertainty intervals for triage dosimetry, dose estimates of all teams together were correctly reported in 100% of the 0 Gy, 50% of the 1.2 Gy and 50% of the 3.5 Gy exposed samples. The order of dose estimates (from lowest to highest) corresponding to three dose categories (unexposed, low dose and highest exposure) were correctly reported by all teams and all chosen genes or gene combinations. Furthermore, if teams reported no exposure or an exposure >3.5 Gy, it was always correctly allocated to the unexposed and the highly exposed group, while low exposed (1.2 Gy) samples sometimes could not be discriminated from highly (3.5 Gy) exposed samples. All teams used FDXR and 78.1% of correct dose estimates used FDXR as one of the predictors. Still, the accuracy of reported dose estimates based on FDXR differed considerably among teams with one team's SAD (0.5 Gy) being comparable to the dose accuracy employing a combination of genes. Using the workflow of this reference team, we performed additional experiments after the exercise on residual RNA and cDNA sent by six teams to the reference team. All samples were processed similarly with the intention to improve the accuracy of dose estimates when employing the same workflow. Re-evaluated dose estimates improved for half of the samples and worsened for the others. In conclusion, this inter-laboratory comparison exercise enabled (1) identification of technical problems and corrections in preparations for future events, (2) confirmed the early and high-throughput capabilities of gene expression, (3) emphasized different biodosimetry approaches using either only FDXR or a gene combination, (4) indicated some improvements in dose estimation with FDXR when employing a similar methodology, which requires further research for the final conclusion and (5) underlined the applicability of gene expression for identification of unexposed and highly exposed samples, supporting medical management in radiological or nuclear scenarios.

Transient Vasodilation in Mouse 4T1 Tumors after Intragastric and Intravenous Administration of Gold Nanoparticles

Gold nanoparticles (AuNPs) are foreseen as a promising tool in nanomedicine, both as drug carriers and radiosensitizers. They have been also proposed as a potential anticancer drug due to the anti-angiogenic effect in tumor tissue. In this work we investigated the effect of citrate-coated AuNPs of nominal diameter 20 nm on the growth and metastatic potential of 4T1 cells originated from a mouse mammary gland tumor inoculated into the mammary fat pad of Balb/ccmdb mice. To evaluate whether AuNPs can prevent the tumor growth, one group of inoculated mice was intragastrically (i.g.) administered with 1 mg/kg of AuNPs daily from day 1 to day 14 after cancer cell implantation. To evaluate whether AuNPs can attenuate the tumor growth, the second group was intravenously (i.v.) administered with 1 or 5 mg/kg of AuNPs, twice on day 5 and day 14 after inoculation. We did not observe any anticancer activity of i.v. nor i.g. administered AuNPs, as they did not affect neither the primary tumor growth rate nor the number of lung metastases. Unexpectedly, both AuNP treatment regimens caused a marked vasodilating effect in the tumor tissue. As no change of potential angiogenic genes (Fgf2, Vegfa) nor inducible nitric oxygenase (Nos2) was observed, we proposed that the vasodilation was caused by AuNP-dependent decomposition of nitrosothiols and direct release of nitric oxide in the tumor tissue.

Genotoxic potential of diesel exhaust particles from the combustion of first- and second-generation biodiesel fuels-the FuelHealth project

Epidemiological data indicate that exposure to diesel exhaust particles (DEPs) from traffic emissions is associated with higher risk of morbidity and mortality related to cardiovascular and pulmonary diseases, accelerated progression of atherosclerotic plaques, and possible lung cancer. While the impact of DEPs from combustion of fossil diesel fuel on human health has been extensively studied, current knowledge of DEPs from combustion of biofuels provides limited and inconsistent information about its mutagenicity and genotoxicity, as well as possible adverse health risks. The objective of the present work was to compare the genotoxicity of DEPs from combustion of two first-generation fuels, 7% fatty acid methyl esters (FAME) (B7) and 20% FAME (B20), and a second-generation 20% FAME/hydrotreated vegetable oil (SHB: synthetic hydrocarbon biofuel) fuel. Our results revealed that particulate engine emissions from each type of biodiesel fuel induced genotoxic effects in BEAS-2B and A549 cells, manifested as the increased levels of single-strand breaks, the increased frequencies of micronuclei, or the deregulated expression of genes involved in DNA damage signaling pathways. We also found that none of the tested DEPs showed the induction of oxidative DNA damage and the gamma-H2AX-detectable double-strand breaks. The most pronounced differences concerning the tested particles were observed for the induction of single-strand breaks, with the greatest genotoxicity being associated with the B7-derived DEPs. The differences in other effects between DEPs from the different biodiesel blend percentage and biodiesel feedstock were also observed, but the magnitude of these variations was limited.

