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Impact of aging on gene expression response to x-ray irradiation using mouse blood.

ABSTRACT: As a radiation biodosimetry tool, gene expression profiling is being developed using mouse and human peripheral blood models. The impact of dose, dose-rate, and radiation quality has been studied with the goal of predicting radiological tissue injury. In this study, we determined the impact of aging on the gene expression profile of blood from mice exposed to radiation. Young (2 mo) and old (21 mo) male mice were irradiated with 4 Gy x-rays, total RNA was isolated from whole blood 24 h later, and subjected to whole genome microarray analysis. Pathway analysis of differentially expressed genes revealed young mice responded to x-ray exposure by significantly upregulating pathways involved in apoptosis and phagocytosis, a process that eliminates apoptotic cells and preserves tissue homeostasis. In contrast, the functional annotation of senescence was overrepresented among differentially expressed genes from irradiated old mice without enrichment of phagocytosis pathways. Pathways associated with hematologic malignancies were enriched in irradiated old mice compared with irradiated young mice. The fibroblast growth factor signaling pathway was underrepresented in older mice under basal conditions. Similarly, brain-related functions were underrepresented in unirradiated old mice. Thus, age-dependent gene expression differences should be considered when developing gene signatures for use in radiation biodosimetry.

SUBMITTER: Broustas CG

PROVIDER: S-EPMC8119453 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background: In the event of an improvised nuclear device or radiological dirty bomb detonation large numbers of people will be exposed to radiation that would require a timely and accurate biodosimetry to identify the highly exposed individuals who would require medical treatment from those who have received low or no radiation (the “worried well”). Gene expression signatures in response to radiation have been derived from mice and human peripheral blood and the impact of a number of variables, such as dose, time, genotype, and gender, on gene expression has been analyzed. However, the impact of aging on radiation gene profiling has not been taken into consideration. Results: Global gene expression was measured in the blood of young (2 mo) and old (21 mo) male C57BL/6J mice 1 day after they were exposed to 4 Gy x-rays or they were sham irradiated (control) using the Agilent Mouse Whole Genome microarrays. Animals exposed to radiation suppressed expression of DNA repair genes with fold-changes being very similar to the two age groups. A notable exception was Mismatch Repair (MMR) that was significantly enriched among the downregulated genes in irradiated old mice (p = 2.34E-09) compared with irradiated young mice (p = 1.62E-04). Furthermore, cardiac hypertrophy signaling (p < 0.002) and the role of NFAT in cardiac hypertrophy (p = 0.01) were predicted to be enriched among the upregulated differentially expressed genes in irradiated old mice, but not irradiated young mice. In contrast, young mice respond to x-ray exposure by significantly upregulating genes involved in phagosome formation (p = 3.09E-07), phagosome maturation (p = 0.001), and Fcγ receptor-mediated phagocytosis (p = 0.03), all crucial processes that eliminates apoptotic cells and preserve tissue homeostasis. Conclusions: We show that age is a variable that has the potential to fundamentally alter the transcriptomic profile of irradiated mouse blood. A number of biological processes, including phagocytosis, are differentially represented in young and old mice exposed to x-ray radiation. Our results highlight the significance of age as a variable that can have profound biological effects that will affect medical management and treatment decisions in case of a radiological emergency.

Project description:BackgroundIn the event of an improvised nuclear device detonation, the prompt radiation exposure would consist of photons plus a neutron component that would contribute to the total dose. As neutrons cause more complex and difficult to repair damage to cells that would result in a more severe health burden to affected individuals, it is paramount to be able to estimate the contribution of neutrons to an estimated dose, to provide information for those making treatment decisions.ResultsMice exposed to either 0.25 or 1 Gy of neutron or 1 or 4 Gy x-ray radiation were sacrificed at 1 or 7 days after exposure. Whole genome microarray analysis identified 7285 and 5045 differentially expressed genes in the blood of mice exposed to neutron or x-ray radiation, respectively. Neutron exposure resulted in mostly downregulated genes, whereas x-rays showed both down- and up-regulated genes. A total of 34 differentially expressed genes were regulated in response to all ≥1 Gy exposures at both times. Of these, 25 genes were consistently downregulated at days 1 and 7, whereas 9 genes, including the transcription factor E2f2, showed bi-directional regulation; being downregulated at day 1, while upregulated at day 7. Gene ontology analysis revealed that genes involved in nucleic acid metabolism processes were persistently downregulated in neutron irradiated mice, whereas genes involved in lipid metabolism were upregulated in x-ray irradiated animals. Most biological processes significantly enriched at both timepoints were consistently represented by either under- or over-expressed genes. In contrast, cell cycle processes were significant among down-regulated genes at day 1, but among up-regulated genes at day 7 after exposure to either neutron or x-rays. Cell cycle genes downregulated at day 1 were mostly distinct from the cell cycle genes upregulated at day 7. However, five cell cycle genes, Fzr1, Ube2c, Ccna2, Nusap1, and Cdc25b, were both downregulated at day 1 and upregulated at day 7.ConclusionsWe describe, for the first time, the gene expression profile of mouse blood cells following exposure to neutrons. We have found that neutron radiation results in both distinct and common gene expression patterns compared with x-ray radiation.

