Abstract
BackgroundExposure to ionizing radiation induces complex stress responses in cells, which can lead to adverse health effects such as cancer. Although a variety of studies investigated gene expression and affected pathways in human fibroblasts after exposure to ionizing radiation, the understanding of underlying mechanisms and biological effects is still incomplete due to different experimental settings and small sample sizes. Therefore, this study aims to identify the time point with the highest number of differentially expressed genes and corresponding pathways in primary human fibroblasts after irradiation at two preselected time points.MethodsFibroblasts from skin biopsies of 15 cell donors were exposed to a high (2Gy) and a low (0.05Gy) dose of X-rays. RNA was extracted and sequenced 2 h and 4 h after exposure. Differentially expressed genes with an adjusted p-value < 0.05 were flagged and used for pathway analyses including prediction of upstream and downstream effects. Principal component analyses were used to examine the effect of two different sequencing runs on quality metrics and variation in expression and alignment and for explorative analysis of the radiation dose and time point of analysis.ResultsMore genes were differentially expressed 4 h after exposure to low and high doses of radiation than after 2 h. In experiments with high dose irradiation and RNA sequencing after 4 h, inactivation of the FAT10 cancer signaling pathway and activation of gluconeogenesis I, glycolysis I, and prostanoid biosynthesis was observed taking p-value (< 0.05) and (in) activating z-score (≥2.00 or ≤ − 2.00) into account. Two hours after high dose irradiation, inactivation of small cell lung cancer signaling was observed. For low dose irradiation experiments, we did not detect any significant (p < 0.05 and z-score ≥ 2.00 or ≤ − 2.00) activated or inactivated pathways for both time points.ConclusionsCompared to 2 h after irradiation, a higher number of differentially expressed genes were found 4 h after exposure to low and high dose ionizing radiation. Differences in gene expression were related to signal transduction pathways of the DNA damage response after 2 h and to metabolic pathways, that might implicate cellular senescence, after 4 h. The time point 4 h will be used to conduct further irradiation experiments in a larger sample.
Highlights
Exposure to ionizing radiation induces complex stress responses in cells, which can lead to adverse health effects such as cancer
They were grouped into 5 matched triplets, each consisting of 1 second primary neoplasm (SPN), 1 first primary neoplasm (FPN), and 1 cancer-free control
FPN diagnoses were lymphoma (n = 6) or leukemia (n = 4) and they were diagnosed at a mean age of 8.10 years
Summary
Exposure to ionizing radiation induces complex stress responses in cells, which can lead to adverse health effects such as cancer. Exposure to ionizing radiation induces complex stress responses in cells (Albrecht et al 2012) and can lead to genomic instability (Kadhim and Hill 2015) These effects are limited to the irradiated cells and observed in adjacent, untreated bystander cells (Mavragani et al 2016). The time point with the highest numbers of DEGs differed from 4 h (Ding et al 2005) over 16 h (Mezentsev and Amundson 2011) and 24 h (Hou et al 2015; Mezentsev and Amundson 2011) to 30 h (Albrecht et al 2012) in a dose-dependent manner Besides these quantitative differences of gene expression in primary human skin fibroblasts, qualitative divergences, like different expression profiles of genes included in p53-associated pathways, have been shown 1 h, 2 h, 4 h and 24 h after exposure to LDIR (0.02 Gray (Gy)) and HDIR (4Gy) (Ding et al 2005)
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