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Radiation dose-rate effects on gene expression for human biodosimetry

ABSTRACT: Background: The effects of dose-rate and its implications on radiation biodosimetry methods are not well studied in the context of large-scale radiological scenarios. There are significant health risks to individuals exposed to an acute dose in such an event, but the most realistic scenario would be a combination of exposure to both high and low dose-rates, from both external and internal radioactivity. It is important therefore, to understand the biological response to prolonged exposure; and further, discover biomarkers that can be used to estimate the extent of damage from low-dose rate exposure and propose appropriate clinical treatment. Methods: We irradiated human whole blood ex vivo to three doses, 0.56 Gy, 2.25 Gy and 4.45 Gy, using two dose rates: 1.1Gy/min and 3.1mGy/min. After 24 hours, we isolated RNA from blood cells and hybridized these to Agilent Whole Human genome microarrays. We validated the microarray results using qRT-PCR. Results: Microarray results showed that there were 454 significantly differentially expressed genes after prolonged exposure to all doses. After acute exposure, 598 genes were differentially expressed to all doses combined. Gene ontology terms enriched in both sets of genes were related to immune processes and B cell mediated immunity. Genes responding to acute exposure was also enriched in functions related to natural killer cell activation and cell-to-cell signaling. As expected, p53 pathway was found to be significantly enriched at all doses and by both dose-rates of radiation. Prediction algorithms were able to distinguish between low dose-rate and acute exposures, on the basis of a group of genes. These maybe candidates for preliminary testing as markers for differences in gene expression based on dose-rate.

ORGANISM(S): Homo sapiens

PROVIDER: GSE65292 | GEO | 2015/04/28

SECONDARY ACCESSION(S): PRJNA273634

REPOSITORIES: GEO

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Project description:Background: The effects of dose-rate and its implications on radiation biodosimetry methods are not well studied in the context of large-scale radiological scenarios. There are significant health risks to individuals exposed to an acute dose in such an event, but the most realistic scenario would be a combination of exposure to both high and low dose-rates, from both external and internal radioactivity. It is important therefore, to understand the biological response to prolonged exposure; and further, discover biomarkers that can be used to estimate the extent of damage from low-dose rate exposure and propose appropriate clinical treatment. Methods: We irradiated human whole blood ex vivo to three doses, 0.56 Gy, 2.25 Gy and 4.45 Gy, using two dose rates: 1.1Gy/min and 3.1mGy/min. After 24 hours, we isolated RNA from blood cells and hybridized these to Agilent Whole Human genome microarrays. We validated the microarray results using qRT-PCR. Results: Microarray results showed that there were 454 significantly differentially expressed genes after prolonged exposure to all doses. After acute exposure, 598 genes were differentially expressed to all doses combined. Gene ontology terms enriched in both sets of genes were related to immune processes and B cell mediated immunity. Genes responding to acute exposure was also enriched in functions related to natural killer cell activation and cell-to-cell signaling. As expected, p53 pathway was found to be significantly enriched at all doses and by both dose-rates of radiation. Prediction algorithms were able to distinguish between low dose-rate and acute exposures, on the basis of a group of genes. These maybe candidates for preliminary testing as markers for differences in gene expression based on dose-rate. Radiation induced gene expression was measured in ex vivo irradiated human blood, at the 24hr time point after irradiation. Doses (0.56 Gy, 2.2 Gy and 4.45 Gy) were delivered by two dose rates, acute dose rate of 1Gy/min and low dose rate of 3.1 mGy/min.

Project description:Purpose: The International Commission on Radiological Protection (ICRP) recently recommended reducing the occupational equivalent dose limit for the lens of the eye. Based primarily on a review of epidemiological data, the absorbed dose threshold is now considered to be 0.5 Gy for induction of acute opacities, reduced from the previous threshold of 2 Gy. However, direct mechanistic evidence to support an understanding of the underlying molecular mechanisms of damage is still lacking. To this end, we explored the effects of a broad dose-range of ionizing radiation exposure on gene expression changes in a human lens epithelial (HLE) cell-line in order to better understand the shape of the dose-response relationship and identify transcriptional thresholds of effects. Methods: HLE cells were exposed to doses of 0, 0.01, 0.05, 0.25, 0.5, 2, and 5 Gy of X-ray radiation at two dose rates (1.62 cGy/min and 38.2 cGy/min). Cell culture lysates were collected 20 h post-exposure and analysed using whole-genome RNA-sequencing. Pathways and dose-thresholds of biological effects were identified using benchmark dose (BMD) modeling. Results: Transcriptional responses were minimal at doses less than 2 Gy. At higher doses there were a significant number of differentially expressed genes (DEGs) (p < 0.05, fold change > |1.5|) at both dose rates, with 1308 DEGs for the low dose rate (LDR) and 840 DEGs for the high dose rate (HDR) exposure. Dose-response modeling showed that a number of genes exhibited non-linear bi-phasic responses, which was verified by digital droplet PCR. BMD analysis showed the majority of the pathways responded at BMD median values in the dose range of 1.5-2.5 Gy, with the lowest BMD median value being 0.6 Gy for the HDR exposure. The minimum pathway BMD median value for LDR exposure, however, was 2.5 Gy. Although the LDR and HDR exposures shared pathways involved in extracellular matrix reorganization and collagen production with BMD median value of 2.9 Gy, HDR exposures were more effective in activating pathways associated with DNA damage response, apoptosis, and cell cycling relative to LDR exposure. Conclusion: Overall, the results suggest that radiation induces complex non-linear transcriptional dose-response relationships that are dose-rate dependent. Pathways shared between the two dose rates may be important contributors to radiation-induced cataractogenesis. BMD analysis suggests that the majority of pathways are activated above 0.6 Gy, which supports current ICRP identified dose thresholds for deterministic effects to the lens of the eye of 0.5 Gy.