A comparative analysis of in vitro toxicity of diesel exhaust particles from combustion of 1st- and 2nd-generation biodiesel fuels in relation to their physicochemical properties-the FuelHealth project

Biodiesels represent more carbon-neutral fuels and are introduced at an increasing extent to reduce emission of greenhouse gases. However, the potential impact of different types and blend concentrations of biodiesel on the toxicity of diesel engine emissions are still relatively scarce and to some extent contradictory. The objective of the present work was to compare the toxicity of diesel exhaust particles (DEP) from combustion of two 1st-generation fuels: 7% fatty acid methyl esters (FAME; B7) and 20% FAME (B20) and a 2nd-generation 20% FAME/HVO (synthetic hydrocarbon biofuel (SHB)) fuel. Our findings indicate that particulate emissions of each type of biodiesel fuel induce cytotoxic effects in BEAS-2B and A549 cells, manifested as cell death (apoptosis or necrosis), decreased protein concentrations, intracellular ROS production, as well as increased expression of antioxidant genes and genes coding for DNA damage-response proteins. The different biodiesel blend percentages and biodiesel feedstocks led to marked differences in chemical composition of the emitted DEP. The different DEPs also displayed statistically significant differences in cytotoxicity in A549 and BEAS-2B cells, but the magnitude of these variations was limited. Overall, it seems that increasing biodiesel blend concentrations from the current 7 to 20% FAME, or substituting 1st-generation FAME biodiesel with 2nd-generation HVO biodiesel (at least below 20% blends), affects the in vitro toxicity of the emitted DEP to some extent, but the biological significance of this may be moderate.

Abstract 236: Heart Failure Remodeling: Local Endogenous Erythropoietin and Erythropoietin Receptor Expression

Erythropoietin (EPO) via erythropoietin receptor (EPOR) maintains myeloid erythropoiesis, however in a failing heart (FH) it seems to exert cytoprotective, antiapoptotic, proangiogenic effects.

Aim: to assess (myocardial) M-EPOR expression and to find out if erythropoietin (M-EPO) is produced in human heart; secondary to elucidate the mechanisms related to M-EPO/M-EPOR expression.

Methods: We used 33 explanted FH, compared to 11 non-failing hearts (NFH). Patients characteristics: left ventricle (LV - EF 22±11%), NTproBNP (5464±4825 pg/ml). Serum variables: iron (62±32ug/dl), ferritin (156±122ng/ml), transferrin receptor (3.8±2.6mg/l), EPO (29.5±44.4mIU/ml), HT (39.8±5.3%), Hb (13.2±1.7g/dl), creatinine clearance (CrCl 68±23 ml/min), Na+ (138±5.4 mmol/l).

Myocardial assesment: M-EPO, M-EPOR, iron storage protein - ferritin (M-FR), iron acquisition protein transferrin receptor (M-TfR), Iron Regulatory Protein 1 (M-IRP1) - by ELISA - ng/mg protein - expression; myocardial iron load - by Instrumental Neutron Activation Analysis, µg/g.

Results: In FH and NFH M-EPO/M-EPOR expression were detected; M-EPO was elevated in failing LV (in FH vs NFH 4.7±1.6 vs 3.7±1.4, p=0.0346; ng/mg protein), no changes in M-EPOR was found. M-EPO correlated with M-EPOR from both ventricles (LV- left r=0.63, p=0.0002; RV - right r=0.42, p=0.0161). With regard to anemia (by WHO), patients were divided into two subgroups: A+ (n=11) and A- (n=22). In A+ vs A- serum EPO (47±23 vs 28±30 mIU/l, p=0.0473) was higher. In myocardium A+ M-TfR was lower than in A- both LV (136±61 vs 218±134; p=0.0446) and RV (130±92 vs 199±143; p=0.0688), however no differences in M-EPO/M-EPOR/M-FR/M-IRP1 and iron load were found. In LV, A+ subgroup, IRP1 correlation with M-EPO (r=0.79, p=0.0107) and M-EPOR (r=0.76, p=0.0184).