Project description:Background: In the event of an improvised nuclear device detonation, the prompt radiation exposure would consist of γ rays plus a neutron component that would contribute to the total dose. As neutrons cause more complex and difficult to repair damage to cells that would result in more severe health burden to affected individuals, it is paramount to be able to estimate the contribution of neutrons to an estimated dose, to provide information for those making treatment decisions. Results: Mice exposed to either 0.25 or 1 Gy of neutron or 1 or 4 Gy x-ray radiation were sacrificed at 1 or 7 days after exposure. Whole genome microarray analysis identified 7,285 and 5,045 differentially expressed genes in the blood of mice exposed to neutron or x-ray radiation, respectively. Neutron exposure resulted in mostly downregulated genes, whereas x-rays showed both down- and up-regulated genes. A total of 34 differentially expressed genes were regulated in response to all ≥1 Gy exposures at both times. Of these, 25 genes were consistently downregulated at days 1 and 7, whereas 9 genes, including the transcription factor E2f2, showed bi-directional regulation; being downregulated at day 1, while upregulated at day 7. Gene ontology analysis revealed that genes involved in nucleic acid metabolism processes were persistently downregulated in neutron irradiated mice, whereas genes involved in lipid metabolism were upregulated in x-ray irradiated animals. Most biological processes significantly enriched at both timepoints were consistently represented by either under- or over-expressed genes. In contrast, cell cycle processes were significant among down-regulated genes at day 1, but among up-regulated genes at day 7 after exposure to either neutron or x-rays. Cell cycle genes downregulated at day 1 were mostly distinct from the cell cycle genes upregulated at day 7. However, five cell cycle genes, Fzr1, Ube2c, Ccna2, Nusap1, and Cdc25b, were both downregulated at day 1 and upregulated at day 7. Conclusions: We describe, for the first time, the gene expression profile of mouse blood cells following exposure to neutrons. We have found that neutron radiation results in both distinct and common gene expression patterns compared with x-ray radiation.

Project description:In the event of an improvised nuclear device or "dirty bomb" in a highly populated area, potentially hundreds of thousands of people will require screening to ensure that exposed individuals receive appropriate treatment. For this reason, there is a need to develop tools for high-throughput radiation biodosimetry. Gene expression represents an emerging approach to biodosimetry and could potentially provide an estimate of both absorbed dose and individual radiation-induced injury. Since approximately 2-4% of humans are thought to be radiosensitive, and would suffer greater radiological injury at a given dose than members of the general population, it is of interest to explore the potential impact of such sensitivity on the biodosimetric gene expression signatures being developed. In this study, we used wild-type mice and genetically engineered mouse models deficient in two DNA repair pathways that can contribute to radiation sensitivity to estimate the maximum effect of differences in radiosensitivity. We compared gene expression in response to a roughly equitoxic (LD50/30) dose of gamma rays in wild-type C57BL/6 (8 Gy) and DNA double-strand break repair-deficient Atm-/- (4 Gy) and Prkdcscid (3 Gy) mutants of C57BL/6. Overall, 780 genes were significantly differentially expressed in wild-type mice one day postirradiation, 232 in Atm-/- and 269 in Prkdcscid. Upstream regulators including TP53 and NFκB were predicted to be activated by radiation exposure in the wild-type mice, but not in either of the DNA repair-deficient mutant strains. There was also a significant muting of the apparent inflammatory response triggered by radiation in both mutant strains. These differences impacted the ability of gene expression signatures developed in wild-type mice to detect potentially fatal radiation exposure in the DNA repair-deficient mice, with the greatest impact on Atm-/- mice. However, the inclusion of mutant mice in gene selection vastly improved performance of the classifiers.

