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Gene expression changes and DNA damage after ex vivo exposure of peripheral blood cells to various CT photon spectra.

ABSTRACT: Dual-energy CT provides enhanced diagnostic power with similar or even reduced radiation dose as compared to single-energy CT. Its principle is based on the distinct physical properties of low and high energetic photons, which, however, may also affect the biological effectiveness and hence the extent of CT-induced cellular damage. Therefore, a comparative analysis of biological effectiveness of dual- and single-energy CT scans with focus on early gene regulation and frequency of radiation-induced DNA double strand breaks (DSBs) was performed. Blood samples from three healthy individuals were irradiated ex vivo with single-energy (80 kV and 150 kV) and dual-energy tube voltages (80 kV/Sn150kV) employing a modern dual source CT scanner resulting in Volume Computed Tomography Dose Index (CTDIvol) of 15.79-18.26 mGy and dose length product (DLP) of 606.7-613.8 mGy*cm. Non-irradiated samples served as a control. Differential gene expression in peripheral blood mononuclear cells was analyzed 6 h after irradiation using whole transcriptome sequencing. DSB frequency was studied by 53BP1 + γH2AX co-immunostaining and microscopic evaluation of their focal accumulation at DSBs. Neither the analysis of gene expression nor DSB frequency provided any evidence for significantly increased biological effectiveness of dual-energy CT in comparison to samples irradiated with particular single-energy CT spectra. Relative to control, irradiated samples were characterized by a significantly higher rate of DSBs (p < 0.001) and the shared upregulation of five genes, AEN, BAX, DDB2, FDXR and EDA2R, which have already been suggested as radiation-induced biomarkers in previous studies. Despite steadily decreasing doses, CT diagnostics remain a genotoxic stressor with impact on gene regulation and DNA integrity. However, no evidence was found that varying X-ray spectra of CT impact the extent of cellular damage.

SUBMITTER: Kaatsch HL

PROVIDER: S-EPMC8187728 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:In the current global scenario there is always a possibility that a terrorist group might acquire material to produce a nuclear device. In the likelihood of a detonation of an improvised nuclear device (IND) the prompt radiation would consist of both photons (gamma rays) and neutrons. As neutrons generally have a high Relative Biological Effectiveness (RBE) for most physiological endpoints, it is important to understand the impact that neutrons would have on the biodosimetry methods that are being developed for medical triage purposes. We have previously reported transcriptomic response in human and mouse blood to neutron exposure and determined its RBE compared to photons for gene induction. In this report, we studied the effect of mixed neutron-photon radiation on gene expression in human peripheral blood in order to mimic an IND type radiation observed increase in number as well as expression level of genes with increasing percentage of neutron in mixed exposures which peaked at 25% neutron exposure which was maximum neutron percentage used for the study. We identified 156 genes that responded significantly to all the neutron-photon mixed exposures. These genes were found to be mainly involved in p53 signaling and DNA damage response. The 25% neutron exposure also showed maximum enrichment of known neutron associated gene ontology terms reported in the previous studies. Analysis of upstream regulators of gene expression showed strong activation of TP53, SLC29A1, PDCD1 and suppression of ANLN, AURK and ANXA2 across all exposures. While AGT was exclusively activated by neutron specific exposures. We confirmed the expression of genes which showed increased expression as a function of increased neutron percentage using quantitative real-time RT-PCR which matched with the microarray data. Thus, the data in this current study clearly indicates that gene expression can be used to estimate the percentage of the neutron component in mixed neutron-photon exposures.

Project description:BackgroundTo identify subjects with rupture-prone atherosclerotic plaques before thrombotic events occur is an unmet clinical need. Thus, this proof-of-concept study aims to determine which rupture-prone plaque features can be detected using clinically available photon-counting computed tomography (PCCT).MethodsIn this retrospective study, advanced atherosclerotic plaques (ex vivo, paraffin-embedded) from the Carotid Plaque Imaging Project were scanned by PCCT with reconstructed energy levels (45, 70, 120, 190 keV). Density in HU was measured in 97 regions of interest (ROIs) representing rupture-prone plaque features as demonstrated by histopathology (thrombus, lipid core, necrosis, fibrosis, intraplaque haemorrhage, calcium). The relationship between HU and energy was then assessed using a mixed-effects model for each plaque feature.ResultsPlaques from five men (age 79 ± 8 [mean ± standard deviation]) were included in the study. Comparing differences in coefficients (b1diff) of matched ROIs on plaque images obtained by PCCT and histology confirmed that calcium was distinguishable from all other analysed features. Of greater novelty, additional rupture-prone plaque features proved discernible from each other, particularly when comparing haemorrhage with fibrous cap (p = 0.017), lipids (p = 0.003) and necrosis (p = 0.004) and thrombus compared to fibrosis (p = 0.048), fibrous cap (p = 0.028), lipids (p = 0.015) and necrosis (p = 0.017).ConclusionsClinically available PCCT detects not only calcification, but also other rupture-prone features of human carotid plaques ex vivo.Relevance statementImproved atherosclerotic plaque characterisation by photon-counting CT provides the ability to distinguish not only calcium, but also rupture-prone plaque features such as haemorrhage and thrombus. This may potentially improve monitoring and risk stratification of atherosclerotic patients in order to prevent strokes.Key points• CT of atherosclerotic plaques mainly detects calcium. • Many components, such as intra-plaque haemorrhage and lipids, determine increased plaque rupture risk. • Ex vivo carotid plaque photon-counting CT distinguishes haemorrhage and thrombus. • Improved plaque photon-counting CT evaluation may refine risk stratification accuracy to prevent strokes.

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Gene expression changes and DNA damage after ex vivo exposure of peripheral blood cells to various CT photon spectra.

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