Project description:Measuring global gene expression using cDNA or oligonucleotide microarrays is an effective approach to understanding the complex mechanisms of the effects of radiation. However, few studies have been carried out that investigate gene expression in vivo after prolonged exposure to low-dose-rate radiation. In this study, C57BL/6J mice were continuously irradiated with ?-rays for 485 days at dose-rates of 0.032 – 13 ?Gy/min. Gene expression profiles in the kidney and testis from irradiated and unirradiated mice were analyzed, and differentially expressed genes were identified. A combination of pathway analysis and hierarchical clustering of differentially expressed genes revealed that expression of genes involved in mitochondrial oxidative phosphorylation was elevated in the kidney after irradiation at the dose-rates of 0.65 ?Gy/min and 13 ?Gy/min. Expression of cell cycle-associated genes was not profoundly modulated in the kidney, in contrast to the response to acute irradiation, suggesting a threshold in the dose-rate for modulation of the expression of cell cycle-related genes in vivo following exposure to radiation. We demonstrated that changes to the gene expression profile in the testis were largely different from those in the kidney. The Gene Ontology categories “DNA metabolism”, “response to DNA damage” and “DNA replication” overlapped significantly with the clusters of genes whose expression decreased with an increase in the dose-rate to the testis. These observations provide a fundamental insight into the organ-specific responses to low-dose-rate radiation. Key Words: kidney, low-dose-rate, radiation, microarray, mitochondrial oxidative phosphorylation, testis 3 biological replicates for each experimental group were analysed. GSE14290_Kidney_raw_data.csv contains the raw data for GSM357146, GSM357425, GSM357426, GSM357452 to GSM357460. GSE14290_Testis_raw_data.csv contains the raw data for GSM357471 to GSM357482. In these files, the sample identifiers are included in the column headers.

Project description:The biomedical consequences of space radiation pose a significant concern for astronauts engaged in deep space. However, the effects of long-term low dose-rate exposures in space environments remain elusive. In this study, we simulated the space radiation environment by exposing human bronchial epithelial cells to low dose-rate (0.0067 Gy/day) α-particles, and continuously irradiated them multiple times to achieve cumulative total doses of 0.2 Gy, 0.4 Gy, and 0.5 Gy, respectively. At the same time, the cells were irradiated with the same total dose in a single exposure to investigate the potential of low dose-rate alpha particles to induce malignant transformation of human bronchial epithelial cells. A comprehensive suite of assays was employed to assess tumorigenic potential, including tumor formation in NOD/SCID mice, immunohistochemistry, CCK-8 proliferation assay, invasion assay, and the evaluation of multicellular spheroid formation during subsequent passages post-irradiation. Moreover, we dissected differential malignant mechanisms in tumor evolution ecosystem induced by the two distinct irradiation modes from systems biology views based on scRNA-seq technology. Our results showed that exposure to α-particles, whether through a single acute exposure or long-term low dose-rate exposures, induced the occurrence and development of tumors. Long-term low dose-rate exposures to α-particles increase the malignancy of induced tumors, but not the risk of carcinogenesis, compared to a single acute exposure with the same total dose. In addition, through scRNA-seq, we found that long-term low dose-rate exposures triggered more copy number variation (CNV) and epithelial-mesenchymal transition (EMT) events, and the activation of DNA damage repair pathways occurred significantly later than with a single acute exposure and involved more specific changes in cellular communication dynamics. In conclusion, our findings provide emerging yet convincing evidence that not only sheds light on why cells exposed to long-term low dose-rate exposures exhibit heightened malignancy, but also offers valuable insights into the genetic determinants driving tumor evolution and heterogeneity.

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Radiation dose-rate effects on gene expression for human biodosimetry

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