Project description:BackgroundThe three-layered meninges cover and protect the central nervous system and form the interface between cerebrospinal fluid and the brain. They are host to a lymphatic system essential for maintaining fluid dynamics inside the cerebrospinal fluid-filled subarachnoid space and across the brain parenchyma via their connection to glymphatic structures. Meningeal fibroblasts lining and traversing the subarachnoid space have direct impact on the composition of the cerebrospinal fluid through endocytotic uptake as well as extensive protein secretion. In addition, the meninges are an active site for immunological processes and act as gatekeeper for immune cells entering the brain. During aging in mice, lymphatic drainage from the brain is less efficient contributing to neurodegenerative processes. Aging also affects the immunological status of the meninges, with increasing numbers of T cells, changing B cell make-up, and altered macrophage complement.MethodsWe employed RNASeq to measure gene expression and to identify differentially expressed genes in meninges isolated from young and aged mice. Using Ingenuity pathway, GO term, and MeSH analyses, we identified regulatory pathways and cellular functions in meninges affected by aging.ResultsAging had profound impact on meningeal gene expression. Pathways related to innate as well as adaptive immunity were affected. We found evidence for increasing numbers of T and B lymphocytes and altered activity profiles for macrophages and other myeloid cells. Furthermore, expression of pro-inflammatory cytokine and chemokine genes increased with aging. Similarly, the complement system seemed to be more active in meninges of aged mice. Altered expression of solute carrier genes pointed to age-dependent changes in cerebrospinal fluid composition. In addition, gene expression for secreted proteins showed age-dependent changes, in particular, genes related to extracellular matrix composition and organization were affected.ConclusionsAging has profound effects on meningeal gene expression; thereby affecting the multifaceted functions meninges perform to maintain the homeostasis of the central nervous system. Thus, age-dependent neurodegenerative processes and cognitive decline are potentially in part driven by altered meningeal function.

Project description:An exaggerated blood pressure (BP) response to exercise has been linked to cardiovascular disease, but little is known about the impact of age and sex on this response. Therefore, this study examined the hemodynamic and skeletal muscle metabolic response to dynamic plantar flexion exercise, at 40% of maximum plantar flexion work rate, in 40 physical activity-matched young (23 ± 1 yr, n = 20) and old (73 ± 2 yr, n = 20), equally distributed, male and female subjects. Central hemodynamics and BP (finometer), popliteal artery blood flow (Doppler ultrasound), and skeletal muscle metabolism (31P-magnetic resonance spectroscopy) were measured during 5 min of plantar flexion exercise. Popliteal artery blood flow and high-energy phosphate responses to exercise were not affected by age or sex, whereas aging, independent of sex, attenuated stroke volume and cardiac output responses. Systolic BP and mean arterial pressure responses were exaggerated in old women (?42 ± 4 and ?28 ± 3 mmHg, respectively), with all other groups exhibiting similar increases in systolic BP (old men: ?27 ± 8 mmHg, young men: ?27 ± 3 mmHg, and young women: ?22 ± 3 mmHg) and mean arterial pressure (old men: ?15 ± 4 mmHg, young men: ?19 ± 2 mmHg, and young women: ?17 ± 2 mmHg). Interestingly, the exercise-induced change in systemic vascular resistance in old women (?0.8 ± 1.0 mmHg·l-1·min-1) was augmented compared with young women and young and old men (?-2.8 ± 0.5, ?-1.6 ± 0.6, and ?-3.18 ± 1.4 mmHg·l-1·min-1, respectively, P < 0.05). Thus, in combination, advancing age and female sex results in an exaggerated BP response to exercise, likely the result of a failure to reduce systemic vascular resistance. NEW & NOTEWORTHY An exaggerated blood pressure response to exercise has been linked to cardiovascular disease; however, little is known about how age and sex impact this response in healthy individuals. During dynamic exercise, older women exhibited an exaggerated blood pressure response driven by an inability to lower systemic vascular resistance.

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Impact of aging on gene expression response to x-ray irradiation using mouse blood.

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