Conclusions: M-EPO/M-EPOR are synthesized locally in human hearts. In failing LV M-EPO synthesis is significantly increased. M-EPO production correlated with M-EPOR expression. M-EPO/EPOR expression is associated with regulatory protein IRP1. The presence of anemia accompanied by high plasma EPO is not connected with modification of myocardial expression: M-EPO/M-EPOR/M-FR/M-IRP1, iron load, except for M-TfR.

Cu,Zn-superoxide dismutase deficiency in mice leads to organ-specific increase in oxidatively damaged DNA and NF-κB1 protein activity

Earlier experimental studies have demonstrated that: i) Cu,Zn-superoxide dismutase deficiency leads to oxidative stress and carcinogenesis; ii) dysregulation of NF-κB pathway can mediate a wide variety of diseases, including cancer. Therefore, we decided, for the first time, to examine the level of oxidative DNA damage and the DNA binding activity of NF-κB proteins in SOD1 knockout, heterozygous and wild-type mice. Two kinds of biomarkers of oxidatively damaged DNA: urinary excretion of 8-oxodG and 8-oxoGua, and the level of oxidatively damaged DNA were analysed using HPLC-GC-MS and HPLC-EC. The DNA binding activity of p50 and p65 proteins in a nuclear extracts was assessed using NF-κB p50/p65 EZ-TFA transcription factor assay. These parameters were determined in the brain, liver, kidney and urine of SOD1 knockout, heterozygous and wild-type mice. The level of 8-oxodG in DNA was higher in the liver and kidney of knockout mice than in wild type. No differences were found in urinary excretion of 8-oxoGua and 8-oxodG between wild type and the SOD1-deficient animals. The activity of the p50 protein was higher in the kidneys, but surprisingly not in the livers of SOD1-deficient mice, whereas p65 activity did not show any variability. Our results indicate that in Cu,Zn-SOD-deficient animals the level of oxidative DNA damage and NF-κB1 activity are elevated in certain organs only, which may provide some explanation for organ-specific ROS-induced carcinogenesis.

Cu,Zn-superoxide dismutase deficiency in mice leads to organ-specific increase in oxidatively damaged DNA and NF-κB1 protein activity

Earlier experimental studies have demonstrated that: i) Cu,Zn-superoxide dismutase deficiency leads to oxidative stress and carcinogenesis; ii) dysregulation of NF-κB pathway can mediate a wide variety of diseases, including cancer. Therefore, we decided, for the first time, to examine the level of oxidative DNA damage and the DNA binding activity of NF-κB proteins in SOD1 knockout, heterozygous and wild-type mice. Two kinds of biomarkers of oxidatively damaged DNA: urinary excretion of 8-oxodG and 8-oxoGua, and the level of oxidatively damaged DNA were analysed using HPLC-GC-MS and HPLC-EC. The DNA binding activity of p50 and p65 proteins in a nuclear extracts was assessed using NF-κB p50/p65 EZ-TFA transcription factor assay. These parameters were determined in the brain, liver, kidney and urine of SOD1 knockout, heterozygous and wild-type mice. The level of 8-oxodG in DNA was higher in the liver and kidney of knockout mice than in wild type. No differences were found in urinary excretion of 8-oxoGua and 8-oxodG between wild type and the SOD1-deficient animals. The activity of the p50 protein was higher in the kidneys, but surprisingly not in the livers of SOD1-deficient mice, whereas p65 activity did not show any variability. Our results indicate that in Cu,Zn-SOD-deficient animals the level of oxidative DNA damage and NF-κB1 activity are elevated in certain organs only, which may provide some explanation for organ-specific ROS-induced carcinogenesis.