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Gene expression response in mouse model of inflammatory bowel disease to ionizing radiation

ABSTRACT: Background: Ionizing Radiation (IR) is a known pro-inflammatory agent and in the process of development of biomarkers for radiation biodosimetry a chronic inflammatory disease condition could act as a confounding factor. Hence, it is important to develop radiation biodosimetry that can distinguish between IR-induced inflammatory responses and pre-existing disease. In this study, we compared the gene expression response of a genetically modified mouse model of inflammatory bowel disease (Il10-/-) with that of a normal wild-type mouse to potentially develop transcriptomic based biodosimetry markers for individual susceptibility to radiation. Results: Wild-type (WT) and Il10-/- mice were exposed to whole body irradiation of 7Gy (LD50/30 for IL10-/-) X-rays. Gene expression responses were studied using high throughput whole genome microarrays in peripheral blood after 24h post-irradiation. Analysis resulted in identification of 1962 and 1844 genes differentially expressed (p < 0.001, FDR < 10%) after radiation exposure in Il10-/- and WT mice respectively. A set of 155 genes were also identified as differentially expressing between WT and Il10-/- mice at the baseline pre-irradiation level. Gene ontology analysis revealed that the baseline differentially expressing genes (155) were mainly involved in Inflammatory response, Glutathione metabolism and fibrosis. Analysis of radiation responsive genes revealed commonality of immune function genes between WT and Il10-/- mice. Gene ontology analysis revealed that innate immune response and p53 signaling processes were strongly associated with up-regulated genes whereas, B-cell development process was found to be significant amongst downregulated genes in response to radiation in the two genotypes. However, specific immune response pathways like MHC class I antigen presentation and response to viral/bacterial infection were particularly associated with radiation responsive genes of Il10-/- mice but not with WT mice. Further analysis of activation status of specific canonical pathways and upstream regulators using IPA-prediction tool revealed significant difference in the activation status of T-cell and hormone mediated signaling as well as regulators of inflammation between WT and Il10-/- after irradiation.

ORGANISM(S): Mus musculus

PROVIDER: GSE114142 | GEO | 2019/04/04

REPOSITORIES: GEO

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Project description:Radiation biodosimetry based on transcriptomic analysis of peripheral blood is a valuable tool to detect radiation exposure after a radiological/nuclear event and obtain useful biological information that could predict tissue and organismal injury. However, confounding factors, including inflammation, can potentially obscure the predictive power of the method. The mitogen-activated protein kinase (MAPK) p38 is normally regulated by the MAP3K-MAP2K pathway in mammalian cells. Members of the p38 MAPK family respond to pro-inflammatory signals and environmental stresses. However, in T cells there is an alternative pathway for p38MAPK activation. This pathway has been shown to play an important role in antigen-receptor-activated T cells and participate in immune and inflammatory responses. Radiation is known to induce a pro-inflammatory response. To examine the role of p38MAPK in response to radiation, we used two mouse models expressing either a p38αMAPK dominant negative (DN) mutation that would be expected to globally suppress p38MAPK signaling or a double knock-in (DKI) mutant, which would be expected to inhibit specifically T cell receptor activation. We exposed wild-type and p38MAPK mutant mice to 7 Gy x-rays and 24 h later we isolated whole blood and performed genome microarray and gene ontology analysis. Comparison between the two mutants (DN, DKI) suggest that the alternative p38MAPK pathway may have wider functions in the response to radiation exposure beyond its well established role as a downstream effector of activated T-cell receptor. Among the differentially enriched pathways, irradiation leads to a significant overrepresentation of pathways associated with morbidity and mortality as well as organismal cell death. In contrast, these pathways were significantly underrepresented in p38MAPKDN and p38MAPKDKI mutant mice, implying that p38MAPK suppression protects mice from the deleterious effects of radiation. Furthermore, radiation exposure resulted in an enrichment of a small number of phagocytosis-related pathways; however, considerably more phagocytosis-related pathways were overrepresented in the p38MAPK mutant mice, implying that p38MAPK signaling, normally, restricts phagocytosis of apoptotic cells after radiation and may, thus, contribute to persistent inflammation. Finally, despite the significant changes in gene expression, we were still able to identify a panel of genes that could accurately distinguish between irradiated and control mice, irrespective of p38MAPK status.

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Gene expression response in mouse model of inflammatory bowel disease to ionizing radiation

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